Recording medium, information recording method, information readout method, and composition for producing recording layer

Abstract

The recording medium in one aspect of the present disclosure has a recording layer. The recording layer contains an aliphatic polymer; and a multi-photon absorbing compound having a multi-photon absorption property, which contains at least one selected from the group consisting of carbon-carbon double bond, carbon-nitrogen double bond, and carbon-carbon triple bond. When the thickness of the recording layer is 100 μm, the transmittance of the recording layer to light of wavelength 405 nm in the thickness direction is 80% or more.

Description

Technical Field

[0001] This disclosure relates to recording media, methods for recording information, methods for reading information, and compositions for making recording layers. Background Technology

[0002] As a technique for increasing the recording capacity of optical information recording media, three-dimensional recording of information on a multilayer volume is known. In the field of three-dimensional recording, to increase recording density, it is necessary to achieve a finer focal point. From the viewpoint of the diffraction limit of the focused laser, to achieve a finer focal point, a laser with a short wavelength is used. As an example of such a laser, the one with a center wavelength of 405 nm, which is standard for Blu-ray discs, can be cited. Therefore, optical information recording media using a laser with a center wavelength of 405 nm are known.

[0003] Examples of related technologies for three-dimensional recording include: optical information recording media in which photosensitive materials, pigments, etc. are dispersed in resin; optical information recording media in which holes or concave and convex shapes are arranged in three dimensions as recording markers; and optical information recording media in which beams from two systems interfere to form a diffraction grating and form a tiny hologram inside.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2013-58283

[0007] Patent Document 2: Japanese Patent No. 5929109

[0008] Patent Document 3: Japanese Patent No. 6154898

[0009] Patent Document 4: Japanese Patent Application Publication No. 2008-261928 Summary of the Invention

[0010] The problem that the invention aims to solve

[0011] In the recording layer of a recording medium, it is required to suppress the increase in single-photon absorption of light with wavelengths in the short wavelength region.

[0012] Methods for solving problems

[0013] One embodiment of the present disclosure includes a recording medium having at least one recording layer.

[0014] The at least one recording layer comprises: an aliphatic polymer; and a multiphoton absorbing compound having multiphoton absorption properties, comprising at least one selected from the group consisting of carbon-carbon double bonds, carbon-nitrogen double bonds, and carbon-carbon triple bonds.

[0015] When the thickness of the at least one recording layer is 100 μm, the transmittance of the at least one recording layer to light with a wavelength of 405 nm in the thickness direction is more than 80%.

[0016] Invention Effects

[0017] This disclosure provides a recording medium having a recording layer that suppresses increased single-photon absorption of light with wavelengths having a short wavelength region. Attached Figure Description

[0018] Figure 1 This is a cross-sectional view showing the general configuration of a recording medium according to one embodiment of the present disclosure.

[0019] Figure 2A This is a flowchart relating to a method for recording information using a recording medium according to an embodiment of the present disclosure.

[0020] Figure 2B This is a flowchart relating to a method for reading information using a recording medium according to an embodiment of the present disclosure.

[0021] Figure 3 It represents compound K. 1 A graph of H-NMR spectrum.

[0022] Figure 4 It represents compound L. 1 A graph of H-NMR spectrum. Detailed Implementation

[0023] (The insights that form the basis of this disclosure)

[0024] Patent Document 1 discloses a method for manufacturing an optical recording resin layer by heating a mixture of an epoxy compound and a curing agent to polymerize and cure it. Patent Document 1 also discloses the use of a laser with a wavelength of 405 nm to record information on an optical recording medium having an optical recording resin layer.

[0025] Patent Document 2 discloses a method for manufacturing a recording layer by heating and curing a mixture of an acetylene-based benzophenone compound, an epoxy compound, and a curing agent that exhibit nonlinear light absorption effects. In Patent Document 2, the epoxy compound has an aromatic ring. Patent Document 2 also discloses recording information on an optical information recording medium having a recording layer using a laser with a wavelength of 405 nm.

[0026] Patent Document 3 discloses a recording layer comprising a pigment-bound polymer compound formed by combining a polymer compound with a single-photon-absorbing pigment. Patent Document 3 also discloses recording information on an optical information recording medium having multiple recording layers.

[0027] Patent Document 4 discloses a resin material for optical recording in which a photopolymerizable monomer and a photoinitiator are dispersed in an epoxy resin. According to Patent Document 4, an optical recording medium having a recording layer formed from the optical recording resin material is capable of holographic recording.

[0028] The recording layer, as a recording medium, can be a thin film, for example, made from a resin material in which photosensitive materials, pigment molecules, etc., are dispersed. This thin film can be manufactured, for example, by the following method: First, a resin material containing a polymer is mixed with a solvent to prepare a coating solution. This coating solution is then applied to a substrate by a method such as spin coating, and the resulting coating film is dried, thereby producing a thin film.

[0029] The recording layer, as a recording medium, can also be a thin film produced by coating a coating solution in which photosensitive materials, pigment molecules, etc., are dispersed in monomers used to form a resin, thereby polymerizing the monomers contained in the resulting coated film. In this method of producing the thin film, the material containing the monomers also includes a curing agent. The polymerization of the monomers is carried out by photopolymerization or thermal polymerization. The photosensitive materials or pigment molecules used to produce this thin film sometimes have polymerizable functional groups.

[0030] In recording media with multiple recording layers, when the single-photon absorption of light used for recording or reading information is high in each recording layer, the light intensity decreases as the light passes through each layer. In this case, the recording and reading sensitivity tends to decrease significantly in recording layers located far from the light source. Therefore, there is a need for recording layers with low single-photon absorption of light used for recording or reading information. In this specification, information reading is sometimes referred to as information reproduction. Single-photon absorption is sometimes referred to as linear absorption.

[0031] To further increase the number of recording layers in a recording medium, it is necessary to reduce the linear absorption of each recording layer and minimize the influence of other recording layers besides the one being recorded or reproduced. To reduce the linear absorption of each recording layer, recording layers containing pigments that have almost no linear absorption band to the light used for recording or reproduction and exhibit nonlinear optical effects are being investigated.

[0032] Furthermore, nonlinear optical effects refer to optical phenomena that occur in a material when intense light, such as laser light, irradiates the material, and these phenomena are proportional to the square or a power higher than the square of the electric field of the irradiating light. Examples of such optical phenomena include absorption, reflection, scattering, and emission. 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 the parametric effect. Examples of third-order nonlinear optical effects proportional to the cube of the electric field of the irradiating light include multiphoton absorption such as two-photon absorption, third harmonic generation (THG), and the Kerr effect. Multiphoton absorption, such as two-photon absorption, can be particularly utilized in recording media with multiple recording layers. In this specification, multiphoton absorption, such as two-photon absorption, is sometimes referred to as nonlinear absorption. Materials capable of nonlinear absorption are sometimes referred to as nonlinear optical materials.

[0033] To date, inorganic materials that can be easily fabricated into single crystals have been developed as nonlinear optical materials. On the other hand, in recent years, there has been a growing expectation to develop nonlinear optical materials formed from organic materials. 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.

[0034] Regarding compounds constituting organic materials, the closer the wavelength used to transition electrons from the ground state to the lowest singlet excited state is to the excitation wavelength of multiphoton absorption, the better the multiphoton absorption characteristics of the organic material; for example, it tends to achieve a large two-photon absorption cross-section. In recording media, light with the same wavelength as the excitation wavelength of multiphoton absorption is usually used for recording or reproduction. Based on this design principle, various compounds have been synthesized. In this specification, in compounds, the transition of electrons from the ground state to the lowest singlet excited state is sometimes referred to as an S0-S1 transition. Furthermore, the two-photon absorption cross-section is an indicator of the efficiency of two-photon absorption. The unit of two-photon absorption cross-section is GM(10⁻¹⁰). -50 cm 4 ·s· molecule -1 Photon -1 ).

[0035] However, according to the research of the inventors of the present invention, when a multiphoton-absorbing compound is used in a recording layer, the linear absorption of the compound tends to increase at the excitation wavelength of multiphoton absorption. Particularly when the excitation wavelength of multiphoton absorption is in the short wavelength region, the linear absorption at the excitation wavelength of multiphoton absorption tends to increase significantly. Furthermore, when the multiphoton-absorbing compound contains at least one selected from the group consisting of carbon-carbon double bonds, carbon-nitrogen double bonds, and carbon-carbon triple bonds, the linear absorption at the excitation wavelength of multiphoton absorption also tends to increase significantly. The inventors of the present invention have conducted in-depth research and have newly discovered that the increase in linear absorption in the multiphoton-absorbing compound is due to: changes in the electronic state of the multiphoton-absorbing compound caused by the interaction between the polymer contained in the recording layer and the multiphoton-absorbing compound; deterioration or decomposition of the multiphoton-absorbing compound from the process of curing the monomer; and the reaction between the multiphoton-absorbing compound and the monomer during the curing process. In particular, the inventors of this invention discovered that even with slight changes in the electronic state of the multiphoton-absorbing compound, the absorption band of the S0-S1 transition in the compound will have a tailing effect, and the linear absorption at the excitation wavelength of multiphoton absorption tends to increase.

[0036] Based on newly discovered insights, the inventors of this invention have determined that by combining a multiphoton absorption compound with an aliphatic polymer, it is possible to suppress tailing of the absorption band of the S0-S1 transition in the multiphoton absorption compound and deterioration of the multiphoton absorption compound, thereby completing the recording medium disclosed herein. Specifically, the inventors have discovered that by combining a multiphoton absorption compound with an aliphatic polymer, it is possible to achieve a recording layer that suppresses the increase in single-photon absorption of 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.

[0037] (Summary of a scheme covered in this disclosure)

[0038] The first solution disclosed herein involves a recording medium having at least one recording layer.

[0039] The at least one recording layer comprises: an aliphatic polymer; and a multiphoton absorbing compound having multiphoton absorption properties, comprising at least one selected from the group consisting of carbon-carbon double bonds, carbon-nitrogen double bonds, and carbon-carbon triple bonds.

[0040] When the thickness of the at least one recording layer is 100 μm, the transmittance of the at least one recording layer to light with a wavelength of 405 nm in the thickness direction is more than 80%.

[0041] According to the first scheme, changes in the electronic states of the multiphoton-absorbing compound are suppressed in the recording layer. Therefore, the increase in single-photon absorption of light with wavelengths in the short-wavelength region is suppressed in the recording layer.

[0042] In a second aspect of this disclosure, for example, according to the recording medium involved in the first aspect, the combined content of the aliphatic polymer and the multiphoton-absorbing compound in the at least one recording layer may also be 95% by weight or more.

[0043] In a third aspect of this disclosure, for example, according to the recording medium involved in the first or second aspect, the aliphatic polymer may also contain structural units derived from an aliphatic monomer, the aliphatic monomer comprising at least one selected from the group consisting of acryloyl, methacryl, epoxy, oxetyl, and vinyl.

