JPH02103751A - Substrate for optical information recording medium - Google Patents

Abstract

PURPOSE:To improve signal characteristics by using the specific polycarbonate synthesized by reaction of diol of satd. cyclic olefin contg. >=1 pieces of specific 5-membered rings and phosgene for a substrate. CONSTITUTION:The polycarbonate which is synthesized by reaction of the diol of the satd. cyclic olefin contg. >=1 pieces of the 5-membered expressed by, for example, formula I and is expressed by, for example, formula II is used for the disk substrate. Since the phenyl group does not exist or is slight in amt. even if the phenyl group exists, an increase of retardation is substantial ly prevented. The excellent signal characteristics are obtd. in this way.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a substrate for optical information recording media such as optical discs,
In particular, the present invention relates to improvements in adhesive tarpions for substrates made of polycarbonate resins.

[Conventional technology]

An optical disc has a structure in which a recording layer is formed directly on a transparent substrate on which signal patterns such as pre-groups and pre-pits are formed, or via an underlayer or the like. This optical disc is equipped with a mechanism in which laser light passes through a transparent substrate to reach a signal pattern, and a signal corresponding to the signal pattern is introduced into a reproducing device.

Conventionally, the substrates that make up optical discs have excellent heat resistance.
Bisphenol-based polycarbonate is used because it has good moldability and excellent transparency. However, when polycarbonate is molded into a substrate due to shear stress during injection molding, it is oriented in the direction of the substrate surface, and a refractive index difference (birefringence) occurs in the direction parallel to and perpendicular to the substrate surface.
Retardation occurs in the obliquely incident component of the focused recording/reproducing light.

Therefore, the C/N deteriorates due to a decrease in signal amplitude and the like.

In order to deal with such problems,
There is a method of forming a substrate using a low retardation material such as an alicyclic polyolefin, as described in Japanese Patent Application Laid-open No. 708, Japanese Patent Application Laid-Open No. 61-115916, and Japanese Patent Application Laid-Open No. 61-1208.16. In addition, a method of introducing phenyl groups into the side chains of polycarbonate to eliminate the influence of the phenyl groups in the main chain (35th Applied Physics Proceedings, ■o1
3. P871 (198B)) has been proposed.

[Problem to be solved by the invention]

However, in the former method, the adhesion of the low retardation material to the optical recording film (especially magneto-optical recording film) is inferior to that of polycarbonate, and in the latter method, the retardation cannot be completely reduced. There is a problem.

The purpose of the present invention is to solve the above-mentioned problems of the prior art, and to provide a light beam with excellent signal characteristics by reducing the retardation caused by the birefringence of polycarbonate while maintaining the properties of polycarbonate such as heat resistance and low moisture absorption. The object of the present invention is to provide a substrate for an optical recording medium that can be used as a recording medium.

[Means to solve the problem]

In order to achieve the above object, the present invention provides a substrate for use in an optical information recording medium on which a signal pattern is formed, in which the substrate contains a diol of a saturated cyclic olefin containing one or more five-membered rings and a phosgene. It is characterized by comprising a polycarbonate synthesized by a reaction with.

〔Example〕

Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a cross-sectional view showing an embodiment of an optical disk using the optical recording medium substrate of the present invention, FIG. 2 is an enlarged cross-sectional view of the main part of FIG. 1, and FIGS. 3 and 4 are views of FIG. It is a sectional view showing another modification of .

In FIG. 1, 1 is a disk-shaped disk substrate, 2 is an underlayer, 3 is a recording layer, 4 is a center hole, 5 is a ventilation hole, and
As shown in the figure, a gap 6 is formed inside by bonding two optical disks together. Note that 7 indicates signal patterns such as pre-groups and pre-pits formed on the disk substrate 1. For the base layer 2, for example, a self-oxidizing substance such as polyvinyl nitrate is used,
The recording layer 3 contains, for example, an organic substance made of indole cyanine having a methine chain. Also,
If necessary, a protective layer 8 is provided on the surface of the recording layer 3 as shown in FIG. 3, and further a protective layer 8 is provided on the outer peripheral surface of the recording layer 3 and the disk substrate 1 as shown in FIG. There is also.

Here, the disk substrate 1 contains diol of a saturated cyclic olefin containing one or more five-membered rings, phosgene (COCl,
Polycarbonate synthesized by reaction with 2) is used.

The 5-membered ring used in the present invention is as shown below. (A) (B) (C) etc.

Moreover, these saturated cyclic olefin diols containing these five-membered rings include:

In particular, 5 in which one of the carbon atoms constituting the five-membered ring shown in (J) to (L) is substituted with a heteroatom such as sulfur, oxygen, nitrogen, etc.
Diols of saturated cyclic olefins containing membered rings and phosgene (
Polycarbonate synthesized by reaction with COC42z) has excellent adhesion to the optical recording layer 3.

In addition, when reacting the diol of a saturated cyclic olefin containing a five-membered ring shown in (J) to (L) with phosgene (COCl2), a sulfone group (-3o□
-) introduced therein has excellent adhesion to the optical recording layer 3.

