TWI905400B - Curable composition, cured product, molding, optical material and plastic lens - Google Patents

Abstract

A curable composition of the present invention comprises: a compound (A) having two or more thioacrylate groups; and a (meth)acrylic polymer (B), wherein the (meth)acrylic polymer (B) comprises 50 mass% or more of a structural unit (b1') derived from a (meth)acrylate (b1) comprising an aromatic group with respect to all structural units.

Description

Hardened components, hardened materials, molded articles, optical materials, and plastic lenses

This invention relates to a curable composition, curable material, molded article, optical material, and plastic lens that provides a curable material with high refractive index, low curing shrinkage, and high heat resistance.

Previously, glass was preferred for optical components due to its diverse refractive index and minimal variation caused by temperature and humidity. However, in recent years, resin products have been increasingly used to meet demands for lightweighting and cost reduction.

To achieve miniaturization and thinning, camera lens modules in smartphones are increasingly using wafer-level lenses. Wafer-level lenses require resin curing materials with high refractive index and excellent heat resistance. Furthermore, in so-called hybrid wafer-level lenses where resin lenses are formed on a glass substrate, low curing shrinkage is required during curing to suppress peeling between the glass substrate and the resin lens caused by residual stress.

As a method for obtaining resin-cured materials with higher refractive index, patent documents 1 and 2 report methods for obtaining transparent materials by photocuring compositions containing thio(meth)acrylates, etc.

[Existing technical literature] [Patent Documents]

[Patent Document 1] International Publication No. 98/24761

[Patent Document 2] Japanese Patent Publication No. 8-325337

However, the compositions obtained using the methods described in Patent Documents 1 and 2 exhibit high hardening shrinkage, posing practical problems, and consequently, the hardened products obtained from these compositions suffer from heat resistance issues.

The inventors have discovered that the problem can be solved by including the monomer in a prescribed amount in an assembly comprising a compound having a thioacrylate group and a (meth)acrylic polymer containing a structural unit derived from a prescribed monomer, thereby completing the present invention.

That is, this invention can be shown below.

[1] A curable composition comprising: a compound (A) having two or more thioacrylate groups; and a (meth)acrylate polymer (B) comprising, relative to all structural units, at least 50% by mass of structural units (b1') derived from an aromatic-containing (meth)acrylate (b1).

[2] The curing composition as described in [1], wherein the Hansen distance Ra between compound (A) having two or more thioacrylate groups and compound (b1) is 6.0 or less.

[3] The curable composition as described in [1] or [2], wherein the aromatic (meth)acrylate (b1) is represented by the following general formula (1).

(In general formula (1), R represents hydrogen or methyl, _X1 and _X2 represent any one of single bond, oxygen atom, sulfur atom, or ester bond, respectively, Y represents a single bond, any hydrogen atom that can be substituted by an alkyl group with 1 to 5 carbon atoms, or a benzene ring, Z represents an oxygen atom or a sulfur atom, and n is 0 or 1.)

[4] A curable composition as described in any of [1] to [3], wherein the (meth)acrylic polymer (B) further comprises a structural unit (b2') terminated with a polymerizable group.

[5] A curable composition as described in any one of [1] to [4], wherein the (meth)acrylic polymer (B) has a weight-average molecular weight of 1,000 to 50,000.

[6] A curable composition as described in any one of [1] to [5], wherein the compound (A) having two or more thioacrylate groups is selected from at least one of the compounds represented by the following chemical formulas.

[7] A hardener is formed by hardening a hardening composition as described in any one of [1] to [6].

[8] A molded article comprising the hardened material as described in [7].

[9] An optical material comprising a molded body as described in [8].

[10] A plastic lens comprising a molded body as described in [8].

According to the present invention, a curable composition is provided that yields a curable material with high refractive index, low curing shrinkage, and high heat resistance. In other words, the curable composition according to the present invention provides a curable material with an excellent balance of these properties. Furthermore, according to the present invention, a curable material formed by curing the curable composition, a molded article containing the curable material, optical components, optical plastic components, etc., are provided.

The invention will now be described based on its embodiments. In this specification, unless otherwise specified, "~" indicates "above" to "below". Furthermore, the term "(meth)acrylic acid" in this specification includes both acrylic acid and methacrylic acid. The same applies to similar expressions such as "(meth)acrylate". In particular, the term "(meth)acrylic acid" in this specification includes both the acrylonitrile group represented by -C(=O)-CH= _CH2 and the methacrylic acid group represented by -C(=O)-C( _CH3 )= _CH2 .

