JP7570865B2 - Resin composition - Google Patents

Description

The present invention relates to a resin composition. More specifically, the present invention relates to a resin composition that has a high refractive index and is excellent at suppressing the aggregation of metal oxide particles.

Polycarbonate with aromatic rings and polymeric materials with a fluorene skeleton are known as high refractive index materials. Refractive index adjusting materials that improve the light extraction efficiency of LEDs and lens materials for imaging systems require materials with a large Abbe number, i.e., low light dispersion. Materials with sulfur or halogen molecules incorporated and materials containing metal oxide nanoparticles have been developed as such materials with high refractive index and low light dispersion.

Various studies have been conducted on sulfur-containing polymeric materials that have a high refractive index and small optical dispersion.
For example, Patent Document 1 describes a molding material having a polyarylene sulfide skeleton in which two hydrogen atoms on a benzene ring are substituted with methyl groups, as a molding material that has excellent moldability in a solution state and can be used as an optical component.
Furthermore, for example, Patent Document 2 describes a molding material having a polyarylene sulfide skeleton in which one hydrogen atom of the benzene ring is substituted with a methyl group, as a molding material that has excellent moldability in a solution state and is capable of forming an optical component having a high refractive index exceeding 1.70.

JP 2015-168790 A JP 2017-52834 A

However, conventional molding materials do not have sufficiently high refractive indexes or visible light transparency, and there is still room for improvement. In recent years, there has been a demand for polymer materials that can be used in a wide range of applications, including optical applications, by having properties such as high transparency and low linear expansion coefficients in addition to a high refractive index. A method of adding metal oxide particles with a high refractive index to achieve a high refractive index is known, but when such particles are added to conventional molding materials, the particles aggregate, causing problems such as reduced handleability of the molding material and reduced transparency of the molded product.

In view of the above-mentioned current situation, the present invention aims to provide a resin composition that has a high refractive index and excellent inhibition of aggregation of metal oxide particles, and can be used as a new optical material.

The inventors conducted various studies on sulfur-containing molding materials and found that a composition containing metal oxide particles coated with a polymeric material and a binder resin, and that at least the polymeric material or the binder resin contains a sulfur-containing aromatic polymer, has an extremely high refractive index and is excellent at suppressing the aggregation of metal oxide particles, and that the composition is useful as an optical material, leading to the completion of the present invention.

That is, the present invention is a resin composition containing metal oxide particles coated with a polymeric material and a binder resin, characterized in that the polymeric material and/or the binder resin contains a polymer having at least one structural unit selected from the group consisting of structural units (A) represented by the following general formula (1), structural units (B) represented by the following general formula (2), and structural units (C) represented by the following general formula (3).

(In the above general formulas (1) to (3), X ¹ , X ² and X ³ are the same or different and each represents a divalent aromatic hydrocarbon group which may have a substituent.)

The structural unit (A) is preferably a structural unit (A-1) represented by the following general formula (1-1), the structural unit (B) is preferably a structural unit (B-1) represented by the following general formula (2-1), and the structural unit (C) is preferably a structural unit (C-1) represented by the following general formula (3-1).

(In formulas (1-1), (2-1), and (3-1), R ¹ , R ^{2 ,} and R ³ are the same or different and each represents a halogen atom, a hydroxyl group, or an alkyl group, an alkoxy group, an aryl group, an aralkyl group, or a sulfur-containing substituent, each of which may have a substituent. a represents the number of R ¹ and is an integer of 0 to 4. b represents the number of R ² and is an integer of 0 to 4. c represents the number of R ³ and is an integer of 0 to 4.)

The polymer preferably has an elemental ratio (O/S) of oxygen atoms O bonded to sulfur atoms S in the main chain to sulfur atoms S in the main chain of 0.1 to 1.5.

The resin composition preferably further contains a compound having a (poly)styrene skeleton.

In the above resin composition, it is preferable that the compound having the (poly)styrene skeleton and the metal oxide particles are covalently bonded.

The above resin composition is preferably for optical use.

The present invention provides a resin composition that has a high refractive index and is excellent at suppressing aggregation of metal oxide particles. The resin composition of the present invention can be suitably used for optical applications such as imaging lens materials.

FIG. 2 shows measurement data of the transmittance of the blend film obtained in Example 1. 1 is a photograph of the blend film obtained in Example 1.

The present invention will be described in detail below.
In addition, a combination of two or more of the individual preferred embodiments of the present invention described below is also a preferred embodiment of the present invention.

Resin Composition The resin composition of the present invention is a resin composition comprising metal oxide particles coated with a polymeric material and a binder resin, and is characterized in that the polymeric material and/or the binder resin comprises a polymer having at least one structural unit selected from the group consisting of a structural unit (A) represented by the following general formula (1), a structural unit (B) represented by the following general formula (2), and a structural unit (C) represented by the following general formula (3).

（式（１）～（３）中、Ｘ^１、Ｘ^２及びＸ^３は、同一又は異なって、置換基を有してもよい２価の芳香族炭化水素基を表す。）

(In formulas (1) to (3), X ¹ , X ² and X ³ are the same or different and each represents a divalent aromatic hydrocarbon group which may have a substituent.)

The resin composition of the present invention has a high refractive index and is excellent at suppressing aggregation of metal oxide particles. It is presumed that the resin composition of the present invention has such properties because the metal oxide particles and the polymer material are uniformly compatible with each other, suppressing particle aggregation.

The resin composition of the present invention contains metal oxide particles coated with a polymeric material and a binder resin. In the resin composition, at least one of the polymeric material and the binder resin contains a polymer having at least one structural unit selected from the group consisting of the structural units (A), (B), and (C). The polymer will first be described.

<Polymer>
In the present invention, the polymer used as the polymer material and/or binder resin includes a polymer having at least one structural unit selected from the group consisting of the structural unit (A) represented by the general formula (1) above, the structural unit (B) represented by the general formula (2) above, and the structural unit (C) represented by the general formula (3) above (hereinafter, also referred to as “polymer (X)”).

In the above general formulae (1), (2) and (3), X ¹ , X ² and X ³ are the same or different and each represents a divalent aromatic hydrocarbon group which may have a substituent.
Examples of the divalent aromatic hydrocarbon group include a phenylene group, a naphthylene group, an anthrylene group, a triphenylene group, a biphenylene group, a phenanthrylene group, etc. Among these, in terms of reducing light dispersion, the divalent aromatic hydrocarbon group is preferably a phenylene group, a naphthylene group, an anthrylene group, a biphenylene group, or a triphenylene group, and more preferably a phenylene group.

The substituent (also referred to as "substituent A") of the divalent aromatic hydrocarbon group is preferably a halogen atom, a hydroxyl group, or an alkyl group, an alkoxy group, an aryl group, an aralkyl group, or a sulfur-containing substituent, which may have a substituent (also referred to as "substituent B").

The halogen atom includes a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom, of which a bromine atom is preferred.

Examples of the alkyl group include methyl, ethyl, n-propyl, isopropyl, n-butyl, s-butyl, t-butyl, pentyl, isopentyl, neopentyl, hexyl, 2-methylpentyl, 3-methylpentyl, 2,2-dimethylbutyl, 2,3-dimethylbutyl, and heptyl. Among these, alkyl groups having 1 to 18 carbon atoms are preferred, alkyl groups having 1 to 6 carbon atoms are more preferred, and methyl groups are even more preferred.

Examples of the alkoxy group include a methoxy group, an ethoxy group, a propoxy group, an isopropoxy group, a s-butoxy group, a t-butoxy group, a pentyloxy group, a phenoxy group, a cyclohexyloxy group, and a benzyloxy group. Among these, an alkoxy group having 1 to 18 carbon atoms is preferred, an alkoxy group having 1 to 6 carbon atoms is more preferred, and a methoxy group is more preferred.

