WO2016093133A1

WO2016093133A1 - Shock absorbing sheet, shock absorbing adhesive sheet, double-sided shock absorbing adhesive sheet for affixing front plate, double-sided shock absorbing adhesive sheet for affixing back plate, and double-sided shock absorbing adhesive sheet for affixing backlight unit

Info

Publication number: WO2016093133A1
Application number: PCT/JP2015/083951
Authority: WO
Inventors: 勇樹岩井; 洋祐中尾; 徳之内田
Original assignee: 積水化学工業株式会社
Priority date: 2014-12-10
Filing date: 2015-12-03
Publication date: 2016-06-16
Also published as: CN106471276A; KR20170094114A; JP2020073817A; CN106471276B; JP6632379B2; JPWO2016093133A1

Abstract

The present invention provides a shock absorbing sheet having excellent shock resistance, which is suitable for use as a base for an adhesive sheet for bonding and affixing a component that constitutes a portable electronic device to the device main body. In addition, one purpose of the present invention is to provide: a shock absorbing adhesive sheet which comprises this shock absorbing sheet; a double-sided shock absorbing adhesive sheet for affixing a front plate; a double-sided shock absorbing adhesive sheet for affixing a back plate; and a double-sided shock absorbing adhesive sheet for affixing a backlight unit. The present invention is a shock absorbing sheet which has at least one shock absorbing layer having a maximum value of the loss tangent tan δ of 0.84 or more at a frequency of from 1.0 × 10⁴ to 1.0 × 10^6.5 Hz at 23°C.

Description

Shock-absorbing sheet, shock-absorbing pressure-sensitive adhesive sheet, shock-absorbing double-sided pressure-sensitive adhesive sheet for fixing the front plate, shock-absorbing double-sided pressure-sensitive adhesive sheet for fixing the back plate, and shock-absorbing double-sided pressure-sensitive adhesive sheet for fixing the backlight unit

The present invention relates to an impact-absorbing sheet excellent in impact resistance, which is suitably used as a base material for a pressure-sensitive adhesive sheet that adheres and fixes a component constituting a portable electronic device to a device body. The present invention also relates to a shock-absorbing pressure-sensitive adhesive sheet having the shock-absorbing sheet, a shock-absorbing double-sided pressure-sensitive adhesive sheet for fixing a front plate, a shock-absorbing double-sided pressure-sensitive adhesive sheet for fixing a back plate, and a shock-absorbing double-sided pressure-sensitive adhesive sheet for fixing a backlight unit. .

In a portable electronic device (for example, a mobile phone, a portable information terminal, etc.) equipped with an image display device or an input device, an adhesive tape is used for assembly. Specifically, for example, a front panel (cover panel) for protecting the surface of a portable electronic device is bonded to a touch panel module or a display panel module, or an adhesive is used to bond a touch panel module and a display panel module. Tape is used. Such an adhesive tape is used by being punched into a frame shape or the like and arranged around the display screen (for example, Patent Documents 1 and 2).

Adhesive tapes used in portable electronic devices are required to have various performances including high adhesive strength. For example, even if an impact is applied, the tape does not peel off, and the component has a strong impact. There is also a need for impact resistance that does not add.
As a method for improving the impact resistance of the pressure-sensitive adhesive tape, for example, a method using a buffering base material such as a foamed material can be mentioned. Patent Document 3 describes a pressure-sensitive adhesive sheet for electronic equipment comprising a cross-linked polyolefin resin foam sheet and a specific acrylic pressure-sensitive adhesive layer laminated and integrated on one surface of the cross-linked polyolefin resin foam sheet.

In recent years, with the enlargement of screens of portable electronic devices, the size of adhesive tapes has been increasing. Further, since the adhesive tape is used in a shape such as a frame shape, the width of the adhesive tape is also being reduced. For this reason, in the adhesive sheet which uses a foam as a base material like the patent document 3, when the impact of dropping etc. is added, the malfunction which an adhesive tape peels easily arises.

JP 2011-081213 A JP 2003-337656 A JP 2011-168727 A

An object of the present invention is to provide an impact-absorbing sheet excellent in impact resistance, which is suitably used as a base material for a pressure-sensitive adhesive sheet for bonding and fixing a component constituting a portable electronic device to a device body. The present invention also provides an impact-absorbing adhesive sheet having the impact-absorbing sheet, a shock-absorbing double-sided adhesive sheet for fixing a front plate, a shock-absorbing double-sided adhesive sheet for fixing a back plate, and a shock-absorbing double-sided adhesive sheet for fixing a backlight unit. The purpose is to provide.

The present invention provides an impact absorbing layer having at least one impact absorbing layer having a maximum value of the loss tangent tan δ of 0.84 or more at a frequency of 1.0 × 10 ⁴ to 1.0 × 10 ^6.5 Hz at 23 ° C. It is a sheet.
The present invention is described in detail below.

In the pressure-sensitive adhesive sheet based on a foam as described in Patent Document 3, examples of a method for improving the impact resistance of the foam include a method of decreasing the foaming ratio of the foam and increasing the density. However, it is technically difficult to lower the foaming ratio below a certain value, and if the foaming ratio is excessively lowered, it approaches a non-foamed body, the flexibility is impaired, and the impact resistance is lowered. For this reason, in the pressure-sensitive adhesive sheet based on the conventional foam as described in Patent Document 3, excellent impact resistance is achieved in a pressure-sensitive adhesive tape whose width has been reduced (for example, a width of 1.0 mm or less). It is difficult.
The inventor shall have an impact-absorbing layer in which the maximum value of the loss tangent tan δ at a specific frequency at 23 ° C. is adjusted to a specific value or more as an impact-absorbing sheet suitably used as a base material for an adhesive sheet. Thus, even when a shock such as a drop is applied to the shock absorbing sheet, the energy by the shock is effectively dissipated as heat or by deformation, and the peeling is suppressed, and the present invention has been completed. .

The shock absorbing sheet of the present invention has at least one shock absorbing layer having a maximum loss tangent tan δ of 0.84 or more at a frequency of 1.0 × 10 ⁴ to 1.0 × 10 ^6.5 Hz at 23 ° C. Have more.
By providing the shock absorbing sheet of the present invention with the above shock absorbing layer, even when a shock such as dropping is applied to the shock absorbing sheet, the energy due to the shock is effectively dissipated as heat or due to deformation. , Peeling is suppressed. The maximum value of the loss tangent tan δ is preferably 1.31 or more, more preferably 1.50 or more, still more preferably 1.80 or more, and particularly preferably 2.00 or more.

The upper limit of the maximum value of the loss tangent tan δ is not particularly limited. However, if there are many viscous components in the shock absorbing layer and the maximum value of the loss tangent tan δ is too large, the shock absorbing layer plastically deforms when absorbing the shock. Since it becomes easy, a preferable upper limit is 3.0 and a more preferable upper limit is 2.7.

