Novel naphthalocyanine dye, method for preparing the same, and optical information recording medium employing the same

Disclosed are a novel naphthalocyanine dye shown in the specification, a method for preparing the same, and an optical information recording medium employing the same. According to the present invention, there can be obtained a novel naphthalocyanine dye, a method for preparing the same, and an optical information recording medium employing the same, which has excellent characteristics in recording/reading out property and in reading stability.

BACKGROUND OF THE INVENTION 
The present invention relates to a novel naphthalocyanine dye, a method for 
preparing the same, and an optical information recording medium employing 
the same. 
An optical information recording medium has an excellent characteristic 
feature that no wearing out or deterioration will not occur since the 
medium is used without coming into contact with a recording or a reading 
out head, and therefore developing researches have been made on various 
kinds of recording mediums. Particularly in the field of heat mode 
recording systems utilizing laser diode and the like, low-melting metals, 
organic polymers and dyes have been proposed as materials capable of 
melting, evaporating and sublimating. Above all, an organic film 
containing an organic polymer or a dye is preferable from view of high 
recording sensitivity, owing to a low heat conductivity and a low melting 
or sublimating temperature. As examples of such dyes, various materials 
such as cyanine dyes and squalirium dyes have been proposed. 
Heretofore, the optical information recording medium in which the dye is 
used as a recording layer has been known, as disclosed in Japanese Patent 
Provisional Publication No. 16948/1981. However, if it is attempted to 
utilize this kind of dye film recording layer as a reflection type optical 
information recording medium, a metallic reflective film will be 
additionally required, which makes the medium constitution complicated and 
leads to the deterioration in information recording/reading out properties 
disadvantageously. In order to overcome this problem, it has been proposed 
to make use of a cyanine type dye or the like having a suitably high 
reflectance, as disclosed in Japanese Patent Provisional Publication No. 
78787/1985. However, the cyanine type dye generally is poor in stability 
against light, and therefore it is liable to be decolorized by repeated 
irradiation of a reading beam at the time of reading after writing, with 
the result that an S/N ratio for the reading decreases inconveniently. 
On the other hand, Japanese Patent Provisional Publication Nos. 25886/1986 
and 177287/1986 propose to employ to the recording layer a 
naphthalocyanine compound as the dye which is excellent in light fastness. 
With regard to the naphthalocyanine dye disclosed in the former 
literature, its reflectance is usually lower as compared with the cyanine 
dye, and for this reason, its recording/reading out properties are poor 
and unsatisfactory. Further, in the latter literature, it is proposed to 
apply a material similar to the naphthalocyanine dye of the present 
invention to the information recording medium, but no examples for 
exhibiting effectiveness as the optical information recording medium have 
not been disclosed at all. Therefore, such a publication does not enable a 
person skilled in the art to judge whether the recording/reading out 
properties are excellent or not, or the level of reflectance is fully 
satisfactory or not. 
In view of such a situation, intensive researches have been conducted to 
eliminate the above-mentioned drawbacks of the conventional techniques. As 
a result, it has been found that a novel naphthalocyanine dye synthesized 
by the present inventors has a reflectance equal to or higher than that of 
a cyanine type dye and is excellent in reading stability, when used to 
form an optical information recording medium, to accomplish the present 
invention. 
SUMMARY OF THE INVENTION 
An object of the present invention is to provide a novel naphthalocyanine 
dye, a method for preparing the same, and an optical information recording 
medium employing the same, which has excellent characteristics in 
recording/reading out property and in reading stability. Namely, the 
present invention provides a novel naphthalocyanine dye represented by the 
general formula (I): 
##STR1## 
wherein R is an alkyl group having 1 to 22 carbon atoms or an aryl group 
and three Rs may be the same or different; M is selected from the group 
consisting of Si, Al, Ti, Ge and Sn; 
Y.sub.1 and Y.sub.2 are selected from the group consisting of OR', OAr, 
OSi(R').sub.3, OSi(Ar).sub.3 and OC(Ar).sub.3 and may be the same of 
different, with the proviso that when M is Al, Y.sub.1 alone should be 
bound to M and Y.sub.2 is absent, in which R' is an alkyl group having 1 
to 22 carbon atoms, and 
Ar is an aryl group or an aralkyl group, 
a method for preparing the same, and an optical information recording 
medium employing the same.

