JP2018172537A - Adhesive composition, adhesive and adhesive sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an adhesive composition excellent in both blister resistance and resistance to moisture/heating whitening, an adhesive and an adhesive sheet.SOLUTION: An adhesive composition contains a (meth)acrylate polymer (A) containing a reactive functional group-containing monomer having (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 monomer units constituting a polymer, and a crosslinking agent (B).SELECTED DRAWING: Figure 1

Description

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

  Various mobile electronic devices such as smartphones and tablet terminals in recent years include a display using a display module having a liquid crystal element, a light emitting diode (LED element), an organic electroluminescence (organic EL) element, and the like. It is also becoming more and more a touch panel.

  In the display as described above, a protective panel is usually provided on the surface side of the display module. With the reduction in thickness and weight of electronic devices, the protective panel has been changed from a conventional glass plate to a plastic plate such as an acrylic plate or a polycarbonate plate.

  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 a gap as described above, that is, an air layer, the difference in refractive index between the protective panel and the air layer, and the reflection loss of light due to the difference in refractive index between the air layer and the display module is large. There is a problem that the image quality deteriorates.

Therefore, it has been proposed to improve the image quality of the display by filling the gap between the protective panel and the display module with an adhesive layer. For example, Patent Document 1 discloses that the shear storage modulus (G ′) at 25 ° C. and 1 Hz is 1.0 × 10 ⁵ Pa or less as an adhesive layer that fills the gap between the protective panel and the display module. And the adhesive layer whose gel fraction is 40% or more is disclosed.

JP 2010-97070 A

  However, if the storage elastic modulus at normal temperature in the pressure-sensitive adhesive layer is lowered as in Patent Document 1, the storage elastic modulus at high temperature is unnecessarily lowered, and a problem occurs under durability conditions. For example, when high-temperature and high-humidity conditions are applied, outgas is generated from a plastic plate, which is a protective panel, and blisters such as bubbles, floats, and peeling occur. Further, in the conventional pressure-sensitive adhesive layer, there is a case where the pressure-sensitive adhesive layer is whitened when it is returned to room temperature and normal humidity after being subjected to high temperature and high humidity (wet heat) conditions.

  This invention is made | formed in view of the above actual conditions, and it aims at providing the adhesive composition, adhesive, and adhesive sheet which are excellent in both blister resistance and wet heat whitening resistance.

  In order to achieve the above object, first, the present invention provides (meth) acrylic acid alkyl ester, a reactive functional group-containing monomer having a reactive functional group in the molecule, and N as monomer units constituting the polymer. -A pressure-sensitive adhesive composition comprising a (meth) acrylic acid ester polymer (A) containing a vinyl carboxylic acid amide and a crosslinking agent (B) is provided (Invention 1).

  In the pressure-sensitive adhesive composition according to the above invention (Invention 1), the N-vinylcarboxylic acid amide is copolymerized in the (meth) acrylic acid ester polymer (A), so that the resulting pressure-sensitive adhesive has high adhesion. It has a high strength and a high cohesive strength, and has excellent blister resistance. In addition, the presence of carboxylic acid amide, which is an excellent hydrophilic group, in the pressure-sensitive adhesive causes whitening of the pressure-sensitive adhesive when the pressure-sensitive adhesive returns to room temperature and humidity after being placed under high-temperature and high-humidity conditions. Is suppressed. Therefore, the pressure-sensitive adhesive obtained by crosslinking the pressure-sensitive adhesive composition is excellent in both blister resistance and moisture heat whitening resistance.

  In the said invention (invention 1), it is preferable that the said (meth) acrylic acid ester polymer (A) does not contain the carboxy group containing monomer which has a carboxy group in a molecule | numerator as a monomer unit which comprises the said polymer. (Invention 2).

  In the said invention (invention 1 and 2), the said reactive functional group containing monomer and said N-vinylcarboxylic acid as a monomer unit which comprises the said polymer in the said (meth) acrylic acid ester polymer (A) The mass ratio with the amide is preferably 95: 5 to 50:50 (Invention 3).

  In the said invention (invention 1-3), the said (meth) acrylic acid ester polymer (A) is 5 mass% or more and 30 mass% of said reactive functional group containing monomers as a monomer unit which comprises the said polymer. % Or less (Invention 4).

  In the said invention (invention 1-4), it is preferable that the weight average molecular weights of the said (meth) acrylic acid ester polymer (A) are 200,000 or more and 2 million or less (invention 5).

  2ndly this invention provides the adhesive formed by bridge | crosslinking the said adhesive composition (invention 1-5) (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).

  The adhesive according to the above inventions (Inventions 6 and 7) preferably has a dielectric constant at 1.0 MHz of 6.5 or less (Invention 8).

  In the said invention (invention 6-8), about 85 degreeC and 85% RH about the laminated body which pinched | interposed the 50-micrometer-thick adhesive layer which consists of the said adhesive between the glass plate and the acrylic resin board of thickness 1mm. Increased haze value by subtracting the haze value before the endurance test from the haze value when stored at room temperature and normal humidity of 23 ° C. and 50% RH after performing the endurance test stored for 120 hours under wet heat conditions Is preferably less than 5 points (Invention 9).

  Thirdly, the present invention includes two release sheets and an adhesive layer sandwiched between the release sheets so as to be in contact with the release surfaces of the two release sheets, and the adhesive layer is the adhesive. A pressure-sensitive adhesive sheet comprising (Inventions 6 to 9) is provided (Invention 10).

  4thly this invention is a laminated body which pinched | interposed the adhesive layer of the said adhesive sheet (invention 10) with the glass plate and the plastic board, Comprising: Under the wet heat conditions of 85 degreeC and 85% RH about the said laminated body Less than 5 points after the endurance test for 120 hours storage, the haze value obtained by subtracting the haze value before the endurance test from the haze value when stored at room temperature and normal humidity of 23 ° C. and 50% RH for 24 hours A laminate is provided.

  The pressure-sensitive adhesive composition, pressure-sensitive adhesive, and pressure-sensitive adhesive sheet according to the present invention are excellent in both blister resistance and moist heat whitening resistance.

It is sectional drawing of the adhesive sheet which concerns on one Embodiment of this invention. It is sectional drawing of the display body which concerns on one Embodiment of this invention.

Hereinafter, embodiments of the present invention will be described.
[Adhesive composition]
The pressure-sensitive adhesive composition according to this embodiment (hereinafter sometimes referred to as “pressure-sensitive adhesive composition P”) is a (meth) acrylic acid alkyl ester as a monomer unit constituting the polymer, and a reactive functional group in the molecule. A (meth) acrylic acid ester polymer (A) containing a reactive functional group-containing monomer having N, a N-vinylcarboxylic acid amide, and a crosslinking agent (B). In the present specification, (meth) acrylic acid means both acrylic acid and methacrylic acid. The same applies to other similar terms. Further, the “polymer” includes the concept of “copolymer”.

  The pressure-sensitive adhesive obtained by cross-linking the pressure-sensitive adhesive composition P according to the present embodiment has a high adhesive strength because the N-vinylcarboxylic acid amide is copolymerized in the (meth) acrylic acid ester polymer (A). In addition, it has a high cohesive force and has excellent blister resistance. For example, a display using a pressure-sensitive adhesive layer obtained by crosslinking the pressure-sensitive adhesive composition P according to this embodiment is placed under a high temperature and high humidity condition (for example, 85 ° C., 85% RH) and is made of a plastic plate or the like. Even when outgas is generated from the display member constituting member, the occurrence of blisters such as bubbles, floating and peeling at the interface between the pressure-sensitive adhesive layer and the display member constituting member is suppressed.

