TW201900799A - Active energy ray-curable adhesive sheet for optical members - Google Patents

Abstract

Provided is a novel adhesive sheet capable of not only realizing both a low dielectric constant and an excellent absorbing property for a stepped portion in a print, but also exceptional handling characteristics as adhesive sheet. An active-energy-ray-curing adhesive sheet containing an acrylic resin (A), wherein the acrylic resin (A) has an active-energy-ray-crosslinking structural unit, and is a (co)polymer of a monomer component including a (meth)acrylic acid ester monomer (a) having a C10 to 24 linear alkyl group, the active-energy-ray-curing adhesive sheet for an optical member having at least all of the following characteristics (1) to (3). (1) A tensile elasticity of 0.03 MPa or higher at a temperature of 23 DEG C (2) A displacement length of 1 mm in a holding power test in which the adhesive sheet is adhered to a stainless steel plate with an adhesion area of 25 mm * 20 mm and a load of 500 gf (4.9 N) is applied for 30 minutes (3) A relative dielectric constant of 3.7 or less at a frequency of 100 kHz.

Description

Active energy ray hardening type adhesive sheet for optical member

The present invention relates to an adhesive sheet having a relatively low dielectric constant and excellent level absorptivity and operability (for example, cutting properties, secondary processability, and storage properties). Among them, it is preferable to form an image display device such as a personal computer, a mobile terminal (PDA), a game machine, a television (TV), a car navigation system, a touch panel, a handwriting tablet, or the like. The optical member used is an active energy ray-curable adhesive sheet.

In recent years, an image display device equipped with a touch sensor function, particularly an image display device equipped with a touch sensor function of an electrostatic capacitance method, has been popularized mainly in a mobile phone or a mobile terminal.

This type of electrostatic capacitance type touch sensor detects the proximity of a conductive object such as a finger from the side of the surface protection panel, and changes the electrostatic capacitance of the capacitor formed between the two electrodes facing through the insulating film to detect the position. Touch sensor.

However, with the recent thinning of components, if the distance between the electrode and the surface of the protective panel is narrowed, and the change in the electrostatic capacitance corresponding to the touch becomes large, the detection signal is prone to noise. Therefore, in order to absorb the change in touch detection sensitivity and suppress the generation of noise of the detection signal for the adhesive sheet used in the filling between the electrode and the surface protection panel, a low dielectric constant of the adhesive sheet is required.

In addition, with the weight reduction or cost reduction of electrodes, electrode substrates are being replaced by glass with resin films. In the case of an electrode in which a conductive thin film is patterned only on one side, two film electrodes, or a glass electrode and a film electrode must be laminated through an adhesive sheet or the like. The adhesive sheet used at this time is also required. Reduced dielectric constant.

As a low-dielectric-constant adhesive sheet, for example, Patent Document 1 discloses a double-sided adhesive sheet, which is characterized by containing an acrylic compound (A) whose relative dielectric constant at a frequency of 100 kHz is 3.0. The following; and an acrylate copolymer (B), in which a (meth) acrylic acid ester monomer and / or a vinyl ether monomer having a linear or branched alkyl group having 1 to 9 carbon atoms in a side chain is copolymerized And get.

According to such a double-sided adhesive sheet, by using a low-dielectric constant acrylic compound (A) having a relative dielectric constant of 3.0 or less at a frequency of 100 kHz, not only the relative dielectric constant of the entire sheet can be reduced, but also Since the whole adhesive sheet can have a crosslinked structure, handling properties (easy handling) can also be improved, and for example, the shape of the sheet can be maintained even when heated. Further, an acrylate copolymer obtained by copolymerizing (meth) acrylate monomers and / or vinyl ether monomers having an alkyl group having 1 to 9 carbon atoms having a linear or branched side chain. B), can obtain better adhesion characteristics, for example, the bonded members will not be foamed or peeled off due to environmental changes such as temperature and humidity, and can have moderate elasticity or depression recovery.

In addition, Patent Document 2 discloses an adhesive that is characterized by including a (meth) acrylic polymer having a carbon number of 8 to 24 by including an ester terminal. Polymerization of the monomer components of the (meth) acrylic acid alkyl ester (a1) of a branched alkyl group and the (meth) acrylic acid alkyl ester (a2) having a linear alkyl group having 8 to 24 carbon atoms at the end of the ester And get.

According to such an adhesive, by the action of the long-chain branched alkyl group and the long-chain linear alkyl group, an adhesive layer with a low dielectric constant can be realized, and the adhesion performance can be satisfied.

Thus, attempts have been made so far to maintain the original function of the adhesive sheet and to reduce the dielectric constant of the adhesive sheet.

In addition, an image display device of a touch panel method is generally configured by combining a surface protection panel, a touch panel, and an image display panel (also collectively referred to as a “composition member for an image display device”).

In recent years, the surface protection panel of an image display device of a touch panel method such as a smart phone or a tablet terminal is made of a plastic material such as an acrylic resin plate or a polycarbonate plate together with tempered glass. The other peripheral parts are printed in black.

In addition, in the touch panel, a plastic film sensor is used together with a glass sensor, or a component that integrates a touch panel function with a surface protection panel (such as TOL), or uses a touch panel. The function of the control panel is integrated as a component of the image display panel (such as an inline type or a table type).

In the field of image display devices centered on mobile phones or mobile terminals, in addition to thinning and high-precision, design diversification has also been performed. Previously, black prints were generally framed on the peripheral edge of the surface protection panel. The concealed part, but with the diversification of design, the frame-shaped concealed part started to be formed by a color other than black. In the case where the concealed portion is formed by a color other than black, the concealability is low. Therefore, the height of the concealed portion, that is, the printed portion tends to be higher than that of black. Therefore, it is required that the adhesive sheet for laminating the constituent members provided with such a printing section follow a large printing step and be filled everywhere.

Therefore, various methods for covering the printing step have been proposed since before. For example, Patent Document 3 discloses a UV-crosslinkable adhesive sheet, which is a (meth) acrylic copolymer containing a (meth) acrylate-containing monomer having a UV-crosslinkable site, And the storage elastic modulus of the adhesive sheet before ultraviolet crosslinking is 5.0 × 10 ⁴ Pa or more and 1.0 × 10 ⁶ Pa or less at 30 ° C. and 1 Hz, and 5.0 × at 80 ° C. or 1 Hz Below 10 ⁴ Pa, the storage elastic modulus of the adhesive sheet after ultraviolet crosslinking is 1.0 × 10 ³ Pa or higher at 130 ° C. and 1 Hz.

According to such an adhesive sheet, by the heating and / or pressing in the stage before the ultraviolet crosslinking, even if the thickness is equal to the height of the step or the bulge (for example, 20 to 30 μm), it can sufficiently follow As a result of the step or bulge, as a result, voids and the like are not generated near the step or bulge, and the internal residual stress of the adhesive sheet near the step or bulge does not become uselessly high. In addition, by bonding the adhesive sheet to the adherend and then performing ultraviolet crosslinking, it is possible to achieve highly reliable adhesion. Thereby, the thickness of the laminated body including the adherend can be suppressed to be thin, and bonding without defects such as voids or uneven color of the liquid crystal can be achieved. Prior Art Literature Patent Literature

Patent Literature 1: Japanese Patent Laid-Open No. 2015-040240 Patent Literature 2: Japanese Patent Laid-Open No. 2013-194170 Patent Literature 3: Japanese Patent Laid-Open No. 2011-184582

[Problems to be solved by the invention]

The adhesive sheet disclosed in the above-mentioned Patent Document 1 or Patent Document 2 maintains the original function of the adhesive sheet, and seeks to lower the dielectric constant of the adhesive sheet, but does not consider the printing step absorbency.

In addition, it is considered that when considering the absorption of the printing step, like the adhesive sheet disclosed in the aforementioned Patent Document 3, the adhesive sheet is imparted with flexibility, although it is thin (for example, 30 to 50 μm), but imparted with flexibility. Excellent printing step absorptivity. However, if the printing step absorptivity is taken into consideration, the workability (for example, cutability, secondary processability, and storage stability) may deteriorate. In addition, the adhesive sheet of the above-mentioned Patent Document 3 does not consider reduction of the dielectric constant.

Therefore, an object of the present invention is to provide not only a low dielectric constant and excellent printing step absorptivity, but also excellent handling properties (such as cutability, secondary processability, and storage stability) as an adhesive sheet. The novel adhesive sheet. [Technical means to solve the problem]

The main feature of the present invention is that it is an active energy ray-curable adhesive sheet containing an acrylic resin (A), and the acrylic resin (A) contains an active energy ray crosslinkable structure portion and has a carbon number The (co) polymer of a monomer component of a linear alkyl (meth) acrylate monomer (a) of 10 to 24 is as follows.

The present invention provides an active energy ray-curable adhesive sheet for an optical member, which contains an acrylic resin (A), and the acrylic resin (A) contains an active energy ray crosslinkable structure portion and has a carbon number. The (co) polymer of a monomer component of a linear alkyl (meth) acrylate monomer (a) of 10 to 24, the optical member has at least the following (1) to an active energy ray-curable adhesive sheet (3) All characteristics. (1) The tensile modulus of elasticity at a temperature of 23 ° C is 0.03 MPa or more. (2) Based on a 25 mm × 20 mm bonding area attached to a stainless steel plate. A load of 500 gf (4.9 N) is applied in the vertical direction. 30 minutes of holding force test with an offset length of 1 mm or more (3) The relative dielectric constant at 100 kHz is 3.7 or less

The present invention also proposes an active energy ray-curable adhesive sheet for an optical member, which contains an acrylic resin (A), and the acrylic resin (A) contains an active energy ray crosslinkable structure and has A (co) polymer of a monomer component of a linear alkyl (meth) acrylate monomer (a) having 10 to 24 carbon atoms, the optical member is made of at least one sheet using an active energy ray-curable adhesive sheet The surface has a region including the above-mentioned acrylic resin (A) having a different storage elastic modulus G ′ at a frequency of 1 Hz and a temperature of 20 ° C. in the thickness direction, and the relative dielectric constant at a frequency of 100 kHz is 3.7 or less. [Effect of the invention]

The active energy ray-curable adhesive sheet for an optical member of the present invention can achieve both low dielectric constant characteristics and excellent printing step absorbency. In addition, it is also excellent in operability (such as cutability, secondary processability, and storage) as an adhesive sheet, and thus can be used to form, for example, a personal computer, a mobile terminal (PDA), a game machine, a television (TV), and a car navigation system. Image display devices such as systems, touch panels, handwriting pads, etc. are preferably used.

