JP2022177737A - Nonlinear absorption material, recording medium, information recording method, and information reading method - Google Patents

Abstract

To provide a nonlinear absorption material with improved nonlinear absorption properties for light with wavelengths in the short wavelength region.SOLUTION: A nonlinear absorption material in one mode of the present disclosure contains a compound represented by formula (1) below:. In formula (1), each of R1 to R10 is a group which contains at least one atom selected from the group consisting of H, C, N, O, F, P, S, Cl, I and Br and is other than a group containing an aromatic ring.SELECTED DRAWING: Figure 1A

Description

TECHNICAL FIELD The present disclosure relates to nonlinear absorbing materials, recording media, information recording methods, and information reading methods.

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

Many studies have been actively carried out on nonlinear optical materials. In particular, inorganic materials from which single crystals can be easily prepared have been developed as nonlinear optical materials. In recent years, the development of nonlinear optical materials made of organic materials is expected. Organic materials not only have a higher degree of design freedom than inorganic materials, but also have large nonlinear optical constants. In addition, organic materials exhibit fast nonlinear responses. In this specification, nonlinear optical materials containing organic materials are sometimes referred to as organic nonlinear optical materials.

Japanese Patent No. 5769151 Japanese Patent No. 5659189 Japanese Patent No. 5821661 JP 2013-242939 A

Harry L. Anderson et al, "Two-Photon Absorption and the Design of Two-Photon Dyes", Angew. Chem. Int. Ed. 2009, Vol. 48, p.

Conventional nonlinear absorption materials have room for improvement in terms of nonlinear absorption characteristics for light having wavelengths in the short wavelength range.

前記式（１）において、Ｒ¹からＲ¹⁰は、互いに独立して、Ｈ、Ｃ、Ｎ、Ｏ、Ｆ、Ｐ、Ｓ、Ｃｌ、Ｉ及びＢｒからなる群より選ばれる少なくとも１つの原子を含み、かつ、芳香環を含む基以外の他の基である。
ただし、前記化合物が下記式（２）で表される場合、Ｒ³及びＲ⁸は、下記要件（ａ）から（ｃ）を満たす。
（ａ）前記Ｒ³及び前記Ｒ⁸からなる群より選ばれる少なくとも１つは、前記Ｒ³又は前記Ｒ⁸に隣接するフェニレン基に直接結合している炭素原子を有する。
（ｂ）前記Ｒ³及び前記Ｒ⁸の両方がアルキル基である場合、前記Ｒ³及び前記Ｒ⁸からなる群より選ばれる少なくとも１つの前記アルキル基の炭素数は、２以下又は５以上である。
（ｃ）前記Ｒ³が水素原子である場合、前記Ｒ⁸は、不飽和炭化水素基、炭素数が３以下又は５以上の飽和炭化水素基、ハロゲン化アルキル基、カルボキシル基、炭素数が２又は４以上のアルコキシカルボニル基、アルデヒド基、アシル基又はアミド基である。

The nonlinear absorbing material in one aspect of the present disclosure comprises:
The compound represented by the following formula (1) is included.

In the above formula (1), R ¹ to R ¹⁰ each independently contain at least one atom selected from the group consisting of H, C, N, O, F, P, S, Cl, I and Br; and a group other than a group containing an aromatic ring.
However, when the compound is represented by the following formula (2), R ³ and R ⁸ satisfy the following requirements (a) to (c).
(a) At least one selected from the group consisting of R ³ and R ⁸ has a carbon atom directly bonded to a phenylene group adjacent to R ³ or R ⁸ .
(b) when both R ³ and R ⁸ are alkyl groups, at least one alkyl group selected from the group consisting of R ³ and R ⁸ has 2 or less or 5 or more carbon atoms; .
(c) when R ³ is a hydrogen atom, R ⁸ is an unsaturated hydrocarbon group, a saturated hydrocarbon group having 3 or less or 5 or more carbon atoms, a halogenated alkyl group, a carboxyl group, or 2 carbon atoms; or 4 or more alkoxycarbonyl groups, aldehyde groups, acyl groups or amido groups.

The present disclosure provides a nonlinear absorption material with improved nonlinear absorption properties for light having wavelengths in the short wavelength range.

FIG. 1A is a flow chart of a method for recording information using a recording medium containing a nonlinear absorbing material according to one embodiment of the present disclosure. FIG. 1B is a flowchart of a method for reading information using a recording medium containing nonlinear absorbing material according to one embodiment of the present disclosure.

(Findings on which this disclosure is based)
Among organic nonlinear optical materials, two-photon absorption materials have attracted particular attention. Two-photon absorption means a phenomenon in which a compound absorbs two photons almost simultaneously and transitions to an excited state. Simultaneous two-photon absorption and staged two-photon absorption are known as two-photon absorption. Simultaneous two-photon absorption is sometimes called non-resonant two-photon absorption. Simultaneous two-photon absorption means two-photon absorption in a wavelength region in which no one-photon absorption band exists. Stepwise two-photon absorption is sometimes called resonant two-photon absorption. In stepwise two-photon absorption, a compound absorbs a first photon and then transitions to a higher excited state by further absorbing a second photon. In stepwise two-photon absorption, a compound absorbs two photons sequentially.

In simultaneous two-photon absorption, the amount of light absorbed by a compound is generally proportional to the square of the intensity of the irradiated light and exhibits nonlinearity. The amount of light absorbed by a compound can be used as an index of the efficiency of two-photon absorption. When the amount of light absorbed by the compound exhibits nonlinearity, for example, the compound can absorb light only near the focal point of laser light having a high electric field intensity. That is, in a sample containing a two-photon absorbing material, compounds can be excited only at desired positions. Compounds that cause simultaneous two-photon absorption in this way provide extremely high spatial resolution, and are therefore being studied for applications such as recording layers of three-dimensional optical memories and photocurable resin compositions for stereolithography. If the two-photon absorption material further has fluorescence properties, the two-photon absorption material can also be applied to fluorescent dye materials used in two-photon fluorescence microscopes and the like. If this two-photon absorption material is used in a three-dimensional optical memory, it may be possible to adopt a method of reading the ON/OFF state of the recording layer based on changes in fluorescence from the two-photon absorption material. Current optical memories adopt a method of reading the ON/OFF state of a recording layer based on changes in light reflectance and light absorption in a two-photon absorption material. However, when this method is applied to a three-dimensional optical memory, crosstalk may occur based on a recording layer different from the recording layer whose ON/OFF state should be read.

