JPS6339156A - Optical recording medium - Google Patents

Abstract

PURPOSE:To improve initial performance and to improve continuous repetitive reproduction performance and light resistance by using iodine or perchloric acid additive of a squarylium dye as a recording film. CONSTITUTION:The recording film 3 is formed by forming an SiO2 film 2 by sputtering on the tracked surface of a substrate 1 and spin-coating the soln. of the iodine additive of the squarylium dye thereon. The squarylium dye to be used is the compd. expressed by the formula, where R1-R4 are an aryl group or satd. hydrocarbon rings, etc., of 5--7-membered rings in which R1 and R2 or R3 and R4 are combined, R5 and R6 are hydrogen or aryl group, alkyl group, Y denotes the element of group VI. The spectral absorption peak is thereby shifted and the recording and reproducing by a semiconductor laser, etc., are permitted; in addition, the medium is stable to external light and repetitive reproduction.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an optical recording medium that can be recorded by a semiconductor laser or the like.

Conventional technology The advent of the information age brings about a dramatic increase in information technology.

The diversified and voluminous information cannot be effectively utilized without a memory medium that has a large capacity and can be accessed quickly. Under these circumstances, recordable optical discs can be rightly said to be the most suitable external memory. Optical discs that can be recorded and played back by users are divided into types that can be rewritten and erased (hereinafter referred to as E/R discs) and types that can be recorded only one time (hereinafter referred to as W10 discs). It is expected that these two will coexist and develop by taking advantage of their respective characteristics.
The most important condition for disks is that they can be mass-produced at low cost.

Recently, coated type W10 discs using organic dyes have been attracting attention as a disc that meets these objectives. (
Reference: Organic Synthetic Chemistry Volume 43, page 334 (1985)
) Problems to be Solved by the Invention There are several conditions that must be met for a dye used as a recording film in an optical disk system using a semiconductor laser or the like as a light source. (1) Shows spectral absorption characteristics in the oscillation wavelength band of semiconductor lasers, etc. (2) It has an appropriate reflectance in the above wavelength range. (3) Dissolve in solvent. As a dye that satisfies these conditions, cyanine dyes can be cited as shown in the above-mentioned references. Since naphthoquinones and phthalocyanines are not soluble in solvents, they cannot be coated to form a film, leaving problems in mass production. It has been known for a long time that some cyanine dyes have spectral absorption in the infrared region, and many studies have been made as materials for use in semiconductor lasers. Some cyanine dyes have excellent initial properties such as sensitivity, solubility, reflectance, and spectral absorption, but they have drawbacks such as fading due to external light such as sunlight and being difficult to reproduce. Continuous irradiation (repeated reproduction) of the weak light used caused the signal to deteriorate, resulting in insufficient reliability. Various stabilizers have been studied to overcome this drawback.

(For example, JP-A-59-81) 94) However, since the cyanine dye itself is very unstable, sufficient stability has not been achieved even after improvement.

Means for Solving the Problems The optical recording medium of the present invention has a recording film layer made of an adduct of squarylium dye with iodine or perchloric acid.

In the state of the dye alone before forming the functional adduct, the spectral absorption maximum is at a wavelength of 700 nm or less, but due to the formation of the adduct, the maximum spectral absorption
The absorption peak shifts to around 00 nm, making it possible to record and reproduce using a semiconductor laser or the like. Furthermore, compared to cyanine dyes, it is more stable against external light and repeated reproduction.

EXAMPLE In the present invention, an optical recording layer containing an iodine or perchloric acid adduct of a squarylium dye represented by the following general formula (1) is formed on a transparent substrate. Formula (1
), R, -R, is an aryl group, and R, and R2, or R3 and R4 are connected to form a 5- to 7-membered heterocycle, an unsaturated hydrocarbon ring, and a saturated hydrocarbon ring. Sometimes it is a hydrogen ring.

In addition, Y in Ni (1) is a group II element, and among them, Ol
S, Se, Te are suitable. That is, it has a structure in which oxazole, thiazole, selenazole rings, etc. are bonded to the squarylium skeleton via a methine group. When these compounds exist alone, the spectral absorption peak exists in the range of 600 to 650 nm, and they cannot be recorded or reproduced by a semiconductor laser. When formed, the spectral absorption peak shifts to longer wavelength by about 200 nm,
This overlaps with the oscillation wavelength range of semiconductor lasers, making it possible to record with semiconductor lasers. The amount of iodine or perchloric acid added is 0.6 to the compound
~1.3 is appropriate. Furthermore, the adduct represented by formula (1) is soluble in organic solvents, and can form a uniform film on a transparent substrate by coating. Here, a spin coating method was used as it is suitable for forming a film on an optical disk.