<Hardened components>

The curable composition of this embodiment comprises: compound (A) having two or more thioacrylate groups; and a (meth)acrylate polymer (B), wherein the (meth)acrylate polymer (B) comprises, relative to all structural units, at least 50% by mass of structural units (b1') derived from aromatic-containing (meth)acrylates (b1).

This allows for the provision of curable compositions that yield curables with high refractive index, low curing shrinkage, and high heat resistance.

[Compound (A) having two or more thioacrylate groups]

In this embodiment, the compound (A) having two or more thioacrylate groups may use any known compound without particular limitation within the scope of achieving the effects of the present invention, but is preferably selected from at least one of 1,8-bis((meth)acrylthio)-4-(meth)acrylthiomethyl-3,6-dithiooctane, bis[2-((meth)acrylthio)ethyl]sulfide, and 1,11-bis((meth)acrylthio)-5,7-bis((meth)acrylthiomethyl)-3,6,9-trithioundecane. These compounds are specifically represented by the following chemical formulas.

[Chemistry 3]

[(Meth)acrylate polymer (B)]

In this embodiment, the (meth)acrylic polymer (B) comprises a structural unit (b1') derived from an aromatic-containing (meth)acrylate (b1).

From the perspective of the effects of this invention, relative to all structural units, structural unit (b1') may contain 50% or more by mass, more preferably 60% or more by mass, even more preferably 65% or more by mass, and even more preferably 80% or more by mass.

Furthermore, it is preferable that the Hansen distance Ra between the compound (A) having two or more thioacrylate groups and the (meth)acrylate (b1) containing aromatic groups is less than 6.0.

This allows for the provision of curable compositions that yield curables with superior high refractive index, low hardening shrinkage, and excellent heat resistance.

The Hansen solubility parameter is an indicator of the degree to which one substance dissolves in another substance. The Hansen solubility parameter can be represented by a three-dimensional vector, specifically by the dispersion term ( _δD ), polarization term ( _δP ), and hydrogen bonding term ( _δH ).

In this embodiment, the Hansen distance Ra is the distance between compound (A) and compound (b1) in a three-dimensional space with the dispersion term ( _δD ), polarization term ( _δP ), and hydrogen bonding term ( _δH ) as coordinates. Specifically, it can be calculated using the following formula.

Formula: Ra=[4(δ _DA -δ _Db1 ) ² +(δ _PA -δ _Pb1 ) ² +(δ _HA -δ _Hb1 ) ² ] ^1/2

The smaller the Hansen distance Ra, the better the compatibility between compound (A) and compound (b1). The Hansen distance Ra can be set preferably below 6.0, more preferably below 5.0, and even better below 4.0.

Therefore, it is believed that in a compound (A) having two or more thioacrylate groups and a (meth)acrylate polymer (B) containing at least 50% by mass of a structural unit (b1') derived from an aromatic (meth)acrylate (b1) relative to all structural units, with the Hansen distance Ra within the aforementioned range, the compatibility between compound (A) and polymer (B) in the curable composition is better. Compound (A) is evenly distributed among polymers (B), resulting in less curing shrinkage. Consequently, the polymers (B) are more firmly bonded together through curing, thereby obtaining a cured product with higher refractive index and better heat resistance.

The aromatic (meth)acrylate (b1) can be any known compound without particular limitation, within the scope of achieving the effects of the invention, but preferably a compound represented by the following general formula (1), and may contain at least one such compound.

In general formula (1), R represents hydrogen or methyl.

_X1 and _X2 independently represent any one of a single bond, an oxygen atom, a sulfur atom, or an ester bond (-C(=O)-O-). _X1 is preferably a single bond or an oxygen atom, and _X2 is preferably a single bond, an oxygen atom, or an ester bond.

Y represents a single bond, an alkyl group of 1 to 5 carbon atoms that can be substituted by an alkyl group, or a benzene ring, preferably an alkyl group of 1 to 4 carbon atoms that can be substituted by two alkyl groups of 1 to 3 carbon atoms.

Z represents oxygen or sulfur atoms, preferably oxygen atoms.

n is either 0 or 1.

As an aromatic (meth)acrylate (b1), specifically, compounds represented by the following chemical formulas can be listed, and at least one can be used.

[Chemistry 5]

In this embodiment, the (meth)acrylic polymer (B) preferably comprises a structural unit (b1') and a structural unit (b2') with a polymerizable group at its end. This results in a cured material with excellent heat resistance, thus suppressing the exudation of polymer components when the cured material is heated.

The structural unit (b2') comprising a polymerizable group at its end may be, to the extent that it enables the effects of the present invention, listed as a structural unit derived from known compounds, preferably including at least one of the structural units selected from the following.

