WO2022149462A1 - Light-absorbing material, recording medium, method for recording information, and method for reading out information - Google Patents

Abstract

A light-absorbing material according to one embodiment of the present disclosure includes a compound represented by formula (1) as a main component. In formula (1): R1 to R30 are independent of each other and include at least one element selected from the group consisting of H, C, N, O, F, P, S, Cl, I, and Br; and L1 to L3 are independent of each other, and are represented by formula (2) or (3).　

Description

Light absorption material, recording medium, information recording method and information reading method

This disclosure relates to a light absorbing material, a recording medium, an information recording method, and an information reading method.

Among optical materials such as light absorbing materials, materials having a non-linear optical effect are called non-linear optical materials. The nonlinear optical effect means that when a substance is irradiated with strong light such as laser light, an optical phenomenon proportional to the square or the square of the electric field of the irradiation light occurs in the substance. Optical phenomena include absorption, reflection, scattering, light emission and the like. Examples of the second-order nonlinear optical effect proportional to the square of the electric field of the irradiation light include second harmonic generation (SHG), Pockels effect, and parametric effect. Examples of the third-order nonlinear optical effect proportional to the cube of the electric field of the irradiation light include two-photon absorption, multiphoton absorption, third harmonic generation (THG), and the Kerr effect. In the present specification, multiphoton absorption such as two-photon absorption may be referred to as non-linear light absorption. A material capable of performing non-linear light absorption may be referred to as a non-linear light absorption material. In particular, a material capable of absorbing two-photons may be referred to as a two-photon absorbing material.

A lot of research has been actively carried out so far on nonlinear optical materials. In particular, as a nonlinear optical material, an inorganic material capable of easily preparing a single crystal has been developed. In recent years, the development of nonlinear optical materials made of organic materials is expected. Examples of the nonlinear optical material made of an organic material include an organic dye. Organic materials not only have a high degree of freedom in design compared to inorganic materials, but also have large nonlinear optical constants. Moreover, in organic materials, the non-linear response is fast. In the present specification, a nonlinear optical material including an organic material may be referred to as an organic nonlinear optical material.

Japanese Patent No. 5821661

There is a demand for a new light absorbing material having two-photon absorption characteristics for light having a wavelength in the short wavelength range.

The light absorbing material in one aspect of the present disclosure is
It contains a compound represented by the following formula (1) as a main component.

In the formula (1), R ¹ to R ³⁰ contain at least one atom selected from the group consisting of H, C, N, O, F, P, S, Cl, I and Br independently of each other. , L ¹ to L ³ are independently represented by the following equations (2) or (3).

In the formula (2), n is 1 or 2, and in the formula (3), R ³¹ to R ³⁴ are independent of each other, H, C, N, O, F, P, S, Cl. , I and Br include at least one atom selected from the group.

The present disclosure provides a novel light absorbing material having two-photon absorption characteristics for light having a wavelength in the short wavelength range.

FIG. 1A is a flowchart relating to a method of recording information using a recording medium including a light absorbing material according to an embodiment of the present disclosure. FIG. 1B is a flowchart relating to a method of reading information using a recording medium including a light absorbing material according to an embodiment of the present disclosure. FIG. 2 is a graph showing the ¹ H-NMR spectrum of compound (9) -1. FIG. 3 is a graph showing the ¹ H-NMR spectrum of compound (9) -2. FIG. 4 is a graph showing the ¹ H-NMR spectrum of compound (13) -7.

(Findings underlying this disclosure)
Among the organic nonlinear optical materials, the two-photon absorption material has attracted particular attention. Two-photon absorption means a phenomenon in which a compound absorbs two photons almost simultaneously and transitions to an excited state. Non-resonant two-photon absorption and resonant two-photon absorption are known as two-photon absorption. Non-resonant two-photon absorption means two-photon absorption in the wavelength range where the absorption band of one photon does not exist. In non-resonant two-photon absorption, the compound absorbs two photons almost simultaneously and transitions to a higher-order excited state. In resonant two-photon absorption, the compound absorbs the first photon and then further absorbs the second photon, thereby transitioning to a higher-order excited state. In resonant two-photon absorption, the compound sequentially absorbs two photons.

In non-resonant two-photon absorption, the amount of light absorbed by the compound is usually proportional to the square of the irradiation light intensity. Therefore, for example, for the light focused by the lens, two-photon absorption by the compound can be generated only in the vicinity of the focal point where the light intensity is high. That is, in a sample containing a two-photon absorption material, the compound can be excited only at a desired position. As described above, since the compound that causes non-resonant two-photon absorption brings extremely high spatial resolution, its application to applications such as a recording layer of a three-dimensional optical memory and a photocurable resin composition for stereolithography is being studied. ..

Research on two-photon absorption materials used in recording layers of three-dimensional optical memories, photocurable resin compositions for stereolithography, etc. is being actively conducted. In the two-photon absorption material, the two-photon absorption cross section (GM value) is used as an index indicating the efficiency of two-photon absorption. The unit of the two-photon absorption cross-sectional area is GM (10 ^-50 cm ⁴ · s · molecule ^-1 · photon ^-1 ). So far, many compounds having a two-photon absorption cross section as large as 500 GM have been reported (for example, Non-Patent Document 1). However, in most reports, the two-photon absorption cross section is measured using laser light with wavelengths longer than 600 nm. In particular, near infrared rays having a wavelength longer than 750 nm may be used as the laser light.

However, in order to apply the two-photon absorption material to industrial applications, a material having a large two-photon absorption cross section is required when irradiated with a laser beam having a shorter wavelength. For example, in the field of optical memory, laser light having a short wavelength is used in order to realize a finer focused spot from the viewpoint of the diffraction limit of the focused laser light. In a three-dimensional optical memory having a multi-layer structure, the recording density can be dramatically improved by using a two-photon absorption material having extremely high spatial resolution. In particular, in the application of three-dimensional optical memory, the Blu-ray (registered trademark) disc standard uses laser light having a center wavelength of 405 nm. Therefore, if a compound having a large two-photon absorption cross section is developed for light in the same wavelength range as this laser light, it can greatly contribute to the development of industry.