  Carboxylic acid amides are excellent hydrophilic groups. When such a hydrophilic group is present in the pressure-sensitive adhesive, even when the pressure-sensitive adhesive is placed under high-temperature and high-humidity conditions, the water that has entered the pressure-sensitive adhesive under the high-temperature and high-humidity conditions returns to normal temperature and humidity. It is presumed that sometimes it is easily removed from the adhesive, and as a result, whitening of the adhesive is suppressed. Therefore, the pressure-sensitive adhesive obtained by crosslinking the pressure-sensitive adhesive composition P according to this embodiment is also excellent in moisture and heat whitening resistance.

  Here, in order to improve the moisture and heat 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 exceeds the amount that contributes to crosslinking. There is also a method of using a large amount. However, in this case, the dielectric constant of the obtained adhesive increases due to the high polarity of the hydroxyl group-containing monomer-derived component. On the other hand, since N-vinylcarboxylic acid amide has low polarity, the dielectric constant can be kept low while improving the wet heat whitening resistance of the resulting adhesive. Thereby, the malfunction of the touch panel resulting from the dielectric constant of an adhesive can be suppressed effectively, and the responsiveness of a touch panel can be improved.

1. Each component (1) (meth) acrylic acid ester polymer (A)
The (meth) acrylic acid ester polymer (A) in this embodiment is a (meth) acrylic acid alkyl ester as a monomer unit constituting the polymer, a reactive functional group-containing monomer having a reactive functional group in the molecule. And N-vinylcarboxylic amide.

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

  The (meth) acrylic acid alkyl ester is preferably a (meth) acrylic acid alkyl ester having 1 to 20 carbon atoms in the alkyl group from the viewpoint of adhesiveness. Examples of the (meth) acrylic acid alkyl ester having 1 to 20 carbon atoms in the alkyl group include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, and (meth) acrylic acid n-. Butyl, n-pentyl (meth) acrylate, n-hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, n-decyl (meth) acrylate, (meth) acrylic acid Examples include n-dodecyl, myristyl (meth) acrylate, palmityl (meth) acrylate, stearyl (meth) acrylate, cyclohexyl (meth) acrylate, isobornyl (meth) acrylate, adamantyl (meth) acrylate, and the like. These may be used alone or in combination of two or more.

  Among these, the (meth) acrylic acid alkyl ester is preferably a (meth) acrylic acid alkyl ester having 5 to 20 carbon atoms in the alkyl group. Thus, the (meth) acrylic acid alkyl ester having a large number of carbon atoms has high hydrophobicity, and can reduce the dielectric constant of the resulting pressure-sensitive adhesive. 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 particularly preferable. 2-ethylhexyl (meth) acrylate with high hydrophobicity is preferred.

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

  In addition, when a (meth) acrylic acid alkyl ester having 5 to 20 carbon atoms in the alkyl group is included, the carbon number of the alkyl group in the (meth) acrylic acid alkyl ester having 1 to 20 carbon atoms in the alkyl group The content ratio of the (meth) acrylic acid alkyl ester of 5 to 20 is preferably 50% by mass or more, particularly preferably 70% by mass or more, and more preferably 85% by mass or more as a lower limit. It is preferable. Thereby, the dielectric constant of the obtained adhesive can be reduced effectively. On the other hand, in the (meth) acrylic acid alkyl ester having 1 to 20 carbon atoms in the alkyl group, the upper limit value of the content ratio of the (meth) acrylic acid alkyl ester having 5 to 20 carbon atoms in the alkyl group is particularly limited. It may be 100% by mass.

  As the above (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 having a glass transition temperature (Tg) of 0 ° C. or less as a homopolymer (soft) It is also preferred to use in combination with a monomer. 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, and particularly preferably 15:85 to 30:70.

  The glass transition temperature (Tg) as a homopolymer of the hard monomer 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 less, particularly preferably 200 ° C. or less, and more preferably 130 ° C. or less.

  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.), adamantyl acrylate (Tg 115 ° C.), and methacrylic acid. And adamantyl (Tg 141 ° C.). These may be used alone or in combination of two or more.

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

  The glass transition temperature (Tg) as a homopolymer of the soft monomer is preferably −20 ° C. or lower, particularly preferably −40 ° C. or lower, and further 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.

  Preferable examples of the soft monomer include acrylic acid alkyl esters having a linear or branched alkyl group having 2 to 12 carbon atoms. Examples thereof include 2-ethylhexyl acrylate (Tg-70 ° C.), n-butyl acrylate (Tg-54 ° C.), and the like, and 2-ethylhexyl acrylate (Tg-70 ° C.) is particularly preferable from the viewpoint of hydrophobicity. These may be used alone or in combination of two or more.

  Moreover, as said (meth) acrylic-acid alkylester, it is also preferable to use at least one part of the said (meth) acrylic-acid alkylester as the monomer (alicyclic structure containing monomer) which has an alicyclic structure as an alkyl group. Since the alicyclic structure-containing monomer has high hydrophobicity, it can be expected to improve the adhesion to the low-polar adherend, and the adhesive of the resulting pressure-sensitive adhesive can be made more excellent. Thereby, the blister resistance becomes more excellent.

  The carbocyclic ring of the alicyclic structure in the alicyclic structure-containing monomer may have a saturated structure or may have an unsaturated bond in part. The alicyclic structure may be a monocyclic alicyclic structure or a polycyclic alicyclic structure such as a bicyclic ring or a tricyclic ring. From the viewpoint of making the distance between the obtained (meth) acrylic acid ester polymer (A) appropriate and imparting high stress relaxation properties to the pressure-sensitive adhesive, the alicyclic structure is a polycyclic alicyclic structure ( A polycyclic structure). Furthermore, considering the compatibility between the (meth) acrylic acid ester polymer (A) and other components, the polycyclic structure is particularly preferably bicyclic to tetracyclic. In addition, from the viewpoint of imparting stress relaxation properties as described above, the carbon number of the alicyclic structure (refers to the total number of carbon atoms of the portion forming the ring, and when multiple rings exist independently) , Which means the total number of carbon atoms) is usually 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 it is preferably 15 or less and particularly preferably 10 or less from the viewpoint of compatibility as described above.

  Specific examples of the alicyclic structure-containing monomer include cyclohexyl (meth) acrylate, dicyclopentanyl (meth) acrylate, adamantyl (meth) acrylate, isobornyl (meth) acrylate, and (meth) acrylic. Dicyclopentenyl acid (meth) acrylate, dicyclopentenyloxyethyl (meth) acrylate, and the like. Among them, dicyclopentanyl (meth) acrylate that exhibits better step following ability and blister resistance under wet heat conditions ( Preferred are alicyclic carbon number: 10), adamantyl (meth) acrylate (carbon number of alicyclic structure: 10) or isobornyl (meth) acrylate (carbon number of alicyclic structure: 7), particularly Isobornyl (meth) acrylate is preferred. 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 alicyclic structure in the (meth) acrylic acid alkyl ester having 1 to 20 carbon atoms in the alkyl group. The proportion of the containing monomer is preferably 1% by mass or more, particularly preferably 5% by mass or more, and more preferably 10% by mass or more. Further, the ratio of the alicyclic structure-containing monomer is preferably 50% by mass or less, particularly preferably 40% by mass or less, and further preferably 30% by mass or less. When the content of the alicyclic structure-containing monomer is within the above range, the resulting adhesive is more excellent in blister resistance and sufficiently exhibits excellent adhesive strength to the transparent conductive film and plastic.

