HK1121854A - Optical information recording medium - Google Patents

Abstract

An optical information recording medium 1 includes a substrate 2 having a through-hole provided at the central portion thereof and a guiding groove 3 provided on a surface at the light-incident side; a reflective layer 4 provided on the surface of the substrate 2 having the guiding groove 3, a recording layer 5 provided on the reflective layer 4 and made of an organic substrate containing a dye; and a light-transmissive cover layer 6 provided on the recording layer 5, wherein the cover layer 6 is made of a curable resin, and a modulus of elasticity of at least a portion of the cover layer 6 facing the recording layer 5 is in the range of about 34 MPa to about 96 MPa at 25℃.

Description

Optical information recording medium

Technical Field

The present invention relates to an optical information recording medium, and more particularly to an optical information recording medium having a higher recording density such as a Blu-ray Disc (BD-R) using a dye in a recording layer.

Background

As an information recording medium, an optical information recording medium such as an optical disc has been widely used. The optical information recording medium includes an optical information recording medium such as a recordable Compact disc (CD-R) in which a reflective layer and a recording layer are formed in this order on a transparent resin substrate having a thickness of 1.2mm and a diameter of 120mm or 80 mm. In recent years, information recording media are required to have higher information recording density. Therefore, it is considered to realize an optical information recording medium such as a recordable DVD (digital versatile disc) (DVD ± R) by using an objective lens having a short laser wavelength and a large Numerical Aperture (NA). Since the allowable tilt angle (tilt) of an optical disc is increased by the reduction in the wavelength and the increase in the NA, the DVD ± R has a structure in which two transparent resin substrates having a thickness of 0.6mm are bonded to each other, and a reflective layer and a recording layer are interposed between the two substrates.

However, in recent years, higher information recording density has been demanded for recording high-precision video data. Therefore, an optical information recording medium such as a recordable blu-ray disc (BD-R) has been proposed, which is configured such that a reflective layer and a recording layer are formed on a light incident surface side of a resin substrate having a thickness of 1.1mm, and a light transmissive cover layer having a thickness of 0.1mm is provided on a surface on which the reflective layer and the recording layer are formed.

As shown in japanese patent application laid-open No. 2003-45079, the optical information recording medium has a diameter and a thickness equal to those of a CD-R (Compact disc-Recordable) and a DVD ± R by forming a reflective layer and a recording layer in this order on a resin substrate having a thickness of 1.1mm and a guide groove (Pregroove) formed on one surface thereof, and providing a cover layer made of a light-transmitting resin having a thickness of 0.1mm on the recording layer. Further, as shown in japanese patent laid-open No. 2003-36562, a protective layer made of a light-transmissive inorganic material may be provided between the recording layer and the cover layer in order to protect the recording layer. The recording layer of such an optical recording medium is composed of an organic material containing a dye such as an azo dye or a cyanine dye, and an inorganic material such as Si, Cu, Sb, Te, or Ge, and data is recorded by forming pits by irradiation with recording laser light.

[ patent document 1] Japanese patent laid-open No. 2003-45079

[ patent document 2] Japanese patent laid-open No. 2003-36562

Disclosure of Invention

[ problems to be solved by the invention ]

However, for BD-R, the following problems exist: the modulation degree of a BD-R using an organic material in the recording layer is lower than that of a BD-R using an inorganic material in the recording layer. Since the change in the optical path length of the recording layer of an organic substance tends to be smaller than that of the recording layer of an inorganic substance, the modulation degree is lower. Here, in order to increase the change in the optical path length, the depth of the guide groove may be increased. However, when the depth of the guide groove is increased, the thickness of the recording layer is increased, the amount of the coloring matter is increased, and the reflectance before recording tends to be lowered. This in turn leads to a smaller change in the optical path length, and thus a lower degree of modulation.

The invention aims to obtain an optical information recording medium with good modulation degree even when an organic substance is used in a recording layer.

[ means for solving problems ]

A first technical means of the present invention is an optical information recording medium comprising: a substrate having a through hole at a central portion thereof and a spiral guide groove on one surface side thereof; a reflective layer formed on a surface of the substrate on which the guide groove is formed; a recording layer formed on the reflective layer and made of an organic substance containing a dye; and a light-transmitting cover layer formed on the recording layer, wherein the cover layer is formed using a cured resin, and the elastic modulus of the side opposite to the recording layer is within a range of 34 to 96MPa at 25 ℃.

