CN112646507A

CN112646507A - Display body and adhesive sheet

Info

Publication number: CN112646507A
Application number: CN202011079907.3A
Authority: CN
Inventors: 小鲭翔; 高桥洋一
Original assignee: Lintec Corp
Current assignee: Lintec Corp
Priority date: 2019-10-10
Filing date: 2020-10-10
Publication date: 2021-04-13
Also published as: TW202124634A; JP2021063152A; JP7336348B2

Abstract

The invention provides an adhesive sheet capable of improving the design of a display body, and a display body with improved design. The adhesive sheet is an adhesive sheet (1) provided with an adhesive layer (11) for bonding one display body constituting member (21) and another display body constituting member (22), wherein the color difference DeltaE between the adhesive layer (11) defined by the CIE1976L a b color system and pure white is less than 95, and the total light transmittance of the adhesive layer (11) is 10% or more.

Description

Display body and adhesive sheet

Technical Field

The present invention relates to a display and an adhesive sheet used for the display.

Background

In recent years, as a display (display), an image display device such as a liquid crystal display device or an organic electroluminescence (organic EL) device is increasingly used in a display such as a television, a monitor (monitor) for a computer, a digital signage, a smartphone, and a tablet terminal.

In the display body as described above, there is a demand for improving design by showing a sense of unity with surrounding members of the display body, for example, with a frame material when the display body is turned off. For this purpose, it is conceivable to color the display body. For example, patent document 1 discloses a technique relating to coloring of a display.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2005-82634

Disclosure of Invention

Technical problem to be solved by the invention

However, since the adhesive sheet disclosed in patent document 1 is colored for the purpose of light-shielding property and light-shielding property, when it is used on the viewer side of a liquid crystal module or an organic EL module, visibility of a display image cannot be ensured.

The present invention has been made in view of the above circumstances, and an object thereof is to provide an adhesive sheet capable of improving design of a display, and a display having improved design.

Means for solving the problems

In order to achieve the above object, the first aspect of the present invention provides an adhesive sheet comprising an adhesive layer for bonding one display element constituting member to another display element constituting member, wherein the adhesive sheet has a color difference Δ E between the adhesive layer and pure white, which is defined by CIE1976L a b color system, of less than 95, and the adhesive layer has a total light transmittance of 10% or more (invention 1).

In the above invention (invention 1), by making the color difference Δ E of the adhesive layer the above, when the display body is turned off, the appearance of the display body can be harmonized with the white surrounding member, and the design can be improved. In the invention (invention 1), the total light transmittance of the adhesive layer is set to the above range, whereby the visibility of an image and a video can be ensured when the display is lit.

In the invention (invention 1), the adhesive layer preferably has a haze value of 0.5% or more and 100% or less (invention 2).

In the above inventions (inventions 1 and 2), the adhesive layer is preferably composed of an adhesive containing a white colorant (invention 3).

In the above inventions (inventions 1 to 3), the content of the white colorant in the adhesive is preferably 0.01 mass% or more and 50 mass% or less (invention 4).

In the above inventions (inventions 1 to 4), the adhesive is preferably an acrylic adhesive (invention 5).

In the above inventions (inventions 1 to 5), the adhesive is preferably obtained by crosslinking an adhesive composition containing at least a (meth) acrylate polymer (a), a crosslinking agent (B), and a white colorant (C) (invention 6).

In the above inventions (inventions 1 to 6), it is preferable that the adhesive sheet includes two release sheets and the adhesive layer is sandwiched between the two release sheets so as to be in contact with release surfaces of the two release sheets (invention 7).

A second aspect of the present invention provides a display device including: the display comprises one display component, another display component, and an adhesive layer for bonding the one display component and the another display component, wherein the adhesive layer is formed from the adhesive layer of the adhesive sheet (inventions 1 to 7) (invention 8).

In the above invention (invention 8), it is preferable that: at least one of the one display element and the other display element has a step on a surface of the one display element and the other display element bonded to each other with the adhesive layer (invention 9).

In the above inventions (inventions 8 and 9), the surrounding member having a white color (invention 10) is preferable.

Effects of the invention

According to the adhesive sheet of the present invention, the design of the display can be improved. In addition, the design of the display body of the present invention is improved.

Drawings

Fig. 1 is a sectional view of an adhesive sheet according to an embodiment of the present invention.

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

Fig. 3 is a plan view of a display body having a frame member according to an embodiment of the present invention.

Description of the reference numerals

1: an adhesive sheet; 11: an adhesive layer; 12a, 12 b: a release sheet; 2: a display body; 21: a first display body constituting member; 22: a second display body constituting member; 3: printing layer; 4: a frame material.

Detailed Description

Hereinafter, embodiments of the present invention will be described.

[ adhesive sheet ]

The pressure-sensitive adhesive sheet according to one embodiment of the present invention is prepared as a pressure-sensitive adhesive layer for bonding one display constituent member to another display constituent member, and is preferably formed by laminating a release sheet on one surface or both surfaces of the pressure-sensitive adhesive layer. The display body and the display body constituting member will be described later.

Fig. 1 shows a specific structure of an example of the adhesive sheet of the present embodiment.

As shown in fig. 1, the adhesive sheet 1 is composed of two

release sheets

12a and 12b and an adhesive layer 11, and the adhesive layer 11 is sandwiched between the two

release sheets

12a and 12b so as to be in contact with the release surfaces of the two

release sheets

12a and 12 b. The release surface of the release sheet in the present specification means a surface having releasability in the release sheet, and includes any one of a surface subjected to a release treatment and a surface showing releasability even if the release treatment is not performed.

1. Each component

1-1. adhesive layer

The adhesive layer 11 of the adhesive sheet 1 of the present embodiment has a color difference Δ E from pure white, which is defined by the CIE1976L a b color system, of less than 95% and a total light transmittance of 10% or more.

The pure white color defined by CIE1976L a b color system has lightness L of 100, chroma a of 0, and chroma b of 0. Therefore, when the measured value of lightness L, the measured value of chroma a, and the measured value of b are denoted by L × M, the color difference Δ E from pure white can be calculated by the following formula (I) for the adhesive layer 11.

[ mathematical formula 1]

The measurement methods (reflected light measurement) of lightness L, chroma a, and chroma b in the present specification are shown in test examples described later.

In the adhesive sheet 1 of the present embodiment, by making the color difference Δ E of the adhesive layer 11 as described above, it is possible to improve design properties by achieving appearance compatibility with a white surrounding member, for example, a white frame material, a white wall, a white printed portion, or the like when the display is turned off. In addition, the white color of the surrounding member does not necessarily have to be the above-described "pure white color".

In the adhesive sheet 1 of the present embodiment, the total light transmittance of the adhesive layer 11 is set to 10% or more, whereby the visibility of an image and a video can be ensured when the display is lit. In addition, the total light transmittance in the present specification is a value measured in accordance with JIS K7361-1: 1997.

From the viewpoint of compatibility with the appearance of a white surrounding member, the color difference Δ E must be less than 95, preferably 80 or less, more preferably 60 or less, particularly preferably 40 or less, and even more preferably 35 or less. The lower limit of the color difference Δ E is not particularly limited, and the minimum value is 0, but considering the relationship with the total light transmittance, the lower limit is preferably 1 or more, more preferably 5 or more, particularly preferably 10 or more, and further preferably 20 or more.

The lightness L × M of the adhesive layer 11 is preferably 3 or more, more preferably 9 or more, particularly preferably 50 or more, and further preferably 65 or more. The lightness L × M is preferably 100 or less, more preferably 90 or less, particularly preferably 83 or less, and further preferably 80 or less. The absolute value of the chromaticity a × M of the adhesive layer 11 is preferably 0 or more, particularly preferably 0.1 or more, and more preferably 0.5 or more. The absolute value of the chromaticity a × M is preferably 10 or less, more preferably 5 or less, particularly preferably 2 or less, and further preferably 1.5 or less. The absolute value of the chromaticity b × M of the adhesive layer 11 is preferably 0 or more, and particularly preferably 0.1 or more. The absolute value of the chromaticity b × M is preferably 10 or less, more preferably 5 or less, particularly preferably 2 or less, and further preferably 1.5 or less. By setting as above, the above-described color difference Δ E and total light transmittance are easily satisfied, and at the same time, a preferable color tone is obtained when the display body is turned off.

From the viewpoint of visibility of images and videos, the total light transmittance of the adhesive layer 11 must be 10% or more, preferably 20% or more, more preferably 30% or more, particularly preferably 40% or more, and further preferably 45% or more. The upper limit of the total light transmittance is usually 100% or less, and considering the relationship with the color difference Δ E, it is preferably 95% or less, more preferably 90% or less, particularly preferably 80% or less, further preferably 70% or less, and most preferably 65% or less.

The haze value of the adhesive layer 11 is preferably 0.5% or more, more preferably 5% or more, particularly preferably 15% or more, further preferably 60% or more, and most preferably 90% or more. This makes it easy to satisfy the color difference Δ E, and to give the obtained display body a sense of unity with the surrounding member of white. The upper limit of the haze value of the adhesive layer 11 is not particularly limited, but is preferably 100% or less, more preferably 99.9% or less, particularly preferably 99.8% or less, and further preferably 99.4% or less. The haze value in the present specification is a value measured according to JIS K7136: 2000.

The adhesive constituting the adhesive layer 11 preferably contains a white colorant, and the color difference Δ E and the total light transmittance (and haze value) can be achieved by appropriately selecting the type and content of the white colorant.

