KR20050025119A - Optical recording medium - Google Patents

Abstract

An optical recording medium which comprises a 0.3 to 2.0 mm-thick substrate made of thermoplastic resin and provided with an emboss pit or guide groove, a reflection layer provided on the substrate, and a 3 to 200 mum-thick transparent protection layer provided thereon, and which reproduces recorded information based on a change in light intensity of a reflected light produced by applying a light beam from the transparent protection layer side, characterized in that the substrate consists of polycarbonate resin having a specific chemical structure and thermoplastic resin having specific physical properties. An optical recording medium for surface recording/reproducing having a simple structure, especially, a high-recording-density optical recording medium is provided.

Description

Optical recording medium {OPTICAL RECORDING MEDIUM}

The present invention relates to an optical information recording medium, and more particularly to an optical information recording medium for surface recording reproduction.

In a conventional optical disc such as a CD or CD-ROM (abbreviated as "CD disc"), an emboss pit in accordance with recording data is formed on one side of a 1.2 mm thick transparent substrate, on which aluminum A reflective film made of (Al) or the like is formed. The information recorded on such a CD disk is reproduced by irradiating a condensing beam on the transparent substrate side opposite to the surface on which the reflective film is formed.

On the other hand, in DVD or DVD-ROM disks (abbreviated as "DVD disks") with higher recording density, finer emboss pits are formed on one side of the 0.6 mm thick transparent substrate than in the case of CD disks. On the furnace, a reflective film made of Al or the like is formed. The reproduction of the information recorded on the recording surface of the DVD disc is performed by irradiating the condensing beam on the transparent substrate side opposite to the surface on which the reflective film is formed, as in the case of the CD disc.

As the material of the 0.6 mm thick substrate, PC (polycarbonate), which is a transparent resin material, is generally used. In a 0.6-mm-thick PC substrate, since the mechanical properties are not sufficient and the substrate is bent as it is, two 0.6-mm PC substrates are bonded together so that the recording surface is inside, and the mechanical properties are secured as a disk having a total thickness of 1.2 mm.

The reason why the thickness of the substrate of the DVD disk is 0.6 mm is to secure the tilt margin. As the track pitch and pit density become denser, the disc tilt and so-called tilt margins decrease. Although the tilt margin can be secured by reducing the substrate thickness from 1.2 mm to 0.6 mm, a decrease in mechanical strength is inevitable.

Therefore, it is proposed to secure the mechanical strength by making the center portion of the disk thick in order to make the substrate thin and to secure the mechanical strength (Japanese Patent Laid-Open No. 9-204686). However, in order to secure mechanical strength, the substrate thickness of the signal recording area was 0.6 mm. In addition, although the thickness of the transparent substrate is reported to be 0.1 mm to 0.6 mm (Japanese Patent Laid-Open No. 9-204688), the thickness of the protective substrate holding the recording film, the film thickness of the reflective film, and the like are not mentioned. There was a problem.

In recent years, various types of optical recording media have been proposed. For example, U.S. Patent No. 5972459 (Japanese Patent Laid-Open No. 11-7658) discloses a support made of a thermoplastic resin, having a thickness of 0.3 to 1.2 mm, a guide groove on the support, and a guide groove on the guide groove. It has a recording area composed of at least a reflective film and a phase change recording film, and a transparent protective layer having a thickness of 3 to 177 µm is formed in at least the recording area, and reproduction is performed when the thickness nonuniformity of the transparent protective layer is Δt. Alternatively, between the numerical aperture (NA) and the wavelength (λ) of the optical system to record and reproduce,

Δt ≦ 5.26 (λ / NA ⁴ ) (μm) (NA is the numerical aperture)

An optical recording medium characterized by satisfying the phosphorus relationship is proposed, and an optical recording medium capable of high capacity can be provided by defining a relationship between the thickness of the transparent protective layer and the thickness nonuniformity.

As an example, conditions necessary for an optical recording medium for achieving a high density of a storage capacity of 8 GB are summarized as follows. That is, the recording / reproducing optical system satisfies λ ≦ 0.68 μm and satisfies N.A./λ≦1.20, the thickness t of the transparent protective layer in the recording area is 3 to 177 μm, and the thickness nonuniformity of the transparent protective layer is

Δt ≦ ± 5.26 (λ / NA ⁴ ) (μm)

Track Pitch P≤0.64 (㎛)

Tolerance ΔP≤ ± 0.04P (μm)

Linear density d≤0.1161 / P (㎛ / bit)

Disc Skew Θ≤84.115 × (λ / NA ³ / t)

Eccentricity E≤67.57P (μm)

Surface Roughness Ra≤ ± 3λ / 100 (in Spot Irradiation Area)

It is

Further, US Patent No. 6159572 (Japanese Patent Laid-Open No. 11-296904) discloses a substrate having a recording surface on which an emboss pit or guide groove is formed, a reflective film formed on the recording surface of this substrate, A protective film formed on the reflective film, wherein the surface is constituted by two surfaces of a first surface on the side where the protective film is formed and a second surface opposite to the first surface, and irradiated with a light beam from the first surface side. An information recording medium for reproducing recording information on the basis of a change in light intensity of reflected light, wherein the distance from the recording surface of the substrate to the first surface is smaller than the thickness of the substrate and the first surface is smooth. Medium "has been proposed. In addition, as a double-sided recording method, a substrate having an "emboss pit or guide groove formed thereon and having opposing first and second recording surfaces, first and second reflective films formed on said first and second recording surfaces, respectively, The surface is comprised by the two surfaces of the 1st surface which is the side in which the said 1st protective film was formed, and the 2nd surface which is the side in which the said 2nd protective film was formed, provided with the 1st and 2nd protective film respectively formed on this 1st and 2nd reflective film, respectively. And an information recording medium for irradiating a light beam from the first surface side and the second surface side, respectively, and reproducing the recording information based on the change in the light intensity of the reflected light, from the first recording surface to the first surface of the substrate. Distance, and the distance from the second recording surface of the substrate to the second surface is 5λ / (4n) or more and 0.6mm or less (λ is the wavelength of the light beam, n is the light of the first or second protective film of light having the wavelengthλ). Refractive index) And an information recording medium having a thickness of 0.6 mm or more and 1.2 mm or less and a distance from the first surface to the second surface of 1.2 mm or less.

