JP2013147569A - Transparent pressure-sensitive adhesive film and image display - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a transparent pressure-sensitive adhesive film the embedding properties of which to a step to be formed in a decoration part can be made excellent and in which seepage from the end of a base material film can be reduced satisfactorily.SOLUTION: The transparent pressure-sensitive adhesive film contains a monomer unit derived from alkyl (meth)acrylate having a 4-18C straight-chain or branched-chain alkyl group and another monomer unit derived from a monomer having a cyclic group. The transparent pressure-sensitive adhesive film has 0.01-0.35 total strain εand 0.01-0.20 plastic strain εwhen such a compression-unloading cycle test is performed at 25°C that 0-0.5 (maximum) MPa of compressive stress is exerted on the transparent pressure-sensitive adhesive film and then the compressive stress is relieved, and 0.25-0.5 total strain εand 0.1-0.3 plastic strain εwhen such the compression-unloading cycle test is performed at 50°C that 0-0.5 (maximum) MPa of the compressive stress is exerted on the transparent pressure-sensitive adhesive film and then the compressive stress is relieved.

Description

  The present invention relates to a transparent adhesive film suitable for use in bonding a transparent protective plate such as glass or plastic and an information input device such as a touch panel, or an image display unit such as a liquid crystal display or an organic electroluminescence display.

  In recent years, a gap between a transparent protective plate or an information input device (such as a touch panel) in an image display device and a display surface of an image display unit, or a gap between a protective plate and an information input device is compared with air. A method has been proposed in which the refractive index is replaced with a transparent material close to the display surface of the protective plate, the information input device, and the image display unit, thereby improving the transparency and suppressing the decrease in luminance and contrast of the image display device.

  By the way, in the information input device and the image display device, it is necessary to provide input / output wiring at the peripheral portion thereof. Generally, in order to prevent these wirings from being seen from the transparent protective plate surface side, generally the peripheral portion of the transparent protective plate A frame-shaped decorative portion is provided by printing or the like. Since the printing step is generated by these decorative portions, the transparent adhesive film to which the transparent protective plate is bonded is required to have excellent embedding property for embedding the vicinity of the printing step without a gap.

  As a method for improving the embedding property of the transparent adhesive film in the printing step, the (meth) acrylic acid alkyl ester having 4 to 18 carbon atoms in the alkyl group, the amide group-containing monomer, and the (meth) acrylic having an alkylene glycol chain. An adhesive film containing a copolymer of an acid ester component (Patent Document 1), or an adhesive film obtained by curing a photocurable adhesive composition mainly composed of an alkyl (meth) acrylate having a prime number of 1 to 12 ( Patent Document 2) has been proposed.

JP 2011-74308 A JP 2009-155503 A

  However, the transparent adhesive films described in Patent Documents 1 and 2 are considered to be excellent to some extent in terms of step embedding properties, but are not necessarily sufficient in terms of suppressing the seepage from the base film. If the flowability of the pressure-sensitive adhesive film is increased in order to improve the step embedding property, the pressure-sensitive adhesive film tends to ooze out from the edge of the base film when the base film is attached. The transparent adhesive film is preferably handled in a state of being sandwiched from both sides by a peelable substrate in order to prevent dust and the like from adhering during storage and transportation. Moreover, it is preferable that the transparent adhesive film is previously cut out with the base material in the size of the corresponding liquid crystal display device.

  Further, in recent years, the number of colored decorative parts other than black or white has been increasing, mainly due to the demand for design. In general, these white or colored decorative portions have a light concealing property inferior to that of black decorative portions, and therefore need to be printed thicker than in the case of black. That is, the printing level difference due to the decorative portion is higher than that in the case of black. Along with this, the transparent adhesive film is required to have better embedding ability in a printing step than before.

  The present invention has been made in view of the above circumstances, and provides a transparent adhesive film that is excellent in embedding in a step formed by a decorative portion or the like and that can sufficiently suppress bleeding from the edge of a base film. The purpose is to do.

  As a result of diligent research to solve the above problems, the present inventors, using a polymer containing a monomer unit derived from a specific monomer, by configuring a transparent adhesive film having a specific compression deformation characteristic, the above I found that the problem could be solved.

  That is, the present invention relates to a crosslinked polymer comprising a monomer unit derived from an alkyl (meth) acrylate having a linear or branched alkyl group having 4 to 18 carbon atoms and a monomer unit derived from a monomer having a cyclic group. The present invention relates to a transparent adhesive film containing When a compression-unloading cycle test in which the transparent adhesive film is unloaded after a compressive stress of 0 MPa to 0.5 MPa at maximum is applied at 25 ° C., the total strain is 0.01 or more and 0.35. The plastic strain is 0.01 or more and 0.20 or less. Further, when a compression-unloading cycle test for unloading the transparent adhesive film after applying a compressive stress of 0 MPa to 0.5 MPa at maximum is performed at 50 ° C., the total strain is 0.25 or more and 0. 0.5 or less, and the plastic strain is 0.1 or more and 0.3 or less.

  When the total strain in the compression-unloading cycle test at 25 ° C. is 0.01 or more and 0.35 or less and the plastic strain is 0.01 or more and 0.20 or less, excessive elastic deformation or Since there is little plastic deformation, the exudation from the edge part of a base material is fully suppressed, and the handleability of a film is excellent. Further, at 50 ° C., by making the total strain 0.25 or more and 0.5 or less, deformation necessary for embedding a step (printing step) due to a decorative part or the like is possible, and the plastic strain is 0.10 or more. By setting it to 0.3 or less, it is possible to reduce the residual stress of the film in the vicinity of the printing step, to maintain the deformation even after unloading, and to ensure embedding in the printing step. Since the residual stress is small, peeling and foaming under high temperature and high humidity conditions can be suppressed. That is, by setting the total strain and the plastic strain to a certain amount or more, the deformation can be made and the residual stress can be reduced.

  It is preferable that the glass transition temperature (Tg) of the said transparent adhesive film is 0-30 degreeC from a viewpoint of exudation suppression, a handleability, and the peelability from a base film.

  The transparent adhesive film is an adhesive comprising a polymerizable monomer selected from acrylic acid and an acrylic acid derivative, an acrylic polymer containing a monomer unit selected from acrylic acid and an acrylic acid derivative, a crosslinking agent, and a photopolymerization initiator. The agent composition is preferably formed by photocuring. In this case, the acrylic acid derivative as the polymerizable monomer or the monomer unit of the acrylic polymer has an alkyl (meth) acrylate having a linear or branched alkyl group having 4 to 18 carbon atoms and a cyclic group. Monomer.

  From the viewpoint of visibility and step embedding, it is more preferable that the transparent adhesive film has a thickness of 0.1 to 0.4 mm.

  The present invention also provides an image display unit, a protective plate disposed opposite to the image display unit, a decorative portion provided on the peripheral portion of the surface of the protective plate on the image display unit side, the decorative portion, and the protective plate And an image display device provided with the transparent adhesive film disposed between the image display unit and the image display unit. Alternatively, the present invention provides an information input device, a protective plate disposed opposite to the information input device, a decorative portion provided on a peripheral portion of the surface of the protective plate on the information input device side, and the decorative portion and the protective plate The said transparent adhesive film arrange | positioned between an information input device and an information display apparatus is provided. In these image display devices, the thickness of the decorative portion may be 10 to 80 μm.

  ADVANTAGE OF THE INVENTION According to this invention, the transparent adhesive film which is excellent in the embedding property to the level | step difference formed by a decoration part, and can fully suppress the oozing-out from the base film edge part can be provided. The transparent adhesive film according to the present invention has excellent transparency and is excellent in terms of resistance to peeling and foaming under high temperature and high humidity conditions. Furthermore, the transparent pressure-sensitive adhesive film according to the present invention has good handleability in that it has an appropriate tackiness.

It is sectional drawing which shows typically one Embodiment of an image display apparatus. It is sectional drawing which shows typically one Embodiment of a liquid crystal display device. It is sectional drawing which shows typically the liquid crystal display device which mounts the touchscreen which is one Embodiment of a liquid crystal display device. It is a graph which shows typically the relation between stress and distortion in a compression-unloading cycle test. It is a schematic diagram which shows the method of a compression-unloading test. It is a top view of the glass substrate which has a glass substrate and a decoration part.

