JP6770569B2 - Adhesive sheet for attaching backlight and backlight unit - Google Patents

Description

The present invention relates to an adhesive sheet for attaching a backlight to be attached to the backlight and such a backlight in a display device having a display unit including a liquid crystal panel, various optical members, and a backlight for illuminating the display unit. It relates to a backlight unit to which an adhesive layer is attached.

In recent years, electronic devices such as mobile phones, smartphones, tablet terminals, and game machines often use liquid crystal display devices as display bodies. Since a display unit including a liquid crystal panel or the like does not emit light by itself, the display device includes a display unit and a backlight that illuminates the display unit.

As a method of arranging the light source of the backlight in 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 under the display unit. From the viewpoint of screen brightness and contrast, direct-type backlights are becoming mainstream. In the direct type backlight, a large number of light emitters, typically a light emitting diode (LED), are provided on the substrate in order to increase the amount of light and make the light uniform.

Here, the display device is usually formed by sticking the display unit and the backlight together with an adhesive sheet and fixing them. Examples of such an adhesive sheet include those disclosed in Patent Documents 1 and 2. Such an adhesive sheet has a plan view frame-like shape, and a display portion and a backlight are bonded to each other at their peripheral edges. Therefore, the inside of the frame-shaped adhesive sheet is a void, and an air layer exists.

Japanese Patent No. 5192682 Japanese Unexamined Patent Publication No. 2007-059386

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

In order to solve the above problem, it is conceivable to attach an adhesive sheet to the entire surface of the backlight, but as described above, a large number of LEDs are provided on the substrate of the backlight. Conventionally, there has been no adhesive sheet that can be attached to the entire surface of such a backlight so that there are no voids. For example, the adhesive sheets disclosed in Patent Documents 1 and 2 have a predetermined performance when used as a frame-shaped portion, but are sufficient to be directly and without gaps attached to a large number of LEDs. It does not have performance.

On the other hand, instead of using an adhesive sheet, it is conceivable to apply an adhesive to the entire surface of the backlight to form an adhesive layer, but there is a problem that productivity is poor.

The present invention has been made in view of the above-mentioned actual conditions, and can be attached to a backlight provided with a plurality of light emitters on a substrate so that the light emitters are sealed without gaps. It is an object of the present invention to provide a backlight sticking adhesive sheet and a backlight unit in which such a backlight sticking adhesive sheet is attached to a backlight.

In order to achieve the above object, first, the present invention provides an adhesive layer provided with an adhesive layer attached to a backlight provided with a plurality of light emitters so as to seal the light emitters. In the sheet, the storage elastic modulus of the pressure-sensitive adhesive layer at 50 ° C. is 0.001 MPa or more and 0.15 MPa or less, and the gel fraction of the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer is 10% or more and 75. % Or less, and the thickness of the pressure-sensitive adhesive layer is 110 μm or more, providing a pressure-sensitive adhesive sheet for attaching a backlight (Invention 1).

According to the above invention (Invention 1), since the pressure-sensitive adhesive layer has the above-mentioned physical properties, the light-emitting body is adhered to a backlight provided with a plurality of light-emitting bodies on the substrate so as to be sealed without voids. The agent layer can be attached.

In the above invention (Invention 1), the storage elastic modulus of the pressure-sensitive adhesive layer at 23 ° C. is preferably 0.01 MPa or more and 0.20 MPa or less (Invention 2).

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

In the above inventions (Inventions 1 to 3), it is preferable to provide two release sheets and the pressure-sensitive adhesive layer sandwiched between the release sheets so as to be in contact with the release surfaces of the two release sheets (invention). 4).

Secondly, the present invention comprises a backlight provided with a plurality of light emitters on one or more substrates, and an adhesive layer attached to the backlight so as to seal the light emitters. Provided is a backlight unit provided, wherein the pressure-sensitive adhesive layer is a pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet for attaching a backlight (Inventions 1 to 4) (Invention 5).

In the above invention (Invention 5), it is preferable that the light emitting body is a light emitting diode (Invention 6).

The adhesive sheet for attaching a backlight according to the present invention can be attached to a backlight provided with a plurality of light emitters on a substrate so that the light emitters are sealed without gaps. Further, in the backlight unit according to the present invention, since the adhesive layer is attached to the backlight so that a plurality of light emitters on the substrate are sealed without voids, deterioration of image quality in the obtained display body is suppressed. can do.

It is sectional drawing of the adhesive sheet for attaching a backlight which concerns on one Embodiment of this invention. It is sectional drawing of the backlight unit which concerns on one Embodiment of this invention. It is sectional drawing of the liquid crystal display device which concerns on one Embodiment of this invention.

Hereinafter, embodiments of the present invention will be described.
[Adhesive sheet for attaching backlight]
The adhesive sheet for attaching a backlight according to an embodiment of the present invention (in the present specification, it may be simply referred to as an "adhesive sheet") is a backlight provided with a plurality of light emitters on a substrate to emit light. It is provided with an adhesive layer to be attached so as to seal the body, and preferably, a release sheet is laminated on one side or both sides of the adhesive layer.

FIG. 1 shows a specific configuration as an example of the adhesive sheet for attaching a backlight according to the present embodiment.
As shown in FIG. 1, the back light sticking adhesive sheet (adhesive sheet) 1 is in contact with the two release sheets 12a and 12b and the release surfaces of the two release sheets 12a and 12b. It is composed of an adhesive layer 11 sandwiched between the release sheets 12a and 12b. The peeling surface of the release sheet in the present specification means a surface of the release sheet that has peelability, and includes both a surface that has been peeled and a surface that exhibits peelability without peeling. ..

1. 1. Each member 1-1. Adhesive layer The adhesive layer 11 of the adhesive sheet 1 according to the present embodiment has a storage elastic modulus of 0.001 MPa or more and 0.15 MPa or less at 50 ° C., and the gel content of the adhesive constituting the pressure-sensitive adhesive layer 11. The rate is 10% or more, 75% or less, and the thickness is 110 μm or more.

Since the pressure-sensitive adhesive layer 11 has the above-mentioned physical properties, the pressure-sensitive adhesive sheet 1 according to the present embodiment is provided with a backlight provided with a plurality of light-emitting bodies on the substrate so that the light-emitting bodies are sealed without voids. The pressure-sensitive adhesive layer 11 can be attached. As a result, since there is no air layer or void between the display unit and the backlight in the obtained display device or the like, it is possible to prevent deterioration of image quality due to light reflection loss.

Specifically, the pressure-retaining elastic modulus of the pressure-sensitive adhesive layer 11 at 50 ° C. is 0.15 MPa or less, and the gel content of the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer 11 is 75% or less. The agent layer 11 exhibits excellent flexibility and stress relaxation property, facilitates embedding of the illuminant, and thus can seal the illuminant without voids.

On the other hand, a plurality of light emitters provided in the backlight may generate heat due to light emission, and when a large number of light emitters are provided, the adhesive layer 11 is exposed to a high temperature condition (durability condition). Become. When the storage elastic modulus of the pressure-sensitive adhesive layer 11 at 50 ° C. is 0.001 MPa or more and the gel fraction is 10% or more, there are no voids due to the pressure-sensitive adhesive layer 11 even under the above-mentioned durability conditions. The seal is easily maintained.

From the viewpoint of luminescent material embedding property, the storage elastic modulus of the pressure-sensitive adhesive layer 11 at 50 ° C. is preferably 0.13 MPa or less, particularly preferably 0.09 MPa or less, and further preferably 0.05 MPa or less. Is preferable. Further, from the viewpoint of luminescent material sealing property under durable conditions, the storage elastic modulus is preferably 0.01 MPa or more, particularly preferably 0.02 MPa or more, and further preferably 0.03 MPa or more. It is preferable to have.

From the viewpoint of luminescent material embedding property, the gel fraction of the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer 11 is preferably 70% or less, particularly preferably 64% or less, and further preferably 57% or less. Is preferable. Further, from the viewpoint of luminescent material sealing property under durable conditions, the gel fraction is preferably 20% or more, more preferably 30% or more, and particularly preferably 40% or more. Further, it is preferably 50% or more.

