JP5742443B2 - Curable composition and optical adhesive - Google Patents

Description

The present invention relates to a curable composition suitable as an optical adhesive used when producing a composite optical element.

A photocurable composition mainly composed of an acrylate compound or the like is widely used as an adhesive for producing an optical element. For adhesives, adhesiveness, curability, mechanical strength, durability, and optical properties are basic performances, but in recent years, the refractive index has become an important performance as the functionality of optical elements increases. In particular, increasing the refractive index of the adhesive is highly desired because the degree of freedom in optical design is expanded. Examples of a composite optical element using an adhesive having a high refractive index include an achromatic lens (achromatic lens) formed by bonding two lenses, and a hybrid aspherical surface formed by combining glass and resin. Examples include prisms having complicated shapes such as lenses and dichroic prisms.
The adhesive used for these applications naturally requires not only a high refractive index but also performance such as photocurability, colorless transparency, and heat resistance.

As a polyfunctional (meth) acrylate compound having a high refractive index, 9,9-bis (4- (2-acryloxyethoxy) phenyl) fluorene (hereinafter referred to as A-BPEF) (refractive index of cured product: 1.62) ), 4,4′-bis (methacryloylthio) diphenyl sulfide (hereinafter referred to as MPSMA) (refractive index of cured product 1.69), and the like. However, since these compounds are solid at room temperature, it is difficult to use them alone.
In general, a polyfunctional (meth) acrylate compound has a large shrinkage due to curing, and causes a decrease in adhesion when used as an adhesive.

On the other hand, an ene / thiol composition combining an ethylenically unsaturated compound such as a (meth) acrylate compound and a thiol compound has a high refractive index cured product because the thiol compound contains a sulfur atom having a high atomic refraction. It is known that However, addition polymerization of thiol groups and ethylenically unsaturated bond groups has fewer crosslinking points than chain polymerization, and the resulting sulfide bonds tend to give a soft cured product. There are issues that tend to soften. In order to obtain sufficient heat resistance, it is necessary to select a polyfunctional ethylenically unsaturated compound and a thiol compound.

Patent Document 1 describes an ene-thiol composition composed of a bifunctional thiol compound containing a 1,4-dithiane ring and triallyl isocyanurate or triallyl cyanurate. However, the refractive index of the cured product is not particularly described. Moreover, since the bifunctional thiol compound is used, the cured product is easily softened at a high temperature (see Comparative Example).
Patent Document 2 describes an ene-thiol composition composed of A-BPEF, an ethylenically unsaturated compound, and a thiol compound. According to the examples, the refractive index of the cured product is at most in the range of 1.58 to 1.61.
Patent Document 3 describes an ene-thiol composition composed of MPSMA, a vinyl monomer, and polythiol. According to the example, the refractive index of the cured product is 1.649 at the maximum. However, MPSMA is easily yellow-colored and has a limit in the amount of dissolution in the composition because it is solid.
Patent Document 4 describes a resin composition composed of a resin component having a fluorene ring and a sulfur-containing compound having a diphenyl sulfide skeleton such as MPSMA, and a resin having a refractive index of 1.724. Illustrated. However, the resin composition in the present invention is substantially a thermoplastic resin obtained by kneading a polyester having a fluorene ring and a sulfur-containing compound and is not a curable composition, and of course, photocurability cannot be imparted.

JP 2000-154251 A JP 2010-254732 A JP 03-021638 A JP 2005-187661 A

Accordingly, an object of the present invention is to provide a curable composition that aims at further increasing the refractive index and also has performance as an optical adhesive such as low shrinkage, photocurability, colorless transparency, and viscosity suitable for work. To provide things.

As a result of intensive studies to solve the above problems, the present inventors have found that a curable composition containing a polythiol oligomer (component A) obtained by reacting polythiol and sulfur and a polyene compound (component B), The inventors have found that it is possible to further increase the refractive index and also have the necessary performance as an optical adhesive, and have reached the present invention.

