Adhesive tape

Abstract

The purpose of the present invention is to provide an adhesive tape which can be less environmentally harmful and which exhibits excellent optical transparency even if exposed to a high temperature and high humidity environment. The present invention is an adhesive tape having an adhesive layer. The adhesive layer contains a (meth)acrylic copolymer. The content of carbon derived from organisms in the adhesive layer is 30% or more. The adhesive tape satisfies at least one configuration selected from the group consisting of the first configuration and the second configuration. First configuration: the water vapor transmission rate P of the adhesive layer, as calculated using formula (i), is 11 g·mm / (m2·day) or more. In formula (i), WVTR denotes the water vapor transmission rate (g / (m2·day)) per unit area for one day of the adhesive layer in an environment having a temperature of 40°C and a relative humidity of 90%, and t denotes the thickness (mm) of the adhesive layer. Second configuration: the (meth)acrylic copolymer contains: at least one type of constituent unit selected from the group consisting of a constituent unit derived from n-heptyl (meth)acrylate and a constituent unit derived from 2-octyl (meth)acrylate; and a constituent unit derived from a nitrogen atom-containing monomer.

Description

adhesive tape

[0001] The present invention relates to an adhesive tape.

[0002] Conventionally, adhesive tapes having an adhesive layer containing an adhesive have been widely used to fix components in electronic components, vehicles, houses, and building materials (e.g., Patent Documents 1 to 3). Specifically, adhesive tapes have been used to adhere a cover panel for protecting the surface of a portable electronic device to a touch panel module or a display panel module, or to adhere a touch panel module to a display panel module.

[0003] JP 2015-052050 A JP 2015-021067 A JP 2015-120876 A

[0004] In recent years, the depletion of petroleum resources and carbon dioxide emissions from the combustion of petroleum-derived products have become a concern. Therefore, efforts have been made, primarily in the medical and packaging fields, to conserve petroleum resources and reduce environmental impact by replacing petroleum-derived materials with bio-derived materials. These efforts have spread to all fields, and the use of bio-derived materials is now being sought in the field of adhesive tapes as well. Furthermore, adhesive tapes used to bond electronic components and the like are required to be resistant to corrosion of metals and metal oxides. Furthermore, adhesive tapes used to bond display panel modules and the like require high optical transparency, but conventional adhesive tapes suffer from the problem of whitening in high-temperature, high-humidity environments.

[0005] An object of the present invention is to provide a pressure-sensitive adhesive tape that can reduce the environmental load and has excellent optical transparency even when exposed to a high-temperature, high-humidity environment.

[0006] Disclosure 1 relates to a pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer, the pressure-sensitive adhesive layer containing a (meth)acrylic copolymer, the pressure-sensitive adhesive layer having a content of bio-derived carbon of 30% or more, and satisfying at least one constitution selected from the group consisting of the following first constitution and the following second constitution: First constitution: The pressure-sensitive adhesive layer has a water vapor permeability coefficient P of 11 g mm / (m ２-day) or longer. Second configuration: the (meth)acrylic copolymer contains at least one structural unit selected from the group consisting of structural units derived from n-heptyl(meth)acrylate and structural units derived from 2-octyl(meth)acrylate, and a structural unit derived from a nitrogen atom-containing monomer. Disclosure 2 is the pressure-sensitive adhesive tape of Disclosure 1 that satisfies the first configuration. Disclosure 3 is the pressure-sensitive adhesive tape of Disclosure 2 that contains at least one structural unit selected from the group consisting of structural units derived from n-heptyl(meth)acrylate and structural units derived from 2-octyl(meth)acrylate. Disclosure 4 is the pressure-sensitive adhesive tape of Disclosure 2 or 3 that contains at least one structural unit selected from the group consisting of structural units derived from a hydroxyl group-containing monomer and structural units derived from a nitrogen atom-containing monomer. Disclosure 5 is the pressure-sensitive adhesive tape of Disclosure 1, 2, 3, or 4 that satisfies the second configuration.

