JP2003059114A - Optical recording medium - Google Patents

Abstract

(57) [Problem] To provide an optical recording medium in which visible information can always be clearly seen irrespective of the circumferential positional relationship at the time of bonding two substrates. SOLUTION: An optical recording medium has two substrates 1 (1A, 1B) each having a recording layer 2 and a reflective layer 3 formed on one plate surface.
They are bonded with an adhesive with the reflection layers 3 facing each other. Visible information is provided on the transparent portion 6 of each substrate. This printing is performed on the surface on the bonding side of each of the substrates 1A and 1B. The visible information on the substrate 1A is relatively close to the center hole 5, and the visible information on the substrate 1B is relatively separated from the center hole 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a disc-shaped optical recording medium, and more particularly to a double-sided recording / reproducing optical recording medium having two transparent substrates bonded together and a reflecting layer and / or recording layer. Regarding

[0002]

2. Description of the Related Art Currently, various optical recording media such as CD-Rs, CD-RWs, and MOs can store a large amount of information and can be easily randomly accessed. It is widely recognized and becoming popular as a memory device. By increasing the amount of information to be handled,
It is desired to increase the recording density.

Among various optical recording media, CD-R and D
An optical recording medium having a recording layer containing an organic dye (hereinafter, also referred to as a dye recording layer) such as VD-R is relatively inexpensive and compatible with a read-only optical recording medium. , Especially widely used.

Among these optical recording media are DVD,
Recording and / or recording on both sides of a medium such as DVD-R
Or there are some that can be played back. For example, taking a DVD-R as an example, as shown in FIG. 3, the recording layer 2 (2A, 2
B) and the reflective layer 3 (3A, 3B) are sequentially laminated, and the substrates 1 (1A, 1B) are bonded to each other with an adhesive (adhesive layer 4). Further, as shown in FIG. 2, a hole 5 penetrating in the thickness direction is provided at the center of the medium.

Usually, the recording layer 2 and the reflective layer 3 are provided separated from the center hole 5 by a predetermined distance, and the circumferential area within a predetermined distance from the center hole 5 is a transparent portion 6, Also, the outer peripheral area (excluding the outermost peripheral edge portion) is the recording portion 7.

In many cases, the manufacturing serial number of each substrate is printed on the transparent portion 6 by ink jet printing, laser marking or the like. This manufacturing serial number is unique for each manufactured board. This manufacturing serial number is a combination of numbers, alphabets, or symbols, and is printed so that rows of characters and the like extend in the circumferential direction when viewed from the center hole.

In the case of a double-sided recording medium, the so-called A side /
Since it is difficult to determine the B side, it is required to provide a code for identification in a portion that does not interfere with optical recording. It may be possible to provide such a code for surface identification on the transparent portion 6.

[0008]

Conventionally, the substrates used for such a double-sided recording medium are often not prepared in advance separately for the A side / B side, and are similarly prepared and similarly manufactured. It has been common to make one optical recording medium by using two substrates on which serial numbers and the like are printed. Therefore, one substrate 1 (1A) and the other substrate 1
In each of (1B), a manufacturing serial number is printed at a position having an equal radius from the center hole 5, and when the substrates 1A and 1B are attached to each other, the manufacturing serial numbers of the substrates may overlap.

Since the manufacturing serial number is provided in the transparent portion 6, the manufacturing serial number of the other substrate can be seen through from the side of one substrate, so that when the manufacturing serial numbers of both substrates overlap, Both manufacturing serial numbers are difficult to read.

The present invention solves such problems and provides an optical recording medium in which visible information such as a manufacturing serial number and A-side / B-side identifying code of a medium is always extremely clear. To aim.

[0011]

The optical recording medium of the present invention (Claim 1) comprises two disk-shaped transparent substrates (a first substrate and a second substrate), a recording layer and / or a reflective layer. An optical recording medium formed by laminating via a layer, wherein the first substrate and the second substrate have a central hole penetrating in the thickness direction,
An area within a predetermined distance from the center hole in the radial direction is a transparent portion having neither the recording layer nor the reflective layer, and the recording layer and / or the reflective layer is provided in an area on the outer peripheral side of the transparent portion. An optical recording medium having a recording portion having the above, wherein visible information (visible information) is printed on the transparent portions of the first substrate and the second substrate, respectively. The visible information is printed relatively close to the hole, the visible information is printed relatively far from the center hole on the second substrate, and the visible information of the first substrate and the visible information of the second substrate are printed. It is characterized by the arrangement relationship that and do not overlap.

