JP2004234820A - Optical information recording medium and manufacturing method of optical information recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical information recording medium on the label surface of which visible information can be recorded by irradiation of a low output laser beam using a laser device for recording/reproducing electronic information without exerting a thermal influence and the like to the electronic information recorded on the medium. <P>SOLUTION: In the optical information recording medium 100 which has a structure wherein a substrate 101, an electronic information recording layer 102, a reflection layer 103, a protective layer 104, a visible information recording layer 105, and an over coat layer forming an outermost layer are successively layered, and wherein the surface roughness of the outermost layer on the label surface side is 1/2 as rough as the wavelength (λ) of the laser beam 108 or less, focusing of the low output laser beam is satisfactorily performed, and visible information is satisfactorily recorded in the visible information recording layer. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

  The present invention relates to an optical information recording medium and the like, and more particularly, to an optical information recording medium and the like in which electronic information is optically recorded / reproduced and visible information is favorably recorded on a label surface side by a laser beam. .

2. Description of the Related Art In recent years, electronic information recording media for recording, storing, and rewriting a large amount of information have been increasingly important as computer peripheral devices. Among them, an optical information recording medium on which recording and reproduction are performed by using a laser beam is attracting attention as a large-capacity recording medium because it can perform high-density information recording, storage, and reproduction. Examples of such optical information recording media include phase-change optical recording media such as CD-RW and DVD-RW, and organic dye-based optical recording media such as CD-R and DVD-R. No.
The contents of the electronic information recorded on such an optical information recording medium can be confirmed by optically reproducing the information. On the other hand, displaying the contents of the electronic information on the surface of the medium as visible information is a matter of information management. It is important. Conventionally, as such a display method, for example, a method of printing and recording the contents of electronic information on a label surface of a medium (a surface opposite to a surface on which electronic information is recorded) by an inkjet printer or a thermal printer, A method of attaching a label or the like on which the content of electronic information is recorded has been adopted. Recently, there has been reported a method of recording visible information by irradiating the visible information recording layer provided on the label side of the medium with the laser light (see Patent Documents 1 and 2). It is expected as a method that can record visible information without any negative influence.

JP 2000-173096 A JP 2001-283364 A

However, the method of recording visible information on the label side of a medium by using a laser beam in Patent Document 1 or Patent Document 2 described above has the following problems. In other words, the method of recording visible information on the label side of the medium with laser light utilizes changes in reaction, melting, and precipitation due to heat. Therefore, it is necessary to pay sufficient attention to the irradiation method. For this reason, in order to reduce the thermal influence on such a medium, it is necessary to use a low-output laser beam. When such a low-output laser beam is used, it is effective to efficiently concentrate the energy of the laser beam by concentrating the low-output laser beam on a layer for recording visible information (a visible information recording layer). However, for that purpose, it is necessary to apply a focus servo.
In addition, in order to efficiently focus low-power laser light on the visible information recording layer and apply stable focus servo, the reflective layer for obtaining return light used for focusing and the visible information recording layer are physically damaged. In some cases, a layer (laser light transmitting layer) composed of a laser light transmitting body for protecting the visible light from the laser light to the visible information recording layer is provided.

However, in this case, if there is an uneven shape on the surface of the visible information recording layer or the laser light transmitting layer, a phenomenon occurs that the laser light irradiated from the label side is irregularly reflected on the surface of the visible information recording layer or the laser light transmitting layer. . When the laser beam is irregularly reflected in this manner, the amount of light incident on the visible information recording layer is reduced, and the visible information cannot be recorded satisfactorily. Further, it becomes difficult to perform focusing stably due to irregular reflection.
The present invention has been made to solve a technical problem that has been highlighted when recording visible information on a visible information recording layer formed on the label side of an optical information recording medium by using such a low-output laser beam. It is.
That is, an object of the present invention is to use a laser device for recording / reproducing electronic information and to irradiate a low-power laser beam so that the electronic information recorded on the medium can be viewed on the label side without adversely affecting the information. An object of the present invention is to provide an optical information recording medium on which information is recorded.
It is another object of the present invention to provide a method for manufacturing an optical information recording medium in which visible information is recorded on the label surface side by irradiating a low-power laser beam.

In order to achieve this object, the optical information recording medium to which the present invention is applied adopts a configuration in which an outermost layer such as a laser light transmitting layer with reduced surface roughness is provided as the outermost layer on the label side. I have. That is, the optical information recording medium to which the present invention is applied is provided on a substrate and directly or via another layer on the substrate, and is visible by a laser beam irradiated from a label surface side opposite to the substrate side. A visible information recording layer on which information is recorded, wherein the surface roughness of the outermost layer on the label surface side is not more than half the wavelength of the laser light emitted from the label surface side. It is. Further, it is preferable that the surface roughness of the outermost layer is 以下 or less of the wavelength of the laser beam.
An optical information recording medium to which the present invention is applied includes a substrate having guide grooves and / or pits for recording and reproduction, and an electronic device on which digital information is recorded on the substrate by at least light irradiated from the substrate side. An information recording layer, a reflective layer formed on the electronic information recording layer, and a visible information recording layer on which visible information is recorded by a laser beam irradiated from a label surface side opposite to the substrate side. The optical information recording medium according to claim 1, wherein a surface roughness of an outermost layer on a label surface side is equal to or less than 波長 of a wavelength of laser light emitted from the label surface side.

