JP6921586B2 - Adhesive Compositions, Adhesives, Adhesive Sheets and Labels - Google Patents

Description

The present invention relates to an adhesive composition, an adhesive and an adhesive sheet suitable for use in a display body, and a display body obtained by using them.

In recent years, various mobile electronic devices such as smartphones and tablet terminals are provided with 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 becoming more and more popular as a touch panel.

In a display as described above, a protective panel is usually provided on the surface side of the display module. With the thinning and weight reduction 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 protective panel and the display module so that the deformed protective panel does not collide with the display module even when the protective panel is deformed by an external force.

However, in the presence of the above-mentioned voids, that is, the air layer, the light reflection loss due to the difference in the refractive index between the protective panel and the air layer and the difference in the refractive index between the air layer and the display module is large, and the display There is a problem that the image quality is deteriorated.

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. However, a frame-shaped print layer may exist as a step on the display module side of the protective panel. If the pressure-sensitive adhesive layer does not follow the step, the pressure-sensitive adhesive layer floats in the vicinity of the step, which causes a loss of light reflection. Therefore, the pressure-sensitive adhesive layer is required to have a step-following property.

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

JP-A-2010-97070

Patent Document 1 attempts to improve the step followability by lowering the storage elastic modulus of the pressure-sensitive adhesive layer at room temperature. However, if the storage elastic modulus at room temperature is lowered as described above, the storage elastic modulus at high temperature is lowered more than necessary, and a problem occurs under durable conditions. For example, when high temperature and high humidity conditions are applied, air bubbles are generated in the vicinity of the step, or outgas is generated from the plastic plate which is a protective panel, and blisters such as air bubbles, floating, and peeling are generated. On the other hand, if the adhesive layer is hardened in order to improve the blister resistance, the step followability is lowered.

Further, in the conventional pressure-sensitive adhesive layer, there may be a problem that the pressure-sensitive adhesive layer is whitened when it is returned to normal temperature and humidity after being subjected to high temperature and high humidity (wet heat) conditions. In order to improve the moisture-heat whitening resistance of the pressure-sensitive adhesive, there is a method in which a hydroxyl group-containing monomer is used in a large amount as a constituent monomer of the acrylic polymer, which is the main component polymer, in excess of the amount that contributes to cross-linking. However, in this case, the high polarity of the hydroxyl group-containing monomer-derived component increases the dielectric constant of the obtained pressure-sensitive adhesive, which may cause the touch panel to malfunction or the responsiveness to decrease.

The present invention has been made in view of the above-mentioned actual conditions, and has an adhesive composition which is excellent in all of step followability, blister resistance and moisture heat whitening resistance, and can keep the dielectric constant low. It is an object of the present invention to provide an object, an adhesive, an adhesive sheet and a display body.

In order to achieve the above object, first, the present invention comprises a (meth) acrylic acid ester polymer (A) containing N-vinylcarboxylic acid amide as a monomer unit constituting the polymer, and active energy ray-curable. Provided is an adhesive composition characterized by containing the component (C) (Invention 1).

After adhering two adherends with a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition according to the above invention (Invention 1), the pressure-sensitive adhesive layer is irradiated with active energy rays to obtain the pressure-sensitive adhesive. The layer cures to become an adhesive layer after curing. After curing, the adhesive layer is cured to improve the film strength. Further, by copolymerizing the N-vinylcarboxylic acid amide with the (meth) acrylic acid ester polymer (A), the obtained pressure-sensitive adhesive has high adhesive strength and high cohesive strength. Due to these synergistic effects, the cured adhesive layer exhibits excellent blister resistance. Further, since the carboxylic acid amide, which is an excellent hydrophilic group, is present in the pressure-sensitive adhesive, when the pressure-sensitive adhesive layer is placed under high-temperature and high-humidity conditions after curing and then returned to normal temperature and humidity, the curing is performed. Whitening of the post-adhesive layer is suppressed. Further, since N-vinylcarboxylic acid amide has a low polarity, it does not improve the dielectric constant while improving the moisture-heat bleaching resistance of the obtained pressure-sensitive adhesive. Further, the cured pressure-sensitive adhesive layer containing the cured product of the active energy ray-curable component (C) tends to have a lower dielectric constant than the pressure-sensitive adhesive layer containing no cured product. For these reasons, the post-curing pressure-sensitive adhesive layer has a low dielectric constant.

In the above invention (Invention 1), the (meth) acrylic acid ester polymer (A) contains a reactive functional group-containing monomer having a reactive functional group in the molecule as a monomer unit constituting the polymer. , The adhesive composition preferably contains a cross-linking agent (B) (Invention 2).

In the above invention (Invention 2), the reactive functional group-containing monomer and the N-vinylcarboxylic acid amide as the monomer unit constituting the polymer in the (meth) acrylic acid ester polymer (A) are used. The mass ratio of is preferably 95: 5 to 50:50 (Invention 3).

In the above inventions (Inventions 2 and 3), the (meth) acrylic acid ester polymer (A) contains the reactive functional group-containing monomer in an amount of 5% by mass or more and 30% by mass as a monomer unit constituting the polymer. % Or less is preferable (Invention 4).

Secondly, the present invention has a crosslinked structure composed of a (meth) acrylic acid ester polymer (A) containing N-vinylcarboxylic acid amide as a monomer unit constituting the polymer and a crosslinking agent (B). At the same time, an active energy ray-curable pressure-sensitive adhesive characterized by containing an active energy ray-curable component (C) is provided (Invention 5).

The pressure-sensitive adhesive according to the above invention (Invention 5) preferably has a gel fraction of 30% or more and 90% or less (Invention 6).

In the above inventions (Inventions 5 and 6), in a laminate in which a pressure-sensitive adhesive layer having a thickness of 50 μm made of the pressure-sensitive adhesive is sandwiched between a glass plate and an acrylic resin plate having a thickness of 1 mm, the pressure-sensitive adhesive layer is subjected to active energy rays. After curing to form an adhesive layer after curing, the laminate was subjected to a durability test in which it was stored for 120 hours under moist heat conditions of 85 ° C. and 85% RH, and then at 23 ° C. and 50% RH. 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 at room temperature and humidity for 24 hours is less than 5 points (Invention 7).

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 pressure-sensitive adhesive layer is the pressure-sensitive adhesive. Provided is an adhesive sheet comprising (Invention 5 to 7) (Invention 8).

Fourth, the present invention provides a cured pressure-sensitive adhesive layer for bonding one display body component, another display body component, and the one display body component and the other display body component to each other. One of the display body constituent members and the other display body constituent members are made of a plastic plate, and the cured pressure-sensitive adhesive layer is used as a monomer unit constituting the polymer. It has a cross-linked structure composed of a (meth) acrylic acid ester polymer (A) containing an N-vinylcarboxylic acid amide and a cross-linking agent (B), and a cured product of an active energy ray-curable component (C). Provided is a display body characterized by containing a pressure-sensitive adhesive (Invention 9).

Fifth, the present invention is a laminate having a cured pressure-sensitive adhesive layer sandwiched between a glass plate and a plastic plate and formed by curing the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet (Invention 8), at 85 ° C., 85. After performing a durability test of storing for 120 hours under moist heat conditions of% RH, the haze value before the durability test was subtracted from the haze value when stored at room temperature and normal humidity of 23 ° C. and 50% RH for 24 hours. Provided is a laminate characterized in that the haze value increase is less than 5 points.

According to the pressure-sensitive adhesive composition, pressure-sensitive adhesive, pressure-sensitive adhesive sheet, and display body according to the present invention, it is excellent in all of step-following property, blister resistance, and moisture-heat bleaching resistance, and the dielectric constant can be suppressed to a low level.

It is sectional drawing of the pressure-sensitive 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 adhesive composition according to the present embodiment (hereinafter, may be referred to as “adhesive composition P”) contains (meth) acrylic acid ester weight containing N-vinylcarboxylic acid amide as a monomer unit constituting the polymer. It contains a coalescence (A) and an active energy ray-curable component (C). Further, the (meth) acrylic acid ester polymer (A) preferably contains a reactive functional group-containing monomer having a reactive functional group in the molecule as a monomer unit constituting the polymer, and is a tacky composition. P preferably further contains the cross-linking agent (B). In addition, in this specification, (meth) acrylic acid means both acrylic acid and methacrylic acid. The same applies to other similar terms. In addition, the concept of "polymer" shall be included in "polymer".

The pressure-sensitive adhesive layer obtained by cross-linking (thermally cross-linking) the pressure-sensitive adhesive composition P according to the present embodiment is still cured by active energy rays at the stage of the pressure-sensitive adhesive sheet, that is, the stage before being attached to the adherend. Since the elastic modulus is relatively low, the stress generated when the material is attached to an adherend such as a display body component can be relaxed. Therefore, even when the pressure-sensitive adhesive sheet is attached to the display body constituent member having a step, the pressure-sensitive adhesive layer easily follows the step, and it is possible to prevent gaps, floats, and the like from occurring in the vicinity of the step.

Further, when the pressure-sensitive adhesive sheet is used, one display body component and another display body component are bonded to each other by the pressure-sensitive adhesive layer, and then the display body component or another display body component is used. The pressure-sensitive adhesive layer is irradiated with active energy rays. As a result, the active energy ray-curable component (C) is cured, and the pressure-sensitive adhesive layer becomes the pressure-sensitive adhesive layer after curing. Since the film strength of this cured adhesive layer is improved by curing, the obtained laminate (display body) was placed under high temperature and high humidity conditions, for example, 85 ° C. and 85% RH conditions for 72 hours. Even in this case, the occurrence of air bubbles, floating, peeling, etc. in the vicinity of the step is suppressed. That is, the cured pressure-sensitive adhesive layer obtained by cross-linking and curing the pressure-sensitive adhesive composition P according to the present embodiment is excellent in step-following property under high temperature and high humidity conditions.

