JP6910097B2 - High refractive index photocurable resin composition - Google Patents

Description

The present invention relates to a photocurable resin having a high refractive index used for bonding an image display member such as a liquid crystal and a plastic cover panel.

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 smart phone or a touch panel, such an acrylic transparent resin is placed 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. By filling and adhering, a technique has been developed that eliminates the air layer between the image display member and the cover panel and prevents a decrease in contrast and brightness. (Patent Document 1).

In this field, there are various required characteristics in terms of physical properties. For example, as a response to a high refractive index that expands the degree of freedom in optical design, a poly having a fluorene ring as a curable composition having low shrinkage and colorless and transparent ( An optical adhesive comprising a meta) acrylate compound, a polythiol compound having a thioalkyl structure, and a photopolymerization initiator has been proposed (Patent Document 2).

However, when acrylate with a fluorene skeleton is used, it is difficult to adjust the hardness to be suitable for adhesion of optical members due to its rigid structure, and there is a problem that the yellow color becomes high in terms of color tone, so there is room for improvement. there were.

JP-A-2005-55641 Patent No. 5810611

The present invention is to provide a transparent resin composition which is a photocurable resin used for an image display and the like and has a high refractive index.

The invention according to claim 1 is a polyfunctional acrylate oligomer (A) having a refractive index of 1.56 or more, a monofunctional (meth) acryloyl monomer (B) containing a polar group, and a urethane resin containing no unsaturated group. A 3-phenoxybenzyl- based acrylate oligomer containing C) and a photoinitiator (D), wherein the (A) has a bifunctional acrylic group , and the blending amount of (A) is based on the total blending amount. Provided is a high refractive index photocurable resin composition having a blending amount of 30 to 60% by weight, a blending amount of (B) of 5 to 20% by weight, and a blending amount of (C) of 3 to 25% by weight.

The invention according to claim 2 is the high refractive index photocurable resin composition according to claim 1, wherein the monofunctional (meth) acryloyl monomer (B) containing the polar group is an acrylate monomer containing a hydroxyl group or an amino group. I will provide a.

The invention according to claim 3 provides the high refractive index photocurable resin composition according to claim 1 or 2 , wherein the unsaturated group-free urethane resin (C) is a polyurethane having a polypropylene glycol skeleton. do.

The photocurable resin of the present invention is useful as a transparent resin composition having a high refractive index that exhibits good adhesion when the display body and the cover panel are bonded to each other.

Hereinafter, the present invention will be described in detail.

The composition of the present invention comprises a polyfunctional acrylate oligomer (A) having a refractive index of 1.56 or more, a monofunctional (meth) acrylate monomer (B) containing a polar group, and a urethane resin containing no unsaturated group. (C) and photoinitiator (D). In addition, in this specification, (meth) acrylate includes both acrylate and methacrylate.

The polyfunctional acrylate oligomer (A) having a refractive index of 1.56 or more used in the present invention is a main component constituting the present composition, and has a refractive index of polycarbonate widely used as a cover panel for a touch panel or a flat display panel. It is almost the same as the refractive index of 1.54. By bringing the refractive index of the resin to be bonded to the cover panel close to each other, reflection at the interface can be reduced and visibility can be improved. The refractive index of 1.56 referred to here means the refractive index of the oligomer itself, and the cover panel is not limited to the one made of polycarbonate. Examples of oligomers having a refractive index of 1.56 or more include naphthalene-based, anthracene-based, fluorene-based, and phenoxybenzyl-based oligomers having a plurality of aromatic rings. Among these, phenoxybenzyl-based oligomers are used from the viewpoint of flexibility. Is preferable.

The weight average molecular weight of (A) used in the present invention is preferably 10,000 to 25,000, more preferably 13,000 to 20,000. When it is 10,000 or more, a sufficient cohesive force can be secured, and when it is 25,000 or less, it is easy to control the viscosity suitable for workability. The weight average molecular weight (hereinafter referred to as "Mw.") Was calculated by measuring and calculating the molecular weight in terms of standard polystyrene using a tetrahydrofuran developing solvent on a column of a styrene vinylbenzene base material by a gel permeation chromatography method.