The present inventors have found that when pits are formed when recording is performed on an optical information recording medium, the pits are formed in a shape recessed in a cover layer by plastically deforming the side of the cover layer facing a recording layer, thereby increasing the change in optical path length and improving the degree of modulation. According to the first technical method, the recording layer is deformed by heat generated at the time of recording, and after cooling, the recording layer is deformed by being sunk in the shape of the cover layer, so that the change in the optical path length is increased, and the modulation degree is improved.

In addition to the first technical means, a second technical means of the present invention is an optical information recording medium, wherein the cover layer is formed of a first resin layer and a second resin layer having a lower elastic modulus than the first resin layer, and the side opposite to the recording layer is formed of the second resin layer.

According to the second technical means, when recording is performed on the optical information recording medium, the durability of the cover layer can be ensured by the first resin layer while the second resin layer is plastically deformed to ensure a sufficient change in optical path length.

In the optical information recording medium of the present invention, a protective layer made of a light-transmissive inorganic material may be provided between the recording layer and the cover layer in order to protect the recording layer. Therefore, in addition to the first and second technical means, a third technical means of the present invention is directed to an optical information recording medium in which a protective layer having a plastic extrusion property and an elastic extrusion property of 40% or less is provided between the recording layer and the cover layer.

In the case where a protective layer is present between the recording layer and the cover layer, in order to obtain the effect of the present invention, the protective layer must also deform in accordance with the deformation of the cover layer. According to the third technical method, the tendency of the protective layer to plastically deform is stronger than the tendency of the protective layer to elastically deform, and therefore the protective layer is easily deformed in accordance with the deformation of the cover layer. Thus, the rate of change (Δ C/N) of C/N (Carrier noise ratio) can be controlled to 1dB or less, and the influence on the modulation degree can be reduced.

[ Effect of the invention ]

According to the present invention, an optical information recording medium having a good degree of modulation can be obtained, wherein an organic substance containing a dye is used for a recording layer.

Drawings

FIG. 1 is an enlarged cross-sectional view of an optical information recording medium according to a first embodiment of the present invention.

FIG. 2 is an enlarged schematic cross-sectional view of an optical information recording medium according to a first embodiment of the present invention after recording.

FIG. 3 is an enlarged cross-sectional view of an optical information recording medium according to a second embodiment of the present invention.

FIG. 4 is an enlarged schematic cross-sectional view of an optical information recording medium according to a second embodiment of the present invention after recording.

FIG. 5 is an enlarged cross-sectional view of an optical information recording medium according to a third embodiment of the present invention.

Fig. 6 is a graph showing a loading curve and an unloading curve in the nanoindentation method.

FIG. 7 is an enlarged schematic cross-sectional view of an optical information recording medium according to a third embodiment of the present invention after recording.

Fig. 8 is a chemical formula showing an example of a dye used in the recording layer.

Wherein ring A represents a heterocyclic ring formed with a nitrogen atom and a carbon atom bonded thereto, ring B represents a benzene ring which may be substituted, ring C represents a heterocyclic ring containing a nitrogen atom bonded thereto, and may be bonded to ring B, and X^-Represents a group which may have an active hydrogen, M²⁺Represents divalent cation metal ion, and all anions are used as azo dye molecules, and represents that 1M is bonded on 2 azo dye molecules²⁺Metal complex formed by molecules.

[ description of symbols ]

1. 11, 21 optical information recording medium

2. 12, 22 substrate

3. 13, 23 guide groove

4. 14, 24 reflective layer

5. 15, 25 recording layer

6. 16, 26 cover layer

7. 17, 27 pits

16a first resin layer

16b second resin layer

28 protective layer

Detailed Description

The first embodiment of the optical information recording medium of the present invention will be described below with reference to fig. 1 to 2. The optical information recording medium 1 shown in fig. 1 includes: a disk-shaped substrate 2 having a through hole (not shown) in the center portion thereof and a guide groove 3 formed in a spiral shape on one surface side; a reflective layer 4 formed on the guide groove 3 of the substrate 2; a recording layer 5 formed on the reflective layer 4 and made of an organic substance containing a dye; and a light-transmissive cover layer 6 provided on the recording layer.

