Nonlinear optical absorption material, recording medium, information recording method, and information reading method

Abstract

The nonlinear light absorption material according to one embodiment of the present disclosure contains, as a main component, a compound represented by formula (1).　In formula (1), R1 to R10 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.

Description

[Technical Field]

[0001] The present disclosure relates to nonlinear optically 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. 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. 5659189 [Patent Document 2] Patent No. 5821661 [Patent Document 3] Japanese Patent Application Laid-Open No. 2013-242939 [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 nonlinear optical absorption materials have room for improvement in terms of improving the nonlinear absorption characteristics for light having wavelengths in the short wavelength region. [Means for solving the problem]

[0007] In one embodiment of the present disclosure, the nonlinear optical absorption 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 10 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. [Effects of the Invention]

[0008] The present disclosure provides a nonlinear optical absorption material suitable for improving the nonlinear absorption characteristics 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 nonlinear optically absorbing material according to an embodiment of the present disclosure. [Figure 1B] FIG. 1B is a flowchart illustrating a method for reading information using a recording medium including a nonlinear optically absorbing material according to an embodiment of the present disclosure. [Figure 2A] FIG. 2A is a graph showing the 1H-NMR spectrum of compound (2)-1. [Figure 2B] FIG. 2B is a graph showing the 13C-NMR spectrum of compound (2)-1. 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 simultaneous two-photon absorption and stepwise two-photon absorption. Simultaneous two-photon absorption is sometimes called non-resonant two-photon absorption. Simultaneous two-photon absorption refers to two-photon absorption in a wavelength range where no single-photon absorption band exists. Stepwise two-photon absorption is sometimes called resonant two-photon absorption. In stepwise two-photon absorption, a compound absorbs the first photon and then absorbs the second photon, transitioning to a higher excited state. In stepwise two-photon absorption, a compound absorbs two photons sequentially.

[0011] In simultaneous two-photon absorption, the amount of light absorbed by a compound is usually proportional to the square of the irradiated light intensity and exhibits nonlinearity. The amount of light absorbed by a compound can be used as an indicator of the efficiency of two-photon absorption. When the amount of light absorbed by a compound exhibits nonlinearity, for example, light absorption by the compound can occur only near the focus of a laser beam with a high electric field strength. In other words, in a sample containing a two-photon absorbing material, the compound can be excited only at the desired position. In this way, compounds that exhibit simultaneous two-photon absorption provide extremely high spatial resolution, and therefore are being considered for use in applications such as recording layers for three-dimensional optical memories and photocurable resin compositions for stereolithography.

[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 required. For example, in the field of three-dimensional optical memory, laser light having a shorter 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 shorter wavelength can 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] In order to apply a compound having two-photon absorption properties to industrial applications, a two-photon absorption material containing the compound must fully exhibit two-photon absorption properties. In this specification, a compound having two-photon absorption properties may be referred to as a two-photon absorption compound. To fully exhibit the two-photon absorption properties of a two-photon absorption material, it is desirable that the two-photon absorption properties per molecule of the two-photon absorption compound be high, and that the density of the two-photon absorption compound in the two-photon absorption material be high. Note that a high two-photon absorption property per molecule of a two-photon absorption compound means that the two-photon absorption cross-section of the two-photon absorption compound is large.

[0015] Two-photon absorption compounds with high two-photon absorption properties per molecular size are suitable for improving the two-photon absorption properties per unit volume of two-photon absorption materials. For example, two-photon absorption compounds with small molecular size and large two-photon absorption cross-sections are suitable for improving the two-photon absorption cross-section per unit volume of two-photon absorption materials. An indicator of the two-photon absorption properties per molecular size of a two-photon absorption compound is the two-photon absorption cross-section per unit weight of the two-photon absorption compound. In this specification, the two-photon absorption cross-section per unit weight of a two-photon absorption compound is sometimes referred to as the GM·mol / g value. The GM·mol / g value is calculated by dividing the two-photon absorption cross-section (GM) of the two-photon absorption compound by the molecular weight (g / mol) of the two-photon absorption compound.

[0016] Patent Documents 1 and 2 disclose compounds having a large two-photon absorption cross section for light having a wavelength around 405 nm. Patent Document 3 discloses an optical information recording medium that can shorten the recording time when using laser light having a wavelength around 405 nm, and a compound contained in the optical information recording medium.

