JPH0818462B2 - Optical recording medium - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an optical recording medium suitable for writing / recording with a laser beam, particularly a semiconductor laser, and more particularly, to an improved optical recording medium which can be used for optical disc and optical card technology. The present invention relates to an optical recording medium.

[Conventional technology]

In general, an optical disc and an optical card form a small (for example, about 1 μ) optically detectable bit formed in a thin recording layer provided on a substrate into a spiral or circular track shape to store high density information. Can be memorized.

To write information on such a disk, a laser focused on the surface of the laser sensitive layer (recording layer) is scanned, and only the surface irradiated with this laser beam forms a pit, and this pit is spiral, It is formed in the form of a circular or linear track. The laser sensitive layer (recording layer) can absorb laser energy to form an optically detectable pit.
For example, in the heat mode recording method, the laser sensitive layer (recording layer) absorbs thermal energy, and a small recess (pit) can be formed at that portion by evaporation or melting. Also,
In another heat mode recording scheme, absorption of the applied laser energy can form a pit with an optically detectable density difference at that location.

The information recorded on this optical disc and optical card is
It is detected by scanning the laser beam along the track and reading the optical change of the part where the pit is formed and the part where the pit is not formed. For example, laser light is scanned along the track and the energy reflected by the disk is monitored by a photodetector. In the portion where the pit is formed, the reflection of the laser light is low and the output of the photodetector is low. on the other hand,
The laser light is sufficiently reflected at the portion where no pit is formed, and the output of the photodetector becomes large.

Optical recording media used for such optical discs and optical cards have mainly used inorganic materials such as metal thin films such as aluminum vapor deposition films, bismuth thin films, tellurium oxide thin films and chalcogenite amorphous glass films. Is proposed. These thin films are generally sensitive to light having a wavelength in the vicinity of 350 to 800 nm, and have high reflectance for laser light, so that they have drawbacks such as low utilization of laser light.

Due to this, in recent years relatively long wavelengths (for example, 780n
Studies have been conducted on organic thin films whose optical properties can be changed by light energy of (m or more). Such an organic thin film is effective, for example, in that a pit can be formed by a semiconductor laser having an oscillation wavelength near 780 nm or 830 nm.

However, generally, an organic compound having an absorption characteristic on the long wavelength side has a problem in that it is unstable to heat.

For example, the handling of the optical recording medium is not necessarily used only in an office equipped with air conditioning,
It is necessary to consider transportation, storage in a warehouse, temperature rise inside the drive device, and the like, and a medium excellent in stability at high temperature is desired. In particular, when the optical recording medium is an optical card, it is difficult to form a hollow structure (air-sandwich structure) in terms of thickness and strength as a card, and the opposite substrate is directly bonded onto the recording layer with an adhesive. It has a laminated structure. As the adhesive used at this time, a hot-melt adhesive that is excellent in workability without lowering the writing sensitivity of the recording layer is effective. However, with a hot-melt adhesive, the temperature is around 100 ° C. for a short time at the time of bonding, so that the recording layer is desired to have more excellent heat resistance.
Furthermore, since optical cards are often handled by individuals and are likely to be handled sparsely, optical cards having excellent environmental stability such as heat resistance are desired.

[Problems to be solved by the invention]

The present invention has been made in view of such a present situation, and its object is to provide excellent optical characteristics and threshold characteristics of recording sensitivity which are excellent in an azulene dye (US Pat. No. 454886), and to provide high recording sensitivity. To provide an optical recording medium having a recording layer composed of a dye thin film that has improved stability even under environmental conditions of high temperature and high humidity without deteriorating characteristics such as that it can be manufactured by a coating method. is there.

[Means for Solving Problems] and [Operation] That is, the present invention is an optical recording medium having a recording layer containing an azurenium salt compound represented by the following general formula [I].

General formula [I] However, in the general formula [I], R _{1 to} R ₇ , R ′ _{1 to} R ′ ₇ represent a hydrogen atom, a halogen atom or a monovalent organic residue,
R ₁ and R ₂ , R ₂ and R ₃ , R ₃ and R ₄ , R ₄ and R ₅ , R ₅ and R ₆ , R ₆ and R ₇ , R ′
₁ and R _'2, R' ₂ and R _'3, R' ₃ and R _'4, R' ₄ and R _'5, R' ₅
And R _'6, and R' may form a condensed ring unsubstituted or substituted with at least one combination among the combinations of ₆ and R _'7.

