Light-absorbing material, recording medium, information recording method, and information reading method

Abstract

A light-absorbing material according to one embodiment of the present disclosure comprises a compound represented by formula (1) as a main component. In formula (1), each of R1 to R14 contains, independently from one another, at least one atom that is selected from the group consisting of H, C, N, O, F, P, S, Cl, I and Br; and n represents an integer of 2 or more.

Description

[Technical Field]

[0001] The present disclosure relates to light-absorbing materials, recording media, methods for recording information, and methods for reading information. [Background technology]

[0002] Among optical materials such as light-absorbing materials, materials that exhibit nonlinear optical effects are called nonlinear optical materials. Nonlinear optical effects refer to the occurrence of optical phenomena in a material when irradiated with strong light such as laser light, which are proportional to the square or higher-order of the electric field of the irradiated light. Examples of optical phenomena include absorption, reflection, scattering, and light emission. Examples of second-order nonlinear optical effects proportional to the square of the electric field of the irradiated light include second-harmonic generation (SHG), the Pockels effect, and the parametric effect. Examples of third-order nonlinear optical effects proportional to the cube of the electric field of the irradiated light include two-photon absorption, multi-photon absorption, third-harmonic generation (THG), and the Kerr effect. In this specification, multi-photon absorption, such as two-photon absorption, is sometimes referred to as nonlinear optical absorption. Materials capable of nonlinear optical absorption are sometimes referred to as nonlinear optical absorption materials. In particular, materials capable of two-photon absorption are sometimes referred to as two-photon absorption materials.

[0003] Much research has been conducted on nonlinear optical materials. In particular, inorganic materials that can be easily prepared as single crystals have been developed as nonlinear optical materials. In recent years, the development of nonlinear optical materials made from organic materials has been anticipated. Examples of nonlinear optical materials made from organic materials include organic dyes. Compared to inorganic materials, organic materials not only have a high degree of design freedom but also have large nonlinear optical constants. Furthermore, organic materials exhibit high-speed nonlinear response. In this specification, nonlinear optical materials containing organic materials may be referred to as organic nonlinear optical materials. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5769151 [Patent Document 2] Patent No. 5821661 [Patent Document 3] Patent No. 5659189 [Non-patent literature]

[0005] [Non-Patent Document 1] Harry L. Anderson et al, "Two-Photon Absorption and the Design of Two-Photon Dyes", Angew. Chem. Int. Ed. 2009, Vol. 48, p. 3244-3266. Summary of the Invention [Problem to be solved by the invention]

[0006] Conventional light-absorbing materials have room for improvement in terms of nonlinear light absorption properties for light having wavelengths in the short wavelength range. [Means for solving the problem]

[0007] In one embodiment of the present disclosure, the light-absorbing material is The compound represented by the following formula (1) is contained as the main component. [ka] In the formula (1), R 1 From R 14 each independently contain at least one atom selected from the group consisting of H, C, N, O, F, P, S, Cl, I and Br, and n is an integer of 2 or more. [Effects of the Invention]

[0008] The present disclosure provides a light-absorbing material with improved nonlinear optical absorption properties for light having wavelengths in the short wavelength range. [Brief explanation of the drawings]

[0009] [Figure 1A] FIG. 1A is a flowchart illustrating a method for recording information using a recording medium including a light-absorbing material according to one embodiment of the present disclosure. [Figure 1B] FIG. 1B is a flowchart illustrating a method for reading information using a recording medium including a light-absorbing material according to one embodiment of the present disclosure. [Figure 2A] FIG. 2A is a graph showing the 1H-NMR spectrum of the compound of Example 1. [Figure 2B] FIG. 2B is an expanded view of the graph of FIG. 2A. [Figure 3A] FIG. 3A is a graph showing the 1H-NMR spectrum of the compound of Example 2. [Figure 3B] FIG. 3B is an expanded view of the graph of FIG. 3A. [Figure 4A] FIG. 4A is a graph showing the 1H-NMR spectrum of the compound of Example 3. [Figure 4B] FIG. 4B is an expanded view of the graph of FIG. 4A. [Figure 5A] FIG. 5A is a graph showing the 1H-NMR spectrum of the compound of Example 4. [Figure 5B] FIG. 5B is an expanded view of the graph of FIG. 5A. [Figure 6A] FIG. 6A is a graph showing the 1H-NMR spectrum of the compound of Example 5. [Figure 6B] FIG. 6B is an expanded view of the graph of FIG. 6A. DETAILED DESCRIPTION OF THE INVENTION

[0010] (Findings that formed the basis of this disclosure) Among organic nonlinear optical materials, two-photon absorption materials have attracted particular attention. Two-photon absorption refers to the phenomenon in which a compound absorbs two photons almost simultaneously and transitions to an excited state. Known two-photon absorption types include non-resonant two-photon absorption and resonant two-photon absorption. Non-resonant two-photon absorption refers to two-photon absorption in a wavelength range where no single-photon absorption band exists. In non-resonant two-photon absorption, a compound absorbs two photons almost simultaneously and transitions to a higher excited state. In resonant two-photon absorption, a compound absorbs the first photon and then absorbs the second photon, transitioning to a higher excited state. In resonant two-photon absorption, a compound absorbs two photons sequentially.

[0011] If the two-photon absorbing material also has fluorescent properties, it can be applied to fluorescent dye materials used in two-photon fluorescence microscopes, etc. If this two-photon absorbing material is used in three-dimensional optical memory, it may be possible to adopt a method for reading the ON / OFF state of a recording layer based on changes in fluorescence from the two-photon absorbing material. Current optical memories use a method for reading the ON / OFF state of a recording layer based on changes in the light reflectance and light absorbance of the two-photon absorbing material. However, when this method is applied to three-dimensional optical memory, crosstalk can occur due to recording layers other than the one whose ON / OFF state should be read.

[0012] In two-photon absorption materials, the two-photon absorption cross section (GM value) is used as an index of two-photon absorption efficiency. The unit of the two-photon absorption cross section is GM (10 -50 cm 4 ·s·molecule -1 photon -1) Up to now, many organic two-photon absorption materials with large two-photon absorption cross sections have been proposed. For example, many compounds with large two-photon absorption cross sections exceeding 500 GM have been reported (e.g., Non-Patent Document 1). However, in most reports, the two-photon absorption cross section was measured using laser light with a wavelength longer than 600 nm. In particular, near-infrared light with a wavelength longer than 750 nm is sometimes used as the laser light.