[0017] As a result of extensive research, the present inventors have newly discovered that a compound represented by formula (1) described below has high nonlinear absorption properties for light having wavelengths in the short wavelength range, leading to the completion of the nonlinear optical absorption material of the present disclosure. Specifically, the present inventors have discovered that a compound represented by formula (1) has a large GM·mol / g value for light having wavelengths in the short wavelength range. In this specification, the short wavelength range refers to a wavelength range including 405 nm, for example, a wavelength range of 390 nm to 420 nm.

[0018] (Summary of one aspect of the present disclosure) The nonlinear optical absorption 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 10 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.

[0019] According to the first aspect, the compound represented by formula (1) tends to have a large GM·mol / g value for light having a wavelength in the short wavelength region. This compound is suitable for improving the two-photon absorption cross section per unit volume of a nonlinear optical absorbing material. That is, a nonlinear optical absorbing material containing the compound represented by formula (1) is suitable for improving the nonlinear absorption characteristics for light having a wavelength in the short wavelength region. Furthermore, the compound represented by formula (1) also tends to have a small molar extinction coefficient for light having a wavelength in the short wavelength region.

[0020] In the second aspect of the present disclosure, for example, in the nonlinear optically absorbing material according to the first aspect, the compound may be represented by the following formula (2) or (3): [ka]

[0021] In the third aspect of the present disclosure, for example, in the nonlinear optical absorption material according to the first aspect, the R 1 From the R 10 may each be a hydrogen atom.

[0022] In a fourth aspect of the present disclosure, for example, in the nonlinear optical absorption material according to any one of the first to third aspects, the compound may have a nonlinear optical absorption effect.

[0023] In the fifth aspect of the present disclosure, for example, the nonlinear optically absorbing material according to any one of the first to fourth aspects may be used in a device that utilizes light having a wavelength of 390 nm or more and 420 nm or less.

[0024] The nonlinear optical absorption materials according to the second to fifth aspects are suitable for improving the nonlinear absorption characteristics of light having a wavelength in the short wavelength range, and are suitable for use in devices that utilize light having a wavelength of 390 nm or more and 420 nm or less.

[0025] A recording medium according to a sixth aspect of the present disclosure includes: The optical recording medium comprises a recording layer containing the nonlinear optical absorption material according to any one of the first to fifth aspects.

[0026] According to the sixth aspect, the nonlinear optical absorption material is suitable for improving the nonlinear absorption characteristics for light having a wavelength in the short wavelength region, and a recording medium including such a nonlinear optical absorption material can record information at a high recording density.

[0027] The information recording method according to the seventh 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 irradiating the light from the light source onto the recording layer of a recording medium containing the nonlinear optical absorption material according to the sixth aspect.

[0028] According to the seventh aspect, the nonlinear light-absorbing material is suitable for improving the nonlinear absorption characteristics for light having a wavelength in the short wavelength region, and according to the information recording method using the recording medium including such a nonlinear light-absorbing material, information can be recorded at a high recording density.

[0029] A method for reading information according to an eighth aspect of the present disclosure is, for example, a method for reading information recorded by the recording method according to the seventh aspect, The reading method includes: measuring optical characteristics of the recording layer by irradiating the recording layer of the recording medium with light; and reading the information from the recording layer.

[0030] In a ninth aspect of the present disclosure, for example, in the information reading method according to the eighth aspect, the optical property may be the intensity of light reflected by the recording layer.

[0031] According to the eighth or ninth aspect, information can be easily read out.

[0032] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. The present disclosure is not limited to the following embodiments.

[0033] (Embodiment) The nonlinear optical absorption material of this embodiment contains a compound A represented by the following formula (1). [ka]

[0034] In formula (1), R 1 From R 10 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 10 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.

[0035] Examples of halogen atoms include F, Cl, Br, and I. In this specification, halogen atoms may be referred to as halogen groups.

[0036] 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.

[0037] 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.

[0038] 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 unsaturated hydrocarbon groups include a vinyl group and an ethynyl group.

[0039] 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.

[0040] 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 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.

