JP3073266B2 - Manufacturing method of optical recording medium - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording medium, and more particularly to a single-plate optical recording medium having a metal reflection layer.

[0002]

2. Description of the Related Art With the rapid progress of the information society in recent years,
The use and study of optical recording media capable of recording much higher density than magnetic recording media have been actively conducted. This optical recording medium includes a read-only type in which information is recorded in advance and can only be reproduced, a write-once type in which information can be recorded and reproduced by a user, and a rewritable type in which information can be recorded, reproduced, and erased. It has been known. In particular, the write-once type is generally cheaper and more excellent in storability than the rewritable type, so that it is becoming widespread as a medium for storing a large amount of data compactly. This write-once optical recording medium has a recording layer on a substrate, such as a metal film such as Te or Bi, or a dye film such as cyanine or phthalocyanine. The recording layer is physically and / or physically irradiated with a laser beam. Alternatively, information is recorded by forming a pit by causing a chemical change, and the pit is read out by a laser beam which is sufficiently weaker than at the time of recording, and reproduction is performed. In such an optical recording medium, a space is generally secured on the recording layer in order to facilitate pit formation. Specifically, a so-called air sandwich structure is adopted in which two substrates having recording layers are bonded together so that the recording layers face each other and a gap is formed between the two substrates.

On the other hand, it is well known that a read-only optical recording medium is widely and widely used as a compact disk (CD), a laser disk, or the like. FIG. 1 shows the structure of this optical recording medium. In this optical recording medium, pits are previously formed on a substrate 1, a metal layer of Au, Al, or the like is provided as a reflective layer 3 on the pit formation surface, and a protective layer 4 is further formed thereon. Especially CD
Is being replaced by a record in Japan because it is easier to handle and can be used semi-permanently than conventional music records. As CDs are widely used in this way, compact disc players (CD players), which are playback devices for CDs, are becoming more and more popular than record players. As described above, in the case of a CD that is very widely used, a substrate having information pits is manufactured by injection molding on the basis of an original master generally called a stamper. This method makes it easy to produce the same CD in large quantities and at low cost, but is not suitable for producing a small amount of CDs because the stamper is expensive. Of course, since a CD is exclusively for reproduction, it is impossible for a user to freely record music and information. Therefore, in order to produce a small amount of CD at low cost,
Alternatively, recordable CDs (write-once CDs) for users to freely record have been actively developed.

Recently, a write-once CD proposed has a structure as shown in FIG. That is, it is a single-plate type optical recording medium in which the recording layer 2 is provided on the substrate 1, the reflective layer 3 is provided thereon, and the protective layer 4 is further provided thereon. With such a structure, the write-once CD after recording can be compatible with a normal read-only CD. That is, by using a single-plate structure instead of an air sandwich structure, the thickness can be reduced to 1.2 mm. It is also assumed that the provision of the reflective layer makes it possible to obtain a reflectance of 70% or more equivalent to that of a read-only CD.

[0005]

As a conventional method for forming a recording layer, a method of dissolving an organic dye in an appropriate solvent and applying the solution on a transparent substrate having pregrooves (guide grooves) formed thereon is used. ing. The coated recording layer has been subjected to an appropriate drying step and then has a reflective layer formed thereon. However, a conventional write-once C having an organic dye-based recording layer on a plastic substrate
In D, the adhesion between the reflective layer and the recording layer is weak, and when the medium is left for a long time under conditions of high temperature and high humidity, water bubbles formed at the interface between the recording layer and the reflective layer called blisters (hereinafter referred to as blisters) Blisters), especially in laser-recorded areas, which has been a problem. Generally, when recording is performed on the recording layer, the decrease in adhesion between the reflective layer and the recording layer and the occurrence of blisters are caused by the C /
This affects the N ratio and second harmonic distortion, leading to an increase in jitter and block error rate. Therefore, it is necessary to improve the recording characteristics by increasing the adhesion between the reflective layer and the recording layer and suppressing the generation of blisters.