  Hereinafter, preferred embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments.

The transparent adhesive film according to the present embodiment includes a polymerizable monomer selected from acrylic acid and an acrylic acid derivative, an acrylic polymer containing a monomer unit selected from acrylic acid and an acrylic acid derivative, a crosslinking agent, and a photopolymerization initiator. It is preferably formed by photocuring a pressure-sensitive adhesive composition containing The pressure-sensitive adhesive composition contains an alkyl (meth) acrylate having an alkyl group having 4 to 18 carbon atoms and a cyclic organic compound (a monomer having a cyclic group) as a monomer unit of a polymerizable monomer or an acrylic polymer. It is preferable. In this specification, “acrylic acid” such as an acrylic acid derivative also includes “methacrylic acid”. A base film may be laminated on one side or both sides of the transparent adhesive film according to the present embodiment to constitute a transparent adhesive film with a base film.
<Adhesive composition>

Hereinafter, it demonstrates for every component which the adhesive composition which concerns on this embodiment contains.
[(A) Acrylic polymer]

  (A) An acrylic polymer refers to a polymer obtained by polymerizing one type of monomer having one (meth) acryloyl group in the molecule, or by copolymerizing two or more types in combination. Within the range not departing from the gist of the present invention, a compound having two or more (meth) acryloyl groups in the molecule or a polymerizable compound having no (meth) acryloyl group (for example, acrylonitrile, styrene, vinyl acetate, A compound having one polymerizable unsaturated bond such as ethylene or propylene in the molecule or a compound having two or more polymerizable unsaturated bonds such as divinylbenzene in the molecule may be copolymerized.

  (A) As an acrylic polymer, for example, (meth) acrylic acid; (meth) acrylic acid amide; methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, tert -Alkyl (meth) acrylates having 1 to 18 carbon atoms in the alkyl group such as butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isodecyl (meth) acrylate, n-lauryl (meth) acrylate, stearyl (meth) acrylate; (Meth) acrylic acid ester having an aromatic ring such as benzyl (meth) acrylate and phenoxyethyl (meth) acrylate; butoxyethylene glycol (meth) acrylate, butoxydiethylene glycol (meth) acrylate, methoxytriethyl (Meth) acrylic acid ester having an alkoxy group such as N-glycol (meth) acrylate; cyclohexyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, isobornyl (meth) acrylate, dicyclopentanyl (meth) acrylate and other fats (Meth) acrylic acid ester having a cyclic group; (meth) acrylic acid ester having a hydroxyl group such as 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate; Tetraethylene glycol monomethyl ether (meth) acrylate, hexaethylene glycol monomethyl ether (meth) acrylate, octaethylene glycol monomethyl ether (meth) acrylate, nonaethylene glycol Polyethylene glycol monomethyl ether (meth) acrylate such as methyl ether (meth) acrylate; polypropylene glycol monomethyl ether (meth) acrylate such as heptapropylene glycol monomethyl ether (meth) acrylate; tetraethylene glycol ethyl ether (meth) acrylate, etc. Polyethylene glycol ethyl ether (meth) acrylate; tetraethylene glycol mono (meth) acrylate, hexaethylene glycol mono (meth) acrylate, octapropylene glycol mono (meth) acrylate, N, N-dimethyl (meth) acrylamide, N, N- Diethyl (meth) acrylamide, Nt-butyl (meth) acrylamide, N, N-isopropyl (meth) acrylamide, Nt-octyl ( ) Acrylamide, N, N-dimethylaminoethyl (meth) acrylamide, N, N-dimethylaminopropyl (meth) acrylamide, substituted acrylamide such as diacetone acrylamide, (meth) acrylamide such as (meth) acryloylmorpholine, etc. Can be mentioned.

  Among the above-mentioned compounds, the acrylic polymer preferably contains a monomer unit derived from a (meth) acrylate having a linear or branched alkyl group having 4 to 18 carbon atoms. The ratio of the (meth) acrylate having an alkyl group having 4 to 18 carbon atoms to the polymer is preferably 5 to 95% by mass, more preferably 10 to 90% by mass, and 50 to 90% by mass. % Is more preferable. In the processability after forming an adhesive film as it is the range of 5-95 mass%, the adhesiveness of transparent base materials, such as glass and a plastic, improves. In general, a polymer having such a copolymerization ratio can be obtained by blending each monomer at the same ratio as the above-mentioned copolymerization ratio and copolymerizing the monomers, so that the polymerization rate is substantially close to 100% by mass. It is preferable.

  Examples of the alkyl (meth) acrylate having 4 to 18 carbon atoms in the alkyl group include n-butyl (meth) acrylate, n-pentyl (meth) acrylate, n-hexyl (meth) acrylate, and n-octyl (meth) acrylate. , Isooctyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, dodecyl (meth) acrylate, stearyl (meth) acrylate, etc., but n-butyl (meth) acrylate, isooctyl (meth) acrylate, 2-ethylhexyl ( (Meth) acrylate, n-octyl (meth) acrylate and the like are preferable, and 2-ethylhexyl (meth) acrylate is particularly preferable. Also, acrylate is more preferable than methacrylate. These (meth) acrylates may be used in combination of two or more.

  Monomers copolymerized with (meth) acrylates having an alkyl group having 4 to 18 carbon atoms are not limited to those described above, but include hydroxyl groups, alkoxy groups, morpholino groups, amino groups, carboxyl groups, cyano groups, carbonyls. Monomers having polar groups such as nitro groups are preferred, and (meth) acrylates having these polar groups are preferred because of their improved adhesion to transparent substrates such as plastics. In particular, from the viewpoint of tackiness, a hydroxyl group represented by the following general formula (x) or an alkoxy group-containing (meth) acrylate is preferable.

CH ₂ = CXCOO (C _m H _2m O) _n R (x)
(In the formula, X is H or CH ₃ , R is H or an alkyl group having 1 to 8 carbon atoms, m is an integer of 2 to 4, and n is an integer of 1 to 10)

  Specific examples of the hydroxyl group or alkoxy group-containing (meth) acrylate represented by the following general formula (x) will be described later.

  As the polymerization method for the acrylic polymer, known polymerization methods such as solution polymerization, emulsion polymerization, suspension polymerization, bulk polymerization and the like can be used.

  As the polymerization initiator, a compound capable of generating radicals by heat can be used. Specifically, benzoyl peroxide, t-butyl perbenzoate, cumene hydroperoxide, diisopropyl peroxydicarbonate, di-n- Propyl peroxydicarbonate, di (2-ethoxyethyl) peroxydicarbonate, t-butylperoxyneodecanoate, t-butylperoxypivalate, (3,5,5-trimethylhexanoyl) peroxide, di Organic peroxides such as propionyl peroxide, diacetyl peroxide, didodecyl peroxide, 2,2′-azobisisobutyronitrile, 2,2′-azobis (2-methylbutyronitrile), 1, 1'-azobis (cyclohexane-1-carbonitrile), 2.2'-azo (2,4-dimethylvaleronitrile), 2,2′-azobis (2,4-dimethyl-4-methoxyvaleronitrile), dimethyl 2,2′-azobis (2-methylpropionate), 4,4 Azo such as' -azobis (4-cyanovaleric acid), 2,2'-azobis (2-hydroxymethylpropionitrile), 2,2'-azobis [2- (imidazolin-2-yl) propane] System compounds and the like.

  The content of the acrylic polymer is preferably 10 to 70% by mass, more preferably 15 to 60% by mass, and particularly preferably 25 to 50% by mass with respect to the total amount of the pressure-sensitive adhesive composition. When the content of the acrylic polymer is 10 to 70% by mass, the viscosity of the pressure-sensitive adhesive composition for an image display device falls within an appropriate viscosity range for producing a pressure-sensitive adhesive film, and the processability becomes good. Moreover, the obtained adhesive film has good adhesiveness to a transparent substrate such as glass or plastic.

  The weight average molecular weight of the acrylic polymer is preferably 50,000 to 700,000, more preferably 80,000 to 500,000 from the viewpoint of coating film characteristics, and 100,000 to 400,000. It is particularly preferred.

