JP6825815B2 - Visibility-enhancing resin composition - Google Patents

Description

The present invention is a photocurable resin used for an image display, etc., a transparent resin composition having excellent reworkability in the step of bonding a display body and an optical member, and a display body and an optical member bonded by these. It relates to a touch panel or a flat panel display including.

Acrylic-based photocurable resins are used in many fields to impart special performance to the surfaces of plastic films and plastic moldings. For example, hard coat films that are applied on PET (polyethylene terephthalate) film to give high hardness are used in large quantities in touch panel products, and adhesive films that give viscosity to PET films are used in the manufacturing process of flat panel display products. But it is used in large quantities.

Acrylic resins are used in various applications by taking advantage of their characteristics of transparency and quick-curing properties, even in fields other than those in which a thin film is applied to the plastic surface to impart special performance. 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 member for protecting the image display member. A technique has been developed in which the air layer between the image display member and the cover member is eliminated by filling and bonding to prevent a decrease in contrast and brightness. (Patent Document 1).

In terms of physical properties, further improvements have been made, and as a resin composition having both shrinkage rate, elastic modulus and high durability (heat resistance, moisture heat resistance), hydrogenated polybutadiene diol, hydrogenated polybutadiene urethane acrylate, and monofunctional alkyl (monofunctional alkyl) A composition comprising a meta) acrylate, a monofunctional hydroxylalkyl (meth) acrylate, and a petroleum resin has been proposed (Patent Document 2). On the other hand, when the display body and the optical member are bonded together with such a resin, it may be necessary to correct them due to contamination of air bubbles or foreign substances, or misalignment of the bonding. In that case, the surface once bonded is peeled off once. , Reworkability to reattach is becoming required. However, it is not easy to achieve both this reworkability and good physical properties, and there is room for improvement.

JP-A-2005-55641 JP 2015-209520

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 excellent reworkability in a step of bonding a display body and an optical member.

The invention according to claim 1 comprises a compound (A) having a number average molecular weight of 3,000 to 8,000 and having a (meth) acrylic group having a hydrogenated polybutadiene skeleton, and a compound (A) having a number average molecular weight of 500 to 5,000. Then, a hydrogenated polybutadiene oligomer (B) having a hydroxyl group at the end, an alicyclic monofunctional (meth) acrylic acid ester monomer (C), a plasticizer (D), and a photopolymerization initiator (E). The content of (A) is 20 to 25% by weight, the content of (B) is 35 to 45% by weight, the content of (C) is 20 to 30% by weight, and the content of (D) is contained. Provided is a photocurable resin composition having an amount of 10 to 20% by weight and a content of a monofunctional (meth) acrylic acid ester monomer having a hydroxyl group of 0 to 2% by weight.

According to a second aspect of the invention, the content of the (E) to provide a photocurable resin composition of claim 1, wherein from 0.1 to 5% by weight of the radically polymerizable component.

The invention according to claim 3 provides the photocurable resin composition according to claim 1 or 2, wherein (D) is a carboxylic acid ester having a viscosity of 500 mPa · s or less at 25 ° C.

The invention according to claim 4 provides the photocurable resin composition according to any one of claims 1 to 3 , wherein the elastic modulus of the cured product is 1.0 × 10 ⁴ Pa or more .

The invention according to claim 5 provides the photocurable resin composition according to any one of claims 1 to 4, which is used for bonding a display body and an optical member in an image display .

The photocurable resin of the present invention is useful as a transparent resin composition having excellent reworkability in the step of bonding the display body and the optical member.

Hereinafter, the present invention will be described in detail.

The composition of the present invention comprises a compound (A) having a number average molecular weight of 3,000 to 8,000 and having a (meth) acrylic group having a hydrogenated polybutadiene skeleton, and a number average molecular weight of 500 to 5, At 000, a hydrogenated polybutadiene-based oligomer (B) having a hydroxyl group at the end, an alicyclic monofunctional (meth) acrylic acid ester monomer (C), a plasticizer (D), and a photopolymerization initiator (E). ). In addition, in this specification, (meth) acrylate includes both acrylate and methacrylate.

