JP7184528B2 - Display body manufacturing method - Google Patents

Description

The present invention relates to a direct bonding film, a display, and a method for manufacturing a display.

Direct bonding is a technique employed in the manufacture of a display using a display module having a liquid crystal element, a light emitting diode (LED) element, an organic electroluminescence (organic EL) element, or the like.

In the display, a protection panel for protecting the display module is arranged on the display module on which an image is displayed. Conventionally, a protective panel has been placed on the display module with an air gap between them. Such a configuration facilitates the manufacture of the display, but has the problem that the display light from the display module is likely to be reflected in the air gap, resulting in deterioration of the visibility of the image.

Therefore, direct bonding is performed in which the display module and the protection panel are adhered with an optically transparent adhesive and the air gap between the display module and the protection panel is filled with the adhesive. By adopting direct bonding, the image contrast is increased, visibility is improved, and glare can be reduced. Furthermore, since there is no air gap, the strength of the display body is increased, and dew condensation and the like can be prevented. A film-like adhesive used for such direct bonding is called a direct bonding film.

By the way, ultraviolet rays are not only harmful to the human body, but also deteriorate the members constituting the equipment. Therefore, the human body or equipment is protected from ultraviolet rays by attaching a member having ultraviolet absorption ability to a material that transmits ultraviolet rays (for example, glass), or by incorporating the member into the device. there is

For example, Patent Literature 1 discloses that a pressure-sensitive adhesive sheet to be bonded to the window glass of a vehicle, building, or the like contains an ultraviolet absorber in the pressure-sensitive adhesive. A pressure-sensitive adhesive containing this ultraviolet absorber is obtained by a polymerization reaction using electron beam irradiation.

Examples of devices to be protected from ultraviolet rays include various mobile electronic devices having a display, such as mobile phones, smart phones, and tablet devices used outdoors. In many cases, a display included in a mobile electronic device has a built-in sensor and also serves as a touch panel.

As described above, since mobile electronic devices are used outdoors, their components deteriorate due to the influence of ultraviolet rays. In order to suppress such deterioration, a member having an ultraviolet absorbing ability is incorporated in the electronic device.

As such a member, it is known that a protective panel arranged on the surface side of the electronic device and a pressure-sensitive adhesive for bonding other constituent members are provided with an ultraviolet absorbing ability. For example, Patent Literature 2 discloses that a pressure-sensitive adhesive sheet for adhering display body constituent members constituting a display body has an ultraviolet absorbing layer.

Further, Patent Documents 3 to 5 disclose that the pressure-sensitive adhesive for bonding together the display body constituting members constituting the display body is an ultraviolet curing type and contains an ultraviolet absorber.

By the way, the pressure-sensitive adhesive for bonding the display body constituent members together has properties required due to the shape of the display body constituent members and the environment to which the display body is exposed, in addition to the ultraviolet absorption ability.

For example, a frame-shaped printed layer may be formed on the display module side of the protection panel and exist as a step in the thickness direction of the display. In the case of a direct bonding film that bonds a protective panel and a display module, if the adhesive layer of the direct bonding film does not follow the step, the adhesive layer lifts up near the step and a gap is formed. . As a result, the air gap causes reflection loss of light, which degrades the image quality of the display. Therefore, the direct bonding film to be bonded to the protective panel having a step is required to follow the step.

Furthermore, as electronic devices become thinner and lighter, it is being considered to change the protective panel from a conventional glass plate to a plastic plate such as an acrylic plate or a polycarbonate plate. In a configuration in which the protective panel and display module are bonded with a direct bonding film, if the protective panel is changed to a plastic plate, outgassing occurs from the plastic plate under high temperature and high humidity conditions, causing air bubbles, lifting, and peeling. There is a new problem that blisters such as For this reason, the pressure-sensitive adhesive layer of the direct bonding film for bonding the display module and the protective panel is increasingly required to have blister resistance.

JP 2013-249345 A JP 2012-211305 A JP 2016-155981 A Japanese Patent No. 5307380 Japanese Patent No. 5528861

The pressure-sensitive adhesive disclosed in Patent Document 1 is not a pressure-sensitive adhesive for adhering constituent members of a display body to each other, so no consideration is given to conformability to unevenness.

The pressure-sensitive adhesive sheet disclosed in Patent Document 2 has a structure in which an pressure-sensitive adhesive layer and an ultraviolet absorbing layer are laminated, and a structure in which a pressure-sensitive adhesive layer containing an ultraviolet absorber is formed. However, when the pressure-sensitive adhesive layer contains an ultraviolet absorber, the pressure-sensitive adhesive is obtained by thermally curing the pressure-sensitive adhesive composition. This pressure-sensitive adhesive has a problem that it is inferior in step followability and blister resistance.

The pressure-sensitive adhesives disclosed in Patent Documents 3 to 5 have a problem that they cannot achieve both high level conformability and high blistering resistance.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a direct bonding film that has UV absorbability and that can achieve both good step followability and good blister resistance. Another object of the present invention is to provide a display configured using the direct bonding film and a manufacturing method thereof.

A first aspect of the present invention is
[1] A direct bonding film having an active energy ray-curable adhesive layer,
The light transmittance of the adhesive layer at a wavelength of 380 nm is 40% or less,
Before the active energy ray irradiation of the adhesive layer, the gel fraction of the adhesive layer is 20% or more and 55% or less,
After irradiation of the adhesive layer with active energy rays, the gel fraction of the adhesive layer is 40% or more and 90% or less,
The direct bonding film is characterized in that the ratio of the gel fraction of the adhesive layer after irradiation with active energy rays to the gel fraction of the adhesive layer before irradiation with active energy rays is 1.05 or more.

[2] According to [1], wherein the ratio of the storage elastic modulus of the adhesive layer after irradiation with active energy rays to the storage elastic modulus of the adhesive layer before irradiation with active energy rays is 1.20 or more. is a direct bonding film.

[3] The direct bonding film according to [2], wherein the adhesive layer has a storage elastic modulus of 0.05 MPa or more and 0.50 MPa or less after irradiation of the adhesive layer with active energy rays.

[4] The direct bonding film according to [2] or [3], wherein the storage elastic modulus of the adhesive layer is 0.01 MPa or more and 0.20 MPa or less before the active energy ray irradiation of the adhesive layer. is.

[5] The direct bonding film according to any one of [1] to [4], wherein the pressure-sensitive adhesive layer has an adhesive strength of 20 N/25 mm or more after the active energy ray irradiation of the pressure-sensitive adhesive layer. be.

[6] The adhesive layer is
A crosslinked structure composed of a (meth)acrylic acid ester copolymer and a thermal crosslinking agent;
an active energy ray-curable component;
A photopolymerization initiator having an absorbance of 1.0 or more at a wavelength of 380 nm in an acetonitrile solution with a concentration of 0.1% by mass;
The direct bonding film according to any one of [1] to [5], comprising an adhesive having an ultraviolet absorber.

[7] The direct bonding film has a release sheet,
The direct bonding film according to any one of [1] to [6], wherein both main surfaces of the adhesive layer are in contact with the release surface of the release sheet.

A second aspect of the present invention is
[8] a first display body constituent member;
a second display body component;
A display body having a post-curing pressure-sensitive adhesive layer for bonding the first display body constituent member and the second display body constituent member to each other,
The post-curing pressure-sensitive adhesive layer is a display member characterized in that the pressure-sensitive adhesive layer of the direct bonding film according to any one of [1] to [7] is cured.

[9] At least one of the first display member and the second display member has a step,
The display body according to [8], wherein the post-curing pressure-sensitive adhesive layer is laminated along a step.

A third aspect of the present invention is
[10] A first display body constituent member and a second display body constituent member are laminated via an adhesive layer of the direct bonding film according to any one of [1] to [7]. a step of making a laminate;
and a step of irradiating an adhesive layer of a laminate with an active energy ray to cure the adhesive layer to form a cured adhesive layer.

[11] At least one of the first display member and the second display member has a step,
The method of manufacturing a display according to [10], wherein the pressure-sensitive adhesive layer is laminated along a step.

ADVANTAGE OF THE INVENTION According to this invention, the direct bonding film which can be compatible with favorable level|step-difference followability|trackability and favorable blister-proof property can be provided, having an ultraviolet absorption ability. Also, a display configured using the direct bonding film and a manufacturing method thereof can be provided.

FIG. 1 is a cross-sectional view of a direct bonding film according to one embodiment of the present invention. FIG. 2 is a cross-sectional view of a laminate according to one embodiment of the invention.

Hereinafter, the present invention will be described in detail based on specific embodiments.

(1. Direct bonding film)
The direct bonding film 1 according to this embodiment has an adhesive layer 11 and release sheets 12a and 12b, as shown in FIG. This pressure-sensitive adhesive layer 11 is cured after being irradiated with active energy rays, and becomes a post-curing pressure-sensitive adhesive layer. The adhesive layer 11 is made of an adhesive which will be described later. The two release sheets 12a and 12b are arranged so that their release surfaces are in contact with both main surfaces of the pressure-sensitive adhesive layer. In other words, the adhesive layer 11 is sandwiched between two release sheets 12a and 12b. In this specification, the release surface of the release sheet refers to the surface of the release sheet that has releasability, and includes both the surface that has been subjected to a release treatment and the surface that exhibits releasability without being subjected to a release treatment. .

The thickness of the adhesive layer 11 is preferably 20 μm or more, more preferably 25 μm or more, even more preferably 30 μm or more, and particularly preferably 50 μm or more. On the other hand, the thickness is preferably 500 μm or less, more preferably 400 μm or less, even more preferably 300 μm or less, and particularly preferably 150 μm or less.

If the thickness is too small, the adhesive strength tends to be low, and the step followability and blister resistance tend to be poor. On the other hand, when the thickness is too large, workability tends to deteriorate.

(1.1. Adhesive)
In this embodiment, the pressure-sensitive adhesive layer 11 is made of the pressure-sensitive adhesive described below.

(1.2. Physical properties of adhesive)
In this embodiment, the adhesive constituting the adhesive layer 11 has physical properties as shown below.

(1.2.1. Light transmittance)
In this embodiment, the light transmittance of the adhesive at a wavelength of 380 nm is 40% or less, preferably 20% or less, more preferably 10% or less. Although the lower limit is not particularly limited, it is usually 0% or more. When the light transmittance of the adhesive is within the above range, at least part of the ultraviolet rays incident on the adhesive cannot pass through the adhesive, so that the adhesive layer 11 made of the adhesive has good ultraviolet absorption ability. can be shown.

(1.2.2. Gel fraction before active energy ray irradiation)
In this embodiment, the gel fraction of the adhesive is changed before and after irradiation with active energy rays. Along with the change in the gel fraction, the adhesive strength and cohesiveness of the adhesive can be changed before and after the active energy ray irradiation.
In this embodiment, the gel fraction of the adhesive before irradiation with active energy rays is preferably 20% or more, more preferably 35% or more, and even more preferably 40% or more. Moreover, the gel fraction is preferably 55% or less, more preferably 50% or less. When the gel fraction of the pressure-sensitive adhesive before irradiation with active energy rays is within the above range, the flexibility of the pressure-sensitive adhesive is improved. As a result, good step followability can be exhibited.

Therefore, when a pressure-sensitive adhesive layer made of a pressure-sensitive adhesive before irradiation with an active energy ray is attached to an adherend having a level difference, the level difference is sufficiently followed, and there is no gap or float between the adherend and the pressure-sensitive adhesive. can be suppressed.

(1.2.3. Gel fraction after active energy ray irradiation)
Further, the gel fraction of the adhesive after irradiation with active energy rays, that is, the gel fraction of the cured adhesive constituting the cured adhesive layer is preferably 40% or more, and preferably 50% or more. is more preferred. Also, the gel fraction is preferably 90% or less, more preferably 80% or less, and preferably 70% or less.

When the gel fraction of the cured pressure-sensitive adhesive is within the above range, the cohesive force of the cured pressure-sensitive adhesive layer tends to increase.