The weight average molecular weight is measured by gel permeation chromatography using a standard polystyrene calibration curve. Measurement conditions can be measured at a measurement temperature of 25 to 40 ° C. using a column for HPLC using a general porous polymer gel and tetrahydrofuran as an eluent. The detector is preferably a differential refractometer (RI detector).
[(B) Polymerizable monomer containing acrylic acid and acrylic acid derivative]

  The acrylic acid derivative of the component (B) is a monomer having one (meth) acryloyl group in the molecule, such as cyclohexyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, isobornyl (meth) acrylate, dicyclopentanyl ( It is preferable to contain an organic compound having at least one cyclic group selected from (meth) acrylic acid esters having an alicyclic group such as (meth) acrylate and (meth) acryloylmorpholine. The content of the cyclic organic compound is preferably 10 to 25% by mass, more preferably 15 to 21% by mass, and more preferably 16 to 20% by mass with respect to the total amount of the pressure-sensitive adhesive composition. Particularly preferred. As a result, it is possible to achieve an effect that the step embedding property, the seepage suppression, and the workability are more excellent.

  Component (B) may contain other monomers in addition to the above-mentioned monomers, and examples thereof include those having one (meth) acryloyl group in the molecule. These monomers are not particularly limited, and known materials can be used, and two or more kinds may be used in combination.

  For example, (meth) acrylic acid; (meth) acrylic acid amide; methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, tert-butyl (meth) acrylate, 2 -C1-C18 alkyl (meth) acrylates of alkyl groups such as ethylhexyl (meth) acrylate, isodecyl (meth) acrylate, n-lauryl (meth) acrylate, stearyl (meth) acrylate; benzyl (meth) acrylate, phenoxy (Meth) acrylic acid ester having an aromatic ring such as ethyl (meth) acrylate; butoxyethylene glycol (meth) acrylate, butoxydiethylene glycol (meth) acrylate, methoxytriethylene glycol (meth) acrylate (Meth) acrylic acid ester having an alkoxy group such as cyclohexyl; having an alicyclic group such as cyclohexyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, isobornyl (meth) acrylate, dicyclopentanyl (meth) acrylate, etc. (Meth) acrylic acid ester; (meth) acrylic acid ester having a hydroxyl group such as 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate; N, N-dimethyl Aminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N-isopropyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, N-hydroxy (Meth) acrylic acid ester having an amide group such as ethyl (meth) acrylamide; (meth) acrylic acid having an isocyanate group such as 2- (2-methacryloyloxyethyloxy) ethyl isocyanate and 2- (meth) acryloyloxyethyl isocyanate Acid esters; polyethylene glycol monomethyl ethers such as tetraethylene glycol monomethyl ether (meth) acrylate, hexaethylene glycol monomethyl ether (meth) acrylate, octaethylene glycol monomethyl ether (meth) acrylate, and nonaethylene glycol methyl ether (meth) acrylate (meta ) Acrylate; polypropylene glycol monomethyl such as heptapropylene glycol monomethyl ether (meth) acrylate Ether ether (meth) acrylate; polyethylene glycol ethyl ether (meth) acrylate such as tetraethylene glycol ethyl ether (meth) acrylate; tetraethylene glycol mono (meth) acrylate, hexaethylene glycol mono (meth) acrylate, octapropylene glycol mono (meta) ) Acrylate and the like.

  It is preferable that the adhesive film of this invention contains the structural unit derived from the hydroxyl group or alkoxy group containing (meth) acrylate shown by the following general formula (x) from an adhesive viewpoint.

  In particular, as the component (B), in addition to the cyclic organic compound, an alkyl (meth) acrylate having an alkyl group having 4 to 18 carbon atoms and a hydroxyl group-containing (meth) acrylate represented by the following general formula (x): It is preferable to use together.

CH ₂ = CXCOO (C _m H _2m O) _n R (x)
(In the formula, X is H or CH ₃ , R is H or an alkyl group having 1 to 8 carbon atoms, m is an integer of 2 to 4, and n is an integer of 1 to 10)

  Examples of the alkyl (meth) acrylate having 4 to 18 carbon atoms in the alkyl group include n-butyl (meth) acrylate, n-pentyl (meth) acrylate, n-hexyl (meth) acrylate, and n-octyl (meth) acrylate. , Isooctyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, dodecyl (meth) acrylate, stearyl (meth) acrylate, etc., but n-butyl (meth) acrylate, isooctyl (meth) acrylate, 2-ethylhexyl ( (Meth) acrylate, n-octyl (meth) acrylate and the like are preferable, and 2-ethylhexyl (meth) acrylate is particularly preferable. Also, acrylate is more preferable than methacrylate. These (meth) acrylates may be used in combination of two or more.

  Examples of the hydroxyl group-containing (meth) acrylate represented by the general formula (x) include 2-hydroxyethyl (meth) acrylate, 1-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl ( Such as (meth) acrylate, 1-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 3-hydroxybutyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 1-hydroxybutyl (meth) acrylate, etc. Hydroxyl group-containing (meth) acrylates; polyethylene glycol mono (meth) acrylates such as diethylene glycol and triethylene glycol; polypropylene glycol mono (such as dipropylene glycol and tripropylene glycol ( ) Acrylates; polybutylene glycol mono (meth) acrylates such as dibutylene glycol and tributylene glycol, etc., but 2-hydroxyethyl (meth) acrylate, 1-hydroxyethyl (meth) acrylate, 2-hydroxypropyl ( (Meth) acrylate, 3-hydroxypropyl (meth) acrylate, 1-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 3-hydroxybutyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 1 -Hydroxybutyl (meth) acrylate is preferred, 2-hydroxyethyl (meth) acrylate and 4-hydroxybutyl (meth) acrylate are particularly preferred, and 4-hydroxybutyl (meth) acrylate But highly preferred. These (meth) acrylates may be used in combination of two or more.

The content of the polymerizable monomer including (B) acrylic acid and acrylic acid derivative monomer in the present embodiment is preferably 5 to 80% by mass, particularly preferably 10 to 70% by mass, based on the total amount of the pressure-sensitive adhesive composition. 40-70 mass% is especially preferable. When content of (B) component is 5-80 mass%, after sticking the obtained adhesive film between a glass substrate and a glass substrate, under high temperature (60 degreeC or more) and high humidity (90%) Generation and peeling of bubbles after the reliability test at RH or higher) can be more significantly suppressed.
[(C) Crosslinking agent]

The crosslinking agent (C) in the present invention preferably has a weight average molecular weight of 1.0 × 10 ⁵ or less. Examples of preferred crosslinking agents are shown in the following general formulas (b) to (g).

  Furthermore, urethane di (meth) acrylate having a urethane bond can also be used. The pressure-sensitive adhesive composition preferably contains a high molecular weight polyurethane di (meth) acrylate having a urethane bond.

  The high molecular weight polyurethane di (meth) acrylate is obtained by reacting a polyhydric alcohol compound, a polyvalent isocyanate compound, and a (meth) acrylate having an isocyanate group or a (meth) acrylate having a hydroxyl group.

  Examples of polyhydric alcohols include propylene glycol, tetramethylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, 1,4-cyclohexanedimethanol, 2-methyl- 1,8-octanediol, 1,9-nonanediol, 3-methyl-1,5-pentanediol, poly1,2-butylene glycol, polypropylene glycol, polytetramethylene glycol, ethylene glycol-propylene glycol block copolymer, Ethylene glycol-tetramethylene glycol copolymer, methylpentanediol modified polytetramethylene glycol, propylene glycol modified polytetramethylene glycol, propylene oxide adduct of bisphenol A Propylene oxide adduct of hydrogenated bisphenol A, propylene oxide adduct of bisphenol F, propylene oxide adduct of hydrogenated bisphenol F and the like.

  Polyisocyanate compounds include tolylene diisocyanate, xylylene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, tetramethylxylylene diisocyanate, isophorone diisocyanate, hydrogenated tolylene diisocyanate, hydrogenated xylylene diisocyanate. Examples thereof include diisocyanates such as isocyanate, hydrogenated diphenylmethane diisocyanate and norbornene diisocyanate, and polymers of diisocyanates described above or urea-modified products and burette-modified products of diisocyanates. These polyhydric alcohols and polyvalent isocyanates can be used alone or in combination of two or more. By reacting a compound having a hydroxyl group at the terminal obtained by reacting such polyurethane with an excess of polyhydric alcohol with (meth) acrylate having acrylic acid, methacrylic acid or isocyanate group, the polyurethane di (meta) ) Acrylate can be obtained.

