JP2008171535A - Optical information recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical information recording medium causing no deterioration of writing and reading characteristics after preservation over an extended period of time and having high reliability. <P>SOLUTION: (1) In the optical information recording medium which includes a substrate, an information recording layer including a recording layer and a cover layer and wherein information is written and read on the information recording layer by irradiation with a laser beam via the cover layer, the cover layer includes an ultraviolet curing resin and an inner hardness Hi defined as hardness H of the cover layer on a side of the information recording layer satisfies the following relationship: 3.8≤Hi≤5.5, when H=3.8584×F/(h×h), wherein h represents an indented depth in a state in which a triangular pyramid indenter with a tip angle of 115° is pressed under F=9.8 mN. (2) In the optical recording medium described in (1), the optical curing resin comprises 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropane-1-on as an optical polymerization initiator. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an optical information recording medium.

As a write-once type optical recording medium capable of recording / reproducing even at a short wavelength equal to or shorter than the blue laser wavelength, the present applicant described in Patent Documents 1 to 3 as a recording layer mainly composed of a metal or metalloid oxide, particularly bismuth oxide. Proposes usefulness. In Japanese Patent Application No. 2005-064328, the main component of the constituent element is bismuth, and the recording layer further includes bismuth oxide. The recording layer further includes B, P, Ga, As, Se, Tc, Pd, Write-once type optical recording medium comprising one or more elements X selected from Ag, Sb, Te, W, Re, Os, Ir, Pt, Au, Hg, Tl, Po, At, and Cd Disclosure.
On the other hand, as an optical disk system of the blue laser generation, a Blu-ray disc standard using a 405 nm blue laser and an optical system with a numerical aperture NA = 0.85 has been proposed, and commercialization has already started. In this standard, in order to ensure a tilt margin in a high NA optical system, the recording / reproducing light is not irradiated from the conventional substrate side but is designed to be irradiated through a cover layer set to a thickness of about 0.1 mm. Has been.

  However, when the cover layer thickness is about 0.1 mm, if it is molded by an injection molding method such as polycarbonate as before, sufficient mechanical strength, plate thickness distribution, and in-plane uniformity of optical characteristics A new problem arises that it becomes impossible to secure the above. For this reason, Patent Document 4 proposes a structure in which a cover layer is provided on the side opposite to the conventional substrate. That is, a phase change recording medium in which a cover layer is thinned by forming a reflective layer, a first dielectric layer, a phase change recording layer, a second dielectric layer, and a cover layer in this order on a substrate made of polycarbonate or the like. Is made. In such a method, a substrate having a pregroove is first injection molded using a stamper, and then a reflective layer, a first dielectric layer, a phase change recording are formed on the surface of the substrate on which the pregroove is formed by a sputtering method or the like. A layer and a second dielectric layer are formed in this order. Then, a cover layer is formed on the surface of the second dielectric layer by spin coating with an ultraviolet curable resin or bonding of a film sheet. As a method for obtaining a cover layer with high film thickness uniformity, a method of applying an ultraviolet curable resin by a spin coating method in which a central hole is closed as in Patent Document 5, or a method of obtaining a cover layer as in Japanese Patent Application No. 2006-48496. There is a method of spin coating by concentrically providing a temperature distribution and changing the viscosity of the ultraviolet curable resin in the radial direction.

In the thus manufactured optical recording medium, the recording / reproducing laser is incident from the opposite side of the substrate, so that the thickness of the substrate can be sufficiently increased. Also, since the substrate is not required to have optical characteristics such as transmittance and birefringence, it is only necessary to perform substrate molding that focuses only on the transferability of the grooves and the mechanical characteristics of the medium. If such an optical recording medium is used, Therefore, it is possible to use a high NA optical recording medium head while sufficiently securing the mechanical strength of the substrate.
However, when the cover layer is formed using an ultraviolet curable resin, there is a problem that the reliability of the optical information recording medium deteriorates. Specifically, in a high-temperature, high-humidity accelerated test at 80 ° C., 85% RH, and 300 h, the reproduction jitter (hereinafter referred to as “archival jitter”) of the recorded part at the initial stage deteriorates, or the unrecorded part after the test Recording jitter (hereinafter referred to as shelf jitter) at the time of recording sometimes deteriorated.

  On the other hand, in Patent Documents 6 to 9, in the UV curable adhesive for bonding DVDs, by using a photopolymerization initiator having a relatively large absorption coefficient in a long wavelength region exceeding about 400 nm, the internal curability is increased. It is disclosed that a highly reliable adhesive structure can be obtained. However, none of the documents describes the application to the cover layer in the optical recording medium having a configuration in which light is incident through the cover layer targeted by the present invention. Each of the documents relates to a read-only medium, and there is no technical disclosure regarding improvement of archival characteristics and shelf characteristics of a recording medium, which is a problem to be solved by the present invention. In addition, there is no description that suggests that there may be a desirable range of internal hardness that is the subject of the present invention.

JP 2003-48375 A JP 2005-161831 A JP 2005-108396 A Japanese Patent No. 3241560 Japanese Patent Application Laid-Open No. 11-213459 JP 2001-49198 A Japanese Patent Application Laid-Open No. 10-120982 Japanese Patent Laid-Open No. 10-8018 Japanese Patent Laid-Open No. 9-169956

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a highly reliable optical information recording medium that does not deteriorate recording and reproduction characteristics even after long-term storage.

The above problems are solved by the following inventions 1) to 2) (hereinafter referred to as the present invention 1 and 2).
1) An optical information recording medium that includes an information recording layer including a recording layer and a cover layer on a substrate, and records and / or reproduces data by irradiating the information recording layer with laser light through the cover layer The cover layer is made of a photo-curing resin, and the indentation depth in the state in which a triangular pyramid indenter with an inter-ridge angle of 115 ° is indented at F = 9.8 mN is h, and the hardness H = 3.8584. The optical information recording is characterized in that the internal hardness Hi, which is the hardness H of the cover layer in contact with the information recording layer, satisfies 3.8 ≦ Hi ≦ 5.5 when × F / (h × h). Medium.
2) The optical information according to 1), wherein the photocurable resin contains 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropan-1-one as a photopolymerization initiator. recoding media.

Hereinafter, the present invention will be described in detail.
The present invention comprises at least an information recording layer including a recording layer and a cover layer on a substrate, and data is recorded and / or reproduced by irradiating the information recording layer with laser light through the cover layer. By spin coating, wherein the cover layer includes a step of supplying a photocurable resin onto the substrate, a step of spreading the photocurable resin by centrifugal force, and a step of curing the photocurable resin by light irradiation. The optical information recording medium thus formed is targeted.
As a result of studying improvements in archival characteristics and shelf characteristics of such an optical information recording medium, the present inventors have found that the internal hardness Hi of the cover layer is important as will be described later. The internal hardness Hi as used herein means that the cover layer is peeled off from the interface with the information recording layer including the recording layer, and fixed on a flat substrate such as a glass substrate with an adhesive or the like with the peeled surface facing up. If it is a measured value but peeling at the interface is not successful, a part of the medium including the cover layer is embedded in a two-component curable resin, and polishing is performed in a direction perpendicular to the cover layer to remove the cover layer. A sample having an exposed cross section can be prepared, and the hardness at a portion about 10 μm away from the information recording layer can be substituted.

The internal hardness Hi of the cover layer can be measured with an ultra-micro hardness meter DUH-211 manufactured by Shimadzu Corporation. In this method, the indenter is pushed down to the load F while increasing the load at a constant rate, and the hardness is obtained by the following equation from the relationship with the pushing depth h at that time.
Hardness H = a × F / (h × h)
Here, a is a constant depending on the shape of the indenter, and in the case of a triangular pyramid indenter having an inter-ridge angle of 115 °, a = 3.8585. If the indentation force is F = 9.8 mN, the indentation depth into the cover layer is 2 to 4 μm, which is sufficiently shallow with respect to the cover layer with a thickness of about 75 to 100 μm. The cured physical properties in the vicinity of the interface with the information recording layer can be evaluated without being influenced by (in general, if the thickness is about 10 times the indentation depth, the influence of the base is said to be negligible. ) If the indentation force is excessively small, it is not preferable because it tends to be affected by system drift, environmental vibration, and the sample fixing method. If the indentation force is too large, the influence in the depth direction will appear as described above. Since it becomes easy, it is not preferable.

