CN107077801B - Adhesives, Adhesive Sheets, and Displays - Google Patents

Abstract

An adhesive for bonding one display body constituting member and another display body constituting member having a step difference at least on a surface on a side to be bonded, the adhesive being obtained by thermally crosslinking and curing an adhesive composition containing: a (meth) acrylate polymer (A) containing a reactive functional group-containing monomer as a monomer unit constituting the polymer, an active energy ray-curable component (B) having a bifunctional or higher, and a thermally crosslinkable crosslinking agent (C); the content of the component (B) in the adhesive composition is such that the gel fraction (G1) of the adhesive and the gel fraction (G2) of the adhesive obtained by thermally crosslinking the adhesive composition from which the component (B) has been removed are substantially the same; when an adhesive layer having a thickness of 600 μm and a width of 10mm is formed, the maximum stress at the time of extension to the elongation at break at a measurement length of 20mm and a drawing rate of 200 mm/min under an environment of 23 ℃ and 50% RH is 2.8N or more.

Description

Adhesives, Adhesive Sheets, and Displays

technical field

The present invention relates to an adhesive, an adhesive sheet for pasting components of a display body, and a display obtained by using the adhesive layer of the adhesive sheet.

Background technique

Recently, various mobile electronic devices such as mobile phones and tablet computer terminals are equipped with displays (displays) with display modules such as liquid crystal components, light-emitting diodes (LED components), and organic electroluminescent diodes (organic EL) components.

In the display, a protective panel is usually installed on the surface side of the display module, and there is a gap between the protective panel and the display module, so that even if the protective panel is deformed by an external force, the deformed protective panel will not touch the display module. .

However, if there is such a gap, that is, if the air layer exists, the light reflection loss due to the difference in refractive index between the protective panel and the air layer and the difference in refractive index between the air layer and the display module will be large, and the image quality of the display will be reduced. question.

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

In order to solve the above problems, Patent Document 1 discloses an adhesive layer as an adhesive layer that fills the gap between the protective panel and the display module. Under the environment of 25°C and 1 Hz, the storage modulus (G' ) is 1.0×10 ⁵ Pa or less, and the gel portion is 40% or more.

prior art literature

patent documents

Patent Document 1: Japanese Patent Laid-Open No. 2010-97070

Contents of the invention

The technical problem to be solved in the present invention

In Patent Document 1, the storage modulus of the adhesive layer is low when left at room temperature, so step followability must be improved. In addition, as another method, it is conceivable to improve step followability by reducing the degree of crosslinking of thermally crosslinkable adhesives, that is, the gel portion. However, if the storage modulus or the gel portion is reduced, the film strength of the adhesive layer is reduced, and the workability is deteriorated. For example, when the adhesive sheet is stamped, the adhesive will adhere to the knife surface, causing problems such as partial loss of the adhesive layer.

The present invention was made in view of the above-mentioned circumstances, and an object of the present invention is to provide an adhesive, an adhesive sheet, and a display using the adhesive sheet that are excellent in step followability and exhibit high film strength.

Technical means to solve technical problems

In order to achieve the above object, firstly, the present invention provides an adhesive for adhering a display body component having a level difference at least on the surface of the side to be pasted and another display body component, characterized in that,

The adhesive is obtained by thermally crosslinking and active energy ray curing an adhesive composition containing (methyl) reactive functional group-containing monomer as a monomer unit constituting a polymer. an acrylate polymer (A), an active energy ray-curable component (B) having a difunctionality or more, and a heat-crosslinkable crosslinking agent (C);

The content of the active energy ray-curable component (B) in the adhesive composition is such that the gel portion (G1) of the adhesive and the active energy ray curable component (B) will be removed from the adhesive composition. The gel portion (G2) of the adhesive obtained by thermally crosslinking the adhesive composition of the energy ray curable component (B) is substantially the same amount; and,

When forming an adhesive layer with a thickness of 600 μm and a width of 10 mm, under the environment of 23 ° C and 50 % RH, the maximum stress when extending to the elongation at break is 2.8 with a measured length of 20 mm and a tensile speed of 200 mm/min. N or more (Invention 1).

The adhesive according to the above invention (Invention 1) has excellent step followability and exhibits high film strength by satisfying the above conditions.

In the above invention (Invention 1), the gel fraction (G1) is preferably 40 to 80% (Invention 2).

In the above inventions (Inventions 1 and 2), when forming an adhesive layer with a thickness of 600 μm and a width of 10 mm, it was stretched at a measured length of 20 mm and a stretching speed of 200 mm/min under an environment of 23° C. and 50% RH. The elongation at break is preferably 1000% or more (Invention 3).

In the above inventions (Inventions 1 to 3), it is preferable that the weight average molecular weight of the (meth)acrylate polymer (A) is 200,000 to 1,000,000 (Invention 4).

In the above inventions (Inventions 1 to 4), the (meth)acrylate polymer (A) preferably contains 5 to 30% by mass of monomers constituting the polymer. The reactive functional group-containing monomer of the body unit (Invention 5).

In the above inventions (Inventions 1-5), it is preferable that the reactive functional groups of the reactive functional group-containing monomers are carboxyl groups and/or hydroxyl groups, and that the cross-linking agent (C) is an isocyanate-based cross-linking agent and/or an epoxy-based Crosslinking agent (Invention 6).

Second, the present invention provides an adhesive sheet having an adhesive layer (Invention 7) formed from the above adhesive (Inventions 1 to 6).

In the above invention (Invention 7), the thickness of the adhesive is preferably 10 to 400 μm (Invention 8).

In the above inventions (Inventions 7 and 8), it is preferable that the adhesive sheet has two release sheets, and the adhesive layer is sandwiched by the release sheets so as to be in contact with the release surfaces of the two release sheets. (Invention 9).

Thirdly, the present invention provides a display body, the display body has:

a display body component having a level difference at least on the surface of the side to be pasted,

another display constituting part, and

The adhesive layer for adhering the one display constituent member and the other display constituent member to each other is characterized in that,

The said adhesive layer is the adhesive layer (invention 10) of the said adhesive sheet (invention 7-9).

In the above invention (Invention 10), the step is frame-shaped in plan view (Invention 11).

Invention effect

The pressure-sensitive adhesive according to the present invention has excellent step followability with the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet, and exhibits high film strength. In the display body obtained using such an adhesive sheet, if there is a step on the side of the adhesive surface, the adhesive layer can follow the step, and even after durability conditions, it is difficult to generate a gap or gap between the step and the adhesive. Air bubbles can maintain the state where the adhesive layer fills the gap.

Description of drawings

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

Fig. 2 is a cross-sectional view of a laminate according to one embodiment of the present invention.

Detailed ways

Embodiments of the present invention will be described below.

[adhesive]

The adhesive according to this embodiment is an adhesive for adhering one display constituent member and another display constituent member having a level difference at least on the surface to be adhered. The display body and the components constituting the display body will be discussed later.

The adhesive of this embodiment is obtained by thermally crosslinking and curing an adhesive composition (hereinafter sometimes referred to as "adhesive composition P") and cured by active energy rays. The adhesive composition contains: A (meth)acrylate polymer (A) containing a reactive functional group monomer as a monomer unit, an active energy ray-curable component (B) having a bifunctionality or more, and a thermally crosslinkable crosslinking agent (C ). It is presumed that in this adhesive, the (meth)acrylate polymer (A) is cross-linked by the cross-linking agent (C) to form a three-dimensional network structure, and the active energy ray-curable components (B) are mutually polymerized, Wrapped around the above-mentioned three-dimensional network structure. Hereinafter, this structure may be referred to as "structure X". In addition, in this specification, (meth)acrylic acid means both acrylic acid and methacrylic acid. The same goes for other similar terms. In addition, the concept of "copolymer" is also included in "polymer".

