JPH08161785A - Optical information recording medium - Google Patents

Abstract

PURPOSE: To maintain a god reproducing characteristic by reproducing a signal by means of a recording and reproducing apparatus in which a low-reflectance medium such as a magneto-optical disk or the like is used as an object. CONSTITUTION: In an optical information recording medium, a transparent substrate 1 in which uneven parts corresponding to information signals are formed is coated with a pigment-containing paint which is composed mainly of a pigment material and of a polymer material, and a pigment-containing layer (a reflection layer) 3 at a reflectance of 15 to 25% is formed. In the optical information recording medium, titanium alkoxide or its polymer as an additive has been added, in a ratio of 5 to 10wt.% with reference to the polymer material, to the pigment-containing paint.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical information recording medium capable of signal reproduction by a recording / reproducing apparatus for a medium having a low reflectance such as a magneto-optical disk.

[0002]

2. Description of the Related Art As optical information recording media, audio compact discs (CD), video laser discs (LD), and the like have already become widespread. These compact discs and laser discs are those in which a reflective layer is provided on a substrate on which pits corresponding to information signals are formed in advance as an uneven shape, and a protective layer is provided if necessary.
This is a read-only type optical disc that only reproduces the recorded information signal. The reflective layer is made of a material having a high reflectance, that is, a low absorptivity, such as Al or Au.

On the other hand, in recent years, unlike the above-mentioned read-only type optical disc, a magneto-optical disc is being developed as an optical information recording medium capable of writing and erasing information. This magneto-optical disk has a recording magnetic layer (for example, a rare earth-transition metal alloy amorphous thin film such as TbFeCo) which has an easy axis of magnetization in the direction perpendicular to the film surface and has a large magneto-optical effect on a substrate.
The recording portion is formed by laminating a reflective layer and a dielectric layer. As such a magneto-optical disk, a small-diameter magneto-optical disk (so-called mini disk) having a diameter of 64 mm has begun to be popularized in a form housed in a cartridge.

By the way, it is preferable that the read-only optical disk can be played back by a magneto-optical disk recording / playback apparatus as well in order to enhance the spread and practicality of both the read-only optical disk and the magneto-optical disk system. I can say.
However, in a read-only type optical disc having an Al film, an Au film or the like as a reflective layer, the reflectance for laser light is 70% or more, which is significantly higher than the reflectance of a magneto-optical disc of 15 to 25%. A signal cannot be reproduced by a recording / reproducing device for a magneto-optical disk.

Therefore, in a read-only type optical disc, A
Attempts have been made to use a dye-containing layer made of a dye material and a polymer material as a reflective layer instead of the l film or Au film. For example, an optical disc using a cyanine dye as the dye material has a reflectance of 15 to 25%, which is about the same as the reflectance of a magneto-optical disc, and is expected as a read-only optical disc applicable to a recording / reproducing device for a magneto-optical disc. It

[0006]

By the way, in the above-mentioned magneto-optical disk system, there is a standard of operating temperature range of -25 to 70 ° C. and relative humidity of 10% to 95% as a world standard. In order for the system to read the information signal, it must also be a medium compliant with this standard.

However, the read-only type optical disc has not been sufficiently studied from such a point of view, and the dye-containing layer may be deteriorated due to water droplets during operation in a high temperature and high humidity environment. In the low reflectance optical disc using the dye-containing layer, the read light is reflected at the substrate / dye-containing layer interface and the dye-containing layer / air interface, respectively, and the signal reproduction is performed utilizing multiple interference. If water drops cause deterioration on the dye-containing layer, such multiple interference of light is disturbed, resulting in a problem in signal reproduction.

Therefore, the present invention has been proposed in view of such a conventional situation, and signal reproduction can be performed by a recording / reproducing apparatus for a medium having a low reflectance such as a magneto-optical disk. At the same time, it is an object of the present invention to provide an optical information recording medium capable of maintaining good reproduction characteristics even in a high temperature and high humidity environment.

[0009]

An optical information recording medium according to the present invention has been proposed in order to achieve the above-mentioned object, and a dye is formed on a transparent substrate on which irregularities corresponding to information signals are formed. In an optical information recording medium in which a reflection layer having a reflectance of 15 to 25% is formed by applying a pigment-containing paint mainly composed of a material and a polymer material, as an additive to the pigment-containing paint, Titanium alkoxide or its polymer is added.

The optical information recording medium to which the present invention is applied has, as shown in FIG. 1, a concave pit portion 2a and a convex land portion 2b corresponding to information signals, guide grooves, and address code pits. The dye-containing layer 3 having a reflectance of 15 to 25% is formed as a reflective layer on the transparent substrate 1. In the optical information recording medium having such a structure, the reading light LB emitted from the transparent substrate 1 side is transparent substrate 1 / dye-containing layer 3
Signal reproduction is carried out by utilizing the fact that multiple reflections occur at the interface and the dye-containing layer 3 / air interface and multiple interference occurs.