In the present invention 1, when the indentation depth in a state in which a triangular pyramid indenter with an inter-ridge angle of 115 ° is indented at F = 9.8 mN is h, hardness H = 3.8484 × F / (h × h) The internal hardness Hi of the cover layer on the side in contact with the information recording layer is set to 3.8 ≦ Hi ≦ 5.5.
If 3.8 ≦ Hi, a medium with little deterioration of archival jitter can be obtained. On the other hand, if Hi exceeds 5.5, shelf jitter deteriorates, so it is necessary to satisfy Hi ≦ 5.5. That is, when 3.8 ≦ Hi ≦ 5.5, a highly reliable medium with good archival jitter and shelf jitter can be obtained.
In order to set the internal hardness Hi of the cover layer on the side in contact with the information recording layer to 3.8 ≦ Hi ≦ 5.5, an oligomer, a monomer (reactive diluent) constituting the photocurable resin, and photopolymerization start What is necessary is just to adjust the kind of agent and these composition ratios suitably. Generally, when the composition ratio of the monomer is increased, the crosslink density is increased, so that the hardness is increased. Furthermore, curing conditions (ultraviolet light intensity, illuminance, wavelength, etc.) may be adjusted as appropriate.
The information recording layer in the present invention refers to a laminated portion of each layer other than the substrate and the cover layer. For example, in FIG. 6 to be described later, it refers to a reflective layer, a first dielectric layer, a recording layer, and a second dielectric layer. However, a multilayer optical information recording medium having two or more such information recording layers via an intermediate layer or the like is also included in the present invention.

The inventors consider the relationship between the internal hardness Hi of the cover layer and the reliability of the optical recording medium as follows.
First, as a result of intensive studies by the present inventors, it was found that there is a difference in hardness between the front and back sides of a cover layer made of an ultraviolet curable resin having a thickness of about 100 μm. The difference in hardness between the front and back surfaces here means that the surface on the side where ultraviolet rays are incident when the cover layer is cured (the surface of the cover layer on which the recording / reproducing beam is incident) and the cover on the side in contact with the information recording layer It is the hardness difference from the back side of the layer.
In general, hardness represents elasto-plastic deformation resistance against indentation of the indenter, so in the case of an ultraviolet curable resin film, the hardness is regarded as a characteristic value that reflects the cured physical properties such as the crosslinking density and elastic modulus of the cured product. be able to. That is, a hardened product having a large hardness tends to have a high elastic modulus and crosslinking density and a high glass transition temperature. On the other hand, when the hardness is small, the elastic modulus and the crosslinking density are small, the glass transition temperature is low, and therefore the heat resistance tends to be low.

  A hardness difference between the front and back surfaces of the cover layer at a hardness due to a minute load that is the subject of the present invention indicates that the above-described cured physical properties are changing in the depth direction. In general, the difference in hardness between the front and back surfaces of the cover layer tends to be lower on the back side than the case where the front side becomes insufficiently cured due to oxygen inhibition during curing. FIG. 1 shows an example of measurement for Mitsubishi Rayon UV curable resin RQ6107. FIG. 1B is a graph showing the average value of FIG. Thus, the hardness of the back surface side of the cover layer is lower than the hardness of the surface, as can be seen from the transmission spectrum of a general UV curable resin cured product composed of a urethane (meth) acrylate compound shown in FIG. Since the ultraviolet curable resin itself has absorption in the ultraviolet region of 400 nm or less, the ultraviolet intensity is weakened inside the film, and the radical generation reaction of the photopolymerization initiator is suppressed, resulting in a lower crosslink density on the back side. It is. Such changes in the cured physical properties in the depth direction are due to differences in the type of light source (spectral characteristics), intensity, and illuminance (= integrated intensity), polymerizable oligomers and monomers that are components of UV curable resins, and photopolymerization initiation. It is thought that it varies depending on the type of agent and the difference in concentration.

Based on the above knowledge, the inventors have determined that the reliability of the medium is not the cured property of the cover layer surface but the cured physical property of the cover layer in contact with the information recording layer, rather than the bulk cured physical property as a film. From the viewpoint of being important, the present invention has been completed. That is, the cured physical properties of the cover layer in contact with the information recording layer were evaluated by a substitute characteristic called hardness, and the following relationship was found for internal hardness Hi, archival jitter, and shelf jitter.
3 and 5 show the relationship between the internal hardness Hi of the cover layer, archival jitter, and shelf jitter for a write-once optical recording medium manufactured in the same manner as in the examples described later. FIG. 4 relates to a write-once type optical recording medium having an internal hardness Hi of 3.5.
As can be seen from FIG. 3, in the case of 3.8 ≦ Hi, the archival jitter can be suppressed to 6.5% or less of the Blu-ray disc standard in the reliability test at 80 ° C., 85% RH and 300 hours. It becomes possible. When the internal hardness Hi is smaller than 3.8, the cross-linking density of the resin inside the cover layer is low, the molecular chain is sparse and water easily permeates, so that it is difficult to obtain a sufficient barrier property against water. For this reason, it is considered that the moisture transmitted through the cover layer erodes the recording layer and the reflective layer. In such a medium, for example, as shown in FIG. 4, a defect in a spike state occurs in the recording signal amplitude, and the reproduction jitter and error rate increase.

On the other hand, as shown in FIG. 5, when the internal hardness Hi exceeds 5.5, the shelf jitter is deteriorated. This is presumably because the internal hardness of the cover layer is increased and the adhesion is insufficient. During recording, thermal stress acts on the interface between the information recording layer and the cover layer, so if the adhesion of the cover layer is insufficient, micro peeling occurs and the thermal conductivity to the cover layer changes. Therefore, it is considered that the jitter deteriorates due to the fluctuation of the signal length. For example, in the case of a long mark in which recording energy is concentrated, cross writing to adjacent tracks is likely to occur. In addition, the space signal following the long mark is also easily affected.
An optical recording medium is essentially a thermal recording that uses light. When the thermal characteristics such as the heat capacity and thermal conductivity of the dielectric layer (protective layer) that sandwiches the recording layer change, the heating temperature and cooling rate of the recording mark portion are changed. It is well known that the change in the temperature and the thermal interference between the front and rear marks or between adjacent tracks change to affect the shape of the recording mark and the recording jitter. It is considered that the same change in thermal characteristics is caused by poor adhesion between the information recording layer and the cover layer.
From the above results, it was found that when the internal hardness Hi is 3.8 ≦ Hi ≦ 5.5, a highly reliable medium with good archival jitter and shelf jitter can be obtained.

As a preferred embodiment of the present invention, the cover layer has at least a radical polymerizable oligomer composed of urethane (meth) acrylate, epoxy (meth) acrylate and / or polyester (meth) acrylate, and reactivity composed of (meth) acrylate monomer. Diluent and 1-hydroxy-cyclohexyl-phenyl-ketone and / or 2-hydroxy-1- {4- [4- (2-hydroxy-2-methyl-propionyl) -benzyl] phenyl} -2-methyl-propane It consists of the composition of the photocurable resin obtained using the photoinitiator which consists of -1-one and 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropan-1-one. An optical information recording medium can be mentioned.
1-hydroxy-cyclohexyl-phenyl-ketone and / or 2-hydroxy-1- {4- [4- (2-hydroxy-2-methyl-propionyl) -benzyl] phenyl} -2-methyl-propan-1-one Is used as a photopolymerization initiator to obtain a cured film with little yellowing over time (a phenomenon in which a substance having light absorption in the blue wavelength region around 400 nm is formed and the cured product appears to turn yellow). It is done. On the other hand, yellowing of the cured film is not preferable because the transmittance at 405 nm changes and the recording / reproducing characteristics of the medium change.
Furthermore, by adding 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropan-1-one to the above initiator, the surface hardenability of the film is enhanced and a flat cover free from surface defects A layer can be obtained.

