JP2012018756A - Evaluation method of optical information medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an evaluation method with which the scratch resistance of a recording/reproducing light incidence surface of an optical information medium can be quantified simply and in such a way that the actual use environment is reflected.SOLUTION: In a method to carry out an evaluation concerning the scratch resistance of a laser beam incidence surface with respect to an optical information medium having a translucent substrate and an information recording medium, in which laser beam entering from the side of the translucent substrate into the information recording layer performs optical recording and/or reproduction, the surface of the optical information medium in which laser beam enters is intentionally worn and then the recording/reproduction properties are measured. Then, the scratch resistance of the surface in which laser beam enters is evaluated based on the measured values.

Description

  The present invention relates to an optical information medium such as a read-only optical disk and an optical recording disk, and a method for evaluating the scratch resistance of the optical information medium.

  In recent years, in optical information media, it has been required to further increase the recording density in order to store vast amounts of information such as moving image information, and research and development has been conducted extensively to further increase the recording capacity. Yes. As one of them, for example, as seen on a DVD (Digital Versatile Disc), the recording / reproducing wavelength is shortened, the numerical aperture (NA) of the objective lens is increased, and the condensing spot diameter of the recording / reproducing light is increased. It has been proposed to reduce. Actually, when compared with a CD (compact disc), the recording / reproducing wavelength λ is changed from 780 nm to 650 nm, and the numerical aperture is changed from 0.45 to 0.60. Surface).

  Recently, as a method for recording high-quality moving images for a long time, the recording / reproducing wavelength is further shortened to about 400 nm and the numerical aperture is increased to 0.85, so that the recording capacity is more than four times that of DVD. Attempts have been made to achieve.

However, several problems arise in realizing a recording / reproducing system with such a high NA. For example, the allowable amount with respect to the tilt of the information recording layer of the medium is reduced. That is, the tilt margin when the recording / reproducing wavelength is λ and the thickness of the substrate is t, that is, the tolerance of the tilt of the information recording layer with respect to the incident light is proportional to λ / [t × (NA) ³ ]. Is known, and the tilt margin decreases rapidly as the NA increases.

Further, when tilt occurs in the optical recording medium, wavefront aberration (coma aberration) occurs. The wavefront aberration coefficient W is expressed by the following formula I.
Formula I W = (1/2) × t × [n ² × sin θ cos θ] NA ³ / (n ² −sin ² θ) ^−5/2

  In the above formula I, n is a refractive index of a transparent substrate (referred to as a translucent substrate in the present specification) through which a laser beam for recording / reproduction passes before reaching the information recording layer, and θ is a tilt angle. is there. From the above formula I, it is necessary to reduce the thickness of the translucent substrate in order to ensure a tilt margin.

  Due to the above circumstances, in DVD, the tilt margin is secured by making the thickness of the translucent substrate about half (about 0.6 mm) of the thickness of the conventional CD substrate (about 1.2 mm). Furthermore, in the system with NA = 0.85, the thickness of the translucent substrate is reduced to about 0.1 mm.

Other problems caused by increasing the NA include a reduction in the depth of focus, and a reduction in the working distance between the surface of the translucent substrate and the objective lens. The depth of focus becomes shallower in inverse proportion to (NA) ² , so that the focus servo tends to become unstable, and as a result, it becomes very sensitive to mechanical accuracy, scratches and dirt on the surface of the translucent substrate. Further, if the objective lens diameter is constant, the working distance becomes shorter as the NA increases, and the possibility that the pickup housing or the objective lens collides with the surface of the translucent substrate is increased. For example, in a system with NA = 0.85, the depth of focus is ± 0.3 μm and the working distance is about 100 to 300 μm, and the focus servo tends to become very unstable.

  Further, the objective lens is made of plastic or glass, but it is general that a protective plate is provided around the lens in consideration of the case where the lens is in contact with the surface of the translucent substrate. In the case of plastic lenses, a protective plate called edge is integrally molded to protect the lens surface. In glass lenses, a plate made of plastic such as acrylic resin or polypropylene is a protective plate (lens protector). ) Is attached around the lens. For this reason, even if the pickup should come into contact with the disk, it is general that the protective plate portion is in contact and the objective lens surface is not damaged.

  By the way, most of optical discs currently commercialized use a rigid substrate made of a thermoplastic resin such as polycarbonate or polymethyl methacrylate as a translucent substrate. That is, information is recorded / reproduced when a laser beam enters the information recording layer from the surface of the resin substrate. These resins are optically homogeneous and have high transparency, and are excellent in moldability, mechanical strength, etc., but have the disadvantage that they have low surface hardness and tend to cause scratches. For this reason, it is generally performed that a hard coat layer is provided as a scratch preventing layer on the surface of the resin substrate. As a method for forming such a hard coat layer, most commonly, a polymerization curable compound having two or more polymerizable functional groups such as acryloyl groups in the molecule is applied to the substrate surface, and an active energy such as ultraviolet rays is applied. A technique is adopted in which a hard coat layer is formed by curing with a wire.

  However, these UV curable resins are superior in abrasion resistance compared to thermoplastic resins such as polycarbonate, but there is a limit to the surface hardness that can be realized, and this is not always necessary for use as an optical information medium. Sufficient wear resistance cannot be obtained. Moreover, in a system in which the recording / reproducing optical system has a high density due to high NA, not only scratches caused by handling of the disc by the user but also scratches caused by the collision of the pickup as described above. Is required. Therefore, there is a need for a hard coat layer with significantly improved hardness compared to the above-described ultraviolet curable resin.

  In order to solve such a problem, a method of forming a hard coat layer containing an inorganic compound as a main component has been proposed.

  For example, in Japanese Patent Application Laid-Open No. 11-203726, an optical disk of a type in which a recording layer and a light transmission layer are sequentially stacked on a substrate and light is incident from the light transmission layer side for recording and / or reproduction is used. A method is disclosed in which an inorganic material such as two or more layers is coated on the surface of a light transmission layer by an ion beam sputtering method or the like, and this is used as a protective film (hard coat layer). However, an inorganic film formed by such a technique as sputtering or vapor deposition has a large internal stress. For this reason, in order to realize sufficient wear resistance, the film is easily self-destructed when the film thickness is several hundred nanometers or more. Therefore, with such an inorganic film, it is difficult to realize a hard coat layer having substantially satisfactory wear resistance.

  JP-A-8-263878 proposes a method in which a thin film mainly composed of silica is formed on a substrate surface from a solution of alkoxysilane or the like by a sol-gel method, and this is used as a protective film (hard coat layer). . However, when an inorganic compound film is formed by such a sol-gel method, baking must be performed at a high temperature exceeding 100 ° C. in order to sufficiently advance the reaction to form a dense film. Therefore, it is extremely difficult to apply to the surface of a translucent substrate made of a resin having low heat resistance.

  Japanese Patent Application Laid-Open No. 2000-132865 describes an information recording medium having a protective layer made of polysilazane. The subject matter described in the publication is an information recording medium having a disk-like or tape-like support. However, this publication does not describe a specific example applied to an optical disc.