[Chemistry 6]

Relative to all structural units, structural unit (b2') preferably contains 0.2% to 8% by mass or more, more preferably 0.5% to 5% by mass or more, and even more preferably 1% to 3% by mass or more. This results in a hardened material with excellent heat resistance.

In this embodiment, the (meth)acrylic polymer (B) may comprise structural units (b1') and (b2'), as well as the structural unit (b3').

The structural unit (b3') is derived from the compound (b3) described later.

[Chemistry 7]

Relative to all structural units, structural unit (b3') preferably contains 1% to 30% or more by mass, more preferably 2% to 20% or more by mass, and even more preferably 3% to 15% or more by mass.

The weight-average molecular weight of the (meth)acrylic polymer (B) can be set to 1,000-50,000, preferably 2,000-30,000, and even more preferably 3,000-25,000.

By using the weight-average molecular weight of the (meth)acrylic polymer (B) within the aforementioned range, a curable composition with excellent coatability can be obtained for forming lenses for optical materials, particularly lenses for wafer-level optical devices (WLO). If the weight-average molecular weight exceeds this range, the compatibility with compound (A) deteriorates, and the viscosity of the curable composition increases, thus worsening operability. In other words, within the aforementioned range, both compatibility with compound (A) and operability are excellent in a balanced manner.

[Synthetic methods for (meth)acrylic polymers (B)]

In this embodiment, a polymerization reaction is carried out in an organic solvent and in the presence of a polymerization initiator with an aromatic-group-containing (meth)acrylate (b1) and, optionally, a compound (b3), to synthesize a polymer. The polymerization reaction can be carried out at approximately 70°C to 140°C for approximately 8 to 15 hours.

Compound (b3) is specifically shown below.

Subsequently, in the presence of polymerization inhibitors, catalysts, etc., the obtained polymer undergoes an addition reaction with the following compound, and the following compound reacts with epoxy groups and/or hydroxyl groups present in the side chains of the polymer to introduce polymerizable groups.

The addition reaction can be carried out at approximately 70°C to 110°C for about 6 to 15 hours.

Based on the above, (meth)acrylic polymer (B) can be obtained.

[Other ingredients]

In addition to the aforementioned components, the hardening composition of this embodiment may further include polymerization initiators, ultraviolet absorbers, resin modifiers, internal release agents, etc.

<Method for manufacturing hardening components>

The curable composition of this embodiment can be obtained by mixing compound (A), polymer (B), and other components as desired, using previously known methods.

In the curable composition of this embodiment, the ratio of the content of compound (A) to the total amount of compound (A) and polymer (B) (compound (A)/[compound (A) + polymer (B)]) can be set to 0.1 or more, preferably 0.2 or more, and more preferably 0.3 or more. By using this ratio within the aforementioned range, the refractive index (nD) of the obtained curable can be further improved.

Furthermore, the ratio of polymer (B) content to the total amount of compound (A) and polymer (B) (polymer (B)/[compound (A) + polymer (B)]) can be set to 0.3 or more, preferably 0.4 or more, and more preferably 0.5 or more. By keeping this ratio within the aforementioned range, the hardening shrinkage rate can be further reduced.

[Molded Body]

A hardened material can be obtained by hardening the hardening component of this embodiment, and a molded body can be obtained by shaping it into a predetermined shape.

The cured material produced by this embodiment has a high refractive index, low curing shrinkage, and high heat resistance, making it suitable for use in optical materials.

As optical materials, examples include: plastic eyeglass lenses, safety glasses, vision correction lenses, lenses for imaging equipment, Fresnel lenses for LCD projectors, biconvex lenses, various plastic lenses such as contact lenses; sealing materials for light-emitting diodes (LEDs); optical waveguides; optical adhesives used in the bonding of wafer-level optical components (WLO) or optical waveguides; anti-reflective films used in optical lenses; transparent coatings used in LCD device components (substrates, light guides, films, sheets, etc.); or sheets or films attached to car windshields or motorcycle helmets; and transparent substrates.

The embodiments of the present invention have been described above, but these are merely illustrative examples. Various other structures may be used without impairing the effectiveness of the present invention.

[Implementation Example]

The invention will now be described in more detail by way of embodiments, but the invention is not limited to these embodiments.

<Calculation of compatibility parameters (Hansen's solubility parameters)>

The Hansen solubility parameters _δD , _δP , and _δH were calculated using the computer software Hansen Solubility Parameter in Practice (HSPiP) version 5.2.05. The obtained values of the compatibility parameters are shown in Table 1.