In order to form such an optical information recording medium, a pigment-containing coating material containing a pigment material and a polymer material as a main component is prepared, and this coating material is applied onto the transparent substrate 1 so that the pigment-containing coating material is contained. The layer 3 may be formed. In the present invention, titanium alkoxide or a polymer thereof is added to the pigment-containing coating material, and the titanium alkoxide is represented by the chemical formula of Ti (OR) ₄ or Ti (OR) _3. It is a thing. Further, the polymer of titanium alkoxide is produced through the hydroxylation reaction, dealcoholization reaction and dehydration reaction as shown in the following formulas (1), (2) and (3).

Ti (OR) ₄ + H ₂ O → Ti (OR) ₃ OH + ROH (1) Ti (OR) ₄ + Ti (OR) ₃ OH → Ti (OR) ₃ OTi (OR) ₃ + ROH ... (2) 2Ti (OR) ₃ OH → Ti (OR) ₃ OTi (OR) ₃ + H ₂ O ... (3) Then, as the polymerization proceeds further, as shown in Chemical formula 1 Become a polymer.

[0013]

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Incidentally, in the present invention, a conventionally known titanium
Alkoxide or its polymer can be used
is there. That is, in Chemical formula 1, R is CH₃, C₂H_Five, C
₃H ₇, C_FourH₁₁Which means either
It may be branched, as long as n is a natural number of 1 or more.
Yes. Above all, R is C₃H₇, C_FourH₁₁In any of
It is preferable that n is a natural number of 1 to 10.

The above-mentioned titanium alkoxide and its polymer are usually obtained in a state of being dissolved in a solvent such as n-butanol or i-propanol. Then, such a titanium alkoxide or a polymer thereof is added in a state of being dissolved in a solvent to a pigment-containing coating material in which a pigment material and a polymer material are dissolved in a solvent. When this dye-containing coating material is applied on the transparent substrate 1 and the solvent is removed by drying from this coating film, the titanium alkoxide or its polymer produces TiO ₂ by hydrolysis, so that a film having water repellency is formed on the surface. The dye-containing layer 3 thus obtained is obtained.

The titanium alkoxide or its polymer is preferably added in an amount of 5 to 10% by weight with respect to the polymer material in the pigment-containing coating. If the addition amount of titanium alkoxide or its polymer is too small, a sufficient water repellency effect cannot be obtained. Also, if there are too many,
Since the hydrolysis reaction of the titanium alkoxide or its polymer does not proceed sufficiently, the water repellent effect deteriorates.

By the way, in the optical information recording medium of the present invention, the reflectance of the dye-containing layer 3 is restricted to 15 to 25% by targeting a medium having a reflectance of 15 to 25% such as a magneto-optical disk. This is to enable signal reproduction by the recording / reproducing apparatus. Therefore, the types and mixing ratios of the dye material and polymer material contained in the dye-containing layer 3 are selected according to this reflectance range. Here, when selecting the materials and the mixing ratio, the real part n of the complex refractive index of the dye-containing layer 3 is set to 1.84.
It is desirable to make it above. In the dye-containing layer 3 having a real part n of the complex refractive index of 1.84 or more, the reflectance can be set to 15 to 25% only by adjusting the film thickness within a practical range, and the film forming conditions can be easily set. Is.

As the dye material, whether it is an organic dye or an inorganic dye, a material for obtaining the reflectance of the reflective layer within the above range, preferably the real part n of the complex refractive index of the dye-containing layer 3 is used.
Any value can be used as long as it can be 1.84 or more.
For example, as the organic dye, NK529 (product name manufactured by Nippon Senshoku Co., Ltd.) shown in Chemical formula 2, SRC8 (product name manufactured by Sony Chuken Co., Ltd.) shown in Chemical formula 3, NK2421 (product name manufactured by Nippon Sensitive Dye Company) shown in chemical formula 4, etc. Cyanine dyes of.

[0019]

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[0020]

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[0021]

[Chemical 4]

Further, a light stabilizer may be added to the dye-containing layer 3 for the purpose of preventing photobleaching of the dye material. As the light stabilizer, those having an electron donating property such as amines, materials having an energy level lower than the energy level of the excited state of the dye material such as nickel complex, and the like are used. For example, IRG003 (trade name, manufactured by Nippon Kayaku Co., Ltd.) shown in Chemical formula 5 can be mentioned.

[0023]

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The polymer material is used for the purpose of improving the hardness of the dye-containing layer and enhancing scratch resistance. As the polymer material, any known material can be used. For example, KR311 shown in Chemical formula 6 (trade name of Shin-Etsu Silicone Co., Ltd.)
Silicon varnish and nitrocellulose are suitable.

