JP2023082895A - Adhesive sheet and liquid crystal display member - Google Patents

Abstract

To provide an adhesive sheet and a liquid crystal display member which are difficult to cause moire and can achieve high brightness even in the use of two liquid crystal cells.SOLUTION: There is provided an adhesive sheet 1 in which when measurement light rays are made to transmit through a sample formed by sticking an adhesive layer 2 to a soda lime glass with a thickness of 1.1 mm from the soda lime glass side, a brightness ratio of the sample with brightness at 15° from the normal of the sample with respect to brightness at 0° in a front face is 0.003 or more, and a depolarization degree calculated by the following expression (1) and expression (2) is 2.20% or less. Expression (1): polarization degree (%)={(transmittance (%) of parallel Nicol-transmittance (%) of cross Nicol/(transmittance (%) of parallel Nicol+transmittance (%) of cross Nicol)}×100. Expression (2): depolarization degree (%)={(polarization degree (%) of reference transparent adhesive layer-polarization degree (%) of adhesive layer)/(polarization degree (%) of reference transparent adhesive layer)}×100.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD The present invention relates to an adhesive sheet suitable for bonding two liquid crystal cells together, and a liquid crystal display member formed by bonding two liquid crystal cells together via an adhesive layer.

2. Description of the Related Art In recent years, as one type of display, a liquid crystal display device having a structure in which two liquid crystal cells are stacked has been known. According to such a liquid crystal display device, the contrast ratio can be greatly improved. In addition, by controlling the brightness of the image in each liquid crystal cell and sending different light information to both eyes, it is possible to display a stereoscopic image.

On the other hand, in the liquid crystal display device as described above, moire is likely to occur due to interference between the liquid crystal cells, and the displayed image becomes difficult to see. Therefore, in Patent Document 1, an attempt is made to alleviate the moire phenomenon by providing a light diffusion layer between two liquid crystal cells.

Japanese Patent Application Laid-Open No. 2007-310376

Here, a polarizing plate is usually arranged in each liquid crystal cell. When a light diffusing member is arranged between the liquid crystal cells in order to eliminate the moiré as described above, a phenomenon is observed in which the polarizing axis of part of the transmitted light is changed by the light diffusing member. Transmitted light whose polarization axis has changed will be blocked by the polarizing plate placed in the liquid crystal cell, which then passes through. Therefore, when a light diffusing member is arranged between the liquid crystal cells, the loss of backlight light increases, and there arises a problem that it becomes difficult to secure the luminance necessary for high-definition image display.

The present invention has been made in view of the actual situation as described above. The purpose is to provide parts.

In order to achieve the above objects, firstly, the present invention provides a pressure-sensitive adhesive sheet having at least a pressure-sensitive adhesive layer, wherein the pressure-sensitive adhesive layer is adhered to a soda lime glass having a thickness of 1.1 mm, and a sample thereof is provided, When the measurement light beam is transmitted from the soda lime glass side, the luminance ratio of the luminance at 15° from the normal line of the sample to the luminance at 0° in front of the sample is 0.003 or more, and the following formula Provided is a pressure-sensitive adhesive sheet characterized by having a degree of depolarization calculated by (1) and formula (2) of 2.20% or less (Invention 1).
Degree of polarization (%) = {(transmittance of parallel Nicols (%) - transmittance of crossed Nicols (%) / (transmittance of parallel Nicols (%) + transmittance of crossed Nicols (%))} x 100 ( 1)
Degree of depolarization (%) = {(Degree of polarization of reference transparent adhesive layer (%) - Degree of polarization of the adhesive layer (%))/(Degree of polarization of reference transparent adhesive layer (%))} x 100 (2)
Parallel Nicol Transmittance: Transmittance (%) of a sample in which an adhesive layer is sandwiched between two parallel Nicol polarizing plates
Transmittance of Crossed Nicols: Transmittance (%) of a sample in which an adhesive layer is sandwiched between two polarizing plates of Crossed Nicols

In the above invention (invention 1), the luminance ratio of the oblique 15° luminance to the front 0° luminance is large as described above, so that when two liquid crystal cells are bonded via the adhesive layer of the adhesive sheet, In addition, moiré is less likely to occur. In addition, since the degree of depolarization is small as described above, the brightness of the liquid crystal cell can be kept high.

In the above invention (invention 1), the pressure-sensitive adhesive layer is a composite pressure-sensitive adhesive layer comprising a light-diffusing pressure-sensitive adhesive layer containing light-diffusing fine particles and a transparent pressure-sensitive adhesive layer containing no light-diffusing fine particles. is preferred (Invention 2).

In the above inventions (inventions 1 and 2), it is preferable to use it for laminating two liquid crystal cells (invention 3).

In the above inventions (inventions 1 to 3), it is preferable that 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 are provided ( Invention 4).

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 5), wherein the adhesive layer is the adhesive layer of the adhesive sheet (Inventions 1 to 4).

According to the pressure-sensitive adhesive sheet and liquid crystal display member of the present invention, moiré hardly occurs even when two liquid crystal cells are used, and high brightness can be achieved.

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 liquid crystal display member 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 includes at least a pressure-sensitive adhesive layer. The pressure-sensitive adhesive sheet according to this embodiment is preferably used for bonding two liquid crystal cells together, but is not limited to this.

In the pressure-sensitive adhesive sheet according to the present embodiment, a sample obtained by attaching the pressure-sensitive adhesive layer to a soda-lime glass having a thickness of 1.1 mm was used, and when the measurement light beam was transmitted from the soda-lime glass side, the sample's method The luminance ratio of the luminance at 15° from the line to the luminance at 0° from the front of the sample is preferably 0.003 or more, and the degree of depolarization is preferably 2.20% or less. The luminance measurement is performed after calibrating so that the front 0° luminance of a blank without a sample is 100. FIG. The details of the method for measuring the brightness in this specification are as shown in the test examples described later.

Further, the degree of depolarization in this specification can be calculated as follows. The transmittance of a sample in which the adhesive layer is sandwiched between two parallel Nicol polarizing plates (polarizing plates showing linear polarization) (transmittance of parallel Nicol; %) and the adhesive layer between two cross Nicol polarizing plates. The degree of polarization (%) is calculated based on the following formula (1) from the transmittance of the sandwiched sample (transmittance of crossed Nicols; %). Also, for the transparent pressure-sensitive adhesive layer used as a reference (reference transparent pressure-sensitive adhesive layer), each transmittance (%) is measured in the same manner as described above, and the degree of polarization (%) is calculated.
Degree of polarization (%) = {(transmittance of parallel Nicols (%) - transmittance of crossed Nicols (%) / (transmittance of parallel Nicols (%) + transmittance of crossed Nicols (%))} x 100 ( 1)
Next, from the degree of polarization (%) obtained above, the depolarization degree (%) is calculated based on the following formula (2).
Degree of depolarization (%) = {(Degree of polarization of reference transparent adhesive layer (%) - Degree of polarization of the adhesive layer (%))/(Degree of polarization of reference transparent adhesive layer (%))} x 100 (2)

The reference transparent pressure-sensitive adhesive layer is not particularly limited as long as it is a pressure-sensitive adhesive layer made of a non-light-diffusing acrylic pressure-sensitive adhesive that does not contain light-diffusing fine particles. Physically, it is preferable to use an adhesive layer made of an acrylic adhesive having a haze of less than 1% and a total light transmittance of 99% or more. As a specific example, “Opteria (registered trademark) MO-3015” manufactured by Lintec Corporation and having a thickness of 250 μm can be used. In addition, the detailed measurement method is as shown in the test example mentioned later.

In the pressure-sensitive adhesive sheet according to the present embodiment, the luminance ratio of the oblique 15° luminance to the front 0° luminance is large as described above, so that when two liquid crystal cells are bonded via the adhesive layer of the pressure-sensitive adhesive sheet In addition, moiré is less likely to occur. In addition, since the degree of depolarization is small as described above, even if two liquid crystal cells are used, there is little luminance loss due to the adhesive sheet, and characters and images can be recognized with good visibility. Visibility can be evaluated, for example, by sandwiching the pressure-sensitive adhesive layer between two parallel Nicol polarizing plates and observing predetermined letters or figures through the laminate.

From the viewpoint of suppressing moire generation, the luminance ratio is preferably 0.003 or more, more preferably 0.006 or more, particularly preferably 0.050 or more, further preferably 0.100. It is preferable that it is above. Although the upper limit of the luminance ratio is not particularly limited, it is preferably 1.00 or less, more preferably 0.99 or less, and particularly preferably 0.50 or less.

Further, from the viewpoint of realizing the high brightness, the degree of depolarization is preferably 2.20% or less, more preferably 1.80% or less, and particularly preferably 1.60% or less. , and more preferably 1.20% or less. Although the lower limit of the degree of depolarization is not particularly limited, it is preferably 0.00% or more, more preferably 0.01% or more, and particularly preferably 0.10% or more.

The lower limit of the front 0° luminance is preferably 0.01 or more, more preferably 0.10 or more, and particularly preferably 0.20 or more, from the viewpoint of increasing the luminance in the straight-ahead direction. It is preferably 0.30 or more. The upper limit of the front 0° luminance is preferably 200 or less, more preferably 100 or less, particularly preferably 50 or less, and further preferably 5 or less. This makes it easier to satisfy the above luminance ratio.

