JP6325481B2 - Adhesive sheet - Google Patents

Description

  The present invention relates to an adhesive sheet.

  Various mobile electronic devices such as mobile phones and tablet terminals in recent years include a display body (display) using a display panel having a liquid crystal element, a light emitting diode (LED element), an organic electroluminescence (organic EL) element, and the like. .

  Such a display is usually provided with a protective plate on the surface side of the display panel. A gap is provided between the protective plate and the display panel so that the deformed protective plate does not hit the display panel even when the protective plate is deformed by an external force.

  However, the presence of the air gap, that is, the air layer as described above, causes a large light reflection loss due to the difference in refractive index between the protective panel and the air layer and the difference in refractive index between the air layer and the display panel. There is a problem that decreases.

  Therefore, it has been proposed to improve the image quality of the display by filling the gap between the protective plate and the display panel with an adhesive.

  By the way, a frame-shaped printed layer may exist as a step on the display panel side of the protective plate. The pressure-sensitive adhesive layer floats in the vicinity of the step or cannot follow the step, or even if it can follow the step in the initial stage, bubbles or float in the vicinity of the step when exposed to high-temperature and high-humidity conditions. -There arises a problem that peeling occurs (hereinafter sometimes referred to as "step following ability"), and the aesthetic appearance of the image display device is impaired.

Here, the shear storage elastic modulus (G ′) at 25 ° C. and 1 Hz is 1.0 × 10 ⁵ Pa as an adhesive layer that fills the gap between the protective panel and the display module in order to follow the step. An adhesive layer having a gel fraction of 40% or more is disclosed (for example, see Patent Document 1).

  However, in the pressure-sensitive adhesive of Patent Document 1, when the display is put under a durable condition such as high temperature and high humidity and then returned to normal temperature and humidity, bubbles are generated between the pressure-sensitive adhesive layer and the adherend ( There is a problem that the transparency of the pressure-sensitive adhesive layer is lowered).

  In order to solve such a problem, a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer containing a (meth) acrylic acid ester copolymer and an active energy ray-curable component has been proposed (see Patent Document 2).

  However, when the pressure-sensitive adhesive sheet of Patent Document 2 is applied to various adherends used for a display, the adhesive force may be insufficient depending on the adherend.

JP 2010-97070 A JP 2014-196451 A

  An object of the present invention is to provide a pressure-sensitive adhesive sheet that has high adhesive strength to various adherends and is excellent in foam resistance (blister resistance) and level difference followability.

Such an object is achieved by the present inventions (1) to ( 6 ) below.
(1) As a monomer unit constituting the polymer , (meth) acrylic acid alkyl ester having an alkyl group having 1 to 8 carbon atoms, a monomer having an alicyclic structure, a monomer having a nitrogen atom (maleimide group) comprises containing the excluding) those containing a (meth) acrylic acid ester polymer, and an active energy ray-curable component, a,
The (meth) acrylic acid ester polymer contains 50% by mass or more and 95% by mass or less of the (meth) acrylic acid alkyl ester as a monomer unit constituting the polymer,
It is formed of a pressure-sensitive adhesive composition containing 0.1 to 10 parts by mass of the active energy ray-curable component with respect to 100 parts by mass of the (meth) acrylic acid ester polymer.
The pressure-sensitive adhesive sheet, wherein the active energy ray-curable component is composed of a 3-6 functional polyfunctional acrylate monomer, and the active energy ray-curable component is present in an uncured state.

( 2 ) The (meth) acrylic acid ester polymer contains 3% by mass to 20% by mass of the monomer having the alicyclic structure as a monomer unit constituting the polymer, and the monomer having the nitrogen atom The pressure-sensitive adhesive sheet according to (1 ) above, containing 1% by mass or more and 20% by mass or less.

( 3 ) The (meth) acrylic acid ester polymer contains a monomer having the alicyclic structure and a monomer having a nitrogen atom as a monomer unit constituting the polymer in total of 5% by mass or more and 40% by mass or less. The pressure-sensitive adhesive sheet according to (1) or (2) above.

( 4 ) The pressure-sensitive adhesive sheet according to any one of (1) to ( 3 ), wherein the alicyclic structure includes an isobornyl skeleton.

( 5 ) The pressure-sensitive adhesive sheet according to any one of (1) to ( 4 ), wherein the monomer having a nitrogen atom has a nitrogen-containing heterocyclic ring.

( 6 ) The pressure-sensitive adhesive sheet according to any one of (1) to ( 5 ), which is used for bonding the protective plate and the display panel.

  According to the present invention, it is possible to provide a pressure-sensitive adhesive sheet that has high adhesion to various adherends (especially transparent conductive film and glass) and is excellent in foam resistance (blister resistance) and step following ability. Can do.

It is sectional drawing which shows an example of the display which bonded the protective plate and the display panel using the adhesive sheet of this invention.

Hereinafter, the present invention will be described in detail based on preferred embodiments.
<1> Adhesive composition The adhesive composition which comprises the adhesive sheet of this embodiment contains the monomer which has an alicyclic structure, and the monomer which has a nitrogen atom as a monomer unit which comprises a polymer ( It comprises a (meth) acrylic acid ester polymer and an active energy ray-curable component.

  By having the characteristics as described above, the pressure-sensitive adhesive sheet of the present embodiment is cured of the pressure-sensitive adhesive sheet obtained by irradiating various adherends (particularly ITO or glass) with active energy rays after being applied. The product (hereinafter sometimes referred to as “cured pressure-sensitive adhesive sheet”) has high adhesive strength. In addition, when there is a step on the bonding surface of the adherend, the pressure-sensitive adhesive sheet of the present embodiment can easily follow the step, and is then irradiated with active energy rays to achieve durability (high temperature and high temperature). Even after storage under wet conditions, it is possible to prevent the generation of voids or bubbles between the bonding surface of the adherend and the adhesive sheet after curing (excellent in step following ability). In addition, the adhesive sheet of the present embodiment is irradiated with active energy rays after being bonded to the adherend even when the adherend is a plastic plate or the like in which the blister property under durability conditions is a problem. By doing so, the generation of bubbles at the interface between the adherend and the cured pressure-sensitive adhesive sheet can be effectively prevented even after exposure to durability conditions (excellent in blister resistance).

Hereinafter, each component which comprises an adhesive composition is demonstrated in detail.
1. (Meth) acrylic acid ester polymer The pressure-sensitive adhesive composition constituting the pressure-sensitive adhesive sheet contains a (meth) acrylic acid ester polymer.