On the other hand, the pressure-sensitive adhesive obtained from the pressure-sensitive adhesive composition P according to the present embodiment has high adhesive strength and high adhesive strength due to the copolymerization of N-vinylcarboxylic acid amide in the (meth) acrylic acid ester polymer (A). It has a high cohesive force. The cured pressure-sensitive adhesive layer exhibits excellent blister resistance due to the synergistic effect of the pressure-sensitive adhesive having high adhesive strength and high cohesive power and the film strength being improved by curing. For example, even when the laminate (display body) is placed under high temperature and high humidity conditions, for example, 85 ° C. and 85% RH for 72 hours, outgas is generated from a display body component made of a plastic plate or the like. After curing, the generation of blister such as air bubbles, floating, and peeling at the interface between the pressure-sensitive adhesive layer and the display body component is suppressed.

Further, the carboxylic acid amide contained in the (meth) acrylic acid ester polymer (A) is an excellent hydrophilic group. When such a hydrophilic group is present in the pressure-sensitive adhesive, even when the cured pressure-sensitive adhesive layer is placed under high-temperature and high-humidity conditions, the moisture that has penetrated into the cured pressure-sensitive adhesive layer under the high-temperature and high-humidity conditions is present. It is presumed that the adhesive layer is easily removed after curing when the temperature returns to normal temperature and humidity, and as a result, whitening of the adhesive layer after curing is suppressed. Therefore, the cured pressure-sensitive adhesive layer is also excellent in moisture-heat whitening resistance.

Here, in order to improve the moisture-heat whitening resistance of the pressure-sensitive adhesive, a hydroxyl group-containing monomer having a hydroxyl group in the molecule as a constituent monomer of the (meth) acrylic acid ester polymer (A) exceeds the amount that contributes to cross-linking. There is also a method of using a large amount. However, in this case, the high polarity of the hydroxyl group-containing monomer-derived component increases the dielectric constant of the obtained pressure-sensitive adhesive. On the other hand, since N-vinylcarboxylic acid amide has a low polarity, it does not improve the dielectric constant while improving the moisture-heat bleaching resistance of the obtained pressure-sensitive adhesive. Further, the cured pressure-sensitive adhesive layer containing the cured product of the active energy ray-curable component (C) tends to have a lower dielectric constant than the pressure-sensitive adhesive layer containing no cured product. For these reasons, the post-curing pressure-sensitive adhesive layer has a low dielectric constant. Therefore, it is possible to effectively suppress the malfunction of the touch panel due to the dielectric constant of the adhesive layer after curing, and it is possible to improve the responsiveness of the touch panel.

1. 1. Each component (1) (meth) acrylic acid ester polymer (A)
The (meth) acrylic acid ester polymer (A) in the present embodiment contains N-vinylcarboxylic acid amide as a monomer unit constituting the polymer, and preferably further (meth) acrylic acid alkyl ester and a molecule. It contains a reactive functional group-containing monomer having a reactive functional group inside.

As described above, the pressure-sensitive adhesive obtained by the (meth) acrylic acid ester polymer (A) containing N-vinylcarboxylic acid amide as the monomer unit constituting the polymer has blister resistance and moisture resistance. It has excellent thermal whitening properties and has a low dielectric constant.

Examples of the N-vinylcarboxylic acid amide include N-vinylformamide, N-vinylacetamide, N-vinyl-N-methylacetamide, N-vinyl-N-methylformamide, N-vinyl-N-ethylformamide, and N-. Examples thereof include vinyl-N-ethylacetamide, N-methyl-N-vinylformamide, N-methyl-N-vinylacetamide and the like. Among the above, N-vinylacetamide is preferable from the viewpoint of blister resistance, moisture 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 N-vinylcarboxylic acid amide in an amount of 0.5% by mass or more, particularly 1% by mass or more, as a monomer unit constituting the polymer. It is preferably contained in an amount of 2% by mass or more. Further, the (meth) acrylic acid ester polymer (A) preferably contains N-vinylcarboxylic acid amide in an amount of 15% by mass or less, and particularly 10% by mass or less, as a monomer unit constituting the polymer. It is preferably contained in an amount of 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 blister resistance and moisture heat whitening resistance are further excellent in the cured pressure-sensitive adhesive layer. Further, the dielectric constant of the obtained pressure-sensitive adhesive, and thus the pressure-sensitive adhesive layer after curing, can be effectively suppressed to a low level.

The (meth) acrylic acid ester polymer (A) in the present embodiment preferably contains a (meth) acrylic acid alkyl ester as a monomer unit constituting the polymer, thereby exhibiting good adhesiveness. can do. The alkyl group may be linear or branched chain, or may have a cyclic structure.

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

Among the above, the (meth) acrylic acid alkyl ester is preferably a (meth) acrylic acid alkyl ester having an alkyl group having 5 to 20 carbon atoms. As described above, the (meth) acrylic acid alkyl ester having a large number of carbon atoms has high hydrophobicity, and the dielectric constant of the obtained pressure-sensitive adhesive can be lowered. As the (meth) acrylic acid alkyl ester having an alkyl group having 5 to 20 carbon atoms, 2-ethylhexyl (meth) acrylic acid, isooctyl (meth) acrylic acid, isobornyl (meth) acrylic acid and the like are preferable, and particularly adhesive and adhesive. 2-Ethylhexyl (meth) acrylate, which has high hydrophobicity, is preferable.

The (meth) acrylic acid ester polymer (A) preferably contains (meth) acrylic acid alkyl ester in an amount of 40% by mass or more, and more preferably 50% by mass or more, as a monomer unit constituting the polymer. It is preferable to contain 55% by mass or more, and further 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 adhesiveness. Further, the (meth) acrylic acid ester polymer (A) preferably contains 90% by mass or less of the (meth) acrylic acid alkyl ester as a monomer unit constituting the polymer, and particularly contains 85% by mass or less. It is preferably contained in an amount of 80% by mass or less. By adjusting the amount of 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).

When the (meth) acrylic acid alkyl ester having 5 to 20 carbon atoms of the alkyl group is contained, the carbon number of the alkyl group in the (meth) acrylic acid alkyl ester having 1 to 20 carbon atoms of the alkyl group is included. The content ratio of the (meth) acrylic acid alkyl ester having a value of 5 to 20 is preferably 50% by mass or more, particularly preferably 70% by mass or more, and further preferably 85% by mass or more as the lower limit value. Is preferable. Thereby, the dielectric constant of the obtained pressure-sensitive adhesive can be effectively lowered. 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 particularly limited. However, 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 (soft monomer) having a glass transition temperature (Tg) of 0 ° C. or less as a homopolymer. It is also preferable to use it in combination with a monomer). This is because the blister resistance and the step followability 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 further preferably 80 ° C. or higher. The glass transition temperature (Tg) is preferably 300 ° C. or lower, particularly preferably 200 ° C. or lower, and further preferably 130 ° C. or lower.

Examples of the hard monomer include methyl acrylate (Tg10 ° C.), methyl methacrylate (Tg105 ° C.), isobornyl acrylate (Tg94 ° C.), isobornyl methacrylate (Tg180 ° C.), adamantyl acrylate (Tg115 ° C.), and methacrylic acid. Adamantane (Tg 141 ° C.) and the like can be mentioned. These may be used alone or in combination of two or more.

Among the above 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. Methyl acrylate and methyl methacrylate are more preferable in consideration of adhesiveness.

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 further preferably −60 ° C. or lower. The glass transition temperature (Tg) is preferably −100 ° C. or higher, particularly preferably −90 ° C. or higher, and further preferably −80 ° C. or higher.

Preferred examples of the soft monomer include acrylic acid alkyl esters having a linear or branched alkyl group having 2 to 12 carbon atoms. For example, 2-ethylhexyl acrylate (Tg-70 ° C.), n-butyl acrylate (Tg-54 ° C.) and the like can be mentioned, 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.

Further, as the (meth) acrylic acid alkyl ester, it is also preferable that at least a part of the (meth) acrylic acid alkyl ester is a monomer having an alicyclic structure as an alkyl group (alicyclic structure-containing monomer). Since the alicyclic structure-containing monomer is bulky, it is presumed that the presence of the monomer in the polymer widens the distance between the polymers, and the obtained adhesive can be made excellent in flexibility. .. As a result, the adhesive becomes more excellent in step followability.

The alicyclic structure carbon ring in the alicyclic structure-containing monomer may have a saturated structure or may have an unsaturated bond as a part. Further, the alicyclic structure may be a monocyclic alicyclic structure or a polycyclic alicyclic structure such as two rings or three rings. From the viewpoint of making the distance between the obtained (meth) acrylic acid ester polymers (A) appropriate and imparting high stress relaxation property to the pressure-sensitive adhesive, the alicyclic structure is a polycyclic alicyclic structure. Polycyclic structure) is preferable. Further, in consideration of the compatibility between the (meth) acrylic acid ester polymer (A) and other components, the polycyclic structure is particularly preferably bicyclic to tetracyclic. Further, from the viewpoint of imparting stress relaxation property as described above, the number of carbon atoms in the alicyclic structure (referring to the total number of carbon atoms in the portion forming the ring, and when a plurality of rings exist independently) , 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 from the viewpoint of compatibility as described above, it is preferably 15 or less, and particularly preferably 10 or less.

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, dicyclopentenyloxyethyl (meth) acrylate, etc., among others, dicyclopenta (meth) acrylate, which exhibits better step followability and blister resistance under high temperature and high humidity conditions. Nyl (carbon number of alicyclic structure: 10), adamantyl (meth) acrylate (carbon number of carbon number of alicyclic structure: 10) or isobornyl (meth) acrylate (carbon number of carbon number of alicyclic structure: 7) is preferable. In particular, isobornyl (meth) acrylate is preferable. 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 of the alkyl group. The proportion of the contained monomer is preferably 1% by mass or more, particularly preferably 5% by mass or more, and further preferably 10% by mass or more. The proportion 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. The obtained adhesive has more excellent step-following property, and also sufficiently exhibits excellent adhesive force to the transparent conductive film and plastic.

