Aminium salt compound and optical recording medium

An aminium salt compound has the structure expressed by the following formula (I) or (II), and an optical recording layer has a recording layer containing the aminium salt compound. ##STR1## wherein X.sup.- indicates a monovalent metal complex anion; and R.sub.1 through R.sub.8 each indicate a hydrogen atom or a monovalent organic residue, and at least one of R.sub.1 through R.sub.8 is a monovalent organic residue selected from the group consisting of a substituted or unsubstituted alkoxyalkyl group, substituted or unsubstituted alkenyl group, substituted or unsubstituted alkynyl group and substituted or unsubstituted aralkyl group; and n is 1 or 2; and ##STR2## wherein X.sup.- indicates a monovalent metal complex anion; and R.sub.1 ' through R.sub.8 ' indicate the atoms that, when taken together in combination R.sub.m ' and R.sub.m+1 ' (m=1, 3, 5 or 7) with a nitrogen atom N, at least one of such combinations forms a substituted or unsubstituted five-membered ring, substituted or unsubstituted six-membered ring or substituted or unsubstituted seven-membered ring; and n is 1 or 2.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to an infrared absorbing compound and an 
optical recording medium using the compound and having excellent 
resistance to reproduction photo-deterioration and preservation stability. 
2. Description of the Related Art 
An optical recording medium such as an optical disk or the like has a 
substrate having spiral, circular or linear grooves. On the substrate is 
provided a recording layer, on which information can be recorded with high 
density by forming optically detectable small pits of, for example, the 
diameter off the pit is about 1 .mu.m, therein. 
For example, when a laser beam converging on the surface of the recording 
layer scans the recording layer, the recording layer absorbs laser energy 
to form optically detectable pits thereon so that information can be 
written thereon. For example, in a heat mode recording system, the 
recording layer absorbs heat energy to form concave pits at absorption 
positions due to evaporation, decomposition or the like, so that 
information is recorded thereon. 
A metal thin film such as an aluminum deposited film or the like, a 
chalcogenide amorphous glass film such as a bismuth thin film, a tellurium 
oxide thin film, or a like film mainly consisting of an inorganic 
substance, has been proposed so far as the recording layer of such an 
optical recording medium. On the other hand, it has recently been proposed 
that an organic dye which exhibits changes in physical properties when 
exposed by light having a relatively long wavelength can be used in a 
recording layer. 
For example, when a polymethine dye, an azulenium dye, a pyrylium dye or 
the like, which exhibits greater sensitivity to exposure by a laser beam, 
is used in an organic dye thin film, a light absorption reflecting a film 
exhibiting metallic luster (a reflectance of about 10 to 50%) is obtained. 
This film enables the formation of an optical recording medium which 
permits both laser recording and reflection reading. Particularly when a 
semiconductor laser having an oscillation wavelength of 650 to 900 nm is 
used as a laser light source with the film, the size and cost of the 
recording apparatus can both be reduced. 
However, when an organic dye is used in recording layer, the organic dye 
tends to deteriorate after repeated irradiation with reproduction light, 
and the reproduction properties of the optical recording medium thereby 
also deteriorate. A known method for solving such a problem involves the 
use of a metal chelate complex (particularly, an Ni chelate complex) as a 
singlet oxygen quencher. However, a metal chelate complex cannot be added 
in an amount which is sufficient to improve the light-resistance of an 
organic dye, because the chelate complex has a low solubility in solvents 
which can be coated on a plastic substrate. 
In another method, which is proposed in U.S. Pat. No. 4,626,496, a double 
salt is formed by a metal complex and a dye, so that a larger amount of 
metal complex can be added to the recording layer. Although the light 
resistance of the organic dye can be improved with this method, the 
density of the organic dye in the recording layer is also decreased, 
thereby decreasing the recording sensitivity. Alternatively, an aminium 
salt or a diimonium salt compound that serves as a stabilizer as disclosed 
in U.S. Pat. Nos. 4,656,121 and 4,923,390, can be added to the recording 
layer in order to improve the light resistance of an organic dye. The 
method of adding an aminium salt or diimonium salt to the recording layer 
has the problem, however, that a large amount of such a salt must be added 
to improve the light resistance because the counter ion is an acid anion. 
In order to solve this problem, an example is disclosed in Japanese Patent 
Laid-Open No. 62-193891, in which a small amount of a double salt complex 
of an aminium salt cation or diimonium salt cation and a metal complex 
anion is added to improve the light resistance. 
Although this method can improve the light resistance and recording 
reproduction properties, when the aminium salt cation or diimonium salt 
cation is substituted by an alkyl amino group, the double salt compound 
with a metal complex anion lacks sufficient solubility in the usual 
solvents. In particular, such a compound has low solubility in solvents 
such as aliphatic hydrocarbons, alcohols, ketones and the like, which can 
be directly applied to a plastic substrate. There is also the problem that 
an optical recording medium having a recording layer formed by a solvent 
coating method frequently has a high noise level. 
In addition, Japanese Patent Laid-Open No. 3-164292 discloses an optical 
disk with excellent light-resistance, which comprises (1) a recording 
layer consisting of a mixture of a diimonium salt cation and a metal 
complex anion and (2) a reflecting layer formed on the recording layer. 
Examples of diimonium salt cations disclosed in the specification of 
3-164292 include a diimonium salt of N,N,N',N'-tetrakis 
(dialkylamino-substituted phenyl)-p-phenylenediamine, a diimonium salt of 
N,N,N'N'-tetrakis (dialkoxyalkylamino-substituted 
phenyl)-p-phenylenediamine, and the like. However, an organic dye 
recording layer containing such a double salt compound has insufficient 
preservation stability under conditions of high temperature and high 
humidity. Also the degree of improvement in light resistance of the 
recording layer is unsatisfactory. 
SUMMARY OF THE INVENTION 
The present invention has been achieved in view of the above problems with 
conventional recording mediums. An object of the present invention is to 
provide a novel aminium salt compound which has a large absorption peak in 
the infrared region and high solubility in an organic solvent that can be 
coated on a plastic substrate. 
Another object of the present invention is to provide an optical recording 
medium that permits a significant improvement in the light resistance of 
an organic dye recording layer and that prevents deterioration of the 
recording density and preservation stability at high temperature and high 
humidity. 
An aminium compound of the present invention is characterized by the 
structure expressed by the following formula (I): 
##STR3## 
wherein X.sup.- indicates a monovalent metal complex anion; R.sub.1 
through R.sub.8 each indicate a hydrogen atom or a monovalent organic 
residue, and at least one of R.sub.1 through R.sub.8 is a monovalent 
organic residue selected from the group consisting of substituted or 
unsubstituted alkoxyalkyl groups, substituted or unsubstituted alkenyl 
groups, substituted or unsubstituted alkynyl groups, and substituted and 
unsubstituted aralkyl groups; and n is 1 or 2. 
In another embodiment, an optical recording medium of the present invention 
comprises a substrate and a recording layer, wherein the recording layer 
contains a compound expressed by the formula (I), as shown and described 
above. 
In a further embodiment, an aminium salt compound of the present invention 
is characterized by the structure thereof expressed by the following 
formula (II): 
##STR4## 
wherein X.sup.- represents a monovalent metal complex anion; R.sub.1 ' 
through R.sub.8 ' represent atom groups in combinations of R.sub.m ' and 
R.sub.m+1 ' (m=1, 3, 5 or 7), at least one of which, together with the 
nitrogen N, forms a substituted or unsubstituted 5-membered ring, a 
substituted or unsubstituted 6-membered ring or a substituted or 
unsubstituted 7-membered ring; and n is 1 or 2. 
In yet another embodiment, an optical recording medium of the present 
invention comprises a substrate and a recording layer, wherein the 
recording layer contains a compound expressed by formula (II), as shown 
and described above.

DETAILED DESCRIPTION OF THE INVENTION 
The present invention is described in detail below. An aminium salt 
compound is expressed by the following formula (I): 
##STR5## 
wherein X.sup.- is a metal complex anion, and R.sub.1 through R.sub.8 of 
the aminium salt cation each indicate a hydrogen atom or a monovalent 
organic residue. In the present invention, at least one of R.sub.1 through 
R.sub.8 is preferably a monovalent organic residue selected from the group 
consisting of a substituted or unsubstituted alkoxyalkyl group, 
substituted or unsubstituted alkenyl group, substituted or unsubstituted 
alkynyl group and substituted or unsubstituted aralkyl group. When at 
least one of R.sub.1 through R.sub.8 is a residue selected from the above 
groups, the aminium compound exhibits improved light-resistance and good 
solvent solubility, as compared with prior aminium compounds. In addition, 
when a recording layer contains the aminium compound of the invention, an 
optical recording medium having excellent light-resistance, stability for 
repeated reproduction, and good productivity can be obtained. 
Examples of monovalent organic residues that are preferable as each of the 
groups R.sub.1 through R.sub.8 in the aminium salt compound expressed by 
the above formula (I) include alkoxyalkyl groups such as methoxymethyl, 
2-methoxyethyl, 3-methoxypropyl, 2-methoxypropyl, 4-methoxybutyl, 
3-methoxybutyl, 2-methoxybutyl, 5-methoxypentyl, 4-methoxypentyl, 
3-methoxypentyl, 2-methoxypentyl, 6-methoxyhexyl, ethoxymethyl, 
2-ethoxyethyl, 3-ethoxypropyl, 2-ethoxypropyl, 4-ethoxybutyl, 
3-ethoxybutyl, 5-ethoxypentyl, ethoxypentyl, 6-ethoxypentyl, 
propoxymethyl, 2-propoxyethyl, 3-propoxypropyl, 4-propoxybutyl, 
5-propoxypentyl groups and the like; substituted alkoxyalkyl groups such 
as cyclomethoxymethyl, 2-difluoromethoxyethyl groups; alkenyl groups such 
as vinyl, propenyl, butenyl, pentenyl, hexenyl, heptenyl, octenyl groups 
and the like; substituted alkenyl groups such as 1,2-dichlorovinyl, 
2,3-dibromopropenyl groups and the like; alkynyl groups such as propargyl, 
butynyl, pentynyl, hexynyl groups and the like; substituted alkynyl groups 
such as 2,3-dichloropropargyl and the like; aralkyl groups such as benzyl, 
phenetyl, .alpha.-naphthylmethyl, .beta.-naphthylmethyl groups and the 
like; substituted aralkyl groups such as carboxybenzyl, sulfobenzyl, 
p-methylbenzyl groups and the like. 
Each of the monovalent organic residues R.sub.1 through R.sub.8 may be an 
alkyl group such as a methyl, ethyl, n-propyl, isopropyl, n-butyl, 
isobutyl, t-butyl, n-amyl, t-amyl, n-hexyl, n-octyl, t-octyl group or the 
like; a substituted alkyl group such as a 2-hydroxyethyl 3-hydroxypropyl 
group or the like. However, at least one of R.sub.1 through R.sub.8, and 
preferably at least two of the combinations of the organic residues 
R.sub.1 and R.sub.2, R.sub.3 and R.sub.4, R.sub.5 and R.sub.6, and R.sub.7 
and R.sub.8, are monovalent organic residues selected from the group 
consisting of substituted or unsubstituted alkoxyalkyl, substituted or 
unsubstituted alkenyl, substituted or unsubstituted alkynyl and 
substituted or unsubstituted aralkyl groups. It is also preferable, to 
improve the preservation stability at high temperature and high humidity 
of the recording layer of the optical recording medium containing the 
aminium salt compound of the present invention, that all the organic 
residues R.sub.1 through R.sub.8 are selected from the group consisting of 
substituted or unsubstituted alkoxyalkyl, substituted or unsubstituted 
alkenyl, substituted or unsubstituted alkynyl and substituted or 
unsubstituted aralkyl groups. A substituted or unsubstituted alkoxyalkyl 
group is especially preferred to further improve the solvent solubility of 
the double salt compound. In the present invention, each of the organic 
residues R.sub.1 through R.sub.8 preferably has 2 to 8 carbon atoms, more 
preferably 3 to 8 carbon atoms. 
