JP2003006920A - Information recording medium - Google Patents

Abstract

(57) [Problem] To provide an information recording medium in which a vibration suppressing layer can be easily formed and which has excellent vibration damping characteristics. An information recording medium having at least a recording layer formed on a resin-made disk-shaped substrate. A vibration suppression layer is provided so as to cover at least a part of the substrate surface directly or via another layer. This vibration suppression layer is made of a resin having a lower hardness than the resin of the substrate, is formed by coating, and has a vibration damping ratio of 0.005 or more. Preferably, the resin is foamed and cured at the time of application and / or thereafter, to form a vibration suppression layer composed of a porous resin layer having a porosity of 10 to 90% by volume.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an information recording medium such as an optical recording medium, and more particularly to an information recording medium having a vibration suppressing layer.

[0002]

2. Description of the Related Art An optical recording medium (optical disk) capable of recording / reproducing information with a laser has a large recording capacity and random access as compared with a conventional recording medium. ,
It is used as a recording medium in fields such as game software and electronic publishing. Optical recording media are classified into two types: a write-once type capable of recording and reproducing information and a rewritable type capable of erasing data after recording. Among them, the write-once compact disc with a single plate structure is a CD-R (Compact).
It is called “Disk Recordable” and has compatibility with a normal read-only CD, so that the number of users has rapidly increased in recent years.

When an information recording medium such as such an optical disk or a magnetic recording medium is rotated at a high speed during signal recording / reproduction, vibration is generated by an air flow generated in the drive. The recording medium also vibrates due to external vibration of the recording / reproducing apparatus.

By suppressing such vibration, for example, in the case of an optical disc, it is possible to reduce the defocus of the recording / reproducing beam spot, improve the accuracy of the recording mark, and reduce the reproducing error. Also, noise due to the vibration of the disc itself can be reduced. Such vibration suppression is particularly important for audio equipment for automobiles.

Conventionally, as a measure for suppressing the vibration of a magnetic recording medium such as a hard disk, there have been adopted methods such as reducing the diameter of the medium, thickening the substrate, and changing the substrate material from aluminum to glass. As a measure for suppressing the vibration of the optical disk, a material having a high vibration damping property (for example, amorphous polyolefin) may be used as the substrate material, or a vibration suppressing film may be adhered to the disk to form the vibration suppressing layer. It is known.

[0006]

On the other hand, the weight saving of the medium,
It has been attempted to use a resin as a substrate of a magnetic recording medium for various purposes such as cost reduction and providing a guide groove on the substrate, but the above vibration countermeasures are insufficient, It was not applicable.

Further, in the case of an optical disk, the above-mentioned amorphous polyolefin is considerably excellent in vibration damping property as compared with polycarbonate which is widely used as a substrate material for the optical disk, but it is expensive and the injection molding condition is not satisfied. There are many restrictions and productivity is poor.

In the method of sticking the resin film for vibration suppression on the plate surface of the information recording medium, it is necessary to position and stick the film on the information recording medium so as to be accurately concentric, which is inferior in productivity. . Also, depending on the adhesive, the stress during vibration is dispersed in the adhesive layer at the interface between the substrate and the film,
The vibration damping effect of the film may not be sufficiently exhibited.

An object of the present invention is to solve the above problems and to provide an information recording medium in which a vibration suppressing layer can be easily formed and which has excellent vibration damping characteristics.

Another object of the present invention is to provide an information recording medium in which a cheap substrate material is sufficient.

[0011]

The information recording medium of the present invention is an information recording medium having at least a recording layer formed on a resin disk-shaped substrate, and the substrate surface is directly or through another layer. A vibration suppressing layer is provided so as to cover at least a part thereof, and the vibration suppressing layer is made of a resin having a hardness lower than that of the resin of the substrate and is formed by coating, and has a vibration damping rate of 0. It is characterized by being 0.005 or more.

The term "hardness" as used herein means DH described later.
It means 115 hardness.