Hereinafter, the embodiment of the present invention will be described in detail, but the following description is an example (representative example) of the embodiment of the present invention, and the present invention is not limited by these contents.

In addition, "(meth) acrylic acid" includes the meanings of acrylic acid and methacrylic acid, and "(meth) acrylfluorenyl" includes the meanings of acrylic and methacrylfluorene, respectively, and "(meth) "Acrylate" includes the meaning of acrylate and methacrylate respectively, and "(co) polymer" includes the meaning of polymer and copolymer. The "sheet" includes a sheet, a film, and an adhesive tape conceptually.

活性 Active energy ray-curable adhesive sheet for optical member≫ The active energy ray-curable adhesive sheet for optical member of the present invention (hereinafter, also referred to as "the present adhesive sheet") contains an acrylic resin (A), and the acrylic Resin (A) is a (co) polymer containing a monomer component of a (meth) acrylic acid ester monomer (a) having a linear alkyl group of 10 to 24 having an active energy ray crosslinkable structural site .

Moreover, this adhesive sheet has at least all the characteristics of the following (1)-(3).

(1) The tensile modulus of elasticity at a temperature of 23 ° C is 0.03 MPa or more. (2) Based on a bonding area of 25 mm × 20 mm in length to a stainless steel plate. 500 gf (4.9 N) is applied in the vertical direction. The deflection length of the holding force test under load for 30 minutes is 1 mm or more. (3) The relative dielectric constant at a frequency of 100 kHz is 3.7 or less.

By having the above-mentioned characteristics, the adhesive sheet can achieve both low dielectric constant characteristics and excellent printing step absorptivity, and can ensure the operability (e.g., cuttability, secondary processability, storage stability) of the adhesive sheet. ).

This adhesive sheet is a (co) polymer containing a monomer component of a (meth) acrylate monomer (a) having a linear alkyl group having 10 to 24 carbon atoms and having an active energy ray crosslinkable structure site. As the acrylic resin (A), an adhesive sheet having a reduced dielectric constant and a tensile elastic modulus or a holding force adjusted in a specific range can be obtained.

(Tensile elastic modulus) The tensile elastic modulus of the adhesive sheet at a temperature of 23 ° C is 0.03 MPa or more. By setting the tensile elastic modulus in such a range, excellent operability can be ensured. From such a viewpoint, the tensile elastic modulus of the present adhesive sheet is preferably 0.03 MPa or more and 1.0 MPa or less, and more preferably 0.03 MPa or more and 0.5 MPa or less.

(Retention force) The offset length of this adhesive sheet based on the above-mentioned retention force test is 1 mm or more. With an offset length of 1 mm or more, it is possible to have printing step absorptivity. From such a viewpoint, the above-mentioned offset length of the present adhesive sheet is preferably 1.0 mm or more and 20 mm or less. The offset length obtained by the holding force test is a value obtained by a method described in the following examples.

This adhesive sheet uses a specific acrylic resin (A) to have a soft property with an offset length of 1 mm or more and a tough property with a tensile elastic modulus of 0.03 MPa or more. In this way, by using the specific acrylic resin (A), the present adhesive sheet can achieve a low dielectric constant, and although it is relatively soft, it has excellent operability such as cutting properties, and has the opposite of printing step absorption and operability. nature. More specifically, by having the above-mentioned characteristics (1) to (3) and adopting an adhesive sheet design composed of a laminated layer as described below, it is possible to have higher printing step absorptivity and operability.

For example, by using a specific acrylic resin (A) and forming a region having a different storage elastic modulus G ′ at a frequency of 1 Hz and a temperature of 20 ° C. from the surface of at least one sheet in the thickness direction, a higher level can be achieved. Expresses printing step absorptivity and operability.

In addition, the tensile elastic modulus refers to the value obtained by the method described in the following examples, and the storage elastic modulus G 'means the storage elastic modulus when the dynamic viscoelasticity is measured by the shear mode. , Refers to the value obtained by the method described in the following examples.

The above-mentioned regions having different storage elastic modulus G 'refer to, for example, a case where two or more layers with different storage elastic modulus G' are included; or although there is no clear interface between layers, there is a storage elastic modulus G ' Different parts of the situation.

Examples of the region including the acrylic resin (A) having different storage elastic modulus G ′ include, for example, at least n layers including the acrylic resin (A), and the first layer and the i-th layer have a frequency of 1 Hz. The forms in which the storage elastic modulus G 'at a temperature of 20 ° C are different from each other (hereinafter, also referred to as "laminated structure"). Among them, n and i are each independently an integer of 2 or more.

In the laminated structure, the i-th layer preferably has a storage elastic modulus G ′ at a frequency of 1 Hz and a temperature of 20 ° C. of 40 kPa or more and 1 MPa or less. By the i-th layer being in the range of the storage elastic modulus G ', the adhesive sheet itself can be made plastic, preventing the adhesive resin from attaching to the punching die or the slit blade, and the adhesive material is wound to the cutting end. The peeling film cannot be peeled off or the end paste overflows.

In the above aspect, the first layer preferably has a storage elastic modulus G ′ at a frequency of 1 Hz and a temperature of 20 ° C. of 30 kPa or more and 70 kPa or less. Since the first layer is in the range of the storage elastic modulus G ′, it has the advantages of following the printing step, or reducing the optical strain near the unevenness after bonding.

The above-mentioned storage elastic modulus G ′ is in addition to changing the type, molecular weight, and composition ratio of each component constituting the adhesive sheet, and can also adjust the amount of active energy ray exposure or the amount of cross-linkable structural sites of the active energy ray. Alternatively, the amount of the cross-linking agent is adjusted, and the degree of cross-linking is adjusted, thereby setting it within the above range.

Among these, it is preferable to contain the following acrylic resin (A).

(Laminated Structure) The present adhesive sheet having the laminated structure has a structure in which n or more layers are laminated. Specifically, the laminated sheet may include a first layer / second layer, a first layer / second layer / third layer, and a second layer. Layer 1/2 / ... / i layer. Moreover, it is not necessary that all layers are adhesive layers, and it is preferred that at least the first (surface layer) and / or the nth layer (back layer) be an adhesive layer.

Therefore, for example, a structure in which the first layer and the second (i = 2) layer include the above-mentioned acrylic resin (A) (n = 2, i = 2), or n is 3, except that n is 2. A three-layer structure and the first layer and the second layer (i = 2) include the form (n = 3, i = 2) of the acrylic resin (A) described above, and may also be a three-layer structure with n of 3 and the first The layer and the third layer (i = 3) include the form (n = 3, i = 3) of the acrylic resin (A).

In the above configuration, in terms of ease of production, a two-layer configuration in which n is 2 and the first layer and the second layer (i = 2) preferably include the above-mentioned acrylic resin (A) (n = 2). (I = 2); and n is a three-layer structure of 3, and the first and second layers (i = 2) include the above-mentioned acrylic resin (A) (n = 3, i = 2).

In terms of making the adhesive sheet itself plastic by an intermediate layer having a moderate hardness, and ensuring step followability by a soft surface layer and a back layer, the present adhesive sheet composed of the above-mentioned laminated layers is most preferably The intermediate layer includes the form of the above-mentioned acrylic resin (A) with respect to the surface layer and the back layer, and the storage elastic modulus G 'of the surface layer and the back layer is different from that of the intermediate layer.

Based on the above, it is preferable that n and i are each independently an integer of 2 or more. When n is 2, n is the same as i, and when n is 3 or more, the relationship of n> i is satisfied.

Based on the above, the present adhesive sheet preferably has a two-layer structure with n being 2 and the first layer and the second layer (i = 2) include the acrylic resin (A) (n = 2, i = 2), and the first The storage elastic modulus G 'of the layer at a frequency of 1 Hz and a temperature of 20 ° C is more than 30 kPa and less than 70 kPa. The storage elastic modulus of the second layer at a frequency of 1 Hz and a temperature of 20 ° C is 40 kPa and more. 1 MPa or less; and preferably a three-layer structure with n of 3 and the first and second layers (i = 2) include the acrylic resin (A) (n = 3, i = 2), and the first layer is The storage elastic modulus G 'at a frequency of 1 Hz and a temperature of 20 ° C is 30 kPa to 70 kPa, and the storage elastic modulus G' of the second layer at a frequency of 1 Hz and a temperature of 20 ° C is 40 kPa and 1 MPa. the following. At this time, the storage elastic modulus G 'of the third layer at a frequency of 1 Hz and a temperature of 20 ° C may be the same as or different from the first layer, and more preferably the same.

(Thickness of the Adhesive Sheet) The thickness of the present adhesive sheet is preferably in the range of 20 μm to 500 μm (except for the case where a substrate sheet is provided). For example, if the thickness is 20 μm or more, the adhesion to the adherend or the shock absorption is not hindered, and if it is 500 μm or less, it can meet the requirements for thinning. Therefore, the thickness of the present adhesive sheet is preferably 20 μm to 500 μm, and more preferably 30 μm or more or 300 μm or less, and more preferably 50 μm or more or 200 μm or less.

In the present adhesive sheet composed of the above-mentioned laminated layers, the ratio of the thickness of the i-th layer (S2) to the total thickness of the first and n-th layers, that is, the total thickness of the surface layer and the back layer (S1) (( S1) / (S2)) is 0.05 ≦ (S1) / (S2) ≦ 2. By setting such a thickness ratio, the help of the thickness of the surface layer and the back layer in the laminated body will not become too large, it will not be too soft, and the workability such as cutting or handling is poor, so it is better. In addition, the followability to the uneven or curved surface is not deteriorated, and the adhesion or wettability to the adherend can be maintained, which is preferable. From this perspective, the ratio of the thickness (S2) of the i-th layer to the total thickness (S1) of the surface layer and the back layer is more preferably 0.1 ≦ (S1) / (S2) ≦ 2, and more preferably 0.1 ≦ ( S1) / (S2) ≦ 1.

(Relative Dielectric Constant) The present adhesive sheet preferably has a relative dielectric constant of 3.7 or less at a frequency of 100 kHz. With a relative dielectric constant of 3.7 or less, the adhesive sheet can function as an insulating layer, and reduce the loss of high-frequency electrical signals such as touch signals. In this respect, the relative dielectric constant of the present adhesive sheet is more preferably 3.5 or less, and even more preferably 3.2 or less. The relative dielectric constant is a value obtained by a method described in the following examples.

<Acrylic resin (A)> This adhesive sheet contains an acrylic resin (A).

