JP7385168B2 - Photocurable adhesive composition - Google Patents

Description

The present invention relates to a photocurable adhesive composition.

2. Description of the Related Art Double-sided adhesive tapes and sheets are used for assembly in portable electronic devices (for example, mobile phones, personal digital assistants, etc.) and in-vehicle electronic devices equipped with image display devices or input devices. For example, double-sided adhesive tapes and sheets are used to adhere a cover panel to a touch panel module or display panel module to protect the surface of a portable electronic device, or to adhere a touch panel module and a display panel module. . Such double-sided adhesive tapes and sheets are, for example, punched out into a frame-like shape and used so as to be placed around a display screen (for example, Patent Documents 1 and 2). Further, double-sided adhesive tapes and sheets are also used for fixing vehicle parts (for example, vehicle panels) to the vehicle body.

In recent years, in applications such as adhesive fixing of parts in large portable electronic devices and adhesive fixing of vehicle parts, it is necessary to bond heavy parts or members together, and the load on double-sided adhesive tapes and sheets is increasing. . In addition, in recent years, mobile electronic devices have become increasingly narrow-framed, in which the periphery of the display screen is narrowed to ensure a wider screen. Therefore, there is a need for high adhesive strength that can securely fix components even if the bonding area is small. Furthermore, when bonding and fixing vehicle parts, there is a demand for a high temperature retention ability that will not peel off even when exposed to high temperatures inside a car in the summer.

As described above, double-sided adhesive tapes and sheets used for fixing electronic device parts and vehicle parts are required to have higher adhesive strength and high temperature holding power than ever before.

Acrylic adhesives are widely used as adhesive layers for such adhesive tapes and sheets because of their excellent transparency, weather resistance, and durability. In addition, as an acrylic adhesive, from the viewpoint of coating properties and adhesive properties, an adhesive made of a (meth)acrylic block copolymer has been proposed (for example, Patent Documents 3 and 4). It is disclosed that it has excellent high-temperature holding power.

On the other hand, due to increasing environmental concerns, there is a shift toward adhesive compositions that do not use organic solvents, and active energy ray-curable adhesives using (meth)acrylic acid esters and photopolymerization initiators have been proposed. . Patent Document 5 and Patent Document 6 disclose active energy ray-curable adhesives using (meth)acrylic block copolymers.

JP2009-242541A JP2009-258274A Japanese Patent Application Publication No. 2016-183275 Special table 2015-520774 publication Special Publication No. 2016-529339 Japanese Patent Application Publication No. 2017-036368

The problem to be solved by the present invention is a photocurable adhesive composition using a (meth)acrylic block copolymer, which has excellent hot creep properties different from those of Patent Document 3 and Patent Document 4. Our goal is to provide adhesives.

The present inventors have discovered that when a specific (meth)acrylic block copolymer and a (meth)acrylate monomer having a substituent containing a phosphorus atom are used in combination, an adhesive with excellent hot creep properties can be produced. That is, the present invention relates to the following adhesive.

(1) (A) (meth)acrylic acid ester polymer block having a glass transition temperature of 50°C or higher (a) 5 to 45% by mass and a (meth)acrylic acid ester polymer having a glass transition temperature of 20°C or lower block (b) a (meth)acrylic block copolymer containing 55 to 95% by mass, and (B) a solvent capable of dissolving and photopolymerizing the (meth)acrylic block copolymer (A); , (C) a photopolymerization initiator, and (D) a (meth)acrylate monomer having a substituent containing a phosphorus atom.
(2) Photocuring according to (1), wherein the (meth)acrylic block copolymer (A) is a triblock copolymer represented by formula (a1)-(b)-(a2). adhesive composition. (The polymer block (a1) and the polymer block (a2) are the same (meth)acrylic acid ester polymer blocks as the polymer block (a), and the polymer block (a1) and the polymer block (a2) may be the same or different.)
(3) The (A) (meth)acrylic block copolymer contains a polymer block (a) containing methyl methacrylate as a monomer unit and a polymer block (b) containing butyl acrylate as a monomer unit (meth). ) The photocurable adhesive composition according to (1) or (2), which is an acrylic block copolymer.
(4) Photocuring according to any one of (1) to (3), wherein the reactive solvent (B) is a monofunctional (meth)acrylate monomer having a substituent containing oxygen or nitrogen atom. adhesive composition.