The content of the active energy ray-curable component (B) in the above-mentioned adhesive composition P is such that the gel portion (G1) of the adhesive according to the present embodiment and the active energy ray-curable component (B) that will be removed from the above-mentioned adhesive composition P The amount of the gel portion (G2) of the adhesive (hereinafter sometimes referred to as "adhesive H") obtained by heat-crosslinking the adhesive composition of the energy ray-curable component (B) is substantially the same. In addition, the term "substantially the same" here refers to a level of 15% or less in the rate of change of the gel fraction shown below.

The rate of change of the gelled portion is determined by heat transfer of an adhesive composition obtained by removing the active energy ray-curable component (B) from the adhesive composition P, where the gelled portion of the adhesive according to the present embodiment is G1 (%). The gel portion of the bonded adhesive H is represented by the following formula when G2 (%) is used.

Change rate of gel part (%)={(G1-G2)/G2}×100

In the adhesive according to the present embodiment, the change rate of the gel portion is preferably 0 to 15%, particularly preferably 0 to 10%, and even more preferably 0 to 4%. In addition, the measurement method of the gel part is the same as that shown in the later test example.

In addition, when the adhesive according to this embodiment forms an adhesive layer having a thickness of 600 μm and a width of 10 mm, it is stretched at a measurement length of 20 mm and a tensile speed of 200 mm/min in an environment of 23° C. and 50% RH. When reaching the breaking elongation, the maximum stress must be above 2.8N. Thus, film strength capable of preventing problems such as lack of adhesive layer during cutting can be obtained. From the same viewpoint, the above-mentioned maximum stress is preferably 3N or more, particularly preferably 4N or more. On the other hand, although the upper limit of the maximum stress is not particularly limited, it is preferably 7N or less, particularly preferably 6N or less, from the viewpoint of not deteriorating the step tracking rate. In addition, the specific method of this tensile test is shown in the test example mentioned later. This maximum stress can be achieved by making the adhesive composition P contain a predetermined amount of the active energy ray-curable component (B).

In the adhesive according to the present embodiment, it is presumed that the adhesive composition P containing the active energy ray-curable component (B) in the above-mentioned amount is thermally crosslinked and cured by active energy rays, thereby forming In the three-dimensional network structure formed by the ester polymer (A) and the crosslinking agent (C), the structure X in which the polymerized active energy ray-curable component (B) is entangled to such an extent that the gelled portion does not substantially change. With this structure X, the adhesive according to this embodiment exhibits excellent stress relaxation properties, and also has excellent step followability. Therefore, when pasting one display component having a level difference on the surface at least on the side to be pasted to another display component, the adhesive according to this embodiment can well follow the level difference, even at a predetermined level. After durable conditions, gaps or bubbles are not easily generated between the step and the adhesive, and the adhesive layer can maintain the state of filling the step (hereinafter, the step followability after the specified durability condition is sometimes referred to as "step followability"). In addition, according to the structure X, the adhesive according to the present embodiment exhibits high film strength, so that, for example, when the adhesive sheet is punched, it is possible to prevent the adhesive from sticking to the blade and causing a part of the adhesive layer to be chipped.

(1) (meth)acrylate polymer (A)

The (meth)acrylate polymer (A) contains a reactive functional group-containing monomer as a monomer unit constituting the polymer. The reactive functional group derived from the reactive functional group-containing monomer reacts with the crosslinking agent (C) to form a crosslinked structure.

The reactive functional group-containing monomer contained in the (meth)acrylate polymer (A) as a monomer unit constituting the polymer preferably includes a monomer having a hydroxyl group in the molecule (hydroxyl-containing monomer), a monomer having a hydroxyl group in the molecule Carboxyl group monomers (carboxyl group-containing monomers), monomers with amino groups in the molecule (amino group-containing monomers), etc. Among these, hydroxyl group-containing monomers and carboxyl group-containing monomers excellent in reactivity with isocyanate crosslinking agents or epoxy crosslinking agents are preferable.

Examples of hydroxyl-containing monomers include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, and 2-hydroxypropyl (meth)acrylate. Hydroxyalkyl (meth)acrylates such as -hydroxybutyl, 3-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and the like. Among them, from the viewpoint of the reactivity of the hydroxyl group in the (meth)acrylate polymer (A) obtained with the crosslinking agent (C) and the copolymerizability with other monomers, 2-hydroxyl (meth)acrylate is preferred. ethyl ester or 4-hydroxybutyl (meth)acrylate. These may be used alone or in combination of two or more.

Examples of carboxyl group-containing monomers include ethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, itaconic acid, and citraconic acid. Among these, acrylic acid is preferable from the viewpoint of the reactivity of the hydroxyl group with the crosslinking agent (C) in the obtained (meth)acrylate polymer (A) and the copolymerizability with other monomers. These may be used alone or in combination of two or more.

As an amino group-containing monomer, aminoethyl (meth)acrylate, n-butylaminoethyl (meth)acrylate, etc. are mentioned, for example. These may be used alone or in combination of two or more.

The (meth)acrylate polymer (A) preferably contains 5 to 30% by mass, particularly preferably 7 to 25% by mass, and more preferably 10 to 20% by mass of a reactive polysaccharide-containing monomer unit constituting the polymer. functional group monomer. When the content of the reactive functional group-containing monomer is 5% by mass or more, crosslinking points can be secured and the above-mentioned structure X can be formed favorably. Moreover, when content of a reactive functional group containing monomer is 30 mass % or less, desired tackiness can be acquired easily.

When the (meth)acrylate polymer (A) contains a hydroxyl group-containing monomer as a reactive functional group-containing monomer constituting the polymer, the content thereof is preferably 10 to 25% by mass, particularly preferably 15 to 20% by mass %. In addition, when the (meth)acrylate polymer (A) contains a carboxyl group-containing monomer as a reactive functional group-containing monomer constituting the polymer, the content thereof is preferably 8 to 25% by mass, particularly preferably 10 to 25% by mass. 15% by mass.

The (meth)acrylate polymer (A) preferably contains an alkyl (meth)acrylate having 1 to 20 carbon atoms in the alkyl group as a monomer unit constituting the polymer. Thereby, the obtained adhesive agent can express favorable adhesiveness. Moreover, the hard monomer mentioned later is removed from this alkyl (meth)acrylate.

Examples of alkyl (meth)acrylates having 1 to 20 carbon atoms in the alkyl group include methyl acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, (methyl) n-butyl acrylate, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, n-(meth)acrylate Decyl ester, n-dodecyl (meth)acrylate, myristyl (meth)acrylate, palmityl (meth)acrylate, stearyl (meth)acrylate, etc. Among them, from the viewpoint of further improving the adhesiveness, (meth)acrylates having an alkyl group having 1 to 8 carbon atoms are preferable, and n-butyl (meth)acrylate and 2-ethyl (meth)acrylate are particularly preferable. hexyl ester. These may be used alone or in combination of two or more.

The (meth)acrylate polymer (A) preferably contains 40 to 95% by mass, particularly preferably 50 to 93% by mass, and more preferably 55 to 90% by mass of an alkyl group as a monomer unit constituting the polymer. Alkyl (meth)acrylate having 1 to 20 carbon atoms.

