JPS63247088A - Optical recording medium - Google Patents

Abstract

PURPOSE:To obtain an optical recording medium having a high contrast ratio and excellent in a reproduction characteristic, by forming a primer layer on a transparent substrate and laminating a recording layer containing a specific polymethylene dye to said layer. CONSTITUTION:A primer layer having a light refractive index lower than a transparent substrate is formed on the transparent substrate and a recording layer composed of a dye material represented by formula [I] (wherein R1, R2, R3, R4, R5 and R6 are a hydrogen atom, an alkyl group, a substituted alkyl group, a cyclic alkyl group, an alkenyl group, an allyl group, an aralkyl group, a substituted aralkyl group, an aryl group, a substituted arkyl group, a stiryl group, a substituted stiryl group, a heterocyclic group or a substituted heterocyclic group, m is 0 or 1, n is 0, 1 or 2 and X(-) is an anion) is laminated to said primer layer. As the transparent substrate, a transparent one composed of glass, an acrylic resin, an epoxy group or the like is used and the light refractive index of the material forming said substrate is desirably 1.45-1.65 in usual. As the primer layer, for example, MgF2 is used as an inorg. film and polytetrafluoroethylene or polyvinylidene fluoride is mainly used as an org. film.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an optical recording medium, and in particular, the present invention relates to an optical recording medium, in particular a recording medium using a light beam.
The present invention relates to an optical recording medium in which a readable recording layer is made of an organic optical recording material.

[Prior Art] Conventionally, organic optical recording media used in optical disk and optical card technologies include organic dyes, organic dye compositions, etc. on a transparent substrate l such as glass or plastic, as shown in FIG.
A recording layer 3 made of an organic optical recording material such as an organometallic complex is provided, and a laser beam with energy necessary for recording is focused on the interface between the substrate l and the recording layer 3 and scanned. Bits are formed only in the areas that are irradiated, and information is recorded with high density. This recorded information is read by scanning with a weak laser beam that does not deform the recording layer and detecting optical changes in reflectance, transmittance, etc. of pit-formed areas and pit-unformed areas.

When the above organic optical recording material is used as a recording layer, compared to inorganic optical recording materials, ■ coating film formation is possible;
It is advantageous in terms of high productivity, (1) high recording sensitivity, and (2) increased recording density.

Further, as the performance required of the dye used in the above-mentioned organic optical recording material, it is desirable that the dye has the following properties. That is, 1. Non-toxic 2. Absorption near 800 nm and large extinction coefficient 3. Good solubility in organic solvents 4. High reflectance near 800 nm in thin film state 5. Thin film state Dye that satisfies these properties to a certain extent: 6. Stable in ultraviolet and visible light 7. Stable in heat 8. Stable against humidity 9. Easy to synthesize. As.

Polymethine dyes have been proposed.

The polymethine dye generally has an absorption peak with a large extinction coefficient near 8:1 Onm, and has excellent performance such as good solubility in organic solvents, but it has a drawback of refractive index, which is a drawback of organic optical recording materials. Due to its small characteristic,
In single-layer optical recording media in which only the recording layer is formed on the substrate, the reflectance of the unrecorded area is low, and even if pits are formed by the recording laser, the contrast ratio between the recorded area and the unrecorded area is small, and the final The drawback was that it was not possible to obtain a large signal.

[Problems to be Solved by the Invention] The present invention has been made to solve the above-mentioned problems of the prior art. By forming a layer and providing a recording layer containing a specific polymethine dye on top of the recording layer, the reflectance can be increased without sacrificing the advantages of using a polymethine dye as a recording layer, and the recorded and unrecorded areas can be separated. The object of the present invention is to provide an optical recording medium with a high contrast ratio and excellent reproduction characteristics.

[Means for Solving the Problems] That is, the present invention forms an undercoat layer having a lower optical refractive index than that of the transparent substrate on a transparent substrate, and forms an undercoat layer having a lower optical refractive index than that of the transparent substrate, and forms an undercoat layer represented by the general formula [I] on the undercoat layer. This optical recording medium is characterized by being formed by laminating Q layers containing a polymethine dye.

General formula [11 (wherein R1, Rt,' R3, Ill,, R8, R6
is a hydrogen atom, an alkyl group, a substituted alkyl group, a cyclic alkyl group, an alkenyl group, an allyl group, an aralkyl group, a substituted aralkyl group, an aryl group, a substituted aryl group, a styryl group, a substituted styryl group, a heterocyclic group, a substituted hetero Indicates a ring group. m
is 0 or 1. (n is O or l, 2, xo is an anion group) The present invention will be described in detail below.

