adhesive sheet

Abstract

To provide an adhesive sheet which has excellent step absorbency, is suitable for punching during processing, and is also excellent in heat shock resistance during use. The present invention provides a pressure-sensitive adhesive sheet containing an acrylic resin, the pressure-sensitive adhesive sheet comprising a compound represented by the following formula (1): 100 =(G 100 ´ 2 +G 100 " 2 ) 1 / 2 (1) G calculated from 100 , and The following formula (2) D = (180° / π) × tan -1 (G 100 ″ / G 100 ´) (2) D is calculated from the following formula (3): G 25 =(G 25 ´ 2 +G 25 " 2 ) 1 / 2 (3) G calculated from 25 A function F(G 25 ,G 100 ,D) G 25 <200, the function F(G 25 ,G 100 , D) is 0 or greater, and G 25 ≧200, the function F(G 25 ,G 100 ,D) is greater than or equal to 0.

Description

[Technical Field]

[0001] The present invention relates to a pressure-sensitive adhesive sheet. [Background technology]

[0002] Adhesive sheets are widely used in a variety of fields, for example, for bonding components (adherends) together. Optical adhesive sheets are used in display devices such as liquid crystal displays (LCDs), or input devices incorporating touch sensors to serve as touch panels. Because their refractive index is closer than that of air to the glass and plastic components of these devices, they function to fill the air gaps between components during bonding, thereby improving the light transmittance of the entire device. However, because optical adhesive sheets are transparent, they must maintain uniform bonding across the entire bonding surface throughout the operating environment.

[0003] Touch panels and liquid crystal displays often contain components with unevenness caused by printing or other factors. For example, in touch panels, wiring for supplying power and circuits for calculating touch position are arranged around a transparent sensor mesh, which requires a colored layer several tens of micrometers thick to be formed around the cover material to conceal them. Therefore, the adhesive sheet to which the cover material is attached must be able to absorb the unevenness of the colored layer. Furthermore, in recent years, the use environments of touch panels have become more diverse, including in-vehicle and factory applications, and they are required to be able to adapt to the expansion and contraction of components due to harsh usage environments, particularly thermal shock at high and low temperatures. For this reason, optical adhesive sheets for touch panels are required to have excellent unevenness-conforming properties and stress relaxation properties. For example, Patent Document 1 discloses an adhesive sheet (thermosetting OCA) in which an acrylic polymer is crosslinked with an isocyanate compound and has a storage modulus of 100 kPa or less at 100°C, and Patent Document 2 discloses an adhesive sheet (ultraviolet-curing OCA) in which an acrylic polymer is crosslinked with a polyfunctional acrylic monomer and has a storage modulus of 30 kPa or more at 23°C.

[0004] Furthermore, when processing touch panels, the adhesive sheet is cut to the size of the touch panel using a punching machine, but if the viscoelastic properties are poorly designed, the cut surface may be disrupted or the sheet may stick to the release film, making it impossible to peel off. Therefore, from the perspective of time efficiency and yield during processing, processing suitability, and in particular punching suitability, is important. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2024-15435 [Patent Document 2] Japanese Patent Application Laid-Open No. 2024-55985 Summary of the Invention [Problem to be solved by the invention]

[0006] Conventional approaches to level difference absorption, as described in prior art documents, have focused primarily on the storage modulus of material design to achieve level difference absorption within a limited range for a specific material configuration. However, the required level difference absorption is not just about filling the gap; it is also essential for practical use to have the ability to adapt to various harsh environments, particularly temperature changes, and processability. While these functions may be influenced by the chemical bond between specific functional groups in the adhesive components and the adherend, physical properties such as viscoelasticity are fundamental. Since the prior art documents all focused only on the storage modulus of viscoelastic properties, they did not necessarily comprehensively satisfy level difference absorption and processability regardless of curing conditions.

[0007] The present invention has been made in view of the above, and aims to provide a pressure-sensitive adhesive sheet that has excellent step absorbency, is suitable for punching during processing, and also has excellent heat shock resistance during use. [Means for solving the problem]

[0008] As a result of intensive research conducted by the inventors to achieve the above object, the present inventors have found a judgment formula F(G) that uses the elastic modulus G and parameter D calculated from the storage elastic modulus and loss elastic modulus at a specific temperature obtained by a viscoelasticity measuring device as viscoelastic properties, specifically, G at 25°C, G at 100°C, and D at 100°C as variables. 25 ,G 100 ,D 100 ) is 0 or more, the above object can be achieved, and the present invention has been completed based on this finding.

[0009] More specifically, the aforementioned G and D are physical properties specific to viscoelastic materials such as pressure-sensitive adhesive compositions, and represent dynamic viscoelasticity that varies depending on temperature and time rate, with temperature and time rate being known to be inversely correlated. Specifically, when G and D are measured at a constant time rate and varying temperature, measurements at low temperatures represent short-term rate behavior, while measurements at high temperatures represent long-term rate behavior. The present inventors focused on G and D measured at a fixed time rate of 1 Hz and varying temperatures. Since the step absorbency, one of the objectives, is the allowable deformation of a pressure-sensitive adhesive composition when a pressure of about 5 atmospheres is continuously applied for about 30 minutes at 40 to 60°C, the inventors concluded that G and D measured at 100°C represent the quality of step absorbency. Specifically, D, which physically represents energy absorption, represents the dissipation of frictional energy generated by the shear movement of polymer chains in an adhesive composition. A larger D facilitates shear movement of polymer chains, increasing the allowable deformation amount, which is advantageous for level difference absorption and broadening the range of G that satisfies level difference absorption. Furthermore, since G represents the amount of deformation of an adhesive composition in response to stress (pressure), we have found that there is an upper limit to G that satisfies level difference absorption, and that this upper limit depends on D. Furthermore, since punching suitability, one of the objectives, specifically refers to the resistance to deformation caused by the instantaneous impact of a punching blade, we have found that G at low or normal temperatures is an appropriate representative value for punching suitability. Physically, the changes in G and D with temperature are due to changes in the ratio between the thermal vibration of polymer chains and intermolecular forces. Reversals between different adhesive compositions are unlikely to occur at adjacent temperatures. Therefore, we concluded that for long-term properties, 100°C is appropriate, which is sufficiently higher than the operating temperature, including lamination, and for short-term properties, 25°C, which is close to the operating temperature, is appropriate. The reason for choosing 25°C is that if the temperature is higher than 25°C, the correlation with 100°C becomes stronger, making it meaningless to add more parameters. Also, the glass transition temperature, at which the physical properties of the viscoelastic material change significantly, may be below about 20°C, making direct comparison of data around Tg inappropriate. We found that a G of about 200 kPa at 25°C provides the best balance of all the above objectives, and that the allowable range widens as D at 100°C increases. Regarding heat shock resistance, if G at 25°C is below a certain level, the residual stress caused by distortion due to temperature contraction and expansion of the components to which the adhesive sheet is bonded (the component in contact with the first surface of the adhesive sheet and the component in contact with the second surface) will be small, and peeling due to heat shock can be suppressed, and if D at 100°C is above a certain level, the effects of heat shock can be absorbed by stress relaxation due to deformation of the adhesive before the adhesive surface peels off due to residual stress. As a result of the above research, specifically, a judgment formula F(G) was established, with variables G at 25°C, G at 100°C, and D at 100°C. 25 ,G 100 ,D 100) is 0 or more, the above object can be achieved, and the present invention has been completed based on this finding.

[0010] That is, the present invention includes, for example, the subject matter described in the following sections. Item 1 A pressure-sensitive adhesive sheet containing an acrylic resin, Storage modulus G obtained from dynamic viscoelasticity measurement at a frequency of 1 Hz and a temperature of 100°C 100 ´ (kPa) and loss modulus G 100 Based on the pressure (kPa), the following formula (1) G 100 =(G 100 ´ 2 +G 100 " 2 ) 1 / 2 (1) G calculated from 100 , and The following formula (2) D = (180° / π) × tan -1 (G 100 ″ / G 100 ´) (2) D calculated from, and Storage modulus G obtained from dynamic viscoelasticity measurement at a frequency of 1 Hz and a temperature of 25°C 25 ´ (kPa) and loss modulus G 25 Based on the pressure (kPa), the following equation (3) G 25 =(G 25 ´ 2 +G 25 " 2 ) 1 / 2 (3) G calculated from 25 , A function F(G 25 ,G 100 ,D) G 25 <200, the function F(G 25 ,G 100 ,D) F(G 25 ,G 100 ,D)=G 25 -2G 100+4D-260 (4) is greater than or equal to 0, G 25 ≧200, the function F(G 25 ,G 100 ,D) F(G 25 ,G 100 ,D)=-G 25 -2G 100 +4D+140 (5) is 0 or greater. Section 2 Item 1. The pressure-sensitive adhesive sheet according to item 1, which is for use in a vehicle. Section 3 Item 3. A pressure-sensitive adhesive sheet with a release sheet, comprising the pressure-sensitive adhesive sheet according to item 1 or 2. Section 4 Item 3. A method for producing a pressure-sensitive adhesive sheet with a release sheet, comprising: The thickness of the pressure-sensitive adhesive sheet is 50 μm or more and 350 μm or less, a laminate obtained by laminating a polyester film coated with a release agent having a thickness of 50 μm or more and 100 μm or less on one surface of the pressure-sensitive adhesive sheet so that the release-agent-coated surface is in contact with the polyester film; A manufacturing method comprising a step of laminating a polyester film coated with a release agent having a thickness of 25 μm or more and 75 μm or less so that the release agent-coated surface of the polyester film is in contact with the other surface of the pressure-sensitive adhesive sheet. Section 5 Item 3. A method for producing a pressure-sensitive adhesive sheet with a release sheet, comprising: The thickness of the pressure-sensitive adhesive sheet is 50 μm or more and 350 μm or less, a step of applying a pressure-sensitive adhesive composition to a release agent-coated surface of a polyester film coated with a release agent having a thickness of 50 μm or more and 100 μm or less to form a coating film; a step of laminating a polyester film coated with a release agent having a thickness of 25 μm or more and 75 μm or less so that the release agent-coated surface of the polyester film is in contact with the exposed surface of the coating film; and curing the coating film by irradiating it with active energy rays to form the pressure-sensitive adhesive sheet. Section 6 The acrylic resin The adhesive has a structure in which an acrylic adhesive resin containing at least a (meth)acrylic acid ester unit and a monomer unit having a crosslinkable functional group is crosslinked with a thermal crosslinking agent, 3. The pressure-sensitive adhesive sheet according to claim 1, wherein the pressure-sensitive adhesive sheet has a gel fraction of 50% or less. [Effects of the Invention]

[0011] The pressure-sensitive adhesive sheet of the present invention has excellent step absorbency, is suitable for punching during processing, and also has excellent heat shock resistance during use. DETAILED DESCRIPTION OF THE INVENTION

[0012]

[0023] In the present specification, the terms "contain" and "comprise" include the concepts of "contain," "comprise," "consist essentially of," and "consist only of."

[0013] In the numerical ranges described in stages in this specification, the upper or lower limit of a certain numerical range can be arbitrarily combined with the upper or lower limit of another numerical range. In the numerical ranges described in this specification, the upper or lower limit of the numerical range may be replaced with a value shown in an example or a value that can be unambiguously derived from an example. In addition, in this specification, numerical values ​​connected with "to" mean a numerical range that includes the numbers before and after "to" as the lower and upper limits.

[0014] The pressure-sensitive adhesive sheet of the present invention is a pressure-sensitive adhesive sheet containing an acrylic resin, Storage modulus G obtained from dynamic viscoelasticity measurement at a frequency of 1 Hz and a temperature of 100°C 100 ´ (kPa) and loss modulus G 100 Based on the pressure (kPa), the following formula (1) G 100 =(G 100 ´ 2 +G 100 " 2 ) 1 / 2 (1) G calculated from 100 , and The following formula (2) D = (180° / π) × tan -1 (G 100 ″ / G 100 ´) (2) D calculated from, and Storage modulus G obtained from dynamic viscoelasticity measurement at a frequency of 1 Hz and a temperature of 25°C 25 ´ (kPa) and loss modulus G 25 Based on the pressure (kPa), the following equation (3) G 25 =(G 25 ´ 2 +G 25 " 2 ) 1 / 2 (3) G calculated from 25 , A function F(G 25 ,G 100 ,D) G 25 <200, the function F(G 25 ,G 100 ,D) F(G 25 ,G 100 ,D)=G 25 -2G 100 +4D-260 (4) is greater than or equal to 0, G 25 ≧200, the function F(G 25 ,G 100 ,D) F(G 25 ,G 100 ,D)=-G 25 -2G 100 +4D+140 (5) is greater than or equal to 0.

