JP2006236518A - Sheet for protective layer formation of optical recording medium, optical recording medium and manufacturing method of those - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sheet for protective layer formation forming a protective layer of an optical recording medium having uniform physical properties, to provide its manufacturing method, and also to provide the optical recording medium provided with the protective layer having the uniform physical properties, and its manufacturing method. <P>SOLUTION: In the sheet 1 for protective layer formation comprising an uncured protective layer 11 and two base materials 12 and 12' sandwiching the uncured protective layer 11, the protective layer 11 before curing is constituted of a composition which contains 10 to 70 mass% energy ray curing compound having ≥25°C melting point and 30 to 90 mass% energy ray curing oligomer which is preferably in a liquid state at 20°C, and does not substantially contain a polymer component having weight average molecular weight of 50,000 or more. The protective layer 11 is press-fixed to an information recording layer (a semitransmission reflection layer 3') and the protective layer 11 is cured by irradiation with an energy ray to form the protective layer 11'. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a sheet for forming a protective layer for protecting the surface of an optical recording medium and a manufacturing method thereof, and an optical recording medium using the sheet and a manufacturing method thereof.

  2. Description of the Related Art An optical disk is composed of an optical disk substrate made of polycarbonate, one or more information recording layers formed on the optical disk substrate, and a protective film bonded to the information recording layer through an adhesive layer Generally known. When the optical disc is read-only, the information recording layer has a concavo-convex pattern forming pits. When the optical disc is rewritable, the information recording layer has a concavo-convex pattern forming grooves and lands. Is done.

  As a method for adhering the protective film and the information recording layer, for example, a photocurable resin is applied to the protective film or the information recording layer to form an adhesive layer, and the protective film and the information recording layer are bonded by the adhesive layer. A method of matching is known (Patent Document 1).

  However, the above-described method requires a step of forming an adhesive layer and a step of bonding a protective film, and thus contributes to an increase in the manufacturing process of the optical disk, and in turn increases the manufacturing cost of the optical disk. It was.

Therefore, recently, an optical disc has been proposed in which a photocurable adhesive film is formed in advance, the photocurable adhesive film is transferred to an information recording layer, and a protective layer is formed by the photocurable adhesive ( Patent Document 2). According to such an optical disc, since a protective layer can be formed directly on the information recording layer without forming an adhesive layer, the conventional optical disc manufacturing process can be reduced by one.
JP-A-10-283683 JP 2002-25110 A

  In the invention described in Patent Document 2, a photocurable adhesive mainly composed of a photocurable (meth) acrylic resin or an ethylene-vinyl acetate copolymer is used, and the photocurable adhesive is contained in ethyl acetate. An adhesive layer is formed by applying an adhesive coating solution prepared by mixing and dissolving on a separator.

  However, in the protective layer obtained by using the adhesive coating liquid as described above, the physical properties such as the refractive index are likely to be non-uniform, and in that case, it is unsuitable as an optical disk.

  The present invention has been made in view of such a situation, and has a protective layer forming sheet capable of forming a protective layer of an optical recording medium having uniform physical properties, a method for producing the same, and uniform physical properties. An object of the present invention is to provide an optical recording medium having a protective layer and a method for producing the same.

  In order to achieve the above object, first, the present invention substantially comprises a polymer component containing 10 to 70% by mass of an energy ray curable compound having a melting point of 25 ° C. or higher and a weight average molecular weight of 50,000 or higher. Provided is a protective layer-forming sheet for an optical recording medium, comprising a pre-curing protective layer comprising a composition not contained.

  An “optical recording medium” in this specification refers to a medium on which information can be optically recorded / reproduced, and is mainly a read-only, write once or rewritable disc-like medium (for example, CD, CD- ROM, CD-R, CD-RW, DVD, DVD-ROM, DVD-R, DVD-RW, DVD-RAM, LD, Blu-ray Disc, MO, etc .; so-called optical disks (including magneto-optical disks) However, it is not necessarily limited to these.

  In the conventional optical disk (Japanese Patent Laid-Open No. 2002-25110), the physical properties of the protective layer obtained by using the adhesive coating liquid are made nonuniform, which is a polymer component (weight average molecular weight of 50) accompanying the solvent volatilization of the adhesive coating liquid. However, in the above-mentioned invention (Invention 1), the physical properties of the protective layer are uniform because it does not substantially contain a polymer component having a weight average molecular weight of 50,000 or more. It will be a thing. In general, a pre-curing protective layer made of a composition containing no polymer component having a weight average molecular weight of 50,000 or more tends to have low shape retention, but in the above invention (invention 1) By using an energy ray curable compound having a melting point of 25 ° C. or higher, a pre-curing protective layer having excellent shape retention can be obtained. According to such a protective layer forming sheet, an optical recording medium having good signal characteristics can be manufactured with a small number of manufacturing steps.