FIG. 1 is a sectional view showing an example of the optical recording medium of the present invention. In FIG. 1, the optical recording medium of the present invention has a transparent substrate l.
Above, an undercoat layer 2 having a lower optical refractive index than the transparent substrate l.
It has a structure in which a recording layer 3 made of a dye material represented by the general formula [I] is laminated thereon.

The transparent substrate used in the present invention is made of glass, acrylic resin, epoxy resin, polycarbonate resin, polyethylene terephthalate, or the like. The optical refractive index of the material forming these transparent substrates is usually 1.4.
A value in the range of 5 to 1.65 is desirable.

In the present invention, the undercoat layer is not particularly limited as long as it has a lower optical refractive index than the transparent substrate used and can form a uniform film, and a wide range of materials can be used.For example, as an inorganic film, MgF2. Yes 41115! As the material, fluororesins such as polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, and polyvinylidene fluoride are mainly used.

The optical refractive index of the undercoat layer is usually in the range of 1.30 to 1.60, preferably 1.30 to 1.50, and
It is desirable that the difference in optical refractive index with the substrate be large.

The thickness of the undercoat layer is usually 50 to 3,000, preferably 100 to 2,000.

In the present invention, the polymethine dye used to form the recording layer is represented by the general formula [I].

In the general formula (1), R1+ R2+ R3, R
4+R5 and R6 are hydrogen atoms or alkyl groups (for example, methyl group, ethyl group, n-propyl group, is.

-probyl group, n-butyl group, 5ec-butyl group, 1s
o-butyl group, t-butyl group, n-amyl group, t-alkyl group, n-hexyl group, n-octyl group, t-octyl group, etc.), and further includes other alkyl groups, such as substituted alkyl groups. groups (e.g. 2-hydroxyethyl group, 3-hydroxypropyl group, 4-hydroxybutyl group, 2-acetoxyethyl group, carboxymethyl group, 2-carboxyethyl group, 3-carboxypropyl group, 2-sulfoethyl group, 3- Sulfopropyl group, 4-sulfobutyl group, 3-
Sulfate propyl group, 4-sulfate butyl group,
N-(methylsulfonyl)-carbamylmethyl group, 3-
(acetylsulfamyl)propyl group, 4-(acetylsulfamyl)butyl group, etc.), cyclic alkyl group (e.g. cyclohexyl group, etc.), alkenyl group (vinyl group, allyl group, propenyl group, butenyl group, pentenyl group) group, hexenyl group, heptenyl group, octenyl group, dodecynyl group, prenyl group, etc.), allyl group (C11□-CH
-Cl, I-), aralkyl groups (e.g., benzyl group, phenethyl group, α-naphthylmethyl group, β-naphthylmethyl group, etc.), substituted aralkyl groups (e.g., carboxybenzyl group, sulfobenzyl group, hydroxybenzyl group, etc.) ).

Furthermore, R,, R2, R3, R,, R1 and R6 are substituted or unsubstituted aryl2! li (e.g. phenyl group, naphthyl group, tolyl group, xylyl group, methoxyphenyl group, dimethoxyphenyl group, trimethoxyphenyl group, ethoxyphenyl group, dimethylaminophenyl group, diethylaminophenyl group, dipropylaminophenyl group, dibenzyl group) aminophenyl group, diphenylaminophenyl group), substituted or unsubstituted heterocyclic group (e.g. pyridyl group, quinolyl group, revidyl group, methylbiridyl group, furyl group, chenyl group, indolyl group, virol group, carbazolyl group, N -ethylcarbazolyl group) or substituted or unsubstituted styryl group (e.g. styryl group, methoxystyryl group, dimethoxystyryl group, trimethoxystyryl group, ethoxystyryl group, dimethylaminostyryl group, diethylaminostyryl group, dipropyl group) aminostyryl group, dibenzylaminostyryl group, diphenylaminostyryl group, 2,2-diphenylvinyl group, 2-phenyl-2-methylvinyl group.