The lower limit of the 15° oblique luminance is preferably 0.01 or more, more preferably 0.10 or more, particularly preferably 0.30 or more, and further preferably 0.60 or more. is preferred. This makes it easier to satisfy the above luminance ratio and more easily achieve high luminance. On the other hand, the upper limit of the 15° oblique luminance is not particularly limited, but is usually preferably 100 or less, more preferably 10 or less, particularly preferably 5 or less, and further preferably 1 or less. Preferably.

The haze value of the pressure-sensitive adhesive layer in the pressure-sensitive adhesive sheet according to the present embodiment is preferably 30% or more, more preferably 40% or more, particularly preferably 50% or more, further preferably 60% or more. is preferably This makes it easier to satisfy the above optical properties. Further, the haze value is preferably 100% or less, more preferably 99% or less, particularly preferably 97% or less, further preferably 95% or less. Thereby, the visibility of the image displayed by the liquid crystal cell is ensured. The haze value in this specification is a value measured according to JIS K7136:2000.

The total light transmittance of the pressure-sensitive adhesive layer in the pressure-sensitive adhesive sheet according to the present embodiment is preferably 80% or more as a lower limit, particularly preferably 90% or more, and further preferably 99% or more. . By setting the total light transmittance of the pressure-sensitive adhesive layer to the above range, the visibility as a display is good. On the other hand, although the upper limit of the total light transmittance of the pressure-sensitive adhesive layer is not particularly limited, it is usually 100% or less. The total light transmittance in this specification is a value measured according to JIS K7361-1:1997.

The pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet according to the present embodiment may consist of a single layer or a plurality of layers, but preferably includes at least a light-diffusing pressure-sensitive adhesive layer having light diffusing properties. Specifically, the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet according to the present embodiment may consist of a single layer of a light-diffusing pressure-sensitive adhesive layer containing light-diffusing fine particles. , and a transparent adhesive layer containing no light-diffusing fine particles.

Since the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet according to the present embodiment has a light-diffusing pressure-sensitive adhesive layer, the above optical properties can be easily satisfied. Further, when the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet according to the present embodiment is a composite pressure-sensitive adhesive layer comprising a light-diffusing pressure-sensitive adhesive layer containing light-diffusing fine particles and a transparent pressure-sensitive adhesive layer containing no light-diffusing fine particles, It is presumed that the transparent pressure-sensitive adhesive layer can relax the stress of the pressure-sensitive adhesive layer against the compression of the liquid crystal cell, which is two rigid plates. As a result, the hard plates can be satisfactorily bonded together, and the occurrence of unevenness in the displayed image can be suppressed.

In the above case, the pressure-sensitive adhesive layer may consist of two layers, a light-diffusing pressure-sensitive adhesive layer and a transparent pressure-sensitive adhesive layer, or the transparent pressure-sensitive adhesive layer, the light-diffusing pressure-sensitive adhesive layer and the transparent pressure-sensitive adhesive layer may be laminated in that order. It may consist of three layers. 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 transparent 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 adhesive layer 2 in this embodiment consists of two layers, a light diffusion adhesive layer 21 in contact with the release sheet 3a and a transparent adhesive layer 22 in contact with the release sheet 3b.

1. Each element 1-1. Adhesive Layer The light-diffusing adhesive layer 21 is preferably made of an adhesive containing light-diffusing fine particles. On the other hand, the transparent adhesive layer 22 is preferably composed of an adhesive that does not contain light diffusing fine particles. In addition, "not containing light diffusing fine particles" means "substantially not containing light diffusing fine particles". A case containing fine particles is also included. The amount is preferably 0.1% by mass or less, particularly preferably 0.01% by mass or less, further preferably 0.001% by mass or less, and preferably 0% by mass. Most preferred.

The type of adhesive that constitutes the light-diffusing adhesive layer 21 and the transparent adhesive layer 22 of the adhesive sheet 1 according to this embodiment is not particularly limited. For example, acrylic adhesives, polyester adhesives, polyurethane adhesives, rubber adhesives, silicone adhesives, and the like may be used. The adhesive may be emulsion type, solvent type or non-solvent type, and may be crosslinked or non-crosslinked. Among them, acrylic pressure-sensitive adhesives are preferable because they have excellent adhesive physical properties, optical properties, and the like. As the acrylic pressure-sensitive adhesive, a cross-linking type is preferable, and a thermal cross-linking type is more preferable. In addition, the acrylic pressure-sensitive adhesive may be active energy ray-curable or non-active energy ray-curable.

The pressure-sensitive adhesive forming the light diffusion pressure-sensitive adhesive layer 21 and the pressure-sensitive adhesive forming the transparent pressure-sensitive adhesive layer 22 may be of the same type or different types, but both are acrylic pressure-sensitive adhesives. Preferably. In addition, one of the adhesive constituting the light diffusion adhesive layer 21 and the adhesive constituting the transparent adhesive layer 22 is an active energy ray-curable acrylic adhesive, and the other is an active energy ray non-curable adhesive. Acrylic pressure-sensitive adhesives may be used, but both are preferably active energy ray-curable acrylic pressure-sensitive adhesives, or both are active energy ray non-curable acrylic pressure-sensitive adhesives.

Hereinafter, the case where the pressure-sensitive adhesive constituting the light diffusion pressure-sensitive adhesive layer 21 and the pressure-sensitive adhesive constituting the transparent pressure-sensitive adhesive layer 22 are both acrylic pressure-sensitive adhesives will be described, but the present invention is not limited thereto. do not have.

The pressure-sensitive adhesive constituting the light diffusion pressure-sensitive adhesive layer 21 and the pressure-sensitive adhesive constituting the transparent pressure-sensitive adhesive layer 22 are adhesive compositions containing a (meth)acrylic acid ester polymer (A) and a cross-linking agent (B). (hereinafter sometimes referred to as "adhesive composition P") is preferably crosslinked. In the case of the light diffusion adhesive layer 21, the adhesive composition P further contains light diffusion fine particles (C). The adhesive composition P also preferably contains an active energy ray-curable component (D), if desired. In this specification, (meth)acrylic acid means both acrylic acid and methacrylic acid. The same applies to other similar terms. In addition, the concept of "copolymer" is also included in "polymer".

(1) Components of adhesive composition (1-1) (meth)acrylic acid ester polymer (A)
The (meth)acrylic acid ester polymer (A) in the present embodiment contains a reactive group-containing monomer having a reactive group that reacts with the cross-linking agent (B) in the molecule as a monomer unit constituting the polymer. is preferred. A reactive group derived from this reactive group-containing monomer reacts with the cross-linking agent (B) to form a cross-linked structure (three-dimensional network structure), thereby obtaining a pressure-sensitive adhesive having desired cohesion.

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, a hydroxyl group-containing monomer or a carboxy group-containing monomer is preferable because of its excellent reactivity with the cross-linking agent (B).

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, from the viewpoint of the reactivity of the hydroxyl group in the obtained (meth)acrylic acid ester polymer (A) with the crosslinking agent (B) and the copolymerizability with other monomers, hydroxy having 1 to 4 carbon atoms A (meth)acrylic acid hydroxyalkyl ester having an alkyl group is preferred. Specifically, for example, 2-hydroxyethyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate and the like are preferred, and 2-hydroxyethyl acrylate and 4-hydroxybutyl acrylate are particularly preferred. be done. 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 (B) 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. Nitrogen atom-containing monomers, which will be described later, are excluded from the amino group-containing monomers.

The (meth)acrylic acid ester polymer (A) preferably contains a reactive group-containing monomer as a lower limit of 5% by mass or more, particularly 10% by mass or more, as a monomer unit constituting the polymer. is preferable, 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 40% by mass or less, particularly 30% by mass or less. It is preferably contained, more preferably 25% by mass or less. When the (meth)acrylic acid ester polymer (A) contains the reactive group-containing monomer in the amount described above as a monomer unit, a good crosslinked structure is formed in the resulting pressure-sensitive adhesive. Moreover, when the light-diffusing fine particles (C) are contained, the dispersibility of the light-diffusing fine particles (C) in the obtained pressure-sensitive adhesive tends to be improved.

It is also preferable that the (meth)acrylic acid ester polymer (A) does not contain a carboxy group-containing monomer as a monomer unit constituting the polymer. Since the carboxyl group is an acid component, the absence of the carboxyl group-containing monomer prevents the adhesive from being applied to objects to which the acid is attached, such as transparent conductive films such as tin-doped indium oxide (ITO), metal films, and the like. Even if it exists, it is possible to suppress those problems (corrosion, resistance value change, etc.) caused by the acid. However, it is permissible to contain a predetermined amount of the carboxy group-containing monomer to the extent that such problems do not occur. Specifically, the (meth)acrylic acid ester polymer (A) contains, as a monomer unit, a carboxy group-containing monomer of 0.1% by mass or less, preferably 0.01% by mass or less, more preferably 0.001% by mass. It is allowed to be contained in an amount of mass % or less.

The (meth)acrylic acid ester polymer (A) preferably contains a (meth)acrylic acid alkyl ester as a monomer unit constituting the polymer. Thereby, favorable adhesiveness can be expressed. Alkyl groups may be straight or branched.

