JP5808975B2 - Double-sided adhesive sheet - Google Patents

Description

  The present invention relates to a double-sided pressure-sensitive adhesive sheet, particularly a double-sided pressure-sensitive adhesive sheet having a desired adhesive force even when the pressure-sensitive adhesive layer is thinned.

The pressure-sensitive adhesive strength of the pressure-sensitive adhesive sheet depends on the composition and polarity of the pressure-sensitive adhesive and the amount of pressure-sensitive adhesive applied on the substrate, that is, the thickness of the pressure-sensitive adhesive layer to be formed. Power increases. The thickness of the pressure-sensitive adhesive layer in the pressure-sensitive adhesive sheet used for labels, tapes, etc. is set according to various purposes, but from the viewpoint of developing a sufficiently high adhesive strength, it is not much less than 10 μm. I have not been told.
However, in recent years, it has been desired to reduce the thickness of electronic devices and optical devices and the like, and adhesive sheets used for joining members of electronic devices and optical devices or temporarily bonding during processing are similarly thin films. Is desired.

Various proposals have been made for reducing the thickness of the pressure-sensitive adhesive layer in a pressure-sensitive adhesive sheet used for bonding or processing members of electronic devices and optical devices. For example, in Patent Documents 1 to 3, in order to improve the removability, the pressure-sensitive adhesive layer is thinned to reduce the adhesive force.
However, as a means for reducing the adhesive strength, the pressure-sensitive adhesive layer may be thinned, but there are cases where it is not desired to reduce the adhesive strength even if the pressure-sensitive adhesive layer is thinned.
For example, in Patent Documents 4 and 5, an object is to provide an optical surface protective film having good adhesion reliability (adhesive strength) to an optical member even when the thickness of the pressure-sensitive adhesive layer is reduced to about 2 to 10 μm. A surface protective film using a rubber-based adhesive has been proposed.
Further, in Patent Document 6, even when the pressure-sensitive adhesive layer is thinned to 1 to 15 μm, the weight average molecular weight composed of a specific monomer is large for the purpose of providing an optical film that can satisfy durability. An optical film using a pressure-sensitive adhesive containing a (meth) acrylic polymer and a crosslinking agent has been proposed.

JP-A-2005-007618 JP 2006-281488 A JP 2009-158503 A JP 2008-133435 A JP 2008-102271 A JP 2007-277510 A

However, in the protective films and optical films disclosed in Patent Documents 4 to 6, a sufficiently high adhesive force is not obtained when the pressure-sensitive adhesive layer is thinned.
In addition, when the pressure-sensitive adhesive layer is thinned, the adhesiveness of the pressure-sensitive adhesive layer to the substrate is lowered when a double-sided pressure-sensitive adhesive sheet having pressure-sensitive adhesive layers on both sides of the substrate is obtained. Therefore, when the adhesive sheet is reapplied or when the adhesive sheet is peeled off from the adherend and discarded after use, the adhesive layer moves to the adherend when it is peeled off again after being attached to the adherend. Such as a problem of occurrence of zipping and the like.
The present invention has a sufficiently high adhesive force even when the pressure-sensitive adhesive layer is thinned, improves the adhesion of the pressure-sensitive adhesive layer to the substrate, and there is no transfer of the pressure-sensitive adhesive layer to the adherend. An object of the present invention is to provide a double-sided PSA sheet that can suppress the occurrence of zipping.

The present inventors use a double-sided pressure-sensitive adhesive sheet having pressure-sensitive adhesive layers on both sides of a substrate, and use a pressure-sensitive adhesive containing a specific component in a specific content as a pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer. Then, it discovered that the said subject could be solved.
That is, the present invention provides the following [1] to [10].
[1] A double-sided pressure-sensitive adhesive sheet having pressure-sensitive adhesive layers on both sides of a substrate, wherein the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer comprises (A) an acrylic copolymer having a crosslinkable functional group, and (B) It contains urethane resin, (C) tackifying resin, and (D) cross-linking agent, and the content of (C) tackifying resin is 100 parts by mass in total of component (A) and component (B). The double-sided pressure-sensitive adhesive sheet is 8 to 35 parts by mass.
[2] The double-sided pressure-sensitive adhesive sheet according to the above [1], wherein the (C) tackifying resin is a terpene phenol resin or a hydrogenated terpene phenol resin.
[3] (B) The urethane resin is obtained by reacting (b3) a chain extender with a terminal isocyanate urethane prepolymer obtained by reacting (b1) a diol with (b2) a polyvalent isocyanate compound. And (b3) the chain extender is (b4) a compound having two hydroxyl groups and / or amino groups and (b5) a compound having three or more hydroxyl groups and / or amino groups, the above [1] or [2 ]. Double-sided pressure-sensitive adhesive sheet according to the above.
[4] The double-sided pressure-sensitive adhesive sheet according to the above [3], wherein the (b1) diol is a glycol having a molecular weight of 1,000 to 3,000.
[5] Double-sided adhesive according to [3] or [4] above, wherein the mass ratio [(b4) / (b5)] of the (b4) component to the (b5) component is 70/30 to 100/0 Sheet.
[6] Both sides according to any one of the above [1] to [5], wherein the crosslinkable functional group of component (A) is derived from an ethylenically unsaturated carboxylic acid or (meth) acrylic acid hydroxyalkyl ester. Adhesive sheet.
[7] The double-sided pressure-sensitive adhesive sheet according to any one of [1] to [6], wherein (D) the crosslinking agent is an isocyanate-based crosslinking agent.
[8] The above [1] to [7], wherein the mass ratio [(A) / (B)] of (A) acrylic copolymer and (B) urethane resin is 1/99 to 40/60. The double-sided pressure-sensitive adhesive sheet according to any of the above.
[9] The double-sided pressure-sensitive adhesive sheet according to any one of [1] to [8], wherein the weight average molecular weight (Mw) of the (A) acrylic copolymer is 300,000 to 1,500,000.
[10] The double-sided pressure-sensitive adhesive sheet according to any one of the above [1] to [9], wherein the pressure-sensitive adhesive layer has a thickness of 0.1 to 5.0 μm and the base material has a thickness of 1 to 12 μm.

  The double-sided pressure-sensitive adhesive sheet of the present invention has excellent adhesive force even when the pressure-sensitive adhesive layer is thinned, and improves the adhesiveness of the pressure-sensitive adhesive layer to the substrate, so that the pressure-sensitive adhesive layer can be transferred to the adherend. It can be a double-sided PSA sheet that is not seen and can suppress the occurrence of zipping. These effects are particularly prominent in an environment at a low temperature (about 5 ° C.).

It is sectional drawing of the double-sided adhesive sheet which shows one aspect | mode of the structure of the double-sided adhesive sheet of this invention.