The aryl group may be a phenyl group, a naphthyl group, an anthryl group, a biphenyl group, a triphenyl group, or the like. Of these, a phenyl group is preferred. The number of carbon atoms in the aryl group is preferably 6 to 30, more preferably 6 to 18, and even more preferably 6 to 12.

The aralkyl group may, for example, be a benzyl group, a phenethyl group, a phenylpropyl group, a phenylpentyl group, a phenylhexyl group, or a phenyloctyl group. The number of carbon atoms in the aralkyl group is preferably 7 to 14, and more preferably 7 to 9.

Examples of the sulfur-containing substituent include a thioalkyl group and a thioaryl group. Of these, a thioalkyl group is preferred. The number of carbon atoms in the sulfur-containing substituent is preferably 1 to 8, more preferably 1 to 6, and even more preferably 1 to 4.

The above alkyl groups, alkoxy groups, aryl groups, aralkyl groups, and sulfur-containing substituents may further have a substituent (substituent B), and examples of the substituent (substituent B) include alkyl groups, halogen atoms, and hydroxyl groups. Among these, from the viewpoint of the solubility of the polymer material, alkyl groups are preferred, and from the viewpoint of the dispersibility of the metal oxide particles, halogen atoms and hydroxyl groups are preferred.

Among these, in terms of being able to further increase the refractive index of the resin composition, the substituent (substituent A) on the divalent aromatic hydrocarbon group is more preferably an alkyl group having 1 to 18 carbon atoms or a sulfur-containing substituent, further preferably a methyl group or a thioalkyl group, and particularly preferably a methyl group.
In addition, from the viewpoint of improving the dispersibility of metal oxide particles, the substituent (substituent A) of the divalent aromatic hydrocarbon group is more preferably a hydroxyl group or a sulfur-containing substituent, further preferably a hydroxyl group, a thioalkyl group, or a thioaryl group, and particularly preferably a hydroxyl group.

The number of substituents A in the divalent aromatic hydrocarbon group is not particularly limited, but a smaller number is preferable in that the refractive index of the polymer material will be further increased. Specifically, the number is preferably 1 to 6, more preferably 1 to 3, and even more preferably 1.

The structural unit (A) is preferably a structural unit (A-1) represented by the following general formula (1-1):

(In the formula, R ¹ 's may be the same or different and each represents a halogen atom, a hydroxyl group, or an alkyl group, an alkoxy group, an aryl group, an aralkyl group, or a sulfur-containing substituent, each of which may have a substituent. a represents the number of R ^1's and is an integer of 0 to 4.)

The structural unit (B) is preferably a structural unit (B-1) represented by the following general formula (2-1):

(In the formula, R ² may be the same or different and represents a halogen atom, a hydroxyl group, or an alkyl group, an alkoxy group, an aryl group, an aralkyl group, or a sulfur-containing substituent, each of which may have a substituent. b represents the number of R ² and is an integer of 0 to 4.)

The structural unit (C) is preferably a structural unit (C-1) represented by the following general formula (3-1):

(In the formula, R ³ may be the same or different and represents a halogen atom, a hydroxyl group, or an alkyl group, an alkoxy group, an aryl group, an aralkyl group, or a sulfur-containing substituent, each of which may have a substituent. c represents the number of R ³ and is an integer of 0 to 4.)

Preferred examples of the alkyl group, alkoxy group, aryl group, aralkyl group, and sulfur-containing substituent, which may have a substituent, represented by R ¹ , R ² , and R ³ above include the same alkyl group, alkoxy group, aryl group, aralkyl group, and sulfur-containing substituent as described for X ¹ in the above general formula (1).
Preferred examples of the substituent that these groups may have include the same groups as the substituent B described above.
When there are multiple R ¹ , R ² and R ³ , they may be the same or different.

a, b, and c each represent the number of substituents on R ¹ , R ² , and R ^3, respectively, and are an integer of 0 to 4, preferably an integer of 0 to 3, and more preferably an integer of 0 to 2.

The polymer (X) may be an alternating copolymer of the structural units (A), (B) and (C), or may be a block copolymer or a random copolymer.
The polymer material may have one or more of the structural units (A), (B), or (C).

The polymer (X) may be in a form containing only one of the structural units (A), (B) and (C), or may be in a form containing two structural units, or may be in a form containing three structural units. These forms and their content ratios can be appropriately selected depending on the purpose and use of the resin composition.
For example, the polymer (X) preferably contains the structural unit (A) above, and more preferably contains this as a main component, in that this can result in a higher refractive index.
In addition, the polymer (X) preferably contains the structural unit (B) above, and more preferably contains this as a main component, in that this allows for both solubility and a high refractive index to be achieved.
In addition, the polymer (X) preferably contains the structural unit (C) above, and more preferably contains this as a main component, in that transparency and a high refractive index can be achieved at the same time.

In view of the above, in the polymer (X), the content of the structural unit (A) is preferably 1 to 100 mol %, more preferably 10 to 100 mol %, and even more preferably 50 to 100 mol %, relative to 100 mol % of all structural units of the polymer, from the viewpoint of a high refractive index.
In this case, the total content of the structural units (B) and (C) is preferably 0 to 99 mol%, more preferably 0 to 90 mol%, and even more preferably 0 to 50 mol%, relative to 100 mol% of all structural units.

In the polymer (X), the content of the structural unit (B) is preferably 1 to 100 mol %, more preferably 10 to 100 mol %, and even more preferably 50 to 100 mol %, relative to 100 mol % of all structural units of the polymer, from the viewpoint of high polarity resulting from solubility.
In this case, the total content of the structural units (A) and (C) is preferably 0 to 99 mol%, more preferably 0 to 90 mol%, and even more preferably 0 to 50 mol%, relative to 100 mol% of all structural units.

In the polymer (X), the content of the structural unit (C) is preferably 1 to 100 mol %, more preferably 10 to 100 mol %, and even more preferably 50 to 100 mol %, relative to 100 mol % of all structural units of the polymer, from the viewpoint of high transparency.
In this case, the total content of the structural units (A) and (B) is preferably 0 to 99 mol%, more preferably 0 to 90 mol%, and even more preferably 0 to 50 mol%, relative to 100 mol% of all structural units.

In the above polymer (X), the total content of the above structural units (A), (B) and (C) is preferably 50 mol% or more, more preferably 80 mol% or more, even more preferably 90 mol% or more, even more preferably 95 mol% or more, and particularly preferably 100 mol%, based on 100 mol% of all structural units in polymer (X).

The polymer (X) may have a structural unit (D) other than the structural units (A), (B) and (C).
Examples of the structural unit (D) include structural units derived from the following monomers.
Carboxyl group-containing (meth)acrylates such as 2-carboxyethyl (meth)acrylate, 2-carboxypropyl (meth)acrylate, 3-carboxypropyl (meth)acrylate, and 4-carboxybutyl (meth)acrylate; phosphoric acid group-containing (meth)acrylates such as 2-(meth)acryloyloxyethyl acid phosphate; epoxy group-containing (meth)acrylates such as glycidyl (meth)acrylate and 3,4-epoxycyclohexylmethyl (meth)acrylate; vinyl ether group-containing (meth)acrylates such as 2-(2-vinyloxyethoxy)ethyl (meth)acrylate, and the like.

The content of the structural unit (D) is preferably 0 to 80 mol%, more preferably 0 to 50 mol%, even more preferably 0 to 20 mol%, even more preferably 0 to 10 mol%, and particularly preferably 0 to 5 mol%, relative to 100 mol% of all structural units in the polymer (X).