The white colorant may be mainly composed of a pigment or a dye. The pigment may be an inorganic pigment or an organic pigment. From the viewpoint of durability of the obtained adhesive, an inorganic pigment is preferable.

The white colorant preferably contains an inorganic pigment such as titanium oxide, zinc oxide, calcium carbonate, or alumina, and is more preferably titanium oxide or zinc oxide, and particularly preferably titanium oxide, from the viewpoint that the total light transmittance is easily maintained to be high even when Δ E is low. These inorganic pigments may be subjected to surface treatment such as organic treatment, silicone treatment, and alumina treatment. The inorganic pigments may be used alone or in combination of two or more.

The white colorant may contain both an inorganic pigment and colorless transparent fine particles such as silica. Thus, a suitable white color can be easily obtained. In this case, the content of the colorless transparent fine particles in the white colorant is preferably 0.01 to 50% by mass, more preferably 0.1 to 30% by mass, particularly preferably 1 to 20% by mass, and further preferably 5 to 10% by mass.

The mode diameter (maximum frequency diameter) of the white colorant is preferably 2nm or more, more preferably 10nm or more, particularly preferably 100nm or more, and further preferably 200nm or more. Thereby, the above-described color difference Δ E is easily satisfied. The mode diameter is preferably 3000nm or less, more preferably 1000nm or less, particularly preferably 800nm or less, and further preferably 600nm or less. Thereby, the above total light transmittance is easily satisfied.

The median particle diameter (D50) of the white colorant is preferably 2nm or more, more preferably 10nm or more, particularly preferably 100nm or more, and further preferably 200nm or more. Thereby, the above-described color difference Δ E is easily satisfied. The median particle diameter is preferably 3000nm or less, more preferably 1000nm or less, particularly preferably 800nm or less, and still more preferably 600nm or less. Thereby, the above total light transmittance is easily satisfied.

In the present specification, the mode diameter and the median particle diameter of the white colorant are values measured by a dynamic light scattering method.

The content of the white colorant in the adhesive constituting the adhesive layer 11 is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, particularly preferably 1% by mass or more, and further preferably 3% by mass or more. Thus, the above-described color difference Δ E can be easily satisfied without excessively increasing the thickness of the adhesive agent layer. The content is preferably 50% by mass or less, more preferably 30% by mass or less, particularly preferably 20% by mass or less, and even more preferably 15% by mass or less, and is preferably 8% by mass or less in view of the excellent step following property even when the adhesive layer is made thin. Thereby, the above total light transmittance is easily satisfied.

From the viewpoint of the relationship with the content of the white colorant and the ease of satisfying the above-mentioned optical properties, the thickness of the adhesive agent layer 11 is preferably 3 μm or more, more preferably 10 μm or more, and particularly preferably 20 μm or more, and is preferably 40 μm or more in view of further improving the step following property.

The thickness of the adhesive layer 11 is preferably 3000 μm or less, more preferably 1000 μm or less, particularly preferably 500 μm or less, and further preferably 300 μm or less, in terms of the above-mentioned limit. When the upper limit of the thickness of the adhesive layer 11 is as described above, the above-described optical properties are easily satisfied due to the content of the white colorant. Further, appearance defects due to squeeze marks and the like are less likely to occur.

The adhesive layer 11 may be formed of a single layer or may be formed by stacking a plurality of layers. The thickness of the adhesive agent layer 11 in the present specification is a value measured according to JIS K7130.

The type of adhesive constituting the adhesive layer 11 of the adhesive sheet 1 of the present embodiment is not particularly limited, and may be any of, for example, an acrylic adhesive, a polyester adhesive, a polyurethane adhesive, a rubber adhesive, a silicone adhesive, and the like. The adhesive may be any of emulsion type, solvent type, and non-solvent type, and may be any of crosslinking type and non-crosslinking type. Among them, acrylic adhesives having excellent adhesive properties, optical characteristics, and the like are preferable.

The acrylic adhesive may be an active energy ray-curable acrylic adhesive or an inactive energy ray-curable acrylic adhesive. Further, as the acrylic pressure-sensitive adhesive, a crosslinking type acrylic pressure-sensitive adhesive is preferable, and a thermal crosslinking type acrylic pressure-sensitive adhesive is more preferable.

Specifically, the adhesive is preferably crosslinked from an adhesive composition containing at least (meth) acrylate polymer (a), a crosslinking agent (B), and a white colorant (C) (hereinafter sometimes referred to as "adhesive composition P"). When the adhesive is an active energy ray-curable adhesive, the adhesive composition P preferably further contains an active energy ray-curable component (D).

The adhesive obtained from the adhesive composition P can exhibit excellent optical characteristics, adhesive force, durability (step following property under high temperature and high humidity conditions), and the like. In the present specification, the term (meth) acrylic acid means acrylic acid and methacrylic acid. Other similar terms are also the same. Further, "polymer" also includes the concept of "copolymer".

(1) Components of adhesive compositions

(1-1) (meth) acrylate ester Polymer (A)

The (meth) acrylate polymer (a) of the present embodiment preferably contains a reactive group-containing monomer having a reactive group reactive with the crosslinking agent (B) in the molecule as a monomer unit constituting the polymer. By reacting the reactive group derived from the reactive group-containing monomer with the crosslinking agent (B), a crosslinked structure (three-dimensional network structure) can be formed, and an adhesive having a desired cohesive force can be obtained.

Examples of the reactive group-containing monomer include a monomer having a hydroxyl group in the molecule (hydroxyl group-containing monomer), a monomer having a carboxyl group in the molecule (carboxyl group-containing monomer), and a monomer having an amino group in the molecule (amino group-containing monomer). Among these, a hydroxyl group-containing monomer or a carboxyl group-containing monomer having excellent reactivity with the crosslinking agent (B) is preferable, and both a hydroxyl group-containing monomer and a carboxyl group-containing monomer may be used.

Examples of the hydroxyl group-containing monomer include hydroxyalkyl (meth) acrylates such as 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 3-hydroxybutyl (meth) acrylate, and 4-hydroxybutyl (meth) acrylate. Among them, hydroxyalkyl (meth) acrylates having a hydroxyalkyl group having 1 to 4 carbon atoms are preferable from the viewpoint of reactivity of the hydroxyl group in the obtained (meth) acrylate polymer (a) with the crosslinking agent (B) and copolymerizability of the hydroxyl group with other monomers. Specifically, for example, 2-hydroxyethyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate and the like are preferably mentioned, and 2-hydroxyethyl acrylate or 4-hydroxybutyl acrylate is particularly preferably mentioned. These hydroxyl group-containing monomers may be used alone or in combination of two or more.

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

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

The lower limit of the content of the reactive group-containing monomer in the (meth) acrylate polymer (a) is preferably 1% by mass or more, particularly preferably 5% by mass or more, and more preferably 10% by mass or more, and when the reactive group-containing monomer is only a hydroxyl group-containing monomer, the content of the reactive group-containing monomer in the (meth) acrylate polymer (a) is preferably 15% by mass or more, particularly preferably 20% by mass or more, as the monomer unit constituting the polymer. In addition, the (meth) acrylate polymer (a) preferably contains 40% by mass or less, particularly preferably 30% by mass or less, and further preferably 25% by mass or less of the reactive group-containing monomer as a monomer unit constituting the polymer, in terms of the above-mentioned limit. When the (meth) acrylate polymer (a) contains the reactive group-containing monomer as a monomer unit in the above-mentioned amount, a favorable crosslinked structure can be formed in the obtained adhesive, and a desired cohesive force can be obtained. Further, the white colorant (C) tends to be well dispersed in the adhesive, and the obtained adhesive is good in reproducibility and uniformity of the optical properties, and is liable to satisfy the above-mentioned color difference Δ E.

Further, the (meth) acrylate polymer (a) preferably does not contain a carboxyl group-containing monomer as a monomer unit constituting the polymer. Since the carboxyl group is an acid component, since the carboxyl group-containing monomer is not contained, even when a substance causing a problem due to an acid, for example, a transparent conductive film such as tin-doped indium oxide (ITO) or a metal film is present in an object to which the adhesive is to be attached, the problem (corrosion, change in resistance value, or the like) caused by the acid can be suppressed. However, it is also permissible to contain a predetermined amount of the carboxyl group-containing monomer to such an extent that the above-described problems do not occur. Specifically, the carboxyl group-containing monomer is allowed to be contained as a monomer unit in the (meth) acrylate polymer (a) in an amount of 0.1% by mass or less, preferably 0.01% by mass or less, and more preferably 0.001% by mass or less.

The (meth) acrylate polymer (a) preferably contains an alkyl (meth) acrylate as a monomer unit constituting the polymer. This can exhibit good adhesion. The alkyl group may be linear or branched.

From the viewpoint of adhesiveness, the alkyl (meth) acrylate is preferably an alkyl (meth) acrylate having an alkyl group with 1 to 20 carbon atoms. Examples of the alkyl (meth) acrylate having an alkyl group with 1 to 20 carbon atoms include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate, n-pentyl (meth) acrylate, n-hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, n-decyl (meth) acrylate, n-dodecyl (meth) acrylate, tetradecyl (meth) acrylate, hexadecyl (meth) acrylate, and octadecyl (meth) acrylate. Among these, from the viewpoint of further improving the adhesion, a (meth) acrylate having an alkyl group with 1 to 8 carbon atoms is preferable, methyl (meth) acrylate, n-butyl (meth) acrylate, or 2-ethylhexyl (meth) acrylate is particularly preferable, and methyl methacrylate, n-butyl acrylate, or 2-ethylhexyl acrylate is further preferable. These alkyl (meth) acrylates may be used alone or in combination of two or more.

