JP3257082B2 - Optical information media - 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 information medium,
In particular, the present invention relates to an optical information medium using an organic dye for a reflective layer.

[0002]

2. Description of the Related Art An optical system in which laser light is condensed on a reflection layer having projections and depressions corresponding to an information signal, and information is reproduced based on a difference in the amount of reflected light reflected at the depression and the projection. Information media are known.

[0003] For example, an Al film is widely used as a reflective layer, and the user writes information by forming further unevenness by the user in addition to the previously formed unevenness.
Information cannot be erased. Therefore, the Al film is
Applications are limited to read-only optical disks.

On the other hand, in recent years, attempts have been made to use a dye-containing layer as a reflective layer. The dye-containing layer is composed of, for example, an organic dye and a polymer material.When the laser light is condensed, the organic dye absorbs the laser light to generate heat, and this heat causes local thermal deformation, for example, expansion. Occurs. As a result, it is possible to erase information by further writing information or by devising the configuration. In addition to a read-only type, a write-once type, in which a user can write once, and a repetitive write / erase type, are possible. It is also expected as a reflective layer of a rewritable optical information medium. For example, as an organic dye contained in the dye-containing layer, a cyanine dye shown in Chemical formula 6 is generally used.

[0005]

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[0006]

However, an optical information medium using a cyanine dye has a problem in storage stability. For example, the optical information medium is set to a temperature of 85 ° C. and a relative humidity of 8
When left in a 5% environment for 96 hours, the maximum absorption wavelength λma
The absorbance at x sharply decreases, the reflectance changes, and the sensitivity of recording and reproduction deteriorates.

Accordingly, the present invention has been proposed in view of such a conventional situation, and can be used not only as a read-only type but also as a write-once type and a rewritable type.
Moreover, an object of the present invention is to provide an optical information medium having excellent storage stability.

[0008]

Means for Solving the Problems As a result of diligent studies conducted by the present inventors to achieve the above object, the optical characteristics of an optical information medium using the above-mentioned cyanine dye are liable to deteriorate. This is because the ionic radius of the counter ion of the cyanine dye is small, and when the ionic radius of the counter ion is large as the cyanine dye, particularly, when the ionic radius is 0.294 nm or more, the optical characteristics are stable. We came to the knowledge that it would be excellent.

The optical information medium of the present invention has been completed based on such findings, and is an optical information medium comprising a dye-containing layer containing a cyanine dye formed on a transparent substrate. It has a cyanine dye containing a first dye represented by Chemical Formula 7 and a second dye represented by Chemical Formula 8, and has an ion radius of 0.294 nm or more. It has as a counter ion of a cyanine dye.

[0010]

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[0011]

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[0012]

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[0013]

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[0014]

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In the optical information medium of the present invention, a dye-containing layer 2 is formed on a transparent substrate 1 as shown in FIG.

The transparent substrate 1 is made of an optically homogeneous material, and a wide range of materials such as polymer materials such as polycarbonate, polymethyl methacrylate, polyolefin and epoxy resin and glass can be used. On the surface of the transparent substrate 1 on which the dye-containing layer 2 is provided, for example, when the optical information medium is used as a write-once type or a rewritable type, recording tracks for servo and address code pits are provided. When used as a reproduction-only type, information pits corresponding to information signals are further provided.

The dye-containing layer is composed of a cyanine dye alone or a cyanine dye and a polymer material.

In the present invention, a cyanine dye having a counter ion ionic radius of 0.294 nm or more is used for the purpose of improving storage stability.

That is, in the optical information medium, the deterioration of the optical characteristics during storage is caused by the fact that the counter ion of the cyanine dye accepts water molecules in the external environment and is affected by its polarity. it is conceivable that. The acceptability of a counter ion for a water molecule depends on the activity of the counter ion, for example, the magnitude of the electrostatic free energy. Would be easily accepted.

