JP6962745B2 - LED curable moisture-proof insulating coating composition - Google Patents

Description

The present invention relates to a moisture-proof insulating coating composition that can be cured in a short time even with an LED (light emitting diode) light source.

When an electronic component such as a semiconductor is mounted on a printed wiring board typified by a base material such as glass epoxy, paper phenol, or polyimide, a moisture-proof insulating coating agent is applied to the connection portion to improve connection reliability. There is. Conventionally, a method of using a thermosetting resin or a method of applying a resin dissolved in an organic solvent and then drying it has been generally used for this coating agent. However, in the case of thermosetting resin, there is a problem in productivity because a heating process is required for resin curing and it takes a long time to cure, and a resin using an organic solvent has a problem that the load on the environment is high because the solvent is volatilized at the time of application. There was.

In order to solve these problems, an ultraviolet curable coating agent that can be cured in a short time has been developed. For example, Patent Document 1 discloses a composition containing polybutadiene having an acryloxy group or a methacryloxy group at the end, a monomer having an unsaturated double bond, and a polymerization initiator. Furthermore, as a light source for ultraviolet rays, as a composition that can be applied to LED light sources that have been rapidly increasing in recent years due to low power consumption, low generation of ozone, and long life, acrylic oligomers and monomers, and acylphosphine oxides are used. Patent Document 2 in which two types of initiators, a system and an alkylphenone system, are used in combination is also disclosed. However, in the case of a member that is flexible on one side, such as the connection between a wire harness and a connector, if the hardness of the cured resin material that coats the contacts is high, the long-term reliability of the connection may decrease, and even with an LED light source, deep curing may occur. There was room for improvement in the required characteristics of excellent properties and low hardness.

JP-A-2009-179655 Japanese Patent No. 5297163

INDUSTRIAL APPLICABILITY The present invention provides a composition which is useful as a moisture-proof insulating coating agent for protecting electrical contacts, can be cured in a short time even when the light source to be irradiated is an LED, has excellent deep curability, and has a low hardness as a cured product. To do.

The invention according to claim 1 comprises a triblock copolymer (A) of methyl methacrylate and butyl acrylate, a monofunctional (meth) acrylate monomer (B) having a glass transition point of a cured product of 8 ° C. or lower, and light. A (meth) acrylate containing a polymerization initiator (C), having a copolymerization ratio of methyl methacrylate in (A) of less than 35% by weight, and (B) having a cyclic skeleton, an alkyl structure, or an ether structure. The present invention provides an LED curable moisture-proof insulating coating agent composition in which the ratio of (C) to the photopolymerizable monomer is 0.05 to 6% by weight.

The invention according to claim 2 is the LED curable moisture-proof insulation according to claim 1, wherein the ratio of (A) to the entire composition is 10 to 85% by weight, and the ratio of (B) is 13 to 85% by weight. A coating composition is provided.

The invention according to claim 3 further provides the LED curable moisture-proof insulating coating composition according to claim 1 or 2, further comprising a bifunctional or higher functional (meth) acrylate monomer (D).

The invention according to claim 4 provides the LED curable moisture-proof insulating coating composition according to any one of claims 1 to 3, wherein the (B) is a (meth) acrylate having a cyclic skeleton or an ether structure.

The invention according to claim 5 provides the LED curable moisture-proof insulating coating composition according to any one of claims 1 to 4 , wherein the cured product has a durometer type A hardness of 60 or less.

The moisture-proof insulating coating composition of the present invention is an ultraviolet-curable resin composition that is excellent in moisture-proof and insulating properties and can be cured in a short time even when the light source to be irradiated is an LED. The object has the property of low hardness.

Hereinafter, the present invention will be described in detail.

The composition of the present invention comprises a triblock copolymer (A) of MMA and BA, a monofunctional (meth) acrylate monomer (B) having a glass transition point of a cured product of 30 ° C. or lower, and photopolymerization initiation. Agent (C). In addition, in this specification, (meth) acrylate includes both acrylate and methacrylate.