FIG. 8 shows a surface defect image of a typical cover layer measured by using an interference type surface profile measuring instrument NewView 6000 manufactured by Zygo. FIG. 8A shows the surface shape, and FIG. 8B shows the line profile. If the surface curability of the photocurable resin is poor or the ultraviolet irradiation intensity used is low, surface defects such as those shown in FIG. Such a defect does not cause much problem when the recording linear velocity is low, but causes a servo error as the recording linear velocity becomes 4 to 8 times faster, leading to an increase in defect rate and a tracking failure.
Such surface defects are considered to be caused by the gas components dissolved in the photocurable resin being aggregated and broken during curing. Generally, radicals generated in the photocurable resin by ultraviolet irradiation disappear due to the reaction with oxygen in the film surface atmosphere, and therefore the curing reaction on the film surface tends to be slower than the inside (the photopolymerization reaction). Oxygen inhibition). When the influence of such oxygen inhibition and the ultraviolet irradiation intensity are insufficient and the curing reaction on the surface is slow, surface defects as shown in FIG. 8 are likely to occur.
Therefore, if 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropan-1-one having excellent surface curability is added to accelerate the curing reaction on the surface, 8 can be reduced, and the defect size can be reduced to a level that does not affect the servo as shown in FIG. FIG. 9 is a surface defect image measured in the same manner as FIG. 8, FIG. 9A shows the surface shape, and FIG. 9B shows the line profile.
A suitable addition amount of the photopolymerization initiator is 1 to 8% by weight in total. Since 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropan-1-one causes yellowing when added in a large amount, the preferred added amount is 0.01 to 0.5. % By weight.

Further, as a preferred embodiment of the present invention, the recording layer is bismuth oxide, and B, Ga, Pd, Ag, Sb, Te, W, Pt, Au, Al, Cr, Mn, In, Co, Fe, Cu, Ni, A write-once type optical recording medium containing at least one kind (element X) selected from Zn, Li, Si, Ge, Zr, Ti, Hf, Sn, Mo, V, and Nb can be given. That is, in order to improve recording / reproduction characteristics and storage stability, an element X other than bismuth is added to the recording layer containing bismuth oxide. Usually, it is preferable that bismuth oxide accounts for about 50 to 95 mol% of the entire recording layer material.
Bismuth oxide and element X do not have to be completely oxidized, and the recording layer may be configured in an oxygen deficient state with respect to the stoichiometric composition. The stoichiometric composition here refers to a composition possessed by a compound that exists stably at normal temperature and normal pressure. For example, an oxide such as Bi ₂ O ₃ , B ₂ O ₃ , Al ₂ O ₃ , TiO ₂ , and In ₂ O ₃ can be said to have a stoichiometric composition. The oxygen deficient state with less oxygen than the stoichiometric composition is BiOx in the case of x <1.5, that is, BiO _1.48 . In the case of a stoichiometric composition without oxygen deficiency, BiO _1.5 is obtained.
When the recording layer is made only of bismuth oxide, it is not practical because deterioration due to reproduction light occurs remarkably or archival jitter increases in storage reliability. Therefore, the addition of at least one element X described above can improve the thermal conductivity, absorption characteristics, recording sensitivity, stability of the recording mark with respect to reproducing light and temperature, and the like.

  For example, regarding the recording sensitivity, when the additive element X is Ge, Sn, Li or the like having an oxide generation enthalpy equivalent to that of Bi, these oxides separate oxygen in the recording film as a single element after sputtering film formation. Therefore, the light absorption rate is improved, and the sensitivity can be improved. Elements such as Li, Na, Mg, K, Ca, and P have the property of being easily vitrified by coexisting with bismuth oxide. Although the mechanism is not clear, a metastable glass state may be associated with increased sensitivity. In addition, elements that are relatively difficult to oxidize, such as Cu, Ag, and Pd, exist as metals themselves, and are considered to improve sensitivity. Since La elements are more easily oxidized than Bi, Bi is likely to exist as a single metal, and is considered to be involved in improving sensitivity.

  Another preferred embodiment of the present invention is an optical information recording medium in which the main component of the recording layer is Bi, B, Ge, and O. The recording layer to which Ge is added increases the light absorption and improves the sensitivity, and exhibits good characteristics particularly in high linear velocity recording. Although the mechanism is not clear, it is believed that addition of Ge suppresses Bi oxidation and facilitates precipitation of Bi metal, thereby increasing light absorption and improving sensitivity. In addition, when Ge is used as an additive element, sensitivity can be improved and a recording power margin can be widened, and stable recording and reproduction can be performed. Desirable Ge content is 0.01 <= Ge / (Bi + B + Ge) <= 0.1 by atomic ratio. When Ge / (Bi + B + Ge) is smaller than 0.01, a sufficient Ge addition effect cannot be obtained. Conversely, if Ge / (Bi + B + Ge) is larger than 0.1, the recording jitter becomes high, which is not preferable.

A configuration example of the optical information recording medium of the present invention is shown in FIG. The light incident surface for recording and reproduction is on the upper side of the figure.
The substrate is manufactured by injection molding of a resin such as polycarbonate, acrylic, or polyolefin, and has a spiral groove on the information recording layer lamination side. In the medium of FIG. 6, since the recording / reproducing laser beam is incident from the cover layer side, the substrate material does not necessarily need to be translucent, and has good mechanical properties such as groove groove transferability and warpage. Although it can be selected from molding materials, in general, an inexpensive polycarbonate resin that has a proven record in CDs and DVDs is selected.
The information recording layer is a phase change type information recording layer containing a phase change type recording material, or a write-once information recording layer made of a dye material or an inorganic material. When the information recording layer is a phase change information recording layer or a write-once information recording layer made of an inorganic material, a reflective layer, a first dielectric layer, a recording layer, and a second dielectric layer are provided on the substrate as the information recording layer. They are formed in this order by a known sputtering method or the like.

As the material of the reflective layer, a material having a sufficiently high reflectance at the wavelength of the reproduction light, for example, a metal such as Au, Al, Ag, Cu, Ti, Cr, Ni, Pt, Ta, Pd, alone or in an alloy is used. Can be used. Among these, Au, Al, and Ag are suitable as a material for the reflective layer because of their high reflectivity and good thermal conductivity. Further, the above metal may be the main component and other elements may be included. Examples of other elements include Mg, Se, Hf, V, Nb, Ru, W, Mn, Re, Fe, Co, Rh, Ir, Mention may be made of metals and metalloids such as Zn, Cd, Ga, In, Si, Ge, Te, Pb, Po, Sn, Bi. It is also possible to form a multilayer film by alternately stacking a low refractive index layer and a high refractive index layer with a material other than metal, and use it as a reflective layer.
The preferred film thickness of the reflective layer is 20 to 300 nm.

