JP2005285211A - Three-dimensional optical recording medium, optical information recording method, three-dimensional optical information recording apparatus, and optical recording/reproducing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To attain a dynamic position correction by introducing a mechanism to specify the position in the inner part of a recording medium for correcting a dynamic position indispensable to a high density recording medium, and to enhance a recording/reading speed and a reliability by enhancing a positional precision. <P>SOLUTION: A two photon three-dimensional optical recording medium wherein a plurality of recording planes capable of recording information are layered in a three-dimensional space in interior of the recording medium has positional information for specifying the position in the inner part of the three-dimensional space in the inner part of the medium. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a high-density optical recording material using two-photon absorption, particularly to a three-dimensional optical recording medium and a high-density optical recording method.

  In general, the nonlinear optical effect is a non-linear optical response proportional to the square of the applied photoelectric field, the third power, or more. In recent years, the third-order nonlinear optical effect has attracted attention, and non-resonant two-photon absorption is particularly attracting attention. Two-photon absorption is a phenomenon in which a compound is excited by simultaneously absorbing two photons, and the case where two-photon absorption occurs in an energy region where there is no (linear) absorption band of the compound is called non-resonant two-photon absorption. . In the following description, two-photon absorption refers to non-resonant two-photon absorption even if not specified.

  By the way, the efficiency of non-resonant two-photon absorption is proportional to the square of the applied photoelectric field (square characteristic of two-photon absorption). For this reason, when a two-dimensional plane is irradiated with a laser, two-photon absorption occurs only at a position where the electric field strength is high in the central portion of the laser spot, and two-photon absorption is completely absent in a portion where the electric field strength is weak in the peripheral portion. Does not happen. On the other hand, in the three-dimensional space, two-photon absorption occurs only in the region where the electric field strength at the focal point where the laser light is collected by the lens is large, and no two-photon absorption occurs in the region outside the focal point because the electric field strength is weak. . Compared with linear absorption where excitation occurs at all positions in proportion to the intensity of the applied photoelectric field, non-resonant two-photon absorption results in excitation at only one point inside the space due to this square characteristic. , The spatial resolution is significantly improved.

  Usually, when non-resonant two-photon absorption is induced, a laser having a wavelength longer than that of a wavelength region in which a (linear) absorption band of a compound exists is often used. Since the laser in the transparent region is used, the laser beam can reach the inside of the sample without being absorbed or scattered, and one point inside the sample can be excited with extremely high spatial resolution due to the square characteristic of non-resonant two-photon absorption. This is a great advantage over ordinary one-photon (linear) absorption.

  On the other hand, optical information recording media (optical discs) capable of recording information only once by laser light are known, and write-once CDs (so-called CD-Rs) and write-once DVDs (so-called DVD-Rs). Etc. have been put to practical use.

  For example, the typical structure of DVD-R is such that the guide groove (pre-groove) for tracking the irradiated laser beam is narrower than half of CD-R (0.74-0.8 μm). Further, a recording layer made of a dye is formed on a transparent disk-shaped substrate, and a light reflecting layer is usually formed on the recording layer, and a protective layer is further formed if necessary.

  Information is recorded on the DVD-R by irradiating with visible laser light (usually in the range of 630 nm to 680 nm), and the irradiated portion of the recording layer absorbs the light and the temperature rises locally. A change (eg, pit generation) occurs and changes its optical properties. On the other hand, reading (reproduction) of information is also performed by irradiating laser light having the same wavelength as the recording laser light, and the part where the optical characteristics of the recording layer have changed (recorded part) and the part that has not changed (unrecorded) Information is reproduced by detecting the difference in reflectance from (part). This difference in reflectance is based on so-called “refractive index modulation”.

  Recently, networks such as the Internet and high-definition TV are rapidly spreading. In addition, HDTV (High Definition Television) will soon be broadcast, and there is an increasing demand for large-capacity recording media for easily and inexpensively recording image information of 50 GB or more, preferably 100 GB or more for consumer use.

  Furthermore, for business use such as computer backup use and broadcast backup use, an optical recording medium capable of recording large-capacity information of about 1 TB or more at high speed and at low cost is required.

  Under such circumstances, a conventional two-dimensional optical recording medium such as a DVD-R has a physical principle that even if the recording / reproducing wavelength is shortened, it is at most about 25 GB on one side and is sufficiently large to meet future requirements. It cannot be said that the recording capacity can be expected.

  Under such circumstances, a three-dimensional optical recording medium has attracted attention as an ultimate high-density, high-capacity recording medium. Three-dimensional optical recording media can be recorded in dozens or hundreds of layers in the three-dimensional (film thickness) direction, resulting in tens or hundreds of times the ultra-high density and ultra-high capacity recording of conventional two-dimensional recording media. That is what we are trying to achieve. In order to provide a three-dimensional optical recording medium, it is necessary to be able to access and write at an arbitrary place in the three-dimensional (film thickness) direction. As a means for this, a method using a two-photon absorption material and holography (interference) There is a method of using.

  In a three-dimensional optical recording medium using a two-photon absorption material, so-called bit recording is possible over tens or hundreds of times based on the physical principle described above, and higher density recording is possible. It can be said to be the ultimate high-density, high-capacity optical recording medium.

  As a three-dimensional optical recording medium using a two-photon absorption material, a method of reading with fluorescence using a fluorescent substance for recording and reproduction (Levic, Eugene, Polis et al., Special Table 2001-524245 [Patent Document 1], Pavel, Eugene et al., JP 2000-512061 [Patent Document 2]), absorption or fluorescence reading using a photochromic compound (Korotif, Nikolai Ai et al., JP 2001-522119 [Patent Document 3], Arsenoff, Villa Dimir et al., JP-T-2001-508221 [Patent Document 4]) and the like have been proposed.

  Also, three-dimensional recording by refractive index modulation is performed in Kawada Jun, Kawada Yoshimasa, JP-A-6-28672 [Patent Document 5], Kawada Kei, Kawada Yoshimasa et al. And JP-A-6-118306 [Patent Document 6]. A recording apparatus, a reproducing apparatus, a reading method, and the like are disclosed.

However, in these two-photon three-dimensional optical recording media and three-dimensional recording / reproducing apparatuses, in order to obtain the three-dimensional position of the recorded information recorded in the optical recording medium, the relative positions of the recording medium and the recording apparatus are set. As a reference, there was only a method of specifying the position on the recording-reproducing apparatus side. Such positioning on the device side is greatly shifted due to variations and warpage of the size of the recording medium, vibrations of the device, and deterioration over time. Therefore, a high-density recording medium that records and reads extremely fine signals. Then it is fatal. On the other hand, if there is a means for obtaining three-dimensional position information inside the three-dimensional recording medium, even if a variation in the size of the medium, warpage, vibration, or deterioration with time occurs, the information is dynamically updated accordingly. It is possible to correct the position flexibly. However, no two-photon optical recording medium having a mechanism for specifying the three-dimensional position inside the optical recording medium has been disclosed so far.
JP-T-2001-524245 Special table 2000-512061 gazette Special table 2001-522119 gazette Special table 2001-508221 gazette JP-A-6-28672 JP-A-6-118306

  As described above, in the two-photon three-dimensional optical recording medium reported so far, in order to specify the three-dimensional position inside the medium, the relative positional relationship between the medium and the recording-reproducing apparatus is used. Based on the above, there was no method other than determining the position on the device side. However, when only the position is determined on the apparatus side, the accuracy of the position information is significantly lowered due to various factors (recording medium manufacturing accuracy, warpage, deformation, vibration of the apparatus, deterioration with time, etc.). In a high-density recording medium, the size of recording bits to be recorded is very small, so that even a slight error inevitably causes a significant decrease in recording-reading performance. To that end, it is indispensable to constantly monitor the status of the recording medium and dynamically correct the position. However, since there is no mechanism for identifying the spatial position inside the recording medium, there have been proposals so far. This dynamic position correction is impossible with the two-photon three-dimensional optical recording medium.

  An object of the present invention is to enable dynamic position correction by introducing a mechanism for specifying the position inside the recording medium for dynamic position correction indispensable for a high-density recording medium. It is to improve the recording-reading speed and improve the reliability by improving the accuracy.

