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

Abstract

One embodiment of the nonlinear light-absorbing material disclosed herein comprises a compound represented by the following formula (1) as its main component. In formula (1), R 1 ~R 10 Each group can be a hydrogen atom, halogen atom, saturated hydrocarbon group, haloalkyl group, unsaturated hydrocarbon group, hydroxyl group, carboxyl group, alkoxycarbonyl group, aldehyde group, acyl group, amide group, nitrile group, alkoxy group, acyloxy group, thiol group, alkylthio group, sulfonic acid group, acylthio group, alkylsulfonyl group, sulfonamide group, primary amino group, secondary amino group, tertiary amino group, or nitro group.

Description

Technical Field

[0001] This disclosure relates to nonlinear light-absorbing materials, recording media, methods for recording information, and methods for reading out information. Background Technology

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

[0003] Numerous studies have been actively conducted on nonlinear optical materials to date. In particular, inorganic materials that can be easily fabricated into single crystals have been developed as nonlinear optical materials. In recent years, the development of nonlinear optical materials incorporating organic materials has been anticipated. Compared to inorganic materials, organic materials not only offer higher design freedom but also possess larger nonlinear optical constants. Furthermore, organic materials exhibit high-speed nonlinear responses. In this specification, nonlinear optical materials incorporating organic materials are sometimes referred to as organic nonlinear optical materials.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent No. 5659189

[0007] Patent Document 2: Japanese Patent No. 5821661

[0008] Patent Document 3: Japanese Patent Application Publication No. 2013-242939

[0009] Non-patent literature

[0010] Non-patent literature 1: Harry L. Anderson et al, “Two-Photon Absorption and the Design of Two-Photon Dyes”, Angew. Chem. Int. Ed. 2009, Vol. 48, pp. 3244-3266. Summary of the Invention

[0011] The problem that the invention aims to solve

[0012] In the case of conventional nonlinear light-absorbing materials, there is room for improvement in the nonlinear absorption characteristics relative to light with short wavelength regions.

[0013] Methods for solving problems

[0014] One embodiment of the nonlinear light-absorbing material disclosed herein comprises

[0015] The compound represented by the following formula (1) is the main component.

[0016] [Chemical Formula 1]

[0017]

[0018] In equation (1) above, R 1 ~R 10 Each group can be a hydrogen atom, halogen atom, saturated hydrocarbon group, haloalkyl group, unsaturated hydrocarbon group, hydroxyl group, carboxyl group, alkoxycarbonyl group, aldehyde group, acyl group, amide group, nitrile group, alkoxy group, acyloxy group, thiol group, alkylthio group, sulfonic acid group, acylthio group, alkylsulfonyl group, sulfonamide group, primary amino group, secondary amino group, tertiary amino group, or nitro group.

[0019] Invention Effects

[0020] This disclosure provides a nonlinear light-absorbing material suitable for improving the nonlinear absorption characteristics of light with respect to wavelengths having a short wavelength region. Attached Figure Description

[0021] Figure 1A This is a flowchart of a method for recording information using a recording medium that incorporates a nonlinear light-absorbing material according to one embodiment of the present disclosure.

[0022] Figure 1B This is a flowchart of a method for reading out information using a recording medium that incorporates a nonlinear light-absorbing material according to one embodiment of the present disclosure.

[0023] Figure 2A It represents compound (2)-1 1 Chart of H-NMR spectra.

[0024] Figure 2B It represents compound (2)-1 13 A chart of C-NMR spectra. Detailed Implementation

[0025] (The insights that form the basis of this disclosure)

[0026] In organic nonlinear optical materials, two-photon absorption materials have attracted particular attention. Two-photon absorption refers to the phenomenon where a compound absorbs two photons almost simultaneously, transitioning to an excited state. Two-photon absorption is known to include simultaneous two-photon absorption and staged 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 region where there is no single-photon absorption band. Staged two-photon absorption is sometimes called resonant two-photon absorption. In staged two-photon absorption, the compound absorbs the first photon and then further absorbs the second photon, transitioning to a higher-order excited state. In staged two-photon absorption, the compound absorbs the two photons sequentially.

[0027] In simultaneous two-photon absorption, the amount of light absorbed by the compound is typically proportional to the square of the intensity of the incident light, exhibiting a nonlinearity. The amount of light absorbed by the compound can be used as an indicator of the efficiency of two-photon absorption. In cases where the absorption of light by the compound exhibits a nonlinearity, for example, light absorption by the compound may only occur near the focal point of a laser with a high electric field intensity. That is, in a sample containing a two-photon absorbing material, the compound can only be excited at the desired location. Compounds that generate simultaneous two-photon absorption in this way offer extremely high spatial resolution, and therefore their applications in recording layers of three-dimensional optical memories, photocurable resin compositions for photomasking, and other applications have been investigated.

[0028] For two-photon absorbing materials, the two-photon absorption cross-sectional area (GM value) is used as an indicator of two-photon absorption efficiency. The unit of two-photon absorption cross-sectional area is GM(10⁻¹⁰). -50 cm 4 ·s·molecule -1 ·photon -1 To date, many organic two-photon absorbing materials with large two-photon absorption cross-sections have been proposed. For example, many compounds with two-photon absorption cross-sections exceeding 500 GM have been reported (e.g., Non-Patent Literature 1). However, in most reports, the two-photon absorption cross-section has been measured using lasers with wavelengths longer than 600 nm. In particular, near-infrared light with wavelengths longer than 750 nm is sometimes used as the laser.

