JP7080144B2 - Photocurable adhesive resin composition - Google Patents

Description

The present invention relates to a photocurable pressure-sensitive adhesive resin composition suitable for bonding an image display member such as a liquid crystal display to a cover member.

Acrylic resin is used for various purposes by taking advantage of its characteristics of transparency and quick-curing property. For example, in an image display such as a smartphone or a touch panel, such an acrylic transparent resin is filled between an image display member such as a liquid crystal display panel or an organic EL display panel for displaying an image and a cover panel for protecting the image display member. A technique has been developed in which the air layer between the image display member and the cover panel is eliminated and the contrast and the brightness are prevented from being lowered by adhering the images. (Patent Document 1).

Further, in the past, the applicant has applied an acrylic oligomer containing a block copolymer (A) of methyl methacrylate and butyl acrylate and a urethane bond in the molecule as an adhesive that can be used for a tape used for laminating an image display member and a cover member. He has invented a pressure-sensitive adhesive resin composition comprising B), a monofunctional acrylic monomer (C), a pressure-sensitive adhesive (D), and a photopolymerization initiator (E). (Patent Document 2)

The present invention is excellent in that the visibility of the image is improved and the scattering of the cover member can be reduced by the adhesive force even when the cover member is suddenly damaged by the force. However, when the cover member has a curved surface instead of a flat shape, strong adhesive force and step followability that can follow the curved surface are required, and in addition, good slitting property when processed into an adhesive tape is also required. , There was room for improvement.

JP-A-2005-55641 Patent No. 6193427

The present invention is an adhesive used for image display displays and the like. By processing it into a tape and using it for bonding an image display member and a cover member, the visibility of an image is improved and strong adhesiveness is obtained. It is an object of the present invention to provide a solvent-free photocurable adhesive resin having excellent slitting property, which enables good bonding even if the cover member has a curved shape because of the step-following property.

The invention according to claim 1 is a compound (A) having a (meth) acrylic group having a polypropylene glycol skeleton having a weight average molecular weight of 10,000 to 100,000, and a monofunctional (meth) acrylate monomer (b1) having a hydroxyl group. A monofunctional (meth) acrylate monomer (B) containing at least an alicyclic monofunctional (meth) acrylate monomer (b2) having no hydroxyl group, a tackifier (C), and a polymer plasticizer (D). ) And the photopolymerization initiator (E), and the total amount of the (C) and (D) blended with respect to the entire composition is 45 to 60% by weight. Provide things.

The invention according to claim 2 provides the photocurable pressure-sensitive adhesive resin composition according to claim 1, wherein the blending amount with respect to the entire composition of the above-mentioned (A) is 10 to 25% by weight .

The invention according to claim 3 provides the photocurable pressure-sensitive adhesive resin composition according to claim 1 or 2, wherein the (C) is a rosin ester-based resin.

The invention according to claim 4 provides the photocurable pressure-sensitive adhesive resin composition according to any one of claims 1 to 3, wherein the (D) is a non-crosslinked urethane-based resin.

The invention according to claim 5 provides the photocurable pressure-sensitive adhesive resin composition according to any one of claims 1 to 4 , which is a pressure-sensitive adhesive for tape applied on a polyethylene terephthalate film.

The invention according to claim 6 provides a differential tape used for bonding a mobile terminal electronic device and a cover member using the photocurable adhesive resin composition according to any one of claims 1 to 5 .

The adhesive resin of the present invention can be used for an adhesive tape having good visibility, high adhesive force, and step followability in bonding an image display member and a cover member, and is solvent-free light having excellent slit properties. It is a curable adhesive resin composition, and is particularly useful for protective glass having a curved surface.

Hereinafter, the present invention will be described in detail.