Here, the "recording portion" is a portion where information can be recorded or a portion where information is recorded.

The optical recording medium of the present invention (claim 2) is formed by bonding two disk-shaped substrates (first substrate and second substrate) to each other. At least one of the substrates is an optical recording medium having a recording layer and / or a reflective layer on its outer surface, wherein the first substrate and the second substrate have a central hole penetrating in the thickness direction, An area within a predetermined distance from the center hole in the radial direction is a transparent portion having neither the recording layer nor the reflective layer, and the recording layer and / or the reflective layer is provided in an area on the outer peripheral side of the transparent portion. In an optical recording medium having a recording portion having the above, and visible information (visible information) is printed on the transparent portions of the first substrate and the second substrate, respectively, in the first substrate,
The visible information is printed relatively close to the center hole.
Visible information is printed on the substrate relatively far from the center hole, and the visible information of the first substrate and the visible information of the second substrate are arranged so as not to overlap each other. It is a thing.

Here, "visible information" (hereinafter referred to as "visible information") may be anything that can be visually discerned by a person, and includes characters, numbers, symbols, pictures and combinations thereof. Can be mentioned. The content of the visible information may be the above-mentioned manufacturing serial number or a code for identifying the A side / B side, but is not particularly limited thereto.

In such an optical recording medium, the visible information printed on the first substrate and the visible information printed on the second substrate are arranged at different distances from the center of the optical recording medium. Therefore, visible information does not overlap with each other regardless of the positional relationship between the substrates in the circumferential direction at the time of bonding the substrates, and the visible information can be clearly viewed on all manufactured optical recording media. Becomes

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a schematic plan view showing the features of the optical recording medium according to the embodiment of the present invention.

The vicinity of the center hole 5 of this optical recording medium is a transparent portion 6, and the outer periphery thereof is a recording portion 7.
Recording and reproduction are performed by irradiating the recording layer 2 of the recording unit 7 with light through the substrate 1 or the protective layer 8.

Visible information is printed on the transparent portion 6. One visible information is printed on the first substrate 1A, and the other visible information is printed on the second substrate 1B. In addition,
This printing may be performed on either side of each of the substrates 1A and 1B, but it is preferable that the printing is performed on the side of the bonding side so that it does not become dirty or disappear even if it is rubbed by a hand or the like.

In this embodiment, the visible information on the first substrate 1A is relatively close to the central hole 5, and the visible information on the second substrate 1B is relatively far from the central hole 5. The distance (maximum radius) from the center of the center hole 5 to the tip of the visible information on the substrate 1A on the outer peripheral side is smaller than the distance (minimum radius) from the center of the center hole 5 to the edge of the visible information on the substrate 1B. small. Therefore, no matter what the circumferential positional relationship (phase) when the substrates 1A and 1B are attached, the visible information on both substrates does not overlap. Therefore, it is possible to clearly see the visible information in all the manufactured optical recording media.

The visible information can be printed by various methods such as ink jet printing and laser marking, but the printing method is not particularly limited. The letters, numbers, symbols, pictures, etc. of the visible information are arbitrary. There are no restrictions on the length, size, or color of visible information.

The optical recording medium of the present invention comprises (a) two disk-shaped transparent substrates which are bonded together, and has a recording layer and / or a reflective layer between the two substrates, or (b) both bonded substrates. It is characterized by having a recording layer and / or a reflective layer on at least one of the outer side surfaces of the substrate.

An example of (a) is the optical recording medium shown in FIG. 3, but the configuration is not limited to this. It is sufficient that at least one recording layer and / or a reflective layer is provided between two substrates. For example, a DVD in which substrates provided with only a reflective layer (without a recording layer) are bonded together. Read-only medium, or a DVD-R, a DVD-RW, a DVD-R formed by laminating substrates provided with a recording layer.
It may be a recordable medium such as a RAM.

The substrates 1A and 1B to be bonded do not necessarily have to have the same layer. For example, a substrate provided with a recording layer and a substrate provided with only a reflective layer may be attached to each other so that one surface can be used for recording and the other surface can be used as a read-only optical recording medium. The other substrate may have neither a recording layer nor a reflective layer as long as it has a reflective layer and / or a reflective layer.