  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). Thus, a three-dimensional network structure is formed as a crosslinked structure. As a result, the resulting pressure-sensitive adhesive has high cohesive force and is more excellent in blister resistance.

  Examples of the reactive functional group-containing monomer include a monomer having a hydroxyl group in the molecule (hydroxyl group-containing monomer), a monomer having a carboxy group in the molecule (carboxy group-containing monomer), and a monomer having an amino group in the molecule (amino group). Preferred monomer). 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 preferable.

  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 And (meth) acrylic acid hydroxyalkyl esters such as 3-hydroxybutyl acrylate and 4-hydroxybutyl (meth) acrylate. Of these, 2-hydroxyethyl (meth) acrylate and 4-hydroxybutyl (meth) acrylate are preferred from the viewpoint of reactivity with the crosslinking agent (B) and copolymerizability with other monomers. Meth) acrylic acid 2-hydroxyethyl is preferred. These may be used alone or in combination of two or more.

  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 these, acrylic acid is preferable from the viewpoint of reactivity with the crosslinking agent (B) and copolymerization with other monomers. These may be used alone or in combination of two or more.

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

  The (meth) acrylic acid ester polymer (A) preferably contains 5% by mass or more, more preferably 10% by mass or more of a reactive functional group-containing monomer as a monomer unit constituting the polymer. More preferably, it is preferably contained in an amount of 15% by mass or more. In addition, the (meth) acrylic acid ester polymer (A) preferably contains 30% by mass or less, and 28% by mass or less of a reactive functional group-containing monomer as a monomer unit constituting the polymer. More preferably, it is preferably contained in an amount of 25% by mass or less, more preferably 20% by mass or less. When the (meth) acrylic acid ester polymer (A) contains a reactive functional group-containing monomer in the above amount as a monomer unit, a good cross-linked structure is formed in the resulting pressure-sensitive adhesive, and the pressure-sensitive adhesive is more excellent in blister resistance. Is obtained. In particular, when the content of the hydroxyl group-containing monomer is 30% by mass or less, an increase in the dielectric constant of the obtained pressure-sensitive adhesive 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 carboxy group-containing monomer as a monomer unit constituting the polymer. Since the carboxy group is an acid component, by not containing a carboxy group-containing monomer, there is a problem that causes a defect due to an acid on the adhesive application target, for example, a transparent conductive film such as tin-doped indium oxide (ITO) or a metal film. Even when it exists, those defects (corrosion, resistance value change, etc.) due to the acid can be suppressed.

  Here, “does not contain a carboxy group-containing monomer” means that it contains substantially no carboxy group-containing monomer, and contains no carboxy group-containing monomer at all. It is allowed to contain a carboxy group-containing monomer to such an extent that no corrosion occurs. Specifically, in the (meth) acrylic acid ester polymer (A), as a monomer unit, a carboxy group-containing monomer is 0.1% by mass or less, preferably 0.01% by mass or less, more preferably 0.001. It is allowed to be contained in an amount of mass% or less.

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

  Examples of N-vinylcarboxylic acid amide include N-vinylformamide, N-vinylacetamide, N-vinyl-N-methylacetamide, N-vinyl-N-methylformamide, N-vinyl-N-ethylformamide, N- Vinyl-N-ethylacetamide, N-methyl-N-vinylformamide, N-methyl-N-vinylacetamide and the like can be mentioned. Among these, N-vinylacetamide is preferable from the viewpoints of blister resistance, wet heat whitening resistance, and dielectric constant. These may be used alone or in combination of two or more.

  The (meth) acrylic acid ester polymer (A) preferably contains 0.5% by mass or more, particularly 1% by mass or more, of N-vinylcarboxylic acid amide as a monomer unit constituting the polymer. It is preferable to contain 2% by mass or more. Further, the (meth) acrylic acid ester polymer (A) preferably contains 15% by mass or less, particularly 10% by mass or less, of N-vinylcarboxylic acid amide as a monomer unit constituting the polymer. It is preferable to contain 8% by 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 resulting pressure-sensitive adhesive has further improved blister resistance and moist heat whitening resistance, In addition, the dielectric constant can be effectively reduced.

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

  Moreover, it is also preferable that the said (meth) acrylic acid ester polymer (A) contains the monomer which has a nitrogen-containing heterocyclic ring in a molecule | numerator as a monomer unit which comprises the said polymer. A monomer having a nitrogen-containing heterocycle is present in the polymer as a structural unit, thereby giving a predetermined polarity to the pressure-sensitive adhesive and making it compatible with adherends having a certain degree of polarity such as glass. It can be excellent.

  Examples of the monomer having a nitrogen-containing heterocyclic ring include N- (meth) acryloylmorpholine, N-vinyl-2-pyrrolidone, N- (meth) acryloylpyrrolidone, N- (meth) acryloylpiperidine, N- (meth) acryloyl. Pyrrolidine, N- (meth) acryloylaziridine, aziridinylethyl (meth) acrylate, 2-vinylpyridine, 4-vinylpyridine, 2-vinylpyrazine, 1-vinylimidazole, N-vinylcarbazole, N-vinylphthalimide, etc. Among them, N- (meth) acryloylmorpholine exhibiting more excellent adhesive strength is preferable, and N-acryloylmorpholine is particularly preferable. 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, particularly 1% by mass or more, of a monomer having a nitrogen-containing heterocyclic ring as a monomer unit constituting the polymer. It is preferable to contain 3% by mass or more. Further, the (meth) acrylic acid ester polymer (A) preferably contains 20% by mass or less of a monomer having a nitrogen-containing heterocyclic ring as the monomer unit constituting the polymer, particularly 15% by mass or less. It is preferable to contain 8% by mass or less. When the content of the monomer having a nitrogen-containing heterocyclic ring is within the above range, the obtained pressure-sensitive adhesive can sufficiently exhibit excellent adhesion to glass.

  The (meth) acrylic acid ester polymer (A) may contain other monomers as monomer units constituting the polymer, if desired. The other monomer is preferably a monomer that does not contain a reactive functional group.

  Examples of the monomer that does not include a reactive functional group include (meth) acrylic acid alkoxyalkyl esters such as methoxyethyl (meth) acrylate and ethoxyethyl (meth) acrylate, vinyl acetate, and styrene. These may be used alone or in combination of two or more.

  The (meth) acrylic acid ester polymer (A) is preferably a linear polymer. By being a linear polymer, entanglement of molecular chains is likely to occur, and an improvement in cohesion can be expected, so that a pressure-sensitive adhesive having better blister resistance can be obtained.

  The (meth) acrylic acid ester polymer (A) is preferably a solution polymer obtained by a solution polymerization method. By being a solution polymer, it becomes easy to obtain a high molecular weight polymer, and an improvement in cohesive force can be expected. Therefore, an adhesive having better blister resistance can be obtained.

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

  The weight average molecular weight of the (meth) acrylic acid ester polymer (A) is preferably 200,000 or more as a lower limit, 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 not less than the above, the resulting adhesive has more excellent blister resistance.