DETAILED DESCRIPTION OF THE INVENTION 
A first aspect of the present invention is directed to a novel 
naphthalocyanine dye represented by the general formula (I) as described 
above. 
The novel naphthalocyanine dye having the above general formula (I) is 
soluble in any of aromatic, halogen type, ether type and ketone type 
solvents, and can be easily purified to heighten its purity. Additionally, 
with regard to the naphthalocyanine dye, its ability to absorb a laser 
diode beam is remarkably high and is not varied depending on the kind, 
concentration and the like of the solvent, and its reflectance and 
stability against light are also high. 
The above-mentioned aromatic solvent includes benzene, toluene, xylene, 
chlorobenzene, 1-chloronaphthalene and quinoline; the above ether type 
solvent includes diethyl ether, dibutyl ether, tetrahydrofuran, ethylene 
glycol monomethyl ether, ethylene glycol dimethyl ether, diethylene glycol 
monomethyl ether and diethylene glycol dimethyl ether; the above ketone 
type solvent includes acetone, methyl ethyl ketone, methyl propyl ketone, 
cyclopentanone, cyclohexanone and acetone alcohol. 
The alkyl group having 1 to 22 carbon atoms represented by R in the general 
formula (I) includes a methyl goup, ethyl group, propyl group, isopropyl 
group, butyl group, sec-butyl group, tert-butyl group, pentyl goup, hexyl 
group, heptyl group, octyl group, nonyl group, decyl group, undecyl group, 
dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, 
hexadecyl group, heptadecyl group, octadecyl group, nonadecyl group, 
eicosyl group, heneicosyl group and docosyl group, and above all, the 
methyl and ethyl groups are preferable. The aryl group represented by R in 
the general formula (I) includes a phenyl group, tolyl group, xylyl group, 
hydroxyphenyl group, naphtyl group, anthryl group and pyrenyl group, and 
above all the phenyl group is preferable. The symbol M in the general 
formula (I) is selected from the group consisting of Si, Al, Ti, Ge and 
Sn, as described above. The symbols Y.sub.1 and Y.sub.2 in the general 
formula (I) are selected from the group consisting of OR', OAr, 
OSi(R').sub.3, OSi(Ar).sub.3 and OC(Ar).sub.3 and may be the same or 
different mutually. Above all, OR' OAr, OSi(R').sub.3 and OSi(Ar).sub.3 
are preferable. When M is Al, Y.sub.1 alone is bound to M and Y.sub.2 is 
absent, and in other cases, Y.sub.1 and Y.sub.2 both are bound thereto. 