[0044] In the fourth aspect of this disclosure, for example, according to the recording medium of the third aspect, the aliphatic monomer may also comprise at least one selected from the group consisting of acryloyl, methacryl, and epoxy groups.

[0045] In the fifth aspect of this disclosure, for example, according to the recording medium involved in the third aspect, the aliphatic monomer may also comprise at least one selected from the group consisting of compound A represented by formula (A), compound B represented by formula (B), compound C represented by formula (C), compound D represented by formula (D), compound E represented by formula (E), compound F represented by formula (F), and compound G represented by formula (G).

[0046] [Chemical Formula Number 1]

[0047]

[0048] In equation (A), R 1 R is a hydrogen atom or a methyl group. 2 It is an aliphatic group.

[0049] In equation (B), R 3 and R 5 Each of the following is an independent hydrogen atom or a methyl group, R 4 It is an aliphatic group.

[0050] In the above formula (C), R 6 R is a hydrogen atom or a methyl group. 7 For aliphatic groups, R 8 It consists of hydrogen atoms or aliphatic groups.

[0051] In the above equation (D), R9 R is a hydrogen atom or a methyl group. 10 For aliphatic groups, R 11 It consists of hydrogen atoms or aliphatic groups.

[0052] In the above formula (E), R 12 and R 14 Each is independently a hydrogen atom or an aliphatic group, R 13 It is an aliphatic group.

[0053] In the above formula (F), R 15 and R 17 Each is independently a hydrogen atom or an aliphatic group, R 16 It is an aliphatic group.

[0054] In the above formula (G), R 18 and R 20 Each is independently a hydrogen atom or an aliphatic group, R 19 It is an aliphatic group.

[0055] In the sixth aspect of this disclosure, for example, according to the recording medium involved in the fifth aspect, the compound A may also contain at least one selected from the group consisting of compound A1 represented by the following formula (A1) and compound A2 represented by the following formula (A2).

[0056] [Chemical Formula Number 2]

[0057]

[0058] In the above formula (A1), n ​​is an integer greater than 0 and less than 11.

[0059] In the seventh aspect of this disclosure, for example, according to the recording medium involved in the fifth or sixth aspect, the compound B may also contain compound B1 represented by the following formula (B1).

[0060] [Chemical Formula Number 3]

[0061]

[0062] In the above formula (B1), m is an integer greater than 1 and less than 4.

[0063] In the eighth aspect of this disclosure, for example, in the recording medium according to any of the fifth to seventh aspects, the compound E may also contain at least one selected from the group consisting of compound E1 represented by the following formula (E1), compound E2 represented by the following formula (E2), and compound E3 represented by the following formula (E3).

[0064] [Chemical Formula Number 4]

[0065]

[0066] In the above formula (E1), x is an integer greater than 1 and less than 12.

[0067] In the above formula (E3), y is an integer greater than 1 and less than 11.

[0068] In the ninth aspect of this disclosure, for example, the recording medium according to any of the first to eighth aspects, wherein the multiphoton-absorbing compound may also contain an aromatic ring.

[0069] According to schemes two through nine, the increase in single-photon absorption of light with wavelengths in the short-wavelength region is suppressed in the recording layer.

[0070] In the tenth embodiment of this disclosure, for example, the recording medium involved in any of the first to ninth embodiments may also have multiple dielectric layers, and the at least one recording layer may also include multiple recording layers, and the multiple recording layers and the multiple dielectric layers may be arranged alternately.

[0071] According to the tenth scheme, since the recording medium has multiple recording layers, the recording medium has a large recording capacity.

[0072] In the eleventh aspect of this disclosure, for example, the recording medium involved in any of the first to tenth aspects can also use light with a wavelength of 390 nm or more and 420 nm or less to record information.

[0073] According to the eleventh scheme, the recording medium is capable of recording information at a high recording density.

[0074] The method of recording information involved in the twelfth scheme of this disclosure includes:

[0075] A light source prepared to emit light with wavelengths above 390nm and below 420nm; and

[0076] The light from the light source is focused and irradiated onto at least one recording layer in the recording medium involved in any of the first to eleventh schemes.

[0077] According to the twelfth scheme, information can be recorded on the recording medium with high recording density.

[0078] The information reading method of the thirteenth scheme of this disclosure is, for example, a method for reading information recorded using the recording method of the twelfth scheme.

[0079] The readout method includes:

[0080] The optical properties of the at least one recording layer are determined by irradiating the at least one recording layer with light; and

[0081] Information is read from the at least one recording layer.

[0082] According to the thirteenth scheme, the information can be easily read.

[0083] The fourteenth aspect of this disclosure relates to a composition for fabricating a recording layer with a transmittance of 80% or more of light with a wavelength of 405 nm in the thickness direction when the thickness is 100 μm.

[0084] The composition comprises:

[0085] Aliphatic monomers; and

[0086] A multiphoton-absorbing compound comprising at least one selected from the group consisting of carbon-carbon double bonds, carbon-nitrogen double bonds, and carbon-carbon triple bonds.

[0087] According to the fourteenth embodiment, changes in the electronic states of the multiphoton-absorbing compound are suppressed in the recording layer formed from the composition. Therefore, the increase in single-photon absorption of light with wavelengths in the short-wavelength region is suppressed in the recording layer.

[0088] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. The present disclosure is not limited to the following embodiments.

[0089] <Implementation Method>

[0090] Figure 1 This is a cross-sectional view showing the schematic configuration of the recording medium 100 according to one embodiment of this disclosure. (e.g.) Figure 1 As shown, the recording medium 100 includes a recording layer 10. The recording layer 10 comprises: an aliphatic polymer; and a multiphoton-absorbing compound, which includes at least one selected from the group consisting of carbon-carbon double bonds, carbon-nitrogen double bonds, and carbon-carbon triple bonds. When the thickness of the recording layer 10 is 100 μm, the transmittance of the recording layer 10 to light with a wavelength of 405 nm in the thickness direction is 80% or more.

[0091] The recording medium 100 may also have multiple recording layers 10. These multiple recording layers 10 may be arranged, for example, in the thickness direction of the recording medium 100. The number of recording layers 10 in the recording medium 100 is not particularly limited, and may be, for example, 2 or more and 1000 or less. The recording medium 100 having multiple recording layers 10 functions as a three-dimensional optical storage device. A specific example of the recording medium 100 is a three-dimensional optical disc.

[0092] The recording medium 100 may also include multiple dielectric layers 20. In the recording medium 100, the multiple recording layers 10 and the multiple dielectric layers 20 may also be arranged alternately. In other words, the multiple recording layers 10 and the multiple dielectric layers 20 may also be stacked alternately. As an example, the multiple recording layers 10 are respectively disposed between two dielectric layers 20, and are in direct contact with each of the two dielectric layers 20. In the recording medium 100, the number of multiple dielectric layers 20 is not particularly limited, for example, 3 or more and 1001 or less.

[0093] [Record Layer]

[0094] As described above, the recording layer 10 comprises an aliphatic polymer. In this specification, an aliphatic polymer refers to a polymer in which the content of aromatic rings is 10% by weight or less. The content of aromatic rings in the aliphatic polymer can be 5% by weight or less, 1% by weight or less, 0.5% by weight or less, 0.1% by weight or less, or 0.01% by weight or less. The aliphatic polymer may also substantially not contain aromatic rings. Aromatic rings include not only aromatic rings composed of carbon atoms, but also heteroaromatic rings containing heteroatoms such as oxygen atoms, nitrogen atoms, and sulfur atoms. Examples of aromatic rings include, for example, benzene rings, naphthalene rings, anthracene rings, phenanthrene rings, furan rings, pyrrole rings, pyridine rings, and thiophene rings.

[0095] Aliphatic polymers, for example, contain structural units derived from aliphatic monomers. Aliphatic monomers are monomers that have polymerizable functional groups but do not contain aromatic rings. As an example, an aliphatic polymer is a polymer of aliphatic monomers. This polymer can be synthesized by thermal polymerization of aliphatic monomers or by photopolymerization of aliphatic monomers. However, aliphatic polymers can also be cured products obtained by reacting aliphatic monomers with a curing agent. Aliphatic polymers may also contain structural units derived from aliphatic monomers, as well as structural units derived from polymerization initiators, structural units derived from curing agents, etc.

[0096] (Aliphatic monomers)

[0097] Aliphatic monomers are composed of atoms such as hydrogen, boron, carbon, nitrogen, oxygen, fluorine, silicon, phosphorus, and sulfur. Aliphatic monomers can contain one or more polymerizable functional groups. There is no particular upper limit to the number of polymerizable functional groups, for example, 10. Aliphatic monomers may contain at least one polymerizable functional group selected from the group consisting of (meth)acryloyl, epoxy, oxetyl, and vinyl. Aliphatic monomers may also contain at least one polymerizable functional group selected from the group consisting of (meth)acryloyl and epoxy. In this specification, (meth)acryloyl refers to at least one group selected from the group consisting of acryloyl and methacryloyl. Aliphatic monomers may also have a methylene group adjacent to a vinyl group. That is, aliphatic monomers may also contain an allyl group. Furthermore, when an aliphatic monomer has two or more free-radical polymerizable functional groups such as (meth)acryloyl and vinyl, the aliphatic monomer can function as a crosslinking agent.

[0098] Aliphatic monomers include, for example, at least one selected from the group consisting of compound A represented by formula (A), compound B represented by formula (B), compound C represented by formula (C), compound D represented by formula (D), compound E represented by formula (E), compound F represented by formula (F), and compound G represented by formula (G).

[0099] [Chemical Formula Number 5]

[0100]

[0101] In equation (A), R 1 The atom can be a hydrogen atom or a methyl group, or it can be a hydrogen atom. Compound A, for example, has a (meth)acryloyl group. Compound A may contain other polymerizable functional groups besides the (meth)acryloyl group, or it may not contain other polymerizable functional groups besides the (meth)acryloyl group.

[0102] In equation (A), R 2 It is an aliphatic group. An aliphatic group is a group that does not contain an aromatic ring. As R 2The aliphatic group, for example, is an alkyl group. The alkyl group can be straight-chain, branched, or cyclic. The number of carbon atoms in the alkyl group is not particularly limited; for example, it can be 1 to 20 or more, or 1 to 15 or more. 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, cyclohexyl, 2-methoxybutyl, and 6-methoxyhexyl.

[0103] Compound A may also include at least one selected from the group consisting of compound A1 represented by the following formula (A1) and compound A2 represented by the following formula (A2).

[0104] [Chemical Formula Number 6]

[0105]

[0106] In formula (A1), n ​​is an integer greater than 0 and less than 11. Specific examples of compound A1 include compound a1 represented by the following formula (a1), compound a2 represented by the following formula (a2), and so on.

[0107] [Chemical Formula Number 7]

[0108]

[0109] In equation (B), R 3 and R 5 Each can be a hydrogen atom or a methyl group, independent of the others. R 3 and R 5 They can also be methyl groups.

