JP2006160984A - Squalium compound and optical recording medium containing squalium compound - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a new squalium compound useful such as for an optical recording medium and an optical recording medium containing the squalium compound. <P>SOLUTION: The squalium compound is shown by general formula (1) (wherein R<SB>1</SB>and R<SB>2</SB>each represents H, a halogen, a hydroxy group and an alkoxy group, R<SB>2</SB>to R<SB>5</SB>and R<SB>8</SB>to R<SB>11</SB>each represents H, a halogen, a hydroxy group and an alkyl group, R<SB>6</SB>and R<SB>7</SB>each represent H, an alkyl group and an aromatic ring, and R<SB>13</SB>represents an alkylene group) and the optical recording medium contains these compounds in a recording layer. The squalium compound shown by general formula (1) has a maximum absorption peak wave length near 405 nm and has a suitable molar absorptivity, and is useful as an organic compound dye for the optical recording medium using a blue laser light. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a novel squarylium compound and an optical recording medium containing the squarylium.

Conventionally, as an optical recording medium, a magneto-optical recording medium, a phase change recording medium, a chalcogen oxide optical recording medium, an organic dye-based optical recording medium, and the like have been proposed. It is excellent in that it is inexpensive and the manufacturing process is easy.
CD-R (CD-Recordable), which is the mainstream of current optical recording media, has a recording capacity of about 0.65 GB, and the demand for higher-density and large-capacity optical recording media as the amount of information increases dramatically. Is growing.

In such an optical recording medium, by using a laser beam with a short wavelength for recording / reproducing information, the beam spot of the laser beam during recording / reproducing can be reduced, and high-density optical recording becomes possible. In recent years, development of semiconductor lasers having shorter oscillation wavelengths has been promoted.
A red semiconductor laser with an oscillation wavelength (680 nm, 650 nm, 635 nm, etc.) shorter than the wavelength of the laser beam (780 nm) used in the current CD-R has been put into practical use, and this enables high-density, large-capacity recording. The realized digital versatile disc (DVD) and the DVD-R, which is a recordable optical recording medium of the same standard, have already been put into practical use.

In order to further advance the above densification in these various devices, development of a blue semiconductor laser, which is a laser having a shorter oscillation wavelength (the oscillation wavelength of a blue semiconductor is 350 nm to 530 nm), is also progressing rapidly. Furthermore, the wavelength used in next-generation optical recording media is 405 nm, and by using an organic compound that has an absorption peak near this wavelength, for example, 405 ± 50 nm, and can be used in the recording layer of the optical recording medium, higher density recording / recording can be achieved. Expected to be reproducible.
As the organic compound, squarylium compounds have been proposed (Japanese Patent Application Laid-Open Nos. 2004-264805 and 2004-258514). These squarylium compounds are 2,4-dihydroxy types in which the 2- and 4-positions of the 4-membered ring are hydroxylated, and the 1- and 3-positions are substituted with aromatic rings.

On the other hand, when information is recorded on an optical recording medium, the recording layer is irradiated with high-energy laser light to decompose and generate heat in the organic compound (dye) in the recording layer, and physical changes or By causing a chemical change, pits corresponding to the recorded information are formed. When reproducing information, the recording layer is irradiated with low-energy laser light, and the information corresponding to the pit is reproduced by detecting that the reflectance of the laser light is different between the part where the pit is formed and the other part. To do.
In order to satisfactorily record and reproduce such information, it is desirable that the organic compound in the recording layer has a high molar extinction coefficient. That is, if the molar extinction coefficient is too low, it becomes difficult to form pits with sufficient sensitivity.

The aforementioned 2,4-dihydroxy type squarylium compound has a main absorption peak at 530 to 600 nm, and is unsuitable as an optical recording medium for the next generation blue semiconductor laser. Furthermore, since these compounds have complex aromatic rings at the 2-position and 4-position of the 4-membered ring, the synthesis takes time and the synthesis cost tends to increase.
The present invention provides a novel squarylium compound and an optical recording medium containing the squarylium, which is an organic compound having an appropriate absorption peak and high molar extinction coefficient for recording and reproducing information by a next-generation blue semiconductor laser. For the purpose.