  In the case of a compound having an isocyanate at the terminal obtained by reacting with an excess of polyisocyanate, a di (meth) acrylate of polyurethane can be obtained by reacting with a (meth) acrylate having a hydroxyl group.

  Examples of the (meth) acrylate having a hydroxyl group include 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 3-hydroxypropyl acrylate, 4-hydroxybutyl acrylate, polyethylene glycol monoacrylate, polypropylene glycol monoacrylate, and ethylene glycol-propylene glycol. Block copolymer monoacrylate, ethylene glycol-tetramethylene glycol copolymer monoacrylate, caprolactone-modified monoacrylate (trade name Plaxel FA series, manufactured by Daicel Chemical Industries), acrylic acid derivatives such as pentaerythritol triacrylate, 2-hydroxyethyl methacrylate, 2 -Hydroxypropyl methacrylate, 3-hydroxypropyl methacrylate 4-hydroxybutyl methacrylate, polyethylene glycol monomethacrylate, polypropylene glycol monomethacrylate, ethylene glycol-propylene glycol block copolymer monomethacrylate, ethylene glycol-tetramethylene glycol copolymer monomethacrylate, caprolactone-modified monomethacrylate (manufactured by Daicel Chemical Industries, Ltd., product) Name: Plaxel FM series) and methacrylic acid derivatives such as pentaerythritol trimethacrylate. These compounds are used alone or in combination of two or more.

Among such polyurethane di (meth) acrylates, the diol component is preferably a polyalkylene glycol such as polypropylene glycol or polytetramethylene glycol, and the diisocyanate component is more preferably isophorone diisocyanate. The weight molecular weight is preferably 2 × 10 ^{4 to} 9 × 10 ⁴ , and more preferably 3 × 10 ^{4 to} 5 × 10 ⁴ . By setting the weight molecular weight to 3 × 10 ⁴ or more, there is a tendency that the occurrence of peeling can be further reduced in a high temperature and high humidity environment. Also by the 9x10 less than ^4, not too high viscosity of the adhesive composition, it is easy to create adhesive film.

  When the cross-linking agent having the bifunctional (meth) acryloyl group has low compatibility with the (A) (meth) acrylic acid derivative polymer and the (B) acrylic acid derivative monomer, the cured product may become cloudy. There is.

Moreover, it is preferable that content of (C) crosslinking agent is 0.5-15 mass% with respect to the whole quantity of an adhesive composition, It is more preferable that it is 1-10 mass%, 3 mass- It is especially preferable that it is 8 mass%. When the content is in the range of 0.5 to 15% by mass, the resulting adhesive film has sufficient adhesiveness, and has a high elasticity and is free from brittleness.
[(D) Photopolymerization initiator]

  (D) The photopolymerization initiator has a curing reaction that proceeds by irradiation with active energy rays, and the active energy rays refer to ultraviolet rays, electron beams, α rays, β rays, γ rays, and the like.

  The selection of the photopolymerization initiator is not particularly limited, and known materials such as benzophenone series, anthraquinone series, benzoyl series, sulfonium salts, diazonium salts, and onium salts can be used.

  More specifically, benzophenone, N, N′-tetramethyl-4,4′-diaminobenzophenone (Michler ketone), N, N-tetraethyl-4,4′-diaminobenzophenone, 4-methoxy-4′-dimethylamino Benzophenone, α-hydroxyisobutylphenone, 2-ethylanthraquinone, t-butylanthraquinone, 1,4-dimethylanthraquinone, 1-chloroanthraquinone, 2,3-dichloroanthraquinone, 3-chloro-2-methylanthraquinone, 1,2- Benzoanthraquinone, 2-phenylanthraquinone, 1,4-naphthoquinone, 9,10-phenanthraquinone, thioxanthone, 2-chlorothioxanthone, 1-hydroxycyclohexyl phenyl ketone, 2,2-dimethoxy-1,2-diphenyl ester Aromatic ketone compounds such as N-1-one and 2-hydroxy-2-methyl-1-phenylpropan-1-one; benzoin compounds such as benzoin, methylbenzoin and ethylbenzoin; benzoin methyl ether, benzoin ethyl ether and benzoin Benzoin ether compounds such as isobutyl ether and benzoin phenyl ether; benzyl, 2,2-diethoxyacetophenone, benzyldimethyl ketal, β- (acridin-9-yl) (meth) acrylic acid ester compound, 9-phenylacridine, 9 -Acridine compounds such as pyridyl acridine, 1,7-diacridinoheptane; 2- (o-chlorophenyl) -4,5-diphenylimidazole dimer, 2- (o-chlorophenyl) -4,5-di (m -Methoxyphenyl) imi Zole dimer, 2- (o-fluorophenyl) -4,5-diphenylimidazole dimer, 2- (o-methoxyphenyl) -4,5-diphenylimidazole dimer, 2- (p-methoxyphenyl) ) -4,5-diphenylimidazole dimer, 2,4-di (p-methoxyphenyl) 5-phenylimidazole dimer, 2- (2,4-dimethoxyphenyl) -4,5-diphenylimidazole dimer , 2,4,5-triarylimidazole dimers such as 2- (p-methylmercaptophenyl) -4,5-diphenylimidazole dimer; 2-benzyl-2-dimethylamino-1- (4- Morpholinophenyl) -1-butanone, 2-methyl-1- [4- (methylthio) phenyl] -2-morpholino-1-propane, bis (2,4,6-trimethyl) Benzoyl) - phenyl phosphine oxide, oligo (2-hydroxy-2-methyl-1- (4- (1-methylvinyl) phenyl) propanone), and the like.

  In particular, those that do not color the pressure-sensitive adhesive composition include 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, and 1- [4- (2-hydroxyethoxy). Α-hydroxyalkylphenone compounds such as -phenyl] -2-hydroxy-2-methyl-1-propan-1-one; bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide, bis (2, Acylphosphine oxide compounds such as 6-dimethoxybenzoyl) -2,4,4-trimethyl-pentylphosphine oxide, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide; oligo (2-hydroxy-2-methyl) -1- (4- (1-methylvinyl) phenyl) propanone) and A combination thereof are preferred.

  In order to produce particularly thick sheets, bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide, bis (2,6-dimethoxybenzoyl) -2,4,4-trimethyl-pentylphosphine A photopolymerization initiator containing an acyl phosphine oxide compound such as oxide, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide is preferable.

  In order to reduce the odor of the sheet, oligo (2-hydroxy-2-methyl-1- (4- (1-methylvinyl) phenyl) propanone) is preferable. A plurality of these photopolymerization initiators may be used in combination.

(D) It is preferable that content of a photoinitiator is 0.1-5 mass% with respect to the whole quantity of an adhesive composition, and 0.1-3 mass% is further more preferable. By setting it as 5 mass% or less, the transmittance | permeability of the obtained adhesive film is high, and a hue does not become yellowish.
[Other additives]

  In addition to the above (A), (B), (C), and (D), the pressure-sensitive adhesive composition may contain various additives as necessary. Examples of the various additives that the pressure-sensitive adhesive composition can contain include, for example, paramethoxy for the purpose of enhancing the storage stability of the pressure-sensitive adhesive composition containing (A), (B), (C), and (D). Polymerization inhibitors such as phenol, adhesives obtained by curing the adhesive composition with light for the purpose of increasing the heat resistance of antioxidants such as triphenylphosphine, HALS for the purpose of enhancing resistance to light such as ultraviolet rays Examples thereof include a light stabilizer such as (Hindered Amine Light Stabilizer), and a silane coupling agent in order to improve adhesion to glass or the like. In addition, when a pressure-sensitive adhesive composition is used to obtain a pressure-sensitive adhesive film, the film is sandwiched between polyethylene terephthalate films and the like. In order to control the peelability from the base material such as the polyethylene terephthalate film, polydimethylsiloxane, fluorine Surfactants such as systems can be included.

  These additives may be used alone or in combination with a plurality of additives. The content of these other additives is usually small compared to the total content of the above (A), (B), (C) and (D), and is generally based on the total amount of the pressure-sensitive adhesive composition. It is about 0.01-5 mass%.