Patent Document 1 discloses a compound having a wavelength of 400 nm or more and 410 nm or less and exhibiting nonlinear light absorption with respect to pulsed laser light having high intensity. In this compound, three aromatic hydrocarbons are bonded to the nitrogen atom. That is, this compound has a tri-branched structure centered on a nitrogen atom. However, this compound has not yet been put into practical use at this stage and is not out of the scope of research. Furthermore, there is room for improvement in the two-photon absorption cross section of this compound. For example, when a compound having a small two-photon absorption cross section is used in a three-dimensional optical memory, it may be necessary to improve the light intensity of the laser beam. Therefore, from the viewpoint of further improving industrial applicability, a compound having a larger two-photon absorption cross section than light having a wavelength of around 405 nm is required.

As a result of diligent studies, the present inventors have newly found that the compound represented by the formula (1) described later has excellent two-photon absorption characteristics with respect to light having a wavelength in the short wavelength range. .. In the present specification, the short wavelength region means a wavelength region including 405 nm, and means, for example, a wavelength region of 390 nm or more and 420 nm or less. In particular, the compound represented by the formula (1) has a large two-photon absorption cross section with respect to light having a wavelength of around 405 nm.

(Summary of one aspect pertaining to this disclosure)
The light absorbing material according to the first aspect of the present disclosure is
It contains a compound represented by the following formula (1) as a main component.

In the formula (1), R ¹ to R ³⁰ contain at least one atom selected from the group consisting of H, C, N, O, F, P, S, Cl, I and Br independently of each other. , L ¹ to L ³ are independently represented by the following equations (2) or (3).

In the formula (2), n is 1 or 2, and in the formula (3), R ³¹ to R ³⁴ are independent of each other, H, C, N, O, F, P, S, Cl. , I and Br include at least one atom selected from the group.

According to the first aspect, the light absorbing material has excellent two-photon absorption characteristics with respect to light having a wavelength in the short wavelength range.

In the second aspect of the present disclosure, for example, in the light absorbing material according to the first aspect, the compound may be represented by the following formula (4).

In the third aspect of the present disclosure, for example, in the light absorbing material according to the first aspect, the compound may be represented by the following formula (5).

In the fourth aspect of the present disclosure, for example, in the light absorbing material according to the first aspect, the compound may be represented by the following formula (6).

In the formula (6), R ³⁵ to R ⁴⁶ contain at least one atom selected from the group consisting of H, C, N, O, F, P, S, Cl, I and Br independently of each other. ..

In the fifth aspect of the present disclosure, for example, in the light absorbing material according to any one of the first to the fourth aspects, the R ¹ to the R ³⁰ are independent of each other, a hydrogen atom, a halogen atom, and an alkyl group. , Alkyl halide group, unsaturated hydrocarbon group, hydroxyl group, carboxyl group, alkoxycarbonyl group, acyl group, amide group, nitrile group, alkoxy group, acyloxy group, thiol group, alkylthio group, sulfonic acid group, acylthio group, It may be an alkylsulfonyl group, a sulfonamide group, a primary amino group, a secondary amino group, a tertiary amino group or a nitro group.

In the sixth aspect of the present disclosure, for example, in the light absorbing material according to any one of the first to fifth aspects, from the R ¹⁶ to the R ¹⁸ , the R ²¹ to the R ²³ , and the R ²⁶ . At least one selected from the group consisting of R ²⁸ may be an electron donating group or an electron withdrawing group.

In the seventh aspect of the present disclosure, for example, in the light absorbing material according to the sixth aspect, the electron-withdrawing group may be a carboxyl group or an alkoxycarbonyl group.

In the eighth aspect of the present disclosure, for example, in the light absorbing material according to the sixth or seventh aspect, the electron-withdrawing group may be -COO (CH ₂ ) ₃ CH ₃ .

In the ninth aspect of the present disclosure, for example, in the light absorbing material according to any one of the first to eighth aspects, at least one selected from the group consisting of the R ¹ to the R ⁶ is a hydrogen atom or a halogen. Atomic, alkyl group with 1 to 5 carbon atoms, alkyl group with 7 or more carbon atoms, alkyl halide group, unsaturated hydrocarbon group, hydroxyl group, carboxyl group, alkoxycarbonyl group, acyl group, amide group, nitrile group, It may be an alkoxy group, an acyloxy group, a thiol group, an alkylthio group, a sulfonic acid group, an acylthio group, an alkylsulfonyl group, a sulfonamide group, a primary amino group, a secondary amino group, a tertiary amino group or a nitro group.

In the tenth aspect of the present disclosure, for example, in the light absorbing material according to the first or second aspect, the compound is represented by the following formula (7), and is composed of the group consisting of the R ¹⁶ , the R ²¹ and the R ²⁶ . At least one selected is a halogen atom, an alkyl group, an alkyl halide group, an unsaturated hydrocarbon group, a hydroxyl group, a carboxyl group, an alkoxycarbonyl group, an acyl group, an amide group, a nitrile group, an alkoxy group, an acyloxy group and a thiol. It may be a group, an alkylthio group, a sulfonic acid group, an acylthio group, an alkylsulfonyl group, a sulfonamide group, a primary amino group, a secondary amino group, a tertiary amino group or a nitro group.

In the eleventh aspect of the present disclosure, for example, in the light absorbing material according to any one of the first to tenth aspects, the compound may have a light absorbing effect.

In the twelfth aspect of the present disclosure, for example, the light absorbing material according to any one of the first to eleventh aspects may be used for a device using light having a wavelength of 390 nm or more and 420 nm or less.

According to the second to twelfth aspects, the light absorbing material has excellent two-photon absorption characteristics with respect to light having a wavelength in the short wavelength range. This light absorbing material is suitable for applications of devices that utilize light having a wavelength of 390 nm or more and 420 nm or less.

The recording medium according to the thirteenth aspect of the present disclosure is
A recording layer including a light absorbing material according to any one of the first to twelfth embodiments is provided.

According to the thirteenth aspect, the light absorbing material has excellent two-photon absorption characteristics with respect to light having a wavelength in the short wavelength range. A recording medium containing such a light absorbing material can record information at a high recording density.