The polymer (X) preferably has an elemental ratio (O/S) of oxygen atoms O bonded to sulfur atoms S in the main chain to sulfur atoms S in the main chain of 0.1 to 1.5. When the elemental ratio is within the above range, the transparency and refractive index are further increased.
The sulfur atom S in the main chain specifically means, for example, the sulfur atom S of -S- in the main chain in the structural unit (A) represented by the general formula (1) above, the sulfur atom S of -SO- in the main chain in the structural unit (B) represented by the general formula (2) above, and the sulfur atom S of -SO ₂ - in the main chain in the structural unit (C) represented by the general formula (3) above.
The oxygen atom bonded to the sulfur atom S in the main chain specifically means, for example, the oxygen atom O of -SO- in the main chain in the structural unit (B) represented by the general formula (2) above, and means the oxygen atom O of -SO ₂ - in the main chain in the structural unit (C) represented by the general formula (3) above.

The element content ratio (O/S) is more preferably 0.3 or more, and even more preferably 0.7 or more, in that transparency can be further increased, and is more preferably 1.3 or less, and even more preferably 1.1 or less, in that the refractive index can be further increased.
The elemental content ratios can be determined by evaluating and measuring the peak intensities of the oxygen 1s orbital (O1s), the carbon 1s orbital (C1s), and the sulfur 2p orbital (S2p) using an X-ray photoelectron spectrometer (XPS).

The polymer (X) preferably has a glass transition temperature (Tg) of 80 to 250° C. When the glass transition temperature is in the above-mentioned range, molding can be easily performed. From the viewpoint of increasing heat resistance, the glass transition temperature is more preferably 90° C. or higher, and even more preferably 100° C. or higher, and from the viewpoint of easy molding, it is more preferably 200° C. or lower.
The glass transition temperature can be determined by a method in which a differential scanning calorimeter (DSC) is used to measure a temperature rise from room temperature to 250° C. (heat rise rate: 10° C./min) in a nitrogen gas atmosphere, and the DSC curve is obtained by evaluating the intersection point of a tangent line at the baseline and the inflection point.

The polymer (X) preferably has an S—O bond energy of 163 eV to 167 eV. When the S—O bond energy is in the above range, the refractive index and transparency can be further increased.
The S—O bond energy can be determined by evaluating the peak top position of the 2p3/2 orbital of the sulfur atom obtained by measurement using X-ray photoelectron spectroscopy (XPS).

The weight average molecular weight (Mw) of the polymer (X) is preferably 500 to 10,000,000. When the weight average molecular weight is within the above range, it can be suitably used as an optical material. From the viewpoint of improving mechanical properties, the weight average molecular weight is more preferably 1,000 or more, even more preferably 3,000 or more, and even more preferably 10,000 or more, and from the viewpoint of reducing melt viscosity, it is more preferably 1,000,000 or less, and even more preferably 100,000 or less.

The dispersity (weight average molecular weight/number average molecular weight) of the polymer (X) is preferably 1 to 10. When the dispersity is within the above range, molding becomes easy. In terms of further improving moldability, the dispersity is more preferably 5 or less, and even more preferably 3 or less.

The weight average molecular weight and number average molecular weight can be determined by measurement using gel permeation chromatography (GPC), specifically, by the method described in the Examples below. The degree of dispersion can be determined by dividing the weight average molecular weight by the number average molecular weight.

The refractive index of the polymer (X) is preferably 1.69 or more. When the refractive index is within the above range, it can be suitably used for various applications such as optical materials (members), machine part materials, electric and electronic part materials, automobile part materials, civil engineering and construction materials, molding materials, etc., as well as paints and adhesive materials. The refractive index is more preferably 1.7 or more, and even more preferably 1.71 or more.
The refractive index can be determined by forming a film having a thickness of 50 nm from the polymer as a measurement sample, and measuring the refractive index using a spectroscopic ellipsometer UVISEL (manufactured by HORIBA Scientific) with Na D line (589 nm).

The Abbe number of the polymer (X) is preferably 10 or more. When the Abbe number is in the above-mentioned range, the light dispersion is small, and the optical material can be suitable for lenses. The Abbe number is more preferably 15 or more, even more preferably 18 or more, and even more preferably 20 or more. From the viewpoint of adjusting the light dispersion, the Abbe number is preferably 60 or less, and more preferably 55 or less.
The Abbe number can be calculated in the same manner as the refractive index by forming a film using the polymer, measuring the refractive indices at D line (589.3 nm), F line (486.1 nm), and C line (656.3 nm) using the spectroscopic ellipsometer, and applying the following calculation formula:
Abbe number ( _vD )=( _nD -1)/( _nF - _nC )
In the formula, n _D , n _F and n _C represent the refractive indices at the Fraunhofer D line (589.3 nm), F line (486.1 nm) and C line (658.3 nm), respectively.

The polymer (X) preferably has a visible light transmittance of 70% or more. When the visible light transmittance is in the above range, it can be suitably used as an optical material. The visible light transmittance is more preferably 80% or more, more preferably 85% or more, and even more preferably 88% or more.
The visible light transmittance is a parallel ray transmittance, and can be determined by measuring a range of 400 nm to 700 nm using a thin film of the polymer having a thickness of 0.02 mm, or by standardizing the thickness to 0.02 mm, with a spectrophotometer (for example, a JASCO ultraviolet-visible-infrared spectrophotometer V-700 series) without using an integrating sphere, with air as the target, and evaluating the minimum transmittance.

The polymer (X) preferably has a linear expansion coefficient of 100 ppm/°C or less. When the linear expansion coefficient of the polymer is within the above range, the polymer becomes an optical material with a small temperature dependency of the refractive index, and can be suitably used for various applications such as optical materials, sealing materials, and coating materials. The linear expansion coefficient is more preferably 60 ppm/°C or less, and even more preferably 30 ppm/°C or less, in terms of further reducing the temperature dependency. The lower limit of the linear expansion coefficient is not particularly limited, but is preferably 1 ppm/°C or more, and even more preferably 3 ppm/°C or more.
The linear expansion coefficient can be determined by measurement according to a method in accordance with JIS K 7197:2012.

The polymer (X) is preferably thermoplastic. When the polymer is thermoplastic, the inclusion of a binder resin made of the polymer improves moldability, such as allowing a thin film to be formed uniformly and complex shapes to be formed with high precision, making it easier to apply the polymer to a wide range of applications.

(Method for producing polymer (X))
The method for producing the polymer (X) is not particularly limited as long as it is a method capable of producing a polymer having at least one of the above-mentioned structural units (A) to (C), and may be a known polymerization method such as polymerizing a monomer component containing a sulfur-containing monomer. In particular, in terms of being able to efficiently produce the polymer, the method for producing the polymer preferably includes a step (1) of polymerizing a monomer component containing a sulfur-containing monomer to obtain a sulfur-containing polymer, and a step (2) of oxidizing the sulfur-containing polymer using an oxidizing agent.

Step (1)
In the above step (1), the sulfur-containing monomer used is not particularly limited as long as it is a monomer containing a sulfur atom, but in the production method of the present invention, it is preferable to obtain a sulfur-containing polymer by oxidative polymerization of the sulfur-containing monomer. As the sulfur-containing monomer from which a sulfur-containing polymer can be obtained by oxidative polymerization, a disulfide compound and a thiol compound are preferably mentioned, and more specifically, for example, a diaryl disulfide compound represented by the following general formula (4) and a thioaryl compound represented by the following formula (5) are more preferably mentioned.