  In the said invention (invention 1), it is preferable that the said composition contains 30-90 mass% of liquid energy ray-curable oligomers further at 20 degreeC (invention 2). When the composition contains such an oligomer, the toughness of the protective layer can be kept moderate, and defects such as cracks can be prevented from occurring in the protective layer during the production process of the optical recording medium.

  In the above inventions (Inventions 1 and 2), the protective layer before curing is laminated on the smooth surface of a substrate having a smooth surface with a surface roughness (Ra) of 0.1 μm or less (Invention 3). Furthermore, it is preferable that the surface roughness (Ra) is sandwiched between the smooth surfaces of two substrates having a smooth surface of 0.1 μm or less (Claim 4).

  According to the above invention (invention 3), the smoothness of at least one surface of the pre-curing protective layer is increased, and better signal characteristics can be obtained by bringing this surface into close contact with the information recording layer. Moreover, according to the said invention (invention 4), since the smoothness of both surfaces of the protective layer before hardening becomes high, a more favorable signal characteristic can be obtained.

  Secondly, the present invention is a method for producing a protective layer-forming sheet for an optical recording medium provided with a pre-curing protective layer, containing 10 to 70% by mass of an energy ray-curable compound having a melting point of 25 ° C. or higher, and having a weight. A composition that does not substantially contain a polymer component having an average molecular weight of 50,000 or more is applied on the first plane without using a solvent, and is sandwiched between the first plane and the second plane. To provide a protective layer forming sheet for an optical recording medium, wherein the pre-curing protective layer is formed.

  Here, the “plane” may be a plane of a sheet-like base material, but is not limited thereto, and may be a plane of a table or the like, for example. Moreover, the thing which has the said plane does not necessarily need to be laminated | stacked on the protection layer before hardening in the sheet | seat for protective layer formation of a recording medium.

  According to the above invention (invention 5), the pre-curing protective layer with high thickness accuracy can be reliably formed. In addition, by applying the above composition without using a solvent, convection of the components in the composition accompanying the volatilization of the solvent does not occur, so the uniformity of the physical properties of the protective layer is made more reliable. be able to.

  In the said invention (invention 5), it is preferable that the said composition contains 30-90 mass% of liquid energy ray-curable oligomers further at 20 degreeC (invention 6).

  Thirdly, the present invention relates to a method for manufacturing an optical recording medium comprising an optical recording medium substrate, one or more information recording layers, and a protective layer. The protective layer-forming sheet of the optical recording medium (Claims 1 to 4) is pressure-bonded, and the protective layer is cured by irradiation with energy rays, thereby forming the protective layer of the optical recording medium. An optical recording medium manufacturing method is provided (claim 7).

  Fourthly, the present invention relates to a method of manufacturing an optical recording medium comprising an optical recording medium substrate, one or more information recording layers, and a protective layer, the outermost information recording layer being The protective layer pre-curing protective layer of the optical recording medium (Claim 3), the surface of the protective layer forming sheet that is in contact with the smooth surface of the substrate is the information recording layer side. Thus, a method for producing an optical recording medium is provided, wherein the protective layer before curing is cured by irradiation with energy rays, thereby forming a protective layer for the optical recording medium. .

  According to the above inventions (Inventions 7 and 8), since a protective layer having uniform physical properties can be formed without forming an adhesive layer, an optical recording medium having good signal characteristics can be obtained.

  Fifthly, the present invention provides an optical recording medium comprising a protective layer obtained by curing the protective layer before curing of the protective layer-forming sheet of the optical recording medium (claims 1 to 4). (Claim 9).

  Sixth, the present invention is obtained by curing an optical recording medium substrate, one or more information recording layers, and a protective layer before curing of a protective layer forming sheet of the optical recording medium (Claim 3). A protective layer, and the protective layer is laminated on the information recording layer, with the surface of the protective layer before curing that is in contact with the smooth surface of the base material being the information recording layer side. An optical recording medium is provided.

  ADVANTAGE OF THE INVENTION According to this invention, the sheet | seat for protective layer formation of the optical recording medium which can form the protective layer which is excellent in shape retention property and has a uniform physical property (for example, refractive index) is obtained. Further, according to the present invention, a protective layer having uniform physical properties can be formed on the information recording layer without using an adhesive layer, whereby an optical recording medium having good signal characteristics can be obtained.

Hereinafter, embodiments of the present invention will be described.
FIG. 1 is a cross-sectional view of a protective layer forming sheet for an optical disc according to an embodiment of the present invention, and FIGS. 2A to 2G are optical discs using the protective layer forming sheet for an optical disc according to the embodiment. It is sectional drawing which shows an example of this manufacturing method.

