JP2018065897A - Photocurable resin composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photocurable resin composition which is a photocurable resin used for an image displaying display or the like, exhibits good adhesiveness in laminating an image display body and a plastic cover panel and causes no floating.SOLUTION: There is provided a photocurable resin composition which comprises: (A) a compound having a weight average molecular weight of 10000 to 100000 and a (meth)acryl group having a hydrogenated polybutadiene skeleton; (B) a monofunctional (meth)acrylic acid ester monomer having a hydroxyl group; (C) an alicyclic monofunctional (meth)acrylic acid ester monomer having no hydroxyl group; and (D) a photopolymerization initiator, wherein the content of the (A) to the whole composition is 30 to 45 wt.%, the content of the (B) is 10 to 25 wt.% and the content of the (C) is 25 to 42 wt.%.SELECTED DRAWING: None

Description

  The present invention relates to a photocurable resin used for bonding an image display member such as liquid crystal and a plastic cover panel, and a touch panel or a flat panel display bonded together.

  Acrylic photocurable resins are used in many fields in order to give special performance to the surface of plastic films and plastic moldings. For example, hard coat films that are coated on a 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 manufacturing processes for flat panel display products. But it is used in large quantities.

  Acrylic resins are used in various applications taking advantage of their characteristics of transparency and fast curing, even in fields other than the field of applying special performance by applying a thin film to the plastic surface. For example, in an image display such as a smartphone 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 that displays an image and a cover panel that protects 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 by filling and bonding to prevent a decrease in contrast and brightness. (Patent Document 1).

In this field, physical properties have been further improved, and as a resin composition having both shrinkage, elastic modulus and high durability (heat resistance, heat and humidity resistance), hydrogenated polybutadiene diol, hydrogenated polybutadiene urethane acrylate, and monofunctional A composition comprising an alkyl (meth) acrylate, a monofunctional hydroxylalkyl (meth) acrylate, and a petroleum resin has been proposed (Patent Document 2). However, when cover panels, which are increasing in in-vehicle use, are made of plastic, the thermal expansion coefficient of the base material to be bonded to the cover panel is different in a high temperature and high humidity environment, and the cover panel warps due to moisture absorption. The adhesive cannot follow the warp of the cover panel, and it may be difficult to ensure adhesion, and there is room for improvement.

JP-A-2005-55641 JP2015-209520A

The present invention provides a transparent resin composition that is a photocurable resin used for an image display display or the like, exhibits good adhesion in bonding of an image display member and a plastic cover panel, and does not generate floating; An object of the present invention is to provide a touch panel or a flat panel display including a display body bonded with the composition and a plastic cover panel.

The invention according to claim 1 is a compound (A) having a (meth) acryl group having a hydrogenated polybutadiene skeleton having a weight average molecular weight of 10,000 to 100,000, and a monofunctional (meth) acrylic acid having a hydroxyl group. The ester monomer (B), an alicyclic monofunctional (meth) acrylic acid ester monomer (C) having no hydroxyl group, and a photopolymerization initiator (D), and the above (A) for the whole composition Provided is a photocurable resin composition having a content of 30 to 45% by weight, a content of (B) of 10 to 25% by weight, and a content of (C) of 25 to 42% by weight.

Invention of Claim 2 provides the photocurable resin composition of Claim 1 whose elastic modulus of the said hardened | cured material is 1.0 * 10 < ⁵ > Pa or more.

The invention according to claim 3 is an elongation until the cured product breaks in a tensile test at an atmospheric temperature of 25 ° C. and a tensile speed of 300 mm / min using a JISK6251 No. 3 dumbbell-shaped test piece having a thickness of 1 mm. The photocurable resin composition according to claim 1 or 2, wherein the rate is 700% or more.

  The invention according to claim 4 further includes the photocurable resin composition according to any one of claims 1 to 3, further comprising a monofunctional acrylate monomer (E) having a linear alkyl group having 10 to 14 carbon atoms. provide.

  The invention according to claim 5 provides a touch panel or flat panel display including the photocurable resin composition according to any one of claims 1 to 4, an image display member, and a plastic cover panel.

A sixth aspect of the present invention provides the flat panel display according to the fifth aspect, wherein the plastic cover panel is a multilayer sheet of polycarbonate and polymethyl methacrylate.

The photocurable resin of the present invention is useful as a transparent resin composition exhibiting good adhesion in bonding a display body and a plastic cover panel.

  The present invention will be described in detail below.

The composition of the present invention comprises a compound (A) having a (meth) acrylic group having a hydrogenated polybutadiene skeleton, a monofunctional (meth) acrylic acid ester monomer (B) having a hydroxyl group, and a hydroxyl group. There are no alicyclic monofunctional (meth) acrylic acid ester monomer (C) and photopolymerization initiator (D). In the present specification, (meth) acrylate includes both acrylate and methacrylate.

