JP7165233B2 - Adhesive sheets and liquid crystal display materials - Google Patents

Description

TECHNICAL FIELD The present invention relates to a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer for bonding two liquid crystal cells, and a liquid crystal display member formed by bonding two liquid crystal cells via the pressure-sensitive adhesive layer.

In recent years, as a type of display, a stereoscopic image display device that displays images stereoscopically has been proposed. ). In such a liquid crystal display device, images are displayed stereoscopically by manipulating the brightness of an image in each liquid crystal cell or by sending different light information to both eyes.

JP 2015-114371 A

However, in the liquid crystal display device as described above, there arises a problem that moire is likely to occur due to interference between liquid crystal cells and the display image becomes difficult to see as the definition of the displayed image is increased. In addition, since two liquid crystal cells are used, the thickness of the liquid crystal display device is larger than that of a normal liquid crystal display device. , there arises a problem that the sharpness of the displayed image is impaired by the transmitted light.

The present invention has been made in view of the actual situation as described above. It is an object of the present invention to provide a pressure-sensitive adhesive sheet and a liquid crystal display member capable of reducing reflection loss at an interface and further preventing moiré from occurring.

In order to achieve the above object, firstly, the present invention has an adhesive layer for bonding two liquid crystal cells, and the adhesive layer has a haze value of 80% or more and 99% or less. (Invention 1).

In the above invention (invention 1), by laminating two liquid crystal cells with an adhesive layer, it is possible to reduce the thickness of the obtained liquid crystal display member. Further, by interposing an adhesive layer between the liquid crystal cells with a refractive index difference smaller than that of air, the reflection loss and the like at each interface between the two liquid crystal cells can be reduced. . By laminating the pressure-sensitive adhesive sheet having the haze value of the pressure-sensitive adhesive layer defined as above between the two liquid layer cells, moire hardly occurs.

In the above invention (invention 1), it is preferable that the pressure-sensitive adhesive layer comprises a plurality of layers, and at least one of the plurality of layers is a light-diffusing pressure-sensitive adhesive layer having light diffusion properties (invention 2).

In the above invention (invention 2), it is preferable that a low-elasticity pressure-sensitive adhesive layer having a lower storage modulus at 23° C. than the light-diffusing pressure-sensitive adhesive layer is present on at least one surface of the pressure-sensitive adhesive layer (invention 3 ).

In the above invention (invention 3), the storage elastic modulus at 23° C. of the low-elasticity pressure-sensitive adhesive layer is preferably 0.01 MPa or more and 0.1 MPa or less (invention 4).

In the above inventions (Inventions 1 to 4), the total thickness of the adhesive layer is preferably 50 μm or more and 1000 μm or less (Invention 5).

In the above inventions (inventions 1 to 5), it is preferable to include two release sheets and the adhesive layer sandwiched between the release sheets so as to be in contact with the release surfaces of the two release sheets ( Invention 6).

A second aspect of the present invention is a liquid crystal display member comprising a first liquid crystal cell, a second liquid crystal cell, and an adhesive layer for adhering the first liquid crystal cell and the second liquid crystal cell together. There is provided a liquid crystal display member (Invention 7), wherein the adhesive layer is the adhesive layer of the adhesive sheet (Inventions 1 to 6).

According to the adhesive sheet and the liquid crystal display member according to the present invention, even if two liquid crystal cells are used, the thickness of the liquid crystal display member can be reduced, and the reflection loss at each interface between the two liquid crystal cells is reduced. can be reduced, and moiré is less likely to occur.

1 is a cross-sectional view of a pressure-sensitive adhesive sheet according to one embodiment of the present invention; FIG. 1 is a cross-sectional view of a pressure-sensitive adhesive sheet according to one embodiment of the present invention; FIG.

Embodiments of the present invention will be described below.
[Adhesive sheet]
A pressure-sensitive adhesive sheet according to one embodiment of the present invention has a pressure-sensitive adhesive layer for bonding two liquid crystal cells. By bonding two liquid crystal cells with the adhesive layer of such an adhesive sheet, it is possible to reduce the thickness of the obtained liquid crystal display member. Further, by interposing an adhesive layer between the liquid crystal cells, the adhesive layer having a refractive index difference smaller than that of air, the reflection loss at each interface between the two liquid crystal cells can be reduced. As a result, it is possible to suppress a decrease in the amount of transmitted light and a decrease in the definition of a displayed image due to the reflection loss.

The adhesive layer of the adhesive sheet according to this embodiment has a haze value of 80% or more and 99% or less. The haze value in this specification is a value measured according to JIS K7136:2000.

When the pressure-sensitive adhesive layer has a haze value of 80% or more, moire hardly occurs when two liquid crystal cells are bonded using the pressure-sensitive adhesive layer. In addition, since the haze value of the pressure-sensitive adhesive layer is 99% or less, the visibility of the image displayed by the liquid crystal cell is ensured. From this point of view, the haze value is preferably 83% or more, particularly preferably 85% or more, further preferably 91% or more. Further, the haze value is preferably 98% or less, particularly preferably 95% or less.

The pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet according to this embodiment is composed of a plurality of layers, and at least one layer is preferably a light-diffusing pressure-sensitive adhesive layer having light diffusing properties. Since the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet according to the present embodiment has the light-diffusing pressure-sensitive adhesive layer, the above haze value can be easily satisfied. However, the light-diffusing pressure-sensitive adhesive layer usually contains light-diffusing fine particles, and tends to have a relatively high elastic modulus (storage elastic modulus). If the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet according to the present embodiment consists of only the light-diffusing pressure-sensitive adhesive layer, when the light-diffusing pressure-sensitive adhesive layer attached to the first liquid crystal cell and the second liquid crystal cell are attached, , unevenness may occur in the displayed image. It is considered that this is due to the following reasons. When liquid crystal cells, which are rigid bodies, are bonded to each other, the light-diffusing pressure-sensitive adhesive layer is compressed in the layer thickness direction because none of them have flexibility, and the stress of the compression is accumulated in the pressure-sensitive adhesive layer. This residual stress becomes a repulsive force and acts on the two liquid crystal cells. Here, it is presumed that the strength (unevenness) of the repulsive force is caused by the existence density (shading) of the light-diffusing fine particles per surface area of the pressure-sensitive adhesive layer in contact with the liquid crystal cell. It is presumed that the uneven repulsive force of the pressure-sensitive adhesive layer against the liquid crystal cell thus generated disturbs the alignment of the liquid crystal cell and causes unevenness in the displayed image. It is presumed that the higher the elasticity of the pressure-sensitive adhesive layer, the greater the repulsive force of the pressure-sensitive adhesive layer against the liquid crystal cell, and the greater the influence on the formation of the unevenness in the display image of the liquid crystal cell.

Therefore, in the pressure-sensitive adhesive layer having a light-diffusing pressure-sensitive adhesive layer as described above, at least one surface (contact surface with the liquid crystal cell) of the pressure-sensitive adhesive layer has a storage elastic modulus at 23 ° C. of the light-diffusing pressure-sensitive adhesive layer It is preferred that there is a low modulus pressure sensitive adhesive layer of less than . It is presumed that the low-elasticity pressure-sensitive adhesive layer can reduce the stress of the pressure-sensitive adhesive layer against compression of the liquid crystal cell, which is two hard plates, by the low-elasticity pressure-sensitive adhesive layer. As a result, it is possible to suppress the occurrence of unevenness in the displayed image. That is, by having the low-elasticity pressure-sensitive adhesive layer as described above in addition to the light-diffusing pressure-sensitive adhesive layer, it is possible to improve the prevention of image display unevenness caused by lamination of liquid crystal cells.

In the above case, the pressure-sensitive adhesive layer may consist of two layers, a light-diffusing pressure-sensitive adhesive layer and a low-elasticity pressure-sensitive adhesive layer, or the low-elasticity pressure-sensitive adhesive layer, the light-diffusing pressure-sensitive adhesive layer, and the low-elasticity pressure-sensitive adhesive layer may be arranged in that order. It may consist of three layers laminated. A preferred example of the pressure-sensitive adhesive layer in this embodiment is composed of two layers, a light-diffusing pressure-sensitive adhesive layer and a low-elasticity pressure-sensitive adhesive layer, and will be described below with reference to the drawings.