  The double-sided pressure-sensitive adhesive sheet of the present invention is a double-sided pressure-sensitive adhesive sheet having pressure-sensitive adhesive layers on both sides of the substrate, and the configuration of the double-sided pressure-sensitive adhesive sheet is not particularly limited as long as it has pressure-sensitive adhesive layers on both sides of the substrate. FIG. 1 is a diagram showing an embodiment of the configuration of the double-sided pressure-sensitive adhesive sheet of the present invention. The structure of the double-sided pressure-sensitive adhesive sheet of the present invention is not limited to the double-sided pressure-sensitive adhesive sheet 1a having the pressure-sensitive adhesive layers 12a and 12b on both surfaces of the substrate 11, as shown in FIG. 1 (a), but as shown in FIG. It may be a double-sided pressure-sensitive adhesive sheet 1b in which release materials 13a and 13b are further laminated on the pressure-sensitive adhesive layers 12a and 12b formed on both surfaces of the base material 11, respectively. In addition, the structure etc. which rolled what further laminated | stacked the peeling material on either one side of the adhesive layer formed in both surfaces of the base material are mentioned.

In the present invention, “thinning the pressure-sensitive adhesive layer” means each thickness of the pressure-sensitive adhesive layer provided on both surfaces of the substrate (for example, Z1 and Z2 in FIGS. 1A and 1B). Hereinafter, it is also referred to as “the thickness of the pressure-sensitive adhesive layer”) of 5.0 μm or less. Even if the thickness of the pressure-sensitive adhesive layer is 5.0 μm or less, the double-sided pressure-sensitive adhesive sheet of the present invention can be a double-sided pressure-sensitive adhesive sheet having a sufficiently high adhesive force and excellent adhesiveness to the substrate of the pressure-sensitive adhesive layer.
The thickness of the pressure-sensitive adhesive layer of the double-sided pressure-sensitive adhesive sheet of the present invention is preferably 0.1 to 5.0 μm, more preferably 0.3 to 3.0 μm, still more preferably 0.5 to 2.0 μm, and still more preferably. 0.7 to 1.5 μm. If it is 0.1 micrometer or more, sufficient adhesive force can be obtained.

[Adhesive]
The pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer used in the present invention includes (A) an acrylic copolymer having a crosslinkable functional group, (B) a urethane resin, (C) a tackifier resin, and (D) a crosslinking agent. And (C) the content of the tackifying resin is 8 to 35 parts by mass with respect to 100 parts by mass in total of the component (A) and the component (B). Moreover, another additive, an organic solvent, etc. can be contained as needed. Hereinafter, each component contained in an adhesive is demonstrated.

<(A) Acrylic copolymer>
The pressure-sensitive adhesive used in the present invention contains (A) an acrylic copolymer having a crosslinkable functional group (hereinafter also referred to as “(A) acrylic copolymer” or “(A) component”). In the present invention, the acrylic copolymer having a crosslinkable functional group is made from a monomer mixture containing (meth) acrylic acid ester as a main component and (D) a crosslinkable functional group-containing monomer that reacts with a crosslinker. As an acrylic copolymer obtained through a polymerization reaction. Therefore, the (A) acrylic copolymer to be used contains at least a structural unit derived from a (meth) acrylic acid ester and a structural unit derived from a crosslinkable functional group-containing monomer.
In the following description, for example, “(meth) acrylic acid” means both acrylic acid and methacrylic acid, and the same applies to other similar terms.

The content of the structural unit derived from the (meth) acrylic acid ester is preferably 70 to 99.9% by mass, more preferably from all structural units of the component (A), from the viewpoint of obtaining sufficient adhesive strength even if it is thinned. Is 80 to 99.5% by mass, more preferably 85 to 99% by mass, and more preferably 88 to 95% by mass.
The content of the structural unit derived from the crosslinkable functional group-containing monomer is preferably from 0.1 to 20% by mass, more preferably from 0.1 to 20% by mass, from the viewpoint of obtaining sufficient adhesive strength even if the film is thinned. Is 0.5 to 15% by mass, more preferably 1 to 12% by mass.
In addition, there is no restriction | limiting in particular about the copolymerization form of (A) acrylic copolymer, Any of a random, a block, and a graft copolymer may be sufficient.

(A) The crosslinkable functional group possessed by the acrylic copolymer is a functional group capable of reacting with the crosslinking agent of component (D), and examples thereof include a carboxy group, a hydroxyl group, and an amino group. Among these, a carboxy group and a hydroxyl group are preferable from the viewpoint of reactivity with the crosslinking agent of the component (D), and a carboxy group is more preferable from the viewpoint of obtaining higher adhesive force.
Moreover, (A) The crosslinkable functional group which an acrylic copolymer has has an ethylenically unsaturated carboxylic acid or ( Those derived from hydroxyalkyl esters of meth) acrylic acid are preferred, and those derived from ethylenically unsaturated carboxylic acids are more preferred.

  Examples of the (meth) acrylic acid ester that is a main component monomer of the acrylic copolymer include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, and butyl (meth) acrylate. , Pentyl (meth) acrylate, hexyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, decyl (meth) acrylate, (meth) acrylic acid Examples include dodecyl, myristyl (meth) acrylate, palmityl (meth) acrylate, stearyl (meth) acrylate, and the like. Among these, butyl (meth) acrylate is preferable from the viewpoint of obtaining sufficient adhesive strength even if the pressure-sensitive adhesive layer is thinned.

These (meth) acrylic acid esters may be used alone or in combination of two or more. In addition, when using 2 or more types together, from the viewpoint of obtaining sufficient adhesive force even if the pressure-sensitive adhesive layer is thinned, the content of butyl acrylate is preferably 50 to 100% by mass in the (meth) acrylic acid ester used. More preferably, it is 70-100 mass%, More preferably, it is 80-100 mass%.
The content of the (meth) acrylic acid ester is preferably 70 to 99.000 in the monomer mixture which is a raw material of the acrylic copolymer, from the viewpoint of obtaining sufficient adhesive strength even when the pressure-sensitive adhesive layer is thinned. 9 mass%, More preferably, it is 80-99.5 mass%, More preferably, it is 85-99 mass%, More preferably, it is 88-95 mass%.

Examples of the monomer having a crosslinkable functional group include (meth) acrylic acid, itaconic acid, crotonic acid, maleic acid, fumaric acid and other ethylenically unsaturated carboxylic acids, (meth) acrylic acid 2-hydroxyethyl, (Meth) acrylic acid 4-hydroxybutyl, (meth) acrylic acid 2-hydroxypropyl, (meth) acrylic acid 3-hydroxypropyl, (meth) acrylic acid 2-hydroxybutyl, (meth) acrylic acid 3-hydroxybutyl, etc. (Meth) acrylic acid hydroxyalkyl ester, (meth) acrylic acid monomethylaminoethyl, (meth) acrylic acid monoethylaminoethyl, (meth) acrylic acid monomethylaminopropyl, (meth) acrylic acid monoethylaminopropyl ( And (meth) acrylic acid monoalkylaminoalkyl In addition, you may use these monomers individually or in combination of 2 or more types.
Among these, from the viewpoint of reactivity with the crosslinking agent, and from the viewpoint of obtaining sufficiently high adhesive force even if the pressure-sensitive adhesive layer is thinned, ethylenically unsaturated carboxylic acid, (meth) acrylic acid hydroxyalkyl ester are preferable, Ethylenically unsaturated carboxylic acids are more preferred.