[0041] In formula (1), R 3 and R 8 At least one selected from the group consisting of may be an electron donating group or an electron withdrawing group. 3 or R 8 The greater the electron donating or electron withdrawing property of R, the greater the electron imbalance in compound A. When compound A has a large electron imbalance, electrons tend to move more widely within compound A when compound A is excited. Such compound A tends to have better two-photon absorption properties. In other words, R 3 and R 8 is an electron donating group or an electron withdrawing group, compound A tends to have a large two-photon absorption cross section. 3 and R 8 Each of may be a hydrogen atom.

[0042] The electron-withdrawing group is, for example, a substituent constant in the Hammett equation, σ p The term "electron-withdrawing group" refers to a substituent in which the value is positive. Examples of electron-withdrawing groups include halogen atoms, 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 carboxyl group or an alkoxycarbonyl group, or may be -COO(CH2)3CH3 or -COO(CH2)7CH3.

[0043] The electron-donating group is, for example, the above σ p The electron-donating group refers to a substituent whose value is negative. Examples of the electron-donating group include an alkyl group, an alkoxy group, a hydroxyl group, and an amino group.

[0044] In formula (1), R 1 , R 5 , R 6 and R 10 Each of the may have a small volume. 1 , R 5 , R 6 and R 10 In this case, steric hindrance is unlikely to occur. Therefore, the planarity of the π-electron conjugated system in compound A tends to be improved. When the π-electron conjugated system of compound A has high planarity, compound A tends to have a large two-photon absorption cross section. R 1 , R 5 , R 6 and R 10 Each of may be a hydrogen atom.

[0045] Furthermore, R 1 , R 2 and R 4 From R 10 may each be a hydrogen atom, and R 1 From R 7 , R 9 and R 10may each be a hydrogen atom. That is, compound A may be compound B represented by the following formula (2) or compound C represented by the following formula (3). [ka]

[0046] R in Equation (2) 3 and R in Eq. (3) 8 is the same as that described above for equation (1). R in equation (2) 3 and R in Eq. (3) 8 Specific examples of R are shown in Table 1 below. 3 may be -H. That is, in formula (1), R 1 From R 10 may each be a hydrogen atom.

[0047] [Table 1]

[0048] The method for synthesizing the compound B represented by formula (2) is not particularly limited. The compound B can be synthesized, for example, by the following method. First, a compound D represented by the following formula (4) is prepared. In formula (4), R 3 is the same as described above for equation (1). [ka]

[0049] Next, a coupling reaction between compound D and β-bromostyrene is carried out. This allows compound B to be synthesized. The conditions for the coupling reaction can be appropriately adjusted depending on the structure of compound D. Compound C of formula (3) can be synthesized by carrying out a coupling reaction similar to the synthesis method for compound B.

[0050] Compound A represented by formula (1) has excellent two-photon absorption properties and tends to have small one-photon absorption with respect to light having a wavelength in the short wavelength region. For example, when compound A is irradiated with light having a wavelength of 405 nm, two-photon absorption may occur in compound A, but one-photon absorption may hardly occur.

[0051] The two-photon absorption cross-section of compound A for light having a wavelength of 405 nm may be greater than 1 GM, greater than 10 GM, greater than 100 GM, or greater than 200 GM. The upper limit of the two-photon absorption cross-section of compound A is not particularly limited, and may be, for example, 5000 GM or 1000 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 direction of irradiation 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 measurement sample undergoes nonlinear optical absorption, the amount of transmitted light will be attenuated when the measurement sample is positioned near the focal point 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 measurement sample, the concentration of compound A in the measurement sample, etc.

[0052] The two-photon absorption cross section may be a calculated value obtained by computational chemistry. Several methods have been proposed for estimating the two-photon absorption cross section by computational chemistry. For example, the calculated value of the two-photon absorption cross section can be calculated based on the second-order nonlinear response theory described in J. Chem. Theory Comput. 2018, Vol. 14, p. 807.

[0053] In this embodiment, compound A tends to have a large two-photon absorption cross section (GM) per unit weight (GM·mol / g value) for light having a wavelength of 405 nm. The GM·mol / g value of compound A may be 0.9 or more, 1.0 or more, 1.5 or more, or 2.0 or more. The upper limit of the GM·mol / g value of compound A is not particularly limited and is, for example, 50.