On the other hand, the storage elastic modulus of the pressure-sensitive adhesive layer 11 at 23 ° C. is preferably 0.20 MPa or less, more preferably 0.18 MPa or less, and particularly 0.15 MPa or less from the viewpoint of illuminant embedding property. It is preferably 0.11 MPa or less. Further, from the viewpoint of luminescent material sealing property under durable conditions, the storage elastic modulus is preferably 0.01 MPa or more, particularly preferably 0.02 MPa or more, and further preferably 0.04 MPa or more. It is preferable to have.

The storage elastic modulus in the present specification is a value measured by the torsional shear method at a measurement frequency of 1 Hz in accordance with JIS K7244-6. Specifically, it is as shown in the test example described later. The method for measuring the gel fraction of the pressure-sensitive adhesive is as shown in a test example described later.

The pressure-sensitive adhesive layer 11 has the above-mentioned storage elastic modulus and gel fraction, and has a thickness of 110 μm or more, so that the light-emitting body can be sealed according to the type of the light-emitting body. From the viewpoint of sealing the luminescent material, the thickness of the pressure-sensitive adhesive layer 11 is preferably 130 μm or more, particularly preferably 160 μm or more, and further preferably 200 μm or more. On the other hand, from the viewpoint of reducing the thickness of the obtained display body, the thickness of the pressure-sensitive adhesive layer 11 is preferably 1000 μm or less, particularly preferably 800 μm or less, and further preferably 500 μm or less.

The ratio of the thickness of the pressure-sensitive adhesive layer 11 to the thickness of the light-emitting body (thickness of the pressure-sensitive adhesive layer / thickness of the light-emitting body) is 1.1 or more from the viewpoint of reliably sealing the light-emitting body. It is preferably 1.4 or more, more preferably 2.0 or more, and further preferably 2.2 or more. On the other hand, the ratio of the thickness is preferably 10 or less, more preferably 8 or less, particularly preferably 5 or less, and further 2. It is preferably 9 or less.

The type of the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer 11 of the pressure-sensitive adhesive sheet 1 according to the present embodiment is not particularly limited as long as the above-mentioned physical property values are satisfied, and for example, an acrylic pressure-sensitive adhesive, a polyester-based pressure-sensitive adhesive, and a polyurethane-based pressure-sensitive adhesive. , Rubber-based pressure-sensitive adhesive, silicone-based pressure-sensitive adhesive, or the like. Further, the pressure-sensitive adhesive may be an emulsion type, a solvent type or a solvent-free type, and may be either a crosslinked type or a non-crosslinked type. Among them, an acrylic pressure-sensitive adhesive that easily satisfies the above-mentioned physical property values is preferable.

The acrylic pressure-sensitive adhesive may be an active energy ray-curable adhesive or an active energy ray non-curable adhesive, but the active energy ray non-curable adhesive does not require a photopolymerization initiator. It is preferably a sex acrylic pressure-sensitive adhesive. As the active energy ray non-curable acrylic pressure-sensitive adhesive, a crosslinked type is particularly preferable, and a heat crosslinked type is further preferable.

The pressure-sensitive adhesive particularly crosslinks a pressure-sensitive composition containing a (meth) acrylic acid ester polymer (A) and a cross-linking agent (B) (hereinafter, may be referred to as “sticky composition P”). It is preferable that the material is made of In addition, 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 "polymer" shall be included in "polymer".

(1) Ingredients of Adhesive Composition (1-1) (Meta) Acrylic Ester Polymer (A)
The (meth) acrylic acid ester polymer (A) in the present embodiment contains a reactive group-containing monomer having a reactive group in the molecule that reacts with the cross-linking agent (B) as a monomer unit constituting the polymer. Is preferable. The 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), and a pressure-sensitive adhesive having the above-mentioned gel fraction and storage elastic modulus can be obtained. It will be easier.

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), and a monomer having an amino group in the molecule (amino group-containing monomer). ) Etc. are preferably mentioned. Among these, a hydroxyl group-containing monomer is particularly preferable from the viewpoint of suppressing the storage elastic modulus to a low level.

Examples of the hydroxyl group-containing monomer include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, and (meth). ) (Meta) Acrylic acid hydroxyalkyl esters such as 3-hydroxybutyl acrylate and 4-hydroxybutyl (meth) acrylic acid can be mentioned. Among them, hydroxy having 1 to 4 carbon atoms is considered from the viewpoint of the reactivity of the obtained (meth) acrylic acid ester polymer (A) with the cross-linking agent (B) of the hydroxyl group and the copolymerizability with other monomers. A (meth) acrylic acid hydroxyalkyl ester having an alkyl group is preferable. Specifically, for example, 2-hydroxyethyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate and the like are preferable, and 2-hydroxyethyl acrylate or 4-hydroxybutyl acrylate are particularly preferable. Be done. These may be used alone or in combination of two or more.

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

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

The (meth) acrylic acid ester polymer (A) preferably contains a reactive group-containing monomer as a lower limit value of 3% by mass or more, and particularly 10% by mass or more, as a monomer unit constituting the polymer. It is preferably contained in an amount of 15% by mass or more. Further, the (meth) acrylic acid ester polymer (A) preferably contains a reactive group-containing monomer as an upper limit value of 35% by mass or less, particularly 30% by mass or less, as a monomer unit constituting the polymer. It is preferably contained, and more preferably 25% by mass or less. When the (meth) acrylic acid ester polymer (A) contains the reactive group-containing monomer in the above amount as the monomer unit, the above-mentioned storage elastic modulus and gel fraction can be easily obtained.

Further, 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 carboxy group is an acid component, by not containing the carboxy group-containing monomer, the adhesive is subject to problems due to the acid, such as the encapsulating resin of the light emitter, the metal wiring of the substrate, and the metal on the substrate. Even when a reflective film or the like is present, it is possible to suppress those defects (deterioration, corrosion, etc.) due to the acid. However, it is permissible to contain a predetermined amount of the carboxy group-containing monomer so as not to cause such a problem. Specifically, in the (meth) acrylic acid ester polymer (A), the carboxy group-containing monomer is contained in an amount of 0.1% by mass or less, preferably 0.01% by mass or less, more preferably 0.001 as a monomer unit. It is permissible to contain 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, good adhesiveness can be exhibited. The alkyl group may be linear or branched chain.

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 the (meth) acrylic acid alkyl ester having an alkyl group having 1 to 20 carbon atoms include methyl (meth) acrylic acid, ethyl (meth) acrylic acid, propyl (meth) acrylic acid, and n- (meth) acrylic acid. Butyl, n-pentyl (meth) acrylic acid, n-hexyl (meth) acrylic acid, 2-ethylhexyl (meth) acrylic acid, isooctyl (meth) acrylic acid, n-decyl (meth) acrylic acid, (meth) acrylic acid Examples thereof include n-dodecyl, myristyl (meth) acrylate, palmityl (meth) acrylate, and stearyl (meth) acrylate. Among them, (meth) acrylic acid ester having 1 to 8 carbon atoms of the alkyl group is preferable from the viewpoint of further improving the adhesiveness, and methyl (meth) acrylate, n-butyl (meth) acrylate or (meth) acrylic. 2-Ethylhexyl acid acid is particularly preferred. These may be used alone or in combination of two or more.

The (meth) acrylic acid ester polymer (A) preferably contains (meth) acrylic acid alkyl ester in an amount of 30% by mass or more, and more preferably 40% by mass or more, as a monomer unit constituting the polymer. It is preferable to contain 50% by mass or more, and more preferably 55% by mass or more. When the lower limit of the content of the (meth) acrylic acid alkyl ester is as described above, the (meth) acrylic acid ester polymer (A) can exhibit suitable tackiness. Further, the (meth) acrylic acid ester polymer (A) preferably contains 97% by mass or less of (meth) acrylic acid alkyl ester as a monomer unit constituting the polymer, and 90% by mass or less. Is more preferable, and it is particularly preferable to contain 80% by mass or less, and further preferably 70% by mass or less. When the upper limit of the content of the (meth) acrylic acid alkyl ester is as described 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). It is possible to easily adjust the gel fraction and the storage elastic modulus.