[0014] Disclosure 6 is the pressure-sensitive adhesive tape of Disclosure 5, wherein the (meth)acrylic copolymer further contains a structural unit derived from a hydroxyl group-containing monomer. Disclosure 7 is the pressure-sensitive adhesive tape of Disclosure 4 or 6, wherein the content of the structural unit derived from the hydroxyl group-containing monomer in the (meth)acrylic copolymer is 5% by mass or more and 30% by mass or less. Disclosure 8 is the pressure-sensitive adhesive tape of Disclosure 1, 2, 3, 4, 5, 6, or 7, wherein the (meth)acrylic copolymer contains a structural unit derived from a (meth)acrylate containing carbon of biological origin. Disclosure 9 is the pressure-sensitive adhesive tape of Disclosure 8, wherein at least one structural unit selected from the group consisting of the structural unit derived from n-heptyl (meth)acrylate and the structural unit derived from 2-octyl (meth)acrylate contains carbon of biological origin. Disclosure 10 is the pressure-sensitive adhesive tape of Disclosure 4, 5, 6, 7, 8, or 9, wherein the structural unit derived from the nitrogen atom-containing monomer contains a structural unit derived from an amide group-containing monomer. The present disclosure 11 is the pressure-sensitive adhesive tape of the present disclosure 4, 5, 6, 7, 8, 9, or 10, wherein the content of the constituent units derived from the nitrogen atom-containing monomer in the (meth)acrylic copolymer is 5% by mass or more and 10% by mass or less.

[0023] Disclosure 12 is the pressure-sensitive adhesive tape of Disclosures 4, 5, 6, 7, 8, 9, 10, or 11, wherein the (meth)acrylic copolymer contains structural units derived from the hydroxyl group-containing monomer and structural units derived from the nitrogen atom-containing monomer in a total content of 10% by mass or more and 30% by mass or less. Disclosure 13 is the pressure-sensitive adhesive tape of Disclosures 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12, wherein the (meth)acrylic copolymer contains structural units derived from a carboxy group-containing monomer, and the content of the structural units derived from the carboxy group-containing monomer in the (meth)acrylic copolymer is less than 0.5% by mass. Disclosure 14 is the pressure-sensitive adhesive tape of Disclosures 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, or 13, wherein the (meth)acrylic copolymer contains structural units derived from isobornyl (meth)acrylate.

[0023] Disclosure 15 is the pressure-sensitive adhesive tape of Disclosure 14, wherein the content of structural units derived from isobornyl (meth)acrylate in the (meth)acrylic copolymer is 10% by mass or more and 45% by mass or less. Disclosure 16 is the pressure-sensitive adhesive tape of Disclosure 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15, wherein the weight-average molecular weight (Mw) of the (meth)acrylic copolymer is 300,000 or more and 900,000 or less. Disclosure 17 is the pressure-sensitive adhesive tape of Disclosure 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, or 16, wherein the pressure-sensitive adhesive layer contains a silane coupling agent. Disclosure 18 is the pressure-sensitive adhesive tape of Disclosures 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, or 17, wherein the pressure-sensitive adhesive layer has a gel fraction of 40% by mass or more and 95% by mass or less. Disclosure 19 is a pressure-sensitive adhesive tape of Disclosures 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, or 17, wherein the pressure-sensitive adhesive layer has a shear storage modulus at 23°C of 0.5 x 10. ５ Pa or more 3.0×10 ６The pressure-sensitive adhesive tape of the present disclosure 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, or 19, wherein the haze value at 20°C or higher and 25°C or lower is less than 3.0%, and the haze value at 20°C or higher and 25°C or lower after standing for 500 hours in an environment of 65°C and 90% RH is less than 3.0%. Disclosure 21 is the pressure-sensitive adhesive tape of Disclosures 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20, wherein the 180° peel strength from glass at 23°C is 10 N / 25 mm or more.

[0007]

[0008] In formula (i), WVTR is the water vapor transmission rate (g / (m)) per unit area of ​​the pressure-sensitive adhesive layer in an environment of 40°C and 90% RH for one day. ２ and t represents the thickness (mm) of the pressure-sensitive adhesive layer. The present invention will be described in detail below. An adhesive tape satisfying the first configuration is also referred to as the "adhesive tape of invention 1," and an adhesive tape satisfying the second configuration is also referred to as the "adhesive tape of invention 2." Furthermore, matters common to the adhesive tape of invention 1 and the adhesive tape of invention 2 will not be specified in particular, or will be described as the "adhesive tape of the present invention."

