KR102620334B1 - Adhesive sheet and display - Google Patents

Abstract

(Problem) To provide an adhesive sheet and display body in which the adhesive layer is excellent in both step followability and blister resistance and has good processability.
(Solution) An adhesive sheet (1) provided with an adhesive layer (2), wherein the adhesive layer (2) includes a first adhesive layer (21) as an outer layer on one face side, and a second adhesive layer as an outer layer on the other face side. It has a third adhesive layer (23) positioned as an intermediate layer between the layer (22) and the first adhesive layer (21) and the second adhesive layer (22), and constitutes the first adhesive layer (21). The adhesive and the adhesive constituting the second adhesive layer 22 each have a storage modulus (G') at 23°C of 0.1 MPa or more, and the third adhesive layer 23 is composed of an active energy ray-curable adhesive, and the adhesive has an active energy ray-curable adhesive. The storage elastic modulus (G') at 23°C before curing of the energy ray-curable adhesive is the storage elastic modulus (G') at 23°C of the adhesive constituting the first adhesive layer (21) and the second adhesive layer (22). ) A pressure-sensitive adhesive sheet (1) that is lower than the storage modulus (G') at 23°C of the pressure-sensitive adhesive that constitutes the pressure-sensitive adhesive.

Description

Adhesive sheet and display material {ADHESIVE SHEET AND DISPLAY}

The present invention relates to a pressure-sensitive adhesive sheet suitable for bonding display body components, and a display body obtained by using the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet.

Various mobile electronic devices such as recent smartphones and tablet terminals are equipped with displays using display modules having liquid crystal elements, light-emitting diodes (LED elements), organic electroluminescence (organic EL) elements, etc. Increasingly, displays are becoming touch panels.

In the above display, a protection panel is usually formed on the surface side of the display module. As electronic devices become thinner and lighter, the protective panels are changing from conventional glass plates to plastic plates such as acrylic plates and polycarbonate plates.

Here, a gap is formed between the protection panel and the display module so that the deformed protection panel does not collide with the display module even when the protection panel is deformed by an external force.

However, if the above-mentioned air gap, or air layer, exists, there is a problem that the reflection loss of light resulting from the refractive index difference between the protective panel and the air layer and the refractive index difference between the air layer and the display module is large, deteriorating the image quality of the display.

Therefore, it has been proposed to improve the image quality of the display by filling the gap between the protection panel and the display module with an adhesive layer. However, on the display module side of the protection panel, a frame-shaped printed layer may exist as a step. If the pressure-sensitive adhesive layer does not follow the level difference, the pressure-sensitive adhesive layer floats in the vicinity of the level difference, resulting in reflection loss of light. Therefore, the adhesive layer is required to have step followability.

In order to solve the above problem, Patent Document 1 is an adhesive layer that fills the gap between the protection panel and the display module, and has a shear storage modulus (G') at 25°C and 1 Hz of 1.0×10 ⁵ Pa or less, Additionally, an adhesive layer having a gel fraction of 40% or more is disclosed.

In the invention disclosed in Patent Document 1, an attempt is made to improve step followability by lowering the storage modulus (G') of the pressure-sensitive adhesive layer at room temperature. However, if the storage elastic modulus (G') at room temperature is lowered as described above, the storage elastic modulus (G') at high temperature decreases more than necessary, causing problems under durability conditions. For example, when high temperature and high humidity conditions are applied, bubbles may be generated near the step, or outgassed from the plastic plate that is the protective panel, causing blisters such as bubbles, floatation, and peeling. On the other hand, if the adhesive layer is hardened to improve blister resistance, step followability deteriorates.

Additionally, if the storage modulus (G') of the adhesive layer is lowered as described above, the film strength of the adhesive layer decreases and processability deteriorates. For example, when punching an adhesive sheet, problems such as the adhesive sticking out from the cut surface and sticking to the blade occur.

On the other hand, in Patent Document 2, in order to solve the problems of step followability and processability as described above, the adhesive layer is composed of two or more layers, the storage shear modulus of the middle layer is made higher than that of the surface layer, and the storage shear modulus of the entire sheet is made higher. An adhesive sheet with press-fit hardness set to a predetermined range is disclosed.

Patent Document 1; Japanese Patent Publication No. 2010-97070 Patent Document 2: Japanese Patent Publication No. 2012-184390

However, since the adhesive sheet of Patent Document 2 has a low storage shear elastic modulus of the surface layer, there is a problem that blisters are generated when it is attached to a protective panel made of a plastic plate and placed under high temperature and high humidity conditions.

The present invention has been made in consideration of such actual conditions, and its purpose is to provide an adhesive sheet and display body in which the adhesive layer has excellent both step followability and blister resistance and has good processability.

In order to achieve the above object, firstly, the present invention is a pressure-sensitive adhesive sheet provided with a pressure-sensitive adhesive layer, wherein the pressure-sensitive adhesive layer includes a first pressure-sensitive adhesive layer as an outer layer on one side of the face, a second pressure-sensitive adhesive layer as an outer layer on the other side, A third adhesive layer is provided as an intermediate layer between the first adhesive layer and the second adhesive layer, and the adhesive constituting the first adhesive layer and the adhesive constituting the second adhesive layer are heated at 23°C. each has a storage elastic modulus (G') of 0.1 MPa or more, the third adhesive layer is composed of an active energy ray-curable adhesive, and the storage elastic modulus (G') at 23° C. before curing of the active energy ray-curable adhesive is , an adhesive characterized in that the storage elastic modulus (G') at 23°C of the adhesive constituting the first adhesive layer is lower than the storage elastic modulus (G') at 23°C of the adhesive constituting the second adhesive layer. A sheet is provided (invention 1).

Second, the present invention is a pressure-sensitive adhesive sheet provided with a pressure-sensitive adhesive layer, wherein the pressure-sensitive adhesive layer includes a first pressure-sensitive adhesive layer as an outer layer on one side, a second pressure-sensitive adhesive layer as an outer layer on the other side, the first pressure-sensitive adhesive layer, and the A third adhesive layer is provided as an intermediate layer between the second adhesive layers, and the adhesive constituting the first adhesive layer and the adhesive constituting the second adhesive layer each have a 100% modulus of 60 kPa or more, and The third adhesive layer is composed of an active energy ray-curable adhesive, and the 100% modulus of the active energy ray-curable adhesive before curing is the 100% modulus of the adhesive constituting the first adhesive layer and the adhesive constituting the second adhesive layer. An adhesive sheet is provided, characterized in that the modulus is lower than 100% (invention 2).

According to the above-described inventions (inventions 1 and 2), the adhesive layer has a third adhesive layer having a low storage modulus (G') or 100% modulus before curing as an intermediate layer, so that the adhesive layer has excellent initial step followability, In addition, the storage modulus (G') or 100% modulus of the first and second adhesive layers, which are the outer layers, is high, and the third adhesive layer is cured by irradiation of active energy rays, so that it can follow steps even under high temperature and high humidity conditions. This is excellent. In addition, the adhesive layer has a high storage modulus (G') or 100% modulus of the first adhesive layer and the second adhesive layer, which are the outer layers, and the third adhesive layer is cured by irradiation of active energy rays, thereby providing blister resistance. This becomes excellent. Furthermore, the adhesive layer has a first adhesive layer and a second adhesive layer having a high storage modulus (G') or 100% modulus as outer layers, and a third adhesive layer having a low storage modulus (G') or 100% modulus before curing. As an intermediate layer, the cross-sectional area of the pressure-sensitive adhesive layer, which has a low storage modulus (G') or 100% modulus before curing, is reduced to improve processability.

In the above inventions (inventions 1 and 2), it is preferable that the adhesive constituting the first adhesive layer and the adhesive constituting the second adhesive layer are adhesives that are not curable by active energy rays (invention 3).

In the above inventions (inventions 1 to 3), the ratio of the thickness of the third adhesive layer to the total thickness of the first adhesive layer and the second adhesive layer is preferably 0.3 or more and 5 or less (invention 4).

In the above inventions (inventions 1 to 4), the total thickness of the adhesive layer is preferably 50 μm or more and 300 μm or less (invention 5).

In the above inventions (inventions 1 to 5), it is preferably used to bond one display body member and another display body member having a step at least on the surface on the side to be joined (invention 6).

In the above inventions (inventions 1 to 6), the adhesive sheet is provided with two release sheets, and the adhesive layer is preferably sandwiched between the release sheets so as to be in contact with the release surfaces of the two release sheets ( Invention 7).

Thirdly, the present invention relates to one display body member having a step at least on the surface of the side to be joined, another display body member, and an adhesive layer for bonding the one display body member and the other display body member to each other. Provided is a display body provided with a display body, wherein the pressure-sensitive adhesive layer is a pressure-sensitive adhesive layer formed by curing the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet (Inventions 1 to 7) (Invention 8).

The adhesive layer of the adhesive sheet and display body according to the present invention is excellent in both step followability and blister resistance, and has good processability.

1 is a cross-sectional view of an adhesive sheet according to an embodiment of the present invention.
Figure 2 is a cross-sectional view of a laminate according to one embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described.

[Adhesive sheet]

A cross-sectional view of an adhesive sheet according to one embodiment of the present invention is shown in Figure 1.

As shown in FIG. 1, the adhesive sheet 1 according to the present embodiment includes two release sheets 31 and 32, and the two release sheets 31 and 32 are in contact with the release surfaces of the two release sheets 31 and 32. It consists of an adhesive layer (2) sandwiched between sheets (31, 32). In addition, the release surface of the release sheet in this specification refers to the surface of the release sheet that has peelability, and includes both a surface that has been subjected to a peeling treatment and a surface that exhibits peelability even without performing a peeling treatment.

The adhesive layer 2 in the present embodiment includes a first adhesive layer as an outer layer on one face side (release sheet 31 side) and a second adhesive layer as an outer layer on the other face side (release sheet 32 side). It is provided with a third adhesive layer (23) positioned as an intermediate layer between the first adhesive layer (21) and the second adhesive layer (22). In this embodiment, the first adhesive layer 21 and the second adhesive layer 22 are each the outermost layer of the adhesive layer 2, and the first adhesive layer 21 is in contact with the release surface of the release sheet 31. and the second adhesive layer 22 is in contact with the release surface of the release sheet 32, but it is not limited to this.

The storage modulus (G') at 23°C of the adhesive constituting the first adhesive layer 21 and the adhesive constituting the second adhesive layer 22 in this embodiment is each 0.1 MPa or more. In addition, the third adhesive layer 23 is composed of an active energy ray-curable adhesive. And, the storage elastic modulus (G') at 23°C before curing of the active energy ray-curable adhesive (before curing by active energy ray irradiation) is 23°C of the adhesive constituting the first adhesive layer 21. is set lower than the storage elastic modulus (G') at 23° C. and the storage elastic modulus (G') of the adhesive constituting the second adhesive layer 22 (above, first alternative condition).

Alternatively, the 100% modulus of the adhesive constituting the first adhesive layer 21 and the adhesive constituting the second adhesive layer 22 in this embodiment is each 60 kPa or more. In addition, the third adhesive layer 23 is composed of an active energy ray-curable adhesive. And, the 100% modulus before curing of the active energy ray-curable adhesive (before curing by active energy ray irradiation) is the 100% modulus of the adhesive constituting the first adhesive layer 21 and the second adhesive layer 22. is set lower than the 100% modulus of the adhesive that constitutes (above, second alternative condition).