Alternatively, an aminium salt compound of the present invention has a 
structure expressed by the following formula (II): 
##STR6## 
wherein X.sup.- indicates a metal complex anion, and R.sub.1 ' through 
R.sub.8 ' in the above aminium salt cation indicate atoms that, when taken 
together in combinations of R.sub.1 ' and R.sub.2 ', R.sub.3 ' and R.sub.4 
', R.sub.5 ' and R.sub.6 ', and R.sub.7 ' and R.sub.8 ', with a nitrogen 
atom N, at least one of such combinations forms a substituted or 
unsubstituted 5-membered ring, a substituted or unsubstituted 6-membered 
ring or a substituted or unsubstituted 7-membered ring. In the present 
invention, examples of useful 5-membered rings include a pyrrolidine ring 
and the like; examples of useful 6-membered rings include a piperidine 
ring, a morpholine ring, and a tetrahydropyridine ring and the like; and 
examples of useful 7-membered rings include a cyclohexylamine ring and the 
like. Further, when each of the combinations R.sub.m ' and R.sub.m+1 ' 
(m=1, 3, 5, or 7) comprises atom groups which form a morpholine ring, the 
solvent solubility of the double salt compound of the invention can be 
desirably even more improved. 
It is especially preferred that at least two of the combinations R.sub.1 ' 
and R.sub.2 ', R.sub.3 ' and R.sub.4 ', R.sub.5 ' and R.sub.6 ', and 
R.sub.7 ' and R.sub.8 ' in the formula (II) form substituted or 
unsubstituted 5-membered, substituted or unsubstituted 6-membered or 
substituted or unsubstituted 7-membered rings. It is even more preferred 
that all combinations R.sub.m ' and R.sub.m+1 ' (m=1, 3, 5, or 7) form 
substituted or unsubstituted 5-membered, substituted or unsubstituted 
6-membered or substituted or unsubstituted 7-membered rings. 
In addition, all aromatic rings in a compound expressed by the formula (I) 
may be substituted by a lower alkyl group having 1 to 5 carbon atoms, a 
lower alkoxy group having 1 to 5 carbon atoms, a halogen atom, a hydroxyl 
group, a cyano group or the like. Finally, "n" in the formulas (I) and 
(II) is either 1 or 2. 
Examples of aminium salt cat ions used in an infrared absorbing compound of 
the present invention expressed by the formula (I) or (II) are shown in 
Table 1-1 and 1-2. In the tables, for the sake of simplicity, for example, 
when n=1, R.sub.2 to R.sub.4 are each an ethyl group, and R.sub.5 to 
R.sub.8 are each a propenyl group, an aminium salt cation expressed by the 
formula (I) is shown as below. 
__________________________________________________________________________ 
##STR7## 
##STR8## 
##STR9## 
##STR10## 
##STR11## 
##STR12## 
##STR13## 
##STR14## 
##STR15## 
__________________________________________________________________________ 
##STR16## 
C.sub.2 H.sub.5 
C.sub.2 H.sub.5 
C.sub.2 H.sub.5 
C.sub.2 H.sub.5 
CH.sub.2CHCH.sub.2 
CH.sub.2 CHCH.sub.2 
CH.sub.2CHCH.sub.2 
CH.sub.2CHCH.sub.2 
__________________________________________________________________________ 
In addition, when n=2, and each of the combinations R.sub.1 ' and R.sub.2 
', R.sub.3 ' and R.sub.4 ', R.sub.5 ' and R.sub.6 ' and R.sub.7 ' and 
R.sub.8 ' forms a 5-membered ring, the aminium salt cation in the formula 
(II) is shown as below. 
__________________________________________________________________________ 
##STR17## 
##STR18## 
##STR19## 
##STR20## 
##STR21## 
##STR22## 
##STR23## 
##STR24## 
##STR25## 
__________________________________________________________________________ 
##STR26## CH.sub.2 CH.sub.2 CH.sub.2 CH.sub.2 
CH.sub.2 CH.sub.2 CH.sub.2 CH.sub.2 
CH.sub.2 CH.sub.2 CH.sub.2 CH.sub.2 
CH.sub.2 CH.sub.2 CH.sub.2 
__________________________________________________________________________ 
CH.sub.2 
3 TABLE I-I 
- 
##STR27## 
##STR28## 
##STR29## 
##STR30## 
##STR31## 
##STR32## 
##STR33## 
##STR34## 
##STR35## 
##STR36## 
101 
##STR37## 
CH.sub.2 CHCH.sub.2 CH.sub.2 CHCH.sub.2 CH.sub.2 CHCH.sub.2 CH.sub.2 
CHCH.sub.2 CH.sub.2 CHCH.sub.2 CH.sub.2 CHCH.sub.2 CH.sub.2 CHCH.sub.2 
CH.sub.2 
CHCH.sub.2 
102 
##STR38## 
C.sub.2 H.sub.4 OCH.sub.3 C.sub.2 H.sub.4 OCH.sub.3 C.sub.2 H.sub.4 
OCH.sub.3 C.sub.2 H.sub.4 OCH.sub.3 C.sub.2 H.sub.4 OCH.sub.3 C.sub.2 
H.sub.4 OCH.sub.3 C.sub.2 H.sub.4 OCH.sub.3 C.sub.2 H.sub.4 OCH.sub.3 
103 
##STR39## 
C.sub.3 H.sub.6 OC.sub.3 H.sub.7 C.sub.3 H.sub.6 OC.sub.3 H.sub.7 
C.sub.3 H.sub.6 OC.sub.3 H.sub.7 C.sub.3 H.sub.6 OC.sub.3 H.sub.7 
C.sub.3 H.sub.6 OC.sub.3 H.sub.7 C.sub.3 H.sub.6 OC.sub.3 H.sub.7 
C.sub.3 H.sub.6 OC.sub.3 H.sub.7 C.sub.3 H.sub.6 OC.sub.3 H.sub.7 
104 
##STR40## 
CH.sub.2 CHCH.sub.2 CH.sub.2 CHCH.sub.2 CH.sub.2 CHCH.sub.2 CH.sub.2 
CHCH.sub.2 CH.sub.2 CHCH.sub.2 CH.sub.2 CHCH.sub.2 CH.sub.2 CHCH.sub.2 
CH.sub.2 
CHCH.sub.2 
105 
##STR41## 
C.sub.2 H.sub.4 CHCH.sub.2 C.sub.2 H.sub.4 CHCH.sub.2 C.sub.2 H.sub.4 C 
CHH.sub.2 C.sub.2 H.sub.4 CHCH.sub.2 C.sub.2 H.sub.4 CHCH.sub.2 C.sub.2 
H.sub.4 CHCH.sub.2 C.sub.2 H.sub.4 CHCH.sub.2 C.sub.2 H.sub.4 CHCH.sub.2 
106 
##STR42## 
C.sub.2 H.sub.4 OC.sub.2 H.sub.5 C.sub.2 H.sub.4 OC.sub.2 H.sub.5 
C.sub.2 H.sub.4 OC.sub.2 H.sub.5 C.sub.2 H.sub.4 OC.sub.2 H.sub.5 
C.sub.2 H.sub.4 OC.sub.2 H.sub.5 C.sub.2 H.sub.4 OC.sub.2 H.sub.5 
C.sub.2 H.sub.4 OC.sub.2 H.sub.5 C.sub.2 H.sub.4 OC.sub.2 H.sub.5 
107 
##STR43## 
##STR44## 
##STR45## 
##STR46## 
##STR47## 
##STR48## 
##STR49## 
##STR50## 
##STR51## 
108 
##STR52## 
C.sub.2 H.sub.4 OCH.sub.3 C.sub.2 H.sub.4 OCH.sub.3 C.sub.2 H.sub.4 
OCH.sub.3 C.sub.2 H.sub.4 OCH.sub.3 C.sub.2 H.sub.4 OCH.sub.3 C.sub.2 
H.sub.4 OCH.sub.3 C.sub.2 H.sub.4 OCH.sub.3 C.sub.2 H.sub.4 OCH.sub.3 
109 
##STR53## 
C.sub.2 H.sub.4 CHCH.sub.2 C.sub.2 H.sub.4 CHCH.sub.2 C.sub.2 H.sub.4 C 
CHH.sub.2 C.sub.2 H.sub.4 CHCH.sub.2 C.sub.2 H.sub.4 CHCH.sub.2 C.sub.2 
H.sub.4 CHCH.sub.2 C.sub.2 H.sub.4 CHCH.sub.2 C.sub.2 H.sub.4 CHCH.sub.2 
110 
##STR54## 
C.sub.2 H.sub.4 OCH.sub.3 C.sub.2 H.sub.4 OCH.sub.3 C.sub.2 H.sub.4 
OCH.sub.3 C.sub.2 H.sub.4 OCH.sub.3 C.sub.3 H.sub.7 C.sub.3 H.sub.7 
C.sub.3 H.sub.7 C.sub.3 
H.sub.7 
111 
##STR55## 
C.sub.2 H.sub.4 OC.sub.2 H.sub.5 C.sub.2 H.sub.4 OC.sub.2 H.sub.5 
C.sub.2 H.sub.5 C.sub.2 H.sub.5 C.sub.2 H.sub.4 OC.sub.2 H.sub.5 C.sub.2 
H.sub.4 OC.sub.2 H.sub.5 C.sub.2 H.sub.5 C.sub.2 
H.sub.5 
112 
##STR56## 
##STR57## 
##STR58## 
##STR59## 
##STR60## 
##STR61## 
##STR62## 
##STR63## 
##STR64## 
113 
##STR65## 
C.sub.2 H.sub.4 OCH.sub.3 C.sub.2 H.sub.4 OCH.sub.3 C.sub.2 H.sub.4 
OCH.sub.3 C.sub.2 H.sub.4 OCH.sub.3 C.sub.2 H.sub.4 OCH.sub.3 C.sub.2 
H.sub.4 OCH.sub.3 C.sub.2 H.sub.4 OCH.sub.3 C.sub.2 H.sub.4 OCH.sub.3 
114 
##STR66## 
CH.sub.2 OC.sub.2 H.sub.5 CH.sub.2 OC.sub.2 H.sub.5 CH.sub.2 OC.sub.2 
H.sub.5 CH.sub.2 OC.sub.2 H.sub.5 CH.sub.2 OC.sub.2 H.sub.5 CH.sub.2 
OC.sub.2 H.sub.5 CH.sub.2 OC.sub.2 H.sub.5 CH.sub.2 OC.sub.2 H.sub.5 
115 
##STR67## 
##STR68## 
##STR69## 
##STR70## 
##STR71## 
##STR72## 
##STR73## 
##STR74## 
##STR75## 
116 
##STR76## 
##STR77## 
##STR78## 
##STR79## 
##STR80## 
##STR81## 
##STR82## 
##STR83## 
##STR84## 
TABLE 1-2 
__________________________________________________________________________ 
##STR85## 
##STR86## 
##STR87## 
##STR88## 
##STR89## 
##STR90## 
##STR91## 
##STR92## 
##STR93## 
##STR94## 
__________________________________________________________________________ 
201 
##STR95## 
CH.sub.2 CH.sub.2 CH.sub.2 CH.sub.2 
CH.sub.2 CH.sub.2 CH.sub.2 CH.sub.2 
CH.sub.2 CH.sub.2 CH.sub.2 CH.sub.2 
CH.sub.2 CH.sub.2 
CH.sub.2 CH.sub.2 
202 
##STR96## 
CH.sub.2 CH.sub.2 CH.sub.2 CH.sub.2 CH.sub.2 
CH.sub.2 CH.sub.2 CH.sub.2 CH.sub.2 CH.sub.2 
CH.sub.2 CH.sub.2 CH.sub.2 CH.sub.2 
CH.sub.2 CH.sub.2 CH.sub.2 
CH.sub.2 CH.sub.2 
CH.sub.2 
203 
##STR97## 
##STR98## 
##STR99## 
##STR100## 
##STR101## 
204 
##STR102## 
##STR103## 
##STR104## 
##STR105## 
##STR106## 
205 
##STR107## 
##STR108## 
##STR109## 
##STR110## 
##STR111## 
206 
##STR112## 
CH.sub.2 CH.sub.2 OCH.sub.2 CH.sub.2 
CH.sub.2 CH.sub.2 OCH.sub.2 CH.sub.2 
CH.sub.2 CH.sub.2 OCH.sub.2 
CH.sub.2 CH.sub.2 CH.sub.2 
OCH.sub.2 CH.sub.2 
207 
##STR113## 
##STR114## 
##STR115## 
##STR116## 
##STR117## 
208 
##STR118## 
CH.sub.2 CH.sub.2 OCH.sub.2 CH.sub.2 
n-C.sub.4 H.sub.9 
n-C.sub.4 H.sub.9 
CH.sub.2 CH.sub.2 OCH.sub.2 
CH.sub.2 n-C.sub.4 H.sub.9 
n-C.sub.4 
__________________________________________________________________________ 
H.sub.9 
A description will now be made of the metal complex anion X.sup.-, which 
accompanies the aminium salt cation. 