JP-A-11-203726 JP-A-8-263878 JP 2000-132865 A

  By the way, the surface hardness used as the hard coat layer and serving as an index of wear resistance of the resin material or inorganic material is generally measured by indentation hardness such as Vickers hardness, scratch hardness, or abrasion test. Is. Among these measurement methods, for example, for the wear test, the amount of wear of the test piece caused by wear should be quantified using the amount of change in various parameters such as the mass, thickness, or light transmittance of the test piece. There are many. In the case of a material that is optically transparent and has a relatively high surface hardness, such as a hard coat layer material of an optical information medium, it is most appropriate to quantify the light transmittance and the amount of change in light diffusion. Specifically, a method of making white parallel light incident on the test piece and measuring its haze value (haze value) is generally used.

  The test piece hardness evaluation method using the haze value measurement is excellent as a method for quantifying the visual deterioration of the test piece due to wear. However, this evaluation method is a macro evaluation using incoherent light, that is, evaluation using non-convergent light, and does not necessarily have a correlation with the degree of deterioration of the recording / reproducing characteristics of the optical information medium due to wear. . Therefore, it is not appropriate as a method for evaluating the performance of the hard coat layer of the optical information medium. Moreover, since the evaluation method by measuring the haze value is to measure the transmitted light of a transparent test piece, when evaluating the hard coat layer of an optical information medium, a self-supporting film equivalent to the hard coat layer is used. Needless to say, measurement is not possible unless prepared beforehand. On the other hand, the wear resistance of the hard coat layer depends on the surface properties of the hard coat layer, the friction coefficient, the film thickness, and the elastic modulus of the constituent material of the hard coat layer, but these are not the only factors affecting the wear resistance. . For example, the hardness of the base material on which the hard coat layer is provided also greatly affects the wear resistance of the surface of the hard coat layer provided thereon. Therefore, even in view of this point, in order to accurately evaluate the performance of the hard coat layer, it is preferable to evaluate in a state where the hard coat layer is formed on an actual optical information medium.

  There has been no evaluation method or inspection method for a hard coat layer that satisfies the various requirements as described above, and therefore, the accurate performance of the hard coat layer could not be grasped. However, in optical disk systems that are currently being put into practical use and have a recording / reproducing optical system with a shorter wavelength and a higher NA by increasing the NA, a translucent substrate is used as compared with current CDs and DVDs. More sensitive to surface scratches and dirt. Accordingly, demands on the wear resistance, scratch resistance and the like of the hard coat layer are more severe than ever, and a method suitable for quantification of these characteristics is strongly demanded.

  Even when the entire light-transmitting substrate is made of a high-hardness material instead of providing a hard coat layer on the surface of the light-transmitting substrate, a recording layer is formed or bonded to another substrate. The scratch resistance of the translucent substrate can vary. Therefore, also in this case, a method capable of evaluating the scratch resistance of the translucent substrate under the same conditions as the actual medium is desired.

  The present invention has been devised in view of such circumstances, and its purpose is to prevent scratches during user handling, and to increase the recording density by increasing the NA of the recording / reproducing optical system. Another object of the present invention is to provide an optical information medium that is less likely to be damaged by a pickup collision during recording and / or reproduction. Another object of the present invention is to provide an evaluation method capable of quantifying the scratch resistance of the recording / reproducing light incident side surface of an optical information medium simply and reflecting the actual use environment. is there.

The above object is achieved by the present inventions (1) to (11) below.
(1) An optical information medium that has a light-transmitting substrate and an information recording layer, and is optically recorded and / or reproduced by a laser beam incident on the information recording layer from the light-transmitting substrate side,
A polysilazane cured film on the laser beam incident side of the translucent substrate;
An optical information medium in which a tensile elastic modulus of the translucent substrate or a tensile elastic modulus of the translucent substrate in a state where the cured polysilazane film is integrated is 200 MPa or more.
(2) The optical information medium according to (1), wherein the translucent substrate includes a resin layer having a thickness of 30 to 300 μm.
(3) The optical information medium according to (1) or (2), wherein the cured polysilazane film has a thickness of 0.2 to 50 μm.
(4) The optical information medium according to any one of (1) to (3), wherein the pencil hardness of the laser beam incident side surface is HB or more.
(5) The cured polysilazane film is formed by laminating a plurality of films having different compositions. When the cured polysilazane film is viewed from the laser beam incident side, a cured film of inorganic polysilazane and a polysilazane introduced with an organic group are used. The optical information medium according to any one of (1) to (4), wherein the cured film is present in this order.
(6) The light according to any one of (1) to (5) above, which has a functional layer having at least one function selected from lubricity, water repellency and oil repellency on the laser beam incident side of the cured polysilazane film. Information medium.
(7) The optical information medium according to (6) above, wherein the functional layer has a thickness of 500 nm or less.
(8) The optical information medium according to (6) or (7), wherein the functional layer is formed of a compound having a hydrolyzable silyl group.
(9) A laser for an optical information medium having a translucent substrate and an information recording layer and optically recorded and / or reproduced by a laser beam incident on the information recording layer from the translucent substrate side A method for evaluating the scratch resistance of the beam incident side surface,
An optical information medium evaluation method for measuring the recording / reproducing characteristics after intentionally wearing the laser beam incident side surface of the optical information medium and evaluating the scratch resistance of the laser beam incident side surface based on the measured value.
(10) The method for evaluating an optical information medium according to (9), wherein a wear ring defined in ISO 9352 is used as means for intentionally wearing the laser beam incident side surface of the optical information medium.
(11) The method for evaluating an optical information medium according to (9) above, wherein # 0000 steel wool is used as means for intentionally wearing the laser beam incident side surface of the optical information medium.

  As a result of searching for a hard coat layer suitable for protecting the translucent substrate surface of the optical information medium, the present inventors have found that a film formed by curing polysilazane is suitable. The application of a cured polysilazane film to a protective layer of an information medium is described in the aforementioned Japanese Patent Application Laid-Open No. 2000-132865. However, what is shown as an example in the same publication is that a 0.2 μm-thick red sensitive layer containing a pigment and a resin binder is provided on a 20 μm-thick polyethylene terephthalate support, and on this red-sensitive layer, It is only a medium provided with a protective layer made of polysilazane having a thickness of 0.1 μm. This publication describes that a preferable dry film thickness of the protective layer is 0.001 to 0.2 μm, and a more preferable dry film thickness is 0.05 to 0.15 μm. The publication does not describe the reason for limiting to the above film thickness range.

  In the example of the publication, since the evaluation is performed in a state where the tape medium is put in the cartridge, the tape medium does not come in contact with other than the cartridge when handling, and the tape medium is hardly damaged. Further, this publication does not pay attention to a pickup collision that causes a problem in an optical disc. On the other hand, since the type of optical disk that is not enclosed in a cartridge is the mainstream, the laser beam incident side surface is easily damaged. Further, as described above, in an optical disk applied to a high NA recording / reproducing system, the pickup easily collides with the laser beam incident side surface. Therefore, excellent wear resistance and scratch resistance are required on the laser beam incident side surface of the optical disk. The cured polysilazane film has high hardness, but in order to obtain the abrasion resistance and scratch resistance required for the laser beam incident side surface of the optical disc, the 0.1 μm thickness described in JP-A-2000-132865 is disclosed. Thickness is not enough.