The photocurable pressure-sensitive adhesive composition according to the present invention is a pressure-sensitive adhesive that has excellent hot creep properties even in a high-temperature environment, and can withstand use in a wide temperature range. Note that in the present invention, "high temperature" refers to a temperature exceeding normal temperature, for example, a temperature of about 80°C.

Embodiments of the present invention will be described in detail below.

The (meth)acrylic block copolymer (A) used in the present invention is a base resin that imparts flexibility and appropriate hardness to the adhesive layer. When this resin is used in a pressure-sensitive adhesive, appropriate cohesive force and stress relaxation properties can be obtained depending on temperature changes, and excellent durability and reliability can be maintained.

The (meth)acrylic block copolymer (A) comprises 5 to 45% by mass of (meth)acrylic acid ester polymer block (a) having a glass transition temperature of 50°C or higher and a glass transition temperature of 20°C or lower. Contains 55 to 95% by mass of a certain (meth)acrylic acid ester polymer block (b).

The glass transition temperature of the polymer block (a) and the polymer block (b) in the present invention is determined by measuring the (A) (meth)acrylic block copolymer using a differential scanning calorimeter (hereinafter sometimes abbreviated as DSC). The extrapolation onset temperature (Tgi) of the transition region of polymer block (a) and polymer block (b) observed in the curves obtained by measuring Temperature at the intersection obtained by extrapolating the tangent; see, for example, Yasutoshi Saito, "Fundamentals of Thermal Analysis for Materials Science" (published by Kyoritsu Shuppan Co., Ltd., December 15, 1990, p. 126). Based on the curve obtained by DSC measurement of the (A) (meth)acrylic block copolymer in the present invention, the glass transition temperature of the polymer block (a), the glass transition temperature of the polymer block (b), etc. The glass transition temperature derived from polymer block (a) is determined by DSC of a polymer having the same chemical structure (monomer composition, stereoregularity, etc.) as polymer block (a). Since it is the same as or close to the glass transition temperature of the measured curve, it can be easily determined, and the same applies to polymer block (b). In addition, the polymer having the same chemical structure as the polymer block (a) can be determined by analyzing the polymer block (a) by ¹ H-NMR, ¹³ C-NMR, etc. Since the chemical structure such as the monomer composition and stereoregularity is known, it can be easily produced by conducting appropriate polymerization so that the chemical structure is reproduced, and the same applies to the polymer block (b). . In addition, when producing the (meth)acrylic block copolymer (A) of the present invention, if the first polymerization step is the step of forming the polymer block (a), the polymer formed in that step It is convenient to use part of block (a) as it is as a sample for DSC measurement of a polymer having the same chemical structure as polymer block (a), and the same applies to polymer block (b). .

The (meth)acrylic block copolymer (A) contains at least one polymer block (a) and one polymer block (b), and preferably has the formula (a1)-(b)-(a2). It is a triblock copolymer represented by: Polymer block (a1) and polymer block (a2) are the same (meth)acrylic acid ester polymer blocks as polymer block (a), and constitute polymer block (a1) and polymer block (a2). The type, molecular weight, etc. of the (meth)acrylic acid ester monomers used may be the same or different.

Examples of the (meth)acrylic acid ester monomer constituting the polymer block (a) include methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, isobutyl methacrylate, sec-butyl methacrylate, tert-butyl methacrylate, and methacrylic acid. Methacrylic acid esters such as cyclohexyl, isobornyl methacrylate, phenyl methacrylate, and 2-hydroxyethyl methacrylate; Acrylic acids such as tert-butyl acrylate, cyclohexyl acrylate, isobornyl acrylate, phenyl acrylate, and 2-hydroxyethyl acrylate Examples include esters. These may be used alone or in combination of two or more. Among these, methyl methacrylate is preferred from the viewpoint of moldability and adhesive properties of the adhesive layer.

