JPH0963118A - Optical recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an optical recording medium having satisfactory durability by regulating the grain size of a metallic reflecting layer to a prescribed value or above and the thickness to a value in a prescribed range. SOLUTION: A recording layer 2 is formed on a substrate 1, a reflecting layer 3 is disposed on the recording layer 2 in an adhered state and the top of the reflecting layer 3 is coated with a protective layer 4. The substrate 1 is transparent at the wavelength of radiated light and the recording layer 2 uses a phthalocyanine dye, especially a phthalocyanine dye having a substituent and a central metallic atom and soluble in an org. solvent. The grain size of the reflecting layer 3 is regulated to >=250Å, preferably 300-500Å. The thickness of the layer 3 is regualted to 700-1,500Å, preferably 800-1,000Å.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an optical recording medium, and more particularly to an optical recording medium having a reflective layer.

[0002]

2. Description of the Related Art In recent years, a recordable or recordable CD has been proposed as an optical recording medium having a reflective layer on a substrate, which is compatible with the compact disc (hereinafter abbreviated as CD) standard. [For example, Nikkei Electronics No.465, P.107,
January 23, 1989] As shown in FIG. 1, this optical recording medium has a recording layer 2, a reflective layer 3 and a protective layer 4 formed in this order on a substrate 1. The recording layer of the optical recording medium is irradiated with a laser beam such as a semiconductor laser at a high power. Then, the recording layer undergoes a physical or chemical change to record information in the form of pits. The pit information can be reproduced by irradiating the formed pits with a low-power laser beam and detecting the reflected light. On the other hand, currently, read-only optical recording media such as compact discs and laser discs, which have been used in place of music records, have music information recorded in advance in the form of pits on the surface of a substrate. It has a structure in which a reflective layer of Au or the like and a protective layer for protecting it are formed. This has basically the same structure as a write-once or recordable CD except that a recording layer is provided instead of the pit portion on the substrate surface. Therefore,
The recorded CD can be played back by a normal CD player as well as a read-only CD. In a recordable optical recording medium, a substance that absorbs at the wavelength of laser light is used for the recording layer, and thus Au having a higher reflectance than Al is usually used for the reflective layer.

[0003]

The present inventors, while searching for the manufacturing conditions of the Au reflective layer in this optical recording medium, surprisingly found that the characteristics of the medium, especially the durability, were changed depending on the manufacturing conditions. I found that it changed. Au is generally said to be chemically stable in metals, but in the state of a thin film, it is easily affected by temperature and humidity, and its physical properties change to affect the characteristics of the medium, especially durability. it is conceivable that.

The inventors of the present invention have investigated the factors that deteriorate the durability, and the crystallinity (crystallite size), which is the physical property of Au, changes depending on the manufacturing conditions and the film thickness, and the crystallite size is the durability of the medium. It was found to have something to do with.

[0005]

The inventors of the present invention have made extensive studies to solve the above problems, and as a result, have come to propose the present invention. That is, this problem is solved by the following invention. (1) An optical recording medium in which at least a recording layer and a metal reflective layer are formed on a substrate, wherein the metal reflective layer has a crystallite size of 250 A or more and a film thickness of 700 to 1500 A. Medium. (2) The optical recording medium according to (1), wherein the reflective layer is made of a metal containing Au as a main component. (3) The recording layer is composed of a phthalocyanine dye (1)
Alternatively, the optical recording medium according to (2). (4) The optical recording medium according to any one of (1) to (3), wherein a recording layer, a reflective layer and a protective layer are provided in this order on a substrate.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION Specific embodiments of the present invention will be described below. The optical recording medium of the present invention has a reflective layer on the substrate. The optical recording medium refers to both a read-only optical read-only medium in which information is recorded in advance and an optical recording medium in which information can be recorded and reproduced. However, here, as a suitable example, an optical recording medium capable of recording and reproducing the latter information, particularly an optical recording medium in which a recording layer, a reflective layer and a protective layer are formed in this order on a substrate will be described. This optical recording medium has a four-layer structure as shown in FIG. That is, a recording layer 2 is formed on a substrate 1, a reflective layer 3 is provided in close contact with the recording layer 2, and a protective layer 4 further covers the reflective layer 3. Basically, the material of the substrate is not particularly limited as long as it is transparent at the wavelengths of the recording light and the reproducing light.