Furthermore, in the present embodiment, the ratio of the gel fraction of the adhesive before irradiation with active energy rays and the gel fraction of the adhesive after irradiation with active energy rays is controlled within a predetermined range. Specifically, the ratio of the gel fraction of the adhesive after irradiation with active energy rays to the gel fraction of the adhesive before irradiation with active energy rays (gel fraction of adhesive after irradiation with active energy rays / irradiation with active energy rays The gel fraction of the previous pressure-sensitive adhesive) is 1.05 or more. That is, the gel fraction of the adhesive after curing is higher than the gel fraction before irradiation with active energy rays. It is considered that this is because the active energy ray-curable component was polymerized by the irradiation of the active energy ray to form a polymerized structure.

By setting the ratio of the gel fractions before and after the active energy ray irradiation within the above range, the pressure-sensitive adhesive can exhibit good conformability to unevenness before curing and have suitable cohesive strength after curing. Therefore, it is possible to improve step followability and blister resistance immediately after the pressure-sensitive adhesive layer is adhered to an adherend, as well as step followability and blister resistance under high-temperature and high-humidity conditions.

The ratio of the gel fractions before and after the active energy ray irradiation is preferably 1.08 or more, more preferably 1.10 or more. On the other hand, the upper limit of the gel fraction ratio before and after the active energy ray irradiation is not particularly limited, but in the present embodiment, it is preferably 5.0 or less, more preferably 2.0 or less, and 1.50 More preferably:

In addition, the gel fraction of the pressure-sensitive adhesive may be measured by the method shown in the test examples described later.

(1.2.4. Storage modulus before active energy ray irradiation)
In the present embodiment, the storage elastic modulus of the adhesive before irradiation with an active energy ray measured at a frequency of 1 kHz is preferably 0.20 MPa or less, more preferably 0.10 MPa or less, and 0.08 MPa or less. It is even more preferable to have On the other hand, the storage modulus is preferably 0.01 MPa or more, more preferably 0.02 MPa or more, and even more preferably 0.04 MPa or more. When the storage elastic modulus of the pressure-sensitive adhesive before irradiation with active energy rays is within the above range, the pressure-sensitive adhesive has good flexibility. As a result, good step followability can be exhibited.

(1.2.5. Storage modulus after active energy ray irradiation)
The storage elastic modulus of the adhesive after irradiation with active energy rays measured at a frequency of 1 kHz, that is, the cured adhesive is preferably 0.50 MPa or less, more preferably 0.20 MPa or less. Moreover, the storage elastic modulus is preferably 0.05 MPa or more, more preferably 0.08 MPa or more, and even more preferably 0.10 MPa or more.

The storage elastic modulus of the adhesive after curing is about one digit higher than the storage elastic modulus before irradiation with active energy rays. This is probably because the active energy ray-curable component was polymerized by the irradiation with the active energy ray to form a polymerized structure, similar to the reason for the increase in the gel fraction. When the storage elastic modulus of the cured pressure-sensitive adhesive is within the above range, the cohesive strength of the cured pressure-sensitive adhesive layer tends to increase.

Furthermore, in the present embodiment, it is preferable that the ratio of the storage elastic modulus of the adhesive before irradiation with active energy rays and the storage elastic modulus of the adhesive after irradiation with active energy rays is within a predetermined range. Specifically, the ratio of the storage elastic modulus of the adhesive after irradiation with active energy rays to the storage elastic modulus of the adhesive before irradiation with active energy rays (storage elastic modulus of adhesive after irradiation with active energy rays / irradiation with active energy rays The storage modulus of the previous pressure-sensitive adhesive) is preferably 1.20 or more. That is, the storage elastic modulus of the adhesive after curing is higher than the storage elastic modulus of the adhesive before irradiation with active energy rays.

By setting the ratio of the storage elastic modulus before and after the irradiation of the active energy ray within the above range, the pressure-sensitive adhesive exhibits good step conformability before curing and is suitable after curing, as in the case of the above gel fraction. can have a strong cohesive force. Therefore, it is possible to improve step followability and blister resistance immediately after the pressure-sensitive adhesive layer is adhered to an adherend, as well as step followability and blister resistance under high-temperature and high-humidity conditions.

The ratio of the storage elastic moduli before and after the active energy ray irradiation is preferably 1.20 or more, more preferably 1.50 or more, and even more preferably 1.80 or more. On the other hand, the upper limit of the ratio of the storage elastic moduli before and after the active energy ray irradiation is not particularly limited, but in the present embodiment, it is preferably 5.0 or less, more preferably 3.0 or less, and 2.0. More preferably: In addition, the storage elastic modulus of the pressure-sensitive adhesive may be measured by the method shown in the test examples described later.

(1.2.6. Adhesion after active energy ray irradiation)
The adhesive after irradiation with active energy rays, that is, the lower limit of the adhesive strength of the cured adhesive to soda lime glass is preferably 20 N/25 mm or more, more preferably 30 N/25 mm or more, and 40 N/ More preferably, it is 25 mm or more. The upper limit of the adhesive strength is not particularly limited, but is generally preferably 80 N/25 mm or less, more preferably 60 N/25 mm or less, and even more preferably 50 N/25 mm or less.

If the adhesive strength of the cured adhesive is too low, the blister resistance tends to be poor. In addition, the pressure-sensitive adhesive tends to float or peel from the vicinity of the step, and the followability to the step under high-temperature and high-humidity conditions tends to be poor. The adhesive strength in this specification basically refers to the adhesive strength measured by the 180 degree peeling method according to JIS Z0237:2009, and the specific measuring method is as shown in the test examples described later.

(1.2.7. Haze value after active energy ray irradiation)
The adhesive after irradiation with active energy rays, that is, the haze value of the cured adhesive is preferably 5% or less, more preferably 1% or less, and even more preferably 0.8% or less. . When the haze value of the cured pressure-sensitive adhesive is 5% or less, the transparency is high and it is suitable for optical applications (for displays). The lower limit of the haze value of the adhesive after curing is not particularly limited, but is usually 0% or more. In addition, the haze value in this specification is a value measured according to JIS K7136:2000, and the specific measurement method is as shown in the test examples described later.

(1.3. Structure and components of adhesive)
The structure and composition of the pressure-sensitive adhesive are not particularly limited as long as the pressure-sensitive adhesive has the physical properties described above, but in the present embodiment, it preferably has the following structure and constituent components.

In this embodiment, the pressure-sensitive adhesive has a crosslinked structure composed of a (meth)acrylic acid ester copolymer (A) and a thermal crosslinking agent (B), and an active energy ray-curable component (C), It is preferable to contain a photopolymerization initiator (D) having an absorbance of 1.0 or more at a wavelength of 380 nm in an acetonitrile solution having a concentration of 0.1% by mass, and an ultraviolet absorber (E). In addition, in this specification, "(meth)acrylate" means both acrylate and methacrylate. The same applies to other similar terms.

This adhesive comprises a (meth)acrylic acid ester copolymer (A), a thermal cross-linking agent (B), an active energy ray-curable component (C), and a wavelength of 380 nm in an acetonitrile solution having a concentration of 0.1% by mass. is obtained by heat-treating an adhesive composition containing a photopolymerization initiator (D) having an absorbance of 1.0 or more and an ultraviolet absorber (E) for thermal crosslinking. Each component will be described in detail below.

(1.3.1. (Meth) acrylic acid ester copolymer)
(Meth)acrylic acid ester copolymer (A) contains, as a monomer unit constituting the copolymer, a reactive group-containing monomer having a reactive group in the molecule that reacts with the thermal cross-linking agent (B) described later. preferably included. A reactive group derived from this reactive group-containing monomer reacts with the thermal cross-linking agent (B) to form a cross-linked structure (three-dimensional network structure), whereby a pressure-sensitive adhesive having relatively high film strength can be obtained. can.

(1.3.1.1. Reactive group-containing monomer)
As the reactive group-containing monomer, a monomer having a hydroxyl group in the molecule (hydroxyl group-containing monomer) is preferable. This is because it has excellent reactivity with the thermal cross-linking agent (B) and has little adverse effect on the adherend.

Examples of hydroxyl group-containing monomers include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, (meth) ) hydroxyalkyl (meth)acrylates such as 3-hydroxybutyl acrylate and 4-hydroxybutyl (meth)acrylate;

Among them, (meth)acrylic acid from the viewpoint of the reactivity between the hydroxyl groups in the resulting (meth)acrylic acid ester copolymer (A) and the thermal cross-linking agent (B) and the copolymerizability with other monomers 2-Hydroxyethyl and 4-hydroxybutyl (meth)acrylate are preferred, and 2-hydroxyethyl acrylate and 4-hydroxybutyl acrylate are more preferred. These may be used alone or in combination of two or more.

The (meth)acrylic acid ester copolymer (A) preferably contains 3% by mass or more, more preferably 10% by mass or more, of a hydroxyl group-containing monomer as a monomer unit constituting the copolymer. , more preferably 15% by mass or more, and particularly preferably 18% by mass or more. In addition, the (meth)acrylic acid ester copolymer (A) preferably contains 50% by mass or less, more preferably 45% by mass or less, of a hydroxyl group-containing monomer as a monomer unit constituting the polymer. Preferably, it is more preferably contained in an amount of 40% by mass or less.

When the (meth)acrylic acid ester copolymer (A) contains a hydroxyl group-containing monomer in the above range as a monomer unit, a good crosslinked structure is formed in the resulting pressure-sensitive adhesive, and the pressure-sensitive adhesive having relatively high film strength. is obtained, and it is excellent in wet heat whitening resistance. This is because a predetermined amount of hydroxyl groups remain in the adhesive.

Hydroxyl groups are hydrophilic groups, and if such hydrophilic groups are present in a predetermined amount in the adhesive, even if the adhesive is placed under high temperature and high humidity conditions, they will penetrate into the adhesive under such high temperature and high humidity conditions. As a result, whitening of the pressure-sensitive adhesive is suppressed when the pressure-sensitive adhesive is returned to normal temperature and normal humidity.

Examples of reactive group-containing monomers other than hydroxyl group-containing monomers include monomers having a carboxy group in the molecule (carboxy group-containing monomers) and monomers having an amino group in the molecule (amino group-containing monomers). Among these, a carboxy group-containing monomer is preferable from the viewpoint of exerting a desired cohesive force even when the (meth)acrylic acid ester copolymer (A) has a relatively low weight average molecular weight.

Carboxy group-containing monomers include, for example, ethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, itaconic acid, and citraconic acid.

Among these, acrylic acid is preferable from the viewpoint of the reactivity between the carboxy group in the resulting (meth)acrylic acid ester copolymer (A) and the thermal cross-linking agent (B) and the copolymerizability with other monomers. . These may be used alone or in combination of two or more.

When the (meth) acrylic ester copolymer (A) contains a carboxy group-containing monomer as a monomer unit constituting the copolymer, the (meth) acrylic ester copolymer (A) contains the carboxy group The monomer content is preferably 5% by mass or more, more preferably 10% by mass or more. In addition, the (meth)acrylic acid ester copolymer (A) preferably contains 30% by mass or less, and preferably 15% by mass or less, of a carboxy group-containing monomer as a monomer unit constituting the polymer. more preferred.

When the (meth)acrylic acid ester copolymer (A) contains a carboxyl group-containing monomer as a monomer unit in the above range, the resulting pressure-sensitive adhesive has a good crosslinked structure and a relatively high film strength. A drug is obtained.

The (meth)acrylic acid ester copolymer (A) preferably contains or does not contain a small amount of a carboxy group-containing monomer as a monomer unit constituting the copolymer. Since the carboxyl group is an acid component, the absence of the carboxyl group-containing monomer prevents the adhesive from being applied to objects to which the acid is attached, such as transparent conductive films such as tin-doped indium oxide (ITO), metal films, and the like. Even if it exists, it is possible to suppress those problems (corrosion, resistance value change, etc.) caused by the acid.

However, it is permissible to contain a predetermined amount of the carboxy group-containing monomer to the extent that the above problems do not occur. Specifically, the (meth)acrylic acid ester copolymer (A) contains less than 5% by mass, preferably 2% by mass or less, more preferably 0.1% by mass or less of a carboxy group-containing monomer as a monomer unit. It is allowed to contain in the amount of

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

(1.3.1.2. (Meth)acrylic acid alkyl ester)
The (meth)acrylic acid ester copolymer (A) preferably contains a (meth)acrylic acid alkyl ester having an alkyl group having 1 to 20 carbon atoms as a monomer unit constituting the copolymer. Thereby, the adhesive can express preferable adhesiveness. In addition, the (meth)acrylic acid alkyl ester having an alkyl group having 1 to 20 carbon atoms preferably has a linear or branched structure from the viewpoint of exhibiting more preferable adhesiveness.