Examples of the (meth)acrylic acid ester monomer constituting the polymer block (b) include n-propyl methacrylate, n-butyl methacrylate, amyl methacrylate, isoamyl methacrylate, n-hexyl methacrylate, and 2-methacrylate. Methacrylic acid esters such as ethylhexyl, pentadecyl methacrylate, dodecyl methacrylate, phenoxyethyl methacrylate, 2-methoxyethyl methacrylate; methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate , isobutyl acrylate, sec-butyl acrylate, amyl acrylate, isoamyl acrylate, n-hexyl acrylate, 2-ethylhexyl acrylate, pentadecyl acrylate, dodecyl acrylate, benzyl acrylate, phenoxyethyl acrylate, acrylic acid Examples include acrylic esters such as 2-methoxyethyl. These may be used alone or in combination of two or more. Among these, from the viewpoint of adhesive properties of the adhesive layer, methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, dodecyl acrylate, phenoxyethyl acrylate, acrylic acid 2-methoxyethyl is preferred.

(A) The (meth)acrylic block copolymer has other polymer blocks in addition to the (meth)acrylic ester polymer block (a) and the (meth)acrylic ester polymer block (b). You may. Examples of other polymer blocks include methacrylic acid, acrylic acid, styrene, α-methylstyrene, p-methylstyrene, m-methylstyrene, acrylonitrile, methacrylonitrile, ethylene, propylene, isobutene, butadiene, isoprene, octene, (Co)polymer blocks composed of monomer units such as vinyl acetate, maleic anhydride, vinyl chloride, vinylidene chloride and/or hydrogenated products thereof; polyethylene terephthalate, polybutylene terephthalate, polylactic acid, polyurethane, polyester Examples include polymer blocks made of dimethylsiloxane.

The (meth)acrylic block copolymer (A) according to the present invention may be synthesized by polymerizing raw material monomers, or a commercially available one may be used. Although the polymerization method is not particularly limited, for example, anionic polymerization method, atom transfer radical polymerization method (ATRP), etc. can be used. A detailed explanation of each polymerization method is omitted here, but as an anionic polymerization method, for example, anionic polymerization is performed using an organic alkali metal compound as a polymerization initiator in the presence of a mineral acid salt such as an alkali metal or alkaline earth metal salt. Known methods such as polymerization, anionic polymerization in the presence of an organic aluminum compound using an organic alkali metal compound as a polymerization initiator, and anionic polymerization using an organic rare earth metal complex as a polymerization initiator can be used. For example, a known method such as a method of polymerizing in the presence of a transition metal compound or a nitrogen-containing compound using an organic halide or a halogenated sulfonyl compound as an initiator can be used. Examples of commercially available products include the "Clarity (registered trademark)" series manufactured by Kuraray Co., Ltd.

The photopolymerizable reactive solvent (B) used in the present invention is a reactive solvent that dissolves the (A) (meth)acrylic block copolymer and at the same time adjusts the viscosity of the adhesive. , also plays a role in imparting hardness to the adhesive layer. Therefore, (B) a photopolymerizable reactive solvent is preferably a good solvent for (A) (meth)acrylic block copolymer and has a low viscosity, such as hydroxyl group, amide group, phenoxy group, etc. Acrylate monomers containing polar groups are preferred.

Specifically, monomers having a hydroxyl group include hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 4-hydroxybutyl ( meth)acrylate, and monomers having an amide group include acrylamide, N,N-dimethylacrylamide, N,N-diethylacrylamide, N-isopropylacrylamide, acrylylmorpholine, and monomers having a phenoxy group. Examples include phenoxyethyl acrylate, 2-hydroxy-3-phenoxypropyl acrylate, methylphenoxyethyl acrylate, phenoxydiethylene glycol acrylate, and phenoxypolyethylene glycol acrylate. These may be used alone or in combination of two or more.