In such an information recording medium, the vibration suppressing layer is formed by coating, and the vibration suppressing layer can be formed extremely easily as compared with the case where a film is stuck. Further, since the vibration suppressing layer is directly attached without the interposition of the adhesive, there is no stress dispersion phenomenon due to the adhesive layer, and a high vibration damping rate of 0.005 or more can be obtained.

This information recording medium damps vibration by the vibration suppressing layer, and even if polycarbonate or the like which has been widely used as the substrate material is used, the vibration can be made sufficiently small.

In the information recording medium of the present invention, the vibration suppressing layer must be provided so as not to interfere with the information recording / reproducing of the recording medium. For example, the information recording medium is an optical recording capable of recording / reproducing with a laser. In the case of a medium, it is preferable that the vibration suppressing layer is provided on the surface (label surface) opposite to the incident surface of the recording / reproducing light. In the case of a magnetic recording medium, if the type of recording on one side of the medium,
Similar to the case of the optical recording medium, the vibration suppressing layer of the present invention may be provided on the surface opposite to the surface on which recording is performed, and in the case of a type having recording layers on both sides, between the recording layer and the substrate, etc. A vibration suppression layer may be provided on the.

When the vibration suppressing layer is provided on the label surface, it is preferable to provide the vibration suppressing layer so as to cover 50% or more of the label surface in order to enhance the vibration damping effect, and the thickness of the vibration suppressing layer is 30. It is preferable to form a thick film of about 200 μm.

In the case of forming such a thick resin layer, the coating may be repeated many times, but when the coating is performed a small number of times (for example, once or twice) and / or after that, the porosity is reduced. It is preferable that the layer thickness is increased by foaming so as to be 10 to 90% by volume.

As the resin which constitutes this vibration suppressing layer,
The thing formed using the UV curable resin composition which has a urethane acrylate oligomer as a main component is suitable.
Screen printing is a suitable method for applying the resin composition.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.
Examples of the information recording medium of the present invention include an optical recording medium and a magnetic recording medium, and are particularly suitable for application to an optical recording medium. This optical recording medium is preferably constructed by laminating at least a recording layer, a reflective layer and a protective layer on a transparent substrate. The stacking order of the layers differs depending on the recording method of the medium, but even in the type in which the recording / reproducing light is emitted through the transparent substrate, the recording / reproducing light is applied to the surface of the recording layer opposite to the surface facing the substrate. Recording / recording
It is preferable to provide a vibration suppressing layer on the surface (label surface) opposite to the reproduction light incident surface.

The optical recording medium currently in use is generally of a type in which recording / reproduction is performed through a transparent substrate, but in this case, a recording layer, a reflective layer and a protective layer are laminated in this order on the substrate. A vibration suppressing layer is formed on or in place of the protective layer. An optical recording medium having this structure will be described below as an example.

As the transparent substrate, for example, a polymer material such as a polycarbonate resin, an acrylic resin, a polystyrene resin, a vinyl chloride resin, an epoxy resin, a polyester resin, an amorphous polyolefin, or an inorganic material such as glass is used. In particular, a polycarbonate resin is preferable because it has a high light transmittance and a small optical anisotropy.

On the surface of the transparent substrate, guide grooves, pits, etc. (groove information, etc.) representing recording positions are usually formed. The groove information and the like are usually given when a substrate is made by injection molding or casting, but may be made by a laser cutting method or a 2P method (Photo-Polymer method). The thickness of the substrate is, for example, 0.3 to 1.5.
However, the present invention is not limited to this.

The recording layer is not particularly limited as long as it can be recorded by irradiation with laser light, and may be either a recording layer made of an inorganic substance or a recording layer made of an organic substance.

In the recording layer made of an inorganic material, for example, Tb / Fe / Co or Dy / F for recording by the photothermomagnetic effect is used.
A rare earth transition metal alloy such as e · Co is used. Also,
Chalcogen-based alloys such as phase change Ge.Te and Ge.Sb.Te may also be used.