  As shown in FIG. 1, a protective layer forming sheet 1 for an optical disc according to this embodiment includes a pre-curing protective layer 11, a base material 12 laminated on one surface of the pre-curing protective layer 11, and pre-curing protection. It consists of a base material 12 ′ laminated on the other surface of the layer 11. However, the base materials 12 and 12 ′ are peeled off when the protective layer forming sheet 1 is used.

  The pre-curing protective layer 11 contains an energy ray curable compound (I) having a melting point of 25 ° C. or higher, preferably an energy ray curable oligomer (II) which is liquid at 20 ° C., and optionally a third component (III). The protective layer 11 ′ of the optical disk D is formed by a composition that does not substantially contain a polymer component having a weight average molecular weight of 50,000 or more and is cured by irradiation with energy rays.

[Energy ray curable compound (I) having a melting point of 25 ° C. or higher]
Examples of the energy ray-curable compound (I) having a melting point of 25 ° C. or higher include behenyl acrylate, polyethylene glycol diacrylate, methoxy polyethylene glycol acrylate, tetramethylol methane tetraacrylate, pentaerythritol diacrylate monostearate, and isocyanuric acid ethylene oxide. Examples include (EO) -modified triacrylate and acrylates such as pentaerythritol tetraacrylate. Among them, behenyl acrylate, polyethylene glycol diacrylate, methoxypolyethylene glycol acrylate, and isocyanuric acid EO-modified triacrylate are preferable.

  When the energy ray curable compound (I) is a polymer, its weight average molecular weight (Mw) is preferably 10,000 or less, particularly preferably 5,000 or less. If the weight average molecular weight of the energy ray curable compound (I) exceeds 10,000, the physical properties of the protective layer 11 ′ may be uneven.

  The melting point of the energy beam curable compound (I) needs to be 25 ° C. or higher. When the melting point is less than 25 ° C., the shape stability of the pre-curing protective layer 11 is low and the handling property is poor. On the other hand, if the melting point is too high, the coating suitability may be reduced. Therefore, it is preferable that melting | fusing point of energy-beam curable compound (I) is 25-100 degreeC, and it is especially preferable that it is 35-80 degreeC.

  In the composition constituting the pre-curing protective layer 11, the content of the energy ray-curable compound (I) is 10 to 70% by mass, preferably 40 to 60% by mass. If content of energy-beam curable compound (I) is less than 10 mass%, the shape stability of the protective layer 11 before hardening will become low. On the other hand, when the content of the energy beam curable compound (I) exceeds 70% by mass, the toughness of the protective layer 11 before curing or the protective layer 11 ′ after curing becomes too low, and the protective layer 11 before curing during the manufacturing process. Or there is a possibility that defects such as cracks may occur in the protective layer 11 ′ after curing.

[Liquid energy ray-curable oligomer (II) at 20 ° C]
Examples of the energy ray-curable oligomer (II) that is liquid at 20 ° C. include oligomers of (meth) acrylates such as urethane (meth) acrylate, polyester (meth) acrylate, and epoxy (meth) acrylate. Urethane (meth) acrylate is preferred.

  The weight average molecular weight (Mw) of the energy ray curable oligomer (II) is preferably 1,000 to 10,000, and more preferably 1,000 to 5,000. If the weight average molecular weight of the energy ray-curable oligomer (II) is less than 1,000, the shape stability of the protective layer 11 before curing may be low, and the flexibility of the protective layer 11 ′ after curing may be low. There is. On the other hand, if the weight average molecular weight of the energy ray-curable oligomer (II) exceeds 10,000, the physical properties of the protective layer 11 'after curing may be made non-uniform.

  The composition constituting the pre-curing protective layer 11 contains the energy ray-curable oligomer (II) that is liquid at 20 ° C. as described above, so that the toughness of the protective layer 11 ′ is kept moderate, and the optical disk D manufacturing process It is possible to prevent defects such as cracks from occurring in the protective layer 11 ′.

  In the composition constituting the pre-curing protective layer 11, the content of the energy ray-curable oligomer (II) is preferably 30 to 90% by mass, and particularly preferably 40 to 60% by mass. When the content of the energy ray-curable oligomer (II) is less than 30% by mass, it is difficult to obtain an effect of appropriately maintaining the toughness of the protective layer 11 before curing or the protective layer 11 ′ after curing. When the content of) exceeds 90% by mass, the homogeneity of the composition becomes low, and the physical properties of the protective layer 11 before curing, and hence the protective layer 11 'after curing, become non-uniform.

[Third component (III)]
The composition constituting the pre-curing protective layer 11 may contain a third component (III) other than the energy beam curable compound (I) and the energy beam curable oligomer (II). Examples of such third component (III) include leveling agents, fine particles, and other additives. In addition, when ultraviolet rays are used as energy rays, the polymerization curing time and the amount of light irradiation can be reduced by adding a photopolymerization initiator as the third component (III).