[0054] The molar absorption coefficient of compound A for light with a wavelength of 405 nm is 100 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 less than 1 mol -1 L cm -1 It may be 0.1 mol or less. -1 L cm -1 The lower limit of the molar extinction coefficient of compound A is not particularly limited, and may be, for example, 0.00001 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. In measuring 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, in measuring the molar extinction coefficient, the concentration of compound A is adjusted to 1 mmol / L or more and 50 mmol / L or less. 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.

[0055] The molar extinction coefficient may be a calculated value using a quantum chemistry calculation program, such as Gaussian 16 (manufactured by Gaussian).

[0056] 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.

[0057] The nonlinear light-absorbing material of this embodiment may contain compound A represented by formula (1) as a main component. "Main component" means the component contained in the nonlinear light-absorbing material in the largest amount by weight. The nonlinear 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 nonlinear light-absorbing material may contain impurities in addition to compound A. The nonlinear light-absorbing material of this embodiment containing compound A functions, for example, as a two-photon absorption material.

[0058] The nonlinear optical absorption 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 nonlinear optical absorption 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 2It 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 such as a semiconductor laser having a pulse width of picoseconds to nanoseconds can be used.

[0059] 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 nonlinear optical absorption material of this embodiment. That is, from another aspect thereof, the present disclosure provides a recording medium including the nonlinear optical absorption material including the above-mentioned compound A.

[0060] The recording layer may further contain a polymer compound that functions as a binder in addition to the nonlinear 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.

[0061] 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 2It 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.

[0062] 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).

[0063] 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.

[0064] 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.

[0065] The information recording and reading methods using the above-mentioned recording medium can be performed, for example, by a known recording device, which 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.

[0066] 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 nonlinear optical absorption material of this embodiment. The photocurable resin composition contains, for example, a polymerizable compound and a polymerization initiator in addition to the nonlinear optical absorption 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.

[0067] 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 nonlinear light-absorbing material of this embodiment. [Example]

[0068] Hereinafter, the present disclosure will be described in more detail with reference to examples. Note that the following examples are merely illustrative, and the present disclosure is not limited to the following examples. In the present disclosure, the compounds used in the examples will be referred to as "compound (X)-Y". "X" refers to the structural formula of the compound. "Y" refers to the substituent R in formula (X). 3 or R 8 The value of "Y" corresponds to that in Table 1. For example, compound (2)-1 is a compound represented by formula (2) and R 3 means a compound in which is the substituent 1 (-H) shown in Table 1.

[0069] [Synthesis of compound (2)-1] First, triphenylphosphine (manufactured by Tokyo Chemical Industry Co., Ltd.), potassium carbonate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), tetrabutylammonium acetate (manufactured by Tokyo Chemical Industry Co., Ltd.), and copper(I) iodide (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) were placed in a reaction vessel, and the atmosphere inside the vessel was replaced with argon. Next, ion-exchanged water, ethynylbenzene (manufactured by Tokyo Chemical Industry Co., Ltd.), and β-bromostyrene (manufactured by Aldrich) were poured into the reaction vessel, and the mixture was stirred at 110°C for 19 hours. The resulting reaction solution was subjected to extraction treatment using ethyl acetate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.). The resulting extract was washed with saturated saline, and then magnesium sulfate was added to dehydrate the extract. Furthermore, the extract was concentrated using a rotary evaporator. The resulting concentrate was purified by silica gel column chromatography to obtain compound (2)-1. Compound (2)-1 was obtained from the following: 1 H-NMR and 13 The compound (2)-1 was identified by C-NMR. 1 FIG. 2B is a graph showing the H-NMR spectrum of compound (2)-1. 13 2A is a graph showing the C-NMR spectrum. In FIG. 2A, the integral value (4.02) of the peak in the range of 7.4 ppm to 7.5 ppm overlaps with other peaks. However, this integral value and peak can be clearly seen from the enlarged view of the center of FIG. 2A. 1 H-NMR spectrum and 13 The C-NMR spectrum was as follows: 1 H-NMR (600MHz, CHLOROFORM-D)δ7.42-7.48 (m, 4H), 7.28-7.36 (m, 6H), 7.05 (d, J=16.5Hz, 1H), 6.39 (d, J=15.8Hz, 1H). 13 C-NMR (151MHz, CHLOROFORM-D)δ141.37, 136.44, 131.63, 128.85, 128.73, 128.46, 128.29, 126.42, 123.52, 108.24, 91.86, 89.01.

