JPH04267193A - Optical recording medium - Google Patents

Abstract

PURPOSE:To enhance the reflectivity of a recording layer of a write once-type optical recording disc which can be a compact disc. CONSTITUTION:The recording layer of an optical recording medium is composed of a blend of either one or more of the first ion conjugate between color cation such as cyanine color and bisphenylenedithiol, and the second ion conjugate between the anion of a complex of transition metal other than copper of bisphenylenedithiol.

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 particularly to a write-once type optical recording disk compatible with compact disks.

0002

2. Description of the Related Art An optical recording disk on which additional writing or recording can be performed has been proposed in accordance with the compact disk (hereinafter abbreviated as CD) standard (Nikkei Electronics January 23, 1989 issue, No. 465). ,P10
7. Kinki Chemical Society Functional Pigments Subcommittee, March 3, 1989, Osaka Science and Technology Center, SPIE vol.
1078 Optical Data Storage
Topical Meeting, 80 1989
etc).

This material is formed by depositing a recording layer containing a dye, an Au reflective layer, and a protective film in this order on a transparent resin substrate. That is, the reflective layer is provided in close contact with the recording layer.

In particular, in the case of a contact type medium in which such a reflective layer and a recording layer containing a dye are provided in close contact with each other,
The extinction coefficient k of the recording layer at the wavelength of recording light and reproduction light is 0.
．． It must have a predetermined value of 0.02 to 0.05, and the reflectance in the unrecorded area must be 60% or more, particularly 70% or more.

By the way, when a dye layer is used as a recording layer, it is known that the light-absorbing dye has low light resistance, and in particular, when repeated reproduction is performed, the dye undergoes photon mode deterioration, which causes reproduction deterioration. There is.

[0006]

[Problems to be Solved by the Invention] In order to prevent reproduction deterioration of this recording layer and improve light resistance, the present inventors have
It has been proposed to use an ionic combination of a dye cation and an anion of a transition metal complex as a singlet oxygen quencher (JP-A-60-159087, JP-A-60-16).
No. 2691, No. 60-203488, No. 60-163
243 etc.).

[0007] In such a conjugate, a dye cation and a quencher anion exist in a one-to-one ratio.

On the other hand, when a cationic dye and a quencher are mixed to form a recording layer, four types of ions, dye cations, quencher ions, and respective counter ions, are mixed into the dye and quencher. It exists according to the ratio. Therefore, when a conjugate is used, since the respective counterions of the dye and the quencher are not present, regeneration deterioration is further reduced and light resistance is improved compared to a mixed system. Therefore, heat mode regeneration deterioration is reduced, and storage stability is also improved. Furthermore, water resistance etc. are also improved.

Furthermore, in a mixed system, the melting point is lowered, the softening point becomes broader, and the thermal stability is lowered, whereas many of the composites have a high and distinct melting point.

[0010] However, the usual quencher anion is
In particular, k is large. For this reason, if a bonded body is used in a contact type medium, the k of the recording layer in particular increases, and the reflectance decreases, making it impossible to perform good reproduction. Therefore, in order to control k to a predetermined value,
It is necessary to further mix other light-absorbing dyes with low k values, resulting in a decrease in light resistance, thermal stability, etc.

[0011] As described above, the reality is that the adhesive type media do not take full advantage of the advantages of the bonded body, which exhibits excellent light resistance.

The main object of the present invention is to have sufficient light resistance, heat resistance and water resistance, as well as sufficient sensitivity, output and C/N.
The object of the present invention is to provide a contact type optical recording medium that provides the following.

[0013]

[Means for Solving the Problems] Such objects are achieved by the present invention as set forth in claims (1) to (5) below.

(1) An optical recording medium comprising a recording layer containing a dye on a substrate, and a reflective layer laminated in close contact with the recording layer, wherein the recording layer contains a dye cation. and an anion of a copper complex of bisphenylene dithiol, and an ionic combination of a dye cation and an anion of a transition metal complex other than copper of bisphenylene dithiol. optical recording medium.

