JP2018024785A - Uv curable type resin composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a UV curable type resin composition which can easily peel LCD from an adherend even at normal temperature and rework the LCD, and can impart good adhesiveness, and to provide an adhesive sheet containing the same.SOLUTION: A UV curable type resin composition contains (A) a UV curable type prepolymer, (B) a UV curable type polyfunctional monomer, (C) a photopolymerization initiator and (D) a silane coupling agent, where the component (A) is urethane(meth)acrylate, and a content of the component (B) is 15-60 pts.mass, a content of the component (C) is 0.5 pts.mass or more and a content of the component (D) is 0.1-5 pts.mass with respect to 100 pts.mass of the component (A).SELECTED DRAWING: None

Description

  The present invention relates to a UV curable resin composition that can be used in a liquid crystal display portion and an adhesive sheet containing the same.

At present, liquid crystal displays (LCDs) have become very common display devices with the spread of digitized electronic devices, such as liquid crystal televisions, PC displays, mobile phone terminals, portable game consoles, calculators, watches, It is used as a display unit for various devices. In particular, in recent years, there has been an LCD obtained by adhering a patterned retardation plate made of glass for the purpose of imparting a 3D function.
Here, the LCD to which the retardation plate is bonded may be collected after use, and only the LCD may be reused. For example, it is required to remove the retardation plate from the LCD and rework the LCD. At this time, in the conventional method, the entire LCD is cooled (in other words, the adhesive is cooled), and the retardation plate is peeled off from the LCD. However, this method requires equipment for cooling and cannot be said to have good workability. Furthermore, since both the retardation film and the LCD have rigidity, there is a problem that one of them is damaged when it is peeled off. In other words, it has been difficult for the conventional adhesive sheet to be easily peeled off after the LCD and the retardation plate are bonded, and to rework the LCD.
In order to solve such problems, an adhesive sheet that can be easily peeled even at room temperature and even if the adherend is as hard as glass has been studied. For example, Patent Document 1 proposes a transparent adhesive film containing an adhesive component and a gas generating agent that generates gas when irradiated with ultraviolet rays. Patent Document 2 proposes a thermal and actinic radiation curable (photocurable) adhesive composition.

JP, 2006-56244, A Special table 2011-508814 gazette

  However, the transparent adhesive film described in Patent Document 1 needs to be exposed during rework, and the actinic radiation curable (photo-curable) adhesive composition described in Patent Document 2 is heated during rework. The adhesive is removed by cutting the adhesive with a wire. That is, there has been a situation in which an adhesive sheet capable of easily peeling off the LCD at normal temperature from an adherend has not been obtained so far while ensuring good adhesiveness.

  In view of the above circumstances, the present invention is a UV curable resin composition capable of easily peeling off an LCD from an adherend even at room temperature and reworking it, and imparting good adhesiveness, and It aims at providing the adhesive sheet containing.

  As a result of intensive studies to solve the above problems, the present inventors have found that (A) a UV curable prepolymer, (B) a UV curable polyfunctional monomer, (C) a photopolymerization initiator, (D ) Silane coupling agent, the component (A) is urethane (meth) acrylate, and the content of the component (B) is 15 to 60 masses per 100 parts by mass of the component (A). UV curable resin composition in which the content of the component (C) is 0.5 parts by mass or more and the content of the component (D) is 0.1 to 5 parts by mass can solve the above problems. The present invention was completed.