The method for recording information according to the fourteenth aspect of the present disclosure is as follows.
Preparing a light source that emits light with a wavelength of 390 nm or more and 420 nm or less,
By condensing the light from the light source and irradiating the recording layer in the recording medium according to the thirteenth aspect,
including.

According to the fourteenth aspect, the light absorbing material has excellent two-photon absorption characteristics with respect to light having a wavelength in the short wavelength range. According to the information recording method using a recording medium including such a light absorbing material, information can be recorded with a high recording density.

The method for reading information according to the fifteenth aspect of the present disclosure is, for example, a method for reading information recorded by the recording method according to the fourteenth aspect.
The reading method is
By irradiating the recording layer in the recording medium with light, the optical characteristics of the recording layer can be measured.
Determining whether or not information is recorded on the recording layer based on the optical characteristics
including.

In the 16th aspect of the present disclosure, for example, in the method of reading information according to the 15th aspect, the optical characteristic may be the intensity of light reflected by the recording layer.

According to the fifteenth or sixteenth aspect, the recording layer in which the information is recorded can be easily identified.

Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. The present disclosure is not limited to the following embodiments.

(Embodiment)
The light absorbing material of the present embodiment contains the compound A represented by the following formula (1).

In formula (1), R ¹ to R ³⁰ contain at least one atom selected from the group consisting of H, C, N, O, F, P, S, Cl, I and Br independently of each other. R ¹ to R ³⁰ are independent of each other, and have a hydrogen atom, a halogen atom, an alkyl group, an alkyl halide group, an unsaturated hydrocarbon group, a hydroxyl group, a carboxyl group, an alkoxycarbonyl group, an acyl group, an amide group and a nitrile group. , Aalkoxy group, acyloxy group, thiol group, alkylthio group, sulfonic acid group, acylthio group, alkylsulfonyl group, sulfonamide group, primary amino group, secondary amino group, tertiary amino group or nitro group. ..

Examples of the halogen atom include F, Cl, Br, I and the like. In the present specification, a halogen atom may be referred to as a halogen group.

The number of carbon atoms of the alkyl group is not particularly limited, and is, for example, 1 or more and 20 or less. The number of carbon atoms of the alkyl group may be 1 or more and 10 or less, or 1 or more and 5 or less, from the viewpoint that compound A can be easily synthesized. In some cases, the alkyl group may have 7 or more carbon atoms. By adjusting the number of carbon atoms of the alkyl group, the solubility of the compound A in the solvent or the resin composition can be adjusted. The alkyl group may be linear, branched chain, or cyclic. The at least one hydrogen atom contained in the alkyl group may be substituted with a group containing at least one atom selected from the group consisting of N, O, P and S. The alkyl group includes a methyl group, an ethyl group, a propyl group, a butyl group, a 2-methylbutyl group, a pentyl group, a hexyl group, a 2,3-dimethylhexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group and an undecyl group. , Dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, hexadecyl group, heptadecyl group, octadecyl group, nonadecyl group, eicosyl group, 2-methoxybutyl group, 6-methoxyhexyl group and the like.

The halogenated alkyl group means a group in which at least one hydrogen atom contained in the alkyl group is substituted with a halogen atom. The alkyl halide group may be a group in which all hydrogen atoms contained in the alkyl group are substituted with halogen atoms. Examples of the alkyl group include those described above. A specific example of an alkyl halide group is -CF ₃ .

Unsaturated hydrocarbon groups include unsaturated bonds such as carbon-carbon double bonds and carbon-carbon triple bonds. The number of unsaturated bonds contained in the unsaturated hydrocarbon group is, for example, 1 or more and 5 or less. The number of carbon atoms of the unsaturated hydrocarbon group is not particularly limited, and may be, for example, 2 or more and 20 or less, 2 or more and 10 or less, or 2 or more and 5 or less. The unsaturated hydrocarbon group may be linear, branched or cyclic, or cyclic. The at least one hydrogen atom contained in the unsaturated hydrocarbon group may be substituted with a group containing at least one atom selected from the group consisting of N, O, P and S. Examples of the unsaturated hydrocarbon group include a vinyl group and an ethynyl group.

The hydroxyl group is represented by -OH. The carboxyl group is represented by -COOH. The alkoxycarbonyl group is represented by -COOR _a . The acyl group is represented by -COR _b . The amide group is represented by -CONR _c R _d . The nitrile group is represented by -CN. The alkoxy group is represented by −OR _e . The acyloxy group is represented by -OCOR _f . The thiol group is represented by -SH. The alkylthio group is represented by -SR _g . The sulfonic acid group is represented by -SO _3H . The acylthio group is represented by -SCOR _h . The alkylsulfonyl group is represented by _{-SO 2} Ri. The sulfonamide group is represented by −SO ₂ NR _j R _k . The primary amino group is represented by -NH ₂ . The secondary amino group is represented by -NHR _l . The tertiary amino group is represented by −NR _m R _n . The nitro group is represented by -NO ₂ . R _a to R _n are alkyl groups independent of each other. Examples of the alkyl group include those described above. However, the amide groups R _c and R _d and the sulfonamide groups R _j and R _k may be hydrogen atoms independently of each other.

Specific examples of the alkoxycarbonyl group are -COOCH ₃ , -COO (CH ₂ ) ₃ CH ₃ and -COO (CH ₂ ) ₇ CH ₃ . A specific example of an acyl group is -COCH ₃ . A specific example of an amide group is -CONH ₂ . Specific examples of the alkoxy group include methoxy group, ethoxy group, 2-methoxyethoxy group, butoxy group, 2-methylbutoxy group, 2-methoxybutoxy group, 4-ethylthiobutoxy group, pentyloxy group, hexyloxy group and heptyl. Oxy group, octyloxy group, nonyloxy group, decyloxy group, undecyloxy group, dodecyloxy group, tridecyloxy group, tetradecyloxy group, pentadecyloxy group, hexadecyloxy group, heptadecyloxy group, octadecyloxy group , Nonadesyloxy group and Eikosyloxy group. A specific example of the acyloxy group is -OCOCH ₃ . A specific example of an alkylthio group is -SCH ₃ . A specific example of an acylthio group is -SCOCH ₃ . A specific example of an alkylsulfonyl group is -SO ₂ CH ₃ . A specific example of a sulfonamide group is -SO ₂ NH ₂ . A specific example of a tertiary amino group is -N (CH ₃ ) ₂ .