  The weight average molecular weight of the (meth) acrylic acid ester polymer (A) is preferably 2 million or less as an upper limit, particularly preferably 1.5 million or less, and more preferably 1 million or less. preferable. When the upper limit value of the weight average molecular weight of the (meth) acrylic acid ester polymer (A) is not more than the above, the adhesive strength of the resulting pressure-sensitive adhesive and the coatability during production become more excellent. In addition, the weight average molecular weight in this specification is the value of standard polystyrene conversion measured by the gel permeation chromatography (GPC) method.

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

  The content of the (meth) acrylic acid ester polymer (A) in the pressure-sensitive adhesive composition P according to this embodiment is preferably 50% by mass or more, particularly 60% by mass or more, as the lower limit. It is preferable that it is 70 mass% or more. When the lower limit value of the content of the (meth) acrylic acid ester polymer (A) is as described above, the adhesive force of the obtained adhesive becomes better. In addition, the content of the (meth) acrylic acid ester polymer (A) is preferably 99.9% by mass or less, particularly preferably 99.8% by mass or less as an upper limit, and further 99 It is preferable that it is 7 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, thereby improving the cohesive force of the pressure-sensitive adhesive and improving the blister resistance. It will be better.

(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. Thereby, the cohesive force of the obtained adhesive improves and the blister resistance is excellent.

  As said crosslinking agent (B), what is necessary is just to react with the reactive functional group which (meth) acrylic acid ester polymer (A) has, for example, isocyanate type crosslinking agent, epoxy type crosslinking agent, amine type crosslinking Agent, melamine-based crosslinking agent, aziridine-based crosslinking agent, hydrazine-based crosslinking agent, aldehyde-based crosslinking agent, oxazoline-based crosslinking agent, metal alkoxide-based crosslinking agent, metal chelate-based crosslinking agent, metal salt-based crosslinking agent, ammonium salt-based crosslinking agent Etc. Among these, 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 that is excellent in reactivity with the hydroxyl group, and (meth) acrylic acid When the reactive functional group which the ester polymer (A) has is a carboxy group, it is preferable to use an epoxy-based crosslinking agent excellent in reactivity with the carboxy group. In addition, 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, alicyclic polyisocyanates such as isophorone diisocyanate and hydrogenated diphenylmethane diisocyanate, and the like. , And their biuret bodies, isocyanurate bodies, and adduct bodies that are a reaction product with low molecular active hydrogen-containing compounds such as ethylene glycol, propylene glycol, neopentyl glycol, trimethylolpropane, and castor oil. Among these, trimethylolpropane-modified aromatic polyisocyanate, particularly trimethylolpropane-modified tolylene diisocyanate and trimethylolpropane-modified xylylene diisocyanate are preferable from the viewpoint of reactivity with hydroxyl groups.

  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, diglycidylaniline, diglycidylamine and the like. Of these, 1,3-bis (N, N-diglycidylaminomethyl) cyclohexane is preferred from the viewpoint of reactivity with a carboxy group.

  The content of the crosslinking agent (B) in the pressure-sensitive adhesive composition P is preferably 0.01 parts by mass or more with respect to 100 parts by mass of the (meth) acrylic acid ester polymer (A). The amount is preferably 05 parts by mass or more, and more preferably 0.1 parts by mass or more. Further, the content is preferably 3 parts by mass or less, particularly preferably 2 parts by mass or less, and further preferably 1 part by mass or less. When the content of the cross-linking agent (B) is in the above range, the degree of cross-linking becomes appropriate, and the resulting adhesive has more excellent blister resistance.

(3) Various additives For the adhesive composition P, if desired, various additives usually used for acrylic adhesives, such as silane coupling agents, ultraviolet absorbers, antistatic agents, tackifiers, oxidation agents, etc. An inhibitor, a light stabilizer, a softening agent, a filler, a refractive index adjusting agent, and the like can be added. In addition, the below-mentioned polymerization solvent and dilution solvent shall not be contained in the additive which comprises the adhesive composition P.

  Here, when the pressure-sensitive adhesive composition P contains a silane coupling agent, the resulting pressure-sensitive adhesive has improved adhesion to a glass member or a plastic plate. Thereby, the obtained adhesive becomes more excellent in blister resistance.

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

  Examples of the silane coupling agent include polymerizable unsaturated group-containing silicon compounds such as vinyltrimethoxysilane, vinyltriethoxysilane, and methacryloxypropyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 2- ( 3,4-epoxycyclohexyl) silicon compounds having an epoxy structure such as ethyltrimethoxysilane, mercapto group-containing silicon compounds such as 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, and 3-mercaptopropyldimethoxymethylsilane Amino group-containing silicon such as 3-aminopropyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropylmethyldimethoxysilane Compound, 3-chloropropyltrimethoxysilane, 3-isocyanatopropyltriethoxysilane, or at least one of them, and alkyl group-containing silicon such as methyltriethoxysilane, ethyltriethoxysilane, methyltrimethoxysilane, ethyltrimethoxysilane Examples include condensates with compounds. 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 is preferably 0.01 parts by mass or more with respect to 100 parts by mass of the (meth) acrylic acid ester polymer (A), In particular, it is preferably 0.05 parts by mass or more, and more preferably 0.1 parts by mass or more. Further, the content is preferably 2 parts by mass or less, particularly preferably 1 part by mass or less, and further preferably 0.5 parts by mass or less.

2. Production of Adhesive Composition Adhesive composition P produced (meth) acrylic acid ester polymer (A), and obtained (meth) acrylic acid ester polymer (A), crosslinking agent (B), Can be produced by adding additives as desired.

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

  Examples of the polymerization initiator include azo compounds and organic peroxides, and two or more kinds may be used in combination. Examples of the azo compound include 2,2′-azobisisobutyronitrile, 2,2′-azobis (2-methylbutyronitrile), 1,1′-azobis (cyclohexane 1-carbonitrile), 2 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] and the like.

  Examples of organic peroxides include benzoyl peroxide, t-butyl perbenzoate, cumene hydroperoxide, diisopropyl peroxydicarbonate, di-n-propyl peroxydicarbonate, and di (2-ethoxyethyl) peroxy. Examples include dicarbonate, t-butyl peroxyneodecanoate, t-butyl peroxybivalate, (3,5,5-trimethylhexanoyl) peroxide, dipropionyl peroxide, diacetyl peroxide and the like.

  In addition, in the said superposition | polymerization process, the weight average molecular weight of the polymer obtained can be adjusted by mix | blending chain transfer agents, such as 2-mercaptoethanol.

  Once the (meth) acrylic acid ester polymer (A) is obtained, add the crosslinking agent (B) and, if desired, a diluting solvent and additives to the solution of the (meth) acrylic acid ester polymer (A). To obtain an adhesive composition P (coating solution) diluted with a solvent. When any of the above components is used in a solid state or when precipitation occurs when mixed with other components in an undiluted state, the component is used alone as a dilution solvent. It may be dissolved or diluted and then mixed with other components.

  Examples of the dilution 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, Alcohols such as 1-methoxy-2-propanol, ketones such as acetone, methyl ethyl ketone, 2-pentanone, isophorone, and cyclohexanone, esters such as ethyl acetate and butyl acetate, and cellosolve solvents such as ethyl cellosolve are used.

