JPH05325259A - Optical recording disk - Google Patents

Abstract

PURPOSE:To improve the reliability of an optical recording disk having a recording layer composed essentially of a dye. CONSTITUTION:This disk is provided with a coating type recording layer 3, a reflective layer 4, a lower protective coat 5 made of a radiation-curable resin covering at least a region capable of recording, and an upper protective coat 6 made of also such a resin covering also at least such a region on a substrate 2. The coat 5 is formed by a spin coating method, the coat 5 has the thickness of 1-10mum, the coat 6 has the thickness of 1-15mum, and the sum of both has the thickness of 5-18mum.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording disc having a coating type recording layer containing a dye as a main component.

[0002]

2. Description of the Related Art Recently, various optical recording disks such as a write-once type and a rewritable type have been attracting attention as a large capacity information carrying medium. Among write-once type optical recording disks, those using a recording layer containing a dye as a main component can be manufactured at low cost because the recording layer can be formed by coating.

As an optical recording disk using a recording layer containing a dye as a main component, a so-called air sandwich structure in which an air layer is provided on the recording layer has been conventionally used, but recently, it is reflected on the surface of the recording layer. An optical recording disk capable of reproduction corresponding to the compact disk (CD) standard has been proposed by providing the layers in close contact (Nikkei Electronics January 23, 1989, No. 465, P.
107, Kinki Chemical Society Functional Dye Subcommittee, 198
March 3, 1997, Osaka Science and Technology Center, PROCEEDINGS SP
IE-THE INTERNATIONAL SOCIETY FOR OPTICAL ENGINEERI
NG VOL.1078 PP80-87, "OPTICAL DATA STORAGE TOPICAL
MEETING "17-19, JANUARY 1989 LOS ANGELES etc.) This optical recording disc is formed by depositing a dye layer, a reflective layer and a protective film in this order on a transparent substrate, and the reflective layer is adhered to the dye layer. By providing the above, it is possible to configure a CD standard disc having a total thickness of 1.2 mm.

An optical recording disk using a dye in the recording layer is a C
In order to reproduce with a D player, the reflectivity of the Al reflective layer used in a normal CD is insufficient, so the Au reflective layer is used in the above proposal. Au has high reflectance and good corrosion resistance, but is expensive. Therefore, high reflectance metals other than Au, such as Ag and C, are used.
The use of u, Cu-based alloys, Al-based alloys, etc. has been considered, but these have insufficient corrosion resistance. The protective layer formed on the reflective layer is a resin coating film, but since the protective layer has defects such as pinholes and cracks, if the reflective layer has insufficient corrosion resistance, water vapor, oxygen, The reflection layer may be deteriorated due to the penetration of the sulfide gas, and the recording layer is also deteriorated due to the penetration thereof, so that sufficient reliability cannot be obtained.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to improve the reliability of an optical recording disc having a recording layer containing a dye as a main component.

[0006]

These objects are achieved by the present invention described in (1) to (6) below.

(1) A coating type recording layer containing a dye as a main component is provided on a substrate, a reflective layer is provided on the recording layer, and radiation is provided on the reflective layer so as to cover at least a recordable area. A lower protective coat made of a cured resin, an upper protective coat made of a radiation curable resin on the lower protective coat so as to cover at least a recordable area, and the lower protective coat formed by a spin coating method. The thickness of the lower protective coat is 1 to 10 μm, the thickness of the upper protective coat is 1 to 15 μm, and the total thickness of the lower protective coat and the upper protective coat is 5 to 18 μm. An optical recording disc characterized by.

(2) The optical recording disk according to (1) above, wherein the upper protective coat is formed by a screen printing method, a spin coating method, a dipping method or a spray coating method.

(3) The optical recording disk according to (1) or (2) above, wherein the lower protective coat and the upper protective coat do not contain pigment particles.

(4) The reflective layer contains Cu, Ti, V,
Ta, Cr, Mo, W, Mn, Fe, Co, Rh, N
The optical recording disk according to any one of (1) to (3) above, which contains at least one element selected from the group consisting of i, Pd, Pt, Ag, Au, Al, N and O.

(5) The optical recording disk according to any one of the above (1) to (4), which has a label printing layer on the upper protective coat or between the lower protective coat and the upper protective coat.

(6) An intermediate protective coat made of a radiation curable resin is provided between the lower protective coat and the upper protective coat so as to cover at least a recordable area, and the lower protective coat, the intermediate protective coat and the upper protective coat are provided. The optical recording disk according to any one of (1) to (5) above, wherein the total coat thickness is 18 μm or less.