[0070] (Comparative Examples 1 to 3) Furthermore, compounds of Comparative Examples 1 to 3 shown in Table 3 were prepared. The compounds of Comparative Examples 1 to 3 are represented by the following formulas (5) to (7), respectively.

[0071] Here, Compound D29, the compound of Comparative Example 1 shown in the following formula (5), was synthesized in accordance with the method described in paragraphs

[0222] to

[0230] of Japanese Patent No. 5659189. Compound 1f, the compound of Comparative Example 2 shown in the following formula (6), was synthesized in accordance with the method described in paragraph

[0083] of Japanese Patent No. 5821661. DPB, the compound of Comparative Example 3, was manufactured by Tokyo Chemical Industry Co., Ltd. [ka]

[0072] <Measurement of two-photon absorption cross section> The two-photon absorption cross sections of the synthesized compounds and comparative compounds were measured for light having a wavelength of 405 nm. The two-photon absorption cross section measurements were performed 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 sections. 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 403 nm to 405 nm. The full width at half maximum of the light from the laser was 4 nm.

[0073] <Prediction of two-photon absorption cross section> The two-photon absorption cross sections of the synthesized compounds and comparative compounds for light with a wavelength of 405 nm were predicted. Specifically, the two-photon absorption cross sections were calculated using density functional theory (DFT) calculations based on the second-order nonlinear response theory described in J. Chem. Theory Comput. 2018, Vol. 14, p. 807. Turbomole version 7.3.1 (COSMOlogic) was used as the software for the DFT calculations. The basis function used was def2-TZVP. The functional used was B3LYP.

[0074] The calculated and measured two-photon absorption cross sections of the synthesized compounds and the comparative compounds were subjected to linear regression. Next, the regression equation obtained by this linear regression was used to calculate the calculated two-photon absorption cross sections of other compounds that differ from the synthesized compounds in terms of the type and position of the substituents.

[0075] <Measurement of molar extinction coefficient> The molar absorption coefficients of the synthesized compounds and the comparative compounds were measured according to the method specified in JIS K0115:2004. Specifically, a solution in which the compound was dissolved in a solvent was first prepared as a measurement sample. The concentration of the compound in the solution was appropriately adjusted within the range of 1 mmol / L to 50 mmol / L depending on the absorbance at a wavelength of 405 nm of the compound to be measured. Next, the absorption spectrum of the measurement sample was measured. The absorbance at a wavelength of 405 nm was read from the obtained spectrum. The molar absorption coefficient was calculated based on the concentration of the compound in the measurement sample and the optical path length of the cell used for the measurement.

[0076] <Prediction of molar extinction coefficient> The molar absorption coefficients of the synthesized compounds and the comparative compounds were predicted. DFT calculations were used to predict the molar absorption coefficients. Specifically, excited-state calculations were first performed on the compounds using Gaussian16 (Gaussian), a quantum chemistry calculation program. The basis function for the excited-state calculations was 6-31++G(d,p). The functional used was B3LYP. The excited-state calculations calculated the energy required to excite the compounds and the oscillator strength (f). The oscillator strength correlates with the molar absorption coefficient. Next, the absorption spectrum was assumed to have a Gaussian distribution, and the half-width was specified. Specifically, the half-width was specified as 0.4 eV, and the absorption spectrum was plotted based on the absorption wavelength and oscillator strength. The absorbance at a wavelength of 405 nm was read from the obtained absorption spectrum. This absorbance was considered to be the calculated molar absorption coefficient.

[0077] Linear regression was performed on the calculated and measured molar extinction coefficients of the synthesized compounds and the comparative compounds. In the linear regression, the coefficient of determination, R 2 The value exceeded 0.9. This confirmed a high correlation between the calculated and measured molar absorption coefficients. Next, using the regression equation obtained by this linear regression, the calculated molar absorption coefficients of other compounds that differed from the synthesized compound in terms of the type and position of the substituents, etc., were calculated.