Here, when the display is subjected to high-temperature and high-humidity conditions, air bubbles may be generated near the level difference, or air may be generated from the plastic plate as a protective panel, resulting in bubbles, floating, peeling, and other problems. In addition to this, the (meth)acrylate polymer (A) preferably contains a hard monomer having a glass transition temperature (Tg) of 70° C. or higher as a homopolymer as a constituent polymer monomer unit. By containing the above-mentioned hard monomer as the monomer unit constituting the (meth)acrylate polymer (A), the cohesive force of the adhesive obtained is improved, and the anti-foaming property in the display body is further improved. In particular, as the monomer unit constituting the (meth)acrylate polymer (A), a monomer having a low glass transition temperature (Tg) of a homopolymer such as 2-ethylhexyl (meth)acrylate ( For example, when a monomer whose Tg is preferably -30° C. or less, particularly preferably -60° C. or less) is used as the main component, the above-mentioned hard monomer is preferably used because the cohesive force tends to decrease. The glass transition temperature (Tg) of the above-mentioned hard monomer as a homopolymer is preferably 75 to 200°C, particularly preferably 80 to 180°C. In addition, when a carboxyl group-containing monomer is used as the reactive functional group-containing monomer in the (meth)acrylate polymer (A), a certain degree of cohesive force can be obtained by the monomer. Therefore, in this case, the above-mentioned hard monomers are not used in most cases.

Examples of the hard monomers include: methyl methacrylate (Tg: 105°C), isobornyl acrylate (Tg: 94°C), isobornyl methacrylate (Tg: 180°C), acrylmorphine Phyline (Tg is 145°C), adamantyl acrylate (Tg is 115°C), adamantyl methacrylate (Tg is 141°C), dimethylacrylamide (Tg is 89°C), acrylamide (Tg is 165°C) ℃), etc. These may be used alone or in combination of two or more.

Among the above-mentioned hard monomers, methyl methacrylate, isobornyl acrylate, and acryloylmorpholine are more preferred from the viewpoint of preventing adverse effects on other properties such as adhesiveness and transparency, and further exerting the performance of the hard monomer. ; From the point of view of further reducing the decrease in step followability, isobornyl acrylate and acryloylmorpholine are particularly preferred.

The (meth)acrylate polymer (A) preferably contains 10 to 45% by mass, particularly preferably 15 to 30% by mass, of the aforementioned hard monomer as a monomer unit constituting the polymer. By containing the said hard monomer in 10 mass % or more, the improvement effect of the anti-foaming property by this monomer unit can be expected. On the other hand, by making the content of the above-mentioned hard monomer 45% by mass or less, the relative shortage of other monomer units in the (meth)acrylate polymer (A) can be prevented, and the obtained The adhesive was excellent in tackiness and step followability.

The (meth)acrylate polymer (A) may contain other monomers as monomer units constituting the polymer as needed. As other monomers, in order not to interfere with the action of the reactive functional group-containing monomer, a monomer having no reactive functional group is preferable. Examples of such other monomers include: alkoxyalkyl (meth)acrylates such as methoxyethyl (meth)acrylate and ethoxyethyl (meth)acrylate; (Meth)acrylates with aliphatic rings such as cyclohexyl acrylate; N,N-dimethylaminoethyl (meth)acrylate, N,N-dimethylaminopropyl (meth)acrylate, etc. have Non-crosslinkable tertiary amino (meth)acrylates; vinyl acetate, styrene, etc. These may be used alone or in combination of two or more.

The polymerization form of the (meth)acrylate polymer (A) may be a random copolymer or a block copolymer.

The weight average molecular weight of a (meth)acrylate polymer (A) becomes like this. Preferably it is 200,000-1 million, Especially preferably, it is 300,000-900,000, More preferably, it is 400,000-700,000. In addition, the weight average molecular weight in this specification is the value converted into standard polystyrene measured by gel permeation chromatography (GPC).

By setting the weight average molecular weight of the (meth)acrylate polymer (A) within the low range as described above, an adhesive agent more excellent in step followability can be obtained. When the weight average molecular weight of a (meth)acrylate polymer (A) exceeds 1 million, step followability may worsen. On the other hand, when the weight average molecular weight of a (meth)acrylate polymer (A) is less than 200,000, the durability of an adhesive agent may worsen.

Moreover, in the adhesive composition P, (meth)acrylate polymer (A) may be used individually by 1 type, and may use it in combination of 2 or more types.

(2) Active energy ray curable component (B)

By making the adhesive composition P contain the difunctional or more active energy ray-curable component (B) in the above-mentioned addition amount, the adhesive obtained by curing the adhesive composition P has excellent step followability, At the same time, it has high film strength.

The active energy ray-curable component (B) is not particularly limited as long as it does not hinder the effects of the present invention and is a component that is cured by irradiation of active energy rays, and may be a monomer, an oligomer, or a polymer, A mixture of them is also possible. Among these, preferably, a polyfunctional acrylate-based monomer having a molecular weight of less than 1,000 excellent in compatibility with (meth)acrylate polymers (A) and the like is used.

Examples of polyfunctional acrylate-based monomers having a molecular weight of less than 1,000 preferably 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 (meth)acrylate, hydroxypivalate neopentyl glycol di(meth)acrylate base) acrylate, dicyclopentyl di(meth)acrylate, caprolactone modified dicyclopentenyl di(meth)acrylate, ethylene oxide modified phosphate di(meth)acrylate, Di(acryloyloxyethyl)isocyanurate, allylated cyclohexyl di(meth)acrylate, ethoxylated bisphenol A diacrylate, 9,9-bis[4-(2 -Difunctional acrylate monomers such as acryloyloxyethoxy)phenyl]fluorene; 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(acryloyloxyethyl)isocyanurate Ester, ε-caprolactone modified tris(2-(meth)acryloyloxyethyl) isocyanurate and other trifunctional acrylate monomers; diglycerol tetra(meth)acrylate, pentaerythritol Four-functional acrylate monomers such as tetra(meth)acrylate; pentafunctional acrylate monomers such as propionic acid-modified dipentaerythritol penta(meth)acrylate; dipentaerythritol hexa(meth)acrylate, Hexafunctional acrylate monomers such as caprolactone-modified dipentaerythritol hexa(meth)acrylate, etc. These may be used alone or in combination of two or more.

As the active energy ray-curable component (B), an active energy ray-curable acrylate oligomer can also be used. The weight average molecular weight of the acrylate oligomer is preferably 50,000 or less. Examples of such acrylate oligomers include: polyester acrylates, epoxy acrylates, urethane acrylates, polyether acrylates, polybutadiene acrylates, silicone acrylates Esters, etc.

The weight average molecular weight of the above-mentioned acrylate oligomer is preferably 50,000 or less, particularly preferably 500 to 50,000, more preferably 3,000 to 40,000. These acrylate oligomers may be used alone or in combination of two or more.

In addition, as the active energy ray-curable component (B), an acrylic polymer adduct (adduct acrylate polymer) having a (meth)acryloyl ((meta)acryloyl) group introduced into the side chain can also be used. ). Such an acrylic polymer adduct can be reacted with a (meth)acryloyl group and a crosslinkable functional group by using a copolymer of (meth)acrylate and a monomer having a crosslinkable functional group in the molecule. The compound of the group reacted with a part of the crosslinkable functional group of the copolymer.

The weight average molecular weight of the above-mentioned acrylate polymer adduct is preferably about 50,000 to 900,000, particularly preferably about 100,000 to 500,000.

The active energy ray-curable component (B) can be used by selecting one of the above-mentioned polyfunctional acrylate monomers, acrylate oligomers, and acrylate polymer adducts, or using a combination of two or more , and other active energy ray-curable components may be used in combination.

The content of the active energy ray-curable component (B) in the adhesive composition P is as described above. Specifically, from the viewpoint of obtaining an appropriate film strength, the content of the active energy ray-curable component (B) is The polymer (A) is preferably at least 0.1 part by mass, particularly preferably at least 0.5 part by mass, further preferably at least 1 part by mass. On the other hand, from the adhesive composition P obtained by removing the active energy ray-curable component (B) from the gel portion (G1) of the adhesive of the present embodiment, thermally crosslinked From the viewpoint that the gel portion (G2) of the adhesive H is substantially the same and excellent step followability is obtained, the content of the active energy ray-curable component (B) is 100 parts by mass of the (meth)acrylate polymer (A), preferably 4 parts by mass or less, more preferably 3 parts by mass or less, particularly preferably 2.5 parts by mass or less, most preferably less than 2.0 parts by mass.

