U.S. patent application number 10/771437 was filed with the patent office on 2004-08-19 for cyanine dyes.
This patent application is currently assigned to KABUSHIKI KAISHA HAYASHIBARA SEIBUTSU KAGAKU KENYUJO. Invention is credited to Hohsaka, Ayako, Kawata, Toshio, Matsuura, Dai, Yasui, Shigeo.
Application Number | 20040161701 10/771437 |
Document ID | / |
Family ID | 27342312 |
Filed Date | 2004-08-19 |
United States Patent
Application |
20040161701 |
Kind Code |
A1 |
Hohsaka, Ayako ; et
al. |
August 19, 2004 |
Cyanine dyes
Abstract
Disclosed are novel trimethine cyanine dyes, light absorbents,
light-resistant improvers, and optical recording media which
comprise the trimethine cyanine dyes. The cyanine dyes exert
satisfactory solubility and heat resistance when used in
high-density optical recording media.
Inventors: |
Hohsaka, Ayako; (Okayama,
JP) ; Matsuura, Dai; (Okayama, JP) ; Kawata,
Toshio; (Okayama, JP) ; Yasui, Shigeo;
(Okayama, JP) |
Correspondence
Address: |
BROWDY AND NEIMARK, P.L.L.C.
PATENT AND TRADEMARK CAUSES
SUITE 300
624 NINTH STREET, N.W.
WASHINGTON
DC
20001-5303
US
|
Assignee: |
KABUSHIKI KAISHA HAYASHIBARA
SEIBUTSU KAGAKU KENYUJO
Okayama-shi
JP
|
Family ID: |
27342312 |
Appl. No.: |
10/771437 |
Filed: |
February 5, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10771437 |
Feb 5, 2004 |
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09783190 |
Feb 12, 2001 |
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6743568 |
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Current U.S.
Class: |
430/270.21 ;
369/284; 428/64.8; 430/270.2; 430/945; G9B/7.151 |
Current CPC
Class: |
G11B 7/2495 20130101;
G11B 7/2534 20130101; Y10S 430/146 20130101; G11B 2007/24612
20130101; G11B 7/2533 20130101; G11B 7/246 20130101; G11B 7/259
20130101; G11B 7/2535 20130101; G11B 7/245 20130101; G11B 7/2531
20130101; G11B 7/2536 20130101; G11B 7/2467 20130101; G11B 7/2492
20130101; C09B 23/06 20130101; G11B 7/2472 20130101; G11B 7/248
20130101; C09B 69/045 20130101 |
Class at
Publication: |
430/270.21 ;
430/270.2; 430/945; 428/064.8; 369/284 |
International
Class: |
G11B 007/24 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 10, 2000 |
JP |
32947/2000 |
Feb 18, 2000 |
JP |
41001/2000 |
Nov 17, 2000 |
JP |
351905/2000 |
Claims
We claim:
1. An optical recording medium, which comprises a trimethine
cyanine dye represented by Formula 1 and has a solubility of at
least 50 mg/ml in diacetone alcohol at 20.degree. C.: 22wherein in
Formula 1, R.sub.1 and R.sub.2 independently represent an
optionally substituted aliphatic hydrocarbon group; Z.sub.1 and
Z.sub.2 independently represent an optionally substituted
naphthalene ring to form a benzoindolenic ring; and X.sup.-
represents an organic metal complex as a counter ion selected from
the group consisting of RF.sub.6.sup.-, ClO.sub.4.sup.-, and
Sb.sub.6.sup.-.
2. The optical recording medium of claim 1, which is capable of
recording information thereon by writing thereon with a laser beam
having a wavelength of around 630 to 680 nm.
3. The optical recording medium of claim 1, which has a
decomposition point of over 272.degree. C.
4. The optical recording medium of claim 1, which has a reflection
efficiency of at least 45%.
5. The optical recording medium of claim 1, which further contains
0.03 to 0.3 mole of a light-resistant improver to one mole of said
trimethine cyanine dye.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to novel organic dye
compounds, and more particularly, to trimethine cyanine dyes which
are useful in high-density optical recording media.
[0003] 2. Description of the Prior Art
[0004] As coming into this multi-media age, the following optical
recording media have been greatly focused:
[0005] (i) compact disc recordable or CD-R, a write-once memory
using compact disc, and
[0006] (ii) digital versatile disc recordable or DVD-R, a
write-once memory using digital video disc.
[0007] Optical recording media can be roughly classified into
inorganic optical recording media which have recording layers
composed of inorganic substances such as tellurium, selenium,
rhodium, carbon, or carbon sulfide; and organic optical recording
media which have recording layers mainly composed of light
absorbents containing organic dye compounds.
[0008] Among such optical recording media, organic optical
recording media can be usually prepared by dissolving a cyanine dye
in an organic solvent such as 2,2,3,3-tetrafluoro-1-propanol
(abbreviated as "TFP" hereinafter), coating the solution on the
surface of a polycarbonate substrate, drying the coated solution to
form a recording layer, and sequentially forming and attaching on
the surface of the recording layer (i) a reflection layer made of a
metal such as gold, silver or copper, and (ii) a protection layer
made of an ultraviolet ray hardening resin. When compared with
inorganic optical recording media, organic ones may have the
drawback that their recording layers may be easily changed by
environmental lights such as reading- and natural-lights. Optical
recording media, however, have the merit that they can be made into
optical recording media at a lesser cost because their recording
layers can be directly formed by coating light absorbents in a
solution form on the surface of substrates. Further, organic
optical recording media, which are composed of organic materials,
are now mainly used as low-cost optical recording media because
they are substantially free of corrosion even when contacted with
moisture or sea water and because information, stored in optical
recording media by a fixed format, can be read out by using
commercialized readers by the establishment of
thermal-deformation-type optical recording media as organic optical
recording media.
[0009] What is urgently required in organic optical recording media
is to increase their storage capacity to suit for this multi-media
age. The research for such an increment, which is now being eagerly
continued in this field, is to shorten the wavelength of a laser
beam for writing information from 775-795 nm, that is irradiated by
conventional GaAlAs semiconductor lasers, to a wavelength of 700 nm
or shorter. However, since most of conventional cyanine dyes
explored for CD-Rs could not appropriately write and read
information by using a laser beam with a wavelength shorter than
700 nm when used in high-density optical recording media such as
DVD-Rs, the cyanine dyes now used could not fulfil the need for
high-storage density required in many fields.
[0010] As another causative for spoiling the high-storage density
of organic optical recording media, there may exist problems of the
thermal decomposition and the heat resistance of dyes. In organic
optical recording media, pits are formed by using heat generated
when dyes absorb a laser beam and then melt and decompose. However,
most of conventional cyanine dyes have a rather lower decomposition
point, and this results in the problem that the part around the
pits and other pit-less part on the recording surface may be easily
deformed by the accumulated heat which is generated when the dyes
are exposed to a reading laser-beam for a relatively-long period of
time because the cyanine dyes have a relatively-low heat
resistance.
[0011] High quality products must be provided in large quantity and
low price to make high density optical recording media such as a
DVD-R fix, as an information recording means for multi-media age,
in place of papers. For the purpose, it is necessary to efficiently
coat light absorbents on a substrate and make optical recording
media with a good recording characteristic and higher stability.
Light absorbents which easily dissolve in organic solvents are
essential, and more particularly, the development of light
absorbents, which less pollute environment and easily dissolve in
non-halogen solvents, has been desired. Although various light
absorbents were provided and some of them have been actually used,
no light absorbent, which can satisfy both the desired light
characteristic and solubility, has been realized.
SUMMARY OF THE INVENTION
[0012] In view of the foregoing, the object of the present
invention is to provide organic dye compounds which exert
satisfactory solubility and heat resistance when used in
high-density optical recording media.
[0013] To attain the above object, the present inventors eagerly
studied and screened compounds. As a result, they found that
specific trimethine cyanine dyes (may be called "cyanine dyes"
hereinafter) which substantially absorb a visible light with a
wavelength of shorter than 700 nm, are obtainable through a step of
reacting benzoindolenium compounds bearing a reactive methyl group
with benzoindolenium compounds bearing a suitable leaving group.
They also found that, when compared with conventional related
compounds, most of the cyanine dyes of the present invention have
the following characteristics: They have significantly-high
solubility in organic solvents which are frequently used in
preparing optical recording media, and more particularly,
non-halogenated solvents, have decomposition points over
272.degree. C., and have relatively-high heat resistances. The
present inventors confirmed that the trimethine cyanine dyes form
minute pits stably on the recording surfaces and at a
relatively-high density when irradiated with a laser beam at a
wavelength of shorter than 700 nm in optical recording media. The
present invention was made based on the creation of novel organic
dye compounds and the discovery of their industrially useful
characteristics.
BRIEF EXPLANATION OF THE ACCOMPANYING DRAWINGS
[0014] FIG. 1 is a visible absorption spectrum of one of the
cyanine dyes of the present invention.
[0015] FIG. 2 is a visible absorption spectrum of a conventional
related compound.