[0078] The measured and calculated values ​​of the two-photon absorption cross section (GM) obtained by the above method, the molar absorption coefficient (mol -1 L cm -1 ) and GM mol / g are shown in Tables 2 and 3. In Tables 2 and 3, GM mol / g values ​​were calculated based on the measured two-photon absorption cross section. For compounds for which no measured two-photon absorption cross section was available, GM mol / g values ​​were calculated based on the calculated two-photon absorption cross section. In Tables 2 and 3, "No Data" means that no data was available.

[0079] [Table 2]

[0080] [Table 3]

[0081] As can be seen from Tables 2 and 3, the compounds of Examples 1 to 41 corresponding to compound A represented by formula (1) all had a two-photon absorption cross-section per unit weight (GM·mol / g) for light having a wavelength of 405 nm, which was greater than that of the comparative compound, exceeding 0.9. These results demonstrate that compound A is suitable for improving the two-photon absorption cross-section per unit volume of nonlinear optical absorbing materials. In other words, nonlinear optical absorbing materials containing compound A are suitable for improving the nonlinear absorption properties for light having wavelengths in the short wavelength range. Furthermore, the compounds of Examples 1 to 41 had relatively small molar extinction coefficients for light having a wavelength of 405 nm, below 10. Thus, compound A exhibits excellent nonlinear optical absorption properties despite its small molecular size.

[0082] In compound A, represented by formula (1), two benzene rings are connected by a linker consisting of a series of carbon-carbon double bonds and carbon-carbon triple bonds. Due to this structure, it is presumed that the transition dipole moment between multiple excited states in compound A is increased, increasing the efficiency of two-photon absorption. This is presumed to be why the compounds in the examples have both a large GM·mol / g value and a small molar extinction coefficient.

[0083] The compounds of Comparative Examples 1 to 3 are different from Compound A. The compounds of Comparative Examples 1 to 3 have small GM·mol / g values ​​for light with a wavelength of 405 nm, which means that a large GM·mol / g value and a small molar extinction coefficient are not compatible. The compounds of Comparative Examples 1 and 2 have large π-electron conjugated systems and therefore large transition dipole moments. Therefore, the two-photon absorption cross sections of Comparative Examples 1 and 2 are relatively large. However, the compounds of Comparative Examples 1 and 2 have small GM·mol / g values ​​due to their large molecular weights. Furthermore, compounds with extended π-electron conjugated systems tend to shift the peak resulting from one-photon absorption to longer wavelengths. It is presumed that the molar extinction coefficient ε of the compounds of Comparative Examples 1 and 2 is significantly increased because part of the wavelength range in which one-photon absorption occurs overlaps with 405 nm. [Industrial Applicability]

[0084] The nonlinear optically 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 nonlinear optically absorbing material of the present disclosure has optical absorption properties that exhibit high nonlinearity for light having wavelengths in the short wavelength range. Therefore, the nonlinear optically absorbing material of the present disclosure can achieve extremely high spatial resolution in applications such as three-dimensional optical memories and modeling machines.

Claims

1. Contains a compound represented by the following formula (1) as a main component: Nonlinear optical absorbing materials. 【Chemistry 1】 In the formula (1), R 1 From R 10 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.

2. The compound is represented by the following formula (2) or (3): The nonlinear optical absorbing material of claim 1 . 【Chemistry 2】

3. The R 1 From the above R 10 are hydrogen atoms, The nonlinear optical absorbing material of claim 1 .

4. The compound has a nonlinear optical absorption effect.

4. The nonlinear optical absorption material according to claim 1.

5. Used in devices that utilize light having a wavelength of 390 nm or more and 420 nm or less, 5. The nonlinear optical absorption material according to claim 1.

6. A recording layer comprising the nonlinear optical absorption material according to any one of claims 1 to 5. Recording medium.

7. 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 a recording medium containing the nonlinear optical absorption material according to claim 6. How information is recorded.

8. A method for reading information recorded by the recording method according to claim 7, comprising: The reading method includes: measuring optical characteristics of the recording layer by irradiating the recording layer of the recording medium with light; reading the information from the recording layer. How to read the information.

9. the optical property is the intensity of light reflected by the recording layer; The reading method according to claim 8.

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