Examples of (meth)acrylic acid alkyl esters having an alkyl group of 1 to 20 carbon atoms include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-(meth)acrylate, Butyl, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, n-decyl (meth)acrylate, (meth)acrylic acid Examples include n-dodecyl, myristyl (meth)acrylate, palmityl (meth)acrylate, and stearyl (meth)acrylate.

Among these, (meth)acrylic acid esters having alkyl groups of 1 to 8 carbon atoms are preferred from the viewpoint of further improving adhesiveness. Specifically, n-butyl (meth)acrylate or 2-ethylhexyl (meth)acrylate is particularly preferred, and n-butyl acrylate or 2-ethylhexyl acrylate is particularly preferred. In addition, these may be used independently and may be used in combination of 2 or more type.

The (meth)acrylic acid ester copolymer (A) contains 40% by mass or more of a (meth)acrylic acid alkyl ester having an alkyl group having 1 to 20 carbon atoms as a monomer unit constituting the copolymer. is preferred, more preferably 50% by mass or more, and even more preferably 60% by mass or more. If the (meth)acrylic acid alkyl ester is contained in an amount of 40% by mass or more, the (meth)acrylic acid ester copolymer (A) can be imparted with suitable adhesiveness.

In addition, it preferably contains 90% by mass or less, more preferably 80% by mass or less, and further preferably contains 70% by mass or less of a (meth)acrylic acid alkyl ester having an alkyl group having 1 to 20 carbon atoms. preferable. By setting the content of the (meth)acrylic acid alkyl ester to 90% by mass or less, the (meth)acrylic acid ester copolymer (A) contains a desired amount of other monomer components for expressing desired properties. can be introduced.

(1.3.1.3. Alicyclic structure-containing monomer)
The (meth)acrylate copolymer (A) preferably contains a monomer having an alicyclic structure in its molecule (alicyclic structure-containing monomer) as a monomer unit constituting the copolymer. Since the alicyclic structure-containing monomer is bulky, it is presumed that the presence of this in the copolymer widens the distance between the polymers. As a result, the pressure-sensitive adhesive to be obtained can be made excellent in flexibility. Therefore, when the (meth)acrylic acid ester polymer (A) contains an alicyclic structure-containing monomer as a monomer unit, the pressure-sensitive adhesive obtained by cross-linking the pressure-sensitive adhesive composition is superior in initial conformability to unevenness. .

The carbon ring of the alicyclic structure in the alicyclic structure-containing monomer may have a saturated structure or may partially have an unsaturated bond. The alicyclic structure may be a monocyclic alicyclic structure or a polycyclic alicyclic structure such as bicyclic or tricyclic. In the obtained (meth)acrylic acid ester copolymer (A), from the viewpoint of widening the distance between the polymers and effectively exhibiting the flexibility of the adhesive, the alicyclic structure is a polycyclic alicyclic A formula structure (polycyclic structure) is preferred. Furthermore, from the viewpoint of compatibility between the (meth)acrylic acid ester copolymer (A) and other components, the above polycyclic structure is particularly preferably bicyclic to tetracyclic.

In the same manner as described above, from the viewpoint of effectively exhibiting the flexibility of the adhesive, the number of carbon atoms in the alicyclic structure (the number of all carbon atoms in the part forming the ring, and multiple rings are independently If present, the total number of carbon atoms) is usually preferably 5 or more, more preferably 7 or more. On the other hand, although the upper limit of the number of carbon atoms in the alicyclic structure is not particularly limited, it is preferably 15 or less, more preferably 10 or less, from the viewpoint of compatibility as described above.

Examples of alicyclic structures include cyclohexyl skeleton, dicyclopentadiene skeleton, adamantane skeleton, isobornyl skeleton, cycloalkane skeleton (cycloheptane skeleton, cyclooctane skeleton, cyclononane skeleton, cyclodecane skeleton, cycloundecane skeleton, cyclododecane skeleton, etc.). , cycloalkene skeleton (cycloheptene skeleton, cyclooctene skeleton, etc.), norbornene skeleton, norbornadiene skeleton, cubane skeleton, basketane skeleton, hausan skeleton, spiro skeleton, and the like.

Among these, from the viewpoint of obtaining more excellent durability, a dicyclopentadiene skeleton (alicyclic structure: 10 carbon atoms), adamantane skeleton (alicyclic structure: 10 carbon atoms) or isobornyl skeleton (alicyclic Those containing 7 carbon atoms in the structure are preferred, and those containing an isobornyl skeleton are more preferred.

Therefore, as the alicyclic structure-containing monomer, a (meth)acrylic acid ester monomer containing the above skeleton is preferable. Specifically, cyclohexyl (meth)acrylate, dicyclopentanyl (meth)acrylate, adamantyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentenyl (meth)acrylate, (meth)acrylic acid dicyclopentenyloxyethyl and the like.

Among these, dicyclopentanyl (meth)acrylate, adamantyl (meth)acrylate, or isobornyl (meth)acrylate are preferred, and isobornyl (meth)acrylate is more preferred, from the viewpoint of obtaining better durability. Isobornyl acrylate is particularly preferred. These may be used individually by 1 type, and may be used in combination of 2 or more type.

The (meth)acrylic acid ester copolymer (A) preferably contains 1% by mass or more of an alicyclic structure-containing monomer as a monomer unit constituting the copolymer, and may contain 4% by mass or more. More preferably, it is contained in an amount of 8% by mass or more. In addition, the (meth)acrylic acid ester copolymer (A) preferably contains 40% by mass or less of an alicyclic structure-containing monomer as a monomer unit constituting the copolymer, and contains 25% by mass or less. is more preferable, and it is even more preferable to contain 15% by mass or less. When the content of the alicyclic structure-containing monomer is within the above range, the pressure-sensitive adhesive to be obtained has good flexibility and excellent initial conformability to unevenness.

(1.3.1.4. Nitrogen atom-containing monomer)
The (meth)acrylic acid ester copolymer (A) preferably contains a monomer having a nitrogen atom in its molecule (nitrogen atom-containing monomer) as a monomer unit constituting the copolymer. The amino group-containing monomers exemplified as reactive group-containing monomers are excluded from the nitrogen atom-containing monomers. By allowing the nitrogen atom-containing monomer to be present in the copolymer as a structural unit, the reaction between the acrylic acid ester copolymer (A) and the thermal cross-linking agent (B) can be promoted, and the adhesive is imparted with polarity. and the cohesive force of the pressure-sensitive adhesive itself can be increased.

Examples of the nitrogen atom-containing monomers include monomers having a tertiary amino group, monomers having an amide group, and monomers having a nitrogen-containing heterocyclic ring. Among these, monomers having a nitrogen-containing heterocyclic ring are preferred.

Examples of monomers having a nitrogen-containing heterocyclic ring include N-(meth)acryloylmorpholine, N-vinyl-2-pyrrolidone, N-(meth)acryloylpyrrolidone, N-(meth)acryloylpiperidine, N-(meth)acryloyl pyrrolidine, N-(meth)acryloylaziridine, aziridinylethyl (meth)acrylate, 2-vinylpyridine, 4-vinylpyridine, 2-vinylpyrazine, 1-vinylimidazole, N-vinylcarbazole, N-vinylphthalimide, etc. mentioned.

Among these, N-(meth)acryloylmorpholine is preferred, and N-acryloylmorpholine is more preferred, from the viewpoint of obtaining superior adhesive strength.

Nitrogen atom-containing monomers other than the above-mentioned nitrogen-containing heterocyclic ring-containing monomers include, for example, (meth)acrylamide, N-methyl(meth)acrylamide, N-methylol(meth)acrylamide, N-tert-butyl(meth)acrylamide , N,N-dimethyl(meth)acrylamide, N,N-ethyl(meth)acrylamide, N,N-dimethylaminopropyl(meth)acrylamide, N-isopropyl(meth)acrylamide, N-phenyl(meth)acrylamide, dimethyl Aminopropyl (meth)acrylamide, N-vinylcaprolactam, dimethylaminoethyl (meth)acrylate and the like can be mentioned.

One type of the nitrogen atom-containing monomer may be used alone, or two or more types may be used in combination.

(Meth) acrylic acid ester copolymer (A) preferably contains 1% by mass or more of a nitrogen atom-containing monomer as a monomer unit constituting the copolymer, more preferably 4% by mass or more, It is more preferable to contain 8% by mass or more. In addition, the (meth)acrylic acid ester copolymer (A) preferably contains 40% by mass or less of a nitrogen atom-containing monomer as a monomer unit constituting the copolymer, and may contain 25% by mass or less. More preferably, it is contained in an amount of 15% by mass or less. When the content of the nitrogen atom-containing monomer is within the above range, the cohesive strength of the obtained pressure-sensitive adhesive is effectively improved.

(1.3.1.5. Others)
The (meth)acrylic acid ester copolymer (A) may contain other monomers as monomer units constituting the copolymer, if necessary. As other monomers, monomers containing no reactive functional groups are preferred. Examples of such other monomers include alkoxyalkyl (meth)acrylates such as methoxyethyl (meth)acrylate and ethoxyethyl (meth)acrylate, vinyl acetate, and styrene. These may be used alone or in combination of two or more.

The polymerization mode of the (meth)acrylate copolymer (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 100,000 or more, particularly preferably 250,000 or more, further preferably 400,000 or more as a lower limit. When the lower limit of the weight-average molecular weight of the (meth)acrylic acid ester polymer (A) is at least the above, the resulting pressure-sensitive adhesive has a higher film strength. Further, the weight average molecular weight of the (meth)acrylic acid ester polymer (A) is preferably 900,000 or less, particularly preferably 750,000 or less, further preferably 600,000 or less as an upper limit. preferable. When the upper limit of the weight-average molecular weight of the (meth)acrylic acid ester polymer (A) is at most the above, the pressure-sensitive adhesive to be obtained has more excellent step followability. In addition, the weight average molecular weight in this specification is the value of standard polystyrene conversion measured by the gel permeation chromatography (GPC) method.

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

(1.3.2. Thermal cross-linking agent)
When the adhesive composition containing the thermal cross-linking agent (B) is heated, the thermal cross-linking agent (B) is cross-linked with the (meth)acrylate copolymer (A) to form a cross-linked structure (three-dimensional network structure). do. Thereby, a pressure-sensitive adhesive having a relatively high coating strength can be obtained.

As the thermal cross-linking agent (B), any one can be used as long as it reacts with the reactive group of the (meth)acrylic acid ester copolymer (A). For example, isocyanate cross-linking agent, epoxy cross-linking agent, amine cross-linking agent, melamine cross-linking agent, aziridine cross-linking agent, hydrazine cross-linking agent, aldehyde cross-linking agent, oxazoline cross-linking agent, metal alkoxide cross-linking agent, metal chelate cross-linking agents, metal salt-based cross-linking agents, ammonium salt-based cross-linking agents, and the like.

These may be selected according to the reactivity of the reactive group of the (meth)acrylate copolymer (A). For example, when the reactive group of the (meth)acrylic acid ester copolymer (A) is a hydroxyl group, it is preferable to use an isocyanate-based cross-linking agent having excellent reactivity with the hydroxyl group. When the reactive group of the (meth)acrylic acid ester copolymer (A) is a carboxy group, it is preferable to use an epoxy-based cross-linking agent having excellent reactivity with the carboxy group. In addition, a thermal crosslinking agent (B) can be used individually by 1 type or in combination of 2 or more types.

The isocyanate-based cross-linking agent contains at least a polyisocyanate compound. Examples of polyisocyanate compounds include aromatic polyisocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate and xylylene diisocyanate, aliphatic polyisocyanates such as hexamethylene diisocyanate, and alicyclic polyisocyanates such as isophorone diisocyanate and hydrogenated diphenylmethane diisocyanate. , and their biuret, isocyanurate, and adducts which are reaction products with low-molecular-weight active hydrogen-containing compounds such as ethylene glycol, propylene glycol, neopentyl glycol, trimethylolpropane, and castor oil.