  The concentration / viscosity of the coating solution thus prepared is not particularly limited as long as it can be coated, and can be appropriately selected depending on the situation. For example, it dilutes so that the density | concentration of the adhesive composition P may be 10-60 mass%. In addition, when obtaining a coating solution, addition of a dilution solvent etc. is not a necessary condition, and if a viscosity etc. which can be coated with the adhesive composition P are not necessary, a dilution solvent does not need to be added. In this case, the adhesive composition P becomes a coating solution using the polymerization solvent of the (meth) acrylic acid ester polymer (A) as a dilution solvent.

[Adhesive]
The pressure-sensitive adhesive according to this embodiment is obtained by crosslinking the pressure-sensitive adhesive composition P. The crosslinking of the pressure-sensitive adhesive composition P can be usually performed by heat treatment. In addition, this heat processing can also serve as the drying process at the time of volatilizing a dilution solvent etc. from the coating film of the adhesive composition P apply | coated to the desired target object.

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

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

  By the heat treatment (and curing), the (meth) acrylic acid ester polymer (A) is sufficiently crosslinked through the crosslinking agent (B). The pressure-sensitive adhesive thus obtained has excellent blister resistance.

The pressure-sensitive adhesive according to this embodiment preferably has the following physical properties.
(1) Gel fraction The gel fraction of the pressure-sensitive adhesive according to this embodiment is preferably 30% or more as a lower limit, 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 is increased, and the blister resistance is more excellent. The gel fraction of the pressure-sensitive adhesive according to this embodiment is preferably 95% or less as an upper limit, particularly preferably 85% or less, and more preferably 80% or less. When the upper limit value of the gel fraction of the pressure-sensitive adhesive is as described above, the pressure-sensitive adhesive is not too hard, a good pressure-sensitive adhesive force is expressed, and the adhesiveness to the adherend becomes more excellent. Here, the measuring method of the gel fraction of an adhesive is as showing to the test example mentioned later.

(2) Dielectric constant The dielectric constant at 1.0 MHz of the pressure-sensitive adhesive according to this embodiment is preferably 6.5 or less, particularly preferably 6.2 or less, and more preferably 5. It is preferable that it is 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 the pressure-sensitive adhesive according to this embodiment is obtained using the (meth) acrylic acid ester polymer (A) having a component derived from N-vinylcarboxylic acid amide, a low dielectric constant as described above is achieved. Can do.

  The lower limit value 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 further It is preferable that it is 4.0 or more. In addition, the measuring method of the dielectric constant of an adhesive is as showing to the test example mentioned later.

(3) Moisture and heat whitening resistance The moisture and heat whitening resistance of the pressure-sensitive adhesive according to this embodiment can be quantitatively evaluated based on the haze value. Specifically, for a laminate in which a 50 μm-thick pressure-sensitive adhesive layer made of the pressure-sensitive adhesive according to the present embodiment is sandwiched between a glass plate and a 1 mm-thick acrylic resin plate, wet heat conditions of 85 ° C. and 85% RH After conducting a durability test for 120 hours under storage, haze value (%) when stored at 23 ° C. and 50% RH at room temperature and humidity for 24 hours (value measured according to JIS K7136: 2000. The same applies hereinafter. ) From which the haze value (%) before the durability test is subtracted is preferably less than 5 points, particularly preferably less than 3 points, and further preferably less than 1 point. If the increase in haze value is as described above, it can be said that the increase in haze value is small even after being placed under wet heat conditions, and whitening of the adhesive is suppressed.

  As described above, in the laminate in which the adhesive layer is sandwiched between the glass plate and the acrylic resin plate, the acrylic resin plate is used under wet heat conditions as compared with the laminate in which the adhesive layer is sandwiched between two glass plates. Since the permeated moisture easily condenses in the laminate, whitening is likely to occur in the pressure-sensitive adhesive layer. However, according to the pressure-sensitive adhesive according to the present embodiment, excellent moisture and heat whitening resistance is exhibited even in the above laminate.

[Adhesive sheet]
The pressure-sensitive adhesive sheet according to this embodiment is a pressure-sensitive adhesive sheet having at least a pressure-sensitive adhesive layer made of the above-mentioned pressure-sensitive adhesive, and preferably a pressure-sensitive adhesive sheet obtained by laminating a release sheet on one or both sides of the pressure-sensitive adhesive layer. .

The specific structure as an example of the adhesive sheet which concerns on this embodiment is shown in FIG.
As shown in FIG. 1, the pressure-sensitive adhesive sheet 1 according to an embodiment includes two release sheets 12a and 12b and the two release sheets 12a so as to be in contact with the release surfaces of the two release sheets 12a and 12b. , 12b and an adhesive layer 11 sandwiched between the two layers. In addition, the release surface of the release sheet in this specification refers to a surface having peelability in the release sheet, and includes both a surface that has been subjected to a release treatment and a surface that exhibits peelability without being subjected to a release treatment. .

1. Each member (1) Adhesive layer The adhesive layer 11 is comprised from the adhesive mentioned above, ie, it is comprised from the adhesive formed by bridge | crosslinking the adhesive composition P. As shown in FIG.

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

  The thickness of the pressure-sensitive adhesive layer 11 is preferably 1000 μm or less as an upper limit, more preferably 600 μm or less, particularly preferably 300 μm or less, and further preferably 150 μm or less. When the upper limit value of the thickness of the pressure-sensitive adhesive layer 11 is as described above, the moisture and heat whitening resistance is further improved, and the excellent blister resistance is easily exhibited. 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 pressure-sensitive adhesive sheet 1 is used, and are peeled off when the pressure-sensitive adhesive sheet 1 (pressure-sensitive adhesive layer 11) is used. In the pressure-sensitive adhesive sheet 1 according to this embodiment, one or both of the release sheets 12a and 12b are not necessarily required.

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

  It is preferable that the peeling surface (especially the surface in contact with the pressure-sensitive adhesive layer 11) of the release sheets 12a and 12b is subjected to a peeling treatment. Examples of the release agent used for the release treatment include alkyd, silicone, fluorine, unsaturated polyester, polyolefin, and wax release agents. Of the release sheets 12a and 12b, one release sheet is preferably a heavy release release sheet having a high release force, and the other release sheet is preferably a light release release sheet having a low release force.

  Although there is no restriction | limiting in particular about the thickness of release sheet 12a, 12b, Usually, it is about 20-150 micrometers.

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 this embodiment is preferably 5% or less, more preferably 3% or less, and particularly preferably 1% or less. Is preferable, and it is preferable that it is 0.5% or less. When the haze value of the pressure-sensitive adhesive layer 11 is 5% or less, the transparency is very high, which is suitable for optical applications (for display bodies). The haze value in this specification is a value measured according to JIS K7136: 2000.

(2) Transmission hue b *
The transmission hue b * defined by the CIE 1976 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, particularly −1. It is preferably 0.5 to 1.5, more preferably −1.0 to 1.0. When the transmission hue b * of the pressure-sensitive adhesive layer 11 is in the above range, the pressure-sensitive adhesive layer 11 is less colored and particularly suitable for display. In this embodiment, the (meth) acrylic acid ester polymer (A) achieves the above-described transmission hue b * by containing an appropriate amount of N-vinylcarboxylic acid amide as a monomer unit constituting the polymer. It is possible. In addition, the measuring method of the transmission hue b * in this specification is as showing in the test example mentioned later.