[0016] FIG. 3 shows the result on DTA and TGA for one of the
cyanine dyes of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0017] The present invention solves the above object by providing
the trimethine cyanine dyes represented by Formula 1, which have
the solubility of at least 50 mg/ml in diacetone alcohol
(abbreviated as "DAA" hereinafter) at 20.degree. C., and have
decomposition points of over 272' (the trimethine cyanine dyes may
be called "cyanine dyes" hereinafter). 1
[0018] In Formula 1, R.sub.1 and R.sub.2 independently represent an
aliphatic hydrocarbon group which is usually selected from those
having up to 8 carbon atoms, such as methyl, ethyl, ethynyl,
propyl, isopropyl, 1-propenyl, 2-propenyl, 2-propynyl, isopropenyl,
butyl, isobutyl, sec-butyl, tert-butyl, 2-butenyl, 1,3-butadienyl,
pentyl, isopentyl, neopentyl, tert-pentyl, 1-methylpentyl,
2-methylpentyl, 2-pentenyl, 2-penten-4-ynyl, hexyl, isohexyl,
5-methylhexyl, heptyl, and octyl groups. These aliphatic
hydrocarbon groups may have one or more substituents, for example,
aliphatic hydrocarbon groups such as methyl, ethyl, propyl,
isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl,
isopentyl, neopentyl and tert-pentyl groups; aromatic hydrocarbon
groups such as phenyl, o-tolyl, m-tolyl, p-tolyl, xylyl, mesityl,
o-cumenyl, m-cumenyl, p-cumenyl, and biphenyl groups; ethers such
as methoxy, trifluoromethoxy, ethoxy, propoxy, isopropoxy, buthoxy,
tert-buthoxy, pentyloxy, phenoxy, and benzyloxy groups; esters such
as methoxycarbonyl, trifluoromethoxycarbonyl, ethoxycarbonyl,
propoxycarbonyl, acetoxy, trifluoroacetoxy, and benzoyloxy groups;
and halogens such as fluorine, chlorine, bromine, and iodine.
Depending on the whole structures of the cyanine dyes, R.sub.1 and
R.sub.2 are differently aliphatic hydrocarbons represented by
C.sub.mH.sub.2m+1 and C.sub.nH.sub.2n+1, where n and m are natural
numbers and counted nine or less in total. Most of the cyanine dyes
have relatively-high solubility in non-halogen solvents such as
diacetone alcohol (abbreviated as "DAA" hereinafter) and
relatively-high decomposition points. The cyanine dyes have a
characteristic of relatively-high heat resistance.
[0019] Z.sub.1 and Z.sub.2 in Formula 1 independently represent a
fused naphthalene ring to form a benzoindolenin ring. Usually, the
benzoindolenin ring independently has either 1H-benzo [e] indole
skeleton or 3H-benzo [g] indole skeleton. One or more hydrogen
atoms in the fused naphthalene ring may be replaced with
substituents, and the substituents include, for example, aliphatic
hydrocarbon groups such as methyl, ethyl, propyl, isopropyl, butyl,
isobutyl, sec-butyl, tert-butyl, pentyl, isopentyl, neopentyl and
tert-pentyl groups; ethers such as methoxy, trifluoromethoxy,
ethoxy, propoxy, isopropoxy, buthoxy, tert-buthoxy, pentyloxy,
phenoxy, and benzyloxy groups; esters such as methoxycarbonyl,
trifluoromethoxycarbonyl, ethoxycarbonyl, propoxycarbonyl, acetoxy,
trifluoroacetoxy, and benzoyloxy groups; alkyl sulfonyl groups such
as meythylsulfonyl, ethylsulfonyl, propylsulfonyl,
isopropylsulfonyl, buthylsulfonyl, tert-buthylsulfonyl, and
pentylsulfonyl groups; alkyl sulfamoyl groups such as
methylsulfamoyl dimethylsulfamoyl, ethylsulfamoyl,
diethylsulfamoyl, propylsulfamoyl, dipropylsulfamoyl,
buthylsulfamoyl, dibuthylsulfamoyl, pentylsulfamoyl, and
dipentylsulfamoyl groups; halogens such as fluorine, chlorine,
bromine, and iodine; and nitro and cyano groups. The cyanine dyes
of the present invention include cis/trans isomers of the cyanine
dyes represented by Formula 1.
[0020] X.sup.- in Formula 1 represents a suitable counter ion.
Depending on uses, such a counter ion is not limited and
appropriately selected on the basis of its solubility in DAA and/or
heat resistance. When used in optical recording media, the counter
ion which does not substantially change the quality of reflection
layers including metals, and more particularly, anions comprising
two or more kinds of elements are desirable. Examples of such
anions are inorganic acid ions such as phosphoric acid ion,
perchloric acid ion, periodic acid ion, hexafluoro phosphoric acid
ion, hexafluoro antimonic acid ion, hexafluoro stannic acid ion,
fluoroboric acid ion, and tetrafluoroboric acid ion; organic acid
ions such as thiocyanic acid ion, benzensulfonic acid ion,
naphthalenesulfonic acid ion, p-toluenesulfonic acid ion,
alkylsulfonic acid ion, benzencarbonic acid ion, alkylcarbonic acid
ion, trihaloalkylcarbonic acid ion, alkylsulfonic acid ion,
trihaloalkylsulfonic acid ion, and nicotinic acid ion; and organic
metal complex anions such azo, bisphenyldithiol, thiocatechol
chelate, thiobisphenorate chelate, and bisdiol-.alpha.-diketone.
Judging from stability such as explosiveness and ease of handling,
anions, which comprise fluorine and metal elements selected from
those of the 15 group in the periodic law table such as phosphorus,
antimony and bismuth, are desirable; hexafluoro phosphoric acid ion
and hexafluoro antimonic acid ion. The cyanine dyes of the present
invention bearing these anions as a counter ion are characteristic
in that they have relatively-high heat resistance, easy
handlability, and solubility in organic solvents such as DAA.
[0021] Further explaining the counter ion of X.sup.-, depending on
uses, desirable anions for the cyanine dyes of the present
invention are organic metal complex anions which improve light
resistance, and more particularly, azo organic metal complex
anions. In the present invention, azo organic metal complex anions
mean a series of complex anions which have a metal atom as a
central atom and bind one or more azo compounds as a ligand to the
central atom. All azo organic metal complex anions, which do not
substantially lower light absorptance of the cyanine dyes and
improve light resistance thereof in practical use, can be used
independently of their chemical structures and production methods.
Azo compounds which bind to a metal atom may be identical or
different each other. The azo organic metal complexes are, for
example, those represented by Formula 6. Since the azo organic
metal complexes represented by Formula 6 do not substantially lower
light absorptance of the cyanine dyes, they can be advantageously
used in the present invention. 2
[0022] In Formula 6, Z.sub.3 through Z.sub.6 represent identical or
different aromatic rings or heterocycles which may contain one or
more substituents. Preferably, the aromatic rings are monocyclic
benzene rings, and the heterocycles which contain one or more
hetero atoms selected from nitrogen, oxygen, sulfur, selenium and
tellurium, for example, those with isooxazolone skeleton,
indazolone skeleton, indandione skeleton, oxazolone skeleton,
thionaphthene skeleton, barbituric acid skeleton, hydantoin
skeleton, pyrazolone skeleton or rhodanine skeleton.
[0023] The aromatic rings and heterocycles may have one or more of
the following substituents; aliphatic hydrocarbon groups such as
methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl,
tert-butyl, pentyl, isopentyl, neopentyl, tert-pentyl,
1-methylpentyl, 2-methylpentyl, hexyl, isohexyl, and 5-methylhexyl
groups; alicyclic hydrocarbon groups such as cyclopropyl,
cyclobuthyl, cyclopentyl, cyclohexyl, and cyclohexenyl groups;
aromatic hydrocarbon groups such as phenyl, biphenyl, o-tolyl,
m-tolyl, p-tolyl, o-cumenyl, m-cumenyl, p-cumenyl, xylyl, mesityl,
styryl, cinnamoyl, and naphthyl groups; esters such as
methoxycarbonyl, ethoxycarbonyl, propoxycarbonyl, acetoxy, and
benzoyloxy groups; substituted or unsubstituted aliphatic,
alicyclic or aromatic amino groups such as primary amino,
methylamino, dimethylamino, ethylamino, diethylamino, propylamino,
dipropylamino, isopropylamino, diisopropylamino, buthylamino, and
dibuthylamino groups; alkylsulfamoyl groups such as
methylsulfamoyl, dimethylsulfamoyl, ethylsulfamoyl,
diethylsulfamoyl, propylsulfamoyl, dipropylsulfamoyl,
isopropylsulfamoyl, diisopropylsulfamoyl, butylsulfamoyl, and
dibutylsulfamoyl groups; carbamoyl, carboxy, cyano, nitro, hydroxy,
sulfo, sulfoamino, and sulfonamido groups.
[0024] Depending on uses, one or more hydrogens in the above
substituents may be replaced with the following groups; aliphatic
hydrocarbon groups such as methyl, ethyl, propyl, isopropyl, butyl,
isobutyl, sec-butyl, tert-butyl, pentyl, isopentyl, tert-pentyl,
1-methylpentyl, 2-methylpentyl, hexyl, isohexyl, and 5-methylhexyl
groups; aromatic hydrocarbon groups such as phenyl, biphenyl,
o-tolyl, m-tolyl, p-tolyl, o-cumenyl, m-cumenyl, p-cumenyl, xylyl,
mesityl, styryl, cinnamoyl, and naphthyl groups; ethers such as
methoxy, ethoxy, propoxy, isopropoxy, buthoxy, isobuthoxy,
sec-buthoxy, tert-buttery, pentyloxy, phenoxy, and benzyloxy
groups; halogens such as fluorine, chlorine, bromine, and iodine;
and carboxy, hydroxy, cyano, and nitro groups.
