WO2025118200A1

WO2025118200A1 - Curable silicone pressure sensitive adhesive composition and use thereof

Info

Publication number: WO2025118200A1
Application number: PCT/CN2023/136900
Authority: WO
Inventors: Jingui JIANG; Maki Itoh; Qing Cao; Aiping Wang; Li Ding; Jiayin ZHU; Chengrong ZHU; Zhihua Liu
Original assignee: Dow Toray Co Ltd; Dow Silicones Corp
Current assignee: Dow Toray Co Ltd; Dow Silicones Corp
Priority date: 2023-12-06
Filing date: 2023-12-06
Publication date: 2025-06-12
Anticipated expiration: 2026-06-06

Abstract

Provided is a curable silicone pressure sensitive adhesive (PSA) composition comprising (A) an organopolysiloxane having alkenyl group in numbers greater than 1 on average per molecule; (B) a branched organopolysiloxane resin having very low content in OH/hydrolysable groups; (C) an organohydrogenpolysiloxane having at least two Si-H bonds in the molecule; (D) a fluoro-silicone polymer without having alkenyl or SiH functionality; and (E) a hydrosilylation reaction catalyst, wherein the mass ratio of component (B) to component (A) is within a range of 0.5 to 3.5, and the amount of component (D) based on combined weights of compositions (A) to (C) is 0.1 to 7.0 mass part on the solid basis. This PSA composition can form a pressure sensitive adhesive layer exhibiting a wet/dry side release force below 15 gf/inch at a peel rate of 0.3 m/min for PSA having a dynamic storage modulus at -20℃ lower than 1 MPa and a thickness of 50 μm.

Description

CURABLE SILICONE PRESSURE SENSITIVE ADHESIVE COMPOSITION AND USE THEREOF

CROSS REFERENCE TO RELATED APPLICATIONS

None.

TECHNICAL FIELD

The present invention relates to a curable silicone pressure sensitive adhesive (PSA) composition, a pressure sensitive adhesive layer made therefrom, use of the PSA layer, and an electronic equipment or electrical device comprising the curable silicone PSA composition.

BACKGROUND

Recently, as more and more flexible electronics appeared on the market, the optically clear adhesives (OCAs) becomes versatile. Usually, for OCAs used as flexible electronics, low Tg and modulus are necessary to achieve a good rheology performance under folding/rolling conditions. Due to excellent rheology, Si-OCAs is a good choice to use in flexible electronics. The PSA for OCAs application is hydrosilylation-curable, essentially consisting of vinyl-functional PDMS gums, SiH crosslinkers and non-vinyl-functional MQ resins. The OCAs is coated on a release liner, cured and covered with another release liner to make a liner/OCA/liner laminate. In the downstream value chain, one side of the liner is peeled off to laminate the OCAs to a substrate, followed by peeling off another side of the liner to laminate to another substrate to assemble display panel etc. However, the OCAs met difficulty in film processing described above due to a very tight release force on nearly all the commercial release liners, especially for release force of wet lamination side, which is the side that the PSA was coated directly the release liner. Generally, the film processing issues include OCAs damage upon peeling off the dry lamination side due to small difference in the release force of the two sides, and surface roughening of the OCAs due to heavy release to lose transparency upon lamination. The softness of the OCAs contributes to these too. Furthermore, a lot of work was done on fluoro-silicone (F-Si) release coating to lower release force of low Tg and modulus, but the decrease of release force was not obvious as customer expected. The actual performance provided by fluoro-silicone coating studies using combinations of perfluoroether substituents and perfluoroalkane substituents and combination of different perfluoroalkane substituents is still in the validation stage.

Patent Document 1 describes a Si PSA layer having fine particles of 2-15 μm in diameter which is able to be handled without a release liner, and no adhesion is observed (with the force below 1 N/cm²) . However, the modulus of the PSA is not specified, and with the presence of particles, the haze values are ≥5%which is unable to be used as an OCA.

Patent Document 2 describes a multi-layer Si PSA of which release force after 46 days at 49℃ is ＜195 gf/inch. However, the release mechanism is stretch release with a first pressure-sensitive adhesive layer facing a release liner and a second comprising an elastomer, and the first pressure-sensitive adhesive comprises a silicone polyurethane block copolymer. The Patent Document 2 is silent about any additives to the PSA to reduce the release force and stretch-releasing PSA of Patent document 2 does not refer to a release force from the liner for specific rheology of the PSA, and since the elastomer layer is attached to the PSA layer, the material cannot be used for assembly applications.

Patent Document 3 describes laminates of fluoro-silicone release liner/Si-PSA/fluoro-silicone release liner with specified composition of the release coating and the PSA, which describes release force for both sides and showing that the PSA is not damaged. However, Patent Document 3 does not refer to specific release force associated with specific rheological property of the PSA, and fails to describe a method to reduce the release force.

Patent Document 4 describes pendant vinyl gum, vinyl resin, pendant CL, long Mw anchorage additive to obtain good adhesion and low modulus. However, in Patent Document 4, there is concern that the release force increases over time due to the resin migration, and no approach for additives such as fluoro-silicone is described. Also, there is another concern that modulus with non-vinyl-functional resin is still higher than the one with methyl resin.

RELATED ART DOCUMENTS

Patent Documents

[Patent Document 1] WO2017010140A1

[Patent Document 2] WO2008141004A1

[Patent Document 3] JP2007326312A

[Patent Document 4] CN112795369A

SUMMARY

PROBLEMS TO BE SOLVED

As mentioned above, no prior art has provided solution for low release force to peel off a “soft” PSA from a release liner, but that is an essential requirement to use such PSAs for display assembly. The present invention has been created in order to solve such problems, and an objective thereof is to provide a curable silicone pressure sensitive adhesive (PSA) composition and a pressure sensitive adhesive layer with low wet/dry side release force for display applications as OCA including foldable displays and automotive displays. Another objective of the present invention is to provide use of the PSA layer as an OCA layer and an electronic equipment or electrical device comprising the curable silicone PSA composition.

MEANS FOR SOLVING THE PROBLEM

As a result of conducting diligent research on the problems described above, the present inventors arrived at the present invention. That is, one objective of the present invention is achieved by addition of a fluoro-containing silicone into the curable silicone pressure sensitive adhesive (PSA) composition which can effectively decrease the release force on both wet side and dry side. Further, the curable silicone pressure sensitive adhesive (PSA) composition can be combined with F-Si release coating to solve the tight release force of Si-OCA used in flexible electronics applications.

Specifically, the problems described above can be solved by a curable silicone pressure sensitive adhesive (PSA) composition, comprising:

(A) an organopolysiloxane having alkenyl group in numbers greater than 1 on average per molecule;

(B) a branched organopolysiloxane resin having the total content of hydroxyl groups and hydrolysable groups with respect to all silicon atoms in the molecule within a range of 2.0 mass %or less;

(C) an organohydrogenpolysiloxane having at least two Si-H bonds in the molecule;

(D) a fluoro-silicone polymer without having alkenyl or SiH functionality; and

(E) a hydrosilylation reaction catalyst,

Wherein the mass ratio of component (B) to component (A) is within a range of 0.5 to 3.5, and the amount of component (D) based on combined weights of compositions (A) to (C) is 0.1 to 7.0 mass part on the solid basis.