As shown in FIG. 1, the pressure-sensitive adhesive sheet 1 according to this embodiment includes two release sheets 3a and 3b, and the two release sheets 3a and 3b so as to be in contact with the release surfaces of the two release sheets 3a and 3b. , and an adhesive layer 2 sandwiched by 3b. However, the release sheets 3a and 3b are not essential components of the adhesive sheet 1, but are peeled off and removed when the adhesive sheet 1 is used. In this specification, the release surface of the release sheet refers to the surface of the release sheet that has releasability, and includes both the surface that has been subjected to a release treatment and the surface that exhibits releasability without being subjected to a release treatment. .

The pressure-sensitive adhesive layer 2 in this embodiment consists of two layers, a light-diffusing pressure-sensitive adhesive layer 21 in contact with the release sheet 3a and a low-elasticity pressure-sensitive adhesive layer 22 in contact with the release sheet 3b.

1. Physical properties (1) Haze value The haze value of the pressure-sensitive adhesive layer 2, in this embodiment, the haze value as a laminate of the light-diffusing pressure-sensitive adhesive layer 21 and the low-elasticity pressure-sensitive adhesive layer 22 is 80% or more and 99% as described above. % or less.

The haze value of the light diffusion pressure-sensitive adhesive layer 21 is preferably 80% or more, more preferably 83% or more, particularly preferably 85% or more, further preferably 91% or more. . Further, the haze value of the light diffusion pressure-sensitive adhesive layer 21 is preferably 99% or less, particularly preferably 98% or less, further preferably 95% or less. When the haze value of the light-diffusing adhesive layer 21 is within the above range, it is easy to set the haze value of the adhesive layer 2 to 80% or more and 99% or less. Moreover, the light-diffusing pressure-sensitive adhesive layer 21 having light-diffusing properties can satisfy the haze value described above.

The upper limit of the haze value of the low-elasticity pressure-sensitive adhesive layer 22 is preferably 1.5% or less, particularly preferably 1.0% or less, and further preferably 0.5% or less. . Since the upper limit of the haze value of the low-elasticity pressure-sensitive adhesive layer 22 is the above, it is not necessary to contain light diffusing fine particles in the low-elasticity pressure-sensitive adhesive layer 22, and therefore the storage elastic modulus of the low-elasticity pressure-sensitive adhesive layer 22 is compared. It is possible to keep it relatively low. Although the lower limit of the haze value of the low-elasticity pressure-sensitive adhesive layer 22 is not particularly limited, it is usually preferably 0%.

(2) Thickness The total thickness of the pressure-sensitive adhesive layer 2, in this embodiment, the total thickness of the light-diffusing pressure-sensitive adhesive layer 21 and the low-elasticity pressure-sensitive adhesive layer 22 is preferably 50 μm or more as a lower limit, particularly It is preferably 75 μm or more, more preferably 100 μm or more. By setting the lower limit of the total thickness of the pressure-sensitive adhesive layer 2 to the above, it becomes easier to satisfy the haze value described above, and it becomes easier to relax the stress of the pressure-sensitive adhesive layer against the compression of the liquid crystal cell, which is two rigid plates. The ability to prevent image display unevenness is further improved. On the other hand, the upper limit of the total thickness of the pressure-sensitive adhesive layer 2 is preferably 1000 μm or less, particularly preferably 700 μm or less, and further preferably 500 μm or less. By setting the upper limit of the total thickness of the pressure-sensitive adhesive layer 2 to the above range, it is possible to prevent the resulting liquid crystal display member from becoming unnecessarily thick.

The lower limit of the thickness of the light diffusion pressure-sensitive adhesive layer 21 is preferably 10 μm or more, particularly preferably 25 μm or more, further preferably 50 μm or more. By setting the lower limit of the thickness of the light-diffusing pressure-sensitive adhesive layer 21 to the above range, it becomes easier to satisfy the haze value described above. On the other hand, the upper limit of the thickness of the light diffusion pressure-sensitive adhesive layer 21 is preferably 200 μm or less, particularly preferably 150 μm or less, further preferably 100 μm or less. By setting the upper limit of the thickness of the light-diffusing pressure-sensitive adhesive layer 21 to the above range, it is possible to prevent the obtained liquid crystal display member from becoming unnecessarily thick.

The lower limit of the thickness of the low-elasticity pressure-sensitive adhesive layer 22 is preferably 25 μm or more, particularly preferably 50 μm or more, further preferably 100 μm or more. By setting the lower limit of the thickness of the low-elasticity adhesive layer 22 to the above range, the stress of the adhesive layer against the compression of the liquid crystal cell, which is two hard plates, can be easily relaxed, and the unevenness of image display can be prevented more effectively. improves. On the other hand, the upper limit of the thickness of the low-elasticity pressure-sensitive adhesive layer 22 is preferably 800 μm or less, particularly preferably 550 μm or less, further preferably 400 μm or less. By setting the upper limit of the thickness of the low-elasticity pressure-sensitive adhesive layer 22 to the above range, it is possible to prevent the obtained liquid crystal display member from becoming unnecessarily thick.

(3) Storage Elastic Modulus The storage elastic modulus (G') of the low-elasticity adhesive layer 22 at 23°C is lower than the storage elastic modulus (G') of the light-diffusing adhesive layer 21 at 23°C. Specifically, the upper limit of the storage elastic modulus (G′) of the low-elasticity pressure-sensitive adhesive layer 22 at 23° C. is preferably 0.1 MPa or less, particularly preferably 0.09 MPa or less. is preferably 0.08 MPa or less. When the upper limit of the storage elastic modulus (G′) of the low-elasticity adhesive layer 22 is the above, it becomes easier to relax the stress of the adhesive layer against the compression of the liquid crystal cell, which is two hard plates, and image display. The ability to prevent unevenness is further improved. In addition, the storage elastic modulus (G') of the low-elasticity pressure-sensitive adhesive layer 22 at 23° C. is preferably 0.01 MPa or more, particularly preferably 0.02 MPa or more, and further preferably 0.01 MPa or more as a lower limit. It is preferably 03 MPa or more. By setting the lower limit of the storage elastic modulus (G') of the low-elasticity pressure-sensitive adhesive layer 22 to the above range, the pressure-sensitive adhesive sheet 1 maintains good handleability. The method for measuring the storage elastic modulus (G') is as shown in the test examples described later.

On the other hand, the storage modulus (G') of the light diffusion pressure-sensitive adhesive layer 21 at 23° C. is not particularly limited, but is usually 0.1 to 3.0 MPa, preferably 0.11 to 2.0 MPa. , particularly preferably 0.12 to 1.0 MPa.

2. Each member (1) Light diffusion adhesive layer The light diffusion adhesive layer 21 has a haze value that can satisfy the value described above for the haze value of the adhesive layer 2, and is made of a material having a predetermined adhesive strength. , is not particularly limited. The light-diffusing adhesive layer 21 is preferably formed from an adhesive composition containing an adhesive component and light-diffusing fine particles.

The adhesive component is not particularly limited as long as it exerts a desired adhesive strength in the liquid crystal display member, has light transmittance, and does not inhibit the effect of the light diffusion fine particles. Examples of such adhesive components include acrylic adhesive components, rubber adhesive components, silicone adhesive components, polyurethane adhesive components, polyester adhesive components, etc. Among them, acrylic adhesive components are preferable from the above viewpoints.

In addition, the adhesive component may be a curable adhesive component or a non-curable adhesive component. However, if light diffusing fine particles are contained, durability and cohesion tend to decrease. It is preferably a curable adhesive component that easily improves durability and cohesion. The curable adhesive component may be an active energy ray-curable adhesive component or a thermosetting adhesive component, but an active energy ray-curable adhesive component is preferred. The active energy ray-curable adhesive component has relatively high durability and cohesion, and is also excellent in handleability.

Therefore, the light-diffusing adhesive layer 21 is preferably formed from an adhesive composition (hereinafter referred to as "adhesive composition P") containing an active energy ray-curable adhesive component and light-diffusing fine particles.

(1-1) Active Energy Ray Curable Adhesive Component The adhesive composition P contains an active energy ray curable adhesive component. The term "active energy ray-curable adhesive component" as used herein refers to a component that cures upon irradiation with an active energy ray and exhibits adhesiveness. ). In the latter case, a component that cures upon exposure to active energy rays and a component that does not cure upon exposure to active energy rays and exhibits adhesiveness may be included.