For example, a polymer material such as a polycarbonate resin, a vinyl chloride resin, an acrylic resin such as polymethylmethacrylate, a polystyrene resin, an epoxy resin, or an inorganic material such as glass is used. These substrate materials are formed into a disk shape by injection molding or the like. If necessary, a groove may be formed on the substrate surface.

The recording layer in the present invention uses a phthalocyanine dye, particularly a phthalocyanine dye having a substituent and soluble in an organic solvent having a metal atom in the center. Examples of the substituent include halogen such as hydrogen, chlorine, bromine and iodine, a substituted or unsubstituted alkyl group, an aryl group, an unsaturated alkyl group, an alkoxyl group, an aryloxy group, an unsaturated alkoxyl group, an alkylthio group, an arylthio group. , Unsaturated alkylthio groups, carboxylic acid ester groups, carboxylic acid amide groups, silyl groups, amino groups and the like. Specific examples of the substituent include a methyl group, an ethyl group, an n-propyl group, an n-butyl group, an isobutyl group, an n-pentyl group, a neopentyl group, an isoamyl group, and 2-methylbutyl as the alkyl group. Group, n-hexyl group, 2-methylpentyl group, 3-methylpentyl group, 4-methylpentyl group, 2-ethylbutyl group, n-heptyl group, 2-
Methylhexyl group, 3-methylhexyl group, 4-methylhexyl group, 5-methylhexyl group, 2-ethylhexyl group, 3-ethylpentyl group, n-octyl group, 2-methylheptyl group, 3-methylheptyl group, 4-methylheptyl group, 5-methylheptyl group, 2-ethylhexyl group, 3-ethylhexyl group, n-nonyl group, n-decyl group, primary alkyl group such as n-dodecyl group, isopropyl group, sec-butyl group, 1-ethylpropyl group, 1-methylbutyl group, 1,2-dimethylpropyl group, 1-methylheptyl group, 1-ethylbutyl group, 1,3-dimethylbutyl group, 1,2-dimethylbutyl group, 1-ethyl- Two
-Methylpropyl group, 1-methylhexyl group, 1-ethylheptyl group, 1-propylbutyl group, 1-isopropyl-2-methylpropyl group, 1-ethyl-2-methylbutyl group, 1-propyl-2-methylpropyl group Group, 1-methylheptyl group, 1-ethylhexyl group, 1-propylpentyl group, 1-isopropylpentyl group, 1-isopropyl-2-methylbutyl group, 1-isopropyl-3-
Methylbutyl group, 1-methyloctyl group, 1-ethylheptyl group, 1-propylhexyl group, 1-isobutyl-
Secondary alkyl groups such as 3-methylbutyl group, tert-butyl group, tert-hexyl group, tert-amino group,
Tertiary alkyl groups such as tert-octyl group, cyclohexyl group, 4-methylcyclohexyl group, 4-ethylcyclohexyl group, 4-tert-butylcyclohexyl group, 4- (2-ethylhexyl) cyclohexyl group, bornyl group, isobornyl group, Cycloalkyl groups such as adamantane group and the like, aryl groups such as phenyl group, ethylphenyl group, butylphenyl group, nonylphenyl group, naphthyl group, butylnaphthyl group, nonylnaphthyl group and the like, and also as unsaturated alkyl group. Is an ethylene group,
Propylene group, butylene group, hexene group, octene group,
Dodecene group, cyclohexene group, butylhexene group and the like can be mentioned. In addition, these alkyl groups, aryl groups,
The unsaturated alkyl group may be substituted with a hydroxyl group, a halogen group, or the like, or may be substituted with the above-mentioned alkyl group or aryl group via an atom such as oxygen, sulfur, or nitrogen.
Examples of the alkyl group or aryl group substituted via oxygen include a methoxymethyl group, a methoxyethyl group, an ethoxymethyl group, an ethoxyethyl group, a butoxyethyl group, an ethoxyethoxyethyl group, a phenoxyethyl group, a methoxypropyl group, and an ethoxy group. A propyl group, a methoxyphenyl group, a butoxyphenyl group, a polyoxyethylene group, a polyoxyethylene group, a polyoxypropylene group, etc. are substituted with an alkyl group or an aryl group through sulfur, such as a methylthioethyl group and an ethylthioethyl group. Group, ethylthiopropyl group, phenylthioethyl group, methylthiophenyl group, butylthiophenyl group, etc., are substituted through nitrogen, such as dimethylaminoethyl group, diethylaminoethyl group, diethylaminopropyl group. The Chill aminophenyl group, dibutyl amino phenyl group.

