JPH0678285B2 - Squarylium compound and optical recording medium containing the compound - Google Patents

Description

TECHNICAL FIELD The present invention relates to a novel squarylium compound and an optical recording material using the compound.

2. Description of the Related Art Optical recording using a laser enables high-density information recording, storage, and reproduction, and thus has been particularly desired for development in recent years.

An example of optical recording is an optical disc.

In general, an optical disc is one in which a thin recording layer provided on a circular substrate is irradiated with laser light focused to about 1 μm to perform high density information recording.

Recording is due to the absorption of irradiated laser energy,
Reproduction of the information generated and recorded by the thermal deformation of the recording layer, such as decomposition, evaporation, and dissolution, which occurs at that location,
This is done by reading the difference in reflectance between the portion where deformation has occurred and the portion where deformation has not occurred, using laser light.

Therefore, it is necessary for the recording medium to absorb the energy of the laser light efficiently, so it has a large absorption for the laser light of the specific wavelength used for recording, and it is used for reproduction in order to accurately reproduce the information. It is necessary that the reflectance with respect to the laser light of the specified wavelength is high.

Various types of optical recording media are known as this type of optical recording medium.

For example, JP-A-55-97033 discloses a substrate in which a single layer of phthalocyanine-based color is provided. Phthalocyanine dyes have problems such as low sensitivity, high decomposition point and difficulty in vapor deposition, and also have extremely low solubility in organic solvents and cannot be used for coating by coating. Further, JP-A-58-83344 and JP-A-58-224793 disclose that a recording layer is provided with a phenalene dye and a naphthoquinone dye, respectively. However, while such a dye has the advantage of being easily vapor deposited, it has a problem of low reflectance. When the reflectance is low, the contrast relating to the reflectance between the portion recorded by the laser beam and the unrecorded portion is low, and it becomes difficult to reproduce the recorded information.

Further, JP-A-59-24692, JP-A-59-67092 and JP-A-59-71895 disclose those in which a cyanine dye is provided in a recording layer. However, while such a dye has the advantage that it can be used for coating by coating, it has the problems of light resistance and deterioration with respect to reproducing light.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention The present invention has high solubility in an organic solvent, coating by coating is possible, high reflectance, good contrast, and excellent light resistance and reproduction light resistance. It is an object of the present invention to provide a dye compound and an optical recording material using the compound.

Means for Solving the Problems The gist of the present invention is to provide a compound represented by the general formula [I] [Wherein R ¹ ′, R ² ′, R ³ ′, R ⁴ ′ and R ⁵ ′ are each a hydrogen atom; an alkyl group having 1 to 25 carbon atoms; an alkoxy group having 1 to 25 carbon atoms; ~ 25 alkoxyalkoxy group; C3-25 alkoxyalkoxyalkoxy group; C1-8 alkyl group, C1-8 alkoxy group or benzyl group which may be substituted with a halogen atom, phenethyl group Or a phenylpropyl group; an alkyl group having 1 to 8 carbon atoms, an alkoxy group having 1 to 8 carbon atoms, or a phenyl group which may be substituted with a halogen atom; or a halogen atom. R ¹ ′ and R ² ′ are linked to each other to form a benzene ring, a cyclohexene ring, a cyclopentene ring, a dihydrothiophene ring, a tetrahydropyridine ring, a furan ring, a dihydrofuran ring, a pyrrole ring, a dihydropyrrole ring or a thiazole ring. May be.

R ¹ and R ² are each substituted with a hydrogen atom; a hydroxyl group, a cyano group, an alkoxy group having 1 to 15 carbon atoms, an alkoxyalkoxy group having 2 to 15 carbon atoms, a halogen atom, a phenylcarbonyloxy group, or a halogen atom. Optionally a phenoxy group, an aryloxy group, a tetrahydrofuryl group,
Substituted with amino group, alkylamino group, dialkylamino group, trialkylamino group, alkoxycarbonyl group, cyclohexyloxycarbonyl group, alkylcarbonyloxy group, phenoxycarbonyl group, alkoxycarbonyloxy group, cyclohexylcarbonyloxy group or phenoxycarbonyloxy group An optionally substituted alkyl group having 1 to 25 carbon atoms; a methyl group, an allyl group optionally substituted with a halogen atom or a phenyl group;
An alkyl group having 9 carbon atoms, an alkoxy group having 1 to 9 carbon atoms, a benzyl group which may be substituted with a halogen atom or a nitro group, a phenethyl group, a phenylpropyl group; or a carbon number 1
It represents an alkyl group having from 9 to 9, an alkoxy group having from 1 to 9 carbon atoms, a phenyl group which may be substituted with a halogen atom or a nitro group, or a naphthyl group. R ¹ and R ² may be linked to each other to form a pyrrolidine ring, a piperidine ring or a morpholine ring together with a nitrogen atom.