[0009] The present inventors have investigated, in a pressure-sensitive adhesive tape containing a (meth)acrylic copolymer in its pressure-sensitive adhesive layer, adjusting the water vapor transmission coefficient of the pressure-sensitive adhesive layer to fall within a specific range, and setting the content of bio-derived carbon in the pressure-sensitive adhesive layer to a specific proportion or more, and using a specific acrylic monomer and a nitrogen atom-containing monomer as monomers constituting the (meth)acrylic copolymer, and setting the content of bio-derived carbon in the pressure-sensitive adhesive layer to a specific proportion or more. As a result, they have found that a pressure-sensitive adhesive tape having a specific configuration can reduce the environmental load and has excellent optical transparency even when exposed to a high-temperature, high-humidity environment, and have completed the present invention.

[0010] The pressure-sensitive adhesive tape of the present invention has a pressure-sensitive adhesive layer. The pressure-sensitive adhesive layer contains a (meth)acrylic copolymer. The lower limit of the bio-derived carbon content in the pressure-sensitive adhesive layer is 30%. When the bio-derived carbon content in the pressure-sensitive adhesive layer is 30% or more, the pressure-sensitive adhesive tape of the present invention is excellent in terms of saving petroleum resources and reducing carbon dioxide emissions, and can reduce the environmental burden. The lower limit of the bio-derived carbon content in the pressure-sensitive adhesive layer is preferably 50%, more preferably 55%, and even more preferably 60%. The upper limit of the bio-derived carbon content is not particularly limited and may be 100%. Note that while bio-derived carbon contains a certain proportion of the radioactive isotope (C-14), petroleum-derived carbon contains almost no C-14. Therefore, the bio-derived carbon content can be calculated by measuring the concentration of C-14 in the pressure-sensitive adhesive layer. Specifically, it can be measured in accordance with ASTM D6866-22, a standard widely used in the bioplastics industry.

[0011] The content of bio-derived carbon in the pressure-sensitive adhesive layer can be adjusted by the content of the (meth)acrylic copolymer containing bio-derived carbon and other components containing bio-derived carbon in the pressure-sensitive adhesive layer.

[0012] The pressure-sensitive adhesive tape of the present invention satisfies at least one constitution selected from the group consisting of the following first constitution and the following second constitution: First constitution: The pressure-sensitive adhesive layer has a water vapor permeability coefficient P calculated by the above formula (i) of 11 g mm / (m ２ Second configuration: the (meth)acrylic copolymer contains at least one structural unit selected from the group consisting of structural units derived from n-heptyl (meth)acrylate and structural units derived from 2-octyl (meth)acrylate, and a structural unit derived from a nitrogen atom-containing monomer. By satisfying the following first configuration and at least one configuration selected from the group consisting of the following second configuration, the pressure-sensitive adhesive tape of the present invention can reduce the environmental load and exhibit excellent optical transparency even when exposed to a high-temperature, high-humidity environment.

[0013] The pressure-sensitive adhesive layer in the pressure-sensitive adhesive tape of the first invention has a lower limit of the water vapor permeability coefficient P calculated from the above formula (i) of 11 g mm / (m ２ The water vapor permeability coefficient P of the pressure-sensitive adhesive layer in the pressure-sensitive adhesive tape of the present invention 1 is 11 g mm / (m ２ ·day) or more, the resulting pressure-sensitive adhesive tape can be prevented from whitening, and the resulting pressure-sensitive adhesive tape can have excellent optical transparency even when exposed to a high-temperature, high-humidity environment. ２ ·day), and a more preferable lower limit is 15 g·mm / (m ２ In addition, the pressure-sensitive adhesive layer in the pressure-sensitive adhesive tape of the second invention has a lower limit of the water vapor permeability coefficient P calculated from the above formula (i) of 11 g mm / (m ２ The water vapor permeability coefficient P of the pressure-sensitive adhesive layer in the pressure-sensitive adhesive tape of the present invention 2 is preferably 11 g·mm / (m ２ ·day) or more, the resulting pressure-sensitive adhesive tape can be further prevented from whitening, and the optical transparency can be further improved even when exposed to a high-temperature, high-humidity environment. A more preferable lower limit of the water vapor transmission coefficient P of the pressure-sensitive adhesive layer in the pressure-sensitive adhesive tape of invention 2 is 13 g·mm / (m ２ ·day), and a more preferable lower limit is 15 g·mm / (m ２ From the viewpoint of preventing deterioration of components such as a display panel module fixed with the adhesive tape due to water vapor, the preferred upper limit of the water vapor permeability coefficient P of the adhesive layer is 30 g mm / (m ２ ·day), and a more preferable upper limit is 25 g·mm / (m ２ ·day), and a more preferable upper limit is 20 g·mm / (m ２The water vapor transmission coefficient P of the pressure-sensitive adhesive layer can be obtained by measuring the water vapor transmission rate WVTR per unit area of ​​the pressure-sensitive adhesive layer for one day at 40°C and 90% RH (hereinafter, sometimes simply referred to as "the water vapor transmission rate WVTR of the pressure-sensitive adhesive layer at 40°C and 90% RH"), and then calculating using the obtained water vapor transmission rate WVTR and the thickness of the pressure-sensitive adhesive layer. The water vapor transmission rate WVTR of the pressure-sensitive adhesive layer at 40°C and 90% RH can be measured in accordance with JIS K 7129B, using a water vapor transmission humidity test using the Mocon method under conditions of 40°C and 90% RH.