The composition of the present invention comprises a compound (A) having a (meth) acrylic group having a polypropylene glycol (hereinafter PPG) skeleton, a monofunctional (meth) acrylate monomer (b1) having a hydroxyl group, and a hydroxyl group. A monofunctional (meth) acrylate monomer (B) containing at least an alicyclic monofunctional (meth) acrylate monomer (b2), a tackifier (C), a polymer plasticizer (D), and photopolymerization initiation. Agent (E). In addition, in this specification, (meth) acrylate includes both acrylate and methacrylate.

The compound (A) having a (meth) acrylic group having a PPG skeleton used in the present invention is a base oligomer constituting a transparent resin composition, and for example, PPG has a compound having a plurality of isocyanate groups and a hydroxyl group. An example is urethane acrylate obtained by reacting (meth) acrylate. PPG is a polyether obtained by ring-opening polymerization of propylene oxide, and since the number of carbon atoms between the ethers is small, it becomes a urethane acrylate having high flexibility and hydrophilicity by having this skeleton. The number of functional groups is preferably bifunctional, and if it is trifunctional or higher, it has a mesh-like polymer structure, so that the rigidity tends to be too high and the followability to a step or a curved surface tends to decrease.

The weight average molecular weight of (A) is 10,000 to 100,000, preferably 15,000 to 50,000, and even more preferably 18,000 to 30,000. If it is less than 10,000, the cohesive force of the cured film is low and the peel strength is lowered, and if it exceeds 100,000, the viscosity of the composition becomes high and it becomes difficult to adjust the viscosity. The weight average molecular weight (hereinafter referred to as Mw) was calculated by measuring and calculating the molecular weight in terms of standard polystyrene by gel permeation chromatography using a tetrahydrofuran eluent on a column using a filler of a styrenedivinylbenzene base material.

The blending amount of (A) with respect to the total composition is preferably 10 to 25% by weight, more preferably 12 to 22% by weight. Sufficient cohesive force and film strength can be secured at 10% by weight or more, and it becomes easy to control the viscosity suitable for workability at 25% by weight or less. Examples of commercially available PPG-based urethane acrylates include Excellate RX8-38 and RX8-39 (trade name: manufactured by Asia Industries, Ltd.).

The monofunctional (meth) acrylate monomer (B) used in the present invention is compounded for the purpose of diluting the highly viscous (A) and at the same time increasing the curing reactivity, and is a monofunctional (meth) acrylate monomer (b1) having a hydroxyl group. ) And at least an alicyclic monofunctional (meth) acrylate monomer (b2) having no hydroxyl group. The blending amount of (B) with respect to the total composition is preferably 20 to 40% by weight, more preferably 25 to 35% by weight. When it is 20% by weight or more, sufficient reactivity can be secured, and when it is 40% by weight or less, sufficient cohesive force and film strength can be secured.

The monofunctional (meth) acrylate monomer (b1) having a hydroxyl group contained in (B) is blended for the purpose of improving the adhesion to glass when the cover member is glass. The blending amount of (b1) with respect to (B) is preferably 15 to 25% by weight, more preferably 18 to 22% by weight. When it is 15% by weight or more, sufficient adhesion with glass can be ensured, and when it is 25% by weight or less, the elastic modulus can be lowered and easily controlled.

Examples of (b1) include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, and 1,4-cyclohexanedi. There are methanol monoacrylate, 4-hydroxycyclohexyl (meth) acrylate and the like, and they can be used alone or in combination of two or more. Among these, 4-hydroxybutyl (meth) acrylate is preferable in terms of molecular weight and handling.

The alicyclic monofunctional (meth) acrylate monomer (b2) containing no hydroxyl group contained in (B) is compounded to dilute (A) and at the same time increase the curing reactivity and elastic modulus. To. The alicyclic structure improves the cohesive force and can increase the elastic modulus. The blending amount of (b2) with respect to (B) is preferably 50 to 70% by weight, more preferably 55 to 65% by weight. Within this range, a good elastic modulus can be ensured.