That is, the present invention is as follows.
[1]
(A) a UV curable prepolymer, (B) a UV curable polyfunctional monomer, (C) a photopolymerization initiator, and (D) a silane coupling agent,
The component (A) is urethane (meth) acrylate,
The content of the component (B) is 15 to 60 parts by mass with respect to 100 parts by mass of the component (A), the content of the component (C) is 0.5 parts by mass or more, and the content of the component (D) UV curable resin composition whose quantity is 0.1-5 mass parts.
[2]
The urethane (meth) acrylate is one or more selected from the group consisting of a urethane (meth) acrylate having a polycarbonate skeleton, a urethane (meth) acrylate having a polyether skeleton, and a urethane (meth) acrylate having a polyester skeleton. The UV curable resin composition according to the above [1].
[3]
The UV curing according to the above [1] or [2], wherein the urethane (meth) acrylate has a weight average molecular weight of 10,000 to 100,000 and a double bond equivalent of 1,000 to 5,000 g / eq. Mold resin composition.
[4]
The UV curable resin composition according to any one of [1] to [3], wherein the (B) UV curable polyfunctional monomer is a (meth) acrylic monomer having two or more functional groups.
[5]
The UV curable resin composition according to any one of [1] to [4], wherein the (C) photopolymerization initiator is an acylphosphine oxide photopolymerization initiator.
[6]
The UV curable resin composition according to the above [5], wherein the acylphosphine oxide photopolymerization initiator is 2,4,6-trimethylbenzoyldiphenylphosphine oxide.
[7]
The UV curable resin composition according to any one of [1] to [6] above, wherein the (D) silane coupling agent is a silane coupling agent having a (meth) acryl group.
[8]
The adhesive sheet containing the UV curable resin composition in any one of said [1]-[7].
[9]
The adhesive sheet according to [8] above, wherein the film thickness after drying is 10 to 250 μm.
[10]
A 3D liquid crystal panel in which an LCD and a patterning retardation plate are laminated,
A 3D liquid crystal panel in which the LCD and the retardation plate are adhered by the adhesive sheet according to the above [8] or [9].
[11]
The 3D liquid crystal panel according to [10], wherein the patterning retardation plate is a glass plate on which a pattern is formed.

  The adhesive sheet containing the UV curable resin composition of the present invention can be easily reworked by peeling off the LCD from the adherend even at room temperature, and can provide good adhesion.

  Hereinafter, modes for carrying out the present invention (hereinafter referred to as “the present embodiment”) will be described in detail. In addition, this invention is not limited to the following embodiment, It can implement by changing variously within the range of the summary.

The UV curable resin composition in this embodiment is
(A) a UV curable prepolymer, (B) a UV curable polyfunctional monomer, (C) a photopolymerization initiator, and (D) a silane coupling agent,
The component (A) is urethane (meth) acrylate,
The content of the component (B) is 15 to 60 parts by mass with respect to 100 parts by mass of the component (A), the content of the component (C) is 0.5 parts by mass or more, and the content of the component (D) The amount is 0.1 to 5 parts by mass.

[(A) UV curable prepolymer]
The UV curable resin composition in the present embodiment includes (A) a UV curable prepolymer (hereinafter also referred to as “component (A)”). The UV curable prepolymer is not particularly limited as long as it is a urethane (meth) acrylate having a urethane structure in the main chain and a (meth) acryl group in the side chain. The urethane (meth) acrylate is not particularly limited, and examples thereof include a urethane (meth) acrylate having a polycarbonate skeleton, a urethane (meth) acrylate having a polyether skeleton, a urethane (meth) acrylate having a polyester skeleton, and the like. Among these, urethane (meth) acrylate having a polycarbonate skeleton is preferable from the viewpoint of non-yellowing of the cured adhesive sheet.

  The urethane (meth) acrylate having a polycarbonate skeleton refers to a prepolymer having a polycarbonate structure and a urethane structure in the main chain and a (meth) acryl group in the side chain. A urethane (meth) acrylate having a polycarbonate skeleton can be obtained, for example, by reacting a polycarbonate diol, a diisocyanate, and a carboxylic acid diol and then reacting glycidyl (meth) acrylate.

  The weight average molecular weight of the polycarbonate diol is preferably 170 to 1,000, more preferably 300 to 700, and still more preferably 400 to 600. When the weight average molecular weight of the polycarbonate diol is in the above range, the urethane prepolymer main chain tends to have film properties necessary for rework.