[0013]

The optical recording disk of the present invention is an optical recording disk having a recording layer containing a dye as a main component and capable of reproducing in accordance with the CD standard.

The optical recording disk of the present invention has a recording layer, a reflective layer, a lower protective coat and an upper protective coat in that order on a substrate. The lower protective coat and the upper protective coat each have coating defects, but the coating defects of both protective coats do not substantially overlap, and both protective coats are provided so as to cover the entire recordable area. Therefore, the coating defect of the lower protective coat is covered by the upper protective coat. Therefore, intrusion of corrosive gas or the like from the outside through coating defects can be prevented, and a highly reliable optical recording disk can be realized. Further, since the reflective layer is protected in this way, a material other than Au can be used for the reflective layer, and an optical recording disk can be manufactured at low cost.

In the present invention, since the lower protective coat is formed by the spin coating method, the reflective layer is not damaged when the lower protective coat is formed. On the other hand, the upper protective coat can be formed by a screen printing method. Therefore, the label printing layer and the upper protective coat can be formed in the same step, and the manufacturing can be performed at low cost.

Japanese Patent Laid-Open No. 1-211257 discloses an optical information recording medium having a label printing layer on the uppermost portion of the medium on a reflective film. In the publication, in the printing step of the label printing layer, a protective film for protecting the reflective film is formed in the first color unit, and label printing is performed in the second and subsequent color units. That is, since the protective film in contact with the reflective film is formed by the printing method, the reflective film may be damaged. Moreover, since the label printing layer in the publication is for displaying a character pattern or a graphic pattern and does not necessarily cover the entire recordable area, two layers of a protective film and a label printing layer are formed on the reflective film. Does not always exist, and the effect of improving reliability is low. Further, in the publication, an ultraviolet curable ink is used, and the first color is solid printing and contains a pigment. However, when the pigment is included, the curability of the resin decreases.

Further, in JP-A-1-243251, an optical system in which a pit is formed on one surface of a transparent resin layer, a metal reflection film is provided in the pit, and a protective layer and a label printing are applied in order. The disc is listed. The protective layer in the publication is made of an ultraviolet curable acrylic resin containing white titanium and is formed by spin coating or printing. In this case as well, similar to Japanese Patent Application Laid-Open No. 1-211257, since the uppermost layer of the disc is the label printing layer, sufficient reliability cannot be obtained. The protective layer of this optical disc corresponds to the lower protective coat in the present invention, but when a pigment such as white titanium is added to the protective layer, high reliability cannot be obtained as described above.

[0018] Further, JP-A-2-7249 and JP-A-2-7249.
JP 149951 discloses that a protective film made of an ultraviolet curable resin is formed by a screen printing method on a disk substrate provided with a recording film or a reflective film in the same device,
A method for producing an optical disk by forming a printing film made of an ultraviolet curable resin on the disk substrate provided with the protective film by a screen printing method is described. When the screen printing is directly performed on the recording film or the reflective film as described above, the recording film or the reflective film may be damaged. Moreover, since the print film on the protective film is a label print film, sufficient reliability cannot be obtained as in the above publications.

Further, Japanese Patent Publication No. 3-75943 discloses an optical information recording medium. The embodiment shown in FIG. 6 has a light absorption layer, a light reflection layer, a hard layer and a protective layer on a substrate. Has a structure in which the layers are sequentially laminated. In this aspect, the resin layer having two layers, that is, the hard layer and the protective layer, is provided on the light reflection layer. In Example 8, which is an example of this aspect, the hard layer is not the radiation curable resin but the silicon acrylic layer. However, since the thickness thereof is as thin as 50 nm, the effect of the present invention cannot be realized. Further, in Examples 5 and 6 of the same publication, an epoxy resin is spin-coated on the light reflecting layer to improve the binding property, and then a protective layer of an ultraviolet curable resin is formed.
These examples also do not have a two-layer structure of radiation curable resin.
This epoxy resin is for improving the binding property, and the effect of improving the corrosion resistance is insufficient.

[0020]

[Specific Structure] The specific structure of the present invention will be described in detail below.

The optical recording disk of the present invention is an optical recording disk which has a reflective layer in close contact with a recording layer containing a dye as a main component and which can be reproduced according to the CD standard. One embodiment of the optical recording disk of the present invention is shown in FIG.

The optical recording disc 1 shown in FIG. 1 has a recording layer 3 containing a dye as a main component on the surface of a substrate 2, and is in close contact with the recording layer 3 to form a reflective layer 4 and a lower portion made of a radiation curable resin. It is a contact-type optical recording disk having a protective coat 5 and an upper protective coat 6 made of a radiation curable resin.