The active energy ray-curable adhesive component preferably contains a non-curable (meth)acrylate polymer and an active energy ray-curable compound. In addition, in this specification, (meth)acrylic acid ester means both acrylic acid ester and methacrylic acid ester. The same applies to other similar terms. In addition, the concept of "copolymer" is also included in "polymer". The active energy ray-curable adhesive component containing the (meth)acrylic acid ester polymer and the active energy ray-curable compound will be mainly described below.

(1-1-1) (Meth)acrylic acid ester polymer (Meth)acrylic acid ester polymer (hereinafter sometimes referred to as "(meth)acrylic acid ester polymer (A)") is the polymer By containing a (meth)acrylic acid alkyl ester having an alkyl group having 1 to 20 carbon atoms as a constituent monomer, preferable adhesiveness can be exhibited. Examples of (meth)acrylic acid alkyl esters having an alkyl group of 1 to 20 carbon atoms include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-(meth)acrylate, Butyl, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, n-decyl (meth)acrylate, (meth)acrylic acid Examples include n-dodecyl, myristyl (meth)acrylate, palmityl (meth)acrylate, and stearyl (meth)acrylate. Among them, from the viewpoint of further improving adhesiveness, (meth)acrylic acid esters having an alkyl group having 1 to 8 carbon atoms are preferable, and n-butyl (meth)acrylate or 2-ethylhexyl (meth)acrylate is particularly preferable. , and 2-ethylhexyl (meth)acrylate are more preferred. In addition, these may be used independently and may be used in combination of 2 or more type.

The (meth)acrylic acid ester polymer (A) preferably contains 40% by mass or more of a (meth)acrylic acid alkyl ester having an alkyl group having 1 to 20 carbon atoms as a monomer unit constituting the polymer. , In particular, it is preferably contained in an amount of 50% by mass or more, more preferably 60% by mass or more. If the (meth)acrylic acid alkyl ester is contained in an amount of 40% by mass or more, the (meth)acrylic acid ester polymer (A) can be imparted with suitable adhesiveness. In addition, it preferably contains 95% by mass or less, particularly preferably 80% by mass or less, further preferably 70% by mass or less of a (meth)acrylic acid alkyl ester having an alkyl group having 1 to 20 carbon atoms. is preferred. By setting the content of the (meth)acrylic acid alkyl ester to 95% by mass or less, a desired amount of other monomer components can be introduced into the (meth)acrylic acid ester polymer (A).

The (meth)acrylic acid ester polymer (A) may contain, as a monomer unit constituting the polymer, a reactive group-containing monomer having a reactive group in the molecule that reacts with the cross-linking agent (C) described later. preferable. The reactive group derived from this reactive group-containing monomer reacts with the cross-linking agent (C) to form a cross-linked structure (three-dimensional network structure), and the light diffusion pressure-sensitive adhesive layer 21 with relatively high cohesion is obtained.

Examples of the reactive group-containing monomer include a monomer having a hydroxyl group in the molecule (hydroxyl group-containing monomer), a monomer having a carboxy group in the molecule (carboxy group-containing monomer), a monomer having an amino group in the molecule (amino group-containing monomer ) and the like are preferably mentioned. Among these, hydroxyl group-containing monomers are particularly preferable because they are excellent in reactivity with the cross-linking agent (C) and have little adverse effect on the adherend.

Examples of hydroxyl group-containing monomers include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, (meth) ) hydroxyalkyl (meth)acrylates such as 3-hydroxybutyl acrylate and 4-hydroxybutyl (meth)acrylate; Among them, 2-hydroxyethyl (meth)acrylate from the viewpoint of the reactivity of the hydroxyl groups in the resulting (meth)acrylic acid ester polymer (A) with the crosslinking agent (C) and the copolymerizability with other monomers and 4-hydroxybutyl (meth)acrylate are preferred, and 2-hydroxyethyl (meth)acrylate is particularly preferred. These may be used alone or in combination of two or more.

Carboxy group-containing monomers include, for example, ethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, itaconic acid, and citraconic acid. Among them, acrylic acid is preferable from the viewpoint of the reactivity of the carboxy group in the obtained (meth)acrylic acid ester polymer (A) with the cross-linking agent (C) and the copolymerizability with other monomers. These may be used alone or in combination of two or more.

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

The (meth)acrylic acid ester polymer (A) preferably contains a reactive group-containing monomer as a lower limit of 1% by mass or more, and preferably contains 5% by mass or more, as a monomer unit constituting the polymer. is more preferable, particularly preferably 10% by mass or more, and more preferably 15% by mass or more. In addition, the (meth)acrylic acid ester polymer (A) preferably contains a reactive group-containing monomer as a monomer unit constituting the polymer in an upper limit of 50% by mass or less, particularly 40% by mass or less. It is preferably contained, more preferably 30% by mass or less. When the (meth)acrylic acid ester polymer (A) contains the reactive group-containing monomer in the above amount as a monomer unit, a good crosslinked structure is formed in the obtained pressure-sensitive adhesive, and the light diffusion pressure-sensitive adhesive with relatively high cohesion. An agent layer 21 is obtained.

The (meth)acrylic acid ester polymer (A) preferably contains a monomer having an alicyclic structure in its molecule (alicyclic structure-containing monomer) as a monomer unit constituting the copolymer. Since the alicyclic structure-containing monomer is bulky, it is presumed that the presence of this in the polymer widens the distance between the polymers, and the obtained pressure-sensitive adhesive can be made excellent in flexibility. . Therefore, by using an alicyclic structure-containing monomer as a constituent monomer unit of the (meth)acrylic acid ester polymer (A), it is possible to obtain a pressure-sensitive adhesive that is excellent in flexibility and has a better ability to prevent image display unevenness. can.

The carbon ring of the alicyclic structure in the alicyclic structure-containing monomer may have a saturated structure or may partially have an unsaturated bond. The alicyclic structure may be a monocyclic alicyclic structure or a polycyclic alicyclic structure such as bicyclic or tricyclic. From the viewpoint of increasing the distance between the resulting (meth)acrylic acid ester polymer (A) and effectively exhibiting the flexibility of the pressure-sensitive adhesive, the alicyclic structure is a polycyclic alicyclic structure ( polycyclic structure). Furthermore, in consideration of compatibility between the (meth)acrylic acid ester polymer (A) and other components, the polycyclic structure is particularly preferably bicyclic to tetracyclic. In the same manner as described above, from the viewpoint of effectively exerting the action of flexibility of the adhesive, the number of carbon atoms in the alicyclic structure (refers to the number of all carbon atoms in the part forming the ring, and multiple rings are independent (which means the total number of carbon atoms when they are present in the form of a compound) is usually preferably 5 or more, particularly preferably 7 or more. On the other hand, although the upper limit of the number of carbon atoms in the alicyclic structure is not particularly limited, it is preferably 15 or less, particularly preferably 10 or less, from the viewpoint of compatibility as described above.

Examples of alicyclic structures include cyclohexyl skeleton, dicyclopentadiene skeleton, adamantane skeleton, isobornyl skeleton, cycloalkane skeleton (cycloheptane skeleton, cyclooctane skeleton, cyclononane skeleton, cyclodecane skeleton, cycloundecane skeleton, cyclododecane skeleton, etc.). , cycloalkene skeletons (cycloheptene skeletons, cyclooctene skeletons, etc.), norbornene skeletons, norbornadiene skeletons, cubane skeletons, basketane skeletons, hausan skeletons, spiro skeletons, etc. Among them, those containing more excellent durability, Those containing a dicyclopentadiene skeleton (the number of carbon atoms in the alicyclic structure: 10), an adamantane skeleton (the number of carbon atoms in the alicyclic structure: 10) or an isobornyl skeleton (the number of carbon atoms in the alicyclic structure: 7) are preferred, particularly Those containing an isobornyl skeleton are preferred.

As the alicyclic structure-containing monomer, a (meth)acrylic acid ester monomer containing the above skeleton is preferable, and specifically, cyclohexyl (meth)acrylate, dicyclopentanyl (meth)acrylate, (meth) adamantyl acrylate, isobornyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, etc., among others, (meth)acrylic, which exhibits better durability Dicyclopentanyl acid, adamantyl (meth)acrylate or isobornyl (meth)acrylate are preferred, and isobornyl (meth)acrylate is particularly preferred. These may be used individually by 1 type, and may be used in combination of 2 or more type.