[0025] As described above, azo organic metal complex anions
represented by Formula 6 can be obtained by combining a metal atom
of M with one or more azo compounds as a ligand, which are
identical or different each other. The metal atom is usually
selected from metal elements of the 3 through 12 groups in the
periodic law table such as scandium, yttrium, titanium, zirconium,
hafnium, vanadium, niobium, tantalum, chrome, molybdenum, tungsten,
manganese, technetium, rhenium, iron, ruthenium, osmium, cobalt,
rhodium, iridium, nickel, palladium, platinum, copper, silver,
gold, zinc, cadmium and mercury. In the field of optical recording
media, cobalt and nickel are usually used because they are easily
obtainable and handlable. A and A' in Formula 6 represent identical
or different hetero atoms selected from elements of the 16 group in
the periodic law table such as oxygen, sulfur, selenium and
tellurium, and they can form a coordinate bond by providing an
electron pair to the above metal atom and may form an atomic group
combined with Z.sub.3 and Z.sub.6.
[0026] The azo organic metal complex anions are, for example, those
represented by Chemical Formulae 1 to 12. In using these anions as
a counter ion for the cyanine dyes of the present invention, they
can be advantageously used in the present invention because they
remarkably improve the light resistance of the cyanine dyes at
wavelengths of 350-850 nm and do not substantially spoil desirable
light absorptance and solubility in organic solvents of the cyanine
dyes. All of azo organic metal complex anions represented by
Chemical Formulae 1 to 12 can be obtained in a satisfactory yield
in accordance with well-known methods which provide aniline or
aniline derivatives in diazo coupling reaction and allow to react
the obtained azo compound in the presence of suitable metal salts
and bases. Cyanine dyes with azo organic metal complex anions as a
counter ion are prepared by heating the cyanine dyes of the present
invention with anions other than azo organic metal complex anions
as a counter ion and salts of the above azo organic metal complex
anions in a suitable solvent at over ambient temperature for 0.1-10
hours under stirring condition. 345
[0027] Concrete examples of the cyanine dyes of the present
invention are those represented by Chemical Formulae 13 to 72,
which have absorption maximum spectra at a wavelength of 580-600 nm
when in a solution form and substantially absorb a visible light
with a wavelength of shorter than 700 nm in a longer wavelength
region of the absorption maximum when in a thin layer form. These
cyanine dyes are very useful as light absorbents of optical
recording media using a visible light with a wavelength of shorter
than 700 nm as a writing light, and more particularly, high-density
optical recording media such as DVD-Rs, etc., which use a laser
beam with a wavelength of 630-680 nm as a writing light. The
cyanine dyes of the present invention, which have an organic metal
complex anion, and more particularly, azo organic metal complex
anion as a counter ion, remarkably have an ability to improve the
light resistance when compared with other cyanine dyes. Thus, they
are useful as light absorbents in DVD-R and light resistance
improvers in recording media such as CD-R which have recording
layers composed of cyanine dyes and use a visible light with a
wavelength from 700 to 800 nm as a writing light, and usually a
laser beam with a wavelength of around 775-795 nm. The cyanine dyes
of the present invention with organic metal complex anions as
counter ions (I) can remarkably improve the light resistance
without substantially changing the light absorbability of optical
recording media when used in combination with the cyanine dyes of
the present invention with anions other than azo organic metal
complex anions as counter ions (II), and more particularly,
perchloric acid ion, fluorine and anions selected from metal
elements from the 15 group in the periodic law table in
high-density optical recording media. The weight ratio of the above
cyanine dyes (I) and (II) can be lowered and highered within the
range from 0.1:1 to 1:0.1, and more preferably from 0.3:1 to 1:0.3.
6789101112131415
[0028] These cyanine dyes of the present invention can be prepared
by various methods. They can be preferably produced through a step
to react a benzoindolenium compound bearing an active methyl group
with a benzoindolenium compound bearing a suitable leaving group
with an economical view point. With the method, the cyanine dyes of
the present invention can be produced in a desirable yield by
reacting a compound represented by Formula 2 having R.sub.1 in
Formula 1 with a compound represented by Formula 3 having R.sub.2
in Formula 1; or reacting a compound represented by Formula 4
having R.sub.1 in Formula 1 with a compound represented by Formula
5 having R.sub.2 in Formula 1. 16
[0029] For example, adequate amounts (usually about equal mols) of
the compounds represented by Formulae 2 and 3 or those represented
by Formulae 4 and 5 are placed in a reaction vessel, and the
resulting mixture is dissolved in an adequate solvent, and then
reacted at ambient temperature or over ambient temperature under
heating and stirring conditions, for example, heating reflux
conditions, in the presence of a basic compound such as sodium
hydroxide, potassium hydroxide, sodium carbonate, potassium
carbonate, sodium carbohydrate, ammonia, triethylamine, piperidine,
pyridine, pyrrolidine, morpholine, aniline, N,N-dimethylaniline,
N,N-diethylaniline, N-methylpyrrolidone, or 1,8-diazabicyclo
[5.4.0]-7-undecene; an acid compound such as hydrochloric acid,
sulfuric acid, nitric acid, methanesulforic acid, p-toluenesulfonic
acid, acetic acid, acetic anhydride, propionic anhydride,
trifluoroacetic acid, or trifluorosulfonic acid; or a Lewis acid
compound such as aluminium chloride, zinc chloride, tin
tetrachloride, or titanium tetrachloride.
[0030] The following solvents can be used: Hydrocarbons such as
pentane, hexane, cyclohexane, octane, benzene, toluene, and xylene;
halogen compounds such as carbon tetrachloride, chloroform,
1,2-dichloroethane, 1,2-dibromoethane, trichloroethylene,
tetrachloroethylene, chlorobenzene, bromobenzene, and
.alpha.-dichlorobenzene; alcohols and phenols such as methanol,
ethanol, 1-propanol, 2-propanol-1-butanol, 2-butanol, isobutyl
alcohol, isopentyl alcohol, cyclohexanol, ethylene glycol,
propylene glycol, 2-methoxyethanol, 2-ethoxyethanol, phenol, benzyl
alcohol, cresol, diethylene glycol, triethylene glycol, and
glycerin; ethers such as diethyl ether, diisopropyl ether,
tetrahydrofuran, tetrahydropyran, 1,4-dioxane, anisole,
1,2-dimethoxyethane, diethylene glycol, dimethyl ether,
dicyclohexyl-18-crown-6, methylcarbinol, and ethylcarbitol; ketones
such as furfural, acetone, ethyl methyl ketone, and cyclohexanone;
acids and acidic derivatives such as acetic acid, acetic anhydride,
trichloroacetic acid, trifluoroacetic acid, propionic anhydride,
ethyl acetate, butyl carbonate, ethylene carbonate, propylene
carbonate, formamide, N-methylformamide, N,N-dimethylformamide,
N-methylacetoamide, N,N-dimethylacetoamide hexamethylphosphoric
triamide, and phosphoric trimethyl; nitriles such as acetonitrile,
propionitrile, succinonitrile, and benzonitrile; nitro compounds
such as nitromethane and nitrobenzene; sulfur-containing compounds
such as dimethylsulfoxide; and water. These solvents can be
appropriately used in combination, if necessary.
[0031] In general, the reactivity decreases as the volume of
solvent increases, while, the uniform heating and stirring becomes
difficult and a side reaction causes easily as the volume of
solvent decreases. Thus, the volume of solvent is desirably up to
100 times, usually 5 to 50 times of the material compounds by
weight. The reaction completes within 10 hours, usually 0.5-10
hours, depending on the kinds of material compounds and reaction
conditions. The process of reaction can be monitored in
conventional methods, for example, thin-layer chromatography, gas
chromatography, and high-performance liquid chromatography.
Thereafter, the cyanine dyes of the present invention with
desirable counter ions can be obtained from the above reaction
mixture directly, and if necessary after treated with conventional
counter ion-exchange reaction. Thus, all the cyanine dyes
represented by Chemical Formulae 13 to 72 can be easily obtained by
the above methods in a desirable yield. All the benzoindolenium
compounds represented by Formulae 2 to 5 can be prepared, for
example, by a method as disclosed in Japanese Patent Kokai No.
316,655/98 applied for by the present applicant. In Formulae 2 to
5, X.sub.1.sup.- and X.sub.2.sup.- are identically or differently
suitable counter ions to X.sup.- in Formula 1, and L is a suitable
leaving group which is usually selected from monovalent groups of
aniline or aniline derivatives such as anilino, p-toluidino,
p-methoxyanilino, p-ethoxycarbonylanilino, and N-acetylanilino
groups.
[0032] The cyanine dyes thus obtained can be used in the form of a
reaction mixture without any further treatment, and usually can be
used after purified by the following conventional methods generally
used for purifying their related compounds; dissolution,
extraction, separation, decantation, filtration, concentration,
thin-layer chromatography, column chromatography, gas
chromatography, high-performance liquid chromatography,
distillation, crystallization, and sublimation. If necessary, two
or more of them can be used in combination. For use as a light
absorbent in high-density optical recording media such as DVD-Rs,
etc., the cyanine dyes of the present invention should preferably
be distilled, crystallized, and/or sublimated prior to use.
[0033] Explaining the uses of the cyanine dyes of the present
invention, they have characteristics in that:
[0034] (i) A relatively-high solubility in non-halogenated
solvents; solubility of at least 50 mg/ml in DAA at 20.degree. C.,
and
[0035] (ii) A strongly-high heat resistance; a decomposition point
of over 272.degree. C.
[0036] The cyanine dyes of the present invention substantially
absorb a visible light with a wavelength of shorter than 700 nm,
and more particularly, a visible light with a wavelength of 630-680
nm when in a thin layer form. Thus, the cyanine dyes of the present
invention can be widely used in a variety of fields such as optical
recording media, photochemical polymerizations, solar batteries and
dyeings, which require the dye compounds with the above
characteristics. In these uses, they are very useful as a light
absorbent in high-density optical recording media such as DVD-Rs
which use a visible light with a wavelength of shorter than 700 nm
as a writing light, and more particularly, one with a wavelength of
630-680 nm.