In two-photon absorption materials, a two-photon absorption cross section (GM value) is used as an indicator of efficiency of two-photon absorption. The unit of the two-photon absorption cross section is GM (10 ⁻⁵⁰ cm ⁴ ·s·molecule ⁻¹ ·photon ⁻¹ ). Many organic two-photon absorption materials with large two-photon absorption cross sections have been proposed so far. For example, many compounds with two-photon absorption cross sections as large as over 500 GM have been reported (eg, Non-Patent Document 1). However, in most reports the two-photon absorption cross section is measured using laser light with a wavelength longer than 600 nm. In particular, near-infrared rays having a wavelength longer than 750 nm are sometimes used as laser light.

However, in order to apply two-photon absorption materials to industrial applications, materials that exhibit two-photon absorption characteristics when irradiated with laser light having a shorter wavelength are required. For example, in the field of three-dimensional optical memory, a laser beam having a short wavelength can realize a finer focused spot, thereby improving the recording density of the three-dimensional optical memory. Also in the field of stereolithography, laser light having a short 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, development of a compound having excellent two-photon absorption properties for light in the same wavelength range as short-wave laser light would greatly contribute to the development of industry.

Furthermore, a light emitting device that emits an ultrashort pulse laser with high light intensity tends to be large and unstable in operation. Therefore, it is difficult to adopt such a light-emitting device for industrial use from the viewpoint of versatility and reliability. Considering this fact, in order to apply a two-photon absorption material to industrial applications, a material that exhibits two-photon absorption characteristics even when irradiated with a laser beam of low light intensity is required.

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

In formula (i), α is the one-photon absorption coefficient (cm ⁻¹ ). α ⁽²⁾ is the two-photon absorption coefficient (cm/W). From equation (i), it can be seen that the incident light intensity I when the one-photon absorption and the two-photon absorption are equal in the sample is expressed by α/α ⁽²⁾ . That is, when the intensity I of incident light is smaller than α/α ⁽²⁾ , one-photon absorption preferentially occurs in the sample. Two-photon absorption occurs preferentially in the sample when the intensity I of the incident light is greater than α/α ⁽²⁾ . Therefore, there is a tendency that the smaller the value of α/α ⁽²⁾ in the sample, the more preferentially two-photon absorption can be achieved by a laser beam with a lower light intensity.

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

From equations (ii) and (iii), it can be seen that α/α ⁽²⁾ is determined by ε/σ. That is, in order to preferentially express two-photon absorption by laser light with low light intensity, the ratio σ/ε of the two-photon absorption cross section σ to the molar extinction coefficient ε is large with respect to the wavelength of the irradiated laser light. is desirable. For a compound, when the value of the ratio σ/ε at a particular wavelength is large, it can be said that the nonlinearity of light absorption at that wavelength is high.

Patent Documents 1 and 2 disclose compounds having a large two-photon absorption cross-section for light having a wavelength around 405 nm. Patent Documents 3 and 4 disclose an optical information recording medium capable of shortening the writing time when using a laser beam having a wavelength of around 405 nm, and a compound contained in the optical information recording medium.

Patent Documents 1 and 3 describe compounds having a large conjugated π-electron system. Furthermore, Patent Document 2 describes a benzophenone derivative having a large π-electron conjugated system. However, when the π-electron conjugated system expands in the compound, the two-photon absorption cross section increases, while the peak derived from one-photon absorption tends to shift to a longer wavelength region. In this specification, the shift of the peak resulting from one-photon absorption to the longer wavelength region is sometimes referred to as long wavelength shift or red shift. As a result of the shift of the peak derived from one-photon absorption to a longer wavelength, part of the wavelength region in which one-photon absorption occurs may overlap with the wavelength of the excitation light. A specific example of the wavelength of the excitation light is 405 nm defined by the Blu-ray (registered trademark) standard. In a compound, when the one-photon absorption by excitation light is large, the nonlinearity of light absorption tends to decrease. A compound with low nonlinearity of light absorption is not suitable for the recording layer of a multi-layered three-dimensional optical memory.

Furthermore, the benzophenone derivative disclosed in Patent Document 2 has an intersystem crossing quantum yield of almost 100%. Since this benzophenone derivative rapidly transitions from a singlet excited state to a triplet excited state, it hardly emits fluorescence. Patent Document 4 discloses diphenylacetylene as a two-photon absorption compound contained in an optical information recording medium. However, diphenylacetylene emits little fluorescence.

As a result of intensive studies, the present inventors have newly found that the compound represented by the formula (1) described later has high nonlinear absorption characteristics with respect to light having a wavelength in the short wavelength region, and the present disclosure completed a nonlinear absorption material. Specifically, the present inventors found that in the compound represented by the formula (1), the ratio σ/ε of the two-photon absorption cross section σ to the molar extinction coefficient ε for light having a wavelength in the short wavelength region It was found that the value is large and the nonlinearity of light absorption tends to be high. Furthermore, this compound also tends to have fluorescent properties. In this specification, the short wavelength range means a wavelength range including 405 nm, for example, a wavelength range of 390 nm or more and 420 nm or less.

前記式（１）において、Ｒ¹からＲ¹⁰は、互いに独立して、Ｈ、Ｃ、Ｎ、Ｏ、Ｆ、Ｐ、Ｓ、Ｃｌ、Ｉ及びＢｒからなる群より選ばれる少なくとも１つの原子を含み、かつ、芳香環を含む基以外の他の基である。
ただし、前記化合物が下記式（２）で表される場合、Ｒ³及びＲ⁸は、下記要件（ａ）から（ｃ）を満たす。
（ａ）前記Ｒ³及び前記Ｒ⁸からなる群より選ばれる少なくとも１つは、前記Ｒ³又は前記Ｒ⁸に隣接するフェニレン基に直接結合している炭素原子を有する。
（ｂ）前記Ｒ³及び前記Ｒ⁸の両方がアルキル基である場合、前記Ｒ³及び前記Ｒ⁸からなる群より選ばれる少なくとも１つの前記アルキル基の炭素数は、２以下又は５以上である。
（ｃ）前記Ｒ³が水素原子である場合、前記Ｒ⁸は、不飽和炭化水素基、炭素数が３以下又は５以上の飽和炭化水素基、ハロゲン化アルキル基、カルボキシル基、炭素数が２又は４以上のアルコキシカルボニル基、アルデヒド基、アシル基又はアミド基である。

(Overview of one aspect of the present disclosure)
The nonlinear absorbent material according to the first aspect of the present disclosure comprises:
The compound represented by the following formula (1) is included.