Note that the maximum value of the loss tangent tan δ at a frequency of 1.0 × 10 ⁴ to 1.0 × 10 ^6.5 Hz at 23 ° C. is a dynamic viscoelasticity measuring device (for example, Rhegel-E4000 manufactured by UBM). Can be determined by measuring the elastic modulus of the shock absorbing layer and synthesizing a master curve. At this time, the “maximum value” of the loss tangent tan δ does not necessarily have to exist within the frequency range of 1.0 × 10 ⁴ to 1.0 × 10 ^6.5 Hz. However, when the “maximum value” is present in the frequency range of 1.0 × 10 ⁴ to 1.0 × 10 ^6.5 Hz, an impact is applied to the shock absorbing sheet at a temperature higher or lower than 23 ° C. Even so, the impact-absorbing sheet can easily absorb the impact stably.
Here, the frequency of 1.0 × 10 ⁴ to 1.0 × 10 ^6.5 Hz means that the object is freely dropped from a height of several tens of centimeters to one tens of centimeters with respect to the shock absorbing sheet. When the shock absorbing sheet is displaced from several micrometers to several tens of micrometers, the frequency is assumed (that is, the frequency when a shock such as dropping is applied to the portable electronic device).

In order to adjust the maximum value of the loss tangent tan δ within the above range, the composition of the shock absorbing layer may be adjusted within the range described later, and among these, the shock absorbing layer preferably contains an elastomer.

The impact-absorbing layer is not particularly limited and may be a foam such as a crosslinked polyolefin foam. In order to adjust the maximum value of the loss tangent tan δ to the above range, a non-foam containing an elastomer or the like. Is preferred.
Examples of the elastomer include styrene elastomers, acrylic elastomers, urethane elastomers, ester elastomers, olefin elastomers, vinyl chloride elastomers, amide elastomers, and the like. These elastomers may be used alone or in combination of two or more. In particular, in order to adjust the maximum value of the loss tangent tan δ within the above range, the elastomer is preferably a styrene elastomer, an olefin elastomer, an acrylic elastomer, or a urethane elastomer, and is a styrene elastomer. Is more preferable.

The styrenic elastomer is not particularly limited as long as it has rubber elasticity at room temperature. However, a polystyrene layer called a hard segment and a soft segment such as ethylene-butylene, ethylene-propylene, and ethylene-butadiene are used. Styrenic elastomers having a diblock or triblock structure are more preferred.
Specific examples of the styrenic elastomer include styrene-butadiene-styrene (SBS) block copolymer, styrene-butadiene-butylene-styrene (SBBS) block copolymer, styrene-ethylene-butylene-styrene (SEBS) block copolymer, water Examples thereof include styrene-butylene rubber (HSBR), styrene-ethylene-propylene-styrene (SEPS) block copolymer, styrene-isobutylene-styrene (SIBS) block copolymer, and styrene-isoprene-styrene (SIS) block copolymer. Among these, SEBS and SEPS are more preferable because they do not have a double bond in the molecular structure and are relatively stable to heat and light.

The styrene content of the styrenic elastomer is not particularly limited, but a preferred lower limit is 3% by weight and a preferred upper limit is 30% by weight. When the styrene content is less than 3% by weight, the heat resistance or cohesion of the shock absorbing layer may be lowered. When the styrene content exceeds 30% by weight, the flexibility of the styrene-based elastomer is impaired, the maximum value of the loss tangent tan δ is lowered, and the impact resistance of the shock absorbing sheet may be lowered. A more preferable lower limit of the styrene content is 4% by weight, and a more preferable upper limit is 25% by weight, a still more preferable lower limit is 5% by weight, and a still more preferable upper limit is 20% by weight.
The content of each block such as styrene in the styrene elastomer can be measured by ¹ H-NMR (1H-nuclear magnetic resonance) measurement or ¹³ C-NMR.

The content of the ethylene skeleton in the soft segment of the styrene-based elastomer is not particularly limited, but a preferable upper limit in 100% by weight of the entire soft segment is 60% by weight. When the content of the ethylene skeleton exceeds 60% by weight, crystallization of the styrene-based elastomer proceeds and flexibility is impaired, so that the maximum value of the loss tangent tan δ is reduced, and the impact resistance of the shock absorbing sheet is reduced. May decrease. A more preferable upper limit of the content of the ethylene skeleton is 50% by weight, and a more preferable upper limit is 40% by weight.
In particular, when the styrene elastomer is SEBS or HSBR, the content of the ethylene skeleton in the soft segment is preferably in the above range. Further, when the styrene elastomer is SEBS or HSBR, the content of the ethylene skeleton in the soft segment is preferably 3% by weight or more, more preferably 4% by weight or more, and more preferably 5% by weight or more. More preferably. When the styrene-based elastomer is SEBS or HSBR and the ethylene skeleton content is 3% by weight or more, the shock absorbing layer has an appropriate glass transition temperature, so the maximum value of the loss tangent tan δ is Easy to adjust to the range. In addition, since the butylene skeleton of SEBS has a large steric hindrance and a structure that easily inhibits crystallization, the value of tan δ is increased and it is easy to exhibit shock absorption. Therefore, the content of the butylene skeleton in the soft segment when the styrene-based elastomer is SEBS is not particularly limited, but is preferably 45% by weight or more. By setting the content of the butylene skeleton to 45% by weight or more, excellent impact resistance can be exhibited. The content of the butylene skeleton is more preferably 60% by weight or more, and further preferably 70% by weight or more.
SEPS is less likely to be crystallized because three or more ethylene skeletons are not continuously connected, and since the propylene skeleton is bulky, the value of tan δ is high, and shock absorption is likely to occur.
Similar to the ethylene skeleton, the 1,4-butadiene skeleton that SBBS has in the soft segment can be easily crystallized, and the flexibility may be impaired. As a result, the maximum value of tan δ is lowered and impact resistance is lowered. Sometimes. Therefore, the total content of ethylene and 1,4-butadiene in the SBBS soft segment is preferably 60% by weight or less, more preferably 50% by weight or less, and further preferably 40% by weight or less. preferable.
Since the isobutylene skeleton contained in SIBS or the like is difficult to crystallize, tan δ can be controlled to be high, but since the frequency of the peak value of tan δ may be outside the specified range, the ethylene skeleton is included in the soft segment. More preferably, the tan δ peak position is adjusted.

Examples of the olefin elastomer include a polymer alloy in which an olefin rubber (eg, EPR, EPDM) is finely dispersed in a matrix of an olefin resin (eg, PP, PE), an olefin crystal-ethylene-butylene-olefin crystal (CEBC). ) Block polymer, styrene-ethylene-butylene-olefin crystal (SEBC) block polymer, and the like. Since the cross-linked olefin elastomer is difficult to exhibit flexibility, a non-cross-linked olefin elastomer is preferable.

Examples of the acrylic elastomer include a block copolymer of methyl methacrylate (MMA) and butyl acrylate (BA).
The content of the methyl methacrylate (MMA) -derived component in the block copolymer of methyl methacrylate (MMA) and butyl acrylate (BA) is not particularly limited, but the preferred lower limit is 1% by weight and the preferred upper limit is 50%. %. When the content of the methyl methacrylate (MMA) -derived component is less than 1% by weight, the heat resistance or cohesive force of the shock absorbing layer may be lowered, and the shock resistance of the shock absorbing sheet may be lowered. When the content of the methyl methacrylate (MMA) -derived component exceeds 50% by weight, the flexibility of the block copolymer is impaired, and the maximum value of the loss tangent tan δ is lowered, and the impact resistance of the shock absorbing sheet. May decrease. The minimum with more preferable content of the said methyl methacrylate (MMA) origin component is 3 weight%, and a more preferable upper limit is 30 weight%.