  However, according to experiments by the present inventors, it was found that the polysilazane cured film has high internal stress, and therefore, when the polysilazane cured film is formed thick, self-destruction is likely to occur. In order to prevent self-destruction of the cured polysilazane film, the present inventors conducted experiments and found that the likelihood of self-destruction is dependent on the tensile elastic modulus of the translucent substrate that is the base of the cured polysilazane film. . Therefore, in the present invention, by limiting the tensile elastic modulus of the translucent substrate, it is possible to form a cured polysilazane film with a sufficient thickness, and as a result, the laser beam incident side surface has sufficient wear resistance, An optical information medium with scratch resistance was realized.

  In the evaluation method of the present invention, the scratch resistance of the surface of the optical information medium on the laser beam incident side can be quantified and evaluated in a simple manner and reflecting the actual use environment.

It is a fragmentary sectional view which shows the example of 1 structure of the optical information medium of this invention. It is a fragmentary sectional view which shows the other structural example of the optical information medium of this invention. It is a fragmentary sectional view which shows the other structural example of the optical information medium of this invention. It is a fragmentary sectional view which shows the other structural example of the optical information medium of this invention. It is a fragmentary sectional view which shows the other structural example of the optical information medium of this invention. It is a fragmentary sectional view which shows the other structural example of the optical information medium of this invention. It is a graph which shows the relationship between a wear cycle number and the fall rate of the reflectance of a medium. It is a graph which shows the relationship between a wear cycle number and the fall rate of the reproduction output level of a medium. It is a graph which shows the relationship between the number of wear cycles and the jitter of a medium.

Optical information medium An optical information medium to which the present invention is applied has a light-transmitting substrate and an information recording layer, and a laser beam is incident on the information recording layer from the light-transmitting substrate side to record and / or optically. Playback is performed. Specific examples of the configuration of such an optical information medium include those shown in FIGS. 1 and 2, for example.

  The optical information medium shown in FIG. 1 is a phase change recording medium. On one surface of a support base 20, a reflective layer 5, a second dielectric layer 32, a recording layer 4 as an information recording layer, and a first dielectric The layer 31, the translucent substrate 21, and the polysilazane cured film 22 are formed in this order. The translucent substrate 21 is a resin layer formed by attaching a resin sheet or applying a resin. A laser beam for recording and / or reproduction is incident on the recording layer 4 through the translucent substrate 21. The medium having the structure shown in FIG. 1 is suitable for high-density recording because the translucent substrate 21 can be thinned, so that the NA of the objective lens of the recording / reproducing optical system can be increased. In the structure shown in FIG. 1, the total thickness of the translucent substrate 21 and the cured polysilazane film 22 is preferably 30 to 300 μm, more preferably 30 to 200 μm. If this thickness is too thin, the optical effect of dust adhering to the laser beam incident side surface of the medium becomes large. On the other hand, if this thickness is too thick, it becomes difficult to achieve a high recording density by increasing the NA.

  In the medium shown in FIG. 2, the first dielectric layer 31, the recording layer 4, the second dielectric layer 32, the reflective layer 5 and the protective layer 6 are formed in this order on one surface of the translucent substrate 21. The polysilazane cured film 22 is formed on the other surface of the translucent substrate 21. In this structure, a light-transmitting substrate 21 having a thickness of about 0.4 to 2 mm and relatively high rigidity is used. In the structure shown in FIG. 2, the arrangement of each layer viewed from the laser beam incident side is the same as that of the medium shown in FIG. 1 except for the protective layer 6.

  The structure shown in FIG. 2 is a structure adopted by a commercially available optical disk such as DVD-RAM or DVD-RW. On the other hand, in the structure shown in FIG. 1, the stacking order of each layer such as the reflective layer and the recording layer is opposite to that in FIG. In this specification, the medium having the structure shown in FIG.

  The present invention can be applied regardless of the type of the recording layer. That is, in addition to the phase change type recording medium shown in the figure, the present invention can be applied to, for example, a pit formation type recording medium and a magneto-optical recording medium. Further, the present invention is not limited to the recordable type as shown in the figure, but can be applied to a reproduction-only type. In that case, the pit row formed integrally with the support base 20 and the reflective layer formed thereon constitute an information recording layer.

  In the present invention, as shown in FIGS. 1 and 2, a polysilazane cured film 22 is provided on the laser beam incident side of the translucent substrate 21. The cured polysilazane film 22 contains silica derived from polysilazane or this and polysilazane. Therefore, the cured polysilazane film 22 has a sufficiently high hardness and excellent wear resistance and scratch resistance. In the reverse laminated type medium shown in FIG. 1, the working distance is reduced by increasing the NA of the objective lens of the recording / reproducing optical system. As a result, the pickup collides with the translucent substrate 21 and is easily damaged. Moreover, in the reverse lamination type, since the translucent substrate 21 is thin, the influence of the scratch on the surface of the translucent substrate 21 is increased. Therefore, the present invention is particularly suitable for a reverse lamination type medium.

  The cured polysilazane film 22 may be composed entirely of silica derived from polysilazane or this and polysilazane, and is entirely dispersed or contained in silica derived from polysilazane or this and polysilazane. May be.

  The thickness of the cured polysilazane film is preferably 0.05 μm or more, more preferably 0.2 μm or more, still more preferably 0.25 μm or more, and most preferably 0.5 μm or more. If the cured polysilazane film is too thin, a sufficient wear resistance effect cannot be obtained.

  Since the polysilazane cured film has a high internal stress, the thicker the polysilazane film is, the easier it is to self-destruct. However, in order to obtain a sufficient medium protection effect, it is necessary to make the cured polysilazane film relatively thick. Further, the cured polysilazane film itself is dense and has high hardness. However, depending on the physical properties of the transparent substrate 21 that is the base, the medium protective effect of the cured polysilazane film may be insufficient. Therefore, in this invention, the tensile elasticity modulus of the translucent base | substrate 21 shall be 200 MPa or more, Preferably it is 400 MPa or more. If the tensile elastic modulus of the translucent substrate 21 is within this range, even if the polysilazane cured film 22 is relatively thick, specifically, the thickness of the polysilazane cured film 22 is 0.2 μm or more, or 0 Even if it is .25 μm or more, and further 0.5 μm or more, self-destruction is unlikely to occur. However, when the polysilazane cured film 22 becomes extremely thick, self-destruction is likely to occur. Therefore, the thickness of the polysilazane cured film 22 is preferably 50 μm or less, more preferably 10 μm, and even more preferably 5 μm or less. Moreover, if the tensile elasticity modulus of the translucent base | substrate 21 is in the said range, the medium protective effect by the polysilazane cured film 22 will become high enough. Specifically, the pencil hardness of the laser beam incident side surface where the polysilazane cured film 22 exists can be set to HB or more. The pencil hardness in the present specification is the pencil hardness defined in ISO / DIS15184: 1996.