They aim to provide an information recording medium capable of securing sufficient tilt margin and mechanical strength even with increasing recording density.

By the way, in the recording medium of these proposals, the material constituting the substrate is not particularly considered. For example, the US Patent No. 6159572 discloses an acrylic resin such as polymethyl methacrylate (PMMA) as the substrate material. And polycarbonate resins, epoxy resins, styrene resins, glass, metals such as Al, alloys and ceramics.

However, in the above-described configuration of the recording medium, it is difficult to avoid the occurrence of skew (SKEW) for the following reasons (1) to (4).

①Injection: The generation of stress (molecular orientation deformation) by the shear stress when resin flows through the cavity.

② Charging completed: When the resin is filled in the cavity, the flow of resin stops abruptly with the sudden stop of the screw movement, and both the resin and the inertial forces of the screw are applied to the substrate.

3. Hold pressure: Since pressure is applied to the resin to prevent backflow of the resin and prevention of sink marks due to volume shrinkage until the resin at the time of injection is sealed, pressure distribution occurs in the entire substrate.

④ Cooling: Stress due to temperature distribution occurs by heat shrink.

Therefore, in JP-A-11-242829, as an improvement,

&Quot; An optical recording medium on which at least a recording layer and a transparent protective layer are formed in order, and light is incident from the transparent protective layer, whereby an information signal is recorded and / or reproduced, wherein the substrate is a side on which the recording layer is formed. And a second resin layer formed of a resin material having a greater flexural modulus than the resin material laminated on the first resin layer to form the first resin layer, the first resin layer forming a surface of the film. Recording medium ".

On the other hand, even if the problem of mechanical characteristics is solved by the above improvement, in the optical recording medium of the one-sided signal, the disk is deformed due to moisture absorption in the environmental change of temperature and humidity.

In the case of DVD discs, a polycarbonate substrate with a normal absorption rate of 0.3% or more is used. Since the 0.6 mm discs are bonded to each other in the opposite direction with the signal side inward, even if the absorption rate is large, absorption can be balanced and deformation is achieved. It did not raise well and did not become a problem. However, high density N.A. (opening ratio) high density discs have signals on one side of the surface layer, so that the absorption balance is different, which causes problems with absorption deformation. In particular, during the operation of the drive, sudden changes are likely to occur in places where the cabin temperature is high and the humidity is low, and a focus error such as the signal cannot be read due to the deformation of the disk is likely to occur.

In order to suppress such absorption deformation, US Patent No. 6201783 (Japanese Patent Laid-Open No. 2000-11449) discloses, "a substrate and a recording layer disposed on the substrate for recording an information signal and a transparent protective layer laminated on the recording layer. A disc-shaped information recording medium having a layer and recording / reproducing an information signal by incidence of light from the transparent protective layer side, the substrate being integrated with a core layer made of a resin and a core layer, and on one side of the information on the recording layer side. As an information recording medium having an unevenness of a signal and consisting of a surface layer made of a resin having fluidity compared to the core layer, it is proposed to use a resin having a water absorption of 0.3% or less as the surface layer resin of the substrate. There is a direction to solve the problem by the complicated substrate configuration by two-color molding, sandwich molding.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a partial schematic view of a disk plane vertical cross section in an example of an optical recording medium applied to the present invention.

2 is a partial schematic view of a disk surface vertical section in another example of the optical recording medium applied to the present invention.

3 is a partial schematic view of a disk surface vertical section in another example of the optical recording medium applied to the present invention.

FIG. 4 shows the change over time of the tilt in a portion of 58 mm from the center of the optical disk caused by environmental changes on the basis of the resting time.

(Embodiment of invention)

EMBODIMENT OF THE INVENTION Hereinafter, the specific embodiment of the optical recording medium of this invention is described in detail with reference to drawings. 1-3 are partial schematic views of the vertical cross section in the disk surface which show an example of the optical recording medium of this invention. In addition, the structure of the optical recording medium proposed by this invention is not limited to the example here.

In the optical recording medium 1 to which the present invention is applied, a light reflection layer 3, a recording layer 4, and a transparent protective layer 5 are sequentially formed on a substrate 2 having a guide groove as shown in FIG. It is done. On the upper surface of the substrate 2, guide grooves formed of a predetermined uneven pattern such as phase pits for recording data information, tracking servo signals, and the like, and fine unevenness such as pregrooves are formed.

As shown in Fig. 2, the optical recording medium 2 has a multilayer structure in which a recording film or a reflective layer and a transparent protective layer are stacked on the substrate 2 having guide grooves, and further, optical recording. In the medium 3, as shown in FIG. 3, embossed pits or guide grooves are formed on both sides of the substrate 2, and the reflective layer and the transparent protective layer are also laminated on both sides in turn. In addition, materials having the same or similar characteristics may be used for the substrate, the light reflection layer, the recording layer, and the transparent protective layer constituting these optical recording media (optical disks).

Hereinafter, the board | substrate which comprises the optical recording medium (henceforth an "optical disk") of this invention is demonstrated in more detail.

The board | substrate 2 is 0.3-2.0 mm in thickness, Preferably it is 0.5-1.1 mm. In this connection, the transparent protective layer has a thickness of 3 to 200 µm, preferably 10 to 120 µm, and the total thickness of the substrate and the transparent protective layer is practically about 1.2 mm in the case of the optical recording medium shown in FIG.

It is preferable that the bending elastic modulus of the thermoplastic resin used for the board | substrate 2 is 24,000 kgf / cm <2> or more, More preferably, it is 26,000 kgf / cm <2> or more, It is most preferable that it is 27,000 kgf / cm <2> or more. If the flexural modulus is less than 24,000 kgf / cm 2, the surface vibration that occurs when the molded optical disk rotates at a high speed becomes large, which is not preferable as an optical disk requiring high density storage capacity. The higher the flexural modulus is, the higher the moldability can be maintained. Usually, it is 37,000 kgf / cm <2> or less, Preferably it is 35,000 kgf / cm <2> or less.

