JP7536493B2 - Optical elements, optical instruments, imaging devices - Google Patents

Description

The present invention relates to an optical element, and an optical device and an imaging device using the optical element, and in particular to an optical element with high secondary dispersion characteristics.

In general, the refractive index of optical materials such as glass and organic resins increases gradually toward the shorter wavelength side. Indices that express the wavelength dispersion of this refractive index include the Abbe number (ν _d ) and the second-order dispersion characteristic (θ _g,F ). The Abbe number and the second-order dispersion characteristic are values that are specific to each optical material, but in most cases, they fall within a certain range.
The Abbe number (ν _d , Abbe number based on the d line) and the second-order dispersion characteristic (θ _g,F ) are expressed by the following equations.
ν _d = (n _d -1)/(n _F -n _C )
θ _g,F = (n _g - n _F )/(n _F - n _C )
n _d : Refractive index at wavelength 587.6 nm n _F : Refractive index at wavelength 486.1 nm n _C : Refractive index at wavelength 656.3 nm _ng : Refractive index at wavelength 435.8 nm However, by designing the composition (material type and molecular structure) of the optical material (glass material, organic resin, etc.) in detail, optical materials with high second-order dispersion characteristics outside the above-mentioned certain range of values have also been synthesized. For example, polyvinylcarbazole, which is an organic resin, has higher second-order dispersion characteristics than general-purpose organic resin materials.
In general, in refractive optical systems, chromatic aberration is reduced by combining glass materials with different dispersion characteristics. For example, in objective lenses for telescopes and the like, a glass material with small dispersion is used as a positive lens and a glass material with large dispersion is used as a negative lens, and chromatic aberration that appears on the axis is corrected by combining these. For this reason, when the lens configuration and number of lenses are restricted or when the glass materials used are limited, it may be very difficult to sufficiently correct chromatic aberration. As one method for solving such problems, optical elements are designed using glass materials with anomalous dispersion characteristics.
Furthermore, when manufacturing optical elements having aspherical shapes with excellent chromatic aberration correction functions, a method of molding an organic resin onto spherical glass or the like has the advantages of being superior in mass productivity, moldability, freedom of shape, and lightweight, rather than using glass material as the material. However, the optical properties of conventional organic resins are within a limited range, and there are few organic resins that exhibit unique dispersion properties.
Patent Document 1 discloses a cured product of a resin precursor containing a (meth)acrylate compound and a curable composition as a resin material having high secondary dispersion properties.

International Publication No. 2019/069488

Although the cured product disclosed in Patent Document 1 has high secondary dispersion properties, due to the components contained in the resin precursor to suppress precipitation of the monomer components, the secondary dispersion properties are reduced compared to the secondary dispersion properties of a cured product of the monomer components alone.
An object of the present invention is to provide a polymerizable composition in which precipitation of contained components is suppressed before curing and which exhibits high secondary dispersion characteristics after curing, and to provide an optical element having a cured product of such a polymerizable composition, and further to provide an optical instrument and an imaging device equipped with such an optical element.

〔上記式（２）中、
Ａ：炭素数１乃至３のアルキレン基である。
Ｐ：アクリロイルオキシ基又はメタクリロイルオキシ基である。
ｑ：０又は１である。〕
本発明の第２は、重合性組成物を重合させてなる硬化物を有する光学素子であって、
前記重合性組成物は、少なくとも芳香族イミド化合物と重合開始剤とを含有し、
前記芳香族イミド化合物が、下記式（３）で示される化合物であることを特徴とする。

〔上記式（３）中、
Ｘ ₁ 、Ｘ ₂ ：それぞれ独立に、炭素数が１乃至６のアルキレン基又はフェニレン基である。
前記アルキレン基の主鎖中のＣＨ ₂ の一つは、少なくとも一つの酸素原子又は硫黄原子に置き換えられていても良い。
前記アルキレン基は、炭素数１乃至６のアルキル基で置換されていても良い。
前記フェニレン基は、水素原子、炭素数１乃至３のアルキル基、主鎖中のＣＨ ₂ の少なくとも一つが酸素原子又は硫黄原子に置き換えられていても良い炭素数１乃至６のアルキレン基、のいずれかで置換されていても良い。
Ｐ ₁ 、Ｐ ₂ ：それぞれ独立に、アクリロイルオキシ基又はメタクリロイルオキシ基である。〕
本発明の第３は、筐体と、前記筐体内に配置された複数のレンズを有する光学系と、を有する光学機器であって、前記複数のレンズの少なくとも一つが上記本発明の光学素子であることを特徴とする。
本発明の第４は、筐体と、前記筐体内に配置された複数のレンズを有する光学系と、前記光学系を通過した光を受光する撮像素子と、を有する撮像装置であって、前記複数のレンズの少なくとも一つが、上記本発明の光学素子であることを特徴とする。 A first aspect of the present invention is an optical element having a cured product obtained by polymerizing a polymerizable composition,
The polymerizable composition contains at least an aromatic imide compound and a polymerization initiator,
The optical element according to the present invention is characterized in that the aromatic imide compound is a compound represented by the following formula (2):

[In the above formula (2),
A: an alkylene group having 1 to 3 carbon atoms.
P: An acryloyloxy group or a methacryloyloxy group.
q is 0 or 1.
A second aspect of the present invention is an optical element having a cured product obtained by polymerizing a polymerizable composition,
The polymerizable composition contains at least an aromatic imide compound and a polymerization initiator,
The aromatic imide compound is a compound represented by the following formula (3):

[In the above formula (3),
X ₁ and X ₂ : each independently represents an alkylene group having 1 to 6 carbon atoms or a phenylene group.
One of the _CH2s in the main chain of the alkylene group may be replaced by at least one oxygen atom or sulfur atom.
The alkylene group may be substituted with an alkyl group having 1 to 6 carbon atoms.
The phenylene group may be substituted with any one of a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, and an alkylene group having 1 to 6 carbon atoms in which at least one CH2 in the main chain _may be replaced with an oxygen atom or a sulfur atom.
P ₁ and P ₂ each independently represent an acryloyloxy group or a methacryloyloxy group.
A third aspect of the present invention is an optical device having a housing and an optical system having a plurality of lenses arranged within the housing, wherein at least one of the plurality of lenses is the optical element of the present invention.
A fourth aspect of the present invention is an imaging device having a housing, an optical system having a plurality of lenses arranged within the housing, and an imaging element that receives light that has passed through the optical system, wherein at least one of the plurality of lenses is the optical element of the present invention described above.