For the first dielectric layer and the second dielectric layer, a high-melting-point material having high transparency such as metal, semiconductor oxide, sulfide, nitride, and carbide can be used. _{Specifically, SiOx, ZnO, SnO 2,} Al 2 O 3, TiO 2, In 2 O 3, MgO, ZrO 2, Ta oxides such _{2 O 5, Si 3 N 4} , AlN, TiN, BN, Examples include nitrides such as ZrN, sulfides such as ZnS and TaS ₄ , and carbides such as SiC, TaC, B ₄ C, WC, TiC, and ZrC, and are used as a single body or a mixture, or as a multilayer structure composed of two or more layers. be able to.
The optimum material for the dielectric layer is determined in consideration of the refractive index, thermal conductivity, chemical stability, mechanical strength, adhesion, and the like. Among them, a mixed film with SiO ₂ containing 60 to 90 mol% of ZnS is desirable because there is no crystallization of the film itself, chemical change with the recording layer, and film deformation under a high temperature environment. In addition, since the thermal conductivity is as low as 0.5 W / mK or less, the heating temperature of the recording mark portion can be kept high, which is advantageous for forming a mark with a high degree of modulation. Most suitable as a body layer.
The first dielectric layer has a function of suppressing the reaction between the recording layer and the reflective layer and appropriately controlling the thermal conductivity to the reflective film, and the preferred film thickness is 5 to 30 nm.
The second dielectric layer has a function of preventing moisture and oxygen from permeating from the cover layer side and suppressing excessive thermal deformation of the cover layer, and a preferable film thickness is 5 to 100 nm.

As described above, a material containing bismuth oxide and element X is preferably used for the recording layer. More preferably, a material composed mainly of Bi, B, and O or a material composed mainly of Bi, B, O, and Ge is used. Such a recording layer is formed by adding, for example, a co-sputtering method including a Bi ₂ O ₃ target and a B ₂ O ₃ target, or further a GeO ₂ target, Bi ₂ O ₃ and B ₂ O ₃ , or further adding GeO _2. It is formed by a sputtering method using an integrally formed target.
In order to set the B content to 0.1 ≦ B / (Bi + B) ≦ 0.5 in terms of atomic ratio, the input power applied to each target is adjusted in the co-sputtering method. In the case of using an integrally formed target, the target composition may be determined in consideration of the composition deviation between the target and the film.
In order to create a state in which Bi and / or B are oxygen deficient with respect to the stoichiometric composition, the target is sintered in a reducing atmosphere to be in an oxygen deficient state, or a film formation rate is obtained using a target having a stoichiometric composition. The film formation conditions such as sputtering pressure may be adjusted to adjust the amount of oxygen deficiency, or reactive sputtering may be performed by adding a reducing gas such as hydrogen to the sputtering atmosphere.
A desirable recording layer thickness is 5 to 30 nm.

The photocurable resin used for the cover layer is at least a radically polymerizable oligomer composed of urethane (meth) acrylate, epoxy (meth) acrylate and / or polyester (meth) acrylate, and reactive dilution composed of (meth) acrylate monomer. Agent, 1-hydroxy-cyclohexyl-phenyl-ketone and / or 2-hydroxy-1- {4- [4- (2-hydroxy-2-methyl-propionyl) -benzyl] phenyl} -2-methyl-propane- It is an ultraviolet curable resin containing a photopolymerization initiator composed of 1-one and 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropan-1-one.
As said urethane (meth) acrylate, what is obtained by making a polyol compound, a polyisocyanate compound, and a hydroxyl-containing (meth) acrylate compound react is mentioned. Specific polyol compounds include polyether polyols, polyester polyols, polycarbonate polyols, polycaprolactone polyols, aliphatic hydrocarbons having two or more hydroxyl groups in the molecule, and alicyclic compounds having two or more hydroxyl groups in the molecule. Examples thereof include hydrocarbons and unsaturated hydrocarbons having two or more hydroxyl groups in the molecule. These polyols can be used alone or in combination of two or more.

Examples of the polyether polyol include aliphatic polyether polyols, alicyclic polyether polyols, and aromatic polyether polyols. Examples of the aliphatic polyether polyol include polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polyhexamethylene glycol, polyheptamethylene glycol, polydecamethylene glycol, pentaerythritol, dipentaerythritol, trimethylolpropane, and trimethylolpropane. A number of alkylene oxide addition polyols such as ethylene oxide addition triols of trimethylol propane, propylene oxide addition triols of trimethylol propane, ethylene oxide and propylene oxide addition triols of trimethylol propane, ethylene oxide addition tetraols of pentaerythritol, ethylene oxide addition hexaols of dipentaerythritol, etc. Dihydric alcohol or two or more types of Io Polyether polyols obtained by polymerizing cyclic compound by ring-opening polymerization.
Examples of the alicyclic polyether polyol include hydrogenated bisphenol A alkylene oxide addition diol, hydrogenated bisphenol F alkylene oxide addition diol, 1,4-cyclohexanediol alkylene oxide addition diol, and the like.
Examples of the aromatic polyether polyol include alkylene oxide addition diol of bisphenol A, alkylene oxide addition diol of bisphenol F, alkylene oxide addition diol of hydroquinone, alkylene oxide addition diol of naphthohydroquinone, alkylene oxide addition diol of anthrahydroquinone, etc. It is done.

  Commercially available products of the above polyether polyols include, as aliphatic polyether polyols, PTMG650, PTMG1000, PTMG2000 [more, manufactured by Mitsubishi Chemical Corporation], PPG1000, EXCENOL1020, EXCENOL2020, EXCENOL3020, EXCENOL4020 [more, Asahi Glass Co., Ltd.] ], PEG1000, Unisafe DC1100, Unisafe DC1800, Unisafe DCB1100, Unisafe DCB1800 [above, manufactured by NOF Corporation], PPTG1000, PPTG2000, PPTG4000, PTG400, PTG650, PTG2000, PTG3000, PTGL1000, PTGL2000 [above, Hodogaya Chemical Industry Co., Ltd.], Z-3001-4, Z-3001-5, PBG200 , PBG2000B [above, Dai-ichi Kogyo Seiyaku Co., Ltd.], TMP30, PNT4 glycol, EDAP4, EDA P8 [more Nippon Emulsifier Co., Ltd.], include Kuodororu [manufactured by Asahi Denka Co., Ltd.]. In addition, examples of the aromatic polyether polyol include Uniol DA400, DA700, DA1000, DB400 [manufactured by Nippon Oil & Fats Co., Ltd.].

The polyester polyol is obtained by reacting a polyhydric alcohol and a polybasic acid. Here, as the polyhydric alcohol, ethylene glycol, polyethylene glycol, propylene glycol, polypropylene glycol, tetramethylene glycol, polytetramethylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol 1,7-heptanediol, 1,8-octanediol, neopentyl glycol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, 1,2-bis (hydroxyethyl) cyclohexane, 2,2-diethyl -1,3-propanediol, 3-methyl-1,5-pentanediol, 1,9-nonanediol, 2-methyl-1,8-octanediol, glycerin, trimethylolpropane, ethyleneoxy of trimethylolpropane Adducts, propylene oxide adducts of trimethylol propane, ethylene oxide and propylene oxide adducts of trimethylol propane, sorbitol, pentaerythritol, dipentaerythritol, alkylene oxide addition polyol, and the like. Examples of the polybasic acid include phthalic acid, isophthalic acid, terephthalic acid, maleic acid, fumaric acid, adipic acid, sebacic acid, and the like.
As a commercially available product of these polyester polyols, Kurapol P1010, Kurapol P2010, PMIPA, PKA-A, PKA-A2, PNA-2000 [manufactured by Kuraray Co., Ltd.] and the like can be used.

Examples of the polycarbonate polyol include polycarbonate diols represented by the following [Chemical Formula 1].
In the formula, R ¹ represents an alkylene group having 2 to 20 carbon atoms, a (poly) ethylene glycol residue, a (poly) propylene glycol residue, or a (poly) tetramethylene glycol residue, and m is an integer of 1 to 30. is there.
Specific examples of R ¹ include residues obtained by removing both terminal hydroxyl groups from the following compounds, that is, 1,4-butanediol, 1,5-pentanediol, neopentylglycol, 1,6-hexanediol, 1, 4-cyclohexanedimethanol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol And residues obtained by removing a hydroxyl group from tetrapropylene glycol and the like.
Commercially available products of the polycarbonate polyol include DN-980, DN-981, DN-982, DN-983 (manufactured by Nippon Polyurethane Industry Co., Ltd.), PC-8000 (manufactured by PPG), PNOC1000, PNOC2000, PMC100. PMC2000 [above, manufactured by Kuraray Co., Ltd.], Plaxel CD-205, CD-208, CD-210, CD-220, CD-205PL, CD-208PL, CD-210PL, CD-220PL, CD-205HL, CD -208HL, CD-210HL, CD-220HL, CD-210T, CD-221T [above, manufactured by Daicel Chemical Industries, Ltd.] can be used.

