CN118667456A

CN118667456A - Adhesive sheet, laminate, and display

Info

Publication number: CN118667456A
Application number: CN202410313361.5A
Authority: CN
Inventors: 小鲭翔
Original assignee: Lintec Corp
Current assignee: Lintec Corp
Priority date: 2023-03-20
Filing date: 2024-03-19
Publication date: 2024-09-20
Also published as: JP2024134184A; KR20240141629A

Abstract

The invention provides an adhesive sheet having an adhesive layer which can well follow the concave-convex shape, has excellent foaming resistance and does not generate optical unevenness. An adhesive sheet comprising an adhesive layer for bonding a first member to a second member, wherein the adhesive layer has a total light transmittance of 85% or less, and when one main surface of the adhesive layer is an A surface and the other main surface is a B surface, the A surface roughness following rate (%) is different from the B surface roughness following rate (%), wherein the A surface roughness following rate (%) indicates the A surface roughness following property when the A surface is bonded to an adherend having a roughness, the B surface roughness following rate (%) indicates the B surface roughness following property when the B surface is bonded to an adherend having a roughness, and the A surface roughness following rate and the B surface roughness following rate are greater than 0%.

Description

Adhesive sheet, laminate, and display

Technical Field

The present invention relates to an adhesive sheet, a laminate, and a display.

Background

In recent years, various mobile electronic devices such as instrument panels, car navigation systems, and consoles of automobiles, smart phones, and tablet terminals have been provided with displays (display bodies) using display modules including liquid crystal elements, light emitting diodes (LED elements), and organic electroluminescence (organic EL) elements.

Such a display module, or a laminate of the display module and another member is generally formed by bonding the display constituent member to the other member by an adhesive layer of an adhesive sheet.

In such a display, it is required to enhance the design of the display by giving the display a sense of unity to peripheral members of the display, for example, a frame material and the display when the display is turned off.

Patent document 1 discloses that a filter laminated on a main body of a plasma display panel has a colored layer having an adhesive and a coloring pigment.

Prior art literature

Patent literature

Patent document 1: japanese patent application laid-open No. 2012-234028

Disclosure of Invention

Technical problem to be solved by the invention

In the invention described in patent document 1, the colored layer is provided so as to be in contact with the transparent substrate and the concealing layer formed in a frame shape on the transparent substrate. Therefore, the adhesive constituting the colored layer needs to sufficiently follow the irregularities caused by the concealing layer and fill the irregularities so that gaps or the like do not occur in the vicinity of the irregularities.

However, when the adhesive follows the irregularities, the adhesive may be deformed. When such deformation occurs, there is a problem that optical properties of the adhesive are changed, and optical unevenness (for example, color unevenness) is caused in light passing through the adhesive layer. As a result, the image displayed on the display body is also optically uneven.

The present invention has been made in view of such a practical situation, and an object of the present invention is to provide an adhesive sheet having an adhesive layer that satisfactorily follows irregularities, is excellent in blister resistance, and does not cause optical unevenness.

Technical means for solving the technical problems

The scheme of the invention is as follows.

(1) An adhesive sheet having an adhesive layer for bonding a first member to a second member, wherein,

The adhesive layer has a total light transmittance of 85% or less,

When one main surface of the adhesive layer is an A surface and the other main surface is a B surface, the A surface roughness following rate (%) is different from the B surface roughness following rate (%) which indicates the A surface roughness following property when the A surface is attached to an adherend having irregularities, the B surface roughness following rate (%) indicates the B surface roughness following property when the B surface is attached to the adherend having irregularities,

The A-plane concave-convex following rate and the B-plane concave-convex following rate are larger than 0%.

(2) The adhesive sheet according to (1), wherein the adhesive layer is composed of two or more layers.

(3) The adhesive sheet according to (1) or (2), wherein the value obtained by subtracting the B-surface roughness following rate from the a-surface roughness following rate is-20% or more and-1% or less.

(4) The adhesive sheet according to any one of (1) to (3), wherein the adhesive layer contains a coloring component.

(5) The adhesive sheet according to any one of (1) to (4), wherein the adhesive layer is an acrylic adhesive having a crosslinked structure.

(6) A laminate is provided with: a first member, a second member, and an adhesive layer for bonding the first member and the second member to each other,

At least one of the first member and the second member has a concave-convex shape,

The adhesive layer of any one of (1) to (5).

(7) A display comprising the laminate according to (6).

Effects of the invention

According to the present invention, an adhesive sheet having an adhesive layer that satisfactorily follows the irregularities, while having excellent blister resistance and free from optical unevenness can be provided.

Drawings

Fig. 1A is a cross-sectional view of one example of the adhesive sheet of the present embodiment.

Fig. 1B is a cross-sectional view of another example of the adhesive sheet of the present embodiment.

Fig. 2 is a cross-sectional view of the laminate of the present embodiment.

Description of the reference numerals

1: An adhesive sheet; 10: an adhesive layer; 11: a first adhesive layer; 12: a second adhesive layer; 10a (11 a): a surface; 10b (12 a): a surface B; 21. 22: a release sheet; 3: a laminate; 31: a first member; 32: and a second member.

Detailed Description

Hereinafter, the present invention will be described in detail with reference to specific embodiments.

(1. Adhesive sheet)

As shown in fig. 1A, the adhesive sheet 1 of the present embodiment has: the adhesive layer 10 and the release sheets 21, 22. The adhesive layer adheres the first member to the second member. In this embodiment, the first member and the second member are members constituting a display (display constituting members).

The display is formed by laminating display constituent members having predetermined functions, and the respective display constituent members are bonded via an adhesive layer. In this case, the display element constituting member itself may have irregularities, or irregularities may be formed on the display element constituting member. If the adhesive layer cannot follow the irregularities, the adhesive layer floats up in the vicinity of the irregularities to generate gaps or the like, and further, the image quality of the display is lowered. Therefore, the adhesive layer is required to be bonded so as to sufficiently follow the irregularities.

In addition, there are also members in which the material of the display body constituent member is changed from glass to plastic. When the material is changed to plastic, if the display component member bonded by the adhesive layer is exposed to a high-temperature and high-humidity environment, there is a problem that outgas from the plastic occurs, and bubbles such as bubbles, floating, peeling and the like are generated. Therefore, the adhesive layer is also required to have foaming resistance.

On the other hand, in order to improve the design of the display, for example, the boundary between the display constituent members is made difficult to be recognized, and when the display is turned off, the frame material of the display and the display are given a sense of unity. Such imparting of the sense of unity can be performed by controlling the optical characteristics (e.g., total light transmittance) of the adhesive layer.

However, in the vicinity of the irregularities, the adhesive layer may be deformed so as to follow the irregularities. When such deformation occurs, the optical properties of the adhesive layer may change, and there may be a difference in optical properties between the deformed portion and the non-deformed portion. As a result, light passing through the adhesive layer is affected, and optical unevenness occurs in the display. Such optical unevenness may be exemplified by color unevenness when the adhesive layer is colored. If optical unevenness such as color unevenness occurs, the design property, image quality, and the like of the display body are reduced, which is not preferable.

In order to cope with the above-described problem, in the present embodiment, the adhesive layer is made as follows. The adhesive layer of the adhesive sheet of the present embodiment can sufficiently follow the irregularities, and can suppress optical irregularities even in the vicinity of the irregularities, and further has good foaming resistance.

(2. Adhesive layer)

The adhesive layer of the adhesive sheet of the present embodiment is composed of an adhesive described later. The adhesive layer may be formed of one layer (single layer) or may be formed of a plurality of two or more layers. In this embodiment, it is preferable that the pressure-sensitive adhesive layer is two or more layers in view of easy realization of physical properties described later.

The thickness of the adhesive layer is preferably 1 to 2000. Mu.m, more preferably 10 to 1200. Mu.m, still more preferably 40 to 900. Mu.m, particularly preferably 80 to 600. Mu.m, even more preferably 100 to 400. Mu.m, and most preferably 150 to 250. Mu.m. When the adhesive layer is composed of a plurality of layers, the thickness is the total thickness of the plurality of layers.

When the adhesive layer is composed of a plurality of layers, the thickness of each adhesive layer is preferably 1 to 1000. Mu.m, more preferably 10 to 600. Mu.m, still more preferably 20 to 300. Mu.m, particularly preferably 25 to 200. Mu.m.

(2.1. Physical Properties of adhesive layer)

The adhesive layer of this embodiment has physical properties as shown below. When the adhesive layer is a plurality of layers, the physical properties shown below are those of the adhesive layer as a whole.

(2.1.1. Concave-convex following Rate of adhesive layer)

In the present embodiment, one main surface of the adhesive layer is referred to as an a-plane and the other main surface is referred to as a B-plane. In fig. 1A, a main surface 10a of the adhesive layer 10 is an a-plane, and a main surface 10B is a B-plane. The a-plane and the B-plane are planes bonded to the display element constituting member.

In the present embodiment, the concave-convex following rate of the a-plane (a-plane concave-convex following rate) and the concave-convex following rate of the B-plane (B-plane concave-convex following rate) are controlled. The unevenness following rate is an index of how much to follow the unevenness such as the step difference of the adherend (display element constituting member) and to attach when the adhesive layer is attached to the adherend. The higher the unevenness following rate, the more the unevenness is sufficiently buried in the adhesive layer near the unevenness having a large level difference, and the adhesion can be made so that a gap or the like is not formed between the adhesive layer and the interface of the unevenness. The following rate of the unevenness can be calculated by the following equation.

Roughness following ratio (%) = { (height (μm) of level difference in a state of being embedded without bubbles, floating, peeling, etc.) after a predetermined endurance test)/(thickness (μm) of adhesive layer) } ×100

The method of testing the unevenness following rate is as shown in the test example described below. When the adhesive layer is made of an active energy ray-curable adhesive, the concave-convex following rate is a concave-convex following rate after the adhesive layer is attached to an adherend and cured by active energy rays.

In this embodiment, the adhesive layer has a surface a concave-convex following rate different from a surface B concave-convex following rate of the adhesive layer, and the surface a concave-convex following rate and the surface B concave-convex following rate are both greater than 0%. By satisfying the above relationship between the concave-convex following ratio of the a-plane and the concave-convex following ratio of the B-plane of the adhesive layer, the adhesive layer can sufficiently follow the concave-convex, and the unevenness of the optical characteristics due to the concave-convex can be suppressed. Further, the foaming resistance is also improved.

The concave-convex following rate of the surface a and the concave-convex following rate of the surface B are preferably 1% to 50%, more preferably 2% to 40%, still more preferably 3% to 30%, particularly preferably 4% to 20%.

The difference between the a-plane concave-convex following rate and the B-plane concave-convex following rate (a-plane concave-convex following rate—b-plane concave-convex following rate) is preferably-20 to-1 percentage point, more preferably-15 to-1.5 percentage points, and still more preferably-10 to-2 percentage points.

(2.1.2. Total light transmittance of adhesive layer)

The adhesive layer of this embodiment has a total light transmittance of 85% or less. Thus, the design of the display can be improved.

From the viewpoint of visibility, the total light transmittance is preferably 3% or more, more preferably 10% or more, further preferably 25% or more, particularly preferably 30% or more, and particularly preferably 35% or more. From the viewpoint of design, the total light transmittance is preferably 75% or less, more preferably 65% or less, further preferably 55% or less, and particularly preferably 50% or less. The total light transmittance in this specification is a value measured in accordance with JISK 7361-1:1997. When the adhesive layer is made of an active energy ray-curable adhesive, the total light transmittance is the total light transmittance after the adhesive layer is attached to an adherend and cured by active energy rays.