In an embodiment according to the present disclosure, at least a portion of component (A) is (A1) a raw rubber-like alkenyl group-containing organopolysiloxane having a viscosity of 100,000 mPa.s or more at 25℃ or having a plasticity number within a range of 50 to 200 as measured in accordance with a method as described in JIS K6249, and the content of a vinyl (CH₂=CH-) moiety of alkenyl group is within a range of 0.005 to 0.400 mass%;

component (B) is (B1) an organopolysiloxane resin or mixture thereof which consists essentially of R³SiO_1/2 units and SiO_4/2 units, where R is a monovalent organic group, and 90 mol %or more of R is an alkyl group having 1 to 6 carbon atoms or a phenyl group; component (C) is present in an amount such that the molar ratio of the amount of SiH groups in component (C) to the total amount of the alkenyl groups in components (A) and (B) is 1 to 100;

component (D) is a polyorganosiloaxane having fluoroalkyl or fluoro-poly-ether substituents; and/or

component (E) is a platinum-based catalyst and is present in an amount such that the content of a platinum based metal in a solid content of the composition is within a range of 0.1 to 200 ppm in the PSA composition (excluding solvents) .

In an embodiment according to the present disclosure, the PSA composition further comprises (A′) a linear organopolysiloxane which does not contain a carbon-carbon double bond-containing reactive group in the molecule.

In an embodiment according to the present disclosure, component (B) is an organopolysiloxane resin or mixture thereof which consists essentially of R³SiO_1/2 units and SiO_4/2 units, where R is methyl.

In an embodiment according to the present disclosure, component (C) is present in an amount such that the molar ratio of the amount of SiH groups in component (C) to the total amount of the alkenyl groups in components (A) and (B) is 10 to 100 or 20 to 60.

In an embodiment according to the present disclosure, the composition further comprises:

(F) a hydrosilylation inhibitor, and/or

(G) a solvent.

In an alternative according to the present disclosure, it provides a pressure sensitive adhesive layer obtained by curing the curable silicone pressure sensitive adhesive (PSA) composition.

In an embodiment according to the present disclosure, the pressure sensitive adhesive layer exhibits a wet/dry side release force below 15 gf/inch at a peel rate of 0.3 m/min for PSA having a dynamic storage modulus at -20℃ lower than 1 MPa and a thickness of 50 μm.

In an alternative according to the present disclosure, it provides use of the pressure sensitive adhesive (PSA) layer in assembly applications.

In an embodiment according to the present disclosure, the PSA layer is used as an optically clear adhesive (OCA) layer for displays.

In an alternative according to the present disclosure, it provides an electronic equipment or electrical device comprising the curable silicone pressure sensitive adhesive (PSA) composition.

EFFECTS OF THIS INVENTION

Through this invention, it can provide a PSA layer with low wet/dry side release force for display applications as OCA including foldable displays and automotive displays. The silicone pressure sensitive adhesive (PSA) laminate formed by the PSA layer can exhibit a wet/dry side release force below 15 gf/inch at a peel rate of 0.3 m/min for PSA having a dynamic storage modulus at -20℃ lower than 1 MPa and a thickness of 50 μm.

DETAILED DESCRIPTION

[Curable silicone pressure sensitive adhesive (PSA) composition]

Firstly, the curable silicone pressure sensitive adhesive (PSA) composition according to the present invention will be described. The composition rapidly cures via a curing reaction containing a hydrosilylation reaction so as to form a pressure sensitive adhesive layer having a wet/dry side release force below 15 gf/inch at a peel rate of 0.3 m/min for PSA having a dynamic storage modulus at -20℃ lower than 1 MPa and a thickness of 50 μm.Hereinafter, each component in the composition, the range of the organopolysiloxane resin, the mass ratio of the organopolysiloxane resin having very low content in its OH/hydrolysable group to the linear organopolysiloxane, and the characteristics of the pressure sensitive adhesive layer will be described below.

In an embodiment according to this invention, the curable PSA composition comprising:

(B) a branched organopolysiloxane resin having the total content of hydroxyl groups and hydrolysable groups with respect to all silicon atoms in the molecule within a range of 2.0 mass %or less, preferably an organopolysiloxane resin containing M siloxyl units and Q siloxyl units;

(D) a fluoro-silicone polymer without having alkenyl or SiH functionality; and

(E) a hydrosilylation reaction catalyst, wherein the mass ratio of component (B) to component (A) is within a range of 0.5 to 3.5, and the amount of component (D) based on combined weights of compositions (A) to (C) is 0.1 to 7.0 mass part on the solid basis. In addition, since the composition contains a hydrosilylation reaction catalyst, the composition may further contain (F) a hydrosilylation inhibitor and (G) a solvent, from the perspective of handleability, and may further contain other additives such as a pigment to such an extent that is not at odds with the object of the present invention.

[Component (A) ]

In this invention, component (A) is an organopolysiloxane having alkenyl group in numbers greater than 1 on average per molecule, with a preferable number of alkenyl groups being no less than 1.5 per molecule, with a more preferable number of alkenyl groups being no less than 2.0 per molecule. In some embodiments according to this invention, the number of alkenyl groups on average per molecule may be in range from 1.01 to 5.0, from 1.01 to 4.0, from 1.01 to 3.0, from 1.01 to 2.0, from 1.01 to 1.5, from 1.5 to 5.0, from 1.5 to 4.0, from 1.5 to 3.0, from 1.5 to 2.0, from 2.0 to 5.0, from 2.0 to 4.0, from 2.0 to 3.0, from 3.0 to 5.0, from 3.0 to 4.0 or from 4.0 to 5.0. Examples of the alkenyl groups in component (A) include alkenyl groups having a carbon number of from 2 to 10, such as vinyl groups, allyl groups, butenyl groups, pentenyl groups, hexenyl groups, and heptenyl groups, with vinyl groups or hexenyl groups being particularly preferable. Examples of the bonding position of the alkenyl groups in component (A) include the molecular chain terminals and/or the molecular side chains. Note that component (A) may contain a single component or may be a mixture of two or more different components.

Examples of silicon-bonded organic groups other than alkenyl groups in the organopolysiloxane of component (A) include alkyl groups such as methyl groups, ethyl groups, propyl groups, butyl groups, pentyl groups, hexyl groups and heptyl groups; aryl groups such as phenyl groups, tolyl groups, xylyl groups and naphthyl groups; aralkyl groups such as benzyl groups and phenethyl groups; and halogenated alkyl groups such as chloromethyl groups, 3-chloropropyl groups and 3, 3, 3-trifluoropropyl groups, with methyl groups and phenyl groups being particularly preferable.

