JP2010195917A - Photopolymerizable composition, optical recording medium, and information recording method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a means for realizing optical recording of high sensitivity and of super-high density. <P>SOLUTION: The photopolymerizable composition includes a radically polymerizable compound represented by general formula (I), a non-resonating two-photon absorption compound, and a binder, wherein R<SP>1</SP>is a hydrogen atom or alkyl, Z<SP>1</SP>is an atomic group forming a ring structure combining adjacently with a carbon atom, a sulfur atom, and a carbon atom combined with the sulfur atom. The photo-recording medium has a recording layer including the photopolymerizable composition, and the information recording method is made on the photo-recording medium. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

The present invention relates to a photopolymerizable composition capable of photopolymerization by two-photon absorption, and more particularly to a photopolymerizable composition capable of radical polymerization utilizing non-resonant two-photon absorption.
Furthermore, the present invention relates to an optical recording medium capable of three-dimensional refractive index modulation and a method for recording information on the optical recording medium.

  2. Description of the Related Art Conventionally, optical information recording media (optical discs) capable of recording information only once with a laser beam are known, such as a write-once CD (so-called CD-R) and a write-once DVD (so-called DVD-R). It has been put into practical use.

  Recently, with the start of digital broadcasting and the spread of Blu-ray discs, the demand for large-capacity recording media is increasing in consumer applications. Furthermore, in computer backup applications, broadcast backup applications, and business applications, there is a demand for optical recording media capable of recording large-capacity information of 1 TB or more at a high speed and at a low cost. Under such circumstances, a conventional two-dimensional optical recording medium such as a DVD-R has a recording capacity of about 25 GB on one side even if the recording / reproducing wavelength is shortened on the physical principle, and can meet future requirements. It cannot be said that a sufficiently large recording capacity can be expected.

  Under such circumstances, a three-dimensional optical recording medium is attracting 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.

In recent years, a method using two-photon absorption has been proposed as a three-dimensional optical recording method. Two-photon absorption is a phenomenon in which a compound is excited by simultaneously absorbing two photons. Among the two-photon absorption, the two-photon absorption occurring in the energy region where the linear absorption band of the compound does not exist is called non-resonant two-photon absorption. 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 inducing non-resonant two-photon absorption, a short-pulse laser in the near-infrared region, which is longer than the wavelength region in which the (linear) absorption band of the compound exists and does not have absorption, is often used. The so-called transparent near-infrared light is used, so that the excitation light can reach the inside of the sample without being absorbed or scattered, and because of the square characteristic of non-resonant two-photon absorption, one point inside the sample has an extremely high spatial resolution. Can be excited.
Therefore, if information recording and polymerization can be performed using excitation energy obtained by non-resonant two-photon absorption, polymerization can be performed in an arbitrary place in a three-dimensional space. Application to a three-dimensional optical recording medium, a fine three-dimensional optical modeling material, and the like is also possible. For example, Non-Patent Documents 1 to 5 propose applying two-photon polymerization based on non-resonant two-photon absorption to optical modeling.

  However, in the methods described in Non-Patent Documents 1 to 5, since a highly efficient two-photon absorption compound and an appropriate polymerization initiator are not used, the efficiency of polymerization is poor. Therefore, these methods must be irradiated with a strong laser beam for a long time in order to perform optical modeling or the like by polymerization, and it is considered practically difficult to use for optical recording.

  On the other hand, the applicant of the present invention uses the non-resonant two-photon absorption compound and the polymerization initiator in combination to cause polymerization using the excitation energy obtained by non-resonant two-photon absorption. It has been found that three-dimensional optical recording is possible by causing refractive index modulation three-dimensionally in the part (see Patent Document 1).

JP 2004-346238 A

Nature. 1999, 398, 51 J. Phys. Org. Chem. 2000, 13, 837 Chem. Phys. Lett. 2001, 340, 444 J. Am. Chem. Soc. 2000, 122, 1217 Oppt. Lett. 1997, 22, p. 132

  The method described in Patent Document 1 can cause refractive index modulation with an extremely high spatial resolution in an arbitrary place in a three-dimensional space, thereby realizing a three-dimensional optical recording medium considered as the ultimate high-density recording medium. Although it is an excellent method that can be performed, it is not necessarily sufficient from the viewpoint of recording sensitivity, and further improvement is required.

  Therefore, an object of the present invention is to provide means for realizing high sensitivity and ultra high density optical recording.

  As a result of intensive studies to achieve the above object, the present inventors have achieved high sensitivity by using a cyclic allyl sulfide compound represented by the following general formula (I) together with a non-resonant two-photon absorption compound. The inventors have found that a three-dimensional optical recording medium capable of recording can be provided, and have completed the present invention.

[一般式(I)中、Ｒ¹は水素原子またはアルキル基を表し、Ｚ¹は隣り合う炭素原子、硫黄原子および該硫黄原子と結合する炭素原子とともに環構造を形成する原子団を表す。]
[２]光記録用重合性組成物である[１]に記載の光重合性組成物。
[３]一般式(I)で表されるラジカル重合性化合物は、下記一般式(II)で表される化合物である[１]または[２]に記載の光重合性組成物。

［一般式(II)中、Ｒ¹は一般式(I)における定義と同義であり、Ｒ¹²は水素原子またはアルキル基を表し、Ｒ¹³、Ｒ¹⁴およびＲ¹⁵はそれぞれ独立に水素原子、アルキル基、アリール基、ヘテロ環基、アルコキシ基、アリールオキシ基、アルキルチオ基、アリールチオ基、アルコキシカルボニル基、アリールオキシカルボニル基、アシルオキシ基、アシルアミノ基、スルホニルアミノ基、アミノ基、アシル基またはハロゲン基を表し、ｍ１は０または１を表す。］
[４]一般式(II)中、Ｒ¹およびＲ¹²は、それぞれ独立に水素原子またはメチル基を表し、Ｒ¹³、Ｒ¹⁴およびＲ¹⁵は、それぞれ独立に水素原子、アルキル基、アリール基、アルコキシ基、アリールオキシ基、アルコキシカルボニル基、アリールオキシカルボニル基、アシルオキシ基、アシルアミノ基、アミノ基またはアシル基を表す[３]に記載の光重合性組成物。
[５]一般式（II）中、Ｒ¹およびＲ¹²はいずれも水素原子を表し、Ｒ¹³、Ｒ¹⁴およびＲ¹⁵は、それぞれ独立に水素原子、アルキル基、アリール基、アルコキシ基、アリールオキシ基またはアシルオキシ基を表し、ｍ１は１を表す[３]に記載の光重合性組成物。
[６]一般式(I)で表されるラジカル重合性化合物は、下記一般式(III)で表される化合物である[１]または[２]に記載の光重合性組成物。

［一般式(II)中、Ｒ¹は一般式(I)における定義と同義であり、Ｒ²³、Ｒ²⁴およびＲ²⁵は、それぞれ独立に水素原子、アルキル基、アリール基、ヘテロ環基、アルコキシ基、アリールオキシ基、アルキルチオ基、アリールチオ基、アルコキシカルボニル基、アリールオキシカルボニル基、アシルオキシ基、アシルアミノ基、スルホニルアミノ基、アミノ基、アシル基またはハロゲン基を表し、ｍ２は０または１を表す。］
[７]一般式(III)中、Ｒ¹は水素原子またはメチル基を表し、Ｒ²³、Ｒ²⁴およびＲ² ₅は、それぞれ独立に水素原子、アルキル基、アリール基、アルコキシ基、アリールオキシ基、アルコキシカルボニル基、アリールオキシカルボニル基、アシルオキシ基、アシルアミノ基、アミノ基またはアシル基を表す[６]に記載の光重合性組成物。
[８]一般式（III）中、Ｒ¹は水素原子またはメチル基を表し、Ｒ²³、Ｒ²⁴およびＲ²⁵は、それぞれ独立に水素原子、アルキル基、アリール基、アルコキシ基、アリールオキシ基またはアシルオキシ基を表し、ｍ２は０を表す[６]に記載の光重合性組成物。
[９]ラジカル重合開始剤を更に含有する[１]〜[８]のいずれかに記載の光重合性組成物。
[１０]前記バインダーは、前記ラジカル重合性化合物とは異なる屈折率を有する[１]〜[９]のいずれかに記載の光重合性組成物。
[１１]前記バインダーは、前記ラジカル重合性化合物よりも低屈折率を有する[１０]に記載の光重合性組成物。
[１２]前記バインダーは、セルロースエステル、ポリビニルアルコール、ポリビニルアセテート、ポリビニルブチラール、ポリビニルホルマール、ポリウレタン、およびフッ素原子含有高分子からなる群から選ばれる少なくとも一つのポリマーである[１]〜[１１]のいずれかに記載の光重合性組成物。
[１３]前記非共鳴２光子吸収化合物は、有機色素である[１]〜[１２]のいずれかに記載の光重合性組成物。
[１４]前記有機色素は、シアニン色素、メロシアニン色素、オキソノール色素およびポリアリール色素からなる群から選ばれる少なくとも一種である[１３]に記載の光重合性組成物。
[１５][１]〜[１４]のいずれかに記載の光重合性組成物を含む記録層を有することを特徴とする光記録媒体。
[１６][１５]に記載の光記録媒体へ光照射することにより情報を記録する情報記録方法であって、
前記照射する光として、前記非共鳴２光子吸収化合物の線形吸収の存在しない波長であって、かつ該化合物の線形吸収帯よりも長波長域の波長のレーザー光を使用することを特徴とする情報記録方法。
[１７]前記光照射により、前記記録層中に屈折率変調を起こすことによって情報を記録する[１６]に記載の情報記録方法。
[１８]前記屈折率変調は、３次元的屈折率変調である[１７]に記載の情報記録方法。 That is, the above object was achieved by the following means.
[1] A photopolymerizable composition comprising a radical polymerizable compound represented by the following general formula (I), a non-resonant two-photon absorption compound, and a binder.

[In the general formula (I), R ¹ represents a hydrogen atom or an alkyl group, and Z ¹ represents an atomic group forming a ring structure with adjacent carbon atoms, sulfur atoms, and carbon atoms bonded to the sulfur atoms. ]
[2] The photopolymerizable composition according to [1], which is a polymerizable composition for optical recording.
[3] The photopolymerizable composition according to [1] or [2], wherein the radical polymerizable compound represented by the general formula (I) is a compound represented by the following general formula (II).

[In the general formula (II), R ¹ is defined as in general formula (I), R ¹² represents a hydrogen atom or an alkyl group, R ^13, R ¹⁴ and R ¹⁵ each independently represent a hydrogen atom, an alkyl Group, aryl group, heterocyclic group, alkoxy group, aryloxy group, alkylthio group, arylthio group, alkoxycarbonyl group, aryloxycarbonyl group, acyloxy group, acylamino group, sulfonylamino group, amino group, acyl group or halogen group M1 represents 0 or 1. ]
[4] In general formula (II), R ¹ and R ¹² each independently represent a hydrogen atom or a methyl group, and R ¹³ , R ¹⁴ and R ¹⁵ each independently represent a hydrogen atom, an alkyl group, an aryl group, The photopolymerizable composition according to [3], which represents an alkoxy group, an aryloxy group, an alkoxycarbonyl group, an aryloxycarbonyl group, an acyloxy group, an acylamino group, an amino group, or an acyl group.
[5] In general formula (II), each of R ¹ and R ¹² represents a hydrogen atom, and R ¹³ , R ¹⁴ and R ¹⁵ are each independently a hydrogen atom, alkyl group, aryl group, alkoxy group, aryloxy The photopolymerizable composition according to [3], which represents a group or an acyloxy group, and m1 represents 1.
[6] The photopolymerizable composition according to [1] or [2], wherein the radical polymerizable compound represented by the general formula (I) is a compound represented by the following general formula (III).