(3) Cross-linking agent (C)

The adhesive composition contains a thermally crosslinkable crosslinking agent (C), and the (meth)acrylate polymer (A) is crosslinked by heating to form a three-dimensional network structure and improve the cohesive force of the obtained adhesive , and impart durability to the adhesive.

As the above-mentioned crosslinking agent (C), it is sufficient as long as it can react with the reactive functional group of the (meth)acrylate polymer (A), for example, isocyanate crosslinking agent, epoxy crosslinking agent Linking agent, amine crosslinking agent, melamine crosslinking agent, aziridine crosslinking agent, hydrazine crosslinking agent, aldehyde crosslinking agent, oxazoline crosslinking agent, metal alkoxide crosslinking agent , metal chelate cross-linking agent, metal salt cross-linking agent, ammonium salt cross-linking agent, etc. Among the above-mentioned crosslinking agents, when the reactive functional group of the (meth)acrylate polymer (A) is a hydroxyl group, it is preferable to use an isocyanate crosslinking agent excellent in reactivity with the hydroxyl group; the (meth)acrylate polymer (A) When the reactive functional group which it has is a carboxyl group, it is preferable to use the epoxy type crosslinking agent excellent in the reactivity with a carboxyl group. Moreover, a crosslinking agent (C) may be used individually by 1 type, and may use it in combination of 2 or more types.

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

Examples of epoxy-based crosslinking agents include 1,3-bis(N,N'-diglycidylaminomethyl)cyclohexane, N,N,N',N'-tetraglycidyl - m-xylylenediamine, ethylene glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylolpropane diglycidyl ether, diglycidyl aniline, diglycidyl amine, etc.

The content of the crosslinking agent (C) in the adhesive composition P is preferably 0.001 to 2 parts by mass, particularly preferably 0.01 to 1 part by mass, based on 100 parts by mass of the (meth)acrylate polymer (A). , and more preferably 0.02 to 0.3 parts by mass. When the content of the crosslinking agent (C) is 0.001 parts by mass or more, the durability improvement effect can be imparted to the obtained adhesive; when the content of the crosslinking agent (C) is 2 parts by mass or less, the degree of crosslinking can be made moderate , the step followability of the obtained adhesive can be well ensured.

(4) Various additives

Various additives commonly used in acrylic adhesives, such as silane coupling agents, photopolymerization initiators, antistatic agents, tackifiers, antioxidants, ultraviolet absorbers, etc., can be added to the adhesive composition P as needed. agent, light stabilizer, softener, filler, refractive index adjuster, etc.

The silane coupling agent is an organosilicon compound having at least one alkoxysilyl group in the molecule, and a silane coupling agent having good compatibility with the (meth)acrylate polymer (A) is preferable. In addition, when the adhesive is used for optical applications, a translucent silane coupling agent is preferable.

Examples of the silane coupling agent include silicon compounds containing polymerizable unsaturated groups such as vinyltrimethoxysilane, vinyltriethoxysilane, and methacryloxypropyltrimethoxysilane; 3-Glycidyl etheroxypropyltrimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane and other silicon compounds with epoxy structure; 3-mercaptopropyltrimethoxy Silane, 3-mercaptopropyltriethoxysilane, 3-mercaptopropyldimethoxymethylsilane and other mercapto-containing silicon compounds; 3-aminopropyltrimethoxysilane, N-(2-aminoethyl )-3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane and other amino-containing silicon compounds; 3-chloropropyltrimethoxysilane ; 3-isocyanatopropyltriethoxysilane; or at least one of these silane coupling agents with methyltriethoxysilane, ethyltriethoxysilane, methyltrimethoxysilane, ethyl A condensate of an alkyl group-containing silicon compound such as trimethoxysilane, etc. These silane coupling agents may be used alone or in combination of two or more.

The amount of the silane coupling agent added is preferably 0.01 to 1.0 parts by mass, particularly preferably 0.05 to 0.5 parts by mass, relative to 100 parts by mass of the (meth)acrylate polymer (A).

Moreover, when using ultraviolet rays as active energy rays of the adhesive composition P, it is preferable that the adhesive composition P further contains a photoinitiator. By containing the photopolymerization initiator as described above, the active energy ray-curable component (B) can be cured efficiently, and also the polymerization curing time and the irradiation amount of active energy rays can be reduced.

As such a photopolymerization initiator, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin n-butyl ether, benzoin isobutyl ether, acetophenone , Dimethylaminoacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2,2-diethoxy-2-phenylacetophenone, 2-hydroxy-2-methyl -1-phenyl-propan-1-one, 1-hydroxycyclohexyl phenyl ketone, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinyl-propan-1- Ketone, 4-(2-hydroxyethoxy)phenyl-2-(hydroxy-2-propyl)ketone, benzophenone, p-phenylbenzophenone, 4,4'-diethylaminobis Benzophenone, dichlorobenzophenone, 2-methylanthraquinone, 2-ethylanthraquinone, 2-tert-butylanthraquinone, 2-aminoanthraquinone, 2-methylthioxanthone, 2-ethylanthraquinone thioxanthone, 2-chlorothioxanthone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, benzyl dimethyl ketal, acetophenone dimethyl ketal , p-dimethylaminobenzoate, oligo[2-hydroxy-2-methyl-1[4-(1-methylvinyl)phenyl]acetone], 2,4,6-trimethyl Benzoyl-diphenyl-phosphine oxide, etc. These photopolymerization initiators may be used alone or in combination of two or more.

The photopolymerization initiator is preferably used in an amount ranging from 2 to 15 parts by mass, particularly preferably from 4 to 12 parts by mass, based on 100 parts by mass of the active energy ray-curable component (B).

(5) Production of adhesive composition

The adhesive composition P can be prepared by producing a (meth)acrylate polymer (A), and then combining the obtained (meth)acrylate polymer (A), an active energy ray-curable component (B), and The crosslinking agent (C) is prepared by mixing and adding additives as necessary.

The (meth)acrylate polymer (A) can be produced by polymerizing a monomer mixture constituting the polymer by a normal radical polymerization method. The polymerization of (meth)acrylate polymer (A) can be performed by the solution polymerization method using a polymerization initiator as needed. Examples of the polymerization solvent include ethyl acetate, n-butyl acetate, isobutyl acetate, toluene, acetone, hexane, methyl ethyl ketone, and the like, and two or more of them may be used in parallel.

As a polymerization initiator, an azo compound, an organic peroxide, etc. are mentioned, and 2 or more types may be used in parallel. Examples of azo compounds include: 2,2'-azobisisobutyronitrile, 2,2'-azobis(2-methylbutyronitrile), 1,1'-azobis(cyclohexane alkane-1-carbonitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(2,4-dimethyl-4-methoxypenta nitrile), dimethyl 2,2'-azobis(2-methylpropionate), 4,4'-azobis(4-cyanovaleric acid), 2,2'-azobis( 2-hydroxymethylpropionitrile), 2,2'-azobis[2-(2-imidazolin-2-yl)propane], etc.

Examples of organic peroxides include: benzoyl peroxide, tert-butyl perbenzoate, cumene hydroperoxide, diisopropyl peroxydicarbonate, di-n-propyl peroxydicarbonate, di( 2-ethoxyethyl)peroxydicarbonate, tert-butyl peroxyneodecanoate, tert-butyl peroxypivalate, (3,5,5-trimethylhexanoyl)peroxide , dipropionyl peroxide, diacetyl peroxide, etc.