  The content of the monomer having a crosslinkable functional group is preferably 0 in the monomer mixture which is a raw material of the acrylic copolymer, from the viewpoint of obtaining sufficient adhesive strength even when the pressure-sensitive adhesive layer is thinned. 0.1 to 20% by mass, more preferably 0.5 to 15% by mass, and still more preferably 1 to 12% by mass.

(A) The acrylic copolymer may contain a structural unit derived from a monomer other than the above as a structural unit.
Examples of other monomers include vinyl esters such as vinyl acetate and vinyl propionate, olefins such as ethylene, propylene, and isobutylene, halogenated olefins such as vinyl chloride and vinylidene chloride, styrene, methylstyrene, and vinyl. Examples thereof include aromatic vinyl monomers such as toluene, diene monomers such as butadiene, isoprene and chloroprene, and nitrile monomers such as (meth) acrylonitrile. These monomers may be used alone or in combination of two or more.

The method for obtaining the (A) acrylic copolymer from these monomer mixtures is not particularly limited, and can be carried out by a known polymerization method in the presence or absence of a solvent. Examples of the solvent to be used include ethyl acetate and toluene.
Further, a polymerization initiator may be used in the polymerization reaction. Examples of the polymerization initiator include azobisisobutyronitrile and benzoyl peroxide. The blending amount of these polymerization initiators is preferably 0.01 to 1 part by mass, more preferably 0.1 to 0.5 part by mass with respect to 100 parts by mass of the monomer mixture.
Moreover, it does not specifically limit as polymerization conditions, However, It is preferable to carry out on the conditions for polymerization temperature 50-90 degreeC and reaction time 2-30 hours.

The weight average molecular weight of the (A) acrylic copolymer thus obtained is preferably 300,000 to 1,500,000, more preferably 400,000 to 1,000,000, and more preferably, from the viewpoint of improving the adhesive performance and the like. 500,000 to 800,000. If it is 300,000 or more, the cohesive force of the pressure-sensitive adhesive layer is improved, and sufficient adhesive force is obtained. Moreover, if it is 1.5 million or less, the elasticity modulus of an adhesive layer will not become high too much and the fall of adhesive force can be suppressed.
In addition, in this invention, a weight average molecular weight (Mw) means the value of standard polystyrene conversion measured by the gel permeation chromatography (GPC) method, and is specifically the value measured by the method as described in an Example. (The same shall apply hereinafter).

<(B) Urethane resin>
The pressure-sensitive adhesive used in the present invention contains (B) urethane resin (hereinafter also referred to as “component (B)”). (B) By containing a urethane resin, a sufficiently high adhesive force can be obtained even if the pressure-sensitive adhesive layer is thinned.
In the present invention, the mass ratio [(A) / (B)] of (A) acrylic copolymer and (B) urethane resin is used to obtain an adhesive having an appropriate elastic modulus, and the adhesive layer is made into a thin film. From the viewpoint of obtaining a sufficient adhesive force even if it is adjusted, it is preferably 1/99 to 40/60, more preferably 5/95 to 30/70, and still more preferably 10/90 to 25/75. If the said mass ratio which shows the ratio of (A) component with respect to (B) component is 1/99 or more, the fall of the adhesive force by an elasticity modulus becoming too low can be avoided, What is 40/60 or less? In this case, it is possible to avoid a decrease in adhesive force due to an excessively high elastic modulus.

  (B) Urethane resin used in the present invention is obtained by reacting (b3) a chain extender with a terminal isocyanate urethane prepolymer obtained by reacting (b1) diol with (b2) a polyvalent isocyanate compound. A urethane resin is preferred.

(B1) Examples of the diol include alkanes such as 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, and 1,7-heptanediol. Examples include diols, alkylene glycols such as ethylene glycol, propylene glycol, diethylene glycol, and dipropylene glycol, polyalkylene glycols such as polyethylene glycol, polypropylene glycol, and polybutylene glycol, and polyoxyalkylene glycols such as polytetramethylene glycol. In addition, you may use these (b1) diols individually or in combination of 2 or more types.
Among these (b1) diols, a medium molecular weight glycol having a weight average molecular weight of about 1000 to 3000 is preferable from the viewpoint of suppressing gelation in the reaction of the obtained terminal isocyanate urethane prepolymer and (b3) chain extender.

(B2) Examples of the polyvalent isocyanate compound include aromatic polyisocyanate, aliphatic polyisocyanate, and alicyclic polyisocyanate.
Examples of the aromatic polyisocyanate include 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, 4,4′-diphenylmethane diisocyanate (MDI), 2,4-tolylene diisocyanate (2,4-TDI), 2 , 6-Tolylene diisocyanate (2,6-TDI), 4,4'-toluidine diisocyanate, 2,4,6-triisocyanate toluene, 1,3,5-triisocyanate benzene, dianisidine diisocyanate, 4,4 ' -Diphenyl ether diisocyanate, 4,4 ', 4 "-triphenylmethane triisocyanate, 1,4-tetramethylxylylene diisocyanate, 1,3-tetramethylxylylene diisocyanate and the like.
Examples of the aliphatic polyisocyanate include trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate (HMDI), pentamethylene diisocyanate, 1,2-propylene diisocyanate, 2,3-butylene diisocyanate, 1,3-butylene diisocyanate, and dodeca. Examples include methylene diisocyanate and 2,4,4-trimethylhexamethylene diisocyanate.
Examples of the alicyclic polyisocyanate include 3-isocyanate methyl-3,5,5-trimethylcyclohexyl isocyanate (IPDI), 1,3-cyclopentane diisocyanate, 1,3-cyclohexane diisocyanate, 1,4-cyclohexane diisocyanate, Methyl-2,4-cyclohexane diisocyanate, methyl-2,6-cyclohexane diisocyanate, 4,4′-methylenebis (cyclohexyl isocyanate), 1,4-bis (isocyanatemethyl) cyclohexane, 1,4-bis (isocyanatemethyl) cyclohexane Etc.
These (b2) polyvalent isocyanate compounds are trimethylolpropane adduct-type modified products of the above polyisocyanates, burette-type modified products reacted with water, and isocyanurate-type modified products containing isocyanurate rings. Also good.

  Among these (b2) polyvalent isocyanate compounds, 4,4′-diphenylmethane diisocyanate (MDI), 2,4-tolylene diisocyanate (2,4-TDI), 2 from the viewpoint of excellent physical properties of the pressure-sensitive adhesive. , 6-tolylene diisocyanate (2,6-TDI), hexamethylene diisocyanate (HMDI), 3-isocyanate methyl-3,5,5-trimethylcyclohexyl isocyanate (IPDI) and modified products thereof Preferably, from the viewpoint of weather resistance, one or more selected from HMDI, IPDI, and modified products thereof are more preferable.

The method for preparing the terminal isocyanate urethane prepolymer is not particularly limited. For example, a method in which the components (b1) and (b2), a urethanization catalyst added as necessary, and a solvent are charged into a reactor and reacted. Etc.
The blending ratio of the components (b1) and (b2) is preferably NCO group / OH group (molar ratio) of 1.1 to 3.0, more preferably 1 from the viewpoint of leaving an isocyanate group at the terminal. It is preferable to mix and react so as to be 2 to 2.5. If it is 1.1 or more, since gelation can be avoided, the tendency to thicken can be suppressed. On the other hand, if it is 3.0 or less, the unreacted polyvalent isocyanate compound concentration in the terminal isocyanate urethane prepolymer does not become too high, and the reaction with the (b3) chain extender described later can proceed smoothly.

