JP2008071439A - Optical information recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical information recording medium provided with an information recording layer and a light transmission layer comprising a light curing resin film on a substrate, nearly free from temporal change of mechanical characteristics and having high quality. <P>SOLUTION: (1) In the optical information recording medium which includes the information recording layer and the light transmission layer comprising the light curing resin film on the substrate and wherein recording/reproduction of data is performed by irradiating the information recording layer with laser light via the light transmission layer, a formula of E'×(1-x/100)≤50 is satisfied when a curing ratio of the light curing resin film and a storage modulus obtained by dynamic viscoelasticity measurement of 10 Hz are defined as x (%) and E' (MPa), respectively. (2) In the optical information recording medium mentioned in (1), E'×(1-x/100)≤30 is satisfied. (3) In the optical information recording medium mentioned in (1) or (2), 500≤E'≤1,500 is satisfied. (4) In the optical information recording medium mentioned in any of (1) to (3), 98≤x≤100 is satisfied. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a high-quality optical information recording medium with little change in mechanical characteristics over time.

Optical information recording media such as DVD-R / RW and DVD + R / RW have been put to practical use as portable media for recording not only character information but also still image information and moving image information. Furthermore, in recent years, the amount of information handled has increased with the progress of digitalization and the spread of broadband, and a new recording system capable of recording and reproducing high-quality moving images with high density and high speed has been demanded.
Against this background, by shortening the recording / reproducing wavelength and increasing the numerical aperture NA (Numerical Aperture), the focused beam diameter is reduced, the recorded mark size is reduced, and the recording density is increased and the speed is increased. An optical information recording system that aims to For example, the current recordable DVD has a recording / reproducing wavelength λ = 650 to 660 nm, a numerical aperture NA = 0.65, and a recording capacity of 4.7 GB. The Blue-ray disc standard, which is an optical disk system having a recording capacity of 25 GB with a number NA of 0.85, has been proposed.

However, various problems arise by increasing the NA of the optical system in this way. For example, an allowable amount of aberration caused by an angle at which the disk surface deviates from the optical axis of the optical pickup, that is, a so-called tilt angle, becomes small. Here, assuming that the wavelength of the recording / reproducing laser beam is λ and the thickness of the substrate is t, the tolerance of the tilt of the optical information recording medium with respect to the optical system, the so-called tilt margin M, is determined by the numerical aperture NA. That is, the tilt margin M is proportional to λ / {t × (NA) ³ }. In order to ensure the tilt margin M below the allowable value of the system, it is necessary to reduce the thickness t of the substrate. Therefore, in such a high NA system, the recording / reproducing light is irradiated not through the conventional substrate side but through the light transmission layer set to a thickness of about 0.1 mm.

However, when the thickness of the light transmission layer 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, the Blue-ray disc standard proposes a structure in which a light transmission layer is provided on the side opposite to the conventional substrate. That is, a reflective layer, a dielectric layer, a recording layer, a dielectric layer, and a light transmission layer are formed in this order on a substrate made of polycarbonate or the like, thereby producing an optical information recording medium in which the light transmission layer is thinned. In this case, the recording layer is a phase change recording film or an inorganic write-once recording film.
In this method, first, a substrate having a pregroove is injection-molded using a stamper, and then a reflection layer, a first dielectric layer, a recording layer are formed on the surface of the substrate on which the pregroove is formed by a sputtering method or the like. The second dielectric layer is formed in this order. Then, a light transmission layer is formed on the surface of the second dielectric layer by bonding of a film sheet or spin coating such as an ultraviolet curable resin (for example, see Patent Documents 1 and 2).
In the optical information recording medium thus manufactured, 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 form the substrate by paying attention only to the transfer characteristics of the grooves and the mechanical characteristics of the medium, and this type of optical information recording medium is used. For example, a high NA optical information recording medium head can be used while sufficiently securing the mechanical strength of the substrate.

  By the way, in the conventional technique for forming a light transmission layer by the above spin coating method, there is a problem that mechanical characteristics, particularly radial tilt characteristics, are remarkably deteriorated by an environmental test assuming long-term storage. For example, in the above-mentioned Blue-ray disc standard, the absolute value of the radial tilt characteristic is ± 0.6 deg. Although it is defined as follows, when considering the margin distribution of the entire optical system and the margin when the temperature and humidity change suddenly, the radial tilt change amount allowed over time is 0.4 deg. The following is desirable. However, in the optical information recording medium in which the light transmission layer is formed by the spin coating method, the change in radial tilt characteristics with time is 0.6 deg. There were frequent problems that exceeded the limit.