The (meth) acrylic acid ester polymer (A) in the present embodiment preferably contains a reactive functional group-containing monomer as a monomer unit constituting the polymer. In this case, when the adhesive composition P is crosslinked (thermally crosslinked), the reaction between the reactive functional group derived from the reactive functional group-containing monomer in the (meth) acrylic acid ester polymer (A) and the crosslinking agent (B). It reacts with the sex functional groups to form a three-dimensional network structure as a crosslinked structure. As a result, the obtained adhesive has a high cohesive force, and is excellent in blister resistance and step followability under high temperature and high humidity conditions.

Examples of the reactive functional group-containing monomer include a monomer having a hydroxyl group in the molecule (hydroxyl-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). (Containing monomer) and the like are preferably mentioned. Among these, a hydroxyl group-containing monomer having excellent reactivity with the cross-linking agent (B) and having 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, and (meth). ) Hydroxyalkyl esters of (meth) acrylic acid such as 3-hydroxybutyl acrylate and 4-hydroxybutyl (meth) acrylic acid can be mentioned. Of these, 2-hydroxyethyl (meth) acrylate and 4-hydroxybutyl (meth) acrylate are particularly preferable from the viewpoint of reactivity with the cross-linking agent (B) and copolymerizability with other monomers. 2-Hydroxyethyl acrylate 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. Of these, acrylic acid is preferable from the viewpoint of reactivity with the cross-linking agent (B) and copolymerizability with other monomers. These may be used alone or in combination of two or more.

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

The (meth) acrylic acid ester polymer (A) preferably contains a reactive functional group-containing monomer in an amount of 5% by mass or more, particularly 10% by mass or more, as a monomer unit constituting the polymer. It is preferable, and it is preferable that the content is 15% by mass or more. Further, the (meth) acrylic acid ester polymer (A) preferably contains a reactive functional group-containing monomer in an amount of 30% by mass or less, and 28% by mass or less, as a monomer unit constituting the polymer. Is more preferable, and it is particularly preferable to contain 25% by mass or less, and further 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 crosslinked structure is formed in the obtained pressure-sensitive adhesive, and blister resistance and high temperature and high humidity conditions are obtained. An excellent adhesive can be obtained due to the step followability underneath. Further, particularly 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, and by extension, the pressure-sensitive adhesive layer after curing is suppressed by the action of the 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, since the carboxy group-containing monomer is not contained, a transparent conductive film such as tin-doped indium oxide (ITO) or a metal film, which causes a problem due to the acid, is attached to the adhesive. Even if it exists, it is possible to suppress those defects (corrosion, change in resistance value, etc.) due to acid.

Here, "not containing a carboxy group-containing monomer" means that the carboxy group-containing monomer is substantially not contained, and in addition to containing no carboxy group-containing monomer, a transparent conductive film using a carboxyl group, a metal wiring, or the like. It is permissible to contain a carboxy group-containing monomer to the extent that the corrosion of the above does not occur. Specifically, in the (meth) acrylic acid ester polymer (A), the carboxy group-containing monomer is contained in an amount of 0.1% by mass or less, preferably 0.01% by mass or less, more preferably 0.001 as a monomer unit. It is permissible to contain it in an amount of mass% or less.

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 to the N-vinylcarboxylic acid amide is 95: 5 to 50: It is preferably 50, particularly 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, moisture heat whitening resistance and dielectric constant are achieved in a well-balanced manner.

Further, 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 allowing a monomer having a nitrogen-containing heterocycle to be present in the polymer as a constituent unit, a predetermined polarity is imparted to the pressure-sensitive adhesive, and the adhesive has an affinity for an adherend having a certain degree of polarity such as glass. It can be excellent.

Examples of the monomer having a nitrogen-containing heterocycle include N- (meth) acryloyl morpholine, N-vinyl-2-pyrrolidone, N- (meth) acryloyl pyrrolidone, N- (meth) acryloyl piperidine, and N- (meth) acryloyl. Pyrrolidine, N- (meth) acryloyl azylidine, aziridinyl ethyl (meth) acrylate, 2-vinylpyridine, 4-vinylpyridine, 2-vinylpyrazine, 1-vinylimidazole, N-vinylcarbazole, N-vinylphthalimide, etc. Among them, N- (meth) acryloylmorpholin, which exhibits more excellent adhesive strength, is preferable, and N-acryloylmorpholin 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 of a monomer having a nitrogen-containing heterocycle as a monomer unit constituting the polymer, and particularly contains 1% by mass or more. It is preferable, and more preferably, it is contained in an amount of 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 heterocycle as a monomer unit constituting the polymer, and particularly contains 15% by mass or less. It is preferably contained in an amount of 8% by mass or less. When the content of the monomer having a nitrogen-containing heterocycle is within the above range, the obtained pressure-sensitive adhesive can sufficiently exert excellent adhesive strength to glass.

If desired, the (meth) acrylic acid ester polymer (A) may contain another monomer as a monomer unit constituting the polymer. As the other monomer, a monomer containing no reactive functional group is preferable.

Examples of the reactive functional group-free monomer include (meth) acrylic acid alkoxyalkyl ester 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. Since it is a linear polymer, entanglement of molecular chains is likely to occur, and improvement in cohesive force can be expected, so that a pressure-sensitive adhesive having better blister resistance can be obtained.

Further, the (meth) acrylic acid ester polymer (A) is preferably a solution polymer obtained by a solution polymerization method. Since it is a solution polymer, a high molecular weight polymer can be easily obtained, and an improvement in cohesive force can be expected, so that a pressure-sensitive 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, particularly preferably 300,000 or more, and further preferably 400,000 or more as the lower limit value. When the lower limit of the weight average molecular weight of the (meth) acrylic acid ester polymer (A) is at least the above, the blister resistance of the obtained pressure-sensitive adhesive becomes more excellent.

The weight average molecular weight of the (meth) acrylic acid ester polymer (A) is preferably 2 million or less, particularly preferably 1.5 million or less, and further preferably 1 million or less as an upper limit value. preferable. When the upper limit of the weight average molecular weight of the (meth) acrylic acid ester polymer (A) is not more than the above, the step-following property of the obtained pressure-sensitive adhesive becomes more excellent. The weight average molecular weight in the present specification is a standard polystyrene-equivalent value measured by a gel permeation chromatography (GPC) method.

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

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 60% by mass or more, as a lower limit value. Is preferable, and more preferably 70% by mass or more. When the lower limit of the content of the (meth) acrylic acid ester polymer (A) is as described above, the adhesive strength of the obtained pressure-sensitive adhesive becomes better. The content of the (meth) acrylic acid ester polymer (A) is preferably 98% by mass or less, particularly preferably 97% by mass or less, and further preferably 96% by mass or less, as an upper limit value. It is preferable to have. By setting the upper limit of the content of the (meth) acrylic acid ester polymer (A) as described above, the contents of the cross-linking agent (B) and the active energy ray-curable component (C) are ensured, and the blister resistance and blister resistance are assured. The step followability under high temperature and high humidity conditions becomes more excellent.

(2) Crosslinking agent (B)
The cross-linking agent (B) cross-links 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 obtained adhesive is improved, and the blister resistance and the step followability under high temperature and high humidity conditions are further improved.

The cross-linking agent (B) may be any one that reacts with the reactive functional group of the (meth) acrylic acid ester polymer (A), and is, for example, an isocyanate-based cross-linking agent, an epoxy-based cross-linking agent, or an amine-based cross-linking agent. Agents, melamine-based cross-linking agents, aziridine-based cross-linking agents, hydrazine-based cross-linking agents, aldehyde-based cross-linking agents, oxazoline-based cross-linking agents, metal alkoxide-based cross-linking agents, metal chelate-based cross-linking agents, metal salt-based cross-linking agents, ammonium salt-based cross-linking agents. And so on. 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 cross-linking agent having excellent reactivity with the hydroxyl group, and (meth) acrylic acid. When the reactive functional group of the ester polymer (A) is a carboxy group, it is preferable to use an epoxy-based cross-linking agent having excellent reactivity with the carboxy group. The cross-linking agent (B) may be used alone or in combination of two or more.

The isocyanate-based cross-linking 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 diisocyanates, and alicyclic polyisocyanates such as hydrogenated diphenylmethane diisocyanate. , And their biurets, isocyanurates, and adducts, which are reactants with low molecular weight active hydrogen-containing compounds such as ethylene glycol, propylene glycol, neopentyl glycol, trimethylolpropane, and castor oil. Of these, trimethylolpropane-modified aromatic polyisocyanates, 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 cross-linking agent include 1,3-bis (N, N-diglycidyl aminomethyl) cyclohexane, N, N, N', N'-tetraglycidyl-m-xylylenediamine, and ethylene glycol diglycidyl ether. , 1,6-Hexanediol diglycidyl ether, trimethylpropan diglycidyl ether, diglycidyl aniline, diglycidyl amine and the like. Of these, 1,3-bis (N, N-diglycidylaminomethyl) cyclohexane is preferable from the viewpoint of reactivity with a carboxy group.

The content of the cross-linking agent (B) in the adhesive composition P is preferably 0.01 part by mass or more with respect to 100 parts by mass of the (meth) acrylic acid ester polymer (A), and in particular, 0. It is preferably 05 parts by mass or more, and more preferably 0.1 parts by mass or more. 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 within the above range, the degree of cross-linking becomes appropriate, and the obtained adhesive has more excellent blister resistance and step followability under high temperature and high humidity conditions. Become.

