JP2016204467A - Two-liquid type urethane adhesive - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a urethane adhesive that has flexibility at room temperature, can retain elasticity even at a high temperature, and can expect impact resistance, followability to steps or the like, and adhesion over the range from a low temperature to a high temperature.SOLUTION: The two-liquid curable type urethane adhesive uses one which is produced by using a urethane prepolymer and a crosslinking agent, in which the urethane prepolymer is produced by using a polyol and a polyisocyanate. In the urethane prepolymer, the polyol has an average functional group number f of 1.7 or more; and the relationship between the average functional group number f of the polyol and the addition amount Eq (equivalent) of the crosslinking agent satisfies the following formula: 1-(f-1.7)×10<Eq<20-(f-1.7)×20 (provided that Eq>0) and which has an elastic modulus at frequency of 1 Hz and 25°C of not more than 2×10Pa and an elastic modulus at frequency of 1 Hz and 80°C of not less than 2×10Pa.SELECTED DRAWING: None

Description

  The present invention relates to a two-component curable urethane pressure-sensitive adhesive. The pressure-sensitive adhesive of the present invention is a pressure-sensitive adhesive that has flexibility at room temperature and can retain elasticity even at high temperatures, and can be expected to have impact resistance, followability to steps, and adhesion from low to high temperatures.

  Adhesives are used in, for example, tapes, labels, seals, cosmetic sheets, non-slip sheets, double-sided adhesive tapes, etc. In recent years, various adhesives such as adhesion of liquid crystal displays and touch panels of personal computers, televisions, mobile phones, etc. Used in the field.

  As the adhesive, for example, an acrylic adhesive, a rubber adhesive, a silicone adhesive, a urethane adhesive, an oxyalkylene adhesive, and the like are known, and particularly recently, a strong adhesive having a strong adhesive force. There is a tendency that acrylic pressure-sensitive adhesives are used in a wide range of applications from mold-type pressure-sensitive adhesives to slightly pressure-sensitive pressure-sensitive adhesives having minute adhesive strength.

  However, the acrylic pressure-sensitive adhesive has problems with odor and skin irritation when the acrylic monomer remains in the pressure-sensitive adhesive. In addition, the acrylic pressure-sensitive adhesive tends to increase in adhesive strength or transferability due to a change with time after being attached to an adherend. For this reason, there is a problem that adhesive residue tends to be generated on the adherend and re-peelability tends to be insufficient. In addition, the acrylic pressure-sensitive adhesive has a problem that it has poor impact resistance at low temperatures due to the use of a comonomer having a high glass transition temperature in order to develop cohesive force, resulting in poor low-temperature characteristics.

  In contrast, urethane adhesives have the advantage that they have a smaller molecular weight than acrylic adhesives and can easily follow changes in the shape of the adherend, but contain a curing agent because it is difficult to increase the molecular weight. This ensures cohesion. In the case of such a pressure-sensitive adhesive with a large amount of curing agent added, the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet has a high modulus of elasticity and cannot sufficiently follow the shape change, or in the case of a pressure-sensitive adhesive with a small amount of hardener added, a manufacturing process. Therefore, there is a demand for a urethane pressure-sensitive adhesive that has high followability to a printing step at room temperature and is excellent in workability that does not flow even at high temperatures.

  For example, Patent Document 1 discloses a polyether polyol having an average number of functional groups per molecule of 2.2 to 3.4, a polyisocyanate compound, a catalyst, and a pressure-sensitive adhesive having low release rate dependency and good transparency. Urethane containing a OH-terminated urethane prepolymer A containing a polyfunctional isocyanate compound B and an OH group of component A and an NCO group of component B in an NCO / OH equivalent ratio of 0.5 to 1.6 An adhesive composition is disclosed.

  However, the urethane pressure-sensitive adhesive composition described in Patent Document 1 has a low molecular weight of the polyether polyol and uses a large amount of trifunctional polyether polyol. There was a problem that bubbles could not be generated. Furthermore, since adhesive force was low, it was inferior to the adhesiveness to a base material. In addition, since the polyol used has a low molecular weight and a relatively large amount of isocyanate is used, many hard domains having crystallinity may be formed. When used in optical applications, there is a concern that transparency is not sufficient. It was.

JP 2006-18295 A

  The present invention has been made in view of the background art described above, and an object of the present invention is to provide a urethane pressure-sensitive adhesive that has flexibility at room temperature and can retain elasticity even at high temperatures, and further has impact resistance. An object of the present invention is to provide a urethane pressure-sensitive adhesive that can be expected to follow a printing step and to adhere from a low temperature to a high temperature.

  As a result of intensive studies to solve the above problems, the present inventors have completed the present invention.

  That is, the present invention relates to a two-component curable urethane pressure-sensitive adhesive as shown below, and a pressure-sensitive adhesive sheet using the same.

[1] A two-component curable urethane pressure-sensitive adhesive obtained by using a urethane prepolymer and a crosslinking agent,
The urethane prepolymer is obtained using a polyol and a polyisocyanate,
The average functional group number f of the polyol is 1.7 or more,
The relationship between the average functional group number f of the polyol and the addition amount Eq (equivalent) of the crosslinking agent is represented by the following formula:
1- (f-1.7) × 10 <Eq <20- (f-1.7) × 20 (where Eq> 0)
And a two-component curable urethane characterized by having an elastic modulus of 2 × 10 ⁵ Pa or less at a frequency of 1 Hz and 25 ° C. and an elastic modulus of 2 × 10 ⁴ Pa or more at a frequency of 1 Hz and 80 ° C. Adhesive.

  [2] The two-part curable urethane pressure-sensitive adhesive as described in [1] above, wherein the gel fraction is in the range of 20 to 65%.

  [3] The two-component curable urethane pressure-sensitive adhesive according to [1] or [2], wherein the gel has a swelling degree of 950% or more.

  [4] The two-part curable urethane pressure-sensitive adhesive according to any one of [1] to [3], wherein the glass transition temperature is in the range of −80 ° C. to −30 ° C.

  [5] The ratio of the loss elastic modulus G ″ and the storage elastic modulus G ′ at a frequency of 1 Hz and 25 ° C. (tan δ) is 0.3 or more, and any one of the above [1] to [4] The two-component curable urethane pressure-sensitive adhesive as described.

  [6] The two-component curable type according to any one of the above [1] to [5], wherein the adhesive strength with non-alkali glass measured by the method of JIS Z0237 is in the range of 3 to 25 N / 25 mm. Urethane adhesive.

[7] The two-component curable urethane adhesive according to any one of [1] to [6] above, wherein the ball tack measured by the method of JIS Z0237 is 6 or more. [8] The method of JIS Z0237 The two-component curable urethane pressure-sensitive adhesive according to any one of the above [1] to [7], wherein the holding power at 40 ° C. measured in step 1 is 10 minutes or more.

  [9] The two-component curable urethane pressure-sensitive adhesive according to any one of the above [1] to [8], wherein the Haze at 40 μm measured by the method of JIS K7136 is 5% or less.

  [10] The two-component curable type according to any one of the above [1] to [8], which has one or more kinds of base materials and a pressure-sensitive adhesive layer provided on the base materials. A pressure-sensitive adhesive sheet, which is a urethane pressure-sensitive adhesive.

  [11] It has one or more kinds of base materials and a pressure-sensitive adhesive layer provided on the base material, and the pressure-sensitive adhesive layer is the two-component curable urethane pressure-sensitive adhesive described in [9]. Features optical adhesive sheet

  The urethane pressure-sensitive adhesive of the present invention has flexibility at room temperature, can retain elasticity even at high temperatures, and can be expected to have impact resistance, followability to printing steps, adhesion from low temperature to high temperature, for example, It can be suitably used as an adhesive layer of an adhesive sheet.

  Hereinafter, the present invention will be described in detail.

The present invention is a two-component curable urethane pressure-sensitive adhesive obtained using a urethane prepolymer and a crosslinking agent,
The urethane prepolymer is obtained using a polyol and a polyisocyanate,
The average functional group number f of the polyol is 1.7 or more,
The relationship between the average functional group number f of the polyol and the addition amount Eq (equivalent) of the crosslinking agent is represented by the following formula:
1- (f-1.7) × 10 <Eq <20- (f-1.7) × 20 (where Eq> 0)
And the elastic modulus at a frequency of 1 Hz and 25 ° C. is 2 × 10 ⁵ Pa or less, and the elastic modulus at a frequency of 1 Hz and 80 ° C. is 2 × 10 ⁴ Pa or more.

Urethane adhesive of the present invention is an elastic modulus at a frequency 1 Hz, 25 ° C. is not more than 2 × ¹⁰ 5 Pa, preferably in the range of ^{3 × 10 4 Pa~2 × 10 5} Pa, more preferably , 6 × 10 ⁴ Pa to 1.9 × 10 ⁵ Pa. If the elastic modulus at a frequency of 1 Hz and 25 ° C. exceeds 2 × 10 ⁵ Pa, a follow-up failure with respect to the deformation of the pressure-sensitive adhesive occurs, and bubbles are generated without being able to follow the steps of the adherend, making it difficult to use. .

The urethane pressure-sensitive adhesive of the present invention is characterized in that the elastic modulus at a frequency of 1 Hz and 80 ° C. is 2 × 10 ⁴ Pa or more. Preferably, it is the range of 2 * 10 < ⁴ > Pa-2 * 10 < ⁵ > Pa, More preferably, it is the range of 2.2 * 10 < ⁴ > Pa-1.5 * 10 < ⁵ > Pa. When the elastic modulus at a frequency of 1 Hz and 80 ° C. is lower than 2 × 10 ⁴ Pa, the heat resistance is poor, the liquid flows in the process of applying heat, the molding is difficult, and the use is difficult. Even at room temperature, the adhesive strength is low due to insufficient cohesion due to insufficient crosslinking, making it difficult to use as a pressure-sensitive adhesive.

  In the present invention, the elastic modulus at 25 ° C. and 80 ° C. is measured using a dynamic viscoelasticity measuring apparatus UBM Rheogel E-4000, measurement temperature −80 ° C. to 200 ° C., temperature increase rate 2 ° C./min, frequency It means the value of the storage elastic modulus G ′ measured at 1 Hz and shear mode conditions at each temperature.

  The gel fraction of the urethane pressure-sensitive adhesive of the present invention is not particularly limited, but a range of 20% to 65% is preferable. More preferably, it is in the range of 22% to 60%, and most preferably in the range of 25% to 55%. A gel fraction of the pressure-sensitive adhesive of 20% to 65% is preferable because good adhesion reliability and impact resistance can be expected.

  Although the swelling degree of the gel of the urethane adhesive of this invention is not specifically limited, It is preferable that it is 950% or more. Of these, a range of 950% to 4000% is preferable, and a range of 1150% to 2500% is more preferable. If the degree of swelling of the gel of the pressure-sensitive adhesive is 950% or more, it is preferable because high gel strength can be expected without the gel becoming too dense.

  The number average molecular weight of the sol of the urethane pressure-sensitive adhesive of the present invention is not particularly limited, but a range of 15000 to 100,000 is preferable. More preferably, it is the range of 35000-80000, Most preferably, it is the range of 40000-70000. If the number average molecular weight of the sol content of the urethane pressure-sensitive adhesive is in the range of 15,000 to 100,000, high adhesive force and holding power can be expected while suppressing the components transferred to the base material.

