TW202026378A - Adhesive sheet for backlight attachment and backlight unit capable of having better display quality with reduced losses of light reflection - Google Patents

Abstract

Provided is an adhesive sheet for attaching a backlight, which can be attached to a backlight provided with a plurality of luminous bodies on a substrate to encapsulate the luminous body without gaps, and a backlight unit which is provided to such an adhesive sheet for attaching a backlight. This adhesive sheet 1 has an adhesive layer 11 attached to a substrate 21 on which a backlight 20 is provided with a plurality of luminous bodies 22 to encapsulate the luminous bodies 22, the storage modulus of the adhesive layer 11 at 50 DEG C is 0.001 MPa or more and 0.15 MPa or less, the gel fraction of the adhesive constituting the adhesive layer 11 is 10% or more and 75% or less, and the thickness, 110 μm or more, of the adhesive layer is an adhesive sheet 1 for backlight attachment.

Description

Adhesive sheet for backlight attachment and backlight unit

The present invention relates to an adhesive sheet for backlight sticking attached to a backlight in a display device having a display portion composed of a liquid crystal panel and various optical members, and a backlight that illuminates the display portion, and the backlight sticking on such a backlight Backlight unit with adhesive layer.

In recent years, in electronic devices such as mobile phones, smart phones, tablet computers, and game consoles, liquid crystal display devices are often used as displays. Since the display portion composed of a liquid crystal panel or the like does not emit light by itself, the display device has a display portion and a backlight that illuminates the display portion.

In the arrangement of the light source of the backlight of the display device, there are a side light type in which the light source is arranged on the side of the light guide plate, and a direct type in which the light source is arranged directly behind the display unit. From the viewpoint of screen brightness and contrast, direct-type backlights have become mainstream. In a direct type backlight, since the amount of light is obtained and the light is uniform, a large number of light-emitting bodies, typically light-emitting diodes (LEDs), are provided on a substrate.

Here, the display device is usually fixed by bonding the display portion and the backlight through an adhesive sheet. Such an adhesive sheet is disclosed in Patent Documents 1 and 2, for example. Such an adhesive sheet has a frame-like shape in a horizontal view, and the display part and the backlight are attached to the edges of these. Therefore, a void is formed inside the frame-shaped adhesive sheet, and an air layer exists. [Previous Patent Document] [Patent Literature]

[Patent Document 1] Japanese Patent No. 5192682 [Patent Document 2] JP 2007-059386 A

[The problem to be solved by the invention]

However, if an air layer exists inside the display device as described above, the difference in refractive index between the air layer and the adjacent layer causes the reflection loss of light to increase, and there is a problem that the image quality of the display device decreases.

In order to solve the above problems, it is considered to stick an adhesive sheet on the entire surface of the backlight. However, as mentioned above, a large number of LEDs are provided on the substrate of the backlight. Conventionally, for the entire surface of such a backlight, there is no adhesive sheet that can be attached without a gap. For example, the pressure-sensitive adhesive sheets disclosed in Patent Documents 1 and 2 have predetermined performance when used as a frame-shaped portion, but they do not have sufficient performance for direct and void-free attachment to most LEDs.

On the other hand, it is considered that the adhesive is not used and the adhesive is coated on the entire surface of the backlight to form an adhesive layer, but there is a problem of poor productivity.

In view of the above-mentioned actual situation, the present invention provides an adhesive sheet for backlight attachment, which is attached to a backlight provided with a plurality of luminous bodies on a substrate to encapsulate the luminous body without voids, and such an adhesive sheet for backlight attachment The purpose of the backlight unit is to attach the backlight. [Technical means to solve the problem]

In order to achieve the above object, firstly, the present invention provides an adhesive sheet for attaching a backlight, which is an adhesive sheet with an adhesive layer attached to a substrate with a backlight provided with a plurality of luminous bodies to encapsulate the light-emitting Body, characterized in that the storage modulus of the adhesive layer at 50°C is 0.001 MPa or more and 0.15 MPa or less, and the gel fraction of the adhesive constituting the adhesive layer is 10% or more and 75% or less, and the adhesive The thickness of the agent layer is 110 μm or more (Invention 1).

According to the above-mentioned invention (Invention 1), the adhesive layer has the above-mentioned physical properties, a backlight having a plurality of luminous bodies is provided on a substrate, and the adhesive layer can be attached without voids to encapsulate the luminous bodies.

In the above invention (Invention 1), it is preferable that the storage modulus of the adhesive layer at 23° C. is 0.01 MPa or more and 0.20 MPa or less (Invention 2).

In the above inventions (Inventions 1 and 2), the above-mentioned adhesive is preferably an acrylic adhesive (Invention 3).

In the above inventions (Inventions 1 to 3), it is preferable to have two release sheets, and the adhesive layer which is in contact with the release surfaces of the two release sheets and sandwiched by the release sheets (Invention 4).

Secondly, the present invention provides a backlight unit, which is a backlight with a plurality of luminous bodies on one or more substrates, and a backlight unit with an adhesive layer attached to the backlight to encapsulate the luminous bodies, It is characterized in that the adhesive layer is the adhesive layer (Invention 5) of the aforementioned adhesive sheet for backlight pasting (Inventions 1 to 4).

In the aforementioned invention (Invention 5), it is preferable that the aforementioned luminous body is a light emitting diode (Invention 6). [Invention Effect]

The adhesive sheet for attaching the backlight of the present invention can be attached to a backlight provided with a plurality of luminous bodies on a substrate, so as to encapsulate the luminous bodies without gaps. In addition, in the backlight unit of the present invention, the plurality of light-emitting bodies on the substrate are encapsulated with an adhesive layer to the backlight without voids, so that the image quality of the resulting display can be prevented from degrading.

[For the implementation of the invention]

The following describes the implementation aspects of the present invention. [Adhesive sheet for backlight sticking] One embodiment of the present invention is an adhesive sheet for attaching a backlight (in this specification, it is only referred to as an "adhesive sheet"), which has an adhesive layer attached to a substrate and a backlight provided with a plurality of luminous bodies to encapsulate the The luminous body is preferably formed by peeling off the sheet on one or both sides of the adhesive layer.

The specific structure of an example of the adhesive sheet for backlight attachment of this embodiment is shown in FIG. As shown in Figure 1, the adhesive sheet for backlight pasting (adhesive sheet) 1 is composed of two release sheets 12a, 12b and the release surfaces of the two release sheets 12a, 12b, and are sandwiched between the two release sheets 12a, 12b. The adhesive layer 11 between the release sheets 12a and 12b is formed. In addition, in this specification, the peeling surface of the peeling sheet means the surface which has peelability in a peeling sheet, and it also includes the surface which performed the peeling process and the surface which was not peeled but showed peelability.

1. Components 1-1. Adhesive layer The adhesive layer 11 of the adhesive sheet 1 of this embodiment has a storage modulus at 50°C of 0.001 MPa or more and 0.15 MPa or less, and the gel fraction of the adhesive constituting the adhesive layer 11 is 10% or more, 75% or less, thickness of 110μm or more.

The adhesive layer 11 has the above-mentioned physical properties. The adhesive sheet 1 of this embodiment enables the adhesive layer 11 to be attached to a back light provided with a plurality of luminous bodies on a substrate to encapsulate the luminous bodies without voids. As a result, there is no air layer or gap between the display unit and the backlight of the obtained display device, etc., and therefore, it is possible to prevent the deterioration of image quality due to the loss of light reflection.

Specifically, the storage modulus of the adhesive layer 11 at 50°C is 0.15 MPa or less, and the gel fraction of the adhesive constituting the adhesive layer 11 is 75% or less, so the adhesive layer 11 exhibits excellent flexibility And stress relaxation, easy to embed the luminous body, and can encapsulate the luminous body without gaps.

On the other hand, a plurality of luminous bodies provided in the backlight may generate heat due to light emission. When a plurality of luminous bodies are provided, the adhesive layer 11 may be exposed to high temperature conditions (durability conditions). The storage modulus of the adhesive layer 11 at 50° C. is 0.001 MPa or more, and the gel fraction is 10% or more. Even under the aforementioned durable conditions, the void-free packaging by the adhesive layer 11 can be easily maintained.

From the viewpoint of embedding of the luminous body, the storage modulus of the adhesive layer 11 at 50° C. is preferably 0.13 MPa or less, particularly preferably 0.09 MPa or less, and more preferably 0.05 MPa or less. In addition, from the viewpoint of the encapsulation of the luminous body under durable conditions, the storage modulus is preferably 0.01 MPa or more, particularly preferably 0.02 MPa or more, and more preferably 0.03 MPa or more.

From the viewpoint of embedding of the light-emitting body, the gel fraction of the adhesive constituting the adhesive layer 11 is preferably 70% or less, particularly 64% or less, and more preferably 57% or less. In addition, from the viewpoint of the encapsulation properties of the luminous body under durable conditions, the gel fraction is preferably 20% or more, preferably 30% or more, particularly preferably 40% or more, and more preferably 50% or more.