[In general formula (II), R ¹ has the same definition as in general formula (I), and R ²³ , R ²⁴ and R ²⁵ each independently represents a hydrogen atom, an alkyl group, an aryl group, a heterocyclic group, an alkoxy group. A group, an aryloxy group, an alkylthio group, an arylthio group, an alkoxycarbonyl group, an aryloxycarbonyl group, an acyloxy group, an acylamino group, a sulfonylamino group, an amino group, an acyl group, or a halogen group, and m2 represents 0 or 1. ]
[7] In the general formula (III), R ¹ represents a hydrogen atom or a methyl group, R ^23, R ²⁴ and R ² ₅ are each independently a hydrogen atom, an alkyl group, an aryl group, an alkoxy group, an aryloxy group The photopolymerizable composition according to [6], which represents an alkoxycarbonyl group, an aryloxycarbonyl group, an acyloxy group, an acylamino group, an amino group, or an acyl group.
[8] In general formula (III), R ¹ represents a hydrogen atom or a methyl group, and R ²³ , R ²⁴ and R ²⁵ are each independently a hydrogen atom, an alkyl group, an aryl group, an alkoxy group, an aryloxy group or The photopolymerizable composition according to [6], which represents an acyloxy group and m2 represents 0.
[9] The photopolymerizable composition according to any one of [1] to [8], further containing a radical polymerization initiator.
[10] The photopolymerizable composition according to any one of [1] to [9], wherein the binder has a refractive index different from that of the radical polymerizable compound.
[11] The photopolymerizable composition according to [10], wherein the binder has a lower refractive index than the radically polymerizable compound.
[12] The binder according to [1] to [11], wherein the binder is at least one polymer selected from the group consisting of cellulose ester, polyvinyl alcohol, polyvinyl acetate, polyvinyl butyral, polyvinyl formal, polyurethane, and a fluorine atom-containing polymer. The photopolymerizable composition in any one.
[13] The photopolymerizable composition according to any one of [1] to [12], wherein the non-resonant two-photon absorption compound is an organic dye.
[14] The photopolymerizable composition according to [13], wherein the organic dye is at least one selected from the group consisting of a cyanine dye, a merocyanine dye, an oxonol dye, and a polyaryl dye.
[15] An optical recording medium comprising a recording layer containing the photopolymerizable composition according to any one of [1] to [14].
[16] An information recording method for recording information by irradiating the optical recording medium according to [15] with light,
As the light to be irradiated, laser light having a wavelength at which linear absorption of the non-resonant two-photon absorption compound does not exist and having a wavelength longer than the linear absorption band of the compound is used. Recording method.
[17] The information recording method according to [16], wherein information is recorded by causing refractive index modulation in the recording layer by the light irradiation.
[18] The information recording method according to [17], wherein the refractive index modulation is three-dimensional refractive index modulation.

The photopolymerizable composition of the present invention can three-dimensionally modulate the refractive index at the laser focus portion (recording portion) and the non-focus portion (non-recording portion), and as a result, reflectivity or transmission of light. Since the rate can be changed, application to a three-dimensional optical recording medium is possible.
Furthermore, according to the present invention, a three-dimensional optical recording medium capable of high sensitivity recording can be provided.

[Photopolymerizable composition]
The photopolymerizable composition of the present invention contains a radically polymerizable compound (cyclic allyl sulfide compound) represented by the following general formula (I), a non-resonant two-photon absorption compound, and a binder, and is optionally a radical. Components such as a polymerization initiator, a chain transfer agent, a heat stabilizer, a plasticizer, and a solvent can be included. In the photopolymerizable composition of the present invention, the non-resonant two-photon absorption compound causes non-resonant two-photon absorption when irradiated with light. The radical polymerizable compound can be produced by the action of a non-resonant two-photon absorption compound serving as a polymerization initiator, or by the action of a radical polymerization initiator that generates radical species by interaction with the non-resonant two-photon absorption compound. Polymerization can occur.

A two-photon absorption compound is a compound that is excited by simultaneously absorbing two photons, and a non-resonant two-photon absorption compound is a two-photon absorption compound in an energy region where there is no linear absorption band of the compound. It is a compound that causes photon absorption (such two-photon absorption is referred to as “non-resonant two-photon absorption”). As described above, the non-resonant two-photon absorption compound can be excited only at one point in the space due to the square characteristic of two-photon absorption. Therefore, by using the excitation energy of the non-resonant two-photon absorption compound, polymerization can occur at an arbitrary place in the three-dimensional space. The photopolymerizable composition of the present invention realizes high sensitivity of three-dimensional optical recording by combining a non-resonant two-photon absorption compound having the above characteristics with a radical polymerizable compound represented by the general formula (I). can do. The cyclic allyl sulfide compound represented by the general formula (I) has a growth radical as an S radical and a hydrogen at the α position of the S atom (hydrogen of the adjacent carbon), so that it can be seen in a thiolene reaction. It has the characteristic that it is not subject to oxygen polymerization inhibition. Therefore, the polymerization reaction is more likely to proceed even in the presence of oxygen or in the presence of dissolved oxygen than methacrylate and acrylate monomers, which are general-purpose radical polymerizable monomers. When an optical recording medium is constructed, dissolved oxygen may also be present in the recording layer. Therefore, when a general-purpose monomer is used, it is subject to some degree of polymerization inhibition. On the other hand, when the cyclic allyl sulfide represented by the general formula (I) is used as a monomer, the polymerization is not hindered, so that recording can be performed with high sensitivity.
As described above, the photopolymerizable composition of the present invention enables highly sensitive three-dimensional optical recording.
Hereinafter, the photopolymerizable composition of the present invention will be described in more detail.

Radical Polymerizable Compound The photopolymerizable composition of the present invention contains a radical polymerizable compound represented by the following general formula (I).

  Hereinafter, the cyclic allyl sulfide compound represented by the general formula (I) will be described.

In the general formula (I), Z ¹ represents an atomic group that forms a ring structure with adjacent carbon atoms, sulfur atoms, and carbon atoms bonded to the sulfur atoms. Examples of the cyclic structure formed by Z ¹ include methylene carbon. In addition to methylene carbon, divalent organic linking groups such as a carbonyl group, a thiocarbonyl group, an oxygen atom, and a sulfur atom are also exemplified. These ring structures are constituted by a combination thereof. The number of ring members is preferably 6 to 9, more preferably 6 to 8, and particularly preferably 7 to 8. Moreover, it is preferable that methylene carbon number of the ring structure is 3-7, It is more preferable that it is 4-6, It is especially preferable that it is 4-5.

In the general formula (I), R ¹ represents a hydrogen atom or an alkyl group. The alkyl group represented by R ¹ may be linear or branched, and may be unsubstituted or may have a substituent. The number of carbon atoms is preferably 1-20, more preferably 1-10, and particularly preferably 1-3. In the present invention, the “carbon number” for a certain group means the carbon number of the portion not containing the substituent for the group having a substituent.

Examples of the alkyl group represented by R ¹ include a methyl group, an ethyl group, a normal propyl group, an isopropyl group, a normal butyl group, an isobutyl group, a tertiary butyl group, a pentyl group, a cyclopentyl group, a hexyl group, a cyclohexyl group, Examples include heptyl group, octyl group, tertiary octyl group, 2-ethylhexyl group, decyl group, dodecyl group, octadecyl group, 2,3-dibromopropyl group, adamantyl group, benzyl group and 4-bromobenzyl group. These may further have a substituent.

In the general formula (I), when the group represented by R ¹ further has a substituent, examples of the substituent include a halogen atom, an alkyl group, an alkenyl group, an alkoxy group, an aryloxy, an alkylthio group, an alkoxycarbonyl group, an aryl Examples thereof include an oxycarbonyl group, an amino group, an acyl group, an alkylaminocarbonyl group, an arylaminocarbonyl group, a sulfonamide group, a cyano group, a carboxy group, a hydroxyl group, and a sulfonic acid group. Among these, a halogen atom, an alkoxy group, and an alkylthio group are particularly preferable. Further, when the cyclic allyl sulfide compound of the general formula (I) is substituted as a substituent, it represents a polyfunctional compound.

In general formula (I), R ¹ represents a hydrogen atom or an alkyl group, and the number of ring members of the ring structure formed together with the carbon atom adjacent to Z ¹ , the sulfur atom, and the carbon atom bonded to the sulfur atom is 6 to 9 and the atomic group represented by Z ¹ preferably contains a carbonyl group, an oxygen atom or a sulfur atom, or a combination thereof in addition to methylene carbon, and R ¹ represents a hydrogen atom or an alkyl group. And the number of ring members of the ring structure formed together with the carbon atom adjacent to Z ¹ , the sulfur atom and the carbon atom bonded to the sulfur atom is 6-8, and the atomic group represented by Z ¹ is methylene carbon It is more preferable that it contains a combination of a carbonyl group and an oxygen atom, or a sulfur atom, R ¹ represents a hydrogen atom or an alkyl group, and a carbon atom adjacent to Z ¹ , a sulfur atom, and It is particularly preferable that the ring structure formed together with the carbon atom bonded to the sulfur atom has 7 to 8 ring members and the atomic group represented by Z ¹ contains a sulfur atom in addition to methylene carbon. The compound represented by the general formula (I) is preferably a compound represented by the general formula (II) or the general formula (III) from the viewpoint of recording characteristics, and is represented by the general formula (II). Particularly preferred is a compound.
Below, the compound represented by general formula (II) and the compound represented by general formula (III) are demonstrated.

Cyclic allyl sulfide compound represented by general formula (II)

In general formula (II), R ¹ has the same definition as in general formula (I), R ¹² represents a hydrogen atom or an alkyl group, and R ¹³ , R ¹⁴ and R ¹⁵ each independently represent a hydrogen atom or an alkyl group. , Aryl group, heterocyclic group, alkoxy group, aryloxy group, alkylthio group, arylthio group, alkoxycarbonyl group, aryloxycarbonyl group, acyloxy group, acylamino group, sulfonylamino group, amino group, acyl group or halogen group , M1 represents 0 or 1.

In the general formula (II), the details of the alkyl group represented by R ¹ , R ¹² , R ¹³ , R ¹⁴ , R ¹⁵ are the same as those described above for the alkyl group in the general formula (I).

In the general formula (II), the aryl group represented by R ¹³ , R ¹⁴ , and R ¹⁵ may be unsubstituted or may have a substituent. The carbon number is preferably 6 to 30, and particularly preferably 6 to 20. Specific examples of the aryl group include a phenyl group, a naphthyl group, and an anthranyl group. These may further have a substituent.

In general formula (II), the heterocyclic group represented by R ¹³ , R ¹⁴ , or R ¹⁵ is preferably a heterocyclic group having 4 to ¹⁴ carbon atoms, and is a heterocyclic group having 4 to 10 carbon atoms. It is more preferable that the heterocyclic group has 5 carbon atoms. Specific examples of the heterocyclic group represented by R ¹³ , R ¹⁴ and R ¹⁵ include a pyridine ring, piperazine ring, thiophene ring, pyrrole ring, imidazole ring, oxazole ring and thiazole ring. These may further have a substituent. Of the heterocycles, a pyridine ring is particularly preferred.

In general formula (II), the alkoxy group represented by R ¹³ , R ¹⁴ , or R ¹⁵ may be linear or branched, and may be unsubstituted or substituted. You may do it. The carbon number is preferably 1-30, and more preferably 1-20. Examples of such alkoxy groups include methoxy, ethoxy, normal propyloxy, isopropyloxy, normal butyloxy, isobutyloxy, tertiary butyloxy, pentyloxy, cyclopentyloxy, hexyloxy. Group, cyclohexyloxy group, heptyloxy group, octyloxy group, tertiary octyloxy group, 2-ethylhexyloxy group, decyloxy group, dodecyloxy group, octadecyloxy group, 2,3-dibromopropyloxy group, adamantyloxy group, Examples include benzyloxy group and 4-bromobenzyloxy group.

In general formula (II), the aryloxy groups represented by R ¹³ , R ¹⁴ , and R ¹⁵ may be unsubstituted or have a substituent. The carbon number is preferably 6 to 30, and particularly preferably 6 to 20. Specific examples include a phenyloxy group, a naphthyloxy group, an anthranyloxy group, and the like.

In formula (II), an alkylthio group represented by R ^13, R ^14, R ^15, which may be branched may be linear, also may be unsubstituted have a substituent You may do it. The carbon number is preferably 1-30, and more preferably 1-20. Examples of such an alkylthio group include a methylthio group, an ethylthio group, a normal propylthio group, an isopropylthio group, a normal butylthio group, an isobutylthio group, a tertiary butylthio group, a pentylthio group, a cyclopentylthio group, a hexylthio group, Cyclohexylthio group, heptylthio group, octylthio group, tertiary octylthio group, 2-ethylhexylthio group, decylthio group, dodecylthio group, octadecylthio group, 2,3-dibromopropylthio group, adamantylthio group, benzylthio group, 4- Examples include a bromobenzylthio group.