  In addition, since it is difficult to peel the polysilazane cured film 22 once formed from the translucent substrate 21, it is difficult to measure the tensile elastic modulus of the translucent substrate 21 after the polysilazane cured film 22 is formed. However, since the cured polysilazane film 22 is extremely thin compared to the translucent substrate 21, the tensile elastic modulus of the translucent substrate 21 measured without peeling off the cured polysilazane film 22 is the tensile elastic modulus of the translucent substrate 21 alone. And not much different. Therefore, in the present invention, the tensile elastic modulus of the translucent substrate 21 in a state where the cured polysilazane film 22 is integrated may be 200 MPa or more, preferably 400 MPa or more.

  The upper limit of the tensile elastic modulus of the translucent substrate 21 or the tensile elastic modulus of the translucent substrate 21 in the state where the cured polysilazane film 22 is integrated is not particularly limited, but from a generally available material, the translucent substrate is used. When 21 is constituted, the upper limit is usually about 3000 MPa.

The tensile modulus in this specification is specified in JIS K7127-1989. In measuring these,
Test piece length: 60 mm,
Specimen width: 10 mm
Distance between marked lines: 40 ± 1mm,
Distance between grips: 44 ± 1mm,
Tensile speed: 30mm / min
Other measurement conditions may conform to JIS K7127-1989. The reason why these conditions are different from those of JIS K7127-1989 is that the dimension (usually about 12 cm in diameter) of the medium (optical disk) is taken into consideration so that the translucent substrate peeled from the medium can be measured.

  The polysilazane cured film 22 is formed by applying a polysilazane solution to the laser beam incident side surface of the translucent substrate 21 and curing it by heating. It is known that polysilazane undergoes a heat treatment in the air, whereby hydrolysis due to moisture in the air proceeds to form dense silica with extremely high purity. In addition, by adding a metal catalyst to the polysilazane solution in advance, the reaction proceeds well even by heating at around 100 ° C., and can be converted into high-purity silica. The heating temperature at this time is preferably 25 to 130 ° C., more preferably 50 to 120 ° C., and the heating time is preferably 10 minutes to 10 hours, more preferably 10 minutes to 5 hours. If the heating temperature is low or the heating time is short, curing may not proceed sufficiently. However, the polysilazane coating can also be cured by allowing it to stand at room temperature. The method for applying the polysilazane solution is not particularly limited, and for example, any of gravure coating, dip coating, spray coating, spin coating, and the like may be used.

The polysilazane used in the present invention may have any Si—N—Si bond, and various conventionally known polysilazanes can be used. Preferred polysilazanes include, for example, cyclic inorganic polysilazanes having a structure of (—Si (H) ₂ —NH—) n, where n = 100 to 50000, chain inorganic polysilazanes, or mixtures thereof, and these inorganic polysilazanes. Examples thereof include polyorganohydrosilazanes in which some or all of the hydrogen atoms bonded to silicon atoms are substituted with organic groups. Further, polysiloxazan containing oxygen in the molecule, polymetallosilazane produced by reaction with metal alkoxide, polyborosilazane produced by reaction with organic boron compound, and the like can also be used. Commercially available polysilazane solutions such as N-L110 (manufactured by TonenGeneral Sekiyu KK) can also be used.

  The cured polysilazane film may be a laminate of a plurality of films having different compositions. Although the cured product of inorganic polysilazane itself has extremely high hardness, a certain thickness or more is required to sufficiently increase the hardness of the film. However, when an attempt is made to form a thick film using inorganic polysilazane, self-destruction tends to occur. On the other hand, a cured product of polysilazane having an organic group introduced has a somewhat low hardness, but is difficult to self-destruct even if it is formed thick. Therefore, if a cured film of polysilazane introduced with an organic group is formed to be relatively thick as an underlayer, and a cured film of inorganic polysilazane is formed to be relatively thin as a surface layer thereon, the laminated film as a whole has a sufficient thickness. Therefore, the hardness of the laminated film is sufficiently high, and the surface hardness of the laminated film is also sufficiently high. In this case, in order to obtain a sufficiently high surface hardness, the thickness of the cured inorganic polysilazane film is preferably 0.05 μm or more, more preferably 0.2 μm or more.

  The cured polysilazane film has extremely high hardness because it contains dense high-purity silica as a main component. Moreover, since the hydrogen atom couple | bonded with the silicon atom or nitrogen atom of polysilazane acts as active hydrogen, the cured film becomes very excellent in adhesiveness with the translucent base | substrate 21 surface. In the polysilazane cured film, polysilazane may be present without being partially converted to silica. In addition, when polysilazane into which an organic group has been introduced is used, the organic group is usually also present in the cured polysilazane film.

  Examples of the solvent used when preparing the polysilazane solution include aromatic hydrocarbon solvents such as benzene, toluene, and xylene, or ether, tetrahydrofuran, methylene chloride, carbon tetrachloride, and the like. However, when the polysilazane solution is directly applied to the surface of the translucent substrate 21, it is necessary to select a solvent that does not attack the constituent material of the translucent substrate 21. Polycarbonate is preferably used as the constituent material of the translucent substrate 21, and examples of the solvent that does not attack the polycarbonate and can be used as a diluting solvent for polysilazane include ether solvents such as dibutyl ether.

  The translucent substrate 21 is a resin layer in the reverse lamination type shown in FIG. 1, and is a plate having a relatively high rigidity in the structure shown in FIG. The translucent substrate 21 in FIG. 1 can be formed, for example, by attaching a resin sheet or applying a resin. Further, a resin may be further applied on the pasted resin sheet, or a plurality of resin coating films may be laminated. The translucent substrate 21 in FIG. 2 can be formed by, for example, injection molding or 2P (photopolymer) method.

  The translucent substrate 21 is preferably composed of a thermoplastic resin such as polycarbonate or polymethyl methacrylate (PMMA), or an active energy ray curable resin such as an acrylic ultraviolet curable resin. In the structure shown in FIG. 2, the translucent substrate 21 may be made of glass, and patterns such as grooves and pits may be provided on the surface by the 2P method.

  The translucent substrate 21 may be composed of a plurality of layers having different constituent materials. The medium shown in FIGS. 3 and 4 has a translucent substrate 21 having a laminated structure of a substrate body 21A and a barrier layer 21B, and the other structures are the same as those shown in FIGS. The barrier layer 21B is provided between the base body 21A and the polysilazane cured film 22, and protects the base body 21A from the coating solvent when the polysilazane solution is applied. For example, since the organic solvent xylene attacks polycarbonate, when the translucent substrate 21 is a resin sheet made of polycarbonate in the structure shown in FIG. 1, xylene cannot be used as a coating solvent for forming a polysilazane cured film. On the other hand, in the structure shown in FIG. 3, if the base body 21A is made of a polycarbonate sheet and the barrier layer is made of an active energy ray-curable resin such as an acrylic resin that is not affected by xylene, xylene can be used as a coating solvent. Can be used, and the degree of freedom in selecting a coating solvent is increased.

