JP2019070102A - Acrylic adhesive composition and adhesive sheet - Google Patents

Abstract

To provide an acrylic adhesive composition which can achieve both light pressure-bonding initial adhesiveness and deformation resistance to a persistent load in a Z-axis direction without depending on high-temperature thermocompression bonding.SOLUTION: There is provided an acrylic adhesive composition which contains an acrylic polymer as a base polymer, and at least one selected from a tackifier resin and a (meth)acrylic oligomer. A weight average molecular weight of the acrylic polymer is greater than 70×10. A degree of dispersion (Mw/Mn) of the acrylic polymer is less than 15.SELECTED DRAWING: None

Description

  The present invention relates to an acrylic pressure-sensitive adhesive composition and a pressure-sensitive adhesive sheet.

  In general, a pressure-sensitive adhesive (also referred to as a pressure-sensitive adhesive, the same applies hereinafter) exhibits a soft solid (viscoelastic) state in a temperature range around room temperature and has a property of easily adhering to an adherend by pressure. Taking advantage of such properties, the pressure-sensitive adhesive is, for example, in the form of a pressure-sensitive adhesive sheet with a substrate having a pressure-sensitive adhesive layer on a support substrate, or in the form of a substrate-less pressure-sensitive adhesive sheet without a support substrate; Are widely used for the purpose of joining, fixing, and protecting members in portable electronic devices. Patent documents 1-4 are mentioned as a technical literature about the double-sided adhesive tape used for the member fixation of a portable electronic device.

JP, 2017-132911, A JP, 2013-100485, A JP 2017-002292 A JP, 2015-147873, A

  Generally, the bonding area of a member fixed in a portable electronic device by a pressure sensitive adhesive sheet is small due to limitations in size, weight and the like. The pressure-sensitive adhesive sheet used for the application needs to have an adhesive force capable of achieving good fixation even in a small area, and the required performance becomes higher level due to the demand for weight reduction and miniaturization. ing. In particular, the touch panel type display mounted type portable electronic device represented by a smartphone is becoming larger in view of the visibility of the display and operability, while the product itself is miniaturized and thinned. For this reason, the adhesive to be used is required to have adhesion and fixing performance under more severe conditions. Specifically, in this application, it goes without saying that the bonding area is limited, for example, by bending an elastic member such as a flexible printed wiring board (FPC) to be accommodated in a limited internal space in the portable electronic device. , It is positioned with a pressure sensitive adhesive sheet with high accuracy, and measures are taken to fix it stably. The pressure-sensitive adhesive used for fixing such a member is required to have deformation resistance capable of continuously resisting the elastic repulsion of the member. In this type of member fixing, a sustained peel deformation load is applied in the thickness direction (also referred to as the Z-axis direction) of the adhesive sheet. At present, the crosslinking property of the pressure-sensitive adhesive is increased to improve the cohesion, and in addition, the required performance is realized by the adhesion and fixation by strong pressure bonding, securing of a sufficient curing time, and the like.

  On the other hand, when aiming at the productivity improvement of products, such as an electronic device, and a production cost reduction, reduction of tact time (process operation time) is considered first. With regard to the pressure-sensitive adhesive sheet to be used, it is required to exhibit a simple adhesion property by light pressure bonding and to exert a desired performance with a shorter curing time. For this purpose, it is necessary to develop good adhesion immediately after the application. Although it is possible to improve the initial adhesion by reducing the degree of crosslinking, the reduction of the degree of crosslinking in the pressure-sensitive adhesive usually causes a reduction in the cohesion, so that the deformation resistance of the pressure-sensitive adhesive to external forces is lowered. In addition, there is a problem that the holding application requiring sustained performance can not withstand the load and causes cohesive failure. Another option is to use thermocompression bonding, but high temperature heating, such as above 60 ° C., severely limits the application. In addition, the handling property tends to be inferior to that at room temperature pressure bonding. In short, there is a contradiction between the sustained deformation resistance required for the fixing of members of portable electronic devices in recent years and the light pressure bonding initial adhesion for reducing the tact time, and the coexistence is not easy. In applications where deformation resistance to a sustained tear-off load in the thickness direction of the pressure-sensitive adhesive sheet is required, sufficient adhesion performance is developed immediately after bonding even in a mode that can be applied by light pressure bonding (light pressure bonding An adhesive sheet having initial adhesion) and resistance to deformation due to a sustained peeling load in the thickness direction (having resistance to a sustained load in the Z-axis direction) provides high performance, This is very significant as it improves the production efficiency of high-performance products.

  The present invention has been made in view of the above circumstances, and it is an acrylic pressure-sensitive adhesive composition capable of achieving both the initial adhesion with light pressure bonding and the deformation resistance to a sustained load in the Z-axis direction regardless of high temperature thermocompression bonding. It aims to provide goods. Another object of the present invention is to provide a pressure-sensitive adhesive sheet capable of achieving both light-press initial adhesion and deformation resistance to a sustained load in the Z-axis direction independently of high temperature thermocompression bonding.

According to the present specification, an acrylic pressure-sensitive adhesive composition is provided. The acrylic pressure-sensitive adhesive composition contains an acrylic polymer as a base polymer, and at least one selected from a tackifying resin and a (meth) acrylic oligomer. In addition, the weight average molecular weight of the acrylic polymer is greater than 70 × 10 ⁴ . Furthermore, the degree of dispersion (Mw / Mn) of the acrylic polymer is less than 15.

By using an acrylic polymer having a weight average molecular weight (Mw) of more than 70 × 10 ⁴ and a Mw / Mn of less than 15 as the base polymer, the cohesion by the relatively uniform high molecular weight is accurately expressed, and sustained It is possible to obtain excellent resistance (modification resistance) to various deformation loads. Moreover, in addition to such an acrylic polymer, by using one or more selected from a tackifying resin and a (meth) acrylic oligomer, sufficient adhesion performance can be obtained immediately after bonding even if the embodiment is applied by light pressure bonding. Express. That is, according to the above-mentioned pressure-sensitive adhesive composition, a pressure-sensitive adhesive sheet is provided which has both the light-press initial adhesion and the deformation resistance to a sustained load in the Z-axis direction. The pressure-sensitive adhesive sheet formed from the above-mentioned pressure-sensitive adhesive composition can be fixed in a state in which the elastic adherend is bent even by light pressure bonding, and can maintain the fixed state continuously. Moreover, since the said adhesive sheet is excellent in the light pressure-bonding initial stage adhesiveness, it is advantageous also at the point which is easy to affix to the fragile adherend which may be damaged by normal pressure bonding.

  In a preferred embodiment of the technology disclosed herein (including an acrylic pressure-sensitive adhesive composition and a pressure-sensitive adhesive sheet, the same applies hereinafter), the acrylic polymer contains an alkyl group having 1 to 6 carbon atoms at the ester end. The alkyl (meth) acrylate which has is polymerized by the ratio of 50 weight% or more. By comprising in this way, the adhesive sheet compatible with the light pressure-bonding initial stage adhesiveness and the deformation resistance with respect to the sustained load of Z-axis direction is preferably obtained.

  In a preferred aspect of the technology disclosed herein, the acrylic polymer is copolymerized with an acidic group-containing monomer. The acidic group-containing monomer introduced into the polymer exhibits an improvement in the cohesion based on its polarity and a bonding ability to a polar adherend. As a result, even in a mode in which the pressure-sensitive adhesive is applied by light pressure bonding, the adhesive preferably exhibits sufficient adhesion performance immediately after application, and is more deformed by a sustained peeling load in the thickness direction. Hateful. Moreover, it is preferable that the copolymerization ratio of the said acidic group containing monomer in the said acryl-type polymer is less than 10 weight%. By setting the copolymerization ratio of the acidic group-containing monomer to less than 10% by weight, the action (flocculation, crosslinking point, etc.) by the acidic group-containing monomer can be appropriately controlled to maintain good initial adhesion with light pressure bonding it can. Moreover, it is more preferable to use acrylic acid as said acidic group containing monomer. By using acrylic acid as the acidic group-containing monomer, it is possible to preferably achieve both light pressure bonding initial adhesion and deformation resistance to a sustained load in the Z-axis direction.

  In a preferable embodiment of the art disclosed herein, the tackifying resin is contained in a ratio of less than 30 parts by weight with respect to 100 parts by weight of the acrylic polymer. By using a tackifying resin in a predetermined amount, it is possible to preferably improve the light-press initial adhesion while securing deformation resistance to a sustained load in the Z-axis direction with a high molecular weight acrylic polymer.

  In a preferred embodiment of the technology disclosed herein, the (meth) acrylic oligomer is contained in a ratio of less than 30 parts by weight with respect to 100 parts by weight of the acrylic polymer. By using a predetermined amount of (meth) acrylic oligomer, it is possible to obtain excellent light pressure bonding initial adhesion, and also to a sustained load in the Z-axis direction even in a usage mode exposed to more severe conditions such as strong repulsion It can exhibit excellent deformation resistance.

  A preferred embodiment of the technology disclosed herein comprises both the tackifying resin and the (meth) acrylic oligomer. In a composition containing a high molecular weight acrylic polymer, by using a tackifying resin and a (meth) acrylic oligomer in combination, it is exposed to more severe conditions such as strong repulsion while obtaining excellent initial adhesion with light pressure bonding. Also in the usage mode, highly excellent deformation resistance can be exhibited against the sustained load in the Z-axis direction.

Moreover, according to the present specification, a pressure-sensitive adhesive sheet provided with an acrylic pressure-sensitive adhesive layer is provided. The acrylic pressure-sensitive adhesive layer contains an acrylic polymer as a base polymer, and at least one selected from a tackifying resin and a (meth) acrylic oligomer. In addition, the weight average molecular weight of the acrylic polymer is greater than 70 × 10 ⁴ . Furthermore, the degree of dispersion (Mw / Mn) of the acrylic polymer is less than 15. According to the pressure-sensitive adhesive sheet of the above-described structure, it is possible to achieve both of the light-press initial adhesion and the deformation resistance to the sustained load in the Z-axis direction.

  Further, according to the present specification, a pressure-sensitive adhesive sheet provided with a pressure-sensitive adhesive layer is provided. The pressure-sensitive adhesive layer has a storage elastic modulus G ′ (25 ° C.) at 25 ° C. of 0.15 MPa or more, and a storage elastic modulus G ′ (85 ° C.) at 85 ° C. of 0.02 MPa or more. Also, 180 ° peel strength (23 ° C. light pressure bond initial bond strength) measured within 1 minute after pressure bonding under conditions of 23 ° C. and pressure load of 0.1 kg, and pressure bonding under conditions of 40 ° C., 0.05 MPa and 3 seconds At least one of the 180 degree peel strength (40 ° C. light pressure bonding initial bond strength) measured within one minute after is satisfied to be 8 N / 20 mm or more.

  The adhesive layer described above has a storage elastic modulus G ′ (25 ° C.) and G ′ (85 ° C.) at 25 ° C. and 85 ° C. of 0.15 MPa or more and 0.02 MPa or more, respectively. Resistant to load In the pressure-sensitive adhesive sheet, at least one of the 23 ° C. light pressure-bonding initial adhesion and the 40 ° C. light pressure-bonding initial adhesion is 8 N / 20 mm or more. The pressure-sensitive adhesive sheet having the above-described 23 ° C. light pressure-bonding initial adhesion can exhibit excellent initial adhesion to the adherend surface by light pressure-bonding in a normal temperature range. Moreover, even if the above-mentioned 23 ° C. light pressure-bonding initial adhesion is not satisfied, if it is a pressure-sensitive adhesive sheet having a 40 ° C. light pressure-bonding initial adhesion of 8 N / 20 mm or more, the restriction applicable to electronic device applications, for example It is possible to exert excellent initial adhesion to the surface of the adherend by light pressure bonding using the above heating (less than 60 ° C., typically about 40 ° C. mild heating). The pressure-sensitive adhesive sheet having the above-described structure exhibits sufficient adhesion performance immediately after being attached and is sustained in the thickness direction, in a mode of being attached by light pressure bonding in a normal temperature range or light pressure bonding using a limited heating temperature. Is difficult to be deformed due to typical peeling off load. That is, according to the present specification, it is possible to provide a pressure-sensitive adhesive sheet capable of achieving both the light pressure-bonding initial adhesion and the deformation resistance to a sustained load in the Z-axis direction, regardless of the high temperature thermocompression bonding. According to the pressure-sensitive adhesive sheet, even in the case of light pressure bonding, the elastic adherend can be fixed in a bent state, and the fixed state can be maintained continuously. Such a pressure-sensitive adhesive sheet can be preferably produced by using any of the acrylic pressure-sensitive adhesive compositions disclosed herein.

  In a preferable embodiment of the pressure-sensitive adhesive sheet disclosed herein, the gel fraction of the pressure-sensitive adhesive layer is 40% by weight or more. With a pressure-sensitive adhesive having a gel fraction of 40% by weight or more, deformation resistance to a sustained load in the Z-axis direction is more suitably developed.

  In a preferred embodiment of the pressure-sensitive adhesive sheet disclosed herein, the pressure-sensitive adhesive layer is an acrylic pressure-sensitive adhesive layer containing an acrylic polymer. By using an acrylic polymer that has a wide range of molecular design options and is relatively easy to design, a pressure-sensitive adhesive sheet having both light-press initial adhesion and deformation resistance to sustained load in the Z-axis direction is suitably produced. be able to.

  In a preferred embodiment of the pressure-sensitive adhesive sheet disclosed herein, the acrylic polymer is crosslinked. By the crosslinking of the acrylic polymer, the cohesiveness of the pressure-sensitive adhesive is enhanced, and the deformation resistance to a sustained load in the Z-axis direction is more preferably exhibited.

  The pressure-sensitive adhesive sheet disclosed herein has a light pressure-bonding initial adhesion, so that tact time reduction can be realized, for example, in the manufacture of electronic devices. When the pressure-sensitive adhesive sheet is used for fixing a member in a portable electronic device, it can contribute to improvement in the productivity of the portable electronic device. Also, since the pressure-sensitive adhesive sheet disclosed herein has a resistance to deformation under a sustained load in the Z-axis direction, the pressure-sensitive adhesive sheet is preferably used for fixing an elastic adherend such as an FPC. According to the pressure-sensitive adhesive sheet, even in light pressure bonding, the elastic adherend can be fixed in a bent state, and the fixed state can be maintained continuously. For example, by using the pressure-sensitive adhesive sheet disclosed herein for fixing an FPC disposed in a portable electronic device, it is possible to simultaneously improve the member accommodation efficiency and the production efficiency of the portable electronic device. .

It is sectional drawing which shows typically one structural example of an adhesive sheet. It is sectional drawing which shows typically the other structural example of an adhesive sheet. It is sectional drawing which shows typically the other structural example of an adhesive sheet. It is sectional drawing which shows typically the other structural example of an adhesive sheet. It is sectional drawing which shows typically the other structural example of an adhesive sheet. It is sectional drawing which shows typically the other structural example of an adhesive sheet. It is a schematic diagram explaining the method of the Z-axis direction deformation resistance test.

  Hereinafter, preferred embodiments of the present invention will be described. Matters other than the matters specifically mentioned in the present specification and necessary for the practice of the present invention are based on the teaching of the practice of the invention described in the present specification and the technical common sense at the time of the application. Can be understood by those skilled in the art. The present invention can be implemented based on the contents disclosed in the present specification and common technical knowledge in the field. Moreover, in the following drawings, the same code | symbol may be attached | subjected and demonstrated to the member and site | part which show the same effect | action, and the overlapping description may be abbreviate | omitted or simplified. In addition, the embodiments described in the drawings are schematically illustrated in order to clearly explain the present invention, and the sizes and scales of the pressure-sensitive adhesive sheet of the present invention actually provided as a product are not necessarily accurately represented. .

In the present specification, as described above, the term "adhesive" refers to a material which exhibits a soft solid (viscoelastic) state in a temperature range near room temperature and has a property of being easily adhered to an adherend by pressure. . The adhesive referred to here is generally a complex tensile modulus E ^* (1 Hz), as defined in “CA Dahlquist,“ Adhesion: Fundamentals and Practice ”, McLaren & Sons, (1966) P. 143”. The material may have a property satisfying <10 ⁷ dyne / cm ² (typically, a material having the above-described property at 25 ° C.).

  In this specification, "(meth) acryloyl" is a meaning which generally refers to acryloyl and methacryloyl. Similarly, “(meth) acrylate” means acrylate and methacrylate, and “(meth) acrylic” generally means acrylic and methacrylic.

  In the present specification, the term "acrylic polymer" refers to a polymer comprising monomer units derived from a monomer having at least one (meth) acryloyl group in one molecule as monomer units constituting the polymer. Hereinafter, a monomer having at least one (meth) acryloyl group in one molecule is also referred to as "acrylic monomer". Acrylic polymers in this specification are defined as polymers comprising monomer units derived from acrylic monomers.

  The pressure-sensitive adhesive sheet disclosed herein may be a pressure-sensitive adhesive sheet with a substrate having the pressure-sensitive adhesive layer on one side or both sides of a substrate (support), and the pressure-sensitive adhesive layer is held by a release liner. It may be a substrate-less pressure-sensitive adhesive sheet of a form or the like. The concept of the pressure-sensitive adhesive sheet as referred to herein may include those referred to as a pressure-sensitive adhesive tape, a pressure-sensitive adhesive label, a pressure-sensitive adhesive film, and the like. The pressure-sensitive adhesive sheet disclosed herein may be in the form of a roll or sheet. Alternatively, it may be a pressure-sensitive adhesive sheet in a form further processed into various shapes.

  The pressure-sensitive adhesive sheet disclosed herein may have, for example, a cross-sectional structure schematically shown in FIGS. Among these, FIG. 1 and FIG. 2 show a configuration example of a double-sided pressure-sensitive adhesive sheet with a substrate. In the pressure-sensitive adhesive sheet 1 shown in FIG. 1, the pressure-sensitive adhesive layers 21 and 22 are provided on each surface (all non-removable) of the substrate 10, and at least the pressure-sensitive adhesive layer side is a peeling surface It has the structure protected by the release liners 31 and 32, respectively. In the pressure-sensitive adhesive sheet 2 shown in FIG. 2, the pressure-sensitive adhesive layers 21 and 22 are provided on each surface of the substrate 10 (all non-removable), and one pressure-sensitive adhesive layer 21 among them is a peeling surface on both sides. It has the structure protected by the release liner 31 which is. This type of pressure-sensitive adhesive sheet 2 has a structure in which the pressure-sensitive adhesive layer 22 is also protected by the release liner 31 by winding the pressure-sensitive adhesive sheet and bringing the other pressure-sensitive adhesive layer 22 into contact with the back surface of the release liner 31. be able to.

  FIG. 3 and FIG. 4 show a configuration example of a substrateless double-sided pressure-sensitive adhesive sheet. The pressure-sensitive adhesive sheet 3 shown in FIG. 3 has a configuration in which both surfaces 21A and 21B of the substrate-less pressure-sensitive adhesive layer 21 are each protected by release liners 31 and 32 having release surfaces at least on the pressure-sensitive adhesive layer side. The pressure-sensitive adhesive sheet 4 shown in FIG. 4 has a configuration in which one surface (pressure-sensitive adhesive surface) 21A of the substrate-less pressure-sensitive adhesive layer 21 is protected by a release liner 31 whose both surfaces are release surfaces. When wound, the other surface (adhesive surface) 21 B of the pressure-sensitive adhesive layer 21 abuts on the rear surface of the release liner 31 so that the other surface 21 B can also be protected by the release liner 31.

  5 and 6 show examples of the configuration of a single-sided pressure-sensitive adhesive sheet with a substrate. In the pressure-sensitive adhesive sheet 5 shown in FIG. 5, the pressure-sensitive adhesive layer 21 is provided on one surface 10A (non-peelable) of the substrate 10, and the surface (pressure-sensitive adhesive surface) 21A of the pressure-sensitive adhesive layer 21 peels at least on the pressure-sensitive adhesive layer side. It has the structure protected by the release liner 31 which becomes a surface. The pressure-sensitive adhesive sheet 6 shown in FIG. 6 has a configuration in which the pressure-sensitive adhesive layer 21 is provided on one surface 10A (non-peelable) of the base material 10. The other surface 10B of the substrate 10 is a peeling surface, and when the pressure-sensitive adhesive sheet 6 is wound, the adhesive layer 21 abuts on the other surface 10B, and the surface (adhesive surface) 21B of the adhesive layer is a substrate The other side 10B is to be protected.

<Pressure-sensitive adhesive layer>
The pressure-sensitive adhesive layer disclosed herein can typically have a storage modulus G ′ (25 ° C.) at 25 ° C. of 0.15 MPa or more. According to the pressure-sensitive adhesive having the G '(25 ° C), good deformation resistance can be preferably exhibited from an early stage after being attached to the adherend. The G ′ (25 ° C.) is preferably 0.17 MPa or more, more preferably 0.2 MPa or more, and still more preferably 0.23 MPa or more. The G ′ (25 ° C.) is particularly preferably 0.25 MPa or more, and may be, for example, 0.3 MPa or more. In addition, the G '(25 ° C) is usually suitably 1.0 MPa or less, preferably from 0.6 MPa or less, more preferably from the viewpoint of coexistence of light pressure bonding initial adhesion and deformation resistance. Is preferably 0.4 MPa or less, more preferably 0.35 MPa or less, for example, 0.3 MPa or less, 0.25 MPa or less, or 0.2 MPa or less.

  The pressure-sensitive adhesive layer disclosed herein suitably has a loss elastic modulus G ′ ′ (25 ° C.) at 25 ° C. of usually 2.0 MPa or less. The above G ′ ′ (25 ° C.) is preferably It is 1.5 MPa or less, more preferably 1.0 MPa or less, still more preferably 0.5 MPa or less. The G ′ ′ (25 ° C.) may be 0.3 MPa or less (eg, 0.25 MPa or less). The G ′ ′ (25 ° C.) is usually suitably 0.01 MPa or more. From the viewpoint of wettability to the surface of adherend, and hence initial adhesion after light pressure bonding, it is preferably 0.05 MPa or more, more preferably 0.1 MPa or more, still more preferably 0.2 MPa or more, for example, 0.25 MPa It may be more than.

  In addition, tan δ (25 ° C.) at 25 ° C. of the pressure-sensitive adhesive layer disclosed herein can be appropriately set in consideration of initial adhesion after light pressure bonding at ordinary temperature and deformation resistance. Here, tan δ (loss tangent) of the pressure-sensitive adhesive (layer) refers to the ratio of loss elastic modulus G ′ ′ to storage elastic modulus G ′ of the pressure-sensitive adhesive (layer). That is, tan δ = G ′ ′ / G ′ is there. The tan δ (25 ° C.) is, for example, suitably about 0.3 or more, preferably about 0.5 or more, more preferably about 0.7 or more, still more preferably about 0 from the viewpoint of deformation resistance. .8 or more, particularly preferably about 0.9 or more (for example, about 1 or more). In addition, tan δ (25 ° C.) is, for example, about 3 or less, and preferably about 2 or less, more preferably about 1.5 or less, and still more preferably about 1.2 or less, from the viewpoint of light adhesion initial adhesion. It is.

  The pressure-sensitive adhesive layer disclosed herein can typically have a storage modulus G ′ (85 ° C.) at 85 ° C. of 0.02 MPa or more. By having the above G ′ (85 ° C.), sustained deformation resistance is preferably obtained. The G ′ (85 ° C.) may specifically be 0.022 MPa or more. Moreover, said G '(85 degreeC) becomes like this. Preferably it is 0.025 Mpa or more, More preferably, it is 0.027 Mpa or more. The above G ′ (85 ° C.) is more preferably about 0.03 MPa or more (eg, 0.035 MPa or more), particularly preferably 0.04 MPa or more, still more preferably 0.05 MPa or more. In addition, the G '(85 ° C.) is usually 1.0 MPa or less, for example, 0.5 MPa or less, typically 0.1 MPa or less. The G ′ (85 ° C.) may be 0.05 MPa or less.