  Examples of the polycaprolactone polyol include ε-caprolactone such as ethylene glycol, polyethylene glycol, propylene glycol, polypropylene glycol, tetramethylene glycol, polytetramethylene glycol, 1,2-polybutylene glycol, 1,6-hexanediol, neo Examples include polycaprolactone diols obtained by addition reaction with diols such as pentyl glycol, 1,4-cyclohexanedimethanol, and 1,4-butanediol. As these commercial products, Plaxel 205, 205AL, 212, 212AL, 220, 220AL (above, manufactured by Daicel Chemical Industries, Ltd.) and the like can be used.

Examples of the aliphatic hydrocarbon having two or more hydroxyl groups in the molecule include ethylene glycol, propylene glycol, tetramethylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, , 7-heptanediol, 1,8-octanediol, 1,9-nonanediol, neopentyl glycol, 2,2-diethyl-1,3-propanediol, 3-methyl-1,5-pentanediol, 2- Examples include methyl-1,8-octanediol, hydroxy-terminated hydrogenated polybutadiene, glycerin, trimethylolpropane, pentaerythritol, and sorbitol.
Examples of the alicyclic hydrocarbon having two or more hydroxyl groups in the molecule include 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, 1,2-bis (hydroxyethyl) cyclohexane, dimethylol such as dicyclopentadiene. Compound, tricyclodecane dimethanol and the like.
Examples of the unsaturated hydrocarbon having two or more hydroxyl groups in the molecule include hydroxy-terminated polybutadiene and hydroxy-terminated polyisoprene.
Furthermore, examples of polyols other than the above include β-methyl-δ-valerolactone diol, castor oil-modified diol, terminal diol compound of polydimethylsiloxane, polydimethylsiloxane carbitol-modified diol, and the like.
The preferred average molecular weight of these polyol compounds is 50 to 15000, particularly preferably 100 to 8000.

  The polyisocyanate compound is preferably a diisocyanate compound, such as 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 1,3-xylylene diisocyanate, 1,4-xylylene diisocyanate, 1,5- Naphthalene diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, 3,3'-dimethyl-4,4'-diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate, 3,3'-dimethylphenylene diisocyanate, 4,4'- Biphenylene diisocyanate, 1,6-hexane diisocyanate, isophorone diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, bis (2-isocyanatoethyl) Rate, 6-isopropyl-1,3-phenyl diisocyanate, lysine diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated xylylene diisocyanate, tetramethylxylylene diisocyanate, and the like. Among these, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, hydrogenated xylylene diisocyanate, isophorone diisocyanate, and hydrogenated diphenylmethane diisocyanate are particularly preferable. These diisocyanates can be used alone or in combination of two or more.

The hydroxyl group-containing (meth) acrylate is a (meth) acrylate having a hydroxyl group in the ester residue. For example, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) Acrylate, 2-hydroxy-3-phenyloxypropyl (meth) acrylate, 1,4-butanediol mono (meth) acrylate, 2-hydroxyalkyl (meth) acryloyl phosphate, 4-hydroxycyclohexyl (meth) acrylate, 1,6 -Hexanediol mono (meth) acrylate, neopentyl glycol mono (meth) acrylate, trimethylolpropane di (meth) acrylate, trimethylolethane di (meth) acrylate, pentaerythritol tri (me ) Acrylate, dipentaerythritol penta (meth) acrylate, or represented by the following general formula [2] (meth) acrylate and the like (wherein, R ² represents a hydrogen atom or a methyl radical, n is 1 to 15 , Preferably an integer of 1 to 4), and compounds obtained by addition reaction of glycidyl group-containing compounds such as alkyl glycidyl ether, allyl glycidyl ether, glycidyl (meth) acrylate and (meth) acrylic acid. it can. Of these, hydroxyalkyl (meth) acrylates such as 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, and 4-hydroxybutyl (meth) acrylate are particularly preferable.

Although the synthesis | combining method of urethane (meth) acrylate suitable for the photocurable resin used for this invention is not restrict | limited in particular, For example, it performs according to the method of following (i)-(iii).
(I) A method in which a polyisocyanate and a hydroxyl group-containing (meth) acrylate are reacted and then reacted in the order of polyol.
(Ii) A method in which a polyol, a polyisocyanate, and a hydroxyl group-containing (meth) acrylate are charged together and reacted.
(Iii) A method of reacting a polyol and a polyisocyanate and then reacting a hydroxyl group-containing (meth) acrylate.
In the synthesis of urethane (meth) acrylate, copper naphthenate, cobalt naphthenate, zinc naphthenate, di-n-butyltin dilaurate, triethylamine, 1,4-diazabicyclo [2.2.2] octane, 1,4 The reaction is preferably carried out using 0.01 to 1 part by weight of a urethanization catalyst such as diaza-2-methylbicyclo [2.2.2] octane with respect to 100 parts by weight of the total amount of the reactants. The reaction temperature in this reaction is usually 0 to 90 ° C, preferably 10 to 80 ° C.
Moreover, the preferable number average molecular weights of urethane (meth) acrylate are 400-40000, and 600-20000 are especially preferable.

Among the radical polymerizable oligomers suitable for the photocurable resin used in the present invention, examples of the epoxy (meth) acrylate include those obtained by reacting a glycidyl ether type epoxy compound with (meth) acrylic acid.
Examples of the glycidyl ether type epoxy compound include diglycidyl ether of bisphenol A or its alkylene oxide adduct, diglycidyl ether of bisphenol F or its alkylene oxide adduct, diglycidyl ether of hydrogenated bisphenol A or its alkylene oxide adduct, hydrogen Diglycidyl ether, ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, butanediol diglycidyl ether, hexanediol diglycidyl ether, cyclohexanedimethanol di Glycidyl ether, polypropylene glycol diglycidyl ether, etc. That.

The epoxy (meth) acrylate suitable for the photocurable resin used in the present invention is, for example, 0.9 to 1.5 mol of (meth) acrylic acid with respect to 1 equivalent of the epoxy group of the glycidyl ether type epoxy compound. More preferably, it is obtained by reacting at a ratio of 0.95 to 1.1 mol. The reaction temperature is preferably 80 to 120 ° C., and the reaction time is about 10 to 35 hours.
In order to accelerate the reaction, for example, a catalyst such as triphenylphosphine, TAP [2,4,6-tris (dimethylaminomethyl) phenol], triethanolamine, tetraethylammonium chloride is preferably used. In addition, a polymerization inhibitor (for example, paramethoxyphenol, methylhydroquinone, etc.) can be used to prevent polymerization during the reaction.
The molecular weight of the epoxy (meth) acrylate is preferably 400 to 10,000.
Moreover, epoxy (meth) acrylate can be used 1 type or in mixture of 2 or more types. When the epoxy (meth) acrylate is contained in the ultraviolet curable resin composition, the content is usually 1 to 30% by weight, preferably 5 to 20% by weight.
Examples of the epoxy (meth) acrylate suitable for the photocurable resin used in the present invention include bisphenol A type epoxy (meth) acrylate and phenol novolac type epoxy (meth) acrylate. Examples of the bisphenol type epoxy resin used for this include bisphenol A type epoxy resins such as Epicoat 828, Epicoat 1001, Epicoat 1004, etc. (all trade names of Yuka Shell Epoxy), Epicoat 4001P, Epicoat 4002P, Epicoat 4003P ( Examples thereof include bisphenol F-type epoxy resins such as the product name of Yuka Shell Epoxy.