According to the present invention, there is provided a curable composition having a high refractive index and also having performance as an optical adhesive such as low shrinkage, photocurability, colorless transparency, and viscosity suitable for work. be able to.

The curable composition of the present invention comprises a polythiol oligomer (A component) obtained by reacting polythiol and sulfur and a polyene compound (B component).
First, the manufacturing method of a polythiol oligomer (A component) is demonstrated.

（１）
（式中、ｐは２〜４の整数を表し、Ｘ_ｐおよびＹ_ｐはそれぞれ独立に水素原子またはメチルチオール基を表す。）

（２）
（式中、ｑは０〜３の整数を表し、Ｒ^１は単なる結合または炭素数１〜３のアルキレン基を表す。）

（３）
（式中、ｒは０〜３の整数を表し、Ｒ２は炭素数１〜３のアルキレン基を表す。） The polythiol used as the raw material of the polythiol oligomer is a compound having two or more thiol groups in one molecule, and may be any of linear, branched, and cyclic. In particular, when pursuing a viscosity suitable for increasing the refractive index and workability of the curable composition, compounds represented by the following general formulas (1) to (3) are preferable.

(1)
(In the formula, p represents an integer of 2 to 4, and X _p and Y _p each independently represent a hydrogen atom or a methylthiol group.)

(2)
(In the formula, q represents an integer of 0 to 3, and R ¹ represents a simple bond or an alkylene group having 1 to 3 carbon atoms.)

(3)
(In the formula, r represents an integer of 0 to 3, and R2 represents an alkylene group having 1 to 3 carbon atoms.)

Incidentally, _X p in the general formula (1), the _{Y p,} for example in the case of p = 2 _represents X _1, X 2, _{Y 1,} and _{Y 2} are each independently substituent. Examples of the compound represented by the general formula (1) include 1,5-dimercapto-3-thiapentane, 2-mercaptomethyl-1,5-dimercapto-3-thiapentane, and 2,4-bis (mercaptomethyl) -1. , 5-dimercapto-3-thiapentane, 4-mercaptomethyl-1,8-dimercapto-3,6-dithiaoctane, 4,8-bis (mercaptomethyl) -1,11-dimercapto-3,6,9-trithia Undecane, 4,7-bis (mercaptomethyl) -1,11-dimercapto-3,6,9-trithiaundecane, 5,7-bis (mercaptomethyl) -1,11-dimercapto-3,6,9- Examples of the compound represented by the general formula (2) include 2,5-dimercapto-1,4-dithiane and 2,5-dimene. Kaputomechiru dithiane, 2,5-mercaptoethyl-1,4-dithiane, and examples of the compound represented by formula (3), xylylenedithiol and the like. Examples of polythiol compounds other than the compounds represented by the general formulas (1) to (3) include ethylene glycol bis (3-mercaptopropionate), trimethiolpropane tris (3-mercaptopropionate), pentaerythritol tetrakis (3 -Mercaptopropionate), benzenedithiol, tolylenedithiol and the like.

Regarding sulfur as a raw material for the polythiol oligomer, sulfur forms many allotropes, and generally well-known cyclic S8 sulfur is preferable. Sulfur may be in any form, for example, crystalline, colloidal, powder, or sulfur.

（６）

（７）
（式中、Ｒは有機基を表し、ｎは１以上の整数を表す。）
に従って進行する。硫黄の使用量は、チオール基１モルに対して、硫黄原子０．２〜０．９５モルの範囲が好ましく、０．２〜０．５モルの範囲がより好ましい。０．２モル未満ではポリチオールの転化率が低すぎて実用的でないし、０．９５モルを超えると光学材料の原料として好ましくない分子量が過大なポリチオールオリゴマーが生成するとともに、未反応の硫黄が残存しやすく好ましくない。 According to Journal of Organic Chemistry, Vol. 32, pages 3833 to 3836 (1967), the reaction of polythiol and sulfur is mainly carried out by the following reaction formulas (6) and (7) when the product is a dimer, for example.