The substrate 2 has recording light and reproducing light (wavelength 60).
It is formed of a resin or glass that is substantially transparent (preferably a transmittance of 88% or more) to a semiconductor laser beam having a wavelength of about 0 to 900 nm, particularly about 770 to 900 nm, particularly 780 nm. This enables recording and reproduction from the back side of the substrate.

The substrate 2 is a disk of a normal size, and has a thickness of 1.2 when used as a recordable CD.
The diameter is about 80 to 120 mm.

As the material of the substrate, it is preferable to use a resin, and various thermoplastic resins such as polycarbonate resin, acrylic resin, amorphous polyolefin and TPX are suitable. The substrate 2 may be manufactured by a known method such as injection molding. At that time, it is preferable to form a predetermined pattern such as the groove 21 on the surface of the substrate for tracking or addressing. After the substrate 2 is manufactured, a resin layer having a predetermined pattern such as a groove may be formed by the 2P method or the like.

The groove is preferably a spiral continuous groove having a depth of 500 to 3000 A, a width of 0.2 to 1.1 .mu.m, especially 0.3 to 0.6 .mu.m, and a land (adjacent grooves are adjacent to each other). Portion) width is 0.5-1.
It is preferably 4 μm, particularly 1.0 to 1.3 μm. With such a configuration of the groove, a good tracking signal can be obtained without lowering the reflection level of the groove portion. Note that the groove may be provided with unevenness for address signals. Moreover, it is preferable that the recording light is irradiated onto the recording layer in the groove.

The recording layer 3 may contain only one type of dye, or may have a structure in which two or more types of dyes are compatible with each other.

When recording a CD signal, the extinction coefficient (imaginary part of the complex refractive index) k of the recording layer 3 at the wavelengths of the recording light and the reproducing light is preferably 0.03 to 0.25. When k is less than 0.03, the absorptivity of the recording layer is reduced, and it becomes difficult to perform recording with normal recording power.
Further, when k exceeds 0.25, the reflectance falls below 60%, making it difficult to perform reproduction according to the CD standard. Note that k is 0.03 to 0.20, especially 0.03 to
A value of 0.15 gives very favorable results.

The refractive index (real part of complex refractive index) n of the recording layer 3 is 1.8 to 4.0, more preferably 2.0 to 4.0.
It is preferably 3.0. When n <1.8, the reflectance is lowered and the signal modulation degree is reduced, so that the reproduction by the CD player tends to be difficult. Further, in order to make n> 4.0, it is difficult to obtain the raw material dye.

The light absorbing dye used in the recording layer 3 has an absorption maximum of 600 to 900 nm, preferably 600 to 900 nm.
800 nm, more preferably 650 to 750 nm,
Other than that, there is no particular limitation, and for example, one or more of cyanine-based, phthalocyanine-based, naphthalocyanine-based, anthraquinone-based, azo-based, triphenylmethane-based, pyrylium or thiapyrylium salt-based, squarylium-based, croconium-based, metal complex dye-based, etc. Two or more kinds may be appropriately selected according to the purpose, but for example, the following dyes are preferable.

Cyanine dyes include indolenine ring,
A cyanine dye having a benzoindolenine ring is particularly preferable.

A quencher may be mixed with the light absorbing dye. Further, an ionic combination of a dye cation and a quencher anion may be used as the light absorbing dye.

As the quencher, acetylacetonate-based, bisdithio-α-diketone-based and bisphenyldithiol-based bisdithiol-based, thiocatechol-based, salicylaldehyde oxime-based, and thiobisphenolate-based metal complexes are preferable. .. Further, amine compounds having a nitrogen radical cation and amine quenchers such as hindered amines are also suitable.

The dye constituting the conjugate is preferably a cyanine dye having an indolenine ring, and the quencher is preferably a metal complex dye such as bisphenyldithiol metal complex.

Details of preferable dyes, quenchers and conjugates are disclosed in JP-A-59-24692 and 59-55.
No. 794, No. 59-55795, No. 59-81194.
No. 59-83695, No. 60-18387, No. 60-19586, No. 60-19587, No. 60-
35054, 60-36190, 60-361.
No. 91, No. 60-44554, No. 60-44555.
No. 60, No. 60-44389, No. 60-44390, No. 60-47069, No. 60-20991, No. 60-.
No. 71294, No. 60-54892, No. 60-712.
No. 95, No. 60-71296, No. 60-73891.
No. 60, No. 60-73892, No. 60-73893, No. 60-83892, No. 60-85449, No. 60-
92893, 60-159087, 60-16
No. 2691, No. 60-203488, No. 60-201.
No. 988, No. 60-234886, No. 60-2348.
No. 92, No. 61-16894, No. 61-11292
No. 61-11294, No. 61-16891, No. 61-8384, No. 61-14988, No. 61-1.
63243, 61-210539, Japanese Patent Application No. 60-
No. 54013, JP-A Nos. 62-30088 and 62-3.
No. 2132, No. 62-31792, CMC Publishing "Chemistry of Functional Dyes" P74-76 and the like.