In the above formula (1), R ¹ to R ¹⁰ each independently contain at least one atom selected from the group consisting of H, C, N, O, F, P, S, Cl, I and Br; and a group other than a group containing an aromatic ring.
However, when the compound is represented by the following formula (2), R ³ and R ⁸ satisfy the following requirements (a) to (c).
(a) At least one selected from the group consisting of R ³ and R ⁸ has a carbon atom directly bonded to a phenylene group adjacent to R ³ or R ⁸ .
(b) when both R ³ and R ⁸ are alkyl groups, at least one alkyl group selected from the group consisting of R ³ and R ⁸ has 2 or less or 5 or more carbon atoms; .
(c) when R ³ is a hydrogen atom, R ⁸ is an unsaturated hydrocarbon group, a saturated hydrocarbon group having 3 or less or 5 or more carbon atoms, a halogenated alkyl group, a carboxyl group, or 2 carbon atoms; or 4 or more alkoxycarbonyl groups, aldehyde groups, acyl groups or amido groups.

The nonlinear absorption material according to the first aspect has a large ratio σ/ε of the two-photon absorption cross section σ to the molar extinction coefficient ε for light having a wavelength in a short wavelength region, and tends to have high nonlinearity in light absorption. be. Thus, the nonlinear absorption material has improved nonlinear absorption characteristics for light having wavelengths in the short wavelength range. Nonlinear absorbing materials according to the first aspect also tend to have fluorescent properties.

In the second aspect of the present disclosure, for example, in the nonlinear absorbing material according to the first aspect, R ¹ to R ¹⁰ are each independently a hydrogen atom, a halogen atom, a saturated hydrocarbon group, a halogenated alkyl 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 , a sulfonamide group, a primary amino group, a secondary amino group, a tertiary amino group or a nitro group.

In the third aspect of the present disclosure, for example, in the nonlinear absorption material according to the first or second aspect, at least one selected from the group consisting of R ³ and R ⁸ is a saturated hydrocarbon group, a halogenated alkyl group , unsaturated hydrocarbon group, hydroxyl group, carboxyl group, aldehyde group, acyl group or alkoxy group.

In the fourth aspect of the present disclosure, for example, in the nonlinear absorption material according to any one of the first to third aspects, at least one selected from the group consisting of R ³ and R ⁸ is an alkyl group or an alkoxy may be a base.

In a fifth aspect of the present disclosure, for example, the nonlinear absorbing material according to any one of the first to fourth aspects is 1-ethynyl-4-(phenylethynyl)benzene, 1-ethyl-4-[(4- at least one selected from the group consisting of methylphenyl)ethynyl]benzene, 1-ethyl-4-[(4-methoxyphenyl)ethynyl]benzene and 1-pentyl-4-[(4-methoxyphenyl)ethynyl]benzene may contain.

In the sixth aspect of the present disclosure, for example, the nonlinear absorption material according to any one of the first to fifth aspects may be used in devices that utilize light having a wavelength of 390 nm or more and 420 nm or less.

According to the second to sixth aspects, the nonlinear absorption material has improved nonlinear absorption characteristics for light having a wavelength in the short wavelength range. Nonlinear absorbing materials according to the second to sixth aspects also tend to have fluorescent properties. This nonlinear absorption material is suitable for use in devices that utilize light having a wavelength of 390 nm or more and 420 nm or less.

A recording medium according to a seventh aspect of the present disclosure includes
A nonlinear absorbing material according to any one of the first through sixth aspects.

According to the seventh aspect, the nonlinear absorption material has improved nonlinear absorption characteristics for light having wavelengths in the short wavelength region. The nonlinear absorbing materials used in the seventh aspect also tend to have fluorescent properties. A recording medium containing such a nonlinear absorption material can record information at a high recording density.

An information recording method according to an eighth aspect of the present disclosure includes:
preparing a light source that emits light having a wavelength of 390 nm or more and 420 nm or less;
condensing the light from the light source and irradiating the recording layer in the recording medium containing the nonlinear absorbing material according to any one of the first to sixth aspects;
Including.

According to the eighth aspect, the nonlinear absorption material has improved nonlinear absorption characteristics for light having wavelengths in the short wavelength region. The nonlinear absorbing materials used in the eighth aspect also tend to have fluorescent properties. According to an information recording method using a recording medium containing such a nonlinear absorption material, information can be recorded at a high recording density.

An information reading method according to a ninth aspect of the present disclosure is, for example, a method for reading information recorded by the recording method according to the eighth aspect,
The reading method is
measuring the optical characteristics of the recording layer by irradiating the recording layer in the recording medium with light;
reading information from the recording layer;
Including.

In the tenth aspect of the present disclosure, for example, in the information reading method according to the ninth aspect, the optical characteristic may be the intensity of fluorescent light emitted from the recording layer.

According to the ninth or tenth aspect, it is possible to suppress the occurrence of crosstalk based on other recording layers when reading information.

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

(embodiment)
The nonlinear absorption material of this embodiment contains compound A represented by the following formula (1).

In formula (1), R ¹ to R ¹⁰ each independently contain at least one atom selected from the group consisting of H, C, N, O, F, P, S, Cl, I and Br, Moreover, it is a group other than a group containing an aromatic ring. In other words, R ¹ to R ¹⁰ do not contain aromatic rings. Aromatic rings include not only those composed of carbon atoms but also heteroaromatic rings containing heteroatoms such as oxygen, nitrogen and sulfur atoms. Examples of aromatic rings include benzene ring, naphthalene ring, anthracene ring, phenanthrene ring, furan ring, pyrrole ring, pyridine ring and thiophene ring. Specific examples of the group containing an aromatic ring include an arylethynyl group (--C.ident.C--Ar) and an arylacyl group (--COAr).