[0029] However, for two-photon absorption materials to be applied in industrial applications, they are considered to need to exhibit two-photon absorption properties when irradiated with lasers of shorter wavelengths. For example, in the field of three-dimensional optical storage, lasers of shorter wavelengths can achieve finer focusing points, thus increasing the recording density of three-dimensional optical storage. In the field of optical modeling, lasers of shorter wavelengths can also achieve higher resolution models. Furthermore, the Blu-ray (registered trademark) optical disc standard uses a laser with a center wavelength of 405 nm. Thus, developing compounds that exhibit excellent two-photon absorption properties relative to light in the same wavelength range as lasers of shorter wavelengths could greatly contribute to industrial development.

[0030] To apply compounds with two-photon absorption properties to industrial applications, the two-photon absorbing material containing the compound needs to fully exhibit these properties. In this specification, compounds with two-photon absorption properties are sometimes referred to as two-photon absorbing compounds. To fully exhibit the two-photon absorption properties of the two-photon absorbing material, it is preferable that each molecule of the two-photon absorbing compound has a high two-photon absorption characteristic, and that the density of the two-photon absorbing compound in the two-photon absorbing material is high. It should be noted that a high two-photon absorption characteristic per molecule of the two-photon absorbing compound implies a large two-photon absorption cross-sectional area.

[0031] Two-photon absorbing compounds with high two-photon absorption characteristics per molecular size are suitable for improving the two-photon absorption characteristics per unit volume of two-photon absorbing materials. For example, two-photon absorbing compounds with small molecular size and large two-photon absorption cross-sectional area are suitable for improving the two-photon absorption cross-sectional area per unit volume of two-photon absorbing materials. As an indicator of the two-photon absorption characteristics per molecular size of a two-photon absorbing compound, the two-photon absorption cross-sectional area per unit weight of the two-photon absorbing compound can be listed. In this specification, the value of the two-photon absorption cross-sectional area per unit weight of the two-photon absorbing 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-sectional area (GM) of the two-photon absorbing compound by the molecular weight (g / mol) of the two-photon absorbing compound.

[0032] Patent documents 1 and 2 disclose compounds having a large two-photon absorption cross-section relative to light with a wavelength around 405 nm. Patent document 3 discloses an optical information recording medium that can shorten recording time when using a laser with a wavelength around 405 nm, and a compound contained in the optical information recording medium.

[0033] The inventors conducted in-depth research and made a new discovery: the compound represented by formula (1) described below exhibits high nonlinear absorption characteristics relative to light with wavelengths having a short wavelength region, thus completing the nonlinear light-absorbing material disclosed herein. Specifically, the inventors found that the compound represented by formula (1) has a large GM·mol / g value relative to light with wavelengths having a short wavelength region. In this specification, the short wavelength region refers to a wavelength region including 405 nm, for example, a wavelength region of 390 nm or more and 420 nm or less.

[0034] (A summary of one embodiment of this disclosure)

[0035] The nonlinear light-absorbing material of the first aspect of this disclosure comprises...

[0036] The compound represented by the following formula (1) is the main component.

[0037] [Chemical Formula 2]

[0038]

[0039] In equation (1) above, R 1 ~R 10 Each group can be a hydrogen atom, halogen atom, saturated hydrocarbon group, haloalkyl group, unsaturated hydrocarbon group, hydroxyl group, carboxyl group, alkoxycarbonyl group, aldehyde group, acyl group, amide group, nitrile group, alkoxy group, acyloxy group, thiol group, alkylthio group, sulfonic acid group, acylthio group, alkylsulfonyl group, sulfonamide group, primary amino group, secondary amino group, tertiary amino group, or nitro group.

[0040] According to the first scheme, the compound represented by formula (1) tends to have a large GM·mol / g value relative to light with wavelengths having a short wavelength region. This compound is suitable for increasing the two-photon absorption cross-section per unit volume of nonlinear light-absorbing materials. That is, nonlinear light-absorbing materials containing the compound represented by formula (1) are suitable for improving the nonlinear absorption characteristics of light with wavelengths having a short wavelength region. Furthermore, the compound represented by formula (1) also tends to have a small molar absorptivity value relative to light with wavelengths having a short wavelength region.

[0041] In the second aspect of this disclosure, for example, the nonlinear light-absorbing material according to the first aspect, the above-mentioned compound may also be represented by the following formula (2) or (3).

[0042] [Chemical Formula 3]

[0043]

[0044] In the third aspect of this disclosure, for example, the nonlinear light-absorbing material according to the first aspect, wherein the aforementioned R 1 ~R above 10They can also be hydrogen atoms.

[0045] In the fourth aspect of this disclosure, for example, the nonlinear light-absorbing material according to any one of the first to third aspects, wherein the above-mentioned compound may also have a nonlinear light absorption effect.

[0046] In the fifth aspect of this disclosure, for example, the nonlinear light-absorbing material according to any one of the first to fourth aspects can also be used in devices that utilize light with wavelengths of 390 nm or more and 420 nm or less.

[0047] The nonlinear light-absorbing materials of schemes 2 to 5 are suitable for improving the nonlinear absorption characteristics of light with wavelengths having a short wavelength region. These nonlinear light-absorbing materials are suitable for applications using devices with wavelengths of light above 390 nm and below 420 nm.

[0048] The recording medium of the sixth embodiment of this disclosure comprises

[0049] The recording layer of the nonlinear light-absorbing material according to any one of the schemes 1 to 5.