The triblock copolymer (A) of MMA and BA used in the present invention is a main polymer constituting an insulating resin coating agent, and is a hard segment composed of P (poly) MMA and soft composed of P (poly) BA. It is composed of segments and has a tri-block structure in which both ends of the soft segment are sandwiched between hard segments. Therefore, it has both the transparency and weather resistance of PMMA and the flexibility and adhesiveness of PBA. Further, the copolymerization ratio of MMA in (A) is 35% or less by weight so that the hardness of the cured product does not become too high. If it exceeds 35%, the hardness of the cured product becomes too high, which may cause a problem when fixing the flexible member with the sealant.

The weight average molecular weight of (A) is preferably 30,000 to 130,000, more preferably 50,000 to 100,000. If it is less than 30,000, the cohesive force of the cured product is too low, and if it exceeds 130,000, the viscosity of the composition becomes high and the workability is lowered. Further, in order to impart elongation and flexibility of the cured product, the hardness of (A) itself is 40 (ISO7619-1 compliant) or less for type A, the tensile strength is 7.0 MPa (ISO37 compliant) or more, and the tensile elongation is 450 MPa (ISO37). ISO37 compliant) or higher is preferable. The weight average molecular weight (hereinafter referred to as "Mw") was measured and calculated by a gel permeation chromatography method using a tetrahydrofuran developing solvent on a column of a styrenedivinylbenzene base material in terms of standard polystyrene.

The blending amount of (A) is preferably 5 to 85% by weight, more preferably 8 to 80% by weight, based on the entire composition. If it is less than 5% by weight, the cohesive force of the cured product is too low, and if it exceeds 85% by weight, the viscosity of the composition becomes too high and the workability is lowered. Commercially available triblock copolymers of MMA and BA include Clarity LA2140e (trade name: manufactured by Kuraray Co., Ltd., MMA content 28%, Mw75000).

The monofunctional monomer (B) used in the present invention plays a role as a reactive diluent and is blended to react with (A) to increase the film hardness. (B) is a low-viscosity monofunctional monomer having excellent compatibility with (A), and the glass transition point of the homopolymerized cured product is 30 ° C. or lower. If the glass transition point exceeds 30 ° C., the hardness of the cured product becomes too high, which makes it unsuitable. The glass transition point notation in (B) and (D) below indicates a homopolymerized cured product.

Examples of the (meth) acrylate having a cyclic skeleton include dicyclopentenyloxyethyl acrylate (glass transition point 15 ° C.), cyclohexyl acrylate (15 ° C.), tetrahydrofurfuryl acrylate (-12 ° C.), and the like alone or 2 More than one type can be used in combination. Among these, tetrahydrofurfuryl acrylate is preferable because it has a low viscosity and excellent compatibility with (A).

Examples of the (meth) acrylate having an alkyl structure and an ether structure include methyl acrylate (8 ° C.), n-butyl methacrylate (20 ° C.), lauryl acrylate (-3 ° C.), isostearyl acrylate (-18 ° C.), 2-. Ethylhexyl methacrylate (-10 ° C) and the like are exemplified, and examples of the (meth) acrylate having a hydroxyl group include 2-hydroxyethyl acrylate (-15 ° C), 2-hydroxypropyl acrylate (-7 ° C) and 4-hydroxybutyl. There are acrylates (-32 ° C) and the like, and they can be used alone or in combination of two or more. Among these, 4-hydroxybutyl acrylate is preferable because it has a low viscosity and excellent compatibility with (A).

Further, by further lowering the glass transition point of (B) to −20 ° C. or lower, the elongation rate of the cured film in a low temperature environment can be improved. For example, ethyl acrylate (-22 ° C), n-butyl acrylate (-54 ° C), lauryl methacrylate (-65 ° C), isodecyl methacrylate (-41 ° C), 2-ethylhexyl acrylate (-85 ° C), ethoxydiethylene glycol acrylate (-85 ° C). -67 ° C), methoxytriethylene glycol acrylate (-50 ° C), etc., and can be used alone or in combination of two or more. Among these, 4-hydroxybutyl acrylate and ethoxydiethylene glycol acrylate are preferable because they have a low viscosity and excellent compatibility with (A).

The blending amount of (B) is 13 to 85% by weight, more preferably 15 to 80% by weight, based on the entire composition. If it is less than 13% by weight, the cohesive force of the cured product is too low and the strength is insufficient, and if it exceeds 85% by weight, the hardness of the cured product becomes too high. Further, 800 parts by weight or less is preferable with respect to 100 parts by weight of the above (A).