  The gel fraction of the urethane pressure-sensitive adhesive of the present invention represents the ratio (%) of insoluble matter that remains undissolved when 0.2 g of pressure-sensitive adhesive is added to 100 ml of ethyl acetate and left to stand for 7 days. The component obtained in this manner was used as the sol content.

  Moreover, the ratio (%) of the weight in the swollen state immediately after taking out the gel part of urethane adhesive, and the weight after drying with an explosion-proof dryer at 80 ° C. for 8 hours was defined as the degree of swelling of the gel.

  Although the glass transition temperature of the urethane adhesive of this invention is not specifically limited, The range of -80 degreeC--30 degreeC is preferable. More preferably, it is the range of -80 degreeC--50 degreeC. If the glass transition temperature is in the range of −80 ° C. to −30 ° C., the adhesive residue and heat resistance are not reduced, and peeling and cracking can be suppressed when dropped even at low temperatures, and high adhesion at low temperatures can be expected. preferable.

  The ratio (tan δ) of the loss elastic modulus G ″ and the storage elastic modulus G ′ at a frequency of 1 Hz and 25 ° C. of the urethane adhesive of the present invention is not particularly limited, but is preferably 0.3 or more. The tan δ at a frequency of 1 Hz and 25 ° C. is preferably in the range of 0.35 to 1.4, more preferably in the range of 0.37 to 0.85. Loss elastic modulus G ″ and storage elastic modulus G at 25 ° C. The ratio of tan (tan δ) is preferably 0.3 or more because it is viscous and can be expected to convert energy into heat and the like, and therefore can be expected to absorb vibration and impact resistance at room temperature.

  In the present invention, tan δ at a glass transition temperature of 25 ° C. is measured at a temperature of −80 ° C. to 200 ° C., a temperature increase rate of 2 ° C./min, a frequency using a dynamic viscoelasticity measuring device UBM Rheogel E-4000. Measurement was performed under 1 Hz and shear mode conditions, and the temperature at which the peak value of tan δ, which is the ratio of the loss elastic modulus G ″ to the storage elastic modulus G ′, was evaluated as the glass transition temperature, and the value at 25 ° C. was 25 ° C. Was evaluated as a ratio (tan δ) between the loss elastic modulus G ″ and the storage elastic modulus G ′.

  Although the adhesive force with the alkali free glass measured by the method of JIS Z0237 of the urethane adhesive of this invention is not specifically limited, It is preferable that it is the range of 3-25N / 25mm, and is the range of 3-15N / 25mm. More preferably. If the adhesive strength with non-alkali glass is in the range of 3 to 25 N / 25 mm, it is preferable because adhesion reliability to the substrate, impact resistance and removability can be expected.

  The adhesive strength of the urethane pressure-sensitive adhesive of the present invention is a value measured according to JIS Z0237 using a 0.7 mm thick Corning Eagle XG as non-alkali glass. Specifically, a 25 μm thick PET film Lumirror S-10 manufactured by Toray Industries Inc. is lined on the adhesive surface, cut to a width of 25 mm, and roll-bonded according to JIS Z0237 to prepare a test piece. Using a tensile tester RTG-1210 manufactured by Orientec Co., in accordance with JIS Z0237, under an atmosphere of 23 ° C. and 50% RH, with a peeling angle of 180 ° and a tensile speed of 300 mm / min, 180 ° peeling The adhesive strength (N / 25 mm) was defined as the adhesive strength.

  Although the ball tack measured by the method of JIS Z0237 of the urethane pressure-sensitive adhesive of the present invention is not particularly limited, it is preferably 6 or more. Especially, it is preferable that it is the range of 6-20, More preferably, it is the range of 6-14. A ball tack of 6 or more is preferable because it is difficult for the pressure-sensitive adhesive to float or peel from the substrate.

  The ball tack of the urethane pressure-sensitive adhesive of the present invention is a value evaluated in accordance with JIS Z0237. Specifically, the ball No. stopped at a pressure-sensitive adhesive distance of 10 cm under the conditions of an inclination angle of 30 degrees and a running distance of 10 cm. It is.

  The retention strength of the urethane pressure-sensitive adhesive used in the present invention measured by the method of JIS Z0237 is not particularly limited, but it is preferably 10 minutes or more, more preferably 100 minutes or more at 40 ° C.

  The holding force of the urethane pressure-sensitive adhesive of the present invention is a value evaluated according to JIS Z0237. Specifically, it is bonded to a SUS substrate with an adhesive surface of 25 mm × 25 mm, and the weight is applied under the conditions of 40 ° C. and a static load of 1 kg. The time to fall was evaluated. If the holding force is 10 minutes or more under the condition of 40 ° C., the migration component is small, and the elastic modulus can be held at a high temperature with high cohesive force.

  Although Haze measured by the method of JISK7136 of the urethane pressure-sensitive adhesive of the present invention is not particularly limited, Haze at 40 μm thickness is preferably 5% or less, and more preferably Haze is 0.8% or less. It is preferable that the haze at a thickness of 40 μm is 5% or less because the transparency is high, the visibility is excellent, and a good appearance can be expected. Although not particularly limited, when used in optical applications such as an optical pressure-sensitive adhesive sheet, the Haze at a thickness of 40 μm is preferably 5% or less. Such an adhesive having a haze of 5% or less at a thickness of 40 μm is preferably produced under the condition that the amount of the crosslinking agent is 7 equivalents or less (molar ratio) with respect to the reactive group of the urethane prepolymer.

  In the present invention, Haze is a value excluding the substrate used for measurement. Specifically, when the haze of the PMMA substrate is 0.2% and the haze in the two-layer structure of PMMA and the adhesive is 0.5%, the haze of the adhesive is 0.5-0.2 = 0. 3%.

  The urethane pressure-sensitive adhesive of the present invention has flexibility at room temperature and can retain elasticity even at high temperatures, and is excellent in vibration absorption, adhesiveness, low temperature characteristics, tackiness, followability to printing steps, impact resistance, and low temperature. Adhesion up to high temperatures can be expected.

  In the urethane pressure-sensitive adhesive of the present invention, a urethane prepolymer obtained using a polyol and a polyisocyanate is used.

  Such a urethane prepolymer is not particularly limited, but preferably has a reactive group in the molecule. The reactive group is not particularly limited, but preferably contains a reactive group that reacts with an isocyanate group such as an active hydrogen group, and a reactive group that reacts with an active hydrogen group such as an isocyanate group, and particularly contains a hydroxyl group at the molecular end. It is preferably a hydroxyl group-terminated urethane prepolymer. A hydroxyl group is a terminal structure when the ratio of the total amount of OH groups possessed by the NCO group and polyol possessed by the polyisocyanate is 1.00 or less. In addition, in the range exceeding 1.00, many isocyanate groups have a terminal structure.

  Although it does not specifically limit as a terminal structure of the urethane prepolymer used for the urethane adhesive of this invention, For example, 1 type (s) or 2 or more types, such as a hydroxyl group, an amino group, an isocyanate group, and an allyl group, are mentioned.

  The number average molecular weight in terms of standard polystyrene of the urethane prepolymer used in the urethane pressure-sensitive adhesive of the present invention is preferably in the range of 30,000 to 300,000, more preferably in the range of 50,000 to 180,000. If the number average molecular weight of the urethane prepolymer is in the range of 30,000 to 300,000, the viscosity of the urethane prepolymer does not become too high, and the resulting urethane cured product can be expected to have good flexibility, which is preferable. The number average molecular weight in terms of standard polystyrene is measured by GPC (gel permeation chromatography) under the conditions of a column temperature of 40 ° C., a flow rate of 1.0 ml / min, and a solvent THF, and a cubic approximate curve calibration curve using standard polystyrene. Can be calculated as

  The viscosity of the urethane prepolymer used in the urethane pressure-sensitive adhesive of the present invention is not particularly limited and is selected depending on the application, but is preferably in the range of 15 to 1000000 Pa · s (25 ° C.), more preferably 15 to 500000 Pa ·. It is the range of s (25 ° C.). When the viscosity of the urethane prepolymer is in the range of 15 to 1,000,000 Pa · s (25 ° C.), a resin having a sufficient molecular weight is formed, and good dispersibility in a solvent and coating properties can be expected.

  Here, as a polyol used for a urethane prepolymer, since favorable softness | flexibility, transparency, and a low temperature characteristic can be anticipated, it is preferable that a polyether polyol is included.

  As the polyether polyol, a bifunctional polyether diol (hereinafter referred to as “polyol A”) is preferable, and a tri- or higher functional polyether polyol (hereinafter referred to as “polyol B”) is included as necessary. It is preferable. It is preferable to contain a bifunctional polyol A and, if necessary, a trifunctional or higher functional polyol B because good flexibility, impact resistance, adhesive strength and tackiness can be expected.

  In the present invention, the polyol A is preferably a compound having an oxyalkylene group and having two hydroxyl groups per molecule in an arbitrary position such as a polymer terminal or a branched chain terminal.

  Examples of such polyol A include bifunctional polyalkylene oxides such as polyoxypropylene glycol, polyoxyethylene glycol, and poly (oxypropylene-oxyethylene) diol, and are not particularly limited. Specifically, Sanyo Chemical Co., Ltd. Sannix PP-1000, PP-2000, PP-3000, PP-4000, Mitsui Chemicals Actol P-22, P-21, P-23, P-28, ED -28, Exenol 720, 1020, 2020, 3020, 4020, 510, 4002, 4010, 4019, 5001, 5005, Preminol 4002, 5005, Preminol S4004, 4011, 4012, 4015, 4008F, 4013F, 4318F, Sun, manufactured by Asahi Glass Co., Ltd. Oil company unio Available as commercial products such as D-1000, D-1200, D-2000, D-4000, PB-700, PEG # 1500, PEG # 2000, Pronon # 102, # 104, # 202B, # 204. it can.

  The polyol A is not limited to one type, and a plurality of types of polyether diols may be mixed and used.

  The polyol A preferably has an oxypropylene group, and may have an oxyethylene group.

  The number average molecular weight (Mn) of the polyol A is preferably in the range of 3000 to 30000. More preferably, it is the range of 3500-20000, Most preferably, it is the range of 4000-15000. The number average molecular weight (Mn) of the polyol A is preferably in the range of 3000 to 30000, since the resulting urethane adhesive can be expected to have good flexibility.

In the present invention, the “number average molecular weight” of the polyol A is based on the hydroxyl value of the polyol A (OHV, the unit is mgKOH / g),
Number average molecular weight = (56100 / OHV) × A value calculated using the number of hydroxyl groups per molecule.

  Here, “OHV” is a value measured according to JIS K1557 6.4. Further, the “number of hydroxyl groups per molecule” means the number of active hydrogen atoms per molecule of the initiator used as a raw material when producing polyol A. For example, ethylene glycol and propylene glycol are 2, Glycerin and trimethylolpropane are 3. If the number of active hydrogen atoms in the initiator cannot be specified in a commercial product, the nominal functional group number is used.

