CN115029071A

CN115029071A - Adhesive sheet and method for producing laminate

Info

Publication number: CN115029071A
Application number: CN202111635604.XA
Authority: CN
Inventors: 福岛裕贵; 高桥洋一
Original assignee: Lintec Corp
Current assignee: Lintec Corp
Priority date: 2021-03-03
Filing date: 2021-12-29
Publication date: 2022-09-09
Also published as: TW202235559A; KR20220124612A; JP2022134475A

Abstract

The invention provides an adhesive sheet and a liquid crystal display member, which are not easy to generate ripples and uneven image display when two liquid crystal boxes are bonded, and have excellent durability, and a manufacturing method of a laminated body. The adhesive sheet (1) is provided with a composite adhesive layer (2), the composite adhesive layer (2) is provided with a light diffusion adhesive layer (21) containing light diffusion particles and a transparent adhesive layer (22) without light diffusion particles, wherein at least the transparent adhesive layer (22) is formed by an active energy ray curing adhesive, the dynamic hardness (DHT115-1) measured on the surface of the transparent adhesive layer (22) side after curing by active energy rays is more than 0.008, and the haze value of the composite adhesive layer (2) is more than 70% and less than 99%.

Description

Adhesive sheet and method for producing laminate

Technical Field

The present invention relates to an adhesive sheet having light diffusion properties and a method for producing a laminate using the adhesive sheet.

Background

In recent years, as one of the displays, a stereoscopic image display device for displaying an image stereoscopically has been proposed, and among them, a liquid crystal display device having a structure in which two liquid crystal cells are stacked has been known (patent document 1 and the like). In the liquid crystal display device, images are stereoscopically displayed by controlling the brightness of images in the liquid crystal cells or transmitting different light ray information to two eyes respectively.

Documents of the prior art

Patent literature

Patent document 1: japanese patent laid-open publication No. 2015-114371

Disclosure of Invention

Technical problem to be solved by the invention

However, in the liquid crystal display device as described above, as the display image is highly refined and as the liquid crystal cells interfere with each other, moire is likely to occur, and the display image is difficult to see. Further, a display device such as a liquid crystal display device is required to have uniform display images and high durability under a high-temperature and high-humidity environment when used particularly for in-vehicle applications and the like.

The present invention has been made in view of the above circumstances, and an object thereof is to provide an adhesive sheet and a method for producing a laminate, which are less likely to cause moire and image display unevenness when two liquid crystal cells are bonded to each other, and which are excellent in durability.

Means for solving the problems

In order to achieve the above object, a first aspect of the present invention provides an adhesive sheet comprising a composite adhesive layer including a light-diffusing adhesive layer containing light-diffusing fine particles and a transparent adhesive layer containing no light-diffusing fine particles, wherein at least the transparent adhesive layer is formed of an active energy ray-curable adhesive, the dynamic hardness (DHT115-1) measured on the surface of the transparent adhesive layer side after curing with an active energy ray is 0.008% or more, and the haze value of the composite adhesive layer is 70% or more and 99% or less (invention 1).

The pressure-sensitive adhesive sheet according to the invention (invention 1) has the above-described configuration and physical properties, and thus, for example, when two liquid crystal cells are bonded, moire and image display unevenness are less likely to occur, and the durability is also excellent.

In the above invention (invention 1), it is preferable that the light diffusing adhesive layer is formed of an active energy ray curable adhesive, and that the dynamic hardness (DHT115-1) measured on the surface of the light diffusing adhesive layer side after curing with an active energy ray is 0.007 or more (invention 2).

In the above inventions (inventions 1 and 2), it is preferable that the dynamic hardness (DHT115-1) measured on the surface on the side of the transparent adhesive agent layer is 0.001 to 0.500 (invention 3).

In the above inventions (inventions 1 to 3), it is preferable that the dynamic hardness (DHT115-1) measured on the surface of the light diffusing adhesive layer side is 0.001 to 0.500 (invention 4).

In the above inventions (inventions 1 to 4), it is preferable that the transparent adhesive layer has an adhesive force to soda lime glass of 1N/25mm or more and 80N/25mm or less (invention 5).

In the above inventions (inventions 1 to 5), it is preferable that the adhesive force of the light diffusing adhesive layer side to soda lime glass is 1N/25mm or more and 80N/25mm or less (invention 6).

In the above inventions (inventions 1 to 6), the thickness of the composite adhesive layer is preferably 70 μm or more and 3000 μm or less (invention 7).

In the above inventions (inventions 1 to 7), it is preferable that the adhesive sheet has two release sheets, and the composite adhesive layer is sandwiched between the release sheets so as to be in contact with release surfaces of the two release sheets (invention 8).

In the above inventions (inventions 1 to 8), the adhesive sheet is preferably used for bonding two hard plates (invention 9).

The second aspect of the present invention provides a method for producing a laminate in which two hard plates are bonded to each other via an adhesive layer, wherein the light-diffusing adhesive layer of the composite adhesive layer of the adhesive sheet (aspects 1 to 9) is bonded to one hard plate, the transparent adhesive layer of the composite adhesive layer is bonded to the other hard plate, and the composite adhesive layer is cured by irradiation with an active energy ray (aspect 10).

The present invention provides an adhesive sheet having a composite adhesive layer including a light-diffusing adhesive layer containing light-diffusing fine particles and a transparent adhesive layer containing no light-diffusing fine particles, wherein at least the transparent adhesive layer is formed of an active energy ray-curable adhesive, the transparent adhesive layer after curing with an active energy ray has a shear storage modulus (refrigerator せ once breakdown rate) G' of 0.07MPa or more and 6MPa or less, and the composite adhesive layer has a haze value of 70% or more and 99% or less (invention 11).

In the above invention (invention 11), the transparent adhesive layer preferably has a shear storage modulus G' of 0.005MPa to 5MPa (invention 12).

In the above-described inventions (inventions 11 and 12), the light diffusing adhesive layer is preferably formed of an active energy ray-curable adhesive, and the shear storage modulus G' of the light diffusing adhesive layer after curing with an active energy ray is preferably 0.07MPa or more and 7MPa or less (invention 13).

In the above inventions (inventions 11 to 13), it is preferable that the shear storage modulus G' of the light diffusing adhesive layer is 0.06MPa or more and 5MPa or less (invention 14).

Effects of the invention

The pressure-sensitive adhesive sheet of the present invention is less likely to cause moire and image display unevenness when two liquid crystal cells are bonded, for example, and is excellent in durability. Further, according to the method for producing a laminate of the present invention, for example, a laminate which is less likely to cause moire and image display unevenness when two liquid crystal cells are bonded and which is excellent in durability can be obtained.

Drawings

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

FIG. 2 is a sectional view of a liquid crystal display element according to an embodiment of the present invention.

Description of the reference numerals

1: an adhesive sheet; 2: a composite adhesive layer; 21: a light diffusing adhesive layer; 22: a transparent adhesive layer; 3a, 3 b: peeling off the sheet; 4: a liquid crystal display member; 5 a: a first liquid crystal cell; 5 b: a second liquid crystal cell.

Detailed Description

Hereinafter, embodiments of the present invention will be described.

[ adhesive sheet ]

The adhesive sheet according to one embodiment of the present invention has a composite adhesive layer including a light-diffusing adhesive layer containing light-diffusing particles and a transparent adhesive layer containing no light-diffusing particles. At least the transparent adhesive layer is formed of an active energy ray-curable adhesive. In the present specification, the "active energy ray-curable adhesive" refers to an adhesive which is cured by irradiation with an active energy ray. Therefore, conventional adhesives that are cured to such an extent that they are not further cured by irradiation with an active energy ray are not included in the "active energy ray-curable adhesives". The phrase "not containing light diffusion fine particles" means "not containing light diffusion fine particles substantially", and includes a case where light diffusion fine particles are contained in an amount not impairing the effects of the present embodiment, in addition to not containing light diffusion fine particles at all. The amount of the light diffusing fine particles is preferably 0.1% by mass or less, particularly preferably 0.01% by mass or less, more preferably 0.001% by mass or less, and most preferably 0% by mass.

In the adhesive sheet of the present embodiment, the dynamic hardness (DHT 115-1; hereinafter, sometimes omitted) measured on the surface on the transparent adhesive layer side after curing with an active energy ray is preferably 0.008 or more, and the haze value of the composite adhesive layer is preferably 70% or more and 99% or less. The method for measuring dynamic hardness (DHT115-1) in the present specification is shown in test examples described later. The haze value in the present specification is a value measured in accordance with JIS K7136: 2000.

In the adhesive sheet of the present embodiment, at least the transparent adhesive layer is formed of an active energy ray-curable adhesive, and the dynamic hardness after curing with an active energy ray is 0.008 or more, whereby the adhesive sheet is excellent in durability under high-temperature and high-humidity conditions. For example, in a laminate obtained by bonding two liquid crystal cells (glass plates as a test) via the composite adhesive layer of the adhesive sheet of the present embodiment and then curing the composite adhesive layer by irradiation with active energy rays, bubbles or peeling at the interface between the composite adhesive layer and the liquid crystal cells (glass plates) can be suppressed even when the laminate is left to stand under high-temperature and high-humidity conditions, for example, under 85 ℃ and 85% RH for 2000 hours.