[0013] However, in order to apply two-photon absorption materials to industrial applications, materials that exhibit two-photon absorption properties when irradiated with laser light having a shorter wavelength are desired. For example, in the field of three-dimensional optical memory, laser light having a short wavelength can realize a finer focused spot, thereby improving the recording density of three-dimensional optical memory. In the field of stereolithography, laser light having a short wavelength can also realize modeling with higher resolution. Furthermore, the Blu-ray (registered trademark) disc standard uses laser light with a central wavelength of 405 nm. Thus, the development of compounds that exhibit excellent two-photon absorption properties for light in the same wavelength range as short-wavelength laser light would greatly contribute to industrial development.

[0014] Furthermore, light-emitting devices that emit high-intensity ultrashort pulse lasers tend to be large and unstable in operation. Therefore, such light-emitting devices are difficult to adopt for industrial applications from the viewpoints of versatility and reliability. In consideration of this, in order to apply two-photon absorption materials to industrial applications, a material that exhibits two-photon absorption properties even when irradiated with low-intensity laser light is desired.

[0015] In a compound having two-photon absorption properties, the relationship between light intensity and two-photon absorption properties is expressed by the following formula (i). In this specification, a compound having two-photon absorption properties may be referred to as a two-photon absorption compound. Formula (i) is a calculation formula for calculating the decrease in light intensity -dI when a sample containing a two-photon absorption compound and having a minute thickness dz is irradiated with light of intensity I. As can be seen from formula (i), the decrease in light intensity -dI is expressed as the sum of a term proportional to the first power of the intensity I of the light incident on the sample and a term proportional to the square of the intensity I.

number

[0016] In formula (i), α is the one-photon absorption coefficient (cm -1 ) α (2) is the two-photon absorption coefficient (cm / W). From equation (i), it is clear that the intensity I of the incident light when the one-photon absorption amount and the two-photon absorption amount are equal in the sample is α / α (2) In other words, the intensity of the incident light I is expressed as α / α (2) When the incident light intensity I is smaller than α / α, one-photon absorption occurs predominantly in the sample. (2) When the α / α ratio in the sample is larger than α, two-photon absorption occurs preferentially. (2) The smaller the value of , the more likely it is that two-photon absorption can be preferentially exhibited by laser light with a lower light intensity.

[0017] Furthermore, α and α (2) can be expressed by the following formulas (ii) and (iii), respectively. In formulas (ii) and (iii), ε is the molar absorption coefficient (mol -1 L cm -1 ) where N is the number of molecules of the compound per unit volume of the sample (mol cm -3 ) N A is the Avogadro constant. σ is the two-photon absorption cross section (GM). h-(Hbar) is the Dirac constant (J·s). ω is the angular frequency of the incident light (rad / s).

number

[0018] From equations (ii) and (iii), α / α (2) is determined by ε / σ. In other words, in order to preferentially induce two-photon absorption using low-intensity laser light, it is desirable that the ratio σ / ε of the two-photon absorption cross section σ to the molar extinction coefficient ε be large for the wavelength of the irradiated laser light. When the ratio σ / ε is large at a specific wavelength for a compound, it can be said that the nonlinearity of light absorption at that wavelength is high.

[0019] Previous attempts have been made to further expand the conjugated system of through-bond pi-conjugated compounds in order to achieve a high two-photon absorption cross section. A through-bond pi-conjugated compound is a compound in which the conjugated system is expanded via covalent bonds. In a through-bond pi-conjugated compound, multiple pi electron clouds interact via covalent bonds. However, expanding the conjugated system of a through-bond pi-conjugated compound tends to shift the absorption wavelength resulting from one-photon absorption to a longer wavelength. In this specification, the shift in the absorption wavelength resulting from one-photon absorption to a longer wavelength is sometimes referred to as a long-wavelength shift or red shift. As a result of the long-wavelength shift in the absorption wavelength resulting from one-photon absorption, part of the wavelength range in which one-photon absorption occurs may overlap with the wavelength of the excitation light. An example of the wavelength of the excitation light is 405 nm, as specified by the Blu-ray (registered trademark) standard. When one-photon absorption occurs in a compound due to excitation light, the ratio σ / ε tends to decrease significantly, resulting in a significant deterioration in nonlinear optical absorption characteristics.

[0020] As a result of extensive research, the present inventors have newly discovered that a compound represented by the formula (1) described below has excellent nonlinear optical absorption properties for light having a wavelength in the short wavelength range. In this specification, the short wavelength range means a wavelength range including 405 nm, for example, a wavelength range of 390 nm to 420 nm. In particular, the compound represented by formula (1) has excellent nonlinear optical absorption properties for light having a wavelength around 405 nm. Furthermore, in this compound, the longer the chain length, the more the nonlinear optical absorption properties tend to improve.

[0021] (Summary of one aspect of the present disclosure) The light-absorbing material according to the first aspect of the present disclosure comprises: The compound represented by the following formula (1) is contained as the main component. [ka] In the formula (1), R 1 From R 14 each independently contain at least one atom selected from the group consisting of H, C, N, O, F, P, S, Cl, I and Br, and n is an integer of 2 or more.

[0022] The light-absorbing material according to the first embodiment tends to exhibit a large ratio σ / ε of the two-photon absorption cross section σ to the molar extinction coefficient ε for light having a wavelength in the short wavelength range, and thus exhibits excellent nonlinear light absorption properties. Thus, the light-absorbing material has improved nonlinear light absorption properties for light having a wavelength in the short wavelength range. When n in formula (1) is 2 or greater, the compound forms, for example, a pi-stacked structure. A pi-stacked structure refers to a structure in which multiple pi electron clouds interact with each other via space. A compound in which a pi-stacked structure is formed within the molecule is sometimes called a through-space pi-conjugated compound. The longer the chain length of a compound of formula (1), the more likely it is that the nonlinear light absorption properties will be improved. Compounds of formula (1) also tend to have high solubility in organic solvents.

[0023] In the second aspect of the present disclosure, for example, in the light-absorbing material according to the first aspect, the R 1From the R 14 may each independently be a hydrogen atom, a halogen atom, a saturated hydrocarbon group, a halogenated alkyl group, an unsaturated hydrocarbon group, a hydroxyl group, a carboxyl group, an alkoxycarbonyl group, an aldehyde group, an acyl group, 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.

[0024] In the third aspect of the present disclosure, for example, in the light-absorbing material according to the first or second aspect, the R 2 , the R 3 , the R 7 , the R 8 , the R 12 and the R 13 At least one selected from the group consisting of may be an electron-donating group.

