JP7448390B2 - UV curable resin composition - Google Patents

Description

The present invention relates to a resin composition that is cured by ultraviolet rays such as those irradiated from an LED light source.

Utilizing the property of being able to cure in a short time, UV-curable resins are used in a wide range of applications, from industrial materials such as coating agents for films and molded objects, sealants for electronic parts and electrical contacts, to everyday products such as adhesives and gel nails. It's being used. Light-emitting diodes (hereinafter referred to as LEDs), which have a low environmental impact, are increasingly being used as ultraviolet light sources in place of existing light sources such as high-pressure mercury lamps and xenon lamps, but LEDs emit light at longer wavelengths than conventional light sources. Since the irradiation intensity is relatively low, if existing UV-curable resins are used as is, surface curing failures are likely to occur, and in particular, when the coating film is thick, deep curing failures are likely to occur. Ta.

Therefore, in the past, the applicant developed a resin composition that can be cured sufficiently even with an LED light source by combining urethane acrylate synthesized from hydrogenated polyisoprene diol, monofunctional (meth)acrylate, paraffin, a silane coupling agent, and a plasticizer. has invented a photocurable resin composition containing the agent (Patent Document 1). This invention was an excellent moisture-proof insulation coating agent with excellent surface and deep curability even when the coating film was as thick as 100 μm, but the curability was not sufficient when the output of the LED light source was low. . For example, in the optical field, where optical fiber arrays are fixed at the base, if even a small amount of tack remains on the surface after curing, it can cause contamination due to adhesion of dust from the surrounding environment, and it can also be used to protect electrical contacts on printed wiring boards. In the electronics field, this contamination can sometimes cause insulation deterioration. Therefore, it is necessary to have good deep and surface hardening properties against low-output LED light sources and to make the surface of the cured film tack-free, and there is room for improvement.

Patent No. 6346980

An object of the present invention is to provide an ultraviolet curable resin composition that is sufficiently cured even with a low-power LED light source, has a colorless and transparent cured product, and has a tack-free film surface after curing.

In order to solve the above problems, the invention as set forth in claim 1 provides a method for combining a (meth)acrylate oligomer (A) with a conjugated diene skeleton, a monofunctional (meth)acrylate monomer (B), a solid paraffin (C), and an α-amino an acetophenone-based photopolymerization initiator (D), and the amount of (C) blended is 1.0 to 5.0 parts by weight per 100 parts by weight of (A) and (B) in total; ) is blended in an amount of 1 to 15 parts by weight based on 100 parts by weight of the total photopolymerization components, and the melting point of (C) is 52° C. or lower.

The invention according to claim 2 provides the ultraviolet curable resin composition according to claim 1, wherein the (B) contains a monomer having an alicyclic skeleton .

The invention according to claim 3 provides the ultraviolet curable resin composition according to claim 2 , wherein the (B) further contains a monomer having a hydroxyl group .

The ultraviolet curable resin composition of the present invention is sufficiently cured even with a low-power LED light source, the color tone of the cured product is colorless and transparent, and the surface of the cured film is tack-free, so it is used as a coating agent for optical applications and electronic fields. It is useful as a fixing adhesive for optical fiber arrays and a protective coating agent for printed wiring boards.

The present invention will be explained in detail below.

The composition of the present invention is composed of a (meth)acrylate oligomer (A) having a conjugated diene skeleton, a monofunctional (meth)acrylate monomer (B), a solid paraffin (C), and a photopolymerization initiator (D). be. In addition, in this specification, (meth)acrylate includes both acrylate and methacrylate.

The (meth)acrylate oligomer (A) having a conjugated diene skeleton of the present invention is a base oligomer constituting a cured film. Examples include urethane acrylate obtained by reacting a polyol having an OH group in a side chain with a compound having a plurality of isocyanate groups and further reacting a (meth)acrylate having a hydroxyl group. As the conjugated diene, polybutadiene and polyisoprene, which are oligomers that have low humidity, excellent insulation properties, and can impart appropriate flexibility to the molded film, are preferred. Further, the double bond of the conjugated diene skeleton is preferably hydrogenated in order to improve weather resistance.

