Curable resin composition, sealing material, and electronic component sealed with cured product of curable resin composition

Abstract

A curable resin composition according to the present invention contains (A) a polyfunctional thiol compound that has 3–6 thiol groups, (B) a polyfunctional epoxy compound that has 3 or 4 epoxy groups, is a liquid at 25°C, and has an epoxy equivalent of no more than 185, and (C) a monofunctional epoxy compound represented by formula 1, the ratio (thiol groups / epoxy groups) of the functional group concentration of the thiol groups of the (A) component and the functional group concentration of the epoxy groups of the (B) component being 0.6–1.3. The curable resin composition makes it possible to form a cured product that has excellent moisture resistance, low-temperature flexibility, and continuous bending resistance (toughness).

Description

A curable resin composition, a encapsulant, and an electronic component encapsulated with the cured product of the curable resin composition.

[0001] The present invention relates to a curable resin composition, a encapsulant, and an electronic component encapsulated with a cured product of the curable resin composition.

[0002] Epoxy resins possess excellent material properties such as insulation, moisture resistance, and adhesion, and are therefore used as the main component in encapsulants and adhesives for electronic components. For electronic components such as organic EL elements, encapsulants are formed to cover the outer perimeter or entire surface to protect them from external factors that cause degradation, such as moisture. Epoxy resins are generally used for these encapsulants, but many epoxy resins are solid at room temperature, making them difficult to work with as they require dissolution with solvents or melting with heat. Furthermore, epoxy resins have low flexibility and are weak against stress such as bending, making them unsuitable for flexible devices and thus lacking versatility.

[0003] To address these problems, it is known that using a thiol-curing, one-component epoxy resin composition, in which a liquid thiol compound is used as a curing agent in a liquid epoxy resin, results in a liquid encapsulant that is easy to work with and has appropriate flexibility (Patent Document 1).

[0004] Japanese Patent Publication No. 2014-1291

[0005] However, while the resin composition described in Patent Document 1 improves flexibility, its moisture resistance is insufficient, resulting in poor protection of electronic components from moisture.

[0006] Furthermore, considering the actual use of electronic components, encapsulating materials are required to maintain excellent moisture resistance while also possessing high flexibility under various temperature conditions. In particular, electronic components used outdoors in cold regions are expected to be exposed to low temperatures, and even in such cases, they must maintain high flexibility. Moreover, encapsulating materials are required to have high toughness to withstand repeated stress changes, such as those caused by repeated bending, but achieving all of these properties simultaneously has been difficult.

[0007] The present invention has been made in view of the above circumstances, and its objectives are to provide a curable resin composition that can form a cured product with excellent moisture resistance, low-temperature flexibility, and continuous bending resistance (toughness), and to provide an electronic component sealed using a cured product of the curable resin composition.

[0008] In other words, the present invention is as follows: (1) A curable resin composition comprising: (A) a polyfunctional thiol compound having 3 to 6 thiol groups; (B) a polyfunctional epoxy compound that is liquid at 25°C, has an epoxy equivalent of 185 or less, and has 3 to 4 epoxy groups; and (C) a monofunctional epoxy compound represented by the following formula 1, wherein the ratio of the functional group concentration of thiol groups in component (A) to the functional group concentration of epoxy groups in component (B) (thiol groups / epoxy groups) is 0.6 to 1.3. (In the formula, n is an integer from 1 to 3. R １ and R ２ (These are, respectively, a hydrogen atom or a methyl group.) [2] The curable resin composition according to [1], wherein component (C) is present in an amount of 0.1 to 15 parts by mass per 100 parts by mass of the total of component (A) and component (B). [3] A sealing material comprising the curable resin composition according to [1] or [2]. [4] An electronic component sealed with a cured product of the curable resin composition according to any one of [1] to [3].

[0009] The curable resin composition of the present invention is suitable for use as a encapsulant for electronic components because it can form a cured product with excellent moisture resistance, low-temperature flexibility, and continuous bending resistance (toughness). Furthermore, since the curable resin composition is in liquid form, it also offers excellent workability.