In the present invention, various metal complex compounds can be used as 
the counter anion. Examples of such metal complex anions include the 
anions represented by the following formulas (II) through (IX), wherein M 
is a transition metal atom such as Ni, Co, Mn, Cu, Pb, Pt or the like. 
##STR119## 
wherein R.sub.9 through R.sub.12 each indicate a hydrogen atom, a 
substituted or unsubstituted alkyl group, substituted or unsubstituted 
amino or substituted or unsubstituted alkoxy group, or a halogen atom. 
##STR120## 
wherein R.sub.13 through R.sub.16 each indicate a substituted or 
unsubstituted alkyl group or a substituted or unsubstituted aryl group or 
a cyano group. 
In a particularly preferred embodiment, at least one of R.sub.13 through 
R.sub.14 of the formula (IV) is an alkoxy-substituted aryl group, such as 
shown below in the following structure: 
##STR121## 
wherein R.sub.17 through R.sub.20 each indicate a hydrogen atom, a 
substituted or unsubstituted alkyl group, a substituted or unsubstituted 
amino group, a substituted or unsubstituted aryl, a substituted or 
unsubstituted alkoxy group, or a halogen atom. 
##STR122## 
wherein R.sub.21 through R.sub.24 each indicate a hydrogen atom, a 
substituted or unsubstituted alkyl group, a substituted or unsubstituted 
amino group, a substituted or unsubstituted aryl group, a substituted or 
unsubstituted alkoxy group, or a halogen atom. 
##STR123## 
wherein R.sub.25 through R.sub.28 each indicate a hydrogen atom, a 
substituted or unsubstituted alkyl group, a substituted or unsubstituted 
amino group, a substituted or unsubstituted aryl group, a substituted or 
unsubstituted alkoxy group, or a halogen atom. 
##STR124## 
Examples of substituted or unsubstituted alkyl groups represented by 
R.sub.9 through R.sub.28 in the formulae (III) through (VII) include 
methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, t-butyl, 
n-amyl, t-amyl, n-hexyl, n-octyl, t-octyl groups and the like. Examples of 
substituted or unsubstituted alkoxy groups include methoxy, ethoxy, 
n-propyloxy, isopropyloxy groups and the like. 
Examples of substituted amino groups represented by R.sub.9 through 
R.sub.12, R.sub.17 through R.sub.20, R.sub.21 through R.sub.24, and 
R.sub.25 through R.sub.28 include dimethylamino, diethylamino, 
dipropylamino, acetylamino, benzoylamino groups and the like. 
Examples of substituted or unsubstituted aryl groups shown by R.sub.13 
through R.sub.16, R.sub.17 through R.sub.20, R.sub.21 through R.sub.24, 
and R.sub.25 through R.sub.28 include phenyl, tolyl, xylyl, ethylphenyl, 
chlorophenyl, nitrophenyl, methoxyphenyl, dimethoxyphenyl, 
trimethoxyphenyl, ethoxyphenyl groups and the like. 
Examples of metal complex anions used in the present invention are shown in 
Tables 2-1 to 2-6. 
TABLE 2-1 
______________________________________ 
Metal complex 
Formula No. M R.sub.9 
R.sub.10 R.sub.11 
R.sub.12 
______________________________________ 
(III) 1 Ni H CH.sub.3 H H 
2 Ni H N(CH.sub.3).sub.2 
H H 
3 Zn H CH.sub.3 H H 
4 Ni H H H H 
5 Ni Cl Cl H Cl 
6 Pd H H H H 
7 Ni H N(CH.sub.3).sub.2 
CH.sub.3 
H 
8 Ni H N(C.sub.2 H.sub.5).sub.2 
H H 
9 Ni H OCH.sub.3 
H H 
10 Cu Cl Cl H Cl 
______________________________________ 
In a particularly preferred embodiment, the metal complex anion has the 
following structure: 
##STR125## 
TABLE 2-2 
__________________________________________________________________________ 
Metal complex 
Formula 
No. 
M R.sub.13 R.sub.14 R.sub.15 R.sub.16 
__________________________________________________________________________ 
(IV) 1 Ni 
##STR126## 
##STR127## 
##STR128## 
2 Ni 
##STR129## 
##STR130## 
##STR131## 
##STR132## 
3 Ni 
##STR133## 
##STR134## 
##STR135## 
##STR136## 
4 Ni 
##STR137## 
##STR138## 
##STR139## 
##STR140## 
5 Ni 
##STR141## 
##STR142## 
##STR143## 
##STR144## 
6 Ni 
##STR145## 
##STR146## 
##STR147## 
##STR148## 
7 Pt 
##STR149## 
##STR150## 
##STR151## 
##STR152## 
8 Ni 
##STR153## 
##STR154## 
##STR155## 
##STR156## 
9 Cu 
##STR157## 
##STR158## 
##STR159## 
##STR160## 
10 Ni 
CH.sub.3 CH.sub.3 CH.sub.3 CH.sub.3 
__________________________________________________________________________ 
TABLE 2-3 
______________________________________ 
Metal complex 
Formula 
No. M R.sub.17 
R.sub.18 R.sub.19 R.sub.20 
______________________________________ 
(V) 1 Ni H H H H 
2 Ni H Cl Cl H 
3 Ni H CH.sub.3 H H 
4 Pt H H H H 
5 Ni H 
##STR161## 
##STR162## 
H 
6 Ni H N(CH.sub.3).sub.2 
N(CH.sub.3).sub.2 
H 
______________________________________ 
TABLE 2-4 
______________________________________ 
Metal complex 
Formula 
No. M R.sub.21 
R.sub.22 
R.sub.23 R.sub.24 
______________________________________ 
(VI) 1 Ni H H H H 
2 Ni H CH.sub.3 
H H 
3 Ni Cl Cl H Cl 
4 Ni H N(CH.sub.3).sub.2 
CH.sub.3 H 
5 Ni H 
##STR163## 
##STR164## 
H 
______________________________________ 
TABLE 2-5 
______________________________________ 
Metal complex 
Formula No. M R.sub.25 
R.sub.26 R.sub.27 
R.sub.28 
______________________________________ 
(VII) 1 Ni N H H H 
2 Ni H OCH.sub.3 
H H 
3 Ni H N(CH.sub.2).sub.2 
H H 
4 Co H Cl Cl H 
5 Ni H C.sub.2 H.sub.5 
H H 
6 Ni H H H 
______________________________________ 
TABLE 2-6 
______________________________________ 
Metal complex 
Formula No. M 
______________________________________ 
(VIII) 1 Ni 
2 Co 
3 Cu 
4 Mn 
(IX) 1 Ni 
2 Pt 
3 Pb 
4 Cu 
______________________________________ 
A compound expressed by the formula (I) or (II) of the present invention is 
a double salt compound in which the aminium salt cation and the metal 
complex compound forms a salt. Examples of such double salt compounds are 
shown in Table 3-1 and 3-2. 
TABLE 3-1 
______________________________________ 
Double salt Aminium salt Metal complex 
compound No. 
compound cation No. 
anion No. 
______________________________________ 
(I)- 1 102 (IV)-5 
2 106 (IV)-5 
3 102 (IV)-2 
4 102 (IV)-1 
5 113 (VII)-3 
6 107 (VIII)-1 
7 108 (IV)-4 
8 102 (III)-5 
9 114 (IV)-2 
10 102 (IV)-5 
11 111 (III)-10 
12 105 (IV)-1 
13 115 (VI)-3 
14 103 (IX)-1 
15 101 (III)-5 
______________________________________ 
TABLE 3-2 
______________________________________ 
Double salt Aminium salt Metal complex 
compound No. 
coopound cation No. 
anion No. 
______________________________________ 
(II)- 1 205 (V)-3 
2 206 (III)-10 
3 204 (IV)-8 
4 203 (IV)-5 
5 206 (IV)-4 
6 206 (III)-5 
7 207 (VI)-1 
8 201 (VII)-2 
9 202 (IX)-2 
10 208 (IV)-3 
______________________________________ 
In the present invention, a double salt compound having a metal complex 
compound anion in which at least one of R.sub.13 through R.sub.16 is an 
alkoxy-substituted aryl group, or a double salt compound in which at least 
one of R.sub.9 through R.sub.12 is a halogen atom, typically exhibits 
excellent solvent solubility. When such a double salt compound is 
incorporated in a recording layer together with an organic dye, the light 
resistance of the recording layer is improved without causing 
deterioration of preservation stability, thereby effectively preventing 
the deterioration of the recording layer due to exposure to reproduction 
light. In the present invention, the double salt compound having a metal 
complex anion shown by the formula (III) or (IV) is thus preferred. A 
double salt compound having the metal complex anion (III)-5 shown in Table 
2-1 or the metal complex anion (IV)-5 shown in Table 2-2 is even more 
preferred. 