[0015] The pressure-sensitive adhesive sheet of the present invention has excellent step absorbency, is resistant to environmental changes, particularly temperature changes, after lamination, and is suitable for punching during processing. Moreover, the pressure-sensitive adhesive sheet of the present invention also has excellent heat shock resistance during use. Therefore, the pressure-sensitive adhesive sheet of the present invention is suitable for optical touch panels used in various applications, and is particularly suitable for use in vehicles.

[0016] As mentioned above, G 100 , G 25 , and D are calculated using a predetermined formula. The physical behavior (mechanical behavior) of a viscoelastic body is affected by both the storage modulus G' (kPa) and the loss modulus G" (kPa). As a parameter that reflects the influence of both, G, which reflects the absolute value, is 100 and G 25 The inventor has devised a value D that reflects the ratio.

[0017] Here, the inventors have 100 and G 25 is named the modulus of elasticity (units are kPa unless otherwise specified). The reason for this is that when the inventor measured the stress σ and strain ε of an adhesive sheet using a tensile tester for measuring the modulus of elasticity (also called Young's modulus) of an elastic body, the ratio of these was found to be roughly equal to the modulus of elasticity G. The word "roughly" is used to describe a viscoelastic body such as an adhesive sheet, since there is no region of ε where the ratio of σ to ε is constant, as in an elastic body, and therefore the ratio is said to be roughly equal when compared with the ratio of σ at a specific ε. Generally, (G' 2 +G″ 2 ) 1 / 2 The technical term for this is "complex modulus." However, for the reasons stated above, in this specification, G 100 and G 25 is expressed as the elastic modulus.

[0018] Viscoelastic materials exhibit different viscoelastic properties depending on the temperature and time scale. The inventors measured the viscoelastic properties of several types of PSA sheets using a viscoelasticity measuring device at a time scale of 1 Hz frequency over a temperature range of -30°C to 130°C, and after extensive investigation into the combinations and ranges of variables that satisfy the requirements for level difference absorbency, punching suitability, and heat shock resistance, they were able to derive the judgment formulas (4) and (5) above.

[0019] Equations (4) and (5) can also be derived by classification analysis using machine learning. Specifically, at least 20 different types of PSA sheets are prepared and evaluated for their step absorption, punching suitability during processing, and heat shock resistance during use, and equations (4) and (5) can be derived based on the evaluation results.

[0020] The technology disclosed in Patent Document 2 uses "displacement length in a holding power test" as a parameter, but while this parameter depends on the thickness of the sample (adhesive sheet), other parameters specified in the document, such as tensile modulus and dielectric constant, do not depend on thickness. In other words, because the technology disclosed in Patent Document 2 includes both parameters that depend on thickness and parameters that do not depend on thickness, it is not possible to take into account the influence of thickness, which may make it impossible to accurately grasp the properties of the adhesive sheet.

[0021] In contrast, in the present invention, the elastic moduli G and D are both parameters that are independent of thickness and are valid regardless of the thickness of the final product, making it possible to accurately predict the physical properties of the adhesive sheet (step absorption ability, punching suitability, heat shock resistance).

[0022] As described above, the pressure-sensitive adhesive sheet of the present invention is 25 <200, the function F(G 25 ,G 100 , D) is 0 or more. This allows the pressure-sensitive adhesive sheet of the present invention to have excellent level difference absorbency, be suitable for punching during processing, and also have excellent heat shock resistance during use.25 <200, the function F(G 25 ,G 100 , D) is below 0, the PSA sheet will have reduced performance in one or more of the following: step absorption, punchability during processing, and heat shock resistance. 25 <200, the function F(G 25 ,G 100 , D) is not particularly limited, and is, for example, 20 or less, preferably 15 or less, and more preferably 10 or less. 25 <200, the function F(G 25 ,G 100 , D) has no particular lower limit, and is, for example, 0 or more, preferably 3 or more, and more preferably 5 or more.

[0023] As described above, the pressure-sensitive adhesive sheet of the present invention is 25 ≧200, the function F(G 25 ,G 100 , D) is 0 or more. This allows the pressure-sensitive adhesive sheet of the present invention to have excellent level difference absorbency, be suitable for punching during processing, and also have excellent heat shock resistance during use. 25 ≧200, the function F(G 25 ,G 100 , D) is below 0, the PSA sheet will have reduced performance in one or more of the following: step absorption, punchability during processing, and heat shock resistance. 25 ≧200, the function F(G 25 ,G 100 , D) is not particularly limited, and is, for example, 20 or less, preferably 15 or less, and more preferably 10 or less. 25 ≧200, the function F(G 25 ,G 100 , D) has no particular lower limit, and is, for example, 0 or more, preferably 3 or more, and more preferably 5 or more.

[0024] G 100is a parameter that affects the mechanical behavior over a long time scale, specifically G 100 By keeping the pressure at about 20 kPa or less, the adhesion property is improved when pressure is applied continuously for about 30 minutes, and the level difference absorption property is improved. 25 is a parameter that affects mechanical behavior on a short time scale; specifically, by setting it to around 200 kPa, it is possible to reduce the overflow of glue due to deformation during punching, improving punching suitability.

[0025] In the pressure-sensitive adhesive sheet of the present invention, the storage modulus G 100 ´ and loss modulus G 100 ″ and storage modulus G 25 ´ and loss modulus G 25 " is a value measured using a dynamic viscoelasticity apparatus "MCR301 (manufactured by Anton Paar)". Specifically, the storage modulus and loss modulus can be measured by using a probe with a diameter of 8 mm and applying a repeated strain of 0.1% at a cycle of 1 Hz while changing the temperature in the measurement chamber from -65°C to 130°C at a temperature increase rate of 3°C / min. Also, by analyzing the waveforms of the stress response σ to the strain input ε at 25°C and 100°C, the amplitude ratio G and phase difference D of ε and σ can be obtained. In this specification, the storage modulus G 100 ´ and loss modulus G 100 ″ and storage modulus G 25 ´ and loss modulus G 25 All units are in kPa unless otherwise specified.

[0026] D is a parameter that has a positive correlation with energy absorption. From the viewpoint of easily suppressing peeling after lamination, D is preferably 25 degrees or more, more preferably 30 degrees or more, and most preferably 35 degrees or more. G 25 is preferably 50 kPa or more, more preferably 80 kPa or more, and most preferably 100 kPa or more. 25 is preferably 500 kPa or less, more preferably 400 kPa or less, and most preferably 300 kPa or less. 100is preferably 0 kPa or more, more preferably 5 kPa or more, and most preferably 10 kPa or more. 100 is preferably 50 kPa or less, more preferably 40 kPa or less, and most preferably 30 kPa or less.

[0027] The elastic modulus G is a parameter that indicates stress relative to strain, and thus correlates with the resistance to stretching (hardness) of the PSA sheet. Meanwhile, D is a phase lag corresponding to heat loss (energy absorption) due to viscosity. At high speeds or low temperatures, the sheet becomes hard (solid-like), while at low speeds or high temperatures, it becomes soft (liquid-like). In other words, speed and temperature have opposite effects. In the present invention, the temperature is continuously changed from -65°C to 130°C at a constant speed (1 Hz) to measure the temperature characteristics of the elastic modulus G and D, which allows the design of a desired PSA sheet. The elastic modulus G and D are also indicators of the ease of shear movement between polymer chains in the PSA composition (described below). Therefore, they can be adjusted by the average molecular weight and degree of crosslinking of the PSA composition or the irradiance of active energy rays (ultraviolet rays) on the PSA composition. The stronger the thermal motion of the polymer molecules, the easier they are to shear, while the stronger the intermolecular forces, the more difficult they are to shear. Since thermal motion increases with increasing temperature, it is presumed that the characteristics of a pressure-sensitive adhesive composition will be revealed in the difference in the properties of the elastic moduli G and D between the low temperature range where intermolecular forces are dominant and the high temperature range where thermal motion is dominant. Based on this, in the present invention, 25°C is selected as the low temperature range and 100°C as the high temperature range, and a pressure-sensitive adhesive sheet can be designed using the function F based on the elastic moduli G and D at each temperature.

[0028] The pressure-sensitive adhesive sheet of the present invention has a function F(G 25 ,G 100 The type of the adhesive is not particularly limited as long as the value of (D) is 0 or greater, and for example, a wide range of adhesive sheets containing known acrylic resins can be used. Therefore, the adhesive sheet of the present invention can be produced using, for example, an adhesive composition containing an acrylic adhesive resin.

[0029] Here, the behavior of the elastic modulus G differs between low (25°C) and high (100°C) temperatures. As the average molecular weight of acrylic adhesive resins (described below) increases, the intermolecular forces between polymers become stronger, making shear more difficult, resulting in a higher elastic modulus G. However, at high temperatures, thermal motion increases, reducing the effect of increased intermolecular forces. Therefore, the contribution of the average molecular weight to the elastic modulus G is greater at low temperatures and smaller at high temperatures. On the other hand, crosslinking is due to covalent bonds that are stronger than intermolecular forces, so the influence of thermal motion is small. The degree of crosslinking correlates with the elastic modulus G independently of temperature, but the degree of correlation varies depending on the crosslinking method (bonding method). Specifically, epoxy-based crosslinking is relatively stronger than isocyanate-based or multifunctional acrylate crosslinking, resulting in a higher elastic modulus G at both low and high temperatures. Because D increases with increased shear, the correlation between the average molecular weight, degree of crosslinking, and type of crosslinking tends to be inverse to that of the elastic modulus G. With UV curing, the irradiance and average molecular weight are inversely correlated. Taking the above into consideration, the desired adhesive sheet can be obtained by appropriately adjusting the type of acrylic adhesive resin, crosslinking structure, and curing method.

[0030] (acrylic adhesive resin) The acrylic adhesive resin contained in the adhesive composition is the main component of the adhesive sheet of the present invention, and is a component that serves as the so-called base polymer of the adhesive sheet.

[0031] The acrylic adhesive resin may contain an acrylic polymer (P1) as an essential component. The acrylic adhesive resin may contain an acrylic polymer (P1) as an essential component and may further contain a polymerizable monomer. In this case, the adhesive resin is a solution (also known as a syrup) in which the acrylic polymer (P1) is dissolved in the polymerizable monomer, and may also be referred to as a partial polymerization product of the acrylic polymer (P1). More specifically, the adhesive resin may contain the acrylic polymer (P1) and a polymerizable monomer of the same type as the monomer for constituting the acrylic polymer (P1).

[0032] The acrylic polymer (P1) can be, for example, a wide variety of known acrylic polymers used to form pressure-sensitive adhesive sheets. For example, the acrylic polymer (P1) can be a polymer of a (meth)acrylic acid ester and a monomer having a crosslinkable functional group that is copolymerizable with the (meth)acrylic acid ester. That is, the acrylic polymer (P1) can contain a (meth)acrylic acid ester unit and a monomer unit having a crosslinkable functional group.

[0033] Examples of (meth)acrylic acid esters include (meth)acrylates having a linear or branched alkyl group, and (meth)acrylates having a ring structure. When the (meth)acrylate has a linear or branched alkyl group, the number of carbon atoms therein can be, for example, 1 to 20, preferably 1 to 15, and more preferably 2 to 10. When the (meth)acrylate has an aromatic ring, the number of carbon atoms therein can be, for example, 5 to 20, preferably 6 to 10.

[0034] Specific examples of (meth)acrylates having a linear or branched alkyl group include methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, t-butyl (meth)acrylate, isopropyl (meth)acrylate, isooctyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, lauryl (meth)acrylate, cetyl (meth)acrylate, stearyl (meth)acrylate, and behenyl (meth)acrylate.