Examples of (b2) include isopentenyl acrylate, dicyclopentenyl (meth) acrylate, dicyclopentenyl (meth) acrylate, dicyclopentenyloxyethyl (meth) acrylate, adamantanyl (meth) acrylate, and tetrahydrofurfuryl (). Meta) There are acrylates and the like, and they can be used alone or in combination of two or more. Among these, isobornyl acrylate having a low viscosity and a low odor is suitable. Further, in order to make it easy to adjust the viscosity of the compound, it is desirable that the viscosity is 500 mPa · s or less.

Since the tackifier (C) used in the present invention is a non-reactive component, it is blended for the purpose of improving the peel strength without causing curing shrinkage. For example, there are rosin ester resin, terpene resin, petroleum resin, styrene resin, Kumaron inden resin, alkylphenol resin and the like, and they can be used alone or in combination of two or more. Among these, a rosin ester resin is preferable because it has excellent compatibility with (A) and (B).

The blending amount of (C) with respect to the entire composition is preferably 25 to 40% by weight, more preferably 28 to 35% by weight. Within this range, sufficient peel strength can be ensured.

Since the polymer plasticizer (D) used in the present invention is a non-reactive component like (C), the purpose is to impart appropriate flexibility to the pressure-sensitive adhesive layer and relieve stress without causing curing shrinkage. Mix with. For example, there are urethane-based resin, polybutadiene-based resin, acrylic-based resin and the like, and they can be used alone or in combination of two or more. Among these, a non-crosslinked urethane resin is preferable because it has excellent compatibility with (A) and (B).

The number average molecular weight (hereinafter referred to as Mn) of (D) is preferably 1,000 to 10,000, more preferably 1,500 to 5,000. When it is 1,000 or more, sufficient peel strength can be secured, and when it is 10,000 or less, it becomes easy to control the viscosity suitable for workability. The blending amount of (D) with respect to the total composition is preferably 15 to 25% by weight, more preferably 18 to 22% by weight. Within this range, sufficient peel strength and stress relaxation can be ensured.

The total blending amount of (C) and (D) with respect to the entire composition is 45 to 60% by weight, preferably 47 to 55% by weight. If it is less than 45% by weight, the adhesive strength and stress relaxation are insufficient, and if it exceeds 60% by weight, the cohesive force of the film is lowered, the peeling strength is lowered, and the slit property when processed into a tape shape is further lowered. Further, by keeping it within this range, good step followability can be realized.

The photopolymerization initiator (E) used in the present invention generates radicals by irradiation with ultraviolet rays, electron beams, etc., and the radicals trigger a polymerization reaction. A general-purpose photopolymerization initiator can be used. By arbitrarily selecting the light absorption wavelength of the polymerization initiator, curability can be imparted over a wide wavelength range from the ultraviolet region to the visible light region. Specifically, 2.2-dimethoxy-1.2-diphenylethan-1-one as a benzyl ketal system, 1-hydroxy-cyclohexyl-phenyl-ketone and 1- [4- (2- (2-) as an α-hydroxyacetophenone system. Hydroxyethoxy) -phenyl] -2-hydroxy-2-methyl-1-propane-1-one is 2-methyl-1- (4-methylthiophenyl) -2-morpholinopropane-1 as an α-aminoacetophenone system. -On is an acylphosphine oxide system such as 2.4.6-trimethylbenzoyl-diphenyl-phosphinoxide and bis (2.4.6-trimethylbenzoyl) -phenylphosphinoxide, which may be used alone or in combination of two or more. Can be used in combination.

Among these, it is preferable to include an α-hydroxyacetophenone type that is less likely to yellow and an acylphosphine oxide type that is excellent in internal curability. In particular, when the cured film is thickened to 100 μm or more, it is effective to use an acylphosphine oxide system in combination. The blending amount is preferably 1 to 10 parts by weight, more preferably 2 to 8 parts by weight, based on 100 parts by weight of the radically polymerizable component. By blending in this range, the composition can be efficiently cured. As commercially available products, there are α-hydroxyacetophenone type Irgacure 184 and 2959, and phosphine oxide type Irgacure TPO and 819 (trade name: manufactured by BASF Japan).