The acrylic resin (A) is preferably a monomer component (a) containing a monomer component of a (meth) acrylate monomer (a) having a linear alkyl group having 10 to 24 carbon atoms having a site having an active energy ray crosslinkable structure. Co) polymer. In addition, the active energy ray crosslinkable structure portion is irradiated with the active energy ray and can react with a part of the acrylic resin (A) or a hardening component other than the acrylic resin (A) to form a crosslinked structure. Structural parts.

Examples of the active energy ray crosslinkable structural site include, for example, a radical polymerizable functional group having a carbon-carbon double bond, such as a functional group having an unsaturated double bond, such as a (meth) acrylfluorenyl group and a vinyl group. Structure; or, for example, a benzophenone structure and the like can be excited by ultraviolet radiation, and in this excited state deprived of hydrogen radicals. In addition, during active energy ray irradiation, in addition to far-ultraviolet rays, ultraviolet rays, near-ultraviolet rays, infrared rays and other electromagnetic waves, X-rays, gamma rays and other electromagnetic waves, electron beams, proton rays, neutron rays, etc. can also be used to harden the speed. In terms of availability, price, etc. of the irradiation device, it is advantageous to use ultraviolet rays for hardening.

In order to introduce a structure containing a radically polymerizable functional group having a carbon-carbon double bond, such as a functional group having an unsaturated double bond, for example, it is necessary to make it have an acrylic resin such as 2-isocyanatoethyl (meth) acrylate The functional group in which the functional group in the reaction is reacted and the monomer having an unsaturated double bond may react with the functional group in the acrylic resin. In addition, in order to introduce a person that can be excited by ultraviolet radiation and deprive of hydrogen radicals in this excited state, a (meth) acrylate monomer (α) containing an active energy ray crosslinkable structural site is used as a copolymerization component. Copolymerization is sufficient.

As the (meth) acrylic acid ester monomer (α) containing a cross-linkable structure site of active energy ray, it is preferable that an efficient cross-linking structure can be formed by active energy rays such as ultraviolet rays and electron beams. It contains a (meth) acrylic acid ester monomer which has a benzophenone structure, Specifically, 4- (meth) acryl methoxy benzophenone etc. are mentioned.

The content of the (meth) acrylic acid ester monomer (α) containing a cross-linkable structural site of the active energy ray is preferably 0.01 to 5% by mass with respect to the entire copolymerization component. Among them, it has a benzophenone structure. The content of the (meth) acrylic acid ester monomer is preferably 0.01 to 5% by mass, more preferably 0.1 to 2% by mass, and still more preferably 0.2 to 1% by mass based on the entire copolymerization component. When the content is too small, the holding force when the crosslinked structure is formed by the active energy ray tends to decrease. When the content is too large, the cohesive force of the entire system tends to be excessively increased and the adhesive force tends to be reduced.

Since the acrylic resin (A) has an active energy ray crosslinkable structural site, the acrylic resin (A) can be effectively hardened (crosslinked). In addition, the acrylic resin (A) can improve cohesion even if it does not contain an acid component. Can have excellent foaming reliability (Among them, excellent ultraviolet (UV) foaming reliability). In this respect, the active energy ray crosslinkable structural site is preferably a benzophenone structure.

Examples of the (meth) acrylate monomer (a) having a linear alkyl group having 10 to 24 carbon atoms include, for example, decyl (meth) acrylate (carbon number 10 of alkyl group), (meth) Lauryl acrylate (carbon number 12), tridecyl (meth) acrylate (carbon number 13), cetyl (meth) acrylate (carbon number 16), stearyl (meth) acrylate ( Carbon number 18), behenyl (meth) acrylate (carbon number 22), and the like. These can be used alone or in combination of two or more. It should be noted that a hydroxyl group-containing single system as a (meth) acrylate monomer having a linear alkyl group having 10 to 24 carbon atoms is regarded as the following (b).

In addition, in the straight-chain (meth) acrylic acid alkyl ester monomer (a) having an alkyl group having 10 to 24 carbon atoms, the dielectric constant can be lowered or the glass transition temperature of the acrylic resin can be reduced. In terms of use, an alkyl methacrylate is preferred, and an alkyl group having 12 to 20 carbon atoms is particularly preferred, and stearyl methacrylate, lauryl methacrylate, and tridecane methacrylate are most preferred. Based ester.

The content of the alkyl (meth) acrylate monomer (a) having a linear alkyl group having 10 to 24 carbon atoms is 50 to 94% by mass, and preferably 60 to 83% by mass relative to the entire (co) polymerization component. %, Particularly preferably 70 to 80% by mass. By setting it as the said range, there exists no possibility that a dielectric constant becomes high, or the thermal stability of resin may fall.

(Hydroxy-containing (meth) acrylate monomer) The acrylic resin (A) preferably further contains a hydroxyl-containing (meth) acrylate monomer (b) in terms of improvement in moisture and heat whitening resistance. A copolymer of a monomer component which is a monomer component other than the above (a).

Examples of the hydroxyl-containing (meth) acrylate monomer (b) include 2-hydroxyethyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, and 5-hydroxy (meth) acrylate. Hydroxyalkyl acrylates such as amyl ester, 6-hydroxyhexyl (meth) acrylate, and 8-hydroxyoctyl (meth) acrylate; caprolactones such as caprolactone-modified 2-hydroxyethyl (meth) acrylate Modified monomers; oxyalkylene modified monomers such as diethylene glycol (meth) acrylate, polyethylene glycol (meth) acrylate; in addition to this, 2-propenyloxy Primary hydroxyl-containing monomers such as ethyl-2-hydroxyethyl phthalate, N-hydroxymethyl (meth) acrylamide, hydroxyethylacrylamide; 2-hydroxypropyl (meth) acrylate, Secondary hydroxyl-containing monomers such as 2-hydroxybutyl (meth) acrylate and 3-chloro-2-hydroxypropyl (meth) acrylate; 2,2-dimethyl-2-hydroxyethyl (meth) acrylate Tertiary hydroxyl-containing monomers. These can be used alone or in combination of two or more.

Among the above, in terms of excellent reactivity with a cross-linking agent and improvement in moist heat and whitening resistance, a primary hydroxyl-containing monomer is preferred, and further, impurities such as di (meth) acrylate are small. In terms of ease of production, 2-hydroxyethyl acrylate and 4-hydroxybutyl acrylate are preferred, and 4-hydroxybutyl acrylate is particularly preferred.

The content ratio of the hydroxyl group-containing (meth) acrylate monomer (b) in the copolymerization component is preferably 5 to 15% by mass, and particularly preferably 8 to 14% by mass, with respect to the entire copolymerization component. It is more preferably 10 to 13% by mass. By setting it as the said range, there is no possibility that a moist-heat whitening resistance may fall or a dielectric constant may become high.

Moreover, as content ratio of the said monomer component (a) and (b) in a copolymerization component, (a) is 50-94 mass%, and (b) is 5-15 mass%.

The free acid contained in the acrylic resin (A) is preferably 1.0% or less, particularly preferably 0.5% or less, and further preferably 0.1% or less. By setting it as the said range, there is no possibility that thermal stability may fall or the metal system to be adhered may be corroded at the time of manufacture of an adhesive sheet. Thus, in order to reduce the free acid content in the acrylic resin (A), it is sufficient to reduce the free acid contained in the hydroxyl group-containing (meth) acrylate monomer (b), and its content is preferably 1.0% or less. It is particularly preferably 0.5% or less, and more preferably 0.1% or less.

The acrylic resin (A) preferably contains a (meth) acrylic acid alkyl monoester having a branched chain-containing alkyl group in terms of keeping the dielectric constant low and efficiently improving cohesion. The copolymer (c) is a monomer component that is a monomer component other than the above (b). When the (meth) acrylic acid alkyl ester monomer having a branched alkyl group has a hydroxyl group, the (meth) acrylic acid ester monomer (b) containing a hydroxyl group is considered.

Examples of the (meth) acrylic acid alkyl ester monomer (c) having a branched alkyl group include, for example, a branched chain monomer having a tertiary carbon in the alkyl group; or a branched group containing a third butyl group. Chain monomer and so on.

A branched single-chain system with tertiary carbon in the alkyl group can efficiently perform hydrogen abstraction and improve cohesion during photocrosslinking. The third-butyl (meth) acrylate-containing branched chain has a third butyl group. Single system can increase cohesion by increasing glass transition temperature. Among them, as the (meth) acrylic acid alkyl ester monomer having a branched alkyl group, it is preferable to use isobutyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, (methyl The third butyl acrylate is particularly preferably 2-ethylhexyl (meth) acrylate or the third butyl (meth) acrylate.

The content ratio (weight ratio) of (a) and (c) in the copolymerization component in the copolymerization component is preferably 100/0 to 70/30, particularly preferably 100/0 to 80/20, and more preferably It is 90/10 to 85/15. By setting it as the said range, there is no possibility that thermal stability may fall or adhesive property may fall.

The acrylic resin (A) may be a copolymer containing, as a copolymerization component, another copolymerizable ethylenically unsaturated monomer as a monomer component, if necessary.

Examples of other ethylenically unsaturated monomers that can be copolymerized include phenyl (meth) acrylate, benzyl (meth) acrylate, phenoxyethyl (meth) acrylate, and phenyl diethylene glycol. Alcohol (meth) acrylate, 2-hydroxy-3-phenoxypropyl (meth) acrylate, phenoxy polyethylene glycol (meth) acrylate, phenoxy polyethylene glycol-polypropylene glycol- Aromatic ring-containing monomers such as (meth) acrylate, o-phenylphenoxyethyl (meth) acrylate, and nonylphenol ethylene oxide adduct (meth) acrylate; (meth) acrylic ring Hexyl ester, cyclohexyloxyalkyl (meth) acrylate, tert-butylcyclohexyloxyethyl (meth) acrylate, isopropyl (meth) acrylate, dicyclopentyl (meth) acrylate And other alicyclic monomers; 2-methoxyethyl (meth) acrylate, 2-ethoxyethyl (meth) acrylate, 3-methoxybutyl (meth) acrylate, (meth) 2-butoxyethyl acrylate, 2-butoxydiethylene glycol (meth) acrylate, methoxydiethylene glycol (meth) acrylate, methoxytriethylene glycol (methyl) Acrylate, ethoxy diethylene glycol (meth) acrylate, Methoxydipropylene glycol (meth) acrylate, methoxypolyethylene glycol (meth) acrylate, octyloxyethylene glycol-polypropylene glycol-mono (meth) acrylate, dodecyloxy Ether-containing monomers such as polyethylene glycol mono (meth) acrylate and stearyloxy polyethylene glycol mono (meth) acrylate; acrylic acid dimerization such as (meth) acrylic acid and β-carboxyethyl acrylate Compounds, butenoic acid, maleic acid, maleic anhydride, fumaric acid, citraconic acid, glutaric acid, itaconic acid, N-glycolic acid, cinnamic acid, etc .; (Meth) acrylamide, N- (n-butoxyalkyl) (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N, N-diethyl (methyl Methyl) acrylamide, N, N-dimethylaminoalkyl (meth) acrylamine and other amine-containing monomers; dimethylaminoethyl (meth) acrylate, (meth) acrylic acid Diethylaminoethyl or its quaternary compound, and other amine-containing monomers; in addition, acrylonitrile, methacrylonitrile, styrene, α-methylstyrene, vinyl acetate, and propylene Acid vinyl ester, vinyl stearate, vinyl chloride, vinylidene chloride, alkane Vinyl vinyl ether, vinyl toluene, vinyl pyridine, vinyl pyrrolidone, dialkyl ikonate, dialkyl fumarate, allyl alcohol, allyl chloride, methyl vinyl Ketones, N-acrylamidomethyltrimethylammonium chloride, allyltrimethylammonium chloride, dimethylallyl vinyl ketone, and the like. These can be used alone or in combination of two or more. From the viewpoint of resistance to metal corrosion, the acrylic resin (A) preferably does not contain an acid component such as a carboxyl group.