  In addition, tan δ (85 ° C.) at 85 ° C. of the pressure-sensitive adhesive layer disclosed herein can be appropriately set in consideration of sustained deformation resistance. The tan δ (85 ° C.) is, for example, suitably about 0.1 or more, preferably about 0.2 or more, more preferably 0.22 or more, still more preferably 0.24 or more (eg, 0.25 or more) ). In addition, tan δ (85 ° C.) is, for example, about 2 or less, preferably about 1 or less, and more preferably about 0.5 or less (eg, about 0.3 or less).

  The pressure-sensitive adhesive layer disclosed herein preferably has a storage elastic modulus G ′ (apply) of 0.6 MPa or less at a temperature (pressure bonding temperature) when the pressure-sensitive adhesive sheet is pressure-bonded to an adherend. The pressure-sensitive adhesive having the G '(apply) can be well wetted on the surface of the adherend even with light pressure bonding and can exhibit excellent initial adhesion. The above G ′ (apply) is more preferably 0.4 MPa or less, further preferably 0.35 MPa or less, and may be, for example, 0.3 MPa or less, or may be 0.25 MPa or less. The G ′ (apply) may be, for example, 0.2 MPa or less. Further, from the viewpoint of achieving both light pressure bonding initial adhesion and deformation resistance, the G '(apply) is suitably larger than 0.12 MPa, preferably 0.15 MPa or more, more preferably 0. The pressure may be 17 MPa or more (e.g., 0.2 MPa or more), more preferably 0.25 MPa or more, and for example, 0.3 MPa or more. The pressure bonding temperature is selected from the range of more than 0 ° C. and less than 60 ° C. from the viewpoint of pressure bonding workability and temperature control. In the case of a pressure-sensitive adhesive sheet used for portable electronic device applications, the pressure bonding temperature is selected from the range of 20 ° C. to 45 ° C. (typically 25 ° C. or 40 ° C., preferably 25 ° C.) due to temperature limitation in the application It is desirable to do. The pressure bonding in the above temperature range is different from the conventional heat pressure bonding performed at about 100 ° C., and is a heat pressure bonding applicable to electronic devices and the like.

In the technology disclosed herein, storage elastic modulus G ′ (25 ° C.), G ′ (85 ° C.), G ′ (apply), loss elastic modulus G ′ ′ (25 ° C.), tan δ (25 ° C.) of adhesive layer And tan δ (85 ° C.) can be determined by measurement of dynamic viscoelasticity Specifically, a plurality of pressure-sensitive adhesive layers (pressure-sensitive adhesive sheets in the case of a substrateless pressure-sensitive adhesive sheet) to be measured are superposed. A pressure-sensitive adhesive layer having a thickness of about 2 mm is prepared by sandwiching a sample obtained by punching this pressure-sensitive adhesive layer into a disk shape having a diameter of 7.9 mm with a parallel plate and fixing the sample. Dynamic visco-elasticity measurement is carried out under the following conditions by Instruments, Inc., ARES or its equivalent), storage elastic modulus G '(25.degree. C.), G' (85.degree. C.), G '(apply), loss elasticity The rates G ′ ′ (25 ° C.), tan δ (25 ° C.) and tan δ (85 ° C.) are determined.
Measurement mode: Shear mode Temperature range: -70 ° C to 150 ° C
· Heating rate: 5 ° C / min
・ Measurement frequency: 1 Hz
Also in the below-mentioned Example, it measures by said method. The pressure-sensitive adhesive layer to be measured can be formed by applying the corresponding pressure-sensitive adhesive composition in layers and drying or curing.

(Adhesive)
In the art disclosed herein, the type of the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer is not particularly limited. For example, acrylic pressure-sensitive adhesives, rubber-based pressure-sensitive adhesives (natural rubber-based, synthetic rubber-based, mixed systems thereof, etc.), silicone-based pressure-sensitive adhesives, polyester-based pressure-sensitive adhesives, urethane-based pressure-sensitive adhesives, polyether-based pressure-sensitive adhesives, polyamide-based It may be a pressure-sensitive adhesive layer including one or more pressure-sensitive adhesives selected from various known pressure-sensitive adhesives such as pressure-sensitive adhesives and fluorine-based pressure-sensitive adhesives. Here, the acrylic pressure-sensitive adhesive refers to a pressure-sensitive adhesive in which a (meth) acrylic polymer is used as a base polymer (a main component in the polymer component, that is, a component contained in excess of 50% by mass). The same applies to rubber pressure sensitive adhesives and other pressure sensitive adhesives. As a preferable pressure-sensitive adhesive layer from the viewpoint of transparency, weather resistance, etc., a pressure-sensitive adhesive layer in which the content ratio of the acrylic pressure-sensitive adhesive is 50% by weight or more, more preferably 70% by weight or more, still more preferably 90% by weight Be The content ratio of the acrylic pressure-sensitive adhesive may be more than 98% by weight, and the pressure-sensitive adhesive layer may be substantially composed of the acrylic pressure-sensitive adhesive.

(Acrylic polymer)
Although not particularly limited, in a preferred embodiment of the technology disclosed herein, the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer and the pressure-sensitive adhesive composition for forming the pressure-sensitive adhesive comprise an acrylic polymer as a base polymer including. The above-mentioned acrylic polymer is preferably a polymer of a monomer raw material which contains an alkyl (meth) acrylate as a main monomer and can further contain a secondary monomer copolymerizable with the main monomer. Here, the main monomer means a component contained in an amount of more than 50% by weight in the above-mentioned monomer raw material.

As the alkyl (meth) acrylate, for example, a compound represented by the following formula (1) can be suitably used.
CH ₂ = C (R ¹ ) COOR ² (1)
Here, R ¹ in the above formula (1) is a hydrogen atom or a methyl group. Further, R ² is a chain alkyl group having 1 to 20 carbon atoms (hereinafter, such a range of number of carbon atoms may be represented as "C _1-20".). An alkyl (meth) acrylate in which R ² is a C _1-14 linear alkyl group is preferable from the viewpoint of storage elastic modulus of the pressure-sensitive adhesive and the like, and R ² is a C _1-10 linear alkyl group Acrylate is more preferred, and alkyl (meth) acrylates wherein R ² is a butyl or 2-ethylhexyl group are particularly preferred.

Examples of alkyl (meth) acrylates in which R ² is a C _1-20 linear alkyl group include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate and n-butyl (Meth) acrylate, isobutyl (meth) acrylate, s-butyl (meth) acrylate, pentyl (meth) acrylate, isopentyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, 2-ethylhexyl (meth) acrylate , Octyl (meth) acrylate, isooctyl (meth) acrylate, nonyl (meth) acrylate, isononyl (meth) acrylate, decyl (meth) acrylate, isodecyl (meth) acrylate, undecyl (meth) Acrylate, dodecyl (meth) acrylate, tridecyl (meth) acrylate, tetradecyl (meth) acrylate, pentadecyl (meth) acrylate, hexadecyl (meth) acrylate, heptadecyl (meth) acrylate, octadecyl (meth) acrylate, nonadecyl (meth) acrylate, Eicosyl (meth) acrylate and the like can be mentioned. These alkyl (meth) acrylates can be used singly or in combination of two or more. Particularly preferred alkyl (meth) acrylates include n-butyl acrylate (BA) and 2-ethylhexyl acrylate (2EHA).

  In the technology disclosed herein, the monomer component constituting the above acrylic polymer contains at least one of BA and 2EHA, and the total amount of BA and 2EHA of the alkyl (meth) acrylate contained in the monomer component is 75% by weight It can be preferably carried out in a mode that occupies% or more (usually 85% by weight or more, for example 90% by weight or more, further 95% by weight or more). The technology disclosed herein can be practiced, for example, in an embodiment in which the alkyl (meth) acrylate contained in the above monomer component is BA alone, an embodiment in which 2EHA is alone, an embodiment in which BA and 2EHA are included, and the like.

  When the monomer component contains BA and 2EHA, the weight ratio of BA to 2EHA (BA / 2EHA) is not particularly limited, and may be, for example, 1/99 or more and 99/1 or less. In a preferred embodiment, the BA / 2EHA can be 60/40 or more (eg, 60/40 or more and 99/1 or less), may be 80/20 or more, and 90/10 or more (eg, 90/10 or more). Or more and not more than 99/1).

The art disclosed herein can be a monomer component constituting the acrylic polymer is preferably carried out in a manner that includes C _1-6 alkyl (meth) acrylate of 50 wt% or more. In other words, the polymerization ratio of C _1-6 alkyl (meth) acrylate in the acrylic polymer is preferably 50 wt% or more. Thus C _1-6 alkyl (meth) acrylate to use as the main monomer can be preferably designed an acrylic polymer that can realize the deformation resistance against sustained load in the Z-axis direction. The ratio of C _1-6 alkyl (meth) acrylate in the monomer component (in other words, the polymerization ratio) is more preferably more than 50% by weight, still more preferably 60% by weight or more, particularly preferably 70% by weight or more (eg 80% by weight or more, and further 85% by weight or more). The upper limit of the proportion of C _1-6 alkyl (meth) acrylate in the monomer component is not particularly limited, and usually not more than 99% by weight, and not more than 97% by weight from the relationship with the use proportion of other copolymerizable monomers It is preferable that the amount be 95% by weight or less. C _1-6 alkyl (meth) acrylates may be used alone or in combination of two or more. As the C _1-6 alkyl (meth) acrylates, preferably C _1-6 alkyl acrylates, more preferably C _2-6 alkyl acrylates, more preferably C _4-6 alkyl acrylates. In another aspect, C _1-6 alkyl (meth) acrylate is preferably a C _1-4 alkyl acrylates, more preferably a C _2-4 alkyl acrylates. BA may be mentioned as preferred examples of the C _1-6 alkyl (meth) acrylate.

  In the embodiment using BA as the main monomer, the copolymerization ratio of BA in the acrylic polymer is preferably 50% by weight or more, more preferably more than 50% by weight, still more preferably 60% by weight or more, particularly preferably It is 70% by weight or more (eg, 80% by weight or more, further 85% by weight or more), and particularly preferably 90% by weight or more (eg, more than 90% by weight). By copolymerizing BA as a main monomer, the pressure sensitive adhesive can be well adhered to the adherend. Further, the copolymerization ratio of BA in the acrylic polymer is not particularly limited, and usually 97 weight% or less, 97 weight from the relationship with the copolymerization ratio of other copolymerizable monomers (for example, acid group-containing monomers) % Or less is appropriate, and 95% by weight or less is preferable.

  In a preferred embodiment of the art disclosed herein, an acid group-containing monomer is used as a monomer copolymerizable with the main monomer, alkyl (meth) acrylate. The acidic group-containing monomer can exhibit the cohesiveness improvement based on its polarity and the good bonding power to the polar adherend. Moreover, when using crosslinking agents, such as an isocyanate type and an epoxy-type crosslinking agent, the said acidic group (typically a carboxyl group) becomes a crosslinking point of acrylic polymer. By these actions, it is possible to preferably realize deformation resistance to a sustained load in the Z-axis direction. By using the acidic group-containing monomer at a predetermined ratio or more, it is possible to preferably design an acrylic polymer that can realize the light pressure-bonding initial adhesion and the deformation resistance to a sustained load in the Z-axis direction.

  As an acidic group containing monomer, a carboxy group containing monomer is used preferably. Examples of carboxy group-containing monomers include ethylenically unsaturated monocarboxylic acids such as acrylic acid (AA), methacrylic acid (MAA), carboxyethyl (meth) acrylate, crotonic acid, isocrotonic acid, etc .; maleic acid, itaconic acid, citraconic acid And ethylenically unsaturated dicarboxylic acids and anhydrides thereof (maleic anhydride, itaconic anhydride, etc.). In addition, the acidic group-containing monomer may be a monomer having a metal salt of a carboxy group (for example, an alkali metal salt). Among them, AA and MAA are preferable, and AA is more preferable. When one or more types of acidic group-containing monomers are used, the ratio of AA to the above-mentioned acidic group-containing monomers is preferably 50% by weight or more, more preferably 70% by weight or more, and still more preferably 90% by weight or more It is. In one particularly preferred aspect, the acidic group-containing monomer consists essentially of AA. Since AA has a complex action such as polarity based on its carboxy group, a role as a crosslinking point, Tg (106 ° C.) and the like, in the acid group-containing monomer disclosed herein, light-press initial adhesion and Z-axis direction It is considered to be an optimal monomer material in order to achieve a balance between deformation resistance against sustained load.

In the technology disclosed herein, the content of the acidic group-containing monomer (typically, a carboxy group-containing monomer) in the monomer component (in other words, the copolymerization ratio of the acidic group-containing monomer in the acrylic polymer) is usually It is suitably 3% by weight or more and 5% by weight or more. By using an acidic group-containing monomer of a predetermined amount or more, an acrylic polymer which can simultaneously achieve the initial adhesion of light pressure bonding and the deformation resistance to the sustained load in the Z-axis direction is preferably based on the aggregation improvement effect etc. It can be realized. The copolymerization ratio of the acidic group-containing monomer in the acrylic polymer may be, for example, 8% by weight or more, 10% by weight or more, 10% by weight or more, and 11% by weight or more. It may be 12% by weight or more. When the pressure bonding temperature is raised to a temperature higher than normal temperature or the like to obtain the light pressure bonding initial adhesion, it is possible to further increase the copolymerization ratio of the acid group-containing monomer in the acrylic polymer. In that case, the copolymerization ratio can be 13% by weight or more, for example, 15% by weight or more. The copolymerization ratio of the acidic group-containing monomer in the acrylic polymer is usually 20% by weight or less, and preferably 18% by weight or less from the viewpoint of maintaining the characteristics of the main monomer. The copolymerization ratio may be 15% by weight or less, for example, 13% by weight or less. In a more preferred embodiment, the copolymerization ratio of the acid group-containing monomer in the acrylic polymer is about 12% by weight or less, more preferably about 10% by weight or less, and particularly preferably about 8% by weight or less. In an acrylic polymer having a monomer composition containing a large amount of C _1-6 alkyl (meth) acrylate (typically, BA), the content of the acidic group-containing monomer (for example, AA) in the monomer component is preferably in the above range It is effective.

In the monomer components constituting the acrylic polymer disclosed herein, the ratio of content C _A of the acidic group-containing monomer to the content C _M of the main monomers mentioned above (typically alkyl (meth) acrylate) (C _A / C _M (%); calculated from C _A / C _M × 100) is usually 3% or more, suitably 5% or more, and 7% or more on a weight basis For example, 8% or more may be sufficient. By using a predetermined amount or more of the acidic group-containing monomer with respect to the main monomer (typically, alkyl (meth) acrylate), based on the adhesion performance by the main monomer and the aggregation improvement effect by the acidic group-containing monomer, etc. An acrylic polymer is preferably realized which can preferably achieve both light-press initial adhesion and deformation resistance to a sustained load in the Z-axis direction. The ratio (C _A / C _M ) may be, for example, 10% or more, 11% or more, or 12% or more. When the pressure bonding temperature is raised to a temperature higher than normal temperature or the like to obtain the light pressure bonding initial adhesion, it is possible to further increase the copolymerization ratio of the acid group-containing monomer in the acrylic polymer. In that case, the ratio (C _A / C _M ) can be 15% or more, for example, 18% or more. The ratio (C _A / C _M ) is usually suitably 25% or less, and preferably 20% or less from the viewpoint of maintaining the properties of the main monomer. The ratio (C _A / C _M ) may be 15% or less, for example 13% or less. In a more preferred embodiment, the ratio (C _A / C _M ) is about 11% or less, and more preferably about 9% or less. In an acrylic polymer having a monomer composition containing a large amount of C _1-6 alkyl (meth) acrylate (typically, BA), the content of the acidic group-containing monomer (for example, AA) in the monomer component is preferably in the above range It is effective.

In the technology disclosed herein, copolymerizable monomers other than carboxy group-containing monomers can be used as the secondary monomer copolymerizable with the main monomer, alkyl (meth) acrylate. As such sub-monomers, for example, the following functional group-containing monomers can be used.
Hydroxyl-containing monomers: for example, hydroxyalkyl (meth) acrylates such as 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, etc. Unsaturated alcohols such as vinyl alcohol and allyl alcohol; polypropylene glycol mono (meth) acrylate.
Amide group-containing monomers: such as (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N-butyl (meth) acrylamide, N-methylol (meth) acrylamide, N-methylolpropane (meth) acrylamide, N-methoxymethyl (Meth) acrylamide, N-butoxymethyl (meth) acrylamide.
Amino group-containing monomer: for example, aminoethyl (meth) acrylate, N, N-dimethylaminoethyl (meth) acrylate, t-butylaminoethyl (meth) acrylate.
Monomers having an epoxy group: for example, glycidyl (meth) acrylate, methyl glycidyl (meth) acrylate, allyl glycidyl ether.
Cyano group-containing monomers: eg acrylonitrile, methacrylonitrile.
Keto group-containing monomers: for example diacetone (meth) acrylamide, diacetone (meth) acrylate, vinyl methyl ketone, vinyl ethyl ketone, allyl acetoacetate, vinyl acetoacetate.
Monomers having a nitrogen atom-containing ring: such as N-vinyl-2-pyrrolidone, N-methylvinylpyrrolidone, N-vinylpyridine, N-vinylpiperidone, N-vinylpyrimidine, N-vinylpiperazine, N-vinylpyrazine, N-vinyl Pyrrole, N-vinylimidazole, N-vinyloxazole, N-vinylmorpholine, N-vinylcaprolactam, N- (meth) acryloylmorpholine.
Alkoxysilyl group-containing monomers: for example, 3- (meth) acryloxypropyltrimethoxysilane, 3- (meth) acryloxypropyltriethoxysilane, 3- (meth) acryloxypropylmethyldimethoxysilane, 3- (meth) acryloxy Propylmethyldiethoxysilane.

  The functional group-containing monomers can be used singly or in combination of two or more. When the monomer component constituting the acrylic polymer contains a functional group-containing monomer, the ratio of the functional group-containing monomer in the monomer component is the resistance to deformation with respect to the initial adhesion after light pressure bonding and the sustained load in the Z axis direction It is determined appropriately according to the performance. The ratio (copolymerization ratio) of the functional group-containing monomer (for example, hydroxyl group-containing monomer) is about 0.01% by weight or more (for example, 0.02% by weight or more, usually 0.03% by weight or more) in the monomer component. It is preferable that the amount be about 0.1 wt% or more (e.g., 0.5 wt% or more, usually 1 wt% or more). The upper limit thereof is preferably about 40% by weight or less (eg, 30% by weight or less, usually 20% by weight or less). In a more preferable aspect, the proportion of the functional group-containing monomer other than the above-mentioned acidic group-containing monomer is, for example, suitably 10% by weight or less, further 5% by weight or less, and may be 1% by weight or less . In a further preferred embodiment, the ratio of the functional group-containing monomer (for example, hydroxyl group-containing monomer) other than the above-mentioned acidic group-containing monomer is about 0.5% by weight or less (for example, about 0.2% by weight or less). The monomer component which comprises an acryl-type polymer may be a thing which does not contain substantially functional group containing monomers other than the said acidic group containing monomer.

As a monomer component which comprises an acryl-type polymer, other copolymerization components other than the acidic group containing monomer mentioned above other submonomers can be used for the purpose of improving the cohesion force of this acryl-type polymer. Examples of such copolymerization components include vinyl ester monomers such as vinyl acetate, vinyl propionate and vinyl laurate; aromatic vinyl compounds such as styrene, substituted styrene (α-methylstyrene and the like) and vinyl toluene; ) Cycloalkyl (meth) acrylates such as acrylate, cyclopentyl (meth) acrylate, isobornyl (meth) acrylate; aryl (meth) acrylates (eg phenyl (meth) acrylate), aryloxyalkyl (meth) acrylates (eg phenoxyethyl (meth) acrylate) Aromatic ring-containing (meth) acrylates such as acrylates), arylalkyl (meth) acrylates (eg benzyl (meth) acrylate), etc .; ethylene, propylene, isoprene, butadiene, isobutyrene Olefin-based monomers such as vinyl chloride, vinyl chloride-containing monomers such as vinyl chloride; isocyanate group-containing monomers such as 2- (meth) acryloyloxyethyl isocyanate; alkoxy groups such as methoxyethyl (meth) acrylate and ethoxyethyl (meth) acrylate Containing monomers; vinyl ether-based monomers such as methyl vinyl ether and ethyl vinyl ether; and the like.
The amount of the other copolymerization component is not particularly limited as long as it is appropriately selected depending on the purpose and application, but usually, it is preferably 10% by weight or less of the monomer component. For example, when a vinyl ester monomer (for example, vinyl acetate) is used as the other copolymerization component, the content thereof is, for example, about 0.1% by weight or more (usually about 0.5% by weight or more) of the monomer component. It is also preferable that the amount be about 20% by weight or less (usually about 10% by weight or less).

  The acrylic polymer is a polyfunctional having at least two polymerizable functional groups (typically radically polymerizable functional groups) having unsaturated double bonds such as (meth) acryloyl group and vinyl group as other monomer components. It may contain a monomer. The cohesive force of the pressure-sensitive adhesive layer can be enhanced by using a polyfunctional monomer as the monomer component. Multifunctional monomers can be used as crosslinking agents.

  Examples of polyfunctional monomers include ethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, penta Erythritol di (meth) acrylate, pentaerythritol tri (meth) acrylate, dipentaerythritol hexa (meth) acrylate, 1,2-ethylene glycol di (meth) acrylate, 1,4-butanediol di (meth) acrylate 1,1, 6-hexanediol di (meth) acrylate, 1,12-dodecanediol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, tetramethylolmethane tri (meth) acrylate ) Of acrylate, esters of polyhydric alcohols and (meth) acrylic acid; allyl (meth) acrylate, vinyl (meth) acrylate, divinylbenzene, epoxy acrylate, polyester acrylate, urethane acrylate. Preferred examples among these include trimethylolpropane tri (meth) acrylate, 1,6-hexanediol di (meth) acrylate and dipentaerythritol hexa (meth) acrylate. Among them, preferred is 1,6-hexanediol di (meth) acrylate. A polyfunctional monomer can be used individually by 1 type or in combination of 2 or more types. From the viewpoint of reactivity and the like, usually, polyfunctional monomers having two or more acryloyl groups are preferred.

  The use amount of the polyfunctional monomer is not particularly limited, and can be appropriately set so as to achieve the purpose of using the polyfunctional monomer. From the viewpoint of achieving a well-balanced balance between the preferred storage modulus disclosed herein and other adhesion performance or other properties, the amount of the polyfunctional monomer used can be about 3% by weight or less of the above monomer component, About 2 wt% or less is preferable, and about 1 wt% or less (for example, about 0.5 wt% or less) is more preferable. The lower limit of the amount used in the case of using a polyfunctional monomer may be greater than 0% by weight, and is not particularly limited. In general, by setting the amount of the polyfunctional monomer to be about 0.001% by weight or more (for example, about 0.01% by weight or more) of the monomer component, the effect of using the polyfunctional monomer can be appropriately exhibited.