In addition, the block copolymer of methyl methacrylate (MMA) and butyl acrylate (BA) may be copolymerized with other copolymerizable acrylic monomers.
Other polymerizable acrylic monomers that can be copolymerized include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-propyl (meth) acrylate, (meth) Alkyl groups such as butyl acrylate and isopropyl (meth) acrylate having 1 to 16 carbon atoms and alkyl groups such as (meth) acrylic acid alkyl ester, tridecyl methacrylate and stearyl (meth) acrylate having 13 to 16 carbon atoms. 18 (meth) acrylic acid alkyl esters, hydroxyalkyl (meth) acrylate, glycerin dimethacrylate, glycidyl (meth) acrylate, 2-methacryloyloxyethyl isocyanate, (meth) acrylic acid, itaconic acid, maleic anhydride, croton Functional mono-acid such as acid, maleic acid, fumaric acid Chromatography, and the like.

Examples of commercially available acrylic elastomers include Clarity LA2330 (manufactured by Kuraray Co., Ltd.).

There are two types of urethane-based elastomers: an incomplete thermoplastic type having partial cross-linking in the molecule, and a complete thermoplastic type that is a completely linear polymer. The incomplete thermoplastic urethane type elastomer is excellent in heat resistance, chemical resistance, mechanical strength and the like.
Examples of the urethane elastomer include, for example, (1) a caprolactone type obtained by addition polymerization of a polysocyanate in the presence of a short-chain polyol to a polylactone ester polyol obtained by ring-opening caprolactone, and (2) adipic acid. An adipic acid type polyol (adipate type) and other ester-based urethane elastomers obtained by addition polymerization of polysocyanates in the presence of short-chain polyols with adipic acid ester polyols with glycols, and (3) obtained by ring-opening polymerization of tetrahydrofuran Examples thereof include PTMG type (ether type) urethane elastomer obtained by addition polymerization of polysocyanate to polytetramethylene glycol (PTMG) in the presence of a short-chain polyol.

Examples of commercially available ester-based urethane elastomers include Elastollan NY585 (manufactured by BASF).
Examples of commercially available PTMG type (ether type) urethane elastomers include Elastollan NY90A (manufactured by BASF), Elastollan NY97A (manufactured by BASF), and the like.

The impact absorbing layer may contain a tackifier resin. By blending a tackifying resin into the impact absorbing layer, the maximum value of the loss tangent tan δ can be easily adjusted to the above range.
The tackifying resin is not particularly limited, and examples thereof include a terpene resin, a rosin resin, and a petroleum resin.

The impact absorbing layer may contain a softening agent because of improved flexibility.
The softener is not particularly limited, and examples thereof include petroleum softeners, liquid rubber softeners, dibasic acid esters, plant softeners, and oil softeners. Examples of the petroleum softener include Fukkorflex 2050N (Fuji Kosan) and Diana Process Oil PW90 (Idemitsu Kosan).

The impact absorbing layer may contain an antioxidant or an ultraviolet absorber because weather resistance is improved.
The antioxidant or ultraviolet absorber is not particularly limited, and examples thereof include phenol-based, amine-based, and benzimidazole-based antioxidants and ultraviolet absorbers. Examples of the phenolic antioxidant include NOCRACK NS-6 (manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.). Examples of the ultraviolet absorber include SEESORB 101 (manufactured by Cypro Corporation).

The shock absorbing layer is preferably colored. By coloring the shock absorbing layer, the light of the liquid crystal display panel incorporated in the portable electronic device can be shielded by the shock absorbing layer.
The colorant is not particularly limited, and pigments, dyes, and the like that are generally blended in pressure-sensitive adhesive sheets used for adhesively fixing components constituting a portable electronic device to the device body can be used. For example, furnace black , Thermal black, acetylene black, channel black, lamp black, ketjen black and other carbon blacks; oxides such as iron oxide, titanium oxide, zinc oxide, magnesium oxide, cobalt oxide, copper oxide, chromium oxide and alumina; calcium sulfate , Sulfates such as barium sulfate, iron sulfate and mercury sulfate; carbonates such as calcium carbonate, magnesium carbonate and dolomite; metal powders such as iron powder, copper powder, tin powder, lead powder and aluminum powder; azo pigments, phthalocyanine Organic pigments such as pigments and dioxazine pigments; graphite and the like. Of these, carbon black is preferable.

The content of the colorant in the shock absorbing layer is not particularly limited, but a preferred lower limit is 0.1% by weight, a preferred upper limit is 10% by weight, a more preferred lower limit is 0.3% by weight, and a more preferred upper limit is 5%. % By weight. If too much of the colorant is added, uneven coloring may occur in the impact absorbing layer due to poor dispersion of the colorant.

The impact absorbing layer may contain fine particles for the purpose of imparting heat resistance, rigidity, conductivity, etc., or weight reduction.
The fine particles are not particularly limited. For example, ceramic fine particles made of silica, talc, mica, alumina, etc., metal fine particles made of copper, nickel, cobalt, gold, etc., polyamide resin, acrylic resin, epoxy resin, ether sulfone resin, polyamide Examples thereof include plastic fine particles made of imide resin and the like, and hollow fine particles made of silica or a resin polymer.
The shock absorbing layer may have a foam structure for the purpose of imparting flexibility. Examples of the method for forming the foam structure include chemical foaming with a foaming agent, physical foaming by gas kneading, and the like, and mixing hollow fine particles.

The thickness of the shock absorbing sheet of the present invention is not particularly limited, but is preferably 50 to 400 μm. When the thickness is less than 50 μm, the impact-absorbing sheet has a reduced strength and may be destroyed when a strong impact is applied. If the thickness exceeds 400 μm, it may be difficult to meet the recent needs for thinning the pressure-sensitive adhesive sheet.

The shock absorbing sheet of the present invention may have other layers in addition to the shock absorbing layer as long as it has at least one shock absorbing layer.
The other layers are not particularly limited. For example, by stacking a resin having a high storage elastic modulus on the shock absorbing layer, it is possible to improve the punching workability or the handleability of the shock absorbing sheet. Moreover, electroconductivity can be provided to an impact-absorbing sheet by laminating | stacking a conductive film on the said impact-absorbing layer. Further, by applying a primer to the shock absorbing layer, adhesion between the shock absorbing layer and a pressure-sensitive adhesive layer to be described later can be improved, or various performances can be imparted to the shock absorbing layer. The resin constituting the other layer is not particularly limited, and examples thereof include high-density polyethylene (HDPE), low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), polypropylene, and a thermoplastic elastomer.
When the shock absorbing sheet of the present invention has other layers, the thickness ratio of the shock absorbing layer in the shock absorbing sheet of the present invention is not particularly limited, but in order for the shock absorbing sheet to have excellent impact resistance, A preferred lower limit is 40%, and a more preferred lower limit is 50%.

The production method of the shock absorbing sheet of the present invention is not particularly limited, and examples thereof include a method in which a solution in which the material of the shock absorbing layer is dissolved is applied to a release film and dried to form the shock absorbing layer. It is done. Moreover, when the impact-absorbing sheet of this invention has another layer in addition to the said impact-absorbing layer, the method etc. which coextrude the material of each layer and obtain a multilayer structure sheet etc. are mentioned, for example.