Further, the hard coat layer may be provided so as to cover the recording layer and the reflective layer and then laminated, and an arbitrary layer may be provided between the substrate and the recording layer, the substrate and the reflective layer, or the recording layer and the reflective layer. You may have.

An example of (b) is the optical recording medium shown in FIG. 4, but the configuration is not limited to this. Recording and reproducing are performed via a thin hard coat layer 8 which has a recording layer and / or a reflection layer on the outer side of the two substrates and is provided so as to cover these. Also in the case of (b), it suffices to have a recording layer and / or a reflective layer on at least one of the outer surfaces of the bonded substrates. The substrates 1A and 1B to be bonded may not have the same layer, and may have any layer between the substrate-recording layer, the substrate-reflective layer, or the recording layer-reflective layer. It is the same as the above (a).

Further, the optical recording medium may be a combination of (a) and (b). That is, two substrates are bonded so that the recording layer and / or the reflective layer provided on one substrate face outward and the recording layer and / or the reflective layer provided on the other substrate face inward. It may be an optical recording medium.

By adopting the present invention, the fact that the visible information on the substrate can be easily viewed is effective when both substrates 1A and 1B have a recording layer, and a recording having a recording layer and a reflective layer is provided. It is particularly effective in the case of possible media.

Next, the substrate and each layer of this optical recording medium will be individually described in detail.

(1) Substrate The material of the substrate in the optical recording medium of the present invention has required strength and durability, and has transparency when recording / reproducing through the substrate as described in (a) above. If it does, it is not particularly limited. The term “transparency” means that the material has translucency required for recording / reproducing at the wavelengths of recording light and reproducing light.

Conventionally used as a substrate material,
For example, acrylic resin, methacrylic resin, polycarbonate resin, polyolefin resin (particularly amorphous polyolefin), polyester resin, polystyrene resin,
Any of those made of a resin such as an epoxy resin, one made of glass, and one having a resin layer made of a radiation curable resin such as a photocurable resin on glass can be used.

From the viewpoint of high productivity, cost, moisture absorption resistance, etc., injection molded polycarbonate is preferable. From the viewpoint of chemical resistance, moisture absorption resistance and the like, amorphous polyolefin is preferable. A glass substrate is preferable from the viewpoint of high-speed response.

A guide groove or pit for recording / reproducing light may be provided on the plate surface of the substrate. Such guide grooves and pits are preferably provided at the time of molding the substrate, but can be provided by using an ultraviolet curable resin layer on the substrate. If the guide groove is spiral, the groove pitch is 0.1 to 2.0.
It is preferably about μm.

Further, as described in (b) above, in the case of an optical recording medium for recording / reproducing without passing through the substrate, the substrate does not need to have transparency, and therefore polycarbonate or the like is used to prevent vibration at high speed rotation. The resin may be filled with a filler such as carbon fiber to increase the rigidity.

(2) Recording Layer The optical recording medium of the present invention is preferably a recordable medium having at least one recording layer.

The material of the recording layer is not particularly limited, and it is an inorganic substance (metal, alloy, etc.) or organic substance (dye, polymer).
It may be appropriately selected from the above.

As the recording layer made of an inorganic material, for example, a recording layer made of a rare earth transition metal alloy such as Tb.Fe.Co or Dy.Fe-Co and used for recording by the photothermomagnetic effect is used. In addition, phase change Ge ・ Te, Ge ・ S
A recording layer made of a chalcogen alloy such as b · Te is also used. A dye is preferable as the organic substance, and an organic dye is preferable because the film can be easily formed.

Specific examples of organic dyes include phthalocyanine dyes, naphthalocyanine dyes, cyanine dyes, azo dyes, squarylium dyes, metal-containing indoaniline dyes, metal-containing azo dyes, and triaryls. Examples thereof include methane dyes, merocyanine dyes, azurenium dyes, naphthoquinone dyes, anthraquinone dyes, indophenol dyes, xanthene dyes, oxazine dyes and pyrylium dyes. Among the organic dyes, metal-containing azo dyes are preferable because they have excellent recording sensitivity and light resistance.

The recording layer is formed by vacuum deposition,
Examples of commonly used thin film forming methods include a sputtering method, a doctor blade method, a casting method, a spin coating method, and a dipping method.

In the case of the organic dye-containing recording layer, the spin coating method is preferable from the viewpoint of mass productivity and cost. Further, the vacuum deposition method is preferable to the coating method from the viewpoint that a recording layer having a uniform thickness can be obtained.

