KR20190092249A - Adhesive sheet and method for producing the same, and image display apparatus - Google Patents

Abstract

The adhesive sheet 5 has a haze of 1% or less, an adhesive force to glass of 2.0N / 10mm or more, a glass transition temperature of -3 ° C or less, and a shear storage modulus at a temperature of 25 ° C of 0.16 MPa or more. . The pressure-sensitive adhesive sheet 5 is, for example, after applying a composition containing an acrylic monomer and / or a partial polymer thereof, and a urethane di (meth) acrylate in a layered manner on a substrate, and irradiating actinic rays to the composition to photocuring It is obtained by performing.

Description

Adhesive sheet, its manufacturing method, and image display apparatus {ADHESIVE SHEET AND METHOD FOR PRODUCING THE SAME, AND IMAGE DISPLAY APPARATUS}

This invention relates to an adhesive sheet and its manufacturing method. Moreover, this invention relates to the image display apparatus using the said adhesive sheet.

As various image display apparatuses, such as a mobile telephone, a smart phone, a car navigation apparatus, the monitor for personal computers, and a television, a liquid crystal display device and an organic electroluminescence display are used widely. For the purpose of preventing damage to the image display panel due to an impact from an external surface, a front transparent plate (also referred to as a "cover window"), such as a transparent resin plate or a glass plate, is provided on the visual side of the image display panel. It may become. Moreover, in recent years, the device provided with a touch panel in the visual recognition side of an image display panel is becoming popular.

As a method of disposing a front transparent member such as a front transparent plate or a touch panel on a front surface of an image display panel, an "interlayer filling structure" for joining an image display panel and a front transparent member through an adhesive sheet is proposed. have. The adhesive sheet may be provided between the touch panel and the front transparent plate in some cases. In the interlayer filling structure, the gap between the members is filled with the pressure-sensitive adhesive, so that the difference in refractive index of the interface is reduced, and the decrease in visibility due to reflection and scattering is suppressed. In addition, in the interlayer filling structure, since the members are bonded to each other by the adhesive sheet and fixed, the advantage that the front transparent member is less likely to occur due to an impact such as falling is less than when the front transparent member is fixed only to the housing. have. In particular, the impact resistance tends to be improved by using a large pressure-sensitive adhesive sheet. Since the adhesive sheet with a large thickness can be formed in uniform thickness, the solvent-free photocurable adhesive is widely used for the adhesive sheet for interlayer filling (for example, refer patent document 1 and patent document 2).

Japanese Patent Publication No. 2014-125524 International Publication No. 2013/161666

Conventionally, the front transparent member, such as a cover window, is larger than a display panel, and the front transparent member and the housing were joined by the adhesive tape etc. in the area | region outside the outer periphery of a display panel. That is, the front transparent member was fixed by the combination of bonding to the housing and bonding to the surface of the display panel by the pressure-sensitive adhesive sheet for interlayer filling.

In recent years, narrowing and bezel-less display apparatuses are progressing mainly on mobile devices, such as a smart phone. With narrowing the softening and bezeling, the size of the display panel 10 is equal to the size of the front transparent member 7 or larger than the size of the display panel. In such a configuration, the housing 9 and the front transparent member 7 cannot be fixed by an adhesive tape or the like, and the front transparent member 7 needs to be fixed only by the adhesive sheet 5 for interlayer filling. (See Figure 2). In connection with this, while the adhesive sheet for interlayer filling requires a higher adhesive force, it is calculated | required that peeling by impacts, such as a fall, does not generate | occur | produce in a wide temperature range.

In addition, when the size of the display panel is equal to the size of the front transparent member or larger than the size of the display panel, in order to fill the gap 90 between the housing 9 and the front transparent member 7, Sealing by a material may be performed. For example, after inflowing the resin material in a molten state into the gap 90, the resin material is sealed by cooling to room temperature to solidify the resin. When a high temperature resin flows into the gap 90, in the vicinity of the gap 90, the front transparent member 7, the housing 9, and the adhesive sheet 5 become a high temperature and are cooled at the time of solidification of the resin. . Along with such a temperature change, even if the dimensional deformation occurs in the front transparent member, the housing, or the like, the adhesive sheet 5 is required to have adhesion durability against deformation stress so that peeling between adherends does not occur.

Since the adhesive sheet for interlayer filling disclosed by patent document 1 etc. has high glass transition temperature, adhesiveness and impact resistance at low temperature are lacking. On the other hand, the adhesive sheet of the low glass temperature disclosed by patent document 2 has low adhesive durability with respect to strain stress, and makes it compatible with the impact resistance at low temperature, and the durability with respect to strain stress at the time of heating and cooling, such as resin sealing. It is difficult.

In view of the above, it is an object of the present invention to provide an adhesive sheet having excellent adhesion resistance against impact resistance and strain stress in a wide temperature range.

This invention relates to the adhesive sheet in which the adhesive containing a base polymer is formed in the sheet form. The haze of an adhesive sheet is 1% or less. As for the glass transition temperature of an adhesive sheet, -3 degrees C or less is preferable. Shear storage modulus at a temperature of 25 ℃ adhesive sheet G 'is more than _{25 ℃} 0.16㎫ preferred. As for the peak top value of the loss tangent of an adhesive sheet, 1.5 or more are preferable.

As a base polymer contained in an adhesive sheet, what the acrylic polymer chain was bridge | crosslinked by the urethane type segment is used, for example. In order to satisfy said various characteristics, it is preferable that content of a urethane type segment with respect to 100 weight part of acrylic polymer chains is 3-30 weight part. As for the weight average molecular weight of a urethane type segment, 4000-50000 are preferable.

The base polymer in which the acrylic polymer chain is crosslinked by a urethane-based segment is, for example, by copolymerization of a monomer component constituting the acrylic polymer chain and a urethane (meth) acrylate having a (meth) acryloyl group at at least two terminals. Obtained. As polyfunctional urethane (meth) acrylate, the urethane di (meth) acrylate which has a (meth) acryloyl group in both terminal is preferable.

As for the weight average molecular weight of urethane di (meth) acrylate, 4000-50000 are preferable. As for the glass transition temperature of urethane (meth) acrylate, 0 degrees C or less is preferable.

The pressure-sensitive adhesive sheet comprising a base polymer in which an acrylic polymer chain is crosslinked by a urethane-based segment may be, for example, coated in layers on a substrate with a composition comprising an acrylic monomer and / or a partial polymer thereof and a urethane di (meth) acrylate. After that, the composition is obtained by irradiating active light with photocuring. It is preferable that content of a urethane (meth) acrylate with respect to a total of 100 weight part of an acryl-type monomer and its partial polymer is 3-30 weight part of an adhesive composition.

The adhesive sheet of this invention is used for the bonding of the transparent member in the image display apparatus by which the transparent member is arrange | positioned at the visual recognition side surface, for example. For example, an image display device is formed by fixing the front transparent member to the visual side of the image display panel through the adhesive sheet.

Since the adhesive sheet of this invention is low in glass transition temperature and large in shear storage elastic modulus, it is compatible with impact resistance, such as fall, and adhesive durability with respect to strain stress in a wide temperature range. The image display apparatus which bonded the cover window etc. to the visual recognition side surface using the adhesive sheet of this invention is excellent in adhesive reliability, and can respond also to narrowing solution softening or bezel-less.

BRIEF DESCRIPTION OF THE DRAWINGS Sectional drawing which shows the structural example of the adhesive sheet with a release film.
2 is a cross-sectional view illustrating a configuration example of an image display device.
3 and 4 are cross-sectional views showing examples of the laminated structure of the optical film with an adhesive sheet.
5A is a photograph showing a state of an interlayer adhesion test, and FIG. 5B is an observation photograph of a sample in which streaked bubbles are generated in an interlayer adhesion test.
It is a schematic diagram which shows the arrangement of a sample in an impact test.

FIG. 1 shows an adhesive sheet with a release film to which release films 1 and 2 are attached on both sides of the adhesive sheet 5. 2 is a cross-sectional view showing a configuration example of an image display apparatus in which the front transparent plate 7 is fixed by using an adhesive sheet.

[Properties of Adhesive Sheet]

In the adhesive sheet of this invention, an adhesive is formed in the sheet form. An adhesive sheet is a transparent adhesive sheet whose haze is 1.0% or less. It is preferable that the shear storage elastic modulus G'25 degreeC in ₂₅ degreeC of an adhesive sheet is 0.16 Mpa or more. As the pressure-sensitive adhesive sheet G _{'25 ℃} the 0.16㎫ or more, the higher the bonding reliability. From a viewpoint of improving adhesive reliability at high temperature, 0.11 Mpa or more is preferable for the shear storage elastic modulus G'80 degreeC in ₈₀ degreeC of an adhesive sheet.

On the other hand, with a view to ensuring the wettability to have a suitable viscosity to the pressure sensitive adhesive sheet, G _{'25 ℃} of the adhesive sheet and the following 1㎫ preferably, 0.5㎫ less it is more preferred, and more preferably less than 0.4㎫. In view of the same, G _{'80 ℃} of the adhesive sheet and the following 0.6㎫ preferably, 0.4㎫ less are more preferred, and more preferably less than 0.3㎫.