On the other hand, the storage modulus of the adhesive layer 11 at 23°C is preferably 0.20 MPa or less, preferably 0.18 MPa or less, particularly preferably 0.15 MPa or less, and particularly preferably 0.11 MPa or less from the viewpoint of luminous body embedding. In addition, from the viewpoint of the encapsulation of the light-emitting body under durable conditions, the storage modulus is preferably 0.01 MPa or more, particularly preferably 0.02 MPa or more, and more preferably 0.04 MPa or more.

The storage modulus in this manual is the value measured by the torsion shear test at a measuring frequency of 1 Hz according to JIS K7244-6. In addition, the method of measuring the gel fraction of the adhesive in this specification is as shown in the test example described later.

Since the adhesive layer 11 has the above-mentioned storage modulus and gel fraction, and has a thickness of 110 μm or more, the light-emitting body can be encapsulated according to the type of the light-emitting body. From the viewpoint of luminous body packaging, the thickness of the adhesive layer 11 is preferably 130 μm or more, particularly preferably 160 μm or more, and more preferably 200 μm or more. On the other hand, from the viewpoint of thinning the resulting display, the thickness of the adhesive layer 11 is preferably 1000 μm or less, particularly preferably 800 μm or less, and more preferably 500 μm or less.

In addition, the ratio of the thickness of the adhesive layer 11 to the thickness of the light-emitting body (the thickness of the adhesive layer/the thickness of the light-emitting body) is preferably 1.1 or more, preferably 1.4 or more, and 2.0 or more from the viewpoint of reliably sealing the light-emitting body Especially good, more than 2.2 is better. On the other hand, the above-mentioned thickness ratio is preferably 10 or less, preferably 8 or less, particularly preferably 5 or less, and more preferably 2.9 or less from the viewpoint of thinning of the obtained display.

The type of adhesive that constitutes the adhesive layer 11 of the adhesive sheet 1 of this embodiment is not particularly limited as long as it satisfies the aforementioned physical properties. For example, acrylic adhesives, polyester adhesives, polyurethane adhesives, rubbers Any of adhesives, silicone adhesives, etc. In addition, the adhesive may be either an emulsion type, a solvent type, or a solvent-free type, and may be either a crosslinked type or a non-crosslinked type. Among these, acrylic adhesives that easily satisfy the aforementioned physical property values are preferred.

In addition, the acrylic adhesive may be active energy ray curable or active energy ray non-curable, but it is preferably an active energy ray non-curable acrylic adhesive that does not require a photopolymerization initiator. Active energy ray non-curable acrylic adhesives are particularly preferably cross-linked, and more preferably thermally cross-linked.

The above-mentioned adhesive is formed by cross-linking an adhesive composition (hereinafter referred to as "adhesive composition P") containing a (meth)acrylate polymer (A) and a cross-linking agent (B) The one is better. In this specification, (meth)acrylic acid means both acrylic acid and methacrylic acid. Other similar terms are also the same. In addition, "polymer" also includes the concept of "copolymer".

(1) Ingredients of the adhesive composition (1-1) (Meth)acrylate polymer (A) In this embodiment, the (meth)acrylate polymer (A) uses a reactive group-containing monomer having a reactive group that reacts with the crosslinking agent (B) in the molecule as the monomer constituting the polymer The unit is better. The reactive groups from the reactive group-containing monomer react with the crosslinking agent (B) to form a crosslinked structure (three-dimensional network structure), and it is easy to obtain an adhesive having the aforementioned gel fraction and storage modulus.

The above-mentioned reactive group-containing monomers preferably include monomers having a hydroxyl group in the molecule (hydroxyl-containing monomers), monomers having a carboxyl group in the molecule (carboxyl group-containing monomers), and monomers having an amine group in the molecule (containing Amino monomer) and so on. Among these, from the viewpoint of maintaining a low storage modulus, hydroxyl-containing monomers are particularly preferred.

Hydroxyl-containing monomers, such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, Hydroxyalkyl (meth)acrylates such as 3-hydroxybutyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate. Among them, from the viewpoint of the reactivity of the hydroxyl group in the obtained (meth)acrylate polymer (A) with the crosslinking agent (B) and the copolymerizability with other monomers, it is assumed that the hydroxyl group has a carbon number of 1 to 4 Hydroxyalkyl (meth)acrylates of alkyl groups are preferred. Specifically, 2-hydroxyethyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, etc. are preferred, and 2-hydroxyethyl acrylate or 4-hydroxybutyl acrylate is particularly preferred. These can be used individually or in combination of 2 or more types.

Carboxyl group-containing monomers such as acrylic acid, methacrylic acid, crotonic acid (crotonic acid), maleic acid (maleic acid), itaconic acid (itaconic acid), citraconic acid (citraconic acid) and other ethylenically unsaturated carboxylic acids acid. Among them, acrylic acid is preferred from the viewpoint of the reactivity of the carboxyl group in the obtained (meth)acrylate polymer (A) and the crosslinking agent (B) and the copolymerization with other monomers. These can be used individually or in combination of 2 or more types.

Amino group-containing monomers, such as aminoethyl (meth)acrylate, n-butylaminoethyl (meth)acrylate, and the like. These can be used individually or in combination of 2 or more types.

The (meth)acrylate polymer (A) preferably contains a reactive group-containing monomer with a lower limit of 3% by mass or more as the monomer unit constituting the polymer, and particularly preferably contains 10% by mass or more , It is more preferable to contain 15% by mass or more. The (meth)acrylate polymer (A) preferably contains a reactive group-containing monomer having an upper limit of 35% by mass or less as the monomer unit constituting the polymer, and preferably contains 30% by mass or less, In particular, the content is preferably 25% by mass or less. When the (meth)acrylate polymer (A) contains the above-mentioned amount of reactive group-containing monomers as monomer units, it is easy to obtain the aforementioned storage modulus and gel fraction.

In addition, the (meth)acrylate polymer (A) preferably does not contain a carboxyl group-containing monomer as a monomer unit constituting the polymer. Since the carboxyl group is an acid component, it does not contain a carboxyl group-containing monomer to prevent defects caused by acid in the adhesive to be attached, such as the encapsulating resin of the light-emitting body, the metal wiring of the substrate, and the metal reflective film on the substrate. In some cases, such defects (deterioration, corrosion, etc.) due to acid can also be suppressed. However, it is allowed to contain a predetermined amount of a carboxyl group-containing monomer to such an extent that such a problem does not occur. Specifically, the (meth)acrylate polymer (A) is allowed to contain 0.1% by mass or less of carboxyl group-containing monomers as monomer units, preferably 0.01% by mass or less, and more preferably 0.001% by mass or less the amount.

The (meth)acrylate polymer (A) preferably contains an alkyl (meth)acrylate as a monomer unit constituting the polymer. As a result, good adhesiveness can be expressed. The alkyl group may be linear or branched.

The alkyl (meth)acrylate is preferably an alkyl (meth)acrylate having 1 to 20 carbon atoms in the alkyl group from the standpoint of adhesiveness. Alkyl (meth)acrylates whose alkyl group has 1 to 20 carbon atoms, such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, and normal (meth)acrylate Butyl ester, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, n-decyl (meth)acrylate, N-dodecyl (meth)acrylate, tetradecyl (meth)acrylate, cetyl (meth)acrylate, stearyl (meth)acrylate, etc. Among them, from the viewpoint of improving the adhesiveness, (meth)acrylates having an alkyl group of 1 to 8 carbon atoms are preferred, and methyl (meth)acrylate, n-butyl (meth)acrylate, or ( 2-ethylhexyl meth)acrylate is particularly preferred. Moreover, these may be used individually or in combination of 2 or more types.

The (meth)acrylate polymer (A) preferably contains 30% by mass or more of alkyl (meth)acrylate as the monomer unit constituting the polymer, preferably 40% by mass or more, and 50% by mass % Or more is particularly preferable, and it is more preferable to contain 55% by mass or more. When the lower limit of the content of the alkyl (meth)acrylate is the above, the (meth)acrylate polymer (A) can exhibit suitable adhesiveness. In addition, the (meth)acrylate polymer (A) preferably contains 97% by mass or less of alkyl (meth)acrylate as the monomer unit constituting the polymer, and preferably contains 90% by mass or less. 80% by mass or less is particularly preferred, and 70% by mass or less is more preferred. When the upper limit of the content of the alkyl (meth)acrylate is the above, an appropriate amount of other monomer components such as monomers containing reactive functional groups can be introduced into the (meth)acrylate polymer (A) , It is easy to adjust the aforementioned gel fraction and storage modulus.

The (meth)acrylate polymer (A) preferably contains a monomer having an alicyclic structure in the molecule (alicyclic structure-containing monomer) as a monomer unit constituting the polymer. Due to the large volume of the alicyclic structure-containing monomer, it exists in the polymer, and it is presumed that the gap between the polymers is increased, and the resulting adhesive can have excellent flexibility. On the other hand, the alicyclic structure-containing monomer itself can provide a certain degree of hardness of the polymer. Therefore, when the (meth)acrylate polymer (A) has an alicyclic structure-containing monomer as the constituent monomer unit, the gel fraction and storage modulus of the resulting adhesive, especially when stored at 50°C The modulus can be easily adjusted within the aforementioned range.