It is also preferable that the (meth) acrylic acid ester polymer (A) contains a monomer having an alicyclic structure in the molecule (alicyclic structure-containing monomer) as a monomer unit constituting the polymer. Since the alicyclic structure-containing monomer is bulky, it is presumed that the presence of the monomer in the polymer widens the distance between the polymers, and the obtained adhesive can be made excellent in flexibility. .. On the other hand, the alicyclic structure-containing monomer itself can impart a certain degree of hardness to the polymer. Therefore, when the (meth) acrylic acid ester polymer (A) has an alicyclic structure-containing monomer as a constituent monomer unit, the gel fraction and storage elastic modulus of the obtained pressure-sensitive adhesive, particularly the storage elastic modulus at 50 ° C., can be determined. It will be easy to adjust to the above range.

The alicyclic structure carbon ring in the alicyclic structure-containing monomer may have a saturated structure or may have an unsaturated bond as a part. Further, the alicyclic structure may be a monocyclic alicyclic structure or a polycyclic alicyclic structure such as two rings or three rings. Similar to the above, from the viewpoint of adjusting the physical property value of the obtained pressure-sensitive adhesive, the alicyclic structure is preferably a polycyclic alicyclic structure (polycyclic structure). Further, in consideration of compatibility between the (meth) acrylic acid ester polymer (A) and other components, the polycyclic structure is particularly preferably bicyclic to tetracyclic. Further, similarly to the above, from the viewpoint of adjusting the physical property value of the obtained pressure-sensitive adhesive, the number of carbon atoms of the alicyclic structure (referring to all the carbon atoms of the portion forming the ring, and a plurality of rings exist independently. In this case, the total number of carbon atoms) is usually preferably 5 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 viewpoint of compatibility as described above, it is preferably 15 or less, and 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, and (meth) acrylic. Examples thereof include dicyclopentenyl acid, dicyclopentenyloxyethyl (meth) acrylate, and among them, dicyclopentanyl (meth) acrylate (carbon number of alicyclic structure) which exhibits better luminescent material embedding property. : 10), adamantyl (meth) acrylate (carbon number of alicyclic structure: 10) or isobornyl (meth) acrylate (carbon number of carbon number of alicyclic structure: 7) is preferable, and isobornyl (meth) acrylate is particularly preferable. preferable. 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 9% by mass or more. Further, the (meth) acrylic acid ester polymer (A) preferably contains 30% by mass or less of an alicyclic structure-containing monomer, and particularly 25% by mass or less, as a monomer unit constituting the polymer. It is preferable that the content is 20% by mass or less. When the content of the alicyclic structure-containing monomer is in the above range, it becomes easy to adjust the obtained pressure-sensitive adhesive to the above-mentioned physical property values.

Further, it is also preferable that the (meth) acrylic acid ester polymer (A) contains a nitrogen atom-containing monomer as a monomer unit constituting the polymer. By allowing a nitrogen atom-containing monomer to be present in the polymer as a constituent unit, the pressure-sensitive adhesive is given a predetermined polarity, and has excellent affinity for an adherend having a certain degree of polarity such as glass. Can be. As the nitrogen atom-containing monomer, the viewpoint of imparting appropriate rigidity to the (meth) acrylic acid ester polymer (A), increasing the gel fraction, and increasing the storage elastic modulus of the obtained adhesive at 50 ° C. to a certain degree. Therefore, a monomer having a nitrogen-containing heterocycle is preferable. Further, 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 constituent pressure-sensitive adhesive, the nitrogen atom-containing monomer forms the (meth) acrylic acid ester polymer (A). It is preferable that no reactive unsaturated double bond group is contained other than one polymerizable group used for the polymerization of. The above-mentioned reactive functional group-containing monomer is excluded from the nitrogen atom-containing monomer referred to here.

Examples of the monomer having a nitrogen-containing heterocycle include N- (meth) acryloylmorpholin, N-vinyl-2-pyrrolidone, N- (meth) acryloylpyrrolidone, N- (meth) acryloylpiperidin, and N- (meth) acryloyl. Pyrrolidin, N- (meth) acryloyl acryloyl, aziridinyl ethyl (meth) acrylate, 2-vinylpyridine, 4-vinylpyridine, 2-vinylpyrazine, 1-vinylimidazole, N-vinylcarbazole, N-vinylphthalimide, etc. Among them, N- (meth) acryloylmorpholin, which exhibits more excellent adhesive strength, is preferable, and N-acryloylmorpholin is particularly preferable. 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, the nitrogen atom-containing monomer is preferably contained in an amount of 1% by mass or more, particularly 2% by mass. It is preferably contained in an amount of% or more, and more preferably 3% by mass or more. Further, the (meth) acrylic acid ester polymer (A) preferably contains the nitrogen atom-containing monomer in an amount of 20% by mass or less, and particularly preferably 15% by mass or less, as a monomer unit constituting the polymer. It is preferable, and it is preferable that the content is 10% by mass or less. When the content of the nitrogen atom-containing monomer is within the above range, the obtained pressure-sensitive adhesive can easily adjust the storage elastic modulus and the gel fraction at 50 ° C. within the above range.

If desired, the (meth) acrylic acid ester polymer (A) may contain another monomer as a monomer unit constituting the polymer. As the other monomer, a monomer containing no reactive functional group is preferable so as not to inhibit the above-mentioned action of the reactive functional group-containing monomer. Examples of such monomers include (meth) acrylic acid alkoxyalkyl esters 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) acrylic acid ester polymer (A) is preferably a linear polymer. Since it is a linear polymer, entanglement of molecular chains is likely to occur, and a pressure-sensitive adhesive having the above-mentioned gel fraction can be easily obtained.

Further, the (meth) acrylic acid ester polymer (A) is preferably a solution polymer obtained by a solution polymerization method. Since it is a solution polymer, a high molecular weight polymer can be easily obtained, and an improvement in cohesive force can be expected. Therefore, it is easy to obtain a pressure-sensitive adhesive having better luminescent material sealing property under durable conditions. In addition, the amount of residual monomers in the pressure-sensitive adhesive is reduced, resulting in excellent light resistance.

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) acrylic acid ester polymer (A) is preferably 200,000 or more as a lower limit value, particularly preferably 300,000 or more, and further preferably 400,000 or more. When the lower limit of the weight average molecular weight of the (meth) acrylic acid ester polymer (A) is equal to or higher than the above, it is easy to satisfy the above-mentioned lower limit of gel fraction and storage elastic modulus.

The weight average molecular weight of the (meth) acrylic acid ester polymer (A) is preferably 2 million or less, particularly preferably 1.5 million or less, and further preferably 1 million or less as an upper limit value. preferable. When the upper limit of the weight average molecular weight of the (meth) acrylic acid ester polymer (A) is not more than the above, it is easy to satisfy the above-mentioned upper limit of the storage elasticity. The weight average molecular weight in the present specification is a standard polystyrene-equivalent value measured by a gel permeation chromatography (GPC) method.

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

(1-2) Crosslinking agent (B)
The cross-linking agent (B) can cross-link the (meth) acrylic acid ester polymer (A) by heating the adhesive composition P, so that a three-dimensional network structure can be satisfactorily formed. As a result, the cohesive force of the obtained pressure-sensitive adhesive is improved, and the gel fraction and storage elastic modulus of the obtained pressure-sensitive adhesive can be easily adjusted within the above-mentioned ranges.

The cross-linking agent (B) may be any one that reacts with the reactive group of the (meth) acrylic acid ester polymer (A), and is, for example, an isocyanate-based cross-linking agent, an epoxy-based cross-linking agent, or an amine-based cross-linking agent. , Melamine-based cross-linking agent, aziridine-based cross-linking agent, hydrazine-based cross-linking agent, aldehyde-based cross-linking agent, oxazoline-based cross-linking agent, metal alkoxide-based cross-linking agent, metal chelate-based cross-linking agent, metal salt-based cross-linking agent, ammonium salt-based cross-linking agent, etc. Can be mentioned. Among the above, when the reactive group of the (meth) acrylic acid ester polymer (A) is a hydroxyl group, it is preferable to use an isocyanate-based cross-linking agent having excellent reactivity with the hydroxyl group, and the (meth) acrylic acid ester. When the reactive group of the polymer (A) is a carboxy group, it is preferable to use an epoxy-based cross-linking agent having excellent reactivity with the carboxy group. As the cross-linking agent (B), one type can be used alone, or two or more types can be used in combination.