Here, when liquid crystal cells as rigid bodies are bonded to each other via the adhesive agent layer, since none of them has flexibility, the adhesive agent layer is compressed in the layer thickness direction, and the compressive stress is accumulated in the adhesive agent layer. This residual stress acts as a repulsive force to the two liquid crystal cells. It is presumed that when the adhesive layer is composed of a light-diffusing adhesive layer, the repulsive force is strong or weak (uneven) depending on the existence density (height) of light-diffusing particles per unit surface area of the light-diffusing adhesive layer in contact with the liquid crystal cell. It is presumed that the resulting unevenness in the repulsive force of the adhesive layer to the liquid crystal cell disturbs the alignment of the liquid crystal cell, and causes unevenness in the display image. In the adhesive sheet of the present embodiment, the above-described unevenness in display images can be suppressed by defining the physical properties of the adhesive layer by the dynamic hardness representing the local elastic behavior from the surface of the adhesive layer toward the thickness direction of the adhesive layer.

Further, it is presumed that, when a transparent adhesive layer having no light diffusion particles is present in addition to the light diffusion adhesive layer like the composite adhesive layer of the adhesive sheet of the present embodiment, the stress unevenness of the light diffusion adhesive layer due to the density of the light diffusion particles due to the compression of the two liquid crystal cells as hard plates can be alleviated by the transparent adhesive layer. This can more effectively suppress the occurrence of unevenness in the display image. That is, since the liquid crystal display device has the transparent adhesive layer as described above in addition to the light diffusing adhesive layer, the performance of preventing image display unevenness caused by attaching liquid crystal cells to each other is improved.

In addition, in the adhesive sheet of the present embodiment, when the haze value of the composite adhesive layer is 70% or more, the composite adhesive layer is less likely to cause moire and further less likely to cause image display unevenness when two liquid crystal cells are bonded. When the haze value of the composite adhesive layer is 99% or less, visibility of a display image by a liquid crystal cell can be ensured.

From the viewpoint of the durability, the dynamic hardness measured on the surface of the transparent adhesive layer side after curing with an active energy ray is preferably 0.008 or more, more preferably 0.010 or more, particularly preferably 0.020 or more, and further preferably 0.025 or more. From the viewpoint of preventing display unevenness, the dynamic hardness is preferably 1.000 or less, more preferably 0.500 or less, particularly preferably 0.100 or less, and further preferably 0.050 or less.

From the viewpoint of suppressing the occurrence of moire, the haze value of the composite adhesive layer is preferably 70% or more, more preferably 80% or more, particularly preferably 84% or more, further preferably 87% or more, and most preferably 90% or more. From the viewpoint of visibility of a displayed image, the haze value of the composite adhesive layer is preferably 99% or less, more preferably 98% or less, and particularly preferably 97% or less.

In view of the durability, in the present embodiment, it is preferable that the light diffusing adhesive layer is also formed of an active energy ray curable adhesive. The dynamic hardness measured on the surface of the light-diffusing adhesive layer side after curing with an active energy ray is preferably 0.007 or more, more preferably 0.009 or more, particularly preferably 0.019 or more, and further preferably 0.024 or more. This makes the laminate more excellent in durability. On the other hand, from the viewpoint of preventing display unevenness, the dynamic hardness is preferably 1.000 or less, more preferably 0.500 or less, particularly preferably 0.100 or less, and further preferably 0.050 or less.

From the viewpoint of workability, the dynamic hardness measured on the surface on the transparent adhesive layer side before curing with an active energy ray is preferably 0.001 or more, more preferably 0.002 or more, particularly preferably 0.003 or more, and further preferably 0.005 or more. From the viewpoint of sufficient adhesion, the dynamic hardness is preferably 0.500 or less, more preferably 0.100 or less, particularly preferably 0.050 or less, and further preferably 0.010 or less.

The dynamic hardness measured on the surface of the light-diffusing adhesive layer side before curing with an active energy ray is preferably 0.001 or more, more preferably 0.002 or more, particularly preferably 0.003 or more, and further preferably 0.004 or more. This effectively suppresses occurrence of unevenness such as partial aggregation of the light diffusing fine particles during attachment, and further improves moire suppression performance. The dynamic hardness is preferably 0.500 or less, more preferably 0.100 or less, particularly preferably 0.050 or less, and further preferably 0.010 or less. This can suppress an increase in stress in the adhesive agent layer due to the adhesion, and can more effectively suppress display unevenness.

The shear storage modulus G '(before curing with an active energy ray/after curing with an active energy ray) of the transparent adhesive layer and the shear storage modulus G' (before curing with an active energy ray and during curing with an inactive energy ray/after curing with an active energy ray) of the light-diffusing adhesive layer are preferably within the ranges specified in the embodiments described below. This makes it easy to set the dynamic hardness within the above range. The method for measuring the shear storage modulus G' in the present specification is as shown in test examples described later.

The gel fraction of the adhesive constituting the transparent adhesive layer before curing with an active energy ray is preferably 25% or more, more preferably 35% or more, particularly preferably 45% or more, and further preferably 50% or more. The gel fraction is preferably 85% or less, more preferably 75% or less, particularly preferably 65% or less, and further preferably 60% or less. When the gel fraction is in the above range, the dynamic hardness and the shear storage modulus G' of the transparent adhesive layer before curing by an active energy ray can be easily brought into preferred ranges. The method for measuring the gel fraction of the adhesive in the present specification is shown in test examples described later.

The gel fraction of the adhesive constituting the transparent adhesive layer after curing with an active energy ray is preferably 40% or more, more preferably 50% or more, particularly preferably 60% or more, and even more preferably 65% or more. The gel fraction is preferably 95% or less, more preferably 90% or less, particularly preferably 80% or less, and further preferably 75% or less. When the gel fraction is in the above range, the dynamic hardness and the shear storage modulus G' of the transparent adhesive layer after curing with an active energy ray can be easily brought into preferred ranges.

The gel fraction of the adhesive (before curing with an active energy ray and when curing with an inactive energy ray) constituting the light diffusing adhesive layer is preferably 30% or more, more preferably 40% or more, particularly preferably 50% or more, and further preferably 55% or more. The gel fraction is preferably 90% or less, more preferably 80% or less, particularly preferably 70% or less, and further preferably 65% or less. When the gel fraction is in the above range, the dynamic hardness and the shear storage modulus G' of the light-diffusing adhesive layer can be easily brought into preferred ranges.

When the adhesive constituting the light diffusing adhesive layer is active energy ray-curable, the gel fraction of the adhesive after curing with an active energy ray is preferably 40% or more, more preferably 50% or more, particularly preferably 60% or more, and further preferably 65% or more. The gel fraction is preferably 95% or less, more preferably 90% or less, particularly preferably 85% or less, and further preferably 80% or less. When the gel fraction is in the above range, the dynamic hardness and the shear storage modulus G' of the light-diffusing adhesive layer after curing with an active energy ray can be easily brought into preferred ranges.

In this embodiment, the composite adhesive layer may be composed of two layers of the light diffusing adhesive layer and the transparent adhesive layer, or may be composed of three layers in which the transparent adhesive layer, the light diffusing adhesive layer, and the transparent adhesive layer are laminated in this order. A preferred example of the composite adhesive layer of the present embodiment is composed of two layers, a light-diffusing adhesive layer and a transparent adhesive layer, and is described below with reference to the drawings.

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

release sheets

3a and 3b and a composite adhesive layer 2, and the composite adhesive layer 2 is sandwiched between the two

release sheets

3a and 3b so as to be in contact with the release surfaces of the two

release sheets

3a and 3 b. However, the

release sheets

3a and 3b are not essential components of the adhesive sheet 1, and may be peeled off and removed when the adhesive sheet 1 is used. The release surface of the release sheet in the present specification means a surface having releasability in the release sheet, and includes any of a surface subjected to a release treatment and a surface which exhibits releasability without being subjected to a release treatment.

The composite adhesive layer 2 of the present embodiment is composed of two layers, a light-diffusing adhesive layer 21 in contact with the release sheet 3a and a transparent adhesive layer 22 in contact with the release sheet 3 b.

1. Each element

1-1. Compound adhesive layer

The type of the adhesive constituting the light diffusing adhesive layer 21 and the transparent adhesive layer 22 of the composite adhesive layer 2 of the present embodiment is not particularly limited as long as the transparent adhesive layer 22 is formed of an active energy ray curable adhesive. For example, any one of an acrylic adhesive, a polyester adhesive, a polyurethane adhesive, a rubber adhesive, and a silicone adhesive may be used. 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 these adhesives, acrylic adhesives having excellent adhesive properties, optical characteristics, and the like are preferable. The acrylic pressure-sensitive adhesive is preferably a crosslinked acrylic pressure-sensitive adhesive, and more preferably a thermally crosslinked acrylic pressure-sensitive adhesive.

The adhesive constituting the light diffusing adhesive layer 21 and the adhesive constituting the transparent adhesive layer 22 may be the same type or different types, and preferably both are active energy ray-curable adhesives, and particularly preferably both are active energy ray-curable acrylic adhesives. This makes it easy to satisfy the above-mentioned physical properties (dynamic hardness and shear storage modulus G' after curing with an active energy ray). In this case, the compositions other than the light diffusing particles may be the same or different. The main polymers may have the same or different monomer compositions. The adhesive constituting the transparent adhesive layer 22 may be an active energy ray-curable acrylic adhesive, and the adhesive constituting the light diffusing adhesive layer 21 may be an inactive energy ray-curable acrylic adhesive.

Hereinafter, a case will be described in which the adhesive constituting the light diffusing adhesive layer 21 and the adhesive constituting the transparent adhesive layer 22 are both active energy ray-curable acrylic adhesives, but the present invention is not limited thereto.