The alkyl group having 1 to 22 carbon atoms represented by R' in Y.sub.1 
and Y.sub.2 includes the above-mentioned examples of the alkyl groups 
represented by R, and above all, the alkyl group having 1 to 18 carbon 
atoms is preferable. The aryl group represented by Ar in Y.sub.1 and 
Y.sub.2 includes the above-mentioned examples of the aryl group 
represented by R, and above all, the phenyl group is preferable. The 
aralkyl group represented by Ar in Y.sub.1 and Y.sub.2 includes a benzyl 
group, phenethyl group, methylbenzyl group and naphthylmethyl group, and 
above all, the benzyl and methylbenzyl groups are preferable. Exemplary 
compounds of the novel naphthalocyanine dye are as follows: 
(1) [(n-C.sub.6 H.sub.13).sub.3 SiO].sub.2 SiNc[Si(CH.sub.3).sub.3 ].sub.4 
Bis(trihexylsilyloxy)-tetrakis(trimethylsilyl)naphthalocyanino-silicon 
(in the above formula, Nc is a naphtalocyanine skeleton) 
(2) [(CH.sub.3).sub.3 SiO].sub.2 SiNc[Si(CH.sub.3).sub.3 ].sub.4 
Bis(trimethylsilyloxy)-tetrakis(trimethylsilyl)naphthalocyanino-silicon 
(3) [(C.sub.2 H.sub.5).sub.3 SiO].sub.2 GeNc[Si(CH.sub.3).sub.3 ].sub.4 
Bis(triethylsilyloxy)-tetrakis(trimethylsilyl)naphthalocyanino-germanium 
(4) [(n-C.sub.4 H.sub.9).sub.3 SiO].sub.2 SnNc[Si(CH.sub.3).sub.3 ].sub.4 
Bis(tributylsilyloxy)-tetrakis(trimethylsilyl)naphthalocyanino-tin 
(5) C.sub.6 H.sub.5 OAlNc[Si(CH.sub.3).sub.3 ].sub.4 
Tetrakis(trimethylsilyl)naphthalocyanino-phenoxyaluminum 
(6) [(n-C.sub.3 H.sub.7).sub.3 SiO].sub.2 TiNc[Si(CH.sub.3).sub.3 ].sub.4 
Bis(tripropylsilyloxy)-tetrakis(dimethylsilyl)naphthalocyanino-titanium 
(7) [(CH.sub.3).sub.3 SiO].sub.2 SiNc[Si(CH.sub.3).sub.2 C.sub.6 H.sub.5 
].sub.4 
Bis(trimethylsilyloxy)-tetrakis(trimethylphenylsilyl)-naphthalocyanino-sili 
con 
(8) (C.sub.2 H.sub.5 O).sub.2 SiNc[Si(C.sub.6 H.sub.5).sub.3 ].sub.4 
Diethoxy-tetrakis(triphenylsilyl)naphthalocyanino(9) 
(9) [(C.sub.6 H.sub.5).sub.3 SiO].sub.2 SiNc[Si(C.sub.2 H.sub.5).sub.3 
].sub.4 
Bis(triphenylsilyloxy)-tetrakis(triethylsilyl)naphthalocyanino-silicon 
(10) [(n-C.sub.4 H.sub.9).sub.3 SiO].sub.2 SiNc[Si(n-C.sub.4 H.sub.9).sub.3 
].sub.4 
Bis(tributylsilyloxy)-tetrakis(tributylsilyl)naphthalocyanino-silicon 
(11) [(C.sub.2 H.sub.5).sub.3 SiO].sub.2 SiNc[Si(CH.sub.3).sub.2 n-C.sub.18 
H.sub.37 ].sub.4 
Bis(triethylsilyloxy)-tetrakis(dimethyloctadecylsilyl)-naphthalocyanino-sil 
icon 
(12) [(C.sub.2 H.sub.5).sub.3 SiO].sub.2 SiNc[Si(CH.sub.3).sub.2 n-C.sub.10 
H.sub.21 ].sub.4 
Bis(triethylsilyloxy)-tetrakis(dimethyldecylsilyl)naphthalocyanino-silicon 
(13) [(C.sub.2 H.sub.5).sub.3 SiO].sub.2 GeNc[Si(CH.sub.3).sub.2 n-C 
.sub.14 H.sub.29 ].sub.4 
Bis(triethylsilyloxy)-tetrakis(dimethyltetradecylsilyl)-naphthalocyanino-ge 
rmanium 
Among these compounds, the compound (3) is preferable. 