On the other hand, the central metal of the phthalocyanine dye is preferably a divalent metal, specifically, Ca or M.
g, Zn, Cu, Ni, Pd, Fe, Pb, Co, P
Examples thereof include t, Cd, Ru and the like. Further, the above phthalocyanine dyes may be used as a mixture of two or more kinds of phthalocyanine dyes, if necessary.
Additives such as a quencher, an ultraviolet absorber, an adhesive and a resin binder may be mixed or introduced as a substituent.

The light absorber has absorption at the wavelength of recording light,
An organic dye is desirable because it is for increasing the sensitivity of the phthalocyanine dye film. For example, naphthalocyanine dye, porphyrin dye, azo dye, pentamethine cyanine dye, squarylium dye, pyrylium dye, thiopyrylium dye, azurenium dye, naphthoquinone dye, anthraquinone dye, indophenol dye, Triphenylmethane dyes, xanthene dyes, indanthrene dyes, indigo dyes, thioindigo dyes, merocyanine dyes, thiazine dyes, acridine dyes, and oxazine dyes are often used. Phthalocyanine dyes are particularly desirable in terms of the absorption wavelength region. These dyes can be used by mixing a plurality of them.

Examples of the combustion accelerator are lead compounds such as tetraethyl lead and tetramethyl lead which are metal anti-knocking agents, and Mn compounds such as simantrene (Mn (C ₅ H ₅ ) (CO) ₃ ). In addition, iron biscyclopentadienyl complex (ferrocene) which is a metallocene compound, T
i, V, Mn, Cr, Co, Ni, Mo, Ru, Rh,
Examples thereof include biscyclopentadienyl metal complexes such as Zr, Lu, Ta, W, Os, Ir, Sc and Y. Among them, ferrocene, ruthenocene, osmosen, nickelocene,
Titanocene and derivatives thereof have a good combustion promoting effect. As the iron-based metal compound, in addition to metallocene, iron formate, iron oxalate, iron laurate, iron naphthenate, iron stearate, iron butyrate and other organic acid iron compounds, acetylacetonato iron complex, phenanthroline iron complex, bispyridine Iron complex, ethylenediamineiron complex, ethylenediaminetetraacetate iron complex, diethylenetriamineiron complex, diethyleneglycoldimethyletheriron complex, diphosphinoiron complex, dimethylglyoximate iron complex, etc. chelate iron complex, carbonyliron complex, cyanoiron complex, ammineiron complex, etc. Of the above, iron halides such as ferric chloride, ferric chloride, ferrous bromide and ferric iron, inorganic iron salts such as iron nitrate and iron sulfate, and iron oxide. The iron-based metal compound used here is soluble in an organic solvent, and
It is desirable to have good resistance to moist heat and light. In particular, acetylacetonate iron complex, iron carbonyl complex and the like are very preferable in that good solubility can be obtained. The above-mentioned combustion accelerator may be introduced with a substituent, mixed in plural, or added with an additive substance such as a binder, if necessary. These dyes are formed on a substrate by a coating method such as a spin coating method or a casting method, a sputtering method, a chemical vapor deposition method, a vacuum vapor deposition method or the like. In the present invention, a spin coating method is most suitable for forming a dye film having a specific shape in a pit portion and a groove portion.