(2.1.3 Haze value of adhesive layer)

The haze value of the adhesive layer of the present embodiment is preferably 0to 80%, more preferably 0.1 to 60%, even more preferably 0.5 to 40%, particularly preferably 1 to 20%, and particularly preferably 1.5 to 10%, from the viewpoint of easily satisfying the required total light transmittance and enabling both of the concealing property and the visibility. In the present specification, the haze value is a value measured according to JISK 7136:2000. When the adhesive layer is made of an active energy ray-curable adhesive, the haze value is a haze value obtained by adhering an adhesive to an adherend and curing the adhesive with an active energy ray.

(2.1.4. Adhesion of adhesive layer)

In the present embodiment, the adhesive force of the adhesive layer A against the soda lime glass (hereinafter also referred to as A-side adhesive force) is preferably 1N/25mm or more and 100N/25mm or less. This can ensure sufficient adhesion to the adhered object, and can easily achieve good step following property and good bubbling resistance.

From the above point of view, the adhesion to the surface A is more preferably 5 to 70N/25mm, still more preferably 10 to 50N/25mm.

In the present embodiment, the adhesive force of the adhesive layer B against the soda lime glass (hereinafter also referred to as B-side adhesive force) is preferably 1N/25mm or more and 100N/25mm or less. This can ensure sufficient adhesion to the adhered object, and can easily achieve good step following property and good bubbling resistance.

From the above point of view, the adhesive force of the B-side is more preferably 5 to 70N/25mm, still more preferably 10 to 50N/25mm.

The above-mentioned adhesive force may be measured by 180-degree peel method according to JIS Z0237:2009. Specific measurement methods are shown in test examples described below.

(2.2. When the adhesive layer is two layers)

As described above, the adhesive layer of the present embodiment is preferably two or more layers. Therefore, the case where the adhesive layer is two layers will be described below. When the adhesive layer is two layers, as shown in fig. 1B, the adhesive sheet 1 of the present embodiment has: the adhesive layer 10 (first adhesive layer 11 and second adhesive layer 12) and the release sheets 21, 22.

The first adhesive layer 11 and the second adhesive layer 12 are laminated to form the adhesive layer 10. In the present embodiment, the main surface 11a of the first adhesive layer 11 bonded to the adherend is referred to as the a-plane, and the main surface 12a of the second adhesive layer 12 bonded to the adherend is referred to as the B-plane.

(2.3. Physical Properties of the first adhesive layer and the second adhesive layer)

The physical properties of the first adhesive layer and the second adhesive layer are not particularly limited as long as the physical properties as a whole of the adhesive layer satisfy the above physical properties.

(2.3.1. Total light transmittance)

In this embodiment, when the first adhesive layer and the second adhesive layer are layers that easily satisfy the visibility of the entire adhesive layer, the total light transmittance of the first adhesive layer and the second adhesive layer is preferably 85 to 100%, more preferably 88 to 96%, and even more preferably 90 to 93%. When the first adhesive layer and the second adhesive layer are layers that are designed so as to easily satisfy the overall design of the adhesive layer, the total light transmittance of the first adhesive layer and the second adhesive layer is preferably 3 to 85%, more preferably 10 to 80%, still more preferably 30 to 75%, particularly preferably 50 to 70%, and particularly preferably 55 to 68%. When the first adhesive layer and the second adhesive layer are active energy ray-curable, the total light transmittance before and after irradiation with active energy rays is preferably within the above range. Thus, the optical properties required for the entire adhesive layer can be easily satisfied.

(2.3.2. Haze value)

In this embodiment, the haze value of the first adhesive layer and the second adhesive layer is preferably 0 to 80%, more preferably 0.01 to 40%, still more preferably 0.05 to 10%, and still more preferably 0.1 to 2%. When the first adhesive layer and the second adhesive layer are active energy ray-curable, the haze value before and after irradiation with active energy rays is preferably within the above range. Thus, the optical properties required for the entire adhesive layer can be easily satisfied.

(2.3.3. Storage modulus)

In this embodiment, the storage modulus G' at 25 ℃ of the first adhesive layer and the second adhesive layer is preferably 0.01 to 10MPa, more preferably 0.04 to 5MPa, still more preferably 0.08 to 2MPa, particularly preferably 0.1 to 1.5MPa, and particularly preferably 0.15 to 1.1MPa.

When the first adhesive layer and the second adhesive layer are active energy ray curable, the storage modulus Gb' at 25 ℃ before irradiation with active energy rays is preferably 0.01 to 1MPa, more preferably 0.03 to 0.5MPa, and even more preferably 0.05 to 0.2MPa. On the other hand, the storage modulus Ga' at 25℃after irradiation with active energy rays is preferably 0.01 to 10MPa, more preferably 0.04 to 5MPa, still more preferably 0.08 to 1MPa, particularly preferably 0.1 to 0.5MPa.

Thus, the first adhesive layer and the second adhesive layer have suitable viscoelasticity, and the display component member and the like have good adhesion to an adherend, and the adhesive force and the like can be easily adjusted within a desired range, thereby exhibiting good concave-convex following property and bubbling resistance. In particular, the ratio of storage modulus described later can be easily satisfied, and an adhesive that can satisfactorily follow the irregularities in the vicinity of the irregularities and can suppress optical irregularities can be obtained.

In the first adhesive layer and the second adhesive layer, when one adhesive layer contains a coloring component described later and the other adhesive layer does not contain a coloring component, the ratio (G1 b '/G2 b') of the storage modulus G1b 'of the adhesive layer containing the coloring component at 25 ℃ before the irradiation of the active energy ray to the storage modulus G2b' of the adhesive layer containing no coloring component at 25 ℃ before the irradiation of the active energy ray is preferably 1.1 to 10000, more preferably 1.2 to 1000, still more preferably 1.3 to 100, still more preferably 1.4 to 50, among which 1.5 to 25, most preferably 1.6 to 15.

In the first adhesive layer and the second adhesive layer, when one adhesive layer contains a coloring component described later and the other adhesive layer does not contain a coloring component, the ratio (G1 a '/G2 a') of the storage modulus G1a 'of the adhesive layer containing the coloring component at 25 ℃ after the irradiation of the active energy ray to the storage modulus G2a' of the adhesive layer containing no coloring component at 25 ℃ before the irradiation of the active energy ray is preferably 1.11 to 10000, more preferably 1.15 to 1000, still more preferably 1.2 to 100, still more preferably 1.24 to 50, among which 1.28 to 25, most preferably 1.3 to 15.

When G1b '/G2b' and G1a '/G2a' satisfy the above ranges, the obtained adhesive sheet easily exhibits desired physical properties, and thus exhibits good concave-convex following properties and blister resistance. In particular, an adhesive that can satisfactorily follow the irregularities in the vicinity of the irregularities and can suppress optical irregularities can be obtained.

(2.3.4. Gel fraction)

In this embodiment, the gel fraction of the first adhesive layer and the second adhesive layer is preferably 30 to 99%, more preferably 40 to 90%, still more preferably 45 to 85%, and particularly preferably 50 to 80%.

When the first adhesive layer and the second adhesive layer are active energy ray-curable, the gel fraction before irradiation with active energy rays is preferably 20 to 80%, more preferably 30 to 70%, still more preferably 40 to 60%, and particularly preferably 45 to 53%. On the other hand, the gel fraction after irradiation with active energy rays is preferably 40 to 99%, more preferably 50 to 95%, still more preferably 55 to 90%, particularly preferably 60 to 80%.

Thus, the first adhesive layer and the second adhesive layer have suitable cohesiveness, the adhesive force and the storage modulus can be easily adjusted to the desired ranges, and good concave-convex following property and foaming resistance can be exhibited. In addition, the above ratio of storage modulus can be easily satisfied, and an adhesive that can satisfactorily follow the irregularities in the vicinity of the irregularities and can suppress optical irregularities can be obtained.

(2.3.5. Adhesion)

As described above, in the present embodiment, the a-side is the main surface of the first adhesive layer, and the B-side is the main surface of the second adhesive layer, and therefore, the adhesive force of the first adhesive layer preferably satisfies the range of the a-side adhesive force described above, and the adhesive force of the second adhesive layer preferably satisfies the range of the B-side adhesive force described above.

(2.4. Composition of first adhesive layer and second adhesive layer)

The composition of the first adhesive layer and the second adhesive layer is not particularly limited as long as the adhesive layer of the present embodiment is configured to have the above-described physical properties. For example, an acrylic adhesive, a polyester adhesive, a polyurethane adhesive, a rubber adhesive, and a silicone adhesive can be exemplified. The adhesive may be any of emulsion type, solvent type, and solvent-free type. The adhesive may be active energy ray-curable or inactive energy ray-curable. Further, the adhesive may or may not have a crosslinked structure. In view of SDGs, a material having a high biomass content, a recyclable or reusable material, and a recycled or reusable material may be used as the material constituting the adhesive. The adhesives constituting the first adhesive layer and the second adhesive layer may be the same or different from each other.

In this embodiment, from the viewpoint of easy realization of the above physical properties and from the viewpoints of adhesion properties, optical properties, and the like, an acrylic adhesive is preferable as the adhesive constituting the first adhesive layer and the second adhesive layer, and an acrylic adhesive having a crosslinked structure is more preferable.

However, from the standpoint of controlling the a-plane roughness following rate to be different from the B-plane roughness following rate, it is preferable that the adhesive composition of the adhesive constituting the first adhesive layer is different from the adhesive composition of the adhesive constituting the second adhesive layer, and it is more preferable that the monomer composition of the main polymer is different.

The acrylic adhesive having a crosslinked structure is preferably an adhesive obtained by crosslinking an adhesive composition containing a (meth) acrylate polymer (a) and a crosslinking agent (B) (hereinafter, sometimes referred to as "adhesive composition P"). The adhesive agent is easy to satisfy the above physical properties and is easy to obtain good adhesion. In the present specification, (meth) acrylic acid refers to both acrylic acid and methacrylic acid. Other similar terms are also the same. The term "polymer" also includes the term "copolymer".

(2.4.1. (Meth) acrylate Polymer

The (meth) acrylate polymer (a) preferably contains, as a monomer unit constituting the polymer, a reactive functional group-containing monomer having a reactive functional group in a molecule which reacts with a crosslinking agent (B) described later. The reactive functional group derived from the reactive functional group-containing monomer reacts with the crosslinking agent (B) to form a crosslinked structure (a three-dimensional network structure), whereby an adhesive having a desired cohesive force can be obtained.

(2.4.1.1. Monomers containing reactive functional groups)

The reactive functional group-containing monomer is preferably 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), or the like. Among them, a hydroxyl group-containing monomer or a carboxyl group-containing monomer excellent in reactivity with the crosslinking agent (B) is preferable. In addition, a hydroxyl group-containing monomer and a carboxyl group-containing monomer may be used simultaneously.

Among them, from the viewpoints of reactivity of hydroxyl groups in the obtained (meth) acrylate polymer (a) with the crosslinking agent (B) and copolymerizability with other monomers, hydroxyalkyl (meth) acrylates having a hydroxyalkyl group having 1 to 4 carbon atoms are preferable. Specifically, 2-hydroxyethyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate and the like are preferable, and in particular, 2-hydroxyethyl acrylate or 4-hydroxybutyl acrylate is preferable. These may be used alone or in combination of two or more.