In this invention, component (A) can be different from component (B) and has a linear organopolysiloxane molecular structure. In some embodiments according to this invention, component (A) is a linear (i.e., chain-form) organopolysiloxane having alkenyl group in numbers greater than 1 on average per molecule. For example, component (A) is preferably a straight chain or partially branched straight chain and may partially include a cyclic three-dimensional network. Preferably, the main chain of the organopolysiloxane consists of repeating diorganosiloxane units (i.e., -SiO_2/2 or D units) and is preferably a straight-chain or branched-chain diorganopolysiloxane capped at both molecular terminals with triorganosiloxy groups. Note that the siloxane units that provide a branched-chain organopolysiloxane are T units or Q units described below.

The properties of component (A) at room temperature may be those of an oily or raw rubber-like substance, with the viscosity of component (A) being no lower than 50 mPa.s and particularly preferably no lower than 100 mPa.s at 25℃. In particular, when the linear organopolysiloxane composition according to the present invention is a solvent type, at least a portion of component (A) is (A1) a raw rubber-like alkenyl group-containing organopolysiloxane having a viscosity of no less than 100,000 mPa.s at 25℃ or having a plasticity number (the thickness when a 1 kgf load applied for 3 minutes to a 4.2 g spherical sample at 25℃ was read up to 1/100 mm and this value was multiplied by 100) within a range of from 50 to 200, preferably 80-200, more preferably 100-200, as measured in accordance with the method as prescribed in JIS K6249.

Note that in order to prevent contact failure, etc., volatile or low molecular weight siloxane oligomers (such as octamethylcyclotetrasiloxane (D4) , decamethylcyclopentasiloxane (D5) , etc. ) in the organopolysiloxanes alkenyl group are preferably reduced or eliminated. The degree can be designed as desired, but must be less than 1%by mass of the total component (A) , less than 0.1%by mass for each siloxane oligomer, and must be reduced to the vicinity of the detection limit as required.

Although the content of alkenyl groups in component (A1) is not particularly limited, the content of the vinyl (CH₂=CH) portion in the alkenyl groups in component (A1) (hereinafter, referred to as the “vinyl content” ) may be in the range of from 0.005 to 0.400 mass%, preferably in the range of from 0.005 to 0.300 mass%, and particularly preferably in the range of from 0.005 to 0.200 mass%.

In some embodiments according to the present invention, component (A) having a lower viscosity than that of component (A1) is also available as component (A) of the present invention. Specifically, an organopolysiloxane (A2) containing alkenyl groups having a viscosity of less than 100,000 mPa.s at 25℃ is available. Here, examples other than the viscosity of component (A2) are the same as component (A1) .

In the present invention, at least a portion, preferably 50 mass%or more, of component (A) is preferably an alkenyl group-containing organopolysiloxane with a high degree of polymerization, which is component (A1) , with 75 to 100 mass%thereof being particularly preferably component (A1) . That is, when component (A1) (= an alkenyl group-containing organopolysiloxane with a higher degree of polymerization) and component (A2) (= an alkenyl group-containing organopolysiloxane with a lower degree of polymerization) are used in combination as component (A) of the present invention, the mass ratios of component (A1) to component (A2) range from 50: 50 to 100: 0, preferably 75:25 to 100: 0, more preferably 75: 25 to 90: 10.

In some embodiments of the present invention, component (A) is added in an amount 10 to 50%by weight, 15 to 45%by weight, 20 to 40%by weight or 25 to 35%by weight, based on the total weight of the curable PSA composition.

[Component (B) ]

In this invention, the branched organopolysiloxane resin of component (B) is an adhesion imparting component imparting adhesive force to a substrate and simultaneously achieves a storage elastic modulus at low temperatures and a practical adhesive force range.

In this invention, component (B) is a branched organopolysiloxane resin having a three dimensional structure. Examples thereof include a branched organopolysiloxane resin comprises R₂SiO_1/2 units (M units) and RSiO_4/2 units (Q units) wherein each R independently represents a monovalent organic group. In particular, this resin (also referred to as MQ resin) is preferably used which consists of R₃SiO_1/2 units (M units) and SiO_4/2 units (Q units) . Also, this component (B) is characterized by its total content of hydroxyl groups and hydrolysable groups with respect to all silicon atoms in the molecule within a range of 2.0 mass %or less, preferably 1.5 mass %or less, more preferably 1.0 mass %or less, most preferably 0.90 mass%or less. When the total content of hydroxyl groups (OH) and hydrolysable groups like C1-C6 alkoxy groups is in said range, unintentional increase in the molecular weight of said organopolysiloxane resin through condensation reaction between the branched organopolysiloxane resin is restricted and the adhesion strength and physical properties for the cured body in this curable silicone PSA composition can be achieved in its designed formulation. Such branched organopolysiloxane resin having low content in hydroxyl groups and hydrolysable groups can be obtained through conventional capping reacting of Si-resin with silazane or hydrophobic silanes.

The monovalent organic group of R is preferably a monovalent hydrocarbon group having a carbon number of from 1 to 10, with examples thereof including alkyl groups having a carbon number of from 1 to 10, alkenyl groups having a carbon number of from 2 to 10, aryl groups having a carbon number of from 6 to 10, cycloalkyl groups having a carbon number of from 6 to 10, benzyl groups, phenylethyl groups and phenylpropyl groups. In particular, 90 mol%or more of R is preferably alkyl groups having 1 to 6 carbon atoms or phenyl groups, while 95 to 100 mol%of R is particularly preferably methyl groups or phenyl groups.

Preferably, component (B) is (B1) an organopolysiloxane resin or mixture thereof which consists essentially of R₃SiO_1/2 units and SiO_4/2 units, where R is a monovalent organic group and 90 mol %or more of R is an alkyl group having 1 to 6 carbon atoms or a phenyl group. When component (B) is a resin consisting of R₃SiO_1/2 units (M units) and SiO_4/2 units (Q units) , the molar ratio of M units to Q units is preferably from 0.5 to 2.0. This is because when the molar ratio is less than 0.5, the adhesive force to the substrate may be diminished, whereas when the molar ratio is greater than 2.0, the cohesive strength of the material constituting the adhesive layer decreases. Moreover, D units and T units may also be included in component (B) to such an extent that does not impair the characteristics of the present invention. Further, in order to prevent contact failure, etc., low molecular weight siloxane oligomer in the organopolysiloxane resins may be reduced or eliminated.

In the present invention, the weight average molecular weight (Mw) of said organopolysiloxane resin serving as component (B) is not limited, and at least one organopolysiloxane resin having specific Mw or a mixture of two or more of organopolysiloxane resin having different Mw can be used as component (B) . From practical viewpoint, Mw of component (B) measured in terms of standard polystyrene by gel permeation chromatography (GPC) ranges from 500 to 20,000 (g/mol) , preferably from 1,000 to 17, 500 (g/mol) , most preferably from 2,000 to 16, 500 (g/mol) .