Here, the electrostatic free energy of the ion is
By regarding the ions as a conductive hard sphere having an electric charge ze and a radius r, the conductive hard sphere is converted from a vacuum into a dielectric constant D (water: 78.
It can be obtained by the Born's equation, which considers the electrostatic free energy when transferred to the solvent of 54). ΔGel ⁰ = −Nz ² e ² / 2r (1-1 / D) Equation of bone As shown from this equation, the smaller the ion radius r, the larger the negative number of the electrostatic free energy of the ion. On the contrary, if the radius r is large, the magnitude of the negative number of the electrostatic free energy is small, and it is difficult to accept water molecules. Accordingly, in a dye-containing layer using a cyanine dye having a counter ion having a large radius r of 0.294 nm or more, the number of water molecules accepted by the counter ion is small, so that the influence is small, and stable optical characteristics are exhibited. .

Incidentally, the counter ion I ⁻ of the conventionally used cyanine dye has an ionic radius of 0.2.
It is as small as 06 nm. Therefore, the magnitude of the negative number of the electrostatic free energy is large (the electrostatic free energy ΔGel).
⁰ : -2.105), high activity. For this reason, it is presumed that the conventional optical information medium causes significant deterioration of the optical characteristics.

The counter ion of a cyanine dye having an ionic radius of 0.294 nm or more includes [C ₆ F
₅ ] ₄ B ⁻ , [C ₆ H ₁₁ Ph] ₄ B ⁻ , [TR
PPh] ₄ B— ^{and the} like.

When the dye-containing layer is composed of a cyanine dye and a polymer material, the polymer material is preferably selected in consideration of the compatibility with the dye. For example, polybutyl butyral, polyvinyl acetoacetal, or the like is used. Can be

Further, an additive may be added to the organic dye-containing layer for the purpose of preventing photo-fading of the dye. As the additive, those having an electron donating property such as amines and those having an energy level lower than the energy level of an excited state of a dye such as a nickel complex are used.

[0025]

In an optical information medium in which a dye-containing layer containing a cyanine dye is formed on a substrate, the ion radius of a counter ion as a cyanine dye is 0.294 nm.
When these are used, even when stored in a high-temperature, high-humidity environment, the optical characteristics are hardly deteriorated, and excellent storage properties are exhibited.

This is considered to be due to the following reasons.

That is, the deterioration of the optical properties of the dye-containing layer is caused by the fact that water molecules in the storage environment are accepted by the counter ion of each cyanine dye, and the structure is affected by the polarity of the accepted water molecules. It is thought that there is. Here, the ease of accepting water molecules as counter ions depends on the ionic radius. Counter ions having a large ionic radius of 0.294 nm or more have low activity and are difficult to accept water molecules in the external environment. Therefore, the dye-containing layer using a cyanine dye having such a counter ion, even if left in a high-temperature and high-humidity environment, has a small influence on the counter ion because the water molecules accepted by the counter ion are small and have good optical characteristics. Will be maintained.

[0028]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described based on experimental results. Experimental Example 1 In this experimental example, an optical information medium was produced using various cyanine dyes having different ion radii of counter ions, and the storage stability thereof was examined.

Examples of the cyanine dyes, the counter ion is I ^- those of (I ^{- -} cyanine, manufactured by Nippon photosensitive dye, Inc.
Product name NK529), counter ions are BF ₄ ^- of those (BF ₄ ^{- -} those of (ClO ₄ ^{- -} cyanine, Japan photosensitive dye trade name NK3750), the counter ion is ClO ₄ - cyanine, manufactured by Nippon photosensitive dye, Inc. Product name NK2670), the counter ion is PF ₆ ^- of those (PF ₆ ^{- -} using cyanine, the four types of Nippon photosensitive dye trade name NK3751). Table 1 shows the structure of the cyanine dye, and Table 1 shows the ion radius of the counter ion of the cyanine dye.

The ion radius of BF ₄ ⁻ among the ion radii of the counter ions shown in Table 1 is obtained by assuming that BF ₄ ⁻ is a tetrahedron, and the bond distance between BF and F Is the sum of the van der Waals radii. Further, ClO ₄ ^- ionic radius of, ClO ₄ ^-
Is a tetrahedron, and is obtained by adding the bond distance of Cl-O and the van der Waals radius of O. PF ₆ ^- ion radius of, PF ₆ ^- which was calculated on the assumption that the a regular octahedron, in which the sum of the van der Waals radii of bond radius and F of PF.