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 from the viewpoints of reactivity of carboxyl groups in the obtained (meth) acrylate polymer (a) with the crosslinking agent (B) shown and copolymerizability with other monomers. These may be used alone or in combination of two or more.

Examples of the amino group-containing monomer include aminoethyl (meth) acrylate, n-butylaminoethyl (meth) acrylate, and the like. These may be used alone or in combination of two or more. The amino group-containing monomer excludes a nitrogen atom-containing monomer described later.

When the (meth) acrylate polymer (a) contains a reactive functional group-containing monomer as a monomer unit constituting the polymer, the (meth) acrylate polymer (a) preferably contains 1 to 40% by mass of the reactive functional group-containing monomer, more preferably 2 to 35% by mass. In particular, when the reactive functional group-containing monomer is a hydroxyl group-containing monomer, the (meth) acrylate polymer (a) preferably contains 5 to 32 mass% of the hydroxyl group-containing monomer, more preferably 10 to 30 mass%, still more preferably 15 to 28 mass%, and particularly preferably 18 to 26 mass%. When the reactive functional group-containing monomer is a carboxyl group-containing monomer, the (meth) acrylate polymer (a) preferably contains 3 to 25 mass% of the carboxyl group-containing monomer, more preferably 4 to 15 mass%, and still more preferably 5 to 10 mass%. Thus, a good crosslinked structure can be formed in the obtained adhesive, and an adhesive having high cohesive force and excellent foaming resistance can be obtained. In addition, the obtained adhesive is easy to satisfy the required adhesive properties, optical properties and the like, and in particular, an adhesive which can well follow the irregularities in the vicinity of the irregularities and can suppress optical unevenness can be obtained.

The (meth) acrylate polymer (a) preferably contains no carboxyl group-containing monomer as a monomer unit constituting the polymer. Since the carboxyl group is an acid component, it is possible to suppress occurrence of defects due to acid on the object to be adhered by the adhesive agent by not containing the carboxyl group-containing monomer, and it is possible to suppress defects (corrosion, change in resistance value, etc.) of these materials due to acid even when a transparent conductive film such as tin-doped indium oxide (ITO) or a metal film is present on the object to be adhered by the adhesive agent.

The term "carboxyl group-free monomer" refers to a monomer that is substantially free of carboxyl groups, and allows the carboxyl group-containing monomer to be contained to such an extent that no corrosion of the transparent conductive film, the metal wiring, or the like due to the carboxyl groups occurs, in addition to the carboxyl group-containing monomer being completely free. Specifically, in the (meth) acrylate polymer (a), the carboxyl group-containing monomer is allowed to be contained as a monomer unit in an amount of less than 0.1 mass%, preferably contained as a monomer unit in an amount of 0.05 mass% or less, and more preferably contained as a monomer unit in an amount of 0.01 mass% or less.

(2.4.1.2 Alkyl (meth) acrylate)

The (meth) acrylic acid ester polymer (A) preferably contains an alkyl (meth) acrylate having 1 to 20 carbon atoms as an alkyl group as a monomer unit constituting the polymer. Thus, the adhesive can express preferable adhesiveness. Further, from the viewpoint of expressing more preferable adhesiveness, it is preferable that the alkyl (meth) acrylate in which the alkyl group has 1 to 20 carbon atoms has a linear or branched structure.

Examples of the alkyl (meth) acrylate having 1 to 20 carbon atoms in the alkyl group include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate, n-pentyl (meth) acrylate, n-hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, n-octyl (meth) acrylate, n-decyl (meth) acrylate, n-dodecyl (meth) acrylate, myristyl (meth) acrylate, palmityl (meth) acrylate, stearyl (meth) acrylate, and the like.

Among them, from the viewpoint of further improving the adhesion, a (meth) acrylate having 1 to 12 carbon atoms in the alkyl group is preferable, and a (meth) acrylate having 1 to 8 carbon atoms in the alkyl group is more preferable. Specifically, methyl (meth) acrylate, n-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, and n-octyl (meth) acrylate are preferable, and methyl methacrylate, n-butyl acrylate, 2-ethylhexyl acrylate, and n-octyl acrylate are particularly preferable. These may be used alone or in combination of two or more.

The (meth) acrylic acid ester polymer (a) preferably contains 30 to 99 mass% of an alkyl (meth) acrylate having 1 to 20 carbon atoms in the alkyl group as a monomer unit constituting the polymer, more preferably 40 to 90 mass%, still more preferably 50 to 80 mass%, particularly preferably 55 to 70 mass%. Thus, it is possible to introduce a desired amount of other monomer components for expressing desired characteristics into the (meth) acrylate polymer (a), and it is easy to impart appropriate adhesive properties, optical characteristics, and the like to the obtained adhesive. In particular, an adhesive is obtained which has excellent concave-convex following property and foaming resistance, and can well follow concave-convex near the concave-convex and inhibit optical unevenness.

The (meth) acrylate polymer (a) preferably contains a monomer having an alicyclic structure in the molecule (alicyclic structure-containing monomer) as a monomer unit constituting the polymer. It is presumed that since the alicyclic structure-containing monomer has a large volume, the presence of the alicyclic structure-containing monomer in the polymer can widen the interval between the polymers, and thus the resulting adhesive can be excellent in flexibility. This makes it easy to satisfy the above-described physical properties such as the concave-convex following rate and the adhesive force, and the concave-convex following property is good.

The alicyclic structure-containing carbon ring in the alicyclic structure-containing monomer may be a saturated structure carbon ring or may have an unsaturated bond in a part thereof. The alicyclic structure may be a monocyclic alicyclic structure, or may be a polycyclic alicyclic structure (polycyclic structure) such as a bicyclic structure or a tricyclic structure. The alicyclic structure is preferably a polycyclic structure in view of making the distance between the obtained (meth) acrylate polymers (a) suitable and imparting a higher stress relaxation property to the adhesive. Further, in view of compatibility between the (meth) acrylate polymer (a) and other components, it is particularly preferable that the above polycyclic structure is a bicyclic to a tetracyclic. In addition, as in the above, from the viewpoint of imparting stress relaxation and compatibility, the number of carbon atoms of the alicyclic structure is usually preferably 5 to 15 (the total number of carbon atoms of the ring-forming portions when a plurality of rings are independently present, the total number of carbon atoms thereof), and more preferably 7 to 10.

Specific examples of the alicyclic structure-containing monomer include cyclohexyl (meth) acrylate, dicyclopentanyl (meth) acrylate, adamantyl (meth) acrylate, isobornyl (meth) acrylate, dicyclopentanyl (meth) acrylate, and dicyclopentanyloxyethyl (meth) acrylate. Among them, dicyclopentanyl (meth) acrylate (having 10 carbon atoms in the alicyclic structure), adamantyl (having 10 carbon atoms in the alicyclic structure), or isobornyl (meth) acrylate (having 7 carbon atoms in the alicyclic structure) is preferable, isobornyl (meth) acrylate is particularly preferable, and isobornyl acrylate is further preferable. These may be used alone or in combination of two or more.

When the (meth) acrylate polymer (a) contains an alicyclic structure-containing monomer as a monomer unit constituting the polymer, the alicyclic structure-containing monomer is preferably contained in an amount of 1 to 30% by mass, more preferably 3 to 26% by mass, still more preferably 6 to 22% by mass, and particularly preferably 9 to 18% by mass. This makes it easy to satisfy the physical properties such as the above-described unevenness following rate and adhesion, and the unevenness following property is good. In particular, an adhesive that can satisfactorily follow the irregularities in the vicinity of the irregularities and can suppress optical irregularities can be obtained.

The (meth) acrylate polymer (a) preferably contains a nitrogen atom-containing monomer as a monomer unit constituting the polymer. By providing a nitrogen atom-containing monomer as a structural unit in the polymer, a predetermined polarity can be imparted to the adhesive, and thus the adhesive can have excellent affinity for an adherend having a certain degree of polarity. From the viewpoint of imparting moderate rigidity to the (meth) acrylate polymer (a), the monomer having a nitrogen-containing heterocyclic ring is preferable as the monomer having a nitrogen atom. In addition, from the viewpoint of improving the degree of freedom of the part derived from the above-mentioned nitrogen atom-containing monomer in the high-dimensional structure of the adhesive, it is preferable that the nitrogen atom-containing monomer contains no reactive unsaturated double bond group other than one polymerizable group used in the polymerization for forming the (meth) acrylate polymer (a).

Examples of the monomer having a nitrogen-containing heterocycle include N- (meth) acryloylmorpholine, N-vinyl-2-pyrrolidone, N- (meth) acryloylpyrrolidone, N- (meth) acryloylpiperidine, N- (meth) acryloylpyrrolidine, N- (meth) acryloylaziridine, aziridinylethyl (meth) acrylate, 2-vinylpyridine, 4-vinylpyridine, 2-vinylpyrazine, 1-vinylimidazole, N-vinylcarbazole, N-vinylphthalimide, and the like. Among them, N- (meth) acryloylmorpholine which exhibits more excellent adhesion is preferable, and N-acryloylmorpholine is particularly preferable. These may be used alone or in combination of two or more.

When the (meth) acrylic acid ester polymer (a) contains a nitrogen atom-containing monomer as a monomer unit constituting the polymer, the nitrogen atom-containing monomer is preferably contained in an amount of 1 to 20% by mass, more preferably 2 to 16% by mass, still more preferably 3 to 12% by mass, and particularly preferably 4 to 8% by mass. This makes it easy to satisfy the above-described physical properties such as the concave-convex following rate and the adhesive force, and the concave-convex following property is good. In particular, an adhesive that can satisfactorily follow the irregularities in the vicinity of the irregularities and can suppress optical irregularities can be obtained.

The (meth) acrylate polymer (a) may further contain other monomers as monomer units constituting the polymer, as required. As the other monomer, a monomer containing no reactive functional group is preferable in order not to interfere with the above-described action of the reactive functional group-containing monomer. Examples of such monomers include alkoxyalkyl (meth) acrylates such as methoxyethyl (meth) acrylate and ethoxyethyl (meth) acrylate, vinyl acetate, and styrene. These may be used alone or in combination of two or more.

The (meth) acrylate polymer (a) is preferably a linear polymer. This makes it easy to cause entanglement of the molecular chains and to improve the cohesive force, and therefore, it is easy to satisfy the above-described physical properties such as the concave-convex following rate and the adhesive force, and the concave-convex following property is good.

The (meth) acrylate polymer (a) is preferably a solution polymer obtained by a solution polymerization method. This makes it easy to obtain a polymer having a high molecular weight, and can be expected to improve the cohesive force, and therefore, it is easy to satisfy the above-described physical properties such as the concave-convex following rate and the adhesive force, and the concave-convex following property is good. In particular, an adhesive that can satisfactorily follow the irregularities in the vicinity of the irregularities and can suppress optical irregularities can be obtained.