R ¹ to R ¹⁰ each independently represent 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, amido 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 may be

Halogen atoms include F, Cl, Br, I and the like. In this specification, a halogen atom may be referred to as a halogen group.

A saturated hydrocarbon group is, for example, an aliphatic saturated hydrocarbon group. A specific example of an aliphatic saturated hydrocarbon group is an alkyl group. The alkyl group may be linear, branched, or cyclic. The number of carbon atoms in the alkyl group is not particularly limited, and is, for example, 1 or more and 20 or less. The number of carbon atoms in the alkyl group may be 1 or more and 10 or less, or 1 or more and 5 or less, from the viewpoint of facilitating synthesis of compound A. By adjusting the carbon number of the alkyl group, the solubility of compound A in the solvent or resin composition can be adjusted. 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. Alkyl groups include methyl, ethyl, propyl, butyl, 2-methylbutyl, pentyl, hexyl, 2,3-dimethylhexyl, heptyl, octyl, nonyl, decyl, and undecyl groups. , dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, hexadecyl group, heptadecyl group, octadecyl group, nonadecyl group, eicosyl group, 2-methoxybutyl group, 6-methoxyhexyl group and the like.

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

Unsaturated hydrocarbon groups contain unsaturated bonds such as carbon-carbon double bonds and carbon-carbon triple bonds. The number of unsaturated bonds contained in the unsaturated hydrocarbon group is, for example, 1 or more and 5 or less. The number of carbon atoms in the unsaturated hydrocarbon group is not particularly limited, and may be, for example, 2 to 20, 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 vinyl groups and ethynyl groups.

A hydroxyl group is represented by -OH. A carboxyl group is represented by -COOH. An alkoxycarbonyl group is represented by -COOR _a . An aldehyde group is represented by -COH. An acyl group is represented by -COR _b . An amide group is represented by -CONR _c R _d . A nitrile group is represented by -CN. An alkoxy group is represented by -OR _e . An acyloxy group is represented by -OCOR _f . A thiol group is represented by —SH. An alkylthio group is represented by -SR _g . A sulfonic acid group is represented by --SO ₃ H. An acylthio group is represented by -SCOR _h . An alkylsulfonyl group is represented by --SO ₂ R _i . A sulfonamide group is represented by --SO ₂ NR _j R _k . A primary amino group is represented by _-NH2 . A secondary amino group is represented by —NHR ₁ . A tertiary amino group is represented by —NR _m R _n . A nitro group is represented by —NO ₂ . R _a to R _n are each independently an alkyl group. Examples of alkyl groups include those described above. However, R _c and R _d of the amide group and R _j and R _k of the sulfonamide group may each independently be a hydrogen atom.

Illustrative examples of alkoxycarbonyl groups are --COOCH ₃ , --COO(CH ₂ ) ₃ CH ₃ and --COO(CH ₂ ) ₇ CH ₃ . A specific example of an acyl group is _-COCH3 . A specific example of an amide group is --CONH ₂ . Specific examples of alkoxy groups include methoxy, ethoxy, 2-methoxyethoxy, butoxy, 2-methylbutoxy, 2-methoxybutoxy, 4-ethylthiobutoxy, pentyloxy, hexyloxy and heptyl. oxy group, octyloxy group, nonyloxy group, decyloxy group, undecyloxy group, dodecyloxy group, tridecyloxy group, tetradecyloxy group, pentadecyloxy group, hexadecyloxy group, heptadecyloxy group, octadecyloxy group , a nonadecyloxy group and an eicosyloxy group. A specific example of an acyloxy group is --OCOCH ₃ . A specific example of an acylthio group is _-SCOCH3 . A specific example of an alkylsulfonyl group is --SO ₂ CH ₃ . A specific example of a sulfonamide group is --SO ₂ NH ₂ . A specific example of a tertiary amino group is --N(CH ₃ ) ₂ .

At least one selected from the group consisting of R ³ and R ⁸ is, for example, a saturated hydrocarbon group, a halogenated alkyl group, an unsaturated hydrocarbon group, a hydroxyl group, a carboxyl group, an aldehyde group, an acyl group or an alkoxy group. . At least one selected from the group consisting of R ³ and R ⁸ may be an alkyl group, a halogenated alkyl group, an unsaturated hydrocarbon group or an alkoxy group, or may be an alkyl group or an alkoxy group. At least one selected from the group consisting of R ³ and R ⁸ may be an unsaturated hydrocarbon group.

However, when compound A is compound B represented by the following formula (2), R ³ and R ⁸ satisfy requirements (a) to (c) below.
(a) at least one selected from the group consisting of R ³ and R ⁸ has a carbon atom directly bonded to the phenylene group adjacent to R ³ or R ⁸ ;
(b) When both R ³ and R ⁸ are alkyl groups, at least one alkyl group selected from the group consisting of R ³ and R ⁸ has 2 or less or 5 or more carbon atoms.
(c) when R ³ is a hydrogen atom, R ⁸ is an unsaturated hydrocarbon group, a saturated hydrocarbon group having 3 or less or 5 or more carbon atoms, a halogenated alkyl group, a carboxyl group, or 2 or 4 carbon atoms; It is the above alkoxycarbonyl group, aldehyde group, acyl group or amido group.

In requirement (a), if R ³ has a carbon atom directly bonded to the phenylene group adjacent to R ³ and requirements (b) and (c) are met, then R ⁸ is , is not particularly limited. In this case, R ⁸ may have an oxygen atom directly attached to the phenylene group adjacent to R ⁸ . Substituents having an oxygen atom directly bonded to a phenylene group include alkoxy groups such as methoxy groups. Each of ^R3 and ^R8 may have a carbon atom directly attached to the phenylene group adjacent to ^R3 or ^R8 .

In requirement (b), at least one alkyl group selected from the group consisting of R ³ and R ⁸ may have 2 or less carbon atoms. At this time, the two-photon absorption cross section per molecular weight of compound B tends to be large. According to such compound B, the two-photon absorption cross section per unit volume of the nonlinear absorption material can be easily increased. In requirement (b), for each of R ³ and R ⁸ , the alkyl group may have 2 or less carbon atoms.