When the (meth)acrylic acid ester polymer (A) contains an alicyclic structure-containing monomer as a monomer unit constituting the polymer, the (meth)acrylic acid ester polymer (A) has an alicyclic structure The monomer content is preferably 1% by mass or more, particularly preferably 5% by mass or more, and more preferably 7% by mass or more. In addition, the (meth)acrylic acid ester polymer (A) preferably contains 20% by mass or less, particularly 15% by mass or less, of an alicyclic structure-containing monomer as a monomer unit constituting the polymer. is preferable, and it is more preferable to contain 10% by mass or less. When the content of the alicyclic structure-containing monomer is within the above range, it is possible to obtain a pressure-sensitive adhesive that is excellent in flexibility and more excellent in preventing unevenness in image display.

The (meth)acrylic acid ester polymer (A) preferably contains a monomer having a nitrogen atom in its molecule (nitrogen atom-containing monomer) as a monomer unit constituting the copolymer. The amino group-containing monomers exemplified as reactive group-containing monomers are excluded from the nitrogen atom-containing monomers. By allowing the nitrogen atom-containing monomer to be present in the polymer as a structural unit, the reaction between the acrylic acid ester polymer (A) and the cross-linking agent (C) is promoted, the polarity is imparted to the adhesive, and the adhesive itself can increase the cohesion of

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

Examples of monomers having a nitrogen-containing heterocyclic ring include N-(meth)acryloylmorpholine, N-vinyl-2-pyrrolidone, N-(meth)acryloylpyrrolidone, N-(meth)acryloylpiperidine, N-(meth)acryloyl pyrrolidine, N-(meth)acryloylaziridine, aziridinylethyl (meth)acrylate, 2-vinylpyridine, 4-vinylpyridine, 2-vinylpyrazine, 1-vinylimidazole, N-vinylcarbazole, N-vinylphthalimide, etc. Among them, N-(meth)acryloylmorpholine, which exhibits superior adhesive strength, is preferred, and N-acryloylmorpholine is particularly preferred.

Examples of nitrogen atom-containing monomers other than the above-mentioned nitrogen-containing heterocyclic ring-containing monomers include (meth)acrylamide, N-methyl(meth)acrylamide, N-methylol(meth)acrylamide, N-tert-butyl (meth)acrylamide, ) acrylamide, N,N-dimethyl (meth)acrylamide, N,N-ethyl (meth)acrylamide, N,N-dimethylaminopropyl (meth)acrylamide, N-isopropyl (meth)acrylamide, N-phenyl (meth)acrylamide , dimethylaminopropyl (meth)acrylamide, N-vinylcaprolactam, dimethylaminoethyl (meth)acrylate and the like can also be used.
One type of the above nitrogen atom-containing monomer may be used alone, or two or more types may be used in combination.

When the (meth)acrylic acid ester polymer (A) contains a nitrogen atom-containing monomer as a monomer unit constituting the polymer, the (meth)acrylic acid ester polymer (A) contains one nitrogen atom-containing monomer. It is preferably contained in an amount of 3% by mass or more, particularly preferably 3% by mass or more, and more preferably 5% by mass or more. In addition, the (meth)acrylic acid ester polymer (A) preferably contains 20% by mass or less, particularly preferably 15% by mass or less, of a nitrogen atom-containing monomer as a monomer unit constituting the polymer. , and more preferably 10% by mass or less. When the content of the nitrogen atom-containing monomer is within the above range, the cohesive strength of the obtained pressure-sensitive adhesive is effectively improved.

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

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

The weight-average molecular weight of the (meth)acrylate polymer (A) is preferably 100,000 or more, particularly preferably 200,000 or more, further preferably 300,000 or more as a lower limit. When the lower limit of the weight-average molecular weight of the (meth)acrylic acid ester polymer (A) is at least the above, the resulting pressure-sensitive adhesive has a higher film strength. In addition, the weight average molecular weight of the (meth)acrylic acid ester polymer (A) is preferably 2,000,000 or less, particularly preferably 900,000 or less, further preferably 700,000 or less as an upper limit. preferable. When the upper limit of the weight average molecular weight of the (meth)acrylic acid ester polymer (A) is the above or less, the durability of the pressure-sensitive adhesive to be obtained will be more excellent. In addition, the weight average molecular weight in this specification is the value of standard polystyrene conversion measured by the gel permeation chromatography (GPC) method.

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

(1-1-2) Active energy ray-curable compound The active energy ray-curable compound contained in the active energy ray-curable adhesive component in the present embodiment (hereinafter sometimes referred to as “active energy ray-curable compound (B)” ) may be a monomer, an oligomer, a polymer, or a mixture thereof, as long as the durability and cohesive strength of the resulting light-diffusing pressure-sensitive adhesive layer 21 are increased to the desired level. may Among them, polyfunctional acrylate-based monomers having excellent compatibility with the (meth)acrylic acid ester polymer (A) and the like are preferable.

In the adhesive composition P of the present embodiment, the active energy ray-curable compounds (B) form chemical bonds with each other by irradiation with active energy rays to form a three-dimensional network structure. By trapping the (meth)acrylate polymer (A) in the structure, the cohesive force is improved, resulting in excellent durability.

Examples of polyfunctional acrylate monomers include 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, and polyethylene glycol di(meth)acrylate. , neopentyl glycol adipate di(meth)acrylate, neopentyl glycol hydroxypivalate di(meth)acrylate, dicyclopentanyl di(meth)acrylate, caprolactone-modified dicyclopentenyl di(meth)acrylate, ethylene oxide-modified phosphate di( Bifunctional types such as meth)acrylate, ethylene oxide-modified isocyanuric acid di(meth)acrylate, di(acryloxyethyl)isocyanurate, allylated cyclohexyl di(meth)acrylate; trimethylolpropane tri(meth)acrylate, dipentaerythritol tri (Meth)acrylates, propionic acid-modified dipentaerythritol tri(meth)acrylate, pentaerythritol tri(meth)acrylate, propylene oxide-modified trimethylolpropane tri(meth)acrylate, tris(acryloxyethyl)isocyanurate, ε-caprolactone-modified trifunctional type such as tris-(2-(meth)acryloxyethyl)isocyanurate, ethylene oxide-modified isocyanuric acid tri(meth)acrylate; tetrafunctional type such as diglycerin tetra(meth)acrylate and pentaerythritol tetra(meth)acrylate pentafunctional type such as propionic acid-modified dipentaerythritol penta(meth)acrylate; and hexafunctional type such as dipentaerythritol hexa(meth)acrylate and caprolactone-modified dipentaerythritol hexa(meth)acrylate. Among them, those having a molecular weight of 1000 or less are more preferable. These may be used individually by 1 type, and may be used in combination of 2 or more type.

The content of the active energy ray-curable compound (B) is preferably 1 part by mass or more, particularly 3 parts by mass or more, with respect to 100 parts by mass of the (meth)acrylate polymer (A). is preferred, and more preferably 5 parts by mass or more. In addition, the content of the active energy ray-curable compound (B) is preferably 30 parts by mass or less, more preferably 25 parts by mass or less, particularly preferably 20 parts by mass or less, and further It is preferably 10 parts by mass or less. When the content of the active energy ray-curable compound (B) is within the above range, the resulting pressure-sensitive adhesive has excellent durability, and the light-diffusing pressure-sensitive adhesive layer 21 obtained has excellent handleability. It becomes a thing. Furthermore, the (meth)acrylic acid ester polymer (A) maintains good adhesiveness.

(1-1-3) Crosslinking agent The adhesive composition P preferably contains a crosslinking agent (C) as an active energy ray-curable adhesive component. When the adhesive component of the adhesive composition P contains a (meth)acrylic acid ester polymer (A) containing a reactive functional group-containing monomer as a monomer unit constituting the polymer and a crosslinking agent (C), When the adhesive composition P is heated, the cross-linking agent (C) reacts with the reactive functional group of the reactive functional group-containing monomer constituting the (meth)acrylic acid ester polymer (A). Thereby, a structure in which the (meth)acrylic acid ester polymer (A) is crosslinked by the crosslinking agent (C) is formed, and the cohesive strength of the resulting pressure-sensitive adhesive is improved.

In addition, in the adhesive composition P in the present embodiment, the active energy ray-curable compound (B) described above improves the cohesive force of the obtained adhesive, thereby improving the durability. However, it is more preferable to use a cross-linking agent (C) in combination, from the viewpoint of further improving the cohesive force while maintaining the appropriate adhesive strength of the pressure-sensitive adhesive and further improving the durability.