[0035] The (meth)acrylate having a ring structure is preferably a (meth)acrylic monomer having an alicyclic or aromatic ring, and more preferably a (meth)acrylic monomer having an alicyclic ring. Examples of the alicyclic ring include cyclopropane, cyclobutane, cyclopentane, cyclohexane, cycloheptane, cyclooctane, cyclononane, cyclodecane, cycloundecane, cyclododecane, norbornene, norbornadiene, dicyclopentane, tetrahydrofuran, and tetrahydropyran. The alicyclic ring may have a spiro structure. Examples of the aromatic ring include benzene, naphthalene, anthracene, pyridine, furan, benzofuran, pyrrole, thiophene, imidazole, and oxazole. Among these, the ring structure is preferably an alicyclic ring, more preferably at least one selected from cyclohexane, dicyclopentane, isobornyl, and benzene, and particularly preferably cyclohexane. The above-mentioned ring structure may further have a substituent. Examples of the substituent include substitutable substituents selected from a halogen atom, a halogenated alkyl group, an alkyl group, an alkenyl group, an acyl group, a hydroxy group, a hydroxyalkyl group, an alkoxy group, an aryl group, a heteroaryl group, an alicyclic group, a cyano group, an epoxy group, an oxetanyl group, a mercapto group, an amino group, and a (meth)acryloyl group.

[0036] The (meth)acrylate having a ring structure preferably has a structure in which a monovalent group having a ring structure is bonded to the ester oxygen of the (meth)acrylate (i.e., it is a (meth)acrylate having a cyclic side chain). In this case, the monovalent group having a ring structure preferably has 3 to 12 carbon atoms, more preferably 4 to 10 carbon atoms, and even more preferably 4 to 8 carbon atoms.

[0037] Specific examples of (meth)acrylates having a ring structure include cyclohexyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, isobornyl (meth)acrylate, benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, 3-phenoxybenzyl (meth)acrylate, O-phenylphenoxyethyl (meth)acrylate, etc. In terms of facilitating the formation of a pressure-sensitive adhesive sheet with excellent outgassing resistance, the (meth)acrylate having a ring structure is preferably one or more selected from the group consisting of cyclohexyl (meth)acrylate and isobornyl (meth)acrylate, and more preferably cyclohexyl (meth)acrylate.

[0038] The (meth)acrylic acid ester constituting the acrylic polymer (P1) is preferably at least one selected from the group consisting of methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, t-butyl (meth)acrylate, isopropyl (meth)acrylate, isooctyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and cyclohexyl (meth)acrylate.

[0039] The (meth)acrylic acid ester unit contained in the acrylic polymer (P1) may be of one type alone or may be of two or more types.

[0040] On the other hand, the monomer for constituting the monomer unit having a crosslinkable functional group can be a wide variety of monomers other than the (meth)acrylic acid esters and having a crosslinkable functional group in the molecule. The type of the crosslinkable functional group is not particularly limited, and examples thereof include a carboxyl group, a hydroxyl group, an amino group, and a glycidyl group.

[0041] Examples of the monomer having a crosslinkable functional group in the molecule include a carboxyl group-containing (meth)acrylate unit, a hydroxy group-containing (meth)acrylate unit, an amino group-containing (meth)acrylate unit, and a glycidyl group-containing (meth)acrylate unit.

[0042] Examples of the carboxyl group-containing (meth)acrylate include acrylic acid and methacrylic acid.

[0043] Examples of hydroxy group-containing (meth)acrylates include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 3-chloro-2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 5-hydroxypentyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 2-hydroxy3-phenoxypropyl (meth)acrylate, 2,2-dimethyl 2-hydroxyethyl (meth)acrylate, 3-chloro 2-hydroxypropyl (meth)acrylate, 2-hydroxy3-phenoxypropyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, and polyalkylene glycol mono(meth)acrylate.

[0044] Examples of the amino group-containing (meth)acrylate include (meth)acrylamide, allylamine, etc. Examples of the glycidyl group-containing (meth)acrylate unit include glycidyl (meth)acrylate, etc.

[0045] The monomer for constituting the monomer unit having a crosslinkable functional group preferably includes one or more selected from the group consisting of carboxyl group-containing (meth)acrylates and hydroxy group-containing (meth)acrylates, and more preferably a hydroxy group-containing (meth)acrylate. Of these, the hydroxy group-containing (meth)acrylate is preferably one or more selected from the group consisting of 2-hydroxyethyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and 6-hydroxyhexyl (meth)acrylate.

[0046] The acrylic polymer (P1) may contain one type of monomer unit having a crosslinkable functional group, or two or more types of monomer units.

[0047] In the acrylic polymer (P1), the content ratio of the (meth)acrylic acid ester units and the monomer units having a crosslinkable functional group is not particularly limited. For example, the acrylic polymer (P1) preferably contains the (meth)acrylic acid ester units in an amount of 40% by mass or more, more preferably 50% by mass or more, even more preferably 60% by mass or more, and particularly preferably 70% by mass or more, and preferably 95% by mass or less, more preferably 90% by mass or less, even more preferably 85% by mass or less, and particularly preferably 80% by mass or less.

[0048] In these cases, the remaining monomer units of the acrylic polymer (P1) are preferably monomer units having a crosslinkable functional group, and are preferably carboxyl group-containing (meth)acrylate units and / or hydroxy group-containing (meth)acrylate units. Specifically, the content of the monomer units having a crosslinkable functional group in the acrylic polymer (P1) is preferably 0.1% by mass, more preferably 5% by mass or more, even more preferably 10% by mass or more, even more preferably 15% by mass or more, particularly preferably 20% by mass or more, and preferably 60% by mass or less, more preferably 50% by mass or less, even more preferably 40% by mass or less, particularly preferably 30% by mass or less.

[0049] The acrylic polymer (P1) may contain other monomer units than those described above, as long as the effects of the present invention are not impaired. The content of the other monomer units may be 20% by mass or less, preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably 1% by mass or less. The acrylic polymer may be composed only of (meth)acrylic acid ester units and monomer units having a crosslinkable functional group. The proportion (molar ratio) of each structural unit in the acrylic polymer can be considered to be the same as the molar ratio of each monomer used in producing the polymer.

[0050] The weight average molecular weight of the acrylic polymer (P1) is preferably greater than 200,000, more preferably 300,000 or more, even more preferably 350,000 or more, and particularly preferably 400,000 or more. The weight average molecular weight of the acrylic polymer (P1) is preferably 1,500,000 or less, more preferably 1,000,000 or less, even more preferably 800,000 or less, and particularly preferably 500,000 or less. In these cases, G 25 As a result, it becomes easier to adjust the function F expressed by the formula (4) or (5) to 0 or more.

[0051] The weight-average molecular weight referred to in the present invention refers to the weight-average molecular weight measured in terms of polystyrene by gel permeation chromatography (GPC). There are no particular limitations on the GPC equipment used in the GPC method. Commercially available GPC measuring instruments, such as the LC-2000Plus series manufactured by JASCO Corporation, with detectors such as RI-2031Plus and UV-2075Plus, can be used. In this case, for example, a GPC column consisting of four columns connected together, including "Shodex KF801," "Shodex KF803L," "Shodex KF800L," and "Shodex KF800D" manufactured by Showa Denko K.K., can be used. The column temperature can be set to 40°C. Tetrahydrofuran is used as the eluent, and measurements are performed at a flow rate of 1.0 ml / min. Typically, a calibration curve is prepared using standard polystyrene, and the weight-average molecular weight (Mw) can be calculated in terms of polystyrene.

[0052] The acrylic polymer (P1) can be produced by a known method. For example, the acrylic polymer can be produced by polymerizing a monomer mixture for forming each structural unit by a known polymerization method. Examples of the polymerization method that can be used include solution polymerization, bulk polymerization, suspension polymerization, and emulsion polymerization. The acrylic polymer can also be obtained from a commercial product.

[0053] The glass transition temperature (Tg) of the acrylic polymer (P1) is not particularly limited, and may be, for example, 0°C or lower, preferably -10°C or lower, more preferably -20°C or lower, and preferably -80°C or higher, more preferably -70°C or higher, even more preferably -60°C or higher, and particularly preferably -50°C or higher.

[0054] The method for adjusting the glass transition temperature of the acrylic polymer (P1) is not particularly limited, and the glass transition temperature can be adjusted to a desired range by, for example, changing the type and composition ratio of the monomers constituting the acrylic polymer (P1). In the present invention, the glass transition temperature of the acrylic polymer (P1) refers to Tg, which is calculated by the following Fox formula based on the composition of the monomers used in the synthesis of the copolymer: Fox formula: 1 / Tg = (W1 / Tg1) + (W2 / Tg2) + + (Wm / Tgm) where W1+W2+···+Wm=1 In the formula, Tg is the glass transition temperature (unit: K) of the acrylic polymer (P1), Tg1, Tg2, ..., Tgm are the glass transition temperatures of the respective homopolymers of m types of monomers (m is an integer) that constitute the acrylic polymer (P1), and W1, W2, ..., Wm are the mass fractions of each structural unit in the acrylic polymer (P1). Note that Tg1 and W1 correspond to each other; that is, the monomer that constitutes the homopolymer that exhibits the glass transition temperature of Tg1 is the same as the monomer that forms the structural unit whose mass fraction is W1. Similarly, Tg2 and W2, ..., Tgm and Wm correspond to each other.

[0055] The glass transition temperature of the homopolymer can be determined, for example, from the value described in the Polymer Handbook, 4th Edition (Wiley-Interscience, 2003). If no such reference is found, the glass transition temperature of the homopolymer can be measured, for example, by a differential scanning calorimeter (DSC). The DSC measurement conditions are as follows: 5 mg of sample, under a nitrogen atmosphere, the temperature is increased from -100°C to 200°C at a rate of 5°C / min in the first measurement (1st run), then cooled to -100°C at a rate of 5°C / min, and then increased from -100°C to 200°C at a rate of 5°C / min in the second measurement (2nd run). Here, the glass transition temperature refers to the intersection of the extension of the baseline on the lower temperature side of the region where the baseline of the DSC curve measured when the temperature is raised from -100°C to 200°C changes to a sigmoid shape in the endothermic direction and the tangent to the inflection point of the sigmoid.

[0056] The acrylic adhesive resin contains the acrylic polymer (P1) and, as described above, may contain the same type of polymerizable monomer as the monomer for constituting the acrylic polymer (P1), and may be in the form of a so-called syrup. The polymerizable monomer contained in the adhesive resin preferably has the same composition as the monomer composition constituting the monomer unit contained in the acrylic polymer (P1). In other words, the adhesive resin is preferably a partial polymer of the acrylic polymer (P1). In this case, the polymer fraction is not particularly limited. The polymer fraction is the content (% by mass) of the resin component relative to the total mass of the resin component (acrylic polymer (P)) and the monomer. The polymer fraction can be, for example, 1 to 50% by mass, and preferably 5 to 30% by mass.

[0057] The acrylic adhesive resin may consist of only the acrylic polymer (P1), or may consist of only the acrylic polymer (P1) and the polymerizable monomer.

[0058] (thermal crosslinking agent) The pressure-sensitive adhesive composition may also contain a thermal crosslinking agent. Examples of the thermal crosslinking agent include known thermal crosslinking agents such as isocyanate compounds, epoxy compounds, oxazoline compounds, aziridine compounds, metal chelate compounds, and butylated melamine compounds. In particular, the thermal crosslinking agent is preferably an isocyanate compound or an epoxy compound. Examples of the isocyanate compound include TDI (tolylene diisocyanate), XDI (xylylene diisocyanate), and HDI (hexamethylene diisocyanate)-based isocyanate compounds.

[0059] Examples of the epoxy compound include a wide range of known epoxy crosslinking agents, such as ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, glycerin diglycidyl ether, neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, N,N,N',N'-tetraglycidyl-m-xylylenediamine, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexanone, trimethylolpropane polyglycidyl ether, diglycerol polyglycidyl ether, polyglycerol polyglycidyl ether, and sorbitol polyglycidyl ether. When the thermal crosslinking agent is an epoxy compound, G 25 , G 100 and D can be easily adjusted to a desired range. 25 and G 100 can be increased, and D can be easily reduced.