In requirement (b), at least one alkyl group selected from the group consisting of R ³ and R ⁸ may have 5 or more carbon atoms. At this time, compound B tends to have high solubility in resins and the like. That is, when the compound B is used as a component of the device material, the compound B easily dissolves in a resin binder or the like contained in the material. According to this compound B, the concentration of compound B in the material can be easily increased. A film having a high concentration of compound B can be easily produced by using a material having a high concentration of compound B. Thus, compound B, which has high solubility in resin binders, is suitable for use in devices. In requirement (b), for each of R ³ and R ⁸ , the alkyl group may have 5 or more carbon atoms. The upper limit of the number of carbon atoms in the alkyl group in requirement (b) is not particularly limited, and is, for example, 20, and may be 10.

In requirement (c), R ⁸ may be an unsaturated hydrocarbon group such as a vinyl group or an ethynyl group. At this time, the quantum yield of fluorescence in compound B tends to be high. In requirement (c), R ⁸ may be a halogenated alkyl group such as —CF ₃ .

Specific examples of the compound B satisfying the requirements (a) to (c) include 1-ethynyl-4-(phenylethynyl)benzene of the following formula (3), 1-ethyl-4-[( 4-methylphenyl)ethynyl]benzene, 1-ethyl-4-[(4-methoxyphenyl)ethynyl]benzene of the following formula (5), 1-pentyl-4-[(4-methoxyphenyl) of the following formula (6) ) ethynyl]benzene, 4-(phenylethynyl)styrene of the following formula (7), 1-(phenylethynyl)-4-(trifluoromethyl)benzene of the following formula (8), bis(4 -hexylphenyl)acetylene and the like.

That is, the compound A represented by the formula (1) has, as the compound B, 1-ethynyl-4-(phenylethynyl)benzene, 1-ethyl-4-[(4-methylphenyl)ethynyl]benzene, 1-ethyl -4-[(4-methoxyphenyl)ethynyl]benzene, 1-pentyl-4-[(4-methoxyphenyl)ethynyl]benzene, 4-(phenylethynyl)styrene, 1-(phenylethynyl)-4-(tri It may contain at least one selected from the group consisting of fluoromethyl)benzene and bis(4-hexylphenyl)acetylene. In particular, compound A is 1-ethynyl-4-(phenylethynyl)benzene, 1-ethyl-4-[(4-methylphenyl)ethynyl]benzene, 1-ethyl-4-[(4-methoxyphenyl)ethynyl] It may contain at least one selected from the group consisting of benzene and 1-pentyl-4-[(4-methoxyphenyl)ethynyl]benzene.

In the compound B satisfying the requirements (a) to (c), the substituents introduced into the benzene ring tend to have low electron-withdrawing or electron-donating properties. Such substituents do not significantly change the size of the π-conjugated system of the diphenylacetylene molecule. With such a substituent, it is possible to suppress a large shift of the peak derived from one-photon absorption to a longer wavelength due to the extension of the π-conjugated system. As a result, in compound B, an increase in the molar absorption coefficient for light in the wavelength range of 390 nm or more and 420 nm or less is suppressed, and the nonlinearity of light absorption tends to be high. In addition, the above substituents can slightly alter the electronic state of the molecule, which also tends to impart fluorescent properties to the diphenylacetylene molecule.

As shown in formula (2), in formula (1), each of R ¹ to R ² , R ⁴ to R ⁷ and R ⁹ to R ¹⁰ may be a hydrogen atom. However, at least one selected from the group consisting of R ¹ to R ² , R ⁴ to R ⁷ and R ⁹ to R ¹⁰ may be a saturated hydrocarbon group or a methyl group. When at least one selected from the group consisting of R ¹ to R ² , R ⁴ to R ⁷ and R ⁹ to R ¹⁰ is a saturated hydrocarbon group, R ³ and R ⁸ may be hydrogen atoms.

In formula (1), when at least one selected from the group consisting of R ¹ to R ² and R ⁴ to R ⁵ is a saturated hydrocarbon group, each of R ⁶ to R ⁷ and R ⁹ to R ¹⁰ is hydrogen It may be an atom. provided that at least one selected from the group consisting of R ¹ to R ² and R ⁴ to R ⁵ is a saturated hydrocarbon group, and at least one selected from the group consisting of R ⁶ to R ⁷ and R ⁹ to R ¹⁰ One may be a saturated hydrocarbon group.

Specific examples of compound A in which at least one selected from the group consisting of R ¹ to R ² , R ⁴ to R ⁷ and R ⁹ to R ¹⁰ is a saturated hydrocarbon group include 1-methyl- 2-(phenylethynyl)benzene, 1-methyl-3-(phenylethynyl)benzene of the following formula (11), di-o-tolylacetylene of the following formula (12), 1-methyl-2 of the following formula (13) -(m-phenylethynyl)benzene and the like.

The method for synthesizing compound A represented by formula (1) is not particularly limited. Compound A can be synthesized, for example, by a Sonogashira cross-coupling reaction. Specifically, first, a compound C represented by the following formula (14) and a compound D represented by the following formula (15) are prepared.

X in formula (14) is a halogen atom such as bromine or iodine, or B(OH) ₂ . R ¹ to R ⁵ in formula (14) and R ⁶ to R ¹⁰ in formula (15) are the same as described above for formula (1). Next, a coupling reaction between compound C and compound D is performed. Thereby, the compound A can be synthesized. The conditions for the coupling reaction can be appropriately adjusted according to the types of substituents of compound C and compound D, for example.

The compound A represented by formula (1) tends to have excellent two-photon absorption characteristics and low one-photon absorption with respect to light having a wavelength in the short wavelength region. As an example, when compound A is irradiated with light having a wavelength of 405 nm, compound A may exhibit two-photon absorption but little one-photon absorption.

The two-photon absorption cross section of Compound A for light having a wavelength of 405 nm may be greater than 1 GM, may be 10 GM or greater, may be 20 GM or greater, or may be 100 GM or greater. The upper limit of the two-photon absorption cross section of compound A is not particularly limited, and is, for example, 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. The Z scan method is widely used as a method for measuring nonlinear optical constants. In the Z scan method, the measurement sample is moved along the irradiation direction of the beam in the vicinity of the focal point where the laser beam is condensed. 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 incident light changes according to the position of the measurement sample. Therefore, when the measurement sample performs nonlinear absorption, the amount of transmitted light is 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 changes in the amount of transmitted light to a theoretical curve predicted from the intensity of incident light, the thickness of the measurement sample, the concentration of compound A in the measurement sample, and the like. .