The cross-linking agent (C) may be one that reacts with the reactive functional group of the (meth)acrylic acid ester polymer (A), and examples thereof include isocyanate cross-linking agents, epoxy cross-linking agents, and amine cross-linking agents. , melamine cross-linking agent, aziridine cross-linking agent, hydrazine cross-linking agent, aldehyde cross-linking agent, oxazoline cross-linking agent, metal alkoxide cross-linking agent, metal chelate cross-linking agent, metal salt cross-linking agent, ammonium salt cross-linking agent, etc. is mentioned. When the (meth)acrylic acid ester polymer (A) has a hydroxyl group as a reactive functional group, among the above, it is preferable to use an isocyanate-based cross-linking agent having excellent reactivity with the hydroxyl group. In addition, a crosslinking agent (C) can be used individually by 1 type or in combination of 2 or more types.

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

The content of the cross-linking agent (C) is preferably 0.01 to 10 parts by mass, particularly 0.05 to 5 parts by mass with respect to 100 parts by mass of the (meth)acrylate polymer (A). preferably 0.1 to 1 part by mass.

(1-1-4) Various Additives The active energy ray-curable adhesive component may optionally contain various additives such as photopolymerization initiators (D), silane coupling agents (E), refractive index modifiers, antistatic agents, agents, tackifiers, antioxidants, UV absorbers, light stabilizers, softeners, fillers, and the like.

When an ultraviolet ray is used as the active energy ray for curing the adhesive composition P, the active energy ray-curable adhesive component preferably contains a photopolymerization initiator (D). By containing the photopolymerization initiator (D), the active energy ray-curable adhesive component can be efficiently cured, and the polymerization curing time and the irradiation dose of the active energy ray can be reduced.

Examples of the photopolymerization initiator (D) include benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin-n-butyl ether, benzoin isobutyl ether, acetophenone, dimethylaminoacetophenone, 2,2-dimethoxy-2- Phenylacetophenone, 2,2-diethoxy-2-phenylacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-hydroxycyclohexylphenylketone, 2-methyl-1-[4-(methylthio) Phenyl]-2-morpholino-propan-1-one, 4-(2-hydroxyethoxy)phenyl-2-(hydroxy-2-propyl)ketone, benzophenone, p-phenylbenzophenone, 4,4′-diethylaminobenzophenone, dichloro Benzophenone, 2-methylanthraquinone, 2-ethylanthraquinone, 2-tertiary-butylanthraquinone, 2-aminoanthraquinone, 2-methylthioxanthone, 2-ethylthioxanthone, 2-chlorothioxanthone, 2,4-dimethylthioxanthone, 2,4- Diethylthioxanthone, benzyl dimethyl ketal, acetophenone dimethyl ketal, p-dimethylaminobenzoate, oligo[2-hydroxy-2-methyl-1[4-(1-methylvinyl)phenyl]propanone], 2,4,6- and trimethylbenzoyl-diphenyl-phosphine oxide. These may be used alone or in combination of two or more.

The photopolymerization initiator (D) is in the range of 0.1 to 20 parts by mass, particularly 1 to 12 parts by mass with respect to 100 parts by mass of the active energy ray-curable compound (B) in the active energy ray-curable adhesive component. is preferably used in an amount of

In addition, the active energy ray-curable adhesive component preferably contains a silane coupling agent (E) from the viewpoint of improving the adhesive strength to the adherend such as the glass surface of the liquid crystal cell. As the silane coupling agent (E), an organosilicon compound having at least one alkoxysilyl group in the molecule, having good compatibility with the adhesive component and having optical transparency is preferred.

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

The content of the silane coupling agent (E) is preferably 0.01 to 10 parts by mass, particularly 0.05 to 5 parts by mass, with respect to 100 parts by mass of the (meth)acrylate polymer (A). part, more preferably 0.1 to 1 part by mass.

(1-2) Light diffusing fine particles The light diffusing fine particles contained in the adhesive composition P according to the present embodiment can satisfy the haze value described above for the adhesive layer 2 having the light diffusing adhesive layer 21 obtained. Anything is fine.

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 fine particles such as acrylic resin, polystyrene resin, polyethylene resin, and epoxy resin. translucent fine particles; fine particles composed of a silicon-containing compound having an intermediate structure between inorganic and organic, such as silicone resin (for example, Tospearl series manufactured by Momentive Performance Materials Japan). Among them, acrylic resin fine particles and fine particles composed of a silicon-containing compound having an intermediate structure between inorganic and organic are preferable from the viewpoint of coping with high-definition pressure-sensitive adhesive layers. In addition, fine particles composed of a silicon-containing compound having an intermediate structure between inorganic and organic are particularly preferable because they exhibit their effects even when added in small amounts, and the adhesiveness of the active energy ray-curable adhesive component is maintained well. . One type of the above light diffusion fine particles may be used alone, or two or more types may be used in combination.

Examples of the acrylic resin fine particles include those composed of homopolymers of methyl methacrylate, copolymers of methyl methacrylate and monomers such as vinyl acetate, styrene, methyl acrylate and ethyl acrylate. be done.

As for the shape of the light diffusing fine particles, spherical fine particles with uniform light diffusion are preferable. The average particle diameter of the light diffusing fine particles measured by the centrifugal sedimentation light transmission method is preferably 1.0 μm or more, particularly preferably 2.0 μm or more, further preferably 2.5 μm or more as a lower limit. . When the lower limit of the average particle diameter is above, good light diffusibility can be obtained, and the pressure-sensitive adhesive layer 2 easily satisfies the haze value described above. On the other hand, the upper limit of the average particle diameter is preferably 10 µm or less, particularly preferably 7 µm or less, and more preferably 5 µm or less. When the upper limit of the average particle diameter is the above, a high-definition display image can be satisfactorily displayed.

In addition, the average particle diameter by the centrifugal sedimentation light transmission method was obtained by sufficiently stirring 1.2 g of fine particles and 98.8 g of isopropyl alcohol as a measurement sample, using a centrifugal automatic particle size distribution analyzer (manufactured by Horiba, Ltd.). CAPA-700) was used.

The content of the light diffusing fine particles in the adhesive composition P is preferably 1.0 parts by mass or more, particularly 1.5 parts by mass, as a lower limit with respect to 100 parts by mass of the active energy ray-curable adhesive component. It is preferably at least 2.0 parts by mass, more preferably at least 2.0 parts by mass. When the lower limit of the content of the light diffusing fine particles is above, the obtained adhesive layer 2 having the light diffusing adhesive layer 21 easily satisfies the haze value described above. In addition, the content of the light diffusing fine particles is preferably 25 parts by mass or less, particularly preferably 20 parts by mass or less, as an upper limit with respect to 100 parts by mass of the active energy ray-curable adhesive component. Furthermore, it is preferably 15 parts by mass or less. When the upper limit of the content of the light diffusing fine particles is above, the adhesiveness of the active energy ray-curable adhesive component is not hindered.

(1-3) Production of Adhesive Composition The adhesive composition P can be produced by mixing an active energy ray-curable adhesive component and light diffusing fine particles. When the active energy ray-curable adhesive component contains the (meth)acrylic acid ester polymer (A), the (meth)acrylic acid ester polymer (A) is first prepared, and the active energy ray-curable compound ( B), light diffusing fine particles, and optionally a cross-linking agent (C) and additives are blended.

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

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

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

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

After the (meth)acrylate polymer (A) is obtained, the solution of the (meth)acrylate polymer (A) is added with the active energy ray-curable compound (B), the light diffusing fine particles, and optionally a cross-linking agent. (C) and additives are added and thoroughly mixed to obtain a solvent-diluted adhesive composition P (coating solution).

Diluting solvents for diluting the adhesive composition P to form a coating solution include, for example, aliphatic hydrocarbons such as hexane, heptane and cyclohexane, aromatic hydrocarbons such as toluene and xylene, methylene chloride and ethylene chloride. Halogenated hydrocarbons, alcohols such as methanol, ethanol, propanol, butanol, 1-methoxy-2-propanol, ketones such as acetone, methyl ethyl ketone, 2-pentanone, isophorone, cyclohexanone, esters such as ethyl acetate and butyl acetate, ethyl A cellosolve-based solvent such as cellosolve is used.