  The diisocyanate is not particularly limited, and for example, 2,4-tolylene diisocyanate (2,4-TDI), 2,6-tolylene diisocyanate (2,6-TDI), 4,4′-diphenylmethane diisocyanate (4 , 4'-MDI), 2,4'-diphenylmethane diisocyanate (2,4'-MDI), 1,4-phenylene diisocyanate, xylylene diisocyanate (XDI), tetramethylxylylene diisocyanate (TMXDI), tolidine diisocyanate (TODI) ), Aromatic isocyanates such as 1,5-naphthalene diisocyanate (NDI); hexamethylene isocyanate (HDI), trimethylhexamethylene diisocyanate (TMHDI), lysine diisocyanate, norbornane diisocyanate Aliphatic polyisocyanates such as methyl (NBDI); alicyclic polyisocyanates such as transcyclohexane-1,4-diisocyanate, isophorone diisocyanate (IPDI), H6XDI (hydrogenated XDI), etc., among others, optical properties (yellow Hexamethylene diisocyanate is preferable from the viewpoint of difficulty in transformation.

  The carboxylic acid diol is not particularly limited, and examples thereof include dimethylolbutanoic acid and dimethylolpropionic acid.

  The urethane (meth) acrylate having a polyether skeleton refers to a prepolymer having a polyether structure and a urethane structure in the main chain and having a (meth) acryl group in the side chain. ) Acrylate refers to a prepolymer having a polyester structure and a urethane structure in the main chain and a (meth) acryl group in the side chain. These prepolymers can be obtained by the same method as the urethane (meth) acrylate having the above polycarbonate skeleton, except that polyether diol and polyester diol are used instead of polycarbonate diol, respectively. At this time, the preferable weight average molecular weight of polyether diol and polyester diol is the same as the preferable weight average molecular weight of polycarbonate diol mentioned above.

(A) The weight average molecular weight of a component becomes like this. Preferably it is 10,000-100,000, More preferably, it is 30,000-70,000, More preferably, it is 40,000-60,000. When the weight average molecular weight is in the above range, the film-forming property and curability are good, and the long-term reliability tends to be good.
Here, the weight average molecular weight refers to a value measured by gel permeation chromatography (GPC) using standard polystyrene having an average molecular weight of about 500 to about 1,000,000.

The double bond equivalent of the component (A) is preferably 1,000 to 5,000 g / eq, more preferably 1,500 to 2,500 g / eq, still more preferably 1,800 to 2,200 g. / Eq. When the double bond equivalent is in the above range, the effect of curing shrinkage is small, the long-term reliability is excellent, the curing is easy, and the rework tends to be easy.
Here, the double bond equivalent means a value calculated by the solid content mass (g) of the carboxyl group-containing (meth) acrylate / the number of moles of the compound having an oxirane ring and an ethylenically unsaturated bond (g / mol).

(A) The glass transition temperature (Tg) of a component becomes like this. Preferably it is -10-20 degreeC, More preferably, it is -5-15 degreeC, More preferably, it is 0-10 degreeC. If the glass transition temperature is in the above range, the balance between long-term reliability and reworkability tends to be good.
Here, the glass transition temperature refers to a value measured by dynamic viscoelasticity measurement (DMA).

[(B) UV curable polyfunctional monomer]
The UV curable resin composition in the present embodiment contains (B) a UV curable polyfunctional monomer (hereinafter also referred to as “component (B)”). In order to enable LCD rework, it is necessary to increase the viscoelasticity at room temperature, but in this embodiment, by adding a UV curable polyfunctional monomer to the UV curable prepolymer, The crosslink density is increased to increase the viscoelasticity at room temperature. Here, the viscoelasticity of the UV curable resin composition can be measured by dynamic viscoelasticity measurement (DMA), and preferably the storage elastic modulus at room temperature (25 ° C.) after curing is 1.0 × 10. ^{8 to} 1.0 × 10 ¹⁰ Pa, more preferably 4.0 × 10 ^{8 to} 5.0 × 10 ⁹ Pa, and still more preferably 6.0 × 10 ^{8 to} 3.0 × 10 ⁹ Pa. is there.

  The component (B) is not particularly limited, and examples thereof include (meth) acrylic monomers. Among these, (meth) acrylic having two or more functional groups from the viewpoint of increasing the crosslinking density and improving the reworkability. Monomers are preferred.