A second aspect of the present invention is directed to a method for 
preparing a novel naphthalocyanine dye represented by the following 
general formula (I): 
##STR2## 
wherein R is an alkyl group having 1 to 22 carbon atoms or an aryl group 
and three Rs may be the same or different; M is selected from the group 
consisting of Si, Al, Ti, Ge and Sn; 
Y.sub.1 and Y.sub.2 are selected from the group consisting of OR', OAr, 
OSi(R').sub.3, OSi(Ar).sub.3 and OC(Ar).sub.3 and may be the same of 
different, with the proviso that when M is Al, Y.sub.1 alone should be 
bound to M and Y.sub.2 is absent, in which R' is an alkyl group having 1 
to 22 carbon atoms, and 
Ar is an aryl group or an aralkyl group, 
which comprises the steps: 
(a) reacting at least one of trialkylsilyl- or 
triarylsilyl-2,3-dicyanonaphthalenes represented by the following general 
formula (II): 
##STR3## 
wherein R is as defined above, with a metal halide represented by the 
following general formula (III): 
EQU MXn (III) 
wherein M is as defined above, X is a halogen atom, and n is a positive 
integer which is the number of X bound to M, 
to form a dihalogenometal-tetrakis(trialkylsilyl or 
triarylsilyl)naphthalocyanine compound represented by the following 
general formula (IV): 
##STR4## 
wherein R, M and X are as defined above, 
(b) hydrolyzing the resulting compound represented by the general formula 
(IV) to form a dihydroxymetal-tetrakis(trialkylsilyl or 
triarylsilyl)naphthalocyanine compound represented by the following 
general formula (V): 
##STR5## 
wherein R and M are as defined above, and 
(c) reacting the resulting compound represented by the general formula (V) 
with an alcohol represented by the general formula (VI): 
EQU R"OH (VI) 
wherein R" is selected from the group consisting of R', Ar, Si(R').sub.3, 
Si(Ar).sub.3 and C(Ar).sub.3 in which R' is an alkyl group having 1 to 22 
carbon atoms, Ar is an aryl group, and R' and Ar may be the same or 
different, or with a halogen compound represented by the following formula 
(VII): 
EQU R"Cl (VII) 
wherein R" is as defined above. 
The novel naphthalocyanine dye represented by the general formula (I) may 
be prepared by reacting under heating the compound represented by the 
general formula (V) with an excess amount of the alcohol represented by 
the general formula (VI) or the halide represented by the general formula 
(VII). In this reaction, a reaction temperature is preferably within the 
range of 80 .degree. to 250.degree. C., and a reaction time is preferably 
within the range of 30 minutes to 10 hours. This reaction may be carried 
out in the absence of or preferably in the presence of a solvent such as 
benzene, toluene, xylene, trimethylbenzene, chlorobenzene, 
dichlorobenzene, trichlorobenzene, 1-chloronaphthalene, tetralin, 
pyridine, .beta.-picoline and quinoline. 
The isolation/purification of the novel naphthalocyanine dye represented by 
the general formula (I) from the resulting reaction mixture may be carried 
out by separating the desired compound from the reaction mixture by use of 
column chromatography or thin-layer chromatography, and then purifying it 
by recrystallization. 
The dihydroxymetal-tetrakis(trialkylsilyl or triarylsilyl)naphthalocyanine 
compound represented by the general formula (V) may be prepared by 
hydrolyzing the compound represented by the general formula (IV) under 
heating. In this hydrolysis, a reaction temperature is preferably within 
the range of 50.degree. to 150.degree. C., and a reaction time is 
preferably within the range of 30 minutes to 10 hours. The hydrolysis is 
preferably performed in a mixed solvent such as pyridine/water, 
pyridine/ammonia water, methanol/ammonia water, ethanol/ammonia water or 
propanol/ammonia water, or alternatively by treating with concentrated 
sulfuric acid and then with ammonia water. 
In the metallic halide having the general formula (III), usable halogen 
atoms are Cl, Br, I and the like. 
The trialkylsilyl- or triarylsilyl-2,3-dicyanonaphthalene represented by 
the general formula (II) are known compounds and may be prepared, for 
example, by the following procedure: 
A 2,3- or 3,4-dimethyltrialkylsilyl- or -triarylsilylbenzene represented by 
the following general formula (VIII): 
##STR6## 
wherein R is an alkyl group having 1 to 22 carbon atoms or an aryl group, 
and N-bromosuccinimide represented by the formula (IX): 
##STR7## 
are subjected to photo-irradiation under heating to form a compound 
represented by the general formula (X): 
##STR8## 
wherein R is an alkyl having 1 to 22 carbon atoms or an aryl group. 