Among 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 epoxy-based cross-linking agents include 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, N,N,N',N'-tetraglycidyl-m-xylylenediamine, ethylene glycol diglycidyl ether. , 1,6-hexanediol diglycidyl ether, trimethylolpropane diglycidyl ether, diglycidylaniline, diglycidylamine and the like. Among these, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane is preferred from the viewpoint of reactivity with carboxy groups.

The content of the thermal cross-linking agent (B) in the adhesive composition is preferably 0.01 parts by mass or more with respect to 100 parts by mass of the (meth)acrylic acid ester copolymer (A). 05 parts by mass or more, more preferably 0.1 parts by mass or more. When the lower limit of the content of the thermal cross-linking agent (B) is the above value, the resulting pressure-sensitive adhesive exhibits good cohesive strength, and a pressure-sensitive adhesive with relatively high film strength can be obtained. The content is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, and even more preferably 0.4 parts by mass or less. By setting the upper limit of the content of the thermal cross-linking agent (B) to the above value, the resulting pressure-sensitive adhesive has sufficient flexibility, and a pressure-sensitive adhesive having excellent initial conformability to unevenness can be obtained.

(1.3.3. Active energy ray-curable component)
The adhesive obtained by thermally crosslinking the adhesive composition contains an uncured active energy ray-curable component (C). Therefore, the adhesive according to this embodiment is an active energy ray-curable adhesive. When this pressure-sensitive adhesive is applied to an adherend and then irradiated with an active energy ray, the polymerization of the active energy ray-curable component (C) is accelerated by the cleavage of the photopolymerization initiator (D), which will be described later. . The polymerized active energy ray-curable component (C) is entangled with a crosslinked structure (three-dimensional network structure) formed by thermally crosslinking the (meth)acrylate copolymer (A) and the thermally crosslinking agent (B). presumed to be A pressure-sensitive adhesive having such a high-order structure is excellent in step followability and blister resistance under high-temperature and high-humidity conditions.

The active energy ray-curable component (C) is not particularly limited as long as it is a component that is cured by irradiation with an active energy ray in the presence of a photopolymerization initiator (D) described below and that provides the above effects. It may be monomeric, oligomeric or polymeric, or a mixture thereof. Among these, polyfunctional acrylate-based monomers having a molecular weight of less than 1,000, which are excellent in compatibility with the (meth)acrylic acid ester copolymer (A) and the like, are preferred.

Bifunctional, trifunctional, tetrafunctional, pentafunctional, and hexafunctional acrylate monomers are preferred as polyfunctional acrylate monomers having a molecular weight of less than 1,000. Bifunctional acrylate monomers include, for example, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, polyethylene glycol di(meth) Acrylates, neopentyl glycol adipate di(meth)acrylate, neopentyl glycol hydroxypivalate di(meth)acrylate, dicyclopentanyl di(meth)acrylate, caprolactone-modified dicyclopentenyl di(meth)acrylate, ethylene oxide-modified diphosphate di(meth)acrylate (meth)acrylate, di(acryloxyethyl)isocyanurate, allylated cyclohexyl di(meth)acrylate, ethoxylated bisphenol A diacrylate, 9,9-bis[4-(2-acryloyloxyethoxy)phenyl]fluorene, etc. mentioned.

Trifunctional acrylate monomers include trimethylolpropane tri(meth)acrylate, dipentaerythritol tri(meth)acrylate, propionic acid-modified dipentaerythritol tri(meth)acrylate, pentaerythritol tri(meth)acrylate, propylene oxide-modified trimethylolpropane tri(meth)acrylate, tris(acryloxyethyl)isocyanurate, ε-caprolactone-modified tris-(2-(meth)acryloxyethyl)isocyanurate and the like.

Examples of tetrafunctional acrylate monomers include diglycerin tetra(meth)acrylate and pentaerythritol tetra(meth)acrylate. Pentafunctional acrylate monomers include propionic acid-modified dipentaerythritol penta(meth)acrylate. Hexafunctional acrylate monomers include dipentaerythritol hexa(meth)acrylate, caprolactone-modified dipentaerythritol hexa(meth)acrylate, and the like.

Among them, di(acryloxyethyl) isocyanurate, tris(acryloxyethyl) isocyanurate, ε-caprolactone-modified tris -(2-(Meth)acryloxyethyl)isocyanurate and other polyfunctional acrylate monomers containing an isocyanurate structure in the molecule are preferred. Among these, more preferred are polyfunctional acrylate-based monomers that are trifunctional or higher and contain an isocyanurate structure in the molecule. Specifically, ε-caprolactone-modified tris-(2-(meth)acryloxyethyl)isocyanurate is particularly preferred. These may be used individually by 1 type, and may be used in combination of 2 or more type.

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

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

Moreover, as the active energy ray-curable component (C), an adduct acrylate 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 a part of the crosslinkable functional group of the copolymer is , (meth)acryloyl group and a compound having a group reactive with a crosslinkable functional group.

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

As the active energy ray-curable component (C), the polyfunctional acrylate-based monomer described above is preferable. Two or more may be used in combination, or these components may 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 is, from the viewpoint of making the above-mentioned gel fraction ratio and storage elastic modulus ratio of the obtained adhesive preferable, a (meth)acrylic It is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and even more preferably 4 parts by mass or more, relative to 100 parts by mass of the acid ester copolymer (A). Thereby, the pressure-sensitive adhesive to be obtained can be made more excellent in step followability and blister resistance under high-temperature and high-humidity conditions. On the other hand, if the above content is too large, the cross-linking of the adhesive after curing with active energy rays will become too dense, resulting in a decrease in adhesive strength, deterioration in blister resistance, and deterioration in durability. tend to From this viewpoint, the upper limit of the content of the active energy ray-curable component (C) is preferably 30 parts by mass or less, more preferably 15 parts by mass or less, and preferably 10 parts by mass or less. More preferred.

(1.3.4. Photoinitiator)
In this embodiment, as the photopolymerization initiator (D), a photopolymerization initiator having an absorbance of 1.0 or more at a wavelength of 380 nm in an acetonitrile solution having a concentration of 0.1% by mass is used. That is, the absorption of light by the photopolymerization initiator (D) occurs even on the relatively long wavelength side, so even if the adhesive according to the present embodiment contains an ultraviolet absorber (E), which will be described later, the ultraviolet absorber The energy of light having a longer wavelength than the light absorbed by (E) can be used to sufficiently polymerize the pressure-sensitive adhesive, and the cured pressure-sensitive adhesive can absorb ultraviolet rays.

The absorbance of the photopolymerization initiator (D) at a wavelength of 380 nm is preferably 1.1 or more, more preferably 1.3 or more. Although the upper limit of the absorbance is not particularly limited, it is usually preferably 2.5 or less, more preferably 2.0 or less. If the absorbance is too high, the curing reaction of the active energy ray-curable component (C) by the photopolymerization initiator (D) may proceed due to ambient light such as a fluorescent lamp during direct bonding film formation or storage. be. Incidentally, the absorbance of the photopolymerization initiator (D) may be measured by the method described later in Examples.

Further, in the photopolymerization initiator (D), the maximum absorption wavelength of the absorbance at a wavelength of 200 to 500 nm in an acetonitrile solution having a concentration of 0.1% by mass is preferably 350 nm or more, more preferably 370 nm or more, and 380 nm. It is more preferable to have the above. When there are a plurality of maximum absorption wavelengths with absorbance of 200 to 500 nm, at least one maximum absorption wavelength should be within the above range.

When the maximum absorption wavelength is within the above range, it is possible to supply the adhesive with enough energy to sufficiently photopolymerize the adhesive according to the present embodiment. As a result, it is possible to obtain a post-curing pressure-sensitive adhesive that is superior in conformability to irregularities and resistance to blistering while having ultraviolet absorbability.

On the other hand, the upper limit of the absorption maximum wavelength is not particularly limited, but, like the absorbance, it is preferably 450 nm or less, more preferably 410 nm or less, from the viewpoint of preventing the progress of the polymerization reaction caused by ambient light. It is preferably 405 nm or less, more preferably 405 nm or less.

Examples of such a photopolymerization initiator (D) include 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide, bis(2,4,6-trimethylbenzoyl)-phenylphosphine 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 is preferably 0.1 parts by mass or more with respect to 100 parts by mass of the (meth)acrylic acid ester copolymer (A). It is more preferably 3 parts by mass or more. Since the lower limit of the content of the photopolymerization initiator (D) is the above, even if the adhesive contains an ultraviolet absorber, when the active energy ray is irradiated, the photopolymerization initiator (D) becomes easy to cleave, and this triggers the acceleration of the polymerization of the active energy ray-curable component (C), making it possible to obtain a sufficiently cured adhesive after curing.

Further, the content of the photopolymerization initiator (D) is preferably 3.0 parts by mass or less with respect to 100 parts by mass of the (meth)acrylic acid ester copolymer (A), and 1.0 parts by mass. The following are more preferable. If the content of the photopolymerization initiator (D) is too high, the photopolymerization initiator tends to remain in the pressure-sensitive adhesive after curing. Due to this, air bubbles are generated, and this tends to lead to deterioration of step followability and deterioration of blister resistance under high-temperature and high-humidity conditions. Therefore, by setting the upper limit of the content of the photopolymerization initiator (D) to the above value, it is possible to obtain a pressure-sensitive adhesive having excellent step conformability and blister resistance.

In addition, the content of the photopolymerization initiator (D) in the adhesive composition is preferably 1 part by mass or more, and 5 parts by mass or more with respect to 100 parts by mass of the active energy ray-curable component (C). It is more preferable to have Since the lower limit of the content of the photopolymerization initiator (D) is the above, even if the adhesive contains an ultraviolet absorber, when the active energy ray is irradiated, the photopolymerization initiator (D) becomes easy to cleave, and this triggers the acceleration of the polymerization of the active energy ray-curable component (C), making it possible to obtain a sufficiently cured adhesive after curing.

The content of the photopolymerization initiator (D) is preferably 30 parts by mass or less, more preferably 15 parts by mass or less, relative to 100 parts by mass of the active energy ray-curable component (C). . When the upper limit of the content of the photopolymerization initiator (D) is the above value, it is possible to prevent the progress of the polymerization reaction caused by ambient light before curing, so that the initial step conformability is improved. An excellent adhesive can be obtained. In addition, after curing, the photopolymerization initiator hardly remains in the adhesive after curing, so that the adhesive becomes excellent in step followability and blister resistance under high-temperature and high-humidity conditions.

(1.3.5. UV absorber)
The adhesive composition contains an ultraviolet absorber (E). As described above, even if the pressure-sensitive adhesive obtained by thermally crosslinking the pressure-sensitive adhesive composition contains the ultraviolet absorber (E), the photopolymerization initiator (D) is sufficiently A cured adhesive can be obtained. As a result, even though the cured adhesive obtained by curing the adhesive has good curability, for example, even if the material of the protective panel of the display is made of glass that transmits ultraviolet rays, the cured adhesive The agent can absorb ultraviolet light. Therefore, it is possible to suppress deterioration of the members constituting the display body.

Examples of the ultraviolet absorber (E) include benzophenone-based ultraviolet absorbers, benzotriazole-based ultraviolet absorbers, triazine-based ultraviolet absorbers, salicylic acid-based ultraviolet absorbers, oxalic acid anilide-based ultraviolet absorbers, and cyanoacrylate-based ultraviolet absorbers. etc. These ultraviolet absorbers can be used singly or in combination of two or more.

Examples of benzophenone-based UV absorbers include 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-octoxybenzophenone, 2-hydroxy-4-benzyloxybenzophenone, 2-hydroxy- 4-methoxy-5-sulfoxybenzophenone, 2-hydroxy-4-methoxy-5-sulfoxytrihydrate benzophenone, 2,2′-dihydroxy-4-methoxybenzophenone, 2,2′,4,4′-tetra Hydroxybenzophenone, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone, 2,2'-dihydroxy-4,4'-dimethoxy-5-sodium sulfoxybenzophenone, bis(5-benzoyl-4-hydroxy- 2-methoxyphenyl)methane, 2-hydroxy-4-n-dodecyloxybenzophenone, 2-hydroxy-4-methoxy-2'-carboxybenzophenone and the like.