(3) Active energy ray-curable component (C)
The pressure-sensitive adhesive obtained by cross-linking (thermally cross-linking) the pressure-sensitive adhesive composition P by containing the active energy ray-curable component (C) in the pressure-sensitive adhesive composition P becomes an active energy ray-curable pressure-sensitive adhesive. .. In this adhesive, the active energy ray-curable components (C) are polymerized with each other by curing by irradiation with active energy rays after the adherend is attached, and the polymerized active energy ray-curable components (C) are (meth) acrylics. It is presumed that it is entwined with the crosslinked structure (three-dimensional network structure) of the acid ester polymer (A). Since the pressure-sensitive adhesive having such a high-order structure has high cohesive force and high film strength, it is excellent in step followability and blister resistance under high temperature and high humidity conditions. Further, the cured pressure-sensitive adhesive layer containing the cured product of the active energy ray-curable component (C) tends to have a lower dielectric constant than the pressure-sensitive adhesive layer containing no cured product. That is, the active energy ray-curable component (C) also contributes to lowering the dielectric constant of the obtained post-curing pressure-sensitive adhesive layer.

The active energy ray-curable component (C) is not particularly limited as long as it is a component that is cured by irradiation with active energy rays and obtains the above effects, and may be any monomer, oligomer or polymer, and they may be used. May be a mixture of. Among them, a polyfunctional acrylate-based monomer having excellent compatibility with the (meth) acrylic acid ester polymer (A) and the like can be preferably mentioned.

Examples of the polyfunctional acrylate-based monomer include 1,4-butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, and polyethylene glycol di (meth) acrylate. , Neopentyl glycol adipate di (meth) acrylate, neopentyl glycol di (meth) acrylate of hydroxypivalate, dicyclopentanyl di (meth) acrylate, caprolactone-modified dicyclopentenyl di (meth) acrylate, ethylene oxide-modified di (meth) acrylate 2 such as meta) acrylate, di (acryloxyethyl) isocyanurate, allylated cyclohexyldi (meth) acrylate, ethoxylated bisphenol A diacrylate, 9,9-bis [4- (2-acryloyloxyethoxy) phenyl] fluorene, etc. Functional type: Trimethylol propanetri (meth) acrylate, dipentaerythritol tri (meth) acrylate, propionic acid-modified dipentaerythritol tri (meth) acrylate, pentaerythritol tri (meth) acrylate, propylene oxide-modified trimethylol propanetri (meth) acrylate ) Acrylate, trifunctional forms such as tris (acryloxyethyl) isocyanurate, ε-caprolactone-modified tris- (2- (meth) acryloxyethyl) isocyanurate; diglycerin tetra (meth) acrylate, pentaerythritol tetra (meth) 4-functional type such as acrylate; 5-functional type such as propionic acid-modified dipentaerythritol penta (meth) acrylate; 6-functional type such as dipentaerythritol hexa (meth) acrylate and caprolactone-modified dipentaerythritol hexa (meth) acrylate Can be mentioned. Among the above, di (acryloxyethyl) isocyanurate, tris (acryloxyethyl) isocyanurate, ε-caprolactone-modified tris from the viewpoint of step followability and blister resistance of the obtained adhesive under high temperature and high humidity conditions. -A polyfunctional acrylate-based monomer having an isocyanurate structure in the molecule such as 2- (2- (meth) acryloxyethyl) isocyanurate is preferable, and a polyfunctional acrylate having a trifunctionality or higher and having an isocyanurate structure in the molecule is preferable. Monomers are more preferred, and ε-caprolactone-modified tris- (2- (meth) acryloxiethyl) isocyanurate is particularly preferred. These may be used individually by 1 type, and may be used in combination of 2 or more type. Further, from the viewpoint of compatibility with the (meth) acrylic acid ester polymer (A), the polyfunctional acrylate-based monomer preferably has a molecular weight of less than 1000.

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

The weight average molecular weight of the acrylate-based oligomer is preferably 50,000 or less, particularly preferably 1,000 to 50,000, and further preferably 3,000 to 40,000. These acrylate-based oligomers may be used alone or in combination of two or more.

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

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

As the active energy ray-curable component (C), one type may be selected from the above-mentioned polyfunctional acrylate-based monomer, acrylate-based oligomer and adduct acrylate-based polymer, or two or more types may be used in combination. It can also be used in combination with other active energy ray-curable components.

The content of the active energy ray-curable component (C) in the adhesive composition P improves the cohesive force of the obtained adhesive and makes it excellent in blister resistance and step followability under high temperature and high humidity conditions. From the viewpoint, the lower limit value is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and 5 parts by mass or more with respect to 100 parts by mass of the (meth) acrylic acid ester polymer (A). It is particularly preferable to have. On the other hand, the content may be 50 parts by mass or less as an upper limit from the viewpoint of preventing the active energy ray-curable component (C) from phase-separating from the (meth) acrylic acid ester polymer (A). It is more preferably 20 parts by mass or less, and further preferably 10 parts by mass or less from the viewpoint of improving the initial step followability.

(4) Photopolymerization initiator (D)
When ultraviolet rays are used as the active energy rays used to cure the active energy ray-curable pressure-sensitive adhesive, the pressure-sensitive adhesive composition P preferably further contains a photopolymerization initiator (D). By containing the photopolymerization initiator (D) in this way, the active energy ray-curable component (C) can be efficiently polymerized, and the polymerization curing time and the irradiation amount of the active energy rays can be reduced. can.

Examples of such a photopolymerization initiator (D) include benzoine, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin-n-butyl ether, benzoin isobutyl ether, acetophenone, dimethylaminoacetophenone, and 2,2-dimethoxy. -2-phenylacetophenone, 2,2-diethoxy-2-phenylacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-hydroxycyclohexylphenylketone, 2-methyl-1- [4- (Methylthio) phenyl] -2-morpholino-propan-1-one, 4- (2-hydroxyethoxy) phenyl-2- (hydroxy-2-propyl) ketone, benzophenone, p-phenylbenzophenone, 4,4'-diethylamino Benzophenone, Dichlorobenzophenone, 2-Methylanthraquinone, 2-Ethylanthraquinone, 2-Turrary-butylanthraquinone, 2-Aminoanthraquinone, 2-Methylthioxanthone, 2-Ethylthioxanthone, 2-Chlorothioxanthone, 2,4-dimethylthioxanthone, 2 , 4-Diethylthioxanthone, benzyl dimethyl ketal, acetophenone dimethyl ketal, p-dimethylaminobenzoic acid ester, oligo [2-hydroxy-2-methyl-1 [4- (1-methylvinyl) phenyl] propanone], 2,4 , 6-trimethylbenzoyl-diphenyl-phosphine oxide and the like. These may be used alone or in combination of two or more.

The content of the photopolymerization initiator (D) in the adhesive composition P is preferably 0.1 part by mass or more as a lower limit value with respect to 100 parts by mass of the active energy ray-curable component (C). In particular, it is preferably 1 part by mass or more. The upper limit is preferably 30 parts by mass or less, and particularly preferably 15 parts by mass or less.

(5) Various Additives The tacky composition P contains various additives usually used for acrylic pressure-sensitive adhesives, such as silane coupling agents, ultraviolet absorbers, antistatic agents, tackifiers, and oxidations, if desired. Inhibitors, light stabilizers, softeners, fillers, refractive index adjusters and the like can be added. The polymerization solvent and the diluting solvent described later are not included in the additives constituting the adhesive composition P.

Here, when the adhesive composition P contains a silane coupling agent, the obtained adhesive has improved adhesion to a glass member or a plastic plate. As a result, the obtained adhesive has better blister resistance.

The silane coupling agent is 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. preferable.

Examples of such a silane coupling agent include polymerizable unsaturated group-containing silicon compounds such as vinyltrimethoxysilane, vinyltriethoxysilane, and methacrypropyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, and 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 compounds such as 3-aminopropyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropylmethyldimethoxysilane, 3-Chloropropyltrimethoxysilane, 3-isocyanuspropyltriethoxysilane, or at least one of these, and alkyl group-containing silicon compounds such as methyltriethoxysilane, ethyltriethoxysilane, methyltrimethoxysilane, and ethyltrimethoxysilane. Examples thereof include a condensate of. 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 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 further preferably 0.1 parts by mass or more. 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 The adhesive composition P produced a (meth) acrylic acid ester polymer (A), and the obtained (meth) acrylic acid ester polymer (A) and an active energy ray-curable component. It can be produced by mixing (C), optionally, a cross-linking agent (B), a photopolymerization initiator (D), and an additive.

The (meth) acrylic acid ester polymer (A) can be produced by polymerizing a mixture of monomers constituting the polymer by a usual radical polymerization method. The polymerization of the (meth) acrylic acid ester polymer (A) 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, and two or more of them may be used in combination.

Examples of the polymerization initiator include azo compounds and organic peroxides, and two or more of them may be used in combination. Examples of the azo compound include 2,2'-azobisisobutyronitrile, 2,2'-azobis (2-methylbutyronitrile), 1,1'-azobis (cyclohexane1-carbonitrile), and 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 the organic peroxide include benzoyl peroxide, t-butyl perbenzoate, cumene hydroperoxide, diisopropyl peroxydicarbonate, di-n-propyl peroxydicarbonate, and di (2-ethoxyethyl) peroxy. Examples thereof include dicarbonate, t-butyl peroxyneodecanoate, t-butyl peroxyvivarate, (3,5,5-trimethylhexanoyl) peroxide, dipropionyl peroxide, diacetyl peroxide and the like.

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

Once the (meth) acrylic acid ester polymer (A) is obtained, the solution of the (meth) acrylic acid ester polymer (A) is mixed with the active energy ray-curable component (C) and, if desired, the cross-linking agent (B). , Photopolymerization initiator (D), additive, and diluting solvent are added and mixed thoroughly to obtain a tacky composition P (coating solution) diluted with the solvent. If any of the above components is in the form of a solid, or if precipitation occurs when the component is mixed with another component in an undiluted state, the component is used alone as a diluting solvent in advance. It may be dissolved or diluted and then mixed with other ingredients.