Japanese Patent No. 3241560 Japanese Patent Application Laid-Open No. 11-213459

  The present invention has been made in view of the above-described circumstances, and includes an information recording layer and a light transmission layer made of a photocurable resin film on a substrate, and has high quality light with little change in mechanical characteristics over time. The purpose is to provide an information recording medium.

The above problems are solved by the following inventions 1) to 4).
1) An information recording layer and a light transmission layer made of a photocurable resin film are provided on a substrate, and data is recorded / reproduced by irradiating the information recording layer with laser light through the light transmission layer. In an optical information recording medium, the following equation is satisfied, where the curing rate of the photocurable resin film is x (%), and the storage modulus obtained from dynamic viscoelasticity measurement at 10 Hz is E ′ (MPa). An optical information recording medium.
E ′ × (1−x / 100) ≦ 50
2) The optical information recording medium according to claim 1, wherein E ′ × (1−x / 100) ≦ 30.
3) The optical information recording medium according to 1) or 2), wherein 500 ≦ E ′ ≦ 1500.
4) The optical information recording medium according to any one of 1) to 3), wherein 98 ≦ x ≦ 100.

Hereinafter, the present invention will be described in detail.
The present inventor relates to an optical information recording medium including an information recording layer and a light transmission layer made of a photocurable resin film on a substrate. The information recording layer here refers to the entire laminate composed of a recording layer, a reflective layer, a dielectric layer, and the like at a portion sandwiched between the substrate and the light transmission layer.
As a result of intensive studies by the present inventors, it has been found that the change in mechanical properties of the optical information recording medium with time as described above is mainly due to the deformation of the medium due to the film contraction of the light transmission layer.
The light transmission layer is made of a photocurable resin film such as an ultraviolet curable resin film or a cationic curable resin film, and an ultraviolet curable resin film is commonly used.
The UV curable resin film is composed of, for example, an epoxy acrylate oligomer, a urethane acrylate oligomer, a polyfunctional acrylic monomer, a monofunctional acrylic monomer, a photopolymerization initiator, various additives, and the like, and is generally formed by coating and curing by a spin coating method. Is done.
However, since an optical information recording medium is usually produced with a fast tact time of 3 to 5 seconds, unreacted monomers, various additives, a photopolymerization initiator excessively added to improve curability, etc. are contained in the cured film. Will remain. These unreacted components are easily discharged out of the film over time due to volatilization or the like, causing film contraction of the light transmission layer, and worsening mechanical characteristics (tilt) of the optical information recording medium by a bimetallic action. The amount of change in mechanical properties increases as the curing rate (= gel fraction) of the cured film decreases, and increases as the rigidity increases.

FIG. 1 shows the curing rate (= gel fraction) x of the light transmission layer cured by changing the components of the ultraviolet curable resin and the curing conditions (ultraviolet illuminance), the optical film thickness change amount Δnd after the reliability acceleration test, and It is the result of investigating the relationship of the weight change amount ΔW.
As shown in the figure, the curing rate x shows a good correlation with the optical film thickness change amount Δnd and the weight change amount ΔW. That is, the lower the curing rate x, the more unreacted components in the ultraviolet curable resin film, and the release causes the film weight to decrease and the optical film thickness to shrink.
Although film shrinkage occurs isotropically, macroscopic film shrinkage mainly appears only in the film thickness direction because one surface of the light transmission layer is bonded to the information recording layer side of the medium.
Specifically, as shown in Table 1, the component ratio of the acrylate oligomer (component A) and the acrylate monomer (component B) in the ultraviolet curable resin was changed, and the ultraviolet illuminance was cured in the range of 400 to 3000 mJ / cm ² . . For curing, UV lamp HP-6 (H bulb) manufactured by Fusion UV System was used and irradiated with ultraviolet rays in a nitrogen environment.
As a result, as shown in FIG. 8, the composition 2 in which the epoxy acrylate component (EPA) of component A and the polyfunctional acrylate of component B (MANDA and TMPTA in Table 1) are large in the resin is less in composition 1 There was a tendency for the curing rate to be higher. Further, the curing rate as the illuminance is low is low, is approximately 1000 mJ / cm ² or more in the curing rate, almost reached a plateau, a large difference was not in 1500~3000mJ / cm ² in the curing rate.