Next, an optical information recording medium to which the present invention is applied is formed on a substrate, and a visible information recording layer on which visible information is recorded by light irradiated from a label surface side opposite to the substrate; An overcoat layer formed on the label side of the information recording layer, wherein the surface roughness of the overcoat layer is not more than half the wavelength of light.
The overcoat layer is preferably formed of a laser light transmitting material, and the overcoat layer is formed so that the lower limit of the thickness of the overcoat layer is 10 μm and the upper limit is 100 μm. Is preferred. Further, the overcoat layer is preferably formed such that the refractive index of the overcoat layer is in the range of 0.4 or more and 2.6 or less. Further, the visible information recording layer is characterized by being formed of a material whose color developing property changes or a material whose transparency changes by light irradiated to the visible information recording layer.

On the other hand, an optical information recording medium to which the present invention is applied includes a substrate, an electronic information recording layer formed on the substrate, on which digital information is recorded by light irradiated from the substrate side, and a substrate side of the electronic information recording layer. And a protective layer formed on the side of the reflective layer opposite to the substrate side, wherein the optical information recording medium is formed on the side of the protective layer opposite to the substrate side. A visible information recording layer on which visible information is recorded by a laser beam irradiated from a label surface side opposite to the substrate side, and a visible information recording layer formed on the label surface side, and the surface roughness is reduced An overcoat layer having a wavelength equal to or less than half the wavelength of the laser light emitted from the surface side.
Further, it is preferable to have a protective layer formed on the opposite side of the reflective layer from the substrate side.

On the other hand, the present invention provides a step of forming an electronic information recording layer on a substrate on which digital information is recorded by light irradiated from the substrate side, and a step of forming a reflective layer above the formed electronic information recording layer And a step of forming a protective layer on the formed reflective layer, and on the formed protective layer, visible information is recorded by light emitted from the label surface side opposite to the substrate side. A step of forming a visible information recording layer, and an overcoat layer having a surface roughness of 以下 or less of the wavelength of light irradiated from the label side is formed on the visible information recording layer by a wet film forming method. And a step of forming the optical information recording medium.
In the optical information recording medium to which the present invention is applied, “visible information” refers to information visually read, such as characters, symbols, images such as illustrations and photographs, and geometric patterns, and “electronic information”. The term “information” means information read by a certain reproducing apparatus, such as information recorded in a digital signal.

  Thus, according to the present invention, there is provided an optical information recording medium capable of recording visible information on a label surface by irradiating a low-power laser.

Hereinafter, an optical information recording medium to which the present embodiment is applied will be described in detail with reference to the drawings.
FIG. 1 is a diagram for explaining the structure of an optical information recording medium to which the present embodiment is applied. The optical information recording medium 100 shown here has a substrate 101, an electronic information recording layer 102 formed on the substrate 101 in order, and a side of the electronic information recording layer 102 opposite to the side on which the laser beam 107 is incident. Has a structure in which a reflective layer 103, a protective layer 104, a visible information recording layer 105, and an overcoat layer 106 that forms the outermost layer are sequentially laminated.
As shown in FIG. 1, an electronic information recording layer 102 provided on an optical information recording medium 100 has a laser beam incident from an objective lens (not shown) of a laser device for recording / reproducing electronic information via a substrate 101. Recording and reproduction of electronic information are performed by the light 107. On the other hand, when the optical information recording medium 100 is turned upside down and set in a laser device for recording / reproducing electronic information, for example, the visible information recording layer 105 is irradiated with laser light emitted from the label side via the overcoat layer 106. Light 108 records visible information. A part of the laser light 108 is reflected by the reflective layer 103 provided below the visible information recording layer 105, and the reflected light 109 is used for focusing for condensing the laser light 108.

The substrate 101 is basically formed of a material transparent to the wavelength of the recording light and the reproduction light for the electronic information recording layer 102. As a material for forming the substrate 101, for example, other than a polymer material such as a polycarbonate resin, an acrylic resin, a methacrylic resin, a polystyrene resin, a vinyl chloride resin, an epoxy resin, a polyester resin, and an amorphous polyolefin resin, And an inorganic material such as glass. In particular, a polycarbonate resin is preferable because it is excellent in terms of high light transmittance, small optical anisotropy, and high mechanical strength. Further, from the viewpoints of chemical resistance, moisture absorption resistance, optical characteristics, and the like, amorphous polyolefin is preferable.
For example, a guide groove or pit for recording / reproducing is provided on a surface of the substrate 101 which is in contact with the electronic information recording layer 102, and is molded by a molding method such as injection molding. Such guide grooves or pits are preferably provided at the time of molding the substrate 101. For example, the guide grooves or pits may be provided on the substrate 101 using an ultraviolet (UV) curable resin. The lower limit of the thickness of the substrate 101 is usually 1.1 mm, preferably 1.15 mm, and the upper limit of the thickness is usually 1.3 mm, preferably 1.25 mm.