In the case of film formation by the spin coating method, the number of rotations is preferably 10 to 15,000 rpm, and after spin coating, a treatment such as heating or exposure to solvent vapor may be performed.

The coating solvent for forming the recording layer by a coating method such as a doctor blade method, a casting method, a spin coating method or a dipping method may be any solvent that does not attack the substrate and is not particularly limited. For example, ketone alcohol solvents such as diacetone alcohol and 3-hydroxy-3-methyl-2-butanone; cellosolve solvents such as methyl cellosolve and ethyl cellosolve; chain hydrocarbon solvents such as n-hexane and n-octane. Cyclic hydrocarbon solvents such as cyclohexane, methylcyclohexane, ethylcyclohexane, dimethylcyclohexane, n-butylcyclohexane, tert-butylcyclohexane, cyclooctane; perfluoroalkyl alcohols such as tetrafluoropropanol, octafluoropentanol, hexafluorobutanol Examples of system solvents include hydroxycarboxylic acid ester solvents such as methyl lactate, ethyl lactate, and methyl 2-hydroxyisobutyrate.

In the case of the vacuum deposition method, for example, a dye and, if necessary, various recording layer components such as additives are put in a crucible installed in a vacuum container, and the inside of the vacuum container is vacuum pumped by a vacuum pump.
After evacuation to about ⁻² to 10 ⁻⁵ Pa, the crucible is heated to evaporate the components of the recording layer and vapor-deposited on the substrate placed facing the crucible to form the recording layer.

The recording layer contains a transition metal chelate compound (eg, acetylacetonato chelate, bisphenyldithiol, salicylaldehyde oxime, a singlet oxygen quencher) in order to improve the stability and light resistance of the recording layer.
Bisdithio-α-diketone, etc.) and a recording sensitivity improver such as a metal compound for improving recording sensitivity. Here, the metal-based compound means that a metal such as a transition metal is contained in the compound in the form of an atom, an ion, a cluster, etc., for example, an ethylenediamine-based complex, an azomethine-based complex, a phenylhydroxyamine-based complex, a phenanthroline-based complex, Organometallic compounds such as dihydroxyazobenzene-based complexes, dioxime-based complexes, nitrosoaminophenol-based complexes, pyridyltriazine-based complexes, acetylacetonate-based complexes, metallocene-based complexes, and porphyrin-based complexes are mentioned. The metal atom is not particularly limited, but a transition metal is preferable.

Further, if necessary, a near infrared laser having a wavelength of about 770 to 830 nm, which is usually used for CD-Rs, and a wavelength 620, which is used for DVD-Rs, are used.
690nm red laser or wavelength 410n
An optical recording medium that is compatible with recording by laser light in a plurality of wavelength ranges by using dyes suitable for recording with a plurality of wavelengths such as so-called blue laser of m or 515 nm together. You can also do it.

Further, when forming the recording layer, a binder, a leveling agent, an antifoaming agent and the like can be used in combination, if necessary. Preferred binders include polyvinyl alcohol, polyvinylpyrrolidone, nitrocellulose, cellulose acetate, ketone resins, acrylic resins, polystyrene resins, urethane resins, polyvinyl butyral, polycarbonate, polyolefins and the like.

The film thickness of the organic dye-containing recording layer is not particularly limited because the suitable film thickness varies depending on the recording method and the like, but is usually 10 nm to 5 μm, preferably 70 nm.
Is about 3 μm.

The phase change recording layer made of an inorganic material may be a known phase change type optical recording layer, for example GeS.
bTe, InSbTe, AgSbTe, AgInSbT
A compound such as e is selected. Among them, {(Sb ₂ T
_{e 3) 1-x (GeTe} ) x} 1-y Sb y alloy (0.2 <x <
0.9, 0 ≦ y <0.1), or Ma _w (Sb _z Te _1
-z ) _1-w alloy (however, 0 ≦ w ≦ 0.3, 0.5 ≦ z ≦
0.9, Ma is In, Ga, Zn, Ge, Sn, Si,
Cu, Au, Ag, Pd, Pt, Pb, Cr, Co,
O, N, S, Se, Ta, Nb, V, Bi, Zr, T
A thin film containing i, Mn, Mo, Rh, and at least one selected from rare earth elements as a main component is stable in both crystalline and amorphous states, and a high-speed phase transition between both states is possible. preferable.

