JPH07109655B2 - Optical disc substrate and optical information recording medium using the substrate - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an optical disk substrate and an optical information recording medium in which the amount of foreign matter is reduced, and particularly to an optical disc in which the amount of foreign matter having a grain size of 1.1 μm or less is reduced. Disk substrate and an optical information recording medium using the optical disk substrate.

[Prior Art] For an optical information recording medium which is a recording medium for recording and / or reproducing information using laser light such as an audio disc, a laser disc, an optical disc memory or a magneto-optical disc, polycarbonate, poly Foreign substances (dust, carbides, etc.) contained in a transparent substrate made of methyl methacrylate, glass, etc., that is, an optical disc substrate.
However, it is known that it has a great influence on the reliability of recording and / or reproducing of information.

In this regard, there has been proposed a technique for reducing foreign matter by filtering foreign matter in the raw material with a filter in the process of purifying or granulating the raw material (Japanese Patent Laid-Open Nos. 61-90345 and 61-90345).
63-91231 etc.). And in these, 0.5 μm
Alternatively, it has been shown that the number of foreign matters having a particle size of 1 μm or more per 1 g of the raw material is related to the performance of the recording / reproducing characteristics, for example, the error rate (bit error rate: BER).

However, these are unclear in relation to the particle size of foreign matter,
It cannot be said that the evaluation method is appropriate, and it cannot completely reduce the BER.

Therefore, the present applicant has adopted the concept of foreign matter strength as a solution to such a problem, and by setting the foreign matter strength below a certain level, the evaluation of the optical disk substrate is actually applied. Prior to filing an application for an optical disc substrate that prevents the deterioration of recording / reproducing characteristics such as BER caused by foreign matter in the substrate, and an optical information recording medium using this optical disc substrate. (Japanese Patent Application No. 1-9993).

[Problems to be Solved by the Invention] However, although the above-mentioned conventional optical disc substrate and optical information recording medium have achieved sufficient results in terms of reduction of BER at the time of manufacture, they are not suitable for high temperature and high humidity environments. There is still room for improvement in the reduction of BER when left for a long time.

The present invention has been made in view of the above circumstances, and does not cause deterioration of information recording / reproducing characteristics even when left in a high temperature and high humidity environment for a long time, and thus is high for a long time (10 years or more). An object is to provide an optical disk substrate and an optical information recording medium that maintain reliability.

As a result of intensive studies conducted by the present inventors in order to achieve the above-mentioned object, the cause of the high BER when left for a long time in a high temperature and high humidity environment is that the submicron size foreign matter present in the disk substrate is It has been found that these foreign substances act as a core and cause hydrolysis due to moisture absorption to generate a polarizing defect with a size of several microns to several tens of microns.

Then, if the foreign matter strength of foreign matter having a particle size of 1.1 μm or less in the optical disk substrate is set to a certain value or less, and preferably the optical disk substrate contains an additive (lubricant) such as fatty acid monoglyceride, the polarization property under high humidity and high temperature conditions is improved. The present invention has been completed by finding that the occurrence of defects can be significantly suppressed.

[Means for Solving the Problems] That is, the optical disc substrate of the present invention has a particle size of 1.1 μm.
The foreign matter strength of foreign matter of m or less is 10,000 μm ² / g or less, preferably, the optical disc substrate is made of a polycarbonate resin having a viscosity average molecular weight of 10,000 to 22000, and more preferably the same. The formula disk substrate contains 0.002 to 5% by weight of monoglyceride of fatty acid having 14 to 30 carbon atoms or beeswax.

The optical information recording medium of the present invention has a structure in which an information recording layer is formed on any one of the above-mentioned optical disc substrates.

In the optical disc substrate of the present invention, the concept of foreign matter strength is adopted as a method of evaluating the amount of foreign matter contained in the substrate.

Here, the "foreign matter strength" is the sum of the product of the square and the number of each particle size of foreign matter having a particle size of 0.5 μm or more per unit weight. The foreign matter is detected in a solution in which a material to be evaluated (raw material, substrate, etc.) is dissolved in a large excess of an organic solvent (particularly methylene chloride). The foreign matter strength is represented by the formula I = Σ {[1/2 (d _i + d _{i + 1} )] ² × (n _i −n _i ′)} / W.