[0025] In a fourth aspect of the present disclosure, for example, in the light-absorbing material according to the third aspect, the electron-donating group may be an alkoxy group.

[0026] In a fifth aspect of the present disclosure, for example, in the light-absorbing material according to the third or fourth aspect, the electron-donating group may be -OCH3.

[0027] In a sixth aspect of the present disclosure, for example, in the light-absorbing material according to any one of the first to fifth aspects, the R 5 and the R 10 At least one selected from the group consisting of may be an electron-withdrawing group.

[0028] In a 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 halogen group.

[0029] In an eighth aspect of the present disclosure, for example, in the light-absorbing material according to any one of the first to seventh aspects, the compound may have a helical structure.

[0030] In a ninth aspect of the present disclosure, for example, in the light-absorbing material according to any one of the first to eighth aspects, the compound may have the property of absorbing specific light.

[0031] In a tenth aspect of the present disclosure, for example, the light-absorbing material according to any one of the first to ninth aspects may be used in a device that utilizes light having a wavelength of 390 nm or more and 420 nm or less.

[0032] According to the second to tenth aspects, the light-absorbing material has improved nonlinear optical absorption properties for light having a wavelength in the short wavelength range, and is suitable for use in devices that utilize light having a wavelength of 390 nm or more and 420 nm or less.

[0033] A recording medium according to an eleventh aspect of the present disclosure includes: The optical recording medium comprises a recording layer containing the light-absorbing material according to any one of the first to tenth aspects.

[0034] According to the eleventh aspect, the light-absorbing material has improved nonlinear light absorption characteristics for light having a wavelength in the short wavelength range, and a recording medium including a recording layer containing such a light-absorbing material can record information at a high recording density.

[0035] An information recording method according to a twelfth aspect of the present disclosure includes: providing a light source that emits light having a wavelength of 390 nm or more and 420 nm or less; and condensing the light from the light source and irradiating the light onto the recording layer of the recording medium according to the eleventh aspect.

[0036] According to the twelfth aspect, the light-absorbing material has improved nonlinear light absorption characteristics for light having a wavelength in the short wavelength range, and an information recording method using a recording medium having a recording layer containing such a light-absorbing material allows information to be recorded at a high recording density.

[0037] A method for reading information according to a thirteenth aspect of the present disclosure is, for example, a method for reading information recorded by the recording method according to the twelfth aspect, The reading method includes: measuring optical properties of the recording layer by irradiating the recording layer with light; and reading the information from the recording layer.

[0038] In a fourteenth aspect of the present disclosure, for example, in the information reading method according to the thirteenth aspect, the optical property may be the intensity of light reflected by the recording layer.

[0039] According to the thirteenth or fourteenth aspect, information can be easily read out.

[0040] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. The present disclosure is not limited to the following embodiments.

[0041] (Embodiment) The light-absorbing material of this embodiment contains a compound A represented by the following formula (1). [ka]

[0042] In formula (1), R 1 From R 14 R each independently contain at least one atom selected from the group consisting of H, C, N, O, F, P, S, Cl, I and Br. 1 From R 14 may each independently be a hydrogen atom, a halogen atom, a saturated hydrocarbon group, a halogenated alkyl group, an unsaturated hydrocarbon group, a hydroxyl group, a carboxyl group, an alkoxycarbonyl group, an aldehyde group, an acyl group, 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.

[0043] Examples of halogen atoms include F, Cl, Br, and I. In this specification, halogen atoms may be referred to as halogen groups.

[0044] The saturated hydrocarbon group is, for example, an aliphatic saturated hydrocarbon group. A specific example of the aliphatic saturated hydrocarbon group is an alkyl group. The number of carbon atoms in the alkyl group is not particularly limited and is, for example, 1 to 20. From the viewpoint of facilitating the synthesis of compound A, the number of carbon atoms in the alkyl group may be 1 to 10 or 1 to 5. By adjusting the number of carbon atoms in the alkyl group, the solubility of compound A in a solvent or resin composition can be adjusted. The alkyl group may be linear, branched, or cyclic. 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. Examples of the alkyl group include 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, an undecyl group, a dodecyl group, a tridecyl group, a tetradecyl group, a pentadecyl group, a hexadecyl group, a heptadecyl group, an octadecyl group, a nonadecyl group, an eicosyl group, a 2-methoxybutyl group, and a 6-methoxyhexyl group.

[0045] The halogenated alkyl group refers to a group in which at least one hydrogen atom contained in an alkyl group is substituted with a halogen atom. The halogenated alkyl 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 mentioned above. A specific example of the halogenated alkyl group is -CF3.

[0046] The unsaturated hydrocarbon group contains an unsaturated bond such as a carbon-carbon double bond or a carbon-carbon triple bond. The number of unsaturated bonds contained in the unsaturated hydrocarbon group is, for example, 1 to 5. The number of carbon atoms in the unsaturated hydrocarbon group is not particularly limited and is, for example, 2 to 20, or may be 2 to 10, or may be 2 to 5. The unsaturated hydrocarbon group may be linear, branched, or cyclic. 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.

[0047] A hydroxyl group is represented by -OH. A carboxyl group is represented by -COOH. An alkoxycarbonyl group is represented by -COOR. a The aldehyde group is represented by -COH. The acyl group is represented by -COR. b The amide group is represented by -CONR c R d A nitrile group is represented by -CN. An alkoxy group is represented by -OR. e The acyloxy group is represented by -OCOR f A thiol group is represented by -SH. An alkylthio group is represented by -SR. g The sulfonic acid group is represented by -SO3H. The acylthio group is represented by -SCOR h The alkylsulfonyl group is represented by -SO2R i The sulfonamide group is represented by -SO2NR j R k A primary amino group is represented by -NH2. A 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 -NO2. R a From R n are each independently an alkyl group. Examples of the alkyl group include those mentioned above. However, the R c and R d , and R of the sulfonamide groupj and R k may be, independently of each other, a hydrogen atom.

[0048] Specific examples of alkoxycarbonyl groups are -COOCH3, -COO(CH2)3CH3, and -COO(CH2)7CH3. Specific examples of acyl groups are -COCH3. Specific examples of amido groups are -CONH2. Specific examples of alkoxy groups are methoxy, ethoxy, 2-methoxyethoxy, butoxy, 2-methylbutoxy, 2-methoxybutoxy, 4-ethylthiobutoxy, pentyloxy, hexyloxy, heptyloxy, octyloxy, nonyloxy, decyloxy, undecyloxy, dodecyloxy, tridecyloxy, tetradecyloxy, pentadecyloxy, hexadecyloxy, heptadecyloxy, octadecyloxy, nonadecyloxy, and eicosyloxy. Specific examples of acyloxy groups are -OCOCH3. A specific example of an alkylthio group is -SCH3. A specific example of an acylthio group is -SCOCH3. A specific example of an alkylsulfonyl group is -SO2CH3. A specific example of a sulfonamide group is -SO2NH2. A specific example of a tertiary amino group is -N(CH3)2.