The electronic information recording layer 102 is formed of a material capable of recording electronic information (information such as information recorded by a digital signal, such as information recorded by a certain reproducing device) by irradiation with a laser beam 107, and is usually made of an organic substance. It is formed as a recording layer made of an inorganic material. The electronic information recording layer 102 may be formed directly on the substrate 101, or may be formed between the substrate 101 and the electronic information recording layer 102 via an optional layer, if necessary. Is also good.
When the electronic information recording layer 102 is a recording layer made of an organic substance, an organic dye is mainly used. Examples of such organic dyes include macrocyclic azaannulene dyes (phthalocyanine dyes, naphthalocyanine dyes, porphyrin dyes, etc.), polymethine dyes (cyanine dyes, merocyanine dyes, squalilium dyes, etc.), anthraquinone dyes, azurenium dyes, azo dyes Dyes, metal-containing azo dyes, metal-containing indoaniline dyes, and the like. Among these, metal-containing azo dyes, cyanine dyes and phthalocyanine dyes are preferred. In particular, metal-containing azo dyes are preferable because of their excellent durability and light resistance.
Examples of the method for forming the electronic information recording layer 102 made of an organic material include a dry thin film forming method such as a vacuum evaporation method and a sputtering method, and a wet thin film forming method generally performed such as a casting method, a spin coating method, and an immersion method. No. Among them, the spin coating method is particularly preferable in terms of mass productivity and cost.

When the electronic information recording layer 102 is formed as a recording layer made of an inorganic substance, for example, a rare-earth transition metal alloy such as Tb-Te-Co or Dy-Fe-Co on which recording is performed by the magneto-optical effect is used. . Further, chalcogen-based alloys such as Ge.Te and Ge.Sb.Te that change phases may be used. These layers may be a single layer or may be composed of two or more layers.
Examples of a method for forming the electronic information recording layer 102 made of an inorganic substance include a vapor deposition method, an ion plating method, and a sputtering method. Among them, the sputtering method is particularly preferable in terms of mass productivity and cost. The thickness of the electronic information recording layer 102 varies depending on the type of the recording layer, but the lower limit is usually 5 nm, preferably 10 nm, and the upper limit is usually 500 nm, preferably 300 nm. The electronic information recording layer 102 of the optical information recording medium 100 to which the present embodiment is applied may be a recordable / erasable phase-change recording layer.

The reflection layer 103 is provided in contact with the electronic information recording layer 102 on the side opposite to the substrate 101, and generally has a function of reflecting the laser beam 107 emitted from the substrate 101 side to the substrate 101 side. When the recording / reproducing guide groove or pit is provided on the substrate 101, the reflective layer 103 has an uneven shape corresponding thereto. As a material for forming the reflective layer 103, a material having a sufficiently high reflectance at the wavelength of the reproduction light can be used, and examples thereof include Au, Al, Ag, Cu, Ti, Cr, Ni, Pt, Ta, and Pd. It is possible to use a metal alone or as an alloy. Among these, Au, Al, and Ag have high reflectivity and are suitable as a material for the reflective layer. Further, those containing Ag as a main component are particularly preferable in terms of low cost and high reflectance.
Examples of a method for forming the reflective layer 103 include an evaporation method, an ion plating method, and a sputtering method. Among them, the sputtering method is particularly preferable in terms of mass productivity and cost. The lower limit of the thickness of the reflective layer 103 is usually 30 nm, preferably 50 nm, and the upper limit is usually 150 nm, preferably 120 nm.

The protective layer 104 is generally formed of a laser light transmitting material, and includes, for example, an ultraviolet (UV) curable resin. Specific examples of the ultraviolet (UV) curable resin include, for example, acrylate resins such as urethane acrylate, epoxy acrylate, and polyester acrylate. Most of these materials are laser light transmitting materials, and thus can be suitably used. One of these ultraviolet (UV) curable resins may be used alone, or two or more thereof may be used in combination. Further, the protective layer 104 may be a single-layer film or a multilayer film having two or more layers.
As a method of forming the protective layer 104 with an ultraviolet (UV) curable resin, usually, an ultraviolet (UV) curable resin is used as it is or after dissolving in a suitable solvent to prepare a coating solution, and then reflecting the coating solution. It can be formed by being applied over the layer 103 and curing by irradiating ultraviolet (UV) light. In this case, as a coating method, a spin coating method, a casting method, or the like can be adopted. In addition, the protective layer 104 can be formed by any of the above-described various coating methods, various wet film formation methods such as a screen printing method, and various dry film formation methods such as a vacuum evaporation method, a sputtering method, and an ion plating method. It is formed by a method appropriately selected according to a material to be used. Among them, a wet film forming method, particularly a spin coating method is preferable, and a spin coating method is generally used. The lower limit of the thickness of the protective layer 104 is usually 1 μm, preferably 3 μm, and the upper limit is usually 15 μm, preferably 10 μm.