[0060] The content of the thermal crosslinking agent is preferably 0.005 parts by mass or more, more preferably 0.01 parts by mass or more, even more preferably 0.02 parts by mass or more, and particularly preferably 0.05 parts by mass or more, relative to 100 parts by mass of the acrylic adhesive resin. The content of the thermal crosslinking agent can be 2.5 parts by mass or less, preferably 0.5 parts by mass or less, more preferably 0.3 parts by mass or less, even more preferably 0.2 parts by mass or less, even more preferably 0.1 parts by mass or less, and particularly preferably 0.08 parts by mass or less, relative to 100 parts by mass of the acrylic adhesive resin. In these cases, G 100 and D can be easily adjusted to a desired range, and as a result, the function F expressed by the formula (4) or (5) can be easily controlled to be 0 or greater.

[0061] (Silane coupling agent) The pressure-sensitive adhesive composition may also contain a silane coupling agent. Examples of silane coupling agents include mercapto-based silane coupling agents containing a mercapto group, epoxy-based silane coupling agents containing an epoxy group, vinyl-based silane coupling agents containing a vinyl group, and isocyanurate-based silane coupling agents. Commercially available silane coupling agents may also be used. Examples of commercially available silane coupling agents include KBM-9659, KBM-5103, KBM-502, KBM-503, KBM-402, and KBM-403 manufactured by Shin-Etsu Chemical Co., Ltd. By including a silane coupling agent in the pressure-sensitive adhesive composition, the adhesion between the pressure-sensitive adhesive sheet formed from the pressure-sensitive adhesive composition and the adherend can be further improved.

[0062] When the pressure-sensitive adhesive composition contains a silane coupling agent, its content is not particularly limited. For example, in order to more easily improve adhesion, the content of the silane coupling agent is preferably 0.01 parts by mass or more, more preferably 0.05 parts by mass or more, and preferably 5 parts by mass or less, more preferably 3 parts by mass or less, even more preferably 1 part by mass or less, and particularly preferably 0.5 parts by mass or less, relative to 100 parts by mass of the acrylic pressure-sensitive adhesive resin.

[0063] The pressure-sensitive adhesive composition may contain only one type of silane coupling agent, or may contain two or more types of silane coupling agents.

[0064] (polyfunctional monomer) The pressure-sensitive adhesive composition may also contain a polyfunctional monomer. In particular, when the acrylic pressure-sensitive adhesive resin is in the form of a syrup, the pressure-sensitive adhesive composition preferably contains a polyfunctional monomer. The polyfunctional monomer is a monomer having two or more reactive functional groups, particularly polymerizable functional groups, in the molecule. Examples of the polymerizable functional group include a wide range of known polymerizable functional groups, specifically an acryloyl group.

[0065] Examples of polyfunctional monomers include (meth)acrylic acid esters of polyhydric alcohols such as ethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, 1,3-butylene glycol di(meth)acrylate, 1,4-butylene glycol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, 1,6-hexanediol diacrylate, polybutylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, diacrylate of bisphenol A diglycidyl ether, trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, and pentaerythritol tetra(meth)acrylate; and vinyl methacrylate.

[0066] The polyfunctional monomer can be produced by a known method or can be obtained from a commercially available product, such as "ATM-4P," "ATM-4PL," and "A-400" manufactured by Shin-Nakamura Chemical Co., Ltd., "PET-30" manufactured by Nippon Kayaku Co., Ltd., or "Viscoat #230" manufactured by Osaka Organic Chemical Industry Co., Ltd.

[0067] In the pressure-sensitive adhesive composition, the content of the polyfunctional monomer is 0.1 parts by mass or more and 10 parts by mass or less relative to 100 parts by mass of the acrylic pressure-sensitive adhesive resin. This allows a pressure-sensitive adhesive sheet obtained from the pressure-sensitive adhesive composition to have sufficient durability after post-curing while being prevented from becoming too hard, and allows for the formation of a pressure-sensitive adhesive sheet that is resistant to peeling and bubble formation even under conditions involving sudden temperature changes after post-curing after bonding adherends together.

[0068] The content of the polyfunctional monomer is preferably 0.05 parts by mass or more, more preferably 0.1 parts by mass or more, even more preferably 0.2 parts by mass or more, and particularly preferably 0.3 parts by mass or more, relative to 100 parts by mass of the acrylic adhesive resin. The content of the polyfunctional monomer is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, even more preferably 3 parts by mass or less, and particularly preferably 1 part by mass or less, relative to 100 parts by mass of the acrylic adhesive resin.

[0069] The pressure-sensitive adhesive composition may contain only one type of polyfunctional monomer, or may contain two or more types of polyfunctional monomers.

[0070] (Photopolymerization initiator) The pressure-sensitive adhesive composition may also contain a photopolymerization initiator. In particular, when the acrylic pressure-sensitive adhesive resin is in the form of a syrup, the pressure-sensitive adhesive composition preferably contains a photopolymerization initiator. The photopolymerization initiator can initiate a polymerization reaction of the polyfunctional monomer and other polymerizable components that may be contained when irradiated with active energy rays. "Active energy rays" in this specification refer to electromagnetic waves or charged particle rays that have an energy quantum, and examples include ultraviolet rays, electron beams, visible light, X-rays, and ion beams. From the viewpoint of versatility, ultraviolet rays or electron beams are preferred, with ultraviolet rays being particularly preferred.

[0071] The photopolymerization initiator may be, for example, a self-cleavage type photoradical polymerization initiator. Note that the self-cleavage type photoradical polymerization initiator is other than the hydrogen abstraction type photopolymerization initiator described below.

[0072] The type of self-cleavage type photoradical polymerization initiator is not particularly limited, and examples thereof include acetophenone-based initiators, benzoin ether-based initiators, hydroxyalkylphenone-based initiators, thioxanthone-based initiators, amine-based initiators, and acylphosphine oxide-based initiators.

[0073] Specific examples of acetophenone initiators include diethoxyacetophenone and benzyl dimethyl ketal. Specific examples of benzoin ether initiators include benzoin and benzoin methyl ether. Specific examples of hydroxyalkylphenone initiators include 1-hydroxycyclohexylphenyl ketone. Specific examples of thioxanthone initiators include 2-isopropylthioxanthone and 2,4-dimethylthioxanthone. Specific examples of amine initiators include triethanolamine and ethyl 4-dimethylbenzoate. Specific examples of acylphosphine oxide initiators include phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide.

[0074] The self-cleaving photoradical polymerization initiator can be produced by a known method or can be obtained from a commercially available product, such as EsacureOne, Omnirad 184, Omnirad 819, Omnirad 1173, Omnirad 2959, Omnirad 127, Omnirad 907, Omnirad 369, Omnirad 379EG, Omnirad TPO, Omnirad TPO H, Irgacure OXE01, or Irgacure OXE02, all manufactured by IGM RESINS BV.

[0075] The photopolymerization initiator may be a self-cleavage type radical photopolymerization initiator or other photopolymerization initiators, such as a hydrogen abstraction type photopolymerization initiator. The hydrogen abstraction type photopolymerization initiator is a photopolymerization initiator in which an initiator photoexcited by irradiation with active energy rays and a hydrogen donor in the system form an exciplex, and the hydrogen from the hydrogen donor is transferred to the exciplex, thereby promoting polymerization. Therefore, the hydrogen abstraction type photopolymerization initiator not only initiates the polymerization reaction of the polyfunctional monomer and other polymerizable components that may be contained, but also acts on the (meth)acrylic copolymer to form a crosslinked structure.

[0076] The type of hydrogen abstraction photopolymerization initiator is not particularly limited, and examples thereof include benzophenone, benzoylbenzoic acid, methyl benzoylbenzoate, 4-phenylbenzophenone, hydroxybenzophenone, 3,3'-dimethyl-4-methoxybenzophenone, 2,4,6-trimethylbenzophenone, 4-methylbenzophenone, thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, camphorquinone, dibenzosuberone, 2-ethylanthraquinone, 3,3',4,4'-tetra(t-butylperoxycarbonyl)benzophenone, benzil, and 9,10-phenanthrenequinone. Among these, the hydrogen abstraction photopolymerization initiator is preferably a benzophenone-based photopolymerization initiator. Examples of benzophenone-based photopolymerization initiators include benzophenone, 4-methylbenzophenone, and 2,4,6-trimethylbenzophenone. The hydrogen abstraction photopolymerization initiator can be produced by a known method or can be obtained from a commercially available product. Examples of commercially available products include TZT and MBF manufactured by IGM Resins, and "SPEED CURE MBP" (e.g., "4MBP") manufactured by Lambson.

[0077] The content of the photopolymerization initiator is 0.1 parts by mass or more and 10 parts by mass or less, preferably 0.1 parts by mass or more, more preferably 0.2 parts by mass or more, more preferably 5 parts by mass or less, even more preferably 2 parts by mass or less, still more preferably 0.5 parts by mass or less, and particularly preferably 0.4 parts by mass or less, relative to 100 parts by mass of the acrylic adhesive resin.

[0078] The pressure-sensitive adhesive composition may contain only one type of photopolymerization initiator, or may contain two or more types of photopolymerization initiators.

[0079] (Adhesive composition) The PSA composition may contain a solvent from the viewpoint of improving the coating property, that is, the PSA composition may be in the form of a solution or a dispersion.

[0080] Examples of the solvent include a wide variety of solvents contained in conventional pressure-sensitive adhesive compositions, and specific examples thereof include hydrocarbons such as hexane, heptane, octane, toluene, xylene, ethylbenzene, cyclohexane, and methylcyclohexane; halogenated hydrocarbons such as dichloromethane, trichloroethane, trichloroethylene, tetrachloroethylene, and dichloropropane; alcohols such as methanol, ethanol, propanol, isopropyl alcohol, butanol, isobutyl alcohol, and diacetone alcohol; ethers such as diethyl ether, diisopropyl ether, dioxane, and tetrahydrofuran; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, isophorone, and cyclohexanone; esters such as methyl acetate, ethyl acetate, butyl acetate, isobutyl acetate, amyl acetate, and ethyl butyrate; and polyols and derivatives thereof such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monomethyl ether acetate, propylene glycol monomethyl ether, propylene glycol monoethyl ether, and propylene glycol monomethyl ether acetate.

[0081] When the pressure-sensitive adhesive composition contains a solvent, the content thereof is not particularly limited, and is, for example, preferably 90 mass % or less, more preferably 70 mass % or less, based on the total mass of the pressure-sensitive adhesive composition. The pressure-sensitive adhesive composition may contain only one type of solvent, or two or more types of solvents.

[0082] In addition to the above, the pressure-sensitive adhesive composition may contain various additives within a range that does not impair the effects of the present invention. The additives can be selected as needed from among plasticizers, antioxidants, metal corrosion inhibitors, tackifiers, ultraviolet absorbers, light stabilizers such as hindered amine compounds, etc.

[0083] The pressure-sensitive adhesive composition preferably contains at least an acrylic adhesive resin and a thermal crosslinking agent, and more preferably contains at least an acrylic adhesive resin containing at least a (meth)acrylic acid ester unit and a monomer unit having a crosslinkable functional group, and a thermal crosslinking agent. That is, the pressure-sensitive adhesive sheet of the present invention preferably has a structure in which an acrylic adhesive resin containing at least a (meth)acrylic acid ester unit and a monomer unit having a crosslinkable functional group is crosslinked with a thermal crosslinking agent.

[0084] The pressure-sensitive adhesive sheet of the present invention can be produced using the pressure-sensitive adhesive composition, and thus the pressure-sensitive adhesive sheet of the present invention comprises a pressure-sensitive adhesive layer formed by curing the pressure-sensitive adhesive composition.

[0085] The method for curing the pressure-sensitive adhesive composition is not particularly limited, and for example, a wide variety of known methods can be employed. Specifically, the method can include a step of applying the pressure-sensitive adhesive composition to a substrate to form a coating film, and a step of irradiating the coating film with active energy rays to obtain a cured product of the pressure-sensitive adhesive composition. This results in a cured product formed by curing the pressure-sensitive adhesive composition, and this cured product can be used as a pressure-sensitive adhesive layer. Alternatively, the method can include a step of applying the pressure-sensitive adhesive composition to a substrate to form a coating film, and a step of heating the coating film to obtain a cured product of the pressure-sensitive adhesive composition. This also results in a cured product formed by curing the pressure-sensitive adhesive composition, and this cured product can be used as a pressure-sensitive adhesive layer.