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

Examples of the epoxy-based cross-linking agent include 1,3-bis (N, N-diglycidyl aminomethyl) cyclohexane, N, N, N', N'-tetraglycidyl-m-xylylenediamine, and ethylene glycol diglycidyl ether. , 1,6-Hexanediol diglycidyl ether, trimethylolpropane diglycidyl ether, diglycidyl aniline, diglycidyl amine and the like. Of these, 1,3-bis (N, N-diglycidylaminomethyl) cyclohexane is preferable from the viewpoint of reactivity with a carboxy group.

The content of the cross-linking agent (B) in the adhesive composition P is preferably 0.01 part by mass or more with respect to 100 parts by mass of the (meth) acrylic acid ester polymer (A), and in particular, 0. It is preferably 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, particularly preferably 5 parts by mass or less, and further preferably 0.4 parts by mass or less. When the content of the cross-linking agent (B) is in the above range, the above-mentioned storage elastic modulus and gel fraction can be easily satisfied.

(1-3) Various Additives The tacky composition P contains various additives usually used for acrylic pressure-sensitive adhesives, such as silane coupling agents, ultraviolet absorbers, antistatic agents, and tackifiers, if desired. , Antioxidants, light stabilizers, softeners, refractive index adjusters, rust preventives and the like can be added. It is assumed that 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. As a result, the adhesion to the backlight (light emitting body, substrate, reflective film) which is an adherend and the optical member such as the diffusing member is improved, and the light emitting body sealing property under durable conditions is further improved. Become.

As the silane coupling agent, an organic silicon compound having at least one alkoxysilyl group in the molecule, which has good compatibility with the (meth) acrylic acid ester polymer (A) and has light transmission. preferable.

Examples of such a silane coupling agent include polymerizable unsaturated group-containing silicon compounds such as vinyltrimethoxysilane, vinyltriethoxysilane, and methacrypropyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, and 2-(. 3,4-Epoxycyclohexyl) Silicon compounds having an epoxy structure such as ethyltrimethoxysilane, mercapto group-containing silicon compounds such as 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-mercaptopropyldimethoxymethylsilane , Amino group-containing silicon compounds such as 3-aminopropyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropylmethyldimethoxysilane, 3-Chloropropyltrimethoxysilane, 3-isocyanuspropyltriethoxysilane, or at least one of these, and alkyl group-containing silicon compounds such as methyltriethoxysilane, ethyltriethoxysilane, methyltrimethoxysilane, and ethyltrimethoxysilane. Examples thereof include a condensate 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 part by mass or more with respect to 100 parts by mass of the (meth) acrylic acid ester polymer (A), and is particularly 0.05. It is preferably parts by mass or more, and more preferably 0.1 parts by mass or more. Further, the content is preferably 1 part by mass or less, particularly preferably 0.5 part by mass or less, and further preferably 0.3 part by mass or less.

(2) Preparation of Adhesive Composition The adhesive composition P produced a (meth) acrylic acid ester polymer (A), and the obtained (meth) acrylic acid ester polymer (A) and a cross-linking agent ( It can be produced by mixing with B) and adding an additive if desired.

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

Examples of the polymerization initiator include azo compounds and organic peroxides, and two or more of them may be used in combination. Examples of the azo compound include 2,2'-azobisisobutyronitrile, 2,2'-azobis (2-methylbutyronitrile), 1,1'-azobis (cyclohexane1-carbonitrile), and 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 the organic peroxide include benzoyl peroxide, t-butylperbenzoate, cumenehydroperoxide, diisopropylperoxydicarbonate, di-n-propylperoxydicarbonate, and di (2-ethoxyethyl) peroxy. Examples thereof include dicarbonate, t-butylperoxyneodecanoate, t-butylperoxyvivarate, (3,5,5-trimethylhexanoyl) peroxide, dipropionyl peroxide, diacetyl peroxide and the like.

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

Once the (meth) acrylic acid ester polymer (A) is obtained, a cross-linking agent (B) and, if desired, a diluting solvent and additives are added to the solution of the (meth) acrylic acid ester polymer (A) sufficiently. To obtain a tacky composition P (coating solution) diluted with a solvent. If any of the above components is in the form of a solid, or if precipitation occurs when the component is mixed with another component in an undiluted state, the component is used alone as a diluting solvent in advance. It may be dissolved or diluted and then mixed 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, methanol, ethanol, propanol and butanol. 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 and viscosity of the coating solution prepared in this manner may be any range as long as it can be coated, and is not particularly limited and can be appropriately selected depending on the situation. For example, the adhesive composition P is diluted so as to have a concentration of 10 to 60% by mass. It should be noted that the addition of a diluting solvent or the like is not a necessary condition when obtaining the coating solution, and the diluting solvent may not be added as long as the adhesive composition P has a coatable viscosity or the like. In this case, the adhesive composition P becomes a coating solution using the polymerization solvent of the (meth) acrylic acid ester polymer (A) as it is as a diluting solvent.

(3) Formation of Adhesive Layer The adhesive layer 11 in the present embodiment is preferably made of a pressure-sensitive adhesive obtained by cross-linking the pressure-sensitive adhesive composition P (coating layer). Crosslinking of the adhesive composition P can usually be carried out by heat treatment. In addition, this heat treatment can also serve as a drying treatment for volatilizing the diluting solvent or the like 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, and particularly preferably 50 seconds to 2 minutes.

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

By the above heat treatment (and curing), the (meth) acrylic acid ester polymer (A) is sufficiently crosslinked via the crosslinking agent (B). The pressure-sensitive adhesive thus obtained can easily satisfy the above-mentioned physical property values.

(4) Physical properties of the pressure-sensitive adhesive The amount of the monomer contained in the pressure-sensitive adhesive in the present embodiment, mainly the remaining amount of the monomer used for the copolymerization of the (meth) acrylic acid ester polymer (A), is 10% by mass or less. Is preferable, and in particular, it is preferably 1% by mass or less, and more preferably less than 0.1% by mass. As a result, the obtained pressure-sensitive adhesive layer 11 has excellent light resistance, and even if it is used for a long time in contact with a plurality of light-emitting bodies that emit light, it is possible to suppress discoloration.

The lower limit of the amount of the monomer contained in the pressure-sensitive adhesive in the present embodiment is most preferably 0% by mass, but usually it is preferably 0.001% by mass or more, and particularly 0.005% by mass or more. It is preferable to have.

1-2. Peeling Sheets The peeling sheets 12a and 12b protect the pressure-sensitive adhesive layer 11 until the time when the pressure-sensitive adhesive sheet 1 is used, and are peeled off when the pressure-sensitive adhesive sheet 1 (the pressure-sensitive adhesive layer 11) is used. In the pressure-sensitive adhesive sheet 1 according to the present embodiment, one or both of the release sheets 12a and 12b are not always necessary.

Examples of the release sheets 12a and 12b 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. Telephthalate 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. In addition, these crosslinked films are also used. Further, these laminated films may be used.

It is preferable that the peeling surfaces (particularly the surfaces in contact with the pressure-sensitive adhesive layer 11) of the release sheets 12a and 12b are subjected to a peeling treatment. Examples of the release agent used in the release treatment include alkyd-based, silicone-based, fluorine-based, unsaturated polyester-based, polyolefin-based, and wax-based release agents. Of the release sheets 12a and 12b, it is preferable that one of the release sheets is a heavy release type release sheet having a large release force and the other release sheet is a light release type release sheet having a small release force.

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

2. Physical Properties (1) Total Light Transmittance The total light transmittance (value measured in accordance with JIS K7361-1: 1997) of the pressure-sensitive adhesive layer 11 of the pressure-sensitive adhesive sheet 1 according to the present embodiment is 90% or more. It is preferable, particularly preferably 93% or more, and further preferably 95% or more. When the total light transmittance is the above, the transparency is high and it is suitable for attaching a backlight.