In the formula (1), at least one selected from the group consisting of R ¹ to R ⁶ is a hydrogen atom, a halogen atom, an alkyl group having 1 or more and 5 or less carbon atoms, an alkyl group having 7 or more carbon atoms, and an alkyl halide group. , Unsaturated hydrocarbon group, hydroxyl group, carboxyl group, alkoxycarbonyl group, acyl group, amide group, nitrile group, alkoxy group, acyloxy group, thiol group, alkylthio group, sulfonic acid group, acylthio group, alkylsulfonyl group, sulfone It may be an amide group, a primary amino group, a secondary amino group, a tertiary amino group or a nitro group. R ¹ to R ⁶ may be a hydrogen atom, an alkyl group having 1 or more carbon atoms or an alkyl group having 7 or more carbon atoms, or an alkyl group having 1 or more carbon atoms and 5 or less carbon atoms, independently of each other. May be good. Each of R ¹ to R ⁶ may be a methyl group.

In formula (1), each of R ⁷ to R ¹⁵ , R ¹⁹ , R ²⁰ , R ²⁴ , R ²⁵ , R ²⁹ and R ³⁰ may have a small volume. At this time, steric hindrance is less likely to occur in R ⁷ to R ¹⁵ , R ¹⁹ , R ²⁰ , R ²⁴ , R ²⁵ , R ²⁹ , and R ³⁰ . Therefore, in the compound A, the flatness of the π-electron conjugated system is improved, so that the compound A tends to have a large two-photon absorption cross section. Each of R ⁷ to R ¹⁵ , R ¹⁹ , R ²⁰ , R ²⁴ , R ²⁵ , R ²⁹ and R ³⁰ may be a hydrogen atom.

In formula (1), at least one selected from the group consisting of R ¹⁶ to R ¹⁸ , R ²¹ to R ²³ , and R ²⁶ to R ²⁸ may be an electron donating group or an electron withdrawing group. For R ¹⁶ to R ¹⁸ , R ²¹ to R ²³ , and R ²⁶ to R ²⁸ , the larger the electron donating property or electron withdrawing property, the larger the electron bias in the compound A. When the electron bias in the compound A is large, the electrons tend to move significantly in the compound A when the compound A is excited. Such compound A may have better two-photon absorption properties. In other words, compound A is a large two-photon when at least one selected from the group consisting of R ¹⁶ to R ¹⁸ , R ²¹ to R ²³ , and R ²⁶ to R ²⁸ is an electron donating group or an electron withdrawing group. May have an absorption cross section. However, each of R ¹⁷ , R ¹⁸ , R ²² , R ²³ , R ²⁷ and R ²⁸ may be a hydrogen atom. At least one selected from the group consisting of R ¹⁶ , R ²¹ and R ²⁶ may be an electron donating group or an electron withdrawing group.

The electron-withdrawing group means, for example, a substituent in which the σ _p value, which is a substituent constant in the Hammett equation, is a positive value. The electron-withdrawing group includes a halogen atom, a carboxyl group, a nitro group, a thiol group, a sulfonic acid group, an acyloxy group, an alkylthio group, an alkylsulfonyl group, a sulfonamide group, an acyl group, an acylthio group, an alkoxycarbonyl group and an alkyl halide. The group etc. can be mentioned. The electron-withdrawing group may be a carboxyl group or an alkoxycarbonyl group, or may be -COO (CH ₂ ) ₃ CH ₃ .

The electron donating group means, for example, a substituent in which the above σ _p value is a negative value. Examples of the electron donating group include an alkyl group, an alkoxy group, a hydroxyl group and an amino group. The electron donating group may be an alkyl group or an alkoxy group.

In the formula (1), L ¹ to L ³ are independently represented by the following formula (2) or (3).

In formula (2), n is 1 or 2. In formula (3), R ³¹ to R ³⁴ contain at least one atom selected from the group consisting of H, C, N, O, F, P, S, Cl, I and Br independently of each other. R ³¹ to R ³⁴ may be hydrogen atoms or the substituents described above in R ¹ to R ³⁰ independently of each other. Each of R ³¹ to R ³⁴ may have a small volume. At this time, steric hindrance is unlikely to occur in R ³¹ to R ³⁴ . Therefore, in the compound A, the flatness of the π-electron conjugated system is improved, so that the compound A tends to have a large two-photon absorption cross section. Each of R ³¹ to R ³⁴ may be a hydrogen atom.

Each of L ¹ to L ³ may be the same as or different from each other. As an example, each of L ¹ to L ³ may be expressed by the equation (2). Compound A may be compound B represented by the following formula (4).

When the compound A is the compound C represented by the following formula (7), at least one selected from the group consisting of R ¹⁶ , R ²¹ and R ²⁶ is a halogen atom, an alkyl group, a halogenated alkyl group, and the like. Unsaturated hydrocarbon group, hydroxyl group, carboxyl group, alkoxycarbonyl group, acyl group, amide group, nitrile group, alkoxy group, acyloxy group, thiol group, alkylthio group, sulfonic acid group, acylthio group, alkylsulfonyl group, sulfonamide It may be a primary amino group, a secondary amino group, a tertiary amino group or a nitro group.

Specific examples of the compound B represented by the formula (4) include the compound D represented by the following formula (8).

In equation (8), the plurality of Z's are the same as each other. The plurality of Zs correspond to R ¹⁶ , R ²¹ and R ²⁶ of the equation (4), respectively. A specific example of Z in the formula (8) is shown in Table 1 below. In formula (8), the plurality of Zs may be —COOH or —COO (CH ₂ ) ₃ CH ₃ .

In equation (8), the plurality of X's are the same as each other. The plurality of Xs correspond to R ¹ to R ⁶ of the equation (4), respectively. The plurality of Xs may be hydrogen atoms or substituents shown in Table 1 above. In the formula (8), the plurality of Xs may be −CH ₃ . That is, the compound D represented by the formula (8) may be the compound E represented by the following formula (9).