[0110] In equation (B), R 4 It is an aliphatic group. Specifically, R... 4 It is a divalent aliphatic group. R 4 It can also have functional groups containing oxygen atoms, such as ether, ester, and hydroxyl groups. In R 4 In this context, the number of functional groups containing oxygen atoms is not particularly limited; for example, it can be 1 or more but less than 10, or it can be 1 or more but less than 5. However, R... 4 It may also not have a functional group containing an oxygen atom.

[0111] R 4It is also possible to include alkylene groups in addition to the functional groups described above, or to include alkylene groups in place of the functional groups described above. Alkylene groups can be linear, branched, or cyclic. The number of carbon atoms in the alkylene group is not particularly limited; for example, it can be 1 to 10, or 1 to 5. At least one hydrogen atom in the alkylene group can also be replaced by a group containing at least one atom selected from the group consisting of N, O, P, and S. As R 4 Examples of alkylene derivatives include methylene, ethylene, propane-1,3-diyl, butane-1,4-diyl, and pentane-1,5-diyl. 4 It can contain polyoxymethylene, polyoxyethylene, and other polyoxymethylene groups.

[0112] Compound B, for example, has two (meth)acryloyl groups. Wherein, in compound B, R... 4 It may also contain a (meth)acryloyl group. In this case, the number of (meth)acryloyl groups in compound B is not particularly limited, for example, it may be 3 or more and 10 or less. Compound B may contain other polymerizable functional groups besides (meth)acryloyl groups, or it may not contain other polymerizable functional groups besides (meth)acryloyl groups.

[0113] Compound B may also include compound B1 represented by the following formula (B1). Other examples of compound B include compound B2 represented by the following formula (B2), compound B3 represented by the following formula (B3), etc.

[0114] [Chemical Formula No. 8]

[0115]

[0116] In formula (B1), m is an integer greater than or equal to 1 and less than 4. In formula (B2), s is an integer greater than or equal to 1 and less than 10. In formula (B3), t is an integer greater than or equal to 1 and less than 10. Specific examples of compound B1 include compound b1 represented by the following formula (b1). Specific examples of compound B2 include compound b2 represented by the following formula (b2). Specific examples of compound B3 include compound b3 represented by the following formula (b3).

[0117] [Chemical Formula Number 9]

[0118]

[0119] In equation (C), R 6 It can be a hydrogen atom or a methyl group. R 7 It is an aliphatic group. As R... 7 Aliphatic groups, for example, can be exemplified by R as a compound B. 4Exemplary aliphatic groups.

[0120] In equation (C), R 8 It can be a hydrogen atom or an aliphatic group, or it can be a hydrogen atom. As R 8 Aliphatic groups, for example, can be exemplified by R as a compound A. 2 An example of an aliphatic group. In formula (C), R 7 and R 8 They can also bond together to form a ring structure.

[0121] Compound C, for example, has one (meth)acryloyl group and one epoxy group. In compound C, R... 7 It may also contain at least one group selected from the group consisting of (meth)acryloyl and epoxy groups. In this case, the number of (meth)acryloyl groups and the number of epoxy groups in compound C are not particularly limited, for example, 3 or more and 10 or less. Compound C may contain other polymerizable functional groups besides (meth)acryloyl and epoxy groups, or it may not contain other polymerizable functional groups besides (meth)acryloyl and epoxy groups.

[0122] Specific examples of compound C include compound C1 represented by the following formula (C1), compound C2 represented by the following formula (C2), and compound C3 represented by the following formula (C3).

[0123] [Chemical Formula Number 10]

[0124]

[0125] In equation (D), R 9 It can be a hydrogen atom or a methyl group, or it can be a hydrogen atom. R 10 It is an aliphatic group. As R... 10 Aliphatic groups, for example, can be exemplified by R as a compound B. 4 Exemplary aliphatic groups.

[0126] In equation (D), R 11 It can be a hydrogen atom or an aliphatic group, or even an aliphatic group. As R 11 Aliphatic groups, for example, can be exemplified by R as a compound A. 2 An example of an aliphatic group. In formula (D), R 10 and R 11 They can also bond together to form a ring structure.

[0127] Compound D, for example, has a (meth)acryloyl group and an oxecyclic butyl group. Wherein, in compound D, R... 10It may also contain at least one group selected from the group consisting of (meth)acryloyl and oxetane. In this case, the number of (meth)acryloyl groups and the number of oxetane groups in compound D are not particularly limited, for example, 3 or more and 10 or less. Compound D may contain other polymerizable functional groups besides (meth)acryloyl and oxetane, or it may not contain other polymerizable functional groups besides (meth)acryloyl and oxetane.

[0128] As a specific example of compound D, compound D1, represented by the following formula (D1), can be cited.

[0129] [Chemical Formula No. 11]

[0130]

[0131] In equation (E), R 12 and R 14 Each is an independent hydrogen atom or an aliphatic group. As R 12 and R 14 Aliphatic groups, for example, can be exemplified by R as a compound A. 2 Exemplary aliphatic groups.

[0132] In equation (E), R 13 It is an aliphatic group. As R... 13 Aliphatic groups, for example, can be exemplified by R as a compound B. 4 An example of an aliphatic group. In formula (E), R 12 and R 13 They can also bond together to form a ring structure. R 13 and R 14 They can also bond together to form a ring structure.

[0133] Compound E, for example, has two epoxy groups. Specifically, in compound E, R... 13 It may also contain epoxy groups. In this case, the number of epoxy groups in compound E is not particularly limited, for example, it can be 3 or more and less than 10. Compound E may contain other polymerizable functional groups besides epoxy groups, or it may not contain other polymerizable functional groups besides epoxy groups.

[0134] Compound E may contain at least one selected from the group consisting of compound E1 represented by formula (E1), compound E2 represented by formula (E2), and compound E3 represented by formula (E3).

[0135] [Chemical Formula Number 12]

[0136]

[0137] In formula (E1), x is an integer greater than or equal to 1 and less than 12. X can also be an integer greater than or equal to 1 and less than 5. Specific examples of compound E1 include compound e1 represented by the following formula (e1), compound e2 represented by the following formula (e2), and so on.

[0138] [Chemical Formula No. 13]

[0139]

[0140] In formula (E3), y is an integer greater than or equal to 1 and less than 11. y can also be an integer greater than or equal to 1 and less than 5. Specific examples of compound E3 include compound e3 represented by the following formula (e3).

[0141] [Chemical Formula No. 14]

[0142]

[0143] Other examples of compound E include compound E4 represented by formula (E4), compound E5 represented by formula (E5), compound E6 represented by formula (E6), compound E7 represented by formula (E7), compound E8 represented by formula (E8), compound E9 represented by formula (E9), compound E10 represented by formula (E10), compound E11 represented by formula (E11), compound E12 represented by formula (E12), compound E13 represented by formula (E13), compound E14 represented by formula (E14), and compound E15 represented by formula (E15).

[0144] [Chemical Formula Number 15]

[0145]

[0146] In equation (F), R 15 and R 17 Each is an independent hydrogen atom or an aliphatic group. As R 15 and R 17 Aliphatic groups, for example, can be exemplified by R as a compound A. 2 Exemplary aliphatic groups.

[0147] In equation (F), R 16 It is an aliphatic group. As R... 16 Aliphatic groups, for example, can be exemplified by R as a compound B. 4 An example of an aliphatic group. In formula (F), R 15 and R 16 They can also bond together to form a ring structure. R 16 and R17 They can also bond together to form a ring structure.

[0148] Compound F, for example, has an epoxy group and an oxetyl group. In compound F, R... 16 It may also contain at least one group selected from the group consisting of epoxy groups and oxetyl groups. In this case, the number of epoxy groups and the number of oxetyl groups in compound F are not particularly limited, for example, 3 or more and 10 or less. Compound F may contain polymerizable functional groups other than epoxy groups and oxetyl groups, or it may not contain polymerizable functional groups other than epoxy groups and oxetyl groups.

[0149] In equation (G), R 18 and R 20 Each is an independent hydrogen atom or an aliphatic group. As R 18 and R 20 Aliphatic groups, for example, can be exemplified by R as a compound A. 2 Exemplary aliphatic groups.

[0150] In equation (G), R 19 It is an aliphatic group. As R... 19 Aliphatic groups, for example, can be exemplified by R as a compound B. 4 An example of an aliphatic group. In formula (G), R 18 and R 19 They can also bond together to form a ring structure. R 19 and R 20 They can also bond together to form a ring structure.

[0151] Compound G, for example, has two oxocyclic butyl groups. In compound G, R... 19 It may also contain oxetane. In this case, the number of oxetane groups in compound G is not particularly limited, for example, it can be 3 or more and 10 or less. Compound G may contain other polymerizable functional groups besides oxetane, or it may not contain other polymerizable functional groups besides oxetane.

[0152] As a specific example of compound G, we can cite compound G1, which is represented by the following formula (G1).

[0153] [Chemical Formula Number 16]

[0154]

[0155] The aliphatic monomers exemplified can be used alone or in combination of two or more. Furthermore, the aliphatic monomer is any monomer that has a polymerizable functional group and does not contain an aromatic ring, and is not limited to the substances mentioned above. For example, aliphatic monomers can be monomers used to form polyesters, monomers used to form polyamides, or monomers used to form polycarbonates.

[0156] In aliphatic polymers, the content of structural units derived from aliphatic monomers can be, for example, 30% by weight or more, 50% by weight or more, 70% by weight or more, 90% by weight or more, 95% by weight or more, or 99% by weight or more. Aliphatic polymers can essentially consist solely of structural units derived from aliphatic monomers.

[0157] (Polymerization initiator)

[0158] As mentioned above, aliphatic polymers may also contain structural units derived from polymerization initiators. The polymerization initiator can be appropriately selected depending on the type of aliphatic monomer used to synthesize the aliphatic polymer. The polymerization initiator may or may not contain aromatic rings.

[0159] Aliphatic monomers having (meth)acryloyl groups as polymerizable functional groups can, for example, undergo photopolymerization. When using these aliphatic monomers to synthesize aliphatic polymers, known photopolymerization initiators can be used as polymerization initiators. Examples of photopolymerization initiators include carbonyl compounds, phosphine oxide compounds, acylphosphine oxide compounds, azo compounds, azido compounds, organic peroxides, organotin compounds, organoborates, onium salts, alkylarylborates, iron-aromatic complexes, diimidazole derivatives, titanocene compounds, triazine compounds, iodonium salts, diaryliodonium salts, organothiols, and halogenated hydrocarbon derivatives. Photopolymerization initiators can also be carbonyl compounds such as 1-hydroxycyclohexylphenyl ketone. The illustrated photopolymerization initiators can be used alone or in combination of two or more. The weight of the photopolymerization initiator used in the synthesis of aliphatic polymers is not particularly limited. It can be 0.1 parts by mass or more and 20 parts by mass or 0.1 parts by mass or 10 parts by mass or 0.1 parts by mass or 5 parts by mass relative to 100 parts by mass of the aliphatic monomer.