In the general formula (II), the arylthio group represented by R ¹³ , R ¹⁴ and R ¹⁵ may be unsubstituted or may have a substituent. The carbon number is preferably 6 to 30, and particularly preferably 6 to 20. Specific examples include a phenylthio group, a naphthylthio group, an anthranylthio group, and the like.

In general formula (II), the alkoxycarbonyl groups represented by R ¹³ , R ¹⁴ , and R ¹⁵ may be unsubstituted or may have a substituent. The carbon number is preferably 1-30, and more preferably 1-20. Examples of such alkoxycarbonyl groups include methyloxycarbonyl group, ethyloxycarbonyl group, normal propyloxycarbonyl group, isopropyloxycarbonyl group, normal butyloxycarbonyl group, isobutyloxycarbonyl group, tertiary butyloxycarbonyl group, pentyloxy Carbonyl group, cyclopentyloxycarbonyl group, hexyloxycarbonyl group, cyclohexyloxycarbonyl group, heptyloxycarbonyl group, octyloxycarbonyl group, tertiary octyloxycarbonyl group, 2-ethylhexyloxycarbonyl group, decyloxycarbonyl group, dodecyloxycarbonyl group Groups and the like.

In the general formula (II), the aryloxycarbonyl group represented by R ¹³ , R ¹⁴ , R ¹⁵ may be unsubstituted or may have a substituent. The carbon number is preferably 7-30, and particularly preferably 7-20. As a specific example. For example, a phenyloxycarbonyl group, a naphthyloxycarbonyl group, an anthranyloxycarbonyl group, etc. are mentioned.

In general formula (II), an acyloxy group represented by R ^13, R ^14, R ¹⁵ may be unsubstituted or may have a substituent. The carbon number is preferably 1-30, and more preferably 1-20. Examples of such acyloxy groups include methylcarbonyloxy group, ethylcarbonyloxy group, normal propylcarbonyloxy group, isopropylcarbonyloxy group, normal butylcarbonyloxy group, isobutylcarbonyloxy group, tertiary butylcarbonyloxy group, pentylcarbonyloxy group. Group, cyclopentylcarbonyloxy group, hexylcarbonyloxy group, cyclohexylcarbonyloxy group, heptylcarbonyloxy group, octylcarbonyloxy group, tertiary octylcarbonyloxy group, 2-ethylhexylcarbonyloxy group, decylcarbonyloxy group, dodecylcarbonyloxy group And benzoyloxy group.

In general formula (II), the acylamino groups represented by R ¹³ , R ¹⁴ , and R ¹⁵ may be unsubstituted or may have a substituent. The carbon number is preferably 1-30, and more preferably 1-20. Examples of such an acylamino group include a methylcarbonylamino group, an ethylcarbonylamino group, and a phenylcarbonylamino group.

In the general formula (II), the sulfonylamino group represented by R ¹³ , R ¹⁴ , or R ¹⁵ may be unsubstituted or may have a substituent. The carbon number is preferably 1-30, and more preferably 1-20. Examples of such a sulfonylamino group include a methylsulfonylamino group, an ethylsulfonylamino group, and a phenylsulfonylamino group.

In general formula (II), the amino group represented by R ¹³ , R ¹⁴ , or R ¹⁵ may be a mono-substituted amino group or a di-substituted amino group, and a di-substituted amino group is preferred. . It may be unsubstituted or may have a substituent. The carbon number is preferably 1-30, and more preferably 1-20. Examples of such an amino group include a dimethylamino group and a diphenylamino group.

In general formula (II), the acyl groups represented by R ¹³ , R ¹⁴ and R ¹⁵ may be unsubstituted or may have a substituent. The carbon number is preferably 1-30, and more preferably 1-20. Examples of such an acyl group include an acetyl group and a benzoyl group.

In the general formula (II), examples of the halogen group represented by R ¹³ , R ¹⁴ , and R ¹⁵ include a chloro group, a bromo group, and an iodo group, and a bromo group is preferable.

In the general formula (II), when the group represented by R ¹ , R ¹² , R ¹³ , R ¹⁴ , R ¹⁵ further has a substituent, the substituent includes a halogen atom, an alkyl group, an alkenyl group, and an alkoxy group. , Aryloxy, alkylthio group, alkoxycarbonyl group, aryloxycarbonyl group, amino group, acyl group, alkylaminocarbonyl group, arylaminocarbonyl group, sulfonamido group, cyano group, carboxy group, hydroxyl group, sulfonic acid group, etc. It is done. Among these, a halogen atom, an alkoxy group, and an alkylthio group are particularly preferable. When the cyclic allyl sulfide compound represented by the general formula (II) is substituted as a substituent, it represents a polyfunctional compound.

  In general formula (II), m1 represents an integer of 0 or 1. m1 is preferably 1.

In a preferred embodiment of the compound represented by the general formula (II), R ¹ and R ¹² each independently represent a hydrogen atom or a methyl group, and R ¹³ , R ¹⁴ and R ¹⁵ each independently represent a hydrogen atom, an alkyl And a compound representing a group, an aryl group, an alkoxy group, an aryloxy group, an alkoxycarbonyl group, an aryloxycarbonyl group, an acyloxy group, an acylamino group, an amino group, or an acyl group. In a more preferred embodiment, in general formula (II), R ¹ and R ¹² are each independently a hydrogen atom or a methyl group, and R ¹³ and R ¹⁴ are each independently a hydrogen atom, an alkyl group, an aryl group, an alkoxy group. , Aryloxy group, alkoxycarbonyl group, aryloxycarbonyl group, acyloxy group, acylamino group, amino group, acyl group, R ¹⁵ is a hydrogen atom, alkyl group, aryl group, acyloxy group, and m1 is 0 or The compound which is 1 can be mentioned. In a more preferred embodiment, in general formula (II), R ¹ and R ¹² are a hydrogen atom or a methyl group, R ¹³ and R ¹⁴ are each independently a hydrogen atom or a methyl group, and R ¹⁵ is an alkyl group or The compound which is an acyloxy group and m1 is 0 or 1 can be mentioned. In a more preferred embodiment, in general formula (II), R ¹ and R ¹² are both hydrogen atoms, and R ¹³ , R ¹⁴ and R ¹⁵ are each independently a hydrogen atom, an alkyl group, an aryl group, an alkoxy group. And a compound in which m1 is 1 is a group, an aryloxy group or an acyloxy group. The most preferred embodiment is a compound in which R ¹ and R ¹² are both hydrogen atoms, R ¹³ and R ¹⁴ are hydrogen atoms, R ¹⁵ is an acyloxy group, and m1 is 1. .

Cyclic allyl sulfide compound represented by general formula (III)

In general formula (III), R ¹ has the same definition as in general formula (I), and R ²³ , R ²⁴ and R ²⁵ are each independently a hydrogen atom, an alkyl group, an aryl group, a heterocyclic group, an alkoxy group, An aryloxy group, an alkylthio group, an arylthio group, an alkoxycarbonyl group, an aryloxycarbonyl group, an acyloxy group, an acylamino group, a sulfonylamino group, an amino group, an acyl group, or a halogen group, and m2 represents 0 or 1.

The details of the alkyl group represented by R ¹ , R ²³ , R ²⁴ , R ²⁵ in general formula (III) are the same as those described above for the alkyl group in general formula (I).

In the general formula (III), the aryl group represented by R ²³ , R ²⁴ and R ²⁵ may be unsubstituted or may have a substituent. The carbon number is preferably 6 to 30, and particularly preferably 6 to 20. Specific examples of the aryl group include a phenyl group, a naphthyl group, and an anthranyl group. These may further have a substituent.

In general formula (III), the heterocyclic group represented by R ²³ , R ²⁴ , or R ²⁵ is preferably a heterocyclic group having 4 to 14 carbon atoms, and is a heterocyclic group having 4 to 10 carbon atoms. It is more preferable that the heterocyclic group has 5 carbon atoms. Specific examples of the heterocyclic group represented by R ²³ , R ²⁴ and R ²⁵ include a pyridine ring, piperazine ring, thiophene ring, pyrrole ring, imidazole ring, oxazole ring and thiazole ring. These may further have a substituent. Of the heterocycles, a pyridine ring is particularly preferred.

In general formula (III), the alkoxy groups represented by R ²³ , R ²⁴ and R ²⁵ may be linear or branched, and may be unsubstituted or substituted. You may do it. The carbon number is preferably 1-30, and more preferably 1-20. Examples of such alkoxy groups include methoxy, ethoxy, normal propyloxy, isopropyloxy, normal butyloxy, isobutyloxy, tertiary butyloxy, pentyloxy, cyclopentyloxy, hexyloxy. Group, cyclohexyloxy group, heptyloxy group, octyloxy group, tertiary octyloxy group, 2-ethylhexyloxy group, decyloxy group, dodecyloxy group, octadecyloxy group, 2,3-dibromopropyloxy group, adamantyloxy group, Examples include benzyloxy group and 4-bromobenzyloxy group.

In general formula (III), the aryloxy groups represented by R ²³ , R ²⁴ , and R ²⁵ may be unsubstituted or have a substituent. The carbon number is preferably 6 to 30, and particularly preferably 6 to 20. Specific examples include a phenyloxy group, a naphthyloxy group, an anthranyloxy group, and the like.

In general formula (III), the alkylthio groups represented by R ²³ , R ²⁴ , and R ²⁵ may be linear or branched, and may be unsubstituted or substituted. You may do it. The carbon number is preferably 1-30, and more preferably 1-20. Examples of such an alkylthio group include a methylthio group, an ethylthio group, a normal propylthio group, an isopropylthio group, a normal butylthio group, an isobutylthio group, a tertiary butylthio group, a pentylthio group, a cyclopentylthio group, a hexylthio group, Cyclohexylthio group, heptylthio group, octylthio group, tertiary octylthio group, 2-ethylhexylthio group, decylthio group, dodecylthio group, octadecylthio group, 2,3-dibromopropylthio group, adamantylthio group, benzylthio group, 4- Examples include a bromobenzylthio group.

In general formula (III), the arylthio groups represented by R ²³ , R ²⁴ and R ²⁵ may be unsubstituted or may have a substituent. The carbon number is preferably 6 to 30, and particularly preferably 6 to 20. Specific examples include a phenylthio group, a naphthylthio group, an anthranylthio group, and the like.

In general formula (III), the alkoxycarbonyl group represented by R ²³ , R ²⁴ and R ²⁵ may be unsubstituted or may have a substituent. The carbon number is preferably 1-30, and more preferably 1-20. Examples of such alkoxycarbonyl groups include methyloxycarbonyl group, ethyloxycarbonyl group, normal propyloxycarbonyl group, isopropyloxycarbonyl group, normal butyloxycarbonyl group, isobutyloxycarbonyl group, tertiary butyloxycarbonyl group, pentyloxy Carbonyl group, cyclopentyloxycarbonyl group, hexyloxycarbonyl group, cyclohexyloxycarbonyl group, heptyloxycarbonyl group, octyloxycarbonyl group, tertiary octyloxycarbonyl group, 2-ethylhexyloxycarbonyl group, decyloxycarbonyl group, dodecyloxycarbonyl group Groups and the like.

In general formula (III), the aryloxycarbonyl group represented by R ²³ , R ²⁴ and R ²⁵ may be unsubstituted or may have a substituent. The carbon number is preferably 7-30, and particularly preferably 7-20. As a specific example. For example, a phenyloxycarbonyl group, a naphthyloxycarbonyl group, an anthranyloxycarbonyl group, etc. are mentioned.

In general formula (III), the acyloxy groups represented by R ²³ , R ²⁴ and R ²⁵ may be unsubstituted or may have a substituent. The carbon number is preferably 1-30, and more preferably 1-20. Examples of such acyloxy groups include methylcarbonyloxy group, ethylcarbonyloxy group, normal propylcarbonyloxy group, isopropylcarbonyloxy group, normal butylcarbonyloxy group, isobutylcarbonyloxy group, tertiary butylcarbonyloxy group, pentylcarbonyloxy group. Group, cyclopentylcarbonyloxy group, hexylcarbonyloxy group, cyclohexylcarbonyloxy group, heptylcarbonyloxy group, octylcarbonyloxy group, tertiary octylcarbonyloxy group, 2-ethylhexylcarbonyloxy group, decylcarbonyloxy group, dodecylcarbonyloxy group And benzoyloxy group.