The optical element of the present invention has a cured product obtained by polymerizing a specific polymerizable composition, and the polymerizable composition has good precipitation of the components contained therein, and the cured product has a high second-order dispersion characteristic (θ _g,F ) of the refractive index, that is, a high chromatic aberration correction function. Therefore, in the optical element of the present invention, chromatic aberration can be efficiently removed, and by using the optical element, it is possible to reduce the weight and size of optical equipment and imaging devices.

1 is a cross-sectional view in the thickness direction that typically illustrates the configuration of one example of an optical element of the present invention. FIG. 1 is a cross-sectional view illustrating a schematic configuration of an imaging device using the optical element of the present invention.

As a result of intensive research, the present inventors have found that high secondary dispersion properties can be obtained in a cured product obtained by polymerizing an aromatic imide compound having a specific cyclic imide structure consisting of an aromatic ring and an imide bond. Furthermore, it has been found that by adjusting the number of aromatic rings and the number of imide bonds that form the cyclic imide structure, it is possible to suppress the crystallinity of the aromatic imide compound in the polymerizable composition while maintaining the secondary dispersion properties of the cured product, and thus the present invention has been achieved.

The following describes the embodiments of the present invention with reference to the drawings. Note that the present invention is not limited to the following embodiments, and the scope of the present invention also includes appropriate modifications and improvements to the following embodiments based on the ordinary knowledge of a person skilled in the art, provided that the modifications and improvements do not deviate from the spirit of the present invention.

[Polymerizable composition]
The polymerizable composition used in the present invention is a liquid containing at least an aromatic imide compound and a polymerization initiator, and can obtain a cured product by polymerization reaction. The aromatic imide compound is characterized in that it has a cyclic imide structure in which a ring is formed by an aromatic ring, and at least one of an acryloyloxy group and a methacryloyloxy group indirectly bonded to a nitrogen atom constituting the cyclic imide structure. Furthermore, the aromatic ring constituting the cyclic imide structure is characterized in that it forms only one cyclic imide structure, that is, the aromatic ring constituting the cyclic imide structure does not form two or more cyclic imide structures.

Hereinafter, the acryloyloxy group and the methacryloyloxy group will be collectively referred to as the "(meth)acryloyloxy group." In addition, the (meth)acryloyloxy group is "indirectly bonded" to the nitrogen atom constituting the cyclic imide structure means that the (meth)acryloyloxy group is not directly bonded to the nitrogen atom, and an atom or group is present between the (meth)acryloyloxy group and the nitrogen atom.

The aromatic imide compound used in the present invention preferably has at least one structure represented by the following formula (1) within the compound. Note that "having a structure represented by formula (1) within the compound" includes cases where the aromatic imide compound is a compound having only the structure represented by formula (1) and cases where the aromatic imide compound has a structure represented by formula (1) and a structure not represented by formula (1).

上記一般式（１）中、Ｘ、Ｙ、Ｐ、ｍ、ｎは以下の通りである。
Ｘ：炭素数が１乃至６のアルキレン基又はフェニレン基である。
前記アルキレン基の主鎖中のＣＨ₂の一つは、少なくとも一つの酸素原子又は硫黄原子に置き換えられていても良い。
前記アルキレン基は、炭素数１乃至６のアルキル基で置換されていても良い。
前記フェニレン基は、水素原子、炭素数１乃至３のアルキル基、主鎖中のＣＨ₂の少なくとも一つが酸素原子又は硫黄原子に置き換えられていても良い炭素数１乃至６のアルキレン基、のいずれかで置換されていても良い。
ｍが２の時、二つのＸは互いに独立して選択される。
Ｙ：４価のビフェニル基又は２価のナフチレン基である。
Ｐ：アクリロイルオキシ基又はメタクリロイルオキシ基である。
ｍ：Ｙがナフチル基の時に１であり、ビフェニル基の時に２である。
ｎ：１乃至４の整数である。

In the above general formula (1), X, Y, P, m and n are as follows:
X is an alkylene group having 1 to 6 carbon atoms or a phenylene group.
One of the _CH2s in the main chain of the alkylene group may be replaced by at least one oxygen atom or sulfur atom.
The alkylene group may be substituted with an alkyl group having 1 to 6 carbon atoms.
The phenylene group may be substituted with any one of a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, and an alkylene group having 1 to 6 carbon atoms in which at least one _CH2 in the main chain may be replaced with an oxygen atom or a sulfur atom.
When m is 2, two X's are selected independently of each other.
Y is a tetravalent biphenyl group or a divalent naphthylene group.
P: An acryloyloxy group or a methacryloyloxy group.
m: is 1 when Y is a naphthyl group, and is 2 when Y is a biphenyl group.
n is an integer from 1 to 4.

In the aromatic imide compound used in the present invention, it is preferable that the aromatic ring of the cyclic imide structure is composed of a monoimide structure in which the aromatic ring is a naphthylene group or a monoimide structure in which the aromatic ring is a phenylene group. By being composed of these cyclic imide structures, high secondary dispersion characteristics are obtained in the cured product while maintaining the crystallinity suppression of the aromatic imide compound in the polymerizable composition. In addition, by introducing a (meth)acryloyloxy group into the nitrogen atom constituting the cyclic imide structure via an alkylene group, a phenylene group, or a phenylene alkylene group, high secondary dispersion characteristics and high transmittance are obtained in the cured product while maintaining the crystallinity suppression in the polymerizable composition.