The adhesive layer 2 in the present embodiment has the above-described three-layer structure, and each adhesive layer 21, 22, and 23 satisfies the above requirements, so that both step followability and blister resistance are excellent. , processability improves. That is, the adhesive layer 2 in the present embodiment is provided as an intermediate layer with a third adhesive layer 23 having a low storage modulus (G') or 100% modulus before curing, so that the adhesive layer 2 has the initial Excellent step followability. Furthermore, the storage elastic modulus (G') or 100% modulus of the outer layer, first adhesive layer 21 and second adhesive layer 22, is high, and the third adhesive layer 23 is cured by irradiation of active energy rays, Even under high temperature and high humidity conditions, step followability is excellent. For example, when the adhesive sheet according to the present embodiment is attached to a display member having a step, the occurrence of gaps, lifting, etc. in the vicinity of the step is suppressed. And, even when left in that state under high temperature and high humidity conditions, for example, 85°C and 85%RH for 72 hours, the occurrence of bubbles, floatation, peeling, etc. near the steps is suppressed. In addition, the adhesive layer 2 in the present embodiment has a high storage modulus (G') or 100% modulus of the first adhesive layer 21 and the second adhesive layer 22, which are the outer layers, and the third adhesive layer 21 has a high storage modulus (G') or 100% modulus. When the layer 23 is hardened by irradiation of active energy rays, it becomes excellent in blister resistance. For example, a display body (display) obtained using the adhesive sheet 1 according to the present embodiment is placed under high temperature and high humidity conditions, for example, 85°C and 85%RH for 72 hours, and is made of a plastic plate or the like. Even when outgassing is generated from the display body member, the generation of blisters such as bubbles, floatation, and peeling at the interface between the adhesive layer and the display body member is suppressed. Furthermore, the adhesive layer 2 in the present embodiment has a first adhesive layer 21 and a second adhesive layer 22 having a high storage modulus (G') or 100% modulus as outer layers, and is stored before curing. The third adhesive layer 23, which has a low elastic modulus (G') or 100% modulus, is used as an intermediate layer. As a result, the cross-sectional area of the adhesive layer portion of the entire adhesive layer 2 with a low storage modulus (G') or 100% modulus before curing is reduced, thereby improving processability. Therefore, for example, when punching the adhesive sheet 1, problems such as the adhesive sticking out from the cut surface and sticking to the blade are suppressed.

As described above, as a first alternative condition, the storage modulus (G') at 23°C of the adhesive constituting the first adhesive layer 21 and the adhesive constituting the second adhesive layer 22 is each 0.1 MPa. or more, preferably 0.12 MPa or more, and particularly preferably 0.14 MPa or more. Moreover, the storage elastic modulus (G') is preferably 0.5 MPa or less, particularly preferably 0.25 MPa or less, and more preferably 0.18 MPa or less. When the storage elastic modulus (G') is 0.5 MPa or less, the step followability of the adhesive layer 2 can be kept high. In addition, the storage elastic modulus (G') of the adhesive constituting the first adhesive layer 21 at 23°C and the storage elastic modulus (G') of the adhesive constituting the second adhesive layer 22 at 23°C are It may be the same or different.

In addition, as a first alternative condition, the storage modulus (G') at 23°C before curing of the active energy ray-curable adhesive constituting the third adhesive layer 23 is that of the adhesive constituting the first adhesive layer 21. is set lower than the storage elastic modulus (G') at 23°C and the storage elastic modulus (G') at 23°C of the adhesive constituting the second adhesive layer 22. As a specific value, the storage modulus (G') is preferably 0.10 MPa or less, particularly preferably 0.09 MPa or less, and more preferably 0.08 MPa or less. Thereby, the level difference followability of the adhesive layer 2 can be made more excellent. Moreover, the storage elastic modulus (G') is preferably 0.01 MPa or more, particularly preferably 0.03 MPa or more, and more preferably 0.06 MPa or more. Thereby, the processability of the adhesive layer 2 can be improved. In addition, the method of measuring the storage modulus (G') is as shown in the test example described later.

Here, the storage modulus (G') at 23°C after curing of the active energy ray-curable adhesive constituting the third adhesive layer 23 (after curing by irradiation with active energy rays) is preferably 0.1 MPa or more, In particular, it is preferable to be 0.11 MPa or more, and more preferably 0.12 MPa or more. As a result, the blister resistance of the adhesive layer 2 and the level difference followability under high temperature and high humidity conditions can be improved. On the one hand, the storage modulus (G') is preferably 0.5 MPa or less, especially 0.3 MPa or less, and more preferably 0.18 MPa or less. This makes it possible to keep the adhesive force of the third adhesive layer 23 high, especially the adhesive force to the first adhesive layer 21 and the second adhesive layer 22.

In addition, the storage modulus (G') at 23°C after curing of the active energy ray-curable adhesive constituting the third adhesive layer 23 is that of the adhesive constituting the first adhesive layer 21 at 23°C. The storage elastic modulus (G') may be smaller or larger than the storage elastic modulus (G') at 23°C of the adhesive constituting the second adhesive layer 22, and both may be the same. Among these, the storage modulus (G') at 23°C after curing of the active energy ray-curable adhesive constituting the third adhesive layer 23 is that of the adhesive constituting the first adhesive layer 21 at 23°C. It is preferable that the storage elastic modulus (G') of the adhesive forming the second adhesive layer 22 is larger than the storage elastic modulus (G') at 23°C. As a result, the adhesive layer 2 becomes more excellent in blister resistance and level difference followability under high temperature and high humidity conditions.

As described above, as a second alternative condition, the 100% modulus of the adhesive constituting the first adhesive layer 21 and the adhesive constituting the second adhesive layer 22 is each 60 kPa or more, preferably 70 kPa. or more, and particularly preferably 80 kPa or more. Moreover, the 100% modulus is preferably 150 kPa or less, particularly preferably 140 kPa or less, and more preferably 130 kPa or less. When the 100% modulus is 150 kPa or less, the step followability of the adhesive layer 2 can be kept high. In addition, the 100% modulus of the adhesive constituting the first adhesive layer 21 and the 100% modulus of the adhesive constituting the second adhesive layer 22 may be the same or different.

In addition, as a second alternative condition, the 100% modulus of the active energy ray-curable adhesive constituting the third adhesive layer 23 before curing is the 100% modulus of the adhesive constituting the first adhesive layer 21 and the second adhesive. It is set lower than the 100% modulus of the adhesive constituting the layer 22. As a specific value, the storage modulus (G') is preferably 60 kPa or less, particularly preferably 50 kPa or less, and more preferably 40 kPa or less. Thereby, the level difference followability of the adhesive layer 2 can be made more excellent. Moreover, the 100% modulus is preferably 5 kPa or more, particularly preferably 10 kPa or more, and more preferably 15 kPa or more. Thereby, the processability of the adhesive layer 2 can be improved. In addition, the method for measuring the 100% modulus is as shown in the test example described later.

Here, the 100% modulus after curing (after curing by irradiation of active energy rays) of the active energy ray-curable adhesive constituting the third adhesive layer 23 is preferably 30 kPa or more, and especially preferably 40 kPa or more, Furthermore, it is preferable that it is 50 kPa or more. As a result, the blister resistance of the adhesive layer 2 and the level difference followability under high temperature and high humidity conditions can be improved. On the other hand, the 100% modulus is preferably 300 kPa or less, especially 200 kPa or less, and more preferably 180 kPa or less. This makes it possible to keep the adhesive force of the third adhesive layer 23 high, especially the adhesive force to the first adhesive layer 21 and the second adhesive layer 22.

In addition, the 100% modulus of the active energy ray-curable adhesive constituting the third adhesive layer 23 after curing (after curing by active energy ray irradiation) is 100% of that of the adhesive constituting the first adhesive layer 21. The modulus may be smaller or larger than the 100% modulus of the adhesive constituting the second adhesive layer 22, and both may be the same. Among these, the 100% modulus after curing of the active energy ray-curable adhesive constituting the third adhesive layer 23 is the 100% modulus of the adhesive constituting the first adhesive layer 21 and the second adhesive layer 22. It is preferable that the modulus is greater than 100% of the constituting adhesive. As a result, the adhesive layer 2 becomes more excellent in blister resistance and level difference followability under high temperature and high humidity conditions.

The ratio of the thickness of the third adhesive layer 23 to the total thickness of the first adhesive layer 21 and the second adhesive layer 22 is preferably 0.3 or more, especially 0.4 or more, and even 0.5 or more. desirable. Additionally, the ratio is preferably 5 or less, especially 3 or less, further preferably 2 or less, and most preferably 0.8 or less. When the ratio falls within the above range, the effects of step followability, blister resistance, and processability described above are exhibited more favorably. In addition, the thickness of each layer is a value measured according to JIS K 7130.

The total thickness of the adhesive layer 2 is preferably 50 μm or more, particularly preferably 75 μm or more, and more preferably 100 μm or more. Moreover, the total thickness is preferably 300 μm or less, especially 250 μm or less, and more preferably 200 μm or less. When the total thickness of the adhesive layer 2 is within the above range, the effects of step followability, blister resistance, and processability described above are exhibited more favorably.

The thickness of the first adhesive layer 21 and the second adhesive layer 22 are preferably 25 μm or more, particularly 30 μm or more, and more preferably 50 μm or more. Moreover, the thickness is preferably 100 μm or less, especially 80 μm or less, and more preferably 75 μm or less. When the thickness falls within the above range, the effects of step followability, blister resistance, and processability described above are exhibited more effectively. In addition, the thickness of the first adhesive layer 21 and the thickness of the second adhesive layer 22 may be the same or different.

The thickness of the third adhesive layer 23 is preferably 25 μm or more, particularly preferably 30 μm or more, and more preferably 50 μm or more. Moreover, the thickness is preferably 150 μm or less, particularly preferably 125 μm or less, further preferably 100 μm or less, and most preferably 75 μm or less. When the thickness falls within the above range, the effects of step followability, blister resistance, and processability described above are exhibited more effectively.

1. First adhesive layer and second adhesive layer

The adhesive constituting the first adhesive layer and the adhesive constituting the second adhesive layer are not particularly limited as long as they satisfy the above-mentioned physical properties, and may be an active energy ray-curable adhesive or an active energy ray non-curable adhesive. It is preferable that the adhesive is non-curable by energy radiation. Thereby, the adhesion (adhesion) to the adherend (particularly the display body member) after irradiating the adhesive layer 2 with active energy rays can be maintained at a higher level. In addition, the adhesive constituting the first adhesive layer and the adhesive constituting the second adhesive layer may be the same adhesive or different adhesives.

Hereinafter, the active energy ray non-curable adhesive will mainly be described. In addition, in the case of an active energy ray-curable adhesive, the same adhesive as the active energy ray-curable adhesive constituting the third adhesive layer 23 described later can be used.

The active energy ray non-curable adhesives constituting the first adhesive layer and the second adhesive layer include, for example, acrylic adhesives, rubber adhesives, silicone adhesives, urethane adhesives, polyester adhesives, polyvinyl ether adhesives, etc. It can be any. Additionally, the adhesive may be of an emulsion type, solvent type, or non-solvent type, and may be of a crosslinked type or non-crosslinked type.

Among the above, acrylic adhesives are preferable. In that case, the adhesive in the present embodiment is preferably obtained from an adhesive composition (hereinafter sometimes referred to as “adhesive composition (P)”) containing the (meth)acrylic acid ester polymer (A). The adhesive composition (P) preferably further contains a crosslinking agent (B), and in that case, the adhesive in this embodiment is obtained by crosslinking the adhesive composition (P). In addition, in this specification, (meth)acrylic acid ester means both acrylic acid ester and methacrylic acid ester. Other similar terms are also the same. In addition, “polymer” shall also include the concept of “copolymer.”

(1) (meth)acrylic acid ester polymer (A)

The (meth)acrylic acid ester polymer (A) can exhibit desirable adhesiveness by containing an alkyl (meth)acrylic acid ester whose alkyl group has 1 to 20 carbon atoms as a monomer unit constituting the polymer. From this point of view, the (meth)acrylic acid ester polymer (A) preferably contains, as a lower limit, 50% by mass or more of (meth)acrylic acid alkyl ester whose alkyl group has 1 to 20 carbon atoms as the monomer unit constituting the polymer, In particular, it is preferable to contain 60% by mass or more, and more preferably 70% by mass or more. When the (meth)acrylic acid alkyl ester is contained in an amount of 50% by mass or more, the (meth)acrylic acid ester polymer (A) can exhibit desirable adhesiveness. Moreover, the (meth)acrylic acid ester polymer (A) preferably contains 97% by mass or less of the above-mentioned (meth)acrylic acid alkyl ester as the monomer unit constituting the polymer as an upper limit, and especially preferably contains 90% by mass or less. Furthermore, it is preferable to contain 85% by mass or less. By containing 97% by mass or less of the above-mentioned (meth)acrylic acid alkyl ester, other monomer components can be introduced in a desirable amount into the (meth)acrylic acid ester polymer (A).