[0086] The PSA composition can be applied using a known coating device, such as a blade coater, air knife coater, roll coater, bar coater, gravure coater, microgravure coater, rod blade coater, lip coater, die coater, or curtain coater.

[0087] The substrate used for coating the pressure-sensitive adhesive composition is not particularly limited. For example, the pressure-sensitive adhesive composition can be coated onto various substrates, such as resin substrates and glass substrates. When the substrate has a release sheet (described later), the pressure-sensitive adhesive composition can also be coated onto this release sheet. The pressure-sensitive adhesive composition can also be directly coated onto the member to be adhered. The thickness of the pressure-sensitive adhesive composition after coating is also not particularly limited and can be appropriately set depending on the desired thickness of the pressure-sensitive adhesive layer (or pressure-sensitive adhesive sheet). After forming the coating film, the coating film may be subjected to a heat treatment or a drying treatment as necessary. By heating the coating film, a crosslinking reaction progresses and a cured product is formed. Alternatively, by irradiating the coating film with active energy rays such as ultraviolet rays, a cured product is formed. The cured product becomes the acrylic resin component contained in the pressure-sensitive adhesive sheet.

[0088] The heating temperature for the coating is preferably between 50°C and 140°C, more preferably between 60°C and 130°C, and most preferably between 70°C and 120°C. When using a thermal crosslinking agent to produce a film, the coating is diluted with a solvent to impart fluidity before application, resulting in the evaporation of the solvent during thermal crosslinking. The solvent has a temperature-dependent vapor pressure and evaporates from the surface of the coating. However, when the coating temperature reaches the solvent's boiling point, the vapor pressure exceeds atmospheric pressure, causing the coating to evaporate within the film, leaving behind bubbles after film formation. Therefore, a method for setting the heating and drying temperatures that takes the solvent's boiling point into account is required. Specifically, one such method involves arranging multiple heating and drying furnaces in series and gradually increasing the temperature in the order of preheating, drying, and crosslinking heating. In particular, when diluting with multiple solvents, the temperature must be increased while taking into account the multiple boiling points. For example, when diluting with ethyl acetate, which has a boiling point of 77°C, a heating / drying furnace can be arranged in five stages in series, with the furnace temperatures set to 70°C, 80°C, 90°C, 100°C, and 110°C in the order from the first stage to the fifth stage. Similarly, when using toluene, which has a boiling point of 111°C, the temperatures can be set to 80°C, 90°C, 100°C, 110°C, and 120°C.

[0089] When the active energy rays are irradiated, radicals are generated, and these radicals cause parallel reactions of polymerization of the main chain and crosslinking, resulting in film formation. UV light from LEDs, chemical lamps, high-pressure mercury lamps, or metal halide lamps can be used as the active energy rays. Because the wavelength spectrum and irradiance characteristics of UV light differ depending on the light source, it is necessary to set irradiation conditions taking these characteristics into account. The parallel reaction is a reactive crystallization process for precipitating an acrylic polymer. It is known that in reactive crystallization, the number of seed crystals can be reduced by suppressing the initial reaction rate, ultimately resulting in large crystals. Therefore, even in the parallel reaction using the active energy rays, the basic principle is to install multiple stages of active energy ray irradiation furnaces in series, arranging them from light sources with low irradiance to light sources with high irradiance. Specifically, the irradiance of the first stage (e.g., the first UV light source) should be set to several mW / cm. 2 , the cumulative light intensity is several hundred to 500 mJ / cm 2 The illumination intensity of the latter stage is 100 to 500 mW / cm 2The total light output is several thousand to 2,500 mJ / cm 2 The light source for the front stage can be a chemical lamp or an LED, and the light source for the rear stage can be a high-pressure mercury lamp, a metal halide lamp, or an LED. Because the light source, the irradiation furnace, and the coating film generate heat due to heat generated by the light source and the heat generated by the parallel reaction, the temperatures of the light source, the reverberatory furnace, and the coating film are adjusted by blowing air to preferably between 30°C and 100°C, more preferably between 35°C and 90°C, and most preferably between 40°C and 80°C.

[0090] The cured product formed as described above can be used as the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet of the present invention. The pressure-sensitive adhesive layer may consist of only the cured product of the pressure-sensitive adhesive, or may contain other components in addition to the cured product of the pressure-sensitive adhesive. The pressure-sensitive adhesive layer may have a single-layer structure or a laminate structure in which multiple layers are laminated.

[0091] The pressure-sensitive adhesive sheet of the present invention may include other layers as long as it includes the pressure-sensitive adhesive layer, or may be formed only from the pressure-sensitive adhesive layer. That is, the pressure-sensitive adhesive sheet preferably consists of only the pressure-sensitive adhesive layer. The pressure-sensitive adhesive sheet of the present invention is preferably a double-sided pressure-sensitive adhesive sheet.

[0092] The gel fraction of the pressure-sensitive adhesive sheet of the present invention is preferably less than 55%. In this case, a pressure-sensitive adhesive sheet including the pressure-sensitive adhesive layer is likely to have excellent step absorbency, punchability during processing, and excellent heat shock resistance during use. The gel fraction of the pressure-sensitive adhesive sheet of the present invention is more preferably 53% or less, even more preferably 50% or less, and particularly preferably 45% or less.

[0093] The method for adjusting the gel fraction of the pressure-sensitive adhesive sheet of the present invention is not particularly limited, and can be adjusted by, for example, a known method. Specifically, the gel fraction of the pressure-sensitive adhesive sheet can be adjusted by adjusting the weight-average molecular weight of the acrylic polymer contained in the pressure-sensitive adhesive layer, the contents of the thermal crosslinking agent and the photopolymerization initiator in the pressure-sensitive adhesive composition, etc.

[0094] The pressure-sensitive adhesive sheet of the present invention may also be a pressure-sensitive adhesive sheet provided with a substrate such as a release sheet on one or both sides. That is, the present invention also encompasses a pressure-sensitive adhesive sheet with a release sheet that includes a pressure-sensitive adhesive sheet and a release sheet.

[0095] Examples of the release sheet include a release laminate sheet having a release sheet substrate and a release agent layer provided on one side of the release sheet substrate, or a polyolefin film such as a polyethylene film or a polypropylene film as a low-polarity substrate. The release sheet substrate in the release laminate sheet is made of paper or a polymer film such as a polyester film. Examples of the release agent that constitutes the release agent layer include general-purpose addition-type or condensation-type silicone-based release agents and long-chain alkyl group-containing compounds. Commercially available release laminate sheets may also be used. Examples include a heavy-duty separator film, which is a release-treated polyethylene terephthalate film manufactured by Teijin DuPont Films, and a light-duty separator film, which is a release-treated polyethylene terephthalate film manufactured by Teijin DuPont Films.

[0096] The adhesive sheet with release sheet can be obtained, for example, by a manufacturing method including a step of laminating a laminate obtained by laminating a polyester film coated with a release agent and having a thickness of 50 μm or more and 100 μm or less to one side of the adhesive sheet so that the release-agent-coated surface of the polyester film is in contact with the other side of the adhesive sheet, and then laminating a polyester film coated with a release agent and having a thickness of 25 μm or more and 75 μm or less to the other side of the adhesive sheet so that the release-agent-coated surface of the polyester film is in contact with the other side of the adhesive sheet.

[0097] Specifically, a polyester film coated with a release agent having a thickness of 50 μm to 100 μm is prepared, and a pressure-sensitive adhesive layer is formed on the release-agent-coated surface using the pressure-sensitive adhesive composition by the method described above. The exposed surface of this pressure-sensitive adhesive layer is then overlaid with the release-agent-coated surface of a polyester film coated with a release agent having a thickness of 25 μm to 75 μm. This forms a pressure-sensitive adhesive sheet with a release sheet.

[0098] Another method for producing a pressure-sensitive adhesive sheet with a release sheet includes the steps of: applying a pressure-sensitive adhesive composition to the release-agent-coated surface of a polyester film coated with a release agent having a thickness of 50 μm or more and 100 μm or less to form a coating film; laminating the release-agent-coated surface of a polyester film coated with a release agent having a thickness of 25 μm or more and 75 μm or less so that it is in contact with the exposed surface of the coating film; and curing the coating film by irradiating with active energy rays to form the pressure-sensitive adhesive sheet. The type of pressure-sensitive adhesive composition used here is the same as the pressure-sensitive adhesive composition described above. The type of active energy rays and the irradiation conditions are also the same as those described above.

[0099] The thickness of the pressure-sensitive adhesive sheet of the present invention can be appropriately set depending on the application, and is, for example, preferably from 10 to 1000 μm, more preferably from 20 to 500 μm, and even more preferably from 50 to 350 μm.

[0100] When used in capacitive touch sensor applications, the pressure-sensitive adhesive sheet of the present invention preferably has a relative dielectric constant of 3.7 or less to enhance sensitivity. The relative dielectric constant refers to a value measured by the following method. First, a sample is prepared by covering both sides of the pressure-sensitive adhesive sheet with a 50 μm-thick PET film (e.g., Toray's Lumirror 50U483). Next, this sample is sandwiched between Keysight dielectric measurement electrodes 16451B, with the inter-electrode distance set to 30 μm greater than the total sample thickness, and the capacitance is calculated by subtracting the contributions of the PET film and air layer from the capacitance measured at an input frequency of 100 kHz using a Keysight impedance analyzer E4990A. The relative dielectric constant is a dimensionless quantity, which is the ratio of the dielectric constant calculated from the capacitance to the dielectric constant of air.

[0101] When the pressure-sensitive adhesive sheet of the present invention is obtained by thermal curing of the pressure-sensitive adhesive composition, the viscoelastic properties can be adjusted within ranges that satisfy the step-conforming ability, punching suitability, and heat shock resistance, for example, by adjusting the weight-average molecular weight of the acrylic polymer (P1) and the amount of thermal crosslinker added, etc. When the pressure-sensitive adhesive sheet of the present invention is obtained by curing with active energy rays, the viscoelastic properties can be adjusted within ranges that satisfy the step-conforming ability, punching suitability, and heat shock resistance, by adjusting the weight-average molecular weight of the acrylic polymer (P1), the amount of polyfunctional monomer added, the amount of photoradical initiator added, the active energy ray irradiation conditions, etc.

[0102] The pressure-sensitive adhesive sheet of the present invention has excellent step absorbency, is suitable for punching during processing, and also has excellent heat shock resistance during use, so it can be used, for example, to bond optical components for display devices, and is particularly suitable for use in vehicles.

[0103] The pressure-sensitive adhesive sheet of the present invention has excellent step absorption properties, absorbing printing steps on the back surface of a cover material (glass or film) and steps in the sensor mesh of a sensor film, and is also heat shock resistant to shrinkage differences between components due to temperature changes after lamination, thereby suppressing peeling and the generation of bubbles even in environments with repeated temperature changes. Therefore, the pressure-sensitive adhesive sheet can form a laminate that has excellent step conformability and excellent heat shock resistance against sudden temperature changes and repeated temperature changes. Examples of laminates include structures in which optical components for display devices, cover materials, sensor films, polarizing plates, and liquid crystal modules are laminated together with a pressure-sensitive adhesive sheet.

[0104] Examples of optical members for display devices include components of optical products such as touch panels, image display devices, etc. Types of optical members include a wide range of known optical members that can be used in touch panels, image display devices, etc. In the present invention, the optical member for display devices may have a surface that is processed into a concave or convex shape.

[0105] Examples of materials for optical components to which the pressure-sensitive adhesive sheet of the present invention is attached include glass, polycarbonate, polyethylene terephthalate, polymethyl methacrylate (polymethyl methacrylate), polyethylene naphthalate, cycloolefin polymer, triacetyl cellulose, polyimide, cellulose acylate, etc. Among these, the adherend preferably contains at least one selected from glass, polycarbonate, and polymethyl methacrylate, and is particularly preferably formed from a resin containing polycarbonate or polymethyl methacrylate.

[0106] An example of an optical member to which the pressure-sensitive adhesive sheet of the present invention can be attached is a light guide plate, and other examples include, for touch panel applications, ITO films in which an ITO film is provided on a transparent resin film, ITO glass in which an ITO film is provided on the surface of a glass plate, transparent conductive films in which a transparent resin film is coated with a conductive polymer, metal mesh sensor films in which a fine metal mesh such as copper or silver is mounted, hard coat films, fingerprint-resistant films, etc. Furthermore, for image display applications, examples include antireflection films, alignment films, polarizing films, retardation films, brightness improvement films, etc. used in liquid crystal display devices.