More specifically, aromatic imide compounds having the structure represented by formula (1) above include aromatic imide compounds having the structure represented by formula (2) or formula (3) below.

The aromatic imide compound having the structure shown in formula (2) is the compound in formula (1) where Y is a naphthylene group, and has one structure shown in formula (1).

上記式（２）中、Ａ、Ｐ、ｑは以下の通りである。
Ａ：炭素数１乃至３のアルキレン基である。
Ｐ：アクリロイルオキシ基又はメタクリロイルオキシ基である。
ｑ：０又は１である。

In the above formula (2), A, P and q are as follows:
A: an alkylene group having 1 to 3 carbon atoms.
P: An acryloyloxy group or a methacryloyloxy group.
q: 0 or 1.

In addition, the aromatic imide compound having the structure shown in the following formula (3) has a structure in which Y in formula (1) is a biphenyl group. In other words, it has two cyclic imide structures in which a ring is formed by an aromatic ring.

上記式（３）中、Ｘ₁、Ｘ₂、Ｐ₁、Ｐ₂は以下の通りである。
Ｘ₁、Ｘ₂：それぞれ独立に、炭素数が１乃至６のアルキレン基又はフェニレン基である。
前記アルキレン基の主鎖中のＣＨ₂の一つは、少なくとも一つの酸素原子又は硫黄原子に置き換えられていても良い。
前記アルキレン基は、炭素数１乃至６のアルキル基で置換されていても良い。
前記フェニレン基は、水素原子、炭素数１乃至３のアルキル基、主鎖中のＣＨ２の少なくとも一つが酸素原子又は硫黄原子に置き換えられていても良い炭素数１乃至６のアルキレン基、のいずれかで置換されていても良い。
Ｐ₁、Ｐ₂：それぞれ独立に、アクリロイルオキシ基又はメタクリロイルオキシ基である。

In the above formula (3), X ₁ , X ₂ , P ₁ and P ₂ are as follows:
X ₁ and X ₂ : each independently represents an alkylene group having 1 to 6 carbon atoms or a phenylene group.
One of the _CH2s in the main chain of the alkylene group may be replaced by at least one oxygen atom or sulfur atom.
The alkylene group may be substituted with an alkyl group having 1 to 6 carbon atoms.
The phenylene group may be substituted with any one of a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, and an alkylene group having 1 to 6 carbon atoms in which at least one CH2 in the main chain may be replaced with an oxygen atom or a sulfur atom.
P ₁ and P ₂ : each independently represents an acryloyloxy group or a methacryloyloxy group.

In an aromatic imide compound having two cyclic imide structures as shown in the above formula (3), by introducing a different structure into each cyclic imide structure, the symmetry of the aromatic imide compound is weakened, and high transmittance is obtained.

In general, compounds with long conjugated structures, such as aromatic compounds, have a smaller band gap than general-purpose materials, and therefore the absorption edge in the ultraviolet region is shifted toward the visible light region. As a result, compounds with long conjugated structures have high refractive index characteristics and high secondary dispersion characteristics. However, simply linking aromatic compounds to construct long conjugated structures does not result in a practical material. For example, large aromatic compounds have issues with synthesis, coloring, and reduced transmittance at the short wavelength side of the visible light region, as well as compatibility with other compounds and crystal precipitation in compositions.

Therefore, when using them as optical materials, it is necessary to adjust the length of the conjugated structure from the viewpoint of improving transmittance and suppressing crystallinity. However, shortening the conjugated structure of aromatic compounds or widening the intermolecular distance by steric hindrance of the substituents in order to improve transmittance or suppress crystallinity also leads to a decrease in the refractive index and secondary dispersion characteristics. The aromatic imide compounds according to the present invention can be considered as follows.

When an aromatic ring forms a ring with an imide bond, the conjugation extends and the polymer shows high secondary dispersion characteristics. However, when one aromatic ring forms a ring with two imide bonds, the conjugation extends and symmetry increases, resulting in high crystallinity. In the present invention, by limiting the number of rings formed by one aromatic ring and an imide bond to one, it is believed that the conjugation can be extended and the secondary dispersion characteristics of the cured product can be improved while breaking the symmetry and suppressing crystallinity. Furthermore, by introducing a methine group into the imide structure and introducing a (meth)acryloyloxy group to each branched end, the steric hindrance of the branched (meth)acryloyloxy group suppresses crystallinity and improves the transmittance of the cured product.

By reducing the crystallinity of the aromatic imide compound, the compatibility with other compounds and resins in the polymerizable composition is improved.

In the above general formulas (1) to (3), examples of the alkyl group having 1 to 3 carbon atoms as a substituent of the phenylene group include a methyl group, an ethyl group, and an n-propyl group. Methyl and ethyl groups are more preferred.

Specific examples of aromatic imide compounds that can be used in the present invention are shown in Tables 1 and 2. The aromatic imide compounds are not limited to these, and may be used alone or in combination.

The method for producing the aromatic imide compound used in the present invention will now be described with reference to an example.
The method for producing the aromatic imide compound having a specific structure used in the present invention is not limited to a specific production route, and any production method can be adopted, and the compound can be synthesized using a known synthesis method.

The imidization reaction can be carried out using a known synthesis method, for example, as described in Journal of American Chemical Society, 130, 14410-14411 (2008).

The (meth)acrylate reaction can be selected arbitrarily. Representative methods that are preferably used include a method of esterifying a hydroxyl group using a (meth)acrylic acid halide or (meth)acrylic anhydride, an ester exchange reaction using an ester of a lower alcohol of (meth)acrylic acid, a direct esterification reaction in which (meth)acrylic acid and the diol are dehydrated and condensed using a dehydrating condensing agent such as N,N'-dicyclohexylcarbodiimide, and a method of overheating (meth)acrylic acid and the diol in the presence of a dehydrating agent such as sulfuric acid.