(A) used in the present invention contains a polyfunctional functional group so that it can react with the (meth) acrylate monomer (B) to form a more polymerized and tough film, but the number of functional groups is cured. Bifunctionals that do not cause too much contraction are preferred.

The blending amount of (A) with respect to the total composition is 30 to 60% by weight, more preferably 35 to 58% by weight. If it is less than 30% by weight, the viscosity becomes low, it becomes difficult to adjust the viscosity suitable for workability, and sufficient film strength may not be ensured. If it exceeds 60% by weight, the viscosity becomes high and it becomes difficult to adjust the viscosity to be suitable for workability.

The (B) used in the present invention plays a role of diluting the highly viscous (A) and at the same time improving the curing reactivity, and the number of functional groups is monofunctional without increasing the curing shrinkage. Polycarbonate, which is widely used as a material for cover panels, has high water vapor permeability, so the permeated water is easily mixed into the cured film. However, if there are polar functional groups in the cured film, the hydrophilicity is improved and water is mixed. However, it becomes difficult to whiten.

The polar functional group has a hydroxyl group, for example, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 1,4-. Cyclohexanedimethanol monoacrylate, 4-hydroxycyclohexyl (meth) acrylate, 5-hydroxycyclooctyl (meth) acrylate and the like can be used alone or in combination of two or more. Of these, 4-hydroxybutyl acrylate is preferable in terms of molecular weight and handling.

Other polar functional groups include amino groups, such as (meth) acrylamide, N, N-dimethylacrylamide, N, N-diethylacrylamide, N, N-dipropyl (meth) acrylamide, N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, N-isopropylacrylamide, N-butyl (meth) acrylamide, Nn-butoxymethyl (meth) acrylamide, N-isobutoxymethyl (meth) acrylamide, N-methoxymethyl (meth) acrylamide , Diacetone acrylamide, hydroxyethyl acrylamide, acrylic loylmorpholin and the like, and can be used alone or in combination of two or more. Among these, acrylic loylmorpholine having a high refractive index is preferable.

The blending amount of (B) with respect to the total composition is 3 to 20% by weight, more preferably 5 to 15% by weight. If it is less than 3% by weight, the moisture resistance is lowered and whitening is likely to occur, and if it exceeds 20% by weight, it is difficult to maintain the refractive index at 1.56 or more.

The unsaturated group-free urethane resin (C) used in the present invention is a polymer having high compatibility with (A), which plays a role of reducing curing shrinkage. Here, the fact that it does not contain an unsaturated group means that it does not have a functional group that polymerizes with (A) and (B) by an active energy ray. Although the refractive index is not particularly specified, it is preferably 1.45 or more, and more preferably 1.50 or more. Mw. Is preferably 1,000 to 30,000, more preferably 2,000 to 20,000. When it is 1,000 or more, the curing shrinkage can be sufficiently reduced, and when it is 30,000 or less, the viscosity suitable for workability can be easily controlled.

The urethane resin (C) used in the present invention has flexibility, but a urethane resin having a polyether skeleton such as polypropylene glycol (hereinafter referred to as PPG) having excellent flexibility is particularly suitable. Although it is as flexible as urethane resin, diene-based polymers such as polybutadiene and polyisoprene are unsuitable because they are inferior in compatibility with (A).

The blending amount of (C) with respect to the total composition is 5 to 25% by weight, more preferably 8 to 20% by weight. If it is less than 5% by weight, the curing shrinkage cannot be sufficiently reduced, and if it exceeds 25% by weight, the refractive index becomes low and it becomes difficult to adjust the viscosity to be suitable for workability.