From the viewpoint of further enhancing the cohesive force between the polymers, the adhesive constituting the light-diffusing adhesive layer 21 and the adhesive constituting the transparent adhesive layer 22 are preferably obtained by crosslinking an adhesive composition containing a (meth) acrylate polymer (a), a crosslinking agent (B), and an active energy ray-curable component (C) (hereinafter sometimes referred to as "adhesive composition P"). In the case of the light diffusing adhesive layer 21, the adhesive composition P further contains light diffusing fine particles (D).

The pressure-sensitive adhesive obtained from the pressure-sensitive adhesive composition P can easily satisfy the above physical properties (dynamic hardness, shear storage modulus G') and can exhibit desired optical properties, adhesive force, and the like. In the present specification, (meth) acrylic acid refers to both acrylic acid and methacrylic acid. Other similar terms are also the same. Further, the term "copolymer" is also included in the term "polymer".

(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. The reactive group derived from the reactive group-containing monomer reacts with the crosslinking agent (B) to form a crosslinked structure (three-dimensional network structure) to give an adhesive having a desired cohesive force.

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 monomers, a hydroxyl group-containing monomer or a carboxyl group-containing monomer having excellent reactivity with the crosslinking agent (B) is preferable.

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 of the obtained (meth) acrylate polymer (a) with the crosslinking agent (B) and copolymerizability with other monomers. Specifically, for example, 2-hydroxyethyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate and the like are preferably used. 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 because of reactivity of the carboxyl group in the obtained (meth) acrylate polymer (a) with the crosslinking agent (B) and copolymerizability 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 amino group-containing monomer does not include a nitrogen atom-containing monomer described later.

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, more preferably 7% by mass or more, particularly preferably 13% by mass or more, further preferably 22% by mass or more, and most preferably 26% by mass or more. In addition, the (meth) acrylate polymer (a) preferably contains 45% by mass or less, more preferably 40% by mass or less, particularly preferably 35% by mass or less, and further preferably 30% 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 good crosslinked structure can be formed in the obtained adhesive, and the dynamic hardness or shear storage modulus G' of the adhesive before curing by an active energy ray can be easily set within a preferable range. In addition, when the light-diffusing fine particles (D) are contained, the dispersibility of the light-diffusing fine particles (D) in the obtained adhesive tends to be good.

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 acidic component, since the carboxyl group-containing monomer is not contained, even when a substance which causes a problem due to an acid, for example, a transparent conductive film such as Indium Tin Oxide (ITO), a metal film, or the like is present in the target to which the adhesive is to be attached, the problem due to the acid (corrosion, change in resistance value, or the like) can be suppressed. However, it is 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 in an amount of 0.01% by mass or less, and more preferably in an amount of 0.001% by mass or less.

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

The alkyl (meth) acrylate is preferably an alkyl (meth) acrylate having an alkyl group with 1 to 20 carbon atoms from the viewpoint of adhesiveness. 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, myristyl (meth) acrylate, palmityl (meth) acrylate, and stearyl (meth) acrylate. Among them, from the viewpoint of further improving the adhesiveness, a (meth) acrylate having an alkyl group with 4 to 8 carbon atoms is preferable, and n-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, or isooctyl (meth) acrylate is particularly preferable. These alkyl (meth) acrylates may be used alone or in combination of two or more.

The (meth) acrylate polymer (a) preferably contains 20% by mass or more, more preferably 30% by mass or more, particularly preferably 40% by mass or more, and further preferably 45% 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 the above value, the (meth) acrylate polymer (a) can exhibit appropriate tackiness. When the light-diffusing fine particles (D) are contained, the dispersibility of the light-diffusing fine particles (D) in the adhesive tends to be good, and the desired tackiness of the (meth) acrylate polymer (a) can be inhibited from being impaired. On the other hand, the (meth) acrylic acid ester polymer (a) preferably contains 90% by mass or less, more preferably 80% by mass or less, particularly preferably 70% by mass or less, and further preferably 60% 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 the above value, 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 further contains a monomer having an alicyclic structure in the molecule (alicyclic structure-containing monomer) as a monomer unit constituting the polymer. The alicyclic structure-containing monomer increases the glass transition temperature of the polymer, and increases the dynamic hardness and shear storage modulus G' of the resulting adhesive. Further, since the alicyclic structure-containing monomer has a large volume, it is presumed that when the alicyclic structure-containing monomer is present in the polymer, the interval between the polymers is enlarged, the viscosity of the coating liquid is lowered, and the thickness of the adhesive layer is easily increased.

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 a polycyclic alicyclic structure. From the above-mentioned viewpoint, polycyclic alicyclic structures (polycyclic structures) are preferable, and bicyclic to tetracyclic polycyclic structures are particularly preferable. From the above viewpoint, the number of carbon atoms of the alicyclic structure (the number of all carbon atoms of the portion indicating a ring, the number of carbon atoms when a plurality of rings are present independently, is preferably 5 to 15, and particularly preferably 7 to 10.

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), isobornyl (meth) acrylate (carbon number of alicyclic structure: 7) or the like, which exerts more excellent durability, is preferable, and isobornyl (meth) acrylate is particularly preferable. These alicyclic structure-containing monomers may be used alone 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 5 mass% or more, and further preferably 7 mass% or more. The content of the alicyclic structure-containing monomer is preferably 20% by mass or less, particularly preferably 15% by mass or less, and still more preferably 10% by mass or less. When the content of the alicyclic structure-containing monomer is in the above range, the dynamic hardness and the shear storage modulus G' can be easily adjusted to the preferred ranges.

The (meth) acrylic acid ester polymer (A) preferably further contains a nitrogen atom-containing monomer as a monomer unit constituting the polymer. By making the monomer containing a nitrogen atom exist as a constituent unit in the polymer, a predetermined polarity is imparted to the adhesive, and the adhesive can be made excellent in affinity for an adherend having a certain polarity such as glass. As the nitrogen atom-containing monomer, a monomer having a nitrogen-containing heterocycle is preferable from the viewpoint of imparting appropriate rigidity to the (meth) acrylate polymer (a). In addition, from the viewpoint of enhancing the degree of freedom of the moiety derived from the nitrogen atom-containing monomer in the higher-order structure of the adhesive agent, it is preferable that the nitrogen atom-containing monomer does not have 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. 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 3% by mass or more, and further preferably 5% by mass or more. The (meth) acrylate polymer (a) preferably contains 20% by mass or less, particularly preferably 15% by mass or less, and further preferably 10% by mass or less of a 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, if necessary. As the other monomer, a monomer not containing a reactive functional group is preferable in order not to inhibit the above-described action of the reactive functional group-containing monomer. 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. Since the linear polymer is likely to cause entanglement of molecular chains and is expected to improve the cohesive force, an adhesive having excellent durability under high-temperature and high-humidity conditions is likely to be obtained.

The (meth) acrylate polymer (a) is preferably a solution polymer obtained by a solution polymerization method. Since a solution polymer can easily give a polymer having a high molecular weight and can be expected to improve the cohesive force, an adhesive having excellent durability under high-temperature and high-humidity conditions can be easily obtained.

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, more preferably 30 ten thousand or more, particularly preferably 40 ten thousand or more, and further preferably 50 ten thousand or more. This improves the dynamic hardness and shear storage modulus G' of the resulting adhesive.

The weight average molecular weight of the (meth) acrylate polymer (a) is preferably 150 ten thousand or less, more preferably 120 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 the above value, the values of the dynamic hardness and the shear storage modulus G' of the obtained adhesive can be reduced, and the thickness of the adhesive layer can be easily increased. 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) may be a crosslinking agent 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 crosslinking agents, an isocyanate-based crosslinking agent having excellent reactivity with a hydroxyl group and a carboxyl group, or an epoxy-based crosslinking agent having excellent reactivity with a carboxyl group 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 products thereof, and adducts thereof with low-molecular active hydrogen-containing compounds such as ethylene glycol, propylene glycol, neopentyl glycol, trimethylolpropane and castor oil. 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.

Examples of the epoxy-based crosslinking agent include 1, 3-bis (N, N-diglycidylaminomethyl) cyclohexane, N, N, N ', N' -tetraglycidylmethylenem-xylylenediamine, ethylene glycol diglycidyl ether, 1, 6-hexanediol diglycidyl ether, trimethylolpropane diglycidyl ether, diglycidylaniline, and diglycidylamine. Among them, 1, 3-bis (N, N-diglycidylaminomethyl) cyclohexane is preferable from the viewpoint of reactivity with a carboxyl group.

The content of the crosslinking agent (B) in the adhesive composition P is preferably 0.01 parts by mass or more, particularly preferably 0.05 parts by mass or more, and more preferably 0.1 parts 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 in the above range, the above physical properties, adhesive force and the like of the obtained adhesive are easily preferable.

(1-3) active energy ray-curable component (C)

It is presumed that in an adhesive obtained by curing an adhesive obtained by crosslinking an adhesive composition P containing an active energy ray-curable component (C) with an active energy ray, the active energy ray-curable component (C) is polymerized with each other, and the polymerized active energy ray-curable component (C) is entangled with a crosslinked structure (three-dimensional network structure) of the (meth) acrylate polymer (a). The adhesive having such a high-order structure is particularly excellent in durability since it easily satisfies the dynamic hardness and shear storage modulus G' after curing with an active energy ray.

The active energy ray-curable component (C) is not particularly limited as long as it can be cured by irradiation with an active energy ray to obtain the above-described effects, and may be any of a monomer, an oligomer, or a polymer, or a mixture thereof. Among them, polyfunctional acrylate monomers having more excellent durability are 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, hydroxypivalic acid neopentyl glycol di (meth) acrylate, dicyclopentyl 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. In addition, from the viewpoint of compatibility with the (meth) acrylate polymer (a), the molecular weight of the polyfunctional acrylate monomer is preferably less than 1000.