Compound A may be compound F represented by the following formula (5).

Specific examples of the compound F include compound G represented by the following formula (10).

In equation (10), the plurality of Z's are the same as each other. The plurality of Zs correspond to R ¹⁶ , R ²¹ and R ²⁶ of the equation (5), respectively. The plurality of Zs may be hydrogen atoms or substituents shown in Table 1 above.

In equation (10), the plurality of X's are the same as each other. The plurality of Xs correspond to R ¹ to R ⁶ of the equation (5), respectively. The plurality of Xs may be hydrogen atoms or substituents shown in Table 1 above. In the formula (10), the plurality of Xs may be −CH ₃ . That is, the compound G represented by the formula (10) may be the compound H represented by the following formula (11).

Each of L ¹ to L ³ of the formula (1) may be expressed by the formula (3). Compound A may be compound I represented by the following formula (6).

In formula (6), R ³⁵ to R ⁴⁶ contain at least one atom selected from the group consisting of H, C, N, O, F, P, S, Cl, I and Br independently of each other. Each of R ³⁵ to R ⁴⁶ corresponds to any of R ³¹ to R ³⁴ in the equation (3).

Specific examples of the compound I include compound J represented by the following formula (12).

In equation (12), the plurality of Z's are the same as each other. The plurality of Zs correspond to R ¹⁶ , R ²¹ and R ²⁶ of the equation (6), respectively. The plurality of Zs may be hydrogen atoms or substituents shown in Table 1 above. In the formula (12), the plurality of Zs may be −H.

In equation (12), the plurality of X's are the same as each other. The plurality of Xs correspond to R ¹ to R ⁶ of the equation (6), respectively. The plurality of Xs may be hydrogen atoms or substituents shown in Table 1 above. In formula (12), the plurality of Xs may be −CH ₃ . That is, the compound J represented by the formula (12) may be the compound K represented by the following formula (13).

The method for synthesizing the compound E represented by the formula (9), the compound H represented by the formula (11), and the compound K represented by the formula (13) is not particularly limited. Compounds E, H and K can be synthesized, for example, by the following methods. First, the compound L represented by the following formula (14) is prepared. Compound L is 10,15-dihydro-2,7,12-triiodo-5,5,10,10,15,15-hexamethyl-5H-tribenzo [a, f, k] trinden.

Next, the Sonogashira coupling reaction is carried out with respect to compound L and compound M having a terminal alkyne. This makes it possible to synthesize compounds E, H and K. The structure of compound M is determined according to the structure of the target compound. The conditions of the coupling reaction can be appropriately adjusted depending on, for example, compounds L and M.

Compound A represented by the formula (1) has excellent two-photon absorption characteristics with respect to light having a wavelength in the short wavelength range. As an example, when compound A is irradiated with light having a wavelength of 405 nm, two-photon absorption occurs remarkably in compound A.

The two-photon absorption cross section of compound A for light having a wavelength of 405 nm may be 1500 GM or more, 2000 GM or more, 3000 GM or more, 4000 GM or more, or 5000 GM. It may be more than 10,000 GM or more. The upper limit of the two-photon absorption cross section of compound A is not particularly limited, and is, for example, 300,000 GM. The two-photon absorption cross section can be measured by, for example, the Z scan method described in J. Opt. Soc. Am. B, 2003, Vol. 20, p. 529. The Z-scan method is widely used as a method for measuring nonlinear optical constants. In the Z scan method, the measurement sample is moved along the irradiation direction of the beam in the vicinity of the focal point where the laser beam is focused. At this time, the change in the amount of light transmitted through the measurement sample is recorded. In the Z scan method, the power density of the incident light changes depending on the position of the measurement sample. Therefore, when the measurement sample absorbs non-linear light, the amount of transmitted light is attenuated when the measurement sample is located near the focal point of the laser beam. The two-photon absorption cross-sectional area can be calculated by fitting the change in the amount of transmitted light to the theoretical curve predicted from the intensity of the incident light, the thickness of the measurement sample, the concentration of compound A in the measurement sample, and the like. ..

When compound A absorbs two photons, compound A absorbs about twice as much energy as the light irradiated to compound A. The wavelength of light having about twice the energy of light having a wavelength of 405 nm is, for example, 200 nm. That is, when compound A is irradiated with light having a wavelength of around 200 nm, monophoton absorption may occur in compound A. Further, in compound A, one-photon absorption may occur for light having a wavelength near the wavelength range in which two-photon absorption occurs.

The light absorbing material of the present embodiment may contain compound A represented by the formula (1) as a main component. The "main component" means the component contained most in the light absorbing material in terms of weight ratio. The light absorbing material is, for example, substantially composed of compound A. By "substantially consisting of" is meant eliminating other components that alter the essential characteristics of the mentioned material. However, the light absorbing material may contain impurities in addition to compound A. The light-absorbing material of the present embodiment functions as a multi-photon absorbing material such as a two-photon absorbing material. In particular, since the light absorbing material of the present embodiment contains the compound A represented by the formula (1), it has excellent two-photon absorption characteristics with respect to light having a wavelength in the short wavelength range.

The light absorbing material of the present embodiment is used, for example, in a device that utilizes light having a wavelength in a short wavelength range. That is, the present disclosure is a light absorption material used for a device using light having a wavelength of 390 nm or more and 420 nm or less, and includes a compound A represented by the formula (1). Provide materials. Examples of such a device include a recording medium, a modeling machine, a fluorescence microscope, and the like. Examples of the recording medium include a three-dimensional optical memory. A specific example of a three-dimensional optical memory is a three-dimensional optical disk. Examples of the modeling machine include an optical modeling machine such as a 3D printer. Examples of the fluorescence microscope include a two-photon fluorescence microscope. The light utilized in these devices has a high photon density, for example, near its focal point. The power density near the focal point of the light used in the device is, for example, 0.1 W / cm ² or more and 1.0 × 10 ²⁰ W / cm ² or less. The power density near the focal point of this light may be 1.0 W / cm ² or more, 1.0 × 10 ² W / cm ² or more, and 1.0 × 10 ⁵ W / cm. It may be ² or more. As the light source of the device, for example, a femtosecond laser such as a titanium sapphire laser or a pulse laser having a pulse width of picoseconds to nanoseconds such as a semiconductor laser can be used.