As for the glass transition temperature of an adhesive sheet, -3 degrees C or less is preferable. -20 degreeC or more is preferable, as for the glass transition temperature of an adhesive sheet, -15 degreeC or more is more preferable, and -13 degreeC or more is more preferable. When a glass transition temperature exists in the said range, since an adhesive sheet has appropriate viscosity also in a low temperature area | region, it exists in the tendency which is excellent in impact resistance.

1.5 or more are preferable, as for the peak top value of tan-delta of an adhesive sheet, 1.6 or more are more preferable, and 1.7 or more are more preferable. The adhesive sheet with a large peak top value of tan-delta has a large viscosity behavior and tends to be excellent in impact resistance.

The shear storage modulus G 'of the pressure sensitive adhesive sheet, the glass transition temperature, and the peak top value of tan δ are determined by viscoelasticity measurement at a frequency of 1 Hz. The glass transition temperature is the temperature (peak top temperature) at which tanδ becomes the maximum. tan δ is the ratio G ″ / G ′ between the storage modulus G ′ and the loss modulus G ″. The storage modulus G 'corresponds to a portion stored as elastic energy when the material is deformed and is an index indicating the degree of hardness. The larger the storage elastic modulus of the pressure-sensitive adhesive sheet, the higher the adhesive holding force, and the peeling due to deformation tends to be suppressed. The loss modulus G "corresponds to the loss energy portion dissipated by internal friction when the material is deformed, and indicates the degree of viscosity. The larger tan δ is, the stronger the viscosity tends to be, the deformation behavior becomes liquid, and the resilient elastic energy is increased. It tends to be small.

Although the upper limit of the peak top value of tan-delta of an adhesive sheet is not specifically limited, Generally, it is 3.0 or less. From the viewpoint of the adhesive holding force, the peak top value of tan δ is preferably 2.7 or less, and more preferably 2.5 or less.

2N / 10mm or more is preferable, 2.5N / 10mm or more is more preferable, and, as for the adhesive force of an adhesive sheet, 3N / 10mm or more is more preferable. When the adhesive force of an adhesive sheet is the said range, peeling of the adhesive sheet from an to-be-adhered body in the case where the impact by stress, a fall by a deformation | transformation, etc. generate | occur | produce can be prevented. Adhesive force is calculated | required by the peeling test of 60 mm / min of tensile velocity, and peeling angle of 180 degree using a glass plate as a to-be-adhered body. Unless otherwise noted, the adhesion is a measurement at 25 ° C.

1N / 10mm or more is preferable, as for the adhesive force in 65 degreeC of an adhesive sheet, 1.5N / 10mm or more is more preferable, and 2N / 10mm or more is more preferable.

The thickness of an adhesive sheet is not specifically limited, What is necessary is just to set by the kind, shape, etc. of a to-be-adhered body. When the member having a printing step is used as the adherend, it is preferable that the thickness of the adhesive sheet is larger than the thickness of the printing step. 30 micrometers or more are preferable, as for the thickness of the adhesive sheet used for bonding a front transparent plate (cover window), 40 micrometers or more are more preferable, and 50 micrometers or more are more preferable. By increasing the thickness of the pressure-sensitive adhesive sheet, there is a tendency that the level difference absorbency and impact resistance increase. Although the upper limit of the thickness of an adhesive sheet is not specifically limited, From a viewpoint of productivity, etc. of an adhesive sheet, 500 micrometers or less are preferable, 300 micrometers or less are more preferable, 250 micrometers or less are more preferable.

[Composition of Adhesive]

As long as the adhesive sheet of this invention satisfy | fills the said characteristic, the composition of an adhesive is not specifically limited, Acrylic polymer, silicone type polymer, polyester, polyurethane, polyamide, polyvinyl ether, vinyl acetate / vinyl chloride copolymer, Polymers such as rubbers such as modified polyolefins, epoxy-based, fluorine-based, natural rubber and synthetic rubbers can be appropriately selected and used.

In particular, an acrylic pressure-sensitive adhesive containing an acrylic polymer is preferably used as the base polymer because it has excellent optical transparency, exhibits proper wettability, cohesion and adhesiveness, and also has excellent weather resistance and heat resistance. Especially, the acrylic base polymer which has a structure in which the acrylic polymer chain was bridge | crosslinked by the urethane type segment is preferable.

[Base polymer]

As the acrylic polymer chain is crosslinked by the urethane-based segment, high adhesion holding force can be exhibited at a low glass transition temperature. It is preferable that content of a urethane type segment with respect to 100 weight part of acrylic polymer chains is 3 weight part or more of a base polymer.

When the amount of the urethane-based segment is excessively large, the viscosity of the pressure-sensitive adhesive decreases with the increase in the crosslinking density, and the step absorbency and the impact resistance may decrease. Moreover, when the quantity of a urethane type segment becomes large too much, transparency of an adhesive sheet may fall and haze may rise. Therefore, 30 weight part or less is preferable with respect to 100 weight part of acrylic polymer chains, and, as for the quantity of the urethane type segment in a base polymer, 25 weight part or less is more preferable.

<Acrylic polymer chain>

An acrylic polymer chain contains (meth) acrylic-acid alkylester as a main structural monomer component. In addition, in this specification, "(meth) acryl" means an acryl and / or methacryl.

As (meth) acrylic-acid alkylester, the (meth) acrylic-acid alkylester whose carbon number of an alkyl group is 1-20 is used suitably. The alkyl group of (meth) acrylic acid may have a branch, and may have a cyclic alkyl group.

As a specific example of the (meth) acrylic-acid alkylester which has a linear alkyl group, methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, isobutyl (meth) acrylate, s-butyl (meth) acrylate, (meth) T-butyl acrylate, pentyl (meth) acrylate, isopentyl (meth) acrylate, neopentyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, (meth) acrylic acid Octyl, isooctyl (meth) acrylate, nonyl (meth) acrylate, isonyl (meth) acrylate, decyl (meth) acrylate, isodecyl (meth) acrylate, undecyl (meth) acrylate, dodecyl (meth) acrylate, Iso tridodecyl (meth) acrylate, tetradecyl (meth) acrylate, isotedecyl (meth) acrylate, pentadecyl (meth) acrylate, cetyl (meth) acrylate, heptadexyl (meth) acrylate, octa (meth) acrylate Decyl, isooctadecyl (meth) acrylate, (meth Nonadecyl acrylate, aralkyl (meth) acrylate, etc. are mentioned.

As a specific example of the (meth) acrylic-acid alkylester which has alicyclic alkyl group, (meth) acrylic-acid cycloalkyl, such as cyclopentyl (meth) acrylate, cyclohexyl (meth) acrylate, cycloheptyl (meth) acrylate, and cyclooctyl (meth) acrylate ester; (Meth) acrylic acid ester which has bicyclic aliphatic hydrocarbon ring, such as isobornyl (meth) acrylate; Dicyclopentanyl (meth) acrylate, dicyclopentanyloxyethyl (meth) acrylate, tricyclopentanyl (meth) acrylate, 1-adamantyl (meth) acrylate, 2-methyl-2-adamantyl ( (Meth) acrylic acid ester which has a tricyclic or more aliphatic hydrocarbon ring, such as a meth) acrylate and 2-ethyl- 2-adamantyl (meth) acrylate, is mentioned.

40 weight% or more is preferable, as for the quantity of the monomer component whole quantity which comprises an acrylic polymer chain, 50 weight% or more is more preferable, and 60 weight% or more is more preferable. From the viewpoint of setting the glass transition temperature (Tg) of the polymer chain to an appropriate range, the amount of the (meth) acrylic acid alkyl ester having a chain alkyl group having 4 to 10 carbon atoms relative to the total amount of the constituent monomer components is 30% by weight. It is preferable that it is the above, It is more preferable that it is 40 weight% or more, It is further more preferable that it is 45 weight% or more. In addition, the monomer component which comprises an acryl-type polymer chain removes urethane (meth) acrylate etc. which become a structural component of a urethane type segment.

The acrylic polymer chain may contain a hydroxyl group containing monomer and a carboxyl group containing monomer as a structural monomer component. When an acrylic polymer chain has a hydroxyl group containing monomer as a structural monomer component, while transparency of an adhesive sheet improves, there exists a tendency for the cloudiness under high temperature, high humidity environment to be suppressed.

As the hydroxyl group-containing monomer, (meth) acrylic acid 2-hydroxyethyl, (meth) acrylic acid 2-hydroxypropyl, (meth) acrylic acid 4-hydroxybutyl, (meth) acrylic acid 6-hydroxyhexyl, (meth) acrylic acid 8 (Meth) acrylic acid esters, such as -hydroxyoctyl, (meth) acrylic acid 10-hydroxydecyl, (meth) acrylic acid 12-hydroxylauryl, and (4-hydroxymethylcyclohexyl) -methylacrylate . Among them, the acrylic polymer chain contains a (meth) acrylic acid ester having a hydroxyalkyl group having 4 to 8 carbon atoms as a constituent monomer component from the viewpoint of high compatibility with the urethane-based segment and improving the transparency of the pressure-sensitive adhesive sheet. It is preferable.