The number of functional groups of the (meth)acryloyloxy group, which is the polymerizable functional group of the aromatic imide compound, is preferably 2 or more from the viewpoints of suppressing crystallinity, transmittance, and compatibility with resins and other compounds, and more preferably 2 from the viewpoint of synthesis.

Next, the polymerizable composition used in the present invention will be described.
In the present invention, the polymerizable composition is a composition containing the above-mentioned aromatic imide compound and a polymerization initiator, and optionally containing a polymerization inhibitor, a photosensitizer, a heat stabilizer, a light stabilizer, an antioxidant, and a resin.

The content of the aromatic imide compound in the polymerizable composition is preferably 1.0% by mass or more and 99% by mass or less, and more preferably 50% by mass or more and 99% by mass or less.

Polymerization initiators include, but are not limited to, those that generate radical species or cationic species upon irradiation with light, and those that generate radical species upon heat.

Polymerization initiators that generate radical species upon irradiation with light include, but are not limited to, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-1-butanone, 1-hydroxy-cyclohexyl-phenyl ketone, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, 4-phenylbenzophenone, 4-phenoxybenzophenone, 4,4'-diphenylbenzophenone, and 4,4'-diphenoxybenzophenone.

As a polymerization initiator that generates cationic species upon irradiation with light, a suitable example is iodonium (4-methylphenyl) [4-(2-methylpropyl) phenyl]-hexafluorophosphate, but this is not limited to this.

Furthermore, examples of polymerization initiators that generate radical species by heat include azo compounds such as azobisisobutylnitrile (AIBN), and peroxides such as benzoyl peroxide, tert-butyl peroxypivalate, tert-butyl peroxyneohexanoate, tert-hexyl peroxyneohexanoate, tert-butyl peroxyneodecanoate, tert-hexyl peroxyneodecanoate, cumyl peroxyneohexanoate, and cumyl peroxyneodecanoate, but are not limited to these.

When the polymerization is initiated by irradiation with ultraviolet light or the like, a known sensitizer can also be used. Representative sensitizers include, but are not limited to, benzophenone, 4,4-diethylaminobenzophenone, 1-hydroxycyclohexyl phenyl ketone, isoamyl p-dimethylaminobenzoate, methyl 4-dimethylaminobenzoate, benzoin, benzoin ethyl ether, benzoin isobutyl ether, benzoin isopropyl ether, 2,2-diethoxyacetophenone, methyl o-benzoylbenzoate, 2-hydroxy-2-methyl-1-phenylpropan-1-one, and acylphosphine oxide.

The ratio of the photopolymerization initiator to the polymerizable resin component can be appropriately selected depending on the amount of light irradiation and the additional heating temperature. It can also be adjusted depending on the target average molecular weight of the resulting polymer.

The amount of photopolymerization initiator used for polymerization (curing) of the polymerizable composition is preferably in the range of 0.01% by mass to 10.00% by mass based on the polymerizable components. Depending on the reactivity of the resin and the wavelength of light irradiation, only one type of photopolymerization initiator can be used, or two or more types can be used in combination.

In addition, in the polymerizable composition, a polymerization inhibitor may be used as necessary to prevent polymerization from proceeding during the polymerization reaction or storage. Examples of polymerization inhibitors include hydroquinones such as p-benzoquinone, hydroquinone, hydroquinone monomethyl ether, and 2,5-diphenylparabenzoquinone, N-oxy radicals such as tetramethylpiperidinyl-N-oxy radical (TEMPO), substituted catechols such as tert-butylcatechol, amines such as phenothiazine, diphenylamine, and phenyl-β-naphthylamine, nitrosobenzene, picric acid, molecular oxygen, sulfur, and copper (II) chloride. Among these, hydroquinones, phenothiazine, and N-oxy radicals are preferred in terms of versatility and polymerization inhibition, and hydroquinones are particularly preferred.

The amount of polymerization inhibitor used is, relative to the aromatic imide compound, usually 10 ppm or more, preferably 50 ppm or more, with the upper limit usually 10,000 ppm or less, preferably 1,000 ppm or less. If the amount is too small, the effect of the polymerization inhibitor will not be manifested, or even if it is manifested, the effect will be small, and polymerization may proceed during the reaction or during concentration in the post-treatment process. Conversely, if the amount is too large, it is not preferable because it may become an impurity when producing the polymerizable composition described below, or may have adverse effects such as inhibiting polymerization reactivity.

There are no particular limitations on the light resistance stabilizer as long as it does not significantly affect the optical properties of the molded product. Representative examples include 2-(2H-benzotriazol-2-yl)-p-cresol, 2-(2H-benzotriazol-2-yl)-4,6-bis(1-methyl-1-phenylethyl)phenol, 2-[5-chloro(2H)-benzotriazol-2-yl]-4-methyl-6-(tert-butyl)phenol, 2-(2H-benzotriazol-2-yl)-4,6-di-tert -pentylphenol, 2-(2H-benzotriazol-2-yl)-4-(1,1,3,3-tetramethylbutyl)phenol, 2,2'-methylenedibis[6-(2H-benzotriazol-2-yl)-4-(1,1,3,3-tetramethylbutyl)]phenol, 2-(2H-benzotriazol-2-yl)-6-dodecyl-4-methylphenol and other benzotriazole-based materials, 2-cyano-3,3-diphenylethyl acrylate, 2-cyano-3,3-diphenylacrylic acid 2-ethylhexyl and other cyanoacrylate-based materials, triazine-based materials, octabenzone, benzophenone-based materials such as 2,2'-4,4'-tetrahydrobenzophenone, and the like. In some cases, the light resistance stabilizer also functions as a photosensitizer, in which case it is not necessary to add it.