As a result of intensive studies by the inventors, the above object of the present invention has been achieved by the following means.
(1) A two-photon three-dimensional optical recording medium in which a plurality of recording planes capable of recording information are stacked in a three-dimensional space inside the recording medium, for specifying a position in the three-dimensional space A three-dimensional optical recording medium having position information inside the medium.
(2) The two-dimensional position information in the recording plane and the position information for specifying an arbitrary recording plane in the laminated recording plane are described in (3). Dimensional optical recording medium.
(3) As a mark for specifying two-dimensional position information in the recording plane, a concentric structure having optical characteristics different from the surroundings is provided, (1) or (2) Three-dimensional optical recording medium.
(4) The helical structure having optical characteristics different from the surroundings as a mark for specifying an arbitrary recording plane in the recording plane formed by stacking, (1) or (2) Three-dimensional optical recording medium.
(5) The three-dimensional optical recording medium according to (3) or (4), wherein the concentric structure and the spiral structure have a wave of an arbitrary frequency.
(6) The three-dimensional optical recording medium according to any one of (1) to (5), wherein the concentric structure is provided in the recording medium or on the substrate surface.
(7) One or a plurality of the helical structures are provided at any position from the central part, the terminal part, or the central part to the terminal part of the recording layer formed by laminating a plurality of recording planes. The three-dimensional optical recording medium according to any one of (1) to (5).
(8) An optical information recording method, wherein information is recorded three-dimensionally on the three-dimensional optical recording medium according to any one of (1) to (7) based on the position information.
(9) The optical information recording method according to (8), further comprising a step of forming the helical structure prior to information recording.
(10) Three-dimensional optical information, wherein information is recorded on the three-dimensional optical recording medium according to any one of (1) to (7) by using the method according to (8) or (9). Recording device.
(11) The three-dimensional optical recording medium according to any one of (1) to (7), wherein the medium includes a two-photon absorption compound, and the refractive index is determined by using the two-photon absorption of the two-photon absorption compound. 2. A two-photon absorption optical recording / reproducing method, wherein recording is performed by modulation or absorptance modulation, and reproduction is performed by irradiating the recording material with light and detecting a difference in reflectance.
(12) Recording is performed on a two-photon absorption optical recording material having a two-photon absorption compound as a three-dimensional optical recording medium by using the two-photon absorption of the two-photon absorption compound, and then recording light. A two-photon absorption optical recording / reproducing method characterized in that reproduction is performed by irradiating a laser beam and detecting a difference in emission intensity.
(13) The three-dimensional optical recording medium has a two-photon absorption compound, and utilizes the two-photon absorption of the two-photon absorption compound, 1) polymerization reaction, 2) color development reaction, 3) latent image color development-color former self-increase A) Sensitive amplification color reaction, 4) latent image color development-chromogen sensitized polymerization reaction, 5) orientation change of compound having intrinsic birefringence, 6) decolorization reaction, 7) foaming, A) The three-dimensional optical recording medium according to any one of (1) to (12), wherein recording is performed by causing any one of refractive index modulation, B) absorption rate modulation, and C) light emission ability modulation.
(14) A three-dimensional optical recording medium comprising the two-photon absorption compound according to (11) or (12).
(15) The three-dimensional optical recording medium according to (13) or (14), wherein the recording using two-photon absorption of the two-photon absorption compound is not rewritable in (13) or (14).
(16) The two-photon absorption compound is represented by a cyanine dye, a merocyanine dye, an oxonol dye, a phthalocyanine dye, an azo dye or the following general formula (1), (13) to (15) The two-photon absorption optical recording material according to any one of the above.

    General formula (1)

In the formula, R ¹ , R ² , R ³ and R ⁴ each independently represent a hydrogen atom or a substituent, and some of R ¹ , R ² , R ³ and R ⁴ are bonded to each other to form a ring. May be formed. n and m each independently represent an integer of 0 to 4, and when n and m are 2 or more, a plurality of R ¹ , R ² , R ³ and R ⁴ may be the same or different. However, n and m are not 0 simultaneously. X ¹ and X ² independently represent an aryl group, a heterocyclic group, or a group represented by General Formula (2).

  General formula (2)

In the formula, R ⁵ represents a hydrogen atom or a substituent, R ⁶ represents a hydrogen atom, an alkyl group, an alkenyl group, an aryl group, or a heterocyclic group, and Z ¹ represents an atomic group forming a 5- or 6-membered ring. .
(17) In (16), the cyanine dye is represented by the following general formula (3), the merocyanine dye is represented by the following general formula (4), and the oxonol dye is represented by the general formula (5). The three-dimensional optical recording medium according to (15).

In the general formulas (3) to (5), Za ₁ , Za ₂ and Za ₃ each represent an atomic group forming a 5-membered or 6-membered nitrogen-containing heterocycle, and Za ₄ , Za ₅ and Za ₆ are each 5 A group of atoms forming a member or six-membered ring is represented. Ra ₁ , Ra ₂ and Ra ₃ each independently represent a hydrogen atom, an alkyl group, an alkenyl group, an aryl group or a heterocyclic group.

Ma _{1 to} Ma ₁₄ each independently represent a methine group, may have a substituent, and may form a ring with another methine group. na ¹ , na ² and na ³ are each 0 or 1, and ka ¹ and ka ³ each represents an integer of 0 to 3. When ka ¹ is 2 or more, the plurality of Ma ₃ and Ma ₄ may be the same or different. When ka ³ is 2 or more, the plurality of Ma ₁₂ and Ma ₁₃ may be the same or different. ka ² represents an integer of 0 to 8, and when ka ² is 2 or more, a plurality of Ma ₁₀ and Ma ₁₁ may be the same or different.

CI represents an ion that neutralizes the electric charge, and y represents a number necessary for neutralizing the electric charge.
(18) A two-photon absorption three-dimensional optical recording / reproducing method comprising the two-photon absorption optical recording / reproducing method according to claim (11) or (12).
(19) A two-photon absorption three-dimensional optical recording medium comprising the three-dimensional optical recording medium according to any one of claims (14) to (17).
(20) A two-photon absorption three-dimensional optical recording medium, wherein the three-dimensional optical recording medium according to any one of claims (13) to (18) is stored in a light-shielding cartridge at the time of storage.
(21) A laser beam having a wavelength longer than that of the linear absorption band of the two-photon absorption compound and having a molar absorption coefficient of linear absorption of 10 or less in the three-dimensional optical recording medium according to claims (13) to (19) A two-photon absorption optical recording method, wherein recording is performed using two-photon absorption induced by irradiation of

  According to the present invention, for dynamic position correction indispensable for a high-density recording medium, a mechanism for specifying the position inside the recording medium is introduced to enable dynamic position correction, and position accuracy is improved. The recording / reading speed can be improved and high reliability can be obtained.

  The optical recording medium of the present invention will be described in detail below.

  An optical recording medium of the present invention is a two-photon three-dimensional optical recording medium in which a plurality of recording planes capable of recording information are stacked in a three-dimensional space inside the medium. Position information for specifying is provided inside the medium.

  The position information for specifying the position in the three-dimensional space inside the medium includes page specifying information for specifying an arbitrary recording plane (hereinafter abbreviated as a page) from a plurality of stacked recording planes. And two-dimensional position information in an arbitrary page are preferably used in combination.

  As a method for providing page information inside the two-photon three-dimensional recording medium, a spiral continuous structure is formed from the incident surface of the recording light or the reading light toward the opposite surface or in the opposite direction. It is preferable to do.

  As long as the helical structure can optically recognize its structure, there are no particular restrictions on the material or composition for forming the structure, but color formation, decoloring, polymerization, formation of voids by foaming, It is preferable to use a change in refractive index, a change in light absorption rate, and a change in light emission intensity due to a change in orientation of a compound having an intrinsic birefringence.

  The helical structure may be provided on the innermost periphery of the three-dimensional optical recording medium, may be provided on the outermost periphery, or may be provided at any place from the inner periphery to the outer periphery. The number may be one or more.

  As a method for giving two-dimensional position information in the page plane to each page inside the two-photon three-dimensional recording medium, concentric circles extending from the center to the end are provided on at least one page inside the recording medium. It is preferable to form a continuous structure.

  The concentric structure is not particularly limited as long as its structure can be optically recognized, but there are no particular restrictions on the material or composition for forming the structure. Coloring, decoloring, polymerization, formation of voids by foaming, It is preferable to use a change in refractive index, a change in light absorption rate, and a change in light emission intensity due to a change in orientation of a compound having an intrinsic birefringence.

  It is also desirable to form only one concentric structure on the substrate. In this case, a structure that provides two-dimensional position information can be obtained by providing a groove having irregularities on the substrate surface.

  The spiral structure for providing page information and the concentric structure for providing two-dimensional position information within the page seem to be used in CD-R and DVD-R guide grooves. It is preferable to have a meandering structure (wobbling), and it is preferable to provide page position and in-page two-dimensional position information according to the wobble amount.

  The helical structure and the concentric structure of the present invention can be provided by being coupled to each other. For example, in this case, since the end of the concentric structure carrying the in-page position information is connected to the end of the concentric structure of the next page, one large spiral structure is formed as a whole.

  Next, the optical information recording method of the present invention will be described. According to the optical information recording method of the present invention, information is recorded on the optical recording medium whose position in the three-dimensional space inside the recording medium can be specified by the above spiral structure and concentric structure based on the position information. An optical information recording method characterized by recording in a dimension. The recording method preferably includes a step of forming a helical structure for carrying page information prior to information recording.

  Next, the two-photon absorption optical recording / reproducing method and the two-photon absorption optical recording material of the present invention will be described in detail.

  As the two-photon absorption optical recording / reproducing method of the present invention, recording by refractive index modulation or absorptance modulation is performed on a two-photon absorption optical recording material having a two-photon absorption compound by utilizing two-photon absorption of the two-photon absorption compound. Then, a method of reproducing by irradiating the recording material with light and detecting a difference in reflectance is preferable.

  On the other hand, after recording is performed on the two-photon absorption optical recording material having the two-photon absorption compound by using the two-photon absorption of the two-photon absorption compound, the recording material is irradiated with light to emit the light. A method of reproducing by detecting a difference in intensity is preferred.

  In this case, the light emission may be fluorescence or phosphorescence, but fluorescence is preferable from the viewpoint of light emission efficiency.

  The two-photon absorption optical recording material as the three-dimensional optical recording medium of the present invention is preferably not subjected to wet processing.

  The two-photon absorption optical recording material of the present invention is preferably a system that cannot be rewritten. Here, the non-rewritable method is a method of recording by irreversible reaction, and indicates a method in which once recorded data can be stored without being rewritten even if it is overwritten and recorded. Therefore, it is suitable for storing important data that requires long-term storage. However, of course, it is possible to newly record in an area that has not been recorded yet. In that sense, it is generally called “write-once type” or “write-once type”.