Examples of the diluting solvent include aliphatic hydrocarbons such as hexane, heptane and cyclohexane, aromatic hydrocarbons such as toluene and xylene, halogenated hydrocarbons such as methylene chloride and ethylene chloride, methanol, ethanol, propanol and 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 and viscosity of the coating solution prepared in this manner may be any range as long as it can be coated, and is not particularly limited and can be appropriately selected depending on the situation. For example, the adhesive composition P is diluted so as to have a concentration of 10 to 60% by mass. It should be noted that the addition of a diluting solvent or the like is not a necessary condition when obtaining the coating solution, and the diluting solvent may not be added as long as the adhesive composition P has a coatable viscosity or the like. In this case, the adhesive composition P becomes a coating solution using the polymerization solvent of the (meth) acrylic acid ester polymer (A) as it is as a diluting solvent.

[Adhesive]
The pressure-sensitive adhesive according to the present embodiment is an active energy ray-curable pressure-sensitive adhesive (a pressure-sensitive adhesive before active energy ray-curing) obtained by cross-linking (thermally cross-linking) the pressure-sensitive adhesive composition P. Crosslinking of the adhesive composition P can usually be carried out by heat treatment. In addition, this heat treatment can also serve as a drying treatment when volatilizing the diluting solvent or the like from the coating film of the adhesive composition P applied to the desired object.

The heating temperature of the heat treatment is preferably 50 to 150 ° C., particularly preferably 70 to 120 ° C. The heating time is preferably 10 seconds to 10 minutes, and 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 required, an adhesive is formed after the curing period has elapsed, and when the curing period is not required, after the heat treatment is completed.

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

The pressure-sensitive adhesive according to this embodiment preferably has the following physical properties.
(1) Gel fraction (before irradiation with active energy rays)
The gel fraction of the pressure-sensitive adhesive (before irradiation with active energy rays) according to the present embodiment is preferably 30% or more, more preferably 40% or more, and particularly preferably 50% or more as a lower limit value. preferable. When the lower limit of the gel fraction of the adhesive before irradiation with active energy rays is the above, the cohesive force of the adhesive becomes high, and the blister resistance after curing by irradiation with active energy rays and the step under high temperature and high humidity conditions. The followability becomes better. The gel fraction of the pressure-sensitive adhesive before irradiation with active energy rays is preferably 90% or less, particularly preferably 85% or less, and further preferably 80% or less as an upper limit value. When the upper limit value of the gel fraction of the pressure-sensitive adhesive before irradiation with the active energy ray is the above, the pressure-sensitive adhesive does not become too hard, and the initial step followability becomes more excellent. Here, the method for measuring the gel fraction of the pressure-sensitive adhesive (before irradiation with active energy rays) is as shown in a test example described later.

(2) Moisture-heat bleaching resistance The moisture-heat bleaching resistance of the pressure-sensitive adhesive according to the present embodiment can be quantitatively evaluated by the haze value. Specifically, in 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, the pressure-sensitive adhesive layer is irradiated with active energy rays. After being cured by The haze value increase after subtracting the haze value (%) before the durability test from the haze value (%) when stored in a damp environment for 24 hours (value measured according to JIS K7136: 2000; the same applies hereinafter) is less than 5 points. It is preferably less than 3 points, more preferably less than 1 point. When the haze value increase is as described above, it can be said that the haze value increase is small even after being placed under moist heat conditions, and the whitening of the adhesive is suppressed.

As described above, in the laminate in which the adhesive layer (adhesive layer after curing) is sandwiched between the glass plate and the acrylic resin plate, the heat and humidity are compared with the laminate in which the adhesive layer is sandwiched between the two glass plates. Under the conditions, the water that has permeated the acrylic resin plate tends to condense in the laminated body, so that the adhesive layer tends to whiten. However, according to the pressure-sensitive adhesive according to the present embodiment, excellent moisture-heat bleaching resistance is exhibited even in the above-mentioned laminated body.

[Adhesive sheet]
The pressure-sensitive adhesive sheet according to the present embodiment is, at least, a pressure-sensitive adhesive sheet having 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. ..

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 the embodiment is in contact with the two release sheets 12a and 12b and the release surfaces of the two release sheets 12a and 12b. , 12b and the pressure-sensitive adhesive layer 11 sandwiched between the two. The peeling surface of the release sheet in the present specification means a surface of the release sheet that has peelability, and includes both a surface that has been peeled and a surface that exhibits peelability without peeling. ..

1. 1. Each member (1) pressure-sensitive adhesive layer The pressure-sensitive adhesive layer 11 is composed of the above-mentioned pressure-sensitive adhesive, that is, is composed of an active energy ray-curable pressure-sensitive adhesive formed by cross-linking (thermally cross-linking) the pressure-sensitive adhesive composition P. ..

The pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer 11 has a cross-linked structure composed of a (meth) acrylic acid ester polymer (A) and a cross-linking agent (B), and has an active energy ray-curable component (C) ( (Before curing) is contained, and if desired, a photopolymerization initiator (D) and an additive are further contained.

The thickness of the pressure-sensitive adhesive layer 11 (value measured according to JIS K7130) in the pressure-sensitive adhesive sheet 1 according to the present embodiment is preferably 10 μm or more, more preferably 25 μm or more, and particularly 50 μm as the lower limit value. The above is preferable. When the lower limit of the thickness of the pressure-sensitive adhesive layer 11 is the above, it is easy to exert a desired adhesive force, and it is possible to secure sufficient step-following property with respect to a normal step of the display body constituent member.

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 further preferably 150 μm or less as an upper limit value. When the upper limit of the thickness of the pressure-sensitive adhesive layer 11 is the above, the moisture-heat bleaching resistance becomes more excellent, and the excellent blister resistance is likely to be 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) Peeling Sheet The peeling sheets 12a and 12b protect the pressure-sensitive adhesive layer 11 until the time when the pressure-sensitive adhesive sheet 1 is used, and are peeled off when the pressure-sensitive adhesive sheet 1 (the pressure-sensitive adhesive layer 11) is used. In the pressure-sensitive adhesive sheet 1 according to the present embodiment, one or both of the release sheets 12a and 12b are not always necessary.

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. Telephthalate 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. In addition, these crosslinked films are also used. Further, these laminated films may be used.

It is preferable that the peeling surfaces (particularly the surfaces in contact with the pressure-sensitive adhesive layer 11) of the peeling sheets 12a and 12b are subjected to a peeling treatment. Examples of the release agent used in the release treatment include alkyd-based, silicone-based, fluorine-based, unsaturated polyester-based, polyolefin-based, and wax-based release agents. Of 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, and particularly 1% or less. Is preferable, and more preferably 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 displays). The haze value of the pressure-sensitive adhesive layer does not change even after curing by irradiation with active energy rays. The haze value in the present specification is a value measured according to JIS K7136: 2000.

(2) Transparent hue b *
The transparent hue b * defined by the CIE1976L * 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 particularly -1. It is preferably .5 to 1.5, and more preferably -1.0 to 1.0. When the transparent hue b * of the pressure-sensitive adhesive layer 11 is in the above range, the pressure-sensitive adhesive layer 11 is less colored and is particularly suitable for a display. In the present embodiment, the (meth) acrylic acid ester polymer (A) achieves the above-mentioned transmission hue b * by containing an appropriate amount of N-vinylcarboxylic acid amide as a monomer unit constituting the polymer. It is possible. The transmitted hue b * of the pressure-sensitive adhesive layer does not change even after curing by irradiation with active energy rays. The method for measuring the transparent hue b * in the present specification is as shown in a test example described later.

(3) Adhesive strength (after irradiation with active energy rays)
When the pressure-sensitive adhesive layer 11 of the pressure-sensitive adhesive sheet 1 according to the present embodiment is cured by irradiation with active energy rays to form a cured pressure-sensitive adhesive layer, the adhesive strength of the pressure-sensitive adhesive sheet to soda lime glass is 5 N / as a lower limit. It is preferably 25 mm or more, particularly preferably 10 N / 25 mm or more, and further preferably 15 N / 25 mm or more. When the adhesive strength of the adhesive sheet 1 is 5 N / 25 mm or more, the blister resistance and the step followability under high temperature and high humidity conditions become more excellent. On the other hand, the upper limit of the adhesive strength is not particularly limited, but is usually preferably 50 N / 25 mm or less, more preferably 45 N / 25 mm or less, and particularly preferably 40 N / 25 mm or less.

The above adhesive strength basically refers to the adhesive strength measured by the 180-degree peeling method according to JIS Z0237: 2009, but the measurement sample has a width of 25 mm and a length of 100 mm, and the measurement sample is attached to the adherend. After pressurizing at 0.5 MPa and 50 ° C. for 20 minutes, the pressure-sensitive adhesive layer was cured by irradiation with active energy rays to form a cured pressure-sensitive adhesive layer, and then under the conditions of normal pressure, 23 ° C. and 50% RH. After leaving it for 24 hours, the measurement shall be performed at a peeling speed of 300 mm / min.

3. 3. Production of Adhesive Sheet As an example of production of the adhesive sheet 1, the coating solution of the adhesive composition P is applied to the peeling surface of one of the release sheets 12a (or 12b) and heat-treated to perform the adhesive composition. After P is thermally crosslinked to form a coating layer, the peeling surface of the other release sheet 12b (or 12a) is superposed on the coating layer. When the curing period is required, the curing period is set, and when the curing period is not required, the coating layer becomes the adhesive layer 11 as it is. As a result, the adhesive sheet 1 is obtained. The conditions for heat treatment and curing are as described above.