[0050] According to the sixth embodiment, the nonlinear light-absorbing material is suitable for improving the nonlinear absorption characteristics of light with respect to wavelengths having a short wavelength region. A recording medium containing such a nonlinear light-absorbing material can record information at a high recording density.

[0051] The method for recording information in the seventh embodiment of this disclosure includes:

[0052] A light source prepared to emit light with wavelengths above 390nm and below 420nm; and

[0053] The light from the aforementioned light source is focused and used to irradiate the recording layer in the recording medium containing the nonlinear light-absorbing material of the sixth scheme.

[0054] According to the seventh embodiment, the nonlinear light-absorbing material is suitable for improving the nonlinear absorption characteristics of light with respect to wavelengths having a short wavelength region. Based on the recording method using a recording medium containing such a nonlinear light-absorbing material, information can be recorded at a high recording density.

[0055] The method for reading information according to the eighth embodiment of this disclosure is, for example, a method for reading information recorded by the recording method of the seventh embodiment.

[0056] The above readout method includes:

[0057] The optical properties of the recording layer were measured by irradiating the recording layer in the recording medium with light; and

[0058] The above information is read from the above recording layer.

[0059] In the ninth aspect of this disclosure, for example, the information readout method according to the eighth aspect, the aforementioned optical characteristic may also be the intensity of light reflected in the aforementioned recording layer.

[0060] According to scheme 8 or 9, the information can be easily read.

[0061] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. The present disclosure is not limited to these embodiments.

[0062] (Implementation Method)

[0063] The nonlinear light-absorbing material of this embodiment comprises compound A represented by the following formula (1).

[0064] [Chemical Formula 4]

[0065]

[0066] In equation (1), R 1 ~R 10 Each contains at least one atom independently selected from the group consisting of H, C, N, O, F, P, S, Cl, I, and Br. 1 ~R 10 They can also be hydrogen atoms, halogen atoms, saturated hydrocarbon groups, haloalkyl groups, unsaturated hydrocarbon groups, hydroxyl groups, carboxyl groups, alkoxycarbonyl groups, aldehyde groups, acyl groups, amide groups, nitrile groups, alkoxy groups, acyloxy groups, thiols, alkylthiols, sulfonic acid groups, acylthiols, alkylsulfonyl groups, sulfonamide groups, primary amino groups, secondary amino groups, tertiary amino groups, or nitro groups, independently of each other.

[0067] Examples of halogen atoms include F, Cl, Br, and I. In this specification, halogen atoms are sometimes referred to as halogen groups.

[0068] Saturated hydrocarbon groups are, for example, aliphatic saturated hydrocarbon groups. Specific examples of aliphatic saturated hydrocarbon groups are alkyl groups. The number of carbon atoms in the alkyl group is not particularly limited, but may be, for example, 1 or more and 20 or less. From the viewpoint of readily synthesizing compound A, the number of carbon atoms in the alkyl group can be 1 or more and 10 or less, or 1 or more and 5 or less. By adjusting the number of carbon atoms in the alkyl group, the solubility of compound A relative to a solvent or resin composition can be adjusted. The alkyl group can be linear, branched, or cyclic. At least one hydrogen atom in the alkyl group can also be substituted by a group containing at least one atom selected from the group consisting of N, O, P, and S. Examples of alkyl groups include methyl, ethyl, propyl, butyl, 2-methylbutyl, pentyl, hexyl, 2,3-dimethylhexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecanyl, octadecyl, nonadecanyl, eicosyl, 2-methoxybutyl, 6-methoxyhexyl, etc.

[0069] A haloalkyl group is a group obtained by replacing at least one hydrogen atom in an alkyl group with a halogen atom. A haloalkyl group can also be a group obtained by replacing all hydrogen atoms in an alkyl group with a halogen atom. Examples of alkyl groups include those mentioned above. A specific example of a haloalkyl group is -CF3.

[0070] Unsaturated hydrocarbon groups contain unsaturated bonds such as carbon-carbon double bonds and carbon-carbon triple bonds. The number of unsaturated bonds in an unsaturated hydrocarbon group is, for example, 1 or more and 5 or less. The number of carbon atoms in an unsaturated hydrocarbon group is not particularly limited; it can be 2 or more and 20 or less, 2 or more and 10 or less, or 2 or more and 5 or less. Unsaturated hydrocarbon groups can be linear, branched, or cyclic. At least one hydrogen atom in an unsaturated hydrocarbon group can be replaced by a group containing at least one atom selected from the group consisting of N, O, P, and S. Examples of unsaturated hydrocarbon groups include vinyl and ethynyl groups.

[0071] Hydroxyl groups are represented by -OH. Carboxyl groups are represented by -COOH. Alkoxy carbonyl groups are represented by -COOR. a The aldehyde group is represented by -COH. The acyl group is represented by -COR. b Indicated by amide group -CONR. c R d Indicated by . Nitrile group is represented by -CN. Alkoxy group is represented by -OR. e Indicated by acyloxy group with -OCOR f The thiol group is represented by -SH. The alkylthio group is represented by -SR. g The sulfonic acid group is represented by -SO3H. The acyl thio group is represented by -SCOR. h Indicated by alkyl sulfonyl group with -SO2R i Indicated. The sulfonamide group is represented by -SO2NR.j R k Primary amines are represented by -NH2. Secondary amines are represented by -NHR. l It is indicated by tertiary amines in the form of -NR. m R n Indicated. The nitro group is represented by -NO2. R a ~R n Each is an alkyl group independently of the others. Examples of alkyl groups include those described above. Wherein, the R of the amide group... c and R d and the R of the sulfonamide group j and R k They can also be hydrogen atoms independently of each other.