It is preferable that the saturated water absorption of the thermoplastic resin in this invention when it is immersed in 23 degreeC pure water further is 0.33 weight% or less. More preferably, it is 0.30 weight% or less. In particular, the saturated water absorption is most preferably 0.27% by weight or less. If the saturation absorption exceeds 0.33% by weight, it is not preferable because the warp deformation of the optical disk easily occurs during the absorption and dehumidification process and the focus error and tracking error easily occur.

The following measurement method was used about the bending deformation in the absorption and dehumidification process of the optical disk. That is, the disk is exposed to a saturated absorption rate at a temperature of 30 ° C. and a humidity of 90% RH (A environment), and then moved to a temperature of 23 ° C. and a humidity of 50% RH (B environment). Tilt change of the part used to mm is measured with time change, and the difference (DELTA Tilt) of the maximum value of a tilt change and the value at the time of reaching a fixed holding state is compared. At this time, the disk ΔTilt is 0.6 degrees or less, preferably 0.5 degrees or less.

Moreover, it is preferable that the load deformation temperature (HDT) measured at 1.82 Mpa according to ASTM D-648 is 125 degreeC or more, It is more preferable that it is 127 degreeC or more, and, as for the thermoplastic resin in this invention, 129 degreeC or more is more preferable. . When the load deformation temperature is lowered, heat resistance as a disk is insufficient. The load deformation temperature is generally 150 ° C. or less, preferably 140 ° C. or less when applied to ordinary injection molding.

In addition, the thermoplastic resin preferably has a loss tangent (tanδ) value of 0.006 or higher, more preferably 0.008 or higher, and most preferably 0.01 or higher according to ISO 6721-4 at 40 ° C and 18 kPa. If the loss tangent (tan δ) is less than 0.006, the vibration damping property of the resin is small and the surface vibration occurring when the molded optical disk rotates at high speed is not preferable. The upper limit of the loss tangent tan δ is generally 0.08 or less and usually 0.07 or less.

Since the disk substrate of the present invention is intended for a high density recording capacity, the resin is required to have a high transfer rate with respect to the guide groove (groove) at the time of molding. According to the measuring method to be described later, the resin has a transfer rate of 95% or more, preferably 98% or more.

In the optical recording medium of the present invention, since the information signal is recorded and / or reproduced by injecting light from the transparent protective layer 5 side, the substrate 2 does not affect the optical recording and / or reproduction characteristics. It does not require transparency in particular. Since two or more kinds of resin blend materials having greatly different refractive indices produce haze due to light scattering, it is not easy to use them as substrate materials such as CD and DVD that require conventional optical characteristics. It is possible to use even the 2 or more types of resin blend material with which refractive index differs greatly for the board | substrate 2 of this invention.

Next, an example of such a thermoplastic resin is given. However, the thermoplastic resin which forms the board | substrate in this invention is not limited to the following examples as long as the characteristic satisfy | fills said (1)-(4).

The thermoplastic resin in the present invention may be a resin having a low water absorption, a good vibration damping property and a good elastic modulus of elasticity, and satisfying the above-mentioned characteristics including a resin having a good heat resistance as a disk material. Examples of such thermoplastic resins may be selected from polycarbonate resins, amorphous polycyclic olefins, hydrogenated polystyrenes, and the like, but are preferably selected from thermoplastic resins mainly containing polycarbonate resins.

The said polycarbonate resin is normally obtained by superposing | polymerizing an aromatic dihydroxy compound and a carbonate bond precursor, for example by a solution method or a melting method. The aromatic dihydroxy compound used herein does not interfere with any compound as long as it can satisfy the above conditions. For example, 2,2-bis (3-methyl-4-hydroxyphenyl) propane, 1,1-bis (4-hydroxyphenyl) cyclohexane, 1,1-bis (4-hydroxyphenyl) -3,3,5-trimethylcyclohexane, 9,9-bis (3-methyl-4-hydroxyphenyl) flu Orene or α, α'-bis (4-hydroxyphenyl) m-diisopropylbenzene is preferred. In addition, said (alpha), (alpha) '-bis (4-hydroxyphenyl) m- diisopropyl benzene is a compound represented by the following chemical structural formula.

The polycarbonate resin may be a homopolycarbonate using the above aromatic dihydroxy compound alone, or may be a copolycarbonate using two or more kinds. And copolycarbonate which combined other dihydroxy compound with said aromatic dihydroxy compound may be sufficient. Examples of other dihydroxy compounds include 2,2-bis (4-hydroxyphenyl) propane (bisphenol A). In this connection, the polycarbonate resin by bisphenol A alone does not correspond to a resin that satisfies all of the above characteristics (1) to (4) of the present invention. The polycarbonate resin may be used alone or as a blend of two or more kinds.

Preferred resin compositions include 1,1-bis (4-hydroxyphenyl) -3,3,5-trimethylcyclohexane (component a-1) and 9,9-bis (4-hydroxy-3-methylphenyl) flu Polymerized using a dihydroxy compound containing at least 20 mol% of at least one aromatic dihydroxy compound (component A) selected from the group consisting of orene (a-2 component) with respect to all the dihydroxy compounds as a bisphenol component It is a thermoplastic resin containing 50 weight% or more of aromatic polycarbonate resins.

Specific examples of more preferred thermoplastic resins include 1,1-bis (4-hydroxyphenyl) -3,3,5-trimethylcyclohexane and / or 9,9-bis (4-hydroxy-3-methylphenyl). Carbonate is a bisphenol component containing fluorene and α, α'-bis (4-hydroxyphenyl) m-diisopropylbenzene in a molar ratio of 20:80 to 70:30, preferably 40:60 to 70:30. The copolymerized polycarbonate resin obtained by making it react with a precursor, or these blend carbonate compositions is mentioned.

Moreover, the blend with another resin (preferably other polycarbonate resin) containing this copolymerization polycarbonate resin 50weight% or more is mentioned.

It is preferable that the said polycarbonate resin melt | dissolves the polymer 0.7g in 100 ml of methylene chloride, and the specific viscosity measured at 20 degreeC is 0.2-0.5, and it is more preferable that it is the range of 0.25-0.4. If the specific viscosity is less than 0.2, the molded product is brittle, and if the viscosity is higher than 0.5, the melt fluidity is poor, resulting in poor molding, and it is difficult to obtain an optically good molded product.