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

The weight average molecular weight of the (meth) acrylate polymer (A) is preferably 10 to 300. Mu.m, more preferably 20 to 250. Mu.m. When the hydroxyl group-containing monomer is contained in the monomer unit constituting the (meth) acrylic acid ester polymer (a) without containing a carboxyl group, the weight average molecular weight is preferably 30 to 180 tens of thousands, more preferably 35 to 120 tens of thousands, still more preferably 40 to 90 tens of thousands, particularly preferably 45 to 75 tens of thousands. When the monomer unit constituting the (meth) acrylic acid ester polymer (a) contains no hydroxyl group-containing monomer but contains a carboxyl group, the weight average molecular weight is preferably 50 to 230 ten thousand, more preferably 100 to 220 ten thousand, and still more preferably 150 to 210 ten thousand. This makes it easy to satisfy the above-mentioned physical properties such as the concave-convex following rate and the adhesive force, and the concave-convex following property is good. In particular, an adhesive that can satisfactorily follow the irregularities in the vicinity of the irregularities and can suppress optical irregularities can be obtained. The weight average molecular weight in the present specification is a value in terms of standard polystyrene measured by Gel Permeation Chromatography (GPC).

In the adhesive composition P, the (meth) acrylate polymer (a) may be used alone or in combination of two or more.

(2.4.2. Crosslinker (B))

The crosslinking agent (B) can crosslink the (meth) acrylate polymer (a) by heating the adhesive composition P, thereby well forming a solid network structure. Thus, the cohesive force of the obtained adhesive is improved, and the above-described physical properties such as the concave-convex following rate and the adhesive force are easily satisfied, and the concave-convex following property is good. In particular, an adhesive that can satisfactorily follow the irregularities in the vicinity of the irregularities and can suppress optical irregularities can be obtained.

The crosslinking agent (B) may be any crosslinking agent that reacts with the reactive functional group of the (meth) acrylate polymer (a). Examples thereof include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, amine-based crosslinking agents, melamine-based crosslinking agents, aziridine-based crosslinking agents, hydrazine-based crosslinking agents, aldehyde-based crosslinking agents, oxazoline-based crosslinking agents, metal alkoxide-based crosslinking agents, metal chelate-based crosslinking agents, metal salt-based crosslinking agents, and ammonium salt-based crosslinking agents. When the reactive functional group of the (meth) acrylate polymer (a) is a hydroxyl group, an isocyanate-based crosslinking agent having excellent reactivity with the hydroxyl group is preferably used. On the other hand, when the reactive functional group of the (meth) acrylate polymer (a) is a carboxyl group, an epoxy-based crosslinking agent having excellent reactivity with the carboxyl group is preferably used, and an isocyanate-based crosslinking agent is preferably used in view of easiness in obtaining a desired crosslinked structure. The crosslinking agent (B) may be used alone or in combination of two or more.

The isocyanate-based crosslinking agent contains at least a polyisocyanate compound. Examples of the polyisocyanate compound include aromatic polyisocyanates such as toluene diisocyanate, diphenylmethane diisocyanate, and xylylene diisocyanate; aliphatic polyisocyanates such as hexamethylene diisocyanate; alicyclic polyisocyanates such as isophorone diisocyanate and hydrogenated diphenylmethane diisocyanate; and their biuret and isocyanurate bodies, adducts as reactants with low molecular active hydrogen-containing compounds such as ethylene glycol, propylene glycol, neopentyl glycol, trimethylolpropane, castor oil, etc. Among them, from the viewpoint of reactivity with hydroxyl groups, trimethylolpropane-modified aromatic polyisocyanates, particularly trimethylolpropane-modified toluene diisocyanate and trimethylolpropane-modified xylylene diisocyanate are preferable.

Examples of the epoxy-based crosslinking agent include 1, 3-bis (N, N-diglycidyl aminomethyl) cyclohexane, N' -tetraglycidyl-m-diphenylene diamine, ethylene glycol diglycidyl ether, 1, 6-hexanediol diglycidyl ether, trimethylolpropane diglycidyl ether, diglycidyl aniline, diglycidyl amine, and the like. Among them, 1, 3-bis (N, N-diglycidyl aminomethyl) cyclohexane is preferable from the viewpoint of reactivity with carboxyl groups.

The content of the crosslinking agent (B) in the adhesive composition P is preferably 0.01 to 10 parts by mass, more preferably 0.04 to 5 parts by mass, still more preferably 0.08 to 1 part by mass, and particularly preferably 0.12 to 0.5 part by mass, per 100 parts by mass of the (meth) acrylate polymer (a). Thus, the obtained adhesive exhibits excellent cohesive force, and is easy to satisfy the above-mentioned physical properties such as the concave-convex following rate and adhesive force, and has excellent concave-convex following property. In particular, an adhesive that can satisfactorily follow the irregularities in the vicinity of the irregularities and can suppress optical irregularities can be obtained.

(2.4.3. Active energy ray-curable component (C))

In the present embodiment, when the adhesive constituting the first adhesive layer and the second adhesive layer is active energy ray-curable, the adhesive composition P preferably contains the active energy ray-curable component (C). It is presumed that, in the adhesive obtained by curing the adhesive obtained by crosslinking the adhesive composition P with active energy rays, the active energy ray-curable component (C) polymerized with each other is entangled in a crosslinked structure (three-dimensional network structure) formed by crosslinking the (meth) acrylate polymer (a) and the crosslinking agent (B). The adhesive having such a high-dimensional structure is easy to satisfy the above-described physical properties such as the concave-convex following rate and the adhesive force, and is excellent in concave-convex following property and bubbling resistance. In particular, an adhesive that can satisfactorily follow the irregularities in the vicinity of the irregularities and can suppress optical irregularities can be obtained.

The active energy ray-curable component (C) is not particularly limited as long as it is a component curable by irradiation with active energy rays and has the above-mentioned effect, and may be any of a monomer, an oligomer, or a polymer, or may be a mixture thereof. Among them, the polyfunctional acrylate monomer is preferable from the viewpoint of easily satisfying the above-mentioned physical properties such as the unevenness following rate and the adhesion, and further, from the viewpoint of easily obtaining excellent foaming resistance. In addition, from the viewpoint of compatibility with the (meth) acrylate polymer (a), the molecular weight of the polyfunctional acrylate monomer is preferably less than 1000.

As the polyfunctional acrylic monomer, preferably of the di-functional, tri-functional, tetra-functional type five-functional and six-functional acrylate monomers.

Examples of the difunctional acrylate monomer include 1, 4-butanediol di (meth) acrylate, 1, 6-hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, neopentyl glycol adipate di (meth) acrylate, hydroxypivalate neopentyl glycol di (meth) acrylate, dicyclopentyl di (meth) acrylate, caprolactone-modified dicyclopentenyl di (meth) acrylate, ethylene oxide-modified phosphoric acid di (meth) acrylate, di (acryloyloxyethyl) isocyanurate, allylated cyclohexyl di (meth) acrylate, ethoxylated bisphenol a diacrylate, 9-bis [4- (2-acryloyloxyethoxy) phenyl ] fluorene, and the like.

Examples of the trifunctional acrylate monomer include trimethylolpropane tri (meth) acrylate, dipentaerythritol tri (meth) acrylate, propionic acid-modified dipentaerythritol tri (meth) acrylate, pentaerythritol tri (meth) acrylate, propylene oxide-modified trimethylolpropane tri (meth) acrylate, tris (acryloxyethyl) isocyanurate, and epsilon-caprolactone-modified tris- (2- (meth) acryloxyethyl) isocyanurate.

Examples of the tetra-functional acrylate monomer include diglycerol tetra (meth) acrylate and pentaerythritol tetra (meth) acrylate. Examples of the pentafunctional acrylate monomer include propionic acid-modified dipentaerythritol penta (meth) acrylate. Examples of the hexafunctional acrylate monomer include dipentaerythritol hexa (meth) acrylate and caprolactone-modified dipentaerythritol hexa (meth) acrylate.

Among them, from the viewpoint of the foaming resistance of the obtained adhesive, di (acryloyloxyethyl) isocyanurate, tri (acryloyloxyethyl) isocyanurate, a polyfunctional acrylate monomer having an isocyanurate structure in the molecule such as epsilon-caprolactone-modified tri- (2- (meth) acryloyloxyethyl) isocyanurate, or a polyfunctional acrylate monomer having a cyclic structure (particularly a cycloalkane structure) in the molecule such as tricyclodecanedimethanol (meth) acrylate, more preferably a polyfunctional acrylate monomer having a trifunctional or higher functionality and having an isocyanurate structure in the molecule, or a polyfunctional acrylate monomer having a difunctional or higher functionality and having a polycyclic structure (particularly a cycloalkane polycyclic structure) in the molecule, particularly preferably epsilon-caprolactone-modified tri- (2- (meth) acryloyloxyethyl) isocyanurate or tricyclodecanedimethanol (meth) acrylate, still more preferably epsilon-caprolactone-modified tri- (2-acryloyloxyethyl) isocyanurate or tricyclodecanedimethanol acrylate, and most preferably epsilon-caprolactone-modified tri- (2-acryloyloxyethyl) isocyanurate. One kind of these may be used alone, or two or more kinds may be used in combination.

The content of the active energy ray-curable component (C) in the adhesive composition P is preferably 1 to 40 parts by mass, more preferably 3 to 32 parts by mass, still more preferably 6 to 24 parts by mass, and particularly preferably 9 to 16 parts by mass or less, per 100 parts by mass of the (meth) acrylate polymer (a). Thus, the cohesive force and the like are improved after irradiation with the active energy rays, and the above-described physical properties such as the concave-convex following rate and the adhesive force are easily satisfied, and the bubbling resistance and the concave-convex following property are more excellent. In particular, an adhesive that can satisfactorily follow the irregularities in the vicinity of the irregularities and can suppress optical irregularities can be obtained.

(2.4.4. Photopolymerization initiator (D))

In the present embodiment, the adhesive composition P contains the active energy ray-curable component (C), and when ultraviolet rays are used as active energy rays, it is preferable that the adhesive composition P contains the photopolymerization initiator (D). This can efficiently cure the active energy ray-curable component (C), and can reduce the polymerization curing time and the irradiation amount of ultraviolet rays.

Examples of the photopolymerization initiator (D) include benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin n-butyl ether, benzoin isobutyl ether, acetophenone, dimethylaminoacetophenone, 2-dimethoxy-2-phenylacetophenone, 2-diethoxy-2-phenylacetophenone, 2-hydroxy-2-methyl-1-phenylpropane-1-one, 1-hydroxycyclohexyl phenyl ketone, 2-methyl-1- [4- (methylthio) phenyl ] -2-morpholino-propane-1-one, 4- (2-hydroxyethoxy) phenyl-2- (hydroxy-2-propyl) ketone, benzophenone, p-phenylbenzophenone, 4' -diethylaminobenzophenone, dichlorobenzophenone, 2-methylanthraquinone, 2-ethylanthraquinone, 2-t-butylanthraquinone, 2-aminothioxanthone, 2-ethylthioxanthone, 2, 4-dimethylthioxanthone, 2, 4-diethylthioxanthone, 2-benzyldimethyl ketal, 2-dimethylbenzyl-2, 4-dimethylbenzyl-2, 6-dimethylbenzoyl ketone, 2-dimethylbenzoyl-2-hydroxy-2- (2-methylbenzoyl) ketone, 2-dimethylbenzoyl ] ketone, 2-dimethylbenzoyl-2-methylbenzoyl-ketone, and the like. These may be used alone or in combination of two or more.

