JP5834474B2 - 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.

Photocurable compositions such as acrylate compounds are widely used as adhesives when producing optical elements. Adhesives, photocurability, mechanical strength, durability, and optical properties are basic performances for adhesives, but in recent years, the refractive index has become an important performance as optical elements become more sophisticated. . In particular, increasing the refractive index of the adhesive is highly desired because the degree of freedom in optical design is expanded. Examples of applications in which an adhesive having a high refractive index is used include an achromatic lens (achromatic lens) composed of two lenses bonded together, a hybrid aspherical lens composed of a composite of glass and resin, and dichroic Examples include prisms having complicated shapes such as prisms. Adhesives used for these applications naturally require not only a high refractive index but also performance such as adhesion, photocurability, colorless transparency, and viscosity suitable for work.

As compounds having a high refractive index, many episulfide compounds containing a high concentration of sulfur atoms in the molecular structure have been found (Patent Documents 1 to 4). For example, the refractive index of a cured product of bis (2,3-epithiopropyl) sulfide is 1.70. Since the episulfide compound has a low viscosity and can be easily injected into a mold, it is suitable for producing a molded article such as a spectacle lens. However, assuming use as an adhesive, if the viscosity is too low, the adhesive may sag or flow, and the adherend may be displaced during pasting, which causes problems in workability. Moreover, since the episulfide compound generally has a large shrinkage due to curing, when used as an adhesive, it causes a decrease in adhesion.

JP-A-9-71580 Japanese Patent Laid-Open No. 9-110979 Japanese Patent Laid-Open No. 9-255781 JP 2001-163874 A

Accordingly, an object of the present invention is to provide a curable composition having a high refractive index and also having performances required as an optical adhesive such as photocurability, low shrinkage, colorless transparency, and viscosity suitable for work. Is to provide.

As a result of intensive studies to solve the above problems, the present inventors have found that a polythiol oligomer (A component), an episulfide compound (B component) and a photobase generator (C component) obtained by reacting polythiol and sulfur. It has been found that the contained curable composition has a viscosity suitable for workability as an adhesive and has a small shrinkage due to curing, and thus is suitable as an optical adhesive. Furthermore, it is preferable to use a basic catalyst when reacting polythiol and sulfur. However, when hindered amine is used as this catalyst, a curable composition having excellent storage stability (the reaction of episulfide is sufficiently slow) is obtained. I found out that Based on the above findings, the present invention has been achieved.

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 photocurability, low shrinkage, 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, an episulfide compound (B component), and a photobase generator (C component).

First, the manufacturing method of a polythiol oligomer (A component) is demonstrated.
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 R ² 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.

According to Journal of Organic Chemistry, Vol. 32, pages 3833 to 3836 (1967), for example, when the product is a dimer, the reaction of polythiol is mainly represented by the following reaction formulas (5) and (6):
(5)
(6)
(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 0.5 to 0.95 mol with respect to 1 mol of thiol groups. 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, unreacted sulfur tends to remain, which 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. In particular, a hindered amine is preferable as the base catalyst. The hindered amine refers to an amine having a substituent on both sides of the amino group. Hindered amines are weak in activity as polymerization catalysts for episulfide compounds due to steric hindrance of substituents. As a result, the curable composition combining the polythiol oligomer and the episulfide compound is sufficiently stable (the polymerization of the episulfide compound is sufficiently slow), and can be stored for a long period of time. As the hindered amine, a compound having a 2,2,6,6-tetramethylpiperidine skeleton is preferable. Specifically, 2,2,6,6-tetramethylpiperidine, 1,2,2,6,6-penta Methylpiperidine, 4-hydroxy-2,2,6,6-tetramethylpiperidine, 4-hydroxy-1,2,2,6,6-pentamethylpiperidine, acrylic acid 2,2,6,6-tetramethyl- 4-piperidyl, 2,2,6,6-tetramethyl-4-piperidyl methacrylate, 1,2,2,6,6-pentamethyl-4-piperidyl acrylate, 1,2,2,6,6 methacrylate -Pentamethyl-4-piperidyl, bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis (1,2,2,6,6-pentamethyl-4-piperid sebacate) Le) and the like. 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 an episulfide compound (B component). However, if an appropriate basic catalyst is not selected, the episulfide compound may be polymerized to cause gelation. Therefore, when a basic catalyst is used, hindered amine is preferable for the reason described above.