Where R ₁ and R ′ ₁ , R ₂ and R ′ ₂ , R ₃ and R ′ ₃ , R ₄ and R ′ ₄ , R ₅ and R ′ ₅ , R ₆ and R ′ _6, and R ₇ and R ′ ₇ At least one of the combinations is a combination of different substituents.

That is, this dye is characterized in that it has a so-called asymmetric form in which the substituents of the azulene rings at both ends of squalic acid are different.

 Hereinafter, the present invention will be described in detail.

The optical recording medium of the present invention has a recording layer composed of a thin film containing an azurenium salt compound represented by the above general formula [I], which absorbs electromagnetic radiation and is subjected to a heat action to cause an optical change by the heat action. Is characterized by.

In the general formula [I], R _{1 to} R ₇ and R ′ _{1 to} R ′ ₇ represent a hydrogen atom, a halogen atom (chlorine atom, bromine atom, iodine atom) or a monovalent organic residue.

The monovalent organic residue can be selected from a wide range, but particularly alkyl groups (methyl, ethyl, n-
Propyl, isopropyl, n-butyl, t-butyl, n
-Amyl, n-hexyl, n-octyl, 2-ethylhexyl, t-octyl, etc.), alkoxy group (methoxy, ethoxy, propoxy, butoxy, etc.), substituted or unsubstituted aryl group (phenyl, tolyl, xylyl, ethylphenyl, Methoxyphenyl, ethoxyphenyl, chlorophenyl, nitrophenyl, dimethylaminophenyl, α-naphthyl, β-naphthyl, etc.), substituted or unsubstituted heterocyclic groups (pyridyl, quinolyl, carbazolyl, furyl, thienyl, pyrazolyl, etc.) substituted Or an unsubstituted aralkyl group (benzyl, 2-phenylethyl, 2-phenyl-1-methylethyl, bromobenzyl, 2-bromophenylethyl, methylbenzyl, methoxybenzyl, nitrobenzyl), an acyl group (acetyl, propionyl, butyryl) Ril, valeryl, benzoyl,
Trioil, naphthoyl, phthaloyl, furoyl, etc.), substituted or unsubstituted amino group (amino, dimethylamino, diethylamino, dipropylamino, acetylamino, benzoylamino, etc.), substituted or unsubstituted styryl group (styryl, dimethylaminostyryl, diethylamino) Styryl, dipropylaminostyryl, methoxystyryl, ethoxystyryl, methylstyryl, etc.), nitro group, hydroxy group, mercapto group, thio-
Ether group, carboxyl group, carboxylic acid ester, carboxylic acid amide, cyano group or substituted or unsubstituted arylazo group (phenylazo, α-naphthylazo, β-
Naphthylazo, dimethylaminophenylazo, chlorophenylazo, nitrophenylazo, methoxyphenylazo, tolylazo and the like).

Also, R ₁ and R ₂ , R ₂ and R ₃ , R ₃ and R ₄ , R ₄ and R ₅ , R ₅ and R ₆ , R ₆
And R _7, R _'1 and R' _2, R _'2 and R' _3, R _'3 and R' _4, R _'4 and R' _5, R _'5 and R' ₆ and R _'6 and R' _At least one of the seven combinations may form a substituted or unsubstituted fused ring. The condensed ring is a 5-membered, 6-membered, or 7-membered condensed ring, and is an aromatic ring (benzene, naphthalene, chlorobenzene, bromobenzene, methylbenzene, ethylbenzene, methoxybenzene, ethoxybenzene, etc.), heterocycle ( Furan ring, benzofuran ring, pyrrole ring, thiophene ring, pyridine ring, quinoline ring, thiazole ring and the like) and aliphatic ring (dimethylene, trimethylene, tetramethylene and the like).

Specific examples of the azurenium salt compound used in the present invention are listed below, but the invention is not limited thereto.

Examples of compounds represented by the general formula [I] The compound represented by the general formula [I] is Angewandtechem
ie (Angebant Kemi), Volume 78, No. 20, P937 (1996)
It can be easily obtained by reacting an azulene compound with squalic acid in a suitable solvent as described in 1. For example, the reaction can be carried out by using a butanol / benzene mixed solvent and removing water azeotropically boiling with benzene from the system. Next, the target asymmetric compound can be separated and purified by a silica gel column.

