JPH07109660B2 - Optical information recording medium - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical information recording medium, and in particular, a substrate having a light-transmitting property and provided on the laser light incident side,
The present invention relates to an optical information recording medium which has at least a protective layer laminated on this substrate and which is optically writable and readable.

[Prior Art] As an optical information recording medium of this type, recorded data and prepits or pregrooves for tracking for reproducing the recorded data are made of a translucent polycarbonate by using a means such as a press in advance. Formed on the substrate such as Au, Ag, Cu,
Compact discs (hereinafter referred to as "CDs") have been put to practical use as read-only optical information recording media in which a reflective film made of a metal film such as Al is formed and a protective layer made of resin is further formed on the reflective film. It is popular.

Such a read-only CD is a so-called ROM-type optical information recording medium in which data is recorded in advance and data cannot be written or erased after that. Most typically, it is already widely used in the information processing department and the audio department. It has been put to practical use.

The specifications for recording and reproducing signals of this CD are so-called CD
It is stipulated as a standard, and a reproducing device conforming to this standard is widely used as a compact disc (CD player).

On the other hand, there is also known a so-called writable optical information recording medium capable of recording data by irradiating a laser beam on the user side.

This optical information recording medium is composed of Te, B on a transparent substrate.
It may have a recording layer made of a metal layer of i, Mn or the like, a dye layer of cyanine, merocyanine, phthalocyanine or the like, and may further have a light reflecting layer on the back surface of the layer. Then, by irradiating the laser beam, the recording layer is deformed, sublimated,
Data is recorded by forming pits by means such as evaporation or modification.

When the recorded data is reproduced, the substrate side is irradiated with laser light having weaker power than during recording, and the signal is read by the difference in reflected light between the pit and the other portion.

In recent years, CDs have also been used for such optical information recording media.
Those satisfying the standard have been proposed. For example, JP-A-61-237239, JP-A-61-239443, and JP-A-62-11975
5, JP-A 1-17234, JP-A 1-100751 and JP-A 1-15
No. 0248 and JP-A Nos. 1-1594840 to 159843.

In these applications, a resin such as polycarbonate or glass has a cyanine dye, a recording layer such as tellurium, and further, a thin metal film such as aluminum or titanium is formed, and an ultraviolet curable resin, silicon oxide (SiO2), or oxide is used. It has a protective layer covered with titanium (TiO2) or the like.

However, when using a writable so-called write-once conventional optical information recording medium using a dye as the light absorbing layer, a dedicated CD player for reproducing a signal recorded on the optical information recording medium is used. New separately required,
A commercially available CD that is widely used for playback-only CDs
There is a problem that it cannot be played on the player.

Therefore, in order to play back as a CD with a commercially available CD player, it is necessary to obtain a playback signal that complies with the CD standard, which is a universal standard.

However, in the technology disclosed heretofore, the CD
Regarding the optical information recording medium capable of obtaining a reproduction signal satisfying the standard, no specific disclosure has been made regarding the constitution capable of satisfying the condition of the protective layer.

The conditions required for the protective layer of the optical information recording medium satisfying this CD standard are the same as those of the conventional ROM type CD,
When the substrate thickness is 1.2 mm ± 0.1 mm, the total disc thickness can be 1.2 mm + 0.3 to −0.1 mm.

In addition, as a condition after recording peculiar to the optical information recording medium for satisfying the CD standard, even if a heat cycle test such as a ZAD test (weather resistance test, JIS C5024) recommended by the CD standard in a blank disc state is performed, the sled Is within ± 0.6 degrees in plane reflection, and even when the above ZAD test is performed in the state of a blank disc, peeling occurs between the substrate and the light absorption layer and between the light absorption layer and the light reflection layer. There is no such thing, it is possible to form pits that do not cause waveform distortion during recording, and the block error rate (BLER) specified in the CD standard can be kept small (specifically 0.03 or less). To be

[Problems to be Solved by the Invention] The present invention has been made in view of the above problems, and has a structure in which a light absorption layer, a light reflection layer, and a protective layer are sequentially stacked on a substrate, and a CD It is an object of the present invention to provide an optical information recording medium which can obtain a reproduction signal satisfying the standard and which has a protective layer under practically appropriate conditions.

[Means for Solving the Problems] That is, the first invention is an optical information recording medium having a substrate which is transparent and is provided on the laser light incident side, and a protective layer which is laminated on the substrate. , The protective layer is
The pencil hardness is 2H or more, and the thermal expansion coefficient α is 1.5 × 10 ^{-5 in the} ambient temperature range of -15 ℃ to 70 ℃.
The optical information recording medium is characterized in that ≦ α ≦ 9.0 × 10 ⁻⁵ (1 / ° C.).