[0049] In formula (1), R 2 , R 3 , R 7 , R 8 , R 12 and R 13 At least one selected from the group consisting of is, for example, an electron-donating group. 2 , R 3 , R 7 , R 8 , R 12 and R 13 Each of R may be an electron donating group. 2 , R 3 , R 7 , R 8 , R 12 or R 13 Compound A, in which is an electron donating group, can be easily synthesized. Compound A also tends to have high nonlinear optical absorption properties.

[0050] The electron-donating group is, for example, a group having a substituent constant σ in the Hammett formula. p The term "-" refers to a substituent whose value is negative. Examples of electron-donating groups include alkyl groups, alkoxy groups, hydroxyl groups, and amino groups. The electron-donating group may be an alkoxy group or -OCH3. The electron-donating group may be an alkyl group or -C(CH3)3.

[0051] In formula (1), R 5 and R 10 At least one selected from the group consisting of is, for example, an electron-withdrawing group. 5 and R 10 Each of R may be an electron-withdrawing group. 5 or R 10 Compound A, in which is an electron-withdrawing group, can be easily synthesized. Compound A also tends to have excellent stability.

[0052] The electron-withdrawing group is, for example, the above σ p The term "-Br" refers to a substituent in which the value is positive. Examples of electron-withdrawing groups include halogen groups, carboxyl groups, nitro groups, thiol groups, sulfonic acid groups, acyloxy groups, alkylthio groups, alkylsulfonyl groups, sulfonamide groups, acyl groups, acylthio groups, alkoxycarbonyl groups, and halogenated alkyl groups. The electron-withdrawing group may be a halogen group or -Br.

[0053] In formula (1), R 1 From R 14 Among them, R 1 , R 4 , R 6 , R 9 , R 11 and R 14 Each of R 1 , R 4 , R 6 , R 9 , R 11 and R 14 In this case, R may have a smaller volume than the substituents other than R. 1, R 4 , R 6 , R 9 , R 11 and R 14 Therefore, in compound A, a pi-stack structure is easily formed, and the nonlinear optical absorption characteristics tend to be improved. 1 , R 4 , R 6 , R 9 , R 11 and R 14 Each of may be a hydrogen atom.

[0054] In formula (1), n ​​is an integer of 2 or more. n may be 6 or more, 10 or more, 12 or more, or 14 or more. The larger the value of n, the longer the chain length of compound A. In compound A, the longer the chain length, the more likely it is that the nonlinear optical absorption properties will be improved. That is, in compound A, unlike conventional through-bond type pi-conjugated compounds, the degradation of nonlinear optical absorption properties tends to be suppressed even when the pi-conjugated system is extended. The upper limit of n is not particularly limited and is, for example, 46. Specific examples of n include 2, 6, 10, 12, and 14.

[0055] Compound A has, for example, a helical structure. The helical structure may be right-handed or left-handed. In the light-absorbing material, compounds A having right-handed helical structures and compounds A having left-handed helical structures may coexist. The helical direction of compound A tends to easily reverse in solution.

[0056] When compound A has a helical structure, a pi-stack structure is easily formed in compound A. For example, when n is 2 in formula (1), compound A has an ortho-phenylene tetramer structure. When compound A has a helical structure, the two ortho-phenylenes located at the ends of compound A can form a pi-stack structure. In formula (1), the larger the value of n, the greater the number of ortho-phenylenes that can form a pi-stack structure. Note that in the ortho-phenylene trimer structure in formula (1) where n is 1, a pi-stack structure is not formed. Therefore, the ortho-phenylene trimer structure hardly exhibits nonlinear optical absorption properties.

[0057] A specific example of the compound A represented by formula (1) is the compound B represented by the following formula (2). [ka]

[0058] In formula (2), multiple Zs are the same. 2 , R 3 , R 7 , R 8 , R 12 and R 13 Each of the X's corresponds to a corresponding one of the plurality of Z's. Z's are, for example, alkoxy groups such as -OCH3. In formula (2), the plurality of X's are the same as each other. R in formula (1) 5 and R 10 Each of the represents a corresponding one of the plurality of X. X is, for example, a halogen group such as -Br.

[0059] The method for synthesizing compound B represented by formula (2) is not particularly limited. Compound B can be synthesized, for example, by utilizing the coupling reaction described in the Examples.

[0060] Compound A represented by formula (1) has a large ratio σ / ε of the two-photon absorption cross section σ to the molar extinction coefficient ε for light having a wavelength in the short wavelength range, and has high nonlinear optical absorption properties. The ratio σ / ε of compound A for light having a wavelength in the short wavelength range tends to be larger than that of conventional two-photon absorption compounds disclosed in, for example, Patent Documents 1 to 3. For example, when compound A is irradiated with light having a wavelength of 405 nm, compound A tends to exhibit significant nonlinear optical absorption. As described above, compound A tends to have improved nonlinear optical absorption properties as the chain length increases. Compound A with improved nonlinear optical absorption properties can, for example, improve the recording density of three-dimensional optical memories.

[0061] The two-photon absorption cross section of compound A for light having a wavelength of 405 nm may be 1 GM or more, 10 GM or more, 30 GM or more, 50 GM or more, 70 GM or more, 100 GM or more, 200 GM or more, or 300 GM or more. The upper limit of the two-photon absorption cross section of compound A is not particularly limited, and is, for example, 10,000 GM. The two-photon absorption cross section can be measured, for example, by 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, a measurement sample is moved along the irradiation direction of a laser beam near the focal point where the beam is focused. At this time, changes in the amount of light transmitted through the measurement sample are recorded. In the Z-scan method, the power density of the incident light changes depending on the position of the measurement sample. Therefore, if the sample undergoes nonlinear optical absorption, the amount of transmitted light will be attenuated when the sample is positioned near the focus of the laser beam. The two-photon absorption cross section can be calculated by fitting the change in the amount of transmitted light to a theoretical curve predicted from the intensity of the incident light, the thickness of the sample, and the concentration of compound A in the sample.