R ₁ and R ′ ₁ , R ₂ and R ′ ₂ , R ₃ and R ′ ₃ , R ₄ and R ′ ₄ , R ₅ and R ′ ₅ , R ₆ and R ′ _6, and R ₇ and R ′ ₇ Among these combinations, it has excellent stability under high temperature and high humidity environment and improved solubility. Particularly preferred examples of different combinations of substituents are:
Hydrogen atom and an alkyl group, a hydrogen atom and an ethyl group, a hydrogen atom and an n-propyl group, a hydrogen atom and an isopropyl group, a hydrogen atom and an n-butyl group, a hydrogen atom and a t-butyl group, and the like. Or a combination of a hydrogen atom and a methoxy group, a hydrogen atom and an ethoxy group, and a hydrogen atom and an alkoxy group.

When R _n -R _{n + 1} or R _n'- R _{n '+ 1} (n and n'are positive integers of 1 to 7) form a condensed ring, R _n -R _{n + 1} or _{R n '-R n' + 1} of one is thiophene, a heterocyclic pyrrole etc., the other is a hydrogen atom and methyl, ethyl, n-propyl, isopropyl, n-
A combination that is a substituent selected from alkyl groups such as butyl and t-butyl is preferable.

The optical recording medium of the present invention, as shown in FIG.
It can be formed by providing the recording layer 2 containing the azurenium salt compound represented by the general formula [I] above.

As the substrate 1, polycarbonate, polyester,
Acrylic resin, polyolefin resin, phenol resin,
It is possible to use epoxy resin, polyamide, plastic such as polyimide, glass, metals or the like.

In forming the recording layer 2, the azurenium salt compound represented by the general formula [I] can be used alone or in combination of two or more, and other dyes, for example, compounds other than the compound of the general formula [I] can be used. Polymethine, Azulene, Pyrylium, Squalium, Croconium,
Triphenylmethane type, xanthene type, anthraquinone type, cyanine type, phthalocyanine type, dioxazine type,
Tetrahydrocholine-based, triphenothiazine-based, phenanthrene-based, aminium salt / diimonium salt-based, metal chelate complex-based dyes, or metals and metal compounds, such as Al, Te, Bi, Sn, In, Se, SnO, TeO ₂ , As, Cd, etc.
Alternatively, they may be mixed and dispersed or laminated with an ultraviolet absorber or the like.

The recording layer 2 is formed on the substrate 1 by various methods such as a coating method and a vapor deposition method. In the case of using a coating method, it can be formed by applying a solution in which an azurenium salt compound is dissolved or dispersed in an organic solvent onto the substrate 1. If necessary, a film can be formed by mixing a binder in the recording layer in consideration of film-forming property and coating film stability.

The organic solvent that can be used during coating varies depending on whether the above-mentioned azurenium salt compound is in a dispersed state or in a dissolved state, but is generally an alcohol type, a ketone type, an amide type, an ether type, an ester type, a fat type. Solvents such as group halogenated hydrocarbons, aromatics, and aliphatic hydrocarbons can be used. Also, as a binder,
For example, nitrocellulose, ethyl cellulose, polystyrene, polyvinylpyrrolidone, polymethyl methacrylate, polyamide and the like can be mentioned. In addition, wax, higher fatty acid, and amides (for example, oleylamide) are used as additives if necessary.

For the above binders, plasticizers such as dioctyl phthalate, dibutyl phthalate, tricresyl phosphate,
An oil agent such as mineral oil or vegetable oil, a dispersant such as sodium alkylbenzene sulfonate, polyoxyethylene alkylphenyl ether, and other additives may be appropriately mixed to enhance the film-forming property and the coating film stability of the recording layer.

The coating can be performed using a coating method such as a dip coating method, a spray coating method, a spinner coating method, a bead coating method, a Meyer bar coating method, a blade coating method, a roller coating method, a gravure coating method.

The content of the azurenium salt compound in the recording layer 2 is usually 40
-100% by weight, preferably 50-100% by weight. 40
If it is less than wt%, sufficient light absorption of the recording layer and sufficient light reflectance for the reproduction laser beam cannot be obtained.

The thickness of the recording layer 2 is 100Å to 20 μm, preferably 2
A suitable value is 00Å to 1 μm. In addition, if a thin film having sufficient light reflectivity with respect to the recording laser light can be stably formed, the thinnest possible film is preferable.

Further, in the optical recording medium of the present invention, as shown in FIG. 2, a protective layer 3 which is transparent to recording and reproducing laser light can be provided on the recording layer 2. The protective layer 3 may be opaque when irradiated with light from the substrate 1 side.

Further, as shown in FIG. 3, an undercoat layer 4 may be provided between the substrate 1 and the recording layer 2.

Further, as shown in FIG. 4, it is possible to use both the protective layer 3 and the undercoat layer 4.

