JP2006048905A - Optical recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical recording medium capable of obtaining good recording / reproducing characteristics for high-speed recording applications.
A disk substrate (reverse laminate 11) in which a reflective layer (1) 102 and a recording layer (1) 103 are laminated on a substrate (1) 101, and a recording layer (2) on a transparent substrate (2) 109. ) 108 and the reflective layer (2) 107 are sequentially laminated to the disk substrate (regular laminate 12) via the transparent resin layer 105. The two-layer type optical recording medium 100 is 25 of the transparent resin layer 105. The product (E × t) of the elastic modulus (E) and thickness (t) at ± 5 ° C. is adjusted in the range of 2.0 × 10 ⁴ MPa · μm to 30.0 × 10 ⁴ MPa · μm. As a result, when recording optical information on the recording layer (1) 103 of the reverse laminated body 11, excessive deformation on the adjacent track portions is suppressed, crosstalk is reduced, and good recording and reproduction for high-speed recording applications. Characteristics are obtained.
[Selection] Figure 1

Description

  The present invention relates to an optical recording medium, and more particularly to an optical recording medium capable of high-speed recording and having good recording / reproduction characteristics.

  In recent years, various optical recording media such as CD-R, CD-RW, and MO can store a large amount of information, and a medium such as a DVD-RAM that can be easily accessed at random has been developed. It is widely recognized as an external storage device in information processing devices such as the above. For example, a typical CD-R having an organic dye-containing recording layer has a dye recording layer and a reflective layer in this order on a transparent disk substrate, and a laminate having a protective layer covering these recording layers and the reflective layer. The structure is such that recording / reproduction is performed with laser light through the substrate. In order to further increase the recording capacity of these optical recording media, a multilayer optical recording medium in which a plurality of recording layers are provided on one medium has been developed. For example, a disk-shaped transparent first substrate is developed. On top of this, a two-layer optical recording medium having two dye recording layers with an intermediate layer made of an ultraviolet curable resin interposed therebetween has been reported (see Patent Document 1).

  Such a two-layer type optical recording medium is formed by forming two disk substrates on which a 2P (Photo Polymerization) method using a transparent stamper and a recording layer and a reflective layer are laminated, and pasting them through a photo-curable resin layer. And how to do it. For example, in the 2P method, a photocurable resin raw material is applied on a first substrate provided with a first recording layer and a first reflective layer, and a transparent stamper having an uneven shape is mounted on the coated surface. After setting, the photocurable resin raw material is cured, and then the transparent stamper is peeled off to transfer the irregularities onto the surface of the photocurable resin. Further, the second recording layer and the second reflective layer are formed on the irregular surface. Are sequentially formed, and finally the second substrate is bonded. Optical information is recorded / reproduced on the two recording layers using recording / reproducing light incident from the first substrate side.

  In the method of adhering two disk substrates on which a recording layer and a reflective layer are laminated, a recording layer and a reflective layer are laminated in this order on a substrate on which a guide groove for a recording track is formed (hereinafter referred to as a “normal laminated body”). A first disk substrate, and a second disk in which a reflective layer and a recording layer are laminated on the substrate in this order (hereinafter also referred to as “reverse laminated body”). The substrate is formed, and a photocurable resin is applied to each disk substrate, and then the coated surfaces are put together to cure the photocurable resin. Optical information is recorded / reproduced on the two recording layers using recording / reproducing light incident from the first disk substrate side. Such a method of adhering two disc substrates does not require a step of transferring the uneven shape of the transparent stamper as in the 2P method, and is considered to be excellent in productivity and cost reduction.

JP 2000-31384 A (see columns (0008) to (0019))

By the way, in an optical recording medium provided with a recording layer containing an organic dye, there is a problem that it is desired to further suppress the occurrence of crosstalk in high-speed recording applications.
That is, the recording layer containing an organic dye usually decomposes the dye that has absorbed the condensed recording laser beam, the thickness of the portion decreases, the pressure increases, and the periphery of the recording layer exposed to a high temperature. Is deformed to form a recording portion. In this case, the deformed recording portion expands to the adjacent track portion, and when recording is performed on a plurality of tracks, crosstalk tends to increase, and a phenomenon that it is difficult to obtain good jitter occurs.
Here, jitter when information is recorded on a plurality of tracks and signals recorded on adjacent tracks are reproduced is referred to as MT (%). In addition, the jitter obtained by reproducing a portion recorded in only one track in a state where there is no recording in an adjacent track is referred to as ST (%). MT (%) includes the influence of crosstalk, while ST (%) does not include the influence of crosstalk.
Furthermore, since the recording pulse is shortened in the case of high speed recording, it is necessary to decompose the dye using a recording laser beam having a higher power than in the case of low speed recording. As a result, since the recording layer is exposed to a higher temperature than in the case of low speed recording, the increase in crosstalk tends to be remarkable.

  The occurrence of such crosstalk occurs particularly in the second recording layer on the back side from the incident surface of the recording / reproducing light in the two-layered optical recording medium formed by the method of adhering two disc substrates. Is noticeable. As described above, the second recording layer of the two-layer optical recording medium formed by the method of adhering two disc substrates is an inverse laminate in which a reflective layer and a recording layer are laminated on a substrate. Provided on the disk substrate. In such a reverse laminated body, when optical information is recorded in the inter-groove portion of the substrate, it is necessary to increase the thickness of the recording layer in the inter-groove portion in order to ensure the recording modulation degree. In this case, since the adjacent track of the recording portion is a groove portion of the substrate, the recording layer thickness is likely to be thicker than that between the grooves. For this reason, as the recording layer film thickness of the groove portion increases, the recording mark spreads laterally and crosstalk tends to increase. Such a difference in recording film thickness between the groove and the groove is likely to occur when an organic dye solution is applied.

  In addition, the second substrate provided on the back side from the recording / reproducing light incident surface in the two-layer type optical recording medium is set to have a shallower guide groove than the conventional one in order to ensure the reflectance of the recording / reproducing light. Has been. For this reason, the physical barrier effect of the guide groove is reduced, excessive deformation due to flow deformation of the resin of the substrate occurs during recording, and crosstalk tends to increase.

The present invention has been made to solve such problems.
That is, an object of the present invention is to provide an optical recording medium capable of obtaining good recording / reproducing characteristics in high-speed recording applications.

In order to solve this problem, in the present invention, the product (E × t) of the elastic modulus (E) and thickness (t) of the transparent resin layer in contact with the reverse laminate is adjusted to a specific range. Yes.
That is, according to the present invention, the thickness of the transparent resin layer includes a substrate, a reverse laminate having a reflective layer and a recording layer in this order, and a transparent resin layer provided on the recording layer side of the reverse laminate. There is provided an optical recording medium in which the product (E × t) of (t) and the elastic modulus (E) at 25 ± 5 ° C. is 2.0 × 10 ⁴ MPa · μm or more.

Here, the product (E × t) of the thickness (t) of the transparent resin layer and the elastic modulus (E) at 25 ± 5 ° C. is preferably 30.0 × 10 ⁴ MPa · μm or less.
Moreover, it is preferable that the elasticity modulus (E) in 25 +/- 5 degreeC of resin which comprises a transparent resin layer is 3.0 * 10 < ³ > MPa or more and 6.0 * 10 < ³ > MPa or less.

  Furthermore, in the optical recording medium to which the present invention is applied, it is preferable that the recording layer constituting the reverse laminate contains an organic dye. In particular, in a two-layer optical recording medium as shown in FIG. 1 to be described later, cross-talk is reduced and MT (%) is improved when recording is performed on a reverse laminate including a substrate, a reflective layer, and a recording layer. . Note that another layer may be provided as appropriate between the substrate and the reflective layer, or between the reflective layer and the recording layer.

  In the optical recording medium to which the present invention is applied, it is preferable to further provide an intermediate layer between the recording layer constituting the reverse laminate and the transparent resin layer in contact therewith. By providing the intermediate layer, it is possible to prevent the component exuding from the transparent resin layer from contaminating or dissolving the recording layer in contact with the transparent resin layer.

  Further, in the optical recording medium to which the present invention is applied, the second reflective layer, the second recording layer, and the transparent substrate are sequentially arranged on the opposite side of the transparent resin layer in contact with the reverse laminate to the reverse laminate. By providing it, it can be developed into a multilayer optical recording medium.

On the other hand, the present invention provides a recording layer in which optical information is recorded / reproduced by light irradiation, a transparent resin layer provided on the light incident surface side of the recording layer, and a recording layer on the side opposite to the light incident surface. The product (E × t) of the thickness (t) of the transparent resin layer and the elastic modulus (E) at 25 ± 5 ° C. is 2.0 × 10 ⁴ MPa · μm or more. It can be grasped as a certain optical recording medium.
That is, in an optical recording medium having a configuration in which a transparent resin layer having a specific numerical value (E × t) is provided on the light incident surface side of a recording layer having a reflective layer on the side opposite to the light incident surface. Excessive deformation to the track portion is suppressed, crosstalk in high-speed recording is reduced, and jitter can be further improved. Such an improvement in performance is not limited to the film surface incident type optical recording medium, but is remarkable in the recording layer provided on the far side from the light incident surface in the multilayer type optical recording medium.
Here, the transparent resin layer is preferably composed of a transparent resin having a glass transition temperature of 150 ° C. or higher. By configuring the transparent resin layer using such a transparent resin, it is considered that the hardness of the transparent resin layer is increased and the jitter is improved.

Further, according to the present invention, there is provided an optical recording medium having a substrate, a reflective layer, a recording layer, and a transparent resin layer in this order, the reflective layer containing a metal mainly composed of silver (Ag), and An optical recording medium having a thickness of 30 nm to 80 nm is provided.
That is, the optical recording medium to which the present invention is applied has a reverse laminated structure having a substrate, a reflective layer, a recording layer, and a transparent resin layer in this order, and a film of a reflective layer containing a metal mainly composed of silver. When the thickness is 30 nm or more and 80 nm or less, a part of the light beam incident on the reflection layer from the recording layer side can be transmitted. Then, energy for recording information on the recording layer is diffused. For example, in the case of a write once optical recording medium in which a recording mark is formed on a recording layer containing an organic dye, the recording mark protrudes to an adjacent track (crosstalk). ) Phenomenon is suppressed, and as a result, jitter can be improved.
Here, it is preferable that the reflective layer contains 50% or more of Ag, and further contains 0.1% by atom of one or more elements of Ti, Bi, Zn, Cu, Pd and rare earth metal mainly composed of Ag. It is preferable to contain -15 atomic%.