The thermoplastic resin of the present invention can be blended with at least one phosphorus compound selected from the group consisting of phosphoric acid, phosphorous acid, phosphonic acid, aphosphonic acid and esters thereof as a heat stabilizer. These phosphorus compounds may be condensates. By mix | blending this phosphorus compound, the thermal stability of this resin for optical discs improves and the molecular weight fall at the time of shaping | molding and color deterioration are prevented.

The compounding quantity of such a heat stabilizer is 0.0001 to 0.05 weight% with respect to this thermoplastic resin, 0.0005 to 0.02 weight% is preferable, and 0.001 to 0.01 weight% is especially preferable.

In the thermoplastic resin of the present invention, an antioxidant commonly known for the purpose of antioxidant can be added. This example may represent a phenolic antioxidant. The range of the preferable addition amount of these antioxidant is 0.0001 to 0.05 weight% with respect to the thermoplastic resin.

And the higher fatty acid ester of monohydric or polyhydric alcohol can also be added to the thermoplastic resin of this invention as needed. By blending the higher fatty acid esters of monohydric or polyhydric alcohols, the releasability from the mold during the molding of the thermoplastic resin is improved, and in the molding of the disc substrate, the release load is small and the deformation and pit shift of the disc substrate due to the release defect can be prevented. Can be. There is also an advantage in that the melt fluidity of the thermoplastic resin is improved.

The ester compounding quantity of such an alcohol and a higher fatty acid is 0.01-2 weight% with respect to the thermoplastic resin, 0.015-0.5 weight% is preferable, and 0.02-0.2 weight% is more preferable.

In the resin for an optical disk substrate of the present invention, in addition, other thermoplastic resins, light stabilizers, colorants, antistatic agents, lubricants, and the like are transferred in a range that does not impair the warpage reduction effect in the moisture absorption and dehumidification process of the disk. Can be added.

In the preparation of the resin composition of the present invention, the mixing of the polycarbonate resins and / or the mixing with other resins may be carried out at each step of a molded article such as a polymer solution, powder or pellets, but is not particularly limited. . Regarding the mixing method, for example, a container equipped with a stirrer can be considered mainly in the step of the polymer solution, and a tumbler, a V-type blender, a mixer, etc. can also be used in the molded part step such as a granular material and pellets. , A banbury mixer, a kneading roll or an extruder or the like is used. In any case, any method may be employed, and the method is not particularly limited. However, since the method for removing foreign matters in the mixing operation is simple, a method of passing a filter having a suitable interval after mixing in a polymer solution is preferable. .

When mixing polycarbonate resin and another resin in a solution, it is preferable to use the solvent in which a polycarbonate resin and another resin are soluble together. In this case, it is preferable to remove impurities and foreign substances such as unreacted components by filtration in a solution state. And in the extrusion process (pelletization process) which obtains the pellet-type resin composition for injection molding, it is preferable to remove a foreign material, such as passing a sintered metal filter etc. which are 50 micrometers or less of filtration precision in a molten state. It is also preferable to add additives, such as antioxidant, such as phosphorus type as needed. In any case, the raw material resin before injection molding needs to keep the content of foreign substances, impurities, solvents, etc. as small as possible.

Next, the shaping | molding method of an optical disk is demonstrated.

When manufacturing an optical disk substrate using the resin for the optical disk substrate, an injection molding machine (including an injection compression molding machine) equipped with a stamper and a pitcher and grooves satisfying the specifications required for the optical recording medium and a surface precision is realized. It is prepared by injection molding method. At this time, the thickness of the disk substrate shall be 0.3-2.0 mm. As the injection molding machine, those generally used can be used. However, in the viewpoint of suppressing the generation of carbides to increase the reliability of the disk substrate, those using a material having low adhesion to the cylinder, screw and resin, and having corrosion resistance and abrasion resistance are used. It is desirable to. It is preferable that the environment in the molding step is as clean as possible in consideration of the object of the present invention. Moreover, it is also important to consider drying so that the material used for shaping | molding may fully dry, and water | moisture content may not arise and the retention which causes decomposition | disassembly of a molten resin will not occur.

It is preferable that the resin for an optical disk substrate in the present invention has sufficient fluidity in which transferability is good at the time of injection molding or injection compression molding.

The optical disk substrate of the present invention becomes an optical disk by forming at least a reflective film on one surface thereof. As this material, a metal element can be used individually or in combination. Among them, Al and Au alone or Al alloy containing 0.5% by weight or more and 10% by weight or less, particularly preferably 3.0% by weight or more and 10% by weight or less, Cr 0.5% by weight or more and 10% by weight or less Preference is given to using Al alloys containing. The reflective film can be formed by means such as an ion beam sputtering method, a DC sputtering method or an RF sputtering method.

This metal thin film (reflective layer) may be used alone, but in addition to the recording layer (4; a phase change film and a dye in the case of DVD-RAM and DVD-R, and a magneto-optical recording film in the case of a magneto-optical disk). And the optical disk of the present invention having the transparent protective layer 5 formed thereon.

As such a phase change film recording material layer, a single chalcogen or a chalcogen compound is used, for example. Specifically, each of Te and Se, Ge-Sb-Te, Ge-Te, In-Sb-Te, In-Se-Te-Ag, In-Se, In-Se-Tl-Co, In-Sb- Chalcogenite materials such as Se, Bi ₂ Te ₃ , BiSe, Sb ₂ Se ₃ , and Sb ₂ Te ₃ are used.

As the magneto-optical recording film layer, a vertical magnetization film having magnetic optical properties such as Kerr effect or Faraday effect such as amorphous alloy thin film such as Tb-Fe-Co or the like is used.

The transparent protective layer 5 is formed on the recording layer 4. The transparent protective layer 5 is made of a material that transmits laser light. Examples of such materials include thermoplastic resins such as polycarbonate and amorphous polycyclic olefin resins, various thermosetting resins, and the like.