Examples of (meth)acrylic acid alkyl esters in which the alkyl group has 1 to 20 carbon atoms include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, and (meth)acrylate. n-pentyl acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, n-decyl (meth)acrylate, n-dodecyl (meth)acrylate, (meth)acrylic acid Myristyl, palmityl (meth)acrylate, stearyl (meth)acrylate, cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, adamantyl (meth)acrylate, etc. are mentioned, and among them, adhesive properties include From the viewpoint of further improvement, it is preferable that (meth)acrylic acid ester whose alkyl group has 4 to 8 carbon atoms is included. These may be used individually, or two or more types may be used in combination. In addition, the alkyl group in the (meth)acrylic acid alkyl ester in which the alkyl group has 1 to 20 carbon atoms refers to a straight-chain, branched-chain, or cyclic alkyl group.

In addition, as an alkyl (meth)acrylic acid ester whose alkyl group has 1 to 20 carbon atoms, a hard monomer whose glass transition temperature (Tg) as a homopolymer exceeds 0°C (preferably 70°C or higher), and a glass transition temperature (Tg) as a homopolymer It is also preferable to use a combination of soft monomers having a temperature (Tg) of 0°C or lower. This is because adhesion and flexibility can be secured with a soft monomer and cohesion can be improved with a hard monomer, thereby improving step followability. In this case, the mass ratio of the hard monomer and the soft monomer is preferably 5:95 to 40:60, and particularly preferably 20:80 to 30:70.

Examples of the hard monomer include methyl acrylate (Tg 10°C), methyl methacrylate (Tg 105°C), isobornyl acrylate (Tg 94°C), isobornyl methacrylate (Tg 180°C), Examples include adamantyl acrylate (Tg 115°C) and adamantyl methacrylate (Tg 141°C). These may be used individually, or two or more types may be used in combination.

Among the above hard monomers, methyl acrylate, methyl methacrylate, and isobornyl acrylate are preferred from the viewpoint of enhancing the performance of the hard monomer while preventing adverse effects on other properties such as adhesiveness and transparency. Considering adhesiveness, methyl acrylate and methyl methacrylate are more preferable, and methyl methacrylate is particularly preferable.

As the soft monomer, an acrylic acid alkyl ester having a linear or branched alkyl group having 2 to 12 carbon atoms is preferably used. For example, 2-ethylhexyl acrylate (Tg -70°C), n-butyl acrylate (Tg -54°C), etc. are preferably used. These may be used individually, or two or more types may be used in combination.

The (meth)acrylic acid ester polymer (A) preferably contains a reactive functional group-containing monomer as a monomer unit constituting the polymer. The reactive functional group derived from this reactive functional group-containing monomer reacts with a crosslinking agent (B) described later, thereby forming a crosslinking structure (three-dimensional network structure), and obtaining an adhesive having the desired cohesive force.

The reactive functional group-containing monomer contained in the (meth)acrylic acid ester polymer (A) as a monomer unit constituting the polymer includes a monomer having a hydroxyl group in the molecule (hydroxyl group-containing monomer), a monomer having a carboxyl group in the molecule (carboxyl group-containing monomer) ), a monomer having an amino group in the molecule (amino group-containing monomer), etc. are preferably mentioned. Among these, hydroxyl group-containing monomers that have excellent reactivity with the crosslinking agent (B) and have little adverse effect on the adherend are particularly preferable.

Examples of hydroxyl group-containing monomers include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, (meth)acrylic acid hydroxyalkyl esters such as 3-hydroxybutyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate. Among them, 2-hydroxyethyl (meth)acrylic acid or 4- (meth)acrylic acid is used in terms of the reactivity of the hydroxyl group in the obtained (meth)acrylic acid ester polymer (A) with the crosslinking agent (B) and copolymerizability with other monomers. Hydroxybutyl is preferred. These may be used individually, or two or more types may be used in combination.

Examples of the carboxyl group-containing monomer include ethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, itaconic acid, and citraconic acid. Among them, acrylic acid is preferable in terms of the reactivity of the carboxyl group in the resulting (meth)acrylic acid ester polymer (A) with the crosslinking agent (B) and copolymerizability with other monomers. These may be used individually, or two or more types may be used in combination.

Examples of amino group-containing monomers include aminoethyl (meth)acrylate, n-butylaminoethyl (meth)acrylate, and the like. These may be used individually, or two or more types may be used in combination.

When the (meth)acrylic acid ester polymer (A) contains a hydroxyl group-containing monomer as a monomer unit constituting the polymer, the content is preferably 3% by mass or more as a lower limit, and especially preferably 10% by mass or more, and further. It is preferable that it is 15 mass % or more. Moreover, the content is preferably 35% by mass or less as an upper limit, especially preferably 30% by mass or less, and more preferably 25% by mass or less. When the (meth)acrylic acid ester polymer (A) contains a hydroxyl group-containing monomer in the above amount as a monomer unit, a predetermined amount of hydroxyl group will remain in the resulting pressure-sensitive adhesive. The hydroxyl group is a hydrophilic group, and when such a hydrophilic group is present in a predetermined amount in the adhesive, even when the adhesive is placed under high temperature and high humidity conditions, it has good compatibility with moisture that has entered the adhesive under the high temperature and high humidity conditions, and as a result, it can be returned to normal temperature and humidity. Whitening of the adhesive is suppressed (excellent moisture-heat whitening resistance).

When the (meth)acrylic acid ester polymer (A) contains a carboxyl group-containing monomer as a monomer unit constituting the polymer, the content is preferably 0.5% by mass or more as a lower limit, more preferably 1% by mass or more, and 6 It is especially preferable that it is mass % or more. Moreover, the content is preferably 20% by mass or less as an upper limit, more preferably 15% by mass or less, and especially preferably 10% by mass or less.

In addition, when the adherend is a material that is likely to be adversely affected by acid, such as a transparent conductive film or metal wiring, the (meth)acrylic acid ester polymer (A) contains a carboxyl group-containing monomer as a monomer unit constituting the polymer. It is desirable not to contain it. Thereby, for example, corrosion of the transparent conductive film or metal wiring or change in the resistance value of the transparent conductive film can be suppressed.

Here, “not containing a carboxyl group-containing monomer” means substantially not containing a carboxyl group-containing monomer, and in addition to not containing any carboxyl group-containing monomer, corrosion of transparent conductive films, metal wiring, etc. due to carboxyl groups. It is allowed to contain a carboxyl group-containing monomer to the extent that it does not occur. Specifically, the (meth)acrylic acid ester polymer (A) is permitted to contain a carboxyl group-containing monomer as a monomer unit in an amount of 0.01% by mass or less, preferably 0.001% by mass or less.

The (meth)acrylic acid ester polymer (A) may contain other monomers as monomer units constituting the polymer, as desired. As the other monomer, a monomer that does not contain a reactive functional group is preferred in order not to interfere with the action of the monomer containing a reactive functional group. Other such monomers include, for example, (meth)acrylic acid alkoxyalkyl esters such as methoxyethyl (meth)acrylate and ethoxyethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, and (meth)acrylic acid. (meth)acrylic acid esters having a non-crosslinkable tertiary amino group such as N,N-dimethylaminopropyl acrylate, (meth)acryloylmorpholine, (meth)acrylamide, dimethylacrylamide, vinyl acetate, styrene, etc. You can. These may be used individually, or two or more types may be used in combination.

The polymerization mode of the (meth)acrylic acid ester polymer (A) may be a random copolymer or a block copolymer.

The lower limit of the weight average molecular weight of the (meth)acrylic acid ester polymer (A) is preferably 200,000 or more, particularly preferably 300,000 or more, and more preferably 400,000 or more. In addition, the weight average molecular weight in this specification is a standard polystyrene conversion value measured by gel permeation chromatography (GPC) method. If the lower limit of the weight average molecular weight of the (meth)acrylic acid ester polymer (A) is more than the above, the adhesive will have better blister resistance and step followability under high temperature and high humidity conditions.

Moreover, the upper limit of the weight average molecular weight of the (meth)acrylic acid ester polymer (A) is preferably 1 million or less, particularly preferably 900,000 or less, and more preferably 700,000 or less. If the upper limit of the weight average molecular weight of the (meth)acrylic acid ester polymer (A) is equal to or less than the above, the pressure-sensitive adhesive will have better step followability when affixed.

In addition, in the adhesive composition (P), the (meth)acrylic acid ester polymer (A) may be used individually or in combination of two or more types.

(2) Cross-linking agent (B)

The adhesive composition (P) preferably contains a crosslinking agent (B). The adhesive composition (P) contains a crosslinking agent (B), which crosslinks the (meth)acrylic acid ester polymer (A) to form a three-dimensional network structure, improves the cohesive strength of the resulting adhesive, improves blister resistance and level difference under high temperature and high humidity conditions. Followability can be further improved.

The crosslinking agent (B) may be any that reacts with the reactive group of the (meth)acrylic acid ester polymer (A), for example, an isocyanate-based crosslinking agent, an epoxy-based crosslinking agent, an amine-based crosslinking agent, a melamine-based crosslinking agent, an aziridine-based crosslinking agent, or a hydrazine-based crosslinking agent. Cross-linking agents, aldehyde-based cross-linking agents, oxazoline-based cross-linking agents, metal alkoxide-based cross-linking agents, metal chelate-based cross-linking agents, metal salt-based cross-linking agents, ammonium salt-based cross-linking agents, and the like. When the (meth)acrylic acid ester polymer (A) contains a hydroxyl group-containing monomer as a monomer unit constituting the polymer, it is preferable to use an isocyanate-based crosslinking agent having excellent reactivity with the hydroxyl group. Moreover, when the (meth)acrylic acid ester polymer (A) contains a carboxyl group-containing monomer as a monomer unit constituting the polymer, it is preferable to use an epoxy-based crosslinking agent having excellent reactivity with the carboxyl group. In addition, the crosslinking agent (B) can be used individually or in combination of two or more types.

The isocyanate-based crosslinking agent contains at least a polyisocyanate compound. Examples of polyisocyanate compounds include aromatic polyisocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate, and xylylene diisocyanate, aliphatic polyisocyanates such as hexamethylene diisocyanate, isophorone diisocyanate, and hydrogenated diphenylmethane. Alicyclic polyisocyanates such as diisocyanate, and their biuret and isocyanurate forms, as well as reactants with low molecular weight active hydrogen-containing compounds such as ethylene glycol, propylene glycol, neopentyl glycol, trimethylolpropane, and castor oil. An adduct body, etc. are mentioned. Among these, from the viewpoint of reactivity with hydroxyl groups, trimethylolpropane-modified aromatic polyisocyanate, especially trimethylolpropane-modified tolylene diisocyanate, is preferable.

Epoxy-based crosslinking agents include, for example, 1,3-bis(N,N'-diglycidylaminomethyl)cyclohexane, N,N,N',N'-tetraglycidyl-m-xylylene. Diamine, ethylene glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylolpropane diglycidyl ether, diglycidyl aniline, diglycidyl amine, etc. are mentioned. Among them, 1,3-bis(N,N'-diglycidylaminomethyl)cyclohexane is preferable from the viewpoint of reactivity with the carboxyl group.

The content of the crosslinking agent (B) in the adhesive composition (P) is preferably 0.001 parts by mass or more as a lower limit with respect to 100 parts by mass of the (meth)acrylic acid ester polymer (A), and especially preferably 0.01 parts by mass or more, and further. is preferably 0.02 parts by mass or more. Moreover, the upper limit is preferably 10 parts by mass or less, especially preferably 5 parts by mass or less, and more preferably 1 part by mass or less.