[0072] Specific examples of alkoxy carbonyl groups are -COOCH3, -COO(CH2)3CH3, and -COO(CH2)7CH3. Specific examples of acyl groups are -COCH3. Specific examples of amide groups are -CONH2. Specific examples of alkoxy groups are methoxy, ethoxy, 2-methoxyethoxy, butoxy, 2-methylbutoxy, 2-methoxybutoxy, 4-ethylthiobutoxy, pentoxy, hexoxy, heptoxy, octoxy, nonoxy, decoxy, undecyloxy, dodecyloxy, tridecyloxy, tetradecyloxy, pentadecyloxy, hexadecyloxy, heptadecanyloxy, octadecyloxy, nonadecanyloxy, and eicosyloxy. Specific examples of acyloxy groups are -OCOCH3. Specific examples of acyl thio groups are -SCOCH3. Specific examples of alkyl sulfonyl groups are -SO2CH3. Specific examples of sulfonamide groups are -SO2NH2. Specific examples of tertiary amino groups are -N(CH3)2.

[0073] In equation (1), the choice is free R. 3 and R 8 At least one of the constituent groups can also be an electron-donating group or an electron-withdrawing group. Regarding R... 3 or R 8 The greater the electron-donating or electron-withdrawing property, the greater the electron deviation within compound A. When the electron deviation within compound A is large, there is a tendency for electrons to move more significantly within compound A when it is excited. Such compounds tend to exhibit superior two-photon absorption properties. In other words, when choosing R... 3 and R 8 When at least one of the constituent groups is an electron-donating or electron-withdrawing group, compound A tends to have a large two-photon absorption cross-section. Among them, R... 3 and R 8 They can also be hydrogen atoms.

[0074] The term "electron-withdrawing group" refers to, for example, the substituent constant σ in the Hammett formula. pSubstituents with positive values. Examples of electron-withdrawing groups include halogen atoms, carboxyl groups, nitro groups, thiols, sulfonic acid groups, acyloxy groups, alkylthiols, alkylsulfonyl groups, sulfonamide groups, acyl groups, acylthiols, alkoxycarbonyl groups, and haloalkyl groups. Electron-withdrawing groups can be carboxyl or alkoxycarbonyl groups, or they can be -COO(CH2)3CH3 or -COO(CH2)7CH3.

[0075] The so-called electron-donating group refers to, for example, the σ group mentioned above. p Substituents with negative values. Examples of electron-donating groups include alkyl, alkoxy, hydroxy, and amino groups.

[0076] In equation (1), R 1 R 5 R 6 and R 10 Each can also have a small volume. In this case, in R... 1 R 5 R 6 and R 10 In this compound, steric hindrance is less likely to occur. Therefore, in compound A, there is a tendency for increased planarity of the π-electron conjugation system. When the π-electron conjugation system of compound A has high planarity, compound A tends to have a large two-photon absorption cross-section. 1 R 5 R 6 and R 10 Each can also be a hydrogen atom.

[0077] Furthermore, it is possible to R 1 R 2 and R 4 ~R 10 Each is a hydrogen atom, or R 1 ~R 7 R 9 and R 10 Each is a hydrogen atom. That is, compound A can also be compound B represented by formula (2) or compound C represented by formula (3).

[0078] [Chemical Formula 5]

[0079]

[0080] R in equation (2) 3 and R in equation (3) 8 The same group as described above for equation (1). The R in equation (2) 3 and R in equation (3) 8 Specific examples are shown in Table 1 below. In equation (2), R 3 It can also be -H. That is, in equation (1), R 1~R 10 Each can also be a hydrogen atom.

[0081] Table 1

[0082] <![CDATA[R 3 and R 8 ]]> 1 -H 2 -F 3 <![CDATA[-CH3]]> 4 <![CDATA[-C2H5]]> 5 <![CDATA[-CF3]]> 6 -OH 7 -COOH 8 <![CDATA[-COOCH3]]> 9 <![CDATA[-COCH3]]> 10 <![CDATA[-CONH2]]> 11 -CN 12 <![CDATA[-OCH3]]> 13 <![CDATA[-OCOCH3]]> 14 -SH 15 <![CDATA[-SO3H]]> 16 <![CDATA[-SCOCH3]]> 17 <![CDATA[-SO2CH3]]> 18 <![CDATA[-SO2NH2]]> 19 <![CDATA[-NH2]]> 20 <![CDATA[-N(CH3)2]]> 21 <![CDATA[-NO2]]>

[0083] The synthesis method of compound B represented by formula (2) is not particularly limited. Compound B can be synthesized, for example, by the following method. First, prepare compound D represented by formula (4) below. In formula (4), R 3 The same group as described above for equation (1).

[0084] [Chemical Formula 6]

[0085]

[0086] Next, a coupling reaction is carried out between compound D and β-bromostyrene. This allows the synthesis of compound B. The conditions for the coupling reaction can be adjusted appropriately, for example, according to the structure of compound D. It should be noted that compound C of formula (3) can be synthesized by performing the same coupling reaction as compound B.