Next, the thus prepared compound having the general formula (X) is reacted 
under heating with fumaronitrile represented by the formula (XI): 
##STR9## 
to form the desired trialkylsilyl- or triarylsilyl-2,3-dicyanonaphthalene 
represented by the general formula (II). In the present invention, if 
necessary, two or more kinds of compounds represented by the general 
formula (II) may be reacted with the metallic halide represented by the 
general formula (III). 
In general, the above reaction of 2,3- or 3,4-dimethyltrialkylsilyl- or 
-triarylsilylbenzene represented by the general formula (VIII) with 
N-bromosuccinimide represented by the formula (IX) may be carried out by 
heating under reflux in an amount of 0.2 mol of the former and 0.8 mol of 
the latter for 4 to 12 hours under the irradiation by use of a 
high-pressure mercury vapor lamp in 200 to 1,000 ml of a solvent which is 
inactive to this photo-irradiation. In this reaction, a peroxide which is 
a radical generator is required to be added as an initiator for the 
photo-reaction. The peroxide includes benzoyl peroxide, octanoyl peroxide, 
cyclohexanone peroxide, isobutyryl peroxide, 2,4-dichlorobenzoyl peroxide 
and methyl ethyl ketone peroxide. In general, the peroxide can be used in 
an amount ranging from 500 mg to 2 g based on 500 ml of the solvent. 
The solvent which is inactive to the photo-irradiation can be suitably 
selected from halogen type solvents such as chloroform and carbon 
tetrachloride, or aromatic solvents such as benzene and chlorobenzene. 
The reaction of the compound represented by the general formula (X) with 
the fumaronitrile represented by the formula (XI) is carried out in the 
presence of 1 mol of the former and 1 to 2 mol of the latter, and in this 
case, a reaction temperature is preferably within the range of 70.degree. 
to 100.degree. C. and a reaction time is preferably within the range of 5 
to 10 hours. Preferable solvent includes polar organic solvents such as 
N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, 
N,N-diethylformamide and N,N-diethylacetamide. 
A third aspect of the present invention is directed to an optical 
information recording medium in which an organic film containing a 
naphthalocyanine dye represented by the following general formula (I) as 
the main component is formed on a substrate: 
##STR10## 
wherein R is an alkyl group having 1 to 22 carbon atoms or an aryl group 
and three Rs may be the same or different; M is selected from the group 
consisting of Si, Al, Ti, Ge and Sn; 
Y.sub.1 and Y.sub.2 are selected from the group consisting of OR', OAr, 
OSi(R').sub.3, OSi(Ar).sub.3 and OC(Ar).sub.3 and may be the same of 
different, with the proviso that when M is Al, Y.sub.1 alone should be 
bound to M and Y.sub.2 is absent, in which R' is an alkyl group having 1 
to 22 carbon atoms, and 
Ar is an aryl group or an aralkyl group, 
In the optical information recording medium, a recording layer comprising 
the novel naphthalocyanine dye of the first aspect of the present 
invention as a main component is provided on a substrate. If desired, 
other layers such as a primary coat and protective layer may be 
additionally formed thereon. 
The usable substrate is known to a person skilled in the art and may be 
permeable or impermeasble to a laser beam used. However, when write and 
read are carried out on the side of the substrate by the laser beam, the 
substrate must be permeable to the laser beam, whereas when writing and 
reading are carried out on the reverse side to the substrate, i.e., on the 
side of the recording layer, the substrate may not be permeable to the 
laser beam. The substrate may be made from a material usually used, and 
examples of the substrate materials include glasses, quartz, ceramic, 
plastics, papers, and plane-like and foil-like metals. If desired, some 
guide grooves having a concavo-convex structure may be formed on the 
substrate. 