The use of the shock absorbing sheet of the present invention is not particularly limited, but it can be used as a base material for a pressure sensitive adhesive sheet for bonding and fixing components constituting a portable electronic device to the main body of a device or a pressure sensitive adhesive sheet for bonding and fixing a vehicle-mounted component. Is preferred. The portable electronic device is not limited to a conventional rigid portable electronic device, and may be a portable electronic device that is exposed to more severe conditions such as a wearable terminal and a bendable (bending) terminal.
Moreover, the shape of the impact-absorbing sheet of the present invention in these uses is not particularly limited, and examples thereof include a rectangle, a frame shape, a circle, an ellipse, and a donut shape.

The shock-absorbing pressure-sensitive adhesive sheet having the shock-absorbing sheet of the present invention and at least one pressure-sensitive adhesive layer is also one aspect of the present invention.
The shock-absorbing pressure-sensitive adhesive tape of the present invention may be a shock-absorbing single-sided pressure-sensitive adhesive sheet in which a pressure-sensitive adhesive layer is formed on one side of the shock-absorbing sheet of the present invention, or the pressure-sensitive adhesive layer on both sides of the shock-absorbing sheet of the present invention. It may be a shock-absorbing double-sided pressure-sensitive adhesive sheet in which is formed. Moreover, when it is an impact-absorbing double-sided pressure-sensitive adhesive sheet, the pressure-sensitive adhesive layers on both sides may have the same composition or different compositions.

The pressure-sensitive adhesive layer preferably contains an acrylic copolymer obtained by copolymerizing a monomer mixture containing butyl acrylate and 2-ethylhexyl acrylate.
The preferred content of butyl acrylate in the total monomer mixture is 10 to 95% by weight. When the content of butyl acrylate is less than 10% by weight, the pressure-sensitive adhesive layer becomes too soft, the cohesive force is lowered, and the heat resistance of the shock-absorbing pressure-sensitive adhesive sheet may be lowered. When the content of butyl acrylate exceeds 95% by weight, the pressure-sensitive adhesive layer is hardened, the adhesive strength or tack is lowered, and the impact resistance of the shock-absorbing pressure-sensitive adhesive sheet may be lowered.
The preferred content of 2-ethylhexyl acrylate in the total monomer mixture is 5 to 70% by weight. When the content of 2-ethylhexyl acrylate is less than 5% by weight, the adhesive strength of the pressure-sensitive adhesive layer is lowered, and the impact resistance of the shock-absorbing pressure-sensitive adhesive sheet may be lowered. When the content of 2-ethylhexyl acrylate exceeds 70% by weight, the pressure-sensitive adhesive layer becomes too soft and the cohesive force is lowered, and the impact resistance of the shock-absorbing pressure-sensitive adhesive sheet may be lowered.

The monomer mixture may contain other copolymerizable monomers other than butyl acrylate and 2-ethylhexyl acrylate as necessary.
Examples of other polymerizable monomers that can be copolymerized include, for example, carbon number of alkyl groups such as methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, and isopropyl (meth) acrylate. (Meth) acrylic acid alkyl ester having 1 to 3 carbon atoms, such as (meth) acrylic acid alkyl ester, tridecyl methacrylate, stearyl (meth) acrylate, and the like, and (meth) acrylic acid hydroxyalkyl And functional monomers such as glycerin dimethacrylate, glycidyl (meth) acrylate, 2-methacryloyloxyethyl isocyanate, (meth) acrylic acid, itaconic acid, maleic anhydride, crotonic acid, maleic acid and fumaric acid.

In order to copolymerize the monomer mixture to obtain the acrylic copolymer, the monomer mixture may be radically reacted in the presence of a polymerization initiator. As a method of radical reaction of the monomer mixture, that is, a polymerization method, a conventionally known method is used, and examples thereof include solution polymerization (boiling point polymerization or constant temperature polymerization), emulsion polymerization, suspension polymerization, bulk polymerization and the like.
The said polymerization initiator is not specifically limited, For example, an organic peroxide, an azo compound, etc. are mentioned. Examples of the organic peroxide include 1,1-bis (t-hexylperoxy) -3,3,5-trimethylcyclohexane, t-hexylperoxypivalate, t-butylperoxypivalate, 2,5 -Dimethyl-2,5-bis (2-ethylhexanoylperoxy) hexane, t-hexylperoxy-2-ethylhexanoate, t-butylperoxy-2-ethylhexanoate, t-butylperoxy Examples include isobutyrate, t-butylperoxy-3,5,5-trimethylhexanoate, and t-butylperoxylaurate. Examples of the azo compound include azobisisobutyronitrile and azobiscyclohexanecarbonitrile. These polymerization initiators may be used alone or in combination of two or more.

The weight average molecular weight (Mw) of the acrylic copolymer is preferably 400,000 to 1,500,000. When the weight average molecular weight is less than 400,000, the pressure-sensitive adhesive layer becomes too soft, the cohesive force is lowered, and the impact resistance of the shock-absorbing pressure-sensitive adhesive sheet may be lowered. When the weight average molecular weight exceeds 1,500,000, the adhesive strength of the pressure-sensitive adhesive layer is lowered, and the impact resistance of the shock-absorbing pressure-sensitive adhesive sheet may be lowered. A more preferable lower limit of the weight average molecular weight is 500,000, and a more preferable upper limit is 1,200,000.
In order to adjust the weight average molecular weight within the above range, polymerization conditions such as a polymerization initiator and a polymerization temperature may be adjusted.
In addition, a weight average molecular weight (Mw) is a weight average molecular weight of standard polystyrene conversion by GPC (Gel Permeation Chromatography: gel permeation chromatography).

The pressure-sensitive adhesive layer preferably contains a tackifier resin.
Examples of the tackifier resins include rosin ester resins, hydrogenated rosin resins, terpene resins, terpene phenol resins, coumarone indene resins, alicyclic saturated hydrocarbon resins, C5 petroleum resins, and C9 resins. Examples include petroleum resins and C5-C9 copolymer petroleum resins. These tackifying resins may be used alone or in combination of two or more.

Although content of the said tackifying resin is not specifically limited, The preferable minimum with respect to 100 weight part of said acrylic copolymers is 10 weight part, and a preferable upper limit is 50 weight part. If the content of the tackifying resin is less than 10 parts by weight, the impact resistance of the shock-absorbing pressure-sensitive adhesive sheet may be lowered. When the content of the tackifying resin exceeds 50 parts by weight, the pressure-sensitive adhesive layer is hardened, the adhesive force or tack is lowered, and the impact resistance of the shock-absorbing pressure-sensitive adhesive sheet may be lowered. A more preferable upper limit of the content of the tackifying resin is 15 parts by weight, and a further preferable upper limit is 40 parts by weight.