  The molecular weight distribution of polyol A is not particularly limited, but is preferably less than 1.16, more preferably less than 1.13, and particularly preferably less than 1.10. By making molecular weight distribution less than 1.16, the viscosity reduction of the prepolymer obtained and the reactivity improvement of prepolymerization can be anticipated.

  In the present invention, the molecular weight distribution (Mw / Mn) of polyol A is a polystyrene equivalent obtained by measuring with gel permeation chromatography (GPC) using a calibration curve prepared using a standard polystyrene sample with a known molecular weight. The molecular weight distribution, which is a value obtained by dividing the GPC mass average molecular weight (Mw) by the GPC number average molecular weight (Mn). The molecular weight distribution by the GPC method can be determined, for example, in terms of polystyrene by measuring at 40 ° C. using tetrahydrofuran as a solvent.

  The degree of unsaturation of polyol A is preferably 0.07 meq / g or less. Especially, the range of 0.01-0.07 meq / g is preferable, More preferably, it is the range of 0.014-0.06 meq / g. If the degree of unsaturation of polyol A is 0.07 meq / g or less, good curability can be expected for the obtained urethane prepolymer, and a reduction in the migration component can be expected.

  When two or more kinds of polyether diols are used in combination to form polyol A, the degree of unsaturation of each polyether diol is preferably 0.07 meq / g or less, but the degree of unsaturation is 0.07 meq / g or more. When using this polyether diol, it may be mixed with other polyether diols so that the average total unsaturation of the mixture is 0.07 meq / g or less.

Degree of unsaturation of the polyol A is an index of the monool content present in the polyol A, it is the average functionality f _A by increasing decreases, in the present invention, they include, "polyol A" Called.

  In the present invention, the “degree of unsaturation (meq / g)” of polyol A is the total amount of unsaturated groups contained in 1 g of polyol A, and conforms to the method specified in JIS K1557 6.7. It is the value measured.

In the present invention, the degree of unsaturation (meq / g) and number average molecular weight of polyol A are given by the following formula:
Unsaturation ≦ Number average molecular weight × 0.00001
It is preferable to satisfy. Above all, the following formula:
Number average molecular weight × 0.0000025 ≦ Unsaturation ≦ Number average molecular weight × 0.000009
Preferably satisfying the following formula:
Number average molecular weight × 0.000003 ≦ Unsaturation ≦ Number average molecular weight × 0.000008
It is further preferable to satisfy It is preferable that the degree of unsaturation of the polyol A be number average molecular weight × 0.00001 or less because a cured product of the obtained urethane prepolymer can be expected to have good flexibility.

  There is no restriction | limiting in particular as a manufacturing method of polyol A, It can manufacture with a conventionally well-known manufacturing method. For example, it can be produced by ring-opening polymerization of alkylene oxide in the presence of a ring-opening polymerization catalyst using a bifunctional initiator.

  The ring-opening polymerization catalyst is not particularly limited. For example, a general-purpose alkali metal compound catalyst such as potassium hydroxide (KOH) or sodium hydroxide; a cesium metal compound catalyst such as cesium hydroxide; a composite such as zinc hexacyanocobaltate complex Metal cyanide complex catalyst; phosphazene catalyst, imino group-containing phosphazenium salt catalyst, barium hydroxide catalyst and the like. These catalysts may be used alone or in combination of two or more.

  Among these catalysts, in order to produce polyol A having a low degree of unsaturation, cesium metal compound catalyst, double metal cyanide complex catalyst, phosphazene catalyst, imino group-containing phosphazenium salt catalyst, barium hydroxide catalyst, etc. Is preferably used. Moreover, since the molecular weight distribution of the obtained polyol A becomes narrow by producing polyol A using an imino group-containing phosphazenium salt catalyst, the viscosity of the polyol A and a prepolymer using the polyol A, and a cured product are reduced. It is preferable because reduction of the migration component can be expected.

  The imino group-containing phosphazenium salt catalyst is not particularly limited as long as it is a compound having an imino group and a PN bond, and examples thereof include compounds represented by the following general formula (for example, JP-A-2011-132179). No. publication).

[In said general formula, R < ₁ > and R < ₂ > respectively independently represents a hydrogen atom or a C1-C20 hydrocarbon group. Incidentally, the R ₁ and R ₂ may be bonded to form a ring structure, R ₁ s or R ₂ together may form a ring structure together. X ⁻ represents a hydroxy anion, an alkoxy anion having 1 to 4 carbon atoms, a carboxy anion, an alkyl carboxy anion having 2 to 5 carbon atoms, or a hydrogen carbonate anion. ]
Although it does not specifically limit as a bifunctional initiator, For example, bifunctional polyols, such as water, propylene glycol, ethylene glycol, diethylene glycol, dipropylene glycol, butylene glycol, 1, 6-hexanediol, polyoxyalkylene diol, Selected from bisphenols such as bisphenol A, bisphenol F, and bisphenol AD, dihydroxybenzenes such as catechol, resorcin, and hydroquinone, and compounds having two active hydrogens such as amines such as methylamine, ethylamine, propylamine, and butylamine One type or two or more types are used.

  Although it does not specifically limit as alkylene oxide, For example, 1 type, or 2 or more types chosen from the group which consists of ethylene oxide, propylene oxide, and butylene oxide is used.

  Of these, polyether diols obtained by using one or two or more of the above-mentioned bifunctional initiators and ring-opening polymerization of one or two or more three-membered alkylene oxides having 2 to 3 carbon atoms are preferred.

  As a method for producing polyol A, specifically, a cesium metal compound catalyst, a double metal cyanide complex catalyst, a phosphazene catalyst, an imino group-containing phosphazenium salt catalyst, a barium hydroxide catalyst, and the like are used. A method of adding alkylene oxide to a molecular weight of 2%, using a bifunctional initiator, potassium hydroxide catalyst, cesium metal compound catalyst, double metal cyanide complex catalyst, phosphazene catalyst, imino group-containing phosphazenium salt catalyst, barium hydroxide Using a catalyst or the like, an alkylene oxide is added to a number average molecular weight of about 200 to 10,000, and then the catalyst is removed or left in a state where the cesium metal compound catalyst, double metal cyanide complex catalyst, phosphazene catalyst, imino group-containing phosphor One or two types of xenium salt catalyst, barium hydroxide catalyst, etc. How to adding an alkylene oxide with 2 or more stages to a predetermined molecular weight with the upper and the like.

  In the present invention, the polyol B is a polyether polyol having an oxyalkylene group and having at least three hydroxyl groups per molecule in any molecule such as a polymer terminal or a branched chain terminal. preferable.

  Examples of such polyol B include trialkyl or higher polyalkylene oxides such as polyoxypropylene polyol, polyoxyethylene polyol, and poly (oxypropylene-oxyethylene) polyol, and are not particularly limited. Specifically, Sanyo Chemicals Sanix GP-1000, GP-1500, GP-3000, GP-4000V, GA-5000S, FA-908, FA-961, FA-921, FA-703, FA-757 , Actol G-28, MN-5000, MN-4000, P-31, MN-1500, Mitsui Chemicals, Inc. Exenol 1030, 4030, 5030, 230, 828, 837, Preminol 3005, 3010, 3015, Asahi Glass Co., Ltd. 3020, 7001, 7006, 701 , Available as PREMINOL S3006,3011, and PREMINOL 7021 (tetrafunctional) commercially available, such as.

  The number of hydroxyl groups per molecule of polyol B is preferably in the range of 3-6, and more preferably in the range of 3-4. If the number of hydroxyl groups per molecule of polyol B is in the range of 3 to 6, it is preferable because good flexibility and adhesiveness can be expected from the obtained urethane adhesive.

  The number of hydroxyl groups per molecule of the polyol B matches the number of active hydrogen atoms of the polyvalent initiator used for producing the polyol B described later. For example, glycerin and trimethylolpropane are 3 and diphenylmethanediamine is 4.

  The number average molecular weight (Mn) of the polyol B is preferably in the range of 5000 to 40000. Especially, the range of 5000-30000 is preferable, More preferably, it is the range of 6000-20000. The number average molecular weight (Mn) of the polyol B is preferably in the range of 5000 to 40000 because good flexibility of the resulting urethane pressure-sensitive adhesive can be expected.

In the present invention, the number average molecular weight of the polyol B is represented by the following formula based on the hydroxyl value of the polyol B (OHV, unit is mgKOH / g):
Number average molecular weight = (56100 / OHV) × A value calculated using the number of hydroxyl groups per molecule.

  Here, “OHV” is a value measured according to JIS K1557 6.4. The “number of hydroxyl groups per molecule” refers to the number of active hydrogen atoms per molecule of the initiator used as a raw material when producing polyol B. If the number of active hydrogen atoms in the initiator cannot be specified with a commercial product, the nominal functional group number is used.

  The molecular weight distribution of the polyol B is not particularly limited, but is preferably less than 1.30, and more preferably less than 1.25. A molecular weight distribution of less than 1.30 is preferred because the resulting urethane prepolymer can be expected to have reduced viscosity and high reactivity.

  In the present invention, the molecular weight distribution (Mw / Mn) of polyol B can be determined by the same method as the molecular weight distribution of polyol A described above.

  The degree of unsaturation of polyol B is preferably 0.07 meq / g or less. Especially, the range of 0.003-0.07 meq / g is preferable, More preferably, it is the range of 0.004-0.06 meq / g. If the degree of unsaturation is 0.07 meq / g or less, good curability of the obtained urethane prepolymer can be expected, and reduction of the migration component can be expected, which is preferable.

  When two or more kinds of polyether polyols are used in combination to form polyol B, the degree of unsaturation of each polyether polyol is preferably 0.07 meq / g or less, but the degree of unsaturation is 0.07 meq / g or more. When the polyether polyol is used, it may be mixed with other polyether polyols so that the average total unsaturation of the mixture is 0.07 meq / g or less.

By degree of unsaturation increases, although the average functionality f _B of the polyol B may decrease, including them in the present invention, it referred to as "Polyol B".

  In the present invention, the “unsaturation degree (meq / g)” of polyol B is the total amount of unsaturated groups contained in 1 g of polyol B, and conforms to the method specified in JIS K1557 6.7. It is the value measured.

In the present invention, the degree of unsaturation and number average molecular weight of polyol B are given by the following formula:
Unsaturation ≦ Number average molecular weight × 0.000009
It is preferable to satisfy the following formula:
Number average molecular weight × 0.0000003 ≦ Unsaturation ≦ Number average molecular weight × 0.000007
It is preferable to satisfy. By setting the degree of unsaturation to a number average molecular weight × 0.000009 or less, the molecular weight of the obtained urethane prepolymer is increased, and an improvement in flexibility can be expected.

  The polyol B is not limited to one type, and a plurality of types of polyether polyols may be mixed and used.

  There is no restriction | limiting in particular as a manufacturing method of polyol B, It can manufacture with a conventionally well-known manufacturing method. For example, it can be produced by ring-opening polymerization of alkylene oxide in the presence of a ring-opening polymerization catalyst using a trifunctional or higher polyvalent initiator.

  As the ring-opening polymerization catalyst, for example, those described above can be used.