The reason for this is that since sulfone groups are introduced into the obtained polycarbonate, electrostatic interaction is formed between the recording layer 3 (or underlayer 2) formed on the polarization of the sulfone groups. This seems to be for the purpose of

In disk substrates having the above-mentioned substrates, phenyl groups are not present, or even if present, they are present in small amounts, so retardation hardly increases and high C/
N signals can be obtained.

Example 1.2.3 Using each of the above-mentioned compounds (J), (K), and (L) as the diol of a saturated cyclic olefin containing a 5-membered ring, reacting each with phosgene (COCl22), A polycarbonate having a molecular weight of 10.000 to 20,000 was synthesized by the so-called phosgene method. At this time, the synthesized polycarbonates are as follows.

Each of the above-mentioned polycarbonates was melted at 300 to 350°C and injected at 1000 kg/cm 2 into an optical disc mold maintained at a mold temperature of 125°C to obtain a molded optical disc substrate. An optical recording layer (or underlayer) was formed on this substrate to obtain an optical recording medium. These optical disk substrates are characterized by heat resistance, water absorption, and mechanical strength (yield strength and elastic modulus).
, each characteristic of retardation was measured. In addition, as Comparative Examples 1 and 2, an optical disk substrate was formed in the same manner as in the above-mentioned Examples using a bisphenol-based polycarbonate (M) and a compound (N) having a structure in which the methyl group of this polycarbonate was replaced with a phenyl group. Then, each characteristic was measured. The results are shown in Table 1.

=10 As is clear from Table 1, in the optical disk substrates made of polycarbonates (G) to (1) of Examples 1, 2, and 3, Comparative Example 1 made of bisphenol-based polycarbonate (M) It has almost the same heat resistance, water absorption rate, and mechanical strength, and has a lower retardation value than Comparative Examples 1 and 2.

Therefore, in the optical disk substrate of Example 1.2.3,
An optical recording medium with excellent signal characteristics can be provided.

Example 4.5.6 Using each of the above-mentioned compounds (J), (K), and (L) as the diol of a saturated cyclic olefin containing a 5-membered ring, when reacting each with phosgene (COCj22), , for each diol, about 1 to 5 moi! % distinction, R
indicates the five-membered rings shown in (A) to (F). ) A polycarbonate with sulfone groups introduced was synthesized. A disk substrate was obtained from this polycarbonate in the same manner as in Example 1.2.3, and its properties were examined. As a result, the adhesiveness with the recording layer (or underlayer) formed on the disk substrate was excellent, and the retardation hardly increased.

FIG. 4 is a graph showing the relationship between recording power and C/N of an optical disk substrate using polycarbonate (/f) of Example 1. In the figure, the solid line is the optical disk substrate of Example 1, and the broken line is 3 is a measurement result of an optical disk substrate according to Comparative Example 1. In Figure 4, the optical disk substrate is 1.80O
The measurement was performed under the conditions of rotation at r, p, and m, lens numerical aperture NA=0.53, and IMH2 width recording signal.

As is clear from FIG. 4, Example 1 exhibits a higher C/N value than Comparative Example 1 at a recording power of about 5 mW or more.

〔Effect of the invention〕

As described above, the present invention has heat resistance and low moisture absorption equivalent to bisphenol-based polycarbonate used in conventional substrates, does not increase retardation, and has excellent signal characteristics. A recording medium can be provided.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of an optical disk using the optical information recording medium substrate of the present invention, FIG. 2 is an enlarged cross-sectional view of the main part of FIG. 1, and FIG.
4 is a sectional view showing a modification of FIG. 2, and FIG. 5 is a graph showing the relationship between recording power and C/N. DESCRIPTION OF SYMBOLS 1... Optical disk substrate, 2... Base layer, 3... Recording layer, 4... Center hole, 5... Ventilation hole, 6... Gap, 7... Signal pattern.

Claims (5)

[Claims] (1) In a substrate on which a signal pattern is formed and used in an optical information recording medium, the substrate is synthesized by a reaction between a saturated cyclic olefin diol containing one or more five-membered rings and phosgene. A substrate for an optical information recording medium characterized by being made of polycarbonate. (2) The 5-membered ring is any of the following cyclic groups (A) -
Claim (1) characterized by any of (F)
The optical information recording medium substrate described above. ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (A) ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (B) ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (C) ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ ( D) ▲There are mathematical formulas, chemical formulas, tables, etc.▼(E) ▲There are mathematical formulas, chemical formulas, tables, etc.▼(F) (3) The polycarbonate is one of the following (G) and (H)
, or (I), the substrate for an optical information recording medium according to claim (1). ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (G) ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (H) ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (I) (4) The optical information recording medium substrate according to claim (1), wherein one of the carbon atoms constituting the five-membered ring is substituted with a heteroatom. (5) The substrate for an optical information recording medium according to claim (1), wherein a sulfone group is introduced into the polycarbonate.