JP2021066771A - Adhesive, adhesive sheet, backlight unit and display device - Google Patents

Abstract

To provide an adhesive, an adhesive sheet, a backlight unit and a display device which achieve suppression of uneven luminance and proper embedding into irregularities.SOLUTION: The present invention relates to an adhesive that contains light diffusion fine particles, has a 1000% modulus of 0.23 N/mm2 or less when a tensile test is performed at 23°C, and has a gel fraction of 10% or more, and an adhesive sheet 1 having an adhesive layer 11 composed of the adhesive.SELECTED DRAWING: Figure 1

Description

The present invention relates to backlight units and display devices, as well as pressure-sensitive adhesives and pressure-sensitive adhesive sheets that can be used in their manufacture.

In recent years, electronic devices such as mobile phones, smartphones, tablet terminals, and game machines often use liquid crystal display devices as display devices. Since a display unit made of a liquid crystal panel or the like does not emit light by itself, a display device using such a display unit is provided with a backlight for illuminating the display unit.

Until now, as a method of arranging the light source of the backlight in the above-mentioned display device, a side light type in which the light source is arranged on the side of the light guide plate has been generally used. On the other hand, recently, from the viewpoint of screen brightness and contrast, a direct type backlight in which a light source is arranged directly under the display unit has begun to be studied. In a direct-type backlight, in order to increase the amount of light and to make the amount of light uniform between the center of the screen and the edge of the screen when used as a display device, a large number of light emitters, typically a light emitting diode (LED). ) Is being studied in the direction of being provided on the substrate.

Here, when a large number of illuminants are used as the light source of the direct type backlight, the illuminants have low water resistance, so it is desirable to seal the illuminants with a resin or the like. Further, when a display device is manufactured using a backlight having a large number of light emitters as a light source, the obtained image becomes uneven in brightness due to the existence region and the non-existence region of the light emitting body.

Patent Document 1 proposes to provide an adhesive layer containing light-scattering particles on the light emitting body of the backlight described above.

Japanese Patent No. 5590582

However, in Patent Document 1, it is necessary to provide the pressure-sensitive adhesive layer by directly coating the pressure-sensitive adhesive on the backlight, and depending on the state of the coating, it may not be possible to sufficiently eliminate the uneven brightness. Further, under high temperature and high humidity, the pressure-sensitive adhesive cannot sufficiently fill the unevenness caused by the light-emitting body, and floating or peeling may occur between the pressure-sensitive adhesive and the light-emitting body.

The present invention has been made in view of such an actual situation, and an object of the present invention is to provide an adhesive, an adhesive sheet, a backlight unit, and a display device having excellent luminance unevenness suppressing property and uneven embedding property.

In order to achieve the above object, firstly, the present invention contains light diffusing fine particles, and the 1000% modulus when subjected to a tensile test at 23 ° C. is 0.23 N / mm ² or less, and the gel fraction is Provided is a pressure-sensitive adhesive characterized in that the content is 10% or more (Invention 1).

In the above invention (Invention 1), since the 1000% modulus and the gel fraction are the above values while containing the light diffusing fine particles, the dispersibility of the light diffusing fine particles is improved and the unevenness is followed. It is easy to exhibit the property that it is easy to maintain the state. As a result, excellent brightness unevenness suppression property can be obtained. In addition, excellent unevenness embedding property can be obtained, and unevenness due to a luminescent material or the like can be sufficiently filled by the adhesive layer not only in the initial stage but also under high temperature and high humidity conditions, and the unevenness and the adhesive layer float at the interface. , Peeling, etc. are suppressed.

The pressure-sensitive adhesive according to the above invention (Invention 1) is preferably an acrylic pressure-sensitive adhesive (Invention 2).

In the above inventions (Inventions 1 and 2), it is preferable to contain a polyrotaxane compound (Invention 3).

In the above inventions (Inventions 1 to 3), it is preferable to contain an active energy ray-curable component (Invention 4).

Secondly, the present invention provides a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer, wherein the pressure-sensitive adhesive layer is composed of the pressure-sensitive adhesives (Inventions 1 to 4) (Invention 5).

In the above invention (Invention 5), the haze value of the pressure-sensitive adhesive layer is preferably 4% or more and 100% or less (Invention 6).

In the above inventions (Inventions 5 and 6), the pressure-sensitive adhesive sheet includes two release sheets, and the pressure-sensitive adhesive layer is sandwiched between the release sheets so as to be in contact with the release surfaces of the two release sheets. (Invention 7).

Thirdly, the present invention is a structure including a backlight having a plurality of light emitting bodies and a pressure-sensitive adhesive layer laminated on the backlight, and the pressure-sensitive adhesive layer is the pressure-sensitive adhesive (Invention 1 to 1). Provided is a backlight unit characterized by being an adhesive layer composed of 4) (Invention 8).

In the above invention (Invention 8), it is preferable that the light emitting body is a light emitting diode (Invention 9).

Fourth, the present invention provides a display device including the backlight unit (inventions 8 and 9) and a display unit laminated on the pressure-sensitive adhesive layer of the backlight unit (invention). 10).

The pressure-sensitive adhesive, pressure-sensitive adhesive sheet, backlight unit, and display device according to the present invention are excellent in brightness unevenness suppression property and unevenness embedding property.

It is sectional drawing of the pressure-sensitive adhesive sheet 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 display device which concerns on one Embodiment of this invention.

Hereinafter, embodiments of the present invention will be described.
[Adhesive]
The pressure-sensitive adhesive according to one embodiment of the present invention contains light-diffusing fine particles, has a 1000% modulus of 0.23 N / mm ² or less when subjected to a tensile test at 23 ° C., and has a gel fraction of 10%. That is all. The method for measuring 1000% modulus and gel fraction in the present specification is as shown in Test Examples described later.

The pressure-sensitive adhesive according to the present embodiment contains the light-diffusing fine particles and has a 1000% modulus and a gel fraction of the above values, so that the light-diffusing fine particles have good dispersibility and follow the unevenness. It is easy to exhibit the property that it is easy to maintain the state. As a result, excellent brightness unevenness suppression property can be obtained. In addition, excellent unevenness embedding property was obtained, and the unevenness caused by the illuminant or the like was sufficiently filled with the adhesive layer not only in the initial stage but also under high temperature and high humidity conditions (for example, 85 ° C., 85% RH, 72 hours). The state can be maintained, and floating at the interface between the unevenness and the pressure-sensitive adhesive layer, and the occurrence of peeling and the like are suppressed.

From the viewpoint of suppressing uneven brightness and embedding unevenness, the 1000% modulus of the pressure-sensitive adhesive according to the present embodiment needs to be 0.23 N / mm ² or less, and 0.19 N / mm ² or less. preferably, more preferably 0.17 N / mm ² or less, and particularly preferably 0.14 N / mm ² or less.

On the other hand, from the viewpoint of obtaining excellent formability cohesion, the 1000% modulus is preferably at 0.01 N / mm ² or more, more preferably 0.04 N / mm ² or more, blister resistance When considering the perspective of gender, particularly preferably at 0.11 N / mm ² or more, more preferably 0.12 N / mm ² or more.

From the viewpoint of suppressing uneven brightness and embedding unevenness under high temperature and high humidity conditions, the gel fraction of the pressure-sensitive adhesive according to the present embodiment needs to be 10% or more, preferably 25% or more. From the viewpoint of blister resistance, it is more preferably 35% or more, particularly preferably 40% or more, and further preferably 45% or more.

Further, from the viewpoint of the dispersibility of the light diffusing fine particles and the initial unevenness embedding property, the gel fraction is preferably 80% or less, more preferably 70% or less, and particularly 60% or less. Is preferable, and more preferably 56% or less.

The type of the pressure-sensitive adhesive according to the present embodiment is not particularly limited as long as it satisfies the above physical properties and does not inhibit the effect of the light-diffusing fine particles. For example, it may be any of an acrylic pressure-sensitive adhesive, a polyester-based pressure-sensitive adhesive, a polyurethane-based pressure-sensitive adhesive, a rubber-based pressure-sensitive adhesive, a silicone-based pressure-sensitive adhesive, and 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 having excellent adhesive physical properties, optical properties, and the like is preferable. As the acrylic pressure-sensitive adhesive, a cross-linked type is preferable, and a heat-cross-linked type is more preferable.