In the spin coating method, a coating solution in which a dye is dissolved or dispersed is used. At this time, the solvent must be selected so as not to damage the substrate. For example, n-hexane, n-octane, aliphatic hydrocarbon solvents such as isooctane, cyclohexane, methylcyclohexane, ethylcyclohexane, propylcyclohexane, dimethylcyclohexane, cyclic hydrocarbon solvents such as diethylcyclohexane, benzene, toluene, xylene, Aromatic hydrocarbon solvents such as ethylbenzene, chloroform, carbon tetrachloride, dichloromethane, 2,2,3
Halogenated hydrocarbon solvent such as 3-tetrafluoro-1-propanol, alcohol solvent such as methanol, ethanol, 1-propanol, 2-propanol, diacetone alcohol, dioxane, tetrahydrofuran, diethyl ether, dibutyl ether, diisopropyl ether, etc. Examples of the ether solvent, cellosolve solvent such as methyl cellosolve and ethyl cellosolve, ketone solvent such as acetone and methyl isobutyl ketone, ester solvent such as ethyl acetate, methyl acetate and butyl acetate. Of course, these organic solvents may be used alone or in combination of two or more.

In forming the phthalocyanine dye film, the boiling point of n-octane, ethylcyclohexane, dimethylcyclohexane, etc. is 12 in the above coating solvent.
An organic solvent of about 0 to 140 ° C. is used alone, or a coating solvent in which dioxane, xylene, toluene, propylcyclohexane, or the like is mixed at a volume ratio of about 0.1 to 10% is often used.

As a preferable coating condition, for example, a low speed rotation (100 to 10) is first performed in an environment of a temperature of 24.degree.
(00 rpm) for 1 to 10 seconds, and immediately thereafter, high speed rotation (2000 to 5000 rpm) applies 10 to 6
A uniform dye film can be formed by drying for 0 seconds. If necessary, the recording layer may be formed not only of one layer but also of a plurality of dyes.

In the present invention, a specific reflective layer is formed on the recording layer. That is, the crystallite size of the reflective layer is 2
50 A or more, preferably 500 A or less, preferably 30
It is 0-500A. The upper limit of the crystallite size is not particularly critical, but considering the productivity of forming the reflective layer, a sufficient effect can be obtained at 500 A or less. If the crystallite size of the reflective layer is smaller than this, 80 ℃ 85%
In the worst case because many dark defects occur in the RH wet heat resistance test, the reproduction may not be possible.

The film thickness is preferably in the range of 700 to 1500A, preferably 800 to 1000A. If the film thickness is much less than 700 A, the crystallite size becomes small and the reflectance decreases, so that an error occurs in the initial stage, and in the worst case, the reproduction becomes impossible. On the other hand, if the film thickness is much thicker than 1500 A, the moisture permeability is lowered, so that the recording layer is apt to have a defect due to the moist-heat resistance test, and an error occurs. In terms of aspects, there is a problem that it becomes expensive.

Conventionally, several proposals have been made regarding the film thickness of the reflective layer. For example, Japanese Patent Laid-Open No. 6-150381
Then, the film thickness of the reflective layer is 1500 A or less, preferably 40 A or less.
0 to 1500 A, according to JP-A-5-47038, the thickness of the reflective layer is 400 A or more, and according to JP-A-4-301494, the thickness of the reflective layer is 400 to 1
Although proposals of 100 A have been made, optical recording media were produced according to these proposals and subjected to a humidity test at 80 ° C. and 85% RH, but there were cases where the characteristics deteriorated.
It is considered that this result suggests that the durability does not depend only on the thickness of the reflective layer but is related to other factors. As a result of investigating this factor, the present inventors found that
They found that the crystallite size of the reflective layer was related. Here, the crystallite size of the metal reflective layer in the present invention will be described. The crystallite size in the present invention is measured by an X-ray diffraction method (abbreviated as XRD). The crystallite size (D _hkl ) is calculated by substituting the measurement data into the Scherrer's formula (1) and [Equation 1] below.