[0062] The molar extinction coefficient of compound A for light with a wavelength of 405 nm is 50 mol-1 L cm -1 may be less than 10 mol -1 L cm -1 may be less than 5 mol -1 L cm -1 It may be 2 mol or less -1 L cm -1 It may be less than 1 mol -1 L cm -1 The lower limit of the molar extinction coefficient of compound A is not particularly limited, and may be, for example, 0.01 mol -1 L cm -1 The molar extinction coefficient can be measured, for example, by a method conforming to the provisions of Japanese Industrial Standards (JIS) K0115:2004. To measure the molar extinction coefficient, a light source is used that irradiates light with a photon density that causes almost no two-photon absorption by compound A. Furthermore, to measure the molar extinction coefficient, the concentration of compound A is adjusted to 500 mmol / L. This concentration is much higher than the concentration used in the measurement test for the molar extinction coefficient of the light absorption peak. The molar extinction coefficient can be used as an index of one-photon absorption.

[0063] Compound A has a molar absorption coefficient ε (mol -1 L cm -1 The ratio σ / ε of the two-photon absorption cross section σ(GM) to the wavelength of light having a wavelength of 405 nm of compound A is large. The ratio σ / ε of compound A to light having a wavelength of 405 nm may be 20 or more, 30 or more, 50 or more, 70 or more, 100 or more, 150 or more, or 200 or more. The upper limit of the ratio σ / ε of compound A is not particularly limited, and is, for example, 5,000.

[0064] When compound A undergoes two-photon absorption, compound A absorbs approximately twice the energy of light irradiated onto compound A. The wavelength of light having approximately twice the energy of light having a wavelength of 405 nm is, for example, 200 nm. When compound A is irradiated with light having a wavelength around 200 nm, one-photon absorption may occur in compound A. Furthermore, compound A may undergo one-photon absorption with light having a wavelength close to the wavelength range in which two-photon absorption occurs.

[0065] Compound A also tends to have high solubility in organic solvents. This solubility is significantly improved when the direction of the helical structure of compound A can be easily reversed in solution. For example, the solubility of compound A in 1 mL of chloroform at 25°C is 100 mg or more. The upper limit of this solubility is not particularly limited, and is, for example, 500 mg. Compound A that is highly soluble in organic solvents is easy to handle and can be easily used in device applications.

[0066] The light-absorbing material of this embodiment may contain compound A represented by formula (1) as a main component. "Main component" refers to the component contained in the light-absorbing material in the largest amount by weight. The light-absorbing material may, for example, consist essentially of compound A. "Consisting essentially of" means excluding other components that alter the essential characteristics of the referenced material. However, the light-absorbing material may contain impurities in addition to compound A. Because the light-absorbing material of this embodiment contains compound A represented by formula (1), it tends to have excellent nonlinear optical absorption properties for light having wavelengths in the short wavelength range. The light-absorbing material of this embodiment containing compound A functions, for example, as a two-photon absorption material.

[0067] The light-absorbing material of this embodiment is used, for example, in devices that use light having a wavelength in the short wavelength range. As an example, the light-absorbing material of this embodiment is used in devices that use light having a wavelength of 390 nm or more and 420 nm or less. Examples of such devices include recording media, modeling machines, and fluorescence microscopes. Examples of recording media include three-dimensional optical memories. A specific example of three-dimensional optical memories is a three-dimensional optical disk. Examples of modeling machines include stereolithography machines such as 3D printers. Examples of fluorescence microscopes include two-photon fluorescence microscopes. The light used in these devices has a high photon density, for example, near its focus. The power density near the focus of the light used in the device is, for example, 0.1 W / cm. 2 Over 1.0 x 10 20 W / cm 2 The power density near the focal point of this light is 1.0 W / cm 2 It may be 1.0 x 10 or more. 2 W / cm 2 It may be 1.0 x 10 or more. 5 W / cm 2 As the light source of the device, for example, a femtosecond laser such as a titanium sapphire laser, or a pulsed laser having a pulse width of picoseconds to nanoseconds such as a semiconductor laser can be used.

[0068] The recording medium includes, for example, a thin film called a recording layer. In the recording medium, information is recorded in the recording layer. As an example, the thin film serving as the recording layer includes the light-absorbing material of this embodiment. That is, from another aspect thereof, the present disclosure provides a recording medium including the light-absorbing material including the above-mentioned compound A.

[0069] 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 also include a dielectric layer in addition to the recording layer. The recording medium may include, 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 stacked.

[0070] Next, a method for recording information using the above-mentioned recording medium will be described. FIG. 1A is a flowchart showing the method for recording information using the above-mentioned recording medium. First, in step S11, a light source is prepared that emits light having a wavelength of 390 nm or more and 420 nm or less. As the light source, for example, a femtosecond laser such as a titanium sapphire laser, or a pulsed laser having a pulse width of picoseconds to nanoseconds such as a semiconductor laser can be used. Next, in step S12, the light from the light source is focused using a lens or the like and irradiated onto the recording layer of the recording medium. More specifically, the light from the light source is focused using a lens or the like and irradiated onto the recording region of the recording medium. The power density near the focus of this light is, for example, 0.1 W / cm. 2 Over 1.0 x 10 20 W / cm 2 The power density near the focal point of this light is 1.0 W / cm 2 It may be 1.0 x 10 or more. 2 W / cm 2 It may be 1.0 x 10 or more. 5 W / cm 2 In this specification, the recording area means a spot that exists in the recording layer and that can record information when irradiated with light.

[0071] In the recording area irradiated with the light, a physical or chemical change occurs. For example, heat is generated when compound A, which has absorbed light, returns from a transition state to a ground state. This heat alters the binder present in the recording area. This changes the optical properties of the recording area. For example, the intensity of light reflected in the recording area, the reflectance of light in the recording area, the absorbance of light in the recording area, and the refractive index of light in the recording area change. In the recording area irradiated with light, the intensity or wavelength of fluorescent light emitted from the recording area may also change. This allows information to be recorded in the recording layer, specifically in the recording area (step S13).

[0072] Next, a method for reading information using the above-described recording medium will be described. FIG. 1B is a flowchart illustrating a method for reading information using the above-described recording medium. First, in step S21, light is irradiated onto the recording layer of the recording medium. More specifically, light is irradiated onto the recording area of ​​the recording medium. The light used in step S21 may be the same as or different from the light used to record information on the recording medium. Next, in step S22, the optical characteristics of the recording layer are measured. More specifically, the optical characteristics of the recording area are measured. In step S22, for example, the intensity of light reflected from the recording area may be measured as the optical characteristics of the recording area. In step S22, the optical characteristics of the recording area may include the reflectance of light in the recording area, the absorptance of light in the recording area, the refractive index of light in the recording area, the intensity of fluorescent light emitted from the recording area, and the wavelength of the fluorescent light. Next, in step S23, information is read from the recording layer, more specifically, the recording area.