  Thus, according to the present invention, an optical recording medium capable of obtaining good recording / reproducing characteristics in high-speed recording applications can be obtained.

Hereinafter, the best mode for carrying out the present invention (hereinafter, an embodiment of the present invention) will be described. In addition, this invention is not limited to the following embodiment, It can implement by changing variously within the range of the summary.
(First embodiment)
FIG. 1 is a diagram for explaining a first embodiment of an optical recording medium to which the present embodiment is applied (in this example, a one-side incident two-layer DVD). In FIG. 1, a disk substrate (reverse laminate 11) in which a reflective layer and a recording layer are laminated on a transparent substrate, a disk substrate (normal laminate 12) in which a recording layer and a reflective layer are sequentially laminated on a transparent substrate, A two-layer optical recording medium 100 is shown.

  As shown in FIG. 1, an optical recording medium 100 includes a disc-shaped light-transmitting substrate (1) 101 in which grooves and lands or prepits are formed as an inverse laminate 11, and a laser of the substrate (1) 101. It has a reflective layer (1) 102 provided on the incident surface side of the light 110, a recording layer (1) 103 containing a dye, and an intermediate layer 104. Further, as the regular laminate 12, a disc-shaped light-transmitting substrate (2) 109 in which grooves and lands or prepits are formed, and a recording layer (2) 108 containing a dye provided on the substrate (2) 109. And a translucent reflective layer (2) 107 that distributes the power of the laser light 110 incident from the substrate (2) 109 side, and a protective coating layer 106 provided on the reflective layer (2) 107. Then, the reverse laminate 11 and the regular laminate 12 are laminated via a transparent resin layer 105 so that the intermediate layer 104 and the protective coat layer 106 face each other, thereby constituting a two-layer optical recording medium 100. ing. The recording layer (1) 103 and the recording layer (2) 108 record and reproduce optical information by the laser beam 110 incident from the substrate (2) 109 side of the positive laminate 12.

(Reverse laminate)
Next, each layer of the reverse laminate 11 constituting the optical recording medium 100 will be described. As shown in FIG. 1, the reverse laminate 11 includes a substrate (1) 101, a reflective layer (1) 102, a recording layer (1) 103, and an intermediate layer 104 (hereinafter referred to as “layer”) stacked on the substrate (1) 101. L1 layer)).

(Substrate (1))
It is desirable that the material constituting the substrate (1) 101 is light transmissive and has excellent optical properties such as a low birefringence. Further, it is desirable to have excellent moldability such as easy injection molding. Furthermore, it is desirable that the hygroscopicity is small. Furthermore, it is desirable to provide shape stability so that the optical recording medium 100 has a certain degree of rigidity. Examples of such materials include, but are not limited to, acrylic resins, methacrylic resins, polycarbonate resins, polyolefin resins (particularly amorphous polyolefins), polyester resins, polystyrene resins, epoxy resins, and glass. It is done. Moreover, what provided the resin layer which consists of radiation curable resins, such as photocurable resin, on base | substrates, such as glass, can be used. Among these, polycarbonate is preferable from the viewpoints of high productivity such as optical characteristics and moldability, cost, low hygroscopicity, and shape stability. Amorphous polyolefin is preferred from the standpoints of chemical resistance and low hygroscopicity. Moreover, a glass substrate is preferable from the viewpoint of high-speed response.

  Further, since the substrate (1) 101 does not necessarily need to be light transmissive, a backing made of an appropriate material can be provided in order to increase mechanical stability and increase rigidity. Examples of such a material include an Al alloy substrate such as an Al—Mg alloy containing Al as a main component; an Mg alloy substrate such as an Mg—Zn alloy containing Mg as a main component; silicon, titanium, ceramics, paper, etc. A substrate or a combination thereof may be mentioned.

  The groove depth of the guide groove portion of the substrate (1) 101 constituting the reverse laminated body 11 is usually λ / 100 or more, preferably 2λ / 100 or more, more preferably 3λ / 100, where λ is the recording / reproducing wavelength. However, λ / 6 or less is preferable. For example, when the wavelength of recording / reproducing light (recording / reproducing wavelength) is λ = 660 nm, the groove depth of the substrate (1) 101 is usually 6.6 nm or more, preferably 13 nm or more, and more preferably 20 nm or more. .

  In this example, the upper limit of the groove depth of the substrate (1) 101 is preferably 110 nm or less. In particular, in the case of the optical recording medium 100 to which the present embodiment is applied, the light amount and the reflected light amount of the laser light 110 incident on the recording layer (1) 103 through the substrate (2) 109 and the transparent resin layer 105 are recorded. Since it is attenuated by the layer (2) 108 and the reflective layer (2) 107 and the reflectance becomes low, the upper limit of the preferable groove depth is 7λ / 100 or less. For example, when the recording / reproducing wavelength is λ = 660 nm, the groove depth of the substrate (1) 101 is preferably 46.2 nm or less. More preferably, it is 6λ / 100 or less.

  The groove width of the substrate (1) 101 in the reverse laminated body 11 is usually T / 10 or more, preferably 2T / 10 or more, more preferably 3T / 10 or more, where T is the track pitch. However, it is usually 8T / 10 or less, preferably 7T / 10 or less, and more preferably 6T / 10 or less. If the groove width of the substrate (1) 101 is within this range, tracking can be performed satisfactorily and sufficient reflectance can be obtained. For example, when the track pitch is 740 nm, the groove width of the substrate (1) 101 is usually 74 nm or more, preferably 148 nm or more, and more preferably 222 nm or more. In this example, the upper limit is usually 592 nm or less, more preferably 518 nm or less, and still more preferably 444 nm or less. The substrate (1) 101 is preferably thick to some extent, and the thickness of the substrate (1) 101 is usually preferably 0.3 mm or more. However, it is 3 mm or less, preferably 1.5 mm or less.

(Reflective layer (1))
The material constituting the reflective layer (1) 102 of the reverse laminate 11 is not particularly limited. For example, Au, Al, Ag, Cu, Ti, Cr, Ni, Pt, Ta, Pd, Mg, Se, Hf , V, Nb, Ru, W, Mn, Re, Fe, Co, Rh, Ir, Zn, Cd, Ga, In, Si, Ge, Te, Pb, Po, Sn, Bi, rare earth metals, and the like It is possible to use the metal alone or as an alloy. Among these, Au, Al, and Ag are preferable, and a metal material containing 50% or more of Ag is particularly preferable from the viewpoint of low cost and high reflectance.

  Moreover, it is preferable to contain 0.1 atomic% to 15 atomic% of at least one element selected from the group consisting of Ag, Ti, Zn, Cu, Pd, Au, and rare earth metals. When two or more elements of Ti, Bi, Zn, Cu, Pd, Au, and rare earth metals are included, each content may be 0.1 to 15 atomic%, but the total content thereof is It is preferable that it is 0.1 atomic%-15 atomic%.

A more preferable alloy composition contains 0.1 atomic% to 15 atomic% of at least one element selected from the group consisting of Ti, Bi, Zn, Cu, Pd, and Au, containing Ag as a main component. , Containing at least one rare earth element in an amount of 0.1 atomic% to 15 atomic%. Of the rare earth metals, neodymium is particularly preferred. Specifically, AgPdCu, AgCuAu, AgCuAuNd, AgCuNd, AgBi, AgBiNd, and the like. The composition ratio of the alloy used in the present embodiment is in the above range.
“Containing Ag as a main component” means that the Ag in the alloy composition is usually 50% or more, preferably 70% or more, more preferably 80% or more. It is also possible to use pure Ag.

As the reflective layer (1) 102, a layer made only of Au is suitable because it has small crystal grains and is excellent in corrosion resistance. It is also possible to use a layer made of Si as the reflective layer (1) 102. Furthermore, it is also possible to form a multilayer film by alternately stacking a low refractive index thin film and a high refractive index thin film using a material other than metal, and use it as a reflective layer.
Examples of the method for forming the reflective layer (1) 102 include sputtering, ion plating, chemical vapor deposition, and vacuum vapor deposition.
It is desirable that the reflective layer (1) 102 in the reverse laminate 11 has high reflectivity and high durability. In order to ensure a high reflectance, the thickness of the reflective layer (1) 102 is usually 30 nm or more, preferably 40 nm or more, and more preferably 50 nm or more. However, in order to shorten the production tact time and reduce the cost, it is usually 400 nm or less, preferably 300 nm or less.

Here, in the optical recording medium 100 to which the present embodiment is applied, when the reflective layer (1) 102 of the reverse laminated body 11 includes a metal whose main component is silver, the thickness of the reflective layer (1) 102 is Is more preferably in the range of 30 nm to 80 nm. In particular, when the thickness of the reflective layer (1) 102 containing silver as a main component is in the range of 30 nm to 80 nm, energy is reduced by balancing the decrease in reflectance and the increase in transmittance of the reflective layer (1) 102. Diffusion occurs, and as a result, crosstalk tends to be improved.
In the reverse laminate 11, when the reflective layer (1) 102 contains a metal containing silver as a main component and the film thickness is in the specific range described above, the reason why the crosstalk tends to be improved is as follows. I think so. That is, as the thickness of the reflective layer (1) 102 is reduced, the reflectance (R) of the reflective layer (1) 102 decreases, while the transmittance (T) of the reflective layer (1) 102 increases. Here, FIG. 5 is a diagram for explaining the relationship between the thickness of the reflective layer and the transmittance (T), and the thickness of the reflective layer and the reflectance (R). FIG. 5A shows the relationship between the thickness of the reflective layer and the transmittance (T), and FIG. 5B shows the relationship between the thickness of the reflective layer and the reflectance (R). As shown in FIG. 5A, the transmittance (T) increases when the thickness of the reflective layer is thinner than around 80 nm, and the transmittance (T) exceeds 5% when the thickness is thinner than 30 nm. Further, as shown in FIG. 5B, the reflectance (R) decreases when the thickness of the reflective layer is thinner than around 80 nm, and the reflectance (R) is less than 85% when the thickness is thinner than 30 nm. . In FIG. 5, the reflectance (R) and the transmittance (T) are the single-layer silver reflective layer (however, the refractive index n = 0.05, the extinction coefficient k = 4) in the case of light having a wavelength of 650 nm. .25).
Thus, energy diffusion occurs as the transmittance (T) of the reflective layer (1) 102 increases. As a result, thermal interference within the recording marks and between the recording marks during recording in the recording layer (1) 103 is reduced. As a result, excessive heat storage and change in the recording layer (1) 103 are suppressed, and crosstalk is reduced. It is thought.
Further, by forming the reflective layer (1) 102 to be thinner than before, the reflective layer (1) 102 tends to cover (trace) the shape of the groove of the substrate more strictly. Therefore, even when the track pitch is narrowed, the groove portion and the inter-groove portion are clearly separated, so that crosstalk may be reduced.
However, if the thickness of the reflective layer (1) 102 is excessively thin, the reflectance (R) is drastically lowered, which is not preferable. Therefore, the film thickness of the recording layer (1) 103 is preferably 30 nm or more, and more preferably 40 nm or more. In general, the thickness of the reflective layer containing a metal whose main component is silver is 100 nm or more, but in this case, the transmittance (T) is low, so that energy diffusion hardly occurs. For this reason, the film thickness of the recording layer (1) 103 is preferably 80 nm or less.
Further, when the reflective layer (1) 102 is formed with a film thickness thinner than the usual 100 nm, the sputtering time can be shortened and the temperature rise of the substrate (1) 101 is reduced during sputtering. For this reason, since the aggregation of sputtered atoms is alleviated, the reflective layer (1) 102 having a small particle size, good quality and low surface roughness can be formed, and cost performance is also improved. The