  In this embodiment, the (meth) acrylic acid ester polymer has a monomer having an alicyclic structure (hereinafter also simply referred to as an alicyclic structure-containing monomer) and a nitrogen atom as monomer units constituting the polymer. Monomer (hereinafter, also simply referred to as nitrogen atom-containing monomer). In addition, in this specification, (meth) acrylic acid ester means both acrylic acid ester and methacrylic acid ester. The same applies to other similar terms. Further, the “polymer” includes the concept of “copolymer”.

  When the pressure-sensitive adhesive composition constituting the pressure-sensitive adhesive sheet of the present embodiment contains the (meth) acrylic acid ester polymer, the pressure-sensitive adhesive sheet of the present embodiment has a transparent conductive film (particularly tin-doped indium oxide after irradiation with active energy rays). A transparent conductive film made of (lTO)), glass, and plastic (particularly, plastics such as polycarbonate and polymethylmethacrylate) and the like exhibit a strong adhesive force to various adherends used in displays.

  In addition, it is thought that the adhesive force with respect to a transparent conductive film contributes mainly by an alicyclic structure containing monomer. Moreover, it is thought that the nitrogen atom-containing monomer mainly contributes to the adhesive strength to glass and plastic. In addition to this, the presence of a bulky alicyclic structure-containing monomer in the polymer as a constituent unit can widen the interval between the polymers and make the resulting pressure-sensitive adhesive sheet excellent in flexibility. . Thereby, an adhesive sheet becomes the thing excellent in the followable | trackability to the surface unevenness | corrugation of a to-be-adhered body. Furthermore, by providing a nitrogen atom-containing monomer as a constituent unit in the polymer, the adhesive composition has a predetermined polarity, and even to an adherend having a certain degree of polarity such as a transparent conductive film or glass, It can be made excellent in affinity. As a result, it is presumed that the following properties and the properties of the affinity are combined, and the resulting pressure-sensitive adhesive sheet is excellent in adhesive force even to the transparent conductive film and glass after irradiation with active energy rays.

  The carbocyclic ring of the alicyclic structure in the alicyclic structure-containing monomer may have a saturated structure or may have an unsaturated bond. The alicyclic structure may be a monocyclic alicyclic structure or a polycyclic alicyclic structure such as a bicyclic ring or a tricyclic ring. The number of carbon atoms in the alicyclic structure is preferably 5 or more, more preferably 6 or more, and even more preferably 7 or more. Further, the carbon number of the alicyclic structure is preferably 20 or less, more preferably 15 or less, and further preferably 12 or less.

  Examples of the alicyclic structure include cyclohexyl skeleton, dicyclopentadiene skeleton, adamantane skeleton, isobornyl skeleton, cycloalkane skeleton (cycloheptane skeleton, cyclooctane skeleton, cyclononane skeleton, cyclodecane skeleton, cycloundecane skeleton, cyclododecane skeleton Etc.), cycloalkene skeleton (cycloheptene skeleton, cyclooctene skeleton, etc.), norbornene skeleton, norbornadiene skeleton, polycyclic skeleton (cuban skeleton, basketetane skeleton, Hausan skeleton, etc.), spiro skeleton, etc. Those containing an isobornyl skeleton that exhibits superior adhesive strength are preferred.

  As the alicyclic structure-containing monomer, a (meth) acrylic acid ester monomer containing the above skeleton is preferable. Specifically, cyclohexyl (meth) acrylate, dicyclopentanyl (meth) acrylate, ( Examples include adamantyl (meth) acrylate, isobornyl (meth) acrylate, dicyclopentenyl (meth) acrylate, dicyclopentenyloxyethyl (meth) acrylate, and the like, and one or more of these are used in combination. be able to. Among these, it is preferable to use isobornyl (meth) acrylate that exhibits superior adhesive strength.

  The (meth) acrylic acid ester polymer preferably contains 3% by mass or more, more preferably 6% by mass or more, and more preferably 9% by mass of the alicyclic structure-containing monomer as a monomer unit constituting the polymer. It is more preferable to contain at least%. Thereby, the adhesive sheet obtained can fully exhibit the outstanding adhesive force (especially the outstanding adhesive force with respect to a transparent conductive film) with respect to a transparent conductive film, glass, and a plastic after active energy ray irradiation. The (meth) acrylic acid ester polymer preferably contains 20% by mass or less, more preferably 18% by mass or less of the alicyclic structure-containing monomer as a monomer unit constituting the polymer. Further, it is more preferable to contain 15% by mass or less. Thereby, content of another monomer component can fully be ensured, and the obtained adhesive sheet can fully exhibit the adhesive force excellent after active energy ray irradiation.

  Examples of the nitrogen atom-containing monomer that the (meth) acrylic acid ester polymer contains as a monomer unit constituting the polymer include a monomer having an amino group, a monomer having an amide group, and a monomer having a nitrogen-containing heterocyclic ring. Can be mentioned. Among these, a monomer having a nitrogen-containing heterocycle is preferable.

  Examples of the monomer having a nitrogen-containing heterocyclic ring include N- (meth) acryloylmorpholine, N-vinyl-2-pyrrolidone, N- (meth) acryloylpyrrolidone, N- (meth) acryloylpiperidine, N- (meth) acryloyl. Pyrrolidine, N- (meth) acryloylaziridine, aziridinylethyl (meth) acrylate, 2-vinylpyridine, 4-vinylpyridine, 2-vinylpyrazine, 1-vinylimidazole, N-vinylcarbazole, N-vinylphthalimide, etc. Can be mentioned. Among these, N- (meth) acryloylmorpholine which exhibits more excellent adhesive strength is preferable, and N-acryloylmorpholine is particularly preferable.

  Examples of nitrogen atom-containing monomers include (meth) acrylamide, N-methyl (meth) acrylamide, N-methylol (meth) acrylamide, N-tert-butyl (meth) acrylamide, and N, N-dimethyl (meth) acrylamide. N, N-ethyl (meth) acrylamide, N, N-dimethylaminopropyl (meth) acrylamide, N-isopropyl (meth) acrylamide, N-phenyl (meth) acrylamide, dimethylaminopropyl (meth) acrylamide, N-vinyl Caprolactam, monomethylaminoethyl (meth) acrylate, monoethylaminoethyl (meth) acrylate, monomethylaminopropyl (meth) acrylate, monoethylaminopropyl (meth) acrylate, dimethylamino (meth) acrylate It is also possible to use the chill and the like.

  The above nitrogen atom containing monomers may be used individually by 1 type, and may be used in combination of 2 or more type.