[0087] Compound A, represented by Equation (1), exhibits excellent two-photon absorption characteristics relative to light with wavelengths in the short wavelength region, and tends to have low single-photon absorption. As an example, when compound A is irradiated with light of a wavelength of 405 nm, two-photon absorption can be generated in compound A, while almost no single-photon absorption is generated.

[0088] The two-photon absorption cross-section (BOC) of compound A relative to light with a wavelength of 405 nm can exceed 1 GM, or even 10 GM or 100 GM, or even 200 GM. There is no particular upper limit to the BOC of compound A; for example, it could be 5000 GM or 1000 GM. The BOC 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 for determining nonlinear optical constants. In the Z-scan method, the sample is moved along the direction of the laser beam near the focal point. The change in the amount of light transmitted through the sample is recorded. In the Z-scan method, the power density of the incident light changes depending on the position of the sample. Therefore, in cases where the sample undergoes nonlinear light absorption, if the sample is located near the focal point of the laser beam, the amount of transmitted light is attenuated. The two-photon absorption cross-section can be calculated by fitting the change in the amount of transmitted light to the theoretical curve predicted by the intensity of the incident light, the thickness of the sample, and the concentration of compound A in the sample.

[0089] The two-photon absorption cross-section can also be calculated using computational chemistry. Several methods for estimating the two-photon absorption cross-section using computational chemistry have been proposed. For example, the calculated value of the two-photon absorption cross-section can be obtained based on the second-order nonlinear response theory described in J. Chem. Theory Comput. 2018, Vol. 14, p. 807.

[0090] In this embodiment, there is a tendency for compound A to have a large two-photon absorption cross-section (GM) per unit weight relative to light with a wavelength of 405 nm (GM·mol / g value). The GM·mol / g value of compound A can be 0.9 or more, 1.0 or more, 1.5 or more, or 2.0 or more. There is no particular upper limit to the GM·mol / g value of compound A, for example, it is 50.

[0091] Compound A has a molar absorptivity of 100 mol% relative to light with a wavelength of 405 nm. -1 ·L·cm -1 The following can also be 10 mol -1 ·L·cm -1 The following can also be 5 mol -1 ·L·cm -1 The following can also be 1 mol -1 ·L·cm -1 Below, it can also be 0.1 mol -1 ·L·cm -1 The following is a lower limit for the molar absorptivity of compound A; it is not specifically limited, for example, it is 0.00001 mol. -1 ·L·cm -1 The molar absorptivity can be measured, for example, according to the method specified in Japanese Industrial Standard (JIS) K0115:2004. In the measurement of the molar absorptivity, a light source with a photon density that produces almost no two-photon absorption by compound A is used. Furthermore, in the measurement of the molar absorptivity, the concentration of compound A is adjusted to be 1 mmol / L or more and 50 mmol / L or less. This concentration is a very high value compared to the concentration used in the measurement experiment of the molar absorptivity of the light absorption peak. The molar absorptivity can be used as an indicator of single-photon absorption.

[0092] The molar absorptivity can also be a calculated value based on a quantum chemical calculation program. For example, Gaussian16 (manufactured by Gaussian) can be used as a quantum chemical calculation program.

[0093] When compound A undergoes two-photon absorption, it absorbs approximately twice the energy of the light irradiating it. The wavelength of light possessing approximately twice the energy of light with a wavelength of 405 nm is, for example, 200 nm. When compound A is irradiated with light having a wavelength around 200 nm, single-photon absorption can also occur in compound A. Furthermore, in compound A, single-photon absorption can also occur for light with wavelengths near the wavelength region that produces two-photon absorption.

[0094] The nonlinear light-absorbing material of this embodiment may also contain compound A, represented by formula (1), as a main component. "Main component" refers to the component most abundant in the nonlinear light-absorbing material by weight. The nonlinear light-absorbing material is, for example, substantially formed of compound A. "Substantially formed of..." means excluding other components that alter the essential characteristics of the material. In addition to containing compound A, the nonlinear light-absorbing material may also contain impurities. The nonlinear light-absorbing material of this embodiment containing compound A functions, for example, as a two-photon absorbing material.

[0095] The nonlinear light-absorbing material of this embodiment is used, for example, in devices that utilize light with wavelengths having a short wavelength region. As an example, the nonlinear light-absorbing material of this embodiment is used in devices that utilize light with wavelengths of 390 nm or more and 420 nm or less. Examples of such devices include recording media, molding machines, and fluorescence microscopes. Examples of recording media include three-dimensional optical storage devices. A specific example of a three-dimensional optical storage device is a three-dimensional optical disc. Examples of molding machines include light molding machines such as 3D printers. Examples of fluorescence microscopes include two-photon fluorescence microscopes. The light used in these devices, for example, has a high photon density near the focal point. The power density near the focal point of the light used in the device is, for example, 0.1 W / cm². 2 Above and 1.0×10 20 W / cm 2 The power density near the focal point of this light can be 1.0 W / cm². 2 The above can also be 1.0 × 10 2 W / cm 2 The above can also be 1.0×10 5 W / cm 2 The above describes the light source for the device. For example, femtosecond lasers such as Ti:sapphire lasers or pulsed lasers with picosecond to nanosecond pulse amplitudes can be used.

[0096] The recording medium, for example, includes a thin film referred to as a recording layer. Information is recorded in the recording layer of the recording medium. As an example, the thin film serving as the recording layer contains the nonlinear light-absorbing material of this embodiment. That is, from another aspect, this disclosure provides a recording medium that includes a nonlinear light-absorbing material comprising the aforementioned compound A.