From the viewpoint of optimizing the dynamic hardness and shear storage modulus G' after curing with an active energy ray and further improving the durability, the content of the active energy ray-curable component (C) in the adhesive composition P is preferably 1 part by mass or more, more preferably 4 parts by mass or more, particularly preferably 6 parts by mass or more, and further preferably 8 parts by mass or more, per 100 parts by mass of the (meth) acrylate polymer (a), to be described below. On the other hand, the content is preferably 50 parts by mass or less, more preferably 30 parts by mass or less, particularly preferably 20 parts by mass or less, and further preferably 15 parts by mass or less, in view of the adhesive force of the adhesive after irradiation with active energy rays, which is the upper limit value.

(1-4) light diffusing particles (D)

The light-diffusing particles (D) may be particles that satisfy the haze value of the obtained composite adhesive layer 2 having the light-diffusing adhesive layer 21.

Examples of the light-diffusing fine particles include inorganic fine particles such as silica, calcium carbonate, aluminum hydroxide, magnesium hydroxide, clay, talc, and titanium dioxide; organic light-transmitting fine particles such as acrylic resin, polystyrene resin, polyethylene resin, and epoxy resin; microparticles formed from a silicon-containing compound having an intermediate structure of inorganic and organic, such as silicone resin (for example, Tospearl series manufactured by Momentive Performance Materials Japan LLC), and the like. Among these, acrylic resin fine particles and fine particles formed of a silicon-containing compound having an inorganic and organic intermediate structure are preferable from the viewpoint of coping with high definition of the adhesive layer. In addition, even if a small amount of fine particles made of a silicon-containing compound having an intermediate structure between inorganic and organic components is added, the effect is exhibited and the adhesiveness of the active energy ray-curable adhesive component is favorably maintained, which is particularly preferable. The light diffusing particles may be used singly or in combination of two or more.

Examples of the acrylic resin fine particles include fine particles formed of a homopolymer of methyl methacrylate or a copolymer of methyl methacrylate and a monomer such as vinyl acetate, styrene, methyl acrylate, or ethyl acrylate.

The shape of the light diffusing fine particles is preferably spherical fine particles with uniform light diffusion. The average particle diameter of the light diffusing fine particles by the centrifugal sedimentation light transmission method is preferably 1.0 μm or more, more preferably 2.0 μm or more, particularly preferably 3.0 μm or more, and further preferably 4.0 μm or more in the lower limit. On the other hand, the upper limit is preferably 10.0 μm or less, particularly preferably 7.0 μm or less, and further preferably 5.0 μm or less. By setting the average particle diameter within the above range, the obtained adhesive satisfies a high total light transmittance, and a haze value within the above range is easily obtained.

The average particle diameter by the centrifugal sedimentation method is measured as follows: 1.2g of the fine particles and 98.8g of isopropyl alcohol were sufficiently stirred, and the mixture was used as a sample for measurement, and measured by using a centrifugal automatic particle size distribution measuring apparatus (HORIBA, manufactured by LTD., CAPA-700).

The lower limit of the content of the light diffusing fine particles in the adhesive composition P is preferably 1 part by mass or more, more preferably 3 parts by mass or more, particularly preferably 8 parts by mass or more, and further preferably 12 parts by mass or more, based on 100 parts by mass of the (meth) acrylate polymer (a). The content of the light diffusing fine particles is preferably 50 parts by mass or less, particularly preferably 40 parts by mass or less, and more preferably 30 parts by mass or less, per 100 parts by mass of the (meth) acrylate polymer (a), as the upper limit. When the content of the light diffusing fine particles is within the above range, the obtained composite adhesive layer 2 having the light diffusing adhesive layer 21 easily satisfies the haze value and easily satisfies the dynamic hardness and the shear storage modulus G'.

(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 thus containing the photopolymerization initiator (E), the active energy ray-curable component (C) 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-morpholinyl-propan-1-one, 4- (2-hydroxyethoxy) phenyl-2- (hydroxy-2-propyl) ketone, benzophenone, and a photopolymerization initiator (E), P-phenylbenzophenone, 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, bis (2,4, 6-trimethylbenzoyl) -phenylphosphine oxide, and the like. These photopolymerization initiators may be used alone or in combination of two or more.

Among the above photopolymerization initiators, preferred are phosphine oxide type photopolymerization initiators which are easily cracked even when irradiated with ultraviolet rays through a plastic plate containing an ultraviolet absorber and easily ensure curing of an adhesive. Specifically, 2,4, 6-trimethylbenzoyl-diphenyl-phosphine oxide, phenylbis (2,4, 6-trimethylbenzoyl) phosphine oxide, and the like are preferable.

The lower limit of 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 more preferably 5 parts by mass or more, per 100 parts by mass of the active energy ray-curable component (C). 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 commonly used in acrylic adhesives, for example, silane coupling agents, rust inhibitors, ultraviolet absorbers, antistatic agents, tackifiers, antioxidants, light stabilizers, softening agents, refractive index modifiers, and the like can be added to the adhesive composition P as needed. The polymerization solvent or the dilution solvent described later is not included in the additives constituting the adhesive composition P.

Among the above additives, the adhesive composition P preferably contains a silane coupling agent. This improves the adhesion to the adherend and improves the durability even when the adherend is a plastic plate or a glass member.

The silane coupling agent is preferably an organosilicon compound having at least one 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 polymerizable unsaturated group-containing silicon compounds such as vinyltrimethoxysilane, vinyltriethoxysilane and methacryloxypropyltrimethoxysilane, epoxy-containing silicon compounds such as 3-glycidoxypropyltrimethoxysilane and 2- (3, 4-epoxycyclohexyl) ethyltrimethoxysilane, mercapto-containing silicon compounds such as 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane and 3-mercaptopropyldimethoxymethylsilane, amino-containing silicon compounds such as 3-aminopropyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropyltrimethoxysilane and N- (2-aminoethyl) -3-aminopropylmethyldimethoxysilane, amino-containing silicon compounds such as N- (2-aminoethyl) -3-aminopropylmethyldimethoxysilane, and the like, 3-chloropropyltrimethoxysilane, 3-isocyanatopropyltriethoxysilane, or a condensate of at least one of these silane coupling agents with an alkyl group-containing silicon compound such as methyltriethoxysilane, ethyltriethoxysilane, methyltrimethoxysilane, ethyltrimethoxysilane, or the like. 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 1.2 parts by mass or less, particularly preferably 0.8 parts by mass or less, and further preferably 0.4 parts 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 active energy ray-curable component (C) are mixed, and the photopolymerization initiator (E), additives, and the like are added as needed. In the case of the light-diffusing adhesive layer 21, light-diffusing fine particles (D) are further incorporated.

The (meth) acrylate polymer (a) can be prepared by polymerizing a mixture of monomers constituting the polymer using 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 necessary. However, the present invention is not limited thereto, and polymerization may be carried out in the absence of 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), and 2, 2' -azobis (2-

Methylpropionic acid) dimethyl ester, 4 ' -azobis (4-cyanovaleric acid), 2 ' -azobis (2-hydroxymethylpropionitrile), 2 ' -azobis [2- (2-imidazolin-2-yl) propane ], and the like.

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, peroxy (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 active energy ray-curable component (C), and, if necessary, a diluting solvent, the photodiffusion particles (D), the photopolymerization initiator (E), additives, and the like are added to a solution of the (meth) acrylate polymer (a) and sufficiently mixed, thereby obtaining a solvent-diluted adhesive composition P (coating solution). In the case where a solid component is used for any of the above components or in the case where the solid component is precipitated when the solid component is mixed with another component in an undiluted state, the solid 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 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 liquid prepared in the above manner are not particularly limited as long as the coating liquid can be applied, and may be appropriately selected depending on the case. For example, the adhesive composition P may be diluted so that the concentration thereof is 10 to 60 mass%. In addition, when obtaining a coating liquid, the addition of a diluting solvent or the like is not an essential condition, and the diluting solvent may not be added as long as the adhesive composition P has a viscosity or the like that allows coating. 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 light diffusing adhesive layer 21 and the transparent adhesive layer 22 of the present embodiment are preferably formed of adhesives each of which is (a coating layer of) the crosslinked 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, if necessary, a curing period of about 1 to 2 weeks may be set at normal temperature (e.g., 23 ℃ C., 50% RH). When the curing period is required, an adhesive is formed after the curing period, and when the curing period is not required, an adhesive is formed 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 composite adhesive layer 2 of the present embodiment can be obtained by laminating a light-diffusing adhesive layer 21 and a transparent adhesive layer 22. The timing of the lamination may be before or after the curing of each adhesive layer. However, in order to further improve the adhesion between the light-diffusing adhesive layer 21 and the transparent adhesive layer 22, it is preferable to laminate the layers before curing the adhesive layers.

(4) Thickness of adhesive layer

The total thickness of the composite adhesive layer 2, that is, the total thickness of the light diffusing adhesive layer 21 and the transparent adhesive layer 22 in the present embodiment is preferably 70 μm or more, particularly preferably 110 μm or more, and more preferably 140 μm or more, as defined below. When the lower limit value of the total thickness of the composite adhesive layer 2 is set to the above value, the haze value is easily satisfied, and the compression stress of the adhesive layer to the liquid crystal cell as two hard plates is easily relaxed, thereby further improving the performance of preventing image display unevenness. On the other hand, the total thickness of the composite adhesive layer 2 is preferably 3000 μm or less, particularly preferably 1000 μm or less, more preferably 500 μm or less, and most preferably 420 μm or less, in terms of the above-mentioned limit. By setting the upper limit value of the total thickness of the composite adhesive layer 2 to the above value, blurring of an image or a decrease in the total light transmittance can be prevented.