In general formula (III), the acylamino group represented by R ²³ , R ²⁴ , or R ²⁵ may be unsubstituted or may have a substituent. The carbon number is preferably 1-30, and more preferably 1-20. Examples of such an acylamino group include a methylcarbonylamino group, an ethylcarbonylamino group, and a phenylcarbonylamino group.

In the general formula (III), the sulfonylamino group represented by R ²³ , R ²⁴ and R ²⁵ may be unsubstituted or may have a substituent. The carbon number is preferably 1-30, and more preferably 1-20. Examples of such a sulfonylamino group include a methylsulfonylamino group, an ethylsulfonylamino group, and a phenylsulfonylamino group.

In general formula (III), the amino group represented by R ²³ , R ²⁴ and R ²⁵ may be a mono-substituted amino group or a di-substituted amino group, and a di-substituted amino group is preferred. . It may be unsubstituted or may have a substituent. The carbon number is preferably 1-30, and more preferably 1-20. Examples of such an amino group include a dimethylamino group and a diphenylamino group.

In general formula (III), the acyl groups represented by R ²³ , R ²⁴ and R ²⁵ may be unsubstituted or may have a substituent. The carbon number is preferably 1-30, and more preferably 1-20. Examples of such an acyl group include an acetyl group and a benzoyl group.

In the general formula (III), examples of the halogen group represented by R ²³ , R ²⁴ , and R ²⁵ include a chloro group, a bromo group, and an iodo group, and a bromo group is preferable.

In the general formula (III), when the group represented by R ¹ , R ²³ , R ²⁴ , or R ²⁵ further has a substituent, examples of the substituent include a halogen atom, alkyl group, alkenyl group, alkoxy group, aryloxy Alkylthio group, alkoxycarbonyl group, aryloxycarbonyl group, amino group, acyl group, alkylaminocarbonyl group, arylaminocarbonyl group, sulfonamido group, cyano group, carboxy group, hydroxyl group, sulfonic acid group and the like. Among these, a halogen atom, an alkoxy group, and an alkylthio group are particularly preferable. When the cyclic allyl sulfide compound represented by the general formula (III) is substituted as a substituent, it represents a polyfunctional compound.

  In general formula (III), m2 represents an integer of 0 or 1. m2 is preferably 0.

In a preferred embodiment of the compound represented by the general formula (III), R ¹ represents a hydrogen atom or a methyl group, and R ²³ , R ²⁴ and R ²⁵ are each independently a hydrogen atom, an alkyl group, an aryl group, an alkoxy group. And a compound representing a group, an aryloxy group, an alkoxycarbonyl group, an aryloxycarbonyl group, an acyloxy group, an acylamino group, an amino group, or an acyl group. In a more preferred embodiment, in general formula (III), R ¹ is a hydrogen atom or a methyl group, and R ²³ and R ²⁴ are each independently a hydrogen atom, an alkyl group, an aryl group, an alkoxy group, an aryloxy group, an alkoxy group. Examples include a carbonyl group, an aryloxycarbonyl group, an acyloxy group, an acylamino group, an amino group, and an acyl group, R ²⁵ is a hydrogen atom, an alkyl group, an aryl group, and an acyloxy group, and m2 is 0 or 1. be able to. In a more preferred embodiment, in general formula (III), R ¹ is a hydrogen atom or a methyl group, R ²³ and R ²⁴ are each independently a hydrogen atom or a methyl group, and R ²⁵ is an alkyl group or an acyloxy group. And a compound in which m2 is 0 or 1. In a more preferred embodiment, in general formula (III), R ¹ is a methyl group, and R ²³ , R ²⁴ and R ²⁵ are each independently a hydrogen atom, an alkyl group, an aryl group, an alkoxy group, an aryloxy group. Alternatively, a compound that is an acyloxy group and m2 is 0 can be given. As the most preferred embodiment, R ¹ is a methyl group, R ^23, R ²⁴ is a hydrogen atom, R ²⁵ is an acyloxy group, and can be exemplified m2 is 0 compounds.

From the viewpoint of recording sensitivity, the radical polymerizable compound preferably exhibits a molar extinction coefficient of 5,000 mol·l · cm ⁻¹ or more in an absorption spectrum in the range of 200 to 1000 nm, and has an absorption in the range of 200 to 500 nm. More preferably, the spectrum shows a molar extinction coefficient of 5,000 mol·l · cm ⁻¹ or more. When the wavelength showing a molar extinction coefficient of 5,000 mol·l · cm ⁻¹ or more is λ ₁ , the radical polymerizable compound preferably has an absorption maximum at the wavelength λ ₁ from the viewpoint of recording sensitivity. Molar extinction coefficient at the absorption maximum wavelength is preferably at 10,000mol · l · cm ^-1 or more, further preferably 30,000mol · l · cm ^-1 or more, 100,000mol · l · cm ^- particularly preferably ¹ or more. The upper limit of the molar extinction coefficient at the absorption maximum is not particularly limited, but is, for example, about 200,000 mol·l · cm ⁻¹ .
The absorption characteristics can be determined from an absorption spectrum measured using a UV-visible spectrophotometer for a solution obtained by dissolving the compound in an appropriate solvent such as methylene chloride.

In order to obtain the aforementioned absorption characteristics, the compound represented by the general formula (I) is represented by the following general formulas (C-1), (C-2), (C-3), (C-4), (C It is preferable that at least one partial structure represented by −5) or (C-6) is included. The compound represented by the general formula (I) can contain, for example, at least one of the above partial structures in one molecule, but the number of the above partial structures in one molecule can be as long as the above-described absorption characteristics are obtained. It is not particularly limited. However, the compound represented by the general formula (I) having the above-described absorption characteristics is not limited to those including the partial structures represented by the following general formulas (C-1) to (C-6). . The inclusion as a partial structure means that the compound represented by the general formula (I), the general formula (II) or the general formula (III) is added to the general formula (C-1), (C-2), (C -3), the partial structure represented by (C-4), (C-5) or (C-6) is included as the same molecule.
Specifically, as substituents in the general formulas (I), (II), and (III), the general formulas (C-1), (C-2), (C-3), (C-4), ( The structure represented by C-5) or (C-6) is linked.

［上記式中、Ｒ³¹、Ｒ³²、Ｒ³³、Ｒ³⁴およびＲ³⁷は、それぞれ独立に、水素原子、アルキル基、アリール基、ヘテロ環基、アルコキシ基、アリールオキシ基、アルコキシカルボニル基、アリールオキシカルボニル基、アシル基、スルホニル基、カルバモイル基、スルファモイル基、アミノ基、アシルオキシ基、アシルアミノ基、水酸基、カルボン酸基、スルホン酸基、ハロゲン基または連結基を表し、Ａ¹およびＡ²は、それぞれ独立に−ＣＲ⁴³Ｒ⁴⁴−、−Ｏ−、−ＮＲ⁴⁵−、−Ｓ−、または−Ｃ（＝Ｏ）−を表し、Ｒ⁴³、Ｒ⁴⁴、Ｒ⁴⁵はそれぞれ独立に水素原子、アルキル基、アリール基または連結基を表す。Ｒ³⁵およびＲ³⁶はそれぞれ独立に電子求引性の置換基または連結基を表し、Ｒ³⁵およびＲ³⁶が互いに結合して環状構造を形成してもよい。Ｒ³⁸、Ｒ³⁹およびＲ⁴⁰はそれぞれ独立に、水素原子、アルキル基または連結基を表し、Ｒ⁴¹およびＲ⁴²はそれぞれ独立に水素原子、アルキル基、アリール基、ヘテロ環基、アシル基、スルホニル基または連結基を表す。部分構造（Ｃ−１）〜（Ｃ−６）は、それぞれ１つ以上の連結基を含む。］

[Wherein R ³¹ , R ³² , R ³³ , R ³⁴ and R ³⁷ are each independently a hydrogen atom, alkyl group, aryl group, heterocyclic group, alkoxy group, aryloxy group, alkoxycarbonyl group, aryl oxycarbonyl group, an acyl group, a sulfonyl group, a carbamoyl group, a sulfamoyl group, an amino group, an acyloxy group, an acylamino group, a hydroxyl group, a carboxylic acid group, a sulfonic acid group, a halogen group or a linking group, a ¹ and a ^2, Each independently represents —CR ⁴³ R ⁴⁴ —, —O—, —NR ⁴⁵ —, —S—, or —C (═O) —, each of R ⁴³ , R ⁴⁴ , and R ⁴⁵ independently represents a hydrogen atom, alkyl Represents a group, an aryl group or a linking group. R ³⁵ and R ³⁶ each independently represent an electron-withdrawing substituent or linking group, and R ³⁵ and R ³⁶ may be bonded to each other to form a cyclic structure. R ³⁸ , R ³⁹ and R ⁴⁰ each independently represents a hydrogen atom, an alkyl group or a linking group, and R ⁴¹ and R ⁴² each independently represent a hydrogen atom, an alkyl group, an aryl group, a heterocyclic group, an acyl group, a sulfonyl group Represents a group or a linking group. Partial structures (C-1) to (C-6) each contain one or more linking groups. ]

Compounds represented by general formula (I), general formula (II) or general formula (III) are represented by general formulas (C-1), (C-2), (C-3), (C-4), ( When the structure represented by C-5) or (C-6) is linked, the linking group is selected from an alkylene group, a phenylene group, —O—, —S—, —CO—, and —NR ⁴⁶ —. Or a combination of two or more thereof. Of these, an alkylene group, —O—, —S—, —CO— or a combination of two or more thereof is preferable, and an alkylene group, —O—, —CO— or a combination of two or more thereof is more preferable. The group, —O— or a combination thereof is particularly preferred, and an ethylene oxide chain having a structural unit of — (OCH ₂ CH ₂ ) — is most preferred.

  Below, the partial structure represented by general formula (C-1), (C-2), (C-3), (C-4), (C-5) or (C-6) is demonstrated.

In the general formulas (C-1) to (C-6), R ³¹ , R ³² , R ³³ , R ³⁴ , R ³⁷ , R ³⁸ , R ³⁹ , R ⁴⁰ , R ⁴¹ , R ⁴² , R ⁴³ , R ⁴⁴ The details of the alkyl group represented by R ⁴⁵ are the same as those described for the alkyl group in formula (I).

In the general formulas (C-1) to (C-6), an aryl group represented by R ³¹ , R ³² , R ³³ , R ³⁴ , R ³⁷ , R ⁴¹ , R ⁴² , R ⁴³ , R ⁴⁴ , R ⁴⁵ The details of are the same as those described for the aryl group in formula (I).

In the general formulas (C-1) to (C-6), the details of the heterocyclic groups represented by R ³¹ , R ³² , R ³³ , R ³⁴ , R ³⁷ , R ⁴¹ , R ⁴² are as follows. It is the same as the explanation of the heterocyclic group in

In the general formulas (C-1) to (C-6), the details of the alkoxy group represented by R ³¹ , R ³² , R ³³ , R ³⁴ , R ³⁷ are explained for the alkoxy group in the general formula (I). It is the same.

In the general formulas (C-1) to (C-6), the details of the aryloxy group represented by R ³¹ , R ³² , R ³³ , R ³⁴ , and R ³⁷ are the same as those of the aryloxy group of the general formula (I). It is the same as the description.

In the general formulas (C-1) to (C-6), the details of the alkoxycarbonyl group represented by R ³¹ , R ³² , R ³³ , R ³⁴ , R ³⁷ are the alkoxycarbonyl groups in the general formula (I). It is the same as that of description.

In formula (C-1) ~ (C -6), R 31, R 32, details of the aryloxycarbonyl group represented by ^{R 33, R 34, R 37} , aryloxy in the general formula (I) The same as described for the carbonyl group.

In the general formulas (C-1) to (C-6), the acyl group represented by R ³¹ , R ³² , R ³³ , R ³⁴ , R ³⁷ , R ⁴¹ , R ⁴² has 1 to 10 carbon atoms. Those having 1 to 6 carbon atoms are more preferable, and those having 4 carbon atoms are most preferable. Specifically, methylcarbonyl group, ethylcarbonyl group, normal propylcarbonyl group, isopropylcarbonyl group, normal butylcarbonyl group, isobutylcarbonyl group, tertiary butylcarbonyl group, pentylcarbonyl group, cyclopentylcarbonyl group, hexylcarbonyl group, cyclohexylcarbonyl Group, heptylcarbonyl group, octylcarbonyl group, tertiary octylcarbonyl group, 2-ethylhexylcarbonyl group, decylcarbonyl group, dodecylcarbonyl group, benzoyl group and the like.