<Synthesis Example 1 (Synthesis of Acrylic Polymer P-1)>

Add 400g of the polymerization solvent 4-hydroxymethyltetrahydropyran (4-MTHP) to a 1000mL four-necked flask equipped with a stirrer, reflux condenser, thermometer, nitrogen inlet, and dry air inlet. While blowing in nitrogen gas, raise the internal temperature to 100℃±2℃.

In a brown bottle, thoroughly stir and mix 354.0 g of A-LEN-10 (ethoxylated o-phenylphenol acrylate: manufactured by Shin-Nakamura Chemical Industry Co., Ltd.), 40.0 g of glycidyl methacrylate, and 8.0 g of PB-O (tert-butyl peroxide of 2-ethylhexanoate), adding dropwise over 5 consecutive hours.

After the addition was complete, the mixture was kept at 100℃±2℃ for 1 hour, then 0.8g of PB-O was added. Another 0.8g was added after 1 hour, and the mixture was kept at this temperature for another 2 hours, thus obtaining a resin containing glycidyl groups (non-volatile component = 50.2%, transparent liquid).

Dry air was blown into the prepared four-necked flask containing glycidyl groups. 0.03 g of methyl hydroquinone was added at an internal temperature of 50℃±2℃, followed by 6.0 g of acrylic acid, and then 0.4 g of tetrabutylammonium bromide. The temperature was then raised to 100℃±2℃ to carry out the addition reaction between the acrylic acid and the glycidyl group-containing resin. The addition reaction was conducted by determining the resin acid value (mgKOH/g), and the endpoint was set at a resin acid value less than 0.5.

The resulting yellow, transparent liquid (acid value (mgKOH/g) = 0.42, non-volatile content = 50.7%, molecular weight (Mw) = 9717) was removed by reduced pressure distillation to obtain the acrylic polymer (P-1).

For the determination of acid value, 1.0 g of resin was weighed into a 1/1/1 (by weight) solution of 4-hydroxymethyltetrahydropyran/xylene/butanol. After the resin dissolved, phenolphthalein was used as an indicator, and titration was performed at 0.1 N KOH.

<Synthesis Examples 2-10 (Synthesis of Acrylic Polymer P-2-P-10)>

Except for changing the monomers other than acrylic acid and the amount of solvent used during the polymerization of the acrylic acid monomers, acrylic polymers (P-2 to P-10) were obtained using the same method as in Synthesis Example 1. The types and proportions of the monomers used, and the molecular weight (Mw) of each acrylic polymer obtained are shown in Table 2.

<Molecular Weight Determination of Acrylic Polymers>

A sample was prepared by dissolving 40 mg of the polymer in 4 ml of tetrahydrofuran.

Subsequently, the samples were analyzed using gel osmosis chromatography (GPC) under the following conditions.

(Testing conditions)

Apparatus: Alliance (manufactured by Waters), Column: Plgel 5μm Mixed-C (molecular weight range: 100-1,000,000, manufactured by Polymerlab) 3 in series, Detector: Differential refractive index detector, Free solution: Tetrahydrofuran, Flow rate: 1.0 mL/min, Column temperature: 40℃, Detector temperature: 40℃, Injection volume: 10 μL.

<Implementation Example 1>

(Preparation of hardened components)

The polymer obtained in Synthesis Example 1 (P-1, 50 parts by weight) as the acrylic polymer (B), 1,8-bisacryloxythio-(4-acryloxythiomethyl-3,6-dithiooctane) (GSTA) (50 parts by weight) synthesized with reference to Japanese Patent Application Publication No. 4-29967 as the curing monomer, and 1-hydroxycyclohexylphenyl ketone (Irg184, manufactured by BASF, 3.0 parts by weight) as the initiator were added to the sample vial and mixed using a mixing rotor until the appearance was uniform, thereby obtaining the curing composition. The viscosity of the obtained composition at 25°C was measured using a Type E viscometer (TVE-25L, manufactured by Toki Industries, Ltd., 0.8° taper × R24), and the result was 1500 mPa·s.

At this point, the Hansen distance between A-LEN-10, the most abundant monomer in the acrylic polymer, and GSTA, the curing monomer, is 3.11.

(Creation of a hardened film)

Apply 0.5 mL of the curable composition to a demolded glass substrate, clamp it onto another demolded glass substrate through a 200 μm thick spacer, and secure the ends with clamps.