A description will now be made of the method of synthesizing the compound 
shown by the formula (I) or (II) of the present invention. 
First, an aminium salt compound having as a counter ion an acid anion (for 
example, perchlorate ion, iodine ion, chlorine ion, hexafluoroantimonate 
ion or the like) is synthesized. This aminium salt compound can be 
obtained by employing the method disclosed in U.S. Pat. Nos. 3,251,881, 
3,575,871 and 3,484,467 and Japanese Patent Laid-Open No. 61-69991. For 
example, the compound can be synthesized by the following method, which 
comprises an Ullmann reaction followed by a reduction reaction: 
##STR165## 
The amino compound obtained by the above Ullmann reaction and reduction 
reaction is then selectively substituted by an alkoxy, alkyl, alkenyl, 
aralkyl or alkynyl group and oxidized to obtain an aminium cation of an 
aminium salt compound expressed by the formula (I). 
When the groups R.sub.1 through R.sub.8 are unsymmetrical, the selective 
substitution must be effected in a multi-step manner. It is thus preferred 
from the viewpoint of cost that the groups R.sub.1 through R.sub.8 be the 
same. 
An aminium salt cation of an aminium salt compound expressed by the formula 
(II) may be synthesized by using an appropriate alkylating agent suitable 
for R.sub.m ' and R.sub.m+1 ' (m=1, 3, 5 or 7) to form, together with 
nitrogen N, a substituted or unsubstituted 5-membered, substituted or 
unsubstituted 6-membered or substituted or unsubstituted 7-membered ring 
during the step of selective substitution, as shown above for the formula 
(I). 
For example, a pyrrolidine ring can be formed by alkylation using 
1,4-dibromobutane, 1,4-dichlorobutane, 1,4-diiodobutane or the like, and a 
piperidine ring can be formed using 1,5-dibromopentane, 
1,5-dichloropentane, 1,5-diiodopentane or the like. A morpholine ring can 
be formed by hydroxyethylation using 2-bromoethanol, followed by an acid 
treatment for dehydration. A tetrahydropyridine ring can be formed by 
methacrylation using methacryl bromide, followed by an acid treatment. A 
cyclohexylamine ring can be formed by 1,6-dibromohexane. 
In particular, the cyclization of an amino group proceeds rapidly and at a 
high yield, as compared with alkylation, and is thus remarkably 
advantageous for production as compared with the conventional cyclization 
of a propyl or butyl group. 
On the other hand, an anion-type metal complex which accompanies the cation 
as a counter ion can be obtained, for example, in accordance with the 
method of Schrauzer et al. as described in the Journal of American 
Chemical Society, Vol. 87, 1483, 1965. Specifically, such a metal complex 
can be synthesized in accordance with either of the following two 
processes: 
##STR166## 
where R and R' each represent an alkyl group, an aromatic ring or the 
like; X is a halogen atom; and M is a transition metal; and 
##STR167## 
The neutral metal complex obtained by the reaction 1) or 2) is changed to 
an anion in dimethylsulfoxide to which p-phenylenediamine has been added, 
and is then changed to a metal complex anion in an alcohol to which a 
quaternary alkyl ammonium salt has been added. In this case, a 
tetraalkylammonium such as N.sup.+ (CH.sub.3).sub.4, N.sup.+ (C.sub.4 
H.sub.9).sub.4, or the like, is particularly preferred as the cation. 
Equal molar amounts of the aminium salt compound and the anion-type metal 
complex are then dissolved in a polar solvent. N,N-dimethylformamide or 
the like is preferred as the polar solvent, and the concentration is 
preferably about 0.01 mol/l. 
Double decomposition is then produced by adding an aqueous solvent, 
preferably water, to the resulting solution until a precipitate is 
obtained. The molar amount of water added may be in considerable excess of 
the molar amounts of the reactants, preferably at least 10 times. 
The reaction temperature is preferably room temperature to about 90.degree. 
C. The resulting from above precipitate is then followed by filtration and 
drying. For purpose of purification of the precipitate, a treatment, that 
is, dissolved the obtained precipitate in a polar solvent and add an 
aqueous solvent to the polar solvent to obtain the precipitate may be 
perform repeatedly, and the precipitates are then recrystallized by 
DMF-methanol or the like to obtain the double salt compound of the present 
invention. 
The double salt compound of the present invention can also be obtained by 
another method in which a neutral intermediate of a metal complex anion is 
dissolved in methylene chloride or the like. An equal molar amount of an 
aminium salt compound that is bonded to an acid anion is added to the 
resulting solution, followed by concentration and recrystallization. The 
double salt compound may also be formed by yet another method in which the 
neutral intermediate of a metal complex anion is dissolved in methylene 
chloride or the like. An equal molar amount of an aminium salt compound is 
added to the resulting solution, followed by concentration and 
recrystallization. 
The resulting double salt compounds, each having an aminium salt cation and 
a metal complex anion, have a maximum absorption wavelength of 900 nm or 
more and an absorption coefficient as large as several hundred thousands. 
Such an infrared absorbing compound is typically used for heat insulating 
films, sunglasses or the like purposes other than as a material for an 
optical recording medium. 
The aminium salt compound of the present invention can be contained in the 
recording layer of an optical recording medium which contains an organic 
dye. 
Generally known, near infrared-absorbing dyes are used together with the 
aminium salt of the present invention to form the organic dye recording 
layer of the optical recording medium. Examples of such dyes include 
cyanine dyes, merocyanine dyes, croconium dyes, squalium dyes, azulenium 
dyes, polymethine dyes, naphthoquinone dyes, pyrylium dyes, phthalocyanine 
dyes, naphthalocyanine dyes, naphtholactam dyes and the like. 
Of the above organic dyes, cation type dyes represented by polymethine 
dyes, cyanine dyes and azulenium dyes are preferable from the viewpoint of 
optimizing the preservation stability of the recording layer. The cation 
type dyes below are especially preferred because they promote good 
recording sensitivity, as well as preventing the preservation stability 
from deteriorating, even when in the form of a mixture with the double 
salt compound of the invention. 
Examples of useful cation dyes include: 
(1) polymethine dyes expressed by the following formula (X): 
##STR168## 
wherein A, B, D and E each indicate a hydrogen atom, or a group selected 
from the group consisting of a substituted or unsubstituted alkyl group, a 
substituted or unsubstituted alkenyl group, a substituted or unsubstituted 
aralkyl group, a substituted or unsubstituted aryl group, a substituted or 
unsubstituted styryl group and a substituted or unsubstituted heterocyclic 
group; r.sub.1 ' and r.sub.2 ' each indicate a hydrogen atom or a group 
selected from the group consisting of a substituted or unsubstituted alkyl 
group, a substituted or unsubstituted cyclic alkyl group, a substituted or 
unsubstituted alkenyl group, a substituted or unsubstituted aralkyl group, 
and a substituted or unsubstituted aryl group; k is 0 or 1; l is 0, 1 or 
2; and G.sup.- indicates an anion; 
(2) dyes expressed by the following formula (XI): 
##STR169## 
wherein A, B, D, E and G.sup.- each indicate the same as that described 
above; r.sub.1 through r.sub.5 each indicate a hydrogen atom, a halogen 
atom, a substituted or unsubstituted alkyl group or a substituted or 
unsubstituted aryl group; Y indicates a divalent organic residue having 
the atoms required to complete a 5-membered or 6-membered ring; and p and 
q are each 0, 1 or 2; 
(3) dyes expressed by the following formula (XII): 
##STR170## 
wherein A, B, D, E, r.sub.1, r.sub.2, r.sub.3, Y and G.sup.- each 
represent the same as that described above; 
(4) dyes expressed by the following formula (XIII): 
##STR171## 
wherein A, B, D, E, r.sub.1, r.sub.2, r.sub.3, r.sub.4, p and q each 
represent the same as that described above; and 
Z.sup.- is 
##STR172## 
(5) azulenium dyes expressed by the following formula (XIV), (XV) or (XVI): 
##STR173## 
wherein R.sub.29 through R.sub.35 each represent a hydrogen atom, a 
halogen atom (chlorine atom, bromine atom, iodine atom), or a monovalent 
organic residue. The monovalent organic residue can be selected from a 
wide range monovalent organic groups. 
Alternatively, at least one of the combinations of R.sub.29 and R.sub.30, 
R.sub.30 and R.sub.31, R.sub.31 and R.sub.32, R.sub.32 and R.sub.33, 
R.sub.33 and R.sub.34, and R.sub.34 and R.sub.35, may form a substituted 
or unsubstituted condensed ring. The condensed ring is a five-membered, 
six-membered or seven-membered condensed ring. Examples of such condensed 
rings include aromatic rings such as benzene, naphthalene, chlorobenzene, 
bromobenzene, methylbenzene, ethylbenzene, methoxybenzene, ethoxybenzene 
and the like rings; heterocycles such as furan, benzofuran, pyrrole, 
thiophene, pyridine, quinoline, thiazole and the like rings; aliphatic 
rings such as dimethylene, trimethylene, tetramethylene rings and the 
like. G.sup.- represents the same anion as that described above. 
F represents a bivalent organic residue bonded by a double bond. Examples 
of such organic residues represented by F of the present invention include 
the groups expressed by the formulae (1) through (11) below. In each of 
the formulae, Q.sup.+ represents the azulenium salt nucleus below, and the 
right side of each formula excluding Q+ represents the organic residue F. 
Azulenium salt nucleus (Q.sup.+) 
##STR174## 
R.sub.29 ' through R.sub.35 ' are the same as R.sub.29 through R.sub.35. 
The azulenium salt nucleus shown by Q+ may be either symmetrical or 
unsymmetrical with the azulene salt nucleus on the right side of the 
formula (3). 
##STR175## 
wherein J indicates the atoms which are preferably nonmetallic required to 
complete a nitrogen-containing heterocycle. 
##STR176## 
wherein R.sub.38 is a substituted or unsubstituted aryl group or a cation 
group thereof. 
##STR177## 
wherein R.sub.39 represents a heterocyclic group or a cation group 
thereof. 
##STR178## 
wherein R.sub.40 represents a hydrogen atom, an alkyl group or a 
substituted or unsubstituted aryl group. 
##STR179## 
wherein Z.sub.2 represents atoms required to complete a pyran, thiapyran, 
selenapyran, telluropyran, benzopyran, benzothiapyran, benzoselenapyran, 
benzotelluropyran, naphthopyran, naphthothiapyran, naphthoselenapyran or 
naphthotelluropyran ring. The group Z.sub.2 may be substituted; 
L is a sulfur atom, an oxygen atom, a selenium atom or a tellurium atom; 
R.sub.41 and R.sub.42 each represent a hydrogen atom, an alkoxy group, a 
substituted or unsubstituted aryl group, an alkenyl group, or a 
heterocyclic group; and 
s represents an integer of 1 to 8. 
Preferred examples of dyes include dyes expressed by the formulae (XVII), 
(XVIII), (XIV), (XX), (XXI), (XXII), (XXIII) and (XXIV). 