Moreover, in the said polymerization process, the weight average molecular weight of the polymer obtained can be adjusted by adding a chain transfer agent, such as 2-mercaptoethanol.

If the (meth)acrylate polymer (A) is obtained, by adding the active energy ray-curable component (B), the crosslinking agent (C) to the solution of the (meth)acrylate polymer (A) and required additives, and thoroughly mixed to obtain adhesive composition P.

(6) Manufacture of adhesive

Adhesive composition P according to this embodiment is obtained by applying the above adhesive composition P to a desired object, thermally crosslinking, and curing by irradiation of active energy rays (active energy ray curing). agent.

Thermal crosslinking of the adhesive composition P can be performed by heat treatment. This heat treatment may also be performed simultaneously with the drying treatment after the adhesive composition P is applied. The heating temperature of the heat treatment is preferably 50 to 150°C, particularly preferably 70 to 120°C. In addition, the heating time is preferably 10 seconds to 10 minutes, particularly preferably 50 seconds to 2 minutes.

Here, the active energy ray refers to 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 exemplified. Among active energy rays, ultraviolet rays, which are easy to handle, are particularly preferable.

Irradiation of ultraviolet rays can be performed using a high-pressure mercury lamp, Fusion H lamp, xenon lamp, etc., and the irradiation amount of ultraviolet rays is preferably about 50 to 1000 mW/cm ² . In addition, the amount of light is preferably 50 to 10000 mJ/cm ² , more preferably 80 to 5000 mJ/cm ² , and particularly preferably 200 to 2000 mJ/cm ² . On the other hand, electron beam irradiation can be performed using an electron beam accelerator or the like, and the irradiation amount of electron beam is preferably about 10 to 1000 krad.

When the adhesive composition P is heat-treated, the (meth)acrylate polymer (A) and the crosslinking agent (C) react to form a crosslinked structure, that is, a three-dimensional network structure. Moreover, when the active energy ray is irradiated to the adhesive composition P, the active energy ray curable component (B) polymerizes, and hardens|cures while being entangled in the said three-dimensional network structure. The pressure-sensitive adhesive according to the present embodiment thus obtained has good step followability and exhibits high film strength.

In addition, when producing the adhesive agent of this embodiment, you may perform heat processing and then irradiate an active energy ray, and you may perform these two processes simultaneously. In addition, it is preferable to provide a curing period of about 1 to 2 weeks at normal temperature (for example: 23° C., 50% RH) after heat treatment or after irradiation of active energy rays.

(7) Gelling part

The gel portion (G1) of the adhesive according to the present embodiment is preferably 40 to 80%, particularly preferably 45 to 70%, and even more preferably 50 to 65%. When the gel fraction (G1) is 40% or more, the film strength of the adhesive can be ensured favorably. In addition, if the gel portion (G1) is 80% or less, the step followability of the adhesive can be ensured favorably.

(8) Elongation at break

When the adhesive according to this embodiment is made into an adhesive layer with a thickness of 600 μm and a width of 10 mm, it is preferable that the breaking elongation when stretched at a length of 20 mm and a tensile speed of 200 mm/min in an environment of 23° C. and 50% RH The degree is 1000% or more, particularly preferably 1100 to 4000%, more preferably 1200 to 2500%. In addition, the specific method of this tensile test is shown in the following test example.

The adhesive according to the present embodiment is obtained by thermally crosslinking and active energy ray curing the above-mentioned adhesive composition P so as to achieve the above-mentioned elongation at break. By making the elongation at break larger as described above, the step followability of the adhesive becomes more excellent.

(9) Segment following rate

The pressure-sensitive adhesive according to the present embodiment preferably has a step following rate (%) represented by the following formula of 20% or more, particularly preferably 25 to 80%, and still more preferably 30 to 70%.

Step tracking rate (%) = {(after the specified durability test, the height of the step (μm) that maintains the state of being filled without gaps or air bubbles)/(thickness of the adhesive layer)}×100

In addition, the test method of step following rate is shown in the test example mentioned later.

The adhesive according to the present embodiment can achieve a large step tracking rate as described above by thermal crosslinking and active energy ray curing of the above-mentioned adhesive composition P.

[adhesive sheet]

As shown in FIG. 1 , the adhesive sheet 1 according to this embodiment is composed of two release sheets 12a, 12b, and the two release sheets 12a, 12b are covered by the two release sheets 12a, 12b so as to be in contact with the release surfaces of the two release sheets 12a, 12b. The sandwiched adhesive layer 11 is formed. In addition, the peeling surface of a peeling sheet in this specification means the peelable surface in a peeling sheet, and includes both the peeling-processed surface and the peelable surface which was not peeled.

(1) Adhesive layer

The adhesive layer 11 of the adhesive sheet 1 is formed of the above-mentioned adhesive, that is, an adhesive obtained by thermally crosslinking the adhesive composition P and curing it with active energy rays.

The thickness of the adhesive layer 11 (value measured in accordance with JIS K7130) is preferably 10 to 1000 μm, more preferably 30 to 400 μm, particularly preferably 50 to 300 μm. In addition, the pressure-sensitive adhesive layer 11 may be formed of a single layer or may be formed by laminating a plurality of layers.

When the thickness of the adhesive layer 11 is less than 10 μm, sufficient step followability may not be obtained. On the other hand, when the thickness of the pressure-sensitive adhesive layer 11 is 1000 μm or less, workability is good.

(2) Peeling sheet

As the release sheets 12a, 12b, polyethylene film, polypropylene film, polybutene film, polybutadiene film, polymethylpentene film, polyvinyl chloride film, vinyl chloride copolymer film, poly Ethylene phthalate film, polyethylene naphthalate film, polybutylene terephthalate film, polyurethane film, ethylene vinyl acetate film, ionomer resin film, ethylene-(meth)acrylic acid copolymer film, ethylene-(meth)acrylate copolymer film, polystyrene film, polycarbonate film, polyimide film, fluororesin film, etc. In addition, crosslinked films of the above-mentioned films may also be used. Furthermore, it may be a laminated film of the above-mentioned films.

It is preferable to perform a peeling process on the peeling surface (particularly, the surface which contacts the adhesive layer 11) of the said peeling sheet 12a, 12b. Examples of the release agent used in the release treatment include alkyd-based, silicone-based, fluorine-based, unsaturated polyester-based, polyolefin-based, and wax-based release agents. In addition, among the release sheets 12a and 12b, it is preferable to use one release sheet as a heavy release type release sheet with a large release force, and use the other release sheet as a light release type release sheet with a small release force.

Although the thickness of the release sheets 12a and 12b is not particularly limited, it is generally about 20 to 150 μm.

(3) Manufacture of adhesive sheets

As a production example of the adhesive sheet 1, the coating liquid of the above-mentioned adhesive composition P is coated on the release surface of one release sheet 12a (or 12b), and then the coated layer is heat-treated, and the adhesive composition P is heat-crosslinked and active energy rays are irradiated to cure the adhesive composition P to form the adhesive layer 11 . The peeling surface of the other peeling sheet 12b (or 12a) is superimposed on the adhesive layer 11 formed in this way, and this is made into the adhesive sheet 1. In addition, the above-mentioned irradiation of active energy rays may be performed after thermally crosslinking the coating layer of the adhesive composition P and superimposing the release surface of the other release sheet 12b (or 12a) on the coating layer.