The recording medium includes, for example, a thin film called a recording layer. In the recording medium, information is recorded on the recording layer. As an example, the thin film as a recording layer contains the light absorbing material of the present embodiment. That is, the present disclosure provides a recording medium provided with a light absorbing material containing the compound A represented by the formula (1) from the other aspect thereof.

The recording layer may further contain a polymer compound that functions as a binder, in addition to the light absorbing material. The recording medium may include a dielectric layer in addition to the recording layer. The recording medium includes, for example, a plurality of recording layers and a plurality of dielectric layers. In the recording medium, a plurality of recording layers and a plurality of dielectric layers may be alternately laminated.

Next, a method of recording information using the above-mentioned recording medium will be described. FIG. 1A is a flowchart relating to a method of recording information using the above-mentioned recording medium. First, in step S11, a light source that emits light having a wavelength of 390 nm or more and 420 nm or less is prepared. As the light source, for example, a femtosecond laser such as a titanium sapphire laser can be used. As the light source, a pulse laser having a pulse width of picoseconds to nanoseconds such as a semiconductor laser may be used. Next, in step S12, the light from the light source is condensed by a lens or the like and irradiated to the recording layer in the recording medium. Specifically, the light from the light source is condensed by a lens or the like and irradiated to the recording area in the recording medium. The power density near the focal point of this light is, for example, 0.1 W / cm ² or more and 1.0 × 10 ²⁰ W / cm ² or less. The power density near the focal point of this light may be 1.0 W / cm ² or more, 1.0 × 10 ² W / cm ² or more, and 1.0 × 10 ⁵ W / cm. It may be ² or more. As used herein, the recording area means a spot that exists in the recording layer and can record information by being irradiated with light.

Physical or chemical changes occur in the recording area irradiated with the above light. For example, heat is generated when compound A, which has absorbed light, returns from the transition state to the ground state. This heat alters the binder present in the recording area. This changes the optical characteristics of the recording area. For example, the intensity of light reflected in the recording area, the reflectance of light in the recording area, the absorption rate of light in the recording area, the refractive index of light in the recording area, and the like change. In the recording area irradiated with light, the intensity of the fluorescent light emitted from the recording area or the wavelength of the fluorescent light may change. As a result, information can be recorded in the recording layer, specifically, the recording area (step S13).

Next, a method of reading information using the above recording medium will be described. FIG. 1B is a flowchart relating to a method of reading information using the above-mentioned recording medium. First, in step S21, the recording layer on the recording medium is irradiated with light. Specifically, the recording area on the recording medium is irradiated with light. The light used in step S21 may be the same as the light used for recording information on the recording medium, or may be different. Next, in step S22, the optical characteristics of the recording layer are measured. Specifically, the optical characteristics of the recording area are measured. In step S22, for example, the intensity of the fluorescent light emitted from the recording area is measured. In step S22, the optical characteristics of the recording area include the intensity of the light reflected in the recording area, the light reflectance in the recording area, the absorption rate of the light in the recording area, the refractive index of the light in the recording area, and the recording area. The intensity of the emitted fluorescent light, the wavelength of the fluorescent light, and the like may be measured. Next, in step S23, information is read from the recording layer, specifically, the recording area.

In the information reading method, the recording area in which the information is recorded can be searched by the following method. First, light is applied to a specific area of the recording medium. This light may be the same as or different from the light used to record the information on the recording medium. Next, the optical characteristics of the area irradiated with light are measured. The optical characteristics include, for example, the intensity of fluorescent light emitted from the region, the intensity of light reflected in the region, the reflectance of light in the region, the absorption rate of light in the region, and the optical characteristics in the region. Examples thereof include the refractive index of light and the wavelength of fluorescent light emitted from the region. Based on the measured optical characteristics, it is determined whether or not the area irradiated with light is the recording area. For example, when the intensity of the fluorescent light emitted from the region is equal to or less than a specific value, it is determined that the region is a recording region. On the other hand, when the intensity of the fluorescent light exceeds a specific value, it is determined that the region is not the recording region. The method for determining whether or not the area irradiated with light is the recording area is not limited to the above method. For example, when the intensity of the fluorescent light emitted from the region exceeds a specific value, it may be determined that the region is a recording region. Further, when the intensity of the fluorescent light emitted from the region is not more than a specific value, it may be determined that the region is not the recording region. If it is determined that the area is not the recording area, the same operation is performed for other areas of the recording medium. This makes it possible to search for a recording area.

The information recording method and reading method using the above-mentioned recording medium can be performed by, for example, a known recording device. The recording device includes, for example, a light source that irradiates a recording area on a recording medium with light, a measuring instrument that measures the optical characteristics of the recording area, and a controller that controls the light source and the measuring instrument.

The modeling machine performs modeling by, for example, irradiating a photocurable resin composition with light and curing the resin composition. As an example, the photocurable resin composition for stereolithography contains the light absorbing material of the present embodiment. The photocurable resin composition contains, for example, a polymerizable compound and a polymerization initiator in addition to the light absorbing material. The photocurable resin composition may further contain an additive such as a binder resin. The photocurable resin composition may contain an epoxy resin.

According to the fluorescence microscope, for example, a biological sample containing a fluorescent dye material can be irradiated with light, and the fluorescence emitted from the dye material can be observed. As an example, the fluorescent dye material to be added to the biological sample contains the light absorbing material of the present embodiment.

Hereinafter, the present disclosure will be described in more detail by way of examples. The following examples are examples, and the present disclosure is not limited to the following examples. In the present disclosure, the compound used in the examples is referred to as "Compound (X) -Y". "X" means the structural formula of the compound. "Y" means the kind of Z in the formula (X). For example, the compound (9) -1 means a compound represented by the formula (9) in which Z is the substituent 1 (-COO (CH ₂ ) ₃ CH ₃ ) shown in Table 1.