The (A) used in the present invention contains a urethane bond obtained by reacting a hydrogenated polybutadiene diol with an isocyanate in addition to a structure in which a (meth) acrylic group is directly bonded to a hydrogenated polybutadiene, and has a urethane bond at the end (meth). ) There are urethane acrylates to which acrylic groups are bonded, but urethane acrylates having both toughness and extensibility are preferable. By hydrogenating the polybutadiene skeleton, it is possible to eliminate the highly reactive double bond and remarkably improve the light resistance to ultraviolet rays and the like.

Examples of the isocyanate used in the urethane acrylate include diphenylmethane diisocyanate, tolylene diisocyanate, hexamethylene diisocyanate, and isophorone diisocyanate. The number average molecular weight of the urethane acrylate is 3,000 to 8,000. If it is less than 3,000, the cohesive force of the cured product is insufficient, and if it exceeds 8,000, the viscosity becomes high and the workability becomes good. The elastic modulus of the cured product is also lowered, and the reworkability is lowered. The number average molecular weight was calculated by measuring and calculating the molecular weight in terms of standard polystyrene using a tetrahydrofuran developing solvent on a column based on styrene vinylbenzene by a gel permeation chromatography method.

The blending amount of (A) with respect to the total composition is 20 to 25% by weight. If it is less than 20% by weight, the elastic modulus becomes low and sufficient cohesive force and film strength cannot be secured, and if it exceeds 25% by weight, the viscosity becomes high. It becomes high and workability decreases. Examples of commercially available hydrogenated butadiene urethane acrylates include Excelate RX71-44 (trade name: manufactured by Asia Industries, Ltd.).

The above-mentioned (B) used in the present invention is a main material constituting a resin film together with (A), and has a role of imparting flexibility to the film and relaxing internal stress without participating in the reaction. It may be blended alone or in combination of two or more kinds of oligomers. Light resistance is reduced by using oligomers that do not contain hydroxyl groups at the ends or have no hydrogenated double bonds. The number average molecular weight is 500 to 5,000, and if it is less than 500, sufficient flexibility cannot be ensured, and if it exceeds 5,000, the viscosity becomes high and workability deteriorates.

The blending amount of (B) is preferably 35 to 45% by weight, and by blending in this range, a sufficient balance between flexibility and hardness of the film can be maintained and an appropriate elastic modulus can be obtained. Commercially available products include GI-1000 and 2000 (trade name: manufactured by Nippon Soda Co., Ltd.), and these may be used alone or in combination of two.

The alicyclic monofunctional (meth) acrylic acid ester monomer (C) used in the present invention is formulated to dilute (A) and (B) and at the same time increase the curing reactivity. It is monofunctional in order to suppress curing shrinkage, and the alicyclic structure can increase the cohesive force and improve the elastic modulus. The blending amount is preferably 20 to 30% by weight, and when it is 20% by weight or more, quick curing can be obtained, and when it is 30% by weight or less, the shrinkage rate can be controlled to be small.

Examples include isobornyl acrylate, dicyclopentanyl (meth) acrylate, dicyclopentenyl (meth) acrylate, dicyclopentenyloxyethyl (meth) acrylate, adamantanyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate and the like. Yes, these may be used alone or in combination of two types. 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.

The plasticizer (D) used in the present invention is an ester compound obtained by synthesizing a carboxylic acid and a higher alcohol, which imparts flexibility to the cured film and weakens the tack when reworking by heating to improve reworkability. It also plays a role in improving. Examples include phthalates, isophthalates, adipates, benzoic acids and the like, which may be used alone or in combination of two or more. The viscosity is preferably 500 mPa · s or less, and an aliphatic carboxylic acid having good compatibility is preferable so that the viscosity of the formulation can be easily adjusted. The blending amount is preferably 10 to 20% by weight, and sufficient flexibility can be ensured at 10% by weight or more, and long-term reliability can be ensured at 20% by weight or less. Commercially available products include Exepearl EH-S (trade name: manufactured by Kao Corporation, 2-ethylhexyl stearate) and the like.

The photopolymerization initiator (E) used in the present invention generates radicals by irradiation with ultraviolet rays or electron beams, 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 0.1 to 5% by weight, more preferably 0.1 to 2% by weight, based on the radically polymerizable component.