  The (meth) acrylic acid ester polymer preferably contains 1% by mass or more of the nitrogen atom-containing monomer as the monomer unit constituting the polymer, more preferably 3% by mass or more. It is more preferable to contain at least%. Thereby, the adhesive sheet obtained can fully exhibit the outstanding adhesive force (especially the outstanding adhesive force with respect to glass and a plastics) with respect to a transparent conductive film, glass, and a plastic after irradiation of an active energy ray. Further, the (meth) acrylic acid ester polymer preferably contains 20% by mass or less of a nitrogen atom-containing monomer as a monomer unit constituting the polymer, more preferably 15% by mass or less. More preferably, the content is 10% by mass or less. Thereby, while content of another monomer component can fully be ensured, it can suppress that a (meth) acrylic acid ester polymer becomes hard too much. As a result, the resulting pressure-sensitive adhesive sheet can sufficiently exhibit excellent adhesive strength after irradiation with active energy rays.

  The (meth) acrylic acid ester polymer preferably contains a alicyclic structure-containing monomer and a nitrogen atom-containing monomer in a total of 5% by mass or more, and a total of 10% by mass or more, as monomer units constituting the polymer. It is more preferable that the total content is 15% by mass or more. Thereby, the adhesive sheet obtained can fully exhibit the outstanding adhesive force with respect to a transparent conductive film, glass, and a plastic after active energy ray irradiation. The (meth) acrylic acid ester polymer preferably contains a total of 40% by mass or less of the alicyclic structure-containing monomer and the nitrogen atom-containing monomer as monomer units constituting the polymer, and a total of 35% by mass. More preferably, the total content is 30% by mass or less. Thereby, it can suppress that a (meth) acrylic acid ester polymer becomes hard too much. As a result, the resulting pressure-sensitive adhesive sheet can sufficiently exhibit excellent adhesive strength after irradiation with active energy rays.

  Moreover, the (meth) acrylic acid ester polymer may contain monomers other than the said alicyclic structure containing monomer and a nitrogen atom containing monomer as a structural unit.

  As such a monomer, (meth) acrylic acid alkyl ester is preferably used, and (meth) acrylic acid alkyl ester having an alkyl group having 1 to 20 carbon atoms is more preferably used. Thereby, the adhesiveness of an adhesive sheet can be made favorable.

  The (meth) acrylic acid ester polymer preferably contains 1 or more and 20 or less (meth) acrylic acid alkyl ester as a main component (the largest component among the monomers constituting the polymer).

Examples of the alkyl group having 1 to 20 carbon atoms in the alkyl group include, for example, methyl acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate, N-pentyl (meth) acrylate, n-hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, n-decyl (meth) acrylate, n- (meth) acrylate Examples include dodecyl, myristyl (meth) acrylate, palmityl (meth) acrylate, stearyl (meth) acrylate, and the like. Among these, from the viewpoint of further improving the adhesiveness, (meth) acrylic acid alkyl esters having 1 to 8 carbon atoms in the alkyl group are preferred, and n-butyl (meth) acrylate and 2-ethylhexyl (meth) acrylate are preferred. Particularly preferred. In addition, these may be used independently and may be used in combination of 2 or more type.

  The (meth) acrylic acid ester polymer preferably contains 50% by mass or more, more preferably 55% by mass or more of (meth) acrylic acid alkyl ester as a monomer unit constituting the polymer. More preferably, the content is at least mass%. Further, the (meth) acrylic acid ester polymer preferably contains 95% by mass or less, more preferably 90% by mass or less, of (meth) acrylic acid alkyl ester as a monomer unit constituting the polymer. More preferably, the content is 80% by mass or less.

  When the pressure-sensitive adhesive composition contains a crosslinking agent, the (meth) acrylic acid ester polymer contains a reactive functional group-containing monomer having a functional group capable of reacting with the crosslinking agent as a monomer unit constituting the polymer. It is preferable to do.

  Examples of the reactive functional group-containing monomer include a monomer having a hydroxyl group in the molecule (hydroxyl group-containing monomer), a monomer having a carboxyl group in the molecule (carboxyl group-containing monomer), and the like. However, it is preferable that the (meth) acrylic acid ester polymer does not contain a carboxyl group-containing monomer as a monomer unit constituting the polymer. Thereby, the obtained adhesive sheet can suppress corroding the transparent conductive film which is a to-be-adhered body, or changing the resistance value of a transparent conductive film.

  Here, “does not contain a carboxyl group-containing monomer” means that it contains substantially no carboxyl group-containing monomer, and does not contain any carboxyl group-containing monomer, and corrosion of the transparent conductive film due to carboxyl groups occurs. It is allowed to contain a carboxyl group-containing monomer to a certain extent. Specifically, the (meth) acrylic acid ester polymer (A) contains a carboxyl group-containing monomer as a monomer unit in an amount of 1.0% by mass or less, preferably 0.5% by mass or less. It is acceptable.

  For the above reason, the (meth) acrylic acid ester polymer preferably contains a hydroxyl group-containing monomer as the reactive functional group-containing monomer constituting the polymer.

  Examples of the hydroxyl group-containing monomer include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, (meth And (meth) acrylic acid hydroxyalkyl esters such as 3-hydroxybutyl acrylate and 4-hydroxybutyl (meth) acrylate. Among these, 2-hydroxyethyl (meth) acrylate or 4-hydroxybutyl (meth) acrylate is preferred from the viewpoint of reactivity with the crosslinking agent and copolymerization with other monomers. These may be used alone or in combination of two or more.

  The (meth) acrylic acid ester polymer preferably contains 5% by mass or more of a reactive functional group-containing monomer as a monomer unit constituting the polymer, more preferably 10% by mass or more, and 15% by mass. It is more preferable to contain at least%. Further, the (meth) acrylic acid ester polymer preferably contains a reactive functional group-containing monomer as a monomer unit constituting the polymer in an amount of 30% by mass or less, more preferably 25% by mass or less. More preferably, the content is 20% by mass or less.

  The (meth) acrylic acid ester polymer may contain a monomer other than the above as a monomer unit constituting the polymer. Examples of the other 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.

  A random copolymer may be sufficient as the superposition | polymerization aspect of a (meth) acrylic acid ester polymer, and a block copolymer may be sufficient as it.

  The weight average molecular weight of the (meth) acrylic acid ester polymer is preferably 300,000 or more, more preferably 400,000 or more, and further preferably 6500,000 or more. Further, the weight average molecular weight of the (meth) acrylic acid ester polymer is preferably 1,200,000 or less, more preferably 1,000,000 or less, and further preferably 700,000 or less. preferable. In addition, the weight average molecular weight in this specification is the value of standard polystyrene conversion measured by the gel permeation chromatography (GPC) method.

  In the pressure-sensitive adhesive composition, the (meth) acrylic acid ester polymer may be used alone or in combination of two or more. The pressure-sensitive adhesive composition may further contain a (meth) acrylic acid ester polymer that does not contain an alicyclic structure-containing monomer and / or a nitrogen atom-containing monomer as a constituent monomer unit.