The composition of the monomer component constituting the acrylic polymer is designed such that the glass transition temperature (Tg) of the acrylic polymer is about −15 ° C. or less (eg, about −70 ° C. or more and −15 ° C. or less) Is appropriate. Here, Tg of an acryl-type polymer means Tg calculated | required by the formula of Fox based on the composition of the said monomer component. The Fox equation, as shown below, is a relationship between the Tg of the copolymer and the glass transition temperature Tgi of a homopolymer obtained by homopolymerizing each of the monomers constituting the copolymer.
1 / Tg = Σ (Wi / Tgi)
In the above Fox equation, Tg is the glass transition temperature (unit: K) of the copolymer, Wi is the weight fraction of the monomer i in the copolymer (copolymerization ratio on a weight basis), and Tgi is the monomer i It represents the glass transition temperature (unit: K) of a homopolymer.

As a glass transition temperature of the homopolymer used for calculation of Tg, the value as described in a well-known data shall be used. For example, for the monomers listed below, the following values are used as the glass transition temperature of the homopolymers of the monomers.
2-ethylhexyl acrylate -70 ° C
n-Butyl acrylate-55 ° C
Ethyl acrylate -22 ° C
Methyl acrylate 8 ° C
Methyl methacrylate 105 ° C
2-hydroxyethyl acrylate -15 ° C
4-hydroxybutyl acrylate -40 ° C
Vinyl acetate 32 ° C
Styrene 100 ° C
Acrylic acid 106 ° C
Methacrylic acid 228 ° C

  As for the glass transition temperature of homopolymers of monomers other than those exemplified above, the numerical values described in “Polymer Handbook” (Third Edition, John Wiley & Sons, Inc., 1989) are used. The highest value is adopted for the monomer of which plural values are described in this document.

The value obtained by the following measurement method shall be used about the monomer in which the glass transition temperature of a homopolymer is not described also in the said literature.
Specifically, 100 parts by weight of a monomer, 0.2 parts by weight of 2,2'-azobisisobutyronitrile and acetic acid as a polymerization solvent in a reactor equipped with a thermometer, a stirrer, a nitrogen introducing pipe and a reflux condenser 200 parts by weight of ethyl is charged and stirred for 1 hour while flowing nitrogen gas. After oxygen in the polymerization system is removed in this manner, the temperature is raised to 63 ° C. and reaction is carried out for 10 hours. Then, it is cooled to room temperature to obtain a homopolymer solution having a solid concentration of 33% by weight. The homopolymer solution is then cast coated on a release liner and dried to make a test sample (sheet-like homopolymer) about 2 mm thick. This test sample is punched out into a disk shape of 7.9 mm in diameter, sandwiched by parallel plates, and shear strain at a frequency of 1 Hz using a visco-elasticity tester (manufactured by TA Instruments Japan, model name "ARES") The visco-elasticity is measured by a shear mode at a temperature rising rate of -70 ° C. to 150 ° C. and a temperature rising rate of 5 ° C./min, and the temperature corresponding to the peak top temperature of tan δ is taken as the Tg of homopolymer.

  Although not particularly limited, the Tg of the acrylic polymer is advantageously about -25 ° C or less, preferably about -35 ° C or less, more preferably about -40 ° C or less from the viewpoint of adhesion. More preferably, it is −45 ° C. or less, for example, −50 ° C. or less, or −55 ° C. or less. In addition, from the viewpoint of the cohesion of the pressure-sensitive adhesive layer, the Tg of the acrylic polymer is usually about −75 ° C. or more, preferably about −70 ° C. or more. The technology disclosed herein can be preferably practiced in an embodiment in which the Tg of the acrylic polymer is about -65 ° C. or more and about -40 ° C. or less (eg, about -65 ° C. or more and about -45 ° C. or less). In a preferred embodiment, the Tg of the acrylic polymer can be about -55 ° C or more and about -45 ° C or less. In another aspect, the Tg of the acrylic polymer can be about -65 ° C or more and about -55 ° C or less. The Tg of the acrylic polymer can be adjusted by appropriately changing the monomer composition (that is, the type and ratio of the monomers used for the synthesis of the polymer).

The Mw of the acrylic polymer is not particularly limited, and may be, for example, about 10 × 10 ⁴ or more and 500 × 10 ⁴ or less. From the viewpoint of cohesiveness, the Mw is usually about 30 × 10 ⁴ or more, and suitably about 45 × 10 ⁴ or more (eg, about 65 × 10 ⁴ or more). In a preferred embodiment, the Mw of the acrylic polymer is 70 × 10 ⁴ or more. Also, in one exemplary aspect of the technology disclosed herein, the Mw of the acrylic polymer is suitably greater than 70 × 10 ⁴ . By using an acrylic polymer having a Mw of more than 70 × 10 ⁴ , excellent deformation resistance to a sustained deformation load can be obtained based on its cohesiveness. The Mw of the acrylic polymer is more preferably about 75 × 10 ⁴ or more, still more preferably about 90 × 10 ⁴ or more, and particularly preferably about 95 × 10 ⁴ or more. In a further particularly preferred embodiment, the Mw is about 100 × 10 ⁴ or more (eg, about 110 × 10 ⁴ or more), and typically 120 × 10 ⁴ or more (eg, 130 × 10 ⁴ or more). The Mw is usually 300 × 10 ⁴ or less (more preferably about 200 × 10 ⁴ or less, for example, about 150 × 10 ⁴ or less). The Mw of the acrylic polymer may be about 140 × 10 ⁴ or less. For example, in the case of an acrylic polymer obtained by a solution polymerization method or an emulsion polymerization method, it is preferable to set Mw in the above range.

  The degree of dispersion (Mw / Mn) of the acrylic polymer disclosed herein is not particularly limited. The degree of dispersion (Mw / Mn) as referred to herein means the degree of dispersion (Mw / Mn) represented by the ratio of weight average molecular weight (Mw) to number average molecular weight (Mn). In a preferred embodiment, the degree of dispersion (Mw / Mn) of the acrylic polymer is less than 15. For example, in the case of an acrylic polymer having a relatively high molecular weight (typically, having a Mw of over 700,000) obtained by a solution polymerization method or an emulsion polymerization method, it is preferable to set Mw / Mn within the above range. The fact that the Mw / Mn of the acrylic polymer is less than 15 means that the polymer has a relatively large amount of a relatively uniform polymer when the polymer has a relatively high molecular weight, and the aggregation based on the polymer is It develops accurately and exhibits excellent resistance to permanent deformation load (deformation resistance). The Mw / Mn is preferably less than 12, more preferably less than 10, and still more preferably less than 8 (eg, 7.5 or less). The Mw / Mn is theoretically 1 or more, and may be, for example, 2 or more, 3 or more, or 4 or more (typically 5 or more).

  In another embodiment, the degree of dispersion (Mw / Mn) of the acrylic polymer is 8 or more and 40 or less. If the Mw / Mn of the acrylic polymer is 8 or more and 40 or less, it may mean that the molecular weight distribution is broad, and a large amount of a low molecular weight polymer and a large molecular weight polymer are contained. The low molecular weight monomer contributes to the development of the initial adhesion after light pressure bonding because of its good wettability to the adherend, and the high molecular weight material exhibits resistance to permanent deformation load (deformation resistance) because of its cohesiveness. . When the Mw / Mn is 8 or more, the initial adhesion is preferably expressed. In addition, when the Mw / Mn is 40 or less, the molecular weight distribution is preferably limited within an appropriate range, and stable characteristics (light-press initial adhesion and deformation resistance) can be obtained. The Mw / Mn may be 10 or more, 12 or more, or 15 or more. The Mw / Mn may be 18 or more (e.g., 20 or more). The Mw / Mn is preferably 35 or less, more preferably 30 or less, and still more preferably 25 or less.

  Mw, Mn and Mw / Mn can be adjusted by polymerization conditions (time, temperature, etc.), use of a chain transfer agent, selection of a polymerization solvent based on a chain transfer constant, etc. Moreover, Mw and Mn are calculated | required from the value of standard polystyrene conversion obtained by GPC (gel permeation chromatography). As a GPC apparatus, model name "HLC-8320GPC" (column: TSKgelGMH-H (S), Tosoh Corp. make) can be used, for example.

<Adhesive composition>
The pressure-sensitive adhesive layer disclosed herein is an adhesive comprising the monomer component of the composition as described above in the form of a polymer, an unpolymerized substance (that is, a form in which a polymerizable functional group is unreacted), or a mixture thereof. It can be formed using an agent composition. The pressure-sensitive adhesive composition is a composition (solvent-type pressure-sensitive adhesive composition) in a form including an adhesive (adhesive component) in an organic solvent, a composition in a form in which the pressure-sensitive adhesive is dispersed in an aqueous solvent (water-dispersed pressure-sensitive adhesive Composition), a composition (active energy ray-curable pressure-sensitive adhesive composition) prepared to form a pressure-sensitive adhesive by curing with active energy rays such as ultraviolet light and radiation, which is applied in a heated and melted state, around room temperature It may be in various forms such as a hot melt adhesive composition which forms an adhesive upon cooling. The technology disclosed herein can be particularly preferably practiced from the viewpoint of adhesive properties and the like, in a mode including a pressure-sensitive adhesive layer formed from a solvent-based pressure-sensitive adhesive composition or an active energy ray-curable pressure-sensitive adhesive composition.

  Here, in the present specification, “active energy ray” refers to an energy ray having energy capable of causing a chemical reaction such as polymerization reaction, crosslinking reaction, decomposition of an initiator, and the like. Examples of the active energy ray include light such as ultraviolet light, visible light and infrared light, radiation such as α-ray, β-ray, γ-ray, electron beam, neutron beam and X-ray.

  The pressure-sensitive adhesive composition is typically a polymer of at least a part of the monomer components of the composition (which may be part of the type of monomer or part of the amount). In the form of The polymerization method for forming the above-mentioned polymer is not particularly limited, and various conventionally known polymerization methods can be appropriately employed. For example, thermal polymerization such as solution polymerization, emulsion polymerization and bulk polymerization (typically performed in the presence of a thermal polymerization initiator); photopolymerization performed by irradiation with light such as ultraviolet light (typically, And the like. Radiation polymerization performed by irradiation with radiation such as β rays and γ rays; and the like can be appropriately adopted. Among these, solution polymerization and photopolymerization are preferable. In these polymerization methods, the mode of polymerization is not particularly limited, and conventionally known monomer supply methods, polymerization conditions (temperature, time, pressure, light irradiation amount, radiation irradiation amount, etc.), use materials other than monomers (polymerization initiator) And surfactants etc. can be selected appropriately.

  For example, in a preferred embodiment, solution polymerization may be employed for the synthesis of acrylic polymers. According to the above-mentioned solution polymerization, a polymerization reaction solution in a form in which an acrylic polymer is dissolved in an organic solvent is obtained. The pressure-sensitive adhesive layer in the art disclosed herein may be formed from a pressure-sensitive adhesive composition including the polymerization reaction solution or an acrylic polymer solution obtained by subjecting the reaction solution to an appropriate post-treatment. As said acrylic polymer solution, what adjusted the said polymerization reaction liquid to the suitable viscosity (density | concentration) as needed can be used. Alternatively, an acrylic polymer solution may be prepared by synthesizing an acrylic polymer by a polymerization method other than solution polymerization (for example, emulsion polymerization, photopolymerization, bulk polymerization, etc.) and dissolving the acrylic polymer in an organic solvent. Good.

  As a monomer supply method at the time of performing solution polymerization, a batch preparation method of supplying all the monomer raw materials at one time, a continuous supply (dropping) method, a divided supply (dropping) method or the like can be appropriately adopted. The polymerization temperature can be appropriately selected according to the type of monomer and solvent used, the type of polymerization initiator, etc., and can be, for example, about 20 ° C. to 170 ° C. (usually about 40 ° C. to 140 ° C.) . In a preferred embodiment, the polymerization temperature can be about 75 ° C. or less (more preferably about 65 ° C. or less, for example, about 45 ° C. to about 65 ° C.).

  The solvent (polymerization solvent) used for solution polymerization can be appropriately selected from conventionally known organic solvents. For example, aromatic compounds such as toluene and xylene (eg, aromatic hydrocarbons); acetates such as ethyl acetate and butyl acetate; aliphatic or alicyclic hydrocarbons such as hexane, cyclohexane and methylcyclohexane; 1 , Halogenated alkanes such as 2-dichloroethane; lower alcohols such as isopropyl alcohol (for example, monohydric alcohols having 1 to 4 carbon atoms); ethers such as tert-butyl methyl ether; ketones such as methyl ethyl ketone and acetone And the like, or any one kind of solvent selected from etc., or a mixed solvent of two or more kinds can be used.

  On the other hand, as another embodiment of the technology disclosed herein, when an active energy ray-curable pressure-sensitive adhesive composition (typically, a photocurable pressure-sensitive adhesive composition) is adopted, the above-mentioned active energy ray-curable pressure-sensitive adhesive From the viewpoint of environmental health etc., the composition preferably contains substantially no organic solvent. For example, a pressure-sensitive adhesive composition having an organic solvent content of about 5% by weight or less (more preferably, about 3% by weight or less, for example, about 0.5% by weight or less) is preferred. Moreover, since it is suitable for formation of the adhesive layer in the form which hardens the liquid film of an adhesive composition between the peeling surfaces of a pair of peeling films so that it may mention later, a solvent (in the meaning including an organic solvent and an aqueous solvent) There is preferred a pressure-sensitive adhesive composition substantially free of For example, an adhesive composition having a solvent content of about 5% by weight or less (more preferably about 3% by weight or less, such as about 0.5% by weight or less) is preferred. In addition, a solvent means the volatile component which should be removed in the formation process of an adhesive layer, ie, the volatile component which is not intended to become a component of the adhesive layer finally formed.

  In the polymerization, a known or commonly used thermal polymerization initiator or photopolymerization initiator may be used depending on the polymerization method, polymerization mode and the like. Such polymerization initiators can be used alone or in appropriate combination of two or more.

  The thermal polymerization initiator is not particularly limited. For example, an azo polymerization initiator, a peroxide initiator, a redox initiator by combination of a peroxide and a reducing agent, a substituted ethane initiator Etc. can be used. More specifically, for example, 2,2'-azobisisobutyronitrile (AIBN), 2,2'-azobis (2-methylpropionamidine) disulfate, 2,2'-azobis (2-amidinopropane) ) Dihydrochloride, 2,2′-azobis [2- (5-methyl-2-imidazolin-2-yl) propane] dihydrochloride, 2,2′-azobis (N, N′-dimethylene isobutylamidine), 2 Azo initiators such as 2′-azobis [N- (2-carboxyethyl) -2-methylpropionamidine] hydrate; persulfates such as potassium persulfate, ammonium persulfate; benzoyl peroxide (BPO), peroxide initiators such as t-butyl hydroperoxide, hydrogen peroxide; substituted ethane initiators such as phenyl-substituted ethane; The combination of a persulfate and sodium hydrogen sulfite eg to redox initiators such as a combination of a peroxide and sodium ascorbate; but the like, without limitation. Thermal polymerization can be preferably carried out, for example, at a temperature of about 20 to 100 ° C. (typically, 40 to 80 ° C.).

  The photopolymerization initiator is not particularly limited. For example, ketal photopolymerization initiator, acetophenone photopolymerization initiator, benzoin ether photopolymerization initiator, acyl phosphine oxide photopolymerization initiator, α- Ketol photopolymerization initiator, aromatic sulfonyl chloride photopolymerization initiator, photoactive oxime photopolymerization initiator, benzoin photopolymerization initiator, benzyl photopolymerization initiator, benzophenone photopolymerization initiator, thioxanthone photo light A polymerization initiator or the like can be used.

Specific examples of the ketal photopolymerization initiator include 2,2-dimethoxy-1,2-diphenylethane-1-one (for example, trade name “IRGACURE 651” manufactured by BASF Corp.) and the like. Specific examples of the acetophenone photopolymerization initiator include 1-hydroxycyclohexyl-phenyl-ketone (for example, trade name “IRGACURE 184” manufactured by BASF Corp.), 4-phenoxydichloroacetophenone, 4-t-butyl-dichloroacetophenone, 1- [4- (2-hydroxyethoxy) -phenyl] -2-hydroxy-2-methyl-1-propan-1-one (eg, trade name “IRGACURE 2959” manufactured by BASF Corp.), 2-hydroxy-2 -Methyl-1-phenyl-propan-1-one (eg, trade name “Darocure 1173” manufactured by BASF Corp.), methoxyacetophenone and the like are included.
Specific examples of the benzoin ether photopolymerization initiator include benzoin ethers such as benzoin methyl ether, benzoin ethyl ether, benzoin propyl ether, benzoin isopropyl ether and benzoin isobutyl ether, and substituted benzoin ethers such as anisole methyl ether.
Specific examples of the acyl phosphine oxide photopolymerization initiator include bis (2,4,6-trimethyl benzoyl) phenyl phosphine oxide (for example, trade name “IRGACURE 819” manufactured by BASF Corp.), bis (2,4,6) -Trimethylbenzoyl) -2,4-di-n-butoxyphenyl phosphine oxide, 2,4,6-trimethyl benzoyl diphenyl phosphine oxide (for example, trade name "Lucillin TPO" manufactured by BASF Corp.), bis (2,6-) Dimethoxybenzoyl) -2,4,4-trimethylpentyl phosphine oxide and the like are included.
Specific examples of the α-ketol photopolymerization initiator include 2-methyl-2-hydroxypropiophenone, 1- [4- (2-hydroxyethyl) phenyl] -2-methylpropan-1-one and the like Be 2-naphthalene sulfonyl chloride etc. are contained in the example of an aromatic sulfonyl chloride type photoinitiator. Specific examples of the photoactive oxime based photopolymerization initiator include 1-phenyl-1,1-propanedione-2- (o-ethoxycarbonyl) -oxime and the like. Specific examples of the benzoin photopolymerization initiator include benzoin and the like. Specific examples of the benzyl-based photopolymerization initiator include benzyl and the like.
Specific examples of benzophenone-based photopolymerization initiators include benzophenone, benzoylbenzoic acid, 3,3'-dimethyl-4-methoxybenzophenone, polyvinyl benzophenone, α-hydroxycyclohexyl phenyl ketone and the like.
Specific examples of thioxanthone photopolymerization initiators include thioxanthone, 2-chlorothioxanthone, 2-methyl thioxanthone, 2,4-dimethyl thioxanthone, isopropyl thioxanthone, 2,4-dichloro thioxanthone, 2,4-diethyl thioxanthone, isopropyl thioxanthone 2,4-diisopropylthioxanthone, dodecyl thioxanthone and the like.

  The amount of the thermal polymerization initiator or the photopolymerization initiator used can be a usual amount according to the polymerization method, polymerization mode, etc., and is not particularly limited. For example, about 0.001 to 5 parts by weight (typically about 0.01 to 2 parts by weight, for example about 0.01 to 1 parts by weight) of a polymerization initiator based on 100 parts by weight of the monomer to be polymerized Can.

(Pressure-sensitive adhesive composition containing monomer component in the form of fully polymerized product)
The pressure-sensitive adhesive composition according to a preferred embodiment contains the monomer component of the agent composition in the form of a completely polymerized product. Such a pressure-sensitive adhesive composition is, for example, a solvent-based pressure-sensitive adhesive composition containing, in an organic solvent, an acrylic polymer which is a complete polymer of monomer components, a water-dispersible pressure-sensitive adhesive in which the above acrylic polymer is dispersed in an aqueous solvent It may be in the form of a composition, etc. In the present specification, the term "completely polymer" means that the polymerization conversion rate is more than 95% by weight.

(Pressure-sensitive adhesive composition containing a polymer of a monomer component and an unpolymerized product)
The pressure-sensitive adhesive composition according to another preferred embodiment contains a polymerization reaction product of a monomer mixture containing at least a part of the monomer component (raw material monomer) of the composition. Typically, part of the above-mentioned monomer component is contained in the form of a polymer, and the balance is contained in the form of an unpolymerized substance (unreacted monomer). The polymerization reaction of the above monomer mixture can be prepared by at least partially polymerizing the monomer mixture.
The above-mentioned polymerization reaction product is preferably a partial polymerization product of the above-mentioned monomer mixture. Such a partially polymerized product is a mixture of a polymerized product derived from the above monomer mixture and an unreacted monomer, and typically exhibits a syrupy form (viscous liquid). Hereinafter, such partially polymerized product of this nature may be referred to as "monomer syrup" or simply "syrup".

  The polymerization method in particular in obtaining the said polymerization reaction material is not restrict | limited, The various polymerization methods as mentioned above can be selected suitably, and can be used. From the viewpoint of efficiency and simplicity, the photopolymerization method can be preferably employed. According to the photopolymerization, the polymerization conversion ratio of the above-mentioned monomer mixture can be easily controlled by the polymerization conditions such as the irradiation amount (light amount) of light.

  The polymerization conversion (monomer conversion) of the monomer mixture in the partially polymerized product is not particularly limited. The polymerization conversion rate can be, for example, about 70% by weight or less, and preferably about 60% by weight or less. From the viewpoint of the preparation easiness of preparation, coatability and the like of the pressure-sensitive adhesive composition containing the above-mentioned partial polymer, the polymerization conversion ratio is usually about 50% by weight or less and about 40% by weight or less (eg about 35%) % Or less) is preferred. Although the lower limit of the polymerization conversion rate is not particularly limited, it is typically about 1% by weight or more, and usually about 5% by weight or more.

  The pressure-sensitive adhesive composition containing a partial polymer of the above monomer mixture can be easily obtained, for example, by partially polymerizing a monomer mixture containing all of the raw material monomers by a suitable polymerization method (for example, a photopolymerization method). The pressure-sensitive adhesive composition containing the partially polymerized product is blended with other components (eg, a photopolymerization initiator, a polyfunctional monomer, a crosslinking agent, a (meth) acrylic oligomer described later, etc.) used as needed obtain. The method of blending such other components is not particularly limited. For example, it may be previously contained in the above-mentioned monomer mixture, or may be added to the above-mentioned partially polymerized product.

  Also, in the pressure-sensitive adhesive composition disclosed herein, a completely polymerized product of a monomer mixture containing some of the monomer types of the monomer components (raw material monomers) was dissolved in the remaining types of monomers or partially polymerized products thereof It may be in the form. Such a form of the pressure-sensitive adhesive composition is also included in the example of the pressure-sensitive adhesive composition containing the polymer of the monomer component and the unpolymerized product.

  As a curing method (polymerization method) when forming a pressure-sensitive adhesive from a pressure-sensitive adhesive composition containing a polymer of a monomer component and an unpolymerized product as described above, a photopolymerization method can be preferably employed. In the pressure-sensitive adhesive composition containing the polymerization reaction product prepared by the photopolymerization method, it is particularly preferable to adopt the photopolymerization method as the curing method. Since the polymerization reaction product obtained by the photopolymerization method already contains a photopolymerization initiator, when the pressure-sensitive adhesive composition containing this polymerization reaction product is further cured to form a pressure-sensitive adhesive, a new photopolymerization initiator is used. It can be light cured without addition. Alternatively, the pressure-sensitive adhesive composition may have a composition in which a photopolymerization initiator is added to the polymerization reaction product prepared by the photopolymerization method, if necessary. The additional photoinitiator may be the same as or different from the photoinitiator used to prepare the polymerization reactant. The pressure-sensitive adhesive composition prepared by a method other than photopolymerization can be made photocurable by adding a photopolymerization initiator. The photocurable pressure-sensitive adhesive composition has an advantage that even a thick pressure-sensitive adhesive layer can be easily formed. In a preferred embodiment, photopolymerization in forming a pressure-sensitive adhesive from a pressure-sensitive adhesive composition can be performed by ultraviolet irradiation. For the ultraviolet irradiation, known high pressure mercury lamps, low pressure mercury lamps, metal halide lamps and the like can be used.