The quencher may be added separately from the light absorbing dye or in the form of a conjugate, but it is not more than 1 mol, particularly 0.05 mol, based on 1 mol of the total amount of the light absorbing dye. ~
It is preferable to add about 0.5 mol. This allows
Light resistance is improved.

The dye used in the recording layer may be selected from the above light-absorbing dyes, dye-quencher mixtures, and dye-quencher conjugates having n and k in the above range. It may be synthesized by newly designing a molecule.

The k of the dye with respect to the recording light and the reproducing light varies from 0 to 2 depending on its skeleton and substituents. Therefore, when selecting a dye having k of 0.03 to 0.25, for example. Is limited in its skeleton and substituents.
For this reason, there are cases where the coating solvent is limited or coating cannot be performed depending on the substrate material. Alternatively, vapor phase film formation may not be possible. In addition, a large amount of labor is required for designing and synthesizing a new molecule.

On the other hand, according to the experiments by the present inventors, the k of the mixed dye layer containing two or more kinds of dyes is almost in the mixing ratio depending on the k of the dye layer composed of each of the dyes used. It turned out to be the corresponding value. Therefore, in the present invention, the recording layer 3 may be formed by compatibilizing two or more kinds of dyes.

In this case, k which is almost proportional to the mixing ratio can be obtained in most of the dye mixing systems. That is, i
The mixing fractions and k of the dyes of the respective species are Ci and ki, respectively.
Then, k becomes approximately ΣCiki. Therefore, k
It is possible to obtain a dye layer having k = 0.03 to 0.25 by mixing the dyes having different ratios with each other while controlling the mixing ratio. Therefore, the dye to be used can be selected from a very wide range of dye groups.

This can also be applied to improve the wavelength dependence. The wavelength of the semiconductor laser is usually in the range of ± 10 nm, and in the commercially available CD player, it is 770 nm to 79 nm.
It is necessary to secure a reflectance of 70% or more in the range of 0 nm. Generally, the k value of a dye has a large wavelength dependency, and even if it is an appropriate value at 780 nm, it often deviates greatly at 770 nm or 790 nm. In such a case, by mixing the second dye, it can be set so that appropriate n and k values are always obtained in the range of 780 ± 10 nm.

As a result, restrictions such as restrictions on the coating solvent are alleviated, and it is possible to use dyes that are easy to synthesize and inexpensive, use dyes that have good characteristics, and use dyes that are sparingly soluble. can do.

When the recording layer 3 is a mixed dye layer, the dyes used may be selected from the range of n = 1.6 to 6.5 and k = 0 to 2.

When measuring n and k, a recording layer is formed on a predetermined transparent substrate to a thickness of, for example, about 400 to 1000 A under actual conditions to prepare a measurement sample. Next, the reflectance of this measurement sample through the substrate or the reflectance from the recording layer side is measured. The reflectance is measured by specular reflection (about 5 °) using the recording / reproducing light wavelength. In addition, the transmittance of the sample is measured. From these measured values, for example, Kyoritsu Zensho "Optics" Kozo Ishiguro P
According to 168 to 178, n and k may be calculated.

The recording layer is formed by a spin coating method in which a coating solution containing a dye and an organic solvent is used and the coating solution is spread and coated on a rotating substrate.

The organic solvent used for the coating liquid for recording formation may be appropriately selected from alcohols, ketones, esters, ethers, aromatics, alkyl halides and the like according to the dye used. However, an organic solvent having two or more functional groups in one molecule is suitable.

After spin coating, the coating film is dried if necessary.

The thickness of the recording layer thus formed is appropriately set according to the desired reflectance and the like, but is usually about 1000 to 3000 A.

A reflective layer 4 is provided on the recording layer 3 so as to be in direct contact therewith. A high reflectance material is used for the reflective layer 4. As such a material, Au, Cu, Ag, Al, an alloy containing these, or the like is preferable, but it is particularly preferable that the reflective layer 4 contains at least Cu because it is relatively inexpensive and has a high reflectance. In particular, Cu, Ti, V, Ta,
Cr, Mo, W, Mn, Fe, Co, Rh, Ni, P
It is preferable to use as the reflective layer a thin film containing at least one element selected from the group consisting of d, Pt, Ag, Au, Al, N and O.