  In addition, the (meth) acrylic acid ester polymer is used in the pressure-sensitive adhesive composition (by itself or a mixture of components in which the reactant remains in the pressure-sensitive adhesive sheet) from the viewpoint of sufficiently exerting the effect of the pressure-sensitive adhesive sheet of this embodiment. In addition, it is preferably contained in an amount of 50% by mass or more, more preferably 60% by mass or more, and particularly preferably 70% by mass or more. preferable. The (meth) acrylic acid ester polymer is preferably contained in the pressure-sensitive adhesive composition in an amount of 99% by mass or less, preferably 98% by mass or less, from the viewpoint of allowing addition of other components. 97 mass% or less is particularly preferable.

2. Active energy ray-curable component The pressure-sensitive adhesive composition constituting the pressure-sensitive adhesive sheet contains an active energy ray-curable component.

  Thus, the adhesive sheet after curing includes an active energy ray-curable component and is cured by irradiation with an active energy ray after being bonded to the adherend, so that the post-curing pressure-sensitive adhesive sheet has a step following property and foam resistance (blister resistance). It will be excellent.

  Here, active energy rays refer to those having energy quanta among electromagnetic waves or charged particle beams, and specific examples include ultraviolet rays and electron beams. Among active energy rays, ultraviolet rays that are easy to handle are particularly preferable.

  The active energy ray-curable component is not particularly limited as long as it is a component that is cured by irradiation with active energy rays without impeding the effects of the present invention, and may be any of a monomer, an oligomer, or a polymer, It may be a mixture. Among these, a polyfunctional acrylate monomer having a molecular weight of less than 1000 and excellent in compatibility with the above-described (meth) acrylic acid ester polymer and the like can be preferably used.

  Examples of polyfunctional acrylate monomers having a molecular weight of less than 1000 include 1,4-butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, and polyethylene glycol diene. (Meth) acrylate, neopentyl glycol adipate di (meth) acrylate, hydroxypivalic acid neopentyl glycol di (meth) acrylate, dicyclopentanyl di (meth) acrylate, caprolactone modified dicyclopentenyl di (meth) acrylate, ethylene oxide modified Di (meth) acrylate phosphate, di (acryloxyethyl) isocyanurate, allylated cyclohexyl di (meth) acrylate, ethoxylated bisphenol A diacrylate, 9,9-bi Bifunctional type such as [4- (2-acryloyloxyethoxy) phenyl] fluorene; trimethylolpropane tri (meth) acrylate, dipentaerythritol tri (meth) acrylate, propionic acid-modified dipentaerythritol tri (meth) acrylate, penta Trifunctional such as erythritol tri (meth) acrylate, propylene oxide modified trimethylolpropane tri (meth) acrylate, tris (acryloxyethyl) isocyanurate, ε-caprolactone modified tris- (2- (meth) acryloxyethyl) isocyanurate Type; tetrafunctional type such as diglycerin tetra (meth) acrylate and pentaerythritol tetra (meth) acrylate; pentafunctional type such as propionic acid-modified dipentaerythritol penta (meth) acrylate And hexafunctional types such as dipentaerythritol hexa (meth) acrylate and caprolactone-modified dipentaerythritol hexa (meth) acrylate. These may be used individually by 1 type and may be used in combination of 2 or more type. In addition, from the viewpoint of improving the blister resistance and the step following ability of the pressure-sensitive adhesive sheet after curing by irradiation with active energy rays, it is preferable that the polyfunctional acrylate monomer contains a trifunctional type or more. The proportion of trifunctional or higher monomers in the entire polyfunctional acrylate monomer is preferably 50% by mass or more, more preferably 70% by mass or more, and particularly preferably 90% by mass or more. In addition, the upper limit of the said ratio is 100 mass%.

  As the active energy ray-curable component, an active energy ray-curable acrylate oligomer can also be used. The acrylate oligomer preferably has a weight average molecular weight of 50,000 or less. Examples of such acrylate oligomers include polyester acrylate, epoxy acrylate, urethane acrylate, polyether acrylate, polybutadiene acrylate, and silicone acrylate.

  The weight average molecular weight of the acrylate oligomer is preferably 50,000 or less, and more preferably 40,000 or less. Further, the weight average molecular weight of the acrylate oligomer is more preferably 500 or more, and further preferably 3,000 or more. These acrylate oligomers may be used alone or in combination of two or more.

  Further, as the active energy ray-curable component, an adduct acrylate polymer in which a group having a (meth) acryloyl group is introduced into the side chain can also be used. Such an adduct acrylate-based polymer uses a copolymer of (meth) acrylic acid ester and a monomer having a crosslinkable functional group in the molecule, and a part of the crosslinkable functional group of the copolymer. , A (meth) acryloyl group and a compound having a group that reacts with a crosslinkable functional group can be reacted.

  The weight average molecular weight of the adduct acrylate polymer is preferably 50,000 or more, and more preferably 100,000 or more. Further, the weight average molecular weight of the adduct acrylate polymer is preferably 900,000 or less, and more preferably 500,000 or less.

  The active energy ray-curable component can be used by selecting one from the above-mentioned polyfunctional acrylate monomers, acrylate oligomers, and adduct acrylate polymers, or can be used in combination of two or more. , And other active energy ray-curable components can be used in combination.

  The content of the active energy ray-curable component in the pressure-sensitive adhesive composition is preferably 0.1 parts by mass or more, and 0.5 parts by mass or more with respect to 100 parts by mass of the (meth) acrylic acid ester polymer. More preferably, it is more preferably 1 part by mass or more. Moreover, it is preferable that content of an active energy ray hardening component (B) is 30 mass parts or less with respect to 100 mass parts of (meth) acrylic acid ester polymer (A), and is 20 mass parts or less. More preferably, it is more preferably 15 parts by mass or less, and particularly preferably less than 10 parts by mass.

3. Crosslinking agent The adhesive composition which comprises an adhesive sheet may contain the crosslinking agent.

  When the pressure-sensitive adhesive composition containing a crosslinking agent is crosslinked, the crosslinking agent reacts with a reactive functional group derived from a reactive functional group-containing monomer constituting the (meth) acrylic acid ester copolymer. Thereby, the structure by which the (meth) acrylic acid ester polymer was bridge | crosslinked with the crosslinking agent is formed, and the cohesion force of the adhesive sheet obtained improves.