[0097] In addition to containing nonlinear light-absorbing materials, the recording layer may further contain polymeric compounds that function as binders. The recording medium may also contain dielectric layers in addition to the recording layers. For example, a recording medium may have multiple recording layers and multiple dielectric layers. In a recording medium, multiple recording layers and multiple dielectric layers may also be stacked alternately.

[0098] Next, the method for recording information using the aforementioned recording medium will be explained. Figure 1A This is a flowchart of a method for recording information using the aforementioned recording medium. First, in step S11, a light source is prepared to emit light with a wavelength of 390 nm or more and 420 nm or less. For example, a femtosecond laser such as a Ti:sapphire laser, or a pulsed laser with a pulse amplitude of picoseconds to nanoseconds, such as a semiconductor laser, can be used as the light source. Next, in step S12, the light from the light source is focused using a lens or the like, and then irradiated onto the recording layer in the recording medium. Specifically, the light from the light source is focused using a lens or the like, and then irradiated onto the recording area in the recording medium. The power density near the focal point of this light is, for example, 0.1 W / cm². 2 Above and 1.0×10 20 W / cm 2 The power density near the focal point of this light can be 1.0 W / cm². 2 The above can also be 1.0 × 10 2 W / cm 2 The above can also be 1.0×10 5 W / cm 2 That's all. In this specification, the term "recording area" refers to a spot existing in the recording layer that can record information when illuminated.

[0099] In the recording area after irradiation with the aforementioned light, physical or chemical changes occur. For example, compound A, which has absorbed light, generates heat when returning from the transition state to the ground state. This heat causes the binder present in the recording area to deteriorate. Consequently, the optical properties of the recording area change. For example, the intensity of light reflected from the recording area, the reflectivity of light in the recording area, the absorptivity of light in the recording area, and the refractive index of light in the recording area change. In the recording area after irradiation with light, sometimes the intensity of fluorescent light emitted from the recording area or the wavelength of the fluorescent light also changes. As a result, information can be recorded in the recording layer, specifically in the recording area (step S13).

[0100] Next, the method for reading information using the aforementioned recording medium will be explained. Figure 1B This is a flowchart of a method for reading information using the aforementioned recording medium. First, in step S21, light is irradiated onto the recording layer of the recording medium. 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 in the recording medium. Next, in step S22, the optical characteristics of the recording layer are measured. Specifically, the optical characteristics of the recording area are measured. In step S22, for example, as an optical characteristic of the recording area, the intensity of light reflected from the recording area is measured. In step S22, as an optical characteristic of the recording area, the reflectivity of light in the recording area, the absorptivity of light in the recording area, the refractive index of light in the recording area, the intensity of fluorescence emitted from the recording area, the wavelength of the fluorescence, etc., may also be measured. Next, in step S23, information is read from the recording layer, specifically the recording area.

[0101] In information readout methods, the recording area containing information can be located using the following method. First, light is irradiated onto a specific area of ​​the recording medium. This light can be the same as or different from the light used to record information on the recording medium. Next, the optical characteristics of the area after irradiation are measured. Examples of optical characteristics include, for instance, the intensity of light reflected from the area, the reflectivity of light in the area, the absorptivity of light in the area, the refractive index of light in the area, the intensity of fluorescence emitted from the area, and the wavelength of fluorescence emitted from the area. Based on the measured optical characteristics, it is determined whether the area after irradiation is a recording area. For example, if the intensity of light reflected from the area is below a certain value, the area is determined to be a recording area. On the other hand, if the intensity of light reflected from the area exceeds a certain value, the area is determined not to be a recording area. It should be noted that the method for determining whether an area after irradiation is a recording area is not limited to the method described above. For example, if the intensity of light reflected from the area exceeds a certain value, the area can also be determined to be a recording area. Furthermore, if the intensity of light reflected from the area is below a certain value, the area can also be determined not to be a recording area. If an area is determined not to be a recording area, the same operation is performed on other areas of the recording medium. This allows the recording area to be located.

[0102] The recording and reading methods for information using the aforementioned recording medium can be performed, for example, by a known recording apparatus. The recording apparatus, for example, includes a light source that illuminates a recording area in the recording medium, a measuring device that measures the optical characteristics of the recording area, and a controller that controls the light source and the measuring device.

[0103] A photoforming machine, for example, cures a photocurable resin composition by irradiating it with light. As an example, the photocurable resin composition for photoforming includes the nonlinear light-absorbing material of this embodiment. In addition to the nonlinear light-absorbing material, the photocurable resin composition may also include a polymerizable compound and a polymerization initiator. The photocurable resin composition may further include additives such as adhesive resins. The photocurable resin composition may also include epoxy resin.

[0104] If a fluorescence microscope is used, for example, light can be shone onto a biological sample containing a fluorescent dye material, and the fluorescence emitted from that dye material can be observed. As an example, the fluorescent dye material to be added to the biological sample includes the nonlinear light-absorbing material of this embodiment.

[0105] Example

[0106] The present disclosure will be further described in detail below through examples. It should be noted that the following examples are merely illustrative, and the present disclosure is not limited to these examples. In this disclosure, the compounds used in the examples are labeled "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 types. The value of “Y” corresponds to Table 1. For example, compound (2)-1 refers to the compound represented by formula (2), and R 3 The compounds are those with substituent 1 (-H) as shown in Table 1.