When the content of the crosslinking agent (B) is within the above-mentioned range, the cohesive force of the resulting pressure-sensitive adhesive becomes desirable, and the blister resistance and step followability under high-temperature, high-humidity conditions of the pressure-sensitive adhesive are improved.

(3) Various additives

The adhesive composition (P) may contain various additives commonly used in acrylic adhesives as desired, such as silane coupling agents, antistatic agents, tackifiers, antioxidants, ultraviolet absorbers, light stabilizers, softeners, fillers, refractive index regulators, etc. can be added.

In addition, the adhesive composition (P) represents a mixture of various components remaining in the adhesive layer as is or in a reacted state, and components removed in the drying process, such as the polymerization solvent or dilution solvent described later, are the adhesive composition ( P) is not included.

Here, when the adhesive composition (P) contains a silane coupling agent, the resulting adhesive has improved adhesion to the glass member or plastic plate. As a result, the obtained adhesive has better blister resistance and step followability under high temperature and high humidity conditions.

The silane coupling agent is preferably an organosilicon compound having at least one alkoxy silyl group in the molecule, has good compatibility with the (meth)acrylic acid ester polymer (A), and has light transparency.

Such silane coupling agents include, for example, silicon compounds containing polymerizable unsaturated groups such as vinyltrimethoxysilane, vinyltriethoxysilane, methacryloxypropyltrimethoxysilane, and 3-glycidoxypropyltrimethoxy. Silane, silicon compounds having an epoxy structure such as 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-mer Mercapto group-containing silicon compounds such as captopropyldimethoxymethylsilane, 3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, and N-(2-aminoethyl) -Silicon compounds containing an amino group such as 3-aminopropylmethyldimethoxysilane, 3-chloropropyltrimethoxysilane, 3-isocyanatepropyltriethoxysilane, or at least one of these, methyltriethoxysilane, and ethyltriethoxysilane. and condensates of alkyl group-containing silicon compounds such as toxysilane, methyltrimethoxysilane, and ethyltrimethoxysilane. These may be used individually or in combination of two or more types.

When the adhesive composition (P) contains a silane coupling agent, the content is preferably 0.01 parts by mass or more as a lower limit for 100 parts by mass of the (meth)acrylic acid ester polymer (A), and especially preferably 0.05 parts by mass or more. , and furthermore, it is preferably 0.1 mass part or more. Moreover, the content is preferably 5 parts by mass or less as an upper limit, especially preferably 1 part by mass or less, and more preferably 0.5 parts by mass or less.

(4) Preparation of adhesive composition

The adhesive composition (P) can be produced by producing a (meth)acrylic acid ester polymer (A) and adding a crosslinking agent (B) and additives to the obtained (meth)acrylic acid ester polymer (A) as desired.

The (meth)acrylic acid ester polymer (A) can be produced by polymerizing a mixture of monomers constituting the polymer by a conventional radical polymerization method. The polymerization of the (meth)acrylic acid ester polymer (A) is preferably carried out by a solution polymerization method using a polymerization initiator as desired. Examples of polymerization solvents include ethyl acetate, n-butyl acetate, isobutyl acetate, toluene, acetone, hexane, methyl ethyl ketone, etc., and two or more types may be used in combination.

Polymerization initiators include azo compounds and organic peroxides, and two or more types may be used in combination. Azo compounds include, for example, 2,2'-azobisisobutyronitrile, 2,2'-azobis(2-methylbutyronitrile), and 1,1'-azobis(cyclohexane 1- carbonitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(2,4-dimethyl-4-methoxyvaleronitrile), dimethyl 2,2' -Azobis(2-methylpropionate), 4,4'-Azobis(4-cyanovaleric acid), 2,2'-Azobis(2-hydroxymethylpropionitrile), 2,2' -Azobis[2-(2-imidazoline-2-yl)propane], etc. can be mentioned.

Organic peroxides include, for example, benzoyl peroxide, t-butylperbenzoate, cumene hydroperoxide, diisopropylperoxydicarbonate, di-n-propylperoxydicarbonate, and di(2-ethoxyethyl)peroxydicarbonate. Carbonate, t-butyl peroxyneodecanoate, t-butyl peroxypivalate, (3,5,5-trimethylhexanoyl) peroxide, dipropionyl peroxide, diacetyl peroxide, etc.

Additionally, in the polymerization step, the weight average molecular weight of the obtained polymer can be adjusted by mixing a chain transfer agent such as 2-mercaptoethanol.

Once the (meth)acrylic acid ester polymer (A) is obtained, the crosslinking agent (B), additives, and diluting solvent are added as desired to the solution of the (meth)acrylic acid ester polymer (A), and mixed sufficiently to obtain a solution diluted with the solvent. An adhesive composition (P) (application solution) is obtained. In addition, when any of the above components is used in a solid state, or when precipitation occurs when mixed with other components in an undiluted state, the component is dissolved or diluted individually in a diluting solvent in advance, and then You may mix it with other ingredients.

Examples of the diluting solvent include aliphatic hydrocarbons such as hexane, heptane, and cyclohexane, aromatic hydrocarbons such as toluene and xylene, halogenated hydrocarbons such as methylene chloride and ethylene chloride, methanol, ethanol, propanol, butanol, 1- Alcohols such as methoxy-2-propanol, ketones such as acetone, methyl ethyl ketone, 2-pentanone, isophorone, and cyclohexanone, esters such as ethyl acetate and butyl acetate, and cellosolve-based solvents such as ethyl cellosolve. etc. are used.

The concentration and viscosity of the coating solution prepared in this way may be within a range that can be coated, and is not particularly limited and can be appropriately selected depending on the situation. For example, the adhesive composition (P) is diluted so that the concentration is 10 to 60 mass%. Additionally, when obtaining an application solution, the addition of a diluting solvent, etc. is not a necessary condition, and if the adhesive composition (P) has a coatable viscosity, etc., there is no need to add a diluting solvent. In this case, the adhesive composition (P) becomes a coating solution using the polymerization solvent of the (meth)acrylic acid ester polymer (A) as a dilution solvent.

(5) Manufacturing of adhesive

The adhesive constituting the first adhesive layer 21 and the adhesive constituting the second adhesive layer 22 can be preferably obtained by crosslinking the adhesive composition (P). Crosslinking of the adhesive composition (P) can usually be performed by heat treatment. In addition, this heat treatment can also serve as a drying treatment for volatilizing a diluting solvent or the like from the coating film of the adhesive composition (P) applied to the desired object.

The heating temperature for the heat treatment is preferably 50 to 150°C, and particularly preferably 70 to 120°C. Moreover, the heating time is preferably 10 seconds to 10 minutes, and particularly preferably 50 seconds to 2 minutes.

After heat treatment, a curing period of about 1 to 2 weeks may be provided at room temperature (for example, 23°C, 50%RH) as needed. If this curing period is necessary, the adhesive is formed after the curing period has elapsed. If the curing period is not necessary, the adhesive is formed after the heat treatment is completed.

By the heat treatment (and curing) described above, the (meth)acrylic acid ester polymer (A) is sufficiently crosslinked (if a crosslinking agent (B) is included, via the crosslinking agent (B)).

(6) Gel fraction

The gel fraction of the adhesive constituting the first adhesive layer 21 and the adhesive constituting the second adhesive layer 22 is preferably 50% or more as a lower limit, especially preferably 60% or more, and further preferably 65% or more. desirable. When the gel fraction of the adhesive is 50% or more, the cohesion of the adhesive increases, and the adhesive layer 2 has better blister resistance and step followability under high temperature and high humidity. Moreover, the gel fraction of the adhesive is preferably 85% or less as an upper limit, especially preferably 80% or less, and more preferably 75% or less. If the gel fraction of the adhesive is 85% or less, the adhesive does not harden excessively and has better step followability. Here, the method for measuring the gel fraction of the adhesive is as shown in the test example described later.

(7) Adhesion

The adhesion of the first adhesive layer 21 (laminated body with the base material) and the second adhesive layer 22 (laminated body with the base material) to soda lime glass is preferably 5 N/25 mm or more as a lower limit, In particular, it is preferable to be 10 N/25 mm or more, and more preferably 15 N/25 mm or more. If the adhesive strength is more than the above, the blister resistance and level difference followability under high temperature and high humidity conditions are excellent. Moreover, the upper limit of the adhesive force is preferably 50 N/25 mm or less, especially 40 N/25 mm or less, and more preferably 35 N/25 mm or less. If the adhesive strength is below the above, good reworkability is obtained, and when a bonding error occurs, it becomes possible to reuse the expensive display body constituent members.

Here, the adhesive force in this specification basically refers to the adhesive force measured by the 180-degree peeling method according to JIS Z 0237:2009. The measurement sample is 25 mm in width and 100 mm in length, and the measurement sample is It is attached to the complex, pressurized at 0.5 MPa and 50°C for 20 minutes, left for 24 hours under conditions of normal pressure, 23°C and 50%RH, and then measured at a peeling speed of 300 mm/min. Additionally, as the substrate, a polyethylene terephthalate film with a thickness of 100 μm is used.

(8) Step tracking rate

The step tracking ratio (%) of the first adhesive layer 21 and the second adhesive layer 22, expressed by the following formula, is preferably 10% or more as a lower limit, especially preferably 15% or more, and furthermore 20% or more. It is desirable. Moreover, the step tracking ratio (%) is preferably 50% or less as an upper limit, especially preferably 45% or less, and more preferably 40% or less.

Step tracking rate (%) = {(After the prescribed durability test, the height of the step that remains filled without bubbles, lifting, peeling, etc. (μm))/(Thickness of adhesive layer)} × 100

In addition, the test method for the step tracking ratio is as shown in the test example described later.

Since the step followability ratio of the first adhesive layer 21 and the second adhesive layer 22 as the outer layer is in the above-described range, the step followability as the adhesive layer 2 of the adhesive sheet 1 according to the present embodiment is higher. It's easy to become excellent.

2. Third adhesive layer

The active energy ray-curable adhesive constituting the third adhesive layer 23 is not particularly limited as long as it satisfies the physical properties described above. The active energy ray-curable adhesive preferably contains at least one of active energy ray-curable monomers, oligomers, and polymers, or a mixture thereof, and in addition, any of active energy ray-non-curable monomers, oligomers, and polymers, or It may contain mixtures of them.

In this embodiment, the active energy ray-curable adhesive constituting the third adhesive layer 23 is obtained from the adhesive composition (Q) containing a (meth)acrylic acid ester polymer (C) and an active energy ray-curable compound (D). It is desirable to obtain The adhesive composition (Q) preferably further contains a crosslinking agent (B), and in that case, the active energy ray-curable adhesive is obtained by crosslinking the adhesive composition (Q).

(1) (meth)acrylic acid ester polymer (C)

The (meth)acrylic acid ester polymer (C) is basically the above-described (meth)acrylic acid ester polymer (A) as long as the active energy ray-curable adhesive constituting the third adhesive layer 23 satisfies the above-mentioned physical properties. same. However, since the third adhesive layer 23 is an intermediate layer and does not come into direct contact with the adherend, it is also preferable that the (meth)acrylic acid ester polymer (C) contains a carboxyl group-containing monomer as a monomer unit constituting the polymer. do.

Moreover, the (meth)acrylic acid ester polymer (C) also preferably contains a nitrogen atom-containing monomer as a monomer unit constituting the polymer. By allowing a nitrogen atom-containing monomer to exist as a structural unit in the polymer, the crosslinking reaction between the reactive functional group of the (meth)acrylic acid ester polymer (C) and the crosslinking agent (B) can be promoted. Examples of the nitrogen atom-containing monomer include monomers having an amino group, monomers having an amide group, monomers having a nitrogen-containing heterocycle, and the like. Among these, from the viewpoint of providing appropriate rigidity to the (meth)acrylic acid ester polymer (C) Monomers having nitrogen-containing heterocycles are preferred.