[0107] (Method for assessing the performance of adhesive sheets) The present invention can include a method for determining the properties of a pressure-sensitive adhesive sheet. Specifically, the method involves determining the storage modulus G obtained from dynamic viscoelasticity measurement of a pressure-sensitive adhesive sheet at a frequency of 1 Hz and a temperature of 100°C. 100 ´ and loss modulus G 100 " and "Storage modulus G obtained from dynamic viscoelasticity measurement at a frequency of 1 Hz and a temperature of 25°C 25 ´ and loss modulus G 25 Based on this, it is possible to accurately predict the physical properties of the adhesive sheet (step absorption, punching suitability, heat shock resistance).

[0108] Specifically, the G of the adhesive sheet to be examined for physical properties 100 ´ and G 100 " and G25 ´ and G 25 Based on these values, G is calculated using the above-mentioned formulas (1), (2), and (3). 100 , D, G 25 Then, G 25 <200, the function F(G 25 ,G 100 ,D) is 0 or more, G 25 If ≧200, the function F(G 25 ,G 100 , D) is 0 or more, the performance of the adhesive sheet can be determined. 25 ,G 100 , D) is 0 or more, the PSA sheet can be judged to have all of the following properties: level difference absorbency, punching suitability, and heat shock resistance.

[0109] From the above, the method for evaluating the performance of the pressure-sensitive adhesive sheet is 25 ,G 100 , D) is 0 or greater, and the performance of the PSA sheet can be easily determined simply by checking using a predetermined formula whether the function is 0 or greater. By using this method, it is possible to easily determine whether the PSA sheet is excellent in level difference absorption, punching suitability, and heat shock resistance, and whether it is suitable for use as an optical component.

[0110] Here, the qualitative relationship between the mechanical properties of the pressure-sensitive adhesive sheet of the present invention and various physical properties will be described. (1) Mechanical properties of viscoelastic materials In the present invention, the processability of a pressure-sensitive adhesive sheet can be predicted using the complex modulus (modulus G). Because the complex modulus depends on temperature and time scale (frequency), the question is which temperature to focus on for the modulus G. Generally, a pressure-sensitive adhesive sheet that is hard at low temperatures also remains hard at high temperatures, but this can sometimes be reversed depending on the average molecular weight and degree of crosslinking. However, reversal at close temperatures is rare. For example, when trends were confirmed for at least 20 types of pressure-sensitive adhesive sheets, there was almost no change in the order of the modulus G of the pressure-sensitive adhesive sheets in the range of 50 to 100°C, and there was also no change in the order between 0°C and 25°C. Therefore, in the present invention, the modulus G at 25°C and 100°C was used to derive Equations (4) and (5). Furthermore, since D has no sensitivity at 25°C, only D at 100°C was used to derive Equations (4) and (5).

[0111] (2) Absorbency of unevenness Step absorption refers to the processability of a material to fill and fill rectangular steps of around 10 μm caused by printing on the adhesive surface, such as when laminating glass to glass with an adhesive sheet. After laminating in a vacuum chamber, the material is pressed in at a temperature and time of 40°C and 6 atmospheres for about 30 minutes, during which the adhesive sheet exhibits liquid-like properties and deforms to fit the rectangular step, thereby filling the gap. Because of the temperature and time involved, the properties at 100°C come into play, and if the elastic modulus G at 100°C is around 20 kPa or less and D at 100°C is greater than around 30°, the polymer chains will be able to move sufficiently to fill the gap.

[0112] (3) Punching suitability Punching suitability indicates the suitability of the adhesive sheet for post-processing quality and workability when punching it with a die blade to a size suitable for lamination. When an adhesive sheet is protected on both sides with release film, it is punched out together with both release films. During this punching process, the adhesive (adhesive layer) in the adhesive sheet may protrude, which becomes even more pronounced when the adhesive sheet is made thick to fill large gaps. Punching is a guillotine-style instantaneous operation, so it is affected by viscoelastic behavior at low temperatures. However, at 0°C, the adhesive becomes solid and differences become less apparent. Therefore, in this invention, the elastic modulus G at 25°C is used as the appropriate temperature.

[0113] (4) Heat shock resistance Heat shock resistance is known to be an index of resistance to peeling due to stress resulting from distortion caused by repeated exposure to temperatures of -40°C for 30 minutes and 130°C for 30 minutes. When testing a glass-adhesive sheet-glass laminate, the temperature-dependent shrinkage of the glass is the same, but the shrinkage of the adhesive sheet is different, resulting in distortion between the glass and the adhesive. The polymer backbone shears to absorb the distortion, and the frictional heat between the polymer chains is released outside the system, thereby relieving stress. D represents the amount of this energy absorption (since tanδ = G" / G', this corresponds to a high ratio of the viscosity term G"). Therefore, while it is desirable for D to be at a certain level or higher across the entire temperature range, distortion occurring in areas that have softened at high temperatures can make the material more susceptible to peeling. Therefore, in this invention, D at 100°C is used to derive equations (4) and (5).

[0114] In specifying the inventions included in the present disclosure, the components (properties, structures, functions, etc.) described in the embodiments of the present disclosure may be combined in any manner. In other words, the present disclosure includes all subject matter consisting of all combinations of the components that can be combined as described in this specification. [Example]

[0115] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples.

[0116] (Production Example 1: Production of acrylic polymer) In a 2L flask equipped with a stirrer, nitrogen inlet tube, condenser, and thermometer, 850g of n-butyl acrylate (BA) and 150g of 2-hydroxyethyl acrylate (2HEA) were dispersed in ethyl acetate as a solvent to a solids concentration of 50%, and the temperature was raised to 85°C in a water bath while the atmosphere inside the flask was replaced with nitrogen through the nitrogen inlet tube. Then, 0.20g of AIBN (azobisisobutyronitrile) was added to the flask, and polymerization was carried out at a constant temperature of 85°C while stirring and cooling, yielding an ethyl acetate solution a1 of an acrylic polymer A1 with a weight average molecular weight of 350,000.

[0117] (Production Example 2: Production of acrylic polymer) In a 2L flask equipped with a stirrer, nitrogen inlet tube, condenser, and thermometer, 850g of n-butyl acrylate (BA) and 150g of 2-hydroxyethyl acrylate (2HEA) were dispersed in ethyl acetate as a solvent to a solids concentration of 50%, and the temperature was raised to 80°C in a water bath while the atmosphere inside the flask was replaced with nitrogen through the nitrogen inlet tube. Then, 0.15g of AIBN (azobisisobutyronitrile) was added to the flask, and polymerization was carried out at a constant temperature of 80°C while stirring and cooling, yielding an ethyl acetate solution a2 of an acrylic polymer A2 with a weight average molecular weight of 450,000.

[0118] (Production Example 3: Production of acrylic polymer) In a 2L flask equipped with a stirrer, nitrogen inlet tube, condenser, and thermometer, 850g of n-butyl acrylate (BA) and 150g of 2-hydroxyethyl acrylate (2HEA) were dispersed in ethyl acetate as a solvent to a solids concentration of 50%, and the temperature was raised to 70°C in a water bath while the atmosphere inside the flask was replaced with nitrogen through the nitrogen inlet tube. Then, 0.12g of AIBN (azobisisobutyronitrile) was added to the flask, and polymerization was carried out at a constant temperature of 70°C while stirring and cooling, yielding an ethyl acetate solution a3 of an acrylic polymer A3 with a weight average molecular weight of 750,000.

[0119] (Production Example 4: Production of acrylic polymer) In a 2L flask equipped with a stirrer, nitrogen inlet tube, condenser, and thermometer, 850g of n-butyl acrylate (BA) and 150g of 2-hydroxyethyl acrylate (2HEA) were dispersed in ethyl acetate as a solvent to a solids concentration of 50%, and the temperature was raised to 65°C in a water bath while the atmosphere inside the flask was replaced with nitrogen through the nitrogen inlet tube. Then, 0.12g of AIBN (azobisisobutyronitrile) was added to the flask, and polymerization was carried out at a constant temperature of 65°C while stirring and cooling, yielding an ethyl acetate solution a4 of acrylic polymer A4 with a weight average molecular weight of 1 million.

[0120] (Production Example 5: Production of syrup) A 2-L flask equipped with a stirrer, nitrogen inlet tube, condenser, and thermometer was charged with a (meth)acrylic monomer mixture consisting of 620 g of n-butyl acrylate (BA), 90 g of cyclohexyl methacrylate (CHMA), and 290 g of 4-hydroxybutyl acrylate (4HBA), along with 0.4 g of n-dodecyl mercaptan. The flask was then heated to 60°C in a water bath while the atmosphere inside the flask was replaced with nitrogen via the nitrogen inlet tube. Then, 0.15 g of AIBN (azobisisobutyronitrile) was added to the flask, and the mixture was allowed to react at a constant temperature of 60°C for 30 minutes with stirring and cooling. An additional (meth)acrylic monomer mixture with the same composition as the (meth)acrylic monomer mixture was added to obtain a syrup of acrylic polymer B with a polymer content of 30% by mass and a weight-average molecular weight of 400,000.

[0121] Example 1 To 100 parts by weight of the solids content of the ethyl acetate solution a1 obtained in Production Example 1, 0.2 parts by weight of a silane coupling agent (KBM-9659 manufactured by Shin-Etsu Chemical Co., Ltd.) and 0.02 parts by weight of an isocyanate-based crosslinking agent (Takenate D-110N manufactured by Mitsui Chemicals Co., Ltd.) were added in this order, followed by degassing and stirring to obtain a pressure-sensitive adhesive composition. This pressure-sensitive adhesive composition was uniformly applied to the release-coated surface of a 100 μm-thick PET film (referred to as "first release sheet"; manufactured by Mitsubishi Chemical Corporation) equipped with a release layer treated with a silicone-based release agent, so that the coating thickness after drying would be 150 μm, using a square applicator. The composition was then heated at 100°C for 3 minutes in an air-circulating thermostatic oven to remove the solvent component and form a pressure-sensitive adhesive layer (referred to as "pressure-sensitive adhesive sheet") through a crosslinking reaction caused by the isocyanate-based crosslinking agent. Furthermore, a 75 μm thick PET film (Mitsubishi Chemical MRF75) with a release layer treated with a silicone-based release agent was attached to the surface of the adhesive layer opposite the first release sheet to obtain an adhesive sheet with release sheets consisting of a first release sheet / adhesive sheet / second release sheet. The gel fraction of the adhesive sheet was 30%.

[0122] Example 2 A pressure-sensitive adhesive sheet with a release sheet was obtained in the same manner as in Example 1, except that ethyl acetate solution a1 was replaced with ethyl acetate solution a2 obtained in Production Example 2 and the amount of isocyanate-based crosslinking agent was changed to 0.08 parts by mass. The gel fraction of the pressure-sensitive adhesive sheet was 40%.

[0123] Example 3 To 100 parts by mass of the syrup obtained in Production Example 5, 0.3 parts by mass of a multifunctional monomer (A-400 manufactured by Shin-Nakamura Chemical Co., Ltd.), 0.2 parts by mass of a silane coupling agent (KBM-9659 manufactured by Shin-Etsu Chemical Co., Ltd.), and 0.5 parts by mass of a photopolymerization initiator (ESACURE ONE manufactured by IGM RESUNS Co., Ltd.) were added in this order, followed by degassing and stirring to obtain a pressure-sensitive adhesive composition. This pressure-sensitive adhesive composition was uniformly applied using a square applicator to the release-coated surface of a 100 μm-thick PET film (referred to as the first release sheet, MRV100 manufactured by Mitsubishi Chemical Co., Ltd.) equipped with a release layer treated with a silicone-based release agent, so that the coating thickness after UV curing was 150 μm, forming a pressure-sensitive adhesive layer. Then, a 75 μm thick PET film (Mitsubishi Chemical MRF75) with a release layer treated with a silicone-based release agent was attached to the surface of the adhesive layer opposite the first release sheet to form a laminate consisting of a first release sheet / adhesive layer / second release sheet. This laminate was measured with an ultraviolet illuminance meter UIT-θ365 manufactured by Ushio Inc. at an illuminance of 3.5 mW / cm. 2 And the cumulative light intensity is 300mJ / cm 2 After the first UV curing treatment under the conditions above, the illuminance was measured with a UV illuminance meter UIT-θ365 manufactured by Ushio Inc. at 200mW / cm 2 And the cumulative light intensity is 2000mJ / cm 2 A second UV curing treatment was carried out under the conditions of , to obtain a pressure-sensitive adhesive sheet with a release sheet, consisting of a first release sheet / pressure-sensitive adhesive sheet / second release sheet. The gel fraction of the pressure-sensitive adhesive sheet was 48%.