  The crosslinking agent is not particularly limited as long as it reacts with the reactive functional group of the (meth) acrylic acid ester polymer. For example, an isocyanate crosslinking agent, an epoxy crosslinking agent, an amine crosslinking agent, a melamine crosslinking. Agents, aziridine crosslinking agents, hydrazine crosslinking agents, aldehyde crosslinking agents, oxazoline crosslinking agents, metal alkoxide crosslinking agents, metal chelate crosslinking agents, metal salt crosslinking agents, ammonium salt crosslinking agents, and the like. When the reactive functional group which the (meth) acrylic acid ester polymer has is a hydroxyl group, among the above, it is preferable to use an isocyanate-based crosslinking agent excellent in reactivity with the hydroxyl group. In addition, a crosslinking agent can be used individually by 1 type or in combination of 2 or more types.

The isocyanate-based crosslinking 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, alicyclic polyisocyanates such as isophorone diisocyanate and hydrogenated diphenylmethane diisocyanate, and the like. , And their biuret bodies, isocyanurate bodies, and adduct bodies that are a reaction product with low molecular active hydrogen-containing compounds such as ethylene glycol, propylene glycol, neopentyl glycol, trimethylolpropane, castor oil, and the like. Among these, trimethylolpropane-modified aromatic polyisocyanate, particularly trimethylolpropane-modified tolylene diisocyanate is preferable from the viewpoint of reactivity with hydroxyl groups.

  The content of the crosslinking agent in the pressure-sensitive adhesive composition constituting the pressure-sensitive adhesive sheet is preferably 0.05 parts by mass or more with respect to 100 parts by mass of the (meth) acrylic acid ester polymer, and is 0.10 parts by mass. More preferably, it is more preferably 0.15 parts by mass or more. The content of the crosslinking agent in the pressure-sensitive adhesive composition is preferably 3.00 parts by mass or less, more preferably 2.00 parts by mass or less, and 1.00 parts by mass or less. Further preferred.

4). Photopolymerization initiator The pressure-sensitive adhesive composition constituting the pressure-sensitive adhesive sheet of the present embodiment may contain a photopolymerization initiator. By including a photopolymerization initiator in the pressure-sensitive adhesive composition, for example, a protective plate having a step and a display panel are bonded using a pressure-sensitive adhesive sheet so that the step is opposed to the display panel, and then active energy rays , The pressure-sensitive adhesive sheet is efficiently cured, and the post-curing pressure-sensitive adhesive sheet has excellent blister resistance and step following ability. As a result, the obtained image display device has excellent durability.

  The photopolymerization initiator is not particularly limited as long as it is usually used, for example, benzophenone, acetophenone, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, benzoin benzoic acid, Methyl benzoin benzoate, benzoin dimethyl ketal, 2,4-diethylthioxanthone, 1-hydroxycyclohexyl phenyl ketone, benzyldiphenyl sulfide, tetramethylthiuram monosulfide, azobisisobutyronitrile, benzyl, dibenzyl, diacetyl, β- Chloranthraquinone, 4- (2-hydroxyethoxy) -phenyl (2-hydroxy-2-propyl) ketone, (2,4,6-trimethylbenzyldiphenyl) Le) phosphine oxide, 2-benzothiazole -N, it can be used N- diethyldithiocarbamate and the like. In addition, a photoinitiator may be used individually by 1 type and may use 2 or more types together.

  Moreover, it is preferable to contain 0.1 mass part or more with respect to 100 mass parts of active energy ray hardening components (B), and, as for a photoinitiator, it is more preferable to contain 1 mass part or more. Moreover, it is preferable to contain 30 mass parts or less with respect to 100 mass parts of active energy ray hardening components (B), and, as for a photoinitiator, it is more preferable to contain 15 mass parts or less.

5. Other components In the pressure-sensitive adhesive composition constituting the pressure-sensitive adhesive sheet, if necessary, various additives usually used in acrylic pressure-sensitive adhesives, such as silane coupling agents, antistatic agents, tackifiers, oxidation agents, etc. An inhibitor, an ultraviolet absorber, a light stabilizer, a softening agent, a filler, a refractive index adjusting agent, and the like can be added.

<2> Production of pressure-sensitive adhesive composition The pressure-sensitive adhesive composition forming the pressure-sensitive adhesive sheet is produced from a (meth) acrylic acid ester polymer, the obtained (meth) acrylic acid ester polymer, and active energy ray curable. While mixing with a component, it can manufacture by adding a crosslinking agent, a photoinitiator, and another additive if desired.

  The (meth) acrylic acid ester polymer can be produced by polymerizing a mixture of monomers constituting the polymer by an ordinary radical polymerization method.

  Polymerization of the monomer constituting the (meth) acrylic acid ester polymer can be carried out by a solution polymerization method or the like using a polymerization initiator as desired. Examples of the polymerization solvent include ethyl acetate, n-butyl acetate, isobutyl acetate, toluene, acetone, hexane, methyl ethyl ketone, and the like. Two or more kinds may be used in combination.

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

  Examples of organic peroxides include benzoyl peroxide, t-butyl perbenzoate, cumene hydroperoxide, diisopropyl peroxydicarbonate, di-n-propyl peroxydicarbonate, and di (2-ethoxyethyl) peroxy. Examples include dicarbonate, t-butyl peroxyneodecanoate, t-butyl peroxybivalate, (3,5,5-trimethylhexanoyl) peroxide, dipropionyl peroxide, diacetyl peroxide and the like.

  In addition, in the said superposition | polymerization process, the weight average molecular weight of the polymer obtained can be adjusted by mix | blending chain transfer agents, such as 2-mercaptoethanol.

  Once the (meth) acrylic acid ester polymer is obtained, add the active energy ray-curable component, and optionally a crosslinking agent, photopolymerization initiator, and other additives to the (meth) acrylic acid ester polymer solution. By sufficiently mixing, a pressure-sensitive adhesive composition is obtained.

<3> Production of pressure-sensitive adhesive sheet and pressure-sensitive adhesive sheet The pressure-sensitive adhesive sheet is obtained by crosslinking the above-described pressure-sensitive adhesive composition.
An adhesive sheet can be manufactured as follows, for example.

First, a release sheet is prepared.
Next, the coating liquid of the said adhesive composition is apply | coated to the peeling surface of a peeling sheet.

  And an adhesive sheet (adhesive sheet of this invention) is obtained by heat-processing with respect to an application layer and bridge | crosslinking an adhesive composition.

  In addition, you may overlap the peeling surface of the other peeling sheet 1 with the adhesive surface which the adhesive sheet exposed as needed.