##STR180## 
In the above formulas (XVII) to (XXIII), L.sub.1 and L.sub.2 each represent 
a substituted nitrogen atom, sulfur atom, oxygen atom, selenium atom or a 
tellurium oxygen. Z.sub.1 represents the atoms required to complete a 
pyrylium, thiopyrylium, selenapyrylium, telluropyrylium, benzopyrylium, 
benzothiopyrylium, benzoselenapyrylium, benzotelluropyrylium, 
naphthopyrylium, naphthothiopyrylium, naphthoselenapyrylium or 
naphthotellurophrylium ring, and may be substituted or unsubstituted; 
Z.sub.2 represents the atoms required to complete a pyran, thiopyran, 
selenapyran, telluropyran, benzopyran, benzothiopyran, benzoselenapyran, 
benzotelluropyran, naphthopyran, naphthothiopyran, naphthoselenapyran or 
naphthotelluropyran ring, and may be substituted or unsubstituted; t is 0 
or 1, and R.sub.43 is a substituted or unsubstituted aryl group or a 
substituted or unsubstituted heterocyclic group; the symbols r.sub.1 ' 
through r.sub.7 ' each indicate a hydrogen atom, or a group selected from 
a substituted or unsubstituted alkyl group, a substituted or unsubstituted 
cyclic alkyl group, a substituted or unsubstituted alkenyl group, a 
substituted or unsubstituted aralkyl group and a substituted or 
unsubstituted aryl group; and the symbols k, q, J, r.sub.1, Y, Z.sup.- and 
G.sup.- are each the same as that described above. 
In addition, K1 and K2 in the above formula (XXIV) each represent a 
substituted or unsubstituted aromatic amine residue, such as a 
heterocyclic amine residue containing an nitrogen, oxygen or sulfur ion, 
or a group expressed by the following formula: 
##STR181## 
wherein A' and B' each represent a hydrogen atom or a C.sub.1 to C.sub.20 
substituted or unsubstituted alkyl, aryl or cycloalkyl group; D' and E' 
each represent a hydrogen atom, an alkyl group, an alkoxy group or a 
halogen atom; and M' is a metal atom such as Ni, Cu, Co or Zn. 
The symbols in the formulas are described in further detail below. 
A, B, D and E each indicate a hydrogen atom or a substituted or 
unsubstituted alkyl group such as a methyl, ethyl, n-propyl, isopropyl, 
n-butyl, sec-butyl, isobutyl, t-butyl, n-amyl, t-amyl, n-hexyl, n-octyl or 
t-octyl group or the like; a cyclic alkyl group such as a cyclohexyl group 
or the like; an alkenyl group such as a vinyl, propenyl, butenyl, 
pentenyl, hexenyl, heptenyl, octenyl, dodecynyl, pulenyl group or the 
like; an aralkyl group such as a benzyl, phenetyl, .alpha.-naphthylmethyl, 
.beta.-naphthylmethyl group or the like; a substituted aralkyl group such 
as a carboxybenzyl, sulfobenzyl, hydroxybenzyl group or the like; a 
substituted or unsubstituted aryl group such as a phenyl, .alpha.-naphtyl, 
.beta.-naphtyl, tolyl, xylyl, biphenyl, ethylphenyl, chlorophenyl, 
dichlorophenyl, bromophenyl, dibromophenyl, nitrophenyl, 
diethylaminophenyl, dimethylaminophenyl, dimethoxyaminophenyl, 
dibenzylaminophenyl or the like. 
The symbols r.sub.1, r.sub.2, r.sub.3, r.sub.4 and r.sub.5 each indicate a 
hydrogen atom, a halogen atom such as a chlorine, bromine, iodine atom or 
the like; a substituted or unsubstituted alkyl group such as a methyl, 
ethyl, n-propyl, isopropyl, n-butyl, t-butyl, n-amyl, n-hexyl, n-octyl, 
2-ethylhexyl or t-octyl group or the like; an alkoxy group such as 
methoxy, ethoxy, propoxy, butoxy or the like; a substituted or 
unsubstituted aryl group such as phenyl, tolyl, xylyl, ethylphenyl, 
chlorophenyl, nitrophenyl, dimethylaminophenyl, .alpha.-naphthyl, 
.beta.-naphthyl or the like. Y indicates a divalent hydrocarbon group such 
as 
##STR182## 
or the like. The five- or six-membered rings may be condensed with a 
benzene ring, a naphthalene ring or the like. 
R.sub.29 through R.sub.35 and R.sub.29 ' through R.sub.35 ' each indicate a 
hydrogen atom; a halogen atom such as a fluorine, chlorine, bromine or 
iodine atom or the like; a substituted or unsubstituted alkyl group such 
as methyl, ethyl, n-propyl, isopropyl, n-butyl, t-butyl, n-amyl, n-hexyl, 
n-octyl, 2-ethylhexyl, t-octyl or the like; a substituted or unsubstituted 
alkoxy group such as methoxy, ethoxy, propoxy, butoxy or the like; a 
substituted or unsubstituted aryl group such as phenyl, tolyl, xylyl, 
ethylphenyl, chlorophenyl, nitrophenyl, dimethylaminophenyl, 
diethylaminophenyl, .alpha.-naphthyl, .beta.-naphthyl, 
dipropylaminophenyl, dibenzylaminophenyl, diphenylaminophenyl or the like; 
a substituted or unsubstituted aralkyl group such as benzyl, 
2-phenylethyl, 2-phenyl-1-methylethyl, bromobenzyl, 2-bromophenylethyl, 
methylbenzyl, nitrobenzyl or the like; an acyl group such as acetyl, 
propionyl, butyryl, valeryl, benzoyl, tolyoyl, naphthoyl, phthaloyl, 
furoyl or the like; a substituted or unsubstituted amino group such as 
amino, dimethylamino, diethylamino, dipropylamino, acetylamino, 
benzoylamino or the like; a substituted or unsubstituted styryl group such 
as styryl, dimethylaminostyryl, diethylaminostyryl, dipropylaminostyryl, 
methylstyryl or the like; a nitro group; a hydroxyl group; a carboxyl 
group; a cyano group; a substituted or unsubstituted arylazo group such as 
phenylazo, .alpha.-naphythylazo, .beta.-naphthylazo, 
dimethylaminophenylazo, chlorophenylazo, nitrophenylazo, methoxyphenylazo, 
tolylazo or the like; a substituted or unsubstituted heterocyclic group 
such as pyridyl, quinolyl, lepidyl, methylpyridyl, furyl, thienyl, 
indolyl, pyrrole, carbazolyl, N-ethylcarbazolyl or the like; a 
2,2-diphenylvinyl group; a 2-phenyl-2-methylvinyl group; a 
2-(dimethylaminophenyl)-2-phenylvinyl group; a 
2-(diethylaminophenyl)-2-phenylvinyl group; a 
2-(dibenzylaminophenyl)-2-phenylvinyl group; a 
2,2-di(diethylaminophenyl)vinyl group; a 2,2-di(methoxyphenyl)vinyl group; 
a 2,2-di(ethoxyphenyl)vinyl group; a 2-(dimethylaminophenyl)-2-methylvinyl 
group; a 2-(diethylaminophenyl)-2-ethylvinyl group or the like. 
R.sub.29 ' through R.sub.35 ' may form a condensed ring in the same way as 
R.sub.29 through R.sub.35. 
R.sub.36 indicates a hydrogen atom; a nitro group; a cyano group; an alkyl 
group such as methyl, ethyl, propyl, butyl or the like; or an aryl group 
such as phenyl, tolyl, xylyl or the like. 
R.sub.37 indicates a substituted or unsubstituted alkyl group such as 
methyl, ethyl, n-propyl, isopropyl, n-butyl, t-butyl, n-amyl, n-hexyl, 
n-octyl, 2-ethylhexyl, t-octyl or the like; a cyclic alkyl group such as 
cyclohexyl, cyclopropyl or the like; an aralkyl group such as benzyl, 
2-phenylethyl, 3-phenylpropyl, 4-phenylbutyl, .alpha.-naphthylmethyl, 
.beta.-naphthylmethyl or the like; a substituted aralkyl group such as 
methylbenzyl, bromobenzyl or the like; an aryl group such as phenyl, 
tolyl, xylyl, .alpha.-naphthyl, .beta.-naphthyl or the like; or a 
substituted aryl group such as chlorophenyl, dichlorophenyl, 
trichlorophenyl, ethylphenyl or the like. 
R.sub.38 indicates a substituted or unsubstituted aryl group such as 
phenyl, tolyl, xylyl, biphenyl, .alpha.-naphthyl, .beta.-naphthyl, 
anthraryl, pyrenyl, chlorophenyl, dichlorophenyl, trichlorophenyl, 
bromophenyl, dibromophenyl, tribromophenyl, ethylphenyl, diethylphenyl, 
nitrophenyl, aminophenyl, dimethylaminophenyl, diethylaminophenyl, 
dipropylaminophenyl, morpholinophenyl, piperidinylphenyl, 
piperazinophenyl, diphenylaminophenyl, acetylaminophenyl, 
benzoylaminophenyl, acetylphenyl, benzoylphenyl, cyanophenyl or the like. 
R.sub.39 indicates a monovalent heterocyclic group induced from a 
heterocycle such as furan, thiophene, benzofuran, thionaphthene, 
dibenzofuran, carbazole, phenothiazine, phenoxazine, pyridine or the like. 
R.sub.40 indicates a hydrogen atom; an alkyl group such as methyl, ethyl, 
propyl, butyl or the like; or a substituted or unsubstituted aryl group 
such as phenyl, tolyl, xylyl, biphenyl, ethylphenyl, chlorophenyl, 
nitrophenyl, aminophenyl, dimethylaminophenyl, diethylaminophenyl, 
acetylaminophenyl, .alpha.-naphthyl, .beta.-naphthyl, anthralyl, pyrenyl 
or the like. 
R.sub.41 and R.sub.42 each indicate a hydrogen atom; an alkyl group such as 
methyl, ethyl, propyl, butyl or the like; an alkoxy group such as methoxy, 
ethoxy, propoxy or the like; an aryl group such as phenyl, tolyl, xylyl, 
chlorophenyl, biphenyl, methoxyphenyl or the like; a substituted or 
unsubstituted styryl group such as styryl, p-methylstyryl, o-chlorostyryl 
or the like; a substituted or unsubstituted 4-phenyl-1,3-butadienyl group 
such as 4-phenyl-1,3-butadienyl, 4-(p-methylphenyl)-1,3-butadienyl or the 
like; or a substituted or unsubstituted heterocyclic group such as 
quinolyl, pyridyl, carbazolyl, furyl or the like. 
J indicates the atoms required to complete a nitrogen-containing 
heterocycle such as pyridine, thiazole, benzothiazole, naphthothiazole, 
oxazole, benzoxazole, naphthoxazole, imidazole, benzimidazole, 
naphthoimidazole, 2-quinoline, 4-quinoline, isoquinoline, indole or the 
like. The group J may be substituted by a halogen atom such as fluorine, 
chlorine, bromine, iodine or the like; an alkyl group such as methyl, 
ethyl, propyl, butyl or the like; an aryl group such as phenyl, tolyl, 
xylyl or the like; or an alkyl such as benzyl, p-trimethyl or the like. 
G.sup.- indicates an anion such as a chloride, bromide, iodide, 
perchlorate, benzenesulfonate, p-toluenesulfonate, methyl sulfate, ethyl 
sulfate, propyl sulfate, tetrafluoroborate, tetraphenylborate, 
hexafluorophosphate, benzenesulfinate, acetate, trifluroacetate, 
propionate, benzoate, oxalate, succinate, malonate, oleate, stearate, 
citrate, monohydrogen diphosphate, dihydrogen monophosphate, 
pentachlorostannate, chlorosulfonate, fluorosulfonate, 
trifluoromethanesulfonate, hexafluoroantimonate, molybdate, tungstate, 
titanate, zirconate ion or the like. 