The concentration/viscosity of the coating solution thus prepared is not particularly limited as long as it is within a range that allows coating, and can be appropriately selected according to the situation. For example, the adhesive composition P is diluted to a concentration of 10 to 50% by mass. When obtaining the coating solution, the addition of a diluent solvent or the like is not a necessary condition, and the diluent solvent may not be added as long as the viscosity of the adhesive composition P allows coating.

(1-4) Formation of light-diffusing pressure-sensitive adhesive layer The light-diffusing pressure-sensitive adhesive layer 21 in the present embodiment is formed by applying the coating solution of the adhesive composition P to a desired object (preferably the release surface of the release sheet 3a). It can be preferably obtained by curing the adhesive composition P by irradiation with active energy rays after coating and drying.

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

Drying of the adhesive composition P may be performed by air drying, but is usually performed by heat treatment (preferably hot air drying). When the heat treatment is performed, the heating temperature is preferably 50 to 150°C, particularly preferably 70 to 120°C. The heating time is preferably 10 seconds to 10 minutes, more preferably 50 seconds to 2 minutes.

As the active energy rays, ultraviolet rays, electron beams, and the like are usually used. The amount of active energy ray irradiation varies depending on the type of energy ray. For example, in the case of ultraviolet rays, the amount of light is preferably 50 to 1000 mJ/cm ² , particularly preferably 100 to 500 mJ/cm ² . In the case of an electron beam, it is preferably about 10 to 1000 krad.

When the active energy ray-curable adhesive component of the adhesive composition P contains the (meth)acrylic acid ester polymer (A), the active energy ray-curable compound (B) and the cross-linking agent (C), the adhesive composition By drying (heating) P, the (meth)acrylate polymer (A) is crosslinked by the crosslinking agent (C) to form a crosslinked structure. Further, by irradiating the adhesive composition P with active energy rays, a plurality of active energy ray-curable compounds (B) are bonded to each other to form a three-dimensional network structure, which is crosslinked by the crosslinking agent (C) (meta ) It is presumed that the acrylic acid ester polymer (A) is trapped within the three-dimensional network structure.

(2) Low-Elasticity Adhesive Layer The low-elasticity adhesive layer 22 is not particularly limited as long as it is made of a material having the aforementioned storage elastic modulus, excellent optical transparency, and predetermined adhesive strength. Such a low-elasticity adhesive layer 22 is preferably formed from an adhesive composition containing an adhesive component, and in particular, it may be formed from an adhesive composition that contains an adhesive component and does not contain light diffusing fine particles. preferable.

The adhesive component includes, for example, an acrylic adhesive component, a rubber adhesive component, a silicone adhesive component, a polyurethane adhesive component, and a polyester adhesive component. Moreover, the adhesive component is preferably a non-curing adhesive component in order to lower the storage elastic modulus.

Therefore, the low-elasticity adhesive layer 22 is preferably formed from an adhesive composition containing a non-curable (meth)acrylate polymer (hereinafter referred to as "adhesive composition Q"). As the non-curable (meth)acrylic acid ester polymer, the (meth)acrylic acid ester polymer (A) described above, which can be used in the light-diffusing pressure-sensitive adhesive layer 21, is preferably used. This (meth)acrylic acid ester polymer (A) may be the same as or different from that used in the light diffusion adhesive layer 21 .

The adhesive composition Q preferably contains a cross-linking agent in order to increase the cohesive strength of the resulting low-elasticity adhesive layer 22 . As the cross-linking agent, the above-described cross-linking agent (C) that can be used in the light diffusion pressure-sensitive adhesive layer 21 is preferably used. This cross-linking agent (C) may be the same as or different from that used in the light diffusion pressure-sensitive adhesive layer 21 .

Adhesive composition Q may optionally contain various additives such as silane coupling agents, refractive index modifiers, antistatic agents, tackifiers, antioxidants, ultraviolet absorbers, light stabilizers, softeners, and antirust agents. It may contain an agent or the like.

The adhesive composition Q preferably contains a silane coupling agent from the viewpoint of improving the adhesive strength to the adherend such as the glass surface of the liquid crystal cell. As the silane coupling agent, the silane coupling agent (E) described above, which can be used in the light-diffusing pressure-sensitive adhesive layer 21, is preferably used. This silane coupling agent (E) may be the same as or different from that used in the light diffusion adhesive layer 21 .

The adhesive composition Q and its coating solution can be produced by the same method as for the adhesive composition P described above. The low-elasticity pressure-sensitive adhesive layer 22 in the present embodiment is preferably obtained by applying a coating solution of the pressure-sensitive adhesive composition Q to a desired object (preferably the release surface of the release sheet 3b) and heat-treating the coating solution. can be done. This heat treatment can be performed in the same manner as the heat treatment for the adhesive composition P, and also serves as a drying treatment for volatilizing the diluent solvent etc. from the coating film of the adhesive composition Q applied to the desired object. can also

After the heat treatment, if necessary, a curing period of about 1 to 2 weeks may be provided at room temperature (eg, 23° C., 50% RH). In addition, this curing period may be provided at a necessary stage when necessary, and is preferably provided after lamination with the light-diffusing pressure-sensitive adhesive layer 21 . In the present specification, the layer of the pressure-sensitive adhesive composition after heat-drying and before curing is also referred to as the "pressure-sensitive adhesive layer".

(3) Release Sheet The release sheets 3a and 3b are not particularly limited, and known plastic films can be used. For example, polyethylene film, polypropylene film, polybutene film, polybutadiene film, polymethylpentene film, polyvinyl chloride film, vinyl chloride copolymer film, polyethylene terephthalate film, polyethylene naphthalate film, polybutylene terephthalate film, polyurethane film, ethylene acetate. Vinyl films, ionomer resin films, ethylene/(meth)acrylic acid copolymer films, ethylene/(meth)acrylic acid ester copolymer films, polystyrene films, polycarbonate films, polyimide films, fluororesin films and the like are used. Crosslinked films of these are also used. Furthermore, a laminated film of these may be used.

The release surfaces of the release sheets 3a and 3b (especially the surfaces in contact with the pressure-sensitive adhesive layer) are preferably subjected to a release treatment. Examples of release agents used in the release treatment include alkyd-based, silicone-based, fluorine-based, unsaturated polyester-based, polyolefin-based, and wax-based release agents. Of the release sheets 3a and 3b, it is preferable that one of the release sheets is a heavy release type release sheet with a large release force, and the other release sheet is a light release type release sheet with a small release force.

Although the thickness of the release sheets 3a and 3b is not particularly limited, it is usually about 20 to 150 μm.

3. Production of Adhesive Sheet As an example of production of the adhesive sheet 1, the release surface of one of the release sheets 3a is coated with the coating liquid of the adhesive composition P, dried, and then irradiated with an active energy ray to diffuse the light diffusion adhesive. The agent layer 21 is formed. Further, a coating liquid of the adhesive composition Q is applied to the release surface of the other release sheet 3b, and the low-elasticity adhesive layer 22 is formed by heat treatment. Then, the light-diffusing adhesive layer 21 on the release sheet 3a and the low-elasticity adhesive layer 22 on the release sheet 3b are pasted together. After that, a curing period may be provided as necessary. As a result, the adhesive sheet 1 is obtained in which the release sheet 3a, the light diffusion adhesive layer 21, the low-elasticity adhesive layer 22, and the release sheet 3b are laminated in that order.

[Liquid crystal display components]
A liquid crystal display member according to one embodiment of the present invention comprises a first liquid crystal cell, a second liquid crystal cell, and a pressure-sensitive adhesive layer for bonding them together. This pressure-sensitive adhesive layer is the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet according to the embodiment described above, and has a haze value of 80% or more and 99% or less. In such a liquid crystal display member, moire hardly occurs due to the action of the pressure-sensitive adhesive layer.

In addition, since the liquid crystal display member according to the present embodiment is formed by laminating the first liquid crystal cell and the second liquid crystal cell with the adhesive layer, it is possible to reduce the thickness of the liquid crystal display member. Furthermore, since the pressure-sensitive adhesive layer having a smaller refractive index difference with the constituent material of the liquid crystal cell than air is interposed between the liquid crystal cells, the reflection loss at each interface between the two liquid crystal cells is reduced. This suppresses a decrease in the amount of transmitted light and a decrease in the definition of a displayed image due to the reflection loss.

A preferred example of the pressure-sensitive adhesive layer in this embodiment is composed of two layers, a light-diffusing pressure-sensitive adhesive layer and a low-elasticity pressure-sensitive adhesive layer, and will be described below with reference to the drawings.