Further, transparency is maintained by adding a monofunctional (meth) acrylate monomer (b3) having an acyclic alkyl group having a carbon number of C8 to 18 having good compatibility with (A) to the present composition. However, the elastic modulus can be adjusted. Examples of (b3) include normal octyl (meth) acrylate, decyl (meth) acrylate, lauryl (meth) acrylate, tridecyl (meth) acrylate, tetradecyl (meth) acrylate, and isostearyl acrylate, among which (A) is used. Lauryl acrylate and isostearyl crylate, which have excellent compatibility with lauryl acrylate and have a relatively high glass transition point, are suitable. The blending amount of (b3) with respect to (B) is preferably 10 to 25% by weight, more preferably 15 to 22% by weight. When the content is 10% by weight or more, flexibility can be imparted to the cured film, and when the content is 25% by weight or less, sufficient strength of the film can be ensured.

Furthermore, the photocurable resin composition of the present invention is a photosensitizer, an antioxidant, a flame retardant, a filler, a silane coupling agent, a colorant, and a polymerization inhibitor as necessary, as long as the performance is not impaired. , Additives such as organic fine particles can be added.

The elastic modulus of the cured product is preferably 5.0 × 10 ⁴ Pa or more, and more preferably 8.0 × 10 ⁴ Pa or more. If it is less than 5.0 × 10 ⁴ Pa, the slit property when processed into a tape tends to decrease.

When the film thickness of the cured product is 300 μm, the 180 ° peel strength between the glass plate and the PET film is preferably 15 N / 25 mm or more, more preferably 25 N / 25 mm or more, and particularly preferably 40 N / 25 mm. If it is less than 15N / 25mm, if the cover panel to be attached to the mobile terminal electronic device has a curved surface, the adhesive strength is too low, making it difficult to follow the curved surface, and even if it follows, it tends to float over time. Become.

The photocurable resin composition of the present invention can be used as a tape-shaped adhesive for adhering an image display body such as a touch panel or a flat panel display, for example, a mobile device terminal and a cover member for protecting the terminal. The photocurable pressure-sensitive adhesive resin composition of the present invention has excellent adhesion to glass materials in particular, and is also excellent in reworkability that there is no adhesive residue when re-bonding due to a bonding error. , Useful for smartphone protective glass applications. Specific examples of the tape manufacturing and usage methods will be described below, but the present invention is not limited to this, and the order of applying the adhesive and the order of bonding the films can be selected at any time.

After applying the pressure-sensitive adhesive to the PET film, it is cured by irradiation with ultraviolet rays to prepare a pressure-sensitive adhesive film (FIG. 1). The coating method is not particularly limited, and known roll coats, die coats, air knife coats, blade coats, spin coats, reverse coats, gravure coats and the like can be used. The thickness to be applied is arbitrary, and for example, 50 to 400 μm can be exemplified, but for a curved glass cover panel, a thick film of 200 to 350 μm is preferable. When the film is thickened, it is preferable to make it solvent-free in order to improve the appearance. As the ultraviolet rays used for curing, known light sources such as high-pressure mercury lamps, carbon arc lamps, xenon lamps, metal halide lamps, LED lamps, and electrodeless lamps are used, and the integrated light amount is, for example, 50 to 1,500 mJ / cm2. The curable composition is cured.

Next, a three-layer structure adhesive sheet (FIG. 2) in which a silicone-based adhesive is sandwiched between the PET film and the PET film having an easy-adhesive layer is separately prepared, and the adhesive prepared above is applied to the easy-adhesive PET surface. The adhesive surface of the film (FIG. 1) is laminated to prepare an adhesive laminated film (FIG. 3) having a five-layer structure. Tapes having different adhesive strengths on the front and back sides, such as this configuration, are generally called differential tapes, and differential tapes that bond a mobile device terminal to a cover member may be particularly called an AB tape.