(Crosslinking agent)
The pressure-sensitive adhesive composition (preferably, a solvent-type pressure-sensitive adhesive composition) used to form the pressure-sensitive adhesive layer preferably contains a crosslinking agent as an optional component. By including a crosslinking agent, the visco-elastic properties disclosed herein can be preferably realized. The pressure-sensitive adhesive layer in the art disclosed herein contains the above-mentioned crosslinking agent in the form after the crosslinking reaction, the form before the crosslinking reaction, the form after the partial crosslinking reaction, and the intermediate or composite forms thereof. obtain. The above-mentioned crosslinking agent is usually contained in the pressure-sensitive adhesive layer solely in the form after the crosslinking reaction.

  The kind in particular of a crosslinking agent is not restrict | limited, It can select suitably from conventionally well-known crosslinking agents, and can use. As such a crosslinking agent, for example, an isocyanate crosslinking agent, an epoxy crosslinking agent, an oxazoline crosslinking agent, an aziridine crosslinking agent, a melamine crosslinking agent, a carbodiimide crosslinking agent, a hydrazine crosslinking agent, an amine crosslinking agent, A peroxide type crosslinking agent, a metal chelate type crosslinking agent, a metal alkoxide type crosslinking agent, a metal salt type crosslinking agent, etc. are mentioned. A crosslinking agent can be used individually by 1 type or in combination of 2 or more types. As a crosslinking agent which can be preferably used in the art indicated here, an isocyanate type crosslinking agent, an epoxy type crosslinking agent, and an oxazoline type crosslinking agent are illustrated.

  As the epoxy crosslinking agent, a compound having two or more epoxy groups in one molecule can be used without particular limitation. The epoxy-type crosslinking agent which has 3-5 epoxy groups in 1 molecule is preferable. The epoxy crosslinking agent can be used singly or in combination of two or more.

  Although it does not specifically limit, as a specific example of an epoxy-type crosslinking agent, N, N, N ', N'-tetraglycidyl m-xylene diamine, 1,3-bis (N, N- diglycidyl aminomethyl), for example And the like) cyclohexane, 1,6-hexanediol diglycidyl ether, polyethylene glycol diglycidyl ether, polyglycerol polyglycidyl ether and the like. Commercially available epoxy crosslinking agents include trade name "TETRAD-C" manufactured by Mitsubishi Gas Chemical Co., Ltd. and trade name "TETRAD-X", trade name "Epiclon CR-5L" manufactured by DIC, manufactured by Nagase ChemteX Trade name "Denacole EX-512", trade name "TEPIC-G" manufactured by Nissan Chemical Industries, Ltd., and the like.

  In the aspect using an epoxy-type crosslinking agent, the amount used is not specifically limited. The amount of the epoxy-based crosslinking agent used may be, for example, more than 0 parts by weight and about 1 part by weight or less (preferably about 0.001 to 0.5 parts by weight) with respect to 100 parts by weight of the acrylic polymer it can. From the viewpoint of suitably exhibiting the effect of improving the cohesion, the use amount of the epoxy-based crosslinking agent is usually about 0.002 parts by weight or more with respect to 100 parts by weight of the acrylic polymer, and preferably It may be about 0.005 parts by weight or more, for example, about 0.01 parts by weight or more, about 0.02 parts by weight or more, or about 0.03 parts by weight or more. Also, from the viewpoint of avoiding insufficient adhesion at the time of light-pressing initial bonding due to excessive crosslinking, the amount of the epoxy-based crosslinking agent used is usually about 0.2 parts by weight or less with respect to 100 parts by weight of the acrylic polymer Preferably, it is about 0.1 parts by weight or less (eg, 0.05 parts by weight or less).

  As an isocyanate type crosslinking agent, polyfunctional isocyanate (A compound which has an average of 2 or more isocyanate groups per molecule and says, and includes the thing which has an isocyanurate structure.) Can be used preferably. An isocyanate type crosslinking agent can be used individually by 1 type or in combination of 2 or more types.

  As a preferable polyfunctional isocyanate, the polyfunctional isocyanate which has an average of three or more isocyanate groups per molecule is illustrated. The trifunctional or higher isocyanate is a multimer (eg, dimer or trimer) of a difunctional or trifunctional isocyanate or an addition reaction of a derivative (eg, polyhydric alcohol and 2 or more polyfunctional isocyanates) Products), polymers and the like. For example, dimer or trimer of diphenylmethane diisocyanate, isocyanurate of hexamethylene diisocyanate (trimer adduct of isocyanurate structure), reaction product of trimethylolpropane and tolylene diisocyanate, trimethylolpropane and hexamer Examples thereof include reaction products with methylene diisocyanate, and polyfunctional isocyanates such as polymethylene polyphenyl isocyanate, polyether polyisocyanate, and polyester polyisocyanate. As commercial products of such polyfunctional isocyanates, trade name "Duranate TPA-100" manufactured by Asahi Kasei Chemicals, trade name "Colonate L" manufactured by Tosoh Corp., "Colonate HL", "Colonate HK", and "Colonate" HX "," Coronate 2096 "and the like.

  In the aspect using an isocyanate type crosslinking agent, the amount used is not specifically limited. The amount of the isocyanate-based crosslinking agent used can be, for example, about 0.5 parts by weight or more and about 10 parts by weight or less with respect to 100 parts by weight of the acrylic polymer. From the viewpoint of cohesion, the use amount of the isocyanate-based crosslinking agent with respect to 100 parts by weight of the acrylic polymer is usually about 0.1 parts by weight or more, and preferably about 0.3 parts by weight or more (eg, 0. It is preferable to set it as 5 parts by weight or more. In a more preferable aspect, the amount of the isocyanate-based crosslinking agent used per 100 parts by weight of the acrylic polymer is about 1 part by weight or more, and may be about 1.5 parts by weight or more. The amount of the isocyanate-based crosslinking agent used is preferably about 8 parts by weight or less, and preferably about 5 parts by weight or less (eg, less than about 4 parts by weight) with respect to 100 parts by weight of the acrylic polymer. preferable. In a more preferable aspect, the amount of the isocyanate-based crosslinking agent used is about 3 parts by weight or less, for example, 2 parts by weight or less based on 100 parts by weight of the acrylic polymer.

  As the oxazoline crosslinking agent, one having one or more oxazoline groups in one molecule can be used without particular limitation. The oxazoline based crosslinking agents can be used alone or in combination of two or more. The oxazoline group may be any of 2-oxazoline group, 3-oxazoline group and 4-oxazoline group. In general, an oxazoline based crosslinking agent having a 2-oxazoline group can be preferably used. For example, a copolymer obtained by copolymerizing an addition-polymerizable oxazoline with another monomer can be used as an oxazoline-based crosslinking agent. Non-limiting examples of such addition polymerizable oxazolines include 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, 2-iso. Examples include propenyl-2-oxazoline, 2-isopropenyl-4-methyl-2-oxazoline, and 2-isopropenyl-5-ethyl-2-oxazoline.

  The crosslinking agent illustrated by Unexamined-Japanese-Patent No. 2009-001673 is contained in the example of an oxazoline type crosslinking agent. Specific examples include a compound having a main chain composed of an acryl skeleton or a styrene skeleton and having an oxazoline group in a side chain of the main chain. As a preferable example, an oxazoline group-containing acrylic polymer having a main chain composed of an acrylic skeleton and having an oxazoline group in a side chain of the main chain is mentioned. As a commercial item of the oxazoline type crosslinking agent, for example, trade name "Epocross WS-500", "Epocross WS-700", "Epocross K-2010E", "Epocross K-2020E", "Epocross K-" manufactured by Nippon Shokubai Co., Ltd. 2030E "and the like.

  In the aspect using an oxazoline type crosslinking agent, the amount used is not particularly limited. The amount of the oxazoline crosslinking agent used can be, for example, 0.05 parts by weight or more, 0.1 parts by weight or more, or 0.5 parts by weight or more with respect to 100 parts by weight of the acrylic polymer. In some embodiments, the use amount of the oxazoline-based crosslinking agent with respect to 100 parts by weight of the acrylic polymer may be 1 part by weight or more, and may be 1.5 parts by weight or more. By increasing the amount of the oxazoline-based crosslinking agent, a higher cohesive force tends to be obtained. The use amount of the oxazoline-based crosslinking agent can be, for example, 10 parts by weight or less, 8 parts by weight or less, 5 parts by weight or less, or 3 parts by weight or less with respect to 100 parts by weight of the acrylic polymer.

  The art disclosed herein can be preferably practiced in the aspect of using at least an epoxy-based crosslinking agent as the crosslinking agent. The epoxy group of the epoxy crosslinking agent can react with an acidic group that can be introduced into the acrylic polymer to build a crosslinked structure. The cohesion of the pressure-sensitive adhesive is enhanced by the crosslinking reaction, and deformation resistance to a sustained load in the Z-axis direction is more preferably exhibited. Examples of such embodiments include an embodiment in which an epoxy-based crosslinking agent is used alone and an embodiment in which an epoxy-based crosslinking agent and another crosslinking agent are used in combination. In one aspect, the pressure-sensitive adhesive composition contains an epoxy-based crosslinking agent as a crosslinking agent but does not substantially contain an isocyanate-based crosslinking agent.

  In another aspect, the pressure-sensitive adhesive composition contains an isocyanate-based crosslinking agent as the crosslinking agent. The isocyanate group of the isocyanate-based crosslinking agent may react with an acidic group that can be introduced into the acrylic polymer in a reaction form different from that of the epoxy-based crosslinking agent to construct a crosslinked structure. In the pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer on at least one surface of the substrate film, it is significant to use an isocyanate-based crosslinking agent from the viewpoint of improving the anchoring property to the substrate film.

In a particularly preferred embodiment, the pressure-sensitive adhesive composition contains both an epoxy-based crosslinking agent and an isocyanate-based crosslinking agent as a crosslinking agent. For example, by using an epoxy-based crosslinking agent and an isocyanate-based crosslinking agent in combination with an acrylic polymer having an acidic group, the deformation resistance to a sustained load in the Z-axis direction can be further added without impairing the initial adhesion of light pressure bonding. It can be improved. Specifically, the resistance to deformation in the Z-axis direction can be maintained for a long period of time, even under conditions of strong repulsion, high temperature, and high humidity as discussed in the examples to be described later. The ratio (C _I / C _E ) of the content C _I of the isocyanate-based crosslinking agent to the content C _E of the epoxy-based crosslinking agent is not particularly limited, and deformation resistance to a sustained load in the Z-axis direction can be obtained Set appropriately. The above ratio (C _I / C _E ) is, for example, suitably more than 1 and about 5 or more, preferably about 15 or more, more preferably about 30 or more, still more preferably about 60 or more, particularly preferably Is about 80 or more (eg, about 100 or more). Further, the ratio (C _I / C _E ) is, for example, about 1000 or less, and suitably about 500 or less, preferably about 200 or less, more preferably about 150 or less, still more preferably about 120 or less (For example, about 80 or less).

  The content of the crosslinking agent (total amount of the crosslinking agent) in the pressure-sensitive adhesive composition disclosed herein is not particularly limited. From the viewpoint of cohesiveness, the content of the crosslinking agent is usually about 0.001 parts by weight or more, and preferably about 0.002 parts by weight or more, with respect to 100 parts by weight of the acrylic polymer. The amount is preferably about 0.005 parts by weight or more, more preferably about 0.01 parts by weight or more, still more preferably about 0.02 parts by weight or more, and particularly preferably about 0.03 parts by weight or more. In addition, from the viewpoint of avoiding a light pressure-bonding initial adhesive deficiency, the content of the crosslinking agent in the pressure-sensitive adhesive composition is usually about 20 parts by weight or less and about 15 parts by weight or less with respect to 100 parts by weight of the acrylic polymer. It is preferable that the amount be about 10 parts by weight or less (eg, about 5 parts by weight or less).

(Tackifying resin)
In a preferred embodiment, the pressure-sensitive adhesive composition (and thus the pressure-sensitive adhesive layer) contains a tackifying resin. Examples of tackifying resins that can be contained in the above-mentioned pressure-sensitive adhesive composition include phenol-based tackifying resins, terpene-based tackifying resins, modified terpene-based tackifying resins, rosin-based tackifying resins, hydrocarbon-based tackifying resins, epoxy-based tackiness One or more selected from a variety of known tackifying resins such as a tackifying resin, a polyamide-based tackifying resin, an elastomer-based tackifying resin, and a ketone-based tackifying resin can be used. The use of a tackifying resin improves the adhesion, including the light compression initial adhesion.

Examples of phenolic tackifying resins include terpene phenolic resins, hydrogenated terpene phenolic resins, alkyl phenolic resins and rosin phenolic resins.
Terpene phenol resin refers to a polymer containing terpene residue and phenol residue, and a copolymer of terpenes and a phenol compound (terpene-phenol copolymer resin) and terpenes or homopolymers or copolymer thereof. It is a concept that includes both of the combination and the phenol-modified one (phenol-modified terpene resin). Preferred examples of terpenes constituting such terpene phenol resin include monoterpenes such as α-pinene, β-pinene, limonene (including d-form, l-form and d / l-form (dipentene)). Can be mentioned. The hydrogenated terpene phenol resin refers to a hydrogenated terpene phenol resin having a structure obtained by hydrogenating such a terpene phenol resin. It is also called hydrogenated terpene phenolic resin.
The alkylphenol resin is a resin (oil-based phenol resin) obtained from alkylphenol and formaldehyde. Examples of alkylphenol resins include those of novolak type and resol type.
The rosin phenolic resin is typically a rosin or phenol modified product of the above-mentioned various rosin derivatives (including rosin esters, unsaturated fatty acid modified rosins and unsaturated fatty acid modified rosin esters). Examples of rosin phenol resins include rosin phenol resins obtained by a method of thermally polymerizing a rosin or the above-mentioned various rosin derivatives with an acid catalyst and thermally polymerizing the same.
Among these phenolic tackifying resins, terpene phenol resin, hydrogenated terpene phenol resin and alkylphenol resin are preferable, terpene phenol resin and hydrogenated terpene phenol resin are more preferable, and terpene phenol resin is more preferable.

Examples of terpene-based tackifying resins include polymers of terpenes (eg, monoterpenes) such as α-pinene, β-pinene, d-limonene, l-limonene, dipentene and the like. It may be a homopolymer of one terpene, or may be a copolymer of two or more terpenes. Examples of homopolymers of one kind of terpenes include α-pinene polymers, β-pinene polymers, and dipentene polymers.
Examples of the modified terpene resin include those obtained by modifying the terpene resin. Specific examples thereof include styrene-modified terpene resins, hydrogenated terpene resins and the like.

  The concept of rosin-based tackifying resin herein includes both rosins and rosin derivative resins. Examples of rosins include unmodified rosins such as gum rosin, wood rosin, tall oil rosin (raw rosin); modified rosins obtained by modifying these unmodified rosins by hydrogenation, disproportionation, polymerization, etc. Such as leveled rosin, polymerized rosin, other chemically modified rosin, etc.).

  Rosin derivative resins are typically derivatives of rosins as described above. The term "rosin-based resin" as used herein includes derivatives of unmodified rosin and derivatives of modified rosin (including hydrogenated rosin, disproportionated rosin and polymerized rosin). For example, rosin esters such as unmodified rosin ester which is an ester of unmodified rosin and an alcohol, modified rosin ester such as modified rosin ester which is an ester of a modified rosin and an alcohol; Saturated fatty acid modified rosins; for example, unsaturated fatty acid modified rosin esters in which rosin esters are modified with unsaturated fatty acids; eg, rosins or various rosin derivatives described above (rosin esters, unsaturated fatty acid modified rosins and unsaturated Rosin alcohols in which the carboxy group of fatty acid-modified rosin esters is reduced and treated; for example, rosins or metal salts of the above-mentioned various rosin derivatives; Specific examples of rosin esters include methyl esters of unmodified rosins or modified rosins (hydrogenated rosins, disproportionated rosins, polymerized rosins, etc.), triethylene glycol esters, glycerin esters, pentaerythritol esters, and the like.

  Examples of hydrocarbon tackifying resins include aliphatic hydrocarbon resins, aromatic hydrocarbon resins, aliphatic cyclic hydrocarbon resins, aliphatic and aromatic petroleum resins (styrene-olefin copolymers, etc.) And various hydrocarbon resins such as aliphatic and alicyclic petroleum resins, hydrogenated hydrocarbon resins, coumarone resins, and coumarone indene resins.

  The softening point of the tackifying resin is not particularly limited. From the viewpoint of improving the cohesive strength, a tackifier resin having a softening point (softening temperature) of about 80 ° C. or more (preferably, about 100 ° C. or more) can be preferably employed. For example, a phenol-based tackifying resin (such as a terpene phenol resin) having such a softening point can be preferably used. In a preferred embodiment, terpene phenol resins having a softening point of about 135 ° C. or more (or about 140 ° C. or more) can be used. The upper limit of the softening point of the tackifying resin is not particularly limited. From the viewpoint of adhesion to an adherend or a substrate film, a tackifier resin having a softening point of about 200 ° C. or less (more preferably about 180 ° C. or less) can be preferably used. In addition, the softening point of tackifying resin can be measured based on the softening point test method (ring and ball method) prescribed | regulated to JISK2207.

  As a preferred embodiment, an embodiment in which the above-mentioned tackifying resin contains one or more kinds of phenol-based tackifying resin (for example, terpene phenol resin) can be mentioned. The technology disclosed herein can be preferably practiced, for example, in an embodiment in which about 25% by weight or more (more preferably about 30% by weight or more) of the total tackifying resin is terpene phenol resin. About 50% by weight or more of the total tackifying resin may be terpene phenol resin, and about 80% by weight or more (eg, about 90% by weight or more) may be terpene phenol resin. Substantially all of the tackifying resin (for example, about 95 wt% to 100 wt%, and further about 99 wt% to 100 wt%) may be a terpene phenol resin.

  The content of the phenolic tackifying resin (for example, terpene phenolic resin) is not particularly limited as long as the desired viscoelastic properties are satisfied. The content of the phenol-based tackifying resin (for example, terpene phenol resin) is usually about 1 part by weight or more with respect to 100 parts by weight of the acrylic polymer from the viewpoint of adhesion (for example, initial adhesion after light pressure bonding) The amount is suitably 5 parts by weight or more, preferably about 8 parts by weight or more (typically 10 parts by weight or more), and more preferably about 12 parts by weight or more (for example 15 parts by weight or more). Further, from the viewpoint of deformation resistance, etc., the content of the above-mentioned phenolic tackifying resin is suitably about 45 parts by weight or less, preferably about 35 parts by weight, with respect to 100 parts by weight of the acrylic polymer. The amount is preferably 30 parts by weight or less, more preferably less than 30 parts by weight (eg, 25 parts by weight or less, typically 20 parts by weight or less).

Although not particularly limited, in one aspect of the technology disclosed herein, the tackifying resin may include a tackifying resin having a hydroxyl value of greater than 20 mg KOH / g. Among them, tackifying resins having a hydroxyl value of 30 mg KOH / g or more are preferable. Hereinafter, tackifying resins having a hydroxyl value of 30 mg KOH / g or more are sometimes referred to as "high hydroxyl value resins". According to the tackifying resin containing such a high hydroxyl value resin, in addition to the adhesive force, a pressure sensitive adhesive layer having a high cohesive force can be realized by interacting with a crosslinking agent such as an isocyanate crosslinking agent. In one aspect, the tackifying resin may contain a high hydroxyl value resin having a hydroxyl value of 50 mg KOH / g or more (more preferably 70 mg KOH / g or more). The high hydroxyl value resin described above (e.g., terpene phenolic resin), for example, a C _1-6 alkyl (meth) acrylate is preferably used in combination with acrylic polymer as a main monomer, with respect to an adherend Can exhibit good adhesion.

  The upper limit of the hydroxyl value of the high hydroxyl value resin is not particularly limited. From the viewpoint of compatibility with the acrylic polymer, the hydroxyl value of the high hydroxyl value resin is usually about 300 mg KOH / g or less, suitably about 200 mg KOH / g or less, preferably about 180 mg KOH / g or less, Preferably, it is about 160 mg KOH / g or less, more preferably about 140 mg KOH / g or less. The technique disclosed herein can be preferably practiced in a mode in which the tackifying resin contains a high hydroxyl value resin (for example, a phenol-based tackifying resin, preferably a terpene phenol resin) having a hydroxyl value of 30 to 160 mg KOH / g. In one aspect, a high hydroxyl value resin having a hydroxyl value of 30 to 80 mg KOH / g (eg, 30 to 65 mg KOH / g) can be preferably employed. In another embodiment, a high hydroxyl value resin having a hydroxyl value of 70 to 140 mg KOH / g can be preferably employed.

Here, as a value of the above-mentioned hydroxyl value, a value measured by potentiometric titration defined in JIS K 0070: 1992 can be adopted. The specific measurement method is as follows.
[Method of measuring hydroxyl value]
1. Reagent (1) As an acetylation reagent, about 12.5 g (about 11.8 mL) of acetic anhydride is taken, pyridine is added to this, the total volume is made 50 mL, and what is fully stirred is used. Alternatively, about 25 g (about 23.5 mL) of acetic anhydride is taken, and to this is added pyridine to make the total volume 100 mL, and used after sufficiently stirring.
(2) As a measuring reagent, 0.5 mol / L potassium hydroxide ethanol solution is used.
(3) In addition, prepare toluene, pyridine, ethanol and distilled water.
2. Operation (1) Approximately 2 g of a sample is precisely weighed in a flat-bottomed flask, 5 mL of an acetylation reagent and 10 mL of pyridine are added, and an air cooling tube is attached.
(2) The above flask is heated in a bath at 100 ° C. for 70 minutes, allowed to cool, 35 mL of toluene is added from the top of the cooling tube as a solvent and stirred, and 1 mL of distilled water is added and stirred. Disassemble. Heat again in the bath for 10 minutes to allow complete decomposition and allow to cool.
(3) Wash the cooling tube with 5 mL of ethanol and remove it. Next, 50 mL of pyridine as a solvent is added and stirred.
(4) Add 25 mL of 0.5 mol / L potassium hydroxide ethanol solution using a whole pipette.
(5) Perform potentiometric titration with a 0.5 mol / L potassium hydroxide ethanol solution. The inflection point of the obtained titration curve is taken as the end point.
(6) In the blank test, the above (1) to (5) are performed without inserting a sample.
3. Calculation The hydroxyl value is calculated by the following equation.
Hydroxyl value (mg KOH / g) = [(B-C) x f x 28.05] / S + D
here,
B: Amount (mL) of 0.5 mol / L potassium hydroxide ethanol solution used in blank test,
C: Amount (mL) of 0.5 mol / L potassium hydroxide ethanol solution used for the sample,
f: Factor of 0.5 mol / L potassium hydroxide ethanol solution,
S: Weight of sample (g),
D: acid number,
28.05: 1/2 of the molecular weight 56.11 of potassium hydroxide,
It is.

  As the high hydroxyl value resin, among the various tackifying resins described above, those having a hydroxyl value of a predetermined value or more can be used. The high hydroxyl value resins can be used singly or in combination of two or more. For example, as a high hydroxyl value resin, a phenol-based tackifying resin having a hydroxyl value of 30 mg KOH / g or more can be preferably adopted. Terpene phenol resin is advantageous because the hydroxyl value can be optionally controlled by the copolymerization ratio of phenol.