The symbols r.sub.1 ', r.sub.2 ', r.sub.3 ', r.sub.4 ', r.sub.5 ', r.sub.6 
' and r.sub.7 ' each indicate a hydrogen atom; an alkyl group such as 
methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, t-butyl, 
n-amyl, t-amyl, n-hexyl, n-octyl, t-octyl or the like; a cyclic alkyl 
group such as cyclohexyl or the like; a substituted or unsubstituted 
alkenyl group such as vinyl, propenyl, butenyl, pentenyl, hexenyl, 
heptenyl, octenyl, dodecynyl, prenyl or the like; an aralkyl group such as 
benzyl, phenethyl, .alpha.-naphthylmethyl, .beta.-naphthylmethyl or the 
like; or a substituted aralkyl group such as carboxybenzyl, sulfobenzyl, 
hydroxybenzyl or the like. 
The amount of the double salt compound of (a) an aminium salt cation shown 
by the formula (I) or (II) and (2) a metal complex anion, which is added 
to a dye, is 1 to 60% by weight, preferably 1 to 40% by weight, and more 
preferably 5 to 25% by weight, on the basis of the total solids content 
relative to the recording layer. The combination of a polymethine dye 
expressed by the formula (X) or (XI) or a cyanine dye expressed by the 
formula (XXI) or (XXII) and the double salt compound of the present 
invention is particularly preferred for use in an optical recording medium 
because the recording sensitivity, the preservation stability, and the 
light resistance of the recording layer are excellent. Further, the 
recording layer deteriorates less as a result of exposure to reproduction 
light. 
In the present invention, a binder comprising an organic dye thin film may 
be contained in the recording layer. Examples of binders that can be used 
include cellulose esters such as nitrocellulose, cellulose phosphate, 
cellulose sulfate, cellulose acetate, cellulose propionate, cellulose 
butyrate, cellulose myristate, cellulose palmitate, cellulose acetate 
propionate, cellulose acetate butyrate and the like; cellulose ethers such 
as methyl cellulose, ethyl cellulose, propyl cellulose, butyl cellulose 
and the like; vinyl resins such as polystyrene, polyvinyl chloride, 
polyvinyl acetate, polyvinyl buryral, polyvinyl acetal, polyvinyl alcohol, 
polyvinyl pyrrolidone and the like; copolymer resins such as 
styrene-butadiene copolymers, styrene-acrylonitrile copolymers, 
styrene-butadiene-acrylonitrile copolymers, vinyl chloride-vinyl acetate 
copolymers and the like; acrylic resins such as polymethyl methacrylate, 
polymethyl acrylate, polybutyl acrylate, polyacrylic acid, polymethacrylic 
acid, polyacrylamide, polyacrylonitrile and the like; polyesters such as 
polyethylene terephthalate and the like; polyacrylate resins such as 
poly(4,4-isopropylidenediphenylene-co-1,4-cyclohexylenedimethylenecarbonat 
e), poly(ethylenedioxy-3,3-phenylenethiocarbonate), 
poly(4,4-isopropylidenediphenylenethiocarbonate-co-terephthalate), 
poly(4,4-isopropylidenediphenylenecarbonate), 
poly(4,4-secbutylidenediphenylenecarbonate), 
poly(4,4-isopropylidenediphenylenecarbonate-block-oxyethylene) and the 
like; polyamides; polyimides; epoxy resins; phenolic resins; polyolefins 
such as polyethylene, polypropylene, chlorinated polyethylene and the 
like. 
In addition, the recording layer may contain a surfactant, an anti-static 
agent, a stabilizer, a dispersing flame retardant, a lubricant, a 
plasticizer and the like. Further, an undercoat layer may be provided 
between the recording layer and the substrate, and a protective layer may 
be provided over the recording layer. 
The undercoat layer is used for providing resistance to solvents or 
improving the reflectance or repeated reproduction properties. The 
protective layer is used to protect the recording layer from flaws, dust, 
soil and the like and to improve the environmental stability of the 
recording layer. An inorganic compound, a metal or an organic polymer 
compound is typically used as a material for those layers. Examples of 
useful inorganic compounds include SiO.sub.2, MgF.sub.2, SiO, TiO.sub.2, 
ZnO, TiN, SiN and the like. Examples of useful metals include Zn, Cu, Ni, 
Al, Cr, Ge, Se, Cd and the like. Examples of useful organic polymer 
compounds include ionomer resins, polyamide resins, vinyl resins, natural 
polymers, epoxy resins, silane coupling agents, silicone resins, liquid 
rubber and the like. 
Examples of materials that can be used as the substrate include plastics 
such as polyester, polycarbonate, acrylic resins, polyolefin resins, 
phenolic resins, epoxy resins, polyamide, polyimide and the like; glass; 
metals; and the like. 
The organic solvent used for coating the layers depends upon the coating 
state, i.e., a dispersed state or a dissolved state. Examples of organic 
solvents that can be used include alcohols such as methanol, ethanol, 
isopropanol, diacetone alcohol and the like; ketones such as acetone, 
methyl ethyl ketone, cyclohexanone and the like; amides such as 
N,N-dimethylformamide, N,N-dimethylacetamide, and the like; sulfoxides 
such as dimethylsulfoxide and the like; ethers such as tetrahydrofuran, 
dioxane, ethylene glycol monomethyl ether and the like; esters such as 
methyl acetate, ethyl acetate, butyl acetate and the like; aliphatic 
halogenated hydrocarbons such as chloroform, methylene chloride, 
dichloroethylene, carbon tetrachloride, trichloroethylene and the like; 
aromatic hydrocarbons such as benzene, toluene, xylene, monochlorobenzene, 
dichlorobenzene and the like; aliphatic hydrocarbons such as n-hexane, 
cyclohexane, ligroin and the like; fluorine solvents such as 
tetrafluoropropanol, pentafluoropropanol and the like. 
The coating of the layers can be performed by a coating method such as a 
dip coating method, a spray coating method, a spinner coating method, a 
bead coating method, a wire bar coating method, a blade coating method, a 
roller coating method, a curtain coating method or the like. 
The thickness of the recording layer formed by using the above solvent is 
50 .ANG. to 100 .mu.m, preferably 200 .ANG. to 1 .mu.m. 
As described above, the present invention has the following advantageous 
effects: 
(1) It is possible to improve significantly the light resistance of the 
organic dye used, thus effectively preventing the deterioration of the 
recording layer of the optical recording medium due to exposure by 
reproduction light. These advantages are achieved by combining the double 
salt compound of the invention together with the organic dye in the 
recording layer. 
In addition, since photodeterioration is prevented even if the amount of 
the double salt compound added is small relative to the dye, an attempt 
can be made to improve the light-resistance of the recording layer, thus 
preventing the photodeterioration due to reproduction light, without 
causing the deterioration of the recording sensitivity of the optical 
recording medium. 
(2) Since the combination of a metal complex and an aminium salt compound 
in which an alkoxyalkyl group, a morpholine ring, an alkenyl group or an 
alkynyl group is introduced easily dissolves in typically used organic 
solvents which do not affect plastics, the productivity of optical 
recording media is significantly increased. 
(3) It is possible to obtain an optical recording medium exhibiting 
excellent preservation stability under conditions of high temperature and 
high humidity. 
(4) It is possible to obtain an optical recording medium having a distinct 
threshold value for laser power without degrading the high reflectance and 
high sensitivity of the organic dye used. 
EXAMPLES 
Although the present invention is described in more detail below with 
reference to the following specific examples, the present invention is not 
limited to the examples. 
Synthetic Example 1 
Double salt compound No. (I)-4 was synthesized by the following method: 
1.4 g of nickel (II) bisdithiobenzyl (trade name: MIR-101 manufactured by 
Midori Chemical) and 1.8 g of p-phenylenediamine were dissolved in 10 ml 
of dimethylsulfoxide. 60 ml of ethanol solution containing 3.2 g 
tetrabutylammonium bromide was then added dropwise to the resulting 
solution. The solution was then agitated to separate red needle-like 
crystals. The crystals obtained were then filtered off, washed with water, 
and purified by recrystallization to obtain 0.8 g nickel (II) 
bisdithiobenzyl tetrabutylammonium. When the absorption spectrum of the 
crystals was measured, the usual .lambda.max 930 nm of MIR-101 had been 
shifted to a longer wavelength of 950 nm. This shift confirmed that 
MIR-101 had changed to an anion. 
0.5 g of the nickel bisditiobenzyl tetrabutylammonium was added to 50 ml of 
a solution of 0.5 g of 
N,N,N',N'-tetrakis-(p-dimethoxyethylaminophenyl)-p-benzoquinone-aminiumper 
chlorate in DMF, followed by heating at 50.degree. C. for 30 hours with 
agitation. The reaction solution was then poured into water, and the 
precipitate obtained were washed with water, dried and then recrystallized 
to obtain 0.7 g of a double salt compound. 
When the double salt compound was measured by a differential scanning 
calorimeter, the peak of the perchlorate usually at 270.degree. C. had 
disappeared. This result and elemental analysis confirmed that the 
intended double salt compound had been obtained. 
______________________________________ 
Elemental analysis values: C.sub.82 H.sub.96 N.sub.6 O.sub.8 S.sub.4 Ni 
(molecular weight 1480.670) 
C H N 
______________________________________ 
Calculated value 
66.52% 6.54% 5.68% 
Measured value 
66.28% 6.65% 5.60% 
______________________________________ 
Synthetic Example 2 
Double salt compound (I)-15 was synthesized by the following method: 
1.0 g 
N,N,N',N'-tetrakis-(p-dipropenylaminophenyl)-p-benzoquinone-aminiumperchlo 
rate was dissolved in 90 ml DMF. 0.7 g nickel-bis(trichlorobenzenedithiol) 
tetra(n-butyl)ammonium (trade name PA-1006 manufactured by Mitsui Toatsu 
Fine Co., Ltd.) was added to the resulting solution, followed by heating 
at 50.degree. C. for 3 hours with agitation. The reaction solution was 
then poured into water to obtain a precipitate. The precipitate obtained 
was washed with water, dried and then recrystallized to obtain 0.95 g of a 
double salt compound. 
When the compound was measured by a differential scanning calorimeter, the 
usual peak of the perchlorate at 270.degree. C. had disappeared. This 
result and the elemental analysis confirmed that the intended double salt 
compound had been obtained. 
______________________________________ 
Elemental analysis values: C.sub.66 H.sub.62 N.sub.6 Cl.sub.6 S.sub.4 Ni 
(molecular weight 1338.948) 
C H N 
______________________________________ 
Calculated value 
59.21% 4.67% 6.28% 
Measured value 
59.33% 4.81% 6.22% 
______________________________________ 
Synthetic Example 3 
Double salt compound (II)-4 was synthesized by the following method: 
0.7 g 
N,N,N',N'-tetrakis-(2-methylpyrrolidinophenyl)-p-benzoquinone-aminiumperch 
lorate was dissolved in 70 ml DMF. 0.68 g 
nickel-bis(trimethoxybenzenedithiol) tetra(n-butyl)ammonium was added to 
the resulting solution, followed by heating at 50.degree. C. for 3 hours 
with agitation. The reaction solution was then poured into water to obtain 
a precipitate. The precipitate obtained was washed with water, dried and 
then recrystallized to obtain a double salt compound. 