In this case, the reflective layer 4 is made of a material having a higher reflectance while maintaining a sufficiently high corrosion resistance.
Cu and Ti, V, Ta, Cr, Mo, W, Mn, F
a thin film containing at least one element selected from the group consisting of e, Co, Rh, Ni, Pd, Pt, Ag, Au and Al, in particular Cu;
It is preferably composed of a thin film containing one or more elements of Rh, Ni, Pd, Pt, Ag, Au and Al.

Since the preferable content of the element in the reflective layer 4 varies depending on the element, it will be divided into the following cases.

Ti, V, Ta, Cr, Mo, W, Mn,
The total content of one or more elements of Fe, Co, Rh, Ni, Pd, Pt and Al in the reflective layer 4 is 20 atomic%.
The following are preferred. If the content exceeds 20 atomic%, the reflectance becomes insufficient. However, if the content is too small, the corrosion resistance decreases, so 0.5 to 20 atomic%, particularly 2-1
5 atom% is preferable.

The total content of Ag and / or Au in the reflective layer 4 is preferably 5 to 99 atom%. If it exceeds the above range, the hardness of the film becomes insufficient,
When the recording layer 3 is irradiated with the recording light to form the pit portion, the reflective layer 4 on the pit portion is deformed due to thermal expansion of the recording layer 3. Therefore, the eye pattern is disturbed and the jitter is increased. If it is less than the above range, the corrosion resistance is insufficient. For example, when it is stored or used for a long period of time under high temperature and high humidity, the reflectance of the film decreases and the error increases. For the above reason, the upper limit of the content of Ag and Au in the reflective layer 4 is more preferably 90 atomic%, and even more preferably 80.
The upper limit of the Au content in the reflective layer 4 is preferably 60 atom%, and the upper limit of the Ag content thereof is preferably 40 atom%. Further, the lower limit is more preferably 6 atom%, further preferably 8 atom%, particularly preferably 10 atom%.

The total content of N and / or O in the reflective layer 4 is preferably 0.5 to 2.0 atomic%. In this case, a film containing substantially no O but containing N is preferable. If the content exceeds the above range, the reflectance tends to be too low and the necessary reflection level during reproduction tends to be lost. If it is less than the above range, the corrosion resistance tends to be insufficient. For this reason, the upper limits of the nitrogen and oxygen contents in the reflective layer 4 are more preferably 1.8 at%, even more preferably 1.6 at%, and particularly preferably 1.4 at%. The lower limit is more preferably 0.7
Atomic%, more preferably 0.8 at%, and particularly preferably 0.9 at%.

A Cu-Ag alloy selected from the above composition range is particularly preferable because it has a high reflectance and is inexpensive.

To form the reflective layer 4, various vapor phase film forming methods such as sputtering and vapor deposition may be used. And
In order to form a thin film containing Cu and N and / or O, it is particularly preferable to carry out reactive sputtering in an atmosphere containing N ₂ or O ₂ in Ar.

The thickness of the reflective layer 4 is preferably 500 A or more. Also, there is no particular upper limit of the thickness, but the cost,
Considering the production work time and the like, it is preferably about 1700 A or less. Thereby, the reflectance of the reflective layer 4 alone is 90% or more, and the reflectance of the unrecorded portion of the medium through the substrate is 60% or more, particularly 70% or more.

A lower protective coat 5 and an upper protective coat 6 are sequentially provided on the reflective layer 4 so as to cover at least the recordable area.

The lower protective coat 5 is formed by spin coating in order to avoid damage to the reflective layer 4. The upper protective coat 6 is preferably formed by spin coating, screen printing, dipping or spray coating. The upper protective coat 6 is formed after the lower protective coat 5 is cured. When the upper protective coat 6 is formed by the screen printing method, unlike the spin coating method, it can be selectively applied only on the recordable area. Therefore, the amount of resin used can be small.

The conditions for spin coating and screen printing are not particularly limited, and may be appropriately determined depending on the viscosity of the coating liquid and the target thickness.

The lower protective coat has a thickness of 1 to 10 μm, particularly 3 to 8 μm, and the upper protective coat has a thickness of 1 to 15 μm.
m, especially 3 to 15 μm. If the thickness is less than the above range, the effect of the present invention becomes insufficient, and it is difficult to form a uniform film having a thickness of less than 2 μm particularly by the screen printing method. On the other hand, when the thickness exceeds the above range, cracks tend to occur due to shrinkage during curing, and the disc tends to warp. The total thickness of the lower protective coat and the upper protective coat is 5 to 18 μm. If the total thickness is less than the above range, the effect of the present invention becomes insufficient, and if the total thickness exceeds the above range, the disk tends to warp when used under adverse conditions such as high temperature and high humidity.