In the above general formulae (4) and (5), A ¹ and A ² may be the same or different and each represents a monovalent aromatic hydrocarbon group which may have a substituent.
Examples of the monovalent aromatic hydrocarbon group represented by ^A1 and ^A2 include a monovalent group obtained by converting the divalent aromatic hydrocarbon group represented by ^X1 in the above general formula (1) into a monovalent group, such as a phenyl group, a naphthyl group, an anthryl group, a triphenyl group, a biphenyl group, a phenanthryl group, etc. Among these, a phenyl group, a naphthyl group, an anthryl group, a biphenyl group, or a triphenyl group is preferred, and a phenyl group is more preferred.

Examples of the substituents possessed by the monovalent aromatic hydrocarbon groups represented by ^A1 and ^A2 include halogen atoms, alkyl groups, alkoxy groups, aryl groups, aralkyl groups, sulfur-containing substituents, etc. Examples of the halogen atoms, alkyl groups, alkoxy groups, aryl groups, aralkyl groups, and sulfur-containing substituents include the same groups as those described above.

The diaryl disulfide compound is preferably a compound represented by the following general formula (4-1):
The above thioaryl compound is preferably a compound represented by the following general formula (5-1).

(In formulas (4-1) and (5-1), R ⁴ , R ⁵ , R ⁶ , R ⁷ , R ⁸ , R ⁹ , R ¹⁰ and R ¹¹ are the same or different and each represents a hydrogen atom, a halogen atom, or an alkyl group, an alkoxy group, an aryl group, an aralkyl group, or a sulfur-containing substituent, each of which may have a substituent.)
The above halogen atom, or the alkyl group, alkoxy group, aryl group, aralkyl group, or sulfur-containing substituent which may have a substituent is the same as each group represented by R ¹ in the above general formula (1-1).
The substituents which these groups may have include the same as those for the substituent B described above, and among these, halogen atoms and hydroxyl groups are preferred.

The disulfide compound can also be prepared by oxidation of a thiol compound. Therefore, in the polymerization step, a thiol compound can also be used as a precursor of the disulfide compound. The disulfide compound can be obtained by oxidatively bonding two molecules of a thiol compound.

The method for oxidizing a thiol compound to obtain a disulfide compound is not particularly limited, and can be performed by a known method, such as a method of oxidation using hydrogen peroxide, iodine, etc.

The above sulfur-containing monomers may be used alone or in combination of two or more.

The above polymerization is preferably oxidative polymerization. The above oxidative polymerization is not particularly limited, and can be carried out by known methods such as a method using a quinone-based compound or a method using a metal compound such as a vanadium compound. In particular, the above oxidative polymerization is preferably carried out using a quinone-based oxidizing agent, in terms of being able to improve transparency. It is preferable to use a metal compound, in terms of the amount used relative to the monomer component being small, resulting in less waste.

Examples of the quinone-based oxidizing agent include 2,3-dichloro-5,6-dicyano-parabenzoquinone (DDQ), 2,3,5,6-tetrachloroparabenzoquinone (chloranil), 2,3,5,6-tetrabromobenzoquinone (bromanil), 2,3,5,6-tetrafluoroparabenzoquinone, anthraquinone, 1,4-naphthoquinone, 2,3-dichloro-1,4-naphthoquinone, 2,3-dibromo-1,4-naphthoquinone, 2,3-dicyano-1,4-naphthoquinone, 3,4,5,6-tetrachloroorthobenzoquinone (orthochloranil), 3,4,5,6-tetrabromoorthobenzoquinone (orthobromanil), and 3,4,5,6-tetrafluorobenzoquinone. Among these, DDQ is preferred because of its high oxidizing power and ease of availability. The quinone-based oxidizing agent may be used alone or in combination with two or more types.

The amount of the quinone-based oxidizing agent added is preferably 0.1 to 3 moles, more preferably 0.8 to 1.5 moles, and even more preferably 0.9 to 1.1 moles, per mole of the sulfur-containing monomer used.

When using the above quinone-based oxidizing agent, an acid may be further added. When the above quinone-based oxidizing agent acts, the quinone compound becomes a hydroquinone dianion, but by adding an acid, the dianion can be stabilized and the oxidizing power can be maintained.

The above acid is not particularly limited, and examples thereof include sulfuric acid, acetic acid, methanesulfonic acid, benzenesulfonic acid, toluenesulfonic acid, trifluoromethanesulfonic acid, 1,1,2,2-tetrafluoroethanesulfonic acid, trifluoroacetic acid, perfluoropropionic acid, and perfluorobutyric acid. Among these, trifluoroacetic acid is preferred in terms of increasing the acidity. The above acids may be used alone or in combination of two or more.

The amount of the acid added is preferably 10 to 1,000 moles, more preferably 50 to 500 moles, and even more preferably 80 to 120 moles, per 100 moles of the total amount of the quinone-based oxidizing agent added.

The reaction temperature is not particularly limited as long as it is a temperature at which polymerization proceeds, but it is preferably 0 to 200°C, more preferably 10°C or higher, and even more preferably 15°C or higher, in that the oxidative polymerization proceeds easily, and is more preferably 180°C or lower, and even more preferably 150°C or lower, in that side reactions can be suppressed.

The reaction time is not particularly limited, but is usually 0.1 to 100 hours, preferably 1 to 80 hours, more preferably 5 to 50 hours, and even more preferably 10 to 24 hours.

A solvent may be used in the polymerization reaction. Preferred solvents include, for example, dichloromethane, chloroform, carbon tetrachloride, 1,2-dichloroethane, tetrachloroethylene, 1,1,2,2-tetrachloroethane, nitromethane, nitrobenzene, chlorobenzene, 1,2-dichlorobenzene, 1,3-dichlorobenzene, N-methylpyrrolidone, tetrahydrofuran, and ethyl acetate.

In the above polymerization reaction, the monomer components including the sulfur-containing monomer may be added successively during the polymerization reaction.
Alternatively, the polymerization may be carried out in multiple stages, for example by oxidatively polymerizing the above-mentioned thiol compound to obtain a disulfide compound, and then oxidatively polymerizing the obtained disulfide compound.

Step (2)
After the step (1), the sulfur-containing polymer is oxidized using an oxidizing agent.
The oxidizing agent used is not particularly limited, and any known oxidizing agent can be used, such as a quinone compound, perbenzoic acid, metachloroperbenzoic acid, lead tetraacetate, thallium acetate, tetracyanoquinodimethane, tetracyanoethylene, cerium (IV) acetylacetonate, manganese (III) acetylacetonate, peroxide, or chloric acid.

Among them, to oxidize a sulfur atom (-S-) contained in the main chain to a sulfonyl (-SO ₂ -), it is preferable to use a peroxide or chloric acid as an oxidizing agent, whereas to convert to a sulfinyl (-SO-), it is preferable to use a peroxide or chloric acid as an oxidizing agent.

Examples of the peroxide include metachloroperbenzoic acid, hydrogen peroxide, ammonium persulfate, sodium persulfate, peracetic acid, and t-butyl hydroperoxide.
Among them, the oxidizing agent is preferably a peroxide, more preferably metachloroperbenzoic acid or hydrogen peroxide, in that it can be dissolved in the same solvent as the sulfur-containing polymer, and further preferably metachloroperbenzoic acid, in that water in which the polymer precipitates is not used and in that oxidation to sulfoxide by an excess of the oxidizing agent is suppressed.

The amount of the oxidizing agent added is not particularly limited as long as the desired oxidation reaction of sulfur atoms proceeds, but typically, it is preferably 0.1 to 10 moles, more preferably 0.5 to 5 moles, and even more preferably 0.8 to 1.5 moles per mole of sulfur atoms in the sulfur-containing polymer.

The reaction temperature of the above oxidation reaction is not particularly limited as long as it is a temperature at which the desired oxidation reaction proceeds, but in terms of facilitating the above oxidation reaction, it is preferably 0 to 200°C, more preferably 10°C or higher, and even more preferably 15°C or higher, and in terms of suppressing side reactions, it is more preferably 180°C or lower, and even more preferably 150°C or lower.