  Specific examples of the photopolymerization initiator include benzophenone, acetophenone, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, benzoin benzoic acid, methyl benzoin benzoate, benzoin dimethyl ketal, 2,4 -Diethylthioxanthone, 1-hydroxycyclohexyl phenyl ketone, benzyldiphenyl sulfide, tetramethylthiuram monosulfide, azobisisobutyronitrile, benzyl, dibenzyl, diacetyl, β-chloranthraquinone, (2,4,6-trimethyl) Benzyldiphenyl) phosphine oxide, 2-benzothiazole-N, N-diethyldithiocarbamate, oligo {2-hydroxy-2-methyl-1 [4- (1-propenyl) phenyl] propanone}, and the like.

  A photoinitiator is 0.1-20 mass parts with respect to 100 mass parts of total amounts of energy-beam curable compound (I) and energy-beam curable oligomer (II), especially 0.5-10 mass parts. It is preferably used in amounts in the range.

  As the leveling agent, for example, a dimethylsiloxane compound, a fluorine compound, a surfactant and the like can be used. By containing such a leveling agent in the composition, the smoothness of the pre-curing protective layer 11 (protective layer 11 ') can be improved.

  In the composition constituting the protective layer 11 before curing, the content of the leveling agent is preferably 0 to 2 parts by mass, particularly 0.01 to 100 parts by mass with respect to 100 parts by mass of the energy beam curable compound (I). The amount is preferably 0.5 parts by mass.

  Examples of the fine particles include inorganic fine particles such as silicon dioxide particles, titanium dioxide particles, aluminum oxide particles, tin oxide particles, calcium carbonate particles, barium sulfate particles, talc, kaolin, and calcium sulfate particles having an average particle size of 0.5 μm or less. In addition, the inorganic oxide fine particles modified with an organic substance, or reactive particles described in, for example, Japanese Patent Application Laid-Open No. 2000-273272 may be used. When the composition contains such fine particles, the hardness of the protective layer 11 ′ obtained can be improved, and scratch protection performance can be imparted to the protective layer 11 ′.

  In the composition constituting the protective layer 11 before curing, the content of the fine particles is preferably 0 to 60 parts by mass, particularly 0 to 50 parts by mass with respect to 100 parts by mass of the energy ray curable compound (I). It is preferable that

  Examples of other additives include ultraviolet absorbers, antioxidants, tackifiers, coupling agents, and dyes. In the composition constituting the protective layer 11 before curing, the content of other additives is 0 to 5 parts by mass in total of the other additives with respect to 100 parts by mass of the energy ray curable compound (I). It is preferable that it is 0-3 mass parts especially.

  The composition constituting the pre-curing protective layer 11 does not substantially contain a polymer component having a weight average molecular weight (Mw) of 50,000 or more. When such a polymer component is contained, the homogeneity of the composition becomes low, and the physical properties of the protective layer 11 before curing, and hence the protective layer 11 'after curing, become non-uniform.

The storage elastic modulus after curing of the composition constituting the pre-curing protective layer 11 is preferably 1 × 10 ⁶ Pa or more, particularly preferably 5 × 10 ⁶ to 1 × 10 ⁸ Pa. Here, the measurement temperature of the “storage modulus after curing” is the same temperature as the storage environment of the optical disk, that is, room temperature.

When the storage elastic modulus after curing of the pre-curing protective layer 11 is less than 1 × 10 ⁶ Pa, the strength of the formed protective layer 11 ′ may be insufficient.

  The transmittance of light having a wavelength of 400 nm or more after curing of the composition constituting the pre-curing protective layer 11 is preferably 85% or more. In an optical disk, a short wavelength laser (for example, a blue-violet laser having a wavelength of 405 nm) may be used to increase the recording capacity, but the cured composition (protective layer 11 ′) has the above transmittance. It is possible to cope with such a short wavelength laser.

The linear expansion coefficient after curing of the composition constituting the pre-curing protective layer 11 (the linear expansion coefficient of the protective layer 11 ′) is such that the optical disk substrate 2 does not warp even when used under wet heat conditions. It is preferably approximately the same as the expansion coefficient. For example, when the optical disk substrate 2 is made of polycarbonate resin, the linear expansion coefficient is usually 0.8 × 10 ⁻⁴ / ° C., and in this case, the linear expansion after curing of the composition constituting the pre-curing protective layer 11 The coefficient is preferably 0.3 × 10 ^{−4 to} 2.5 × 10 ⁻⁴ / ° C., and particularly preferably 0.6 × 10 ^{−4 to} 2.0 × 10 ⁻⁴ / ° C.

  The refractive index after curing of the composition constituting the pre-curing protective layer 11 is preferably 1.45 to 1.75, and particularly preferably 1.45 to 1.55. In an optical disc, a hard coat layer may be provided on the surface of the protective layer 11 ′ to prevent scratches, but when the refractive index after curing of the composition (the refractive index of the protective layer 11 ′) is out of the above range, It is often very different from the refractive index of the hard coat layer, which may adversely affect signal characteristics.