The thickness of the light diffusing adhesive layer 21 is preferably 10 μm or more, particularly preferably 20 μm or more, and more preferably 40 μm or more in the lower limit. When the lower limit of the thickness of the light diffusing adhesive layer 21 is set to the above value, the haze value described above is easily satisfied. On the other hand, the thickness of the light diffusing adhesive layer 21 is preferably 300 μm or less, particularly preferably 100 μm or less, and further preferably 80 μm or less, as defined above. By setting the upper limit of the thickness of the light diffusing adhesive layer 21 to the above value, blurring of an image or a decrease in the total light transmittance can be prevented.

The thickness of the transparent adhesive layer 22 is preferably 20 μm or more, particularly preferably 40 μm or more, and more preferably 80 μm or more, as defined below. When the lower limit of the thickness of the transparent adhesive layer 22 is set to the above value, the compressive stress of the adhesive layer to the liquid crystal cell as two hard plates is easily relaxed, and the performance of preventing image display unevenness is further improved. On the other hand, the thickness of the transparent adhesive layer 22 is preferably 2700 μm or less, particularly preferably 900 μm or less, more preferably 420 μm or less, and most preferably 340 μm or less, in terms of the above-mentioned limit. By setting the upper limit of the thickness of the transparent adhesive layer 22 to the above value, blurring of an image or a decrease in the total light transmittance can be prevented.

1-2. Release sheet

The

release sheets

3a and 3b protect the composite adhesive layer 2 until the time of using the adhesive sheet 1, and are released when the adhesive sheet 1 (composite adhesive layer 2) is used. In the adhesive sheet 1 of the present embodiment, one or both of the

release sheets

3a, 3b are not necessary.

Examples of the

release sheets

3a and 3b 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 composite adhesive layer 2) of the

release sheets

3a and 3b 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

3a and 3b, one is preferably a heavy release type release sheet having a large release force, and the other is preferably a light release type release sheet having a small release force. For example, the release sheet 3a on the side in contact with the light diffusing adhesive layer 21 may be a light release type release sheet, the release sheet 3b on the side in contact with the transparent adhesive layer 22 may be a heavy release type release sheet, the release sheet 3a on the side in contact with the light diffusing adhesive layer 21 may be a heavy release type release sheet, and the release sheet 3b on the side in contact with the transparent adhesive layer 22 may be a light release type release sheet.

The thickness of the

release sheets

3a and 3b is not particularly limited, but is usually about 20 to 150 μm.

2. Production of adhesive sheet

As one production example of the adhesive sheet 1, a coating solution of the adhesive composition P for forming the transparent adhesive layer 22 is applied to the release surface of one release sheet 3a, and heat treatment is performed to thermally crosslink the adhesive composition P to form a coating layer, thereby obtaining a release sheet 3a with a coating layer. Further, a coating solution of the adhesive composition P for forming the light-diffusing adhesive layer 21 was applied to the release surface of the other release sheet 3b, and heat treatment was performed to thermally crosslink the adhesive composition P to form a coating layer, thereby obtaining a release sheet 3b with a coating layer. Then, the coated release sheet 3a and the coated release sheet 3b are bonded so that the two coated layers are in contact with each other. Here, a plurality of release sheets with coating layers may be produced, and the coating layers may be laminated in a desired number and in a desired lamination order. When the curing period is required, the laminated coating layer becomes the composite adhesive layer 2 by providing the curing period, and when the curing period is not required, the laminated coating layer directly becomes the composite adhesive layer 2. Thus, the adhesive sheet 1 having the composite adhesive layer 2 was obtained, and the composite adhesive layer 2 was a laminate of the light diffusion adhesive layer 21 and the transparent adhesive layer 22. The conditions for the heat treatment and aging are as described above.

In addition, the coating layer for forming the transparent adhesive layer 22 and the coating layer for forming the light diffusion adhesive layer 21 may be sandwiched by two release sheets, respectively, and one release sheet may be peeled off when the coating layer for forming the transparent adhesive layer 22 and the coating layer for forming the light diffusion adhesive layer 21 are bonded.

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

3. Physical Properties

(1) Adhesive force

From the viewpoint of durability, the adhesive force of the transparent adhesive layer 22 side of the adhesive sheet 1 of the present embodiment to soda-lime glass is preferably 1N/25mm or more, more preferably 10N/25mm or more, particularly preferably 20N/25mm or more, and further preferably 30N/25mm or more. The above-mentioned adhesive force is preferably 80N/25mm or less, more preferably 70N/25mm or less, particularly preferably 60N/25mm or less, and still more preferably 50N/25mm or less. This can provide excellent reworkability, and can reuse the adherend when a bonding error occurs.

The adhesive sheet 1 of the present embodiment has an adhesive force to soda-lime glass on the side of the transparent adhesive layer 22 after curing with an active energy ray (after being attached to an adherend and then irradiated with active energy), which is preferably 1N/25mm or more, more preferably 10N/25mm or more, particularly preferably 20N/25mm or more, and further preferably 30N/25mm or more. This makes the durability under high-temperature and high-humidity conditions more excellent. The above adhesion is preferably 80N/25mm or less, more preferably 70N/25mm

The thickness is particularly preferably 60N/25mm or less, and more preferably 50N/25mm or less. This can provide good reworkability.

From the viewpoint of durability, the adhesive force of the light diffusing adhesive layer 21 side of the adhesive sheet 1 of the present embodiment to soda lime glass is preferably 1N/25mm or more, and more preferably 10N/25mm

The above is preferably 15N/25mm or more, and more preferably 25N/25mm or more. The above-mentioned adhesive force is preferably 80N/25mm or less, more preferably 60N/25mm or less, particularly preferably 40N/25mm or less, and still more preferably 35N/25mm or less. This can provide excellent reworkability, and can reuse the adherend when a bonding error occurs.

The adhesive sheet 1 of the present embodiment has an adhesive force to soda-lime glass on the light-diffusing adhesive layer 21 side after curing with an active energy ray (after being attached to an adherend and then irradiated with active energy), which is preferably 1N/25mm or more, more preferably 10N/25mm or more, particularly preferably 20N/25mm or more, and further preferably 25N/25mm or more. This makes the durability under high-temperature and high-humidity conditions more excellent. The above adhesion is preferably 80N/25mm or less, more preferably 70N/25mm

The thickness is particularly preferably 60N/25mm or less, and more preferably 45N/25mm or less. This can provide good reworkability.

Here, the adhesive force in the present specification means an adhesive force obtained by substantially measuring by a 180 degree peel method based on JIS Z0237:2009, wherein a measurement sample is made 25mm wide and 100mm long, the measurement sample is attached to an adherend, pressurized at 0.5MPa and 50 ℃ for 20 minutes, left under normal pressure at 23 ℃ and 50% RH for 24 hours, and then measured at a peel speed of 300 mm/minute.

(2) Total light transmittance

The total light transmittance of the composite adhesive layer 2 of the adhesive sheet 1 of the present embodiment is preferably 80% or more, more preferably 85% or more, and particularly preferably 90% or more. When the total light transmittance is in the above range, the transparency is extremely high, and the optical film is particularly suitable for optical applications (for displays). The method for measuring the total light transmittance is shown in the test examples described below.

4. Other embodiments

The adhesive sheet of the present embodiment includes a composite adhesive layer including a light-diffusing adhesive layer containing light-diffusing fine particles and a transparent adhesive layer containing no light-diffusing fine particles, at least the transparent adhesive layer is formed of an active energy ray-curable adhesive, the shear storage modulus G' of the transparent adhesive layer after curing by an active energy ray is 0.07MPa or more and 6MPa or less, and the haze value of the composite adhesive layer is 70% or more and 99% or less. When two liquid crystal cells are bonded using the adhesive sheet, for example, moire and display unevenness of an image are less likely to occur as in the above embodiment. In addition, the durability under high temperature and high humidity conditions is excellent particularly by the action of the shear storage modulus G'.

The adhesive sheet of the above embodiment defines the physical properties of the adhesive layer by the dynamic hardness representing the local elastic behavior from the surface of the adhesive layer toward the thickness direction of the adhesive layer. In contrast, the adhesive sheet of the present embodiment utilizes the shear storage modulus G' indicating the overall elastic behavior of each of the light diffusing adhesive layer and the transparent adhesive layer to define the physical properties of each of the adhesive layers. This provides the same excellent durability as the adhesive sheet of the above embodiment, and can suppress unevenness of a display image when liquid crystal cells are bonded to each other.

From the viewpoint of durability, the shear storage modulus G' of the transparent adhesive layer after curing with an active energy ray is preferably 0.07MPa or more, more preferably 0.10MPa or more, particularly preferably 0.20MPa or more, and further preferably 0.30MPa or more. In addition, the shear storage modulus G' of the transparent adhesive layer after curing with an active energy ray is preferably 6MPa or less, more preferably 1.4MPa or less, particularly preferably 0.8MPa or less, and further preferably 0.5MPa or less, from the viewpoint of preventing display unevenness.

From the viewpoint of further improving the durability, the shear storage modulus G' of the transparent adhesive layer (before curing with an active energy ray) is preferably 0.005MPa or more, more preferably 0.010MPa or more, particularly preferably 0.040MPa or more, and further preferably 0.080MPa or more. In addition, from the viewpoint of the property of preventing image unevenness, the shear storage modulus G' of the transparent adhesive layer (before curing with an active energy ray) is preferably 5MPa or less, more preferably 1.0MPa or less, particularly preferably 0.6MPa or less, and further preferably 0.2MPa or less.