The two-photon absorption cross section may be a calculated value by computational chemistry. Several methods have been proposed to estimate 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.

The molar extinction coefficient of Compound A for light having a wavelength of 405 nm may be 100 mol ^-1 ·L · cm ^-1 or less, may be 10 mol ^-1 ·L · cm ^-1 or less, or may be 1 mol ^-1 ·L·cm ⁻¹ or less, or 0.1 mol ⁻¹ ·L·cm ⁻¹ or less. The lower limit of the molar extinction coefficient of compound A is not particularly limited, and is, 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 the measurement of the molar extinction coefficient, a light source that irradiates light with a photon density at which compound A hardly causes two-photon absorption is used. In addition, the concentration of Compound A is adjusted to 500 mmol/L for the measurement of molar extinction coefficient. This concentration is a very high value compared with the concentration in the measurement test of the molar extinction coefficient of the light absorption peak. The molar extinction coefficient can be used as a measure of one-photon absorption.

The molar extinction coefficient may be a value calculated by a quantum chemical calculation program. As a quantum chemical calculation program, for example, Gaussian16 (manufactured by Gaussian) can be used.

Compound A tends to have a large ratio σ/ε of the two-photon absorption cross section σ (GM) to the molar extinction coefficient ε (mol ⁻¹ ·L·cm ⁻¹ ) for light having a wavelength in the short wavelength region. be. The ratio σ/ε of compound A to light having a wavelength of 405 nm may be 1600 or more, 1700 or more, 1900 or more, 2000 or more, or 2500 or more. or 3000 or more. The upper limit of the ratio σ/ε of compound A is not particularly limited, and is 10,000, for example.

When the compound A absorbs two photons, the compound A absorbs about twice the energy of the light with which the compound A is irradiated. A wavelength of light having about twice the energy of light having a wavelength of 405 nm is, for example, 200 nm. One-photon absorption may occur in compound A when compound A is irradiated with light having a wavelength of around 200 nm. Furthermore, in compound A, one-photon absorption may occur with respect to light having a wavelength in the vicinity of the wavelength region in which two-photon absorption occurs.

Compound A also tends to emit fluorescent light. The wavelength of the fluorescent light emitted by compound A may be 405 nm or more and 660 nm or less, or in some cases, 300 nm or more and 650 nm or less. The fluorescence quantum yield Φf of compound A may be 0.05 or more, 0.1 or more, or 0.5 or more. The upper limit of the fluorescence quantum yield Φf in compound A is not particularly limited, and is, for example, 0.99. As used herein, "quantum yield" specifically means internal quantum yield. The fluorescence quantum yield can be measured, for example, by a commercially available absolute PL quantum yield measurement device.

The nonlinear absorption material of this embodiment may contain compound A represented by formula (1) as a main component. By "major component" is meant the component contained in the non-linear absorbent material in the largest proportion by weight. The nonlinear absorption material consists essentially of compound A, for example. "Consisting essentially of" means excluding other ingredients that modify the essential characteristics of the referenced material. However, the nonlinear absorption material may contain impurities in addition to the compound A. The nonlinear absorption material of this embodiment containing compound A functions, for example, as a two-photon absorption material.

The nonlinear absorption material of this embodiment is used, for example, in devices that utilize light having wavelengths in the short wavelength range. As an example, the nonlinear absorption material of this embodiment is used in devices that utilize light having a wavelength of 390 nm or more and 420 nm or less. Such devices include recording media, modeling machines, fluorescence microscopes, and the like. Recording media include, for example, a three-dimensional optical memory. A specific example of a three-dimensional optical memory is a three-dimensional optical disk. Examples of modeling machines include optical modeling machines such as 3D printers. Fluorescence microscopes include, for example, two-photon fluorescence microscopes. The light utilized in these devices, for example, has a high photon density near its focal point. The power density near the focal point of light used in the device is, for example, 0.1 W/cm ² or more and 1.0×10 ²⁰ W/cm ² or less. The power density near the focal point of this light may be 1.0 W/cm ² or more, 1.0×10 ² W/cm ² or more, or 1.0×10 ⁵ W/cm It may be ² or more. As a light source for the device, for example, a femtosecond laser such as a titanium sapphire laser, or a pulsed laser having a pulse width of picosecond to nanosecond such as a semiconductor laser can be used.

A recording medium comprises, for example, a thin film called a recording layer. Information is recorded in a recording layer of a recording medium. As an example, a thin film as a recording layer contains the nonlinear absorption material of this embodiment. That is, from another aspect, the present disclosure provides a recording medium comprising a nonlinear absorbing material containing compound A described above.

The recording layer may further contain a polymer compound that functions as a binder, in addition to the nonlinear absorption material. The recording medium may have a dielectric layer in addition to the recording layer. The recording medium comprises, for example, multiple recording layers and multiple dielectric layers. In the recording medium, a plurality of recording layers and a plurality of dielectric layers may be alternately laminated.

Next, a method of recording information using the above recording medium will be described. FIG. 1A is a flow chart of an information recording method using the above recording medium. First, in step S11, a light source that emits light having a wavelength of 390 nm or more and 420 nm or less is prepared. As the light source, for example, a femtosecond laser such as a titanium sapphire laser, or a pulse 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 condensed by a lens or the like, and the recording layer of the recording medium is irradiated with the light. Specifically, the light from the light source is condensed by a lens or the like, and the recording area of the recording medium is irradiated with the light. The power density near the focal point of this light is, for example, 0.1 W/cm ² or more and 1.0×10 ²⁰ W/cm ² or less. The power density near the focal point of this light may be 1.0 W/cm ² or more, 1.0×10 ² W/cm ² or more, or 1.0×10 ⁵ W/cm It may be ² or more. In this specification, the recording area means a spot existing in the recording layer and capable of recording information by being irradiated with light.

A physical change or a chemical change occurs in the recording area irradiated with the light, and the optical characteristics of the recording area change. For example, the intensity of fluorescent light emitted from the recording area is reduced. In the recording area irradiated with light, the intensity of light reflected in the recording area, the reflectance of light in the recording area, the absorption rate of light in the recording area, the refractive index of light in the recording area, and the light emitted from the recording area The wavelength of the fluorescent light, etc., may also change. Thereby, information can be recorded in the recording layer, more specifically, in the recording area (step S13).