  The thickness of the pre-curing protective layer 11 composed of the above composition is determined based on the standard of the optical disk. For example, in the case of a single-sided single-layer Blu-ray Disc, it is 100 μm. It is about 95-105 micrometers, Preferably it is about 97-103 micrometers.

  Of the base materials 12 and 12 ′ laminated on the pre-curing protective layer 11 as described above, the base material to be peeled first (the base material 12 ′ in the present embodiment) is relative to the pre-curing protective layer 11. The base material to be peeled later (the base material 12 in this embodiment) needs to have peelability with respect to the cured protective layer 11 ′.

  Specifically, the peeling force (peeling force A) on the surface on the protective layer 11 side before curing of the base material (base material 12 ′) to be peeled first is preferably 150 mN / 25 mm or less, and is peeled later. The peeling force (peeling force B) of the surface on the protective layer 11 side of the base material (base material 12) to be cured is preferably a peeling force A or more and 200 mN / 25 mm or less.

  Moreover, the surface roughness (Ra) of the surface on the protective layer 11 side before curing of the base material 12, 12 ′, particularly the base material (base material 12 ′) that is peeled first, is 0.1 μm or less. And more preferably 0.05 μm or less. When the base materials 12 and 12 ′ have such surface roughness (Ra), smoothness can be imparted to the pre-curing protective layer 11, thereby obtaining good signal characteristics. In particular, since the surface on the information recording layer side of the pre-curing protective layer 11 (protective layer 11 ′) has a great influence on the signal characteristics of the optical disc, the base material (base material 12 ′) to be peeled first is not cured. Control of the surface roughness (Ra) of the surface on the protective layer 11 side is important.

  Examples of such base materials 12 and 12 'include polyethylene, polypropylene, polybutene, polybutadiene, vinyl chloride, ionomer, ethylene-methacrylic acid copolymer, polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, polyimide, and polyether. A transparent film made of a resin such as imide, polyaramid, polyetherketone, polyetheretherketone, polyphenylene sulfide, poly (4-methylpentene-1), polytetrafluoroethylene or a cross-linked resin, as required It is preferable to use those that have been subjected to a release treatment with a release agent such as a silicone resin, alkyd resin, fluororesin, unsaturated polyester resin, polyolefin resin, or wax.

  The thickness of the base materials 12 and 12 ′ is usually about 5 to 300 μm, preferably 20 to 100 μm.

  In order to manufacture the protective layer forming sheet 1 according to the present embodiment, first, a composition constituting the pre-curing protective layer 11 is prepared, and the composition is formed on the base material 12 or the base material 12 ′ (on the base material). When the peeling treatment is applied, the coating is applied on the peeling treatment surface.

  Here, in the application of the composition, it is preferable to apply the composition by heating without using a solvent so that the composition has a viscosity suitable for application. This is because when a solvent is used, convection occurs in the components in the composition as it volatilizes, and the physical properties of the pre-curing protective layer 11 and thus the protective layer 11 'after curing may become non-uniform. The heating temperature of the composition is usually preferably about 70 to 100 ° C.

  For application of the composition, for example, a coating machine such as a kiss roll coater, reverse roll coater, knife coater, roll knife coater, die coater or the like can be used.

  Next, another substrate 12 ′ or substrate 12 (or a release treatment surface when the substrate is peeled) is superposed on the surface of the coated composition. The pre-curing protective layer 11 is formed so as to be sandwiched between the materials 12 and 12 '.

  Since the protective layer 11 before curing of the protective layer forming sheet 1 manufactured in this manner is sandwiched between the two base materials 12 and 12 ', the thickness accuracy is high. In addition, since the surface state of the pre-curing protective layer 11 side of the base materials 12 and 12 ′ is transferred to the surface of the pre-curing protective layer 11, the surface of the base materials 12 and 12 ′ on the pre-curing protective layer 11 side is transferred. If the smoothness is increased, the smoothness of the surface of the pre-curing protective layer 11 is also increased.

  Next, an example of a method for producing an optical disk (single-sided, two-layer type) using the protective layer forming sheet 1 will be described.

  First, as shown in FIG. 2A, an optical disk substrate 2 having a concavo-convex pattern of pits or grooves / lands is manufactured. The optical disk substrate 2 is usually made of polycarbonate and can be formed by a molding method such as injection molding.

  On the concave-convex pattern of the optical disk substrate 2, as shown in FIG. 2B, the reflective layer 3 is formed by means such as sputtering. In the present optical disc D, the reflective layer 3 serves as an information recording layer. The reflective layer 3 may be a single layer film, or may be a multilayer film composed of, for example, a reflective film, a dielectric film, a phase change film, and a dielectric film.