(Recording layer (1))
The recording layer (1) 103 in the reverse laminated body 11 usually contains a dye having the same sensitivity as that of a recording layer used in a single-sided recording medium such as CD-R, DVD-R, DVD + R. Such a dye is preferably a dye compound having a maximum absorption wavelength λmax in the visible light to near infrared region of about 350 nm to 900 nm and suitable for recording with a blue to near microwave laser. Among them, a near-infrared laser having a wavelength of about 770 nm to 830 nm (for example, 780 nm and 830 nm) used for a normal CD-R, and a red laser having a wavelength of about 620 nm to 690 nm for a DVD-R (for example, 635 nm, (660 nm, 680 nm), and a dye suitable for recording by a so-called blue laser or the like having a wavelength of 410 nm or 515 nm. It is also possible to use a phase change material.

  Although it does not specifically limit as a pigment | dye used for the recording layer (1) 103, Usually, an organic pigment | dye material is used. Organic dye materials include, for example, macrocyclic azaannulene dyes (phthalocyanine dyes, naphthalocyanine dyes, porphyrin dyes, etc.), pyromethene dyes, polymethine dyes (cyanine dyes, merocyanine dyes, squarylium dyes, etc.), anthraquinone dyes, azurenium And dyes containing metal, metal-containing azo dyes, metal-containing indoaniline dyes, and the like. Among these, metal-containing azo dyes are preferable because they are excellent in recording sensitivity and excellent in durability and light resistance. These dyes may be used alone or in combination.

  The recording layer (1) 103 has a transition metal chelate compound (for example, acetylacetonate chelate, bisphenyldithiol, salicylaldehyde oxime, bisdithiol) as a singlet oxygen quencher to improve the stability and light resistance of the recording layer. α-diketone and the like) and a recording sensitivity improver such as a metal compound for improving the recording sensitivity. Here, the metal compound refers to a compound in which a metal such as a transition metal is included in the compound in the form of atoms, ions, clusters, etc., for example, ethylenediamine complex, azomethine complex, phenylhydroxyamine complex, phenanthroline complex. Organic metal compounds such as dihydroxyazobenzene complex, dioxime complex, nitrosoaminophenol complex, pyridyltriazine complex, acetylacetonate complex, metallocene complex, and porphyrin complex. Although it does not specifically limit as a metal atom, It is preferable that it is a transition metal.

  Furthermore, the recording layer (1) 103 can be used in combination with a binder, a leveling agent, an antifoaming agent, or the like, if necessary. Preferable binders include polyvinyl alcohol, polyvinyl pyrrolidone, nitrocellulose, cellulose acetate, ketone resin, acrylic resin, polystyrene resin, urethane resin, polyvinyl butyral, polycarbonate, polyolefin and the like.

  The film formation method of the recording layer (1) 103 is not particularly limited, but generally a thin film forming method generally performed such as a vacuum deposition method, a sputtering method, a doctor blade method, a casting method, a spin coating method, or an immersion method is used. Although mentioned, a wet film-forming method such as a spin coat method is preferable from the viewpoint of mass productivity and cost. Moreover, the vacuum evaporation method is preferable from the point that a uniform recording layer is obtained.

  In the case of film formation by spin coating, the number of rotations is preferably 10 rpm to 15000 rpm, and after spin coating, a heat treatment is generally performed to remove the solvent. The coating solvent for forming the recording layer by a coating method such as a doctor blade method, a casting method, a spin coating method, or a dipping method may be any solvent that does not attack the substrate and is not particularly limited. For example, ketone alcohol solvents such as diacetone alcohol and 3-hydroxy-3-methyl-2-butanone; cellosolv solvents such as methyl cellosolve and ethyl cellosolve; chain hydrocarbon solvents such as n-hexane and n-octane Cyclic hydrocarbon solvents such as cyclohexane, methylcyclohexane, ethylcyclohexane, dimethylcyclohexane, n-butylcyclohexane, tert-butylcyclohexane and cyclooctane; perfluoroalkyl alcohols such as tetrafluoropropanol, octafluoropentanol and hexafluorobutanol Examples of the solvent include hydroxycarboxylic acid ester solvents such as methyl lactate, ethyl lactate, and methyl 2-hydroxyisobutyrate.

  The heat treatment for removing these solvents is usually performed at a temperature slightly lower than the boiling point of the solvent used from the viewpoint of removing the solvent and using simple equipment, and is usually 60 ° C to 100 ° C. It is done in the range. The method for the heat treatment is not particularly limited. For example, after forming a film containing a dye-containing solution for forming the recording layer (1) 103 on the substrate (1) 101, a predetermined temperature is applied. And a predetermined time (usually 5 minutes or more, preferably 10 minutes or more, but usually within 30 minutes, preferably within 20 minutes). Further, a method of heating the substrate (1) 101 by irradiating infrared rays or far infrared rays for a short time (for example, 5 seconds to 5 minutes) is also possible.

In the case of the vacuum deposition method, for example, an organic dye and recording layer components such as various additives as necessary are put in a crucible installed in a vacuum vessel, and the inside of the vacuum vessel is 10 ⁻² by an appropriate vacuum pump. After evacuating to about 10 ⁻⁵ Pa, the crucible is heated to evaporate the recording layer components and evaporated onto a substrate placed facing the crucible.

  The thickness of the recording layer (1) 103 of the reverse laminate 11 is usually 50 nm or more, preferably 60 nm or more, but usually 150 nm or less, preferably 100 nm or less. When the thickness of the recording layer (1) 103 is within this range, it is possible to suppress a decrease in sensitivity while ensuring a sufficient recording signal amplitude. Further, when the thickness of the recording layer (1) 103 is excessively large, the sensitivity may be lowered.

(Middle layer)
The intermediate layer 104 is provided on the reverse laminated body 11 as necessary. In general, the intermediate layer 104 is provided between the recording layer (1) 103 and the transparent resin layer 105 in order to prevent components that ooze from the transparent resin layer 105 from contaminating or dissolving the recording layer (1) 103. It is done. The thickness of the intermediate layer 104 is usually 1 nm or more, preferably 2 nm or more. If the thickness of the intermediate layer 104 is within this range, the component that exudes from the transparent resin layer 105 can be effectively suppressed. However, the thickness of the intermediate layer 104 is preferably 2000 nm or less, and more preferably 500 nm or less. When the thickness of the intermediate layer 104 is within this range, it is possible to prevent a decrease in light transmittance. Further, in the case where the intermediate layer 104 is a layer made of an inorganic material, it may take time to form a film. Therefore, in order to suppress a decrease in productivity and increase the film stress in a favorable range, The thickness is preferably 200 nm or less. In particular, when a metal is used for the intermediate layer 104, the thickness of the intermediate layer 104 is preferably 20 nm or less in order to prevent the light transmittance from being excessively reduced.

Examples of the material constituting the intermediate layer 104 include dielectrics such as a metal thin film, silicon oxide, silicon nitride, MgF ₂ , SnO _{2, and} ZnS—SnO ₂ .
Incidentally, between the substrate (1) 101 and the recording layer (1) 103, between the substrate (2) 109 and the recording layer (2) 108, and between the recording layer (2) 108 and the reflective layer (2) 107. Alternatively, a layer made of the same material as the intermediate layer 104 may be provided.

(Transparent resin layer)
Next, the transparent resin layer 105 provided in contact with the incident surface side of the laser beam 110 of the reverse laminate 11 will be described.
The transparent resin layer 105 in the two-layer type optical recording medium 100 to which the present exemplary embodiment is applied is light transmissive so that the laser beam 110 incident from the substrate (2) 109 side reaches the recording layer (1) 103. Consists of materials. In particular, in relation to the reverse laminate 11, the product (E × t) of the elastic modulus (E) (unit: MPa) of the transparent resin layer 105 and the thickness (t) (unit: μm) of the transparent resin layer 105 is used. ) (Unit: MPa · μm) has a size equal to or larger than a predetermined numerical value, so that in the recording of optical information of the recording layer (1) 103 of the reverse laminated body 11, the adjacent track portion is excessively deformed. Can be suppressed. As a result, the optical recording medium 100 has reduced crosstalk in high-speed recording of the L1 layer and improved jitter. Here, “transparent” in the transparent resin layer 105 means that the transparent resin layer 105 does not have a structure for scattering the laser light 110 incident on the optical recording medium 100. Here, “scattering” refers to scattering that has a great influence on the recording / reproducing characteristics of the optical recording medium 100.