Among them, phosphine oxide photopolymerization initiators are preferable in view of easy cracking upon irradiation with ultraviolet light and easy and reliable curing of the adhesive. Specifically, 2,4, 6-trimethylbenzoyl-diphenyl-phosphine oxide, phenylbis (2, 4, 6-trimethylbenzoyl) phosphine oxide and the like are preferable. The optical member as an adherend may have a member having ultraviolet shielding properties, but even when ultraviolet rays are irradiated through such an ultraviolet shielding member which is not likely to transmit ultraviolet rays, the active energy ray-curable component (C) can be cured by the photopolymerization initiator which is the phosphine oxide-based photopolymerization initiator.

The content of the photopolymerization initiator (D) in the adhesive composition P is preferably 1 to 30 parts by mass, more preferably 4 to 22 parts by mass, and even more preferably 8 to 15 parts by mass, per 100 parts by mass of the active energy ray-curable component (C). Thus, the obtained adhesive sheet is easy to satisfy the required physical properties, and excellent concave-convex following property and foaming resistance are easy to obtain. In particular, an adhesive that can satisfactorily follow the irregularities in the vicinity of the irregularities and can suppress optical irregularities can be obtained.

(2.4.5. Coloring component (E))

In this embodiment, at least one of the first adhesive layer and the second adhesive layer preferably contains a coloring component (E). When the plurality of layers contain the coloring component (E), the coloring components may be the same as or different from each other. By containing the coloring component (E), the total light transmittance and haze value of the adhesive layer can be adjusted to desired ranges, and the design of the display to which the adhesive layer is attached can be improved. When the adhesive layer is one layer, it is preferable that the adhesive layer contains a coloring component (E). When the adhesive layer is composed of three or more layers, at least one layer preferably contains a coloring component (E).

The coloring component (E) may be a pigment or a dye. The pigment may be an inorganic pigment or an organic pigment. From the viewpoint of durability of the obtained adhesive, an inorganic pigment is preferable. The color of the coloring component (E) may be appropriately selected depending on the purpose, but usually, dark colors such as black, tea, dark blue, violet, and blue are preferable, and black is particularly preferable.

Examples of the inorganic pigment include carbon black, cobalt-based pigment, iron-based pigment, chromium-based pigment, titanium-based pigment, vanadium-based pigment, zirconium-based pigment, molybdenum-based pigment, ruthenium-based pigment, platinum-based pigment, ITO (indium tin oxide) based pigment, ATO (antimony tin oxide) based pigment, and the like.

Examples of the organic pigment and organic dye include an aminium (aminium) dye, a cyanine dye, a merocyanine dye, a croconium dye, a squarylium dye, a chamomile blue (azulenium) dye, a polymethine dye, a naphthoquinone dye, a pyrylium dye, a phthalocyanine dye, a naphthalocyanine dye, a naphthalenimine (naphtholactam) dye, an azo dye, a condensed azo dye, an indigo dye, a perinone (perinone) dye, a perylene dye, a dioxazine dye, a quinacridone dye, an isoindolinone dye, a quinolinone dye, a pyrrole dye, a thioindigo dye, a metal complex dye, a dithiol metal complex dye, an indophenol dye, a triallylmethane dye, an anthraquinone dye, a dioxazine dye, a naphthoquinone dye, an azomethine dye, a benzimidazolone dye, a pyranone dye, and a pyranone dye.

Examples of the black pigment include carbon black, copper oxide, ferroferric oxide, manganese dioxide, nigrosine, and activated carbon. Examples of the black dye include a high-concentration vegetable dye and an azo dye.

The above pigment or dye can be appropriately used in combination, thereby obtaining the target physical properties of the adhesive layer.

Among the coloring components (E), carbon black, nigrosine-based black dyes and chromate-based black dyes are preferable in that the above-mentioned physical properties are easily satisfied and the design of the display is improved. The carbon black may or may not be subjected to a predetermined treatment (for example, a solvation treatment) on its surface.

From the standpoint of optical characteristics, it is preferable that the coloring component (E) satisfies the characteristics shown below.

The average haze value of the coloring component (E), which is a liquid obtained by diluting the coloring component with ethyl acetate by 1 ten thousand times, is preferably 1 to 60%, more preferably 2 to 40%, even more preferably 3 to 20%, and particularly preferably 4 to 10% of the average value of the haze value at 780nm and the haze value at 380 nm. By using such a coloring component (E) in an appropriate amount, the optical properties (total light transmittance, haze value, etc.) of the adhesive layer described above can be easily satisfied.

Further, the difference between the haze value at 780nm and the haze value at 380nm of the liquid obtained by diluting the coloring component (E) with ethyl acetate by 1 ten thousand times is preferably 0 to 30%, more preferably 0.1 to 22%, particularly preferably 0.5 to 14%, and still more preferably 1 to 8%. By using such a coloring component (E) in an appropriate amount, the optical properties (total light transmittance, haze value, etc.) of the adhesive layer described above can be easily satisfied.

The haze value at 780nm of the liquid obtained by diluting the coloring component (E) 1 ten thousand times with ethyl acetate is preferably 0.1 to 50%, more preferably 0.5 to 35%, particularly preferably 1 to 20%, and further preferably 2 to 10%. The haze value of the liquid obtained by diluting the coloring component with ethyl acetate 1 ten thousand times at 380nm is preferably 1 to 60%, more preferably 3 to 45%, particularly preferably 6 to 30%, and further preferably 10 to 20%. Thus, the optical properties (total light transmittance, haze value, etc.) of the adhesive layer are easily satisfied.

Further, the standard deviation of the haze value of the liquid obtained by diluting the coloring component (E) with ethyl acetate 1 ten thousand times is preferably 0.1 to 10, more preferably 0.5 to 6, particularly preferably 1 to 3, at each wavelength (i.e., 380nm, 385nm, 390nm, & gt, 775nm, 780 nm) having a pitch of 5nm in the wavelength region of 380nm to 780 nm. Thus, the optical properties (total light transmittance, haze value, etc.) of the adhesive layer can be easily satisfied.

The content of the coloring component (E) is preferably 0.01 to 10 parts by mass, more preferably 0.05 to 5 parts by mass, still more preferably 0.1 to 1 part by mass, and particularly preferably 0.2 to 0.5 part by mass, per 100 parts by mass of the (meth) acrylate polymer (a). Thus, the optical properties described above can be easily satisfied, and the concave-convex following rate can be easily satisfied, thereby maintaining the required adhesive force or cohesive force. In particular, an adhesive that can satisfactorily follow the irregularities in the vicinity of the irregularities and can suppress optical irregularities can be obtained.

(2.4.6. Other additives)

The adhesive composition P may contain other additives as needed. Examples of such additives include silane coupling agents, ultraviolet absorbers, antistatic agents, tackifiers, antioxidants, light stabilizers, rust inhibitors, infrared absorbers, softeners, fillers, and refractive index regulators. The polymerization solvent or the dilution solvent described later is not included in the additives constituting the adhesive composition P.

(2.5. Other constructions of adhesive layer)

As shown in fig. 1A, when the adhesive layer 10 is formed of one layer, the adhesive constituting the adhesive layer 10 may be formed using the adhesive composition P. As a method of making the a-plane concave-convex following rate different from the B-plane concave-convex following rate, for example, a method of forming an inclined structure in which the hardness of the adhesive changes from the a-plane side to the B-plane side in the thickness direction is exemplified.

In addition, when the adhesive layer is composed of two layers, the structure in which the first adhesive layer and the second adhesive layer are in contact is described as shown in fig. 1B, but the first adhesive layer and the second adhesive layer may be not in contact. As such a configuration, for example, a configuration in which the first adhesive layer and the second adhesive layer are laminated with a member having no tackiness interposed therebetween is exemplified. Specifically, a configuration in which a first adhesive layer is formed on one main surface of a base material made of a resin film or the like and a second adhesive layer is formed on the other main surface is exemplified.

When the adhesive layer is formed of three or more layers, the adhesive composition P may be used to form an adhesive for forming each layer so that the physical properties of the adhesive layer as a whole are satisfied.

(2.6. Release sheet)

The release sheets 21 and 22 are materials for protecting the adhesive layer 10 until the adhesive sheet 1 is used, and are peeled off when the adhesive sheet 1 is used. In the adhesive sheet 1 of the present embodiment, one or both of the release sheets 21, 22 are not necessarily required.

Examples of the release sheet include polyethylene film, polypropylene film, polybutylene film, polybutadiene film, polymethylpentene film, polyvinyl chloride film, vinyl chloride copolymer film, polyethylene terephthalate film, 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, polycarbonate film, polyimide film, and fluororesin film. In addition, crosslinked films of these films may also be used. Further, these films may be laminated films. In view of SDGs, a material having a high biomass content, a material that can be recycled or reused, and a recycled or reused material may be used as the material constituting the release sheet.

The release surface (particularly, the surface in contact with the adhesive layer) of the release sheet is preferably subjected to a release treatment. Examples of the release agent used in the release treatment include release agents such as alcohol acids, silicones, fluorine compounds, unsaturated polyesters, polyolefins, and waxes. In addition, it is preferable that one of the release sheets is a heavy release type release sheet having a large release force, and the other release sheet is a light release type release sheet having a small release force.

The thickness of the release sheet is not particularly limited, and is usually about 20 to 150. Mu.m.

(3. Preparation of adhesive composition)

The adhesive composition P can be prepared, for example, by first preparing the (meth) acrylate polymer (a) and mixing the resulting (meth) acrylate polymer (a) with the crosslinking agent (B). If necessary, the composition can be prepared by further mixing the active energy ray-curable component (C), the photopolymerization initiator (D) and the coloring component (E).

The (meth) acrylic acid ester polymer (a) can be produced by polymerizing a mixture of monomers constituting the polymer by a usual radical polymerization method. The polymerization of the (meth) acrylic acid ester polymer (a) may be carried out by a solution polymerization method or the like using a polymerization initiator as needed. Examples of the polymerization solvent include ethyl acetate, n-butyl acetate, isobutyl acetate, toluene, acetone, hexane, and methyl ethyl ketone, and two or more of them may be used simultaneously. Examples of the polymerization initiator include azo compounds and organic peroxides, and two or more of them may be used simultaneously. In the polymerization step, a chain transfer agent such as 2-mercaptoethanol may be blended to adjust the weight average molecular weight of the polymer obtained.

After the (meth) acrylate polymer (a) is obtained, the crosslinking agent (B), the active energy ray-curable component (C) if necessary, the photopolymerization initiator (D), the coloring component (E), other additives, a diluting solvent, and the like are added to the solution of the (meth) acrylate polymer (a) and thoroughly mixed to obtain the adhesive composition P (coating solution) diluted with the solvent. In addition, when a solid substance is used as one of the above components, or when the solid substance is mixed with other components in an undiluted state and precipitation occurs, the component may be dissolved or diluted in a diluting solvent alone in advance and then mixed with the other components.

As the diluting solvent, for example, aliphatic hydrocarbons such as hexane, heptane, cyclohexane, etc. can be used; aromatic hydrocarbons such as toluene and xylene; halogenated hydrocarbons such as methylene chloride and dichloroethane; alcohols such as methanol, ethanol, propanol, butanol, and 1-methoxy-2-propanol; ketones such as acetone, methyl ethyl ketone, 2-pentanone, isophorone, and cyclohexanone; esters such as ethyl acetate and butyl acetate; cellosolve solvents such as ethyl cellosolve and the like.