In the case of a phase change recording layer, its thickness is usually 1
0 nm or more and 100 nm or less, preferably 10 n
The recording layer having a thickness of m or more and 30 nm or less is often obtained by sputtering an alloy target in an inert gas, particularly Ar gas.

The recording layer is usually covered with protective layers on the upper and lower sides.

The material of the protective layer is determined in consideration of the refractive index, thermal conductivity, chemical stability, mechanical strength, adhesion and the like. In general, metal or semiconductor oxides, sulfides, nitrides, and fluorides such as Ca, Mg, and Li having high transparency and high melting point can be used. These oxides, sulfides, nitrides, and fluorides do not necessarily have to have a stoichiometric composition, and it is also effective to control the composition or mix them for controlling the refractive index and the like. Considering the repetitive recording characteristics, the dielectric mixture is preferable. More specifically, Z
A mixture of nS and rare earth sulfides and heat resistant compounds such as oxides, nitrides, and carbides can be used. For example ZnS and SiO
The mixture of ₂ is often used for the protective layer of a phase change optical disc.

The thickness of the protective layer is usually 10 to 500 nm.

The lower protective layer, which is provided in contact with the surface of the recording layer on which incident light such as recording light or reproducing light is incident, is required to suppress substrate deformation due to heat during recording, and is usually 50 nm or more. If it is too thin, microscopic substrate deformation may be accumulated during repetitive overwriting, and reproduction light may be scattered to significantly increase noise. The upper limit of the thickness is usually about 200 nm from the viewpoint of film formation time.

The upper protective layer provided in contact with the surface of the recording layer opposite to the incident surface of the recording light or the reproducing light is
In order to suppress the deformation of the recording layer, it is usually 5 nm or more, preferably 10 nm or more. On the other hand, if it is too thick, microscopic plastic deformation is likely to accumulate during repeated overwriting inside the upper protective layer, which again scatters the reproduction light and increases noise. The upper limit value is usually 60 nm, preferably 50 nm.

(3) Reflective Layer In the optical recording medium of the present invention, the reflective layer is preferably a metal or an alloy. In particular, the wavelength of the recording / reproducing light is 500n.
When the length is shorter than m, the surface roughness of the reflective layer is important for obtaining a good recording / reproducing signal, and it is preferable that the surface roughness is 2 nm or less, more preferably 1 nm or less.

Examples of the metal or alloy are those having a sufficiently high reflectance at the wavelength of the reproduction light, such as Au, Al, Ag, Cu,
Metals of Ti, Cr, Ni, Pt, Ta, Cr and Pd can be used alone or as an alloy. Among these, Au, Al,
Ag has a high reflectance and is suitable as a material for the reflective layer. In addition to containing these as main components, the following may be included. For example, Mg, Se, Hf, V, Nb, Ru, W, Mn, Re, F
e, Co, Rh, Ir, Cu, Zn, Cd, Ga, In, Si, Ge, Te, P
Mention may be made of metals and semimetals such as b, Po, Sn and Bi. Among them, those containing Ag as a main component are particularly preferable in that the cost is low, high reflectance is likely to occur, and when a print receiving layer described later is provided, a white background color and a beautiful one can be obtained. Here, the main component has a content rate of 50%
The above is said.

As an example of a suitable alloy composition, 0.1 to 15 atom% of silver is the main component and at least one element selected from the group consisting of titanium, zinc, copper, palladium and gold is used.
The thing contained is mentioned. In addition, titanium, zinc, copper,
When two or more of palladium and gold are included, each is 0.1
It may be up to 15 atom%, but the sum of them is 0.1.
It is preferably ˜15 atomic%.

Further, an alloy containing silver as a main component and containing 0.1 to 15 atom% of at least one rare earth element is also preferable. Of the rare earths, neodymium is preferred.

As the reflective layer, a layer made of only gold or a gold alloy layer obtained by adding silver, copper, titanium, aluminum or the like to gold is also preferable because it has excellent corrosion resistance. However, it is more expensive than silver alloy.

A more preferable alloy composition contains silver as a main component and 0.1 to 15 atom% of at least one element selected from the group consisting of titanium, zinc, copper, palladium and gold, and at least one element. Rare earth element of 0.1 to 15
Atomic% content.

The thickness of the reflective layer is 20 to 400 nm, especially 40.
Approximately 200 nm is preferable.