The said acrylic resin (A) can be manufactured by superposing | polymerizing suitably selecting the said polymerization component. As the polymerization method of the acrylic resin (A), for example, conventionally known polymerization methods such as solution polymerization, suspension polymerization, block polymerization, and emulsion polymerization can be used. In the present invention, it can be safely and stably composed of an arbitrary monomer. In terms of producing the acrylic resin (A), it is preferably produced by solution polymerization.

An example of a preferred method for producing the acrylic resin (A) used in the present invention is shown below. First, a copolymerization component and a polymerization initiator are mixed or dropped in an organic solvent, and solution polymerization is performed to obtain an acrylic resin (A) solution.

(Organic solvent) Examples of the organic solvent used in the polymerization reaction include aromatic hydrocarbons such as toluene and xylene; aliphatic hydrocarbons such as hexane; esters such as ethyl acetate and butyl acetate; N- Aliphatic alcohols such as propanol and isopropanol; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, etc. Among these solvents, it is preferable to use a solvent having a boiling point of 70 ° C. or less from the point that the solvent can be distilled off from the acrylic resin solution obtained by the solution polymerization to efficiently produce a solvent-free acrylic resin. Solvent.

Examples of the organic solvent having a boiling point of 70 ° C or lower include hydrocarbon solvents such as n-hexane (67 ° C), alcohol solvents such as methanol (65 ° C), and esters such as methyl acetate (54 ° C). Solvents, ketone solvents such as acetone (56 ° C), diethyl ether (35 ° C), dichloromethane (40 ° C), tetrahydrofuran (66 ° C), etc. Among them, in terms of versatility or safety, Preferably, acetone and methyl acetate are used, and acetone is particularly preferably used. In addition, the numerical value in () after the name of each organic solvent mentioned above is a boiling point.

(Polymerization initiator) As the polymerization initiator used in the above-mentioned polymerization reaction, an azo-based polymerization initiator or a peroxide-based polymerization initiator, which is a general radical polymerization initiator, can be used as the polymerization initiator. Examples of the azo-based polymerization initiator include 2,2'-azobis (2-methylbutyronitrile), 2,2'-azobisisobutyronitrile, and (1-phenylethyl) coupler. Azodiphenylmethane, 2,2'-azobis (2,4-dimethylvaleronitrile), 2,2'-azobis (2-cyclopropylpropionitrile), 2,2'-azo Examples of the peroxide-based polymerization initiator include nitrogen bis (4-methoxy-2,4-dimethylvaleronitrile), and the like include benzamidine peroxide, ditributyl peroxide, and hydrogen. Cumene peroxide, lauryl peroxide, third butyl pervalerate, third hexyl pervalerate, third hexyl peroxypivalate, diisopropyl percarbonate, peroxy Diisobutyrium oxide and the like. These can be used individually or in combination of 2 or more types.

In the production of the above-mentioned acrylic resin (A), it is preferred to use a reaction solvent for solution polymerization with a boiling point of 70 ° C. or lower, and carry out the polymerization at a relatively low temperature. At this time, if a polymerization initiator having a high half-life temperature of 10 hours is used, it is easy to remain the polymerization initiator. If the polymerization initiator is remained, the solvent is distilled off from the acrylic resin (A) solution described below. The acrylic resin tends to gel during the step.

Therefore, from the viewpoint of stably performing the step of distilling off the solvent from the acrylic resin (A) solution obtained by the solution polymerization, it is preferred that the above-mentioned polymerization initiator is used for a half-life temperature of less than 10 hours. Polymerization initiators at 60 ° C, of which 2,2'-azobis (2,4-dimethylvaleronitrile) (52 ° C), 2,2'-azobis (2-cyclopropane) are preferred Propionitrile) (49.6 ° C), 2,2'-azobis (4-methoxy2,4-dimethylvaleronitrile) (30 ° C), tert-butyl pervalerate (54.6 ° C) ), Tert-hexyl pivalate (53.2 ° C), tert-hexyl peroxyneodecanoate (44.5 ° C), diisopropyl peroxycarbonate (40.5 ° C), diisobutylphosphonium peroxide (32.7 ℃), particularly preferably 2,2'-azobis (2,4-dimethylvaleronitrile) (52 ° C), and trihexyl pivalate (53.2 ° C). In addition, the numerical value in () after the name of each compound is the 10-hour half-life temperature of each compound.

The amount of the polymerization initiator used is usually 0.001 to 10 parts by mass, preferably 0.1 to 8 parts by mass, more preferably 0.5 to 6 parts by mass, and even more preferably 1 to 100 parts by mass of the polymerization component. 4 parts by mass, particularly preferably 1.5 to 3 parts by mass, and most preferably 2 to 2.5 parts by mass. By setting it as the said range, there exists no possibility that the polymerization rate of an acrylic resin may fall, or residual monomer may increase, or the weight average molecular weight of an acrylic resin may become high.

(Polymerization conditions, etc.) Regarding the polymerization conditions for solution polymerization, the polymerization may be performed according to conventionally known polymerization conditions. For example, a polymerization component containing a (meth) acrylic monomer and a polymerization initiator may be mixed or dropped in a solvent. Polymerization is carried out under specific polymerization conditions.

The polymerization temperature in the above-mentioned polymerization reaction is usually 40 to 120 ° C. In terms of allowing the reaction to proceed stably, it is preferably 50 to 90 ° C, more preferably 55 to 75 ° C, and particularly preferably 60 to 70 ° C. By setting it as the said range, there is no possibility that an acryl-type resin (A) will gel easily, or the activity of a polymerization initiator will fall, and a polymerization rate will fall, and a residual monomer may increase.

The polymerization time in the polymerization reaction (the time before the start of the shrinking heating when the following shrinking heating is performed) is not particularly limited, and it is 0.5 hours or more from the last addition of the polymerization initiator. It is preferably at least 1 hour, more preferably at least 2 hours, and even more preferably at least 5 hours. In addition, in terms of easy removal of heat, the polymerization reaction is preferably performed while refluxing the solvent.

In the production of the acrylic resin (A), in order to reduce the amount of the residual polymerization initiator, it is preferable to perform longitudinal heating to thermally decompose the polymerization initiator.

The longitudinal heating temperature is preferably performed at a temperature higher than the 10-hour half-life temperature of the polymerization initiator. Specifically, it is usually 40 to 150 ° C. In terms of suppressing gelation, it is preferably 55 to 130 ° C, particularly preferably 75 to 95 ° C. By setting it as the said range, there is no possibility that an acryl-type resin (A) will yellow, or a polymerization monomer or a polymerization initiator will remain, and the acryl-type resin (A) may fall over time and thermal stability.

In this way, an acrylic resin (A) solution can be obtained. Then, the solvent was distilled off from the obtained acrylic resin (A) solution. The step of distilling off the solvent from the acrylic resin (A) solution can be performed by a known general method. As a method of distilling off the solvent, there is a method of distilling off the solvent by heating; or by reducing the pressure The method of distilling off the solvent, etc., is preferably a method of distilling off by heating under reduced pressure in terms of efficiently distilling off the solvent.

The temperature in the case where the solvent is distilled off by heating is preferably performed at 60 to 150 ° C. In terms of minimizing the amount of residual solvent, it is particularly preferable to keep the acrylic resin at 60 to 80 ° C. (A) The reaction solution after polymerization is carried out to distill off the solvent, and the solvent is then distilled off at 80 to 150 ° C. Furthermore, from the viewpoint of suppressing gelation of the acrylic resin (A), it is preferred that the temperature during solvent removal is not performed at 150 ° C or higher.

The pressure in the case where the solvent is distilled off under reduced pressure is preferably performed at 20 to 101.3 kPa. In terms of keeping the amount of the residual solvent extremely small, it is particularly preferable to maintain the pressure within a range of 50 to 101.3 kPa. After the solvent in the reaction solution was distilled off, the residual solvent was distilled off at 0 to 50 kPa. In this way, an acrylic resin (A) can be produced.

The weight average molecular weight of the above-mentioned acrylic resin (A) is preferably 100,000 or more, more preferably 150,000 to 1.5 million, particularly preferably 200,000 to 1,000,000, particularly preferably 250,000 to 800,000, and among them, particularly preferred It is 300,000 to 600,000. By setting it as the said range, there is no possibility that viscosity will become high too much, coating property or handling property may fall, or cohesion may fall, and durability may fall. In addition, the weight average molecular weight of the said acrylic resin (A) is a weight average molecular weight at the time of completion of manufacture, and is a weight average molecular weight of the acrylic resin (A) which did not heat, etc. after manufacture.

The dispersion (weight average molecular weight / number average molecular weight) of the acrylic resin (A) is preferably 15 or less, more preferably 10 or less, particularly preferably 7 or less, and even more preferably 5 or less. By setting it as such a range, there exists no possibility that durability of each layer may fall, foaming, etc. may arise, or workability may fall. Furthermore, in terms of manufacturing limits, the lower limit of dispersion is usually 1.1.