A second invention is a substrate having a light-transmitting property and provided on the laser light incident side, a light absorbing layer provided on the substrate and made of an organic dye absorbing the laser light, and a light absorbing layer on the light absorbing layer. An optical information recording medium having a light-reflecting layer for reflecting the laser light and a protective layer provided on the light-reflecting layer, the protective layer having a pencil hardness of 2H or more. , The ambient temperature is −
Thermal expansion coefficient α is 1.5 × 10 ^-5 ≤ ≤15 ° C to 70 ° C
The optical information recording medium is characterized in that α ≦ 9.0 × 10 ⁻⁵ (1 / ° C.).

Next, the present invention will be described more specifically based on FIGS. 1 to 6.

FIG. 1 is a partially cutaway perspective view of an optical information recording medium 1 according to the present invention, FIG. 2 is a longitudinal sectional view of a main part of the optical information recording medium 1 before recording, and FIG. 3 is the optical information recording medium. FIG. 3 is a longitudinal sectional view of a main part after the recording of No. 1.

The optical information recording medium 1 includes a transparent substrate 2 and the substrate 2.
It has a light absorption layer 3 formed thereon, a light reflection layer 4 formed on the light absorption layer 3, and a protective layer 5 formed on the light reflection layer 4. An intermediate layer (not shown) may be provided between the substrate 2 and the light absorption layer 3 and between the light absorption layer 3 and the light reflection layer 4, if necessary.

A pre-groove 6 is spirally formed on the substrate 2. To the left and right of the pregroove 6, parts other than the pregroove 6, that is, lands 7 are located.

The substrate 2 and the light absorption layer 3 are in contact with each other by the first layer boundary 8. The light absorption layer 3 and the light reflection layer 4 are in contact with each other by the second layer boundary 9. The light reflecting layer 4 and the protective layer 5 are in contact with each other by a third layer boundary 10.

By integrating the protective layer 5 and the substrate 2 at their circumferential portions, the strength of the optical information recording medium 1 as a whole is improved and the internal light absorbing layer 3 and the light reflecting layer 4 are made more reliable. Can be protected.

As shown in FIG. 3, when the optical information recording medium 1 is irradiated with recording light (recording laser light) L1, the light absorption layer 3 absorbs the energy of the laser light L1 to generate heat, and the substrate 2 side The pit 11 is formed due to thermal deformation. In some cases, an optical change may occur in the light absorption layer 3.

In particular, as shown in FIG. 2, the real part of the complex refractive index of the light absorption layer 3 is nabs.

The average film thickness of the light absorption layer 3 is dav. The average film thickness dav here is (volume of light absorbing layer 3) / (light absorbing layer 3)
The area of the region where is formed).

The imaginary part of the complex refractive index of the light absorption layer 3 is kabs.

The wavelength of the reproduction light (reproduction laser light) L2 is λ.

Next, the optical parameter defined by ρ = nabs · dav / λ will be described.

From the results of experiments and simulations conducted by the present inventors, it was noted that ρ = nabs · dav / λ is a very important parameter. That is, the optical information recording medium 1 having a structure in which the light absorption layer 3 and the light reflection layer 4 are provided on the substrate 2.
In order to obtain an output signal in which the reflectance specified in the CD standard is 70% or more, the modulation factor I11 / Itop is 60% or more, and the modulation factor I3 / Itop is 0.3 to 0.7, Ρ = nabs · d given by the real part nabs of the complex refractive index of the absorption layer 3, its average film thickness dav, and the wavelength λ of the reproduction light.
By setting av / λ within the range of 0.05 ≦ ρ ≦ 1.6,
It has been found that the reflectance can easily be set to 70% or more in conformity with the CD standard.

When ρ is smaller than 0.05, the thickness of the light absorption layer 3
It is not practical in manufacturing because dav needs to be considerably thin, 0.05 μm or less.

Therefore, within the range of 0.05 ≦ ρ ≦ 0.6, 0.30 ≦
The range of ρ ≦ 0.6 is practical, and the range of 0.1 or more is desirable to obtain sufficient modulation, and the range of 0.45 ± 0.1 is most desirable to obtain stable recording characteristics with large modulation. It can be said that

Furthermore, as shown in FIG. 4, even if ρ is in the range of 0.6 or more, the reflectance can exceed 70% at the peak point on the graph.