When the light diffusing adhesive layer is formed of an active energy ray-curable adhesive, the shear storage modulus G' of the light diffusing adhesive layer after curing with an active energy ray is preferably 0.07MPa or more, more preferably 0.10MPa or more, particularly preferably 0.15MPa or more, and further preferably 0.20MPa or more. This makes the durability more excellent. In addition, from the viewpoint of preventing the property of showing unevenness, the shear storage modulus G' of the light-diffusing adhesive layer after curing with an active energy ray is preferably 7MPa or less, more preferably 2.0MPa or less, and particularly preferably 1.0MPa

Hereinafter, more preferably 0.7MPa or less.

From the viewpoint of the property of preventing image unevenness caused by bonding liquid crystal cells, the shear storage modulus G' of the light diffusing adhesive layer (before curing with an active energy ray and when curing with an inactive energy ray) is preferably 5MPa or less, more preferably 1.0MPa or less, particularly preferably 0.6MPa or less, and further preferably 0.2MPa or less. Further, from the viewpoint of durability, the shear storage modulus G' of the light-diffusing adhesive layer (before curing with an active energy ray and when curing with an inactive energy ray) is preferably 0.06MPa or more, and more preferably 0.08MPa

The above ratio is preferably 0.10MPa or more, and more preferably 0.12MPa or more.

The thickness and physical properties other than dynamic hardness of each layer and the composite adhesive layer are the same as those of the above embodiment. The transparent adhesive layer and the light diffusing adhesive layer having the above physical properties can be preferably formed of the adhesive (adhesive composition P) described in the above embodiment.

[ method for producing laminate ]

In one embodiment of the present invention, a laminate in which two hard plates are bonded to each other with an adhesive layer can be produced using the adhesive sheet of the above embodiment. In the method for producing a laminate according to one embodiment of the present invention, the light diffusing adhesive layer 21 of the composite adhesive layer 2 of the adhesive sheet 1 is bonded to one hard sheet, and then the transparent adhesive layer 22 of the composite adhesive layer 2 is bonded to the other hard sheet. Then, the composite adhesive layer is cured by irradiation with an active energy ray through any one of the hard plates.

In the case of bonding two hard sheets with an adhesive layer, generally, a first hard sheet is bonded to one surface of the adhesive layer, and then a second hard sheet is bonded to the other surface of the adhesive layer. In this case, the second hard sheet to be bonded later is strongly pressed against the adhesive layer so that air is not incorporated into the interface between the second hard sheet and the adhesive layer. In this case, a contact portion of the adhesive agent layer with the second hard plate, particularly a contact portion that is initially in contact with the second hard plate is easily deformed, and when the light diffusing adhesive agent layer is present in the contact portion, the dispersion state of the light diffusing particles is easily disturbed, and uniformity of light diffusion may be reduced. However, when the light diffusing adhesive layer is first bonded to one (first) hard plate and then the transparent adhesive layer is bonded to the other (second) hard plate as described above, the deformation of the light diffusing adhesive layer can be suppressed and the uniformity of light diffusion can be maintained well. As a result, for example, when two liquid crystal cells as hard plates are bonded, the occurrence of moire can be uniformly suppressed, and the occurrence of unevenness in a display image can be more effectively suppressed.

In addition, the "hard plate" in the present specification means a plate-shaped member having hardness that hardly bends. Examples of the hard sheet include a glass sheet, a plastic sheet, a sheet in which various functional layers (a transparent conductive film, a metal layer, a silica layer, a hard coat layer, an antiglare layer, and the like) are provided on the glass sheet or the plastic sheet, a display module such as a Liquid Crystal (LCD) module (liquid crystal cell), a Light Emitting Diode (LED) module, and an organic electroluminescence (organic EL) module, and a laminate including an optical member or a display module which is a part of the display module.

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

The ultraviolet irradiation can be carried out by a high-pressure mercury lamp, Fusion H lamp, xenon lamp, etc., and the ultraviolet irradiation dose is preferably 50 to 1000mW/cm in illuminance ² About, preferably 100-500 mW/cm ² Left and right. In addition, the light quantity is preferably 50 to 10000mJ/cm ² More preferably 200 to 7000mJ/cm ² Particularly preferably 500 to 3000mJ/cm ² . On the other hand, the electron beam irradiation may be performed by an electron beam accelerator or the like, and the irradiation amount of the electron beam is preferably about 10 to 1000 krad.

[ liquid Crystal display Member ]

The liquid crystal display member according to one embodiment of the present invention includes a first liquid crystal cell, a second liquid crystal cell, and an adhesive layer that bonds the first liquid crystal cell and the second liquid crystal cell to each other. The adhesive layer is a composite adhesive layer of the adhesive sheet of the above embodiment. The liquid crystal display member is less likely to have moire and image display unevenness due to the action of the composite adhesive layer, and is excellent in durability under high-temperature and high-humidity conditions.

A preferred example of the adhesive agent layer of the present embodiment is a composite adhesive agent layer composed of two layers, a light diffusing adhesive agent layer and a transparent adhesive agent layer, and is described below with reference to the drawings.

As shown in fig. 2, the liquid crystal display member 4 of the present embodiment is configured by including a first liquid crystal cell 5a, a second liquid crystal cell 5b, and a composite adhesive layer 2 in which the first liquid crystal cell 5a and the second liquid crystal cell 5b are bonded to each other. The composite adhesive layer 2 of the present embodiment is composed of two layers, a light-diffusing adhesive layer 21 in contact with the first liquid crystal cell 5a and a transparent adhesive layer 22 in contact with the second liquid crystal cell 5 b.

The light diffusing adhesive layer 21 and the transparent adhesive layer 22 are the light diffusing adhesive layer 21 and the transparent adhesive layer 22 in the adhesive sheet 1, and the configuration thereof is described in detail above.

The first liquid crystal cell 5a and the second liquid crystal cell 5b are generally used in a Liquid Crystal (LCD) display, particularly a liquid crystal display that displays a stereoscopic image, but are not particularly limited. In addition, the "liquid crystal cell" may be referred to as a "liquid crystal panel", a "liquid crystal module", a "liquid crystal display element", or the like.

The first liquid crystal cell 5a and the second liquid crystal cell 5b are usually hard plates, and the thickness thereof is usually about 0.5 to 5.0mm, preferably about 1.0 to 3.0 mm.

A preferred method for producing the liquid crystal display element 4 will be described. The invention is not so limited. First, the release sheet 3a (preferably a light release type release sheet) is peeled off from the adhesive sheet 1 to expose the light diffusing adhesive layer 21, and the exposed light diffusing adhesive layer 21 is attached to one surface of the first liquid crystal cell 5 a. At this time, the surface of the adhesive sheet 1 opposite to the surface in contact with the liquid crystal cell 5a maintains a state in which the flexible release sheet 3b is adhered. Therefore, the stress unevenness generated when the light diffusing adhesive layer 21 is attached to the liquid crystal cell 5a is immediately eliminated. The transparent adhesive layer 22 functions as a buffer material when attached to the liquid crystal cell 5a, and can suppress application of excessive pressure to the liquid crystal cell 5 a. These effects prevent the alignment disorder of the liquid crystal cell 5a at this stage, which is a cause of image display unevenness in forming the liquid crystal display member 4.

Then, a release sheet 3b (preferably a heavy release type release sheet) is peeled from the adhesive sheet 1 (composite adhesive layer 2) attached to the first liquid crystal cell 5a to expose the transparent adhesive layer 22, and the second liquid crystal cell 5b is attached to the exposed transparent adhesive layer 22. Here, by bonding to the liquid crystal cell 5b, stress is generated in the composite adhesive layer 2. However, since the composite adhesive layer 2 includes the transparent adhesive layer 22, stress on the light diffusing adhesive layer 21 is relaxed, and occurrence of stress unevenness due to the existence density of light diffusing fine particles can be prevented. In the liquid crystal display member 4 obtained as described above, alignment disorder of the

liquid crystal cells

5a and 5b due to stress unevenness caused by the light diffusing adhesive layer 21 in the composite adhesive layer 2 can be prevented, and thus occurrence of display image unevenness can be suppressed, and a display image can be displayed well.

Further, the release sheet 3b (preferably a light release type release sheet) may be peeled off from the adhesive sheet 1, the transparent adhesive layer 22 and the second liquid crystal cell 5b may be bonded, and then the release sheet 3a (preferably a heavy release type release sheet) may be peeled off, and the light diffusion adhesive layer 21 and the first liquid crystal cell 5a may be bonded.

After the first liquid crystal cell 5a, the composite adhesive layer 2, and the second liquid crystal cell 5b are laminated as described above, the composite adhesive layer 2 (the transparent adhesive layer 22, or the transparent adhesive layer 22 and the light diffusing adhesive layer 21) is cured by irradiating active energy rays from the first liquid crystal cell 5a or the second liquid crystal cell 5b side. The irradiation conditions of the active energy ray are as described above.

The embodiments described above are described for easy understanding of the present invention, and are not described for limiting the present invention. Therefore, each element disclosed in the above embodiments also covers all design variations and equivalents falling within the technical scope of the present invention.

For example, the composite adhesive layer 2 in the adhesive sheet 1 may have a structure of 3 or more layers. In addition, any of the

release sheets

3a and 3b in the adhesive sheet 1 may be omitted.