<Transparent adhesive film>
Next, the adhesive film obtained by irradiating the adhesive composition with active energy rays and curing it will be described below. The pressure-sensitive adhesive composition can be used as a pressure-sensitive adhesive in a liquid state as it is, but is preferably used as a sheet-like pressure-sensitive adhesive film. The method for producing the adhesive film is exemplified below. By irradiation with active energy rays, including monomer units derived from alkyl (meth) acrylates having a linear or branched alkyl group having 4 to 18 carbon atoms, and monomer units derived from monomers having a cyclic group An optional cross-linked polymer is formed.

The pressure-sensitive adhesive film is obtained by applying a pressure-sensitive adhesive composition on a substrate film in a sheet form and irradiating it with an active energy ray to be cured. As the light source of the active energy ray, a light source having a light emission distribution at a wavelength of 400 nm or less is preferable. Can be used. Moreover, although irradiation energy is not specifically limited, Usually, it is about 500-5000 mJ / cm < ² >.

  When a compression-unloading cycle test is performed at 25 ° C., in which a compressive stress of 0 MPa to 0.5 MPa is applied to the transparent adhesive film and then unloaded, the total strain of the transparent adhesive film is 0.01 It may be 0.35 or less. From a practical viewpoint, the total strain is preferably 0.1 or more and 0.35 or less. The plastic strain at 25 ° C. is preferably 0.01 or more and 0.20 or less, but more preferably 0.05 or more and 0.20 or less from a practical viewpoint.

  When the compression-unloading cycle test is performed at 50 ° C. on the transparent adhesive film, the total strain of the transparent adhesive film is preferably 0.25 or more and 0.5 or less, but from a practical viewpoint. 0.3 to 0.5 is more preferable. The plastic strain at 50 ° C. is preferably from 0.1 to 0.3, but more preferably from 0.12 to 0.25 from a practical viewpoint.

  The irradiation energy of the active energy ray irradiated to the pressure-sensitive adhesive composition for forming the pressure-sensitive adhesive film is preferably adjusted as appropriate so that the total strain and plastic strain of the pressure-sensitive adhesive film are within the above ranges.

FIG. 4 is a graph schematically showing the relationship between stress and strain in the compression-unloading cycle test. In the figure, ε ₁ represents total strain and ε ₃ represents plastic strain. The total strain ε ₁ is the sum of the plastic strain ε ₃ and the elastic strain ε ₂ . Here, the “strain” means a nominal strain obtained by dividing the displacement amount of the thickness changed by compression by the thickness of the pressure-sensitive adhesive film before compression. Originally, since it is a compressive strain, a negative notation, that is, “total strain is 0.25 or more” should be written as “total strain is −0.25 or less”, but it is misunderstood when expressing the absolute amount of strain in large or small. In this case, even in the case of a strain in the compression direction, the positive direction is used.

  Although the thickness of the adhesive film of this embodiment is not specifically limited by a use application and a method, About 0.1-0.4 mm is preferable. Within this range, a particularly excellent effect is exhibited as a transparent adhesive film for laminating an optical member on a display.

  It is preferable that the glass transition temperature of a transparent adhesive film is 0 degreeC or more and 30 degrees C or less.

  The transparent adhesive film according to this embodiment preferably has a light transmittance of 80% or more with respect to light rays in the visible light region (wavelength: 380 to 780 nm). The light transmittance is more preferably 90% or more.

The storage elastic modulus at 25 ° C. of the transparent adhesive film is preferably 1.0 × 10 ³ Pa or more and 1.0 × 10 ⁶ Pa or less, and 1.0 × 10 ⁴ Pa or more and 5.0 × 10 ⁵ Pa or less. More preferably. For the storage elastic modulus, a sample (transparent adhesive film) having a thickness of 0.5 mm, a length of 10 mm, and a width of 10 mm was prepared, and a dynamic viscoelasticity measuring device (for example, Reometric Scientific RSA II: measurement frequency 1 Hz: shear sandwich) Mode).

  The adhesiveness (peel strength) of the transparent adhesive film to the glass (soda lime glass) substrate is preferably 5 N / 10 mm or more and 20 N / 10 mm or less, and more preferably 6 N / 10 mm or more and 15 N / 10 mm or less.

<Image display device>
Hereinafter, an image display device that can be manufactured by using the pressure-sensitive adhesive composition of the present embodiment will be described.

  FIG. 1 is a cross-sectional view showing an embodiment of an image display device. An image display device 100 shown in FIG. 1 is provided on the peripheral portion of the image display unit 1, a transparent protective plate 40 disposed opposite to the image display unit 1, and the surface of the transparent protective plate 40 on the image display unit 1 side. The decorative portion 5, the information input device 30 provided between the transparent protective plate 40 and the image display unit 1, and the transparent adhesive film 31 disposed between the information input device 30 and the transparent protective plate 40, The transparent adhesive film 32 is disposed between the information input device 30 and the image display unit 1. In addition to transparency, the transparent adhesive film is required not to peel off or foam under high temperature and high humidity conditions. The thickness of the decoration part 5 is 10-80 micrometers, for example. As the transparent adhesive film 31 and / or the transparent adhesive film 32, the transparent adhesive film according to this embodiment may be used.

  FIG. 2 is a side sectional view schematically showing one embodiment of a liquid crystal display device as an image display device. A liquid crystal display device 101 shown in FIG. 2 includes an image display unit 1 in which a backlight system 50, a polarizing plate 22, a liquid crystal display cell 10, and a polarizing plate 20 are laminated in this order, and a polarization that is on the viewing side of the liquid crystal display device. The transparent resin layer 32 provided on the upper surface of the plate 20 and the transparent protective plate 40 provided on the surface thereof are configured. The transparent resin layer 32 is composed of a cured product of the pressure-sensitive adhesive composition of the present embodiment.

  FIG. 3 is a side sectional view schematically showing a liquid crystal display device equipped with a touch panel, which is an embodiment of a liquid crystal display device as an image display device. 3 includes an image display unit 1 in which a backlight system 50, a polarizing plate 22, a liquid crystal display cell 10, and a polarizing plate 20 are stacked in this order, and polarized light on the viewing side of the liquid crystal display device. A transparent resin layer 32 provided on the upper surface of the plate 20; a touch panel (information input device) 30 provided on the upper surface of the transparent resin layer 32; a transparent resin layer 31 provided on the upper surface of the touch panel 30; It comprises a transparent protective plate 40 provided.

In the liquid crystal display device 103 of FIG. 3, transparent resin layers are interposed both between the image display unit 1 and the touch panel 30 and between the touch panel 30 and the transparent protective plate 40. It suffices to intervene in at least one of these. When the touch panel is on-cell, the touch panel and the liquid crystal display cell are integrated. As a specific example, the liquid crystal display cell 10 of the liquid crystal display device of FIG. 2 is replaced with an on-cell.
In addition, when the level | step difference by the decoration part is formed on the transparent protective substrate 40 or the touch panel 30, it is transparent with the touch panel 30 on the conditions of 50 to 80 degreeC, 0.3 to 0.8 MPa, and 5 to 60 minutes. It is preferable to bond the protective substrate 40 with an adhesive film.

  According to the image display device shown in FIGS. 1 to 3, the cured product of the pressure-sensitive adhesive composition of the present embodiment is provided as the transparent resin layer (transparent pressure-sensitive adhesive film) 31 or 32. A clear and high-contrast image can be obtained.

  The liquid crystal display cell 10 can be made of a liquid crystal material well known in the art. Further, depending on the control method of the liquid crystal material, it is classified into TN (Twisted Nematic) system, STN (Super-twisted nematic) system, VA (Virtual Alignment) system, IPS (In-Place-Switching) system, etc. Then, it may be a liquid crystal display cell using any control method.

As the polarizing plates 20 and 22, a polarizing plate common in this technical field can be used.
The surfaces of these polarizing plates may be subjected to treatments such as antireflection, antifouling, and hard coat. Such surface treatment may be performed on one side of the polarizing plate or on both sides thereof.

  As the touch panel 30, what is generally used in this technical field can be used.

  The transparent resin layer 31 or 32 can be formed with a thickness of 0.02 mm to 3 mm, for example. In particular, the pressure-sensitive adhesive composition of this embodiment is effective for thick films, and can be suitably used when forming the transparent resin layer 31 or 32 of 0.1 mm or more.

