KR102476682B1 - Adhesive composition, adhesive and adhesive sheet - Google Patents

Abstract

An object of the present invention is to provide an adhesive composition, an adhesive, and an adhesive sheet excellent in both blister resistance and moist heat whitening resistance.
As a means for solving these problems, a (meth)acrylic acid ester polymer comprising a (meth)acrylic acid alkyl ester, a reactive functional group-containing monomer having a reactive functional group in the molecule, and N-vinylcarboxylic acid amide as a monomer unit constituting the polymer. An adhesive composition containing (A) and a crosslinking agent (B) is provided.

Description

Adhesive composition, adhesive and adhesive sheet {ADHESIVE COMPOSITION, ADHESIVE AND ADHESIVE SHEET}

The present invention relates to an adhesive composition suitable for use in a display body (display), an adhesive, and an adhesive sheet.

Recently, various mobile electronic devices such as smart phones and tablet terminals have displays using display modules having liquid crystal elements, light emitting diodes (LED elements), organic electroluminescence (organic EL) elements, and the like. There are many cases where the display becomes a touch panel.

In the display as described above, usually, a protection panel is provided on the surface side of the display module. BACKGROUND OF THE INVENTION [0002] With the thinning and weight reduction of electronic devices, the protective panels have been changed from conventional glass plates to plastic plates such as acrylic plates and polycarbonate plates.

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

However, if there is such a void, that is, an air layer, there is a problem that the reflection loss of light 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 is large, and the image quality of the display deteriorates. .

Therefore, it is proposed to improve the image quality of the display by filling the gap between the protection panel and the display module with an adhesive layer. For example, Patent Document 1 is a pressure-sensitive adhesive layer filling a gap between a protection panel and a display module, and has a shear storage modulus (G′) of 1.0×10 ⁵ Pa or less at 25° C. and 1 Hz, and A pressure-sensitive adhesive layer having a gel fraction of 40% or more is disclosed.

Japanese Patent Laid-Open No. 2010-97070

However, as in Patent Document 1, when the storage modulus at normal temperature in the pressure-sensitive adhesive layer is lowered, the storage modulus at high temperature is lowered more than necessary, causing problems under durability conditions. For example, when high-temperature, high-humidity conditions are implemented, outgas is generated from the plastic plate serving as a protective panel, and blisters such as bubbles, floating, and peeling occur. Further, in the conventional pressure-sensitive adhesive layer, a problem of whitening of the pressure-sensitive adhesive layer may occur when the pressure-sensitive adhesive layer is returned to normal temperature and normal humidity after being subjected to high-temperature, high-humidity (moist heat) conditions.

The present invention was made in view of the above facts, and an object of the present invention is to provide an adhesive composition, an adhesive, and an adhesive sheet that are excellent in both blister resistance and heat-and-moisture whitening resistance.

In order to achieve the above object, the present invention firstly, as a monomer unit constituting a polymer, (meth) acrylic acid alkyl ester, a reactive functional group-containing monomer having a reactive functional group in the molecule, and N-vinylcarboxylic acid amide (meth) ) An adhesive composition characterized by containing an acrylic acid ester polymer (A) and a crosslinking agent (B) is provided (Invention 1).

In the adhesive composition according to the above invention (Invention 1), N-vinylcarboxylic acid amide is copolymerized in the (meth)acrylic acid ester polymer (A), so that the resulting adhesive has high adhesive strength and high cohesive strength. It turns out to be excellent. In addition, since carboxylic acid amide, which is an excellent hydrophilic group, is present in the pressure-sensitive adhesive, whitening of the pressure-sensitive adhesive is suppressed when the pressure-sensitive adhesive is returned to normal temperature and humidity after being exposed to high temperature and high humidity conditions. Accordingly, the pressure-sensitive adhesive obtained by crosslinking the above-mentioned pressure-sensitive adhesive composition is excellent in both blister resistance and heat-and-moisture whitening resistance.

In the above invention (Invention 1), it is preferable that the (meth)acrylic acid ester polymer (A) does not contain a carboxy group-containing monomer having a carboxyl group in the molecule as a monomer unit constituting the polymer (Invention 2).

In the above inventions (Inventions 1 and 2), the mass ratio between the reactive functional group-containing monomer as a monomer unit constituting the polymer and the N-vinylcarboxylic acid amide in the (meth)acrylic acid ester polymer (A) is It is preferably 95:5 to 50:50 (Invention 3).

In the above inventions (Inventions 1 to 3), the (meth)acrylic acid ester polymer (A) contains 5% by mass or more and 30% by mass or less of the reactive functional group-containing monomer as a monomer unit constituting the polymer. Preferred (Invention 4).

In the above inventions (Inventions 1 to 4), it is preferable that the weight average molecular weight of the (meth)acrylic acid ester polymer (A) is 200,000 or more and 2,000,000 or less (Invention 5).

Second, the present invention provides a pressure-sensitive adhesive obtained by crosslinking the above-mentioned adhesive composition (Invention 1 to 5) (Invention 6).

The pressure-sensitive adhesive according to the above invention (Invention 6) preferably has a gel fraction of 30% or more and 95% or less (Invention 7).

It is preferable that the adhesive according to the above inventions (Inventions 6 and 7) has a permittivity of 6.5 or less at 1.0 MHz (Invention 8).

In the above inventions (Inventions 6 to 8), the 50 μm-thick adhesive layer made of the above-mentioned adhesive is sandwiched between a glass plate and a 1-mm-thick acrylic resin plate, 85 ° C., 85% RH under moist heat conditions of 120 It is preferable that the increase in haze value obtained by subtracting the haze value before the durability test from the haze value when stored for 24 hours at room temperature and normal humidity at 23° C. and 50% RH after carrying out an endurance test for storage for a period of time is less than 5 points (invention 9).

Thirdly, the present invention includes two release sheets and a pressure-sensitive adhesive layer sandwiched between the release sheets so as to come into contact with the release surfaces of the two release sheets, wherein the pressure-sensitive adhesive layer comprises the pressure-sensitive adhesive (Invention 6). to 9) is provided (Invention 10).

Fourth, the present invention is a laminate in which the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet (Invention 10) is sandwiched between a glass plate and a plastic plate, and an endurance test of storing the laminate for 120 hours under a moist heat condition of 85 ° C. and 85% RH was performed. After that, the haze value obtained by subtracting the haze value before the durability test from the haze value when stored at room temperature and normal humidity at 23 ° C. and 50% RH for 24 hours is less than 5 points.

According to the adhesive composition, the adhesive and the adhesive sheet according to the present invention, they are excellent in both blister resistance and heat-and-moisture whitening resistance.

1 is a cross-sectional view of an adhesive sheet according to an embodiment of the present invention.
2 is a cross-sectional view of a display body according to an embodiment of the present invention.

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of this invention is described.

[Adhesive composition]

The adhesive composition according to the present embodiment (hereinafter sometimes referred to as “adhesive composition P”) includes, as monomer units constituting the polymer, a (meth)acrylic acid alkyl ester, a reactive functional group-containing monomer having a reactive functional group in the molecule, and N - A (meth)acrylic acid ester polymer (A) containing vinyl carboxylic acid amide and a crosslinking agent (B) are contained. In addition, in this specification, (meth)acrylic acid means both acrylic acid and methacrylic acid. The same goes for other similar terms. In addition, "polymer" shall also include the concept of "copolymer".

The pressure-sensitive adhesive obtained by crosslinking the pressure-sensitive adhesive composition P according to the present embodiment has high adhesive strength and high cohesive strength due to copolymerization of N-vinylcarboxylic acid amide in the (meth)acrylic acid ester polymer (A). It turns out to be excellent. For example, a display using a pressure-sensitive adhesive layer obtained by crosslinking the pressure-sensitive adhesive composition P according to the present embodiment is placed under high-temperature, high-humidity conditions (eg, 85 ° C., 85% RH), and a display body composed of a plastic plate or the like Even when outgas is generated from the member, generation of blisters such as bubbles, floating, peeling, etc. at the interface between the pressure-sensitive adhesive layer and the member constituting the display body is suppressed.

Also, carboxylic acid amide is an excellent hydrophilic group. If such a hydrophilic group is present in the adhesive, even when the adhesive is placed under high temperature and high humidity conditions, moisture that has penetrated into the adhesive under the high temperature and high humidity conditions is presumed to be easily released from the adhesive when returned to room temperature and normal humidity. As a result, Whitening of the adhesive is suppressed. Accordingly, the pressure-sensitive adhesive obtained by crosslinking the pressure-sensitive adhesive composition P according to the present embodiment is also excellent in heat-and-moisture whitening resistance.