[0037] Explaining the use in optical recording media, the cyanine
dyes of the present invention can be used for preparing optical
recording media in accordance with the processes for conventional
ones because they do not require any special treatment and
processing. For example, the cyanine dyes of the present invention
as a light absorbent can be mixed with one or more other organic
dye compounds with the properties of substantially absorbing a
visible light so as to modulate the reflection and/or absorption by
a recording layer, along with one or more light-resistant
improvers, binders, dispersing agents, flame retardants,
lubricants, antistatic agents, surfactants, thermal interference
inhibitor, and plasticizers, if necessary. The resulting mixtures
are then dissolved in organic solvents, and the solutions are
homogeneously coated over either surface of substrates in such a
manner of using spraying, soaking, roller coating, or rotatory
coating method; and dried to form thin layers as recording layers
made of light absorbents, and if necessary, followed by forming
reflection layers to be closely attached on the recording layers by
means of vacuum deposition, chemical vapor deposition, sputtering,
or implanting method using metals and alloys such as gold, silver,
copper, platinum, aluminum, cobalt, tin, nickel, iron, and chromium
to impart a reflection efficiency of 45% or more, and preferably
55% or more; forming reflection layers to be closely attached on
the recording layers by using commonly used materials for organic
reflection layers; or coating over the recording layers ultraviolet
ray hardening resins or thermosetting resins, which contain flame
retardants, stabilizers, and/or antistatic agents, to protect the
recording layers from scratches, dusts, spoils, etc., and then
hardening the coatings by either irradiating light or heating to
form protection layers to be closely attached on the reflection
layers. In substrates with the recording-, reflection- and
protection-layers formed as described above, each protection layer
is attached together with adhesives or adhesive sheets, etc, or a
protective plate with the same material and form as a substrate is
attached to a protection layer, if necessary.
[0038] As another organic dye compounds usable together with the
present cyanine dyes, any organic dye compounds can be used as long
as they substantially absorb a visible light and can modulate a
light reflection rate and a light absorption rate of a recording
layer of an optical recording medium. As the above organic dye
compounds, the following compounds can be used in an appropriate
combination, if necessary: Acridine dye, azaannulene dye, azo dye,
anthraquinone dye, indigo dye, indanthrene dye, oxazine dye,
xanthene dye, dioxazine dye, thiazine dye, thioindigo dye,
tetrapyrapolphyradine dye, triphenylmethane dye, triphenylthiazine
dye, naphthoquinone dye, phthalocyanine dye, benzoquinone dye,
benzopyran dye, benzofuranone dye, porphyrin dye, rhodamine dye,
and cyanine dye in which the same or different rings are bound to
both ends of a polymethine chain such as monomethine, dimethine,
trimethine, tetramethine, pentamethine, hexamethine, or
heptamethine. The chains and rings may have one or more
substituents. Examples of the rings are imidazolin ring, imidazole
ring, banzoimidazole ring, .alpha.-naphthimidazole ring,
.beta.-naphthimidazole ring, indole ring, isoindole ring,
indolenine ring, isoindolenine ring, benzoindolenine ring,
pyridinoindolenine ring, oxazoline ring, oxazole ring, isooxazole
ring, benzooxazole ring, pyridinooxazole ring,
.alpha.-naphthoxazole ring, .beta.-naphthoxazole ring, selenazoline
ring, selenazole ring, benzoselenazole ring,
.alpha.-naphthselenazole ring, .beta.-naphthselenazole ring,
thiazoline ring, thiazole ring, isothiazole ring, benzothiazole
ring, .alpha.-naphththiazole ring, .beta.-naphththiazole ring,
tellurazoline ring, tellurazole ring, benzotellurazole ring,
.alpha.-naphthtellurazole ring, .beta.-naphthtellurazole ring,
acridine ring, anthracene ring, isoquinoline ring, isopyrrole ring,
imidanoxaline ring, indandione ring, indazole ring, indaline ring,
oxadiazole ring, carbazolering, xanthine ring, quinazoline ring,
quinoxaline ring, quinoline ring, chroman ring, cyclohexanedion
ring, cyclopentandion ring, cinnoline ring, thiodiazole ring,
thiooxazolidone ring, thiophene ring, thionaphthene ring,
thiobarbituric acid ring, thiohydantoin ring, tetrazole ring,
triazine ring, naphthalene ring, naphthyridine ring, piperazine
ring, pyrazine ring, pyrazole ring, pyrazoline ring, pyrazolidine
ring, pyrazolone ring, pyran ring, pyridine ring, pyridazine ring,
pyrrolidine ring, pyrylium ring, pyrrolidine ring, pyrroline ring,
pyrrole ring, phenazine ring, phenanthridine ring, phenanthrene
ring, phenanthroline ring, phthalazine ring, pteridine ring,
furazane ring, furan ring, purine ring, benzene ring, benzoxazine
ring, benzopyran ring, morpholine ring, and rhodanine ring.
[0039] The light-resistant improvers used in the present invention
are, for example, nitroso compounds such as nitrosodiphenylamine,
nitrosoaniline, nitrosophenol, and nitrosonaphthol and metal
complexes such as tetracyanoquinodimethane compounds, diimmonium
compounds, and "NKX-1199"
(bis[2'-chloro-3-methoxy-4-(2-methoxyethoxy)dithiobenzyl]nicke- l)
produced by Hayashibara Biochemical Laboratories, Inc., Okayama,
Japan, and formazane metal complexes, which all can be
appropriately used in combination, if necessary. Preferable
light-resistant improvers are those which contain formazane metal
compounds, and most preferable ones are formazane compounds, which
have a pyridine-ring at C-5 and a pyridine- or furan-ring at C-3 of
a formazane skeleton as disclosed in Japanese Patent Application
No. 163,036/99 (PCT Kokai No. WO00/75111), titled "Formazane metal
complexes" applied for by the present applicant; and complexes to
metals such as nickel, zinc, cobalt, iron, copper, and palladium,
which have one or more tautomers of the aforesaid compounds as a
ligand. In the case of using such a light-resistant improver in
combination, the cyanine dyes of the present invention can be
effectively prevented from undesirable changing in deterioration,
fading, color changing, and quality changing, which are inducible
by environmental lights such reading- and natural-lights, without
lowering the solubility of the cyanine dyes in organic solvents and
substantially deteriorating preferable optical characteristics.
More particularly, formazane metal complexes effectively improve
the following features in high-density optical recording media in
combination with a mixture of the cyanine dyes of the present
invention having the aforesaid organic metal complex anions as a
counter ion and the cyanine dyes of the present invention having
anions other than azo organic metal complex anions as a counter
ion:
[0040] (i) light resistance of the cyanine dyes of the present
invention,
[0041] (ii) sensitivity of optical recording media,
[0042] (iii) modulation characteristic,
[0043] (iv) resolution, and
[0044] (v) electrical characteristics such as a jitter
characteristic.
[0045] As the composition ratio, 0.01-1 moles, and preferably
0.03-0.3 moles of a light-resistant improver(s)-can be incorporated
into one mole of the present cyanine dye(s) while increasing or
decreasing the ratio. Depending on uses, the cyanine dyes of the
present invention with organic metal complex anions as a counter
ion, and more particularly, azo organic metal complex anions, have
a relatively-high light resistance in themselves, and thus the
aforesaid light-resistant improvers may not be required or required
with only a small amount.
[0046] The cyanine dyes of the present invention have
satisfactory-high solubility in organic solvents without
substantially causing negative problem for actual use, and do not
substantially restrict organic solvents used for coating the
cyanine dyes on substrates. Thus, in the preparation of optical
recording media according to the present invention, suitable
organic solvents can be selected from the following ones which are
appropriately used in combination: DAA and TFP frequently used to
prepare optical recording media and the following organic solvents
other than DAA and TFP: For example, hydrocarbons such as hexane,
cyclohexane, methylcyclolhexane, dimethylcyclohexane,
ethylcyclohexane, isopropylcyclohexane, tert-butylcyclohexane,
octane, cyclooctane, benzene, toluene, and xylene; halogen
compounds such as carbon tetrachloride, chloroform,
1,2-dichloroethane, 1,2-dibromoethane, trichloroethylene,
tetrachloroethylene, chlorobenzene, bromobenzene, and
.alpha.-dichlorobenzene; alcohols and phenols such as methanol,
ethanol, 2,2,2-trifluoroethanol, 2-methoxyethanol (methyl
cellosolve), 2-ethoxyethanol (ethyl cellosolve),
2-isopropoxy-1-ethanol, 1-propanol, 2-propanol,
1-methoxy-2-propanol, 1-ethoxy-2-propanol, 1-butanol,
1-methxy-2-butanol, 3-methoxy-1-butanol, 4-methoxy-1-butanol,
isobutyl alcohol, isopentyl alcohol, cyclohexanol, ethylene glycol,
propylene glycol, glycerine, phenol, benzyl alcohol, and cresol;
ethers such as diethyl ether, diisopropyl ether, tetrahydrofuran,
tetrahydropyran, 1,4-dioxane, anisole, 1,2-dimethoxyethane,
diethylene glycol dimethyl ether, dicyclohexyl-18-crown-6,
methylcarbinol, and ethylcarbitol; ketones such as furfural,
acetone, ethyl methyl ketone, and cyclohexanone; esters such as
ethyl acetate, butyl acetate, ethylene carbonate, propylene
carbonate, and trimethyl phosphate; amides such as formamide,
N-methyl formamide, N,N-dimethylformamide, and hexamethylphosphoric
triamide; nitriles such as acetonitrile, propionitrile, and
succinonitrile; nitro compounds such as nitromethane and
nitrobenzene; amines such as ethylene diamine, pyridine,
piperidine, morpholine, and N-methylpyrrolidone; and
sulfur-containing compounds such as dimethylsulfoxide and
sulfolane. These organic solvents can be used in an appropriate
combination.