When the visible information recording layer 105 is irradiated with light, usually, the recording material constituting the layer is discolored, and as a result, the visible information (images such as characters, symbols, illustrations and photographs, geometric patterns, etc.) , Information visually read). The recording material that constitutes the visible information recording layer 105 is not particularly limited, but as a substance that changes the absorption of visible light, it is roughly classified into the following (a) a type in which the coloring property changes, and (b) a transparent type. And the type whose gender changes.
(A) Examples of the recording material of the type in which the coloring property changes include organic dyes generally used for optical recording of electronic information. Examples of such organic dyes include macrocyclic azaannulene dyes such as phthalocyanine dyes, naphthalocyanine dyes, and porphyrin dyes; polymethine dyes such as cyanine dyes, merocyanine dyes, and squalylium dyes; Azo dyes, metal-containing azo dyes, metal-containing indoaniline dyes, and the like.

  Further, a leuco dye having a lactone ring portion in the molecular structure may be mentioned. Leuco dyes are preferred because the contrast during color development is high and the amount of heat required for color development can be kept low. Specific examples of leuco dyes include, for example, 3-diethylamino-7-chloroanilinofluoran, 3-diethylamino-6-methyl-7-anilinofluoran, 3-dibutylamino-6-methyl-7-anilino Fluoran, 3-diethylamino-6-methyl-7-2, 4-xyridinofluoran, 3-diethylamino-6-methyl-7- (m-toluidino) -fluoran, 3-diethylamino-7,8-benzofluro Fluoran compounds such as silane and 3-diethylamino-6-methyl-7-xidinofluoran; crystal violet lactone, 3- (4-diethylamino-2-ethoxyphenyl) -3- (1-ethyl2-methylindole-3) -Yl) -4-azaphthalide, 3- (4-diethylaminophenyl) -3- (1-ethyl2-methyl Ndoru-3-yl) phthalide, 3,3-bis (1-n-butyl-2-methylindole-3-yl) phthalide compounds such phthalide and the like. Of these, phthalide compounds are preferred.

If necessary, an electron-accepting compound, a dye that absorbs laser light for recording and generates heat, and the like are used in combination with these leuco dyes. In this case, examples of the electron-accepting compound include an organic phosphoric acid compound having an aliphatic group having 6 or more carbon atoms, an aliphatic carboxylic acid compound, and a phenol compound. Preferably, it is a phenol compound.
Specific examples of the electron-accepting compound include organic phosphoric acid compounds such as dodecylphosphonic acid, tetradecylphosphonic acid, hexadecylphosphonic acid, octadecylphosphonic acid, and eicosylphosphonic acid. As the aliphatic carboxylic acid compound, α-hydroxydecanoic acid, α-hydroxytetradecanoic acid, α-hydroxyhexadecanoic acid, α-hydroxyoctadecanoic acid, α-hydroxypentadecanoic acid, α-hydroxyeicosanoic acid, α-hydroxydokosan Acids, α-hydroxytetracosanoic acid, α-hydroxyhexacosanoic acid, α-hydroxyoctacosanoic acid and the like.

Examples of the phenol compound include a gallic acid compound, a benzoic acid compound, and a bisphenol compound. Specific examples of these compounds include, for example, gallic acid compounds such as methyl gallate, propyl gallate, butyl gallate, lauryl gallate and the like. Examples of the benzoic acid compound include methyl p-hydroxybenzoate, ethyl p-hydroxybenzoate, and 2,4-didroxybenzoic acid. Examples of the bisphenol-based compound include bisphenol S and bisphenol A. Furthermore, 4'-hydroxy-4-octadecyl benzanilide, N-octadecyl-4-hydroxybenzamide, N- (4-hydroxyphenyl) -N'-octadecyl urea, 4-hydroxyphenylpropiono-behenyl hydrazide and the like can be mentioned. These electron accepting compounds may be used alone or in combination of two or more.
Examples of the laser light absorbing dye include the various dyes described above as organic dyes used for optical recording of electronic information, and infrared absorbing dyes such as bisanthrone-based and indoaniline-based dyes.