[0014] Generally, the water vapor transmission rate WVTR is inversely proportional to the thickness of the object to be measured, and therefore the water vapor transmission rate WVTR of the PSA layer at 40°C and 90% RH is inversely proportional to the thickness of the PSA layer. Therefore, by using the water vapor transmission coefficient P of the PSA layer obtained by multiplying the water vapor transmission rate WVTR of the PSA layer at 40°C and 90% RH by the thickness of the PSA layer, the water vapor transmission rate of the PSA layer can be calculated as a value independent of the thickness of the PSA layer.

[0015] As a method for adjusting the water vapor transmission coefficient P of the pressure-sensitive adhesive layer and the water vapor transmission rate WVTR of the pressure-sensitive adhesive layer at 40°C and 90% RH, for example, a method for adjusting the composition of the (meth)acrylic copolymer described later or the type of additive described later is preferred.

[0016] The preferred lower limit of the thickness of the pressure-sensitive adhesive layer is 5 μm, and the preferred upper limit is 500 μm. When the thickness of the pressure-sensitive adhesive layer is 5 μm or more, the resulting pressure-sensitive adhesive tape has higher adhesive strength. When the thickness of the pressure-sensitive adhesive layer is 500 μm or less, the pressure-sensitive adhesive tape of the present invention can be more suitably used for fixing electronic components. The more preferred lower limit of the thickness of the pressure-sensitive adhesive layer is 10 μm, and even more preferred lower limit is 25 μm, and even more preferred upper limit is 300 μm, and even more preferred upper limit is 250 μm.

[0017] In the pressure-sensitive adhesive tape of the second invention, the (meth)acrylic copolymer comprises at least one structural unit selected from the group consisting of structural units derived from n-heptyl (meth)acrylate and structural units derived from 2-octyl (meth)acrylate. When the (meth)acrylic copolymer comprises at least one structural unit selected from the group consisting of structural units derived from n-heptyl (meth)acrylate and structural units derived from 2-octyl (meth)acrylate, the resulting pressure-sensitive adhesive tape has high adhesive strength. Furthermore, in the pressure-sensitive adhesive tape of the first invention, the (meth)acrylic copolymer preferably comprises at least one structural unit selected from the group consisting of structural units derived from n-heptyl (meth)acrylate and structural units derived from 2-octyl (meth)acrylate. When the (meth)acrylic copolymer comprises at least one structural unit selected from the group consisting of structural units derived from n-heptyl (meth)acrylate and structural units derived from 2-octyl (meth)acrylate, the resulting pressure-sensitive adhesive tape has high adhesive strength. In this specification, "(meth)acrylic" means acrylic or methacrylic, and "(meth)acrylate" means acrylate or methacrylate.

[0018] The (meth)acrylic copolymer preferably contains structural units derived from a (meth)acrylate containing bio-derived carbon. When the (meth)acrylic copolymer contains structural units derived from a (meth)acrylate containing bio-derived carbon, the content of bio-derived carbon in the pressure-sensitive adhesive layer increases, and the environmental impact of the resulting pressure-sensitive adhesive tape can be further reduced. In this specification, "containing bio-derived carbon" means that the bio-based carbon content of the compound measured according to ASTM D6866-22 is 1% or more.