In the formula, I is the foreign matter strength, d _i is the i-th particle size classification value (μm), n _i is less than the particle size d _{i + 1} and more than the particle size d _i , and is detected in the solution. N _i ′ is the number of foreign matters contained in the solution before use, and W is the weight (g) of the material.

An example of setting the particle size classification value is as follows.

d ₁ = 0.5 (μm) d ₆ = 5.0 (μm) d ₂ = 0.6 (μm) d ₇ = 10.0 (μm) d ₃ = 0.7 (μm) d ₈ = 20.0 (μm) d ₄ = 1.1 (μm) d ₉ = 25.0 (μm) d ₅ = 2.5 (μm) When foreign particles with a particle size exceeding 25.0 μm are detected, use appropriate values of d ₁₀ , d _11, etc.

In the above example of setting the particle size classification value, in the case of "foreign matter strength of foreign matter of 1.1 μm or less", the value of the foreign matter strength calculated using d _{1 to} d ₄ is shown.

A liquid particle counter (manufactured by HIAC-ROYCO) or the like is used as a device for measuring the concentration of foreign matter in each particle size category.

As used herein, the term "foreign matter" is essentially a contaminant, such as an impurity, that enters the optical disc substrate from various ways.
It means dust or a carbide of a raw material resin. Further, the bit error rate of the optical disc substrate can be accurately evaluated by using the above-mentioned foreign substance strength calculated from the "foreign substance" which is a component insoluble in methylene chloride.

According to the present invention, in order to obtain sufficient reliability as a disk substrate used for an optical information recording medium, it is necessary to set the particle strength of particles having a particle size of 1.1 μm or less to 10,000 μm ² / g or less. If the foreign matter strength of foreign matter having a particle size of 1.1 μm or less exceeds 10,000 μm ² / g, the information recording medium including the disc substrate
Under the conditions of high temperature and high humidity, the foreign matter absorbs moisture to generate a polarization defect, which causes a bit error, and reduces the reliability of the optical disk substrate.

The foreign matter strength of foreign matter with a particle size of 1.1 μm or less is 9500 μm ² /
It is preferably g or less in order to obtain more sufficient reliability. In addition, the foreign matter strength of foreign matter with a particle size of 0.5 to 25 μm is 1 × 1
0 is preferably set to ^{5 μm 2} / g or less.

When the foreign matter strength of foreign matter having a particle size of 0.5 to ²⁵ μm exceeds 1 × 10 ⁵ μm ² / g, the information recording medium including the disc substrate is
The foreign matter surely causes a bit error and reduces the reliability of the optical disc substrate.

The raw material resin used for the optical disc substrate of the present invention can be used without particular limitation as long as it is a resin excellent in optical characteristics such as transparency and moldability. For example, polycarbonate resin, acrylic resin, amorphous polyolefin or the like can be used. From the viewpoint of heat resistance, strength, and cost, it is preferable to use a polycarbonate resin.

The polycarbonate resin here is not particularly limited, for example, a viscosity average molecular weight of 10000 to 22000, preferably 12000 to 20000, by a reaction of a dihydric phenol and a carbonic acid ester such as phosgene or diphenyl carbonate. It is manufactured. Examples of dihydric phenols include hydroquinone, 4,4′-dioxyphenyl, bis (hydroxyphenyl) alkane, bis (hydroxyphenyl) cycloalkane, bis (hydroxyphenyl) ether, bis (hydroxyphenyl) ketone, bis (hydroxy). Examples thereof include phenyl) sulfide, bis (hydroxyphenyl) sulfone, and their lower alkyl and halogen substitution products.
2'-bis (4-hydroxyphenyl) propane (hereinafter referred to as bisphenol A), 1,1-bis (4-hydroxyphenyl) ethane, 2,2-bis (4-hydroxyphenyl) -hexafluoropropane, etc. Preferably.

Further, these dihydric phenols can be used alone or in a mixture.

Further, as the polycarbonate used in the present invention,
It may have a partially branched structure.

The viscosity average molecular weight of 10,000 to 22,000 can be controlled by adding an end terminating agent such as pt-butylphenol during the production of the polycarbonate. When the viscosity average molecular weight is less than 10,000, the strength of the disk substrate cannot be put to practical use, and when it exceeds 22,000, a disk substrate having sufficient performance in terms of moldability or optical properties cannot be obtained.