[0018]

[Equation 1] Dhkl is the crystallite size (A), K is a constant (usually 0.
9), λ is the X-ray wavelength (1.54056 for Cu tube)
A) and β are half-widths of X-ray diffraction peaks (values obtained by correcting the spread of diffraction peaks by an apparatus using a crystalline silicon sample that is an NBS standard), and θ is a Bragg angle (angle of diffraction peaks). is there.

The material of the reflective layer has a sufficiently high reflectance at the wavelength of the reproduction light, for example, Au, Al, Ag, C.
Metals of u, Ti, Cr, Ni, Pt, Ta, Cr and Pd can be used alone or as an alloy.
Among them, Au and Al have high reflectivity and are suitable as a material for the reflective layer. In addition, the following may be included. For example, Mg, Se, Hf, V, Nb, Ru,
W, Mn, Re, Fe, Co, Rh, Ir, Cu, Z
n, Cd, Ga, In, Si, Ge, Te, Pb, P
Mention may be made of metals such as o, Sn and Bi and semimetals. Further, those containing Au as a main component are preferable because a reflection layer having high reflectance can be easily obtained. Here, the main component means a component having a content of 50% or more. It is also possible to form a multilayer film by alternately stacking low-refractive-index thin films and high-refractive-index thin films with a material other than a metal, and use it as a reflective layer. Examples of the method of forming the reflective layer include a sputtering method, a chemical vapor deposition method, a vacuum vapor deposition method and the like.
Among them, the sputtering method is the most frequently used technique.

For example, as shown in FIG. 2, when an Au reflective film is formed by DC magnetron sputtering (sputtering apparatus CDI800 manufactured by Balzers), the crystallite size of Au in the reflective film depends on the sputtering power and the sputtering gas pressure. It depends on and has a relationship as shown in the figure. That is, when the sputtering power is 2.5 kW, the sputter gas pressure is 3.0 mTorr or higher, and when the sputter gas pressure is 5.0 kW, the crystallite size is 2 unless the sputter gas pressure is set to 8.0 mTorr or higher, for example, 10 mTorr or higher.
It turns out that it will not exceed 50A. Therefore, in the present invention, the sputtering power and the sputtering gas pressure may be set in the shaded area where the crystallite size is 250 A or more. In the case of other devices, a similar relationship can be easily obtained.

If the manufacturing conditions of the reflective layer are outside the shaded area, the crystallite size will be 250 A or less, and defects will occur in the durability test such as 80 ° C. 85% wet heat resistance test and ZAD cold heat cycle test for the medium. When reproduced, an error occurs, and in the worst case, reproduction cannot be performed. Regarding the film thickness, the film forming speed is determined by the selected conditions, and therefore the film thickness is 700 to 1500 A, preferably 900 A.
The sputtering time may be set so as to be about 1000 A. The thickness of the reflective layer is measured by a stylus type step gauge (DEKTAK) which is generally used.

For example, when the sputtering power is 2.5 kW and the sputtering gas pressure is 10.0 mTorr, the film forming rate is 15.
Since it is 0 A / second, the sputtering time may be set to 6 seconds in order to obtain the film thickness of 900 A. If the film thickness is less than 700 A, the film thickness becomes too thin and the reflectance becomes low.
An error may occur during playback, and in the worst case, playback may become impossible. On the other hand, if the film thickness is much thicker than 1500 A, the moisture permeability of the reflective film is reduced, and defects such as blister are likely to occur in the durability test, which may cause an error, and the cost of the reflective layer is not good. .