The weight average molecular weight (hereinafter referred to as Mw) of (A) is preferably 3,000 to 100,000, more preferably 5,000 to 60,000, particularly preferably 10,000 to 50,000. By setting it to 3,000 or more, sufficient flexibility and film cohesive force can be obtained, and by setting it to 100,000 or less, it becomes easier to adjust the viscosity to suit workability. Note that Mw was calculated by measuring the molecular weight in terms of standard polystyrene by gel permeation chromatography using a column using a styrene divinylbenzene-based packing material and using a tetrahydrofuran eluent.

The blending amount of (A) is preferably 10 to 50% by weight, more preferably 12 to 45% by weight, and particularly 15 to 40% by weight based on the total solid content from the viewpoint of moisture permeability of the cured product and property balance of the composition. preferable. By setting the content to 10% by weight or more, sufficient film cohesive force can be ensured, and by setting the content to 50% by weight or less, sufficient compatibility with solid paraffin can be ensured, and the viscosity can be easily adjusted to suit workability.

The monofunctional (meth)acrylate monomer (B) used in the present invention is blended to dilute (A) and simultaneously react with (A) to increase film hardness. From the viewpoint of the rigidity of the cured product, compatibility with (A), etc., it is preferable to include a monomer having an alicyclic skeleton.

Examples of the monomer having an alicyclic skeleton include dicyclopentenyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, isobornyl (meth)acrylate, adamantanyl (meth)acrylate, and cyclohexyl (meth)acrylate. They can be used alone or in combination of two or more. Among these, it is preferable to include isobornyl acrylate (hereinafter referred to as IBXA), which has low viscosity and low skin irritation and odor.

The blending amount of (B) is preferably 40 to 75% by weight, more preferably 45 to 70% by weight based on the total solid content, in view of the balance of properties such as film strength and viscosity. By setting the content to 40% by weight or more, sufficient compatibility with solid paraffin can be ensured and sufficient curability can be ensured, and by setting the content to 75% by weight or less, sufficient film cohesion can be ensured. can. The ratio of (B) to the total of photocurable components (A) and (B) is preferably 50 to 85% by weight, more preferably 52 to 82% by weight.

The ratio of the monomer having an alicyclic skeleton in (B) is preferably 60% by weight or more, more preferably 80% by weight or more, and particularly preferably 90% by weight or more. By setting the content to 60% by weight or more, surface hardening properties can be further improved.

By further blending a monomer having a hydroxyl group with the above (B), the adhesion to the adherend can be improved. This effect is particularly remarkable when the adherend is glass or metal. The proportion of the monomer having a hydroxyl group in (B) is preferably 35% by weight or less, more preferably 30% by weight or less, particularly preferably 28% by weight or less.
By setting the content to 35% by weight or less, sufficient moisture permeability can be ensured.

As other acrylate monomers, (A) and (meth)acrylate monomers having a linear alkyl group having good compatibility with monomers having an alicyclic skeleton are preferred. For example, ethyl (meth)acrylate, n-propyl (meth)acrylate, n-butyl (meth)acrylate, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, n-octyl (meth)acrylate, lauryl (meth)acrylate, ) acrylate, tridecyl (meth)acrylate, stearyl (meth)acrylate, etc., which can be used alone or in combination of two or more types. When the number of C's is 4 or less, odor and volatility tend to be high, and when it is 12 or more, curability tends to decrease. Among these, n-octyl acrylate is preferred because it has high dilutability, low odor, and low outgas. Monomers having an amino group or a heterocyclic skeleton, which are more polar than an alkyl group, tend to reduce storage stability and are therefore undesirable.

The solid paraffin (C) used in the present invention is solid at room temperature (20° C.±15° C.), and is blended for the purpose of making the surface of the cured film tack-free. In addition, the curing characteristics for LED light sources can be improved, and the amount of photocuring agent added can be suppressed. The melting point is 52° C. or lower, preferably 50° C. or lower, but paraffin that is liquid at room temperature is not preferred because it becomes highly volatile. If it exceeds 52° C., the solubility will decrease, storage stability will deteriorate, and it will not be possible to mix in an amount that will make the cured surface tack-free.