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

  Moreover, crosslinking of the pressure-sensitive adhesive composition can be performed by heat treatment. This heat treatment can also serve as a drying treatment after the application of the pressure-sensitive adhesive composition. The heating temperature of the heat treatment is preferably 50 ° C. or higher, and more preferably 70 ° C. or higher. Moreover, it is preferable that the heating temperature of heat processing is 150 degrees C or less, and it is more preferable that it is 120 degrees C or less. Further, the heating time is preferably 10 seconds or more, and more preferably 50 seconds or more. The heating time is preferably 10 minutes or less, more preferably 2 minutes or less.

  The thickness of the pressure-sensitive adhesive sheet obtained as described above (value measured according to JIS K7130) is preferably 10 μm or more, and preferably 30 μm or more from the viewpoint of excellent step following ability. Is more preferably 50 μm or more. In addition, the thickness of the pressure-sensitive adhesive sheet is preferably 1000 μm or less, more preferably 400 μm or less, and even more preferably 300 μm or less from the viewpoint of ensuring the workability of the pressure-sensitive adhesive sheet. The pressure-sensitive adhesive sheet may be formed as a single layer, or may be formed by laminating a plurality of layers.

Moreover, an adhesive sheet can also be manufactured as follows.
First, two release sheets are prepared.

  A coating liquid of the pressure-sensitive adhesive composition is applied to the release surface of one prepared release sheet, and the pressure-sensitive adhesive composition is cross-linked by performing a heat treatment on the coating layer to form a first pressure-sensitive adhesive sheet. . Moreover, the coating liquid of the said adhesive composition is apply | coated to the peeling surface of the other peeling sheet, a heat processing is performed with respect to an application layer, a pressure sensitive adhesive composition is bridge | crosslinked, and a 2nd adhesive sheet is formed. . Then, the exposed pressure-sensitive adhesive surfaces of the two pressure-sensitive adhesive sheets are bonded to each other, and a third pressure-sensitive adhesive sheet having the total thickness of the first pressure-sensitive adhesive sheet and the second pressure-sensitive adhesive sheet (the pressure-sensitive adhesive of the present invention). Sheet).

  The method for applying the coating liquid for the pressure-sensitive adhesive composition and the conditions for the heat treatment on the applied pressure-sensitive adhesive composition are as described above.

<4> Display (image display device)
FIG. 1 is a cross-sectional view showing an example of a display in which a protective plate and a display panel are bonded using the pressure-sensitive adhesive sheet of the present invention. In the following description, the upper side in the figure is referred to as “upper” or “upper”, and the lower side is referred to as “lower” or “lower”.

  The display (image display device) 100 includes a protective plate 21, a display panel 22, and a post-curing pressure-sensitive adhesive sheet 11 (cured product of the pressure-sensitive adhesive sheet of the present invention) cured by irradiation with active energy rays.

  As shown in FIG. 1, the protective plate 21 preferably has a step (printing layer) 3 on the side in contact with the cured adhesive sheet 11. The height of the step 3 is preferably 3 μm or more and 45 μm or less. Even if there is such a step 3, the pressure-sensitive adhesive sheet of the present invention follows the step 3 well. And after irradiating an active energy ray through either one or both surfaces of the protection board 21 or the display panel 22, the obtained adhesive sheet 11 after hardening has high adhesive force, blister resistance, and level | step difference followability. Can be fully demonstrated.

  In addition, the said active energy ray means what has an energy quantum in electromagnetic waves or a charged particle beam, for example, an ultraviolet-ray, an electron beam, etc. are mentioned. From the viewpoint of easy handling, ultraviolet rays are preferable.

Irradiation with ultraviolet rays can be performed with a high-pressure mercury lamp, a fusion H lamp, a xenon lamp, or the like. As for the irradiation amount of an ultraviolet-ray, it is preferable that illumination intensity is about 50-1000 mW / cm < ² >. Further, the light quantity is preferably 50~10000mJ / cm ^2, more preferably 100~5000mJ / cm ^2, and particularly preferably 200~1500mJ / cm ^2.

  Examples of the display 100 include a liquid crystal (LCD) display, a light emitting diode (LED) display, an organic electroluminescence (organic EL) display, electronic paper, and the like, and may be a touch panel.

  The protective plate 21 is preferably a protective plate made of a laminated body including the glass plate, the plastic plate, or the like. In this case, the printing layer 3 is generally formed in a frame shape on the cured adhesive sheet 11 side of the protective plate 21.

  The display panel 22 is a display module (for example, a liquid crystal (LCD) module, a light emitting diode (LED) module, an organic electroluminescence (organic EL) module, etc.) or a part thereof (for example, an optical member such as a polarizing plate). It is preferable.

  The glass plate is not particularly limited. For example, chemically tempered glass, alkali-free glass, quartz glass, soda lime glass, barium / strontium-containing glass, aluminosilicate glass, lead glass, borosilicate glass, barium borosilicate Glass etc. are mentioned. Although the thickness of a glass plate is not specifically limited, Usually, it is 0.1-5 mm, Preferably it is 0.2-2 mm.

  The plastic plate is not particularly limited, and examples thereof include an acrylic plate and a polycarbonate plate. Although the thickness of a plastic board is not specifically limited, Usually, it is 0.2-5 mm, Preferably it is 0.4-3 mm.

  Various functional layers (transparent conductive film, metal layer, silica layer, hard coat layer, antiglare layer, etc.) may be provided on one or both surfaces of the glass plate or plastic plate, or an optical member. May be laminated. Moreover, the transparent conductive film and the metal layer may be patterned.

  Examples of the optical member include a polarizing plate (polarizing film), a polarizer, a retardation plate (retarding film), a viewing angle compensation film, a brightness enhancement film, a contrast enhancement film, a liquid crystal polymer film, a diffusion film, and a hard coat film. And a semi-transmissive reflective film.

  The material which comprises the printing layer 3 is not specifically limited, The well-known material for printing is used. The thickness of the printed layer 3, that is, the height of the step, is preferably 3 μm or more and 45 μm or less, more preferably 5 μm or more and 35 μm or less, further preferably 7 μm or more and 25 μm or less, and more preferably 7 μm or more and 15 μm or less. It is particularly preferred that

  In order to manufacture the display 100, as an example, first, an adhesive sheet having release sheets on both sides is cut into a size corresponding to the protective plate 21 and the display panel 22.

  Next, one release sheet of the pressure-sensitive adhesive sheet is peeled off, and the pressure-sensitive adhesive surface exposed of the pressure-sensitive adhesive sheet is bonded to the surface of the protective plate 21 on the side where the printing layer 3 is present. Thereafter, the other release sheet is peeled off from the adhesive sheet, and the exposed adhesive surface of the adhesive sheet and the display panel 22 are bonded together. Thereafter, the adhesive sheet 11 is obtained after curing by irradiating the adhesive sheet with active energy rays through the protective plate 21 or the display panel 22.