(2) When the reproduction light is irradiated from the substrate side, the reflectance of the unrecorded portion is 60% or more, and the reflectance of the recorded portion is 60% or less of the reflectance of the unrecorded portion. ).

(3) The optical recording medium according to (1) or (2) above, wherein the recording layer has an extinction coefficient k of 0.02 to 0.25 at the wavelengths of recording light and reproduction light.

(4) The optical recording medium according to any one of (1) to (3) above, wherein the dye cation is a cyanine dye cation.

(5) The optical recording medium according to (4) above, wherein the cyanine dye cation is an indolenine cyanine dye cation.

[0019]

[Function] In the present invention, in the recording layer, a dye cation and an anion of a copper complex of bisphenylene dithiol are added to the recording layer.
and an ionic binder in which copper in the complex anion of the first ionic binder is replaced with a transition metal other than copper is used. This mixture of ionic binders has a small extinction coefficient k of 0.02 to 0.05, and k can be controlled to a predetermined value depending on the mixing ratio.
Good recording and reproducing characteristics can be obtained.

[0020]

[Specific Configuration] The specific configuration of the present invention will be explained in detail below.

FIG. 1 shows an example of the optical recording medium 1 of the present invention. This optical recording medium 1 is of a contact type, having a recording layer 3 containing a dye on a substrate 2, and a reflective layer 4 and a protective film 5 formed in close contact with the recording layer 3.

The substrate 2 receives recording light and reproducing light (600~
Substantially transparent (about 900 nm, especially about 770 to 830 nm, especially 780 nm)
It is preferably made of resin or glass with a transmittance of 80% or more. This allows recording and reproduction from the back side of the substrate. The substrate 2 is in the shape of a normal size disk, and when used as a CD, the thickness is 1.2 m.
The diameter is approximately 80 to 120 mm.

In this case, it is preferable to use resin as the substrate material, and various thermoplastic resins such as polycarbonate resin, acrylic resin, amorphous polyolefin, and TPX are suitable. In addition, if necessary, at least one of the outer surface and the inner surface of the substrate 2, and if necessary,
An oxygen-blocking film may be formed on the inner and outer peripheral surfaces.

It is preferable that a groove for tracking is formed on the surface of the substrate 2 on which the recording layer 3 is formed. The groove is preferably a continuous spiral groove, with a depth of 250 to 1800A and a width of 0.3 to 1.1
μm, especially 0.4 to 0.6 μm, land (portion between adjacent grooves) width 0.5 to 1.3 μm,
In particular, it is preferably 1.0 to 1.2 μm.

By configuring the groove in this manner, a good tracking signal can be obtained without lowering the reflection level of the groove portion. Incidentally, the groove can also be provided with concavities and convexities for address signals.

In the present invention, when the substrate has a groove, it is preferable that the recording light be irradiated onto the recording layer within the groove. That is, the optical recording medium of the present invention is preferably used as an optical recording medium for groove recording. By performing groove recording, the effective thickness of the recording layer can be increased.

Furthermore, a resin layer (not shown) may be formed on the substrate 2 by, for example, the 2P method, and the resin layer may be provided with grooves for tracking and irregularities for address signals. There is no particular restriction on the resin material constituting the resin layer, and it may be appropriately selected from known resins used in the so-called 2P method.
Radiation curable compounds are used. Note that the hub may be integrated into the substrate. It is preferable that glass fiber be mixed into the hub to prevent breakage and cracks.

The recording layer 3 contains a mixture of combinations described below, and the extinction coefficient (imaginary part of the complex refractive index) k of the recording layer 3 at the recording and reproducing light wavelengths is 0.02 to 0.05. , particularly preferably 0.03 to 0.05.

When k is less than 0.02, the absorption rate of the recording layer decreases, making it difficult to perform recording with normal recording power. Moreover, when k exceeds 0.05, the reflectance becomes 60
%, making it difficult to perform playback according to the CD standard.