The concentration and viscosity of the coating solution prepared in this manner are not particularly limited as long as they are within a coatable range, and may be appropriately selected according to circumstances. For example, the adhesive composition P is diluted so that the concentration thereof is 10 to 60 mass%. In addition, the addition of a diluting solvent or the like is not necessary in obtaining the coating solution, and if the adhesive composition P has a coatable viscosity or the like, the diluting solvent may not be added. In this case, the adhesive composition P is a coating solution in which the polymerization solvent of the (meth) acrylate polymer (a) is directly used as a diluting solvent.

(4. Preparation of adhesive)

The adhesive constituting the adhesive layer is preferably obtained by crosslinking the adhesive composition P. Crosslinking of the adhesive composition P can be generally carried out by a heat treatment. In addition, the drying treatment when the diluting solvent or the like is volatilized from the coating layer of the adhesive composition P applied to the desired object may also be used as the heating treatment. The adhesive layer may be preferably formed by applying the adhesive composition P to a desired object, performing a heat treatment, and then curing the adhesive composition P by irradiation with active energy rays.

In the case of the adhesive composition P, the heating temperature of the heat treatment is preferably 50 to 150℃and more preferably 70 to 120 ℃. In the case of the adhesive composition P, the heating time is preferably 10 seconds to 10 minutes, more preferably 50 seconds to 2 minutes.

The active energy ray is an active energy ray having an energy quantum in an electromagnetic wave or a charged particle beam, and specifically, ultraviolet rays, electron beams, and the like are mentioned. Among active energy rays, ultraviolet rays which are easy to handle are particularly preferable. The irradiation of ultraviolet rays can be performed using a high-pressure mercury lamp, an H lamp manufactured by Heraeus corporation, a xenon lamp, or the like.

When the adhesive composition P is cured by irradiation with active energy rays after the heat treatment, the irradiation amount of ultraviolet rays is preferably about 50 to 1000mW/cm ². The light amount is preferably 50 to 10000mJ/cm ², more preferably 80 to 5000mJ/cm ², and particularly preferably 200 to 2000mJ/cm ². On the other hand, the electron beam irradiation may be performed by an electron beam accelerator or the like, and the irradiation amount of the electron beam is preferably about 10 to 1000 krad.

If necessary, the curing period may be set at about 1 to 2 weeks at normal temperature (for example, 23 ℃ C., relative humidity: 50%). When curing is required, an adhesive having a crosslinked structure can be obtained after the curing period.

When curing is not required, an adhesive having a crosslinked structure can be obtained after the heat treatment is completed.

(5. Production of adhesive sheet)

The method for producing the adhesive sheet is not particularly limited, and may be produced by a known method. For example, the coating liquid of the adhesive composition P is applied to the release surface of one release sheet, and the adhesive composition P is crosslinked by heat treatment to form a coating layer having a predetermined thickness. And overlapping the stripping surface of the other stripping sheet on the formed coating layer. When curing is required, the coating layer becomes an adhesive layer through a prescribed curing period. In addition, when curing is not required, the coating layer directly becomes an adhesive layer. Thus, an adhesive sheet can be obtained.

When the adhesive layer is formed in two layers, for example, a coating liquid of the adhesive composition P for forming one adhesive layer (for example, a first adhesive layer) is applied to the release surface of one release sheet, and the adhesive composition is heat-treated and crosslinked to form a coating layer, thereby obtaining a release sheet with a coating layer. Further, a coating liquid of the adhesive composition P for forming another adhesive layer (for example, a second adhesive layer) is coated on the release surface of the other release sheet, and the adhesive composition is heat-treated and crosslinked to form a coating layer, thereby obtaining a release sheet with a coating layer. The release sheet with the coating layer and the release sheet with the coating layer are bonded so that the two coating layers are in contact with each other.

When the adhesive layer is three or more layers, a plurality of release sheets with coating layers may be produced, and these coating layers may be laminated in a desired number and in a desired lamination order.

When curing is required, the coating layer becomes an adhesive layer after a prescribed curing period. In addition, when curing is not required, the coating layer directly becomes an adhesive layer. When the adhesive layer is active energy ray-curable, the adhesive layer may be cured by irradiation of active energy rays as needed. Through the above steps, the adhesive sheet 1 is obtained.

Examples of the method of applying the coating liquid of the adhesive composition P include a bar coating method, a blade coating method, a roll coating method, a blade coating method, a die coating method, a gravure coating method, and the like.

(6. Use of adhesive sheet)

The adhesive sheet of the present embodiment can be used in the following manner. First, one release sheet is removed from the adhesive sheet, and the exposed adhesive layer is bonded to the first member (or the second member). Then, the other release sheet is peeled off, and the exposed adhesive layer is bonded to the second member. Thus, the first member and the second member are laminated via the adhesive layer, thereby obtaining an integrated laminated body.

When the adhesive layer is active energy ray-curable, the adhesive layer of the obtained laminate may be irradiated with a predetermined active energy ray as needed to cure the adhesive layer, thereby producing a cured adhesive layer.

When the adhesive constituting the adhesive layer contains an active energy ray-curable component, the adhesive layer is bonded to the first member or the second member before irradiation with active energy rays, and therefore the adhesive layer is soft although containing a crosslinked structure, and even if irregularities are formed on the first member and/or the second member, the irregularities can be sufficiently followed, and occurrence of gaps, floating, and the like in the vicinity of the irregularities can be suppressed.

Then, the adhesive layer is bonded to the optical member in a relatively soft state, and then, a predetermined active energy ray is irradiated to the adhesive layer, thereby curing the adhesive layer. Therefore, the cohesive force of the cured adhesive layer can be improved in a state where the concave-convex following property is good, and thus both the concave-convex following property and the bubbling resistance can be achieved. In particular, an adhesive that can satisfactorily follow the irregularities in the vicinity of the irregularities and can suppress optical irregularities can be obtained.

(7. Laminate)

As shown in fig. 2, the laminate 3 of the present embodiment is configured by including a first member 31 (one display constituting member) having irregularities 41, a second member 32 (the other display constituting member), and an adhesive layer 10 interposed therebetween and bonding the first member 31 and the second member 32 to each other.

Since the adhesive layer 10 in the laminate 3 is the adhesive layer 10 of the adhesive sheet 1 or the cured adhesive layer, it can sufficiently follow and adhere to the irregularities 41. Therefore, the concave-convex following property and the bubbling resistance are good. In addition, even in the vicinity of the irregularities, optical unevenness can be suppressed.

The laminate 3 is preferably a display itself or a member constituting a part of the display. Examples of the display include a vehicle-mounted display provided in a dashboard, a vehicle navigation system, various instruments of a console, and the like of an automobile; display bodies of smart phones, tablet computer terminals and the like for users in general; display bodies of commercial tablet computer terminals or digital signage and the like; a display body for an outdoor digital signage or the like. Examples of the type of display include an organic electroluminescence (organic EL) display, an electrophoretic display (electronic paper), a liquid crystal display using a plastic substrate (film) as a substrate, and a Light Emitting Diode (LED) display. The touch panel may be a touch panel having a position input means.

In addition, these display bodies may also be flexible displays. The flexible display may be a display including a member that is bent once and maintained in a bent state at the time of manufacture, or may be a display including a member that can be repeatedly bent (including bending). Examples of the flexible display include a folding display, a scroll display, and a retractable display.

When the laminate 3 is a display itself or a member (display constituent member) constituting a part of the display, the irregularities 41 in the laminate 3 may be irregularities of the display constituent member itself or irregularities due to other constituent elements formed on the display constituent member. Examples of the irregularities caused by such other constituent elements include a level difference caused by the printed layer, a level difference caused by the light emitting body, and the like.

When the irregularities are level differences due to the printed layers, a protective panel made of a laminate including a glass plate, a plastic plate, or the like is exemplified as the display element constituting member on which the printed layers are formed, in addition to the glass plate, the plastic plate, or the like. The printed layer is typically formed in a frame shape on the protective panel. The material constituting the printing layer is not particularly limited, and a known printing material can be used. The thickness of the printed layer, i.e., the height of the step, is preferably 3 to 40. Mu.m, more preferably 5 to 35. Mu.m, still more preferably 7 to 30. Mu.m, still more preferably 10 to 25. Mu.m. This allows the adhesive layer to sufficiently follow the step.

The glass plate is not particularly limited, and examples thereof include chemically strengthened glass, alkali-free glass, quartz glass, soda lime glass, barium-strontium-containing glass, aluminosilicate glass, lead glass, borosilicate glass, barium borosilicate glass, and the like. The thickness of the glass plate is not particularly limited, but is usually 0.1 to 5mm, preferably 0.2 to 2mm.

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

Various functional layers (transparent conductive film, metal layer, silicon layer, hard coat layer, antiglare layer, antireflection layer, light diffusion layer, optical adjustment layer, ultraviolet light absorption layer, writing feeling improvement layer, etc.) may be provided on one or both surfaces of the glass plate or plastic plate, or an optical member may be laminated. In addition, the transparent conductive film and the metal layer may be patterned.

The display constituent member is preferably an optical member, a display module (for example, a Liquid Crystal (LCD) module, a Light Emitting Diode (LED) module, an organic electroluminescence (organic EL) module, an electrophoretic display, or the like), an optical member that is a part of the display module, or a laminate including the display module. Examples of the optical member include a scattering preventing film, a polarizing plate (polarizing film), a polarizing plate, a retardation plate (retardation film), a viewing angle compensating film, a brightness improving film, a contrast improving film, a liquid crystal polymer film, a diffusion film, a semi-transmissive reflective film, and a transparent conductive film. Examples of the scattering preventing film include a hard coat film in which a hard coat layer is formed on one surface of a base film.

When the irregularities are level differences due to the light emitting body, a substrate having the light emitting body can be exemplified as a display body constituent member on which the light emitting body is formed. Such a substrate may be a direct-lit backlight. Examples of such a backlight include a backlight of a liquid crystal display. Examples of the light-emitting body include a light-emitting diode (LED), a Laser Diode (LD), an organic electroluminescent light-emitting element, and an inorganic electroluminescent element. Among them, from the viewpoint of sealing property of the adhesive layer, an LED is preferable, and a mini LED or a micro LED is particularly preferable.

The thickness of the light-emitting body is preferably 10 to 300. Mu.m, more preferably 30 to 200. Mu.m, still more preferably 50 to 150. Mu.m, particularly preferably 80 to 120. Mu.m. When a plurality of light emitters are provided, the width of the gap between adjacent light emitters is preferably 0.01 to 100mm, more preferably 0.1 to 10mm, and even more preferably 0.5 to 4mm. The shape of the light-emitting body is not particularly limited, and is generally a rectangular parallelepiped, a hemispherical shape, or the like. The size of the light-emitting body is not particularly limited, but from the viewpoint of sealing property of the light-emitting body, the diameter or one side in plan view is preferably 0.01 to 100mm, more preferably 0.1 to 10mm.

An example of manufacturing the laminated body 3 is shown. First, one release sheet 21 of the adhesive sheet 1 is released, and the exposed adhesive layer 10 of the adhesive sheet 1 is bonded to one surface of the first member 31.

Then, the other release sheet 22 is peeled off from the adhesive layer 10 of the adhesive sheet 1, and the exposed adhesive layer 10 of the adhesive sheet 1 is bonded to the second member 32, thereby obtaining the laminate 3. In addition, as another example, the bonding order of the first member 31 and the second member 32 may be changed.