  The isocyanate group content (NCO%) in the terminal isocyanate urethane prepolymer is JIS K 1603, although it varies depending on the reactivity of the components (b1) and (b2) used and the blending amount of the (b3) chain extender. Is preferably 0.5 to 12% by mass, more preferably 1 to 4% by mass. If it is 0.5 mass% or more, the reaction with the (b3) chain extender can be sufficiently advanced, and if it is 12 mass% or less, the reaction with the (b3) chain extender is sufficiently controlled. be able to.

Although there is no restriction | limiting in particular as a catalyst used in terminal isocyanate urethane prepolymer formation reaction, A tertiary amine type compound, an organometallic type compound, etc. are mentioned.
Examples of the tertiary amine compound include triethylamine, triethylenediamine, N, N-dimethylbenzylamine, N-methylmorpholine, 1,8-diazabicyclo [5.4.0] undecene-7 (DBU) and the like.
Examples of organometallic compounds include tin compounds and non-tin compounds.
Examples of tin compounds include dibutyltin dichloride, dibutyltin oxide, dibutyltin dibromide, dibutyltin dimaleate, dibutyltin dilaurate (DBTDL), dibutyltin diacetate, dibutyltin sulfide, tributyltin sulfide, tributyltin oxide, tributyltin Examples include acetate, triethyltin ethoxide, tributyltin ethoxide, dioctyltin oxide, tributyltin chloride, tributyltin trichloroacetate, and tin 2-ethylhexanoate.
Non-tin compounds include, for example, titanium compounds such as dibutyltitanium dichloride, tetrabutyltitanate, butoxytitanium trichloride, and lead compounds such as lead oleate, lead 2-ethylhexanoate, lead benzoate, and lead naphthenate. Iron compounds such as iron 2-ethylhexanoate and iron acetylacetonate, cobalt compounds such as cobalt benzoate and cobalt 2-ethylhexanoate, zinc compounds such as zinc naphthenate and zinc 2-ethylhexanoate, Examples thereof include zirconium naphthenate.
Among these catalysts, DBTDL, tin 2-ethylhexanoate, and tetrabutyl titanate are preferable. In addition, you may use these catalysts individually or in combination of 2 or more types.

  The addition amount of the catalyst used in the reaction is preferably 0.0001 to 1 part by mass, more preferably 0.005 to 0.1 part by mass with respect to 100 parts by mass of the component (b1) from the viewpoint of reactivity. It is.

  Solvents used in the reaction include aromatic hydrocarbons such as toluene and xylene, aliphatic hydrocarbons such as hexane, esters such as ethyl acetate and butyl acetate, ketones such as methyl ethyl ketone (MEK), dimethylformamide, and cyclohexanone. Etc. These solvents may be used alone or in combination of two or more.

  As reaction temperature in the said reaction, Preferably it is 120 degrees C or less, More preferably, it is 70-100 degreeC. If it is 120 degrees C or less, an alohanate reaction can suppress progress, the terminal isocyanate group prepolymer which has a predetermined molecular weight and structure can be synthesize | combined, and reaction rate can fully be controlled. The reaction time in the reaction is preferably 2 to 20 hours, for example, when the reaction temperature is 70 to 100 ° C.

The terminal isocyanate urethane prepolymer obtained as described above becomes a urethane resin by a chain extension reaction with the (b3) chain extender.
(B3) The chain extender is not particularly limited, but (b4) a compound having two hydroxyl groups and / or amino groups, and (b5) a compound having three or more hydroxyl groups and / or amino groups are preferably used. .

The component (b4) is not particularly limited as long as it is a compound having two hydroxyl groups and / or amino groups, but from the viewpoint of further preventing a decrease in adhesive strength, aliphatic diol, aliphatic diamine, alkanolamine, bisphenol. At least one compound selected from the group consisting of aromatic diamines is preferred.
Examples of the aliphatic diol include alkanediols such as 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, and 1,7-heptanediol. And alkylene glycols such as ethylene glycol, propylene glycol, diethylene glycol and dipropylene glycol.
Examples of the aliphatic diamine include ethylenediamine, 1,3-propanediamine, 1,4-butanediamine, 1,5-pentanediamine, 1,6-hexanediamine, and the like.
Examples of the alkanolamine include monoethanolamine, monopropanolamine, isopropanolamine and the like.
Examples of bisphenol include bisphenol A and the like.
Examples of the aromatic diamine include diphenylmethanediamine, tolylenediamine, xylylenediamine, and the like.

  The component (b5) is not particularly limited as long as it is a compound having three or more hydroxyl groups and / or amino groups, but polyols such as trimethylolpropane, ditrimethylolpropane, pentaerythritol, dipentaerythritol, 1-amino- Examples include amino alcohols such as 2,3-propanediol, 1-methylamino-2,3-propanediol, and N- (2-hydroxypropylethanolamine), and ethylene oxide or propylene oxide adducts of tetramethylxylylenediamine. .

The amino group and / or hydroxyl group in the components (b4) and (b5) are preferably a primary amino group, a secondary amino group, or a primary hydroxyl group from the viewpoint of reactivity with an isocyanate group.
The mass ratio [(b4) / (b5)] of the component (b4) and the component (b5) to be blended is preferably 70/30 to 100/0, more preferably 75/25 to 95/5, still more preferably 80/20 to 90/10. If the said mass ratio which shows the ratio of (b4) component with respect to (b5) component is 70/30 or more, even if it makes an adhesive layer thin, the fall of adhesive force can be suppressed and a urethane resin is obtained. In the chain extension reaction, gelation can be avoided and a desired pressure-sensitive adhesive can be obtained.

Examples of the chain extension reaction include (1) a method in which a solution of an isocyanate group-terminated prepolymer is charged into a reactor, and a chain extender is dropped into the reactor to cause a reaction, and (2) a chain extender is charged in the reactor. , A method in which a solution of an isocyanate group-terminated prepolymer is dropped and reacted, (3) a method in which a solution of an isocyanate group-terminated prepolymer is diluted with a solvent, and then a predetermined amount of a chain extender is charged into the reactor to react. Is mentioned. Since the isocyanate group gradually decreases and a uniform resin is easily obtained, the method (1) or (3) is preferable.
As the solvent, the same solvents that can be used for the terminal isocyanate group-terminated prepolymer formation reaction can be used.

  The addition amount of the chain extender (total addition amount of the components (b4) and (b5)) varies depending on the NCO group content of the isocyanate group-terminated prepolymer, but the NCO group of the urethane resin after chain extension is preferably The amount is 0.01 to 1.0% by mass, more preferably 0.05 to 0.2% by mass. If it is 0.01 mass% or more, chain | strand extension can fully be performed and the urethane resin of a desired molecular weight will be obtained. Moreover, if it is 1.0 mass% or less, the phenomenon which is rapidly thickened and gelatinized at the time of chain extension reaction can be suppressed.