Examples of benzotriazole-based UV absorbers include 2-(2-hydroxy-5-methylphenyl)benzotriazole, 2-(2-hydroxy-5-tert-octylphenyl)benzotriazole, 2-(2-hydroxy- 3,5-dicumylphenyl)phenylbenzotriazole, 2-(2-hydroxy-3-tert-butyl-5-methylphenyl)-5-chlorobenzotriazole, 2,2′-methylenebis[4-(1,1 ,3,3-tetramethylbutyl)-6-(2H-benzotriazol-2-yl)phenol], 2-(2-hydroxy-3,5-di-tert-butylphenyl)benzotriazole, 2-(2 -hydroxy-3,5-di-tert-butylphenyl)-5-chlorobenzotriazole, 2-(2-hydroxy-3,5-di-tert-amylphenyl)benzotriazole, 2-(2-hydroxy-5 -tert-octylphenyl)benzotriazole, 2-(2-hydroxy-5-tert-butylphenyl)benzotriazole, 2-(2-hydroxy-4-octoxyphenyl)benzotriazole, 2,2′-methylenebis(4 -cumyl-6-benzotriazolephenyl), 2,2′-p-phenylenebis(1,3-benzoxazin-4-one, 2-[2-hydroxy-3-(3,4,5,6-tetrahydro and phthalimidomethyl)-5-methylphenyl]benzotriazole.

Examples of triazine-based UV absorbers include 2-(2-hydroxy-4-methoxyphenyl)-4,6-diphenyl-1,3,5-triazine, 2-(2-hydroxy-4-ethoxyphenyl)- 4,6-diphenyl-1,3,5-triazine, 2-(2-hydroxy-4-propoxyphenyl)-4,6-diphenyl-1,3,5-triazine, 2-(2-hydroxy-4- butoxyphenyl)-4,6-diphenyl-1,3,5-triazine, 2-(2-hydroxy-4-hexyloxyphenyl)-4,6-diphenyl-1,3,5-triazine, 2-(2 -hydroxy-4-octyloxyphenyl)-4,6-diphenyl-1,3,5-triazine, 2-(2-hydroxy-4-dodecyloxyphenyl)-4,6-diphenyl-1,3,5- triazine, 2-(2-hydroxy-4-benzyloxyphenyl)-4,6-diphenyl-1,3,5-triazine, 2,4-bis(2-hydroxy-4-butoxyphenyl)-6-(2 ,4-dibutoxyphenyl)-1,3-5-triazine, 2,4,6-tris(2-hydroxy-4-hexyloxy-3-methylphenyl)-1,3,5-triazine, 2-( 2-hydroxy-4-[1-octyloxycarbonylethoxy]phenyl)-4,6-bis(4-phenylphenyl)-1,3,5-triazine, 2-[4-[(2-hydroxy-3- dodecyloxypropyl)oxy]-2-hydroxyphenyl]-4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine, 2-[4-[(2-hydroxy-3-tridecyl oxypropyl)oxy]-2-hydroxyphenyl]-4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine, 2-[4-[(2-hydroxy-3-(2' -ethyl)hexyl)oxy]-2-hydroxyphenyl]-4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine, 2,4-bis(2,4-dimethylphenyl)- 6-[2-hydroxy-4-(3-octyloxy-2-hydroxypropyloxy)-5-α-cumylphenyl]-s-triazine, 2,4-bis(2,4-dimethylphenyl)-6-[ 2-hydroxy-4-(3-nonyloxy-2-hydroxypropyloxy)-5-α-cumylphenyl]-s-triazine 2,4-bis(2,4-dimethylphenyl)-6-[ 2-hydroxy-4-(3-decyloxy-2-hydroxypropyloxy)-5-α-cumylphenyl]-s-triazine, 2-(2-hydroxy-4-acryloyloxyethoxyphenyl)-4,6-bis( 2,4-dimethylphenyl)-1,3,5-triazine and the like.

Examples of salicylic acid-based ultraviolet absorbers include phenyl salicylate, p-tert-butylphenyl salicylate, and p-octylphenyl salicylate.

Examples of cyanoacrylate ultraviolet absorbers include 2-ethylhexyl-2-cyano-3,3'-diphenyl acrylate and ethyl-2-cyano-3,3'-diphenyl acrylate.

Among these, benzophenone UV absorbers, benzotriazole UV absorbers, and triazine UV absorbers are preferred, and benzophenone UV absorbers and benzotriazole UV absorbers are more preferred.

The content of the ultraviolet absorber (E) is preferably 1 part by mass or more, more preferably 2 parts by mass or more, relative to 100 parts by mass of the (meth)acrylate copolymer (A). , 4 parts by mass or more. Also, the content of the ultraviolet absorber (E) is preferably 25 parts by mass or less, more preferably 15 parts by mass or less, and even more preferably 8 parts by mass or less. If the content of the ultraviolet absorber (E) is too small, the absorption of ultraviolet rays becomes insufficient, and there is a tendency that deterioration of the members constituting the display cannot be suppressed. On the other hand, if the content of the ultraviolet absorber (E) is too high, the light used for curing the adhesive is also absorbed to some extent, and the adhesive tends to be insufficiently cured. Step followability and blister resistance deteriorate.

Further, the content of the ultraviolet absorber (E) is preferably 1 part by mass or more, more preferably 5 parts by mass or more, relative to 1 part by mass of the photopolymerization initiator (D), and 8 parts by mass. More preferably, it is at least 1 part.

Further, the content is preferably 50 parts by mass or less, more preferably 30 parts by mass or less, and 15 parts by mass or less with respect to 1 part by mass of the photopolymerization initiator (D). More preferred. When the content of the ultraviolet absorber (E) with respect to the photopolymerization initiator (D) is within the above range, the photopolymerization initiator is cleaved and sufficiently cured while the ultraviolet absorption is sufficient. It is possible to obtain an adhesive that can be As a result, the post-curing pressure-sensitive adhesive can suppress deterioration of members constituting the display body.

(1.3.6. Silane coupling agent)
The adhesive composition preferably further contains a silane coupling agent (F). As a result, when the adherend includes a glass member, the adhesion between the adhesive and the post-curing adhesive and the glass member is improved. In addition, even when the adherend includes a plastic member, the adhesion between the pressure-sensitive adhesive and the pressure-sensitive adhesive after curing and the plastic plate is improved. Therefore, the pressure-sensitive adhesive containing the silane coupling agent (F) and the pressure-sensitive adhesive after curing are superior in step followability under high-temperature and high-humidity conditions.

In the present embodiment, the silane coupling agent (F) is preferably an organosilicon compound having at least one alkoxysilyl group in the molecule and having optical transparency.

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

The content of the silane coupling agent (F) is preferably at least 0.05 parts by mass, and at least 0.1 parts by mass with respect to 100 parts by mass of the (meth)acrylate copolymer (A). more preferably 0.2 parts by mass or more. The content is preferably 3 parts by mass or less, more preferably 1 part by mass or less, and even more preferably 0.5 parts by mass or less.

(1.3.7. Other additives)
The pressure-sensitive adhesive according to this embodiment may contain various additives as necessary. Examples of such additives include antistatic agents, tackifiers, antioxidants, light stabilizers, softeners, fillers, and refractive index modifiers.

(1.3.8. Production of adhesive composition)
The adhesive composition is prepared by producing a (meth)acrylic acid ester copolymer (A), and adding a thermal crosslinking agent (B), an active energy It can be produced by adding the radiation-curable component (C), the photopolymerization initiator (D), and the ultraviolet absorber (E) and mixing them thoroughly. A silane coupling agent (F), additives and the like may be added as necessary. The (meth)acrylate copolymer (A) may be produced as follows.

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

Examples of polymerization initiators include azo compounds and organic peroxides, and two or more of them may be used in combination. Examples of azo compounds include 2,2′-azobisisobutyronitrile, 2,2′-azobis(2-methylbutyronitrile), 1,1′-azobis(cyclohexane 1-carbonitrile), 2 ,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(2,4-dimethyl-4-methoxyvaleronitrile), dimethyl 2,2'-azobis(2-methylpropionate) , 4,4′-azobis(4-cyanovaleric acid), 2,2′-azobis(2-hydroxymethylpropionitrile), 2,2′-azobis[2-(2-imidazolin-2-yl) propane] and the like.

Examples of organic peroxides include benzoyl peroxide, t-butylperbenzoate, cumene hydroperoxide, diisopropylperoxydicarbonate, di-n-propylperoxydicarbonate, di(2-ethoxyethyl)peroxy dicarbonate, t-butylperoxyneodecanoate, t-butylperoxybivalate, (3,5,5-trimethylhexanoyl)peroxide, dipropionylperoxide, diacetylperoxide and the like.

The weight average molecular weight of the resulting polymer can be adjusted by adding a chain transfer agent such as 2-mercaptoethanol in the polymerization step.

(1.3.9. Production of adhesive)
The adhesive is obtained by thermally crosslinking the (meth)acrylate copolymer (A) in the adhesive composition with the thermal crosslinking agent (B). That is, thermal crosslinking of the adhesive composition is performed by heat treatment. This heat treatment can also serve as a drying treatment after application of the adhesive composition.

The heating temperature of the heat treatment is preferably 50 to 150°C, more preferably 70 to 120°C. The heating time is preferably 10 seconds to 10 minutes, more preferably 50 seconds to 2 minutes. Furthermore, it is particularly preferable to provide a curing period of about 1 to 2 weeks at normal temperature (eg, 23° C., 50% RH) after the heat treatment.

By the above heat treatment (and curing), the (meth)acrylic acid ester copolymer (A) is satisfactorily crosslinked via the thermal crosslinking agent (B) to form a crosslinked structure. Through such steps, the pressure-sensitive adhesive according to the present embodiment is obtained.

In addition, other components contained in the adhesive composition (active energy ray-curable component (C), photopolymerization initiator (D), ultraviolet absorber (E), etc.) are before and after thermal crosslinking, and the content and properties are It does not change.

(1.4. Release sheet)
The release sheets 12a and 12b protect the adhesive layer 11 until the direct bonding film 1 is used, and are peeled off when the direct bonding film 1 (adhesive layer 11) is used. In the direct bonding film 1 according to this embodiment, one or both of the release sheets 12a and 12b are not necessarily required.

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

The release surfaces of the release sheets 12a and 12b (especially the surfaces in contact with the pressure-sensitive adhesive layer 11) are preferably subjected to a release treatment. Examples of release agents 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 of the release sheets is a heavy release type release sheet with a large release force, and the other release sheet is a light release type release sheet with a small release force.

The thickness of the release sheets 12a and 12b is not particularly limited, but is usually 20 μm or more and 200 μm or less.

(2. Production of direct bonding film)
A method for manufacturing the direct bonding film 1 is not particularly limited, and it may be manufactured by a known method. For example, the adhesive composition coating liquid is applied to the release surface of one of the release sheets 12a (or 12b), and heat treatment is performed to thermally crosslink the adhesive composition to form a coating having a predetermined thickness. form a layer. The release surface of the other release sheet 12b (or 12a) is overlaid on the formed coating layer. If a curing period is required, a curing period is provided, and if the curing period is not required, the coating layer becomes the adhesive layer 11 as it is. As a result, the direct bonding film 1 is obtained.

As another production example of the direct bonding film 1, the adhesive composition coating liquid is applied to the release surface of one release sheet 12a, heat treatment is performed to thermally crosslink the adhesive composition, and the coating is applied. A layer is formed to obtain a release sheet 12a with a coating layer. Further, the adhesive composition coating solution is applied to the release surface of the other release sheet 12b, and heat treatment is performed to thermally crosslink the adhesive composition to form a coating layer. A release sheet 12b is obtained. Then, the release sheet 12a with the coating layer and the release sheet 12b with the coating layer are pasted together so that both coating layers are in contact with each other. When a curing period is required, the curing period is set, and when the curing period is not required, the laminated coating layer becomes the adhesive layer 11 as it is. As a result, the direct bonding film 1 is obtained. According to this production example, even when the pressure-sensitive adhesive layer 11 is thick, it is possible to produce stably.

Examples of methods for applying the adhesive composition coating liquid include bar coating, knife coating, roll coating, blade coating, die coating, gravure coating, and the like.