As the transparent substrate, glass, polymethyl methacrylate, polycarbonate, polyamideimide, etc. can be used. Alternatively, a groove for tracking servo may be formed on a transparent substrate, and the dye film described in the present invention may be formed thereon.

If there is a possibility that the dye solution may dissolve the transparent substrate, a thin transparent protective film may be formed on the substrate in advance. As the transparent protective film, 5iOz, SiO% alkylsilane, polysiloxane, etc. are suitable.

Example 1 As shown in the figure, the fin has a thickness of 1.2 mm and a depth of 0.06 μ on the surface.
A groove with a width of 0.6μ (hereinafter referred to as a track) is 1.6μ
A SiO□ film 2 having a thickness of 10 nm is formed by sputtering on a surface of a polymethyl methacrylate (hereinafter referred to as PMMA) type substrate 1 having tracks formed in a pinched spiral shape. A methylene chloride solution of an iodine adduct of a compound represented by the following formula (2) was spin-coated onto this to form a recording film 3 having a thickness of 60 nm.

While rotating the substrate, light from a semiconductor laser (hereinafter referred to as LD) focused by a collimating lens with a numerical aperture of 0.5 was irradiated onto the track, and an IMIfz signal was recorded. At this time, the recording power was 4 rnW, and the rotation speed was a constant linear velocity of 3 m/sec.

Table 1 shows the characteristics when the recorded signal was reproduced at 0.4 mW. Table 1 also shows the results of repeated playback tests on the same trunk and measurement of the amount of decrease in playback C/H from the initial value after 106 consecutive plays. In addition, the playback C/
The results of measuring the decrease in N are also shown in Table 1 as a fading test.
It was shown to.

Example 2 An optical disc was prepared by applying the iodine adducts of the compounds represented by the following formulas (3) to (6) to a thickness of 60 nm on a PMMA substrate having the same shape as in Example 1 using the same method as the recording film. Table 1 shows the results of evaluation on the same items as in Example 1.

Cz Hs Cz II s
Comparative Example 1 An optical disc was prepared by coating a cyanine dye compound represented by the following formula (7) to a thickness of 60 nm on a PMMA substrate having the same shape as in Example 1 to a thickness of 60 nm.
Table 1 shows the results of evaluation on the same items.

Example 3 On a polycarbonate substrate of the same shape as in Example 1, a perchloric acid adduct of the compounds shown in (2) to (3) was applied to a thickness of 6On+n using the same method to create an optical disc as a recording film. Table 2 shows the results of evaluation on the same items as in Example 1.

Comparative Example 2 An optical disc was prepared and used as a recording film by applying the compound represented by formula (2) alone to a thickness of 60 nm without using an iodine adduct using the same method as in Example 1 on a PMMA substrate having the same shape as in Example 1. Table 2 shows the results of evaluation on the same items as in Example 1.

Table 2 Effects of the Invention As described above, the optical recording medium of the present invention having a recording film made of an iodine or perchloric acid adduct of a squarylium compound has good initial performance, and has excellent continuous repeated playback performance. Excellent light resistance.

[Brief explanation of the drawing]

The figure is a sectional view for explaining the structure of the optical recording medium of the present invention. 1...Transparent substrate, 2...Transparent protective film,
3...Recording film.

Claims (4)

[Claims] (1) An optical recording medium comprising a transparent substrate and a recording film layer formed on the transparent substrate and containing an iodine or perchloric acid adduct of squarylium dye as at least one component. (2) The optical recording medium according to claim (1), wherein the squarylium dye is a compound represented by the following general formula. ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (In the formula, R_1-R_4 are aryl groups, or are R_1 and R_2 or R_3 and R_4 connected to a 5- to 7-membered saturated hydrocarbon ring, aromatic carbon It is either a hydrogen ring or a heterocycle, R_5 and R_6 are hydrogen, an aryl group, or an alkyl group, and Y represents a Group VI element, respectively.) (3) Claim No. 1 in which the Group VI element in the squarylium dye is oxygen sulfur, selenium, or tellurium.
1) The optical recording medium described in item 1). (4) The optical recording medium according to claim (1), wherein recording and reproduction are performed using a semiconductor laser in the recording film layer.