As the (meth)acrylic acid alkyl ester, a (meth)acrylic acid alkyl ester having an alkyl group having 1 to 20 carbon atoms is preferable from the viewpoint of adhesiveness. Examples of (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 the adhesiveness, (meth)acrylic acid esters having an alkyl group having 4 to 8 carbon atoms are preferable, such as n-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, or ( Particularly preferred is isooctyl meth)acrylate, more preferred are n-butyl acrylate, 2-ethylhexyl acrylate, or isooctyl acrylate. 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, particularly 50% by mass or more, of (meth)acrylic acid alkyl ester as monomer units constituting the polymer. It is preferably contained in an amount of 75% by mass or more. When the lower limit of the content of the (meth)acrylic acid alkyl ester is the above, the (meth)acrylic acid ester polymer (A) can exhibit suitable adhesiveness. In addition, the difference in refractive index between the (meth)acrylic acid ester polymer (A) and the light diffusion fine particles (C) can be kept small. On the other hand, the (meth)acrylic acid ester polymer (A) preferably contains 95% by mass or less, and preferably 90% by mass or less, of (meth)acrylic acid alkyl ester as a monomer unit constituting the polymer. is more preferable, and it is particularly preferable to contain 85% by mass or less. When the upper limit of the content of the (meth)acrylic acid alkyl ester is the above, a suitable amount of another monomer component such as a reactive functional group-containing monomer is introduced into the (meth)acrylic acid ester polymer (A). be able to.

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 polymer. The alicyclic structure-containing monomer raises the glass transition temperature of the polymer and increases the storage elastic modulus of the resulting pressure-sensitive adhesive. In addition, 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, making the resulting pressure-sensitive adhesive excellent in conformability to unevenness. be able to.

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 exhibiting the step conformability of the obtained adhesive, the alicyclic structure is preferably 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 addition, the number of carbon atoms in the alicyclic structure (refers to the total number of carbon atoms in the ring-forming portion, and when multiple rings are present independently, refers to the total number of carbon atoms) is usually 5. It is preferably 7 or more, and particularly preferably 7 or more. On the other hand, the upper limit of the number of carbon atoms in the alicyclic structure is not particularly limited, but from the same viewpoint as above, it is preferably 15 or less, particularly preferably 10 or less.

Specific examples of the alicyclic structure-containing monomer include cyclohexyl (meth)acrylate, dicyclopentanyl (meth)acrylate, adamantyl (meth)acrylate, isobornyl (meth)acrylate, (meth)acrylic Examples include dicyclopentenyl acid, dicyclopentenyloxyethyl (meth)acrylate, and among them, dicyclopentenyl (meth)acrylate (the number of carbon atoms in the alicyclic structure: 10), adamantyl (meth)acrylate (the number of carbon atoms in the alicyclic structure: 10) or isobornyl (meth)acrylate (the number of carbon atoms in the alicyclic structure: 7) is preferred, and isobornyl (meth)acrylate is particularly preferred. and isobornyl acrylate are 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, it preferably contains 1% by mass or more of the alicyclic structure-containing monomer. , In particular, it is preferably contained in an amount of 5% by mass or more, and more preferably 10% by mass or more. Also, the content is preferably 30% by mass or less, particularly preferably 25% by mass or less, and further preferably 20% by mass or less. When the content of the alicyclic structure-containing monomer is within the above range, it becomes easier to adjust the optical properties described above to the preferable range.

The (meth)acrylic acid ester polymer (A) preferably contains a nitrogen atom-containing monomer as a monomer unit constituting the polymer. Predetermined polarity is imparted to the pressure-sensitive adhesive by allowing nitrogen atom-containing monomers to be present in the polymer as structural units, and excellent affinity is obtained even for adherends having a certain degree of polarity, such as glass. can be As the nitrogen atom-containing monomer, a monomer having a nitrogen-containing heterocyclic ring is preferable from the viewpoint of imparting appropriate rigidity to the (meth)acrylic acid ester polymer (A). In addition, from the viewpoint of increasing the degree of freedom of the portion derived from the nitrogen atom-containing monomer in the higher-order structure of the pressure-sensitive adhesive, the nitrogen atom-containing monomer forms the (meth)acrylic acid ester polymer (A). preferably contains no reactive unsaturated double bond groups other than the one polymerizable group used in the polymerization of .

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. 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 a nitrogen atom-containing monomer as a monomer unit constituting the polymer, it preferably contains 1 mass% or more of the nitrogen atom-containing monomer, particularly 2 mass. % or more, more preferably 4 mass % or more. In addition, the (meth)acrylic acid ester polymer (A) preferably contains 24% by mass or less of the nitrogen atom-containing monomer, and particularly 16% by mass or less, as a monomer unit constituting the polymer. It is preferably contained in an amount of 8% by mass or less. When the content of the nitrogen atom-containing monomer is within the above range, the resulting pressure-sensitive adhesive can sufficiently exhibit excellent adhesive strength to glass.

The (meth)acrylic acid ester polymer (A) preferably contains a monomer having an aromatic ring structure in the molecule (aromatic ring-containing monomer) as a monomer unit constituting the polymer. By using such an aromatic ring-containing monomer, the resulting (meth)acrylate polymer (A) can have a high refractive index.

A (meth)acrylic acid ester having an aromatic ring is preferable as the aromatic ring-containing monomer. Examples of the aromatic ring include benzene ring, naphthalene ring, anthracene ring, biphenyl ring, fluorene ring, etc. Among them, benzene ring is preferred. Examples of (meth)acrylic acid esters having a benzene ring include benzyl (meth)acrylate, benzyloxyethyl (meth)acrylate, phenoxyethyl (meth)acrylate, phenoxydiethylene glycol (meth)acrylate, and ethylene oxide-modified Examples include cresol (meth)acrylate, ethylene oxide-modified nonylphenol (meth)acrylate, biphenyloxyethyl (meth)acrylate, styrene, etc. Among them, benzyl (meth)acrylate and phenoxyethyl (meth)acrylate are preferred. . These may be used alone or in combination of two or more.

When the (meth)acrylic acid ester polymer (A) contains an aromatic ring-containing monomer as a monomer unit constituting the polymer, it preferably contains 1 mass% or more of the aromatic ring-containing monomer, particularly 10 mass. % or more, more preferably 26 mass % or more. Also, the content is preferably 60% by mass or less, particularly preferably 50% by mass or less, and further preferably 40% by mass or less. When the content of the aromatic ring-containing monomer is within the above range, even if the light diffusion fine particles (C) with a high refractive index are used, the refractive index between the (meth)acrylic acid ester polymer (A) and the fine particles (C) It becomes easy to adjust the rate difference to a desired range.

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 so as not to inhibit the above-described effects of the reactive functional group-containing monomers. Examples of such monomers include alkoxyalkyl (meth)acrylates such as methoxyethyl (meth)acrylate and ethoxyethyl (meth)acrylate, vinyl acetate, and styrene. These may be used alone or in combination of two or more.

The (meth)acrylate polymer (A) is preferably a linear polymer. By being a straight-chain polymer, entanglement of molecular chains is likely to occur, and an improvement in cohesive strength can be expected.

Moreover, the (meth)acrylate polymer (A) is preferably a solution polymer obtained by a solution polymerization method. Since it is a solution polymer, it becomes easy to obtain a polymer with a high molecular weight, and an improvement in cohesion can be expected.

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 200,000 or more, more preferably 300,000 or more, and particularly preferably 400,000 or more. As a result, the durability and step followability under high-temperature and high-humidity conditions are further improved. Further, the weight average molecular weight is more preferably 500,000 or more. This makes it possible to obtain a high storage elastic modulus to the extent that the pressure-sensitive adhesive containing the light-diffusing fine particles (C) exhibits sufficient cohesion. In addition, there is a tendency to improve the dispersibility of the light diffusing fine particles (C) in the pressure-sensitive adhesive.

In addition, the weight average molecular weight of the (meth)acrylate polymer (A) is preferably 1,500,000 or less, more preferably 1,200,000 or less, and particularly preferably 1,000,000 or less as an upper limit. , and more preferably 800,000 or less. When the upper limit of the weight-average molecular weight of the (meth)acrylic acid ester polymer (A) is above, the initial conformability to irregularities is more excellent. The weight average molecular weight in this specification is a value in terms of standard polystyrene measured by a 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.

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

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

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

The content of the cross-linking agent (B) in the adhesive composition P is preferably 0.01 parts by mass or more, particularly 0.01 part by mass, based on 100 parts by mass of the (meth)acrylic acid ester polymer (A). 05 parts by mass or more, and more preferably 0.1 parts by mass or more. 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 parts by mass or less. is preferred. When the content of the cross-linking agent (B) is within the above range, the storage elastic modulus, gel fraction, adhesive strength, etc. of the resulting pressure-sensitive adhesive tend to be suitable.

(1-3) Light diffusion microparticles (C)
The light diffusing fine particles (C) may be any as long as the adhesive layer 2 (light diffusing adhesive layer 21) can satisfy the physical properties described above.

Examples of light diffusing fine particles (C) include inorganic fine particles such as silica, calcium carbonate, aluminum hydroxide, magnesium hydroxide, clay, talc and titanium dioxide; organic fine particles such as acrylic resins, polystyrene resins, polyethylene resins and epoxy resins; light-transmitting fine particles of the system; 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, fine particles made of silicone resin are preferable. This makes it easier to keep the difference in refractive index from the (meth)acrylic acid ester (A) within the range described below. The above light diffusing fine particles (C) may be used singly or in combination of two or more.