In the two-layer optical recording medium 100 to which this embodiment is applied, the elastic modulus (E) of the transparent resin layer 105 (unit: MPa, measured at a temperature of 25 ± 5 ° C.) and the transparent resin layer 105. Product (E × t) (unit: MPa · μm) with thickness (t) (unit: μm) of 2.0 × 10 ⁴ MPa · μm or more, preferably 2.5 × 10 ⁴ MPa · μm or more, more preferably 4.0 × 10 ⁴ MPa · μm or more, still more preferably 5.0 × 10 ⁴ MPa · μm or more, particularly preferably 7.0 × 10 ⁴ MPa · μm or more, and particularly preferably Is 9.0 × 10 ⁴ MPa · μm or more, and most preferably 10.0 × 10 ⁴ MPa · μm or more. When (E × t) is 2.0 × 10 ⁴ MPa · μm or more, the mechanical strength (rigidity) of the transparent resin layer 105 can be secured, and the recording layer (1) of the L1 layer (FIG. 1) In the recording of the optical information 103, excessive deformation can be suppressed in the adjacent track portion.

However, the upper limit of the product (E × t) (unit: MPa · μm) of the elastic modulus (E) (unit: MPa) of the transparent resin layer 105 and the thickness (t) (unit: μm) of the transparent resin layer 105 Is usually 30.0 × 10 ⁴ MPa · μm or less, preferably 21.0 × 10 ⁴ MPa · μm or less, more preferably 17.5 × 10 ⁴ MPa · μm or less, and even more preferably 13.5 × 10 ⁴ MPa · μm or less. When the upper limit of (E × t) is 30.0 × 10 ⁴ MPa · μm or less, the L1 layer (FIG. 1) of the two-layer optical recording medium 100 can be focused well, and recording can be performed. The layer (1) 103 can be appropriately recorded and reproduced. Further, for example, in the case of a film surface incident type optical recording medium, the focal length of the objective lens can be reduced, and high-density recording can be performed satisfactorily.

As the resin constituting the transparent resin layer 105, the elastic modulus (E) is usually 1.0 × 10 ³ MPa or more, preferably 2.0 × 10 ³ MPa or more, more preferably 3.0 × 10 ^3. MPa or more, more preferably 4.0 × 10 ³ MPa or more. By forming the transparent resin layer 105 using a resin having an elastic modulus (E) of 1.0 × 10 ³ MPa or more and (E × t) of 2.0 × 10 ⁴ MPa · μm or more, L1 In the recording / reproducing of the layer (FIG. 1), the so-called confinement effect is further enhanced. However, the upper limit of the elastic modulus (E) is usually 6.0 × 10 ³ MPa or less. By using a resin having an elastic modulus (E) of 6.0 × 10 ³ MPa or less, for example, the transparent resin layer 105 can be formed by a solution method such as coating, which is industrially advantageous.

  Next, the thickness (t) of the transparent resin layer 105 will be described. FIG. 3 is a diagram for explaining the thickness (t) of the transparent resin layer. FIG. 3A shows a case where the transparent resin layer is composed of a single resin, and FIG. 3B shows a case where the transparent resin layer is composed of a plurality of resin layers. That is, the thickness (t) of the transparent resin layer 105 is determined when the transparent resin layer 105 is made of a single resin (case a) and when the transparent resin layer 105 is made of a plurality of resin layers ( Case b) is explained as follows.

(Case a)
As shown to Fig.3 (a), when the transparent resin layer which contact | connects a reverse laminated body is comprised with single resin, it is 1/2 (h / 2) of the film thickness (h) of a transparent resin layer. The thickness of the transparent resin layer is defined as the thickness of the portion on the side in contact with the reverse laminate.
When the transparent resin layer 105 is made of a single resin, it is the portion that is in contact with the reverse laminate 11 of the transparent resin layer 105 that has a great influence on the crosstalk of the L1 layer of the reverse laminate 11. Conceivable. That is, when the optical information is recorded on the recording layer (1) 103 of the L1 layer, the portion of the transparent resin layer 105 that is not in contact with the reverse laminate 11 is a local region that suppresses expansion in the adjacent track direction. It is thought that the work which gives binding power is scarce. Therefore, when the transparent resin layer 105 is made of a single resin, it is half of the distance between the L1 layer and the L0 layer (see FIG. 1), and the portion on the side in contact with the reverse laminated body 11 The film thickness is defined as the thickness (t) of the transparent resin layer 105.

  In the case of the two-layer optical recording medium 100 shown in FIG. 1, the film thickness (h) of the transparent resin layer 105 is usually 200 μm or less, preferably 100 μm, more preferably 80 μm or less. In particular, in the DVD double-layer disc standard, the distance between the L1 layer and the L0 layer is preferably 40 μm to 70 μm. In this case, the film thickness (h) of the transparent resin layer 105 is preferably 70 μm or less. For example, in the case (case a), the thickness (t) of the transparent resin layer 105 is usually 20 μm or more. If the film thickness (h) of the transparent resin layer 105 is 5 μm or less, the thickness (t) of the transparent resin layer 105 is 5 μm. When the film thickness (h) of the transparent resin layer 105 is 35 μm or more, the thickness (t) of the transparent resin layer 105 is set to 35 μm.

In the case (case a), when the thickness (t) of the transparent resin layer 105 is within this range, the L1 layer of the two-layer optical recording medium 100 can be focused well, and the L0 layer And the L1 layer can be optically separated and reproduced satisfactorily, and the recording layer (1) 103 can be appropriately recorded and reproduced. For example, as will be described later, in the case of a film surface incident type optical recording medium as shown in FIG. 2, the focal length of the objective lens can be reduced, and high-density recording can be performed satisfactorily. In particular, in the two-layer optical recording medium 100, the thickness (t) of the transparent resin layer 105 in the case (case a) is most preferably 20 μm to 28 μm. When the thickness (t) of the transparent resin layer 105 in the case (c) is within such a range, the elastic modulus (E) of the transparent resin layer 105 and the thickness (t) of the transparent resin layer 105 When the product (E × t) is 2.0 × 10 ⁴ (MPa · μm) or more, stable L1 layer recording is possible.

(Case b)
Next, as shown in FIG. 3B, the transparent resin layer is composed of a plurality of resin layers (transparent resin layer (1), transparent resin layer (2)... Transparent resin layer (n)). The thickness (t) of the transparent resin layer is defined as the thickness of the resin layer in contact with the reverse laminate among the plurality of resin layers. However, when the film thickness of the transparent resin layer (1) in contact with the reverse laminate is 35 μm or more, the thickness (t) of the transparent resin layer is 35 μm.

  As a manufacturing method of the two-layer optical recording medium 100, for example, a light-transmitting resin A is applied on the reverse laminate 11 having the L1 layer, and on the positive laminate 12 having the L0 layer. There is a method in which resin B is applied, resin A and resin B are brought into contact with each other and cured to prepare a two-layer disc. In this case, as described above, the resin layer on the side of the transparent resin layer 105 that is not in contact with the reverse laminate 11 (resin layer composed of the resin B) transmits optical information to the recording layer (1) 103 of the L1 layer. In the case of recording, it is considered that the function of giving local restraining force that suppresses expansion in the adjacent track direction is poor. Therefore, an ultraviolet curable resin, an ultraviolet curable adhesive, or the like different from the resin layer on the side in contact with the reverse laminate 11 can be used for the resin layer on the front laminate 12 side having the L0 layer. In addition, the transparent resin layer 105 is preferably formed by laminating a flexible resin layer that can relieve the overall stress and a resin layer having (E × t) equal to or greater than a predetermined value.

  In the case (b), the entire film thickness of the transparent resin layer 105 of the two-layer optical recording medium 100 is usually 200 μm or less, preferably 100 μm or less, more preferably 80 μm or less. In particular, in the DVD double-layer disc standard, the distance between the L1 layer and the L0 layer is 40 μm to 70 μm. When the film thickness of the resin layer (FIG. 3 (b) transparent resin layer (1)) in contact with the reverse laminate 11 among the transparent resin layers 105 composed of a plurality of resin layers is 35 μm or more, a transparent resin The thickness (t) of the layer 105 is 35 μm. The film thickness of the resin layer in contact with the reverse laminate 11 (FIG. 3 (b) transparent resin layer (1)) is usually preferably 3 μm or more, more preferably 4 μm or more, further preferably 10 μm, and particularly preferably 15 μm or more. is there. When the thickness (t) of the transparent resin layer 105 is excessively small, the crosstalk reduction effect may not be sufficiently exhibited.

  In addition, when the film thickness of the resin layer (FIG. 3 (b) transparent resin layer (1)) in contact with the reverse laminate 11 among the transparent resin layers 105 composed of a plurality of resin layers is 5 μm or less, the thickness is With (t) being 5 μm, (E × t) is calculated by the following method. That is, the product (E × t) of the elastic modulus (E) of the transparent resin layer 105 and the thickness (t) of the transparent resin layer 105 is a transparent resin as a composite of resin layers corresponding to a thickness (t) of 5 μm. It calculates from a layer (1) and a transparent resin layer (2). That is, for example, the elastic modulus of the resin layer in contact with the reverse laminate 11 (FIG. 3B, transparent resin layer (1)) is E1, the film thickness is 1 μm, and the resin layer in contact with the reverse laminate 11 (FIG. 3B). When the elastic modulus E2 of the resin layer (transparent resin layer (2) in FIG. 3B) adjacent to the transparent resin layer (1)), (E × t) is calculated as E1 × 1 + E2 × 4. In this example, the total film thickness of the transparent resin layer (1) and the transparent resin layer (2) is 5 μm or more. For example, when the transparent resin layer (1), the transparent resin layer (2), and the transparent resin layer (3) are 5 μm, (E × t) may be calculated according to the calculation example described above.

Next, specific examples of the material constituting the transparent resin layer 105 will be described.
Examples of the material constituting the transparent resin layer 105 include a thermoplastic resin, a thermosetting resin, an electron beam curable resin, an ultraviolet curable resin (including a delayed curable type), and the like. The material which comprises the transparent resin layer 105 is suitably selected from these. A thermoplastic resin, a thermosetting resin, etc. can be formed by dissolving in an appropriate solvent as necessary to prepare a coating solution, applying the solution, and drying (heating). The ultraviolet curable resin can be formed by preparing a coating solution as it is or by dissolving it in a suitable solvent, and then applying the coating solution and curing it by irradiating with ultraviolet light. These materials may be used alone or in combination.

As a coating method, a method such as a spin coating method or a casting method is used, and among these, the spin coating method is preferable. High-viscosity resin can be applied and formed by screen printing or the like. As the ultraviolet curable resin, it is preferable to use a resin that is liquid at 20 ° C. to 40 ° C. This is because productivity can be improved because it can be applied without using a solvent. The viscosity of the coating solution is preferably adjusted to be 20 mPa · s to 1.0 × 10 ³ mPa · s.