R ³ is Or —SO ₂ R ⁶ (R ⁵ and R ⁶ are each a hydroxyl group, a cyano group, an alkoxy group having 1 to 15 carbon atoms, an alkoxyalkoxy group having 1 to 15 carbon atoms, a halogen atom, a phenylcarbonyloxy group, an allyloxy group. A phenoxy group optionally substituted with a halogen atom, a tetrahydrofuryl group,
Substituted with amino group, alkylamino group, dialkylamino group, trialkylamino group, alkoxycarbonyl group, cyclohexyloxycarbonyl group, alkylcarbonyloxy group, phenoxycarbonyl group, alkoxycarbonyloxy group, cyclohexylcarbonyloxy group or phenoxycarbonyloxy group Optionally substituted alkyl group having 1 to 25 carbon atoms; alkoxy group having 1 to 8 carbon atoms;
Vinyl group optionally substituted by methyl group or phenyl group; cyclohexyl group; cyclohexyloxy group; allyl group optionally substituted by methyl group, halogen atom or phenyl group; alkyl group having 1 to 9 carbon atoms, carbon Number 1
9 alkoxy group, benzyl group optionally substituted with halogen atom or nitro group, phenethyl group or phenylpropyl group; alkyl group having 1 to 9 carbon atoms, 1 to 9 carbon atoms
The phenyl group or naphthyl group which may be substituted with an alkoxy group, a halogen atom or a nitro group; or a phenoxy group. ) Is represented.

R ⁴ represents a hydrogen atom; or an alkoxy group having 1 to 8 carbon atoms or an alkoxy group having 1 to 8 carbon atoms which may be substituted with an alkoxyalkoxy group. ] An optical recording material comprising a squarylium compound represented by: and a recording layer containing the compound.

As the substituent of the azulenyl group A of the general formula [I], an alkyl group which may have a substituent (for example, an alkyl group having 1 to 25 carbon atoms, preferably an alkyl group having 1 to 8 carbon atoms). Or an alkoxy group which may have a substituent (for example, an alkoxy group having 1 to 25 carbon atoms, preferably an alkoxy group having 1 to 8 carbon atoms, which has a substituent such as an alkoxy group or an alkoxyalkoxy group) Or an aralkyl group which may have a substituent (for example,
Alkyl group having 1 to 8 carbon atoms, benzyl group optionally substituted with an alkoxy group or a halogen atom, phenethyl group, phenylpropyl group) or an aryl group optionally having a substituent (for example, the above-mentioned aralkyl group) And a halogen atom such as a chlorine atom or a bromine atom.

Further, even if the azulenium ring of the azulenyl group is condensed with a benzene ring, a cyclohexene ring, a cyclopentene ring, a dihydrothiophenene ring, a tetrahydropyridine ring, a furan ring, a dihydrofuran ring, a pyrrole ring, a dihydropyrrole ring, a thiazole ring, etc. Good.

As R ¹ and R ^{2 in} the general formula [I], a hydrogen atom or
C1 to C25 optionally having a substituent, preferably C1 to C10 alkyl group; allyl optionally having a substituent; benzyl optionally having a substituent, Examples thereof include aralkyl groups such as phenyl group and phenylpropyl group; aryl groups such as phenyl group and naphthyl group which may have a substituent. As the substituent of the alkyl group, for example, a hydroxyl group, a cyano group, a carbon number of 1 to 1
15 alkoxy group, alkoxyalkoxy group, fluorine atom, chlorine atom, halogen atom such as bromine atom, arylcarbonyloxy group, allyloxy group, aryloxy group, tetrahydrofuryl group, amino group, alkylamino group, dialkylamino group, Examples thereof include a trialkylamino group, an alkoxycarbonyl group, a cyclohexyloxycarbonyl group, an alkylcarbonyloxy group, an aryloxycarbonyl group, an alkoxycarbonyloxy group, a cyclohexylcarbonyloxy group and an aryloxycarbonyloxy group.