  Examples of the tri- or higher functional polyvalent initiator include glycerin, trimethylolpropane, 1,2,6-hexanetriol, Sanyo Chemicals Sanix GP-250, GP-400, GP-600, GP-1000, and the like. A compound having three or more active hydrogens such as triols such as trifunctional low molecular weight polyols, tetraols such as pentaerythritol and diglycerin, hexols, ammonia, ethanolamine, diethanolamine, triethanolamines and other amines Or it can use 2 or more types.

  As the alkylene oxide, for example, those described above can be used.

  Among these, it was obtained by using one or more initiators having three or more functional groups and ring-opening polymerizing one or two or more three-membered alkylene oxides having 2 to 3 carbon atoms. Polyoxyalkylene polyol is preferred.

  In this invention, there is no restriction | limiting in particular as a manufacturing method of polyol B, It can manufacture with a conventionally well-known manufacturing method. For example, using a cesium metal compound catalyst, a double metal cyanide complex catalyst, a phosphazene catalyst, an imino group-containing phosphazenium salt catalyst, a barium hydroxide catalyst, etc. in one stage or two or more stages in a trifunctional or higher initiator. A method of adding alkylene oxide to a predetermined molecular weight can be mentioned.

  In the present invention, the average functional group number f of the polyol is a value determined by the following formula.

f = (1000 fn / Mn) / [{(1000 / Mn) one (USV / fn)} + USV]
Here, fn is the number of hydroxyl groups, Mn is the number average molecular weight, and USV is the degree of unsaturation. The number of hydroxyl groups fn refers to the number of active hydrogen atoms per molecule of initiator used as a raw material when producing polyol A or polyol B. For example, ethylene glycol and propylene glycol are 2, and glycerin and trimethylolpropane. Is 3. In the case of a commercial product, the nominal functional group number was used. The average functional group number f of polyol A is f _A , and the average functional group number f of polyol B is f _B.

In the present invention, when polyol A and polyol B are used in combination as the polyol used for the urethane prepolymer, the average functional group number f _ave can be calculated as follows.

_{f ave = (f A × W} A / M A + f B × W B / M B) / (W A / M A + W B / M B)
The average functionality of f _A polyol A, W _A is the weight of the polyol A, M _A is the number average molecular weight of the polyol A, f _B is the average functionality of the polyol B, W _B is a polyether polyol parts of, M _B represents the number average molecular weight of the polyol B.

  In the present invention, the average functional group number f of the polyol used for the urethane prepolymer is 1.7 or more, more preferably 1.75 or more, and particularly preferably 1.8 or more. Further, the average functional group number f of the polyol is preferably 2.2 or less, more preferably 2.19 or less, and particularly preferably 2.15 or less. If the average functional group number f of the polyol is 1.7 or more and 2.2 or less, the urethane prepolymer is not gelled, has good handling properties and good curability, and the resulting cured product has high flexibility. In addition, since adhesion to a base material can be expected, it can be expected that the generation of bubbles will be suppressed by following the step even in close contact particularly in applications where the step portion is large.

  In the present invention, the molar ratio of polyol A in the polyol used for the urethane prepolymer is not particularly limited, but is preferably in the range of 30% or more in the polyol, and more preferably in the range of 51% or more. If it is 30% or more in the polyol, good flexibility and impact resistance can be expected.

  In the present invention, the molar ratio of polyol B in the polyol used for the urethane prepolymer is not particularly limited, but is preferably 70% or less, more preferably 49% or less in the polyol. If it is 70% or less in a polyol, since favorable softness | flexibility and impact resistance can be anticipated, it is preferable.

  In the present invention, the polyisocyanate used for the urethane prepolymer is not particularly limited, and a compound having at least two isocyanate groups can be used.

  For example, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 2,4′-diphenylmethane diisocyanate, 4,4′-diphenylmethane diisocyanate, 1,5-naphthalene diisocyanate, tolidine diisocyanate, xylylene diisocyanate, 1, 3-phenylene diisocyanate, 1,4-phenylene diisocyanate, lysine diisocyanate, triphenylmethane triisocyanate, tetramethylxylene diisocyanate, 1,6-hexamethylene diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, isophorone diisocyanate, 1,4- Cyclohexane diisocyanate, norbornane diisocyanate, lysine ester triisocyanate, 1,6,11-un Can triisocyanate, 1,8-diisocyanate-4-isocyanate methyloctane, 1,3,6-hexamethylene triisocyanate, bicycloheptane triisocyanate, trimethylhexamethylene diisocyanate, isocyanate-containing prepolymers by reacting them with polyols, and these Or a mixture of two or more thereof. Furthermore, modified products of these isocyanates (urethane group, carbodiimide group, allophanate group, urea group, burette group, isocyanurate group, amide group, imide group, uretonimine group, uretdione group or oxazolidone group-containing modified product) and polymethylene Condensates (sometimes referred to as polynuclear bodies) such as polyphenylene polyisocyanate (polymeric MDI) are also included.

  Of these, aliphatic isocyanates, alicyclic isocyanates, and modified products thereof are preferable because flexibility, impact resistance, and transparency are easily exhibited. For example, 1,6-hexamethylene diisocyanate, isophorone diisocyanate, fat Group isocyanate-containing prepolymer, alicyclic isocyanate-containing prepolymer, modified products of these isocyanates (urethane group, carbodiimide group, allophanate group, urea group, burette group, isocyanurate group, amide group, imide group, uretonimine group, Uretodione group or oxazolidone group-containing modified product) is preferred. These isocyanates may be used alone or in combination.

  Examples of the isocyanate-containing prepolymer include a reaction product of polyoxyalkylene monoalkyl ether, isotridecanol, hexyldecanol, monool such as ethylhexanol and butyltetraglycol, polyol, monoamine, polyamine and the like and isocyanate.

  In the present invention, the amount of polyisocyanate added to the urethane prepolymer is the molar ratio of the total amount of NCO groups possessed by the polyisocyanate and the total amount of OH groups possessed by the polyol ([total amount of NCO groups] / [total amount of OH groups]). The range is 0.85 to 1.15 (molar ratio), preferably the molar ratio of the total amount of NCO groups possessed by the polyisocyanate and the total amount of OH groups possessed by the polyol is 0.85 to 1.05 (molar ratio). It is a range. Among these, since an OH group-terminated prepolymer having high storage stability can be obtained, the ratio of the total amount of OH groups of the polyisocyanate and NCO groups of the polyisocyanate is in the range of 0.85 to 0.99 (molar ratio). Is particularly preferred. If the molar ratio of the total amount of NCO groups possessed by the polyisocyanate and the total amount of OH groups possessed by the polyol is in the range of 0.85 to 1.15, the molecular weight of the urethane prepolymer is high and the resulting urethane adhesive has high flexibility. Can be expected.

  In the present invention, active polyol compounds other than polyol A and polyol B (hereinafter referred to as “other active hydrogen compounds”) can be used as the polyol. Although it does not specifically limit as another active hydrogen compound, For example, it is a compound which has at least 1 active hydrogen group per molecule, such as water, polyhydric carboxylic acid, a polyamine, a polyol. When using other active hydrogen compounds, the amount of other active hydrogen compounds added is not particularly limited, but if it is too large, the flexibility and transparency of the resulting urethane adhesive may be reduced. The total amount of polyol is preferably 40 parts by weight or less based on 100 parts by weight.

  In the case of using other active hydrogen compounds in addition to polyol A and polyol B, the amount of polyisocyanate added is the total amount of NCO groups of polyisocyanate, polyether diol A, polyether polyol B, and other active hydrogen compounds. It is preferable that the molar ratio with respect to the total amount of OH groups is 0.85 to 1.15 (molar ratio).

  In the present invention, the method for synthesizing the urethane prepolymer is not particularly limited. For example, a polyol, if necessary, other active hydrogen compounds, and a polyisocyanate, a urethanization catalyst, a solvent, an antifoaming material, other additives, etc. A method of urethanization reaction in the presence of Therefore, the obtained urethane prepolymer may contain a urethanization catalyst, an antifoaming material, an additive and the like.

  Here, the temperature of the urethanization reaction is not particularly limited, but is preferably 120 ° C. or lower, more preferably 50 to 110 ° C. If it is 120 degrees C or less, since the urethane prepolymer of control of reaction rate and a predetermined number average molecular weight and structure is easy to be obtained, it is preferable.

  Therefore, the urethanization reaction is preferably performed at 120 ° C. or lower for 1 to 20 hours. The end point of the reaction can be determined by measuring the residual amount of isocyanate by titration or disappearance of the isocyanate peak by IR measurement.

  The urethanization reaction is not particularly limited, but a solvent may be used to facilitate reaction control. Examples of the solvent include methyl ethyl ketone, ethyl acetate, toluene, xylene, acetone, benzene, dioxane, acetonitrile, tetrahydrofuran, diglyme, dimethyl sulfoxide, N-methylpyrrolidone, dimethylformamide and the like. In view of the solubility of the urethane prepolymer, the boiling point of the solvent, etc., ethyl acetate, toluene, methyl ethyl ketone or a mixed solvent thereof is particularly preferable. These solvents may be added at an arbitrary timing such as the initial stage of the reaction, the middle of the reaction, or after the completion of the reaction.

  The urethane prepolymer concentration (including unreacted raw materials excluding the solvent) when a solvent is used during the urethanization reaction is not particularly limited and is selected depending on the use, but preferably in the range of 10 to 90% by weight. More preferably, it is in the range of 20 to 55% by weight. If the urethane prepolymer concentration in the urethane prepolymer solution is in the range of 10 to 90% by weight, the decrease in the reactivity of urethanization is small, and an improvement in handling properties can be expected, which is preferable.

  A known urethanization catalyst can be used when the urethane prepolymer of the present invention is synthesized. For example, a tertiary amine compound, an organometallic compound, etc. are mentioned.

  The tertiary amine compound is not particularly limited, and examples thereof include triethylamine, triethylenediamine, N, N-dimethylbenzylamine, N-methylmorpholine, diazabicycloundecene (also known as DBU) and the like. Two or more types can be used in combination.

  Although it does not specifically limit as an organometallic type compound, A tin type compound and a non-tin type compound can be mentioned.

  Although it does not specifically limit as a tin-type compound, For example, dibutyltin dichloride, dibutyltin oxide, dibutyltin dibromide, dibutyltin dimaleate, dibutyltin dilaurate (alias: DBTDL), dibutyltin diacetate, dibutyltin sulfide, tributyltin Sulfide, tributyltin oxide, tributyltin acetate, triethyltin ethoxide, tributyltin ethoxide, dioctyltin oxide, tributyltin chloride, tributyltin trichloroacetate, dioctyltin dilaurate (also known as DOTDL), tin 2-ethylhexanoate, etc. .

  Although it does not specifically limit as a non-tin type compound, For example, titanium system, such as dibutyltitanium dichloride, tetrabutyltitanate, butoxytitanium trichloride, lead oleate, lead 2-ethylhexanoate, lead benzoate, lead naphthenate, etc. Lead system, iron system such as iron 2-ethylhexanoate and iron acetylacetonate, cobalt system such as cobalt benzoate and cobalt 2-ethylhexanoate, zinc system such as zinc naphthenate and zinc 2-ethylhexanoate, Examples thereof include zirconium naphthenate.