The constituent material of the barrier layer 21B is not particularly limited. In addition to an active energy ray curable resin such as an ultraviolet curable resin, an inorganic material such as a dispersion of colloidal silica in such a resin or an SiO ₂ film formed by sputtering. What is necessary is just to select suitably according to the kind of coating solvents, such as a thin film.

  The thickness of the barrier layer may be set so as to obtain a sufficient protective effect against the coating solvent, but it is usually preferably selected from the range of 50 nm to 200 μm. As shown in FIG. When the substrate 21 is a thin reverse laminated type, it is preferable to select from the range of 50 nm to 10 μm.

  It should be noted that the translucent substrate 21 having a laminated structure is not limited to the case where the barrier layer as described above is provided. For example, in order to realize both good optical characteristics and high strength in the translucent substrate 21, for controlling physical properties of the translucent substrate 21, such as when a relatively soft layer and a relatively hard layer are laminated. There may be.

  The surface of the base of the polysilazane cured film 22, that is, the surface of the translucent substrate 21 may be subjected to surface modification by high energy ray treatment such as plasma, corona discharge, or ultraviolet rays as necessary. Further, when the base is composed of an active energy ray-curable resin, the amount of active energy rays is appropriately controlled to temporarily stop the polymerization reaction of the base, and a polysilazane solution is applied to the base surface. After the application, a treatment for irradiating the active energy ray again to complete the polymerization reaction of the base may be performed. Any of the above treatments is effective in improving the adhesion between the cured polysilazane film and the underlying layer, and as a result, the surface hardness of the cured polysilazane film can be further increased.

  The cured polysilazane film can realize extremely high wear resistance only with this film, but other layers may be provided on the surface of the cured polysilazane film as necessary. The other layer is preferably a functional layer having at least one function selected from lubricity, water repellency and oil repellency. The medium shown in FIGS. 5 and 6 has the functional layer 23 on the surface of the polysilazane cured film 22, and the other structure is the same as that shown in FIGS. 1 and 4. For example, if the surface of the polysilazane cured film 22 is covered with the functional layer 23 having lubricity, the wear resistance of the surface and the resistance against pick-up collision can be further increased. Further, if the surface of the polysilazane cured film 22 is covered with the functional layer 23 having water repellency or oil repellency, it becomes difficult for dirt to adhere, and even if it adheres, it becomes easy to wipe off.

The surface of the functional layer having lubricity desirably has a dynamic friction coefficient defined by ISO 8295: 1995 of 0.4 or less, preferably 0.3 or less. In the measurement, a smooth glass plate is used as the counterpart material. The lower limit of the dynamic friction coefficient is not particularly limited, but it is usually difficult to make the dynamic friction coefficient less than 0.03. On the other hand, water repellency and oil repellency can be uniquely expressed by a critical surface tension (γc / mNm ⁻¹ ), which is a measure of the surface free energy of the substance. This can be obtained from the actual measured contact angle, and the contact angle (θ / rad) on the surface of a smooth material can be determined for several saturated hydrocarbon liquids (surface tension: γ ₁ / mNm ⁻¹ ) with known surface tension. measured value extrapolated to cos [theta] = 1 in plots of cos [theta] and gamma ₁ are [gamma] c. In order for a substance to repel a liquid, the γc of the substance needs to be lower than the surface tension γ ₁ of the liquid.

  As the functional layer constituent material, a material used for general purposes can be used. Specific examples include higher fatty acid esters such as butyl stearate and butyl myristate and derivatives thereof, silicone oils typified by dimethylsiloxane derivatives, modified materials thereof, fluorinated hydrocarbon lubricants and derivatives thereof. Etc. Moreover, since the functional layer is provided on the surface of the cured polysilazane film, it is also preferable that the functional layer is composed of a fluorinated hydrocarbon silane coupling agent. This silane coupling agent generally has a structure in which a fluorinated hydrocarbon chain is bonded to a hydrolyzable silyl group. Since the silyl group and the polysilazane cured film surface form a strong chemical bond by hydrolysis reaction, the functional layer made of the silane coupling agent is excellent in durability. In the present invention, a material having two or more functions selected from lubricity, water repellency, and oil repellency can be used as appropriate. The materials having lubricity, water repellency, and oil repellency are disclosed in, for example, JP-A-11-213444 and JP-A-6-187663.

  The thickness of the functional layer is preferably 500 nm or less, and more preferably 100 nm or less. If the functional layer is too thick, the surface hardness of the cured polysilazane film may not be reflected in the hardness of the medium surface, and the optical transparency of the functional layer may be deteriorated. However, in order to sufficiently exhibit functions such as lubricity, water repellency, and oil repellency, the thickness of the functional layer is preferably 1 nm or more.

Evaluation method of the optical information medium will now be described how to evaluate the scratch resistance of the recording / reproducing light incident surface of the optical information medium.

  The present inventors diligently investigated the correlation between the degree of wear of the translucent substrate whose surface was worn by various methods and the recording / reproducing characteristics of the optical information medium after the translucent substrate was worn. As a result, it was confirmed that there was a relatively strong correlation between the degree of wear of the translucent substrate and the reflectivity, jitter, error rate, etc. when recording / reproducing after wear.

  That is, when an appropriate wear method is selected, characteristics such as reflectance and jitter of the optical information medium are expressed as a function of wear conditions such as wear time. Therefore, in the evaluation method of the present invention, the electrical characteristics such as reflectivity, jitter, and error rate are evaluated after intentionally wearing the light-transmitting substrate surface of the optical information medium using a predetermined wear method. Thus, it is possible to quantify the abrasion resistance and scratch resistance of the translucent substrate in an actual optical information medium.

  In the evaluation of the translucent substrate of the medium, the method for intentionally wearing the surface and the means used for wearing are not particularly limited as long as the wear can occur with good reproducibility. However, since it is not preferable that the evaluation takes too much time, the wear treatment preferably takes about 1 to 60 minutes, more preferably about 1 to 30 minutes, resulting in wear exceeding wear that can occur in the actual use environment of the optical information medium. It is desirable to use such methods and means.

  Specific wear methods include, for example, standardized test methods such as a wear test method using wear wheels as defined in ISO 9352 and a wear test method using abrasives as defined in JIS K7205, or A method of wearing with steel wool is preferred.

  The wear test method using a wear wheel defined in ISO 9352 is a test method generally called a Taber wear test, and is performed by the following method. In this method, a test machine in which two wheel-shaped grinding wheels called wear wheels are arranged at predetermined positions on a turntable is used to place a sample on the turntable. Thereafter, a predetermined load is applied to the wear wheel, and the turntable is rotated by a motor. At this time, the wear wheel is configured to grind the sample surface while maintaining a certain inclination with respect to the direction in which the turntable rotates. Several types of wear wheels with different materials and grindstone particle sizes are available. By selecting the type of wear wheel, the load during wear, the number of rotations of the turntable, etc., the wear resistance of the sample is appropriately selected. Can know. In the case of a general hard coat layer in an optical information medium, any elastic wear ring of CS-10, CS-10F and CS-17 is used, and a load of 2.5N to 9.8N. It is preferable to wear the turntable by rotating it in the range of 10 to 500 times.