[0006]

Means for Solving the Problems The present inventors have made intensive studies to solve the above problems, and as a result, when forming a reflective layer, the amount of residual solvent contained in the recording layer was reduced to a specific value or less. The inventors have found that by reducing the amount, the adhesion between the substrate and the recording layer can be increased and the occurrence of blisters during recording can be greatly suppressed, and the present invention has been accomplished. That is, the present invention relates to a method for manufacturing an optical recording medium in which a recording layer, a reflective layer, and a protective layer are provided in this order on a substrate, wherein the recording layer contains a phthalocyanine dye, and the residual solvent contained in the recording layer ( Halogenated hydrocarbons and fluorine
A method for producing an optical recording medium, characterized in that a reflective layer is formed when the amount of a fluorinated ether is less than 10% by weight with respect to the recording layer.

Hereinafter, the components of the present invention will be described in detail. The configuration of the optical recording medium of the present invention is the write-once type C shown in FIG.
It is basically the same as D. That is, a recording layer 2 for forming a pit by absorbing a laser beam is provided on a transparent substrate 1 in which a pregroove (guide groove) is formed.
A reflective layer 3 for increasing the reflectance is provided on the recording layer, and a protective layer 4 for protecting the recording layer and the reflective layer is further provided thereon.
As the material of the substrate, a material which substantially transmits light of a semiconductor laser and is used for an ordinary optical recording medium,
Anything can be used. For example, a polymer material such as a polycarbonate resin, an acrylic resin, a polystyrene resin, a vinyl chloride resin, an epoxy resin, a polyester resin, and an amorphous polyolefin, or an inorganic material such as glass can be used. These materials are used as substrates on which pregrooves are formed by injection molding or 2P method.

The recording layer is not particularly limited as long as it absorbs the recording laser beam, causes a physical and / or chemical change, and can read its shape change with the reproducing laser beam. For example, the following various organic dyes having absorption in a semiconductor laser wavelength range can be used. That is, phthalocyanine dyes, naphthalocyanine dyes, cyanine dyes, squarylium dyes, pyrylium dyes, thiopyrylium dyes,
Azulenium dyes, naphthoquinone dyes, anthraquinone dyes, metal salt dyes such as Ni and Cr, indophenol dyes, triphenylmethane dyes, xanthene dyes, indanthrene dyes, indigo dyes, thioindigo dyes And merocyanine dyes, thiazine dyes, acridine dyes, oxazine dyes, and azo dyes. Among them, phthalocyanine dyes are particularly preferable because of their high light resistance and durability.

These dyes may be used alone or
A mixture of two or more dyes may be used. Further, if necessary, additives such as an ultraviolet absorber, a singlet oxygen quencher, and a binder can be added. These substances
A recording layer is formed by forming a uniform film on the substrate. At this time, it is preferable to adjust the thickness of the recording layer and the concentration of the light absorbing component in advance so that a sufficient reflectance can be obtained after the formation of the reflective film. As a method for forming the recording layer, a coating method such as a spin coating method, a dip coating method, and a bar coating method can be used. In this method, a substance to be used as a recording layer is dissolved in a solvent to prepare a coating solution, which is applied on the substrate and then dried to form a film. As the solvent at this time, the following various organic solvents can be used. That is, aliphatic hydrocarbons such as n-hexane, n-octane, isooctane and cyclohexane; aromatic hydrocarbons such as toluene and xylene; halogenated hydrocarbons such as 1,2-dichloroethane and chloroform; methanol, ethanol, isopropanol and the like Alcohols such as diethyl ether, dibutyl ether and dioxane; cellosolves such as methyl cellosolve and ethyl cellosolve; ketones such as methyl ethyl ketone and cyclohexanone; esters such as ethyl acetate and butyl acetate; 2,2,3,3-tetrafluoropropanol And the like can be used. These organic solvents may be used alone or as a mixture. When these solvents are used, it is needless to say that it is necessary to not only dissolve the substance used as the recording layer but also select a substance that does not damage the substrate used at this time.