  Specifically, as the component (B), those having two functional groups include 1,4-butanediol di (meth) acrylate, ethylene glycol di (meth) acrylate, glycerin di (meth) acrylate, tri Cyclodecane dimethanol diacrylate is exemplified, and those having three functional groups include trimethylolpropane triacrylate, trimethylolmethane tri (meth) acrylate, trimethylolpropane propylene oxide modified tri (meth) acrylate, Examples of those having four or more functional groups include dipentaerythritol tetra (meth) acrylate, pentaerythritol ethylene oxide modified tetra (meth) acrylate, pentaerythritol tetra (meth) acrylate, and pentaerythritol ethylene oxide. Modified tetra (meth) acrylate, ditrimethylolpropane tetra (meth) acrylate, dipentaerythritol hexaacrylate and the like. Among them, (meth) acrylic monomers having four or more functional groups are preferable from the viewpoint of reworkability. Dipentaerythritol hexaacrylate having 6 functional groups is more preferable.

  (A) Content of (B) component with respect to 100 mass parts of components is 15-60 mass parts, Preferably it is 18-40 mass parts, More preferably, it is 20-30 mass parts. When the content of the component (B) is less than 15 parts by mass, the adhesiveness after curing is high and the reworkability at room temperature is inferior, and when it exceeds 60 parts by mass, the adhesiveness is not sufficient and long-term reliability Inferior. In addition, when the content of the component (B) with respect to 100 parts by mass of the component (A) is adjusted to the above range, the melt viscosity of the resin composition is maintained in a certain range, so that bonding unevenness and image disturbance are caused. There is an advantage that it is difficult to occur.

[(C) Photopolymerization initiator]
The UV curable resin composition in the present embodiment contains (C) a photopolymerization initiator (hereinafter also referred to as “component (C)”). The photopolymerization initiator is not particularly limited. For example, any photopolymerization initiator such as an acylphosphine oxide photopolymerization initiator, an alkylphenone photopolymerization initiator, and an intramolecular hydrogen abstraction photopolymerization initiator can be used. Among them, acylphosphine oxide photopolymerization initiators are preferable from the viewpoints of reactivity and uniformity of curing. Specific examples include 2,4,6-trimethylbenzoylphenylphosphine oxide, 2,2-dimethoxy-1,2-diphenylethane-1-one, phenylglyoxylic acid methyl ester, etc. Among them, radical generation From the viewpoint of high efficiency and deep curability, 2,4,6-trimethylbenzoylphenylphosphine oxide is preferable.

  (A) Content of (C) component with respect to 100 mass parts of component is 0.5 mass part or more, Preferably it is 1.0 mass part or more, More preferably, it is 1.5 mass part or more. (C) When content of a photoinitiator is above, hardening reactivity becomes favorable and it exists in the tendency for rework property and long-term reliability to improve. The upper limit of the content of the component (C) is not particularly limited, but if it is too large, the optical properties tend to deteriorate, and therefore it is preferably 7.0 parts by mass or less.

[(D) Silane coupling agent]
The UV curable resin composition in the present embodiment further includes (D) a silane coupling agent (hereinafter also referred to as “(D) component”) in addition to the components (A) to (C). As described above, the UV curable resin composition of the present embodiment includes a UV curable polyfunctional monomer, thereby increasing viscoelasticity at room temperature and enabling LCP rework. On the other hand, when the viscoelasticity is high, the adhesiveness with the adherend tends to decrease. In this embodiment, adhesive force is maintained by including a silane coupling agent in the UV curable resin composition, and long-term reliability is improved particularly when the adherend is a glass plate.

  (D) It does not specifically limit as a component, For example, any silane coupling agents, such as a monomer type silane coupling agent, an alkoxy oligomer type silane coupling agent, and a polyfunctional silane coupling agent, can be used. Among them, a silane coupling agent having a (meth) acryl group is preferable from the viewpoint of improving adhesion when the adherend is glass and maintaining long-term reliability, and 3-acryloxypropyltrimethoxysilane is more preferable. preferable.

  (A) Content of (D) component with respect to 100 mass parts of component is 0.1-5 mass parts, Preferably it is 0.5-3.0 mass parts, More preferably, 0.5-1. 5 parts by mass. When the content of component (D) is in the above range, the balance between long-term reliability and reworkability tends to be good.