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

In the information reading method, the recording area in which the information is recorded can be found by the following method. First, a specific area of the recording medium is irradiated with light. This light may be the same as or different from the light used to record information on the recording medium. Next, the optical properties of the region irradiated with light are measured. The optical characteristics include, for example, the intensity of fluorescent light emitted from the region, the intensity of light reflected from the region, the reflectance of light at the region, the absorptivity of light at the region, and the Examples include the refractive index of light, the wavelength of fluorescent light emitted from the region, and the like. Based on the measured optical characteristics, it is determined whether or not the area irradiated with light is a recording area. For example, when the intensity of fluorescent light emitted 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, when the intensity of fluorescent light exceeds a specific value, it is determined that the area is 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, when the intensity of fluorescent light emitted from the area exceeds a specific value, it may be determined that the area is a recording area. Alternatively, if the intensity of fluorescent light emitted from the area is equal to or less than a specific value, it may be determined that the area is not a recording area. If it is determined that the area is not a recording area, the same operation is performed on another area of the recording medium. This makes it possible to search for a recording area.

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

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

According to a fluorescence microscope, for example, it is possible to irradiate a biological sample containing a fluorescent dye material with light and observe fluorescence emitted from the dye material. As an example, a fluorescent dye material to be added to a biological sample contains the nonlinear absorption material of this embodiment.

EXAMPLES The present disclosure will be described in further detail below with reference to examples. In addition, the following examples are examples, and the present disclosure is not limited to the following examples.

First, the compounds of Examples 1 to 11 and Comparative Examples 1 to 7 shown in Table 1 were prepared. The compounds of Comparative Examples 1 to 7 are represented by the following formulas (16) to (22), respectively.

<Measurement of two-photon absorption cross section>
For the compounds of Examples 1 to 4 and Comparative Examples 1 to 7, two-photon absorption cross sections were measured for light having a wavelength of 405 nm. Two-photon absorption cross sections were measured using the Z scan method described in J. Opt. Soc. Am. B, 2003, Vol. 20, p. A titanium sapphire pulsed laser was used as a light source for measuring the two-photon absorption cross section. Specifically, the sample was irradiated with the second harmonic of a titanium sapphire pulsed laser. The pulse width of the laser was 80 fs. The laser repetition frequency 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 was light with a wavelength of 405 nm. Specifically, the light from the laser had a center wavelength between 403 nm and 405 nm. The full width at half maximum of the light from the laser was 4 nm.

<Prediction of two-photon absorption cross section>
Predictions of two-photon absorption cross sections for light having a wavelength of 405 nm were made for the compounds of Examples 1-4. Specifically, the two-photon absorption cross section was calculated by density functional theory (DFT) calculation based on the second-order nonlinear response theory described in J. Chem. Theory Comput. 2018, Vol. 14, p. 807. . For the DFT calculation, Turbomole version 7.3.1 (manufactured by COSMOlogic) was used as software. As a basis function, def2-TZVP was used. B3LYP was used as the functional.

Linear regression was performed on the calculated and measured two-photon absorption cross sections of the compounds of Examples 1-4. Next, using the regression equation obtained by this linear regression, the calculated values of the two-photon absorption cross sections of the compounds of Examples 5 to 11 shown in Table 1 were calculated.

<Measurement of molar extinction coefficient>
The molar extinction coefficients of the compounds of Examples 1 to 4 and Comparative Examples 1 to 7 were measured according to JIS K0115:2004. Specifically, first, a measurement sample with a compound concentration adjusted to 500 mmol/L was prepared. An absorption spectrum was measured for the measurement sample. The absorbance at a wavelength of 405 nm was read from the resulting spectrum. The molar extinction coefficient was calculated based on the concentration of the compound in the measurement sample and the optical path length of the cell used for measurement.

<Prediction of molar extinction coefficient>
Predictions of molar extinction coefficients were made for the compounds of Examples 1-4. DFT calculations were used to predict molar extinction coefficients. Specifically, first, excited state calculations were performed for compounds using Gaussian 16 (manufactured by Gaussian), which is a quantum chemical calculation program. In the excited state calculation, 6-31++G(d, p) was used as a basis function. B3LYP was used as the functional. By excited state calculation, the energy for exciting the compound and the oscillator strength f (oscillator strength) were calculated. Oscillator strength correlates with the molar extinction coefficient. Next, the absorption spectrum was assumed to be a Gaussian distribution, and the half-width was specified. Specifically, the absorption spectrum was drawn based on the absorption wavelength and the oscillator strength, with the half-value width defined as 0.4 eV. Absorbance at a wavelength of 405 nm was read from the obtained absorption spectrum. This absorbance was taken as the calculated molar extinction coefficient.

Linear regression was performed on the calculated and observed molar extinction coefficients of the compounds of Examples 1-4. Next, using the regression equation obtained by this linear regression, the calculated values of the molar extinction coefficients of the compounds of Examples 5 to 11 shown in Table 1 were calculated.

<Measurement of fluorescence quantum yield>
The internal quantum yield of fluorescence was measured for the compounds of Examples 1 to 4 and Comparative Examples 1 to 7. Measurement samples were prepared by dissolving compounds in chloroform (CLF) solvent or dimethylsulfoxide (DMSO) solvent. For the measurement, an absolute PL quantum yield measuring device (C9920-02 manufactured by Hamamatsu Photonics) was used. The excitation wavelength was set to the peak wavelength of one-photon absorption of the compound. The measurement wavelength was appropriately adjusted in the range of 350 nm or more and 650 nm or less so as not to overlap with the absorption wavelength band of the compound. As a reference, the solvent used to dissolve the compound was taken.

Measured and calculated values of the two-photon absorption cross section σ (GM) obtained by the above method, measured and calculated values of the molar extinction coefficient ε (mol ⁻¹ L cm ⁻¹ ), the ratio σ/ε, Table 1 also shows the fluorescence quantum yield Φf(−). In Table 1, the ratio σ/ε was calculated based on the measured values of the two-photon absorption cross section and the measured values of the molar extinction coefficient. For compounds for which actual measurements of the two-photon absorption cross section and molar extinction coefficient were not obtained, the ratio σ/ε was calculated based on these calculated values. In Table 1, "No Data" means that no data has been obtained.