  Among the radically polymerizable oligomers suitable for the photocurable resin used in the present invention, as the polyester (meth) acrylate, for example, a polyester polyol obtained by a reaction between a polyhydric alcohol and a polybasic acid, (meth) acrylic acid, These reactants can be mentioned. Examples of the polyhydric alcohol used here include neopentyl glycol, ethylene glycol, propylene glycol, 1,6-hexanediol, and trimethylolpropane. Examples of the polybasic acid include succinic acid, phthalic acid, Examples include hexahydrophthalic anhydride, adipic acid, azelaic acid, and tetrahydrophthalic anhydride.

Examples of the reactive diluent composed of a (meth) acrylate monomer suitable for the photocurable resin used in the present invention include (meth) acrylate compounds having at least one (meth) acryloyl group in one molecule. As these components, any of a monofunctional compound having only one (meth) acryloyl group and a polyfunctional compound having two or more may be used, or they may be used in combination at an appropriate ratio.
As the monofunctional compound, hydroxyalkyl (meth) acrylates such as 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, and 4-hydroxybutyl (meth) acrylate are used from the viewpoint of improving the moisture and heat resistance of the optical disc. Preferably used. Other monofunctional compounds include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, butyl (meth) acrylate, amyl (meth) acrylate, and isobutyl (meth). Acrylate, t-butyl (meth) acrylate, pentyl (meth) acrylate, isoamyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, octyl (meth) acrylate, isooctyl (meth) acrylate, 2-ethylhexyl ( (Meth) acrylate, nonyl (meth) acrylate, decyl (meth) acrylate, isodecyl (meth) acrylate, undecyl (meth) acrylate, dodecyl (meth) acrylate, lauryl ( Acrylate), octadecyl (meth) acrylate, stearyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, butoxyethyl (meth) acrylate, ethoxydiethylene glycol (meth) acrylate, benzyl (meth) acrylate, cyclohexyl (meth) acrylate, Phenoxyethyl (meth) acrylate, polyethylene glycol mono (meth) acrylate, polypropylene glycol mono (meth) acrylate, methoxyethylene glycol mono (meth) acrylate, ethoxyethyl (meth) acrylate, ethoxyethoxyethyl (meth) acrylate, methoxypolyethylene glycol (Meth) acrylate, methoxypolypropylene glycol (meth) acrylate, dicyclope Tadienyl (meth) acrylate, dicyclopentanyl (meth) acrylate, dicyclopentenyl (meth) acrylate, tricyclodecanyl (meth) acrylate, bornyl (meth) acrylate, isobornyl (meth) acrylate, adamantyl (meth) acrylate, Dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, 7-amino-3,7-dimethyloctyl (meth) acrylate, (meth) acryloylmorpholine, 2- (meth) acryloyloxyethylphthalic acid, 2- ( (Meth) acryloyloxyethyl hexahydrophthalic acid, 2- (meth) acryloyloxypropylphthalic acid, 2- (meth) acryloyloxypropyltetrahydrophthalic acid, 2- (meth) acryloyloxy Propylhexahydrophthalic acid, 2- (meth) acryloyloxyethyl succinic acid, trifluoroethyl (meth) acrylate, tetrafluoropropyl (meth) acrylate, hexafluoropropyl (meth) acrylate, octafluoropentyl (meth) acrylate, hepta Decafluorodecyl (meth) acrylate, mono [2- (meth) acryloyloxyethyl] phosphate, mono [2- (meth) acryloyloxyethyl] diphenyl phosphate, mono [2- (meth) acryloyloxypropyl] phosphate, etc. It is done.

  As these commercial products, Aronix M101, M102, M110, M111, M113, M114, M117, M120, M152, M154, M5300, M5400, M5500, M5600 (above, manufactured by Toagosei Co., Ltd.), KAYARAD TC-110S , R-128H, R629, R644 (manufactured by Nippon Kayaku Co., Ltd.), IPAA, AIB, SBAA, TBA, IAAA, HEXA, CHA, NOAA, IOAA, IAA, LA, TDA, MSAA, CAA, HDAA, LTA, STA, ISAA-1, ODAA, NDAA, IBXA, ADAA, TCDA, 2-MTA, DMA, Biscote # 150, # 150D, # 155, # 158, # 160, # 190, # 190D, # 192, # 193, # 220, # 320, # 311HP, # 2000, # 2100, # 2150, # 2180, MTG [manufactured by Osaka Organic Chemical Industry Co., Ltd.], NK ester M-20G, M-40G, M-90G, M-230G, CB-1, SA, S, AMP-10G, AMP-20G, AMP-60G, AMP-90G, A-SA, NLA [above, manufactured by Shin-Nakamura Chemical Co., Ltd.], ACMO [produced by Kojin Co., Ltd.], light acrylate IA-A, LA, SA, BO-A, EC-A, MTG-A, DPM-A, PO-A, P-200A, THF-A, IB-XA, HOA-MS, HOA- MPL, HOA-MPE, HOA-HH, IO-A, BZ-A, NP-EA, NP-10EA, HOB-A, FA-108, epoxy ester M-600A, light ester P-M [above, Kyoeisha Chemical Co., Ltd. FA-511, FA-512A, FA-513A [above, manufactured by Hitachi Chemical Co., Ltd.], AR-100, MR-100, MR-200, MR-260 [above, Daihachi Chemical ( Co., Ltd.], JAMP-100, JAMP-514, JPA-514 [above, manufactured by Johoku Chemical Co., Ltd.] and the like.

  Examples of the polyfunctional compound include ethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, 1,4-butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, 1,9-nonanediol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, dipropylene glycol di ( (Meth) acrylate, tripropylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, hydroxypivalic acid neopenty Glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, ditrimethylolpropane tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate, Dipentaerythritol hexa (meth) acrylate, trimethylolpropane trioxyethyl (meth) acrylate, trimethylolpropane polyoxyethyl (meth) acrylate, trimethylolpropane trioxypropyl (meth) acrylate, trimethylolpropane polyoxyethyl (meta) ) Acrylate, tris (2-hydroxyethyl) isocyanurate di (meth) acrylate, tris (2-hydroxyethyl) L) Isocyanurate tri (meth) acrylate, ethylene oxide-added bisphenol A di (meth) acrylate, ethylene oxide-added bisphenol F di (meth) acrylate, propylene oxide-added bisphenol A di (meth) acrylate, propylene oxide-added bisphenol F di (meth) Acrylate, tricyclodecane dimethanol di (meth) acrylate, bisphenol A diepoxy di (meth) acrylate, bisphenol F diepoxy di (meth) acrylate, bis [2- (meth) acryloyloxyethyl] phosphate, bis [2- (meth) acryloyl And polyfunctional (meth) acrylates such as oxypropyl] phosphate and tris [2- (meth) acryloyloxyethyl] phosphate.

  As these commercial products, SA-1002, SA-2006, SA-2007, SA-4100, SA-5001, SA-6000, SA-7600, SA-8000, SA-9000 [above, Mitsubishi Chemical Corporation] Manufactured by], Biscote # 195, # 195D, # 214HP, # 215, # 215D, # 230, # 230D, # 260, # 295, # 295D, # 300, # 310HP, # 310HG, # 312, # 335HP, # 335D, # 360, GPT, # 400, V # 540, # 700, GPT [above, manufactured by Osaka Organic Chemical Industry Co., Ltd.], KAYARADMANDA, R-526, NPGDA, PEG400DA, R-167, HX-220, HX -620, R-551, R-712, R-604, R-684, GPO-303, TMPTA THE-330, TPA-320, TPA-330, PET-30, RP-1040, T-1420, DPHA, D-310, D-330, DPCA-20, DPCA-30, DPCA-60, DPCA-120 [ As described above, manufactured by Nippon Kayaku Co., Ltd.], Aronix M-210, M-208, M-215, M-220, M-225, M-233, M-240, M-245, M-260, M- 270, M-305, M-309, M-310, M-315, M-320, M-350, M-360, M-400, M-408, M-450 [above, manufactured by Toagosei Co., Ltd. SR-212, SR-213, SR-355 (above, manufactured by Sartomer), SP-1506, SP-1507, SP-1509, SP-1519-1, SP-1563, SP-2500, V 60, VR77, VR90 [above, manufactured by Showa Polymer Co., Ltd.], Light Ester P-2M [above, manufactured by Kyoeisha Chemical Co., Ltd.], Biscoat 3PA [Osaka Organic Chemical Co., Ltd.], EB-169, EB-179, EB-3603, R-DX63182 [manufactured by Daicel UCB Co., Ltd.] and the like.