[0047] Particularly, the cyanine dyes of the present invention have
relatively-high solubility in easily-volatile organic solvents such
as TFP and DAA, and thus they are substantially free of
crystallization when dissolved in the above organic solvents, spun
coated on substrates, and then dried without substantially causing
dye crystals and inconsistency of the thickness and the surface of
the layers formed on optical recording media. When the cyanine dyes
of the present invention dissolve in the alcohols such as DAA
before coated on the substrates, the solvents do not damage the
substrates and pollute the environment.
[0048] Conventional substrates can be used in the present invention
and usually processed with suitable materials, for example, into
discs, 12 cm in diameter and 0.1-1.2 mm in thickness, to suite to
final use by the methods such as compression molding, injection
molding, compression-injection molding, photopolymerization method
(2P method), thermosetting integral method, and lightsetting
integral method. These discs can be used in single or plural after
appropriately attached them together with adhesive sheets or
adhesive agents, etc. In principal, any materials for substrates
can be used in the present invention as long as they are
substantially transparent and have a transmissivity of at least
80%, and preferably at least 90% or more at wavelengths ranging
from 400 nm to 800 nm. Examples of such materials are glasses,
ceramics, and others such as plastics including polyacrylate,
polymethyl methacrylate, polycarbonate, polystyrene (styrene
copolymer), polymethylpenten, polyester, polyolefin, polyimide,
polyetherimide, polysulfone, polyethersulfone, polyarylate,
polycarbonate/polystyrene alloy, polyestercarbonate,
polyphthalatecarbonate, polycarbonateacrylate, non-crystalline
polyolefin, methacrylate copolymer,
diallylcarbonatediethylene-glycol, epoxy resin, and phenolic resin,
where polycarbonate is most frequently used. In plastic substrates,
concaves for expression of synchronizing signals and addresses of
tracks and sectors are usually transferred to the internal circle
of the tracks during their formation. The form of concaves is not
specifically restricted and is preferably formed to give 0.3-0.8
.mu.m in average wide and 70-200 nm in depth.
[0049] The light absorbents of the present invention can be
prepared into 0.5-5 w/w % solutions of the organic solvents as
mentioned above while considering the viscosity of the solutions,
and then uniformly coated onto a substrate to form a dried
recording layer with 10-1,000 nm, and preferably 50-300 nm in
thickness. Prior to the coating, a preliminary layer can be formed
over the substrate to improve the protection and the
adhesion-ability to the substrate, if necessary. Materials of the
preliminary layer are, for example, high-molecular substances such
as ionomer resins, polyamide resins, vinyl resins, natural resins,
silicon, and liquid rubbers. In the case of using binders, the
following polymers can be used alone or in combination in a weight
ratio of 0.01-10 times of the cyanine dye(s): Cellulose esters such
as nitrocellulose, cellulose phosphate, cellulose sulfate,
cellulose acetate, cellulose propionate, cellulose lactate,
cellulose palmitate, and cellulose acetate/propionate; cellulose
ethers such as methyl cellulose, ethyl cellulose, propyl cellulose,
and butyl cellulose; vinyl resins such as polystyrene, poly(vinyl
chloride), poly(vinyl acetate), poly(vinyl acetal), poly(vinyl
butyral), poly(vinyl formal), poly(vinyl alcohol), and poly(vinyl
pyrrolidone); copolymer resins such as styrene-butadiene
copolymers, styrene-acrylonitrile copolymers,
styrene-butadiene-acrylonitrile copolymers, vinyl chloride-vinyl
acetate copolymers, and maleic anhydride copolymers; acrylic resins
such as poly(methyl methacrylate), poly(methyl acrylate),
polyacrylate, polymethacrylate, polyacrylamide, and
polyacrylonitrile; polyesters such as poly(ethylene terephthalate);
and polyolefins such as polyethylene, chlorinated polyethylene, and
polypropylene.
[0050] Explaining the method for using the optical recording media
according to the present invention, the high density optical
recording media of the present invention such as DVD-Rs can write
informations at a relatively-high density by using a visible light
with a wavelength shorter than 700 nm, and more particularly, a
laser beam with a wavelength around 630-680 nm irradiated by
semiconductor lasers such as those of AlGaInP, GaAsP, GaAlAs,
InGaP, InGaAsP or InGaAlP; or YAG laser combined with second
harmonic generation inducing element (SHG element). To read
recorded informations, laser beams are used with wavelengths
identical to or slightly longer or shorter than those used for
writing informations. As for the laser power for writing and
reading informations, in the optical recording media of the present
invention, it is preferably be set to a relatively-high level,
which exceeds the threshold of the energy required for forming
pits, to write information, while it is suitably be set to a
relatively-low level, i.e., a level of below the threshold when
used for reading the recorded informations, although the power
levels can be varied depending on the types and ratios of the
light-resistant improvers used in combination with the cyanine
dyes: Generally, the levels can be controlled to powers at least 5
mW, and usually 10-50 mW for writing; and to powers of 0.1-5 mW for
reading. The recorded informations are read by detecting the
changes of both the reflection light level and the transmission
light level in the pits and the pit-less part on the surface of
optical recording media by the light pick-up method.
[0051] Accordingly, in the present optical recording media, minute
pits with a pit width of below 0.834 .mu.m/pit and a track pitch of
below 1.6 .mu.m that is commonly used in a standard CD-R, can be
formed at a relatively-high density by a light pick-up using a
visible light with a wavelength of shorter than 700 nm, and
particularly a laser beam with a wavelength around 630-680 nm. For
example, using a substrate, 12 cm in diameter, it can realize an
extremely-high density optical recording medium with an optical
recording capacity far exceeding 0.682 GB (giga bytes) per one side
i.e., a recording capacity of about two hours of information of
voices and images, the level of which could hardly be attained by
conventional cyanine dyes.
[0052] Since the optical recording media of the present invention
can record information of characters, images, voices, and other
digital data at a relatively-high density, they are extremely
useful as recording media for professional and family use to
record, backup, and keep documents, data, and computer softwares.
Particular examples of the types of industries and the forms of
information to which the optical recording media can be applied are
as follows: Drawings of constructions and engineering works, maps,
ledgers of loads and rivers, aperture cards, architectural
sketches, documents of disaster protection, wiring diagrams,
arrangement plans, informations of news papers and magazines, local
information, and construction specifications, which all relate to
constructions and engineering works; blueprints, ingredient tables,
prescriptions, product specifications, product price tables, part's
lists, information for maintenance, case study files of accidents
and troubles, manuals for claims, production schemes, technical
documents, sketches, details, company's house-made product files,
technical reports, and analysis reports, which are all used in
productions; information of companies, records of stock prices,
statistical documents, contracts, customer's lists, documents of
application/notification/licenses/authoriz- ation, and business
reports, which are all used in money; information of real property
and transportations, sketches of constructions, maps, and local
information, which are all used for customer's information for
sales; diagrams of writings and pipe arrangements for electric and
gas supplies, documents of disaster protection, tables of operation
manuals, documents of investigations, and technical reports;
medical cartes, files of clinical histories and case studies, and
diagrams for medical care/institution relationships; texts,
collections of questions, educational documents, and statistical
information, which are all used in private and preparatory schools;
scientific papers, records in academic societies, monthly reports
of researches, data of researches, documentary records and indexes
thereof, which are all used in universities, colleges, and research
institutes; inspection data, literatures, patent publications,
weather maps, analytical records of data, and customer's files,
which are all used for information; case studies on laws;
membership lists, history notes, records of works/products,
competition data, and data of meetings/congresses, which
organizations/associations; sightseeing information and traffic
information, which are all used for sightseeing; indexes of
homemade publications, information of news papers and magazines,
who's who files, sport records, telop files, and scripts, which are
all used in mass communications and publishers; and maps, ledgers
of roads and livers, fingerprint files, resident cards, documents
of application/notification/license/authorization, statistical
documents, and public documents, which are all used in government
offices. Particularly, the write-once type optical recording media
of the present invention can be advantageously useful for storing
records of cartes and official documents, and used as electric
libraries for art galleries, libraries, museums, broadcasting
stations, etc.
[0053] As a rather specific use, the optical recording media of the
present invention can be used to edit compact discs, digital video
discs, laser discs, MD (a mini disc as an information recording
system using photomagnetic disc), CDV (a laser disc using compact
disc), DTA (an information recording system using magnetic tape),
CD-ROM (a read-only memory using compact disc), DVD-ROM (a
read-only memory using digital video disc), DVD-RAM (a writable and
readable memory using digital video disc), digital photos, movies,
video softwares, audio softwares, computer graphics, publishing
products, broadcasting programs, commercial messages, game
softwares, etc.; and used as external program recording means for
large size of computers and car navigation systems.
[0054] Hereinbefore described are the application examples of the
cyanine dyes of the present invention to the field of organic
optical recording media which use laser beams with wavelengths of
shorter than 700 nm as a writing light. However, in the field of
optical recording media, the cyanine dyes of the present invention
can be also advantageously used as materials for changing or
regulating the optical absorption rate or optical reflection rate
in the optical recording media such as commonly used CD-Rs and
other high-density optical recording media by using in combination,
for example, together with one or more other organic dye compounds
which are sensitive to laser beams with wavelengths of 775-795 nm.