In the pressure-sensitive adhesive layer, a crosslinking structure may be formed between main chains of the resin (the acrylic copolymer and / or the tackifying resin) constituting the pressure-sensitive adhesive layer by adding a crosslinking agent. preferable.
The said crosslinking agent is not specifically limited, For example, an isocyanate type crosslinking agent, an aziridine type crosslinking agent, an epoxy-type crosslinking agent, a metal chelate type crosslinking agent etc. are mentioned. Of these, isocyanate-based crosslinking agents are preferred. By adding an isocyanate-based crosslinking agent to the pressure-sensitive adhesive layer, the isocyanate group of the isocyanate-based crosslinking agent reacts with the alcoholic hydroxyl group in the resin constituting the pressure-sensitive adhesive layer, thereby cross-linking the pressure-sensitive adhesive layer. It becomes loose. Therefore, the pressure-sensitive adhesive layer can disperse the peeling stress applied intermittently, and has a resistance to peeling from the adherend against the peeling stress caused by the deformation of the adherend when a strong impact is applied. More improved.
The addition amount of the cross-linking agent is preferably 0.01 to 10 parts by weight, more preferably 0.1 to 5 parts by weight with respect to 100 parts by weight of the acrylic copolymer.

If the degree of cross-linking of the pressure-sensitive adhesive layer is too high or too low, the pressure-sensitive adhesive layer may be easily peeled off from the adherend due to peeling stress caused by deformation of the adherend. 60 wt% is preferred, 15 to 50 wt% is more preferred, and 20 to 45 wt% is particularly preferred.
The degree of cross-linking of the pressure-sensitive adhesive layer was determined by collecting W1 (g) of the pressure-sensitive adhesive layer, immersing this pressure-sensitive adhesive layer in ethyl acetate at 23 ° C. for 24 hours, and filtering the insoluble matter with a 200-mesh wire mesh. The residue on the wire net is vacuum-dried, and the weight W2 (g) of the dry residue is measured, and calculated by the following formula (1).
Crosslinking degree (% by weight) = 100 × W2 / W1 (1)

The pressure-sensitive adhesive layer may contain plasticizers, emulsifiers, softeners, fillers, additives such as pigments and dyes, and other resins such as rosin resins, if necessary.

The thickness of the pressure-sensitive adhesive layer is not particularly limited, but the thickness of the pressure-sensitive adhesive layer (thickness of the pressure-sensitive adhesive layer on one side) is preferably 10 to 150 μm. When the thickness is less than 10 μm, the pressure-sensitive adhesive layer may have reduced impact resistance. When the thickness exceeds 150 μm, the pressure-sensitive adhesive layer may have impaired reworkability or removability.

The shock absorbing adhesive sheet of the present invention preferably has a total thickness of 100 to 400 μm. If the total thickness is less than 100 μm, the impact resistance of the impact-absorbing pressure-sensitive adhesive sheet may be lowered. When the total thickness exceeds 400 μm, the shock-absorbing pressure-sensitive adhesive sheet may not be suitable for use in bonding and fixing components constituting the portable electronic device to the device body.

The compressive strength of the impact-absorbing pressure-sensitive adhesive sheet of the present invention is not particularly limited, but a preferable lower limit of 25% compressive strength is 10 kPa, and a preferable upper limit is 2000 kPa. When the 25% compressive strength is less than 10 kPa, the impact-absorbing sheet as a base material may ooze sideways when the impact-absorbing pressure-sensitive adhesive sheet is pressure-bonded to an adherend. When the 25% compressive strength exceeds 2000 kPa, when the impact-absorbing pressure-sensitive adhesive sheet is attached to the adherend, the air between the adherend and the shock-absorbing pressure-sensitive adhesive sheet is difficult to escape and the sticking property is deteriorated. There is. The more preferable lower limit of the 25% compressive strength is 30 kPa, and the more preferable upper limit is 1000 kPa.

Examples of the method for producing the impact-absorbing pressure-sensitive adhesive sheet of the present invention include the following methods.
First, a solution of an adhesive a is prepared by adding a solvent to an acrylic copolymer, a tackifying resin, and a cross-linking agent as required, and the solution of the adhesive a is applied to the surface of the shock absorbing sheet as a substrate. The adhesive layer a is formed by applying and completely removing the solvent in the solution by drying. Next, the release film is superimposed on the formed pressure-sensitive adhesive layer a so that the release treatment surface faces the pressure-sensitive adhesive layer a.
Next, a release film different from the above release film is prepared, a solution of the adhesive b is applied to the release treatment surface of the release film, and the solvent in the solution is completely removed by drying, thereby releasing the release film. A laminated film in which the pressure-sensitive adhesive layer b is formed on the surface of the mold film is produced. The obtained laminated film is laminated on the back surface of the shock absorbing sheet on which the pressure-sensitive adhesive layer a is formed, with the pressure-sensitive adhesive layer b facing the back surface of the shock-absorbing sheet to produce a laminated body. Then, by pressing the laminate with a rubber roller or the like, an impact-absorbing adhesive sheet having an adhesive layer on both sides of the impact-absorbing sheet and having the surface of the adhesive layer covered with a release film can be obtained. it can.

In addition, two sets of laminated films are produced in the same manner, and these laminated films are superposed on both sides of the shock absorbing sheet as a base material with the adhesive layer of the laminated film facing the shock absorbing sheet. A laminate is produced, and the laminate is pressed by a rubber roller or the like, thereby having an adhesive layer on both sides of the impact-absorbing sheet and the surface of the adhesive layer being covered with a release film. A sheet may be obtained.

Although the use of the impact-absorbing pressure-sensitive adhesive sheet of the present invention is not particularly limited, the use for bonding and fixing components constituting the portable electronic device to the device main body and the use for bonding and fixing vehicle-mounted components are preferable. Specifically, the shock-absorbing pressure-sensitive adhesive sheet of the present invention can be used, for example, as a shock-absorbing pressure-sensitive adhesive sheet for bonding and fixing a liquid crystal display panel of a portable electronic device to a device body. The portable electronic device is not limited to a conventional rigid portable electronic device, and may be a portable electronic device that is exposed to more severe conditions such as a wearable terminal and a bendable (bending) terminal.
Moreover, the shape of the impact-absorbing pressure-sensitive adhesive sheet of the present invention in these applications is not particularly limited, and examples thereof include a rectangle, a frame shape, a circle, an ellipse, and a donut shape.

In particular, the shock-absorbing double-sided pressure-sensitive adhesive sheet of the present invention has a frame-shaped shape as a shock-absorbing double-sided pressure-sensitive adhesive sheet for fixing a front plate, a shock-absorbing double-sided pressure-sensitive adhesive sheet for fixing a back plate, and a shock-absorbing double-sided pressure-sensitive adhesive sheet for fixing a backlight unit. When used as, it is possible to effectively prevent the portable electronic device from being damaged even when an impact such as dropping is applied. In particular, high impact resistance can be exhibited even when the frame-like pressure-sensitive adhesive sheet is narrowed (for example, a width of 1.0 mm or less) with the recent increase in screen size of portable electronic devices.

FIG. 1 is a schematic diagram illustrating a structure of a front plate and a display unit of a general portable electronic device. 1 includes a bottom frame 2, a reflection film 3, a light guide plate 4, a PC mold 5, an optical film 6 (a diffusion sheet, a prism sheet, etc.), a double-sided adhesive for fixing a backlight unit. The sheet 7, the liquid crystal panel 8, the highly transparent tape 9, the touch panel module 10, the highly transparent tape 11, the double-sided pressure-sensitive adhesive sheet 12 for fixing the front plate, and the front plate (cover panel) 13 are laminated in this order. 14 is an LED light source, and 15 is a flexible printed circuit board.