The viscosity average molecular weight [Mv] is determined by measuring the specific viscosity η _sp of the polycarbonate resin in a methylene chloride solution at 20 ° C., and using the formula η _sp /C=[η](1+0.28 η _sp ), where C is a polycarbonate Resin concentration (g / l)] and [η] = 1.23 × 10 ⁻⁵ M _v ^0.83 .

Raw material polycarbonate used for injection molding is a low molecular weight component produced by a conventionally known method, and then filtered in a solution state, or a granular raw material is washed with a poor solvent such as acetone under heating conditions. It is preferable to remove impurities such as unreacted components and foreign substances and foreign substances. In any case, it is necessary that the content of foreign substances, impurities, solvents, etc. in the raw material before injection molding be as low as possible.

If necessary, it is possible to add additives such as phosphorus-based antioxidants.

As the resin other than the polycarbonate-based resin, an acrylic-based resin such as polymethylmethacrylate, a copolymer of methylmethacrylate and other methacrylic acid ester, an acrylic ester or a styrene-based monomer, or an amorphous polyolefin (for example, Random copolymers of ethylene and cycloolefins) and the like can be used.

In the optical disc substrate of the present invention, in the polycarbonate resin which is a raw material resin, monoglyceride of a fatty acid having 14 to 30 carbon atoms, preferably 16 to 24 carbon atoms or beeswax
When the content is 0.002 to 5% by weight, and more preferably 0.005 to 0.3% by weight, the occurrence of polarizing defects is suppressed, although the reason is not clear.

Examples of the fatty acid monoglyceride include saturated monohydric fatty acid monoglyceride such as stearic acid monoglyceride and behenic acid monoglyceride, and mixtures thereof.

Examples of the beeswax include navy blue bleached beeswax (manufactured by Nikko Fine Products Co., Ltd.).

Beeswax is secreted from the eight wax lines in the lower abdomen of the bee and is a material for nesting.
The main component is an ester of fatty acid.

The optical disk substrate of the present invention is preferably manufactured by injection molding, and the resin temperature during injection molding is 300 to 400.
℃, the mold temperature is usually 50 ~ 140 ℃, preferably 80 ~ 130
℃. Further, it is preferable to select a material or the like so as to reduce mixing of metal components during the injection molding.

Alternatively, only the mold surface temperature may be heated to a glass transition temperature or higher by using a high frequency wave and the like, and may be cooled to a temperature at which the disk substrate can be taken out after the resin injection. By doing so, a substrate having more excellent optical characteristics can be obtained.

Next, the optical information recording medium of the present invention can be obtained by forming a known information recording layer or the like on the above-mentioned optical disc substrate.

For example, a concrete example of the information recording medium of the present invention is as shown in FIGS. 1 (a) and 1 (b).

Here, FIG. 1 (a) shows an example of an information recording medium having a double-sided recording structure. In FIG. 1, reference numeral 1 is an optical disk substrate made of a polycarbonate resin. 2 is an information recording layer, F _e, C transition metal and T _b of _o such, G _d, N _d, comprising a combination of rare earth, such as D _y material (eg G _d -F _e -C
_o system, T _b -F _e -C _o based material) is deposited, is formed to a thickness of approximately normal 300~1000Å by means such as sputtering. Reference numeral 3 is a protective layer for protecting the recording layer 2, which is made of silicon-based ceramics or the like. Reference numeral 4 denotes an adhesive layer, which is formed of a thermosetting resin or the like and usually has a thickness of about 40 to 60 μm.

FIG. 1B shows an example of an information recording medium having a single-sided recording structure. Here, the optical disc substrate 1a, the information recording layer 2, and the protective layer 3 for protecting the recording layer 2 are the same as those shown in FIG. 1 (a). Reference numeral 4'denotes an overcoat layer, which is made of an ultraviolet curable resin or the like and is usually formed to a thickness of about 10 to 20 .mu.m.

The optical information recording medium in which the information recording layer is formed on the optical disk substrate in this manner is mainly used as a write-once type or a rewritable type.

The information recording layer is not limited to the magneto-optical type, but may be an organic recording layer (for example, phthalocyanine or tetracarbonylcyanine) as long as it can be recorded by laser light or the like.