Although not particularly limited, as the tackifying resin in the technology disclosed herein, a tackifying resin having a hydroxyl value of less than 30 mg KOH / g (for example, less than 20 mg KOH / g) can be used. Hereinafter, a tackifier resin having a hydroxyl value of less than 30 mg KOH / g may be referred to as a "low hydroxyl value resin". The hydroxyl value of the low hydroxyl value resin may be about 15 mg KOH / g or less, or about 10 mg KOH / g or less. The lower limit of the hydroxyl value of the low hydroxyl value resin is not particularly limited, and may be substantially 0 mg KOH / g. Such a low hydroxyl value resin (for example, terpene phenol resin) is preferably used, for example, in combination with an acrylic polymer containing C _7-10 alkyl (meth) acrylate as a main monomer, to obtain adhesion to adherends. It can exhibit well.

  Although not particularly limited, when using a high hydroxyl value resin, the ratio of the high hydroxyl value resin (for example, terpene phenol resin) to the entire tackifying resin contained in the adhesive layer is, for example, about 25% by weight or more And preferably about 30% by weight or more, more preferably about 50% by weight or more (eg, about 80% by weight or more, typically about 90% by weight or more). Substantially all (for example, about 95 to 100% by weight, and further about 99 to 100% by weight) of the tackifying resin may be a high hydroxyl value resin.

  In the aspect using tackifying resin, the content of the tackifying resin is not particularly limited. The content of the tackifying resin is usually 1 part by weight or more, and can be about 5 parts by weight or more with respect to 100 parts by weight of the acrylic polymer, and about 8 parts by weight or more (for example, about 10 parts by weight or more) It is appropriate to use The art disclosed herein can be preferably practiced in an embodiment in which the content of the tackifier resin is about 12 parts by weight or more (eg, about 15 parts by weight or more) with respect to 100 parts by weight of the acrylic polymer. The upper limit of the content of the tackifier resin is not particularly limited. From the viewpoint of compatibility with the acrylic polymer and deformation resistance, the content of the tackifying resin relative to 100 parts by weight of the acrylic polymer is suitably about 70 parts by weight or less, preferably about 55 parts by weight or less More preferably, it is about 45 parts by weight or less (eg, about 40 parts by weight or less, typically about 30 parts by weight or less). In a preferred embodiment, the content of the tackifier resin is less than 30 parts by weight, more preferably about 25 parts by weight or less, and still more preferably about 20 parts by weight or less based on 100 parts by weight of the acrylic polymer.

((Meth) acrylic oligomers)
The pressure-sensitive adhesive composition (and the pressure-sensitive adhesive layer) disclosed herein can contain (meth) acrylic oligomers from the viewpoint of improving adhesion and the like. As the (meth) acrylic oligomer, the Tg of a copolymer corresponding to the composition of the above monomer component (typically, the Tg of a (meth) acrylic polymer contained in a pressure-sensitive adhesive formed from a pressure-sensitive adhesive composition It is preferable to use a polymer having a Tg higher than that corresponding to the above. By containing a (meth) acrylic oligomer, the adhesive strength of the pressure-sensitive adhesive can be improved.

  The (meth) acrylic oligomer preferably has a Tg of about 0 ° C. to about 300 ° C., preferably about 20 ° C. to about 300 ° C., and more preferably about 40 ° C. to about 300 ° C. Adhesiveness can be improved suitably because Tg is in the above-mentioned range. In a preferred embodiment, the Tg of the (meth) acrylic oligomer is about 30 ° C. or more, more preferably about 50 ° C. or more (eg, about 60 ° C. or more), from the cohesiveness of the pressure-sensitive adhesive, and light pressure bonding From the viewpoint of initial adhesion, it is preferably about 200 ° C. or less, more preferably about 150 ° C. or less, still more preferably about 100 ° C. or less (eg, about 80 ° C. or less). The Tg of the (meth) acrylic oligomer is a value calculated based on the Fox equation, as is the Tg of the copolymer corresponding to the composition of the monomer component.

  The weight average molecular weight (Mw) of the (meth) acrylic oligomer may be typically about 1000 or more and less than about 30000, preferably about 1500 or more and less than about 20000, more preferably about 2000 or more and less than about 10000. It is preferable for Mw to be in the above-mentioned range because good adhesion and retention characteristics can be obtained. In a preferred embodiment, the Mw of the (meth) acrylic oligomer is about 2500 or more (for example, about 3000 or more) from the viewpoint of deformation resistance to a sustained load in the Z-axis direction, and a light pressure-bonding initial adhesion viewpoint Is preferably about 7,000 or less, more preferably about 5,000 or less (eg, about 4,500 or less, typically about 400 or less). The Mw of the (meth) acrylic oligomer can be measured by gel permeation chromatography (GPC) and determined as a value in terms of standard polystyrene. Specifically, it is measured by using a TSO gel GMH-H (20) × 2 column as a column in HPLC 8020 manufactured by Tosoh Corporation under the condition of a flow rate of about 0.5 ml / min with a tetrahydrofuran solvent.

  Examples of the monomer constituting the (meth) acrylic oligomer include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, butyl (meth) acrylate and isobutyl (meth) acrylate, s-butyl (meth) acrylate, t-butyl (meth) acrylate, pentyl (meth) acrylate, isopentyl (meth) acrylate, hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, heptyl (meth) acrylate, octyl ( (Meth) acrylate, isooctyl (meth) acrylate, nonyl (meth) acrylate, isononyl (meth) acrylate, decyl (meth) acrylate, isodecyl (meth) acrylate, undecyl (un) Ta) Acrylate, alkyl (meth) acrylate such as dodecyl (meth) acrylate; cyclohexyl (meth) acrylate, isobornyl (meth) acrylate, (meth) acrylic acid such as dicyclopentanyl (meth) acrylate and alicyclic Esters with alcohols (alicyclic hydrocarbon group-containing (meth) acrylates); aryl (meth) acrylates such as phenyl (meth) acrylates and benzyl (meth) acrylates; (meth) acrylates obtained from terpene compound derivative alcohols; Etc. can be mentioned. Such (meth) acrylates can be used alone or in combination of two or more.

  Examples of (meth) acrylic oligomers include alkyl (meth) acrylates having a branched structure such as isobutyl (meth) acrylate and t-butyl (meth) acrylate; cyclohexyl (meth) acrylate and isobornyl (meth) acrylate; Esters of (meth) acrylic acid with alicyclic alcohol such as dicyclopentanyl (meth) acrylate (alicyclic hydrocarbon group-containing (meth) acrylate); phenyl (meth) acrylate and benzyl (meth) acrylate Containing as a monomer unit an acrylic monomer having a relatively bulky structure, represented by (meth) acrylates having a cyclic structure such as aryl (meth) acrylates and the like, and further adhesion of the pressure-sensitive adhesive layer Preferred from the viewpoint of being able to improveIn addition, in the case of employing ultraviolet light in the synthesis of (meth) acrylic oligomers or in the preparation of the pressure-sensitive adhesive layer, those having a saturated bond are preferable in that they hardly cause polymerization inhibition, and the alkyl group is branched An alkyl (meth) acrylate having a structure or an ester with an alicyclic alcohol (alicyclic hydrocarbon group-containing (meth) acrylate) can be suitably used as a monomer constituting a (meth) acrylic oligomer. In addition, said branched alkyl (meth) acrylate, alicyclic hydrocarbon group (meth) acrylate, and aryl (meth) acrylate all correspond to the (meth) acrylate monomer in the technique disclosed here. The alicyclic hydrocarbon group may be a saturated or unsaturated alicyclic hydrocarbon group.

  The proportion of (meth) acrylate monomer (for example, alicyclic hydrocarbon group-containing (meth) acrylate) in all monomer components constituting the (meth) acrylic oligomer is typically more than 50% by weight, and preferably Is 60% by weight or more, more preferably 70% by weight or more (eg, 80% by weight or more, and further 90% by weight or more). In a preferred embodiment, the (meth) acrylic oligomer has a monomer composition consisting essentially of (meth) acrylate monomers.

  As a constituent monomer component of the (meth) acrylic oligomer, a functional group-containing monomer can be used in addition to the above (meth) acrylate monomer. Preferred examples of the functional group-containing monomer include monomers having a nitrogen atom-containing ring (typically, a nitrogen atom-containing heterocyclic ring) such as N-vinyl-2-pyrrolidone, N-acryloyl morpholine, etc .; N, N-dimethylamino Amino group-containing monomers such as ethyl (meth) acrylate; amide group-containing monomers such as N, N-diethyl (meth) acrylamide; carboxyl group-containing monomers such as AA, MAA; hydroxyl group-containing such as 2-hydroxyethyl (meth) acrylate And monomers. These functional group containing monomers can be used individually by 1 type or in combination of 2 or more types. Among them, carboxyl group-containing monomers are preferable, and AA is particularly preferable.

  When all monomer components constituting the (meth) acrylic oligomer contain functional group-containing monomers, the ratio of functional group-containing monomers (for example, carboxyl group-containing monomers such as AA) in the total monomer components is about 1% by weight It is appropriate to set the above, preferably 2% by weight or more, more preferably 3% by weight or more, and approximately 15% by weight or less, preferably 10% by weight or less, more preferably It is 7% by weight or less.

  The (meth) acrylic oligomer can be formed by polymerizing its constituent monomer components. The polymerization method and the polymerization mode are not particularly limited, and various conventionally known polymerization methods (for example, solution polymerization, emulsion polymerization, bulk polymerization, photopolymerization, radiation polymerization and the like) can be adopted in appropriate modes. The types of polymerization initiators (eg, azo-based polymerization initiators such as AIBN) that can be used as required are generally as exemplified in the synthesis of acrylic polymers, and the amount of polymerization initiator, and optionally used The amount of the chain transfer agent such as n-dodecyl mercaptan is appropriately set based on technical common knowledge so as to obtain a desired molecular weight, and thus the detailed description is omitted here.

  From the above viewpoints, preferable (meth) acrylic oligomers include, for example, dicyclopentanyl methacrylate (DCPMA), cyclohexyl methacrylate (CHMA), isobornyl methacrylate (IBXMA), isobornyl acrylate (IBXA), Besides homopolymers of cyclopentanyl acrylate (DCPA), 1-adamantyl methacrylate (ADMA) and 1-adamantyl acrylate (ADA), copolymers of CHMA and isobutyl methacrylate (IBMA), co-products of CHMA and IBXMA Polymer, copolymer of CHMA and acryloyl morpholine (ACMO), copolymer of CHMA and diethyl acrylamide (DEAA), copolymer of CHMA and AA, co-polymer of ADA and methyl methacrylate (MMA) Coalesced, copolymers of DCPMA and IBXMA, copolymers of DCPMA and MMA, and the like.

  When the (meth) acrylic oligomer is contained in the pressure-sensitive adhesive composition disclosed herein, its content is, for example, 0.1 parts by weight or more (eg, 1 part by weight or more) with respect to 100 parts by weight of the acrylic polymer. It is appropriate to do. From the viewpoint of exerting the effect of the (meth) acrylic oligomer better, the content of the (meth) acrylic oligomer is preferably about 5 parts by weight or more, more preferably about 8 parts by weight or more, still more preferably about It is 10 parts by weight or more, particularly preferably about 12 parts by weight or more. Also, from the viewpoint of compatibility with the acrylic polymer, the content of the (meth) acrylic oligomer is suitably less than 50 parts by weight (eg less than 40 parts by weight), preferably 30 parts by weight The amount is less, more preferably about 25 parts by weight or less, still more preferably about 20 parts by weight or less.

In a preferred embodiment, the pressure-sensitive adhesive composition (and thus the pressure-sensitive adhesive layer) contains one or more of the tackifying resins described above and one or more of (meth) acrylic oligomers. In a composition containing a high molecular weight acrylic polymer, by using a tackifying resin and a (meth) acrylic oligomer in combination, it is exposed to more severe conditions such as strong repulsion while obtaining excellent initial adhesion with light pressure bonding. Also in the usage mode, highly excellent deformation resistance can be exhibited against the sustained load in the Z-axis direction. The ratio of content of _{C O} content _{C T} and (meth) acrylic oligomer of tackifying resin is not particularly limited, for example, _C T: _{C O} 1: 9 to 9: 1 and it is appropriate to , Preferably 2: 8 to 8: 2, more preferably 3: 7 to 7: 3, and still more preferably 4: 6 to 6: 4.

  The total amount (total amount) of the tackifying resin and the (meth) acrylic oligomer contained in the pressure-sensitive adhesive composition according to a preferred embodiment (and thus the pressure-sensitive adhesive layer) preferably exerts the effect of the technology disclosed herein. The amount is preferably about 1 part by weight or more, preferably about 10 parts by weight or more, more preferably about 16 parts by weight or more, still more preferably 20 parts by weight or more, particularly preferably 25 parts by weight or more The amount is suitably less than 120 parts by weight (eg, about 80 parts by weight or less), preferably less than 60 parts by weight, more preferably about 50 parts by weight or less, still more preferably about 40 parts by weight or less.

(Other additives)
In the pressure-sensitive adhesive composition, in addition to the above-described components, if necessary, a leveling agent, a crosslinking aid, a plasticizer, a softener, an antistatic agent, an antiaging agent, an ultraviolet absorber, an antioxidant, a light stabilizer And the like, various additives common in the field of pressure-sensitive adhesives may be included. With respect to such various additives, conventionally known ones can be used by a conventional method, and since they do not particularly characterize the present invention, detailed description will be omitted.

  The pressure-sensitive adhesive layer disclosed herein can be formed by a conventionally known method. For example, a method (direct method) of forming a pressure-sensitive adhesive layer by directly applying (typically applying) the pressure-sensitive adhesive composition to a non-peelable substrate and drying or curing the composition can be employed. In addition, by applying a pressure-sensitive adhesive composition to a surface (peeling surface) having releasability and drying or curing it to form a pressure-sensitive adhesive layer on the surface, adhesion of a substrate-less material comprising only the pressure-sensitive adhesive layer Sheets can be made. Furthermore, a method (transfer method) of transferring the pressure-sensitive adhesive layer formed on the release surface to a non-peelable substrate may be employed. As said peeling surface, the surface of a peeling liner, the base-material back surface etc. which were peel-treated can be utilized. Although the pressure-sensitive adhesive layer disclosed herein is typically formed continuously, it is not limited to such a form, and it may be, for example, a regular or random pattern such as a dot shape or a stripe shape. It may be a pressure-sensitive adhesive layer formed.

  As a method of applying the pressure-sensitive adhesive composition, various conventionally known methods can be used. Specifically, for example, roll coat, kiss roll coat, gravure coat, reverse coat, roll brush, spray coat, dip roll coat, bar coat, knife coat, air knife coat, curtain coat, lip coat, die coater etc. Methods such as extrusion coating may be mentioned.

  In one aspect of the technology disclosed herein, the drying of the pressure-sensitive adhesive composition is preferably performed under heating, from the viewpoint of promoting the crosslinking reaction, improving the production efficiency, and the like. The drying temperature can be, for example, about 40 to 150 ° C., and usually, preferably about 60 to 130 ° C. After drying the pressure-sensitive adhesive composition, aging is further performed for the purpose of adjustment of component migration in the pressure-sensitive adhesive layer, progress of the crosslinking reaction, relaxation of distortion which may exist in the base film and the pressure-sensitive adhesive layer, etc. It is also good.

  In another aspect, in the pressure-sensitive adhesive sheet disclosed herein, the surface obtained by drying or curing the liquid film of the pressure-sensitive adhesive composition on the release surface of the release film and curing on the release surface is the first adhesive surface. It can be suitably produced by a method including forming a pressure-sensitive adhesive layer. According to this method, the pressure-sensitive adhesive composition (liquid film) in a fluid state is dried or cured in contact with the above-mentioned release surface, whereby the smoothness of the pressure-sensitive adhesive layer surface formed in contact with the release surface is obtained. It can be controlled precisely. For example, by using a release film provided with a release surface having appropriate smoothness, it is possible to stably (reproducibly) manufacture a first adhesive surface having desired smoothness.

  The pressure-sensitive adhesive sheet disclosed herein can be preferably produced by a method including forming a pressure-sensitive adhesive layer by drying or curing a liquid film of the pressure-sensitive adhesive composition between the release surfaces of a pair of release films. This method is suitable as a method for producing a substrateless double-sided pressure-sensitive adhesive sheet. In addition, by bonding the substrate-less double-sided pressure-sensitive adhesive sheet thus obtained to the non-peeling surface of the supporting substrate, it can be preferably applied to the production of a single-sided pressure-sensitive adhesive sheet with a substrate or a double-sided pressure-sensitive adhesive sheet with a substrate . As a method of arranging a liquid film of the pressure-sensitive adhesive composition between the peeling surfaces of the pair of peeling films, a liquid pressure-sensitive adhesive composition is applied to the peeling surface of the first peeling film, and then a liquid of the pressure-sensitive adhesive composition A method of covering the membrane with a second release film can be employed. As another method, the first release film and the second release film are supplied with a release surface facing each other between a pair of rolls, and a liquid pressure-sensitive adhesive composition is supplied between the release surfaces. Can be mentioned.

  The thickness of the pressure-sensitive adhesive layer is not particularly limited. The thickness of the pressure-sensitive adhesive layer is usually about 300 μm or less, preferably about 200 μm or less, more preferably about 150 μm or less, and still more preferably about 100 μm or less. In the pressure-sensitive adhesive sheet according to a preferred embodiment, the thickness of the pressure-sensitive adhesive layer is about 70 μm or less (usually 60 μm or less), and may be about 50 μm or less, for example, about 40 μm or less. The lower limit of the thickness of the pressure-sensitive adhesive layer is not particularly limited, but from the viewpoint of adhesiveness and adhereability to an adherend, it is advantageously about 3 μm or more, preferably about 6 μm or more, more preferably about 10 μm or more (For example, about 15 μm or more), more preferably about 25 μm or more, for example, about 35 μm or more, or about 45 μm or more. The technology disclosed herein can be suitably implemented, for example, in the form of a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer having a thickness of about 10 μm or more and about 150 μm or less (preferably about 15 μm or more and about 50 μm or less). As a suitable example, a substrateless double-sided adhesive pressure-sensitive adhesive sheet consisting only of a pressure-sensitive adhesive layer of the above thickness can be mentioned.

(Gel fraction)
Although not particularly limited, the gel fraction of the pressure-sensitive adhesive layer disclosed herein can be, for example, 20% or more on a weight basis, and usually 30% or more, which is suitable. % Or more is preferable. By increasing the gel fraction of the pressure-sensitive adhesive layer within a suitable range, deformation resistance to a sustained load in the Z-axis direction tends to be easily obtained. In the technology disclosed herein, it is more preferable to use an adhesive layer having a gel fraction of 40% or more. The gel fraction is more preferably 45% or more, particularly preferably 50% or more. The gel fraction may be, for example, 55% or more. On the other hand, if the gel fraction is too high, the light pressure bonding initial adhesion may tend to be insufficient. From this viewpoint, the gel fraction of the pressure-sensitive adhesive layer is preferably 90% or less, more preferably 80% or less, and still more preferably 70% or less (eg, 65% or less).

Here, the "gel fraction of the pressure-sensitive adhesive layer" refers to a value measured by the following method. The gel fraction can be grasped as a weight ratio of ethyl acetate insoluble in the pressure-sensitive adhesive layer.
[Method of measuring gel fraction]
About 0.1 g of a pressure-sensitive adhesive sample (weight Wg ₁ ) is wrapped with a porous polytetrafluoroethylene membrane (weight Wg ₂ ) having an average pore diameter of 0.2 μm in a drawstring shape, and the mouth is tied with a tacho yarn (weight Wg ₃ ). As the porous polytetrafluoroethylene (PTFE) membrane, a trade name "Nithoflon (registered trademark) NTF 1122" (average pore diameter 0.2 μm, porosity 75%, thickness 85 μm) available from Nitto Denko Corporation or equivalent thereof Use the goods.
This package is immersed in 50 mL of ethyl acetate and kept at room temperature (typically 23 ° C.) for 7 days to elute only the sol component in the pressure-sensitive adhesive layer out of the film, and then the package is removed and placed on the outer surface The adhering ethyl acetate is wiped off, the packet is dried at 130 ° C. for 2 hours, and the weight (Wg ₄ ) of the packet is measured. The gel fraction F _G of the pressure-sensitive adhesive layer can be obtained by substituting each value into the following equation. The same method is adopted in the following embodiments.
Gel fraction F _G (%) = [(Wg _4- Wg _2- Wg ₃ ) / Wg ₁ ] × 100

<Base material>
In the embodiment in which the pressure-sensitive adhesive sheet disclosed herein is in the form of a single-sided pressure-sensitive adhesive sheet or a double-sided pressure-sensitive adhesive sheet with a substrate, resin films, foam films Body substrate), paper, cloth, metal foil, composites of these, etc. can be used.

  The art disclosed herein can be practiced in the form of a pressure-sensitive adhesive sheet with a substrate in a form having the above-mentioned pressure-sensitive adhesive layer on at least one surface of a substrate film (support). For example, it can be implemented in the form of a double-sided pressure-sensitive adhesive sheet with a substrate having the above-mentioned pressure-sensitive adhesive layer on one surface and the other surface of a substrate film.

  As a base film, what contains a resin film as a base film can be used preferably. The base film is typically an independently shape-retainable (independent) member. The substrate film in the art disclosed herein may be substantially composed of such a base film. Alternatively, the base film may include an auxiliary layer in addition to the base film. Examples of the auxiliary layer include an undercoat layer provided on the surface of the base film, an antistatic layer, and a colored layer.

  The said resin film is a film which uses a resin material as a main component (The component contained over 50 weight% in the said resin film). Examples of the resin film include polyolefin resin films such as polyethylene (PE), polypropylene (PP), ethylene / propylene copolymer, etc .; polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), etc. Of polyester resins, vinyl chloride resins, vinyl acetate resins, polyimide resins, polyamide resins, fluorine resins, cellophanes, and the like. The resin film may be a rubber-based film such as a natural rubber film or a butyl rubber film. Among them, polyester films are preferable from the viewpoint of handling properties and processability, and among them, PET films are particularly preferable. In the present specification, “resin film” is typically a non-porous sheet, and is a concept that is distinguished from so-called non-woven fabrics and woven fabrics (in other words, concepts excluding non-woven fabrics and woven fabrics) is there.

  The resin film may have a single layer structure, or may have a multilayer structure of two layers, three layers or more. From the viewpoint of shape stability, the resin film preferably has a single layer structure. In the case of a multilayer structure, at least one layer (preferably all layers) is preferably a layer having a continuous structure of the above-mentioned resin (for example, polyester resin). The method for producing the resin film may be any method known in the related art, as appropriate, and is not particularly limited. For example, conventionally known general film forming methods such as extrusion molding, inflation molding, T-die cast molding, calendar roll molding and the like can be appropriately adopted.

  In another embodiment, paper, cloth or metal is used as the base material. Examples of paper that can be used for the base film include Japanese paper, kraft paper, glassine paper, high quality paper, synthetic paper, top coated paper and the like. Examples of the cloth include woven and non-woven fabrics made of various fibrous substances singly or by blending. Examples of the fibrous material include cotton, cotton wool, manila hemp, pulp, rayon, acetate fiber, polyester fiber, polyvinyl alcohol fiber, polyamide fiber, polyolefin fiber and the like. An aluminum foil, copper foil, etc. are mentioned as an example of the metal foil which may be used for a base film.

  The term "nonwoven fabric" as used herein refers to a non-woven fabric for pressure-sensitive adhesive sheets mainly used in the field of pressure-sensitive adhesive tapes and other pressure-sensitive adhesive sheets, and is typically produced using a general paper machine. (It is sometimes called so-called "paper"). Moreover, the resin film here is a non-porous resin sheet typically, Comprising: For example, it is the concept distinguished from a nonwoven fabric (namely, it does not contain a nonwoven fabric). The resin film may be any of a non-stretched film, a uniaxially stretched film, and a biaxially stretched film. In addition, the surface of the substrate on which the pressure-sensitive adhesive layer is provided may be subjected to surface treatment such as application of an undercoat, corona discharge treatment, or plasma treatment.