Here, in order to improve the heat-and-moisture whitening resistance of the pressure-sensitive adhesive, as a constituent monomer of the (meth)acrylic acid ester polymer (A), a hydroxyl group-containing monomer having a hydroxyl group in the molecule is used in a large amount exceeding the amount contributing to crosslinking. There is also a way. However, in this case, the high polarity of the component derived from the hydroxyl group-containing monomer increases the dielectric constant of the pressure-sensitive adhesive obtained. On the other hand, since N-vinylcarboxylic acid amide has low polarity, it is possible to suppress the dielectric constant to a low level while improving the heat-and-moisture whitening resistance of the resulting adhesive. Thereby, malfunction of the touch panel caused by the dielectric constant of the adhesive can be effectively suppressed, and the responsiveness of the touch panel can be improved.

1. Each ingredient

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

The (meth)acrylic acid ester polymer (A) in the present embodiment includes, as monomer units constituting the polymer, a (meth)acrylic acid alkyl ester, a reactive functional group-containing monomer having a reactive functional group in the molecule, and N-vinylcarboxylic acid amide. includes

The (meth)acrylic acid ester polymer (A) in the present embodiment can express desirable adhesiveness by containing (meth)acrylic acid alkyl ester as a monomer unit constituting the polymer. The alkyl group may be linear or branched, and may have a cyclic structure.

As the (meth)acrylic acid alkyl ester, from the viewpoint of adhesiveness, a (meth)acrylic acid alkyl ester having 1 to 20 carbon atoms in the alkyl group is preferable. Examples of (meth)acrylic acid alkyl esters having 1 to 20 carbon atoms in the alkyl group include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, and (meth)acrylic acid. n-pentyl, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, n-decyl (meth)acrylate, n-dodecyl (meth)acrylate, pre-(meth)acrylate steel, palmityl (meth)acrylate, stearyl (meth)acrylate, cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, adamantyl (meth)acrylate, and the like. These may be used independently and may be used in combination of 2 or more type.

As the (meth)acrylic acid alkyl ester, among the above, a (meth)acrylic acid alkyl ester having 5 to 20 carbon atoms in the alkyl group is preferable. Thus, (meth)acrylic acid alkyl ester having a large number of carbon atoms has high hydrophobicity and can reduce the dielectric constant of the adhesive obtained. As the (meth)acrylic acid alkyl ester having 5 to 20 carbon atoms in the alkyl group, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, isobornyl (meth)acrylate, and the like are preferable, and particularly have high adhesiveness and hydrophobicity. 2-ethylhexyl (meth)acrylate is preferred.

The (meth)acrylic acid ester polymer (A) preferably contains 40% by mass or more of (meth)acrylic acid alkyl ester as a monomer unit constituting the polymer, more preferably 50% by mass or more, and 55% by mass It is particularly preferable to contain % or more, and it is more preferable to contain 65% by mass or more. When 40 mass % or more of the said (meth)acrylic acid alkyl ester is contained, the (meth)acrylic acid ester polymer (A) can exhibit suitable adhesiveness. Further, the (meth)acrylic acid ester polymer (A) preferably contains 90% by mass or less of (meth)acrylic acid alkyl ester as a monomer unit constituting the polymer, particularly preferably 85% by mass or less, It is more preferable to contain 80 mass % or less. By setting the amount of the alkyl (meth)acrylate to 90% by mass or less, a suitable amount of other monomer components can be introduced into the (meth)acrylic acid ester polymer (A).

Further, when a (meth)acrylic acid alkyl ester having 5 to 20 carbon atoms in an alkyl group is included, (meth)acrylic acid alkyl esters having 5 to 20 carbon atoms in the alkyl group in (meth)acrylic acid alkyl esters having 1 to 20 carbon atoms in the alkyl group As for the content ratio of alkyl acrylate ester, as a lower limit, it is preferable that it is 50 mass % or more, it is especially preferable that it is 70 mass % or more, and it is more preferable that it is 85 mass % or more. Thereby, the dielectric constant of the adhesive obtained can be reduced effectively. On the other hand, the upper limit of the content ratio of the (meth)acrylic acid alkyl ester having 5 to 20 carbon atoms in the alkyl group in the (meth)acrylic acid alkyl ester having 1 to 20 carbon atoms in the alkyl group is not particularly limited, and may be 100 mass%. do.

As the (meth)acrylic acid alkyl ester, a monomer (hard monomer) having a glass transition temperature (Tg) of more than 0°C as a homopolymer and a monomer (soft monomer) having a glass transition temperature (Tg) of 0°C or less as a homopolymer are selected. It is also preferable to use them in combination. This is because the blister resistance can be further improved by improving the cohesive force with the hard monomer while ensuring the adhesiveness and flexibility with the soft monomer. In this case, the mass ratio of the hard monomer to the soft monomer is preferably 5:95 to 40:60, particularly preferably 15:85 to 30:70.

The glass transition temperature (Tg) of the hard monomer as a homopolymer is preferably 40°C or higher, particularly preferably 60°C or higher, and more preferably 80°C or higher. The glass transition temperature (Tg) is preferably 300°C or lower, particularly preferably 200°C or lower, and more preferably 130°C or lower.

Examples of the hard monomer include methyl acrylate (Tg 10° C.), methyl methacrylate (Tg 105° C.), isobornyl acrylate (Tg 94° C.), isobornyl methacrylate (Tg 180° C.), and acrylic acid. Adamantyl (Tg 115°C), adamantyl methacrylate (Tg 141°C), and the like. These may be used independently and may be used in combination of 2 or more type.

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

The glass transition temperature (Tg) of the soft monomer as a homopolymer is preferably -20°C or lower, particularly preferably -40°C or lower, and more preferably -60°C or lower. The glass transition temperature (Tg) is preferably -100°C or higher, particularly preferably -90°C or higher, and more preferably -80°C or higher.

As said soft monomer, the acrylic acid alkylester which has a C2-C12 linear or branched alkyl group is mentioned preferably. Examples thereof include 2-ethylhexyl acrylate (Tg -70°C) and n-butyl acrylate (Tg -54°C), and 2-ethylhexyl acrylate (Tg -70°C) is particularly preferred from the viewpoint of hydrophobicity. do. These may be used independently and may be used in combination of 2 or more type.

Moreover, it is also preferable to make at least a part of the said (meth)acrylic acid alkylester the monomer which has an alicyclic structure as an alkyl group (alicyclic structure containing monomer) as said alkyl (meth)acrylate. Since the alicyclic structure-containing monomer has high hydrophobicity, an improvement in adhesion to a low-polarity adherend can be expected, and the adhesive properties of the resulting pressure-sensitive adhesive can be further improved. This makes the blister resistance more excellent.

The carbocyclic ring of the alicyclic structure in the alicyclic structure-containing monomer may have a saturated structure or may partially have an unsaturated bond. Further, the alicyclic structure may be a monocyclic alicyclic structure or a polycyclic alicyclic structure such as bicyclic or tricyclic. It is preferable that the alicyclic structure is a polycyclic alicyclic structure (polycyclic structure) from the viewpoint of providing an appropriate distance between the obtained (meth)acrylic acid ester polymers (A) and imparting higher stress relaxation properties to the pressure-sensitive adhesive. Do. In consideration of compatibility between the (meth)acrylic acid ester polymer (A) and other components, the polycyclic structure is particularly preferably bicyclic or tetracyclic. In addition, as in the above, from the viewpoint of imparting stress relaxation properties, the number of carbon atoms in the alicyclic structure (refers to all carbon atoms in the portion forming the ring, and refers to the total number of carbon atoms when a plurality of rings exist independently) , preferably 5 or more, and particularly preferably 7 or more. On the other hand, the upper limit of the number of carbon atoms in the alicyclic structure is not particularly limited, but is preferably 15 or less, particularly preferably 10 or less, from the viewpoint of compatibility similar to the above.

Specifically, as the alicyclic structure-containing monomer, cyclohexyl (meth)acrylate, dicyclopentanyl (meth)acrylate, adamantyl (meth)acrylate, isobornyl (meth)acrylate, dicyclophene (meth)acrylate tenyl, dicyclopentenyloxyethyl (meth)acrylate, etc., among others, dicyclopentanyl (meth)acrylate (carbon number of alicyclic structure: 10), adamantyl (meth)acrylate (carbon number of alicyclic structure: 10) or isobornyl (meth)acrylate (carbon number of alicyclic structure: 7) is preferred, and isobornyl (meth)acrylate is particularly preferred. Do. These may be used individually by 1 type, and may be used in combination of 2 or more type.