  As the transparent protective plate 40, a general optical transparent substrate can be used. Specific examples thereof include inorganic plates such as glass plates and quartz plates, resin plates such as acrylic plates and polycarbonate plates, and resin sheets such as thick polyester sheets. When high surface hardness is required, a plate such as glass or acrylic is preferable, and a glass plate is more preferable. The surface of these transparent protective substrates may be subjected to treatments such as antireflection, antifouling, and hard coating. Such surface treatment may be performed on one side of the transparent protective substrate or on both sides. A plurality of transparent protective substrates can be used in combination.

  The backlight system 50 typically includes a reflecting unit such as a reflecting plate and an illuminating unit such as a lamp.

  The liquid crystal display device of FIG. 2 can be manufactured by a manufacturing method including a step of interposing the adhesive film of the present embodiment between the image display unit and the protective panel.

  The liquid crystal display device of FIG. 3 is manufactured by a manufacturing method including the step of interposing the adhesive film of the present embodiment between the image display unit and the touch panel and / or between the touch panel and the protective panel. be able to. As a method for interposing the pressure-sensitive adhesive composition, the same method as in the liquid crystal display device of FIG.

  Curing can also be promoted by heating the laminated body containing light irradiation or the pressure-sensitive adhesive composition.

  The liquid crystal display device that can be manufactured by using the pressure-sensitive adhesive composition of the present embodiment has been described above, but the image display device that can be manufactured by using the pressure-sensitive adhesive composition of the present embodiment. However, the present invention is not limited thereto, and can be applied to a plasma display (PDP), a cathode ray tube (CRT), a field emission display (FED), an organic EL display, a 3D display, electronic paper, and the like.

  A general optical transparent substrate can be used for the front plate or the transparent protective plate of the image display device. Specific examples include a glass plate, an inorganic plate such as quartz, a plastic (organic) plate such as an acrylic resin plate, a polycarbonate plate and a polyethylene terephthalate plate, and a resin sheet such as a thick polyester sheet.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to the following examples.

(Synthesis of acrylic polymer)
Into a reaction vessel equipped with a condenser, thermometer, stirrer, dropping funnel and nitrogen injection tube, 84.0 g of 2-ethylhexyl acrylate, 36.0 g of 2-hydroxyethyl acrylate and 150.0 g of methyl isobutyl ketone are taken as initial monomers. The mixture was heated from room temperature (25 ° C.) to 70 ° C. in 15 minutes while replacing with nitrogen at 100 ml / min. Thereafter, while maintaining this temperature, a solution prepared by dissolving 0.6 g of lauroyl peroxide in 21.0 g of 2-ethylhexyl acrylate and 9.0 g of 2-hydroxyethyl acrylate as additional monomers was added dropwise over 60 minutes. The reaction was further continued for 2 hours. Subsequently, by distilling off methyl isobutyl ketone, an acrylic polymer containing a monomer unit derived from 2-ethylhexyl acrylate and a monomer unit derived from 2-hydroxyethyl acrylate in a mass ratio of 7: 3 (weight average molecular weight 180, 000). An acrylic polymer (weight average molecular weight 55,000) composed of similar monomer units was also synthesized.

(Synthesis of polymer crosslinking agent 1)
285.3 g of polypropylene glycol (molecular weight 2,000), 24.5 g of lactone-modified hydroxyethyl acrylate, p-methoxyphenol as a polymerization inhibitor in a reaction vessel equipped with a cooling tube, thermometer, stirring device, dropping funnel and air injection tube Taking 0.13 g and 0.5 g of dibutyltin dilaurate as a catalyst, raising the temperature to 75 ° C. while flowing air, then dropping 39.6 g of isophorone diisocyanate uniformly over 2 hours while stirring at 70 to 75 ° C. Went. When the reaction was allowed to proceed for 5 hours after the completion of the dropwise addition, 24.5 g of lactone-modified hydroxyethyl acrylate was further added and reacted for 1 hour. As a result of IR measurement, it was confirmed that the isocyanate group had disappeared, and the reaction was terminated. Polyurethane acrylate 1 (weight average molecular weight 30) having polypropylene glycol and isophorone diisocyanate as monomer units and having polymerizable unsaturated bonds at both ends. , 000).

(Synthesis of polymer crosslinking agent 2)
Polycarbonate diol (molecular weight 500) 100g, polytetramethylene glycol (molecular weight 850) 85g, diethylene glycol (molecular weight 110) 10.6g, 2-in a reaction vessel equipped with a cooling tube, thermometer, stirrer, dropping funnel and air injection tube Take 10.4 g of hydroxyethyl acrylate, 0.3 g of p-methoquinone as a polymerization inhibitor and 0.3 g of dibutyltin dilaurate as a catalyst, raise the temperature to 70 ° C. while flowing air, and then trimethylhexarate while stirring at 70 to 75 ° C. 79.8 g of methylene diisocyanate was uniformly added dropwise over 2 hours to carry out the reaction. When the reaction was completed for 5 hours after the completion of the dropwise addition, 10.4 g of hydroxyethyl acrylate was further added, and the reaction was performed for 1 hour. As a result of IR measurement, it was confirmed that the isocyanate group had disappeared, and the reaction was terminated. Thus, polyurethane acrylate 2 (weight average molecular weight 5,000) having a polymerizable unsaturated bond at both ends was obtained.

(Polymer crosslinking agent 3)
To 100 parts by mass of the acrylic copolymer (weight average molecular weight 180,000) containing a monomer unit derived from 2-ethylhexyl acrylate and a monomer unit derived from 2-hydroxyethyl acrylate in a mass ratio of 7: 3, 2-methacryloyloxyethyl By adding 1 part by mass of isocyanate, a polymer crosslinking agent 3 having a methacryloyl group was obtained.

Example 1
As an acrylic acid derivative, 39.3 parts by mass of 2-ethylhexyl acrylate, 18.7 parts by mass of acryloylmorpholine, 4.2 parts by mass of 4-hydroxybutyl acrylate, derived from a monomer unit derived from 2-ethylhexyl acrylate and 2-hydroxyethyl acrylate 30.8 parts by mass of the above-mentioned acrylic polymer (weight average molecular weight 180,000) containing 7 to 3 mass units of monomer, 6.5 parts by mass of the above polyurethane acrylate 1 as a crosslinking agent, and 1 as a photopolymerization initiator -0.5 part by mass of hydroxy-cyclohexyl-phenyl-ketone was weighed, mixed with stirring and degassed under vacuum. Thereafter, the mixture was applied onto a 125 μm-thick release-processed PET film so that the thickness after curing was 0.25 mm, and a 50-μm-thick release-processed PET film was further stacked to suppress photocuring inhibition. Then, a transparent adhesive film 1 was obtained by irradiating with ultraviolet rays at 2,000 mJ using an ultraviolet irradiation device.

Example 2
As an acrylic acid derivative, 34.2 parts by mass of 2-ethylhexyl acrylate, 20.0 parts by mass of acryloylmorpholine, 4.2 parts by mass of 4-hydroxybutyl acrylate, derived from a monomer unit derived from 2-ethylhexyl acrylate and 2-hydroxyethyl acrylate 35.0 parts by mass of the above-mentioned acrylic polymer (weight average molecular weight 180,000) containing 7 to 3 monomer units, 6.1 parts by mass of the above polyurethane acrylate 1 as a crosslinking agent, and 1 as a photopolymerization initiator -0.5 part by mass of hydroxy-cyclohexyl-phenyl-ketone was weighed, mixed with stirring and degassed under vacuum. Thereafter, the mixture was applied onto a 125 μm-thick release-processed PET film so that the thickness after curing was 0.25 mm, and a 50-μm-thick release-processed PET film was further stacked to suppress photocuring inhibition. Then, a transparent adhesive film 2 was obtained by irradiating with 2,000 mJ of ultraviolet rays using an ultraviolet irradiation device.

Example 3
As acrylic acid derivatives, 22.0 parts by mass of 2-ethylhexyl acrylate, 16.0 parts by mass of acryloylmorpholine, 4.2 parts by mass of 4-hydroxybutyl acrylate, monomer units derived from 2-ethylhexyl acrylate and 2-hydroxyethyl acrylate 30.8 parts by mass of the above-mentioned acrylic polymer (weight average molecular weight 180,000) containing a monomer unit derived at a mass ratio of 7: 3, 6.5 parts by mass of the above polyurethane acrylate 1 as a crosslinking agent, and as a photopolymerization initiator 0.5 part by mass of 1-hydroxy-cyclohexyl-phenyl-ketone was weighed, mixed with stirring, and degassed under vacuum. Thereafter, the mixture was applied onto a 125 μm-thick release-processed PET film so that the thickness after curing was 0.25 mm, and a 50-μm-thick release-processed PET film was further stacked to suppress photocuring inhibition. Then, a transparent adhesive film 3 was obtained by irradiating with 2,000 mJ of ultraviolet rays using an ultraviolet irradiation device.