[0160] When synthesizing aliphatic polymers using aliphatic monomers with epoxy groups as polymerizable functional groups, cationic polymerization initiators, anionic polymerization initiators, etc., can be used as polymerization initiators. Amines, thiols, acid anhydrides, carboxylic acids, imidazoles, etc., can also be used as polymerization initiators. The illustrated polymerization initiators can be used alone or in combination of two or more. The weight of the aforementioned polymerization initiators used in the synthesis of aliphatic polymers is not particularly limited, but relative to 100 parts by mass of the aliphatic monomer, it can be, for example, 0.05 parts by mass or more and 10 parts by mass or less, 0.1 parts by mass or more and 5 parts by mass or less, or 0.1 parts by mass or more and 2 parts by mass or less.

[0161] (Curing agent)

[0162] As mentioned above, aliphatic polymers may also contain structural units derived from curing agents. The curing agent can be appropriately selected based on the type of aliphatic monomer used to synthesize the aliphatic polymer. The curing agent may or may not contain aromatic rings.

[0163] When synthesizing aliphatic polymers using aliphatic monomers having epoxy groups as polymerizable functional groups, a compound having functional groups capable of reacting with epoxy groups can be used as a curing agent. In this compound, the number of functional groups capable of reacting with epoxy groups is, for example, one or more, or two or more. Examples of such compounds include acid anhydrides, carboxylic acids, amines, hydrazides, polythiols, and polyols. The curing agent can be an anhydride such as cis-1,2-cyclohexanecarboxylic anhydride. The illustrated curing agents can be used alone or in combination of two or more.

[0164] In aliphatic polymers, the content of structural units from curing agents is not particularly limited, for example, it can be less than 70% by weight, less than 50% by weight, less than 30% by weight, or less than 10% by weight.

[0165] (Other ingredients)

[0166] Aliphatic polymers may also contain structural units from components other than aliphatic monomers, polymerization initiators, and curing agents. Examples of these other components include crosslinking agents that differ from aliphatic monomers. Crosslinking agents may have two or more polymerizable functional groups. Examples of polymerizable functional groups included in crosslinking agents include (meth)acryloyl groups, vinyl groups, and other free-radical polymerizable functional groups. Crosslinking agents containing free-radical polymerizable functional groups are suitable for crosslinking aliphatic monomers containing one (meth)acryloyl group. Crosslinking agents may also have a methylene or phenyl group adjacent to the vinyl group. That is, crosslinking agents may also contain allyl or styryl groups. Crosslinking agents may be used alone or in combination of two or more.

[0167] (Physical properties of aliphatic polymers)

[0168] Aliphatic polymers can also absorb almost no light in the short wavelength range. In particular, aliphatic polymers can also absorb almost no light at a wavelength of 405 nm.

[0169] Recording layer 10, for example, contains an aliphatic polymer as a major component. "Main component" refers to the component most abundantly contained in recording layer 10 by weight. The content of the aliphatic polymer in recording layer 10 is, for example, 50% by weight or more, 70% by weight or more, or 90% by weight or more. There is no particular upper limit to the content of the aliphatic polymer, for example, 98% by weight.

[0170] (Multiphoton absorption compound)

[0171] As described above, the recording layer 10 contains a multiphoton-absorbing compound. In this specification, a multiphoton-absorbing compound refers to a compound exhibiting multiphoton absorption properties. Multiphoton-absorbing compounds are sometimes also referred to as nonlinear absorbing pigments. Typically, a multiphoton-absorbing compound is a two-photon-absorbing compound exhibiting two-photon absorption properties. For example, a multiphoton-absorbing compound exhibits multiphoton absorption properties for light with wavelengths in the short wavelength region. As an example, a multiphoton-absorbing compound exhibits multiphoton absorption properties for light with a wavelength of 405 nm.

[0172] As described above, the multiphoton absorption compound contains at least one element selected from the group consisting of carbon-carbon double bonds, carbon-nitrogen double bonds, and carbon-carbon triple bonds. Furthermore, the multiphoton absorption compound may also contain an aromatic ring. The aromatic ring contained in the multiphoton absorption compound can be an aromatic ring composed of carbon atoms, or a heteroaromatic ring containing heteroatoms such as oxygen atoms, nitrogen atoms, and sulfur atoms. Examples of aromatic rings included in the multiphoton absorption compound include benzene rings, naphthalene rings, anthracene rings, phenanthrene rings, furan rings, pyrrole rings, pyridine rings, and thiophene rings. The multiphoton absorption compound may also contain a benzene ring as an aromatic ring. The number of aromatic rings contained in the multiphoton absorption compound is not particularly limited; for example, it can be 2 or more, 3 or more, or 5 or more. The upper limit for the number of aromatic rings is not particularly limited; for example, it can be 15. In the multiphoton absorption compound, multiple aromatic rings can be connected by a bond selected from the group consisting of carbon-carbon double bonds, carbon-nitrogen double bonds, and carbon-carbon triple bonds. The multiple aromatic rings contained in the multiphoton absorption compound may be identical or different.

[0173] Multiphoton-absorbing compounds are represented, for example, by the following formula (1).

[0174] [Chemical Formula No. 17]

[0175]

[0176] In equation (1), R 21 To R 26 Each is an independent hydrogen atom (where R is...) 21 To R 26 (Excluding cases where all atoms are hydrogen) or a substituent containing at least one of the following groups: carbon-carbon double bond, carbon-nitrogen double bond, and carbon-carbon triple bond. Selected from R 21 To R 26 At least one of the groups can be arylethynyl or arylbutadienyl. Specific examples of compounds represented by formula (1) include compound H represented by formula (H), compound I represented by formula (I), compound J represented by formula (J), etc.

[0177] [Chemical Formula No. 18]

[0178]

[0179]

[0180] The compound represented by formula (1) can also be represented by the following formula (2).

[0181] [Chemical Formula No. 19]

[0182]

[0183] In equation (2), R 27 To R 53 Each atom independently contains at least one atom selected from the group consisting of H, C, N, O, F, P, S, Cl, I, and Br. 27 To R 53 They can also be hydrogen atoms, halogen atoms, alkyl groups, haloalkyl groups, unsaturated hydrocarbon groups, hydroxyl groups, carboxyl groups, alkoxy carbonyl 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.

[0184] Examples of halogen atoms include F, Cl, Br, and I. In this specification, halogen atoms are sometimes referred to as halogen groups.

[0185] The number of carbon atoms in an alkyl group is not particularly limited, for example, it can be 1 or more and 20 or less. The number of carbon atoms in an alkyl group can be 1 or more and 10 or less, or 1 or more and 5 or less. Alkyl groups can be straight-chain, branched, or cyclic. At least one hydrogen atom in an alkyl group can 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, and 6-methoxyhexyl.

[0186] A haloalkyl group is a group in which at least one hydrogen atom of an alkyl group is replaced by a halogen atom. A haloalkyl group can also be a group in which all hydrogen atoms of an alkyl group are replaced by halogen atoms. Examples of alkyl groups include those mentioned above. A specific example of a haloalkyl group is -CF3.

[0187] 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, for example, 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.

[0188] Hydroxyl groups are represented by -OH. Carboxyl groups are represented by -COOH. Alkoxy carbonyl groups are represented by -COOR. a Indicated by -COR. Acyl groups are represented by -COR. b Indicated. Acylamino groups are represented by -CONR. c R d Indicated by . Nitrile group is represented by -CN. Alkyl group is represented by -OR. e Indicated by -OCOR. Acyl groups are represented by... f The thiol group is represented by -SH. The alkylthiol 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 -SO2R. Alkyl sulfonyl groups are represented by -SO2R. i Indicated. Sulfonamides are represented by -SO2NR. j R k Primary amines are represented by -NH2. Secondary amines are represented by -NHR. l Indicated. Tertiary amines are represented by -NR. m R nThe nitro group is represented by -NO2. R a To R n Each is an alkyl group independently of the others. Examples of alkyl groups include those described above. Among them, the R of the amide group... c and R d and R of sulfonamide j and R k They can be hydrogen atoms independently of each other.

[0189] 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 sulfonyl amides are -SO2NH2. Specific examples of tertiary amines are -N(CH3)2.

[0190] The compound represented by formula (2) can be represented by the following formula (3).

[0191] [Chemical Formula Number 20]

[0192]

[0193] In equation (3), multiple Z values ​​are identical. These multiple Z values ​​are respectively related to R in equation (2). 39 R 44 and R 49 Correspondingly. In formula (3), multiple Z can be -C(CH3)3. That is, as a specific example of a compound represented by formula (3), compound K, etc., represented by the following formula (K) can be given.

[0194] [Chemical Formula No. 21]

[0195]

[0196] Furthermore, the compound represented by formula (1) can also be represented by the following formula (4).

[0197] [Chemical Formula No. 22]

[0198]

[0199] In equation (4), R 54 To R 80 It contains at least one atom selected independently from the group consisting of H, C, N, O, F, P, S, Cl, I, and Br. R 54 To R 80 They can also be hydrogen atoms, halogen atoms, alkyl groups, haloalkyl groups, unsaturated hydrocarbon groups, hydroxyl groups, carboxyl groups, alkoxycarbonyl 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, which can be independently represented by R in formula (2). 27 To R 53 The above-mentioned substituents.

[0200] The compound represented by formula (4) can be represented by the following formula (5).

[0201] [Chemical Formula No. 23]

[0202]

[0203] In equation (5), multiple Z values ​​are identical. These multiple Z values ​​are respectively related to R in equation (4). 66 R 71 and R 76 Correspondingly, in formula (5), the plurality of Z can be halogen atoms, alkyl groups, haloalkyl groups, unsaturated hydrocarbon groups, hydroxyl groups, carboxyl groups, alkoxycarbonyl groups, acyl groups, amide groups, acyloxy groups, thiols, alkylthiols, sulfonyl sulfonyl groups, sulfonyl amides, primary amino groups, or secondary amino groups. As a specific example of the plurality of Z, -COO(CH2)3CH3 can be given. That is, as a specific example of a compound represented by formula (5), compounds such as L represented by the following formula (L) can be given.

[0204] [Chemical Formula No. 24]

[0205]

[0206] Recording layer 10 may, for example, contain at least one selected from the group consisting of compounds H to L as a multiphoton absorbing compound. Recording layer 10 may contain at least one selected from the group consisting of compounds H and compounds J to L, or it may contain compound L.

[0207] (Physical properties of multiphoton absorption compounds)

[0208] The two-photon absorption cross-section (BCR) of multiphoton absorbing compounds for light with a wavelength of 405 nm can be greater than 1 GM, greater than 10 GM, greater than 100 GM, greater than 1000 GM, greater than 10000 GM, or greater than 20000 GM. There is no particular upper limit to the BCR of multiphoton absorbing compounds; for example, it can be 150000 GM. The BCR can be determined, 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 irradiation 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 varies depending on the position of the sample. Therefore, in the case of nonlinear absorption by the sample, if the sample is located near the focal point of the laser beam, the amount of transmitted light is attenuated. For a theoretical curve predicted by the intensity of incident light, the thickness of the sample, and the concentration of multiphoton-absorbing compounds in the sample, the two-photon absorption cross-section can be calculated by fitting the change in the amount of transmitted light.