Monomers having a nitrogen-containing heterocycle include, for example, N-(meth)acryloylmorpholine, N-vinyl-2-pyrrolidone, N-(meth)acryloylpyrrolidone, and N-(meth) ) Acryloylpiperidine, N-(meth)acryloylpyrrolidine, N-(meth)acryloylaziridine, aziridinylethyl (meth)acrylate, 2-vinylpyridine, 4-vinylpyridine, 2 - Examples include vinylpyrazine, 1-vinylimidazole, N-vinylcarbazole, and N-vinylphthalimide. Among them, N-(meth)acryloylmorpholine, which exhibits better adhesiveness, is preferable. And N-acryloylmorpholine is particularly preferred.

In addition, as nitrogen atom-containing monomers, for example, (meth)acrylamide, N-methyl (meth)acrylamide, N-methylol (meth)acrylamide, N-tert-butyl (meth)acrylamide, N, N-dimethyl(meth)acrylamide, N,N-ethyl(meth)acrylamide, N,N-dimethylaminopropyl(meth)acrylamide, N-isopropyl(meth)acrylamide, N-phenyl(meth)acrylamide Amide, dimethylaminopropyl (meth)acrylamide, N-vinylcaprolactam, monomethylaminoethyl (meth)acrylate, monoethylaminoethyl (meth)acrylate, monomethylaminopropyl (meth)acrylate, monoethyl (meth)acrylate Aminopropyl, dimethylaminoethyl (meth)acrylate, etc. can also be used.

The above nitrogen atom-containing monomers may be used individually or in combination of two or more types.

When the (meth)acrylic acid ester polymer (C) contains a nitrogen atom-containing monomer as a monomer unit constituting the polymer, it preferably contains 1% by mass or more of the nitrogen atom-containing monomer, and especially contains 2% by mass or more. It is preferable to do so, and it is further preferable to contain 3% by mass or more. In addition, the (meth)acrylic acid ester polymer (A) preferably contains 20% by mass or less of the nitrogen atom-containing monomer as the monomer unit constituting the polymer, and especially preferably contains 15% by mass or less, and further preferably contains 15% by mass or less of the nitrogen atom-containing monomer. It is preferable to contain 10% by mass or less. If the content of the nitrogen atom-containing monomer is within the above range, the effect of promoting the crosslinking reaction between the (meth)acrylic acid ester polymer (C) and the crosslinking agent (B) can be favorably obtained.

(2) Active energy ray curable compound (D)

When the adhesive composition (Q) contains an active energy ray-curable compound (D), when the active energy ray-curable adhesive obtained by heat crosslinking the adhesive composition (Q) is cured by irradiation of an active energy ray, the active energy ray-curable compound (D) polymerizes with each other, and the polymerized active energy ray-curable compound (D) is presumed to be wrapped around the crosslinked structure (three-dimensional network structure) of the (meth)acrylic acid ester polymer (A). Since the adhesive having such a higher-order structure has high cohesive force and exhibits a relatively high elastic modulus, the adhesive layer 2 having the third adhesive layer 23 as an intermediate layer has better blister resistance.

The active energy ray-curable compound (D) is cured by irradiation of an active energy ray, and is not particularly limited as long as it is a compound that obtains the above effect. It may be a monomer, an oligomer, or a polymer, or a mixture thereof. Among them, polyfunctional acrylate-based monomers with a molecular weight of less than 1000 that have excellent compatibility with (meth)acrylic acid ester polymer (C) and the like are preferable.

Examples of polyfunctional acrylate-based monomers with a molecular weight of less than 1000 include 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, and neopentyl glycol di(meth)acrylate. Latex, polyethylene glycol di(meth)acrylate, neopentyl glycol adipate di(meth)acrylate, hydroxypivalic acid neopentyl glycol di(meth)acrylate, dicyclopentanyl di(meth)acrylate, caprolactone modified Dicyclopentenyl di(meth)acrylate, ethylene oxide modified phosphoric acid di(meth)acrylate, di(acryloxyethyl)isocyanurate, allylated cyclohexyl di(meth)acrylate, ethoxylated bisphenol A diacrylate. , 9,9-bis[4-(2-acryloyloxyethoxy)phenyl]fluorene, etc.; Trimethylolpropane tri(meth)acrylate, dipentaerythritol tri(meth)acrylate, propionic acid modified dipentaerythritol tri(meth)acrylate, pentaerythritol tri(meth)acrylate, propylene oxide modified trimethylolpropane trifunctional types such as tri(meth)acrylate, tris(acryloxyethyl)isocyanurate, and ε-caprolactone-modified tris-(2-(meth)acryloxyethyl)isocyanurate; Tetrafunctional types such as diglycerin tetra(meth)acrylate and pentaerythritol tetra(meth)acrylate; Pentafunctional types such as propionic acid-modified dipentaerythritol penta(meth)acrylate; and hexafunctional types such as dipentaerythritol hexa(meth)acrylate and caprolactone-modified dipentaerythritol hexa(meth)acrylate. Among the above, pentaerythritol tri(meth)acrylate and ε-caprolactone modified tris-(2-(meth)acryloxyethyl)isocyanurate are preferred from the viewpoint of blistering resistance of the obtained adhesive. These may be used individually or in combination of two or more types.

As the active energy ray-curable compound (D), an active energy ray-curable acrylate-based oligomer can also be used. This acrylate-based oligomer preferably has a weight average molecular weight of 50,000 or less. Examples of such acrylate-based oligomers include polyester acrylate-based, epoxy acrylate-based, urethane acrylate-based, polyether acrylate-based, polybutadiene acrylate-based, and silicone acrylate-based.

The weight average molecular weight of the acrylate-based oligomer is preferably 50,000 or less as an upper limit, and particularly preferably 40,000 or less. Moreover, the weight average molecular weight is preferably 500 or more as a lower limit, and particularly preferably 3,000 or more. These acrylate-based oligomers may be used individually or in combination of two or more types.

Additionally, as the active energy ray-curable compound (D), an adduct acrylate-based polymer in which a group having a (meth)acryloyl group is introduced into the side chain can also be used. Such an adduct acrylate-based polymer uses a copolymer of (meth)acrylic acid ester and a monomer having a crosslinkable functional group in the molecule, and a (meth)acryloyl group and crosslinks a part of the crosslinkable functional group of the copolymer. It can be obtained by reacting a compound having a group that reacts with a sexual functional group.

The weight average molecular weight of the adduct acrylate-based polymer is preferably 50,000 or more as a lower limit, and particularly preferably 100,000 or more. Moreover, as for the weight average molecular weight, it is preferable that it is 900,000 or less as an upper limit, and it is especially preferable that it is 500,000 or less.

The active energy ray-curable compound (D) may be selected from the above-mentioned polyfunctional acrylate-based monomers, acrylate-based oligomers, and adduct acrylate-based polymers, and may be used in combination of two or more types. It can also be used in combination with other active energy ray-curable components.

The content of the active energy ray-curable compound (D) in the adhesive composition (Q) is 100 parts by mass of the (meth)acrylic acid ester polymer (C) from the viewpoint of improving the cohesion of the resulting adhesive and ensuring excellent blister resistance. The lower limit is preferably 0.5 parts by mass or more, more preferably 1.0 parts by mass or more, and especially preferably 3.0 parts by mass or more. On the other hand, the upper limit of the content is preferably 50 parts by mass or less, and more preferably 20 parts by mass or less, from the viewpoint of preventing phase separation of the active energy ray-curable compound (D) from the (meth)acrylic acid ester polymer (C). Also, from the viewpoint of improving blister resistance, it is particularly preferable that it is 12 parts by mass or less.

(3) Cross-linking agent (B)

The adhesive composition (Q) preferably contains a crosslinking agent (B). The adhesive composition (Q) contains a crosslinking agent (B), which crosslinks the (meth)acrylic acid ester polymer (C) to form a three-dimensional network structure, further improving the cohesion of the resulting adhesive, and improving blister resistance and high temperature and high humidity conditions. The step followability under the bottom can be further improved. As the crosslinking agent (B), the same agent as described for the adhesive composition (P) can be used, and the amount used is also the same.

(4) Photopolymerization initiator (E)

When curing the active energy ray-curable adhesive constituting the third adhesive layer 23 and using ultraviolet rays as the irradiated active energy ray, the adhesive composition (Q) further contains a photopolymerization initiator (E). desirable. By containing the photopolymerization initiator (E) in this way, the active energy ray-curable compound (D) can be polymerized efficiently, and the polymerization curing time and the irradiation amount of the active energy ray can be reduced.

Examples of such photopolymerization initiators (E) include benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin-n-butyl ether, benzoin isobutyl ether, acetophenone, and dimethyl. Aminoacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2,2-diethoxy-2-phenylacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1- Hydroxycyclohexylphenylketone, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholino-propan-1-one, 4-(2-hydroxyethoxy)phenyl-2-( Hydroxy-2-propyl) ketone, benzophenone, p-phenylbenzophenone, 4,4'-diethylaminobenzophenone, dichlorobenzophenone, 2-methylanthraquinone, 2-ethylanthraquinone, 2-tertiary- Butylanthraquinone, 2-aminoanthraquinone, 2-methylthioxanthone, 2-ethylthioxanthone, 2-chlorothioxanthone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, Benzyl dimethyl ketal, acetophenone dimethyl ketal, p-dimethylaminobenzoic acid ester, oligo[2-hydroxy-2-methyl-1[4-(1-methylvinyl)phenyl]propanone], 2,4,6-trimethyl Benzoyl-diphenyl-phosphine oxide, etc. can be mentioned. These may be used individually, or two or more types may be used in combination.

The content of the photopolymerization initiator (E) in the adhesive composition (Q) is preferably 0.1 part by mass or more as a lower limit with respect to 100 parts by mass of the active energy ray-curable compound (D), and especially preferably 1 part by mass or more. Moreover, the upper limit is preferably 30 parts by mass or less, and particularly preferably 10 parts by mass or less.

(5) Various additives

The adhesive composition (Q) may contain various additives commonly used in acrylic adhesives as desired, such as silane coupling agents, antistatic agents, tackifiers, antioxidants, ultraviolet absorbers, light stabilizers, softeners, fillers, refractive index regulators, etc. can be added.

In addition, the adhesive composition (Q) represents a mixture of various components remaining in the adhesive layer as is or in a reacted state, and components removed in the drying process, such as the polymerization solvent or dilution solvent described later, are the adhesive composition ( Q) Not included.

(6) Preparation of adhesive composition

The adhesive composition (Q) is prepared by preparing a (meth)acrylic acid ester polymer (C), mixing the obtained (meth)acrylic acid ester polymer (C) with an active energy ray-curable compound (D), and adding a crosslinking agent (D) as desired. B), it can be prepared by adding a photopolymerization initiator (E) and additives. Specifically, it can be manufactured by the same method as the adhesive composition (P).

(7) Manufacturing of adhesive

The active energy ray-curable adhesive constituting the third adhesive layer 23 can be preferably obtained by crosslinking (thermal crosslinking) the adhesive composition (Q). Crosslinking of the adhesive composition (Q) can be performed by the same method as the adhesive composition (P).

(6) Gel fraction

The gel fraction before curing of the active energy ray-curable adhesive constituting the third adhesive layer 23 is preferably 40% or more as a lower limit, particularly preferably 45% or more, and further preferably 50% or more. If the gel fraction before curing is 40% or more, the cohesion of the active energy ray-curable adhesive increases, and the processability of the adhesive layer 2 becomes better. Additionally, the gel fraction before curing is preferably 75% or less as an upper limit, particularly preferably 70% or less, and more preferably 65% or less. If the gel fraction before curing is 75% or less, the active energy ray-curable adhesive does not harden excessively, and the initial step followability of the adhesive layer 2 becomes more excellent.

The gel fraction after curing of the active energy ray-curable adhesive constituting the third adhesive layer 23 (after curing by irradiation with active energy rays) is preferably 70% or more as a lower limit, and especially preferably 75% or more, and further. is preferably 79% or more. If the gel fraction after curing is 70% or more, the cohesive force increases, and the blister resistance and level difference followability under high temperature and high humidity become more excellent. Additionally, the gel fraction after curing is preferably 95% or less as an upper limit, particularly preferably 92% or less, and more preferably 90% or less. If the gel fraction after curing is 95% or less, the adhesion between the adjacent first and second adhesive layers 21 and 22 becomes excellent, and the blister resistance and step followability under high temperature and high humidity become more excellent. Here, the method for measuring the gel fraction of the active energy ray-curable adhesive is as shown in the test example described later.