  Next, as the recording material (b) of a type in which the transparency changes, for example, an organic low-molecular compound that is dispersed in a resin base material at about 0.1 to 2 μm and melts or crystallizes by heat treatment can be cited. As such a compound, for example, a known organic low molecular weight compound having 12 or more carbon atoms such as a higher fatty acid can be used. Such an organic low-molecular compound may be a compound composed of a fatty acid, an aliphatic dibasic acid, a ketone, an ether, an alcohol, a fatty acid ester and a derivative thereof, or a mixture of one or more of them. It can also be used.

Among the organic low molecular weight compounds that are melted or crystallized by heat treatment, fatty acid alkyl esters having 12 or more carbon atoms have a low melting point (mp) and are preferred because they are melted and crystallized by heat treatment at a relatively low temperature. Furthermore, by using a fatty acid alkyl ester having 12 or more carbon atoms and an aliphatic dibasic acid having a high melting point (mp) having 10 or more carbon atoms in combination and adjusting the mixing ratio of the fatty acid alkyl ester and the aliphatic dibasic acid, It is possible to adjust the temperature region to be transparent, and to change the degree of transparency and cloudiness at a predetermined temperature.
Examples of fatty acid alkyl esters having 12 or more carbon atoms include methyl stearate, ethyl stearate, butyl stearate, octyl stearate, stearyl stearate, behenyl stearate, methyl behenate, ethyl behenate, butyl behenate, behenate Octyl acid, stearyl behenate, behenyl behenate, methyl lignoserate, ethyl lignocerate and the like can be mentioned.
Examples of the aliphatic dibasic acid having 10 or more carbon atoms include sebacic acid, dodecandioic acid, tetradecandioic acid, eicosantioic acid, and the like. When a fatty acid alkyl ester having 12 or more carbon atoms and an aliphatic dibasic acid having 10 or more carbon atoms are used in combination, the mixing ratio is (fatty acid alkyl ester having 12 or more carbon atoms) :( aliphatic alkyl ester having 10 or more carbon atoms). Dibasic acid) is preferably about 1: 1 to 10: 1, more preferably 2: 1 to 6: 1. Since the aliphatic dibasic acid on the high melting point side is thought to play a role in controlling the crystallization behavior as a seed crystal of the fatty acid alkyl ester on the low melting point side, its effect may be lost if the blending amount is excessively small. On the contrary, if the amount is too large, the contrast may be reduced.

  As a method for forming the visible information recording layer 105, a known wet thin film forming method as described in the section of the method for forming the electronic information recording layer 102 can be used. Among them, a spin coating method or a screen printing method is preferable, and a spin coating method is more preferable. The lower limit of the thickness of the visible information recording layer 105 is usually 0.1 μm, preferably 0.5 μm, and the upper limit of the thickness is usually 5 μm, preferably 3 μm.

The overcoat layer 106 is provided on the label side of the visible information recording layer 105 so as to protect the visible information recording layer 105 from physical damage or the like and to efficiently narrow the laser beam 108 to the visible information recording layer 105. To form the outermost layer. The material constituting the overcoat layer 106 is not particularly limited as long as it is a material that protects the visible information recording layer 105 from external force and the like and is transparent to laser light.
As a material constituting the overcoat layer 106, as an organic substance, a thermoplastic resin, a thermosetting resin, an electron beam curable resin, an ultraviolet (UV) curable resin, or the like can be given. The overcoat layer 106 can be formed by dissolving a thermoplastic resin, a thermosetting resin, or the like in a suitable solvent, applying a coating solution, and drying the coating solution. The ultraviolet (UV) curable resin is applied as it is or after dissolving in an appropriate solvent to prepare a coating solution, and then applying the coating solution, and irradiating with ultraviolet (UV) light to cure the overcoat layer 106. Can be formed. As the ultraviolet (UV) curable resin, for example, acrylate resins such as urethane acrylate, epoxy acrylate, and polyester acrylate can be used. Examples of the inorganic substance include SiO ₂ , SiN ₄ , MgF ₂ , and SnO ₂ . These materials may be used alone or in a combination of two or more. Further, the overcoat layer 106 may be a single-layer film or a multilayer film of two or more layers as long as it is transparent to the laser beam 108.

The overcoat layer 106 is preferably formed by a wet film forming method using the above-described various organic substances. As the wet film forming method, a spin coating method, a casting method, a screen printing method, or the like can be employed as in the case of the protective layer 104 described above. Among them, the spin coating method is particularly preferred because of its high surface smoothness. In particular, when the overcoat layer 106 is formed, if a transparent substrate made of a laser-transmissive material is to be bonded in advance, it is necessary to perform accurate alignment of the substrate, and air bubbles are generated in the adhesive layer. Various measures in the manufacturing process are required, such as reducing the pressure in the bonding process so as not to enter. Therefore, from the viewpoint of productivity, it is more advantageous to provide the overcoat layer 106 by a wet film forming method such as spin coating or screen printing.
The lower limit of the thickness of the overcoat layer 106 is 10 μm, preferably 20 μm, and the upper limit of the thickness is 100 μm, preferably 80 μm. When the thickness of the overcoat layer 106 is lower than the lower limit, the sufficient protection function of the visible information recording layer 105 may not be maintained. In addition, the surface of the overcoat layer 106 is likely to be rough due to the influence of the surface roughness of the lower visible information recording layer 105. Further, when the thickness is higher than the upper limit value, when forming the overcoat layer 106 by coating, overlapping coating or the like is required, and the forming process becomes complicated. Further, there is a possibility that a problem such as an increase in the warpage of the disk due to the curing shrinkage of the coating material may occur.