When optical recording media are coated by using laser beams with
longer wavelengths such as laser beams with wavelengths of 775-795
nm as a writing light, the cyanine dyes of the present invention
can be used not to directly form pits on substrates but to
indirectly form pits in such a manner that the excitation energy of
laser beams with wavelengths around 630-680 nm is allowed to
transfer to the aforesaid organic dye compounds via the cyanine
dyes by using the cyanine dyes along with one or more other organic
dye compounds which are sensitive to a light with a longer
wavelength, e.g., a laser beam with a longer wavelength of 775-795
nm, resulting in a decomposition of the organic dye compounds. The
optical recording media as referred to in the present invention
mean optical recording media in general which use the
characteristics of the cyanine dyes of the present invention that
substantially absorb a visible light with a wavelength shorter than
700 nm in addition to organic optical recording media, thermal
coloration method using the chemical reaction of coloring agents
and developers using the heat generated when organic dye compounds
absorb light, and the technique called "moth-eye type technique"
which uses the phenomenon of that the above heat smooths the
pattern of periodical unevenness provided on the surface of the
substrates.
[0055] As described above, the cyanine dyes of the present
invention are useful as a light-resistant improver in recording
media such as CD-Rs which have recording layers composed of cyanine
dyes and use a visible light with a wavelength from 700 nm to 800
nm as a writing light, and usually a laser beam with a wavelength
around 775-795 nm. In the optical recording media, the cyanine dyes
used in combination with the cyanine dyes of the present invention
are, for example, pentamethine cyanine dyes in which the same or
different 1H-benzo [e] indole skeleton or 3H-benzo [g] indole
skeleton are bound to both ends of a pentamethine chain, as
disclosed in Japanese Patent Kokai Nos. 203,692/91, 203,693/91,
239,149/93, and 199,045/94 applied for by the same applicant as the
present invention. As an additive volume of the cyanine dyes of the
present invention for these cyanine dyes, the light resistance is
not desirably improved when the additive volume is a
relatively-low-level, while the electrical characteristic of
optical recording media is deteriorated when the additive volume is
a relatively-high level. Usually, 0.5-50%(w/w), and preferably
3-30%(w/w), of the cyanine dye(s) of the present invention can be
incorporated into other cyanine dye(s) while increasing or
decreasing the volume. As a light-resistant improver, one or more
other light-resistant improvers can be used with the cyanine dyes
of the present invention, if necessarily. For example, formazane
metal complexes are more desirably used because they exert good
amorphousness and relatively-high heat resistance to the cyanine
dyes of the present invention and other cyanine dyes when formed in
a thin layer.
[0056] When the cyanine dyes of the present invention are used as a
light-resistant improver which uses a visible light with a
wavelength of longer than 700 nm as a writing light such as CD-Rs,
they are not necessarily incorporated into a recording layer. For
example, the cyanine dyes of the present invention are incorporated
into a preliminary layer, or they are dissolved in suitable
solvents with one or more of the aforesaid binders, and the
solutions are coated on the whole or the part of surface irradiated
by a writing light to form a protection membrane composed of the
cyanine dyes of the present invention, if necessarily. The
preliminary layer and the protection membrane can protect a
recording layer from environmental lights such as natural- and
artificial-lights and remarkably improve durability of optical
recording media, and more particularly electrical characteristics
such as a jitter characteristic and a rate of block error. When the
solution is covered on the outside of substrate, informations such
as characters, figures, pictures, numerals, and symbols can be
printed or written on the outside of substrate by using the
solution as a printing material or paint.
[0057] Since the cyanine dyes of the present invention
substantially absorb a visible light with a wavelength shorter than
700 nm, the light absorbents containing the cyanine dyes according
to the present invention can be used in the aforesaid optical
recording media and also used as materials for polymerizing
polymerizable compounds by exposing a visible light,
photosensitizing solar batteries, and dying clothes, as well as
materials for laser active substances in dye lasers. If necessary,
in combination with one or more other light absorbents capable of
absorbing light in ultraviolet, visible and/or infrared regions,
the light absorbents can be used in clothes in general and others
including building/bedding/decorating products such as a drape,
lace, casement, print, casement cloth, roll screen, shutter, shop
curtain, blanket, thick bedquilt including comforter, peripheral
material for the thick bedquilt, cover for the thick bedquilt,
cotton for the thick bedquilt, bed sheet, cushion, pillow, pillow
cover, cushion, mat, carpet, sleeping bag, tent, interior finish
for car, and window glasses including car window glass; sanitary
and health goods such as a paper diaper, diaper cover, eyeglasses,
monocle, and lorgnette; internal base sheets, linings, and
materials for shoes; wrappers; materials for umbrellas; parasols;
stuffed toys; lighting devices; filters, panels and screens for
information displaying devices such as televisions and personal
computers which use cathode-ray tubes, liquid crystal displays,
electrolytic luminous displays, and plasma displays; sunglasses;
sunroofs; sun visors; pet bottles; refrigerators; vinyl houses;
lawns; optical fibers; prepaid cards; and peeping windows in
electric ovens, and other type ovens. When used as wrapping
materials, injection materials, and vessels for the above products,
the light absorbents of the present invention prevent living bodies
and products from troubles and discomforts caused by environmental
lights such as natural- and artificial-lights or even lower the
troubles and discomforts, and furthermore they can advantageously
regulate the color, tint, and appearance and control the light
reflected by or passed through the products to a desirable color
balance.
[0058] The following examples describe the preferred embodiments of
the present invention:
EXAMPLE 1
[0059] Cyanine Dye
[0060] Thirty milliliters of acetonitrile were placed in a reaction
vessel, mixed with 15 g of
1-buthyl-3,3-dimethyl-2-[(phenylamino)ethenyl]-
benzoindolenium=tosylate, and 10.4 g of
1-ethyl-2,3,3-trimethylbenzoindole- nium=tosylate, and then admixed
with 3.3 ml of acetic anhydride at ambient temperature under
stirring conditions. The resulting mixture was admixed with 9.7 ml
of triethylamine drop by drop and reacted for one hour. Thereafter,
the reaction mixture was appropriately admixed with water, allowed
to stand for a while, slanted to remove an aqueous phase,
appropriately admixed with methanol, and dissolved under heating
conditions. The resulting solution was filtrated, and the filtrate
was admixed with 20 ml of a solution including 11.3 g of ammonium
phosphate hexafluoride drop by drop under stirring conditions. The
solution was reacted by heating at 70.degree. C. in a thermo-bath
for 30 min and cooled to ambient temperature. After the reaction,
the formed crystal was collected by filtration and dried to obtain
10.5 g of a golden-green crystal of the cyanine dye represented by
Chemical Formula 19.
[0061] A part of the crystal was measured in a conventional manner
for a melting point, resulting in a melting point of
245-252.degree. C.
EXAMPLE 2
[0062] Cyanine Dye
[0063] Twelve grams of a golden-green crystal of the cyanine dye
represented by Chemical Formula 20 was obtained similarly as in
Example 1 except for replacing 11.3 g of ammonium phosphate
hexafluoride with 9.14 g of potassium antimonate hexafluoride.
[0064] A part of the crystal was measured in a conventional manner
for a melting point, resulting in a melting point of
228-232.degree. C.
EXAMPLE 3
[0065] Cyanine Dye
[0066] One hundred twenty milliliters of acetonitrile were placed
in a reaction vessel, mixed with 12.2 g of the azo compound
represented by Chemical Formula 77, and 4.0 g of cobaltous
diacetate tetrahydrate, and further admixed with 11.7 ml of
triethylamine drop by drop at 65.degree. C. under stirring
conditions and reacted for one hour under the same conditions.
Thereafter, the reaction mixture was filtrated, and the filtrate
was distilled to remove acetonitrile and to give 2/3 of the volume.
The resulting solution was mixed with 100 ml of ethanol to disperse
and left at ambient temperature for a time. The formed crystal was
collected by filtration, washed with ethanol and water, and dried
to obtain a greenish brown crystal of a triethylammonium salt of
the azo organic metal complex anion represented by Chemical Formula
4. A part of the crystal was measured in a conventional manner, and
the triethylammonium salt have an absorption maximum with a
wavelength of 479 nm when dissolved in methanol, and have a melting
point of 327.8.degree. C. 17
[0067] Two hundred milliliters of acetonitrile were placed in a
reaction vessel, mixed with 5.0 g of the cyanine dye represented by
Chemical Formula 41, and 337 ml of an acetonitrile solution
including 6.75 g of a triethylammonium salt of azo organic metal
complex anion represented by Chemical Formula 4, and reacted by
heating at 80' under stirring condition. After the reaction, the
resulting solution was distilled to remove acetonitrile, and the
residue was mixed with 400 ml of ethanol, heated at 60.degree. C.
for 30 min, and cooled to ambient temperature. The formed crystal
was collected by filtration, washed with ethanol and water, and
dried to obtain 9.4 g of a bright green crystal of the cyanine dye
represented by Chemical Formula 43 with an azo organic metal
complex anion as a counter ion.