Organic dyes are mainly used in the recording layer made of an organic material. Such organic dyes include macrocyclic azaannulene dyes (phthalocyanine dyes, naphthalocyanine dyes, porphyrin dyes, etc.), polymethine dyes (cyanine dyes, merocyanine dyes, stawarylium dyes, etc.), anthraquinone dyes, azurenium dyes, metal-containing dyes. Examples thereof include azo dyes and metal-containing indoaniline dyes. Particularly, metal-containing azo dyes are preferable because they are excellent in durability and light resistance.

The dye-containing recording layer is usually spin coated,
The film is formed by a coating method such as spray coating, dip coating, or roll coating. At this time, as the solvent, diacetone alcohol, a ketone alcohol solvent such as 3-hydroxy-3-methyl-2-butanone, a cellosolve solvent such as methyl cellosolve and ethyl cellosolve, perfluoro such as tetrofluoropropanol and octafluoropentanol. Alkyl alcohol solvents, hydroxyethyl solvents such as methyl lactate and methyl 2-hydroxy-isobutyrate are preferably used.

The thickness of the recording layer is, for example, 10 to 5000 n.
However, the present invention is not limited to this.

The reflective layer is preferably composed of a metal such as gold, silver or aluminum, and particularly preferably composed of silver. The metal reflection layer is formed by, for example, a vapor deposition method, a sputtering method, or an ion plating method. An intermediate layer may be provided between the metal reflection layer and the recording layer for the purpose of improving the adhesion between the layers or for the purpose of increasing the reflectance. The thickness of the reflective layer is, for example, 50 to 200.
However, the present invention is not limited to this.

The protective layer is preferably formed of a UV curable resin composition which is easy to form.

The protective layer is formed by applying the UV curable resin composition described above by a method such as spin coating, dip coating, bar coating, blade coating, air knife coating, roll coating or screen printing, followed by UV irradiation. Is done by doing. As the UV lamp, a mercury lamp, a high pressure mercury lamp, an ultrahigh pressure mercury lamp, a metal halide lamp, or the like is used. The irradiation energy amount is usually 150 to 2
000 mJ / cm ² , preferably 250 to 1000 mJ
/ Cm ² range is selected. The thickness of the protective layer is 3 to 2
About 0 μm is preferable.

On the protective layer or instead of the protective layer, a vibration suppressing layer made of a resin having a hardness lower than that of the resin of the substrate is formed.

The thickness of this vibration suppressing layer is preferably 30.
μm or more, particularly preferably 50 μm or more and 200 μm or less. If it is 30 μm or less, the vibration suppressing effect may be insufficient.

If it exceeds 200 μm, the method for forming the layer is limited and the productivity may be poor. Note that, for example, in the CD thickness standard, the upper limit of the substrate is 1.3 mm, and the upper limit of the total thickness is 1.5 mm.
If it exceeds (200 μm), the total thickness may exceed 1.5 mm. Generally, the thickness of the information recording medium of the present invention is preferably about 1.0 to 1.5 mm.

This vibration suppressing layer is preferably provided so as to cover 50% or more, particularly 70% or more, of the label surface in order to obtain a sufficient vibration suppressing effect.

To form this vibration suppressing layer, the resin composition is applied onto the protective layer and cured by the same coating method as used to form the protective layer. The vibration suppressing layer thus formed by the coating method directly adheres to the lower layer (for example, the protective layer) without using an adhesive, so that there is no dispersion of vibration stress due to the adhesive layer and high vibration Attenuation rate can be obtained. As the coating method, a screen printing method is preferable because it is easy to form a coating film at a predetermined position on the substrate with a predetermined film thickness.

When the vibration suppressing layer having a relatively large film thickness of about 30 to 200 μm is formed by a coating method, particularly a usual screen printing method or spin coating method, a coating film which can be formed by one coating step. Since the thickness of is small,
It is necessary to repeat the application a number of times, resulting in low productivity.

Therefore, in the present invention, it is preferable to increase the thickness of the layer by forming the vibration suppressing layer as a porous resin layer during coating and / or in the subsequent foaming step. The porous resin layer may have either closed cells or open cells.