The formation of the recording layer can be achieved in accordance with a 
coating method, a printing method or an evaporating method. In the case of 
the optical information recording medium, the utilization of the coating 
method is economically advantageous to form the recording layer, and also 
in the present invention, it is desirable to make use of the coating 
method or printing method. In the case of the coating method, a solvent is 
used such as toluene, chloroform, dichloroethane and methyl ethyl ketone 
and the like, and it may be carried out by spraying, roller coating, spin 
coating or dipping and the like. 
The optical information recording medium employs, as the recording layer, 
the organic film mainly comprising the novel naphthalocyanine dye which 
has suitable absorbance and reflectance in the wavelength range of the 
laser beam and which is excellent in light stability, and therefore it 
possesses good recording/reading out properties and improved reading 
stability. In addition, the novel naphthalocyanine dye is excellent in 
solubility in various organic solvents, and the formation process of the 
recording layer is also predominant over conventional techniques. 
EXAMPLES 
Now, the present invention is described in detail in reference to Examples, 
but it should not be limited to these Examples. 
EXAMPLE 1 
Synthesis of 
Bis(triethylsilyloxy)-tetrakis(trimethyl)-naphthalocyanino-germanium 
(Exemplary compound No. 3) 
(i) Synthesis of 4-trimethylsilyl-o-xylene 
To 14.4 g of magnesium turnings which had been sufficiently dried, a small 
amount of an iodine crystal and then 250 ml of ethyl ether were added. A 
solution of 92.5 g of 4-bromo-o-xylene in 100 ml of ethyl ether was added 
dropwise to the resulting mixture over about 2 hours in a nitrogen 
atmosphere under gentle reflux. After completion of addition, stirring was 
continued for about 1 hour to prepare a Grignard reagent completely. 
To a solution of trimethylchlorosilane (90 g) and ethyl ether (250 ml) was 
added dropwise the thus prepared Grignard reagent over about 1 hour under 
reflux, and then the reflux was additionally continued for 1 hour. After 
cooling on an ice bath, an aqueous saturated ammonium chloride solution 
was added dropwise thereto in order to decompose the Grignard reagent, 
followed by separating an ether layer from the reaction mixture. The 
remaining aqueous solution was extracted three times with benzene, and the 
resulting extracts were collected and then dried with anhydrous magnesium 
sulfate. This solution was concentrated and distilled under reduced 
pressure to obtain 40 g of colorless liquid of 4-trimethylsilyl- o-xylene 
at a boiling point of 98.degree. to 103.degree. C./27 to 30 mmHg. 
(ii) Synthesis of 6-trimethylsilyl-2,3-dicyanonaphthalene 
One gram of benzoyl peroxide was added to 500 ml of a carbon tetrachloride 
solution containing 35.6 g of 4-trimethylsilyl-o-xylene and 142.4 g of 
N-bromosuccinimide. The solution was irradiated by a high-pressure mercury 
lamp (100 W) for about 12 hours under reflux. After cooling, precipitated 
white crystals were removed by filtration, and the carbon tetrachloride 
solution which was a mother liquor was concentrated sufficiently under 
reduced pressure. The resulting light brown oil was then dissolved in 800 
ml of anhydrous N,N-dimethylformamide, and 27 g of fumaronitrile and then 
200 g of sodium iodide were added thereto with adequate stirring. The 
solution was then stirred at 75.degree. C. for about 7 hours in a nitrogen 
atmosphere. After the reaction, the solution was poured into about 4 kg of 
ice, and sodium hydrogensulfite was added thereto gradually until the 
red-brown tint of the aqueous solution changed into a light yellow. A 
slightly excess amount of sodium hydrogensulfite was added thereto, and 
stirring was then carried out for a certain period of time. The solution 
was allowed to stand overnight at room temperature. A precipitated light 
yellow solid was filtered, washed with water sufficiently, and further 
washed with methanol several times. The resulting solid was then 
recrystallized from ethanol/acetone to obtain 16 g of colorless 
crystalline, 6-trimethylsilyl-2,3-dicyanonaphthalene. 