As a method of forming the reflective layer, for example,
The sputtering method, the ion plating method, the chemical vapor deposition method, the vacuum vapor deposition method and the like can be mentioned. Further, a known inorganic or organic intermediate layer may be provided on the substrate or below the reflective layer in order to improve reflectance, recording characteristics, adhesion, and the like.

When the optical recording medium of the present invention is used as a read-only medium, it is not necessary to provide the recording layer. For example, a metal reflective layer is provided on a substrate in which pits corresponding to recorded information are provided in advance. It may be bonded to form an optical recording medium.

(4) Hard coat layer In the optical recording medium having any of the structures (a) and (b) described above, a hard coat layer may be provided as a layer for covering the recording layer and the reflective layer. In particular, in the case of the optical recording medium having the above-mentioned constitution (b), the hard coat layer is an essential constitutional requirement, and as represented by the constitution shown in FIG. 4, light is irradiated through the hard coat layer 8. , Record and play.

The material of the hard coat layer is not particularly limited as long as it protects the reflective layer and the recording layer from external force. For example, as the material of the organic substance, a thermoplastic resin, a thermosetting resin, an electron beam curable resin, a UV curable resin and the like can be mentioned. Further, as the inorganic substance, Si
_{O 2, SiN 4, MgF 2} , SnO 2 and the like.

The thermoplastic resin, thermosetting resin and the like can be formed by dissolving in a suitable solvent, applying a coating solution, and drying. The UV curable resin can be formed as it is or by dissolving it in a suitable solvent to prepare a coating solution, applying the coating solution, and irradiating it with UV light to cure it. As a UV curable resin,
For example, an acrylate resin such as urethane acrylate, epoxy acrylate, polyester acrylate can be used. These materials may be used alone or as a mixture, and may be used not only as one layer but also as a multilayer film.

As the hard coat layer, a UV curable resin is preferable.

As the method for forming the hard coat layer, as with the recording layer containing an organic dye, a coating method such as a spin coating method or a casting method, a sputtering method or a chemical vapor deposition method may be used. Method is preferred.

The hard coat layer may be formed by adhering a thin film or sheet-like thin film made of the above resin with an adhesive. As the adhesive, various kinds of adhesives such as a room temperature curable adhesive, a thermosetting adhesive, an electron beam curable adhesive, and a UV curable adhesive can be used.
There is no particular limitation.

The film thickness of the hard coat layer is from 0.1 μm to
It is 0.3 mm, preferably 0.1 μm to 200 μm. In the case of the optical recording medium having the above-mentioned configuration (a), 2
The thickness of the hard coat layer existing between the substrates is 0.1 to
About 100 μm is preferable, and about 0.3 μm to 30 μm is particularly preferable.

(5) Other Layers In the present invention, layers other than the recording layer and the reflective layer may be included. As such a layer, in addition to the above-mentioned layers such as a protective layer provided in contact with the recording layer and a hard coat layer for covering and protecting the recording layer and the reflective layer, an undercoat layer between the substrate and the recording layer. And a barrier layer for preventing diffusion and permeation of components between layers.

(6) Adhesive As the adhesive for adhering the substrates having the respective layers formed thereon, a thermoplastic adhesive, a thermosetting adhesive, an electron beam curable adhesive, a UV curable adhesive, etc. Various adhesives can be used and are not particularly limited. A UV curable adhesive is preferred.

(7) Laser, etc. The laser light used for the optical recording medium of the present invention includes N ₂ , He-Cd, Ar, He-Ne, ruby, semiconductor, dye laser, etc., but it is lightweight. A semiconductor laser is preferable because it is compact, compact, and easy to handle.

Recording on the optical recording medium of the present invention obtained as described above was carried out in a recording layer of 1 μm on both surfaces of the substrate.
It is performed by irradiating a laser beam focused to a certain degree.
In the portion irradiated with laser light, thermal deformation of the recording layer such as decomposition, heat generation, and dissolution occurs due to absorption of laser light energy, and optical characteristics change.

The recorded information is reproduced by reading the difference in reflectance between the portion where the change in the optical characteristics is caused and the portion where the change in the optical characteristic is not caused by the laser light.