The photopolymerization initiator (D) used in the present invention generates radicals by irradiation with ultraviolet rays, electron beams, etc., and the radicals trigger a polymerization reaction, and a general-purpose photopolymerization initiator may be used. Specifically, 2-hirodoxy-1- {4- [4- (2-hydroxy-2-methyl-propionyl) -benzyl] phenyl} -2-methyl-propan-1-one, 1-hydroxy-cyclohexyl-phenyl -Ketone, bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide, 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide, 2-hydroxy-2-methyl-1-phenyl-propane-1 -On, 1- [4- (2-hydroxyethoxy) -phenyl] -2-hydroxy-2-methyl-1-propane-1-one, etc. may be used alone or in combination of two or more. The blending amount is preferably 0.05 to 5 parts by weight, more preferably 0.1 to 3 parts by weight, based on 100 parts by weight of the radically polymerizable component.

Furthermore, the photocurable resin composition of the present invention contains a reactive diluent, a plasticizer, a tackifier, an antioxidant, a flame retardant, a filler, a silane coupling agent, and a polymerization inhibitor as long as the performance is not impaired. Additives such as agents can be used in combination.

As the reactive diluent, a 3-phenoxybenzyl acrylate monomer having good compatibility with (A), having a low viscosity, and being able to maintain a high refractive index of the cured product is preferable. The blending amount with respect to the total composition is preferably 40% by weight or less.

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 of room temperature of 25 ° C. and relative humidity of 65%.

Example 1
As an acrylate oligomer (A) having a refractive index of 1.56 or more, 70 parts by weight of AMHR-7 (trade name: manufactured by Negami Kogyo Co., Ltd., 3-phenoxybenzyl acrylate oligomer having a bifunctional acrylic group) is diluted with 30 parts by weight of POB-A. Mw. 15,000) contains 4HBA (trade name: 4 hydroxybutyl acrylate manufactured by Osaka Organic Chemical Industry Co., Ltd.) as a monofunctional (meth) acrylate monomer (B) containing a polar group, and contains an unsaturated group. FZ-100 (trade name: manufactured by Asia Industries, Ltd., PPG skeleton polyurethane, Mw. 2,300, refractive index 1.48) was used as the polymer component (C), and Irgacure819 (trade name: BASF) was used as the photoinitiator (D). POB-A (trade name: Kyoeisha Chemical Co., Ltd., 3-phenoxybenzyl acrylate) as a reactive diluent was stirred with the formulation shown in Table 1 until uniformly dissolved, and the high amount of Example 1 was obtained. A photocurable transparent resin composition having a refractive index was prepared.

Examples 2-6
In addition to the material used in Example 1, 70 parts by weight of AMHR-5 (trade name: manufactured by Negami Kogyo Co., Ltd., 3-phenoxybenzyl acrylate oligomer having a bifunctional acrylic group) as (A) was added to 30 parts by weight of POB-A. The diluted product, Mw. 18,000), and ACMO (trade name: Acryloylmorpholin manufactured by KJ Chemicals Co., Ltd.) as (B) were stirred until uniformly dissolved in the formulation shown in Table 1, and Examples 2 to 6 were performed. The high refractive index photocurable transparent resin composition of the above was prepared.

Comparative Examples 1 to 7
In addition to the materials used in the examples, HR-1N (manufactured by Negami Kogyo Co., Ltd., polymer of 3-phenoxybenzyl acrylate, Mw. 16,000) and Polyvest110 (trade name: manufactured by Ebonic Co., Ltd.) as polymers containing no unsaturated group. The non-functional liquid polybutadiene) was stirred with the formulation shown in Table 1 until it was uniformly dissolved to prepare the high refractive index photocurable transparent resin composition of Comparative Examples 1 to 7.

Table 1

The evaluation method was as follows.

Using a UV curing conditions <br/> Fusion UV Systems Japan Ltd. electrodeless UV irradiation apparatus F300S / LC-6B, the output at D bulb 100 mW / cm ^2, integrated light quantity was 3000 mJ / cm ^2.