[Compound (9) -1]
First, in a 100 mL eggplant-shaped flask, 10,15-dihydro-2,7,12-triiodo-5,5,10,10,15,15-hexamethyl-5H-tribenzo [a, f, k] tribenzo [a, f, k] tribenzo as a raw material (Manufactured by Tokyo Chemical Industry Co., Ltd.) and butyl 4-ethynylbenzoate, and tetrahydrofuran (THF, manufactured by Fujifilm Wako Junyaku Co., Ltd.) and diisopropylamine (manufactured by Tokyo Chemical Industry Co., Ltd.) are added as solvents, and the raw materials are dissolved in the solvent. I let you. Catalytic amounts of bis (triphenylphosphine) palladium (II) dichloride and copper (I) iodide were further added to the resulting solution. The solution was then stirred at room temperature for 12 hours. After removing the solvent from the obtained reaction solution, extraction treatment was performed using ethyl acetate (manufactured by Wako Pure Chemical Industries, Ltd.). The obtained extract was purified by silica gel column chromatography to obtain compound (9) -1. Compound (9) -1 corresponds to a compound in which a plurality of Z's are -COO (CH ₂ ) ₃ CH ₃ with respect to the compound E represented by the above formula (9). Compound (9) -1 was identified by ¹ H-NMR. FIG. 2 is a graph showing the ¹ H-NMR spectrum of compound (9) -1. The ¹ H-NMR spectrum of compound (9) -1 was as follows.
¹ H-NMR (600MHz, CHLOROFORM-D) δ8.29 (d, J = 8.3Hz, 3H), 8.06 (d, J = 8.3Hz, 6H), 7.74 (s, 3H), 7.66-7.62 (m, 9H), 4.36 (t, J = 6.5Hz, 6H), 1.91 (s, 18H), 1.81-1.76 (m, 6H), 1.51 (td, J = 14.8, 7.6Hz, 6H), 1.01 (t, J = 7.2Hz, 9H).

[Compound (9) -2]
First, the above compound (9) -1 was put into a 100 mL eggplant-shaped flask as a raw material, and THF (manufactured by Wako Pure Chemical Industries, Ltd.) was added as a solvent, and the raw material was dissolved in the solvent. Next, potassium hydroxide (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was further added. The obtained solution was heated under reflux for 12 hours with stirring using a stirrer. After the reaction in the solution was completed, dilute hydrochloric acid was added to the solution. This acidified the solution and precipitated a solid. This solid was washed with ethyl acetate (manufactured by Wako Pure Chemical Industries, Ltd.) to give compound (9) -2. Compound (9) -2 corresponds to a compound in which a plurality of Z is -COOH with respect to the compound E represented by the above-mentioned formula (9). Compound (9) -2 was identified by ¹ H-NMR. FIG. 3 is a graph showing the ¹ H-NMR spectrum of compound (9) -2. The ^{1 1} H-NMR spectrum of compound (9) -2 was as follows.
¹ H-NMR (600MHz, DMSO-D6) δ13.18 (s, 3H), 8.33 (d, J = 8.3Hz, 3H), 8.02-8.00 (m, 9H), 7.74 (d, J = 7.3Hz, 9H), 1.86 (s, 18H).

[Compound (13) -7]
First, in a 100 mL eggplant-shaped flask, 10,15-dihydro-2,7,12-triiodo-5,5,10,10,15,15-hexamethyl-5H-tribenzo [a, f, k] tribenzo [a, f, k] tribenzo as a raw material (Manufactured by Tokyo Chemical Industry Co., Ltd.) and 1-ethynyl-4- (phenylethynyl) benzene, and THF (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) and diisopropylamine (manufactured by Tokyo Chemical Industry Co., Ltd.) are added as solvents to prepare the raw materials. It was dissolved in a solvent. Catalytic amounts of bis (triphenylphosphine) palladium (II) dichloride and copper (I) iodide were further added to the resulting solution. The solution was then stirred at room temperature for 12 hours. After removing the solvent from the obtained reaction solution, extraction treatment was performed using chloroform (manufactured by Wako Pure Chemical Industries, Ltd.). The obtained extract was purified by silica gel column chromatography to obtain compound (13) -7. Compound (13) -7 corresponds to a compound in which a plurality of Z are hydrogen atoms with respect to the compound K represented by the above formula (13). Compound (13) -7 was identified by ¹ H-NMR. FIG. 4 is a graph showing the ¹ H-NMR spectrum of compound (13) -7. The ¹ H-NMR spectrum of compound (13) -7 was as follows.
¹ H-NMR (600MHz, CHLOROFORM-D) δ8.28 (d, J = 8.3Hz, 3H), 7.73 (s, 3H), 7.62-7.54 (m, 21H), 7.36 (m, 9H), 1.91 ( s, 18H).

<Measurement of two-photon absorption cross section>
The two-photon absorption cross section of the synthesized compound was measured for light having a wavelength of 405 nm. The two-photon absorption cross section was measured using the Z scan method described in J. Opt. Soc. Am. B, 2003, Vol. 20, p. 529. A titanium sapphire pulse laser was used as a light source for measuring the two-photon absorption cross section. Specifically, the sample was irradiated with a second high frequency of a titanium sapphire pulse laser. The pulse width of the laser was 80 fs. The laser repeat frequency was 1 kHz. The average power of the laser was varied in the range of 0.01 mW or more and 0.08 mW or less. The light from the laser was light with a wavelength of 405 nm. Specifically, the light from the laser had a center wavelength of 402 nm or more and 404 nm or less. The full width at half maximum of the light from the laser was 4 nm.

<Prediction of two-photon absorption cross section by machine learning>
Next, the two-photon absorption cross section was predicted by machine learning for the synthesized compound and other compounds having a Z type different from that of the synthesized compound. Specifically, first, about 70 kinds of compounds having a known two-photon absorption cross section were prepared as learning data. Half of these compounds were used as training data and the other half were used as test data. Based on these training data, the two-photon absorption cross section was predicted by random forest, and the prediction accuracy was evaluated. Cheminformatics software RDkit was used for the random forest. As a result, a prediction model with a coefficient of determination of R ² of 0.75 or more was obtained. Using this prediction model, the two-photon absorption cross section was predicted for the synthesized compound and other compounds having a Z type different from that of the synthesized compound.