The reaction temperature in the chain extension reaction is preferably 20 to 80 ° C. If it is 20 degreeC or more, chain extension reaction can be advanced at sufficient speed | rate. On the other hand, if it is 80 degrees C or less, reaction rate can fully be controlled and the urethane resin which has a desired molecular weight and structure will be obtained. When the chain extension reaction is performed in the presence of a solvent, the reaction temperature is preferably not higher than the boiling point of the solvent, and particularly preferably 40 to 60 ° C. in the presence of MEK and ethyl acetate.
The reaction time in the chain extension reaction is preferably 1 to 20 hours, for example, when the reaction temperature is 40 to 80 ° C.

An end terminator may be used to terminate the chain extension reaction.
Examples of the terminal terminator include a compound having only one hydrogen capable of reacting with an isocyanate group or a compound having only one amino group.
Examples of the compound having only one hydrogen capable of reacting with an isocyanate group include monool compounds such as methanol and ethanol.
As the compound having only one amino group, a compound having a primary amino group or a secondary amino group can be used, and examples thereof include diethylamine and morpholine.
A compound having one primary amino group has two reactive hydrogens, but the reactive hydrogen remaining after one reactive hydrogen has reacted is substantially less reactive. Equivalent to monofunctionality.
The addition amount of the terminal stopper is preferably such that the terminal stopper is 1 mole or more and 2 moles or less with respect to 1 mole of the terminal isocyanate group remaining after the chain extension reaction. If the addition amount of the terminal terminator is less than 1 mol, an isocyanate group remains after the termination reaction, and the resulting urethane resin becomes unstable. On the other hand, when the addition amount of the terminal terminator exceeds 2 mol, the low molecular weight urethane resin tends to increase.

  (B) The weight average molecular weight of a urethane resin becomes like this. Preferably it is 10,000-300,000, More preferably, it is 30,000-250,000, More preferably, it is 50,000-200,000. If it is 10,000 or more, it is preferable because the adhesive properties, particularly the holding power tends to be improved, and if it is 300,000 or less, gelation can be avoided.

<(C) Tackifying resin>
The pressure-sensitive adhesive used in the present invention contains (C) a tackifier resin (hereinafter also referred to as “component (C)”). (C) By containing a tackifier resin, it is possible to obtain a desired and sufficiently high adhesive force even if the pressure-sensitive adhesive layer is thinned, and to improve the adhesiveness of the pressure-sensitive adhesive layer to the base material. To the adherend can be suppressed, and these effects are particularly prominent in a low-temperature environment.

(C) As tackifying resins, natural resin-based tackifying resins such as rosin-based resins and terpene-based resins, polymerization-based tackifying resins such as pure / monomer-based petroleum resins, and condensation-based tackifying resins such as phenol-based resins One synthetic resin-based tackifying resin is mentioned.
Among these, terpene-based resins are preferable, and terpene phenol resins or hydrogenated terpene phenol resins are more preferable from the viewpoints of compatibility, adhesion of the pressure-sensitive adhesive layer to the base material, and improvement in adhesive strength.

(C) Although content of tackifying resin is 8-35 mass parts with respect to a total of 100 mass parts of (A) component and (B) component, Preferably it is 10-30 mass parts, More preferably, it is 15 ˜25 parts by mass.
When the content is less than 10 parts by mass, the adhesive strength is not sufficiently improved, the adhesiveness of the adhesive layer to the substrate is lowered, and the adhesive is transferred. On the other hand, when it exceeds 35 parts by mass, particularly in a low temperature environment, the adhesive strength is reduced, the adhesiveness of the adhesive layer to the substrate is reduced, and zipping is observed.

  (C) The softening point of the tackifier resin is preferably 80 to 150 ° C., more preferably 90 to 140 ° C., and still more preferably 95 from the viewpoint of improving the adhesion of the pressure-sensitive adhesive layer to the base material and the adhesive performance. ~ 130 ° C. In the present invention, the softening point is a value measured according to JIS K 2531 (the same applies hereinafter).

<(D) Crosslinking agent>
The adhesive used in the present invention contains a crosslinking agent capable of reacting with the crosslinkable functional group in the component (A) from the viewpoint of increasing the cohesive force and obtaining a desired adhesive force.
Examples of the crosslinking agent include an isocyanate crosslinking agent, an epoxy crosslinking agent, an aziridine crosslinking agent, a metal chelate crosslinking agent and an amine crosslinking agent, and an amino resin crosslinking agent.

Examples of the isocyanate crosslinking agent include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 1,3-xylylene diisocyanate, 1,4-xylylene diisocyanate, diphenylmethane-4,4′-diisocyanate, Polyvalent isocyanate compounds such as diphenylmethane-2,4′-diisocyanate, 3-methyldiphenylmethane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, dicyclohexylmethane-4,4′-diisocyanate, dicyclohexylmethane-2,4′-diisocyanate, lysine isocyanate Is mentioned.
The polyvalent isocyanate compound may be a trimethylolpropane adduct type modified product of the above compound, a burette type modified product reacted with water, or an isocyanurate type modified product containing an isocyanurate ring.

The epoxy-based crosslinking agent is not particularly limited as long as it has two or more epoxy groups or glycidyl groups in the molecule, but a polyfunctional epoxy compound containing two or more glycidyl groups in the molecule is preferable.
Examples of the polyfunctional epoxy compound containing two or more glycidyl groups in the molecule include diglycidyl ether of bisphenol A and oligomers thereof, diglycidyl ether of hydrogenated bisphenol A and oligomers thereof, orthophthalic acid diglycidyl ester, isophthalate Acid diglycidyl ester, terephthalic acid diglycidyl ester, p-oxybenzoic acid glycidyl ester, tetrahydrophthalic acid diglycidyl ester, hexahydrophthalic acid diglycidyl ester, succinic acid diglycidyl ester, adipic acid diglycidyl ester, sebacic acid di Glycidyl ester, ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, 1,6-hexanedi Diglycidyl ether and polyalkylene glycol diglycidyl ether, trimellitic acid triglycidyl ester, triglycidyl isocyanurate, 1,4-diglycidyloxybenzene, diglycidyl propylene urea, glycerol triglycidyl ether, trimethylolpropane di or tri Examples thereof include glycidyl ether, pentaerythritol di or triglycidyl ether, triglycidyl ether of glycerol alkylene oxide adduct, diglycidyl amine such as diglycidyl aniline, and the like.

  Although it does not specifically limit as an aziridine type crosslinking agent, As a specific example, 1,1'- (methylene-di-p-phenylene) bis-3, 3- aziridinyl urea, 1,1'- (hexamethylene) Bis-3,3-aziridinyl urea, 2,4,6-triaziridinyl-1,3,5-triazine, trimethylolpropane-tris- (2-aziridinylpropionate) and the like can be mentioned.

  Examples of the metal chelate-based crosslinking agent include compounds in which acetylacetone, ethyl acetoacetate, and the like are coordinated to a polyvalent metal such as aluminum, iron, copper, zinc, tin, titanium, nickel, antimony, magnesium, vanadium, chromium, and zirconium. Etc.