Of these reactive diluents, it is particularly preferable to use a combination of the aforementioned hydroxyalkyl (meth) acrylate and polyfunctional (meth) acrylate.
The component composition of the photocurable resin used in the present invention is 30 to 70% by weight of radical polymerizable oligomer, 30 to 70% by weight of reactive diluent, and 1 to 8% by weight of the total amount of photopolymerization initiator. It is preferable to do this. Furthermore, about several percent of additives (antioxidants, polymerization inhibitors, etc.) may be included.
Suitable photoinitiators for the present invention are 1-hydroxy-cyclohexyl-phenyl-ketone and / or 2-hydroxy-1- {4- [4- (2-hydroxy-2-methyl-propionyl) -benzyl] phenyl. } -2-methyl-propan-1-one and 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropan-1-one, which are photopolymerization initiators, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, 2,2-dimethoxy-1,2-diphenylethane-1-one, 1- [4- (2-hydroxyethoxy) -phenyl]- 2-hydroxy-2-methyl-1-propan-1-one, 2-methyl- [4- (methylthio) phenyl] -2-morpholino-1-propanone, 2-chlorothioxanthone, , 4-dimethyl thioxanthone, 2,4-diisopropyl thioxanthone, may be blended isopropylthioxanthone and the like.
Moreover, in order to improve the internal curability of the cured product, a photopolymerization initiator having sensitivity in a wavelength region of 400 nm or more may be included. As such a photopolymerization initiator, phenylglyoxylic acid methyl ester (absorption coefficient at 405 nm = 24 ml / g · cm), bis (2,4,6-trimethylbenzoyl) phenylphosphine oxide (900 ml / g · cm), 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) butanone-1 (280 ml / g · cm), 2-dimethylamino-2- (4-methyl-benzyl) -1- (4-morpholin-4-yl-phenyl) butan-1-one (280 ml / g · cm), 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (165 ml / g · cm) and the like. .

The cover layer may be formed by using a known method in which the center hole is closed and the UV curable resin is spin-coated, or the method of the present applicant in which the viscosity of the resin is controlled in the radial direction by heating the substrate and spin-coated. .
An example of the method for forming the cover layer will be described with reference to FIG.
First, as shown in FIG. 7A, the center hole of the medium is closed with a center hole mask of φ19 mm, and an ultraviolet curable resin is supplied near the center of the mask. Next, the substrate is rotated at 800 to 1500 rpm according to the viscosity of the resin to be used to spread the resin. At this time, it is preferable to condense the halogen lamp light on the outer periphery of the medium using a condensing optical system as shown in FIG. 7B and perform partial heating to flatten the resin reservoir in this part. Next, the center hole mask is removed, and the resin layer is cured by an ultraviolet light source as shown in FIG. 7C, whereby an optical information recording medium having the structure shown in FIG. 6 is obtained.

Irradiation of energy beam to be irradiated is preferably 50~2000mJ / cm ^2, particularly preferably 200~1500mJ / cm ^2. Any lamp that can irradiate energy rays used for curing can be used, for example, a low-pressure, high-pressure or ultrahigh-pressure mercury lamp, metal halide lamp, (pulse) xenon lamp, or electrodeless discharge lamp. The wavelength of energy rays that can be used for curing the ultraviolet curable resin composition is 150 to 450 nm.
Furthermore, although not shown in FIG. 6, a hard coat layer (ultraviolet curable resin) for imparting surface scratch resistance and antifouling properties by the same spin coating method on the cover layer (light incident side). A photocurable resin layer in which a layer or an inorganic substance is dispersed, an inorganic layer, or the like may be provided. In this case, according to the Blu-ray disc standard, the film thickness of the entire light transmission layer including the cover layer and the hard coat layer is 100 ± 2 μm where the refractive index n is n = 1.6.
As described above, the configuration example of the phase-change optical information recording medium according to the present invention has been described as an example in which one information recording layer is provided. However, a multilayer optical information recording medium having two or more information recording layers through an intermediate layer. It may be.

According to the first aspect of the present invention, since 3.8 ≦ Hi, a multilayer optical information recording medium with good archival jitter can be obtained, and furthermore, since Hi ≦ 5.5, multilayer optical information with good shelf jitter can be obtained. A recording medium is obtained.
According to the second aspect of the present invention, the photocurable resin contains 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropan-1-one as a photopolymerization initiator. Surface curability can be improved. For this reason, the surface defect of the cover layer can be suppressed (the defect as shown in FIG. 8 can be eliminated and the state as shown in FIG. 9 can be obtained). Errors can be reduced.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples. In Examples, Comparative Examples, Tables 1 and 2, parts are parts by weight unless otherwise specified.

Examples 1-5, Comparative Examples 1-2
First, 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 a guide groove with a groove depth of 20 nm and a track pitch of 0.32 μm, a target having the following composition was used. The laminated film was sequentially formed by a sputtering method to form an information recording layer.
(1) Reflective layer Al-1.0 wt% Ti (film thickness 35 nm)
(2) First dielectric layer Si ₃ N ₄ (film thickness 10 nm)
(3) Phase change recording layer Bi ₂ O ₃ -35 mol% B ₂ O ₃ (film thickness 16 nm)
(4) Second dielectric layer ZnS-20 mol% SiO ₂ (film thickness 10 nm)
Next, an ultraviolet curable resin having the composition shown in Table 1 is formed on the information recording layer by a spin coating method, and 400 mW / cm ^{2 in} a nitrogen environment using a UV lamp HP-6 manufactured by Fusion UV System. The film was cured by ultraviolet irradiation for 5 seconds to produce a write-once optical recording medium (so-called Blu-ray disc standard-compliant write-once optical recording medium) of the present invention as a cover layer having a thickness of about 1.2 mm.
The UV curable resins used in the examples and comparative examples shown in Table 1 are 15% by weight of bisphenol A glycidyl ether diacrylate (EPA manufactured by Nippon Kayaku Co., Ltd.), polyester urethane acrylate (UX-4101 manufactured by Nippon Kayaku Co., Ltd.). ) 30% by weight of 3 monomers of hydroxyethyl methacrylate (HEMA manufactured by Toagosei Co., Ltd.), neopentyl glycol diacrylate hydrohybalate (MANDA manufactured by Nippon Kayaku Co., Ltd.) At a ratio shown in Table 1, and as a photopolymerization initiator, 1-hydroxy-cyclohexyl-phenyl ketone (IRGACURE 184 manufactured by Ciba Specialty Chemicals) and 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl)- Butanone-1 ( RGACURE369) is obtained by reaction, in total 5% by weight. In Table 1, the composition of the highly curable monomer and the photopolymerization initiator was adjusted so that the internal hardness Hi of the cover layer increased in the order of Comparative Example 1, Examples 1 to 5, and Comparative Example 2.