The amount of light resistance stabilizer used in the polymerization (curing) of the polymerizable composition of the present invention is preferably in the range of 0.01% by mass to 10.00% by mass based on the total amount of polymerizable components.

There are no particular limitations on the heat stabilizer as long as it does not significantly affect the optical properties of the molded product, and examples include pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)]propionate, octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, benzenepropanoic acid, 3,5-bis(1,1-dimethylethyl)-4-hydroxy, C7-C9 side chain alkyl ester, and 4,6-bis(octylthiomethyl)-o-cresol. , 4,6-bis(dodecylthiomethyl)-o-cresol, hindered phenol-based materials such as ethylene bis(oxyethylene) bis[3-(5-tert-butyl-4-hydroxy-m-tolyl)]propionate, hexamethylene bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)]propionate, phosphorus-based materials such as tris(2,4-di-tert-butylphenyl)phosphite, and sulfur-based materials such as dioctadecyl 3,3'-thiodipropionate can be used.

There are no particular limitations on the antioxidant as long as it does not significantly affect the optical properties of the cured product. Representative examples include hindered amine-based materials such as bis(2,2,6,6-tetramethyl-4-piperidyl)sebacate and bis(1,2,2,6,6-pentamethyl-4-piperidyl)[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]butylmalonate. The amount of antioxidant added to the polymerizable composition is preferably in the range of 0.01% by mass to 10.00% by mass based on the total amount of polymerizable components.

The polymerizable composition may contain a resin. The resin is not particularly limited, and examples thereof include 1,3-adamantanediol dimethacrylate, 1,3-adamantanedimethanol dimethacrylate, tricyclodecane dimethanol diacrylate, pentaerythritol tetraacrylate, propoxylated neopentyl glycol diacrylate, dipropylene glycol diacrylate, ethoxylated bisphenol A dimethacrylate, tris(2-hydroxyethyl)isocyanurate triacrylate, 2(2-ethoxyethoxy)ethyl acrylate, stearyl acrylate, tetrahydrofuran, and the like. Furfuryl acrylate, 2-phenoxyethyl acrylate, isodecyl acrylate, isobornyl acrylate, isobornyl methacrylate, 1,3-butylene glycol diacrylate, 1,4-butanediol diacrylate, diethylene glycol diacrylate, 1,6-hexanediol diacrylate, triethylene glycol diacrylate, tripropylene glycol diacrylate, dipropylene glycol diacrylate, triethylene glycol dimethacrylate, ethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, 1,4-butanediol dimethacrylate, diethylene glycol dimethacrylate, 1,6-hexanediol dimethacrylate, tripropylene glycol dimethacrylate, dipropylene glycol dimethacrylate, trimethylolpropane trimethacrylate, 9,9-bis[4-(2-acryloyloxyethoxy)phenyl]fluorene, 9,9-bis[4-(2-methacryloyloxyethoxy)phenyl]fluorene, 9,9-bis[4-(2-acryloyloxy)phenyl]fluorene, 9,9-bis[4-(2-methacryloyloxy)phenyl]fluorene, benzyl acrylate, benzyl methacrylate Acrylate, butoxyethyl acrylate, butoxymethyl methacrylate, cyclohexyl acrylate, cyclohexyl methacrylate, 2-hydroxyethyl acrylate, 2-hydroxymethyl methacrylate, glycidyl acrylate, glycidyl methacrylate, phenoxyethyl acrylate, phenoxyethyl methacrylate, phenyl methacrylate, ethylene glycol diacrylate, ethylene glycol dimethacrylate, diethylene glycol diacrylate, diethylene glycol dimethacrylate, triethylene glycol diacrylate, triethylene glycol dimethacrylate acrylate, tetraethylene glycol diacrylate, tetraethylene glycol dimethacrylate, polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, neopentyl glycol diacrylate, neopentyl glycol dimethacrylate, ethylene glycol bisglycidyl acrylate, ethylene glycol bisglycidyl methacrylate, bisphenol A diacrylate, bisphenol A dimethacrylate, 2,2-bis(4-acryloxyethoxyphenyl)propane, 2,2-bis(4-methacryloxyethoxyphenyl)propane, 2,2-bis( 4-acryloxydiethoxyphenyl)propane, 2,2-bis(4-methacryloxydiethoxyphenyl)propane, bisphenol F diacrylate, bisphenol F dimethacrylate, 1,1-bis(4-acryloxyethoxyphenyl)methane, 1,1-bis(4-methacryloxyethoxyphenyl)methane, 1,1-bis(4-acryloxydiethoxyphenyl)methane, 1,1-bis(4-methacryloxydiethoxyphenyl)methane, 1,1-bis(4-acryloxyethoxyphenyl)sulfone, 1,1-bis(4-methacryloxyethoxyphenyl)sulfone, 1,1-bis(4-acryloxyethoxyphenyl)methane 1,1-bis(4-methacryloxydiethoxyphenyl)sulfone, 1,1-bis(4-methacryloxydiethoxyphenyl)sulfone, dimethyloltricyclodecane diacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, glycerol diacrylate, glycerol dimethacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, pentaerythritol tetramethacrylate, methylthioacrylate, methylthiomethacrylate, phenylthioacrylate, benzylthiomethacrylate, xylylenedithiol diacrylate butyl ether, xylylenedithiol dimethacrylate, mercaptoethyl sulfide diacrylate, mercaptoethyl sulfide dimethacrylate and other (meth)acrylate compounds; allyl compounds such as allyl glycidyl ether, diallyl phthalate, diallyl terephthalate, diallyl isophthalate, diallyl carbonate, diethylene glycol bisallyl carbonate; vinyl compounds such as styrene, chlorostyrene, methylstyrene, bromostyrene, dibromostyrene, divinylbenzene, 3,9-divinylspirobi(m-dioxane), diisopropenylbenzene and the like, but are not limited to these.