The pressure-sensitive adhesive according to the present embodiment may be non-curable with active energy rays or curable with active energy rays, but from the viewpoint of blister resistance, it is cured with active energy rays. It is preferably of sex. The "active energy ray-curable pressure-sensitive adhesive" in the present specification means a pressure-sensitive adhesive that is cured by irradiation with active energy rays. Therefore, a pressure-sensitive adhesive that has been cured to the extent that it cannot be cured by the conventional irradiation with active energy rays is not included in the "active energy ray-curable pressure-sensitive adhesive".

The pressure-sensitive adhesive according to the present embodiment preferably contains a polyrotaxane compound from the viewpoint of easily satisfying the above-mentioned physical properties. Specifically, the pressure-sensitive adhesive according to the present embodiment includes a (meth) acrylic acid ester polymer (A), a cross-linking agent (B), light-diffusing fine particles (C), and optionally a polyrotaxane compound (D). , The adhesive composition containing the active energy ray-curable component (E) (hereinafter, may be referred to as "adhesive composition P") is crosslinked. The pressure-sensitive adhesive obtained by cross-linking the pressure-sensitive adhesive composition P can more easily satisfy the above-mentioned 1000% modulus and gel fraction. 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. 1. Ingredients of Adhesive Composition P (1) (Meta) Acrylic Acid Ester Polymer (A)
The (meth) acrylic acid ester polymer (A) in the present embodiment contains a reactive group-containing monomer having a reactive group 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 a desired cohesive force can be obtained.

Examples of the reactive group-containing monomer include a monomer having a hydroxyl group in the molecule (hydroxyl group-containing monomer), a monomer having a carboxy group in the molecule (carboxy group-containing monomer), 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 or a carboxy group-containing monomer having excellent reactivity with the cross-linking agent (B) is preferable.

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). ) Hydroxyalkyl esters of (meth) acrylic acid 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 nitrogen atom-containing monomer described later is excluded from this amino group-containing monomer.

The (meth) acrylic acid ester polymer (A) preferably contains a reactive group-containing monomer as a lower limit value of 1% by mass or more, and particularly 7% 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 40% 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 a reactive group-containing monomer as a monomer unit in the above amount, a good crosslinked structure is formed in the obtained pressure-sensitive adhesive, and the above-mentioned 1000% modulus and gel fraction are formed. Is easier to fill. Further, the dispersibility of the light diffusing fine particles (C) in the obtained pressure-sensitive adhesive tends to be improved.

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, since the carboxy group-containing monomer is not contained, a transparent conductive film such as tin-doped indium oxide (ITO) or a metal film, which causes a problem due to the acid, is attached to the adhesive. Even if it exists, it is possible to suppress those defects (corrosion, change in resistance value, etc.) due to 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) acrylate, n-hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, n-decyl (meth) acrylate, (meth) acrylate Examples thereof include n-dodecyl, myristyl (meth) acrylate, palmityl (meth) acrylate, and stearyl (meth) acrylate. Among them, (meth) acrylic acid ester having 4 to 8 carbon atoms of the alkyl group is preferable, and n-butyl (meth) acrylate, (from the viewpoint of further improving the adhesiveness or lowering the 1000% modulus. 2-Ethylhexyl acrylate or isooctyl (meth) acrylate is particularly preferred, and n-butyl acrylate, 2-ethylhexyl acrylate, or isooctyl acrylate is even more 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. In addition, the light diffusing fine particles (C) tend to have good dispersibility in the adhesive, and the (meth) acrylic acid ester polymer (A) is suppressed from impairing the desired adhesiveness. On the other hand, the (meth) acrylic acid ester polymer (A) preferably contains (meth) acrylic acid alkyl ester in an amount of 90% by mass or less, and 80% by mass or less, as a monomer unit constituting the polymer. Is more preferable, and it is particularly preferable to contain 70% by mass or less, and further preferably 65% 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). be able to.

The (meth) acrylic acid ester polymer (A) preferably 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 above-mentioned 1000% modulus is easily satisfied.

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. From the viewpoint of making the distance between the obtained (meth) acrylic acid ester polymers (A) appropriate and leading to a low 1000% modulus, the alicyclic structure is a polycyclic alicyclic structure (polycyclic structure). ) Is preferable. Further, in consideration of the compatibility between the (meth) acrylic acid ester polymer (A) and other components, the polycyclic structure is particularly preferably bicyclic to tetracyclic. Further, from the viewpoint of lowering the 1000% modulus as described above, the number of carbon atoms in the alicyclic structure (referring to the total number of carbon atoms in the portion forming the ring, when a plurality of rings are independently present). Refers to 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 same viewpoint 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. Dicyclopentenyl acid, dicyclopentenyloxyethyl (meth) acrylate, etc., among others, dicyclopentanyl (meth) acrylate (carbon number of alicyclic structure:) which exhibits more excellent unevenness 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. Further, isobornyl acrylate is 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, the alicyclic structure-containing monomer is produced from the viewpoint of lowering the 1000% modulus. Is preferably contained in an amount of 1% by mass or more, particularly preferably 5% by mass or more, and further preferably 10% by mass or more. From the same viewpoint as above, the content of the alicyclic structure-containing monomer is preferably 40% by mass or less, particularly preferably 30% by mass or less, and further preferably 20% by mass or less. preferable.

The (meth) acrylic acid ester polymer (A) preferably 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, a predetermined polarity is imparted to the pressure-sensitive adhesive, and the adhesive has excellent affinity for an adherend having a certain degree of polarity such as glass. Can be. As the nitrogen atom-containing monomer, a monomer having a nitrogen-containing heterocycle is preferable from the viewpoint of imparting appropriate rigidity to the (meth) acrylic acid ester polymer (A). 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.

Examples of the monomer having a nitrogen-containing heterocycle include N- (meth) acryloyl morpholine, N-vinyl-2-pyrrolidone, N- (meth) acryloyl pyrrolidone, N- (meth) acryloyl piperidine, and N- (meth) acryloyl. Pyrrolidine, N- (meth) acryloyl azylidine, 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, it preferably contains the nitrogen atom-containing monomer in an amount of 0.1% by mass or more, particularly. It is preferably contained in an amount of 1% by mass 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 10% by mass or less, as a monomer unit constituting the polymer. It is preferable, and it is preferable that the content is 7% by mass or less. When the content of the nitrogen atom-containing monomer is within the above range, the obtained pressure-sensitive adhesive can sufficiently exert excellent adhesive strength to glass.

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 improvement in cohesive force can be expected. Therefore, it is easy to obtain an adhesive having excellent unevenness embedding property under high temperature and high humidity conditions.

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, a pressure-sensitive adhesive having excellent unevenness embedding property under high temperature and high humidity conditions can be easily obtained.

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 300,000 from the viewpoint of facilitating the realization of the gel fraction by ensuring sufficient entanglement between the (meth) acrylic acid ester polymers (A). The above is preferable, the amount is more preferably 400,000 or more, and particularly preferably 500,000 or more. Further, from the viewpoint of making it easier to realize an elongation of 1000%, it is more preferably 600,000 or more.

The weight average molecular weight of the (meth) acrylic acid ester polymer (A) is preferably 2 million or less, particularly preferably 1.3 million or less, and further preferably 900,000 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 as described above, the value of 1000% modulus of the obtained adhesive tends to be suitable, and the uneven embedding property is more excellent. Become. 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, the (meth) acrylic acid ester polymer (A) may be used alone or in combination of two or more.

(2) Crosslinking agent (B)
The cross-linking agent (B) may be any as long as it can react with the reactive group of the (meth) acrylic acid ester polymer (A). When the adhesive composition P contains the polyrotaxane compound (D), it is preferably capable of reacting with the reactive group of the cyclic molecule of the polyrotaxane compound (D). In this case, the cross-linking agent (B) forms a cross-linking agent adduct with the polyrotaxane compound (D), and the cross-linking agent adduct cross-links the (meth) acrylic acid ester polymers (A) with each other. As a result, the balance between the 1000% modulus and the gel fraction of the obtained pressure-sensitive adhesive is improved, and more excellent unevenness embedding property is exhibited.