Said (A) used by this invention is a base oligomer which comprises a transparent resin composition, for example, is obtained by making the compound which has several isocyanate, and the (meth) acrylate which has a hydroxyl group react with a polyol. The polyol to be used is a hydrogenated polybutadiene system that has high transparency and can impart appropriate flexibility to the molded film. By hydrogenating the polybutadiene skeleton, there is no double bond with high reactivity, and the light resistance against ultraviolet rays or the like can be remarkably improved.

Examples of the isocyanate used in the urethane acrylate include diphenylmethane diisocyanate, tolylene diisocyanate, xylylene diisocyanate, hexamethylene diisocyanate, and isophorone diisocyanate. Among these, aliphatic hexamethylene diisocyanate or isophorone diisocyanate having excellent weather stability is preferable. Examples of the (meth) acrylate having a hydroxyl group include 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 4-hydroxybutyl acrylate, and 2-hydroxyethyl methacrylate. Among these, versatility is high and low molecular weight. And 2-hydroxyethyl acrylate is preferable in that it hardly affects the physical properties of the skeleton.

The weight average molecular weight of (A) is 10,000 to 100,000, more preferably 15,000 to 50,000. If the ratio is less than 10,000, the proportion of the flexible polybutadiene portion is decreased, so that the elongation is decreased, and if it exceeds 100,000, the viscosity of the composition is increased and it is difficult to adjust the viscosity. The weight average molecular weight (hereinafter referred to as “Mw.”) Was measured and calculated by a gel permeation chromatography method using a tetrahydrofuran solvent in a column of a styrene vinyl benzene base material and a molecular weight in terms of standard polystyrene.

The blending amount of (A) with respect to the total composition is 30 to 45% by weight, and more preferably 33 to 40% by weight. If it is less than 30% by weight, sufficient cohesive force and film strength cannot be ensured. Examples of commercially available hydrogenated butadiene-based urethane acrylate include Excelate RX 71-25 (trade name: manufactured by Asia Industrial Co., Ltd., Mw. 26,000).

The (B) used in the present invention is blended in order to dilute the highly viscous (A) and simultaneously increase the curing reactivity, improve the hydrophilicity of the cured film and prevent white turbidity. Polycarbonate, in particular, has a high water vapor permeability, so that moisture can easily be mixed into the cured film, and by mixing (meth) acrylate having a hydroxyl group, the mixed water can be dissolved. The blending amount of (B) with respect to the total composition is 10 to 25% by weight, and more preferably 12 to 20% by weight. If it is less than 10% by weight, the moisture resistance under high temperature and high humidity becomes insufficient, and if it is 25% by weight or more, the haze of the cured product tends to increase.

Examples of (B) include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, and 1,4-cyclohexanedimethanol mono There are acrylate, 4-hydroxycyclohexyl (meth) acrylate, and the like, which 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.

  Said (C) used by this invention is mix | blended in order to raise hardening reactivity and to raise an elasticity modulus simultaneously with diluting (A). The alicyclic structure improves cohesion and improves the elastic modulus. The blending amount of (C) with respect to the total composition is 25 to 42% by weight, and more preferably 30 to 38% by weight. If it is less than 25% by weight, a sufficient elastic modulus cannot be ensured, and if it is 42% by weight or more, the shrinkage of the cured product becomes large and it becomes impossible to follow the warp of the cover panel.

Examples of (C) include isobornyl acrylate, dicyclopentanyl (meth) acrylate, dicyclopentenyl (meth) acrylate, dicyclopentenyloxyethyl (meth) acrylate, adamantanyl (meth) acrylate, and tetrahydrofurfuryl (meth). There are acrylates and the like, and these may be used alone or in combination. Among these, low viscosity and low odor isobornyl acrylate is preferable. In order to easily adjust the viscosity of the blend, the viscosity is desirably 500 mPa · s or less.

  The photopolymerization initiator (D) used in the present invention may be a general-purpose photopolymerization initiator because radicals are generated by irradiation with ultraviolet rays or electron beams, and the radicals trigger a polymerization reaction. Specifically, 2-hydroxy-1- {4- [4- (2-hydroxy-2-methyl-propionyl) -benzyl] phenyl} -2-methyl-propan-1-one, 1-hydroxy-cyclohexyl-phenyl -Ketones, bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide, 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide, 2-hydroxy-2-methyl-1-phenyl-propane-1 -One, 1- [4- (2-hydroxyethoxy) -phenyl] -2-hydroxy-2-methyl-1-propan-1-one, and the like may be used alone or in combination of two or more. The amount is preferably 0.05 to 10% by weight, more preferably 0.1 to 5% by weight, based on the radical polymerizable component.