The carbocyclic ring of the alicyclic structure containing the alicyclic structure monomer may have a saturated structure or may have a part of unsaturated bonds. The alicyclic structure may be a monocyclic alicyclic structure, or a polycyclic alicyclic structure such as bicyclic and tricyclic. As described above, from the viewpoint of adjusting the physical properties of the obtained adhesive, the alicyclic structure is preferably a polycyclic alicyclic structure (polycyclic structure). Furthermore, considering the compatibility of the (meth)acrylate polymer (A) with other components, the above-mentioned polycyclic structure is particularly preferably bicyclic to tetracyclic. Also, as described above, from the viewpoint of adjusting the physical properties of the adhesive obtained, the carbon number of the alicyclic structure (means the total number of carbons in the part forming the ring, and when multiple rings exist independently, it represents the total carbon Number), usually 5 or more is preferred, 7 or more is particularly preferred. On the other hand, the upper limit of the carbon number of the alicyclic structure is not particularly limited. From the viewpoint of compatibility with the above, 15 or less is preferable, and 10 or less is particularly preferable.

The above-mentioned alicyclic structure-containing monomers are specifically, for example, cyclohexyl (meth)acrylate, dicyclopentyl (meth)acrylate, adamantyl (meth)acrylate, isobornyl (meth)acrylate, (meth) Dicyclopentenyl acrylate, dicyclopentenyloxyethyl (meth)acrylate, etc., among them, dicyclopentyl (meth)acrylate (alicyclic carbon Number: 10), adamantyl (meth)acrylate (carbon number of alicyclic structure: 10), or isobornyl (meth)acrylate (carbon number of alicyclic structure: 7) is preferred, especially (former Base) isobornyl acrylate is preferred. These can be used individually or in combination of 2 or more types.

In the case where the (meth)acrylate polymer (A) contains an alicyclic structure-containing monomer as the monomer unit constituting the polymer, it is preferable to contain 1% by mass or more of the alicyclic structure-containing monomer, especially It is preferably 5% by mass or more, and more preferably 9% by mass or more. In addition, the (meth)acrylate polymer (A) preferably contains 30% by mass or less of alicyclic structure-containing monomers as the monomer units constituting the polymer, and particularly preferably contains 25% by mass or less, and more It is better to contain 20% by mass or less. When the content of the alicyclic structure-containing monomer is in the above range, it is easy to adjust the resulting adhesive to the above physical property value.

It is also preferable that the (meth)acrylate polymer (A) contains a nitrogen atom-containing monomer as a monomer unit constituting the polymer. Because the nitrogen atom-containing monomer is present in the polymer as a structural unit, it can provide the specified polarity of the adhesive, and it can also become a good affinity for adherends with a certain degree of polarity such as glass. The above-mentioned nitrogen-containing monomers have moderate rigidity in the (meth)acrylate polymer (A), increase the gel fraction, and increase the storage modulus of the resulting adhesive at 50°C to a specified level. Monomers with nitrogen-containing heterocycles are preferred. From the viewpoint of increasing the degree of freedom of the part derived from the above-mentioned nitrogen-containing monomer in the high-dimensional structure of the formed adhesive, the nitrogen-containing monomer is preferably used to form (meth)acrylate polymer Those that do not contain a reactive unsaturated double bond group other than one polymerizable group used in the polymerization of the substance (A). In addition, the nitrogen atom-containing monomer described herein excludes the aforementioned reactive functional group-containing monomer.

、1-乙烯基咪唑、N-乙烯基咔唑、N-乙烯基酞醯亞胺等，其中，以發揮更優良黏著力的N-(甲基)丙烯醯基嗎啉為佳，特別以N-丙烯醯基嗎啉為佳。這些可單獨使用，也可組合2種以上使用。Monomers with nitrogen-containing heterocycles, such as N-(meth)acryloylmorpholine, N-vinyl-2-pyrrolidone, N-(meth)acryloylpyrrolidone, N-(methyl) Yl)acryloyl piperidine, N-(meth)acryloyl pyrrolidine, N-(meth)acryloyl pyrrolidine, N-(meth)acryloyl acridine, (meth)acrylic acid acrylethyl, 2-vinylpyridine , 4-vinylpyridine, 2-vinylpyridine

, 1-vinylimidazole, N-vinylcarbazole, N-vinylphthalimide, etc. Among them, N-(meth)acryloylmorpholine, which exhibits better adhesion, is preferred, especially N -Acrylic morpholine is preferred. These can be used individually or in combination of 2 or more types.

In the case where the (meth)acrylate polymer (A) contains a nitrogen atom-containing monomer as the monomer unit constituting the polymer, the nitrogen atom-containing monomer is preferably 1% by mass or more, especially 2 It is better to contain at least 3% by mass, and more preferably to contain at least 3% by mass. In addition, the (meth)acrylate polymer (A) preferably contains 20% by mass or less of nitrogen atom-containing monomers as the monomer units constituting the polymer, and particularly preferably contains 15% by mass or less, and more preferably The content is preferably 10% by mass or less. If the content of the nitrogen atom-containing monomer is within the above range, it is easy to adjust the storage modulus and gel fraction of the resulting adhesive at 50° C. within the above range.

The (meth)acrylate polymer (A) may optionally contain other monomers as monomer units constituting the polymer. In order not to hinder the aforementioned effects of the reactive functional group-containing monomer, the other monomer is preferably a monomer that does not contain a reactive functional group. Examples of such monomers are alkoxyalkyl (meth)acrylates such as methoxyethyl (meth)acrylate, ethoxyethyl (meth)acrylate, etc., ethyl acetate, styrene, and the like. These can be used individually or in combination of 2 or more types.

The (meth)acrylate polymer (A) is preferably a linear polymer. Since it is a linear polymer, entanglement of molecular chains easily occurs, and it is easy to obtain an adhesive having the aforementioned gel fraction.

In addition, the (meth)acrylate polymer (A) is preferably a solution polymer obtained by a solution polymerization method. Since it is a solution polymer, it is easy to obtain a high-molecular-weight polymer, and an improvement in cohesive force can be expected. Therefore, it is easy to obtain an adhesive with better encapsulation properties of the light-emitting body under durable conditions. In addition, the amount of residual monomers in the adhesive is reduced and the light resistance is excellent.

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

The lower limit of the weight average molecular weight of the (meth)acrylate polymer (A) is preferably 200,000 or more, particularly 300,000 or more, and more preferably 400,000 or more. When the lower limit of the weight average molecular weight of the (meth)acrylate polymer (A) is the above, it is easy to satisfy the aforementioned lower limit of the gel fraction and storage modulus.

Moreover, the upper limit of the weight average molecular weight of the (meth)acrylate polymer (A) is preferably 2 million or less, preferably 1.5 million or less, and particularly preferably 1 million or less. When the upper limit value of the weight average molecular weight of the (meth)acrylate polymer (A) is below the above, it is easy to satisfy the upper limit of the aforementioned storage modulus. In addition, the weight average molecular weight in this specification is the value converted from the standard polystyrene measured by the gel permeation chromatography (GPC) method.

Moreover, in the adhesive composition P, (meth)acrylate polymer (A) may be used individually by 1 type, and may be used in combination of 2 or more types.

(1-2) Crosslinking agent (B) The crosslinking agent (B) can crosslink the (meth)acrylate polymer (A) by heating the adhesive composition P to form a three-dimensional network structure well. Therefore, the cohesive force of the obtained adhesive is improved, and the gel fraction and storage modulus of the obtained adhesive are easily adjusted within the above-mentioned range.

The above-mentioned crosslinking agent (B) may be a reactive group with the (meth)acrylate polymer (A), such as isocyanate crosslinking agents, epoxy crosslinking agents, amine crosslinking agents, Melamine-based cross-linking agents, acridine-based cross-linking agents, hydrazine cross-linking agents, aldehyde-based cross-linking agents, azoline-based cross-linking agents, metal alkoxide-based cross-linking agents, metal chelating agents cross-linking Agent, metal salt crosslinking agent, ammonium salt crosslinking agent, etc. Among the above, when the reactive group of the (meth)acrylate polymer (A) is a hydroxyl group, it is preferable to use an isocyanate-based crosslinking agent with excellent reactivity with the hydroxyl group. (A) When the reactive group is a carboxyl group, it is preferable to use an epoxy-based crosslinking agent having excellent reactivity with the carboxyl group. Moreover, a crosslinking agent (B) may be used individually by 1 type, and may be used in combination of 2 or more types.

The isocyanate-based crosslinking agent contains at least a polyisocyanate compound. Polyisocyanate compounds such as toluene diisocyanate, diphenylmethane diisocyanate, xylylene diisocyanate (xylylene diisocyanate) and other aromatic polyisocyanates, hexamethylene diisocyanate and other aliphatic polyisocyanates, isophorone diisocyanate Alicyclic polyisocyanates such as isocyanate, hydrogenated diphenylmethane diisocyanate, etc., and these biuret (biuret) body, trimeric isocyanate body, more for example and ethylene glycol, propylene glycol, neopentyl glycol, three Adducts of reactants of small molecules such as hydroxymethyl propane and castor oil containing active hydrogen compounds. Among them, from the viewpoint of reactivity with hydroxyl groups, aromatic polyisocyanates modified by trimethylolpropane, especially trimethylolpropane modified toluene diisocyanate and trimethylolpropane modified xylene diisocyanate are good.