  In the optical information recording medium 100 to which the present embodiment is applied, the surface roughness of the overcoat layer 106 forming the outermost layer on the label surface side is equal to or less than １ ／ of the wavelength (λ) of the laser light, preferably 1 / 4 or less. Here, the surface roughness of the overcoat layer 106 is obtained as an arithmetic average roughness (Ra) measured according to JIS B0601. The measurement area of the surface roughness may be any area in which visible information is recorded and used by irradiating a laser beam. In the optical information recording medium 100 to which the present embodiment is applied, the surface roughness of the overcoat layer 106 is set to １ ／ or less, preferably １ ／ or less of the wavelength (λ) of the laser light. In addition, irregular reflection of the laser beam 108 emitted from the label side on the surface of the overcoat layer 106 is reduced. Therefore, the amount of light incident on the visible information recording layer 105 is secured, and the reflected light 109 reflecting the laser light 108 emitted from the label side is stabilized, and focusing is performed by the stable reflected light 109. This makes it possible to record clear visible information on the visible information recording layer 105 using low-power laser light.

As described above, the optical information recording medium 100 to which the present embodiment is applied is characterized in that the surface roughness of the overcoat layer 106 is １ ／ or less of the wavelength (λ) of the laser light.
In general, the visible information recording layer provided as a lower layer of the overcoat layer often contains a particle component, and the surface of the visible information recording layer has unevenness having a height of about 1 μm to 3 μm. If an overcoat layer is arbitrarily provided on such a visible information recording layer, the surface roughness of the overcoat layer becomes rough due to the influence of the lower visible information recording layer. On the other hand, a commonly used laser beam is a semiconductor laser beam having a wavelength (λ) of about 300 nm to 800 nm. Therefore, if an overcoat layer is arbitrarily provided on the visible information recording layer having irregularities of about 1 μm to 3 μm in height, the surface roughness of the overcoat layer is reduced to の of the wavelength (λ) of the laser beam. Cannot be less than
In this embodiment mode, the surface roughness of the overcoat layer 106 can be reduced to の of the wavelength (λ) of the laser light by appropriately selecting a method for forming the overcoat layer 106 and a material for forming the overcoat layer 106. It is prepared as follows. In order for the surface roughness of the overcoat layer 106 to be 以下 or less of the wavelength (λ) of the laser beam, a relatively low-viscosity material is applied on the visible information recording layer 105 so that the overcoat layer 106 becomes It is preferably formed. Specific examples of such a material include a material having a viscosity of 50 cps or more and 7000 cps or less. When the viscosity of the material for forming the overcoat layer 106 is within this range, unevenness on the surface of the overcoat layer 106 is less likely to occur, and the surface roughness of the overcoat layer 106 can be reduced. After the formation of the overcoat layer 106, the surface may be subjected to a surface treatment such as polishing to suppress the surface roughness of the overcoat layer 106 to 以下 or less of the wavelength (λ).

  Further, in order to stably reduce the surface roughness of the overcoat layer 106, as described above, the viscosity of the material forming the overcoat layer 106 is set to 50 cps or more and 7000 cps or less. It is very effective to set the height to 10 μm or more and 100 μm or less. The reflectance on the surface of the overcoat layer 106 is preferably, for example, 20% or less. In this case, the refractive index of the overcoat layer 106 is preferably about 0.4 or more and 2.6 or less. Further, in order to make the reflectance on the surface of the overcoat layer 106 10% or less, the refractive index of the overcoat layer 106 is preferably 0.5 or more and 1.9 or less.

  The optical information recording medium to which the present embodiment is applied may have an arbitrary layer other than the above. For example, when a recording layer made of an inorganic substance is used as the electronic information recording layer 102, an arbitrary layer may be provided between each layer or the outermost layer of the medium, such as providing a dielectric layer sandwiching the electronic information recording layer 102. May be. Further, the visible information recording layer does not necessarily require all the layers described above. For example, the visible information recording layer may have the function of the overcoat layer by omitting the overcoat layer. In this case, since the visible information recording layer is the outermost layer, the surface roughness of the visible information recording layer needs to be 以下 or less, preferably １ ／ or less of the wavelength (λ) of the laser beam. .