The substrate 2 is a resin substrate having a thickness t of 1.1mm and a diameter of 120 mm. The substrate 2 can be used by selecting any of various materials used as substrate materials for conventional optical information recording media. Specifically, there may be mentioned acrylic resins such as polycarbonate and polymethyl methacrylate, vinyl chloride resins such as polyvinyl chloride and vinyl chloride copolymers, epoxy resins, amorphous polyolefins (amorphous polyofin), polyester resins, metals such as aluminum, and glass, and these may be used in combination or in admixture as required. Among these materials, thermoplastic resins are preferable, and polycarbonate is particularly preferable, from the viewpoints of moldability, moisture resistance, dimensional stability, and low price. The substrate 2 may be formed using an injection molding method. At this time, a mold presser (stamp) is provided in the mold, thereby forming the spiral guide groove 3 in the substrate 2. The guide grooves 3 are formed at a pitch of 0.35 μm or 0.32 μm, and the pits are formed in the guide grooves 3.

The reflective layer 4 is formed of a thin metal film having a high reflectance such as Ag alloy or Al alloy, and is formed by a method such as sputtering. The recording layer 5 is formed of an organic substance containing a dye, and is formed by dissolving a dye such as an azo dye or a cyanine dye in, for example, a TFP (tetrafluoropropanol) solution and applying the solution by a spin coating method.

The cover layer 6 is formed of a light-transmitting resin, and a cured resin cured by ultraviolet rays or radiation having a thickness of 0.1mm is formed by a method such as spin coating. The light transmittance of the cover layer 6 is measured by measuring the cover layer 6 having a thickness of 0.1mm after hardening with light having a wavelength of 405nm using a spectrophotometer, and is 70% or more, preferably 80% or more. The cover layer 6 is formed of a cured resin having an elastic modulus at 25 ℃ in the range of 34 to 96 MPa. Here, the modulus of elasticity at 25 ℃ was measured by the nanoindentation method (Korea Steel technology/Vol.52 No.2(Sep.2002) P74 to P77). Further, since the cover layer 6 made of a cured resin having an elastic modulus in the range of 34 to 96MPa is relatively soft and easily damaged, a hard coat layer (not shown) made of an acrylic resin or the like may be provided on the surface on the light incident side.

Here, the operation of the first embodiment of the optical information recording medium of the present invention will be described with reference to fig. 2. When the optical information recording medium 1 is irradiated with a recording laser beam (not shown), the dye of the recording layer 5 in the guide groove 3 is decomposed to form pits 7. At this time, heat is generated in the recording layer 5, and the substrate 2 and the cover layer 6 are thermally deformed. The substrate 2 is made of a material that is less likely to be thermally deformed in order to ensure good tracking (tracking). Therefore, in terms of thermal deformation, the cover layer 6 having a low elastic modulus is increased in thermal deformation. Thus, the pit 7 is recessed in the cover layer 6.

Since the modulus of elasticity of the cover layer 6 is relatively low, the dimples 7 formed in the shape of being recessed in the cover layer 6 maintain the shape of being recessed in the cover layer 6 after cooling. As described above, by forming the pits 7 in a shape recessed in the cover layer 6, the change in the optical path length becomes large, and the space in which the refractive index approaches 1 increases, so that the change in the refractive index in appearance can be improved, and a good degree of modulation can be obtained.

The reason why the elastic modulus is specified to be within the range of 34 to 96MPa will be described. If the modulus of elasticity of the cover layer 6 is made low, thermal deformation is likely to occur. On the other hand, when the elastic modulus is too low, spontaneous deformation is likely to occur due to a change with time after recording. For example, when the optical information recording medium is subjected to a pressure in the thickness direction by its own weight, the portion of the pit 7 recessed in the cover layer 6 is deformed in the thickness direction, and the change in the optical path length is reduced. Therefore, even if the recording medium has a sufficient modulation degree, for example, a modulation degree of 40% or more, the modulation degree is lower than 40% due to the change with time. Therefore, in order to reduce the change of the modulation degree with time, the elastic modulus must be 34MPa or more. On the other hand, if the modulus of elasticity of the cover layer 6 is too high, thermal deformation is less likely to occur, and thus pits having a sufficient modulation degree at the time of recording cannot be formed. Therefore, in order to obtain a sufficient degree of modulation at the time of recording, for example, a degree of modulation of 40% or more, the elastic modulus must be 96MPa or less.