In the present invention, it is necessary to form the reflective layer under the condition that the remaining amount of the solvent with respect to the organic dye is 10% by weight or less in the recording layer. When the film formation is performed when the residual amount of the solvent is larger than 10% by weight, the blister generation rate at the interface between the recording layer and the reflective layer is greatly increased when the medium is left under a condition of high temperature and high humidity for a long time. Let me do it. At this time, the adhesion between the reflective layer and the recording layer is deteriorated, and the reflective layer is easily peeled. When such blisters are generated or peeled off, signal recording / reproduction becomes impossible, causing a serious problem. In the present invention, the generation of blisters at the interface between the recording layer and the reflective layer when left for a long time under conditions of high temperature and high humidity can be achieved by regulating the residual amount of the solvent to 2% by weight or less based on the recording layer. It can be reduced to almost zero.

Controlling the amount of the solvent remaining in the organic dye under the conditions specified in the present invention is usually quite difficult to achieve by simply allowing it to stand naturally. Therefore, it is important to properly control the drying conditions after film formation. For example, after the recording layer is applied, vacuum drying, air drying, or high-temperature drying is intentionally performed so that the remaining amount of the solvent in the recording layer is adjusted to be within the range specified in the present invention for the first time. You can do it. This condition can easily be determined experimentally. To measure the residual solvent, determine the loss on drying by peeling the recording layer, determine from the peak intensity ratio by infrared spectroscopy, qualitatively and quantitatively by dissolving in another solvent and gas chromatography Is possible. Therefore, if the remaining amount of the solvent does not sufficiently decrease to the range specified in the present invention under a certain drying condition, the drying is further continued while performing the analysis until the desired remaining amount is obtained. It is only necessary to determine the conditions. The thickness of the recording layer is not particularly limited, but is usually about 30 to 500 nm.

On the recording layer, a metal reflective layer is formed.
This reflective layer may consist of only a single metal,
One or two or more other elements may be contained as subcomponents. As this component element, for example, Au, A
g, Al, Cu, Cr, Ni, Si, Ge and the like. As a method for forming the reflective layer, a method such as a vacuum evaporation method, a sputtering method, and a chemical vapor deposition method (CVD) can be used. The thickness of the reflective layer is usually 3
It is about 0 to 500 nm. A protective layer is provided on the reflective layer. This protective layer is not particularly limited as long as it can protect the recording film and the reflective film. For example, polycarbonate, acrylic, polystyrene, vinyl chloride, epoxy,
Polymer materials such as polyester, SiO ₂ , A
Inorganic substances such as l ₂ O ₃ and AlN can be used.
Above all, an ultraviolet curable acrylic resin is preferable because the protective layer can be easily formed. These may be used alone or as a mixture. Moreover, as a multilayer film,
More than one seed may be used. The thickness of the protective layer is
It is about 3 to 50 μm.

[0013]

Embodiments of the present invention will be described below. Example 1 A coating solution was prepared by dissolving 0.6 g of vanadyl tetraoctylnaphthalocyanine dye in 20 ml of n-octane. This solution was spin-coated at 1200 rpm on a polycarbonate injection-molded substrate (outer diameter 120 mm, thickness 1.2 mm, track pitch 1.6 μm) with a spiral groove, and the degree of vacuum was 1 × 10 6
Vacuum-dried at ^-4 torr and 50 ° C for 12 hours.
20 nm was formed. In order to measure the amount of residual solvent in the recording layer, one substrate having the recording layer was placed on chloroform 5
The solution was immersed in 0 ml for 30 seconds to elute the organic dye layer in chloroform, and the solution was subjected to gas chromatography measurement. As a result, it was confirmed that 2% by weight of the residual solvent was present in the recording layer. Further, using the same substrate, a pure Au film having a thickness of 90 nm was formed on the recording layer. Further, an ultraviolet curable resin was spin-coated on the reflective layer, and then cured by irradiating ultraviolet light to form a protective layer having a thickness of 4 μm.
An optical disk evaluation device DDU-1000 (manufactured by Pulstec Industrial Co., Ltd., laser wavelength 781 nm) and an EFM encoder (KENW) were added to the optical recording medium thus manufactured.
Recording was performed at a linear velocity of 1.4 m / s and a recording laser power of 7 mW using OOD Corporation. Set the recording medium to a temperature of 80
After a moist heat resistance test was performed for 2000 hours in a thermo-hygrostat at 85 ° C. and a humidity of 85%, the disc surface was observed with an optical microscope. A peel test of this medium was performed using an adhesive tape (Scotch 810), but no peeling of the reflective film was observed.