(6)

(7)
(In the formula, R represents an organic group, and n represents an integer of 1 or more.)
Proceed according to. The amount of sulfur used is preferably in the range of 0.2 to 0.95 mol of sulfur atoms and more preferably in the range of 0.2 to 0.5 mol with respect to 1 mol of thiol group. If it is less than 0.2 mol, the conversion rate of polythiol is too low to be practical, and if it exceeds 0.95 mol, a polythiol oligomer having an excessive molecular weight which is not preferable as a raw material for optical materials is generated and unreacted sulfur remains. It is easy to do and is not preferable.

The reaction between polythiol and sulfur proceeds by heating in the presence or absence of a basic catalyst, but a method using a basic catalyst is preferred. Examples of the basic catalyst include amines, ammonium salts, phosphines, and phosphonium salts. The amount of the basic catalyst used is preferably in the range of 0.005 to 5 mol and more preferably in the range of 0.05 to 0.5 mol with respect to 100 mol of the thiol group contained in the raw polythiol.

Each raw material is added by adding a catalyst to the polythiol and sulfur mixed solution, adding sulfur to the polythiol and catalyst mixed solution, or adding the polythiol and sulfur mixed solution to the polythiol and sulfur mixed solution. May be. In order to allow the reaction to proceed gently, the catalyst and sulfur may be added in several portions.

You may perform reaction of polythiol and sulfur in presence of a polyene compound (B component). Since the reaction between polythiol and sulfur is accompanied by the generation of hydrogen sulfide, the reaction is preferably performed under exhaust or reduced pressure. You may use a solvent as needed. When a solvent is used, a post-process for distilling off the solvent is required. Although reaction temperature is not specifically limited, The range of 0-100 degreeC is preferable, and you may raise temperature gradually, seeing the progress of reaction. The reaction time depends on various conditions such as the type of raw material, the ratio of polythiol and sulfur, and the reaction temperature, and thus cannot be defined unconditionally, but the reaction is continued until no unreacted sulfur remains.

Next, the curable composition of this invention is demonstrated.
The curable composition of the present invention comprises the polythiol oligomer (A component) and the polyene compound (B component) described above.

（４）
（式中、Ｘは硫黄原子またはスルホニル基を表し、Ｚは（メタ）アクリロイル基、ビニル基、またはアリル基を表わす。）

（５）
（式中、ｍおよびｎは、ｍとｎの合計が０〜４を満たす整数を表し、Ｒ^３は炭素数１〜５のアルキレン基を表し、Ｒ^４は水素原子またはメチル基を表し、Ｒ^５は水素原子またはメチル基を表す。）
一般式（４）で表わされる化合物の例としては、４，４’−ビス（メタクリロイルチオ）ジフェニルスルフィド、４，４’−ビス（メタクリロイルチオ）ジフェニルスルホン等が挙げられ、一般式（５）で表わされる化合物としては、９，９−ビス（４−（２−アクリロキシエトキシ）フェニル）フルオレン等が挙げられる。 The polyene compound (component B) is a compound having two or more ethylenically unsaturated bond groups in one molecule, and examples of the ethylenically unsaturated bond group include acryloyl group, methacryloyl group, vinyl group, and allyl group. Can be mentioned. In particular, when pursuing a high refractive index of the curable composition, a compound having an aromatic ring or a heterocyclic ring in the molecule is preferable. Examples of such a compound include triallyl isocyanurate, triallyl cyanurate, diallyl phthalate. , Diallyl isophthalate, diallyl terephthalate, triallyl trimellitic acid, tetraallyl pyromellitic acid, a compound represented by general formula (4), a compound represented by general formula (5), and the like.

(4)
(In the formula, X represents a sulfur atom or a sulfonyl group, and Z represents a (meth) acryloyl group, a vinyl group, or an allyl group.)