[0031]

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[0032]

Table 1 Various optical information media were prepared using these cyanine dyes. The produced optical information medium has a dye-containing layer formed on a substrate on which concavities and convexities corresponding to information signals are formed, and multiplexes light at the dye-containing layer / transparent substrate interface and the dye-containing layer / air interface. This is a read-only optical information recording medium that reproduces a signal using interference.

First, the following materials were mixed at a predetermined composition ratio to prepare a pigment-containing paint.

Materials and Composition Ratio of Dye-Containing Paint First Organic Dye (Cyanine Dye) Second Organic Dye (SRC, trade name SRC-8) Singlet oxygen inactivator (Nippon Kayaku Co., Ltd. Name IRG-00
3) Polymer material (polyvinyl acetoacetal, manufactured by Denki Kagaku Kogyo) Solvent (3-hydroxy-3-methyl-2-butanone, manufactured by Tokyo Chemical Industry Co., Ltd.) First organic dye: second organic dye: singlet Oxygen quencher:
Polymer material: solvent = 1: 1: 0.2: 1.5: 100 The structures of the second organic dye and the singlet oxygen inactivator are shown in Chemical formulas 13 and 14, respectively. Table 2 shows the types of cyanine dyes used.

[0035]

[Table 2]

[0036]

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[0037]

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This pigment-containing paint is applied on a polycarbonate substrate on which irregularities corresponding to information signals have been cut to form a pigment-containing layer.
~ Medium 4) was prepared. The real part n of the refractive index at the wavelength of the semiconductor laser light (780 nm) of the formed dye-containing layer was 1.84 or more.

Each optical information medium produced in this manner was left for 96 hours in a high-temperature and high-humidity tank at a temperature of 85 ° C. and a relative humidity of 85%. Then, the absorption spectrum and the reflectance of the portion corresponding to the convex portion of the substrate were measured, and the change due to standing was examined. FIGS. 2 to 5 also show the absorption spectra before and after standing, and show the maximum absorption wavelength λ of the absorption spectrum before standing.
Table 3 shows the absorbance at max. Table 4 shows the reflectance before and after standing, and FIG. 6 shows the relationship between the ion radius of the counter ion and the amount of change in the reflectance.

[0040]

[Table 3]

[0041]

[Table 4]

As can be seen from FIGS. 2 to 5 and Table 3, in the above-mentioned optical information medium, a phenomenon is observed in which the absorption spectrum changes before and after standing, and in particular, the absorbance at the maximum absorption wavelength decreases. However, the rate of decrease in the absorbance differs depending on the cyanine dye used, and when I ⁻ − cyanine is used, when BF ₄ ⁻ − cyanine is used, when ClO ₄ ⁻ − cyanine is used, PF ₆ ⁻
-The order is larger in the case of using cyanine, that is, the smaller the ion radius of the counter ion of the cyanine dye is, the smaller the value is.

Further, as can be seen from Table 4 and FIG. 6, the reflectance also shows a similar tendency, and decreases with standing, but this reduction also occurs when the ion radius of the counter ion of the cyanine dye is large. It can be kept small.
In addition, the amount of change in reflectance must be practically kept within 25%. However, if a cyanine dye having a counter ion ion radius of 0.294 nm or more is used, this condition can be satisfied. Is clear from FIG.

Therefore, from this fact, it is effective to regulate the ionic radius of the counter ion as a cyanine dye in an optical information medium in order to make the optical characteristics less likely to deteriorate and excellent in storage stability. all right.

Causes deterioration of the optical properties of the dye-containing layer.
Examination of Inducing Factors As described above, the optical properties of cyanine dyes are significantly degraded as the ion radius of the counter ion is smaller. Inducing factors that cause such optical property degradation include:
Water molecules present in heat or in a standing environment are conceivable. Thus, the effects of heat and water molecules on the above four types of cyanine dyes were examined as follows.

First, the effect of heat on the cyanine dye is
It was examined by Tg-DTA (thermogravimetric analysis). FIGS. 7 to 10 show the Tg-DTA curves of the respective cyanine dyes.
Table 5 shows the melting points determined by the TA curve.