Lower protective coat 5 and upper protective coat 6
Is composed of a radiation curable resin. Specifically, it is preferably composed of a radiation-curable compound or a substance obtained by radiation-curing a composition for polymerization thereof. Examples thereof include acrylic acid having an unsaturated double bond that is sensitive to ionization energy and exhibits radical polymerizability, methacrylic acid, an acrylic double bond such as an ester compound thereof, or a diallyl phthalate. Examples thereof include monomers, oligomers and polymers having or introduced in the molecule a group capable of being crosslinked or polymerized by radiation such as an allyl double bond, an unsaturated double bond such as maleic acid and a maleic acid derivative. It is preferable that these are polyfunctional, particularly trifunctional or more, and even if only one type is used, it is 2
You may use together 1 or more types.

The radiation curable monomer has a molecular weight of 2
A compound of less than 000 has a molecular weight of 20 as an oligomer.
Those of 00 to 10,000 are preferable. These include styrene, ethyl acrylate, ethylene glycol diacrylate, ethylene glycol dimethacrylate, diethylene glycol diacrylate, diethylene glycol methacrylate, 1,6-hexane glycol diacrylate, 1,6-hexane glycol dimethacrylate, etc., but particularly preferred ones As, pentaerythritol tetraacrylate (methacrylate), pentaerythritol acrylate (methacrylate), trimethylolpropane triacrylate (methacrylate), trimethylolpropane diacrylate (methacrylate), acrylic modified urethane elastomer,
Alternatively, those into which a functional group such as COOH is introduced, acrylate (methacrylate) of a phenol ethylene oxide adduct, an acrylic group (methacrylic group) or ε-in the pentaerythritol condensed ring shown in Japanese Patent Application No. 62-072888. Examples thereof include caprolactone-acryl group-containing compounds, and acrylic group-containing monomers and / or oligomers such as special acrylates disclosed in Japanese Patent Application No. 62-072888. Besides this,
Examples of radiation-curable oligomers include oligoester acrylates, acrylic modified urethane elastomers, and those into which a functional group such as COOH is introduced.

In addition to the above compounds, or in place of this, a radiation curable compound obtained by radiation-sensitively modifying a thermoplastic resin may be used. Specific examples of such a radiation curable resin include acrylic double bonds having an unsaturated double bond exhibiting radical polymerizability, acrylic double bonds such as methacrylic acid, or ester compounds thereof, and diallyl phthalate. It is a resin that contains or introduces into the molecule of a thermoplastic resin a group capable of being crosslinked or polymerized by irradiation with radiation, such as an allyl double bond, an unsaturated bond such as maleic acid or a maleic acid derivative. Examples of thermoplastic resins that can be modified into radiation curable resins include vinyl chloride copolymers, saturated polyester resins, polyvinyl alcohol resins, epoxy resins, phenoxy resins, and fibrin derivatives. Other resins that can be used for radiation-sensitive modification include polyfunctional polyester resins, polyetherester resins, polyvinylpyrrolidone resins and derivatives (P
VP olefin copolymer), polyamide resin, polyimide resin, phenol resin, spiro acetal resin, acrylic resin containing at least one hydroxyl group-containing acrylic ester and methacrylic ester as a polymerization component are also effective.

Since the coating composition for polymerization is cured by irradiation of radiation, especially irradiation of ultraviolet rays, it is preferable that the composition for polymerization contains a photopolymerization initiator or a sensitizer. The photopolymerization initiator or sensitizer used is not particularly limited, and may be appropriately selected from ordinary ones such as acetophenone-based, benzoin-based, benzophenone-based, and thioxanthone-based. A plurality of compounds may be used in combination as the photopolymerization initiator or the sensitizer. The content of the photopolymerization initiator in the composition for polymerization may be usually about 0.5 to 5% by weight. Such a composition for polymerization may be synthesized according to a conventional method, or may be prepared using a commercially available compound.

As the composition containing a radiation-curable compound for forming each protective coat, a composition containing an epoxy resin and a cationic photopolymerization catalyst is also preferably used.

As the epoxy resin, an alicyclic epoxy resin is preferable, and one having two or more epoxy groups in the molecule is particularly preferable. As alicyclic epoxy resin,
3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate, bis- (3,4
-Epoxycyclohexylmethyl) adipate, bis-
(3,4-epoxycyclohexyl) adipate, 2-
(3,4-epoxycyclohexyl-5,5-spiro-
One or more of 3,4-epoxy) cyclohexane-meta-dioxane, bis (2,3-epoxycyclopentyl) ether, vinylcyclohexene dioxide and the like are preferable. The epoxy equivalent of the alicyclic epoxy resin is not particularly limited, but 60 to 3 because good curability can be obtained.
00, especially 100 to 200 is preferable.