In addition, the above weight average molecular weight is a weight average molecular weight obtained by standard polystyrene molecular weight conversion, and is a high performance liquid chromatograph (manufactured by Waters Corporation of Japan, Detector) ") Using a column: Shodex GPC KF-806L (Excluding limit molecular weight: 2 × 10 ⁷ , separation range: 100 ～ 2 × 10 ⁷ , theoretical number of segments: 10,000 segments / piece, filler material: styrene- Divinylbenzene copolymer, filler particle size: 10 μm) measured in series of three, the number average molecular weight can also be measured using the same method. The degree of dispersion is determined from the weight average molecular weight and the number average molecular weight.

The glass transition temperature (Tg) of the acrylic resin (A) is preferably -100 to 50 ° C, more preferably -80 to 0 ° C, and still more preferably -70 to -10 ° C. By setting it as the said range, there is no possibility that the melt viscosity of an acrylic resin (A) becomes high, or the heating temperature required at the time of coating becomes high, and there exists a possibility that the stability of an acrylic resin (A) may be impaired. In addition, there is no possibility that the step-following property, the adhesive force, or the thermal durability is reduced.

It should be noted that the glass transition temperature is calculated based on the following Equation 1 of Fox. [Number 1] Tg: glass transition temperature (K) of copolymer Tga: glass transition temperature (K) of homopolymer of monomer A Wa: weight fraction of monomer A Tgb: glass transition temperature of homopolymer of monomer B ( K) Wb: weight fraction of monomer B Tgn: glass transition temperature of homopolymer of monomer N (K) Wn: weight fraction of monomer N (Wa + Wb + .... + Wn = 1)

The melt viscosity (mPa · s) of the acrylic resin (A) at 100 ° C is preferably 1,000 to 10,000,000 mPa · s, more preferably 50,000 to 1,000,000 mPa · s, and still more preferably 200,000 to 600,000 mPa · s. By setting it as the said range, there is no possibility that the durability may become insufficient due to a molecular weight fall, or a handleability may fall and it may become difficult to apply.

The viscosity is a value obtained by performing measurement under the conditions of a load of 30 kg, a hole diameter of 1.0 mm, a mold length of 10 mm, and a measurement temperature of 100 ° C. using a rheometer manufactured by Shimadzu Corporation.

The acrylic resin (A) is preferably a solvent-free acrylic resin that does not substantially contain a solvent, and the solvent content of the acrylic resin (A) is preferably 2% by mass or less, and more preferably 0.00001 to 2% by mass. It is particularly preferably 0.0001 to 1% by mass, and particularly preferably 0.001 to 0.1% by mass. By setting it as the said range, there is no possibility that a bubble may generate | occur | produce, or durability may fall.

The amount of residual monomers in the acrylic resin (A) is preferably 2% by mass or less, more preferably 0.00001 to 1.5% by mass, and still more preferably 0.0001 to 1.0% by mass. By setting it as the said range, there is no possibility that molecular weight will increase at the time of heating, coating property or adhesive property will fall, or a bubble may generate | occur | produce and durability may fall.

In addition, the solvent content and the amount of residual monomers in the acrylic resin (A) were diluted 20 times with acrylic resin (A) using toluene, and a gas chromatograph / mass detector (GC: Agilent Technologies) was used. The company manufactured 7890A GCsystem, MSD: 5975inert manufactured by Agilent Technologies).

The content of volatile components in the acrylic resin (A) (usually, the solvent and the residual monomers are the main components) is preferably 2% by mass or less, more preferably 0.00001 to 1.5% by mass, and still more preferably 0.0001 to 1.0% by mass. %. By setting it as the said range, there is no possibility that the molecular weight of an acrylic resin (A) will increase at the time of heating, a coating property may fall, or adhesive physical property may fall, or a bubble may generate | occur | produce, and durability may fall.

The content of volatile components in the acrylic resin (A) is a value calculated by heating the acrylic resin (A) in a hot air dryer at 130 ° C. for 1 hour, and based on the change in weight before and after heating. .

<Crosslinking agent> In order to improve the cohesiveness of the workability (for example, cutting properties, secondary processability, and storage properties) of the adhesive sheet, the present adhesive sheet can also be obtained by removing the acrylic resin ( A composition containing a crosslinking agent (B) in addition to A) is formed.

Examples of the crosslinking agent (B) include those having a group selected from (meth) acrylfluorenyl, epoxy, isocyano, carboxyl, hydroxyl, carbodiimide, oxazoline, and aziridine. The crosslinking agent of at least one type of crosslinkable functional group among a pyridyl group, a vinyl group, an amino group, an imino group, and a fluorenyl group may be used singly or in combination of two or more kinds. The crosslinkable functional group can be protected by a deprotectable protecting group.

Among them, a polyfunctional (meth) acrylate having two or more (meth) acrylfluorenyl groups; an isocyanate group, an epoxy group, a melamine group, a diol group, Multifunctional organic functional resins with organic functional groups such as siloxyalkyl and amine groups; organometallic compounds with metal complexes such as zinc, aluminum, sodium, zirconium, and calcium.

Examples of the polyfunctional (meth) acrylate include 1,4-butanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, and glycerol di (meth) acrylate , Glycerol glycidyl ether di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, 1,9-nonanediol di (meth) acrylate, tricyclodecane dimethanol (Meth) acrylate, bisphenol A polyethoxydi (meth) acrylate, bisphenol A polyalkoxydi (meth) acrylate, bisphenol F polyalkoxydi (meth) acrylic acid Ester, polyalkylene glycol di (meth) acrylate, trimethylolpropane trioxyethyl (meth) acrylate, ε-caprolactone modified tri (2-hydroxyethyl) isocyanuric acid Tri (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tri (meth) acrylate ethoxylate, pentaerythritol tetra (meth) acrylate, propionate Pentaerythritol tetra (meth) acrylate, ethoxylated pentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, polyethylene glycol di (meth) acrylate, isocyanate Tris (acryloxyethyl) acid, pentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, dipentaerythritol penta (meth) acrylate, tripentaerythritol hexa (meth) acrylate , Tripentaerythritol penta (meth) acrylate, neopentyl glycol di (meth) acrylate, ε-caprolactone adduct of neopentyl glycol hydroxypivalate (methyl) ) UV curing type such as acrylate, trimethylolpropane tri (meth) acrylate, alkoxylated trimethylolpropane tri (meth) acrylate, di-trimethylolpropane tetra (meth) acrylate, etc. Polyfunctional monomers; and low polyfunctional acrylates such as polyester (meth) acrylate, epoxy (meth) acrylate, (meth) acrylate urethane, and polyether (meth) acrylate Polymer class.

Among the above-listed compounds, from the viewpoint of improving the adhesion to the adherend or the effect of suppressing moist heat whitening, it is preferable that the polyfunctional (meth) acrylate monomer contains a hydroxyl group or a carboxyl group, Polyfunctional monomers or oligomers of polar functional groups such as amido. Among these, it is preferable to use a polyfunctional (meth) acrylate having a hydroxyl group or an amido group.

In addition, in order to adjust effects such as adhesion, moist heat resistance, and heat resistance, a monofunctional or polyfunctional (meth) acrylate that reacts with a crosslinking agent may be further added.

From the viewpoint of maintaining the balance between the flexibility and cohesiveness of the adhesive composition, the content of the crosslinking agent is preferably contained in a ratio of 0.1 to 20 parts by mass relative to 100 parts by mass of the acrylic resin (A), wherein , Particularly preferably, a ratio of 0.5 parts by mass or more or 15 parts by mass or less, and particularly preferably, a ratio of 1 part by mass or more or 13 parts by mass or less.

In terms of imparting more excellent workability (for example, cuttability, secondary processability, and storage stability), the present adhesive sheet composed of the above-mentioned laminated layer preferably contains a crosslinking agent (B) in the i-th layer, of which, Most preferably, it is a layer other than the first and nth layers, that is, a layer other than the surface layer and the back layer.

<Photopolymerization initiator> This adhesive sheet contains an acrylic resin (A), and from the viewpoint of stabilizing the reaction upon irradiation with active energy rays, it may contain photopolymerization in addition to the acrylic resin (A). A composition of the initiator (C) is formed.

The photopolymerization initiator (C) is not particularly limited as long as it generates radicals by the action of light. Examples include acetophenone-based, benzoin-based, benzophenone-based, and 9-oxygen. sulfur For photopolymerization initiators such as fluorene-based and fluorenylphosphine oxide-based systems, it is preferable to use a hydrogen-abstracting type benzophenone-based photopolymerization in terms of efficient crosslinking between molecules or molecules. Agent.

Examples of the benzophenone-based photopolymerization initiator include benzophenone, benzophenone benzoic acid, 3,3'-dimethyl-4-methoxybenzophenone, and polyvinyldiene. Benzophenone and so on. These can be used alone or in combination of two or more.

Moreover, as an auxiliary agent of these photopolymerization initiators, for example, triethanolamine, triisopropanolamine, 4,4'-dimethylaminobenzophenone (Michlerone), 4, 4'-Diethylaminobenzophenone, 2-dimethylaminoethylbenzoic acid, 4-dimethylaminobenzoic acid ethyl ester, 4-dimethylaminobenzoic acid (n-butoxy Methyl) ethyl ester, 4-dimethylaminobenzoic acid isoamyl ester, 4-dimethylaminobenzoic acid 2-ethylhexyl ester, 2,4-diethyl 9-oxysulfide 2,4-diisopropyl 9-oxysulfur Wait. These auxiliaries may be used alone or in combination of two or more.

The blending amount of such a photopolymerization initiator (C) is preferably 0.01 to 10 parts by mass, more preferably 0.1 to 5 parts by mass, and even more preferably 100 parts by mass of the acrylic resin (A). 0.5 to 2 parts by mass. If such a blending amount is too small, there is no fear that the curing speed will be reduced or the curing will become insufficient.

<Other Ingredients> The adhesive sheet may be formed of a composition containing a well-known component formulated in a general adhesive composition in addition to the above. For example, it may suitably contain adhesion-imparting resins or processing aids (such as oil components), silane coupling agents, antioxidants, light stabilizers, metal deactivators, ultraviolet absorbers (UVA), light stabilizers (HALS), and rust prevention. Additives, anti-aging agents, hygroscopic agents, hydrolysis inhibitors, nucleating agents and other additives. Inorganic or organic nanofine particles are also included. Among these, it is more preferable to include a rust inhibitor or an adhesion-imparting agent. Further, a reaction catalyst (a tertiary amine compound, a quaternary ammonium compound, a tin laurate compound, etc.) may be appropriately contained as necessary.