As for the shape of the light diffusing fine particles (C), spherical fine particles with uniform light diffusion are preferable. The average particle diameter of the light diffusing fine particles (C) measured by the centrifugal sedimentation light transmission method is preferably 1.0 μm or more, particularly preferably 2.0 μm or more, further preferably 3.0 μm or more as a lower limit. is preferred. When the lower limit of the average particle size is above, the 15° oblique luminance tends to fall within the preferable range. On the other hand, the upper limit of the average particle diameter is preferably 10 μm or less, particularly preferably 8 μm or less, and further preferably 6 μm or less. When the upper limit value of the average particle size is above, the 0° front luminance tends to fall within a preferable range, and a high-definition display image can be displayed satisfactorily.

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 refractive index of the light diffusing fine particles (C) is preferably 1.20 or higher, more preferably 1.30 or higher, and particularly preferably 1.40 or higher. Also, the refractive index of the light diffusing fine particles is preferably 1.80 or less, more preferably 1.60 or less, and particularly preferably 1.54 or less. When the refractive index of the light diffusing fine particles is within the above range, the optical properties described above are more likely to be satisfied.

The refractive index of the light diffusing fine particles can be measured, for example, by the following method. That is, fine particles are placed on a slide glass, a refractive index standard solution is dropped on the fine particles, and a cover glass is covered to prepare a sample. The sample is observed under a microscope, and the refractive index of the refractive index standard solution at which the outline of the fine particles becomes most difficult to see is taken as the refractive index of the fine particles.

The absolute value of the difference (refractive index difference) between the refractive index of the light diffusing fine particles (C) and the refractive index of the (meth)acrylic ester polymer (A) is preferably 0.004 or more, and preferably 0.004 or more. 008 or more, particularly preferably 0.010 or more, and further preferably 0.020 or more. The absolute value of the refractive index difference is preferably 0.100 or less, more preferably 0.090 or less, particularly preferably 0.070 or less, and further preferably 0.050 or less. Preferably. When the absolute value of the refractive index difference is within the above range, the optical physical properties described above are easily satisfied.

The refractive index of the (meth)acrylic acid ester polymer (A) can be measured using an Abbe refractometer (manufactured by Atago Co., Ltd., for example) under the conditions of a measurement wavelength of 589 nm and a measurement temperature of 23°C. .

The content of the light diffusing fine particles (C) in the adhesive composition P may be any amount that can satisfy the physical properties described above. Specifically, the content of the light diffusing fine particles (C) is preferably 1% by mass or more, more preferably 5% by mass or more, and particularly preferably 10% by mass or more. In addition, the content of the light diffusing fine particles (C) is preferably 40% by mass or less, more preferably 30% by mass or less, particularly more preferably 20% by mass or less, further preferably 15% by mass. % or less. When the content of the light diffusing fine particles (C) is within the above range, the optical properties described above are easily satisfied.

(1-4) Active energy ray-curable component (D)
When the adhesive constituting the light diffusion adhesive layer 21 or the adhesive constituting the transparent adhesive layer 22 is an active energy ray-curable adhesive, the adhesive composition P further contains an active energy ray-curable component ( D) is preferably contained.

In the adhesive obtained by crosslinking the adhesive composition P containing the active energy ray-curable component (D), the active energy ray-curable component (D) is polymerized with each other, and the It is presumed that the polymerized active energy ray-curable component (D) is entangled with the crosslinked structure (three-dimensional network structure) of the (meth)acrylate polymer (A). A pressure-sensitive adhesive having such a high-order structure is particularly excellent in durability and conformability to unevenness under high-temperature and high-humidity conditions.

The active energy ray-curable component (D) is not particularly limited as long as it is a component that cures by irradiation with an active energy ray and provides the above effects, and may be any of monomers, oligomers or polymers. may be a mixture of Among them, polyfunctional acrylate-based monomers, which are more excellent in durability, are preferred.

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, tricyclodecanedimethanol (meth)acrylate, caprolactone-modified dicyclopentenyl di( meth)acrylate, ethylene oxide-modified phosphoric acid di(meth)acrylate, di(acryloxyethyl)isocyanurate, allylated cyclohexyl di(meth)acrylate, ethoxylated bisphenol A diacrylate, 9,9-bis[4-(2- Bifunctional type such as acryloyloxyethoxy)phenyl]fluorene; trimethylolpropane tri(meth)acrylate, dipentaerythritol tri(meth)acrylate, propionic acid-modified dipentaerythritol tri(meth)acrylate, pentaerythritol tri(meth)acrylate , propylene oxide-modified trimethylolpropane tri(meth)acrylate, tris(acryloxyethyl) isocyanurate, ε-caprolactone-modified tris-(2-(meth)acryloxyethyl) isocyanurate; diglycerin tetra ( Tetrafunctional type such as meth)acrylate and pentaerythritol tetra(meth)acrylate; Pentafunctional type such as propionic acid-modified dipentaerythritol penta(meth)acrylate; Dipentaerythritol hexa(meth)acrylate, caprolactone-modified dipentaerythritol hexa( Hexafunctional type such as meth)acrylate and the like can be mentioned. These may be used individually by 1 type, and may be used in combination of 2 or more type. From the viewpoint of compatibility with the (meth)acrylic acid ester polymer (A), the polyfunctional acrylate monomer preferably has a molecular weight of less than 1,000.

The content of the active energy ray-curable component (D) in the adhesive composition P is, from the viewpoint of improving durability and conformability to unevenness, relative to 100 parts by mass of the (meth)acrylic acid ester polymer (A), The lower limit is preferably 1 part by mass or more, particularly preferably 3 parts by mass or more, and further preferably 6 parts by mass or more. On the other hand, the content is preferably 30 parts by mass or less, particularly preferably 20 parts by mass or less, and 10 parts by mass or less as an upper limit from the viewpoint of the adhesive strength of the adhesive after irradiation with active energy rays. is more preferable.

(1-5) Photopolymerization initiator (E)
When the adhesive constituting the light diffusion adhesive layer 21 or the adhesive constituting the transparent adhesive layer 22 is an active energy ray-curable adhesive, when ultraviolet rays are used as the active energy ray for curing the adhesive Preferably, the adhesive composition P further contains a photopolymerization initiator (E). By containing the photopolymerization initiator (E) in this way, the active energy ray-curable component (D) can be efficiently polymerized, and the polymerization curing time and the irradiation dose of the active energy ray can be reduced. can.

Examples of such photoinitiators (E) 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'-diethylamino Benzophenone, dichlorobenzophenone, 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-trimethylbenzoyl-diphenyl-phosphine oxide, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide and the like. These may be used alone or in combination of two or more.

Among the above, a phosphine oxide-based photopolymerization initiator is preferred because it is easily cleaved and easily cures the pressure-sensitive adhesive even when irradiated with ultraviolet rays through a material containing an ultraviolet absorber. Specifically, 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide and the like are preferred.

The content of the photopolymerization initiator (E) in the adhesive composition P is preferably 0.1 parts by mass or more as a lower limit with respect to 100 parts by mass of the active energy ray-curable component (D). In particular, it is preferably 1 part by mass or more, more preferably 5 parts by mass or more. Also, 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 The adhesive composition P may optionally contain various additives commonly used in acrylic adhesives, such as silane coupling agents, antistatic agents, rust inhibitors, and ultraviolet absorbers. , tackifiers, antioxidants, light stabilizers, softeners, refractive index modifiers and the like can be added. It should be noted that a polymerization solvent and a dilution solvent, which will be described later, are not included in the additives constituting the adhesive composition P.

The adhesive composition P preferably contains a silane coupling agent among the above. As a result, even if the material of the adherend is plastic or glass, the adhesion to the adherend is improved, and the durability and step conformability under high temperature and high humidity conditions are superior. become a thing.

As the silane coupling agent, an organosilicon compound having at least one alkoxysilyl group in the molecule, having good compatibility with the (meth)acrylic acid ester polymer (A), and having optical transparency. preferable.

Such silane coupling agents include, for example, vinyltrimethoxysilane, vinyltriethoxysilane, methacryloxypropyltrimethoxysilane and like silicon compounds containing polymerizable unsaturated groups, 3-glycidoxypropyltrimethoxysilane, 2-( Silicon compounds having an epoxy structure such as 3,4-epoxycyclohexyl)ethyltrimethoxysilane, mercapto group-containing silicon compounds such as 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, and 3-mercaptopropyldimethoxymethylsilane , 3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane and other amino group-containing silicon compounds, 3-chloropropyltrimethoxysilane, 3-isocyanatopropyltriethoxysilane, or at least one of these, and an alkyl group-containing silicon compound such as methyltriethoxysilane, ethyltriethoxysilane, methyltrimethoxysilane, ethyltrimethoxysilane, etc. and condensates of. 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 in the adhesive composition P is preferably 0.01 parts by mass or more, particularly 0.05 parts by mass, relative to 100 parts by mass of the (meth)acrylic acid ester polymer (A). It is preferably at least 0.1 part by mass, more preferably at least 0.1 part by mass. Also, 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.