For each write-once optical recording medium, write-once Blu-ray disc standard (BD-R Version 1...) Using an optical disc evaluation apparatus ODU-1000 (wavelength: 405 nm, NA: 0.85) manufactured by Pulstec Industrial Co., Ltd. 1. Recording is performed under 1 × speed recording conditions conforming to 1), and the values of archival jitter and shelf jitter after a reliability test at a temperature of 80 ° C., a humidity of 85% RH, and 300 hours are evaluated. Those satisfying 5% or less were rated as “◯”, and those exceeding 6.5% were rated as “X”.
As can be seen from Table 1, the media of Examples 1 to 5 having an internal hardness Hi of 3.8 ≦ Hi ≦ 5.5 have both archival jitter and shelf jitter of 6.5% or less, and are highly reliable. It was a medium.
On the other hand, since the medium of Comparative Example 1 had Hi <3.8, there was no problem with the shelf jitter, but the archival jitter increased to 7.2%.
Further, since the medium of Comparative Example 2 had 5.5 <Hi, there was no problem with archival jitter, but the shelf jitter deteriorated to 7.8%.
From the above, it can be seen that when 3.8 ≦ Hi ≦ 5.5, a highly reliable medium satisfying both the standard values of archival jitter and shelf jitter can be obtained.

・ EPA… Bisphenol A glycidyl ether diacrylate (manufactured by Nippon Kayaku Co., Ltd.)
・ UX-4101 ... Polyester urethane acrylate (Nippon Kayaku Co., Ltd.)
・ HEMA ... Hydroxyethyl methacrylate (manufactured by Toagosei Co., Ltd.)
・ MANDA… Hydropentylic acid neopentyl glycol diacrylate (manufactured by Nippon Kayaku Co., Ltd.)
・ TMPTA: Trimethylolpropane triacrylate (Toagosei Co., Ltd.)
IRGACURE184 ... 1-hydroxy-cyclohexyl-phenylketone IRGACURE369 ... 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone-1

Examples 6-8, Comparative Examples 3-4
On the same substrate as used in Example 1, a five-layered film was sequentially formed by sputtering using a target having the following composition to form an information recording layer.
(1) Reflective layer Ag-0.5 wt% Bi (film thickness 60 nm)
(2) First dielectric layer Si ₃ N ₄ (film thickness 4 nm)
ZnS-20 mol% SiO ₂ (film thickness 14 nm)
(3) Phase change recording layer Bi ₂ O ₃ -25 mol% B ₂ O ₃ -5 mol% GeO ₂
(Film thickness 14 nm)
(4) Second dielectric layer ZnS-20 mol% SiO ₂ (film thickness 55 nm)
Next, an ultraviolet curable resin having the composition shown in Table 2 was formed on the information recording layer by a spin coating method, and 400 mW / cm ^{2 in} a nitrogen environment using a UV lamp HP-6 manufactured by Fusion UV System. The film was cured by ultraviolet irradiation for 5 seconds to produce a write-once optical recording medium (so-called Blu-ray disc standard-compliant write-once optical recording medium) of the present invention as a cover layer having a thickness of about 1.2 mm.

For each write-once optical recording medium, write-once Blu-ray disc standard (BD-R Version 1...) Using an optical disc evaluation apparatus ODU-1000 (wavelength: 405 nm, NA: 0.85) manufactured by Pulstec Industrial Co., Ltd. Recorded under 4x speed recording conditions according to 2), evaluated the values of archival jitter and shelf jitter after a reliability test at a temperature of 80 ° C, humidity of 85% RH, and 300 hours. A value satisfying a jitter value of 6.5% or less was defined as a jitter characteristic “◯”, and a value exceeding 6.5% was defined as “X”. Further, the residual error in the <3.2 kHz band, which will be described later, that satisfied the standard <80 nm was evaluated as a residual error “◯”, and the residual error that exceeded the standard was “×”.
As can be seen from Table 2, the media of Examples 6 to 8 having an internal hardness Hi of 3.8 ≦ Hi ≦ 5.5 have both archival jitter and shelf jitter of 6.5% or less, and are highly reliable media. Met.
On the other hand, since the medium of Comparative Example 3 had Hi <3.8, there was no problem with the shelf jitter, but the archival jitter increased to 7.0%.
Further, since the medium of Comparative Example 4 was 5.5 <Hi, there was no problem with archival jitter, but the shelf jitter deteriorated to 8.0%.
When recording was performed on the media of Examples 1 to 5 at a recording speed of 4 ×, the jitter was 6.2 to 6.4% at an optimum recording power of 10.2 mW, and the jitter ≦ 6.5% was satisfied. The possible recording power range (power margin) was very narrow.
On the other hand, the media of Examples 6 to 8 were media having an optimum recording power of 8.0 mW and jitter of 5.3 to 5.5, and having high sensitivity and a wide power margin in high-speed recording. Thus, it can be seen that a recording material composed mainly of Bi, B, O and Ge can provide a medium with good sensitivity and power margin in high-speed recording.

Next, for the media of Examples 6-8 and Comparative Examples 3-4, Dr. Schenk ISM. The surface defect of the cover layer was inspected using the near dark field method of a blue + inspection machine.
As a result, several tens of surface defects as shown in FIG. 8 were detected in the media of Example 6 and Comparative Examples 3 and 4. Such a defect is not a problem when the recording linear velocity is low. However, when the residual error was measured by tracking across this defect at 4 × speed using the optical disk evaluation apparatus ODU-1000, the residual focus error of <3.2 kHz was 75 to 135 nm, and the standard <80 nm. Could not be satisfied.
On the other hand, in the media of Examples 7 and 8 containing 0.05% of 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropan-1-one as a photopolymerization initiator, A defect having such a size was not detected, and a defect as shown in FIG. 9 was rarely observed under a microscope.
Similarly, when the residual error was measured by tracking the defective portion, the residual focus error of <3.2 kHz was 65 nm or less, and the standard <80 nm was satisfied.
Thus, by including 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropan-1-one having high surface curability as a photopolymerization initiator, defects on the surface of the cover layer are suppressed. In addition, it is possible to obtain a medium having a small residual error and excellent servo characteristics.

-EPA, UX-4101, HEMA, MANDA, TMPTA are the same as Table 1.
IRGACURE127 ... 2-hydroxy-1- {4- [4- (2-hydroxy-
2-methylpropionyl) benzyl] phenyl} -2-methylpropan-1-one IRGACURE907 ... 2-methyl-1- [4- (methylthio) phenyl] -2
Morpholinopropan-1-one

The figure which shows an example of the front-back hardness difference of a cover layer. (A) Measurement data, (b) A graph of average values. The figure which shows the transmission spectrum of a general ultraviolet curing resin hardened | cured material. The figure which shows the relationship between the internal hardness Hi of a cover layer, and archival jitter. The figure which shows an example of the signal waveform which the defect generate | occur | produced in the recording part. (A) Before reliability test, (b) After reliability test. The figure which shows the relationship between the internal hardness Hi of a cover layer, and shelf jitter. The figure which shows the structural example of the optical information recording medium of this invention. The figure which shows an example of the formation method of a cover layer. (A) A step of closing the center hole of the medium with a mask, supplying an ultraviolet curable resin near the center of the mask, and then rotating the substrate to spread the resin. (B) A step of condensing halogen lamp light on the outer periphery of the medium using a condensing optical system to flatten the resin reservoir. (C) A step of removing the center hole mask and curing the resin layer with ultraviolet rays. The figure which shows the surface defect image of a typical cover layer. (A) Surface shape, (b) Line profile. The figure which shows the surface defect image of the cover layer which reduced the defect size to the level which does not affect a servo. (A) Surface shape, (b) Line profile.

Claims (2)

  An optical information recording medium having an information recording layer including a recording layer and a cover layer on a substrate, and recording and / or reproducing data by irradiating the information recording layer with laser light through the cover layer. The cover layer is made of a photo-curing resin, and the indentation depth in a state in which a triangular pyramid indenter having an inter-ridge angle of 115 ° is indented at F = 9.8 mN is h, and the hardness is H = 3.8854 × F. / (H × h), an optical information recording medium characterized in that the internal hardness Hi, which is the hardness H of the cover layer on the side in contact with the information recording layer, satisfies 3.8 ≦ Hi ≦ 5.5.   2. The optical information recording according to claim 1, wherein the photocurable resin contains 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropan-1-one as a photopolymerization initiator. Medium.