As another production example of the adhesive sheet 1, the coating solution of the above-mentioned adhesive composition P is applied to the release surface of one release sheet 12a, and the applied layer is heat-treated to thermally crosslink the adhesive composition P. Simultaneously, active energy rays are irradiated to cure the adhesive composition P to form a first adhesive layer. In addition, the coating liquid of the above-mentioned adhesive composition P is applied on the release surface of the other release sheet 12b, and the applied layer is heat-treated to thermally crosslink the adhesive composition P and irradiated with active energy rays. , to cure the adhesive composition P to form a second adhesive layer. Next, the release sheet 12a with the first adhesive layer and the release sheet 12b with the second adhesive layer are attached so that both the adhesive layers are in contact with each other, and this is used as the adhesive sheet 1 . In addition, the adhesive sheet 1 may be obtained by bringing the respective coating layers into contact with each other at a stage before thermal crosslinking, and then collectively irradiating active energy rays, instead of separating the first adhesive layer and the second adhesive layer. An adhesive sheet 1 was obtained after formation.

As a method of applying the coating liquid of the above-mentioned adhesive composition P, for example, a bar coating method, a knife coating method, a roll coating method, a plate coating method, a die coating method, a gravure coating method, etc. can be used. . The conditions for the heat treatment of the applied adhesive composition P are as described above.

In the above-mentioned adhesive sheet 1, since the adhesive layer 11 has excellent level followability, after it is pasted on a display member with a level difference, even if it is under a predetermined durability condition, it is not easy to be separated from the level difference and the adhesive layer. There are gaps or air bubbles between 11, and the adhesive layer 11 can fill up the difference. In addition, since the film strength of the adhesive layer 11 is high, for example, when the adhesive sheet 1 is press-worked, it is possible to suppress the occurrence of problems such as a part of the adhesive layer 11 being chipped due to the adhesive adhering to the blade.

(4) Haze value

The haze value (value measured according to JIS K7136:2000) of the adhesive layer 11 according to the present embodiment is preferably 3% or less, particularly preferably 2% or less, further preferably 1% or less. When the haze value is 3% or less, the transparency is very high and it is suitable for use in optical applications.

(5) Adhesion

The adhesive sheet 1 according to the present embodiment is preferably 5 N/25 mm or higher in adhesive force (value measured in accordance with JIS Z0237:2009), more preferably 10 N/25 mm or higher, in order to exhibit good step followability even after durable conditions. Particularly preferably, it is 25N/25mm or more. In addition, from the viewpoint of imparting reworkability to the adhesive sheet 1, the above-mentioned adhesive force is preferably 50 N/25 mm or less, more preferably 40 N/25 mm or less, particularly preferably 35 N/25 mm or less. In addition, the details of the test method of the adhesive force are as described in the test example.

[display body]

As shown in FIG. 2 , the display body 2 according to this embodiment is constituted by including: a first display body component 21 (a display body component component) having a step at least on the surface on the side to be pasted; and a second display body. Member 22 (another display constituent member) and adhesive layer 11 positioned between first display constituent member 21 and second display constituent member 22 for affixing them to each other. In the display body 2 according to the present embodiment, the first display body constituent member 21 has a step on the surface on the side of the adhesive layer 11 , specifically, a step due to the printed layer 3 .

Examples of the display body 2 include a liquid crystal (LCD) display, a light emitting diode (LED) display, an organic electroluminescence (organic EL) display, electronic paper, and the like, and may be a touch panel.

The first display constituting member 21 is preferably a protective plate composed of a laminate including a glass plate or a plastic plate, or the like. In such a case, generally, the printed layer 3 is formed in a frame shape on the adhesive layer 11 side of the first display component 21 .

The second display component 22 is preferably a display module (for example: liquid crystal (LCD) module, light emitting diode (LED) module, organic electroluminescence (organic EL) module, etc.), or a part thereof (for example: polarizer, etc. optical components).

The above-mentioned 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, and barium borosilicate glass. acid glass etc. Although the thickness of the glass plate is not particularly limited, it is generally 0.1 to 5 mm, preferably 0.2 to 2 mm.

Although it does not specifically limit as said plastic board, An acrylic board, a polycarbonate board, etc. are mentioned. The thickness of the plastic plate is not particularly limited, but is generally 0.2 to 5 mm, preferably 0.4 to 3 mm.

In addition, various functional layers (transparent conductive film, metal layer, silicon dioxide layer, hard coat layer, anti-glare layer, etc.) can be provided on one or both sides of the glass plate or plastic plate, and optical components can also be laminated. . In addition, the transparent conductive film and the metal layer can also be patterned.

Examples of the above-mentioned optical member include: polarizing plate (polarizing film), polarizing plate, retardation plate (retardation film), viewing angle compensation film, brightness enhancement film, contrast enhancement film, liquid crystal polymer film, diffusion film, hard coat layer film, semi-transmissive reflective film, etc.

The material constituting the printing layer 3 is not particularly limited, and known materials for printing can be used. The thickness of the printing layer 3 , that is, the height of the step is preferably 3 to 45 μm, particularly preferably 5 to 35 μm, more preferably 7 to 25 μm, and most preferably 7 to 15 μm.

For manufacturing the above-mentioned display body 2 , as an example, first, the adhesive sheet 1 is cut into a size corresponding to the first display body constituent member 21 and the second display body constituent member 22 . During cutting, the thickness direction of the adhesive sheet 1 may be cut entirely, or the other release sheet 12b of the adhesive sheet 1 may not be cut, but the adhesive layer 11 and one release sheet 12a may be cut in half. At this time, since the film strength of the adhesive layer 11 is high, it is possible to suppress a problem that a part of the adhesive layer 11 is chipped due to the adhesive sticking to the blade.

Next, after one peeling sheet 12a of the adhesive sheet 1 is peeled off, the exposed adhesive layer 11 of the adhesive sheet 1 is attached to the surface of the first display component 21 on which the printed layer 3 exists. Thereafter, the other release sheet 12 b is peeled off from the adhesive layer 11 of the adhesive sheet 1 , and the exposed adhesive layer 11 of the adhesive sheet 1 is bonded to the second display body component 22 .

In the above-mentioned process, when the adhesive layer 11 and the first display body component 21 are pasted, since the step followability of the adhesive layer 11 is good, even after a predetermined durability condition, it is not easy to be formed by the printed layer 3. A gap is generated between the level difference and the adhesive layer 11, and the adhesive layer 11 can fill up the level difference.

The embodiments described above are described for easy understanding of the present invention, and are not described for limiting the present invention. Therefore, each element disclosed in the above-mentioned embodiment also includes all design modifications or equivalents within the technical scope of the present invention.

For example, either one of the release sheets 12a and 12b of the adhesive sheet 1 may be omitted. In addition, the first display constituting member 21 may have steps other than the printed layer 3 or may not have steps. Furthermore, not only the first display constituent member 21 but also the second display constituent member 22 may have a step on the side of the adhesive layer 11 .

Example

Hereinafter, the present invention will be further specifically described by way of examples and the like, but the scope of the present invention is not limited to these examples and the like.

[Example 1]

1. Preparation of (meth)acrylate polymer

Copolymerize 90 parts by mass of n-butyl acrylate and 10 parts by mass of acrylic acid to prepare a (meth)acrylate polymer (A), and measure the molecular weight of the (meth)acrylate polymer (A) by the method described later , The weight average molecular weight (Mw) is 400,000.

2. Preparation of Adhesive Composition

100 parts by mass of the (meth)acrylate polymer (A) obtained in the above step (1) (value in terms of solid content; the same applies below), and tris(propylene) as the active energy ray-curable component (B) Acyloxyethyl) isocyanurate (manufactured by TOAGOSEI CO., LTD., product name "M-315") 0.1 parts by mass, and 1,3-bis( N,N-diglycidylaminomethyl)cyclohexane (manufactured by MITSUBISH GAS CHEMICAL COMPANY, INC., product name "TETRAD-C", solid content concentration: 100% by mass) 0.05 parts by mass, and as silane coupling 0.2 parts by mass of 3-glycidyloxypropyltrimethoxysilane (manufactured by SHIN-ETSU CHEMICAL CO., LTD., product name "KBM-403") was mixed, and then 10 1-Hydroxycyclohexyl phenyl ketone (manufactured by BASF Corporation, product name "IRGACURE184") was added as a photopolymerization initiator at a mass %, diluted with methyl ethyl ketone after sufficient stirring, and an adhesiveness with a solid content concentration of 37 mass % was obtained. Composition coating solution.