When the (meth)acrylic acid ester polymer (A) contains an alicyclic structure-containing monomer as a constituent monomer unit, the ratio of the alicyclic structure-containing monomer in the (meth)acrylic acid alkyl ester having 1 to 20 carbon atoms in the alkyl group is It is preferably 1% by mass or more, particularly preferably 5% by mass or more, and more preferably 10% by mass or more. The ratio of the alicyclic structure-containing monomer is preferably 50% by mass or less, particularly preferably 40% by mass or less, and more preferably 30% by mass or less. When the content of the alicyclic structure-containing monomer is within the above range, the blister resistance of the resulting pressure-sensitive adhesive is more excellent, and excellent adhesive strength to transparent conductive films and plastics is sufficiently exhibited.

The (meth)acrylic acid ester polymer (A) in the present embodiment contains a reactive functional group-containing monomer as a monomer unit constituting the polymer. When the adhesive composition P is crosslinked, the reactive functional group derived from the reactive functional group-containing monomer in the (meth)acrylic acid ester polymer (A) reacts with the reactive functional group of the crosslinking agent (B) to form a three-dimensional network structure as a crosslinked structure. As a result, the resulting pressure-sensitive adhesive has high cohesive force and has more excellent blister resistance.

Preferable examples of the reactive functional group-containing monomer include monomers having a hydroxyl group in the molecule (hydroxyl group-containing monomers), monomers having a carboxy group in the molecule (carboxy group-containing monomers), monomers having an amino group in the molecule (amino group-containing monomers), and the like. can Among these, a hydroxyl group-containing monomer that is excellent in reactivity with the crosslinking agent (B) and has little adverse effect on the adherend is particularly preferred.

Examples of the hydroxyl group-containing monomer include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, ( (meth)acrylic acid hydroxyalkyl esters such as 3-hydroxybutyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate; and the like. Among them, from the viewpoint of reactivity with the crosslinking agent (B) and copolymerizability with other monomers, 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate are preferred, and 2-hydroxy (meth)acrylate is preferred. Roxyethyl is particularly preferred. These may be used independently and may be used in combination of 2 or more type.

Examples of the carboxy 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 viewpoint of reactivity with the crosslinking agent (B) and copolymerizability with other monomers. These may be used independently and may be used in combination of 2 or more type.

Examples of the amino group-containing monomer include aminoethyl (meth)acrylate and n-butylaminoethyl (meth)acrylate. These may be used independently and may be used in combination of 2 or more type.

The (meth)acrylic acid ester polymer (A) preferably contains, as a monomer unit constituting the polymer, 5% by mass or more of a reactive functional group-containing monomer, particularly preferably 10% by mass or more, and 15% by mass It is more preferable to contain more than one. Further, the (meth)acrylic acid ester polymer (A) preferably contains, as a monomer unit constituting the polymer, 30% by mass or less of a reactive functional group-containing monomer, more preferably 28% by mass or less, and 25% by mass or less. It is particularly preferable to contain 20% by mass or less, and more preferably 20% by mass or less. When the (meth)acrylic acid ester polymer (A) contains the reactive functional group-containing monomer in the above amount as a monomer unit, a good cross-linked structure is formed in the resulting adhesive, and an adhesive having more excellent blister resistance is obtained. In addition, especially when the content of the hydroxyl group-containing monomer is 30% by mass or less, an increase in the dielectric constant of the pressure-sensitive adhesive obtained is suppressed by the action of N-vinylcarboxylic acid amide.

On the other hand, it is also preferable that the (meth)acrylic acid ester polymer (A) does not contain a carboxyl group-containing monomer as a monomer unit constituting the polymer. Since the carboxy group is an acid component, by not containing the carboxy group-containing monomer, the object to which the adhesive is attached is defective due to acid, for example, a transparent conductive film or metal film such as tin-doped indium oxide (ITO) Even when such substances are present, their defects (corrosion, change in resistance value, etc.) due to acid can be suppressed.

Here, “not containing a carboxy group-containing monomer” means substantially not containing a carboxy group-containing monomer, and in addition to not containing a carboxy group-containing monomer at all, a transparent conductive film or metal wiring by carboxy group It is allowed to contain a carboxyl group-containing monomer to the extent that corrosion does not occur. Specifically, in the (meth)acrylic acid ester polymer (A), as a monomer unit, a carboxyl group-containing monomer is contained in an amount of 0.1% by mass or less, preferably 0.01% by mass or less, and more preferably 0.001% by mass or less. is to allow

The (meth)acrylic acid ester polymer (A) in the present embodiment contains N-vinylcarboxylic acid amide as a monomer unit constituting the polymer. Thereby, while the obtained adhesive is excellent in both blister resistance and heat-and-moisture whitening resistance, its dielectric constant is suppressed low.

As N-vinylcarboxylic acid amide, for example, N-vinylformamide, N-vinylacetamide, N-vinyl-N-methylacetamide, N-vinyl-N-methylformamide, N-vinyl-N-ethyl formamide, N-vinyl-N-ethylacetamide, N-methyl-N-vinylformamide, N-methyl-N-vinylacetamide and the like. Among the above, N-vinylacetamide is preferable from the viewpoints of blister resistance, heat-and-moisture whitening resistance, and dielectric constant. These may be used independently and may be used in combination of 2 or more type.

The (meth)acrylic acid ester polymer (A) preferably contains, as a monomer unit constituting the polymer, 0.5% by mass or more of N-vinylcarboxylic acid amide, particularly preferably 1% by mass or more, and 2% by mass % or more is more preferable. Further, the (meth)acrylic acid ester polymer (A) preferably contains 15% by mass or less of N-vinylcarboxylic acid amide as a monomer unit constituting the polymer, particularly preferably 10% by mass or less, It is more preferable to contain 8 mass % or less. When the (meth)acrylic acid ester polymer (A) contains N-vinylcarboxylic acid amide in the above amount as a monomer unit, the obtained adhesive has better blister resistance and heat-and-moisture whitening resistance, and also has an effective dielectric constant. restrained low.

In the (meth)acrylic acid ester polymer (A), the mass ratio of a reactive functional group-containing monomer as a monomer unit constituting the polymer and N-vinylcarboxylic acid amide is preferably 95:5 to 50:50, and 85: Particularly preferred is 15 to 60:40, more preferably 80:20 to 65:35. When the mass ratio is within the range described above, blister resistance, heat-and-moisture whitening resistance, and permittivity are achieved in a well-balanced manner.

It is also preferable that the (meth)acrylic acid ester polymer (A) contains a monomer having a nitrogen-containing heterocycle in the molecule as a monomer unit constituting the polymer. By presenting a monomer having a nitrogen-containing heterocycle as a structural unit in the polymer, a predetermined polarity is imparted to the pressure-sensitive adhesive, and it can be made excellent in affinity even to an adherend having a certain degree of polarity such as glass.

Examples of the monomer having a nitrogen-containing heterocycle include N-(meth)acryloylmorpholine, N-vinyl-2-pyrrolidone, N-(meth)acryloylpyrrolidone, and N-(meth)acryloyl morpholine. 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, and among them, N-(meth)acryloylmorpholine, which exhibits more excellent adhesive strength, is preferred. , N-acryloylmorpholine is particularly preferred. These may be used individually by 1 type, and may be used in combination of 2 or more type.

The (meth)acrylic acid ester polymer (A) preferably contains 0.5% by mass or more of a monomer having a nitrogen-containing heterocycle as a monomer unit constituting the polymer, particularly preferably 1% by mass or more, and 3 It is more preferable to contain more than mass %. Further, the (meth)acrylic acid ester polymer (A) preferably contains 20% by mass or less of a monomer having a nitrogen-containing heterocycle as a monomer unit constituting the polymer, particularly preferably 15% by mass or less, , It is more preferable to contain 8 mass % or less. When the content of the monomer having a nitrogen-containing heterocycle is within the above range, the resulting pressure-sensitive adhesive can sufficiently exhibit excellent adhesive strength to glass.

The (meth)acrylic acid ester polymer (A) may contain other monomers as a monomer unit constituting the polymer as desired. As another monomer, the monomer which does not contain a reactive functional group is preferable.

As a monomer which does not contain a reactive functional group, (meth)acrylic acid alkoxyalkyl ester, such as methoxyethyl (meth)acrylate and ethoxyethyl (meth)acrylate, vinyl acetate, styrene, etc. are mentioned, for example. These may be used independently and may be used in combination of 2 or more type.