  Examples of amine-based crosslinking agents include polyamines such as aliphatic polyamines (for example, triethylenetetramine, tetraethylenepentamine, ethylenediamine, N, N-dicinnamylidene-1,6-hexanediamine, trimethylenediamine, hexamethylenediamine carbamate, ethanolamine. 3,9-bis (3-aminopropyl) -2,4,8,10-tetraoxa-2-spiro [5.5] undecane and the like) and salts thereof; aromatic polyamines (for example, diaminodiphenylmethane, xylylenediamine) , Phenylenediamine, diaminodiphenylsulfone and the like.

  Examples of amino resin-based crosslinking agents include methoxylated methylol urea, methoxylated methylol N, N-ethyleneurea, methoxylated methylol dicyandiamide, methoxylated methylol melamine, methoxylated methylol benzoguanamine, butoxylated methylol melamine, butoxylated methylol benzoguanamine, and the like. Preferably, methoxylated methylol melamine, butoxylated methylol melamine, methylolated benzoguanamine and the like can be mentioned.

  Among these, an isocyanate-based crosslinking agent is preferable from the viewpoint of obtaining high adhesive force even when the pressure-sensitive adhesive layer is thinned. In addition, you may use said crosslinking agent individually or in combination of 2 or more types.

  The content of the crosslinking agent is preferably 0.01 to 8 parts by mass with respect to a total of 100 parts by mass of the component (A) and the component (B) from the viewpoint of obtaining high adhesive strength even if the pressure-sensitive adhesive layer is thinned. More preferably, it is 0.05-5 mass parts, More preferably, it is 0.1-3 mass parts.

<Other ingredients>
The pressure-sensitive adhesive used in the present invention can be blended with other components as long as the effects of the present invention are not impaired. Examples of other components include ultraviolet absorbers, antioxidants, antiseptics, antifungal agents, plasticizers, antifoaming agents, and wettability adjusting agents.

[Base material]
There is no restriction | limiting in particular as a base material used for the double-sided adhesive sheet of this invention, According to the intended purpose of using a double-sided adhesive sheet, it selects suitably. For example, woven or non-woven fabric using fibers such as rayon, acrylic and polyester; paper such as fine paper, glassine paper, impregnated paper and coated paper; metal foil such as aluminum and copper; urethane foam, polyethylene foam, etc. Foams: polyester films such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polyurethane film, polyethylene film, polypropylene film, polyvinyl chloride film, polyvinylidene chloride film, polyvinyl alcohol film, ethylene-vinyl acetate copolymer film Plastic films such as polystyrene film, polycarbonate film, acrylic resin film, norbornene resin film, cycloolefin resin film; and laminates of two or more of these That.
Among these, a polyester film such as polyethylene terephthalate and a polyvinyl chloride film are preferable from the viewpoints of thickness accuracy, surface smoothness, and availability that are required as the film is thinned.

  The thickness of the substrate is preferably 1 to 12 μm, more preferably 1.5 to 8 μm, and still more preferably 2 to 6 μm from the viewpoint of easy handling and obtaining a double-sided pressure-sensitive adhesive sheet. .

[Peeling material]
Although there is no restriction | limiting in particular as a peeling material used for the double-sided adhesive sheet of this invention, From the viewpoint of the ease of handling, the peeling sheet which apply | coated the release agent on the base material is preferable. The release sheet may be one in which a release agent is applied to both surfaces of the substrate and subjected to a release treatment, or may be one in which the release agent is applied to only one surface of the substrate and subjected to the release treatment.
Examples of the base material of the release sheet include paper base materials such as glassine paper, coated paper, cast coated paper, laminated paper obtained by laminating a thermoplastic resin such as polyethylene on these paper base materials, or polyethylene terephthalate, polybutylene terephthalate. And polyester films such as polyethylene naphthalate, and plastic films such as polyolefin films such as polypropylene and polyethylene.
Examples of the release agent include rubber elastomers such as olefin resins, isoprene resins, butadiene resins, long chain alkyl resins, alkyd resins, fluorine resins, silicone resins, and the like.

Although there is no restriction | limiting in particular as thickness of a peeling sheet, Usually, 20-200 micrometers, Preferably it is 25-150 micrometers.
The thickness of the release sheet of the release sheet after drying is not particularly limited. However, when the release agent is applied in a solution state, it is preferably 0.01 to 2.0 μm, more preferably 0.03. When the plastic film is used as the base material of the release sheet, the thickness of the plastic film is preferably 3 to 50 μm, more preferably 5 to 40 μm.

[Method for producing double-sided PSA sheet]
The manufacturing method of the double-sided adhesive sheet of this invention is not specifically limited. For example, in the case of the double-sided pressure-sensitive adhesive sheet 1a shown in FIG. 1 (a), the pressure-sensitive adhesive layer 12a is formed by applying a pressure-sensitive adhesive on one surface of the base material 11 and drying it. Similarly, a pressure-sensitive adhesive can be applied on the surface and dried to form a pressure-sensitive adhesive layer 12b. Moreover, if it is the double-sided adhesive sheet 1b shown in FIG.1 (b), after apply | coating an adhesive on the surface of the peeling material 13a and making it dry and forming the adhesive layer 12a, on this adhesive layer 12a The base material 11 is bonded together to produce a single-sided pressure-sensitive adhesive sheet. Separately, a pressure-sensitive adhesive is similarly applied on the surface of the release material 13b and dried to form a pressure-sensitive adhesive layer 12b. The pressure-sensitive adhesive layer 12b and the substrate of the single-sided pressure-sensitive adhesive sheet prepared earlier are prepared. It is possible to produce a double-sided pressure-sensitive adhesive sheet 1b with a release material by laminating it with a surface opposite to the pressure-sensitive adhesive layer 12a. Further, the release material can be further removed to obtain the double-sided pressure-sensitive adhesive sheet 1a shown in FIG.

When applying the pressure-sensitive adhesive of the present invention, it is preferable to dilute with an organic solvent in order to easily form a thin pressure-sensitive adhesive layer on the substrate.
Examples of the organic solvent to be used include toluene, ethyl acetate, methyl ethyl ketone, and the like. By blending these organic solvents and setting the pressure-sensitive adhesive to be used to an appropriate solid content concentration, a thinned pressure-sensitive adhesive layer can be formed. The solid content concentration of the pressure-sensitive adhesive to be used is preferably 5 to 60% by mass, more preferably 10 to 40% by mass. If the amount is 5% by mass or more, the amount of the solvent used is sufficient, and if it is 60% by mass or less, the viscosity becomes appropriate and workability is improved when the adhesive solution is applied.
When the resin contained in the pressure-sensitive adhesive is produced, if the produced resin is contained in an organic solvent, it may be diluted with the same organic solvent and prepared to have the solid content concentration. Good.

The method for forming the pressure-sensitive adhesive layer on the substrate or the release material is not particularly limited, and examples thereof include a method for forming a pressure-sensitive adhesive (solution) containing the above organic solvent by a known coating method.
Examples of the coating method include known methods such as spin coating, spray coating, bar coating, knife coating, roll coating, blade coating, die coating, and gravure coating.
In addition, in order to prevent residual solvents and low-boiling components, and when a cross-linking agent is blended, in order to promote cross-linking (reaction) and develop adhesiveness, it is heated after being applied to a substrate or a release material. It is preferable to process.
As temperature conditions of heat processing, Preferably it is 70-150 degreeC, More preferably, it is 80-120 degreeC. The treatment time for the heat treatment is preferably 30 seconds to 5 minutes, more preferably 40 to 180 seconds.