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 (component A), episulfide compound (component B), and photobase generator (component C) described above.
An episulfide compound (component B) is a compound having one or more episulfide groups in one molecule. In particular, when pursuing higher refractive index of the curable composition, the following general formula (4)
(4)
(In the formula, m is an integer of 0 to 6, n is an integer of 0 to 4, R ³ and R ⁴ are each independently a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, R ⁵ , R 4 ⁶ is each independently an alkylene group having 1 to 10 carbon atoms.)
The compound represented by these is preferable. Examples of the episulfide compound represented by the general formula (4) include bis (2,3-epithiopropyl) sulfide.

Although the episulfide compound represented by the general formula (4) has a large shrinkage due to curing, the shrinkage accompanying the curing can be suppressed by copolymerizing with the polythiol oligomer. The episulfide compound represented by the general formula (4) generally has a low viscosity, but is adjusted to a viscosity excellent in workability by mixing with the polythiol oligomer.

Assuming use of the curable composition as an adhesive, if the viscosity is too low, the adhesive may sag or flow, or the substrate may be displaced during bonding. 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 bubbles are bitten during the bonding. Viscosity suitable for workability 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 100 to 50,000 mPa · s, more Preferably it is the range of 500-10,000 mPa * s.

About content of a polythiol oligomer, the range of 10-70 weight part is preferable with respect to 100 weight part of curable compositions, and the range of 20-50 weight part is further more preferable. If 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, and if it exceeds 70 parts by weight, the toughness of the cured product is lowered, which is not preferable.

The photobase generator (component C) is a compound that generates a base by photolysis with actinic rays. In particular, since the polymerization of episulfide compounds is promoted by amidine such as DBN (diazabicyclononene) and DBU (diazabicycloundecene), photobase generators that generate these bases are preferred. Specifically, the amidinium ketone (the left side of the following formula (7)) forming the tetraarylborate salt described in JP-T-2001-513765 and the aryl described in JP-T-2005-511536. Examples include 1,3-diamine (left side of the following formula (8)) substituted with an alkyl group. These may be used alone or in combination of two or more. The addition amount of the photobase generator is preferably in the range of 0.01 to 10 parts by weight, more preferably in the range of 0.1 to 5 parts by weight with respect to 100 parts by weight of the curable composition.
(7)
(8)

In addition to the photobase generator, a photosensitizer may be included. By adding the photosensitizer, the photodecomposition of the photobase generator is accelerated, and the curing time of the photocurable composition can be shortened. Specific examples of the photosensitizer include benzophenones, thioxanthones, anthraquinones, camphorquinones, benzyls, Michler ketones, and anthracenes. These may be used alone or in combination of two or more. The addition amount of the photosensitizer is preferably in the range of 0.01 to 10 parts by weight and more preferably in the range of 0.1 to 5 parts by weight with respect to 100 parts by weight of the curable composition.

If necessary, a polymerization inhibitor, a polymerization inhibitor, an antioxidant, an ultraviolet absorber, a silane coupling agent, a release agent, a pigment, a dye, and the like can be added to the curable composition. . Moreover, you may perform filtration, defoaming, etc. as needed.

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 rate, 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, 40 g of 2,5-dimercaptomethyl-1,4-dithiane and 0.05 g of tributylamine were taken and stirred well. 6.0 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.