In the direct bonding film 1 according to this embodiment, the pressure-sensitive adhesive layer 11 has a crosslinked structure, so the film strength of the pressure-sensitive adhesive layer 11 is relatively high. As a result, when the direct bonding film 1 is cut or the like, problems such as the adhesive protruding from the cut surface and adhering to the blade can be suppressed. In addition, the oozing of the adhesive from the adhesive layer 11 during storage of the direct bonding film 1 is also suppressed.

(3. Use of direct bonding film)
The direct bonding film 1 according to this embodiment is used as follows. First, the pressure-sensitive adhesive layer 11 of the direct bonding film 1 is bonded to the first display body constituent member and the second display body constituent member. Subsequently, the pressure-sensitive adhesive layer 11 is irradiated with a predetermined active energy ray through the first display body-constituting member or the second display body-constituting member, and the pressure-sensitive adhesive layer 11 is cured to form a cured pressure-sensitive adhesive layer. (This is referred to as a post-curing adhesive layer 11' in FIG. 2, which will be described later).

Before irradiation with active energy rays, in the present embodiment, the adhesive constituting the adhesive layer 11 contains both a crosslinked structure and an uncured active energy ray-curable component, and thus has a predetermined cohesive force. while having a relatively soft pressure-sensitive adhesive layer. Therefore, when the direct bonding film 1 is applied to a member constituting a display body having a step, the pressure-sensitive adhesive layer 11 sufficiently follows the step, and the occurrence of gaps, floats, etc. near the step is suppressed.

Then, after the pressure-sensitive adhesive layer is attached to the display body-constituting member in a relatively soft state, the pressure-sensitive adhesive layer is irradiated with a predetermined active energy ray to harden the pressure-sensitive adhesive layer. At this time, even if the adhesive layer contains an ultraviolet absorber, the wavelength at which the photopolymerization initiator can cleave is on the relatively long wavelength side. Promoted. As a result, it is possible to increase the cohesive force of the cured pressure-sensitive adhesive layer while having a good level difference followability while having an ultraviolet absorbing ability. Therefore, good blister resistance is obtained.

In particular, even when the obtained laminate (display body) is placed under high temperature and high humidity conditions, for example, under conditions of 85° C. and 85% RH for 72 hours, air bubbles, floating, peeling, etc. may occur near the steps. Suppressed. Furthermore, the generation of blisters such as air bubbles, floating, and peeling at the interface between the display body-constituting member and the post-curing pressure-sensitive adhesive layer is also suppressed. That is, the direct bonding film 1 according to the present embodiment has an ultraviolet absorbing ability, and is excellent not only in the initial step followability but also in step followability and blister resistance under high-temperature and high-humidity conditions.

(4. Display body)
As shown in FIG. 2, the display body 2 according to the present embodiment includes a first display body-constituting member 21 having a step, a second display body-constituting member 22, and a first display body-constituting member 21 positioned between them. It has a post-curing adhesive layer 11' for bonding the display body forming member 21 and the second display body forming member 22 to each other. The post-curing adhesive layer 11′ is a cured product obtained by curing the adhesive layer 11 shown in FIG. This step is caused by the thickness of the printed layer 3 formed on the first display body-constituting member 21 .

(4.1. Adhesive layer after curing)
The cured pressure-sensitive adhesive layer 11' is obtained by curing the pressure-sensitive adhesive layer 11 of the direct bonding film 1 by irradiation with active energy rays. In the present embodiment, the post-curing pressure-sensitive adhesive layer 11′ has a crosslinked structure composed of the (meth)acrylic acid ester copolymer (A) and the thermal crosslinking agent (B), and is active energy ray-curable. It consists of a pressure-sensitive adhesive containing a structure (polymerized structure) obtained by polymerizing and curing the component (C), a photopolymerization initiator (D), and an ultraviolet absorber (E). The polymerized structure is presumed to be entwined with a crosslinked structure composed of the (meth)acrylic acid ester copolymer (A) and the thermal crosslinking agent (B). By having a structure in which a plurality of three-dimensional structures are intertwined, the cured pressure-sensitive adhesive layer has high cohesive strength. Therefore, not only the normal blister resistance but also the blister resistance under high temperature and high humidity conditions is good.

In addition, as long as the effect of the present invention can be obtained, the post-curing adhesive constituting the post-curing adhesive layer 11′ contains a photopolymerization initiator (D) that has not been cleaved even by irradiation with an active energy ray. It may be In this embodiment, the residual amount of the photopolymerization initiator in the adhesive after curing is preferably 0.1% by mass or less, and more preferably 0.01% by mass or less.

(4.2. Other configurations of the display body)
Examples of the display 2 include a liquid crystal (LCD) display, a light emitting diode (LED) display, an organic electroluminescence (organic EL) display, electronic paper, and the like, and may be a touch panel. Moreover, as the display body 2, the member which comprises those parts may be sufficient.

The first display member constituting member 21 is preferably a protective panel made of a glass plate, a plastic plate or the like, or a laminated body including them. In this case, the printed layer 3 is generally formed in a frame shape on the post-curing adhesive layer 11 ′ side of the first display member constituting member 21 .

As described above, in the present embodiment, even if the protective panel as the first display body constituent member 21 in the display body 2 is made of a glass plate, the post-curing adhesive layer 11' absorbs ultraviolet light. Therefore, it is possible to suppress the deterioration of other members constituting the display body. In the display 2, even if the protective panel as the first display-body-constituting member 21 is made of a plastic plate, the post-curing pressure-sensitive adhesive layer 11' has excellent blister resistance. Furthermore, when the protective panel is made of a plastic plate, moisture in the air easily permeates the plastic plate, so when placed under high-temperature and high-humidity conditions, for example, moisture easily penetrates into the adhesive. As a result, when the temperature is returned to normal temperature and normal humidity, whitening of the adhesive tends to occur due to the infiltrated moisture. Even in such a case, when the pressure-sensitive adhesive of the present invention contains a hydroxyl group-containing monomer as a reactive group-containing monomer constituting the (meth)acrylic acid ester copolymer (A), compatibility with infiltrated moisture is As a result, the whitening of the pressure-sensitive adhesive when returned to normal temperature and normal humidity is suppressed, and the whitening resistance to wet heat is excellent.

Examples of the above-mentioned glass plate include, but are not limited to, chemically strengthened glass, alkali-free glass, quartz glass, soda lime glass, barium/strontium-containing glass, aluminosilicate glass, lead glass, borosilicate glass, and barium borosilicate glass. acid glass and the like. Although the thickness of the glass plate is not particularly limited, it is usually 0.1 mm or more, preferably 0.2 mm or more. Moreover, the thickness is usually 5 mm or less, preferably 2 mm or less.

Examples of the plastic plate include, but are not limited to, an acrylic plate, a polycarbonate plate, and the like. Although the thickness of the plastic plate is not particularly limited, it is usually 0.2 mm or more, preferably 0.4 mm or more. Moreover, the thickness is usually 5 mm or less, preferably 3 mm or less.

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

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

Examples of the optical member include anti-scattering films, polarizing plates (polarizing films), polarizers, retardation plates (retardation films), viewing angle compensation films, brightness enhancement films, contrast enhancement films, liquid crystal polymer films, and diffusion films. , transflective films, transparent conductive films, and the like. Examples of the anti-scattering film include a hard coat film in which a hard coat layer is formed on one side of a base film.

The material constituting the printing layer 3 is not particularly limited, and known materials for printing are used. The thickness of the printed layer 3, that is, the height of the step, is preferably 3 μm or more, preferably 5 μm or more, more preferably 7 μm or more, further preferably 10 μm or more, further preferably 20 μm or more. is particularly preferred. Moreover, the height is preferably 50 μm or less, more preferably 35 μm or less.

(4.4. Production of display)
In order to manufacture the above-described display body 2, as an example, one release sheet 12a of the direct bonding film 1 is peeled off, and the exposed adhesive layer 11 of the direct bonding film 1 is transferred to the first display body constituent member 21. is laminated on the side on which the printed layer 3 is present. Thereafter, the other release sheet 12b is peeled off from the adhesive layer 11 of the direct bonding film 1, and the exposed adhesive layer 11 of the direct bonding film 1 and the second display member constituting member 22 are pasted together. As another example, the bonding order of the first display body forming member 21 and the second display body forming member 22 may be changed.

An example of a method for manufacturing the display 2 will be shown. First, one of the release sheets 12a of the direct bonding film 1 is peeled off, and the exposed adhesive layer 11 of the direct bonding film 1 is adhered to the surface of the first display body component 21 on which the printed layer 3 is present. match. At this time, since the pressure-sensitive adhesive layer 11 is excellent in initial step followability, the occurrence of gaps and floats near the step due to the printed layer 3 is suppressed.

Next, the other release sheet 12b is peeled off from the adhesive layer 11 of the direct bonding film 1, and the exposed adhesive layer 11 of the direct bonding film 1 and the second display member constituting member 22 are bonded to form a laminate. get As another example, the bonding order of the first display body forming member 21 and the second display body forming member 22 may be changed.

After that, the adhesive layer 11 in the laminate is irradiated with an active energy ray. In this embodiment, as a result, the active energy ray-curable component (C) in the adhesive layer 11 is polymerized, and the adhesive layer 11 is cured to become the cured adhesive layer 11'.

The active energy ray refers to an electromagnetic wave or a charged particle beam that has an energy quantum, and specifically includes ultraviolet rays, electron beams, and the like. In this embodiment, the active energy ray is preferably an active energy ray containing light having a wavelength of 200 to 450 nm.

As the active energy ray that satisfies the above conditions, for example, a light source capable of irradiating ultraviolet rays, such as a high-pressure mercury lamp, a fusion H lamp, and a xenon lamp, may be used. In the case of a high-pressure mercury lamp, the main wavelength is 365 nm, but since light with wavelengths of 405 nm and 436 nm is also emitted, light with longer wavelengths than the main wavelength can be used for curing the pressure-sensitive adhesive layer 11. .

As for the irradiation amount of the active energy rays, the illuminance is preferably 50 mW/cm ² or more and 1000 mW/cm ² or less. The amount of light is preferably 50 mJ/cm ² or more, more preferably 80 mJ/cm ² or more, and even more preferably 200 mJ/cm ² or more. Also, the amount of light is preferably 10000 mJ/cm ² or less, more preferably 5000 mJ/cm ² or less, and even more preferably 2000 mJ/cm ² or less.

The display body 2 is obtained through the above steps. In the 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 can be used under high temperature and high humidity conditions (for example, 85 ° C., 85% RH, 72 hours). Even when placed, the occurrence of air bubbles, floating, peeling, etc. near the steps is suppressed.

In addition, in the display 2, since the post-curing pressure-sensitive adhesive layer 11′ has excellent blister resistance, the display 2 is placed under high temperature and high humidity conditions (eg, 85° C., 85% RH, 72 hours), Even when outgassing is generated from display body constituent members made of plastic plates or the like, the generation of blisters such as air bubbles, floating, and peeling at the interface between the post-curing adhesive layer 11′ and the display body constituent members 21 and 22 is suppressed. be done.

(5. Effect in this embodiment)
In the present embodiment, the adhesive layer of the direct bonding film has a low light transmittance in a predetermined wavelength range to impart ultraviolet absorption ability to the adhesive layer, and the gel content of the adhesive layer before and after the active energy ray irradiation. By controlling the ratio within a predetermined range, both good step followability and good blister resistance are achieved. Furthermore, the above effects are further enhanced by setting the storage elastic modulus of the adhesive layer before and after irradiation with active energy rays and the adhesive strength of the adhesive layer after irradiation with active energy rays within a predetermined range.

As a specific configuration of the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer that achieves such characteristics, the pressure-sensitive adhesive is formed by curing a (meth)acrylic acid ester copolymer and a thermal cross-linking agent through a cross-linking reaction. In addition to the existence of a crosslinked structure (three-dimensional network structure), the active energy ray-curable component is allowed to exist as it is without being polymerized (cured). In other words, a cured product and an uncured product coexist in the adhesive.

The crosslinked structure is a cured product, and the pressure-sensitive adhesive having the crosslinked structure provides a predetermined cohesive force. On the other hand, it is considered that the active energy ray-curable component is not polymerized (cured) and remains as an uncured product in the gaps of the crosslinked structure. As a result, the adhesive has a predetermined strength due to the crosslinked structure, and the active energy ray-curable component, which is an uncured product, works as a component that improves the plasticity of the adhesive. Therefore, when the adhesive is attached to an adherend, even if there is a step on the adherend, the adhesive sufficiently follows the step, and even in the vicinity of the step, the adhesion between the adherend and the adhesive is sufficient. Do not create voids such as gaps and floats between them.