2-(dimethylaminophenyl)-2-phenylvinyl group, 2-(diethylaminophenyl)-2-phenylvinyl group, 2-(dibenzylaminophenyl)-2-phenylvinyl group, 2,2-di(diethylaminophenyl) )
vinyl group, 2,2-di(methoxyphenyl)vinyl group,
2,2-di(ethoxyphenyl)vinyl group, 2-(dimethylaminophenyl)-2-methylvinyl group, 2-(diethylaminophenyl)-2-ethylvinyl group, etc.). m is O or l, and n is 0.1 or 2.

xo represents an anion group, such as chloride ion, bromide ion, iodide ion, perchlorate ion, benzenesulfonate ion, p-toluenesulfonate ion, methyl sulfate ion, ethyl sulfate ion, Propyl sulfate ion, tetrafluoroborate ion, tetraphenylborate ion, hexafluorophosphate ion, benzenesulfinate ion, acetate ion,
trifluoroacetate ion, propionacetate ion,
Benzoate ion, oxalate ion, succinate ion, malonate ion, oleate ion, stearate ion, citrate ion, -hydrogen diphosphate ion, dihydrogen-phosphate ion , pentachlorostannate ion, chlorosulfonate ion, fluorosulfonate ion, trifluoromethanesulfonate ion,
hexafluoroantimonate ion, molybdate ion, tungstate ion, titanate ion,
Represents an anion such as zirconate ion.

Next, representative examples of polymethine dyes represented by the general formula [11] will be listed, but the invention is not limited to these.

-I D-12 D-13 D-24 These polymethine compounds are described in Bernard S, Wildi et al., J.

A■, Cheta, Soc (Journal of American Chemical Society) 80 3772
~3777 (1958)
Ann (Liebig-Annarendel-Chemie) 204-216 of H. Schmidt et al. or Earl Wurzinger (R.

Wlzinger et al., Chin,
Acta (Helvetica stain force Acta) 2436
It can be easily obtained by synthesis according to the synthesis method disclosed in No. 9 and others.

Such dyes generally have an absorption peak with a large extinction coefficient near 800 nm, and also have good solubility in organic solvents, making them excellent as optical information recording media.

Further, the recording layer may contain a binder in addition to the dye. Suitable binders can be selected from a wide range of resins. Specifically, nitrocellulose, cellulose phosphate, cellulose sulfate, cellulose acetate, cellulose propionate, /v! Cellulose esters such as cellulose m, cellulose myristate, cellulose valmitate, cellulose acetate/propionate, cellulose acetate/acetate, methylcellulose, ethylcellulose,
Cellulose ethers such as propyl cellulose and butyl cellulose, polystyrene, polyvinyl chloride, polyvinyl acetate, polyvinyl butyral, polyvinyl acetal, polyvinyl alcohol, vinyl resins such as polyvinylpyrrolidone, styrene-butadiene copolymer, styrene-acrylonitrile copolymer, styrene - Copolymer resins such as butadiene-acrylonitrile copolymer, vinyl chloride-vinyl acetate copolymer, acrylic resins such as polymethyl methacrylate, polymethyl acrylate, polybutyl acrylate, polyacrylic acid, polymethacrylic acid, polyacrylamide, polyacrylonitrile, Polyesters such as polyethylene terephthalate, poly(4,4'-isopropylidene, diphenylene-co-1,4-cyclohexylene dimethylene carbonate), poly(ethylenedioxy-3,3'-phenylene thiocarbonate), poly(4,4, 4'-isopropylidene diphenylene carbonate coater terephthalate)
, poly(4,4'-isopropylidene diphenylene carbonate), poly(4,4'-5ec-butylidene diphenylene carbonate), poly(4,4'-isopropylidene diphenylene carbonate-block-oxyethylene), etc. Polyarylate resins, polyamides, polyimides, epoxy resins, phenol resins, polyolefins such as polyethylene, polypropylene, and chlorinated polyethylene can be used.

Organic solvents that can be used during coating should be in a dispersed state or
Or, it depends on whether it is in an amorphous state,
Generally, alcohols such as methanol, ethanol, isopropanol, acetone, methyl ethyl ketone,
Ketones such as cyclohexanone, amides such as N,N-dimethylformamide, N,N-dimethylacetamide, sulfoxides such as dimethylsulfoxide, ethers such as tetrahydrofuran, dioxane, ethylene glycol monomethyl ether, methyl acetate, ethyl acetate, Esters such as butyl acetate, chloroform,
Aliphatic halogenated hydrocarbons such as methylene chloride, dichloroethylene, carbon tetrachloride, and trichlorethylene, or aromatics such as benzene, toluene, xylene, monochlorobenzene, dichlorobenzene, and anisole can be used.