The means for forming the transparent protective layer is, for example, a method of attaching a transparent plate such as a sheet or a glass plate made of thermoplastic resin such as polycarbonate or amorphous polycyclic olefin resin on the recording layer 4, or ultraviolet curable resin. The method of apply | coating by a spin coat etc. method and forming by irradiating an ultraviolet-ray is mentioned. And this transparent protective layer is limited to the thickness of 3-200 micrometers in order to suppress coma aberration considerably small.

It is preferable that the transparent protective layer is formed from the transparent resin which satisfy | fills the characteristic (1)-(4) similar to the thermoplastic resin of the board | substrate of this invention, and it is especially preferable to be formed from the same resin as the resin of a board | substrate.

The above is an example of the basic configuration of the optical recording medium (optical disk) of the present invention. In addition to this configuration, a dielectric layer can be formed to control optical and thermal characteristics. In this case, the light reflection layer 3, the first dielectric layer, the recording layer 4, the second dielectric layer, and the transparent protective layer 5 can be formed on the substrate 2 in this order.

(Tasks to be solved by the invention)

MEANS TO SOLVE THE PROBLEM The present inventors earnestly researched and reached | attained this invention in order to provide the board | substrate of the optical recording medium of the said type of a simple structure, without making a complicated structure in view of the trend of the prior art as mentioned above.

(Means to solve the task)

According to the researches of the present inventors, the object of the present invention is a 0.3-2.0 mm thick substrate formed of a thermoplastic resin with emboss pits or guide grooves, a reflective layer formed on the substrate, and a thickness of 3 to 200 µm formed thereon. An optical recording medium having a transparent protective layer and irradiating a light beam from the surface side of the transparent protective layer and reproducing the recording information based on a change in the light intensity of the reflected light, the substrate comprising:

(Iii) at least 1 selected from the group consisting of 1,1-bis (4-hydroxyphenyl) -3,3,5-trimethylcyclohexane and 9,9-bis (4-hydroxy-3-methylphenyl) fluorene Formed of a thermoplastic resin containing at least 50% by weight of an aromatic polycarbonate resin polymerized with a dihydroxy compound containing at least 20 mol% of a species of aromatic dihydroxy compound relative to all dihydroxy compounds as a bisphenol component More generally the substrate,

(Ii) It is achieved by the optical recording medium characterized by being formed from the thermoplastic resin which has the characteristics of following (1)-(4).

(1) the flexural modulus is 24,000kgf / cm 2 or more,

(2) the saturated water absorption is 0.33% by weight or less,

(3) the load deformation temperature is 125 ° C or higher, and

(4) Loss tangent (tan δ) is 0.006 or more.

The optical recording medium of the present invention is an optical recording medium for recording and reproducing a recording medium by irradiating a light beam from the surface side of a transparent protective layer having a thickness of 3 to 200 µm. For example, the present invention can be applied to an optical recording medium using a blue violet semiconductor laser having a wavelength of 405 nm. Such an optical recording medium is sometimes called a Blu-ray Disc in contrast to a conventional CD or DVD.

An Example is given to the following and this invention is further demonstrated to it. In the examples, parts are parts by weight. In addition, evaluation is based on the following method.

(1) load deformation temperature

According to ASTM D-648 it was measured at a load of 1.82 MPa.

(2) Saturation water absorption

6 g of the sheet having a thickness of 1.2 mm was immersed in pure water at 23 ° C., and the weight change rate was measured after 20 days.

(3) flexural modulus

After pelleting at 120 degreeC for 5 hours, it measured by the injection molding machine [SG-150 by Sumitomo Heavy Industries, Ltd.] using the test piece injection-molded at the cylinder temperature of 340 degreeC according to ASTM-D-0790.

(4) the manufacturing method of the standard disk

The disk substrate of 120 mm diameter and 1.2 mm thickness was injection-molded from each pellet using M35B-D-DM by Meiki Manufacturing Co., Ltd. equipped with the stamper of groove depth 40 nm and groove pitch 0.6 micrometer. Table 1 shows the molding conditions of each substrate (set to conditions giving high transfer rate). Thereafter, a reflective film, a dielectric layer 1, a phase change recording film, and a dielectric layer 2 having the following constitution are sputter-deposited on a disk substrate obtained by injection molding in order, and a thin film cover layer made of polycarbonate is adhered thereon. The target optical disk was obtained.

Reflective film: 100 nm Ag, Pt, Pd, Cu alloy (TTT40-A manufactured by Vnaxis)

Dielectric layer 1: 15 nm ZnS-SiO ₂ layer

Phase change recording film: GeSbTe layer of 15 nm

Dielectric layer 2: 40 nm ZnS-SiO ₂ layer

Cover layer: 80 micrometers polycarbonate (Teijin Chemical Co., Ltd. product C-1400) layer which provided the 20 micrometers isocyanate crosslinking acrylic adhesive

(5) Initial machine characteristics

Ten disks were left to stand in a temperature of 23 ° C. and a 50% humidity RH environment for two days or more with spacers interposed so as not to contact each other. The tilt (initial disk shape) was evaluated by the Japan E-M Co., Ltd. three-dimensional shape measuring machine DLD-3000U at the time when the change of the tilt with respect to heat contraction and the environment change was stabilized, and it was set as the initial mechanical characteristic. The value is the average of 10 disks.

(6) Transfer rate

The groove depth (d) of the place where the radius is 58 mm in each board | substrate created for the measurement of said initial mechanical characteristic (58) is measured using Seiko Epson AFM-3800N, and transfer rate is calculated | required from the following formula.

Transfer rate (%) = (d / 40) x 100

(7) ΔTilt

Discs with initial mechanical properties were exposed to saturated absorption in an environment (A environment) at a temperature of 30 ° C. and a humidity of 90 ° C. RH, and then moved to a temperature of 23 ° C. and a 50% RH environment (B environment). .

Tilt change of the part that becomes 58mm from the center caused by environmental change after the movement is measured according to the time change by Japan E-M Co., Ltd. 3D shape measuring device DLD-3000U, and the tilt change reaches the maximum value and remains constant. The difference of the value when it reached a state was made into (DELTA) Tilt.

(8) loss tangent (tanδ)

It measured at 40 degreeC and 18kPa using RDAII by the company Rheometry in accordance with ISO 6721-4.