<The manufacturing method of this adhesive sheet> This adhesive sheet can be manufactured by the resin which contains the said acrylic resin (A) and the crosslinking agent (B) and photoinitiator (C) as needed The composition is applied (coated) to a substrate sheet or a release sheet in a state of being melted by heat, and then cooled. In addition, for example, the present adhesive sheet composed of a laminate can be produced by applying (applying) the above-mentioned resin composition to a base material sheet or a release sheet in a state of being melted by heat, Thereafter, cooling is performed to form a first layer, and the resin composition is coated (coated) on the formed first layer, followed by cooling to form a second layer, and this operation is repeatedly performed to form an i layer; or The resin composition is melted by heating, and the first layer to the i-th layer are formed in advance in the same manner as described above, and then the respective coated (applied) surfaces are bonded to each other; or the resin is combined by heating The material is melted, and the first layer to the i-th layer are simultaneously formed by coextrusion.

The coating (coating) method is not particularly limited as long as it is a general coating method, and examples thereof include roll coating, die coating, gravure coating, doctor blade coating, and screen printing. method.

The adhesive sheet may be an adhesive sheet with a base material sheet provided with an adhesive layer on a base material sheet, or an adhesive sheet without a base material provided with an adhesive layer on a release sheet. .

Examples of the base material sheet include polyethylene naphthalate, polyethylene terephthalate, polybutylene terephthalate, and polyethylene terephthalate / isophthalic acid. Polyester resins such as ester copolymers; polyolefin resins such as polyethylene, polypropylene, and polymethylpentene; polyvinyl fluoride, polyvinylidene fluoride, and polyvinyl fluoride (polyfluoroethylene) (polyfluoroethylene) resin; polyamides such as nylon 6, nylon 6,6; polyvinyl chloride, polyvinyl chloride / vinyl acetate copolymer, ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, polyvinyl alcohol, Vinyl polymers such as vinylon; cellulose resins such as cellulose triacetate and cellulan; acrylic resins such as polymethyl methacrylate, polyethyl methacrylate, polyethyl acrylate, and polybutyl acrylate; Polystyrene; polycarbonate; polyarylate; polyimide and other synthetic resin sheets, aluminum, copper, iron metal foils, papers such as dory paper, cellophane, including glass fibers, natural fibers, synthetic fibers, etc. Woven or non-woven. These base material sheets may be used in the form of a single layer body, or in the form of a multilayer body in which two or more kinds are laminated. Among these, a synthetic resin sheet is preferable in terms of weight reduction and the like.

As the above-mentioned release sheet, for example, those obtained by subjecting various synthetic resin sheets, papers, cloths, nonwoven fabrics, and the like exemplified in the above-mentioned substrate sheet to a release treatment can be used. As the release sheet, a silicon-based release sheet is preferably used.

<How to use this adhesive sheet> This adhesive sheet is preferably used after being adhered to an adhered member and irradiated with active energy rays. Therefore, when the adhesive sheet is irradiated with active energy rays in such a way that the accumulated light quantity at 365 nm becomes 2000 mJ or more, the elastic modulus of the first layer is stored at a frequency of 1 Hz and a temperature of 80 ° C before and after the irradiation. The difference between the number G '(the storage elastic modulus G' after irradiation-the storage elastic modulus G 'before irradiation) becomes 5 kPa or more, and the storage elastic modulus G of the i-th layer at a frequency of 1 Hz and a temperature of 80 ° C The difference (the storage elastic modulus G 'after irradiation-the storage elastic modulus G' before irradiation) becomes 2 kPa or more.

In the above configuration, in terms of imparting step absorption and resistance to foaming reliability, the first layer preferably has a difference in storage elastic modulus G ′ at a frequency of 1 Hz and a temperature of 80 ° C. (after irradiation) The storage elastic modulus G '-the storage elastic modulus G' before irradiation becomes 5 kPa or more, and the i-th layer is preferably the difference between the storage elastic modulus G 'at a frequency of 1 Hz and a temperature of 80 ° C (after irradiation The storage elastic modulus G '-the storage elastic modulus G' before irradiation becomes 4 kPa or more.

In this way, this adhesive sheet has room for hardening by active energy rays. Among them, if the degree of hardening is adjusted in advance with a difference in storage elastic modulus within the above range, a low dielectric constant can be achieved, and Has very high absorption of printing steps. Moreover, the storage elastic modulus G ′ can be adjusted by the above method.

(Application) The adhesive sheet can be used for bonding optical components, for example, components of image display devices. Examples of the constituent elements of the image display device include a liquid crystal display (LCD) such as a personal computer, a mobile terminal (PDA), a game machine, a television (TV), a car navigation system, a touch panel, and a tablet. Structural components of image display devices such as PDP (plasma display panel) or EL (electroluminescence).

To give a specific example, in an image display device of a mobile phone, a polarizing film or the like is laminated on a liquid crystal panel display (LCD), and a plastic protective panel is laminated thereon via an adhesive or a sheet. At this time, PVA (polyvinyl alcohol, polyvinyl alcohol) or triacetam cellulose resin may be used as a constituent material of the polarizing film, and it is judged that these easily release gas.

Therefore, a laminated body including a protective panel / the adhesive sheet / polarizing film is produced, and active energy rays are irradiated through the constituent members (protective panel or polarizing film) of the image display device to improve the storage elasticity of the adhesive sheet. Therefore, even when used at high temperatures, foaming caused by the gas released from the protective panel or the polarizing film can be effectively suppressed. [Example]

Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited to the following examples.

In addition, in the following examples and comparative examples, the measurement and processing of the following physical properties were performed under the following conditions.

(Laminate Sheet 1 for Intermediate Layer Formation) 58.5 parts by mass of a mixture of lauryl methacrylate and tridecyl methacrylate (SLMA) and 15 parts by mass of 2-ethylhexyl methacrylate (2EHMA) were prepared. Random copolymerization of 15 parts by mass of n-stearyl methacrylate (SMA), 11 parts by mass of 4-hydroxybutyl acrylate (4HBA), and 0.5 parts by mass of 4-methacryloxyoxybenzophenone (MBP) The resulting acrylic resin A. 50 g of a UV curing resin propoxypentaerythritol triacrylate ("ATM-4PL" manufactured by Shin Nakamura Chemical Co., Ltd.) as a crosslinking agent was melt-kneaded in 1 kg of this acrylic resin A to prepare a composition for an intermediate resin layer ( A-1). 100 µm thick "Diafoil MRQ" manufactured by Mitsubishi Chemical Co., Ltd. with two release films, that is, two polyethylene terephthalate films that have been peeled off (Thickness: 75 μm), sandwiching the composition (A-1), using a laminator, forming into a sheet shape at a temperature of 80 ° C. so as to have a thickness of 90 μm, to produce an interlayer forming laminated sheet 1 (intermediate layer) The thickness of the resin layer (A-1) was 90 μm).

(Laminate Sheet 2 for Intermediate Layer Formation) 44.5 parts by mass of a mixture of lauryl methacrylate and tridecyl methacrylate (SLMA) and 10 parts by mass of 2-ethylhexyl methacrylate (2EHMA) were prepared. Random copolymerization of 35 parts by mass of n-stearyl methacrylate (SMA), 10 parts by mass of 4-hydroxybutyl acrylate (4HBA), and 0.5 parts by mass of 4-methacryloxybenzophenone (MBP) The resulting acrylic resin B. 50 g of a UV-curable resin propoxylate pentaerythritol triacrylate ("ATM-4PL" manufactured by Shin Nakamura Chemical Co., Ltd.) as a crosslinking agent was melt-kneaded in 1 kg of this acrylic resin B to prepare a composition for an intermediate resin layer ( B-1). 100 µm thick "Diafoil MRQ" manufactured by Mitsubishi Chemical Co., Ltd. with two release films, that is, two polyethylene terephthalate films that have been peeled off (Thickness: 75 μm), sandwiching the composition (B-1), using a laminator, forming into a sheet shape at a temperature of 80 ° C. so as to have a thickness of 90 μm, to produce an intermediate layer forming laminated sheet 2 (intermediate layer) The thickness of the resin layer (B-1) is 90 μm).

(Laminate Sheet 3 for Intermediate Layer Formation) 52.5 parts by mass of a mixture (SLMA) of lauryl methacrylate and tridecyl methacrylate and 20 parts by mass of 2-ethylhexyl methacrylate (2EHMA) were prepared. Random copolymerization of 15 parts by mass of n-stearyl methacrylate (SMA), 12 parts by mass of 2-hydroxyethyl acrylate (2HEA), and 0.5 parts by mass of 4-methacryloxyoxybenzophenone (MBP) The resulting acrylic resin C. 50 g of a UV-curable resin propoxylate pentaerythritol triacrylate ("ATM-4PL" manufactured by Shin Nakamura Chemical Co., Ltd.) as a crosslinking agent was melt-kneaded in 1 kg of this acrylic resin C to prepare a composition for an intermediate resin layer ( C-1). 100 µm thick "Diafoil MRQ" manufactured by Mitsubishi Chemical Co., Ltd. with two release films, that is, two polyethylene terephthalate films that have been peeled off (Thickness: 75 μm), sandwiching the composition (C-1), using a laminator, forming into a sheet shape at a temperature of 80 ° C. so as to have a thickness of 90 μm, to produce an interlayer forming laminated sheet 3 (intermediate layer) The thickness of the resin layer (C-1) is 90 μm).

(Laminate Sheet 4 for Intermediate Layer Formation) 82.6 parts by mass of a mixture of lauryl methacrylate and tridecyl methacrylate (SLMA), 5 parts by mass of third butyl methacrylate (tBMA), and acrylic acid were prepared. An acrylic resin D obtained by random copolymerization of 12 parts by mass of 4-hydroxybutyl ester (4HBA) and 0.5 parts by mass of 4-methacryloxybenzophenone (MBP). 50 g of a UV-curable resin propoxylate pentaerythritol triacrylate ("ATM-4PL" manufactured by Shin Nakamura Chemical Co., Ltd.) as a crosslinking agent was melt-kneaded in 1 kg of this acrylic resin D to prepare a composition for an intermediate resin layer ( D-1). 100 µm thick "Diafoil MRQ" manufactured by Mitsubishi Chemical Co., Ltd. with two release films, that is, two polyethylene terephthalate films that have been peeled off (Thickness: 75 μm), sandwiching the composition (D-1), using a laminator, forming into a sheet shape at a temperature of 80 ° C. so as to have a thickness of 90 μm, to produce an intermediate layer forming laminated sheet 4 (intermediate layer) The thickness of the resin layer (D-1) is 90 μm).