It is preferable that the (meth)acrylic acid ester polymer (A) is a linear polymer. By being a straight-chain polymer, entanglement of the molecular chains is likely to occur, and since an improvement in cohesive force can be expected, an adhesive having more excellent blister resistance can be obtained.

In addition, it is preferable that the (meth)acrylic acid ester polymer (A) is a solution polymerized product obtained by a solution polymerization method. Since it becomes easy to obtain a polymer of high molecular weight by being a solution polymeric material, and improvement of cohesion force can be expected, the adhesive more excellent in blister resistance is obtained.

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

As a lower limit, the weight average molecular weight of the (meth)acrylic acid ester polymer (A) is preferably 200,000 or more, particularly preferably 300,000 or more, and more preferably 400,000 or more. When the lower limit of the weight average molecular weight of the (meth)acrylic acid ester polymer (A) is above the above, the blister resistance of the pressure-sensitive adhesive obtained becomes more excellent.

Moreover, as for the weight average molecular weight of a (meth)acrylic acid ester polymer (A), as an upper limit, it is preferable that it is 2 million or less, it is especially preferable that it is 1.5 million or less, and it is more preferable that it is 1 million or less. When the upper limit of the weight average molecular weight of the (meth)acrylic acid ester polymer (A) is below the above, the adhesive strength of the adhesive obtained and the coatability at the time of production become more excellent. In addition, the weight average molecular weight in this specification is a standard polystyrene conversion value measured by the gel permeation chromatography (GPC) method.

Moreover, in the adhesive composition P, (meth)acrylic acid ester polymer (A) may be used individually by 1 type, and may be used in combination of 2 or more type.

As a lower limit, the content of the (meth)acrylic acid ester polymer (A) in the adhesive composition P according to the present embodiment is preferably 50% by mass or more, particularly preferably 60% by mass or more, and further preferably 70% by mass or more. desirable. When the lower limit of the content of the (meth)acrylic acid ester polymer (A) is the above, the adhesive force of the pressure-sensitive adhesive obtained becomes more favorable. The content of the (meth)acrylic acid ester polymer (A) is, as an upper limit, preferably 99.9% by mass or less, particularly preferably 99.8% by mass or less, and more preferably 99.7% by mass or less. When the upper limit of the content of the (meth)acrylic acid ester polymer (A) is the above, the content of the crosslinking agent (B) is ensured, and therefore the cohesive force of the pressure-sensitive adhesive is improved, resulting in better blister resistance.

(2) crosslinking agent (B)

The crosslinking agent (B) crosslinks the (meth)acrylic acid ester polymer (A) by heating the adhesive composition P to form a three-dimensional network structure. As a result, the cohesive force of the pressure-sensitive adhesive obtained is improved, and the blister resistance becomes excellent.

The crosslinking agent (B) may be one that reacts with the reactive functional group of the (meth)acrylic acid ester polymer (A), and examples thereof include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, amine-based crosslinking agents, melamine-based crosslinking agents, aziridine-based crosslinking agents, A hydrazine type crosslinking agent, an aldehyde type crosslinking agent, an oxazoline type crosslinking agent, a metal alkoxide type crosslinking agent, a metal chelate type crosslinking agent, a metal salt type crosslinking agent, an ammonium salt type crosslinking agent, etc. are mentioned. Among the above, when the reactive functional group of the (meth)acrylic acid ester polymer (A) is a hydroxyl group, it is preferable to use an isocyanate-based crosslinking agent having excellent reactivity with hydroxyl groups, and the (meth)acrylic acid ester polymer (A) has When the reactive functional group is a carboxy group, it is preferable to use an epoxy-based crosslinking agent having excellent reactivity with a carboxy group. Moreover, a crosslinking agent (B) can be used individually by 1 type or in combination of 2 or more types.

The isocyanate-based crosslinking agent contains at least a polyisocyanate compound. Examples of the polyisocyanate compound include aromatic polyisocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate, and xylylene diisocyanate, aliphatic polyisocyanates such as hexamethylene diisocyanate, isophorone diisocyanate, and hydrogenated diphenylmethane diisocyanate. Adducts that are reactants with alicyclic polyisocyanates such as isocyanates, their biurets and isocyanurates, and low molecular weight active hydrogen-containing compounds such as ethylene glycol, propylene glycol, neopentyl glycol, trimethylolpropane and castor oil A sieve etc. are mentioned. Among them, from the viewpoint of reactivity with hydroxyl groups, trimethylolpropane-modified aromatic polyisocyanate, trimethylolpropane-modified tolylene diisocyanate, and trimethylolpropane-modified xylylene diisocyanate are particularly preferred.

Examples of the epoxy-based crosslinking agent 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. are mentioned. Among them, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane is preferable from the viewpoint of reactivity with a carboxy group.

The content of the crosslinking agent (B) in the adhesive composition P is preferably 0.01 part by mass or more, particularly preferably 0.05 part by mass or more, and 0.1 part by mass or more with respect to 100 parts by mass of the (meth)acrylic acid ester polymer (A). it is more preferable The content is preferably 3 parts by mass or less, particularly preferably 2 parts by mass or less, and more preferably 1 part by mass or less. When the content of the crosslinking agent (B) is in the above range, the degree of crosslinking is appropriate, and the blister resistance of the resulting pressure-sensitive adhesive is more excellent.

(3) Various additives

To the adhesive composition P, if desired, various additives commonly used in acrylic adhesives, such as silane coupling agents, ultraviolet absorbers, antistatic agents, tackifiers, antioxidants, light stabilizers, softeners, fillers, refractive index modifiers, etc. are added. can do. In addition, the polymerization solvent and dilution solvent mentioned later shall not be included in the additives constituting the adhesive composition P.

Here, when adhesive composition P contains a silane coupling agent, the adhesive obtained improves adhesiveness with a glass member or a plastic plate. Thereby, the obtained adhesive becomes what is more excellent in blister resistance.

As the silane coupling agent, an organosilicon compound having at least one alkoxysilyl group in the molecule, which has good compatibility with the (meth)acrylic acid ester polymer (A) and has light transmittance is preferable.

Examples of such a silane coupling agent include polymerizable unsaturated group-containing silicon compounds such as vinyltrimethoxysilane, vinyltriethoxysilane, and methacryloxypropyltrimethoxysilane; and 3-glycidoxypropyltrimethoxysilane. , 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, silicon compounds having an epoxy structure, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-mercapto Mercapto group-containing silicon compounds such as propyldimethoxymethylsilane, 3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, N-(2-aminoethyl)- Amino group-containing silicon compounds such as 3-aminopropylmethyldimethoxysilane, 3-chloropropyltrimethoxysilane, 3-isocyanatepropyltriethoxysilane, or at least one of these, methyltriethoxysilane, and ethyltriethoxy and condensates with alkyl group-containing silicon compounds such as silane, methyltrimethoxysilane, and ethyltrimethoxysilane. These may be used individually by 1 type, and may be used in combination of 2 or more type.

When the adhesive composition P contains a silane coupling agent, the content thereof is preferably 0.01 part by mass or more, particularly preferably 0.05 part by mass or more, and 0.1 part by mass with respect to 100 parts by mass of the (meth)acrylic acid ester polymer (A). It is more desirable that it is equal to or greater than negative. The content is preferably 2 parts by mass or less, particularly preferably 1 part by mass or less, and more preferably 0.5 parts by mass or less.

2. Preparation of adhesive composition

The adhesive composition P can be prepared by preparing a (meth)acrylic acid ester polymer (A), mixing the resulting (meth)acrylic acid ester polymer (A) with a crosslinking agent (B), and adding additives as desired. have.

The (meth)acrylic acid ester polymer (A) can be produced by polymerizing a mixture of monomers constituting the polymer by a normal radical polymerization method. Polymerization of the (meth)acrylic acid ester polymer (A) is preferably carried out by a solution polymerization method using a polymerization initiator as desired. As a polymerization solvent, ethyl acetate, n-butyl acetate, isobutyl acetate, toluene, acetone, hexane, methyl ethyl ketone etc. are mentioned, for example, You may use 2 or more types together.

As a polymerization initiator, an azo compound, an organic peroxide, etc. are mentioned, You may use 2 or more types together. Examples of the azo-based compound include 2,2'-azobisisobutyronitrile, 2,2'-azobis(2-methylbutyronitrile), and 1,1'-azobis(cyclohexane 1-carbonitrile). tril), 2,2'-azobis (2,4-dimethylvaleronitrile), 2,2'-azobis (2,4-dimethyl-4-methoxyvaleronitrile), dimethyl 2,2'- Azobis (2-methylpropionate), 4,4'-azobis (4-cyanovaleric acid), 2,2'-azobis (2-hydroxymethylpropionitrile), 2,2'- Azobis[2-(2-imidazolin-2-yl)propane] etc. are mentioned.