The reaction time is not particularly limited, but is usually 0.1 to 100 hours, preferably 1 to 80 hours, more preferably 5 to 50 hours, and even more preferably 10 to 24 hours.

In the oxidation reaction of the above step (2), a solvent may be used, and preferred examples of the solvent include the same solvent as that used in the polymerization step of the above step (1).

The polymer obtained in the above step (2) may contain residual acid, etc., so it is preferable to wash it. The washing method is not particularly limited, and examples include methods using water, acid, base, etc. In addition, in order to remove unreacted substances, the polymer may be passed through a filter or washed with a solvent. The above solvent is not particularly limited, but the same solvent as the reaction solvent can be used.

The method for producing the polymer (X) may include other steps in addition to the steps (1) and (2). Examples of the other steps include an aging step, a neutralization step, a dilution step, a drying step, a concentration step, and a purification step. These steps can be carried out by known methods.

<Metal oxide particles coated with polymeric material>
The metal oxide particles coated with the polymer material are particles in a state where a polymer material is attached to a part or all of the surface of the metal oxide particles to form a coating layer. The attachment refers to a state where the surface of the metal oxide particles and the polymer material are bonded by a covalent bond. Such a bonded state can be confirmed, for example, by whether or not the polymer material separates from the metal oxide particles when extracted and washed with a solvent.
From the viewpoint of preventing aggregation of the metal oxide particles, it is preferable that the entire surface of the metal oxide particles is covered with a polymer material.

From the viewpoint of high refractive index and dispersibility in resin, the thickness of the coating layer is preferably 0.1 to 100 nm, more preferably 1 to 20 nm, and even more preferably 1 to 10 nm. The thickness of the coating layer can be measured by a pyrolysis method using TGA. In addition, the thickness of the coating film can be estimated by comparing FE-SEM and TEM.

The amount of the coating layer (coating amount) is preferably 0.1 to 500 mass% relative to 100 mass% of the metal oxide particles coated with the polymer material, more preferably 5 to 100 mass%, and even more preferably 10 to 50 mass%.
The content of the coating layer can be determined by thermogravimetric differential thermal analysis (TG-DTA).

(Metal oxide particles)
The metal oxide particles to be coated with the polymer material include particles of a single metal oxide consisting of one metal element, a composite oxide consisting of two or more metal elements, and a solid solution oxide consisting of the single metal oxide or the composite oxide and a different element as a solid solution. The different element may be a metal element or a non-metal element other than oxygen, such as nitrogen or fluorine.
Examples of the metal elements include lithium (Li), sodium (Na), potassium (K), magnesium (Mg), calcium (Ca), manganese (Mn), strontium (Sr), barium (Ba), titanium (Ti), zirconium (Zr), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), aluminum (Al), tin (Sn), silicon (Si), cerium (Se), and indium (In).

Examples of the single metal oxide include magnesium oxide, calcium oxide, strontium oxide, barium oxide, titanium oxide, zinc oxide, cerium oxide, silicon oxide, tin oxide, zirconium oxide, aluminum oxide, and indium oxide.
Examples of the composite oxide include perovskite-type composite oxides such as barium titanate, barium strontium titanate, strontium titanate, barium zirconium strontium titanate, barium zirconium titanate, and lead zirconate titanate; spinel-type composite oxides such as spinel and lithium titanate; and composite oxides such as aluminum titanate.
The solid solution oxide may be, for example, a solid solution oxide in which a different metal element and/or a nonmetal element other than oxygen, such as nitrogen or fluorine, is dissolved in the single metal oxide or composite oxide.
These metal oxide particles may be used alone or in combination of two or more kinds.

Among these, particles of zirconium oxide, titanium oxide, or silicon dioxide are more preferred in terms of further improving transparency and reducing the linear expansion of the resin composition, and particles of zirconium oxide or titanium oxide are more preferred in terms of improving the refractive index of the resin composition. Perovskite-type oxide particles are preferred in terms of having a high relative dielectric constant and allowing the resin composition to be suitably used as a ferroelectric material or piezoelectric material. Particles of boron nitride, aluminum hydroxide, and aluminum titanate are preferred in terms of having a high thermal conductivity and allowing the resin composition to be suitably used as a heat dissipation material.

Furthermore, the above-mentioned metal oxide particles are more preferably oxide particles containing Ti, Zr, Ce, Zn, In, Al, Si, or Sn as the main metal element, since they have no or little absorption in the visible light range and therefore coloring due to inorganic substances is suppressed, making it easy to obtain a colorless and transparent composition, and even more preferably particles of titanium oxide, zirconium oxide, cerium oxide, zinc oxide, indium oxide, aluminum oxide, silicon oxide, or tin oxide.

The shape of the metal oxide particles is not particularly limited and may be, for example, irregular, spherical, plate-like, rod-like, polyhedral, etc.

The average particle size of the metal oxide particles is preferably 1 nm or more and 1000 nm or less. When the average particle size of the metal oxide particles is in the above range, the transmittance of the visible light region and the infrared region can be improved. The average particle size of the metal oxide particles is more preferably 5 nm or more, and even more preferably 10 nm or more, and more preferably 100 nm or less, and even more preferably 50 nm or less.
The average particle size is determined by observing the metal oxide with a SEM (magnification 1,000 to 100,000 times, preferably 10,000 times), analyzing the obtained image to determine the particle size (circular area equivalent diameter) of about 10 to 1,000 individual particles (primary particles), and evaluating the 50% particle size based on the number-based particle size distribution. For the image analysis, known image analysis software (for example, Mac-View manufactured by Mountech Co., Ltd.) can be used.

The content of the metal oxide particles coated with the polymer material can be set appropriately depending on the purpose and use of the resin composition, but is usually preferably 5 to 95% by mass relative to 100% by mass of the total solid content of the resin composition. In terms of high refractive index, the content of the metal oxide particles is more preferably 20% by mass or more, even more preferably 40% by mass or more, and even more preferably 60% by mass or more, relative to 100% by mass of the total solid content of the resin composition, and from the viewpoint of transparency, it is more preferably 90% by mass or less, and even more preferably 80% by mass or less.

(Preparation of metal oxide particles coated with polymeric material)
The method for coating the metal oxide particles with the above-mentioned polymeric material is not particularly limited, and any known method can be used, such as a method using a silane coupling agent, a method of reacting a compound having a phosphate group, or a method of reacting a carboxylic acid group. Among these, the method of coating the metal oxide particles with the above-mentioned polymeric material using a silane coupling agent is preferred.

As a method of using the above-mentioned silane coupling agent, for example, there is a method in which the surface of metal oxide particles is treated with a silane coupling agent, and then the surface-treated metal oxide particles are reacted with a polymer material.

The silane coupling agent is not particularly limited, and any known silane coupling agent can be used, but among them, silane coupling agents having a halogen atom, a vinyl group, an acrylic group, or a methacrylic group are preferred, and silane coupling agents having a halogen atom or a vinyl group are more preferred.

The above-mentioned silane coupling agent having a halogen atom can be prepared by reacting a silane compound having a group capable of reacting with an acid group with a compound having an acid group and a halogen atom.
Preferred examples of the group capable of reacting with the acid group include an epoxy group.
Preferred examples of the acid group include a carboxyl group, a phosphoric acid group, and a sulfo group.

In the above surface treatment, the amount of the silane coupling agent used is preferably 0.1 to 1000 parts by mass, more preferably 1 to 100 parts by mass, and even more preferably 10 to 80 parts by mass, per 100 parts by mass of the metal oxide particles.

In the above surface treatment, the treatment temperature is preferably 0 to 150°C, and more preferably 10 to 100°C. The treatment time is preferably 1 to 100 hours, and more preferably 1 to 24 hours.