In the range of 0.6 <ρ <1.6, there are two peak points,
It is known that the reflectance is always in the range of 0.6 <ρ <1.10 and the range of 1.10 <ρ <1.6, and a high reflectance can be obtained at those peak points.

When ρ> 1.6, the film thickness becomes large, making it difficult to control the film thickness, which is not practical in manufacturing.

A graph showing the relationship between ρ and the reflectance is an exponential function,
It is expressed as a function combined with a periodic function, and the amplitude of the periodic function increases as ρ increases.

The amplitude of such a periodic function changes with parameters such as the complex refractive index of the layers forming the optical information recording medium 1, the film thickness, and their homogeneity. For example, when the refractive index of the layer on the side where the light is incident from the light absorption layer 3 is small, the reflectance is shifted in the direction in which the reflectance becomes high as a whole graph.

This graph also shows the imaginary part kab of the complex refractive index of the light absorption layer 3.
Expressed as an exponential function with s and dav as parameters,
It is also known that the larger the kabs, the larger the attenuation of the reflectance of the entire graph, as shown in FIG.

To obtain high reflectance, this kabs needs to be 0.3 or less.

As can be seen from the figure, if this kabs is 0.3 or less, the reflectance will improve as it approaches 0. Therefore,
This range is most desirable. However, the recording sensitivity becomes poorer as it gets closer to 0, so that it needs to be larger than 0. Specifically, a range of 0.01 or more is desirable, and actually, a range of about 0.05 is desirable.

The light absorption layer 3 is homogeneous and the real part nabs of its complex refractive index,
The simulation by the present inventors has shown that the period of the points showing the peaks in the graph of FIG. 4 does not change unless the film thickness dav has a non-uniform distribution.

It is possible to increase the reflectance at the bottom point of the graph in FIG. 4 by controlling the above parameter conditions depending on the conditions. However, when ρ is set near the bottom point, It is difficult to obtain a large degree of modulation, and in some cases, the reflectance may be higher than that before recording. Therefore, it is desirable to set ρ near the peak point.

Next, the material and physical properties of each layer will be described.

First, the translucent substrate 2 has a refractive index for laser light.
A material having a high transparency within the range of 1.4 to 1.6 and formed mainly of a resin having excellent impact resistance, such as a glass plate, an acrylic plate or an epoxy plate is used. Also, the substrate 2
Other layers, for example, a solvent resistant layer such as Si2 or an enhancement layer may be coated thereon.

These materials are molded by means such as injection molding. The thickness of the substrate 2 is 1.1mm to 1.5mm so that it conforms to the CD standard.
Is desirable.

In order to sufficiently obtain the effects of the present invention, the material of the substrate 2 is preferably polycarbonate. Further, it is desirable that the substrate 2 has a coefficient of thermal expansion α of about 5.0 × 10 ^{−5 to} 7.0 × 10 ⁻⁵ (1 / ° C.).

Tracking guide means is provided on the surface of the substrate 2 on the light absorption layer 3 side. The tracking guide means may be address pits formed of pits formed at predetermined intervals, so-called sample servos, but pregrooves 6 formed in a spiral shape (FIGS. 2 and 3).
Is desirable. The spiral pre-groove 6 is used to guide tracking when recording a data signal.

The depth of the pre-groove 6 may be any under normal conditions, but a depth of 30 to 250 nm is preferable, and a depth of 60 to 180 nm is more preferable. desirable. The width of the pre-groove 6 is 0.
3 to 1.3 μm is desirable.

The distance between the pre-grooves 6 and the so-called tracking pitch is preferably 1.6 μm.

Further, the tracking means such as the pre-groove 6 may have time code information (ATIP: Absolute Time In Pregroove) at the edge of the pre-groove 6.

The pre-groove 6 is usually formed by pressing a stamper at the time of injection molding of the substrate 2, but even if it is cut by a laser or manufactured by the 2P method (Photo-Polymer method). Good.

Next, the light absorption layer 3 is a layer formed of a light absorption substance formed on the tracking guide means of the substrate 2 and is a layer which is heated, melted, sublimated, deformed or modified by irradiating a laser. Is. The light absorbing layer 3 contains, for example, a cyanine dye dissolved in a solvent,
This is formed by uniformly coating the surface of the substrate 2 by means of spin coating or the like.