[0047]

[Table 5]

As can be seen from FIGS. 7 to 10 and Table 5,
All four types of cyanine dyes have melting points around 260 ° C. This indicates that the four types of cyanine dyes have almost no difference in heat stability. If the above optical property deterioration is induced by heat, the magnitude of the optical property deterioration differs depending on the type of the cyanine dye as shown in Experimental Example 1, so that even in the four kinds of cyanine dyes, There should be differences in thermal stability. The fact that there is no difference in thermal stability between the four types of cyanine dyes indicates that the above optical property deterioration is not caused by heat.

Next, the influence of water molecules in the standing environment on the cyanine dye was examined as follows. First, a cyanine dye cyclohexanone solution was spin-coated on a slide glass to form a cyanine dye thin film. Then
About this cyanine dye thin film, temperature 22 degrees (room temperature),
It was left in a high-temperature and high-humidity tank maintained at a relative humidity of 90% for 240 hours, and a change in absorption spectrum was observed. FIG. 1 shows the absorption spectra before and after leaving each cyanine dye thin film.
1 to 14 show the absorbance at the maximum absorption wavelength λmax of the absorption spectrum before standing.

[0050]

[Table 6]

As can be seen from FIGS. 11 to 14 and Table 6, the absorption spectrum of the cyanine dye thin film changes upon standing, and the absorbance at the maximum absorption wavelength λmax decreases. Rate of decrease in absorbance will depend cyanine dye used, I ^- - the case of using the cyanine, BF
₄ ^- - the case of using the cyanine, ClO 4 _- ^- the case of using the cyanine, PF 6 _- ^- in the order in the case of using the cyanine, i.e. large enough if the ionic radius of the counter ion of cyanine dyes is small. (In particular, the counter ion of the ionic radius is smallest I ^- - Cyanine a maximum absorption wavelength by the high humidity environment left is 668.4
Short wavelength shift from nm to 662.8 nm. This is similar to the tendency of the above-mentioned optical characteristic deterioration. This suggests that the deterioration of the optical characteristics is induced by water molecules in the neglected environment.

The system induced by water molecules in the storage environment
Examination of the degradation mechanism of optical property degradation of anine dye The optical property degradation of cyanine dye induced by water molecules in the storage environment is caused by the formation of reaction products due to the chemical reaction between cyanine dye and water or The solvent effect of water (the effect of polarity) is possible.

Therefore, the presence or absence of a reaction product after contacting the four types of cyanine dyes with water molecules and the difference in optical characteristics when the four types of cyanine dyes were present in solvents having different polarities were examined.

First, the presence or absence of the reaction product was examined by measuring the FT-IR spectrum of the cyanine dye thin film left in a high humidity environment in the above experiment.
For comparison, the FT-IR spectrum of the cyanine dye thin film before standing was similarly measured. FT-IR spectrum of each cyanine dye thin film after standing and F-IR spectrum before standing
The T-IR spectrum is shown in FIGS.

FT-IR before leaving each cyanine dye thin film
Comparing the spectrum and the FT-IR spectrum after standing, it can be seen that there is almost no difference between the two spectra.
If the cyanine dye and the water molecule undergo a chemical reaction during the standing to generate a reaction product, a peak corresponding to an OH group or the like should appear in the FT-IR spectrum after the standing. The absence of such a peak in the spectrum after standing means that the cyanine dye and the water molecule did not undergo a chemical reaction during standing, and this indicates that the chemical was not induced by water molecules in the storage environment. It was suggested that the deterioration of the optical properties of the cyanine dye was not caused by the formation of a reaction product due to the chemical reaction between the water molecule and the cyanine dye.

For further confirmation, a very small amount of a cyanine dye was added to water to prepare a dilute solution of the cyanine dye.
The change in absorption spectrum due to standing was examined. Concentration of each cyanine dye diluted solution and maximum absorption wavelength λ before and after standing
Table 7 shows the absorbance at max.

[0057]

[Table 7]

As can be seen from Table 7, the absorbance at the maximum absorption wavelength λmax of each of the dilute solutions of the cyanine dyes is almost the same between before and after standing. This means that the deterioration of the optical properties of the cyanine dye induced by the water molecule does not proceed with time after the contact between the water molecule and the cyanine dye. It was suggested that the property deterioration was not due to the chemical reaction between the water molecule and the cyanine dye.