[0107] [Synthesis of compound (2)-1]

[0108] First, triphenylphosphine (manufactured by Tokyo Chemical Industry Co., Ltd.), potassium carbonate (manufactured by FUJIFILM WakoPure Chemical Corporation), tetrabutylammonium acetate (manufactured by Tokyo Chemical Industry Co., Ltd.), and copper iodide (I) (manufactured by FUJIFILM Wako Pure Chemical Corporation) were added to the reaction vessel, and the vessel was purged with argon. Next, deionized water, acetylenol (manufactured by Tokyo Chemical Industry Co., Ltd.), and β-bromostyrene (manufactured by Aldrich) were injected into the reaction vessel, and the mixture was stirred at 110°C for 19 hours. The resulting reaction solution was extracted with ethyl acetate (manufactured by FUJIFILM Wako Pure Chemical Corporation). The extract was washed with saturated brine, and then magnesium sulfate was added to dehydrate the extract. The extract was then concentrated using a rotary evaporator. The concentrate was purified by silica gel column chromatography to obtain compound (2)-1. Compound (2)-1 was purified by... 1 H-NMR and 13 Identification was performed using C-NMR. Figure 2A It represents compound (2)-1 1 Chart of H-NMR spectra. Figure 2B It represents compound (2)-1 13 A chart of C-NMR spectra. It should be noted that... Figure 2A In the peak range of 7.4 ppm to 7.5 ppm, the integral value (4.02) overlaps with other peaks. However, this integral value and peak can be determined by... Figure 2A The magnified view of the central part is clearly read. Compound (2)-1 1 H-NMR spectra and 13 The C-NMR spectra are as follows.

[0109] 1H-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).

[0110] 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.

[0111] (Comparative Examples 1-3)

[0112] Furthermore, the 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).

[0113] Of these, the compound D29 of Comparative Example 1 shown in formula (5) below was synthesized using the method described in paragraphs

[0222] to

[0230] of Japanese Patent No. 5659189. The compound 1f of Comparative Example 2 shown in formula (6) below was synthesized using the method described in paragraph

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

[0114] [Chemical Formula 7]

[0115]

[0116] Determination of Two-Photon Absorption Cross-Section

[0117] For the synthesized compounds and the compounds of the comparative examples, the two-photon absorption cross-section (BCR) relative to light with a wavelength of 405 nm was measured. The BCR was measured using the Z-scan method described in J. Opt. Soc. Am. B, 2003, Vol. 20, p. 529. A Ti:sapphire pulsed laser was used as the light source for measuring the BCR. Specifically, the sample was irradiated with the second harmonic of the Ti:sapphire pulsed laser. The laser pulse amplitude was 80 fs. The laser repetition frequency was 1 kHz. The average power of the laser varied within 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 center wavelength of 403 nm to 405 nm. The full width at half maximum (FW) of the light from the laser was 4 nm.

[0118] <Prediction of Two-Photon Absorption Cross-Section>

[0119] For the synthesized compounds and comparative examples, the two-photon absorption cross-section relative to light with a wavelength of 405 nm was predicted. Specifically, the two-photon absorption cross-section was calculated using the density functional theory (DFT) based on the quadratic nonlinear response theory described in J. Chem. Theory Comput. 2018, Vol. 14, p. 807. In the DFT calculation, Turboomole version 7.3.1 (manufactured by COSMOlogic) was used as the software. def2-TZVP was used as the basis function. B3LYP was used as the functional.

[0120] Linear regression was performed on the calculated and measured values ​​of the two-photon absorption cross-section for the synthesized compound and the comparative example compound. Then, using the regression equation obtained from this linear regression, the calculated values ​​of the two-photon absorption cross-section were calculated for other compounds that differed from the synthesized compound in terms of the type and position of substituents.

[0121] <Determination of molar absorptivity>

[0122] For the synthesized compounds and the compounds of the comparative examples, the molar absorptivity was determined according to the method specified in JIS K0115:2004. Specifically, firstly, as the test sample, a solution was prepared by dissolving the compound in a solvent. The concentration of the compound in the solution was appropriately adjusted to ensure that the absorbance of the compound at a wavelength of 405 nm was between 1 mmol / L and 50 mmol / L. Next, the absorption spectrum was measured for the test sample. The absorbance at a wavelength of 405 nm was read from the obtained spectrum. Based on the concentration of the compound in the test sample and the optical path length of the cell used for measurement, the molar absorptivity was calculated.

[0123] <Prediction of molar absorptivity>

[0124] The molar absorptivity was predicted for both the synthesized compounds and the comparative compounds. The molar absorptivity was predicted using DFT calculations. Specifically, firstly, excited-state calculations were performed on the compounds using Gaussian16 (manufactured by Gaussian Corporation), a quantum chemical calculation program. In the excited-state calculations, 6 - 31++G(d, p) was used as the basis function, and B3LYP was used as the generalization function. The excited-state calculations yielded the energy used to excite the compounds and the oscillator strength f. The oscillator strength is related to the molar absorptivity. Next, the absorption spectrum was assumed to be Gaussian, and a half-amplitude was defined. Specifically, the half-amplitude was defined as 0.4 eV, and the absorption spectrum was plotted based on the absorption wavelength and the oscillator strength. The absorbance at a wavelength of 405 nm was read from the obtained absorption spectrum. This absorbance was considered the calculated value of the molar absorptivity.