The material used for the light absorbing layer 3 can obtain the effects of the present invention as long as it is a known optical recording material, but a light absorbing organic dye is preferable. Specifically, polymethine dyes, triarylmethane dyes, pyrylium dyes, phenanthrene dyes, tetradehydrocholine dyes, triarylamine dyes, squarylium dyes, croconic methine dyes, merocyanine dyes, etc. Examples thereof include light-absorbing organic dyes, but the present invention is not limited thereto, and the effects of the present invention can be obtained as long as they are known optical recording materials.

The light absorption layer 3 made of the above cyanine dye is nabs, kabs
Since it is easy to set the numerical value of 1, the reproduction signal having high reflectance and high modulation can be obtained, and the optical information recording medium 1 conforming to the CD standard can be easily obtained.

The light absorbing layer 3 may contain other dyes, resins (for example, thermoplastic resins such as nitrocellulose, thermoplastic elastomers), liquid rubber, and the like.

Specifically, isobutylene, maleic anhydride copolymer,
Examples thereof include ethylene vinyl acetate copolymer, chlorinated polypropylene, polyethylene oxide, polyamide, nylon, coumarone resin, ketone resin, vinyl acetate, polystyrene, PVA (polyvinyl alcohol), PVE (polyvinyl ester) and the like.

Cellulose derivatives include carboxymethyl cellulose, nitrocellulose, HPC (hydroxypropyl cellulose), HEC (hydroxyethyl cellulose), MC
(Methyl cellulose), EC (Ethyl cellulose), EHEC
(Ethyl hydroxyethyl cellulose), CMEC (carboxymethyl ethyl cellulose) and the like.

Examples of the oligomer include oligostyrene and methylstyrene oligomer.

Examples of elastomer rubbers include styrene block copolymers and urethane-based thermoplastic elastomers.

The light absorbing layer 3 is obtained by dissolving the above dye and any additives using a known organic solvent (eg, ketone alcohol, acetylacetone, methyl cellosolve, toluene, etc.), and then dissolving them on the substrate 2 on which the pregroove 6 is formed. Surface of the
Alternatively, another layer on the substrate 2 is formed on the coated surface.

Examples of forming means in this case include a vapor deposition method, an LB method, and a spin coating method.
A spin coating method is preferable in which the layer thickness can be controlled by adjusting the viscosity, the drying rate of the solvent, and the like.

As a method of adjusting the layer thickness of the light absorption layer 3, specifically, a method of changing the rotation speed of spin coating, a method of spin coating by mixing substances having different viscosities, a method of dissolving using plural kinds of solvents Examples of the method include spin coating using a light absorbing substance, or spin coating using a mixture of high boiling substances.

Next, the light reflection layer 4 is a metal film, and, for example,
Gold, silver, copper, aluminum, or an alloy containing these is formed by a method such as a vapor deposition method or a sputtering method. Among these, a metal film mainly composed of gold or an alloy containing gold is preferable because it needs to have a reflectance of 70% or more.

Further, in order to prevent oxidation of the light reflection layer 4, another layer such as an oxidation resistant layer may be provided on the light reflection layer 4.

Next, the protective layer 5 is formed of a resin having excellent impact resistance similar to that of the substrate 2. For example, an ultraviolet curable resin is applied by a spin coating method and irradiated with ultraviolet rays to be cured to form the resin. In addition, epoxy resin, acrylic resin, silicone-based hard coat resin, etc. may be used.

In general, the protective layer 5 can be obtained by applying monomers and oligomers of an organic compound that can be polymerized into a polymer and then performing a crosslinking reaction. However, the material is not limited to an organic compound, and an inorganic material may be formed by a known means such as a sputtering method or a vapor deposition method.

In addition, when it is obtained as an organic polymer by a cross-linking reaction, from the viewpoint of workability, a reaction is initiated with a mixture of monomers and oligomers of organic heavy compounds having one or more reactive acryloyl groups (-CH = CH2) in the molecule. A method of adding a small amount of an agent and a reaction catalyst, applying a liquid mixture of these, and irradiating with an ultraviolet ray or an electron beam to crosslink is advantageous.

However, the method of cross-linking is not limited to this, and may be one in which cross-linking proceeds by heat such as an epoxy resin or a urethane resin, or by using moisture in the air such as a dialkoxysilane coupling agent. It may be one in which the polymerization reaction proceeds.

The main chain and side chains of the crosslinked product thus obtained may be saturated or unsaturated linear hydrocarbons, or may contain cyclic compounds such as melamine and bisphenol. In addition, a polyether containing one or more ether bonds in the main chain or side chain of this crosslinked product, a polyester containing an ester bond, a polyurethane containing a urethane bond, an ionomer containing an ionic bond, a polyamide containing an amide bond, an imide bond. It may include other bonds such as polyimide containing, polysulfone containing sulfone bond, and polysulfide containing sulfide bond. It may be a copolymer compound containing two or more of these bonds, or may be a block polymer.