1-35 weight% is preferable, as for the quantity of the hydroxy-group containing monomer with respect to the monomer component whole quantity which comprises an acrylic polymer chain | strand, 3-30 weight% is more preferable, 5-25 weight% is still more preferable.

Examples of the carboxyl group-containing (meth) acrylic acid esters include acrylic monomers such as (meth) acrylic acid, carboxyethyl (meth) acrylate and carboxypentyl (meth) acrylate, itaconic acid, maleic acid, fumaric acid and crotonic acid.

The acrylic polymer chain may contain the nitrogen containing monomer as a structural monomer component. As the nitrogen-containing monomer, N-vinylpyrrolidone, methylvinylpyrrolidone, vinylpyridine, vinylpiperidone, vinylpyrimidine, vinylpiperazine, vinylpyrazine, vinylpyrrole, vinylimidazole, vinyl oxazole, vinyl mor Vinyl monomers such as polyline, (meth) acryloyl morpholine, N-vinylcarboxylic acid amides and N-vinyl caprolactam, and cyanoacrylate monomers such as acrylonitrile and methacrylonitrile. Can be mentioned.

When an acryl-type polymer chain contains high polar monomers, such as a hydroxyl-containing monomer and a carboxyl group-containing monomer, as a structural monomer component, the cohesion force of an adhesive increases and there exists a tendency for the adhesive retention at high temperature to improve. On the other hand, when content of a high polar monomer is excessively large, glass transition temperature may become high and the adhesiveness and impact resistance at low temperature may fall. Therefore, as for the high polar monomer amount (total of a hydroxyl group containing monomer, a carboxyl group containing monomer, and a nitrogen containing monomer) with respect to the monomer component whole quantity which comprises an acrylic polymer chain, 3-40 weight% is preferable, and 5 to 35 weight% Is more preferable, and 10-30 weight% is still more preferable. Moreover, 1-25 weight% is preferable, as for the quantity of the nitrogen containing monomer with respect to the monomer component whole quantity which comprises an acrylic polymer chain | strand, 2-20 weight% is more preferable, and its 3-15 weight% is still more preferable.

The acrylic polymer chain is, as monomer components other than the above, an acid anhydride group-containing monomer, a caprolactone adduct of (meth) acrylic acid, a sulfonic acid group-containing monomer, a phosphate group-containing monomer, vinyl acetate, vinyl propionate, styrene, α-methylstyrene, and the like. Vinyl monomers; Cyanoacrylate monomers such as acrylonitrile and methacrylonitrile; Epoxy group-containing monomers such as glycidyl (meth) acrylate; Glycol-based acrylic ester monomers such as polyethylene glycol (meth) acrylate, polypropylene glycol (meth) acrylate, methoxyethylene glycol (meth) acrylate, and methoxypolypropylene glycol (meth) acrylate; Acrylic acid ester system monomers, such as (meth) acrylic acid tetrahydrofurfuryl, fluorine (meth) acrylate, silicone (meth) acrylate, and 2-methoxyethyl (meth) acrylate, etc. may be included.

The acrylic polymer chain may contain a polyfunctional monomer or oligomer. A polyfunctional compound contains 2 or more of polymerizable functional groups which have unsaturated double bonds, such as a (meth) acryloyl group or a vinyl group, in 1 molecule. Examples of the polyfunctional compound include polyethylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, polytetramethylene glycol di (meth) acrylate, bisphenol Aethylene oxide modified di (meth) acrylate, and bisphenol A Propylene oxide modified di (meth) acrylate, alkanediol di (meth) acrylate, tricyclodecane dimethanol di (meth) acrylate, ethoxylated isocyanuric acid triacrylate, pentaerythritol tri (meth) acrylic Rate, pentaerythritol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, ditrimethylolpropane tetra (meth) acrylate, ethoxylated pentaerythritol tetra (meth) acrylate, pentaerythritol tetra ( Meth) acrylate, dipentaerythritol poly (meth) acrylate, dipentaerythritol hexa (meth) acrylate, neopentyl glycoldi ( Agent) acrylate, and the like glycerin di (meth) acrylate, epoxy (meth) acrylate, butadiene (meth) acrylate, isoprene, (meth) acrylate.

A branched structure (bridge | crosslinking structure) is introduce | transduced into a polymer chain because an acryl-type polymer chain contains a polyfunctional monomer as a structural monomer component. As mentioned later, in the adhesive of this invention, a crosslinked structure is introduce | transduced into an acrylic polymer chain by a urethane type segment. When the amount of the crosslinked structure introduced by the polyfunctional monomer component other than the urethane-based segment is increased, the low temperature adhesive force of the pressure-sensitive adhesive may be lowered. Therefore, 3 weight% or less is preferable, as for the quantity of the polyfunctional compound (except urethane acrylate) with respect to the monomer component whole quantity which comprises an acrylic polymer chain | strand, 1 weight% or less is more preferable, 0.5 weight% or less More preferably, 0.3 weight% or less is especially preferable.

It is preferable that an acrylic polymer chain has the largest content of (meth) acrylic-acid alkylester among said monomer components. The characteristic of an adhesive sheet tends to be influenced by the kind of monomer (main monomer) which has the most content among the structural monomers of an acryl-type polymer chain. For example, when the main monomer of an acryl-type polymer chain is a (meth) acrylic-acid alkylester which has a C6 or less chain alkyl group, the peak top value of tan-delta becomes large and there exists a tendency for impact resistance to improve. In particular, when acrylic acid C ₄ alkyl esters such as butyl acrylate are the main monomers, the peak top value of tan δ tends to increase. 30-80 weight% is preferable, as for the quantity of the (meth) acrylic-acid alkylester which has a C6 or less chain alkyl group with respect to the monomer component whole quantity which comprises an acrylic polymer chain, 35-75 weight% is more preferable, 40- 70 weight% is more preferable. In particular, it is preferable that content of butyl acrylate as a structural monomer component is the said range.

As for the theoretical Tg of an acryl-type polymer chain, -50 degreeC or more is preferable. The theoretical Tg of the acrylic polymer chain is preferably -10 ° C or lower, more preferably -20 ° C or lower, still more preferably -25 ° C or lower. The theory Tg is computed by the following Fox formula from the glass transition temperature Tg _i of the homopolymer of the structural monomer component of an acryl-type polymer chain, and the weight fraction W _i of each monomer component.

1 / Tg = Σ (W _i / Tg _i )

Tg is the glass transition temperature (unit: K) of the polymer chain, W _i is the weight fraction of the monomer component i constituting the segment (copolymer ratio on a weight basis), and Tg _i is the glass transition temperature (unit of the homopolymer of the monomer component i). : K). As a glass transition temperature of a homopolymer, the numerical value described in the 3rd edition of Polymer Handbook (John Wiley & Sons, Inc., 1989) can be employ | adopted. As for homopolymer Tg of the monomer which is not described in the said document, what is necessary is just to employ | adopt the peak top temperature of the loss tangent (tan-delta) by dynamic viscoelasticity measurement.

<Urethane Segment>

The urethane-based segment is a molecular chain having a urethane bond, and a crosslinked structure is introduced into the acrylic polymer chain by covalently bonding both ends of the urethane-based segment with the acrylic polymer chain.

(Structure of Urethane Segment)

Urethane-based segments are typically obtained by reacting diols with diisocyanates and comprise polyurethane chains. From the viewpoint of obtaining a pressure-sensitive adhesive capable of both low temperature adhesiveness and high temperature holding force, the molecular weight of the polyurethane chain in the urethane-based segment is preferably 4000 to 50000, more preferably 4500 to 40000, and even more preferably 5000 to 30000.

The larger the molecular weight of the polyurethane chain in the urethane-based segment, the longer the distance between the crosslinking points of the acrylic polymer chain. When the molecular weight of the polyurethane chain is excessively small and the distance between the crosslinking points is short, the storage modulus increases with the increase of the cohesive force. In connection with this, since the viscosity of an adhesive sheet falls and tan-delta falls, there exists a tendency for impact resistance to fall. When the molecular weight of a polyurethane chain is excessively large and the distance between bridge | crosslinking points is long, a storage elastic modulus may be small and adhesive holding power may be inadequate. When the molecular weight of a polyurethane chain is the said range, since an adhesive has moderate cohesion, an impact resistance and adhesion | attachment holding force can be made compatible.

As a diol used for formation of a polyurethane chain, Low molecular weight diols, such as ethylene glycol, diethylene glycol, propylene glycol, butylene glycol, hexamethylene glycol; And high molecular weight polyols such as polyester polyols, polyether polyols, polycarbonate polyols, acrylic polyols, epoxy polyols, and caprolactone polyols.

Polyether polyol is obtained by ring-opening addition polymerization of alkylene oxide to polyhydric alcohol. Examples of the alkylene oxide include ethylene oxide, propylene oxide, butylene oxide, styrene oxide, tetrahydrofuran and the like. As a polyhydric alcohol, the diol mentioned above, glycerin, trimethylol propane, etc. are mentioned.