(Laminated sheet 5 for intermediate layer formation) Prepared by random copolymerization of 77 parts by mass of 2-ethylhexyl acrylate (2EHA), 19 parts by mass of vinyl acetate (VA), and 4 parts by mass of acrylic acid (AA). Acrylic resin E. 50 g of a UV-curable resin propoxylate pentaerythritol triacrylate ("ATM-4PL" manufactured by Shin Nakamura Chemical Co., Ltd.) as a crosslinking agent was melt-kneaded in 1 kg of this acrylic resin E, and 2 as a photoinitiator. 15 g of a mixture of 4,6-trimethylbenzophenone and 4-methylbenzophenone ("Esacure TZT" manufactured by Lanberti) to prepare a composition (E-1) for an intermediate resin layer. 100 µm thick "Diafoil MRQ" manufactured by Mitsubishi Chemical Co., Ltd. with two release films, that is, two polyethylene terephthalate films that have been peeled off (Thickness: 75 μm), sandwiching the composition (E-1), using a laminator, forming into a sheet shape at a temperature of 80 ° C. so as to have a thickness of 90 μm, to produce an intermediate layer forming laminated sheet 5 (intermediate layer) The thickness of the resin layer (E-1) was 90 μm).

(Laminated sheet 1 for forming the outermost layer) Two release films, that is, two polyethylene terephthalate films ("Diafoil MRV-V06" manufactured by Mitsubishi Chemical Co., Ltd.), having a thickness of 100 μm "Diafoil MRQ" manufactured by / Mitsubishi Chemical Co., Ltd., with a thickness of 75 μm) sandwiching the above-mentioned acrylic resin A, and using a laminator, it was shaped into a sheet shape so as to have a thickness of 30 μm to produce a laminated sheet for outermost layer formation 1 (The thickness of the adhesive layer A is 30 μm).

(Laminated sheet 2 for outermost layer formation) Two release films, that is, two polyethylene terephthalate films ("Diafoil MRV-V06" manufactured by Mitsubishi Chemical Co., Ltd.), having a thickness of 100 μm "Diafoil MRQ" manufactured by / Mitsubishi Chemical Co., Ltd. with a thickness of 75 μm) sandwiched the above-mentioned acrylic resin B, and using a laminator, it was shaped into a sheet shape at a temperature of 80 ° C. so as to have a thickness of 30 μm to form the outermost layer. A laminated sheet 2 (thickness of the adhesive layer B of 30 μm) was used.

(Laminated sheet 3 for outermost layer formation) Two release films, that is, two polyethylene terephthalate films ("Diafoil MRV-V06" manufactured by Mitsubishi Chemical Co., Ltd.), having a thickness of 100 μm "Diafoil MRQ" manufactured by / Mitsubishi Chemical Co., Ltd. with a thickness of 75 μm) sandwiched the above-mentioned acrylic resin C, and using a laminator, it was shaped into a sheet shape at a temperature of 80 ° C so as to have a thickness of 30 μm to form the outermost layer. A laminated sheet 3 (thickness of the adhesive layer C of 30 μm) was used.

(Laminated sheet 4 for outermost layer formation) Two release films, that is, two polyethylene terephthalate films ("Diafoil MRV-V06" manufactured by Mitsubishi Chemical Co., Ltd.), having a thickness of 100 μm "Diafoil MRQ" manufactured by / Mitsubishi Chemical Co., Ltd., with a thickness of 75 μm) sandwiching the above-mentioned acrylic resin D, using a laminator, forming into a sheet shape at a temperature of 80 ° C. so as to have a thickness of 30 μm, and forming the outermost layer A laminated sheet 4 (thickness of the adhesive layer D of 30 μm) was used.

(Laminated sheet 5 for outermost layer formation) Two release films, that is, two polyethylene terephthalate films ("Diafoil MRV-V06" manufactured by Mitsubishi Chemical Co., Ltd.), having a thickness of 100 μm "Diafoil MRQ" manufactured by Mitsubishi Chemical Co., Ltd. (75 μm thick) sandwiched between 1 kg of the above-mentioned acrylic resin E and melt-kneaded 2,4,6-trimethylbenzophenone and 4 as photoinitiators. -Methylbenzophenone mixture ("Esacure TZT" manufactured by Lanberti company) 15 g of the outermost resin layer composition E ', using a laminator, at a temperature of 80 ° C to a thickness of 30 μm The method was shaped into a sheet shape, and a laminated sheet 5 for forming the outermost layer (the thickness of the adhesive layer E was 30 μm) was produced. [Example 1]

<Production of Adhesive Sheet 1> The PET films on both sides of the intermediate resin layer (A-1) in the intermediate resin layer forming laminated sheet 1 are peeled off in order, and the outermost layer forming laminated sheet 1 is peeled off. For the PET film on one side of the adhesive layer A, the exposed adhesive surface is sequentially laminated on both surfaces of (A-1) by a laminator to produce a multilayer adhesive sheet including A / (A-1) / A material. After lamination, through the polyethylene terephthalate film remaining on the surface, the ultraviolet light was irradiated with a high-pressure mercury lamp so that the cumulative light quantity at 365 nm became 500 mJ, and A and (A-1) were crosslinked by ultraviolet to produce Adhesive sheet 1 (total thickness 150 μm). In addition, the adhesive sheet 1 adjusts the irradiation amount of ultraviolet rays, and is in a semi-hardened state, that is, a state where there is room for further hardening. [Example 2]

<Production of Adhesive Sheet 2> An adhesive sheet 2 was produced in the same manner as in Example 1 except that (B-1) was used as the intermediate resin layer and B was used as the outermost layer. [Example 3]

<Production of Adhesive Sheet 3> An adhesive sheet 3 was produced in the same manner as in Example 1 except that (C-1) was used as the intermediate resin layer and C was used as the outermost layer. [Example 4]

<Production of Adhesive Sheet 4> An adhesive sheet 4 was produced in the same manner as in Example 1 except that (D-1) was used as the intermediate resin layer and D was used as the outermost layer. [Example 5]

<Production of Adhesive Sheet 5> An adhesive sheet 5 was produced in the same manner as in Example 1 except that (A-1) was used as the intermediate resin layer and B was used as the outermost layer. [Example 6]

<Production of Adhesive Sheet 6> An adhesive sheet 6 was produced in the same manner as in Example 1 except that (B-1) was used as the intermediate resin layer and A was used as the outermost layer. [Example 7]

<Production of Adhesive Sheet 7> An adhesive sheet 7 was produced in the same manner as in Example 1 except that (C-1) was used as the intermediate resin layer and A was used as the outermost layer. [Example 8]

<Production of Adhesive Sheet 8> An adhesive sheet 8 was produced in the same manner as in Example 1 except that (A-1) was used as the intermediate resin layer and C was used as the outermost layer. [Example 9]

<Production of Adhesive Sheet 9> An adhesive sheet 9 was produced in the same manner as in Example 1 except that (B-1) was used as the intermediate resin layer and C was used as the outermost layer. [Example 10]

<Production of Adhesive Sheet 10> An adhesive sheet 10 was produced in the same manner as in Example 1 except that (C-1) was used as the intermediate resin layer and B was used as the outermost layer. [Comparative Example 1]

<Production of Adhesive Sheet 11> Two release films, that is, two polyethylene terephthalate films ("Diafoil MRV-V06" manufactured by Mitsubishi Chemical Co., Ltd.), having a thickness of 100 μm / Mitsubishi "Diafoil MRQ" manufactured by Chemical Co., Ltd., having a thickness of 75 μm, sandwiched the above composition (A-1), and was laminated into a sheet shape so as to have a thickness of 150 μm using a laminator to produce an adhesive sheet 11. [Comparative Example 2]

<Production of Adhesive Sheet 12> An adhesive sheet 12 was produced in the same manner as in Comparative Example 1 except that the composition (B-1) was used instead of the composition (A-1). [Comparative Example 3]

<Production of Adhesive Sheet 13> An adhesive sheet 13 was produced in the same manner as in Comparative Example 1 except that the composition (C-1) was used instead of the composition (A-1). [Comparative Example 4]

<Production of Adhesive Sheet 14> An adhesive sheet 14 was produced in the same manner as in Comparative Example 1 except that the composition (D-1) was used instead of the composition (A-1). [Comparative Example 5]

<Production of Adhesive Sheet 15> An adhesive sheet 15 was produced in the same manner as in Comparative Example 1 except that the acrylic resin A was used instead of the composition (A-1). [Comparative Example 6]

<Production of Adhesive Sheet 16> An adhesive sheet 16 was produced in the same manner as in Comparative Example 1 except that the acrylic resin B was used instead of the composition (A-1). [Comparative Example 7]

<Production of Adhesive Sheet 17> An adhesive sheet 17 was produced in the same manner as in Comparative Example 1 except that the acrylic resin C was used instead of the composition (A-1). [Comparative Example 8]

<Production of Adhesive Sheet 18> An adhesive sheet 18 was produced in the same manner as in Comparative Example 1 except that the acrylic resin D was used instead of the composition (A-1). [Comparative Example 9]

<Production of Adhesive Sheet 19> An adhesive sheet 19 was produced in the same manner as in Comparative Example 1 except that the composition E ′ was used instead of the composition (A-1). [Comparative Example 10]

<Production of Adhesive Sheet 20> An adhesive sheet 20 was produced in the same manner as in Comparative Example 1 except that the composition (E-1) was used instead of the composition (A-1). [Comparative Example 11]

<Production of Adhesive Sheet 21> An adhesive sheet 21 was produced in the same manner as in Example 1 except that (E-1) was used as the intermediate resin layer and E 'was used as the outermost layer.

<Tensile Modulus of Elasticity> The adhesive sheets 1 to 21 produced in the examples and comparative examples were cut into a width of 20 mm and a length of 80 mm, and attached to a paper pattern (60) as shown in FIG. 1 (A). mm × 80 mm, window part in the center), and clamp the paper pattern up and down on a tensile tester ("205 type tester" manufactured by Intesco), as shown in Figure 1 (B) and Figure 1 (C), Cut cuts obliquely on the two lateral sides of the paper sample, cut off the paper sample from top to bottom, and perform a tensile test with a distance between the chucks of 40 mm and a tensile speed of 300 mm / min. Symbol 1 in FIG. 1 is a paper pattern, and symbol 2 is an adhesive sheet. Then, the tensile elastic modulus (MPa) was calculated. The calculation results are shown in Table 3.