  In the above-mentioned resin film (for example, PET film), if necessary, filler (inorganic filler, organic filler, etc.), colorant, dispersant (surfactant, etc.), anti-aging agent, antioxidant, ultraviolet light Various additives such as an absorbent, an antistatic agent, a lubricant, and a plasticizer may be blended. The blending ratio of various additives is usually less than about 30% by weight (eg, less than about 20% by weight, preferably less than about 10% by weight).

  The surface of the substrate film may be subjected to conventionally known surface treatment such as corona discharge treatment, plasma treatment, ultraviolet irradiation treatment, acid treatment, alkali treatment, application of a primer and the like. Such surface treatment may be treatment to improve the adhesion between the substrate film and the pressure-sensitive adhesive layer, in other words, the anchorability of the pressure-sensitive adhesive layer to the substrate film.

  The thickness of the base film disclosed herein is not particularly limited. The thickness of the base film (for example, resin film) can be, for example, about 200 μm or less, preferably about 150 μm or less, and more preferably about 100 μm or less, from the viewpoint of preventing the pressure-sensitive adhesive sheet from becoming excessively thick. The thickness of the substrate film may be about 70 μm or less, about 50 μm or less, or about 30 μm or less (eg, about 25 μm or less), depending on the use purpose and use mode of the pressure-sensitive adhesive sheet. In one embodiment, the thickness of the substrate film may be about 20 μm or less, about 15 μm or less, or about 10 μm or less (eg, about 5 μm or less). By reducing the thickness of the base film, the thickness of the pressure-sensitive adhesive layer can be increased even if the total thickness of the pressure-sensitive adhesive sheet is the same. This can be advantageous from the viewpoint of improving the adhesion to the substrate. The lower limit of the thickness of the substrate film is not particularly limited. The thickness of the base film is usually about 0.5 μm or more (eg, 1 μm or more), preferably about 2 μm or more, for example, about 4 μm or more, from the viewpoints of handleability and processability of the adhesive sheet. . In one aspect, the thickness of the substrate film can be about 6 μm or more, may be about 8 μm or more, and may be about 10 μm or more (eg, more than 10 μm).

<Foam base>
In another preferred embodiment, a foam substrate is used as the substrate. The foam substrate disclosed herein is a substrate provided with a portion having cells (cell structure), and is typically a substrate including at least one layer of layered foam (foam layer). is there. The foam substrate may be a substrate composed of one or more foam layers. The foam substrate may be, for example, a substrate substantially constituted of only one or two or more foam layers. Although it does not specifically limit, the foam substrate which consists of a foam layer of a single layer (one layer) as a suitable example of a foam substrate in the art indicated here is mentioned.

  The thickness of the foam substrate is not particularly limited, and can be appropriately set according to the strength and flexibility of the pressure-sensitive adhesive sheet, the purpose of use, and the like. From the viewpoint of thinning, the thickness of the foam substrate is usually 1 mm or less, suitably 0.70 mm or less, preferably 0.40 mm or less, and more preferably 0.30 mm or less. The technique disclosed herein is preferably carried out in an aspect in which the thickness of the foam substrate is 0.25 mm or less (typically 0.18 mm or less, for example 0.16 mm or less) from the viewpoint of processability and the like. obtain. In addition, from the viewpoint of the impact resistance of the pressure-sensitive adhesive sheet, the thickness of the foam substrate is usually 0.04 mm or more, suitably 0.05 mm or more, preferably 0.06 mm or more, 0.07 mm The above (for example, 0.08 mm or more) is more preferable. The technology disclosed herein is preferably carried out in a mode in which the thickness of the foam substrate is 0.10 mm or more (typically, 0.10 mm or more, preferably 0.12 mm or more, for example, 0.13 mm or more). obtain. As the thickness of the foam substrate is increased, the impact resistance tends to be improved.

The density of the foam substrate (the apparent density, hereinafter the same unless otherwise specified) is not particularly limited, and may be, for example, 0.1 to 0.9 g / cm ³ . From the viewpoint of impact resistance, the density of the foam substrate is, 0.8 g / cm ³ or less are suitable, 0.7 g / cm ³ or less (e.g., 0.6 g / cm ³ or less) are preferred. In one embodiment, the density of the foam substrate may be less than 0.5 g / cm ^3, may be less than 0.4 g / cm ³ (e.g., 0.5 g / cm ³ or less). From the viewpoint of impact resistance, the density of the foam substrate is preferably 0.12 g / cm ³ or more, more preferably 0.15 g / cm ³ or more, and 0.2 g / cm ³ or more (eg 0.3 g / Cm ³ or more) is more preferable. In one aspect, the density of the foam substrate may be 0.4 g / cm ³ or more, may be 0.5 g / cm ³ or more (eg, more than 0.5 g / cm ³ ), and even 0 It may be .55 g / cm ³ or more. In addition, the density (apparent density) of a foam base material can be measured based on JISK6767.

  The average cell diameter of the foam substrate is not particularly limited, but from the viewpoint of stress dispersion, 300 μm or less is preferable, 200 μm or less is more preferable, and 150 μm or less is more preferable. The lower limit of the average cell diameter is not particularly limited, but is usually 10 μm or more, preferably 20 μm or more, more preferably 30 μm or more, and still more preferably 40 μm or more (eg, 50 μm or more). In one aspect, the average cell diameter may be 55 μm or more, and may be 60 μm or more. In addition, an average cell diameter here says the average cell diameter of a true sphere conversion obtained by observing the cross section of a foam base material with an electron microscope.

  The cell structure of the foam constituting the foam substrate disclosed herein is not particularly limited. The cell structure may be any of an open cell structure, a closed cell structure, and a semicontinuous semi-closed cell structure. From the viewpoint of impact absorption, a closed cell structure or a semicontinuous semi-closed cell structure is preferred.

The 25% compressive strength C ₂₅ of the foam substrate is not particularly limited, and may be, for example, 20 kPa or more (typically, 30 kPa or more, or 40 kPa or more). C ₂₅ is usually suitably more than 250 kPa, more 300 kPa (e.g. 400kPa or higher) is preferred. A pressure-sensitive adhesive sheet provided with such a foam base can exhibit good durability against impact such as falling. For example, tearing of the adhesive sheet due to impact may be better prevented. The upper limit of the C ₂₅ is not particularly limited, but is usually 1300kPa or less (e.g. 1200kPa or less) are suitable. In one aspect, C ₂₅ may be 1000 kPa or less, 800 kPa or less, or 600 kPa or less (e.g., 500 kPa or less), or 360 kPa or less. In a preferred alternative embodiment, the C ₂₅ of the foam substrate can be from 20 kPa to 200 kPa (typically 30 kPa to 150 kPa, such as 40 kPa to 120 kPa). A pressure-sensitive adhesive sheet provided with such a foam base can be excellent in cushioning properties. For example, peeling of the pressure-sensitive adhesive sheet can be better prevented by the foam substrate absorbing a drop impact.

The 25% compressive strength C ₂₅ of the foam substrate is obtained by stacking the foam substrate cut into a square of 30 mm square and sandwiching the measurement sample having a thickness of about 2 mm between a pair of flat plates, which is initially used. The load (load at a compression ratio of 25%) when compressed by a thickness corresponding to 25% of the thickness. That is, the load when the measurement sample is compressed to a thickness corresponding to 75% of the initial thickness. The said compressive strength is measured based on JISK6767. As a specific measurement procedure, the measurement sample is set at the central portion of the pair of flat plates, and the flat plate is continuously compressed to a predetermined compression ratio by narrowing the distance between the flat plates. Measure the load after the lapse. The compressive strength of the foam substrate can be controlled, for example, by the degree of crosslinking or density of the material constituting the foam substrate, the size or shape of the cells, and the like.

  The tensile elongation of the foam substrate is not particularly limited. For example, a foam substrate having a tensile elongation in the machine direction (MD) of 200% to 800% (more preferably 400% to 600%) may be suitably employed. Further, a foam base having a tensile elongation in the width direction (TD) of 50% to 800% (more preferably 200% to 500%) is preferable. The elongation of the foam substrate is measured in accordance with JIS K 6767. The elongation of the foam substrate can be controlled, for example, by the degree of crosslinking, the apparent density (the expansion ratio) and the like.

  The tensile strength (tensile strength) of the foam substrate is not particularly limited. For example, a foam substrate having a tensile strength in the flow direction (MD) of 5 MPa to 35 MPa (preferably 10 MPa to 30 MPa) can be suitably employed. Further, a foam base having a tensile strength in the width direction (TD) of 1 MPa to 25 MPa (more preferably 5 MPa to 20 MPa) is preferable. The tensile strength of the foam base is measured in accordance with JIS K 6767. The tensile strength of the foam substrate can be controlled, for example, by the degree of crosslinking, the apparent density (the expansion ratio), and the like.

  The material of the foam base is not particularly limited. In general, a foam substrate comprising a foam layer formed by a foam of a plastic material (plastic foam) is preferred. The plastic material (meaning including the rubber material) for forming the plastic foam is not particularly limited, and can be appropriately selected from known plastic materials. A plastic material can be used individually by 1 type or in combination of 2 or more types suitably.

  Specific examples of plastic foams include polyolefin resin foams such as PE foams and PP foams; polyester foams such as PET foams, PEN foams and PBT foams; Polyvinyl chloride resin foam such as polyvinyl chloride foam; vinyl acetate resin foam; polyphenylene sulfide resin foam; aliphatic polyamide (nylon) resin foam, wholly aromatic polyamide (aramid) Foams made of amide resin such as foams made of resin; foams made of polyimide resin; foam made of polyetheretherketone (PEEK); foam made of styrene resin such as foam made of polystyrene; foam made of polyurethane resin etc And urethane-based resin foams; and the like. Alternatively, as the plastic foam, a rubber-based resin foam such as polychloroprene rubber foam may be used.

  As a preferable foam, a polyolefin resin foam (hereinafter, also referred to as "polyolefin foam") is exemplified. As a plastic material (that is, polyolefin resin) which comprises a polyolefin foam, various polyolefin resin well-known or usual can be used without a limitation in particular. For example, PE such as low density polyethylene (LDPE), linear low density polyethylene (LLDPE), high density polyethylene (HDPE), PP, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer and the like can be mentioned. Examples of LLDPE include Ziegler-Natta catalyst-based linear low density polyethylene, metallocene catalyst-based linear low density polyethylene, and the like. Such polyolefin resins can be used singly or in appropriate combination of two or more.

  Preferred examples of the foam substrate in the technology disclosed herein include a PE-based foam substrate substantially composed of a foam of a PE-based resin from the viewpoint of impact resistance, waterproofness, dust resistance, etc. And polyolefin-based foam substrates such as PP-based foam substrates substantially composed of a PP-based resin foam. Here, the PE-based resin refers to a resin containing ethylene as a main monomer (that is, the main component in the monomer), and in addition to HDPE, LDPE, LLDPE, etc., ethylene-copolymer ratio exceeds 50% by weight. It may include a propylene copolymer, an ethylene-vinyl acetate copolymer and the like. Similarly, a PP-based resin refers to a resin containing propylene as a main monomer. A PE-based foam substrate can be preferably employed as a foam substrate in the art disclosed herein.

The method for producing the plastic foam (typically, a polyolefin foam) is not particularly limited, and various known methods can be appropriately adopted. For example, it can be manufactured by a method including a molding step, a crosslinking step and a foaming step of the plastic material or the plastic foam. Moreover, the drawing process may be included as needed.
Examples of the method for crosslinking the plastic foam include a chemical crosslinking method using an organic peroxide or the like, an ionizing radiation crosslinking method using ionizing radiation, and the like, and these methods may be used in combination. Examples of the ionizing radiation include electron beams, α rays, β rays, and γ rays. The dose of ionizing radiation is not particularly limited, and can be set to an appropriate dose in consideration of the target physical properties (for example, the degree of crosslinking) of the foam substrate and the like.

  The above foam base material may, if necessary, be a filler (inorganic filler, organic filler, etc.), an antioxidant, an antioxidant, an ultraviolet absorber, an antistatic agent, a lubricant, a plasticizer, a flame retardant, Various additives such as surfactants may be blended.

  The foam substrate in the technology disclosed herein is black or white in order to exhibit desired design and optical properties (for example, light shielding property, light reflectivity, etc.) in a pressure-sensitive adhesive sheet provided with the foam substrate. It may be colored etc. For this coloring, known organic or inorganic colorants can be used singly or in appropriate combination of two or more.

  An appropriate surface treatment may be applied to the surface of the foam substrate, if necessary. This surface treatment can be, for example, a chemical or physical treatment to enhance adhesion to an adjacent material (eg, an adhesive layer). Examples of such surface treatment include corona discharge treatment, chromic acid treatment, ozone exposure, flame exposure, ultraviolet irradiation treatment, plasma treatment, application of a primer, and the like.

<Peeling liner>
In the art disclosed herein, a release liner can be used during formation of the pressure-sensitive adhesive layer, preparation of the pressure-sensitive adhesive sheet, storage of the pressure-sensitive adhesive sheet before use, distribution, shape processing, and the like. The release liner is not particularly limited. For example, a release liner having a release-treated layer on the surface of a liner substrate such as a resin film or paper, a fluorine-based polymer (such as polytetrafluoroethylene), or a polyolefin-based resin (PE, A release liner made of a low adhesive material such as PP can be used. The release treatment layer may be formed, for example, by surface treatment of the liner base material with a release treatment agent such as silicone, long chain alkyl, fluorine, or molybdenum sulfide.

<Adhesive sheet>
The pressure-sensitive adhesive sheet disclosed herein has a 180 ° peel strength (23 ° C. light pressure bond initial adhesion) measured within 1 minute after pressure bonding under conditions of 23 ° C. and a pressure load of 0.1 kg, and 40 ° C., 0.05 MPa It is preferable that at least one of the 180 degree peel strength (40 ° C. light pressure bond initial bond strength) measured within 1 minute after pressure bonding under the condition of 3 seconds satisfies 8 N / 20 mm or more. The pressure-sensitive adhesive sheet satisfying the above-mentioned characteristics can preferably exhibit excellent initial adhesion to the surface of an adherend by light pressure bonding in a normal temperature range or light pressure bonding using a limited heating temperature. The above-mentioned pressure-sensitive adhesive sheet can achieve desired light-pressing initial adhesion in the above-mentioned pressure-bonding temperature range, so even in applications where heating above 60 ° C is difficult (for example, electronic device applications), normal temperature or mild heating It can be preferably used in the pasting mode. Moreover, such an adhesive sheet is excellent also in the handling property compared with the conventional thermocompression bonding.

  The pressure-sensitive adhesive sheet disclosed herein has a 180 ° peel strength (23 ° C. light pressure bonding initial bond strength) measured within 1 minute after pressure bonding under conditions of 23 ° C. and a pressure load of 0.1 kg is 8 N / 20 mm or more Is preferred. By satisfying this characteristic, it is possible to exhibit excellent initial adhesion with light pressure bonding to various adherends (for example, materials used as portable electronic device members). Moreover, the adhesive sheet which is excellent in light pressure-bonding initial stage adhesiveness is also advantageous in the point to which the adhesion | pasting to the fragile adherend which may be damaged by normal pressure-bonding is easy. The 23 ° C. light pressure bonding initial adhesion is more preferably 10 N / 20 mm or more, still more preferably 12 N / 20 mm or more, and particularly preferably 14 N / 20 mm or more. The upper limit of the initial adhesive strength at 23 ° C. for light compression bonding is not particularly limited, but usually about 30 N / 20 mm or less (eg, about 20 N / 20 mm or less) is appropriate. The above-mentioned 23 ° C. light pressure bonding initial adhesion is specifically measured by the method described in the below-mentioned Examples.

  In addition, the pressure-sensitive adhesive sheet disclosed herein is heat-pressed under the conditions of 40 ° C., 0.05 MPa, 3 seconds, and has a 180 ° peel strength (40 ° C. light pressure-bond initial adhesion) measured within 1 minute after pressure bonding. And 8 N / 20 mm or more. By satisfying this characteristic, excellent light-press initial adhesion can be exhibited by thermocompression bonding by heating at about 40 ° C. (in other words, mild thermocompression bonding). Unlike the conventional thermocompression bonding performed at about 100 ° C., the thermocompression bonding is thermocompression bonding applicable to electronic devices and the like. The 40 ° C. light pressure bonding initial adhesion is more preferably 10 N / 20 mm or more, still more preferably 12 N / 20 mm or more, particularly preferably 14 N / 20 mm or more, and most preferably 18 N / 20 mm or more. The upper limit of the initial adhesive strength at 40 ° C. for light pressure bonding is not particularly limited, but usually about 30 N / 20 mm or less (eg, about 25 N / 20 mm or less) is suitable. The above-mentioned 40 ° C. light pressure bonding initial adhesion is specifically measured by the method described in the below-mentioned Examples.

  In addition, the pressure-sensitive adhesive sheet disclosed herein has an acceptable level of deformation resistance in the Z-axis direction deformation resistance test (23 ° C. or 40 ° C.) measured using a PET film having a thickness of 75 μm in Examples described later. (That is, peeling does not occur). The pressure-sensitive adhesive sheet satisfying the above-mentioned characteristics has excellent light pressure-sensitive adhesion and deformation resistance excellent for a peeling load substantially consisting only of the thickness direction (Z-axis direction) of the pressure-sensitive adhesive sheet, and in the direction It is hard to be deformed due to the continuous peeling load.

  In the pressure-sensitive adhesive sheet disclosed herein, at the end of measurement in the Z-axis direction deformation resistance test which is measured under the conditions of 65 ° C. 90% RH 72 hours using a PET film having a thickness of 125 μm in an example described later. The floating height of may be less than 1000 μm. The pressure-sensitive adhesive sheet satisfying the above-mentioned characteristics has particularly excellent deformation resistance to a peeling load substantially consisting only of the thickness direction (Z-axis direction) of the pressure-sensitive adhesive sheet, and is persistent in the direction Particularly difficult to deform under peeling load. In addition, it exhibits stable deformation resistance even when the adhesive sheet attached to the adherend (for example, a portable electronic device or a module that is a component thereof) is exposed to high temperature and high humidity conditions during storage etc. It can. The floating height is preferably less than 700 μm, more preferably less than 500 μm, still more preferably less than 300 μm, and particularly preferably less than 200 μm (eg, less than 150 μm). The floating height is a height including the thickness of the pressure-sensitive adhesive sheet (50 μm in the example described later).

  Moreover, as for the adhesive sheet disclosed here, it is preferable that the adhesive force after 30 minutes aging measured according to JISZ 0237: 2000 is 8 N / 20 mm or more. The pressure-sensitive adhesive sheet having adhesion after curing for 30 minutes exhibits good adhesion to an adherend. The pressure-sensitive adhesive sheet having the adhesive strength tends to exhibit good adhesion to resin materials used for electronic devices such as polycarbonate (PC) and polyimide (PI). The adhesion after 30 minutes of curing is more preferably 10 N / 20 mm or more, still more preferably 12 N / 20 mm or more, and particularly preferably 14 N / 20 mm or more (eg, 18 N / 20 mm or more). The upper limit of the adhesive strength after curing for 30 minutes is not particularly limited, but usually about 30 N / 20 mm or less (for example, about 25 N / 20 mm or less) is suitable. The adhesion after 30 minutes of curing is specifically measured by the method described in the examples below.

  In the pressure-sensitive adhesive sheet according to a preferable embodiment, it is preferable that the expression rate of the 23 ° C. light pressure-bonding initial adhesion be greater than 50%. The above-mentioned 23 ° C. light pressure bonding initial adhesion development rate can be determined from the formula: 23 ° C. light pressure bonding initial adhesion development rate (%) = (23 ° C. light compression initial bonding initial adhesion / 30 minutes post curing adhesive strength) × 100; it can. The units for the 23 ° C. light crimp initial adhesion and after 30 minutes aging are the same (typically [N / 20 mm]). The pressure-sensitive adhesive sheet exhibiting the above expression rate is preferably used in applications where good adhesion is required immediately after attachment by light pressure bonding, because the initial adhesive force at 23 ° C. light pressure bonding is large compared to the adhesion after curing. The expression rate of the above-mentioned 23 ° C. light pressure-bonding initial adhesion is more preferably 55% or more, still more preferably 60% or more, and particularly preferably 65% or more. By combining the techniques disclosed herein, the expression rate can be 70% or more, or even 75% or more. Although the upper limit of the above-mentioned 23 ° C. light pressure bonding initial adhesion development rate is ideally 100%, it may be about 90% or less (for example, 85% or less).

  The pressure-sensitive adhesive sheet according to another preferred embodiment preferably has an expression rate of 40 ° C. light pressure bonding initial adhesion of greater than 50%. The above-mentioned 40 ° C. light pressure bonding initial adhesion development rate can be obtained from the formula: 40 ° C. light pressure bonding initial adhesion development rate (%) = (40 ° C. light compression initial bonding initial adhesion / 30 minutes adhesion after curing) × 100; it can. The unit of 40 ° C. light pressure bonding initial adhesion and adhesion after 30 minutes curing is the same (typically (N / 20 mm)). By satisfying this characteristic, the pressure-sensitive adhesive sheet can exhibit excellent light pressure-bonding initial adhesion by thermocompression bonding by heating at about 40 ° C. The expression rate of the above-mentioned 40 ° C. light pressure bonding initial adhesion is more preferably 55% or more, still more preferably 60% or more, and particularly preferably 65% or more. By combining the techniques disclosed herein, the expression rate can be 70% or more, or even 75% or more. The upper limit of the above-mentioned 40 ° C. light pressure bonding initial adhesion development rate is ideally 100%, but may be about 90% or less (eg, 85% or less).

  When the pressure-sensitive adhesive sheet disclosed herein is a substrate-less pressure-sensitive adhesive sheet substantially consisting of only the pressure-sensitive adhesive layer, the storage elastic modulus G ′ (25 ° C.) at 25 ° C. of the pressure-sensitive adhesive sheet is 0. 0. It may be 15 MPa or more. The pressure-sensitive adhesive sheet having the storage elastic modulus G ′ (25 ° C.) can preferably exhibit good deformation resistance from an early stage after being attached to an adherend. The G ′ (25 ° C.) is preferably 0.17 MPa or more, more preferably 0.2 MPa or more, and still more preferably 0.23 MPa or more. The G ′ (25 ° C.) is particularly preferably 0.25 MPa or more, and may be, for example, 0.3 MPa or more. In addition, the G '(25 ° C) is usually suitably 1.0 MPa or less, preferably from 0.6 MPa or less, more preferably from the viewpoint of coexistence of light pressure bonding initial adhesion and deformation resistance. Is preferably 0.4 MPa or less, more preferably 0.35 MPa or less, for example, 0.3 MPa or less, 0.25 MPa or less, or 0.2 MPa or less.

  In addition, when the pressure-sensitive adhesive sheet disclosed herein is a substrate-less pressure-sensitive adhesive sheet substantially consisting only of a pressure-sensitive adhesive layer, the storage elastic modulus G ′ (85 ° C.) at 85 ° C. of the pressure-sensitive adhesive sheet is 0. 0. It may be 02 MPa or more. Thereby, a pressure-sensitive adhesive sheet having sustained deformation resistance can be preferably obtained. Specifically, the G ′ (85 ° C.) is 0.022 MPa or more, preferably 0.025 MPa or more, and more preferably 0.027 MPa or more. The above G ′ (85 ° C.) is more preferably about 0.03 MPa or more (eg, 0.035 MPa or more), particularly preferably 0.04 MPa or more, still more preferably 0.05 MPa or more. In addition, the G '(85 ° C.) is usually 1.0 MPa or less, for example, 0.5 MPa or less, typically 0.1 MPa or less. The G ′ (85 ° C.) may be 0.05 MPa or less.