Therefore, in view of productivity, it is desirable to set the film forming rate to the highest possible condition and to shorten the sputtering time as much as possible. When producing a reflective layer having the same film thickness, the lower the sputtering power and the higher the sputtering gas pressure, the slower the deposition rate and the longer the sputtering time. Therefore, if the crystallite size of the reflection film is too large, the sputtering time will be long, and the characteristics will be good, but the efficiency will not be good in manufacturing. Further, an intermediate layer such as a reflection amplification layer or an adhesive layer may be provided between the recording layer and the reflective layer in order to increase the reflectance and improve the adhesion.

The material used for the intermediate layer is preferably one having a large refractive index at the wavelength of the reproduction light. For example, inorganic materials include Si ₃ N ₄ , AlN, ZnS, ZnS and Si.
O ₂ mixture, SiO ₂ , TiO ₂ , CeO ₂ , Al ₂
There are O ₃ , V ₂ O ₅ , ZnSe, Sb ₂ S _{3 and the} like, and these materials may be used alone or in combination of two or more. On the other hand, as the organic material, cyanine dyes, phthalocyanine dyes, naphthalocyanine dyes, porphyrin dyes, azo dyes, squarylium dyes, pyrylium dyes, thiopyrylium dyes, azurenium dyes, naphthoquinone dyes, anthraquinone dyes Dyes, indophenol dyes, triphenylmethane dyes, xanthene dyes, indanthrene dyes, indigo dyes, thioindigo dyes, merocyanine dyes, thiazine dyes, acridine dyes, oxazine dyes, etc. Polystyrene, polyvinyl acetate, polycarbonate, polyethylene, polypropylene, polyacrylic acid ester, polymethacrylic acid ester, styrene-acrylonitrile copolymer, polyvinyl alcohol, polyvinyl acetal, polyvinyl chloride Butyral, polyvinyl formal, polyvinyl pyrrolidone, high molecular compounds such as poly-para-hydroxy styrene.

Further, a protective layer may be formed on the reflective layer. The material of the protective layer is not particularly limited as long as it protects the reflective layer from external force. Examples of the organic substance include a thermoplastic resin, a thermosetting resin, and a UV curable resin. UV curable resins are preferred. or,
Inorganic substances include SiO ₂ , SiN ₄ , MgF ₂ , S
nO _{2 and the} like can be mentioned. A thermoplastic resin, a thermosetting resin, or the like can be formed by dissolving in an appropriate solvent, applying a coating solution, and drying. UV curable resin is
It 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 with UV light to cure the coating solution. As the 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, or may be used not only as a single layer but also as a multilayer film. As a method of forming the protective layer, a coating method such as a spin coating method or a casting method, a sputtering method, a chemical vapor deposition method, or the like is used as in the recording layer, and among them, the spin coating method is preferable.

[0026]

The optical recording medium of the present invention has an Au reflective layer having a high crystallinity as defined in the present invention. According to the present invention, by controlling the film thickness and the crystallite size of the Au reflective layer within a specific range, an optical recording medium having excellent durability and recording / reproducing characteristics can be realized. The present invention is applicable not only to a recordable or recordable CD but also to a read-only CD. That is, the occurrence of the above defects is suppressed by setting the crystallite size of the Au reflective layer formed on the substrate in which the information is recorded in advance in the form of pits or the like to 250 A or more and the film thickness within the range of 700 to 1500 A. It is possible to obtain good durability. Hereinafter, an example of an embodiment of the present invention will be described with reference to examples.

[0027]

【Example】

Example 1 0.25 g of the phthalocyanine dye represented by the formula (1) and [Chemical formula 1] was added to ethylcyclohexane at 3% o-.
A dye solution was prepared by dissolving in 10 ml of a coating solvent containing xylene. The substrate is made of polycarbonate resin and has a continuous guide groove with a diameter of 120 mmφ and a thickness of 1.2 mm.
The disk-shaped one was used. A dye solution was spin-coated on this substrate at a rotation speed of 1500 rpm and dried at 70 ° C. for 2 hours to form a recording layer.