[0076]

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

Example 1 Thickness with a guide groove having a track pitch of 0.74 μm and a thickness of 0.
DV with a thickness of 0.72 on a substrate having a diameter of 6 mm, a diameter of 120 mm, and a diameter of a central hole of 15 mm, which is 0.72 (the absorbance at a wavelength of 598 nm measured with air as a reference)
A metal-containing azo dye recording layer for D-R is provided, and 120 is formed thereon.
After providing a silver alloy reflection layer of 1 nm, 1 is formed on each substrate.
The visible information was printed with an ink jet character of 0 point size. One board was printed on a radius of 11 mm from the center, and the other board was printed on a radius of 15 mm from the center (the character position is the distance from the center of the board to the center of the character). is there.). The distance from the substrate center to the outermost periphery of the transparent portion is 17 mm. After that, these substrates were pasted together with a UV curable adhesive (“SK7100” manufactured by Sony Chemicals Co., Ltd.).

As a result, the visible information of this optical recording medium never overlapped with each other regardless of the phase of both substrates, and could be clearly read from any surface.

[0079]

As described above, according to the present invention, regardless of the circumferential positional relationship when the two substrates are bonded together,
Provided is an optical recording medium capable of always clearly visualizing visible information.

[Brief description of drawings]

FIG. 1 is a plan view showing a configuration of an optical recording medium according to an embodiment of the present invention.

FIG. 2 is a plan view showing a configuration of an optical recording medium according to a conventional example.

FIG. 3 is an example of a cross-sectional view in the thickness direction showing the configuration of the optical recording medium according to the embodiment of the invention.

FIG. 4 is another example of a cross-sectional view in the thickness direction showing the configuration of the optical recording medium according to the embodiment of the invention.

[Explanation of symbols]

1 substrate 2 recording layers 3 reflective layer 4 Adhesive layer 5 center hole 6 Transparent part 7 Recording section 8 Hard coat layer

Claims (11)

[Claims] 1. An optical recording medium comprising two disk-shaped transparent substrates (a first substrate and a second substrate) bonded to each other with a recording layer and / or a reflecting layer interposed therebetween. The second substrate and the second substrate each have a central hole penetrating in the thickness direction, and a region within a predetermined distance in the radial direction from the central hole is a transparent portion having neither the recording layer nor the reflective layer. , The recording portion having the recording layer and / or the reflection layer is provided in an area on the outer peripheral side of the transparent portion, and visible information (visible information) is provided on the transparent portions of the first substrate and the second substrate, respectively. ) Is printed, visible information is printed on the first substrate relatively close to the center hole, and visible information is printed on the second substrate relatively far from the center hole. The information is printed, and the visible information of the first substrate and the visible information of the second substrate are Optical recording medium, characterized in that has a become not positional relationship. 2. A disc-shaped substrate (a first substrate and a second substrate) bonded together to form a first substrate and a second substrate.
At least one of the substrates has a recording layer and / or an outer surface.
Alternatively, in the optical recording medium having a reflective layer, the first substrate and the second substrate have a central hole penetrating in the thickness direction, and an area within a predetermined distance in the radial direction from the central hole is the recording layer. And a reflective part, which is a transparent part having neither a reflective layer nor a recording part having the recording layer and / or the reflective layer in a region on the outer peripheral side of the transparent part. In an optical recording medium in which visible information (visible information) is printed on transparent portions of a substrate, visible information is printed on the first substrate relatively close to the central hole, and Visible information is printed on the substrate relatively far from the center hole, and the visible information of the first substrate and the visible information of the second substrate are arranged so as not to overlap each other. recoding media. 3. The optical recording medium according to claim 1, wherein the visible information extends in the circumferential direction with respect to the center of the optical recording medium. 4. The optical recording medium according to claim 1, wherein the visible information is printed on a bonding surface of a substrate. 5. The optical recording medium according to claim 1, wherein the visible information is a manufacturing serial number. 6. The optical recording medium according to claim 1, wherein the visible information includes a code for discriminating between front and back surfaces (A surface and B surface) of the medium. 7. The optical recording medium according to claim 1, wherein the optical recording medium is a recordable medium having a recording layer. 8. The optical recording medium according to claim 7, wherein the optical recording medium is a recordable medium having a recording layer and a reflective layer. 9. The optical recording medium according to claim 7, wherein the recording layer contains an organic dye. 10. The optical recording medium according to claim 1, wherein the optical recording medium is a read-only medium having a reflective layer and no recording layer. 11. An optical recording medium according to claim 1, wherein two substrates are bonded together by using a UV curable adhesive.