Examples of the antistatic agent include ionic compounds, nonionic compounds, etc. Among them, ionic compounds are preferable. As the ionic compound, a nitrogen-containing onium salt, a sulfur-containing onium salt, a phosphorus-containing onium salt, an alkali metal salt or an alkaline earth metal salt is preferable, and from the viewpoint of durability, a nitrogen-containing onium salt or an alkali metal salt is particularly preferable. The nitrogen-containing onium salt is an ionic compound composed of a nitrogen-containing heterocyclic cation (e.g., pyridine ring, imidazole ring, etc.) and its counter anion (e.g., halogenated phosphate anion, sulfonylimide anion, etc.). preferable.

Specific examples of nitrogen-containing onium salts having a pyridine ring and a sulfonylimide anion include 1-decylpyridinium bis(fluorosulfonyl)imide, 1-ethylpyridinium bis(fluorosulfonyl)imide, 1-butylpyridinium bis(fluorosulfonyl) imide, 1-hexylpyridinium bis(fluorosulfonyl)imide, 1-butyl-3-methylpyridinium bis(fluorosulfonyl)imide, 1-butyl-4-methylpyridinium bis(fluorosulfonyl)imide, 1-hexyl-3 -methylpyridinium bis(fluorosulfonyl)imide, 1-butyl-3,4-dimethylpyridinium bis(fluorosulfonyl)imide, 4-methyl-1-octylpyridinium bis(fluorosulfonyl)imide and the like.

The content of the antistatic agent in the adhesive composition P is preferably 0.01 to 30% by mass, particularly preferably 0.1 to 10% by mass, further preferably 1 to 8% by mass. Preferably.

(2) Preparation of adhesive composition The adhesive composition P is produced by producing a (meth) acrylic acid ester polymer (A), the obtained (meth) acrylic acid ester polymer (A), and a cross-linking agent ( B) and, if desired, the active energy ray-curable component (D), the photopolymerization initiator (E), additives and the like are added. In the case of the light diffusion pressure-sensitive adhesive layer 21, light diffusion fine particles (C) are further blended.

The (meth)acrylic acid ester polymer (A) can be produced by polymerizing a mixture of monomers constituting the polymer by a conventional radical polymerization method. Polymerization of the (meth)acrylic acid ester polymer (A) is preferably carried out by a solution polymerization method, optionally using a polymerization initiator. However, the present invention is not limited to this, and may be polymerized without a solvent. Examples of the polymerization solvent include ethyl acetate, n-butyl acetate, isobutyl acetate, toluene, acetone, hexane, and methyl ethyl ketone, and two or more of them may be used 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-butyl perbenzoate, 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)acrylic acid ester polymer (A) is obtained, the solution of the (meth)acrylic acid ester polymer (A) is added with the cross-linking agent (B), and if desired, a diluent solvent, light diffusing fine particles (C), An active energy ray-curable component (D), a photopolymerization initiator (E), additives and the like are added and thoroughly mixed to obtain a solvent-diluted adhesive composition P (coating solution). In any of the above components, if a solid one is used, or if precipitation occurs when mixed with other components in an undiluted state, the component is added alone in advance to a dilution solvent. It may be dissolved or diluted prior to mixing with other ingredients.

Examples of the diluting solvent include aliphatic hydrocarbons such as hexane, heptane and cyclohexane; aromatic hydrocarbons such as toluene and xylene; halogenated hydrocarbons such as methylene chloride and ethylene chloride; Alcohols such as 1-methoxy-2-propanol, ketones such as acetone, methyl ethyl ketone, 2-pentanone, isophorone and cyclohexanone, esters such as ethyl acetate and butyl acetate, and cellosolve solvents such as ethyl cellosolve are used.

The concentration/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 concentration of the adhesive composition P is diluted to 10 to 60% 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. In this case, the adhesive composition P becomes a coating solution in which the polymerization solvent for the (meth)acrylic acid ester polymer (A) is used as the diluting solvent.

(3) Formation of Adhesive Layer It is preferable that each of the light diffusion adhesive layer 21 and the transparent adhesive layer 22 in the present embodiment is made of an adhesive obtained by cross-linking (the coating layer of) the adhesive composition P. Crosslinking of the adhesive composition P can usually be performed by heat treatment. This heat treatment can also serve as a drying treatment for volatilizing the diluent solvent from the coating layer of the adhesive composition P applied to the desired object.

The heating temperature of the heat treatment is preferably 50 to 150°C, particularly preferably 70 to 120°C. The heating time is preferably 10 seconds to 10 minutes, more preferably 50 seconds to 2 minutes.

After the heat treatment, if necessary, a curing period of about 1 to 2 weeks may be provided at room temperature (eg, 23° C., 50% RH). If the curing period is required, the adhesive is formed after the curing period has elapsed, and if the curing period is not required, the adhesive is formed after the heat treatment is completed.

By the above heat treatment (and curing), the (meth)acrylate polymer (A) is sufficiently crosslinked via the crosslinking agent (B).

The adhesive layer 2 in this embodiment can be obtained by laminating the light diffusion adhesive layer 21 and the transparent adhesive layer 22 . The timing of lamination may be before curing each pressure-sensitive adhesive layer or after curing. However, in order to further increase the adhesion between the light-diffusing adhesive layer 21 and the transparent adhesive layer 22, it is preferable to laminate the adhesive layers before curing them.

1-2. Release Sheet The release sheets 3a and 3b protect the adhesive layer 2 until the adhesive sheet 1 is used, and are peeled off when the adhesive sheet 1 (adhesive layer 2) is used. In the adhesive sheet 1 according to this embodiment, one or both of the release sheets 3a and 3b are not necessarily required.

Examples of the release sheets 3a and 3b include polyethylene film, polypropylene film, polybutene film, polybutadiene film, polymethylpentene film, polyvinyl chloride film, vinyl chloride copolymer film, polyethylene terephthalate film, polyethylene naphthalate film, and polybutylene. Terephthalate film, polyurethane film, ethylene vinyl acetate film, ionomer resin film, ethylene/(meth)acrylic acid copolymer film, ethylene/(meth)acrylic acid ester copolymer film, polystyrene film, polycarbonate film, polyimide film, fluorine A resin film or the like is used. Crosslinked films of these are also used. Furthermore, a laminated film of these may be used.

The release surfaces of the release sheets 3a and 3b (especially the surfaces in contact with the pressure-sensitive adhesive layer 2) 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.

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

2. Manufacture of Adhesive Sheet As an example of manufacturing 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, followed by heat treatment. Then, the adhesive composition P is thermally crosslinked 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 diffusion adhesive layer 21 is applied to the release surface of the other release sheet 3b, and heat treatment is performed to thermally crosslink the adhesive composition P, A coating layer is formed to obtain a release sheet 3b with a coating layer. Then, the release sheet 3a with the coating layer and the release sheet 3b with the coating layer are pasted together so that both coating layers are in contact with each other. Here, a plurality of release sheets with coating layers may be prepared, and the coating layers may be pasted together in a desired number and in a desired lamination order. When a curing period is required, the curing period is set, and when the curing period is not required, the laminated coating layer becomes the pressure-sensitive adhesive layer 2 as it is. As a result, the pressure-sensitive adhesive sheet 1 having the pressure-sensitive adhesive layer 2 that is a laminate of the light diffusion pressure-sensitive adhesive layer 21 and the transparent pressure-sensitive adhesive layer 22 is obtained. The conditions for heat treatment and curing are as described above.

The coating layer for forming the transparent adhesive layer 22 and the coating layer for forming the light diffusion adhesive layer 21 may each be held between two release sheets to form the transparent adhesive layer 22. When the coating layer for forming the light-diffusing adhesive layer 21 and the coating layer for forming the light-diffusing pressure-sensitive adhesive layer 21 are laminated, one of the release sheets may be peeled off.

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

3. Physical Properties (1) 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 transparent 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, and most preferably 200 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 optical properties described above, and the stress of the pressure-sensitive adhesive layer against compression of the liquid crystal cell, which is two rigid plates, is easily alleviated. The ability to bond to a hard plate and the ability to prevent unevenness in image display are 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 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. Also, the thickness of the light-diffusing pressure-sensitive adhesive layer 21 is preferably 200 μm or less, particularly preferably 150 μm or less, further preferably 100 μm or less. When the thickness of the light-diffusing pressure-sensitive adhesive layer 21 is within the above range, it becomes easier to satisfy the optical property values described above.

The lower limit of the thickness of the transparent 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 transparent adhesive layer 22 to the above, 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 hard plate bonding property and image display unevenness can be improved. The prevention of is further improved. On the other hand, the upper limit of the thickness of the transparent 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 transparent pressure-sensitive adhesive layer 22 to the above range, it is possible to prevent the obtained liquid crystal display member from becoming unnecessarily thick.

(2) Gel Fraction The gel fraction of the adhesive constituting the adhesive layer 2 is preferably 30% or more, and preferably 40% or more, from the viewpoint of durability and step conformability under high temperature and high humidity conditions. is more preferably 45% or more, and more preferably 50% or more. Further, the gel fraction is preferably 90% or less, more preferably 80% or less, particularly preferably 70% or less, further preferably 65% or less. Thereby, the sticking property to the liquid crystal cell becomes more excellent. In addition, the method for measuring the gel fraction of the pressure-sensitive adhesive in this specification is as shown in the test examples described later.