Further, in order to improve the moisture resistance of these crosslinked products, a side chain may contain fluorocarbon or the like, and an epoxy resin may be contained in order to prevent deterioration due to hydrogen halide.

Further, in order to improve the adhesiveness with the light reflection layer 4, the side chain may contain a hydroxyl group, a carboxyl group, an acryl group, an amino group, a vinyl acetate group, or the like, and the main chain or the side chain may be a base. An acid may be included.

When forming the protective layer 5, during the coating, the resin and its reactive agent,
In addition to the reaction initiator and the like, a solvent and a diluent may be contained in order to improve coatability. Moreover, in order to stabilize the coating film, a leveling agent, a plasticizer, an antioxidant,
An antistatic agent, etc. may be contained. Further, it may be colored with a pigment or a dye, if necessary.

The hardness of the resin can be changed depending on the crosslink density of the crosslinked structure or the concentration of the reactive acroyl, and also depends on the degree of freedom of molecular rotation of the oligomer itself which can be the main chain.

In addition, in the optical information recording medium 1 according to the present invention, the layer behind the light absorbing layer 3, such as the light reflecting layer 4 and the protective layer 5, is heat-treated with respect to the substrate 2 as compared with the layer in which the pits 11 are formed. It is desirable to use a material having a high deformation temperature and a high hardness. Forming the layer on the back side with a layer having a high hardness is effective in reducing the block error rate of the recording signal specified in the CD standard.

Within the operating environment temperature specified in the CD standard, that is, -15 ℃
Within the range of 70 ° C., the hardness of the protective layer 5 is set to 2H or more in pencil hardness so that the light reflecting layer 4 of the light absorbing layer 3
The deformation of the second layer boundary 9 on the side can be suppressed to be small.
As a result, waveform distortion can be suppressed, and good recording with a small block error rate (BLER) can be performed.

As shown in FIG. 6, BLER tends to increase as the hardness of the protective layer 5 decreases. According to the study of the present inventors, at a pencil hardness of H or less, after the weather resistance test,
Only optical information recording media with a large BLER exceeding the upper limit of the CD standard can be obtained.

Next, the coefficient of thermal expansion α of the protective layer 5 is set to 1.5 × 10 ^{−5 to} 9.0 × 10 ⁻⁵ within the operating environment temperature range of −15 ° C. to 70 ° C.
By setting it within the range of (1 / ° C.), the protective layer 5 exhibits the same thermal volume change as the substrate 2, so that it becomes difficult for the optical information recording medium 1 as a whole to warp even when heat is applied. .

When α is less than 1.5 × 10 ⁻⁵ , the substrate 2 expands more due to expansion during heating, so that the optical information recording medium 1 is deflected toward the protective layer 5 side, and tensile tension is generated in each layer of the substrate 2. This causes an increase in the jitter of the recording pit 11.

When α is larger than 9.0 × 10 ⁻⁵ , the protective layer 5 expands more due to expansion during heating, so that the protective layer 5 sags, and between the light absorbing layer 3 and the light reflecting layer 4, and Delamination occurs between the light reflecting layer 4 and the protective layer 5.

By setting the shrinkage ratio of the protective layer 5 at the time of curing to 12% or less, even after a heat cycle test is performed so that no distortion of the resin remains after curing, the protective layer 5 has It was found that no cracks occurred. .

Considering the mechanical strength, the shrinkage rate of the protective layer 5 is preferably 10% or less.

Furthermore, between the light reflection layer 4 and the protective layer 5, the light reflection layer 4 is provided.
It is also possible to interpose an oxidation resistant layer for preventing the oxidation of the.

[Operation] The optical information recording medium according to the present invention can be recorded by a known optical information recording device. An outline will be given below. That is, the optical information recording medium 1 is arranged so that the surface of the transparent substrate 2 faces the side of the optical information recording apparatus where the laser irradiation means, that is, the pickup is provided. This optical information recording medium 1
The optical absorption layer 3 of the optical information recording medium 1 is picked up by the pickup while the laser spot modulated into the signal conforming to the CD standard is tracked by the tracking guide means while being rotated by the spindle motor.
The pit 11 is formed by irradiating the pit 11.