After irradiating one side of the obtained laminate with ultraviolet light at 365nm and an exposure dose of 500mJ/ ^cm² using an electrodeless lamp (H-type lamp), the cured material was demolded from the glass substrate and heated at 80°C for 30 minutes in a nitrogen atmosphere to obtain a cured film with a thickness of 200μm.

The refractive index, heat resistance, and shrinkage during curing of the obtained hardened film were measured using the method described below. The results are shown in Table 3.

<Determination of Refractive Index>

The refractive index of the cured resin was measured using an Abbe refractometer (DR-M2, manufactured by Atago Inc.). An RE-3520 (589nm, D-ray, manufactured by Atago Inc.) was used as the interference filter, and RE-1196 (naphthalene monobromide, manufactured by Atago Inc.) was used as the intermediate solution. The sample temperature was set to 25°C for the measurements.

<Determination of Hardening Shrinkage Rate>

The specific gravity d1 of the curing component was determined using a hydrometer bottle (JIS 8804). Additionally, the specific gravity d2 of the cured film was determined using Archimedes' method (JIS 8807). Using these specific gravity values, the curing shrinkage rate (%) was calculated using the following formula.

Formula: Hardening shrinkage rate (%) = (1 - d1/d2) × 100

<Determination of Permeability>

The hardened films in each embodiment were heated on a heating plate at 270°C for 2 minutes. The changes in appearance before and after heating were visually observed, and the films were evaluated according to the following criteria.

(baseline)

○ (Good): The appearance of the hardened film remains unchanged.

△(Middle): Slight exudation was observed on the surface of the hardened film, but the appearance remained unchanged.

× (Poor): Exudation was found on the surface of the hardened film, and changes in its appearance were also observed.

<Examples 2-10, Comparative Examples 1-5>

Except for changing the acrylic polymer (B) and curing monomer (A), the tests were conducted in the same manner as in Example 1. The acrylic polymer (B) and curing monomer (A) used, along with the various evaluation results, are shown in Table 3. The Hansen distance in the table is the Hansen distance between the most abundant raw material monomer (b1) in the acrylic polymer (B) and the curing monomer (A) in the curing composition. Furthermore, the compatibility in the table was evaluated according to the following criteria.

(baseline)

○ (Good): The acrylic polymer is uniformly compatible with the curable monomer.

× (Poor): The acrylic polymer and the curable monomer separate into two phases, exhibiting non-uniform compatibility.

[Table 2]

According to embodiments of the present invention, based on the curable composition (Table 3), a high-refractive-index curable with low curing shrinkage and thus suppressed exudation of polymer components can be provided. The curable composition uses a compound (A) having two or more thioacrylate groups and a (meth)acrylate polymer (B) comprising at least 50% by mass of a structural unit (b1') derived from an aromatic (meth)acrylate (b1) relative to all structural units. In other words, the curable composition according to the present invention provides a curable with an excellent balance of these properties.

This application claims priority based on Japanese Patent Application No. 2021-044779, filed on March 18, 2021, and seeks to incorporate all the contents disclosed therein into this application.

Claims (8)

A curable composition comprising: a compound (A) having two or more thioacrylate groups; and a (meth)acrylate polymer (B), wherein the compound (A) having two or more thioacrylate groups is selected from at least one of the compounds represented by the following chemical formulas, the (meth)acrylate polymer (B) comprising, with respect to all structural units, at least 50% by mass of a structural unit (b1') derived from an aromatic (meth)acrylate (b1), and the Hansen distance Ra between the compound (A) having two or more thioacrylate groups and the aromatic (meth)acrylate (b1) is less than 6.0. . The curable composition as described in claim 1, wherein the aromatic (meth)acrylate (b1) is represented by the following general formula (1), (In general formula (1), R represents hydrogen or methyl, _X1 and _X2 represent any one of single bond, oxygen atom, sulfur atom, ester bond, Y represents single bond, any hydrogen atom can be replaced by alkyl group of carbon number 1 to 5, or benzene ring, Z represents oxygen atom, sulfur atom, and n is 0 or 1). The curable composition as described in claim 1 or claim 2, wherein the (meth)acrylic polymer (B) further comprises a structural unit (b2') comprising a polymerizable group at the end, wherein the structural unit (b2') comprising a polymerizable group at the end comprises at least one of the structural units selected from the following: . The curable composition as described in claim 1 or claim 2, wherein the (meth)acrylic polymer (B) has a weight average molecular weight of 1,000 to 50,000. A hardener is formed by hardening a hardening composition as described in any one of claims 1 to 4. A molded article comprising the hardened material as described in claim 5. An optical material comprising a molded body as described in claim 6. A plastic lens comprising a molded body as described in claim 6.