Next, the PET film on the acrylic pressure-sensitive adhesive side of the pressure-sensitive adhesive laminated film (FIG. 3) is peeled off and bonded to a thin film glass to be a cover member. At that time, if necessary, an autoclave, a vacuum laminator, or the like is used to remove bubbles remaining between the glass surface and the adhesive. After that, the PET film on the silicone-based adhesive side is peeled off and attached to the image display panel surface. By inserting and laminating this adhesive laminated film between the thin glass and the image display panel (Fig. 4), the air layer is eliminated and the contrast and brightness are prevented from decreasing, and at the same time, sudden force is applied to the glass surface and it is damaged. Even in this case, it is possible to reduce the scattering of glass due to its adhesive strength, and it can be used for electronic devices such as mobile phones, tablet terminals, digital cameras, televisions, and personal computer monitors.

Hereinafter, the present invention will be described in detail based on Examples and Comparative Examples, but only specific examples thereof 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%.

Examples 1 to 4
As (A), RX8-39 (trade name: manufactured by Asia Industries, Ltd., PPG skeleton urethane acrylate, Mw.24,000) and RX8-38 (trade name: manufactured by Asia Industries, Ltd., PPG skeleton urethane acrylate, Mw.20,000). ) As (b1), 4HBA (trade name: manufactured by Osaka Organic Chemical Industry Co., Ltd., 4-hydroxybutyl acrylate), and IBXA (trade name: manufactured by Kyoeisha Chemical Co., Ltd., isobornyl acrylate) as (b2). LA (trade name: Kyoeisha Chemical Co., Ltd., lauryl acrylate) and ISTA (trade name: Osaka Organic Chemical Industry Co., Ltd., isostearyl acrylate), and KE311 (trade name: Arakawa Chemical Industry Co., Ltd., rosin ester) as (C). (System), FZ100 (trade name: manufactured by Asia Industries, Ltd., non-crosslinked urethane resin, Mn2100) as (D), and Irgacure184 and IrgacureTPO (trade name: manufactured by BASF Japan) as (E), in the formulation shown in Table 1. The photocurable adhesive resin compositions of Examples 1 to 4 were prepared by stirring until they were uniformly dissolved.

Comparative Examples 1 to 5
In addition to the materials used in the examples, as oligomers, RX71-25LA70 (trade name: manufactured by Asia Industries, Ltd., hydrided polybutadiene skeleton urethane acrylate, Mw.26,000, solid content 70% LA dilution) and UC203 (trade name:). GI1000 (trade name: Nippon Soda Co., Ltd., double-ended hydroxylated polybutadiene, Mn1500) and GI1000 (trade name: Nippon Soda Co., Ltd., both-terminal hydroxylated polybutadiene, Mn1500) and GI1000 (trade name: Nippon Soda Co., Ltd. DINCH (trade name: manufactured by BASF Japan, diiononylcyclohexanedicarboxylate) was stirred until uniformly dissolved in the formulation shown in Table 1 to prepare the photocurable pressure-sensitive adhesive resin compositions of Comparative Examples 1 to 5.

Table 1

The evaluation method was as follows.

Ultraviolet curing conditions Using a high-voltage electrode mercury lamp H04-L41 manufactured by Igraphic Co., Ltd., the output was 100 mW / cm ² and the integrated light intensity was 800 mJ / cm ² .

Viscosity: Using a cone plate type viscometer RE-215R manufactured by Toki Sangyo, measured at a cone angle of 3 ° × R17.65 at 25 ± 1 ° C and a rotation speed of 10 rpm, and measured at 10,000 to 10,000 mPa · s. , The case outside this range was marked as x.