[Mass ratio of component (B) to component (A) ]

The curable pressure sensitive adhesive organopolysiloxane composition according to the present invention characteristically has a mass ratio of component (B) (which is a branched organopolysiloxane resin) to component (A) (which is a reactive siloxane component) within the specific range. To achieve the technical effects of the present invention, the mass ratio of component (B) to component (A) is within a range of 0.5 to 3.5, 0.5 to 2.5, 0.5 to 1.5, 0.5 to 0.75, 0.75 to 3.5, 0.75 to 3.0, 0.75 to 2.5, 0.75 to 1.5, 1.5 to 3.5, 1.5 to 2.5 or 2.5 to 3.5. If components (A) and (A′) are used at above mass ratio, even if the mass ratio of component (B) to component (A) is within a range of more than 1.8 to 2.4, the technical effects of the present invention can also be achieved.

[Component (C) ]

In this invention, component (C) is an organohydrogenpolysiloxane having two or more Si-H bonds per molecule and is a crosslinking agent in the organopolysiloxane composition of the present invention. The molecular structure of component (C) is not particularly limited, with examples thereof including a straight chain, a partially branched straight chain, a branched chain, a cyclic, or an organopolysiloxane resin structure, and with a straight chain, a partially branched straight chain, or an organopolysiloxane resin structure being preferable. The bonding position of silicon-bonded hydrogen atoms is not particularly limited, with examples thereof including molecular terminals, side chains, or both molecular terminals and side chains. The content of the silicon-bonded hydrogen atoms is from 0.1 to 2.0 mass%preferably from 0.5 to 1.7 mass%.

Exemplary silicon-bonded organic groups in component (C) include: alkyl groups having 1 to 8 carbon atoms such as methyl groups, ethyl groups, propyl groups, butyl groups and octyl groups; aryl groups such as phenyl groups and tolyl groups; aralkyl groups such as benzyl groups and phenethyl groups; and halogenated alkyl groups such as 3-chloropropyl groups and 3, 3, 3-trifluoropropyl groups, wherein 50%moles or more of the total number thereof are preferably alkyl groups having 1 to 8 carbon atoms or phenyl groups. From the perspective of ease of manufacture and compatibility with the preferred components (A) and (B) described above, the other organic groups are preferably methyl groups or phenyl groups.

When component (C) of the present invention is an organohydrogenpolysiloxane, which is an organopolysiloxane resin, examples thereof include organopolysiloxane copolymers consisting of siloxane units represented by the general formula: R’₃SiO_1/2, siloxane units represented by the general formula R’₂HSiO_1/2, and siloxane units represented by the formula: SiO_4/2; organopolysiloxane copolymers consisting of siloxane units represented by the general formula: R’₂HSiO_1/2 and siloxane units represented by the formula: SiO_4/2; organopolysiloxane copolymers consisting of siloxane units represented by the general formula: R’₂HSiO_1/2 and siloxane units represented by the formula: R’SiO_3/2; organopolysiloxane copolymers consisting of siloxane units represented by the general formula: R’HSiO_2/2, siloxane units represented by the general formula: R’SiO_3/2, or siloxane units represented by the formula: HSiO_3/2; and mixtures of two or more types of these organopolysiloxanes. Note that R’ in the formulas is an alkyl group having a carbon number of from 1 to 8, an aryl group, an aralkyl group, or a halogenated alkyl group, with examples thereof being the same as those described above.

Specific examples of component (C) include tris (dimethylhydrogensiloxy) methylsilane, tetra (dimethylhydrogensiloxy) silane, methylhydrogenpolysiloxanes capped at both terminals with trimethylsiloxy groups, dimethylsiloxane/methylhydrogensiloxane copolymers capped at both terminals with trimethylsiloxy groups, dimethylsiloxane/methylhydrogensiloxane copolymers capped at both terminals with dimethylhydrogensiloxy groups, cyclic methylhydrogen oligosiloxanes, cyclic methylhydrogensiloxane/dimethylsiloxane copolymers, methylhydrogensiloxane/diphenylsiloxane copolymers capped at both molecular terminals with trimethylsiloxy groups, methylhydrogensiloxane/diphenylsiloxane/dimethylsiloxane copolymers capped at both molecular terminals with trimethylsiloxy groups, hydrolytic condensates of trimethylsilanes, copolymers consisting of (CH₃) ₂HSiO_1/2 units and SiO_4/2 units, copolymers consisting of (CH₃) ₂HSiO_1/2 units, SiO_4/2 units, and (C₆H₅) SiO_3/2 units, copolymers consisting of (CH₃) ₂HSiO_1/2 units and CH₃SiO_3/2 units, and mixtures of two or more types thereof.

In the case of a straight-chain structure, in particular, a methylhydrogenpolysiloxane represented by the molecular structural formula: RTMe₂SiO (Me₂SiO) _q (HMeSiO) _rSiMe₂RT (wherein, Me is a methyl group, RT is a methyl group or a hydrogen atom, and subscripts q and r are numbers satisfying 0.3≤r/ (q+r) ≤1 and 5≤ (q+r) ≤200) is preferable. Note that component (C) may use two or more different types in combination.

Similarly, the following organosiloxanes may be given as examples. Note that in the formulas, Me and Ph respectively represent a methyl group and a phenyl group, m is an integer from 1 to 100, n is an integer from 1 to 50, and b, c, d and e are each positive number, where the sum of b, c, d, and e in one molecule is 1.

HMe₂SiO (Ph₂SiO) _mSiMe₂H

HMePhSiO (Ph₂SiO) _mSiMePhH

HMePhSiO (Ph₂SiO) _m (MePhSiO) _nSiMePhH

HMePhSiO (Ph₂SiO) _m (Me₂SiO) _nSiMePhH

(HMe₂SiO_1/2) _b (PhSiO_3/2) _c

(HMePhSiO_1/2) _b (PhSiO_3/2) _c

(HMePhSiO_1/2) _b (HMe₂SiO_1/2) _c (PhSiO_3/2) _d

(HMe₂SiO_1/2) _b (Ph₂SiO2/2) _c (PhSiO_3/2) _d

(HMePhSiO_1/2) _b (Ph₂SiO2/2) _c (PhSiO_3/2) _d

(HMePhSiO_1/2) _b (HMe₂SiO_1/2) _c (Ph₂SiO2/2) _d (PhSiO_3/2) _e.

[SiH/Vi ratio]

The composition according to the present invention is hydrosilylation reaction curable and the usage amount of component (C) is not particularly limited as long as the composition can sufficiently cure via a hydrosilylation reaction. However, the amount of silicon atom-bonded hydrogen atom (SiH) groups in component (C) with respect to the sum of the amount (substance amount) of alkenyl groups in component (A) and the amount (substance amount) of alkenyl groups in component (B) in the composition, that is, the molar ratio, is preferably within a range of 1 to 100, 5 to 80, 10 to 70; and may be within a range of 15 to 60, within a range of 20 to 50, or within a range of 30 to 40.