Examples of organic peroxides include benzoyl peroxide, t-butyl perbenzoate, cumene hydroperoxide, diisopropyl peroxydicarbonate, di-n-propylperoxydicarbonate, and di(2-ethoxyethyl)peroxydicarbonate. , t-butylperoxyneodecanoate, t-butylperoxypivalate, (3,5,5-trimethylhexanoyl) peroxide, dipropionyl peroxide, diacetyl peroxide and the like.

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

When the (meth)acrylic acid ester polymer (A) is obtained, the crosslinking agent (B) and, if desired, a diluting solvent and additives are added to the solution of the (meth)acrylic acid ester polymer (A), and sufficiently mixed with a solvent. A diluted adhesive composition P (coating solution) is obtained. In addition, in any one of the above components, when a solid component is used, or when precipitation occurs when mixed with other components in an undiluted state, the component alone is dissolved or diluted in a dilution solvent in advance. After that, you may mix with other components.

Examples of the diluting solvent include aliphatic hydrocarbons such as hexane, heptane, and cyclohexane, aromatic hydrocarbons such as toluene and xylene, halogenated hydrocarbons such as methylene chloride and ethylene chloride, methanol, ethanol, propanol, butanol, and 1-methyl Alcohols such as toxy-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, etc. this is used

The concentration/viscosity of the coating solution prepared in this way is not particularly limited as long as it is within a range that can be coated, and can be appropriately selected according to the situation. For example, it is diluted so that the concentration of adhesive composition P may become 10-60 mass %. In addition, in obtaining the coating solution, addition of a diluting solvent is not a necessary condition, and as long as the adhesive composition P has a coatingable viscosity or the like, it is not necessary to add a diluting solvent. In this case, the adhesive composition P is a coating solution in which the polymerization solvent of the (meth)acrylic acid ester polymer (A) is used as a diluting solvent.

〔adhesive〕

The adhesive according to the present embodiment is formed by crosslinking the adhesive composition P. Crosslinking of the adhesive composition P can usually be performed by heat treatment. In addition, this heat treatment can also serve as a drying treatment when volatilizing a diluting solvent or the like from a coating film of the adhesive composition P applied to a desired object.

It is preferable that it is 50-150 degreeC, and, as for the heating temperature of heat treatment, it is especially preferable that it is 70-120 degreeC. Moreover, it is preferable that it is 10 second - 10 minutes, and, as for heating time, it is especially preferable that it is 50 second - 2 minutes.

After the heat treatment, a curing period of about 1 to 2 weeks may be provided at normal temperature (for example, 23°C, 50% RH) as needed. When this curing period is required, the adhesive is formed after the curing period has elapsed, and when the curing period is unnecessary, after completion of the heat treatment.

By the heat treatment (and curing) described above, the (meth)acrylic acid ester polymer (A) is sufficiently crosslinked via the crosslinking agent (B). The adhesive thus obtained is excellent in blister resistance.

The pressure-sensitive adhesive according to the present embodiment preferably has the following physical properties.

(1) Gel fraction

The lower limit of the gel fraction of the pressure-sensitive adhesive according to the present embodiment is preferably 30% or more, more preferably 40% or more, and particularly preferably 50% or more. When the lower limit of the gel fraction of the pressure-sensitive adhesive is the above, the cohesive force of the pressure-sensitive adhesive increases and the blister resistance becomes more excellent. The upper limit of the gel fraction of the pressure-sensitive adhesive according to the present embodiment is preferably 95% or less, particularly preferably 85% or less, and more preferably 80% or less. When the upper limit of the gel fraction of the pressure-sensitive adhesive is the above, the pressure-sensitive adhesive does not become too hard, exhibits good adhesive strength, and has better adhesion to adherends. Here, the method for measuring the gel fraction of the pressure-sensitive adhesive is as shown in the test examples described later.

(2) Permittivity

The upper limit of the dielectric constant at 1.0 MHz of the pressure-sensitive adhesive according to the present embodiment is preferably 6.5 or less, particularly preferably 6.2 or less, and more preferably 5.8 or less. When the upper limit value of the dielectric constant is the above, it can contribute to suppression of malfunction of the touch panel and improvement of responsiveness. If it is the adhesive according to this embodiment obtained using the (meth)acrylic acid ester polymer (A) which has a component derived from N-vinyl carboxylic acid amide, the dielectric constant as low as mentioned above can be achieved.

The lower limit of the dielectric constant at 1.0 MHz of the pressure-sensitive adhesive according to the present embodiment is not particularly limited, but is usually preferably 3.5 or more, particularly preferably 3.8 or more, and more preferably 4.0 or more. In addition, the measuring method of the dielectric constant of an adhesive is as showing the test example mentioned later.

(3) Moisture heat whitening resistance

The moisture-heat whitening resistance of the pressure-sensitive adhesive according to the present embodiment can be quantitatively evaluated by haze value. Specifically, with respect to a laminate in which a pressure-sensitive adhesive layer having a thickness of 50 μm made of the pressure-sensitive adhesive according to the present embodiment is sandwiched between a glass plate and an acrylic resin plate having a thickness of 1 mm, stored for 120 hours under moist heat conditions of 85 ° C. and 85% RH After the durability test, haze value (%) when stored at normal temperature and humidity of 23 ° C. and 50% RH for 24 hours (value measured in accordance with JIS K7136: 2000. Same as below), haze value before durability test ( %) is preferably less than 5 points, particularly preferably less than 3 points, and more preferably less than 1 point. If the increase in haze value is the above, it can be said that the increase in haze value is small even after being placed under moist heat conditions, and whitening of the adhesive is suppressed.

As described above, in the laminate in which the pressure-sensitive adhesive layer is sandwiched between the glass plate and the acrylic resin plate, compared to the laminate in which the adhesive layer is sandwiched between two glass plates, moisture passing through the acrylic resin plate under moist heat conditions is less likely to condense in the laminate. Since it is easy, whitening is likely to occur in the pressure-sensitive adhesive layer. However, according to the pressure-sensitive adhesive according to the present embodiment, excellent heat-and-moisture whitening resistance is exhibited also in the above laminate.

[adhesive sheet]

The PSA sheet according to the present embodiment is a PSA sheet having at least a PSA layer made of the PSA layer described above, and is preferably a PSA sheet obtained by laminating a release sheet on one or both surfaces of the PSA layer.

Fig. 1 shows a specific configuration as an example of the pressure-sensitive adhesive sheet according to the present embodiment.

As shown in FIG. 1 , the pressure-sensitive adhesive sheet 1 according to one embodiment includes two release sheets 12a and 12b and the release surfaces of the two release sheets 12a and 12b so as to be in contact with each other. It is composed of an adhesive layer 11 sandwiched between sheets of release sheets 12a and 12b. In addition, the release surface of the release sheet in this specification refers to the side having release properties in the release sheet, and includes both the side subjected to the release treatment and the side showing release property even without the release treatment.

1. Each member

(1) adhesive layer

The adhesive layer 11 is comprised from the above-mentioned adhesive, ie, it is comprised from the adhesive formed by crosslinking the adhesive composition P.

The thickness of the pressure-sensitive adhesive layer 11 in the pressure-sensitive adhesive sheet 1 according to the present embodiment (value measured based on JIS K7130) is preferably 10 μm or more as a lower limit, more preferably 25 μm or more, and 50 μm or more. It is particularly preferable that it is .mu.m or larger. If the lower limit of the thickness of the pressure-sensitive adhesive layer 11 is the above, it is easy to exhibit desired adhesive force.

The upper limit of the thickness of the pressure-sensitive adhesive layer 11 is preferably 1000 μm or less, more preferably 600 μm or less, particularly preferably 300 μm or less, and still more preferably 150 μm or less. When the upper limit of the thickness of the pressure-sensitive adhesive layer 11 is the above, it becomes a thing more excellent in heat-and-moisture whitening resistance, and it is easy to exhibit excellent blister resistance. In addition, the pressure-sensitive adhesive layer 11 may be formed as a single layer or may be formed by laminating a plurality of layers.

(2) release sheet

The release sheets 12a and 12b protect the pressure-sensitive adhesive layer 11 until the time of use of the pressure-sensitive adhesive sheet 1, and are peeled off when the pressure-sensitive adhesive sheet 1 (pressure-sensitive adhesive layer 11) is used. In the adhesive sheet 1 according to the present embodiment, one or both of the release sheets 12a and 12b are not necessarily required.