  The two-photon absorption optical recording material of the present invention has a two-photon absorption compound and uses the two-photon absorption of the two-photon absorption compound to 1) polymerization reaction, 2) color reaction, and 3) latent image color development-color development. Self-sensitized amplification color development reaction, 4) latent image color development-color development body sensitized polymerization reaction, 5) orientation change of compound having intrinsic birefringence, 6) decolorization reaction, 7) foaming A two-photon absorption optical recording material is preferable, in which recording is performed by causing any one of A) refractive index modulation, B) absorptance modulation, and C) luminous intensity modulation.

  A laser is preferably used for recording of the two-photon absorption optical recording material of the present invention. The light used in the present invention is preferably ultraviolet light having a wavelength of 200 to 2000 nm, visible light, or infrared light, more preferably ultraviolet light having a wavelength of 300 to 1000 nm, visible light, or infrared light, and further preferably. Is visible light or infrared light of 400 to 800 nm.

  The laser that can be used is not particularly limited, but specifically, it is also used in a solid laser such as Ti-sapphire having an oscillation wavelength near a central wavelength of 1000 nm, a fiber laser, a CD-R having an oscillation wavelength near 780 nm, or the like. Preferred are semiconductor lasers, solid lasers, fiber lasers, semiconductor lasers used in DVD-R having an oscillation wavelength in the range of 620 to 680 nm, solid lasers, GaN lasers having an oscillation wavelength in the vicinity of 400 to 415 nm, etc. Can be used.

  In addition, a solid SHG laser such as a YAG / SHG laser having an oscillation wavelength in the visible light region, a semiconductor SHG laser, or the like can be preferably used.

  The laser used in the present invention may be a pulsed laser or a CW laser.

  When recording on the two-photon absorption optical recording material of the present invention, a laser having a wavelength longer than the linear absorption band of the two-photon absorption compound and having a linear (one-photon) absorption molar extinction coefficient of 10 or less. Recording is preferably performed using two-photon absorption induced by irradiation with light, preferably 1 or less, more preferably 0.1 or less, and most preferably no linear absorption. .

  The light used for reproduction is preferably the above laser light, for example. Further, although the power or pulse shape is the same or different, it is more preferable to reproduce by using a laser having the same wavelength as that at the time of recording.

  Examples of the light used for reproduction include carbon arc, high-pressure mercury lamp, xenon lamp, metal halide lamp, fluorescent lamp, tungsten lamp, LED, and organic EL. In order to irradiate light in a specific wavelength range, it is also preferable to use a sharp cut filter, a band pass filter, a diffraction grating, or the like as necessary.

  In the two-photon absorption optical recording material of the present invention, the size of the reaction part or coloring part produced by recording is preferably in the range of 10 nm to 100 μm, more preferably in the range of 50 nm to 5 μm, and 50 nm. More preferably, it is in the range of ˜2 μm.

  Further, in order to enable the reproduction of the recording material, the size of the reaction part or the color development part is preferably 1/20 to 20 times the irradiation light wavelength, and is 1/10 to 10 times as large. It is more preferable that the size is 1/5 to 5 times.

  In the two-photon absorption optical recording material of the present invention, after the two-photon recording, a fixing step may be performed by light (ordinary one-photon), heat, or both.

  In particular, when an acid proliferating agent or a base proliferating agent is used in the two-photon absorption optical recording material of the present invention, it is preferable to use heating for fixing in order to make the acid proliferating agent or base proliferating agent function effectively.

  In the case of photofixing, the entire surface of the two-photon absorption optical recording material is irradiated with ultraviolet light or visible light (non-interference exposure). Preferably, the light source used includes a visible light laser, an ultraviolet light laser, a carbon arc, a high-pressure mercury lamp, a xenon lamp, a metal halide lamp, a fluorescent lamp, a tungsten lamp, an LED, an organic EL, and the like.

  It is also preferable to use a laser used for recording as a light source for light fixing as it is or by changing the power, pulse, condensing degree, wavelength and the like.

  In the case of thermal fixing, the fixing step is preferably performed at 40 ° C to 160 ° C, more preferably 60 ° C to 130 ° C.

  When both photofixing and heat fixing are performed, light and heat may be applied simultaneously, or light and heat may be added separately.

  In the two-photon absorption optical recording material of the present invention, the chemical reaction, color development reaction, and the like that occur by performing two-photon absorption are reactions that do not involve thermal decomposition, that is, the photon mode, particularly in terms of high sensitivity. preferable.

  That is, it is preferable to record with a mechanism different from the method that is practically used in the existing CD-R and DVD-R, particularly when considering the writing transfer speed in the recording material.

  The two-photon absorption optical recording / reproducing method of the present invention is preferably used for an optical recording / reproducing method such as DVD-R and DVD-BL (BR), a near-field optical recording / reproducing method, a three-dimensional optical recording / reproducing method, and the like. More preferably, it is preferably used for a three-dimensional optical recording / reproducing method. That is, the two-photon absorption optical recording / reproducing method of the present invention is preferably used for the two-photon absorption three-dimensional optical recording / reproducing method.

  Similarly, the two-photon absorption optical recording material of the present invention is preferably used for optical recording media such as DVD-R and DVD-BL (BR), near-field optical recording media, and three-dimensional optical recording media. More preferably, it is used for a three-dimensional optical recording material or medium. That is, the two-photon absorption optical recording material of the present invention is preferably used for a two-photon absorption three-dimensional optical recording medium.

  When the two-photon absorption optical recording material of the present invention is used for an optical recording medium, the two-photon absorption optical recording material is preferably stored in a light shielding cartridge during storage.

  Further, the two-photon absorption compound and the two-photon absorption optical recording material of the present invention may perform multiphoton absorption of three or more photons.

  First, the two-photon absorption compound used in the two-photon absorption optical recording material of the present invention will be described in detail.

  The two-photon absorption compound of the present invention is a compound that performs non-resonant two-photon absorption (a phenomenon in which two photons are simultaneously excited in an energy region where no (linear) absorption band of the compound exists).

  When applied to a two-photon absorption optical recording material, particularly a two-photon absorption three-dimensional optical recording material, an excited state is efficiently generated by performing two-photon absorption with high sensitivity in order to achieve a high transfer (recording) speed. A two-photon absorbing compound that can be used is needed.

The efficiency with which a two-photon absorption compound performs two-photon absorption is represented by a two-photon absorption cross section δ and is defined by 1GM = 1 × 10 ⁻⁵⁰ cm ⁴ s / photon. The two-photon absorption cross-sectional area δ of the two-photon absorption compound in the two-photon absorption optical recording material of the present invention is preferably 100 GM or more from the viewpoint of improving the writing speed, reducing the size of the laser and reducing the cost, and is 1000 GM or more. Is more preferably 5000 GM or more, and most preferably 10,000 GM or more.

  The two-photon absorption compound of the present invention is preferably an organic compound.

  In the present invention, when a specific moiety is referred to as a “group”, unless otherwise specified, it may be substituted with one or more (up to the maximum possible) substituents. It means that it is not necessary. For example, “alkyl group” means a substituted or unsubstituted alkyl group. In addition, the substituent that can be used in the compound in the present invention may be any substituent.

  In the present invention, when a specific moiety is referred to as “ring”, or when “group” includes “ring”, it may be monocyclic or condensed unless otherwise specified. May not be substituted.

  For example, the “aryl group” may be a phenyl group, a naphthyl group, or a substituted phenyl group.

  In addition, a pigment | dye here is a general term with respect to the compound which has a part of absorption in an ultraviolet region (preferably 200-400 nm) visible region (400-700 nm) or a near infrared region (preferably 700-2000 nm), More preferably Is a general term for compounds having a part of absorption in the visible region.

  Any two-photon absorption compound in the present invention may be used. For example, cyanine dye, hemicyanine dye, streptocyanine dye, styryl dye, pyrylium dye, merocyanine dye, trinuclear merocyanine dye, tetranuclear merocyanine dye, rhodacyanine dye, complex Cyanine dye, complex merocyanine dye, allopolar dye, arylidene dye, oxonol dye, hemioxonol dye, squalium dye, croconium dye, azurenium dye, coumarin dye, ketocoumarin dye, styrylcoumarin dye, pyran dye, anthraquinone dye, quinone dye, tri Phenylmethane dye, diphenylmethane dye, xanthene dye, thioxanthene dye, phenothiazine dye, phenoxazine dye, phenazine dye, azo Element, azomethine dye, fluorenone dye, diarylethene dye, spiropyran dye, fulgide dye, perylene dye, phthaloperylene dye, indigo dye, polyene dye, acridine dye, acridinone dye, diphenylamine dye, quinacridone dye, quinophthalone dye, porphyrin dye, azaporphyrin dye Chlorophyll dyes, phthalocyanine dyes, fused aromatic dyes, styrenic dyes, metallocene dyes, metal complex dyes, phenylene vinylene dyes, stilbazolium dyes, more preferably cyanine dyes, hemicyanine dyes, streptocyanine dyes, styryl dyes , Pyrylium dye, merocyanine dye, arylidene dye, oxonol dye, squalium dye, ketocoumarin dye, styrylcoumarin dye, pyran dye Thioxanthene dye, phenothiazine dye, phenoxazine dye, phenazine dye, azo dye, polyene dye, azaporphyrin dye, chlorophyll dye, phthalocyanine dye, metal complex dye, more preferably cyanine dye, merocyanine dye, oxonol dye, azo dye Phthalocyanine dyes, more preferably cyanine dyes, merocyanine dyes, and oxonol dyes, and most preferably cyanine dyes.