[0028]

Embedded image A Balzers sputtering device (CDI
-800) was used to form an Au reflective layer having a thickness of 900 A by a DC magnetron sputtering method. At this time, argon gas was used as the sputtering gas. Sputtering conditions are sputtering power of 2.5 kW and sputtering gas pressure of 5.
The setting was 0 mTorr and the sputtering time was 4.0 seconds.

Further, an ultraviolet curable resin SD-
17 (manufactured by Dainippon Ink and Chemicals, Inc.) was spin-coated, and then irradiated with ultraviolet rays to form a protective layer having a thickness of 6 μm. The crystallite size of the reflective layer at this time was measured using an XRD measuring device (RINT manufactured by Rigaku Denki Co., Ltd.), and the result was 270
A.

Using a commercially available CD writer (CDD521 manufactured by Philips), the sample thus produced was E
The FM signal was recorded. After recording, the error rate was measured using an optical disk evaluation device DDU-1000 manufactured by Pulstec Industrial Co., Ltd. and a CD decoder (DR-3553) manufactured by KENWOOD. This sample is programmed with a constant temperature and humidity chamber (E
TAC HIFLEX-FX2200)
℃ 85% RH humidity and heat resistance test, 200, 500, 1
The error rate was measured after 000, 1500 and 2000 hours.

Example 2 A medium was prepared in the same manner as in Example 1 except that the sputtering power was 1.5 kW, the sputtering gas pressure was 5.0 mTorr, and the sputtering time was 6.9 seconds. At this time, the reflective layer had a film thickness of 1000 A and a crystallite size of 290 A. An EFM signal was recorded using a commercially available CD writer in the same manner as in Example 1, and the error rate was measured. Further, in the same manner as in Example 1, 80 ° C. and 85% R
An H wet heat resistance test was performed.

[Example 3] In Example 1, the sputtering power was 2.5 kW, the sputtering gas pressure was 20.0 mTorr,
A medium was prepared in the same manner except that the sputtering time was 4.3 seconds. At this time, the reflective layer had a film thickness of 1000 A and a crystallite size of 350 A. An EFM signal was recorded using a commercially available CD writer in the same manner as in Example 1, and the error rate was measured. Further, in the same manner as in Example 1, 80 ° C. and 85% R
An H wet heat resistance test was performed.

Example 4 In Example 1, the sputtering power was 1.5 kW, the sputtering gas pressure was 20.0 mTorr,
A medium was prepared in the same manner except that the sputtering time was 7.2 seconds. At this time, the reflective layer had a film thickness of 1100A and a crystallite size of 380A. An EFM signal was recorded using a commercially available CD writer in the same manner as in Example 1, and the error rate was measured. Further, in the same manner as in Example 1, 80 ° C. and 85% R
An H wet heat resistance test was performed.

[Example 5] In Example 1, the sputtering power was 5.0 kW, the sputtering gas pressure was 20.0 mTorr,
A medium was prepared in the same manner except that the sputtering time was 3.2 seconds. At this time, the thickness of the reflective layer was 900 A and the crystallite size was 300 A. Commercially available C as in Example 1
The EFM signal was recorded using a D writer, and the error rate was measured. Also, in the same manner as in Example 1, 80 ° C. 85% RH
A moist heat resistance test was conducted.

[Sixth Embodiment] In the first embodiment, the sputtering power is 5.0 kW, the sputtering gas pressure is 10.0 mTorr,
A medium was prepared in the same manner except that the sputtering time was 3.1 seconds. At this time, the reflective layer had a film thickness of 900 A and a crystallite size of 290 A. Commercially available C as in Example 1
The EFM signal was recorded using a D writer, and the error rate was measured. Also, in the same manner as in Example 1, 80 ° C. 85% RH
A moist heat resistance test was conducted.

Comparative Example 1 An optical recording medium was prepared in the same manner as in Example 1, except that the sputtering power was 2.5 kW, the argon gas pressure was 2.0 mTorr, and the sputtering time was 4.1 sec. At this time, the thickness of the reflective layer is 900
A, the crystallite size was 230A. An EFM signal was recorded using a commercially available CD writer in the same manner as in Example 1, and the error rate was measured. Further, a humidity and heat resistance test at 80 ° C. and 85% RH was performed in the same manner as in Example 1.