In FIG. 2, the schematic diagram explaining the usage method of the double-sided adhesive sheet for front plate fixing and the double-sided adhesive sheet for backplate fixing was shown. In FIG. 2, configurations other than the front plate, the double-sided pressure-sensitive adhesive sheet for fixing the front plate, the housing frame, the double-sided pressure-sensitive adhesive sheet for fixing the back plate, and the back plate are omitted for simplification.
The double-sided pressure-sensitive adhesive sheet 12 for fixing the front plate has a role of adhering and fixing the front plate (cover panel) to the touch panel module or the display panel module. In FIG. A front plate (cover panel) 13 is bonded and fixed to the housing frame 18.
When the portable electronic device has a back plate, the back plate 17 is bonded and fixed to the housing frame 18 by the double-sided adhesive sheet 16 for fixing the back plate.

By using the shock-absorbing double-sided pressure-sensitive adhesive sheet of the present invention as such a double-sided pressure-sensitive adhesive sheet for fixing a front plate or a double-sided pressure-sensitive adhesive sheet for fixing a back plate, a portable electronic device having extremely excellent impact resistance can be obtained.
A shock absorbing double-sided pressure-sensitive adhesive sheet for fixing a front plate for fixing a front plate in a portable electronic device, the double-sided pressure-sensitive adhesive tape of the present invention, and an adhesive layer formed on both sides of the shock-absorbing sheet, A shock-absorbing double-sided pressure-sensitive adhesive sheet for fixing a front plate is also one aspect of the present invention.
A shock absorbing double-sided pressure-sensitive adhesive sheet double-sided pressure-sensitive adhesive sheet for fixing a back plate for fixing a back plate in a portable electronic device, the shock-absorbing sheet of the present invention, and an adhesive layer formed on both sides of the shock-absorbing sheet, An impact-absorbing double-sided pressure-sensitive adhesive sheet for fixing a back plate having the above is also one aspect of the present invention.

The double-sided pressure-sensitive adhesive sheet 7 for fixing the backlight unit has a role of bonding and fixing the backlight unit to the PC mold 5 and the liquid crystal panel 8. In FIG. 1, the reflective film 3, the light guide plate 4, the optical film 6, the LED light source 14, and the flexible printed circuit board 15 constitute a backlight unit.
In FIG. 3, the schematic diagram explaining the usage method of the double-sided adhesive sheet for backlight unit fixation was shown. In FIG. 3, configurations other than the double-sided pressure-sensitive adhesive sheet 7 for fixing the backlight unit, the PC mold 5, and the backlight unit 19 are omitted for simplification.

By using the shock-absorbing double-sided pressure-sensitive adhesive sheet of the present invention as such a double-sided pressure-sensitive adhesive sheet for fixing a backlight unit, a portable electronic device having extremely excellent impact resistance can be obtained.
A shock-absorbing double-sided pressure-sensitive adhesive sheet for fixing a backlight unit for fixing a backlight unit in a portable electronic device, the double-sided pressure-sensitive adhesive tape of the present invention, and an adhesive formed on both sides of the shock-absorbing sheet An impact-absorbing double-sided pressure-sensitive adhesive sheet for fixing a backlight unit having a layer is also one aspect of the present invention.

ADVANTAGE OF THE INVENTION According to this invention, the impact-absorbing sheet excellent in impact resistance used suitably as a base material of the adhesive sheet which adhere | attaches and fixes the components which comprise a portable electronic device to an apparatus main body can be provided. Further, according to the present invention, the impact-absorbing adhesive sheet having the impact-absorbing sheet, the shock-absorbing double-sided adhesive sheet for fixing the front plate, the shock-absorbing double-sided adhesive sheet for fixing the back plate, and the shock-absorbing double-sided adhesive for fixing the backlight unit Sheets can be provided.

It is a schematic diagram which shows the structure of the front board and display unit of a general portable electronic device. It is a schematic diagram explaining the usage method of the double-sided pressure-sensitive adhesive sheet for fixing the front plate and the double-sided pressure-sensitive adhesive sheet for fixing the back plate. It is a schematic diagram explaining the usage method of the double-sided adhesive sheet for backlight unit fixation. It is a schematic diagram which shows the drop impact test of an impact-absorbing adhesive sheet.

EXAMPLES The present invention will be described in more detail with reference to examples below, but the present invention is not limited to these examples.

(Preparation of adhesive A)
In a reactor equipped with a thermometer, a stirrer, and a condenser, 79.9 parts by weight of butyl acrylate, 5 parts by weight of ethyl acrylate, 12 parts by weight of 2-ethylhexyl acrylate, 3 parts by weight of acrylic acid, 0.1 part by weight of 2-hydroxyethyl acrylate And 82 parts by weight of ethyl acetate were added and purged with nitrogen, and then the reactor was heated to start refluxing. Subsequently, 0.15 parts by weight of azobisisobutyronitrile was added as a polymerization initiator in the reactor. The solution was refluxed at 77 ° C. for 5 hours to obtain a solution of the acrylic copolymer (a). When the weight average molecular weight of the obtained acrylic copolymer (a) was measured by a GPC method using “2690 Separations Model” manufactured by Water Co. as a column, it was 650,000.
10 parts by weight of polymerized rosin ester, 16 parts by weight of terpenephenol, 10 parts by weight of hydrogenated rosin ester with respect to 100 parts by weight of the solid content of acrylic copolymer (a) contained in the resulting solution of acrylic copolymer (a). Parts by weight, 100 parts by weight of ethyl acetate, and further 6.2 parts by weight of an isocyanate-based crosslinking agent (trade name “Coronate L45” manufactured by Nippon Polyurethane Co., Ltd.) with respect to 100 parts by weight of the solid content of the acrylic polymer (a). Was added and stirred to obtain an adhesive A.

(Example 1)
(1) Production of impact-absorbing sheet 150 g of styrene-ethylene-butylene-styrene (SEBS) block copolymer (Dynalon “8905P” manufactured by JSR) was placed in a beaker containing 250 g of toluene, and stirred for 1 hour to be sufficiently dissolved. . The solution was applied to a release PET film having a thickness of 75 μm subjected to a silicon release treatment using an applicator, and the solvent was dried at 110 ° C. for 4 minutes to form a non-foamed impact absorbing layer having a thickness of 150 μm. An impact absorbing sheet was obtained.
The impact absorbing sheet is cut into a width of 5 mm × 30 mm, and the long side of 30 mm is chucked with a dynamic viscoelasticity measuring apparatus (Rheogel-E4000 manufactured by UBM) with a chuck interval of 15 mm, and the temperature rising rate is 5 ° C./min. The tensile viscoelastic modulus is measured in the range of −60 ° C. to 100 ° C., and a master curve is synthesized at a reference temperature of 23 ° C., whereby the frequency at 23 ° C. is 1.0 × 10 ⁴ to 1.0 × 10 ^6.5 Hz. The maximum value of loss tangent tan δ was calculated as 1.4. The frequency at which the loss tangent tan δ takes a maximum value was 1.0 × 10 ^4.17 Hz.