  When the two-photon absorption compound of the present invention is a cyanine dye, it is preferably represented by the general formula (3).

In the general formula (3), Za ₁ and Za ₂ each represent an atomic group forming a 5-membered or 6-membered nitrogen-containing heterocycle. The 5-membered or 6-membered nitrogen-containing heterocycle formed is preferably an oxazole nucleus having 3 to 25 carbon atoms (hereinafter referred to as C number) (for example, 2-3-ethyloxazolyl, 2-3-sulfopropyloxa Zolyl, 2-3-sulfopropylbenzoxazolyl, 2-3-ethylbenzoxazolyl, 2-3-sulfopropyl-γ-naphthoxazolyl, 2-3-ethyl-α-naphthoxazolyl , 2-3-methyl-β-naphthoxazolyl, 2-3-sulfopropyl-β-naphthoxazolyl, 2-5-chloro-3-ethyl-α-naphthoxazolyl, 2-5-chloro -3-ethylbenzoxazolyl, 2-5-chloro-3-sulfopropylbenzoxazolyl, 2-5,6-dichloro-3-sulfopropylbenzoxazolyl, 2-5-bromo-3-sulfo Lopylbenzoxazolyl, 2-3-ethyl-5-phenylbenzoxazolyl, 2-5-phenyl-3-sulfopropylbenzoxazolyl, 2-5- (4-bromophenyl) -3-sulfo Butyl benzoxazolyl, 2-5- (1-pyrrolyl) -3-sulfopropylbenzoxazolyl, 2-5,6-dimethyl-3-sulfopropylbenzoxazolyl, 2-3-ethyl-5 Methoxybenzoxazolyl, 2-3-ethyl-5-sulfobenzoxazolyl), thiazole nucleus having 3 to 25 carbon atoms (for example, 2-3-ethylthiazolyl, 2-3-sulfopropylthiazolyl) 2-3-ethylbenzothiazolyl, 2-3-sulfopropylbenzothiazolyl, 2-3-methyl-β-naphthothiazolyl, 2-3-sulfopropyl-γ- Futhiazolyl, 2-3,5-dimethylbenzothiazolyl, 2-5-chloro-3-ethylbenzothiazolyl, 2-5-chloro-3-sulfopropylbenzothiazolyl, 2-3-ethyl-5 -Iodobenzothiazolyl, 2-5-bromo-3-methylbenzothiazolyl, 2-3-ethyl-5-methoxybenzothiazolyl, 2-5-phenyl-3-sulfopropylbenzothiazolyl An imidazole nucleus having 3 to 25 carbon atoms (for example, 2-1,3-diethylimidazolyl, 2-5,6-dichloro-1,3-diethylbenzimidazolyl, 2-5,6-dichloro-3- Ethyl-1-sulfopropylbenzimidazolyl, 2-5-chloro-6-cyano-1,3-diethylbenzimidazolyl, 2-5-chloro-1,3-diethyl-6-trif Such as oromethylbenzimidazolyl), C10-30 indolenine nucleus (for example, 3,3-dimethyl-1-pentylindolenine, 3,3, -dimethyl-1-sulfopropylindolenine, 5-carboxy -1,3,3-trimethylindolenine, 5-carbamoyl-1,3,3-trimethylindolenine, 1,3,3, -trimethyl-4,5-benzoindolenine), C number 9 -25 quinoline nuclei (e.g., 2-1 -ethylquinolyl, 2-1 -sulfobutylquinolyl, 4-1 -pentylquinolyl, 4-1 -sulfoethylquinolyl, 4-1 -methyl-7-chloroquinolyl, ), A C 3-25 selenazole nucleus (for example, 2-3 methylbenzoselenazolyl), a C 5-25 pyri (For example, 2-pyridyl and the like) and the like, and in addition, thiazoline nucleus, oxazoline nucleus, selenazoline nucleus, tellurazoline nucleus, tellurazole nucleus, benzotelrazole nucleus, imidazoline nucleus, imidazo [4,5- Quinoxaline] nucleus, oxadiazole nucleus, thiadiazole nucleus, tetrazole nucleus, pyrimidine nucleus.

  These may be substituted, and for example, an alkyl group, an alkenyl group, a cycloalkyl group, an aryl group, a heterocyclic group, an alkynyl group, a halogen atom, an amino group, a cyano group, a nitro group, a hydroxyl group, Mercapto group, carboxyl group, sulfo group, phosphonic acid group, acyl group, alkoxy group, aryloxy group, alkylthio group, arylthio group, alkylsulfonyl group, arylsulfonyl group, sulfamoyl group, carbamoyl group, acylamino group, imino group, acyloxy Group, alkoxycarbonyl group, carbamoylamino group, more preferably alkyl group, aryl group, heterocyclic group, halogen atom, cyano group, carboxyl group, sulfo group, alkoxy group, sulfamoyl group, carbamoyl group, alkoxycarbonyl group. A group.

  These heterocycles may be further condensed. Preferred examples of the condensed ring include a benzene ring, a benzofuran ring, a pyridine ring, a pyrrole ring, an indole ring, and a thiophene ring.

More preferably, the 5- or 6-membered nitrogen-containing heterocycle formed by Za ₁ and Za ₂ is an oxazole nucleus, an imidazole nucleus, a thiazole nucleus, or an indolenine ring, and more preferably an oxazole nucleus, an imidazole nucleus, or an indolenine ring. A ring, most preferably an oxazole nucleus, and particularly preferably a benzoxazole ring.

Ra ₁ and Ra ₂ are each independently a hydrogen atom or an alkyl group (preferably having a C number of 1 to 20, for example, methyl, ethyl, n-propyl, isopropyl, n-butyl, n-pentyl, benzyl, 3-sulfopropyl. , 4-sulfobutyl, 3-methyl-3-sulfopropyl, 2′-sulfobenzyl, carboxymethyl, 5-carboxypentyl), alkenyl group (preferably having 2 to 20 carbon atoms, for example, vinyl, allyl), aryl group ( Preferably C number 6-20, for example phenyl, 2-chlorophenyl, 4-methoxyphenyl, 3-methylphenyl, 1-naphthyl), heterocyclic group (preferably C number 1-20, for example pyridyl, thienyl, furyl , Thiazolyl, imidazolyl, pyrazolyl, pyrrolidino, piperidino, morpholino), more preferably an alkyl group ( Preferably, it is a C 1-6 alkyl group) or a sulfoalkyl group (preferably 3-sulfopropyl, 4-sulfobutyl, 3-methyl-3-sulfopropyl, 2′-sulfobenzyl).

Ma _{1 to} Ma ₇ each represent a methine group and may have a substituent (examples of preferred substituents are the same as examples of substituents on Za ₁ and Za ₂ ), and preferably an alkyl group as a substituent , Halogen atom, nitro group, alkoxy group, aryl group, nitro group, heterocyclic group, aryloxy group, acylamino group, carbamoyl group, sulfo group, hydroxy group, carboxy group, alkylthio group, cyano group, etc. More preferably, it is an alkyl group.

Ma _{1 to} Ma ₇ are preferably an unsubstituted methine group or an alkyl group (preferably having a C number of 1 to 6) substituted methine group, more preferably an unsubstituted, ethyl group-substituted, or methyl group-substituted methine group.

Ma _{1 to} Ma ₇ may be linked to each other to form a ring, and preferred examples of the ring formed include a cyclohexene ring, a cyclopentene ring, a benzene ring, and a thiophene ring.

na ¹ and na ² are 0 or 1, preferably 0.

ka ¹ represents an integer of 0 to 3, more preferably ka ¹ represents 0 to 2, and further preferably ka ¹ represents 1 or 2.

When ka ¹ is 2 or more, a plurality of Ma ₃ and Ma ₄ may be the same or different.

  CI represents an ion that neutralizes the electric charge, and y represents a number necessary for neutralizing the electric charge.

  When the two-photon absorption compound of the present invention is a merocyanine dye, it is preferably represented by the general formula (4).

In the general formula (4), Za ₃ represents an atomic group forming a 5- or 6-membered nitrogen-containing heterocycle (preferred examples are the same as Za ₁ and Za ₂ ), and these may be substituted (preferred substitution) Examples of the group are the same as those of the substituents on Za ₁ and Za ₂ )), and these heterocyclic rings may be further condensed.

More preferably, the 5- or 6-membered nitrogen-containing heterocyclic ring formed by Za ₃ is an oxazole nucleus, an imidazole nucleus, a thiazole nucleus or an indolenine ring, and more preferably a benzoxazole nucleus, a benzothiazole ring or an indolenine ring. It is.

Za ₄ represents an atomic group forming a 5-membered or 6-membered ring. The ring formed from Za ₄ is a part generally called an acidic nucleus, and is defined by James, The Theory of the Photographic Process, 4th edition, Macmillan, 1977, p. 198. Za ₄ is preferably 2-pyrazolone-5-one, pyrazolidine-3,5-dione, imidazolin-5-one, hydantoin, 2 or 4-thiohydantoin, 2-iminooxazolidine-4-one, 2-oxazoline- 5-one, 2-thiooxazoline-2,4-dione, isorhodanine, rhodanine, indan-1,3-dione, thiophen-3-one, thiophen-3-one-1,1-dioxide, indoline-2-one Indoline-3-one, 2-oxoindazolium, 5,7-dioxo-6,7-dihydrothiazolo [3,2-a] pyrimidine, 3,4-dihydroisoquinolin-4-one, 1,3 -Dioxane-4,6-dione, barbituric acid, 2-thiobarbituric acid, coumarin-2,4-dione, indazolin-2-one, pyri Examples include nuclei such as do [1,2-a] pyrimidine-1,3-dione, pyrazolo [1,5-b] quinazolone, and pyrazolopyridone.