As another production example of the pressure-sensitive adhesive sheet 1, the coating solution of the pressure-sensitive adhesive composition P is applied to the peel-off surface of one of the release sheets 12a, heat-treated to heat-crosslink the pressure-sensitive adhesive composition P, and then coated. A layer is formed to obtain a release sheet 12a with a coating layer. Further, the coating solution of the adhesive composition P is applied to the peeling surface of the other release sheet 12b, heat-treated to heat-crosslink the adhesive composition P to form a coating layer, and the coating layer is attached. To obtain the release sheet 12b of. Then, the release sheet 12a with the coating layer and the release sheet 12b with the coating layer are bonded so that both coating layers are in contact with each other. When the curing period is required, the curing period is set, and when the curing period is not required, the laminated coating layer becomes the pressure-sensitive adhesive layer 11. As a result, the adhesive sheet 1 is obtained. According to this production example, stable production is possible even when the pressure-sensitive adhesive layer 11 is thick.

As a method for 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 and the like can be used.

[Display body]
As shown in FIG. 2, the display body 2 according to the present embodiment has a first display body constituent member 21 (one display body constituent member) having a step on at least the surface on the side to be bonded, and a second display body constituent member 21 (one display body constituent member). A post-curing adhesive layer 11 that is located between the display body component 22 (another display body component) and attaches the first display body component 21 and the second display body component 22 to each other. 'And is configured. In the display body 2 according to the present embodiment, the first display body component 21 has a step on the surface on the adhesive layer 11'side after curing, and specifically, has a step due to the printing layer 3. doing.

The cured pressure-sensitive adhesive layer 11'in the display body 2 is obtained by curing the pressure-sensitive adhesive layer 11 of the pressure-sensitive adhesive sheet 1 described above by irradiation with energy rays. The pressure-sensitive adhesive constituting the cured pressure-sensitive adhesive layer 11'has a cross-linked structure composed of a (meth) acrylic acid ester polymer (A) and a cross-linking agent (B), and has an energy ray-curable component (C). ) Is contained, and if desired, a photopolymerization initiator (D) and an additive are further contained. The polymerized energy ray-curable component (C) is entwined with a crosslinked structure composed of a (meth) acrylic acid ester polymer (A) and a thermal crosslinking agent (B) to form a higher-order structure. Presumed.

The photopolymerization initiator (D) contained in the pressure-sensitive adhesive constituting the cured pressure-sensitive adhesive layer 11'is such that the photopolymerization initiator (D) contained in the pressure-sensitive adhesive composition P is irradiated with energy rays. It remains without cleaving. Therefore, the content thereof is not large, and is usually 0.0001% by mass or more and 0.1% by mass or less, preferably 0.0001% by mass or more and 0.01% by mass or less in the pressure-sensitive adhesive. ..

The cured pressure-sensitive adhesive layer 11'(the pressure-sensitive adhesive) preferably has the following physical properties.
(1) Gel fraction (after irradiation with active energy rays)
The gel fraction of the adhesive (after irradiation with active energy rays) of the adhesive layer 11'after curing is preferably 60% or more, particularly preferably 65% or more, and further 70% or more. Is preferable. The gel fraction of the adhesive of the adhesive layer 11'after curing is higher than the gel fraction of the adhesive of the adhesive layer 11 before the active energy ray curing due to the curing of the active energy ray-curable component (C). It gets higher. When the lower limit of the gel fraction of the adhesive after irradiation with active energy rays is the above, the step followability and blister resistance of the adhesive layer 11'after curing of the display body under high temperature and high humidity conditions are more excellent. It becomes a thing.

The gel fraction of the adhesive (after irradiation with active energy rays) of the adhesive layer 11'after curing is preferably 95% or less, particularly preferably 93% or less, and further 90% or less. Is preferable. When the upper limit of the gel fraction of the adhesive of the post-curing pressure-sensitive adhesive layer 11'is the above, it is possible to prevent the adhesive strength of the post-curing pressure-sensitive adhesive layer 11' from being lowered and the durability from being deteriorated. The method for measuring the gel fraction of the adhesive (after irradiation with active energy rays) of the adhesive layer 11'after curing is as shown in a test example described later.

(2) Step-following rate The cured adhesive layer 11's preferably has a step-following rate (%) represented by the following formula of 15% or more as a lower limit value, and more preferably 20% or more. In particular, it is preferably 25% or more, and more preferably 35% or more. The upper limit of the step follow-up rate is not particularly limited, but is usually preferably 80% or less, and particularly preferably 70% or less.
Step follow-up rate (%) = {(Height of step (μm) maintained in a buried state without air bubbles, floating, peeling, etc. after a predetermined durability test) / (Thickness of adhesive layer)} × 100
The test method for the step follow-up rate is as shown in a test example described later.

Since the step follow-up rate of the cured pressure-sensitive adhesive layer 11'is within the above range, the cured pressure-sensitive adhesive layer 11'is a display body constituent member (first display body constituent member 21) even after undergoing a durability test. It follows the step well and suppresses the occurrence of air bubbles, floating, peeling, etc. in the vicinity of the step, thereby suppressing the occurrence of light reflection loss.

(3) Dielectric constant The dielectric constant of the adhesive (after irradiation with active energy rays) of the adhesive layer 11'after curing at 1.0 MHz is preferably 6.0 or less as an upper limit value, and is particularly 5.8. It is preferably less than or equal to, and more preferably 5.5 or less. When the upper limit value of the dielectric constant is the above, it is possible to contribute to the suppression of the malfunction of the touch panel and the improvement of the responsiveness. If the post-curing pressure-sensitive adhesive layer 11'formed by using the (meth) acrylic acid ester polymer (A) having a component derived from N-vinylcarboxylic acid amide and the active energy ray-curable component (C), A low dielectric constant can be achieved as described above.

The lower limit of the dielectric constant of the adhesive (after irradiation with active energy rays) of the adhesive layer 11'after curing at 1.0 MHz is not particularly limited, but is usually preferably 3.5 or more, and particularly 3 It is preferably 8.8 or more, and more preferably 4.0 or more. Since the dielectric constant of the pressure-sensitive adhesive changes before and after irradiation with active energy rays, the dielectric constant after irradiation with active energy rays is important. The method for measuring the dielectric constant of the pressure-sensitive adhesive is as shown in a test example described later.

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. Further, the display body 2 may be a member constituting a part of them.

The first display body component 21 is preferably a protective panel made of a glass plate, a plastic plate, or the like, or a laminate containing them, and is particularly preferably a plastic plate. In this case, the print layer 3 is generally formed in a frame shape on the pressure-sensitive adhesive layer 11 side of the first display body constituent member 21.

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

The plastic plate is not particularly limited, and examples thereof include an acrylic resin 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.

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

The second display body component 22 is an optical member to be attached to the first display body component 21, a display body module (for example, a liquid crystal (LCD) module, a light emitting diode (LED) module, an organic electroluminescence (organic)). An EL) module or the like), an optical member as a part of the display body module, or a laminated body including the display body module is preferable.

Examples of the optical member include a shatterproof film, a polarizing plate (polarizing film), a polarizer, a retardation plate (phase difference film), a viewing angle compensation film, a brightness improving film, a contrast improving film, a liquid crystal polymer film, and a diffusion film. , Semi-transmissive reflective film, transparent conductive film and the like. Examples of the shatterproof film include a hard coat film in which a hard coat layer is formed on one side of the 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 print layer 3, that is, the lower limit of 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 the above, it is possible to sufficiently secure concealment such as making the electrical wiring invisible from the viewer side. The upper limit is preferably 50 μm or less, more preferably 35 μm or less, particularly preferably 25 μm or less, and even more preferably 20 μm or less. By setting the upper limit value as described above, it is possible to prevent deterioration of the step followability of the pressure-sensitive adhesive layer 11 with respect to the printing layer 3.

In order to manufacture the display body 2, as an example, one of the release sheets 12a of the pressure-sensitive adhesive sheet 1 is peeled off, and the exposed pressure-sensitive adhesive layer 11 of the pressure-sensitive adhesive sheet 1 is separated from the printing layer of the first display body component 21. It is affixed to the surface on the side where 3 exists. At this time, since the pressure-sensitive adhesive layer 11 is excellent in the initial step-following property, it is possible to prevent gaps and floating from occurring in the vicinity of the step due to the printing layer 3.

Next, the other release sheet 12b is peeled 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 component 22 are bonded to each other to obtain a laminated body. .. Further, 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.

Then, the pressure-sensitive adhesive layer 11 in the laminated body is irradiated with active energy rays. As a result, the energy ray-curable component (C) in the pressure-sensitive adhesive layer 11 is polymerized, and the pressure-sensitive adhesive layer 11 is cured to become the pressure-sensitive adhesive layer 11'after curing. The pressure-sensitive adhesive layer 11 is usually irradiated with energy rays through either the first display body component 21 or the second display body component 22, preferably the first display body as a protective panel. This is done through the component 21.

Here, the active energy ray refers to an electromagnetic wave or a charged particle beam having an energy quantum, and specific examples thereof include ultraviolet rays and electron beams. Among the active energy rays, ultraviolet rays, which are easy to handle, are particularly preferable.

The irradiation of ultraviolet rays can be performed by a high-pressure mercury lamp, a fusion H lamp, a xenon lamp or the like, and the irradiation amount of ultraviolet rays is preferably about ^{50 to 1000 mW / cm 2 in illuminance.} Further, the light quantity is preferably 50~10000mJ / cm ^2, more preferably 80~5000mJ / cm ^2, and particularly preferably 200~2000mJ / cm ^2. On the other hand, the irradiation of the electron beam can be performed by an electron beam accelerator or the like, and the irradiation amount of the electron beam is preferably about 10 to 1000 grad.

In the above display body 2, since the adhesive layer 11'after curing has excellent step followability even under high temperature and high humidity conditions, the display body 2 is under high temperature and high humidity conditions (for example, 85 ° C., 85% RH, 72 hours). ), Bubbles, floating, peeling, etc. are suppressed in the vicinity of the step.