The present invention is first represented by the following general formula (1) (in the general formula (1), R ₁ and R ₁₂ are each independently a halogen atom, a hydroxyl group, a substituted or unsubstituted alkoxy group, a substituted or Represents an unsubstituted phenoxy group, R _{2 to} R ₅ and R _{8 to} R ₁₁ each independently represent a hydrogen atom, a halogen atom, a hydroxyl group, or a substituted or unsubstituted alkyl group, and R ₆ and R ₇ each represent Independently represents a hydrogen atom, a substituted or unsubstituted alkyl group or a substituted or unsubstituted aromatic ring, and R ₁₃ represents an optionally substituted alkylene group having 1 to 5 carbon atoms). Second, represented by the following general formula (2) (in the general formula (2), R ₂₁ , R ₂₂ and R ₂₃ are each independently a halogen atom, hydroxyl group, substituted or unsubstituted) An alkoxy group or substituted or unsubstituted phenoxy R _{24 to} R ₃₅ each independently represents a hydrogen atom, a halogen atom, a hydroxyl group or a substituted or unsubstituted alkyl group, and R _{36 to} R ₃₈ each independently represents a hydrogen atom, a substituted or unsubstituted group. R ₃₉ represents —CR ₄₀ (R ₄₀ represents a hydrogen atom, a halogen, a hydroxyl group, a substituted or unsubstituted alkoxy group, or a substituted or unsubstituted alkyl group). Or a substituted or unsubstituted trivalent hydrocarbon group having 2 to 8 carbon atoms). Thirdly, it is represented by the following general formula (3) (general formula (3 R _{51 to} R ₅₄ each independently represents a halogen atom, a hydroxyl group, a substituted or unsubstituted alkoxy group or a substituted or unsubstituted phenoxy group, and R _{55 to} R ₇₀ each independently represents a hydrogen atom or a halogen atom. Atom, hydroxyl group or Represents a substituted or unsubstituted alkyl group, R _{71 to} R ₇₄ each independently represents a hydrogen atom, a substituted or unsubstituted alkyl group or a substituted or unsubstituted aromatic ring, and R ₇₅ represents substituted or unsubstituted. And an optical recording medium comprising a substrate and a recording layer formed on the substrate. In an optical recording medium including a substrate and a recording layer formed on the substrate, the recording layer contains at least one of squarylium compounds represented by the general formulas (1) to (3). An optical recording medium characterized by the above.

The present invention will be described in detail below.
The squarylium compound of the present invention is an organic compound represented by any one of the general formulas (1) to (3). The compounds of the general formulas (1) to (3) contain two, three and four 1,2-dione type four-membered rings, which are characteristic of the squarylium compound, in order.
In each of the above general formulas, R ₁ , R ₁₂ , R ₂₁ , R ₂₂ , R ₂₃ and R _{51 to} R ₅₄ bonded to the 4-membered ring are a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, etc. A halogen atom; a hydroxyl group; or an unsubstituted alkoxy group having 1 to 6 carbon atoms such as a methoxy group, an ethoxy group, an n-propoxy group, an isopropoxy group, an n-butoxy group, a sec-butoxy group, and a tert-butoxy group; A substituted alkoxy group such as a group or a benzyloxy group; an atom or substituent selected from a substituted or unsubstituted phenoxy group such as a phenoxy group or a 4-chlorophenoxy group;

In the above general formulas, R _{2 to} R ₅ , R _{8 to} R ₁₁ , R _{24 to} R _35, and R _{55 to} R ₇₀ bonded to the benzene ring may be the same or different and are a hydrogen atom; a chlorine atom , Halogen atoms such as bromine atom and iodine atom; hydroxyl group; carbon number 1 such as methyl group, ethyl group, propyl group, isopropyl group, n-butyl group, sec-butyl group, tert-butyl group, n-heptyl group -8 linear or branched unsubstituted alkyl group; a substituted alkyl group such as chloromethyl group; and a cycloalkyl group having 5 to 6 carbon atoms such as cyclopentyl group and cyclohexyl group.
In the above general formulas, R ₆ , R ₇ , R _{36 to} R ₃₈ and R _{71 to} R ₇₄ bonded to nitrogen may be the same or different, and are hydrogen atoms; methyl groups, ethyl groups, propyl groups , An isopropyl group, an n-butyl group, a sec-butyl group, a tert-butyl group, an n-heptyl group, etc., a linear or branched unsubstituted alkyl group having 1 to 8 carbon atoms; a chloromethyl group, a fluoromethyl group, a bromomethyl Group, trifluoromethyl group, 2,2,2-trifluoroethyl group, halogen (especially fluorine) substituted alkyl group such as 3,3,3-trifluoropropyl group and hydroxy substituted alkyl group such as hydroxymethyl group, etc. Various substituted alkyl groups to be included; selected from cycloalkyl groups having 5 to 6 carbon atoms such as cyclopentyl group and cyclohexyl group.
R ₁₃ is an alkylene group having 1 to 5 carbon atoms which may have branches such as —CH ₂ CH ₂ CH ₂ CH ₂ — and —CH ₂ CH (CH ₃ ) CH ₂ —, and R ₃₉ Is —CR ₄₀ (R ₄₀ represents a hydrogen atom, a halogen, a hydroxyl group, a substituted or unsubstituted alkoxy group, a substituted or unsubstituted alkyl group), or a substituted or unsubstituted trivalent carbon atom having 2 to 8 carbon atoms. Represents a hydrogen group, and R ₇₅ represents a substituted or unsubstituted tetravalent hydrocarbon group having 2 to 8 carbon atoms.