When the adhesive constituting the adhesive layer 2 (at least one of the light diffusion adhesive layer 2 and the transparent adhesive layer 22) is active energy ray-curable, the gel fraction of the adhesive after active energy ray curing is , is preferably 60% or more, more preferably 70% or more, and particularly preferably 75% or more. As a result, the durability and step followability under high-temperature and high-humidity conditions are further improved. Moreover, the gel fraction after the active energy ray curing is preferably 95% or less, more preferably 85% or less, and particularly preferably 80% or less. As a result, good adhesive strength is exhibited, and the adhesiveness to the adherend becomes more excellent.

(3) Adhesive strength Adhesive strength to soda lime glass on the light diffusion adhesive layer 21 side of the adhesive layer 2 of the adhesive sheet 1 according to the present embodiment is from the viewpoint of durability and step followability under high temperature and high humidity conditions. Therefore, it is preferably 5 N/25 mm or more, more preferably 10 N/25 mm or more, particularly preferably 20 N/25 mm or more, further preferably 25 N/25 mm or more. The adhesive strength is preferably 100 N/25 mm or less, more preferably 80 N/25 mm or less, particularly preferably 60 N/25 mm or less, and further preferably 50 N/25 mm or less. . As a result, good reworkability can be obtained, and the adherend can be reused even when a lamination error occurs.

When the light-diffusing pressure-sensitive adhesive layer 21 is active energy ray-curable, the adhesive strength of the light-diffusing pressure-sensitive adhesive layer 21 side of the pressure-sensitive adhesive layer 2 to soda lime glass after irradiation with active energy rays is 10 N/25 mm or more. It is preferably 20 N/25 mm or more, particularly preferably 40 N/25 mm or more, further preferably 60 N/25 mm or more. As a result, the durability and step followability under high-temperature and high-humidity conditions are further improved. The adhesive strength is preferably 100 N/25 mm or less, more preferably 90 N/25 mm or less, particularly preferably 80 N/25 mm or less, and further preferably 75 N/25 mm or less. .

The adhesive strength of the transparent adhesive layer 22 side of the adhesive layer 2 of the adhesive sheet 1 according to the present embodiment to soda lime glass is 5 N/25 mm or more from the viewpoint of durability and step conformability under high temperature and high humidity conditions. , more preferably 10 N/25 mm or more, particularly preferably 20 N/25 mm or more, further preferably 25 N/25 mm or more. The adhesive strength is preferably 100 N/25 mm or less, more preferably 80 N/25 mm or less, particularly preferably 60 N/25 mm or less, and further preferably 50 N/25 mm or less. . As a result, good reworkability can be obtained, and the adherend can be reused even when a lamination error occurs.

When the transparent adhesive layer 22 is active energy ray-curable, the adhesive strength of the transparent adhesive layer 22 side of the adhesive layer 2 to soda lime glass after irradiation with active energy rays is preferably 10 N/25 mm or more. It is more preferably 20 N/25 mm or more, particularly preferably 40 N/25 mm or more, further preferably 60 N/25 mm or more. As a result, the durability and step followability under high-temperature and high-humidity conditions are further improved. The adhesive strength is preferably 100 N/25 mm or less, more preferably 90 N/25 mm or less, particularly preferably 80 N/25 mm or less, and further preferably 75 N/25 mm or less. .

Here, the adhesive strength in this specification basically refers to the adhesive strength measured by the 180 degree peeling method according to JIS Z0237: 2009, but the measurement sample has a width of 25 mm and a length of 100 mm. It is attached to an adherend, pressurized at 0.5 MPa and 50° C. for 20 minutes, then left under normal pressure, 23° C. and 50% RH for 24 hours, and then measured at a peel rate of 300 mm/min. shall be

[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 satisfies the optical properties described above. Due to the action of the pressure-sensitive adhesive layer, such a liquid crystal display member is less susceptible to moiré and can achieve high brightness.

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 transparent 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 transparent adhesive layer 22 in contact with the second liquid crystal cell 5b.

The light-diffusing pressure-sensitive adhesive layer 21 and the transparent pressure-sensitive adhesive layer 22 are the light-diffusing pressure-sensitive adhesive layer 21 and the transparent pressure-sensitive adhesive layer 22 of the pressure-sensitive adhesive sheet 1 described above, 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, especially liquid crystal displays that display stereoscopic images or display 4K or 8K high-definition images. , is 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 the state in which the release sheet 3b having flexibility 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, the transparent pressure-sensitive adhesive layer 22 functions as a cushioning material when attached to the liquid crystal cell 5a, and can prevent 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 transparent adhesive layer 22, and the exposed transparent adhesive layer 22 is coated with the second adhesive layer. The liquid crystal cell 5b is pasted. Here, stress is generated in the pressure-sensitive adhesive layer 2 by lamination with the liquid crystal cell 5b. However, since the pressure-sensitive adhesive layer 2 has the transparent pressure-sensitive adhesive layer 22, the stress is alleviated, and the stress is prevented from acting on the liquid crystal cells 5a and 5b. Furthermore, the transparent pressure-sensitive adhesive layer 22 also adjusts the excessive pressure during lamination of the liquid crystal cell 5b. In the liquid crystal display member 4 obtained in this way, the alignment of the liquid crystal cells 5a and 5b is prevented from being disturbed by the residual stress of the pressure-sensitive adhesive layer 2 and the resulting uneven repulsive force, thereby suppressing the occurrence of uneven display images. The display image is displayed satisfactorily. In addition, the cushioning properties of the transparent adhesive layer 22 can prevent air bubbles from forming at the interface when the liquid crystal cells 5a and 5b, which are hard plates, are stuck together.

When the adhesive layer 2 (the light diffusion adhesive layer 21 and/or the transparent adhesive layer 22) is active energy ray-curable, the first liquid crystal cell 5a and the second liquid crystal cell 5b are attached as described above. After combining, the adhesive layer 2 is irradiated with active energy rays through the first liquid crystal cell 5a or the second liquid crystal cell 5b to cure the adhesive layer 2 . As a result, the pressure-sensitive adhesive layer 2 becomes more excellent in durability and conformability to irregularities.

The active energy ray refers to an electromagnetic wave or a charged particle beam that has energy quanta, and specifically includes ultraviolet rays, electron beams, and the like. Among active energy rays, ultraviolet rays are particularly preferable because they are easy to handle.

Ultraviolet irradiation can ^be performed by a high-pressure mercury lamp, a fusion H lamp, a xenon lamp, or ^the like. is preferred. The amount of light is preferably 50 to 10000 mJ/cm ² , more preferably 200 to 7000 mJ/cm ² and particularly preferably 500 to 3000 mJ/cm ² . On the other hand, electron beam irradiation can be performed by an electron beam accelerator or the like, and the electron beam irradiation dose is preferably about 10 to 1000 krad.

Due to the action of the adhesive layer 2 that satisfies the optical properties described above, the liquid crystal display member 4 hardly causes moiré and can obtain a display image with high brightness.

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 embodiment 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.

[Example 1]
1. Preparation of adhesive composition for light diffusion adhesive layer 27.5 parts by mass of n-butyl acrylate, 27.5 parts by mass of 2-ethylhexyl acrylate, 15 parts by mass of isobornyl acrylate, 5 parts by mass of N-acryloylmorpholine, and 25 parts by mass of 2-hydroxyethyl acrylate were copolymerized by a solution polymerization method to prepare a (meth)acrylic acid ester 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

100 parts by mass of the (meth)acrylic acid ester polymer (A) obtained above (solid content conversion value; the same applies hereinafter), and trimethylolpropane-modified tolylene diisocyanate (manufactured by Toyochem Co., Ltd., product Name "BHS8515") 0.2 parts by mass and fine particles (C1; Momentive Performance Materials Co., Ltd. Japan Co., Ltd., product name "Tospearl 145", average particle size: 4.5 µm, refractive index: 1.43) 13.5 parts by mass, and 0.5 parts by mass of 3-glycidoxypropyltrimethoxysilane as a silane coupling agent. 13 parts by mass were mixed, sufficiently stirred, and diluted with methyl ethyl ketone to obtain a coating solution of the adhesive composition for the light diffusion adhesive layer.

2. Preparation of adhesive composition for transparent adhesive layer Prepare an adhesive composition for the transparent adhesive layer in the same manner as the adhesive composition for the light-diffusing adhesive layer, except that the light-diffusing fine particles (C) are not blended. bottom.

3. Formation of Light Diffusion Adhesive Layer Step 1 above. The coating solution of the adhesive composition for the light diffusion adhesive layer prepared in , is applied to a light release type release sheet (Lintec Co., Ltd., product name "SP-PET382120") in which one side of a polyethylene terephthalate film is release-treated with a silicone release agent. ) with a knife coater. Then, the coating film was heat-treated at 90° C. for 1 minute to form a light-diffusing pressure-sensitive adhesive layer with a thickness of 50 μm.

4. Formation of transparent pressure-sensitive adhesive layer Step 2 above. A heavy release type release sheet (manufactured by Lintec, product name: "SP-PET752150") in which one side of a polyethylene terephthalate film is release-treated with a silicone-based release agent. was applied to the release-treated surface of the sheet with a knife coater. Then, the coating film was heat-treated at 90° C. for 1 minute to form a transparent pressure-sensitive adhesive layer with a thickness of 50 μm.

Similarly, a 50 μm-thick transparent adhesive was applied to the release-treated surface of a light-release release sheet (manufactured by Lintec, product name “SP-PET382120”) in which one side of a polyethylene terephthalate film was treated with a silicone-based release agent. An agent layer was formed, and three sheets of this were produced. The transparent adhesive layer on the light release type release sheet was laminated to the transparent adhesive layer on the heavy release type release sheet, and the light release type release sheet was peeled off. This process was repeated to form a transparent pressure-sensitive adhesive layer with a thickness of 200 μm on the heavy release type release sheet.