The content of the polymethine dye represented by the general formula [I] in the recording layer 3 is usually 70 to 100%, preferably 9%.
0 to 100% by weight is desirable. If it is less than 70% by weight, sufficient light absorption of the recording layer and sufficient light reflectance for reproduction laser light cannot be obtained.

The thickness of the recording layer 3 varies depending on the purpose of use, but is usually 400 to 2000, preferably 500 to 150.
0 people is appropriate. Note that, if a thin film having sufficient optical reflectivity for the recording laser beam can be stably formed, it is better to make it as thin as possible.

[Function] The optical recording medium of the present invention, as shown in FIG. 2, forms an undercoat layer on a transparent substrate with a lower optical refractive index than that of the transparent substrate,
Since the recording layer is laminated thereon, the refractive index of each substance shown in the same:jSZ diagram is relatively different from that of the recording layer 3.
Transparent substrate l>undercoat layer 2>air layer 7. Therefore, in the unrecorded area, the undercoat layer 2 functions as a reflection enhancing film, and in the recorded area 6, it functions as an anti-reflection film, so the recording is Part 6
It is estimated that the difference between the reflectance of the recorded area and the unrecorded area becomes large, and a high contrast ratio can be obtained.

[Example] The present invention will be described in detail below with reference to Examples.

Examples 1 to 3 Disc-shaped optical recording media having the structure shown in FIG. 4 were produced in the following manner.

Polycarbonate disk transparent substrate 1 with an inner diameter of 35 mm, an outer diameter of 200 layers, a thickness of 1.2 layers, and an optical refractive index of 1.58.
On ゜1', a subbing layer 2゜2' is made of the substances shown in Table 1.
was formed. Polymethine dyes shown in Table 1 were dissolved thereon using a prescribed solvent, and spin code was applied.
Written by approximately 800 people [! ! A film of J3°3' was formed.

Place the two substrates prepared in this manner with the recording layer side inside, and add a 0.5-inch outer circumferential spacer 4. Inner spacer 4
' was sandwiched to form a hollow structure, and bonded together using two-component poxy adhesive 5.

This optical recording medium has a laser power of 8 mW and a rotation speed of 4 t.
Recording was performed from the substrate side under the conditions of a/sec, frequency of 500 Hz, reproduction with a reproduction laser power of 1 mW, and the contrast ratio between the recorded portion and the unrecorded portion was calculated from the reflectance measurement results. The results are shown in Table 1.

Comparative Examples 1 to 3 For comparison, samples were prepared in which the recording layer was directly formed without adding the subbing layers 2 and 2' as shown in Fig. 5, and the samples were recorded under the same conditions and the contrast ratio was calculated. .

It was calculated from the reflectance (R2: reflectance of the recorded area).

The results are also listed in Table 1.

Table 1 From the above results, MgF2. It can be seen that the sample with the polytetrafluoroethylene subbing layer has a higher contrast ratio and is a medium with better reproduction characteristics.

[Effects of the Invention] As explained above, according to the present invention, by forming F-Jiv, which has a lower optical refractive index than the substrate, in the subbing layer of the recording layer, the recording layer alone has a difference between recorded areas and unrecorded areas. Even organic optical recording materials that have a small contrast ratio can be improved in contrast ratio and can be made into optical recording media with excellent reproduction characteristics.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an example of the optical recording medium of the present invention, and FIG.
The figure is a sectional view showing the state of the optical recording medium of the present invention after recording.
Figure 3 is a cross-sectional view of a conventional optical recording medium, and Figure 4 is Example 1.
FIG. 5 is a cross-sectional view showing the disk-shaped optical recording media of Comparative Examples 1-3. 1.1'...Transparent substrate 2.2''-...Undercoat layer 3
．． 3'...Recording layer 4...Outer spacer 4
'... Inner spacer 5... Adhesive 6... Recording part 7... Air layer Figure 2 Figure 3

Claims (1)

[Claims] A subbing layer having a lower optical refractive index than that of the transparent substrate is formed on a transparent substrate, and a recording layer containing a polymethine dye represented by the general formula [I] is laminated thereon. An optical recording medium characterized by: General formula [I] ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (In the formula, R_1, R_2, R_3, R_4, R_5, R_
6 is a hydrogen atom, an alkyl group, a substituted alkyl group, a cyclic alkyl group, an alkenyl group, an allyl group, an aralkyl group, a substituted aralkyl group, an aryl group, a substituted aryl group, a styryl group, a substituted styryl group, a heterocyclic group, a substituted hetero Indicates a ring group. m is 0 or 1, n is 0, 1, or 2, and X^e represents an anion group. )