As described above, two embodiments of the optical information recording medium to which the present invention is applied have been described. However, the present embodiment is not limited to the above-described embodiment, and various modifications can be made. For example, the optical information recording medium may have a plurality of electronic recording layers. Optical information using a substrate (first substrate) having a guide groove and / or pit having a thickness of about 0.6 mm and a so-called dummy substrate (second substrate) having no guide groove and / or pit. In the case of a recording medium, a laminated structure including a first substrate / electronic information recording layer / reflection layer / adhesion layer / second substrate / visible information recording layer / overcoat layer, or a first substrate / electronic information recording layer The present invention can be applied to a laminated structure of / reflective layer / adhesive layer / visible information recording layer / second substrate /. In this case, the overcoat layer and the second substrate side are the label side, respectively, and other layers may be provided as needed between each layer or as the outermost layer.
Furthermore, the present invention is not limited to a so-called substrate-surface incident type optical disk, but may be any so-called film-surface incident type optical recording medium in which information is recorded and reproduced by irradiating a laser beam from the protective layer side (that is, the film surface side). -The present invention can be applied to a laminated structure including a bar coat layer / visible information recording layer / substrate / reflection layer / electronic information recording layer / protective layer. In this case, the overcoat layer side is the label side, and the substrate has guide grooves and / or pits on the side where the information recording layer is provided. Further, other layers may be provided as needed between each layer or as the outermost layer.

Hereinafter, an optical information recording medium to which the present embodiment is applied will be described more specifically with reference to examples. The present embodiment is not limited to the examples.
(1) Recording of Visible Information on Optical Information Recording Medium FIG. 2 is a diagram for explaining a recording apparatus that records visible information on an optical information recording medium having a visible information recording layer. The recording device 200 shown in FIG. 2 is adapted to record visible information on an optical information recording medium 11 having a visible information recording layer by a normal optical disk drive, and the optical information recording medium 11 is mounted. The apparatus includes a spindle 12, a spindle motor 13 for rotating the spindle 12, a stepping motor 14 for feed feed, a screw shaft 15 rotated by the stepping motor 14, and a pickup 16 moved to an arbitrary position.
As shown in FIG. 2, this recording apparatus 200 mounts an optical information recording medium 11 on a spindle 12 and rotates it by a spindle motor 13, and also rotates a screw shaft 15 by a stepping motor 14 for feed feed, and The pickup 16 is moved to the position. The spindle motor 13 performs servo with an FG pulse signal, and adjusts the optical information recording medium 11 to an arbitrary rotation speed. The optical information recording medium 11 is focused on by the focus servo, and the laser light 17 is condensed to write visible information on the optical information recording medium 11. At this time, the laser power is controlled by the front monitor so that writing can be performed with an appropriate power. The write signal irradiates a pulse having a duty of about 50% on the optical information recording medium 11 with an output of 40 to 50 mW. The spindle rotation speed is 160 to 2560 rpm.
(2) Measurement of Surface Roughness of Overcoat Layer The arithmetic average roughness (Ra) of the surface of the overcoat layer was measured using a surface roughness measuring device (MITSUTOYO SURFEST 402 type) in accordance with JIS B0601. . The smaller the numerical value, the smoother the surface (unit: μm).

(Examples 1 to 6, Comparative Examples 1 to 3)
A polycarbonate resin substrate having a groove of 0.45 μm in width and 155 nm in depth and a thickness of 1.2 mm was formed by injection molding. On this substrate, a fluorine-containing alcohol solution of a metal-containing azo dye was applied by spin coating, and dried at 90 ° C. for 15 minutes to form an electronic information recording layer having a thickness of 70 nm. Next, on this electronic information recording layer, Ag was sputtered to form a reflective layer having a thickness of 70 nm. Further, an ultraviolet (UV) curable resin ("SD-374" manufactured by Dainippon Ink and Chemicals, Inc.) mainly composed of an acrylate monomer is applied on the reflective layer by spin coating, and then irradiated with ultraviolet (UV) light. And cured to form a protective layer having a thickness of 7 μm, thereby producing a CD-R. Subsequently, on this protective layer, 0.2 parts by weight of the color-forming organic dye shown in Table 1, 0.6 parts by weight of the electron-accepting compound composed of a phenolic compound, and 0.1 parts by weight of the bisanthrone-based infrared absorbing dye. A color-forming organic dye composition obtained by blending 2.0 parts by weight of toluene with 05 parts by weight and 4 parts by weight of polymethyl methacrylate (10% by weight toluene solution) is applied by spin coating, After drying for 30 minutes, a visible information recording layer was formed. Then, on this visible information recording layer, an ultraviolet (UV) curable resin mainly composed of an acrylate monomer is applied by spin coating, and the resin is cured by irradiating ultraviolet (UV) light to form a 20 μm thick overcoat. A coat layer (refractive index: 1.5) was formed, and nine types of optical information recording media having different surface roughnesses of the overcoat layer shown in Table 1 were produced.