When the compound was measured by a differential scanning calorimeter, the 
usual peak of the perchlorate at 270.degree. C. had disappeared. This 
result and the elemental analysis confirmed that the intended double salt 
compound had been obtained. 
______________________________________ 
Elemental analysis values: C.sub.90 H.sub.108 N.sub.6 O.sub.12 S.sub.4 
Ni 
(molecular weight 1652.850) 
C H N 
______________________________________ 
Calculated value 
65.40% 6.59% 5.09% 
Measured value 
65.29% 6.51% 5.14% 
______________________________________ 
Example 1 
Pre-grooves (12) comprising strips, each having a width of 3 .mu.m and a 
length of 85 mm at a pitch of 12 .mu.m, were provided by a heat press 
method on a polycarbonate (referred to as "PC" hereinafter) substrate (11) 
of a wallet size (54 mm long and 85 mm wide) and having a thickness of 0.4 
mm. A solution obtained by dissolving (1) 3 parts by weight of a mixture 
containing IR-820 (manufactured by Nippon Kayaku Co., Ltd. ) as a 
polymethine dye and the above double salt compound No. (I)-1 at a ratio by 
weight of 80:20 in (2) 97 parts by weight of diacetone alcohol, was coated 
on the substrate (11) by a bar coating method to obtain a recording layer 
(13) having a thickness of 950 .ANG.. 
A wallet-size PC substrate (15) having a thickness of 0.3 mm was then 
laminated over the recording layer (13) through an acrylate-ethylene 
copolymer dry film (14) and was bonded thereto by heat rolling to produce 
an optical card with an adhesive structure (refer to FIGS. 1 and 2). 
Using an optical card recording/reproducing apparatus (manufacture by Canon 
Inc., the reflectance of the recording layer was measured by applying a 
semiconductor laser beam which had an oscillation wavelength of 830 nm and 
an output of 0.2 mW, to the above-described optical card having a 
thickness of 0.4 mm. Information was recorded on the tracks between the 
respective pregrooves by a semiconductor laser having an oscillation 
wavelength of 830 nm with a recording power of 3.5 mW and a recording 
pulse of 80 .mu.sec. The information was reproduced with a reproducing 
power of 0.2 mW through a PC substrate having a thickness of 0.4 mm while 
driving the optical card in the direction of the pregrooves at a rate of 
60 mm/sec. The contrast ratio [(A-B)/A] (A: signal strength of unrecorded 
portion, B: signal strength of recorded portion) was measured. 
The reflectance and contrast of the optical card were also measured after 
the card was allowed to stand at 65.degree. C. and 85% RH for 1000 hours 
to test environmental preservation stability. 
Another optical card was formed by the same method as described above, and 
information was recorded thereon. After the optical card was irradiated 
with a xenon lamp light of 1 kW/m.sup.2 for 200 hours, the reflectance and 
contrast were measured to test light resistance stability. 
The results obtained are shown in Table 4. 
Example 2 
An optical card was produced by the same method as that employed in Example 
1, except that the double salt compound No. (I)-1 used in Example 1 was 
changed to the double salt compound No. (I)-4. The optical card was 
evaluated by the same methods as described above for Example 1. The 
results obtained are shown in Table 4. 
TABLE 4 
__________________________________________________________________________ 
Environmental preservation 
Light-resistance stability 
stability After storage at 
after irradiation with xenon 
Initial 65.degree. C. and 85% RH for 1000 hr 
lamp of 1 kW/m.sup.2 for 200 hr 
Example 
Reflectance (%) 
Contrast ratio 
Reflectance (%) 
Contrast ratio 
Reflectance (%) 
Contrast ratio 
__________________________________________________________________________ 
1 15.1 0.65 13.6 0.58 13.0 0.55 
2 15.2 0.66 13.8 0.59 13.2 0.57 
__________________________________________________________________________ 
Examples 3 and 4 
An optical card was produced by the same method as that described for 
Example 1, except that the combination of the polymethine dye and the 
double salt compound, which was used in Example 1, was changed to each of 
the combinations of dyes and double salt compounds shown be low. 
__________________________________________________________________________ 
Double salt 
Ratio by 
Example 
Organic dye compound No. 
weight 
__________________________________________________________________________ 
##STR183## (I)-1 85:15 
4 " (I)-15 85:15 
__________________________________________________________________________ 
Comparative Example 1 
An optical card was produced by the same method as that described for 
Example 3, except that the double salt compound (I)-1 used in Example 3 
was lacking. The resulting optical card was evaluated by the same methods. 
The results of evaluating Examples 3 and 4 and Comparative Example 1 are 
shown in Table 5. 
TABLE 5 
__________________________________________________________________________ 
Environmental preservation 
Light-resistance stability 
stability After storage at 
after irradiation with xenon 
Initial 65.degree. C. and 85% RH for 1000 hr 
lamp of 1 kW/m.sup.2 for 200 hr 
Example 
Reflectance (%) 
Contrast ratio 
Reflectance (%) 
Contrast ratio 
Reflectance (%) 
Contrast ratio 
__________________________________________________________________________ 
3 16.0 0.68 13.9 0.58 13.2 0.56 
4 16.1 0.69 14.0 0.58 13.4 0.57 
.sup. 1* 
16.6 0.71 13.9 0.56 6.7 immeasurable 
__________________________________________________________________________ 
1*) Comparative Example No. 
Comparative Examples 2 to 4 
An optical card was produced by the same method as that described for 
Example 3, except that the double salt compound No. (I)-1 used in Example 
3 was changed to each of the compounds shown in Table 6 below. 
TABLE 6 
__________________________________________________________________________ 
##STR184## 
##STR185## 
##STR186## 
##STR187## 
##STR188## 
##STR189## 
##STR190## 
##STR191## 
An optical card was produced by the same method as that described for 
Example 3, except that the double salt compound No. (I)-1 used in Example 
3 was changed to double salt compound expressed by the following formula. 
The card was evaluated by the same method. 
##STR192## 
Comparative Example 6 
An optical card was produced by the same method as that described for 
Example 4, except that the double salt compound No. (I)-15 used in Example 
4 was changed to a double salt compound expressed by the following 
formula, and was evaluated by the same method. 
##STR193## 
TABLE 7 
__________________________________________________________________________ 
Environmental preservation 
Light-resistance stability 
stability After storage at 
after irradiation with xenon 
Comparative 
Initial 65.degree. C. and 85% RH for 1000 
lamp of 1 kW/m.sup.2 for 200 hr 
Example 
Reflectance (%) 
Contrast ratio 
Reflectance (%) 
Contrast ratio 
Reflectance (%) 
Contrast 
__________________________________________________________________________ 
ratio 
2 16.0 0.68 11.1 0.47 13.1 0.56 
3 15.9 0.68 13.5 0.56 11.0 0.48 
4 16.2 0.69 11.9 0.49 13.2 0.55 
5 16.1 0.68 13.7 0.56 13.0 0.54 
6 16.0 0.68 13.8 0.55 13.1 0.55 
__________________________________________________________________________ 
Example 5 and Comparative Example 7 
An optical card of Example 5 was produced by the same method as that 
described for Example 3, and an optical card of Comparative Example 7 was 
produced by the same method as that employed in Comparative Example 5. 
The optical cards of Example 5 and Comparative Example 7 were attached to 
the optical card recording/reproducing apparatus (manufactured by Canon 
Inc.). The reflectance of the light reflected from the recording layer of 
each of the optical cards was measured by continuously applying a 
semiconductor laser having an oscillation wavelength of 830 nm and an 
output of 0.2 mW to a point of the recording layer and through the PC 
substrate having a thickness of 0.4 mm without driving the optical card. 
The reproduction light deterioration time was determined by measuring the 
time required for the initial reflectance value of the recording layer to 
decrease by 5%, 95% of the initial reflectance value. The results of these 
measurements of Example 5 and Comparative Example 7 are shown in Table 8. 
TABLE 8 
______________________________________ 
Reproduction light 
deterioration time (sec) 
______________________________________ 
Example 5 250 
Comparative 160 
Example 7 
______________________________________ 
Example 6 and Comparative Example 8 
An optical card of Example 6 was produced by the same method as that 
employed in Example 4, and an optical card of Comparative Example 8 was 
produced by the same method as that employed in Comparative Example 6. 
The reproducing light deterioration time of each of the optical cards of 
Example 6 and Comparative Example 8 was measured by the same method as 
that employed in Example 5. 
The results of measurement of Example 6 and Comparative Example 8 are shown 
in Table 9. 
TABLE 9 
______________________________________ 
Reproduction light 
deterioration time (sec) 
______________________________________ 
Example 6 245 
Comparative 150 
Example 8 
______________________________________ 
Examples 7 to 11 
An optical card was produced by the same method as that described for 
Example 1, except that the combination of the polymethine dye and the 
double sample compound, which was used in Example 1, was changed to each 
of the combinations shown in Table 10. 
Comparative Example 9 
An optical card was produced by the same method as that employed in Example 
11, except that the double salt compound No. (I)-11 used in Example 8 was 
removed. 
The results of measurement of Examples 7 to 11 and Comparative Example 9 
are shown in Table 11. 
TABLE 10 
__________________________________________________________________________ 
Double salt 
Ratio 
Example 
Organic dye compound No. 
by weight 
__________________________________________________________________________ 
##STR194## (II)-4 80:20 
8 
##STR195## (II)-11 90:10 
9 
##STR196## (I)-13 95:5 
10 
##STR197## (II)-3 85:15 
11 
##STR198## (I)-3 75:25 
__________________________________________________________________________ 
TABLE 11 
__________________________________________________________________________ 
Environmental preservation 
Light-resistance stability 
stability After storage at 
after irradiation with xenon 
Initial 65.degree. C. and 85% RH for 1000 hr 
lamp of 1 kW/m.sup.2 for 200 hr 
Example 
Reflectance (%) 
Contrast ratio 
Reflectance (%) 
Contrast ratio 
Reflectance (%) 
Contrast ratio 
__________________________________________________________________________ 
7 15.6 0.65 13.6 0.57 13.1 0.55 
8 16.0 0.68 13.8 0.58 13.0 0.55 
9 16.1 0.70 13.2 0.58 12.9 0.55 
10 16.0 0.68 13.6 0.58 13.1 0.56 
11 15.6 0.67 13.9 0.60 13.7 0.60 
.sup. 9* 
19.4 0.70 13.6 0.57 5.9 immeasurable 
__________________________________________________________________________ 
9*: Comparative Example No 
Examples 12 to 15 
A PC substrate in circular shape having a diameter of 130 mm.phi. and a 
thickness of 1.2 mm was produced by injection molding and provided with 
spiral tracking grooves having a width of 0.6 .mu.m and a pitch of 1.6 
.mu.m formed on the surface thereof. A solution obtained by dissolving (1) 
5 parts by weight of each of the mixtures of the organic dyes shown in 
Table 12 below and (2) the double salt compounds in 95 parts by weight of 
diacetone alcohol was coated on the grooves surface of the substrate by 
spin coating to form a recording layer having a thickness of 950 .ANG.. 