The elastic modulus of the entire cover layer 6 does not need to be in the range of 34 to 96MPa, and only the elastic modulus of the side facing the recording layer may be in the range of 34 to 96 MPa. Here, the portion having an elastic modulus in the range of 34 to 96MPa on the side opposite to the recording layer 5 means, for example, a portion having a distance of 19 to 30 μm from the interface between the recording layer 5 and the cover layer 6. However, since the dimples 7 are formed in the guide groove 3, the thickness of the portion where this guide groove 3 exists may be problematic. Then, the thickness of the portion having an elastic modulus in the range of 34 to 96MPa on the side facing the recording layer at this time becomes the thickness on the guide groove 3.

Next, a second embodiment of the optical information recording medium of the present invention will be described with reference to fig. 3 to 4. The optical information recording medium 11 shown in fig. 3 is different from the optical information recording medium 1 of the first embodiment in that the cover layer 16 has a two-layer structure formed of a first resin layer 16a having a relatively high elastic modulus and a second resin layer 16b having a relatively low elastic modulus, and the second resin layer 16b is formed in a portion where the elastic modulus of the side facing the recording layer 15 is in a range of 34 to 96 MPa.

The cover layer 16 is formed in the following manner: after the reflective layer 14 and the recording layer 15 are sequentially formed on the surface of the substrate 12 on which the guide grooves 13 are formed, a cured resin to be the second resin layer 16b is applied on the recording layer 15 by a spin coating method, and after the second resin layer 16b is cured, a cured resin to be the first resin layer 16a is applied by a spin coating method and then cured. Thus, the first resin layer 16a and the second resin layer 16b were combined to form the cover layer 16 having a thickness of 0.1 mm.

Since the second resin layer 16b forms a portion having an elastic modulus in the range of 34 to 96MPa on the side opposite to the recording layer 15, the thickness t of this portion in the guide groove 13 is preferably in the range of 19 to 30 μm. If the thickness of the portion is within this range, the amount of deformation that can obtain a good degree of modulation can be ensured.

Here, the operation of the second embodiment of the optical information recording medium of the present invention will be described with reference to fig. 4. When the optical information recording medium 11 is irradiated with a recording laser beam (not shown), the dye of the recording layer 15 in the guide groove 13 is decomposed to form pits 17. At this time, the recording layer 15 generates heat, causing thermal deformation of the second resin layer 16 b. Thus, the pit 17 is formed in a shape recessed into the cover layer 16.

Since the second resin layer 16b has a relatively low elastic modulus and is in the range of 34 to 96MPa at 25 ℃, the dimples 17 formed in the shape of being recessed in the second resin layer 16b maintain the shape of being recessed in the second resin layer 16b after cooling. Thus, the pits 17 are formed in a shape recessed in the second resin layer 16b, and thus, the change in the optical path length becomes large, and the space in which the refractive index approaches 1 increases, so that the change in the refractive index in appearance can be improved, and a good degree of modulation can be obtained.

Next, a third embodiment of the optical information recording medium of the present invention will be described with reference to fig. 5 to 7. The optical information recording medium 21 shown in fig. 5 is different from the optical information recording medium 1 of the first embodiment in that the optical information recording medium 21 shown in fig. 5 is provided with a protective layer 28 formed of a light-transmissive inorganic material between the recording layer 25 and the cover layer 26.

The protective layer 28 is intended to prevent a mixed phenomenon such as diffusion of a coloring matter contained in the recording layer 25 into the cover layer 26 during formation of the cover layer 26, or penetration of a hardening resin solvent or the like for forming the cover layer 26 into the recording layer 25. Examples of the material constituting the protective layer 28 include silicon oxide, particularly silicon dioxide, and oxides such as zinc oxide, cerium oxide, and yttrium oxide; sulfides such as zinc sulfide and yttrium sulfide; nitrides such as silicon nitride; silicon carbide; mixtures of oxides and sulfur, and alloys described below, and the like. The protective layer 28 is formed by sputtering or the like.

In the optical information recording medium 21 having the above-described structure, when the cover layer 26 is deformed, the protective layer 28 must be deformed in accordance with the deformation. In order to deform the protective layer 28 in accordance with the deformation of the cover layer 26, the extrusion plasticity/elasticity of the protective layer 28 can be set to 40% or less, whereby the rate of change Δ C/N of C/N can be controlled to 1dB or less, and the influence on the modulation degree can be reduced. The extrusion plasticity/elasticity is defined herein as follows:

extrusion plasticity & elasticity [% ] ═

(elastic plastic deformation equivalent) × 100/(elastic plastic deformation equivalent + plastic deformation equivalent).