[0025]

[Chemical 6]

As the transparent substrate 1 on which the reflective layer composed of the dye-containing layer 3 as described above is formed, those used in ordinary optical information recording media can be used, such as glass and polycarbonate ( PC), polyethylene terephthalate (PET) and the like.

[0027]

In an optical information recording medium in which a reflective layer is formed on a transparent substrate on which irregularities corresponding to information signals are formed, a dye material and a polymer material are mainly used as the reflective layer, and the reflectance is 15 to When the 25% dye-containing layer is used, signal reproduction can be performed by a recording / reproducing apparatus for a medium having a reflectance of 15 to 25% such as a magneto-optical disk.

When titanium alkoxide or a polymer thereof is further added to a pigment-containing coating obtained by dissolving a pigment material and a polymer material in a solvent, TiO ₂ is produced by the hydrolysis of the titanium alkoxide or its polymer and the surface is repelled. A dye-containing layer having a water-soluble film is obtained. The optical information recording medium having the dye-containing layer formed as a reflection layer in this way, even if it is operated in a high humidity environment, the water-repellent effect of the dye-containing layer surface causes Good reproduction characteristics are maintained without deterioration or deterioration.

[0029]

EXAMPLES Preferred examples of the present invention will be described based on experimental results.

Example 1 In this example, a pigment material, a polymer material, a light stabilizer and an additive were used, and a pigment material: a polymer material: a light stabilizer: an additive = 1: 1: 0.2. The pigment-containing coating material was prepared by dissolving in a solvent at a weight ratio of 0.05 (100 by weight ratio). The following materials were used as the dye material, polymer material, light stabilizer, additive, and solvent.

Dye material: Cyanine dye shown in Chemical formula 4 (Nippon Sensitive Dye Co., trade name NK2421) Polymer material: Silicon varnish shown in Chemical formula 6 (Shin-Etsu Silicone Co., trade name KR311) Light stabilizer: Singlet oxygen deactivator shown in Chemical formula 5 (manufactured by Nippon Kayaku Co., Ltd., trade name IRG-003) Additive: Titanium alkoxide represented by Chemical formula 1 with R = C ₃ H ₇ and n = 1 (Nippon Soda Company name, Al) Solvent: 3-hydroxy-3-methyl-2-butanone (manufactured by Tokyo Kasei Kogyo Co., Ltd.) The pigment-containing coating material prepared in this manner is used as a transparent substrate on which pits and lands are formed in advance. After applied by spin coating on the above, it was dried to form a dye-containing layer, and an optical disk was produced. This is a sample disk of Example 1.

Example 2 In this example, as an additive, R = C ₃ H ₇ ,
A pigment-containing coating material was prepared in the same manner as in Example 1 except that a polymer of titanium alkoxide represented by n = 10 (manufactured by Nippon Soda Co., Ltd., trade name A10) was used. Then, this was coated on a transparent substrate in the same manner as in Example 1 and then dried to prepare an optical disc, and a sample disc of Example 2 was obtained.

Example 3 In this example, as an additive material, R = C ₄ H ₉ ,
Titanium alkoxide represented by n = 1 (manufactured by Nippon Soda Co., Ltd.,
A pigment-containing coating material was prepared in the same manner as in Example 1 except that the product name Bl) was used. Then, this was coated on a transparent substrate in the same manner as in Example 1 and then dried to prepare an optical disc, and a sample disc of Example 3 was obtained.

Example 4 In this example, as an additive, R = C ₄ H ₉ ,
A pigment-containing coating material was prepared in the same manner as in Example 1 except that a polymer of titanium alkoxide represented by n = 4 (manufactured by Nippon Soda Co., Ltd., trade name B4) was used. Then, this was coated on a transparent substrate in the same manner as in Example 1 and then dried to produce an optical disc, and a sample disc of Example 4 was obtained.

Example 5 In this example, as an additive, R = C ₄ H ₉ ,
A pigment-containing coating material was prepared in the same manner as in Example 1 except that a titanium alkoxide polymer represented by n = 10 (manufactured by Nippon Soda Co., Ltd., trade name B10) was used. Then, this was coated on a transparent substrate in the same manner as in Example 1 and then dried to prepare an optical disc, and a sample disc of Example 5 was obtained.

Comparative Example 1 For comparison, a pigment-containing coating material was prepared in the same manner as in Example 1 except that the additive made of titanium alkoxide or its polymer was not used. Then, this was applied on a transparent substrate in the same manner as in Example 1 and then dried to prepare an optical disc, and Comparative Example 1
I got a sample disk of.

Evaluation of Characteristics With respect to the sample disks of Examples 1 to 5 and Comparative Example 1 produced as described above, it was examined whether or not good reproduction characteristics could be maintained even in a high temperature and high humidity environment.