Further, the total light transmittance of the pressure-sensitive adhesive layer 11 after the pressure-sensitive adhesive sheet 1 according to the present embodiment is left under the conditions of 50 ° C. and 50% RH for 500 hours is preferably 90% or more, particularly 93. It is preferably% or more, and more preferably 95% or more. When the total light transmittance is as described above, the light emitter in contact with the pressure-sensitive adhesive layer 11 has high transparency even under heat-resistant conditions such that the heat-generating state continues for a long time, and is more suitable for attaching a backlight. Become.

Further, the total light transmittance of the pressure-sensitive adhesive layer 11 after irradiating the pressure-sensitive adhesive sheet 1 according to the present embodiment with ultraviolet rays at an illuminance of 500 mW / m ² for 500 hours is preferably 90% or more, particularly 93%. It is preferably more than 95%, and more preferably 95% or more. When the total light transmittance is as described above, it can be said that the light emitting body in contact with the adhesive layer 11 has excellent light resistance even under the condition that the light emitting state continues for a long time, and is used for attaching a backlight. Will be more suitable.

(2) Haze value The haze value of the pressure-sensitive adhesive layer 11 of the pressure-sensitive adhesive sheet 1 according to the present embodiment is preferably 30% or less, more preferably 20% or less, and particularly preferably 10% or less. It is preferable, and more preferably 1% or less. Since the haze value of the pressure-sensitive adhesive layer 11 is as described above, it has excellent light transmission and is suitable for attaching a backlight. The haze value is a characteristic value including the thickness of the pressure-sensitive adhesive layer, and it is preferable to satisfy the haze value regardless of the thickness of the pressure-sensitive adhesive layer.

Even if the pressure-sensitive adhesive layer 11 in the present embodiment has a thickness of 250 μm, it can easily satisfy the haze value. In the pressure-sensitive adhesive sheet 1 according to the present embodiment, the above-mentioned low haze value can be achieved by using the pressure-sensitive adhesive composition P described above.

Further, the haze value of the pressure-sensitive adhesive layer 11 after the pressure-sensitive adhesive sheet 1 according to the present embodiment is left under the conditions of 50 ° C. and 50% RH for 500 hours is preferably 30% or less, preferably 20% or less. It is more preferably present, particularly preferably 10% or less, and further preferably 1% or less. When this haze value is the above, the transparency is high even under heat-resistant conditions such that the light emitting body in contact with the pressure-sensitive adhesive layer 11 continues to generate heat for a long time, which makes it more suitable for attaching a backlight. ..

Further, the haze value of the pressure-sensitive adhesive layer 11 after irradiating the pressure-sensitive adhesive sheet 1 according to the present embodiment with ultraviolet rays at an illuminance of 500 mW / m ² for 500 hours is preferably 30% or less, preferably 20% or less. It is more preferable, particularly preferably 10% or less, and further preferably 1% or less. When the total light transmittance is as described above, it can be said that the light emitting body in contact with the adhesive layer 11 has excellent light resistance even under the condition that the light emitting state continues for a long time, and is used for attaching a backlight. Will be more suitable.

Under any condition, the lower limit of the haze value of the pressure-sensitive adhesive layer 11 of the pressure-sensitive adhesive sheet 1 according to the present embodiment is not particularly limited, and is preferably 0% or more, preferably 0.1% or more. Is more preferable. Here, the haze value in the present specification is a value measured according to JIS K7136: 2000.

(3) Color Taste The adhesive layer 11 in the present embodiment preferably has a chromaticity a * defined by the CIE1976L * a * b * color system of -5.0 to 5.0, particularly-. It is preferably 3.0 to 3.0, and more preferably -2.0 to 2.0. Further, the pressure-sensitive adhesive layer 11 in the present embodiment preferably has a chromaticity b * defined by the CIE1976L * a * b * color system of -5.0 to 5.0, and particularly preferably -3.0 to 5.0. It is preferably 3.0, and more preferably -2.0 to 2.0. When the chromaticity a * and the chromaticity b * are in the above ranges, the pressure-sensitive adhesive layer 11 becomes almost colorless and transparent, and is suitable for attaching a backlight.

Further, the chromaticity a * of the pressure-sensitive adhesive layer 11 after the pressure-sensitive adhesive sheet 1 according to the present embodiment is left under the conditions of 50 ° C. and 50% RH for 500 hours may be −5.0 to 5.0. It is preferable, in particular, it is preferably -3.0 to 3.0, and further preferably -2.0 to 2.0. The chromaticity b * is preferably -5.0 to 5.0, particularly preferably -3.0 to 3.0, and further preferably -2.0 to 2.0. Is preferable. When the chromaticity a * and the chromaticity b * are in the above ranges, the pressure-sensitive adhesive layer 11 is almost colorless and transparent even under heat-resistant conditions such that the illuminant in contact with the pressure-sensitive adhesive layer 11 continues to generate heat for a long time. It becomes more suitable for attaching a backlight.

Further, the chromaticity a * of the pressure-sensitive adhesive layer 11 after irradiating the pressure-sensitive adhesive sheet 1 according to the present embodiment with ultraviolet rays at an illuminance of 500 mW / m ² for 500 hours may be −5.0 to 5.0. It is preferable, in particular, it is preferably -3.0 to 3.0, and further preferably -2.0 to 2.0. The chromaticity b * is preferably -5.0 to 5.0, particularly preferably -3.0 to 3.0, and further preferably -2.0 to 2.0. Is preferable. When the chromaticity a * and the chromaticity b * are in the above ranges, the pressure-sensitive adhesive layer 11 is almost colorless and transparent even under the condition that the light emitting state in contact with the pressure-sensitive adhesive layer 11 continues for a long time. It can be said that it has excellent light resistance, which makes it more suitable for attaching a backlight.

The methods for measuring the chromaticity a * and the chromaticity b * in the present specification are as shown in the test examples described later.

(4) Adhesive Strength The adhesive strength of the adhesive sheet 1 according to the present embodiment to soda lime glass at 23 ° C. is preferably 10 N / 25 mm or more, more preferably 13 N / 25 mm or more as a lower limit value, and particularly preferably 13 N / 25 mm or more. It is preferably 15 N / 25 mm or more, and more preferably 26 N / 25 mm or more. When the lower limit value of the adhesive force is the above, the light emitting body sealing property becomes more excellent. Further, the adhesive force of the adhesive sheet 1 according to the present embodiment to soda lime glass at 23 ° C. is preferably 100 N / 25 mm or less, more preferably 80 N / 25 mm or less, and 50 N / 25 mm or less as an upper limit value. Is particularly preferable. When the upper limit of the adhesive strength is the above, good reworkability can be obtained.

Here, the adhesive force at 23 ° C. in the present specification basically means the adhesive force 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. The measurement sample was attached to the adherend, pressurized at 0.5 MPa and 50 ° C. for 20 minutes, left to stand for 24 hours under the conditions of normal pressure, 23 ° C. and 50% RH, and then the peeling speed was set to 300 mm / min. It shall be measured.

The adhesive strength of the pressure-sensitive adhesive sheet 1 according to the present embodiment to soda lime glass at 50 ° C. is preferably 2N / 25 mm or more, particularly preferably 4N / 25 mm or more, and further 6N / 25 mm or more as a lower limit value. Is preferable. When the lower limit of the adhesive strength is the above, the light emitting body sealing property under heat resistant conditions becomes more excellent. The adhesive force of the pressure-sensitive adhesive sheet 1 according to the present embodiment to soda lime glass at 50 ° C. is not particularly limited, but is preferably 100 N / 25 mm or less, more preferably 80 N / 25 mm or less, and 50 N / 25 mm or less. It is particularly preferably 25 mm or less.

Here, the adhesive force at 50 ° C. in the present specification basically means the adhesive force 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. The measurement sample was attached to the adherend, pressurized at 0.5 MPa and 50 ° C. for 20 minutes, left at normal pressure, 50 ° C. and 50% RH for 6 hours, and then the peeling speed was set to 300 mm / min. It shall be measured.