Epoxy resin crosslinking agents such as 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, N,N,N',N'-tetraglycidyl-m- Xylene diamine, ethylene glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylolpropane diglycidyl ether, diglycidyl aniline, bicyclic Oxypropylamine and so on. Among them, from the viewpoint of reactivity with a carboxyl group, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane is preferred.

The content of the crosslinking agent (B) in the adhesive composition P is preferably 0.01 parts by mass or more, particularly preferably 0.05 parts by mass or more, 0.1 parts by mass relative to 100 parts by mass of the (meth)acrylate polymer (A) More than a portion is better. In addition, the content is preferably 10 parts by mass or less, particularly preferably 5 parts by mass or less, and more preferably 0.4 parts by mass or less. If the content of the crosslinking agent (B) is in the above range, it is easier to satisfy the above gel fraction and storage modulus.

(1-3) Various additives In the adhesive composition P, various additives commonly used can be added to the acrylic adhesive as needed, such as silane coupling agent, ultraviolet absorber, antistatic agent, tackifier, antioxidant, light stabilizer, softener, refractive index Adjusting agent, anti-rust agent, etc. In addition, the polymerization solvent and the dilution solvent described later are not included in the additives constituting the adhesive composition P.

Among the above, the adhesive composition P preferably contains a silane coupling agent. Therefore, the adhesiveness with optical elements such as the backlight (luminous body, substrate, reflective film) and diffuser of the adherend is improved, and the encapsulation of the luminous body under durable conditions is more excellent.

The silane coupling agent is an organosilicon compound having at least one alkoxysilyl group in the molecule, and has good compatibility with the (meth)acrylate polymer (A) and is preferably light-transmitting.

Such a silane coupling agent, for example, ethylene trimethoxysilane, ethylene triethoxysilane, methacryloxypropyl trimethoxysilane, and other polymerizable unsaturated group-containing silicon compounds, 3-epoxypropyl Silicon compounds with epoxy structure such as propyltrimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropane Sulfhydryl-containing silicon compounds such as triethoxysilane, 3-mercaptopropyldimethoxymethylsilane, 3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3 -Aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane and other amino group-containing silicon compounds, 3-chloropropyltrimethoxysilane Triethoxysilane, 3-isocyanate propyltriethoxysilane, or at least one of these and methyltriethoxysilane, ethyltriethoxysilane, methyltrimethoxysilane, ethyltrimethoxysilane Condensates of silicon compounds containing alkyl groups. These may be used individually by 1 type, and may be used in combination of 2 or more types.

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

(2) Making of adhesive composition Adhesive composition P can be produced by producing (meth)acrylate polymer (A), mixing the obtained (meth)acrylate polymer (A) and crosslinking agent (B), and adding additives as necessary .

The (meth)acrylate polymer (A) can be produced by polymerizing a mixture of monomers constituting the polymer by a general radical polymerization method. The polymerization of the (meth)acrylate polymer (A) is preferably carried out by a solution polymerization method using a polymerization initiator as necessary. For the polymerization solution, for example, ethyl acetate, n-butyl acetate, isobutyl acetate, toluene, acetone, hexane, methyl ethyl ketone, etc., two or more kinds may be used in combination.

The polymerization initiator, for example, an azo compound, an organic peroxide, etc., may be used in combination of two or more kinds. Azo compounds such as 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), 2,2 '-Azobis(2-methylpropionic acid) dimethyl ester, 4,4'-Azobis(4-cyanovaleric acid), 2,2'-Azobis(2-hydroxymethylpropionitrile) , 2,2'-Azobis[2-(2-imidazolin-2-yl)propane] and the like.

Organic peroxides such as benzyl peroxide, tertiary butyl peroxybenzoate, cumene hydroperoxide, diisopropyl peroxydicarbonate, di-n-propyl peroxydicarbonate, di(2-ethyl (Oxyethyl) peroxydicarbonate, tertiary butyl peroxyneodecanoate, tertiary butyl peroxide, trimethylacetate, peroxide (3,5,5-trimethylhexyl), dipropylene peroxide Diethyl peroxide, diacetyl peroxide, etc.

In addition, in the above-mentioned polymerization step, the weight average molecular weight of the obtained polymer can be adjusted by formulating a chain transfer agent such as 2-mercaptoethanol.

If the (meth)acrylate polymer (A) is obtained, the crosslinking agent (B) is added to the solution of the (meth)acrylate polymer (A), and the diluent solvent and additives are added as necessary, and after thorough mixing, The adhesive composition P (coating solution) diluted with a solvent was obtained. In addition, when any of the above-mentioned components are used in a solid state, or when they precipitate when mixed with other components in an undiluted state, the component may be dissolved in advance alone or diluted in a dilution solvent and mixed with other components.

The above-mentioned diluting solvent uses, for example, aliphatic hydrocarbons such as hexane, heptane, and cyclohexane, aromatic hydrocarbons such as toluene and xylene, methylene chloride, ethylene chloride, etc. Halogenated hydrocarbons, methanol, ethanol, propanol, butanol, 1-methoxy-2-propanol and other alcohols, acetone, methyl ethyl ketone, 2-pentanone, isophorone (isophorone), cyclohexanone, etc. Esters such as ketones, ethyl acetate, and butyl acetate, cellosolve solvents such as ethyl ceresol, etc.

The concentration and viscosity of the coating solution prepared in this way can be in the coatable range, there is no particular limitation, and it 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. In addition, when the coating solution is obtained, the addition of a dilution solvent or the like is not a necessary condition, and if the adhesive composition P has a viscosity or the like that can be applied, the dilution solvent may not be added. In this case, the adhesive composition P is a coating solution in which the polymerization solvent of the (meth)acrylate polymer (A) is directly used as the diluting solvent.

(3) Formation of adhesive layer The adhesive layer 11 in this embodiment is preferably composed of an adhesive that crosslinks the adhesive composition P (the coating layer). The crosslinking of the adhesive composition P can usually be performed by heat treatment. In addition, this heat treatment may also be used as a drying treatment when the coating layer of the adhesive composition P applied to the desired object volatilizes the dilution solvent.

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

After the heat treatment, the aging time may be set at normal temperature (for example, 23°C, 50%RH) for about 1 to 2 weeks as needed. In the case where this aging time is necessary, after the aging time has elapsed, when the aging time is not required, the adhesive is formed after the heat treatment is completed.

Through the above-mentioned heat treatment (and aging), the (meth)acrylate polymer (A) is sufficiently cross-linked through the cross-linking agent (B). The adhesive thus obtained easily satisfies the above-mentioned physical property values.

(4) Physical properties of adhesive The amount of monomers contained in the adhesive of this embodiment is mainly the residual amount of monomers used in the copolymerization of the (meth)acrylate polymer (A), preferably 10% by mass or less, especially 1 mass % Or less is better, and more preferably less than 0.1% by mass. Therefore, the resulting adhesive layer 11 has excellent light resistance, and can suppress discoloration even if it is used for a long time in a state where it is in contact with a plurality of light-emitting bodies that emit light.

The lower limit of the amount of monomers contained in the adhesive of this embodiment is preferably 0% by mass, usually 0.001% by mass or more, and particularly preferably 0.005% by mass or more.

1-2. Peeling sheet The peeling sheets 12a and 12b protect the adhesive layer 11 until the adhesive sheet 1 is used, and are peeled when the adhesive sheet 1 (adhesive layer 11) is used. In the adhesive sheet 1 of this embodiment, one or both of the peeling sheets 12a and 12b are not essential.

The release sheets 12a, 12b use, for example, polyethylene film, polypropylene film, polybutene film, polybutadiene film, polymethylpentene film, polyvinyl chloride film, vinyl chloride copolymer film, polyethylene terephthalate Diester film, polyethylene naphthalate film, polybutylene terephthalate film, polyurethane film, ethylene ethyl acetate film, ionomer resin film, ethylene•(meth)acrylic acid copolymer film, ethylene •(Meth)acrylate copolymer film, polystyrene film, polycarbonate film, polyimide film, fluororesin film, etc. These crosslinked films can also be used. Furthermore, a laminated film of this type may also be used.

It is preferable to perform a peeling process on the peeling surface of the said peeling sheet 12a, 12b (especially the surface contacting the adhesive layer 11). The release agent used for the release treatment, for example, alkyd, silicone, fluorine, unsaturated polyester, polyolefin, wax release agent. Among the peeling sheets 12a and 12b, one of the peeling sheets is preferably a heavy peeling type peeling sheet with a large peeling force, and the other peeling sheet is a light peeling type peeling sheet with a small peeling force.

The thickness of the release sheets 12a and 12b is not particularly limited, but is usually about 20 to 150 μm.

2. Physical properties (1) Total light transmittance The total light transmittance of the adhesive layer 11 of the adhesive sheet 1 of this embodiment (value measured according to JIS K7361-1:1997 standards) is preferably 90% or more, especially 93% or more, and more More than 95% is preferred. When the total light transmittance is as described above, the transparency is high, making it suitable for use as a backlight sticker.