Examples

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

Production example 1 preparation of coating layer with Release sheet for light diffusing adhesive layer

Preparation of (meth) acrylate polymers

The (meth) acrylate polymer (a) was prepared by copolymerizing 25 parts by mass of N-butyl acrylate, 25 parts by mass of 2-ethylhexyl acrylate, 10 parts by mass of isobornyl acrylate, 10 parts by mass of N-acryloylmorpholine and 30 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 50 ten thousand.

2. Preparation of adhesive composition

100 parts by mass (solid content equivalent; the same shall apply hereinafter) of the (meth) acrylate polymer (A) obtained in the above step 1, 0.2 parts by mass of trimethylolpropane-modified tolylene diisocyanate (TOYOCHEM CO., LTD., manufactured by "BHS 8515") as the crosslinking agent (B), 9.0 parts by mass of ε -caprolactone-modified tris (2-acryloyloxyethyl) isocyanurate (SHIN-NAKAMURA CHEMICAL CO., LTD., manufactured by "NK ESTER A-9300-1 CL") as the active energy ray-curable component (C), 15 parts by mass of microparticles (manufactured by "moment Performance Materials LLC") formed of a silicone resin (a silicon-containing compound having an intermediate structure between inorganic and organic) as the light-diffusing microparticles (D), a product name "Tospearl 145", an average particle diameter: 4.5 μm), and 0.9 parts by mass of 2 as the photopolymerization initiator (E), 4, 6-trimethylbenzoyl-diphenyl-phosphine oxide and 0.3 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) ]

BA: acrylic acid n-butyl ester

2 EHA: 2-ethylhexyl acrylate

IBXA: acrylic acid isobornyl ester

ACMO (acyl-amino): n-acryloyl morpholine

HEA: 2-Hydroxyethyl acrylate

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")

And (3) epoxy: 1, 3-bis (N, N-diglycidylaminomethyl) cyclohexane (MITSUBISHI GAS CHEMICAL COMPANY, manufactured by INC., product name "TETRAD-C")

[ light-diffusing particles (D) ]

D1: microparticles having an average particle diameter of 4.5 μm formed of a silicone resin (silicon-containing compound having an intermediate structure of inorganic and organic structures) (manufactured by Momentive Performance Materials Japan LLC under the product name "Tospearl 145", refractive index: 1.43)

D2: spherical polymethyl methacrylate-polystyrene copolymer fine particles having an average particle diameter of 5.0. mu.m (manufactured by Sekisui Kasei Co., Ltd., product name "XX-23 LA", refractive index: 1.525)

3. Formation of coating layer

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 381031") which had been subjected to a release treatment on one surface of a polyethylene terephthalate film using a silicone-based release agent, using a blade coater, and heat-treated at 90 ℃ for 1 minute to form a coating layer (thickness: 50 μm). Thus, a coating layer with a release sheet was obtained, which had a composition of a coating layer (thickness: 50 μm) of the light release type release sheet/light diffusing adhesive layer. In addition, when used in the test examples, the coating layer of the tape release sheet was aged at 23 ℃ and 50% RH for 7 days to obtain a light diffusing adhesive layer of the tape release sheet.

The thickness of the coating layer was measured by a constant pressure thickness gauge (product name "PG-02" manufactured by dele corporation) in accordance with JIS K7130 (the same applies hereinafter).

Production examples 2 to 8 (production of coating layer with Release sheet for light-diffusing adhesive layer)

A coating layer with a release sheet and a light diffusion adhesive layer with a release sheet for a light diffusion adhesive layer were produced in the same manner as in production example 1, except that the kind and the ratio of each monomer constituting the (meth) acrylate polymer (a), the weight average molecular weight (Mw) of the (meth) acrylate polymer (a), the kind and the blending amount of the crosslinking agent (B), the blending amount of the active energy ray-curable component (C), the kind and the blending amount of the light diffusion fine particles (D), the blending amount of the photopolymerization initiator (E), and the blending amount of the silane coupling agent were changed as shown in table 1.

Production examples 9 to 10 (production of coating layer with Release sheet for transparent adhesive layer)

The kinds and proportions of the monomers constituting the (meth) acrylate polymer (A), the weight-average molecular weight (Mw) of the (meth) acrylate polymer (A), the blending amount of the crosslinking agent (B), the blending amount of the active energy ray-curable component (C), the blending amount of the light-diffusing fine particles (D) (not blended), the blending amount of the photopolymerization initiator (E), and the blending amount of the silane coupling agent were changed as shown in Table 1, and coated on the release-treated surface of a heavy release type release sheet (manufactured by LINTEC Corporation, product name "SP-PET 752150") instead of the light release type release sheet, in addition to that, a coating layer with a release sheet and a transparent adhesive layer with a release sheet were prepared in the same manner as in production example 1, the coating layer (thickness: 50 μm) of the heavy release sheet/transparent adhesive layer.

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

< measurement Condition >

GPC measurement apparatus: HLC-8020 manufactured by TOSOH CORPORATION

GPC column (passage in the following order): TSK guard column HXL-H manufactured by TOSOH CORPORATION

TSK gel GMHXL(×2)

TSK gel G2000HXL

Determination of the solvent: tetrahydrofuran (THF)

Measurement temperature: 40 deg.C

[ example 1]

The coating layer for the light-diffusing adhesive layer prepared in production example 1 and the coating layer for the transparent adhesive layer prepared in production example 9 were bonded, and then cured at 23 ℃ and 50% RH for 7 days. In this manner, an adhesive sheet (light diffusing adhesive layer + transparent adhesive layer — composite adhesive layer) composed of a light-releasing type release sheet/light diffusing adhesive layer (50 μm)/transparent adhesive layer (50 μm)/heavy-releasing type release sheet was produced.

Examples 2 to 8 and comparative examples 1 to 3

Adhesive sheets were produced in the same manner as in example 1, except that the types of the light diffusing adhesive layers (production examples 1 to 8) and the types of the transparent adhesive layers (production examples 9 to 10), and the thicknesses and the total thicknesses of the transparent adhesive layers were changed as shown in table 2. The thickness of the transparent adhesive layer was changed by laminating a desired number of coating layers (50 μm) of the transparent adhesive layer of the transparent adhesive sheet prepared in each production example.

[ test example 1] (measurement of gel fraction)

The light-diffusing adhesive layer with a release sheet and the transparent adhesive layer with a release sheet prepared in each production example were cut into a size of 80mm × 80 mm. Each adhesive layer was 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.

Then, the adhesive wrapped in the polyester net was immersed in ethyl acetate at room temperature (23 ℃) 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 of the adhesive itself was calculated by weighing it with a precision balance and subtracting the mass of the web alone. The mass at this time was designated as M2. Gel fraction (%) is expressed as (M2/M1). times.100.

This led to the gel fraction of the adhesive. The results are shown in Table 2.

The light-diffusing adhesive layer and the transparent adhesive layer prepared in each production example were irradiated with active energy rays (ultraviolet rays; UV) under the following conditions to cure each adhesive layer, thereby producing a cured adhesive layer. The gel fraction (after UV) of the adhesive of the cured adhesive layer was derived in the same manner as described above. The results are shown in Table 2.

< active energy ray irradiation Condition >

Using high-pressure mercury lamps

Illuminance of 200mW/cm ² The light quantity was 1000mJ/cm ²

UV illuminance/photometer Using "UVPF-A1" manufactured by EYE GRAPHICS Co., Ltd "

[ test example 2] (measurement of dynamic hardness)

The heavy-release type release sheet was peeled from the adhesive sheet produced in the examples and comparative examples, and the exposed transparent adhesive layer was adhered and fixed to a glass plate. Then, the light-release sheet was peeled off, and the exposed photodiffusion adhesive layer was pressed against a diamond-made triangular pyramid indenter having an included angle of 115 ° at a load speed of 0.0142 mN/second in an environment of 23 ℃ using a Dynamic ultramicro Hardness meter (manufactured by Shimadzu Corporation, product name "Shimadzu Dynamic Ultra Micro Hardness tester DUH-W201S") until the depth reached 4 μm or the test force reached 1mN, and after holding for 15 seconds, the pressing depth D (μm) and the test force P (mN) were read, and the Dynamic Hardness (DHT 115-1; before UV) was determined by the following calculation formula.

Dynamic hardness (DHT115-1) ═ 3.8584 XP/D ²

Where 3.8584 is a constant based on the shape of the indenter.

Further, the light-release type release sheet was peeled from the adhesive sheet produced in the examples and comparative examples, and the exposed light diffusing adhesive layer was adhered and fixed to a glass plate. Then, the heavy-release type release sheet was peeled off, and the exposed transparent adhesive layer was tested in the same manner as described above to determine the dynamic hardness (DHT115-1, before UV).

Next, the heavy-release type release sheet was peeled from the adhesive sheet produced in the examples and comparative examples, and the exposed transparent adhesive layer was attached and fixed to a glass plate. Then, the composite adhesive layer was cured by irradiation with active energy rays (ultraviolet rays; UV) through a light-release type release sheet under the same conditions as in test example 1. Then, the light-peelable release sheet was peeled off, and the exposed photodiffusion adhesive layer after curing with an active energy ray was tested in the same manner as described above to determine the dynamic hardness (DHT 115-1; after UV). In addition, the transparent adhesive layer after curing with an active energy ray was tested in the same manner as described above to determine the dynamic hardness (DHT 115-1; after UV). The respective results are shown in table 2.

[ test example 3] (measurement of shear storage modulus G')

The light-diffusing adhesive layer and the transparent adhesive layer prepared in each production example were laminated in layers to prepare a laminate having a thickness of 800 μm. From the laminate of the obtained adhesive layers, a cylindrical body (height 800 μm) having a diameter of 8mm was punched out as a sample.