After the adhesive is attached to the adherend, the adhesive is irradiated with active energy rays. At this time, although the ultraviolet absorber contained in the adhesive absorbs the active energy ray, the wavelength range of light having sufficient absorbance for the photopolymerization initiator to advance the polymerization reaction and the light absorbed by the ultraviolet absorber is different from the wavelength range of Therefore, the photopolymerization initiator is cleaved by the active energy ray that is not absorbed by the ultraviolet absorber, and the polymerization (curing) of the active energy ray-curable component present without being cured is accelerated. As a result, it is considered that a polymerized structure is formed so as to be entangled with the crosslinked structure. Since the curing of the active energy ray-curable component is performed in a state in which it is sufficiently adhered to the adherend, after curing with the active energy ray, the crosslinked structure and the polymerized structure interact appropriately, resulting in step follow-up. It can exhibit a degree of cohesive strength that cannot be exhibited in the state before curing, which has good properties.

As described above, in the above-described embodiment, in the pressure-sensitive adhesive, by combining the curing (thermal curing) before bonding to the adherend and the curing (activation energy ray curing) after bonding to the adherend, the step followability and resistance are improved. A very high level of blister resistance can be achieved. Moreover, since the adhesive contains an ultraviolet absorber, it is possible to effectively suppress deterioration of the members constituting the display.

Therefore, a display body in which a structural member having a step and other structural members are adhered using this pressure-sensitive adhesive is sufficiently protected from ultraviolet rays and can maintain good image quality.

(6. Modification)
In the embodiment described above, the direct bonding film has two release sheets 12a and 12b, but one or both of the release sheets 12a and 12b in the direct bonding film 1 may be omitted.

Also, the first display member constituting member 21 may have steps other than the printed layer 3 . Furthermore, not only the first display body constituent member 21 but also the second display body constituent member 22 may have a step on the post-curing adhesive layer 11' side.

Although the embodiments of the present invention have been described above, the present invention is by no means limited to the above embodiments, and may be modified in various ways within the scope of the present invention.

EXAMPLES The present invention will be described in more detail below using examples, but the present invention is not limited to these examples.

(Production example 1)
1. Preparation of (meth)acrylate copolymer 60 parts by weight of 2-ethylhexyl acrylate, 10 parts by weight of isobornyl acrylate, 10 parts by weight of N-acryloylmorpholine, and 20 parts by weight of 2-hydroxyethyl acrylate are copolymerized. , (meth)acrylic acid ester copolymer (A) was prepared. The weight average molecular weight (Mw) of the obtained (meth)acrylic acid ester copolymer (A) was measured by the method described below and found to be 500,000.

The weight average molecular weight (Mw) is the polystyrene-equivalent weight average molecular weight measured under the following conditions using gel permeation chromatography (GPC) (GPC measurement).
(Measurement condition)
・ GPC measurement device: HLC-8020 manufactured by Tosoh Corporation
・ GPC column (passed in the following order): TSK guard column HXL-H manufactured by Tosoh Corporation
TSK gel GMHXL (x2)
TSK gel G2000HXL
・Measurement solvent: tetrahydrofuran ・Measurement temperature: 40°C

2. Preparation of adhesive composition 100 parts by mass of the (meth)acrylic acid ester copolymer (A) obtained in the above step 1 (solid content conversion value; the same applies hereinafter), and trimethylolpropane as a thermal cross-linking agent (B) 0.2 parts by mass of modified tolylene diisocyanate, 5.0 parts by mass of ε-caprolactone-modified tris-(2-acryloxyethyl) isocyanurate as an active energy ray-curable component (C), and a photopolymerization initiator (D ) as 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide 0.5 parts by mass, 3.0 parts by mass of 2-dihydroxy-4-methoxybenzophenone as the ultraviolet absorber (E), and silane coupling 0.3 parts by mass of 3-glycidoxypropyltrimethoxysilane as agent (F) was mixed, thoroughly stirred, and diluted with methyl ethyl ketone to obtain an adhesive composition having a solid content concentration of 50% by mass. A coating solution was obtained.

3. Production of Direct Bonding Film The coating solution of the obtained adhesive composition was applied to a heavy release type release sheet (manufactured by Lintec Corporation, product name "SP-PET752150") in which one side of a polyethylene terephthalate film was release treated with a silicone release agent. It was applied to the release-treated surface with a knife coater. Then, the coating layer is heat-treated at 90° C. for 1 minute to promote a thermal cross-linking reaction, thereby forming a cross-linked structure composed of the (meth)acrylic acid ester copolymer (A) and the thermal cross-linking agent (B). A coating layer was formed from the pressure-sensitive adhesive.

Next, the coated layer on the heavy release release sheet obtained above and a light release release sheet (manufactured by Lintec, product name "SP-PET382120") obtained by releasing a polyethylene terephthalate film on one side with a silicone release agent. are laminated so that the release-treated surface of the light-release release sheet is in contact with the coating layer, and cured for 7 days under conditions of 23 ° C. and 50% RH to form an adhesive layer with a thickness of 50 μm. A direct bonding film having a structure of heavy release type release sheet/adhesive layer (thickness: 50 μm)/light release type release sheet was produced. The thickness of the pressure-sensitive adhesive layer is a value measured in accordance with JIS K7130 using a constant pressure thickness measuring instrument (manufactured by Teclock, product name "PG-02").

(Examples 2 to 9, Comparative Examples 1 to 4)
A direct bonding film was produced in the same manner as in Example 1, except that the type and amount of the photopolymerization initiator (D) and the type and amount of the ultraviolet absorber (E) were changed as shown in Table 1. .

Details such as abbreviations in Table 1 are as follows.
((Meth) acrylic acid ester copolymer (A))
2EHA: 2-ethylhexyl acrylate IBXA: isobornyl acrylate ACMO: N-acryloylmorpholine HEA: 2-hydroxyethyl acrylate (thermal cross-linking agent (B))
B1: trimethylolpropane-modified tolylene diisocyanate B2: trimethylolpropane-modified xylene diisocyanate (active energy ray-curable component (C))
C1: ε-caprolactone-modified tris-(2-acryloxyethyl) isocyanurate (photoinitiator (D))
D1: 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide D2: A mixture of 1-hydroxycyclohexylphenyl ketone and benzophenone at a mass ratio of 1:1 (ultraviolet absorber (E))
E1: 2-dihydroxy-4-methoxybenzophenone E2: 2-methoxy-1-methylethyl acetate, benzenepropanoic acid, 3-(2H-benzotriazol-2-yl)-5-(1,1-dimethylethyl)- 4-hydroxy, C7-9 side chain and linear alkyl esters E3: Octyl-3-(3-t-butyl-4-hydroxy-5-(5-chloro-2H-benzotriazol-2-yl)phenyl)propionate +2-ethylhexyl-3-(3-t-butyl-4-hydroxy-5-(5-chloro-2H-benzotriazol-2-yl)phenyl)propionate (silane coupling agent (F))
F1: 3-glycidoxypropyltrimethoxysilane

In addition, an acetonitrile solution with a concentration of 0.1% by mass of photopolymerization initiators D1 and D2 was prepared, and the absorbance in the wavelength range of 200 to 500 nm in the solution was measured by ultraviolet-visible-near-infrared (UV-Vis-NIR) spectrophotometry. (manufactured by Shimadzu Corporation, product name “UV-3600”). Based on the results, the absorbance at a wavelength of 380 nm and the maximum absorption wavelength in the above measurement range were derived. Table 1 shows the results.

(Evaluation of UV absorbability)
The light release type release sheet was peeled off from the direct bonding films obtained in Examples and Comparative Examples, and the exposed adhesive layer was attached to soda lime glass (manufactured by Nippon Sheet Glass Co., Ltd.) having a thickness of 1.1 mm. After that, the heavy release type release sheet was peeled off to obtain an evaluation sample before irradiation with active energy rays. In addition, the exposed adhesive layer was directly irradiated with ultraviolet rays under the following conditions to cure the adhesive layer to form a cured adhesive layer, thereby obtaining a sample for evaluation after irradiation with active energy rays.

The pressure-sensitive adhesive layer of the obtained evaluation sample is irradiated with light in a wavelength range of 300 to 800 nm using an ultraviolet-visible-near-infrared spectrophotometer (manufactured by Shimadzu Corporation, UV-3600) to determine the light transmission of the pressure-sensitive adhesive layer. The light transmittance of the pressure-sensitive adhesive layer at 380 nm (before irradiation with active energy rays and after irradiation with active energy rays) was derived. A sample in which the derived light transmittance of the adhesive layer at 380 nm is 40% or less is judged to have ultraviolet absorption ability, and a sample in which the derived light transmittance of the adhesive layer at 380 nm exceeds 40% is judged to have ultraviolet absorption ability. determined that there is no Table 2 shows the results.

In Comparative Example 1, which does not have an ability to absorb ultraviolet rays, the transmittance becomes greater than 0 (begins to transmit ultraviolet rays without being absorbed) at a wavelength of around 300 nm before and after irradiation with active energy rays, and at a wavelength of 350 nm, the transmittance is A result of over 80% has already been obtained.

On the other hand, in Examples 1 to 9, the transmittance is 0 up to a wavelength of 370 nm. is below In other words, it was confirmed that there was a very large difference between the examples and the comparative examples with respect to the ultraviolet absorbability at least in the ultraviolet region with a wavelength of 300 to 380 nm.
<Ultraviolet irradiation conditions>
・Using a high-pressure mercury lamp ・Illuminance 200mW/cm ² , Light intensity 2000mJ/cm ²
・Using “UVPF-A1” manufactured by Eye Graphics Co., Ltd. for UV illuminance and photometer

(Evaluation of gel fraction: before active energy ray irradiation)
The direct bonding films obtained in Examples and Comparative Examples were cut into a size of 80 mm × 80 mm, the pressure-sensitive adhesive layer was wrapped in a polyester mesh (mesh size 200), and the mass was weighed with a precision balance. By subtracting the mass of the mesh alone, the mass of the adhesive alone was calculated. Let the mass at this time be M1.

Next, the adhesive wrapped in the polyester mesh was immersed in ethyl acetate at room temperature (23° C.) for 72 hours. After that, the pressure-sensitive adhesive was taken out and 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 of 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. Let the mass at this time be M2. A gel fraction (%) is represented by (M2/M1)×100. From this, the gel fraction of the adhesive (before active energy ray irradiation) was derived. Table 2 shows the results.

(Evaluation of gel fraction: after active energy ray irradiation)
The light release type release sheet was peeled off from the direct bonding films obtained in Examples and Comparative Examples, and the exposed adhesive layer was directly irradiated with active energy rays under the conditions described above to cure the adhesive layer. After curing, it was used as an adhesive layer. The gel fraction (after active energy ray irradiation; direct irradiation) was derived in the same manner as described above for the cured adhesive of the cured adhesive layer. Table 2 shows the results.

(Evaluation of gel fraction: ratio of gel fraction of adhesive before and after irradiation with active energy rays)
From the derived gel fraction of the adhesive before irradiation with active energy rays and the gel fraction of the cured adhesive after irradiation with active energy rays, the gel fraction of the adhesive before and after irradiation with active energy rays is obtained from the following formula. We derived the ratio of Table 2 shows the results.
Ratio of gel fraction of adhesive before and after irradiation with active energy ray = (gel fraction of cured adhesive after irradiation with active energy ray/gel fraction of adhesive before irradiation with active energy ray)

(Curability evaluation)
If the gel fraction after irradiation with active energy rays is greater than the gel fraction before irradiation with active energy rays, it indicates that the pressure-sensitive adhesive layer is cured. The curability of a sample having a gel fraction ratio of 1.05 or more before and after radiation irradiation is indicated by “○”, and the curability of a sample having a gel fraction ratio of less than 1.05 is indicated by “×”. Notated. Table 2 shows the results.