  On the other hand, in a wear method using steel wool, a method of using # 0000 as a polishing steel wool, pressing it against a sample with a predetermined load, and reciprocating a predetermined number of times is generally used.

  Among the above test methods, the reproducibility of the test results is good, and it can be applied to a relatively wide variety of materials by selecting the type of wear wheel and applied load, and it is an internationally standardized test method. Therefore, it is most preferable to use a wear test method using a wear ring. However, a method of wearing with steel wool may be used because it does not require a special device and is simple.

  In the method generally used in the past, the degree of wear of the sample worn by the various wear test methods described above is quantified by the amount of change in various parameters such as the thickness, mass, and optical scattering amount of the sample. Normally, in the evaluation method of the present invention, the worn optical information medium is directly evaluated by the optical disk drive.

  In the evaluation method of the present invention, the recording / reproduction characteristics to be evaluated are not particularly limited. Specifically, for example, the reflectance, the modulation degree, or the RF signal flatness during reproduction of the medium; Jitter, output level, CN ratio (carrier to noise ratio), or error rate for any of the recorded signal and additional recording signal; pp (peak-to-peak) value of the focus sensitivity curve at the linear velocity during recording or reproduction , The amount of residual error in the focus error signal, or the ratio between the pp value and the amount of residual error. One or more of these can be evaluated and measured. The focus sensitivity curve is usually called an “S” curve, and is described, for example, on page 81 of “Optical Disc Technology” published by Radio Technology Co., Ltd. on February 10, 1989. From this focus sensitivity curve, the pp value of the focus error signal output, that is, the difference between the peak value of the plus side output and the peak value of the minus side output is obtained and expressed as F. On the other hand, the residual error of the focus error signal When the output pp value of the component is obtained and expressed by R, if R / F is small, specifically, if R / F is 10% or less, jitter during reproduction is sufficiently small, Also, write errors are sufficiently reduced.

  An optical information medium to which the evaluation method of the present invention is applied has an information recording layer and a translucent substrate, and a laser beam for recording and / or reproduction is incident on the information recording layer through the translucent substrate. There is no particular limitation as long as it is used. That is, it has the same configuration as the optical information medium of the present invention described above.

  Specific examples of the present invention are shown below. However, the present invention is not limited to the following examples. A comparative example is also shown.

Example 1 (reverse lamination type)
Medium 1
A medium 1 having the same structure as that shown in FIG. 1 except for the reproduction-only type was produced by the following procedure.

  First, a polycarbonate substrate (outer diameter 120 mm, thickness 1.2 mm) on which random signal information has been previously formed as prepits is used as a support base 20, and the surface of the support base 20 provided with the prepits is made of aluminum. A reflective layer having a thickness of 100 nm was formed by sputtering. Subsequently, a translucent substrate 21 was formed by applying a UV curable resin film (SD301 manufactured by Dainippon Ink & Chemicals, Inc.) to a thickness of 100 μm on this layer and curing it by UV coating. The cured translucent substrate 21 was peeled from the reflective layer and the tensile elastic modulus was measured and found to be 970 MPa.

  Next, a xylene solution of inorganic polysilazane (N-L110 manufactured by TonenGeneral Sekiyu KK, solid concentration 20% (mass percentage)) was applied on the translucent substrate 21 by spin coating, and left at room temperature for 1 minute. Then, it was cured by heating at 100 ° C. for 30 minutes to form a cured polysilazane film 22. The thickness of the cured polysilazane film 22 was 0.2 μm. In this medium 1, a signal is reproduced by making a laser beam incident on the reflective layer from the polysilazane cured film 22 side.

  In this medium, the pencil hardness on the laser beam incident side surface was H.

Medium 2 (comparison)
A medium 2 was produced in the same manner as the medium 1 except that the cured polysilazane film was not provided. In this medium, the pencil hardness of the surface on the laser beam incident side was B.

Medium 3
A medium 3 having the same structure as that shown in FIG. In this medium 3, a functional layer 23 made of silicone oil (KF96 manufactured by Shin-Etsu Silicone Co., Ltd., viscosity 10,000 cP) having a thickness of about 100 nm is formed on the surface of the cured polysilazane film 22 of the medium 1 by spin coating. . The dynamic friction coefficient of the surface of the functional layer 23 according to ISO 8295: 1995 was 0.25. The pencil hardness on the laser beam incident side surface did not change even when the functional layer 23 was provided.

Evaluation Each of the above media was inserted into an optical disk drive, and the bit error rate (BER) of the reproduction signal was measured. The laser wavelength of the optical disk drive used for evaluation is 650 nm. Next, set the medium 1 on the Taber abrasion tester, wear it by rotating the turntable 10 times with a load of 4.9 N using the wear wheel CS-10F, and measure the BER after abrasion in the same manner as above. did. Thereafter, the disc was worn by further rotating the turntable 40 times (a total of 50 rotations) using the wear wheel, and the BER was measured in the same manner. BER has a correlation with the occurrence of scratches, and the BER rises due to the occurrence of scratches. For the initial BER after 10-turn wear and after 50-turn wear, the case of less than 1.0 × 10 ⁻⁴ was evaluated as “◯”, and the case of 1.0 × 10 ⁻⁴ or more was ^evaluated as “×”. The results are shown in Table 1.

  In addition, in order to evaluate the influence of the pickup colliding with the medium during the reproduction operation, the DDU-1000 manufactured by Pulstec Industrial Co., Ltd. is modified so that the pickup intentionally contacts the medium during the rotation of the medium. did. While rotating the medium at a constant linear velocity (6.0 m / s), the pickup was brought into contact with the medium at a radius of 40 mm and slid for 3 minutes. The focus error signal was checked and before and after the pickup was slid. To check if the waveform is disturbed. A case where no change was observed in the focus error signal was indicated by ◎, a case where the signal was slightly disturbed was indicated by ○, and a case where a large amount of noise was observed was indicated by ×. The results are shown in Table 1. In this evaluation, the lens protector is in contact with the disk surface, and the material thereof is polypropylene.

  As can be seen from Table 1, in the medium 1 provided with the polysilazane cured film, scars did not occur even when worn, and no BER degradation was observed. On the other hand, in the medium 2 in which the polysilazane cured film was not provided, it was found that the BER was significantly deteriorated and the wear resistance was inferior. Further, it has been found that noise is significantly generated in the medium 2 while the signal 1 is less disturbed by the contact and sliding of the pickup. Further, it can be seen that the medium 3 provided with the functional layer made of silicone oil has less disturbance of the focus error signal than the medium 1 after the pickup slides.

Next, a medium 1A was produced in the same manner as the medium 1 except that a cured polysilazane film was formed by the following procedure. In this medium 1A, first, a cured film of polysilazane (N-L710 manufactured by TonenGeneral Sekiyu KK) into which an organic group was introduced was formed on the translucent substrate 21 to a thickness of 1 μm. Next, a cured film of inorganic polysilazane was formed on the cured film in the same manner as the medium 1 so as to have a thickness of 0.2 μm. In this medium 1A, the pencil hardness of the laser beam incident side surface was equivalent to that of medium 1. The medium 1A and the medium 1 were subjected to the above evaluation using a Taber abrasion tester. However, in order to tighten the evaluation conditions, the turntable was rotated 100 times. As a result, the BER after abrasion was 1.0 × 10 ⁻⁴ or more in the medium 1, but less than 1.0 × 10 ^{−4 in the} medium 1A, and the effect of forming a thick polysilazane cured film is obtained. It could be confirmed.

  Further, a medium 1B was produced in the same manner as the medium 1A except that the translucent substrate 21 was composed of an ultraviolet curable resin layer having a tensile elastic modulus of 150 MPa. In this medium 1B, self-destruction (crack) occurred in the cured polysilazane film.

  A medium 1C was produced in the same manner as the medium 1 except that the thickness of the cured polysilazane film 22 was 0.5 μm. When this medium 1C was evaluated under the same conditions as the medium 1A, a result equivalent to that of the medium 1A was obtained. On the other hand, a medium 1D was produced in the same manner as the medium 1C except that the translucent substrate 21 was composed of an ultraviolet curable resin layer having a tensile elastic modulus of 150 MPa. In this medium 1D, self-destruction (crack) occurred in the cured polysilazane film.

Example 2
Medium 4
A commercially available DVD-RAM (recording capacity 2.6 GB / surface) was prepared. DVD-RAM is a phase change recording medium, has a structure substantially similar to that of the medium shown in FIG. 2, and has a structure in which protective layers 6 of this structure are bonded together. The recording layer 4 is mainly made of Ge, Sb and Te, and the translucent substrate 21 is a polycarbonate substrate having a thickness of 0.6 mm.

Using this DVD-RAM, the medium 4 having the structure shown in FIG. First, a polycarbonate substrate of DVD-RAM is used as the base body 21A, and an ultraviolet curable acrylic resin (HOD-3200 manufactured by Nippon Kayaku Co., Ltd.) is applied to the surface of the laser beam incident side by a spin coat method. The barrier layer 21B having a thickness of 3.3 μm was formed by curing with a high-pressure mercury lamp (irradiation amount: 300 mJ / cm ² ). The tensile elastic modulus of the translucent substrate 21 was 1340 MPa.

Subsequently, a cured polysilazane film 22 was formed on the surface of the barrier layer 21B in the same manner as the medium 1. Next, 1.0 J / cm ² of ultraviolet light was irradiated through the cured polysilazane film 2 to completely cure the barrier layer 21B. In this medium, the pencil hardness on the laser beam incident side surface was H.

  Random signals were recorded in an area having a radius of 39.5 to 57.5 mm with respect to this medium 4, and then the same evaluation as that of the medium 1 was performed. As a result, good results were obtained as with the medium 1. . The results regarding the focus error signal after sliding the pickup are shown in Table 2.

Medium 5 (comparison)
A medium 5 was produced in the same manner as the medium 4 except that the polysilazane cured film 22 was not provided and the ultraviolet ray irradiation amount at the time of forming the barrier layer 21B was 1.0 J / cm ² . In this medium, the pencil hardness on the laser beam incident side surface was 2B.

  When this medium 5 was evaluated in the same manner as the medium 4, the result was the same as that of the medium 2 in which the polysilazane cured film was not provided, which was clearly inferior to the medium 4. The results regarding the focus error signal after sliding the pickup are shown in Table 2.

Medium 6
A medium 6 having the structure shown in FIG. 6 was produced. In this medium 6, a functional layer 23 having a thickness of about 10 nm is formed on the surface of the cured polysilazane film 22 of the medium 4. The functional layer 23 is formed by applying a 0.1% (mass percentage) perfluorohexane solution of a water- and oil-repellent silane coupling agent (DSX manufactured by Daikin Industries, Ltd.) by spin coating, and at 60 ° C. in the atmosphere. It was formed by heating for 10 hours for chemical adsorption.

  The dynamic friction coefficient according to ISO 8295: 1995 of the surface of the functional layer 23 of this medium was 0.20. Moreover, the contact angle of water with respect to the surface of the functional layer 23 was 114.0 degrees, and the contact angle of n-hexadecane was 63.8 degrees. The pencil hardness on the laser beam incident side surface did not change even when the functional layer 23 was provided.

  When this medium was evaluated in the same manner as the medium 1, the BER after abrasion was as good as that of the medium 4. Further, the focus error signal after sliding the pickup is shown in Table 2, but it was confirmed that noise was suppressed more than that of the medium 4. Furthermore, it has been found that the medium 6 is less likely to have dirt such as fingerprints attached to the surface, and is excellent in wiping property even if it adheres.

  A medium was produced in the same manner as the medium 4 except that the cured polysilazane film 22 was formed in the same manner as the medium 1A and the medium 1C of Example 1, respectively. In these media, the same as the medium 1A and the medium 1C. Excellent wear resistance was obtained.

  About the said medium 6 and the medium 3 of Example 1, the dry wes (Asahi Kasei Kogyo Co., Ltd. Bencott lint-free CT-8) was slid 20 times on the surface of the functional layer 23. FIG. The load during sliding was about 10N. When the contact angle of water on the surface of the functional layer 23 was measured before and after sliding, the medium 3 had 98.3 degrees before sliding and 83.5 degrees after sliding. I found out. On the other hand, in the medium 6, it was 114.0 degrees before sliding and 112.5 degrees after sliding, and it was confirmed that the silane coupling agent was highly resistant to wiping.

Example 3
Medium 7
Except for the reproduction-only type, a medium 7 having the same structure as that shown in FIG.

  First, a polycarbonate substrate (outer diameter 120 mm, thickness 0.6 mm) on which random signal information is formed in advance as prepits is used as a base body 21A, and on the opposite side of the prepit formation surface, the same barrier layer 21B as that of the medium 4 is used. Formed. The tensile elastic modulus of the translucent substrate 21 was 1340 MPa. Subsequently, a cured polysilazane film 22 was formed on the surface of the barrier layer 21B in the same manner as the medium 1.

  Next, an aluminum reflective layer (thickness: 100 nm) was formed on the prepit formation surface of the substrate by a sputtering method. Subsequently, a polycarbonate substrate (outer diameter 120 mm, thickness 0.6 mm) having no pre-pits is formed on the surface of the reflective layer, and an ultraviolet curable adhesive (acrylic, cured adhesive layer thickness 5). 0.0 μm) to form an optical disc. This is designated as medium 7. In this medium 7, a signal is reproduced by making a laser beam incident on the reflective layer from the surface of the cured polysilazane film.

  When this medium 7 was evaluated in the same manner as the medium 1, the same result as the medium 1 was obtained. Further, except that the cured polysilazane film 22 was formed in the same manner as the medium 1A and the medium 1C of Example 1, media were manufactured in the same manner as the medium 7, and in these media, similar to the medium 1A and the medium 1C. Excellent wear resistance was obtained.

Medium 8 (comparison)
A medium 8 was produced in the same manner as the medium 7 except that the cured polysilazane film was not provided and the ultraviolet ray irradiation amount during the formation of the barrier layer was 1.0 J / cm ² . In this medium 8, the signal is reproduced by making a laser beam incident on the reflection layer from the surface of the barrier layer.

  When this medium 8 was evaluated in the same manner as the medium 1, it was found that the medium 8 was the same as the medium 2 without the polysilazane cured film and was clearly inferior to the medium 7.

Example 4 (Evaluation of scratch resistance)
Sample No. 1
An optical recording disk sample having the structure shown in FIG. 4 was produced by the following procedure.

  First, a disk-shaped substrate (made of polycarbonate, diameter 120 mm, thickness 0.6 mm) on which a groove is formed is used as the substrate body 21A of the translucent substrate 21, and the surface on which the groove is not formed is the same as the medium 7. A barrier layer 21B was formed. Next, a cured polysilazane film 22 was formed on the surface of the barrier layer 21B to form a hard coat layer. The groove depth was 18 nm and the recording track pitch was 0.74 μm.

Next, a first dielectric layer 31 having a two-layer structure was formed by a sputtering method on the side of the translucent substrate 21 on which the groove was formed. Of the two layers, the layer present on the translucent substrate 21 side had a composition of ZnS (80 mol%)-SiO ₂ (20 mol%) and a thickness of 80 nm. On the other hand, the layer present on the recording layer 4 side had a composition of ZnS (50 mol%)-SiO ₂ (50 mol%) and a thickness of 5 nm.

Next, an 18 nm thick recording layer 4 was formed by sputtering using an alloy target made of a phase change material. The composition (atomic ratio) of the recording layer 4 was Sb ₇₄ Tb ₁₈ Ge ₇ In ₁ .

Next, a second dielectric layer 32 having a thickness of 19 nm was formed by sputtering using a ZnS (50 mol%)-SiO ₂ (50 mol%) target.

Next, the reflective layer 5 made of Al ₉₈ Cr ₂ (atomic ratio) was formed by sputtering.

  Next, an ultraviolet curable resin (SK5110 manufactured by Sony Chemical Co., Ltd.) was applied by a spin coating method, and the protective layer 6 having a thickness of 5 μm was formed by irradiating with ultraviolet rays. Thereafter, a dummy substrate made of polycarbonate (diameter 120 mm, thickness 0.6 mm) was bonded onto the protective layer with an ultraviolet curable adhesive to prepare an optical recording disk sample.

Sample No. 2
Instead of the polysilazane cured film, an ultraviolet curable resin (SD318 manufactured by Dainippon Ink & Chemicals, Inc.) is applied by a spin coating method so that the film thickness after curing is 2.5 μm, and then hard coated layer. Formed. Further, no barrier layer was provided. Other than this, an optical recording disk sample was produced in the same manner as Sample No. 1.

Sample No. 3
An optical recording disk sample was prepared in the same manner as Sample No. 1 except that the barrier layer and the hard coat layer were not provided.

Evaluation The recording layer of each sample thus prepared was initialized (crystallized) with a bulk eraser, and then placed on an optical recording medium evaluation apparatus.
Laser wavelength: 650 nm,
Laser power: 1.0 mW
Objective lens numerical aperture NA: 0.60,
Linear velocity: 3.5m / s
Under the conditions, the reflectance of the unrecorded portion was measured while tracking the groove. Next, after recording a 1-7 modulated signal (shortest signal length 2T) in the groove, the output level and jitter of the reproduced signal were measured. These results are shown in Table 3. This jitter is obtained by measuring the reproduction signal with a time interval analyzer (manufactured by Yokogawa Electric Corporation) to obtain “signal fluctuation (σ)”, and assuming that the detection window width is Tw,
σ / Tw (%)
Calculated by If this jitter is 13% or less, the error falls within an allowable range. However, in order to sufficiently secure various margins, it is desirable that this jitter is 10% or less, more preferably 9% or less.

  Subsequently, each sample was set in a Taber abrasion tester, and the laser beam incident side surface of the sample was worn with a load of 4.9 N using a wear wheel CS-10F. Table 3 shows the number of wear cycles (turntable rotation speed). Thereafter, the reflectance of the unrecorded portion at the worn portion, the output level of the signal recorded before the wear, and the jitter were measured in the same manner as described above. These results are shown in Table 3. The output level in Table 3 is a relative value normalized with the value before wear taken as 100. Table 3 also shows the reflectivity before wear and the reduction rate of the output level after wear with respect to the reflectivity and output level before wear.

  In addition, the graph which shows the relationship with the wear cycle number about the fall rate of a reflectance, the fall rate of an output level, and a jitter among each measured value shown in Table 3 is shown in FIG.7, FIG.8 and FIG.9, respectively.

  It can be seen from Table 3 and FIGS. 7 to 9 that excellent scratch resistance can be obtained by forming the laser beam incident side surface of the optical disc from a polysilazane cured film.

  Further, from FIG. 7, when the wear ring test defined in ISO 9352 is used as the wear method in the evaluation method of the present invention, the reduction rate of the reflectance is the square root of the number of wear cycles (ie, wear time) in any medium. Can be confirmed. Further, it can be confirmed from FIG. 8 that the rate of decrease of the output level is also proportional to the square root of the number of wear cycles. On the other hand, it can be seen from FIG. 9 that the jitter value has a linear correlation with the number of wear cycles.

  From the above results, regardless of whether reflectivity, output level, or jitter is used as an evaluation target, the change is expressed as a function of wear time and significantly reflects the scratch resistance of the translucent substrate surface. I understand that That is, it can be seen that the evaluation method of the present invention is useful as a method for evaluating the scratch resistance, wear resistance, etc. of the translucent substrate in the optical information medium.

2 Translucent Base 20 Support Base 21 Translucent Base 21A Base Body 21B Barrier Layer 22 Polysilazane Cured Film 23 Functional Layer 4 Recording Layer 5 Reflective Layer 6 Protective Layer 31 First Dielectric Layer 32 Second Dielectric Layer

Claims (2)

A laser beam incident side with respect to an optical information medium having a translucent substrate and an information recording layer and optically recorded and / or reproduced by a laser beam incident on the information recording layer from the translucent substrate side A method for evaluating the scratch resistance of a surface,
In an optical information medium evaluation method for measuring the recording / reproducing characteristics after intentionally wearing the laser beam incident side surface of the optical information medium and evaluating the scratch resistance of the laser beam incident side surface based on the measured value ,
A method for evaluating an optical information medium, in which a wear ring defined in ISO 9352 is used as a means for intentionally wearing the laser beam incident side surface of the optical information medium, and jitter is measured as a recording / reproduction characteristic measurement. A laser beam incident side with respect to an optical information medium having a translucent substrate and an information recording layer and optically recorded and / or reproduced by a laser beam incident on the information recording layer from the translucent substrate side A method for evaluating the scratch resistance of a surface,
In an optical information medium evaluation method for measuring the recording / reproducing characteristics after intentionally wearing the laser beam incident side surface of the optical information medium and evaluating the scratch resistance of the laser beam incident side surface based on the measured value ,
A method for evaluating an optical information medium, wherein # 0000 steel wool is used as a means for intentionally wearing the laser beam incident side surface of the optical information medium, and jitter is measured as a recording / reproduction characteristic measurement.

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