Examples of the release sheets 12a and 12b include a polyethylene film, a polypropylene film, a polybutene film, a polybutadiene film, a polymethylpentene film, a polyvinyl chloride film, a vinyl chloride copolymer film, a polyethylene terephthalate film, and polyethylene. Naphthalate film, polybutylene terephthalate film, polyurethane film, ethylene vinyl acetate film, ionomer resin film, ethylene/(meth)acrylic acid copolymer film, ethylene/(meth)acrylic acid ester copolymer film, polystyrene film, poly A carbonate film, a polyimide film, a fluororesin film or the like is used. Moreover, these crosslinked films are also used. Moreover, these laminated|multilayer films may be sufficient.

It is preferable that a peeling treatment is performed on the peeling surfaces (particularly, the surfaces in contact with the pressure-sensitive adhesive layer 11) of the peeling sheets 12a and 12b. Examples of release agents used in the release treatment include alkyd, silicone, fluorine, unsaturated polyester, polyolefin, and wax release agents. Among the release sheets 12a and 12b, it is preferable that one release sheet 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 sheets 12a and 12b is not particularly limited, but is usually about 20 to 150 μm.

2. Physical properties

(1) Haze value

The haze value of the pressure-sensitive adhesive layer 11 of the pressure-sensitive adhesive sheet 1 according to the present embodiment is preferably 5% or less, more preferably 3% or less, particularly preferably 1% or less, and still more preferably 0.5% or less. do. When the haze value of the pressure-sensitive adhesive layer 11 is 5% or less, transparency is very high, and it is suitable as an optical use (for display bodies). In addition, the haze value in this specification is taken as the value measured based on JISK7136:2000.

(2) Transmission color b*

The transmission color b* defined by the CIE1976 L*a*b* color system of the pressure-sensitive adhesive layer 11 of the pressure-sensitive adhesive sheet 1 according to the present embodiment is preferably -2.0 to 2.0, and preferably -1.5 to 1.5. It is particularly preferable, and it is more preferable that it is -1.0 to 1.0. When the transmitted color b* of the pressure-sensitive adhesive layer 11 is within the above range, the pressure-sensitive adhesive layer 11 becomes less colored and is particularly suitable for use in displays. In this embodiment, the (meth)acrylic acid ester polymer (A) can achieve the above-described transmission color b* by containing an appropriate amount of N-vinylcarboxylic acid amide as a monomer unit constituting the polymer. In addition, the measurement method of the transmitted color b* in this specification is as showing in the test example mentioned later.

(3) Adhesion

The lower limit of the adhesive strength of the pressure-sensitive adhesive sheet 1 according to the present embodiment to soda lime glass is preferably 5 N/25 mm or more, particularly preferably 10 N/25 mm or more, and more preferably 15 N/25 mm or more. If the adhesive force of the adhesive sheet 1 is 5 N/25 mm or more, the blister resistance becomes more excellent. The upper limit of the adhesive strength of the pressure-sensitive adhesive sheet 1 according to the present embodiment to soda lime glass is preferably 50 N/25 mm or less, more preferably 45 N/25 mm or less, particularly preferably 40 N/25 mm or less. Do. When the adhesive strength of the adhesive sheet 1 is 50 N/25 mm or less, good reworkability is obtained, and expensive display body constituent members can be reused in the event of bonding errors.

Here, the adhesive force in this specification basically refers to the adhesive force measured by the 180-degree peeling method based on JIS Z0237:2009, but the measurement sample is 25 mm wide and 100 mm long, and the measurement sample is attached to the adherend, pressurized at 0.5 MPa and 50°C for 20 minutes, then allowed to stand for 24 hours under conditions of normal pressure, 23°C and 50% RH, and then the peeling rate is measured at 300 mm/min.

3. Manufacture of adhesive sheet

As an example of production of the PSA sheet 1, the coating solution of the PSA composition P is applied to the release surface of one of the release sheets 12a (or 12b), heat treatment is performed, and the PSA composition P is thermally cross-linked to apply the coating. After forming the layer, the release surface of the other release sheet 12b (or 12a) is superimposed on the application layer. When a curing period is required, a curing period is provided, and when a curing period is unnecessary, the coating layer becomes the pressure-sensitive adhesive layer 11 as it is. In this way, the pressure-sensitive adhesive sheet 1 is obtained. The heat treatment and curing conditions are as described above.

As another production example of the PSA sheet 1, a coating solution of the PSA composition P is applied to the release surface of one release sheet 12a, heat treatment is performed to thermally cross-link the PSA composition, and a coating layer is formed. , the release sheet 12a with a coating layer is obtained. Further, the coating solution of the adhesive composition P is applied to the release surface of the other release sheet 12b, and heat treatment is performed to thermally crosslink the adhesive composition P to form a coating layer, thereby forming a release sheet with a coating layer. (12b) is obtained. And the release sheet 12a with an application layer and the release sheet 12b with an application layer are bonded together so that both application layers may contact each other. When a curing period is required, a curing period is provided, and when a curing period is not required, the above-described laminated coating layer becomes the pressure-sensitive adhesive layer 11 as it is. In this way, the pressure-sensitive adhesive sheet 1 is obtained. According to this manufacturing example, even when the adhesive layer 11 is thick, it becomes possible to manufacture stably.

As a method of applying the coating solution of the adhesive composition P, for example, a bar coating method, a knife coating method, a roll coating method, a blade coating method, a die coating method, a gravure coating method, or the like can be used.

[display body]

As shown in FIG. 2 , the display body 2 according to the present embodiment includes a first display body constituent member 21 (one display body constituent member) and a second display body constituent member 22 (another display body constituent member). body constituent member), and an adhesive layer 11 located between them and bonding the first display body constituent member 21 and the second display body constituent member 22 to each other. In the display body 2 according to the present embodiment, the first display body constituent member 21 may have a level difference such as the printed layer 3 on the surface on the pressure-sensitive adhesive layer 11 side.

The pressure-sensitive adhesive layer 11 of the display body 2 is the pressure-sensitive adhesive layer 11 of the pressure-sensitive adhesive sheet 1 described above.

As the display body 2, a liquid crystal (LCD) display, a light emitting diode (LED) display, an organic electroluminescence (organic EL) display, electronic paper, etc. are mentioned, for example, and a touch panel may be sufficient. Moreover, as the display body 2, the member which comprises one part of them may be sufficient.

It is preferable that the 1st display body component 21 is a protective panel which consists of a glass plate, a plastic plate, etc., as well as a laminate containing them. In this case, it is common that the printed layer 3 is formed on the side of the pressure-sensitive adhesive layer 11 of the first display body constituent member 21 in the shape of a picture frame.

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. can be heard Although the thickness of a glass plate is not specifically limited, Usually, it is 0.1-5 mm, Preferably it is 0.2-2 mm.

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

In addition, various functional layers (transparent conductive film, metal layer, silica layer, hard coat layer, anti-glare 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 second display member 22 includes an optical member to be attached to the first display member 21, a display module (e.g., a liquid crystal (LCD) module, a light emitting diode (LED) module, an organic electro A luminescence (organic EL) module, etc.), an optical member as a part of the display module, or a laminate comprising the display module is preferable.

Examples of the optical member include a scattering prevention film, a polarizing plate (polarizing film), a polarizer, a retardation plate (retardation film), a viewing angle compensation film, a luminance enhancing film, a contrast enhancing film, a liquid crystal polymer film, a diffusion film, and a transflective reflection film. A film, a transparent conductive film, etc. are mentioned. Examples of the anti-scattering film include a hard coat film formed by forming a hard coat layer on one side of a base film.

The material constituting the print layer 3 is not particularly limited, and a known material for printing is used. The thickness of the printed layer 3, that is, the lower limit of the step height is preferably 3 μm or more, more preferably 5 μm or more, particularly preferably 7 μm or more, and most preferably 10 μm or more. When the lower limit is equal to or greater than the above, the concealment property such as making the electric wiring invisible from the viewer side can be sufficiently secured. The upper limit is preferably 50 μm or less, more preferably 35 μm or less, particularly preferably 25 μm or less, and still more preferably 20 μm or less. When the upper limit is equal to or less than the above, deterioration in step conformability of the pressure-sensitive adhesive layer 11 to the printed layer 3 can be prevented.

In order to manufacture the display body 2, as an example, one release sheet 12a of the adhesive sheet 1 is peeled off, and the exposed adhesive layer 11 of the adhesive sheet 1 is removed as a first display body. It is bonded to the surface of the component member 21 on the side where the printed layer 3 exists.