Specifically, it is either to foam at the same time in the step of applying the material for forming the vibration suppression layer, to foam after the application step, or to perform both. For example, when forming the layer by a screen printing method, a material that generates bubbles when passing through the screen may be used.

Usually, the coating material for screen printing includes
An antifoaming agent is added, and it is devised so that the bubbles disappear immediately after application.In the present invention, for example, a coating material containing no antifoaming agent is used, or the type or amount of the antifoaming agent is changed. By making an appropriate selection, the bubbles generated during coating (passing through the screen) can be cured without being eliminated, and the apparent coating film thickness can be increased.

The number of bubbles, the size of the diameter, the distribution of the diameter, etc.
It is changed by adjusting the viscosity of the material used for forming the porous resin layer described later, the composition, the amount of the defoaming agent, the roughness of the screen, the time until exposure after screen printing. Immediately after printing, the distribution of bubble diameters is narrow, and as time passes, the bubbles are integrated and become bubbles with a large diameter, so the number of bubbles decreases and the distribution spreads. Also, some of the bubbles disappear. From the viewpoint of aesthetics, it is preferable to cure immediately after printing, and before the bubbles are eliminated so much.

According to this method, a large film thickness of about 30 to 200 μm can be obtained by one or two coating steps by ordinary screen printing. A screen of 200 to 350 mesh / inch is usually used, but the screen is not limited to this.

The material for forming the vibration suppressing layer is not particularly limited as long as the hardness of the obtained layer is within the range of the present invention, but a UV curable resin generally used for screen printing on the label surface of an optical recording medium. It may be selected from among the compositions.

Specifically, 20 to 80% by weight of the following acrylate oligomer, 10 to 70% by weight of the following acrylic monomer, and 1 to 1 of the following photoradical initiators.
A UV curable resin composition composed of 0% by weight or the like is preferable.

Acrylate oligomer Epoxy acrylate oligomer formed by reacting epoxy resin such as bisphenol A, F, S or novolac with (meth) acrylic acid; polyurethane consisting of hexamethylene diisocyanate and 1,6-hexanediol and 2-
(Di) isocyanate such as a reaction product with hydroxyethyl acrylate, a diisocyanate oligomer obtained by reacting a polyester diol composed of adipic acid and 1,6-hexanediol, and tolylene diisocyanate with 2-hydroxyethyl acrylate A urethane acrylate oligomer formed by reacting a compound, a polyhydric alcohol, and (meth) acrylic acid; a polyester diol consisting of a ring-opening polymer of phthalic anhydride and propylene oxide and an ester of acrylic acid, adipic acid and 1,6- Esters of polyester diol consisting of hexanediol and acrylic acid, esters of triol consisting of reaction product of trimellitic acid and diethylene glycol and acrylic acid, ring-opening polymer of δ-valerolactone and acrylic acid. An ester acrylate oligomer formed by reacting a polyhydric alcohol such as tellurium, a polybasic acid or an anhydride thereof, and (meth) acrylic acid; a polyhydric alcohol obtained by adding ethylene oxide or propylene oxide to a hydroxyl group-containing compound, polyethylene glycol , Ether acrylate oligomers obtained by reacting (meth) acrylic acid with polypropylene glycol, etc.