[0209] The molar absorptivity ε0 of a multiphoton-absorbing compound for light with a wavelength of 405 nm can be less than 2000 L / (mol·cm), less than 1000 L / (mol·cm), less than 100 L / (mol·cm), less than 50 L / (mol·cm), or less than 10 L / (mol·cm). There is no particular limitation on the lower limit of the molar absorptivity ε0 of the multiphoton-absorbing compound; for example, it can be 0.01 L / (mol·cm). The molar absorptivity ε0 can be measured, for example, by the method specified in Japanese Industrial Standard (JIS) K0115:2004. In the measurement of the molar absorptivity ε0, a light source that irradiates light with a photon density that produces almost no multiphoton absorption caused by the multiphoton-absorbing compound is used.

[0210] When a multiphoton-absorbing compound undergoes two-photon absorption, it absorbs approximately twice the energy of the light irradiated onto it. The wavelength of light possessing approximately twice the energy of light with a wavelength of 405 nm is, for example, 200 nm. That is, when a multiphoton-absorbing compound is irradiated with light having a wavelength around 200 nm, single-photon absorption can also occur within the compound. Furthermore, in the multiphoton-absorbing compound, single-photon absorption can also occur for light with wavelengths near the region where two-photon absorption occurs.

[0211] The content of the multiphoton-absorbing compound in the recording layer 10 is, for example, less than 50% by weight, which can be less than 30% by weight or less, or less than 10% by weight. There is no particular limitation on the lower limit of the content of the multiphoton-absorbing compound, for example, it can be 2% by weight.

[0212] In the recording layer 10, the combined content of the aliphatic polymer and the multiphoton-absorbing compound is, for example, 80% by weight or more, 90% by weight or more, 95% by weight or more, 97% by weight or more, or 99% by weight or more. The recording layer 10 is, for example, substantially composed only of the aliphatic polymer and the multiphoton-absorbing compound. "Substantially composed of..." means excluding other components that alter the essential characteristics of the material mentioned. However, in addition to the aliphatic polymer and the multiphoton-absorbing compound, the recording layer 10 may also contain impurities.

[0213] (Method for creating a recording layer)

[0214] The recording layer 10 can be fabricated, for example, by the following method. First, a coating solution comprising an aliphatic monomer and a multiphoton-absorbing compound is prepared. This coating solution corresponds to the composition used to fabricate the recording layer 10 of the recording medium 100. That is, the composition used to fabricate the recording layer 10 of the recording medium 100 has an aliphatic monomer and a multiphoton-absorbing compound comprising at least one selected from the group consisting of carbon-carbon double bonds, carbon-nitrogen double bonds, and carbon-carbon triple bonds.

[0215] The coating liquid may also contain polymerization initiators, curing agents, curing accelerators, crosslinking agents, etc., as needed. The aforementioned polymer initiators, curing agents, and crosslinking agents can be used. For example, tertiary amines such as 2,4,6-tris(dimethylaminomethyl)phenol can be used as curing accelerators. Tertiary amines are suitable for promoting the curing reaction of aliphatic monomers containing epoxy groups.

[0216] Next, the coating liquid is applied to the substrate to form a coated film. A glass substrate can be used as an example of a substrate. Alternatively, the coating liquid can be applied directly to the dielectric layer 20 without being applied to the substrate. As an example, the coated film can also be formed by filling the space between two substrates with the coating liquid. Next, the coated film is given energy such as heat or light. If the aliphatic monomers included in the coated film have epoxy groups, heat energy can also be given to the coated film. For example, heat energy can be given to the coated film by heating it at a temperature of 70°C or higher for more than 1 hour. If the aliphatic monomers included in the coated film include (meth)acryloyl groups, vinyl groups, etc., light energy can also be given to the coated film. For example, light energy can be given by heating the coated film at a temperature of 20 mW / cm². 2The power density is applied to the coating film by irradiating it with light of a wavelength of 365 nm. By applying energy to the coating film, polymerization or curing reactions of the aliphatic monomers contained in the coating film are carried out. This allows the fabrication of the recording layer 10.

[0217] Furthermore, when fabricating the recording layer 10, if an aliphatic monomer containing photopolymerizable functional groups such as (meth)acryloyl or vinyl groups is photopolymerized, the aliphatic monomer may sometimes react with a multiphoton-absorbing compound having carbon-carbon triple bonds. Due to the reaction between the multiphoton-absorbing compound and the aliphatic monomer, the multiphoton-absorbing compound may sometimes slightly deteriorate. Therefore, when using an aliphatic monomer containing photopolymerizable functional groups to fabricate an aliphatic polymer, the coating film may not contain a multiphoton-absorbing compound having carbon-carbon triple bonds. That is, even when the recording layer 10 contains an aliphatic polymer having structural units derived from an aliphatic monomer containing photopolymerizable functional groups, the recording layer 10 may not contain a multiphoton-absorbing compound having carbon-carbon triple bonds.

[0218] (The physical properties of the recording layer)

[0219] The recording layer 10 is, for example, a thin film with a thickness of more than 1 nm and less than 100 μm. However, the thickness of the recording layer 10 may also exceed 100 μm.

[0220] As described above, regarding the recording layer 10, when the thickness of the recording layer 10 is 100 μm, the transmittance of light with a wavelength of 405 nm in the thickness direction is 80% or more. This transmittance can be 84% or more, 90% or more, 95% or more, or 99% or more.

[0221] The aforementioned transmittance can be measured using the recording layer 10 itself as the test sample, according to the method specified in JIS K 0115:2004. Specifically, firstly, light with a wavelength of 405 nm is irradiated onto the recording layer 10. Irradiation is performed in such a way that the light propagates in the thickness direction of the recording layer 10. A light source that irradiates light with a photon density that produces almost no multiphoton absorption caused by the multiphoton absorption compound is used as the light source. Next, the absorbance A of the recording layer 10 at a wavelength of 405 nm is read from the light transmitted through the recording layer 10. Based on the absorbance A, the transmittance T of the recording layer 10 at a wavelength of 405 nm can be calculated using the following formula (I).

[0222] Transmittance T = 10 (-A) (I)

[0223] Next, the obtained transmittance T is converted to a value when the thickness of the recording layer 10 is 100 μm. In detail, the transmittance when the thickness of the recording layer 10 is 100 μm can be calculated based on the transmittance T and the actual thickness t (μm) of the recording layer 10 using the following formula (II).

[0224] Transmittance per 100μm thickness = T (100 / t) (II)

[0225] In the recording layer 10 of this embodiment, almost no interaction occurs between the aliphatic polymer and the multiphoton-absorbing compound. Therefore, the electronic state of the multiphoton-absorbing compound remains almost unchanged in the recording layer 10. Furthermore, almost no deterioration of the multiphoton-absorbing compound occurs due to polymerization or curing reactions of the aliphatic monomers. Therefore, the increase in linear absorption at the excitation wavelength of multiphoton absorption is suppressed in the recording layer 10. In particular, the increase in single-photon absorption of light with wavelengths having short wavelength regions is suppressed in the recording layer 10.

[0226] The suppression of increased single-photon absorption in the recording layer 10 can be evaluated by the molar absorptivity ε of the multiphoton-absorbing compound contained in the recording layer 10 for light with a wavelength of 405 nm. The molar absorptivity ε can be determined by the following method: First, a test sample having the same composition and shape as the recording layer 10 is prepared, except that the concentration of the multiphoton-absorbing compound is 0.1 mmol / L or more and 10 mmol / L or less, and the thickness is 0.5 mm or more and 1 mm or less. Alternatively, if the concentration of the multiphoton-absorbing compound in the recording layer 10 is 0.1 mmol / L or more and 10 mmol / L or less, and the thickness of the recording layer 10 is 0.5 mm or more and 1 mm or less, the recording layer 10 itself can also be used as the test sample. Next, light with a wavelength of 405 nm is irradiated onto the test sample. The irradiation is performed such that the light travels along the thickness direction of the test sample. As the light source, a light source that irradiates light with a photon density that produces almost no multiphoton absorption caused by the multiphoton-absorbing compound is used. Next, the absorbance A1 of the test sample at a wavelength of 405 nm is read from the light transmitted through the test sample. Based on the absorbance A1, the concentration C (mol / L) of the multiphoton-absorbing compound in the test sample, and the thickness t1 (cm) of the test sample, the molar absorptivity (L / (mol·cm)) is calculated using the following equation (III). The calculated molar absorptivity can be regarded as the molar absorptivity ε of the multiphoton-absorbing compound contained in the recording layer 10 at a wavelength of 405 nm.

[0227] Molar absorptivity = Absorbance A1 / (Concentration C × Thickness t1) (III)

[0228] As an example, when the recording layer 10 contains compound H as a multiphoton absorbing compound, the molar absorptivity ε of compound H can be less than 50 L / (mol·cm), less than 40 L / (mol·cm), or less than 30 L / (mol·cm). There is no particular limitation on the lower limit of the molar absorptivity ε of compound H; for example, it can be 1 L / (mol·cm).

[0229] When the recording layer 10 contains compound I as a multiphoton absorbing compound, the molar absorptivity ε of compound I can be less than 200 L / (mol·cm), less than 100 L / (mol·cm), or less than 50 L / (mol·cm). There is no particular limitation on the lower limit of the molar absorptivity ε of compound I; for example, it can be 10 L / (mol·cm).

[0230] When the recording layer 10 contains compound J as a multiphoton absorbing compound, the molar absorptivity ε of compound J can be less than 1000 L / (mol·cm), less than 500 L / (mol·cm), or less than 200 L / (mol·cm). There is no particular limitation on the lower limit of the molar absorptivity ε of compound J; for example, it can be 100 L / (mol·cm).

[0231] When the recording layer 10 contains compound K as a multiphoton absorbing compound, the molar absorptivity ε of compound K can be less than 2000 L / (mol·cm), less than 1700 L / (mol·cm), or less than 1600 L / (mol·cm). There is no particular limitation on the lower limit of the molar absorptivity ε of compound K, for example, it can be 1000 L / (mol·cm).

[0232] When the recording layer 10 contains compound L as a multiphoton absorbing compound, the molar absorptivity ε of compound L can be less than 200 L / (mol·cm), less than 100 L / (mol·cm), or less than 60 L / (mol·cm). There is no particular limitation on the lower limit of the molar absorptivity ε of compound L; for example, it can be 15 L / (mol·cm).