The squarylium compounds of the general formulas (1) to (3) are generally yellow plate crystals, insoluble in water, hardly soluble in hexane, and soluble in many other organic solvents.
Preferred specific examples of the squarylium compounds of the general formulas (1) to (3) include the following compounds, and the compounds of the present invention are not limited to these. Of the following compounds, compounds (1) to (8) are squarylium dimers, compounds (9) to (14) are squarylium trimers, and compounds (15) to (20) are squarylium tetramers.

The synthesis of the squarylium dimer of the general formula (1) (for example, R ₁ is OH, R _{2 to} R ₁₂ are hydrogen, and R ₁₃ is linear —CH ₂ CH ₂ CH ₂ CH ₂ —) is as follows, for example. Do it.
1,4-dibromobutane and aniline (theoretical amount of 1: 2 molar ratio) are reacted to form de-HBr with the former C-Br and the latter N—H, and the 1- and 4-positions are anilinolated. Synthesized butane. Subsequently, 2-fold moles of 3,4-dichlorocyclo-3-butene-1,2-dione are reacted with the substituted butane to react the aniline para-position hydrogen with the 3,4-dichlorocyclo-3-butene-1 described above. , 2-dione is dehydrochlorinated and further hydrolyzed to obtain the target compound.
Similarly, in the case of the squarylium trimer of the general formula (2), a tribromo-substituted alkane is reacted with aniline (a molar ratio of 1: 3 in theory) to obtain an alkane substituted with 3 equivalents of aniline. Dehydrochlorination between the para-position hydrogen of each anilino group and 3,4-dichlorocyclo-3-butene-1,2-dione, followed by further hydrolysis yields the target compound.
In the case of the squarylium tetramer of the general formula (3), it can be similarly synthesized using a tetrabromo-substituted alkane as a starting material.

In the case of the synthesis method, 2 to 4 molecules of hydroxycyclo-3-butene-1,2-dione substituted aniline bonded to the central alkane are the same molecule. Each substituted aniline of the squarylium compound of the present invention may have a different substituent. In this case, the target compound may be synthesized by introducing an appropriate protective group.
The synthesis of the squarylium compounds of the general formulas (1) to (3) in which each substituted aniline has the same substituent can be achieved by simply adjusting the number of substituted halogens of the halogen-substituted alkane as a raw material by 2 to 4 Alternatively, tetramers can be easily synthesized.

By the way, the present inventors have studied a squarylium compound conventionally used in a recording layer of an optical recording medium, and searched for a compound having an absorption peak near 405 nm desirable for a next-generation blue semiconductor laser. It was not obtained. That is, it was tried to measure the absorption peak of various squarylium compounds by changing the type of substituent and the substitution position, but all of them were about 530 to 600 nm as described above, and a compound having an absorption peak near 405 nm was not obtained. .
The inventors presumed this reason as follows. That is, the conventional squarylium compound for optical recording media has a 2,4-dihydroxy type squarylium four-membered ring structure, and the squarylium compound having a 2,4-dihydroxy type four-membered ring structure is not limited to the type of substituent or the substitution. It is impossible to change the wavelength of the absorption peak significantly by changing the position.