[Other ingredients]
In addition to the components (A) to (D) described above, the UV curable resin composition in the present embodiment includes various fillers such as silica, alumina, hydrated alumina, antioxidants, ultraviolet absorbers, and light stabilizers. In addition, additives such as an antistatic agent, a leveling agent, an antifoaming agent, a color pigment, and an organic solvent, which are usually added to an adhesive, may be included.

[Adhesive sheet]
The adhesive sheet in this embodiment contains the UV curable resin composition described above. Specifically, for example, after applying and drying a resin composition on a protective film such as PET, by providing a protective film on the opposite side, an adhesive sheet having protective films on both sides is obtained. Can do. In particular, the UV curable resin composition is preferably made into a varnish using an organic solvent, and then applied onto a protective film and dried. The organic solvent used at this time is not particularly limited, and examples thereof include toluene, methyl ethyl ketone, cyclohexanone, propylene glycol monomethyl ether, dimethylacetamide and the like. Of these, methyl ethyl ketone is preferable from the viewpoint of solubility. Moreover, the content of the organic solvent in the varnish is preferably 30 to 90 parts by mass, and more preferably 40 to 70 parts by mass with respect to 100 parts by mass of the component (A).

  The protective film is not particularly limited, and includes, for example, a film made of one or more resins selected from the group consisting of polyethylene terephthalate, polyethylene naphthalate, and polybutylene terephthalate. Therefore, a film made of polyethylene terephthalate resin is preferable.

  The protective film may be subjected to a release treatment on the surface to which the resin composition is applied. Since the release treatment is performed on the protective film, the protective film can be easily peeled at the time of use, so that the handleability is improved. The release treatment is not particularly limited. For example, a release agent such as a silicone release agent, a fluorine release agent, a long-chain alkyl graft polymer release agent, a surface treatment method by plasma treatment, etc. Can be used.

  As a method of applying the UV curable resin composition to the protective film, a comma coater, a die coater, a gravure coater, or the like can be appropriately employed depending on the coating thickness.

  Drying of the UV curable resin composition can be carried out with an in-line dryer or the like, and the drying conditions at that time can be appropriately adjusted depending on the type and amount of each component. The thickness of the adhesive sheet after drying is preferably 10 to 250 μm, more preferably 25 to 125 μm, and still more preferably 30 to 75 μm. When the thickness of the adhesive sheet is within the above range, the adhesiveness is good and the long-term reliability is improved. In the present embodiment, the long-term reliability specifically means that the adhesion between the LCD and the patterning phase difference plate is good, so that it is difficult for the deviation to occur, and the result observer can observe a good 3D image. Including that. Furthermore, when the thickness of the adhesive sheet is within the above range, the distance between the LCD and the patterning phase difference plate is appropriate, and an appropriate viewing angle can be secured when a 3D image is viewed.

[3D LCD panel]
The 3D liquid crystal panel in the present embodiment is obtained by laminating an LCD and a patterning retardation plate, and the LCD and the retardation plate are bonded by the adhesive sheet in the present embodiment. The 3D liquid crystal panel can be obtained, for example, by pasting an adhesive sheet on a retardation plate, pasting an LCD on top of the adhesive sheet, and further curing the adhesive sheet by UV irradiation.

As the patterning retardation plate, a glass plate on which a pattern is formed can be used.
In addition, the UV curable resin composition in the present embodiment can be used not only for the application of the 3D liquid crystal panel but also for all applications assuming reworking a display device such as an LCD or an organic EL. Examples of such applications include touch sensor panels and digital signage.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further more concretely, this invention is not limited only to these Examples.

The components and materials used in Examples and Comparative Examples are as follows.
[(A) component: UV curable prepolymer]
According to the following synthesis examples 1 to 3 and comparative synthesis example 1, UV curable prepolymers (a) to (d) were produced.