Here, the mixing ratio of this adhesive composition is shown in Table 1. In addition, details such as the codes described in Table 1 are as follows.

[(meth)acrylate polymer]

BA: n-butyl acrylate

AA: Acrylic

2EHA: 2-Ethylhexyl Acrylate

MMA: methyl methacrylate

HEA: 2-Hydroxyethyl Acrylate

IBXA: Isobornyl Acrylate

ACMO: Acryloylmorpholine

VAc: vinyl acetate

[Active energy ray curable ingredient]

M-315: Tris(acryloyloxyethyl)isocyanurate (manufactured by TOAGOSEI CO., LTD., product name "M-315")

A-400: polyethylene glycol diacrylate (manufactured by SHIN-NAKAMURA CHEMICAL CO., LTD., product name "A-400", molecular weight of polyethylene glycol: 400)

A-TMM-3: pentaerythritol triacrylate (manufactured by SHIN-NAKAMURA CHEMICAL CO., LTD., product name "A-TMM-3")

A-DPH: dipentaerythritol hexaacrylate (manufactured by SHIN-NAKAMURA CHEMICAL CO., LTD., product name "A-DPH")

[Crosslinking agent]

Epoxy-1: 1,3-bis(N,N'-diglycidylaminomethyl)cyclohexane (manufactured by MITSUBISH GAS CHEMICAL COMPANY, INC., product name "TETRAD-C")

Epoxy-2: N,N,N',N'-tetraglycidyl-m-xylylenediamine (manufactured by MITSUBISH GAS CHEMICAL COMPANY, INC., product name "TETRAD-X")

Isocyanate: trimethylolpropane-modified toluene diisocyanate (manufactured by SOKEN CHEMICAL & ENGINEERING CO., LTD., product name "L-45")

3. Manufacture of adhesive sheet

Peel off one side of the polyethylene terephthalate film with a silane-based release agent to form a heavy-peel release sheet (manufactured by LINTEC CORPORATION, product name "SP-PET752150"), and use a scraper on the peel-off surface A coater coats the obtained coating solution of the adhesive composition. In addition, after the application layer was heat-treated at 100° C. for 2 minutes, ultraviolet rays were irradiated under the following conditions to form a first adhesive layer having a thickness of 25 μm.

[UV irradiation conditions]

Light source: high pressure mercury lamp

·Amount of light: 500mJ/cm ²

·Illuminance: 200mW/cm ²

In addition, the illuminance and light quantity were confirmed with the UV illuminance-light quantity meter "UVPF-36" manufactured by EYE GRAPHICS CO., LTD.

Similarly, one side of the polyethylene terephthalate film was peeled off with a silane-based release agent to form a light-peeling type release sheet (manufactured by LINTEC CORPORATION, product name "SP-PET382120"), and on the release-treated surface The obtained coating solution of the adhesive composition was coated with a knife coater. In addition, the application layer was heat-processed at 100° C. for 2 minutes, and then irradiated with ultraviolet rays in the same manner as above to form a second pressure-sensitive adhesive layer having a thickness of 25 μm.

Next, the heavy release type release sheet with the first adhesive layer obtained above and the light release type release sheet with the second adhesive layer obtained above are placed in such a manner that the two adhesive layers are in contact with each other. Pasting was carried out to prepare an adhesive sheet having a structure of a heavy-release type release sheet/adhesive layer (thickness: 50 μm)/light-release type release sheet. In addition, the thickness of the adhesive layer is a value measured using a constant pressure thickness meter (manufactured by TECLOCK CORPORATION, product name "PG-02") in accordance with JIS K7130.

[Examples 2 to 17, Comparative Examples 1 to 4]

In addition to the proportion of each monomer constituting the (meth)acrylate polymer (A), the weight average molecular weight of the (meth)acrylate polymer (A), the type of active energy ray-curable component (B) and the addition The amount, the type and addition amount of the crosslinking agent (C), and the addition amount of the silane coupling agent were changed as shown in Table 1, and an adhesive sheet was produced in the same manner as in Example 1. In addition, Comparative Examples 1 and 4 were not subjected to ultraviolet irradiation treatment.

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

＜Measurement conditions＞

・GPC measurement device: manufactured by TOSOH CORPORATION, HLC-8020

・GPC column (passed in the following order): manufactured by TOSOH CORPORATION

TSK guard column HXL-H

TSK gel GMHXL (×2)

TSK gel G2000HXL

·Measurement solvent: tetrahydrofuran

·Measurement temperature: 40℃

[Test Example 1] (Measurement of Adhesive Force)

Peel off the easy-release type release sheet from the adhesive sheets obtained in Examples and Comparative Examples, and stick the exposed adhesive layer on a polyethylene terephthalate film (TOYOBO CO., LTD. .Manufacturing, PET A4300, thickness: 100μm) easy-adhesive layer. This laminated body was cut out to a size of 25 mm in width and 100 mm in length, and this was used as a sample. The heavy release type release sheet was peeled off from this sample, and the exposed adhesive layer was stuck to soda lime glass (manufactured by NIPPON SHEET GLASS CO., LTD.).

Then, after standing for 24 hours under normal pressure, 23°C, 50%RH, according to JIS Z0237:2009, use a tensile tester (ORIENTEC CO. ., LTD. manufacture, product name "TENSILON") test adhesion (N/25mm). The results are shown in Table 2.

[Test Example 2] (Measurement of haze value)

Regarding the adhesive layers of the adhesive sheets obtained in Examples and Comparative Examples, a haze meter (manufactured by NIPPON DENSHOKU INDUSTRIES CO., LTD., product name "NDH-2000") was used in accordance with JIS K7361-1:1997. ) to measure the haze value (%). The results are shown in Table 2.

[Test Example 3] (Measurement of Gel Part)

The adhesive sheets obtained in the examples and comparative examples were cut into a size of 80 mm × 80 mm, and the adhesive layer was wrapped in a polyester net (mesh size 200), and placed on a precision balance to measure its mass; By subtracting the mass of the web alone, the mass of the adhesive alone can be calculated. Let the mass at this time be M1.

Then, the above-mentioned adhesive coated in the polyester mesh was soaked in ethyl acetate at room temperature (23° C.) for 24 hours. Then, the adhesive was taken out, and air-dried for 24 hours in an environment with a temperature of 23° C. and a relative humidity of 50%, and further, dried in an oven at 80° C. for 12 hours. After drying, the mass was measured with a precision balance, and the mass of the adhesive alone was calculated by subtracting the mass of the net alone. Let the mass at this time be M2. The gel fraction (G1; %) is represented by (M2/M1)×100. The results are shown in Table 2.

[Test Example 4] (Measurement of Change Rate of Gel Part)

In Examples and Comparative Examples, an adhesive composition was produced in the same manner as above except that the active energy ray-curable component (B) was not added. Using this adhesive composition, an adhesive sheet was produced in the same manner as above except that no ultraviolet irradiation treatment was performed. With regard to the adhesive layer of the obtained adhesive sheet, the gel portion (G2; %) was measured by the same method as in Test Example 3. When this gel portion is referred to as G2 and the gel portion measured in Test Example 3 is referred to as G1, the rate of change (%) of the gel portion represented by the following formula can be calculated. The results are shown in Table 2.