  Therefore, the present inventors. The structure of the 4-membered ring of the squarylium compound for optical recording media is converted from the conventional 2,4-dihydroxy type to the 1,2 dione type, and the absorption peak of the resulting 1,2 dione type squarylium compound is the next generation. The present inventors found that it exists in the vicinity of 405 nm, which is desirable for a blue semiconductor laser, and filed an application regarding an optical recording medium containing a single squarylium compound having the 4-membered ring structure (Japanese Patent Application No. 2004-301406).

The squarylium compound having a single four-membered ring structure has a maximum peak absorption wavelength (λ _max ) of 360 to 435 nm and a molar extinction coefficient of 1 × 10 ⁴ to 1 × 10 ^5. Therefore, it is suitable for clear and reliable pit formation.
The present inventors diligently studied the applicability of the above-described novel squarylium compounds of the general formulas (1) to (3) in an optical recording medium, and reached the optical recording medium of the present invention.
The optical recording medium of the present invention includes a base material and a recording layer formed on the base material, and the recording layer contains at least a part of the squarylium compound of the general formulas (1) to (3). It is characterized by.

The squarylium compounds of the general formulas (1) to (3) have a maximum peak absorption wavelength (λ _max ) of 350 to 450 nm, preferably 355 to 420 nm, more preferably 365 to 410 nm. In other words, most of the squarylium compounds have a maximum peak absorption wavelength at ± 30 nm around the maximum peak absorption wavelength of 405 nm desirable for the next-generation blue semiconductor laser. Although this absorption wavelength partially overlaps with the absorption wavelength of the single squalylium compound having the four-membered ring structure, it has a different range and can be used properly depending on the application.
Further, the squarylium compounds of the general formulas (1) to (3) usually have a molar extinction coefficient of 5 × 10 ^{4 to} 20 × 10 ⁵ , and this molar extinction coefficient is suitable for clear and reliable pit formation. .
Each squarylium compound is easily dissolved in a solvent, and a recording layer containing the squarylium compound can be easily and reliably formed on the substrate.

The squarylium compounds of the general formulas (1) to (3) can be synthesized by the method as described above. According to this synthesis method, the skeleton of the squarylium compound is reacted with aniline or a derivative thereof and the aforementioned 1,2-dione compound. Can be formed in a one-step reaction. Therefore, it can be seen that the target compound can be obtained with a simpler synthesis route, that is, with fewer processes, as compared with other squarylium compounds for blue lasers used in conventional optical recording media. However, the squarylium compounds of the general formulas (1) to (3) may be synthesized through other routes.
The recording layer may contain the squarylium compounds of the general formulas (1) to (3) alone or may be a mixture of a plurality of compounds. Furthermore, in addition to the squarylium compound, other dyes such as azo dyes, phthalocyanine dyes, and cyanine dyes may be contained.

The optical information recording medium of the present invention has a configuration in which a recording layer, a light reflecting layer, and a protective layer are arranged in this order on a disk-like substrate on which a pregroup having a constant track pitch is formed, or a light reflecting layer and a recording layer on the substrate. A structure having a layer and a protective layer in this order is preferable. In addition, two laminates in which a recording layer and a light reflecting layer are provided on a transparent disk-like substrate on which a pregroup having a constant track pitch is formed are bonded so that each recording layer is inside. The configuration is also preferable. Hereinafter, the optical recording medium of the present invention will be described using the medium having this structure as an example.
The material of the substrate in the optical recording medium of the present invention can be arbitrarily selected from various materials used as a substrate of a conventional optical information recording medium. Examples of the substrate material include glass, polycarbonate resin, acrylic resin such as polymethyl methacrylate, polyvinyl chloride resin such as polyvinyl chloride resin and vinyl chloride copolymer, epoxy resin, amorphous polyolefin resin, and polyester resin. Among these materials, injection molded polycarbonate is preferable from the viewpoints of moisture resistance, dimensional stability, and price. A resin substrate or a resin layer may be provided in contact with the recording layer, and guide grooves or pits for recording / reproducing light may be provided on the resin substrate or resin layer. When the guide groove has a spiral shape, the groove pitch is preferably about 0.5 to 1.2 μm.