The blending amount of (C) is preferably 0.5 to 5.0 parts by weight, and 0.8 to 4.0 parts by weight based on 100 parts by weight of the photocurable components (A) and (B). is more preferred, and 2.8 to 3.5 parts by weight is particularly preferred. When the amount is 0.5 parts by weight or more, sufficient tack-free formation of the cured surface can be expected, and when the amount is 5 parts by weight or less, sufficient storage stability can be ensured. In particular, by setting the amount to 2.8 parts by weight or more, surface hardening properties can be further improved.

The photopolymerization initiator (D) used in the present invention generates radicals upon irradiation with ultraviolet rays, electron beams, etc., and these radicals trigger a polymerization reaction, and have an α-aminoacetophenone skeleton. α-Aminoacetophenone has an absorption band even above 380 nm, which is the emission wavelength of LEDs, and has excellent surface and internal curing properties, such as 2-methyl-1-(4-methylthiophenyl)-2-morpholinopropane-1- 1, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1, and the like. In particular, the former is preferable because it causes less yellowing of the cured product than the latter. Further, photopolymerization initiators other than α-aminoacetophenone may be used in combination, such as benzyl ketal, α-hydroxyacetophenone, and acylphosphine oxide. However, it is not possible to use a photopolymerization initiator other than α-aminoacetophenone alone because storage stability will decrease.

The blending amount of (D) is preferably 1 to 15 parts by weight, more preferably 3 to 12 parts by weight, based on 100 parts by weight of the total photopolymerization components. When the amount is 1 part by weight or more, sufficient curing is possible, and when it is 15 parts by weight or less, sufficient storage stability can be ensured without excessive addition.

In addition to the above, by further blending acrylate silane (E), the adhesion to the adherend can be improved, and this effect is particularly significant when the adherend is glass. Examples include methacryloxypropyldimethoxysilane, methacryloxypropyltrimethoxysilane, methacryloxypropyldiethoxysilane, methacryloxypropyltriethoxysilane, acryloxypropyltrimethoxysilane, etc., which may be used alone or in combination of two or more. Can be done. Among these, acryloxypropyltrimethoxysilane is preferred in terms of adhesive reliability. The blending amount of (E) is preferably 5% by weight or less, more preferably 2% by weight or less based on the total solid content. Commercially available products include KBM-5103 (trade name: 3-acryloxypropyltrimethoxysilane, manufactured by Shin-Etsu Chemical Co., Ltd.) and KBM-503 (trade name: 3-methacryloxypropyltriethoxysilane, manufactured by Shin-Etsu Chemical Co., Ltd.).

This composition may contain photosensitizers, antioxidants, polymerization inhibitors, hardening aids, antifoaming agents, flame retardants, fillers, colorants, leveling agents, dispersants, thixotropic agents, and organic fine particles as required. Additives such as can be used together.

The photosensitizer is blended for the purpose of absorbing ultraviolet light in the long wavelength range and propagating it to (D), thereby improving the polymerization rate, deep curing properties, and adhesion. Examples include cyanine dyes, coumarin dyes, titanocene compounds, thioxanthone compounds, and polycyclic aromatic compounds. Preferably, the compound is an anthracene derivative. The amount of photosensitizer to be blended is preferably 1 to 20 parts by weight, more preferably 3 to 10 parts by weight, per 100 parts by weight of (D). By setting it as this range, sufficient sensitization effect can be obtained even in a long wavelength region of 380 nm or more. Commercially available products include Anthracure UVS-1101 (trade name: Kawasaki Kasei Kogyo Co., Ltd., 9,10-diethoxyanthracene), UVS-1331 (trade name: Kawasaki Chemical Co., Ltd., 9,10-butoxyanthracene), and the like.