(5)
(In the formula, m and n represent an integer in which the sum of m and n satisfies 0 to 4, R ³ represents an alkylene group having 1 to 5 carbon atoms, R ⁴ represents a hydrogen atom or a methyl group, R ⁵ represents a hydrogen atom or a methyl group.)
Examples of the compound represented by the general formula (4) include 4,4′-bis (methacryloylthio) diphenyl sulfide, 4,4′-bis (methacryloylthio) diphenyl sulfone, and the like. Examples of the compound represented include 9,9-bis (4- (2-acryloxyethoxy) phenyl) fluorene.

About content of a polythiol oligomer, the range of 10-80 weight part is preferable with respect to 100 weight part of curable compositions, and the range of 20-70 weight part is further more preferable. When the content of the polythiol oligomer is less than 10 parts by weight, the effect of increasing the viscosity or reducing the shrinkage is reduced.

If necessary, a polymerization inhibitor, an antioxidant, a light stabilizer (HALS), an ultraviolet absorber, a silane coupling agent, a release agent, a pigment, a dye, and the like may be added to the curable composition of the present invention. Is possible.

The curable composition of the present invention is cured by irradiation with actinic rays such as ultraviolet light and visible light in the presence of a radical photopolymerization initiator. The radical photopolymerization initiator is not particularly limited as long as it generates an active free radical by photolysis. Specific examples of such compounds include 2,2-methoxy-1,2-diphenylethane-1-one, 1-hydroxy-cyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenylpropane-1- ON, 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone-1, Examples thereof include bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide, 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide, and the like. The radical photopolymerization initiators may be used alone or in combination of two or more. Although the content is not specifically limited, The range of 0.1-10 weight part is preferable with respect to 100 weight part of curable compositions, The range of 0.5-5 wt% is more preferable.

Assuming that the viscosity of the curable composition is used as an adhesive, if the viscosity is too low, the adhesive may sag or flow, or the adherend may be displaced during lamination, which is not preferable. On the other hand, if the viscosity is too high, it is not preferable because it becomes difficult to discharge or apply the adhesive, or the air bubbles are bitten at the time of pasting. The viscosity suitable for workability as referred to in the present invention depends on the use form of the adhesive such as the coating method and the laminating method, but cannot be defined unconditionally, but is preferably in the range of 500 to 20,000 mPa · s, more Preferably it is the range of 1,000-10,000 mPa * s.

EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. In addition, the cure shrinkage rate in an Example was computed from the refractive index before and behind hardening according to the following formula.
X = (1−d1 / d2) × 100 [%]
R = (n ² −1) / (n ² +2) × M / d
Since R / M is constant before and after curing,
X = [1-{(n1 ² -1) / (n1 ² +2)} / {(n2 ² -1) / (n2 ² +2)}] × 100 [%]
(Where X is the curing shrinkage ratio, d is the specific gravity, d1 is the specific gravity before curing, d2 is the specific gravity after curing, R is the molecular refraction, n is the refractive index, n1 is the refractive index before curing, and n2 is the after curing. The refractive index of M and M represents the molecular weight.)
The viscosity of the curable composition was measured at a temperature of 25 ° C. using a cone / plate viscometer DV-II + (manufactured by Brookfield). The refractive indexes of the curable composition and the cured product were measured using an Abbe refractometer NAR-3T (manufactured by Atago Co., Ltd.). The transmittance of the cured product was measured using a spectrophotometer U-3500 (manufactured by Hitachi High-Tech) at a thickness of 0.25 mm and a wavelength of 400 nm.

Example 1
In a 300 ml flask, 65 g of 4-mercaptomethyl-1,8-dimercapto-3,6-dithiaoctane and 0.05 g of dicyclohexylmethylamine were taken and stirred well. 4.7 g of sulfur powder was slowly added dropwise in several portions at room temperature. When sulfur powder was added, the solution turned yellow and gas was generated. After the generation of gas became slow, the temperature was raised to 60 ° C. while flowing nitrogen gas through the liquid surface, and stirring was continued for 3 hours. As the reaction progressed, gas generation almost disappeared and the solution became colorless and transparent. The polythiol oligomer was produced by the above procedure.
After cooling the polythiol oligomer to room temperature, 35 g of triallyl isocyanurate was added and stirred until uniform. The curable composition was produced in the above procedure.