Example 1

929.2 parts of ion-exchanged water and 61.3 parts of 48% sodium hydroxide aqueous solution were added to a reactor equipped with a thermometer, a stirrer, and a reflux cooler (1,1-bis (4-hydroxyphenyl) -3,3,5-trimethylcyclohexane (component a). -1) 43.9 parts of α, α'-bis (4-hydroxyphenyl) m-diisopropylbenzene (component a-2) and 0.17 parts of hydrosulfite were dissolved, followed by 1.51 parts of p-tert-butylphenol. And 637.9 parts of methylene chloride were added, 0.09 parts of triethylamines were added, and 32.4 parts of phosgene were blown over 40 minutes at 15-25 degreeC under stirring. After completion of the phosgene blowing, 15.6 parts of a 48% aqueous sodium hydroxide solution was added thereto, and stirred at 28 to 33 ° C. for 1 hour to terminate the reaction. After completion of the reaction, the product was diluted with methylene chloride, washed with water, hydrochloric acid and washed with water. When the conductivity of the aqueous phase was almost the same as that of ion-exchanged water, methylene chloride was used as a kneader that formed a containment chamber having a foreign material outlet in the bearing part. Was evaporated to obtain 86.4 parts of a colorless polymer having a ratio of component a-1 and a-2 by 53:47 and a specific viscosity of 0.27 (yield 97%).

0.005% trisnonylphenyl phosphate, 0.003% trimethyl phosphate, 0.030% stearic acid monoglycerides were added to the polycarbonate resin powder, and pelletized using a φ 30 mm twin screw extruder equipped with a vent. Note) Injection molding was carried out using 120 mmφ and 0.6 mm thick disk substrates using M35B-D-DM. Using this disk substrate, an optical disk was produced based on the standard disk manufacturing method. Initial mechanical properties and ΔTilt and loss tangent of this disc were evaluated. The tilt change (shown on the basis of stability time) of the part which becomes 58 mm from the center which arises from an evaluation result and an environmental change is shown in Table 1 and FIG. 4, respectively.

Example 2

32,165 parts of ion-exchanged water and 1,757 parts of sodium hydroxide were added to a reactor equipped with a thermometer, a stirrer, a reflux condenser and a phosgene blower tube, and 9,9-bis (3-methyl-4-hydroxyphenyl) fluorene (component a-3). ) 2,213 parts and 3,039 parts of α, α'-bis (4-hydroxyphenyl) m-diisopropylbenzene (component a-4) and 11 parts of hydrosulfite were dissolved, followed by addition of 10,950 parts of methylene chloride and stirring under stirring 16-18 1,667 parts of phosgene was blown at 60 ° C. over 60 minutes. After completion of the phosgene blowing, 92 parts of p-tert-butylphenol and 293 parts of nitrile hydroxide were added, and 4 parts of triethylamine were further added, followed by stirring at 30 ° C. for 1 hour to terminate the reaction. After the completion of the reaction, the product was diluted with methylene chloride, washed with water, hydrochloric acid, washed with water, and methylene chloride was evaporated with kneader when the conductivity of the aqueous phase was about the same as that of ion-exchanged water. 5,550 parts of white granules whose ratio of 4 is 40:60 by molar ratio were obtained (yield 96%). The specific viscosity of this granule was 0.245, and the secondary transition temperature (Tg) was 143 degreeC.

0.005% of trisnonylphenyl phosphate, 0.003% of trimethyl phosphate, 0.030% of stearic acid monoglyceride was added to the resin powder, and pelletized by using a φ 30 mm twin screw extruder equipped with a vent. A 120 mm phi and 1.2 mm thick disk substrate was injection molded using the manufactured M35B-D-DM. This disk substrate was used to obtain a standard disk. Initial mechanical properties and ΔTilt and loss tangent of this disc were evaluated. The tilt change (shown on the basis of stability time) of the part which becomes 58 mm from the center which arises from an evaluation result and an environmental change is shown in Table 1 and FIG. 4, respectively.

Example 3

(A) Synthesis of polycarbonate homopolymer (polymer A) from bisphenol A;

11,057 parts of ion-exchanged water and 1,560 parts of 48% aqueous sodium hydroxide solution were dissolved in a reactor equipped with a thermometer, a stirrer, and a reflux cooler, and then 2,134 parts of bisphenol A and 2.1 parts of hydrosulfite were added thereto, followed by addition of 6,445 parts of methylene chloride and stirring under 15-20. 1,005 parts of phosgene were blown at 60 ° C. over 60 minutes. After completion of the phosgene blowing, 92 parts of p-tert-butylphenol and 830 parts of 48% sodium hydroxide aqueous solution were added, stirred and emulsified, and then 0.09 parts of triethylamine was added and stirred at 28 to 33 ° C. for 1 hour to terminate the reaction. After completion of the reaction, the product solution was transferred to a centrifugal extractor equipped with a porous plate (Utrex EP-02 manufactured by Hitachi, Ltd.) for ion exchange water flow rate of 1,000 ml / min, reaction product solution flow rate of 1,500 ml / min, and rotational speed of 3,500 rpm. The centrifugation operation was repeated under conditions, and methylene chloride was evaporated by a kneader in which an isolation chamber having a foreign matter outlet was formed in the bearing portion when the conductivity of the aqueous phase was about the same as that of the ion-exchanged water. Yield 92%).

(B) synthesis of polycarbonate copolymer (polymer B);

Into a reactor equipped with a thermometer, a stirrer and a reflux condenser, 929.2 parts of ion-exchanged water and 61.3 parts of 48% sodium hydroxide aqueous solution were added. 1,1-bis (4-hydroxyphenyl) -3,3,5-trimethylcyclohexane (component a -1) 43.9 parts of α, α'-bis (4-hydroxyphenyl) m-diisopropylbenzene (component a-2) and 0.17 parts of hydrosulfite were dissolved, followed by 1.51 parts of p-tert-butylphenol. And 637.9 parts of methylene chloride were added, 0.09 part of triethylamine was added, and 32.4 parts of phosgene were blown in 40 minutes over 15-25 degreeC under stirring. After completion of the phosgene blowing, 15.6 parts of a 48% aqueous sodium hydroxide solution was added thereto, and stirred at 28 to 33 ° C. for 1 hour to terminate the reaction. After completion of the reaction, the product was diluted with methylene chloride, washed with water, hydrochloric acid and washed with water. When the conductivity of the aqueous phase was almost the same as that of ion-exchanged water, methylene chloride was used as a kneader that formed a containment chamber having a foreign material outlet in the bearing part. Was evaporated to obtain 86.4 parts of a colorless polymer having a specific viscosity of 0.27 of 53:47 in a molar ratio of component a-1 and component a-2 (yield 97%).