Polyester polyol is polyester which has a hydroxyl group at the terminal, and is obtained by reacting polybasic acid and a polyhydric alcohol so that alcohol equivalent may become excess with respect to carboxylic acid equivalent. As the polybasic acid component and the polyhydric alcohol component constituting the polyester polyol, a combination of a dibasic acid and a diol is preferable.

As a dibasic acid component, Aromatic dicarboxylic acid, such as orthophthalic acid, isophthalic acid, a terephthalic acid; Alicyclic dicarboxylic acids such as hexahydrophthalic acid, tetrahydrophthalic acid, 1,3-cyclohexanedicarboxylic acid, and 1,4-cyclohexanedicarboxylic acid; Aliphatic dicas, such as oxalic acid, succinic acid, malonic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, decandicarboxylic acid, dodecanedicarboxylic acid, and octadecanedicarboxylic acid Carboxylic acid; Acid anhydride, lower alcohol ester, etc. of these dicarboxylic acid are mentioned.

As the diol component, ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, pentanediol, 1,6-hexanediol, 1,8 Octanediol, 1,10-decanediol, diethylene glycol, triethylene glycol, polyethylene glycol, dipropylene glycol, polypropylene glycol, 1,4-cyclohexanedimethanol, 1,4-cyclohexanediol, bisphenol A, Bisphenol F, hydrogenated bisphenol A, hydrogenated bisphenol F, etc. are mentioned.

As a polycarbonate polyol, Polycarbonate polyol obtained by polycondensation reaction of a diol component and a phosgene; Diol component and diester carbonate, such as dimethyl carbonate, diethyl carbonate, dipropyl carbonate, diisopropyl carbonate, dibutyl carbonate, ethyl butyl carbonate, ethylene carbonate, propylene carbonate, diphenyl carbonate, dibenzyl carbonate Polycarbonate polyols obtained by transesterified condensation of the above compounds; Copolymerized polycarbonate polyols obtained by using two or more types of polyol components in combination; Polycarbonate polyol obtained by esterifying the said various polycarbonate polyol and carboxyl group-containing compound; Polycarbonate polyols obtained by etherification of the various polycarbonate polyols and hydroxyl group-containing compounds; Polycarbonate polyol obtained by transesterifying the said various polycarbonate polyol and ester compound; Polycarbonate polyol obtained by transesterifying the said various polycarbonate polyol and a hydroxyl-containing compound; Polyester-based polycarbonate polyols obtained by polycondensation of the above-mentioned various polycarbonate polyols and dicarboxylic acid compounds; The copolymerized polyether polycarbonate polyol etc. which are obtained by copolymerizing the said various polycarbonate polyol and alkylene oxide are mentioned.

Polyacryl polyol is obtained by copolymerizing the monomer component which has a (meth) acrylic acid ester and a hydroxyl group. As a monomer which has a hydroxyl group, (meth) acrylic-acid 2-hydroxyethyl, (meth) acrylic-acid 2-hydroxypropyl, (meth) acrylic-acid 3-hydroxypropyl, (meth) acrylic acid 2-hydroxybutyl, (meth) acrylic acid Hydroxyalkyl esters of (meth) acrylic acid, such as 4-hydroxybutyl and 2-hydroxypentyl (meth) acrylic acid; (Meth) acrylic acid monoesters of polyhydric alcohols such as glycerin and trimethylolpropane; N-methylol (meth) acrylamide etc. are mentioned. As (meth) acrylic acid ester, methyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, cyclohexyl (meth) acrylate, etc. are mentioned.

The polyacryl polyol may contain the monomer component of that excepting the above as a copolymerization component. As a copolymerization monomer component of that excepting the above, unsaturated monocarboxylic acids, such as (meth) acrylic acid; Unsaturated dicarboxylic acids such as maleic acid and anhydrides thereof, and mono or diesters; Unsaturated nitriles such as (meth) acrylonitrile; Unsaturated amides such as (meth) acrylamide and N-methylol (meth) acrylamide; Vinyl esters such as vinyl acetate and vinyl propionate; Vinyl ethers such as methyl vinyl ether; Α-olefins such as ethylene and propylene; Halogenated α, β-unsaturated aliphatic monomers such as vinyl chloride and vinylidene chloride; (Alpha), (beta)-unsaturated aromatic monomers, such as styrene and (alpha) -methylstyrene, etc. are mentioned.

The diisocyanate used for formation of a polyurethane chain may be any of aromatic diisocyanate and aliphatic. As aromatic diisocyanate, 1, 5- naphthalene diisocyanate, 4,4'- diphenylmethane diisocyanate (MDI), 4,4'- diphenyl dimethyl methane diisocyanate, tetramethyl diphenylmethane diisocyanate, 1,3 -Phenylene diisocyanate, 1,4-phenylene diisocyanate, 2-chloro-1,4-phenyl diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, xylylene diisocyanate, 4,4 ' -Diphenyl ether diisocyanate, 4,4'- diphenyl sulfoxy diisocyanate, 4,4'- diphenyl sulfone diisocyanate, 4,4'- biphenyl diisocyanate, etc. are mentioned. Examples of the aliphatic diisocyanate include butane-1,4-diisocyanate, hexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, and cyclohexane-1,4- Diisocyanate, isophorone diisocyanate, dicyclohexyl methane-4,4'- diisocyanate, 1, 3-bis (isocyanatomethyl) cyclohexane, methylcyclohexane diisocyanate, etc. are mentioned.

As the diisocyanate, derivatives of isocyanate compounds can also be used. Examples of the derivative of the isocyanate compound include dimers of polyisocyanates, trimers of isocyanates (isocyanurates), polymer MDI, adducts with trimethylolpropane, biuret modifications, allophanate modifications, urea modifications, and the like. Can be mentioned. As a diisocyanate component, you may use the urethane prepolymer which has an isocyanate group at the terminal.

(Introduction of crosslinked structure for acrylic polymer chain by urethane-based segment)

By using the compound which has a functional group copolymerizable with the monomer component which comprises an acrylic polymer chain at the terminal of a polyurethane chain, or the compound which has a functional group which can react with the carboxy group, a hydroxyl group, etc. contained in an acrylic polymer chain at the terminal of a polyurethane chain, The crosslinked structure by a urethane type segment can be introduce | transduced into an acryl-type polymer chain. Urethane di (meth) acrylate having a (meth) acryloyl group at both ends of the urethane chain since it is easy to introduce a crosslinking point into the acrylic polymer chain uniformly and has excellent compatibility between the acrylic polymer chain and the urethane-based segment. It is preferable to introduce a crosslinked structure by the urethane-based segment using. For example, the crosslinked structure by a urethane type segment can be introduce | transduced into an acryl-type polymer chain by copolymerizing the monomer component which comprises an acryl-type polymer chain, and urethane di (meth) acrylate.

Urethane di (meth) acrylate which has a (meth) acryloyl group in both terminal is obtained by using the (meth) acryl compound which has a hydroxyl group in addition to a diol component, for example in superposition | polymerization of a polyurethane. From the viewpoint of controlling the chain length (molecular weight) of the urethane-based segment, diol and diisocyanate are reacted so that isocyanate is excessive to synthesize an isocyanate terminated polyurethane, and then a (meth) acryl compound having a hydroxyl group is added to It is preferable to make the terminal isocyanate group and the hydroxyl group of a (meth) acryl compound react.

By reacting a polyhydric alcohol and a polyisocyanate compound so that a polyisocyanate compound becomes excess, the urethane chain which has an isocyanate group in the terminal is obtained. In order to obtain an isocyanate terminated polyurethane, the diol component and the diisocyanate component may be used so that the NCO / OH (equivalent ratio) is preferably 1.1 to 2.0, more preferably 1.15 to 1.5. You may add a diisocyanate component, after making it react by mixing substantially equivalent amount of a diol component and a diisocyanate component.

As a (meth) acryl compound which has a hydroxyl group, (meth) acrylic-acid hydroxyethyl, (meth) acrylic-acid hydroxypropyl, (meth) acrylic-acid hydroxybutyl, (meth) acrylic-acid hydroxyhexyl, hydroxymethyl acrylamide, and hydroxy Ethyl acrylamide etc. are mentioned.

As urethane (meth) acrylate, in each company such as Arakawa Kagaku High School, Shin-Nakamura Kagaku High School, Toa Kosei, Kyoeisha Kagaku, Nippon Kayaku, Nippon Kosei Kagaku High School, Nagami High School, Daicel Allnex You may use the commercial item sold. 4000-50000 are preferable, as for the weight average molecular weight of a urethane (meth) acrylate, 4500-40000 are more preferable, 5000-30000 are more preferable.

0 degrees C or less is preferable, as for the glass transition temperature of a urethane (meth) acrylate, -10 degrees C or less is more preferable, and -20 degrees C or less is still more preferable. By using a low Tg urethane acrylate, even when a crosslinked structure is introduced by the urethane-based segment to increase the cohesive force of the base polymer, an adhesive excellent in low temperature adhesive strength is obtained. Although the lower limit of the glass transition temperature of urethane (meth) acrylate is not specifically limited, From a viewpoint of obtaining the adhesive excellent in high temperature holding force, -100 degreeC or more is preferable, -90 degreeC or more is more preferable, -80 degreeC or more More preferred.