Examples of the cross-linking agent (B) include isocyanate-based cross-linking agents, epoxy-based cross-linking agents, amine-based cross-linking agents, melamine-based cross-linking agents, aziridine-based cross-linking agents, hydrazine-based cross-linking agents, aldehyde-based cross-linking agents, oxazoline-based cross-linking agents, and metal alkoxides. Examples thereof include a system cross-linking agent, a metal chelate-based cross-linking agent, a metal salt-based cross-linking agent, and an ammonium salt-based cross-linking agent. Among these, an isocyanate-based cross-linking agent having high reactivity with a hydroxyl group is preferable. The polyrotaxane compound (D) often has a hydroxyl group as a reactive group, and in that case, the cross-linking agent can be sufficiently added to the polyrotaxane compound (D). The cross-linking agent (B) may be used alone or in combination of two or more.

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 polyisocyanate, particularly trimethylolpropane-modified tolylene diisocyanate, is 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, N, N, N', N'-tetraglycidyl-m-xylylenediamine are preferable from the viewpoint of reactivity with the carboxy group.

The content of the cross-linking agent (B) in the adhesive composition P is preferably 0.001 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 01 parts by mass or more, and more preferably 0.1 parts by mass or more. The content of the cross-linking agent (B) is preferably 10 parts by mass or less, particularly preferably 1 part by mass or less, based on 100 parts by mass of the (meth) acrylic acid ester polymer (A). Further, it is preferably 0.5 parts by mass or less. When the content of the cross-linking agent (B) is in the above range, the obtained pressure-sensitive adhesive tends to have a suitable 1000% modulus, gel fraction, adhesive strength and the like.

(3) Light diffusing fine particles (C)
The light diffusing fine particles (C) may be any as long as the pressure-sensitive adhesive can satisfy the above-mentioned physical properties and can exert the effect of suppressing luminance unevenness due to the predetermined light diffusing property.

Examples of the light-diffusing fine particles (C) include inorganic light-diffusing fine particles such as silica, calcium carbonate, aluminum hydroxide, magnesium hydroxide, clay, talc, and titanium dioxide; acrylic resin, polystyrene resin, polyethylene resin, epoxy resin, and the like. Organic light-diffusing fine particles; light-diffusing fine particles made of silicon-containing compounds having an intermediate structure between inorganic and organic such as silicone resin (for example, Tospearl series manufactured by Momentive Performance Materials Japan) Can be mentioned. Among them, light diffusing fine particles made of acrylic resin or silicone resin are preferable. As a result, the obtained adhesive has excellent light diffusivity. The above light diffusing fine particles (C) may be used alone or in combination of two or more.

As the shape of the light diffusing fine particles (C), spherical light diffusing fine particles having uniform light diffusion are preferable. The average particle size of the light diffusing fine particles (C) by the centrifugal sedimentation light transmission method is preferably 0.5 μm or more, particularly preferably 1 μm or more, and further preferably 3 μm or more as a lower limit value. When the lower limit of the average particle size is the above, the obtained pressure-sensitive adhesive becomes more excellent in light diffusivity. On the other hand, the average particle size is preferably 10 μm or less, particularly preferably 7 μm or less, and further preferably 5 μm or less as the upper limit value. When the upper limit value of the average particle size is the above, a high-definition display image can be displayed satisfactorily.

The average particle size obtained by the centrifugal sedimentation light transmission method is obtained by sufficiently stirring 1.2 g of light diffusing fine particles and 98.8 g of isopropyl alcohol as a measurement sample, and a centrifugal automatic particle size distribution measuring device (HORIBA, Ltd.). It was measured using CAPA-700).

The content of the light diffusing fine particles (C) in the adhesive composition P is preferably 0.1% by mass or more, more preferably 1% by mass or more, and particularly preferably 3% by mass or more. It is preferable, and more preferably 7% by mass or more. As a result, the light diffusivity of the obtained pressure-sensitive adhesive becomes more excellent. The content of the light diffusing fine particles (C) is preferably 40% by mass or less, more preferably 30% by mass or less, particularly preferably 20% by mass or less, and further preferably 10% by mass. The following is preferable. This makes it easier for the obtained pressure-sensitive adhesive to exert the desired adhesive strength.

(4) Polyrotaxane compound (D)
The polyrotaxane compound (D) is a compound in which a linear molecule penetrates through the openings of at least two cyclic molecules and has block groups at both ends of the linear molecule. In this polyrotaxane compound (D), the cyclic molecule can freely move on the linear molecule, but the cyclic molecule has a structure in which the cyclic molecule cannot escape from the linear molecule due to the block group. That is, the linear molecule and the cyclic molecule maintain their morphology not by a chemical bond such as a covalent bond but by a so-called mechanical bond.

The pressure-sensitive adhesive (tacky composition P) according to the present embodiment contains the polyrotaxane compound (D) having such a mechanical bond, so that 1000% modulus can easily satisfy a preferable value and is excellent in uneven embedding property. It becomes a thing. In particular, when the cyclic molecule of the polyrotaxane compound (D) is a cyclic oligosaccharide having a hydroxyl group as a reactive group, when an isocyanate-based cross-linking agent is used as the cross-linking agent (B), the isocyanate-based cross-linking agent is used. The (meth) acrylic acid ester polymer (A) and the polyrotaxane compound (D) (cyclic molecule) are crosslinked via the crosslink, and the cyclic molecule freely moves on the linear molecule in the polyrotaxane compound (D). As a result, the flexibility as a crosslinked body is remarkably improved. As a result, the balance between the 1000% modulus and the gel fraction of the obtained pressure-sensitive adhesive is improved, and more excellent unevenness embedding property is exhibited.

The reactive group contained in the cyclic molecule of the polyrotaxane compound (D) is not particularly limited as long as it can react with the reactive group of the cross-linking agent (B), and examples thereof include a hydroxyl group and a carboxy group. Hydroxyl groups are preferred.

The polyrotaxane compound (D) in the present embodiment preferably has a cyclic oligosaccharide as a cyclic molecule. Cyclic oligosaccharides have a hydroxyl group as a reactive group in the unmodified state. Further, by using a cyclic oligosaccharide as the cyclic molecule of the polyrotaxane compound (D), an appropriate ring diameter can be selected, and thereby the effect of the movement of the cyclic molecule on the linear molecule is exhibited. Cheap. Furthermore, it is easy to introduce various substituents and the like, which makes it possible to adjust the physical properties of the obtained pressure-sensitive adhesive. Further, the cyclic oligosaccharide has an advantage that it is easily available. In addition, in this specification, "cyclic" of "cyclic molecule" or "cyclic oligosaccharide" means substantially "cyclic". That is, the cyclic molecule does not have to be completely ring-closed, and may have a helical structure, for example, as long as it can move on the linear molecule.

The hydroxyl group of the cyclic oligosaccharide as a reactive group may be the original hydroxyl group of the cyclic oligosaccharide (meaning the state before modification), or the hydroxyl group introduced into the cyclic oligosaccharide as a substituent. You may.

The hydroxyl value of the cyclic molecule is preferably 10 mgKOH / g or more, more preferably 30 mgKOH / g or more, and particularly preferably 50 mgKOH / g or more as the lower limit value. When the lower limit of the hydroxyl value is the above, the polyrotaxane compound (D) can sufficiently react with the cross-linking agent (B). The hydroxyl value of the cyclic molecule is preferably 1000 mgKOH / g or less, more preferably 200 mgKOH / g or less, and particularly preferably 100 mgKOH / g or less as the upper limit value. When the upper limit of the hydroxyl value exceeds the above value, a large number of crosslinks occur in the same cyclic molecule, so that the cyclic molecule itself becomes a crosslink point, and the effect of the crosslink point of the polyrotaxane compound (D) as a whole can be exhibited. As a result, sufficient flexibility may not be ensured in the obtained adhesive.

The linear molecule of the polyrotaxane compound (D) is a molecule or substance that is encapsulated in a cyclic molecule and can be integrated by a mechanical bond rather than a chemical bond such as a covalent bond, and is linear. If so, there is no particular limitation. In addition, in this specification, "straight line" of "linear molecule" means that it is substantially "straight line". That is, the linear molecule may have a branched chain as long as the cyclic molecule can move on the linear molecule.

As the linear molecule of the polyrotaxane compound (D), for example, polyethylene glycol, polypropylene glycol, polyisoprene, polyisobutylene, polybutadiene, polytetrahydrofuran, polyacrylic acid ester, polydimethylsiloxane, polyethylene, polypropylene and the like are preferable. Two or more kinds of linear molecules may be mixed in the adhesive composition P.