The reflectance of the recording layer also changes depending on k, but even if k is constant, the reflectance changes when the film thickness is changed. Therefore, setting the film thickness is important, including other characteristics. For example, when k=0.04, as shown in FIG.
At 3200A, a reflectance of 70% or more can be obtained. In this case, FIG. 2 shows a polycarbonate substrate (n=1.5
8. Graph of reflectance when a recording layer of n=2.5 and k=0.4 with different film thicknesses is formed on top of (k=0), and a 1000A Au reflective layer is formed on top of this. , which is in good agreement with the simulation results.

The refractive index (real part of the complex refractive index) n of the recording layer is 1.8 to 4.0, more preferably 2.2 to 3.
．． It is preferable that it is 3. When n<1.8, the reflectance decreases and reproduction according to the CD standard tends to become difficult. Moreover, in order to make n>4.0, it is difficult to obtain raw material pigments.

The conjugates used are first and second ionic conjugates of a dye cation and a singlet oxygen quencher anion.

The anion of the singlet oxygen quencher of the first ionic binder used is an anion of a copper complex of bisphenylene dithiol, and the one represented by the formula 1 is particularly preferable.

[0034]

[Chemical formula 1]

In formula 1, R1 to R4 are each a hydrogen atom, preferably an alkyl group having 1 to 8 carbon atoms, a halogen atom, an amino group, or an amino group having 1 carbon atom.
It is preferable that it is an amino group substituted with an alkyl group of -5 or the like.

These quencher anions are usually 4
A cation such as a class ammonium ion is present as a counter ion. Such a quencher can be easily synthesized according to conventional methods.

The k of such a copper complex is very small, 6
It becomes almost 0 in the range of 00 to 900 nm. And the k of the conjugate obtained from these quencher anions is
It is approximately equal to or slightly smaller than k of the dye cation. In addition, due to the properties of the dye cation, the wavelength dependence of k of the conjugate is either flat with respect to wavelength or k on the short wavelength side.
tends to become larger.

Specific examples of anionic quenchers having a quencher anion Q- represented by formula 1 are listed below.

In the following, when any one of R1 to R4 is H, it will not be displayed.

[0040]

The anion of the singlet oxygen quencher of the second ionic bond is an anion of a complex of bisphenylene dithiol with a transition metal other than copper, and the one represented by formula 2 is particularly preferred.

[0042]

[Case 2]

In Chemical Formula 2, R1 to R4 have the same meanings as above, and M represents a transition metal atom such as Ni, Co, Pd, Pb, etc.

Specific examples of anionic quenchers having a quencher anion Q'- represented by the formula 2 are given below.

[0045]

These quencher anions, unlike copper complexes, have a relatively large k in the range of 600 to 900 nm. Therefore, the k of the conjugate using these is generally larger than the k of the dye cation. This tendency is particularly noticeable on the long wavelength side, and by selecting a dye cation, if the first conjugate using a copper complex has wavelength dependence, the second conjugate can have an opposite wavelength dependence. By mixing these, the k of the first conjugate can be
By compensating for the wavelength dependence of k, it is possible to form an extremely flat recording layer with a wavelength dependence of k at a predetermined value of k.

The light-absorbing cationic dye used in the first and second ionic binders of the present invention is not particularly limited, and has an absorption maximum of 600 to 900 nm, preferably 600 to 900 nm.
Cationic dyes with a wavelength of 800 nm, more preferably 650 to 750 nm, such as cyanine dyes, pyrylium dyes,
Although thiapyrylium dyes, azulenium dyes, etc. can be used, cyanine dyes are preferred. The cyanine dye is particularly preferably an indolenine-based cyanine dye having an indolenine ring, a benzindolenine ring, a dibenzoindolenine ring, or the like. Indolenine cyanine dyes may have a bilaterally symmetrical structure, but in order to improve solubility, it is necessary to have an asymmetrical ring structure, and in addition to or in place of this, an asymmetrical N-alkyl group. It is preferable to have Specific examples of dyes having particularly suitable dye cations are listed below.