[(B) component: UV curable polyfunctional monomer]
(1) UV curable polyfunctional monomer (a)
Dipentaerythritol hexaacrylate, manufactured by Daicel Ornex, product name "DPHA"
(2) UV curable polyfunctional monomer (b)
Tricyclodecane dimethanol diacrylate, manufactured by Daicel Ornex Co., Ltd., product name “IRR214-K”
(3) UV curable polyfunctional monomer (c)
Trimethylolpropane triacrylate, product name “TMPTA” manufactured by Daicel Ornex Co., Ltd.
(4) UV curable polyfunctional monomer (d)
Ethoxylated phenyl acrylate (monofunctional)
Product name "EBECRYL110" manufactured by Daicel Ornex

[(C) component: photopolymerization initiator]
(1) Photopolymerization initiator (a)
2,4,6-Trimethylbenzoylphenylphosphine oxide manufactured by BASF, trade name “Irgacure TPO”, acylphosphine oxide photopolymerization initiator (2) photopolymerization initiator (b)
2,2-dimethoxy-1,2-diphenylethane-1-one manufactured by BASF, trade name “Irgacure 651”, alkylphenone photopolymerization initiator (3) photopolymerization initiator (c)
Phenylglyoxylic acid methyl ester manufactured by BASF, trade name “Irgacure MBF”, intramolecular hydrogen abstraction type photopolymerization initiator

[(D) component: silane coupling agent]
(1) Silane coupling agent (a)
Monomer type silane coupling agent, manufactured by Shin-Etsu Chemical Co., Ltd., trade name “KBM-5103”, 3-acryloxypropyltrimethoxysilane (2) silane coupling agent (b)
Alkoxy oligomer type silane coupling agent, trade name “KR-513” manufactured by Shin-Etsu Chemical Co., Ltd.
(3) Silane coupling agent (c)
Multifunctional silane coupling agent, trade name “X-12-1050” manufactured by Shin-Etsu Chemical Co., Ltd.

  Each evaluation method and measurement method are as follows.

[Reworkability]
(1) Sample preparation procedure The one-sided PET film of the adhesive sheet was peeled off and bonded to glass (0.7 t, 19 inches) by lamination, and autoclaved. Lamination is carried out using a roll laminate at a lami roll temperature of 25 to 40 ° C., a lami roll linear pressure of 1.0 to 2.0 kgf / cm, and a lami roll speed of 0.3 to 2.0 m / min. The autoclave is at a temperature of 60 ° C. and a pressure The test was carried out at 0.6 MPa for 10 minutes. The other PET film was peeled off, bonded by LCD and vacuum lamination, autoclaved again, and then UV-exposed to obtain a test sample. The vacuum lamination was performed at a temperature of 25 to 50 ° C., a pressure of 0.01 to 0.05 MPa, a vacuum drawing of 60 s, and a pressure of 30 s. The autoclave was carried out at a temperature of 60 ° C., a pressure of 0.6 MPa, and a time of 1 hr. The UV exposure was performed using an ultra-high pressure mercury lamp light source so that the integrated light amount was 3000 mJ / cm ² .
(2) Measurement method After leaving the test sample at room temperature for 24 hours or more, the adherend (glass, LCD) after the glass was peeled off was observed and evaluated according to the following.
◎: The adherend was not damaged and could be easily reworked ○: The adherend was not damaged and rework was possible ×: Rework was difficult

[Adhesiveness]
(1) Sample preparation procedure A test sample was prepared by the same procedure as the reworkability.
(2) Measuring method The test sample was left standing in a humidifier. The conditions were a temperature of 50 ° C., a humidity of 80% and a time of 240 hours. Then, it was left at room temperature for 24 hours. The difference in the glass bonding position when compared with the start of standing in a humidifier, the presence or absence of floating and foaming were observed and evaluated according to the following.
○: Misalignment, float, and foaming of glass did not occur. ×: Misalignment, float, and foaming of glass occurred.

[Adhesiveness]
(1) Sample preparation procedure A test sample was prepared by the same procedure as the reworkability.
(2) Measuring method The display of the test sample was turned on and evaluated according to the following.
○: Bonding unevenness and 3D displacement did not occur in the display image (no double image was generated)
X: Bonding unevenness and 3D shift occurred in the display image (there was a double image)