[Comparative Example 1] An optical recording medium was prepared and a signal was recorded in Example 1 without performing vacuum drying after spin coating. In this comparative example, the residual solvent was measured in the same manner as in Example 1 after forming the recording layer, and it was confirmed that 11% by weight of the residual solvent was present in the recording layer. As a result of performing blister observation in the same manner as in Example 1, 1
Fifty-three blisters were observed in a cm × 1 cm square.
When a peeling test was conducted, the reflective film and the recording film were peeled off, and the reflective film and the protective film were peeled off together with the adhesive tape.

Example 2 A coating solution was prepared by dissolving 0.41 g of a cyanine dye NK529 (Nihon Kosaku Dye) in 10 ml of methyl cellosolve. This solution was applied to a polycarbonate injection molded substrate with a spiral groove (outer diameter 1).
20mm, thickness 1.2mm, track pitch 1.6μ
m) after spin-coating on it at 1000 rpm
Air drying at 60 ° C for 12 hours in an oven.
0 nm was formed. The measurement of the residual solvent in the recording layer was performed in Example 1.
When the same procedure was carried out as in
% By weight. Next, a pure Au film having a thickness of 80 nm was formed on the recording layer. Further, an ultraviolet curable resin was spin-coated on the reflective layer, and then cured by irradiating ultraviolet light to form a protective layer having a thickness of 4 μm. Recording was performed on the optical recording medium thus produced in the same manner as in Example 1 at a recording laser power of 7.5 mW. After performing the heat and moisture resistance test in the same manner as in Example 1, when the disk surface was observed with an optical microscope, six blisters were confirmed in a square of 1 cm × 1 cm. In addition, adhesive tape (Scot
ch 810), a peel test of this medium was performed, but no peeling of the reflective film was observed.

[Comparative Example 2] An optical recording medium was prepared and a signal was recorded in Example 2 without spinning and drying after spin coating. Also in this comparative example, the residual solvent in the recording layer was measured in the same manner as in Example 1 after forming the recording layer. As a result, it was confirmed that 17% by weight of the residual solvent was present in the recording layer. As a result of performing blister observation in the same manner as in Example 1, 96 blisters were confirmed in 1 cm × 1 cm square. When a peeling test was conducted, the reflective film and the recording film were peeled off, and the reflective film and the protective film were peeled off together with the adhesive tape.

[0017]

As described above, according to the present invention, it is possible to provide an optical recording medium in which the occurrence of blisters is suppressed by regulating the residual solvent concentration, and the recording layer and the reflective layer have good adhesion. It is.

[Brief description of the drawings]

FIG. 1 is a sectional view of a read-only CD.

FIG. 2 is a sectional view showing an example of a write-once CD.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Recording layer 3 Reflective layer 4 Protective layer

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-63-193345 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B41M 5/26

Claims (3)

(57) [Claims] 1. A method for manufacturing an optical recording medium, comprising a recording layer, a reflective layer, and a protective layer provided on a substrate in this order,
The recording layer contains a phthalocyanine dye, and the residual solvent contained in the recording layer (halogenated hydrocarbon and fluorinated)
10% by weight based on the recording layer )
A method for manufacturing an optical recording medium, comprising forming a reflective layer at the following times. 2. The method for producing an optical recording medium according to claim 1, wherein the amount of the residual solvent contained in the recording layer is 2% by weight or less based on the recording layer. 3. An optical recording medium manufactured by the method according to claim 1.