  Next, as shown in FIG. 2C, an energy ray curable stamper receiving layer 4 is formed on the reflective layer 3. The stamper-receiving layer 4 may be formed by pasting a stamper-receiving layer formed in advance in a sheet shape, or by applying a coating agent for the stamper-receiving layer 4 by a spin coat method or the like. Also good. As a material for the stamper-receiving layer 4, for example, the energy ray-curable compound (I) described above can be used.

  When the stamper receiving layer 4 is formed, as shown in FIG. 2D, the stamper S is pressed against the stamper receiving layer 4, and the uneven pattern of the stamper S is transferred to the stamper receiving layer 4. In addition, although the shape of the stamper S illustrated in FIG. 2D is a plate shape, the shape is not limited to this, and may be a roll shape.

  In this state, the energy ray irradiation device is used to irradiate the stamper receiving layer 4 with energy rays to cure the stamper receiving layer 4. As energy rays, ultraviolet rays, electron beams, etc. are usually used.

  When the stamper receiving layer 4 is cured to form pits or grooves / lands by the uneven pattern of the stamper S, the stamper S and the stamper receiving layer 4 are separated, and as shown in FIG. A transflective layer 3 ′ is formed on the uneven pattern 4 by means such as sputtering. The semi-transmissive reflective layer 3 ′ may be a single layer film, or may be a multilayer film composed of a semi-transmissive reflective film, a dielectric film, a phase change film, a dielectric film, and the like.

  And one base material 12 'of the protective layer forming sheet 1 is peeled and removed to expose the protective layer 11 before curing, and as shown in FIG. Crimp to the 3 'surface. In this state, an energy irradiation apparatus is used to irradiate the pre-curing protective layer 11 with energy rays to cure the pre-curing protective layer 11 to form a protective layer 11 ′.

As energy rays, ultraviolet rays, electron beams and the like are usually used, and preferably ultraviolet rays are used. The amount of energy beam irradiation varies depending on the type of energy beam. For example, in the case of ultraviolet rays, the amount of light is preferably about 100 to 500 mJ / cm ² , and in the case of an electron beam, it is preferably about 10 to 1000 krad.

  When the protective layer 11 before curing is cured to form the protective layer 11 ′, the other substrate 12 of the protective layer forming sheet 1 is peeled and removed as shown in FIG. An overcoat layer such as a hard coat layer and an antifouling layer is formed on the surface of the layer 11 ′ to obtain an optical disc D.

  As the hard coat layer, a polyester (meth) acrylate, urethane (meth) acrylate or epoxy (meth) acrylate having two or more (meth) acryloyl groups in the molecule and a (meth) acrylate monomer are subjected to an energy ray curing reaction. However, the present invention is not limited to this, and for example, a material made of a material having a siloxane bond can be used.

  As a material constituting the antifouling layer, for example, a fluorine compound, a dimethylsiloxane compound, a fluorine-modified dimethylsiloxane compound, or the like can be used.

  According to the optical disk manufacturing method using the protective layer forming sheet 1 as described above, it is not necessary to provide an adhesive layer when forming the protective layer 11 ′, so that the optical disk D can be manufactured with a small number of manufacturing steps. Moreover, as a composition constituting the pre-curing protective layer 11, a pre-curing protective layer is obtained by using a composition containing substantially no polymer component and containing an energy ray-curable compound having a melting point of 25 ° C. or higher. 11 has a high shape-retaining property, and the physical properties such as the refractive index of the protective layer 11 ′ are uniform, so that the obtained optical disc D has good signal characteristics and a high manufacturing yield.

  In the optical disc manufacturing method described above, a single-sided dual-layer type optical disc was manufactured using the protective layer forming sheet 1, but the present invention is not limited to this. For example, the protective layer forming sheet 1 is used. A single-sided single-layer optical disk or the like can also be manufactured.

  The embodiment described above is described for facilitating understanding of the present invention, and is not described for limiting the present invention. Therefore, each element disclosed in the above embodiment is intended to include all design changes and equivalents belonging to the technical scope of the present invention.

  For example, the base material 12 or the base material 12 ′ in the protective layer forming sheet 1 may be omitted.

  EXAMPLES Hereinafter, although an Example etc. demonstrate this invention further more concretely, the scope of the present invention is not limited to these Examples etc.

[Example 1]
Polyethylene glycol diacrylate as an energy ray-curable compound having a melting point of 25 ° C. or higher (manufactured by Shin-Nakamura Chemical Co., Ltd., NK ester A-1000, solid content concentration: 100%, melting point: 37-39 ° C., weight average molecular weight: 1108) 50 parts by mass and 50 parts by mass of urethane acrylate as a liquid energy ray-curable oligomer at 20 ° C. (Dainippon Ink Co., Ltd., Unidick RS24-156, weight average molecular weight: 1600, solid content concentration: 100%), 1 part of 1-hydroxycyclohexyl phenyl ketone (manufactured by Ciba Specialty Chemicals, Irgacure 184, solid content concentration: 100% by mass) as a photopolymerization initiator is mixed and stirred while heating at 80 ° C. Was used as a coating solution.