The number average molecular weight of the linear molecules of the polyrotaxane compound (D) is preferably 3,000 or more, particularly preferably 10,000 or more, and further preferably 20,000 or more. When the lower limit of the number average molecular weight is the above, the amount of movement of the cyclic molecule on the linear molecule is secured, and the flexibility of the crosslinked structure due to the polyrotaxane compound (D) can be sufficiently obtained. The number average molecular weight of the linear molecules of the polyrotaxane compound (D) is preferably 300,000 or less, particularly preferably 200,000 or less, and further preferably 1,000,000 or less. .. When the upper limit of the number average molecular weight is the above, the solubility of the polyrotaxane compound (D) in the solvent becomes good.

The blocking group of the polyrotaxane compound (D) is not particularly limited as long as it is a group capable of retaining the skewered form of the cyclic molecule by the linear molecule. Examples of such a group include a bulky group and an ionic group.

The polyrotaxane compound (D) described above can be obtained by a conventionally known method (for example, the method described in JP-A-2005-154675).

When the adhesive composition P according to the present embodiment contains the polyrotaxane compound (D), the content of the polyrotaxane compound (D) is 0 with respect to 100 parts by mass of the (meth) acrylic acid ester polymer (A). It is preferably 1 part by mass or more, particularly preferably 1 part by mass or more, and further preferably 10 parts by mass or more. When the lower limit of the content of the polyrotaxane compound (D) is as described above, the 1000% modulus and gel fraction of the obtained pressure-sensitive adhesive tend to be suitable values. The content of the polyrotaxane compound (D) is preferably 40 parts by mass or less, more preferably 30 parts by mass or less, and particularly preferably 20 parts by mass or less. When the upper limit of the content of the polyrotaxane compound (D) is as described above, the adhesive strength of the obtained pressure-sensitive adhesive can be made sufficient.

(5) Active energy ray-curable component (E)
In a pressure-sensitive adhesive obtained by cross-linking a pressure-sensitive adhesive composition P containing an active energy ray-curable component (E) with active energy ray-cured, the active energy ray-curable components (E) are polymerized with each other, and the pressure-sensitive adhesive is polymerized with each other. It is presumed that the polymerized active energy ray-curable component (E) is entwined with the crosslinked structure (three-dimensional network structure) of the (meth) acrylic acid ester polymer (A) (and the polyrotaxane compound (D)). The pressure-sensitive adhesive having such a higher-order structure increases the gel fraction to a predetermined extent and has excellent blister resistance.

The active energy ray-curable component (E) is not particularly limited as long as it is a component that is cured by irradiation with active energy rays and obtains the above effects, and may be any of monomers, oligomers, and polymers, and they may be used. May be a mixture of. Among them, a polyfunctional acrylate-based monomer having excellent blister resistance can be preferably mentioned.

Examples of the polyfunctional acrylate-based monomer include 1,4-butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, and polyethylene glycol di (meth) acrylate. , Neopentyl glycol adipate di (meth) acrylate, neopentyl glycol di (meth) acrylate of hydroxypivalate, dicyclopentanyl di (meth) acrylate, tricyclodecanedimethanol (meth) acrylate, caprolactone-modified dicyclopentenyldi ( Meta) acrylate, ethylene oxide modified di (meth) acrylate, di (acryloxyethyl) isocyanurate, allylated cyclohexyl di (meth) acrylate, ethoxylated bisphenol A diacrylate, 9,9-bis [4- (2-) Bifunctional type such as acryloyloxyethoxy) phenyl] fluorene; trimethylpropantri (meth) acrylate, dipentaerythritol tri (meth) acrylate, propionic acid-modified dipentaerythritol tri (meth) acrylate, pentaerythritol tri (meth) acrylate , Protinoxide-modified trimethylolpropane tri (meth) acrylate, tris (acryloxyethyl) isocyanurate, ε-caprolactone-modified tris- (2- (meth) acryloxyethyl) isocyanurate, etc. Four-functional types such as meta) acrylate and pentaerythritol tetra (meth) acrylate; pentafunctional type such as propionic acid-modified dipentaerythritol penta (meth) acrylate; dipentaerythritol hexa (meth) acrylate and caprolactone-modified dipentaerythritol hexa ( Examples thereof include a hexafunctional type such as meta) acrylate. These may be used individually by 1 type, and may be used in combination of 2 or more type. Further, from the viewpoint of compatibility with the (meth) acrylic acid ester polymer (A), the polyfunctional acrylate-based monomer preferably has a molecular weight of less than 1000.

When the target pressure-sensitive adhesive is an active energy ray-curable pressure-sensitive adhesive, the content of the active energy ray-curable component (E) in the pressure-sensitive adhesive is set as a lower limit value from the viewpoint of effectively exerting blister resistance. It is preferably 0.1% by mass or more, particularly preferably 1% by mass or more, and further preferably 2% by mass or more. On the other hand, the content is preferably 20% by mass or less, particularly preferably 10% by mass or less, and 5% by mass or less as an upper limit value from the viewpoint of the adhesive strength of the pressure-sensitive adhesive after irradiation with active energy rays. Is more preferable.

(6) Photopolymerization initiator (F)
When ultraviolet rays are used as the active energy rays for curing the active energy ray-curable pressure-sensitive adhesive, the pressure-sensitive adhesive composition P preferably further contains a photopolymerization initiator (F). By containing the photopolymerization initiator (F) in this way, the active energy ray-curable component (D) can be efficiently polymerized, and the polymerization curing time and the irradiation amount of the active energy rays can be reduced. it can.

Examples of such a photopolymerization initiator (F) include benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin-n-butyl ether, benzoin isobutyl ether, acetophenone, dimethylaminoacetophenone, and 2,2-dimethoxy. -2-phenylacetophenone, 2,2-diethoxy-2-phenylacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-hydroxycyclohexylphenylketone, 2-methyl-1- [4- (Methylthio) phenyl] -2-morpholino-propan-1-one, 4- (2-hydroxyethoxy) phenyl-2- (hydroxy-2-propyl) ketone, benzophenone, p-phenylbenzophenone, 4,4'-diethylamino Benzophenone, Dichlorobenzophenone, 2-Methylanthraquinone, 2-Ethylanthraquinone, 2-Turrary-butylanthraquinone, 2-Aminoanthraquinone, 2-Methylthioxanthone, 2-Ethylthioxanthone, 2-Chlorothioxanthone, 2,4-dimethylthioxanthone, 2 , 4-Diethylthioxanthone, benzyl dimethyl ketal, acetophenone dimethyl ketal, p-dimethylaminobenzoic acid ester, oligo [2-hydroxy-2-methyl-1 [4- (1-methylvinyl) phenyl] propanone], 2,4 , 6-trimethylbenzoyl-diphenyl-phosphine oxide, bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide and the like. These may be used alone or in combination of two or more.

When the target pressure-sensitive adhesive is an active energy ray-curable pressure-sensitive adhesive, the content of the photopolymerization initiator (F) in the pressure-sensitive adhesive composition P is 100 parts by mass of the active energy ray-curable component (C). The lower limit is preferably 0.1 part by mass or more, particularly preferably 1 part by mass or more, and further preferably 5 parts by mass or more. Further, the upper limit value is preferably 30 parts by mass or less, particularly preferably 20 parts by mass or less, and further preferably 12 parts by mass or less.

(7) Various Additives The adhesive composition P contains various additives usually used for acrylic pressure-sensitive adhesives, such as silane coupling agents, rust preventives, ultraviolet absorbers, antistatic agents, and adhesives, if desired. Additives, antioxidants, light stabilizers, softeners, refractive index adjusters and the like can be added. The polymerization solvent and the diluting solvent described later are not included in the additives constituting the adhesive composition P.

The adhesive composition P preferably contains a silane coupling agent among the above. As a result, regardless of whether the adherend is a plastic member or a glass member, the adhesion to the adherend is improved, and the uneven embedding property under high temperature and high humidity conditions becomes more excellent. ..

The silane coupling agent is an organosilicon 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 transmittance. 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, and 3-mercaptopropyldimethoxymethylsilane , 3-Aminopropyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropylmethyldimethoxysilane and other amino group-containing silicon compounds, 3-Chloropropyltrimethoxysilane, 3-isocyanuppropyltriethoxysilane, 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, particularly 0.05 by mass, based on 100 parts by mass of the (meth) acrylic acid ester polymer (A). It is preferably parts by mass or more, and more preferably 0.1 parts by mass or more. The content is preferably 1.2 parts by mass or less, particularly preferably 0.8 parts by mass or less, and further preferably 0.4 parts by mass or less.