By blending the antioxidant, it is possible to prevent deterioration of the physical properties of the film after curing. Examples of antioxidants include phenol-based, phosphorus-based, phenol-phosphorus-based, and sulfur-based antioxidants, which can be used alone or in combination of two or more. The amount of antioxidant added is preferably 5% by weight or less, more preferably 2% by weight or less based on the total solid content. Commercially available products include Sumilizer GP (trade name: manufactured by Sumitomo Chemical Co., Ltd., phenol phosphorus type).

By blending the polymerization inhibitor, it is possible to prevent thickening and improve storage stability. Examples of antioxidants include pyrocatechol, hydroquinone derivatives, dibutylhydroxytoluene (hereinafter referred to as BHT), and they can be used alone or in combination of two or more. The amount of the polymerization inhibitor blended is preferably 5% by weight or less, more preferably 3% by weight or less based on the total solid content.

When used as a protective coating agent such as that used to protect electrical contacts on printed wiring boards, it is preferable to have lower moisture permeability in order to ensure insulation.For example, in the cup method at 50°C and 95% relative humidity 50 g or less is preferable, and 30 g or less is more preferable. Also, the adhesive force to the polyimide film is preferably 5 N/cm or more, more preferably 10 N/cm or more.

Hereinafter, the present invention will be explained in detail based on Examples and Comparative Examples, but these are intended to be specific examples and are not particularly limited to these. Unless otherwise specified, the measurements were performed at a room temperature of 25° C. and a relative humidity of 65%. Moreover, the blending amount indicates parts by weight.

Examples 1 to 9
As the above (A), RX71-72 (trade name: manufactured by Asia Kogyo Co., Ltd., hydrogenated polyisoprene skeleton, Mw 42,000) and RX71-67 (trade name: manufactured by Asia Kogyo Co., Ltd., hydrogenated polybutadiene skeleton, Mw 24,000) and UC-203M (product name: manufactured by Kuraray Co., Ltd., butadiene skeleton, Mw 40,000) was used as (B) IB-XA (product name: manufactured by Kyoeisha Chemical Co., Ltd., isobornyl acrylate) and 4-HBA (product name: Osaka FA-513AS (product name: Hitachi Chemical Co., Ltd., dicyclopentanyl acrylate) and NOAA (product name: Osaka Organic Chemical Industry Co., Ltd., n-octyl acrylate) , (C) was solid paraffin (manufactured by Nippon Seirin Co., Ltd., melting point 48°C), (D) was Omnirad 907 (product name: IGM, α-aminoacetophenone type), and (E) was KBM-5103 (product name). UVS-1101 (product name: Kawasaki Chemical Co., Ltd., anthracene derivative) was used as a photosensitizer; Sumilizer GP (product name: anthracene derivative) was used as an antioxidant. : manufactured by Sumitomo Chemical Co., Ltd., phenol phosphorus type), using BHT as a polymerization inhibitor, and stirring until uniformly dissolved according to the formulation shown in Table 1 to prepare ultraviolet curable resin compositions of Examples 1 to 9.

Comparative examples 1 to 4
In addition to the materials used in the examples, solid paraffin (manufactured by Nippon Seirin Co., Ltd., melting point 53°C) and solid paraffin (manufactured by Kishida Chemical Co., Ltd., melting point 61°C) were used as photopolymerization initiators such as Omnirad TPO (trade name: IGM Co., Ltd.). UV-curable resin compositions of Comparative Examples 1 to 4 were prepared by stirring until uniformly dissolved using the formulations listed in Table 1.

Table 1

The evaluation method was as follows.

Color tone: An ultraviolet curable resin composition was coated on a glass plate to a thickness of 100 μm, and then a Panasonic LED-UV irradiation device UD-40 was used to produce an output of 150 mW/cm ² and an integrated light amount of 1000 mJ/cm. The color of the cured product cured under cm ² conditions was visually confirmed, and a colorless or almost colorless state was rated ○, and a case where the color was deep and clearly visible was rated ×.