When using a urethane (meth) acrylate to introduce a crosslinked structure by a urethane-based segment into the acrylic polymer chain, the glass transition temperature of the urethane-based segment of the base polymer is approximately the same as the glass transition temperature of the urethane (meth) acrylate. Do.

<Preparation of base polymer>

The polymer in which the crosslinked structure by the urethane type segment was introduce | transduced into the acryl-type polymer chain can be superposed | polymerized by various well-known methods. When using urethane (meth) acrylate as a structural component of a urethane type segment, what is necessary is just to copolymerize the monomer component and urethane (meth) acrylate which comprise an acryl-type polymer chain.

As for the usage-amount of a urethane (meth) acrylate, 3-30 weight part is preferable with respect to 100 weight part of monomer components for forming an acrylic polymer chain, and 4-25 weight part is more preferable. By adjusting the usage-amount of urethane (meth) acrylate, the base polymer whose content of a urethane type segment is the above-mentioned range can be prepared. When content of a urethane type segment is too small, there exists a tendency for the adhesive holding force of an adhesive sheet to fall by cohesive fall of a base polymer. When the content of the urethane-based segment is excessively large, the viscosity of the pressure-sensitive adhesive sheet decreases with the increase in the cohesiveness of the base polymer, and the impact resistance tends to decrease.

As polymerization method of a base polymer, photopolymerization is preferable. In the photopolymerization, the polymer can be prepared without using a solvent. Therefore, no dry removal of the solvent is required at the time of formation of the pressure sensitive adhesive sheet, and a large pressure sensitive adhesive sheet can be uniformly formed.

In preparation of a base polymer, the whole quantity of the urethane (meth) acrylate for introduce | transducing the monomer component and crosslinked structure which comprise an acryl-type polymer chain may be made to react at once, and you may superpose | polymerize in multistep. As a method of superposing | polymerizing in multiple stages, the monofunctional monomer which comprises an acrylic polymer chain is superposed | polymerized, a prepolymer composition is formed (prepolymerization), and polyfunctional compounds, such as urethane di (meth) acrylate, are added to the syrup of a prepolymer composition. And the method of superposing | polymerizing (main polymerization) a prepolymer composition and a polyfunctional monomer is preferable. The prepolymer composition is a partial polymer containing a low polymerization degree polymer and an unreacted monomer.

By performing prepolymerization of the component of an acryl-type polymer, the branching point (crosslinking point) by polyfunctional compounds, such as urethane di (meth) acrylate, can be introduce | transduced uniformly into an acryl-type polymer chain. Moreover, after apply | coating the mixture (adhesive composition) of a low molecular weight polymer or partial polymerization product, and the unpolymerized monomer component on a base material, you may perform this superposition | polymerization on a base material and form an adhesive sheet.

Since low-polymerization compositions, such as a prepolymer composition, are excellent in applicability with low viscosity, the method of performing superposition | polymerization on a base material after apply | coating the adhesive composition which is a mixture of a prepolymer composition and a polyfunctional compound can improve productivity of an adhesive sheet. In addition, the thickness of an adhesive sheet can be made uniform.

[Adhesive sheet]

As mentioned above, the prepolymer composition of low polymerization degree is prepared by prepolymerization, the adhesive composition which added the polyfunctional compound etc. to the prepolymer composition is apply | coated in layers on a base material, and the adhesive composition on a base material (main polymerization) is performed. By this, an adhesive sheet is obtained.

<Prepolymerization>

A prepolymer composition can be prepared by polymerizing the composition which mixed the monomer component and polymerization initiator which comprise an acryl-type polymer chain, for example. The composition for prepolymer formation may contain the polyfunctional compound (polyfunctional monomer or polyfunctional oligomer). For example, a part of the polyfunctional compound which becomes a raw material of a polymer may be contained in the composition for prepolymer formation, and after polymerizing a prepolymer, the remainder of a polyfunctional compound may be added to this polymerization.

It is preferable that the composition for prepolymer formation contains a photoinitiator. As a photoinitiator, a benzoin ether type photoinitiator, an acetophenone type photoinitiator, the (alpha)-ketol type photoinitiator, an aromatic sulfonyl chloride type photoinitiator, a photoactive oxime type photoinitiator, a benzoin type photoinitiator, a benzyl type photoinitiator, benzo A phenone type photoinitiator, a ketal type photoinitiator, a thioxanthone type photoinitiator, an acyl phosphine oxide type photoinitiator, etc. are mentioned.

In the case of superposition | polymerization, you may use a chain transfer agent, a polymerization inhibitor (polymerization retardant), etc. for the purpose of molecular weight adjustment, etc. As the chain transfer agent, α-thioglycerol, lauryl mercaptan, glycidyl mercaptan, mercaptoacetic acid, 2-mercaptoethanol, thioglycolic acid, thioglycolic acid 2-ethylhexyl, 2,3-dimercapto-1- Thiols, such as a propanol, (alpha) -methylstyrene dimer, etc. are mentioned.

The composition for prepolymer formation may contain a chain transfer agent etc. as needed other than a monomer and a polymerization initiator. The polymerization initiator and chain transfer agent used for prepolymerization are not specifically limited, For example, the photoinitiator and chain transfer agent mentioned above can be used.

Although the polymerization rate of a prepolymer is not specifically limited, From a viewpoint of making it suitable viscosity for application | coating on a base material, 3-50 weight% is preferable and 5-40 weight% is more preferable. The polymerization rate of the prepolymer can be adjusted to a desired range by adjusting the kind and the amount of the photopolymerization initiator, the irradiation intensity of the active light such as UV light, the irradiation time, and the like. The polymerization rate of a prepolymer is computed by the following formula from the weight before and behind heating when it heats at 130 degreeC for 3 hours. The polymerization rate of the pressure sensitive adhesive sheet is also calculated by the same method.

Polymerization rate (%) = weight after drying / weight before drying × 100

<Preparation of adhesive composition>

A urethane (meth) acrylate and the remainder of the monomer component which comprises an acryl-type polymer chain, a polymerization initiator, a chain transfer agent, other additives, etc. are mixed with the said prepolymer composition, and the adhesive composition is prepared as needed. It is preferable that an adhesive composition has a viscosity (for example, about 0.5-20 Pa.s) suitable for application | coating on a base material. The viscosity of an adhesive composition can be made into an appropriate range by adjusting the polymerization rate of a prepolymer, the addition amount of a urethane (meth) acrylate, the composition, molecular weight, addition amount, etc. of other components (for example, oligomer). You may use a thickening additive etc. for the purpose of viscosity adjustment, etc.

The polymerization initiator and the chain transfer agent used for this polymerization are not specifically limited, For example, the photoinitiator and chain transfer agent mentioned above can be used. When the polymerization initiator at the time of prepolymerization remains inactivated in a prepolymer composition, addition of the polymerization initiator for this polymerization can be skipped.

(Oligomer)

The adhesive composition may contain various oligomers for the purpose of adjustment of the adhesive force of an adhesive sheet, viscosity adjustment, etc. As an oligomer, what has a weight average molecular weight about 1000-30000, for example is used. As an oligomer, an acrylic oligomer is preferable at the point which is excellent in compatibility with an acrylic base polymer.

An acryl-type oligomer contains (meth) acrylic-acid alkylester as a main structural monomer component. Especially, the (meth) acrylic-acid alkylester (chain alkyl (meth) acrylate) which has a linear alkyl group as a structural monomer component, and the (meth) acrylic-acid alkylester (alicyclic alkyl (meth) acrylate) which has an alicyclic alkyl group It is preferable to include. Specific examples of the chain alkyl (meth) acrylate and alicyclic alkyl (meth) acrylate are as exemplified above as constituent monomers of the acrylic polymer chain.

20 degreeC or more is preferable, as for the glass transition temperature of an acryl-type oligomer, 30 degreeC or more is more preferable, and 40 degreeC or more is more preferable. There exists a tendency for the adhesive holding force of an adhesive sheet to improve by using together the low Tg base polymer and the high Tg acrylic oligomer which the crosslinked structure by the urethane type segment introduce | transduced. Although the upper limit of the glass transition temperature of an acryl-type oligomer is not specifically limited, Generally, it is 200 degrees C or less, 180 degrees C or less is preferable, and 160 degrees C or less is more preferable. The glass transition temperature of an acryl-type oligomer is computed by the above Fox formula.

Among the exemplary (meth) acrylic acid alkyl esters, methyl methacrylate is preferable as the chain alkyl (meth) acrylate because of its high glass transition temperature and excellent compatibility with the base polymer. As alicyclic alkyl (meth) acrylate, dicyclopentanyl acrylate, dicyclopentanyl methacrylate, cyclohexyl acrylate, and cyclohexyl methacrylate are preferable. That is, an acryl-type oligomer contains 1 or more types chosen from the group which consists of dicyclopentanyl acrylate, dicyclopentanyl methacrylate, cyclohexyl acrylate, and cyclohexyl methacrylate as a structural monomer component, and contains methyl methacrylate. It is preferable.