As can be seen from Table 1, in the compounds of Examples 1 to 3, 5 to 9 and 11, the ratio σ/ε to light having a wavelength of 405 nm is greater than that of the compounds of the comparative examples, and is 1900 or more. there were. In the compounds of Examples 4 and 10, the value of the ratio σ/ε was comparable to that of the compound of Comparative Example 1, while the value of the two-photon absorption cross section σ was larger than that of the compound of Comparative Example 1. From this result, it can be seen that compound A has high nonlinearity of light absorption with respect to light having a wavelength in a short wavelength region, and has improved nonlinear absorption characteristics. In addition, the compounds of Examples 1-4 also possessed fluorescent properties.

Diphenylacetylene of Comparative Example 1 hardly emitted fluorescence. It has been reported that diphenylacetylene has a high intersystem crossing quantum yield at room temperature, which results in a very low fluorescence quantum yield.

In the compounds of Comparative Examples 2 to 4 in which a halogen group was introduced into diphenylacetylene, the σ/ε ratio values were greatly reduced compared to diphenylacetylene. It is presumed that in the compounds of Comparative Examples 2 to 4, the LUMO energy of diphenylacetylene was lowered by the electron-withdrawing halogen group. It is presumed that the reduction in LUMO energy reduced the energy required to excite the compound to the lowest one-photon absorption permissible level, and red-shifted the peak wavelength of one-photon absorption. As a result, it is presumed that the molar extinction coefficient ε for light having a wavelength of 405 nm was greatly increased and the ratio σ/ε was a small value.

All of the compounds of Comparative Examples 5 to 7 had a ratio σ/ε of less than 100 for light having a wavelength of 405 nm. These compounds have a large π-electron conjugated system and thus a large transition dipole moment. Therefore, in Comparative Examples 5 to 7, the two-photon absorption cross-sectional area σ was a large value. However, in compounds having an extended π-electron conjugated system, the peak derived from one-photon absorption tends to shift to longer wavelength regions. In the compounds of Comparative Examples 5 to 7, part of the wavelength region where one-photon absorption occurs overlaps with 405 nm, so that the molar extinction coefficient ε is greatly increased. be done.

The nonlinear absorption material of the present disclosure can be used for applications such as recording layers of three-dimensional optical memories and photocurable resin compositions for stereolithography. The nonlinear absorption material of the present disclosure has light absorption characteristics that exhibit high nonlinearity with respect to light having wavelengths in the short wavelength region. Therefore, the nonlinear absorption material of the present disclosure can achieve extremely high spatial resolution in applications such as three-dimensional optical memory and modeling machines. In addition, the nonlinear absorbing materials of the present disclosure also tend to have high fluorescence quantum yields. Therefore, if a nonlinear absorption material is used in the recording layer of a three-dimensional optical memory, a method of reading the ON/OFF state of the recording layer based on changes in fluorescence from the nonlinear absorption material can be adopted. The nonlinear absorption material of the present disclosure can also be used for fluorescent dye materials used in two-photon fluorescence microscopes and the like. According to the nonlinear absorption material of the present disclosure, compared to conventional nonlinear absorption materials, it is possible to cause two-photon absorption more favorably than one-photon absorption even when irradiated with a laser beam of low light intensity.

Claims (10)

A nonlinear absorption material containing a compound represented by the following formula (1).

In the above formula (1), R ¹ to R ¹⁰ each independently contain at least one atom selected from the group consisting of H, C, N, O, F, P, S, Cl, I and Br; and a group other than a group containing an aromatic ring.
However, when the compound is represented by the following formula (2), R ³ and R ⁸ satisfy the following requirements (a) to (c).
(a) At least one selected from the group consisting of R ³ and R ⁸ has a carbon atom directly bonded to a phenylene group adjacent to R ³ or R ⁸ .
(b) when both R ³ and R ⁸ are alkyl groups, at least one alkyl group selected from the group consisting of R ³ and R ⁸ has 2 or less or 5 or more carbon atoms; .
(c) when R ³ is a hydrogen atom, R ⁸ is an unsaturated hydrocarbon group, a saturated hydrocarbon group having 3 or less or 5 or more carbon atoms, a halogenated alkyl group, a carboxyl group, or 2 carbon atoms; or 4 or more alkoxycarbonyl groups, aldehyde groups, acyl groups or amido groups.

R ¹ to R ¹⁰ each independently represent 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, and an acyl group. 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 2. The nonlinear absorbing material of claim 1, which is a nitro group. At least one selected from the group consisting of R ³ and R ⁸ is a saturated hydrocarbon group, a halogenated alkyl group, an unsaturated hydrocarbon group, a hydroxyl group, a carboxyl group, an aldehyde group, an acyl group, or an alkoxy group. A nonlinear absorbing material according to claim 1 or 2. 4. The nonlinear absorption material according to any one of claims ¹ to 3, wherein at least one selected from the group consisting of R3 and ^R8 is an alkyl group or an alkoxy group. Said compounds include 1-ethynyl-4-(phenylethynyl)benzene, 1-ethyl-4-[(4-methylphenyl)ethynyl]benzene, 1-ethyl-4-[(4-methoxyphenyl)ethynyl]benzene and 5. The nonlinear absorption material according to any one of claims 1 to 4, comprising at least one selected from the group consisting of 1-pentyl-4-[(4-methoxyphenyl)ethynyl]benzene. 6. The nonlinear absorption material according to any one of claims 1 to 5, which is used in a device utilizing light having a wavelength of 390 nm or more and 420 nm or less. A recording medium comprising a non-linear absorbing material according to any one of claims 1-6. preparing a light source that emits light having a wavelength of 390 nm or more and 420 nm or less;
Condensing the light from the light source and irradiating the recording layer in the recording medium containing the nonlinear absorption material according to any one of claims 1 to 6,
method of recording information, including A method for reading information recorded by the recording method according to claim 8,
The reading method is
measuring the optical characteristics of the recording layer by irradiating the recording layer in the recording medium with light;
reading information from the recording layer;
A method of reading information, comprising: 10. The reading method according to claim 9, wherein said optical property is the intensity of fluorescent light emitted from said recording layer.

Images