[Physical properties of double-sided PSA sheet]
The adhesive strength at normal temperature (23 ° C., 50% RH (relative humidity)) of the double-sided PSA sheet of the present invention produced as described above is preferably 5.0 N / 25 mm in the measurement method described in the Examples. More preferably, it is 6.0 N / 25 mm or more, more preferably 6.5 N / 25 mm or more, and still more preferably 6.8 N / 25 mm.
Moreover, the double-sided pressure-sensitive adhesive sheet of the present invention exhibits excellent adhesive performance even at low temperatures. The adhesive strength at a low temperature (5 ° C., 50% RH) of the double-sided PSA sheet of the present invention is preferably 5.0 N / 25 mm or more, more preferably 6.0 N / 25 mm or more, in the measurement method described in the Examples. More preferably, it is 6.5 N / 25mm or more, More preferably, it is 7.0 N / 25mm or more.
Furthermore, since the double-sided pressure-sensitive adhesive sheet of the present invention is excellent in the adhesiveness of the pressure-sensitive adhesive layer to the base material in any environment of normal temperature and low temperature, the transfer of the pressure-sensitive adhesive to the adherend can be suppressed. .

The weight average molecular weight (Mw) shown in the description of the following examples is a value obtained by measurement under the following conditions using “HLC-8020” manufactured by Tosoh Corporation and calculated in terms of standard polystyrene.
(Measurement condition)
Column: “TSK guard column HXL-H” “TSK gel GMHXL (× 2)” “TSK gel G2000HXL” (both manufactured by Tosoh Corporation)
Column temperature: 40 ° C
Developing solvent: Tetrahydrofuran Flow rate: 1.0 mL / min

Production Example 1
(Preparation of acrylic copolymer solution)
As a monomer component, 90 parts by mass of butyl acrylate and 10 parts by mass of acrylic acid, 200 parts by mass of ethyl acetate as a solvent, and 0.2 parts by mass of azobisisobutyronitrile as a polymerization initiator are placed in a reactor. Mixed. After deaeration with nitrogen gas for 4 hours, the temperature was gradually raised to 60 ° C., and then the polymerization reaction was carried out with stirring for 24 hours. An ethyl acetate solution containing an acrylic copolymer (solid content concentration: about 33% by mass, Weight average molecular weight: 650,000).

Production Example 2
(Preparation of urethane resin solution)
(B1) 100 parts by mass of polypropylene glycol (weight average molecular weight: 2000) as the diol, (b2) 10.1 parts by mass of hexamethylene diisocyanate (NCO group / OH group (molar ratio)) = 1.2 as the polyvalent isocyanate compound ) As a catalyst, the temperature was gradually raised to 0.01 parts by weight of dibutyltin dilaurate and 85 ° C., followed by stirring for 2 hours to obtain a terminal isocyanate urethane prepolymer.
After adding 110 mass parts of toluene to the obtained terminal isocyanate urethane prepolymer and removing the temperature to room temperature, 0.48 mass parts of 1,4-butanediol corresponding to the component (b4) is used as the chain extender (b3). b5) 0.12 parts by mass of trimethylolpropane, which is a component, was dropped and gradually heated to 70 ° C., then stirred for 2 hours, and a toluene solution containing a urethane resin (solid content concentration: about 50.2% by mass, weight) Average molecular weight: 160,000).

Example 1
(A) As acrylic copolymer, 20 parts by mass (solid content) of ethyl acetate solution of acrylic copolymer prepared in Production Example 1, and (B) Toluene of urethane resin prepared in Production Example 2 as urethane resin 80 parts by mass (solid content) of the solution, (C) 10 parts by mass (solid content) of a terpene phenol resin (manufactured by Yasuhara Chemical Co., Ltd., trade name “YS Polystar T100”, softening point: 95 to 105 ° C.) as a tackifier resin ), (D) As a cross-linking agent, an isocyanate-based cross-linking agent (manufactured by Nippon Polyurethane Co., Ltd., trade name “Coronate L”, a modified product of tolylene diisocyanate (trimethylolpropane adduct) ) A mixture of 2 parts by mass (solid content) was diluted with ethyl acetate so that the solid content was 10% by mass to obtain a solution of the pressure-sensitive adhesive composition.
This solution was applied to a silicone-treated 38 μm polyester film (trade name “SP-PET 381031”, manufactured by Lintec Corporation) so that the thickness of the pressure-sensitive adhesive layer after drying was 1 μm, and dried at 100 ° C. for 1 minute. Later, it was bonded to a polyester film having a thickness of 2 μm (trade name “Lumirror 2D C61” manufactured by Toray Industries, Inc.) as a substrate (bonding the first pressure-sensitive adhesive layer). Next, the solution was applied to a silicone-treated 38 μm polyester film (trade name “SP-PET382150” manufactured by Lintec Corporation) so that the thickness of the pressure-sensitive adhesive layer after drying was 1 μm, and then at 100 ° C. for 1 minute. After drying, the double-sided pressure-sensitive adhesive sheet was obtained by bonding to the surface of the substrate opposite to the side where the first pressure-sensitive adhesive layer was bonded.

Example 2
(C) Adhesive composition as in Example 1 except that 20 parts by mass (solid content) of a toluene solution of a terpene phenol resin (manufactured by Yasuhara Chemical Co., Ltd., trade name “YS Polystar T100”) was used as the component (C). The solution of the thing was prepared and the double-sided adhesive sheet was obtained.

Example 3
(C) Adhesive composition as in Example 1 except that 30 parts by mass (solid content) of a toluene solution of a terpene phenol resin (manufactured by Yasuhara Chemical Co., Ltd., trade name “YS Polystar T100”) was used as the component (C). The solution of the thing was prepared and the double-sided adhesive sheet was obtained.

Example 4
(C) As a component, except that 10 parts by mass (solid content) of a toluene solution of a hydrogenated terpene phenol-based resin (manufactured by Yasuhara Chemical Co., Ltd., trade name “YS Polystar NH125”, softening point: 120 to 130 ° C.) was used. In the same manner as in Example 1, a solution of the pressure-sensitive adhesive composition was prepared to obtain a double-sided pressure-sensitive adhesive sheet.

Example 5
(C) As component 1, except that 20 parts by mass (solid content) of a toluene solution of a hydrogenated terpene phenol resin (trade name “YS Polystar NH125” manufactured by Yasuhara Chemical Co., Ltd.) was used. A solution of the agent composition was prepared to obtain a double-sided PSA sheet.

Example 6
(C) As component 1, except that 30 parts by mass (solid content) of a toluene solution of a hydrogenated terpene phenol resin (trade name “YS Polystar NH125” manufactured by Yasuhara Chemical Co., Ltd.) was used. A solution of the agent composition was prepared to obtain a double-sided PSA sheet.