  Among the materials constituting the transparent resin layer 105, an ultraviolet curable resin is preferable because of its high transparency and a short curing time, which is advantageous in manufacturing. Examples of the ultraviolet curable resin include a radical ultraviolet curable resin and a cationic ultraviolet curable resin, both of which can be used. As the radical ultraviolet curable resin, a composition containing an ultraviolet curable compound and a photopolymerization initiator as essential components is used. As an ultraviolet curable compound, monofunctional (meth) acrylate and polyfunctional (meth) acrylate can be used as a polymerizable monomer component. These can be used alone or in combination of two or more. Here, acrylate and methacrylate are collectively referred to as (meth) acrylate.

  Examples of monofunctional (meth) acrylates include methyl, ethyl, propyl, butyl, amyl, 2-ethylhexyl, octyl, nonyl, dodecyl, hexadecyl, octadecyl, cyclohexyl, benzyl, methoxyethyl, butoxyethyl, and phenoxyethyl as substituents. , Nonylphenoxyethyl, tetrahydrofurfuryl, glycidyl, 2-hydroxyethyl, 2-hydroxypropyl, 3-chloro-2-hydroxypropyl, dimethylaminoethyl, diethylaminoethyl, nonylphenoxyethyl tetrahydrofurfuryl, caprolactone-modified tetrahydrofurfuryl, And (meth) acrylate having a group such as isobornyl, dicyclopentanyl, dicyclopentenyl, dicyclopentenyloxyethyl and the like.

  Examples of the polyfunctional (meth) acrylate include 1,3-butylene glycol, 1,4-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, neo Di (meth) acrylates such as pentyl glycol, 1,8-octanediol, 1,9-nonanediol, tricyclodecane dimethanol, ethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, polypropylene glycol, And di (meth) acrylate of tris (2-hydroxyethyl) isocyanurate.

  In addition, di (meth) acrylate of diol obtained by adding 4 mol or more of ethylene oxide or propylene oxide to 1 mol of neopentyl glycol, and diol obtained by adding 2 mol of ethylene oxide or propylene oxide to 1 mol of bisphenol A Di (meth) acrylate, 3 mol or more of ethylene oxide or propylene oxide added to 1 mol of trimethylolpropane, diol or tri (meth) acrylate of triol, 4 mol or more of ethylene oxide or propylene per 1 mol of bisphenol A Di (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, dipentaerythritol, and diols obtained by adding oxide. (Meth) acrylate, ethylene oxide-modified phosphoric acid (meth) acrylate, ethylene oxide-modified alkylated phosphoric acid (meth) acrylate.

  Moreover, as what can be used together with these polymerizable monomers, polyester (meth) acrylate, polyether (meth) acrylate, epoxy (meth) acrylate, urethane (meth) acrylate etc. are mentioned as a polymerizable oligomer.

  Furthermore, a photopolymerization initiator is usually blended with the radical ultraviolet curable resin. The photopolymerization initiator is preferably a molecular cleavage type or a hydrogen abstraction type. As such a photopolymerization initiator, examples of the molecular cleavage type include benzoin isobutyl ether, 2,4-diethylthioxanthone, 2-isopropylthioxanthone, benzyl, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, 2- Examples include benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butan-1-one, bis (2,6-dimethoxybenzoyl) -2, 4,4-trimethylpentylphosphine oxide, and the like.

  Further, 1-hydroxycyclohexyl phenyl ketone, benzoin ethyl ether, benzyldimethyl ketal, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1- (4-isopropylphenyl) -2-hydroxy-2-methyl Propan-1-one and 2-methyl-1- (4-methylthiophenyl) -2-morpholinopropan-1-one may be used in combination. Examples of the hydrogen abstraction type photopolymerization initiator include benzophenone, 4-phenylbenzophenone, isophthalphenone, 4-benzoyl-4'-methyl-diphenyl sulfide, and the like.

  A sensitizer can be used in combination with these photopolymerization initiators. Examples of the sensitizer include trimethylamine, methyldimethanolamine, triethanolamine, p-diethylaminoacetophenone, ethyl p-dimethylaminobenzoate, isoamyl p-dimethylaminobenzoate, N, N-dimethylbenzylamine and 4, 4′-bis (diethylamino) benzophenone and the like can be mentioned.

  Examples of the cationic ultraviolet curable resin include an epoxy resin containing a cationic polymerization type photoinitiator. Examples of the epoxy resin include bisphenol A-epichlorohydrin type, alicyclic epoxy, long chain aliphatic type, brominated epoxy resin, glycidyl ester type, glycidyl ether type, and heterocyclic type. As the epoxy resin, it is preferable to use a resin having a low content of free chlorine and chlorine ions. The amount of chlorine is preferably 1% by weight or less, more preferably 0.5% by weight or less.

  Examples of the cationic polymerization type photoinitiator include sulfonium salts, iodonium salts, diazonium salts and the like. Examples of the iodonium salt include diphenyliodonium hexafluorophosphate, diphenyliodonium hexafluoroantimonate, diphenyliodonium tetrafluoroborate, diphenyliodonium tetrakis (pentafluorophenyl) borate, bis (dodecylphenyl) iodonium hexafluorophosphate, bis (dodecyl). Phenyl) iodonium hexafluoroantimonate, bis (dodecylphenyl) iodonium tetrafluoroborate, bis (dodecylphenyl) iodonium tetrakis (pentafluorophenyl) borate and the like.

  Further, 4-methylphenyl-4- (1-methylethyl) phenyliodonium hexafluorophosphate, 4-methylphenyl-4- (1-methylethyl) phenyliodonium hexafluoroantimonate, 4-methylphenyl-4- (1 -Methylethyl) phenyliodonium tetrafluoroborate, 4-methylphenyl-4- (1-methylethyl) phenyliodonium tetrakis (pentafluorophenyl) borate and the like.

  The proportion of the cationic polymerization photoinitiator per 100 parts by weight of the cationic ultraviolet curable resin is usually 0.1 to 20 parts by weight, preferably 0.2 to 5 parts by weight. A known photosensitizer can be used in combination in order to use the near-ultraviolet region and the visible region of the ultraviolet light source more effectively. Examples of the photosensitizer at this time include anthracene, phenothiazine, benzylmethyl ketal, benzophenone, and acetophenone.

  In addition, for UV curable resins, as necessary, other additives include thermal polymerization inhibitors, antioxidants represented by hindered phenols, hindered amines, phosphites, plasticizers, epoxy silanes, mercaptosilanes, and the like. Silane coupling agents represented by (meth) acrylic silane and the like can also be blended for the purpose of improving various properties. These are selected from those having excellent solubility in ultraviolet curable compounds and those that do not impair ultraviolet transparency.

In the optical recording medium 100 to which this embodiment is applied, the product (E × t) of the elastic modulus (E) and the thickness (t) of the transparent resin layer 105 is 2.0 × 10 ⁴ MPa · μm or more. Specific means for achieving the above are not particularly limited, but in order to expand the adjustment range of the film thickness while preparing a resin having an appropriate hardness within the optimum film thickness range, the following methods may be mentioned. . For example, a method of increasing the composition of a monomer component having 2 or more, preferably 3 or more methacryloyl groups in the molecule as the above-mentioned ultraviolet curable resin; side chain such as polyester diol mixed with a linear polymer diol A method of increasing the composition of the containing polymer diol component; a method of increasing the intramolecular bond by lowering the side chain of the oligomer component whose main chain is a hard segment; polyisocyanate compound, amino resin, epoxy compound, silane compound, Examples thereof include a method of adding a predetermined amount of a crosslinking agent such as a metal chelate compound. By such means, the elastic modulus of the transparent resin layer 105 itself can be increased, and the glass transition temperature (Tg) of the resin constituting the transparent resin layer 105 can be increased to, for example, about 150 ° C. or more.

Among the ultraviolet curable resins, a cationic ultraviolet curable resin that can be applied by spin coating is preferable because of its low light scattering property and low viscosity. Furthermore, when the thickness of the transparent resin layer 105 is 10 μm or more, it is not necessary to consider the inhibition of curing by oxygen, so there are many types, and the blending ratio and the degree of freedom of composition are large. It is preferable to use it.
In addition, it is possible to detect a transparent resin layer also from an optical recording medium (product) by the following method.
(1) The optical disk is broken and the taken-out disk cross section is observed with a secondary electron microscope (SEM) to observe the fine structure (structure) of the transparent resin layer. If the difference in the microstructure of the transparent resin layer is observed between the transparent resin layers in the thickness direction, it is understood that the transparent resin layer is a laminate of different resins.
(2) The cross section of the transparent resin layer is measured by a microscopic FT-IR method to obtain an infrared absorption spectrum of the transparent resin layer. Compared with the infrared absorption spectrum of the resin used as the reference sample by the above method, the composition of the resin can be specified to some extent in relation to the reference spectrum. If there is a difference in the infrared absorption spectrum between the transparent resin layers in the thickness direction, it is understood that the layers are laminated with different resins. Their composition can also be specified to some extent by comparison with the above reference sample.
(3) The transparent resin layer can be analyzed by a pyrolysis GC-MS method to know the resin composition.
(4) The transparent resin layer is peeled off and taken out, and its Tg and elastic modulus can be directly measured by a dynamic viscoelasticity measuring device.

(Normal laminate)
Next, the positive laminated body 12 which comprises the optical recording medium 100 with which this Embodiment is applied is demonstrated. As shown in FIG. 1, the positive laminate 12 includes a substrate (2) 109 having an incident surface of a laser beam 110 as recording / reproducing light, a recording layer (2) 108, and a reflective layer on the substrate (2) 109. (2) 107 and a protective coat layer 106 are sequentially laminated (hereinafter also referred to as L0 layer).

  The substrate (2) 109 of the positive laminate 12 is made of the same material as the substrate (1) 101 of the reverse laminate 11. However, the substrate (2) 109 needs to be light transmissive. The groove width (half width) of the substrate (2) 109 is usually 2T / 10 or more, preferably 3T / 9 or more, where T is the track pitch. If it is this range, a sufficient reflectance can be secured. For example, when the track pitch is 740 nm, the groove width of the substrate (2) 109 is usually 148 nm or more, preferably 246 nm or more. However, the groove width of the substrate (2) 109 is usually 7T / 10 or less, preferably 6T / 10 or less. For example, when the track pitch is 740 nm, the groove width of the light-transmitting substrate (2) 109 is usually 518 nm or less, preferably 444 nm or less, because the groove shape transferability can be improved.