Peeling strength: A pressure-sensitive adhesive resin composition is applied onto a PET film A4300 (trade name: manufactured by Toyobo Co., Ltd., thickness 50 μm) so as to have a thickness of 300 μm, and a light peeling PET film E7006 (manufactured by Toyobo Co., Ltd., 75 μm) is applied thereto. Was laminated and then cured by ultraviolet rays under the above curing conditions. After that, it was cut to a width of 25 mm, the light peeling PET film was peeled off, and the one attached to the white plate glass was used as a test piece. Then, the peel strength of 180 ° was measured with respect to the white plate glass surface, and 15 N / 25 mm or more was marked with ◯, and the following was marked with x.

Elastic modulus: Using HAAKEMARS40 manufactured by Thermo Fisher Scientific Co., Ltd., using a sample prepared by adjusting a resin composition having a diameter of 20 mmΦ and a film thickness of 1 mm under the above curing conditions, a storage elastic modulus in a shearing mode of 25 ° C. and 1 Hz was obtained. The measurement was performed, and 5.0 × 10 ⁴ Pa or more was designated as ◯, and less than 5.0 × 10 ⁴ Pa was designated as ×.

Evaluation results <br /> Table 2

Each resin composition of the example obtained good results in all evaluations of viscosity, elastic modulus and peel strength.

On the other hand, Comparative Example 1 which does not contain (A) has a low peel strength, Comparative Example 2 has poor compatibility, Comparative Example 3 which does not contain (b2) is whitened after curing, and Comparative Example 4 which does not contain (D). Is unsuitable in terms of elastic modulus and peel strength, and Comparative Example 5 in which the total compounding amounts of (C) and (D) are low has a low elastic modulus, and neither of them is suitable for the present invention.

INDUSTRIAL APPLICABILITY The present invention has good visibility, adhesion, and step followability in bonding a display body such as an image display and a cover member. Therefore, the AB tape for protective glass of a smartphone having a curved surface (smartphone application). It is useful for differential tapes).

Cross section of film coated with photocurable adhesive resin composition Cross section of a three-layer structure laminated film sandwiching a silicone-based adhesive Cross section of a laminated film having a five-layer structure in which FIGS. 1 and 2 are bonded together. Cross section of thin film glass and image display panel bonded together with the film shown in Fig. 3.

1 Peeling PET film 2 Photocurable adhesive resin composition 3 Easy-adhesive PET film 4 Silicone adhesive 5 Peeling PET film 6 Thin film glass 7 Image display panel

Claims (6)

A compound (A) having a (meth) acrylic group having a polypropylene glycol skeleton having a weight average molecular weight of 10,000 to 100,000, a monofunctional (meth) acrylate monomer (b1) having a hydroxyl group, and a fat having no hydroxyl group. A monofunctional (meth) acrylate monomer (B) containing at least a cyclic monofunctional (meth) acrylate monomer (b2), a tackifier (C), a polymer plasticizer (D), and a photopolymerization initiator ( A photocurable pressure-sensitive adhesive resin composition comprising E) and, wherein the total blending amount of (C) and (D) with respect to the entire composition is 45 to 60% by weight. The photocurable pressure-sensitive adhesive resin composition according to claim 1, wherein the blending amount of the composition (A) is 10 to 25% by weight . The photocurable pressure-sensitive adhesive resin composition according to claim 1 or 2, wherein the (C) is a rosin ester-based resin. The photocurable pressure-sensitive adhesive resin composition according to any one of claims 1 to 3, wherein the (D) is a non-crosslinked urethane resin. The photocurable pressure-sensitive adhesive resin composition according to any one of claims 1 to 4 , which is a pressure-sensitive adhesive for tape applied on a polyethylene terephthalate film. A differential tape used for bonding a mobile terminal electronic device and a cover member using the photocurable adhesive resin composition according to any one of claims 1 to 5 .

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