(9) Adhesion

The lower limit of the adhesive force of the active energy ray-curable adhesive (laminated body with the base material) constituting the third adhesive layer 23 to soda-lime glass is preferably 20 N/25 mm or more, and especially 25 N/25 mm or more. It is preferable that it is more than 30N/25mm. If the adhesive strength before curing is above or higher, the adhesiveness of the first adhesive layer 21 and the second adhesive layer 22 increases, and interlayer peeling in the adhesive layer 2 can be suppressed. Additionally, the upper limit of the adhesive force is not particularly limited, but is generally preferably 50 N/25 mm or less, and particularly preferably 45 N/25 mm or less.

The adhesive strength of the active energy ray-curable adhesive (laminated body with the base material) constituting the third adhesive layer 23 to soda-lime glass after curing (after curing by irradiation with active energy rays) is 20 N/25 mm as a lower limit. It is preferable that it is more than 25N/25mm, and it is especially preferable that it is more than 30N/25mm. If the adhesive strength after curing is above or higher, the adhesiveness of the first adhesive layer 21 and the second adhesive layer 22 increases, and the resulting product (display body) has high durability. Additionally, the upper limit of the adhesive force is not particularly limited, but is generally preferably 55 N/25 mm or less, and particularly preferably 50 N/25 mm or less.

(10) Step tracking rate

The step tracking ratio (%) after curing of the third adhesive layer 23 (after curing by irradiation with active energy rays) is preferably 30% or more as a lower limit, especially preferably 35% or more, and furthermore, 40% or more. It is desirable. Moreover, the step tracking ratio (%) is preferably 65% or less as an upper limit, especially preferably 60% or less, and more preferably 55% or less.

When the level difference tracking ratio of the third adhesive layer 23 as an intermediate layer is within the above-mentioned range, the level difference tracking property becomes more excellent as the adhesive layer 2 of the adhesive sheet 1 according to the present embodiment.

3. Release sheet

The release sheets 31 and 32 protect the adhesive layer 2 until the adhesive sheet 1 is used, and are peeled off when the adhesive sheet 1 (adhesive layer 2) is used. In the adhesive sheet 1 according to the present embodiment, one or both of the release sheets 31 and 32 are not necessarily required.

The release sheets 31 and 32 include, for example, polyethylene film, polypropylene film, polybutene film, polybutadiene film, polymethylpentene film, polyvinyl chloride film, vinyl chloride copolymer film, polyethylene terephthalate film, and polyethylene. Naphthalate film, polybutylene terephthalate film, polyurethane film, ethylene vinyl acetate film, ionomer resin film, ethylene/(meth)acrylic acid copolymer film, ethylene/(meth)acrylic acid ester copolymer film, polystyrene film, poly Carbonate film, polyimide film, fluororesin film, etc. are used. Additionally, these crosslinked films are also used. Additionally, these laminated films may be used.

It is preferable that the peeling surface of the peeling sheets 31 and 32 (particularly the surface in contact with the adhesive layer 2) is subjected to a peeling treatment. Examples of the release agents used in the release treatment include alkyd-based, silicone-based, fluorine-based, unsaturated polyester-based, polyolefin-based, and wax-based release agents. Furthermore, it is preferable that one of the release sheets 31 and 32 is a heavy release type release sheet with a large release force, and the other release sheet is a light release type release sheet with a small release force.

There is no particular limitation on the thickness of the release sheets 31 and 32, but it is usually about 20 to 150 μm.

4. Physical properties of adhesive sheet

(1) Step following rate

The step tracking ratio (%) after curing of the adhesive layer 2 of the adhesive sheet 1 according to the present embodiment (after curing by irradiation with active energy rays) is preferably 25% or more as a lower limit, and especially 30% or more. It is preferable, and it is further preferable that it is 40% or more. Moreover, the step tracking rate (%) is preferably 60% or less as an upper limit, especially preferably 55% or less, and more preferably 50% or less.

Since the pressure-sensitive adhesive layer 2 in this embodiment has excellent level difference followability as described above, it can achieve the high level difference followability as described above. As a result, the adhesive layer 2 follows well the level difference of the display body member, and even after an endurance test, the occurrence of bubbles, floatation, peeling, etc. near the level difference is suppressed, thereby preventing reflection loss of light. is suppressed.

(2) 100% modulus

The 100% modulus of the adhesive layer 2 of the adhesive sheet 1 according to the present embodiment before curing (before curing by irradiation with active energy rays) is preferably 40 kPa or more as a lower limit, and especially preferably 50 kPa or more. , and further preferably 60 kPa or more. When the lower limit of the 100% modulus is above or higher, the adhesive layer 2 has better processability. Moreover, the 100% modulus before curing of the adhesive layer 2 is preferably 200 kPa or less as an upper limit, especially preferably 150 kPa or less, and more preferably 90 kPa or less. When the upper limit of the 100% modulus is below the above value, the pressure-sensitive adhesive layer 2 has better initial level difference followability.

The lower limit of the 100% modulus of the adhesive layer 2 of the adhesive sheet 1 according to the present embodiment (after curing by irradiation with active energy rays) is preferably 70 kPa or more, and particularly preferably 80 kPa or more. , furthermore, it is preferably 125 kPa or more. When the lower limit of the 100% modulus is above or higher, the adhesive layer 2 has better blister resistance and step followability under high temperature and high humidity. Moreover, the 100% modulus before curing of the adhesive layer 2 is preferably 200 kPa or less as an upper limit, especially preferably 170 kPa or less, and more preferably 150 kPa or less. When the upper limit of the 100% modulus is below the above, it becomes easy to maintain high adhesion (adhesion) of the adhesive layer 2 to the adherend (display member).

5. Preparation of adhesive sheet

In one manufacturing example of the adhesive sheet (1), the coating liquid of the adhesive composition (P) is applied to the release surface of one of the release sheets (31), heat treatment is performed, and the adhesive composition (P) is heat-crosslinked. , an application layer is formed to obtain a release sheet 31 with an application layer of the adhesive composition (P) formed thereon. Additionally, the coating liquid of the adhesive composition (P) is applied to the peeling surface of the other release sheet 32, heat treatment is performed to thermally crosslink the adhesive composition (P), and an application layer is formed, forming the adhesive composition ( A release sheet 32 on which the application layer of P) is formed is obtained. Additionally, the coating liquid of the adhesive composition (Q) is applied to the release surface of another release sheet, and subjected to heat treatment to thermally crosslink the adhesive composition (Q) to form an application layer, thereby forming a coating layer of the adhesive composition (Q). A release sheet with an applied layer formed thereon is obtained.

Next, the release sheet 31 with the application layer of the adhesive composition (P) and the release sheet with the application layer of the adhesive composition (Q) are bonded together so that both application layers are in contact with each other, and the adhesive composition (Q) is applied. The release sheet is peeled from the layer. Next, the release sheet 32 on which the applied layer of the adhesive composition (Q) and the applied layer of the adhesive composition (P) are formed are bonded so that both the applied layers are in contact with each other. When a curing period is necessary, a curing period is provided, and when a curing period is unnecessary, the applied layer of the adhesive composition (P) of one of the above-described layers is the first adhesive layer 21 and the applied layer of the adhesive composition (Q). This third adhesive layer 23 and the other application layer of the adhesive composition (P) become the second adhesive layer 22. Thereby, the adhesive sheet (1) in which the adhesive layer (2) consisting of the first adhesive layer (21), the third adhesive layer (23), and the second adhesive layer (22) is sandwiched between the release sheets (31, 32). obtained. In addition, the curing of the coating layer of the adhesive composition may be performed after the coating layer of the adhesive composition is bonded to form three layers as described above, or may be performed before bonding.

As a method for applying the coating liquid of the adhesive composition (P), for example, a bar coat method, a knife coat method, a roll coat method, a blade coat method, a die coat method, a gravure coat method, etc. can be used.

Since the adhesive sheet 1 according to the present embodiment has good processability, problems such as the adhesive sticking out from the cut surface and sticking to the blade are suppressed when the adhesive sheet 1 is punched or processed. do.

〔Display type〕

As shown in FIG. 2, the display body 4 according to the present embodiment includes a first display body member 51 (one display body member) having a step at least on the surface on the side to be joined, and a second display body member 51. a display structural member 52 (another display structural member) and an adhesive layer 2 positioned between them and bonding the first display structural member 51 and the second display structural member 52 to each other. It is comprised of: In the display body 4 according to the present embodiment, the first display body member 51 has a step on the surface on the adhesive layer 2 side, and specifically has a step due to the printing layer 6. .

The adhesive layer 2 in the display body 4 is obtained by curing the adhesive layer 2 (especially the third adhesive layer 23) of the adhesive sheet 1 described above by irradiation with active energy rays ( For convenience, the same names and symbols are used). Here, an active energy ray refers to an electromagnetic wave or a charged particle ray having energy quantum, and specifically includes ultraviolet rays or electron rays. Among active energy rays, ultraviolet rays, which are easy to handle, are particularly preferable.

Irradiation of ultraviolet rays can be performed by a high-pressure mercury lamp, fusion H lamp, xenon lamp, etc., and the amount of irradiation of ultraviolet rays is preferably around 50 to 1000 mW/cm2. Moreover, the amount of light is preferably 50 to 10,000 mJ/cm2, more preferably 80 to 5,000 mJ/cm2, and especially preferably 200 to 2,000 mJ/cm2. Meanwhile, irradiation of electron beams can be performed using an electron beam accelerator or the like, and the amount of electron beam irradiation is preferably about 10 to 1000 krad.

Irradiation of active energy rays to the pressure-sensitive adhesive layer 2 is performed after bonding the first display member 51 and the second display member 52 to each other by the pressure-sensitive adhesive layer 2. Among the structural members 51 and the second display body structural members 52, it is preferable to carry out the treatment over the member that transmits the active energy ray.

When the adhesive layer 2 is irradiated with active energy rays, the active energy ray-curable compound (D) in the third adhesive layer 23 in particular polymerizes and hardens. The adhesive layer 2, which is cured by irradiation of active energy rays (in particular, the third adhesive layer 23 is cured), has very excellent blister resistance and step followability under high temperature and high humidity.

Examples of the display body 4 include liquid crystal (LCD) displays, light-emitting diode (LED) displays, organic electroluminescence (organic EL) displays, and electronic paper, and may be a touch panel. Additionally, the display body 4 may be a member constituting a part of them.

The first display structural member 51 is preferably a protective panel made of a glass plate, a plastic plate, etc., as well as a laminate containing them. In this case, the printing layer 6 is generally formed in a frame shape on the adhesive layer 2 side of the first display body member 51.

The glass plate is not particularly limited and includes, for example, chemically strengthened glass, alkali-free glass, quartz glass, soda lime glass, glass containing barium/strontium, aluminosilicate glass, lead glass, borosilicate glass, barium borosilicate glass, etc. I can hear it. The thickness of the glass plate is not particularly limited, but is usually 0.1 to 5 mm, and preferably 0.2 to 2 mm.

The plastic plate is not particularly limited, and examples include acrylic plates and polycarbonate plates. The thickness of the plastic plate is not particularly limited, but is usually 0.2 to 5 mm, and preferably 0.4 to 3 mm.

Additionally, various functional layers (transparent conductive film, metal layer, silica layer, hard coat layer, anti-glare layer, etc.) may be formed on one or both sides of the glass or plastic plate, and optical members may be laminated. Additionally, the transparent conductive film and metal layer may be patterned.

The second display structural member 52 is an optical member to be attached to the first display structural member 51, a display module (e.g., a liquid crystal (LCD) module, a light emitting diode (LED) module, an organic electroluminescent Nesence (organic EL) module, etc.), an optical member as part of a display module, or a laminate containing a display module is preferable.