In contrast, in order to improve adhesion to a substrate of glass, etc., the number of SiH groups per molecule can be designed to be 10 or more and 20 or more, is preferably more than 20, and more preferably 22 or more. For example, the substance amount of silicon atom-bonded hydrogen atoms (SiH) groups in component (C) with respect to the sum of the amount (substance amount) of alkenyl groups in component (A) and the amount (substance amount) of alkenyl groups in component (B) in the composition can be designed so as to be in a range of 10 to 60 and a range of 10 to 50. When the amount of the SiH groups falls below the abovementioned lower limit, the technical effect of improving adhesion to the substrate may not be achieved. In contrast, when the amount of the SiH groups exceeds the abovementioned upper limit, the amount of unreacted residual curing agent becomes large, which may have adverse effects on curing physical properties such as the brittleness of the cured product or may cause problems such as gas generation. However, a pressure sensitive adhesive layer can be formed which is sufficient for practical use even when the SiH/Vi ratio of the composition is outside the abovementioned range.

In some embodiments of the present invention, component (C) is added in an amount 0.1 to 2%by weight, 0.2 to 1.5%by weight, 0.4 to 1.2%by weight or 0.6 to 1.0%by weight, based on the total weight of the curable PSA composition.

[Component (D) ]

The curable silicone pressure sensitive adhesive (PSA) composition further comprises a fluoro-silicone polymer without having alkenyl or SiH functionality which can effectively decrease the release force on both the wet side and the dry side. The fluoro-silicone polymer may have 15 mol %to 29 mol%fluoroalkyl groups, and alternatively at least 16 mol %, alternatively at least 17 mol %, alternatively at least 18 mol %, and alternatively at least 19 mol %, of fluoroalkyl groups, while at the same time, the fluoro-silicone polymer may contain up to 28 mol %of fluoroalkyl groups, and alternatively up to 27 mol %of fluoroalkyl groups. In some embodiments of the present invention, the fluoro-silicone polymer is free of organic groups capable of undergoing hydrosilylation reaction under the conditions described herein, such as aliphatically unsaturated hydrocarbon groups, e.g., alkenyl groups, and SiH functionality.

The fluoroalkyl groups may have the following formula: C_nF_2n + 1-R-, C_nF_2n + 1-R-O-R-or F (CF (CF₃) CF₂O) _nCF (CF₃) -R-O-R-, where R is an independently divalent hydrocarbon radical, n is an integer of 1 to 20. The degree of polymerization of the fluoro-silicone polymer is 100 to 10,000, 500 to 8,000, 1,000 to 6,000 or 3,000 to 4,000. To achieve the technical purpose, the amount for the fluoro-silicone polymer is 0.1 to 7.0 mass parts, 0.1 to 5.0 mass parts, 0.1 to 4.0 mass parts, 0.5 to 3.0 mass parts, or 1.0 to 2.0 mass parts based on combined weights of components (A) to (C) on solid basis without any solvent.

Examples of fluoro-silicone polymer suitable for use in the PSA composition described herein include: (D-1) trimethylsilyl-terminated, poly (dimethyl) -co- (methyl monofluorohexyl) siloxane, (D-2) trimethylsiloxy-terminated, poly (dimethyl/methyl, 1, 3, 3, 3-trifluoropropyl) siloxane; (D-3) trimethylsiloxy-terminated, poly (dimethyl/methyl, perfluorobutylethyl) siloxane; (D-4) trimethylsiloxy-terminated, poly (dimethyl/methyl, perfluorohexylethyl) siloxane; (D-5) a combination of two or more of (D-1) to (D-5) . Suitable fluoro-silicone polymer for use in the PSA composition can be commercially available from Dow Silicones Corporation and those fluoro-silicone polymers disclosed in U.S. Patent 10, 494, 484 to Hori et al., which discloses various organopolysiloxanes having fluorine-atom containing organic groups for use as release control agents for release coatings, but not for use in silicone pressure sensitive adhesives.

[Component (E) ]

The curable PSA composition of the present invention contains a hydrosilylation reaction catalyst (E) . Examples of hydrosilylation reaction catalysts include platinum-based catalysts, rhodium-based catalysts, and palladium-based catalysts, with platinum-based catalysts preferable in that they markedly accelerate the curing of the present composition. Examples of this platinum based catalyst include platinum fine powder, chloroplatinic acid, an alcohol solution of chloroplatinic acid, a platinum-alkenyl siloxane complex, a platinum-olefin complex, and a platinum-carbonyl complex, with a platinum-alkenyl siloxane complex particularly preferable. Examples of this alkenyl siloxane include 1, 3-divinyl- 1, 1, 3, 3-tetramethyldisiloxane, 1, 3, 5, 7-tetramethyl-1, 3, 5, 7-tetravinylcyclotetrasiloxane, alkenyl siloxanes in which some of the methyl groups of these alkenyl siloxanes are substituted with groups selected from the group consisting of nitriles, amides, dioxolanes, sulfolanes, ethyl groups, phenyl groups, or the like, and alkenyl siloxanes in which the vinyl groups of these alkenyl siloxanes are substituted with allyl groups, hexenyl groups, or the like. In particular, 1, 3-divinyl-1, 1, 3, 3-tetramethyldisiloxane is preferable because the platinum-alkenyl siloxane complex has good stability. As the catalyst for promoting the hydrosilylation reaction, a non-platinum based metal catalyst such as iron, ruthenium, iron/cobalt, or the like may be used.

While the content of the hydrosilylation reaction catalyst is not particularly limited thereto in the present invention, the amount of the platinum based metal with respect to the total amount of solids in the composition (i.e. excluding solvents) is within a range of 0.1 to 200 ppm, and may be within a range of 0.1 to 150 ppm, within a range of 0.1 to 100 ppm, or within a range of 0.1 to 50 ppm. Here, the platinum-based metal is a metal element of group VIII consisting of platinum, rhodium, palladium, ruthenium, and iridium; however, in practical use, the content of the platinum metal excluding the ligands of the hydrosilylation catalyst is preferably within the range described above. Note that the solid content is a component that forms the cured layer (primarily a main agent, an adhesion-imparting component, a crosslinking agent, a catalyst, and other non-volatile components) when the organopolysiloxane composition of the present invention is subjected to a curing reaction and does not include volatile components such as solvents that volatilize at the time of heat curing.

When the content of the platinum based metal in the organopolysiloxane composition according to the present invention is 60 ppm or less, 50 ppm or less, 35 ppm or less, 30 ppm or less, 25 ppm or less, or 20 ppm or less, this may suppress discoloration or coloration of the transparent pressure sensitive adhesive layer, in particular, after curing or when heated or exposed to high energy rays such as UV rays. Meanwhile, from the perspective of the curability of the organopolysiloxane composition, the content of the platinum-based metal is not lower than 0.1 ppm, as when the content is lower than this lower limit, this may cause curing defects.

[Component (F) ]

In this Invention, component (F) is a hydrosilylation inhibitor (=a curing retarder or curing inhibitor) and is compounded in order to suppress crosslinking reactions between the alkenyl groups in the composition and the SiH groups in component (C) so as to extend the usable life at ordinary temperatures and enhance the storage stability. Accordingly, in practical use, the component (F) may be added to the curable silicone pressure sensitive adhesive (PSA) composition according to the present invention.