More preferably, the ring formed from Za ₄ is 2-pyrazolone-5-one, pyrazolidine-3,5-dione, rhodanine, indan-1,3-dione, thiophen-3-one, thiophen-3-one- 1,1-dioxide, 1,3-dioxane-4,6-dione, barbituric acid, 2-thiobarbituric acid, coumarin-2,4-dione, more preferably pyrazolidine-3,5-dione, Indan-1,3-dione, 1,3-dioxane-4,6-dione, barbituric acid, 2-thiobarbituric acid, most preferably pyrazolidine-3,5-dione, barbituric acid, 2- Thiobarbituric acid.

The ring formed from Za ₄ may be substituted (preferred examples of the substituent are the same as the examples of the substituent on Za ₃ ). More preferably, the substituent is preferably an alkyl group, an aryl group, a heterocyclic group, a halogen. An atom, a cyano group, a carboxyl group, a sulfo group, an alkoxy group, a sulfamoyl group, a carbamoyl group, and an alkoxycarbonyl group.

  These heterocycles may be further condensed. Preferred examples of the condensed ring include a benzene ring, a benzofuran ring, a pyridine ring, a pyrrole ring, an indole ring, and a thiophene ring.

Ra ₃ is independently a hydrogen atom, an alkyl group, an alkenyl group, an aryl group, or a heterocyclic group (preferred examples are the same as Ra ₁ and Ra ₂ ), more preferably an alkyl group (preferably having a C number of 1 to 1). 6 alkyl group) or a sulfoalkyl group (preferably 3-sulfopropyl, 4-sulfobutyl, 3-methyl-3-sulfopropyl, 2′-sulfobenzyl).

Ma _{8 to} Ma ₁₁ each represent a methine group and may have a substituent (examples of preferred substituents are the same as examples of substituents on Za ₁ and Za ₂ ), and preferably an alkyl group as a substituent , Halogen atom, nitro group, alkoxy group, aryl group, nitro group, heterocyclic group, aryloxy group, acylamino group, carbamoyl group, sulfo group, hydroxy group, carboxy group, alkylthio group, cyano group, etc. More preferably, it is an alkyl group.
Ma _{8 to} Ma ₁₁ are preferably unsubstituted methine groups or alkyl groups (preferably having a C number of 1 to 6) substituted methine groups, and more preferably unsubstituted, ethyl group-substituted, and methyl group-substituted methine groups.

Ma _{8 to} Ma ₁₁ may be linked to each other to form a ring, and preferred examples of the ring formed include a cyclohexene ring, a cyclopentene ring, a benzene ring, and a thiophene ring.

na ³ is 0 or 1, preferably 0.

ka ² represents an integer of 0 to 8, preferably an integer of 0 to 4, more preferably an integer of 1 to 3.

When ka ² is 2 or more, the plurality of Ma ₁₀ and Ma ₁₁ may be the same or different.

  CI represents an ion that neutralizes the electric charge, and y represents a number necessary for neutralizing the electric charge.

  When the two-photon absorption compound of the present invention is an oxonol dye, it is preferably represented by the general formula (5).

In the general formula (5), Za ₅ and Za ₆ each represent a group of atoms forming a 5-membered or 6-membered ring (preferred examples are the same as Za ₄ ), and these may be substituted (examples of preferred substituents). Is the same as the example of the substituent on Za ₄ ), and these heterocyclic rings may be further condensed.

More preferably, the ring formed from Za ₅ and Za ₆ is more preferably 2-pyrazolone-5-one, pyrazolidine-3,5-dione, rhodanine, indan-1,3-dione, thiophen-3-one, thiophene-3. -One-1,1-dioxide, 1,3-dioxane-4,6-dione, barbituric acid, 2-thiobarbituric acid, coumarin-2,4-dione, more preferably barbituric acid, 2- Thiobarbituric acid, most preferably barbituric acid.

Ma _{12 to} Ma ₁₄ each represent a methine group and may have a substituent (preferred examples of the substituent are the same as the examples of the substituent on Za ₅ and Za ₆ ), and the substituent is preferably alkyl. Group, halogen atom, nitro group, alkoxy group, aryl group, nitro group, heterocyclic group, aryloxy group, acylamino group, carbamoyl group, sulfo group, hydroxy group, carboxy group, alkylthio group, cyano group, etc. An alkyl group, a halogen atom, an alkoxy group, an aryl group, a heterocyclic group, a carbamoyl group, and a carboxy group are more preferable, and an alkyl group, an aryl group, and a heterocyclic group are more preferable.

Ma _{12 to} Ma ₁₄ are preferably unsubstituted methine groups.

Ma _{12 to} Ma ₁₄ may be linked to each other to form a ring, and preferred examples of the ring formed include a cyclohexene ring, a cyclopentene ring, a benzene ring, and a thiophene ring.

ka ³ represents an integer of 0 to 3, preferably an integer of 0 to 2, and more preferably 1 or 2.

When ka ³ is 2 or more, Ma ₁₂ and Ma ₁₃ may be the same or different.

  CI represents an ion that neutralizes the electric charge, and y represents a number necessary for neutralizing the electric charge.

  The two-photon absorption compound of the present invention is also preferably represented by the general formula (1).

In the general formula (1), R ¹ , R ² , R ³ and R ⁴ each independently represents a hydrogen atom or a substituent, and the substituent is preferably an alkyl group, an alkenyl group, a cycloalkyl group, an aryl group, It is a heterocyclic group. R ¹ , R ² , R ³ and R ⁴ are preferably hydrogen atoms or alkyl groups, and some (preferably two) of R ¹ , R ² , R ³ and R ⁴ are bonded to each other to form a ring. May be formed. In particular, R ¹ and R ³ are preferably bonded to form a ring, and the ring formed with the carbonyl carbon atom is preferably a 6-membered ring, a 5-membered ring or a 4-membered ring, and a 5-membered ring or A 4-membered ring is more preferable, and a 5-membered ring is most preferable.

In General formula (1), n and m represent the integer of 0-4 each independently, Preferably the integer of 1-4 is represented. However, n and m are not 0 simultaneously.
When n and m are 2 or more, a plurality of R ¹ , R ² , R ³ and R ⁴ may be the same or different.

X ¹ and X ² are independently an aryl group [preferably a C 6-20, preferably a substituted aryl group (for example, a substituted phenyl group, a substituted naphthyl group, a substituent of Ma ₁ to Ma ₇ as an example of a substituent, preferably And more preferably an alkyl group, an aryl group, a heterocyclic group, a halogen atom, an amino group, a hydroxyl group, an alkoxy group, an aryloxy group, an aryl group substituted with an acylamino group, and more preferably an alkyl group Represents an aryl group substituted with an amino group, a hydroxyl group, an alkoxy group or an acylamino group, and most preferably a phenyl group substituted with a dialkylamino group or a diarylamino group at the 4-position. At that time, a plurality of substituents may be linked to form a ring, and a preferred ring formed includes a julolidine ring. ], A heterocyclic group (preferably having 1 to 20 carbon atoms, preferably 3 to 8 membered ring, more preferably 5 or 6 membered ring such as pyridyl, thienyl, furyl, thiazolyl, imidazolyl, pyrazolyl, pyrrolyl, indolyl, carbazolyl, Phenothiazino, pyrrolidino, piperidino, morpholino, more preferably indolyl, carbazolyl, pyrrolyl, phenothiazino, the heterocycle may be substituted, and preferred substituents are the same as in the case of the aryl group), or the general formula (2) Represents a group represented by

In the general formula (2), R ⁵ represents a hydrogen atom or a substituent (preferred examples are the same as those of R ^{1 to} R ⁴ ), preferably a hydrogen atom or an alkyl group, and more preferably a hydrogen atom.

R ⁶ represents a hydrogen atom, an alkyl group, an alkenyl group, an aryl group, or a heterocyclic group (preferable examples of these substituents are the same as R ^{1 to} R ⁴ ), preferably an alkyl group (preferably having a C number of 1 to 6 alkyl groups).

Z ¹ represents an atomic group forming a 5- or 6-membered ring.

  The heterocycle formed is preferably an indolenine ring, azaindolenine ring, pyrazoline ring, benzothiazole ring, thiazole ring, thiazoline ring, benzoxazole ring, oxazole ring, oxazoline ring, benzimidazole ring, imidazole ring, thiadiazole ring Quinoline ring, pyridine ring, more preferably indolenine ring, azaindolenine ring, pyrazoline ring, benzothiazole ring, thiazole ring, thiazoline ring, benzoxazole ring, oxazole ring, oxazoline ring, benzimidazole ring, thiadiazole ring A quinoline ring, most preferably an indolenine ring, an azaindolenine ring, a benzothiazole ring, a benzoxazole ring, or a benzimidazole ring.

The heterocycle formed by Z ¹ may have a substituent (examples of preferred substituents are the same as examples of substituents on Za ₁ and Za ₂ ), and more preferably an alkyl group, aryl A group, a heterocyclic group, a halogen atom, a carboxyl group, a sulfo group, an alkoxy group, a carbamoyl group, and an alkoxycarbonyl group.