EXAMPLE 4
[0068] Cyanine Dye
[0069] Forty milliliters of acetonitrile were placed in a reaction
vessel, mixed with 7.08 g of the azo compound represented by
Chemical Formula 78, and 2.57 g of cobaltous diacetate
tetrahydrate, and further admixed with 7.5 ml of triethylamine drop
by drop at 65.degree. C. under stirring conditions and reacted for
one hour under the same conditions. Thereafter, the reaction
mixture was filtrated, and the filtrate was distilled to remove
acetonitrile and to give 2/3 of the volume. The resulting solution
was mixed with 80 ml of ethanol to disperse and left at ambient
temperature for a while. The formed crystal was collected by
filtration, washed with ethanol and water, and dried to obtain a
greenish brown crystal of a triethylammonium salt of the azo
organic metal complex anion represented by Chemical Formula 6. A
part of the crystal was measured in a conventional manner,
revealing that the triethylammonium salt had an absorption-maximum
with a wavelength of 465 nm when dissolved in methanol and had a
melting point of 270.2.degree. C. 18
[0070] Two hundred milliliters of acetonitrile were placed in a
reaction vessel, mixed with 6.2 g of the cyanine dye represented by
Chemical Formula 15, and 1,000 ml of an acetonitrile solution
containing 10 g of the triethylammonium salt of azo organic metal
complex anion represented by Chemical Formula 6 as mentioned above,
and reacted by heating at 80.degree. C. under stirring conditions.
After the reaction, the resulting solution was distilled to remove
acetonitrile and to give 2/3 of the volume and left for a while to
cool down. The formed crystal was collected by filtration, washed
with ethanol, and dried to obtain 4.8 g of a bright green crystal
of the cyanine dye represented by Chemical Formula 22 with an azo
organic metal complex anion as a counter ion.
EXAMPLE 5
[0071] Cyanine Dye
[0072] Forty milliliters of acetonitrile were placed in a reaction
vessel, mixed with 10 g of the azo compound represented by Chemical
Formula 79, and 3.98 g of cobaltous diacetate tetrahydrate, and
further admixed with 8.47 ml of triethylamine drop by drop at
65.degree. C. under stirring conditions and reacted for one hour
under the same conditions. Thereafter, the reaction mixture was
treated similarly as in Example 3 to obtain a greenish brown
crystal of the triethylammonium salt of azo organic metal complex
anion represented by Chemical Formula 12. A part of the crystal was
measured in a conventional manner, revealing that the
triethylammonium salt had an absorption maximum with a wavelength
of 537 nm when dissolved in methanol. 19
[0073] One hundred fifty milliliters of acetonitrile were placed in
a reaction vessel, mixed with 2.3 g of the cyanine dye represented
by Chemical Formula 33, and 500 ml of an acetonitrile solution
containing 2.2 g of the triethylammonium salt of azo organic metal
complex anion represented by Chemical Formula 12, and reacted by
heating at 80.degree. C. under stirring conditions. The reaction
mixture was treated similarly as in Example 3 to obtain 9.4 g of a
bright greenish brown crystal of the cyanine dye represented by
Chemical Formula 35.
[0074] Although the production conditions and yields are varied in
some degrees depending on the structures of the cyanine dyes of the
present invention, all the cyanine dyes of the present invention,
including the compounds represented by Chemical Formulae 13 to 72,
can be produced by the methods in Examples 1 to 5 or in accordance
therewith.
EXAMPLE 6
[0075] Light Absorption Characteristic of Cyanine Dye
[0076] The cyanine dyes as listed in Table 1 of the present
invention were measured for visible absorption spectra when
dissolved in methanol and formed into layers over glasses. In
parallel, conventional related compounds represented by Chemical
Formulae 73 to 76 were measured for visible absorption spectra. The
maximum absorption spectra in each conditions are tabulated in
Table 1. FIGS. 1 and 2 show visible-absorption spectra of the
cyanine dye of the present invention represented by chemical
Formula 20 and the conventional related compound represented by
Chemical Formula 74 respectively, when dissolved in methanol.
20
1 TABLE 1 Maximum absorption Cyanine dye wavelength (nm) Solubility
Decomposition Compound R.sub.1 R.sub.2 X.sup.- Solution Thin layer
(mg/ml) point (.degree. C.) Remarks Chemical Formula16 CH.sub.3
CH.sub.3 Chemical Formula 4 584 605 1.1 314.5 Present invention
Chemical Formula42 CH.sub.3 CH.sub.3 Chemical Formula 1 590 612
0.26 317.7 Present invention Chemical Formula43 CH.sub.3 CH.sub.3
Chemical Formula 4 591 617 2.7 304.7 Present invention Chemical
Formula13 CH.sub.3 C.sub.4H.sub.9 PF.sub.6.sup.- 586 613 143 264.7
Present invention Chemical Formula14 CH.sub.3 C.sub.4H.sub.9
SbF.sub.6.sup.- 586 613 73 279.8 Present invention Chemical
Formula19 C.sub.2H.sub.5 C.sub.4H.sub.9 PF.sub.6.sup.- 587 610 23
281.6 Present invention Chemical Formula20 C.sub.2H.sub.5
C.sub.4H.sub.9 SbF.sub.6.sup.- 587 612 140 281.8 Present invention
Chemical Formula21 C.sub.2H.sub.5 C.sub.3H.sub.7 Chemical Formula 4
587 611 2.8 307.9 Present invention Chemical Formula29
C.sub.3H.sub.7 C.sub.3H.sub.7 SbF.sub.6.sup.- 588 613 36 293.3
Present invention Chemical Formula30 C.sub.3H.sub.7 C.sub.4H.sub.9
PF.sub.6.sup.- 588 613 15 289.4 Present invention Chemical
Formula31 C.sub.3H.sub.7 C.sub.4H.sub.9 SbF.sub.6.sup.- 588 613 141
285.0 Present invention Chemical Formula50 C.sub.4H.sub.9 CH.sub.3
CIO.sub.4.sup.- 593 626 64 261.3 Present invention Chemical
Formula56 C.sub.4H.sub.9 CH.sub.3 Chemical Formula 1 592 625 187
261.4 Present invention Chemical Formula53 C.sub.4H.sub.9
C.sub.2H.sub.5 CIO.sub.4.sup.- 594 627 >200 244.5 Present
invention Chemical Formula33 C.sub.4H.sub.9 C.sub.4H.sub.9
SbF.sub.6.sup.- 589 613 61 284.2 Present invention Chemical
Formula34 C.sub.4H.sub.9 C.sub.4H.sub.9 Chemical Formula 4 587 613
1.1 310.6 Present invention Chemical Formula35 C.sub.4H.sub.9
C.sub.4H.sub.9 Chemical Formula12 586 613 6.4 280.1 Present
invention Chemical Formula38 C.sub.5H.sub.11 C.sub.4H.sub.9
CIO.sub.4.sup.- 587 613 >190 262.7 Present invention Chemical
Formula39 C.sub.5H.sub.11 C.sub.4H.sub.9 SbF.sub.6.sup.- 588 613 88
281.8 Present invention Chemical Formula40 C.sub.5H.sub.11
C.sub.5H.sub.11 SbF.sub.6.sup.- 588 613 94 257.3 Present invention
Chemical Formula73 CH.sub.3 C.sub.4H.sub.9 CIO.sub.4.sup.- 585 612
42 242.2 Control Chemical Formula74 C.sub.2H.sub.5 C.sub.4H.sub.9
CIO.sub.4.sup.- 587 612 22 271.5 Control Chemical Formula75
C.sub.3H.sub.7 C.sub.4H.sub.9 CIO.sub.4.sup.- 588 613 19 269.0
Control Chemical Formula76 C.sub.4H.sub.9 C.sub.4H.sub.9
CIO.sub.4.sup.- 588 613 17 266.1 Control
[0077] As shown in Table 1, all of the cyanine dyes of the present
invention have absorption maxima at wavelengths around 580-600 nm
when dissolved in methanol similarly as in the conventional related
compounds represented by Chemical Formulae 73 to 76, and at
wavelengths around 600-630 nm when formed in a thin layer. As shown
in the visible absorption spectra of FIGS. 1 and 2, the absorption
end of a longer wavelength region of the cyanine dye of the present
invention represented by Chemical Formula 20 extended to a
wavelength around 700 nm when formed in a thin layer similarly as
in the conventional related compounds represented by Chemical
Formula 74. These results showed that the cyanine dyes of the
present invention are useful for high-density optical recording
media such as DVD-Rs, because they substantially absorb a visible
light with a wavelength of shorter than 0.700 nm, and more
particularly, a laser beam with a wavelength around 630-680 nm.
EXAMPLE 7
[0078] Solubility of Cyanine Dye
[0079] For the cyanine dyes in Table 1, they were measured in a
conventional manner for solubility in DDA at 20%. In parallel,
conventional related compounds represented by Chemical Formulae 73
to 76 were also measured for solubility in DAA in a similar way.
The results are also shown in Table 1.
[0080] As found in the results in Table 1, most of the cyanine dyes
of the present invention had higher solubilities than those of the
conventional related compounds. The solubilities of conventional
related compounds were under 50 mg/ml in DAA, while the
solubilities of all the cyanine dyes of the present invention
measured were almost equal to or higher than those of the
conventional related compounds
EXAMPLE 8
[0081] Decomposition Point of Cyanine Dye
[0082] An adequate amount of any one of the cyanine dyes in Table 1
as a test specimen was placed in a vessel and subjected to
conventional differential thermal analysis (hereinafter abbreviated
as "DTA") and thermogravimetric analysis (hereinafter abbreviated
as "TGA") using "MODEL TG/DTA 220", a digital thermo analyzer
commercialized by Seiko Instruments Inc., Tokyo, Japan, to
determine their decomposition points, i.e., temperatures at which
the cyanine dyes as test specimens begin to lose their weight on
TGA. In parallel, conventional related compounds represented by
Chemical Formulae 73 and 76 were analyzed similarly as above. The
results are also shown in Table 1. FIG. 3 shows the results of DTA
and TGA of the cyanine dye represented by Chemical Formula 19 of
the present invention, respectively. In DTA and TGA, the
environmental temperature was set to an increasing temperature mode
at a rate of 10.degree. C./min.