[0010] The curable resin composition of the present invention comprises the following (A) to (C) as essential components and is suitable as a sealing material.

[0011] In this invention, the numerical range "○○ to ××" includes the lower limit ("○○") and upper limit ("××") unless otherwise specified. In other words, it more precisely means "greater than or equal to ○○ and less than or equal to ××".

[0012] <Component (A)> Component (A) is a polyfunctional thiol compound having 3 to 6 thiol groups per molecule. Component (A) can be used alone or in combination of two or more types. By including such a compound, a thiol-epoxy reaction can proceed with the epoxy compound, thereby enhancing the curability. The thioether bonds formed can flexibly change their bond angles compared to the bonds of atoms such as C, O, and N, allowing for high-density curing where atoms fill the gaps between bonds, resulting in a cured product with excellent moisture resistance. Furthermore, cured products having thioether bonds with flexibly changing bond angles can also possess high flexibility.

[0013] Component (A) is preferably a compound represented by the following formula 2. (In the formula, a is an integer from 3 to 6, R ３ (It is an organic group with 3-6 valent atoms and 10-60 carbon atoms.)

[0014] In formula 2, a is an integer from 3 to 6, preferably from 4 to 6, and more preferably 6, from the viewpoint that the cured product can exhibit excellent moisture resistance. If a in the formula is within this range, a cured product that possesses both moisture resistance and flexibility can be obtained. Also, R ３ From a similar viewpoint, the valentity is 3 to 6, preferably 4 to 6, and more preferably 6. ３ The number of carbon atoms is 10 to 60, preferably 10 to 45, and more preferably 12 to 30. ３ If the number of carbon atoms is within this range, a sufficiently crosslinked product with excellent moisture resistance can be obtained.

[0015] An organic group is a group that contains C and may further contain at least one element selected from the group consisting of Si, N, P, O, and S. The organic group may be a polymer having repeating units. Furthermore, its structure may contain groups such as ketone groups, ester groups, ether groups, hydroxyl groups, amide groups, thioether groups, isocyanurate groups, and glycoluryl groups.

[0016] Specifically, component (A) includes dipentaerythritol hexakis(3-mercaptopropionate), trimethylolpropanetris(2-mercaptoacetate), trimethylolpropanetris(3-mercaptopropionate), trimethylolethanetris(2-mercaptoacetate), trimethylolethanetris(3-mercaptopropionate), pentaerythritol tetrakis(2 -Mercaptoacetate), pentaerythritol tetrakis(3-mercaptopropionate), 1,2,3-tris(2-mercaptoethylthio)propane, 1,2,3-tris(3-mercaptopropylthio)propane, 4-mercaptomethyl-1,8-dimercapto-3,6-dithiaoctane, 5,7-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane, 4,7-di Examples include mercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane, 4,8-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane, tetrakis(2-mercaptoethylthiomethyl)methane, tetrakis(3-mercaptopropylthiomethyl)methane, 1,3,5-tris(mercaptoethyleneoxy)benzene, tris-[(3-mercaptopropionyloxy)-ethyl]-isocyanurate, pentaerythritol tetrakis(3-mercaptobutyrate), 1,3,5-tris(2-(3-sulfanylbutanoyloxy)ethyl)-1,3,5-triazinan-2,4,6-trione, trimethylolpropane tris(3-mercaptobutyrate), pentaerythritol tripropanthol, and pentaerythritol tetrapropanthol.

[0017] Among the compounds represented by Formula 2 above, those having an ester bond are preferred from the viewpoint of being able to increase the toughness of the cured product. Furthermore, thiol compounds can be classified into primary thiols or secondary thiols depending on the bonding position of the thiol group, but primary thiols are preferred from the viewpoint of being able to increase the flexibility of the cured product. Among these, pentaerythritol tetrakis (3-mercaptopropionate) is preferred because it can increase the flexibility and toughness of the cured product, and dipentaerythritol hexakis (3-mercaptopropionate) is more preferred because, in addition to increasing the flexibility and toughness of the cured product, it also has excellent moisture resistance.