Specifically, each sample disk was placed at 65 ° C.
Store in a constant temperature / humidity chamber of / 95% for 4 days, and before and after that, C
The value of 1, C2 error was investigated. The C1 error is
The C1 code in the error correction circuit indicates the number of times a correctable random error is corrected as an average value for 1 second. On the other hand, the C2 error indicates the number of C2 codes in the error correction circuit that have corrected an error (burst error) that requires interpolation due to a relatively large defect. Here, by using an MD analyzer (manufactured by Sony Disc Technology Co., Ltd.), the number of C1 flags and C2 flags output from a CIRC (Cross Interleaved Reed-Solomon Code) decoder is measured to obtain C1 and C2. Checked for errors.

Table 1 shows the measurement results for each sample disk.

[0040]

[Table 1]

From Table 1, in the sample disk of Comparative Example 1 in which the titanium alkoxide or the polymer thereof was not added, the C1 error rate was increased by about 9 times due to storage, and C2 error indicating non-recovery occurred. In the sample disks of Examples 1 to 5 containing titanium alkoxide or a polymer thereof,
It can be seen that neither the increase in the C1 error rate due to the storage nor the occurrence of the C2 error is observed.

From the above, it was found that addition of titanium alkoxide or its polymer to the dye-containing coating can prevent alteration and deterioration of the dye-containing layer even in a high temperature and high humidity environment. Next, the relationship between the amount of the additive made of titanium alkoxide or its polymer and the number of C2 errors generated was examined. Specifically, an optical disk was prepared in the same manner as in Examples 1 to 5 except that the amount of each additive added to the polymer material was changed in the range of 0 to 20% by weight.
After storage in a constant temperature / humidity bath of ° C / 95% for 4 days, the occurrence of C2 error was investigated.

An optical disc manufactured in the same manner as in Example 1 except that the amount of the additive A1 added was changed to C2.
The result of measuring the error is shown in FIG. 2, and the result of measuring the C2 error of the optical disc manufactured in the same manner as in Example 2 except that the addition amount of the additive A10 was changed is shown in FIG.
The relationship between the amount of each additive added and the number of C2 errors is shown. Further, the C2 error was measured for the optical disc manufactured in the same manner as in Example 3 except that the addition amount of the additive B1 was changed. FIG. 5 shows the result of measuring the C2 error for the optical disk manufactured in the same manner as in Example 4, and the C2 error was measured for the optical disk manufactured in the same manner as in Example 5 except that the addition amount of the additive B10 was changed. The results obtained are shown in FIG. 6 as the relationship between the amount of each additive added and the number of C2 errors.

From FIGS. 2 to 6, the rate of occurrence of C2 error is
It depends on the amount of the additive made of titanium alkoxide or its polymer, and it can be seen that the occurrence of C2 error can be suppressed to 0 by setting the amount of the additive in the range of 5 to 10% by weight. From this, it was found that the humidity resistance of the optical disk can be improved by adjusting the addition amount of the additive made of titanium alkoxide or its polymer.

[0045]

As is apparent from the above description, when the present invention is applied, it becomes possible to perform signal reproduction by a recording / reproducing apparatus for a low-reflectance medium such as a magneto-optical disk, and it is possible to perform moisture resistance. It is possible to provide an optical information recording medium which is excellent in characteristics and does not undergo alteration or deterioration in the dye-containing layer itself even when it is operated in a high humidity environment, and thus can maintain good reproduction characteristics.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of an essential part showing a configuration example of an optical information recording medium to which the present invention is applied.

FIG. 2 is a characteristic diagram showing the relationship between the amount of additive A1 added and the number of times a C2 error occurs.

FIG. 3 is a characteristic diagram showing the relationship between the amount of additive A10 added and the number of times a C2 error occurs.

FIG. 4 is a characteristic diagram showing the relationship between the amount of additive B1 added and the number of times a C2 error occurs.

FIG. 5 is a characteristic diagram showing the relationship between the amount of additive B4 added and the number of occurrences of C2 error.

FIG. 6 is a characteristic diagram showing the relationship between the amount of additive B10 added and the number of occurrences of C2 errors.

[Explanation of symbols]

 1 Transparent substrate 2a Pit part 2b Land part 3 Dye-containing layer

Claims (2)

[Claims] 1. A reflectance of 15 to 25 is obtained by applying a pigment-containing coating material mainly composed of a pigment material and a polymer material on a transparent substrate on which irregularities corresponding to information signals are formed.
% Of the reflective layer is formed, titanium alkoxide or a polymer thereof is added as an additive to the pigment-containing coating material. 2. The optical information recording medium according to claim 1, wherein the additive is added in a proportion of 5 to 10% by weight with respect to the polymer material.