Specific examples of component (F) include acetylenic compounds, eneyne compounds, organic nitrogen compounds, organic phosphorus compounds, and oxime compounds. Specific examples include: alkyne alcohols such as 3-methyl-1-butyne-3-ol, 3, 5-dimethyl-1-hexyne-3-ol, 3-methyl-1-pentyne-3-ol, 1-ethynyl-1-cyclohexanol, phenyl butanol, and the like; eneyne compounds such as 3-methyl-3-pentene-1-yne, 3, 5-dimethyl-1-hexyne-3-yne, and the like; methylalkenylcyclosiloxanes such as 2-ethynyl-4-methyl-2-pentene, 1, 3, 5, 7-tetramethyl-1, 3, 5, 7-tetravinylcyclotetrasiloxane, 1, 3, 5, 7-tetramethyl-1, 3, 5, 7-tetrahexenylcyclotetrasiloxane, and the like, as well as benzotriazoles.

From the perspective of the curing behavior of the composition, the curable silicone pressure sensitive adhesive (PSA) composition of the present invention is preferably curable at 80 to 200℃ with an increase in viscosity within 1.5-fold after 8 hours at room temperature following the preparation of the composition. The suppression of thickening is important from the perspective of handleability, pot life, and characteristics after curing and contains a large excess of component (C) , wherein, even if the content of the platinum-based metal is optionally low, the curability can be ensured by curing at high temperature of at least a certain temperature (80 to 200℃) . Note that such a composition can be realized by selecting a suitable combination and compounded amounts of each of the components described above, the hydrosilylation catalyst, and component (F) .

[Component G]

In addition to the components described above, the curable silicone pressure sensitive adhesive (PSA) composition of the present invention may also contain an organic solvent as a solvent G. The type and blending amount of the organic solvent can be adjusted taking the coating workability, etc. into consideration. Exemplary organic solvents include: aromatic hydrocarbon-based solvents such as toluene, xylene and benzene; aliphatic hydrocarbon-based solvents such as heptane, hexane, octane and isoparaffin; ester- based solvents such as ethyl acetate and isobutyl acetate; ether-based solvents such as diisopropyl ether and 1, 4-dioxane; chlorinated aliphatic hydrocarbon-based solvents such as trichloroethylene, perchloroethylene and methylene chloride; and solvent volatile oils; with two or more types capable of being combined in accordance with the wettability of the sheet-like substrate or the like. The compounded amount of the organic solvent is preferably an amount such that a mixture of components (A) to (D) can be uniformly applied to a sheet-like substrate surface. For example, the compounded amount may be from 5 to 3000 parts by mass per total amount of 100 parts by mass of components (A) , (B) and (D) .

[Additives]

The organopolysiloxane composition of the present invention may optionally contain components other than the components described above to such an extent that does not impair the technical effects of the present invention. For example, the composition may contain: an adhesion promoter; a non-reactive organopolysiloxane such as a polydimethylsiloxane or a polydimethyldiphenylsiloxane; an antioxidant such as a phenol-type, a quinone-type, an amine-type, a phosphorus-type, a phosphite-type, a sulfur-type or a thioether-type antioxidant; a flame retardant such as a phosphate ester-type, a halogen-type, a phosphorus-type or an antimony-type flame retardant; and one or more types of antistatic agents consisting of a cationic surfactant, an anionic surfactant, a non-ionic surfactant or the like. Note that, in addition to these components, pigments, dyes, inorganic microparticles (e.g., reinforcing fillers, dielectric fillers, conductive fillers, thermally conductive fillers) , etc. can be optionally blended.

[ (A′) linear organopolysiloxane which does not contain a carbon-carbon double bond-containing reactive group in the molecule]

The organopolysiloxane composition according to the present invention can comprise a non-reactive organopolysiloxane such as a polydimethylsiloxane or polydimethyldiphenylsiloxane that does not contain a carbon-carbon double bond-containing reactive group such as an alkenyl group, acryl group or methacryl group. As a result, it may be possible to improve the loss coefficient (tan δ) , storage elastic modulus (G′) , loss modulus (G″) and adhesion of the pressure sensitive adhesive layer. For example, the loss coefficient of the pressure sensitive adhesive layer can be increased using a polydimethyl siloxane having a hydroxyl group terminal, or a polydimethylsiloxane or polydimethyldiphenylsiloxane having a trimethylsiloxy terminal, with such compositions included within the scope of the present invention.

Preferably, component (A′) is (A′1) a raw rubber-like organopolysiloxane having a viscosity of 100,000 mPa.s or more at 25℃ or having a plasticity number within a range of 50 to 200 as measured in accordance with a method as described in JIS K6249.

In a preferred embodiment of this invention, 50 to 100 mass%of said component (A) is (A1) a raw rubber-like alkenyl group-containing organopolysiloxane having a viscosity of 100,000 mPa.s or more at 25℃ or having a plasticity number within a range of 50 to 200 as measured in accordance with a method as described in JIS K6249, and the content of a vinyl (CH2=CH-) moiety of alkenyl group is within a range of 0.005 to 0.400 mass%; 50 to 100 mass%of said optional component (A′) is (A′1) a raw rubber-like organopolysiloxane having a viscosity of 100,000 mPa.s or more at 25℃ or having a plasticity number within a range of 50 to 200 as measured in accordance with a method as described in JIS K6249; and the mass ratio of component (A) to component (A′) ranges from 100: 0 to 40: 60 in the composition.

[Forming a PSA layer using a curable silicone PSA composition]

The method of preparing the silicone PSA composition is not particularly limited and is performed by homogeneously mixing the respective components. A solvent may be added as necessary and the composition may be prepared by mixing at a temperature of from 0 to 200℃ using a known stirrer or kneader.

Aforementioned silicone PSA composition forms a cured PSA layer when applied to a substrate such as a PET film and forms a cured product by heating under temperature conditions of from 80 to 200℃, preferably under temperature conditions of from 90 to 190℃. Examples of application methods include gravure coating, offset coating, offset gravure, roll coating, reverse roll coating, air knife coating, curtain coating and comma coating.

The cured PSA layer from said curable silicone PSA composition is arranged between the functional layers to bond/assemble the layers in the electronic article of this invention.

[Curable silicone pressure sensitive adhesive (PSA) laminate]

In an embodiment of the present disclosure, a pressure sensitive adhesive layer is obtained by curing the PSA composition. In an embodiment of the present disclosure, the pressure sensitive adhesive layer is utilized in assembly applications, which require a wet/dry side release force below 15 gf/inch at a peel rate of 0.3 m/min for PSA having a dynamic storage modulus at -20℃ lower than 1 MPa and a thickness of 50 μm. In an embodiment of the present disclosure, the PSA is used as an optically clear adhesive (OCA) for displays.

In an embodiment of the present disclosure, it also provides an electronic equipment or electrical device comprising the silicone pressure sensitive adhesive (PSA) laminate

[Methods of applying the curable silicone PSA composition]

As to the application methods to the substrate, gravure coating, offset coating, offset gravure, roll coating using an offset transfer roll coater, reverse roll coating, air knife coating, curtain coating using a curtain flow coater or the like, comma coating, Meyer bar, or another known method used for the purpose of forming a cured layer may be used without limitation.