(3) Adhesive strength 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 as a lower limit, particularly preferably 10 N / 25 mm or more, and further 15 N / It is preferable that it is 25 mm or more. When the adhesive strength of the adhesive sheet 1 is 5 N / 25 mm or more, the blister resistance is more excellent. Moreover, it is preferable that the adhesive force with respect to the soda-lime glass of the adhesive sheet 1 which concerns on this embodiment is 50 N / 25mm or less as an upper limit, It is more preferable that it is 45 N / 25mm or less, It is 40 N / 25mm or less Is particularly preferred. When the adhesive strength of the pressure-sensitive adhesive sheet 1 is 50 N / 25 mm or less, good reworkability is obtained, and when a bonding error occurs, an expensive display member can be reused.

  Here, the adhesive force in the present specification basically means an adhesive force measured by a 180-degree peeling method according to JIS Z0237: 2009. The measurement sample is 25 mm wide and 100 mm long. Affixed to the adherend, pressurized at 0.5 MPa, 50 ° C. for 20 minutes, left under normal pressure, 23 ° C., 50% RH for 24 hours, and then measured at a peeling rate of 300 mm / min. Shall.

3. Production of pressure-sensitive adhesive sheet As a production example of pressure-sensitive adhesive sheet 1, a pressure-sensitive adhesive composition is prepared by applying a coating solution of the pressure-sensitive adhesive composition P to the release surface of one release sheet 12a (or 12b) and subjecting it to heat treatment. After P is thermally crosslinked to form a coating layer, the release surface of the other release sheet 12b (or 12a) is superimposed on the coating layer. When a curing period is required, a curing period is set, and when the curing period is unnecessary, the coating layer becomes the pressure-sensitive adhesive layer 11 as it is. Thereby, the said adhesive sheet 1 is obtained. The conditions for the heat treatment and curing are as described above.

  As another production example of the pressure-sensitive adhesive sheet 1, a coating solution of the above-mentioned pressure-sensitive adhesive composition P is applied to the release surface of one release sheet 12a, heat-treated to thermally cross-link the pressure-sensitive adhesive composition P, and then applied. A layer is formed to obtain a release sheet 12a with a coating layer. Moreover, the coating solution of the said adhesive composition P is apply | coated to the peeling surface of the other peeling sheet 12b, heat processing is performed, the adhesive composition P is heat-crosslinked, a coating layer is formed, and a coating layer is attached. The release sheet 12b is obtained. And the peeling sheet 12a with an application layer and the peeling sheet 12b with an application layer are bonded together so that both application layers may mutually contact. When the curing period is necessary, the curing period is set, and when the curing period is unnecessary, the above-mentioned laminated application layer becomes the pressure-sensitive adhesive layer 11 as it is. Thereby, the said adhesive sheet 1 is obtained. According to this production example, even when the pressure-sensitive adhesive layer 11 is thick, it can be stably produced.

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

[Display]
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 (other display body constituent members). ) And the pressure-sensitive adhesive layer 11 which is located between them and bonds the first display member constituting member 21 and the second display member constituting member 22 to each other. In the display body 2 according to the present embodiment, the first display body constituting member 21 may have a step such as the printed layer 3 on the surface on the pressure-sensitive adhesive layer 11 side.

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

  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. Moreover, as the display body 2, the member which comprises those some may be sufficient.

  It is preferable that the 1st display body structural member 21 is a protection panel which consists of a laminated body etc. other than a glass plate, a plastic plate, etc. In this case, the printing layer 3 is generally formed in a frame shape on the pressure-sensitive adhesive layer 11 side in the first display member constituting member 21.

  The glass plate is not particularly limited. For example, chemically tempered glass, alkali-free glass, quartz glass, soda lime glass, barium / strontium-containing glass, aluminosilicate glass, lead glass, borosilicate glass, barium borosilicate Glass etc. are mentioned. 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. Although the thickness of a plastic board is not specifically limited, Usually, it is 0.2-5 mm, Preferably it is 0.4-3 mm.

  Various functional layers (transparent conductive film, metal layer, silica layer, hard coat layer, antiglare layer, etc.) may be provided on one or both surfaces of the glass plate or plastic plate, or an optical member. May be laminated. Moreover, the transparent conductive film and the metal layer may be patterned.

  The second display member constituting member 22 includes an optical member to be attached to the first display member constituting member 21, a display member module (for example, a liquid crystal (LCD) module, a light emitting diode (LED) module, an organic electroluminescence (organic) EL) module, etc.), an optical member as a part of the display module, or a laminate including the display module.

  Examples of the optical member include a scattering prevention film, a polarizing plate (polarizing film), a polarizer, a retardation plate (retarding film), a viewing angle compensation film, a brightness enhancement film, a contrast enhancement film, a liquid crystal polymer film, and a diffusion film. , Transflective film, transparent conductive film, and the like. Examples of the scattering prevention film include a hard coat film in which a hard coat layer is formed on one side of a base film.

  The material which comprises the printing layer 3 is not specifically limited, The well-known material for printing is used. The lower limit of the thickness of the printing layer 3, that is, the height of the step, is preferably 3 μm or more, more preferably 5 μm or more, particularly preferably 7 μm or more, and most preferably 10 μm or more. preferable. When the lower limit value is equal to or greater than the above, it is possible to sufficiently ensure concealability such as making the electrical wiring invisible from the viewer side. The upper limit value is preferably 50 μm or less, more preferably 35 μm or less, particularly preferably 25 μm or less, and further preferably 20 μm or less. When the upper limit is less than or equal to the above, it is possible to prevent deterioration in the step following ability of the pressure-sensitive adhesive layer 11 with respect to the print layer 3.

  In order to manufacture the said display body 2, as an example, one peeling sheet 12a of the adhesive sheet 1 is peeled, and the adhesive layer 11 which the adhesive sheet 1 exposed is used as the printing layer of the 1st display body structural member 21. It is bonded to the surface on the side where 3 is present.

  Then, the other peeling sheet 12b is peeled from the pressure-sensitive adhesive layer 11 of the pressure-sensitive adhesive sheet 1, and the pressure-sensitive adhesive layer 11 exposed from the pressure-sensitive adhesive sheet 1 and the second display member constituting member 22 are bonded together. As another example, the bonding order of the first display member constituting member 21 and the second display member constituting member 22 may be switched.

  In the display body 2 described above, for example, the display body 2 is outgassed from the first display body constituent member 21 and / or the second display body constituent member 22 under high temperature and high humidity conditions (for example, 85 ° C., 85% RH). Since the pressure-sensitive adhesive layer 11 is excellent in blister resistance even if the occurrence of bubbles, bubbles, floats, and the like at the interface between the pressure-sensitive adhesive layer 11 and the first display member constituting member 21 and / or the second display member constituting member 22, Generation | occurrence | production of blisters, such as peeling, is suppressed.

  Moreover, since the said adhesive layer 11 is excellent in heat-and-moisture-resistant whitening resistance, after the display body 2 was put on high-temperature, high-humidity conditions (for example, 85 degreeC, 85% RH), it returned to normal temperature normal humidity. Even in this case, whitening of the pressure-sensitive adhesive layer 11 is suppressed. According to the display body 2 according to the present embodiment, in particular, one of the first display body constituting member 21 and the second display body constituting member 22 is a plastic plate having a thickness of 1 mm or more, and the other is a glass plate. Even if it exists, the outstanding heat-and-heat whitening resistance is exhibited.

  Furthermore, since the dielectric constant of the pressure-sensitive adhesive layer 11 is kept low, even if 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. Moreover, the responsiveness of the touch panel is good.