As shown in FIG. 2, the liquid crystal display member 4 according to this embodiment includes a first liquid crystal cell 5a, a second liquid crystal cell 5b, and an adhesive layer 2 for bonding them together. be. The adhesive layer 2 in this embodiment consists of two layers, a light diffusion adhesive layer 21 in contact with the first liquid crystal cell 5a and a low elasticity adhesive layer 22 in contact with the second liquid crystal cell 5b.

The light-diffusing pressure-sensitive adhesive layer 21 and the low-elasticity pressure-sensitive adhesive layer 22 are the light-diffusing pressure-sensitive adhesive layer 21 and the low-elasticity pressure-sensitive adhesive layer 22 in the above-described pressure-sensitive adhesive sheet 1, and the details of their configurations are as described above.

The first liquid crystal cell 5a and the second liquid crystal cell 5b are commonly used in liquid crystal (LCD) displays, particularly liquid crystal displays that display stereoscopic images, and are not particularly limited. A "liquid crystal cell" may also be called 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 rigid bodies, and their thickness is usually about 0.5 to 5.0 mm, preferably about 1.0 to 3.0 mm. is.

In order to manufacture the liquid crystal display member 4, first, the release sheet 3a is peeled from the adhesive sheet 1 to expose the light diffusion adhesive layer 21, and the exposed light diffusion adhesive layer 21 is used as the first liquid crystal cell. Attached to one side of 5a. At this time, the surface of the pressure-sensitive adhesive sheet 1 opposite to the surface in contact with the liquid crystal cell 5a maintains a state in which a flexible release sheet 3b is attached. Therefore, the stress of the light-diffusing pressure-sensitive adhesive layer 21 generated when it is attached to the liquid crystal cell 5a is immediately eliminated. In addition, when attached to the liquid crystal cell 5a, the low-elasticity pressure-sensitive adhesive layer 22 serves as a cushioning material, thereby suppressing excessive pressure from being applied to the liquid crystal cell 5a. By these actions, it is possible to prevent the disorder of the alignment of the liquid crystal cells 5a, which causes uneven image display during the formation of the liquid crystal display member 4, at this stage.

Next, the release sheet 3b is peeled off from the adhesive sheet 1 (adhesive layer 2) attached to the first liquid crystal cell 5a to expose the low-elasticity adhesive layer 22. No. 2 liquid crystal cell 5b is pasted. Here, stress is generated in the pressure-sensitive adhesive layer 2 by bonding with the second liquid crystal cell 5b. However, since the pressure-sensitive adhesive layer 2 has the low-elasticity pressure-sensitive adhesive layer 22, the stress is relieved, and the stress is prevented from acting on the first liquid crystal cell 5a and the second liquid crystal cell 5b. Furthermore, excessive pressure during lamination of the second liquid crystal cell 5b is also adjusted by the low-elasticity pressure-sensitive adhesive layer 22. FIG. In the liquid crystal display member 4 thus obtained, the alignment of the liquid crystal cells 5a and 5b is prevented from being disturbed due to the residual stress of the pressure-sensitive adhesive layer 2 and the unevenness of the repulsive force caused by the stress, thereby suppressing the occurrence of unevenness in the displayed image. The display image is displayed satisfactorily.

In addition, the liquid crystal display member 4 is resistant to moiré due to the action of the pressure-sensitive adhesive layer 2 having a specified haze value, particularly the light-diffusing pressure-sensitive adhesive layer 21, and has excellent visibility of displayed images.

The embodiments described above are described to facilitate understanding of the present invention, and are not described to limit the present invention. Therefore, each element disclosed in the above embodiments is meant to include all design changes and equivalents that fall within the technical scope of the present invention.

For example, the adhesive layer 2 in the adhesive sheet 1 may have a structure of three or more layers. Either one of the release sheets 3a and 3b in the adhesive sheet 1 may be omitted.

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

[Production Example 1] (Preparation of adhesive composition for light diffusion adhesive layer)
1. Preparation of (meth)acrylate polymer 60 parts by weight of 2-ethylhexyl acrylate, 10 parts by weight of isobornyl acrylate, 10 parts by weight of N-acryloylmorpholine, and 20 parts by weight of 2-hydroxyethyl acrylate were copolymerized by a solution polymerization method. Polymerization was performed to prepare a (meth)acrylate polymer (A). When the molecular weight of this (meth)acrylic acid ester polymer (A) was measured by the following method, the weight average molecular weight (Mw) was 500,000.

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

2. Preparation of adhesive composition for light diffusion adhesive layer 100 parts by mass (solid content conversion value; the same applies hereinafter) of the (meth) acrylic acid ester polymer (A) obtained in the above step 1, and active energy ray-curable 5 parts by mass of a mixture of ethylene oxide-modified isocyanuric acid diacrylate and ethylene oxide-modified isocyanuric acid tri(meth)acrylate (manufactured by Toagosei Co., Ltd., product name "Aronix M315") as component (B), and a photopolymerization initiator (D) 0.25 parts by weight of 2-hydroxy-2-methyl-1-phenylpropan-1-one and 0.25 parts by weight of benzophenone, and 0.2 parts by weight of trimethylolpropane-modified tolylene diisocyanate as a cross-linking agent (C) , 0.3 parts by mass of 3-glycidoxypropyltrimethoxysilane as a silane coupling agent (E), and fine particles composed of a silicon-containing compound having an intermediate structure between inorganic and organic as light diffusing fine particles ( Momentive Performance Materials Japan, product name “Tospearl 145L”, average particle size: 4.5 μm, refractive index: 1.43) 1 part by mass, thoroughly stirred, and diluted with methyl ethyl ketone By doing so, a coating solution of the adhesive composition P for the light diffusion adhesive layer was obtained.

[Production Examples 2 to 4] (Preparation of adhesive composition for light diffusion adhesive layer)
A coating solution of a pressure-sensitive adhesive composition for a light-diffusing pressure-sensitive adhesive layer was prepared in the same manner as in Production Example 1, except that the type and blending amount of the light-diffusing fine particles were changed as shown in Table 1.

[Production Example 5] (Preparation of adhesive composition for low-elasticity adhesive layer)
100 parts by mass of the (meth)acrylic acid ester polymer (A) obtained in Step 1 of Production Example 1, 0.2 parts by mass of trimethylolpropane-modified tolylene diisocyanate as a cross-linking agent (C), and silane coupling 0.3 parts by mass of 3-glycidoxypropyltrimethoxysilane as an agent (E), stirred thoroughly, and diluted with methyl ethyl ketone to prepare a pressure-sensitive adhesive composition Q for a low-elasticity pressure-sensitive adhesive layer. was obtained.

Here, Table 1 shows each formulation (solid content conversion value) of the adhesive composition when the (meth)acrylic acid ester polymer (A) is 100 parts by mass (solid content conversion value). Details of abbreviations and the like in Table 1 are as follows.
[(Meth) acrylic ester polymer (A)]
2EHA: 2-ethylhexyl acrylate IBXA: isobornyl acrylate ACMO: N-acryloylmorpholine HEA: 2-hydroxyethyl acrylate
[Light Diffusion Fine Particles]
Tospearl 145L: Fine particles composed of a silicon-containing compound having an intermediate structure between inorganic and organic (manufactured by Momentive Performance Materials Japan, product name "Tospearl 145L", average particle size: 4.5 μm, refractive index: 1 .43)
XX-16LA: Spherical polymethyl methacrylate-polystyrene copolymer fine particles (manufactured by Sekisui Plastics Co., Ltd., product name “XX-16LA”, average particle size: 2.5 μm, refractive index: 1.55)

[Example 1]
1. Formation of light-diffusing pressure-sensitive adhesive layer The coating solution of the pressure-sensitive adhesive composition P for the light-diffusing pressure-sensitive adhesive layer prepared in Production Example 2 was applied to a light-release type release sheet (one side of a polyethylene terephthalate film was release-treated with a silicone-based release agent) ( It was applied to the release-treated surface of Lintec Co., Ltd., product name "SP-PET382120") using a knife coater. Then, the coating film was heat-treated at 90° C. for 1 minute to form a coating layer.

Then, the coating layer was irradiated with ultraviolet rays under the following conditions to cure the coating layer, thereby forming a light-diffusing pressure-sensitive adhesive layer having a thickness of 100 μm.
<Ultraviolet irradiation conditions>
・Electrodeless lamp H bulb manufactured by Fusion Co., Ltd. ・Illuminance 600 mW/cm ² , Light intensity 150 mJ/cm ²
・The UV illuminance/photometer uses “UVPF-36” manufactured by Eye Graphics Co., Ltd.