2. Preparation of Adhesive Composition P 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 (B). And the light diffusing fine particles (C) are mixed, and if desired, a polyrotaxane compound (D), an active energy ray-curable component (E), a photopolymerization initiator (F), an additive and the like are added to prepare the mixture. be able to.

The (meth) acrylic acid ester polymer (A) can be produced by polymerizing a mixture of monomers constituting the polymer by a usual 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. However, the present invention is not limited to this, and polymerization may be carried out without a solvent. 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-butyl perbenzoate, cumene hydroperoxide, diisopropyl peroxydicarbonate, di-n-propyl peroxydicarbonate, and di (2-ethoxyethyl) peroxy. Examples thereof include dicarbonate, t-butyl peroxyneodecanoate, t-butyl peroxyvivarate, (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, the solution of the (meth) acrylic acid ester polymer (A) is mixed with the cross-linking agent (B), the light-diffusing fine particles (C), and optionally a diluting solvent and polyrotaxane. The adhesive composition P (coating solution) diluted with a solvent by adding the compound (D), the active energy ray-curable component (E), the photopolymerization initiator (F), the additive and the like and mixing them sufficiently. ). 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. 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. 3. Production of Adhesive An adhesive can be obtained by cross-linking the adhesive composition P. 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 when volatilizing the diluting solvent or the like from the coating film 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). When this curing period is required, an adhesive is formed after the curing period has elapsed, and when 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) (and the polyrotaxane compound (D)) is crosslinked via the cross-linking agent (B) to obtain a pressure-sensitive adhesive.

[Adhesive sheet]
The pressure-sensitive adhesive sheet according to the present embodiment has a pressure-sensitive adhesive layer made of the above-mentioned pressure-sensitive adhesive. FIG. 1 shows a specific configuration as an example of the pressure-sensitive adhesive sheet according to the present embodiment. As shown in FIG. 1, the pressure-sensitive adhesive sheet 1 according to the embodiment is in contact with the two release sheets 12a and 12b and the release surfaces of the two release sheets 12a and 12b. , 12b and the pressure-sensitive adhesive layer 11 sandwiched between the two. 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) pressure-sensitive adhesive layer The pressure-sensitive adhesive layer 11 is composed of the pressure-sensitive adhesive according to the above-described embodiment, and is preferably composed of a pressure-sensitive adhesive formed by cross-linking the pressure-sensitive adhesive composition P.

The thickness of the pressure-sensitive adhesive layer 11 (value measured according to JIS K7130) in the pressure-sensitive adhesive sheet 1 according to the present embodiment is preferably 10 μm or more, more preferably 20 μm or more as a lower limit value. As a result, the unevenness of the backlight can be embedded by the pressure-sensitive adhesive layer 11, and the desired light diffusivity can be obtained. The thickness of the pressure-sensitive adhesive layer 11 is preferably 3000 μm or less, more preferably 1000 μm or less, particularly preferably 500 μm or less, and further preferably 300 μm or less as an upper limit value. As a result, the desired light diffusivity can be easily obtained, and the processability is also good. The pressure-sensitive adhesive layer 11 may be formed as a single layer, or may be formed by laminating a plurality of layers.

(2) Peeling Sheet 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 peeling 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 release sheet 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) Haze Value The haze value of the pressure-sensitive adhesive layer 11 according to the present embodiment (value measured according to JIS K7136: 2000) is preferably 4% or more, preferably 10% or more, as a lower limit value. More preferably, it is particularly preferably 35% or more, and further preferably 56% or more. As a result, good light diffusivity and, by extension, good brightness unevenness suppression property can be easily obtained. On the other hand, from the viewpoint of visibility of the display device, the haze value of the pressure-sensitive adhesive layer 11 is preferably 100% or less, more preferably 99% or less, particularly preferably 98% or less, and further. Is preferably 97% or less. When the pressure-sensitive adhesive is active energy ray-curable, the haze value of the pressure-sensitive adhesive layer 11 after active energy ray-curing is preferably within the above range for the same reason as described above.

(2) 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 preferably 80% or more. In particular, it is preferably 90% or more, and more preferably 95% or more. When the total light transmittance is the above, the visibility as a display device becomes good. On the other hand, the upper limit of the total light transmittance is not particularly limited, but is usually 100% or less. When the pressure-sensitive adhesive is active energy ray-curable, the total light transmittance of the pressure-sensitive adhesive layer 11 after active energy ray-curing is preferably within the above range for the same reason as described above.

(3) Adhesive Strength The adhesive strength of the pressure-sensitive adhesive sheet 1 according to the present embodiment to soda lime glass is preferably 1 N / 25 mm or more as a lower limit value, particularly preferably 5 N / 25 mm or more, and further 15 N / 25 mm. It is preferably 25 mm or more. When the lower limit of the adhesive strength is the above, the uneven embedding property under high temperature and high humidity conditions becomes more excellent. The adhesive strength of the pressure-sensitive adhesive sheet 1 according to the present embodiment to soda lime glass is preferably 70 N / 25 mm or less, more preferably 60 N / 25 mm or less, and 50 N / 25 mm or less as an upper limit value. Is particularly preferable. When the upper limit value of the adhesive force of the adhesive sheet is the above, good reworkability can be obtained, and if a bonding error occurs, an expensive display body component can be reused.

When the pressure-sensitive adhesive layer 11 according to the present embodiment is inactive energy ray-curable, the adhesive strength of the pressure-sensitive adhesive layer 11 after irradiation with the active energy ray is preferably 1 N / 25 mm or more, and is preferably 10 N / 25 mm or more. It is more preferable, particularly preferably 14 N / 25 mm or more, and further preferably 18 N / 25 mm or more. As a result, the uneven embedding property and the blister resistance under high temperature and high humidity conditions are improved. Further, from the viewpoint of good reworkability, the adhesive strength is preferably 70 N / 25 mm or less, more preferably 60 N / 25 mm or less, and particularly preferably 55 N / 25 mm or less.

Here, the adhesive strength in the present specification basically means the adhesive strength measured by the 180-degree peeling method according to JIS Z0237: 2009, but the measurement sample is 25 mm wide and 100 mm long, and the measurement sample is used. It is attached to an adherend, pressurized at 0.5 MPa and 50 ° C. for 20 minutes, left at normal pressure, 23 ° C. and 50% RH for 24 hours, and then measured at a peeling speed of 300 mm / min. It shall be.

(4) L * a * b * color system The brightness L * defined by the CIE1976 L * a * b * color system of the pressure-sensitive adhesive layer 11 of the pressure-sensitive adhesive sheet 1 according to the present embodiment is 10 or more. It is preferable, particularly preferably 60 or more, and further preferably 90 or more. Further, the brightness L * is preferably 100 or less, particularly preferably 99 or less, and further preferably 98 or less. When the brightness L * of the pressure-sensitive adhesive layer 11 is in the above range, the visibility of the obtained display device becomes good. When the pressure-sensitive adhesive is active energy ray-curable, it is preferable that the pressure-sensitive adhesive layer 11 after curing is also within the above range.

The absolute value of the chromaticity a * defined by the CIE1976L * a * b * color system of the pressure-sensitive adhesive layer 11 of the pressure-sensitive adhesive sheet 1 according to the present embodiment is preferably 0 or more, and particularly 0.1 or more. It is preferably present, and more preferably 0.2 or more. The absolute value of the chromaticity a * is preferably 10 or less, particularly preferably 5 or less, and further preferably 1 or less. On the other hand, the absolute value of the chromaticity b * defined by the CIE1976L * a * b * color system of the pressure-sensitive adhesive layer 11 of the pressure-sensitive adhesive sheet 1 according to the present embodiment is preferably 0 or more, and particularly 0.1. It is preferably more than 0.2, and more preferably 0.2 or more. The absolute value of the chromaticity b * is preferably 10 or less, particularly preferably 5 or less, and further preferably 1 or less. When the chromaticity a * and b * of the pressure-sensitive adhesive layer 11 are in the above range, it can be said that the pressure-sensitive adhesive layer 11 is less colored and has excellent colorless transparency, and is particularly suitable for a display. Become. When the pressure-sensitive adhesive is active energy ray-curable, it is preferable that the pressure-sensitive adhesive layer 11 after curing is also within the above range.