  The groove depth of the substrate (2) 109 is usually preferably λ / 10 or more when the recording / reproducing light wavelength is λ, because a sufficient reflectance can be secured. More preferably, it is λ / 8 or more, more preferably λ / 6 or more. For example, when the wavelength of recording / reproducing light (recording / reproducing wavelength) is λ = 660 nm, the groove depth of the substrate (2) 109 is usually 66 nm or more, preferably 83 nm or more, and more preferably 110 nm or more. However, the upper limit of the groove depth of the substrate (2) 109 is usually preferably 2λ / 5 or less because the transferability of the groove shape can be improved, and more preferably 2λ / 7 or less. For example, when the recording / reproducing wavelength is 660 nm, it is usually 264 nm or less, preferably 189 nm or less.

(Recording layer (2))
The recording layer (2) 108 of the positive laminate 12 contains the same dye as the recording layer (1) 103 of the reverse laminate 11. The thickness of the recording layer (2) 108 of the positive laminate 12 is not particularly limited because the suitable film thickness differs depending on the recording method or the like, but is usually 20 nm or more, preferably 30 nm, in order to obtain a sufficient degree of modulation. It is above, Especially preferably, it is 40 nm or more. However, since it is necessary to transmit light, it is usually 200 nm or less, preferably 180 nm or less, more preferably 150 nm or less. The thickness of the recording layer (2) 108 indicates the thickness of the thick film portion (the thickness of the recording layer (2) 108 in the groove portion of the substrate (2) 109).

(Reflective layer (2))
The reflective layer (2) 107 of the regular laminate 12 is made of the same material as the reflective layer (1) 102 of the reverse laminate 11. The reflective layer (2) 107 of the positive laminate 12 has a small absorption of the laser beam 110, which is a recording / reproducing light incident from the substrate (2) 109 side, has a light transmittance of usually 40% or more, and is usually Therefore, it is necessary to have an appropriate light reflectance of 30% or more. For example, an appropriate transmittance can be provided by providing a thin metal with high reflectivity. Moreover, it is desirable that there is some degree of corrosion resistance. Furthermore, the recording layer (2) 108 located below the reflective layer (2) 107 is not affected by other components that ooze out from the upper layer (here, the transparent resin layer 105) of the reflective layer (2) 107. It is desirable to have sex.

  The thickness of the reflective layer (2) 107 is usually 50 nm or less, preferably 30 nm or less, more preferably 25 nm or less in order to ensure that the light transmittance is usually 40% or more. However, since the recording layer (2) 108 is not affected by the component exuding from the upper layer of the reflective layer (2) 107, it is usually 3 nm or more, preferably 5 nm or more.

(Protective coat layer)
The protective coating layer 106 of the regular laminate 12 is provided on the transparent resin layer 105 side of the reflective layer (2) 107 for the purpose of preventing oxidation of the reflective layer (2) 107, and preventing dust or scratches. The material of the protective coat layer 106 is not particularly limited as long as it protects the reflective layer (2) 107. Examples of the material of the organic substance include a thermoplastic resin, a thermosetting resin, an electron beam curable resin, and an ultraviolet curable resin. Examples of the inorganic substance include dielectrics such as silicon oxide, silicon nitride, MgF ₂ , and SnO ₂ . Especially, it is preferable to laminate | stack an ultraviolet curable resin layer. The protective coat layer 106 is not necessarily provided, and the transparent resin layer 105 may be directly formed on the reflective layer (2) 107.

(Second Embodiment)
Next, FIG. 2 is a diagram for explaining a second embodiment of an optical recording medium to which the present embodiment is applied. FIG. 2 shows a film surface incident type optical recording medium 200 in which optical information is recorded / reproduced by recording / reproducing light incident from the side opposite to the substrate side. As shown in FIG. 2, the optical recording medium 200 protects the substrate 201, the reflective layer 202 provided on the substrate 201, the recording layer 203 laminated on the reflective layer 202, and the recording layer 203. For this purpose, a transparent resin layer 205 is further laminated on the incident surface side of the laser beam 210 on the reverse laminate including the intermediate layer 204 provided for the purpose. In the optical recording medium 200, information is recorded / reproduced by a laser beam 210 applied to the recording layer 203 from the transparent resin layer 205 side. The intermediate layer 204 is provided as necessary, and is not necessarily essential.

The substrate 201 constituting the inverse laminate is formed using the same material as the substrate (1) 101 of the inverse laminate 11 in the optical recording medium 100 of the first embodiment. Similarly, the materials constituting the reflective layer 202, the recording layer 203, and the intermediate layer 204 are the reflective layer (1) 102 and the recording layer of the reverse laminate 11 of the optical recording medium 100 of the first embodiment, respectively. (1) The same materials as those described in 103 and the intermediate layer 104 can be used. The thickness of each layer is the same as the range described in the optical recording medium 100 described above.
Further, the transparent resin layer 205 is configured using the same material as the transparent resin layer 105 in the optical recording medium 100 described above, and the product of the elastic modulus (E) and thickness (t) of the transparent resin layer 205. (E × t) is prepared in the same range as the transparent resin layer 105 in the optical recording medium 100 of the first embodiment. That is, the thickness (t) of the transparent resin layer 205 is the same as that of the transparent resin layer 105 in the optical recording medium 100 of the first embodiment. The thickness (t) of the portion of the resin layer 205 that is a half (h / 2) of the thickness (h) of the resin layer 205 and that is in contact with the reverse laminate is the thickness (t) of the transparent resin layer. When the transparent resin layer 205 is composed of a plurality of resin layers, the thickness of the resin layer in contact with the reverse laminate among these resin layers is the thickness (t) of the transparent resin layer 205. However, when the film thickness of the resin layer in contact with the reverse laminate is 35 μm or more, the thickness (t) of the transparent resin layer 205 is set to 35 μm.

Hereinafter, the present embodiment will be described more specifically based on examples. In addition, this Embodiment is not limited to a following example, unless the summary is exceeded.
(Example 1 to Example 7)
As described below, a two-layer optical recording medium having a reverse laminate was prepared, and MT (%) and ST (%) of optical information recorded on the recording layer (1) constituting the reverse laminate were measured. .

(Preparation of optical recording medium)
(1) (Preparation of reverse laminate)
First, a substrate having a diameter of 120 mm and a thickness of 0.60 mm in which grooves having a pitch of 0.74 μm, a width of 330 nm, and a depth of 30 nm are formed by injection molding polycarbonate using a Ni stamper having grooves formed on the surface. (1) was formed. Next, an Ag—Bi—Nd alloy was sputtered to a thickness of 80 nm on the substrate (1) to form a reflective layer (1). Next, a tetrafluoropropanol solution (concentration 2% by weight) of a mixture (A: B = 60: 40% by weight) of a metal-containing azo dye represented by the following chemical formula (A: B = 60: 40% by weight) is prepared as an organic dye compound. Then, it was dropped on the reflective layer (1), spin-coated, and then dried at 70 ° C. for 30 minutes to form a recording layer (1). The thickness of the recording layer (1) is the film thickness of the groove (recording layer thickness of the groove of the reverse laminate in FIG. 1) and the film thickness of the groove (recording layer of the groove of the reverse laminate in FIG. 1). The film thickness was about 80 nm.

Subsequently, on the recording layer (1), ZnS—SiO ₂ (composition ratio: 80:20 atomic%) was sputtered to a thickness of 130 nm to form an intermediate layer, thereby preparing a disc 1 having a reverse laminate.

(2) (Preparation of regular laminate)
A polycarbonate substrate (2) having guide grooves having a depth of 160 nm, a width of 300 nm, and a track pitch of 740 nm was prepared, and the above-described metal-containing azo dye was formed on the surface of the substrate (2) where the guide grooves were formed. A tetrafluoropropanol solution (concentration 1 wt% to 2 wt%) of a mixture of A and Dye B (A: B = 60: 40 wt%) was added dropwise, spin-coated, and then dried at 70 ° C. for 30 minutes, A recording layer (2) was formed. The thickness of the recording layer (2) (FIG. 1: the recording layer thickness of the groove of the positive laminate) was about 100 nm. Next, an Ag-Bi alloy (Bi: 1.0 atomic%) is sputtered to 17 nm on the recording layer (2) to form a reflective layer (2). Further, an ultraviolet curable resin (2) is formed on the reflective layer (2). SD347) was spin-coated and cured to form a protective coating layer having a thickness of 3 μm, and a positively laminated disk 2 was prepared.

(3) (Preparation of two-layer type optical recording medium)
On the intermediate layer of the disk 1 which is the reverse laminate prepared by the above-described method, resin A (Dainippon Ink Co., Ltd. radical UV curable resin: elastic modulus (E) = 4.0 × 10 ³ MPa, The glass transition temperature (Tg) = 174 ° C. was applied by adjusting the spin coat rotation speed so that the film thickness was 23 μm. Moreover, on the protective coating layer of the disk 2 which is a regular laminate, resin F (Dainippon Ink Co., Ltd. radical UV curable resin SD-6036: elastic modulus (E) = 680 MPa, glass transition temperature (Tg) = 50 ° C.) was similarly applied by adjusting the spin coat rotation speed so that the film thickness was 23 μm. Next, the disc 1 and the disc 2 each coated with resin are overlapped so that the surfaces coated with the resin face each other, and then, ultraviolet rays are irradiated from the substrate (2) side of the disc 2 (regular laminate). Then, the resin A and the resin F were cured to form a transparent resin layer made of the resin A and a transparent resin layer made of the resin F, respectively, to prepare a two-layer type optical recording medium (Sample 1).

  Subsequently, in the same manner as in Sample 1, the resin F was applied on the protective coating layer of the disk 2 which is a positive laminate so as to have a film thickness of 23 μm. On the other hand, as shown in Table 1, for the disk 1 that is a reverse laminate, a resin B, a resin C, and a resin D having a predetermined elastic modulus (E) are respectively formed on the intermediate layer of the reverse laminate, as shown in Table 1. The disc 1 coated with these resins and the disc 2 coated with the resin F are opposite to each other in the same manner as the sample 1 with the surface coated with the resin. And then irradiating ultraviolet rays from the substrate (2) side of the disk 2 (regular laminate) to cure each applied resin to form a transparent resin layer made of two types of resins. Thus, two-layer type optical recording media were prepared (Sample 3, Sample 5, Sample 6, Sample 7).