To 100 parts by weight of the curable composition, 3 parts by weight of 1-hydroxy-cyclohexyl phenyl ketone was added, stirred until uniform, and degassed under reduced pressure. This was sandwiched between two release-treated glass plates, irradiated with light from a metal halide lamp (120 W / cm) for 3 minutes from a distance of 30 cm, and then the cured film was peeled off from the glass plate. A cured film having a thickness of 0.25 mm was produced by the above procedure.
The physical properties of the curable composition and the cured film were as shown in Table 1.

Examples 2-5
A curable composition and a cured product were prepared in the same manner as in Example 1 except that the types and amounts of polythiol, sulfur, and polyene compound were changed to those shown in Table 1. The physical properties of the curable composition and the cured product were as shown in Table 1.

Comparative Example 1
In a 300 ml flask, 55 g of 2,5-dimercaptomethyl-1,4-dithiane and 45 g of triallyl isocyanurate were taken and stirred until uniform. The curable composition was produced in the above procedure.
A cured film was produced in the same manner as in Example 1. The physical properties of the curable composition and the cured product were as shown in Table 2. In addition, the value which performance is inferior compared with an Example was underlined.

Comparative Examples 2-4
A curable composition and a cured product were prepared in the same manner as in Comparative Example 1 except that the types and amounts of the thiol compound and ethylenically unsaturated compound were changed to those shown in Table 2. The physical properties of the curable composition and the cured product were as shown in Table 2. In addition, the value which performance is inferior compared with an Example was underlined.

補足説明
比較例３：ＭＰＳＭＡ（ｂ−２）が溶けきらなかったため、測定できなかった。

Supplementary explanation Comparative example 3: Since MPSMA (b-2) was not completely dissolved, it could not be measured.

Explanation of Abbreviations in Table (a-1) 4-Mercaptomethyl-1,8-dimercapto-3,6-dithiaoctane (a-2) 2,5-dimercaptomethyl-1,4-dithiane (a-3) m -Xylylenedithiol (a-4) 1,5-dimercapto-3-thiapentane (b-1) triallyl isocyanurate (b-2) 4,4'-bis (methacryloylthio) diphenyl sulfide (b-3) trimellit Acid triallyl (b-4) 2,2-bis (4- (acryloxydiethoxy) phenyl) propane

Claims (4)

A curable composition containing a polythiol oligomer (component A) obtained by reacting polythiol and sulfur and a polyene compound (component B) , wherein the polythiol has the following general formula (1) and the following general formula (2) , One or more compounds selected from the group consisting of the following general formula (3), wherein the polyene compound (component B) is triallyl isocyanurate, triallyl cyanurate, diallyl phthalate, diallyl isophthalate, diallyl terephthalate, tri One or more selected from the group consisting of triallyl meritate, tetraallyl pyromellitic acid, compound represented by general formula (4), compound represented by general formula (5), and 100 parts by weight of curable composition The polythiol oligomer (component A) is 20 to 70 parts by weight, and when reacting polythiol and sulfur Ratio of Richioru and sulfur, to a thiol group 1 mole sulfur atom curable composition is in the range of 0.2 to 0.5 mol.

(1)
(In the formula, p represents an integer of 2 to 4, and X _p and Y _p each independently represent a hydrogen atom or a methylthiol group.)

(2)
(In the formula, q represents an integer of 0 to 3, and R ¹ represents a simple bond or an alkylene group having 1 to 3 carbon atoms.)

(3)
(In the formula, r represents an integer of 0 to 3, and R ² represents an alkylene group having 1 to 3 carbon atoms.)

(4)
(In the formula, X represents a sulfur atom or a sulfonyl group, and Z represents a (meth) acryloyl group, a vinyl group, or an allyl group.)

An optical adhesive comprising the curable composition according to claim 1 . The optical adhesive according to claim 2, wherein the viscosity is in the range of 500 to 20,000 mPa · s. The optical adhesive for lenses and / or prisms according to claim 2 or 3.