The resin may be a thermoplastic resin, for example, a polyolefin-based resin such as an ethylene homopolymer, a random or block copolymer of ethylene with one or more α-olefins such as propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, etc., a random or block copolymer of ethylene with one or more α-olefins such as vinyl acetate, acrylic acid, methacrylic acid, methyl acrylate, methyl methacrylate, a propylene homopolymer, a random or block copolymer of propylene with one or more α-olefins other than propylene such as 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, etc., a 1-butene homopolymer, an ionomer resin, or a mixture of these polymers; a hydrocarbon atom-based resin such as a petroleum resin or a terpene resin. Polyester resins such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; polyamide resins such as nylon 6, nylon 66, nylon 11, nylon 12, nylon 610, nylon 6/66, nylon 66/610, and nylon MXD; acrylic resins such as polymethyl methacrylate; styrene, acrylonitrile resins such as polystyrene, styrene-acrylonitrile copolymer, styrene-acrylonitrile-butadiene copolymer, and polyacrylonitrile; polyvinyl alcohol resins such as polyvinyl alcohol and ethylene-vinyl alcohol copolymer; polycarbonate resins; polyketone resins; polymethylene oxide resins; polysulfone resins; polyimide resins; and polyamideimide resins. These can be used alone or in combination of two or more.
Preferably, acrylate resins and methacrylate resins are used.

The content of the resin contained in the polymerizable composition is preferably 0.01% by mass to 99% by mass, and more preferably 0.01% by mass to 50% by mass, taking into consideration the refractive index characteristics of the resulting polymerizable composition and the brittleness of the molded product. Furthermore, in order to maintain the secondary dispersion characteristics and transmittance, the content is more preferably 0.01% by mass to 20% by mass.

[Optical elements]
Next, an optical element according to the present invention will be described with reference to the drawings.
The optical element of the present invention is characterized by having a cured product obtained by polymerizing the above-mentioned polymerizable composition, and is preferably a laminate of a transparent substrate and the cured product. The cured product exhibits high second-order dispersion characteristics of 0.60 to 0.74, so that the optical element of the present invention can efficiently remove chromatic aberration.
Fig. 1 shows a schematic cross-sectional view in the thickness direction of an embodiment of the optical element of the present invention. Fig. 1(a) shows a thin film of a cured product 1 obtained by polymerizing the polymerizable composition on one surface of a transparent substrate 2.

Transparent resin or transparent glass can be used for the transparent substrate 2. In this specification, "transparent" means that the transmittance of the entire visible light (light having a wavelength in the range of 380 nm to 780 nm) is 30% or more. The transparent substrates 2 and 3 are preferably made of glass, and examples of the materials that can be used include general optical glass such as silicate glass, borosilicate glass, and phosphate glass, quartz glass, and glass ceramics. The transparent base material 20 is preferably circular when viewed in a plane.

The optical element of FIG. 1(a) can be produced, for example, by forming a thin layer structure on a transparent substrate. Specifically, a mold made of a metal material is placed at a certain distance from the transparent substrate 2, and the gap between the mold and the transparent substrate 2 is filled with a fluid polymerizable composition, which is then lightly pressed down to form the mold. If necessary, the polymerizable composition is polymerized while maintaining the mold in that state.

The light irradiation for such a polymerization reaction is carried out using light of a suitable wavelength, usually ultraviolet light or visible light, corresponding to the mechanism caused by radical generation using a photopolymerization initiator. For example, light is uniformly irradiated onto the raw materials of the polymerizable composition, such as the monomers, through a light-transmitting material used as the transparent substrate 2. The amount of irradiated light is appropriately selected according to the mechanism caused by radical generation using the photopolymerization initiator and the content ratio of the photopolymerization initiator contained.

On the other hand, in the polymerization of the polymerizable composition by such a photopolymerization reaction, it is more preferable that the irradiated light is uniformly irradiated over the entire polymerizable composition that has been molded. Therefore, it is more preferable to select light of a wavelength that can be uniformly irradiated through the light-transmitting material used for the transparent substrate 2. In this case, it is more preferable for the present invention to reduce the thickness of the cured product 1 formed on the transparent substrate 2.

In FIG. 1(b), a thin film of a cured product 1 formed by polymerizing the polymerizable composition of the present invention is sandwiched between transparent substrates. In FIG. 1(b), the transparent substrates 2 and 3 each have a concave surface on the opposing side and are in contact with each other at the periphery, and the cured product 1 is a lens-like material with convex surfaces on both sides. The transparent substrates 2 and 3 can be made of a transparent resin or transparent glass, and are preferably made of glass. As glass, general optical glass such as silicate glass, borosilicate glass, and phosphate glass, quartz glass, and glass ceramics can be used. The transparent substrates 2 and 3 are preferably circular when viewed in a plane.

The optical element of FIG. 1(b) can be produced, for example, by pouring the polymerizable composition of the present invention between the transparent substrates 2 and 3 and gently pressing them together to form the shape. Then, while maintaining this state, the polymerizable composition is photopolymerized. This produces a laminate in which the cured product 1 is sandwiched between the transparent substrates 2 and 3.

Similarly, molded articles can also be produced by thermal polymerization. In this case, it is desirable to make the overall temperature more uniform, and reducing the total thickness of the molded article of the polymerizable composition formed on the substrate of the light-transmitting material is more suitable for the present invention. In addition, when increasing the total thickness of the molded article of the polymerizable composition to be formed, it is necessary to select the amount of irradiation, irradiation intensity, light source, etc., taking into consideration the film thickness, absorption of the resin component, and absorption of the fine particle component.

[Optical equipment]
Specific application examples of the optical element of the present invention will be described. Specific application examples include lenses constituting optical equipment (photography optical system) for cameras and video cameras, and lenses constituting optical equipment (projection optical system) for liquid crystal projectors. It can also be used as a pickup lens for DVD recorders and the like. These optical systems are composed of a plurality of lenses arranged in a housing, and at least one of the plurality of lenses can be the optical element described above.