3. 3. Production of Adhesive Sheet As an example of production of the adhesive sheet 1, the coating solution of the adhesive composition P is applied to the peeling surface of one of the release sheets 12a (or 12b) and heat-treated to perform the adhesive composition. After P is thermally crosslinked to form a coating layer, the peeling surface of the other release sheet 12b (or 12a) is superposed on the coating layer. When the curing period is required, the curing period is set, and when the curing period is not required, the coating layer becomes the adhesive layer 11 as it is. As a result, the adhesive sheet 1 is obtained. The conditions for heat treatment and curing are as described above.

As another production example of the pressure-sensitive adhesive sheet 1, a coating solution of the pressure-sensitive adhesive composition P is applied to the peel-off surface of one of the release sheets 12a, heat-treated, and the pressure-sensitive adhesive composition P is thermally cross-linked and coated. A layer is formed to obtain a release sheet 12a with a coating layer. Further, the coating solution of the adhesive composition P is applied to the peeling surface of the other release sheet 12b, heat treatment is performed to heat-crosslink the adhesive composition P to form a coating layer, and the coating layer is attached. To obtain the release sheet 12b of. Then, the release sheet 12a with the coating layer and the release sheet 12b with the coating layer are bonded so that both coating layers are in contact with each other. Here, a plurality of release sheets with a coating layer may be prepared, and a desired number of the coating layers may be bonded together. When the 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 11. As a result, the adhesive sheet 1 is obtained. According to this production example, stable production is possible even when the pressure-sensitive adhesive layer 11 is thick.

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 and the like can be used.

[Backlight unit]
A backlight unit according to an embodiment of the present invention is shown in FIG.
As shown in FIG. 2, the backlight unit 2 according to the present embodiment includes a backlight 20 in which a plurality of light emitting bodies 22 are provided on one or more substrates 21, and the light emitting body on the backlight 20. 22 is provided with an adhesive layer 11 attached so as to be sealed.

The pressure-sensitive adhesive layer 11 in the backlight unit 2 is the pressure-sensitive adhesive layer 11 of the above-mentioned pressure-sensitive adhesive sheet 1 for attaching a backlight. The plurality of light emitters 22 are hermetically sealed by the pressure-sensitive adhesive layer 11. As a result, since there are no air layers or voids inside the obtained display body, deterioration of image quality due to light reflection loss can be prevented.

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

The substrate 21 may be integrally formed so that a plurality of light emitters 22 are mounted together, or the substrate 21 is separated from each other so that one light emitter 22 is mounted on one substrate 21. It may be formed. When separately formed, each substrate 21 is usually fixed to a frame, a support, a housing, or the like. In the present embodiment, as shown in FIG. 2, it is preferable that the substrate 21 is integrally formed so that a plurality of light emitters 22 are mounted together.

A reflective layer may be formed on the surface of the substrate 21 on the adhesive layer 11 side, or a reflective member may be provided. As a result, the brightness of the backlight 20 can be effectively improved. As the material of the reflective layer and the reflective member, known materials can be adopted.

Examples of the type of the light emitting body 22 include a light emitting diode (LED), a laser diode (LD), an organic electroluminescence light emitting element, an inorganic electroluminescence light emitting element, and the like. Among these, LEDs are preferable, and mini LEDs or micro LEDs are particularly preferable, from the viewpoint of sealing performance by the pressure-sensitive adhesive layer 11.

The thickness of the illuminant 22 is preferably 10 μm or more, more preferably 30 μm or more, particularly preferably 50 μm or more, and further preferably 80 μm or more. The thickness of the light emitter 22 is preferably 300 μm or less, particularly preferably 150 μm or less, and further preferably 100 μm or less. With the pressure-sensitive adhesive layer 11 according to the present embodiment, even if the thickness of the light emitting body 22 is within the above range, the light emitting body 22 can be easily sealed without voids.

The width of the gap between the illuminants 22 adjacent to each other is preferably 0.01 mm or more, particularly preferably 0.1 mm or more, and further preferably 0.5 mm or more. The width of the gap is preferably 100 mm or less, more preferably 10 mm or less, particularly preferably 4 mm or less, and further preferably 2 mm or less. With the pressure-sensitive adhesive layer 11 according to the present embodiment, even if the width of the gap between the light emitting bodies 22 adjacent to each other is within the above range, the light emitting body 22 can be easily sealed without any voids.

The shape of the illuminant 22 is not particularly limited, but is usually rectangular parallelepiped, hemispherical, or the like. The size of the illuminant 22 is also not particularly limited, but from the viewpoint of illuminant sealing property, one side or diameter in a plan view is preferably 0.01 to 100 mm, more preferably 0.1 to 10 mm. In particular, it is preferably 0.2 to 5 mm, and more preferably 0.5 to 2 mm.

Here, a display body using the backlight unit 2 according to the present embodiment will be described. The type of display body is not particularly limited as long as it is a type that uses a backlight unit, but a liquid crystal display device is mainly exemplified.

A liquid crystal display device as an example in this embodiment is shown in FIG.
As shown in FIG. 3, the liquid crystal display device 3 according to the present embodiment includes the backlight unit 2 described above, a diffusion member 31 laminated on the adhesive layer 11 of the backlight unit 2, and a backlight in the diffusion member 31. A liquid crystal panel 32 laminated on the opposite side of the unit 2 is provided. The backlight 20 in the liquid crystal display device 3 corresponds to a direct type backlight.

The diffusion member 31 is a member that diffuses the light emitted from the backlight unit 2, and the diffusion member 31 can effectively suppress the occurrence of uneven brightness. As the diffusion member 31, known members can be adopted, and for example, a diffusion plate, a diffusion film, a combination thereof, or the like can be used. As the liquid crystal panel 32, a known one can be adopted.

A desired optical member is provided between the pressure-sensitive adhesive layer 11 and the diffusion member 31, between the diffusion member 31 and the liquid crystal panel 32, or on the surface of the liquid crystal panel 32 opposite to the diffusion member 31. You may. Examples of such an optical member include a brightness improving film, a contrast improving film, a viewing angle compensating film, a transparent conductive film, a liquid crystal polymer film, a transflective reflective film, and a shatterproof film.

In order to manufacture the liquid crystal display device 3 according to the present embodiment, for example, one of the release sheets 12a of the adhesive sheet 1 is peeled off, and the exposed adhesive layer 11 of the adhesive sheet 1 is removed from the light emitting body 22 of the backlight 20. Adhere to the side where is present.

After that, the other release sheet 12b is peeled from the pressure-sensitive adhesive layer 11 of the pressure-sensitive adhesive sheet 1, and the exposed pressure-sensitive adhesive layer 11 of the pressure-sensitive adhesive sheet 1 and the diffusion member 31 are bonded together. Then, the diffusion member 31 and the liquid crystal panel 32 are bonded together using a desired adhesive sheet. Further, as another example, the bonding order of the backlight 20 and the diffusion member 31 may be changed.

In the liquid crystal display device 3, since the plurality of light emitters 22 in the backlight unit 2 are sealed by the pressure-sensitive adhesive layer 11 without gaps, deterioration of image quality due to light reflection loss is prevented. Further, even if the liquid crystal display device 3 is placed under durable conditions such as 85 ° C., 85% RH, and 72 hours, the liquid crystal display device 3 floats at the interface between the adhesive layer 11 and the light emitting body 22, and peels off. This is suppressed, and the sealing of the illuminant 22 by the pressure-sensitive adhesive layer 11 is well maintained.

The embodiments described above are described for facilitating the understanding of the present invention, and are not described for limiting the present invention. Therefore, each element disclosed in the above embodiment is intended to include all design changes and equivalents belonging to the technical scope of the present invention.

For example, either or both of the release sheets 12a and 12b in the pressure-sensitive adhesive sheet 1 may be omitted, and desired optical members may be laminated in place of the release sheets 12a and / or 12b.

Hereinafter, 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. 1. Preparation of (meth) Acrylic Acid Ester Polymer 60 parts by mass of 2-ethylhexyl acrylate, 10 parts by mass of isobornyl acrylate, 10 parts by mass of N-acryloyl morpholine, and 20 parts by mass of 2-hydroxyethyl acrylate are copolymerized by a solution polymerization method. It was polymerized 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 method described later, the weight average molecular weight (Mw) was 500,000.