In formula (C-1) ~ (C -6), as a sulfonyl group represented by ^{R 31, R 32, R 33} , R 34, R 37, R 41, R 42, 1 to 10 carbon atoms Those having 1 to 6 carbon atoms are more preferable, and those having 1 to 4 carbon atoms are most preferable. Specifically, methylsulfonyl group, ethylsulfonyl group, normal propylsulfonyl group, isopropylsulfonyl group, normal butylsulfonyl group, isobutylsulfonyl group, tertiary butylsulfonyl group, pentylsulfonyl group, cyclopentylsulfonyl group, hexylsulfonyl group, cyclohexylsulfonyl Group, heptylsulfonyl group, octylsulfonyl group, tertiary octylsulfonyl group, 2-ethylhexylsulfonyl group, decylsulfonyl group, dodecylsulfonyl group, and the like.

In the general formulas (C-1) to (C-6), the carbamoyl group represented by R ³¹ , R ³² , R ³³ , R ³⁴ , R ³⁷ is preferably a carbamoyl group having 1 to 12 carbon atoms. A carbamoyl group having 1 to 6 is more preferable. Examples of such a carbamoyl group include a methylcarbamoyl group, an ethylcarbamoyl group, a normalpropylcarbamoyl group, an isopropylcarbamoyl group, a normalbutylcarbamoyl group, an isobutylcarbamoyl group, a tertiary butylcarbamoyl group, and a phenylcarbamoyl group. The carbamoyl group may be further substituted with a substituent.

In the general formulas (C-1) to (C-6), the sulfamoyl group represented by R ³¹ , R ³² , R ³³ , R ³⁴ , R ³⁷ is preferably a sulfamoyl group having 1 to 12 carbon atoms. A sulfamoyl group of 1 to 6 is more preferable. Examples of such a sulfamoyl group include a methylsulfamoyl group, an ethylsulfamoyl group, a normalpropylsulfamoyl group, an isopropylsulfamoyl group, a normalbutylsulfamoyl group, an isobutylsulfamoyl group, and tertiary butyl. Examples thereof include a sulfamoyl group and a phenylsulfamoyl group. The sulfamoyl group may be further substituted with a substituent.

In the general formulas (C-1) to (C-6), the details of the amino groups represented by R ³¹ , R ³² , R ³³ , R ³⁴ , and R ³⁷ are explained for the amino group in the general formula (I). It is the same.

In the general formulas (C-1) to (C-6), the details of the acyloxy group represented by R ³¹ , R ³² , R ³³ , R ³⁴ , R ³⁷ are explained for the acyloxy group in the general formula (I). It is the same.

In the general formulas (C-1) to (C-6), the details of the acylamino group represented by R ³¹ , R ³² , R ³³ , R ³⁴ , R ³⁷ are explained for the acylamino group in the general formula (I). It is the same.

In formula (C-1) ~ (C -6), R 31, are ^{R 32, R 33, R 34} , a halogen group represented by R ³⁷ detailed, description of the halogen group in the general formula (I) It is the same.

In the above formulas (C-1) to (C-6), A ¹ and A ² are each independently —CR ⁴³ R ⁴⁴ —, —O—, —NR ⁴⁵ —, —S—, or —C (= O)-. A ¹ and A ² are preferably ^{-CR 43 R 44 -, - O} -, - NR 45 -, or a -S-, more preferably -O -, - NR ⁴⁵ -, or -S- and and More preferably —NR ⁴⁵ — or —S—.

As a specific combination of A ¹ and A ² , a combination of ^one of A ¹ and A ² and the other is (—CR ⁴³ R ⁴⁴ —, —NR ⁴⁵ —), (—S—, —S—). ), (—NR ⁴⁵ —, —S—), (—O—, —NR ⁴⁵ —), (—NR ⁴⁵ —, —NR ⁴⁵ —), (—C (═O) —, —NR ⁴⁵ —) Preferably, (—S—, —S—), (—NR ⁴⁵ —, —S—), (—O—, —NR ⁴⁵ —), (—NR ⁴⁵ —, —NR ⁴⁵ —) are preferred. More preferably, (—NR ⁴⁵ —, —S—), (—O—, —NR ⁴⁵ —) are preferred, and (—NR ⁴⁵ —, —S—) is most preferred.

In the general formulas (C-1) to (C-6), the electron-withdrawing substituents represented by R ³⁵ and R ³⁶ are substituents whose Hammett substituent constant σ _p value is a positive value. and a, preferably is a sigma _p value of 0.2 or more, the upper limit being 1.0 or less substituents. Specific examples of the electron withdrawing group having a σ _p value of 0.2 or more include an acyl group, a formyl group, an acyloxy group, an acylthio group, a carbamoyl group, an oxycarbonyl group, a cyano group, a nitro group, a dialkylphosphono group, Diarylphosphono group, dialkylphosphinyl group, diarylphosphinyl group, phosphoryl group, alkylsulfinyl group, arylsulfinyl group, alkylsulfonyl group, arylsulfonyl group, sulfonyloxy group, acylthio group, sulfamoyl group, thiocyanate group, thio A carbonyl group, an imino group, an imino group substituted with an N atom, a carboxy group (or a salt thereof), an alkyl group substituted with at least two halogen atoms, an alkoxy group substituted with at least two halogen atoms, Substituted with at least two halogen atoms Aryloxy groups, acylamino groups, alkylamino groups substituted with at least two or more halogen atoms, alkylthio groups substituted with at least two or more halogen atoms, other electrons having a σ _p value of 0.2 or more Examples thereof include an aryl group substituted with an attractive group, a heterocyclic group, a halogen atom, an azo group, and a selenocyanate group. For Hammett σp values, see Hansch, C .; Leo, A .; Taft, R .; W. Chem. Rev. 1991, 91, 165-195. Among these, a cyano group, an oxycarbonyl group, an acyl group, and a sulfonyl group are preferable.

The substituent represented by R ³⁵ and the substituent represented by R ³⁶ can take various combinations. Preferred combinations include the following combinations 1 to 9. In the combinations 2, 3 and 4, the substituent represented by R ³⁵ and the substituent represented by R ³⁶ may be the same or different.

(Combination 1) R ³⁵ : Cyano group, R ³⁶ : Cyano group (Combination 2) R ³⁵ : Acyl group, R ³⁶ : Acyl group (Combination 3) R ³⁵ : Oxycarbonyl group, R ³⁶ : Oxycarbonyl group (Combination 4) ) R ³⁵ : sulfonyl group, R ³⁶ : sulfonyl group (combination 5) R ³⁵ : cyano group, R ³⁶ : oxycarbonyl group (combination 6) R ³⁵ : cyano group, R ³⁶ : acyl group (combination 7) R ³⁵ : Oxycarbonyl group, R ³⁶ : acyl group (combination 8) R ³⁵ : acyl group, R ³⁶ : sulfonyl group (combination 9) R ³⁵ : oxycarbonyl group, R ³⁶ : sulfonyl group

Among the above combinations, combinations 1, 3, 4, 5, and 9 are more preferable, and combination 5 is most preferable. In general formulas (C-1) to (C-6), R ³⁵ and R ³⁶ may be bonded to each other to form a cyclic structure. When bonded, they may be linked by a carbon chain or may contain N, O, S atoms, and the like.

As described above, the general formulas (C-1), (C-2), (C-3), (C-4), (C-5) or (C-6) are represented by the general formulas (I), (II ) Or (III), at least one linking group is included in the partial structure. That is, any one or more of R ³¹ , R ³² , R ³³ , R ³⁴ , R ³⁷ , R ³⁸ , R ³⁹ , R ⁴⁰ , R ⁴¹ , R ⁴² , R ⁴³ , R ⁴⁴ , R ⁴⁵ Group is present as a linking group, and the general formula (C-1), (C-2), (C-3), (C-4), (C-5) or (C-6) is the above linking group And is included in the compound represented by the general formula (I), (II) or (III). Each partial structure may contain one linking group. The details of the linking group are as described above.

  Specific examples of the cyclic allyl sulfide compounds represented by the general formulas (I), (II), and (III) are shown below. However, the present invention is not limited to the following specific examples.

  For example, Macromolecules. 1994, 27, 7935. Macromolecules, 1996, 29, 6983., Macromolecules, 2000, 33, 6722. and J. Po1ym. Sci .: Part A Polym. Chem. 2001, 39, 202 and the like. For details of the synthesis method, the examples described later can also be referred to.

  In the photopolymerizable composition of the present invention, only one kind of the radical polymerizable compound may be used, or two or more kinds thereof may be used in combination. The content of the radical polymerizable compound in the photopolymerizable composition of the present invention is preferably 5 to 60% by mass, more preferably 15 to 50% by mass, from the viewpoint of high sensitivity recording.

  Further, the radically polymerizable compound represented by the general formula (I) may be used in combination with other polymerizable monomers. Examples of other monomers used in combination include acryloylmorpholine, phenoxyethyl acrylate, isobornyl acrylate, 2-hydroxypropyl acrylate, 2-ethylhexyl acrylate, 1,6-hexanediol diacrylate, tripropylene glycol diacrylate, and neopentyl. Glycol PO-modified diacrylate, 1,9-nonanediol diacrylate, hydroxypivalate neopentyl glycol diacrylate, EO-modified bisphenol A diacrylate, polyethylene glycol diacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, pentaerythritol hexaacrylate , EO-modified glycerol triacrylate, trimethylol proppant Acrylate, EO-modified trimethylolpropane triacrylate, 2-naphth-1-oxyethyl acrylate, 2-carbazoyl-9-ylethyl acrylate, (trimethylsilyloxy) dimethylsilylpropyl acrylate, vinyl-1-naphthoate, 2,4,6 -Tribromophenyl acrylate, pentabromo acrylate, phenylthioethyl acrylate, tetrahydrofurfuryl acrylate, bisphenoxyethanol fluorene acrylate, styrene, p-chlorostyrene, N-vinyl carbazole, N-vinyl pyropydon and the like. Among these, phenoxyethyl acrylate, 2,4,6-tribromophenyl acrylate, pentabromoacrylate, and bisphenoxyethanol full orange acrylate are preferable, and 2,4,6-tribromophenyl acrylate and bisphenoxyethanol full orange acrylate are more preferable. When used in combination with other polymerizable monomers, the amount of polymerizable monomer used in combination in the total polymerizable monomer is preferably 50% by mass or less.

Non-resonant two-photon absorption compound The two-photon absorption compound contained in the photopolymerizable composition of the present invention is a compound that causes non-resonant two-photon absorption. A non-resonant two-photon absorption compound is a compound that causes a phenomenon (non-resonant two-photon absorption) that is excited by simultaneously absorbing two photons in an energy region where there is no linear absorption band of the compound. Non-resonant two-photon absorption is usually induced in the wavelength region longer than the absorption band where there is no linear absorption of the compound. Two-photon absorption can be caused by using so-called near-infrared light in a transparent region, so that excitation light can reach the inside of the sample without being absorbed or scattered. One point can be excited with extremely high spatial resolution.

  The non-resonant two-photon absorption compound can be an organic dye. Here, the dye refers to a compound having a part of absorption in the ultraviolet region (preferably 200 to 400 nm), the visible light region (400 to 700 nm), or the near infrared region (preferably 700 to 2000 nm). The organic dye is preferably a compound having a part of absorption in the visible light region.

  As the organic dye, a cyanine dye, a merocyanine dye, an oxonol dye, and a polyaryl dye are preferable. Specific structures of the two-photon absorption compounds for cyanine dyes, merocyanine dyes, and oxonol dyes are described in detail in JP-A Nos. 2004-346238, 2007-87532, and 2007-262155. Yes. A polyaryl dye can be used as the two-photon absorption compound at a shorter wavelength (for example, shorter than 700 nm). The polyaryl dye is a compound having a structure represented by the following general formula (IV).