[optical properties]
(1) Sample preparation procedure The one-sided PET film of the adhesive sheet was peeled off and bonded to optical glass (40 mm square) by vacuum lamination. The vacuum lamination was performed at a temperature of 25 to 50 ° C., a pressure of 0.01 to 0.05 MPa, a vacuuming of 10 s, and a pressure of 10 s. The other PET film was peeled off and bonded to an optical glass under the same conditions as the above vacuum lamination, then subjected to autoclave treatment, and then UV exposed to obtain a test sample. The autoclave was carried out at a temperature of 60 ° C., a pressure of 0.6 MPa, and a time of 1 hr. The UV exposure was performed using an ultra-high pressure mercury lamp light source so that the integrated light amount was 3000 mJ / cm ² .
The yellow index (YI) of the test sample was measured using a spectrophotometer (U-4100 manufactured by Hitachi High Technology). The measurement conditions were C light source, transmission, wavelength λ = 380 to 760 nm.
◎: YI value less than 1.5 ○: YI value 1.5 value or more and less than 2 ×: YI value 2 or more

(Synthesis Example 1) UV curable prepolymer (a)
In a four-necked flask equipped with a thermometer, a condenser, and a stirrer, 33.3 parts by mass of hexamethylene diisocyanate (product name: HDI, abbreviated name: HDI, manufactured by Tosoh Corporation) and polycarbonate diol 59 having a weight average molecular weight of 400 .4 parts by mass, 7.3 parts by mass of dimethylolbutanoic acid, 1 part by mass of an organic tin compound such as dibutyltin laurate as a catalyst, and 100 parts by mass of methyl ethyl ketone as an organic solvent are put in a reaction vessel, and the mixture is kept at 70 ° C. for 24 hours. Reacted.
In order to confirm the reaction state of the obtained synthesized product, analysis was performed using an IR measuring instrument. In the IR chart, it was confirmed that the NCO characteristic absorption (2270 cm ⁻¹ ) of the composite had disappeared, and it was confirmed that the composite was a urethane acrylate having a carboxyl group.
Next, 100 parts by weight of the urethane acrylate having a carboxyl group, 7.1 parts by weight of glycidyl methacrylate, 0.7 parts by weight of triethylamine as a catalyst, and 0.05 parts by weight of hydroquinone as a polymerization inhibitor are used in a reaction vessel. The mixture was reacted at 75 ° C. for 12 hours and subjected to addition reaction to obtain a UV curable prepolymer (a).
The addition reaction was terminated when the acid value measured according to the following method became 5 mgKOH / g or less. The obtained UV curable prepolymer (a) had a weight average molecular weight of 50,000, a solid content concentration of 50% by mass, a double bond equivalent of 2,000 g / eq, and a Tg of 5 ° C.

(Acid value measuring method)
Weigh 1 g of resin solids, add mixed solvent (mass ratio: toluene / methanol = 50/50), add appropriate amount of phenolphthalein solution as indicator after dissolution, and titrate with 0.1N aqueous potassium hydroxide solution. The acid value was measured by the following formula (α).
x = 10 × Vf × 56.1 / (Wp × I) (α)
(In the formula (α), x represents an acid value (mgKOH / g), Vf represents a titration amount (mL) of a 0.1 N KOH aqueous solution, Wp represents the mass (g) of the measured resin solution, I represents the ratio of non-volatile content in the measured resin solution (mass%).)

(Synthesis Example 2) UV curable prepolymer (b)
A UV curable prepolymer (b) was obtained in the same manner as in Synthesis Example 1 except that polyether diol was used instead of polycarbonate diol.

(Synthesis Example 3) UV curable prepolymer (c)
A UV curable prepolymer (c) was obtained in the same manner as in Synthesis Example 1 except that polyester diol was used instead of polycarbonate diol.