Change rate of gel part (%)={(G1-G2)/G2}×100

[Test Example 5] (tensile test)

The adhesive layer of the adhesive sheet obtained in the Example and the comparative example was laminated|stacked several layers so that the total thickness might be 600 micrometers, and it cut out the sample of width 10mm x length 75mm. The above-mentioned sample was placed in a tensile testing machine (manufactured by ORIENTEC CO., LTD., product name "TENSILON") in such a way that the sample measurement site was 10 mm in width x 20 mm in length (stretching direction), at 23° C., 50% RH Under ambient conditions, the tensile tester was used to extend the sample at a tensile speed of 200 mm/min, and measure the elongation at break (%). In addition, the sample was stretched to the elongation at break, and the maximum stress (N) was measured. The results are shown in Table 2.

[Test Example 6] (Evaluation of Foaming Resistance)

A transparent conductive film made of a polyethylene terephthalate film (manufactured by OIKE & CO., LTD., ITO film, thickness: 125 μm) provided with a transparent conductive film formed of indium tin oxide (ITO) on one side, and a transparent conductive film made of Polycarbonate (PC) sheet (manufactured by MITSUBISHGAS CHEMICAL COMPANY, INC., product name "IUPIRON SHEET MR58", thickness: 1 mm) or acrylic sheet made of polymethyl methacrylate (PMMA) (MITSUBISH GAS CHEMICAL COMPANY, INC. .manufacture, product name "IUPIRON·SHEET MR200", thickness: 1mm), sandwiched the adhesive layer of the adhesive sheet obtained in the Example and the comparative example, and obtained the laminated body.

The obtained laminate was autoclaved at 50° C. and 0.5 MPa for 30 minutes, and then left to stand at normal pressure at 23° C. and 50% RH for 15 hours. Next, it stored for 72 hours under durable conditions of 85 degreeC and 85%RH. Thereafter, the presence or absence of air bubbles, floating, or peeling of the adhesive layer was checked visually, and the anti-foaming property was evaluated according to the following criteria. The results are shown in Table 2.

◎…There are no bubbles, floating and peeling phenomena at all.

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

×...A bubble, floating or peeling with a diameter of more than 0.1 mm was generated.

[Test Example 7] (Evaluation of film strength)

The adhesive layers of the adhesive sheets obtained in Examples and Comparative Examples were laminated several times so that the total thickness became 1 mm, and a cutting device (manufactured by OGINO SEISAKUSHO CO., LTD., product name "SUPER CUTTER PN1-600 ”) to cut the laminated body. The cut surface (length: 100 mm) of the pressure-sensitive adhesive layer after cutting was observed visually, and film strength was evaluated according to the following reference|standard. The results are shown in Table 2.

○: There is no defect in the adhesive layer on the cut surface (high film strength)

×: There is a defect in the adhesive layer on the cut surface (low film strength)

[Test Example 8] (Evaluation of Step Followability)

On the surface of a glass plate (manufactured by NSG PRECISION, product name "CORNING Glass EAGLE XG", length 90 mm x width 50 mm x thickness 0.5 mm), UV curable ink (manufactured by TEIKOKU PRINTING INKS MFG.CO., LTD., product name "POS-911SUMI") is screen-printed in a frame shape (outline: length 90mm x width 50mm, thickness 5mm), and the coating thickness is any one of 5μm, 10μm, 15μm and 20μm. Next, irradiate ultraviolet light (80W/cm ² , 2 metal halide lamps, lamp height 15cm, belt speed 10-15m/min), to cure the above-mentioned ultraviolet curable ink that has been printed, and to produce The height of the step difference: any one of 5 μm, 10 μm, 15 μm and 20 μm) with a step difference glass plate.

Peel off the easy-release type release sheet from the adhesive sheet obtained in Examples and Comparative Examples, and stick the exposed adhesive layer on a polyethylene terephthalate film (TOYOBO CO., LTD. manufactured, product name "PETA4300", thickness: 100 μm). Next, the heavy release type release sheet was peeled off to expose the adhesive layer. Then, using a laminator (manufactured by FUJIPLA INC., product name "LPD3214"), the above-mentioned laminate was laminated on each glass plate with a step so that the adhesive layer covered the entire surface of the frame-shaped printing surface, and this was used as an evaluation with samples.

The obtained evaluation sample was autoclaved at 50° C. and 0.5 MPa for 30 minutes, and then left to stand at normal pressure, 23° C., and 50% RH for 24 hours. Next, it stored for 72 hours under the durable conditions of 85 degreeC and 85%RH (durability test), and evaluated step followability after that. The level followability is judged by whether the adhesive layer completely fills the printing level. If gaps or bubbles are observed at the interface between the printing level and the adhesive layer, it is judged that the printing level cannot be followed. Here, step followability was evaluated as a step follow rate (%) represented by the following formula. The results are shown in Table 2.

Step tracking rate (%) = {(after the durability test, the height of the step without gaps or air bubbles (μm))/(thickness of the adhesive layer: 50 μm)}×100

[Table 1]

[Table 2]

It can be clearly seen from Table 2 that the adhesive layer obtained in the examples has excellent step followability and high film strength.

Industrial Applicability

The pressure-sensitive adhesive sheet of the present invention can be suitably used for, for example, bonding of a display module and a protection plate having a step.

Explanation of reference signs

1...Adhesive sheet; 11...Adhesive layer; 12a, 12b...Release sheet; 2...Display body; 21...1st display body constituent member; 22...2nd display body constituent member; 3...Print layer.

Claims (9)

1. An adhesive sheet comprising an adhesive layer formed of an adhesive and two release sheets, the adhesive layer being sandwiched by the release sheets so as to be in contact with the release surfaces of the two release sheets, It is characterized in that, The adhesive layer is used for adhering a display body component and another display body component that have a level difference at least on the surface of the side to be pasted, The adhesive is obtained by thermally crosslinking and active energy ray curing an adhesive composition containing (methyl) reactive functional group-containing monomer as a monomer unit constituting a polymer. Acrylate polymer A, active energy ray curable component B with a functionality of more than two, and thermally crosslinkable crosslinking agent C; The content of the active energy ray-curable component B in the adhesive composition is such that the gel portion G1 of the adhesive and the active energy ray-curable component B will be removed from the adhesive composition. Substantially the same amount of the gel portion G2 of the adhesive formed by thermally crosslinking the adhesive composition of component B; and, When forming an adhesive layer with a thickness of 600 μm and a width of 10 mm, the maximum stress when extended to the elongation at break is 2.8 N at a measured length of 20 mm and a tensile speed of 200 mm/min in an environment of 23°C and 50% RH above. 2 . The adhesive sheet according to claim 1 , wherein the gel portion G1 is 40-80%. 3 . 3. The adhesive sheet according to claim 1, wherein when forming an adhesive layer having a thickness of 600 μm and a width of 10 mm, the measured length is 20 mm and the tensile speed is The elongation at break when stretched at 200 mm/min is 1000% or more. 4 . The adhesive sheet according to claim 1 , wherein the (meth)acrylate polymer A has a weight average molecular weight of 200,000 to 1 million. 5. The adhesive sheet according to claim 1, wherein the (meth)acrylate polymer A contains 5 to 30% by mass of the reactive functional group-containing monomer unit constituting the polymer. monomer. 6. The adhesive sheet according to claim 1, characterized in that, The reactive functional group of the reactive functional group-containing monomer is carboxyl and/or hydroxyl, The crosslinking agent C is an isocyanate crosslinking agent and/or an epoxy crosslinking agent. 7. The adhesive sheet according to claim 1, wherein the adhesive layer has a thickness of 10-400 μm. 8. A display body having: a display body component having a level difference at least on the surface of the side to be pasted, another display constituting part, and The adhesive layer for adhering the one display constituent member and the other display constituent member to each other is characterized in that, The adhesive layer is the adhesive layer of the adhesive sheet according to any one of claims 1 to 7. 9 . The display body according to claim 8 , wherein the level difference is frame-shaped when viewed from above.

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