2. Formation of low-elasticity pressure-sensitive adhesive layer The coating solution of the pressure-sensitive adhesive composition Q for the low-elasticity pressure-sensitive adhesive layer prepared in Production Example 5 was applied to a polyethylene terephthalate film on one side of which was treated with a silicone-based release agent to form a heavy-release release sheet ( It was applied to the release-treated surface of Lintec Co., Ltd., product name "SP-PET752150") using a knife coater. Then, the coating film was heat-treated at 90° C. for 1 minute to form a low-elastic pressure-sensitive adhesive layer with a thickness of 50 μm.

3. Production of pressure-sensitive adhesive sheet After bonding the light-diffusing pressure-sensitive adhesive layer on the light-release release sheet obtained in step 1 above and the low-elasticity pressure-sensitive adhesive layer on the heavy-release release sheet obtained in step 2 above , 23 ° C., 50% RH for 7 days, a light release release sheet, a light diffusion adhesive layer (100 μm thick), a low elastic adhesive layer (50 μm thick), and a heavy release type A release sheet was laminated in that order to obtain a pressure-sensitive adhesive sheet. The thickness of each pressure-sensitive adhesive layer is a value measured using a constant-pressure thickness gauge (manufactured by Teclock, product name "PG-02") in accordance with JIS K7130.

[Examples 2 to 6, Comparative Examples 1 to 2]
A pressure-sensitive adhesive sheet was produced in the same manner as in Example 1, except that the type of pressure-sensitive adhesive composition for the light-diffusing pressure-sensitive adhesive layer and the thickness of each pressure-sensitive adhesive layer were changed as shown in Table 2.

[Test Example 1] (Measurement of storage modulus (G'))
A plurality of 50 μm-thick light-diffusing pressure-sensitive adhesive layers and low-elasticity pressure-sensitive adhesive layers formed in the same manner as in Examples and Comparative Examples were laminated to form a laminate having a thickness of 800 μm. A cylinder with a diameter of 8 mm (height: 800 μm) was punched out from the laminate of the pressure-sensitive adhesive layers thus obtained, and this was used as a sample.

For the above sample, in accordance with JIS K7244-6, a storage modulus (G') (MPa ) was measured. Table 2 shows the results.
Measurement frequency: 1Hz
Measurement temperature: 23°C

[Test Example 2] (Measurement of haze value)
Each haze value of the light diffusion pressure-sensitive adhesive layer, the low-elasticity pressure-sensitive adhesive layer, and the pressure-sensitive adhesive layer as a laminate thereof formed in Examples and Comparative Examples was measured using a haze meter (manufactured by Nippon Denshoku Industries Co., Ltd., product name "NDH2000"). ) in accordance with JIS K7105. Table 2 shows the results.

[Test Example 3] (Evaluation of Moire)
The light-releasing release sheet on the side of the light-diffusing pressure-sensitive adhesive layer in the pressure-sensitive adhesive sheets obtained in Examples and Comparative Examples was peeled off, and the exposed light-diffusing pressure-sensitive adhesive layer was placed on a tablet terminal (manufactured by Apple Inc., product name "iPad (registered trademark)”, resolution: 264 ppi). Next, the heavy release type release sheet on the low-elasticity adhesive layer side of the adhesive sheet is peeled off, and a liquid crystal mask having a lattice of 20ppi to 180ppi (in increments of 20ppi) is attached to the exposed low-elasticity adhesive layer, A liquid crystal display was obtained.

The screen of the tablet terminal is displayed in full green (RGB values (R, G, B) = 0, 255, 0), and the liquid crystal display is viewed from a direction of 60 degrees from the normal line of the screen on the liquid crystal mask side. The degree of moire seen in 1 was evaluated according to the following criteria. Table 2 shows the results.
⊚: No moiré was generated in the liquid crystal displays related to all the liquid crystal masks, and the same results were obtained even when the direction of visual observation was varied.
◯: No moire occurred in the liquid crystal display bodies related to all the liquid crystal masks.
Δ: Moiré occurred in some liquid crystal display elements related to the liquid crystal mask.
x: Moiré occurred in the liquid crystal display bodies related to all the liquid crystal masks.

[Test Example 4] (Evaluation of image display unevenness prevention property)
A first liquid crystal cell and a second liquid crystal cell were prepared, and the first liquid crystal cell was adsorbed by an adsorption device. Next, the light-releasing release sheet on the side of the light-diffusing pressure-sensitive adhesive layer in the pressure-sensitive adhesive sheets obtained in Examples and Comparative Examples was peeled off, and the exposed light-diffusing pressure-sensitive adhesive layer was attached to one side of the first liquid crystal cell. . Next, the heavy release type release sheet on the side of the low-elasticity adhesive layer in the adhesive sheet is peeled off, and the exposed low-elasticity adhesive layer is attached to an atmospheric pressure lamination machine (manufactured by Suntec Co., Ltd., product name "TMS-SA"). ) was used to bond the second liquid crystal cell at a bonding speed of 30 mm/sec and a roller pressure of 0.3 MPa. Specifically, while one end of the second liquid crystal cell is supported by a glass presser, the second liquid crystal cell is adhered to the low-elasticity pressure-sensitive adhesive layer by a roller from the other end of the second liquid crystal cell. The roller was rotated to one end of the second liquid crystal cell, and finally the glass presser was removed.

After that, in a state where the first and second liquid crystal cells are stuck together, an image is displayed using white light as backlight light, and the displayed image is visually observed from the side of the first liquid crystal cell, and the image is displayed according to the following criteria. The ability to prevent unevenness was evaluated. Table 2 shows the results.
A: The image was displayed without any problem.
x: Unevenness occurred in the displayed image.

As can be seen from Table 2, according to the pressure-sensitive adhesive sheets obtained in Examples, moire hardly occurs in the obtained liquid crystal display member, and the property of preventing unevenness in image display is excellent.

The pressure-sensitive adhesive sheet and liquid crystal display member according to the present invention can be suitably used for a stereoscopic image display device.

Reference Signs List 1 Adhesive sheet 2 Adhesive layer 21 Light diffusion adhesive layer 22 Low elastic adhesive layers 3a, 3b Release sheet 4 Liquid crystal display member 5a First liquid crystal cell 5b Second liquid crystal cell

Claims (7)

Having an adhesive layer for bonding two liquid crystal cells ,
The adhesive layer has a haze value of 80% or more and 99% or less,
The pressure-sensitive adhesive layer consists of a plurality of layers,
At least one layer of the plurality of layers is a light-diffusing pressure-sensitive adhesive layer having light-diffusing properties,
A pressure-sensitive adhesive sheet, wherein at least one surface of the pressure-sensitive adhesive layer has a layer formed from an adhesive composition containing an adhesive component and not containing light diffusing fine particles. 2. The layer according to claim 1, wherein a storage elastic modulus at 23° C. of the layer formed from the adhesive composition containing the adhesive component and not containing the light-diffusing fine particles is lower than that of the light-diffusing adhesive layer. adhesive sheet. 2. The storage elastic modulus at 23° C. of the layer formed from the adhesive composition containing the adhesive component and not containing the light diffusing fine particles is 0.01 MPa or more and 0.1 MPa or less. 2. The pressure-sensitive adhesive sheet according to 2. The pressure-sensitive adhesive sheet according to any one of claims 1 to 3, wherein the light diffusion pressure-sensitive adhesive layer has a storage elastic modulus at 23°C of 0.1 MPa or more and 3.0 MPa or less. The pressure-sensitive adhesive sheet according to any one of claims 1 to 4, wherein the total thickness of the pressure-sensitive adhesive layer is 50 µm or more and 1000 µm or less. two release sheets;
The pressure-sensitive adhesive sheet according to any one of claims 1 to 5, further comprising the pressure-sensitive adhesive layer sandwiched between the two release sheets so as to be in contact with the release surfaces of the two release sheets. a first liquid crystal cell;
a second liquid crystal cell;
A liquid crystal display member comprising an adhesive layer for bonding the first liquid crystal cell and the second liquid crystal cell together,
A liquid crystal display member, wherein the adhesive layer is the adhesive layer of the adhesive sheet according to any one of claims 1 to 6.

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