(C) Preparation of Resin Composition

The polymer weight ratio (polymer A: polymer B) of the methylene chloride solution of the homopolymer (polymer A) of bisphenol A synthesized in (A) and the copolymer of polymer B synthesized in (B) was 80: Each was charged into a vessel equipped with a stirrer so as to be 20, followed by stirring and mixing. After mixing, the mixture was passed through a filter having a graduated interval of 0.3 µm, and then the mixed solution was added to a kneader in which an isolation chamber having a foreign matter outlet was formed, and methylene chloride was evaporated to obtain a polycarbonate resin granule.

0.005% of trisnonylphenyl phosphate, 0.003% of trimethyl phosphate, 0.030% of stearic acid monoglyceride was added to the resin powder, and pelletized by using a φ 30 mm twin screw extruder equipped with a vent. A 120 mm phi and 1.2 mm thick disk substrate was injection molded using the manufactured M35B-D-DM. This disk substrate was used to obtain a standard disk. Initial mechanical properties and ΔTilt and loss tangent of this disc were evaluated.

The tilt change (shown on the basis of stability time) of the part which becomes 58 mm from the center which arises from an evaluation result and an environmental change is shown in Table 1 and FIG. 4, respectively.

Example 4

A methylene chloride solution of a homopolymer of polymer bisphenol A (polymer A) synthesized in Example 3 (A) and a copolymer of polymer B synthesized in (B) was used in a polymer weight ratio (polymer A: polymer B). ) Was put into a container equipped with a stirrer so as to be 60:40, and stirred and mixed. After mixing, the mixture was passed through a filter having a graduated interval of 0.3 µm, and then the mixed solution was added to a kneader in which an isolation chamber having a foreign matter outlet was formed, and methylene chloride was evaporated to obtain a polycarbonate resin granule.

0.005% of trisnonylphenyl phosphate, 0.003% of trimethyl phosphate, 0.030% of stearic acid monoglyceride was added to the resin powder, and pelletized by using a φ 30 mm twin screw extruder equipped with a vent. A 120 mm phi and 1.2 mm thick disk substrate was injection molded using the manufactured M35B-D-DM. This disk substrate was used to obtain a standard disk. Initial mechanical properties and ΔTilt and loss tangent of this disc were evaluated.

The tilt change (shown on the basis of stability time) of the part which becomes 58 mm from the center which arises from an evaluation result and an environmental change is shown in Table 1 and FIG. 4, respectively.

Example 5

(Component a-1) / (component a-2) = 47/53 (molar ratio) by the same method as Example 1 except having set (component a-1) to 38.9 parts and (component a-2) to 49.1 parts 87.5 parts (yield 98%) of colorless polymers were obtained.

An optical disk was produced in the same manner as in Example 1, and the respective characteristics were evaluated.

Comparative Example 1

Rom and Haas Japan produced polymethyl methacrylate (VLD-100) was injection molded using a disk substrate of 120 mm φ and 1.2 mm thick using M35B-D-DM manufactured by Meiki Corporation. This disc substrate was used to make a standard disc. Initial mechanical properties, ΔTilt, and loss tangent of the disc were evaluated. The tilt change (shown on the basis of stability time) of the part which becomes 58 mm from the center which arises from an evaluation result and an environmental change is shown in Table 1 and FIG. 4, respectively.

Comparative Example 2

A polystyrene (HF77) manufactured by A & M Styrene Co., Ltd. was injection molded into a disk substrate having a diameter of 120 mm and a thickness of 1.2 mm using M35B-D-DM manufactured by Meiki Manufacturing Co., Ltd. This disc substrate was used to obtain a standard disc. Initial mechanical properties, ΔTilt, and loss tangent of the disc were evaluated. The tilt change (shown on the basis of stability time) of the part which becomes 58 mm from the center which arises from an evaluation result and an environmental change is shown in Table 1 and FIG. 4, respectively.

Comparative Example 3

120 mmφ using the polycarbonate resin (panlite AD-5503 (pellet)) made from Teijin Chemical Co., Ltd. as a homopolymer of bisphenol A, and using M35B-D-DM by Meiki Manufacturing Co., Ltd. 1.2 mm thick disk substrates were injection molded. This disc substrate was used to obtain a standard disc. Initial mechanical properties, ΔTilt, and loss tangent of the disc were evaluated. The evaluation results are shown in Table 1.

Cylinder temperature (℃) Force of mold clamping (ton) Mold temperature (℃) Load deformation temperature (℃) Flexural Modulus (kgf / ㎠) Example 1 320 32 125 130 28000 Example 2 120 130 32000 Example 3 119 127 25100 Example 4 118 127 26100 Comparative Example 1 81 89 37000 Comparative Example 2 80 89 30000 Comparative Example 3 120 127 23900

Saturated Absorption Rate (wt%) Initial mechanical properties (degrees) ΔTilt (degrees) tanδ % Transfer Example 1 0.21 0.20 0.37 0.014 100 Example 2 0.25 0.20 0.46 0.039 100 Example 3 0.32 0.30 0.59 0.007 100 Example 4 0.30 0.35 0.53 0.009 100 Comparative Example 1 2.00 0.36 5.00 or more 0.078 100 Comparative Example 2 0.05 0.35 0.01 or less 0.015 100 Comparative Example 3 0.35 - 0.7 0.006 100

As shown in Table 1, the resins shown in Examples 1 to 4 and the resins of Example 5 had a saturated water absorption of 0.33% by weight or less, a load deformation temperature of 125 ° C or more, and ΔTilt can be suppressed to 1.0 or less. . In addition, since the flexural modulus and loss tangent tan δ are sufficiently large, it is possible to suppress the surface vibration occurring when the molded optical disk rotates at high speed.