[0018] Component (A) may be a commercially available product or a synthesized product. For example, it can be obtained by esterifying a polyhydric alcohol such as pentaerythritol with a mercapto group-containing carboxylic acid such as 3-mercaptopropionic acid using a known method.

[0019] <Component (B)> Component (B) is a polyfunctional epoxy compound that is liquid at 25°C, has an epoxy equivalent of 185 or less, and contains 3 to 4 epoxy groups per molecule. Component (B) can be used alone or in combination of two or more types. Because such a compound is liquid, it can be easily mixed with thiol compounds to obtain a liquid curable resin composition. The liquid curable resin composition can be easily applied to any location, thus offering excellent workability. Furthermore, (B) undergoes a thiol-epoxy reaction with thiol compounds to obtain a cured product, which has excellent moisture resistance and possesses both flexibility and toughness. The epoxy equivalent can be determined by the method described in JIS K7236, and the epoxy equivalent of component (B) is 185 or less, preferably 150 or less. If the epoxy equivalent is within this range, a cured product with a high density of crosslinking points and excellent moisture resistance can be obtained.

[0020] Component (B) has 3 to 4 epoxy groups per molecule, preferably 4. Within this range, a cured product can be obtained that has a high density of crosslinking points, excellent moisture resistance, and high toughness.

[0021] Examples of component (B) include bisphenol A type epoxy resin, bisphenol F type epoxy resin, naphthalene type epoxy resin, biphenyl type epoxy resin, glycidylamine type epoxy resin, glycidyl ester type epoxy resin, alicyclic epoxy resin, dicyclopentadiene type epoxy resin, polyether type epoxy resin, novolac type epoxy resin, biphenyl type epoxy resin, and epoxy resin having a butadiene structure.

[0022] Examples of compounds having three epoxy groups in one molecule include Denacol EX-321 (polyether-type epoxy resin) manufactured by Nagase ChemteX, jER152 (novolac-type epoxy resin) manufactured by Mitsubishi Chemical Corporation, and jER630 (glycidylamine-type epoxy resin) manufactured by Mitsubishi Chemical Corporation. Examples of compounds having four epoxy groups in one molecule include Showfree BATG (bisphenol A-type epoxy resin) manufactured by Resonaq, Showfree PETG (polyether-type epoxy resin) manufactured by Resonaq, TETRAD-X (glycidylamine-type epoxy resin) manufactured by Mitsubishi Gas Chemical Corporation, TETRAD-C (glycidylamine-type epoxy resin) manufactured by Mitsubishi Gas Chemical Corporation, and jER604 (glycidylamine-type epoxy resin) manufactured by Mitsubishi Chemical Corporation.

[0023] Component (B) is preferable because it has aromatic rings in its molecule, as intermolecular forces between aromatic rings in the cured product allow it to exhibit excellent moisture resistance while maintaining high flexibility and toughness. Furthermore, glycidylamine-type epoxy compounds are preferable because the nitrogen atoms contained in component (B) interact with other components in the cured product, thereby increasing toughness. Glycidylamine-type epoxy compounds having aromatic rings are even preferable because they have excellent moisture resistance and can increase toughness.

[0024] <Component (C)> Component (C) is a compound represented by the following formula 1. Component (C) can be used alone or in combination of two or more. The curable resin composition containing Component (C) can obtain a cured product with high toughness while maintaining excellent moisture resistance. (n in the formula is an integer of 1 to 3. R １ and R ２ are each a hydrogen atom or a methyl group.)

[0025] From the viewpoint that the cured product of the curable resin composition can exhibit high toughness, n in Formula 1 is an integer of 1 to 3, and an integer of 1 to 2 is preferable. If n in the formula is within this range, a cured product having higher toughness while maintaining excellent moisture resistance can be obtained.