Acrylic monomer 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, phenoxyethyl acrylate, nonylphenoxyethyl acrylate, N-vinylpyrrolidone, 2-hydroxyethylacryloyl phosphate, tetrahydrofurfuryl acrylate, tetrahydro Furfuryloxyethyl acrylate, tetrahydrofurfuryloxyhexanolide acrylate, acrylate of 1,3-dioxane alcohol ε-caprolactone adduct, 1,
Monofunctional monomers such as 3-dioxolane acrylate; cyclopentenyl acrylate, 1,6-hexanediol diacrylate, diethylene glycol diacrylate, tripropylene glycol diacrylate, neopentyl glycol diacrylate, polyethylene glycol (400) diacrylate, hydroxypivalin Acid ester neopentyl glycol diacrylate, neopentyl glycol adipate diacrylate, di-acrylate of neopentyl glycol hydroxypivalate ε-caprolactone adduct, 2- (2-hydroxy-1,1-dimethylethyl) -5-hydroxy Methyl-5-ethyl-1,3-dioxane diacrylate,
Tricyclodecane dimethylol diacrylate, diacrylate of ε-caprolactone adduct of tricyclodecane dimethylol, trimethylol propane triacrylate, pentaerythritol triacrylate, dipentaerythritol hexaacrylate, propionic acid
Polyfunctional monomers such as dipentaerythritol triacrylate, hydroxypivalaldehyde-modified dimethylolpropane triacrylate, propionic acid / dipentaerythritol tetraacrylate, and ditrimethylolpropane tetraacrylate

Photo radical initiator acetophenone compound, propiophenone compound,
Anthraquinone compounds, thioxanthone compounds, etc.

The UV-curable resin composition may contain silica, titanium oxide, fillers such as various resin fine particles, and coloring materials such as pigments and dyes, as in the case of printing on the label surface of an optical recording medium. , A polymerization terminator, a storage stabilizer, a dispersant, an antifoaming agent, a binder resin other than the ultraviolet curable resin, etc. may be contained. As such, it is more preferable not to include the defoaming agent that is usually contained.

The hardness of the vibration suppressing layer in the information recording medium of the present invention depends on the material used for forming the layer (for example, the above-mentioned U).
V-curable resin composition) depends on the type and content of monomers and oligomers contained in the V-curable resin composition, the content of optional components such as binder resin, and the like, but it is preferable that the monomer contains a relatively large amount of monofunctional monomer rather than polyfunctional monomer. The hardness tends to be low, and the hardness tends to be low when a large amount of urethane acrylate oligomer is included as an oligomer. Particularly, the urethane acrylate oligomer is 50 to 8
Those containing 0% by weight are preferable.

When the vibration suppressing layer is a porous resin layer, the vibration damping rate of the information recording medium is high because the vibration damping rate of the resin and the vibration damping characteristic of the air in the void overlap. Become.

When the porous resin layer is formed, it is preferable to foam it so that the porosity is 10 to 90% by volume, particularly 20 to 80% by volume.

In the present invention, the method for measuring the porosity is as follows. That is, the void area is measured from the surface by image processing, the void shape is approximated to a sphere, individual volumes are calculated and summed, and the void ratio is calculated from the total layer thickness. When the measurement area of the surface of the vibration suppressing layer A, and the individual void volume d _i, the thickness of the vibration suppressing layer measured with a micrometer t, porosity R is represented by the following formula.

[0052]

[Equation 1]

When the vibration suppressing layer is a porous resin layer formed at the time of screen printing, actually, as shown in FIG. 2, the surface of the porous resin layer 9 has a convex bulge portion. It is expected that a large number of (bubble portions) 10 are present, and in the film thickness measurement with a micrometer, the value of t in FIG. 2, that is, from the interface between the porous resin layer 9 of the vibration suppression layer and the adjacent layer to the porous resin layer. It is considered that the distance to the apex 9A of the convex portion 9 is measured. But even in this case,
The “porosity” in the present invention is, as shown in FIG. 3, a constant thickness of the vibration suppressing layer, which is the thickness t measured by a micrometer (where t is the average value of the values measured by one information recording medium). It is assumed that the layer 11 is a layer 11 and the volume ratio of the bubble portion 10 in the layer is represented.

When the porosity is lower than 10% by volume,
The productivity improvement effect is poor. On the other hand, when it exceeds 90% by volume, the physical strength of the resin layer becomes small, and the scratch resistance and the like decrease.