  In addition, when the pressure-sensitive adhesive sheet disclosed herein is a substrate-less pressure-sensitive adhesive sheet substantially consisting only of a pressure-sensitive adhesive layer, the pressure-sensitive adhesive sheet adheres the pressure-sensitive adhesive sheet from the viewpoint of light pressure bonding initial adhesion. The storage elastic modulus G ′ (apply) at the temperature (crimping temperature) when the steel sheet is crimped to may be 0.6 MPa or less. The above G ′ (apply) is preferably 0.4 MPa or less, more preferably 0.35 MPa or less, and may be, for example, 0.3 MPa or less, or may be 0.25 MPa or less. The G ′ (apply) may be, for example, 0.2 MPa or less. Further, from the viewpoint of achieving both light pressure bonding initial adhesion and deformation resistance, the G '(apply) is suitably larger than 0.12 MPa, preferably 0.15 MPa or more, more preferably 0. The pressure may be 17 MPa or more (e.g., 0.2 MPa or more), more preferably 0.25 MPa or more, and for example, 0.3 MPa or more. The pressure bonding temperature is selected from the range of more than 0 ° C. and less than 60 ° C. from the viewpoint of pressure bonding workability and temperature control. In the case of a pressure-sensitive adhesive sheet used for portable electronic device applications, it is desirable to select the pressure bonding temperature from the range of 20 ° C. to 45 ° C. (typically 25 ° C. or 40 ° C.) because of temperature limitations in the application.

  When the pressure-sensitive adhesive sheet disclosed herein is a substrate-less pressure-sensitive adhesive sheet substantially consisting only of a pressure-sensitive adhesive layer, the pressure-sensitive adhesive sheet generally has a loss elastic modulus G ′ ′ (25 ° C.) at 25 ° C. The above G ′ ′ (25 ° C.) is preferably 1.5 MPa or less, more preferably 1.0 MPa or less, and still more preferably 0.5 MPa or less. The G ′ ′ (25 ° C.) may be 0.3 MPa or less (eg, 0.25 MPa or less). The G ′ ′ (25 ° C.) is usually suitably 0.01 MPa or more. From the viewpoint of wettability to the surface of adherend, and hence initial adhesion after light pressure bonding, it is preferably 0.05 MPa or more, more preferably 0.1 MPa or more, still more preferably 0.2 MPa or more, for example, 0.25 MPa It may be more than.

  When the pressure-sensitive adhesive sheet disclosed herein is a substrate-less pressure-sensitive adhesive sheet substantially consisting only of a pressure-sensitive adhesive layer, tan δ (25 ° C.) at 25 ° C. of the above-mentioned pressure-sensitive adhesive sheet is, for example, about 0.3 or more And in view of deformation resistance, it is preferably about 0.5 or more, more preferably about 0.7 or more, still more preferably about 0.8 or more, particularly preferably about 0.9 or more For example, about 1 or more). The above-mentioned tan δ (25 ° C.) is, for example, suitably about 3 or less, and preferably about 2 or less, more preferably about 1.5 or less, still more preferably about 1.2 or less, from the viewpoint of light adhesion initial adhesion. It is below.

  When the pressure-sensitive adhesive sheet disclosed herein is a substrate-less pressure-sensitive adhesive sheet substantially consisting only of the pressure-sensitive adhesive layer, tan δ (85 ° C.) at 85 ° C. of the above-mentioned pressure-sensitive adhesive sheet is, for example, about 0.1 or more It is suitable that the ratio is preferably 0.2 or more, more preferably 0.22 or more, and still more preferably 0.24 or more (e.g., 0.25 or more). The above-mentioned tan δ (85 ° C.) is, for example, about 2 or less, preferably about 1 or less, and more preferably about 0.5 or less (eg, about 0.3 or less).

  The storage elastic modulus G ′ (25 ° C.), G ′ (85 ° C.), G ′ (apply), loss elastic modulus G ′ ′ (25 ° C.), tan δ (25 ° C.) and tan δ (85 ° C.) of the pressure-sensitive adhesive sheet are It can be determined in the same manner as the dynamic viscoelasticity measurement for the pressure-sensitive adhesive layer.

  The pressure-sensitive adhesive sheet according to a preferred embodiment is a substrate-less double-sided adhesive pressure-sensitive adhesive sheet (substrate-less double-sided pressure-sensitive adhesive sheet) substantially composed only of a pressure-sensitive adhesive layer. Such a substrate-less pressure-sensitive adhesive sheet is excellent in followability, and thus adheres well to an adherend having a level difference, for example, and can exhibit excellent adhesion performance. In addition, when the rigid materials are fixed to each other, pressure bonding unevenness does not easily occur, and good adhesion and fixation can be easily realized. Therefore, the present invention can be preferably used for joining members of electronic devices in which a rigid member such as a wiring board or a housing which can have a step is disposed. The substrate-less double-sided pressure-sensitive adhesive sheet is formed of the pressure-sensitive adhesive layer in its entire thickness, and therefore can exert stronger adhesion (for example, light pressure-sensitive adhesion) in a limited thickness space. Therefore, it can be particularly preferably utilized for member bonding applications of portable electronic devices.

  The total thickness of the pressure-sensitive adhesive sheet (not including the release liner) disclosed herein is not particularly limited. The total thickness of the pressure-sensitive adhesive sheet may be, for example, about 500 μm or less, usually about 350 μm or less, and preferably about 250 μm or less (eg, about 200 μm or less). The technology disclosed herein is preferably in the form of a pressure-sensitive adhesive sheet (typically a double-sided pressure-sensitive adhesive sheet) having a total thickness of about 150 μm or less (more preferably about 100 μm or less, more preferably less than about 60 μm, for example about 55 μm or less). It can be implemented. The lower limit of the total thickness of the pressure-sensitive adhesive sheet is not particularly limited, but usually about 10 μm or more is suitable, about 20 μm or more is preferable, and about 30 μm or more is more preferable. When the pressure-sensitive adhesive sheet comprises a foam substrate, the upper limit of the total thickness of the pressure-sensitive adhesive sheet is usually 1.5 mm or less, preferably 1 mm or less, more preferably 0.5 mm or less is there.

<Use>
The pressure-sensitive adhesive sheet disclosed herein has both light-press initial adhesion and deformation resistance to a sustained load in the Z-axis direction. Taking advantage of such characteristics, the pressure-sensitive adhesive sheet can be used in various applications where light pressure-bonding initial adhesion and deformation resistance to a sustained load in the Z-axis direction are required. For example, it can be preferably used for the application which fixes various members by light pressure bonding. As a typical example, there is a member fixing application of various electronic devices whose tact time is strictly controlled for mass production. For example, by using the pressure-sensitive adhesive sheet disclosed herein for fixing members in various portable devices (portable devices), limited heating (less than 60 ° C.) applicable to normal temperature or electronic device applications The light-crimping initial adhesion based on mild heating (typically about 40 ° C.) can be used to reduce the tact time of portable electronic device manufacturing, which can contribute to the improvement of the productivity. Non-limiting examples of the portable electronic device include a mobile phone, a smartphone, a tablet computer, a laptop computer, various wearable devices (for example, a wristwear type worn on the wrist like a wristwatch, a clip or a strap, etc. Eyewear type including modular type, glasses type (single eye type and binocular type, including head mount type) to be attached to a part of the product, clothes type to attach to the shirt, socks, hat, etc. Like earwear type attached to the ear), digital camera, digital video camera, audio equipment (portable music player, IC recorder etc), calculator (such as calculator), portable game equipment, electronic dictionary, electronic organizer, electronic book, in-vehicle Information devices, portable radios, portable televisions, portable printers, portable scanners, portable modems and the like. In this specification, "portable" is not enough to be only portable, but it is relatively easy for an individual (standard adult) to have portability. Shall be meant.

  The pressure-sensitive adhesive sheet (typically, a double-sided pressure-sensitive adhesive sheet) disclosed herein can be used in the form of a bonding material processed into various shapes to fix the members constituting the portable electronic device as described above. Among them, it can be preferably used for a portable electronic device having a liquid crystal display device. For example, an electronic device (typically, a portable electronic device such as a smart phone) having a display unit (which may be a display unit of a liquid crystal display device) such as a touch panel display In an apparatus in which an elastic member such as FPC or the like is folded and stored in an internal space, the pressure-sensitive adhesive sheet disclosed herein is preferably used for fixing the elastic adherend. By using the pressure-sensitive adhesive sheet disclosed herein, the elastic adherend can be fixed in a bent state even with light pressure bonding, and the fixed state can be maintained continuously. By this, the said elastic member accommodated in the state which was bend | folded in the limited internal space in a portable electronic device can be precisely positioned by the adhesive sheet disclosed here, and can be hold | maintained in a stable fixed state. Moreover, as a material arrange | positioned as mentioned above inside a portable electronic device, it has polarity like polycarbonate and a polyimide, and a rigid material is mentioned. The pressure-sensitive adhesive sheet disclosed herein can preferably exhibit light-press initial adhesion and deformation resistance to a sustained load in the Z-axis direction with respect to this type of material (polar and rigid resin material).

  The development of an electronic device (typically, a portable electronic device such as a smartphone or a tablet personal computer) having a display unit (which may be a display unit of a liquid crystal display device) such as the touch panel display described above It is being aimed at coexistence with the development and high functionality. In order to increase the screen size, measures have been taken to bend and accommodate an elastic member such as the above-mentioned FPC or the like in the internal space. On the other hand, with regard to high functionality, new functions such as pressure sensitive sensors with higher precision pressure sensing performance and face authentication lock release function have been embodied, and higher performance and higher quality products are realized In order to achieve this, high integration of circuits, such as FPCs, is essential. Examples of means for highly integrating circuits include double-sided type FPCs and multilayer FPCs, but both are directionality of rigidity increase of FPCs, and Z as evaluated in the Z-axis direction deformation resistance test described later. It is expected that the improvement of the deformation resistance to the sustained load in the axial direction will be a required characteristic. The pressure-sensitive adhesive sheet according to a preferred embodiment of the technology disclosed herein exhibits excellent deformation resistance under more severe conditions such as the Z-axis direction deformation resistance test under strong rebound, high temperature and high humidity conditions described later. As it may be, it can be better adapted to the above-mentioned next-generation type touch panel display-equipped electronic device (typically, a touch panel display-equipped portable electronic device such as a smartphone), and can be preferably used.

Items disclosed by this specification include the following.
(1) An acrylic polymer as a base polymer, and at least one selected from a tackifying resin and a (meth) acrylic oligomer
The weight average molecular weight of the acrylic polymer is greater than 70 × 10 ⁴ ,
The acrylic adhesive composition whose dispersion degree (Mw / Mn) of the said acrylic polymer is less than 15.
(2) The acrylic according to (1) above, wherein the acrylic polymer is polymerized in a proportion of 50% by weight or more of an alkyl (meth) acrylate having an alkyl group having 1 to 6 carbon atoms at the ester end Adhesive composition.
(3) The acrylic pressure-sensitive adhesive composition according to (1) or (2), wherein the acrylic polymer is a copolymer of an acidic group-containing monomer.
(4) The adhesive sheet as described in said (3) whose copolymerization ratio of the said acidic group containing monomer in the said acryl-type polymer is less than 10 weight%.
(5) The acrylic pressure-sensitive adhesive composition according to any one of the above (1) to (4), wherein the tackifying resin is contained in a ratio of less than 30 parts by weight with respect to 100 parts by weight of the acrylic polymer object.
(6) The acrylic polymer according to any one of the above (1) to (5), wherein the (meth) acrylic oligomer is contained in a proportion of less than 30 parts by weight with respect to 100 parts by weight of the acrylic polymer Adhesive composition.
(7) The acrylic adhesive composition in any one of said (1)-(6) which contains both the said tackifying resin and the said (meth) acrylic-type oligomer.

(8) An acrylic pressure-sensitive adhesive layer comprising an acrylic polymer as a base polymer, and at least one selected from a tackifying resin and a (meth) acrylic oligomer.
The weight average molecular weight of the acrylic polymer is greater than 70 × 10 ⁴ ,
The adhesive sheet whose dispersion degree (Mw / Mn) of the said acryl-type polymer is less than 15.
(9) The adhesive according to (8), wherein the acrylic polymer is polymerized in a proportion of 50% by weight or more of an alkyl (meth) acrylate having an alkyl group having 1 to 6 carbon atoms at the ester end Sheet.
(10) The pressure-sensitive adhesive sheet according to (8) or (9), wherein the acrylic polymer is a copolymer of an acidic group-containing monomer.
(11) The adhesive sheet as described in said (10) whose copolymerization ratio of the said acidic group containing monomer in the said acryl-type polymer is less than 10 weight%.
(12) In the acrylic pressure-sensitive adhesive layer, the tackifying resin is contained in a ratio of less than 30 parts by weight with respect to 100 parts by weight of the acrylic polymer. Adhesive sheet as described in.
(13) In the acrylic pressure-sensitive adhesive layer, the (meth) acrylic oligomer is contained in a ratio of less than 30 parts by weight with respect to 100 parts by weight of the acrylic polymer, (8) to (12) The adhesive sheet as described in any of the above.
(14) The pressure-sensitive adhesive sheet according to any one of (8) to (13), wherein the acrylic pressure-sensitive adhesive layer contains both the tackifier resin and the (meth) acrylic oligomer.

(15) The adhesive sheet in any one of said (8)-(14) whose storage-elastic-modulus G '(25 degreeC) in 25 degreeC is 0.15 Mpa or more.
(16) The pressure-sensitive adhesive sheet according to any one of (8) to (15), wherein the pressure-sensitive adhesive layer has a storage elastic modulus G ′ (85 ° C.) at 85 ° C. of 0.02 MPa or more.
(17) 180 ° peel strength measured within 1 minute after crimping under conditions of 23 ° C. and crimping load 0.1 kg, and measured within 1 minute after crimping under conditions of 40 ° C., 0.05 MPa and 3 seconds The pressure-sensitive adhesive sheet according to any one of the above (8) to (16), which satisfies that at least one of the 180 degree peel strengths is 8 N / 20 mm or more.
(18) The adhesive sheet in any one of said (8)-(17) whose gel fraction of the said adhesive layer is 40 weight% or more.
(19) The adhesive sheet according to any one of the above (8) to (18), wherein the acrylic polymer is crosslinked.
(20) The pressure-sensitive adhesive sheet according to any one of the above (8) to (19), wherein the acrylic polymer is copolymerized with n-butyl acrylate in a proportion of 50% by weight or more.
(21) Any one of the above (8) to (20), wherein the pressure-sensitive adhesive layer contains the tackifying resin, and about 50% by weight or more of the tackifying resin is a phenolic tackifying resin (for example, terpene phenol resin) Pressure sensitive adhesive sheet described in.
(22) The pressure-sensitive adhesive sheet according to (21), wherein the phenolic tackifying resin comprises a terpene phenolic resin having a hydroxyl value of less than about 30 mg KOH / g.
(23) The pressure-sensitive adhesive sheet according to any one of (8) to (22), wherein the pressure-sensitive adhesive layer has a loss elastic modulus G ′ ′ (25 ° C.) at 25 ° C. of 2.0 MPa or less.
(24) The adhesive according to any one of the above (8) to (23), wherein the pressure-sensitive adhesive layer is a pressure-sensitive adhesive layer formed from a solvent-based pressure-sensitive adhesive composition or an active energy ray-curable pressure-sensitive adhesive composition. Sheet.
(25) The adhesive sheet in any one of said (8)-(24) comprised as a base-material-less adhesive sheet which consists only of the said adhesive layer.
(26) The adhesive sheet in any one of said (8)-(25) comprised as a double-sided adhesive adhesive sheet whose thickness is less than 60 micrometers.
(27) The adhesive sheet in any one of said (8)-(26) in which the expression rate of 23 degreeC light pressure-bonding initial stage adhesiveness is larger than 50%.

(28) It is an adhesive sheet provided with an adhesive layer,
The pressure-sensitive adhesive layer has a storage modulus G ′ (25 ° C.) at 25 ° C. of 0.15 MPa or more, and a storage modulus G ′ (85 ° C.) at 85 ° C. of 0.02 MPa or more,
180 ° peel strength measured within 1 minute after crimping under conditions of 23 ° C. and 0.1 kg of crimping load, and 180 ° peeling measured within 1 minute after crimping under conditions of 40 ° C., 0.05 MPa and 3 seconds A pressure-sensitive adhesive sheet satisfying that at least one of the strengths is 8 N / 20 mm or more.
(29) The adhesive sheet as described in said (28) whose gel fraction of the said adhesive layer is 40 weight% or more.
(30) The pressure-sensitive adhesive sheet according to (28) or (29), wherein the pressure-sensitive adhesive layer is an acrylic pressure-sensitive adhesive layer containing an acrylic polymer.
(31) The acrylic polymer according to (30), wherein an alkyl (meth) acrylate having an alkyl group having 1 to 6 carbon atoms at an ester end is copolymerized in a proportion of 50% by weight or more. Adhesive sheet.
(32) The pressure-sensitive adhesive sheet according to (30) or (31), wherein the acrylic polymer is a copolymer of an acidic group-containing monomer.
(33) The adhesive sheet as described in said (32) whose said acidic group containing monomer is acrylic acid.
(34) The adhesive sheet as described in said (32) or (33) whose copolymerization ratio of the said acidic group containing monomer in the said acryl-type polymer is less than 10 weight%.
(35) The adhesive sheet in any one of said (30)-(34) in which the said acryl-type polymer is bridge | crosslinked.
(36) The adhesive sheet in any one of said (30)-(35) in which the weight average molecular weight (Mw) of the said acryl-type polymer is larger than 70 * 10 ⁴ .
(37) The pressure-sensitive adhesive sheet according to any one of the above (30) to (36), wherein the acrylic polymer is copolymerized with n-butyl acrylate in a proportion of 50% by weight or more.
(38) Any one of the above (28) to (37), wherein the pressure-sensitive adhesive layer contains a tackifying resin, and about 50% by weight or more of the tackifying resin is a phenolic tackifying resin (for example, terpene phenolic resin) Adhesive sheet as described in.
(39) The pressure-sensitive adhesive sheet according to (38), wherein the phenolic tackifying resin comprises a terpene phenolic resin having a hydroxyl value of less than about 30 mg KOH / g.
(40) The pressure-sensitive adhesive sheet according to any one of the above (28) to (39), wherein the pressure-sensitive adhesive layer has a loss elastic modulus G ′ ′ (25 ° C.) at 25 ° C. of 2.0 MPa or less.
(41) The adhesive according to any one of the above (28) to (40), wherein the pressure-sensitive adhesive layer is a pressure-sensitive adhesive layer formed from a solvent-based pressure-sensitive adhesive composition or an active energy ray-curable pressure-sensitive adhesive composition. Sheet.
(42) The adhesive sheet in any one of said (28)-(41) comprised as a base-material-less adhesive sheet which consists only of the said adhesive layer.
(43) The adhesive sheet in any one of said (28)-(42) comprised as a double-sided adhesive adhesive sheet whose thickness is less than 60 micrometers.
(44) The adhesive sheet in any one of said (28)-(43) in which the expression rate of 23 degreeC light pressure-bonding initial stage adhesiveness is larger than 50%.

(45) The adhesive sheet in any one of said (8)-(44) used in order to fix a member in a portable electronic device.
(46) The adhesive sheet in any one of said (8)-(45) used in order to fix a flexible printed wiring board.
(47) The pressure-sensitive adhesive sheet according to any one of (8) to (46), which is used to fix a flexible printed wiring board accommodated in a bent state in a portable electronic device.

  The following examples illustrate some of the embodiments of the present invention, but are not intended to limit the present invention to those shown. In the following description, "parts" and "%" are on a weight basis unless otherwise noted.

«Experiment 1»
<Example 1-1>
(Preparation of acrylic polymer solution)
Into a reaction vessel equipped with a stirrer, thermometer, nitrogen gas inlet tube, reflux condenser and dropping funnel, 90 parts of 2EHA as monomer components and 10 parts of AA are charged, and further, ethyl acetate and toluene as a polymerization solvent are approximately 1: 1 ( It added at the ratio of volume ratio), and stirred for 2 hours, introduce | transducing nitrogen gas. Thus, after removing oxygen in the polymerization system, 0.2 parts of BPO was added as a polymerization initiator, and solution polymerization was performed at 60 ° C. for 6 hours to obtain a solution of an acrylic polymer according to this example.

(Preparation of pressure-sensitive adhesive composition)
In the solution of the acrylic polymer obtained above, 0.05 part of an epoxy-based crosslinking agent (trade name "TETRAD-C", 1,3-bis (N ,, N, per 100 parts of the acrylic polymer contained in the solution) N-diglycidylaminomethyl) cyclohexane, manufactured by Mitsubishi Gas Chemical Co., Ltd., and 20 parts of a terpene phenol resin (trade name “Tamanor 803L”, manufactured by Arakawa Chemical Industries, Ltd., softening point about 145 to 160 ° C., hydroxyl value 1 -20 mg KOH / g) was added and stirred and mixed to prepare a pressure-sensitive adhesive composition according to this example.

(Production of adhesive sheet)
As release liner A, a release film made of polyester (trade name "Diafoil MRV", 75 μm thick, manufactured by Mitsubishi Polyester Corp.) having release treated on one side as release liner B, release treated on one side as release liner B A release film made of polyester (trade name "Diafoil MRF", thickness 38 μm, manufactured by Mitsubishi Polyester Corporation), which is a release surface, was prepared. The pressure-sensitive adhesive composition obtained above was applied to the release surface of release liner A and dried at 100 ° C. for 2 minutes to form a 50 μm-thick pressure-sensitive adhesive layer. A release liner B was placed on the exposed pressure-sensitive adhesive surface of the pressure-sensitive adhesive layer so that the release surface was on the pressure-sensitive adhesive layer side, to produce a substrate-less double-sided pressure-sensitive adhesive sheet according to this example.

<Example 1-2 to Example 1-5>
Basically, a solution of an acrylic polymer according to each example was prepared in the same manner as in Example 1-1 except that the monomer composition shown in Table 1 was used. A pressure-sensitive adhesive composition according to each example was prepared in the same manner as in Example 1-1 using the obtained acrylic polymer, and a substrate-less double-sided adhesive pressure-sensitive adhesive sheet according to each example was produced.

<Example 1-6>
(Preparation of pressure-sensitive adhesive composition)
In a monomer mixture in which 90 parts of 2EHA as a monomer component and 10 parts of AA are mixed, 2,2-dimethoxy-1,2-diphenylethan-1-one (manufactured by BASF, trade name “IRGACURE 651”) as a photopolymerization initiator A mixture of 0.05 part and 0.05 part of 1-hydroxycyclohexyl-phenyl-ketone (manufactured by BASF, trade name “IRGACURE 184”) was irradiated with ultraviolet light (UV) until the viscosity became about 15 Pa · s. Partial polymer (monomer syrup) was obtained. To this monomer syrup, 0.1 part of 1,6-hexanediol diacrylate was added and uniformly mixed to prepare a pressure-sensitive adhesive composition. The viscosity was measured using a BH viscometer under the conditions of a rotor (No. 5 rotor), a rotation speed of 10 rpm, and a measurement temperature of 30 ° C.