As the substituent of the allyl group, an alkyl group such as a methyl group,
A halogen atom such as a chlorine atom and an aryl group such as a phenyl group can be exemplified. Examples of the substituent of the aralkyl group and the aryl group include an alkyl group having 1 to 9 carbon atoms,
Examples thereof include an alkoxy group, a chlorine atom, a bromine atom, a fluorine atom, a halogen atom such as an iodine atom, and a nitro group.

In addition, R ¹ and R ² are connected to each other to form 5 together with the nitrogen atom.
It may form a membered ring or a 6-membered heterocycle, for example, a pyrrolidine ring, a piperidine ring, or a morpholine ring.

The substituents R ⁵ and R ⁶ are an alkyl group which may have a substituent,
An alkoxy group, a vinyl group, a cycloalkyl group, a cycloalkyloxy group, an allyl group, an aralkyl group, an aryl group, an aryloxy group or the like is shown, and as a substituent of these alkyl group, allyl group, aralkyl group or aryl group, The alkyl group in R ¹ and R ² , the aralkyl group, and the same groups as those described as the substituents of the aryl group can be exemplified, and the substituent of the vinyl group can be an alkyl group such as a methyl group or a phenyl group. And other aryl groups.

The substituent R ⁴ is a hydrogen atom or an alkoxy group which may have a substituent (for example, an alkoxy group having 1 to 8 carbon atoms), and the substituent is an alkoxy group having 1 to 8 carbon atoms or An alkoxy alkoxy group etc. can be mentioned.

The squarylium compound represented by the general formula [I] of the present invention is an azulene compound which may have a substituent (represented by "A" in the general formula [I]) and a general formula [II]. Benzene derivative shown (Wherein R ¹ , R ² , R ³ and R ⁴ have the same meanings as those in the above general formula [I]) and the formula [III]. Shown 3,4-dihydroxy-3-cyclobutene-1,2-
It can be easily produced by reacting with dione.

Further, as the solvent used in the production reaction,
For example, alcohols such as methanol, ethanol, 1-propanol, isopropanol, 1-butanol, 2-butanol, amyl alcohol, 1-hexanol, cyclohexanol, 1-heptanol, 1-nonanol, or these alcohols and benzene, toluene. ,
Examples thereof include a mixed solvent with an aromatic hydrocarbon solvent such as xylene and chlorobenzene. The reaction temperature in the production reaction is usually 70 to 150 ° C., preferably 90.
Temperatures of ~ 120 ° C are used.

The squarylium compound represented by the general formula [I] of the present invention is soluble in a wide variety of solvents.

For example, chloroform, dichloromethane, dichloroethane, dibromoethane, halogen-containing hydrocarbon solvents such as tetrachloroethane, diethyl ether, dioxane, tetrahydrofuran, ether solvents such as dimethoxyethane, ethyl acetate, ester solvents such as ethylcellosolve acetate, Ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, acetamide, N, N
-Amidic solvents such as dimethylacetamide and N-methylpyrrolidone, alcoholic solvents such as methanol, ethanol and methylcellosolve, aromatic hydrocarbon solvents such as benzene, toluene, xylene and chlorobenzene, and solvents such as dimethyl sulfoxide. It is soluble.

Examples of the substrate material of the optical recording material of the present invention include glass and plastics. Plastics are preferable in terms of safety and lightness. Examples of the plastics include acrylic resin, methacrylic resin, polycarbonate resin, vinyl chloride resin, vinyl acetate resin, polyester resin, polyethylene resin, polypropylene resin, polyamide resin polystyrene resin, and epoxy resin.

Examples of the method for forming the recording layer include known methods such as a method of vacuum deposition on a substrate, a method of coating with a resin solution and a method of dissolving in a solvent and coating or dipping. In particular, the compound of the present invention has good solubility in a solvent and is suitable for a coating method.

The film formation by coating is obtained by, for example, dissolving the compound represented by the general formula [I] in a solvent, optionally mixing it with a binder, and spin-coating. Examples of the binder include polyimide resin, polyamide resin, polystyrene resin, acrylic resin, polyester resin, polycarbonate resin, and cellulosic resin.

At that time, it is desirable that the ratio of the squarylium compound as a light absorbing substance to the resin is 10 wt% or more.