In addition, the total light transmittance of the adhesive layer 11 after placing the adhesive sheet 1 of the present embodiment under the conditions of 50°C and 50%RH for 500 hours is preferably 90% or more, especially 93% or more. Better, more preferably more than 95%. When the total light transmittance is as described above, even when the heat-generating state of the luminous body in contact with the adhesive layer 11 is a heat-resistant condition that lasts for a long time, the transparency is still high, making it more suitable for use as a backlight attachment.

Furthermore, for the adhesive sheet 1 of this embodiment, the total light transmittance of the adhesive layer 11 after irradiating ultraviolet rays with an illuminance of 500mW/m ^{2 for} 500 hours is preferably 90% or more, especially 93% or more. , More preferably more than 95%. When the total light transmittance is as described above, even if the light-emitting state of the light-emitting body in contact with the adhesive layer 11 continues for a long time, it can be said to have excellent light resistance, making it more suitable for use as a backlight stick.

(2) Haze value The haze value of the adhesive layer 11 of the adhesive sheet 1 of the present embodiment is preferably 30% or less, preferably 20% or less, especially 10% or less, and more preferably 1% or less. Since the haze value of the adhesive layer 11 is as described above, the light transmittance is excellent, and it is suitable for use as a backlight paste. In addition, the above-mentioned haze value is a characteristic value that also includes the thickness of the adhesive layer, and it is preferable that the above-mentioned haze value is satisfied regardless of the thickness of the adhesive layer.

Even if the thickness of the adhesive layer 11 of this embodiment is thicker than 250 μm, it is easy to satisfy the above-mentioned haze value. The adhesive sheet 1 of this embodiment can achieve the low haze value as described above by using the adhesive composition P described above.

In addition, the haze value of the adhesive layer 11 after placing the adhesive sheet 1 of this embodiment under the conditions of 50°C and 50%RH for 500 hours is preferably 30% or less, preferably 20% or less, especially 10% or less is better, more preferably 1% or less. When the haze value is as described above, even when the heat-generating state of the light-emitting body in contact with the adhesive layer 11 is a heat-resistant condition that lasts for a long time, the transparency is still high, and it is more suitable for a backlight application.

Furthermore, for the adhesive sheet 1 of this embodiment, the haze value of the adhesive layer 11 after irradiating ultraviolet rays with an illuminance of 500mW/m ^{2 for} 500 hours is preferably 30% or less, 20% or less, especially 10 % Or less is better, more preferably 1% or less. When the total light transmittance is as described above, even if the light-emitting state of the light-emitting body in contact with the adhesive layer 11 continues for a long time, it can be said to have excellent light resistance, making it more suitable for use as a backlight stick.

In addition, even under any conditions, the lower limit of the haze value of the adhesive layer 11 of the adhesive sheet 1 of this embodiment is not particularly limited, but is preferably 0% or more, and more preferably 0.1% or more. Here, the haze value in this specification is a value measured according to JIS K7136:2000.

(3) Color The chromaticity a* of the adhesive layer 11 of this embodiment is based on the CIE1976L*a*b* color system, preferably -5.0~5.0, especially -3.0~3.0, and even more preferably -2.0~2.0 Better. In addition, the chromaticity b* of the adhesive layer 11 of this embodiment is based on the CIE1976L*a*b* color system, preferably -5.0~5.0, especially -3.0~3.0, and even more preferably -2.0~ 2.0 is better. When the chromaticity a* and the chromaticity b* are in the above-mentioned range, the adhesive layer 11 is close to colorless and transparent, making it suitable for use as a backlight sticker.

In addition, the chromaticity a* of the adhesive layer 11 after placing the adhesive sheet 1 of the present embodiment under the conditions of 50°C and 50%RH for 500 hours is preferably -5.0~5.0, especially -3.0~3.0 Better, more preferably -2.0~2.0. The color b* is preferably -5.0~5.0, especially -3.0~3.0 is better, and even more preferably -2.0~2.0. When the chromaticity a* and the chromaticity b* are in the above range, even if the heat-generating state of the luminous body in contact with the adhesive layer 11 is a long-term heat-resistant condition, the adhesive layer 11 is still close to colorless and transparent, making it more suitable for making For the backlight sticker.

Furthermore, for the adhesive sheet 1 of this embodiment, the chromaticity a* of the adhesive layer 11 after irradiating ultraviolet rays with an illuminance of 500mW/m ^{2 for} 500 hours is preferably -5.0~5.0, especially -3.0~3.0 Better, more preferably -2.0~2.0. The color b* is preferably -5.0~5.0, especially -3.0~3.0 is better, and even more preferably -2.0~2.0. When the chromaticity a* and the chromaticity b* are in the above range, even if the light-emitting state of the luminous body in contact with the adhesive layer 11 continues for a long time, the adhesive layer 11 is still close to colorless and transparent, which can be said to have excellent light resistance. Become more suitable as a backlight sticker.

In addition, the measurement methods of the chromaticity a* and the chromaticity b* in this specification are as described in the test examples described later.

(4) Adhesion The lower limit of the adhesive force of the adhesive sheet 1 of this embodiment to the soda lime glass at 23°C is preferably 10N/25mm or more, preferably 13N/25mm or more, especially 15N/25mm or more, and more preferably 26N/ More than 25mm is preferred. When the lower limit of the adhesive force is the above, the luminous body encapsulation is more excellent. In addition, the upper limit of the adhesive force of the adhesive sheet 1 to the soda lime glass at 23° C. of this embodiment is preferably 100N/25mm or less, 80N/25mm or less, and 50N/25mm or less particularly preferably. The upper limit of the adhesive force is the above, and good reworkability can be obtained.

Here, the adhesive force at 23°C in this specification basically refers to the adhesive force measured according to the 180 degree peeling method of JIS Z0237:2009. The measurement sample is 25mm wide and 100mm long, and the measurement sample is attached The adherend was pressed at 50°C for 20 minutes at 0.5 MPa, and then placed under normal pressure, 23°C, and 50% RH for 24 hours, and measured at a peeling speed of 300 mm/min.

The lower limit of the adhesive force of the adhesive sheet 1 of this embodiment to the soda lime glass at 50°C is preferably 2N/25mm or more, especially 4N/25mm or more, and more preferably 6N/25mm or more. When the lower limit of the adhesive force is the above, the luminous body encapsulation under heat-resistant conditions is more excellent. Furthermore, the upper limit of the adhesive force of the adhesive sheet 1 of this embodiment to the soda lime glass at 50°C is not particularly limited. It is preferably 100N/25mm or less, 80N/25mm or less, and 50N/25mm or less particularly preferably .

The method of measuring the adhesive force at 50°C in this manual basically refers to the adhesive force measured according to the 180 degree peeling method of JIS Z0237:2009. The measurement sample is 25mm wide and 100mm long, and the measurement sample is attached Attach it to the adherend, press it at 50°C for 20 minutes at 0.5 MPa, then leave it for 6 hours under the conditions of normal pressure, 50°C, and 50% RH, and measure at a peeling speed of 300 mm/min.

3. Manufacture of Adhesive Sheet An example of the production of the adhesive sheet 1 is to apply the above-mentioned coating solution of the adhesive composition P on the peeling surface of one of the peeling sheets 12a (or 12b), and heat-process the adhesive composition P to thermally crosslink the adhesive composition P After the coating layer is formed, the coating layer is superimposed on the release surface of the other release sheet 12b (or 12a). In the case where the aging time is necessary, after the aging time is left, if the aging time is not required, the coating layer is directly formed into the adhesive layer 11. Through this, the above-mentioned adhesive sheet 1 was obtained. The conditions of heat treatment and maturation are the same as described above.

Another example of the production of the adhesive sheet 1 is to apply the above-mentioned coating solution of the adhesive composition P on the peeling surface of one of the peeling sheets 12a, and heat-treat the adhesive composition P to thermally crosslink the adhesive composition P to form a coating A cloth layer, a release sheet 12a with a coating layer was obtained. On the peeling surface of the other peeling sheet 12b, the coating solution of the adhesive composition P is applied, and heat treatment is performed to thermally crosslink the adhesive composition P to form a coating layer to obtain a coating layer的release sheet 12b. After that, the release sheet 12a with a coating layer and the release sheet 12b with a coating layer are bonded together so that the two coating layers are in contact with each other. Here, it is also possible to produce a plurality of release sheets with coating layers, and to bond only the desired number of coating layers. In the case where the aging time is necessary, the standing aging time is passed, and in the case where the aging time is not required, the adhesive layer 11 is directly formed from the above-mentioned laminated coating layer. Through this, the above-mentioned adhesive sheet 1 was obtained. According to this manufacturing example, even when the adhesive layer 11 is thick, stable manufacturing is possible.

As a method of applying the coating solution of the adhesive composition P, for example, a bar coating method, a knife coating method, a roll coating method, a plate coating method, a nozzle coating method, a gravure coating method, etc. can be used.