(2) Manufacture of double-sided pressure-sensitive adhesive sheet Adhesive A was applied to a 75 μm-thick release PET film that had been subjected to silicon release treatment using an applicator and dried at 110 ° C. for 3 minutes to form a 50 μm-thick adhesive layer did. This pressure-sensitive adhesive layer was bonded to the impact-absorbing sheet obtained above using a silicon roller to obtain a single-sided pressure-sensitive adhesive sheet. The shock absorbing sheet was previously subjected to corona treatment on both surfaces under the conditions of 270 W and 18 m / min using a corona treatment device (“CT-0212” manufactured by Kasuga Electric Co., Ltd.).
In the same manner, the release PET film on the surface opposite to the impact-absorbing sheet was peeled off, and the same pressure-sensitive adhesive layer as above was bonded. Thereafter, curing was performed at 40 ° C. for 48 hours. Thereby, a double-sided pressure-sensitive adhesive sheet having a total thickness of 250 μm, which was covered with a release PET film on both sides, was obtained.

(Examples 2 to 12)
Example 1 and Example 1 except that the material of the shock absorbing layer, the thickness of the shock absorbing layer, the maximum value of the loss tangent tan δ of the shock absorbing layer, and the thickness of the adhesive layer were changed as described in Table 5 and Table 6. Similarly, a double-sided PSA sheet was obtained.
In addition, the material of the shock absorbing layer shown below was used.
-SEBS block copolymer (Tough Tech "H1221" manufactured by Asahi Kasei Corporation)
・ SEBS block copolymer (Dynalon “8600P” manufactured by JSR)
・ SEBS block copolymer (Dynalon “8300P” manufactured by JSR)
・ SEBS block copolymer (Dynalon “8906P” manufactured by JSR)
・ SEBS block copolymer (Tough Tech "H1062" manufactured by Asahi Kasei Corporation)
HSBR block copolymer (Dynalon “1320P” manufactured by JSR)
・ SEPS block copolymer (Kuraray Septon "2063")
SIBS block copolymer (Shibustar “062UM” manufactured by Kaneka)
・ Acrylic elastomer (Kuraray “Clarity 2330”)
・ Acrylic elastomer (clarity “2140e” manufactured by Kuraray Co., Ltd.)

(Example 13)
As described in Table 6, the material of the shock absorbing layer, the thickness of the shock absorbing layer, the maximum value of the loss tangent tan δ of the shock absorbing layer, and the thickness of the pressure-sensitive adhesive layer were changed as in Example 1. A double-sided PSA sheet was obtained.
Instead of applying the solution in which the material of the shock absorbing layer was dissolved to the release film and drying it to form the shock absorbing layer, the following sheet material was obtained and used for the shock absorbing layer.
-Urethane elastomer ("DUS614" manufactured by Seadam)

(Example 14)
As described in Table 6, the material of the shock absorbing layer, the thickness of the shock absorbing layer, the maximum value of the loss tangent tan δ of the shock absorbing layer, and the thickness of the pressure-sensitive adhesive layer were changed as in Example 1. A double-sided PSA sheet was obtained.
Instead of forming a shock absorbing layer by applying a solution in which the material of the shock absorbing layer is dissolved to a release film and drying it, polyethylene (PE) is formed on both sides of a SEBS block copolymer (Dynalon “8600” manufactured by JSR). ) (Sumikasen F218-0 manufactured by Sumitomo Chemical Co., Ltd.) was used as an impact absorbing sheet. When the thickness ratio of each layer in the cross section of the three-layer structure sheet was measured using VHX-500 (manufactured by Keyence Corporation), PE: SEBS (Dynalon “8600”): PE = 20: 110: 20.

(Comparative Examples 1 to 4)
As described in Table 7, the material of the shock absorbing layer, the thickness of the shock absorbing layer, the maximum value of the loss tangent tan δ of the shock absorbing layer, and the thickness of the pressure-sensitive adhesive layer were changed in the same manner as in Example 1. A double-sided PSA sheet was obtained.
Instead of applying the solution in which the material of the shock absorbing layer was dissolved to the release film and drying it to form the shock absorbing layer, the following sheet material was obtained and used for the shock absorbing layer.
-Urethane elastomer ("DUS213" manufactured by Seadam)
-Urethane elastomer ("DUS203" manufactured by Seadam)
・ PE foam (Polyolefin foam "XLH-0502" manufactured by Sekisui Chemical Co., Ltd.)
・ PET film (Lumilar "S10" manufactured by Toray Industries, Inc.)

(Comparative Examples 5 to 8)
As described in Table 7, the material of the shock absorbing layer, the thickness of the shock absorbing layer, the maximum value of the loss tangent tan δ of the shock absorbing layer, and the thickness of the pressure-sensitive adhesive layer were changed in the same manner as in Example 1. A double-sided PSA sheet was obtained.
In addition, the material of the shock absorbing layer shown below was used.
-SEBS block copolymer (Tough Tech "H1041" manufactured by Asahi Kasei Corporation)
SBBS block copolymer (Tough Tech “P1083” manufactured by Asahi Kasei Corporation)
SBBS block copolymer (Tough Tech “P2000” manufactured by Asahi Kasei Corporation)
・ Acrylic elastomer (Kuraray “Clarity“ 2250 ”)

(Comparative Example 9)
As described in Table 7, the material of the shock absorbing layer, the thickness of the shock absorbing layer, the maximum value of the loss tangent tan δ of the shock absorbing layer, and the thickness of the pressure-sensitive adhesive layer were changed in the same manner as in Example 1. A double-sided PSA sheet was obtained.
An impact absorbing layer was formed as shown below.
13.5 parts by weight of polymerized rosin ester (“D-160” manufactured by Arakawa Chemical Industries, Ltd.), terpene with respect to 100 parts by weight of the solid content of the acrylic copolymer (a) obtained in the above (Preparation of adhesive A) 18 parts by weight of phenol (“G-150” manufactured by Yasuhara Chemical Co., Ltd.), 13.5 parts by weight of hydrogenated rosin ester (“Ester Gum H” manufactured by Arakawa Chemical Industries, Ltd.), and solid content of acrylic polymer (a) of 100% by weight 7.9 parts by weight of an isocyanate-based cross-linking agent (trade name “Coronate L45” manufactured by Nippon Polyurethane Co., Ltd.) is added to the part, and the solution obtained by stirring the silicon mold release treatment is applied to a 75 μm-thick release agent. A PET film (Nippa Corporation, product number V2) was applied using an applicator, dried at 110 ° C. for 4 minutes, and then cured at 40 ° C. for 48 hours to form an impact-absorbing layer having a thickness of 200 μm. It was obtained acrylic pressure-sensitive adhesive sheet.

<Composition of the material of the shock absorbing layer>
Among the materials of the shock absorbing layer used in Examples and Comparative Examples, a styrene-ethylene-butylene-styrene (SEBS) block copolymer was used with a nuclear magnetic resonance apparatus (“ADVANCE 400” manufactured by Bruker BioSpin Corporation), and a solvent. Table 1 shows the styrene, ethylene and butylene contents measured by ¹ H-NMR (1H-nuclear magnetic resonance) measurement using deuterated chloroform and ¹³ C-NMR. The numbers in parentheses in Table 1 are the ratio of each component in 100 parts by weight of the soft segment.