  Further, no resin is applied on the disk 2 that is the normal laminate, while the disk 1 that is the reverse laminate is formed on the intermediate layer of the disk 1 as shown in Table 1, as shown in Table 1. C is applied so as to have a predetermined thickness (t) shown in Table 1, and the disk 1 coated with resin and the disk 2 not coated with resin are overlapped, and then the disk 2 (regular laminate) Were irradiated with ultraviolet rays from the substrate (2) side to cure each applied resin, and a transparent resin layer made of a single resin was formed to prepare a two-layer type optical recording medium (Sample 2, Sample 4). ).

In addition, the thickness (t) of the transparent resin layer shown in Table 1 is about the optical recording media of Sample 1, Sample 3, Sample 5, Sample 6, and Sample 7 having transparent resin layers made of two types of resins. It is the thickness of the resin layer in contact with the reverse laminate (case b), and for the optical recording media of Sample 2 and Sample 4 having a transparent resin layer made of a single resin, it is half the film thickness of the entire transparent resin layer. 1 (case a). The total film thickness of the transparent resin layer in the optical recording media of Samples 1 to 7 is 46 μm.
On the recording layer (1) constituting the reverse laminate in the optical recording medium (sample 1 to sample 7) thus prepared, optical information is recorded under the following high-speed recording conditions, and the recorded optical information is reproduced, MT (%) and ST (%) were measured. The results are shown in Table 1.

The conditions for high-speed recording of optical information are as follows.
Evaluation machine: DDU-1000 manufactured by Pulse Tech (wavelength 662 nm, NA = 0.65)
Recording speed: 4 times faster than DVD (Linear measure 15.3m / s)
Recording pulse strategy: DVD-R standard Ver. Compliant with the description in 2.1.
Recording power: 26 mW to 27.5 mW
Recording power margin: 3 mW or more Jitter measurement: Playback at 1 × speed.

(Reference Examples 1 to 3)
A two-layer optical recording medium having a reverse laminate was prepared as follows, and MT (%) and ST (%) of optical information were measured in the same manner as in Example 1.
Similar to Sample 1 used in Example 1, Resin F was applied on the protective coating layer of the disk 2 as a positive laminate so as to have a film thickness of 23 μm. On the other hand, as shown in Table 1, for the disk 1 that is an inversely laminated body, the resin E and the resin C having a predetermined elastic modulus (E) are respectively shown in Table 1 on the intermediate layer of the inversely laminated body. The disk 1 coated with these resins and the disk 2 coated with the resin F are coated so as to have a predetermined thickness (t), and the surfaces coated with the resin are opposed to each other in the same manner as the sample 1. Next, ultraviolet rays are irradiated from the substrate (2) side of the disk 2 (regular laminate) to cure each applied resin to form a transparent resin layer made of two types of resins. Layer-type optical recording media were prepared (Sample 8, Sample 9).

  Further, no resin is applied on the disk 2 which is a normal laminate, while the resin 1 which is a reverse laminate is represented by the resin F on the intermediate layer of the disk 1 as shown in Table 1. The disc 1 coated with the resin F and the disc 2 coated with the resin F are overlapped with each other, and then the substrate of the disc 2 (regular laminate) ( 2) The resin applied by irradiating ultraviolet rays from the side was cured to form a transparent resin layer made of a single resin to prepare a two-layer type optical recording medium (Sample 10).

In addition, the thickness (t) of the transparent resin layers of Sample 8 to Sample 10 is the same as that of the resin layer in contact with the reverse laminate for the optical recording media of Sample 8 and Sample 9 having transparent resin layers made of two types of resins. The thickness (case b) of sample 10 having a transparent resin layer made of a single resin is half the thickness of the entire transparent resin layer (case a). The total film thickness of the transparent resin layer in the optical recording media of Sample 8 to Sample 10 is 46 μm.
For the optical recording media (sample 8 to sample 10) prepared in this manner, optical information was recorded on the recording layer (1) constituting the reverse laminated body under high-speed recording conditions in the same manner as in Example 1. Information was reproduced and MT (%) and ST (%) were measured. The results are shown in Table 1.

  In Table 1, the elastic modulus (E (unit: MPa)) of the resin used for the preparation of the transparent resin layer in samples 1 to 10, the thickness of the transparent resin layer (t (unit: μm)), glass The transition temperature (Tg (unit: ° C)) is also shown. The elastic modulus (E) was measured using a dynamic viscoelasticity tester (manufactured by Leo Vibron: DDV series) under the conditions of a measurement frequency of 3.5 Hz and a temperature increase rate of 3 ° C./min.

  The thickness of the transparent resin layer was measured based on a secondary electron beam observation image (SEM image) obtained by a scanning electron microscope or a cross-sectional image obtained by a transmission electron microscope. The thickness (t) is an average value of the 5-point measurement results.

In Table 1, the resins used for preparing the transparent resin layer are as follows.
Resin A: Radical UV curable resin manufactured by Dainippon Ink Co., Ltd. (elastic modulus: 1.4 × 10 ³ MPa / (150 ° C.))
Resin B: Radical UV curable resin manufactured by Dainippon Ink Co., Ltd. (elastic modulus: 1.05 × 10 ³ MPa / (150 ° C.))
Resin C: Radical UV curable resin SD-347 manufactured by Dainippon Ink Co., Ltd. (elastic modulus: 340 MPa / (150 ° C.))
Resin D: Radical UV curable resin SD-394 manufactured by Dainippon Ink Co., Ltd. (elastic modulus: 66 MPa / (150 ° C.))
Resin E: Radical UV curable resin SD-318 manufactured by Dainippon Ink Co., Ltd. (elastic modulus: 280 MPa / (150 ° C.))
Resin F: Radical UV curable resin SD-6036 manufactured by Dainippon Ink Co., Ltd. (elastic modulus: 0 MPa / (150 ° C.))
In particular, in the resin A and the resin B, a predetermined elastic modulus (E) and glass transition temperature are obtained by combining an acrylic monomer having a high crosslinking density and an acrylic monomer having a rigid structure in the crosslinked structure by the method described above. (Tg) was controlled.

Next, the results shown in Table 1 will be described.
FIG. 4 is a diagram illustrating the relationship between (E × t) and MT (%) for Sample 1 to Sample 10. FIG. In FIG. 4, based on the results shown in Table 1, in samples 1 to 10, the product (E) of the elastic modulus (E) of the transparent resin layer in contact with the reverse laminate and the thickness (t) of the transparent resin layer The numerical value of MT (%) based on the reproduction signal of the optical information recorded on the recording layer (1) of the reverse laminated body is plotted against xt) (horizontal axis).

As shown in FIG. 4, when (E × t) is 2.0 × 10 ⁴ MPa · μm or more and MT (%) is 8% or less, when it exceeds 4.0 × 10 ⁴ MPa · μm, 7.5 %, 6.0 × 10 ⁴ MPa · μm, which is around 7%. Furthermore, when it exceeds 6.9 × 10 ⁴ Pa · μm, the MT (%) is around 6.5%, and at 9.0 × 10 ⁴ MPa · μm or more, the MT (%) is stably around 6.5%. A good value is obtained. Further, it is shown that at 10.0 × 10 ⁴ MPa · μm or more, MT (%) is in an ideal state where the minimum value is maintained.

In consideration of the glass transition temperature of the resin shown in Table 1, the glass transition temperature of the transparent resin layer in contact with the reverse laminate is preferably 150 ° C. or higher. It is considered that a resin having a higher glass transition temperature can form a harder transparent resin layer.
The preferable condition of the evaluation method is that a semiconductor laser having a wavelength of 662 nm is mounted as an evaluation machine, and an evaluation machine with an objective lens numerical aperture (NA) of 0.65 is used. (Recording linear velocity: 15.3 m / s), and reproduction is performed at a single speed of DVD using the same evaluator. The shortest mark length for recording is 0.44 μm.

  From the results shown in FIG. 4, when the product (E × t) of the elastic modulus (E) and the thickness (t) of the transparent resin layer in contact with the reverse laminate is greater than a certain value, the recording layer in the reverse laminate When recording at high speed in (1), MT (%) is worse when continuous track recording is performed without emptying the track, compared to ST (%) when single track recording is not performed on adjacent tracks. The problem of doing can be avoided.

  That is, adjusting the hardness and strength as bulk indicated by the product (E × t) of the elastic modulus (E) and thickness (t) of the transparent resin layer in contact with the reverse laminate to a specific range. As a result, it is possible to provide an optical recording medium having good jitter that suppresses excessive deformation extending to adjacent track portions in the structure of an inversely stacked body and has low crosstalk in high-speed recording. As an example in which high-density recording is possible, there are cases where, for example, good recording characteristics can be secured under recording conditions where the shortest recording mark length is 0.44 μm or less.

  Since normal optical disc products are recorded without emptying the track, MT (%) is a value that reflects the signal quality of the optical disc. MT (%) generally needs to be less than 10%, preferably 8% or less, and more preferably 7% or less. If it exceeds 10%, the error tends to increase.

As sample 1 to sample 10 were evaluated, unlike consumer equipment, MT (%) is usually used when recording / reproducing with an evaluation machine that does not include fluctuation factors such as individual differences of semiconductor lasers mounted on the pickup. 8% or less, preferably 7.5% or less, more preferably 7% or less. If MT (%) exceeds 8%, the manufacturing margin may not be sufficiently guaranteed.
Similarly, ST (%) when recording / reproducing with the evaluator is usually required to be 7% or less. When this value is exceeded, MT (%) tends to be 8% or more in continuous recording.

  Note that the wider the power margin of MT (%), the better. For example, the power margin for obtaining MT (%) of 9% or less is preferably 2.5 mW or more, more preferably 3 mW or more, and further preferably 4 mW or more. When the power margin is excessively small, the light amount fluctuation of the laser light source accompanying the temperature change or the like becomes larger than the power margin, and there is a possibility that good recording characteristics cannot be obtained. In all of Samples 1 to 10, the recording power margin was 3 mW or more.