When the adhesive layer 10 is active energy ray-curable, the adhesive layer 10 is bonded to the first member 31 and the second member 32, and then the active energy rays are irradiated to the adhesive layer 10, if necessary. Thus, the active energy ray-curable component (C) in the adhesive layer 10 is polymerized, and the laminate 3 after curing the adhesive layer 10 is obtained.

(8. Display body)

The display of the present embodiment includes the above-described laminate, and may be constituted by only the laminate, or may be constituted by including one or more laminates and other members. When one laminate is laminated with another laminate or when a laminate is laminated with another member, it is preferable to laminate the laminate via the adhesive layer of the adhesive sheet. Thus, the method is applicable to a variety of applications. The display of this embodiment is excellent in the concave-convex following property, bubbling resistance, and design property, and can suppress optical unevenness.

In the present specification, unless otherwise indicated, the term "X to Y" (X, Y is an arbitrary number) means "X or more and Y or less" and includes the term "preferably greater than X" or "preferably less than Y". In addition, unless otherwise indicated, when referring to "X or higher" (X is an arbitrary number), the meaning of "preferably greater than X" is included, and unless otherwise indicated, when referring to "Y or lower" (Y is an arbitrary number), the meaning of "preferably less than Y" is also included.

The embodiments of the present invention have been described above, but the present invention is not limited to the above embodiments, and may be modified in various ways within the scope of the present invention.

Production example 1

1. Preparation of (meth) acrylate polymers

The (meth) acrylate polymer (a) was prepared by copolymerizing 25 parts by mass of N-butyl acrylate, 30 parts by mass of 2-ethylhexyl acrylate, 5 parts by mass of N-acryloylmorpholine, 10 parts by mass of isobornyl acrylate, 5 parts by mass of methyl methacrylate and 25 parts by mass of 2-hydroxyethyl acrylate. The molecular weight of the obtained (meth) acrylate polymer (a) was measured by the method shown below, and as a result, the weight average molecular weight (Mw) was 50 ten thousand.

The weight average molecular weight (Mw) is a polystyrene-equivalent weight average molecular weight measured using Gel Permeation Chromatography (GPC) and under the following conditions (GPC measurement).

(Measurement conditions)

GPC measurement apparatus: TOSOH CORPORATION, HLC-8020

GPC column (passing in the following order): TOSOH CORPORATION manufacture of

TSK guard column HXL-H

TSK gel GMHXL(×2)

TSK gel G2000HXL

Measuring solvent: tetrahydrofuran (THF)

Measurement temperature: 40 DEG C

2. Preparation of adhesive composition

100 Parts by mass of the (meth) acrylate copolymer (A) (solid content equivalent; the same applies hereinafter), 0.2 part by mass of an isocyanate-based crosslinking agent (Mitsui Chemicals, inc. manufactured under the product name "TAKENATE D-101E", isocyanate type: toluene diisocyanate, modified form: trimethylolpropane adduct) as the crosslinking agent (B), and 0.25 part by mass of a black pigment as the coloring component (E) were mixed, sufficiently stirred, and diluted with methyl ethyl ketone to obtain a coating solution of the adhesive composition.

3. Production of adhesive layer

The coating solution of the obtained adhesive composition was applied to the release treated surface of a release sheet having one surface of a polyethylene terephthalate film release-treated with a silicone-based release agent using a blade coater. Then, the coating layer was subjected to a heat treatment at 90 ℃ for 1 minute to perform a crosslinking reaction, thereby forming a coating layer.

Next, the coating layer on the release sheet obtained above was bonded to the release treated surface of the release sheet obtained by releasing one side of the polyethylene terephthalate film with the silicone release agent so as to bring the coating layer into contact, and cured under conditions of 23 ℃ and 50% relative humidity for 7 days, thereby producing an adhesive layer (non-active energy ray-curable) having a thickness of 25 μm.

The thickness of the adhesive layer was measured in accordance with JIS K7130 by using a constant pressure thickness measuring instrument (PG-02 manufactured by TECLOCK Co.).

Production examples 2 to 7

An adhesive layer was produced in the same manner as in production example 1, except that the composition of the (meth) acrylate polymer (a), the kind and blending amount of the crosslinking agent (B), the kind and blending amount of the active energy ray-curable component (C), the kind and blending amount of the photopolymerization initiator (D), the blending amount of the coloring component (E), and the thickness of the adhesive layer were changed as shown in table 1. In production examples 4 and 5, the coating layer was irradiated with active energy rays (ultraviolet rays; UV) through a release sheet to be cured. The irradiation conditions of the active energy rays are as follows. In addition, the dyed PET film is also shown in table 1 for convenience.

< Active energy ray irradiation condition (hereinafter referred to as "condition A") >

Using high-pressure mercury lamps

The illuminance was 200mW/cm ² and the light quantity was 2000mJ/cm ²

UV illuminance-light meter using EYE GRAPHICS co., ltd, manufactured "UVPF-A1".

In table 1, the amounts of the crosslinking agent (B), the active energy ray-curable component (C), the photopolymerization initiator (D), and the coloring component (E) blended are amounts (solid content conversion) relative to 100 parts by mass of the (meth) acrylate polymer (a) (solid content conversion). Since the adhesives of production examples 4 and 5 were cured, the adhesives of production examples 1, 4, 5 and 7 were inactive energy ray-curable, and the adhesives of production examples 2, 3 and 6 were active energy ray-curable.

TABLE 1

Details of the abbreviations and the like described in table 1 are as follows. The optical properties of the coloring component (E) are shown in table 2, which are obtained by diluting the coloring component E1 shown in table 1 by 1 ten thousand times with ethyl acetate. The optical characteristics shown in Table 2 were calculated from haze values (%) obtained by using a haze meter (manufactured by NIPPON DENSHOKU INDUSTRIESCO., LTD. under the product name "SH-7000") according to JIS K7136:2000 for the above-mentioned dilutions. The difference between the haze values is a difference between the haze value at the wavelength of 780nm and the haze value at the wavelength of 380nm, the average haze value is an average value between the haze value at the wavelength of 780nm and the haze value at the wavelength of 380nm, and the standard deviation of the haze value is a standard deviation of the haze value at each wavelength of 5nm at a pitch of 380nm to 780nm in the wavelength region.

(Meth) acrylate Polymer (A)

BA: acrylic acid n-butyl ester

2EHA: 2-ethylhexyl acrylate

ACMO: n-acryloylmorpholine

IBXA: isobornyl acrylate

MMA: methyl methacrylate

HEA: acrylic acid 2-hydroxy ethyl ester

4HBA: acrylic acid 4-hydroxybutyl ester

AAc: acrylic acid

(Crosslinking agent (B))

B1: isocyanate-based crosslinking agent (manufactured by Mitsui Chemicals, inc. under the product name "TAKENATE D-101E", isocyanate-based type: toluene diisocyanate, modified form: trimethylolpropane adduct)

B2: isocyanate-based crosslinking agent (manufactured by Mitsui Chemicals, inc. under the product name "TAKENATE D-110N", isocyanate-based type: xylylene diisocyanate, modified form: trimethylolpropane adduct)

(Active energy ray-curable component (C))

C1: epsilon-caprolactone-modified tris- (2-acryloyloxyethyl) isocyanurate (SHIN-NAKAMURA CHEMICAL CO, manufactured by LTD. Product name "NK ESTER A-9300-1 CL")

C2: tris- (2-acryloyloxyethyl) isocyanurate (SHIN-NAKAMURA CHEMICAL CO, manufactured by LTD. Product name "NK ESTER A-9300")

(Photopolymerization initiator (D))

D1:2,4, 6-trimethylbenzoyl-diphenyl-phosphine oxide

D2: 1-hydroxy cyclohexyl phenyl ketone and benzophenone in the mass ratio of 1:1

(Coloring component (E))

E1: carbon black pigment

TABLE 2

(Measurement of total light transmittance)

The adhesive layers obtained in production examples 1 to 7 were bonded to glass, and the resultant was used as a sample for measurement. The total light transmittance (%) was measured for the above measurement sample by using a haze meter (manufactured by NIPPON DENSHOKU INDUSTRIESCO., LTD., product name "SH-7000") according to JISK7361-1:1997, based on the background measurement (background measurement) using glass. The results are shown in Table 3. In production examples 2, 3 and 6, the total transmittance before and after irradiation with active energy rays (ultraviolet rays; UV) was measured in the same manner as described above. The irradiation condition of the active energy ray is the condition a described above.

(Determination of haze value)

The adhesive layers obtained in production examples 1 to 7 were measured for haze value (%) from the adhesive layer side according to JISK7136:2000 using a haze meter (NIPPON DENSHOKU INDUSTRIES CO., LTD., product name "SH-7000"). The obtained haze value (%) is shown in table 3. In production examples 2, 3 and 6, haze values before and after irradiation with active energy rays (ultraviolet rays; UV) were measured in the same manner as described above. The irradiation condition of the active energy ray is the condition a described above.

(Measurement of adhesive force of adhesive layer)

The release sheet was peeled off from the adhesive layers obtained in production examples 1 to 7, and the exposed adhesive layer was bonded to an easy-to-adhere layer of a polyethylene terephthalate (PET) film (toyobaco., ltd. Manufactured under the product name "COSMOSHINE A4160", thickness: 100 μm) having an easy-to-adhere layer, to obtain a laminate of release sheet/adhesive layer/PET film. The obtained laminate was cut into a sheet having a width of 25mm and a length of 100mm, and the sheet was used as a sample.

The release sheet was peeled off from the above sample at 23 ℃ under a relative humidity of 50%, and the exposed adhesive layer was attached to soda lime glass (Nippon SHEET GLASS co., ltd.) and then pressed at 50 ℃ under 0.5MPa for 20 minutes using an autoclave manufactured by KURIHARA SEISAKUSHO co., ltd. Then, after being left at 23℃and a relative humidity of 50%, the adhesive force (N/25 mm) was measured at a peeling speed of 300 mm/min and a peeling angle of 180 degrees using a tensile tester (ORIENTEC Co., LTD. Manufactured by LTD. Product name "TENSILON"). Conditions other than those described herein were measured according to JISZ 0237:2009. The results are shown in Table 3. In production examples 2, 3 and 6, the adhesion before and after irradiation with active energy rays (ultraviolet rays; UV) was measured in the same manner as described above. The irradiation condition of the active energy ray is the condition a described above.

(Storage modulus of adhesive layer)

The adhesive layers obtained in production examples 1 to 7 were laminated to obtain a laminate having a thickness of 3 mm. From the laminate of the obtained adhesive layers, a cylinder (height: 3 mm) having a diameter of 8mm was punched out, and this was used as a sample for measuring storage modulus.

According to JISK7244-6, the storage modulus of a measurement sample was measured by a torsional shear method using a viscoelasticity measuring apparatus (MCR 301, manufactured by Anton Paar Co., ltd.) at a measurement temperature of 25℃and a measurement frequency of 1 Hz. The results are shown in Table 3. In production examples 2, 3 and 6, the storage modulus before and after irradiation with active energy rays (ultraviolet rays; UV) was measured in the same manner as described above. The irradiation condition of the active energy ray is the condition a described above.