(Comparative Synthesis Example 1) UV curable prepolymer (d)
A reaction vessel equipped with a stirrer, a thermometer, a dropping funnel, and a nitrogen introduction tube was charged with 100.0 g of methoxypropanol propylene glycol monomethyl ether (PGM) as a polymerization solvent, and the temperature was raised to 80 degrees with stirring under a nitrogen stream. . 13.5 parts by weight of styrene, 67 parts by weight of ethyl acrylate, 11.5 parts by weight of acrylic acid, and 0.5 g of azobisisobutyronitrile as a radical polymerization initiator were mixed at 80 ° C. It was dripped from the dropping funnel over 3 hours while keeping the temperature. After completion of dropping, the reaction solution was heated to 90 ° C. while stirring, and further stirred for 2 hours while maintaining the temperature of the reaction solution at 90 ° C. to obtain a copolymer.
Next, 100 parts by mass of the copolymer obtained, 7.8 parts by mass of glycidyl methacrylate, 0.8 part by mass of triethylamine as a catalyst, and 0.05 part by polymerization of hydroquinone as a polymerization inhibitor were put in a reaction vessel, and 100 A UV curable prepolymer (d) was obtained by reacting at 12 ° C. for 12 hours and carrying out an addition reaction.
The addition reaction was terminated when the acid value became 5 mgKOH / g or less. Moreover, the obtained UV curable prepolymer (d) had a weight average molecular weight of 45,000, a solid content concentration of 47% by mass, and a Tg of 3 ° C.

Example 1
(1) Preparation of UV curable resin composition In a reaction vessel, 100 parts by mass of UV curable prepolymer (a) is added, and further 25 parts by mass of UV curable polyfunctional monomer (a), a photopolymerization initiator. (A) 1.5 parts by mass, 1 part by mass of a silane coupling agent (a), and 140 parts by mass of methyl ethyl ketone as a solvent were added and stirred to obtain a resin composition.
(2) Preparation of adhesive sheet After the resin composition obtained in (1) above was applied on a 38 μm PET film so that the thickness after drying was 30 μm or more, and dried at 130 ° C. for 5 minutes. A PET film was also installed on the opposite side, and an adhesive sheet provided with a PET film on both sides was obtained.
Using the obtained adhesive sheet, reworkability, adhesiveness, bonding property, and optical properties were evaluated.

(Examples 2 to 20), (Comparative Examples 1 to 7)

A UV curable resin composition and an adhesive sheet were obtained in the same manner as in Example 1 except that the type and content of each component were changed as described in Tables 1 to 3.
Using the obtained adhesive sheet, reworkability, adhesiveness, bonding property, and optical properties were evaluated.

  The adhesive sheet containing the UV curable resin composition of the present invention has industrial applicability as an adhesive for a liquid crystal display or the like.

Claims (11)

(A) a UV curable prepolymer, (B) a UV curable polyfunctional monomer, (C) a photopolymerization initiator, and (D) a silane coupling agent,
The component (A) is urethane (meth) acrylate,
The content of the component (B) is 15 to 60 parts by mass with respect to 100 parts by mass of the component (A), the content of the component (C) is 0.5 parts by mass or more, and the content of the component (D) UV curable resin composition whose quantity is 0.1-5 mass parts.   The urethane (meth) acrylate is one or more selected from the group consisting of a urethane (meth) acrylate having a polycarbonate skeleton, a urethane (meth) acrylate having a polyether skeleton, and a urethane (meth) acrylate having a polyester skeleton. The UV curable resin composition according to claim 1.   The UV curable resin composition according to claim 1 or 2, wherein the urethane (meth) acrylate has a weight average molecular weight of 10,000 to 100,000 and a double bond equivalent of 1,000 to 5,000 g / eq. object.   The UV curable resin composition according to any one of claims 1 to 3, wherein the (B) UV curable polyfunctional monomer is a (meth) acrylic monomer having two or more functional groups.   The UV curable resin composition according to any one of claims 1 to 4, wherein the (C) photopolymerization initiator is an acylphosphine oxide photopolymerization initiator.   The UV curable resin composition according to claim 5, wherein the acylphosphine oxide photopolymerization initiator is 2,4,6-trimethylbenzoyldiphenylphosphine oxide.   The UV curable resin composition according to claim 1, wherein the (D) silane coupling agent is a silane coupling agent having a (meth) acryl group.   The adhesive sheet containing the UV curable resin composition of any one of Claims 1-7.   The adhesive sheet of Claim 8 whose film thickness after drying is 10-250 micrometers. A 3D liquid crystal panel in which an LCD and a patterning retardation plate are laminated,
A 3D liquid crystal panel in which the LCD and the retardation film are bonded by the adhesive sheet according to claim 8.   The 3D liquid crystal panel according to claim 10, wherein the patterning retardation plate is a glass plate on which a pattern is formed.