  Among the urethanization catalysts, dibutyltin dilaurate (also known as DBTDL), dioctyltin dilaurate (also known as DOTDL), tin 2-ethylhexanoate and the like are preferable in terms of reactivity and hygiene.

  Catalysts such as tertiary amine compounds and organometallic compounds can be used alone or in combination.

  The amount of the urethanization catalyst added during the synthesis of the urethane prepolymer of the present invention is not particularly limited, but if it is too small, the productivity may be lowered, and if it is too large, the reaction becomes uneven and the physical properties are unstable. Therefore, with respect to 100 parts by weight of the total amount of polyether diol A and polyether polyol B, and other active hydrogen compounds added as necessary, the above-mentioned tertiary amine compound has a content of 0.01 to In the case of 15 parts by weight and the above-described organometallic compound, the range of 0.0001 to 5 parts by weight is preferable. After the synthesis, these catalysts may be removed or may remain.

  The urethane prepolymer of the present invention can be chain extended using a chain extender in order to promote high molecular weight. Although not particularly limited, for example, glycols such as ethylene glycol, 1,4-butanediol, neopentyl glycol, butylethylpentanediol, glycerin, trimethylolpropane, pentaerythritol, ethylenediamine, N-aminoethylethanolamine, piperazine, The chain can be extended using a polyvalent amine such as isophoronediamine or xylylenediamine.

  In the present invention, the urethane prepolymer can be used as a urethane prepolymer solution obtained using a urethane prepolymer and a solvent in consideration of handling properties as a two-component curable urethane adhesive obtained using the urethane prepolymer. preferable.

  Examples of the solvent include methyl ethyl ketone, ethyl acetate, toluene, xylene, acetone, benzene, dioxane, acetonitrile, tetrahydrofuran, diglyme, dimethyl sulfoxide, N-methylpyrrolidone, dimethylformamide and the like. Among these, ethyl acetate, toluene, methyl ethyl ketone, or a mixed solvent thereof is particularly preferable from the viewpoint of the solubility of the urethane prepolymer, the boiling point of the solvent, and the like.

  In the present invention, the concentration of the urethane prepolymer in the urethane prepolymer solution is selected according to the use and is not particularly limited, but is preferably in the range of 10 to 90% by weight, more preferably 20 to 70% by weight. Range. If the concentration of the urethane prepolymer in the urethane prepolymer solution is in the range of 10 to 90% by weight, a decrease in reactivity is small and an improvement in handling properties can be expected, which is preferable.

  In the present invention, the viscosity of the urethane prepolymer solution is selected depending on the application, and is preferably in the range of 0.1 to 100 Pa · s (25 ° C.), more preferably in the range of 1 to 50 Pa · s (25 ° C.). If the viscosity of the urethane prepolymer solution is in the range of 0.1 to 100 Pa · s (25 ° C.), it is preferable because the fluidity of the liquid is moderate and good handling properties can be expected.

  The two-component curable urethane pressure-sensitive adhesive of the present invention is obtained using the above-described urethane prepolymer and a crosslinking agent.

  The cross-linking agent used in the two-component curable urethane pressure-sensitive adhesive of the present invention is not particularly limited as long as it is a compound having reactivity with an active hydrogen group or a compound having reactivity with an isocyanate group. For example, isocyanate crosslinking agent, aziridine crosslinking agent, epoxy crosslinking agent, melamine resin, urea resin, metal chelate crosslinking agent, polyol crosslinking agent, amine crosslinking agent, moisture and the like can be mentioned. Since these crosslinking agents are generally liquid, they can be used as they are, but if necessary, they may be diluted with an organic solvent.

  In the urethane prepolymer, when the molar ratio of the total amount of NCO groups derived from polyisocyanate and the total amount of OH groups derived from polyol ([NCO group total amount] / [total OH group amount]) is 1.00 or less, as a crosslinking agent Is preferably a compound having reactivity with an active hydrogen group. Examples of such a crosslinking agent include isocyanate-based crosslinking agents, aziridine-based crosslinking agents, epoxy crosslinking agents, melamine resins, urea resins, metal chelate-based crosslinking agents, and the like. Among these, an isocyanate-based crosslinking agent and an epoxy crosslinking agent are preferable because they easily exhibit performance such as heat resistance.

  On the other hand, in the urethane prepolymer, in the range where the molar ratio of the total amount of NCO groups derived from polyisocyanate and the total amount of OH groups derived from polyol exceeds 1.00, the crosslinking agent has reactivity with isocyanate groups. A compound is preferred. Examples of such a crosslinking agent include a polyol crosslinking agent, an amine-based crosslinking agent, and moisture.

  When other active hydrogen compounds are used in addition to polyol A and polyol B, the molar ratio between the total amount of NCO groups of polyisocyanate and the total amount of OH groups of polyol A, polyol B and other active hydrogen compounds is used. A cross-linking agent may be selected.

  As the isocyanate-based crosslinking agent, a compound having at least two isocyanate groups can be used and is not particularly limited. For example, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 2,4′-diphenylmethane diisocyanate, 4,4′-diphenylmethane diisocyanate, 1,5-naphthalene diisocyanate, tolidine diisocyanate, xylylene diisocyanate, 1, 3-phenylene diisocyanate, 1,4-phenylene diisocyanate, lysine diisocyanate, triphenylmethane triisocyanate, tetramethylxylene diisocyanate, 1,6-hexamethylene diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, isophorone diisocyanate, 1,4- Cyclohexane diisocyanate, norbornane diisocyanate, lysine ester triisocyanate, 1,6,11-un Can triisocyanate, 1,8-diisocyanate-4-isocyanate methyloctane, 1,3,6-hexamethylene triisocyanate, bicycloheptane triisocyanate, trimethylhexamethylene diisocyanate, isocyanate-containing urethane prepolymers by reaction of them with polyols, and A mixture of two or more of these may be used. Furthermore, modified products of these isocyanates (urethane group, carbodiimide group, allophanate group, urea group, burette group, isocyanurate group, amide group, imide group, uretonimine group, uretdione group or oxazolidone group-containing modified product) and polymethylene Condensates (sometimes referred to as polynuclear bodies) such as polyphenylene polyisocyanate (polymeric MDI) are also included.

  Among these, since the flexibility and transparency of the urethane pressure-sensitive adhesive are easily expressed, aliphatic isocyanates, alicyclic isocyanates, and modified products thereof are preferable. For example, 1,6-hexamethylene diisocyanate, isophorone diisocyanate, fat Group polyisocyanate-containing urethane prepolymer, alicyclic polyisocyanate-containing urethane prepolymer, modified products of these polyisocyanates (urethane group, carbodiimide group, allophanate group, urea group, burette group, isocyanurate group, amide group, imide Group, uretonimine group, uretdione group or oxazolidone group-containing modified product) is preferable. These isocyanates may be used alone or in combination. More preferably, it is a polyisocyanate having an allophanate group, an alicyclic isocyanate having an allophanate group, or a mixture containing one or more of these allophanate-modified isocyanates, and is not particularly limited, but for example, Tosoh Corporation Coronate 2770, Coronate 2785, Coronate 2792, and a mixture containing one or more of these.

  Although it does not specifically limit as an epoxy-type crosslinking agent, The amine type epoxy crosslinking agent which has an epoxy group and an amino group, a non-amine type epoxy crosslinking agent is mentioned, for example, bisphenol A, an epichlorohydrin type epoxy resin, ethylene glycidyl ether, Polyethylene glycol diglycidyl ether, glycerin diglycidyl ether, glycerin triglycidyl ether, 1,6-hexanediol glycidyl ether, trimethylolpropane triglycidyl ether, diglycidyl aniline, diamine glycidyl amine, N, N, N ', N'- Tetraglycidyl-m-xylylenediamine and 1,3-bis (N, N'-diamineglycidylaminomethyl) cyclohexane, 2,2'one [[2,2bis (oxirane-2-ylylmethoxy) Chill) Single 1,3 one propanediyl] bis (oxymethylene)] bis oxirane and the like of these two or more mixtures thereof. Although not particularly limited, for example, commercially available products such as Tetrad C and Tetrad X manufactured by Mitsubishi Gas Chemical Company, Denacol EX-411 manufactured by Nagase ChemteX, Denacol EX212, Denacol EX214, and E-5C manufactured by Soken Chemical Co., Ltd. may be mentioned.

  The polyol crosslinking agent is not particularly limited as long as it has two or more active hydrogen groups, and is not limited to ethylene glycol, propylene glycol, 1,4-butylene glycol, 1,5-pentamethylene glycol, 1,6- Examples include hexamethylene glycol, trimethylol propane, short chain low molecular weight alkylene polyol, polyoxypropylene polyol, polyoxyethylene propylene polyol polyethylene glycol, polyester polyol, and mixtures of two or more thereof. Among these, since a cured product having excellent curability and transparency can be obtained, the polyol crosslinking agent which does not contain an aromatic ring in the polyol and has a number average molecular weight of less than 8000 is preferable.

  The amine-based crosslinking agent is not particularly limited, but ethylenediamine, trimethylenediamine, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, triethylenetetramine, diethylenetriamine, triaminopropane, 2,2,4-trimethylhexamethylenediamine. , 2-hydroxyethylethylenediamine, N- (2-hydroxyethyl) propylenediamine, (2-hydroxyethylpropylene) diamine, (di-2-hydroxyethylethylene) diamine, (di-2-hydroxyethylpropylene) diamine, ( 2-hydroxypropylethylene) diamine, (di-2-hydroxypropylethylene) diamine, aliphatic polyamines such as piperazine, isophoronediamine, dicyclohexylmethane-4,4 -Alicyclic polyamines such as diamine, phenylenediamine, xylylenediamine, 2,4-tolylenediamine, 2,6-tolylenediamine, diethyltoluenediamine, 3,3'-dichloro-4,4'-diaminodiphenylmethane Aromatic diamines such as 4,4′-bis- (seC-butyl) diphenylmethane, polyoxyalkylene polyamines such as JeffAmine D-2000, and mixtures of two or more thereof.

  In the present invention, the number of functional groups of the crosslinking agent is not particularly limited, but is preferably in the range of 2-6, more preferably in the range of 2-3. If the number of functional groups of the cross-linking agent is in the range of 2 to 6, it is preferable because the cross-linking tends to proceed uniformly and the curing is difficult to be insufficient.

  When a trifunctional or higher functional polyol is used for the urethane prepolymer, the number of functional groups of the crosslinking agent is preferably in the range of 2 to 4, and most preferably in the range of 2 to 3. In the case where a trifunctional or higher functional polyol is not used in the urethane prepolymer, the number of functional groups of the cross-linking agent is preferably in the range of 2-6, more preferably in the range of 2-5, and most preferably 2.3. It is the range of ~ 4. When using 2 or more types of crosslinking agents, it is preferable to satisfy the above range with the average number of functional groups.