5. Production of adhesive sheet Step 3 above. and the light-diffusing pressure-sensitive adhesive layer on the light-release type release sheet obtained in step 4. After laminating the transparent adhesive layer on the heavy release type release sheet obtained in , curing for 7 days under conditions of 23 ° C. and 50% RH, the light release type release sheet and the light diffusion adhesive layer ( (thickness: 50 μm), a transparent adhesive layer (thickness: 200 μm), and a heavy release type release sheet laminated in that order to obtain an 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.

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)]
BA: n-butyl acrylate 2EHA: 2-ethylhexyl acrylate IBXA: isobornyl acrylate ACMO: N-acryloylmorpholine HEA: 2-hydroxyethyl acrylate PhEA: phenoxyethyl acrylate
[Light Diffusion Fine Particles]
C1: Fine particles made of silicone resin (silicon-containing compound having an intermediate structure between inorganic and organic) with an average particle diameter of 4.5 μm (manufactured by Momentive Performance Materials Japan, product name “Tospearl 145”, refractive index 1.43)
C2: Spherical organic fine particles with an average particle diameter of 3 μm (manufactured by Sekisui Plastics Co., Ltd., product name “SSX-103”, refractive index 1.49)
C3: Spherical polymethyl methacrylate-polystyrene copolymer fine particles with an average particle diameter of 3 μm (manufactured by Sekisui Plastics Co., Ltd., product name “XX-22LA”, refractive index 1.53)

[Examples 2 to 11, Comparative Examples 1 to 5]
The type and ratio of each monomer constituting the (meth)acrylic acid ester polymer (A), the amount of the cross-linking agent (B), the type and amount of the light diffusing fine particles (C), the amount of the silane coupling agent, A pressure-sensitive adhesive sheet was produced in the same manner as in Example 1, except that the thicknesses of the light-diffusing pressure-sensitive adhesive layer and the transparent pressure-sensitive adhesive layer were changed as shown in Table 1. In Examples 9 and 10, the pressure-sensitive adhesive layer was composed only of the light-diffusing pressure-sensitive adhesive layer.

In Example 6, ε -Caprolactone-modified tris-(2-acryloxyethyl) isocyanurate (manufactured by Shin-Nakamura Chemical Co., Ltd., product name "NK Ester A-9300-1CL") 8 parts by mass, and 2,4, as a photopolymerization initiator (E) 0.8 parts by mass of 6-trimethylbenzoyl-diphenyl-phosphine oxide was added, and the light diffusion adhesive layer and the transparent adhesive layer were made into active energy ray-curable adhesive layers.

Further, in Example 7, in the preparation of the pressure-sensitive adhesive composition for the light diffusion pressure-sensitive adhesive layer and the pressure-sensitive adhesive composition for the transparent pressure-sensitive adhesive layer, as an antistatic agent, an ionic liquid 4 5 parts by mass of -methyl-1-octylpyridinium bis(fluorosulfonyl)imide were added respectively.

[Test Example 1] (Measurement of refractive index)
The refractive index of the (meth)acrylate polymer (A) prepared in Examples and Comparative Examples was measured using an Abbe refractometer (manufactured by Atago Co., Ltd.) at a measurement wavelength of 589 nm and a measurement temperature of 23°C. bottom. Table 1 shows the results.

Based on the above results, the absolute value of the refractive index difference, which is the difference between the refractive index of the (meth)acrylic acid ester polymer (A) and the refractive index of the light diffusing fine particles (C), was calculated. Table 2 shows the results.

[Test Example 2] (Measurement of gel fraction)
The pressure-sensitive adhesive sheets produced in Examples and Comparative Examples were cut into a size of 80 mm × 80 mm, the pressure-sensitive adhesive layer was wrapped in a polyester mesh (mesh size 200), and the mass was weighed with a precision balance. The mass of the adhesive alone was calculated by subtracting the mass of . Let the mass at this time be M1.

Next, the adhesive wrapped in the polyester mesh was immersed in ethyl acetate at room temperature (23° C.) for 24 hours. After that, the pressure-sensitive adhesive was taken out and air-dried for 24 hours under an environment of a temperature of 23° C. and a relative humidity of 50%, and further dried in an oven of 80° C. for 12 hours. After drying, the mass was weighed with a precision balance, and the mass of the adhesive alone was calculated by subtracting the mass of the mesh alone. Let the mass at this time be M2. A gel fraction (%) is represented by (M2/M1)×100. From this, the gel fraction (before UV; %) of the adhesive was derived. Table 2 shows the results.

In addition, the adhesive layer of the adhesive sheet produced in Example 6 was irradiated with active energy rays (ultraviolet rays; UV) under the following conditions through the light release type release sheet to cure the adhesive layer. It was used as a post-adhesive layer. The gel fraction (after UV; %) was derived in the same manner as described above for the adhesive in the post-curing adhesive layer. Table 2 shows the results.

<Active energy ray irradiation conditions>
・Using a high-pressure mercury lamp ・Illuminance 200mW/cm ² , Light intensity 1000mJ/cm ²
・Using “UVPF-A1” manufactured by Eye Graphics Co., Ltd. for UV illuminance and photometer

[Test Example 3] (Measurement of total light transmittance)
The pressure-sensitive adhesive layers of the pressure-sensitive adhesive sheets produced in Examples and Comparative Examples were attached to glass to prepare measurement samples. After performing background measurement on glass, the above measurement sample was measured according to JIS K7361-1: 1997 with a haze meter (manufactured by Nippon Denshoku Industries, product name "SH-7000"). Transmittance (%) was measured. Table 2 shows the results.

[Test Example 4] (Measurement of haze value)
The pressure-sensitive adhesive layers of the pressure-sensitive adhesive sheets produced in Examples and Comparative Examples were attached to glass to prepare measurement samples. After performing background measurement with glass, the haze value (% ) was measured. Table 2 shows the results.

[Test Example 5] (Measurement of luminance)
The light-release type release sheet was peeled off from the pressure-sensitive adhesive sheets produced in Examples and Comparative Examples, and the exposed pressure-sensitive adhesive layer was applied to soda lime glass having a thickness of 1.1 mm. Next, a sample was obtained by peeling off the heavy release type release sheet from the adhesive layer. The sample was placed in a small scattering meter (manufactured by Lighttech, product name "Mini-Diff V2") so that the measurement light beam (white light of 100 (no unit)) was incident from the soda lime glass side. Then, in an environment of 23° C. and 50% RH, at a measurement wavelength of 622 nm, the luminance is measured from each angle of 0° in front of the sample (directly in front of the sample) and 15° from the normal line of the sample (15° diagonally). bottom. The brightness measurement was calibrated so that the front 0° brightness was 100 in a blank measurement in which no sample was placed.

Further, from the above measurement results, the luminance ratio (15° oblique luminance/0° front luminance) of the luminance at 15° oblique (15° oblique luminance) to the luminance at 0° front (0° front luminance) was calculated. Each result is shown in Table 2.

[Test Example 6] (Measurement of degree of depolarization)
From the pressure-sensitive adhesive sheets produced in Examples and Comparative Examples, the release sheets on both sides were peeled off, and the two polarizing plates (polarizing plates showing linear polarization) were aligned (parallel Nicol) so that the polarization axes of the two polarizing plates were aligned. Sample A was prepared by applying a plate to both sides of the adhesive layer. Further, from the pressure-sensitive adhesive sheets produced in Examples and Comparative Examples, the release sheets on both sides were peeled off, and the two polarizing plates were placed on the pressure-sensitive adhesive layer so that the polarization axes of the two polarizing plates were perpendicular to each other (crossed Nicols). A sample B was prepared by affixing to both sides of the

On the other hand, a reference transparent pressure-sensitive adhesive layer (manufactured by Lintec, product name “Opteria MO-3015”, thickness: 250 μm) was also prepared in the same manner as above. In preparing Sample A and Sample B, the pressure-sensitive adhesive layer of each example and the reference transparent pressure-sensitive adhesive layer were arranged side by side on the same polarizing plate and laminated. As a result, the arrangement of the polarizing plates of the pressure-sensitive adhesive layer of each example and the reference transparent pressure-sensitive adhesive layer are completely matched.

Next, using an ultraviolet-visible-near-infrared (UV-Vis-NIR) spectrophotometer (manufactured by Shimadzu Corporation, product name “UV-3600”), at a wavelength of 550 nm, the transmittance of sample A (parallel Nicol %) and the transmittance of sample B (transmittance of crossed Nicols; %) were measured. Based on each obtained transmittance, the degree of polarization (%) was calculated from the following formula (1).
Degree of polarization (%) = {(transmittance of parallel Nicols (%) - transmittance of crossed Nicols (%) / (transmittance of parallel Nicols (%) + transmittance of crossed Nicols (%))} x 100 ( 1)

Based on the degree of polarization (%) obtained above, the degree of depolarization (%) of each example was calculated from the following formula (2). Table 2 shows the results.
Degree of depolarization (%) = {(Degree of polarization (%) of reference transparent adhesive layer - Degree of polarization (%) of each example)/(Degree of polarization (%) of reference transparent adhesive layer)} x 100 (2 )

[Test Example 7] (Measurement of adhesive strength)
The release sheet on the transparent adhesive layer side was peeled off from the adhesive sheets produced in Examples and Comparative Examples, and the exposed transparent adhesive layer was covered with a polyethylene terephthalate (PET) film having an easy-adhesion layer (manufactured by Toyobo Co., Ltd., product name " PET A4300", thickness: 100 μm) to obtain a laminate of release sheet/adhesive layer/PET film. The laminate thus obtained was cut to a width of 25 mm and a length of 100 mm.