The photopolymerization initiator (C) used in the present invention generates radicals by absorption of ultraviolet rays, electron beams, etc., and the radicals trigger a polymerization reaction, and has an absorption band matching the emission wavelength of the LED. Properties are needed. When curing to a deep part with a limited exposure amount, if the amount of the initiator is too large, the light energy is consumed before reaching the deep part and the deep part becomes uncured, so it is important to adjust the amount. Become. The blending amount is 0.05 to 6% by weight, more preferably 0.1 to 5% by weight, based on 100% by weight of the photopolymerizable monomer. If it is less than 0.05% by weight, the curability becomes insufficient, and if it exceeds 6% by weight, the deep curing becomes insufficient. The photopolymerizable monomer referred to here refers to all of the above-mentioned (B), bifunctional or higher (meth) acrylate monomer (D), and other (meth) acrylate monomers.

Specifically, as (C), 2.2-dimethoxy-1.2-diphenylethane-1-one, 1-hydroxy-cyclohexyl-phenyl-ketone, 2-hydroxy-2-methyl-1-phenyl-propane. -1-one, 1- [4- (2-hydroxyethoxy) -phenyl] -2-hydroxy-2-methyl-1-propane-1-one, 2-hirodoxy-1- {4- [4- (2) -Hydroxy-2-methyl-propionyl) -benzyl] phenyl} -2-methyl-propan-1-one, 2.4.6-trimethylbenzoyl-diphenyl-phosphenyl oxide, bis (2.4.6-trimethylbenzoyl) ) -Phenylphosphinoxide, 2-methyl-1- (4-methylthiophenyl) -2-morpholinopropane-1-one, etc., which can be used alone or in combination of two or more. Commercially available products include Irgacure 184, Irgacure TPO, and Darocur 4265 (trade name: manufactured by BASF Japan Ltd.).

A bifunctional or higher functional (meth) acrylate monomer (D) can be further added to the composition. By blending (D), a crosslinked structure can be formed with (B), and the cohesive force of the cured film can be enhanced. Examples of the bifunctional or higher functional (meth) acrylate monomer include ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol diacrylate, polyethylene glycol diacrylate, dipropylene glycol diacrylate, tripropylene glycol diacrylate, and polypropylene glycol diacrylate. , 1.4-Butanediol di (meth) acrylate, 1.6-hexanediol di (meth) acrylate, 1.9-nonanediol di (meth) acrylate, 1.10-decanediol di (meth) acrylate, neo Pentyl glycol dimethacrylate, 3-methyl-1.5 pentandiol diacrylate, 2-hydroxy-3-acryloyloxypropyl methacrylate, tricyclodecanedimethanol diacrylate, dicyclopentanyl diacrylate, trimethyl propantri (methacrylate) ) Acrylate, trimethylolpropane tetra (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol tetra (meth) acrylate and the like. Among these, glycol-modified diacrylate having an ether bond in the skeleton that gives flexibility to the cured product is preferable, and bifunctional tripropylene glycol diacrylate is particularly preferable.

Similar to (B), the flexibility of the cured film can be controlled by lowering the glass transition point in (D), especially when the glass transition point in (B) is −20 ° C. or lower. By setting the glass transition point of (D) to −20 ° C. or lower, the elongation rate of the cured film in a low temperature environment can be further improved. For example, EO-modified (3) trimethylolpropane triacrylate (-40 ° C), EO-modified (15) trimethylolpropane triacrylate (-32 ° C), 1.12-dodecanediol dimethacrylate (-37 ° C), EO-modified. There are (20) bisphenol A diacrylate (-37 ° C.), EO-modified (30) bisphenol A diacrylate (-57 ° C.), and the like, which can be used alone or in combination of two or more. Of these, EO-modified bisphenol A diacrylate is preferred.

The blending amount of (D) is preferably 20% by weight or less based on the entire composition. If it exceeds 20% by weight, the cross-linking reaction of the cured product proceeds too much, and the hardness of the cured product tends to be too high. Further, 100 parts by weight or less is preferable with respect to 100 parts by weight of the above (A).

The composition may contain curing aids, silane coupling agents, plasticizers, sensitizers, antioxidants, antioxidants, defoamers, flame retardants, fillers, polymerization inhibitors, colorants, as required. Additives such as leveling agents, dispersants, thiox-imparting agents, organic and inorganic fine particles, and fillers can be used in combination.