  In this invention, the addition amount Eq of a crosslinking agent has the preferable range of 0.0001 equivalent-20 equivalent (molar ratio) with respect to the reactive group of a urethane prepolymer. Especially, the range of 0.01-15 equivalent is especially preferable, More preferably, it is the range of 0.05-10 equivalent. When the addition amount Eq of the crosslinking agent is in the range of 0.0001 equivalent to 20 equivalents (molar ratio) with respect to the reactive group of the urethane prepolymer (including moisture in the system), it has good curability. However, it is preferable because high flexibility and adhesive strength can be expected.

  When a trifunctional or higher functional polyol is used for the urethane prepolymer, the addition amount Eq of the crosslinking agent is preferably in the range of 0.0001 equivalents to 10 equivalents (molar ratio). Especially, the range of 0.01-7 equivalent is especially preferable, More preferably, it is the range of 0.1-2 equivalent. When a tri- or higher functional polyol is used for the urethane prepolymer, the addition amount Eq of the crosslinking agent has good curability and high transparency as long as it is in the range of 0.0001 equivalent to 10 equivalents (molar ratio). It is preferable because flexibility and adhesive strength can be expected. When the urethane prepolymer does not contain a trifunctional or higher functional polyol, the addition amount Eq of the crosslinking agent is preferably in the range of 2 equivalents to 20 equivalents (molar ratio). Especially, the range of 2-15 equivalent is especially preferable, More preferably, it is the range of 3-10 equivalent. When the urethane prepolymer does not contain a trifunctional polyol, it is preferable that the addition amount Eq of the crosslinking agent is in the range of 2 equivalents to 20 equivalents (molar ratio) because good flexibility and adhesive strength can be expected.

  When the urethane pressure-sensitive adhesive of the present invention is used for optical applications such as an optical pressure-sensitive adhesive sheet, the amount of the crosslinking agent added is preferably 7 equivalents or less (molar ratio). Especially, the range of 0.01-5 equivalent is especially preferable, More preferably, it is the range of 0.01-3 equivalent. When the addition amount of the crosslinking agent is 7 equivalents or less, the deterioration of Haze due to the deterioration of compatibility with the urethane prepolymer is slight, and high transparency can be expected.

In the present invention, the average functional group number f of the polyol in the urethane prepolymer and the addition amount Eq (equivalent) of the crosslinking agent are represented by the following formula:
1- (f-1.7) × 10 <Eq <20- (f-1.7) × 20 (where Eq> 0)
Meet.

Above all, the following formula:
1- (f-1.7) × 7 <Eq <20- (f-1.7) × 30 (where Eq> 0)
Preferably satisfying the following formula:
2- (f-1.7) × 7 <Eq <20- (f-1.7) × 40 (where Eq> 0)
It is further preferable to satisfy

  When the addition amount Eq (equivalent) of the crosslinking agent is 1- (f-1.7) × 10 or less, the obtained urethane pressure-sensitive adhesive is insufficiently cured, so that the heat resistance is poor and the heat is applied. It is difficult to mold due to liquid flow, and the obtained adhesive also has many migratory components and is difficult to use.

  In addition, when the addition amount Eq (equivalent) of the cross-linking agent is 20− (f−1.7) × 20 or more, the curing progresses too much, the adhesiveness is poor, and the follow-up failure to the deformation of the pressure-sensitive adhesive also occurs. It is difficult to use because it generates bubbles without following / adhering to the steps of the body.

  The pressure-sensitive adhesive sheet of the present invention has at least one substrate and a pressure-sensitive adhesive layer provided on the substrate, and the pressure-sensitive adhesive layer is the two-component curable urethane pressure-sensitive adhesive of the present invention. Its features.

  As a base material used for the adhesive sheet of this invention, a release film, a core material, etc. are mentioned, for example. Examples of such a release film include PET, PP, TPX, films obtained by releasing these with silicone, fluorine, and the like, and commercially available products include Purex A31, A33, A35 manufactured by Teijin DuPont. And mold release PET such as A43. Examples of the core material include a nonwoven fabric, a PET film, and a PP film.

  As the laminated structure of the pressure-sensitive adhesive sheet of the present invention, for example, a base material-less pressure-sensitive adhesive sheet having a three-layer structure in which both surfaces are sandwiched by a release film (specifically, release PET or the like), a core material is used for the pressure-sensitive adhesive layer. Examples thereof include a double-sided pressure-sensitive adhesive sheet having a 5-layer structure.

  Although it does not specifically limit as thickness of the adhesive layer in the adhesive sheet of this invention, Preferably it is the range of 10 micrometers-1000 micrometers, More preferably, it is the range of 15 micrometers-250 micrometers, Most preferably, it is 20 micrometers-130 micrometers. Particularly in the case of an optical pressure-sensitive adhesive sheet for a film sensor, a range of 20 μm to 150 μm is preferable, and in the case of an optical pressure-sensitive adhesive sheet for a glass sensor between a touch panel and a cover panel, a range of 50 μm to 250 μm is preferable.

  The shape of the pressure-sensitive adhesive sheet of the present invention is not particularly limited and may be a desired shape. For example, it may be in the form of a roll or may be cut and provided in the form of a sheet.

  As a method for producing the pressure-sensitive adhesive sheet of the present invention, it can be produced by curing a urethane prepolymer (preferably a urethane prepolymer solution) and a crosslinking agent in a predetermined shape on a substrate. It can be produced in a predetermined shape by defoaming and drying. For example, it can be formed into a sheet or film by coating, and after mixing a urethane prepolymer (preferably a urethane prepolymer solution) and a crosslinking agent at a predetermined ratio, a roll coater, a gravure coater, a microgravure Examples of the coating method include a coater, a reverse coater, an air knife coater, a comma coater, and a die coater. Using these coating methods, after applying a mixture of a urethane prepolymer (preferably a urethane prepolymer solution) and a crosslinking agent to one or both sides of the substrate, defoaming, heating, and drying are performed as necessary. It is desirable. As a heating method, a generally used method such as hot air drying, hot roll drying, infrared irradiation, or the like can be used. The drying temperature is not particularly limited, but is preferably 50 to 200 ° C, more preferably 70 to 180 ° C, and still more preferably 80 to 150 ° C. When a thermoplastic resin is used as the substrate, the drying temperature is preferably below its melting point. A drying temperature in the range of 50 to 200 ° C. is preferable because deterioration of the base material and change in color tone hardly occur.

  The use of the urethane pressure-sensitive adhesive and pressure-sensitive adhesive sheet of the present invention is not particularly limited, but since the pressure-sensitive adhesive layer is excellent in transparency, flexibility, and low-temperature characteristics, tape, label, seal, cosmetic sheet, non-slip sheet, Examples include double-sided adhesive tape. Specifically, packaging tape, label tape, masking tape, packaging tape for office and home use such as craft tape, medical tape such as adhesive bandage, wallpaper tape, foam tape, and elastic adhesive for construction Tapes for electronic materials used in tapes, personal computers, televisions, mobile phones, automobiles, solar cells, other household appliances, optical adhesive sheets such as liquid crystal displays and touch panels, surface protection tapes, waterproof tapes, and conductive tapes in manufacturing processes And a heat-radiating tape.

  Since the urethane pressure-sensitive adhesive and pressure-sensitive adhesive sheet of the present invention are excellent in flexibility, for example, surface protective tapes and foam tapes for manufacturing electronic materials, applications with unevenness such as tapes for automobiles, applications with aspects, elastic modulus Because of its low temperature dependence, it can be suitably used for adhesion in applications where the temperature change is large, such as architectural tapes such as structural adhesives and temporary fixing tapes, and tapes for electronic materials that are heated in the manufacturing process. Moreover, since the cured | curing material excellent in transparency is obtained, it can be used for optical uses, such as a touchscreen use, Specifically, optical adhesive sheets, such as a smart phone, a tablet PC, a notebook personal computer, are mentioned. Especially, it can use suitably for adhesion of various films.

  The optical pressure-sensitive adhesive sheet of the present invention is a pressure-sensitive adhesive sheet used for optical applications, obtained using the urethane pressure-sensitive adhesive of the present invention. Specific optical applications are not particularly limited, but functional films in fields such as touch panels and displays for mobile phones, smartphones, car navigation systems, personal computers, ticket vending machines, ITO films, silver meshes, copper meshes, polarizing plates, etc. A pressure-sensitive adhesive sheet used for adhesion and the like. The operation method of the touch panel is not particularly limited, and can be suitably used for a resistance film type, a capacitance type, an optical type, an ultrasonic type, an electromagnetic induction type, and the like.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not construed as being limited to the following examples unless it exceeds the gist. The materials and evaluation methods used in the following Examples and Comparative Examples are as shown below.

  As the raw materials described in Table 2 and Table 3, the following were used.

<Raw materials>
1) Polyol and other active hydrogen compounds

<Polyol A>
Polyols A1 and A2: Polyether diol obtained by adding propylene oxide to polyoxypropylene glycol having a bifunctional molecular weight of 400 using an imino group-containing phosphazenium salt (IPZ) catalyst.
Polyols A3 and A4: After adding propylene oxide to polyoxypropylene glycol having a bifunctional molecular weight of 400 using a double metal cyanide complex (DMC) catalyst made in China, imino group-containing phosphazenium salt (IPZ) catalyst Polyether diol with propylene oxide added.
Polyol A5: Commercially available general-purpose polyoxypropylene glycol.
<Polyol B>
Polyol B1: A commercially available low-unsaturation polyoxypropylene triol.
Polyol B2: Polyether polyol synthesized by the same method as polyol A3 except that pentaerythritol was used as the initiator.
<Other polyols>
Polyol A6: Diethylene adipate-based polyester polyol (Nipporan 1004 manufactured by Tosoh Corporation)
These polyols were used after heating and vacuum dehydration before use.

2) Polyisocyanate Polyisocyanate C1: 1,6-hexamethylene diisocyanate (HDI)
3) Crosslinking agent Crosslinking agent 1: Allophanate-modified bifunctional HDI-based crosslinking agent (Coronate 2770 manufactured by Tosoh Corporation).
Crosslinking agent 2: 50% by weight of a mixture of 50% by weight of an allophanate-modified bifunctional HDI-based crosslinker (Coronate 2770 manufactured by Tosoh Corporation) and about 3 functional nurate-modified HDI-based crosslinker (Coronate HX manufactured by Tosoh Corporation).
Cross-linking agent 3: TDI-based cross-linking agent (Tosoh Coronate L).

(Analysis of polyol properties)
<Hydroxyl value, number average molecular weight>
The hydroxyl value was measured according to the method of JIS-K1557-1. The number average molecular weight of the polyol was defined as the number average molecular weight of the polyol, which was calculated from the product of the number of functional groups of the initiator used for production (the nominal number of functional groups on the market) and the molecular weight per hydroxyl group of the polyol.

<Unsaturation>
It measured according to the method of JIS-K1557-6.

<Molecular weight distribution (Mw / Mn)>
To the sample bottle, 10 mg of polyol and 10 ml of THF were added, dissolved by allowing to stand overnight, and then filtered through a PTFE cartridge filter (0.5 μm) to obtain a sample. RI detector RI8020 was used as a detector, and TSKgelGMR-H _HR L × 2 in series and HLC-8020GPC were used as measurement columns (both manufactured by Tosoh Corporation). As measurement conditions, measurement was performed under the conditions of a column temperature of 40 ° C., a flow rate of 1.0 ml / min, and a solvent THF, and a molecular weight distribution (Mw / Mn) of a third-order approximation curve using standard polystyrene manufactured by Tosoh Corporation was used as a calibration curve. Analysis was performed.