In the reaction between the surface-treated metal oxide particles and the polymeric material, the amount of the polymeric material used is preferably 1 to 10,000 parts by mass, and more preferably 10 to 1,000 parts by mass, per 100 parts by mass of the surface-treated metal oxide particles.

In the reaction between the surface-treated metal oxide particles and the polymeric material, the reaction temperature is preferably 0 to 150°C, and more preferably 10 to 120°C.
The reaction time is not particularly limited, but is preferably 1 to 100 hours, and more preferably 1 to 48 hours.

The above surface treatment process and reaction process may be carried out in a solvent. The solvent to be used is not particularly limited, and examples thereof include alcohol-based solvents such as methanol, ethanol, propanol, butanol, and propylene glycol monomethyl ether; ketone-based solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; ester-based solvents such as ethyl acetate, isopropyl acetate, butyl acetate, and γ-butyrolactone; ether-based solvents such as diethyl ether, diisopropyl ether, 1,2-dimethoxyethane (DME), and tetrahydrofuran (THF); aromatic hydrocarbon-based solvents such as toluene and xylene; halogenated hydrocarbon-based solvents such as chlorobenzene, fluorobenzene, dichloromethane, chloroform, carbon tetrachloride, 1,2-dichloroethane, and benzotrifluoride; amide-based solvents such as dimethylformamide (DMF), dimethylacetamide, and N-methylpyrrolidone; dimethylsulfoxide (DMSO), nitromethane, and the like.

In the above-mentioned surface treatment process and reaction process, additives such as catalysts that are typically used in surface treatment processes and reaction processes may be further used. The types and amounts of these additives may be appropriately determined based on known techniques.

After the reaction, metal oxide particles having a surface coated with the polymer material can be obtained through optional steps such as a washing step and a solvent removal step, if necessary. The washing step and the solvent removal step can be carried out by a known method.

The reaction process between the surface-treated metal oxide particles and the polymeric material may be a process of polymerizing a monomer component for forming the polymeric material in the presence of the surface-treated metal oxide particles, instead of using the polymeric material. This method also makes it possible to prepare metal oxide particles coated with a polymeric material.

The above polymerization process may be carried out by appropriately selecting from known polymerization methods depending on the monomer components used, etc. In addition, in the above polymerization process, known additives that are commonly used, such as initiators, catalysts, and solvents, may also be used as appropriate.

<Binder resin>
The resin composition of the present invention further contains a binder resin.
As described above, the binder resin preferably contains the polymer (X).
As the binder resin, one type of the polymer (X) may be used, or two or more types of the polymer (X) may be used.
The polymer (X) used as the binder resin may be the same as or different from the polymer (X) used as the polymer material.

The content of the binder resin can be set appropriately depending on the purpose and application of the resin composition, but is preferably 1 to 1000% by mass relative to 100% by mass of the total solid content of the resin composition. In terms of imparting flexibility and crack resistance, the content of the binder resin is more preferably 10% by mass or more, even more preferably 30% by mass or more, more preferably 500% by mass or less, and even more preferably 200% by mass or less relative to 100% by mass of the total solid content of the resin composition.

<Compound having a (poly)styrene skeleton>
The resin composition of the present invention preferably further contains a compound having a (poly)styrene skeleton (hereinafter also referred to as "compound (Y)"). The compound having a (poly)styrene skeleton can be used as the above-mentioned polymer material or binder resin other than the above-mentioned polymer (X). For example, in the resin composition of the present invention, the polymer (X) is used as the polymer material, and the compound having a (poly)styrene skeleton is used as the binder resin, or the compound having a (poly)styrene skeleton is used as the polymer material, and the polymer (X) is used as the binder resin, or the polymer material and the binder resin are both used as the polymer (X). Among them, the polymer (X) is preferably used as both the polymer material and the binder resin in terms of high refraction.

The compound (Y) having a (poly)styrene skeleton is a compound having a structure represented by the following general formula (6).

(In the formula, R ¹² , R ¹³ and R ¹⁴ are the same or different and each represents a hydrogen atom or a methyl group; R ¹⁵ , R ¹⁶ , R ¹⁷ , R ¹⁸ and R ¹⁹ are the same or different and each represents a hydrogen atom, an alkyl group or an alkoxy group.)

In the formula, the alkyl groups represented by R ¹⁵ , R ¹⁶ , R ¹⁷ , R ¹⁸ and R ¹⁹ may be linear, branched or cyclic, but are preferably linear or branched. The number of carbon atoms in the alkyl groups is preferably 1 to 18, more preferably 1 to 8, and even more preferably 1 to 3.

In the formula, the alkoxy group represented by R ¹⁵ , R ¹⁶ , R 17 , R ¹⁸ and R ¹⁹ preferably has 1 to 18 carbon atoms, more ^preferably has 1 to 8 carbon atoms, and further preferably has 1 to 3 carbon atoms.

Specific examples of the compound (Y) include compounds such as styrene, α-methylstyrene, and 4-methylstyrene, as well as polymers thereof. Among these, (poly)styrene is preferred because of its good compatibility with the polymer (X).

The compound (Y) preferably has a number average molecular weight of 500 to 30,000,000, more preferably 1,000 to 100,000, and even more preferably 2,000 to 10,000, in order to increase the compatibility with the polymer (X).
The compound (Y) preferably has a polydispersity (Mw/Mn) of 1-10, more preferably 1-5, and even more preferably 1-2.
The number average molecular weight and dispersity can be determined by the same method as the above-mentioned method for measuring the molecular weight of the polymer (X).

The glass transition temperature (Tg) of the compound (Y) is preferably 80 to 250°C, more preferably 90°C or higher, more preferably 100°C or higher, more preferably 200°C or lower, and even more preferably 180°C or lower.
The glass transition temperature can be determined in the same manner as for the glass transition temperature of the polymer (X).

In the case of the resin composition containing the compound (Y), the compound (Y) is preferably covalently bonded to the metal oxide particles, and in this case, the compound (Y) is used as the polymer material that coats the metal oxide particles.
The covalent bond between the compound (Y) and the metal oxide particles can be confirmed by a method similar to the method for confirming the state in which the metal oxide particles are coated with the polymer material described above.

When the compound (Y) is used as the polymer material, the content of the compound (Y) is preferably the content of the polymer material described above. When the compound (Y) is used as the binder resin, the content of the compound (Y) is preferably the content of the binder resin described above.

<Other ingredients>
In addition to the above-mentioned components, the resin composition may contain, for example, resins other than those mentioned above, pigments, dyes, antioxidants, ultraviolet absorbers, reactive diluents, light stabilizers, plasticizers, non-reactive compounds, chain transfer agents, thermal polymerization initiators, anaerobic polymerization initiators, polymerization inhibitors, inorganic fillers, organic fillers, adhesion improvers such as coupling agents, heat stabilizers, antibacterial and antifungal agents, flame retardants, matting agents, defoamers, leveling agents, wetting and dispersing agents, anti-settling agents, thickeners and anti-sagging agents, color separation inhibitors, emulsifiers, slip and scratch inhibitors, skinning inhibitors, drying agents, antifouling agents, antistatic agents, conductive agents (electrostatic assistants), solvents, and other components. These components may be used alone or in combination of two or more. These components can be appropriately selected from known ones and used. In addition, the blending amounts of these can be appropriately set.

When the resin composition is for use in optical materials, it may contain other components as appropriate depending on the application of the optical material. Specific examples of the other components include ultraviolet absorbers, IR cutters, reactive diluents, pigments, detergents, antioxidants, light stabilizers, plasticizers, non-reactive compounds, and defoamers.