Example 4
As the acrylic acid derivative, 39.7 parts by mass of 2-ethylhexyl acrylate, 18.7 parts by mass of acryloylmorpholine, a monomer unit derived from 2-ethylhexyl acrylate and a monomer unit derived from 2-hydroxyethyl acrylate in a mass ratio of 7: 3 Including 21.7 parts by mass of the acrylic polymer (weight average molecular weight 180,000), 13.3 parts by mass of the acrylic polymer (weight average molecular weight 55,000), 6.1 parts by mass of the polyurethane acrylate 1 as a crosslinking agent As a photopolymerization initiator, 0.5 part by mass of 1-hydroxy-cyclohexyl-phenyl-ketone was weighed, mixed with stirring and degassed under vacuum. Thereafter, the mixture was applied onto a 125 μm-thick release-processed PET film so that the thickness after curing was 0.25 mm, and a 50-μm-thick release-processed PET film was further stacked to suppress photocuring inhibition. Then, a transparent adhesive film 4 was obtained by irradiating with 2,000 mJ of ultraviolet rays using an ultraviolet irradiation device.

Example 5
As an acrylic acid derivative, 39.3 parts by mass of 2-ethylhexyl acrylate, 18.7 parts by mass of dicyclopentanyl acrylate, 4.2 parts by mass of 4-hydroxybutyl acrylate, a monomer unit derived from 2-ethylhexyl acrylate, and 2-hydroxyethyl 30.8 parts by mass of the above acrylic polymer (weight average molecular weight 180,000) containing a monomer unit derived from acrylate at a mass ratio of 7: 3, 6.5 parts by mass of the above polyurethane acrylate 1 as a cross-linking agent, and start of photopolymerization As an agent, 0.5 part by mass of 1-hydroxy-cyclohexyl-phenyl-ketone was weighed, mixed with stirring, and degassed by vacuum. Thereafter, the mixture was applied onto a 125 μm-thick release-processed PET film so that the thickness after curing was 0.25 mm, and a 50-μm-thick release-processed PET film was further stacked to suppress photocuring inhibition. From this, a transparent adhesive film 5 was obtained by irradiating ultraviolet rays with 2,000 mJ using an ultraviolet irradiation device.

Example 6
As an acrylic acid derivative, 39.3 parts by mass of 2-ethylhexyl acrylate, 18.7 parts by mass of isobornyl acrylate, 4.2 parts by mass of 4-hydroxybutyl acrylate, a monomer unit derived from 2-ethylhexyl acrylate and 2-hydroxyethyl acrylate 30.8 parts by mass of the above-mentioned acrylic polymer (weight average molecular weight 180,000) containing 7 to 3 monomer units derived from the above, 6.5 parts by mass of the above polyurethane acrylate 1 as a crosslinking agent, a photopolymerization initiator As a sample, 0.5 part by mass of 1-hydroxy-cyclohexyl-phenyl-ketone was weighed, mixed with stirring, and degassed under vacuum. Thereafter, the mixture was applied onto a 125 μm-thick release-processed PET film so that the thickness after curing was 0.25 mm, and a 50-μm-thick release-processed PET film was further stacked to suppress photocuring inhibition. Then, the transparent adhesive film 6 was obtained by irradiating the ultraviolet ray with 2,000 mJ using an ultraviolet irradiation device.

Comparative Example 1
Terpenic hydrogenated resin (Clearon P-85: manufactured by Yasuhara Chemical Co., Ltd.) 3 parts by mass as a polymer component, dicyclopentenyloxyethyl methacrylate (FA512A: manufactured by Hitachi Chemical Co., Ltd.) 12 parts by mass, 2-methacrylic acid 2- Hydroxypropyl 2 parts by mass, benzyl methacrylate 4.4 parts by mass, terminal acrylated polyisoprene (UC-102: manufactured by Kuraray Co., Ltd.) 57 parts by mass, polybutadiene (Polyoil 110: manufactured by Evonik Degussa) 20 parts by mass, light As a polymerization initiator, 1-hydroxy-cyclohexyl-phenyl-ketone (I-184: Ciba Geigy) 0.2 parts by mass, 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide (TPO: DKSH) 1 .4 parts by mass were weighed, mixed with stirring, and degassed under vacuum. Thereafter, the mixture was applied onto a 125 μm-thick release-processed PET film so that the thickness after curing was 0.25 mm, and a 50-μm-thick release-processed PET film was further stacked to suppress photocuring inhibition. Then, a transparent adhesive film 7 was obtained by irradiating with 2,000 mJ of ultraviolet rays using an ultraviolet irradiation device.

Comparative Example 2
As an acrylic acid derivative, 35.7 parts by mass of 2-ethylhexyl acrylate, 27.9 parts by mass of acryloylmorpholine, a monomer unit derived from 2-ethylhexyl acrylate and a monomer unit derived from 2-hydroxyethyl acrylate in a weight ratio of 7: 3 35.8 parts by mass of the acrylic polymer (weight average molecular weight 180,000) containing, 0.45 parts by mass of the polyurethane acrylate 2 as a crosslinking agent, 0.15 parts by mass of 1,9-nonanediol diacrylate, photopolymerization As an initiator, 0.5 part by mass of 1-hydroxy-cyclohexyl-phenyl-ketone was weighed, mixed with stirring, and degassed under vacuum. Thereafter, the mixture was applied onto a 125 μm-thick release-processed PET film so that the thickness after curing was 0.25 mm, and a 50-μm-thick release-processed PET film was further stacked to suppress photocuring inhibition. Then, a transparent adhesive film 8 was obtained by irradiating with 2,000 mJ of ultraviolet rays using an ultraviolet irradiation device.

Comparative Example 3
As acrylic acid derivative, 40.4 parts by mass of 2-ethylhexyl acrylate, 21.1 parts by mass of acryloylmorpholine, a monomer unit derived from 2-ethylhexyl acrylate and a monomer unit derived from 2-hydroxyethyl acrylate are included at a mass ratio of 7: 3. 34.0 parts by mass of the acrylic polymer (weight average molecular weight 180,000), 4.0 parts by mass of the polymer crosslinking agent 3 as a crosslinking agent, and 1-hydroxy-cyclohexyl-phenyl-ketone as a photopolymerization initiator. 5 parts by mass were weighed, mixed with stirring, and degassed by vacuum. Thereafter, the mixture was applied onto a 125 μm-thick release-processed PET film so that the thickness after curing was 0.25 mm, and a 50-μm-thick release-processed PET film was further stacked to suppress photocuring inhibition. Then, a transparent adhesive film 9 was obtained by irradiating with 2,000 mJ of ultraviolet rays using an ultraviolet irradiation device.

Comparative Example 4
As an acrylic acid derivative, 58.0 parts by mass of 2-ethylhexyl acrylate, 4.2 parts by mass of 4-hydroxybutyl acrylate, a monomer unit derived from 2-ethylhexyl acrylate and a monomer unit derived from 2-hydroxyethyl acrylate are in a mass ratio of 7 : 30.8 parts by mass of the acrylic polymer (weight average molecular weight 180,000) contained in 3; 6.5 parts by mass of the above-mentioned polyurethane acrylate 1 as a crosslinking agent; 1-hydroxy-cyclohexyl-phenyl as a photopolymerization initiator -0.5 parts by mass of ketone was weighed, stirred and mixed, and vacuum degassed. Thereafter, the mixture was applied onto a 125 μm-thick release-processed PET film so that the thickness after curing was 0.25 mm, and a 50-μm-thick release-processed PET film was further stacked to suppress photocuring inhibition. Then, the transparent adhesive film 10 was obtained by irradiating the ultraviolet ray with 2,000 mJ using an ultraviolet irradiation device.

  The transparent adhesive films obtained in each Example and each Comparative Example were evaluated by the following test methods. The evaluation results are shown in Tables 1 and 2.