[一般式（IV）中、ＸおよびＹは、それぞれ独立にハメットの置換基定数（σp値）がゼロ以上の値を有する置換基を表し、ｎは１〜４の範囲の整数を表し、Ｒは置換基を表し、Ｒが複数存在する場合は同一でもそれぞれ異なってもよく、ｍは０〜４の範囲の整数を表す。]

[In General Formula (IV), X and Y each independently represent a substituent having a Hammett's substituent constant (σp value) of zero or more, n represents an integer in the range of 1 to 4, Represents a substituent, and when a plurality of Rs are present, they may be the same or different, and m represents an integer in the range of 0-4. ]

  In the general formula (IV), X and Y represent a so-called electron-withdrawing group in which the σp value in the Hammett formula is zero or more, preferably a trifluoromethyl group, a heterocyclic group, a halogen atom, A cyano group, a nitro group, an alkylsulfonyl group, an arylsulfonyl group, a sulfamoyl group, a carbamoyl group, an acyl group, an acyloxy group, an alkoxycarbonyl group, and the like, more preferably a trifluoromethyl group, a cyano group, an acyl group, and an acyloxy group. Group or an alkoxycarbonyl group, and most preferably a cyano group or a benzoyl group. Among these substituents, an alkylsulfonyl group, an arylsulfonyl group, a sulfamoyl group, a carbamoyl group, an acyl group, an acyloxy group, and an alkoxycarbonyl group are further added for various purposes in addition to imparting solubility to a solvent. It may have a substituent, and preferred examples of such a substituent include an alkyl group, an alkoxy group, an alkoxyalkyl group, and an aryloxy group.

  n represents an integer in the range of 1 to 4, more preferably 2 or 3, and most preferably 2. As n is 5 or more, linear absorption comes out on the longer wavelength side, and non-resonant two-photon absorption recording using recording light having a wavelength shorter than 700 nm becomes more difficult.

  R represents a substituent, and the substituent is not particularly limited, and specific examples include an alkyl group, an alkoxy group, an alkoxyalkyl group, and an aryloxy group. m represents an integer in the range of 0-4.

  Hereinafter, in the compound having the structure represented by the general formula (IV), X and Y are desirably so-called electron-withdrawing groups in which Hammett's substituent constant σp value is a positive value. State that.

  According to T. Kogej, et al., Chem. Phys. Lett., 298, 1 (1998)), the two-photon absorption efficiency of an organic compound, that is, the two-photon absorption cross section δ, is expressed by the third-order molecular polarizability (2 It has the following relationship with the imaginary part of (second hyperpolarizability) γ.

Here, c: speed of light, ν: frequency, n: refractive index, ε ₀ : dielectric constant in vacuum, ω: frequency of photons, Im: imaginary part. The imaginary part of γ (Imγ) is the dipole moment between | g> and | e>; the dipole moment between Mge, | g> and | e '>; between Mge', | g> and | e> Dipole moment difference; Δμge, transition energy; Ege, damping factor;

Here, P represents a commutative operator.
Therefore, if the value of Formula (2) is calculated, it is possible to predict the two-photon absorption cross section of the compound. Therefore, the most stable structure of the ground state is calculated by the DFT method using the B3LYP functional with 6-31G * as the basis function, and Mge, Mee ', and Ege are calculated based on the result, and the value of Imγ is calculated. be able to. For example, in the compound having the structure represented by the general formula (IV), the maximum value of Imγ obtained from the calculation of a quaterphenyl compound in which X and Y are substituted with a methoxy group as an electron donating substituent is 1 In this case, as the other substituent, the relative value of the Imγ maximum value of a molecule having a so-called electron withdrawing group in which Hammett's substituent constant σp value is a positive value is large.
In the compound having the structure represented by the above general formula (IV), in the quaterphenyl compound in which X and Y are substituted by the methoxy group of the electron donating group, Imγ is small and both X and Y are electron withdrawing substitution. In general, Imγ greatly increases in molecules substituted with a group. As mentioned earlier, since the two-photon absorption cross section δ is theoretically proportional to the imaginary part of the third-order hyperpolarizability γ, that is, Imγ, X and Y are both electron-withdrawing substituents from these calculations. A substituted structure is desirable.

  The compound having the structure represented by the general formula (IV) is preferably a compound having a structure represented by the following general formula (V).

In the general formula (V), X, Y, n, R, and m are the same as those defined in the general formula (IV).
In the compound having the structure represented by the general formula (IV) or the general formula (V), X and Y may be the same or different from each other, but the two-photon absorption cross section tends to increase as they differ. It is preferable.
Specific examples of the compound having a structure represented by the general formula (IV) or the general formula (V) are not particularly limited, but include the following.

  In the photopolymerizable composition of the present invention, the nonresonant two-photon absorption compound may be used alone or in combination of two or more. The content of the non-resonant two-photon absorption compound in the photopolymerizable composition of the present invention is preferably 0.01 to 10% by mass, more preferably 0.1 to 7% by mass, from the viewpoint of improving recording sensitivity and polymerization efficiency. It is.

Radical polymerization initiator wherein the radically polymerizable compound, by serving the non-resonant two-photon absorption compound is a radical polymerization initiator, or non-resonant two-photon absorption compound and a radical polymerization initiator that generates a radical species by the interaction of Photopolymerization can be caused by the action of. The photopolymerizable composition of the present invention preferably contains a radical polymerization initiator separately from the non-resonant two-photon absorption compound from the viewpoint of polymerization efficiency. The interaction between the non-resonant two-photon absorption compound and the radical polymerizable compound is due to energy transfer or electron transfer. The polymerization initiator is not particularly limited as long as it can interact with the non-resonant two-photon absorption compound. For example, a bisimidazole-based polymerization initiator can be used as the radical polymerization initiator. As the bisimidazole-based polymerization initiator, bis (2,4,5-triphenyl) imidazole derivatives, specifically, for example, bis (2,4,5-triphenyl) imidazole, 2- (o-chlorophenyl)- 4,5-bis (m-methoxyphenyl) -imidazole dimer (CDM-HABI), 1,1'-biimidazole, 2,2'-bis (o-chlorophenyl) -4,4'5,5'-tetra Examples include phenyl (o-Cl-HABI), 1H-imidazole, 2,5-bis (o-chlorophenyl) -4- [3,4-dimethoxyphenyl] -dimer (TCTM-HABI), and the like. The bisimidazole polymerization initiator can also be used together with a hydrogen donor. Preferred examples of the hydrogen donor include 2-mercaptobenzoxazole, 2-mercaptobenzothiazole, 4-methyl-4H-1,2,4-triazole-3-thiol, and the like. In addition, the specific structure of the radical polymerization initiator that can be used in the present invention is described in detail in JP-A No. 2004-346238. These may be used individually by 1 type and may use 2 or more types together. The content of the radically polymerizable composition in the photopolymerizable composition of the present invention is preferably 0.01 to 10% by mass, more preferably 0.1 to 7% by mass, from the viewpoint of polymerization efficiency.

Binder The binder in the photopolymerizable composition of the present invention is usually used for the purpose of improving the film formability of the composition before polymerization, the uniformity of the film thickness, the stability during storage and the like. As the binder, those having good compatibility with various components (radical polymerizable compound, polymerization initiator, non-resonant two-photon absorption compound, etc.) contained in the composition are preferable.

  As the binder, a solvent-soluble thermoplastic polymer is preferable, and they can be used alone or in combination with each other.

  When light irradiation (exposure) is performed on a coating film formed by applying the photopolymerizable composition of the present invention, photopolymerization is started in a portion where light is strong, and a concentration gradient of the radical polymerizable compound can be generated accordingly. It is considered that the diffusion transfer of the radical polymerizable compound occurs from the weak part to the strong part. The reason why three-dimensional refractive index modulation can occur in the photopolymerizable composition of the present invention is that the region in which the radical polymerizable compound is present densely and the binder polymer depending on the intensity of the recording light as a result of the diffusion transfer. This is considered to be due to the difference in refractive index between these regions. In order to increase the recording sensitivity, it is preferable that the radically polymerizable compound and the binder have different refractive indexes. As a result, the radical polymerizable compound and its polymerization reaction product and the binder in the portion irradiated with the laser beam (laser focal portion) and the non-irradiated portion (non-focal portion) by photopolymerization caused by non-resonant two-photon absorption. The composition ratio becomes non-uniform, a large refractive index modulation can occur, and the recording sensitivity can be increased. The refractive index modulation formed is preferably greater than 0.005, more preferably greater than 0.01, and even more preferably greater than 0.05. The difference between the refractive index of the radical polymerizable compound and the binder may be either the refractive index of the polymerizable compound or the refractive index of the binder, but from the viewpoint of recording sensitivity, the binder Is more preferably lower in refractive index than radically polymerizable compounds.

  In order to change the refractive index of the radically polymerizable compound and the binder, either the radically polymerizable compound or the binder has at least one aryl group, aromatic heterocyclic group, chlorine atom, bromine atom, iodine atom, It preferably contains a sulfur atom and the other does not contain them, and the radical polymerizable compound contains at least one aryl group, aromatic heterocyclic group, chlorine atom, bromine atom, iodine atom, sulfur atom, It is preferable not to contain.

  Examples of preferred binders will be described below, divided into A) refractive index: radical polymerizable compound> binder embodiment and B) refractive index: binder> radically polymerizable compound.

A) Refractive Index: Polymerizable Compound> Preferred Examples of Binders in the Mode of Binder (hereinafter referred to as “Low Refractive Index Binder”) Specific examples of preferred low refractive index binders include acrylates and alpha-alkyl acrylate esters, acidic polymers And interpolymers (eg polymethyl methacrylate and polyethyl methacrylate, copolymers of methyl methacrylate and other alkyl (meth) acrylates), polyvinyl esters (eg polyvinyl acetate, polyacetic acid / vinyl acrylate, poly Acetic acid / vinyl methacrylate and hydrolyzable polyvinyl acetate), ethylene / vinyl acetate copolymers, saturated and unsaturated polyurethanes, butadiene and isoprene polymers and copolymers, weights on the order of 4,000 to 1,000,000 Average High molecular weight poly (ethylene oxide) of polyglycol having molecular weight, epoxidized product (for example, epoxidized product having acrylate or methacrylate group), polyamide (for example, N-methoxymethyl polyhexamethylene adipamide), cellulose ester (for example, cellulose Acetate, cellulose acetate succinate and cellulose acetate butyrate), cellulose ethers (eg, methylcellulose, ethylcellulose, ethylbenzylcellulose), polycarbonates, polyvinyl acetals (eg, polyvinyl butyral and polyvinyl formal), polyvinyl alcohol, polyvinylpyrrolidone, US Pat. , 458,311 and in U.S. Pat. No. 4,273,857, acid-containing polymers and copolymers, And amphoteric polymer binders disclosed in U.S. Pat. No. 4,293,635, more preferably cellulose acetate butyrate polymer, cellulose acetate lactate polymer, polymethyl methacrylate, methyl methacrylate / methacrylic acid And acrylic polymers and interpolymers including methyl methacrylate / acrylic acid copolymer, methyl methacrylate / acrylic acid or C2-C4 alkyl methacrylate / acrylic acid or methacrylic acid terpolymer, polyvinyl acetate, polyvinyl Examples include acetal, polyvinyl butyral, polyvinyl formal, and mixtures thereof.

  A fluorine atom-containing polymer is also preferable as the low refractive index binder. Preferably, fluoroolefin is an essential component, and one or more selected from alkyl vinyl ether, alicyclic vinyl ether, hydroxy vinyl ether, olefin, haloolefin, unsaturated carboxylic acid and ester thereof, and carboxylic acid vinyl ester Examples thereof include polymers soluble in an organic solvent containing an unsaturated monomer as a copolymerization component. More preferably, the weight average molecular weight is from 5,000 to 200,000, and the fluorine atom content is from 5 to 70% by mass.