The elastic modulus of the cured product needs to be 1.0 × 10 ⁴ Pa or more, preferably 1.0 × 10 ⁵ Pa or more. If it is less than 1.0 × 10 ⁴ Pa, the adhesive force with the base material exceeds the cohesive force of the cured film, and the cured film is easily torn off when peeled by rework, and the reworkability is lowered.

The photocurable resin composition of the present invention may contain a monofunctional (meth) acrylate having a hydroxy group as a reactive diluent. By having a hydroxy group, the adhesive force with the glass is improved, but if it exceeds 3% by weight, the elastic modulus tends to be too low and the reworkability tends to decrease, and it is preferably 2% by weight or less. Examples of monofunctional (meth) acrylates having a hydroxy group include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 1, There are 4-cyclohexanedimethanol monoacrylate, 4-hydroxycyclohexyl (meth) acrylate and the like, and among these, 4-hydroxybutyl acrylate is preferable.

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

The photocurable resin composition of the present invention can be used as an adhesive for adhering a display body such as a touch panel or a flat panel display to an optical member for protecting the display body. Specific examples of the optical member include a protective sheet and a protective plate, and the materials thereof include, for example, PET, COP (cycloolefin polymer), PMMA (polymethylmethacrylate), PC (polycarbonate), and glass. The display body and the optical member bonded with the photocurable resin composition of the present invention can be incorporated into electronic devices such as mobile phones, tablet terminals, digital cameras, televisions, and personal computer monitors as display panels for images and the like. ..

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
RX71-44 (trade name: manufactured by Asia Industries, Ltd., hydrogenated butadiene-based urethane acrylate) as a compound (A) having a (meth) acrylic group having a hydrogenated polybutadiene skeleton and having a number average molecular weight of 3,000 to 8,000. , Mn. 4,400) as a hydrogenated polybutadiene-based oligomer (B) having a number average molecular weight of 500 to 5,000 and having a hydroxyl group at the end, GI-2000 (trade name: manufactured by Nippon Soda Co., Ltd., containing a terminal hydroxyl group). Plastic IB-XA (trade name: Isobornyl acrylate manufactured by Kyoeisha Chemical Co., Ltd.) as an alicyclic monofunctional (meth) acrylic acid ester monomer (C) using hydrogenated polybutadiene type, Mn. 2,100). Exepearl EH-S (trade name: manufactured by Kao Co., Ltd., 2-ethylhexyl stearate) as the agent (D), and Irgacure 184 and Irgacure 819 (trade name: manufactured by BASF Japan) as the photopolymerization initiator (E) are blended as shown in Table 1. The photocurable transparent resin composition of Example 1 was prepared by stirring until it was uniformly dissolved in. Here, Mn. Indicates the number average molecular weight.

Examples 2-8
In addition to the materials used in Example 1, GI-1000 (trade name: manufactured by Nippon Soda Co., Ltd., terminal hydroxyl group-containing hydropolybutadiene system, Mn. 1,500) was used as the above (B), and FA- was used as the above (C). 511AS (trade name: Hitachi Kasei Co., Ltd., dicyclopentenyl acrylate) and FA-513M (trade name: Hitachi Kasei Co., Ltd., dicyclopentanyl methacrylate), and other 4HBA (trade name: Osaka Organic Chemical Industry Co., Ltd., 4) -Hydroxybutyl acrylate) was stirred with the formulation shown in Table 1 until it was uniformly dissolved to prepare the photocurable transparent resin composition of Examples 2 to 8.

Comparative Examples 1 to 7
In addition to the materials used in the examples, as hydrogenated polybutadiene-based urethane acrylates, RX71-25 (trade name: manufactured by Asia Industries, Ltd., hydrogenated butadiene-based urethane acrylate, Mn.20,000) and 13-275 (commodity). Name: Rahn, Mn. 10,500), NOAA (trade name: Osaka Organic Chemical Industry, Normal Octyl Acrylate) as monofunctional acrylate, and Hexamol DINCH (trade name: BASF Japan, Ltd.) as (D). , 1,2-Cyclohexanedicarboxylic acid diisononyl ester) as a tackifier and Alcon P-90 (trade name: Arakawa Chemical Industry Co., Ltd., fully hydrogenated petroleum resin) is stirred until uniformly dissolved in the formulation shown in Table 1. The photocurable transparent resin compositions of Comparative Examples 1 to 7 were prepared.