The resin composition preferably has a glass transition temperature (Tg) of 80 to 400° C. When the glass transition temperature is in the above-mentioned range, molding can be easily performed. From the viewpoint of increasing heat resistance, the glass transition temperature is more preferably 100° C. or higher, and even more preferably 115° C. or higher, and from the viewpoint of facilitating molding, it is more preferably 300° C. or lower, and even more preferably 200° C. or lower.
The glass transition temperature can be determined by the same method as the above-mentioned method for measuring the glass transition temperature of the polymer.

The resin composition preferably has a refractive index of 1.6 or more. When the refractive index is in the above range, the resin composition can be suitably used as an optical material, etc. The refractive index is more preferably 1.65 or more, and further preferably 1.7 or more.
The refractive index can be determined by the same method as the above-mentioned method for measuring the refractive index of a polymer.

The resin composition preferably has an Abbe number of 10 or more. When the Abbe number is in the above-mentioned range, the light dispersion is small, and the optical material can be suitable for lenses. The Abbe number is more preferably 15 or more, even more preferably 20 or more, and even more preferably 30 or more. From the viewpoint of adjusting the light dispersion, the Abbe number is more preferably 60 or less, and even more preferably 50 or less.
The Abbe number can be determined by the same method as the above-mentioned method for measuring the Abbe number of a polymer.

The resin composition preferably has a visible light transmittance of 75% or more. When the visible light transmittance is in the above range, the resin composition can be suitably used as an optical material. The visible light transmittance is more preferably 80% or more, more preferably 85% or more, and even more preferably 88% or more.
The visible light transmittance can be determined by the same method as the above-mentioned method for measuring the visible light transmittance of a polymer.

The resin composition preferably has a linear expansion coefficient of 70 ppm/°C or less. When the linear expansion coefficient of the resin composition is within the above range, the refractive index change due to temperature is small, and the resin composition can be suitably used for various applications such as optical materials, sealing materials, and coating materials. The linear expansion coefficient is more preferably 50 ppm/°C or less, and even more preferably 20 ppm/°C or less, in terms of being able to suppress changes in optical properties due to temperature changes. The lower limit of the linear expansion coefficient is not particularly limited, but is preferably 1 ppm/°C or more, and even more preferably 3 ppm/°C or more.
The linear expansion coefficient can be determined by measurement according to a method in accordance with JIS K 7197:2012.

The method for producing the resin composition is not particularly limited, and examples thereof include a method of mixing the metal oxide particles, the binder resin, and, if necessary, other components. Examples of the mixing include known means such as a bead mill, a roll mill, a ball mill, a jet mill, a kneader, and a blender.

<Applications>
INDUSTRIAL APPLICABILITY The resin composition of the present invention has a high refractive index and excellent transparency, and therefore can be suitably used in applications requiring a high refractive index or high transparency.

The resin composition of the present invention is used for various applications, such as imaging lenses, optical materials (components), machine part materials, electrical and electronic part materials, automobile part materials, civil engineering and construction materials, molding materials, as well as paints and adhesive materials. In particular, it is suitable for use in optical materials, optical device components, display device components, etc., and is more preferably used for optical purposes. Specific examples of such applications include optical applications such as eyeglass lenses, imaging lenses for cameras such as (digital) cameras, mobile phone cameras, and vehicle-mounted cameras, light beam focusing lenses, and lenses for light diffusion, LED sealants, optical adhesives, optical transmission bonding materials, filters, diffraction gratings, prisms, light guides, watch glasses, and transparent glass and cover glass for display devices; optical device applications such as photosensors, photoswitches, LEDs, light-emitting elements, optical waveguides, multiplexers, splitters, disconnectors, optical splitters, and optical fiber adhesives; and display device applications such as substrates for display elements such as LCDs, organic ELs, and PDPs, substrates for color filters, substrates for touch panels, display protective films, display backlights, light guide plates, anti-reflection films, and anti-fogging films.

The resin composition is preferably thermoplastic. If it is thermoplastic, it is easy to mold and has excellent productivity.

The resin composition can also be suitably used as a molding material. The molding method is not particularly limited, and examples thereof include injection molding, extrusion molding, the T-die method, the inflation method, and other methods generally known as methods for processing thermoplastic resins. The resin composition may also be molded into a desired shape by a casting method, coating method, or other method. The shape is not particularly limited, and examples thereof include various known shapes such as lenses, sheets, and films.

As described above, the resin composition of the present invention has a high refractive index and is excellent at suppressing aggregation of metal oxide particles, and can be suitably used for various applications such as optical applications.

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

In the examples, each evaluation was carried out by the following methods.
<Weight average molecular weight (Mw), number average molecular weight (Mn), dispersity (Mw/Mn)>
The weight average molecular weight and number average molecular weight of the polymer were determined by gel permeation chromatography (GPC) under the following conditions. The dispersity was calculated by dividing the weight average molecular weight by the number average molecular weight.
Equipment: SHIMAZU, CBM-20A
Detector: Differential refractive index detector (RI) (SHIMAZU, SPD-20MA), and ultraviolet-visible-infrared spectrophotometer (SHIMAZU, SPD-20MA)
Column: TOSOH, TSKgel Super HM-N
Column temperature: 40°C
Flow rate: 0.3mL/min
Calibration curve: Polystyrene Standards
Eluent: Chloroform

<Infrared Spectroscopic Analysis (IR)>
The IR measurement was carried out under the following conditions.
Apparatus: JASCO Fourier transform infrared spectrophotometer (FT/IR-6100)
Sample preparation: Approximately 2 mg of sample was diluted with approximately 300 mg of dry potassium bromide (KBr). The mixture was ground in a mortar and pestle and molded.

<Thermogravimetric analysis (TGA, TG-DTA)>
The measurements were carried out under the following conditions.
Equipment: Rigaku TG8120
Conditions: Measurement temperature range 20-200°C (heating rate: 10.0 deg/min, held for 30 minutes after reaching 200°C)
Sampling interval: 1.0 sec
Atmosphere: _N2 50mL/min

<X-ray diffraction measurement (XRD)>
The measurements were carried out under the following conditions.
Equipment: Rigaku Corporation, RINT-Ultima III
X-ray source: Cu Kα ray Measurement range: 2θ=10-60°
Sampling interval: 0.04°
Scanning speed: 10°/min

<Glass transition temperature (Tg)>
A differential scanning calorimeter (DSC) manufactured by Seiko Instruments Inc. was used, and α-alumina was used as a reference. The temperature was raised from room temperature to 250° C. at a heating rate of 10° C./min. The DSC curve was obtained, and the evaluation was performed based on the intersection point of the tangent line at the baseline and the inflection point.

<Transmittance of blend film>
The measurement was performed using a spectrophotometer (V-700 series ultraviolet, visible, and infrared spectrophotometer manufactured by JASCO Corporation). Air was used as a control sample. The visible light transmittance was evaluated at 400 nm.

<Refractive index ( _nD )>
The phase difference of the polarized light before and after incidence and the reflection deviation ratio of the obtained film were measured using a spectroscopic ellipsometer UVISEL manufactured by HORIBA Scientific Co., Ltd. The complex refractive index was obtained using preset values for the wavelength (450 nm) and incident angle (75°) of the incident light, and the refractive index at 190-2000 nm was calculated, and the refractive index at a wavelength of 589.3 nm was obtained.
Unless otherwise specified, 30 mg of the polymer or resin composition was dissolved in 1,1,2,2-tetrachloroethane (1 ml) and passed through a membrane filter having a pore size of 0.2 μm. 0.4 ml of the solution that passed through the filter was drop-cast onto a glass substrate (2 cm × 2 cm) to obtain a film having a thickness of about 50 nm, which was then measured.