Table 2 shows the measured and predicted values of the two-photon absorption cross section obtained by the above method. In Table 2, "No Data" means that no data has been acquired.

Next, the compounds shown in Table 3 below were prepared as compounds different from the compound A represented by the formula (1). The compound 1f of Comparative Example 1 is represented by the following formula (15).

Next, for the compounds shown in Table 3, the two-photon absorption cross section was measured and predicted by the above method. The results are shown in Table 3.

As can be seen from Table 2, in each of the compounds of Examples 1 to 14 corresponding to the compound A represented by the formula (1), the two-photon absorption cross-sectional area for light having a wavelength of 405 nm exceeded 1500 GM. Compared to the compounds of Comparative Examples 1 to 6 shown in Table 3, the compounds of Examples 1 to 14 had a very large two-photon absorption cross section. From this result, it can be seen that the compound A represented by the formula (1) has excellent two-photon absorption characteristics with respect to light having a wavelength in the short wavelength range. Compound A represented by the formula (1) has a trifurcated structure having an angstrom as a central skeleton. In other words, compound A has a π-electron conjugated system that is expanded and exhibits high planarity. Due to such a structure, compound A is presumed to have excellent two-photon absorption properties.

The light absorbing material of the present disclosure can be used for applications such as a recording layer of a three-dimensional optical memory and a photocurable resin composition for stereolithography. The light absorbing material of the present disclosure tends to have excellent two-photon absorption characteristics with respect to light having a wavelength in the short wavelength range. Therefore, the light absorbing material of the present disclosure can realize extremely high spatial resolution in applications such as a three-dimensional optical memory and a modeling machine. According to the light absorbing material of the present disclosure, it is possible to absorb two photons with a laser beam having a smaller light intensity than that of a conventional light absorbing material.

Claims (16)

1. A light absorbing material containing a compound represented by the following formula (1) as a main component.
   

   

   In the above formula (1)
   R ¹ to R ³⁰ contain at least one atom selected from the group consisting of H, C, N, O, F, P, S, Cl, I and Br independently of each other.
   L ¹ to L ³ are independently represented by the following equations (2) or (3).
   

   

   In the formula (2), n is 1 or 2.
   In the formula (3), R ³¹ to R ³⁴ contain at least one atom selected from the group consisting of H, C, N, O, F, P, S, Cl, I and Br independently of each other. ..
2. The compound is represented by the following formula (4).
   The light absorbing material according to claim 1.
   

   
3. The compound is represented by the following formula (5).
   The light absorbing material according to claim 1.
   

   
4. The compound is represented by the following formula (6).
   The light absorbing material according to claim 1.
   

   

   In the formula (6), R ³⁵ to R ⁴⁶ contain at least one atom selected from the group consisting of H, C, N, O, F, P, S, Cl, I and Br independently of each other. ..
5. The R ¹ to R ³⁰ are independent of each other and have a hydrogen atom, a halogen atom, an alkyl group, an alkyl halide group, an unsaturated hydrocarbon group, a hydroxyl group, a carboxyl group, an alkoxycarbonyl group, an acyl group and an amide group. A nitrile group, an alkoxy group, an acyloxy group, a thiol group, an alkylthio group, a sulfonic acid group, an acylthio group, an alkylsulfonyl group, a sulfonamide group, a primary amino group, a secondary amino group, a tertiary amino group or a nitro group.
   The light absorbing material according to any one of claims 1 to 4.
6. At least one selected from the group consisting of R ¹⁶ to R ¹⁸ , R ²¹ to R ²³ , and R ²⁶ to R ²⁸ is an electron donating group or an electron withdrawing group.
   The light absorbing material according to any one of claims 1 to 5.
7. The electron-withdrawing group is a carboxyl group or an alkoxycarbonyl group.
   The light absorbing material according to claim 6.
8. The electron-withdrawing group is -COO (CH ₂ ) ₃ CH ₃ .
   The light absorbing material according to claim 6 or 7.
9. At least one selected from the group consisting of R ¹ to R ⁶ is a hydrogen atom, a halogen atom, an alkyl group having 1 or more and 5 or less carbon atoms, an alkyl group having 7 or more carbon atoms, an alkyl halide group, and unsaturated carbide. Hydrogen group, hydroxyl group, carboxyl group, alkoxycarbonyl group, acyl group, amide group, nitrile group, alkoxy group, acyloxy group, thiol group, alkylthio group, sulfonic acid group, acylthio group, alkylsulfonyl group, sulfonamide group, 1 A primary amino group, a secondary amino group, a tertiary amino group or a nitro group,
   The light absorbing material according to any one of claims 1 to 8.
10. The compound is represented by the following formula (7), and at least one selected from the group consisting of R ¹⁶ , R ²¹ and R ²⁶ is a halogen atom, an alkyl group, an alkyl halide group, or an unsaturated hydrocarbon group. , Hydroxyl group, carboxyl group, alkoxycarbonyl group, acyl group, amide group, nitrile group, alkoxy group, acyloxy group, thiol group, alkylthio group, sulfonic acid group, acylthio group, alkylsulfonyl group, sulfonamide group, primary amino Group, secondary amino group, tertiary amino group or nitro group,
    The light absorbing material according to claim 1 or 2.
    

    
11. The compound has a light absorption effect.
    The light absorbing material according to any one of claims 1 to 10.
12. Used for devices that utilize light with a wavelength of 390 nm or more and 420 nm or less.
    The light absorbing material according to any one of claims 1 to 11.
13. A recording medium including a recording layer containing the light absorbing material according to any one of claims 1 to 12.
14. Preparing a light source that emits light with a wavelength of 390 nm or more and 420 nm or less,
    Condensing the light from the light source and irradiating the recording layer in the recording medium according to claim 13 with the light.
    How to record information, including.
15. A method of reading information recorded by the recording method according to claim 14.
    The reading method is
    By irradiating the recording layer in the recording medium with light, the optical characteristics of the recording layer can be measured.
    Determining whether or not information is recorded on the recording layer based on the optical characteristics
    How to read information, including.
16. The optical characteristic is the intensity of the light reflected by the recording layer.
    The reading method according to claim 15.

Images