The nine types of optical information recording media produced in this manner are set in the recording device 200 shown in FIG. 2, respectively, and a low-output laser beam having a wavelength (λ) of 780 nm and an output of 50 mw is applied to the label surface of the optical information recording medium. Irradiated from the side, visible information was recorded on the visible information recording layer, and the quality of focusing was indicated based on the following criteria. Table 1 shows the results.
A: Focusing can be performed very stably.
：: Focusing can be performed almost stably.
X: Focusing cannot be performed stably.

  From the results shown in Table 1, when the visible information recording layer was irradiated with low-power laser light having a wavelength (λ) of 780 nm, the surface roughness of the overcoat layer was １ ／ or less of the wavelength of the laser light (0.05 to 0.05). In the optical information recording medium (Examples 1 to 6) having a wavelength of 0.36 μm), focusing of a low-output laser beam having a wavelength (λ) of 780 nm and an output of 50 mw was performed well, and visible information was recorded on a visible information recording layer. It can be seen that recording is performed well. On the other hand, in the case of an optical information recording medium (Comparative Examples 1 to 3) in which the surface roughness of the overcoat layer exceeds half the wavelength of the laser light (0.65 to 0.90 μm), It can be seen that focusing of light cannot be performed favorably, and as a result, it is difficult to record clear visible information on the visible information recording layer.

FIG. 2 is a diagram for explaining a structure of an optical information recording medium to which the present embodiment is applied. FIG. 2 is a diagram for explaining a recording device that records visible information on an optical information recording medium having a visible information recording layer.

Explanation of reference numerals

11, 100 optical information recording medium, 12 spindle, 13 spindle motor, 14 stepping motor, 15 screw shaft, 16 pickup, 17 laser beam, 101 substrate, 102 electronic information recording layer, 103 Reflective layer, 104: protective layer, 105: visible information recording layer, 106: overcoat layer, 107: laser light, 108: laser light, 109: reflected light, 200: recording device

Claims (11)

Board and
A visible information recording layer provided directly or via another layer on the substrate, where visible information is recorded by laser light irradiated from a label surface side opposite to the substrate side,
An optical information recording medium, characterized in that the surface roughness of the outermost layer on the label surface side is not more than 1/2 of the wavelength of laser light emitted from the label surface side. A substrate having a guide groove and / or a pit for recording and reproduction;
On the substrate, at least, an electronic information recording layer in which digital information is recorded by light emitted from the substrate side,
A reflective layer formed on the electronic information recording layer;
A visible information recording layer in which visible information is recorded by a laser beam irradiated from a label surface side opposite to the substrate side, and
An optical information recording medium, characterized in that the surface roughness of the outermost layer on the label surface side is not more than 1/2 of the wavelength of laser light emitted from the label surface side. A visible information recording layer formed on a substrate, in which visible information is recorded by light emitted from a label surface side opposite to the substrate,
An overcoat layer formed on the label surface side of the visible information recording layer,
An optical information recording medium, wherein the surface roughness of the overcoat layer is not more than half the wavelength of light.   3. The optical information recording medium according to claim 1, wherein the visible information recording layer has an overcoat layer formed on the label surface side of the visible information recording layer.   5. The optical information recording medium according to claim 3, wherein the overcoat layer is formed of a laser light transmitting material.   The optical information recording medium according to claim 3, wherein the overcoat layer has a lower limit of the thickness of the overcoat layer of 10 μm and an upper limit of 100 μm.   The optical information recording medium according to claim 3, wherein the overcoat layer has a refractive index of the cover coat layer in a range of 0.4 or more and 2.6 or less.   4. The visible information recording layer according to claim 1, wherein the visible information recording layer is formed of a material whose color developing property changes or a material whose transparency changes by light applied to the visible information recording layer. Optical information recording medium. Board and
An electronic information recording layer formed on the substrate and recording digital information by light emitted from the substrate side,
A reflective layer formed on the opposite side of the electronic information recording layer from the substrate side,
A visible information recording layer formed on the opposite side to the substrate side of the reflective layer, where visible information is recorded by light emitted from a label surface side opposite to the substrate side,
And an overcoat layer formed on the label surface side of the visible information recording layer and having a surface roughness of 以下 or less of a wavelength of light emitted from the label surface side. recoding media.   The optical information recording medium according to claim 9, further comprising a protective layer formed on a side of the reflection layer opposite to the substrate. Forming an electronic information recording layer on a substrate on which digital information is recorded by light emitted from the substrate side,
Forming a reflective layer on the formed electronic information recording layer,
Forming a protective layer on the reflective layer thus formed,
A step of forming a visible information recording layer on which visible information is recorded by light emitted from a label surface side opposite to the substrate side, on the formed protective layer,
Forming, by a wet film forming method, an overcoat layer having a surface roughness of 照射 or less of a wavelength of light irradiated from the label surface side on the formed visible information recording layer. Manufacturing method of an optical information recording medium.

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