Thereafter, the other release sheet 12b is peeled off from the pressure-sensitive adhesive layer 11 of the pressure-sensitive adhesive sheet 1, and the exposed pressure-sensitive adhesive layer 11 of the pressure-sensitive adhesive sheet 1 and the second display body constituent member 22 are separated. combine As another example, the bonding order of the first display body constituent member 21 and the second display body constituent member 22 may be changed.

In the above display body 2, it is placed under, for example, high temperature and high humidity conditions (eg, 85° C., 85% RH), and the first display body constituent member 21 and/or the second display body constituent member Even if outgas is generated from (22), since the pressure-sensitive adhesive layer 11 has excellent blister resistance, the pressure-sensitive adhesive layer 11 and the first display member constituent member 21 and/or the second display member constituent member ( 22), the occurrence of blisters such as bubbles, floating, peeling, etc. is suppressed.

In addition, since the pressure-sensitive adhesive layer 11 is excellent in heat-and-moisture whitening resistance, after the display body 2 is placed under, for example, high-temperature, high-humidity conditions (eg, 85° C., 85% RH), room temperature and normal humidity Even when it is returned to , whitening of the pressure-sensitive adhesive layer 11 is suppressed. According to the display body 2 according to the present embodiment, in particular, even if one of the first display body constituent member 21 and the second display body constituent member 22 is a plastic plate having a thickness of 1 mm or more and the other is a glass plate. , excellent moisture-heat whitening resistance is exhibited.

In addition, since the dielectric constant of the pressure-sensitive adhesive layer 11 is suppressed low, even when the display body 2 is a touch panel, malfunction of the touch panel due to the dielectric constant of the pressure-sensitive adhesive layer 11 is effectively suppressed. , the responsiveness of the touch panel is good.

The embodiments described above are described for facilitating understanding of the present invention, and are not described for limiting the present invention. Therefore, each element disclosed in the above embodiment is intended to include all design changes and equivalents belonging to the technical scope of the present invention.

For example, one or both of the release sheets 12a and 12b in the adhesive sheet 1 may be omitted, and a desired optical member may be laminated instead of the release sheets 12a and/or 12b. In addition, the first display body constituent member 21 may not have a level difference.

(Example)

Hereinafter, the present invention will be described more specifically by 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)acrylic acid ester polymer (A)

60 parts by mass of 2-ethylhexyl acrylate, 5 parts by mass of 4-acryloylmorpholine, 15 parts by mass of isobornyl acrylate, 5 parts by mass of N-vinylacetamide, and 15 parts by mass of 2-hydroxyethyl acrylate by solution polymerization method was copolymerized by the above to prepare a (meth)acrylic acid ester polymer (A). When the molecular weight of this (meth)acrylic acid ester polymer (A) was measured by the method mentioned later, the weight average molecular weight (Mw) was 500,000.

2. Preparation of adhesive composition

100 parts by mass of the (meth)acrylic acid ester polymer (A) obtained in the above step 1 (solid content conversion value; as follows), and trimethylolpropane-modified tolylene diisocyanate (manufactured by Toyo Chem, product name "BHS8515") as a crosslinking agent (B) 0.15 Part by mass and 0.30 part by mass of 3-glycidoxypropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., product name "KBM-403") as a silane coupling agent, stirred sufficiently, and diluted with methyl ethyl ketone. , to obtain a coating solution of the adhesive composition.

Here, Table 1 shows each formulation (value in terms of solid content) of the adhesive composition when the (meth)acrylic acid ester polymer (A) is 100 parts by mass (value in terms of solid content). In addition, the details of the abbreviation or the like described in Table 1 are as follows.

[(meth)acrylic acid ester polymer (A)]

2EHA: 2-ethylhexyl acrylate

ACMO: 4-acryloylmorpholine

IBXA: isobornyl acrylate

NVA: N-vinylacetamide

HEA: 2-hydroxyethyl acrylate

MMA: methyl methacrylate

BA: n-butyl acrylate

[Crosslinking agent (B)]

TDI: Trimethylolpropane-modified tolylene diisocyanate (manufactured by Toyo Chem, product name "BHS8515")

Epoxy system: 1,3-bis(N,N'-diglycidylaminomethyl)cyclohexane (manufactured by Mitsubishi Gas Chemical Co., Ltd., product name "TETRAD-C")

3. Manufacture of adhesive sheet

The coating solution of the adhesive composition obtained in the above step 2 is applied with a knife coater to the release-treated surface of a heavy-release type release sheet (manufactured by Lintex, product name "SP-PET752150") in which one side of the polyethylene terephthalate film has been subjected to release treatment with a silicone-based release agent. did. Then, the coated layer was subjected to heat treatment at 90°C for 1 minute to form a coated layer.

Next, an easy-peelable release sheet (manufactured by Lintex, product name "SP-PET382120") in which the coating layer on the heavy release-type release sheet obtained above and one side of the polyethylene terephthalate film were subjected to release treatment with a silicone-based release agent was prepared. By attaching the peeling treated surface to contact the coating layer and curing for 7 days under conditions of 23 ° C. and 50% RH, the structure of heavy release type release sheet / pressure-sensitive adhesive layer (thickness: 25 μm) / light release type release sheet A first adhesive sheet was produced.

In addition, the coating solution of the adhesive composition obtained in the above step 2 is applied to the release-treated surface of a heavy-release type release sheet (product name "SP-PET752150" manufactured by Lintec Corporation) in which one side of the polyethylene terephthalate film is subjected to release treatment with a silicone-based release agent, and is applied with a knife coater. After applying, a heat treatment was performed at 90° C. for 1 minute to form a coating layer (thickness: 25 μm). Similarly, the coating solution of the adhesive composition obtained in the above step 2 is applied to the release-treated surface of an easy-to-peel type release sheet (product name "SP-PET382120" manufactured by Lintex) in which one side of the polyethylene terephthalate film has been subjected to release treatment with a silicone-based release agent, using a knife coater. After applying, a heat treatment was performed at 90° C. for 1 minute to form a coating layer (thickness: 25 μm).

Next, the heavy release type release sheet with a coating layer obtained above and the light release type release sheet with a coating layer obtained above were bonded together so that both the coating layers were in contact with each other, and maintained at 23° C. and 50% RH for 7 days. By curing, a second PSA sheet composed of a heavy peel type release sheet/a pressure-sensitive adhesive layer (thickness: 50 μm)/light release type release sheet was produced.

In addition, the thickness of the said adhesive layer is a value measured using the static pressure thickness meter (made by Techrox, product name "PG-02") based on JISK7130.

[Examples 2 to 3, Comparative Examples 1 to 4]

Table 1 shows the type and ratio of each monomer constituting the (meth)acrylic acid ester polymer (A), the weight average molecular weight (Mw) of the (meth)acrylic acid ester polymer (A), and the type and compounding amount of the crosslinking agent (B). 1st and 2nd adhesive sheets were manufactured similarly to Example 1 except changing as mentioned above.

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

<Measurement conditions>

・GPC measuring device: 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 gel fraction)

The first PSA sheet (thickness of PSA layer: 25 μm) obtained in Examples and Comparative Examples was cut into a size of 80 mm × 80 mm, and the PSA layer was wrapped with a polyester mesh (mesh size: 200). was weighed with a precision balance, and the mass of the adhesive alone was calculated by subtracting the mass of the mesh alone. Let the mass at this time be M1.

Next, the adhesive wrapped with the polyester mesh was immersed in ethyl acetate at room temperature (23°C) for 24 hours. After that, the adhesive was taken out, air-dried for 24 hours in an environment of a temperature of 23°C and a relative humidity of 50%, and further, it was made to dry 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 mesh alone. Let the mass at this time be M2. The gel fraction (%) is represented by (M2/M1) x 100. The results are shown in Table 2.

[Test Example 2] (measurement of haze value)

For the adhesive layer of the first adhesive sheet (thickness of the adhesive layer: 25 µm) obtained in Examples and Comparative Examples, haze meter (manufactured by Nippon Denshoku Kogyo Co., Ltd., product name "NDH-2000") in accordance with JIS K7136:2000 The haze value (%) was measured using The results are shown in Table 2.

[Test Example 3] (measurement of adhesive force)

The easy-to-peel type release sheet was peeled off from the first PSA sheet (thickness of the PSA layer: 25 μm) obtained in Examples and Comparative Examples, and the exposed PSA layer was made of polyethylene terephthalate (PET) having an easily adhesive layer. It was bonded to the easily bonding layer of a film (manufactured by Toyobo, product name "PET A4300", thickness: 100 µm) to obtain a laminate of release sheet/adhesive layer/PET film. The obtained laminate was cut into 25 mm width and 100 mm length, and this was used as a sample.