[Backlight Unit] The backlight unit of one embodiment of the present invention is shown in FIG. 2. As shown in Figure 2, the backlight unit 2 of this embodiment has a backlight 20 in which a plurality of luminous bodies 22 are arranged on one or more than two substrates 21, and is attached to the backlight 20 to encapsulate the luminous bodies 22 of the adhesive layer 11 is constituted.

The adhesive layer 11 of the backlight unit 2 is the adhesive layer 11 of the adhesive sheet 1 for attaching the backlight. The plurality of luminous bodies 22 are encapsulated without voids through the adhesive layer 11. As a result, the obtained display has no air layer and voids inside, which can prevent the deterioration of image quality caused by the reflection loss of light.

The substrate 21 is not particularly limited, and those generally used for backlights can be used. The substrate 21 is usually a printed circuit board (PCB substrate; Printed Circuit Board).

The substrate 21 may be integrally formed with a plurality of luminous bodies 22 in an integrated manner, or may be separately formed in a manner of mounting one luminous body 22 on one substrate 21. In the case of separate formation, each substrate 21 is usually fixed to a frame, a support, a frame, or the like. In this embodiment, as shown in FIG. 2, it is preferable that a plurality of light-emitting bodies 22 are integrally formed on the substrate 21 in an integrated manner.

A reflective layer may be formed on the surface of the substrate 21 on the side of the adhesive layer 11, or a reflective element may be provided. Therefore, the brightness caused by the backlight 20 can be efficiently improved. The materials of the reflective layer and the reflective element can be known ones.

The type of the light-emitting body 22 includes, for example, a light-emitting diode (LED), a laser diode (LD), an organic electroluminescence element, and an inorganic electroluminescence element. Among these, from the viewpoint of the encapsulation property of the adhesive layer 11, LEDs are preferred, and in particular, sub-millimeter light-emitting diodes (Mini LED) or micro-light-emitting diodes (Micro LED) are preferred.

The thickness of the luminous body 22 is preferably 10 μm or more, preferably 30 μm or more, particularly preferably 50 μm or more, and more preferably 80 μm or more. In addition, the thickness of the luminous body 22 is preferably 300 μm or less, particularly preferably 150 μm or less, and more preferably 100 μm or less. With the adhesive layer 11 of this embodiment, even if the thickness of the luminous body 22 is in the above range, the luminous body 22 is easily sealed without voids.

In addition, the gap width of the luminous bodies 22 adjacent to each other is preferably 0.01 mm or more, particularly preferably 0.1 mm or more, and more preferably 0.5 mm or more. Furthermore, the aforementioned gap width is preferably 100 mm or less, preferably 10 mm or less, particularly preferably 4 mm or less, and more preferably 2 mm or less. In the case of the adhesive layer 11 of the present embodiment, even if the gap width of the adjacent luminous bodies 22 is within the above range, the luminous bodies 22 can be easily sealed without voids.

The shape of the light-emitting body 22 is not particularly limited, and is usually a rectangular parallelepiped shape, a hemispherical shape, or the like. The size of the luminous body 22 is not particularly limited, but from the viewpoint of the encapsulation of the luminous body, the side or diameter in plan view is preferably 0.01-100mm, preferably 0.1-10mm, particularly preferably 0.2-5mm, more preferably 0.5-2mm Better.

Here, the display using the backlight unit 2 of this embodiment will be described. The type of display is not particularly limited as long as it is a type using a backlight unit, but it is mainly exemplified by a liquid crystal display device.

An example of the liquid crystal display device of this embodiment is shown in FIG. 3. As shown in FIG. 3, the liquid crystal display device 3 of this embodiment has the above-mentioned backlight unit 2, the diffusion element 31 laminated on the adhesive layer 11 of the backlight unit 2, and the diffusion element 31 laminated on the diffusion element 31 is opposite to the backlight unit 2. The liquid crystal panel 32 on the side is formed. Here, the backlight 20 of the liquid crystal display device 3 corresponds to a direct type backlight.

The diffusion element 31 is an element that diffuses the light irradiated from the backlight unit 2. Due to the diffusion element 31, the occurrence of uneven brightness can be effectively suppressed. The diffusion element 31 can use known ones, such as a diffusion plate and a diffusion film, and a combination of these can be used. The liquid crystal panel 32 can also be a well-known one.

In addition, between the adhesive layer 11 and the diffusion element 31, between the diffusion element 31 and the liquid crystal panel 32, or on the surface of the liquid crystal panel 32 opposite to the diffusion element 31, a desired optical element may be provided. Such optical elements include, for example, brightness enhancement films, contrast enhancement films, viewing angle compensation films, transparent conductive films, liquid crystal polymer films, transflective films, anti-scatter films, and the like.

In manufacturing the liquid crystal display device 3 of this embodiment, for example, one peeling sheet 12a of the adhesive sheet 1 is peeled off, and the exposed adhesive layer 11 of the adhesive sheet 1 is attached to the surface of the backlight 20 on the side where the light-emitting body 22 exists. .

After that, the other release sheet 12b is peeled off from the adhesive layer 11 of the adhesive sheet 1, and the adhesive layer 11 exposed on the adhesive sheet 1 and the diffusion element 31 are bonded together. After that, using a desired adhesive sheet, the diffusion element 31 and the liquid crystal panel 32 are bonded together. In another example, the order of bonding the backlight 20 and the diffusion element 31 may be changed.

In the above-mentioned liquid crystal display device 3, the plurality of light-emitting bodies 22 of the backlight unit 2 are encapsulated without voids by the adhesive layer 11, and therefore it is possible to prevent the deterioration of the image quality due to the reflection loss of light. In addition, even if the liquid crystal display device 3 is placed under durable conditions, such as 85°C, 85%RH, and 72 hours, it can suppress the occurrence of floating, peeling, etc. at the interface between the adhesive layer 11 and the luminous body 22 , The encapsulation of the luminous body 22 due to the adhesive layer 11 can be maintained well.

The embodiments described above are described for easy understanding of the present invention, and are not described to limit the present invention. Therefore, the elements disclosed in the above embodiments also include all design changes or equivalents belonging to the technical field of the present invention.

For example, either or both of the release sheets 12a and 12b of the adhesive sheet 1 may be omitted, or a desired optical element may be laminated instead of the release sheets 12a and/or 12b. [Example]

Hereinafter, the present invention will be further specifically described through examples and the like, but the scope of the present invention is not limited to these examples and the like.

[Example 1] 1. Production of (meth)acrylate polymer 60 parts by mass of 2-ethylhexyl acrylate, 10 parts by mass of isobornyl acrylate, 10 parts by mass of N-propenylmorpholine, and 20 parts by mass of 2-hydroxyethyl acrylate were copolymerized by solution polymerization , To produce (meth)acrylate polymer (A). The molecular weight of this (meth)acrylate polymer (A), measured by the method described later, was a weight average molecular weight (Mw) of 500,000.

2. Production of adhesive composition Mix 100 parts by mass of the (meth)acrylate polymer (A) obtained in step 1 above (solid content conversion value, the same below), and trimethylolpropane as a crosslinking agent (B) modified toluene diisocyanate ( TOYOCHEM, product name "BHS8515") 0.15 parts by mass, and 0.2 parts by mass of 3-glycidylpropyltrimethoxysilane as a silane coupling agent, stir well, and dilute with methyl ethyl ketone to obtain a coating of the adhesive composition Cloth solution.

Here, each formulation (solid content conversion value) of the adhesive composition when the (meth)acrylate polymer (A) is 100 parts by mass (solid content conversion value) is shown in Table 1. In addition, the detailed information such as the code numbers listed in Table 1 are as follows. [(Meth)acrylate polymer (A)] 2EHA: 2-ethylhexyl acrylate IBXA: Isobornyl acrylate ACMO: N-acryloylmorpholine HEA: 2-hydroxyethyl acrylate BA: n-butyl acrylate AA: Acrylic MA: methyl acrylate EA: ethyl acrylate [Crosslinker (B)] TDI: Trimethylolpropane modified toluene diisocyanate (manufactured by TOYOCHEM, product name "BHS8515") XDI: Trimethylolpropane modified xylene diisocyanate (manufactured by Soken Chemical Co., Ltd., product name "TD-75") Epoxy resin: 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane (manufactured by Mitsubishi Gas Chemical Corporation, product name "TETRAD-C") A1 chelating agent: aluminum triacetylacetonate (manufactured by Soken Chemical Co., Ltd., product name "M-5A")

3. Manufacture of Adhesive Sheet The coating solution of the adhesive composition obtained in the above step 2 was coated on one side of polyethylene terephthalate by a knife coating method, and a heavy release type release sheet ( After the release-treated surface of the Lintech company, product name "SP-PET752150"), a coating layer (thickness: about 50 μm) was formed by heat treatment at 90°C for 1 minute to produce a heavy-release type release sheet with a coating layer.

On the other hand, the coating solution of the adhesive composition obtained in the above step 2 is coated on one side of the polyethylene terephthalate by the knife coating method, and the silicone release agent is used for the light release After the release-treated surface of a type release sheet (manufactured by Lintech, product name "SP-PET381130"), heat treatment at 90°C for 1 minute to form a coating layer (thickness: about 50 μm) to produce a light release type with a coating layer Peel off the piece. Four lightly peelable release sheets with a coating layer were produced.