[0073] In the information reading method, the recording area where information is recorded can be found by the following method. First, light is irradiated onto a specific area of ​​the recording medium. This light may be the same as or different from the light used to record information on the recording medium. Next, the optical characteristics of the area irradiated with light are measured. Examples of optical characteristics include the intensity of light reflected from the area, the reflectance of light in the area, the absorbance of light in the area, the refractive index of light in the area, the intensity of fluorescent light emitted from the area, and the wavelength of fluorescent light emitted from the area. Whether or not the area irradiated with light is a recording area is determined based on the measured optical characteristics. For example, if the intensity of light reflected from the area is equal to or less than a specific value, the area is determined to be a recording area. On the other hand, if the intensity of light reflected from the area is greater than a specific value, the area is determined to be not a recording area. Note that the method for determining whether or not the area irradiated with light is a recording area is not limited to the above method. For example, if the intensity of light reflected from the area is greater than a specific value, the area may be determined to be a recording area. Alternatively, if the intensity of light reflected from the area is equal to or less than a specific value, the area may be determined to be a non-recorded area. If it is determined to be a non-recorded area, the same operation is performed on other areas of the recording medium. This allows the search for a recorded area.

[0074] The information recording and reading methods using the above-mentioned recording medium can be performed, for example, by a known recording device that includes, for example, a light source that irradiates a recording area of ​​the recording medium with light, a measuring device that measures the optical characteristics of the recording area, and a controller that controls the light source and the measuring device.

[0075] The modeling machine performs modeling by, for example, irradiating a photocurable resin composition with light and curing the resin composition. As an example, a photocurable resin composition for stereolithography contains the light-absorbing material of this 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 also contain an epoxy resin.

[0076] The fluorescence microscope can be used to irradiate a biological sample containing a fluorescent dye material with light and observe the fluorescence emitted from the dye material. For example, the fluorescent dye material to be added to the biological sample contains the light-absorbing material of this embodiment. [Example]

[0077] The present disclosure will be described in more detail below with reference to examples. Note that the following examples are merely illustrative and the present disclosure is not limited to the following examples.

[0078] [Example 1] (Synthesis of compound OP4Br) First, a tetrahydrofuran solution containing 2,2'-dibromo-4,4',5,5'-tetramethoxybiphenyl was prepared under an argon atmosphere. Next, 28 mmol of a 1.57 mol / L n-butyllithium hexane solution was added to this solution and stirred at -78°C for 30 minutes. Next, copper cyanide powder (1.04 g, 12 mmol) was added to this reaction solution and stirred at room temperature for 2 hours. Next, duroquinone powder (5.70 g, 35 mmol) was added to this reaction solution and stirred at room temperature for 1.5 hours. This allowed the coupling reaction of 2,2'-dibromo-4,4',5,5'-tetramethoxybiphenyl to proceed. Next, this reaction solution was poured into aqueous ammonia, and the organic layer was extracted with ethyl acetate. The extracted organic layer was washed with saturated aqueous ammonium chloride and water and dried over magnesium sulfate. After drying, the ethyl acetate was removed by vacuum distillation. The resulting crude product was purified by column chromatography to synthesize compound OP4Br of Example 1. The compound OP4Br is represented by the following formula (3). [ka]

[0079] The compound OP4Br is 1 The compound OP4Br of Example 1 was identified by H-NMR and mass spectrometry. 12B is an enlarged view of the graph in FIG. 2A. 1 The results of H-NMR spectrum and mass analysis by high-resolution mass spectrometer (HRMS) using electrospray ionization-time-of-flight mass spectrometry were as follows: 1 The H-NMR spectrum reveals that the peaks originating from the hydrogen atoms attached to the benzene ring are shifted upfield, indicating that the compound OP4Br has a helical structure. 1 H NMR (600MHz, CD3CN): δ(ppm) 7.15-6.73 (m, 6H), 6.43 (br. 2H), 3.78 (s. 6H), 3.74 (br. 12H), 3.51 (s. 6H). HRMS (ESI-TOF mass): calcd. for C 32 H 32 Br2O8[M] + : m / z=704.04; found: 704.00.

[0080] [Example 2] (Synthesis of compound OP8Br) First, a tetrahydrofuran solution (42 mL) containing compound OP4Br (1.01 g, 1.4 mmol) synthesized in Example 1 was prepared under an argon atmosphere. Next, 2.2 mmol of a 1.58 mol / L n-butyllithium hexane solution was added to this solution and stirred at -78°C for 30 minutes. Next, copper cyanide powder (64.6 mg, 0.72 mmol) was added to this reaction solution and stirred at room temperature for 2 hours. Next, duroquinone powder (356 mg, 2.2 mmol) was added to this reaction solution and stirred at room temperature for 1.5 hours. This allowed the coupling reaction of compound OP4Br to proceed. Next, this reaction solution was poured into aqueous ammonia, and the organic layer was extracted with ethyl acetate. The extracted organic layer was washed with saturated aqueous ammonium chloride and water and dried over anhydrous magnesium sulfate. After drying, the ethyl acetate was removed by vacuum distillation. The resulting crude product was purified by column chromatography to synthesize compound OP8Br of Example 2. The compound OP8Br is represented by the following formula (4). [ka]

[0081] The compound OP8Br is 1 The compound OP8Br of Example 2 was identified by H-NMR. 1 3B is an enlarged view of the graph in FIG. 3A. 1 The H-NMR spectrum was as follows: 1 The H-NMR spectrum reveals that compound OP8Br has a helical structure. 1H NMR (600MHz, CD3CN): δ(ppm) 6.73 (s, 2H), 6.72 (s, 2H), 6.48 (s, 2H), 5.90 (s, 2H), 5.89 (s, 2H), 5.83 (s, 2H), 5.77 (s, 2H), 5.34 (s, 2H), 3.73 (s, 6H), 3.71 (s, 6H), 3.70 (s, 6H), 3.55 (s, 6H), 3.54 (s, 6H), 3.48 (s, 6H), 3.46 (s, 6H), 3.09 (s, 6H).