The (meth) acrylate polymer (a) preferably contains 40% by mass or more, particularly preferably 50% by mass or more, and further preferably 60% by mass or more of an alkyl (meth) acrylate as a monomer unit constituting the polymer. When the lower limit of the content of the alkyl (meth) acrylate is as described above, the (meth) acrylate polymer (a) can exhibit appropriate tackiness. Further, the white colorant (C) tends to have good dispersibility in the adhesive, and the (meth) acrylate polymer (a) is prevented from impairing the desired adhesive properties. Thus, the obtained adhesive can exhibit appropriate adhesiveness, and the reproducibility and uniformity of the optical properties are improved, and the color difference Δ E can be easily satisfied. The (meth) acrylate polymer (a) preferably contains 99% by mass or less, more preferably 95% by mass or less, particularly preferably 90% by mass or less, and further preferably 85% by mass or less of an alkyl (meth) acrylate as a monomer unit constituting the polymer. When the upper limit of the content of the alkyl (meth) acrylate is as described above, an appropriate amount of other monomer components such as a reactive functional group-containing monomer can be introduced into the (meth) acrylate polymer (a).

The (meth) acrylate polymer (a) preferably contains a monomer having an alicyclic structure in the molecule (alicyclic structure-containing monomer) as a monomer unit constituting the polymer. Since the alicyclic structure-containing monomer has a large volume, it is presumed that the presence of the alicyclic structure-containing monomer in the polymer enlarges the interval between the polymers, and the resulting adhesive is excellent in flexibility. This provides excellent step following properties of the adhesive.

The alicyclic carbon ring in the alicyclic structure-containing monomer may be a saturated carbon ring or a carbon ring having an unsaturated bond in a part thereof. The alicyclic structure may be a monocyclic alicyclic structure, or may be a polycyclic alicyclic structure such as a bicyclic structure or a tricyclic structure. The alicyclic structure is preferably a polycyclic alicyclic structure (polycyclic structure) from the viewpoint of making the distance between the obtained (meth) acrylate polymers (a) appropriate and imparting higher stress relaxation property to the adhesive. Further, the polycyclic structure is particularly preferably a bicyclic ring to tetracyclic ring in view of compatibility of the (meth) acrylate polymer (a) with other components. In addition, from the viewpoint of providing stress relaxation properties as described above, the number of carbon atoms of the alicyclic structure (the number of all carbon atoms of the portion indicating a ring, which means the total number of carbon atoms when a plurality of rings are present independently) is preferably 5 or more in general, and more preferably 7 or more in particular. On the other hand, the upper limit of the number of carbon atoms of the alicyclic structure is not particularly limited, but is preferably 15 or less, and particularly preferably 10 or less, from the viewpoint of compatibility as described above.

Specific examples of the alicyclic structure-containing monomer include cyclohexyl (meth) acrylate, dicyclopentanyl (meth) acrylate, adamantyl (meth) acrylate, isobornyl (meth) acrylate, dicyclopentenyl (meth) acrylate, dicyclopentenyloxyethyl (meth) acrylate, etc., and among them, dicyclopentanyl (meth) acrylate (carbon number of alicyclic structure: 10), adamantyl (meth) acrylate (carbon number of alicyclic structure: 10), or isobornyl (meth) acrylate (carbon number of alicyclic structure: 7) which exhibits more excellent step following property is preferable, isobornyl (meth) acrylate is particularly preferable, and isobornyl acrylate is more preferable. These alicyclic structure-containing monomers may be used singly or in combination of two or more.

When the (meth) acrylate polymer (a) contains an alicyclic structure-containing monomer as a monomer unit constituting the polymer, the alicyclic structure-containing monomer is contained preferably in an amount of 1 mass% or more, particularly preferably 4 mass% or more, and further preferably 8 mass% or more. The (meth) acrylate polymer (a) preferably contains 30% by mass or less, particularly preferably 22% by mass or less, and further preferably 14% by mass or less of an alicyclic structure-containing monomer as a monomer unit constituting the polymer. When the content of the alicyclic structure-containing monomer is within the above range, the obtained adhesive is more excellent in step following property and also more excellent in adhesive force to a plastic.

Further, the (meth) acrylic acid ester polymer (a) preferably contains a nitrogen atom-containing monomer as a monomer unit constituting the polymer. By having a monomer containing a nitrogen atom as a constituent unit in a polymer, a predetermined polarity can be imparted to an adhesive, and the adhesive is excellent in affinity even for an adherend having a certain polarity such as glass. From the viewpoint of imparting suitable rigidity to the (meth) acrylate polymer (a), the nitrogen atom-containing monomer is preferably a monomer having a nitrogen-containing heterocycle. In addition, from the viewpoint of enhancing the degree of freedom of the moiety derived from the nitrogen atom-containing monomer in the high-dimensional structure of the adhesive agent, it is preferable that the nitrogen atom-containing monomer does not contain a reactive unsaturated double bond group other than one polymerizable group used in the polymerization for forming the (meth) acrylate polymer (a).

Examples of the monomer having a nitrogen-containing heterocycle include N- (meth) acryloylmorpholine, N-vinyl-2-pyrrolidone, N- (meth) acryloylpyrrolidone, N- (meth) acryloylpiperidine, N- (meth) acryloylpyrrolidine, N- (meth) acryloylaziridine, aziridinylethyl (meth) acrylate, 2-vinylpyridine, 4-vinylpyridine, 2-vinylpyrazine, 1-vinylimidazole, N-vinylcarbazole, N-vinylphthalimide, and the like, and among them, N- (meth) acryloylmorpholine which exhibits more excellent adhesive force is preferable, and N-acryloylmorpholine is particularly preferable. These monomers having a nitrogen-containing heterocycle may be used alone or in combination of two or more.

When the (meth) acrylate polymer (a) contains a nitrogen atom-containing monomer as a monomer unit constituting the polymer, the content of the nitrogen atom-containing monomer is preferably 1% by mass or more, particularly preferably 4% by mass or more, and more preferably 8% by mass or more. The (meth) acrylate polymer (a) preferably contains 20% by mass or less, particularly preferably 16% by mass or less, and further preferably 12% by mass or less of the nitrogen atom-containing monomer as a monomer unit constituting the polymer. When the content of the nitrogen atom-containing monomer is within the above range, the resulting adhesive can sufficiently exhibit excellent adhesion to glass.

The (meth) acrylate polymer (a) may contain other monomers as the monomer unit constituting the polymer, as required. In order not to inhibit the above-mentioned action of the reactive functional group-containing monomer, as the other monomer, a monomer not containing a reactive functional group is preferable. Examples of the monomer include alkoxyalkyl (meth) acrylates such as methoxyethyl (meth) acrylate and ethoxyethyl (meth) acrylate, vinyl acetate, and styrene. These other monomers may be used alone or in combination of two or more.

The (meth) acrylate polymer (a) is preferably a linear polymer. By making the polymer linear, entanglement of molecular chains is easily caused, and improvement of cohesive force can be expected. Therefore, the obtained adhesive is easy to exhibit appropriate gel fraction, adhesive force and the like, and is easy to have excellent step following property under high temperature and high humidity conditions.

The (meth) acrylate polymer (a) is preferably a solution polymer obtained by a solution polymerization method. By using a solution polymer, a polymer having a high molecular weight can be easily obtained, and improvement of the cohesive force can be expected. Therefore, the obtained adhesive is easy to exhibit appropriate gel fraction, adhesive force and the like, and is easy to have excellent step following property under high temperature and high humidity conditions.

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

The weight average molecular weight of the (meth) acrylate polymer (a) is preferably 20 ten thousand or more, particularly preferably 30 ten thousand or more, and more preferably 40 ten thousand or more, in the lower limit value. When the lower limit of the weight average molecular weight of the (meth) acrylate polymer (a) is as described above, the gel fraction and the storage modulus of the obtained adhesive are easily appropriate, and the step difference following property under high temperature and high humidity conditions is further excellent. Further, since the white colorant (C) tends to be well dispersed in the adhesive, the obtained adhesive has good reproducibility and uniformity of the optical properties, and easily satisfies the color difference Δ E.

The weight average molecular weight of the (meth) acrylate polymer (a) is preferably 200 ten thousand or less, more preferably 150 ten thousand or less, particularly preferably 100 ten thousand or less, and further preferably 80 ten thousand or less, as defined above. When the upper limit of the weight average molecular weight of the (meth) acrylate polymer (a) is set to the above range, the gel fraction and the storage modulus of the obtained adhesive are easily appropriate, and the initial level difference following property is further excellent. The weight average molecular weight in the present specification is a value in terms of standard polystyrene measured by a Gel Permeation Chromatography (GPC) method.

In the adhesive composition P, one kind of the (meth) acrylate polymer (a) may be used alone, or two or more kinds may be used in combination.

(1-2) crosslinking agent (B)

The crosslinking agent (B) can crosslink the (meth) acrylate polymer (a) by heating the adhesive composition P, and can favorably form a three-dimensional network structure. This improves the cohesive force of the obtained adhesive, and the step following property under high temperature and high humidity conditions is excellent.