The hardness of the cured product is preferably 60 or less with a durometer type A hardness based on JIK6253. When the type A hardness is 60 or more, when a flexible structure such as a wire harness is fixed to a terminal and the contacts are fixed with a moisture-proof insulating coating agent, stress is applied to the connection part between the cured product and the wire harness. Is easy to concentrate, and there is a risk that long-term connection reliability will decrease.

The elongation rate of the cured product at −35 ° C. is preferably 100% or more. If the elongation rate is less than 100%, cracks may occur when performing a heat cycle test in which cold heat is repeated under extremely severe conditions, and long-term insulation reliability deteriorates in harsh environments such as extremely low temperatures. There is a risk. The elastic modulus of the cured product at −35 ° C. is preferably 100 MPa or less. When the elastic modulus exceeds 100 MPa, cracks may occur in the heat cycle test as in the case where the elongation rate is low, and the long-term insulation reliability may decrease in a harsh environment.

Hereinafter, the present invention will be described in detail based on Examples and Comparative Examples, but specific examples are shown and the present invention is not particularly limited thereto. Unless otherwise specified, the measurement was performed under the conditions that the room temperature was 25 ° C. and the relative humidity was 65%. Further, Examples 8 and 9 are described as reference examples.

Example 1
Clarity LA2140e (trade name: manufactured by Kuraray Co., Ltd., MMA content 28%, Mw75000) as a triblock copolymer (A) of MMA and BA, and THFA (trade name: manufactured by Kyoeisha Chemical Co., Ltd.) as a monofunctional monomer (B). , Tetrahydrofurfuryl acrylate), Irgacure 184 and Irgacure TPO (trade name: manufactured by BASF Japan) as the initiator (C), and M220 (trade name: manufactured by MIWON, tripropylene) as the bifunctional (meth) acrylate monomer (D). Glycol diacrylate) was used, and the mixture was stirred until uniformly dissolved in the formulation shown in Table 1 to prepare the moisture-proof insulating coating composition of Example 1.

Examples 2-12
In addition to the materials used in Example 1, 4HBA (trade name: 4 hydroxybutyl acrylate manufactured by Osaka Organic Chemical Co., Ltd.), CHA (trade name: cyclohexyl acrylate manufactured by Kyoeisha Chemical Co., Ltd.) and ECA (commodity name) are used as (B). Name: ethoxydiethylene glycol acrylate manufactured by Kyoeisha Chemical Co., Ltd.), M2300 (trade name: MIWON Co., Ltd., EO-modified (30) bisphenol A diacrylate) and DCPA (trade name: dicyclopentadiene manufactured by Kyoeisha Chemical Co., Ltd.) Using diacrylate), the blending amount was changed as shown in Table 1 and stirred until uniformly dissolved to prepare the moisture-proof insulating coating composition of Examples 2 to 12.

Comparative Examples 1 to 8
In addition to the materials used in the examples, LA1114 (trade name: Clare, diblock copolymer) and LA4285 (trade name: Clare, MMA ratio over 35% by weight) as block copolymers of MMA and BA. DEAA (trade name: KJ Chemicals, diethylacrylamide) and FA-512M (trade name: Hitachi Kasei, dicyclopentenyloxyethylene methacrylate) as monofunctional acrylic monomers having a glass transition point of more than 30 ° C. NISSOTE-2000 (trade name: manufactured by Nippon Soda Co., Ltd.) and New Frontier R-1220 (trade name: manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) as urethane acrylates, and ARUFRON UH-2000 (trade name: Toa Synthetic Co., Ltd.) as a solvent-free acrylic polymer. The moisture-proof insulating coating composition of Comparative Examples 1 to 8 was prepared by stirring until the mixture was uniformly dissolved according to the formulation shown in Table 2.

Table 1 (weight part)

Table 2 (weight part)

The evaluation method was as follows.

Surface tack: Put the moisture-proof insulating coating agent composition in a polypropylene container of Φ23 mm so that the film thickness is 6 mm, and use Panasonic's LED-UV irradiation device UD-40 under the condition of output 1000 mW / cm2 (wavelength 365 nm). After irradiating for 4 seconds to cure, the presence or absence of stickiness on the surface of the cured product was confirmed by touch, and non-stickiness was marked as ◯ and presence was marked as x.