[0048]

[Chemical 3]

[0049]

[C4]

[0050]

[C5]

These dye cations combine with various acid anions to form cationic dyes.

Such a cationic dye and anionic quencher can be easily synthesized as a combination of a dye cation and a quencher anion by the method described in the above publication.

Specific examples of the conjugates of the present invention are listed below. In addition, for example, the anion of the above quencher Q1 is Q-
1. The cation of dye D1 is expressed as D+ 1, etc.

First ionic binder C1 D+ 1 Q
−1C2 D+ 2
Q- 1C3 D+ 3
Q- 1C4 D+ 4
Q-1C5D
+ 5 Q- 1C6
D+ 6 Q- 1C7
D+ 7 Q- 1C8
D+ 8 Q- 1C
9 D+ 1 Q-
5C10 D+ 1
Q- 6C11 D+ 3
Q- 6C12 D+ 4
Q-6

The k of these first ionic bonds is about 0 to 0.01, and n is about 2.2 to 2.6.

Second ionic binder C20 D+ 2 Q'
-1C21 D+ 3
Q'-1C22 D+ 4
Q'-1C23 D+ 5
Q'-1C24 D+ 6
Q'-1C25 D+ 7
Q'-1C26 D+
2 Q'-2C27
D+ 2 Q'-3C28
D+ 2 Q'-4C29
D+ 2 Q'-5C30
D+ 2 Q'-6C31
D+ 7 Q'-5

[
[0057] The k of these second ionic binders is 0.005.
~0.2, and n is approximately 2.2 to 2.6.

In the present invention, the first ionic bond of Q-, which is a copper complex as an anion of the singlet oxygen quencher, and a dye cation, and a transition compound in which the central metal is other than copper, preferably represented by the formula 2, are used. Cation Q' of metal complex
The recording layer is formed using one or a mixture of two or more of the second ionic bond of - and the dye cation.

The mixing ratio of the first conjugate D+ Q- and the second conjugate D+ Q'- is such that the extinction coefficient k is 0.0.
It may be determined to have a predetermined value of 3 to 0.05, but the molar ratio of D+ Q- /D+ Q'- is 1:0.
The ratio is preferably 0.05 to 1:50, particularly 1:0.1 to 1:10.

Furthermore, by mixing the first and second conjugates, it is possible to set appropriate n and k values at all times in the range of 770 to 830 nm, for example.

When measuring n and k, a measurement sample is prepared by depositing a recording layer on a predetermined transparent substrate to a thickness of, for example, about 400 to 800 Å under actual conditions. Next, the reflectance through the substrate or from the recording layer side is measured. The reflectance is measured by specular reflection (approximately 5°) using the recording/reproducing light wavelength. Also, measure the transmittance of the sample. From these measured values, for example, according to Kyoritsu Zensho "Optics" Kozo Ishiguro P168-178, n, k
All you have to do is calculate.

The recording layer of the present invention may be formed from one or more of the copper complex anion bond and the nickel complex anion bond, respectively. In addition, other light-absorbing dyes, quenchers, and conjugates may be contained. However, the first and second combinations of the present invention can be used in a total of 80 to 80% of the recording layer.
Preferably, it accounts for 100% by weight.

[0063] The thickness of such recording layer 3 is 1000~
It is preferable to set it to 3000A. Outside this range, the reflectance may be too high, resulting in low sensitivity, or conversely, a decrease in sensitivity, or even an increase in jitter, making it difficult to perform reproduction in accordance with the CD standard.

[0064] Although there is no particular restriction on the method of forming the recording layer 3,
In the present invention, it is preferable to apply the layer by coating, since the flexibility and ease of dye selection, medium design, and manufacturing are further expanded. For coating the recording layer 3, ketone type, ester type, ether type, aromatic type, halogenated alkyl type,
Various solvents such as alcohol-based solvents can be used, and there is a great degree of freedom in solvent selection. For application, spin coating or the like may be used. Note that the recording layer 3 may be formed of a vapor-deposited film depending on the case.