The crosslinking agent (B) may be a substance that reacts with the reactive group of the (meth) acrylate polymer (a), and examples thereof include isocyanate crosslinking agents, epoxy crosslinking agents, amine crosslinking agents, melamine crosslinking agents, aziridine crosslinking agents, hydrazine crosslinking agents, aldehyde crosslinking agents, oxazoline crosslinking agents, metal alkoxide crosslinking agents, metal chelate crosslinking agents, metal salt crosslinking agents, and ammonium salt crosslinking agents. Among the above, an isocyanate-based crosslinking agent having excellent reactivity with the reactive group of the (meth) acrylate polymer (a) is preferably used. The crosslinking agent (B) may be used alone or in combination of two or more.

The isocyanate-based crosslinking agent contains at least a polyisocyanate compound. Examples of the polyisocyanate compound include aromatic polyisocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate, and xylylene diisocyanate; aliphatic polyisocyanates such as hexamethylene diisocyanate; alicyclic polyisocyanates such as isophorone diisocyanate and hydrogenated diphenylmethane diisocyanate; and biuret and isocyanurate derivatives thereof; and adducts as reactants with low-molecular active hydrogen-containing compounds such as ethylene glycol, propylene glycol, neopentyl glycol, trimethylolpropane, castor oil, and the like. Among them, trimethylolpropane-modified aromatic polyisocyanates are preferable from the viewpoint of reactivity with hydroxyl groups, and trimethylolpropane-modified tolylene diisocyanate and trimethylolpropane-modified xylylene diisocyanate are particularly preferable.

The content of the crosslinking agent (B) in the adhesive composition P is preferably 0.01 part by mass or more, particularly preferably 0.05 part by mass or more, and more preferably 0.1 part by mass or more, relative to 100 parts by mass of the (meth) acrylate polymer (a). The content is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, particularly preferably 1 part by mass or less, and further preferably 0.4 part by mass or less. When the content of the crosslinking agent (B) is within the above range, the obtained adhesive exhibits good cohesive force, the values of gel fraction, adhesive force and the like are easily appropriate, and the step difference following property under high-temperature and high-humidity conditions is further excellent.

(1-3) white colorant (C)

The white colorant (C) is the above-mentioned white colorant. The specific species and content are as described above.

(1-4) active energy ray-curable component (D)

It is presumed that in an adhesive obtained by curing an adhesive obtained by crosslinking the adhesive composition P with an active energy ray, the active energy ray-curable components (D) are polymerized with each other, and the polymerized active energy ray-curable components (D) are entangled with the crosslinked structure (three-dimensional network structure) of the (meth) acrylate polymer (a). The adhesive having a high-dimensional structure is particularly excellent in step following properties under high-temperature and high-humidity conditions.

The active energy ray-curable component (D) is not particularly limited as long as it is a component that can be cured by irradiation with an active energy ray and can obtain the above-described effects, and may be any of a monomer, an oligomer, or a polymer, or a mixture of these. Among them, a polyfunctional acrylate monomer having more excellent step following property under high temperature and high humidity conditions can be preferably used.

Examples of the polyfunctional acrylate monomer include 1, 4-butanediol di (meth) acrylate, 1, 6-hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, neopentyl glycol adipate di (meth) acrylate, neopentyl glycol hydroxypivalate di (meth) acrylate, dicyclopentanyl di (meth) acrylate, bifunctional types such as tricyclodecane dimethanol (meth) acrylate, caprolactone-modified dicyclopentenyl di (meth) acrylate, ethylene oxide-modified phosphoric acid di (meth) acrylate, di (acryloyloxyethyl) isocyanurate, allylated cyclohexyl di (meth) acrylate, ethoxylated bisphenol a diacrylate, and 9, 9-bis [4- (2-acryloyloxyethoxy) phenyl ] fluorene; trifunctional types such as trimethylolpropane tri (meth) acrylate, dipentaerythritol tri (meth) acrylate, propionic acid-modified dipentaerythritol tri (meth) acrylate, pentaerythritol tri (meth) acrylate, propylene oxide-modified trimethylolpropane tri (meth) acrylate, tris (acryloyloxyethyl) isocyanurate, and e-caprolactone-modified tris (2- (meth) acryloyloxyethyl) isocyanurate; tetrafunctional types such as diglycerin tetra (meth) acrylate and pentaerythritol tetra (meth) acrylate; pentafunctional types such as propionic acid-modified dipentaerythritol penta (meth) acrylate; and hexa-functional types such as dipentaerythritol hexa (meth) acrylate and caprolactone-modified dipentaerythritol hexa (meth) acrylate. These polyfunctional acrylate monomers may be used alone or in combination of two or more. Further, the molecular weight of the polyfunctional acrylate monomer is preferably less than 1000 from the viewpoint of compatibility with the (meth) acrylate polymer (a).

When the adhesive composition P contains the active energy ray-curable component (D), the content of the active energy ray-curable component (D) in the adhesive composition P is preferably 1 part by mass or more, particularly preferably 3 parts by mass or more, and further preferably 4 parts by mass or more, based on 100 parts by mass of the (meth) acrylate polymer (a), in the following limit. On the other hand, the content is preferably 30 parts by mass or less, particularly preferably 20 parts by mass or less, and more preferably 14 parts by mass or less in terms of the upper limit of the adhesive force of the adhesive after curing with an active energy ray, and is preferably 9 parts by mass or less in terms of the ease with which a higher adhesive force can be exerted. When the content of the active energy ray-curable component (D) is in the above range, the values of the gel fraction, the adhesive force, and the like of the adhesive after curing with an active energy ray are easily appropriate, and the step difference following property under high temperature and high humidity conditions is further excellent.

(1-5) photopolymerization initiator (E)

When ultraviolet rays are used as the active energy rays for curing the adhesive composition P, the adhesive composition P preferably further contains a photopolymerization initiator (E). By containing the photopolymerization initiator (E) in this manner, the active energy ray-curable component (D) can be efficiently polymerized, and the polymerization curing time and the irradiation dose of active energy rays can be reduced.

Examples of the photopolymerization initiator (E) include benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin n-butyl ether, benzoin isobutyl ether, acetophenone, dimethylaminoacetophenone, 2-dimethoxy-2-phenylacetophenone, 2-diethoxy-2-phenylacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-hydroxycyclohexylphenyl ketone, 2-methyl-1- [4- (methylthio) phenyl ] -2-morpholino-1-propanone, 4- (2-hydroxyethoxy) phenyl-2- (hydroxy-2-propyl) ketone, benzophenone, p-phenylbenzophenone, and the like, 4, 4' -diethylaminobenzophenone, dichlorobenzophenone, 2-methylanthraquinone, 2-ethylanthraquinone, 2-tert-butylanthraquinone, 2-aminoanthraquinone, 2-methylthioxanthone, 2-ethylthioxanthone, 2-chlorothioxanthone, 2, 4-dimethylthioxanthone, 2, 4-diethylthioxanthone, benzildimethylketal, acetophenone dimethylketal, p-dimethylaminobenzoate, oligo [ 2-hydroxy-2-methyl-1 [4- (1-methylvinyl) phenyl ] propanone ], 2,4, 6-trimethylbenzoyl-diphenyl-phosphine oxide, phenylbis (2,4, 6-trimethylbenzoyl) phosphine oxide, and the like. These photopolymerization initiators may be used alone or in combination of two or more.

When the adhesive composition P contains the photopolymerization initiator (E), the content of the photopolymerization initiator (E) in the adhesive composition P is preferably 0.1 part by mass or more, particularly preferably 1 part by mass or more, and further preferably 5 parts by mass or more, based on 100 parts by mass of the active energy ray-curable component (D), as the lower limit value. The upper limit is preferably 30 parts by mass or less, particularly preferably 20 parts by mass or less, and further preferably 12 parts by mass or less.

(1-6) various additives

Various additives generally used in acrylic adhesives, for example, silane coupling agents, rust inhibitors, ultraviolet absorbers, antistatic agents, tackifiers, antioxidants, light stabilizers, softeners, refractive index modifiers, and the like can be added to the adhesive composition P as needed. In addition, a polymerization solvent or a dilution solvent described later is not included in the additive constituting the adhesive composition P.

Among the above, the adhesive composition P preferably contains a silane coupling agent. Thus, the adhesion to the adherend is improved regardless of whether the adherend is a plastic plate or a glass member, and the step following property under high-temperature and high-humidity conditions is further improved.

The silane coupling agent is preferably an organosilicon compound having at least 1 alkoxysilyl group in the molecule, which has good compatibility with the (meth) acrylate polymer (a) and light transmittance.

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

The content of the silane coupling agent in the adhesive composition P is preferably 0.01 part by mass or more, particularly preferably 0.05 part by mass or more, and more preferably 0.1 part by mass or more, relative to 100 parts by mass of the (meth) acrylate polymer (a). The content is preferably 1 part by mass or less, particularly preferably 0.5 part by mass or less, and further preferably 0.3 part by mass or less.

(2) Preparation of adhesive composition

The adhesive composition P can be prepared by: the (meth) acrylate polymer (a) is prepared, and the obtained (meth) acrylate polymer (a), the crosslinking agent (B), and the white colorant (C) are mixed, and if necessary, the active energy ray-curable component (D), the photopolymerization initiator (E), and additives are added.

The (meth) acrylate polymer (a) can be prepared by polymerizing a mixture of monomers constituting the polymer by a general radical polymerization method. The polymerization of the (meth) acrylate polymer (a) is preferably carried out by a solution polymerization method using a polymerization initiator as needed. However, the present invention is not limited thereto, and polymerization may be carried out without a solvent. 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 simultaneously.