[0082] [Example 3] (Synthesis of compound OP12Br) First, an ortho-phenylene dodecamer represented by the following formula (5) was prepared. [ka]

[0083] Next, a dimethylformamide solution (20 mL) containing N-bromosuccinimide (18.5 g, 1.1 mmol) and the above ortho-phenylene dodecamer (0.90 g, 0.5 mmol) was prepared and stirred at 0°C for 1 hour. The solution was then warmed to room temperature and stirred for 4 hours. This allowed the bromination reaction of the ortho-phenylene dodecamer to proceed. The reaction solution was then poured into water and extracted with chloroform. The extract was washed with saturated saline and dried over magnesium sulfate. After drying, the chloroform was removed by vacuum distillation. The resulting crude product was purified by column chromatography to synthesize compound OP12Br of Example 3. Compound OP12Br is represented by the following formula (6). [ka]

[0084] The compound OP12Br is 1 The compound OP12Br of Example 3 was identified by H-NMR. 14B is an enlarged view of the graph in FIG. 4A. 1 The H-NMR spectrum was as follows: 1 The H-NMR spectrum reveals that compound OP12Br has a helical structure. 1 H NMR (600MHz, CD3CN): δ(ppm) 6.64 (s, 2H), 6.64 (s, 2H), 6.37 (s, 2H), 5.83 (s, 2H), 5.76 (s, 2H), 5.74 (s, 2H), 5.55 (s, 2H), 5.53 (s, 2H), 5.51 (s, 2H), 5.50 (s, 2H), 5.40 (s, 2H), 5.14 (s, 2H), 3.68 (s, 6H), 3.66 (s, 6H), 3.65 (s, 6H), 3.50 (s, 6H), 3.47 (s, 6H), 3.43 (s, 6H), 3.43 (s, 6H), 3.42 (s, 6H), 3.40 (s,6H), 3.39 (s, 6H), 3.38 (s, 6H).

[0085] [Example 4] (Synthesis of compound OP14Br) First, an ortho-phenylene 14-mer represented by the following formula (7) was prepared. [ka]

[0086] Next, a dimethylformamide solution (20 mL) containing N-bromosuccinimide (9.3 g, 0.53 mmol) and the above ortho-phenylene 14-mer (0.59 g, 0.25 mmol) was prepared and stirred at 0°C for 1 hour. The solution was then warmed to room temperature and stirred for 4 hours. This allowed the bromination reaction of the ortho-phenylene 14-mer to proceed. The reaction solution was then poured into water and extracted with chloroform. The extract was washed with saturated saline and dried over magnesium sulfate. After drying, the chloroform was removed by vacuum distillation. The resulting crude product was purified by column chromatography to synthesize compound OP14Br of Example 4. Compound OP14Br is represented by the following formula (8). [ka]

[0087] The compound OP14Br is 1 The compound OP14Br of Example 4 was identified by H-NMR. 1 5B is an enlarged view of the graph in FIG. 5A. 1 The H-NMR spectrum was as follows: 1 The H-NMR spectrum reveals that compound OP14Br has a helical structure. 1H NMR (600MHz, CD3CN): δ(ppm) 6.63 (s, 2H), 6.62 (s, 2H), 6.36 (s, 2H), 5.85 (s, 2H), 5.74 (s, 2H), 5.69 (s, 2H), 5.54 (s, 2H), 5.50 (s, 2H), 5.46 (s, 2H), 5.45 (s, 2H), 5.42 (s, 2H), 5.37 (s,2H), 5.35 (s, 2H), 5.12 (s, 2H), 3.67 (s, 6H), 3.65 (s, 6H), 3.64 (s, 6H), 3.48 (s, 6H), 3.47 (s, 6H), 3.42 (s, 6H), 3.41 (s, 6H), 3.40 (s, 6H), 3.39 (s, 6H), 3.369 (s, 12H), 3.365 (s, 12H), 3.02 (s, 6H).

[0088] [Example 5] (Synthesis of compound OP16Br) First, a tetrahydrofuran solution (60 mL) containing compound OP8Br (1.0 g, 0.80 mmol) synthesized in Example 2 was prepared under an argon atmosphere. Next, 3.2 mmol of a 1.8 mol / L t-butyllithium hexane solution was added to this solution and stirred at -78°C for 10 minutes. This solution was further stirred at -40°C for 15 minutes and then cooled to -78°C again. Next, copper cyanide powder (72 mg, 0.8 mmol) was added to the resulting reaction solution and stirred at room temperature for 1.5 hours. Next, duroquinone powder (200 mg, 1.2 mmol) was added to this reaction solution and stirred at room temperature for 12 hours. This allowed the coupling reaction of compound OP8Br to proceed. Next, this reaction solution was poured into aqueous ammonia, and the organic layer was extracted with ethyl acetate. The extracted organic layer was washed with saturated aqueous ammonium chloride and water and dried over anhydrous magnesium sulfate. After drying, the ethyl acetate was removed by vacuum distillation. The obtained crude product was purified by column chromatography to synthesize compound OP16Br of Example 5. Compound OP16Br is represented by the following formula (9). [ka]

[0089] The compound OP16Br is 1 The compound OP16Br of Example 5 was identified by H-NMR and mass spectrometry. 1 6B is an enlarged view of the graph in FIG. 6A. 1 The results of H-NMR spectrum and mass analysis by high-resolution mass spectrometer (HRMS) using electrospray ionization-time-of-flight mass spectrometry were as follows: 1 The H-NMR spectrum reveals that compound OP16Br has a helical structure. 1 H NMR (600MHz, CD3CN): δ(ppm) 6.624 (s, 2H), 6.616 (s, 2H), 6.36 (s, 2H), 5.84(s, 2H), 5.73 (s, 2H), 5.68 (s, 2H), 5.52 (s, 2H), 5.48 (s, 2H), 5.45 (s, 2H), 5.43 (s, 2H), 5.37 (s, 2H), 5.36 (s, 2H), 5.33 (s, 2H), 5.32 (s, 2H), 5.30 (s, 2H), 5.10 (s, 2H), 3.67 (s, 6H), 3.64 (s, 6H), 3.63 (s, 6H), 3.47 (s, 6H), 3.45 (s, 6H), 3.401 (s, 6H), 3.398 (s, 6H), 3.39 (s, 6H), 3.37 (s, 6H), 3.36 (s, 6H), 3.354 (s, 12H), 3.349 (s, 6H), 3.341 (s, 6H), 3.337 (s, 6H), 3.02 (s, 6H). HRMS (ESI-TOF mass): calcd. for C 128 H 128 BrO 32 [M] + : m / z=2334.68; found: 2335.12.