[Imaging device]
Fig. 2 shows a configuration of a single-lens reflex digital camera 10 as an example of a preferred embodiment of an imaging device using the optical element of the present invention. Fig. 2 is a schematic cross-sectional view including the optical axis of the optical element used. In Fig. 2, a camera body 12 and a lens barrel 11, which is an optical device, are coupled together, and the lens barrel 11 is a so-called interchangeable lens that can be attached to and detached from the camera body 12.

Light from a subject is captured through an optical system consisting of multiple lenses 13, 15, etc., arranged on the optical axis of the photographing optical system inside the housing 30 of the lens barrel 11. The optical element of the present invention can be used for the lenses 13, 15, for example. Here, the lens 15 is supported by the inner tube 14, and is movably supported relative to the outer tube of the lens barrel 11 for focusing and zooming.

During the observation period before shooting, light from the subject is reflected by the main mirror 17 in the housing 31 of the camera body, passes through the prism 21, and then the photographed image is displayed to the photographer through the viewfinder lens 22. The main mirror 17 is, for example, a half mirror, and the light that passes through the main mirror is reflected by the sub-mirror 18 toward the AF (autofocus) unit 23, and this reflected light is used, for example, for distance measurement. The main mirror 17 is attached and supported by the main mirror holder 40, for example, by gluing. During shooting, the main mirror 17 and the sub-mirror 18 are moved out of the optical path via a driving mechanism (not shown), the shutter 19 is opened, and the image sensor 20 receives the light that enters from the lens barrel 11 and passes through the photographing optical system, forming a photographed light image. The aperture 16 is configured so that the brightness and focal depth during shooting can be changed by changing the opening area.

Note that, although the imaging device has been described here using a single-lens reflex digital camera, the optical element of the present invention can also be used in smartphones, compact digital cameras, and the like.

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples as long as it does not deviate from the gist of the invention. The synthesized product was analyzed using an NMR device (product name "JNM-ECA400" manufactured by JEOL Ltd.).

(Synthesis Example 1)
(1) Synthesis of E1 intermediate A mixture of 10 g of 4,4'-biphthalic anhydride, 4.1 g of 2-(4-aminophenyl)ethanol, and 50 ml of dimethylacetamide was added dropwise to a 200 ml three-neck flask under room temperature and nitrogen flow while stirring. After the addition was completed, the mixture was heated to 100°C and stirred at that temperature for 6 hours. After the reaction was completed, the vessel was cooled and concentrated under reduced pressure. Purification was performed by silica gel column chromatography to obtain 8.8 g of a monoimide body in which a 2-phenylethyl alcohol structure was introduced only on one side. A 300 ml three-neck flask was charged with 8.0 g of the monoimide body, 4.1 g of 2-aminobenzyl alcohol, and 40 ml of dimethylacetamide, and the mixture was heated and refluxed for 5 hours. After heating and refluxing, the vessel was cooled and concentrated under reduced pressure. The residue was purified by silica gel column chromatography to obtain 9.7 g of E1 intermediate (yield 50%).

(2) Synthesis of E1 In a nitrogen atmosphere, 8.0 g of E1 intermediate, 200 mL of tetrahydrofuran, 0.11 g of hydroquinone monomethyl ether (MEHQ), and 7.6 mL of triethylamine were added to a 500 mL three-neck flask, and 9.3 g of methacrylic anhydride was added dropwise and heated under reflux and stirring for 20 hours. The reaction solution was diluted with toluene, and the resulting organic layer was washed with an acidic and basic aqueous solution, and then the organic layer was dried with saturated saline and anhydrous magnesium sulfate. The crude product obtained by removing the solvent was purified by silica gel chromatography to obtain 6.1 g (yield 61%) of the exemplary compound E1 of the aromatic imide compound shown in Table 1.

(Synthesis Example 2)
(1) Synthesis of E3 intermediate Under a nitrogen atmosphere, 8.0 g of 4,4'-biphthalic anhydride, 8.2 g of 2-(4-aminophenyl)ethanol, and 40 ml of dimethylacetamide were placed in a 200 mL three-neck flask and heated under reflux for 6 hours. After the reaction was completed, the vessel was cooled to 20°C, 100 ml of ion-exchanged water was added, and the mixture was stirred for 1 hour and then filtered. The residue was washed with toluene to obtain 10.4 g of E3 intermediate.

(2) Synthesis of E3 In a nitrogen atmosphere, 8.0 g of E3 intermediate, 200 mL of tetrahydrofuran, 0.11 g of hydroquinone monomethyl ether (MEHQ), and 7.6 mL of triethylamine were added to a 500 mL three-neck flask, and 9.3 g of methacrylic anhydride was added dropwise and heated under reflux and stirring for 20 hours. The reaction solution was diluted with toluene, and the resulting organic layer was washed with an acidic and basic aqueous solution, and then the organic layer was dried with saturated saline and anhydrous magnesium sulfate. The crude product obtained by removing the solvent was purified by silica gel chromatography to obtain 4.1 g (yield 41%) of the exemplary compound E3 of the aromatic imide compound shown in Table 1.