  The embodiment described above is described for facilitating understanding of the present invention, and is 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 pressure-sensitive adhesive sheet 1 may be omitted, and a desired optical member may be laminated instead of the release sheets 12a and / or 12b. Moreover, the 1st display body structural member 21 may not have a level | step difference.

  EXAMPLES Hereinafter, although an Example etc. demonstrate this invention further more concretely, the scope of the present invention is not limited to these Examples etc.

[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 2-hydroxy acrylate 15 parts by mass of ethyl was copolymerized by a solution polymerization method 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 described later, the weight average molecular weight (Mw) was 500,000.

2. Preparation of Adhesive Composition 100 parts by mass (converted to solid content; the same applies hereinafter) of the (meth) acrylic acid ester polymer (A) obtained in Step 1 above, and trimethylolpropane-modified tris as a crosslinking agent (B) 0.15 parts by mass of diisocyanate (manufactured by Toyochem, product name “BHS8515”) and 3-glycidoxypropyltrimethoxysilane as a silane coupling agent (manufactured by Shin-Etsu Chemical Co., Ltd., product name “KBM-403”) A coating solution of an adhesive composition was obtained by mixing with 0.30 parts by mass, sufficiently stirring, and diluting with methyl ethyl ketone.

Here, Table 1 shows each formulation (solid content converted value) of the adhesive composition when the (meth) acrylic acid ester polymer (A) is 100 parts by mass (solid content converted value). Details of the abbreviations and 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 (Toyochem, product name “BHS8515”)
Epoxy system: 1,3-bis (N, N′-diglycidylaminomethyl) cyclohexane (Mitsubishi Gas Chemical Co., Ltd., product name “TETRAD-C”)

3. Manufacture of an adhesive sheet The coating solution of the adhesive composition obtained by the said process 2 is the heavy peeling type release sheet (product name "SP-PET752150 by the Lintec company) which peeled one side of the polyethylene terephthalate film with the silicone type release agent. It applied | coated with the knife coater to the peeling process surface of "). And the application layer was heat-processed at 90 degreeC for 1 minute (s), and the application layer was formed.

  Next, a light release type release sheet (product name “SP-PET382120”, manufactured by Lintec Corporation) in which the coating layer on the heavy release type release sheet obtained above and one side of the polyethylene terephthalate film were release-treated with a silicone-based release agent Are bonded so that the release-treated surface of the light release-type release sheet is in contact with the coating layer, and is cured for 7 days under the conditions of 23 ° C. and 50% RH. A first pressure-sensitive adhesive sheet having a structure of layer (thickness: 25 μm) / light release type release sheet was produced.

  Moreover, the heavy peeling type peeling sheet (product name "SP-PET752150" by the Lintec company) which peeled one side of the polyethylene terephthalate film with the silicone type release agent from the coating solution of the adhesive composition obtained at the said process 2 After coating with a knife coater on the peel-treated surface, a coating layer (thickness: 25 μm) was formed by heat treatment at 90 ° C. for 1 minute. Similarly, the light release release sheet (product name “SP-PET 382120”, manufactured by Lintec Co., Ltd.) obtained by removing one surface of the polyethylene terephthalate film with a silicone-based release agent from the coating solution of the adhesive composition obtained in Step 2 above. ) Was applied with a knife coater, followed by heat treatment at 90 ° C. for 1 minute to form a coating layer (thickness: 25 μm).

  Subsequently, the heavy release type release sheet with the coating layer obtained above and the light release type release sheet with the coating layer obtained above were bonded so that both coating layers were in contact with each other. Then, by curing for 7 days under the condition of 50% RH, a second pressure-sensitive adhesive sheet having a structure of heavy release type release sheet / pressure-sensitive adhesive layer (thickness: 50 μm) / light release type release sheet was produced.

  In addition, the thickness of the said adhesive layer is the value measured using the constant pressure thickness measuring device (The product name "PG-02" by the Teclock company) based on JISK7130.

[Examples 2-3, Comparative Examples 1-4]
Types and proportions of monomers constituting the (meth) acrylate polymer (A), weight average molecular weight (Mw) of the (meth) acrylate polymer (A), and types and blends of the crosslinking agent (B) First and second adhesive sheets were produced in the same manner as in Example 1 except that the amount was changed as shown in Table 1.

Here, the above-mentioned weight average molecular weight (Mw) is a polystyrene-reduced weight average molecular weight measured under the following conditions (GPC measurement) using gel permeation chromatography (GPC).
<Measurement conditions>
GPC measurement device: manufactured by Tosoh Corporation, HLC-8020
GPC column (passed in the following order): TSK guard column HXL-H manufactured by Tosoh Corporation
TSK gel GMHXL (× 2)
TSK gel G2000HXL
・ Measurement solvent: Tetrahydrofuran ・ Measurement temperature: 40 ° C.

[Test Example 1] (Measurement of gel fraction)
The first pressure-sensitive adhesive sheet (thickness of the pressure-sensitive adhesive layer: 25 μm) obtained in Examples and Comparative Examples was cut into a size of 80 mm × 80 mm, and the pressure-sensitive adhesive layer was wrapped in a polyester mesh (mesh size 200). The mass of the pressure-sensitive adhesive alone was calculated by weighing the mass with a precision balance and subtracting the mass of the mesh alone. The mass at this time is M1.

  Next, the pressure-sensitive adhesive wrapped in the polyester mesh was immersed in ethyl acetate at room temperature (23 ° C.) for 24 hours. Thereafter, the pressure-sensitive 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 dried in an oven at 80 ° C. for 12 hours. After drying, the mass was weighed with a precision balance, and the mass of the pressure sensitive adhesive alone was calculated by subtracting the mass of the mesh alone. The mass at this time is M2. The gel fraction (%) is represented by (M2 / M1) × 100. The results are shown in Table 2.

[Test Example 2] (Measurement of haze value)
About the adhesive layer of the 1st adhesive sheet (thickness of an adhesive layer: 25 micrometers) obtained by the Example and the comparative example, according to JISK7136: 2000, a haze meter (Nippon Denshoku Industries Co., Ltd. make, product name) The haze value (%) was measured using “NDH-2000”). The results are shown in Table 2.

[Test Example 3] (Measurement of adhesive strength)
The light release release sheet was peeled from the first pressure-sensitive adhesive sheet (pressure-sensitive adhesive layer thickness: 25 μm) obtained in Examples and Comparative Examples, and the exposed pressure-sensitive adhesive layer was replaced with polyethylene terephthalate (PET ) The film (Toyobo Co., Ltd., product name “PET A4300”, thickness: 100 μm) was bonded to an easy adhesion layer to obtain a laminate of release sheet / adhesive layer / PET film. The obtained laminate was cut into a width of 25 mm and a length of 100 mm, and this was used as a sample.

  In an environment of 23 ° C. and 50% RH, the heavy release type release sheet is peeled off from the above sample, and the exposed adhesive layer is attached to soda lime glass (manufactured by Nippon Sheet Glass Co., Ltd.). And pressurized at 0.5 MPa and 50 ° C. for 20 minutes. Then, after leaving for 24 hours under the conditions of 23 ° C. and 50% RH, using a tensile tester (Orientec, Tensilon), the adhesive strength (N / 25 mm). Conditions other than those described here were measured according to JIS Z0237: 2009. The results are shown in Table 2.