In the case of film formation by the spinner method, the rotation speed is preferably 500 to 5000 rpm, and after spin coating, treatment such as heating or applying to solvent vapor may be performed depending on the case. In order to improve the stability and light resistance of the recording material, a transition metal chelate compound (eg, acetylacetonate chelate, bisphenyldithiol, salicylaldehyde oxime, bisdithio-α) is used as a singlet oxygen quencher.
-Diketone, etc.) or a tertiary amine compound may be contained. Further, other dyes can be used in combination as required. Other types of squarylium dyes may be used, or phthalocyanine dyes, naphthoquinone dyes, anthraquinone dyes, triarylmethane dyes, azo dyes, cyanine dyes, indophenol dyes, croconium dyes, naphtholactam dyes, and other dyes. But it's okay.

Doctor blade method, cast method, spinner method, dipping method, especially as a coating solvent when forming the recording layer by a coating method such as spinner method, the boiling point of bromoform, dibromoethane, ethyl cellosolve, xylene, chlorobenzene, cyclohexanone, etc. Those having a temperature of 120 to 160 ° C. are preferably used.

The thickness of the recording layer of the optical recording material of the present invention is usually 100Å
˜5 μm, preferably 500 Å to 3 μm.

The recording layer of the optical recording medium of the present invention may be provided on both sides of the substrate, or may be provided on only one side.

Recording on the recording medium obtained as described above is performed by irradiating a recording layer provided on both sides or one side of the substrate with a laser beam focused to about 1 μm, preferably a semiconductor laser beam. In the portion irradiated with laser light, thermal deformation of the recording layer such as decomposition, evaporation, and melting occurs due to absorption of laser energy.

The recorded information is reproduced by using a laser beam to read the difference in reflectance between a portion where thermal deformation has occurred and a portion where thermal deformation has not occurred.

As the light source, various lasers such as He-Ne laser, Ar laser, and semiconductor laser can be used, but the semiconductor laser is particularly preferable in terms of cost and size.

As a semiconductor laser, the central wavelength is 830 nm and the central wavelength is 780.
nm and shorter wavelength lasers can be used.

EXAMPLES Next, the present invention will be described more specifically with reference to Examples.
The invention is not limited by these examples.

Example 1 3,4-Dihydroxy-3-cyclobutene-1,2-dione 15
30 ml of n-butyl alcohol was added to mg and heated to about 100 ° C. to dissolve.

To this solution, 260 mg of 1,4-dimethyl-7-iso-propylazulene (guaiazulene), m-benzoylamino-N, N
-Add 310 mg of dimethylaniline and 15 ml of toluene, add 1
While water generated at 05 to 110 ° C was distilled off azeotropically, the reaction was carried out by stirring for about 20 minutes. After cooling, the reaction solution was purified by column chromatography to give the following structural formula: A compound represented by The compound had a melting point of 186-187 ° C. The maximum absorption wavelength of the absorption spectrum of this compound in chloroform was 724 nm.

The squarylium compound of this example was dissolved in 1,1,2,2-tetrachloroethane, and spin-coated (rotation speed 1500 rp
m) is applied on the methacrylic resin substrate, and the film thickness is 900
A thin film of Å was obtained. The maximum absorption wavelength of the thin film is 775 nm,
The peak was wide.

A semiconductor laser beam with a central wavelength of 830 nm is output to this thin film 4
Irradiation with a beam diameter of about 1 μm at mW resulted in the formation of extremely clear holes (bits) with a width of about 1 μm and a bit length of about 2 μm. The carrier level / noise level (C / N) ratio is 5
It was 2 dB.

The light resistance and the resistance to reproduction light were also good.

Example 2 In Example 1, m-acetylamino-N, N-diethylaniline was used in place of m-benzoylamino-N, N-dimethylaniline, and the following structural formula is shown according to the method of Example 1. The compound was obtained.

The maximum absorption wavelength of the absorption spectrum of this compound in chloroform was 725 nm.

This compound was applied in the same manner as in Example 1 to obtain a thin film of 880Å. The maximum absorption wavelength of the thin film was 776 nm. When the C / N ratio was measured in the same manner as in Example 1, it was 52 dB. It was also excellent in light resistance and resistance to reproducing light.

Example 3 The squarylium compound shown in Table 1 synthesized according to Example 1 was formed into a film on a methacrylic resin plate under the same conditions as in Example 1.

Table 1 shows the maximum absorption wavelength of the squarylium compounds of the present invention in chloroform and the maximum absorption wavelength of the thin film.

When the obtained coating film was irradiated with a semiconductor laser beam having a central wavelength of 830 nm, a hole (bit) having an extremely clear contour was formed. The reflectance was high and the C / N ratio was excellent. Also,
The light resistance and the resistance to reproduction light were also good.