(iii) Synthesis of 
bis(triethylsilyloxy)-tetrakis-(trimethylsilyl)naphthalocyanino-germanium 
To a mixture of 12.5 g of 6-trimethylsilyl-2,3-dicyanonaphthalene, about 
100 mg of ammonium molybdate and 50 g of urea, 2.8 ml of germanium 
tetrachloride were added, followed by heating at 240.degree. C. for 2.5 
hours. After cooling, water was added to the reaction mixture. The 
resulting precipitate was filtered and washed with water and then with 
methanol sufficiently, thereby to obtain 0.68 g of a black-green crystal. 
The electronic spectrum (CHCl.sub.3 solution) of this crystal is shown in 
FIG. 1. It could be presumed from the results of the spectrum that the 
crystal was tetrakis(trimethylsilyl)naphthalocyaninodichlorogermanium, 
which was used for the next reaction without any further purification. 
Then, 0.38 g of the thus obtained crystal was added to a mixed solvent 
containing 39 ml of water, 10 ml of ethanol and 10 ml of concentrated 
ammonia water, and reflux was carried out for about 2 hours. After 
cooling, the reaction mixture was filtered, washed with methanol about 10 
times, and dried, to obtain 0.29 g of a black-green solid. The electronic 
spectrum (CHCl.sub.3 solution) of this solid is shown in FIG. 2. It could 
be presumed from the results of the spectrum that this solid was 
tetrakis(trimethylsilyl)naphthalocyanino-dihydroxygermanium, which was 
then used for the next reaction without any further purification. One gram 
of triethylsilanol was added to 20 ml of chlorobenzene solution containing 
0.21 g of the thus obtained black-green solid, and reflux was carried out 
for about 1 hour, followed by continuing concentration until the amount of 
the solution was approximately halved. After cooling, about 100 ml of 
methanol were added thereto, and the resulting precipitate was then 
collected by filtration and washed with methanol sufficiently. The washed 
solid was then subjected to an alumina column chromatography using benzene 
as a developing solvent, thereby to obtain 0.13 g of a green crystal. It 
was confirmed from the undermentioned analytical results that the thus 
obtained crystal was 
bis(triethylsilyloxy)-tetrakis(trimethylsilyl)naphthalocyanino-germanium. 
The electronic spectrum (CHCl.sub.3 solution) is shown in FIG. 3. The 
results of the elemental analysis are as follows: 
______________________________________ 
C H N 
______________________________________ 
Calcd. (%) 66.93 6.71 8.67 
Found (%) 67.18 6.85 8.41 
______________________________________ 
Formation of the Recording Medium and Recording Test 
Bis(triethylsilyloxy)-tetrakis(trimethylsilyl)naphthalocyanino-germanium 
[(C.sub.2 H.sub.5).sub.3 SiO].sub.2 GeNC[Si(CH.sub.3).sub.3 ].sub.4 
synthesized in the above manner was dissolved in chloroform, and a glass 
substrate was coated with this material by means of a spin coating method 
to obtain a recording layer having a thickness of 70 nm. The recording 
medium thus obtained was then irradiated with a laser diode beam having a 
wavelength of 830 nm on the side of the glass substrate, to evaluate the 
recording characteristics. As a result, it was appreciated that recording 
was possible at 4.9 mW. Further, the reading stability of the medium was 
evaluated by irradiating a reading beam at 1 mW repeatedly, and it was 
appreciated that its reflectance did not change even when the irradiation 
was repeated 10.sup.6 times. 
EXAMPLE 2 
Bis(trihexylsilyloxy)-tetrakis(trimethylsilyl)naphthalocyanino silicon 
[(n-C.sub.6 H.sub.13).sub.3 SiO].sub.2 SiNc[Si(CH.sub.3).sub.3 ].sub.4 
(Exemplary compound No. 1) was dissolved in toluene, and a recording layer 
having a thickness of 50 nm was formed on a glass substrate by means of a 
spin coating method. The resulting recording medium was then irradiated 
with a laser diode beam having a wavelength of 830 nm on the side of the 
glass substrate in the same manner as in Example 1, to evaluate the 
recording characteristics. As a result, it was appreciated that the 
recording operation was possible at a beam diameter of 1.6 .mu.m, a linear 
velocity of 0.5 m/sec. and 4.2 mW. Further, to evaluate the reading 
stability, a reading beam at 1 mW was irradiated repeatedly in the same 
manner as in Example 1, and it was appreciated that change in reflectance 
did not occur even when the irradiation was repeated 10.sup.6 times. 