The elastic modulus in the cured product is preferably 1.0 × 10 ⁵ Pa or more. If it is less than 1.0 × 10 ⁵ Pa, when the plastic cover panel warps in a high-temperature and high-humidity environment, the resin composition cannot follow the deformation, and floating or peeling occurs due to insufficient adhesion. .

  The elongation percentage in the cured product is preferably 700% or more. If it is less than 700%, the resin composition cannot follow the deformation when the plastic cover panel warps in a high-temperature and high-humidity environment, as in the case where the elastic modulus is low. Insufficient float or peeling.

Further, by adding a monofunctional acrylate monomer (E) having a straight chain alkyl group having 10 to 14 carbon atoms, which has good compatibility with the above (A), the transparency is maintained. Viscosity can be adjusted. Examples of (E) include decyl acrylate, lauryl acrylate, tetradecyl acrylate, and the like. Among these, lauryl acrylate having excellent compatibility with (A) and a relatively high glass transition point is preferable. The blending amount of (E) with respect to the total composition is preferably less than 20% by weight, and if it is 20% by weight or more, the cohesive force of the cured film tends to decrease and the elastic modulus tends to decrease.

In addition, the photo-curable resin composition of the present invention is a plasticizer, a tackifier, an antioxidant, a flame retardant, a filler, a silane coupling agent, and a polymerization inhibitor as necessary, as long as the performance is not impaired. Such additives and solvents can be used in combination.

The photocurable resin composition of the present invention can be used as an adhesive for bonding an image display member such as a touch panel or a flat panel display and a cover panel for protecting the image display member. Examples of plastic cover panel materials include PC (polycarbonate) and PMMA (polymethylmethacrylate). Especially when a PMMA sheet with excellent scratch resistance is installed on the surface, warping due to moisture absorption increases, resulting in impact resistance. Warp is suppressed by making it multi-layered with PC which is excellent in the thickness. As the structure of the multilayered sheet, there are, for example, a two-layer structure of PMMA / PC and a three-layer structure of PMMA / PC / PMMA. And scratch resistance can be improved, and outgas from the PC can be suppressed. The thickness of the multilayered sheet is generally 1 mm to 3 mm, but is not particularly specified. Commercially available multilayered sheets include panlite sheets (trade name: manufactured by Teijin Limited), technoloy (trade name: sold by Sumika Acrylic), Shine Tech (Wavelock Advanced, manufactured by Technology Corporation), and the like. The image display body and the cover panel bonded together with the photocurable resin composition of the present invention can be incorporated into an electronic device such as a mobile phone, a tablet terminal, a digital camera, a television, a personal computer monitor, etc. as a display panel for images. it can.

EXAMPLES Hereinafter, although this invention is demonstrated in detail based on an Example and a comparative example, a specific example is shown and it does not specifically limit to these. In addition, when there is no description, it measured on the conditions of 25 degreeC relative humidity 65% of room temperature.

Example 1
As a compound (A) having a (meth) acrylic group having a hydrogenated polybutadiene skeleton, RX71-25 (trade name: hydrogenated butadiene urethane acrylate, Mw. 26,000, manufactured by Asia Industrial Co., Ltd.) is used. As functional (meth) acrylic acid ester monomer (B), 4HBA (trade name: manufactured by Osaka Organic Chemical Industry Co., Ltd., 4-hydroxybutyl acrylate) is used as an alicyclic monofunctional (meth) acrylic acid ester monomer having no hydroxyl group ( IB-XA (trade name: manufactured by Kyoeisha Chemical Co., Ltd., isobornyl acrylate) as C), Irgacure 819 (trade name: manufactured by BASF Japan) as the photopolymerization initiator (D), and monofunctional acrylic having a linear alkyl group LA (trade name: manufactured by Kyoeisha Chemical Co., Ltd., lauryl acrylate) as the acid ester monomer (E) It stirred until it melt | dissolved uniformly by the mixing | blending of Table 1, and the photocurable transparent resin composition of Example 1 was prepared.

Examples 2-4
The materials used in Example 1 were stirred until they were uniformly dissolved according to the formulation shown in Table 1, and the photocurable transparent resin compositions of Examples 2 to 4 were prepared.

Comparative Examples 1-6
In addition to the materials used in the examples, as a hydrogenated polybutadiene-based urethane acrylate, RX71-44 (trade name: hydrogenated butadiene-based urethane acrylate, Mn. 4,000, manufactured by Asia Kogyo Co., Ltd.) is used as (B). Until HOA (N) (trade name: manufactured by Kyoeisha Chemical Co., Ltd., 2-hydroxyethyl acrylate) is monofunctional acrylate and DMAA (trade name: manufactured by KJ Chemicals Co., Ltd., dimethylacrylamide) is uniformly dissolved in the formulation shown in Table 1. The photocurable transparent resin composition of Comparative Examples 1-6 was prepared by stirring.

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.