  A film thickness of the coating solution is 100 μm on a polyethylene terephthalate film (Mitsubishi Chemical Polyester Film, PET75T600, thickness: 75 μm, Ra: 0.01 μm, peeling force: 160 mN / 25 mm) as the base 12 After being coated using a die coater as described above, a release film (SP-PET 7501, thickness: 75 μm, Ra: 0, manufactured by Lintec Co., Ltd.) as a base material 12 ′ peel-treated with a silicone resin-based release agent thereon. .015 μm, peeling force: 100 mN / 25 mm) was laminated to obtain a protective layer forming sheet comprising two films and a pre-curing protective layer sandwiched between them.

[Example 2]
Methoxypolyethylene glycol acrylate (manufactured by Shin-Nakamura Chemical Co., Ltd., NK ester AM-230G, solid content concentration: 100%, melting point: 40 ° C., weight average molecular weight: 1054) is used as an energy ray curable compound having a melting point of 25 ° C. or higher. A coating solution for the protective layer was prepared in the same manner as in Example 1 except that. Then, using the obtained coating liquid, a protective layer forming sheet was produced in the same manner as in Example 1.

[Comparative Example 1]
1,6-hexane acrylate (manufactured by Shin-Nakamura Chemical Co., Ltd., NK ester A-HD-N, solid content concentration: 100%, melting point: 8-10 ° C., weight average molecular weight: 226) instead of polyethylene glycol diacrylate A protective layer coating solution was prepared in the same manner as in Example 1 except that. Then, using the obtained coating liquid, a protective layer forming sheet was produced in the same manner as in Example 1.

[Test example]
1. Shape retention property A pressure of 1.0 N / cm ² was applied to the protective layer-forming sheets (uncured) obtained in the examples and comparative examples for 10 minutes, and the presence or absence of deformation of the protective layer before curing was visually confirmed. A case where no deformation was observed is indicated by ○, and a case where deformation was recognized is indicated by ×. The results are shown in Table 1.

2. Storage elastic modulus / surface roughness / linear expansion coefficient / transmittance / refractive index The protective layer forming sheets obtained in the examples and comparative examples were irradiated with ultraviolet rays from the polyethylene terephthalate film side (manufactured by Lintec Corporation, apparatus name) : Adwill RAD-2000 m / 8, irradiation conditions: illuminance: 310 mW / cm ² , light quantity: 200 mJ / cm ² ), the protective layer before curing was cured to obtain a protective layer.

  The release film and the polyethylene terephthalate film were peeled from the protective layer, and the surface roughness (Ra) of the surface of the protective layer that was in contact with the polyethylene terephthalate film, the storage elastic modulus of the protective layer, and the linear expansion were as follows. The coefficient, 400 nm transmittance and refractive index were measured. The results are shown in Table 1.

Surface roughness (Ra): A contact type surface roughness meter (manufactured by Mitutoyo Corporation, SV3000S4) was used and measured according to ISO 4287.
Storage modulus: A value at 30 ° C. was measured at 11 Hz using a viscoelasticity measuring device (Orientec, Leo Vibron DDV-II-EP).
Linear expansion coefficient: Measured using a thermal analyzer (manufactured by Mac Science, system WS002).
400 nm transmittance: measured using a spectrophotometer (manufactured by Shimadzu Corporation, UV-3101PC).
Refractive index: Measured according to JIS K7142 using an Abbe refractometer (manufactured by Atago Co., Ltd.).

3. Refractive index uniformity The refractive index uniformity of the protective layer cured as described above was determined. Specifically, one side of the cured protective layer is painted black with a commercially available black pen, with the black painted surface facing down, under a three-wavelength fluorescent lamp (manufactured by Toshiba, Mellow 5N, three-wavelength daylight white) FLR40S EX-N / M / 36-H 40 type 36 watts), whether or not the interference fringes are uniform was visually confirmed. As a control, the uniformity of interference fringes was confirmed in the same manner for a polycarbonate film (Pure Ace C110-100, manufactured by Teijin Chemicals Limited, thickness: 100 μm). Compared with the polycarbonate film, the case where the uniformity of the interference fringes is equal is indicated by ◯, and the case where the interference fringes are non-uniform is indicated by ×. The results are shown in Table 1.

  As is clear from Table 1, the protective layer forming sheets prepared in the examples are excellent in shape retention, and the protective layer obtained from the protective layer forming sheet has physical properties suitable for optical disks. The refractive index uniformity was excellent.