3. 3. Production of Adhesive Sheet As an example of production of the adhesive sheet 1, a case where the adhesive composition P is used will be described. The coating liquid of the adhesive composition P is applied to the peeling surface of one of the release sheets 12a (or 12b), heat-treated to heat-crosslink the adhesive composition P to form a coating layer, and then the coating is applied. The peeling surface of the other peeling sheet 12b (or 12a) is superposed on the 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 liquid of the pressure-sensitive adhesive composition P is applied to the peel-off surface of one of the release sheets 12a, and heat treatment is performed to heat-crosslink the pressure-sensitive adhesive composition P to obtain a coating layer. To obtain a release sheet 12a with a coating layer. Further, the coating liquid of the adhesive composition P is applied to the peeling surface of the other release sheet 12b, heat treatment is performed to thermally 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. 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, even when the pressure-sensitive adhesive layer 11 is thick, stable production is possible.

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

[Backlight unit]
The backlight unit according to the embodiment of the present invention includes a backlight having a plurality of light emitters and an adhesive layer laminated on the backlight. Since the backlight unit has a plurality of light emitting bodies, it often has irregularities on the surface on the adhesive layer side.

FIG. 2 shows a specific configuration as an example of the backlight unit according to the present embodiment. As shown in FIG. 2, the backlight unit 2 according to the embodiment includes a backlight 20 and an adhesive layer 11 laminated on the backlight 20.

1. 1. Component (1) Backlight The backlight 20 includes one or more substrates 21 and a plurality of light emitters 22 provided on the substrate 21. The backlight 20 has irregularities due to a plurality of light emitters 22.

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 formed separately, 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. Thereby, the brightness by 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 5 μm or more, more preferably 50 μm or more, particularly preferably 100 μm or more, and further preferably 200 μm or more. The thickness of the illuminant 22 is preferably 1000 μm or less, particularly preferably 500 μm or less, and further preferably 250 μm or less.

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.

The shape of the light emitting body 22 is not particularly limited, but is usually a rectangular parallelepiped shape, a hemispherical shape, 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.

(2) Adhesive Layer The pressure-sensitive adhesive layer 11 in the present embodiment is composed of the pressure-sensitive adhesive according to the above-described embodiment, and preferably is composed of a pressure-sensitive adhesive formed by cross-linking the pressure-sensitive adhesive composition P. Further, the pressure-sensitive adhesive layer 11 in the present embodiment is preferably the pressure-sensitive adhesive layer 11 of the pressure-sensitive adhesive sheet 1 described above.

The pressure-sensitive adhesive layer 11 in the present embodiment embeds the unevenness of the light emitting body 22. That is, the plurality of light emitters 22 are sealed by the pressure-sensitive adhesive layer 11 without any voids. As a result, the water resistance is improved, and the light emitting body 22 (particularly the LED) can be protected from moisture. Further, the pressure-sensitive adhesive layer 11 diffuses the light emitted from the backlight 20 and effectively suppresses the occurrence of uneven brightness.

The pressure-sensitive adhesive layer 11 may be laminated in direct contact with the backlight 20, or may be indirectly laminated via another layer or member.

2. Manufacture of Backlight Unit In order to manufacture the backlight unit 2 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 of the adhesive sheet 1 is removed from the backlight 20. It is attached to the surface on the side where the light emitting body 22 of the above exists. When the pressure-sensitive adhesive layer is inactive energy ray-curable, the pressure-sensitive adhesive layer 11 may be cured by irradiating the pressure-sensitive adhesive layer 11 with active energy rays from the release sheet 12b side at this stage.

Next, the other release sheet 12b is peeled from the pressure-sensitive adhesive layer 11 of the pressure-sensitive adhesive sheet 1 at a desired timing. The peeling of the release sheet 12b is preferably performed when the display device 3 described later is manufactured, and it is preferable to protect the pressure-sensitive adhesive layer 11 with the release sheet 12b until then.

3. 3. Other Configuration A sealing material may be provided between the backlight 20 and the pressure-sensitive adhesive layer 11. Even in that case, irregularities are often formed on the surface of the sealing material opposite to the backlight 20, and these irregularities can be absorbed by the pressure-sensitive adhesive layer 11.

[Display device]
A display device according to an embodiment of the present invention includes a backlight unit according to the above-described embodiment and a display unit laminated on an adhesive layer of the backlight unit. The display unit may be laminated in direct contact with the pressure-sensitive adhesive layer, or may be indirectly laminated via another layer or member.

A display device as an example in this embodiment is shown in FIG.
As shown in FIG. 3, the display device 3 according to the present embodiment includes the backlight unit 2 described above and a display unit 30 laminated on the pressure-sensitive adhesive layer 11 of the backlight unit 2. The backlight 20 in the display device 3 corresponds to a direct type backlight.

Examples of the type of display device 3 include a liquid crystal display (LCD), a light emitting diode (LED) display, an organic electroluminescence (organic EL) display, electronic paper, and the like. The display device 3 may be a touch panel. Among the above, a liquid crystal display (liquid crystal display device) having a high need for a backlight is preferable.

The display unit 30 includes, for example, a liquid crystal panel, but is not limited thereto, and is used in combination with, for example, a part of the constituent members of the liquid crystal panel or for adding or enhancing the function of the liquid crystal panel. It may be an optical member (for example, a light diffusing plate, an ultraviolet absorbing filter, etc.). As the display unit 30, a known one can be adopted.

In order to manufacture the display device 3 according to the present embodiment, the adhesive layer 11 exposed in the backlight unit 2 and the display unit 30 are bonded together. When the release sheet 12b is laminated on the pressure-sensitive adhesive layer 11, the release sheet 12b is peeled off to expose the pressure-sensitive adhesive layer 11, and then the pressure-sensitive adhesive layer 11 and the display unit 30 are attached to each other. Stick them together.

When the pressure-sensitive adhesive layer 11 is active energy ray-curable, the pressure-sensitive adhesive layer 11 is irradiated with active energy rays from a desired side to cure the pressure-sensitive adhesive layer 11. The active energy ray refers to an electromagnetic wave or a charged particle beam having an energy quantum, and specific examples thereof include ultraviolet rays and electron beams. Among the active energy rays, ultraviolet rays, which are easy to handle, are particularly preferable.

Irradiation of ultraviolet rays, a high-pressure mercury lamp, a fusion H lamp, can be carried out by a xenon lamp or the like, the dose of ultraviolet ray is preferably illuminance is 50~1000mW / cm ² approximately, 100~500mW / cm ² of about Is preferable. Further, the light quantity is preferably 50~10000mJ / cm ^2, more preferably 200~7000mJ / cm ^2, and particularly preferably 500~3000mJ / cm ^2. On the other hand, the irradiation of the electron beam can be performed by an electron beam accelerator or the like, and the irradiation amount of the electron beam is preferably about 10 to 1000 grad.

When the pressure-sensitive adhesive layer 11 is active energy ray-curable, the gel fraction of the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer 11 after active energy ray-curing is 15% from the viewpoint of embedding unevenness under high temperature and high humidity conditions. It is preferably 45% or more, more preferably 45% or more, and from the viewpoint of blister resistance, it is particularly preferably 55% or more, and further preferably 60% or more. Further, from the viewpoint of maintaining good adhesive strength, the gel fraction is preferably 99% or less, more preferably 90% or less, particularly preferably 80% or less, and further 70. % Or less is preferable.

In manufacturing the display device 3 according to the present embodiment, the pressure-sensitive adhesive layer 11 may be attached to the display unit 30 first, and then the pressure-sensitive adhesive layer 11 and the backlight 20 may be attached to each other.

Here, a desired optical member may be provided between the pressure-sensitive adhesive layer 11 and the display unit 30, or on the surface of the display unit 30 opposite to the pressure-sensitive adhesive layer 11. 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 semitransmissive reflective film, a shatterproof film, and a light diffusing plate.

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 one of the release sheets 12a and 12b in the adhesive sheet 1 may be omitted.

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 55 parts by mass of 2-ethylhexyl acrylate, 5 parts by mass of n-butyl acrylate, 15 parts by mass of isobonyl acrylate, 5 parts by mass of N-acryloyl morpholine and 2-hydroxyethyl acrylate 20 A (meth) acrylic acid ester polymer (A) was prepared by copolymerizing parts by mass. 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 700,000.