Here, the curing rate x (%) of the resin film may be measured as follows.
First, the light transmission layer is peeled off from the interface with the information recording layer, and the resin film is sampled. Next, the weighing value of the resin film is m (g), the resin film is ultrasonically washed in an organic solvent such as acetone and methyl ethyl ketone, and the weighing value after eluting unreacted substances is n (g). It can be calculated by the following formula.
x = n / m × 100 (%)
In FIG. 1, the change in optical film thickness Δnd and the change in weight ΔW tend to be slightly smaller than the curing rate x. The reliability of the gel fraction measurement by forced elution using such an organic solvent is more reliable. This is probably because the amount of unreacted components eluted is slightly larger than in the accelerated test. The optical film thickness change amount Δnd can be obtained from the Fourier analysis of the reflection spectrum by an interference film thickness measuring instrument or the like in an actual optical information recording medium. The weight change amount ΔW can be obtained from the actual weight change of the medium.

From FIG. 1, it was recalled that the release of unreacted components in the ultraviolet curable resin film caused the film to shrink after the storage test, and the radial tilt angle of the optical recording medium changed. Furthermore, the greater the amount of unreacted component released (1-x / 100) and the greater the storage elastic modulus E ′ of the resin film, the stronger the contraction force of the film and the greater the change in radial tilt angle. It was thought to be. Therefore, a reliability test for 300 hours at 80 ° C. and 85% RH was performed on the medium whose curing rate was evaluated in FIG. 1, and the relationship between E ′ × (1−x / 100) and the radial tilt change amount ΔRD was examined. However, the result as shown in FIG. 2 was obtained.
From FIG. 2, it can be seen that the change in tilt after the reliability test is larger in the film having the smaller curing rate x and the larger storage elastic modulus E ′. That is, in order to suppress the tilt change after the reliability test, a resin material and a curing process that reduce E ′ × (1−x / 100) may be selected.

  Here, the storage elastic modulus E ′ is measured as follows. First, as in the case of the curing rate measurement, a strip-shaped film of about several mm × 40 to 60 mm is cut out as a test piece from the resin film of the light transmission layer peeled from the interface with the information recording layer. Next, using a commercially available tensile rheometer, a dynamic viscoelastic analysis was performed at a tensile frequency of about 10 Hz while raising the test piece from room temperature at a rate of temperature increase of about 2 ° C./min. Is the storage elastic modulus E ′ treated in the present invention. As shown in FIG. 3, the dynamic viscoelastic analysis is a viscoelastic physical property of a cured resin, more specifically, storage elastic modulus E ′, loss elastic modulus E ″, glass transition temperature Tg (usually loss tangent tan δ = E ”/ E ′ peak temperature). For example, in FIG. 3, the glass transition temperature is 58 ° C. and the storage elastic modulus E ′ is about 1700 MPa.

Based on the above research results, in the present invention, the following formulas are satisfied for the curing rate x and the storage elastic modulus E ′.
E ′ × (1−x / 100) ≦ 50
E ′ × (1−x / 100) and the radial tilt change amount ΔRD indicating the degree of deterioration of the mechanical characteristics over time have a correspondence relationship having a variation as shown in FIG. 2, and ΔRD ≦ 0.6 deg. It is difficult to clearly define the critical range of E ′ × (1−x / 100) that satisfies the above.
However, it is desirable that E ′ × (1−x / 100) ≦ 50 when using a line passing through the maximum value of variation shown in FIG. That is, the range satisfying this expression is the range shown by (2) in FIG. When E ′ × (1−x / 100) is 50 or less, ΔRD is ΔRD ≦ 0.6 deg. In the range of (2) in FIG. Thus, the medium is less deteriorated in mechanical properties over time. Conversely, when E ′ × (1−x / 100) exceeds 50, ΔRD is stably set to 0.6 deg. It becomes impossible to suppress below.