[0090] [Comparative Examples 1 and 2] Hexakis(phenylethynyl)benzene (HPEB), a compound of Comparative Example 1 represented by the following formula (10), was synthesized according to the method described in K. Kondo et al., J. Chem. Soc., Chem. Commun. 1995, 55-56, and W. Tao et al., J. Org. Chem. 1990, 55, 63-66. Compound 1f, a compound of Comparative Example 2 represented by the following formula (11), was synthesized according to the method disclosed in paragraph

[0083] of Patent Document 2. [ka]

[0091] <Measurement of two-photon absorption cross section> The two-photon absorption cross section of the compounds of the examples and comparative examples 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 pulsed laser was used as the light source for measuring the two-photon absorption cross section. Specifically, the second harmonic of the titanium sapphire pulsed laser was irradiated onto the sample. The laser pulse width was 80 fs. The laser repetition rate was 1 kHz. The average laser power was varied in the range of 0.01 mW to 0.08 mW. The light from the laser had a wavelength of 405 nm. Specifically, the light from the laser had a central wavelength of 402 nm to 404 nm. The full width at half maximum of the light from the laser was 4 nm.

[0092] <Measurement of molar extinction coefficient> The molar absorption coefficients of the compounds in the examples and comparative examples were measured according to the method specified in JIS K0115:2004. Specifically, a measurement sample was prepared in which the compound concentration was adjusted to 500 mmol / L. The absorption spectrum of the measurement sample was measured. From the obtained spectrum, the absorbance at a wavelength of 405 nm was read. The molar absorption coefficient was calculated based on the compound concentration in the measurement sample and the optical path length of the cell used for the measurement.

[0093] The two-photon absorption cross section σ(GM) and molar absorption coefficient ε(mol -1 L cm -1 ) and the ratio σ / ε are shown in Table 1.

[0094] [Table 1]

[0095] In conventional through-bond pi-conjugated compounds, improving the ratio σ / ε, which reflects the nonlinear optical absorption properties, required increasing the two-photon absorption cross section σ while decreasing the molar extinction coefficient ε. Generally, the two-photon absorption cross section σ is increased by extending the pi-conjugated dye. However, as the chain length increases, the light absorption wavelength shifts to longer wavelengths, and the molar extinction coefficient ε at the excitation wavelength (405 nm) increases. This approach has limitations in improving the nonlinear optical absorption properties. The through-space pi-conjugated compound of the present disclosure has a chemical structure corresponding to compound A represented by formula (1). Because the through-space pi-conjugated compound has a helical structure twisted at a steep angle, extending the chain length does not result in a longer wavelength shift of the light absorption wavelength, and it is possible to suppress an increase in the molar extinction coefficient ε. In other words, extending the chain length of a through-space pi-conjugated compound improves the nonlinear optical absorption properties of the through-space pi-conjugated compound.

[0096] As can be seen from Table 1, in the compounds of Examples 1 to 5 corresponding to compound A represented by formula (1), even when the chain length is extended, the two-photon absorption cross section σ increases, but the increase in the molar absorption coefficient ε is suppressed. As a result, compared to the compounds of the comparative examples, it can be seen that the nonlinear optical absorption characteristic σ / ε is improved, and the two-photon absorption characteristics are also improved. Therefore, the dye using the through-space conjugated system of the present disclosure can achieve both an increase in the two-photon absorption cross section and a decrease in the molar absorption coefficient as the chain length is extended, thereby further improving the nonlinear optical absorption characteristics.

[0097] It should be noted that the two-photon absorption cross section of the compound OP3Br, which has an ortho-phenylene trimer structure, could not be measured using the above method. The compound OP3Br is represented by the following formula (12). From this result, it can be seen that n in formula (1) must be an integer of 2 or greater. In other words, compound A must be a tetramer or higher of ortho-phenylene. [ka] [Industrial Applicability]

[0098] The light-absorbing material of the present disclosure can be used in applications such as recording layers for three-dimensional optical memories and photocurable resin compositions for stereolithography. The light-absorbing material of the present disclosure has light absorption properties that exhibit high nonlinearity for light having wavelengths in the short wavelength range. Therefore, the light-absorbing material of the present disclosure can achieve extremely high spatial resolution in applications such as three-dimensional optical memories and modeling machines. Compared to conventional light-absorbing materials, the light-absorbing material of the present disclosure can cause two-photon absorption to occur more frequently than one-photon absorption, even when irradiated with laser light of low light intensity.

Claims

1. Contains a compound represented by the following formula (1) as a main component: Light-absorbing material. 【Chemical 1】 In the formula (1), R 1 From R 14 each independently contain at least one atom selected from the group consisting of H, C, N, O, F, P, S, Cl, I and Br, n is an integer of 2 or more.

2. The R 1 From the above R 14 are each independently a hydrogen atom, a halogen atom, a saturated hydrocarbon group, a halogenated alkyl group, an unsaturated hydrocarbon group, a hydroxyl group, a carboxyl group, an alkoxycarbonyl group, an aldehyde group, an acyl group, 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 of claim 1 .

3. The R 2 , the R 3 , the R 7 , the R 8 , the R 12 and the R 13 At least one selected from the group consisting of is an electron donating group, 3. The light-absorbing material according to claim 1 or 2.

4. the electron donating group is an alkoxy group; The light-absorbing material of claim 3 .

5. The electron donating group is —OCH 3 That is, The light-absorbing material according to claim 3 or 4.

6. The R 5 and the R 10 At least one selected from the group consisting of is an electron-withdrawing group, 6. A light-absorbing material according to claim 1.

7. The electron-withdrawing group is a halogen group. The light-absorbing material of claim 6.

8. The compound has a helical structure.

8. A light-absorbing material according to any one of claims 1 to 7.

9. The compound has specific light absorbing properties.

9. A light-absorbing material according to any one of claims 1 to 8.

10. Used in devices that utilize light having a wavelength of 390 nm or more and 420 nm or less, 10. A light-absorbing material according to any one of claims 1 to 9.

11. A recording layer comprising the light-absorbing material according to any one of claims 1 to 10. Recording medium.

12. providing a light source that emits light having a wavelength of 390 nm or more and 420 nm or less; and irradiating the light from the light source onto the recording layer of the recording medium according to claim 11. How information is recorded.

13. A method for reading information recorded by the recording method according to claim 12, comprising: The reading method includes: measuring optical properties of the recording layer by irradiating the recording layer with light; reading the information from the recording layer. How to read the information.

14. the optical property is the intensity of light reflected by the recording layer; The reading method according to claim 13.

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