Further, in the display body 2, since the adhesive layer 11'after curing has excellent blister resistance, the display body 2 is placed under high temperature and high humidity conditions (for example, 85 ° C., 85% RH, 72 hours). Even when outgas is generated from the first display body component 21 and / or the second display body component 22, air bubbles, floats, and float at the interface between the cured adhesive layer 11'and the display body components 21 and 22. The occurrence of blister such as peeling is suppressed.

Further, in the display body 2, since the adhesive layer 11'after curing is excellent in moisture and heat whitening resistance, the display body 2 is placed under high temperature and high humidity conditions (for example, 85 ° C., 85% RH, 120 hours). Even when the temperature is returned to normal temperature and humidity after being rubbed, whitening of the pressure-sensitive adhesive layer 11'after curing is suppressed. According to the display body 2 according to the present embodiment, in particular, 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. Even if there is, excellent moisture heat whitening resistance is exhibited.

Further, since the dielectric constant of the cured adhesive layer 11'is suppressed to a low level, even when the display body 2 is a touch panel, the touch panel malfunctions due to the dielectric constant of the cured adhesive layer 11'. Is effectively suppressed, and the responsiveness of the touch panel is good.

The embodiments described above are described for facilitating the 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, either one of the release sheets 12a and 12b in the adhesive sheet 1 may be omitted. Further, the first display body constituent member 21 may or may not have a step other than the print layer 3. Further, not only the first display body constituent member 21 but also the second display body constituent member 22 may have a step on the adhesive layer 11'side after curing.

Hereinafter, the present invention will be described in more detail with reference to Examples and the like, but the scope of the present invention is not limited to these Examples and the like.

[Example 1]
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-hydroxyacrylate. A (meth) acrylic acid ester polymer (A) was prepared by copolymerizing 15 parts by mass of ethyl by a solution polymerization method. 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 (solid content conversion value; the same applies hereinafter) of the (meth) acrylic acid ester polymer (A) obtained in the above step 1 and trimethylolpropane-modified bird as a cross-linking agent (B). 0.15 parts by mass of range isocyanate (manufactured by Toyochem Co., Ltd., product name "BHS8515") and 5 parts by mass of ε-caprolactone-modified tris- (2-acryloxyethyl) isocyanurate as an active energy ray-curable component (C). , 0.5 parts by mass of a mixture of benzophenone and 1-hydroxycyclohexylphenyl ketone as a photopolymerization initiator (D) in a 1: 1 mass ratio, and 3-glycidoxypropyltri as a silane coupling agent. A coating solution of the adhesive composition was obtained by mixing 0.30 parts by mass of methoxysilane (manufactured by Shin-Etsu Chemical Industry Co., Ltd., product name "KBM-403"), stirring thoroughly, and diluting with methyl ethyl ketone. ..

Here, Table 1 shows each formulation (solid content conversion value) of the adhesive composition when the (meth) acrylic acid ester polymer (A) is 100 parts by mass (solid content conversion value). Details of the abbreviations and the like shown in Table 1 are as follows.
[(Meta) acrylic acid ester polymer (A)]
2EHA: 2-ethylhexyl acrylate ACMO: 4-acryloylmorpholin 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 Toyochem, product name "BHS8515")
Epoxy type: 1,3-bis (N, N'-diglycidylaminomethyl) cyclohexane (manufactured by Mitsubishi Gas Chemical Company, product name "TETRAD-C")

3. 3. Manufacture of Adhesive Sheet A heavy release type release sheet (manufactured by Lintec Corporation, product name "SP-PET752150") in which one side of a polyethylene terephthalate film is peeled off with a silicone-based release agent from the coating solution of the adhesive composition obtained in step 2 above. ”) Was applied to the peeled surface with a knife coater. Then, the coating layer was heat-treated at 90 ° C. for 1 minute to form a coating layer.

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

Further, a heavy peeling type release sheet (manufactured by Lintec Corporation, product name "SP-PET752150") obtained by peeling one side of a polyethylene terephthalate film with a silicone-based release agent from the coating solution of the adhesive composition obtained in the above step 2. After applying with a knife coater to the peeled surface of the above, a coating layer (thickness: 25 μm) was formed by heat treatment at 90 ° C. for 1 minute. Similarly, a light peeling type release sheet (manufactured by Lintec Corporation, product name "SP-PET382120") obtained by peeling one side of a polyethylene terephthalate film with a silicone-based release agent from the coating solution of the adhesive composition obtained in the above step 2. ) Was coated with a knife coater and then heat-treated at 90 ° C. for 1 minute to form a coating layer (thickness: 25 μm).

Next, 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 are bonded together so that both coating layers are in contact with each other, and the temperature is 23 ° C. By curing for 7 days under the condition of 50% RH, a second pressure-sensitive adhesive sheet having a structure of a heavy-release type release sheet / adhesive layer (thickness: 50 μm) / light-release type release sheet was prepared.

The thickness of the pressure-sensitive adhesive layer is a value measured using a constant pressure thickness measuring device (manufactured by Teclock Co., Ltd., product name "PG-02") in accordance with JIS K7130.

[Examples 2 to 3 and Comparative Examples 1 to 5]
Type and ratio of each monomer constituting the (meth) acrylic acid ester polymer (A), weight average molecular weight (Mw) of the (meth) acrylic acid ester polymer (A), type and blending amount of the cross-linking agent (B). , The first and second adhesions in the same manner as in Example 1 except that the blending amount of the active energy ray-curable component (C) and the blending amount of the photopolymerization initiator (D) are changed as shown in Table 1. Manufactured the sheet.

Here, the above-mentioned weight average molecular weight (Mw) is a polystyrene-equivalent weight average molecular weight measured under the following conditions (GPC measurement) using gel permeation chromatography (GPC).
<Measurement conditions>
-GPC measuring device: HLC-8020 manufactured by Tosoh Corporation
-GPC column (passed in the following order): TSK guard volume HXL-H manufactured by Tosoh Corporation
TSK gel GMHXL (x2)
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 was weighed with a precision balance, and the mass of the adhesive alone was calculated by subtracting the mass of the mesh alone. The mass at this time is M1.

Next, the pressure-sensitive adhesive wrapped in the polyester mesh was immersed in ethyl acetate at room temperature (23 ° C.) for 24 hours. Then, 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 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 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. As a result, the gel fraction of the pressure-sensitive adhesive (before UV irradiation) was derived. The results are shown in Table 2.

On the other hand, with respect to 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, ultraviolet rays (UV) were applied to the pressure-sensitive adhesive layer through the lightly peelable release sheet under the following conditions. The pressure-sensitive adhesive layer was cured to obtain a pressure-sensitive adhesive layer after curing. For the pressure-sensitive adhesive in the cured pressure-sensitive adhesive layer, the gel fraction (after UV irradiation) was derived in the same manner as described above. The results are shown in Table 2.

<Ultraviolet irradiation conditions>
・ Uses high-pressure mercury lamp ・ Illuminance 200mW / cm ² , light intensity 2000mJ / cm ²
・ UV illuminance / photometer uses "UVPF-A1" manufactured by iGraphics.

[Test Example 2] (Measurement of haze value)
Regarding the adhesive layer of the first adhesive sheet (adhesive layer thickness: 25 μm) obtained in Examples and Comparative Examples, a haze meter (manufactured by Nippon Denshoku Industries Co., Ltd., product name) according to JIS K7136: 2000. The haze value (%) was measured using "NDH-2000"). The results are shown in Table 2.

[Test Example 3] (Measurement of transmitted hue b *)
Simultaneous photometric spectroscopic chromaticity meter (manufactured by Nippon Denshoku Industries Co., Ltd., product name "SQ2000") for the pressure-sensitive adhesive layer of the first pressure-sensitive adhesive sheet (thickness of pressure-sensitive adhesive layer: 25 μm) obtained in Examples and Comparative Examples. ) Was used to measure the transmitted hue b * defined by the CIE1976L * a * b * color system. The results are shown in Table 2.

[Test Example 4] (Measurement of adhesive strength)
The lightly peelable release sheet was peeled off from the first pressure-sensitive adhesive sheet (thickness of the pressure-sensitive adhesive layer: 25 μm) obtained in Examples and Comparative Examples, and the exposed pressure-sensitive adhesive layer was separated from the exposed pressure-sensitive adhesive layer by polyethylene terephthalate (PET) having an easy-adhesive layer. ) A film (manufactured by Toyo Boseki Co., Ltd., product name "PET A4300", thickness: 100 μm) was bonded to an easy-adhesive layer to obtain a laminate of a release sheet / adhesive layer / PET film. The obtained laminate was cut into a width of 25 mm and a length of 100 mm.

In an environment of 23 ° C. and 50% RH, the heavy-release type release sheet was peeled off from the above laminate, and the exposed adhesive layer was attached to soda lime glass (manufactured by Nippon Sheet Glass Co., Ltd.) and placed in an autoclave manufactured by Kurihara Seisakusho. The pressure was increased at 0.5 MPa and 50 ° C. for 20 minutes. Then, the pressure-sensitive adhesive layer was irradiated with ultraviolet rays (UV) through the PET film under the same ultraviolet irradiation conditions as in Test Example 1, and the pressure-sensitive adhesive layer was cured to obtain a cured pressure-sensitive adhesive layer. After leaving it for 24 hours under the conditions of 23 ° C. and 50% RH, the sample having the adhesive layer after curing was subjected to a peeling speed of 300 mm / min and a peeling angle using a tensile tester (Tencilon, manufactured by Orientec). The adhesive strength (after UV irradiation; N / 25 mm) was measured under the condition of 180 degrees. Conditions other than those described here were measured in accordance with JIS Z 0237: 2009. The results are shown in Table 2.

[Test Example 5] (Evaluation of blister resistance)
A polyethylene terephthalate film in which 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 is provided with a transparent conductive film made of tin-doped indium oxide (ITO) on one side. It was sandwiched between a transparent conductive film (manufactured by Oike Kogyo Co., Ltd., ITO film, thickness: 125 μm) and an acrylic resin plate (manufactured by Mitsubishi Rayon Co., Ltd., product name “Acrylite MR-200”, thickness: 1 mm). Then, it was autoclaved for 30 minutes under the conditions of 50 ° C. and 0.5 MPa, and left at normal pressure at 23 ° C. and 50% RH for 24 hours.