The undercoat layer has (a) improved adhesion, (b) barrier against water or gas, (c) improved storage stability of the recording layer,
It is provided for the purpose of (d) improving the reflectance, (e) protecting the substrate from a solvent, and (f) forming a pre-groove. For the purpose of (a), various polymer materials such as ionomer resins, polyamide resins, vinyl resins, natural polymers, silicones, liquid rubbers or various substances such as silane coupling agents are used. For the purposes of (b) and (c), in addition to the above polymeric materials, inorganic compounds such as SiO ₂ , MgF ₂ , SiO, TiO ₂ , ZnO, TiN,
Metals or semi-metals such as SiN such as Zn, Cu, S, Ni, Cr, Ge, S
e, Cd, Ag, Al, etc. can be used. For the purpose of (d), a metal such as Al or Ag, or an organic thin film having a metallic luster such as a cyanine dye or a methine dye can be used. For the purposes of (e) and (f), an ultraviolet curable resin, a thermosetting resin, a thermoplastic resin or the like can be used. The thickness of the undercoat layer is 50Å to 100μ
m, preferably 200 to 30 μm.

In addition, the protective layer is provided for the purpose of protection from scratches, dust, dirt, etc., and improvement of storage stability and reflectance of the recording layer, and the same material as the undercoat layer may be used as the material thereof. it can. The thickness of the protective layer is 100 Å or more, preferably 1000 Å or more.

At this time, the azurenium salt compound of the general formula [I] of the present invention may be contained in the undercoat layer and / or the protective layer. Further, the undercoat layer or the protective layer may contain a stabilizer, a dispersant, a flame retardant, a lubricant, an antistatic agent, a surfactant, a plasticizer and the like.

Further, as another constitution of the optical recording medium according to the present invention, the recording layer 2 is formed by using two recording mediums of the same constitution shown in FIGS. It may be a so-called air-sun-gate structure that is placed inside and sealed, or may be a so-called close-contact structure (bonding structure) that is adhered via the protective layer 3.

The optical recording medium of the present invention can be recorded by irradiation with a gas laser such as a helium-neon laser (oscillation wavelength 633 nm), but is preferably a laser having a wavelength of 750 nm or more, particularly a gallium-aluminum-arsenic semiconductor laser. A method of recording by irradiation with a laser beam having an oscillation wavelength in the near infrared or infrared region such as (oscillation wavelength of 830 nm) is suitable. Further, the laser beam described above can be used for reading. On this occasion,
Writing and reading can be performed with a laser having the same wavelength, or can be performed with lasers having different wavelengths.

〔Example〕

Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited thereto.

Example 1 A polycarbonate having a diameter of 130 mmφ and a thickness of 1.2 mm and provided with a pre-groove by intrusion molding (hereinafter referred to as “PC”).
(Abbreviated as) azurenium salt compound No.
A solution prepared by dissolving 3 parts by weight of the azurenium salt compound of (1) in 97 parts by weight of diacetone alcohol was applied by a spinner coating method and then dried to obtain an 800 Å organic thin film recording layer.

The optical recording medium thus created was mounted on a turntable, the turntable was rotated by a motor to 1800 rpm, and a semiconductor laser with an oscillation wavelength of 830 nm was used.
Information is written from the substrate side to the recording layer with a spot size of 1.5 μm, a recording power of 6 mW, and a recording frequency of 3 MHz, and read at a read power of 0.8 mW, and the reproduced waveform is spectrum analyzed (scanning filter, band width 30 KHz) and C / The N ratio was measured.

Next, the same recording medium, the recorded portion in said measurement condition was measured C / N ratio after reading repeated 10 ⁵ times.

Furthermore, the same recording medium produced under the above conditions was heated at 60 ° C. and 90 ° C.
The sample was allowed to stand for 2000 hours under the condition of% RH, and the environmental storage stability test was performed, and then the transmittance (830 nm measurement) and the C / N ratio were measured. Table 1 shows the results.

Examples 2 to 9 The compounds of azurenium salt compound No. (1) used in Example 1 were converted into Nos. (2), (4), (8), (12) and (1
In place of 6), (21), (26), and (28), recording media were prepared in the same manner as in Example 1, and optical recording media of Examples 2 to 9 were prepared.

The optical recording media of Examples 2 to 9 were measured in the same manner as in Example 1. The results are shown in Table 2.

Comparative Examples 1 to 3 As a comparison of the asymmetric azurenium salt compounds, the following symmetric azurenium salt compounds No. (31), (32), (33)
Recording media were prepared in the same manner as in Example 1, and Comparative Examples 1 to 3 were prepared.