[0124] (Comparative Example 1) Except for changing the amount of isocyanate-based crosslinking agent to 0.3 parts by mass, a pressure-sensitive adhesive sheet with a release sheet was obtained in the same manner as in Example 1. The gel fraction of the pressure-sensitive adhesive sheet was 44%.

[0125] (Comparative Example 2) A release sheet-attached pressure-sensitive adhesive sheet was obtained in the same manner as in Example 2, except that the amount of isocyanate-based crosslinking agent was changed to 0.2 parts by mass. The gel fraction of the pressure-sensitive adhesive sheet was 50%.

[0126] (Comparative Example 3) A pressure-sensitive adhesive sheet with a release sheet was obtained in the same manner as in Example 1, except that ethyl acetate solution a1 was replaced with ethyl acetate solution a3 obtained in Production Example 3 and the amount of isocyanate-based crosslinking agent was changed to 0.1 parts by mass. The gel fraction of the pressure-sensitive adhesive sheet was 65%.

[0127] Comparative Example 4 A pressure-sensitive adhesive sheet with a release sheet was obtained in the same manner as in Example 1, except that ethyl acetate solution a1 was replaced with ethyl acetate solution a4 obtained in Production Example 4 and the amount of isocyanate-based crosslinking agent was changed to 0.05 parts by mass. The gel fraction of the pressure-sensitive adhesive sheet was 70%.

[0128] (Comparative example 5a) To 100 parts by mass of the syrup obtained in Production Example 5, 0.5 parts by mass of a multifunctional monomer (A-400 manufactured by Shin-Nakamura Chemical Co., Ltd.), 0.2 parts by mass of a silane coupling agent (KBM-9659 manufactured by Shin-Etsu Chemical Co., Ltd.), and 0.3 parts by mass of a photopolymerization initiator (ESACURE ONE manufactured by IGM RESUNS Co., Ltd.) were added in this order, followed by degassing and stirring to obtain a pressure-sensitive adhesive composition. This pressure-sensitive adhesive composition was uniformly applied using a square applicator to the release-coated surface of a 100 μm-thick PET film (referred to as the first release sheet, MRV100 manufactured by Mitsubishi Chemical Co., Ltd.) equipped with a release layer treated with a silicone-based release agent, so that the coating thickness after UV curing was 150 μm, forming a pressure-sensitive adhesive layer. Then, a 75 μm thick PET film (Mitsubishi Chemical MRF75) with a release layer treated with a silicone-based release agent was attached to the side of the pressure-sensitive adhesive layer opposite the first release sheet, to form a laminate consisting of a first release sheet / pressure-sensitive adhesive layer / second release sheet. This laminate was measured with an ultraviolet illuminance meter UIT-θ365 manufactured by Ushio Inc. at an illuminance of 4.0 mW / cm. 2 And the cumulative light intensity is 250mJ / cm 2 After the first UV curing treatment under the conditions above, the illuminance was measured with a UV illuminance meter UIT-θ365 manufactured by Ushio Inc. at 200mW / cm 2 And the cumulative light intensity is 2000mJ / cm 2A second UV curing treatment was carried out under the conditions of (a) to (c) to obtain a pressure-sensitive adhesive sheet with a release sheet, which consisted of a first release sheet / pressure-sensitive adhesive sheet / second release sheet. The gel fraction of the pressure-sensitive adhesive sheet was 55%.

[0129] Example 4 Except for changing the amount of isocyanate-based crosslinking agent used to 2.5 parts by mass, a release sheet-attached pressure-sensitive adhesive sheet consisting of a first release sheet / pressure-sensitive adhesive sheet / second release sheet was obtained in the same manner as in Example 1. The gel fraction of the pressure-sensitive adhesive sheet was 60%.

[0130] (Comparative Example 5b) Except for changing the amount of isocyanate-based crosslinking agent used to 0.8 parts by mass, a release sheet-attached pressure-sensitive adhesive sheet consisting of a first release sheet / pressure-sensitive adhesive sheet / second release sheet was obtained in the same manner as in Example 1. The gel fraction of the pressure-sensitive adhesive sheet was 50%.

[0131] (Comparative Example 6) Except for changing the amount of isocyanate-based crosslinking agent used to 0.4 parts by mass, a pressure-sensitive adhesive sheet with release sheets consisting of a first release sheet / pressure-sensitive adhesive sheet / second release sheet was obtained in the same manner as in Example 1. The gel fraction of the pressure-sensitive adhesive sheet was 46%.

[0132] (Comparative Example 7) Except for changing the amount of isocyanate-based crosslinking agent used to 0.2 parts by mass, a release sheet-attached pressure-sensitive adhesive sheet consisting of a first release sheet / pressure-sensitive adhesive sheet / second release sheet was obtained in the same manner as in Example 1. The gel fraction of the pressure-sensitive adhesive sheet was 42%.

[0133] Example 5 Except for changing the amount of isocyanate-based crosslinking agent used to 0.1 parts by mass, a release sheet-attached pressure-sensitive adhesive sheet consisting of a first release sheet / pressure-sensitive adhesive sheet / second release sheet was obtained in the same manner as in Example 1. The gel fraction of the pressure-sensitive adhesive sheet was 38%.

[0134] (Comparative Example 8) Except for changing the amount of isocyanate-based crosslinking agent used to 1 part by mass, a release sheet-attached pressure-sensitive adhesive sheet consisting of a first release sheet / pressure-sensitive adhesive sheet / second release sheet was obtained in the same manner as in Example 2. The gel fraction of the pressure-sensitive adhesive sheet was 60%.

[0135] (Comparative Example 9) Except for changing the amount of isocyanate-based crosslinking agent used to 0.4 parts by mass, a pressure-sensitive adhesive sheet with release sheets consisting of a first release sheet / pressure-sensitive adhesive sheet / second release sheet was obtained in the same manner as in Example 2. The gel fraction of the pressure-sensitive adhesive sheet was 55%.

[0136] Example 6 Except for changing the amount of isocyanate-based crosslinking agent used to 0.05 parts by mass, a release sheet-attached pressure-sensitive adhesive sheet consisting of a first release sheet / pressure-sensitive adhesive sheet / second release sheet was obtained in the same manner as in Example 2. The gel fraction of the pressure-sensitive adhesive sheet was 40%.

[0137] Example 7 Except for changing the amount of isocyanate-based crosslinking agent used to 0.02 parts by mass, a release sheet-attached pressure-sensitive adhesive sheet consisting of a first release sheet / pressure-sensitive adhesive sheet / second release sheet was obtained in the same manner as in Example 2. The gel fraction of the pressure-sensitive adhesive sheet was 35%.

[0138] (Comparative Example 10) Except for changing the amount of isocyanate-based crosslinking agent used to 0.3 parts by mass, a pressure-sensitive adhesive sheet with a release sheet consisting of a first release sheet / pressure-sensitive adhesive sheet / second release sheet was obtained in the same manner as in Comparative Example 3. The gel fraction of the pressure-sensitive adhesive sheet was 75%.

[0139] (Comparative Example 11) Except for changing the amount of isocyanate-based crosslinking agent used to 0.1 parts by mass, a release sheet-attached pressure-sensitive adhesive sheet consisting of a first release sheet / pressure-sensitive adhesive sheet / second release sheet was obtained in the same manner as in Comparative Example 4. The gel fraction of the pressure-sensitive adhesive sheet was 77%.

[0140] (Comparative Example 12) Except for changing the amount of isocyanate-based crosslinking agent used to 0.03 parts by mass, a release sheet-attached pressure-sensitive adhesive sheet consisting of a first release sheet / pressure-sensitive adhesive sheet / second release sheet was obtained in the same manner as in Comparative Example 4. The gel fraction of the pressure-sensitive adhesive sheet was 65%.

[0141] (Comparative Example 13) Except for changing the amount of isocyanate-based crosslinking agent used to 0.01 parts by mass, a pressure-sensitive adhesive sheet with a release sheet consisting of a first release sheet / pressure-sensitive adhesive sheet / second release sheet was obtained in the same manner as in Comparative Example 4. The gel fraction of the pressure-sensitive adhesive sheet was 55%.

[0142] Example 8 Except for changing the amount of polyfunctional monomer used to 0.2 parts by mass, a release sheet-attached pressure-sensitive adhesive sheet consisting of a first release sheet / pressure-sensitive adhesive sheet / second release sheet was obtained in the same manner as in Example 3. The gel fraction of the pressure-sensitive adhesive sheet was 45%.

[0143] (Comparative Example 14) Except for changing the isocyanate-based crosslinking agent to an epoxy crosslinking agent (E-AX) and changing the amount used to 0.2 parts by mass, a release sheet-attached pressure-sensitive adhesive sheet consisting of a first release sheet / pressure-sensitive adhesive sheet / second release sheet was obtained in the same manner as in Example 1. The gel fraction of the pressure-sensitive adhesive sheet was 42%.

[0144] (Comparative Example 15) Except for changing the isocyanate-based crosslinking agent to an epoxy crosslinking agent (E-AX) and changing the amount used to 0.2 parts by mass, a release sheet-attached pressure-sensitive adhesive sheet consisting of a first release sheet / pressure-sensitive adhesive sheet / second release sheet was obtained in the same manner as in Example 2. The gel fraction of the pressure-sensitive adhesive sheet was 50%.

[0145] (Comparative Example 16) The irradiation conditions of the first ultraviolet ray were measured with a UV illuminance meter UIT-θ365 manufactured by Ushio Inc., and the illuminance was 3.0 mW / cm 2 And the cumulative light intensity is 350mJ / cm 2A pressure-sensitive adhesive sheet with a release sheet consisting of a first release sheet / pressure-sensitive adhesive sheet / second release sheet was obtained in the same manner as in Example 3, except for changing the conditions to: The gel fraction of the pressure-sensitive adhesive sheet was 50%.

[0146] (Comparative Example 17) A release sheet-attached adhesive sheet consisting of a first release sheet / adhesive sheet / second release sheet was obtained in the same manner as in Comparative Example 16, except that the amount of polyfunctional monomer used was changed to 0.7 parts by mass. The gel fraction of the adhesive sheet was 54%.

[0147] (Comparative Example 18) Except for changing the isocyanate-based crosslinking agent to an epoxy crosslinking agent (E-AX) and changing the amount used to 0.05 parts by mass, a release sheet-attached pressure-sensitive adhesive sheet consisting of a first release sheet / pressure-sensitive adhesive sheet / second release sheet was obtained in the same manner as in Example 2. The gel fraction of the pressure-sensitive adhesive sheet was 41%.

[0148] Example 9 Except for changing the isocyanate-based crosslinking agent to an epoxy crosslinking agent (E-AX) and changing the amount used to 0.1 parts by mass, a release sheet-attached pressure-sensitive adhesive sheet consisting of a first release sheet / pressure-sensitive adhesive sheet / second release sheet was obtained in the same manner as in Example 1. The gel fraction of the pressure-sensitive adhesive sheet was 38%.

[0149] Example 10 Except for changing the isocyanate-based crosslinking agent to an epoxy crosslinking agent (E-AX) and changing the amount used to 0.05 parts by mass, a release sheet-attached pressure-sensitive adhesive sheet consisting of a first release sheet / pressure-sensitive adhesive sheet / second release sheet was obtained in the same manner as in Example 1. The gel fraction of the pressure-sensitive adhesive sheet was 34%.

[0150] (Comparative Example 19) Except for changing the isocyanate-based crosslinking agent to an epoxy crosslinking agent (E-AX) and changing the amount used to 0.02 parts by mass, a pressure-sensitive adhesive sheet with release sheets consisting of a first release sheet / pressure-sensitive adhesive sheet / second release sheet was obtained in the same manner as in Example 2. The gel fraction of the pressure-sensitive adhesive sheet was 36%.