[Production example]
An optical disc substrate made of polycarbonate having a thickness of 1.1 mm, an outer diameter of 120 mm, and an inner diameter of 15 mm and having an uneven pattern on one side was molded by injection molding. A reflective layer made of a silver alloy and having a thickness of about 150 nm was formed on the concavo-convex pattern of the optical disk substrate by sputtering.

  The optical disk manufacturing sheet manufactured in the example was cut into the same shape as the optical disk substrate by punching, and then one release film (base material 12 ') was peeled off, and the exposed pre-curing protective layer was used as the optical disk. The pressure was applied to the reflective layer surface on the substrate with a pressure of 20N.

Next, the protective layer before curing is irradiated with ultraviolet rays from the other release film (base material 12) side (using Lintec's Adwill RAD-2000m / 8. Irradiation conditions: illuminance: 310 mW / cm ² , light amount: 200 mJ / cm ² ), after curing the protective layer before curing, the other release film (base material 12) was peeled off to obtain an optical disk on which the protective layer was formed. The obtained optical disk had good signal characteristics because a protective layer having uniform physical properties could be formed without forming an adhesive layer.

  INDUSTRIAL APPLICABILITY The present invention is useful for manufacturing an optical recording medium having a uniform protective layer physical property and good signal characteristics with a small number of manufacturing steps and high yield.

It is sectional drawing of the sheet | seat for protective layer formation of the optical disk which concerns on one Embodiment of this invention. It is sectional drawing which shows an example of the optical disk manufacturing method using the sheet | seat for protective layer formation of the optical disk which concerns on the embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Sheet | seat for protective layer formation of an optical disk (optical recording medium) 11 ... Pre-cure protective layer 11 '... Protective layer 12, 12' ... Base material 2 ... Optical disk substrate 3 ... Reflective layer 3 '... Semi-transmissive reflective layer 4 ... Stamper Receptive layer

Claims (10)

  A pre-curing protective layer comprising a composition containing 10 to 70% by mass of an energy ray-curable compound having a melting point of 25 ° C. or more and substantially not containing a polymer component having a weight average molecular weight of 50,000 or more is provided. A protective layer forming sheet for an optical recording medium.   The sheet for forming a protective layer of an optical recording medium according to claim 1, wherein the composition further contains 30 to 90% by mass of an energy ray-curable oligomer that is liquid at 20 ° C.   The optical recording medium according to claim 1, wherein the protective layer before curing is laminated on the smooth surface of a substrate having a smooth surface with a surface roughness (Ra) of 0.1 μm or less. A protective layer forming sheet.   The said pre-curing protective layer is sandwiched between said smooth surfaces of two substrates having a smooth surface with a surface roughness (Ra) of 0.1 µm or less. A protective layer-forming sheet for optical recording media. A method for producing a protective layer forming sheet for an optical recording medium comprising a pre-curing protective layer,
A composition containing 10 to 70% by mass of an energy ray-curable compound having a melting point of 25 ° C. or higher and containing substantially no polymer component having a weight average molecular weight of 50,000 or higher is used without using a solvent. A method for producing a protective layer-forming sheet for an optical recording medium, wherein the pre-curing protective layer is formed by coating on a flat surface and sandwiching between the first flat surface and the second flat surface.   The method for producing a protective layer forming sheet for an optical recording medium according to claim 5, wherein the composition further contains 30 to 90% by mass of an energy ray-curable oligomer that is liquid at 20 ° C. An optical recording medium manufacturing method comprising an optical recording medium substrate, one or more information recording layers, and a protective layer,
Crimping the protective layer before curing of the protective layer forming sheet of the optical recording medium according to any one of claims 1 to 4 to the outermost information recording layer,
A method for producing an optical recording medium, comprising: curing the pre-curing protective layer by irradiation of energy rays to form a protective layer of the optical recording medium. An optical recording medium manufacturing method comprising an optical recording medium substrate, one or more information recording layers, and a protective layer,
The protective layer before curing of the protective layer forming sheet of the optical recording medium according to claim 3, with respect to the outermost information recording layer, on the side in contact with the smooth surface of the substrate in the protective layer forming sheet Crimp so that the surface is on the information recording layer side,
A method for producing an optical recording medium, comprising: curing the pre-curing protective layer by irradiation of energy rays to form a protective layer of the optical recording medium.   An optical recording medium comprising a protective layer formed by curing the protective layer before curing of the protective layer forming sheet of the optical recording medium according to claim 1. An optical recording medium substrate, one or more information recording layers, and a protective layer formed by curing the protective layer before curing of the protective layer forming sheet of the optical recording medium according to claim 3,
The optical recording medium is characterized in that the protective layer is laminated on the information recording layer with the surface of the protective layer before curing that is in contact with the smooth surface of the substrate as the information recording layer side.

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