X ¹ and X ² are each preferably an aryl group or a group represented by the general formula (2), more preferably an aryl group substituted with a dialkylamino group or a diarylamino group at the 4-position, or a general formula (2) Represented by the group represented.

The two-photon absorption compound of the present invention preferably has a hydrogen bonding group in the molecule. Here, the hydrogen-bonding group represents a group that donates hydrogen or a group that accepts hydrogen in a hydrogen bond, and a group having both properties is more preferable. As the hydrogen bonding group of the present invention, either —COOH or —CONH ₂ is preferable.

  The two-photon absorption compound of the present invention may be used in a monomer state or in an associated state. Here, the dye chromophores are fixed in a specific spatial arrangement by a bond such as a covalent bond or a coordinate bond, or various intermolecular forces (hydrogen bond, van der Waals force, Coulomb force, etc.) This state is generally referred to as an association (or aggregation) state. From the viewpoint of the absorption wavelength of the aggregate, the aggregate whose absorption shifts to a short wavelength with respect to monomer absorption is defined as an H aggregate (the dimer is specially called a dimer), and the aggregate whose shift is shifted to a long wavelength. Called coalescence.

  The compound of the present invention may be either short wavelength (H-association) or long wavelength (J-association) or both by association, but it is more preferable to form a J-aggregate.

  Whether or not it is in an associated state can be confirmed by a change in absorption (absorption λmax, ε, absorption type) from the monomer state as described above.

  The two-photon absorption compound of the present invention has two or more chromophores that perform two-photon absorption in a molecule even when used in an intermolecular association state, and is used in a state in which they absorb two-photons in an intramolecular association state. May be.

  The intermolecular association state of a compound can be formed in various ways.

For example, in a solution system, an aqueous solution to which a matrix such as gelatin is added (for example, 0.5 wt% gelatin / compound 10 ⁻⁴ M aqueous solution), an aqueous solution to which a salt such as KCl is added (for example, KCl 5% · compound 2 × 10 ⁻³ M A method of dissolving the compound in an aqueous solution), a method of dissolving the compound in a good solvent and adding a poor solvent later (for example, DMF-water system, chloroform-toluene system, etc.) and the like.

  Examples of film systems include polymer dispersion systems, amorphous systems, crystal systems, and LB film systems.

  Furthermore, molecules can be adsorbed, chemically bonded, or self-assembled into bulk or fine particle (μm to nm size) semiconductors (eg, silver halide, titanium oxide, etc.), bulk or fine particle metals (eg, gold, silver, platinum, etc.). Inter-association states can also be formed. Spectral sensitization by cyanine dye J-associative adsorption on silver halide crystals in a color silver salt photograph utilizes this technique.

  The number of compounds involved in the intermolecular association may be two or a very large number of compounds.

  Although the preferable specific example of the two-photon absorption compound used by this invention is given to the following, this invention is not limited to these.

  Preferred examples of other two-photon absorption compounds are described in Japanese Patent Application No. 2003-284959 as a synthesis example of a two-photon absorption compound.

  As described above, the two-photon absorption optical recording material of the present invention has a two-photon absorption compound, and utilizes two-photon absorption of the two-photon absorption compound, 1) a polymerization reaction, 2) a color reaction, and 3) Latent image coloring-coloring body self-sensitized amplification coloring reaction, 4) latent image coloring-coloring body sensitized polymerization reaction, 5) orientation change of compound having intrinsic birefringence, 6) decoloring reaction, 7) foaming, Recording is preferably performed by any one of A) refractive index modulation, B) absorptance modulation, and C) emission intensity modulation.

  Accordingly, a preferred recording method 1) to 7) for causing any one of A) refractive index modulation, B) absorption rate modulation, and C) emission intensity modulation will be described next.

  Here, recording by A) refractive index modulation can be performed by any of the above methods 1) to 7). Recording by B) absorption rate modulation and C) emission intensity can be recorded by the methods 2), 3), 5) and 6).

The above recording methods will be described below.
1) Recording by polymerization reaction Preferably, it has at least a two-photon absorption compound, a polymerization initiator, a polymerizable compound and a binder, and the refractive index of the polymerizable compound and the binder is different, and by photopolymerization caused by non-resonant two-photon absorption, This is a system in which the refractive index modulation is performed by making the composition ratio of the polymerizable compound and the polymerization reaction product thereof and the binder nonuniform in the laser focus portion and the non-focus portion.

  It is preferable that either one of the polymerizable compound or the binder contains at least one aryl group, aromatic heterocyclic group, chlorine atom, bromine atom, iodine atom or sulfur atom, and the other one does not contain them.

  Preferred polymerization initiators are ketones, organic peroxides, trihalomethyl-substituted triazines, diazonium salts, diaryliodonium salts, sulfonium salts, borates, diaryl iodonium organic boron complexes, sulfonium organic boron Radical polymerization initiator (radical generator) or cationic polymerization of complex, cationic two-photon absorption compound, organic boron complex, anionic two-photon absorption compound, onium salt complex, metal arene complex, or sulfonate ester Examples include initiators (acid generators) or those having both functions.

  Specific examples of preferred polymerization initiators, polymerizable compounds, and binders include those described in Japanese Patent Application No. 2003-146527.

  An anionic polymerization and an anionic polymerization initiator (base generator) are also preferably used. In this case, specific examples include those described in Japanese Patent Application No. 2003-178083.

  When using a radical polymerization initiator, it is preferable to have an ethylenically unsaturated group such as an acryloyl group, a methacryloyl group, a styryl group, or a vinyl group as the polymerizable compound, and when using a cationic polymerization initiator or an anionic polymerization initiator. It preferably has an oxirane ring, an oxetane ring or a vinyl ether group.

  Specific examples of preferred polymerization initiators in the present invention are listed below, but the present invention is not limited thereto.

2) Recording by coloring reaction In the present invention, the coloring reaction indicates a reaction in which the shape of the absorption spectrum changes in the ultraviolet light, visible light, and infrared light regions of 200 to 2000 nm, and more preferably the absorption spectrum. In FIG. 4, a reaction in which either λmax is a longer wavelength or ε is increased, more preferably, a reaction in which both of them occur is shown. Further, it is more preferable that the color reaction occurs in a wavelength region of 200 to 1000 nm, and it is more preferable that the color reaction occurs in a wavelength region of 300 to 900 nm.

  When the recording is based on a color development reaction, preferably, the two-photon absorption compound capable of absorbing at least two photons and generating an excited state and a color reaction by electron transfer or energy transfer from the two-photon absorption compound excited state, It is preferable to include a recording component capable of recording a refractive index difference, an absorptivity difference, or a light emission intensity difference.

  Further, it is more preferable that the recording component contains a dye precursor capable of becoming a color former whose absorption has been extended from the original state by electron transfer or energy transfer from the excited state of the two-photon absorption compound.

  Here, the refractive index of the dye generally takes a high value in the region having a longer wavelength from the vicinity of the linear absorption maximum wavelength (λmax), and particularly takes a very high value in a region having a wavelength as long as 200 nm from λmax to λmax, Some dyes have high values exceeding 2 and in some cases exceeding 2.5. On the other hand, organic compounds that are not pigments such as binder polymers usually have a refractive index of about 1.4 to 1.6.

Therefore, it can be seen that coloring the dye precursor by two-photon absorption of the two-photon absorption compound can preferably form not only an absorption difference but also a large refractive index difference.
When recording using a difference in refractive index in the two-photon absorption optical recording material of the present invention, the refractive index of the dye formed from the recording component is preferably maximized in the vicinity of the laser wavelength used for reproduction.

  Further, when recording using a difference in light emission intensity, it is preferable that there is a difference in light emission intensity when the color former and the dye precursor are irradiated with light having a certain wavelength during reproduction.

As the recording component, the following combinations are preferable. About these, the example described in Japanese Patent Application No. 2003-284959 is mentioned as a specific example preferably.
i) A combination comprising at least an acid color-forming dye precursor as a dye precursor and an acid generator. A combination further containing an acid proliferating agent if necessary.

  As the acid generator, diaryl iodonium salts, sulfonium salts and sulfonic acid esters are preferable, and the above-mentioned acid generator (cationic polymerization initiator) can be preferably used.

  The color former generated from the acid color-formable dye precursor is preferably a xanthene dye, a fluorane dye or a triphenylmethane dye. Particularly preferred specific examples of the acid coloring dye precursor are listed below, but the present invention is not limited thereto.

ii) A combination including at least a base color-forming dye precursor as a dye precursor, a base generator, and, if necessary, a base proliferating agent.
As the base generator, the aforementioned base generator (anionic polymerization initiator) is preferably mentioned, and as the base color-forming dye precursor, a dissociation azo dye, a dissociation azomethine dye, a dissociation oxonol dye, a dissociation xanthene dye , Dissociated fluorane dyes, and non-dissociated isomers of dissociated triphenylmethane dyes.

  Particularly preferred specific examples of the base color-forming dye precursor are listed below, but the present invention is not limited thereto.

iii) an organic compound portion having a function of breaking a covalent bond by electron transfer or energy transfer with an excited state of a two-photon absorption compound, and an organic compound having a feature that becomes a color former when covalently bonded and released Including compounds where the moiety is covalently bonded. A combination further containing a base if necessary. Particularly preferred specific examples are listed below, but the present invention is not limited thereto.

iV) When a compound that reacts by electron transfer with an excited state of a two-photon absorption compound to change the absorption form is included. So-called electrochromic compounds can be preferably used.
3) Latent image color development—Recording by color former self-sensitized amplification color development reaction Preferably, at least a first step of producing a color image having a different absorption form from a two-photon absorption compound as a latent image by two-photon absorption exposure; The colored body is self-sensitized and amplified by irradiating the colored body latent light with light having a wavelength range where the molar absorption coefficient of linear (1-photon) absorption of the two-photon absorption compound is 5000 or less to cause linear absorption of the colored body. The two-photon absorption optical recording method has a second step of recording as a refractive index difference, an absorption difference, or a light emission intensity difference, and is preferable in terms of high-speed writing, high S / N ratio reproduction, and the like.