COMATIVE EXAMPLE 
Cyanine type dye NK-2905 (made by Nippon Kanko-Shikiso Kenkyusho Co., 
Ltd.)) was dissolved in dichloroethane, and a recording layer having a 
thickness of 50 nm was formed on a glass substrate by means of a spin 
coating method. This recording medium was irradiated with a laser beam in 
the same manner as in Example 1, and in this case, the recording operation 
was possible at 4.8 mW. However, according to the evaluation of the 
reading stability, the reflectance of the medium began to decrease from a 
point of about 4.times.10.sup.4 times of the irradiation and lowered to 
70% of the initial reflectance after the irradiation was repeated 10.sup.6 
times. 
EXAMPLE 3 
A glass substrate was coated with 
bis(tributylsilyloxy)-tetrakis(trimethylsilyl)naphthalocyanino-tin 
[(n-C.sub.4 H.sub.9).sub.3 -SiO].sub.2 -SnNc[Si(CH.sub.3).sub.3 ].sub.4 
(Exemplary compound No.4) by means of a spin coating method to obtain a 
recording layer having a thickness of 80 nm. The obtained recording medium 
was then irradiated with a laser beam in the same way as in Example 1, and 
it was appreciated that recording was possible at 5.8 mW. Further, the 
reading stability of the medium was evaluated in the same manner as in 
Example 1, and it was also appreciated that its reflectance did not change 
even when the irradiation was repeated 10.sup.6 times. 
EXAMPLE 4 
A polycarbonate substrate was coated with each of naphthalocyanine 
compounds shown in the following table by a vapor deposition method to 
form a recording medium thereon having a thickness of 50 nm. 
Recording/reading out properties and reading stability were evaluated in 
the same manner as in Example 1, and the results are set forth in the 
following table. 
TABLE 
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Recording Reading 
Naphthalocyanine compound 
sensitivity 
stability 
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C.sub.6 H.sub.5 OAlNc[Si(CH.sub.3).sub.3 ].sub.4 
5.5 mW &gt;10.sup.6 times 
(Exemplary compound No. 5) 
[(n-C.sub.3 H.sub.7).sub.3 SiO].sub.2 TiNc[Si(CH.sub.3).sub.3 ].sub.4 
5.0 mW &gt;10.sup.6 times 
(Exemplary compound No. 6) 
(C.sub.2 H.sub.5 O).sub.2 SiNc[Si(C.sub.6 H.sub.5).sub.3 ].sub.4 
4.6 mW &gt;10.sup.6 times 
(Exemplary compound No. 8) 
[(C.sub.6 H.sub.5).sub.3 SiO].sub.2 SiNc[Si(C.sub.2 H.sub.5).sub.3 
].sub.4 4.4 mw &gt;10.sup.6 times 
(Exemplary compound No. 9) 
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EXAMPLE 5 
A mixture of [(n-C.sub.6 H.sub.13).sub.3 SiO].sub.2 SiNc[Si(CH.sub.3).sub.3 
].sub.4 and polystyrene in a ratio of 2:1 was dissolved in toluene, and a 
glass substrate was coated with the resulting mixture to obtain a 
recording layer having a thickness of 60 nm. Evaluation was made in the 
same manner as in Example 1, and it was appreciated that the recording 
sensitivity and reading stability of the recording layer were 4.8 mW and 
10.sup.6 times or more, respectively. 
The optical information recording medium of the third aspect of the present 
invention by use of a new naphthalocyanine dye of the first aspect 
prepared in accordance with the second aspect of the present invention 
have been found to have excellent recording/reading out properties, and 
improved reading stability as compared with conventional organic dye 
recording mediums.