2. Preparation of Adhesive Composition 100 parts by mass (solid content conversion value; the same applies hereinafter) of the (meth) acrylic acid ester polymer (A) obtained in the above step 1 and a trimethylolpropane-modified bird as a cross-linking agent (B). 0.15 parts by mass of range isocyanate (manufactured by Toyochem, product name "BHS8515") and 0.2 parts by mass of 3-glycidoxypropyltrimethoxysilane as a silane coupling agent are mixed and thoroughly stirred. , A coating solution of the adhesive composition was obtained by diluting with methyl ethyl ketone.

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 the abbreviations and the like shown in Table 1 are as follows.
[(Meta) Acrylic Ester Polymer (A)]
2EHA: 2-ethylhexyl acrylate IBXA: isobornyl acrylate ACMO: N-acryloylmorpholine HEA: 2-hydroxyethyl acrylate BA: n-butyl acrylate AA: MA acrylate MA: methyl acrylate EA: ethyl acrylate
[Crosslinking agent (B)]
TDI: Trimethylolpropane-modified tolylene diisocyanate (manufactured by Toyochem, product name "BHS8515")
XDI: Trimethylolpropane-modified xylylene diisocyanate (manufactured by Soken Chemical Co., Ltd., product name "TD-75")
Epoxy: 1,3-bis (N, N-diglycidylaminomethyl) cyclohexane (manufactured by Mitsubishi Gas Chemical Company, product name "TETRAD-C")
Al chelate: Aluminum trisacetylacetone (manufactured by Soken Chemical Co., Ltd., product name "M-5A")

3. 3. Manufacture of Adhesive Sheet A heavy release type release sheet (manufactured by Lintec Corporation, product name "SP-PET752150") in which one side of a polyethylene terephthalate film is peeled off with a silicone-based release agent from the coating solution of the adhesive composition obtained in the above step 2. After applying with a knife coater to the peeling surface of ()), a coating layer (thickness: about 50 μm) is formed by heat treatment at 90 ° C. for 1 minute to prepare a heavy peeling type release sheet with a coating layer. did.

On the other hand, a light release type release sheet (manufactured by Lintec Corporation, product name "SP-PET381130") obtained by peeling one side of a polyethylene terephthalate film with a silicone-based release agent from the coating solution of the adhesive composition obtained in the above step 2. After applying with a knife coater to the peeling surface of the above, heat treatment was performed at 90 ° C. for 1 minute to form a coating layer (thickness: about 50 μm), thereby producing a light peeling type release sheet with a coating layer. .. Four light release type release sheets with the coating layer were prepared.

The surface on the coating layer side of the heavy peeling type release sheet with the coating layer obtained above and the surface on the coating layer side of the light peeling type release sheet with the first coating layer obtained above are bonded together. A first laminated body was obtained in which a coating layer having a total thickness of about 100 μm was sandwiched between a heavy release type release sheet and a light release type release sheet.

Next, the surface of the light release type release sheet with the second coating layer on the coating layer side is attached to the exposed surface of the coating layer exposed by peeling the light release type release sheet from the first laminate. A second laminate was obtained in which the coating layer having a total thickness of about 150 μm was sandwiched between the heavy-release type release sheet and the light-release type release sheet.

Next, the surface of the light release type release sheet with the third coating layer on the coating layer side is bonded to the exposed surface of the coating layer exposed by peeling the light release type release sheet from the second laminate. Then, a third laminated body was obtained in which the coating layer having a total thickness of about 200 μm was sandwiched between the heavy release type release sheet and the light release type release sheet.

Subsequently, the surface of the light release type release sheet with the fourth coating layer on the coating layer side is attached to the exposed surface of the coating layer exposed by peeling the light release type release sheet from the third laminate. In combination, a fourth laminated body was obtained in which the coating layer having a total thickness of about 250 μm was sandwiched between the heavy release type release sheet and the light release type release sheet.

The fourth laminate is cured under the conditions of 23 ° C. and 50% RH for 7 days to form a heavy release type release sheet / adhesive layer (thickness: 250 μm) / light release type release sheet. An adhesive sheet was prepared.

The thickness of the pressure-sensitive adhesive layer is a value measured using a constant pressure thickness measuring device (manufactured by Teclock Co., Ltd., product name "PG-02") in accordance with JIS K7130.

[Examples 2 to 6 and Comparative Examples 1 to 3]
Types and proportions of each monomer constituting the (meth) acrylic acid ester polymer (A), weight average molecular weight (Mw) of the (meth) acrylic acid ester polymer (A), type and blending amount of the cross-linking agent (B). A pressure-sensitive adhesive sheet was produced in the same manner as in Example 1 except that the blending amount of the silane coupling agent and the thickness of the pressure-sensitive adhesive layer were changed as shown in Table 1. In Example 3 and Comparative Example 2, the thickness of the pressure-sensitive adhesive layer was changed by changing the number of layers of the coating layer formed on the lightly peelable release sheet.

Here, the above-mentioned weight average molecular weight (Mw) is a polystyrene-equivalent weight average molecular weight measured under the following conditions (GPC measurement) using gel permeation chromatography (GPC).
<Measurement conditions>
-Measuring device: HLC-8320 manufactured by Tosoh Corporation
-GPC column (passed in the following order): TSK gel superH-H manufactured by Tosoh Corporation
TSK gel superHM-H
TSK gel superH2000
・ Measurement solvent: tetrahydrofuran ・ Measurement temperature: 40 ° C

[Test Example 1] (Measurement of gel fraction)
The adhesive sheets obtained in Examples and Comparative Examples were cut into a size of 80 mm × 80 mm, the adhesive layer was wrapped in a polyester mesh (mesh size 200), the mass was weighed with a precision balance, and the above mesh was used. The mass of the adhesive alone was calculated by subtracting the mass of a single substance. The mass at this time is M1.

Next, the pressure-sensitive adhesive wrapped in the polyester mesh was immersed in ethyl acetate at room temperature (23 ° C.) for 24 hours. Then, the adhesive was taken out, air-dried for 24 hours in an environment of a temperature of 23 ° C. and a relative humidity of 50%, and further dried in an oven at 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. The mass at this time is M2. The gel fraction (%) is represented by (M2 / M1) × 100. The results are shown in Table 2.

[Test Example 2] (Measurement of storage elastic modulus)
The release sheet was peeled off from the pressure-sensitive adhesive sheets obtained in Examples and Comparative Examples, and a plurality of pressure-sensitive adhesive layers were laminated so as to have a thickness of 3 mm. A cylinder (height 3 mm) having a diameter of 8 mm was punched out from the obtained laminated body of the pressure-sensitive adhesive layer, and this was used as a sample.

The above sample is subjected to a torsional shear method using a viscoelasticity measuring device (manufactured by Physica, product name "MCR300") in accordance with JIS K7244-6, and has a storage elastic modulus (MPa) at 23 ° C. and 50 ° C. under the following conditions. ) Was measured. The results are shown in Table 2.
Measurement frequency: 1Hz
Measurement temperature: 23 ° C, 50 ° C

[Test Example 3] (Measurement of adhesive strength)
The light release type release sheet is peeled off from the adhesive sheets obtained in Examples and Comparative Examples, and the exposed adhesive layer is a polyethylene terephthalate (PET) film having an easy adhesive layer (manufactured by Toyo Spinning Co., Ltd., product name "PET A4300"). , Thickness: 100 μm), and a laminate of a release sheet / adhesive layer / PET film was obtained. 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-release type release sheet is peeled off from the above sample, the exposed adhesive layer is attached to soda lime glass (manufactured by Nippon Sheet Glass Co., Ltd.), and then the autoclave manufactured by Kurihara Seisakusho Co., Ltd. is used. The pressure was increased at 0.5 MPa and 50 ° C. for 20 minutes. Then, it was left for 24 hours under the conditions of 23 ° C. and 50% RH, or left for 6 hours under the conditions of 50 ° C. and 50% RH.