  As the fluoroolefin in the fluorine atom-containing polymer, tetrafluoroethylene, chlorotrifluoroethylene, vinyl fluoride, vinylidene fluoride, or the like is used. In addition, as other copolymerization components, alkyl vinyl ethers include ethyl vinyl ether, isobutyl vinyl ether, n-butyl vinyl ether, alicyclic vinyl ethers such as cyclohexyl vinyl ether and derivatives thereof, hydroxy vinyl ethers such as hydroxybutyl vinyl ether, olefins and halo. Examples of olefins include ethylene, propylene, isobutylene, vinyl chloride, and vinylidene chloride. Examples of carboxylic acid vinyl esters include vinyl acetate and n-vinyl butyrate. Examples of unsaturated carboxylic acids and esters include (meth) acrylic acid and crotonic acid. Unsaturated carboxylic acids and methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, iso (meth) acrylate C1-C18 alkyl esters of (meth) acrylic acid, such as lopyr, butyl (meth) acrylate, hexyl (meth) acrylate, octyl (meth) acrylate, lauryl (meth) acrylate, hydroxyethyl (meth) C2-C8 hydroxyalkyl esters of (meth) acrylic acid such as acrylate, hydroxypropyl (meth) acrylate, and N, N-dimethylaminoethyl (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate, etc. Can be mentioned. These radical polymerizable monomers may be used singly or in combination of two or more, and if necessary, a part of the monomer may be used as another radical polymerizable monomer such as styrene, α -You may substitute with vinyl compounds, such as methylstyrene, vinyl toluene, and (meth) acrylonitrile. Further, as other monomer derivatives, carboxylic acid group-containing fluoroolefin, glycidyl group-containing vinyl ether, and the like can also be used.

  Specific examples of the aforementioned fluorine atom-containing polymer include, for example, “Lumiflon” series (for example, Lumiflon LF200, weight average molecular weight: about 50,000) manufactured by Asahi Glass Co., Ltd., which is soluble in an organic solvent having a hydroxyl group. In addition, organic solvent-soluble fluorine atom-containing polymers are also marketed by Daikin Industries, Ltd., Central Glass Co., Ltd., and Penwort Co., Ltd., and these can also be used.

  Among the low refractive index binders described above, as a binder suitable for use in combination with the radical polymerizable compound and the non-resonant two-photon absorption compound, cellulose ester, polyvinyl alcohol, polyvinyl acetate, polyvinyl butyral, polyvinyl formal, polyurethane, And at least one polymer selected from the group consisting of fluorine atom-containing polymers.

B) Refractive index: Binder> Preferable example of the binder in the aspect of polymerizable compound (hereinafter referred to as “high refractive index binder”)
Specific examples of preferable high refractive index binders include polystyrene polymers, and copolymers such as acrylonitrile, maleic anhydride, acrylic acid, methacrylic acid and esters thereof, and vinylidene chloride copolymers (eg, vinylidene chloride / acrylonitrile). Copolymer, vinylidene chloride / methacrylate copolymer, vinylidene chloride / vinyl acetate copolymer), polyvinyl chloride and copolymers (eg, polyvinyl chloride / acetate, vinyl chloride / acrylonitrile copolymer), polyvinyl benzal synthesis Rubber (for example, butadiene / acrylonitrile copolymer, acrylonitrile / butadiene / styrene copolymer, methacrylate / acrylonitrile / butadiene / styrene copolymer, 2-chlorobutadiene-1,3 polymer, chlorinated rubber) , Styrene / butadiene / styrene, styrene / isoprene / styrene block copolymer), copolyesters (e.g., formula HO (CH ₂₎ polymethylene glycol nOH (n in the formula is an integer of 2 to 10), and (1) produced from reaction products of hexahydroterephthalic acid, sebacic acid and terephthalic acid, (2) terephthalic acid, isophthalic acid and sebacic acid, (3) terephthalic acid and sebacic acid, (4) terephthalic acid and isophthalic acid And (5) mixtures of the glycols and (i) terephthalic acid, isophthalic acid and sebacic acid, and (ii) copolyesters made from terephthalic acid, isophthalic acid, sebacic acid and adipic acid), polyN -Vinylcarbazole and copolymers thereof, and H.I. Examples include carbazole-containing polymerization as disclosed in Journal of Polymer Science: Polymer Chemistry Edition, Vol. 18, pages 9 to 18 (1979) by Kamogawa et al., More preferably polystyrene, poly (styrene / acrylonitrile), poly (polystyrene). (Styrene / methyl methacrylate), and polyvinyl benzal and mixtures thereof.

  Content of the binder in the photopolymerizable composition of this invention is 10-90 mass%, for example, Preferably it is 45-75 mass%.

Other Components The photopolymerizable composition of the present invention can contain an appropriate amount of additives such as a chain transfer agent, a heat stabilizer, a plasticizer, and a solvent as necessary.

  The photopolymerizable composition of the present invention may preferably contain a chain transfer agent. Preferred chain transfer agents are thiols such as 2-mercaptobenzoxazole, 2-mercaptobenzthiazole, 2-mercaptobenzimidazole, 4-methyl-4H-1,2,4-triazole-3-thiol, 4 , 4-thiobisbenzenethiol, p-bromobenzenethiol, thiocyanuric acid, 1,4-bis (mercaptomethyl) benzene, p-toluenethiol, etc., as described in U.S. Pat. No. 4,414,312 and JP-A 64-13144 Thiols, disulfides described in JP-A-2-291561, thiones described in U.S. Pat. No. 3,558,322 and JP-A-64-17048, O-acylthiohydroxamates described in JP-A-2-291560, and N -Alkoxypyridinethiones are also included. In particular, when the polymerization initiator is 2,4,5-triphenylimidazolyl dimer, it is preferable to use a chain transfer agent. The amount of the chain transfer agent used is preferably 1.0 to 30% by mass relative to the entire composition.

A heat stabilizer (thermal polymerization inhibitor) can be added to the photopolymerizable composition of the present invention for the purpose of preventing polymerization during storage and maintaining storage stability.
Useful heat stabilizers include hydroquinone, phenidone, p-methoxyphenol, alkyl and aryl substituted hydroquinones and quinones, catechol, t-butylcatechol, pyrogallol, 2-naphthol, 2,6-di-t-butyl- p-cresol, phenothiazine, chloranneal and the like are included. Also useful are dinitroso dimers described in US Pat. No. 4,168,982 to Pazos.
The heat stabilizer is preferably added in the range of 0.001 to 5 parts by mass with respect to 100 parts by mass of the radical polymerizable compound.

Plasticizers can be used to alter the adhesion, flexibility, hardness, and other mechanical properties of the photopolymerizable composition. The plasticizer also has the effect of promoting the movement of the radical polymerizable compound and increasing the refractive index modulation amount.
Examples of the plasticizer include triethylene glycol dicaprylate, triethylene glycol bis (2-ethylhexanoate), tetraethylene glycol diheptanoate, diethyl sebacate, dibutyl suberate, tris (2-ethylhexyl) phosphate, Examples include tricresyl phosphate and dibutyl phthalate. What is necessary is just to set the addition amount of a plasticizer suitably.

  The various components described above can be synthesized by known methods, and some are available as commercial products.

  The photopolymerizable composition of the present invention can be prepared by a usual method. For example, the above-mentioned essential components and optional components can be mixed as they are, or can be prepared by adding a solvent as necessary.

  Examples of the solvent include ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone, acetone and cyclohexanone, ester solvents such as ethyl acetate, butyl acetate, ethylene glycol diacetate, ethyl lactate and cellosolve acetate, cyclohexane, toluene and xylene. Hydrocarbon solvents, ether solvents such as tetrahydrofuran, dioxane, diethyl ether, cellosolv solvents such as methyl cellosolve, ethyl cellosolve, butyl cellosolve, dimethyl cellosolve, methanol, ethanol, n-propanol, 2-propanol, n-butanol, di Alcohol solvents such as acetone alcohol, fluorine solvents such as 2,2,3,3-tetrafluoropropanol, dichloromethane, chloroform, 1,2-di Halogenated hydrocarbon solvents such as Roroetan, N, may be mentioned amide solvents such as N- dimethylformamide.

  The photopolymerizable composition of the present invention can be applied directly onto a substrate, spin-coated, or cast as a film and then laminated to the substrate by conventional methods. The solvent used can be removed by evaporation during drying.

  The photopolymerizable composition of the present invention is a two-photon absorption polymerizable composition that utilizes two-photon absorption (non-resonant two-photon absorption) in a polymerization reaction, and can be used for various applications that use photopolymerization. It is suitable for optical recording applications and is particularly suitable for a three-dimensional optical recording medium because it can perform three-dimensional refractive index modulation. The photopolymerizable composition of the present invention is preferably subjected to a refractive index modulation recording by irradiating light such as laser light, and then irradiating the entire surface with UV or visible light to cause one-photon absorption to perform a fixing treatment. . Further, it is also preferable to perform heating at 40 to 160 ° C.

[Optical recording medium]
The optical recording medium of the present invention has a recording layer containing the photopolymerizable composition of the present invention. That is, the recording layer contains the radical polymerizable composition, the nonresonant two-photon absorption compound and the binder, and optionally contains components such as a radical polymerization initiator.

The recording layer is preferably provided directly on the support or indirectly through another layer.
As the support, a transparent base film can be used. For example, a polyethylene film, a polypropylene film, a polyvinyl fluoride film, a polyvinylidene fluoride film, a polyvinyl chloride film, a polyvinylidene chloride film, ethylene-vinyl. Alcohol film, polyvinyl alcohol film, polymethyl methacrylate film, polyethersulfone film, polyetheretherketone film, polyamide film, tetrafluoroethylene-perfluoroalkylvinylether copolymer film, polyester film such as polyethylene terephthalate film, polyimide film, etc. A resin film is exemplified as a representative one.
Although the thickness of a support body is suitably selected according to the objective, generally it is 2-200 micrometers, Preferably it is the range of 10-50 micrometers.

  The optical recording medium of the present invention can be formed by coating the photopolymerizable composition of the present invention on a support. The recording layer forming coating solution can be prepared by dissolving the photopolymerizable composition in an appropriate solvent as described above, and this can be prepared by a method such as a spin coater, gravure coater, comma coater, or bar coater. The optical recording medium of the present invention can be obtained by coating on a support substrate and drying.

  The thickness of the recording layer is preferably as thick as possible in order to record as high density and large capacity as possible in a certain volume, but even in this case, if the optical density (OD) of the recording layer is high, the magnitude of the change in the refractive index of the material will be reduced. Since it cannot be used, it is preferable that the optical density at the wavelength of the recording light and the reading light is low. From these viewpoints, the thickness of the recording layer is preferably 50 to 2000 μm, more preferably 100 to 1000 μm, and most preferably in the range of 200 to 500 μm. Further, from the viewpoint of uniformly polymerizing and hardening the recording layer to the deep part, the optical density (OD) of the recording layer at this thickness is preferably 0.4 or less, more preferably 0.3 or less, and 0 Most preferably, it is 2 or less.

  Moreover, when the coating layer after drying has adhesiveness etc., a protective film can be laminated | stacked and the surface can be protected. It is also possible to laminate a film having oxygen barrier properties on the recording layer. As the protective film or the oxygen barrier film, for example, a thin film having a thickness of about 0.1 to 5 μm made of the material exemplified as the support substrate film can be used, and this is laminated. Use it. In this case, the contact surface of the laminate film with the recording layer can be subjected to release treatment so that it can be easily peeled off later.

  The optical recording medium of the present invention is a two-photon absorption optical recording medium that performs recording using two-photon absorption, and three-dimensional refractive index modulation is possible by photopolymerization caused by non-resonant two-photon absorption. It is suitable as an optical recording medium. Recording on the optical information recording medium of the present invention is performed by performing a recording process by exposure. In order to cause a two-photon absorption reaction, it is preferable to use a pulse laser. The peak output of the laser is preferably 1 kW to 100 GW, and the pulse width is preferably 1 femtosecond to 10 nanoseconds. As the laser light source to be used, a solid-state laser or fiber laser having an oscillation wavelength near the wavelength center of 1000 nm, a semiconductor laser having an oscillation wavelength near 780 nm, a solid-state laser, a fiber laser, a semiconductor laser having an oscillation wavelength in the range of 620 to 680 nm, A solid laser or the like can be used. A preferred embodiment of the information recording method on the optical recording medium of the present invention is as described later for the information recording method of the present invention.

  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.