The recording layer is formed by a generally used thin film forming method such as a vapor phase method such as a vacuum deposition method, a sputtering method, or a CVD method, a liquid phase method such as a doctor blade method, a cast method, a spin coating method, or an immersion method. However, the spin coating method is preferable from the viewpoint of mass productivity and cost.
The solvent for the liquid phase method is not particularly limited as long as it does not attack the substrate. For example, esters such as butyl acetate, ethyl lactate and cellosolve acetate; ketones such as methyl ethyl ketone, cyclohexanone and methyl isobutyl ketone; chlorinated hydrocarbons such as dichloromethane, 1,2-dichloroethane and chloroform; amides such as dimethylformamide; Hydrocarbons; ethers such as dibutyl ether, diethyl ether, tetrahydrofuran, dioxane; alcohols such as ethanol, n-propanol, isopropanol, n-butanol, diacetone alcohol; 2,2,3,3-tetrafluoropropanol, etc. Fluorine-based solvents; glycols such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, propylene glycol monomethyl ether And the like ethers. The above solvents can be used alone or in combination of two or more in consideration of the solubility of the compound used.

The thickness of the recording layer is generally in the range of 20 to 500 nm, preferably in the range of 30 to 300 nm, and more preferably in the range of 50 to 150 nm.
The recording layer uses a singlet oxygen quencher to improve the light resistance of the recording layer. Examples of the singlet quencher include transition metal chelate complexes such as acetylacetonate chelate, bisphenyldithiol, saltylaldehyde oxime, and bisdithio-α-diketone, aromatic nitroso compounds, aminium compounds, iminium compounds, and bisiminium compounds. The amount of these components used is usually in the range of 0.1 to 50% by weight, preferably in the range of 3 to 40% by weight, based on the amount of the squarylium compound.

The light reflecting layer described above may be formed on the recording layer, and the thickness thereof is preferably 50 to 300 nm. As a material of the light reflecting layer, a material having a sufficiently high reflectance at the wavelength of the reproduction light, for example, Au, Al, Ag, Cu, Ti, Cr, Ni, Pt, Ta, and Pd metal alone or in an alloy is used. It is possible to use. Among these, Au, Al, and Ag have high reflectivity and are suitable as the material for the reflective layer. The reflective layer can be formed on the substrate or the recording layer, for example, by vapor deposition, sputtering or ion plating of the light reflective material. The layer thickness of the light reflecting layer is generally in the range of 10 to 300 nm, and preferably in the range of 50 to 200 nm.
The material of the above-described protective layer that can be formed on the reflective layer is not particularly limited as long as it protects the reflective layer from external force. Examples of the organic material include thermoplastic resins, thermosetting resins, electron beam curable resins, and UV curable resins. Examples of inorganic substances include SiO ₂ , Si ₃ N ₄ , SnO _{2 and the} like.

  A thermoplastic resin, a thermosetting resin, or the like can be formed by dissolving in an appropriate solvent, applying a coating solution, and drying. The UV curable resin can be formed by preparing a coating solution as it is or by dissolving in a suitable solvent, and then applying the coating solution and curing it by irradiating with UV light. As the UV curable resin, for example, acrylate resins such as urethane acrylate, epoxy acrylate, and polyester acrylate can be used. These materials may be used alone or in combination, and may be used not only as a single layer but also as a multilayer film. As a method for forming the protective layer, a coating method such as a spin coating method and a casting method, a sputtering method, a chemical vapor deposition method, and the like are used as in the recording layer. Among these, a spin coating method is preferable. The thickness of the protective layer is generally in the range of 0.1 to 100 μm, but is preferably 3 to 30 μm in the present invention.

The laser beam used for the optical recording medium of the present invention is preferably as short as possible for high-density recording, but is preferably a blue-violet semiconductor laser beam of 350 to 430 nm, and more preferably oscillation of 390 to 415 nm. Blue-violet semiconductor laser light having a wavelength.
Recording on the optical recording medium of the present invention obtained as described above is performed by irradiating the recording layer provided on both sides or one side of the substrate with laser light focused to about 0.4 to 0.6 μm. In the portion irradiated with the laser beam, thermal deformation of the recording layer such as decomposition, heat generation and dissolution due to absorption of laser beam energy occurs, and the optical characteristics change. Reproduction of recorded information is performed by reading the difference in reflectance between the portion where the change in optical characteristics has occurred and the portion where the change has not occurred, with laser light.