Here, the definition of the extrusion plasticity and elasticity is explained in detail based on the graph shown in fig. 6. In the nanoindentation method, when a test load is applied to a sample, a loading curve a is drawn and brought to a displacement point e, and to an intersection point c of the displacement point e and the test load. The test load is then removed and the unloading curve b is plotted and brought to the displacement d. In this case, the area of the region a surrounded by the loading curve a, the unloading curve B, and the displacement axis is set to the plastic deformation equivalent [ N · m ], and the area of the region B surrounded by the unloading curve B, the displacement axis, and a perpendicular line connecting the point c and the point e is set to the elastic plastic deformation equivalent [ N · m ]. According to the above formula, if the extrusion plasticity/elasticity is small, the point d approaches the point e, and the area of the region B is small, resulting in a stronger tendency of plastic deformation than elastic deformation.

Here, the operation of the third embodiment of the optical information recording medium of the present invention will be described with reference to fig. 7. When the optical information recording medium 21 is irradiated with a recording laser beam (not shown), the dye of the recording layer 25 in the guide groove 23 is decomposed to form pits 27. At this time, the recording layer 25 generates heat, causing the protective layer 28 to thermally deform along with the second resin layer 16 b. Thus, the pit 27 is formed in a shape recessed into the cover layer 26.

Since the modulus of elasticity of the cover layer 26 is relatively low and is in the range of 34 to 96MPa at 25 ℃, the dimples 27 formed so as to be sunk into the cover layer 26 maintain the shape sunk into the cover layer 26 after cooling. Further, the protective layer 28 has a strong tendency to be plastically deformed when the extrusion plasticity/elasticity is 40% or less, and therefore deforms in accordance with the deformation of the cover layer 26. As described above, since the cover layer 6 is easily thermally deformed, the pits 27 are formed in a shape recessed into the cover layer 26, and thus, the change in the optical path length becomes large, and the space where the refractive index approaches 1 increases, so that the change in the refractive index in appearance can be improved, and a good modulation degree can be obtained. Further, since the protective layer 28 is easily deformed in accordance with the deformation of the cover layer 26, Δ C/N can be controlled to 1dB or less, thereby reducing the influence on the modulation degree.

The covering layer 26 in the present embodiment is formed of a single resin layer, and the same effects can be obtained when the covering layer 26 is formed of two resin layers as in the second embodiment. The lower limit of the extrusion plasticity/elasticity is not particularly limited, but is preferably 10% or more in order to prevent the protective layer 28 from being deformed by locally applying pressure.

Here, effects of the optical information recording medium of the present invention will be described according to the following examples.

(example 1)

A disk-shaped polycarbonate substrate having a through-hole in the center portion thereof, guide grooves with a tracking pitch of 0.32 μm, an outer diameter of 120mm and a thickness of 1.1mm was produced by injection molding. An Ag alloy was sputtered on the surface of the substrate on which the guide grooves were formed to form a reflective layer having a thickness of 100 nm. Thereafter, a dye solution obtained by dissolving the dye shown in fig. 8 in a TFP solvent was applied by a spin coating method and dried at 80 ℃ for 30 minutes to form a recording layer. Preparing a quantity of the substrate sample for testing.

Next, UV (UltraViolet) curable resins having different elastic moduli at 25 ℃ after curing were applied to each prepared sample by a spin coating method, and then cured to form a second resin layer having a thickness of 25 μm. Next, a UV curable resin having an elastic modulus of 1700MPa at 25 ℃ after curing was applied to each sample by a spin coating method, and then cured to form a first resin layer, and the first resin layer and a second resin layer were combined to form a coating layer having a thickness of 0.1 mm.

A sample of the optical information recording medium obtained by the above method was evaluated for recording/reproducing characteristics under the conditions of a wavelength of 405nm, a Numerical Aperture (NA) of 0.85 and a linear velocity of 4.92m/s using a commercially available recording/reproducing apparatus (e.g., ODU-1000 manufactured by Pulstec industries, Ltd.) to obtain an initial modulation degree. Then, the mixture was left at 25 ℃ and 30% humidity for one month to determine the degree of preparation again. The cover was then peeled off from the substrate, the pigment was washed off, and the elastic modulus of the second resin layer was determined by nanoindentation method under a test load of 0.1mN at 25 ℃. The degree of modulation was 40% or more. The results are shown in Table 1.