(Example 8)
As described below, a two-layer optical recording medium having a reverse laminate was prepared, and MT (%) and ST (%) of optical information recorded on the recording layer (1) constituting the reverse laminate were measured. .
First, by using a Ni stamper with grooves formed on the surface, polycarbonate is injection molded to form a groove having a track pitch of 0.74 μm, a groove width of 330 nm, and a groove depth of 30 nm. A 60 mm substrate (1) was formed. Next, an Ag-Bi (0.35 atomic%)-Nd (0.2 atomic%) alloy was sputtered to 80 nm on the substrate (1) to form a reflective layer (1). Next, a tetrafluoropropanol solution (concentration 2% by weight) of a mixture of pigments similar to the azo pigment of Example 1 (weight ratio 50:50) was prepared, dropped onto the reflective layer (1), and spin-coated. Thereafter, the recording layer (1) was formed by drying at 70 ° C. for 30 minutes. The thickness of the recording layer (1) is the film thickness of the groove (in FIG. 1, the recording layer thickness of the groove of the reverse laminate 11) and the film thickness of the groove (in FIG. 1, between the grooves of the reverse laminate 11). Part of the recording layer) was about 80 nm. Subsequently, an intermediate layer made of an inorganic material was formed on the recording layer (1) to prepare an inversely laminated disc 1.
A positive laminate was prepared in the same manner as in Example 1.
On the intermediate layer of the disk 1 which is the reverse laminate prepared by the above-described method, resin B (radical ultraviolet curable resin manufactured by Dainippon Ink Co., Ltd .: elastic modulus (E) = 3.0 × 10 ³ MPa, glass (Transition temperature (Tg) = 181 ° C.) was applied by adjusting the spin coating rotational speed so that the film thickness was 25 μm. Further, the resin B was applied onto the film surface of the disk 2 which is a positive laminate, with the spin coat rotation speed adjusted so that the film thickness was 25 μm, as with the disk 1. Next, the disc 1 and the disc 2 each coated with resin are overlapped so that the surfaces coated with the resin face each other, and then, ultraviolet rays are irradiated from the substrate (2) side of the disc 2 (regular laminate). Then, the resin B was cured to form a transparent resin layer to prepare a two-layer type optical recording medium.
Optical information is recorded on the recording layer (1) constituting the reverse laminate in the optical recording medium thus prepared under the following recording conditions, and the recorded optical information is reproduced, and MT (%) and ST (% ) Was measured. The optical information recording conditions are as follows.
Evaluator: 2,4X recording / Pulstec DDU-1000 (wavelength 662 nm, NA = 0.65)
8X recording / ODU-1000T5 manufactured by Pulse Tech (wavelength 658.5 nm, NA = 0.65)
Recording speed: 2.4 times as fast as DVD (linear velocity: 9.22 m / s: hereinafter referred to as 2.4X, where 1 × is assumed to be 3.84 m / s) and 8 × (linear velocity) 30.72 m / s: hereinafter, described as 8X)
Recording pulse strategy: DVD + R standard Ver. Compliant with the description in 2.1.
Jitter measurement: Played back at 1x speed.
The recording power was 21.6 mW for 2.4X recording, P0 = 50 mW, and Pm = 29.5 mW for 8X recording. The results are shown in Table 2 together with the results of Comparative Example 1 and Comparative Example 2 below.

(Comparative Example 1 and Comparative Example 2)
In Example 8, the thickness of the reflective layer (1) was set to 100 nm (Comparative Example 1) and 120 nm (Comparative Example 2), respectively. Otherwise, the two-layer optical recording medium (Comparative with Comparative Example 1 was compared). Two samples of Example 2) were prepared, and 2.4X recording and 8X recording were performed in the same manner as in Example 8. The results are shown in Table 2.
In Comparative Example 1, the recording power is 21.6 mW for 2.4X recording, P0 = 50 mW, and P0 = 29.5 mW for 8X recording. Comparative Example 2 is 22.2 mW for 2.4X recording, P0 = 52 mW for 8X recording, and P0 = 30.5 mW.

FIG. 6 is a diagram in which the value of (MT (%) − ST (%)) is plotted with respect to the film thickness of the reflective layer (1) based on the results shown in Table 2. As shown in FIG. 6, it can be seen that the value of (MT (%) − ST (%)) increases and the crosstalk tends to decrease as the thickness of the reflective layer (1) increases. The value of (MT (%) − ST (%)) is almost saturated at a film thickness of 100 nm or more, but the crosstalk is lower than that at the film thickness of 80 nm.
From the results shown in FIG. 6, the crosstalk (MT (%) − ST (%) is obtained by setting the thickness of the reflective layer (1) to be less than the thickness of the conventional reflective layer (usually 100 nm or more). )) Tend to be improved.
As already described with reference to FIG. 5B, when the thickness of the reflective layer is 40 nm or less, the reflectance tends to decrease, and when the thickness is 30 nm or less, the reflectance is greatly decreased. Tend to. Therefore, it is not preferable that the thickness of the reflective layer (1) is so thin that it is less than 30 nm.

In the present embodiment, a method for manufacturing a two-layer type optical recording medium by attaching two disk substrates has been described. However, a two-layer type optical recording medium is manufactured by a 2P method using a transparent stamper. It is also possible to do.
In the case of the 2P method, for example, an ultraviolet curable resin layer is formed on the reflective layer (2) of the positive laminate by spin coating or the like, and a transparent resin stamper is placed on the resin layer. In this state, the ultraviolet curable resin layer is cured by irradiating ultraviolet rays from the transparent resin stamper side, and when sufficiently cured, the resin stamper is peeled off to form a transparent resin layer having guide grooves and prepits on the surface. On the transparent resin layer thus formed, a recording layer (1) containing an organic dye is formed by spin coating or the like and dried. On the recording layer (1), a reflective layer ( 1) is formed, an adhesive layer is provided on the reflective layer (1), and the substrate (1) is bonded through an adhesive to prepare a two-layer optical recording medium.

  As described above, the optical recording medium 100 to which the present exemplary embodiment is applied is provided with the transparent resin layer 105, and recording marks are provided in the groove portion (land portion) of the substrate (1) 101 of the reverse laminate 11. When formed, it is possible to suppress an increase in crosstalk due to the recording mark protruding from the dye thick film portion in the groove portion adjacent to the inter-groove portion.

  Furthermore, the present inventors may reduce crosstalk by a parameter different from thermal conductivity by reducing the thickness of the reflective layer (1) 102 within a specific film thickness range in this study. I found.

  In addition, this application is based on the Japanese application (Japanese Patent Application No. 2004-199770) for which it applied on July 6, 2004, The whole is used by reference.

It is a figure explaining 1st Embodiment of the optical recording medium with which this Embodiment is applied. It is a figure explaining 2nd Embodiment of the optical recording medium with which this Embodiment is applied. It is a figure explaining thickness (t) of a transparent resin layer. FIG. 3A shows a case where the transparent resin layer is made of a single resin, and FIG. 3B shows a case where the transparent resin layer is made of a plurality of resin layers. It is a figure explaining the relationship between (Ext) and MT (%) of sample 1 to sample 10. It is a figure explaining the relationship between the film thickness of a reflective layer, and the transmittance | permeability (T) and the film thickness of a reflective layer, and a reflectance (R). It is the figure which plotted the value of (MT (%)-ST (%)) with respect to the film thickness of a reflection layer (1) based on the result shown in Table 2. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... Reverse laminated body, 12 ... Normal laminated body, 100, 200 ... Optical recording medium, 101 ... Substrate (1), 102 ... Reflective layer (1), 103 ... Recording layer (1), 104, 204 ... Intermediate layer, 105, 205 ... Transparent resin layer, 106 ... Protective coating layer, 107 ... Reflective layer (2), 108 ... Recording layer (2), 109 ... Substrate (2), 110, 210 ... Laser light, 201 ... Substrate, 202 ... Reflective layer, 203 ... recording layer

Claims (14)

A reverse laminate having a substrate, a reflective layer, and a recording layer in this order;
A transparent resin layer provided on the recording layer side of the reverse laminate,
An optical recording medium characterized in that a product (E × t) of a thickness (t) of the transparent resin layer and an elastic modulus (E) at 25 ± 5 ° C. is 2.0 × 10 ⁴ MPa · μm or more. . The product (E × t) of the thickness (t) of the transparent resin layer and the elastic modulus (E) at 25 ± 5 ° C. is 30.0 × 10 ⁴ MPa · μm or less. The optical recording medium according to 1. 2. The elastic modulus (E) at 25 ± 5 ° C. of the resin constituting the transparent resin layer is 3.0 × 10 ³ MPa or more and 6.0 × 10 ³ MPa or less. Optical recording medium.   The optical recording medium according to claim 1, wherein the transparent resin layer has a thickness (h) of 20 μm to 200 μm.   The optical recording medium according to claim 1, wherein the recording layer is an organic dye-containing recording layer.   The optical recording medium according to claim 1, further comprising an intermediate layer between the recording layer and the transparent resin layer.   2. The optical recording medium according to claim 1, wherein a second reflective layer, a second recording layer, and a transparent substrate are further provided in order on the opposite side of the transparent resin layer from the reverse laminate side. A recording layer on which information is recorded and / or reproduced by light irradiation; and
A transparent resin layer provided on the light incident surface side of the recording layer;
A reflective layer provided on the opposite side of the light incident surface of the recording layer,
An optical recording medium characterized in that a product (E × t) of a thickness (t) of the transparent resin layer and an elastic modulus (E) at 25 ± 5 ° C. is 2.0 × 10 ⁴ MPa · μm or more. .   The optical recording medium according to claim 8, wherein the transparent resin layer is made of a transparent resin having a glass transition temperature of 150 ° C. or higher.   Furthermore, it has a second reflective layer and a second recording layer in this order directly on the light incident surface side of the transparent resin layer or via another layer, and the recording layer and the second recording layer The optical recording medium according to claim 8, wherein the distance between the optical recording medium and the recording medium is 40 μm to 70 μm. An optical recording medium having a substrate, a reflective layer, a recording layer, and a transparent resin layer in this order,
The optical recording medium, wherein the reflective layer contains a metal containing silver (Ag) as a main component and has a thickness of 30 nm to 80 nm.   The optical recording medium according to claim 11, wherein the reflective layer contains 50% or more of Ag.   The optical recording medium according to claim 11, wherein the recording layer contains an organic dye material. The said transparent resin layer is comprised from resin whose elasticity modulus (E) in 25 +/- 5 degreeC is 3.0 * 10 < ³ > MPa or more and 6.0 * 10 < ³ > MPa or less. Optical recording medium.

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