Then, under the same environment as the above conditions (23 ° C., 50% RH / 50 ° C., 50% RH), a tensile tester (manufactured by Orientec, product name "Tensilon") was used, and the peeling speed was 300 mm / min. The adhesive strength (N / 25 mm) at 23 ° C. and 50 ° C. was measured under the condition of a peeling angle of 180 degrees. Conditions other than those described here were measured in accordance with JIS Z 0237: 2009. The results are shown in Table 2.

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

A plurality of adhesive tapes from which the other release sheet is peeled off from the adhesive tape to expose the adhesive layer have a size of 70 mm × 70 mm so that the width of the gap between the adjacent adhesive tapes is 5 mm, 3 mm or 1 mm. It was affixed to a soda lime glass plate (manufactured by Nippon Sheet Glass Co., Ltd.) and used as an adherend.

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

In an environment of 23 ° C. and 50% RH, the heavy-release type release sheet was peeled off from the laminate to expose the pressure-sensitive adhesive layer. Then, using a laminator (manufactured by Fujipla, product name "LPD3214"), the laminate was laminated on the adherend so that the adhesive layer covered each adhesive tape, and this was used as an evaluation sample.

The obtained evaluation sample was autoclaved under the conditions of 50 ° C. and 0.5 MPa for 30 minutes, and then left at normal pressure at 23 ° C. and 50% RH for 24 hours. First, in this state, the state of the interface between the adherend and the pressure-sensitive adhesive layer was visually observed, and the implantability (before durability) was evaluated based on the following criteria. The results are shown in Table 2.
◎: No floating / peeling ○: No floating / peeling, but bubbles generated ×: Floating / peeling occurred

Next, the evaluation sample was stored for 72 hours under moist heat conditions of 85 ° C. and 85% RH (durability test), and then the implantability (after durability) was evaluated in the same manner as described above. The results are shown in Table 2.

[Test Example 5] (Measurement of total light transmittance)
The light peeling type peeling sheet was peeled from the pressure-sensitive adhesive sheets obtained in Examples and Comparative Examples, and the exposed pressure-sensitive adhesive layer was attached to glass to prepare a sample for measurement. After performing background measurement with glass, the heavy release type release sheet is peeled off from the above measurement sample to expose the adhesive surface, and haze is performed under the condition of 23 ° C. according to JIS K7361-1: 1997. The total light transmittance (before durability;%) was measured using a meter (manufactured by Nippon Denshoku Kogyo Co., Ltd., product name "NDH-5000"). The results are shown in Table 3.

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

On the other hand, the above measurement sample was put into a light resistance tester (manufactured by Suga Test Instruments Co., Ltd., product name "ultraviolet fade meter U48", light source: carbon arc lamp), and ultraviolet rays (illuminance: 500 mW) from the heavy peeling type release sheet side. / M ² ) was irradiated for 500 hours. Then, the total light transmittance (after the light resistance test;%) was measured in the same manner as above. The results are shown in Table 3.

[Test Example 6] (Measurement of haze value)
The light peeling type peeling sheet was peeled from the pressure-sensitive adhesive sheets obtained in Examples and Comparative Examples, and the exposed pressure-sensitive adhesive layer was attached to glass to prepare a sample for measurement. After performing background measurement with glass, the heavy-release type release sheet is peeled off from the above-mentioned measurement sample to expose the adhesive surface, and under the condition of 23 ° C., a haze meter (haze meter) according to JIS K7136: 2000. The haze value (before durability;%) was measured using a product name "NDH-5000" manufactured by Nippon Denshoku Kogyo Co., Ltd. The results are shown in Table 3.

Next, the measurement sample was stored for 500 hours under high temperature conditions of 50 ° C. and 50% RH (heat resistance test), and then the haze value (after heat resistance test;%) was measured in the same manner as above. The results are shown in Table 3.

On the other hand, the above measurement sample was put into a light resistance tester (manufactured by Suga Test Instruments Co., Ltd., product name "ultraviolet fade meter U48", light source: carbon arc lamp), and ultraviolet rays (illuminance: 500 mW) from the heavy peeling type release sheet side. / M ² ) was irradiated for 500 hours. Then, the haze value (after the light resistance test;%) was measured in the same manner as above. The results are shown in Table 3.

[Test Example 7] (Measurement of L * a * b *)
For the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheets obtained in Examples and Comparative Examples, a simultaneous photometric spectroscopic chromaticity meter (manufactured by Nippon Denshoku Kogyo Co., Ltd., product name "SQ2000") was used, and CIE1976L * a * b * color was used. The chromaticity a * and chromaticity b * (before endurance) defined by the system were measured. The results are shown in Table 3.

Next, the adhesive sheet is stored for 500 hours under high temperature conditions of 50 ° C. and 50% RH (heat resistance test), and then chromaticity a * and chromaticity b * (after the heat resistance test) in the same manner as described above. Was measured. The results are shown in Table 3.

On the other hand, the above adhesive sheet was put into a light resistance tester (manufactured by Suga Test Instruments Co., Ltd., product name "ultraviolet fade meter U48", light source: carbon arc lamp), and ultraviolet rays (illuminance: 500 mW /) from the heavy peeling type release sheet side. m ² ) was irradiated for 500 hours. Then, the chromaticity a * and the chromaticity b * (after the light resistance test) were measured in the same manner as described above. The results are shown in Table 3.

[Test Example 8] (Measurement of residual monomer amount)
0.02 g of the pressure-sensitive adhesive was isolated from the pressure-sensitive adhesive sheets obtained in Examples and Comparative Examples, respectively, and the pressure-sensitive adhesive was placed in a vial having a volume of 22 mL and held at 120 ° C. for 30 minutes. Then, the gas phase component in the vial was introduced into a gas chromatograph (manufactured by Hewlett-Packard, product name "6890 type") using a headspace sampler (manufactured by PerkinElmer, product name "Tarhomatrix 40"). Component analysis was performed. As the separation column, HP-5 manufactured by Hewlett-Packard Co., Ltd. was used. As a result, it was confirmed that the amount of residual monomer was less than 0.1% by mass in the pressure-sensitive adhesives of all the examples.

As can be seen from Table 2, the pressure-sensitive adhesive sheet obtained in the examples was excellent in embedding property both before and after the durability test. Further, as can be seen from Table 3, the pressure-sensitive adhesive sheet obtained in the examples had a high degree of colorless transparency before the durability test, after the heat resistance test, and after the light resistance test.

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

1 ... Adhesive sheet for attaching backlight 11 ... Adhesive layer 12a, 12b ... Peeling sheet 2 ... Backlight unit 20 ... Backlight 21 ... Substrate 22 ... Light emitter 3 ... Liquid crystal display device 31 ... Diffusion member 32 ... Liquid crystal panel

Claims (5)

An adhesive sheet provided with an adhesive layer attached so as to seal the light emitters on a backlight provided with a plurality of light emitters on a substrate.
The storage elastic modulus of the pressure-sensitive adhesive layer at 50 ° C. is 0.001 MPa or more and 0.09 MPa or less.
The haze value of the pressure-sensitive adhesive layer is 20% or less.
The gel fraction of the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer is 10% or more and 75% or less.
The pressure-sensitive adhesive is an acrylic pressure-sensitive adhesive that is non-curable with active energy rays .
A pressure-sensitive adhesive sheet for attaching a backlight, wherein the pressure-sensitive adhesive layer has a thickness of 130 μm or more. The adhesive sheet for attaching a backlight according to claim 1, wherein the adhesive layer has a storage elastic modulus of 0.01 MPa or more and 0.20 MPa or less at 23 ° C. Two release sheets and
The adhesive sheet for attaching a backlight according to claim 1 or 2, further comprising the adhesive layer sandwiched between the release sheets so as to be in contact with the release surfaces of the two release sheets. A backlight in which a plurality of light emitters are provided on one or more substrates, and
A backlight unit provided with an adhesive layer attached to the backlight so as to seal the light emitting body.
A backlight unit, wherein the pressure-sensitive adhesive layer is the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet for attaching a backlight according to any one of claims 1 to 3. The backlight unit according to claim 4, wherein the light emitting body is a light emitting diode.

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