The optical recording media of Comparative Examples 1 to 3 were measured in the same manner as in Example 1. The results are shown in Table 2.

Compound No. Examples 10 and 11 The following compounds No. (34) and (35) and the azurenium salt compound No. (15) were mixed with diacetone alcohol in a weight ratio of 1: 2, respectively, and the same method as in Example 1 was performed. And an organic thin film recording layer having a dry film thickness of 850Å was provided to prepare optical recording media of Examples 10 and 11, respectively.

The optical recording media of Examples 10 and 11 thus produced were measured in the same manner as in Example 1. Table 3 shows the results.

Comparative Example 4 Except that the compound No. (15) used in Example 10 was omitted.
An optical recording medium was prepared in the same manner as in Example 10, and the same measurement was performed. The results are also shown in Table 3.

Example 12 2 parts by weight of the compound of the above compound No. (3) and a nitrocellulose resin (Ohhales Rucker, Daicel Chemical Co., Ltd.)
Made by mixing 1 part by weight of diacetone alcohol with 97 parts by weight of a spinner coating method to form a pregroove by infusion molding and having a diameter of 130 mmφ and a thickness of 1.2 mm.
It was applied onto a PC substrate to obtain an organic thin film recording layer having a dry film thickness of 1000Å.

The optical recording medium thus prepared was measured in the same manner as in Example 1. The results are shown in Table 4.

Examples 13 to 15 Compound No. (3) used in Example 12 was replaced with the above compound No.
In place of (10), (18) and (22), recording media were prepared in the same manner as in Example 12, and optical recording media of Examples 13 to 15 were prepared.

The optical recording media of Examples 13 to 15 were measured in the same manner as in Example 1. The results are shown in Table 4.

Example 16 A pregroove was prepared by hot pressing on a PC board having a wallet size of 0.4 mm, and 3 parts by weight of the azurenium salt compound No. (1) compound was mixed with 97 parts by weight of diacetone alcohol. The liquid thus obtained was applied by a bar coating method and then dried to obtain an organic thin film recording layer of 1000 liters. Further, it was adhered to a PC substrate having a wallet size of 0.3 mm and a thickness of 0.3 mm through an ethylene-vinyl acetate film via a hot roll method to prepare an optical recording medium having a contact structure.

The optical recording medium thus prepared was mounted on a stage driven in the XY directions, and a semiconductor laser having an oscillation wavelength of 830 nm was used to form a spot size 3.0 on the organic thin film recording layer from the PC substrate side having a thickness of 0.4 mm. Information is written in the Y-axis direction with a recording pulse of 80 μsec with a recording power of 4.0 mW and a reproduction power of 0.4 mW, and the contrast ratio Was measured.

Furthermore, the same recording medium produced under the above conditions was used in Example 1.
An environmental protection stability test was conducted under the same conditions as in 1. and then the transmittance and contrast ratio were measured. The results are shown in Table 5.
Shown in

[Advantages of the Invention] As described above, the optical recording medium of the present invention can improve the stability under high temperature and high humidity environmental conditions without deteriorating the excellent properties of the azulene compound. It was Furthermore, it has excellent solubility in general-purpose solvents,
It has become possible to provide an optical recording medium with excellent productivity that can be directly applied to a substrate that is easily immersed in an organic solvent such as polycarbonate.

[Brief description of drawings]

1 to 4 are sectional views showing embodiments of the optical recording medium of the present invention. 1 ... Substrate 2 ... Recording layer 3 ... Protective layer 4 ... Undercoat layer

Claims (1)

[Claims] 1. An optical recording medium having a recording layer containing an azurenium salt compound represented by the following general formula [I]. However, in the general formula [I], R _{1 to} R ₇ , R ′ _{1 to} R ′ ₇ represent a hydrogen atom, a halogen atom or a substituent which is a monovalent organic residue, and R ₁ and R ₂ , R ₂ R ₃ , R ₃ and R ₄ , R ₄ and R ₅ , R ₅ and R ₆ ,
R ₆ and R _7, R _'1 and R' _2, R _'2 and R' _3, R _'3 and R' _4, R _'4 and R' _5, R a _'5 and R' ₆ and R _'6 it may form a condensed ring unsubstituted or substituted with one combination among the combinations of R _'7. Where R ₁ and R ′ ₁ , R ₂ and R ′ ₂ , R ₃ and R ′ ₃ , R ₄ and R ′ ₄ , R ₅ and R ′ ₅ , R ₆ and R ′ _6, and R ₇ and R ′ ₇ At least one of the combinations is a combination of different substituents.