10-90 weight% is preferable, as for the quantity of the alicyclic alkyl (meth) acrylate with respect to the monomer component whole quantity which comprises an acryl-type oligomer, 20-80 weight% is more preferable, 30-70 weight% is still more preferable. 10-90 weight% is preferable, as for the quantity of the chain alkyl (meth) acrylate with respect to the monomer component whole quantity which comprises an acryl-type oligomer, 20-80 weight% is more preferable, 30-70 weight% is still more preferable.

1000-30000 are preferable, as for the weight average molecular weight of an acryl-type oligomer, 1500-10000 are more preferable, 2000-8000 are still more preferable. There exists a tendency for the adhesive force and adhesive holding force of an adhesive to improve by using the acryl-type oligomer which has the molecular weight of the said range.

An acryl-type oligomer is obtained by superposing | polymerizing the said monomer component by various polymerization methods. In the case of superposition | polymerization of an acryl-type oligomer, you may use various polymerization initiators. Moreover, you may use a chain transfer agent for the purpose of adjustment of molecular weight.

When including an oligomer component, such as an acryl-type oligomer, in an adhesive composition, 0.5-20 weight part is preferable with respect to 100 weight part of said base polymers, 1-15 weight part is more preferable, 2-10 weight part More preferred. When content of the oligomer in an adhesive composition is the said range, there exists a tendency for the adhesiveness at high temperature and high temperature holding force to improve.

(Silane coupling agent)

You may add a silane coupling agent in an adhesive composition for the purpose of adjustment of an adhesive force. When a silane coupling agent is added to an adhesive composition, the addition amount is about 0.01-5.0 weight part normally with respect to 100 weight part of base polymers, and it is preferable that it is about 0.03-2.0 weight part.

(Bridge)

The base polymer may have a crosslinked structure other than said polyfunctional compound as needed. By including a crosslinking agent in an adhesive composition, a crosslinked structure can be introduce | transduced into a base polymer. As a crosslinking agent, the compound which reacts with functional groups, such as a hydroxyl group and a carboxy group, contained in a polymer is mentioned. Specific examples of the crosslinking agent include an isocyanate crosslinking agent, an epoxy crosslinking agent, an oxazoline crosslinking agent, an aziridine crosslinking agent, a carbodiimide crosslinking agent, and a metal chelate crosslinking agent.

When the amount of introduction of the crosslinked structure other than the urethane-based segment is increased, the viscosity may decrease and the impact resistance may decrease. Therefore, 3 weight part or less is preferable with respect to 100 weight part of base polymers, as for the usage-amount of a crosslinking agent, 2 weight part or less is more preferable, and 1 weight part or less is still more preferable.

(Other additives)

In addition to each component of the said illustration, the adhesive composition may contain additives, such as a tackifier, a plasticizer, a softener, a deterioration agent, a filler, a coloring agent, a ultraviolet absorber, antioxidant, surfactant, an antistatic agent.

<Application and Main Polymerization of Adhesive Composition>

After apply | coating an adhesive composition on a base material in layer form, photocuring is performed by irradiating an actinic light. When photocuring, it is preferable to attach a cover sheet to the surface of an application layer, to irradiate actinic light in the state which clamped the adhesive composition between two sheets, and to prevent the inhibition of polymerization by oxygen.

Arbitrary appropriate base materials are used as a base material and cover sheet used for formation of an adhesive sheet. The release film which has a release layer in the contact surface with a base material and a cover sheet may be sufficient.

As a film base material of a release film, the film containing various resin materials is used. Examples of the resin material include polyester resins such as polyethylene terephthalate and polyethylene naphthalate, acetate resins, polyether sulfone resins, polycarbonate resins, polyamide resins, polyimide resins, polyolefin resins, ( Meth) acrylic resin, polyvinyl chloride resin, polyvinylidene chloride resin, polystyrene resin, polyvinyl alcohol resin, polyarylate resin, polyphenylene sulfide resin and the like. Among these, polyester resins, such as polyethylene terephthalate, are especially preferable. 10-200 micrometers is preferable and, as for the thickness of a film base material, 25-150 micrometers is more preferable. As a material of a mold release layer, a silicone type mold release agent, a fluorine type mold release agent, a long chain alkyl type mold release agent, a fatty acid amide type mold release agent, etc. are mentioned. The thickness of the release layer is generally about 10 to 2000 nm.

As a coating method of the adhesive composition on a base material, it is a roll coat, a kiss roll coat, a gravure coat, a reverse coat, a roll brush, a spray coat, a dip roll coat, a bar coat, a knife coat, an air knife coat, a curtain coat, a lip coat, Various methods, such as a die coater, are used.

This polymerization is performed by irradiating actinic light to the adhesive composition apply | coated in layers on the base material. In this polymerization, the unreacted monomer component and urethane (meth) acrylate in a prepolymer composition react, and the base polymer in which the crosslinked structure by the urethane type segment was introduce | transduced into the acrylic polymer chain is obtained.

What is necessary is just to select an active light according to the kind of polymerizable components, such as a monomer and a urethane (meth) acrylate, the kind of a photoinitiator, etc., and generally, ultraviolet-ray and / or short wavelength visible light are used. As for accumulated light quantity of irradiation light, about 100-5000mJ / cm <2> is preferable. The light source for light irradiation is not particularly limited as long as the photopolymerization initiator included in the pressure-sensitive adhesive composition can irradiate light in a wavelength range having sensitivity, and it is not limited to an LED light source, a high pressure mercury lamp, an ultra high pressure mercury lamp, a metal halide lamp, and a xenon lamp. Etc. are used preferably. 97% or more is preferable, as for the polymerization rate of the adhesive sheet after this superposition | polymerization, 98% or more is more preferable, and 99% or more is more preferable. In order to increase the polymerization rate, the pressure-sensitive adhesive sheet after photocuring may be heated to volatilize a remaining monomer, an unreacted polymerization initiator, or the like.

By bonding the release films 1 and 2 to the surface of the adhesive sheet 5, as shown in FIG. 1, the adhesive sheet which the release film adhered to on both surfaces is obtained. You may use the release film used as a base material and a cover sheet at the time of formation of an adhesive sheet as a release film 1 and 2 as it is.

When the release films 1 and 2 are provided on both surfaces of the adhesive sheet 5, the thickness of one release film 1 and the thickness of the other release film 2 may be same or different. The peeling force at the time of peeling the release film adhering to one side from the adhesive sheet 5 and the peeling force at the time of peeling the release film adhering to the other surface from the adhesive sheet 5 differ, even if it is the same. You may also When the peeling force of both is different, the release film 2 (light peeling film) with relatively small peeling force is peeled from the adhesive sheet 5 first, and it bonds with a 1st adherend, and peeling force is relatively The workability at the time of peeling the large mold release film 1 (heavy peeling film) and bonding with a 2nd to-be-adhered body is excellent.

[Image display device]

The adhesive sheet of this invention can be used for joining various transparent members and an opaque member. The kind of adherend is not specifically limited, Various resin materials, glass, a metal, etc. are mentioned. Since the adhesive sheet of this invention is high in transparency, it is suitable for joining of optical members, such as an image display apparatus. In particular, since the adhesive sheet of this invention is excellent in the durability and impact resistance of adhesion | attachment, it is used suitably for joining of transparent members, such as a front transparent plate and a touch panel, to the visual side of an image display apparatus.

FIG. 2: is sectional drawing which shows the example of laminated structure of the image display apparatus by which the front transparent plate 7 was bonded by the adhesive sheet 5 to the visual recognition side surface of the image display panel 10. As shown in FIG. The image display panel 10 is provided with the polarizing plate 3 bonded by the adhesive sheet 4 to the visual recognition side surface of image display cells 6, such as a liquid crystal cell and an organic electroluminescent cell. The front transparent plate 7 may have a step formed by the printing layer 76 or the like on the periphery of one surface of the transparent flat plate 71. As the transparent plate 71, for example, a transparent resin plate such as acrylic resin or polycarbonate resin, a glass plate, or the like is used. The transparent plate 71 may have a touch panel function. As a touch panel, the touch panel of arbitrary systems, such as a resistive film system, a capacitive system, an optical system, and an ultrasonic system, is used.

The polarizing plate 3 provided on the surface of the image display panel 10 and the front transparent plate 7 are bonded through the adhesive sheet 5. The bonding order is not specifically limited, The bonding of the adhesive sheet 5 to the image display panel 10 may be performed first, and the bonding sheet 5 to the front transparent plate 7 may be performed first. . In addition, the joining of both can also be performed simultaneously. After peeling one release film (hard peeling film) 2 from a viewpoint of workability of bonding, etc., after bonding the exposed surface of the adhesive sheet 5 to the image display panel 10, It is preferable that the release film 1 (heavy peeling film) is peeled off, and the exposed surface of the adhesive sheet is bonded to the front transparent plate 7.