[0026] Specifically, as Component (C), benzyl phenyl glycidyl ether, methyl benzyl phenyl glycidyl ether, cumyl phenyl glycidyl ether, dibenzyl phenyl glycidyl ether, dimethyl benzyl phenyl glycidyl ether, dicumyl phenyl glycidyl ether, tribenzyl phenyl glycidyl ether, trityl benzyl phenyl glycidyl ether, and tricumyl phenyl glycidyl ether can be mentioned.

[0027] From the viewpoint of maintaining excellent flexibility, both R １ and R ２ are preferably both hydrogen atoms or one of R １ and R ２ is a hydrogen atom and the other is a methyl group. Further, from the viewpoint of maintaining more excellent moisture resistance, it is more preferable that one of R １ and R ２ is a hydrogen atom and the other is a methyl group.

[0028] <Other Components> The curable resin composition of the present invention may contain additives such as polymerizable compounds (meth)acrylic compounds, (meth)allyl compounds, phenolic compounds, surfactants, silane coupling agents, polymerization initiators, curing accelerators, acid generators, base generators, ultraviolet absorbers, light stabilizers, antioxidants, polymerization inhibitors, fillers, leveling agents, adhesion promoters, plasticizers, defoamers, light shielding materials, conductive materials, spacers, and shape stabilizers, to the extent that they do not hinder the objectives of the present invention.

[0029] <Composition Ratio (Mixing Ratio)> In order for the cured product of the curable resin composition of the present invention to have low moisture permeability, high flexibility regardless of the operating temperature environment, and high toughness that can withstand repeated stress changes, it is preferable that component (C) is 0.1 to 15 parts by mass, more preferably 1 to 10 parts by mass, and even more preferably 3 to 8 parts by mass, per 100 parts by mass of the total of component (A) and component (B). Furthermore, the ratio of the functional group concentration of thiol groups in component (A) to the functional group concentration of epoxy groups in component (B) (thiol group / epoxy group) is 0.6 to 1.3, and preferably 0.8 to 1.2. The functional group concentration of thiol groups is expressed as the number of parts by mass of (A) in a total of 100 parts by mass of (A) and (B) × the number of thiol groups in one molecule of (A) / the molecular weight of (A), and the functional group concentration of epoxy groups is expressed as the number of parts by mass of (B) in a total of 100 parts by mass of (A) and (B) / the epoxy equivalent of (B).

[0030] In the curable resin composition of the present invention, the total proportion of components (A), (B), and (C) is preferably 70% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more.

[0031] <Electronic Components> The curable resin composition of the present invention can be used in a wide range of electronic component applications, and in particular, in electronic component applications such as printed circuit boards, semiconductor elements, LED elements, organic EL elements, solar cell elements, and liquid crystal display elements.

[0032] <Formation of Electronic Component> The electronic component of the present invention is formed by applying the curable resin composition of the present invention onto a substrate on which the electronic component is formed and curing the curable resin composition by heating, or by applying the curable resin composition of the present invention onto one of two substrates, then overlaying the other substrate, and curing the curable resin composition by heating.

[0033] The method for applying the above curable resin composition is not particularly limited, and for example, dispenser coating, inkjet method, screen printing method, or a method of manual coating with a syringe or brush can be applied.

[0034] The curing conditions of the above curable resin composition preferably have a temperature of 60°C to 120°C and a time of 15 minutes to 6 hours, and more preferably have a temperature of 70°C to 100°C and a time of 30 minutes to 3 hours.

[0035] Next, the present invention will be described more specifically by giving examples and comparative examples.

[0036] <Evaluation Method> The curable resin compositions in each of the examples and comparative examples were evaluated for their performance by the following method. In the present invention, ◎ and ○ were judged as having good evaluation, and × was judged as having poor evaluation.