  Here, the “latent image” means “a refractive index difference, an absorptivity difference, or a luminescence intensity difference formed after the second step, preferably a refractive index difference, an absorptance difference, or a luminescence intensity that is preferably 1/5 or less. Difference ”(that is, preferably an amplification step of 5 times or more is performed in the second step), more preferably 1/10 or less, and even more preferably 1/30 or less of refractive index and absorption. It is a rate or emission intensity difference image (that is, an amplification step of 10 times or more, more preferably 30 times or more is performed in the second step).

  Here, the second step is preferably light irradiation, heat application, or both, more preferably light irradiation, and the light to be irradiated is the entire surface exposure (so-called solid exposure, blanket exposure, non-image). Wise exposure) is preferable.

  Preferred examples of the light source to be used include a visible light laser, an ultraviolet light laser, an infrared light laser, a carbon arc, a high pressure mercury lamp, a xenon lamp, a metal halide lamp, a fluorescent lamp, a tungsten lamp, an LED, and an organic EL. In order to irradiate light in a specific wavelength range, it is also preferable to use a sharp cut filter, a band pass filter, a diffraction grating, or the like as necessary.

Furthermore, as a two-photon absorption optical recording material capable of such a two-photon absorption optical recording method, at least,
1) a two-photon absorption compound capable of absorbing two photons and generating an excited state in the first step;
2) including a dye precursor that can be a color former that has a wavelength longer than that of the original state and has absorption in a wavelength range different from the linear absorption of the two-photon absorption compound, and from the excited state of the two-photon absorption compound or the color former Recording component that can be recorded as a difference in refractive index, a difference in absorption rate or a difference in emission intensity by electron transfer or energy transfer,
It is preferable to contain.

  Preferred examples of the recording component are the same as those described in 2) Color development reaction.

  In the wavelength range of the light irradiated in the second step, the molar absorption coefficient of linear absorption of the two-photon absorption compound is more preferably 1000 or less, and further preferably 500 or less.

  Further, in the wavelength range of the light irradiated in the second step, the molar extinction coefficient of the color former is more preferably 5000 or more, and further preferably 10,000 or more.

  The concept of “latent image color development—colored body self-sensitized amplification color reaction system” will be described below.

  For example, a two-photon absorption optical recording material is irradiated with a 780 nm laser, and a two-photon absorption compound absorbs two photons to generate an excited state. By transferring energy or electrons from the excited state of the two-photon absorption compound to the recording component, the dye precursor contained in the recording component is changed to a color former to form a latent image by color development (the first step). Next, light in a wavelength range of 680 to 740 nm is irradiated to cause linear absorption of the color former, and the color former is amplified and generated by self-sensitization of the color former (the second step). Since the latent image is not generated in the non-recorded portion where the laser is not irradiated in the first step, the self-sensitized coloring reaction hardly occurs even in the second step, and as a result, the recording portion and the non-recording portion are largely refracted. Rate modulation, absorption rate modulation, or emission intensity modulation can be formed. For example, by using a 780 nm laser again and irradiating the recorded two-photon absorption optical recording material, it becomes possible to reproduce the light by the difference in the reflectance of the light based on the large difference in refractive index between the recording part and the non-recording part. A two-photon absorption (three-dimensional) optical recording medium by recording and reproduction can be provided.

As a specific example of the latent image color development-chromogen self-sensitized amplification color development reaction, an example described in Japanese Patent Application No. 2003-300058 is preferable.
4) Latent image coloring-recording by color former-sensitized polymerization reaction Preferably, at least a first step of producing a color former as a latent image by two-photon absorption and color development by irradiating the color former latent image with light A two-photon absorption optical recording method characterized by having a second step of recording by forming a refractive index difference by causing polymerization based on linear absorption of the body, and is excellent in high-speed writing, storage stability, etc. .

  In the second step, a method in which polymerization is caused while self-sensitizing amplification production is performed is also preferable.

Furthermore, as a two-photon absorption optical recording material capable of such a two-photon absorption optical recording method, at least,
1) a two-photon absorption compound capable of absorbing two photons and generating an excited state in the first step;
2) Absorption is increased in wavelength from the original state by transferring electrons or energy from the excited state of the two-photon absorption compound in the first step or from the excited state of the color former in the second step, and two-photon absorption. A group of dye precursors capable of becoming a color former having absorption in a wavelength range of 5000 or less in the linear absorption molar absorption coefficient of the compound;
3) a polymerization initiator capable of initiating polymerization of the polymerizable compound by electron transfer or energy transfer from the excited state of the two-photon absorption compound in the first step;
4) a polymerizable compound,
5) binder,
It is preferable to contain.

  Preferred examples of the recording component are the same as those described in 2) Color development reaction.

  Preferred examples of the polymerization initiator, the polymerizable compound and the binder are the same as those described in 1) polymerization reaction.

  In the wavelength range of the light irradiated in the second step, the molar absorption coefficient of linear absorption of the two-photon absorption compound is more preferably 1000 or less, and further preferably 500 or less.

In the wavelength range of the light irradiated in the second step, the molar extinction coefficient of the color former is more preferably 5000 or more, and further preferably 10,000 or more. The two-photon absorption optical recording method of the present invention and In the two-photon absorption optical recording material capable of such recording, the two-photon absorption dye is formed by either the first step, the second step, or the fixing step by subsequent light irradiation, heat application, or both. It is preferable to decompose and fix in terms of storage stability and nondestructive regeneration, and further, either the first step, the second step, or the subsequent fixing step by light irradiation, heat application, or both More preferably, the two-photon absorbing dye is decomposed and fixed by either the second step or the fixing step by the subsequent light irradiation, heat application, or both.

The concept of “latent image color development-colored material sensitized polymerization reaction method” will be described below.
For example, a two-photon absorption optical recording material is irradiated with a 780 nm laser, and the two-photon absorption compound absorbs the two-photon absorption optical recording material to generate an excited state. By transferring energy or electrons from the excited state of the two-photon absorption compound to the dye precursor group, the dye precursor contained in the dye precursor group is changed to a color former to form a latent image by color development (the first is described above). Process). Next, irradiation with a laser beam of 780 nm causes linear absorption of the color former, and the polymerization initiator is activated by electron transfer or energy transfer to initiate polymerization. For example, when the refractive index of the polymerizable compound is larger than that of the binder, the refractive index increases because the polymerizable compound gathers at the portion where the polymerization occurs (second step). In the first step, a latent image is not generated in the unrecorded portion that has not been irradiated with the laser. Therefore, polymerization does not occur so much in the second step, and the abundance ratio of the binder is increased. Thus, refractive index modulation can be formed. Provided a two-photon absorption optical recording material that is excellent in non-destructive reproduction and storability and is colorless and transparent if the two-photon absorption compound and the colored body can be decomposed and decolored by the first and second steps or further fixing step. can do.

For example, when a 780 nm laser is used again to irradiate a recorded two-photon absorption optical recording material, reproduction is possible due to the difference in the reflectance of light based on the difference in refractive index between the recording part and the non-recording part. In this case where a (three-dimensional) optical recording medium can be provided, a 780 nm laser can be used for recording in the first step, photopolymerization amplification in the second step, and reproduction.

Preferable examples of the latent image color development-colored material sensitized polymerization reaction include those described in Japanese Patent Application No. 2003-31744.
5) Recording by changing the orientation of a compound having an intrinsic birefringence Preferably, the orientation of a compound having an intrinsic birefringence is changed by two-photon absorption, and the compound is refracted in a manner that cannot be rewritten by fixing it by a chemical reaction. This is a method of recording as rate modulation. As the compound having an intrinsic birefringence, a liquid crystal compound is preferable, a low molecular liquid crystal compound is more preferable, and a low molecular liquid crystal compound having a polymerizable group is further preferable. Preferable examples include the examples described in Japanese Patent Application No. 2003-327594.
6) Recording by decoloring reaction Preferably, there is a method of decoloring a two-photon absorption compound by two-photon absorption in a recording part by the following method i) or ii).
i) a two-photon absorption optical recording material in which the two-photon absorption compound erases itself by two-photon absorption in the recording unit;
ii) At least a two-photon absorption compound and a decolorant precursor different from the two-photon absorption compound, and after the two-photon absorption compound generates an excited state by two-photon absorption, the decolorant precursor and energy transfer Or a two-photon absorption optical recording material in which a decolorant is generated from the decolorizer precursor by electron transfer, and the decolorizer decolors the two-photon absorption compound,
In this case, the decolorizer precursor is preferably a radical generator, acid generator, base generator, nucleophile generator, electrophile generator, triplet oxygen, particularly a radical generator, An acid generator and a base generator are preferable, and in this case, the examples given in 1) Polymerization reaction are preferably used.