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

Examples of the organic peroxide include benzoyl peroxide, tert-butyl peroxybenzoate, cumene hydroperoxide, diisopropyl peroxydicarbonate, di-n-propyl peroxydicarbonate, di (2-ethoxyethyl) peroxydicarbonate, tert-butyl peroxyneodecanoate, tert-butyl peroxypivalate, 3,5, 5-trimethylhexanoyl peroxide, dipropyl peroxide, and diacetyl peroxide.

In the polymerization step, a chain transfer agent such as 2-mercaptoethanol is added to adjust the weight average molecular weight of the obtained polymer.

After the (meth) acrylate polymer (a) is obtained, the crosslinking agent (B), the white colorant (C), and if necessary, a diluting solvent, the active energy ray-curable component (D), the photopolymerization initiator (E), and additives are added to a solution of the (meth) acrylate polymer (a) and sufficiently mixed to obtain the adhesive composition P (coating solution) diluted with the solvent. In the case where a solid substance is used for any of the above-mentioned components, or in the case where a precipitate is formed when the solid substance is mixed with another component in an undiluted state, the component may be dissolved or diluted in a diluting solvent in advance and then mixed with another component.

Examples of the diluting solvent include aliphatic hydrocarbons such as hexane, heptane and cyclohexane; aromatic hydrocarbons such as toluene and xylene; halogenated hydrocarbons such as dichloromethane and 1, 2-dichloroethane; alcohols such as methanol, ethanol, propanol, butanol, and 1-methoxy-2-propanol; ketones such as acetone, methyl ethyl ketone, 2-pentanone, isophorone, and cyclohexanone; esters such as ethyl acetate and butyl acetate; and cellosolve solvents such as ethyl cellosolve.

The concentration and viscosity of the coating solution prepared in this manner are not particularly limited as long as they are in a range in which the coating solution can be applied, and may be appropriately selected depending on the case. For example, the adhesive composition P is diluted so that the concentration thereof is 10 to 60 mass%. In addition, when obtaining the coating solution, it is not essential to add a diluting solvent or the like, and the diluting solvent may not be added as long as the adhesive composition P has a viscosity capable of being coated or the like. In this case, the adhesive composition P is a coating solution in which the polymerization solvent of the (meth) acrylate polymer (a) is directly used as a dilution solvent.

(3) Formation of adhesive layer

The adhesive layer 11 of the present embodiment is preferably composed of an adhesive obtained by crosslinking (the coating layer of) the adhesive composition P. The crosslinking of the adhesive composition P can generally be carried out by heat treatment. Further, the drying treatment when evaporating the diluting solvent or the like from the coating layer of the adhesive composition P applied to the desired object may be used as the heating treatment.

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

After the heat treatment, a curing period of about 1 to 2 weeks may be set at normal temperature (e.g., 23 ℃ C., 50% RH) as necessary. When the curing period is required, the adhesive is formed after the curing period, and when the curing period is not required, the adhesive is formed directly after the heat treatment is completed.

By the above-mentioned heat treatment (and curing), the (meth) acrylate polymer (a) is sufficiently crosslinked via the crosslinking agent (B). The adhesive obtained in this way easily satisfies the required values of gel fraction, storage modulus, adhesive force, and the like, and has excellent step following properties under high-temperature and high-humidity conditions.

(4) Physical Properties of adhesive

(4-1) gel fraction

The gel fraction of the adhesive constituting the adhesive agent layer 11 of the present embodiment is preferably 20% or more, more preferably 30% or more, particularly preferably 40% or more, further preferably 48% or more, and most preferably 55% or more, in terms of the lower limit. When the lower limit of the gel fraction of the adhesive is as described above, the cohesive force of the adhesive increases, and the step following property under high-temperature and high-humidity conditions becomes more excellent. In addition, the gel fraction of the pressure-sensitive adhesive of the present embodiment is preferably 99% or less, more preferably 90% or less, particularly preferably 80% or less, and further preferably 74% or less, at the upper limit. When the upper limit of the gel fraction of the adhesive is as described above, the adhesive does not become too hard, and the initial step following property and the step following property under high-temperature and high-humidity conditions are both excellent. Further, a good adhesive force is exhibited, and the adhesiveness to an adherend becomes further excellent. Here, the method of measuring the gel fraction of the adhesive is shown in the test examples described later.

When the adhesive is curable with an active energy ray, the gel fraction of the adhesive after curing with an active energy ray is preferably 30% or more, more preferably 40% or more, particularly preferably 55% or more, and further preferably 65% or more, as the lower limit value. The gel fraction is preferably 99% or less, more preferably 90% or less, particularly preferably 85% or less, and further preferably 80% or less, at the upper limit. When the gel fraction of the adhesive after curing with an active energy ray is in the above range, the step difference following property under high temperature and high humidity conditions becomes more excellent. Further, a good adhesive force is exhibited, and the adhesiveness to an adherend becomes further excellent.

(4-2) storage modulus

The lower limit of the storage modulus of the adhesive constituting the adhesive layer 11 of the present embodiment at 23 ℃ is preferably 0.001MPa or more, particularly preferably 0.01MPa or more, more preferably 0.04MPa or more, and most preferably 0.07MPa or more. When the lower limit of the storage modulus is set to the above value, the step following property under high temperature and high humidity conditions is excellent. The storage modulus is preferably 3MPa or less, particularly preferably 1MPa or less, more preferably 0.5MPa or less, and most preferably 0.2MPa or less, as an upper limit. When the upper limit value of the storage modulus is set to the above value, the initial level difference following property is excellent. The storage modulus in the present specification is a value measured by a torsional shear method (ね manufactured by りせ one turn at one turn) at a measurement frequency of 1Hz in accordance with JIS K7244-6. Specifically, the following test examples are shown.

When the adhesive is curable with an active energy ray, the storage modulus at 23 ℃ of the adhesive after curing with an active energy ray is preferably 0.10MPa or more, more preferably 0.15MPa or more, particularly preferably 0.20MPa or more, and further preferably 0.25MPa or more, as the lower limit value. When the lower limit of the storage modulus is set to the above value, the step following property under high temperature and high humidity conditions is further improved. The storage modulus is preferably 5MPa or less, particularly preferably 1MPa or less, and more preferably 0.5MPa or less, as an upper limit. When the upper limit of the storage modulus is set to the above value, the adhesiveness is excellent.

1-2. Release sheet

The

release sheets

12a and 12b protect the adhesive layer 11 until the adhesive sheet 1 is used, and are released when the adhesive sheet 1 (adhesive layer 11) is used. In the adhesive sheet 1 of the present embodiment, one or both of the

release sheets

12a, 12b are not essential.

Examples of the

release sheets

12a and 12b include a polyethylene film, a polypropylene film, a polybutylene film, a polybutadiene film, a polymethylpentene film, a polyvinyl chloride film, a vinyl chloride copolymer film, a polyethylene terephthalate film, a polyethylene naphthalate film, a polybutylene terephthalate film, a polyurethane film, an ethylene-vinyl acetate film, an ionomer resin film, an ethylene- (meth) acrylic acid copolymer film, an ethylene- (meth) acrylate copolymer film, a polystyrene film, a polycarbonate film, a polyimide film, and a fluororesin film. In addition, crosslinked films of these films may also be used. Further, a laminated film of these films may be used.

The release surfaces (particularly, the surfaces in contact with the adhesive agent layer 11) of the

release sheets

12a and 12b are preferably subjected to a release treatment. Examples of the release agent used for 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, one release sheet is preferably a heavy release type release sheet having a large release force, and the other release sheet is preferably a light release type release sheet having a small release force.

The thickness of the

release sheets

12a and 12b is not particularly limited, but is usually about 20 to 150 μm.

2. Physical Properties

(1) Adhesive force

The adhesive force of the adhesive sheet 1 of the present embodiment to soda-lime glass is preferably 1N/25mm or more, more preferably 5N/25mm or more, particularly preferably 10N/25mm or more, and further preferably 15N/25mm or more, in terms of the lower limit. When the lower limit of the adhesive force is as described above, the step difference following property under high temperature and high humidity conditions becomes more excellent. The adhesion is preferably 70N/25mm or less, more preferably 60N/25mm or less, and particularly preferably 50N/25mm or less, as an upper limit value. When the upper limit value of the adhesive force is set as described above, excellent reworkability can be obtained, and the display body constituting member, particularly an expensive display body constituting member, can be reused when a bonding error occurs.

When the adhesive constituting the adhesive layer 11 is an active energy ray-curable adhesive, the adhesive strength of the adhesive sheet 1 of the present embodiment to soda-lime glass after irradiation with active energy rays is preferably 5N/25mm or more, more preferably 10N/25mm or more, particularly preferably 20N/25mm or more, and further preferably 25N/25mm or more, in terms of the lower limit. When the lower limit of the adhesive force is as described above, the step difference following property under high temperature and high humidity conditions becomes more excellent. The adhesion is preferably 70N/25mm or less, more preferably 60N/25mm or less, and particularly preferably 50N/25mm or less, as an upper limit value. When the upper limit of the adhesive force is as described above, good reworkability can be obtained, and the display member constituting member, particularly an expensive display member constituting member, can be reused when a bonding error occurs.