<Element content ratio O/S ratio>
A sample was prepared by spin-coating 0.25 ml of the polymer solution onto a silicon wafer to form a film, and the film was analyzed using a JEOL photoelectron spectrometer (JPS-9010TR, XPS device, light source: Mg, X-ray output: 400 W). The peak intensity derived from the 2p orbital of the sulfur atom and the peak intensity derived from the 1s orbital of the oxygen atom were measured, and the integral ratio was calculated to calculate the O/S ratio. The peak intensities derived from the above were also measured, and the O/S ratio was calculated taking the results into consideration.
The measurement method and the position of the bond energy were based on Handbook of X-ray Photoelectron Spectroscopy (published by JEOL in March 1991).

Example 1
(Synthesis of poly(2,6-dimethyldisulfide) (PMPS))
In a nitrogen atmosphere, 3,3',5,5'-tetramethyldiphenyl disulfide (5 g, 18 mmol) was added to a 1,1,2,2-tetrachloroethane solution (10 ml) of 2,3-dichloro-5,6-dicyano-parabenzoquinone (DDQ, 2 M) and trifluoromethanesulfonic acid (1 M) in a 50 ml three-neck flask, and oxidative polymerization was carried out by stirring at room temperature for 40 hours. After 40 hours, the 1,1,2,2-tetrachloroethane solution was dropped into hydrochloric acid-acidified methanol, and the powder was collected with a glass filter. Thereafter, the mixture was washed with an aqueous potassium hydroxide solution (0.1 M) and pure water, and dried in vacuum to obtain a polymer (PMPS). The glass transition temperature of the polymer was 162°C. The O/S ratio was 0.02. The refractive index was 1.69.

(Bromo-modification of titanium oxide particle surface)
In a 30 mL flask, 3-glycidyloxypropyltrimethoxysilane SCA-ep (1.00 g, 4.23 mmol) and 2-bromo-2-methylpropionic acid (0.84 g, 5.00 mmol) were dissolved in 4 mL of tetrahydrofuran (THF) and reacted for 20 hours at 70° C. After separation with water/chloroform and drying under reduced pressure, a bromo-containing silane coupling agent (SCA-Br) was obtained as a yellow viscous liquid.
Next, anatase-type _TiO2 microparticles (manufactured by Aldrich, particle size <25 nm, 1.0 g) were dispersed in toluene (60 mL), and the obtained SCA-Br (0.40 g) and triethanolamine (TEA) (0.1 mL) were added and reacted for 24 hours at 50°C under a _N2 atmosphere. After washing with toluene and chloroform in a dialysis membrane and drying under reduced pressure, titanium oxide microparticles TiO2 _- Br having bromo groups on the surface were obtained as a white powder.
From the IR, peaks due to C-H stretching at around 2900 cm ^-1 , C=O stretching at around 1700 cm ^-1 , and O-Si-O stretching at around 1100 cm ^-1 were observed, supporting the progress of the reaction. Furthermore, from the TGA, the modification portion was calculated to be 11 wt % (0.19 mmol of Br initiator per 1 g of TiO ₂ -Br).

(Polystyrene modification of titanium oxide particle surface by ATRP (Atom Transfer Radical Polymerization))
As an initiator, TiO ₂ -Br (0.10 g, Br: 1 eq) obtained above and 2-bromoisobutyric acid ethyl EBiB (3 eq) were stirred in anisole, and styrene (460 eq) and CuBr/PMDETA catalyst (3 eq) were added as monomers, degassed, and reacted at 90°C for 24 hours. After the reaction, the reaction solution was dissolved and dispersed in chloroform, the supernatant was collected by centrifugation, and free polystyrene was removed by precipitation purification in methanol. The precipitate obtained by centrifugation was dispersed again in chloroform, precipitated and purified in methanol, and centrifuged to obtain polystyrene-modified titanium oxide fine particles TiO ₂ -PS as white powder. The fine particles TiO ₂ -PS were evaluated by TG-DTA, and the weight ratio of TiO ₂ /PS was 78 wt%/22 wt% from the decomposition weight of polystyrene (PS), and Tg was 90°C. The molecular weight of the PS was evaluated to be Mn=6100 and Mw/Mn=1.1.
From the IR, aliphatic and aromatic ring C-H stretching was observed around 2900 to 3050 cm ^-1 , and aromatic ring stretching was observed around 1500 cm ^-1 . Furthermore, from the XRD, a crystalline peak derived from anatase type _TiO2 and an amorphous broad peak derived from polystyrene were observed around 2θ = 15° to 30°. The above supported the progress of the reaction.

(Compatibility evaluation and optical properties of TiO ₂ -PS/PMPS blend films)
The TiO ₂ -PS (Tg: 94° C.) prepared above and PMPS (Tg: 162° C.) were dissolved and dispersed in toluene at a weight ratio of 1/1 at 20 mg/mL to prepare a resin composition.
The obtained resin composition was formed into a film on a glass substrate by a drop casting method. The blend film obtained by drop casting was visually transparent. Furthermore, DSC showed a single glass transition point (Tg: 120° C.). This confirmed the good compatibility (uniformity) of TiO ₂ -PS and PMPS.
The transmittance of the resulting blend film was measured and was found to be high, at 80% or more, in the visible light range (400 to 700 nm), and 84.8% at 400 nm.
1 shows the measurement data of the transmittance of the blend film obtained in Example 1. FIG. 2 shows a photograph of the blend film obtained in Example 1.
The refractive index of the resulting blend film was 1.68.
From the above, it was confirmed that the resin compositions of the Examples had a high refractive index, were excellent in suppressing the aggregation of metal oxide particles, and gave blend films with high transmittance.

Claims (4)

A resin composition comprising metal oxide particles coated with a polymer material and a binder resin,
The polymer material and/or the binder resin includes a polymer having at least one structural unit selected from the group consisting of a structural unit (A) represented by the following general formula (1), a structural unit (B) represented by the following general formula (2), and a structural unit (C) represented by the following general formula (3):
In the resin composition, the polymeric material and the binder resin contain the polymer, and the surfaces of the metal oxide particles and the polymeric material are bonded by a covalent bond, or the polymeric material contains the polymer and the binder resin contains a compound having a (poly)styrene skeleton, or the polymeric material contains the compound having a (poly)styrene skeleton and the binder resin contains the polymer,
The coating amount of the polymeric material is 10 to 50% by mass based on 100% by mass of the metal oxide particles coated with the polymeric material.

(In the formulas (1) to (3), X ¹ , X ² and X ³ are the same or different and each represents a phenylene group, a naphthylene group, an anthrylene group, a biphenylene group or a triphenylene group which may have a substituent.) The structural unit (A) is a structural unit (A-1) represented by the following general formula (1-1):
The structural unit (B) is a structural unit (B-1) represented by the following general formula (2-1):
2. The optical resin composition according to claim 1, wherein the structural unit (C) is a structural unit (C-1) represented by the following general formula (3-1):

(In formulas (1-1), (2-1), and (3-1), R ¹ , R ^{2 ,} and R ³ are the same or different and each represents a halogen atom, a hydroxyl group, or an alkyl group, an alkoxy group, an aryl group, an aralkyl group, or a sulfur-containing substituent, each of which may have a substituent. a represents the number of R ¹ and is an integer of 0 to 4. b represents the number of R ² and is an integer of 0 to 4. c represents the number of R ³ and is an integer of 0 to 4.) The optical resin composition according to claim 1 or 2, characterized in that the polymer has an elemental content ratio (O/S) of oxygen atoms O bonded to sulfur atoms S in the main chain to sulfur atoms S in the main chain of 0.02 to 1.3. The optical resin composition according to any one of claims 1 to 3, characterized in that the compound having a (poly)styrene skeleton and metal oxide particles are covalently bonded.

Images