[0233] [Dielectric layer]

[0234] The dielectric layer 20 appropriately adjusts the reflectivity and absorptivity for light used for recording or reading information. Examples of materials for the dielectric layer 20 include oxides such as ZrO2, HfO2, ZnO, SiO2, SnO2, Cr2O3, TiO2, In2O3, Ga2O3, Y2O3, CeO2, and DyO2, sulfides such as ZnS and CdS, and mixtures thereof. Examples of mixtures include ZrO2-SiO2, ZrO2-SiO2-Cr2O3, ZrO2-SiO2-Ga2O3, HfO2-SiO2-Cr2O3, ZrO2-SiO2-In2O3, and ZnS-SiO2. The dielectric layer 20 can also be an organic material. Examples of organic materials include thermoplastic resins, thermosetting resins, UV-curable resins, electron beam-curable resins, and adhesives. Examples of UV-curable resins include mixtures of polyurethane resins, acrylic resins, polyurethane acrylate resins, epoxy resins, fluorinated polymers such as perfluoropolyethers, siloxane polymers such as polydimethylsiloxane, and photopolymerization initiators.

[0235] The thickness of the dielectric layer 20 is not particularly limited; for example, it can be 5 nm or more and 100 μm or less, or it can be 5 nm or more and 80 nm or less.

[0236] [Other layers]

[0237] The recording medium 100 also includes other layers besides the recording layer 10 and the dielectric layer 20. Examples of these other layers include an adhesive layer and a reflective layer. For example, an adhesive layer is disposed between the recording layer 10 and the dielectric layer 20. The adhesive layer allows for easy bonding of the recording layer 10 and the dielectric layer 20. The reflective layer is, for example, a thin film of an Ag alloy containing Ag as its main component. The reflective layer is disposed, for example, between the recording layer 10 and the dielectric layer 20 or between the recording layer 10 and the adhesive layer.

[0238] [How to use recording media]

[0239] When recording information into the recording medium 100 of this embodiment, light with a wavelength having a short wavelength region is used, for example. As an example, when recording information into the recording medium 100, light with a wavelength of 390 nm or more and 420 nm or less is used. The light used in the recording medium 100 has, for example, a high photon density near its focal point. The power density near the focal point of the light used in the recording medium 100 is, for example, 0.1 W / cm². 2 Above and 1.0×10 20 W / cm 2 Below. The power density near the focal point of this light can be 1.0 W / cm². 2 The above can also be 1.0 × 102 W / cm 2 The above can also be 1.0×10 5 W / cm 2 The above applies. As a light source used in the recording medium 100, for example, a femtosecond laser such as a Ti:sapphire laser, or a pulsed laser with a pulse width of picosecond to nanosecond, such as a semiconductor laser, can be used.

[0240] Next, the method for recording information using the recording medium 100 will be described. Figure 2A This is a flowchart related to the method of recording information using the recording medium 100. 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 width of picosecond to nanosecond, 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 irradiated onto the recording layer 10 in the recording medium 100. Specifically, the light from the light source is focused using a lens or the like and irradiated onto the recording area in the recording medium 100. 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 recording area refers to a point existing in the recording layer 10 that can record information when illuminated by light.

[0241] In the aforementioned recording area irradiated with light, physical or chemical changes occur, thereby altering the optical properties of the recording area. 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, the refractive index of light in the recording area, the intensity of fluorescence emitted from the recording area, and the wavelength of the fluorescence light change. As an example, the intensity of light reflected from the recording area or the intensity of fluorescence emitted from the recording area decreases. As a result, information can be recorded in the recording layer 10, specifically in the recording area (step S13).

[0242] Next, the method for reading information using the recording medium 100 will be explained. Figure 2BThis is a flowchart related to the method for reading information using the recording medium 100. First, in step S21, light is irradiated onto the recording layer 10 of the recording medium 100. Specifically, light is irradiated onto the recording area of ​​the recording medium 100. The light used in step S21 may be the same as or different from the light used to record information on the recording medium 100. Next, in step S22, the optical characteristics of the recording layer 10 are measured. Specifically, the optical characteristics of the recording area are measured. In step S22, for example, as optical characteristics of the recording area, the intensity of light reflected from the recording area or the intensity of fluorescent light emitted from the recording area are measured. In step S22, as optical characteristics 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 wavelength of fluorescent light emitted from the recording area, etc., may also be measured. Next, in step S23, information is read from the recording layer 10, specifically from the recording area.

[0243] In information readout methods, the recording area containing information can be searched using the following method. First, light is irradiated onto a specific area of ​​the recording medium. This light may be the same as or different from the light used to record information on the recording medium. Next, the optical characteristics of the irradiated area 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 irradiated area 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. Furthermore, the method for determining whether an irradiated area is a recording area is not limited to the above method. For example, if the intensity of light reflected from the area exceeds a certain value, the area may be determined to be a recording area. Additionally, if the intensity of light reflected from the area is below a certain value, the area may 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 for the search for recording areas.

[0244] The recording and reading methods of information using the recording medium 100 can be performed, for example, by a known recording apparatus. The recording apparatus may include, for example, a light source that illuminates a recording area in the recording medium 100; a measuring device that measures the optical characteristics of the recording area; and a controller that controls the light source and the measuring device.

[0245] Example

[0246] The present disclosure will now be described in more detail through examples. Furthermore, the following examples are merely illustrative, and the present disclosure is not limited to these examples.

[0247] <Multiphoton Absorption Compounds>

[0248] First, compounds H to L were prepared as multiphoton absorption compounds. Commercially available products (manufactured by Sigma-Aldrich) were used as compounds H and I. Compounds J to L were synthesized using the following method.

[0249] [Synthesis of Compound J]

[0250] Compound J was synthesized according to the methods described in K. Kondo et al., J. Chem. Soc., Chem. Commun. 1995, pp. 55-56, and W. Tao et al., J. Org. Chem. 1990, Vol. 55, pp. 63-69.

[0251] [Synthesis of compound K]

[0252] First, 1,3,5-tris(4-formylphenyl)benzene (manufactured by Tokyo Chemical Industry Co., Ltd.) and 4-tert-butylaniline (manufactured by Tokyo Chemical Industry Co., Ltd.) were dissolved in ethanol. The resulting solution was heated under reflux with stirring for 12 hours. The solid was filtered from the reaction solution and washed with ethanol. The solid was dried under vacuum to obtain compound K. Compound K was then... 1 H-NMR identification. Figure 3 It represents compound K. 1 The 1H-NMR spectrum curve of compound K. 1 The H-NMR spectrum is as follows.

[0253] 1 ¹H-NMR (600MHz, chloroform-D) δ 1.36 (s, 27H), 7.23 (d, J = 9.0Hz, 6H), 7.44 (d, J = 8.4Hz, 6H), 7.83 (d, J = 8.4Hz, 6H), 7.91 (s, 3H), 8.04 (d, J = 8.4Hz, 6H), 8.56 (s, 3H).

[0254] [Synthesis of Compound L]

[0255] 1,3,5-Tris[4'-(ethynyl)phenyl]benzene (manufactured by BLD PHARMATECH) and methyl 4-iodobenzoate (manufactured by Tokyo Chemical Industry Co., Ltd.) were dissolved in triethylamine. A catalyst amount of triphenylphosphine (manufactured by Tokyo Chemical Industry Co., Ltd.), bis(triphenylphosphine)palladium(II) chloride (manufactured by Tokyo Chemical Industry Co., Ltd.), and copper iodide(I) (manufactured by Fujifilm and Koko Pure Chemical Co., Ltd.) was further added to the resulting solution. The solution was then stirred at room temperature for 16 hours. Hydrochloric acid was added to the resulting reaction solution for neutralization. The reaction solution was then extracted with ethyl acetate. Magnesium sulfate was added to the resulting extract to dehydrate it. Magnesium sulfate was then filtered off the extract. The resulting filtrate was concentrated using a rotary evaporator. The concentrate was purified by silica gel column chromatography. The purified product was then dissolved in a mixture of tetrahydrofuran and methanol (v / v = 1:1). An aqueous solution of sodium hydroxide was added to the resulting solution, and the mixture was heated under reflux with stirring overnight. After the reaction in solution is complete, dilute hydrochloric acid is added to the solution. This acidifies the solution, causing a solid to precipitate. The precursor of compound L is obtained by washing the solid with pure water.

[0256] Next, a suspension was prepared by adding butanol solvent to the precursor of compound L. Then, thionyl chloride (manufactured by Fujifilm and Kosei Chemicals) was added to the suspension, and the mixture was heated under reflux overnight with stirring. A white solid was filtered from the resulting reaction solution and washed with methanol. The solid was extracted with chloroform. Magnesium sulfate was added to the extract to dehydrate it. Magnesium sulfate was then filtered from the extract. The filtrate was concentrated using a rotary evaporator. The concentrate was purified by silica gel column chromatography to obtain compound L. Compound L was then purified by... 1 H-NMR identification. Figure 4 It represents compound L. 1 The 1H-NMR spectrum curve of compound L. 1 The H-NMR spectrum is as follows.

[0257] 1 H-NMR (600MHz, chloroform-D) δ8.05(d,J=9.0Hz,6H),7.83(s,3H),7.73(d,J=8.3Hz,6H),7.68(d,J=8.3Hz,6H),7.62( d,J=8.3Hz,6H),4.35(t,J=6.5Hz,6H),1.75-1.80(m,6H),1.50(td,J=14.8,7.3Hz,6H),1.00(t,J=7.6Hz,9H).

[0258] (Example A1)

[0259] First, the following materials are mixed by stirring to produce a uniformly mixed resin precursor (i).

[0260] Aliphatic monomer: 1,7-octadiene diester (compound e1, manufactured by Tokyo Chemical Industry Co., Ltd.) 5000 parts by weight

[0261] Curing agent: 5420 parts by weight of cis-1,2-cyclohexanecarboxylic anhydride (manufactured by Tokyo Chemical Industry Co., Ltd.)

[0262] Curing accelerator: 50 parts by weight of 2,4,6-tris(dimethylaminomethyl)phenol (manufactured by Kanto Chemical Co., Ltd.)

[0263] Next, the following materials were mixed by stirring to obtain a uniformly mixed coating solution. The concentration of the multiphoton absorbing compound in the coating solution was 10.0 mmol / L.

[0264] Resin precursor: Resin precursor (i) 5 mL

[0265] Multiphoton absorption compound: Compound H1 0.3 mg

[0266] Next, two glass substrates were prepared. These glass substrates were 20 mm long, 20 mm wide, and 1 mm thick. Then, spacers were used to separate the two glass substrates and place them opposite each other. A 1 mm thick glass substrate was used as the spacer. Next, the above-described mixture was filled into the space formed between the two glass substrates to create a coating film. Then, the coating film was heated at 90°C for 7 hours. This caused the aliphatic monomer and curing agent to react, resulting in the recording layer of Example A1.

[0267] (Example A2)

[0268] Except that resin precursor (ii) is used instead of resin precursor (i), the recording layer of Example A2 is obtained by the same method as in Example A1. Resin precursor (ii) is prepared by uniformly mixing the following materials by stirring.