Appearance after curing: A photocurable resin composition is applied to a white plate glass (manufactured by Matsunami Glass Industry Co., Ltd.) with a thickness of 1 mm so as to have a thickness of 200 μm, and the white plate glass is bonded onto the white plate glass to achieve the above ultraviolet curing. It was cured under the conditions to prepare a test piece. Using a haze meter HAZEGAED2 (manufactured by Gardner), the haze was measured by subtracting the glass content sandwiching the resin, and a haze value of less than 1.0 was defined as ◯, and a haze value of less than 1.0 was defined as x.

Viscosity: Using a cone plate type viscometer RC-550R 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 1,000 to 15,000 mPa · s. , The case outside this range was marked with x.

Refractive rate: A silicone sheet hollowed out to 40 mm x 8 mm is placed on the release surface of a release PET film (manufactured by Toyo Spinning Co., Ltd., trade name E7002) having a thickness of 100 μm, and the photocurable resin composition has a thickness of 50 μm. The PET film was applied, and the PET film was placed on the PET film and cured under the above-mentioned ultraviolet curing conditions. Then, the PET film was peeled off to obtain a cured resin product. After that, the refractive index at 589 nm on the D line was measured using an Appe refractometer DR-M2 manufactured by Atago. The test piece was set on the prism surface, and 1-bromonaphthalene was used as the intermediate solution. The evaluation was ◯ for 1.56 or more and x for less than 1.56.

Curing shrinkage: Measured according to the JIS K 6833 specific gravity cup method. A curing shrinkage rate of less than 5% was evaluated as ◯, and a curing shrinkage rate of 5% or more was evaluated as x.

Reliability: A 1 mm thick white plate glass (manufactured by Matsunami Glass Industry Co., Ltd.) is coated with a photocurable resin composition having a thickness of 200 μm on 76 mm × 104 mm, and the same white plate glass is laminated on the photocurable resin composition. It was cured with and used as a test piece. After the test piece was allowed to stand in a constant temperature and humidity chamber of 85 ° C. × 85% RH for 500 hours, those without floating or peeling were marked with ◯, and those with some were marked with ×.

Evaluation result <br /> Table 2

Each resin composition of the example obtained good results in all evaluations of appearance, viscosity, refractive index, curing shrinkage and reliability.

On the other hand, Comparative Examples 1, 2 and 7 in which a material other than polyurethane was blended as (C), Comparative Example 3 in which the upper limit of blending in (C) was exceeded, Comparative Example 4 in which (B) was omitted, and Comparative Example in which (C) was omitted. In Comparative Example 6 in which the lower limit of compounding of 5 and (A) was exceeded, one of the evaluation items had a × evaluation, which was not suitable for the present invention.

INDUSTRIAL APPLICABILITY The present invention is useful as a transparent resin composition which is a visibility-improving resin that exhibits good adhesion when a display body such as an image display display and a plastic cover panel are bonded to each other and does not cause floating.

Claims (3)

A polyfunctional acrylate oligomer (A) having a refractive index of 1.56 or more, a monofunctional (meth) acryloyl monomer (B) containing a polar group, a urethane resin (C) containing no unsaturated group, and a photoinitiator ( A 3-phenoxybenzyl-based acrylate oligomer containing D) and (A) having a bifunctional acrylic group , wherein the blending amount of (A) is 30 to 60% by weight based on the total blending amount. A high refractive index photocurable resin composition in which the blending amount of B) is 5 to 20% by weight and the blending amount of (C) is 3 to 25% by weight. The high refractive index photocurable resin composition according to claim 1, wherein the monofunctional (meth) acryloyl monomer (B) containing a polar group is an acrylate monomer containing a hydroxyl group or an amino group. The high refractive index photocurable resin composition according to any one of claims 1 or 2, wherein the unsaturated group-free urethane resin (C) is a polyurethane having a polypropylene glycol skeleton.