(Urethane prepolymer synthesis example 1)
Predetermined amounts of polyol A1 and polyisocyanate C1 were added to a four-necked separable flask equipped with a stirrer, a reflux condenser, a nitrogen inlet tube, and a thermometer, and the reaction was performed by raising the temperature to 70 ° C. The NCO group in the reactor contents was traced by dibutylamine back titration, and the completion of the reaction was confirmed using an infrared spectrophotometer to obtain the urethane prepolymer of Example 1.

  Urethane prepolymers other than the urethane prepolymer synthesis example 1 were synthesized in the same manner, and DBTDL was appropriately added using a microsyringe within a range not exceeding 0.02% by weight as a catalyst depending on the reaction rate and the like. In addition, methyl ethyl ketone as a solvent was appropriately added within a range not exceeding 80% by weight depending on the stirring conditions and the like.

(Urethane prepolymer solution production example 1)
Super-dehydrated methyl ethyl ketone was added as a solvent to the urethane prepolymer obtained in Synthesis Example 1 and dissolved by stirring while heating to prepare a solution having a urethane prepolymer concentration of 50%. The water content of this urethane prepolymer solution was measured with a Karl Fischer moisture meter.

  A urethane prepolymer other than the urethane prepolymer solution Production Example 1 and a urethane prepolymer solution were also added in the same manner as necessary, and the urethane prepolymer concentration was 10% to 100% by weight (none Solvent).

(Urethane pressure-sensitive adhesive, pressure-sensitive adhesive sheet production example 1)
About 10 g of the solution obtained in the urethane prepolymer solution production example 1, 5 equivalents of a crosslinking agent 2 (corresponding mixture of coronate 2770 and coronate HX) with respect to the amount of active hydrogen groups in which the urethane prepolymer and water in the solution are combined. ) Was added to the sample bottle and stirred with a pencil mixer until uniform. The urethane prepolymer composition was allowed to stand while heating at 50 ° C. for 30 minutes to remove bubbles in the system, and cooled to room temperature. The mixture was coated on release PET (Purex manufactured by Teijin DuPont) with an applicator so as to have a dry thickness of 40 μm, and left in an explosion-proof dryer heated to 80 ° C. for 30 minutes to remove the solvent. At this point, the remaining amount of NCO groups was about 20% immediately after mixing. After completion of drying, release PET (Purex manufactured by Teijin DuPont Co., Ltd.) having a difference in release force from the base material side was pasted back and forth with a roller 3 times so that no bubbles would enter the cured product surface. Then, it left still in a constant temperature room of 23-25 degreeC and 50% RH, and the loss | disappearance of NCO group was confirmed in IR three days later. A sheet having a three-layer structure of release PET / cured product / release PET having a cured product thickness of 40 μm was prepared and used as a cured product evaluation sample (adhesive sheet) of Example 1.

  Similarly to Example 1, a cured sheet was prepared under the same conditions using a predetermined amount and type of cross-linking agent with respect to the amount of active hydrogen groups in which the urethane prepolymer and the water in the solution were combined. It was set as -14 hardened | cured material evaluation sample.

(Example of evaluation of adhesive properties)
<Elastic modulus (25 ° C, 80 ° C)>
According to the urethane adhesive and pressure-sensitive adhesive sheet production examples, the obtained urethane pressure-sensitive adhesive was peeled off from the release PET and folded to obtain a measurement sample. Using a dynamic viscoelasticity measuring device UBM Rheogel E-4000, measurement is performed at a measurement temperature of −80 ° C. to 200 ° C., a temperature increase rate of 2 ° C./min, a frequency of 1 Hz, and a shear mode condition. The storage elastic modulus G ′ at ° C. was evaluated. If G ′ at 25 ° C. is 2 × 10 ⁵ Pa or less, it is flexible at room temperature and evaluated that followability can be expected even when closely attached to a substrate including a printed step (evaluation ○). If G ′ at 80 ° C. is 2 × 10 ⁴ Pa or more, the shape is maintained at a high temperature, and it is evaluated that adhesion at a high temperature can be expected (evaluation ○). Outside the range, the evaluation was x.

<Gel fraction, swelling degree>
In accordance with the urethane adhesive and adhesive sheet production examples, the obtained cured product is peeled off from the release PET, 0.2 g lightly attached to a 200 mesh wire net, and then the wire mesh attached to the adhesive side is folded inward. The weight was measured by sealing the mouth several times with a staple so that it would not come out except through the mesh. A wire mesh bag with 0.2 g of adhesive was added to 100 ml of ethyl acetate and allowed to stand for 7 days, then taken out without crushing, and the weight immediately after was measured. The collected wire bag was dried at 80 ° C. for 8 hours with an explosion-proof dryer, and the weight after drying was measured. From the weight obtained by subtracting the wire mesh / stapler after drying and the weight of the pressure-sensitive adhesive attached before the test, the ratio (%) of the insoluble matter that remained without being calculated was evaluated as the gel fraction. Further, the ratio (%) of the weight obtained by removing the weight of the wire mesh bag from the weight after drying and the weight in the swollen state immediately after removal was evaluated as the degree of swelling of the gel.

<Number average molecular weight of sol>
The number average molecular weight was evaluated by THF-based GPC using the soluble component obtained by concentrating the ethyl acetate-soluble component at the time of gel fraction evaluation as a sol component. Specifically, RI detector RI8020 was used as a detector, and TSKgelGMR-HHRL × 2 in series and HLC-8020GPC were used as measurement columns (all manufactured by Tosoh Corporation). The measurement conditions are a column temperature of 40 ° C., a flow rate of 1.0 ml / min, and a solvent THF, and the number average molecular weight (Mn) is analyzed using a cubic approximate curve using standard polystyrene manufactured by Tosoh Corporation as a calibration curve. Went.

<Glass transition temperature, tan δ at 25 ° C.>
According to the urethane pressure-sensitive adhesive and pressure-sensitive adhesive sheet production examples, the obtained cured product was peeled off from the release PET and folded to obtain a measurement sample. Using a dynamic viscoelasticity measuring device UBM Rheogel E-4000, measurement is performed at a measurement temperature of −80 ° C. to 200 ° C., a temperature increase rate of 2 ° C./min, a frequency of 1 Hz, and a shear mode condition. The temperature at which the peak value of tan δ, which is the ratio of loss elastic modulus G ″ to “, is evaluated as the glass transition temperature, and the value at 25 ° C. is the ratio of loss elastic modulus G ″ at 25 ° C. to storage elastic modulus G ′ ( tan δ). Evaluated that low glass transition temperature has good low temperature characteristics and good adhesion at low temperature, and that tan δ at 25 ° C. is high, converts energy to heat well at room temperature, so that impact resistance can be expected. . When the glass transition temperature was −30 ° C. or lower, “good”, and when it exceeded −30 ° C., “x”.

<Adhesive strength>
According to the urethane adhesive and pressure-sensitive adhesive sheet production examples, the release PET of the obtained sheet was peeled off on one side, and a PET film Toray Co., Ltd. Lumirror S-10 having a thickness of 25 μm was lined on the pressure-sensitive adhesive surface. The test piece was cut to a width of 25 mm and roll-bonded to Eagle XG made by alkali-free glass plate Corning in accordance with JIS Z0237. Using a tensile tester Tensilon TG-1210 manufactured by Orientec Co., Ltd., a 180 ° peel test was performed in accordance with JIS Z0237, and 180 ° peel strength (N / 25 mm) was measured. The measurement was performed in an atmosphere of 23 ° C. and 50% RH under conditions of a peeling angle of 180 ° and a tensile speed of 300 mm / min. The number of tests was 2 times or more, and the average value was calculated. It evaluated that the adhesiveness to the base material at room temperature was expectable, so that adhesive force was high. If the adhesive strength was 3 N / 25 mm or more, it was rated as “◯” if it was less than 3 N / 25 mm.

<Retention force>
According to the urethane adhesive and pressure-sensitive adhesive sheet production examples, the obtained cured product was peeled off from the release PET, and a 25 μm-thick PET film Lumirror S-10 manufactured by Toray Industries Inc. was lined on the pressure-sensitive adhesive surface. The release PET on the other side was peeled off, and bonded to a SUS substrate with an adhesive surface of 25 mm × 25 mm to obtain a test piece, which was evaluated according to JIS Z0237. Specifically, the time until the weight dropped under the conditions of 40 ° C. and a static load of 1 kg was measured. When the holding power was high, the cohesive strength of the pressure-sensitive adhesive was high, and it was evaluated that removability and adhesion reliability could be expected. ○ (good) when the holding power exceeds 100 minutes, Δ (pass) when the holding power is 10 minutes to 100 minutes, and x for less than 10 minutes.

<Ball tack>
According to the urethane adhesive and pressure-sensitive adhesive sheet production examples, the obtained cured product was peeled off from the release PET, and a 25 μm-thick PET film Lumirror S-10 manufactured by Toray Industries Inc. was lined on the pressure-sensitive adhesive surface. Another surface of the release PET was peeled off and evaluated according to JIS Z0237. A predetermined steel ball was rolled onto the adhesive surface under the conditions of an inclination angle of 30 degrees and a running distance of 10 cm, and the ball no. Evaluated. If the ball tack is 6 or more, it is evaluated as good tackiness.

<Haze (white turbidity)>
According to the urethane adhesive and pressure-sensitive adhesive sheet production example, the obtained release sheet of the pressure-sensitive adhesive sheet having a thickness of 40 μm was peeled off on one side and bonded to a PMMA base material Acrylite L # 001 clear manufactured by Mitsubishi Rayon using a roller. The release PET on the other surface was peeled off, the total light transmittance and Haze were measured with NDH5000, and the Haze obtained by subtracting the Haze of the PMMA substrate alone was evaluated. Specifically, when the haze of the PMMA base material is 0.2%, and the two-layer structure of PMMA2 and the adhesive is 0.5%, 0.5% −0.2% = Haze 0.3% of the adhesive evaluated. When the haze of the pressure-sensitive adhesive was 0.8% or less, it was evaluated as ◯ (excellent), when it exceeded 0.8% to 5%, Δ (passed), and when it exceeded 5%, x.

  Urethane adhesives were synthesized according to the formulations shown in Tables 2 and 3, and their characteristics were evaluated. The results of Examples 1 to 14 are shown in Table 2, and the results of Comparative Examples 1 to 11 are shown in Table 3.

Examples 1-6.
It was found that all of them are adhesives having low elasticity at 25 ° C. and excellent flexibility, high elasticity at 80 ° C. and capable of maintaining the shape even at high temperatures, and good step followability and workability. The gel fractions of these pressure-sensitive adhesives were all in the range of 25% to 49%, and the degree of gel swelling was 1200% or more. The molecular weight of the sol was in the range of 40000-70000.

  These pressure-sensitive adhesives have high tan δ, adhesive strength, ball tack, and holding power, and can be expected to have impact resistance, adhesion, and adhesion reliability, and can be expected to have low glass transition temperature and adhesion from low temperature to high temperature. .