After the adhesive sheet 5 and the front transparent plate 7 are bonded together, non-flat portions such as the interface between the flat plate 71 portion of the adhesive sheet 5 and the front transparent plate 7 and the printing layer 76 are formed. Defoaming may be performed to remove nearby bubbles. As a defoaming method, the appropriate method, such as heating, pressurization, and pressure reduction, can be employ | adopted. For example, bonding may be performed while suppressing mixing of bubbles under reduced pressure and heating, and then pressurization may be performed simultaneously with heating by an autoclave process or the like for the purpose of suppressing delay bubbles or the like. When defoaming is performed by heating, heating temperature is generally about 40-150 degreeC. When pressurization is performed, the pressure is generally about 0.05 MPa to 2 MPa.

In the case where the gap 90 exists between the housing 9 and the front transparent plate 7, it is preferable to fill the gap 90 with a resin material or the like to seal the gap. As described above, the pressure sensitive adhesive sheet 5 is excellent in adhesive reliability in a wide temperature range because of its large shear storage modulus. Therefore, even when stress deformation occurs in the bonding interface of the pressure sensitive adhesive sheet due to the temperature change at the time of sealing by the resin material or the like, peeling at the bonding interface can be suppressed. In addition, since the adhesive sheet 5 has a low glass transition temperature and a large peak top value of tan δ, the adhesive sheet 5 is excellent in impact resistance over a wide temperature range, and peeling due to impact such as falling is unlikely to occur.

[Optical Film with Adhesive Sheet]

As shown in FIG. 1, the adhesive sheet of this invention can also be used as a film with an adhesive by which the adhesive sheet was fixed to an optical film etc. in addition to the form which the release film adhered to on both surfaces. For example, in the form shown in FIG. 3, the release film 1 is attached to one surface of the adhesive sheet 5, and the polarizing plate 3 is fixed to the other surface of the adhesive sheet 5. . In the form shown in FIG. 4, the adhesive sheet 4 is further formed on the polarizing plate 3, and the release film 2 is attached thereto.

Thus, in the form in which optical films, such as a polarizing plate, were previously bonded to the adhesive sheet, the release film 1 adhering to the surface of the adhesive sheet 5 may be peeled off, and bonding with the front transparent member may be performed.

EXAMPLE

Although an Example and a comparative example are given to the following and this invention is demonstrated in detail, this invention is not limited to these Examples.

[Production of Acrylic Oligomer]

60 parts by weight of dicyclopentanyl methacrylate (DCPMA), 40 parts by weight of methyl methacrylate (MMA), 3.5 parts by weight of α-thioglycerol as a chain transfer agent, and 100 parts by weight of toluene as a polymerization solvent, were mixed at 70 ° C. under a nitrogen atmosphere. Stirred for 1 hour. Next, 0.2 part by weight of 2,2'-azobisisobutyronitrile (AIBN) was added as a thermal polymerization initiator, and after reacting at 70 ° C for 2 hours, the temperature was raised to 80 ° C and allowed to react for 2 hours. Then, the reaction liquid was heated to 130 degreeC, the toluene, the chain transfer agent, and the unreacted monomer were removed and dried, and the solid acrylic oligomer was obtained. The weight average molecular weight of the acrylic oligomer was 5100.

Example 1

(Polymerization of Prepolymer)

As the monomer component for forming the prepolymer, 52.8 parts by weight of butyl acrylate (BA), 10.9 parts by weight of cyclohexyl acrylate (CHA), 9.7 parts by weight of N-vinyl-2-pyrrolidone (NVP), 4-hydroxybutyl acrylate (4HBA) ) 14.8 parts by weight, and 11.8 parts by weight of isostearyl acrylate (ISTA), and a photopolymerization initiator (&quot; irgacure 184 &quot; made by BASF: 0.035 part by weight and 0.035 parts by weight &quot; irgacure 651 &quot; Ultraviolet was irradiated and superposed | polymerized until the viscosity (BH viscometer No. 5 rotor, 10 rpm, measurement temperature 30 degreeC) became about 20 Pa.s, and the prepolymer composition (polymerization rate; about 9%) was obtained.

(Preparation of photocurable adhesive composition)

As said urethane (meth) acrylate, said prepolymer composition is terminal acrylic modified polyether urethane (Nippon Kosei Chemical Co., Ltd. "UV-3300B"): 7 weight part, and terminal acrylic modified polyester urethane (Nippon Kosei Chemical Co., Ltd.) High school agent "UV-3010B"): 3 weight part, said acrylic oligomer: 5 weight part, As a photoinitiator, Irgacure 184: 0.05 weight part and Irgacure 651: 0.57 weight part, As a chain transfer agent, (alpha)- Methyl styrene dimer (Nichi Oil "Nofmer MSD"): 0.1 weight part, and 0.3 weight part of "KBM403" by Shin-Etsu Chemical Co., Ltd. as a silane coupling agent were added, these were mixed uniformly, and the adhesive composition was prepared.

(Production of the adhesion sheet)

The above photocurable pressure-sensitive adhesive composition is formed on a substrate by using a 75 μm-thick polyethylene terephthalate (PET) film (“Diafoyl MRF75” manufactured by Mitsubishi Chemical) having a silicon-based release layer formed on the surface thereof as a substrate (and a heavy peeling film). It applied so that it might become 150 micrometers, and the application layer was formed. A 75-micrometer-thick PET film ("Diafoyl MRE75" made by Mitsubishi Chemical Corporation) with one side | surface peeled by silicon peeling process was bonded as this cover layer (curable peeling film) on this application layer. The laminated body was irradiated with ultraviolet rays with a black light positioned so that the irradiation intensity on the irradiation surface immediately below the lamp was 5 kW / cm 2 from the cover sheet side, thereby photocuring, and having a thickness of 150 µm and polymerization. An adhesive sheet having a rate of 99% was obtained.

[Examples 2 to 5 and Comparative Examples 1 to 8]

The kind and addition amount of the input monomer composition in superposition | polymerization of a prepolymer, and the polyfunctional compound (urethane acrylate and / or polyfunctional acrylate), an acryl oligomer, a photoinitiator, and a chain transfer agent added to an adhesive composition are shown in Table 1. Changed as well. Other than that was carried out similarly to Example 1, the photocurable adhesive composition was prepared, the coating onto the base material, and the photocuring were performed, and the adhesive sheet was obtained.

[evaluation]

<Weight average molecular weight>

The weight average molecular weight (Mw) of an acryl oligomer and urethane (meth) acrylate was measured by the GPC (gel permeation chromatography) apparatus (product name "HLC-8120GPC") of a plasticizer. As the measurement sample, a filtrate obtained by dissolving the base polymer in tetrahydrofuran to form a 0.1% by weight solution was filtered with a 0.45 μm membrane filter. The measurement conditions of GPC are as follows.

(Measuring conditions)

Column: Tosoh Corporation, G7000HXL + GMHXL + GMHXL

Column Size: Each 7.8mmφ × 30cm (Total Column Length: 90cm)

Column temperature: 40 ° C, flow rate: 0.8 mL / min

Injection volume: 100μL

Eluent: tetrahydrofuran

Detector: Differential Refractometer (RI)

Standard sample: polystyrene

<Storage Modulus, Glass Transition Temperature and Tanδ Peak Value of Adhesive Sheet>

The adhesive sheet was laminated | stacked 10 sheets, and it was set as thickness about 1.5 mm as a sample for a measurement. The dynamic viscoelasticity measurement was performed on condition of the following conditions using "Advanced Rheometric Expansion System (ARES)" by Rheometric Scientific.

(Measuring conditions)

Deformation mode: torsion

Measuring frequency: 1 Hz

Temperature rise rate: 5 ℃ / min

Shape: Parallel Plate 7.9㎜φ

The shear storage modulus was determined by reading the storage modulus G 'at each temperature from the measurement results. The temperature (peak top temperature) which the loss tangent (tan-delta) becomes the maximum was made into the glass transition temperature of an adhesive sheet. Moreover, the value (peak top value) of tan-delta in glass transition temperature was read.

<Adhesive force>

After peeling a light peeling film from an adhesive sheet, bonding a 50-micrometer-thick PET film, cutting it to width 10mm x length 100mm, peeling a heavy peeling film, crimping | bonding to a glass plate with a 5 kg roller, and measuring adhesive force A sample was prepared. After holding the sample for measuring the adhesive force for 30 minutes in an environment of 25 ° C. or 65 ° C., using a tensile tester, the test piece was peeled from the glass plate under a condition of a tensile speed of 300 mm / min and a peel angle of 180 ° to remove the peel force. Measured.

<Haze>

Haze using a haze meter ("HM-150" manufactured by Murakami Shikisai Kijutsu Genkyujo Co., Ltd.) using a test piece bonded to an adhesive sheet with an alkali-free glass (92% of total light transmittance and 0.4% of haze) having a thickness of 800 µm. Was measured. The value which removed the haze (0.4%) of the alkali free glass from the measured value was made into the haze of the adhesive sheet.