[0083] As shown in Table 1 and FIG. 3, all the conventional related
compounds represented by Chemical Formulae 73 to 76 had
decomposition points under 272.degree. C., while most of the
cyanine dyes of the present invention measured had remarkably
higher decomposition points than those of the conventional related
compounds, indicating that their heat resistance was
relatively-high. Varying depending on glass transition temperature
of substrate, when used as a light absorbent in optical recording
media, dyes with a relatively-low heat resistance can be generally
used to write information by using a lower-power laser beam as the
merit, however, as the drawback, when exposed to a laser beam for a
relatively-long period of time on reading, the dyes tend to
accumulate heat and deform parts around pits and other pitless
parts on recording surfaces, resulting in large jitters and reading
errors. The fact that the cyanine dyes of the present invention
have relatively-high decomposition points shows that high-density
optical recording media having a relatively-small jitter,
insubstantial reading error, and satisfactory stability of exposure
to environmental light such as reading light and natural light can
be obtained by using the cyanine dyes of the present invention as a
light absorbent.
EXAMPLE 9
[0084] Optical Recording Medium
[0085] The cyanine dye represented by Chemical Formula 15, 19, 20,
31, or 41 was added to TFP to give a respective concentration of
2.0% (w/w), and the mixture was mixed with, as a light resistant
improver, a formazane metal complex in which were bound two
molecules of a formazane compound represented by Chemical Formula
80 in an amount of 0.2% (w/w), and heated for a time, followed by
ultrasonically dissolving the contents. The resulting solution was
in a conventional manner filtrated by a membrane, homogeneously
coated in a rotatory manner over one side of a polycarbonate disc
substrate, 12 cm in diameter and 0.6 mm in thickness, to which had
been transferred concaves, 0.74 .mu.m in trackpitch, 0.03 .mu.m in
width and 76 nm in depth, for expressing synchronizing signals and
addresses of tracks and sectors, to give a thickness of 100 nm by
an injection molding. Thereafter, the substrate was spattered with
silver to form a reflection layer, 100 nm in thickness, to be
closely attached on the surface of the recording layer, and the
reflection layer was homogeneously coated in a rotatory manner with
"DAICURE CLEAR SD1700", as a known ultraviolet ray hardening resin
commercialized by Dainippon Ink and Chemicals, Inc., Tokyo, Japan,
and irradiated to form a protection layer to be closely attached on
the surface of the reflection layer, followed by closely attaching
and sticking a polycarbonate disc protection plate on the surface
of the protection layer to obtain five types of optical recording
media. 21
[0086] All of the optical recording media of this Example with good
sensitivity, modulation characteristic, resolution, and electrical
characteristics such as a jitter characteristic have a recording
capacity of over 4 GB and can write large amounts of information of
documents, images, voices, and digitals at a relatively-high
density by a light pick-up using a visible light with a wavelength
of shorter than 700 nm, and more particularly, a laser beam with an
oscillation wavelength around 630-680 nm. Microscopic observation
of the recorded surface of the optical recording media of this
example, which had been written information by a semiconductor
laser element with an oscillation wavelength of 658 nm, revealed
that minute pits with a size of less than one .mu.m/pit were formed
at a track pitch of below one .mu.m.
EXAMPLE 10
[0087] Optical Recording Medium
[0088] Five types of optical recording media were obtained
similarly as in Example 9 except for replacing a formazane metal
complex with a conventional diimmonium compound, "IRG022" by Nippon
Kayaku Co., Ltd., Tokyo, Japan.
[0089] All of the optical recording media of this Example with good
sensitivity, modulation characteristic, resolution, and electrical
characteristics such as a jitter characteristic have a recording
capacity of over 4 GB and can write large amounts of information of
documents, images, voices, and digitals at a relatively-high
density by a light pick-up using a visible light with a wavelength
of shorter than 700 nm, and more particularly, a laser beam with an
oscillation wavelength around 630-680 nm. Microscopic observation
of the recorded surface of the optical recording media of this
example, which had been written information by a semiconductor
laser element with an oscillation wavelength of 658 nm, revealed
that minute pits with a size of less than one .mu.m/pit were formed
at a track pitch of below one .mu.m.
EXAMPLE 11
[0090] Optical Recording Medium
[0091] The cyanine dye represented by Chemical Formula 13, 29, or
50 as a light-resistant improver was added to DAA to give a
respective concentration of 2.0% (w/w), and the mixture was heated
for a time, followed by ultrasonically dissolving the contents. The
resulting resulting solution was in a conventional manner filtrated
by a membrane, homogeneously coated in a rotatory manner over one
side of a polycarbonate disc substrate, 12 cm in diameter and 0.6
mm in thickness, to which had been transferred concaves, 0.74 .mu.m
in trackpitch, 0.03 .mu.m in width and 76 nm in depth, for
expressing synchronizing signals and addresses of tracks and
sectors, to give a thickness of 100 mm by an injection molding.
Thereafter, the substrate was spattered with silver to form a
reflection layer, 100 nm in thickness, to be closely attached on
the surface of the recording layer, and the reflection layer was
homogeneously coated in a rotatory manner with "DAICURE CLEAR
SD1700", as a known ultraviolet ray hardening resin commercialized
by Dainippon Ink and Chemicals, Inc., Tokyo, Japan, and irradiated
to form a protection layer to be closely attached on the surface of
the reflection layer, followed by closely attaching and sticking a
polycarbonate disc protection plate, 12 cm in diameter and 0.6 mm
in thickness, on the surface of the protection layer to obtain
three types of optical recording media.
[0092] All of the optical recording media of this Example with good
sensitivity, modulation characteristic, resolution, and electrical
characteristics such as a jitter characteristic have a recording
capacity of over 4 GB and can write large amounts of information of
documents, images, voices, and digitals at a relatively-high
density by a light pick-up using a visible light with a wavelength
of shorter than 700 nm, and more particularly a laser beam with an
oscillation wavelength around 630-680 nm. Microscopic observation
of the recorded surface of the optical recording medium of this
example, which had been written information by a semiconductor
laser element with an oscillation wavelength of 658 nm, revealed
that minute pits with a size of less than one .mu.m/pit were formed
at a track pitch of below one .mu.m.
EXAMPLE 12
[0093] Optical Recording Media
[0094] Two types of optical recording media were obtained similarly
as in Example 9 except for a light absorbent with an equivalent
mixture of the cyanine dyes represented by Chemical Formulae 15 and
16 by weight, or the cyanine dyes represented by Chemical Formulae
41 and 43.
[0095] All of the optical recording media of this Example with good
sensitivity, modulation characteristic, resolution, and electrical
characteristics such as a jitter characteristic have a recording
capacity of over 4 GB and can write large amounts of information of
documents, images, voices, and digitals at a relatively-high
density by a light pick-up using a visible light with a wavelength
of shorter than 700 nm, and more particularly a laser beam with an
oscillation wavelength around 630-680 nm. Microscopic observation
of the recorded surface of the optical recording media of this
example, which had been written information by a semiconductor
laser element with an oscillation wavelength of 658 nm, revealed
that minute pits with a size of less than one .mu.m/pit were formed
at a track pitch of below one .mu.m.
[0096] As described above, the present invention was made based on
the creation of novel cyanine dyes and the findings of their
industrially usable characteristics. The cyanine dyes substantially
absorb a visible light with a wavelength of shorter than 700 nm,
have relatively-high solubility in organic solvents such as DAA and
a relatively-high heat resistance. Accordingly, the cyanine dyes of
the present invention can be advantageously used as a light
absorbent in optical recording media in the form of a DVD-R in
which stable minute pits should be formed on a restricted recording
surface at a relatively-high density by using, as a reading light,
a visible light with a wavelength of shorter than 700 nm, and more
particularly, a laser beam with a wavelength around 630-680 nm in
writing information.
[0097] Comparing with CD-Rs now used in this field, the organic
optical recording media of the present invention, which write
information by using a visible light with a wavelength shorter than
700 nm, and more particularly, a laser beam with a wavelength
around 630-680 nm, can form more minute pits at a narrower track
pitch, and this results in advantageous characteristics of that
they can record very large amounts of information of characters,
images and/or voices at a relatively-high density. Thus, the cost
per a bit required for recording information can be beneficially
lowered by a large margin.
[0098] Since the cyanine dyes of the present invention remarkably
improve the light resistance of other cyanine dyes without
substantially absorbing visible light with wavelengths of longer
than 700 nm, they can be advantageously used as a light-resistant
improver, for example, in CD-Rs, and more particularly, high-speed
writable CD-Rs now commercially available, which have recording
layers composed of other cyanine dyes that substantially absorb
visible light with wavelengths of longer than 700 nm and need laser
beams with wavelengths around 775-795 nm as a writing light.
[0099] The useful cyanine dyes can be easily obtained in a
desirable amount by the method of the present invention through a
step of reacting a benzoindolenium compound having an active methyl
group with a benzoindolenium compound having suitable leaving
groups.
[0100] The present invention having such outstanding effects and
functions is a significant invention that will greatly contribute
to this art.
[0101] While what are at present considered to be the preferred
embodiments of the invention have been described, it will be
understood that various modifications may be made therein, and the
appended claims are intended to cover all such modifications as
fall within the true spirits and scope of the invention.
* * * * *