Another protective PC substrate was laminated over the recording layer by 
using an ultraviolet-curing adhesive with spacers of 0.3 mm being provided 
at the inner and outer peripheral sides of the recording layer. As a 
result, an optical disk having an air sandwich structure was obtained. 
Information was then written on the thus-produced optical disk with a 
recording power of 8 mW and a recording frequency of 3 MHz. The recorded 
information was read with a reading power of 0.8 mW by applying a 
semiconductor laser beam having an oscillation wavelength of 830 nm to the 
disk through a PC substrate while rotating the optical disk att 1800 rpm. 
The C/N ratio (carrier/noise ratio) was measured by spectrum analysis of 
the reproduced waveform (scanning filter, band width 30 kHz). 
The C/N ratio was also measured after information was repeatedly reproduced 
10.sup.5 times from the portion of the optical disk on which information 
was recorded. In addition, the reflectance of recording light having a 
wavelength of 830 nm was measured through the PC substrate by a 
spectrophotometer (trade name: U-3400 manufactured by Hitachi Inc.). 
The optical disk was also subjected to tests for environmental preservation 
stability and light-resistance stability under the same conditions as 
those in Example 1. The same disk was then tested with respect to the 
reflectance of the recording layer and the C/N ratio of the recording pit. 
The results obtained are shown in Table 13. 
TABLE 12 
__________________________________________________________________________ 
Double salt 
Example 
Organic dye compound No. 
Ratio by 
__________________________________________________________________________ 
weight 
12 
##STR199## (I)-8 80:20 
13 IR-820 (produced by Nippon Kayaku Co., Ltd.) 
(I)-9 85:15 
14 
##STR200## (II)-5 80:20 
15 
##STR201## (I)-5 95:5 
__________________________________________________________________________ 
Comparative Examples 10 and 11 
Optical disks were produced by the same methods as those employed in 
Examples 12 and 15 respectively, except that the double salt compound Nos. 
(I)-8 and (I)-5 used in Examples 12 and 15 were lacking from the recording 
layer. These disks were evaluated by the same methods, and the results 
obtained are shown in Table 13. 
Comparative Example 12 
An optical disk was produced by the same method as that employed in Example 
12 with the exception that the metal complex compounds below were 
substituted for the double salt compound No. (I)-8 used in Example 12. The 
results are shown in Table 13. 
As seen from Table 13, because crystals separated out after coating due to 
the low solubility of the metal complex compound, the signal reproduced 
from the optical disk exhibited a very wide noise level. Thus, the C/N 
ratio could not be measured. 
##STR202## 
TABLE 13 
__________________________________________________________________________ 
After 10.sup.5 
Environmental preservation 
Light-resistance stability 
repeated 
stability After storage at 
After irradiation with xenon 
Initial reproductions 
65.degree. C. and 85% RH for 1000 
lamp of 1 kW/m.sup.2 for 200 
hr 
Example 
Reflectance (%) 
C/N (dB) 
C/N (dB) 
Reflectance (%) 
C/N (dB) 
Reflectance (%) 
C/N (dB) 
__________________________________________________________________________ 
12 26.2 56.7 53.8 23.6 50.5 22.8 49.9 
13 26.5 57.7 55.4 24.4 53.7 23.9 52.5 
14 26.8 59.0 54.4 23.7 51.4 22.8 50.8 
15 26.8 58.5 53.8 22.8 50.3 23.0 50.9 
.sup. 10* 
27.3 61.1 46.7 23.7 51 13.7 x 
.sup. 11* 
30.2 60.4 38.9 23.0 50.3 12.1 x 
.sup. 12* 
26.1 x -- 20.9 -- 18.3 -- 
__________________________________________________________________________ 
10*, 11* and 12*: Comparative Examples Nos. 
x: immeasurable 
Examples 16 and 17 
A spiral regroove was provided on a polymethyl methacrylate (hereinafter 
referred to as "PMMA") substrate in circular shape having a diameter of 
130 mm.phi. and a thickness of 1.2 mm by a 2P method (photopolymer method) 
using an epoxy-acrylate ultraviolet-curing resin. An optical disk was 
produced by the same method as that employed in Example 12, except that a 
solution obtained by dissolving in 1,2-dichloroethane 2 parts by weight of 
each of the combinations of the organic dyes and double salt compounds 
shown in Table 14 was coated on the substrate by the spinner coating 
method to form a recording layer. The recording layer comprised an organic 
thin film having a dry thickness of 900 .ANG.. 
The thus-produced optical disk was evaluated by the same tests as that 
performed in Example 12. The results are shown in Table 16. 
TABLE 14 
__________________________________________________________________________ 
Double 
Ratio 
compound 
by 
Example 
Organic dye No. weight 
__________________________________________________________________________ 
16 
##STR203## (II)-2 
90:10 
17 
##STR204## (I)-2 85:15 
__________________________________________________________________________ 
Examples 18 and 19 
An optical disk was produced by the same method as that employed in Example 
8, except that a solution obtained by dissolving (1) 4 parts by weight of 
each of the combinations of the organic dyes and double salt compounds 
shown in Table 15 and (2) 1 part by weight of nitrocellulose resin 
(Orhaless Lacquer manufactured by Deicel Chemical Industries, Ltd.) in (3) 
95 parts by weight of diacetone alcohol was coated on a polycarbonate 
substrate in circular shape. The substrate had a diameter of 130 mm.phi., 
a thickness of 1.2 mm, and was provided with pregrooves. The resulting 
recording layer comprised an organic thin film having a dry thickness of 
950 .ANG.. 
The thus-produced optical disk was evaluated by the same tests as that 
performed in Example 8. The results are shown in Table 16. 
TABLE 15 
__________________________________________________________________________ 
Double salt 
Ratio 
Example 
Organic dye compound No. 
by weight 
__________________________________________________________________________ 
18 
##STR205## (I)-14 75:25 
19 
##STR206## (II)-9 80:20 
__________________________________________________________________________ 
TABLE 16 
__________________________________________________________________________ 
After 10.sup.5 
Environmental preservation 
Light-resistance stability 
repeated 
stability After storage at 
After irradiation with xenon 
Initial reproductions 
65.degree. C. and 85% RH for 1000 
lamp of 1 kW/m.sup.2 for 200 
hr 
Example 
Reflectance (%) 
C/N (dB) 
C/N (dB) 
Reflectance (%) 
C/N (dB) 
Reflectance (%) 
C/N (dB) 
__________________________________________________________________________ 
16 26.3 59.2 55.1 22.6 50.9 22.4 49.7 
17 26.5 59.7 55.5 23.3 51.9 22.8 51.3 
18 25.1 54.0 51.8 22.1 47.4 22.1 48.1 
19 25.2 53.0 50.4 22.1 46.1 22.0 46.1 
__________________________________________________________________________ 
Example 20 
A solution obtained by dissolving (1) 3 parts by weight of the mixture of 
organic dye and double salt compound No. (I)-1 (weight ratio 80:20) that 
was used in Example 1 in (2) 97 parts by weight of diacetone alcohol was 
coated on the wallet size PC substrate of Example 1 by the roll coating 
method to produce a recording layer. The substrate had a thickness of 0.4 
mm and was provided with pregrooves. The resulting recording layer had a 
dry thickness of 1000 .ANG.. 
Recording layers were continuously coated on 200 PC substrates, which were 
0.4 mm thick, by the same method as that described above, and 200 optical 
cards were then produced by the same method as that employed in Example 1. 
Each of the optical cards was numbered in order of coating. Then card Nos. 
1, 10, 50, 100 and 200 which were produced by using the substrate Nos. 1, 
10, 50, 100 and 200 was attached to an optical card recording/reproducing 
apparatus. Information was recorded on the recording tracks between the 
respective pregrooves by using a semiconductor laser from the side of the 
PC substrate while driving the optical card in the direction along the 
pregrooves at a rate of 60 mm/sec. The semiconductor layer had an 
oscillation wavelength of 830 nm with a spot size of 3 .mu.m.phi., a 
recording power of 3.5 mW, and a recording pulse of 50 .mu.sec. The 
information was then read with a reading power of 0.2 mW, and the C/N 
ratio was measured by spectrum analysis of the reproduced waveform 
(scanning filter band width 1 kHz). The results obtained are shown in 
Table 17. 
Example 21 
200 optical cards were produced by the same method as that employed in 
Example 20 with the exception that the double salt compound No. (I)-1 used 
in Example 20 was changed to No. (I)-8. The C/N ratios of optical card 
Nos. 1, 10, 50, 100 and 200 in order of coating were measured by the same 
method as that employed in Example 20. The results obtained are shown in 
Table 17. 
Example 22 
200 optical cards were produced by the same method as that employed in 
Example 20 with the exception that the double salt compound No. (I)-1 used 
in Example 20 was changed to No. (I)-4. The C/N ratios of optical card 
Nos. 1, 10, 50, 100 and 200 in order of coating were measured by the same 
method as that employed in Example 20. The results obtained are shown in 
Table 17. 
Comparative Example 13 
200 optical cards were produced by the same method as that employed in 
Example 20 with the exception that the double salt compound No. (I)-1 used 
in Example 20 was changed to the double salt compound used in Comparative 
Example 6. The C/N ratios of optical card Nos. 1, 10, 50, 100 and 200 were 
measured by the same method as that employed in Example 20. The results 
obtained are shown in Table 1. 
TABLE 17 
______________________________________ 
C/N ratio (noise level) (dB) 
No. 1 No. 10 No. 50 No. 100 
No. 200 
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Example 20 
49.8 49.8 49.7 49.7 49.6 
(-68.0) (-68.0) (-68.0) 
(-67.9) 
(-67.8) 
Example 21 
49.5 49.5 49.4 49.4 49.3 
(-67.9) (-67.9) (-67.8) 
(-67.8) 
(-67.7) 
Example 22 
49.7 49.7 49.7 49.6 49.6 
(-68.0) (-68.0) (-68.0) 
(-67.9) 
(-67.8) 
Comparative 
48.5 48.3 47.9 45.5 44.2 
Example 13 
(-67.2) (-67.1) (-66.8) 
(-64.5) 
(-62.3) 
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In Comparative Example 13, the noise level increased and the the C/N ratio 
decreased as the coating numbers of disks increased. This is possibly 
caused by the low solvent solubility of the double salt compound used in 
Comparative Example 14. Solid crystals, for example, are easily produced 
by only a small change in the concentration of the coating solution during 
the coating of a plurality of substrates, resulting in increased noise 
levels. On the other hand, the combination of the aminium salt cation and 
the metal complex anion used in each of Examples 20 to 22 of the present 
invention exhibits a high solubility in a solvent that does not affect 
plastics. Thus, hardly any crystals are produced by concentration changes 
during processing. It is thus thought that no crystals are formed in the 
recording layer, thereby constantly producing recording media having low 
noise levels. 
While the present invention has been described with respect to what is 
presently considered to be the preferred embodiments, it is to be 
understood that the invention is not limited to the disclosed embodiments. 
To the contrary, the invention is intended to cover various modifications 
and equivalent arrangements included within the spirit and scope of the 
appended claims. The scope of the following claims is to be accorded the 
broadest interpretation so as to encompass all such modifications and 
equivalent elements and functions.