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.

Reworkability: A cured resin composition is applied to a white plate glass (manufactured by Matsunami Glass Industry Co., Ltd.) with a thickness of 1 mm to a thickness of 200 μm, and the white plate glass having a thickness of 1 mm is bonded and cured under the above conditions. After that, let it stand on a hot plate at 150 ° C for 5 minutes and then take it out, bend the lower glass, or physically peel off the upper glass with a spatula etc., and the cured product will peel off without coagulation failure. Was marked with ◯, and the case where the cured product coagulated and fractured or the glass could not be peeled off was marked with ×.

Cross-peel strength: A blue plate glass with a thickness of 2 mm (manufactured by Matsunami Glass Industry Co., Ltd.) is coated with a cured resin composition at the center of 20 x 60 mm so that the thickness is 200 μm and the diameter is 10 mm, and the same blue plate glass is bonded so as to intersect. Cure under conditions. After that, using a tensile tester Technograph TGI-1kN (manufactured by Minebea), the peel strength when pulled at a crosshead speed of 10 mm / min was marked with ◯, and less than 0.1 MPa was marked with x.

High temperature and high humidity reliability: Using the same test piece as the reworkability evaluation in which white plate glass was bonded with a cured resin, let it stand for 500 hours in an environment of 85 ° C. and 85% RH, and then use the haze meter HAZEGAED2 (manufactured by Gardener). The haze was measured by subtracting the glass content sandwiching the resin, and a haze value of 1.0 or less was defined as ◯, and a haze value of 1.0 or more was defined as x.

Elastic modulus: Using HAAKERheoStress600 (manufactured by Thermo Scientific), sample B with a diameter of 20 mmΦ was used to measure the storage elastic modulus in shear shear mode at 25 ° C. and 1 Hz. 1.0 × 10 ⁴ Pa or more was ○, and the following × And said.

Evaluation result <br /> Table 2

Each resin composition of the example obtained good results in all evaluations of reworkability, cross peel strength, high temperature and high humidity reliability and elastic modulus.

On the other hand, Comparative Examples 1, 2, 6 and 7 containing 3% or more of a hydroxyl group-containing monofunctional acrylate are inferior in reworkability and include hydrogenated polybutadiene urethane acrylate having a number average molecular weight of more than 8,000. , 5 had poor high-temperature and high-humidity reliability and a low elastic modulus, and none of them was suitable for the present invention.

The present invention is useful as a transparent resin composition having high durability and excellent reworkability in the step of bonding the display body and the optical member.

Claims (5)

Compound (A) having a (meth) acrylic group having a hydrogenated polybutadiene skeleton with a number average molecular weight of 3,000 to 8,000 and hydrogen having a number average molecular weight of 500 to 5,000 and having a hydroxyl group at the terminal. It contains the added polybutadiene-based oligomer (B), an alicyclic monofunctional (meth) acrylic acid ester monomer (C), a plasticizer (D), and a photopolymerization initiator (E), and contains the above (A). The amount is 20 to 25% by weight, the content of (B) is 35 to 45% by weight, the content of (C) is 20 to 30% by weight, and the content of (D) is 10 to 20% by weight. A photocurable resin composition in which the content of a monofunctional (meth) acrylic acid ester monomer having a hydroxyl group is 0 to 2% by weight. The photocurable resin composition according to claim 1, wherein the content of (E) is 0.1 to 5% by weight with respect to the radically polymerizable component. The photocurable resin composition according to claim 1 or 2, wherein (D) is a carboxylic acid ester having a viscosity of 500 mPa · s or less at 25 ° C. The photocurable resin composition according to any one of claims 1 to 3, wherein the cured product has an elastic modulus of 1.0 × 10 ⁴ Pa or more. The photocurable resin composition according to any one of claims 1 to 4, which is used for bonding a display body and an optical member in an image display.