Next, the difference in the optical characteristics of the cyanine dye when the cyanine dye was present in various solvents having different polarities was examined. Water, iso-propanol, and methanol were used as the solvent. The Et values of the above solvents are as shown in Table 8. The Et value is an index of the polarity of the solvent, and the maximum wavelength of the charge transfer absorber in a solvent of pyridinium-N-phenol betaine (the structure is shown in Chemical Formula 15) at a temperature of 25 ° C. Is converted into an energy unit, and is obtained by the following equation.

Et = (Z−13.36) /1.259·
2.388 · 10 ⁻⁴ (kJ / mol) Z: transition energy at the absorption position It indicates that a solvent having a larger Et value has a higher polarity.

[0061]

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[0062]

[Table 8]

Each cyanine dye was converted to water, methanol, iso
The maximum absorption wavelength λm when present in propanol
ax, the molar absorption coefficient ε at the maximum absorption wavelength λmax is shown in Tables 9 to 11, the relationship between the Et value and the maximum absorption wavelength λmax is shown in FIGS. 23 to 26, and the relationship between the Et value and the molar absorption coefficient at the maximum absorption wavelength λmax is shown. These are shown in FIGS. 27 to 30, respectively.

[0064]

[Table 9]

[0065]

[Table 10]

[0066]

[Table 11]

As can be seen from FIGS. 23 to 30 and Tables 9 to 11, the cyanine dye changes its maximum absorption wavelength λmax and molar absorption coefficient ε depending on the polarity of the solvent. The maximum absorption wavelength λmax is on the short wavelength side, and the molar absorption coefficient ε is a small value. This means that the optical properties of cyanine dyes are affected by the polarity of water molecules in a standing environment. It was suggested that this was caused by the influence on the body.

Here, assuming that the deterioration of the optical characteristics of the optical information medium is caused by the influence of the polarity of water on the cyanine dye, the deterioration of the optical characteristics is due to the small ion radius of the counter ion. The reason why the use of a dye is more likely to occur will be discussed below.

It is believed that cyanine dyes are affected by the acceptance of water molecules by counter ions. Here, it is considered that the smaller the ion radius, the smaller the negative number of the electrostatic free energy, and the easier the ions are to accept water molecules in a leaving environment. For this reason, in a dye-containing layer using a cyanine dye having a counter ion with a small ion radius, many counter ions accept water molecules during standing, and are affected by their polarities, which greatly deteriorates optical characteristics. It is presumed.

For reference, Table 12 shows I ⁻ , BF ₄ ⁻ , ClO ₄ ⁻ , and PF ₆ ⁻ obtained by the bone equation.
Shows the electrostatic free energy ΔGel ⁰ of the sample.

[0071]

[Table 12]

[0072]

As is clear from the above description, the optical information medium of the present invention uses an ion having an ion radius of 0.294 nm or more as the counter ion for the cyanine dye. Therefore, the magnitude of the negative number of the electrostatic free energy increases, and the number of water molecules accepted by the counter ion decreases.
Even when stored in a high-temperature and high-humidity environment, the optical characteristics are hardly deteriorated, and excellent preservability can be obtained.

Therefore, according to the present invention, it is possible to use an optical information medium which can be used not only as a read-only type but also as a write-once type and a rewritable type, and which has excellent storage stability. Become.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of a main part showing one configuration example of an optical information medium of the present invention.

[2] I ^- - before standing high temperature and high humidity environment of the optical information medium using cyanine is a characteristic diagram showing together the absorption spectrum after standing.

[3] BF 4 ^{- -} before standing high temperature and high humidity environment of the optical information medium using cyanine is a characteristic diagram showing together the absorption spectrum after standing.

[4] ClO 4 ^{- -} before standing high temperature and high humidity environment of the optical information medium using cyanine is a characteristic diagram showing together the absorption spectrum after standing.

[5] PF 6 ^{- -} before standing high temperature and high humidity environment of the optical information medium using cyanine is a characteristic diagram showing together the absorption spectrum after standing.

FIG. 6 is a characteristic diagram showing the relationship between the ion radius of counter ions and the amount of change in reflectance due to standing.