The amount of the photopolymerizable reactive solvent (B) added is such that it completely dissolves the (A) (meth)acrylic block copolymer and that the photocurable pressure-sensitive adhesive composition is adhesive. The amount is not particularly limited as long as it functions as an agent, but it is preferably 30 parts by mass or more and 300 parts by mass or less, for example, with respect to 100 parts by mass of the (meth)acrylic block copolymer (A).

The photopolymerization initiator (C) used in the present invention generates radicals upon irradiation with ultraviolet rays, electron beams, etc., and the radicals trigger a polymerization reaction, and may be any general-purpose photopolymerization initiator. Specifically, benzoin ethers such as benzoin ethyl ether, benzoin butyl ether and benzoin isopropyl ether; benzophenones such as 4,4'-bisdimethylaminobenzophenone and 4,4'-bisdiethylaminobenzophenone; acetophenone, 2,2- Dimethoxy-2-phenylacetophenone, 2,2-diethoxy-2-phenylacetophenone, 1,1-dichloroacetophenone, 1-hydroxycyclohexylphenylketone, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, 1-[4-(2-hydroxyethoxy)-phenyl-]-2-hydroxy-2-methyl-1-propan-1-one, 2-hydroxy-1-{4-[4-(2-hydroxy-2 -Methyl-propionyl)-benzyl]phenyl}-2-methyl-propan-1-one, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholino-propan-1-one, 2-benzyl- 2-dimethylamino-1-(4-morpholinophenyl)-butanone-1, 2-dimethylamino-2-(4-methylbenzyl)-1-(4-morpholin-4-yl-phenyl)-butan-1- 2, Phosphine oxides such as 4,6-trimethylbenzoyldiphenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide; ethyl-p-dimethylaminobenzoate, (2-dimethylamino)ethylbenzoate , amine synergists such as bis-4,4'-dimethylaminobenzophenone, and the like.

The photopolymerization initiator (C) may be used alone or in combination of two or more in any proportion. There is no particular restriction on the amount of the photoinitiator added, but if the amount added is too small, curing may not proceed to the deep part, resulting in poor curing, so (A) (meth)acrylic block copolymer 100 It is preferably at least 0.05 part by weight, more preferably at least 0.1 part by weight, and even more preferably at least 1 part by weight. In addition, if too much initiator is used, the initiator may remain and adversely affect the cured properties, so the amount added should be 30 parts by weight or less per 100 parts by weight of (A) (meth)acrylic block copolymer. is preferable, 20 parts by weight or less is more preferable, and even more preferably 10 parts by weight or less.

(D) The (meth)acrylate monomer having a substituent containing a phosphorus atom used in the present invention is incorporated into crosslinking during photocuring by the (meth)acrylate moiety, and after photocuring by the substituent containing a phosphorus atom. After forming the adhesive layer, it is expected that the adhesion to the member to which it is attached will be improved.

Examples of the (meth)acrylate monomer having a substituent containing a phosphorus atom (D) include 2-methacryloyloxyethyl phosphate, bis-(2-methacryloyloxyethyl) phosphate, 2-acryloyloxyethyl phosphate, Bis-(2-acryloyloxyethyl) phosphate, Methyl-(2-methacryloyloxyethyl) phosphate, Ethyl methacryloyloxyethyl phosphate, Methyl acryloyloxyethyl phosphate, Ethyl acryloyloxyethyl phosphate, Propyl acryloyloxy phosphate Ethyl, isobutyl acryloyloxyethyl phosphate, ethylhexyl acryloyloxyethyl phosphate, halopropyl acryloyloxyethyl phosphate, haloisobutyl acryloyloxyethyl phosphate, or haloethylhexyl acryloyloxyethyl phosphate, vinylphosphonic acid, allylphosphonic acid, allyl Mention may be made of phosphinic acid, β-methacryloyloxyethylphosphinic acid, diallylphosphinic acid, β-methacryloyloxyethyl)phosphinic acid, and allylmethacryloyloxyethylphosphinic acid, especially 2-methacryloyloxyethyl phosphate or bis-(2 -methacryloyloxyethyl) is preferred.