The surface on the coating layer side of the heavy release release sheet with a coating layer obtained above and the surface on the coating layer side of the first light release release sheet with a coating layer obtained above are bonded together, A first laminate formed of coating layers with a total thickness of about 100 μm sandwiched between a heavy release release sheet and a light release release sheet was obtained.

Next, the lightly peelable release sheet is peeled from the first laminate to expose the exposed surface of the coating layer, and the surface of the second lightly peelable release sheet with a coating layer on the coating layer side is bonded to obtain a heavy A second laminate formed by a peelable peeling sheet and a light peeling peeling sheet sandwiching a coating layer with a total thickness of about 150 μm.

Next, the lightly peelable release sheet is peeled from the second layered body to expose the exposed surface of the coating layer, and the third lightly peelable release sheet with a coating layer is bonded to the coated layer side surface to obtain a heavy A third layered body formed by a peelable peeling sheet and a light peeling peeling sheet sandwiching a coating layer with a total thickness of about 200 μm.

Next, the lightly peelable release sheet is peeled from the third laminate to expose the exposed surface of the coating layer, and the surface of the fourth lightly peelable release sheet with a coating layer on the coating layer side is bonded to obtain the A fourth laminate formed by a peelable release sheet and a lightly peelable release sheet sandwiching a coating layer with a total thickness of about 250 μm.

The fourth layered body was aged for 7 days under the conditions of 23° C. and 50% RH to produce an adhesive sheet having a structure of a heavy peeling type release sheet/adhesive layer (thickness: 250 μm)/light peeling type release sheet.

In addition, the thickness of the adhesive layer is a value measured in accordance with JIS K7130 using a constant pressure thickness measuring device (manufactured by TECLOCK, product name "PG-02").

[Examples 2~6, Comparative Examples 1~3] The type and ratio of monomers constituting the (meth)acrylate polymer (A), the weight average molecular weight (Mw) of the (meth)acrylate polymer (A), and the type and amount of crosslinking agent (B) , The blending amount of the silane coupling agent and the thickness of the adhesive layer are the same as those in Example 1 except for the changes shown in Table 1. In addition, in Example 3 and Comparative Example 2, the thickness of the adhesive layer was changed by changing the number of layers of the coating layer formed on the light-peelable release sheet.

Here, the above-mentioned weight average molecular weight (Mw) is a weight average molecular weight in terms of polystyrene measured (GPC measurement) using a gel permeation chromatography (GPC) method under the following conditions. >Measurement conditions> •Measuring device: TOSOH Corporation, HLC-8320 •GPC string (through the following sequence): TOSOH Corporation TSK gel superH-H TSK gel superHM-H TSK gel superH2000 •Measuring solvent: tetrahydrofuran •Measuring temperature: 40℃

[Test Example 1] (Measurement of Gel Fraction) The adhesive sheets obtained in the Examples and Comparative Examples were cut into a size of 80mm×80mm, the adhesive layer was wrapped in a polyester mesh (mesh size 200), and the mass was weighed on a precision balance, minus the weight of the above-mentioned mesh Separate the mass, calculate the mass of only the adhesive. At this time, it is recorded as mass M1.

Next, the adhesive wrapped in the polyester mesh was immersed in ethyl acetate at room temperature (23°C) for 24 hours. After that, take out the adhesive and dry it in the air for 24 hours at a temperature of 23°C and a relative humidity of 50%, and then dry it in an oven at 80°C for 12 hours. After drying, weigh its mass on a precision balance and subtract the individual mass of the above net to calculate the mass of only the adhesive. At this time, it is recorded as mass M2. Gel fraction (%) is expressed as (M2/M1)×100. The results are shown in Table 2.

[Test Example 2] (Measurement of Storage Modulus) The release sheet was peeled off from the adhesive sheets obtained in the Examples and Comparative Examples, and a plurality of adhesive layers were laminated so as to have a thickness of 3 mm. A cylinder with a diameter of 8 mm (height 3 mm) was punched out from the resulting laminate of adhesive layers, and this was used as a sample.

For the above-mentioned samples, according to JIS K7244-6, using a viscoelasticity measuring device (manufactured by Physica, product name "MCR300"), the storage modulus (MPa) at 23°C and 50°C was measured under the following conditions by a torsion shear test. The results are shown in Table 2. Measuring frequency: 1Hz Measuring temperature: 23℃, 50℃

[Test Example 3] (Measurement of Adhesion) From the adhesive sheets obtained in the Examples and Comparative Examples, the light-peelable release sheet was peeled, and the exposed adhesive layer and a polyethylene terephthalate (PET) film with an easy-adhesive layer (manufactured by Toyobo Co., Ltd., product name "PET) A4300", thickness: 100μm) easy-to-adhesive layer was attached to obtain a laminate of release sheet/adhesive layer/PET film. The obtained laminate was cut into a width of 25 mm and a length of 100 mm, and this was used as a sample.

In an environment of 23°C and 50%RH, the heavy-peelable release sheet was peeled from the above sample, and the exposed adhesive layer was attached to soda lime glass (manufactured by Nippon Sheet Glass Co., Ltd.), and then used in a sterilization autoclave manufactured by Kurihara Manufacturing Co., Ltd. Press 0.5MPa and 50°C for 20 minutes. After that, it was left at 23°C and 50%RH for 24 hours, or at 50°C and 50%RH for 6 hours.

After that, under the same environment as the above conditions (23℃･50%RH/50℃･50%RH), using a tensile testing machine (manufactured by ORIENTEC, product name "Tensilon"), at a peeling speed of 300mm/min, Under the condition of a peeling angle of 180 degrees, the adhesive force (N/25mm) at 23°C and 50°C was measured. Conditions other than those described here are measured in accordance with JIS Z0237:2009. The results are shown in Table 2.

[Test Example 4] (Evaluation of Implantability) An adhesive sheet (manufactured by Lintech, product name "MO-T015C") formed by sandwiching an acrylic adhesive layer (thickness 25 μm) between two release sheets was prepared, and one release sheet was peeled off. The exposed adhesive layer and an easy-adhesive layer of PET film (manufactured by Toyobo Co., Ltd., product name "PET A4300", thickness: 75μm) with an easy-adhesive layer were bonded together to obtain a laminate of release sheet/adhesive layer/PET film . The obtained laminate was cut into a width of 1 mm and a length of 70 mm, and used as an adhesive tape, and a plurality of the adhesive tapes were produced.

Peel off the other release sheet from the above adhesive tape, and attach the multiple adhesive tapes that expose the adhesive layer to a gap width of 5mm, 3mm or 1mm between adjacent adhesive tapes on a 70mm×70mm soda lime glass ( Nippon Sheet Glass Co., Ltd.), these are used as the adherend.

On the other hand, from the adhesive sheets obtained in the Examples and Comparative Examples, the light-peelable release sheet was peeled off, and the exposed adhesive layer and the PET film with the easy-adhesive layer (manufactured by Toyobo Co., Ltd., product name "PET A4300", thickness: 50μm) easy-to-adhesive layer was bonded to obtain a laminate of release sheet/adhesive layer/PET film. After that, the laminated body is cut into a size of 70mm×70mm.

In an environment of 23° C. and 50% RH, the heavy-peelable release sheet was peeled off from the laminate to expose the adhesive layer. Next, using a laminator (manufactured by FUJIPLA, product name "LPD3214"), each adhesive tape was covered with an adhesive layer to layer the laminate on the above-mentioned adhesive volume, and these were used as samples for evaluation.

After the obtained evaluation sample was treated in a sterilizer under the conditions of 50° C. and 0.5 MPa for 30 minutes, it was left for 24 hours under the conditions of normal temperature, 23° C. and 50% RH. First, visually observe the state of the interface between the adherend and the adhesive layer in this state, and evaluate the embedding properties (before durability) based on the following criteria. The results are shown in Table 2. ◎: No floating or peeling ○: No floating, peeling, but bubbles ×: Floating, peeling occurs

After that, the samples for evaluation were stored under damp heat conditions of 85°C and 85% RH for 72 hours (endurance test), and then the embedding properties were evaluated as described above (after durability). The results are shown in Table 2.

[Test Example 5] (Measurement of total light transmittance) From the adhesive sheets obtained in the examples and comparative examples, the light-peelable release sheet was peeled off, and the exposed adhesive layer and glass were bonded together, and these were used as samples for measurement. In the background measurement with glass, the heavy-peelable release sheet was peeled from the above-mentioned measurement sample to expose the adhesive surface. At 23°C, according to JIS K7361-1:1997, a haze meter (manufactured by Nippon Denshoku Industries, Ltd.) was used. , Product name "NDH-5000") to measure total light transmittance (before durability; %). The results are shown in Table 3.

After that, the measurement sample was stored under high temperature conditions of 50°C and 50%RH for 500 hours (heat resistance test), and then the total light transmittance was measured as described above (after heat resistance test; %). The results are shown in Table 3.