EFFECTS OF THE INVENTION Since the squarylium compound of the present invention has high solubility in various organic solvents, it can be coated by coating when producing an optical recording material. Further, since the compound has a high reflectance, a good contrast, and excellent light resistance and reproduction light resistance, it is possible to obtain an excellent optical recording material by incorporating the compound as a light absorbing substance into the recording layer. You can

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical display location C07C 233/80 271/28 307/02 C07D 295/12 307/52 G11B 7/24 A 7215-5D

Claims (2)

[Claims] 1. A general formula [I] [Wherein R ¹ ′, R ² ′, R ³ ′, R ⁴ ′ and R ⁵ ′ are each a hydrogen atom; an alkyl group having 1 to 25 carbon atoms; an alkoxy group having 1 to 25 carbon atoms; ~ 25 alkoxyalkoxy group; C3-25 alkoxyalkoxyalkoxy group; C1-8 alkyl group, C1-8 alkoxy group or benzyl group which may be substituted with a halogen atom, phenethyl group Or a phenylpropyl group; an alkyl group having 1 to 8 carbon atoms, an alkoxy group having 1 to 8 carbon atoms, or a phenyl group which may be substituted with a halogen atom; or a halogen atom. R ¹ ′ and R ² ′ are linked to each other to form a benzene ring, a cyclohexene ring, a cyclopentene ring, a dihydrothiophene ring, a tetrahydropyridine ring, a furan ring,
It may form a dihydrofuran ring, a pyrrole ring, a dihydropyrrole ring or a thiazole ring. R ¹ and R ² are each substituted with a hydrogen atom; a hydroxyl group, a cyano group, an alkoxy group having 1 to 15 carbon atoms, an alkoxyalkoxy group having 2 to 15 carbon atoms, a halogen atom, a phenylcarbonyloxy group, or a halogen atom. Optionally a phenoxy group, an aryloxy group, a tetrahydrofuryl group,
Substituted with amino group, alkylamino group, dialkylamino group, trialkylamino group, alkoxycarbonyl group, cyclohexyloxycarbonyl group, alkylcarbonyloxy group, phenoxycarbonyl group, alkoxycarbonyloxy group, cyclohexylcarbonyloxy group or phenoxycarbonyloxy group An optionally substituted alkyl group having 1 to 25 carbon atoms; a methyl group, an allyl group optionally substituted with a halogen atom or a phenyl group;
An alkyl group having 9 carbon atoms, an alkoxy group having 1 to 9 carbon atoms, a benzyl group which may be substituted with a halogen atom or a nitro group, a phenethyl group, a phenylpropyl group; or a carbon number 1
It represents an alkyl group having from 9 to 9, an alkoxy group having from 1 to 9 carbon atoms, a phenyl group which may be substituted with a halogen atom or a nitro group, or a naphthyl group. R ¹ and R ² may be linked to each other to form a pyrrolidine ring, a piperidine ring or a morpholine ring together with a nitrogen atom. R ³ is Or —SO ₂ R ⁶ (R ⁵ and R ⁶ are each a hydroxyl group, a cyano group, an alkoxy group having 1 to 15 carbon atoms, an alkoxyalkoxy group having 1 to 15 carbon atoms, a halogen atom, a phenylcarbonyloxy group, an allyloxy group. A phenoxy group optionally substituted with a halogen atom, a tetrahydrofuryl group,
Substituted with amino group, alkylamino group, dialkylamino group, trialkylamino group, alkoxycarbonyl group, cyclohexyloxycarbonyl group, alkylcarbonyloxy group, phenoxycarbonyl group, alkoxycarbonyloxy group, cyclohexylcarbonyloxy group or phenoxycarbonyloxy group Optionally substituted alkyl group having 1 to 25 carbon atoms; alkoxy group having 1 to 8 carbon atoms;
Vinyl group optionally substituted by methyl group or phenyl group; cyclohexyl group; cyclohexyloxy group; allyl group optionally substituted by methyl group, halogen atom or phenyl group; alkyl group having 1 to 9 carbon atoms, carbon Number 1
9 alkoxy group, benzyl group optionally substituted with halogen atom or nitro group, phenethyl group or phenylpropyl group; alkyl group having 1 to 9 carbon atoms, 1 to 9 carbon atoms