[Information recording method]
The information recording method of the present invention records information by irradiating the optical information recording medium of the present invention with light. The light irradiated here is a laser beam having a wavelength where there is no linear absorption of the non-resonant two-photon absorption compound and having a wavelength longer than the linear absorption band of the compound. By using a laser beam having the above wavelength, non-resonant two-photon absorption can be caused. As a result, the radical polymerizable compound is photopolymerized to modulate the refractive index in the recording layer, preferably three-dimensional refraction. Information can be recorded by rate modulation.
The wavelength of the irradiated light may be determined according to the absorption characteristics of the non-resonant two-photon absorption compound included in the recording layer, but is in the range of 400 to 1600 nm, for example, and the excitation light is not subjected to absorption or scattering. Laser light having a wavelength of 400 to 850 nm is preferably used because it can reach the inside of the recording layer and can excite one point in the recording layer with extremely high resolution due to the square characteristic of non-resonant two-photon absorption.

  The present invention will be further described below with reference to examples. However, this invention is not limited to the aspect shown in the Example.

[Synthesis example of radically polymerizable compound]
The following exemplary compounds were synthesized according to the following scheme.

Among the exemplary compounds synthesized by the above scheme, the following compounds were identified by ¹ H NMR. The results are shown below.
M-17; ¹ H NMR (300 MHz, CDCl ₃ ) δ2.00 (s, 3H), 3.05 (m, 4H), 3.21 (s, 4H), 4.95 (m, 1H), 5.20 (s, 2H)
M-18; ¹ H NMR (300 MHz, CDCl ₃ ) δ 3.16 (d, 2H), 3.18 (d, 2H), 3.23 (s, 4H), 5.20 (s, 2H), 5.20 (m, 1H) , 7.30 (m, 3H), 8.0 (m, 3H)
M-46; ¹ H NMR (300 MHz, CDCl ₃ ) δ 3.16 (d, 2H), 3.18 (d, 2H), 3.24 (s, 4H), 5.20 (s, 2H), 5.22 (m, 1H) , 7.36 (m, 2H), 7.79 (dd, 1H), 7.80 (dd, 1H)
M-47; ¹ H NMR (300 MHz, CDCl ₃ ) δ 3.16 (d, 2H), 3.18 (d, 2H), 3.24 (s, 4H), 5.20 (s, 2H), 5.20 (m, 1H) , 7.30 (dd, 1H), 7.48 (d, 1H), 7.79 (d, 1H) M-44; ¹ H NMR (300 MHz, CDCl ₃ ) δ2.00 (s, 3H), 2.80-3.80 (m, 7H), 4.10-4.30 (m, 2H), 4.85 (d, 2H)
M-35; ¹ H NMR (300 MHz, CDCl ₃ ) δ2.95 (m, 2H), 2.36 (s, 2H), 4.50 (m, 2H), 5.60 (s, 1H), 5.85 (s, 1H)
^{MD-1; 1 H NMR (} 300 MHz, CDCl 3) δ1.01 (t, 3H), 1.53 (dd, 2H), 1.87~1.99 (m, 2H), 3.07 (dd, 4H), 3.18~3.33 ( m, 4H), 4.62 (dd, 2H), 5.09-5.19 (m, 1H), 5.26 (s, 2H), 7.25-7.34 (m, 2H), 7.47 (t, 1H), 7.68 (d, 1H) (Λmax = 341.0, ε = 40859 (in CH ₂ Cl ₂ ))
MD-2; ¹ H NMR (300 MHz, CDCl ₃ ) δ1.02 (t, 3H), 1.56 (dd, 2H), 1.90 to 2.00 (m, 2H), 2.6.2 to 2.71 (m, 4H), 3.08 (dd, 4H), 3.24 (s, 4H), 4.39 to 4.49 (m, 4H), 4.60 (dd, 2H), 5.01 to 5.09 (m, 1H), 5.23 (s, 2H), 7.29 to 7.34 ( m, 2H), 7.47 (t, 1H), 7.69 (d, 1H) (λmax = 341.0, ε = 41139 (in CH ₂ Cl ₂ ))

[Example 1]
Preparation of Photopolymerizable Composition A photopolymerizable composition having the following composition was mixed in a glove box under a nitrogen atmosphere to prepare a photopolymerizable composition.
Radical polymerization compound: Exemplified compound M-18 1.15g
Non-resonant two-photon absorption compound: DEAW 0.02g
Polymerization initiator: Cl-HABI 0.03g
Binder: Cellulose acetate butyrate (CAB) 1.25g
Chain transfer agent: A-1 0.045g
Solvent: 7.8 g of dichloromethane

[Examples 2 and 3]
A photopolymerizable composition was prepared in the same manner as in Example 1 except that the exemplified compounds shown in Table 1 were used in place of the radical polymerizable compound M-18.

[Example 4]
A photopolymerizable composition was prepared in the same manner as in Example 1 except that polyvinyl acetate (PVAc) was used instead of CAB as a binder.

[Comparative Examples 1 and 2]
Photopolymerizability in the same manner as in Example 1 except that the following comparative compounds R-1 and R-2 (compounds described in JP-A-2004-346238) were used in place of the radical polymerizable compound M-18. A composition was prepared.

Measurement of Refractive Index A solution prepared by adjusting the radical polymerizable compound and binder shown in Table 1 to 10 ⁻³ mol / L with methylene chloride was spin-coated on a glass substrate to obtain a coated sample. They were measured by ellipsometry (manufactured by Woollam Japan) to determine the refractive index nD. The results are shown in Table 2 below.

Confirmation of absorption characteristics of Exemplified Compound MD-1 and Compound DEAW Absorption spectra of the above Exemplified Compound MD-1 and Compound DEAW solution (solvent: methylene chloride, solution concentration: 1 × 10 ⁻⁵ mol / L) were measured using UV-3600 (Shimadzu). And the absorption characteristics were determined from the absorption spectrum. The absorption characteristics of Exemplified Compound MD-1 were λmax = 341.0 nm and the molar extinction coefficient ε = 40738 mol·l · cm ⁻¹ at λmax. The absorption characteristics of Compound DEAW are λmax = 494 nm, molar extinction coefficient ε = 73400 mol·l · cm ^{−1 at} λmax, molar extinction coefficient ε = 0 mol·l · cm ⁻¹ at wavelength 800 nm, and linear absorption at wavelength 800 nm. Did not exist. Furthermore, in the absorption spectrum of the compound DEAW, it was confirmed that a linear absorption band was present on the shorter wavelength side than 800 nm.

[Examples 5 to 8, Comparative Examples 3 and 4]
Preparation of optical recording medium (two-photon absorption medium) The photopolymerizable composition shown in Table 3 was spin-coated on a preparation glass plate, and the solvent was dried to form a recording layer. The film thickness of the recording layer was in the range of 5-10 μm. Further, a sample having an overcoat (oxygen barrier film) was produced by further pressing a PET film on the formed recording layer.

Evaluation of Recording Sensitivity Recording sensitivity was evaluated by performing recording and reproduction on the optical recording media of Examples 5 to 8 and Comparative Examples 3 and 4 by the following method.
Using a Ti: Sapphire pulse laser (pulse width: 100 fs, repetition rate: 80 MHz, average output: 1 W, peak power: 100 kW) that can be measured in the wavelength range from 700 nm to 1000 nm, the pulse light of 800 nm of the laser is used for each optical recording medium. Was recorded by converging with an NA 0.6 lens.
For recording reproduction, a reflected light signal obtained by irradiating a 660 nm semiconductor laser was read out. The case where the reflected light signal was very high was judged as ◎, the case where it was high as ○, the case where it was moderate as Δ, and the case where the signal was not visible as ×. The results are shown in Table 3.

Evaluation Results As shown in Table 3, the optical recording media of Examples 5 to 8 using the photopolymerizable compositions of Examples 1 to 4 were comparative examples using the photopolymerizable compositions of Comparative Examples 1 and 2. Compared with the optical recording media of 3 and 4, all had excellent recording sensitivity.

  Since the photopolymerizable composition of the present invention can perform higher density recording, it is suitable for production of a three-dimensional recording medium capable of high density recording.

Claims (18)

A photopolymerizable composition comprising a radical polymerizable compound represented by the following general formula (I), a non-resonant two-photon absorption compound, and a binder.

[In the general formula (I), R ¹ represents a hydrogen atom or an alkyl group, and Z ¹ represents an atomic group forming a ring structure with adjacent carbon atoms, sulfur atoms, and carbon atoms bonded to the sulfur atoms. ] The photopolymerizable composition according to claim 1, which is a polymerizable composition for optical recording. The photopolymerizable composition according to claim 1 or 2, wherein the radically polymerizable compound represented by the general formula (I) is a compound represented by the following general formula (II).

[In general formula (II), R ¹ has the same definition as in general formula (I), R ¹² represents a hydrogen atom or an alkyl group, and R ¹³ , R ¹⁴ and R ¹⁵ are each independently a hydrogen atom, alkyl Group, aryl group, heterocyclic group, alkoxy group, aryloxy group, alkylthio group, arylthio group, alkoxycarbonyl group, aryloxycarbonyl group, acyloxy group, acylamino group, sulfonylamino group, amino group, acyl group or halogen group M1 represents 0 or 1. ] In general formula (II), R ¹ and R ¹² each independently represent a hydrogen atom or a methyl group, and R ¹³ , R ¹⁴ and R ¹⁵ each independently represent a hydrogen atom, an alkyl group, an aryl group, an alkoxy group, The photopolymerizable composition according to claim 3, which represents an aryloxy group, an alkoxycarbonyl group, an aryloxycarbonyl group, an acyloxy group, an acylamino group, an amino group, or an acyl group. In the general formula (II), R ¹ and R ¹² are both hydrogen, R ^13, R ¹⁴ and R ¹⁵ each independently represent a hydrogen atom, an alkyl group, an aryl group, an alkoxy group, an aryloxy group or acyloxy The photopolymerizable composition according to claim 3, which represents a group and m1 represents 1. The photopolymerizable composition according to claim 1 or 2, wherein the radically polymerizable compound represented by the general formula (I) is a compound represented by the following general formula (III).

[In general formula (II), R ¹ has the same definition as in general formula (I), and R ²³ , R ²⁴ and R ²⁵ each independently represents a hydrogen atom, an alkyl group, an aryl group, a heterocyclic group, an alkoxy group. A group, an aryloxy group, an alkylthio group, an arylthio group, an alkoxycarbonyl group, an aryloxycarbonyl group, an acyloxy group, an acylamino group, a sulfonylamino group, an amino group, an acyl group, or a halogen group, and m2 represents 0 or 1. ] In the general formula (III), R ¹ represents a hydrogen atom or a methyl group, R ^23, R ²⁴ and R ² ₅ are each independently a hydrogen atom, an alkyl group, an aryl group, an alkoxy group, an aryloxy group, an alkoxycarbonyl The photopolymerizable composition according to claim 6, which represents a group, an aryloxycarbonyl group, an acyloxy group, an acylamino group, an amino group, or an acyl group. In the general formula (III), R ¹ represents a hydrogen atom or a methyl group, R ^23, R ²⁴ and R ²⁵ each independently represent a hydrogen atom, an alkyl group, an aryl group, an alkoxy group, an aryloxy group or an acyloxy group The photopolymerizable composition according to claim 6, wherein m2 represents 0. The photopolymerizable composition according to any one of claims 1 to 8, further comprising a radical polymerization initiator. The photopolymerizable composition according to any one of claims 1 to 9, wherein the binder has a refractive index different from that of the radical polymerizable compound. The photopolymerizable composition according to claim 10, wherein the binder has a lower refractive index than the radically polymerizable compound. The binder according to any one of claims 1 to 11, wherein the binder is at least one polymer selected from the group consisting of cellulose ester, polyvinyl alcohol, polyvinyl acetate, polyvinyl butyral, polyvinyl formal, polyurethane, and a fluorine atom-containing polymer. The photopolymerizable composition as described. The photopolymerizable composition according to claim 1, wherein the non-resonant two-photon absorption compound is an organic dye. The photopolymerizable composition according to claim 13, wherein the organic dye is at least one selected from the group consisting of a cyanine dye, a merocyanine dye, an oxonol dye, and a polyaryl dye. An optical recording medium comprising a recording layer comprising the photopolymerizable composition according to claim 1. An information recording method for recording information by irradiating the optical recording medium according to claim 15 with light,
As the light to be irradiated, laser light having a wavelength at which linear absorption of the non-resonant two-photon absorption compound does not exist and having a wavelength longer than the linear absorption band of the compound is used. Recording method. The information recording method according to claim 16, wherein information is recorded by causing refractive index modulation in the recording layer by the light irradiation. The information recording method according to claim 17, wherein the refractive index modulation is three-dimensional refractive index modulation.