  In the display 100 obtained by the above process, since the pressure-sensitive adhesive sheet is excellent in step following ability, it is difficult to form a gap between the step due to the printed layer 3 and the post-curing pressure-sensitive adhesive sheet 11 even after a predetermined durability condition. It will be a thing. Moreover, since the adhesive sheet is excellent in adhesive strength and blister resistance, the display 100 obtained is highly reliable.

  As mentioned above, although preferred embodiment of the adhesive sheet of this invention was described, this invention is not limited to these.

  For example, in the above-described embodiment, the protective plate has been described as having a printing step, but the pressure-sensitive adhesive sheet of the present invention can also be applied to a sheet having no printing step.

  EXAMPLES Hereinafter, although an Example etc. demonstrate this invention further more concretely, the scope of the present invention is not limited to these Examples etc.

1. Production of adhesive sheet (Example 1)
(1) (meth) acrylic acid ester polymer 65 parts by mass of 2-ethylhexyl acrylate, 5 parts by mass of N-acryloylmorpholine, 15 parts by mass of isobornyl acrylate and 15 parts by mass of 2-hydroxyethyl acrylate, A (meth) acrylic acid ester polymer was prepared. When the molecular weight of this (meth) acrylic acid ester polymer was measured by the method described later, the weight average molecular weight (Mw) was 500,000.

(2) Preparation of pressure-sensitive adhesive composition 100 parts by mass of the (meth) acrylic acid ester polymer obtained in the above step (1) (solid content converted value; the same applies hereinafter) and ε-caprolactone as an active energy ray-curable component Modified tris- (2-acryloxyethyl) isocyanurate (manufactured by Shin-Nakamura Chemical Co., Ltd., product name “NK Ester A-9300-1CL”) 5.0 parts by weight, trimethylolpropane modified tolylene diisocyanate (isocyanate-based crosslinking agent) Toyochem Co., Ltd., product name “BHS8515”) 0.15 parts by mass and photopolymerization initiator (BASF Co., Ltd., product name “Irgacure 500”) 0.5 parts by mass are mixed and stirred thoroughly to obtain methyl ethyl ketone. Was applied to obtain a coating solution of the pressure-sensitive adhesive composition having a solid content concentration of 50% by mass.

(3) Production of pressure-sensitive adhesive sheet A heavy-peelable release sheet (product name "SP-PET752150", manufactured by Lintec Corporation) obtained by subjecting one side of a polyethylene terephthalate film to a release treatment using a silicone-based release agent. ) Was applied with a knife coater. Then, the coating layer was heat-treated at 90 ° C. for 1 minute to form a first pressure-sensitive adhesive sheet having a thickness of 25 μm.

  Similarly, a release treatment of a light release release sheet (product name “SP-PET 382120” manufactured by Lintec Corporation) in which one side of a polyethylene terephthalate film was release-treated with a silicone-based release agent was applied to the obtained adhesive composition coating solution. The surface was coated with a knife coater. Then, the coating layer was heat-treated at 90 ° C. for 1 minute to form a second pressure-sensitive adhesive sheet having a thickness of 25 μm.

  Next, the first and second pressure-sensitive adhesive sheets obtained above are bonded so that both exposed pressure-sensitive adhesive surfaces are in contact with each other, a light release-type release sheet on one side, and a heavy release-type release sheet on the other side A third pressure-sensitive adhesive sheet (thickness: 50 μm) was prepared. The thickness of the pressure-sensitive adhesive sheet is a value measured using a constant pressure thickness measuring instrument (manufactured by Teclock, product name “PG-02”) according to JIS K7130.

(Examples 2 and 3, Comparative Examples 1 to 3)
The third pressure-sensitive adhesive is the same as in Example 1 except that the ratio of each monomer constituting the (meth) acrylic acid ester polymer, the type and blending amount of the active energy ray-curable component are changed as shown in Table 1. A sheet was produced.

  Table 1 shows the composition and the like of the pressure-sensitive adhesive composition used for forming the pressure-sensitive adhesive sheets of the above Examples and Comparative Examples.

  In Table 1, 2-ethylhexyl acrylate is “2EHA”, N-acryloylmorpholine is “ACMO”, isobornyl acrylate is “IBXA”, 2-hydroxyethyl acrylate is “HEA”, and methyl methacrylate is “MMA”. Ε-caprolactone-modified tris- (2-acryloxyethyl) isocyanurate (manufactured by Shin-Nakamura Chemical Co., Ltd., product name “NK Ester A-9300-1CL”) as an active energy ray-curable component Pentaerythritol hexaacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd., trade name “NK Ester A-DPH”) is “hexagonal”, and terpene resin (made by Yashara Chemical Co., Ltd., trade name “Clearon K4100”) as a tackifier resin is terpene resin. It showed.

  Moreover, 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: manufactured by Tosoh Corp., HLC-8020-GPC column (passed in the following order): Tosoh Corp. TSK guard column HXL-H
TSK gel GMHXL (× 2)
TSK gel G2000HXL
・ Measurement solvent: Tetrahydrofuran ・ Measurement temperature: 40 ° C.

2. Evaluation [Adhesive strength measurement]
The light-peelable release sheet of the third pressure-sensitive adhesive sheet obtained in each Example and each Comparative Example was peeled off, and the exposed pressure-sensitive adhesive surface was covered with a polyethylene terephthalate film having an easy-adhesion layer (Toyobo Co., Ltd., PET A4300, thickness: 100 μm) easy adhesion layer. The laminate was cut into a width of 25 mm and a length of 100 mm, and this was used as a sample for measuring adhesive strength. The heavy release release sheet was peeled off from the sample, and the exposed adhesive surface was attached to soda lime glass (manufactured by Nippon Sheet Glass Co., Ltd.), and irradiated with ultraviolet rays under the following conditions.

(UV irradiation conditions)
・ Light source: High-pressure mercury lamp ・ Light quantity: 1000 mJ / cm ²
Illuminance: 200 mW / cm ²
Then, after leaving for 24 hours under the conditions of normal pressure, 23 ° C. and 50% RH, using a tensile tester (Orientec, product name “Tensilon”) according to JIS Z0237: 2009, the peeling rate. The adhesive strength (N / 25 mm) was measured under the conditions of 300 mm / min and peeling angle of 180 °.

  In addition, the heavy release type release sheet is peeled from the sample, and the exposed adhesive surface is a polyethylene terephthalate film (obtained by Oike Kogyo Co., Ltd., ITO film, with a transparent conductive film made of tin-doped indium oxide (lITO) on one side. The adhesive strength (N / 25 mm) was measured in the same manner as described above.