In an environment of 23 ° C. and 50% RH, the release sheet on the diffusion adhesive layer side was peeled off from the laminate, and the exposed diffusion adhesive layer was attached to soda lime glass (manufactured by Nippon Sheet Glass Co., Ltd.). Pressurized at 0.5 MPa and 50° C. for 20 minutes in an autoclave manufactured by Seisakusho. After that, it was left for 24 hours under conditions of 23° C. and 50% RH, and this was used as a sample. Then, using a tensile tester (manufactured by Orientec Co., Ltd., product name "Tensilon"), the adhesive strength (before UV; N / 25 mm) on the diffusion adhesive layer side was measured under the conditions of a peeling speed of 300 mm / min and a peeling angle of 180 degrees. It was measured. Conditions other than those described here were measured according to JIS Z0237:2009. The adhesive strength (before UV; N/25 mm) on the side of the transparent adhesive layer was also measured in the same manner as above.

In Example 6, the above sample was irradiated with an active energy ray through the PET film under the same conditions as in Test Example 2 to cure the pressure-sensitive adhesive layer to obtain a post-curing pressure-sensitive adhesive layer. After curing, the adhesive layer was measured for adhesive strength (after UV; N/25 mm) in the same manner as described above. Table 2 shows the results.

[Test Example 8] (Evaluation of Moire)
The release sheet on the side of the transparent adhesive layer in the adhesive sheets produced in Examples and Comparative Examples was peeled off, and the exposed transparent adhesive layer was applied to a tablet device (manufactured by Apple Inc., product name “iPad (registered trademark)”, resolution: 264 ppi) display screen. Next, the release sheet on the light diffusion adhesive layer side of the adhesive sheet is peeled off, and a liquid crystal mask having a lattice of 20 ppi to 180 ppi (in increments of 20 ppi) is attached to the exposed light diffusion adhesive layer, and the liquid crystal display. got

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.
⊚: Moire did not occur in the liquid crystal display bodies related to all the liquid crystal masks.
◯: No moiré occurred in most of the liquid crystal displays associated with the liquid crystal masks.
Δ: Moiré occurred on most of the liquid crystal displays associated with the liquid crystal masks.
x: Moiré occurred in the liquid crystal display bodies related to all the liquid crystal masks.

[Test Example 9] (Evaluation of brightness and visibility)
The pressure-sensitive adhesive layers of the pressure-sensitive adhesive sheets produced in Examples and Comparative Examples were sandwiched between two parallel Nicol polarizing plates, and this laminate was used as a sample.

A visible object (A4 size) displaying gray characters (“LINTEC” characters, font size 32, MSP Gothic) in a black background is placed at a position 1 cm from the sample, and the visible object is displayed through the sample. was visually recognized. The viewer visually recognized the sample at a position 50 cm away from the sample in an environment with a brightness of 780 lx (lux). Then, luminance and visibility were evaluated based on the following criteria. Table 2 shows the results.
A: Characters were clearly recognized.
O: Characters were recognized.
Δ: Letters appeared blurred.
x: Characters could not be recognized.

[Test Example 10] (Evaluation of durability)
The adhesive layers of the adhesive sheets produced in Examples and Comparative Examples were sandwiched between two soda-lime glass plates (manufactured by Nippon Sheet Glass Co., Ltd., thickness: 0.7 mm). Then, it was autoclaved under the conditions of 50° C. and 0.5 MPa for 30 minutes, and left at normal pressure, 23° C. and 50% RH for 24 hours.

The obtained laminate was stored for 1000 hours under high temperature and high humidity conditions of 60° C. and 95% RH. Then, the state of the interface between the pressure-sensitive adhesive layer and the adherend (soda lime glass plate) was visually observed, and the durability was evaluated according to the following criteria. Table 2 shows the results.
O: No generation of air bubbles was observed.
×: Generation of air bubbles was confirmed.

[Test Example 11] (Evaluation of step followability)
On the surface of a glass plate (manufactured by NSG Precision Co., Ltd., product name “Corning Glass Eagle XG”, length 90 mm × width 50 mm × thickness 0.5 mm), ultraviolet curable ink (manufactured by Teikoku Ink Co., Ltd., product name “POS-911 ink”) ) was screen-printed into a picture frame (outer shape: 90 mm long, 50 mm wide, 5 mm wide). Next, ultraviolet rays are irradiated (80 W/cm ² , 2 metal halide lamps, lamp height 15 cm, belt speed 10 to 15 m/min) to cure the printed UV curable ink, and the height of the step due to printing Stepped glass plates having thicknesses of 5 μm, 10 μm, 15 μm and 20 μm were produced.

The release sheet on the side of the light-diffusing pressure-sensitive adhesive layer was peeled off from the pressure-sensitive adhesive sheets obtained in Examples and Comparative Examples, and the exposed light-diffusing pressure-sensitive adhesive layer was applied to a soda lime glass plate (manufactured by Nippon Sheet Glass Co., Ltd., thickness: 0.7 mm). was pasted on. Then, the release sheet on the side of the transparent adhesive layer was peeled off to expose the transparent adhesive layer. Then, using a laminator (manufactured by Fujipla Co., Ltd., product name "LPD3214"), the laminate was laminated to each stepped glass plate so that the adhesive layer (composite adhesive layer) covered the entire surface of the frame-shaped print. . After that, it was autoclaved under conditions of 50° C. and 0.5 MPa for 30 minutes, and left at normal pressure, 23° C. and 50% RH for 24 hours.

Next, it was stored for 250 hours under wet heat conditions of 85° C. and 85% RH (endurance test). After that, the step followability was evaluated based on the following criteria. Table 2 shows the results.
◯: There were no air bubbles, no lifting, and no peeling at all height differences.
x: Bubbles, lifting, or peeling occurred at any of the steps.

In Example 6, before the endurance test, an active energy ray was irradiated through the soda lime glass plate under the same conditions as in Test Example 2 to cure the adhesive layer and cure the adhesive layer. The level difference followability was evaluated in the same manner as described above for the cured pressure-sensitive adhesive layer obtained as above. Table 2 shows the results.

As can be seen from Table 2, according to the pressure-sensitive adhesive sheets produced in Examples, the occurrence of moiré could be suppressed in the resulting liquid crystal display. Moreover, the adhesive layers of the adhesive sheets produced in Examples had high visibility when sandwiched between polarizing plates, that is, could achieve high brightness. Furthermore, the pressure-sensitive adhesive sheets produced in Examples were also excellent in durability and step followability.

The pressure-sensitive adhesive sheet and liquid crystal display member according to the present invention can be suitably used in a display device using two liquid crystal cells.

DESCRIPTION OF SYMBOLS 1... Adhesive sheet 2... Adhesive layer 21... Light diffusion adhesive layer 22... Transparent adhesive layers 3a, 3b... Release sheet 4... Liquid crystal display member 5a... First liquid crystal cell 5b... Second liquid crystal cell

Claims (5)

A pressure-sensitive adhesive sheet comprising at least a pressure-sensitive adhesive layer,
A sample obtained by attaching the pressure-sensitive adhesive layer to a soda lime glass with a thickness of 1.1 mm was used as a sample, and when a measurement light beam was transmitted from the soda lime glass side, the luminance at 15 ° from the normal line of the sample was measured. The luminance ratio to the luminance at 0° in front of the sample is 0.003 or more,
A pressure-sensitive adhesive sheet having a degree of depolarization calculated by the following formulas (1) and (2) of 2.20% or less.
Degree of polarization (%) = {(transmittance of parallel Nicols (%) - transmittance of crossed Nicols (%) / (transmittance of parallel Nicols (%) + transmittance of crossed Nicols (%))} x 100 ( 1)
Degree of depolarization (%) = {(Degree of polarization of reference transparent adhesive layer (%) - Degree of polarization of the adhesive layer (%))/(Degree of polarization of reference transparent adhesive layer (%))} x 100 (2)
Parallel Nicol Transmittance: Transmittance (%) of a sample in which an adhesive layer is sandwiched between two parallel Nicol polarizing plates
Transmittance of Crossed Nicols: Transmittance (%) of a sample in which an adhesive layer is sandwiched between two polarizing plates of Crossed Nicols 2. The pressure-sensitive adhesive layer according to claim 1, wherein the pressure-sensitive adhesive layer is a composite pressure-sensitive adhesive layer comprising a light-diffusing pressure-sensitive adhesive layer containing light-diffusing fine particles and a transparent pressure-sensitive adhesive layer not containing light-diffusing fine particles. adhesive sheet. 3. The pressure-sensitive adhesive sheet according to claim 1, which is used for bonding two liquid crystal cells. two release sheets;
The pressure-sensitive adhesive sheet according to any one of claims 1 to 3, 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 pressure-sensitive adhesive layer is the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet according to any one of claims 1 to 4.

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