Among the materials of the shock absorbing layer used in the examples and comparative examples, a styrene-ethylene-propylene-styrene (SEPS) block copolymer was used with a nuclear magnetic resonance apparatus (“ADVANCE 400” manufactured by Bruker BioSpin Corporation) and a solvent. Table 2 shows the styrene, ethylene, and propylene contents measured by ¹ H-NMR (1H-nuclear magnetic resonance) measurement and ¹³ C-NMR using deuterated chloroform. The numbers in parentheses in Table 2 represent the ratio of each component in 100 parts by weight of the soft segment.

Among the materials of the shock absorbing layer used in the comparative example, for the styrene-butadiene-butylene-styrene (SBBS) block copolymer, a nuclear magnetic resonance apparatus (“ADVANCE 400” manufactured by Bruker BioSpin Corporation) is used and deuterated chloroform as a solvent. Table 3 shows the contents of styrene, ethylene, 1,4-butadiene and butylene as measured by ¹ H-NMR (1H-nuclear magnetic resonance) measurement using ¹³ and ¹³ C-NMR. The numbers in parentheses in Table 3 are the ratio of each component in 100 parts by weight of the soft segment.

Among the materials of the shock absorbing layer used in the examples, for styrene-isobutylene-styrene (SIBS) block copolymers, a nuclear magnetic resonance apparatus (“ADVANCE 400” manufactured by Bruker BioSpin Corporation) was used, and deuterated chloroform was used as a solvent. Table 4 shows the styrene and isobutylene contents measured by ¹ H-NMR (1H-nuclear magnetic resonance) measurement and ¹³ C-NMR.

<Evaluation>
The following evaluation was performed about the double-sided adhesive sheet obtained by the Example and the comparative example. The evaluation results are shown in Tables 5-7.

(1) Drop impact test <Production of test equipment>
In FIG. 4, the schematic diagram of the drop impact test of the double-sided adhesive sheet (impact-absorbing adhesive sheet) obtained by the Example and the comparative example is shown. The obtained double-sided PSA sheet was punched into an outer diameter of 46 mm, a length of 61 mm, an inner diameter of 44 mm, and a length of 59 mm to produce a frame-shaped test piece having a width of 1 mm. Next, as shown in FIG. 4 (a), the square hole is approximately at the center of the test piece 41 from which the release paper has been peeled off from the polycarbonate plate 43 having a thickness of 38 mm and a square hole having a length of 50 mm and a thickness of 2 mm. After being pasted so that the test piece 41 is located, a polycarbonate plate 42 having a width of 55 mm, a length of 65 mm, and a thickness of 1 mm is pasted from the upper surface of the test piece 41 so that the test piece 41 is located substantially in the center, and the test apparatus was assembled. .
Thereafter, a pressure of 5 kgf was applied for 10 seconds from the side of the polycarbonate plate positioned on the upper surface of the test apparatus, and the polycarbonate plate positioned on the upper and lower sides and the test piece were pressed and left at room temperature for 24 hours.

<Drop impact resistance judgment>
As shown in FIG. 4B, the produced test apparatus was turned over and fixed to the support base, and an iron ball 44 weighing 300 g and passing through the square hole was dropped so as to pass through the square hole. The height at which the iron ball was dropped was gradually increased, and the height at which the iron ball was dropped when the test piece and the polycarbonate plate were peeled off by the impact applied by the dropping of the iron ball was measured. The determination when the result was 120 cm or more was ◎, the determination when it was 80 cm or more and less than 120 cm was ○, and the determination when it was less than 80 cm was ×.

(2) Measurement of 25% compressive strength The obtained double-sided PSA sheet was cut into 15 mm x 15 mm and stacked until it became about 5 mm to obtain a laminate sample. After measuring the thickness of the laminate sample, it was sandwiched between 1 mm thick PC plates and compressed at a rate of 10 mm / min with “Autograph AGS-X” manufactured by Shimadzu Corporation. The stress when compressed to 25% of the original thickness was determined, and the compressive strength was calculated by dividing by the area.

DESCRIPTION OF SYMBOLS 1 Front plate and display unit of portable electronic equipment 2 Bottom frame 3 Reflective film 4 Light guide plate 5 PC mold 6 Optical film 7 Double-sided adhesive sheet 8 for fixing a backlight unit Liquid crystal panel 9 Highly transparent tape 10 Touch panel module 11 Highly transparent tape 12 Double-sided pressure-sensitive adhesive sheet 13 for fixing the face plate Front face plate (cover panel)
DESCRIPTION OF SYMBOLS 14 LED light source 15 Flexible printed circuit board 16 Double-sided adhesive sheet 17 for back plate fixation Back plate 18 Case frame 19 Backlight unit 41 Test piece (frame shape)
42 Polycarbonate plate (1mm thickness)
43 Polycarbonate plate (2mm thick)
44 Iron ball (300 g)

Claims

Impact having at least one impact absorbing layer having a maximum value of loss tangent tan δ of 0.84 or more at a frequency of 1.0 × 10 4 to 1.0 × 10 6.5 Hz at 23 ° C. Absorption sheet.
2. The impact-absorbing sheet according to claim 1, wherein the maximum value of the loss tangent tan δ at a frequency of 1.0 × 10 4 to 1.0 × 10 6.5 Hz at 23 ° C. is 1.31 or more.
The shock absorbing sheet according to claim 1 or 2, wherein the shock absorbing layer contains an elastomer.
4. The impact absorbing sheet according to claim 3, wherein the elastomer is a styrene elastomer, an olefin elastomer, an acrylic elastomer or a urethane elastomer.
5. The impact absorbing sheet according to claim 1, wherein the thickness is 50 to 400 μm.
The shock absorbing sheet according to claim 1, 2, 3, 4, or 5, wherein the shock absorbing sheet is used as a base material of a pressure-sensitive adhesive sheet for adhering and fixing a component constituting a portable electronic device to a device main body.
An impact-absorbing pressure-sensitive adhesive sheet comprising the impact-absorbing sheet according to claim 1, and at least one pressure-sensitive adhesive layer.
A shock absorbing double-sided pressure-sensitive adhesive sheet double-sided pressure-sensitive adhesive sheet for fixing a front plate for bonding and fixing a front plate in a portable electronic device,
A shock-absorbing double-sided pressure-sensitive adhesive sheet for fixing a front plate, comprising: the shock-absorbing sheet according to claim 1; and an adhesive layer formed on both sides of the shock-absorbing sheet. .
A shock absorbing double-sided pressure-sensitive adhesive sheet double-sided pressure-sensitive adhesive sheet for fixing a back plate for bonding and fixing a back plate in a portable electronic device,
A shock-absorbing double-sided pressure-sensitive adhesive sheet for fixing to a back plate, comprising the shock-absorbing sheet according to claim 1, and a pressure-sensitive adhesive layer formed on both sides of the shock-absorbing sheet. .
A shock-absorbing double-sided pressure-sensitive adhesive sheet double-sided pressure-sensitive adhesive sheet for fixing a backlight unit for bonding and fixing a backlight unit in a portable electronic device,
A shock-absorbing double-sided adhesive for fixing a backlight unit, comprising the impact-absorbing sheet according to claim 1, and an adhesive layer formed on both sides of the impact-absorbing sheet. Sheet.