In the present invention, the hardness of the substrate and the vibration suppressing layer is
The degree is tested with a diamond triangular indenter (diameter of 115 degrees)
An indenter immediately before unloading after being loaded with a load (0.1g) for a certain period of time
D calculated from the indentation depth H and the test load P by the following formula
It is defined as H115 hardness. [DH115 hardness] = 37.838 P / H^Two P: Test weight 0.1g H: Indenter depth (μm)

The vibration damping rate is increased by making the hardness of the vibration suppressing layer smaller than the hardness of the substrate. That is, the smaller the hardness of the vibration suppressing layer is, the higher the damping effect is exhibited even if the layer thickness is thin, which is preferable. Normally, when the hardness of the vibration suppression layer is about 70% of the hardness of the substrate, the layer thickness 100
The vibration damping rate becomes 0.005 or more at about μm and is 20%.
If the thickness is about 30 μm, the vibration damping rate is 0.0
It becomes more than 05.

However, for example, a resin having a DH115 hardness of less than 1 is difficult to manufacture and it is difficult to obtain the material. If the hardness of the outermost layer of the medium is too low, the durability may be problematic. In practice, the hardness of the vibration suppressing layer is preferably 70% or less of the hardness of the substrate, and more preferably 50% or less. The vibration damping rate of the information recording medium of the present invention is 0.005 or more, more preferably 0.006 or more.

The method of measuring the vibration damping rate is as shown in FIG.

An oscillation signal (generally a swept sine wave) output from the controller 1 is input to the electrodynamic vibrator 3 via the power amplifier (amplifier) 2 so that the disk 4 is centered. Vibrate. Acceleration pickup 5 is used to ensure that vibration is input to disk 4 at a constant acceleration.
Are provided, and feedback control is performed by the controller 1.

The displacement amount at the end of the disk 4 is measured by the non-contact type laser displacement meter 6 and converted by the converter 7. The frequency response function is calculated by inputting the oscillation signal, the response signal detected by the non-contact displacement gauge, and the signal of the controller 1 to the frequency response analysis device 8, and the vibration damping rate (ζ) is calculated.
Ask for.

Specifically, the output signal has a peak value at the resonance frequency (the frequency at which the natural frequency of the disk matches the input frequency). Output / input = X / X _S = 1 / 2ζ = Q (peak value) ∴ζ = 1 / 2Q This ζ is the vibration damping rate.

In the optical recording medium of the present invention, writing (recording) and / or reading (reproduction) of information is preferably performed by a laser beam focused to about 1 μm.
That is, recording is performed by melting, evaporation, sublimation, deformation, modification or the like in the laser light irradiation portion (recording portion) of the recording layer. Then, the reproduction is performed by reading the difference in reflectance between the laser light irradiation portion and the non-irradiation portion with the laser light. A semiconductor laser beam is preferably used as the laser beam.

When the information recording medium of the present invention is an optical recording medium, the recording layer, the reflection layer, and the protective layer are sequentially laminated on the substrate, or the order of laminating these layers is changed (for example, Layered in the order of substrate / reflection layer / recording layer / protection layer,
In addition to recording / playback from the protective layer side, etc., DVD
It may be a bonded type medium having at least a recording layer and a reflective layer between two substrates, such as -R and DVD-RW.

In either case, if the recording / reproducing can be performed on only one side of the medium, the vibration suppressing layer of the present invention may be provided on the surface (label surface) opposite to the incident surface of the recording / reproducing light. Of course, in the case of the above-mentioned DVD medium, for example, the vibration suppressing layer of the present invention may be provided by coating directly on the substrate surface corresponding to the label surface or through another layer.

[0065]

EXAMPLES The present invention will be described in more detail with reference to examples below, but the present invention is not limited to the following examples as long as the gist thereof is not exceeded.

Example 1 A solution of a metal-containing azo dye was dropped onto a injection-molded polycarbonate resin substrate (diameter 12 cm, hardness 17.3) having a depth of 1600 Å and a width of 0.45 μm and a spin coating method. Was applied at a rotation speed of 5000 rpm and then dried at 100 ° C. for 30 minutes to form a recording layer. Then, on the above recording layer by a sputtering method,
A silver film having a film thickness of 800 Å (80 nm) was formed to form a reflective layer. Then, a UV-curable resin composition was spin-coated on the entire surface of the reflective layer and then irradiated with ultraviolet rays to be cured to form a protective layer of 5 μm. A UV curable resin composition having the composition shown in Table 1 was screen-printed once on the entire surface of this protective layer so as to have a film thickness of 12 μm, and then irradiated with ultraviolet rays to be cured to form a vibration suppressing layer.