It is desirable to irradiate the optical information recording medium with a laser spot having a wavelength λ of around 780 nm. In addition, the linear velocity must be 1.2 to 1.4 m / sec and the recording power can be about 6 to 9 mW in relation to the CD standard. That is, recording can be performed by increasing the recording power of a commercially available CD player as compared with that during reproduction.

Thus, the optical information recording medium 1 capable of obtaining a reproduction signal satisfying the CD standard can be easily produced.

In the optical information recording medium 1 according to the present invention, as shown in FIG. 3, when the light absorbing layer 3 is irradiated with the recording laser light L1 from the substrate 2 side, the light absorbing layer 3 absorbs the laser light L1. Heat is generated, the surface of the substrate 2 is locally deformed, and the substrate 2
It is desirable that pits 11 are formed on the surface.

Alternatively, the light absorption layer 3 may cause an optical change so that the pit 11 is formed.

Further, the components melted and decomposed by the irradiation of the laser beam L1 are diffused into the softened substrate 2 and partially mixed with the components forming the substrate 2 to be compounded there, and the light absorption layer 3 and the substrate there. In some cases, a pit 11 may be formed by forming a portion that is optically different from the other portion of 2.

The reproduction of the recording signal is performed by irradiating the laser light L2 for reproduction from the substrate 2 side, and the reflected light of the pit 11 portion and the pit 11 are reproduced.
It is performed by reading the difference in brightness of the optical phase difference from the reflected light of the other part.

Further, in the present invention, in addition to the optical information recording medium 1 in which the light absorption layer 3 is formed on almost the entire surface of the substrate 2, a part of the substrate 2 is a recordable area having the light absorption layer 3 and the other part is a CD. It is also applicable to an optical information recording medium which is a ROM area having pits 11 in which a format signal can be reproduced. In such an optical information recording medium, for example, a pit for signal reproduction is previously formed by a stamper or the like in a portion which becomes a ROM area on the surface of the substrate 2, and the light absorption layer 3 is formed only in the storable area outside thereof. It was done.

In such an optical information recording medium, a large amount of uniform data can be recorded in advance in the ROM area by a press or the like, and since there is no light absorption layer 3 there, erroneous erasure or other data can be recorded. There is no risk of incorrect recording. Further, data unique to the user can be arbitrarily recorded in the area having the light absorption layer 3. And this recorded data is a CD
Since it can be reproduced with a signal conforming to the standard,
The information in the ROM area can be reproduced by a commercially available CD player.

[Examples] Next, examples of the optical information recording medium according to the present invention will be described below.

Example 1 A spiral pregroove 6 having a width of 0.5 μm, a depth of 0.08 μm, and a pitch of 1.6 μm is formed, a thickness of 1.2 mm, and an outer diameter of 1
A polycarbonate substrate having a diameter of 20 mm and an inner diameter of 15 mm was molded by an injection molding method.

Next, as an organic dye for forming the light absorption layer, 0.65
g of 1,1′-dibutyl 3,3,3 ′, 3 ′ tetramethyl 4,5,4 ′,
Dissolve 5'-dibenzoindodicarbocyanine perchlorate (NK-3219, manufactured by Nihon Sensitive Dye Co., Ltd.) in 10 ml of diacetone alcohol solvent, and spin coat this on the above substrate while appropriately changing the rotation speed. Thus, a light absorption layer made of a dye film having an average film thickness dav of 0.13 μm was formed.

A 50 nm-thick Au film was formed on the entire surface of this disk by a vacuum evaporation method to obtain a light reflection layer. Furthermore, 3 g of an ultraviolet curable resin (SN5X-9685 manufactured by San Nopco Co., Ltd.) was applied on the light reflecting layer by a spin coating method, and was irradiated with ultraviolet rays from a low pressure mercury lamp of 120 W / cm at 6 m / min for curing. , Thickness 8 μm
To form a protective layer.

The surface hardness of the protective layer on the glass surface under this condition is a pencil hardness of 4H.

Further, the thermal expansion coefficient α in the temperature range of −15 to 70 ° C. is 1.5
× 10 ^-5 ≦ α ≦ 6.5 × 10 ^-5 (1 / ° C).

Further, the shrinkage percentage upon curing was 10.8%.

The optical information recording medium thus obtained was irradiated with a semiconductor laser having a wavelength of 780 nm at a linear velocity of 1.2 m / sec and a recording power of 6.0 mW, and the EFM
The signal was recorded.

A commercially available CD player (Aurex XR-V
73, playback light wavelength 780nm, playback power 0.5mW laser)
The block error rate is 1.8 × 10 ^-3
Met.