<Interlayer Adhesiveness>

(Production of test sample)

The pressure-sensitive adhesive sheet is cut out to a size of 75 mm x 45 mm, the light peeling film is peeled from the pressure-sensitive adhesive sheet, and a roll laminator (inter-roll pressure: 0.2 MPa, conveying speed) is placed at the center of the glass plate (100 mm x 50 mm) having a thickness of 500 µm. : 100 mm / min). Thereafter, the heavy peeling film was peeled off, and a glass plate (50 mm × 100 mm) having a thickness of 500 μm, in which black ink having a thickness of 30 μm was printed in a frame shape on the periphery, was subjected to vacuum compression (surface pressure of 0.3 MPa, pressure of 100 kPa). By bonding. In the ink printing area | region of a glass plate, the short side direction was 5 mm from both ends, and the long side direction was 15 mm from both ends, and the black ink layer was in contact with the area | region of 5 mm from the edge of the four sides of an adhesive sheet. This sample was processed by autoclave (50 degreeC, 0.5 Mpa) for 30 minutes.

After holding the said sample for 30 minutes in 60 degreeC environment, as shown to FIG. 5A, the polystyrene sheet of thickness 200micrometer was inserted between two glass plates to the distance of 1 mm from the edge part of an adhesive sheet, Hold for 10 seconds. The edge part of the adhesive sheet was observed with the digital microscope of 20 times magnification. It was set as OK that neither NG, bubble, and peeling generate | occur | produced that peeling of the stripe-shaped bubble (refer FIG. 5B) or the adhesive sheet from a glass plate occurred.

<Impact resistance>

Except having changed the size of the glass plate in which the printing layer of a black ink is not formed into 100 mm x 70 mm, the glass plate is bonded to both surfaces of an adhesive sheet similarly to the sample preparation for said interlayer adhesion test, and an autoclave is carried out. The test sample was produced. As shown in FIG. 6, the both ends of the short side direction of the test sample 95 are arrange | positioned at intervals of 60 mm so that the glass plate 7 in which the printing layer 76 was formed may be lower side, on the die 93 arrange | positioned. The upper surface of the end of the glass plate 5 in which the printing layer was not formed was fixed to the die 80 with an adhesive tape (not shown). After holding the test sample 95 fixed on the die 93 with an adhesive tape for 24 hours in an environment of −5 ° C., taking out at room temperature within 40 seconds, a metal sphere 97 having a mass of 11 g on the glass plate 7 was obtained. Was dropped from a height of 300 mm to perform an impact resistance test.

In the impact resistance test, in order to make the dropping position of the metal sphere constant, a normal guide 99 is used, and each of the short side direction and the long side direction is 10 from the corner of the inner edge of the frame of the print area of the print layer 76. The metal sphere 97 was dropped to the position spaced mm. Two tests were performed and it was OK that peeling of a glass plate did not generate | occur | produce in either test, and made into NG that peeling of a glass plate occurred in either or both of two times.

[Evaluation results]

Table 1 shows the results of the formulation of the pressure-sensitive adhesive composition used for the production of each pressure-sensitive adhesive sheet and the pressure-sensitive adhesive sheet. In addition, in Table 1, each component is described by the following abbreviations.

<Acrylic monomer>

BA: Butyl acrylate

2HEA: 2-ethylhexyl acrylate

CHA: Cyclohexyl acrylate

NVP: N-vinyl-2-pyrrolidone

4HBA: 4-hydroxybutyl acrylate

2HEA: 2-hydroxyethyl acrylate

ISTA: isostearyl acrylate

<Urethane acrylate>

UV-3300B: Nippon Kosei Chemical Co., Ltd. "UV-3300B" (weight average molecular weight approximately 12000, polyetherurethane diacrylate of glass transition temperature -30 degrees Celsius)

3400: polyetherurethane diacrylate having a weight average molecular weight of about 3400)

Shinakamura Kagaku Kogyo Co., Ltd. "UA-4200" (polyetherurethane diacrylate of weight average molecular weight approximately 1000)

UN-350: Negami high school `` artresin UN-350 '' (weight average molecular weight approximately 12500, polyester urethane diacrylate of glass transition temperature -57 degrees Celsius)

UV-3010B: Nippon Kosei Chemical Co., Ltd. "UV-3010B" (polyester urethane diacrylate of weight average molecular weight approximately 18000)

Urethane monoacrylate: polyether urethane monoacrylate with a weight average molecular weight of about 1300)

<Polyfunctional acrylate>

HDDA: Hexanediol diacrylate

<Photoinitiator>

Irg651: irgacure651 (2,2-dimethoxy-1,2-diphenylethan-1-one)

Irg184: Irgacure 184 (1-hydroxycyclohexyl-phenyl-ketone)

In Examples 1 and 2 using the adhesive composition which added urethane diacrylate to the prepolymer composition obtained by the prepolymerization of the acryl-type monomer which has butyl acrylate as a main monomer, both interlayer adhesiveness and drop impact durability were favorable.

In Comparative Example 1 using a low molecular weight urethane diacrylate, the adhesive force to the adherend of the pressure-sensitive adhesive sheet was small, resulting in poor interlayer adhesion and drop impact durability. In the comparative example 2 which increased the addition amount of urethane diacrylate, the haze of the adhesive sheet was high and transparency fell. In the comparative example 3 which used urethane monoacrylate, the shear storage elastic modulus of an adhesive sheet was low, and adhesive durability fell.

Also in Example 3, Example 4, and Example 5 which changed the composition of the acryl-type monomer in the composition for prepolymer formation, it showed the favorable adhesive characteristic similarly to Example 1, 2.

Without the use of a urethane-based material, in the comparison that lower the glass transition temperature by adjusting the composition of the acrylic monomer of Example 4, the smaller the G _{'25 ℃} and G' _{80 ℃} of the adhesive sheet, the adhesion reliability declined. In Comparative Example 5 in which the cohesiveness was increased by increasing the ratio of the polar monomers (NVB and 4HBA) in the acrylic monomer component, the adhesion was good, but the impact resistance was lowered because the glass transition temperature was high. Also in Comparative Example 8, the same tendency was observed.

In the comparative example 6 which raised the ratio of the polyfunctional acrylate in an adhesive composition, since the peak top value of tan-delta was small and viscosity was low, adhesive force became inadequate and impact resistance also fell. The same tendency was observed in Comparative Example 7 in which a crosslinked structure was introduced by a low molecular weight urethane diacrylate. In these comparative examples, tan δ is compared to Examples 1 to 5 and the like in which the main monomer of the acrylic polymer chain is C ₈ alkyl ester (2-hydroxyethyl acrylate) or the main monomer is C ₄ alkyl ester (butyl acrylate). Is thought to be one of the small factors.

From these results, the adhesive sheet containing the base polymer which introduce | transduced the crosslinked structure into the acrylic polymer chain using the urethane diacrylate which has a predetermined molecular weight shows high shear storage elastic modulus even at low glass transition temperature, and tan-delta is large Therefore, it turns out that adhesive durability and impact resistance are compatible.

5: adhesive sheet
1, 2: release film
3: polarizer
4: adhesive sheet
6: image display cell
10: image display panel
7: front transparent plate
9: housing
100: image display device

Claims (10)

An adhesive sheet is an adhesive sheet formed in the sheet form,
Haze is 1% or less,
Adhesion to glass is at least 2.0N / 10 mm,
The glass transition temperature is below -3 ° C,
The adhesive sheet whose shear storage modulus in temperature 25 degreeC is 0.16 Mpa or more. The method of claim 1,
The adhesive sheet whose peak top value of a loss tangent is 1.5 or more. The method according to claim 1 or 2,
The pressure-sensitive adhesive contains a base polymer, the acrylic polymer chain is crosslinked by the urethane-based segment,
The said base polymer is the adhesive sheet whose content of a urethane type segment with respect to 100 weight part of said acrylic polymer chains is 3-30 weight part. The method of claim 3,
The adhesive sheet whose weight average molecular weights of the said urethane type segments are 4000-50000. The method of claim 3,
The base polymer has a crosslinked structure of the urethane-based segment in the acrylic polymer chain by copolymerization of a monomer component constituting the acrylic polymer chain and a urethane (meth) acrylate having a (meth) acryloyl group at its terminal. The adhesive sheet introduced. It is a manufacturing method of the adhesive sheet of Claim 1,
A method for producing a pressure-sensitive adhesive sheet, wherein the composition comprising an acrylic monomer and / or a partial polymer thereof and a urethane di (meth) acrylate are applied in a layered manner on a substrate, followed by irradiating active light to the composition. The method of claim 6,
The said composition is a manufacturing method of the adhesive sheet whose content of the urethane (meth) acrylate with respect to a total of 100 weight part of the said acryl-type monomer and its partial polymer is 3-30 weight part. The method according to claim 6 or 7,
The weight average molecular weight of the said urethane di (meth) acrylate is a manufacturing method of the adhesive sheet which is 4000-50000. The method according to claim 6 or 7,
The glass transition temperature of the said urethane (meth) acrylate is a manufacturing method of the adhesive sheet which is 0 degrees C or less. The image display apparatus by which the front transparent member is adhered to the visual recognition side surface of an image display panel by the adhesive sheet in any one of Claims 1-5.

Images