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 trimethylolpropane as a cross-linking agent (B). Light composed of 0.3 parts by mass of modified tolylene diisocyanate (manufactured by Toyochem Co., Ltd., product name "BHS8515") and silicone resin (silicon-containing compound having an intermediate structure between inorganic and organic) as light diffusing fine particles (C). Diffused fine particles (C1; manufactured by Momentive Performance Materials Japan, product name "Tospearl 145", average particle size: 4.5 μm) and 5 parts by mass, and polymer compound (D) (manufactured by Advanced Soft Materials, Inc., Product name "SELM Superpolymer SH3400P", linear molecule: polyethylene glycol, cyclic molecule: α-cyclodextrin having hydroxypropyl group and caprolactone chain, block group: adamantan group, weight average molecular weight (Mw) 700,000, hydroxyl value 72 mgKOH / g) 15 parts by mass and ε-caprolactone-modified tris- (2-acryloxyethyl) isocyanurate as an active energy ray-curable component (E) (manufactured by Shin-Nakamura Chemical Co., Ltd., product name "NK ester A-9300" -1CL ") 5 parts by mass and a mixture of benzophenone as a photopolymerization initiator (F) and 1-hydroxycyclohexylphenylketone (mass ratio 50:50) (manufactured by IGM isocyanate, product name" Omnirad 500 ") 0 .5 parts by mass and 0.15 parts by mass of 3-glycidoxypropyltrimethoxysilane (manufactured by Shinetsu Chemical Industry Co., Ltd., product name "KBM-403") as a silane coupling agent are mixed and sufficiently stirred. The 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 acid ester polymer (A)]
2EHA: 2-ethylhexyl acrylate BA: n-butyl acrylate IBXA: isobornyl acrylate ACMO: N-acryloyl morpholine HEA: 2-hydroxyethyl acrylate
[Light diffusing fine particles (C)]
C1: Light-diffusing fine particles (manufactured by Momentive Performance Materials Japan) made of a silicone resin (silicon-containing compound having an intermediate structure between inorganic and organic) having an average particle size of 4.5 μm, product name “Tospearl 145”, Refractive index: 1.43)
C2: Light-diffusing fine particles made of acrylic resin with an average particle size of 3.5 μm and a refractive index of 1.550.

3. 3. Manufacture of Adhesive Sheet Peeling of 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 obtained coating solution of the adhesive composition. The treated surface was coated with a knife coater and then heat-treated at 90 ° C. for 1 minute to form a coated layer.

Next, the coating layer on the heavy-release type release sheet obtained above and the light-release type release sheet obtained by peeling one side of the polyethylene terephthalate film with a silicone-based release agent (manufactured by Lintec, product name "SP-PET38131"). And are bonded so that the peeled surface of the light peeling type peeling sheet comes into contact with the coating layer, and the heavy peeling type peeling sheet / the coating layer of the adhesive layer (thickness: 25 μm) / the light peeling type peeling sheet An adhesive sheet having a composition was produced.

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 (the same applies hereinafter).

[Examples 2-9, Comparative Examples 1-6]
Blending amount of cross-linking agent (B), type and blending amount of light diffusing fine particles (C), blending amount of polyrotaxane compound (D), blending amount of active energy ray-curable component (E), photopolymerization initiator (F) A pressure-sensitive adhesive sheet was produced in the same manner as in Example 1 except that the blending amount of the above and the thickness of the pressure-sensitive adhesive layer were changed as shown in Table 1. Since the pressure-sensitive adhesive layer in the pressure-sensitive adhesive sheet of Example 7 did not contain the active energy ray-curable component (E) and the photopolymerization initiator (F), it was non-curable with active energy rays. Further, the thickness of the pressure-sensitive adhesive layer was changed by changing the thickness and / or the number of layers of the pressure-sensitive adhesive layer formed on the release sheet.

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>
-GPC measuring device: HLC-8020 manufactured by Tosoh Corporation
-GPC column (passed in the following order): TSK guard volume HXL-H manufactured by Tosoh Corporation
TSK gel GMHXL (x2)
TSK gel G2000HXL
-Measurement solvent: tetrahydrofuran-Measurement temperature: 40 ° C

[Test Example 1] (Measurement of 1000% modulus)
A plurality of adhesive layers of the pressure-sensitive adhesive sheets obtained in Examples and Comparative Examples were laminated to make a total thickness of 600 μm, and then a sample having a width of 10 mm and a length of 75 mm was cut out. The above sample was set in a tensile tester (manufactured by Orientec, product name "Tencilon") so that the sample measurement site had a width of 10 mm and a length of 20 mm (extension direction), and the sample was measured in an environment of 23 ° C. and 50% RH. It was stretched at a tensile speed of 200 mm / min using a tensile tester, and the stress value at which the elongation rate was 1000% was measured as ^{1000% modulus (N / mm 2).} The results are shown in Table 2.

[Test Example 2] (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 pressure-sensitive 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. As a result, the gel fraction (before UV;%) of the pressure-sensitive adhesive was derived. The results are shown in Table 2.

On the other hand, the pressure-sensitive adhesive layers of the pressure-sensitive adhesive sheets (other than Example 7) obtained in Examples and Comparative Examples are irradiated with active energy rays (ultraviolet rays; UV) under the following conditions through the light-release type release sheet. , The pressure-sensitive adhesive layer was cured. For the pressure-sensitive adhesive in the pressure-sensitive adhesive layer after curing, the gel fraction (after UV;%) was derived in the same manner as above. The results are shown in Table 2.

<Activation energy ray irradiation conditions>
・ Uses high-pressure mercury lamp ・ Illuminance 200mW / cm ² , light intensity 1000mJ / cm ²
・ UV illuminance / photometer uses "UVPF-A1" manufactured by iGraphics.

[Test Example 3] (Measurement of haze value)
The pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheets produced in Examples and Comparative Examples was bonded to glass, and this was used as a measurement sample. After performing background measurement with glass, the haze value (UV) of the above measurement sample using a haze meter (manufactured by Nippon Denshoku Kogyo Co., Ltd., product name "SH-7000") according to JIS K7136: 2000. Previous;%) was measured. The results are shown in Table 2.

Next, the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet (other than Example 7) was irradiated with active energy rays under the same conditions as in Test Example 2 to cure the pressure-sensitive adhesive layer. The haze value (after UV;%) of the cured pressure-sensitive adhesive layer was measured in the same manner as described above. The results are shown in Table 2.

[Test Example 4] (Measurement of total light transmittance)
The pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheets produced in Examples and Comparative Examples was bonded to glass, and this was used as a measurement sample. After performing background measurement with glass, all light rays of the above measurement sample were measured using a haze meter (manufactured by Nippon Denshoku Kogyo Co., Ltd., product name "SH-7000") in accordance with JIS K7361-1: 1997. The transmittance (before UV;%) was measured. The results are shown in Table 2.

Next, the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet (other than Example 7) was irradiated with active energy rays under the same conditions as in Test Example 2 to cure the pressure-sensitive adhesive layer. The total light transmittance (after UV;%) of the cured pressure-sensitive adhesive layer was measured in the same manner as described above. The results are shown in Table 2.

[Test Example 5] (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 laminated body of a heavy peeling type 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.

In an environment of 23 ° C. and 50% RH, the heavy-release type release sheet is peeled off from the above laminate, and the exposed adhesive layer is attached to soda lime glass (manufactured by Nippon Sheet Glass Co., Ltd.) and then autoclave manufactured by Kurihara Seisakusho Co., Ltd. Pressurized at 0.5 MPa and 50 ° C. for 20 minutes. Then, it was left for 24 hours under the condition of 23 ° C. and 50% RH, and this was used as a sample. Then, using a tensile tester (manufactured by Orientec Co., Ltd., product name "Tencilon"), the adhesive strength (before UV; N / 25 mm) was measured under the conditions of a peeling speed of 300 mm / min and a peeling angle of 180 degrees. Conditions other than those described here were measured in accordance with JIS Z0237: 2009. The results are shown in Table 2.

Next, the above sample (other than Example 7) was irradiated with active energy rays through the PET film under the same conditions as in Test Example 2 to cure the pressure-sensitive adhesive layer. The adhesive strength (after UV; N / 25 mm) of the cured pressure-sensitive adhesive layer was measured in the same manner as described above. The results are shown in Table 2.

[Test Example 6] (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 the CIE1976L * a * b * color was used. Brightness L *, chromaticity a * and chromaticity b * (before UV) defined by the system were measured. The results are shown in Table 2.