[0269] Aliphatic monomer: 1,2-cyclohexanedicarboxylic acid diglycidyl ester (compound E2, manufactured by Tokyo Chemical Industry Co., Ltd.) 8000 parts by weight

[0270] Curing agent: 4330 parts by weight of cis-1,2-cyclohexanecarboxylic anhydride

[0271] Curing accelerator: 80 parts by weight of 2,4,6-tris(dimethylaminomethyl)phenol

[0272] (Example A3)

[0273] Except that 10 mL of resin precursor (iii) was used instead of resin precursor (i) and the coating film was heated at 90°C for 18 hours, the recording layer of Example A3 was obtained by the same method as in Example A1. Resin precursor (iii) was prepared by uniformly mixing the following materials by stirring. Furthermore, the number average molecular weight of polyethylene glycol diglycidyl ether was 500. The concentration of the multiphoton absorbing compound in the coating solution was 5.0 mmol / L.

[0274] Aliphatic monomer: 10,000 parts by weight of polyethylene glycol diglycidyl ether (compound E3, manufactured by Sigma-Aldrich).

[0275] Curing agent: 3080 parts by weight of cis-1,2-cyclohexanecarboxylic anhydride

[0276] Curing accelerator: 100 parts by weight of 2,4,6-tris(dimethylaminomethyl)phenol

[0277] (Example A4)

[0278] Except that 10 mL of resin precursor (iv) was used instead of resin precursor (i) and the aliphatic monomer polymerization reaction was carried out by irradiating the coating film with light from a light-emitting diode (LED) without heating the coating film, the recording layer of Example A4 was obtained by the same method as in Example A1. The wavelength of the light irradiated onto the coating film was 365 nm. The power density of the light irradiated onto the coating film was 50 mW / cm². 2 The resin precursor (iv) is prepared by uniformly mixing the following materials through stirring.

[0279] Aliphatic monomer: Dodecyl acrylate (compound a1, manufactured by Tokyo Chemical Industry Co., Ltd.) 9000 parts by weight

[0280] Aliphatic monomer: 1,6-hexanediol diacrylate (compound B3, manufactured by Tokyo Chemical Industry Co., Ltd.) 900 parts by weight

[0281] Polymerization initiator: 90 parts by weight of 1-hydroxycyclohexylphenyl ketone (manufactured by Tokyo Chemical Industry Co., Ltd.) (Example A5)

[0282] The recording layer of Example A5 was obtained by the same method as in Example A4, except that 25 mL of resin precursor (v) was used instead of resin precursor (iv). Resin precursor (v) was prepared by uniformly mixing the following materials with stirring. The concentration of the multiphoton absorbing compound in the coating solution was 2.0 mmol / L.

[0283] Aliphatic monomer: Octyl acrylate (compound a2, manufactured by Tokyo Chemical Industry Co., Ltd.) 9000 parts by weight

[0284] Aliphatic monomer: 1,6-hexanediol diacrylate (compound B3) 900 parts by weight

[0285] Polymerization initiator: 90 parts by weight of 1-hydroxycyclohexylphenyl ketone

[0286] (Example A6)

[0287] The recording layer of Example A6 was obtained by the same method as in Example A4, except that 25 mL of resin precursor (vi) was used instead of resin precursor (iv). The resin precursor (vi) was prepared by uniformly mixing the following materials by stirring.

[0288] Aliphatic monomer: cyclohexyl acrylate (compound A2, manufactured by Tokyo Chemical Industry Co., Ltd.) 9000 parts by weight

[0289] Aliphatic monomer: 1,6-hexanediol diacrylate (compound B3) 900 parts by weight

[0290] Polymerization initiator: 90 parts by weight of 1-hydroxycyclohexylphenyl ketone

[0291] (Example A7)

[0292] The recording layer of Example A7 was obtained by the same method as in Example A4, except that 10 mL of resin precursor (vii) was used instead of resin precursor (iv). Resin precursor (vii) was prepared by uniformly mixing the following materials by stirring.

[0293] Aliphatic monomer: Tetraethylene glycol dimethacrylate (compound b1, manufactured by Sigma-Aldrich) 9750 parts by weight

[0294] Polymerization initiator: 250 parts by weight of 1-hydroxycyclohexylphenyl ketone

[0295] (Comparative Example A1)

[0296] The recording layer of Comparative Example A1 was obtained by the same method as in Example A4, except that 10 mL of resin precursor (viii) was used instead of resin precursor (iv). The resin precursor (viii) was prepared by uniformly mixing the following materials by stirring. The recording layer of Comparative Example A1 contained an aromatic polymer with an aromatic ring content significantly exceeding 10% by weight.

[0297] Aromatic monomer: 2-phenoxyethyl acrylate (manufactured by Tokyo Chemical Industry Co., Ltd.) 9000 parts by weight

[0298] Aliphatic monomer: 1,6-hexanediol diacrylate (compound B3) 900 parts by weight

[0299] Polymerization initiator: 90 parts by weight of 1-hydroxycyclohexylphenyl ketone

[0300] (Comparative Example A2)

[0301] The recording layer of Comparative Example A2 was obtained by the same method as in Example A4, except that 10 mL of resin precursor (ix) was used instead of resin precursor (iv). The resin precursor (ix) was prepared by uniformly mixing the following materials by stirring. The recording layer of Comparative Example A2 contained an aromatic polymer with an aromatic ring content significantly exceeding 10% by weight.

[0302] Aromatic monomer: Benzyl acrylate (manufactured by Tokyo Chemical Industry Co., Ltd.) 9000 parts by weight

[0303] Aliphatic monomer: 1,6-hexanediol diacrylate (compound B3) 900 parts by weight

[0304] Polymerization initiator: 90 parts by weight of 1-hydroxycyclohexylphenyl ketone

[0305] (Comparative Example A3)

[0306] Except that resin precursor (x) was used instead of resin precursor (i) and the coating film was heated at 90°C for 10 hours, the recording layer of Comparative Example A3 was obtained by the same method as in Example A1. Resin precursor (x) was prepared by uniformly mixing the following materials through stirring. The recording layer of Comparative Example A3 contained an aromatic polymer with an aromatic ring content significantly exceeding 10% by weight.

[0307] Aromatic monomer: 9900 parts by weight of 1,6-bis(2,3-epoxypropoxy)naphthalene (HP-4032D manufactured by DIC).

[0308] Curing accelerator: 100 parts by weight of 2,4,6-tris(dimethylaminomethyl)phenol

[0309] [Determination of molar absorptivity ε]

[0310] For the multiphoton-absorbing compounds contained in the recording layers of Examples A1 to A7 and Comparative Examples A1 to A3, the molar absorptivity ε for light with a wavelength of 405 nm was determined using the method described above. The results are shown in Table 1.

[0311] [Measurement of transmittance]

[0312] For the recording layers of Examples A1 to A7, the transmittance of light with a wavelength of 405 nm in the thickness direction when the thickness is 100 μm was determined using the method described above. The results are shown in Table 1.

[0313] Table 1

[0314]

[0315] (Example B1)

[0316] Except for the use of 19.5 mg of compound K as the multiphoton absorbing compound and 5 mL of resin precursor (i), the recording layer of Example B1 was obtained by the same method as in Example A1. The concentration of the multiphoton absorbing compound in the coating solution was 5.0 mmol / L.

[0317] (Example B2)

[0318] Except for the use of 19.5 mg of compound K as a multiphoton absorption compound and 5 mL of resin precursor (ii), the recording layer of Example B2 was obtained by the same method as in Example A2.

[0319] (Example B3)

[0320] Except for the use of 1.2 mg of compound K as the multiphoton absorbing compound and 10 mL of resin precursor (iv), the recording layer of Example B3 was obtained by the same method as in Example A4. The concentration of the multiphoton absorbing compound in the coating solution was 0.15 mmol / L.

[0321] (Example B4)

[0322] Except for using 3.1 mg of compound K as the multiphoton absorbing compound and 25 mL of resin precursor (v), the recording layer of Example B4 was obtained by the same method as in Example A5. The concentration of the multiphoton absorbing compound in the coating solution was 0.16 mmol / L.

[0323] (Example B5)

[0324] Except for the use of 3.1 mg of compound K as a multiphoton absorption compound and 25 mL of resin precursor (vi), the recording layer of Example B5 was obtained by the same method as in Example A6.

[0325] (Example B6)

[0326] Except for the use of 1.2 mg of compound K as a multiphoton absorption compound and the use of 10 mL of resin precursor (vii), the recording layer of Example B6 was obtained by the same method as in Example A7.

[0327] (Comparative Example B1)

[0328] Except for using 1.2 mg of compound K as a multiphoton absorption compound and 10 mL of resin precursor (viii), the recording layer of Comparative Example B1 was obtained by the same method as Comparative Example A1.

[0329] (Comparative Example B2)

[0330] Except that 1.2 mg of compound K was used as the multiphoton absorption compound and 10 mL of resin precursor (ix) was used, the recording layer of Comparative Example B2 was obtained by the same method as Comparative Example A2.

[0331] (Comparative Example B3)

[0332] Except for using 19.5 mg of compound K as a multiphoton absorption compound and 5 mL of resin precursor (x), the recording layer of Comparative Example B3 was obtained by the same method as Comparative Example A3.

[0333] [Determination of molar absorptivity ε]

[0334] For the multiphoton-absorbing compounds contained in the recording layers of Examples B1 to B6 and Comparative Examples B1 to B3, the molar absorptivity ε for light with a wavelength of 405 nm was measured using the method described above. The results are shown in Table 2.

[0335] [Measurement of transmittance]

[0336] For the recording layers of Examples B1 to B6, the transmittance of light with a wavelength of 405 nm in the thickness direction when the thickness is 100 μm was determined using the method described above. The results are shown in Table 2.

[0337] Table 2

[0338]

[0339] (Example C1)

[0340] Except for using 6.9 mg of compound I as the multiphoton absorption compound and 5 mL of resin precursor (i), the recording layer of Example C1 was obtained by the same method as in Example A1. The concentration of the multiphoton absorption compound in the coating solution was 5.0 mmol / L.

[0341] (Example C2)

[0342] Except for the use of 13.9 mg of compound I as the multiphoton absorbing compound and 5 mL of resin precursor (ii), the recording layer of Example C2 was obtained by the same method as in Example A2. The concentration of the multiphoton absorbing compound in the coating solution was 10.0 mmol / L.

[0343] (Example C3)

[0344] Except for the use of 13.9 mg of Compound I as the multiphoton absorbing compound and 10 mL of resin precursor (iii), the recording layer of Example C3 was obtained by the same method as in Example A3. The concentration of the multiphoton absorbing compound in the coating solution was 5.0 mmol / L.

[0345] (Comparative Example C1)

[0346] Except for using 6.9 mg of compound I as a multiphoton absorption compound and 5 mL of resin precursor (viii), the recording layer of comparative example C1 was obtained by the same method as comparative example A1.

[0347] (Comparative Example C2)

[0348] Except that 6.9 mg of compound I was used as the multiphoton absorption compound and 5 mL of resin precursor (ix) was used, the recording layer of comparative example C2 was obtained by the same method as comparative example A2.