On the other hand, the above-mentioned sample for measurement was put into a light resistance tester (manufactured by SUGA Test Equipment Co., Ltd., product name "Ultraviolet FADE METER U48", light source: carbon arc lamp), and ultraviolet light was irradiated from the side of the heavy peeling peeling sheet (illuminance: 500mW/m ² ) 500 hours. After that, measure the total light transmittance as above (after light resistance test; %). The results are shown in Table 3.

[Test Example 6] (Measurement of Haze Value) From the adhesive sheets obtained in the examples and comparative examples, the light-peelable release sheet was peeled off, and the exposed adhesive layer and glass were bonded together, and these were used as samples for measurement. In the background measurement with glass, the heavy-peelable release sheet was peeled from the above-mentioned measurement sample to expose the adhesive surface. At 23°C, according to JIS K7136:2000, a haze meter (manufactured by Nippon Denshoku Kogyo Co., Ltd.) was used. Name "NDH-5000") to measure the haze value (before durability: %). The results are shown in Table 3.

After that, store the above-mentioned sample for measurement under high temperature conditions of 50°C and 50%RH for 500 hours (heat resistance test), and then measure the haze value as described above (after heat resistance test; %). The results are shown in Table 3.

On the other hand, the above-mentioned sample for measurement was put into a light resistance tester (manufactured by SUGA Test Equipment Co., Ltd., product name "Ultraviolet FADE METER U48", light source: carbon arc lamp), and ultraviolet light was irradiated from the side of the heavy peeling peeling sheet (illuminance: 500mW/m ² ) 500 hours. After that, measure the haze value as above (after light resistance test; %). The results are shown in Table 3.

[Test Example 7] (Measurement of L*a*b*) For the adhesive layer of the adhesive sheets obtained in the Examples and Comparative Examples, a simultaneous photometric spectrophotometer (manufactured by Nippon Denshoku Kogyo Co., Ltd., product name "SQ2000") was used to measure the CIE1976L*a*b* color system. Chroma a* and chroma b* (before endurance). The results are shown in Table 3.

After that, the above-mentioned adhesive sheet was stored under high temperature conditions of 50°C and 50%RH for 500 hours (heat resistance test), and then the chromaticity a* and chromaticity b* were measured as above (after the heat resistance test). The results are shown in Table 3.

On the other hand, the above-mentioned adhesive sheet was put into a light resistance tester (manufactured by SUGA Test Equipment Co., Ltd., product name "Ultraviolet FADE METER U48", light source: carbon arc lamp), and ultraviolet light was irradiated from the side of the heavy peeling peeling sheet (illuminance: 500mW/m ² ) 500 hours. After that, measure the chromaticity a* and the chromaticity b* as above (after the light resistance test). The results are shown in Table 3.

[Test Example 8] (Measurement of Residual Monomer Amount) 0.02 g of the adhesive was separated from the adhesive sheets obtained in the Examples and Comparative Examples, and the adhesive was put into a 22 mL vial, and maintained at 120°C for 30 minutes. After that, using a headspace sampler (manufactured by PerkinElmer, product name "Turbomatrix 40"), the gas phase components in the vial were introduced into the gas chromatography column (manufactured by Hewlett-Packard, product name " Type 6890"), and perform component analysis. In addition, HP-5 manufactured by Hewlett-Packard was used as the separation column. The results confirmed that the amount of residual monomers was less than 0.1% by mass in the adhesive of any example.

[Table 1] (Meth)acrylate polymer (A) Crosslinking agent (B) Silane coupling agent Adhesive layer thickness (μm) composition Mw species Mass parts Mass parts Example 1 2EHA/IBXA/ACMO/HEA =60/10/10/20 500000 TDI 0.15 0.2 250 Example 2 0.15 - 250 Example 3 0.15 0.2 150 Example 4 XDI 0.15 0.2 250 Example 5 BA/AA=90/10 400000 Epoxy resin 0.05 0.2 250 Example 6 BA/MA/HEA=60/20/20 800 000 TDI 0.25 0.2 250 Comparative example 1 2EHA/IBXA/ACMO/HEA =60/10/10/20 500000 TDI 3 0.2 250 Comparative example 2 0.15 0.2 100 Comparative example 3 BA/EA/AA=75/20/5 1000000 AI chelator 0.7 - 250

[Table 2] Gel fraction (%) Storage modulus (MPa) Adhesion (N/25mm) Embeddedness assessment 23℃ 50℃ 23℃ 50℃ Tape interval: 5mm Tape interval: 3mm Tape interval: 1mm Before endurance After durability Before endurance After durability Before endurance After durability Example 1 55 0.07 0.03 33 9 ◎ ◎ ◎ ◎ ◎ ◎ Example 2 55 0.07 0.03 32 8 ◎ ◎ ◎ ◎ ◎ ◎ Example 3 55 0.07 0.03 28 10 ◎ ◎ ◎ ◎ ◎ 〇 Example 4 55 0.07 0.03 34 8 ◎ ◎ ◎ ◎ ◎ ◎ Example 5 58 0.16 0.07 43 33 ◎ 〇 ◎ 〇 ◎ 〇 Example 6 68 0.13 0.07 30 15 ◎ ◎ ◎ 〇 〇 〇 Comparative example 1 95 0.21 0.14 8 1 × × × × × × Comparative example 2 55 0.07 0.03 25 11 × × × × × × Comparative example 3 80 0.16 0.12 twenty three 35 × × × × × ×

[table 3] Total light transmittance (%) Haze value (%) a* b* Before endurance After heat test After light resistance test Before endurance After heat test After light resistance test Before endurance After heat test After light resistance test Before endurance After heat test After light resistance test Example 1 99≦ 99≦ 99≦ 0.5 0.4 0.5 -0.3 -0.3 -0.3 0.2 0.3 0.4 Example 2 99≦ 99≦ 99≦ 0.4 0.5 0.5 -0.3 -0.3 -0.3 0.2 0.3 0.4 Example 3 99≦ 99≦ 99≦ 0.4 0.4 0.5 -0.3 -0.3 -0.3 0.3 0.3 0.4 Example 4 99≦ 99≦ 99≦ 0.4 0.5 0.5 -0.3 -0.3 -0.2 0.2 0.3 0.3 Example 5 99≦ 99≦ 99≦ 0.5 0.5 0.5 -0.3 -0.3 -0.3 0.3 0.2 0.3 Example 6 99≦ 99≦ 99≦ 0.5 0.4 0.4 -0.3 -0.2 -0.2 0.3 0.4 0.5 Comparative example 1 99≦ 99≦ 99≦ 0.5 0.6 0.6 -0.3 -0.3 -0.3 0.3 0.5 0.7 Comparative example 2 99≦ 99≦ 99≦ 0.4 0.4 0.5 -0.3 -0.2 -0.3 0.3 0.3 0.4 Comparative example 3 99≦ 99≦ 99≦ 0.5 0.5 0.5 -0.4 -0.3 -0.3 0.5 0.5 0.5

It can be seen from Table 2 that the adhesive sheets obtained in the examples have excellent embedding properties before and after the durability test. It can be seen from Table 3 that the adhesive sheets obtained in the examples have a high degree of colorlessness and transparency before the durability test, after the heat resistance test, and after the light resistance test. [Industry Availability]

The adhesive sheet and backlight unit for attaching a backlight of the present invention can be suitably used in, for example, a liquid crystal display device using a direct type backlight.

1: Adhesive sheet for backlight attachment 11: Adhesive layer 12a, 12b: peeling sheet 2: Backlight unit 20: Backlight 21: substrate 22: luminous body 3: Liquid crystal display device 31: Diffusion element 32: LCD panel

Figure 1 is a cross-sectional view of an adhesive sheet for backlight attachment according to an embodiment of the present invention. Figure 2 is a cross-sectional view of a backlight unit according to an embodiment of the present invention. Figure 3 is a cross-sectional view of a liquid crystal display device according to an embodiment of the present invention.

1: Adhesive sheet for backlight attachment

11: Adhesive layer

12a, 12b: peeling sheet

Claims (6)

An adhesive sheet for backlight attachment, which is an adhesive sheet with an adhesive layer attached to a backlight provided with a plurality of luminous bodies on a substrate to encapsulate the luminous bodies, and is characterized in that: The storage modulus of the adhesive layer at 50°C is above 0.001 MPa and below 0.15 MPa, The gel fraction of the adhesive constituting the adhesive layer is 10% or more and 75% or less, The thickness of the adhesive layer is 110 μm or more. The adhesive sheet for backlight attachment according to claim 1, wherein the storage modulus of the adhesive layer at 23° C. is 0.01 MPa or more and 0.20 MPa or less. The adhesive sheet for backlight attachment according to claim 1, wherein the adhesive is an acrylic adhesive. The adhesive sheet for attaching a backlight as described in claim 1, which has 2 peel-off sheets, and The adhesive layer which is in contact with the release surfaces of the two release sheets and is sandwiched by the release sheets. A backlight unit with A backlight with a plurality of luminous bodies on one or more than two substrates, and A backlight unit attached to the aforementioned backlight to encapsulate the adhesive layer of the luminous body, It is characterized in that the adhesive layer is the adhesive layer of the adhesive sheet for backlight attachment according to any one of claims 1 to 4. The backlight unit according to claim 5, wherein the light-emitting body is a light-emitting diode.

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