[0125] Linear regression was performed on the calculated and measured values ​​of the molar absorptivity of the synthesized compounds and the comparative examples. In the linear regression, R0 was used as the coefficient of determination. 2 The value exceeds 0.9. Therefore, a high correlation can be confirmed between the calculated and measured values ​​of the molar absorptivity. Next, using the regression equation obtained through this linear regression, the calculated molar absorptivity is calculated for other compounds whose substituent types and positions differ from the synthesized compound.

[0126] The measured and calculated values ​​of the two-photon absorption cross-section (GM) and the molar absorptivity (mol) obtained by the above method are presented. -1 ·L·cm -1The measured and calculated values ​​of the two-photon absorption cross-section (G·mol / g) are shown in Tables 2 and 3. In Tables 2 and 3, the G·mol / g values ​​are calculated based on the measured values ​​of the two-photon absorption cross-section. For compounds for which measured values ​​of the two-photon absorption cross-section were not available, the G·mol / g values ​​are calculated based on the calculated values ​​of the two-photon absorption cross-section. In Tables 2 and 3, "No Data" indicates that no data was obtained.

[0127] Table 2

[0128]

[0129] Table 3

[0130]

[0131] As can be seen from Tables 2 and 3, for the compounds of Examples 1 to 41 corresponding to compound A represented by formula (1), the value of the two-photon absorption cross-section per unit weight (GM·mol / g value) relative to light with a wavelength of 405 nm is greater than that of the comparative example compounds, exceeding 0.9. From this result, it is known that compound A is suitable for increasing the two-photon absorption cross-section per unit volume of nonlinear light-absorbing materials. That is, it is known that nonlinear light-absorbing materials containing compound A are suitable for improving the nonlinear absorption characteristics relative to light with wavelengths having a short wavelength region. Furthermore, for the compounds of Examples 1 to 41, the value of the molar absorptivity relative to light with a wavelength of 405 nm is less than 10, which is a relatively small value. Thus, it is known that compound A has a small molecular size and exhibits excellent nonlinear light absorption characteristics.

[0132] In the case of compound A represented by formula (1), the two benzene rings are linked by a linking group obtained by a continuous arrangement of carbon-carbon double and triple bonds. Due to this structure, it is presumed that the transition dipole moment between multiple excited states is increased, and the efficiency of two-photon absorption is increased in compound A. Thus, in the compounds of the examples, it is presumed that a large GM·mol / g value and a small molar absorptivity are both achieved.

[0133] The compounds in Comparative Examples 1-3 are different from compound A. Regarding the compounds in Comparative Examples 1-3, since their GM·mol / g values ​​relative to light with a wavelength of 405 nm are small, a large GM·mol / g value and a small molar absorptivity are not balanced. The compounds in Comparative Examples 1 and 2 have large π-electron conjugation systems, resulting in large transition dipole moments. Therefore, the two-photon absorption cross-sections of Comparative Examples 1 and 2 are relatively large. However, the compounds in Comparative Examples 1 and 2 have small GM·mol / g values ​​due to their large molecular weight. Furthermore, compounds with expanded π-electron conjugation systems tend to have peaks shifting towards longer wavelengths from single-photon absorption. For the compounds in Comparative Examples 1 and 2, it is presumed that a portion of the wavelength region producing single-photon absorption overlaps with 405 nm, thereby significantly increasing the molar absorptivity ε.

[0134] Industrial availability

[0135] The nonlinear light-absorbing material disclosed herein can be used in recording layers of three-dimensional optical memories, photocurable resin compositions for photomasking, and other applications. The nonlinear light-absorbing material of this disclosure exhibits highly nonlinear light absorption characteristics relative to light with wavelengths in the short wavelength region. Therefore, the nonlinear light-absorbing material of this disclosure can achieve extremely high spatial resolution in applications such as three-dimensional optical memories and modeling machines.

Claims

1. A nonlinear light-absorbing material comprising, as a main component, a compound represented by the following formula (1), In the above equation (1), R 1 ~R 10 Each group can be a hydrogen atom, halogen atom, saturated hydrocarbon group, haloalkyl group, unsaturated hydrocarbon group, hydroxyl group, carboxyl group, alkoxycarbonyl group, aldehyde group, acyl group, amide group, nitrile group, alkoxy group, acyloxy group, thiol group, alkylthio group, sulfonic acid group, acylthio group, alkylsulfonyl group, sulfonamide group, primary amino group, secondary amino group, tertiary amino group, or nitro group.

2. The nonlinear light-absorbing material according to claim 1, wherein, The compound is represented by the following formula (2) or (3), 3. The nonlinear light-absorbing material according to claim 1, wherein, The R 1 ~The R mentioned 10 Each is a hydrogen atom.

4. The nonlinear light-absorbing material according to any one of claims 1 to 3, wherein, The compound exhibits a nonlinear light absorption effect.

5. The nonlinear light-absorbing material according to any one of claims 1 to 4, which is used in devices utilizing light having a wavelength of 390 nm or more and 420 nm or less.

6. A recording medium comprising a recording layer comprising the nonlinear light-absorbing material according to any one of claims 1 to 5.

7. A method for recording information, comprising: A light source prepared to emit light with wavelengths above 390nm and below 420nm; and The light from the light source is focused to irradiate the recording layer in the recording medium containing the nonlinear light-absorbing material of claim 6.

8. A method for reading information, which is a method for reading information recorded by the recording method of claim 7. The readout method includes: The optical properties of the recording layer are measured by irradiating the recording layer in the recording medium with light; and The information is read from the recording layer.

9. The readout method according to claim 8, wherein, The optical property is the intensity of light reflected from the recording layer.

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