[0151] (Comparative Example 20) Except for changing the isocyanate-based crosslinking agent to an epoxy crosslinking agent (E-AX) and changing the amount used to 0.01 parts by mass, a pressure-sensitive adhesive sheet with release sheets consisting of a first release sheet / pressure-sensitive adhesive sheet / second release sheet was obtained in the same manner as in Comparative Example 3. The gel fraction of the pressure-sensitive adhesive sheet was 46%.

[0152] (Comparative Example 21) Except for changing the amount of isocyanate-based crosslinking agent used to 0.005 parts by mass, a pressure-sensitive adhesive sheet with a release sheet consisting of a first release sheet / pressure-sensitive adhesive sheet / second release sheet was obtained in the same manner as in Comparative Example 20. The gel fraction of the pressure-sensitive adhesive sheet was 42%.

[0153] Example 11 Except for changing the amount of polyfunctional monomer used to 0.07 parts by mass, a pressure-sensitive adhesive sheet with release sheets consisting of a first release sheet / pressure-sensitive adhesive sheet / second release sheet was obtained in the same manner as in Example 3. The gel fraction of the pressure-sensitive adhesive sheet was 40%.

[0154] (Example 11') The amount of polyfunctional monomer used was changed to 0.06 parts by mass, and the irradiation conditions of the first ultraviolet light were changed to an illuminance of 3.0 mW / cm as measured by a Ushio Inc. ultraviolet illuminance meter UIT-θ365. 2 And the cumulative light intensity is 350mJ / cm 2 A pressure-sensitive adhesive sheet with a release sheet consisting of a first release sheet / pressure-sensitive adhesive sheet / second release sheet was obtained in the same manner as in Example 3, except for changing the conditions to: The gel fraction of the pressure-sensitive adhesive sheet was 40%.

[0155] (Comparative Example 23) The amount of polyfunctional monomer used was changed to 0.08 parts by mass, and the irradiation conditions of the first ultraviolet light were changed to an illuminance of 4.0 mW / cm as measured by a Ushio Inc. ultraviolet illuminance meter UIT-θ365. 2 And the cumulative light intensity is 250mJ / cm 2A pressure-sensitive adhesive sheet with a release sheet consisting of a first release sheet / pressure-sensitive adhesive sheet / second release sheet was obtained in the same manner as in Example 3, except for changing the conditions to: The gel fraction of the pressure-sensitive adhesive sheet was 40%.

[0156] (Comparative Example 24) The amount of polyfunctional monomer used was changed to 0.03 parts by mass, and the irradiation conditions of the first ultraviolet light were changed to an illuminance of 4.0 mW / cm as measured by a Ushio Inc. ultraviolet illuminance meter UIT-θ365. 2 And the cumulative light intensity is 250mJ / cm 2 A pressure-sensitive adhesive sheet with a release sheet consisting of a first release sheet / pressure-sensitive adhesive sheet / second release sheet was obtained in the same manner as in Example 3, except for changing the conditions to: The gel fraction of the pressure-sensitive adhesive sheet was 35%.

[0157] Example 12 The amount of polyfunctional monomer used was changed to 0.025 parts by mass, and the irradiation conditions of the first ultraviolet light were changed to an illuminance of 3.0 mW / cm as measured by an ultraviolet illuminance meter UIT-θ365 manufactured by Ushio Inc. 2 And the cumulative light intensity is 350mJ / cm 2 A pressure-sensitive adhesive sheet with a release sheet consisting of a first release sheet / pressure-sensitive adhesive sheet / second release sheet was obtained in the same manner as in Example 3, except for changing the conditions to: The gel fraction of the pressure-sensitive adhesive sheet was 35%.

[0158] Example 13 The amount of polyfunctional monomer used was changed to 0.3 parts by mass, and the irradiation conditions of the first ultraviolet light were changed to an illuminance of 4.0 mW / cm as measured by a Ushio Inc. ultraviolet illuminance meter UIT-θ365. 2 And the cumulative light intensity is 250mJ / cm 2 A pressure-sensitive adhesive sheet with release sheets consisting of a first release sheet / pressure-sensitive adhesive sheet / second release sheet was obtained in the same manner as in Example 3, except for changing the conditions to: The gel fraction of the pressure-sensitive adhesive sheet was 42%.

[0159] (Evaluation method) [Gel fraction] Approximately 100 mg of sample (adhesive sheet) was wrapped in a 150 mesh stainless steel net and immersed in approximately 40 mL of ethyl acetate in a 50 mL glass bottle at 40°C for 24 hours, and then the entire stainless steel net with the sample wrapped around it was washed by shaking and immersing it in approximately 40 mL of ethyl acetate at approximately 40°C for 30 seconds, and then the ethyl acetate adhering to the stainless steel net was wiped off with a cloth and dried in a dryer at 100°C for 60 minutes, and then weighed, and the remaining weight of the sample was calculated using the following formula. Gel fraction (%) = 100 × (weight of sample after immersion) ÷ (original weight of sample) It was calculated as follows.

[0160] [Punching evaluation] The adhesive sheet with release sheet was cut into a sample measuring 70 mm x 120 mm, and this was then punched out using a punching blade machined to a size of 54 mm x 94 mm at 25°C under atmospheric pressure to prepare an evaluation sample. After the light release PET film of the evaluation sample was peeled off diagonally from the corner at an angle of 180° in 1 to 3 seconds, or during peeling, it was visually confirmed whether or not any areas of the adhesive layer on the side of the heavy release PET film had peeled off or lifted, and the evaluation was based on the following criteria. ≪Judgment criteria≫ ◯: No peeling or lifting was observed on the surface of the adhesive layer facing the heavy release PET film. ×: Peeling or lifting was observed on the surface of the adhesive layer on the heavy release PET film side.

[0161] [Evaluation of step absorption] After peeling off the light-release PET film (second release sheet) from the adhesive sheet with release sheet, the adhesive layer of the sample was laminated with a hand roller to a 70mm x 120mm x 0.7mm glass plate with a border print 10% thicker than the adhesive layer. The heavy-release PET film (first release sheet) was then peeled off, and the sample was laminated to a flat, clean 70mm x 120mm x 0.7mm flat glass using a vacuum laminator (Joyo Engineering Vacuum Laminating Machine JE2020B-MVH) to obtain a laminate. This laminate was subjected to a pressure-heat lamination process at 40°C and 0.5MPa (gauge pressure) for 30 minutes, then left in air for 24 hours, and then left in a dry environment at 85°C for 24 hours. The laminate was visually observed and evaluated according to the following criteria. ≪Judgment criteria≫ ◯: No peeling was observed on the adhesive surface. ×: Peeling was observed on the bonded surface.

[0162] [Heat shock resistance evaluation] After the step absorbency evaluation, the laminate was left to stand for 30 minutes in an atmosphere of 85°C, and then immediately left to stand for 30 minutes in an atmosphere of -40°C, which constituted one cycle. This cycle was repeated without any interval for a total of 200 cycles, after which the laminate was visually observed and evaluated according to the following criteria. ≪Judgment criteria≫ ◯: No peeling was observed on the adhesive surface. ×: Peeling was observed on the bonded surface.

[0163] [Dynamic viscoelasticity measurement] A laminated sheet having a thickness of 1000 μm or more was prepared by laminating multiple pressure-sensitive adhesive sheets. This laminated sheet was pressurized in an autoclave at 40°C and 0.5 MPa for 20 minutes to prepare a measurement sample. This sample was subjected to dynamic viscoelasticity measurement using a dynamic viscoelasticity analyzer MCR301 (manufactured by Anton Paar), and the G 100 ´(kPa), G 100 ″(kPa), G 25 ´ (kPa) and G 25 (kPa) was measured. Using these values, G was calculated using the above formulas (1), (2) and (3). 100 , D and G 25 was calculated. This calculation was performed by outputting the data using the software attached to the dynamic viscoelasticity device. A probe with a diameter of 8 mm was used for the measurement, and a repeated strain of 0.1% was applied at a cycle of 1 Hz while the temperature in the measurement chamber was changed from -65°C to 130°C at a temperature rise rate of 3°C / min. The waveforms of the stress response σ to the strain input ε at 25°C and 100°C were analyzed to obtain the amplitude ratio G and phase difference D between ε and σ. Then, G 25 If it is less than 200, then from the above formula (4), G 25 If ≧200, the function F(G 25 ,G 100 , D) is greater than or equal to 0.

[0164] Table 1 shows the G 100 , D and G 25 The calculation results of function F, the determination results of function F, and the results of the step absorbency evaluation, punching evaluation, and heat shock resistance evaluation of the pressure-sensitive adhesive sheets of each example and comparative example are shown.

[0165] As shown in Table 1, the pressure-sensitive adhesive sheets obtained in each example exhibited a function F(G 25 ,G 100 , D) was 0 or more, and the adhesive sheets obtained in the comparative examples had excellent step absorbability, were suitable for punching during processing, and also had excellent heat shock resistance during use. 25 ,G 100 , D) was less than 0, and the film did not have all of the properties of step absorbency, punchability, and heat shock resistance.

[0166] [Table 1]

Claims

1. A pressure-sensitive adhesive sheet containing an acrylic resin, Storage modulus G obtained from dynamic viscoelasticity measurement at a frequency of 1 Hz and a temperature of 100°C １００ ' (kPa) and loss modulus G １００ Based on "(kPa), the following formula (1) G １００ =(G １００ ´ ２ +G １００ ″ ２ ) １／２ (1) G calculated from １００ , and The following formula (2) ==(180° / π)×tan －１ (1 １００ ″ / １００ ´) (2) D calculated from, and Storage modulus G obtained from dynamic viscoelasticity measurement at a frequency of 1 Hz and a temperature of 25°C ２５ ' (kPa) and loss modulus G ２５ Based on "(kPa), the following formula (3) G ２５ =(G ２５ ´ ２ +G ２５ ″ ２ ) １／２ (3) G calculated from ２５ , A function F(G ２５ , G １００ , D) G ２５ <200, the function F(G ２５ , G １００ , D) F(G ２５ ,G １００ ,D)=G ２５ -2G １００ +4D-260 (4) is greater than or equal to 0, G ２５ If ≧200, the function F(G ２５ , G １００ , D) F(G ２５ ,G １００ ,D)=-G ２５ -2G １００ +4D+140 (5) is 0 or more.

2. The pressure-sensitive adhesive sheet according to claim 1 , which is for use in a vehicle.

3. A pressure-sensitive adhesive sheet with a release sheet, comprising the pressure-sensitive adhesive sheet according to claim 1 or 2.

4. A method for producing the release sheet-attached pressure-sensitive adhesive sheet according to claim 3, comprising the steps of: The thickness of the pressure-sensitive adhesive sheet is 50 μm or more and 350 μm or less, a laminate obtained by laminating a polyester film coated with a release agent having a thickness of 50 μm or more and 100 μm or less on one surface of the pressure-sensitive adhesive sheet so that the release-agent-coated surface is in contact with the polyester film; The manufacturing method comprises a step of laminating a polyester film coated with a release agent having a thickness of 25 μm or more and 75 μm or less so that the release agent-coated surface of the polyester film is in contact with the other surface of the pressure-sensitive adhesive sheet.

5. A method for producing the release sheet-attached pressure-sensitive adhesive sheet according to claim 3, comprising the steps of: The thickness of the pressure-sensitive adhesive sheet is 50 μm or more and 350 μm or less, a step of applying a pressure-sensitive adhesive composition to a release agent-coated surface of a polyester film having a thickness of 50 μm or more and 100 μm or less to form a coating film; a step of laminating a polyester film coated with a release agent having a thickness of 25 μm or more and 75 μm or less so that the release agent-coated surface of the polyester film is in contact with the exposed surface of the coating film; and curing the coating film by irradiating it with active energy rays to form the pressure-sensitive adhesive sheet.

6. The acrylic resin The adhesive has a structure in which an acrylic adhesive resin containing at least a (meth)acrylic acid ester unit and a monomer unit having a crosslinkable functional group is crosslinked with a thermal crosslinking agent, The pressure-sensitive adhesive sheet according to claim 1 or 2, wherein the pressure-sensitive adhesive sheet has a gel fraction of 50% or less.

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