Comparative Example 2 An optical recording medium was prepared in the same manner as in Example 1, except that the sputtering power was 1.5 kW, the argon gas pressure was 2.0 mTorr, and the sputtering time was 6.7 sec. At this time, the thickness of the reflective layer is 100.
At 0A, the crystallite size was 230A. An EFM signal was recorded using a commercially available CD writer in the same manner as in Example 1, and the error rate was measured. Further, a humidity and heat resistance test at 80 ° C. and 85% RH was performed in the same manner as in Example 1.

Comparative Example 3 An optical recording medium was prepared in the same manner as in Example 1, except that the sputtering power was 5.0 kW, the argon gas pressure was 2.0 mTorr, and the sputtering time was 2.9 sec. At this time, the thickness of the reflective layer is 900
A, the crystallite size was 230A. An EFM signal was recorded using a commercially available CD writer in the same manner as in Example 1, and the error rate was measured. Further, a humidity and heat resistance test at 80 ° C. and 85% RH was performed in the same manner as in Example 1.

Comparative Example 4 An optical recording medium was prepared in the same manner as in Example 1, except that the sputtering power was 5.0 kW, the argon gas pressure was 5.0 mTorr, and the sputtering time was 3.0 sec. At this time, the thickness of the reflective layer is 900
A, the crystallite size was 230A. An EFM signal was recorded using a commercially available CD writer in the same manner as in Example 1, and the error rate was measured. Further, a humidity and heat resistance test at 80 ° C. and 85% RH was performed in the same manner as in Example 1.

Comparative Example 5 An optical recording medium was prepared in the same manner as in Example 1, except that the sputtering power was 2.5 kW, the argon gas pressure was 5.0 mTorr, and the sputtering time was 2.2 sec. At this time, the thickness of the reflective layer is 500
A, the crystallite size was 270A. An EFM signal was recorded using a commercially available CD writer in the same manner as in Example 1, and the error rate was measured. Further, a humidity and heat resistance test at 80 ° C. and 85% RH was performed in the same manner as in Example 1.

Comparative Example 6 An optical recording medium was prepared in the same manner as in Example 1, except that the sputtering power was 2.5 kW, the argon gas pressure was 5.0 mTorr, and the sputtering time was 8.1 sec. At this time, the thickness of the reflective layer is 200
At 0A, the crystallite size was 270A. An EFM signal was recorded using a commercially available CD writer in the same manner as in Example 1, and the error rate was measured. Further, a humidity and heat resistance test at 80 ° C. and 85% RH was performed in the same manner as in Example 1. The results of Examples and Comparative Examples are shown in Table 1 above.

[0042]

[Table 1]

[0043]

According to the present invention, by setting the crystallite size of the reflective layer to 250 A or more and the film thickness to 700 to 1500 A, it becomes possible to provide an optical recording medium having good durability.

[Brief description of drawings]

FIG. 1 is a sectional view showing a layer configuration of an optical recording medium.

FIG. 2 is a graph showing the relationship between the sputtering conditions (sputtering power and sputtering pressure) and the crystallite size of the Au reflective film.

[Explanation of symbols]

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

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Sumio Hirose 1190 Kasama-cho, Sakae-ku, Yokohama-shi, Kanagawa Mitsui Toatsu Chemical Co., Ltd.

Claims (4)

[Claims] 1. An optical recording medium having at least a recording layer and a metal reflective layer formed on a substrate, wherein the metal reflective layer has a crystallite size of 250 A or more and a film thickness of 700 to 150.
An optical recording medium characterized by 0A. 2. The optical recording medium according to claim 1, wherein the reflective layer is made of a metal containing Au as a main component. 3. The optical recording medium according to claim 1, wherein the recording layer comprises a phthalocyanine dye. 4. The optical recording medium according to claim 1, wherein a recording layer, a reflective layer and a protective layer are provided in this order on a substrate.