[ Table 1]

	Comparative example 1	Comparative example 2	Example 1	Example 2	Example 3	Example 4	Comparative example 3
								Modulus of elasticity (MPa)	14	27	34	56	77	96	117
Initial degree of modulation (%)	45	44	43	42	41	40	38
								After one month the modulation [% ]]	33	38	43	42	41	40	38

According to the results, if the elastic modulus is within the range of 34 to 96MPa, the degree of preparation after one month can be maintained at 40% or more, and good results can be obtained.

(example 2)

A disk-shaped polycarbonate substrate having a through-hole in the center portion thereof, guide grooves with a tracking pitch of 0.32 μm, an outer diameter of 120mm and a thickness of 1.1mm was produced by injection molding. An Ag alloy was sputtered on the surface of the substrate on which the guide grooves were formed to form a reflective layer having a thickness of 100 nm. Thereafter, a dye solution obtained by dissolving the dye shown in fig. 8 in a TFP solvent was applied by a spin coating method and dried at 80 ℃ for 30 minutes to form a recording layer. Preparing a quantity of the substrate sample for testing.

Next, a light-transmissive protective layer material having different extrusion plasticity/elasticity values was sputtered on each sample to form a protective layer having a thickness of 0.5 μm. Then, a UV-curable resin having an elastic modulus of 35MPa at 25 ℃ after curing was applied to each prepared sample by a spin coating method, and then cured to form a second resin layer having a thickness of 25 μm. Next, a UV curable resin having an elastic modulus of 1700MPa at 25 ℃ after curing was applied to each sample by a spin coating method, and then cured to form a first resin layer, and the first resin layer and a second resin layer were combined to form a coating layer having a thickness of 0.1 mm.

A sample of the optical information recording medium obtained in this manner was continuously recorded for 6T (1T length: 0.08 μm) under conditions of a line speed of 4.92m/s, a reproduction power of 0.35mW, a recording power of 5.5mW, and a reproduction power at the time of recording (bias power) of 1.2mW using a commercially available recording and reproducing apparatus (for example, ODU-1000 manufactured by Pulstec co., ltd.), and the C/N after recording was measured using a spectrum analyzer (spectral analyzer). Subsequently, the reproduction power was increased to 0.55mW and the same track was reproduced for 1 minute, and after 1 minute, the reproduction power was returned to 0.35mW, and the C/N was measured again by using the spectrum analyzer. Δ C/N was determined from the difference between the initial C/N and the C/N obtained after 1 minute of regeneration at a power of 0.55 mW.

The coating was peeled off from the substrate, the pigment was washed off, and the protective layer was removed, and the elastic plastic deformation equivalent and the plastic deformation equivalent of each sample, in which Δ C/N was measured, were determined by the nanoindentation method under a test load of 0.1mN to calculate the extrusion plastoelasticity. The results are shown in Table 2.

[ Table 2]

	Sample 10	Sample 11	Sample 12	Sample 13
					Elastic plastic deformation equivalent (N Mm)	3.64E-13	4.61E-13	3.54E-13	2.40E-13
Equivalent plastic deformation (N Mm)	1.57E-13	2.63E-13	5.31E-13	5.73E-13
					Extrusion plasticity-elasticity (%)	69.87	63.67	40.00	29.52
ΔC/N(dB)	20.29	20.01	0.66	0.105

From the above results, if the extrusion plasticity and the extrusion elasticity are 40% or less, Δ C/N is 1dB or less, and a protective layer that does not affect the modulation degree can be obtained.

Claims (3)

1. An optical information recording medium comprising: a substrate having a through hole at a central portion thereof and a spiral guide groove on one surface side thereof; a reflective layer formed on a surface of the substrate on which the guide groove is formed; a recording layer formed on the reflective layer and made of an organic substance containing a dye; and a light-transmissive cover layer formed on the recording layer, the optical information recording medium being characterized in that:

the cover layer is formed of a cured resin, and has an elastic modulus at 25 ℃ in the range of 34 to 96MPa on the side facing the recording layer.

2. The optical information recording medium according to claim 1, wherein: the cover layer is composed of a first resin layer and a second resin layer having a lower elastic modulus than the first resin layer, and the side opposite to the recording layer is formed of the second resin layer.

3. The optical information recording medium according to claim 1 or 2, wherein: a protective layer is provided between the recording layer and the cover layer, and the protective layer has a squeeze plasticity and a squeeze elasticity of 40% or less.