Specific examples of the decoloring method, decoloring agent precursor, decoloring agent and the like of i) and ii) preferably include the examples described in Japanese Patent Application No. 2003-276684.
7) Recording by foaming Preferably, there is a method in which foaming is caused by two-photon absorption in the recording part by the following method i) or ii).
i) a two-photon absorption optical recording material having a two-photon absorption compound having at least a foamable portion, and being excited by two-photon absorption so that the foamable portion generates a gas to create bubbles; ii) at least two The photon-absorbing compound and the two-photon-absorbing compound have different foamable compounds, and the two-photon-absorbing compound generates an excited state by two-photon absorption, and then expands by transferring energy or electrons to the foamable compound. Examples include a two-photon absorption optical recording material in which a compound generates gas to create bubbles.

At that time, the gas generated from the foamable portion of i) or the foamable compound of ii) is any of N ₂ , CO ₂ , SO ₂ , SO ₃ , NO ₂ , O ₂ , and iC ₄ H _8. preferable.

  Specific examples of the foaming method, foamable site and foamable compound of i) and ii) are preferably the examples described in Japanese Patent Application No. 2003-274096.

  In addition to the sensitizing dye, interference fringe recording component, polymerization initiator, polymerizable compound, binder and the like as described above, the two-photon absorption optical recording material of the present invention further comprises an electron donating compound, an electron accepting agent as necessary. Additives such as a chemical compound, a chain transfer agent, a crosslinking agent, a heat stabilizer, a plasticizer, and a solvent can be used.

  The electron-donating compound has the ability to reduce the radical cation of the two-photon absorption compound or color former, and the electron-accepting compound has the ability to oxidize the radical anion of the two-photon absorption compound or color former. It has a function of regenerating a compound or color former. Specifically, for example, the example described in Japanese Patent Application No. 2003-284959 is mentioned as a preferable example.

  As specific examples of the chain transfer agent, the crosslinking agent, the heat stabilizer, the plasticizer, the solvent and the like, examples described in Japanese Patent Application No. 2003-146527 can be given.

[Example]
Specific examples of the present invention will be described below. Of course, the present invention is not limited to these examples.

<Preparation of coating solution for two-photon optical recording medium>
A spin coat coating solution having the following composition was prepared.
Two-photon absorption compound: D-104 1 part by weight acid generator: I-5 8 parts by weight acid coloring dye precursor: L-4 7 parts by weight Binder: poly (methyl methacrylate-co-ethyl acrylate) (manufactured by Aldrich) (Average molecular weight 101,000) 84 parts by mass Solvent: 4 times mass of chloroform component <Preparation of two-photon optical recording medium>
Silver is deposited by sputtering on the guide groove side surface of a polycarbonate substrate (diameter: 120 mm, thickness: 0.6 mm) on which concentric guide grooves having wobbles (track pitch: 1.6 μm) are formed by injection molding. Further, the above coating solution was applied on the upper surface by spin coating to produce a two-photon optical recording medium having a recording layer (thickness: about 20 μm).
<Information recording by two-photon absorption>
When recording information by using a Ti: sapphirere laser with a wavelength of 780 nm (pulse width 100 fs, repetition rate 80 MHz, average output 1 W) to induce a color reaction by two-photon absorption to develop a blue dye, along the guide groove Information recording can be performed. Further, when the written information is read out by irradiating with 660 nm laser light, the information can be read out well along the guide groove.

Claims (21)

  A two-photon three-dimensional optical recording medium in which a plurality of recording planes on which information can be recorded is laminated inside a three-dimensional space inside the recording medium, and position information for specifying the position inside the three-dimensional space A three-dimensional optical recording medium characterized by having the inside of the medium.   2. The three-dimensional light according to claim 1, comprising two-dimensional position information in the recording plane and position information for specifying an arbitrary recording plane in the laminated recording plane. recoding media.   3. The three-dimensional optical recording according to claim 1 or 2, wherein a concentric structure having optical characteristics different from the surroundings is used as a mark for specifying two-dimensional position information in the recording plane. Medium.   3. The three-dimensional optical recording according to claim 1 or 2, wherein a spiral structure having optical characteristics different from the surroundings is used as a mark for specifying an arbitrary recording plane in the recording plane formed by laminating. Medium.   The three-dimensional optical recording medium according to claim 3 or 4, wherein the concentric structure and the spiral structure have undulations of an arbitrary frequency.   6. The three-dimensional optical recording medium according to claim 1, wherein the concentric structure is provided in the recording medium or on a substrate surface.   2. A recording layer comprising a plurality of recording planes, wherein one or a plurality of the helical structures are provided at a central portion, a terminal portion, or an arbitrary position from the central portion to the terminal portion. A three-dimensional optical recording medium according to any one of?   8. An optical information recording method, wherein information is recorded three-dimensionally on the three-dimensional optical recording medium according to claim 1 on the basis of the position information.   9. The optical information recording method according to claim 8, further comprising a step of forming the helical structure prior to information recording.   A three-dimensional optical information recording apparatus for recording information on the three-dimensional optical recording medium according to any one of claims 1 to 7, using the method according to claim 8 or 9.   The three-dimensional optical recording medium according to claim 1, wherein the medium includes a two-photon absorption compound, and refractive index modulation or absorptance modulation is performed using two-photon absorption of the two-photon absorption compound. A two-photon absorption optical recording / reproducing method comprising: reproducing after recording by irradiating a recording material with light and detecting a difference in reflectance.   The two-photon absorption optical recording material having the two-photon absorption compound as the three-dimensional optical recording medium is recorded by light emission modulation using the two-photon absorption of the two-photon absorption compound, and then the recording material is irradiated with light. Then, the two-photon absorption optical recording / reproducing method is characterized in that reproduction is performed by detecting the difference in emission intensity.   The three-dimensional optical recording medium has a two-photon absorption compound and uses the two-photon absorption of the two-photon absorption compound to 1) polymerization reaction, 2) color development reaction, 3) latent image color development-chromogen self-sensitized amplification Coloring reaction, 4) Latent image coloring-coloring body sensitized polymerization reaction, 5) Orientation change of compound having intrinsic birefringence, 6) Decoloring reaction, 7) Foaming, A) Refractive index 8. The three-dimensional optical recording medium according to claim 1, wherein recording is performed by causing any one of modulation, B) absorption rate modulation, and C) light emission ability modulation. A three-dimensional optical recording medium comprising the two-photon absorption compound according to claim 11 or 12.   15. The three-dimensional optical recording medium according to claim 14, wherein the recording using the two-photon absorption of the two-photon absorption compound is a method that cannot be rewritten. The three-dimensional optical recording medium according to claim 14 or 15, wherein the two-photon absorption compound is represented by a cyanine dye, a merocyanine dye, an oxonol dye, a phthalocyanine dye, an azo dye, or the following general formula (1). .
General formula (1)

In the formula, R ¹ , R ² , R ³ and R ⁴ each independently represent a hydrogen atom or a substituent, and some of R ¹ , R ² , R ³ and R ⁴ are bonded to each other to form a ring. May be formed. n and m each independently represent an integer of 0 to 4, and when n and m are 2 or more, a plurality of R ¹ , R ² , R ³ and R ⁴ may be the same or different. However, n and m are not 0 simultaneously. X ¹ and X ² independently represent an aryl group, a heterocyclic group, or a group represented by General Formula (2).
General formula (2)

In the formula, R ⁵ represents a hydrogen atom or a substituent, R ⁶ represents a hydrogen atom, an alkyl group, an alkenyl group, an aryl group, or a heterocyclic group, and Z ¹ represents an atomic group forming a 5- or 6-membered ring. . The cyanine dye according to claim 16, wherein the cyanine dye is represented by the following general formula (3), the merocyanine dye is represented by the following general formula (4), and the oxonol dye is represented by the general formula (5). Three-dimensional optical recording medium.

In the general formulas (3) to (5), Za ₁ , Za ₂ and Za ₃ each represent an atomic group forming a 5-membered or 6-membered nitrogen-containing heterocycle, and Za ₄ , Za ₅ and Za ₆ are each 5 A group of atoms forming a member or six-membered ring is represented. Ra ₁ , Ra ₂ and Ra ₃ each independently represent a hydrogen atom, an alkyl group, an alkenyl group, an aryl group or a heterocyclic group.
Ma _{1 to} Ma ₁₄ each independently represent a methine group, may have a substituent, and may form a ring with another methine group. na ¹ , na ² and na ³ are each 0 or 1, and ka ¹ and ka ³ each represents an integer of 0 to 3. When ka ¹ is 2 or more, the plurality of Ma ₃ and Ma ₄ may be the same or different. When ka ³ is 2 or more, the plurality of Ma ₁₂ and Ma ₁₃ may be the same or different. ka ² represents an integer of 0 to 8, and when ka ² is 2 or more, a plurality of Ma ₁₀ and Ma ₁₁ may be the same or different.
CI represents an ion that neutralizes the electric charge, and y represents a number necessary for neutralizing the electric charge.   A two-photon absorption three-dimensional optical recording / reproducing method comprising the two-photon absorption optical recording / reproducing method according to claim 11 or 12.   A two-photon absorption three-dimensional optical recording medium comprising the three-dimensional optical recording medium according to claim 14.   19. A two-photon absorption three-dimensional optical recording medium, wherein the three-dimensional optical recording medium according to claim 13 is stored in a light shielding cartridge during storage. Induced by irradiating the two-photon three-dimensional optical recording medium according to any one of claims 13 to 19 with a laser beam having a wavelength longer than the linear absorption band of the two-photon absorption compound and having a linear absorption molar absorption coefficient of 10 or less. A two-photon absorption optical recording method, wherein recording is performed using the two-photon absorption performed.