A reflective layer is provided in direct contact with such recording layer 3. The reflective layer 4 may be made of a high reflectivity metal or alloy such as Au, Ag, or Cu.

The thickness of the reflective layer 4 is preferably 500 Å or more, and may be deposited by vapor deposition, sputtering, or the like. There is no particular limit to the upper limit of the thickness, but in consideration of cost, production time, etc., it is preferably about 1200 A or less. As a result, 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.

Preferably, a protective film 5 is provided on the reflective layer 4. The protective film 5 may be formed of various resin materials such as ultraviolet curing resin, and usually has a thickness of about 0.1 to 100 μm. The protective film 5 may be in the form of a layer or a sheet.

The protective film 9 is preferably a radiation-cured coating film containing a radiation-curable compound and a photopolymerizable sensitizer. The hardness of the protective film 5 is 25
Pencil hardness (JIS K-5400) at °C, H
-8H, especially 2H-7H. With this configuration, the eye pattern becomes good and jitter is significantly reduced. In addition, even when stored under high temperature/humidity or changing temperature/humidity conditions,
Peeling between the protective film and the reflective layer does not occur. More specifically,
If the hardness of the protective film is softer than H, the eye pattern will be distorted.
If the jitter increases and the coating becomes harder than 8H, the coating film becomes brittle and the film forming ability decreases, and the adhesive force with the reflective layer decreases.

[0069] The radiation-curable compound used for forming such a protective film preferably contains oligoester acrylate. Oligoester acrylate is an oligoester compound having multiple acrylate groups or methacrylate groups. Preferable oligoester acrylates have a molecular weight of 1,000 to 10,000;
Preferably 2,000 to 7,000, and the degree of polymerization is 2 to 1.
0, preferably 3 to 5. Also, among these, 2 acrylate groups or methacrylate groups
Polyfunctional oligoester acrylates having ~6, preferably 3 to 6 are preferred. Further, in addition to or in place of the above-mentioned compounds, a radiation-curable compound obtained by radiation-sensitizing a thermoplastic resin may be used.

The thickness of the protective film of such a radiation-curable compound is 0.1 to 30 μm, more preferably 1 to 10 μm.
It is m. When the film thickness is less than 0.1 μm, it is difficult to form a uniform film, the moisture-proofing effect in a humid atmosphere is insufficient, and the durability of the recording layer decreases. Moreover, the jitter prevention effect is reduced. If the thickness exceeds 30 μm, the recording medium tends to warp and cracks in the protective film tend to occur due to shrinkage during curing of the resin film.

[0071] Such a coating film is usually formed by spinner coating, gravure coating, spray coating, dipping, etc.
The layer may be formed by combining various known methods. The conditions for forming the coating film at this time may be appropriately determined in consideration of the viscosity of the mixture of coating film composition, the intended coating thickness, etc.

[0072] Examples of the radiation irradiated for curing the protective film include ultraviolet rays and electron beams, but ultraviolet rays are preferred. When ultraviolet rays are used, a photopolymerizable sensitizer is usually added to the radiation-curable compound as described above.

Examples of photopolymerization sensitizers include benzoin series such as benzoin methyl ether, benzoin ethyl ether, α-methylbenzoin, α-chlordeoxybenzoin, benzophenone, acetophenone, morpholinodimethylmethyl-4-methylthiophenyl ketone,
Examples include ketones such as bisdialkylaminobenzophenone, quinones such as anthraquinone and phenanthraquinone, and sulfides such as benzyl disulfide and tetramethylthiuram monosulfide.

[0074] A coating film containing such a photopolymerizable sensitizer and a radiation-curable compound can be cured by ultraviolet rays by various known methods. For example, an ultraviolet light bulb such as a xenon discharge tube or a mercury discharge tube may be used. Moreover, an electron beam can also be used depending on the case.

To perform recording or additional writing on the optical recording medium 1 having such a structure, recording light of, for example, 780 nm is irradiated in a pulsed manner through the substrate 2.