[Blister resistance evaluation]
The polyethylene terephthalate in which the light release type release sheet of the third adhesive sheet obtained in each Example and each Comparative Example was peeled off, and the exposed adhesive surface was provided with a transparent conductive film made of tin-doped indium oxide (ITO) on one side The film was bonded to a transparent conductive film (made by Oike Kogyo Co., Ltd., ITO film, thickness: 125 μm). Next, the heavy release type release sheet of the pressure-sensitive adhesive sheet is peeled off, and the exposed pressure-sensitive adhesive surface is an acrylic plate made of polymethyl methacrylate (PMMA) (product name “Iupilon sheet MR200”, manufactured by Mitsubishi Gas Chemical Co., Inc.), thickness: 1 mm) and irradiated with ultraviolet rays under the following conditions to obtain a laminate in which the ITO film and the acrylic plate were bonded with an adhesive sheet after curing.

(UV irradiation conditions)
・ Light source: High-pressure mercury lamp ・ Light quantity: 1000 mJ / cm ²
Illuminance: 200 mW / cm ²
The obtained laminate was autoclaved for 30 minutes under the conditions of 50 ° C. and 0.5 MPa, and then allowed to stand at normal pressure, 23 ° C. and 50% RH for 15 hours. Subsequently, it was stored for 72 hours under 85 ° C. and 85% RH durability conditions. After that, it was taken out at 23 ° C. and 50% RH. Immediately after that, it was visually checked whether there were bubbles, floats or peeling at the interface between the adhesive sheet and the acrylic plate after curing, and blister resistance was evaluated according to the following criteria. did.

A: There were no bubbles, no floating, and no peeling.
B: Only bubbles having a diameter of 0.2 mm or less were generated.
C: Bubbles having a diameter of more than 0.2 mm, floating or peeling occurred.

[Step difference tracking evaluation]
On the surface of a glass plate (manufactured by NSG Precision, product name “Corning Glass Eagle XG”, length 90 mm × width 50 mm × thickness 0.5 mm), UV curable ink (product name “POS-911 Black”, manufactured by Teikoku Ink Co., Ltd.) ) Was screen-printed in a frame shape (outside: vertical 90 mm × width 50 mm, width 5 mm) so that the coating thickness was 25 μm. Next, irradiation with ultraviolet rays (80 W / cm ² , ^two metal halide lamps, lamp height of 15 cm, belt speed of 10 to 15 m / min) is performed to cure the printed ultraviolet curable ink, and a level difference due to printing (level difference) A stepped glass plate having a thickness of 25 μm) was produced.

  The light-peelable release sheet was peeled from the third pressure-sensitive adhesive sheet obtained in each example and each comparative example, and the exposed pressure-sensitive adhesive surface was covered with a polyethylene terephthalate film having an easy-adhesive layer (product name “PET A4300” manufactured by Toyobo Co., Ltd.). , Thickness: 100 μm). Next, the heavy release type release sheet was peeled off to expose the adhesive surface. Then, using a laminator (product name “LPD3214”, manufactured by Fuji Pla Co., Ltd.), the above laminate is laminated on each stepped glass plate so that the adhesive layer covers the entire frame-like printed surface, and irradiated with ultraviolet rays under the following conditions. This was used as a sample for evaluation.

(UV irradiation conditions)
・ Light source: High-pressure mercury lamp ・ Light quantity: 1000 mJ / cm ²
Illuminance: 200 mW / cm ²
The obtained sample for evaluation was stored for 72 hours under an endurance condition of 85 ° C. and 85% RH. Thereafter, the sample was taken out at 23 ° C. and 50% RH. Immediately after that, it was visually confirmed whether there was no air bubble at the interface between the adhesive sheet and the glass plate after curing (particularly in the vicinity of the step due to printing). The step following ability was evaluated according to the standard.

A: There were no bubbles.
B: Only bubbles having a diameter of 0.2 mm or less were confirmed.
C: Bubbles having a diameter of more than 0.2 mm, floating or peeling were confirmed.

[Measurement of haze value]
About the 3rd adhesive sheet obtained by the Example and the comparative example, according to JISK7361-1: 1997, using a haze meter (Nippon Denshoku Industries Co., Ltd. product name "NDH-5000"), a haze value ( %). Considering use in a display, the haze value is preferably 2% or less, more preferably 1% or less, and particularly preferably 0.5% or less.
These results are shown in Table 2.

  As is clear from Table 2, the pressure-sensitive adhesive sheet of the present invention exhibited high adhesive strength to the transparent conductive film and glass by ultraviolet irradiation. Moreover, the adhesive sheet of this invention was excellent in blister resistance and level | step difference followability by ultraviolet irradiation. On the other hand, sufficient results were not obtained in the comparative example.

3 steps (printing layer)
11 Adhesive sheet after curing (cured product of adhesive sheet)
21 Protective plate 22 Display panel 100 Display

Claims (6)

As monomer units constituting the polymer , (meth) acrylic acid alkyl ester having 1 to 8 carbon atoms in the alkyl group, a monomer having an alicyclic structure, and a monomer having a nitrogen atom (containing a maleimide group) They include excluded) containing a (meth) acrylic acid ester polymer, and an active energy ray-curable component, a,
The (meth) acrylic acid ester polymer contains 50% by mass or more and 95% by mass or less of the (meth) acrylic acid alkyl ester as a monomer unit constituting the polymer,
It is formed of a pressure-sensitive adhesive composition containing 0.1 to 10 parts by mass of the active energy ray-curable component with respect to 100 parts by mass of the (meth) acrylic acid ester polymer.
The pressure-sensitive adhesive sheet, wherein the active energy ray-curable component is composed of a 3-6 functional polyfunctional acrylate monomer, and the active energy ray-curable component is present in an uncured state. The (meth) acrylic acid ester polymer contains 3% by mass to 20% by mass of the monomer having the alicyclic structure as a monomer unit constituting the polymer, and 1% of the monomer having the nitrogen atom. The pressure-sensitive adhesive sheet according to claim 1, which is contained in an amount of 20% to 20% by mass. The said (meth) acrylic acid ester polymer contains the monomer which has the said alicyclic structure, and the monomer which has the said nitrogen atom as a monomer unit which comprises the said polymer in total 5 mass% or more and 40 mass% or less. The pressure-sensitive adhesive sheet according to 1 or 2 . The pressure-sensitive adhesive sheet according to any one of claims 1 to 3 , wherein the alicyclic structure includes an isobornyl skeleton. The pressure-sensitive adhesive sheet according to any one of claims 1 to 4 , wherein the monomer having a nitrogen atom has a nitrogen-containing heterocyclic ring. The pressure-sensitive adhesive sheet according to any one of claims 1 to 5 , which is used for bonding a protective plate and a display panel.

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