For the above sample, the shear storage modulus G' (before UV; MPa) was measured by the torsional shear method (ね was manufactured by リせ one end another) using a viscoelasticity measuring apparatus (manufactured by Antopa corporation, product name "MCR 301") according to JIS K7244-1 under the following conditions. The results are shown in Table 2.

Measuring frequency: 1Hz

Measuring temperature: 23 deg.C

The same samples as those described above were irradiated with active energy rays (ultraviolet rays; UV) under the same conditions as in test example 1 to cure the active energy ray-curable adhesive, thereby obtaining active energy ray-cured samples. With respect to the obtained sample after curing with active energy rays, the shear storage modulus G' (after UV; MPa) at 23 ℃ was measured in the same manner as the sample before curing with active energy rays. The results are shown in Table 2.

[ test example 4] (measurement of haze value)

The composite adhesive layer of the adhesive sheet produced in the examples and comparative examples was bonded to soda-lime glass, and this was used as a measurement sample. After the background measurement using soda lime glass, the haze value (%) of the above-mentioned sample for measurement was measured using a haze meter (NIPPON DENSHOKU INDUSTRIES co., ltd., product name "NDH 5000") based on JIS K7136: 2000. The results are shown in Table 2.

[ test example 5] (measurement of Total light transmittance)

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

[ test example 6] (measurement of adhesive force)

The light release sheet was peeled from the adhesive sheets produced in examples and comparative examples, and the exposed light diffusing adhesive layer was bonded to an easy adhesive layer of a polyethylene terephthalate (PET) film (TOYOBO co., ltd., product name "PET a 4300" with a thickness of 100 μm) having an easy adhesive layer, to obtain a laminate of a heavy release sheet/a composite adhesive layer/a PET film. The obtained laminate was cut into pieces of 25mm wide and 100mm long.

The heavy-release type release Sheet was peeled from the laminate under an atmosphere of 23 ℃ and 50% RH, and the exposed transparent adhesive layer was attached to soda-lime Glass (manufactured by Nippon Sheet Glass co., ltd.) and pressurized at 0.5MPa and 50 ℃ for 20 minutes using an autoclave manufactured by kurihia SEISAKUSHO co., ltd. Then, the sample was left at 23 ℃ and 50% RH for 24 hours. Then, a tensile tester (ORIENTEC co., LTD, product name) was used

"TENSILON") was measured for the adhesive force under the conditions of a peeling speed of 300 mm/min and a peeling angle of 180 degrees (transparent adhesive layer. UV front; n/25 mm). The conditions not described herein were measured according to JIS Z0237: 2009.

Then, the sample was irradiated with active energy rays through a PET film under the same conditions as in test example 1 to cure the composite adhesive layer, thereby producing a cured composite adhesive layer. The adhesion of the cured composite adhesive layer was measured in the same manner as described above (transparent adhesive layer. after UV; N/25 mm). The results are shown in Table 2.

Further, the adhesive force before UV (light diffusing adhesive layer. before UV; N/25mm) on the light diffusing adhesive layer side and the adhesive force after UV (light diffusing adhesive layer. after UV; N/25mm) on the light diffusing adhesive layer side were measured in the same manner as described above. The results are shown in Table 2.

[ test example 7] (evaluation of waviness suppression)

Of the pressure-sensitive adhesive sheets produced in the examples and comparative examples, a light-release type pressure-sensitive adhesive sheet was peeled off, and the exposed light-diffusing pressure-sensitive adhesive layer was attached to the surface of a display screen of a flat terminal (product name "iPad (registered trademark)", manufactured by Apple inc., resolution: 264 ppi). Then, a heavy-release type release sheet among the above adhesive sheets was peeled off, and a liquid crystal mask having a lattice of 20 to 180ppi (increasing in units of 20 ppi) was attached to the exposed transparent adhesive layer, thereby obtaining a liquid crystal display.

The screen of the panel terminal was adjusted to a full-screen green display (RGB values (R, G, B) ═ 0,255,0), and the moire suppression performance was evaluated according to the following criteria, based on the degree of moire observed visually from a direction 60 degrees from the normal line of the screen on the liquid crystal mask side, with respect to the liquid crystal display. The results are shown in Table 2.

Very good: no moire was generated on the liquid crystal display covered by all the liquid crystal masks.

Good: no moire was generated on the liquid crystal display covered by almost all the liquid crystal masks.

X: moire is generated on the liquid crystal display covered by all the liquid crystal masks.

[ test example 8] (evaluation of the Performance for preventing image display unevenness)

First and second liquid crystal cells are prepared, and the first liquid crystal cell is adsorbed by an adsorption device. Then, of the pressure-sensitive adhesive sheets produced in examples and comparative examples, the light-release type pressure-sensitive adhesive sheet was peeled off, and the exposed light-diffusing pressure-sensitive adhesive layer was attached to one surface of the first liquid crystal cell. Then, the heavy-release type release sheet of the adhesive sheets was peeled off, and the second liquid crystal cell was bonded to the exposed transparent adhesive layer at a bonding speed of 30 mm/sec and a roll pressure of 0.3MPa using a bonding machine (SUN-TEC co., ltd., product name "TMS-SA") under atmospheric pressure. Specifically, while one end portion of the second liquid crystal cell is supported by the glass press, the second liquid crystal cell is pressed against the transparent adhesive layer from the other end portion side of the second liquid crystal cell by a roller, the roller is rolled to the one end portion of the second liquid crystal cell, and finally the glass press is removed.

Then, in a state where the first and second liquid crystal cells were bonded, an image was displayed using white light as a backlight, and the performance of preventing image display unevenness was evaluated according to the following criteria by visually observing the displayed image from the first liquid crystal cell side. The results are shown in Table 2.

Circa … shows a completely uniform image.

Good … produces little unevenness in the displayed image, but to the extent that there is no problem in practical use.

X … produces unevenness in the display image.

[ test example 9] (evaluation of durability)

The composite adhesive layer of the adhesive Sheet produced in example and comparative example was sandwiched by two soda-lime Glass plates (manufactured by Nippon Sheet Glass co., ltd., thickness: 0.7 mm). Then, the plate was subjected to autoclave treatment at 50 ℃ and 0.5MPa for 30 minutes and left at normal pressure, 23 ℃ and 50% RH for 24 hours.

Then, the composite adhesive layer was irradiated with active energy rays through a soda-lime glass plate under the same conditions as in test example 1, and the composite adhesive layer was cured.

The obtained laminate was stored at 85 ℃ under high temperature and high humidity conditions of 85% RH for 2000 hours. Then, the state of the interface between the composite adhesive layer and the adherend (soda-lime glass plate) was visually confirmed, and the durability was evaluated according to the following criteria. The results are shown in Table 2.

Circa … no bubbles were generated at all.

Good results … produced a few bubbles, but were of a degree that had no problem in practical applications.

X … produced a large number of bubbles.

[ Table 1]

As is clear from table 2, the pressure-sensitive adhesive sheets produced in the examples were less likely to have moire and uneven image display, and had excellent durability.

Industrial applicability

The adhesive sheet of the present invention is applicable to a stereoscopic image display device. The method for producing a laminate of the present invention is suitable for producing a liquid crystal display member by bonding two liquid crystal cells.

Claims

1. An adhesive sheet having a composite adhesive layer comprising a light-diffusing adhesive layer containing light-diffusing particles and a transparent adhesive layer containing no light-diffusing particles, the adhesive sheet being characterized in that,

at least the transparent adhesive layer is formed of an active energy ray-curable adhesive,

a dynamic hardness (DHT115-1) measured on the surface of the transparent adhesive layer side after curing with an active energy ray of 0.008 or more,

the haze value of the composite adhesive layer is 70% to 99%.

2. The adhesive sheet according to claim 1,

the light-diffusing adhesive layer is formed of an active energy ray-curable adhesive,

and a dynamic hardness (DHT115-1) measured on the surface of the light-diffusing adhesive layer side after curing with an active energy ray of 0.007 or more.

3. The adhesive sheet according to claim 1, wherein the dynamic hardness (DHT115-1) measured on the surface on the side of the transparent adhesive layer is 0.001 to 0.500.

4. The adhesive sheet according to claim 1, wherein a dynamic hardness (DHT115-1) measured on the surface on the light-diffusing adhesive layer side is 0.001 or more and 0.500 or less.

5. The adhesive sheet according to claim 1, wherein the adhesive force of the transparent adhesive layer side to soda-lime glass is 1N/25mm or more and 80N/25mm or less.

6. The adhesive sheet according to claim 1, wherein the adhesive force of the light diffusing adhesive layer side to soda lime glass is 1N/25mm or more and 80N/25mm or less.

7. The adhesive sheet according to claim 1, wherein the thickness of the composite adhesive layer is 70 μm or more and 3000 μm or less.

8. The adhesive sheet according to claim 1,

it is provided with two peeling sheets,

the composite adhesive layer is sandwiched between the two release sheets so as to be in contact with the release surfaces of the two release sheets.

9. The adhesive sheet according to claim 1, which is used for bonding two hard sheets.

10. A method for producing a laminate comprising two hard plates bonded to each other via an adhesive layer, characterized in that,

bonding the light diffusing adhesive layer of the composite adhesive layer of the adhesive sheet according to any one of claims 1 to 9 to a hard plate,

then, the transparent adhesive layer of the composite adhesive layer is bonded with the other hard plate,

then, the composite adhesive layer is cured by irradiation with active energy rays.