The coating amount can be designed at a desired thickness in accordance with the application such as a display device, as one example, the thickness of the pressure sensitive adhesive layer after curing may be from 1 to 1000 μm, from 5 to 900 μm, or from 10 to 800 μm; however, there is no limitation thereto.

The pressure sensitive adhesive layer according to the present invention may be a single layer or a multilayer structure obtained by laminating two or more pressure sensitive adhesive layers, in accordance with the required characteristics. Multiple pressure sensitive adhesive layer may be formed by bonding the pressure sensitive adhesive films (which are formed film by film) thereto, or the step of applying and curing the pressure sensitive adhesive layer-forming organopolysiloxane composition may be carried out multiple times on a film substrate (including a release layer) , etc.

The pressure sensitive adhesive layer according to the present invention may serve as other functional layers selected from a dielectric layer, conductive layer, heat dissipation layer, insulating layer, reinforcing layer, etc., in addition to adhering or sticking functions between members. Also, as interlayer silicone-based PSA layer, in addition to adhering or sticking functions between members, the silicone-based PSA layer of this invention can be applied as a damping/shock-absorption layer.

Preferably, since said interlayer adhesive layer have both assembly/bonding layer function and damping/shock-absorption layer function, the electronic article having the silicone-based PSA layer of this invention need not have further interlayer damping/shock-absorption layer arranged between two functional layers. For this bifunctional feature of said interlayer adhesive layer, through this invention, the electronic article can be constructed without using other interlayer damping/shock-absorption layers other than the interlayer adhesive layer according to the present invention between two functional layers.

In one preferred embodiment, the electronic article having the silicone-based PSA layer of this invention as its interlayer adhesive layer is LED or OLED type display devices and its module thereof having a structure that transparent displaying unit is directly bonded or assembled to other functional unit with said interlayer adhesive layer, wherein the interlayer adhesive layer is a single adhesive/assembly layer sandwiched between said units in the display device. Since the display devices having the silicone-based PSA layer can be designed to be substantively free from additional interlayer damping/shock-absorption layer except for said interlayer adhesive layer of the present invention (i.e. omitting thick and multi-layered damping/shock-absorption layer from the devices) , the overall thickness of said display can be thinner and lighter in comparison with conventional devices.

When the cured layer obtained by curing the organopolysiloxane composition of the present invention is a pressure sensitive adhesive layer, in particular, a pressure sensitive adhesive layer, the cured layer is preferably treated as a laminate film that is peelably adhered to a film substrate provided with a release layer having a release-coating capability. The release layer may also be referred to as a release liner, a separator, a release layer, or a release coating layer, and may preferably be a release layer having a release coating ability such as a silicone-based release agent, a fluorine-based release agent, an alkyd-based release agent, or a fluorosilicone-based release agent, or the release layer may be formed as a substrate itself which is not prone to adhering to the resin sheet for a pressure sensitive adhesive layer of the present invention by forming physically fine irregularities in the surface of the substrate. In particular, in the laminated body according to the present invention, a release layer obtained by curing a fluorosilicone release agent is preferably used as the release layer.

The cured product obtained by curing the organopolysiloxane composition according to the present invention has both viscoelasticity and adhesive strength as described above, making it useful as a member of various types of electronic equipment or electrical devices as elastic adhesive members. In particular, it is useful as an electronic material, a member for a display device, or a member for a transducer (including sensors, speakers, actuators, and generators) , with a suitable application for the cured product being a member for an electronic part or a display device. The cured product according to the present invention may be transparent or opaque, wherein, in particular, a film-shaped cured product, particularly a substantially transparent pressure sensitive adhesive film, is suitable as a member for a display panel or a display, and is particularly useful in so-called touch panel applications in which a device, particularly an electronic device, can be operated by touching a screen with a fingertip or the like. Moreover, the opaque elastic adhesive layer is not required to have transparency, making it particularly useful for applications of film-like or sheet-like members used in sensors, speakers, actuators, etc. which require constant elasticity or flexibility in the adhesive layer itself.

In particular, the pressure sensitive adhesive layer obtained by curing the organopolysiloxane composition according to the present invention is capable of achieving a pressure sensitive adhesive characteristic equivalent to conventional silicone pressure sensitive adhesive layers and can improve adhesion to the substrate of a display device, etc. without causing problems of poor curing or reduced curability.

EXAMPLES

These examples are intended to illustrate the invention to one skilled in the art and are not to be interpreted as limiting the scope of the invention set forth in the claims. Note that “cured” in each of the examples, comparative examples, and reference examples means that each composition has fully cured under the respective curing conditions.

[Preparation of curable silicone pressure sensitive adhesive (PSA) composition] The curable silicone pressure sensitive adhesive (PSA) composition described in each Example and Comparative Example was prepared using the components shown in Table 1.

Table 1. Components of the curable silicone PSA composition

[Preparation of silicone pressure sensitive adhesive (PSA) laminate]

The curable silicone pressure sensitive adhesive (PSA) laminates of Examples (IE1-6) and Comparative Examples (CE1-5) were prepared using the liners listed in Table 2.

Table 2. Release liners (50 μm thick)

[Wet/dry side release force measurement]

The curable silicone pressure sensitive adhesive (PSA) composition was coated on the release liners (I) to (III) described in Table 2, respectively, for the thickness of 50 μm after cure, followed by curing in a 150℃ oven for 3 min. Onto the cured composition, another liner was laminated. The release liner side that the organopolysiloxane composition before cure was coated was denoted as the “wet side” and the release liner side that the release liner was laminated onto the cured organopolysiloxane composition was denoted as the “dry side” . The 50 μm thick organopolysiloxane film between two release liner films was cut into 1 inch wide strips. The wet side liner film was stuck to a 5 mm thick plastic sheet using a double-sided adhesive tape. Using an Adhesion/Release Tester AR-1500 equipped with a 1 kgf load cell, the plastic sheet was fixed vertically at the lower part of the tensile tester clamp together with the wet side liner coated with the organopolysiloxane and the dry side liner film was peeled off upwards vertically at the cross head speed of 0.3 m/min at 23℃/50%RH, to measure the dry side release force. The organopolysiloxane on the wet side liner was then laminated to a 50 μm thick liner. The PET film was stuck to the plastic sheet in the same way and the wet side liner was peeled off in the same manner.

Example 1

20.98 parts by weight of the vinyl functional polydimethylsiloxane gum A, 37.48 parts by weight of the MQ silicone resin B, and 20.98 parts by weight of component G toluene as a solvent were sufficiently mixed at room temperature, after which 0.44 parts by weight of component C, 0.3 parts by weight of component D-1 and 0.1 parts by weight of component F (a hydrosilylation inhibitor) were added to the mixture. Finally, component E (i.e., a platinum based hydrosilylation reaction catalyst in 10 ppm) was added to the mixture and was mixed well to form a curable silicone pressure sensitive adhesive (PSA) composition. According to Release force measurement described above, the wet/dry release force was measured, with the evaluation results indicated in Table 3.

Example 2

Except that 0.6 parts by weight of component D-1 was added to the mixture, the curable silicone pressure sensitive adhesive (PSA) composition of Example 2 was formed in a manner similar to that of Example 1. According to Release force measurement described above, the wet/dry release force was measured, with the evaluation results indicated in Table 3.