[Examples] Hereinafter, the present invention will be described in detail based on Examples, but the present invention is not limited thereto.

Production of Optical Disc Substrate A polycarbonate resin having a viscosity average molecular weight [Mv] shown in Table 1 and a foreign matter strength, to which the amount of fatty acid monoglyceride or beeswax shown in the same table was added was used as a raw material. Then, molding was carried out at a molding temperature of 335 ° C. and a mold temperature of 118 ° C. to manufacture optical disk substrates having a substrate size (diameter) of 130 mmφ and a thickness of 1.2 mm (Examples 1 to 7 and Comparative Examples 1 to 1).
4).

In addition, behenic acid monoglyceride was used as the fatty acid monoglyceride, and navy blue bleached beeswax (manufactured by Nikko Fine Products Co., Ltd.) was used as the beeswax.

Accelerated deterioration test Under high temperature and high humidity conditions of temperature 80 ° C. and humidity 90% RH, the optical disc substrates (10 sheets each) obtained in Examples 1 to 7 and Comparative Examples 1 to 4 were left for 2000 hours, An accelerated deterioration test was conducted.

Next, the number of polarizing defects in the optical disc substrate was detected with the optical microscope in the transmission polarization mode and in the crossed Nicols state, and the average value per sheet was calculated.

The results are shown in Table 1.

The disk substrate obtained in Examples 1 to 7 and Comparative Examples 1 to 4 were prepared above optical information recording medium, by sputtering, the thickness of 800 Å T _b -F
_e -C _o based layer (recording layer), a silicon-based ceramic layer (protective layer) having a thickness of 800 Å, was formed with a thickness of 15μm ultraviolet curing resin layer (overcoat layer), an optical information recording medium of a single-sided recording structure Was manufactured.

Accelerated deterioration test After measuring the initial value BER ₀ of the bit error rate of the optical information recording medium obtained above, an accelerated deterioration test was performed for 2000 hours under the same conditions as the above-mentioned accelerated deterioration test of the disk substrate, and the subsequent bits The error rate value BER2000 was measured. The results are shown in Table 1.

As it is clear from Table 1, the following optical disk substrate and an optical information recording medium foreign material strength of less foreign matter particle size 1.1μm is 10000 ² / g, as compared to those foreign substances strength exceeds 10000 ² / g The number of polarization defects is small and the increase in BER is low.

In addition, when fatty acid monoglyceride is added or beeswax is added, the number of occurrence of polarization defects is smaller and the increase of BER is lower than that of the case without addition.

Although the optical disc substrate and the like have been described in the above embodiments, the optical disc substrate and the optical information recording medium according to the present invention perform reproduction, additional recording, and rewriting of information using laser light. It means a substrate and a recording medium, and includes, for example, an optical card and the like.

[Effects of the Invention] As described above, according to the present invention, the foreign matter strength of foreign matter having a particle size of 1.1 μm or less is set to 10,000 μm ² / g or less. Without happening,
It is possible to obtain a highly reliable optical disc substrate.

In addition, since polarization defects do not occur even under high temperature and high humidity conditions, an increase in bit error rate (BER) is suppressed, and therefore excellent high temperature and high humidity resistance characteristics, long service life, and reliable A high optical information recording medium can be obtained.

[Brief description of drawings]

FIG. 1 (a) is a configuration diagram showing a specific example of a double-sided recording structure in the optical information recording medium of the present invention, and FIG. 1 (b) is a configuration diagram showing a specific example of a single-sided recording structure. 1: Optical disc substrate 2: Information recording layer 3: Protective layer 4: Adhesive tank 4 ': Overcoat layer

Claims (4)

[Claims] 1. The foreign matter strength of foreign matter having a particle size of 1.1 μm or less is 100.
An optical disk substrate characterized by having a size of 00 μm ² / g or less. 2. The optical disk substrate according to claim 1, which is made of a polycarbonate resin having a viscosity average molecular weight of 10000 to 22000. 3. The optical disc substrate according to claim 1, which contains 0.002 to 5% by weight of a monoglyceride of a fatty acid having 14 to 30 carbon atoms or beeswax. 4. An optical information recording medium comprising the optical disk substrate according to claim 1, 2 or 3 and an information recording layer carried thereon.