[0019] It is preferred that at least one structural unit selected from the group consisting of the structural units derived from n-heptyl(meth)acrylate and the structural units derived from 2-octyl(meth)acrylate contains bio-derived carbon. When at least one structural unit selected from the group consisting of the structural units derived from n-heptyl(meth)acrylate and the structural units derived from 2-octyl(meth)acrylate contains bio-derived carbon, the content of bio-derived carbon in the pressure-sensitive adhesive layer increases, and the environmental impact of the resulting pressure-sensitive adhesive tape can be further reduced. In other words, when the (meth)acrylic copolymer contains at least one structural unit selected from the group consisting of structural units derived from n-heptyl(meth)acrylate containing bio-derived carbon and structural units derived from 2-octyl(meth)acrylate containing bio-derived carbon, the resulting pressure-sensitive adhesive tape can further reduce the environmental impact and have higher adhesive strength.

[0020] The n-heptyl (meth)acrylate containing bio-derived carbon and the 2-octyl (meth)acrylate containing bio-derived carbon are not particularly limited as long as they contain bio-derived carbon. However, they are preferably synthesized by esterification of a bio-derived material, such as n-heptyl alcohol or 2-octanol, with (meth)acrylic acid. They are also preferably synthesized by transesterification of a bio-derived material, such as n-heptyl alcohol or 2-octanol, with a (meth)acrylic acid ester. The bio-derived n-heptyl alcohol can be obtained inexpensively and easily by cracking a material extracted from plants or animals (e.g., ricinoleic acid derived from castor oil). The bio-derived 2-octanol can be obtained inexpensively and easily by alkali-melting a material extracted from plants or animals (e.g., ricinoleic acid derived from castor oil).

[0021] The preferred lower limit of the total content of the structural units derived from n-heptyl (meth)acrylate and the structural units derived from 2-octyl (meth)acrylate in the (meth)acrylic copolymer is 25% by mass. When the total content of the structural units derived from n-heptyl (meth)acrylate and the structural units derived from 2-octyl (meth)acrylate is 25% by mass or more, the resulting pressure-sensitive adhesive tape has higher adhesive strength. Furthermore, when the total content of the structural units derived from n-heptyl (meth)acrylate containing bio-derived carbon and the structural units derived from 2-octyl (meth)acrylate containing bio-derived carbon is 25% by mass or more, the content of bio-derived carbon in the pressure-sensitive adhesive layer can be further increased. A more preferred lower limit of the total content of the structural units derived from n-heptyl (meth)acrylate and the 2-octyl (meth)acrylate is 35% by mass, an even more preferred lower limit is 45% by mass, and an even more preferred lower limit is 55% by mass. Furthermore, from the viewpoint of adjusting the haze value at room temperature (20°C or higher and 25°C or lower) after leaving the pressure-sensitive adhesive tape of the present invention (described later) at rest for 500 hours in an environment of 65°C and 90% RH, the upper limit of the total content of the structural units derived from n-heptyl(meth)acrylate and the structural units derived from 2-octyl(meth)acrylate is preferably 90% by mass, more preferably 85% by mass, and even more preferably 80% by mass. When the (meth)acrylic copolymer does not contain the structural units derived from n-heptyl(meth)acrylate or the structural units derived from 2-octyl(meth)acrylate, the total content of the structural units derived from n-heptyl(meth)acrylate and the structural units derived from 2-octyl(meth)acrylate is defined as the content of the structural units derived from n-heptyl(meth)acrylate or the structural units derived from 2-octyl(meth)acrylate alone contained in the acrylic copolymer. The content ratio of the constituent unit derived from n-heptyl (meth)acrylate and the constituent unit derived from 2-octyl (meth)acrylate in the (meth)acrylic copolymer can be determined by mass spectrometry of the (meth)acrylic copolymer and １H-NMR measurement is carried out, and the value can be calculated from the integrated intensity ratio of the hydrogen peak derived from n-heptyl(meth)acrylate or 2-octyl(meth)acrylate.

[0022] The (meth)acrylic copolymer preferably contains a structural unit derived from isobornyl (meth)acrylate. When the (meth)acrylic copolymer contains a structural unit derived from isobornyl (meth)acrylate, the cohesive strength of the pressure-sensitive adhesive layer increases, and the resulting pressure-sensitive adhesive tape has higher adhesive strength.