The optical members include, for example, an anti-shatter film, a polarizer (polarizing film), a polarizer, a retardation plate (retardation film), a viewing angle compensation film, a brightness enhancement film, a contrast enhancement film, a liquid crystal polymer film, a diffusion film, and a transflective film. Reflective films, transparent conductive films, etc. can be mentioned. Examples of the anti-scattering film include a hard coat film in which a hard coat layer is formed on one side of a base film.

The material constituting the printing layer 6 is not particularly limited, and known materials for printing are used. The lower limit of the thickness of the printed layer 6, that is, the height of the step, is preferably 3 μm or more, more preferably 5 μm or more, particularly preferably 7 μm or more, and most preferably 10 μm or more. When the lower limit is greater than the above, it is possible to sufficiently ensure concealment, such as making the electric wiring invisible from the viewer's side. Moreover, the upper limit is preferably 50 μm or less, more preferably 35 μm or less, particularly preferably 25 μm or less, and even more preferably 20 μm or less. When the upper limit is below the above, it is possible to prevent deterioration of the level difference followability of the adhesive layer 2 with respect to the printing layer 6.

In order to manufacture the display body 4, as an example, one release sheet 31 of the adhesive sheet 1 is peeled off, and the exposed adhesive layer 2 of the adhesive sheet 1 is applied to the first display body structural member. It is bonded to the surface of (51) on the side where the printed layer (6) exists. At this time, since the pressure-sensitive adhesive layer 2 has excellent level difference followability, the occurrence of gaps or floaters near the level difference caused by the printing layer 6 is suppressed.

Thereafter, the other release sheet 32 is peeled from the adhesive layer 2 of the adhesive sheet 1 to expose the exposed adhesive layer 2 and the second display body member 52 of the adhesive sheet 1. Join together. Moreover, as another example, the order of joining the first display body structural member 51 and the second display body structural member 52 may be replaced.

In the above display body (4), since the adhesive layer (2) has excellent blister resistance, the display body (4) is placed under high temperature and high humidity conditions (e.g., 85°C, 85%RH, 72 hours). Even if outgassing is generated from the display member made of a plastic plate or the like, blisters such as bubbles, floatation, and peeling are generated at the interface between the adhesive layer 2 and the display member 51 and 52. is suppressed.

In addition, in the display body 4, since the adhesive layer 2 has excellent step followability even under high temperature and high humidity conditions, the display body 4 can be used under high temperature and high humidity conditions (e.g., 85°C, 85%RH). , 72 hours), the occurrence of bubbles, lifting, peeling, etc. near the step is suppressed.

The embodiments described above are described to facilitate understanding of the present invention, and are not described to limit the present invention. Therefore, each element disclosed in the above embodiment is intended to include all design changes and equivalents that fall within the technical scope of the present invention.

For example, one or both of the release sheets 31 and 32 in the adhesive sheet 1 may be omitted, and a desired optical member may be laminated instead of the release sheets 31 and/or 32. . In addition, other layers may exist between the first adhesive layer 21 and/or the second adhesive layer 22 and the third adhesive layer 23 in the adhesive layer 2, and the adhesive layer 2 On the outside of the first adhesive layer 21 and/or the second adhesive layer 22 (on the release sheet 31, 32 side), another layer may further exist.

In addition, the first display body structural member 51 may have a level difference other than that of the printing layer 6. Furthermore, not only the first display body member 51 but also the second display body member 52 may have a step on the adhesive layer 2 side.

Example

Hereinafter, the present invention will be described in more detail through examples, etc., but the scope of the present invention is not limited to these examples.

[Production Example 1]

-Production of a laminate having a first adhesive layer or a second adhesive layer-

(1) Preparation of (meth)acrylic acid ester polymer (A)

60 parts by mass of 2-ethylhexyl acrylate, 20 parts by mass of methyl methacrylate, and 20 parts by mass of 2-hydroxyethyl acrylate were copolymerized to prepare (meth)acrylic acid ester polymer (A). The molecular weight of this (meth)acrylic acid ester polymer (A) was measured by the method described later, and the weight average molecular weight (Mw) was 600,000.

(2) Preparation of adhesive composition (P)

100 parts by mass of the (meth)acrylic acid ester polymer (A) obtained in the above step (1) (solid content conversion value; the same below), and trimethylolpropane-modified tolylene diisocyanate (manufactured by Nippon Polyurethane Co., Ltd., product name “Colo”) as a crosslinking agent (B) 0.25 parts by mass of "Nate L") and 0.30 parts by mass of 3-glycidoxypropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., product name "KBM-403") as a silane coupling agent were mixed, stirred sufficiently, and dissolved in methyl ethyl ketone. By diluting, a coating solution of the adhesive composition (P) with a solid content concentration of 35% by mass was obtained.

Here, Table 1 shows the respective formulations (converted to solid content) of the adhesive composition when the (meth)acrylic acid ester polymer is 100 parts by mass (converted to solid content).

In addition, details such as abbreviations listed in Table 1 are as follows.

[(meth)acrylic acid ester polymer]

2EHA: 2-ethylhexyl acrylate

MMA: Methyl methacrylate

HEA: 2-hydroxyethyl acrylate

BA: n-butyl acrylate

IBXMA: Isobornyl methacrylate

IBXA: Isobornyl acrylate

ACMO: 4-acryloylmorpholine

AA: Acrylic acid

[Cross-linking agent]

TDI type: Trimethylolpropane-modified tolylene diisocyanate (manufactured by Nippon Polyurethane Co., Ltd., product name “Colonate L”)

Epoxy type: 1,3-bis(N,N'-diglycidylaminomethyl)cyclohexane (manufactured by Mitsubishi Gas Chemical Company, product name “TETRAD C-5”)

(3) Production of laminate

The coating solution of the adhesive composition (P) obtained in the above step (2) was applied to the peeled surface of a medium-release type release sheet (manufactured by Lintec, product name "SP-PET752150"), where one side of a polyethylene terephthalate film was peeled with a silicone-based release agent. After applying with a knife coater, heat treatment was performed at 90°C for 1 minute to form an application layer (thickness: 25㎛). Similarly, the coating solution of the adhesive composition obtained in Step 2 above was applied to the peeled surface of a light-release type release sheet (manufactured by Lintec, product name "SP-PET382120"), where one side of the polyethylene terephthalate film was peeled with a silicone-based release agent, using a knife coater. After application, heat treatment was performed at 90°C for 1 minute to form an application layer (thickness: 25 μm).

Next, the heavy release type release sheet with the application layer obtained above and the light release type release sheet with the application layer obtained above are bonded so that both application layers are in contact with each other, and cured for 7 days under conditions of 23°C and 50%RH. By doing this, a laminate consisting of a heavy release type release sheet/adhesive layer (thickness: 50 μm)/light release type release sheet was produced. Additionally, this adhesive layer is composed of an active energy ray non-curable adhesive and corresponds to the first adhesive layer and the second adhesive layer.

The thickness of the adhesive layer is a value measured using a static pressure thickness meter (manufactured by Techroc, product name “PG-02”) in accordance with JIS K 7130.

[Production Examples 2 to 3]

Same as Preparation Example 1 except that the type and ratio of each monomer constituting the (meth)acrylic acid ester polymer (A) and the weight average molecular weight of the (meth)acrylic acid ester polymer (A) are changed as shown in Table 1. A laminate was manufactured in this way.

[Production Example 4]

-Production of a laminate having a third adhesive layer-

(1) Preparation of (meth)acrylic acid ester polymer (C)

60 parts by mass of 2-ethylhexyl acrylate, 10 parts by mass of isobornyl acrylate, 10 parts by mass of 4-acryloyl morpholine, and 20 parts by mass of 2-hydroxyethyl acrylate are copolymerized to produce (meth)acrylic acid ester polymer (C). It was prepared. The molecular weight of this (meth)acrylic acid ester polymer (C) was measured by the method described later, and the weight average molecular weight (Mw) was 500,000.

(2) Preparation of adhesive composition (Q)

100 parts by mass of the (meth)acrylic acid ester polymer (C) obtained in the above step (1), and ε-caprolactone-modified tris(2-acryloxyethyl)isocyanurate as the active energy ray-curable compound (D) (Shin Nakamura) A mixture of 5.0 parts by mass of (manufactured by Chemicals, product name "NK Ester A-9300-1CL") and benzophenone and 1-hydroxycyclohexylphenyl ketone as a photopolymerization initiator (E) at a mass ratio of 1:1 (manufactured by BASF) 0.50 parts by mass of product name “Irgacure 500”), 0.25 parts by mass of trimethylolpropane-modified tolylene diisocyanate (manufactured by Nippon Polyurethane Co., Ltd., product name “Colonate L”) as a crosslinking agent (B), and 3-gly as a silane coupling agent. Applying the adhesive composition (Q) with a solid content concentration of 48% by mass by mixing 0.30 parts by mass of sidoxypropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., product name "KBM-403"), stirring sufficiently, and diluting with methyl ethyl ketone. A solution was obtained.

(3) Production of laminate

Using the coating solution of the adhesive composition (Q) obtained in the above step (2), in the same manner as the adhesive composition (P) described above, a medium release type release sheet/adhesive layer (thickness: 50 μm)/light release type release sheet was prepared. A laminate consisting of the composition was manufactured. Additionally, this adhesive layer is composed of an active energy ray-curable adhesive and corresponds to the third adhesive layer.

[Production Example 5]

The type and ratio of each monomer constituting the (meth)acrylic acid ester polymer (A), the weight average molecular weight of the (meth)acrylic acid ester polymer (A), the ratio of the active energy ray curable compound (D), and the photopolymerization initiator (E) A laminate was manufactured in the same manner as in Production Example 4, except that the ratio and the type and ratio of the crosslinking agent (B) were changed as shown in Table 1.

Here, the above-mentioned weight average molecular weight (Mw) is the weight average molecular weight in terms of polystyrene measured (GPC measurement) under the following conditions using gel permeation chromatography (GPC).

＜Measurement conditions＞

·GPC measurement device: Tosoh Corporation, HLC-8020

·GPC column (passed in the following order): Tosoh Corporation

TSK guard column HXL-H

TSK gel GMHXL (×2)

TSK gel G2000HXL

·Measurement solvent: tetrahydrofuran

·Measurement temperature: 40℃

[Example 1]

The light release type release sheet is peeled from the laminate obtained in Production Example 1, and the light release type release sheet is peeled from the laminate obtained in Production Example 4, and the exposed first adhesive layer and the third adhesive layer are placed in contact with each other. Combined, the heavy release type release sheet was peeled from the third adhesive layer. Next, the light release type release sheet is peeled from the laminate obtained in Production Example 1, and the exposed second adhesive layer and the third adhesive layer are bonded so that they are in contact with each other, and the first adhesive layer, the third adhesive layer, and the second adhesive layer are formed. An adhesive sheet was obtained in which an adhesive layer consisting of layers was sandwiched between two heavy release type release sheets.

[Examples 2 to 6, Comparative Examples 1 to 7]

The adhesive layers of the laminates produced in Production Examples 1 to 5 were laminated in the stacking order shown in Table 2, and an adhesive sheet was manufactured in the same manner as in Example 1. At this time, the thickness of each adhesive layer was changed so that it became the thickness shown in Table 2.

[Test Example 1] (Measurement of gel fraction)

The laminate produced in Production Examples 1 to 5 was cut to a size of 80 mm x 80 mm, the adhesive layer was wrapped in a polyester mesh (mesh size 200), the mass was weighed with a precision balance, and the mesh alone The mass of the adhesive alone was calculated by subtracting the mass of . The mass at this time is set to M1.

Next, the adhesive wrapped in the polyester mesh was immersed in ethyl acetate at room temperature (23°C) for 24 hours. After that, the adhesive was taken out, air-dried for 24 hours in an environment with a temperature of 23°C and a relative humidity of 50%, and further dried in an oven at 80°C for 12 hours. After drying, the mass was weighed using a precision balance, and the mass of the adhesive alone was calculated by subtracting the mass of the mesh alone. The mass at this time is set to M2. Gel fraction (%) is expressed as (M2/M1) x 100. The results are shown in Table 3.