Here, the adhesive force in the present specification means an adhesive force measured basically by a 180 degree peel method based on JIS Z0237:2009, and is a value measured by making a measurement sample 25mm wide and 100mm long, attaching the measurement sample to an adherend, pressurizing at 0.5MPa and 50 ℃ for 20 minutes, then leaving under normal pressure, 23 ℃ and 50% RH for 24 hours, and then measuring at a peel speed of 300 mm/minute. The adhesive force after irradiation with an active energy ray means the adhesive force of an adhesive agent layer which is adhered to an adherend and then cured by irradiation with an active energy ray.

(2) Step following rate

Regarding the step following property under high temperature and high humidity conditions, the step following rate (%) of the adhesive agent layer 11 represented by the following formula is preferably 5% or more, more preferably 10% or more, particularly preferably 20% or more, further preferably 30% or more, and most preferably 40% or more. This makes it possible to obtain excellent step following properties under high-temperature and high-humidity conditions, and in this case, excellent step following properties at the initial stage (at the time of bonding). The upper limit of the level difference following rate is not particularly limited, but is usually preferably 80% or less, and particularly preferably 70% or less.

The step following ratio (%) { (height of step (μm) in which no bubble, floating, peeling, or the like was present after the durability test and the embedded state was maintained))/(thickness of adhesive layer) } × 100

The test method of the stepped portion following ratio is shown in test examples described later. In addition, the step following ratio of the active energy ray-curable adhesive agent layer means a step following ratio of an adhesive agent layer which is cured by irradiation with an active energy ray after being attached to an adherend.

3. Production of adhesive sheet

As one example of the production of the adhesive sheet 1, a coating solution of the adhesive composition P is applied to the release surface of one release sheet 12a (or 12b), heat treatment is performed to thermally crosslink the adhesive composition P to form a coating layer, and then the coating layer is laminated to the release surface of the other release sheet 12b (or 12 a). When the curing period is required, the coating layer becomes the adhesive layer 11 by providing the curing period, and when the curing period is not required, the coating layer directly becomes the adhesive layer 11. Thus, the adhesive sheet 1 is obtained. The conditions for heat treatment and aging are as described above.

As another production example of the adhesive sheet 1, a coating solution of the adhesive composition P is applied to the release surface of one release sheet 12a, and heat treatment is performed to thermally crosslink the adhesive composition P to form a coating layer, thereby obtaining a release sheet 12a with a coating layer. Further, the coating solution of the adhesive composition P is applied to the release surface of the other release sheet 12b, and heat treatment is performed to thermally crosslink the adhesive composition P to form a coating layer, thereby obtaining a release sheet 12b with a coating layer. Then, the coated release sheet 12a and the coated release sheet 12b are bonded to each other so that the two coated layers are in contact with each other. Here, a plurality of coated release sheets may be produced, and a desired number of the coated layers may be attached. When the curing period is required, the laminated coating layer becomes the adhesive layer 11 by providing the curing period, and when the curing period is not required, the laminated coating layer directly becomes the adhesive layer 11. Thus, the adhesive sheet 1 is obtained. According to this production example, even when the adhesive agent layer 11 is thick, stable production can be performed.

Examples of the method for applying the coating solution of the adhesive composition P include bar coating, blade coating, roll coating, blade coating (blade coating), die coating, and gravure coating.

[ display body ]

Examples of the type of the display (display) according to the present embodiment include a television, a monitor for a computer, a monitor for various devices, a digital signage, a smartphone, and a display for a tablet terminal. These display bodies are sometimes required to have appearance compatibility with white surrounding members, for example, white frame members, white walls, white printed portions, and the like. However, the display body of the present invention is not limited thereto.

As shown in fig. 2, the display 2 of the present embodiment includes a first display component 21 (one display component), a second display component 22 (the other display component), and an adhesive layer 11, and the adhesive layer 11 is located between the first display component 21 and the second display component 22, and bonds the first display component 21 and the second display component 22 to each other.

At least one of the first display element constituting member 21 and the second display element constituting member 22 may have a step on the surface on the side bonded with the adhesive layer 11. In the present embodiment shown in fig. 2, the first display element constituting member 21 has a step such as the printed layer 3 on the surface on the adhesive layer 11 side.

The adhesive layer 11 in the display 2 is formed of the adhesive layer 11 of the adhesive sheet 1. Specifically, the adhesive layer 11 in the display 2 may be the adhesive layer 11 itself of the adhesive sheet 1, or may be formed by curing the adhesive layer 11 with an active energy ray.

Examples of the display 2 include a Liquid Crystal Display (LCD), a Light Emitting Diode (LED) display, an organic electroluminescence (organic EL) display, and electronic paper, and may be a touch panel. Further, the member may be a member constituting a part of them.

The first display element constituting member 21 is preferably a protective panel made of a laminate including a glass plate, a plastic plate, and the like, in addition to the glass plate, the plastic plate, and the like. In this case, the printed layer 3 is usually formed in a frame shape on the adhesive layer 11 side of the first display element constituting member 21.

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

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

Further, various functional layers (a transparent conductive film, a metal layer, a silica layer, a hard coat layer, an antiglare layer, etc.) may be provided on one surface or both surfaces of the glass plate or the plastic plate, and an optical member may be laminated. In addition, the transparent conductive film and the metal layer may also be patterned.

The second display element constituting member 22 is preferably an optical member to be attached to the first display element constituting member 21, a display element module (for example, a liquid crystal module, a Light Emitting Diode (LED) module, an organic electroluminescence (organic EL) module, or the like), or a laminate including the display element module.

Examples of the optical member include an anti-scattering film, a polarizing film, a retardation film, a viewing angle compensation film, a brightness enhancement film, a contrast enhancement film, a liquid crystal polymer film, a diffusion film, a transflective film, a transparent conductive film, and a film sensor. Examples of the anti-scattering film include a hard coat film in which a hard coat layer is formed on one surface of a base film.

The color of the printed layer 3 of the present embodiment is preferably white. The material constituting the printed layer 3 is not particularly limited, and a known material for printing can be used. The lower limit of the thickness of the printed layer 3, that is, the height of the step is preferably 3 μm or more, more preferably 5 μm or more, particularly preferably 7 μm or more, and most preferably 10 μm or more. By setting the lower limit value to the above value, it is possible to sufficiently ensure concealment of the electric wiring lines and the like from the observer side. The upper limit is preferably 200 μm or less, more preferably 100 μm or less, and particularly preferably 30 μm or less. By setting the upper limit to the above value or less, it is possible to prevent the step-difference following property of the adhesive layer 11 to the printed layer 3 from being deteriorated.

In order to manufacture the display 2, one release sheet 12a of the adhesive sheet 1 is peeled off, and the adhesive layer 11 exposed in the adhesive sheet 1 is bonded to the surface of the first display constituting member 21 on the side where the printed layer 3 is present.

Then, the other release sheet 12b is peeled off from the adhesive layer 11 of the adhesive sheet 1, and the adhesive layer 11 exposed in the adhesive sheet 1 and the second display constituent member 22 are bonded. In addition, as another example, the order of attaching the first display body constituting member 21 and the second display body constituting member 22 may be switched.

When the adhesive layer 11 is active energy ray-curable, the first display structure constituting member 21 and the second display structure constituting member 22 are bonded via the adhesive layer 11 as described above, and then the adhesive layer 11 is irradiated with active energy rays. Thereby, the energy ray-curable component (D) in the adhesive layer 11 is polymerized, and the adhesive layer 11 is cured. The irradiation of the energy ray to the adhesive layer 11 is usually performed through either the first display element constituting member 21 or the second display element constituting member 22, and preferably through the first display element constituting member 21 as a protective panel.

The active energy ray is an active energy ray having an energy quantum in an electromagnetic wave or a charged particle beam, and specifically, ultraviolet rays, electron beams, and the like are exemplified. Among the active energy rays, ultraviolet rays which are easy to handle are particularly preferable.

The ultraviolet irradiation may be performed using a high-pressure mercury lamp, fusion H lamp (fusion H lamp), xenon lamp, or the like, and the amount of ultraviolet irradiation is preferably 50 to 1000mW/cm in illuminance meter²About, preferably 100 to 500mW/cm²Left and right. In addition, the light quantity is preferably 50 to 10000mJ/cm²More preferably 200 to 7000mJ/cm²Particularly preferably 500 to 3000mJ/cm². On the other hand, the electron beam irradiation may be performed by using an electron beam accelerator or the like, and the irradiation amount of the electron beam is preferably about 10 to 1000 krad.

Here, as shown in fig. 3, the display body 2 of the present embodiment may have a white frame member 4 in the peripheral portion of the display body 2.

The display 2 has excellent appearance compatibility by giving a feeling of unity to the white frame member 4 due to the physical properties of the adhesive layer 11. Further, the display 2 ensures visibility as a display.

Further, in the display 2, when the adhesive agent layer 11 is formed of the adhesive composition P, the adhesive agent layer 11 is excellent in step following property under high temperature and high humidity conditions, and therefore, for example, even when the display 2 is left under high temperature and high humidity conditions (for example, 85 ℃ and 85% RH), generation of bubbles, floating, peeling, and the like in the vicinity of the step can be suppressed.

The embodiments described above are described for easy understanding of the present invention, and are not described for limiting the present invention. Therefore, the elements disclosed in the above embodiments also cover all design changes and equivalents that fall within the technical scope of the present invention.