[0037] <Moisture Resistance> The curable resin compositions produced in the examples and comparative examples were applied onto a release film (E-7002 manufactured by Toyobo Co., Ltd.) using an applicator, heated in an oven at 100°C for 1 hour, and then the cured product was peeled off from the release film to obtain a cured product sample (film thickness of the cured product: 100 μm). The moisture permeability of the obtained cured product sample was evaluated by a method conforming to JIS Z 0208 "Test Method for Permeation Humidity of Moistureproof Packaging Materials". The temperature and humidity conditions were carried out at 60°C / 90%. The lower the moisture permeability, the better the moisture resistance, and the results are described in each table. ◎: The moisture permeability is less than 35 g / m ２ ·24 h. ○: The moisture permeability is 35 g / m ２ ·24 h or more and 90 g / m ２ ·24 h or less. ×: The moisture permeability is 90 g / m ２ ·Exceeds 24 h.

[0038] <Low Temperature Flexibility> The curable resin compositions produced in the examples and comparative examples were coated onto a release film (Toyobo E-7002) using an applicator, heated in an oven at 100°C for 1 hour, and then the cured film was peeled off the release film to obtain a cured sample (cured film thickness: 30 μm). The obtained cured sample was left to stand in a 0°C low-temperature bath for 3 hours, then wrapped around an 8 mm rod for 1 minute, and visually observed to evaluate the low-temperature flexibility. In this evaluation result, a higher low-temperature flexibility indicates superior flexibility. ◎: No breakage or minute cracks occur in the cured sample. ○: The cured sample does not break, but minute cracks can be observed. ×: The cured sample breaks.

[0039] <Continuous Bending Resistance> The curable resin compositions prepared in the examples and comparative examples were coated onto PET film (Toyobo A-4360, 100 μm) using an applicator, and heated in an oven at 100°C for 1 hour to obtain cured samples (cured film thickness: 30 μm). The obtained cured samples were fixed to a durability tester (Yuasa System Equipment DMLHB-P150), and tested under the conditions of a load of 100 g, radius of 30 mm, 90-degree bending, and 30 rpm. The cured samples were visually inspected every 500 bending cycles to evaluate the continuous bending resistance. Samples that did not break or crack, or did not peel off the PET film, for a large number of cycles showed superior continuous bending resistance, and the results are listed in each table. In this evaluation, higher continuous bending resistance indicates superior toughness. ◎: No breakage or cracking occurred in the cured material, or the cured material did not peel off the PET film, even after more than 3000 cycles. ○: Between 1000 and 3000 cycles, the cured material may rupture or crack, or peel off the PET film. ×: Within 1000 cycles, the cured material may rupture or crack, or peel off the PET film.

[0040] The ingredients used are listed below.

[0041] <Components (A)> A-1: ​​Dipentaerythritol hexakis(3-mercaptopropionate) [Number of thiol groups: 6, Molecular weight: 783.0] A-2: Pentaerythritol tetrakis(3-mercaptopropionate) [Number of thiol groups: 4, Molecular weight: 488.6] A-3: Pentaerythritol tetrakis(3-mercaptobutyrate) [Number of thiol groups: 4, Molecular weight: 544.8] A-4: Pentaerythritol tetrapropanthol [Number of thiol groups: 4, Molecular weight: 432.7] A-5: Tris-[(3-mercaptopropionyloxy)-ethyl]-isocyanurate [Number of thiol groups: 3, Molecular weight: 525.6] A-6: Tetraethylene glycol bis(3-mercaptopropionate) [Number of thiol groups: 2, Molecular weight: 372.0]