Storage stability: After preparing the ultraviolet curable resin composition, leave it at room temperature for 72 hours and visually check the state of liquid separation. If it is uniformly dissolved, ○ means that paraffin is separated on the surface. The case was marked as ×.

Surface hardening: An ultraviolet curable resin composition was applied to a thickness of 100 μm on a glass plate, and then ultraviolet rays were irradiated on top of it using Panasonic's LED-UV irradiation device UD-40 under the following three conditions. The presence or absence of stickiness on the surface of the film was confirmed by touch with a finger. ◎ indicates that there is no tack and the surface is completely cured, ○ indicates that some tack remains but no adhesive remains on fingers, and × indicates that tack remains and sticks to fingers.
Condition 1: Output 150mW/cm ² , integrated light amount 1000mJ/cm ²
Condition 2: Output 150mW/cm ² , integrated light amount 1500mJ/cm ²
Condition 3: Output 1500 mW/cm ² , cumulative light amount 2000 mJ/cm ² (only Examples 10 and 11 containing hydroxyl groups were carried out)

Adhesiveness: Apply an ultraviolet curable resin composition to a thickness of 100 to 150 μm on a 25 μm thick polyimide film, cover with a PET film, and use Panasonic's LED-UV irradiation device UD-40 to produce an output of 1500 mW. /cm ² and the cumulative light amount was 2000 mJ/cm ² . Thereafter, the polyimide film and the cured resin were separated using a universal testing machine at a peeling speed of 60 mm/min. The strength after 180° peeling was measured, and 10 N/cm or more was rated ◎, 5 N/cm or more but less than 10 N/cm was rated ○, and less than 5 N/cm was rated ×. (Executed only Examples 10 and 11 containing hydroxyl groups)

Moisture permeability: A 1 mm thick cured product obtained by curing an ultraviolet curable resin composition using a Panasonic LED-UV irradiation device UD-40 at an output of 1500 mW/cm ² and an integrated light amount of 2000 mJ/cm ² was used. Set it in a humidity cup and let it stand for 24 hours at 50℃ and 95% relative humidity according to JIS Z0208, then measure the moisture permeability. 30g/ ^m2 less than 24h is ◎, 30g/ ^m2 24h or more 50g Less than 24h/m ² was rated ○, and 50g/m ² 24h or more was rated x. (Executed only Examples 10 and 11 containing hydroxyl groups)

Evaluation results Table 2

The Examples had no problems and were good in all respects including color tone, storage stability, and surface hardening properties. In particular, Examples 1, 2, 5, 6, 8, and 9 in which the proportion of monomers having an alicyclic skeleton in (B) was 100% by weight and 3 parts by weight of (C) were blended had very excellent surface hardening properties. was. Furthermore, Examples 10 and 11 containing monomers having hydroxyl groups had low moisture permeability and good adhesive strength.

On the other hand, Comparative Example 1 in which different photoinitiators were blended, Comparative Examples 2 and 3 in which solid paraffin with a high melting point was blended, had poor storage stability, and Comparative Example 4, which did not contain (C), had poor surface hardening properties. All of them were not suitable for the present invention.

The ultraviolet curable resin composition of the present invention is sufficiently cured even with a low-power LED light source, and the film surface after curing is tack-free. It is useful as a protective coating agent for wiring boards.

Claims (3)

Contains a (meth)acrylate oligomer (A) having a conjugated diene skeleton, a monofunctional (meth)acrylate monomer (B), a solid paraffin (C), and an α-aminoacetophenone photopolymerization initiator ( D ), The amount of (C) is 1.0 to 5.0 parts by weight per 100 parts by weight of (A) and (B), and the amount of (D) is 1.0 to 5.0 parts by weight per 100 parts of total photopolymerization components. 1 to 15 parts by weight, and an ultraviolet curable resin composition characterized in that the melting point of (C) is 52° C. or lower. The ultraviolet curable resin composition according to claim 1, wherein the (B) contains a monomer having an alicyclic skeleton. The ultraviolet curable resin composition according to claim 2 , wherein the (B) further contains a monomer having a hydroxyl group.