After this, this optical information recording medium was heated at a temperature of 70 ° C and a humidity of 55% RH.
A weather resistance test was carried out for 250 hours. After returning to room temperature, BLER
Was measured again and found to be 5.2 × 10 ⁻³ . This value sufficiently satisfies the standard value of Red Book, which is one of the CD standards.

The warp angle of the optical information recording medium at this time was 0.4 degrees. This angle also satisfies the standard value of the Red Book.

After the above-mentioned test, a weathering test under the same conditions was conducted for a total of 1000 hours, but BLER and sled thereafter showed almost no change.

Comparative Example 1 A polycarbonate substrate molded in the same manner as in Example 1,
As the organic dye for forming the light absorption layer, the same dye as in Example 1 was spin-coated at the same concentration to give an average film thickness da.
A light absorbing layer made of a dye film having v of 0.13 μm was formed.

A 50 nm-thick Au film was formed on the entire surface of this disk by a vacuum evaporation method to obtain a light reflection layer.

Further, several kinds of monofunctional acrylate monomers and polyfunctional acrylate oligomers (Aronix, manufactured by Toagosei Kagaku Kogyo Co., Ltd.) were mixed on the light reflection layer, and 2 wt% of this acrylate mixture of 1-hydroxycyclohexyl phenyl ketone (Ciba Geigy). , Irgacure
184) was added as a photoinitiator. 3 g of this paint was applied to the above-mentioned light-reflecting layer by a spin coating method in the same manner as in Example, and ultraviolet rays from a low pressure mercury lamp of 120 W / cm were applied to this at 4 m / min.
To irradiate and cure to form a protective layer having a thickness of 6 μm.

The surface hardness of the protective layer on the glass surface under this condition is a pencil hardness of 6H.

The coefficient of thermal expansion α in the temperature range −15 to 70 ° C. is 0.8
It was × 10 ^-5 ≦ α ≦ 3.0 × 10 ^-5 (1 / ° C).

Furthermore, the shrinkage factor upon curing was 13.8%.

When the optical information recording medium thus obtained was recorded and reproduced in the same manner as in Example 1, the block error rate was 3.1.
It was × 10 ^-3 .

After this, this optical information recording medium was heated at a temperature of 70 ° C and a humidity of 55% RH.
A weather resistance test was carried out for 250 hours. After returning to room temperature, BLER
Was measured again and found to be 4.8 × 10 ^-2 . This value does not meet the CD standard.

The warp angle of the optical information recording medium at this time was 1.2 degrees. This angle also does not satisfy the standard value of the above CD.

Example 2 A light absorbing layer was formed in the same manner as in Example 1 on the polycarbonate substrate molded in the same manner as in Example 1 above, and a light reflecting layer was further formed in the same manner as in Example 1.

3 g of UV curable resin (EX-708 manufactured by Dainippon Ink and Chemicals Co., Ltd.) was applied onto this light reflecting layer by spin coating, and applied to this.
Ultraviolet rays from a 120 W / cm low-pressure mercury lamp were irradiated at 6 m / min for curing to form a protective layer having a thickness of 10 μm.

The surface hardness of the protective layer on the glass surface under this condition is a pencil hardness of 2H.

Further, the thermal expansion coefficient α in the temperature range of −15 to 70 ° C. is 1.5
× 10 ^-5 ≦ α ≦ 6.5 × 10 ^-5 (1 / ° C).

Furthermore, the shrinkage factor upon curing was 9.2%.

Recording and reproduction were performed on the optical information recording medium thus obtained in the same manner as in Example 1, and the block error rate was 2.
It was 0 × 10 ^-3 .

Then, the optical information recording medium was changed from a temperature of 25 ° C. and a humidity of 55% RH to a temperature of 70 ° C. and a humidity of 65% RH in 2 hours. After keeping this state for 4 hours, the temperature is 25 ° C and the humidity is 55 in 2 hours.
The weather resistance test in which the temperature was returned to% RH and the temperature was raised again after 1 hour was repeated 10 times. After that, when BLER is measured again, it is 1.1 × 1
It was 0 ^-2 . This value sufficiently satisfies the standard value of Red Book, which is one of the CD standards.

At this time, neither cracks nor bulges on the protective layer in the optical information recording medium and changes in other layers were observed.