For example, either one or both of the

release sheets

12a and 12b in the adhesive sheet 1 may be omitted, and further, a desired optical member may be laminated instead of the release sheets 12a and/or 12 b. Further, the first display body constituting member 21 may not have a level difference. Further, not only the first display element constituting member 21 but also the second display element constituting member 22 may have a step difference on the adhesive agent layer 11 side.

Examples

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

[ example 1]

Preparation of (meth) acrylate polymers

The (meth) acrylate polymer (a) was prepared by copolymerizing 70 parts by mass of 2-ethylhexyl acrylate, 15 parts by mass of methyl methacrylate, and 15 parts by mass of 2-hydroxyethyl acrylate by a solution polymerization method. The molecular weight of the (meth) acrylate polymer (a) was measured by the method described later, and the weight average molecular weight (Mw) was 70 ten thousand.

2. Preparation of adhesive composition

100 parts by mass (in terms of solid content; the same applies hereinafter) of the (meth) acrylic acid ester polymer (A) obtained in the above step 1, 0.2 parts by mass of trimethylolpropane-modified tolylene diisocyanate (TOYOCHEM CO., LTD., product name "BHS 8515") as a crosslinking agent (B), 1.0 part by mass of a titanium oxide-based colorant (C) as a white-based colorant, and 0.2 part by mass of 3-glycidoxypropyltrimethoxysilane as a silane coupling agent were mixed, sufficiently stirred, and diluted with methyl ethyl ketone to obtain a coating solution of an adhesive composition.

Table 1 shows the respective compounding ratios (solid content equivalent) of the adhesive compositions when the (meth) acrylate polymer (a) is 100 parts by mass (solid content equivalent). The abbreviations and the like shown in table 1 are as follows.

[ (meth) acrylic ester Polymer (A) ]

2 EHA: 2-ethylhexyl acrylate

MMA: methacrylic acid methyl ester

HEA: 2-Hydroxyethyl acrylate

IBXA: acrylic acid isobornyl ester

ACMO: n-acryloyl morpholine

BA: acrylic acid n-butyl ester

AA: acrylic acid

[ crosslinking agent (B) ]

TDI: trimethylolpropane-modified toluene diisocyanate (TOYOCHEM CO., LTD., product name "BHS 8515")

XDI: trimethylolpropane-modified xylylene diisocyanate (manufactured by Soken Chemical & Engineering Co., Ltd., product name "TD-75")

The composition of the titanium oxide-based colorant as the white-based colorant (C) is: 91.2% by mass of titanium oxide, 0.8% by mass of zinc oxide, and 8% by mass of silica. The titanium oxide-based colorant had a mode diameter of 420nm and a median particle diameter of 420 nm. The particle size was measured by a dynamic light scattering method (using a Nanotrac Wave apparatus manufactured by microtrac bell corp.).

3. Production of adhesive sheet

The coating solution of the adhesive composition obtained in the above step 2 was coated on the release-treated surface of a heavy release type release sheet (manufactured by Lintec Corporation, product name "SP-PET 752150") obtained by subjecting one surface of a polyethylene terephthalate film to a release treatment using a silicone-based release agent, using a blade coater. Then, the coating layer was subjected to heat treatment at 90 ℃ for 1 minute to form a coating layer (thickness: 50 μm), thereby producing a coated heavy release sheet.

On the other hand, the coating solution of the adhesive composition obtained in the above step 2 was coated on the release-treated surface of a light release type release sheet (manufactured by LINTEC Corporation, product name "SP-PET 382120") which was release-treated on one surface of the polyethylene terephthalate film using a silicone-based release agent, using a blade coater. Then, the coating layer was subjected to heat treatment at 90 ℃ for 1 minute to form a coating layer (thickness: 50 μm), thereby producing a light release type release sheet with a coating layer.

The surface on the coating layer side of the heavy release sheet with the coating layer obtained above was bonded to the surface on the coating layer side of the light release sheet with the coating layer obtained above, to obtain a laminate in which the coating layer having a thickness of 100 μm was sandwiched between the heavy release sheet and the light release sheet.

Then, the laminate was aged at 23 ℃ and 50% RH for 7 days to produce an adhesive sheet having a structure of a heavy release type release sheet/an adhesive layer (thickness: 100 μm)/a light release type release sheet.

The thickness of the adhesive agent layer is a value measured by using a constant pressure thickness measuring instrument (TECLOCK co., ltd., product name "PG-02") in accordance with JIS K7130.

Examples 2 to 10 and comparative examples 1 to 2

An adhesive sheet was produced in the same manner as in example 1, except that the kind and ratio of each monomer constituting the (meth) acrylate polymer (a), the weight average molecular weight (Mw) of the (meth) acrylate polymer (a), the kind of the crosslinking agent (B), the blending amount of the white colorant (C), and the thickness of the adhesive layer were changed as shown in table 1. In examples 6 to 9, an adhesive composition further containing 5 parts by mass of epsilon-caprolactone-modified tris (2-acryloyloxyethyl) isocyanurate (SHIN-NAKAMURA CHEMICAL co., ltd., product name "NK ester a-9300-1 CL" manufactured by SHIN-NAKAMURA CHEMICAL co., ltd.) as an active energy ray-curable component (D) and 0.5 parts by mass of 2,4, 6-trimethylbenzoyl-diphenyl-phosphine oxide as a photopolymerization initiator (E) was prepared, and an active energy ray-curable adhesive layer was formed using the adhesive composition. In addition, the thickness of the adhesive layer is changed by changing the thickness and the number of layers of the adhesive layer formed on the release sheet.

The weight average molecular weight (Mw) is a polystyrene-equivalent weight average molecular weight measured by Gel Permeation Chromatography (GPC) under the following conditions (GPC measurement).

< measurement conditions >

GPC measurement apparatus: HLC-8020 manufactured by TOSOH CORPORATION

GPC column (passage in the following order): TOSOH CORPORATION, Inc

TSK guard column HXL-H

TSK gel GMHXL(×2)

TSK gel G2000HXL

Determination of the solvent: tetrahydrofuran (THF)

Measurement temperature: 40 deg.C

[ test example 1] (measurement of gel fraction)

The adhesive sheets obtained in examples and comparative examples were cut into 80mm × 80mm sizes, the adhesive layers were wrapped in a polyester mesh (mesh size 200), the mass thereof was weighed using a precision balance, and the mass of the mesh alone was subtracted to calculate the mass of the adhesive itself. The mass at this time was designated as M1.

Subsequently, the adhesive wrapped in the polyester net was immersed in ethyl acetate at room temperature (23 ℃ C.) for 24 hours. Then, the adhesive was taken out, air-dried at 23 ℃ and a relative humidity of 50% for 24 hours, and further dried in an oven at 80 ℃ for 12 hours. After drying, the mass was weighed with a precision balance, and the mass of the web alone was subtracted, thereby calculating the mass of the adhesive itself. The mass at this time was designated as M2. Gel fraction (%) was expressed as (M2/M1). times.100. This led to the derivation of the gel fraction of the adhesive (before UV irradiation). The results are shown in Table 2.

On the other hand, the adhesive layer of the adhesive sheet obtained in examples 6 to 9 was irradiated with active energy rays (ultraviolet rays; UV) through the light-release type release sheet under the following conditions to cure the adhesive layer. The gel fraction (after UV irradiation) of the adhesive in the cured adhesive layer was derived in the same manner as described above. The results are shown in Table 2.

< conditions for irradiation with active energy ray >

Using high-pressure mercury lamps

Illuminance of 200mW/cm²Light quantity 2000mJ/cm²

UV illuminance-photometer Using "UVPF-A1" manufactured by Eye graphics Co., Ltd "

[ test example 2] (measurement of L.a.b.)

The light-release type release Sheet was peeled from the adhesive sheets obtained in examples and comparative examples, and the exposed adhesive layer was attached to a soda-lime Glass plate (manufactured by Nippon Sheet Glass co., Ltd). Then, a heavy release sheet was peeled from the adhesive layer, and a surface of a polycarbonate resin plate side of a plastic plate (MITSUBISHI GAS CHEMICAL COMPANY, inc., product name "Iupilon sheet MR 58U", thickness: 1mm) in which a polymethyl methacrylate resin layer was laminated on a polycarbonate resin plate was attached to the exposed adhesive layer to prepare a sample.

The lightness L (L × M), the chromaticity a (a × M), and the chromaticity b (b × M) defined in the color system of CIE1976L a × b were measured on the plastic sheet-side surface of the obtained sample using a simultaneous photometric spectroscopic colorimeter (NIPPON DENSHOKU industies co., ltd., product name "SQ 2000"). Further, the color difference Δ E is calculated from the above result and by the following formula (I). The results are shown in Table 2.

[ mathematical formula 2]

[ test example 3] (measurement of Total light transmittance)

The adhesive layers of the adhesive sheets obtained in examples and comparative examples were bonded to glass, and the bonded adhesive layers were used as measurement samples. The total light transmittance (%) of the above-mentioned measurement sample was measured using a haze meter (NIPPON DENSHOKU INDUSTRIES Co., LTD., manufactured by LTD., product name "NDH-5000") in accordance with JIS K7361-1:1997 on the basis of background measurement (background measurement) using glass. The results are shown in Table 2.

[ test example 4] (measurement of haze value)

The adhesive layers of the adhesive sheets obtained in examples and comparative examples were bonded to glass, and the bonded adhesive layers were used as measurement samples. The haze value (total light haze value;%) of the above-mentioned measurement sample was measured by a haze meter (NIPPON DENSHOKU INDUSTRIES Co., LTD., product name "NDH-5000") according to JIS K7136:2000, after background measurement using glass. The results are shown in Table 2.