(Total strain and plastic strain)
A compression-unloading test was performed using a microforce precision testing machine (model 5548 manufactured by Instron) to unload after applying a compressive stress to the transparent adhesive film. FIG. 5 is a schematic diagram showing a compression-unloading test method. One release film is peeled off, and the other transparent release film 11 is laminated on the cylindrical planar indenter 12 having a diameter of 13 mm (cross-sectional area of 133 mm ² ) placed on the load cell 13. Arranged. In this state, by moving the cross head 14 at a speed of 2.5 × 10 ⁻⁴ mm / s, the transparent adhesive film was compressed from the minimum stress of 0 MPa to the maximum stress of 0.5 MPa. Subsequently, the crosshead 14 was moved in the opposite direction at the same speed, and unloaded from the maximum stress of 0.5 MPa until the stress became 0 MPa. By this compression-unloading test, the stress-strain curve shown in FIG. 4 was obtained. In the obtained stress-strain curve, the strain ε ₁ at the maximum stress of 0.5 MPa was defined as the total strain, and the strain ε ₃ when unloaded to 0 Ma was defined as the plastic strain. Although it is often a negative notation because it is a compressive strain, for the sake of convenience in expressing the absolute amount of strain in terms of magnitude, here, even a strain in the compressing direction is indicated in the positive direction. This compression-unloading test was performed at 25 ° C and 50 ° C.

(Glass-transition temperature)
The dynamic viscoelasticity of the transparent adhesive film was measured using RSA2 manufactured by Rheometrics Scientific under the conditions of a frequency of 1 Hz, a heating rate of 5 minutes / minute, and a shear mode. The peak temperature of the loss tangent calculated from the loss modulus / storage modulus was taken as the glass transition temperature.

(Embeddability in printing steps)
Using the transparent protective plate with a decoration part shown in FIG. 6, the embedding property to the printing level | step difference of a transparent adhesive film was evaluated. The transparent protective plate with a decoration part shown in FIG. 6 has a size of 86.6 mm × 56.0 mm, a glass substrate 40 having a thickness of 0.7 mm, and a black having a thickness of 0.04 mm formed on the glass substrate. And a decorative part made of printing. The decorative portion has the same outer dimensions as the glass plate, and has an opening with an inner dimension of 68.0 × 45.0 mm. The glass substrate was used as a substitute for an input device or an image display device, and the embeddability was evaluated. First, a transparent adhesive film was laminated on a glass substrate at room temperature using a roll. Subsequently, the transparent protective plate with a decoration part was bonded together to the transparent adhesive film, and the sample for evaluation was prepared. This sample was put into a pressure degassing apparatus and subjected to heat and pressure treatment at 50 ° C. and 0.5 MPa for 30 minutes. Observe the presence or absence of air bubbles or bubbles near the printed step of the sample after processing. If air bubbles or air bubbles remain, embeddability: x (defect). Judged.

(Exudation property)
The transparent adhesive film was cut with a cutter together with the release film attached to both sides, and bleeding of the cut end face was observed with a microscope. When the transparent adhesive film protruded from the edge of the release film, the bleeding property was judged as x (defect), and when it did not protrude, the bleeding property was judged as ◯ (good).

(Foam resistance under high temperature conditions)
A sample for evaluation similar to the embedding property in the printing step was treated at a high temperature of 80 ° C. for 12 hours, and peeling and foaming of the bonded surface were observed. When peeling or foaming was observed, foaming resistance: x (defect), and when peeling or foaming was not observed, foaming resistance: ○ (good) was determined.
(Adhesive to glass)

  The release film was peeled off from the transparent adhesive film, a highly transparent polyethylene terephthalate film (A4100 manufactured by Toyobo Co., Ltd.) was bonded to one side, and the other side was bonded to glass. Thereafter, the adhesion to glass was measured by a 180 ° peeling test based on JIS Z 0237 using a tensile tester (TRC-121 manufactured by Orientec). The peeling test was performed at a measurement temperature of 25 ° C., a pulling speed of 60 mm / min, and a sample width of 10 mm.

  As in Examples 1 to 6, when the total strain is 0.25 or more and 0.5 or less and the plastic strain is 0.10 or more and 0.3 or less at 50 ° C., the embedding property in the printing step is excellent. Further, when the total strain at 25 ° C. was 0.01 or more and 0.35 or less and the plastic strain was 0.01 or more and 0.20 or less, the bleeding property was excellent.

  On the other hand, in Comparative Example 1, since the glass transition temperature is −20 ° C. or lower, the difference between the total strain and the plastic strain is small at 50 ° C. and 25 ° C., and the total strain and the plastic strain at 50 ° C. are both small. Was inferior. In Comparative Example 2, the total strain at 50 ° C. was 0.25 or more, but the glass transition temperature was higher than 30 ° C., the plastic strain was small, and the embedding property was inferior. In Comparative Example 3, the total strain and plastic strain at 50 ° C. are sufficiently large and the embedding property is excellent. However, even at 25 ° C., the total strain is 0.35 or more and the plastic strain is 0.2 or more, and the exudation property is inferior. It was. Similarly, in Comparative Example 4, the total strain and plastic strain at 50 ° C. are sufficiently large and the embedding property is excellent. However, even at 25 ° C., the total strain is 0.35 or more and the plastic strain is 0.2 or more, and the exudation property is improved. It was inferior.

  As described above, when the total strain at 50 ° C. is 0.25 or more and 0.5 or less and the plastic strain is 0.10 or more and 0.3 or less, the embedding property in the printing step is excellent, and at 25 ° C. When the total strain is 0.01 or more and 0.35 or less and the plastic strain is 0.01 or more and 0.20 or less, the exudation property is excellent. It was confirmed that this is an appropriate physical property index.

DESCRIPTION OF SYMBOLS 1 ... Image display unit, 5 ... Decoration part, 10 ... Liquid crystal display cell, 20, 22 ... Polarizing plate, 30 ... Information input device (touch panel), 31, 32 ... Transparent adhesive film (transparent resin layer) 40 ... Protection plate, 50 ... Backlight system, 100, 101, 103 ... Image display device (liquid crystal display device).

Claims (6)

A transparent adhesive film comprising a monomer unit derived from an alkyl (meth) acrylate having a linear or branched alkyl group having 4 to 18 carbon atoms, and a monomer unit derived from a monomer having a cyclic group,
When a compression-unloading cycle test in which the transparent adhesive film is unloaded after a compressive stress of 0 MPa to 0.5 MPa at maximum is applied at 25 ° C., the total strain is 0.01 or more and 0.35. And the plastic strain is 0.01 or more and 0.20 or less, and
When the compression-unloading cycle test in which the transparent adhesive film is unloaded after applying a compressive stress of 0 MPa to 0.5 MPa at the maximum, the total strain is 0.25 or more and 0.5. A transparent adhesive film having a plastic strain of 0.1 or more and 0.3 or less.   The transparent adhesive film of Claim 1 whose glass transition temperature is 0-30 degreeC.   A polymerization monomer selected from acrylic acid and an acrylic acid derivative; an acrylic polymer containing a polymerizable monomer selected from acrylic acid and an acrylic acid derivative as monomer units; a crosslinking agent; and a photopolymerization initiator. An alkyl (meth) acrylate having a linear or branched alkyl group having 4 to 18 carbon atoms, a monomer having a cyclic group, and the acrylic acid derivative as a functional monomer or as a monomer unit of the acrylic polymer; The transparent adhesive film of Claim 1 or 2 formed by photocuring the adhesive composition containing this.   The transparent adhesive film as described in any one of Claims 1-3 which has a thickness of 0.1-0.4 mm. An image display unit; a protective plate disposed opposite to the image display unit; a decorative portion provided on a peripheral portion of a surface of the protective plate on the image display unit side; the decorative portion and the protective plate; The transparent adhesive film according to any one of claims 1 to 4, which is disposed between the image display unit,
The image display apparatus whose thickness of the said decoration part is 10-80 micrometers. An information input device; a protective plate disposed opposite to the information input device; a decorative portion provided on a peripheral portion of a surface of the protective plate on the information input device side; the decorative portion and the protective plate; The transparent adhesive film according to any one of claims 1 to 4 disposed between the information input device,
The image display apparatus whose thickness of the said decoration part is 10-80 micrometers.

Images