As explained above, the squarylium compounds of the general formulas (1) to (3) are novel compounds.
These new squarylium compounds are different from the squarylium compounds conventionally used for optical recording media, and have a maximum peak absorption wavelength of around 405 nm (mostly 405 nm ± 30 nm, most of which are desirable for next-generation blue semiconductor lasers) Is present at ± 10 nm). And has a moderate molar extinction coefficient.
Therefore, the optical recording medium containing the squarylium compound having the above structure in the recording layer can be preferably used for a blue semiconductor laser, and high-density recording and reproduction, which are features for a blue semiconductor laser, can be reliably realized.

  Hereinafter, the synthesis of the squarylium compound of the present invention and the optical recording medium containing the obtained squarylium compound will be described more specifically with reference to examples, but the present invention is not limited thereto.

Example 1 Synthesis of 1,4-butenedi (N, N′-dimethylaniline) (Compound A)
N-methylaniline (5.40 g, 50 mmol) and 1,4-dibromobutane (5.40 g, 25 mmol) are placed in a three-necked eggplant flask equipped with a condenser, and toluene and potassium carbonate are added. did. After completion of the reaction, the solvent was removed under reduced pressure by filtration under reduced pressure. Purification by column chromatography (silica gel Wakogel C-300, developing solvent: toluene) gave Compound A (3.62 g, 13.5 mmol).

Yield 54%; LC-MS (m / z) 268 ([M ⁺ ])

  In each example, mass spectrometry (LC-MS) was measured by a Waters Alliance LC-MS system. Elemental analysis was performed by YANACO-CHN-CORDER MT-3 using acetanilide as a standard substance. The UV-Vis spectrum was measured by SHIMADZU UV-3100.

[Example 2] Synthesis of squarylium dimer (chloride, compound B) Under a nitrogen atmosphere, a three-necked eggplant flask equipped with a condenser tube was subjected to 3,4-dichlorocyclo-3-butene-1,2-dione. (4.08 g, 27 mmol) and Compound A (3.62 g, 13.5 mmol) were added, dehydrated toluene (30 ml) was added thereto, and the mixture was stirred at room temperature for 24 hours. After completion of the reaction, the reaction mixture was washed with distilled water and sodium hydrogen carbonate, and the solvent was distilled off under reduced pressure. The solid was purified by column chromatography (silica gel (Wakogel C-300, developing solvent: toluene)) to obtain a yellow solid (Compound B, 3.22 g, 6.5 mmol).

Yield 48%; LC-MS (m / z) 496 ([M ⁺ ]), elemental analysis: calculated value; C ₂₆ H ₂₂ NCl ₂ N ₂ O ₄ ; C62.79, H4.46, N5.63 ( %), Analysis value: C62.66, H4.37, N5.73 (%)

[Example 3] Synthesis of squarylium dimer (hydroxylated product, compound C) Compound B (3.00 g, 6.0 mmol) was placed in a three-necked eggplant flask equipped with a condenser, acetic acid (10 ml) and distilled water (10 ml). Was added. After refluxing at 90 ° C. for 6 hours, the mixture was cooled to room temperature, collected by filtration under reduced pressure, and dried under reduced pressure to obtain a yellow solid (compound C, 2.50 g, 5.4 mmol).

Yield 90%; LC-MS (m / z) 460 ([M ⁺ ]), elemental analysis: calculated value; C ₂₆ H ₂₅ N ₂ O ₆ ; C67.82, H5.25, N6.08 (%) Analytical value: C67.85, H5.36, N5.67 (%)

Example 4 Synthesis of squarylium trimer (Compound D)
Example except that 1,4-dibromo-2-bromomethylbutane (6.8 g, 22 mmol) was used instead of 1,4-dibromobutane, and the amount of N-methylaniline was 7.2 g (68 mmol). A yellow solid (compound D, 8.6 g, 13 mmol) was obtained according to 1-3.

Yield 58%; LC-MS (m / z) 675 ([M ⁺ ]), elemental analysis: calculated value; C ₃₈ H ₃₃ N ₃ O ₉ ; C67.55, H4.92, N6.22 (%) Analytical value: C67.30, H4.88, N6.01 (%)

Example 5 Synthesis of squarylium tetramer (Compound E)
Except that 1,4-dibromo-2,3-dibromomethylbutane (9.0 g, 22 mmol) was used instead of 1,4-dibromobutane, and the amount of N-methylaniline was 9.6 g (90 mmol). A yellow solid (Compound E, 9.8 g, 11 mmol) was obtained according to Example 4.