(Evaluation of storage elastic modulus: before active energy ray irradiation)
The light release type release sheet was peeled off from the direct bonding films obtained in Examples and Comparative Examples, and the exposed pressure-sensitive adhesive layer was punched out into a circle with a diameter of 10 mm to obtain an evaluation sample for measuring the viscoelasticity of the pressure-sensitive adhesive layer. Obtained. Using a viscoelasticity measuring device (manufactured by TA Instruments Co., Ltd., ARES), a strain with a frequency of 1 Hz was applied to the evaluation sample, and the storage elastic modulus was measured from -50 to 150°C. Table 2 shows the results.

(Evaluation of storage elastic modulus: after active energy ray irradiation)
The light release type release sheet was peeled off from the direct bonding films obtained in Examples and Comparative Examples, and the exposed adhesive layer was directly irradiated with active energy rays under the conditions described above to cure the adhesive layer. After curing, it was used as an adhesive layer. The storage elastic modulus (after active energy ray irradiation) of this cured pressure-sensitive adhesive layer was measured in the same manner as described above. Table 2 shows the results.

(Evaluation of storage elastic modulus: ratio of storage elastic modulus of adhesive before and after curing)
From the derived storage elastic modulus of the adhesive before irradiation with active energy rays and the storage elastic modulus of the cured adhesive after irradiation with active energy rays, the storage elastic modulus of the adhesive before and after irradiation with active energy rays is obtained from the following formula. We derived the ratio of Table 2 shows the results.
Ratio of storage elastic modulus of adhesive before and after irradiation with active energy ray = (storage elastic modulus of cured adhesive after irradiation with active energy ray/storage elastic modulus of adhesive before irradiation with active energy ray)

(Evaluation of adhesive strength)
A polyethylene terephthalate (PET) film (manufactured by Toyobo Co., Ltd., product name “PET A4300”, thickness: 100 μm) having an easy-adhesive layer obtained by peeling the light-releasing release sheet from the direct bonding films obtained in Examples and Comparative Examples. to obtain a laminate of release sheet/adhesive layer (50 μm)/PET film. The laminate thus obtained was cut into a piece having a width of 25 mm and a length of 150 mm, which was used as a sample.

In an environment of 23 ° C. and 50% RH, the heavy release type release sheet was peeled off from the above sample, and the exposed adhesive layer was attached to soda lime glass (manufactured by Nippon Sheet Glass Co., Ltd., total light transmittance: 99% or more). After that, pressure bonding was performed by reciprocating a roller of 2 kg once. Next, the adhesive layer was cured by irradiating the active energy ray under the conditions described above through the soda lime glass to obtain the cured adhesive layer. Then, after leaving it for 24 hours under the conditions of 23 ° C. and 50% RH, using a tensile tester (manufactured by Orientec, Tensilon), the adhesive strength (N /25 mm) was measured. Conditions other than those described here were measured according to JIS Z0237:2009. Table 2 shows the results.

(Evaluation of haze value)
A light release type release sheet was peeled off from the direct bonding films obtained in Examples and Comparative Examples, and attached to soda lime glass (manufactured by Nippon Sheet Glass Co., Ltd., total light transmittance: 99% or more) with a thickness of 1.1 mm. After that, the adhesive layer was directly irradiated with the active energy ray under the conditions described above through the soda lime glass, the adhesive layer was cured to form a cured adhesive layer, and the heavy release release sheet was peeled off to obtain an evaluation sample.

A haze value (%) was measured by irradiating measurement light from a haze meter (manufactured by Nippon Denshoku Industries Co., Ltd., product name "NDH-7000") from the adhesive layer side of the evaluation sample. Each measurement was performed three times, and the average value thereof was calculated. Conditions other than those described here were measured according to JIS K7136:2000. Table 2 shows the results.

(Evaluation of blister resistance)
The adhesive layers of the direct bonding films obtained in Examples and Comparative Examples were attached to soda lime glass (manufactured by Nippon Sheet Glass Co., Ltd.). Furthermore, the heavy release type release sheet is peeled off from the direct bonding film, and the exposed adhesive layer is a resin plate (thickness: 0.7 mm, containing no ultraviolet absorber) having a polymethyl methacrylate layer and a polycarbonate layer. A sample for evaluation was obtained by attaching it to the surface on the polycarbonate layer side. After that, the sample for evaluation was autoclaved for 30 minutes under conditions of 50° C. and 0.5 MPa, and left at normal pressure, 23° C. and 50% RH for 24 hours.

The pressure-sensitive adhesive layer after the autoclave treatment was irradiated with ultraviolet rays under the conditions described above through the resin plate to cure the pressure-sensitive adhesive layer to obtain a cured pressure-sensitive adhesive layer. Then, it was stored for 240 hours under high temperature and high humidity conditions of 85° C. and 85% RH. Thereafter, the state of the interface between the adhesive layer and the adherend after curing was visually observed, and the blister resistance was evaluated according to the following criteria. Table 2 shows the results.
◎…No air bubbles or floating/peeling occurred ○…Slight foaming occurred (no large bubbles or peeling)
×…Bubbles, traces of bubbles, or floating/peeling occurred

(Evaluation of step followability)
On the surface of a glass plate (manufactured by NSG Precision Co., Ltd., product name “Corning Glass Eagle XG”, length 90 mm × width 50 mm × thickness 0.5 mm), ultraviolet curable ink (manufactured by Teikoku Ink Co., Ltd., product name “POS-911 ink”) ) was screen-printed into a picture frame (outer shape: length 90 mm, width 50 mm, width 5 mm) so that the coating thickness would be any one of 5 μm, 10 μm, and 20 μm. Next, ultraviolet rays are irradiated (80 W/cm ² , 2 metal halide lamps, lamp height 15 cm, belt speed 10 to 15 m/min) to cure the printed UV curable ink, and the height of the step due to printing A stepped glass plate having a thickness of any one of 5 μm, 10 μm, and 20 μm was produced.

The light release type release sheet is peeled off from the direct bonding films obtained in Examples and Comparative Examples, and the exposed adhesive layer is treated with a laminator (manufactured by Fujipla Co., Ltd., product name “LPD3214”) to make the adhesive layer have a picture frame shape. was laminated on each stepped glass plate so as to cover the entire printed surface of the sheet. Next, peel off the heavy release type release sheet to expose the adhesive layer, and use the laminator to apply a glass plate (manufactured by NSG Precision Co., Ltd., product name "Corning Glass Eagle XG", length 90 mm to the exposed adhesive layer surface. x 50 mm in width x 0.5 mm in thickness) was laminated with the above laminator to obtain a sample for evaluation. After that, the sample for evaluation was autoclaved for 30 minutes under conditions of 50° C. and 0.5 MPa, and left at normal pressure, 23° C. and 50% RH for 24 hours.

(A) Evaluation of initial level difference followability At each level difference, visually confirm whether or not there are bubbles or floating peeling in the pressure-sensitive adhesive layer (especially near the level difference due to the printed layer) of the evaluation sample obtained as described above. , the following criteria were used to evaluate the initial step followability. Table 2 shows the results.
A: Follows all steps, and no air bubbles or floating peeling is observed.
B: When the step height was 20 μm, air bubbles and floating peeling were observed in the step portion.
C: Bubbles and peeling were observed at the step heights of 10 and 20 μm.
D: Bubbles and floating peeling are observed at all stepped portions.

(B) Evaluation of durability (step followability after durability) The adhesive layer of the evaluation sample obtained above was irradiated with an active energy ray under the conditions described above through the glass plate, and the adhesive layer was cured to form an adhesive layer after curing. Then, it is stored for 240 hours under high temperature and high humidity conditions of 85 ° C. and 85% RH (durability test), and then visually confirms the pressure-sensitive adhesive layer (especially the vicinity of the step due to the printed layer), and the initial step. According to the followability evaluation criteria, the step followability after the endurance test was evaluated. Table 2 shows the results.

(Evaluation of wet heat whitening resistance)
The adhesive layer of the direct bonding film obtained in Examples or Comparative Examples was attached to soda lime glass (manufactured by Nippon Sheet Glass Co., Ltd.). Furthermore, the heavy release type release sheet is peeled off from the direct bonding film, and the exposed adhesive layer is a resin plate (thickness: 0.7 mm, containing no ultraviolet absorber) having a polymethyl methacrylate layer and a polycarbonate layer. A sample for evaluation was obtained by attaching it to the surface on the polycarbonate layer side. After that, the sample for evaluation was autoclaved for 30 minutes under conditions of 50° C. and 0.5 MPa, and left at normal pressure, 23° C. and 50% RH for 24 hours. Then, using a haze meter (manufactured by Nippon Denshoku Industries Co., Ltd., product name "NDH2000"), the haze value (%) before evaluation of wet heat whitening resistance was measured according to JIS K7136:2000.

Next, the laminate was stored under high temperature and high humidity conditions of 85° C. and 85% RH for 240 hours. After that, the temperature is returned to normal temperature and normal humidity of 23° C. and 50% RH, and the haze value (%) after evaluating the wet heat whitening resistance is measured using the above haze meter according to JIS K7136:2000. It was measured. In addition, the said haze value was measured within 30 minutes after returning a laminated body to normal temperature normal humidity.

From the value obtained by subtracting the haze value (%) before evaluation of wet heat whitening resistance from the haze value (%) after evaluation of wet heat whitening resistance (difference in haze value before and after durability: points), based on the following criteria Wet heat whitening resistance was evaluated. Table 2 shows the results.
A: The difference in haze value before and after durability is less than 1.5 points.
○: The difference in haze value before and after durability is 1.5 points or more and 5 points or less.
x: The difference in haze value before and after durability exceeds 5 points.

The direct bonding film of the present invention can be suitably used, for example, for bonding display body constituent members.

DESCRIPTION OF SYMBOLS 1... Direct bonding film 11... Adhesive layer 12a, 12b... Release sheet 2... Display body 21... First display body constituent member 22... Second display body constituent member 3... Printed layer

Claims (7)

A step of producing a laminate by bonding the first display body constituent member and the second display body constituent member via the adhesive layer of the direct bonding film;
A step of irradiating the adhesive layer of the laminate with an active energy ray to cure the adhesive layer to form a cured adhesive layer,
The pressure-sensitive adhesive layer is
A crosslinked structure composed of a (meth)acrylic acid ester copolymer and a thermal crosslinking agent;
an uncured active energy ray-curable component;
A photopolymerization initiator having an absorbance of 1.0 or more at a wavelength of 380 nm in an acetonitrile solution with a concentration of 0.1% by mass;
Consists of an adhesive having an ultraviolet absorber,
The light transmittance of the adhesive layer at a wavelength of 380 nm is 40% or less,
The gel fraction of the pressure-sensitive adhesive layer is 20% or more and 50 % or less before the irradiation of the active energy ray to the pressure-sensitive adhesive layer,
After irradiation of the adhesive layer with active energy rays, the gel fraction of the adhesive layer is 40% or more and 90% or less,
A method for producing a display, wherein the ratio of the gel fraction of the adhesive layer after irradiation with active energy rays to the gel fraction of the adhesive layer before irradiation with active energy rays is 1.05 or more. 2. The method according to claim 1, wherein the ratio of the storage elastic modulus of the adhesive layer after irradiation with active energy rays to the storage elastic modulus of the adhesive layer before irradiation with active energy rays is 1.20 or more. A method of manufacturing a display. 3. The method of manufacturing a display according to claim 2, wherein the adhesive layer has a storage elastic modulus of 0.05 MPa or more and 0.50 MPa or less after being irradiated with active energy rays. 4. The method of manufacturing a display according to claim 2, wherein the pressure-sensitive adhesive layer has a storage elastic modulus of 0.01 MPa or more and 0.20 MPa or less before the active energy ray is applied to the pressure-sensitive adhesive layer. 5. The method of manufacturing a display according to claim 1, wherein the pressure-sensitive adhesive layer has an adhesive force of 20 N/25 mm or more after being irradiated with active energy rays. 6. Any one of claims 1 to 5, wherein the content of the ultraviolet absorber is 2 parts by mass or more and 25 parts by mass or less with respect to 100 parts by mass of the (meth)acrylate copolymer. A method for manufacturing the described display. at least one of the first display body component and the second display body component has a step;
7. The method of manufacturing a display according to any one of claims 1 to 6 , wherein the pressure-sensitive adhesive layer is adhered along the step.

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