Example 3

Except that 0.9 parts by weight of component D-1 was added to the mixture, the curable silicone pressure sensitive adhesive (PSA) composition of Example 3 was formed in a manner similar to that of Example 1. According to Release force measurement described above, the wet/dry release force was measured, with the evaluation results indicated in Table 3.

Example 4

Except that 1.2 parts by weight of component D-1 was added to the mixture, the curable silicone pressure sensitive adhesive (PSA) composition of Example 4 was formed in a manner similar to that of Example 1. According to Release force measurement described above, the wet/dry release force was measured, with the evaluation results indicated in Table 3.

Example 5

Except that 1.5 parts by weight of component D-1 was added to the mixture, the curable silicone pressure sensitive adhesive (PSA) composition of Example 5 was formed in a manner similar to that of Example 1. According to Release force measurement described above, the wet/dry release force was measured, with the evaluation results indicated in Table 3.

Example 6

Except that 1.8 parts by weight of component D-1 was added to the mixture, the curable silicone pressure sensitive adhesive (PSA) composition of Example 6 was formed in a manner similar to that of Example 1. According to Release force measurement described above, the wet/dry release force was measured, with the evaluation results indicated in Table 3.

Comparative Example 1

Except that no component D-1 was added to the mixture, the curable silicone pressure sensitive adhesive (PSA) composition of Comparative Example 1 was formed in a manner similar to that of Example 1. According to Release force measurement described above, the wet/dry release force was measured, with the evaluation results indicated in Table 3.

Comparative Example 2

Except that 0.29 parts by weight of component D-5 was added to the mixture, the curable silicone pressure sensitive adhesive (PSA) composition of Comparative Example 2 was formed in a manner similar to that of Example 1. According to Release force measurement described above, the wet/dry release force was measured, with the evaluation results indicated in Table 3.

Comparative Example 3

Except that 0.3 parts by weight of component D-2 was added to the mixture, the curable silicone pressure sensitive adhesive (PSA) composition of Comparative Example 3 was formed in a manner similar to that of Example 1. According to Release force measurement described above, the wet/dry release force was measured, with the evaluation results indicated in Table 3.

Comparative Example 4

Except that 0.3 parts by weight of component D-3 was added to the mixture, the curable silicone pressure sensitive adhesive (PSA) composition of Comparative Example 4 was formed in a manner similar to that of Example 1. According to Release force measurement described above, the wet/dry release force was measured, with the evaluation results indicated in Table 3.

Comparative Example 5

Except that 0.3 parts by weight of component D-4 was added to the mixture, the curable silicone pressure sensitive adhesive (PSA) composition of Comparative Example 5 was formed in a manner similar to that of Example 1. According to Release force measurement described above, the wet/dry release force was measured, with the evaluation results indicated in Table 3.

Table 3. Properties

Note: “n.a. ” means the release force measurement was not done.

The release force values on RF50FL169 in Examples 1-6 were less than 20 gf/inch for both the dry and the wet side, while those in CE showed the values greater than 20 gf/inch, without significant reduction in adhesive strength.

Claims

A curable silicone pressure sensitive adhesive (PSA) composition, comprising:

(A) an organopolysiloxane having alkenyl group in numbers greater than 1 on average per molecule;

(B) a branched organopolysiloxane resin having the total content of hydroxyl groups and hydrolysable groups with respect to all silicon atoms in the molecule within a range of 2.0 mass %or less;

(C) an organohydrogenpolysiloxane having at least two Si-H bonds in the molecule;

(D) a fluoro-silicone polymer without having alkenyl or SiH functionality; and

(E) a hydrosilylation reaction catalyst,

wherein the mass ratio of component (B) to component (A) is within a range of 0.5 to 3.5, and the amount of component (D) based on combined weights of compositions (A) to (C) is 0.1 to 7.0 mass parts on the solid basis.
The curable silicone pressure sensitive adhesive (PSA) composition according to claim 1, wherein at least a portion of component (A) is (A1) a raw rubber-like alkenyl group-containing organopolysiloxane having a viscosity of 100,000 mPa. s or more at 25℃ or having a plasticity number within a range of 50 to 200 as measured in accordance with a method as described in JIS K6249, and the content of a vinyl (CH₂=CH-) moiety of alkenyl group is within a range of 0.005 to 0.400 mass%;

component (B) is (B1) an organopolysiloxane resin or mixture thereof which consists essentially of R³SiO_1/2 units and SiO_4/2 units, where R is a monovalent organic group, and 90 mol %or more of R is an alkyl group having 1 to 6 carbon atoms or a phenyl group;

component (C) is present in an amount such that the molar ratio of the amount of SiH groups in component (C) to the total amount of the alkenyl groups in components (A) and (B) is 0.1 to 100;

component (D) is a polyorganosiloaxane having fluoroalkyl or fluoro-poly-ether substituents, without having alkenyl or SiH functionality; and/or

component (E) is a platinum-based catalyst and is present in an amount such that the content of a platinum based metal in a solid content of the composition is within a range of 0.1 to 200 ppm in the PSA composition.
The curable silicone pressure sensitive adhesive (PSA) composition according to claim 1, wherein the composition further comprises (A′) a linear organopolysiloxane which does not contain a carbon-carbon double bond-containing reactive group in the molecule.
The curable silicone pressure sensitive adhesive (PSA) composition according to claim 1, wherein component (B) is an organopolysiloxane resin or mixture thereof which consists essentially of R³SiO_1/2 units and SiO_4/2 units, where R is methyl.
The curable silicone pressure sensitive adhesive (PSA) composition according to claim 1, wherein component (C) is present in an amount such that the molar ratio of the amount of SiH groups in component (C) to the total amount of the alkenyl groups in components (A) and (B) is 10 to 100.
The curable silicone pressure sensitive adhesive (PSA) composition according to claim 1, wherein component (C) is present in an amount such that the molar ratio of the amount of SiH groups in component (C) to the total amount of the alkenyl groups in components (A) and (B) is 20 to 60.
The curable silicone pressure sensitive adhesive (PSA) composition according to claim 1, wherein the composition further comprises:

(F) a hydrosilylation inhibitor, and/or

(G) a solvent.
A pressure sensitive adhesive layer obtained by curing the curable silicone pressure sensitive adhesive (PSA) composition according to any one of claims 1-7.
The pressure sensitive adhesive layer according to claim 8, which exhibits a wet/dry side release force below 15 gf/inch at a peel rate of 0.3 m/min for PSA having a dynamic storage modulus at -20℃ lower than 1 MPa and a thickness of 50 μm.
Use of the pressure sensitive adhesive (PSA) layer according to claim 8 in assembly applications.
Use according to claim 10, wherein the PSA layer is used as an optically clear adhesive (OCA) layer for displays.
Use according to claim 10, wherein the PSA layer is used in combination with F-Si release coating.
An electronic equipment or electrical device comprising the curable silicone pressure sensitive adhesive (PSA) composition according to any one of claims 1-7.