The amount of the (D) (meth)acrylate monomer having a substituent containing a phosphorus atom may be used alone or in combination of two or more in any proportion. (D) The (meth)acrylate monomer having a substituent containing a phosphorus atom is a compound that improves the hot creep property of the composition of the present invention, so if the amount added is small, the effect will be poorly expressed. Therefore, the amount of the (D) (meth)acrylate monomer having a substituent containing a phosphorus atom added is preferably 0.01 part by mass or more, more preferably 1 part or more. Furthermore, if the amount added is too large, the properties as an adhesive of the present invention may be adversely affected, so the amount of (D) (meth)acrylate monomer having a substituent containing a phosphorus atom added is 30 parts by mass or less. It is preferable.

The pressure-sensitive adhesive composition of the present invention may optionally include (meth)acrylate monomers other than component (B) and component (D), a tackifier, a plasticizer, an antioxidant, and a wettability agent to the extent that performance is not impaired. Various additives such as regulators may be included.

EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to these descriptions in any way.

(Examples 1 to 7, Comparative Example 1)
The components listed in Table 1 were stirred until uniformly dissolved to prepare photocurable adhesive compositions of Examples 1 to 7 and Comparative Example 1. The formulation is as shown in Table 1 below.

In Table 1, the amount of each compounded substance is shown in g, and the details of each compounded substance are as follows.
*1 LK9243: (Meth)acrylic triblock copolymer (product name "Clarity LK9243", polymer block (a) uses methyl methacrylate, polymer block (b) uses butyl acrylate and 2-ethylhexyl acrylate. (meth)acrylic block copolymer, manufactured by Kuraray Co., Ltd.)
*2 LA2140: (meth)acrylic triblock copolymer (product name "Clarity LA2140", (meth)acrylic using methyl methacrylate for the polymer block (a) and butyl acrylate for the polymer block (b) block copolymer, manufactured by Kuraray Co., Ltd.)
*3 4HBA: 4-hydroxybutyl acrylate *4 IrgTPO: 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide (product name "IRGACURETPO", manufactured by BASF)
*5 P-2M: 2-Methachloroyloxyethyl acid phosphate (product name "Light Ester P-2M", manufactured by Kyoeisha Chemical Co., Ltd.)
*6 LA: Lauryl acrylate *7 K125: Terpene phenol resin (product name "YS Polystar K125", manufactured by Yasuhara Chemical Co., Ltd.)

The evaluation method was as follows.
Hot creep test:
One PET film was prepared as the first adherend, and one SUS board with a hole at one end was prepared as the second adherend.The surface of the first adherend was degreased with isopropyl alcohol, and the The surface of No. 2 adherend was degreased with acetone. The photocurable adhesive composition according to Example 1 was uniformly applied to the degreased surface of the first adherend so that the thickness was 100 μm and the application area was 25×25 mm ² . Next, the photocurable adhesive composition according to Example 1 applied to the first adherend was irradiated with ultraviolet rays (UV) [Irradiation conditions: UV-LED lamp (wavelength 365 nm, illuminance: 1000 mW/cm ² ), integrated light amount: 3000 mJ/cm ² ], and was cured. Immediately after curing, the portion of the degreased second adherend opposite to the holed end is coated with the first adherend so as to sandwich the photocurable adhesive composition cured by UV light irradiation. A test piece was prepared by attaching the test piece to the body and pressing it with a 2 kg roller twice. Subsequently, this test piece was cured for 24 hours in an environment of 23° C. and 50% RH. After curing, an S-shaped hook was attached to the hole in the SUS plate of the test piece, and the test piece was hung vertically with the SUS plate side facing upward. Subsequently, a 1 kg weight was attached to the end of the PET film, and a load was applied in the shear direction of the test piece, that is, in the vertical direction. The loaded test piece was attached to the ceiling of a hot air dryer (hot air circulation constant temperature dryer: 41-S4 manufactured by Satake Kagaku Kikai Co., Ltd.) set at 80°C via the S-shaped hook, and left undisturbed for 24 hours. Then, a hot creep test was conducted. ◎ for almost no deviation (less than 1.0 mm), ○ for small deviation (1.0 mm or more and less than 1.5 mm), △ for large deviation (1.5 mm or more and less than 25 mm). Those in which the PET film and the SUS plate were peeled off and the weight fell were evaluated as ×.