The phenyl group or naphthyl group which may be substituted with an alkoxy group, a halogen atom or a nitro group; or a phenoxy group. ) Is represented. R ⁴ represents a hydrogen atom; or an alkoxy group having 1 to 8 carbon atoms or an alkoxy group having 1 to 8 carbon atoms which may be substituted with an alkoxyalkoxy group. ] The squarylium compound represented by these. 2. A general formula [I] [Wherein R ¹ ′, R ² ′, R ³ ′, R ⁴ ′ and R ⁵ ′ are each a hydrogen atom; an alkyl group having 1 to 25 carbon atoms; an alkoxy group having 1 to 25 carbon atoms; ~ 25 alkoxyalkoxy group; C3-25 alkoxyalkoxyalkoxy group; C1-8 alkyl group, C1-8 alkoxy group or benzyl group which may be substituted with a halogen atom, phenethyl group Or a phenylpropyl group; an alkyl group having 1 to 8 carbon atoms, an alkoxy group having 1 to 8 carbon atoms, or a phenyl group which may be substituted with a halogen atom; or a halogen atom. R ¹ ′ and R ² ′ are linked to each other to form a benzene ring, a cyclohexene ring, a cyclopentene ring, a dihydrothiophene ring, a tetrahydropyridine ring, a furan ring,
It may form a dihydrofuran ring, a pyrrole ring, a dihydropyrrole ring or a thiazole ring. R ¹ and R ² are each substituted with a hydrogen atom; a hydroxyl group, a cyano group, an alkoxy group having 1 to 15 carbon atoms, an alkoxyalkoxy group having 2 to 15 carbon atoms, a halogen atom, a phenylcarbonyloxy group, or a halogen atom. Optionally a phenoxy group, an aryloxy group, a tetrahydrofuryl group,
Substituted with amino group, alkylamino group, dialkylamino group, trialkylamino group, alkoxycarbonyl group, cyclohexyloxycarbonyl group, alkylcarbonyloxy group, phenoxycarbonyl group, alkoxycarbonyloxy group, cyclohexylcarbonyloxy group or phenoxycarbonyloxy group An optionally substituted alkyl group having 1 to 25 carbon atoms; a methyl group, an allyl group optionally substituted with a halogen atom or a phenyl group;
An alkyl group having 9 carbon atoms, an alkoxy group having 1 to 9 carbon atoms, a benzyl group which may be substituted with a halogen atom or a nitro group, a phenethyl group, a phenylpropyl group; or a carbon number 1
It represents an alkyl group having from 9 to 9, an alkoxy group having from 1 to 9 carbon atoms, a phenyl group which may be substituted with a halogen atom or a nitro group, or a naphthyl group. R ¹ and R ² may be linked to each other to form a pyrrolidine ring, a piperidine ring or a morpholine ring together with a nitrogen atom. R ³ is Or —SO ₂ R ⁶ (R ⁵ and R ⁶ are each a hydroxyl group, a cyano group, an alkoxy group having 1 to 15 carbon atoms, an alkoxyalkoxy group having 1 to 15 carbon atoms, a halogen atom, a phenylcarbonyloxy group, an allyloxy group. A phenoxy group optionally substituted with a halogen atom, a tetrahydrofuryl group,
Substituted with amino group, alkylamino group, dialkylamino group, trialkylamino group, alkoxycarbonyl group, cyclohexyloxycarbonyl group, alkylcarbonyloxy group, phenoxycarbonyl group, alkoxycarbonyloxy group, cyclohexylcarbonyloxy group or phenoxycarbonyloxy group Optionally substituted alkyl group having 1 to 25 carbon atoms; alkoxy group having 1 to 8 carbon atoms;
Vinyl group optionally substituted by methyl group or phenyl group; cyclohexyl group; cyclohexyloxy group; allyl group optionally substituted by methyl group, halogen atom or phenyl group; alkyl group having 1 to 9 carbon atoms, carbon Number 1
9 alkoxy group, benzyl group optionally substituted with halogen atom or nitro group, phenethyl group or phenylpropyl group; alkyl group having 1 to 9 carbon atoms, 1 to 9 carbon atoms
The phenyl group or naphthyl group which may be substituted with an alkoxy group, a halogen atom or a nitro group; or a phenoxy group. ) Is represented. R ⁴ represents a hydrogen atom; or an alkoxy group having 1 to 8 carbon atoms or an alkoxy group having 1 to 8 carbon atoms which may be substituted with an alkoxyalkoxy group. ] An optical recording material comprising a recording layer containing a squarylium compound represented by: