JPS5996544A - Optical information recording medium - Google Patents

Abstract

PURPOSE:To reduce the power of a recording medium for recording by regulating the total amount of components with <=about 400 low mol.wt. such as a monomer and an oligomer remaining in a substrate to a specified wt% or more. CONSTITUTION:The total amount of components with <=about 400 low mol.wt. present in a substrate is finally regulated to >=0.8wt%. The components include additives such as a mold releasing agent, a polymn. initiator, a mol.wt. regulator, a stabilizer, a lubricant and a plasticizer, low molecular components remaining in the substrate such as a monomer and an oligomer, and substances stuck to a molded body as the substrate. A vapor-deposited Sb2Se3 layer of 350Angstrom thickness is formed as a recording layer 12 on a PMMA substrate 11 of 1.2mm. thickness obtd. by injection molding, and on the layer 12, a vapor-deposited Bi2Ti3 layer of 492Angstrom thickness is formed as a reflecting layer 13 to obtain an optical information recording medium 14.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an optical information recording medium suitable for application to optical video discs, optical digital audio discs, and the like.

BACKGROUND ART AND PROBLEMS Regarding general video discs, digital audio discs, etc., information recording media that allow general users to record 1+1 information have not yet become widespread. In order to enable general users to record information on optical recording media such as video discs and digital audio discs, information that can be recorded with as little power as possible is required. A recording medium is required. In this type of information recording medium, various efforts have been made to reduce the power of the recording material layer. For example, in the information recording medium proposed by the applicant earlier, the recording layer is mainly composed of a diaphragm layer whose optical properties change due to heat, and this medium is An information recording medium has been proposed in which a modulated laser beam is irradiated to convert the optical energy into thermal energy so that optical characteristic changes can be obtained in recording (c)1). This information recording medium is, for example, a so-called casting plate formed by casting and polymerizing a transparent substrate such as a glass plate or polymethyl methacrylate (PMMA), as shown in FIG. On a substrate (1) made of a molded plate etc. by injection molding, a recording layer (2) made of Sb and Se of 350 mm thick and 51 m of Se is provided, and on top of this, for example, a layer made of Bj of 492 mm thick, Te, etc. is placed. A reflective layer (3) is provided, and as shown by the arrow a in FIG. By converting the optical energy of a laser beam into thermal energy and heating it, optical characteristics (1), for example, changes in transmittance (1) and reflectance (1) in accordance with the written information are obtained, and the recording is performed by forming optical recording bits. There has been provided an information recording medium designed to reduce the recording power.

However, in the past, the reduction of recording power in this type of information recording medium has mainly been carried out with respect to the recording layer, and considerations regarding the substrate material have only focused on the thermal conductivity of the substrate. do not have.

In other words, the substrate (1) in an optical information recording medium in which recording is mainly caused by heat, that is, recording bits are formed by a change in optical properties, depends on its thermal constants (thermal conductivity, thermal diffusion constant). It is said that the higher the thermal conductivity of the substrate, the more difficult it is to record, and the higher the heat storage property of the substrate material, the easier it is to record.

However, in practice, the recording power in such an optical information recording medium, particularly in an information recording medium in which the recording is made as a change in optical characteristics such as light transmittance 2 reflectance, is as follows. The results do not necessarily depend significantly on the thermal constant of the substrate material.

Purpose of the Invention The present invention makes it possible to significantly reduce the recording power in an information recording medium in which recording is performed as changes in optical characteristics such as light transmittance and reflectance. The present invention aims to provide an optical information recording medium.

Summary of the Invention In the present invention, as a result of various research and considerations by the present inventors, as described above, there is provided an information recording system in which the recording is performed as a change in optical characteristics such as light transmittance and reflectance. In a medium, the reduction of the recording power is largely influenced by the overall composition of the low molecular weight components, i.e., volatile components, that ultimately remain on the substrate that supports the recording layer on which optical recording is performed. This invention was made based on this research.

That is, in the present invention, in an optical information recording medium having a recording layer on which optical property changes are recorded on a substrate, the substrate contains a mold release agent, 9 a polymerization initiator, 2 a molecular weight regulator, The total amount of low molecular weight additives with a molecular weight of about 400 or less such as stabilizers, lubricants, and plasticizers, low molecular weight components such as monomers and oligomers remaining on this substrate, and low molecular weight substances added to the molded body as a substrate. The total amount of low molecular weight components having a molecular weight of about 400 or less is made to be present in the final substrate component in an amount of at least 0.0% by weight.

Examples Example 1 As shown in Fig. 2, a PMMA substrate (11) with a thickness of 2 mm and a thickness of 3
A recording layer a consisting of vapor-deposited layers of 8b and 8e of 50X was deposited, and on top of this a reflective layer (13) consisting of a vapor-deposited layer of Bi and i'e of 492 J was deposited. Optical information
A recording medium (14) is obtained, and this is designated as sample number 1. This example 1. That is, in the molded body of the substrate 01) in sample number 1, a mold release agent having a molecular weight of 240 to 400, a polymerization initiator, residual monomers, etc., containing a total low molecular weight of 1.2% by weight was used.

Example 2 The structure was the same as that of Example 1, but a similar PMA injection molded body having a total low molecular weight of 1.0% by weight was used as the substrate αυ. The information storage medium according to Example 2 is designated as sample number 2.

Example 3゜Example 1. With the same structure as that, the substrate Ql) is a similar PM with a total low molecular weight of 0.8 to 0.9% by weight.
An MA injection molded body was used. This Example 3.
Sample number 3 is the information recording medium according to the above.

Comparative Examples 1 to 3 Example 1. Even with the same configuration as that, the substrate (11
), one low molecular weight company has 0.6% and 0.5%, respectively.
Information recording media were prepared using similar PM and Mk injection molded bodies containing 0.4% by weight and 0.4% by weight, respectively, and these were designated as sample numbers 4 to 6.

Example 4゜Example 1. With the same structure as above, a polycarbonate (PC') injection molded body having a total low molecular weight of about 200 ppm was used as the substrate 01). This example 4. Sample number 7 is the information recording medium according to the above.

For each sample 1 to 7, disks with a recording portion of 100 mm in diameter were obtained, and the number of rotations was 1800 mm for each of these disks.
Recordings were carried out by a semiconductor laser at a wavelength of 8300 rpm and 120 rnA. The actual recording power on the disk surface at this time corresponds to 3.6 mW. As is clear from Table 1, Samples 1 to 3 according to the present invention are as follows:
It can be seen that compared to Samples 4 to 6, a higher reproduction output, or in other words, a reduction in recording power, can be achieved.

In addition, PMMA is used as a substrate material in Samples 1 to 6, and PC is used in Sample 7, and the thermal conductivity of PMMA is 5cal・-1-1-1 secm *C0, Thermal diffusion constant is 1.2 crn-
s is moderate, while those of PC are 4.6 cal-s'-'-cm'-C'', 0.
82 cm -s, and according to the comparison of these thermal constants, samples 1 to 3 according to the present invention have inferior recording and reproducing characteristics when using I'MMA compared to when using PC. According to the above, it can be seen that a sample showing characteristics comparable to or better than Sample 7 using PC can be obtained.

Furthermore, as the disk diameter increases, the relative linear velocity of its rotation to the laser beam increases at the periphery, so the optimal disk recording power to achieve good recording also at the periphery increases. . FIG. 3 shows the relationship between the diameter of this disk and the optimum disk recording power for good recording. However, when using a conventional PMMA substrate made by low molecular weight casting with less than 0.8 weight M%, the curves (2no and 0231 each have a low molecular weight of 1.0 weight). %, 1.6% by weight of similar PMMA
In the case according to the present invention using a substrate, these curves (
As is clear from comparing 2υ with (sha) and (c), in the case of the present invention, it is found that the optimum recording power can be sufficiently lowered. Even if the diameter of the disk is 200 mm, the recording power will be as follows from the curve (21 mm).
), it can be seen that the conventional recording hole with a diameter of 120πm is sufficient.

Effects of the Invention As described above, according to the optical information recording medium of the present invention, the recording power can be reduced.

The drive current of the writing laser beam can be reduced,
Along with this, the service life of the laser beam can be extended, and it will also contribute to the popularization of video discs and audio discs that can be used by general users. Furthermore, it is possible to create a large-diameter disk with the same power, and the benefits are extremely large in terms of increasing the recorded content.

Although the reason for the reduction in recording power or the improvement in reproduction output in the recording medium according to the present invention has not yet been clearly elucidated, it is possible that the substrate αυ contains a low-molecular material, that is, a volatile component. Therefore, the substrate (1) is heated by heating the recording layer by laser beam irradiation during recording.
This is thought to be due to the fact that bubbles or bulges are generated in the heated recording portion on the recording layer side in 1) due to the volatilization effect of the volatile components, which also causes changes in optical characteristics due to shape changes in the recording portion.

[Brief explanation of the drawing]

FIG. 1 is an enlarged sectional view of an information recording medium to be compared with the present invention, FIG. 2 is an enlarged sectional view of an example of an optical information recording medium according to the invention, and FIG. 3 is an enlarged sectional view of an information recording medium according to the present invention. FIG. 3 is a characteristic curve diagram showing the relationship with the optimum disc recording power. αυ is the substrate, αυ is the recording layer, and 03) is the reflective layer. Figure 3 ``Suff Reception (Liu Shun) → Procedural Amendment, Chief Examiner of the Japan Patent Office), Indication of the case 1982 Patent Application No. 205802, Title of the invention
Relationship with the case of a person who puts heavy pressure on optical type (W report n media 3) Patent applicant address: Tokyo Parts For Omen 61” If+ No. 7-35 Name (2+8) Sony Corporation Representative Director Yu Oga Betsu, Number of inventions increased by amendment

Claims (1)

[Scope of Claim] A release agent double polymerization initiator added to the substrate in an optical information recording medium having a recording layer on which changes in optical properties are recorded. The total amount of all low molecular weight components with a molecular weight of about 400 or less, such as low molecular weight additives, stabilizers, lubricants, plasticizers, monomers and oligomers remaining on the substrate, is 0.8 m! To have more than %! Optical information recording medium with LW.