As can be seen from Table 1, the adhesive composition containing the (meth)acrylate monomer having a substituent containing a phosphorus atom had excellent hot creep properties.

The photocurable pressure-sensitive adhesive composition according to the present invention is a pressure-sensitive adhesive that has excellent adhesive strength even in a high-temperature environment, and can withstand use in a wide temperature range.

Claims (3)

A photocurable adhesive composition having excellent hot creep properties,
(A) (meth)acrylic acid ester polymer block (a) 5 to 45% by mass having a glass transition temperature of 50°C or higher; and (meth)acrylic acid ester polymer block (meth)acrylic acid ester polymer block having a glass transition temperature of 20°C or lower ( b) a (meth)acrylic block copolymer containing 55 to 95% by mass;
(B) a reactive solvent that dissolves the (meth)acrylic block copolymer (A) and is photopolymerizable;
(C) a photopolymerization initiator;
(D) a (meth)acrylate monomer having a substituent containing a phosphorus atom;
Contains
The (meth)acrylic block copolymer (A) is a triblock copolymer represented by the formula (a1)-(b)-(a2) (polymer block (a1), polymer block ( a2) is the same (meth)acrylic acid ester polymer block as the polymer block (a), and the polymer block (a1) and the polymer block (a2) may be the same or different. ),
The amount of the (meth)acrylate monomer having a substituent containing a phosphorus atom (D) added is 0.01 parts by mass or more and 30 parts by mass or less,
The hot creep property test was conducted using a PET film as a first adherend whose surface was degreased with isopropyl alcohol, and a SUS plate having a hole at one end as a second adherend whose surface was degreased with acetone. was prepared, the photocurable adhesive composition was uniformly applied to the surface of the first adherend to a thickness of 100 μm and a coating area of 25 x 25 mm2, and ultraviolet (UV) light was applied to the surface of the first adherend ^. Immediately after curing by irradiating the curable adhesive composition [irradiation conditions: UV-LED lamp (wavelength 365 nm, illuminance: 1000 mW/cm ² ), cumulative light amount: 3000 mJ/cm ² ], the second adherend is cured. The part opposite to the one end having the hole is pasted to the first adherend so as to sandwich the cured photocurable adhesive composition, and pressed with two reciprocations of a 2 kg roller. After curing the prepared test piece in an environment of 23°C and 50% RH for 24 hours, an S-shaped hook was attached to the hole of the second adherend of the test piece, and the second adherend side was facing upward. The test piece was hung vertically so that When the test piece is attached to the ceiling via the S-shaped hook and left undisturbed for 24 hours, the deviation between the first adherend and the second adherend is less than 1.5 mm. Photocurable adhesive composition. The (meth)acrylic block copolymer (A) is a (meth)acrylic block copolymer containing a polymer block (a) containing methyl methacrylate as a monomer unit and a polymer block (b) containing butyl acrylate as a monomer unit. The photocurable adhesive composition according to claim 1, which is a block copolymer. The photocurable pressure-sensitive adhesive composition according to claim 1 or 2, wherein the reactive solvent (B) is a monofunctional (meth)acrylate monomer having a substituent containing an oxygen or nitrogen atom.