In an environment of 23° C. and 50% RH, the heavy release type release sheet was peeled off from the sample, and the exposed pressure-sensitive adhesive layer was adhered to soda lime glass (manufactured by Nippon Itagalas Co., Ltd.), followed by 0.5 It was pressurized for 20 minutes at MPa and 50°C. Then, after leaving it to stand for 24 hours under the conditions of 23 ° C. and 50% RH, using a tensile tester (manufactured by Orientex Co., Ltd., Tensilon), the adhesive force (N / 25 mm) was measured. Conditions other than those described here were measured in accordance with JIS Z0237:2009. The results are shown in Table 2.

[Test Example 4] (Measurement of transmitted color b*)

For the pressure-sensitive adhesive layer of the first pressure-sensitive adhesive sheet (thickness of the pressure-sensitive adhesive layer: 25 μm) obtained in Examples and Comparative Examples, using a simultaneous photometric spectroscopic colorimeter (manufactured by Nippon Denshoku Kogyo Co., Ltd., product name “SQ2000”), CIE1976 L* The transmitted color b* defined by the a*b* colorimetric system was measured. The results are shown in Table 2.

[Test Example 5] (Evaluation of blister resistance)

A polyethylene terephthalate film having a transparent conductive film made of tin-doped indium oxide (ITO) on one side of the pressure-sensitive adhesive layer of the second pressure-sensitive adhesive sheet (thickness of the pressure-sensitive adhesive layer: 50 μm) obtained in Examples and Comparative Examples (manufactured by Oike Kogyo Co., Ltd.) An ITO film, thickness: 125 μm) transparent conductive film and an acrylic resin board made of polymethyl methacrylate (PMMA) (manufactured by Mitsubishi Rayon Co., Ltd., product name “Acrylite MR-200”, thickness: 1 mm) sandwiched, A laminate was obtained.

The obtained laminate (sample) was autoclaved for 30 minutes under conditions of 50°C and 0.5 MPa, and then left at normal pressure, 23°C, and 50% RH for 24 hours. Next, it was stored for 72 hours under high-temperature, high-humidity conditions of 85°C and 85% RH. After that, it was visually confirmed whether or not the pressure-sensitive adhesive layer did not have air bubbles or floating/peeling, and the blister resistance was evaluated according to the following criteria. The results are shown in Table 2.

○: No air bubbles, lifting, or peeling

×: Air bubbles, floating/peeling occurred

[Test Example 6] (Evaluation of damp heat whitening resistance)

The pressure-sensitive adhesive layer of the second pressure-sensitive adhesive sheet (thickness of the pressure-sensitive adhesive layer: 50 μm) obtained in Examples and Comparative Examples was prepared by mixing an alkali-free glass plate with a thickness of 1.1 mm and an acrylic resin plate with a thickness of 1 mm (manufactured by Mitsubishi Rayon Co., Ltd., product name “Acry”). light MR-200”) to obtain a laminate.

The obtained laminate (sample) was autoclaved for 30 minutes under conditions of 50°C and 0.5 MPa, and then left at normal pressure, 23°C, and 50% RH for 24 hours. About this laminated body, haze value (%) was measured based on JISK7136:2000 using the haze meter (made by Nippon Denshoku Kogyo Co., Ltd., product name "NDH2000").

Next, the laminate was stored for 120 hours under moist heat conditions of 85°C and 85% RH. Then, it was left to stand at 23 degreeC and 50% RH normal temperature and normal humidity for 24 hours. About the said laminated body, haze value (%) was measured based on JISK7136:2000 using the haze meter (made by Nippon Denshoku Kogyo Co., Ltd., product name "NDH2000").

Based on the above result, the haze value before wet heat conditions was subtracted from the haze value after wet heat conditions, and the haze value increase (point) after wet heat conditions was calculated. Based on the result, heat-and-moisture whitening resistance was evaluated according to the following criteria. The results are shown in Table 2.

◎: haze value increase is less than 1.0 point

○: Haze value increase is 1.0 points or more and less than 5.0 points

×: Haze value increase is 5.0 points or more

[Test Example 7] (Calculation of permittivity)

On one side of a polyethylene terephthalate film having a thickness of 50 μm, a pressure-sensitive adhesive layer having a thickness of 100 μm was formed in the same manner as in Examples and Comparative Examples, and a polyethylene terephthalate film having a thickness of 50 μm was bonded to the pressure-sensitive adhesive layer. It was cut into x 50 mm. About the obtained laminated body, the capacitance (C1) was measured using the impedance analyzer ("HP-4194A" by Nippon Hewlett-Packard Co., Ltd.). Further, two polyethylene terephthalate films having a thickness of 50 μm were overlapped and cut into 50 mm x 50 mm, and the capacitance (C2) was similarly measured. And, from the values of C1 and C2, the calculation formula of the series connection capacitor

1/C1=1/C2+1/C3

Based on this, the capacitance (C3) of the pressure-sensitive adhesive was calculated. Based on this capacitance C3, the dielectric constant epsilon _s of the adhesive was computed from the following formula. The results are shown in Table 2.

ε _s = (C3×d)/(ε ₀ × S)

ε _s : permittivity of adhesive

ε ₀ : permittivity of vacuum (8.854×10 ^-12 )

C3: capacitance of adhesive

S: Area of the pressure-sensitive adhesive layer

d: thickness of the adhesive layer

[Table 1]

[Table 2]

As can be seen from Table 2, the PSA sheets obtained in Examples were excellent in both blister resistance and heat-and-moisture whitening resistance, and also exhibited a low dielectric constant.

The adhesive composition, adhesive, and adhesive sheet of the present invention can be suitably used for bonding a protective panel made of, for example, a plastic plate and a desired display body constituent member.

1: adhesive sheet
11: adhesive layer
12a, 12b: release sheet
2: indicator
21: first display body constituent member
22: second display body constituent member
3: printing layer

Claims (10)

As a monomer unit constituting the polymer, (meth)acrylic acid ester polymer containing a (meth)acrylic acid alkyl ester having 5 to 20 carbon atoms in an alkyl group, a reactive functional group-containing monomer having a reactive functional group in the molecule, and N-vinylcarboxylic acid amide ( A) and
Crosslinking agent (B)
contains,
The (meth)acrylic acid ester polymer (A) contains 0.5% by mass or more and 15% by mass or less of the N-vinylcarboxylic acid amide as a monomer unit constituting the polymer,
In the (meth)acrylic acid ester polymer (A), the mass ratio of the reactive functional group-containing monomer as a monomer unit constituting the polymer and the N-vinylcarboxylic acid amide is 85:15 to 50:50.
An adhesive composition, characterized in that. According to claim 1,
An adhesive composition characterized in that the (meth)acrylic acid ester polymer (A) does not contain a carboxyl group-containing monomer having a carboxyl group in the molecule as a monomer unit constituting the polymer. delete According to claim 1,
The adhesive composition characterized by the above-mentioned (meth)acrylic acid ester polymer (A) containing 5 mass % or more and 30 mass % or less of the said reactive functional group containing monomer as a monomer unit which comprises the said polymer. According to claim 1,
The weight average molecular weight of the said (meth)acrylic acid ester polymer (A) is 200,000 or more and 2 million or less, The adhesive composition characterized by the above-mentioned. An adhesive formed by crosslinking the adhesive composition according to any one of claims 1, 2, 4 and 5. According to claim 6,
A pressure-sensitive adhesive characterized in that the gel fraction is 30% or more and 95% or less. According to claim 6,
An adhesive characterized by having a dielectric constant of 6.5 or less at 1.0 MHz. According to claim 6,
After carrying out an endurance test of storing for 120 hours under moist heat conditions of 85 ° C. and 85% RH with respect to a laminate in which an adhesive layer having a thickness of 50 μm composed of the above-mentioned adhesive is sandwiched between a glass plate and an acrylic resin plate having a thickness of 1 mm, 23 ° C. , The haze value obtained by subtracting the haze value before the durability test from the haze value when stored at normal temperature and humidity of 50% RH for 24 hours is less than 5 points. two release sheets;
An adhesive layer sandwiched by the release sheet so as to come into contact with the release surfaces of the two release sheets,
The pressure-sensitive adhesive layer is made of the pressure-sensitive adhesive according to claim 6.
An adhesive sheet characterized in that

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