Viscosity: Measured using a cone plate viscometer RC-550R manufactured by Toki Sangyo Co., Ltd. with a cone angle of 3 ° × R17.65 at 25 ± 1 ° C. and a rotation speed of 1 rpm, and 1,000 to 10,000 mPa · s The case where it was out of this range was marked as x.

Elastic modulus: The storage elastic modulus of shear shear mode at 25 ° C. and 1 Hz was measured by using HAAKERheoStress 600 (Thermo Scientific) using Sample B with a diameter of 20 mmΦ, and ◯ is below 1.0 × 10 ⁵ Pa and below. It was.

Elongation rate: A sample obtained by punching a composition having a thickness of 1 mm cured under the above ultraviolet curing conditions with a No. 3 dumbbell mold in accordance with JIS K6251 is used as a test piece. Using a tensile / compression tester Technograph TGI-1kN, the distance between chucks was set to 70 mm, a tensile test was performed at a crosshead speed of 300 mm / min, and the elongation was calculated from the displacement until breaking. The calculation formula is as follows. The elongation is 700% or more, and the following is x.
Elongation rate (%) = displacement at break (length) ÷ 70 mm × 100
Example) When breaking without elongation: 70mm ÷ 70mm × 100 = 100%

  Cover panel adhesion: 1 mm thick, 100 × 100 mm glass plate coated with 200 μm thick resin composition on one side, 1 mm thick, 110 × 110 mm plastic cover panel pan line sheet PCHA-51 (trade name) : Teijin Ltd., double-sided hard-coated PMMA and PC laminate), the glass plate and the cover panel are bonded together with the resin composition, and cured from the glass plate side by UV irradiation under the above UV curing conditions. The sample was used as a test piece. After standing for 100 hours in a high-temperature and high-humidity environment of 85 ° C x 85% RH, the appearance is visually checked after standing at room temperature for 12 hours. If there is no abnormality such as lifting or peeling, ○, did.

Haze (before treatment): Using a haze meter HAZEGAED2 (manufactured by Gardner), the haze value of the sample used in the above cover sheet floating test before the high temperature and high humidity environment treatment was measured, and the haze of the cover sheet and glass was subtracted. A change value of 1.0% or less was marked with ◯, and a change value exceeding x was marked with ×.

Haze (after treatment): Using a haze meter HAZEGAED2 (manufactured by Gardner), the haze value after the high temperature and high humidity environment treatment of the sample used in the above cover sheet floating test was measured, and the haze of the cover sheet and glass was subtracted. A change value of 1.0% or less was marked with ◯, and a change value exceeding x was marked with ×.

Evaluation results <br/> Table 2

Each resin composition of the examples obtained good results in all evaluations of viscosity, elastic modulus, elongation, cover panel adhesion and haze.

On the other hand, Comparative Example 1 in which (A) exceeds the upper limit, Comparative Example 2 in which (B) exceeds the upper limit, Comparative Example 3 in which (C) exceeds the upper limit, Comparative Example 4 using ureac having a small weight average molecular weight, (C Comparative Examples 5 and 6 that do not contain) have problems in any of the evaluation items of viscosity, elastic modulus, elongation, cover panel adhesion, and haze, and are not suitable for the present invention.

INDUSTRIAL APPLICABILITY The present invention is useful as a transparent resin composition that is a visibility improving resin that exhibits good adhesion in bonding a display body such as an image display display and a plastic cover panel, and does not generate floating.

Claims (6)

A compound (A) having a (meth) acrylic group having a hydrogenated polybutadiene skeleton having a weight average molecular weight of 10,000 to 100,000, a monofunctional (meth) acrylic acid ester monomer (B) having a hydroxyl group, and a hydroxyl group The alicyclic monofunctional (meth) acrylic acid ester monomer (C) that does not contain a photopolymerization initiator (D), and the content (A) relative to the entire composition is 30 to 45% by weight The photocurable resin composition wherein the content of (B) is 10 to 25% by weight and the content of (C) is 25 to 42% by weight. The photocurable resin composition of Claim 1 whose elastic modulus of the said hardened | cured material is 1.0 * 10 < ⁵ > Pa or more.   Using a JIS K6251 No. 3 dumbbell-shaped test piece having a thickness of 1 mm, the cured product has an elongation rate of 700% or more until it breaks in a tensile test at an atmospheric temperature of 25 ° C. and a tensile speed of 300 mm / min. The photocurable resin composition of Claim 1 or 2.   The photocurable resin composition according to any one of claims 1 to 3, further comprising a monofunctional acrylate monomer (E) having a linear alkyl group having 10 to 14 carbon atoms. A touch panel or flat panel display comprising the photocurable resin composition according to claim 1, an image display member, and a plastic cover panel. 6. The flat panel display according to claim 5, wherein the plastic cover panel is a multilayer sheet of polycarbonate and polymethyl methacrylate.