[0042] <Components (B)> B-1: jER604 (glycidylamine type epoxy resin) manufactured by Mitsubishi Chemical Corporation [Number of epoxy groups: 4, epoxy equivalent: 116] B-2: Showfree BATG (bisphenol A type epoxy resin) manufactured by Resonaq Corporation [Number of epoxy groups: 4, epoxy equivalent: 125] B-3: Showfree PETG (polyether type epoxy resin) manufactured by Resonaq Corporation [Number of epoxy groups: 4, epoxy equivalent: 91] B-4: jER630 (glycidylamine type epoxy resin) manufactured by Mitsubishi Chemical Corporation [Number of epoxy groups: 3, epoxy equivalent: 97] B-5: jER152 (novolac type epoxy resin) manufactured by Mitsubishi Chemical Corporation [Number of epoxy groups: 3, epoxy equivalent: 178] B-6: Denacol Ex622 (polyether type epoxy resin) manufactured by Nagase Chemtec Corporation [Number of epoxy groups: 4, epoxy equivalent: 191] B-7: Mitsubishi Chemical Corporation's jER828 (Bisphenol A type epoxy resin) [Number of epoxy groups: 2, Epoxy equivalent: 184]

[0043] <Component (C)> C-1: Dimethylbenzylphenylglycidyl ether (n=2, R １ : Hydrogen atom, R ２ : Methyl group) C-2: Dibenzylphenylglycidyl ether (n=2, R １ : Hydrogen atom, R ２ : Hydrogen atom) C-3: Phenylglycidyl ether

[0044] [Example 1] 55 parts by mass of dipentaerythritol hexakis(3-mercaptopropionate) (A-1) as component (A), 45 parts by mass of jER604 (B-1) as component (B), and 5 parts by mass of dimethylbenzylphenyl glycidyl ether (C-1) as component (C) were added to a planetary mixer and mixed and stirred for 2 hours to obtain a curable resin composition. Various evaluations were performed using this curable resin composition. The results are shown in Table 1.

[0045] [Example 2-18, Comparative Example 1-7] Curable resin compositions were obtained in the same manner as in Example 1, except that the components and parts by mass were changed as shown in Tables 1 and 2 below. Each evaluation was performed using the curable resin composition. The results are shown in Tables 1 and 2.

[0046]

[0047]

[0048] The results of the above tests show that the curable resin compositions of each example contain components (A) to (C), and therefore can form cured products with excellent moisture resistance, low-temperature flexibility, and continuous bending resistance (toughness).

[0049] On the other hand, in Comparative Example 1, since component (A) of the present invention was not contained, the cured product of the curable resin composition had low moisture resistance and toughness.

[0050] In Comparative Examples 2 and 3, since component (B) of the present invention was not contained, the cured products of the curable resin compositions had poor moisture resistance and toughness.

[0051] In Comparative Example 4, the ratio of the functional group concentration of thiol groups in component (A) to the functional group concentration of epoxy groups in component (B) (thiol groups / epoxy groups) was smaller than the specified range, resulting in a cured product of the curable resin composition with low flexibility and toughness.

[0052] In Comparative Example 5, the ratio of the functional group concentration of thiol groups in component (A) to the functional group concentration of epoxy groups in component (B) (thiol groups / epoxy groups) was greater than the specified range, resulting in a cured product of the curable resin composition with low moisture resistance and toughness.

[0053] In Comparative Examples 6 and 7, since component (C) of the present invention was not contained, the cured products of the curable resin compositions had low toughness.

Claims

1. A curable resin composition comprising: component (A) a polyfunctional thiol compound having 3 to 6 thiol groups; component (B) a polyfunctional epoxy compound that is liquid at 25°C, has an epoxy equivalent of 185 or less, and has 3 to 4 epoxy groups; and component (C) a monofunctional epoxy compound represented by the following formula 1, wherein the ratio of the functional group concentration of thiol groups in component (A) to the functional group concentration of epoxy groups in component (B) (thiol groups / epoxy groups) is 0.6 to 1.

3. (In the formula, n is an integer from 1 to 3. R １ and R ２ (Each of these is either a hydrogen atom or a methyl group.) 2. The curable resin composition according to claim 1, wherein component (C) is present in an amount of 0.1 to 15 parts by mass relative to a total of 100 parts by mass of component (A) and component (B).

3. A sealing material comprising the curable resin composition according to claim 1 or 2.

4. An electronic component sealed with a cured product of the curable resin composition according to claim 1 or 2.

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