The photocationic polymerization catalyst may be any known one and is not particularly limited. For example, a complex of one or more metal fluoroborate and boron trifluoride,
Bis (perfluoroalkylsulfonyl) methane metal salt, aryldiazonium compound, aromatic onium salt of 6A group element, aromatic onium salt of 5A group element, 3A group ~
Dicarbonyl chelate of Group 5A element, thiopyrylium salt, MF ₆ anion (where M is P, As or S
Group 6A elements having b), triarylsulfonium complex salts, aromatic iodonium complex salts, aromatic sulfonium complex salts and the like can be used, and in particular, polyarylsulfonium complex salts, aromatic sulfonium salts or iodonium salts of halogen-containing complex ions, 3A It is preferable to use one or more aromatic onium salts of Group 5A, Group 5A and Group 6A elements.

A photocationic polymerization catalyst containing an organometallic compound and a photodegradable organosilicon compound can also be used. Since such a cationic photopolymerization catalyst is a non-strong acid type, it is possible to avoid adverse effects on the highly corrosive recording layer of the magneto-optical recording disk. As the organometallic compound, Ti, V, Cr, Mn, Fe, Co,
A complex compound in which an alkoxy group, a phenoxy group, a β-diketonato group or the like is bonded to a metal atom such as Ni, Cu, Zn, Al or Zr is preferable. Among these, organoaluminum compounds are particularly preferable, and specifically, trismethoxyaluminum, trispropionatoaluminum, tristrifluoroacetylaluminum, and trisethylacetoacetonatoaluminum are preferable.

The photodegradable organic silicon compound produces silanol upon irradiation with light such as ultraviolet rays,
A silicon compound having a peroxysilano group, an o-nitrobenzyl group, an α-ketosilyl group or the like is preferable.

The content of the photocationic polymerization catalyst in the composition is 0.05 to 0.
It is preferably 7 parts by weight, particularly 0.1 to 0.5 parts by weight.

Among these, it is preferable that a radiation-curable compound having an acrylic group is used and a coating film containing a photopolymerization sensitizer or an initiator is radiation-cured, especially ultraviolet-cured.

After spin coating or printing, the coating film is irradiated with ultraviolet rays to be cured. However, in some cases, the ultraviolet rays may be irradiated after heating, or an electron beam or the like may be irradiated instead of the ultraviolet rays. The intensity of ultraviolet light applied to the coating film is usually 50 mW
/ cm ² or more, irradiation dose is usually 500 to 2000 mJ / c
It should be about m ² . Further, as the ultraviolet ray source, a normal one such as a mercury lamp may be used. The above compounds undergo radical polymerization upon irradiation with ultraviolet rays.

The lower protective coat and the upper protective coat may optionally contain various pigment particles, but if the pigment particles are too much, the resin will not cure sufficiently. It is preferable not to include pigment particles.
Further, since the protective coat containing no pigment is transparent, it is possible to easily inspect the reflective layer for defects after the protective coat is formed.

Further, at least 1 is included in the optical recording disk.
A label printing layer may be provided, which is composed of layers of printing layers. The label printing layer is usually provided on the upper protective coat, but it may be provided between the lower protective coat and the upper protective coat. In this case, after the lower protective coat is cured, the label printing layer is printed and cured, and then the upper protective coat is printed and cured. The label printing layer is preferably formed by printing a radiation curable resin composition containing various pigments and curing it, but a thermosetting ink may also be used.

In the present invention, the protective coat may have a multi-layered structure of three or more layers if necessary. In this case, at least one intermediate protective coat made of a radiation curable resin is formed between the lower protective coat and the upper protective coat so as to cover at least the recordable area. The composition and forming method of the intermediate protective coat are not particularly limited, and may be formed according to the upper protective coat. However, even when the number of layers is three or more, the total thickness of the protective coat is preferably 18 μm or less.

In order to perform recording or additional recording on the optical recording disc 1 having such a structure, for example, recording light of 780 nm is used.
Irradiation is performed in a pulse shape through the substrate 2 to change the light reflectance of the irradiation portion. When the recording light is irradiated, the recording layer 3 absorbs the light and generates heat, and at the same time, the substrate 2 is also heated. As a result, in the vicinity of the interface between the substrate 2 and the recording layer 3, the recording layer material such as a dye is melted or decomposed, pressure is applied to the interface between the recording layer 3 and the substrate 2, and the bottom surface or side wall of the groove is deformed. Sometimes.