Example 1
(1) Measurement of secondary dispersion characteristics A polymerizable composition containing a spacer having a thickness of 500 μm, the exemplary aromatic imide compound E1 synthesized in Synthesis Example 1 above, a polymerization inhibitor (methoxyphenol, Fujifilm Wako Pure Chemical Industries, Ltd.), a polymerization initiator (Irgacure TPO, diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide, etc., was placed on a high refractive index glass substrate having a thickness of 1 mm ("S-TIH11" manufactured by HOYA Corporation). Next, a quartz glass substrate was placed on the polymerizable composition to be measured and spread to a thickness of 500 μm via the spacer. The polymerizable composition sandwiched between two glass substrates was polymerized by irradiating the sample with a high pressure mercury lamp ("EX250" manufactured by HOYA-SCHOTT Corporation) equipped with a short wavelength cut filter (UV: 385 nm) as a light source. After curing, the sample was heated at 100°C for 12 hours to complete the reaction, and a measurement sample was prepared. The refractive index of the measurement sample was measured using an Abbe refractometer (manufactured by Kalnew Optical Co., Ltd.), and the secondary dispersion characteristic (θ _g,F ) was calculated from the refractive index and evaluated according to the following criteria. The refractive index of the glass substrate must be higher than that of the cured product of the polymerizable composition. Table 3 shows the evaluation results.
A: 0.70 or more B: 0.65 or more and less than 0.70 C: 0.60 or more and less than 0.65

(2) Transmittance Measurement In the same manner as in (1) above, transmittance measurement samples with a cured product thickness of 500 μm and 1000 μm were prepared. The 500 μm thick transmittance measurement sample may be the refractive index measurement sample prepared for measuring the above-mentioned secondary dispersion characteristics. The transmittance of the transmittance measurement samples with each film thickness was measured with a spectrophotometer (Hitachi High-Technologies Corporation "U-4000" (product name)), converted to internal transmittance at 420 nm (500 μm), and evaluated according to the following criteria. Table 3 shows the evaluation results.
A: 93% or more B: 90% or more but less than 93% C: 87% or more but less than 90%

(3) Evaluation of State of Polymerizable Composition The state of the polymerizable composition of (1) above at 23° C. was visually evaluated. Table 3 shows the evaluation results.

Example 2
A measurement sample was prepared in the same manner as in Example 1, except that the aromatic imide compound was changed to Exemplary compound E5 shown in Table 1, and the secondary dispersion characteristics and transmittance were measured in the same manner, and the state of the polymerizable composition was evaluated. The results are shown in Table 3.

Example 3
A measurement sample was prepared in the same manner as in Example 1, except that Resin 1 was added to the polymerizable composition so that the ratio of Exemplary Compound E1 to Resin 1 (1,6-hexanediol methacrylate, manufactured by Tokyo Chemical Industry Co., Ltd.) was 90:10 (mass ratio), and the secondary dispersion characteristic (θ _g,F ) and transmittance were measured to evaluate the state of the polymerizable composition. The results are shown in Table 3.

(Examples 4 to 7, Reference Examples 8 to 12 )
Measurement samples were prepared in the same manner as in Example 2, except that the exemplary compounds, the types of resins, and the mass ratios of the exemplary compounds and resins were changed as shown in Table 3, and the secondary dispersion characteristics (θ _g,F ) and transmittance were measured to evaluate the state of the polymerizable composition. The results are shown in Table 3. Resin 2 is triethylene glycol dimethacrylate manufactured by Tokyo Chemical Industry Co., Ltd. Resin 3 is tricyclodecane dimethanol diacrylate manufactured by Shin-Nakamura Chemical Co., Ltd.

(Comparative Example 1)
Instead of using the exemplary compound E1, a comparative compound having a structure represented by the following formula (4) was used. The components were mixed and placed on a glass substrate in the same manner as in Example 1. The glass substrate was then heated to dissolve the mixture. A 12.5 μm spacer and quartz glass were placed on the mixture to be measured, and the mixture was spread through the spacer to a thickness of 12.5 μm to prepare a measurement sample. The refractive index of the measurement sample was measured, and the second-order dispersion characteristic (θ _g,F ) was calculated from the refractive index. Note that the measurement sample was crystallized at 23° C., so the transmittance measurement was not performed. The results are shown in Table 3.

As shown in Table 3, the cured product of the polymerizable composition of the present invention has a high secondary dispersion characteristic of 0.60 to 0.74.

Claims (10)

An optical element having a cured product obtained by polymerizing a polymerizable composition,
The polymerizable composition contains at least an aromatic imide compound and a polymerization initiator,
The optical element according to the present invention is characterized in that the aromatic imide compound is a compound represented by the following formula (2):

[In the above formula (2),
A: an alkylene group having 1 to 3 carbon atoms.
P: an acryloyloxy group or a methacryloyloxy group.
q is 0 or 1. An optical element having a cured product obtained by polymerizing a polymerizable composition,
The polymerizable composition contains at least an aromatic imide compound and a polymerization initiator,
The optical element according to the present invention is characterized in that the aromatic imide compound is a compound represented by the following formula (3):

[In the above formula (3),
X ₁ and X ₂ : each independently represents an alkylene group having 1 to 6 carbon atoms or a phenylene group.
One of the _CH2s in the main chain of the alkylene group may be replaced by at least one oxygen atom or sulfur atom.
The alkylene group may be substituted with an alkyl group having 1 to 6 carbon atoms.
The phenylene group may be substituted with any one of a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, and an alkylene group having 1 to 6 carbon atoms in which at least one _CH2 in the main chain may be replaced with an oxygen atom or a sulfur atom.
P ₁ and P ₂ each independently represent an acryloyloxy group or a methacryloyloxy group. 3. The optical element according to claim 2 , wherein _X1 and _X2 in the formula (3) are different from each other. 4. The optical element according to claim 1 , wherein the polymerizable composition contains at least one of an acrylate resin and a methacrylate resin in an amount of 0.01% by mass to 20.0% by mass. 5. The optical element according to claim 1 , wherein the cured product has a secondary dispersion characteristic of 0.60 or more and 0.74 or less. The optical element according to claim 1 , wherein the cured product is laminated on a transparent substrate. 7. The optical element according to claim 1, wherein the cured product is sandwiched between two transparent substrates. An optical device having a housing and an optical system having a plurality of lenses disposed within the housing,
An optical device, wherein at least one of the plurality of lenses is the optical element according to claim 1 . An imaging device having a housing, an optical system having a plurality of lenses arranged in the housing, and an imaging element that receives light that has passed through the optical system,
An imaging device, wherein at least one of the plurality of lenses is the optical element according to claim 1 . 10. The imaging device according to claim 9 , which is a camera.

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