To this polythiol oligomer (component A), bis (2,3-epithiopropyl) sulfide 60 g (component B), the following structural formula (9)
(9)
0.2 g (component C) of a photobase generator represented by the formula (1) and 1 g of 4-benzoyl-4′-methyldiphenyl sulfide as a sensitizer were added and stirred until uniform. The curable composition was produced in the above procedure. The viscosity of the curable composition was 900 mPa · s (20 ° C.). Moreover, when it preserve | saved for one week at 5 degreeC, the curable composition was gelatinized.

The curable composition 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 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.

Example 2
In a 300 ml flask, 40 g of 2,5-dimercaptomethyl-1,4-dithiane, 60 g of bis (2,3-epithiopropyl) sulfide, 1,2,2,6,6-pentamethyl-4-piperidyl methacrylate .1 g was taken and stirred well. 6.0 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. After cooling to room temperature, 0.2 g (C component) of the photobase generator represented by the above structural formula (9) and 1 g of 4-benzoyl-4′-methyldiphenyl sulfide as a sensitizer were added and uniformly added. Stir until. The curable composition was produced in the above procedure. The viscosity of the curable composition was 1,000 mPa · s (20 ° C.). The viscosity after storage at 5 ° C. for 1 week was 1,100 mPa · s (20 ° C.).

A cured product was prepared in the same manner as in Example 1. The physical properties of the curable composition and the cured film were as shown in Table 1.

Examples 3-9
A curable composition and a cured product were produced in the same manner as in Example 2 except that the types and amounts of polythiol, sulfur, and episulfide 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
100 g of bis (2,3-epithiopropyl) sulfide, 0.2 g (C component) of the photobase generator represented by the above structural formula (9), and 4-benzoyl-4′-methyldiphenyl sulfide as the sensitizer 1 g was added and stirred until uniform. The curable composition was produced in the above procedure.
A cured product 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, physical properties that are inferior to those of the examples are underlined.

Comparative Example 2
2,5-dimercaptomethyl-1,4-dithiane 20 g, bis (2,3-epithiopropyl) sulfide 80 g, photobase generator 0.2 g (C component) represented by the structural formula (9), Then, 1 g of 4-benzoyl-4′-methyldiphenyl sulfide was added as a sensitizer and stirred until uniform. The curable composition was produced in the above procedure.
A cured product 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, physical properties that are inferior to those of the examples are underlined.

Explanation of Abbreviations in Table (a-1) 2,5-Dimercaptomethyl-1,4-dithiane (a-2) m-xylylenedithiol (a-3) 1,5-dimercapto-3-thiapentane (b- 1) Tributylamine (b-2) 1,2,2,6,6-pentamethyl-4-piperidyl (c-1) bis (2,3-epithiopropyl) sulfide methacrylate

Claims (7)

A curable composition containing a polythiol oligomer (A component), an episulfide compound (B component), and a photobase generator (C component) obtained by reacting polythiol and sulfur, and reacting polythiol with sulfur A curable composition using a hindered amine as a reaction catalyst . The curable composition according to claim 1, wherein the polythiol is at least one selected from the group consisting of the following general formula (1), the following general formula (2), and the following general formula (3).
(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.) The curable composition according to claim 1 or 2, wherein the ratio of polythiol and sulfur in the reaction of polythiol and sulfur is in the range of 0.2 to 0.95 mol of sulfur atom with respect to 1 mol of thiol group. object. The curable composition according to any one of claims 1 to 3, wherein the hindered amine is a compound having a 2,2,6,6-tetramethylpiperidine skeleton. The curable composition according to any one of claims 1 to 4 , wherein the episulfide compound (component B) is a compound represented by the following general formula (4).
(4)
(In the formula, m is an integer of 0 to 6, n is an integer of 0 to 4, R ³ and R ⁴ are each independently a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, R ⁵ , R 4 ⁶ is each independently an alkylene group having 1 to 10 carbon atoms.) The curable composition according to claim 5 , wherein the compound represented by the general formula (4) is bis (2,3-epithiopropyl) sulfide. Optical adhesive comprising a cured composition according to any one of claims 1 6.