As a result, the recording layer 3 absorbs light and generates heat, and the substrate 2 is also heated at the same time. As a result, the recording layer material such as the dye is melted or decomposed near the interface between the substrate 2 and the recording layer 3, and pressure is applied to the interface between the recording layer 3 and the substrate 2, causing the bottom wall and side wall of the groove 23 to be damaged. Transform.

In this case, a decomposed product layer 61 containing melted or decomposed products of the recording layer 3 usually remains in a shape that covers the bottom of the groove 23 and the boundary with the substrate 2. Moreover, since the surface layer of the substrate has a predetermined thermal softening point, the decomposed product layer 61 further penetrates into the substrate side in a convex shape, and the shape of the pit portion 6 is formed larger. The amount of dent in the substrate 2 is the pit portion 6
The larger the size, the larger the depth, and the depth is about 300A or less.

The material of the decomposed product layer 61 is a material that does not substantially contain the substrate material, and is composed of a decomposed product of the recording layer material or a mixture of the decomposed product of the recording layer material and the recording layer material. The thickness of the decomposed product layer 61 is usually about 30 to 100% of the thickness of the recording layer 3 in the groove. Usually, a void is formed on the decomposed product layer 61 at the interface with the reflective layer, and the decomposed product layer 61 and the void 63 are formed in the pit portion 6 . The void 63 is usually 5 to 70% of the thickness of the recording layer 3.
It is about the same thickness.

Further, the external shape and concave shape of the pit portion are also good. Further, due to the presence of the skin layer, the pit shape becomes larger and better, resulting in improved C/N and improved sensitivity.

[0080]

[Examples] Hereinafter, the present invention will be explained in more detail by giving specific examples of the present invention.

Example 1 A recording layer containing a dye was formed on a polycarbonate substrate having tracking grooves.

The recording layer was formed by spin coating while rotating the substrate at 500 rpm. A 3.5 wt % diacetone alcohol solution was used as the coating solution. The thickness of the dye layer after drying was 2000 Å.

The dye contained in the recording layer is the above-mentioned D+1.
using the copper complex Q-1 as a quencher and the ionic conjugate D+ 1Q-1(C1) of the above combination.
was created.

Apart from this, a complex Q'- in which the central metal of D+ 2 and chemical formula 2 as a quencher is nickel.
An ionic conjugate D+ 1Q'-1 (C20) was prepared from 1 and C1 and C20 were mixed.

The mixing ratio of the two types of ionic binders C1 and C20, the refractive index (n) and extinction coefficient (k) of the recording layer at 770, 780 and 790 nm, and the melting point (
mp) are shown in Table 1 below. n and k were determined by forming a film containing the above-mentioned dye on a measurement substrate to a dry film thickness of 600 Å to form a test recording layer, and measuring n and k of this test recording layer. This measurement was carried out in accordance with the description in "Optics" (written by Kozo Ishiguro, published by Kyoritsu Zensho), pages 168 to 178.

[0086]

[Table 1]

On this recording layer, A is deposited by sputtering.
A reflective layer was formed by forming an n film to a thickness of 1000 Å, and a protective film was further formed.

The protective film was formed by spinner coating a coating composition containing the following radiation-curable compound and photopolymerizable sensitizer.

(Coating composition) Multifunctional oligoester acrylate [30% by weight of oligoester acrylate (trifunctional or higher), 70% by weight of trimethylpropane acrylate, trade name Aronix M-8030; manufactured by Toagosei Co., Ltd.]
100 parts by weight photopolymerizable sensitizer (Compound A: trade name IRGACURE907; manufactured by Nippon Ciba Geigy)


5 parts by weight

After coating the coating composition, it was cross-linked and cured by irradiation with ultraviolet rays of 120 W/cm for 15 seconds to form a cured film. The pencil hardness of this film was 2H.

For each sample obtained, a wavelength of 780n
Compact disc signals were recorded using a 7 mW laser and then reproduced using a commercially available compact disc player.