A 300 mesh / inch screen was used for screen printing, and a UV composition having no defoaming agent was used.
By using the curable resin composition, bubbles were generated in the vibration suppressing layer during printing, and a porous resin layer was formed. The time from the screen printing to the start of ultraviolet irradiation was about 10 seconds.

Table 2 shows the measurement results of the film thickness, porosity and hardness of the resin layer as the vibration suppressing layer, and the vibration damping ratio of the optical disk.

Examples 2, 3, 4 Example 1 except that the number of times of screen printing was 2 times (Example 2), 3 times (Example 3) or 5 times (Example 4).
An optical disc was manufactured in the same manner as in. Table 2 shows the measurement results of characteristics and the like.

Example 5 The screen printing film thickness of the resin layer as the vibration suppressing layer was set to 30.
The optical disk was manufactured in the same manner as in Example 1 except that the time from the completion of screen printing to the start of ultraviolet irradiation was shortened (to about 1 second) in order to make the diameter of the bubbles uniform and change the expansion ratio. Table 2 shows the measurement results of characteristics and the like.

Examples 6 and 7 An optical disk was manufactured in the same manner as in Example 1 except that the number of times of screen printing was 2 times (Example 6) or 3 times (Example 7). Table 2 shows the measurement results of characteristics and the like.

Example 8 An optical disk was manufactured in the same manner as in Example 1 except that the composition 'shown in Table 1 was used as the UV curable resin composition and the number of times of screen printing was 6 times. Table 2 shows the measurement results of characteristics and the like.

Since the composition 'contains an antifoaming agent, bubbles were not generated during screen printing, and the obtained vibration suppressing layer did not become a porous resin layer.

Examples 9 and 10 Except that the resin composition for forming the resin layer as the vibration suppressing layer was the composition (Example 9) or (Example 10) in Table 1 and the number of screen printing was 3 times. An optical disc was manufactured in the same manner as in Example 1. The expansion ratio is also the same as in Example 1. Table 2 shows the measurement results of characteristics and the like.

Comparative Example 1 The vibration damping ratio was measured for the substrate itself on which none of the recording layer, the reflective layer, the protective layer and the vibration suppressing layer was formed. The results are shown in Table 2.

Comparative Example 2 Examples 1 to 1 except that the vibration suppressing layer was not formed at all.
An optical disc was manufactured in the same manner as in 10. The expansion ratio is also the same as in Example 1. Table 2 shows the measurement results of characteristics and the like.

Comparative Examples 3 and 4 Same as Example 9 except that the resin composition for forming the resin layer as the vibration suppressing layer was the composition shown in Table 1 (Comparative Example 3) or (Comparative Example 4). Then, an optical disc was manufactured. The expansion ratio is also the same as in Example 1. Table 2 shows the measurement results of characteristics and the like.

Comparative Example 5 An example except that a polycarbonate film having a thickness of 100 μm and a hardness of 18.0 was adhered by a radical curable UV-curable acrylic adhesive (adhesive layer thickness of 10 μm) as a vibration suppressing layer. Optical discs were manufactured in the same manner as in 1 to 10. Note that neither the adhesive layer nor the polycarbonate film is a porous layer.

Table 2 shows the measurement results of characteristics and the like.

From Table 2, the substrate itself (Comparative Example 1),
In the case where only the recording layer, the reflective layer and the protective layer are formed on this (Comparative Example 2), the vibration damping rate is 0.0046 for all.
On the other hand, in each of Examples 1 to 10 in which the vibration suppressing layer made of the resin layer is formed, the vibration damping rate is 0.005 or more, and it is recognized that the optical disk of the present invention has excellent vibration damping rate characteristics. .