[0349] (Comparative Example C3)

[0350] Except for using 13.9 mg of compound I as a multiphoton absorption compound and 5 mL of resin precursor (x), the recording layer of comparative example C3 was obtained by the same method as comparative example A3.

[0351] [Determination of molar absorptivity ε]

[0352] For the multiphoton-absorbing compounds contained in the recording layers of Examples C1 to C3 and Comparative Examples C1 to C3, the molar absorptivity ε for light with a wavelength of 405 nm was measured using the method described above. The results are shown in Table 3.

[0353] [Measurement of transmittance]

[0354] For the recording layers of Examples C1 to C3, the transmittance of light with a wavelength of 405 nm in the thickness direction when the thickness is 100 μm was determined using the method described above. The results are shown in Table 3.

[0355] Table 3

[0356]

[0357] (Example D1)

[0358] Except for using 7.2 mg of compound L as the multiphoton absorbing compound and 5 mL of resin precursor (i), the recording layer of Example D1 was obtained by the same method as in Example A1. The concentration of the multiphoton absorbing compound in the coating solution was 1.6 mmol / L.

[0359] (Example D2)

[0360] Except for using 7.2 mg of compound L as a multiphoton absorption compound and 5 mL of resin precursor (ii), the recording layer of Example D2 was obtained by the same method as in Example A2.

[0361] (Example D3)

[0362] Except that 7.2 mg of compound L was used as the multiphoton absorption compound, and 5 mL of resin precursor (xi) was used instead of resin precursor (i), the recording layer of Example D3 was obtained by the same method as in Example A1. The resin precursor (xi) was prepared by uniformly mixing the following materials by stirring.

[0363] Aliphatic monomer: 1,5-hexadiene diester (compound e2, manufactured by Tokyo Chemical Industry Co., Ltd.) 5000 parts by weight

[0364] Curing agent: 6750 parts by weight of cis-1,2-cyclohexanecarboxylic anhydride

[0365] Curing accelerator: 50 parts by weight of 2,4,6-tris(dimethylaminomethyl)phenol

[0366] (Comparative Example D1)

[0367] Except that 9.0 mg of compound L was used as the multiphoton absorption compound and 5 mL of resin precursor (viii), the recording layer of Comparative Example D1 was obtained by the same method as Comparative Example A1. The concentration of the multiphoton absorption compound in the coating solution was 2.0 mmol / L.

[0368] (Comparative Example D2)

[0369] Except that 4.5 mg of compound L was used as the multiphoton absorption compound and 5 mL of resin precursor (ix) was used, the recording layer of Comparative Example D2 was obtained by the same method as Comparative Example A2. The concentration of the multiphoton absorption compound in the coating solution was 1.0 mmol / L.

[0370] (Comparative Example D3)

[0371] Except that 36.0 mg of compound L was used as the multiphoton absorption compound and 5 mL of resin precursor (x) was used, the recording layer of Comparative Example C3 was obtained by the same method as Comparative Example A3. The concentration of the multiphoton absorption compound in the coating solution was 7.9 mmol / L.

[0372] [Determination of molar absorptivity ε]

[0373] For the multiphoton-absorbing compounds contained in the recording layers of Examples D1 to D3 and Comparative Examples D1 to D3, the molar absorptivity ε for light with a wavelength of 405 nm was measured using the method described above. The results are shown in Table 4.

[0374] [Measurement of transmittance]

[0375] For the recording layers of Examples D1 to D3, the transmittance of light with a wavelength of 405 nm in the thickness direction when the thickness is 100 μm was determined using the method described above. The results are shown in Table 4.

[0376] Table 4

[0377]

[0378] (Example E1)

[0379] Except for using 4.7 mg of compound J as the multiphoton absorption compound and 5 mL of resin precursor (i), the recording layer of Example E1 was obtained by the same method as in Example A1. The concentration of the multiphoton absorption compound in the coating solution was 2.0 mmol / L.

[0380] (Comparative Example E1)

[0381] Except for using 4.7 mg of compound J as a multiphoton absorption compound and 5 mL of resin precursor (x), the recording layer of comparative example E1 was obtained by the same method as comparative example A3.

[0382] [Determination of molar absorptivity ε]

[0383] For the multiphoton-absorbing compounds contained in the recording layers of Example E1 and Comparative Example E1, the molar absorptivity ε for light with a wavelength of 405 nm was measured using the method described above. The results are shown in Table 5.

[0384] [Measurement of transmittance]

[0385] For the recording layer of Example E1, the transmittance of light with a wavelength of 405 nm in the thickness direction when the thickness is 100 μm was determined using the method described above. The results are shown in Table 5.

[0386] Table 5

[0387]

[0388] As shown in Tables 1 to 5, if the types of multiphoton absorbing compounds are the same, the molar absorptivity of the multiphoton absorbing compounds for light with a wavelength of 405 nm is smaller in the recording layer of the embodiment containing aliphatic polymers compared to the recording layer of the comparative example containing aromatic polymers. Based on this result, it can be said that in the recording layer containing both aliphatic polymers and multiphoton absorbing compounds, the increase in single-photon absorption of light with wavelengths in the short wavelength region is suppressed.

[0389] In the recording layer of the comparative example containing an aromatic polymer, an interaction occurs between the aromatic polymer and the multiphoton-absorbing compound, thereby presumably causing a change in the electronic state of the multiphoton-absorbing compound. Specifically, the multiphoton-absorbing compounds in the recording layer of the comparative examples all contain at least one selected from the group consisting of carbon-carbon double bonds, carbon-nitrogen double bonds, and carbon-carbon triple bonds, and contain aromatic rings, thus presumably resulting in a strong interaction with the aromatic polymer. In the recording layer of the comparative examples, it is presumably due to changes in the electronic state of the multiphoton-absorbing compound, etc., that the absorption band of the S0-S1 transition in the compound has a tail in the long wavelength region. In the recording layer of the comparative examples, it is presumably that a portion of the wavelength region where single-photon absorption occurs overlaps with 405 nm, thereby significantly increasing the molar absorptivity ε.

[0390] Industrial availability

[0391] The recording medium disclosed herein can be used as a three-dimensional optical memory having multiple recording layers. In the recording layers of the recording medium of this disclosure, the increase in single-photon absorption of light used for recording or reading information is suppressed. Therefore, according to the recording medium of this disclosure, a three-dimensional optical memory with a greater number of recording layers than ever before can be realized.

[0392] Explanation of reference numerals in the attached figures

[0393] 10 Recording Layer

[0394] 20 Dielectric layer

[0395] 100 Recording media.

Claims

1. A recording medium having at least one recording layer, wherein, The at least one recording layer includes: Aliphatic polymers; and A multiphoton-absorbing compound exhibiting multiphoton absorption properties, comprising at least one element selected from the group consisting of carbon-carbon double bonds, carbon-nitrogen double bonds, and carbon-carbon triple bonds. When the thickness of the at least one recording layer is 100 μm, the transmittance of the at least one recording layer to light with a wavelength of 405 nm in the thickness direction is more than 80%.

2. The recording medium according to claim 1, wherein, In the at least one recording layer, the combined content of the aliphatic polymer and the multiphoton-absorbing compound is 95% by weight or more.

3. The recording medium according to claim 1 or 2, wherein, The aliphatic polymer comprises structural units derived from aliphatic monomers. The aliphatic monomer comprises at least one selected from the group consisting of acryloyl, methacryl, epoxy, oxobutyl, and vinyl.

4. The recording medium according to claim 3, wherein, The aliphatic monomer comprises at least one selected from the group consisting of acryloyl, methacryloyl, and epoxy groups.

5. The recording medium according to claim 3, wherein, The aliphatic monomer comprises at least one selected from the group consisting of compound A represented by formula (A), compound B represented by formula (B), compound C represented by formula (C), compound D represented by formula (D), compound E represented by formula (E), compound F represented by formula (F), and compound G represented by formula (G). [Chemical Formula Number 1] In equation (A), R 1 R is a hydrogen atom or a methyl group. 2 It is an aliphatic group. In equation (B), R 3 and R 5 Each of the following is an independent hydrogen atom or a methyl group, R 4 It is an aliphatic group. In the above formula (C), R 6 R is a hydrogen atom or a methyl group. 7 For aliphatic groups, R 8 It is a hydrogen atom or an aliphatic group. In the above equation (D), R 9 R is a hydrogen atom or a methyl group. 10 For aliphatic groups, R 11 It is a hydrogen atom or an aliphatic group. In the above formula (E), R 12 and R 14 Each is independently a hydrogen atom or an aliphatic group, R 13 It is an aliphatic group. In the above formula (F), R 15 and R 17 Each is independently a hydrogen atom or an aliphatic group, R 16 It is an aliphatic group. In the above formula (G), R 18 and R 20 Each is independently a hydrogen atom or an aliphatic group, R 19 It is an aliphatic group.

6. The recording medium according to claim 5, wherein, The compound A comprises at least one selected from the group consisting of compound A1 represented by the following formula (A1) and compound A2 represented by the following formula (A2). [Chemical Formula Number 2] In the above formula (A1), n ​​is an integer greater than 0 and less than 11.

7. The recording medium according to claim 5 or 6, wherein, The compound B comprises compound B1 represented by the following formula (B1), [Chemical Formula Number 3] In the above formula (B1), m is an integer greater than 1 and less than 4.

8. The recording medium according to any one of claims 5 to 7, wherein, The compound E comprises at least one selected from the group consisting of compound E1 represented by formula (E1), compound E2 represented by formula (E2), and compound E3 represented by formula (E3). [Chemical Formula Number 4] In the above formula (E1), x is an integer greater than 1 and less than 12. In the above formula (E3), y is an integer greater than 1 and less than 11.

9. The recording medium according to any one of claims 1 to 8, wherein, The multiphoton-absorbing compound contains an aromatic ring.

10. The recording medium according to any one of claims 1 to 9, wherein, The recording medium also has multiple dielectric layers. The at least one recording layer comprises multiple recording layers. The plurality of recording layers and the plurality of dielectric layers are arranged alternately.

11. The recording medium according to any one of claims 1 to 10, which uses light having a wavelength of 390 nm or more and 420 nm or less to record information.

12. 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 and irradiated onto at least one recording layer in the recording medium according to any one of claims 1 to 11.

13. A method for reading information, which is a method for reading information recorded using the recording method described in claim 12. The readout method includes: The optical properties of the at least one recording layer are determined by irradiating the at least one recording layer with light; and Information is read from the at least one recording layer.

14. A composition for fabricating a recording layer with a thickness of 100 μm and a transmittance of more than 80% for light with a wavelength of 405 nm in the thickness direction. The composition comprises: Aliphatic monomers; and A multiphoton-absorbing compound having multiphoton absorption properties, comprising at least one selected from the group consisting of carbon-carbon double bonds, carbon-nitrogen double bonds, and carbon-carbon triple bonds.

Images