Comparative Example 1
(C) Adhesive composition in the same manner as in Example 1 except that 5 parts by mass (solid content) of a toluene solution of a terpene phenol resin (trade name “YS Polystar T100” manufactured by Yasuhara Chemical Co., Ltd.) was used as the component. The solution of the thing was prepared and the double-sided adhesive sheet was obtained.

Comparative Example 2
(C) Adhesive composition in the same manner as in Example 1 except that 40 parts by mass (solid content) of a toluene solution of a terpene phenol resin (trade name “YS Polystar T100” manufactured by Yashara Chemical Co., Ltd.) was used as the component. The solution of the thing was prepared and the double-sided adhesive sheet was obtained.

Comparative Example 3
(C) As component 1, except that 5 parts by mass (solid content) of a toluene solution of hydrogenated terpene phenol resin (trade name “YS Polystar NH125” manufactured by Yasuhara Chemical Co., Ltd.) was used, A solution of the agent composition was prepared to obtain a double-sided PSA sheet.

Comparative Example 4
(C) As component 1, except that 40 parts by mass (solid content) of a toluene solution of hydrogenated terpene phenol resin (trade name “YS Polystar NH125” manufactured by Yasuhara Chemical Co., Ltd.) was used, A solution of the agent composition was prepared to obtain a double-sided PSA sheet.

Comparative Example 5
(C) Except not having used the tackifier of a component, it carried out similarly to Example 1, the solution of the adhesive composition was prepared, and the double-sided adhesive sheet was obtained.

The double-sided PSA sheet obtained as described above was evaluated by performing the following tests. The evaluation results are shown in Table 1.
(Test 1) Adhesive strength measurement After producing the adhesive sheet, the release sheet (SP-PET 381031) was peeled off at 23 ° C. and 50% RH, and a polyester film having a thickness of 25 μm (trade name “T100” manufactured by Mitsubishi Plastics, Inc.). Then, the other release sheet (SP-PET 381031) of the adhesive sheet test piece cut to 25 mm × 300 mm is peeled off and attached to the adherend (SUS304 steel plate) via the adhesive layer. did. Based on JIS Z0237: 2000, the adhesive strength at 24 hours after application was measured at a pulling rate of 300 mm / min by a 180 ° peeling method. Moreover, the peeling form at the time of measurement was observed. The peeling form shown in Table 1 shows the following state.
Interfacial fracture: Interfacial fracture was observed at the interface between the pressure-sensitive adhesive layer and the adherend.
-Adhesive transfer: Transfer of the adhesive to the adherend was observed.
-Zipping: Zipping of the adhesive was observed.

(Test 2) Low-temperature adhesive strength measurement After preparing the pressure-sensitive adhesive sheet, a pressure-sensitive adhesive sheet test piece cut to 25 mm × 300 mm was attached to an adherend (SUS304 steel plate) in a 5 ° C. and 50% RH environment to obtain a test sample. Based on JIS Z0237: 2000, the adhesive strength at 24 hours after application was measured at a pulling rate of 300 mm / min by a 180 ° peeling method. Moreover, the peeling form at the time of measurement was observed. The peeling form shown in Table 1 is the same as the state shown in Test 1 above.

From Table 1, the double-sided pressure-sensitive adhesive sheets obtained in Examples 1 to 6 of the present invention have excellent adhesive strength at both normal temperature and low temperature, and good adhesion to the base material of the pressure-sensitive adhesive layer. Therefore, the transfer of the adhesive to the adherend is not observed.
On the other hand, the double-sided pressure-sensitive adhesive sheets of Comparative Examples 1, 3, and 5 had insufficient adhesive strength, the adhesiveness of the pressure-sensitive adhesive layer to the base material was inferior, and the pressure-sensitive adhesive transferred to the adherend. In addition, the double-sided PSA sheets of Comparative Examples 2 and 4 were significantly lower in adhesive strength in a low-temperature environment than in a normal temperature environment, and further zipping was observed.

  The double-sided pressure-sensitive adhesive sheet of the present invention has a sufficiently high adhesive force even when the pressure-sensitive adhesive layer is thinned, and has excellent adhesion to the base material of the pressure-sensitive adhesive layer. It can be a double-sided pressure-sensitive adhesive sheet that does not migrate, and these effects are particularly remarkable in a low-temperature environment. Therefore, it can contribute to miniaturization and thinning of portable electronic devices, and is particularly suitable for applications such as electronic devices and optical devices that are often used in a low temperature environment.

DESCRIPTION OF SYMBOLS 1a, 1b Double-sided adhesive sheet 11 Base material 12a, 12b Adhesive layer 13a, 13b Release material

Claims (10)

A double-sided pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer on both sides of a substrate,
The pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer contains (A) an acrylic copolymer having a crosslinkable functional group, (B) a urethane resin, (C) a tackifier resin, and (D) a crosslinking agent. And
(C) the content of the tackifying resin, per 100 parts by weight of component (A) and component (B), Ri 8 to 35 parts by mass der,
(B) The urethane resin is obtained by reacting (b3) a chain extender with a terminal isocyanate urethane prepolymer obtained by reacting (b1) a diol with (b2) a polyvalent isocyanate compound,
(B3) The chain extender is one or more selected from the group consisting of (b4) a compound having two hydroxyl groups and / or amino groups, and (b5) a compound having three or more hydroxyl groups and / or amino groups. A compound comprising:
The double-sided pressure-sensitive adhesive sheet having a mass ratio [(b4) / (b5)] of the component (b4) and the component (b5) of 70/30 to 100/0 .   The double-sided pressure-sensitive adhesive sheet according to claim 1, wherein the component (b4) is at least one compound selected from the group consisting of aliphatic diols, aliphatic diamines, alkanolamines, bisphenols, and aromatic diamines.   (C) The double-sided adhesive sheet of Claim 1 or 2 whose softening point of tackifying resin is 95-130 degreeC.   (C) The double-sided pressure-sensitive adhesive sheet according to any one of claims 1 to 3, wherein the tackifying resin is a terpene phenol resin or a hydrogenated terpene phenol resin. (B1) The double-sided pressure-sensitive adhesive sheet according to any one of claims 1 to 4 , wherein the diol is a glycol having a molecular weight of 1,000 to 3,000.   The double-sided pressure-sensitive adhesive sheet according to any one of claims 1 to 5, wherein the crosslinkable functional group of component (A) is derived from an ethylenically unsaturated carboxylic acid or a (meth) acrylic acid hydroxyalkyl ester.   (D) The double-sided pressure-sensitive adhesive sheet according to any one of claims 1 to 6, wherein the crosslinking agent is an isocyanate-based crosslinking agent.   The mass ratio [(A) / (B)] of (A) acrylic copolymer and (B) urethane resin is 1/99 to 40/60. Double-sided adhesive sheet.   (A) The double-sided adhesive sheet in any one of Claims 1-8 whose weight average molecular weights (Mw) of an acryl-type copolymer are 300,000-1,500,000.   The double-sided pressure-sensitive adhesive sheet according to any one of claims 1 to 9, wherein the pressure-sensitive adhesive layer has a thickness of 0.1 to 5.0 µm and the base material has a thickness of 1 to 12 µm.