The pressure-sensitive adhesive layer of the obtained laminate was irradiated with ultraviolet rays through the resin plate under the same conditions as in Test Example 1 to cure the pressure-sensitive adhesive layer to obtain a cured pressure-sensitive adhesive layer. Then, it was stored for 72 hours under high temperature and high humidity conditions of 85 ° C. and 85% RH. Then, after curing, the state at the interface between the pressure-sensitive adhesive layer and the adherend was visually confirmed, and the blister resistance was evaluated according to the following criteria. The results are shown in Table 2.
〇… There were no bubbles, floating or peeling.
×… Bubbles, floating / peeling occurred.

[Test Example 6] (Measurement of step follow-up rate)
On the surface of a glass plate (manufactured by NSG Precision Co., Ltd., product name "Corning Glass Eagle XG", length 90 mm x width 50 mm x thickness 0.5 mm), UV curable ink (manufactured by Teikoku Inks, product name "POS-911 ink") ) Was screen-printed in a frame shape (outer shape: length 90 mm × width 50 mm, width 5 mm) so that the coating thickness was any one of 10 μm, 15 μm, and 20 μm. Next, the printed ultraviolet curable ink is cured by irradiating with ultraviolet rays (80 W / cm ² , 2 metal halide lamps, lamp height 15 cm, belt speed 10 to 15 m / min), and a step (height of the step) due to printing is cured. A stepped glass plate having one of 10 μm, 15 μm, and 20 μm) was produced.

The light peeling type peeling sheet was peeled off from the second pressure-sensitive adhesive sheet (thickness of the pressure-sensitive adhesive layer: 50 μm) obtained in Examples and Comparative Examples, and the exposed pressure-sensitive adhesive layer was separated from the exposed pressure-sensitive adhesive layer by polyethylene terephthalate (PET) having an easy-adhesive layer. It was bonded to an easy-adhesion layer of a film (manufactured by Toyo Boseki Co., Ltd., product name "PET A4300", thickness: 100 μm). Next, the heavy-release type release sheet is peeled off to expose the pressure-sensitive adhesive layer, and using a laminator (manufactured by Fujipla, product name "LPD3214"), each step is provided so that the pressure-sensitive adhesive layer covers the entire surface of the frame-shaped print. Laminated on a glass plate. Then, it was autoclaved for 30 minutes under the conditions of 50 ° C. and 0.5 MPa, and left at normal pressure at 23 ° C. and 50% RH for 24 hours.

The pressure-sensitive adhesive layer of the obtained laminate was irradiated with ultraviolet rays through the PET film under the same conditions as in Test Example 1 to cure the pressure-sensitive adhesive layer to obtain a cured pressure-sensitive adhesive layer. Then, it was stored for 72 hours under high temperature and high humidity conditions of 85 ° C. and 85% RH (durability test), and then the step followability was evaluated. The step followability is judged by whether or not the printed step is completely filled with the cured adhesive layer, and if bubbles, floats, peeling, etc. are observed at the interface between the printed step and the cured adhesive layer, , It is judged that the printing step could not be followed. Here, the step followability was evaluated as the step follow rate (%) represented by the following formula. The results are shown in Table 2.
Step follow-up rate (%) = {(Height of step (μm) maintained in a buried state without bubbles, floating, peeling, etc. after durability test) / (Thickness of adhesive layer after curing)} × 100

[Test Example 7] (Evaluation of moisture heat bleaching 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 formed by a non-alkali glass plate having a thickness of 1.1 mm and an acrylic resin plate having a thickness of 1 mm (thickness: 50 μm). A laminate was obtained by sandwiching it with a product name "Acrylite MR-200" manufactured by Mitsubishi Rayon Co., Ltd.).

The obtained laminate was autoclaved under the conditions of 50 ° C. and 0.5 MPa for 30 minutes, and then left at normal pressure at 23 ° C. and 50% RH for 24 hours. Then, the pressure-sensitive adhesive layer of the laminated body was irradiated with ultraviolet rays through the acrylic resin plate under the same conditions as in Test Example 1 to cure the pressure-sensitive adhesive layer to obtain a cured pressure-sensitive adhesive layer. The haze value (%) of this laminate (sample) was measured using a haze meter (manufactured by Nippon Denshoku Industries Co., Ltd., product name "NDH2000") according to JIS K7136: 2000.

Next, the laminate was stored for 120 hours under moist heat conditions of 85 ° C. and 85% RH, and then left for 24 hours at room temperature and normal humidity of 23 ° C. and 50% RH. The haze value (%) of the laminate was measured using a haze meter (manufactured by Nippon Denshoku Industries Co., Ltd., product name "NDH2000") according to JIS K7136: 2000.

Based on the above results, the haze value increase (points) after the moist heat condition was calculated by subtracting the haze value before the moist heat condition from the haze value after the moist heat condition. Based on the results, the moisture and heat whitening resistance was evaluated according to the following criteria. The results are shown in Table 2.
◎… Haze value increase is less than 1.0 points ○… 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 8] (Calculation of permittivity)
An adhesive layer having a thickness of 100 μm is formed on one side of a polyethylene terephthalate film having a thickness of 50 μm in the same manner as in Examples and Comparative Examples, and a polyethylene terephthalate film having a thickness of 50 μm is attached to the adhesive layer. It was cut into 50 mm × 50 mm. Then, it was irradiated with ultraviolet rays (UV) under the following conditions to cure the pressure-sensitive adhesive layer to obtain a cured pressure-sensitive adhesive layer.
<Ultraviolet irradiation conditions>
・ Uses high-pressure mercury lamp ・ Illuminance 200mW / cm ² , light intensity 1000mJ / cm ²
・ UV illuminance / photometer uses "UVPF-A1" manufactured by iGraphics.

The capacitance (C1) of the obtained laminate was measured using an impedance analyzer (“HP-4194A” manufactured by Hewlett-Packard Japan). Further, two polyethylene terephthalate films having a thickness of 50 μm were laminated and cut into a size of 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
The capacitance (C3) of the pressure-sensitive adhesive was calculated based on the above. Based on this capacitance C3, the dielectric constant ε _s of the pressure-sensitive adhesive was calculated 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 adhesive layer after curing d: Thickness of adhesive layer after curing

As can be seen from Table 2, the cured pressure-sensitive adhesive layer formed by using the pressure-sensitive adhesive sheet obtained in the examples is excellent in all of blister resistance, step followability and moisture heat whitening resistance. , The dielectric constant also showed a low value.

The pressure-sensitive adhesive composition, pressure-sensitive adhesive, and pressure-sensitive adhesive sheet of the present invention can be suitably used for bonding, for example, a protective panel made of a plastic plate and a desired display body component. Further, the display body according to the present invention is suitable as, for example, a capacitance type touch panel.

1 ... Adhesive sheet 11 ... Adhesive layer 12a, 12b ... Peeling sheet 2 ... Display 11'... After curing Adhesive layer 21 ... First display component 22 ... Second display component 3 ... Printing layer

Claims (8)

A (meth) acrylic acid ester polymer (A) containing N-vinylcarboxylic acid amide as a monomer unit constituting the polymer, and
Cross-linking agent (B) and
Contains the active energy ray-curable component (C) ,
The (meth) acrylic acid ester polymer (A) is characterized by containing a reactive functional group-containing monomer having a reactive functional group in the molecule as a monomer unit constituting the polymer. Adhesive 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 to the N-vinylcarboxylic acid amide is 95: 5 to 5. The adhesive composition according to claim 1 , wherein the ratio is 50:50. The (meth) acrylic acid ester polymer (A) is, according to claim 1 as a monomer unit constituting the polymer, wherein the reactive functional group-containing monomer 5 mass% or more, characterized in that it contains 30 wt% or less or an adhesive composition according to 2. It has a cross-linked structure composed of a (meth) acrylic acid ester polymer (A) containing N-vinylcarboxylic acid amide as a monomer unit constituting the polymer and a cross-linking agent (B), and has a cross-linked structure.
An active energy ray-curable pressure-sensitive adhesive comprising the active energy ray-curable component (C). The pressure-sensitive adhesive according to claim 4 , wherein the gel fraction is 30% or more and 90% or less. In a laminate in which a pressure-sensitive adhesive layer having a thickness of 50 μm made of the pressure-sensitive adhesive is sandwiched between a glass plate and an acrylic resin plate having a thickness of 1 mm, the pressure-sensitive adhesive layer is cured by irradiation with active energy rays to cure the pressure-sensitive adhesive layer. After that, the laminate was subjected to a durability test of storing it under moist heat conditions of 85 ° C. and 85% RH for 120 hours, and then haze when it was stored at room temperature and normal humidity of 23 ° C. and 50% RH for 24 hours. The pressure-sensitive adhesive according to claim 4 or 5 , wherein the haze value increase obtained by subtracting the haze value before the durability test from the value is less than 5 points. Two release sheets and
It is provided with an adhesive layer sandwiched between the release sheets so as to be in contact with the release surfaces of the two release sheets.
A pressure-sensitive adhesive sheet, wherein the pressure-sensitive adhesive layer comprises the pressure-sensitive adhesive according to any one of claims 4 to 6. One display body component and
With other display body components,
A display body including a cured adhesive layer for bonding the one display body component and the other display body component to each other.
At least one of the one display body component and the other display body component is made of a plastic plate.
The cured pressure-sensitive adhesive layer has a cross-linked structure composed of a (meth) acrylic acid ester polymer (A) containing N-vinylcarboxylic acid amide as a monomer unit constituting the polymer and a cross-linking agent (B). A display body comprising a pressure-sensitive adhesive containing a cured product of an active energy ray-curable component (C).

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