Since PMMA of Comparative Example 1 had a high saturated water absorption of 2.0%, ΔTilt was found to be very large, which is 5.0 or more, which is not suitable for practical use. Moreover, since the polystyrene of the comparative example 2 had a low water absorption, (DELTA) Tilt was able to be suppressed very small, but since the glass transition point (Tg) was low, the heat resistance as a disk substrate was inferior.

Since the polycarbonate resin of Comparative Example 3 has a slightly high saturation absorption rate of 0.35% and a slight lack of flexural modulus, the polycarbonate resin is not sufficiently satisfactory as a characteristic of the disk substrate, and in particular, the maximum change value (ΔTilt) of the tilt angle is 0.7 °. This may interfere with reading of the record. Moreover, the board | substrate of the comparative example 3 has low transfer rate, and is unsatisfactory in the shaping | molding characteristic as a board | substrate.

The optical recording medium of the present invention is directed to an optical disk in which at least a reflective film, a recording layer and a transparent protective layer are sequentially formed on a substrate, and light is irradiated from the transparent protective layer side to record and / or reproduce information symbols. In this optical disk, a recording capacity of more than 15 GB has been developed on one side of a disk having a diameter of 12 cm. However, the optical disk substrate of the present invention is not a complicated configuration, and it is possible to apply it to them sufficiently.

Claims (25)

A transparent protective layer having a thickness of 3 to 200 탆 formed on the reflective layer and a reflective layer formed on the substrate, the substrate having a thickness of 0.3 to 2.0 mm formed of an emboss pit or guide groove formed of a thermoplastic resin; An optical recording medium which irradiates a light beam from the surface side of a layer and reproduces recording information on the basis of a change in light intensity of the reflected light, The substrate includes 1,1-bis (4-hydroxyphenyl) -3,3,5-trimethylcyclohexane (component a-1) and 9,9-bis (4-hydroxy-3-methylphenyl) fluorene Aromatic polymerized using the dihydroxy compound containing at least 20 mol% of at least 1 type of aromatic dihydroxy compound (component A) chosen from the group which consists of (a-2 component) with respect to all the dihydroxy compounds as a bisphenol component. An optical recording medium comprising a thermoplastic resin containing 50% by weight or more of polycarbonate resin. The method of claim 1, The substrate includes 1,1-bis (4-hydroxyphenyl) -3,3,5-trimethylcyclohexane (component a-1) and 9,9-bis (4-hydroxy-3-methylphenyl) fluorene at least one aromatic dihydroxy compound (component A) and α, α'-bis (4-hydroxyphenyl) m-diisopropylbenzene (component B) selected from the group consisting of (a-2 component) Component: B Component = 20: The optical recording medium formed from the thermoplastic resin containing 50 weight% or more of aromatic polycarbonate resin superposed | polymerized using the dihydroxy compound contained in the molar ratio of 80-70: 30 as a bisphenol component. The method of claim 1, And the substrate is formed of a thermoplastic resin having a flexural modulus of 24,000 kgf / cm 2 or more. The method of claim 1, And the substrate is formed of a thermoplastic resin having a saturated water absorption of 0.33% by weight or less. The method of claim 1, The substrate is formed of a thermoplastic resin having a load deformation temperature of 125 ° C. or higher. The method of claim 1, The substrate is formed of a thermoplastic resin having a loss tangent (tan δ) of 0.006 or more. The method of claim 1, The substrate is formed of a thermoplastic resin having a transfer rate of 95% or more. The method of claim 1, The substrate is formed of a thermoplastic resin having a characteristic that the maximum change value (ΔTilt) of the tilt angle is 0.6 ° or less. The method of claim 1, The substrate is an optical recording medium formed of a blend of two or more thermoplastic resins. The method of claim 1, The transparent protective layer is formed of the same thermoplastic resin as the thermoplastic resin forming the substrate. The method of claim 1, An optical recording medium having a recording layer between the reflective layer and the transparent protective layer. The method of claim 11, An optical recording medium having a multilayer structure in which the reflective layer or the recording layer is laminated in multiple layers. 0.3-2.0 mm-thick board | substrate with an emboss pit or guide groove formed from the thermoplastic resin, the reflective layer formed on this board | substrate, and the transparent protective layer of 3-200 micrometers thickness formed on this reflective layer, The surface side of the said transparent protective layer An optical recording medium for irradiating a light beam from the back and reproducing the recording information on the basis of a change in the light intensity of the reflected light, The substrate, (1) the flexural modulus is 24,000kgf / cm 2 or more, (2) the saturated water absorption is 0.33% by weight or less, (3) the load deformation temperature is 125 ° C or higher, and (4) An optical recording medium comprising a thermoplastic resin having a loss tangent (tan δ) of 0.006 or more. The method of claim 13, The substrate is formed of a thermoplastic resin having a flexural modulus of 26,000 kgf / cm 2 or more. The method of claim 13, And the substrate is formed of a thermoplastic resin having a saturation absorption rate of 0.30 wt% or less. The method of claim 13, The substrate is formed of a thermoplastic resin having a load deformation temperature of 127 ° C. or higher. The method of claim 13, The substrate is formed of a thermoplastic resin having a loss tangent (tan δ) of 0.008 or more. The method of claim 13, The substrate is formed of a thermoplastic resin having a transfer rate of 95% or more. The method of claim 13, The substrate is formed of a thermoplastic resin having a characteristic that the maximum change value (ΔTilt) of the tilt angle is 0.6 ° or less. The method of claim 13, The substrate is an optical recording medium formed of an aromatic polycarbonate resin. The method of claim 13, The substrate is an optical recording medium formed of a blend of two or more thermoplastic resins. The method of claim 13, The transparent protective layer is an optical recording medium which satisfies the characteristics (1) to (4) of the thermoplastic resin according to claim 13 and is formed of a transparent thermoplastic resin. The method of claim 13, The transparent protective layer is formed of the same thermoplastic resin as the thermoplastic resin forming the substrate. The method of claim 13, An optical recording medium having a recording layer between the reflective layer and the transparent protective layer. The method of claim 24, An optical recording medium having a multilayer structure in which the reflective layer or the recording layer is laminated in multiple layers.