Deep cure: Take out the above-mentioned cured product from the container, leave it at 23 ± 2 ° C for 1 hour, measure the thickness of the cured product with a micrometer, and if the thickness is 6 mm, it is ○, if there is an uncured part and there is no 6 mm. Was set to x.

Hardness: The surface on the opposite side of the cured product irradiated with UV was measured using a Type A durometer hardness meter manufactured by TECLOCK in accordance with JIK6253, and A60 or less was accepted.

Elastic modulus, tensile strength, elongation: A sample obtained by punching a composition having a thickness of 1 mm cured under the above ultraviolet curing conditions with a No. 8 dumbbell mold conforming to JIS K6251 as a test piece. Using the tensile compression tester Technograph TGI-1kN, the chuck distance was set to 33 mm, the tensile test was performed at a crosshead speed of 10 mm / min, and the tensile strength was determined under three conditions of -35 ° C, 25 ° C, and 85 ° C. The measurement was performed, and the elongation rate was calculated by the following formula from the displacement until the fracture.
Elongation rate (%) = Displacement at break (length) ÷ 33 mm x 100
Example) When broken without stretching at all: 0 mm ÷ 33 mm × 100 = 0%

Cold shock test: After 500 cycles of cold shock of -40 ° C x 0.5 hours ⇔ 85 ° C x 0.5 hours, the presence or absence of cracks was visually observed, and the presence or absence of cracks was marked as ◯ and the presence or absence was marked as x. As the measurement sample, a container made of polyacetal having a size of 6 mm × 8 mm × 5 mm was filled with resin and cured under the above-mentioned ultraviolet curing conditions.

Evaluation results Table 3

Table 4

In the examples, there were no problems in all aspects of surface tack, deep hardening degree, and hardness, and they were good. Further, in Examples 9 to 12 in which the glass transition point of (B) is −20 ° C. or lower, the elastic modulus at −35 ° C. is 100 MPa or less, the elongation rate is 100% or more, and the result of the heat cycle test shows that cracks are not present. It was very good without it.

On the other hand, in Comparative Example 1 in which the amount of the initiator compounded was out of the upper limit, the deep part was not cured, and in Comparative Example 2 in which the amount was out of the lower limit, the curing was insufficient and other evaluations could not be performed. Comparative Example 3 in which the glass transition point of the monomer exceeds 30 ° C. has high hardness, Comparative Example 4 of the diblock copolymer has surface tack remaining, and Comparative Example 5 of a triblock copolymer having an MMA ratio of 35% by weight or more. And 6 had high hardness. Comparative Examples 7 and 8 not including (A) had problems in hardness or surface tack, and none of them was suitable for the present invention.

The present invention is an ultraviolet curable resin composition which is excellent in moisture-proof and insulating properties and can be cured in a short time even when the light source to be irradiated is an LED. It has and is useful as a moisture-proof insulating coating agent composition that protects electrical contacts.

Claims (5)

A triblock copolymer (A) of methyl methacrylate and butyl acrylate, a monofunctional (meth) acrylate monomer (B) having a glass transition point of the cured product at 8 ° C. or lower, and a photopolymerization initiator (C). The copolymerization ratio of methyl methacrylate in the above (A) is less than 35% by weight, and the above (B) is a (meth) acrylate having a cyclic skeleton or an alkyl structure or an ether structure with respect to a photopolymerizable monomer. An LED curable moisture-proof insulating coating agent composition in which the ratio of (C) is 0.05 to 6% by weight. The LED curable moisture-proof insulating coating composition according to claim 1, wherein the ratio of (A) to the entire composition is 10 to 85% by weight, and the ratio of (B) is 13 to 85% by weight. The LED curable moisture-proof insulating coating composition according to claim 1 or 2, further comprising a bifunctional or higher functional (meth) acrylate monomer (D). The LED curable moisture-proof insulating coating composition according to any one of claims 1 to 3, wherein (B) is a (meth) acrylate having a cyclic skeleton or an ether structure. The LED curable moisture-proof insulating coating composition according to any one of claims 1 to 4 , wherein the cured product has a durometer type A hardness of 60 or less.