Examples 7-11.
It was found that all of them are adhesives having low elasticity at 25 ° C. and excellent flexibility, high elasticity at 80 ° C. and capable of maintaining the shape even at high temperatures, and good step followability and workability. The gel fractions of these pressure-sensitive adhesives were all in the range of 25% to 41%, and the degree of gel swelling was 2000% or more. The molecular weight of the sol was in the range of 40000-70000.

  These pressure-sensitive adhesives have high tan δ, adhesive strength, ball tack, and holding power, and can be expected to have impact resistance, adhesion, and adhesion reliability, and can be expected to have low glass transition temperature and adhesion from low temperature to high temperature. .

Examples 12 and 13.
It was found to be an adhesive having a low elastic modulus at 25 ° C. and excellent flexibility, having a high elastic modulus at 80 ° C. and capable of maintaining its shape even at high temperatures, and having good step following ability and workability. Although the gel fraction was as high as 55 to 65% and tan δ was low (accepted), the adhesive strength, ball tack, and holding power were high, impact resistance, adhesion, and adhesion reliability could be expected, and glass transition It was found that the adhesive strength from low temperature to high temperature can be expected at a low temperature. The swelling degree of the gel was 1300% or more, and the molecular weight of the sol was in the range of 40000-70000.

Example 14
It was found to be an adhesive having a low elastic modulus at 25 ° C. and excellent flexibility, having a high elastic modulus at 80 ° C. and capable of maintaining its shape even at high temperatures, and having good step following ability and workability. Gel fraction is as low as 5% and holding power is low (pass), but tan δ, adhesive strength and ball tack are high, impact resistance, adhesion and adhesion reliability can be expected, and glass transition temperature is low. It was found that adhesion from low temperature to high temperature can be expected. The swelling degree of the gel was 2000% or more, and the molecular weight of the sol was in the range of 40000-70000.

Example 15.
The haze of a 40 μm thick adhesive synthesized according to the formulation of Example 1 was measured. The pressure-sensitive adhesive layer had a Haze (excluding 0.2% for PMMA base material) of 2.7%, and was a pressure-sensitive adhesive that could be expected to be applied to an optical pressure-sensitive adhesive.

Example 16
The haze of a 40 μm thick adhesive synthesized according to the formulation of Example 3 was measured. The adhesive layer had a Haze (excluding 0.2% for PMMA base material) of 0.3%, and was an adhesive that could be expected to be applied to an optical adhesive.

Example 17.
The haze of a 40 μm thick adhesive synthesized according to the formulation of Example 4 was measured. The pressure-sensitive adhesive layer had a Haze (excluding 0.2% for the PMMA base material) of 3.5%, and was a pressure-sensitive adhesive that could be expected to be applied to an optical pressure-sensitive adhesive.

Example 18
The haze of a 40 μm thick adhesive synthesized according to the formulation of Example 7 was measured. The pressure-sensitive adhesive layer had a Haze (excluding 0.2% for the PMMA base material) of 0.2%, and was a pressure-sensitive adhesive that could be expected to be applied to an optical pressure-sensitive adhesive.

Example 19.
The haze of a 40 μm thick adhesive synthesized according to the formulation of Example 8 was measured. The adhesive layer had a Haze (excluding 0.2% for PMMA base material) of 0.3%, and was an adhesive that could be expected to be applied to an optical adhesive.

Example 20.
The haze of a 40 μm thick adhesive synthesized according to the formulation of Example 9 was measured. The pressure-sensitive adhesive layer had a Haze (excluding 0.2% for the PMMA base material) of 0.2%, and was a pressure-sensitive adhesive that could be expected to be applied to an optical pressure-sensitive adhesive.

Example 21.
The haze of a 40 μm thick adhesive synthesized according to the formulation of Example 10 was measured. Haze (excluding 0.2% of PMMA base material) of the pressure-sensitive adhesive layer was 0.1%, and it was a pressure-sensitive adhesive that could be expected to be applied to an optical pressure-sensitive adhesive.

Example 22.
The haze of a 40 μm thick adhesive synthesized according to the formulation of Example 11 was measured. The pressure-sensitive adhesive layer had a Haze (excluding 0.2% for the PMMA base material) of 0.2%, and was a pressure-sensitive adhesive that could be expected to be applied to an optical pressure-sensitive adhesive.

Example 23.
The haze of a 40 μm thick adhesive synthesized according to the formulation of Example 12 was measured. The pressure-sensitive adhesive layer had a Haze (excluding 0.2% for the PMMA base material) of 2.5%, and was a pressure-sensitive adhesive that could be expected to be applied to an optical pressure-sensitive adhesive.

Example 24.
The haze of a 40 μm thick adhesive synthesized according to the formulation of Example 14 was measured. Haze (excluding 0.2% of PMMA base material) of the pressure-sensitive adhesive layer was 0.1%, and it was a pressure-sensitive adhesive that could be expected to be applied to an optical pressure-sensitive adhesive.

Comparative Examples 1, 2, 5, 6, 7
Although the elastic modulus at 25 ° C. is low, the elastic modulus at 80 ° C. is also low (Evaluation ×). It is an adhesive that cannot retain its shape at high temperatures and cannot be processed, and the gel fraction is lower than 20%. It was.
This pressure-sensitive adhesive had a gel fraction lower than 20% and lacked cohesive strength, so that it could not be evaluated by cohesive failure at the time of preparing a test piece, and adhesive strength, tackiness and holding power could not be evaluated.

Comparative Examples 3 and 4.
Although the elastic modulus at 80 ° C. is high, the elastic modulus at 25 ° C. is high (evaluation ×) and the flexibility at room temperature is low, and the adhesive cannot be expected to follow a step. This pressure-sensitive adhesive was an adhesive having poor tackiness (evaluation x), and the adhesive force, holding power, and tan δ were also low (passed).
In addition, the number average molecular weight of the sol in Comparative Example 3 is 20000, and the number average molecular weight of the sol in Comparative Example 4 is 34000, which is lower than that of the Examples, and is crosslinked when the urethane prepolymer molecular weight is low. There is a possibility that the molecular weight between the cross-linking points is lower and the elastic modulus at 25 ° C. is higher.

Comparative Example 8
Although the elastic modulus at 25 ° C. is low, the elastic modulus at 80 ° C. is also low (Evaluation ×). It is an adhesive that cannot retain its shape at high temperatures and cannot be processed, and the gel fraction is lower than 20%. It was.
This pressure-sensitive adhesive was a pressure-sensitive adhesive having a gel fraction lower than 20% and insufficient cohesive force, and therefore low adhesive strength and holding power (evaluation x), and adhesion could not be expected.

Comparative Example 9
Although the elastic modulus at 80 ° C. is high, the elastic modulus at 25 ° C. is high (evaluation ×) and the flexibility at room temperature is low, and the adhesive cannot be expected to follow a step.
This pressure-sensitive adhesive was a pressure-sensitive adhesive having a high gel fraction of 85% and a low tan δ at 25 ° C. (evaluation ×), and thus could not be expected in impact resistance.

Comparative Example 10
A urethane prepolymer was synthesized using a general-purpose bifunctional PPG having a large amount of monool, and the properties of the cured product were evaluated. This pressure-sensitive adhesive has a low elastic modulus at 25 ° C., but also has a very low elastic modulus at 80 ° C. (Evaluation ×). It was lower than 20%.

  This pressure-sensitive adhesive has a low sol number average molecular weight of 9000 and a gel fraction of less than 20%, so it is estimated that the cohesive force is insufficient, and has low adhesive force and holding power (evaluation x), and adhesion cannot be expected. Met.

Comparative Example 11
A urethane prepolymer was synthesized using 100 parts of polyester polyol instead of 100 parts of polyether polyol, and the properties of the cured product were evaluated.
Although the elastic modulus at 80 ° C. is high, the elastic modulus at 25 ° C. is high (evaluation ×) and the flexibility at room temperature is low, and the adhesive cannot be expected to follow a step. Moreover, since the gel fraction was high, the degree of swelling of the gel was low, and tan δ was also low (Evaluation ×), it was an adhesive that could not be expected for impact resistance.
It was an adhesive having a glass transition temperature of -20 ° C. or more and inferior low temperature characteristics. Therefore, it was an adhesive that cannot be expected from low temperature to high temperature adhesion.

Comparative Example 12
The haze of a 40 μm thick adhesive synthesized according to the formulation of Comparative Example 1 was measured. The pressure-sensitive adhesive layer had a haze (excluding 0.2% for the PMMA base material) of 14.2%, which was not expected to be applied to an optical pressure-sensitive adhesive.

Claims (11)

A two-component curable urethane pressure-sensitive adhesive obtained using a urethane prepolymer and a crosslinking agent,
The urethane prepolymer is obtained using a polyol and a polyisocyanate,
The average functional group number f of the polyol is 1.7 or more,
The relationship between the average functional group number f of the polyol and the addition amount Eq (equivalent) of the crosslinking agent is represented by the following formula:
1- (f-1.7) × 10 <Eq <20- (f-1.7) × 20 (where Eq> 0)
And a two-component curable urethane characterized by having an elastic modulus of 2 × 10 ⁵ Pa or less at a frequency of 1 Hz and 25 ° C. and an elastic modulus of 2 × 10 ⁴ Pa or more at a frequency of 1 Hz and 80 ° C. Adhesive. The two-part curable urethane pressure-sensitive adhesive according to claim 1, wherein the gel fraction is in the range of 20 to 65%. The two-component curable urethane pressure-sensitive adhesive according to claim 1 or 2, wherein the degree of swelling of the gel is 950% or more. The two-part curable urethane pressure-sensitive adhesive according to any one of claims 1 to 3, wherein the glass transition temperature is in the range of -80 ° C to -30 ° C. The two-component curable type according to any one of claims 1 to 4, wherein a ratio (tan δ) of loss elastic modulus G "and storage elastic modulus G 'at a frequency of 1 Hz and 25 ° C is 0.3 or more. Urethane adhesive. The two-component curable urethane pressure-sensitive adhesive according to any one of claims 1 to 5, wherein the adhesive strength with non-alkali glass measured by the method of JIS Z0237 is in the range of 3 to 25 N / 25 mm. The two-part curable urethane pressure-sensitive adhesive according to any one of claims 1 to 6, wherein the ball tack measured by the method of JIS Z0237 is 6 or more. The two-component curable urethane pressure-sensitive adhesive according to any one of claims 1 to 7, wherein the holding force at 40 ° C measured by the method of JIS Z0237 is 10 minutes or more. The two-part curable urethane pressure-sensitive adhesive according to any one of claims 1 to 8, wherein the Haze at 40 µm measured by the method of JIS K7136 is 5% or less. It has a 1 or more types of base material and the adhesive layer provided on the base material, and an adhesive layer is the two-component curable urethane adhesive in any one of Claims 1-8. A pressure-sensitive adhesive sheet characterized by An optical system comprising one or more base materials and a pressure-sensitive adhesive layer provided on the base material, wherein the pressure-sensitive adhesive layer is the two-component curable urethane pressure-sensitive adhesive according to claim 9. Adhesive sheet