Yield 50%; LC-MS (m / z) 890 ([M ⁺ ]), elemental analysis: calculated value; C ₅₀ H ₄₂ N ₄ O ₁₂ ; C67.41, H4.75, N6.29 (%) Analytical value: C66.94, H4.56, N6.33 (%)

Next, compounds B to E were dissolved in chloroform and methanol to a concentration of 5 μM, the absorption wavelength (λ _max ) of the maximum peak was measured from the absorption spectrum for each solution, and the molar extinction coefficient (ε) was further measured. . The results are shown in Table 1. For reference, λ _max and ε of compounds F and G, which are squarylium monomers, are shown in Table 1.
Further, FIG. 1 shows an absorption spectrum of the compound C (solvent: methanol).

[Consideration of Examples]
As can be seen from Table 1, compounds B and C, which are squarylium compound dimers, compound D, which is a trimer, and compound E, which is a tetramer, each have a maximum peak absorption wavelength (λ _max ) at 360 to 435 nm. The absorption wavelength is close to 405 nm, which is desirable as a next-generation blue semiconductor laser optical recording medium, and is very useful as an organic compound dye in the recording layer of the blue semiconductor laser optical recording medium.
Moreover, these squarylium compounds have a molar extinction coefficient of 5 × 10 ^{4 to} 20 × 10 ⁵ , which is much higher than the molar extinction coefficient of the squarylium monomer, which is sufficient for recording and reproduction and causes pit disturbance due to excessive heat generation. There is almost nothing.
From these, it was found that the squarylium compounds of the examples are very excellent organic compound dyes for optical recording media compatible with blue semiconductor lasers.

Absorption spectrum of Compound C.

Claims (5)

Represented by the following general formula (1) (in the general formula (1), R ₁ and R ₁₂ each independently represents a halogen atom, a hydroxyl group, a substituted or unsubstituted alkoxy group or a substituted or unsubstituted phenoxy group; R _{2 to} R ₅ and R _{8 to} R ₁₁ each independently represent a hydrogen atom, a halogen atom, a hydroxyl group or a substituted or unsubstituted alkyl group, and R ₆ and R ₇ each independently represent a hydrogen atom, a substituted or A squarylium compound, wherein an unsubstituted alkyl group or a substituted or unsubstituted aromatic ring is represented, and R ₁₃ represents an optionally substituted alkylene group having 1 to 5 carbon atoms.

Represented by the following general formula (2) (in the general formula (2), R ₂₁ , R ₂₂ and R ₂₃ are each independently a halogen atom, a hydroxyl group, a substituted or unsubstituted alkoxy group or a substituted or unsubstituted phenoxy group) R _{24 to} R ₃₅ each independently represents a hydrogen atom, a halogen atom, a hydroxyl group or a substituted or unsubstituted alkyl group, and R _{36 to} R ₃₈ each independently represents a hydrogen atom, a substituted or unsubstituted group. Represents an alkyl group or a substituted or unsubstituted aromatic ring, R ₃₉ represents —CR ₄₀ (R ₄₀ represents a hydrogen atom, a halogen, a hydroxyl group, a substituted or unsubstituted alkoxy group, a substituted or unsubstituted alkyl group), Or a substituted or unsubstituted trivalent hydrocarbon group having 2 to 8 carbon atoms).

Represented by the following general formula (3) (in the general formula (3), R _{51 to} R ₅₄ each independently represents a halogen atom, a hydroxyl group, a substituted or unsubstituted alkoxy group, or a substituted or unsubstituted phenoxy group; each R ₅₅ to R ₇₀ independently represent a hydrogen atom, a halogen atom, a hydroxyl group or a substituted or unsubstituted alkyl group, R ₇₁ to R ₇₄ each independently represent a hydrogen atom, a substituted or unsubstituted alkyl group, or substituted or an unsubstituted aromatic ring, R ₇₅ represents a tetravalent hydrocarbon group having 2 to 8 carbon atoms substituted or unsubstituted) that squarylium compound characterized.

  In an optical recording medium comprising a substrate and a recording layer formed on the substrate, the recording layer comprises at least one of squarylium compounds represented by general formulas (1) to (3) of claims 1 to 3. An optical recording medium comprising:   The optical recording medium according to claim 4, wherein the wavelength of laser light used for recording or reproducing information is 350 to 450 nm.

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