More preferably, the following formula is satisfied with respect to the curing rate x and the storage elastic modulus E ′.
E ′ × (1-x / 100) ≦ 30
This formula is satisfied within the range of (3) in FIG. 5, and an optical recording medium having a resin film satisfying this formula has a radial tilt variation Δ of 0.4 deg. The deterioration of mechanical properties is particularly small as follows. In other words, because the balance between mechanical strength (rigidity) and curing rate of photo-curing resin is excellent, sufficient recording / reproduction is possible even with time-dependent fluctuations on the drive unit side, sudden changes in temperature and humidity of the entire system, etc. It is a high quality medium with a margin.
A desirable range of the storage elastic modulus E ′ is 500 ≦ E ′ ≦ 1500 (MPa). When the storage elastic modulus E ′ of the resin film is smaller than 500 MPa, it is difficult to obtain sufficient protection performance as a protective film of the information recording layer. On the other hand, if it is greater than 1500 MPa, the amount of warpage accompanying curing shrinkage increases, and the mechanical properties at the initial stage of production are impaired, which is not preferable.
A desirable range of the curing rate x is 98 ≦ x ≦ 100. When the curing rate is 98% or more, the storage elastic modulus E ′ satisfying E ′ × (1−x / 100) ≦ 30 becomes E ′ ≦ 1500 (MPa), and a medium having excellent mechanical properties at the initial stage of manufacture is obtained. It is done. The curing rate x is preferably 98% or more, but theoretically does not exceed 100%.

A specific layer structure of the optical information recording medium of the present invention will be described by taking the phase change optical information recording medium shown in FIG. 6 as an example.
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 optical information recording medium of the present invention, since the recording / reproducing laser beam is incident from the light transmission layer side, the substrate material does not necessarily have to be light-transmitting, and the groove groove transferability, warpage, etc. A molding material having good characteristics can be selected, but usually, a polycarbonate resin that has a proven record in CDs and DVDs and is inexpensive is selected.

The information recording layer includes a phase change recording layer. In FIG. 6, a reflective layer, a first dielectric layer, a phase change recording layer, and a second dielectric layer are formed on a substrate in this order by a known sputtering method or the like.
In general, an Ag alloy containing Ag as a main component is used for the reflective layer, and the film has a thickness of about 100 to 250 nm because it has sufficient cooling ability. Specific examples of the Ag alloy include Ag-Bi, Ag-In, Ag-Pd-Cu, and Ag-Nd-Cu. These alloy elements are added in order to suppress aggregation and crystal grain growth in a high temperature environment of the Ag film, but the total content is 3 atoms so as not to impair the good thermal conductivity of Ag. % Or less is desirable.

For the first dielectric layer and the second dielectric layer, a high-melting-point material having high transparency such as an oxide, sulfide, nitride, or carbide of metal or semiconductor can be used. Specific _{examples, SiOx, ZnO, SnO 2,} Al 2 O 3, TiO 2, In 2 O 3, MgO, ZrO 2, Ta 2 O metal oxide such as _{5, Si 3 N 4, AlN} , TiN, BN Nitrides such as ZrN, sulfides such as ZnS and TaS ₄ , carbides such as SiC, TaC, B ₄ C, WC, TiC, and ZrC, and as a single layer or a mixture, and as a multilayer structure composed of two or more layers Can be used. Among these, an optimal material is selected in consideration of refractive index, thermal conductivity, chemical stability, mechanical strength, adhesion, and the like. Among these, a mixed film with SiO ₂ containing 60 to 90 mol% of ZnS is preferable because it does not cause repeated recording, crystallization of the film itself in a high temperature environment, chemical change, and film deformation. In addition, since the thermal conductivity is as low as .about.0.5 W / mK, the dielectric film in contact with the recording layer is also advantageous in that the melting peak temperature of the recording layer is kept high and it is advantageous for forming an amorphous mark having a high degree of modulation. As best.

As the phase change recording layer, a known GeTe—Sb ₂ Te ₃ pseudo binary material represented by Ge ₂ Sb ₂ Te ₅ or an SbTe eutectic material represented by AgInSbTeGe can be used. In particular, when an optical system having a recording / reproducing wavelength of 405 ± 15 nm and an objective lens numerical aperture NA = 0.85 ± 0.5 is used, phase change recording mainly composed of an alloy of Ge, Sb, Sn, and Mn. The material is preferable because of excellent reproduction light stability and storage reliability (amorphous mark stability).
The preferred composition (atomic%) of each element is 5 ≦ Ge ≦ 20, 45 ≦ Sb ≦ 70, 10 ≦ Sn ≦ 20, and 0 <Mn ≦ 20. Since Ge raises the crystallization temperature and improves the storage stability, but repeatedly deteriorates the recording characteristics, it is desirable not to exceed 20 atomic%. Conversely, in order to ensure storage reliability in a high temperature and high humidity environment, it is necessary to contain 5 atomic% or more. Sn needs to be contained in an amount of 10 atomic% or more in order to obtain sufficient reflectance and contrast at a wavelength of 405 nm. However, if there is too much Sn, the recording characteristics are impaired as in the case of Ge, so it is desirable that it does not exceed 20 atomic%. Since Mn has a smaller adverse effect on reflectivity reduction and recording jitter than Ge, Mn is added instead of Ge when slowing down the crystallization rate. Since Mn repeatedly deteriorates the recording characteristics like Ge, it is desirable that Mn does not exceed 20 atomic%. Since Sn and Sb are elements that increase the crystallization speed and Ge and Mn are elements that decrease the crystallization speed, the composition ratio of each element is optimized in consideration of the overall recording characteristics and the target recording linear velocity. Basically, the target recording linear velocity is designed by the Ge—Sb system, and Mn is substituted for Ge and Sn is substituted for Sb by appropriate amounts. If Sb + Sn exceeds 90 atomic%, the crystallization speed becomes too fast and it becomes difficult to form an amorphous mark. Therefore, the upper limit of Sb is preferably 70 atomic%. In order to set the recording linear velocity to 5 to 30 m / s at 10 ≦ Sn ≦ 20 atomic%, it is preferable to set Sb to 45 atomic% or more. Further, the total amount of Ge, Sb, Sn, and Mn may be 95 atomic% or more and may include 5 atomic% or less of a fifth element for improving recording characteristics, storage reliability, and the like.

On the second dielectric layer, a light transmission layer made of a photocurable resin such as the above-described ultraviolet curable resin is provided by a spin coat method or the like. Further, a hard coat layer may be provided on the light transmission layer by spin coating or the like.
When recording / reproducing is performed using an optical system having a wavelength of 405 ± 15 nm and a numerical aperture NA = 0.85 ± 0.5 of the objective lens, the thickness of the light transmission layer for securing a sufficient tilt margin is 5 to 5. 200 micrometers is preferable, More preferably, it is 5-120 micrometers.
As described above, the example of the layer structure of the phase change optical information recording medium according to the present invention has been shown. However, the recording layer may be a dye recording layer or an inorganic recording layer for additional recording.
As the inorganic recording layer of the write-once type optical information recording medium, a material that causes an irreversible change in refractive index or absorption coefficient by absorption of a recording laser is used. Bi-B-O, Bi-Fe-O, Te-Pd- An oxide-based material such as O is preferable.
Further, it may be a multilayer recording medium having two or more information recording layers via an intermediate layer.

  According to the present invention, the light transmission layer made of a photocurable resin has an excellent balance of mechanical strength (rigidity) and curing rate (gel fraction), so that it has excellent tilt characteristics immediately after production and Change in tilt characteristics is 0.4 to 0.6 deg. A high-quality optical information recording medium suppressed as follows can be provided.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further more concretely, this invention is not limited by these Examples.

Examples 1-2 and Comparative Examples 1-3
First, a polycarbonate substrate (product name: ST3000, manufactured by Teijin Bayer Polytech Co., Ltd.) having a groove depth of 22 mm, a groove width of 0.16 μm, a groove groove having a track pitch of 0.32 μm, a thickness of 1.1 mm, and a diameter of 120 mm is prepared. The information recording layer was sequentially formed by the sputtering method.
(1) Reflective layer: Ag-0.5 atomic% Bi, film thickness 140 nm
(2) First dielectric layer: ZnS · 20 mol% SiO ₂ film thickness 8 nm
(3) Phase change recording layer: Ge ₁₁ Sb _62.5 Sn ₂₀ Mn _6.5 film thickness 14 nm
(4) Second dielectric layer: ZnS / 30 mol% SiO ₂ film thickness 40 nm
Next, as shown in FIG. 7A, the center hole of the medium is closed with a mask material of φ19 mm, and an ultraviolet curable resin prepared in the ratio of Table 2 is supplied near the center of the mask to form a film after curing. It was shaken off by 900-1300 rotation so that thickness might be set to about 100 micrometers. When the resin is shaken off, as shown in FIG. 7B, the condensing optical system condenses the halogen lamp light on the outer periphery of the medium and performs partial heating to flatten the resin pool (ski jump) at the rim portion. did.
Next, the center hole mask is removed, and the resin layer is cured at an illuminance of 700 to 1000 mJ / cm ² using a UV lamp HP-6 (H bulb) manufactured by Fusion UV System, as shown in FIG. A phase change optical information recording medium having a layer structure shown in FIG. 6 was obtained.
Next, these optical information recording media were subjected to a disk surface power of 600 mW, a linear velocity of 3 m / s, and a feed amount by an initialization apparatus equipped with a large aperture LD having a wavelength of 800 nm and a beam diameter of 200 μm × 1 μm (radial direction × track direction). Initialization (crystallization of the recording layer) was performed while feeding at 36 μm / rotation.

Subsequently, the cured physical properties of the resin film and the tilt change ΔRD before and after the high temperature and high humidity test (80 ° C., 85% RH, 300 hours) were evaluated. The cured physical property of the resin film is a polymer thermal property measuring apparatus manufactured by Seiko Instruments Inc., cut out from a resin film of a light transmission layer peeled off from the interface with the information recording layer as a 5 mm × 50 mm strip film. : Using EXSTR6000, the dynamic viscoelasticity was evaluated at a heating rate = 2 ° C./min and a tensile frequency = 10 Hz, and a storage elastic modulus E ′ at 25 ° C. was obtained. Moreover, about the remaining resin film, the hardening rate x was calculated | required from the mass change before and behind the methyl ethyl ketone 8-hour immersion.
The amount of tilt change ΔRD is equal to Dr. Using a MT-200 manufactured by Shenk, the maximum radial tilt angle after the high temperature and high humidity test- (maximum radial tilt angle immediately after production) was obtained.
These evaluation results and the value of E ′ × (1−x / 100) are shown together in Table 2. The determination is that the radial tilt change amount is 0.6 deg. In the following cases, “◯”, 0.4 deg. In the following cases, “◎”, 0.6 deg. The case where the value was exceeded was defined as “×”.

The following can be said for the optical information recording media of Examples 1-2 and Comparative Examples 1-3.
Since the optical information recording medium of Example 1 has E × (1-x / 100) of 50 or less, the radial tilt variation after the environmental test is 0.6 deg. It was a small and high-quality medium as follows. Furthermore, since the optical information recording medium of Example 2 had E × (1-x / 100) of 30 or less, the amount of change in radial tilt after the environmental test was particularly small, and was a high quality medium.
In the optical information recording media of Comparative Examples 1 to 3, since E × (1−x / 100) exceeds 50, the tilt change is 0.6 deg. It has exceeded. In Comparative Example 3, a resin having the same composition as in Example 1 was used, but the curing rate was low because of insufficient UV illumination, particularly E × (1−x / 100), and the amount of tilt change was also very large. It is had.

The figure which shows the relationship between the hardening rate x of an ultraviolet curable resin, the optical film thickness variation | change_quantity (DELTA) nd of a light transmissive layer after a reliability acceleration test, and the weight variation | change_quantity (DELTA) W when the structural component and curing method of an ultraviolet curable resin are changed. . The result of investigating the relationship between E ′ × (1−x / 100) and the radial tilt change Δ (Angular dev. Rad.) After the reliability test (after storage at 80 ° C. and 85% RH for 300 hours) is shown. Figure. The figure which shows an example of a dynamic viscoelasticity measurement result. The figure which shows the part of E'x (1-x / 100) <= 50 in FIG. The figure which shows the part of E'x (1-x / 100) <= 30 in FIG. The figure which shows the layer structural example of a phase change type | mold optical information recording medium. The figure which shows the formation process of a light transmissive layer. (A) Blocking the center hole of the medium with a mask material, supplying UV-curing resin near the center of the mask and shaking it off, (b) Condensing halogen lamp light to the periphery of the medium by a condensing optical system and partially (C) removing the center hole mask and curing the resin layer with a 2 kW xenon flash lamp light source. The figure which shows the relationship between ultraviolet illumination intensity and a cure rate.

Claims (4)

Optical information that includes an information recording layer and a light transmissive layer made of a photocurable resin film on a substrate, and that records and reproduces data by irradiating the information recording layer with laser light through the light transmissive layer. The recording medium is characterized in that the following equation is satisfied, where the curing rate of the photocurable resin film is x (%), and the storage modulus obtained from the dynamic viscoelasticity measurement at 10 Hz is E ′ (MPa). Optical information recording medium.
E ′ × (1−x / 100) ≦ 50   2. The optical information recording medium according to claim 1, wherein E ′ × (1−x / 100) ≦ 30.   3. The optical information recording medium according to claim 1, wherein 500 ≦ E ′ ≦ 1500. The optical information recording medium according to claim 1, wherein 98 ≦ x ≦ 100.

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