[7] I ^- - it is a characteristic diagram showing the thermogravimetric analysis result of the cyanine.

[8] BF 4 ^{- -} it is a characteristic diagram showing the thermogravimetric analysis result of the cyanine.

[9] ClO 4 ^{- -} it is a characteristic diagram showing the thermogravimetric analysis result of the cyanine.

[10] PF 6 ^{- -} it is a characteristic diagram showing the thermogravimetric analysis result of the cyanine.

FIG. 11: Before leaving the I ⁻ − cyanine thin film in a high humidity environment,
It is a characteristic view also showing the absorption spectrum after standing.

[12] BF 4 ^{- -} before standing high humidity environment of cyanine thin, is a characteristic diagram showing together the absorption spectrum after standing.

FIG. 13 is a characteristic diagram also showing absorption spectra of a ClO ^{4 −} —cyanine thin film before and after standing in a high-humidity environment.

[14] PF 6 ^{- -} before standing high humidity environment of cyanine thin, it is a characteristic diagram showing together the absorption spectrum after standing.

FIG. 15 is a characteristic diagram showing an FT-IR spectrum of an I ⁻ − cyanine thin film after being left in a high humidity environment.

FIG. 16 is a characteristic diagram showing an FT-IR spectrum of the I ⁻ -cyanine thin film before it is left in a high-humidity environment.

[Figure 17] BF 4 ^{- -} it is a characteristic diagram showing the FT-IR spectrum after standing high humidity environment of cyanine film.

[Figure 18] BF 4 ^{- -} is a characteristic diagram showing the FT-IR spectrum before standing under a high humidity environment of cyanine film.

[19] ClO ^{4 -} - it is a characteristic diagram showing the FT-IR spectrum after standing high humidity environment of cyanine film.

[Figure 20] ClO ^{4 -} - is a characteristic diagram showing the FT-IR spectrum before standing under a high humidity environment of cyanine film.

[Figure 21] PF 6 ^{- -} is a characteristic diagram showing the FT-IR spectrum after standing high humidity environment of cyanine film.

[Figure 22] PF 6 ^{- -} is a characteristic diagram showing the FT-IR spectrum before standing under a high humidity environment of cyanine film.

[Figure 23] I ^- - is a characteristic diagram showing the relationship Et and maximum absorption wave number of the solvent for cyanine.

[Figure 24] BF 4 ^{- -} is a characteristic diagram showing the relationship Et and maximum absorption wave number of the solvent for cyanine.

[Figure 25] ClO ^{4 -} - Et solvent for cyanine
FIG. 4 is a characteristic diagram showing a relationship between a value and a maximum absorption wave number.

[Figure 26] PF 6 ^{- -} is a characteristic diagram showing the relationship Et and maximum absorption wave number of the solvent for cyanine.

FIG. 27 is a characteristic diagram showing the relationship between the Et value of the solvent and the molar extinction coefficient ε at the molar maximum absorption wavelength λmax for I ⁻ -cyanine.

[Figure 28] BF 4 ^{- -} is a characteristic diagram showing the relationship of the molar extinction coefficient ε in Et and maximum absorption wavelength λmax of the solvent for cyanine.

[Figure 29] ClO ^{4 -} - Et solvent for cyanine
FIG. 9 is a characteristic diagram showing a relationship between the value and the molar absorption coefficient ε at the maximum absorption wavelength λmax.

[Figure 30] PF 6 ^{- -} is a characteristic diagram showing the relationship of the molar extinction coefficient ε in Et and maximum absorption wavelength λmax of the solvent for cyanine.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G11B 7/24 516 B41M 5/26

Claims (1)

(57) [Claims] 1. An optical information medium in which a dye-containing layer containing a cyanine dye is formed on a transparent substrate, wherein the first color represented by the chemical formula 1 and the second color represented by the chemical formula 2 are provided.
A cyanine dye containing iodine, and an ionic radius as a counter ion of the first dye.
Is 0.294 nm or more and is represented by Chemical Formula 3, Chemical Formula 4, or Chemical Formula 5.
An optical information medium having any of the following ions . Embedded image Embedded image Embedded image Embedded image Embedded image