[ test example 5] (measurement of storage modulus)

The release sheets were peeled from the adhesive sheets obtained in examples and comparative examples, and the adhesive layers were laminated so that the thickness thereof became 3 mm. A cylindrical body (height: 3mm) having a diameter of 8mm was punched out of the laminate of the obtained adhesive layer, and this was used as a sample.

The storage modulus (MPa; before UV irradiation) of the above sample was measured by the torsional shear method using a viscoelasticity measuring apparatus (product name "MCR 300" manufactured by Physica) in accordance with JIS K7244-6 under the following conditions. The results are shown in Table 2.

Measuring frequency: 1Hz

Measuring temperature: 23 deg.C

The adhesive layer of the adhesive sheet obtained in examples 6 to 9 was irradiated with active energy rays (ultraviolet rays; UV) through a light-release type release sheet under the same conditions as in test example 1 to cure the adhesive layer. The storage modulus (after UV irradiation) of the adhesive of the cured adhesive layer was derived in the same manner as described above. The results are shown in Table 2.

[ test example 6] (measurement of adhesive force)

The light release sheet was peeled from the pressure-sensitive adhesive sheets obtained in examples and comparative examples, and the exposed pressure-sensitive adhesive layer was bonded to an easy-adhesive layer of a polyethylene terephthalate (PET) film (TOYOBO co., ltd., product name "PET a 4300" thickness: 100 μm) having an easy-adhesive layer, to obtain a laminate of a heavy release sheet/pressure-sensitive adhesive layer/PET. The obtained laminate was cut into a width of 25mm and a length of 100mm to obtain a sample.

The heavy-release type release Sheet was peeled from the sample at 23 ℃ and 50% RH, and the exposed adhesive layer was attached to soda-lime Glass (manufactured by Nippon Sheet Glass co., ltd.), followed by pressurization at 0.5MPa and 50 ℃ for 20 minutes using an autoclave manufactured by kurihia SEISAKUSHO co., ltd. Then, the mixture was left at 23 ℃ and 50% RH for 24 hours.

Next, the adhesive force (before UV irradiation; N/25mm) was measured using a tensile tester (product name "TENSILON" manufactured by ORIENTEC CORPORATION) under the conditions of a peeling speed of 300 mm/min and a peeling angle of 180 degrees. The conditions not described herein were measured according to JIS Z0237: 2009. The results are shown in Table 2.

In examples 6 to 9, after the adhesive layer was attached to soda-lime glass in the same manner as described above, the adhesive layer was irradiated with active energy rays through the PET film under the same conditions as in test example 1, and the adhesive force after curing the adhesive layer (after UV irradiation) was measured. The results are shown in Table 2.

[ test example 7] (measurement of step following Rate)

An ultraviolet curable ink (Teikoku Printing Inks Mfg. Co., Ltd., product name "POS-911 ink" manufactured by Ltd.) was screen-printed in a frame shape (outer shape: 90mm in length × 50mm in width, 5mm in width) at a predetermined thickness on the surface of a Glass plate (product name "Corning Glass Eagle XG", manufactured by NSG Precision Co., Ltd., product name "POS-911 ink") to form a frame shape. Then, ultraviolet rays (80W/cm) were irradiated²2 halogen lamps, a lamp height of 15cm, a belt speed of 10 to 15 m/min), and curing the printed ultraviolet curable ink to produce a printed ultraviolet curable ink having a step (height of step: any one height among 110 μm, 30 μm, 15 μm, 12.5 μm, 10 μm, 7.5 μm, and 5 μm).

The light release type release sheet was peeled from the adhesive sheets obtained in examples and comparative examples, and the exposed adhesive layer was bonded to an easy adhesion layer of a polyethylene terephthalate (PET) film (TOYOBO co., ltd., product name "PET a 4300" with a thickness of 100 μm) having an easy adhesion layer. Then, the heavy-release sheet was peeled off to expose the adhesive layer, and the exposed adhesive layer was laminated on each glass plate having a step difference so that the adhesive layer covered the entire frame-shaped printed surface using a laminator (product name "LPD 3214" manufactured by fujiapla inc.). Then, the plate was autoclaved at 50 ℃ and 0.5MPa for 20 minutes, and left to stand at normal pressure, 23 ℃ and 50% RH for 24 hours.

In examples 6 to 9, the adhesive agent layer was cured by irradiating the PET film with active energy rays under the same conditions as in test example 1. Subsequently, the resultant was stored at 85 ℃ and 85% RH for 72 hours (durability test). Then, the level difference followability was evaluated as a level difference followability (%) shown by the following formula. The results are shown in Table 2.

The step following ratio (%) (height of step (μm) in which no bubble, floating, peeling, or the like was present after the durability test and the embedded state was maintained))/(thickness of the adhesive layer) x 100

[ test example 8] (evaluation of Black concealment and appearance harmony)

The adhesive sheets obtained in examples and comparative examples were cut into a length of 70mm × a width of 70mm, and the adhesive layers of the adhesive sheets were bonded so as to be sandwiched between two pieces of soda-lime Glass (70 mm × 1.1mm in length × 70mm × thickness, manufactured by Nippon Sheet Glass co. In examples 6 to 9, the adhesive layer was cured by irradiating the sample with an active energy ray through a soda-lime glass plate under the same conditions as in test example 1.

The obtained sample was laminated on the entire surface of a flat panel terminal (manufactured by Apple inc., product name "iPad (registered trademark)", pixel density: 264ppi, white printed portion having a frame shape) which had a light turned off and which included both a display portion (black) and a white printed portion having a frame shape. The samples were visually evaluated for black concealment and appearance compatibility according to the following criteria. The results are shown in Table 2.

< evaluation criterion of Black concealment >

C. whatever the viewing angle, the color is white, and the black color of the display cannot be seen at all.

Good, white when viewed from an oblique direction, and black of the display is not seen at all, but black of the display is slightly seen when viewed from the front.

Δ · does suppress the black color of the display, but the black color of the display is seen when viewed from an oblique direction.

X · even when viewed from an oblique direction, the black color of the display is very apparent.

< evaluation criterion of appearance harmony >

C · it is difficult to distinguish the boundary between the display portion and the white printed portion of the tablet terminal regardless of the viewing angle.

When viewed from the front, although it is difficult to distinguish the boundary between the display portion and the white printed portion of the tablet terminal, the boundary can be sufficiently distinguished by changing the viewing angle.

Δ · · even when viewed from the front, the boundary between the display portion and the white printed portion of the tablet terminal was recognized, but the effect of providing the sample was confirmed.

Even when viewed from the front, the visibility of the boundary of the display portion and the white printed portion of the tablet terminal is unchanged from the case where no sample is provided.

[ test example 9] (evaluation of visibility)

In a display (product name "LITEBOOK A574/H" manufactured by Fujitsu Limited) having a size of 15.6 inches and a resolution of 1366X 768, various characters (fonts: MS PGthisic; "あ" - "," A "-" "Z", and "0" - "9") of black are displayed at a size of 100% of 10.5 lbs on a white background.

The sample obtained in test example 8 was set on the above display. Then, whether or not characters are recognizable is visually checked at a position 50cm from the display, and the visibility is evaluated by the following criteria.

The results are shown in Table 2.

Very good: all the words can be recognized.

O: some characters cannot be recognized depending on the type of the character.

X: failing to recognize most of the text.

[ Table 1]

As is clear from table 2, the display using the adhesive sheet obtained in the example is excellent in black concealment, appearance harmony with a white body, and visibility.

Industrial applicability

The adhesive sheet of the present invention can be suitably used for bonding display body constituent members to each other in, for example, a display body having a white frame material and a display body hung on a white wall.

Claims

1. An adhesive sheet comprising an adhesive layer for bonding one display constituent member to another display constituent member, wherein the adhesive sheet is characterized in that,

the colour difference Δ E between the adhesive layer and pure white, defined by the CIE1976L a b color system, is less than 95,

the total light transmittance of the adhesive layer is 10% or more.

2. The adhesive sheet according to claim 1, wherein the haze value of the adhesive layer is 0.5% or more and 100% or less.

3. The adhesive sheet according to claim 1, wherein the adhesive layer is composed of an adhesive containing a white colorant.

4. The pressure-sensitive adhesive sheet according to claim 1, wherein the content of the white colorant in the pressure-sensitive adhesive is 0.01% by mass or more and 50% by mass or less.

5. The adhesive sheet according to claim 1, wherein the adhesive is an acrylic adhesive.

6. The pressure-sensitive adhesive sheet according to claim 1, wherein the pressure-sensitive adhesive is obtained by crosslinking a pressure-sensitive adhesive composition containing at least a (meth) acrylate polymer (A), a crosslinking agent (B) and a white coloring agent (C).

7. The adhesive sheet according to claim 1, comprising two release sheets and the adhesive layer, wherein the adhesive layer is sandwiched between the release sheets so as to be in contact with release surfaces of the two release sheets.

8. A display body, comprising: a display comprising a first display component, a second display component, and an adhesive layer for bonding the first display component and the second display component to each other, wherein the adhesive layer is formed from the adhesive layer of the adhesive sheet according to any one of claims 1 to 7.

9. The display according to claim 8, wherein at least one of the one display constituent member and the other display constituent member has a step on a surface on a side to be bonded with the adhesive layer.

10. Display body according to claim 8, characterised in that it has white surrounding members.