(Comparative Example 2) A polycarbonate substrate molded in the same manner as in Example 1
Similarly, a light absorbing layer is formed, and then a light reflecting layer is further formed. Further, 3 g of an ultraviolet curable resin (SN-8395 manufactured by San Nopco Co., Ltd.) is applied on the light reflecting layer by the spin coating method so as to form the light reflecting layer. Then, this was irradiated with ultraviolet rays from a low-pressure mercury lamp of 120 W / cm at 6 m / min and cured to form a protective layer having a thickness of 8 μm.

The surface hardness of the protective layer on the glass surface under this condition is a pencil hardness of 5H.

The coefficient of thermal expansion α in the temperature range −15 to 70 ° C. is 0.8
It was × 10 ^-5 ≦ α ≦ 3.0 × 10 ^-5 (1 / ° C).

Furthermore, the shrinkage percentage upon curing was 15%.

When the optical information recording medium thus obtained was recorded and reproduced in the same manner as in Example 1, the block error rate was 1.7.
It was × 10 ^-3 .

After that, this optical information recording medium was changed from a temperature of 25 ° C and a humidity of 55% RH to a temperature of 70 ° C and a humidity of 65% RH in 2 hours, and this state was maintained for 4 hours, and then a temperature of 25 ° C in 2 hours. , Humidity 55%
The weather resistance test of returning to RH and heating again 1 hour later was repeated 10 times.

After that, when the optical information recording medium was observed, cracks accompanied by peeling occurred in the protective layer, and the cracks reached the light absorbing layer.

Moreover, it was impossible to measure the BLER value due to the cracking at this time.

As described above, according to the present invention, the pencil hardness of the protective layer,
And by setting the thermal expansion coefficient to a predetermined value, it is possible to satisfy the standard value of the block error rate value specified in the CD standard, and to provide an optical information recording medium excellent in weather resistance. You can

[Brief description of drawings]

FIG. 1 is a partially cutaway perspective view of an optical information recording medium 1 according to the present invention, FIG. 2 is a longitudinal sectional view of an essential part of the optical information recording medium 1, and FIG. 3 is a pit 11 in a pregroove 6. 4 is a graph showing the relationship between ρ (= nabs · dav / λ) and the reflectance, and FIG. 5 is the complex refractive index kabs of the light absorption layer 3 and the reflection. FIG. 6 is a graph showing the relationship between the pencil hardness of the protective layer and the block error rate (BLER). 1 ... Optical information recording medium 2 ... Translucent substrate 3 ... Light absorbing layer 4 ... Light reflecting layer 5 ... Protective layer 6 ... Pre-groove 7 ... Land 8 ... First layer boundary 9 ...... Second layer boundary 10 …… Third layer boundary 11 …… Pits nabs …… Real part of complex refractive index of light absorption layer 3 kabs …… Imaginary part of complex refractive index of light absorption layer 3 dav …… Average film thickness of the light absorption layer 3 λ …… Reproduction light wavelength L1 …… Recording laser light L2 …… Reproduction laser light

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Toru Fujii 6-16-20 Ueno Taito-ku, Tokyo 6-16-20 Ueno Electric Co., Ltd. (72) Inventor Takanobu Matsumoto 6-16-20 Ueno Taito-ku, Tokyo Taiyo (56) Reference JP 63-188837 (JP, A) JP 2-10533 (JP, A) JP 3-232130 (JP, A) JP 3-232132 ( JP, A)

Claims (2)

[Claims] 1. A substrate having a light-transmitting property and provided on a laser light incident side, a light reflecting layer made of a metal film for reflecting the laser light and being laminated on the substrate, and a light reflecting layer made on the light reflecting layer. An optical information recording medium having a protective layer, wherein the protective layer has a pencil hardness of 2H or more and a thermal expansion coefficient α of 1.5 × 10 ^{−5 in} an environment temperature range of −15 ° C. to 70 ° C. An optical information recording medium characterized in that ≦ α ≦ 9.0 × 10 ⁻⁵ (1 / ° C.). 2. A substrate having a light-transmitting property and provided on the laser light incident side, a light absorbing layer composed of an organic dye which is laminated on the substrate and absorbs the laser light, and a light absorbing layer on the light absorbing layer. An optical information recording medium having a light-reflecting layer formed of a metal film that reflects the laser light while being laminated, and a protective layer that is laminated on the light-reflecting layer, wherein the protective layer has a pencil hardness of 2H or more. The optical information recording medium is characterized by having a coefficient of thermal expansion α of 1.5 × 10 ⁻⁵ ≦ α ≦ 9.0 × 10 ⁻⁵ (1 / ° C) in an ambient temperature range of −15 ° C. to 70 ° C.