(Production of adhesive sheet)
The release liner A (75 micrometers in thickness) and B (38 micrometers in thickness) similar to the said Example 1-1 were prepared, and the adhesive composition obtained above was apply | coated to the peeling surface of release liner A. The application amount of the pressure-sensitive adhesive composition was adjusted so that the thickness of the finally formed pressure-sensitive adhesive layer would be 150 μm. Next, a release liner B was placed on the coated film of the pressure-sensitive adhesive composition such that the release surface was in contact with the coated film. Thus, the coating film was shielded from oxygen. Then, the above-mentioned pressure-sensitive adhesive composition is made to proceed by causing a polymerization reaction to proceed for 3 minutes by irradiating an ultraviolet ray (trade name "Blacklight" manufactured by Toshiba Corporation) of 5 mW / cm ² from both sides of the coating film of the pressure-sensitive adhesive composition. The composition was cured to form a pressure-sensitive adhesive layer, and a pressure-sensitive adhesive sheet according to this example comprising the pressure-sensitive adhesive layer (that is, an ultraviolet-cured product of the coating film) was obtained. In addition, the value of the said illumination intensity is a measured value by industrial UV checker (The Topcon company make, brand name "UVR-T1", light receiving part model UD-T36) of peak sensitivity wavelength about 350 nm.

<Example 1-7>
A substrate-less double-sided adhesive pressure-sensitive adhesive sheet according to this example was prepared in the same manner as in Example 1-6 except that the monomer composition shown in Table 1 was used.

Example 1-8
(Preparation of acrylic polymer solution)
In a reaction vessel equipped with a stirrer, thermometer, nitrogen gas inlet tube, reflux condenser and dropping funnel, 93 parts of BA as a monomer component, 7 parts of AA and 0.05 parts of 4-hydroxybutyl acrylate (4HBA), and a polymerization solvent Of ethyl acetate and stirred for 2 hours while introducing nitrogen gas. After oxygen in the polymerization system was removed in this manner, 0.1 part of AIBN was added as a polymerization initiator, and solution polymerization was performed at 60 ° C. for 6 hours to obtain a solution of an acrylic polymer according to this example.

(Production of adhesive sheet)
In the solution of the acrylic polymer obtained above, 1.5 parts of an isocyanate-based crosslinking agent (trade name "Corronate L", 3 quantities of trimethylolpropane / tolylene diisocyanate with respect to 100 parts of the acrylic polymer contained in the solution) 75% ethyl acetate solution of adducts, Tosoh Co., Ltd., and 0.01 parts of an epoxy crosslinking agent (trade name "TETRAD-C", 1,3-bis (N, N-diglycidylaminomethyl) cyclo Hexane, manufactured by Mitsubishi Gas Chemical Company, 15 parts of terpene phenol resin (trade name “YS Polystar S-145 manufactured by Yashara Chemical Co., Ltd., softening point about 145 ° C., hydroxyl value 70 to 110 mg KOH / g), 15 parts The (meth) acrylic oligomers of the following were added and stirred and mixed to prepare a pressure-sensitive adhesive composition according to this example.
A substrate-less double-sided adhesive pressure-sensitive adhesive sheet according to this example was produced in the same manner as Example 1-1 using the obtained pressure-sensitive adhesive composition.
As the (meth) acrylic oligomer, one prepared by the following method was used. Specifically, in a reaction vessel equipped with a stirrer, thermometer, nitrogen gas inlet tube, reflux condenser, dropping funnel, 95 parts of CHMA and 5 parts of AA, 10 parts of AIBN as a polymerization initiator, and toluene as a polymerization solvent After stirring for 1 hour in a nitrogen stream to remove oxygen in the polymerization system, the temperature was raised to 85 ° C. and reaction was carried out for 5 hours to obtain a (meth) acrylic oligomer having a solid content concentration of 50%. Mw of the obtained (meth) acrylic oligomer was 3600.

<Example 1-9 to Example 1-12>
Basically, a solution of an acrylic polymer according to each example was prepared in the same manner as in Example 1-1 except that the monomer composition shown in Table 1 was used. A pressure-sensitive adhesive composition according to each example was prepared in the same manner as in Example 1-1, using the obtained acrylic polymer. In Example 1-11, 3 parts of an isocyanate crosslinking agent (trade name "Corronate L", 75% acetic acid of trimethylolpropane / tolylene diisocyanate trimer adduct, in place of the epoxy crosslinking agent as a crosslinking agent. An ethyl solution (manufactured by Tosoh Corporation) was used. The obtained pressure-sensitive adhesive composition was used to prepare a substrate-less double-sided adhesive pressure-sensitive adhesive sheet according to Example 1-9 to Example 1-12 in the same manner as Example 1-1.

[23 ° C light pressure bonding initial adhesion]
The adhesive sheet according to each example was cut into a size of 20 mm in width and 100 mm in length to prepare a sample piece. On one adhesive surface of the above-mentioned adhesive sheet, a PET film with a thickness of 50 μm is adhered and backed. In the measurement of the single-sided pressure-sensitive adhesive sheet with a substrate, the above-mentioned backing film is unnecessary. The adhesive surface of the sample piece was crimped to a stainless steel plate (SUS304BA plate) under an environment of 23 ° C. and 50% RH to prepare a measurement sample. The pressure bonding was performed by reciprocating a 0.1 kg roller once. The peel strength [N / 20 mm] of the measurement sample was measured at a tensile speed of 300 mm / min and a peel angle of 180 degrees under an environment of 23 ° C. and 50% RH using a tensile tester. The measurement of the said peeling strength was performed within less than one minute after the sticking to a stainless steel plate. In addition, although "a precision universal testing machine autograph AG-IS 50N" by Shimadzu Corporation Corp. was used as a tensile testing machine, the equivalent measurement result can be obtained also by using the equivalent.

[40 ° C light pressure bonding initial adhesion]
The adhesive sheet which concerns on Example 1-4, Example 1-5, Example 1-9-Example 1-12 was cut into the size of width 20 mm and length 100 mm, and the sample piece was produced. On one adhesive surface of the above-mentioned adhesive sheet, a PET film with a thickness of 50 μm is adhered and backed. In the measurement of the single-sided pressure-sensitive adhesive sheet with a substrate, the above-mentioned backing film is unnecessary. The adhesive surface of the above sample piece is crimped to a stainless steel plate (SUS304BA plate) under the conditions of 0.05 MPa for 3 seconds using a press set at a temperature of 40 ° C. under an environment of 23 ° C. and 50% RH. The measurement sample was prepared. The peel strength [N / 20 mm] of the measurement sample was measured at a tensile speed of 300 mm / min and a peel angle of 180 degrees under an environment of 23 ° C. and 50% RH using a tensile tester. The measurement of the said peeling strength was performed within less than one minute from the crimping | compression-bonding to a stainless steel plate. In addition, although "a precision universal testing machine autograph AG-IS 50N" by Shimadzu Corporation Corp. was used as a tensile testing machine, the equivalent measurement result can be obtained also by using the equivalent.

[Adhesive power after 30 minutes curing]
The adhesive sheet according to each example was cut into a size of 20 mm in width and 100 mm in length to prepare a sample piece. On one adhesive surface of the above-mentioned adhesive sheet, a PET film with a thickness of 50 μm is adhered and backed. In addition, a backing film is unnecessary in the measurement of the single-sided adhesive sheet with a base material. The adhesive surface of the sample piece was crimped to a stainless steel plate (SUS304BA plate) under an environment of 23 ° C. and 50% RH to prepare a measurement sample. The pressure bonding was performed by reciprocating a 2 kg roller once. The measurement sample is allowed to stand in an environment of 23 ° C. and 50% RH for 30 minutes, and then, using a tensile tester, according to JIS Z 0237: 2000, conditions of a tensile speed of 300 mm / min and a peeling angle of 180 °. The peel strength [N / 20 mm] was measured. This value was taken as adhesion after curing for 30 minutes. In addition, although "a precision universal testing machine autograph AG-IS 50N" by Shimadzu Corporation Corp. was used as a tensile testing machine, the equivalent measurement result can be obtained also by using the equivalent.

[Z-axis direction deformation resistance test]
Prepare a polycarbonate (PC) plate 50 of 30 mm in length, 10 mm in width and 2 mm in thickness and a PET film 60 of 100 mm in length, 10 mm in width and 75 μm in thickness as shown in FIG. The PC plate 50 and the PET film 60 were fixed so that one end in the longitudinal direction of the PC plate 50 and the PET film 60 were aligned, and the remaining portion of the PET film 60 was protruded from the other end of the PC plate 50 . A commercially available double-sided pressure-sensitive adhesive tape (manufactured by Nitto Denko, "No. 5000 NS") was used for the above-mentioned fixation.
A pressure-sensitive adhesive sheet sample piece 70 was prepared by cutting the pressure-sensitive adhesive sheet according to each example in which both pressure-sensitive adhesive surfaces were protected by two release liners to a size of 3 mm wide and 10 mm long. The surface of the PC plate 50 opposite to the fixing surface of the PET film is disposed on the upper side, and one release liner is peeled off from the adhesive sheet sample piece 70, and the width direction of the PC plate 50 and the length of the adhesive sheet sample piece 70 Stick the adhesive sheet sample piece 70 on the upper surface of the PC plate 50 so that the widthwise ends of the adhesive sheet sample piece 70 are on the line of 7 mm and 10 mm from the other end on the upper surface of the PC plate 50. Fixed. The above fixing was performed by reciprocating the upper surface protected by the other release liner of the adhesive sheet sample piece 70 with a 2 kg roller once.
Next, in an environment of 23 ° C. and 50% RH, the other release liner of the pressure-sensitive adhesive sheet sample piece 70 stuck to the PC plate 50 is peeled off, and as shown in FIG. Projecting the portion (length 70 mm) from the PC board 50 of the PET film 60 fixed to the back to the PC board 50 side, and make the adhesive sheet sample piece 70 and the other end (free end) of the PET film 60 coincide. The other end of the folded PET film 60 was fixed to the upper surface of the PC plate 50 via the adhesive sheet sample piece 70 by reciprocating a 0.1 kg roller once from the PET film 60. It is observed for 60 minutes whether or not the PET film 60 peels from the adhesive sheet sample piece 70, and the adhesion retention of the adhesive sheet sample piece 70 to the adhesive sheet thickness direction based on the elastic repulsion of the folded PET film 60 is 23 ° C. It evaluated as Z-axis direction deformation resistance. The case where the adhesion state of the adhesive sheet sample piece 70 and the PET film 60 was maintained was determined as “pass”, and the case where the PET film 60 was peeled off as shown in FIG. 7C was determined as “reject”.
About the adhesive sheet which concerns on Example 1-4, Example 1-5, Example 1-9-Example 1-12, 40 degreeC Z-axis direction deformation resistance was further evaluated. In this evaluation method, bonding of the PET film 60 and the adhesive sheet sample piece 70 is not performed by one reciprocation of a roller of 0.1 kg, but using a press set at a temperature of 40 ° C., a condition of 0.05 MPa for 3 seconds I went there. Others evaluated the 40 degreeC Z-axis direction deformation resistance by the method similar to the above.
According to this evaluation method, unlike the conventional evaluation of repulsion resistance, it is possible to evaluate the light pressure bonding initial adhesion and the deformation resistance to a peeling load substantially consisting only of the thickness direction (Z-axis direction) of the adhesive sheet. Further, continuous deformation resistance can be evaluated by further observation over time.

  Mw, Mw / Mn of the acrylic polymer according to each example, G ′ (25 ° C.) [MPa], G ′ (85 ° C.) [MPa], G ′ (40 ° C.) [MPa], G ′ ′ of the pressure-sensitive adhesive layer (25 ° C) [MPa], gel fraction [%], 23 ° C light pressure bonding initial adhesion [N / 20 mm] of adhesive sheet, 40 ° C light pressure bonding initial adhesion [N / 20 mm], adhesion after 30 minutes aging The evaluation results of [N / 20 mm] and Z-axis direction deformation resistance test (23 ° C. and 40 ° C.) are shown in Table 1 together with the monomer composition of the acrylic polymer of each example.

  As shown in Table 1, the storage modulus G ′ (25 ° C.) of the pressure-sensitive adhesive layer is 0.15 MPa or more, G ′ (85 ° C.) is 0.02 MPa or more, and 23 ° C. The pressure-sensitive adhesive sheets of Examples 1-1 to 1-8, in which the initial adhesive strength at 8 ° C. for light pressure bonding is 8 N / 20 mm or more, have light initial pressure bonding at a predetermined pressure bonding temperature, and resistance to deformation in the Z-axis direction The exam was at pass level. Specifically, the adhesive sheet according to Example 1-1 to Example 1-3 and Example 1-6 to Example 1-8 in which the initial bonding strength at 23 ° C. light pressure bonding was 8 N / 20 mm or more is the light pressure bonding at 23 ° C. It had good initial adhesion, and resistance to sustained load in the Z-axis direction under light pressure bonding at 23 ° C. In Examples 1-4 and 1-5, although the light pressure bonding initial adhesion at 23 ° C. was unmeasurable, the 40 ° C. light pressure bonding initial adhesion was good, and the Z axis direction deformation resistance test (40 ° C.) In the above, it had a pass level of deformation resistance. In Examples 1-4 and 1-5, the backing PET film is peeled off in both the 40 ° C. light pressure bonding initial adhesion measurement and the adhesion measurement after curing for 30 minutes, and has a strong adhesion exceeding 20 N / 20 mm. It is thought that On the other hand, the adhesive sheet according to Example 1-9 to Example 1-12 is less than 8 N / 20 mm in both the 23 ° C. light pressure bonding initial adhesion and 40 ° C. light pressure bonding initial adhesion, and 23 ° C. and 40 ° C. The Z-axis direction deformation resistance test performed by pressure bonding was a result of failure. In Examples 1-9 to 1-11, in which the storage elastic modulus G ′ (25 ° C.) was less than 0.15 MPa, the deformation resistance at the initial stage of bonding was low, and this also failed in the Z-axis direction deformation resistance test It is considered to be one of the

«Experiment 2»
[Elastic Repulsion Evaluation in Z-axis Direction Deformation Resistance Test]
The influence of the thickness of the PET film used in the Z-axis direction deformation resistance test was evaluated in order to further improve the deformation resistance to the sustained load in the Z-axis direction. Specifically, a PET film having a length of 100 mm and a width of 50 mm and having a thickness shown in Table 2 is prepared, and each PET film is prepared in the same manner as the Z-axis direction deformation resistance test except that the adhesive sheet is not used. After fixing to a PC board, one end (free end) in the longitudinal direction was folded like a hairpin when viewed from the side to coincide with the other end (fixed end). Then, the free end of the PET film was released from the force holding it, and the return repulsion [N / 50 mm] at that time was read with a commercially available load cell. The results are shown in Table 2.

  As shown in Table 2, as the thickness of the PET film increased, the repelling force of the PET film folded in a hairpin shape increased. Specifically, when the PET films having a thickness of 75 μm and a thickness of 125 μm are compared, the one having a thickness of 125 μm produces about 4.8 times the repulsive force of a thickness of 75 μm.

«Experiment 3»
Based on the results of Experiment 2, test conditions that are more severe than the Z-axis direction deformation resistance test of Experiment 1 were set, and an adhesive sheet capable of withstanding it, that is, capable of exhibiting better deformation resistance was examined. .

<Example 3-1>
In the same manner as in Example 1-8 of Experiment 1, a substrate-less double-sided adhesive pressure-sensitive adhesive sheet (50 μm in thickness) according to this example was produced.

<Example 3-2 to Example 3-6>
Using the same acrylic polymer (Mw 1,320,000, Mw / Mn = 5.85) as the acrylic polymer used in Example 3-1, changing the composition of the tackifier resin and the crosslinking agent, and using the same basic as Example 3-1 The pressure-sensitive adhesive composition according to each example was prepared in the same manner as in the above. A substrate-less double-sided adhesive pressure-sensitive adhesive sheet according to each example was produced in the same manner as in Example 3-1 using the obtained pressure-sensitive adhesive composition.
The (meth) acrylic oligomer used in Example 3-2 and Example 3-3 is the same (meth) acrylic oligomer (Mw 3600) as that used in Example 3-1. In addition, terpene phenol resin A in the table is a trade name “YS Polystar S-145” (softening point about 145 ° C., hydroxyl value 70 to 110 mg KOH / g) manufactured by Yasuhara Chemical Co., Ltd., and terpene phenol resin B is manufactured by Yasuhara Chemical Co. It is a trade name "YS Polystar T-115" (softening point: about 115 ° C, hydroxyl value: 30 to 60 mg KOH / g).

[Z-axis direction deformation resistance test (strong reaction, high temperature, high humidity conditions)]
Using a PET film of 100 mm in length, 10 mm in width, and 125 μm in thickness as the PET film folded back and fixed with the adhesive sheet sample piece, in the same manner as in the Z axis direction deformation resistance test of Experiment 1, The free end of the PET film was fixed by one reciprocation of a 0.1 kg roller in an environment of 23 ° C. and 50% RH, and then exposed to an environment of 65 ° C. and 90% RH. After exposure to the same environment for 72 hours, check whether the adhesion between the adhesive sheet sample piece and the PET film is maintained, and if it is held, the floating height of the PET film from the adhesive sheet sample piece [μm ] Was measured using a microscope. Three measurements were taken and the lowest value recorded. The floating height is a height including the thickness of the adhesive sheet sample piece.
According to this evaluation method, according to the result of Experiment 2, the high temperature and high humidity of 65 ° C. and 90% RH is about the resistance to repulsive force (deformation resistance) which is about 4.8 times the deformation resistance in the Z-axis direction of Experiment 1. It is possible to evaluate under the severe conditions of The PET film does not peel off in this evaluation test, and those with limited float height are excellent in light pressure bonding initial adhesion to a peeling load consisting essentially only of the thickness direction (Z-axis direction) of the adhesive sheet It can be evaluated that it exhibits a particularly excellent resistance (deformation resistance) to a sustained peeling load in the direction, as well as having a property.

  G ′ (25 ° C.) [MPa], G ′ ′ (25 ° C.) [MPa], tan δ (25 ° C.) (G ′ ′ / G ′), G ′ (85 ° C.) [MPa] of the pressure-sensitive adhesive layer according to each example The evaluation results of tan δ (85 ° C.) (G ′ ′ / G ′) and Z-axis direction deformation resistance test (strong reaction, high temperature, high humidity conditions) are shown in Table 3 together with the composition of the adhesive of each example.

As shown in Table 3, it is selected from an acrylic polymer having a Mw of greater than 70 × 10 ⁴ and a dispersion degree (Mw / Mn) of less than 15, a tackifying resin and a (meth) acrylic oligomer The pressure-sensitive adhesive sheet according to Examples 3-1 to 3-5 including the pressure-sensitive adhesive layer including at least one kind is Z at a light compression bonding at 23 ° C. in a Z-axis direction deformation resistance test under strong, high temperature and high humidity conditions. It has excellent deformation resistance to sustained loads in the axial direction. That is, the above-mentioned pressure-sensitive adhesive sheet achieves not only high-temperature thermocompression bonding but both initial adhesion in light compression and deformation resistance to a sustained load in the Z-axis direction, and is excellent even under severe conditions of strong repulsion, high temperature and high humidity. Demonstrated excellent deformation resistance. Among them, in Examples 3-1 to 3-3 in which the tackifying resin and the (meth) acrylic oligomer are used in combination, the floating height after the Z-axis direction deformation resistance test under the conditions of strong repulsion, high temperature, and high humidity is 400 μm or less In particular, it exhibited excellent deformation resistance. On the other hand, the pressure-sensitive adhesive sheet of Example 3-6 in which neither tackifying resin nor (meth) acrylic oligomer was used was a PET film during measurement of the above-mentioned Z axis direction deformation resistance test (strong reaction, high temperature, high humidity condition). Was peeled off, and could not bear the deformation load in the Z-axis direction.

As mentioned above, although the specific example of this invention was described in detail, these are only an illustration and do not limit a claim. The art set forth in the claims includes various variations and modifications of the specific examples illustrated above.

1,2,3,4,5,6 Adhesive sheet 10 Base material 21,22 Adhesive layer 31,32 Release liner

Claims (18)

An acrylic polymer as a base polymer, and at least one selected from a tackifying resin and a (meth) acrylic oligomer;
The weight average molecular weight of the acrylic polymer is greater than 70 × 10 ⁴ ,
The acrylic adhesive composition whose dispersion degree (Mw / Mn) of the said acrylic polymer is less than 15.   The acrylic pressure-sensitive adhesive composition according to claim 1, wherein the acrylic polymer is polymerized in a proportion of 50% by weight or more of an alkyl (meth) acrylate having an alkyl group having 1 to 6 carbon atoms at an ester end. object.   The acrylic adhesive composition according to claim 1 or 2, wherein the acrylic polymer is copolymerized with an acidic group-containing monomer.   The pressure-sensitive adhesive sheet according to claim 3, wherein the copolymerization ratio of the acidic group-containing monomer in the acrylic polymer is less than 10% by weight.   The acrylic pressure-sensitive adhesive composition according to any one of claims 1 to 4, wherein the tackifying resin is contained in a ratio of less than 30 parts by weight with respect to 100 parts by weight of the acrylic polymer.   The acrylic pressure-sensitive adhesive composition according to any one of claims 1 to 5, wherein the (meth) acrylic oligomer is contained in a ratio of less than 30 parts by weight with respect to 100 parts by weight of the acrylic polymer. .   The acrylic adhesive composition as described in any one of Claims 1-6 containing both the said tackifying resin and the said (meth) acrylic-type oligomer. And an acrylic pressure-sensitive adhesive layer comprising an acrylic polymer as a base polymer and at least one selected from a tackifying resin and a (meth) acrylic oligomer.
The weight average molecular weight of the acrylic polymer is greater than 70 × 10 ⁴ ,
The adhesive sheet whose dispersion degree (Mw / Mn) of the said acryl-type polymer is less than 15. A pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer,
The pressure-sensitive adhesive layer has a storage modulus G ′ (25 ° C.) at 25 ° C. of 0.15 MPa or more, and a storage modulus G ′ (85 ° C.) at 85 ° C. of 0.02 MPa or more,
180 ° peel strength measured within 1 minute after crimping under conditions of 23 ° C. and 0.1 kg of crimping load, and 180 ° peeling measured within 1 minute after crimping under conditions of 40 ° C., 0.05 MPa and 3 seconds A pressure-sensitive adhesive sheet satisfying that at least one of the strengths is 8 N / 20 mm or more.   The pressure-sensitive adhesive sheet according to claim 8, wherein a gel fraction of the pressure-sensitive adhesive layer is 40% by weight or more.   The pressure-sensitive adhesive sheet according to claim 9, wherein the pressure-sensitive adhesive layer is an acrylic pressure-sensitive adhesive layer containing an acrylic polymer.   12. The pressure-sensitive adhesive sheet according to claim 8, wherein the acrylic polymer is copolymerized with 50% by weight or more of an alkyl (meth) acrylate having an alkyl group having 1 to 6 carbon atoms at an ester end. .   The pressure-sensitive adhesive sheet according to claim 8, wherein the acrylic polymer has a copolymer containing an acidic group-containing monomer.   The pressure-sensitive adhesive sheet according to claim 13, wherein the acidic group-containing monomer is acrylic acid.   The pressure-sensitive adhesive sheet according to claim 13, wherein a copolymerization ratio of the acidic group-containing monomer in the acrylic polymer is less than 10% by weight.   The pressure-sensitive adhesive sheet according to any one of claims 8, 11, 12, 13, 14 or 15, wherein the acrylic polymer is crosslinked.   The pressure-sensitive adhesive sheet according to any one of claims 8 to 16, which is used to fix a member in a portable electronic device. The pressure-sensitive adhesive sheet according to any one of claims 8 to 17, which is used to fix a flexible printed wiring board.

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