<Processability> The Thomson punching machine was used to cut the adhesive sheets 1 to 21 produced in the examples and comparative examples with a Thomson blade of 50 mm × 80 mm, and the cut end portions were visually observed. Its shape. Then, those who have a paste overflow at the end of the sheet are judged as "×", and those who do not exist are judged as "○". The determination results are shown in Table 3.

<Retention force test> After cutting the adhesive sheets 1 to 21 produced in the examples and comparative examples to 30 mm × 80 mm, the one-sided release film was peeled off, and the one-sided surface of the adhesive sheet was used to gather the substrate. Ethylene terephthalate films (thickness: 38 μm) were laminated by hand pressing and cut into 25 mm × 80 mm short strips as test pieces. Next, the remaining release film was peeled off, and the test piece and the SUS (stainless steel) plate (120 mm × 50 mm × thickness 1.2 mm) standing vertically were overlapped by a length of 20 mm by hand pressing. At this time, the bonding area of the transparent double-sided adhesive sheet and the SUS (stainless steel) plate becomes 25 mm × 20 mm. Thereafter, the test piece was cured at 40 ° C for 15 minutes, and then a 4.9 N lead hammer was mounted and hung on the test piece in a vertical direction. After standing for 30 minutes, the adhesion of the SUS (stainless steel) plate to the test piece was measured. Offset length (mm) of position offset downward. The measurement results are shown in Table 3.

＜ Printing step followability test ＞ A black print (full light transmittance of 0%) with a width of 10 mm and a thickness of 40 μm is performed on the peripheral portion of a soda-lime glass of 60 mm × 90 mm × 0.5 mm in thickness. A glass substrate for evaluation of a printing step of 40 μm. The glass substrate for evaluation is a substitute for an image display device constituent member having a stepped portion having a height of 30 μm to 50 μm and a flat surface portion on a bonding surface. A polarizing plate ("NWF-KDSEGHC-ST22" manufactured by Nitto Denko Corporation) was prepared as an adherend for a test to be bonded to the glass substrate for evaluation, and it was laminated on the entire surface in advance. Single-sided glass plate (60 × 90 mm × t 0.5 mm). One of the peeling films of the adhesive sheets 1 to 21 cut in the processability evaluation was peeled, and the exposed adhesive surface was bonded by a hand pressure roller so as to cover the printing step portion of the glass substrate. Next, the remaining release film was peeled off, and the untreated soda-lime glass was pressure-bonded to the exposed adhesive surface under reduced pressure (absolute pressure 5 kPa), and then subjected to an autoclave treatment (60 ° C, 0.2 MPa, 20 minutes) Then, fine bonding was performed to produce a laminated body for evaluation of printing step followability. After the laminated body for follow-up evaluation of printing steps was left to stand for one day under normal conditions (temperature: 23 ° C., humidity: 50%), the appearance was visually observed, and those who raised or peeled the adhesive sheet near the printing steps were evaluated as “× ", And those with no bulge or peeling were evaluated as" ○ ". The evaluation results are shown in Table 3.

<Relative permittivity> The adhesive sheets 1 to 21 produced in the examples and comparative examples were cut into a circle with a diameter of 25 mm, and bonded to an LCR (inductance capacitance resistance) with the release film on both sides peeled off. Capacitance and resistance) The measuring unit (manufactured by Keysight Technologie) measures the relative dielectric constant at 23 ° C. and 50% RH at an applied voltage of 1 V and a frequency of 100 kHz. The measurement results are shown in Table 3.

<Storage Elastic Modulus (G ')> The dynamic storage elastic modulus (G') at 20 ° C is obtained by using the active energy ray-curable adhesive sheets 1 to 10 obtained in a plurality of examples and the intermediate among them. The layers (sheets for forming the intermediate layer in the semi-hardened state) and the outermost layers (sheets for forming the outermost layer in the semi-hardened state) are laminated so as to have a thickness of 1 mm to 2 mm, and punched to a diameter of 20 mm The round one is used as a measurement sample, and a rheometer ("MARS" manufactured by Hidehiro Seiki Co., Ltd.) is used. An adhesion jig: f20 mm parallel plate, strain: 0.5%, frequency: 1 Hz, temperature: -50 to 200 ° C, heating rate: 3 ° C / min, the dynamic storage elastic modulus G 'at 20 ° C was measured. The measurement results are shown in Table 1. Moreover, the dynamic storage elastic modulus (G ') of 20 degreeC was also measured for the adhesive sheets 11-21 similarly to the above. The measurement results are shown in Table 3. The dynamic storage elastic modulus (G ′) at 80 ° C. refers to the intermediate layer (the sheet 4 for forming an intermediate layer in a semi-hardened state) of the active energy ray-curable adhesive sheet 4 obtained in Example 4 and The outermost layer (the outermost layer forming sheet 4 in the semi-hardened state) is irradiated with ultraviolet rays so that the accumulated light amount at 365 nm becomes 2000 mJ or more, and the intermediate layer forming sheet 4 and the outermost layer forming sheet after ultraviolet irradiation are produced. 4. Each was measured under the same conditions as above. The measurement results are shown in Table 2.

<UV foaming test> (Production of UV irradiation test sample) One of the adhesive sheets 1 to 21 produced in the Examples and Comparative Examples was peeled off, and the roll was laminated to a thickness of 150 mm × 200 mm and 1 mm Soda-lime glass. Then, the remaining mold release film was peeled off, and the glass plate was 238 mm × 182 mm × 0.8 mm thick by roll bonding, and subjected to autoclave treatment (80 ° C., gage pressure 0.2 MPa, 20 minutes) for precise bonding. From the glass side with a thickness of 0.8 mm, the ultraviolet ray at a wavelength of 365 nm reached 2000 mJ / cm ² , and the adhesive sheet was irradiated with ultraviolet rays by a high-pressure mercury lamp to harden the adhesive sheet to produce a laminated body.

(Test method) The laminated body was put in a xenon UV irradiation device (Suntest CPS: manufactured by Toyo Seiki), and the appearance after UV irradiation treatment was performed for 24 hours at 765 W / m ² at a temperature of 60 ° C was observed. Those who produced bubbles with a diameter of 5 mm or more on the adhesive sheet were judged as "× (poor)", those who saw bubbles with a diameter of 5 mm or less as "△ (fair)", and those who had no foam and no change in appearance were judged as "○ (better)".

[Table 1]

[Table 2]

[table 3] [Industrial availability]

The active energy ray-curable adhesive sheet for an optical member of the present invention is formed by using a specific acrylic resin (A) in a manner having specific properties, and can achieve both a low dielectric constant and an excellent printing step. Absorptivity can be preferably used when forming an image display device such as a personal computer, a mobile terminal (PDA), a game machine, a television (TV), a car navigation system, a touch panel, a tablet, and the like.

1‧‧‧ pattern

2‧‧‧ Adhesive sheet

1 (A) to (C) are schematic diagrams of samples of a tensile elastic modulus measurement test in Examples and Comparative Examples.

Claims (10)

An active energy ray-curable adhesive sheet for an optical member, which contains an acrylic resin (A), and the acrylic resin (A) contains an active energy ray crosslinkable structure portion and has a carbon number of 10 to 24 The (co) polymer of the monomer component of the linear alkyl (meth) acrylate monomer (a), the optical member has at least the following active energy ray-curable adhesive sheet (1) to (3) All the characteristics: (1) The tensile modulus of elasticity at a temperature of 23 ° C is 0.03 MPa or more (2) Based on a 25 mm × 20 mm bonding area attached to a stainless steel plate, 500 gf (4.9 N) The offset length of the holding force test under load for 30 minutes is 1 mm or more. (3) The relative dielectric constant at a frequency of 100 kHz is 3.7 or less. An active energy ray-curable adhesive sheet for an optical member, which contains an acrylic resin (A), and the acrylic resin (A) contains an active energy ray crosslinkable structure portion and has a carbon number of 10 to 24 (Co) polymer of a monomer component of a linear alkyl (meth) acrylate monomer (a), the optical member uses an active energy ray-curable adhesive sheet from at least one sheet surface in the thickness direction A region including the above-mentioned acrylic resin (A) having a different storage elastic modulus G ′ at a frequency of 1 Hz and a temperature of 20 ° C., and a relative dielectric constant at a frequency of 100 kHz is 3.7 or less. For example, the active energy ray hardening type adhesive sheet for an optical component of claim 2, which has at least n layers in the thickness direction from the surface of at least one sheet, and the first layer and the i layer have a frequency of 1 Hz and a temperature of 20 ° C. The storage elastic modulus G 'of the i-th layer is different from 40 kPa and 1 MPa at a frequency of 1 Hz and a temperature of 20 ° C. (Where n and i are independently 2 or more. Integer). For example, the active energy ray-curable adhesive sheet for an optical member of claim 3, wherein the storage elastic modulus G 'of the first layer at a frequency of 1 Hz and a temperature of 20 ° C is 30 kPa or more and 70 kPa or less. The active energy ray-curable pressure-sensitive adhesive sheet for an optical member according to any one of claims 2 to 4, wherein the i-th layer comprises a crosslinking agent (B). For example, if the active energy ray-curable adhesive sheet for an optical member according to any one of claims 3 to 5 is irradiated with an active energy ray such that the cumulative light amount at 365 nm becomes 2000 mJ or more, before and after the irradiation, the first The difference between the storage elastic modulus G 'of 1 layer at a frequency of 1 Hz and a temperature of 80 ° C (the storage elastic modulus G' after irradiation-the storage elastic modulus G 'before irradiation) becomes 5 kPa or more, and the i-th layer The difference between the storage elastic modulus G 'at a frequency of 1 Hz and a temperature of 80 ° C (the storage elastic modulus G' after irradiation-the storage elastic modulus G 'before irradiation) becomes 2 kPa or more. The active energy ray-curable adhesive sheet for an optical member according to any one of claims 1 to 6, wherein the active energy ray crosslinkable structural site is a benzophenone-based crosslinked structure. The active energy ray-curable pressure-sensitive adhesive sheet for an optical member according to any one of claims 1 to 7, wherein the acrylic resin (A) contains a hydroxyl group-containing (methyl) group in addition to the monomer (a). A copolymer of monomer components of the acrylate monomer (b). The active energy ray-curable adhesive sheet for an optical member according to any one of claims 1 to 8, wherein the acrylic resin (A) is in addition to the monomer (b), and further includes a branched alkyl group. A copolymer of monomer components of the alkyl (meth) acrylate monomer (c). For example, the active energy ray-curable adhesive sheet for an optical member according to claim 9, wherein the content ratio (weight ratio) of the monomers (a) and (c) in the copolymer of the acrylic resin (A) is 100 / 0 to 70/30.