In addition, for the adhesive layers of the laminates of Production Examples 4 and 5, the gel fraction was measured before and after irradiation of ultraviolet rays to the adhesive layer (irradiation from the heavy release type release sheet side). In the table, the results before ultraviolet irradiation are described as “Before UV”, and the results after ultraviolet irradiation are described as “After UV” (hereinafter, the same applies). The ultraviolet irradiation conditions are as follows.

＜Ultraviolet irradiation conditions＞

· Use of Fusion’s electrodeless lamp H valve

· Illuminance 500mW/㎠, light quantity 200mJ/㎠

· UV illuminance/photometer uses “UVPF-36” manufactured by iGraphics.

[Test Example 2] (Measurement of adhesive force)

The light release type release sheet was peeled from the laminate produced in Production Examples 1 to 5, and the exposed adhesive layer was replaced with a polyethylene terephthalate (PET) film having an easy-adhesion layer (manufactured by Toyobo, product name "PET A4300", thickness: 100 ㎛) layer to obtain a laminate of release sheet/adhesive layer/PET film. The obtained laminate was cut to 25 mm in width and 100 mm in length, and this was used as a sample.

In an environment of 23°C and 50%RH, the medium-release type release sheet was peeled from the sample, and the exposed adhesive layer was attached to soda-lime glass (manufactured by Nippon Itagarasu Co., Ltd.), followed by 0.5 °C in an autoclave manufactured by Kurihara Seisakusho Co., Ltd. Pressurized at MPa and 50°C for 20 minutes. After that, it was left to stand for 24 hours under the conditions of 23°C and 50%RH, and then, using a tensile tester (Tensilon, manufactured by Orientec), the adhesive strength (N/25) was measured under the conditions of a peeling speed of 300 mm/min and a peeling angle of 180 degrees. mm) was measured. Conditions other than those described here were measured based on JIS Z 0237:2009. The results are shown in Table 3.

In addition, for the laminates of Production Examples 4 and 5, after sticking them to soda lime glass and pressurizing them in an autoclave in the same manner as above, the adhesive layer was irradiated with ultraviolet rays through the soda lime glass, and then, as described above. In the same way, the adhesive strength after being left for 24 hours was also measured. The ultraviolet irradiation conditions were the same as Test Example 1.

[Test Example 3] (Measurement of storage modulus (G'))

The adhesive layers of the laminates produced in Production Examples 1 to 5 were laminated in multiple layers to obtain a laminate with a thickness of 3 mm. From the obtained laminate of the adhesive layer, a cylindrical body (3 mm in height) with a diameter of 8 mm was punched out, and this was used as a sample.

For the sample, the storage modulus (G') (MPa) was measured by the torsional shear method using a viscoelasticity meter (DYNAMIC ANALAYZER, manufactured by REOMETRIC) in accordance with JIS K 7244-6 under the following conditions. The results are shown in Table 3.

Measurement frequency: 1Hz

Measurement temperature: 23℃

In addition, for the adhesive layers of the laminates of Production Examples 4 and 5, the storage modulus (G') was measured before and after irradiating the laminates with ultraviolet rays. The ultraviolet irradiation conditions were the same as Test Example 1.

[Test Example 4] (Measurement of 100% modulus)

The adhesive layers of the laminates produced in Production Examples 1 to 5 were laminated in multiple layers to a total thickness of 800 μm, and then a sample of 10 mm in width x 75 mm in length was cut out. Set the sample in a tensile tester (manufactured by Orientec, product name “Tensilon”) so that the sample measurement area is 10 mm wide x 25 mm long (in the direction of elongation), and run the tensile tester in an environment of 23°C and 50%RH. It was stretched at a tensile speed of 200 mm/min, and the stress value at which the elongation rate was 100% was calculated (measured) as 100% modulus (kPa) using a stress-strain curve (SS curve). The results are shown in Table 3.

In addition, for the adhesive layers of the laminates of Production Examples 4 and 5, the 100% modulus (kPa) was measured before and after irradiating the laminates with ultraviolet rays. The ultraviolet irradiation conditions were the same as Test Example 1.

In addition, the 100% modulus (kPa) was measured for the adhesive layer of the adhesive sheet obtained in Examples 1 to 6 and Comparative Examples 6 to 7 by the same method as above (For Comparative Examples 1 to 5, Production Example 1 Since the result is the same as ∼5, the test is omitted). However, for examples and comparative examples other than Example 2, multiple layers of adhesive layers (three-layer structure) were laminated to have a total thickness of 750 μm. The results are shown in Table 4. Additionally, for the adhesive layers of the adhesive sheets obtained in Examples 1 to 6 and Comparative Example 6, the 100% modulus (kPa) was measured before and after irradiating the adhesive layer with ultraviolet rays. The ultraviolet irradiation conditions were the same as Test Example 1.

[Test Example 5] (Evaluation of blister resistance)

The adhesive layer of the laminate produced in Production Examples 1 to 5 and the adhesive layer of the adhesive sheet obtained in Examples 1 to 6 and Comparative Examples 1 to 7 were formed on one side of polyethylene with a transparent conductive film made of tin-doped indium oxide (ITO). A transparent conductive film of terephthalate film (manufactured by Oike Industries, Ltd., ITO film, thickness: 125 ㎛), and a polycarbonate (PC) plate (manufactured by Mitsubishi Gas Chemical Company, Eupiron Sheet MR58, thickness: 1 mm) or polymethylmethane. It was sandwiched between acrylic plates made of acrylate (PMMA) (Mitsubishi Gas Chemical Co., Ltd., Eupiron Sheet MR200, thickness: 1 mm) to obtain a laminate.

The obtained laminate was autoclaved for 30 minutes under conditions of 50°C and 0.5 MPa. Then, the adhesive layer was irradiated with ultraviolet rays over the PC plate or the acrylic plate under the same ultraviolet irradiation conditions as in Test Example 1, and the adhesive layer was cured (the adhesive layers of Production Examples 1 to 3, Comparative Examples 1 to 3 and 7). (excluding the adhesive layer).

The sample obtained as described above was left at normal pressure, 23°C, and 50%RH for 15 hours. Next, it was stored for 72 hours under durable conditions of 85°C and 85%RH. After that, it was visually confirmed whether there were any bubbles, floaters, or peeling in the adhesive layer, and the blister resistance was evaluated based on the following criteria. The results are shown in Tables 3 and 4.

◎ … There were no bubbles, lifting, or peeling.

○ … Only bubbles with a diameter of 0.1 mm or less were generated.

× … Bubbles exceeding 0.1 mm in diameter, lifting, or peeling occurred.

[Test Example 6] (Measurement of step tracking rate)

On the surface of a glass plate (manufactured by NSG Precision, product name “Corning Glass Eagle ) in a frame shape (external appearance: It was screen printed (90 mm long x 50 mm wide, 5 mm wide). Next, the printed ultraviolet curable ink is cured by irradiation with ultraviolet rays (80 W/cm2, metal halide lamp 2 lights, lamp height 15 cm, belt speed 10 to 15 m/min), and the level difference due to printing (of the level difference) is cured. A stepped glass plate having a height of: 5㎛, 10㎛, 15㎛, 20㎛, 25㎛, 30㎛, 35㎛, 40㎛, 45㎛, 50㎛, 55㎛, 60㎛) was produced.

One release sheet was peeled off from the laminates produced in Production Examples 1 to 5 and the adhesive sheets obtained in Examples and Comparative Examples, and the exposed adhesive layer was replaced with a polyethylene terephthalate film (manufactured by Toyobo Corporation, product name "PET") having an easy-adhesion layer. It was bonded to an easy-adhesion layer of “A4300”, thickness: 100 μm). Next, the other release sheet was peeled off to expose the adhesive layer. Then, using a laminator (manufactured by Fujipla, product name "LPD3214"), the above-mentioned laminate was laminated to each step glass plate so that the adhesive layer covered the entire frame-shaped printing surface. Afterwards, it was autoclaved for 30 minutes under conditions of 50°C and 0.5 MPa.

The adhesive layer was irradiated with ultraviolet rays through the PET film under the same ultraviolet irradiation conditions as in Test Example 1, and the adhesive layer was cured (the adhesive layers of Preparation Examples 1 to 3 and the adhesive layers of Comparative Examples 1 to 3 and 7 were except).

The evaluation sample obtained as described above was stored under high temperature and high humidity conditions of 85°C and 85%RH for 72 hours (durability test), and then the step followability was evaluated. Step followability is judged by whether or not the printing step is completely filled by the adhesive layer. If bubbles, lifting, peeling, etc. are observed at the interface between the printing step and the adhesive layer, it is judged that the printing step cannot be followed. Here, the step followability was evaluated as the step followability rate (%) expressed by the following formula. The results are shown in Tables 3 and 4.

Step tracking rate (%) = {(After the durability test, the height of the step that remained filled without bubbles, floatation, peeling, etc. (μm)) / (thickness of adhesive layer)} × 100

[Test Example 7] (Evaluation of processability)

The adhesive sheets obtained in the examples and comparative examples were cut with an automatic cutter (manufactured by Ogino Seisakusho, product name "Super Cutter OSS-PN1 Model N-L"). The cut surface (length: 100 mm) of the adhesive sheet after cutting was visually confirmed, and processability was evaluated according to the following standards. The results are shown in Table 4.

○: No protruding adhesive layer.

×: The adhesive layer protrudes.

As can be seen from Table 4, the adhesive sheets obtained in the examples were excellent in both step followability and blister resistance, and had good processability.

The adhesive sheet of the present invention can be suitably used, for example, for bonding a protective panel having a step to a desired display body member.

One … adhesive sheet
2 … adhesive layer
21 … First adhesive layer
22 … Second adhesive layer
23 … Third adhesive layer
31, 32... peel sheet
4 … indicator
51 … First display member
52 … Second display body member
6 … printing layer

Claims (10)

delete delete delete delete delete delete delete delete An adhesive sheet provided with an adhesive layer,
The adhesive layer,
A first adhesive layer as an outer layer on one side,
A second adhesive layer as an outer layer on the other side,
A third adhesive layer positioned as an intermediate layer between the first adhesive layer and the second adhesive layer.
It is equipped with
The storage modulus (G') of the adhesive constituting the first adhesive layer and the adhesive constituting the second adhesive layer is each 0.1 MPa or more at 23°C,
The third adhesive layer is composed of an active energy ray-curable adhesive before curing,
The storage elastic modulus (G') at 23°C before curing of the active energy ray-curable adhesive is the storage elastic modulus (G') at 23°C of the adhesive constituting the first adhesive layer and the second adhesive layer. Prepare the pressure-sensitive adhesive sheet having a storage modulus (G') lower than that of the constituting pressure-sensitive adhesive at 23°C,
After bonding one display body member and another display body member to each other by the adhesive layer,
A method of manufacturing a display body, comprising irradiating an active energy ray beyond a member that transmits the active energy ray among the one display body member and the other display body member and curing the adhesive layer. An adhesive sheet provided with an adhesive layer,
The adhesive layer,
A first adhesive layer as an outer layer on one side,
A second adhesive layer as an outer layer on the other side,
A third adhesive layer positioned as an intermediate layer between the first adhesive layer and the second adhesive layer.
It is equipped with
The 100% modulus of the adhesive constituting the first adhesive layer and the adhesive constituting the second adhesive layer is each 60 kPa or more,
The third adhesive layer is composed of an active energy ray-curable adhesive before curing,
Prepare the adhesive sheet in which the 100% modulus of the active energy ray-curable adhesive before curing is lower than the 100% modulus of the adhesive constituting the first adhesive layer and the 100% modulus of the adhesive constituting the second adhesive layer, ,
After bonding one display body member and another display body member to each other by the adhesive layer,
A method of manufacturing a display body, comprising irradiating an active energy ray beyond a member that transmits the active energy ray among the one display body member and the other display body member and curing the adhesive layer.