[Test Example 4] (Measurement of transmitted hue b *)
For the pressure-sensitive adhesive layer of the first pressure-sensitive adhesive sheet (pressure-sensitive adhesive layer thickness: 25 μm) obtained in Examples and Comparative Examples, a simultaneous photometric spectroscopic chromaticity meter (manufactured by Nippon Denshoku Industries Co., Ltd., product name “SQ2000”) ) Was used to measure the transmitted hue b * defined by the CIE 1976 L * a * b * color system. The results are shown in Table 2.

[Test Example 5] (Evaluation of blister resistance)
A polyethylene terephthalate film in which a transparent conductive film made of tin-doped indium oxide (ITO) is provided on one side of the pressure-sensitive adhesive layer of the second pressure-sensitive adhesive sheet (pressure-sensitive adhesive layer thickness: 50 μm) obtained in Examples and Comparative Examples (Oike Kogyo Co., Ltd., ITO film, thickness: 125 μm) transparent conductive film and polymethylmethacrylate (PMMA) acrylic resin plate (Mitsubishi Rayon Co., Ltd., product name “Acrylite MR-200”, thickness : 1 mm) to obtain a laminate.

The obtained laminate (sample) was autoclaved for 30 minutes at 50 ° C. and 0.5 MPa, and then allowed to stand at normal pressure, 23 ° C. and 50% RH for 24 hours. Subsequently, it was stored for 72 hours under high temperature and high humidity conditions of 85 ° C. and 85% RH. Thereafter, the pressure-sensitive adhesive layer was visually confirmed as to whether there were any bubbles, floating or peeling, and blister resistance was evaluated according to the following criteria. The results are shown in Table 2.
〇… There were no air bubbles, no floating or peeling.
X: Bubbles, floating and peeling occurred.

[Test Example 6] (Evaluation of resistance to moist heat whitening)
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 using a non-alkali glass plate having a thickness of 1.1 mm and an acrylic resin plate having a thickness of 1 mm ( It was sandwiched between Mitsubishi Rayon Co., Ltd. (product name “Acrylite MR-200”) to obtain a laminate.

  The obtained laminate (sample) was autoclaved for 30 minutes at 50 ° C. and 0.5 MPa, and then allowed to stand at normal pressure, 23 ° C. and 50% RH for 24 hours. About this laminated body, haze value (%) was measured according to JISK7136: 2000 using the haze meter (The Nippon Denshoku Industries Co., Ltd. make, product name "NDH2000").

  Next, the laminate was stored for 120 hours under wet heat conditions of 85 ° C. and 85% RH. Then, it was left at room temperature and normal humidity of 23 ° C. and 50% RH for 24 hours. About the said laminated body, haze value (%) was measured according to JISK7136: 2000 using the haze meter (The Nippon Denshoku Industries Co., Ltd. make, product name "NDH2000").

Based on the above results, a haze value increase (points) after the wet heat condition was calculated by subtracting the haze value before the wet heat condition from the haze value after the wet heat condition. Based on the results, moisture and heat whitening resistance was evaluated according to the following criteria. The results are shown in Table 2.
◎… Haze increase is less than 1.0 point ○… Haze increase is 1.0 point or more, less than 5.0 point ×… Haze increase is 5.0 point or more

[Test Example 7] (Calculation of dielectric constant)
After forming a 100 μm thick adhesive layer on one side of a 50 μm thick polyethylene terephthalate film in the same manner as in the Examples and Comparative Examples, a 50 μm thick polyethylene terephthalate film was bonded to the adhesive layer. It cut | judged to 50 mm x 50 mm. About the obtained laminated body, the electrostatic capacitance (C1) was measured using the impedance analyzer (Nippon Hewlett-Packard company make, "HP-4194A"). Further, two polyethylene terephthalate films having a thickness of 50 μm were stacked and cut into 50 mm × 50 mm, and the capacitance (C2) was measured in the same manner. Then, from the values of C1 and C2, the calculation formula of the series connected capacitor 1 / C1 = 1 / C2 + 1 / C3
Based on the above, the capacitance (C3) of the adhesive was calculated. Based on this capacitance C3, the dielectric constant ε _s of the adhesive was calculated from the following formula. The results are shown in Table 2.

ε _s = (C3 × d) / (ε ₀ × S)
ε _s : dielectric constant of adhesive ε ₀ : dielectric constant of vacuum (8.854 × 10 ⁻¹² )
C3: Capacitance of the adhesive S: Area of the adhesive layer d: Thickness of the adhesive layer

  As can be seen from Table 2, the pressure-sensitive adhesive sheets obtained in the examples were excellent in both blister resistance and moist heat whitening resistance, and exhibited a low dielectric constant.

  The pressure-sensitive adhesive composition, pressure-sensitive adhesive and pressure-sensitive adhesive sheet of the present invention can be suitably used, for example, for bonding between a protective panel made of a plastic plate and a desired display member constituting member.

DESCRIPTION OF SYMBOLS 1 ... Adhesive sheet 11 ... Adhesive layer 12a, 12b ... Release sheet 2 ... Display body 21 ... 1st display body structural member 22 ... 2nd display body structural member 3 ... Print layer

Claims (10)

(Meth) acrylic acid ester polymer comprising (meth) acrylic acid alkyl ester, reactive functional group-containing monomer having a reactive functional group in the molecule, and N-vinylcarboxylic acid amide as monomer units constituting the polymer (A) and
A pressure-sensitive adhesive composition comprising a crosslinking agent (B).   The pressure-sensitive adhesive according to claim 1, wherein the (meth) acrylic acid ester polymer (A) does not include a carboxy group-containing monomer having a carboxy group in the molecule as a monomer unit constituting the polymer. Sex composition.   In the (meth) acrylic acid ester polymer (A), the mass ratio of the reactive functional group-containing monomer as the monomer unit constituting the polymer and the N-vinylcarboxylic acid amide is 95: 5 to It is 50:50, The adhesive composition of Claim 1 or 2 characterized by the above-mentioned.   The said (meth) acrylic acid ester polymer (A) contains the said reactive functional group containing monomer 5 mass% or more and 30 mass% or less as a monomer unit which comprises the said polymer. The adhesive composition as described in any one of -3.   The pressure-sensitive adhesive composition according to any one of claims 1 to 4, wherein the (meth) acrylic acid ester polymer (A) has a weight average molecular weight of 200,000 or more and 2,000,000 or less.   The adhesive which bridge | crosslinks the adhesive composition as described in any one of Claims 1-5.   The pressure-sensitive adhesive according to claim 6, wherein the gel fraction is 30% or more and 95% or less.   The pressure-sensitive adhesive according to claim 6 or 7, wherein a dielectric constant at 1.0 MHz is 6.5 or less.   Durability test for 120 hours of storage at 85 ° C and 85% RH for a laminate in which a 50 µm thick adhesive layer made of the above adhesive is sandwiched between a glass plate and a 1 mm thick acrylic resin plate The haze value increase obtained by subtracting the haze value before the durability test from the haze value when stored at room temperature and normal humidity of 23 ° C. and 50% RH for 24 hours is less than 5 points. The pressure-sensitive adhesive according to any one of claims 6 to 8. Two release sheets,
An adhesive layer sandwiched between the release sheets so as to be in contact with the release surfaces of the two release sheets;
The said adhesive layer consists of an adhesive as described in any one of Claims 6-9, The adhesive sheet characterized by the above-mentioned.

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