On the other hand, in Comparative Examples 3 and 4 in which the resin layer formed by coating and foaming has high hardness and Comparative Example 5 in which a polycarbonate film having high hardness is adhered, the vibration damping ratio is It's worse than one or two.

[0082]

[Table 1]

[0083]

[Table 2]

[Sound Quality Evaluation] Examples 7 and 8 and Comparative Example 2
Regarding the optical disc (CD-R disc) obtained in
Sony Sony CD writer "CDW900E (recording wavelength: 780 nm)" was used to record the following songs at 1x speed (linear velocity 1.2 m / s) and a commercially available CD player (playback wavelength: 780 nm) was used. Let the sound quality evaluation engineer listen to the sound that was played back, and the sound volume, the clearness of the sound, the tone color,
The sound quality was comprehensively evaluated from the viewpoints of sound volume, sound field (spread of sound). The evaluation criteria are as follows, and the evaluation results are shown in Table 3 separately for treble and bass. Song name: "The Star on the Earth" (singer Miyuki Nakajima) Evaluation criteria: ◎ Very good ○ Excellent △ Somewhat excellent × Inferior

[0085]

[Table 3]

As is clear from Table 3, the CD-R discs of Examples 7 and 8 in which the vibration suppressing layer was provided on the label surface were the CD-R of Comparative Example 2 in which the vibration suppressing layer was not provided.
Compared to the disc, it received a good sound quality evaluation, especially in the high range. Example 7 in which the vibration suppressing layer is a porous resin layer
Had a higher sound quality rating.

[0087]

As described above, according to the present invention, it is possible to easily manufacture an information recording medium having excellent vibration damping characteristics. This information recording medium having excellent vibration damping characteristics has small vibrations at high speed rotation, stable recording / reproduction, and low rotation noise.

[Brief description of drawings]

FIG. 1 is a block diagram of an apparatus for measuring a vibration damping rate.

FIG. 2 is a schematic cross-sectional view illustrating the thickness of a vibration suppressing layer in the information recording medium of the present invention.

FIG. 3 is a schematic cross-sectional view illustrating the thickness of a vibration suppressing layer in the information recording medium of the present invention.

[Explanation of symbols]

1 controller 2 amplifier 3 shakers 4 discs 5 Accelerometer 6 Laser displacement meter 7 converter 8 analyzer 9 Porous resin layer 10 Voids (air bubbles) 11 Hypothetical vibration suppression layer

Continued front page    F-term (reference) 5D029 NA12 NA14 NA16 NA17 NA19                 5D075 EE03 FG10                 5D121 AA03 EE21 EE23

Claims (8)

[Claims] 1. An information recording medium in which at least a recording layer is formed on a resin disk-shaped substrate, and a vibration suppressing layer is provided so as to cover at least a part of the substrate surface directly or through another layer. The vibration suppressing layer is made of a resin having a hardness lower than that of the resin of the substrate and is formed by coating, and the vibration damping rate is 0.005 or more. Medium. 2. The information recording medium according to claim 1, wherein the information recording medium is an optical recording medium capable of recording / reproducing with a laser, and the vibration suppressing layer has a surface (hereinafter referred to as a surface opposite to an incident surface of recording / reproducing light). , "Label surface"). 3. The information recording medium according to claim 2, wherein the vibration suppressing layer is provided so as to cover 50% or more of the label surface of the information recording medium. 4. The information recording medium according to claim 1, wherein the vibration suppressing layer has a thickness of 30 to 200 μm. 5. The information recording medium according to claim 1, wherein the vibration suppressing layer is a porous resin layer having a porosity of 10 to 90% by volume. 6. The porous resin layer according to claim 5,
An information recording medium formed at the time of application and / or by a foaming step thereafter. 7. The resin forming the vibration suppressing layer according to claim 1, which is formed by using a UV curable resin composition containing a urethane acrylate oligomer as a main component. An information recording medium characterized by: 8. The information recording medium according to claim 1, wherein the coating is screen printing.