As a result, a reflectance of 70% or more was obtained in the unrecorded area, and the reflectance of the recorded area of the 11T pulse of the CD signal was 40% or less of that of the unrecorded area, allowing for good recording and reproduction. I was able to do that.

[0093] Also, for this sample, 0.5kw of X
Irradiate the e-lamp through the substrate from a distance of 15 cm,
Light resistance was evaluated by measuring the dye residual rate after 20 hours.

[0094] The dye residual rate is (100-R)/(100
-R0) [where R0 and R are the reflectances at 780 nm at the initial stage and after irradiation, respectively]. The results are shown in Table 2.

Furthermore, 70°C, relative humidity 10% and 6
The samples were stored at 0° C. and 90% relative humidity for 250 hours and 500 hours, respectively, and regenerated after storage to evaluate heat resistance and humidity resistance.

The evaluation is as follows. ○: No increase in errors △: There is some increase in errors ×: error increase

The results are shown in Table 2.

[0098]

[Table 2]

From the results shown in Tables 1 and 2, it can be seen that the recording layer using the composite of the present invention has predetermined values of n, k and reflectance, and exhibits good recording and reproducing characteristics. Furthermore, it can be seen that the light resistance, heat resistance, and moisture resistance exhibit significantly superior properties compared to the mixed system.

Example 2 Sample No. 1 was prepared in the same manner as in Example 1, except that the bond was changed to C7 and C25 and the recording layer composition shown in Table 1 was used.
2 was prepared and the same evaluation was performed. The results are shown in Tables 1 and 2. This material also exhibited good characteristics as a recording layer.

Example 3 Sample No. 3 was prepared in the same manner except that the first conjugate was C6 and the second conjugate was C25. 3 was prepared and the same evaluation was performed. The results are also listed in Tables 1 and 2.

Comparative Example 1 Sample No. 4 was prepared and the same evaluation was performed. The results are also listed in Tables 1 and 2.

Comparative Example 2 Sample No. 2 was prepared by incorporating C20, the ionic binder used in Example 1, alone on the recording layer. 5 was prepared and the same evaluation was performed. The results are also listed in Tables 1 and 2.

From the above results, sample No. of the present invention.
1~No. Sample No. 3 is a comparative example. 4 and no.
．． It is clear that it gives better results than 5.

[0105]

[Effect of the invention] According to the present invention, it has high reflectance, light resistance,
An optical recording medium having a recording layer with high durability such as heat resistance and moisture resistance can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a partial cross-sectional view showing one example of an optical recording medium of the present invention.

FIG. 2 is a graph showing changes in reflectance when the thickness of the recording layer is changed.

[Explanation of symbols]

1 Optical recording medium 2　　　　Substrate 21 Land section 23 Groove 24 Board pit part 3 Recording layer 4 Reflective layer 5 Protective film 6 Pit part 61　Decomposed product layer 63 void

Claims (5)

[Claims] 1. An optical recording medium comprising a recording layer containing a dye on a substrate, and a reflective layer laminated in close contact with the recording layer, the recording layer comprising a dye cation and a reflective layer. An ionic bond of bisphenylene dithiol with an anion of a copper complex, and an ionic bond of a dye cation with an anion of a transition metal complex other than copper of bisphenylene dithiol.
An optical recording medium characterized by containing a mixture of at least one species. 2. The substrate according to claim 1, wherein when the reproduction light is irradiated from the substrate side, the reflectance of the unrecorded portion is 60% or more, and the reflectance of the recorded portion is 60% or less of the reflectance of the unrecorded portion. The optical recording medium described. 3. The optical recording medium according to claim 1, wherein the recording layer has an extinction coefficient k of 0.02 to 0.05 at the wavelengths of recording light and reproduction light. 4. The optical recording medium according to claim 1, wherein the dye cation is a cyanine dye cation. 5. The optical recording medium according to claim 4, wherein the cyanine dye cation is an indolenine cyanine dye cation.