[0078]

EXAMPLES The present invention will be described in more detail below by showing specific examples of the present invention. An optical recording disk sample having the structure shown in FIG. 1 was produced. First, a recording layer 3 containing a dye was formed by spin coating on a polycarbonate resin substrate 2 having a spiral continuous groove and a diameter of 120 mm and a thickness of 1.2 mm. A 70 atomic% Cu-30 atomic% Ag thin film having a thickness of 1500 A was formed on the recording layer 3 by sputtering to form a reflective layer 4, and a lower protective coat 5 and an upper protective coat 6 were sequentially formed on the reflective layer 4. ..

The coating liquid used for forming the recording layer 3 contains a dye and an organic solvent. As the dye, the following dyes A1 and A2 and a singlet oxygen quencher were used, and the content of A1 in the dye was The content of A2 was 60% by weight, the content of A2 was 30% by weight, and the content of singlet oxygen quencher was 10% by weight.

[0080]

[Chemical 1]

As the organic solvent, diacetone alcohol was used. The pigment content in the coating liquid was 5% by weight. The thickness of the recording layer was 2000A.

The lower protective coat and the upper protective coat of each sample were formed as follows. <Sample No. 1 (Comparative Example)> An ultraviolet curable resin (SD-17 manufactured by Dainippon Ink) was applied by spin coating,
UV curing was applied to form a 16 μm thick lower protective coat. No top protective coat was formed.

<Sample No. 2 (Example)> Sample N
A bottom protective coat was formed as in o.1. However, the thickness of the lower protective coat was 6 μm. Then, SD-17 was applied onto the lower protective coat by spin coating and ultraviolet curing was performed to form an upper protective coat having a thickness of 10 μm.

<Sample No. 3 (Example)> Sample N
o. Form the bottom protective coat as in 2 and then
UV curable resin (UVOPT550 clear made by Teikoku Ink) so that the entire surface of the lower protective coat is covered by screen printing.
Film is formed and UV cured to a thickness of 10 μm
A top protective coat of.

Each of the above samples was reproduced on a commercially available compact disc player to measure the C1 error. The same measurement was carried out after storage in an environment of 80 ° C. and 80% RH for 50 hours and storage in a 1% H ₂ S gas atmosphere for 50 hours. The results are shown in Table 1. The C1 error was measured for 10 minutes and the average value per second was shown. The CD standard for C1 errors is 220 (counts / second) or less.

[0086]

[Table 1]

From the results shown in Table 1, the effect of the present invention is clear. A sample in which the lower protective coat was formed by the screen printing method was also prepared, but in this sample, the initial C1 error was increased as compared with the samples shown in Table 1. This increase in error is considered to be due to damage to the reflective layer.

[Brief description of drawings]

FIG. 1 is a partial sectional view showing an example of an optical recording disk of the present invention.

[Explanation of symbols]

 1 Optical Recording Disk 2 Substrate 21 Groove 3 Recording Layer 4 Reflective Layer 5 Lower Protective Coating 6 Upper Protective Coating

Claims (6)

[Claims] 1. A coating type recording layer containing a dye as a main component is provided on a substrate, a reflective layer is provided on the recording layer, and radiation curing is performed so as to cover at least a recordable area on the reflective layer. A lower protective coat made of a resin, an upper protective coat made of a radiation curable resin on the lower protective coat so as to cover at least the recordable area, and the lower protective coat formed by a spin coating method. The thickness of the lower protective coat is 1 to 10 μm, the thickness of the upper protective coat is 1 to 15 μm, and the total thickness of the lower protective coat and the upper protective coat is 5 to 18 μm. Characteristic optical recording disc. 2. The optical recording disk according to claim 1, wherein the upper protective coat is formed by a screen printing method, a spin coating method, a dipping method or a spray coating method. 3. The optical recording disk according to claim 1, wherein the lower protective coat and the upper protective coat do not contain pigment particles. 4. The reflective layer comprises Cu, Ti, V, Ta,
Cr, Mo, W, Mn, Fe, Co, Rh, Ni, P
The optical recording disk according to any one of claims 1 to 3, further comprising at least one element selected from the group consisting of d, Pt, Ag, Au, Al, N and O. 5. The optical recording disc according to claim 1, further comprising a label printing layer on the upper protective coat or between the lower protective coat and the upper protective coat. 6. An intermediate protective coat made of a radiation curable resin is provided between the lower protective coat and the upper protective coat so as to cover at least a recordable area, and the lower protective coat, the intermediate protective coat and the upper protective coat are provided. The optical recording disc according to any one of claims 1 to 5, wherein the total thickness is less than 18 µm.