Next, the pressure-sensitive adhesive layers of the pressure-sensitive adhesive sheets (other than Example 7) obtained in Examples and Comparative Examples were irradiated with active energy rays under the same conditions as in Test Example 2 to cure the pressure-sensitive adhesive layer. .. The lightness L *, chromaticity a *, and chromaticity b * (after UV) were measured for the cured pressure-sensitive adhesive layer in the same manner as described above. The results are shown in Table 2.

[Test Example 7] (Evaluation of uneven embedding property)
On the surface of a glass plate (manufactured by NSG Precision Co., Ltd., product name "Corning Glass Eagle XG", length 90 mm x width 50 mm x thickness 0.5 mm), UV curable ink (manufactured by Teikoku Inks, product name "POS-911 ink") ) Was screen-printed in a frame shape (outer shape: length 90 mm × width 50 mm, width 5 mm) so that the coating thickness was any one of 5 μm, 10 μm, 15 μm, 20 μm, and 25 μm. Next, the printed ultraviolet curable ink is cured by irradiating with ultraviolet rays (80 W / cm2, 2 metal halide lamps, lamp height 15 cm, belt speed 10 to 15 m / min), and a step (height of the step) due to printing is cured. : A stepped glass plate having any one of 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, and 100 μm) was produced.

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 film having an easy adhesive layer (manufactured by Toyobo Co., Ltd., product name "PET A4300", thickness: It was bonded to an easy-adhesion layer of 100 μm). Next, the heavy-release type release sheet was peeled off to expose the pressure-sensitive adhesive layer. Then, using a laminator (manufactured by Fujipla, product name "LPD3214"), the laminate was laminated on each stepped glass plate so that the adhesive layer covered the entire surface of the frame-shaped print, and this was used as an evaluation sample. did.

The obtained evaluation sample was autoclaved for 30 minutes under the conditions of 50 ° C. and 0.5 MPa, and then left at normal pressure at 23 ° C. and 50% RH for 24 hours. Then, it was stored for 72 hours under high temperature and high humidity conditions of 85 ° C. and 85% RH (durability test), and then the unevenness embedding property was evaluated. The unevenness embedding property is judged by whether or not the printing step (unevenness) is completely filled by the adhesive layer, and if air bubbles, floating, peeling, etc. are observed at the interface between the printing step and the adhesive layer, It is determined that the printing step (unevenness) was not filled by the adhesive layer. Here, the uneven embedding property was calculated as the step follow-up rate (%) represented by the following formula, and evaluated according to the following criteria. The results are shown in Table 2.
Step follow-up rate (%) = {(After the durability test, the height of the step maintained in a buried state without bubbles, floating, peeling, etc. (μm)) / (Thickness of adhesive layer (μm)} × 100
<Evaluation criteria for embedding unevenness>
◎… Step follow rate 40% or more ○… Step follow rate less than 40%, 30% or more △… Step follow rate less than 30%, 20% or more ×… Step follow rate less than 20%

[Test Example 8] (Evaluation of brightness unevenness suppression)
As a surface light source, a liquid crystal display device of a tablet terminal (manufactured by Apple Inc., product name "iPad (registered trademark)", resolution: 264 ppi) was prepared. The surface of the liquid crystal display device was covered with a stainless steel mesh to obtain a pseudo-backlight. The conditions of the above liquid crystal display device and the details of the stainless steel mesh are as follows.
<Liquid crystal display device>
-Display color: White-Brightness setting: Maximum-Number of pixels: 980 x 980
<Stainless steel mesh>
-Stainless steel type: SUS316
・ Weave: Plain weave ・ Wire diameter: 50 μm
・ Opening: 204 μm
・ Aperture ratio: 64.5%
-Number of meshes: 100 (/ 25.4 mm)

On the other hand, the light release type release sheet was peeled from the adhesive sheets obtained in Examples and Comparative Examples, and the exposed adhesive layer was attached to a soda lime glass plate (manufactured by Nippon Sheet Glass Co., Ltd., thickness: 0.7 mm). , A laminate composed of a heavy release type release sheet / adhesive layer / soda lime glass plate was obtained.

By placing the laminated body on the pseudo-backlight so that the heavy-release type release sheet side is in contact with the pseudo-backlight, a pseudo display device A having a backlight unit was obtained. A sensory evaluation was performed to see if the metal wire could be visually confirmed from a position 30 cm directly above the pseudo display device A. Based on the results, the brightness unevenness suppression property was evaluated according to the following criteria. The results are shown in Table 2.
⊚… The metal wire was concealed and the brightness distribution was uniform.
◯… A metal wire can be confirmed by staring, but the brightness distribution was almost uniform.
×: The metal wire was clearly confirmed, and the brightness distribution was not uniform.

[Test Example 9] (Evaluation of blister resistance)
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 plastic plate in which a PMMA layer was laminated on a PC plate (manufactured by Mitsubishi Gas Chemical Company, product name "Iupilon Sheet". MR58U ”, thickness: 0.7 mm, containing an ultraviolet absorber) was bonded to the PC plate side to obtain a plastic plate with an adhesive layer.

The heavy-release type release sheet is peeled off from the plastic plate with the adhesive layer obtained above, and the plastic plate is separated through the exposed adhesive layer into a soda lime glass plate having a size of 70 mm × 150 mm (manufactured by Nippon Sheet Glass Co., Ltd.). , Thickness: 0.7 mm). Then, it was autoclaved for 30 minutes under the conditions of 50 ° C. and 0.5 MPa, and left at normal pressure at 23 ° C. and 50% RH for 24 hours.

Next, the pressure-sensitive adhesive layer is irradiated with active energy rays through the plastic plate under the same conditions as in Test Example 2 (other than Example 7) to cure the pressure-sensitive adhesive layer, thereby causing a pseudo display device B. Got

The pseudo display device B was stored for 72 hours under high temperature and high humidity conditions of 85 ° C. and 85% RH. Then, the state at the interface between the pressure-sensitive adhesive layer and the adherend (plastic plate, soda lime glass plate) was visually confirmed, and the blister resistance was evaluated according to the following criteria. The results are shown in Table 2.
◎… There were no bubbles, floats, or peeling.
○… Small bubbles were generated.
×… Bubbles, floats, and peeling occurred on the whole.

As can be seen from Table 2, the pressure-sensitive adhesive sheet produced in the examples was excellent in uneven embedding property and brightness unevenness suppressing property. Further, the pressure-sensitive adhesive sheets produced in Examples 1 to 4, 7 and 9 were also excellent in blister resistance.

The pressure-sensitive adhesive, pressure-sensitive adhesive sheet, and backlight unit according to the present invention are suitable for display devices, especially liquid crystal display devices, which are required to have uneven embedding property and brightness unevenness suppression property.

1 ... Adhesive sheet 11 ... Adhesive layer 12a, 12b ... Release sheet 2 ... Backlight unit 20 ... Backlight 21 ... Substrate 22 ... Light emitter 3 ... Display device 30 ... Display unit

Claims (10)

Contains light diffusing fine particles,
The 1000% modulus when the tensile test was performed at 23 ° C. was 0.23 N / mm ² or less.
An adhesive having a gel fraction of 10% or more. The pressure-sensitive adhesive according to claim 1, wherein the pressure-sensitive adhesive is an acrylic pressure-sensitive adhesive. The pressure-sensitive adhesive according to claim 1 or 2, which comprises a polyrotaxane compound. The pressure-sensitive adhesive according to any one of claims 1 to 3, which contains an active energy ray-curable component. An adhesive sheet having an adhesive layer,
A pressure-sensitive adhesive sheet, wherein the pressure-sensitive adhesive layer comprises the pressure-sensitive adhesive according to any one of claims 1 to 4. The pressure-sensitive adhesive sheet according to claim 5, wherein the haze value of the pressure-sensitive adhesive layer is 4% or more and 100% or less. The adhesive sheet includes two release sheets.
The adhesive sheet according to claim 5 or 6, wherein the pressure-sensitive adhesive layer is sandwiched between the release sheets so as to be in contact with the release surfaces of the two release sheets. A backlight with multiple illuminants and
A structure including an adhesive layer laminated on the backlight.
A backlight unit, wherein the pressure-sensitive adhesive layer is a pressure-sensitive adhesive layer made of the pressure-sensitive adhesive according to any one of claims 1 to 4. The backlight unit according to claim 8, wherein the light emitting body is a light emitting diode. With the backlight unit according to claim 8 or 9.
A display device including a display unit laminated on the pressure-sensitive adhesive layer of the backlight unit.

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