(Evaluation of gel fraction of adhesive)

The adhesive layers obtained in production examples 1 to 7 were cut into 80mm×80mm sizes, and the colored adhesive layers were wrapped in a polyester mesh (product name: tebubali # 200), and the mass thereof was weighed using a precision balance. The individual masses of the webs are subtracted from the weighing values, from which the mass of the adhesive alone is calculated. The mass at this time was denoted as M1.

Then, the adhesive coated in the polyester net was immersed in ethyl acetate at room temperature (23 ℃) for 24 hours. The web was then removed, air-dried at 23℃and 50% relative humidity for 24 hours, and further dried in an oven at 80℃for 12 hours. After drying, the mass was weighed with a precision balance. The individual masses of the webs are subtracted from the weighing values, from which the mass of the adhesive alone is calculated. The mass at this time was denoted as M2. Using the obtained M1 and M2, gel fraction was calculated according to the following formula. The results are shown in Table 3.

Gel fraction (%) = (M2/M1) ×100

In addition, as in the measurement of the total light transmittance, the gel fraction before and after irradiation with active energy rays (ultraviolet rays; UV) was measured in the same manner as described above for production examples 2,3 and 6. The irradiation condition of the active energy ray is the condition a described above.

TABLE 3

Example 1

Two adhesive layers obtained in production example 2 were laminated to prepare a first adhesive layer having a thickness of 50. Mu.m. Next, 6 adhesive layers obtained in production example 6 were laminated to prepare a second adhesive layer having a thickness of 150. Mu.m. The main surface of the obtained first adhesive layer was bonded to the main surface of the second adhesive layer, and an adhesive sheet having the structure shown in table 4 was obtained.

(Examples 2 to 5 and comparative examples 1 to 3)

The adhesive layers of production examples 1 to 7 were selected so that the combinations shown in table 4 were formed between the first adhesive layer and the second adhesive layer, and the adhesive sheets were obtained by laminating the adhesive layers so that the thicknesses shown in table 4 were formed. The adhesive layer of example 5 is three layers. In comparative example 3, the adhesive layer of production example 3 was formed on both principal surfaces of the dyed PET film (dyed PET). For convenience, the thickness of the dyed PET is shown in table 1, and the storage modulus, total light transmittance, haze, and gel fraction are shown in table 3.

TABLE 4

(Concave-convex following Rate)

Ultraviolet curable ink (Teikoku PRINTING INKS mfg.co., ltd., product name "POS-911 BLACK") was screen-printed in a frame-like form (external form: 90mm long x 50mm transverse, 5mm wide) on the surface of a glass plate (product name "Corning GLASS EAGLE XG", product name 90mm long x 50mm wide x 0.5mm thick). Next, ultraviolet rays (80W/cm ², 2 metal halogen lamps, 15cm in lamp height, 10 to 15 m/min in conveyor speed) were irradiated to cure the printed ultraviolet-curable ink, thereby producing a glass plate having a step difference (height of step difference: any one of 5 μm, 10 μm, 15 μm,20 μm and 25 μm) due to printing.

The release sheet was peeled from the adhesive sheets produced in examples and comparative examples so as to expose the main surface of the second adhesive layer. The exposed second adhesive layer was bonded to a polyethylene terephthalate (PET) film (TOYOBO co., ltd. Manufactured, product name

"COSMOSHINE A4160", thickness: 100 μm) of the easy-to-adhere layer. Then, the other release sheet is peeled off to expose the main surface (a surface) of the first adhesive layer. Then, the adhesive layers were laminated on each of the glass plates with step differences using a laminator (manufactured by FUJIPLA inc. Product name "LPD 3214") so that the main surface (a surface) of the first adhesive layer covered the entire frame-shaped printed surface, and this was used as an evaluation sample.

The obtained sample for evaluation was subjected to autoclave treatment at 50℃and 0.5MPa for 30 minutes, and then left to stand at normal pressure and 23℃for 24 hours at a relative humidity of 50%. The adhesive sheets produced in examples 1 and 3 and comparative examples 1 to 3 were irradiated with active energy rays through a PET film under the above-mentioned condition a to cure the adhesive layer.

Then, the film was stored at 85℃under high temperature and high humidity conditions with a relative humidity of 85% for 72 hours (endurance test), and then the concave-convex following property of the A-plane was evaluated. The following property of the irregularities is determined by whether the printed level difference is completely embedded in the adhesive layer, and when bubbles, floating, peeling, and the like are observed at the interface between the printed level difference and the adhesive layer, it is determined that the irregularities of the printed level difference cannot be followed. The concave-convex following property was evaluated by a concave-convex following rate (%) shown in the following formula. The results are shown in Table 5.

Bump following ratio (%) = { (height (μm) of level difference in a state of being embedded without bubbles, floating, peeling, etc.) after the endurance test)/(thickness of adhesive layer) } ×100

In addition, the concave-convex following property of the B surface was evaluated in the same manner as described above. The results are shown in Table 5. Further, the difference between the concave-convex following rates (a-plane concave-convex following rate-B-plane concave-convex following rate) is calculated from the obtained a-plane concave-convex following rate and B-plane concave-convex following rate. The results are shown in Table 5.

(Total light transmittance)

The total light transmittance of the adhesive layers of the adhesive sheets fabricated in examples and comparative examples was measured by the same method as the measurement of the total light transmittance described above. The results are shown in Table 5. The adhesive sheets produced in examples 1 and 3 and comparative examples 1 to 3 were irradiated with active energy rays through a PET film under the above-mentioned condition a to cure the adhesive layer.

(Haze value)

The haze values of the adhesive layers of the adhesive sheets produced in examples and comparative examples were measured by the same method as the above measurement of haze values. The results are shown in Table 5. The adhesive sheets produced in examples 1 and 3 and comparative examples 1 to 3 were irradiated with active energy rays through a PET film under the above-mentioned condition a to cure the adhesive layer.

(Ratio of storage modulus of colored adhesive layer to storage modulus of transparent adhesive layer)

The ratio of the storage modulus (G1 b ') of the colored adhesive layer (the adhesive layer containing carbon black) to the storage modulus (G2 b') of the transparent adhesive layer (the adhesive layer containing no carbon black) in the adhesive layers of the adhesive sheets produced in the examples and comparative examples was calculated. The results are shown in Table 5. The adhesive sheets produced in examples 1 and 3 and comparative examples 1 to 3 were irradiated with active energy rays through a PET film under the above condition a, and the storage moduli (G1 a 'and G2 a') after curing the adhesive layers were calculated as the above ratio.

(Evaluation of concave-convex following Property and mottle 1)

As an adherend, a glass plate with a step (height of step: 25 μm) and a glass plate without a step (manufactured by NSG Precision Co., ltd., product name "Corning GLASS EAGLE XG", length 90 mm. Times. Width 50 mm. Times. Thickness 0.5 mm) were prepared by the same method as that of the glass plate with a step produced in the measurement of the unevenness following rate. In table 5, the glass with the level difference is referred to as a concave-convex plate, and the glass plate without the level difference is referred to as a smooth plate.

The release sheet was peeled off from the adhesive sheets produced in examples and comparative examples, and the exposed first adhesive layer was attached to a smooth plate. Then, the release sheet is peeled off from the adhesive sheet, and the exposed second adhesive layer is bonded to the uneven plate.

The structure obtained in the above manner was placed on a tablet personal computer terminal (manufactured by Apple corporation, product name "iPad (registered trademark)", resolution: 264 ppi) with the concave-convex plate side facing downward. For this sample, the entire surface of the tablet terminal was displayed as white, and the vicinity of the level difference was observed with naked eyes, and the concave-convex following property was evaluated according to the following criteria. The results are shown in Table 5.

No floating/peeling of …

X … float and peel

Further, the vicinity of the level difference was observed with naked eyes, and the color unevenness was evaluated according to the following criteria. The results are shown in Table 5.

And (3) the following materials: no stain was identified either from 60 degrees of tilt or from frontal observation

O: the stain was identified when viewed at 60 degrees oblique, but not when viewed from the front

X: the color spots can be identified from the front

(Evaluation of concave-convex following Property and mottle 2)

The following property of the unevenness and the color unevenness were evaluated in the same manner as described above except that the second adhesive layer was attached to the uneven plate and then the first adhesive layer was attached to the smooth plate. The results are shown in Table 5.

(Evaluation of foaming resistance)

The release sheet was peeled off from the adhesive sheet obtained in examples and comparative examples, and the exposed adhesive was attached to an ITO vapor-deposited film (OIKE & co., ltd., product name "TETOLIGHT TCFKH150NMH 2-125-U6/T2"). Further, the release Sheet was peeled off from the adhesive Sheet, and the exposed adhesive layer was attached to a polycarbonate-side surface of a resin Sheet (manufactured by MITSUBISHI GAS CHEMICAL compass, inc. And product name "Iupilon-Sheet MR58U", containing an ultraviolet absorber, thickness: 1 mm) having a polymethyl methacrylate resin layer laminated on a polycarbonate resin Sheet, to obtain a sample for evaluation. The adhesive sheets produced in examples 1 and 3 and comparative examples 1 to 3 were irradiated with active energy rays through a plastic plate under the same conditions as in production example 1 to cure the adhesive layer.

Then, the sample for evaluation was subjected to autoclave treatment at 50℃and 0.5MPa for 20 minutes, left at normal pressure and 23℃and a relative humidity of 50% for 12 hours, and then stored at 85℃and a relative humidity of 85% for 72 hours under high temperature and high humidity conditions. Then, the state of the interface between the adhesive layer and the adherend was confirmed by visual observation, and the bubbling resistance was evaluated according to the following criteria.

The results are shown in Table 5.

Very good … has no bubbles or floating/peeling

The level of no problem, i.e., no floating or peeling of …, and only a small amount of bubbles were generated

X … causes floating and peeling

TABLE 5

From table 5, it was confirmed that the adhesive sheets of examples 1 to 5 can suppress unevenness-induced unevenness and also have both unevenness following property and bubbling resistance.

Industrial applicability

The adhesive sheet of the present invention can be suitably used for bonding members constituting a display body, for example.

Claims

1. An adhesive sheet having an adhesive layer for bonding a first member to a second member, wherein,

The adhesive layer has a total light transmittance of 85% or less,

When one main surface of the adhesive layer is an a-surface and the other main surface is a B-surface, a-surface roughness following rate (%) is different from a B-surface roughness following rate (%), the a-surface roughness following rate (%) indicates a following property of the a-surface against the roughness when the a-surface is bonded to an adherend having the roughness, the B-surface roughness following rate (%) indicates a following property of the B-surface against the roughness when the B-surface is bonded to the adherend having the roughness,

The A-surface roughness following rate and the B-surface roughness following rate are greater than 0%.

2. The adhesive sheet according to claim 1, wherein,

The adhesive layer is composed of two or more layers.

3. The adhesive sheet according to claim 1 or 2, wherein,

The value obtained by subtracting the B-surface unevenness following rate from the a-surface unevenness following rate is-20 percentage points or more and-1 percentage point or less.

4. The adhesive sheet according to claim 1 or 2, wherein,

The adhesive layer includes a coloring component.

5. The adhesive sheet according to claim 1 or 2, wherein,

The adhesive layer is an acrylic adhesive having a crosslinked structure.

6. A laminate is provided with: a first member, a second member, and an adhesive layer adhering the first member and the second member to each other,

At least one of the first member and the second member has a concave-convex,

The adhesive layer is the adhesive layer of the adhesive sheet according to any one of claims 1 to 5.

7. A display comprising the laminate according to claim 6.