[0023] The isobornyl (meth)acrylate preferably contains bio-derived carbon. By including the isobornyl (meth)acrylate in the bio-derived carbon, the content of bio-derived carbon in the pressure-sensitive adhesive layer can be further increased, and the environmental load of the resulting pressure-sensitive adhesive tape can be further reduced.

[0024] The isobornyl (meth)acrylate containing bio-derived carbon is not particularly limited as long as it contains bio-derived carbon, but is preferably synthesized by reacting camphene, a bio-derived material, with (meth)acrylic acid. Camphene, a bio-derived material, can be obtained inexpensively and easily, for example, by isomerizing pinene extracted from pine resin.

[0025] When the (meth)acrylic copolymer contains the structural unit derived from isobornyl (meth)acrylate, the preferred lower limit of the content of the structural unit derived from isobornyl (meth)acrylate in the (meth)acrylic copolymer is 3% by mass, and the preferred upper limit is 45% by mass. When the content of the structural unit derived from isobornyl (meth)acrylate is 3% by mass or more, the cohesive strength of the pressure-sensitive adhesive layer becomes greater, and the resulting pressure-sensitive adhesive tape has higher adhesive strength. When the content of the structural unit derived from isobornyl (meth)acrylate is 45% by mass or less, the pressure-sensitive adhesive layer does not become too hard, and the resulting pressure-sensitive adhesive tape has higher adhesive strength. The content of the structural units derived from isobornyl (meth)acrylate in the (meth)acrylic copolymer is more preferably 5% by mass, even more preferably 10% by mass, even more preferably 15% by mass, and particularly preferably 18% by mass, and more preferably 40% by mass, even more preferably 30% by mass, even more preferably 25% by mass, and particularly preferably 22% by mass. The content of the structural units derived from isobornyl (meth)acrylate in the (meth)acrylic copolymer is determined by mass spectrometry of the (meth)acrylic copolymer and １ H-NMR measurement can be carried out and the concentration can be calculated from the integrated intensity ratio of the hydrogen peak derived from isobornyl (meth)acrylate.

[0026] In the pressure-sensitive adhesive tape of the first invention, the (meth)acrylic copolymer preferably further comprises at least one structural unit selected from the group consisting of structural units derived from hydroxyl group-containing monomers and structural units derived from nitrogen atom-containing monomers. When the (meth)acrylic copolymer comprises at least one structural unit selected from the group consisting of structural units derived from hydroxyl group-containing monomers and structural units derived from nitrogen atom-containing monomers, the polarity of the pressure-sensitive adhesive layer is increased, making it easier to adjust the water vapor permeability coefficient P of the pressure-sensitive adhesive layer to the above-mentioned range. As a result, the resulting pressure-sensitive adhesive tape can be more effectively prevented from whitening even when exposed to a high-temperature, high-humidity environment, resulting in more excellent optical transparency. Furthermore, when the pressure-sensitive adhesive layer contains a crosslinking agent described below, the (meth)acrylic copolymer comprises structural units derived from hydroxyl group-containing monomers, which facilitates crosslinking when the pressure-sensitive adhesive layer contains a crosslinking agent described below. This increases the durability of the pressure-sensitive adhesive layer against slippage and deformation of the adherend under high-temperature, high-humidity environments, and further improves the adhesion of the resulting pressure-sensitive adhesive tape to the adherend. When the (meth)acrylic copolymer contains a structural unit derived from a nitrogen atom-containing monomer, the cohesive strength of the pressure-sensitive adhesive layer increases, and the resulting pressure-sensitive adhesive tape has higher adhesive strength. The structural unit derived from the hydroxyl group-containing monomer and the structural unit derived from the nitrogen atom-containing monomer may be used alone or in combination of two or more thereof.

[0027] In the pressure-sensitive adhesive tape of the present invention 2, the (meth)acrylic copolymer contains a structural unit derived from a nitrogen-atom-containing monomer. The (meth)acrylic copolymer contains a structural unit derived from a nitrogen-atom-containing monomer, which increases the polarity of the pressure-sensitive adhesive layer and prevents whitening of the resulting pressure-sensitive adhesive tape even when exposed to a high-temperature, high-humidity environment, resulting in excellent optical transparency. Furthermore, the cohesive strength of the pressure-sensitive adhesive layer increases, resulting in a high adhesive strength of the resulting pressure-sensitive adhesive tape.

[0028] In the pressure-sensitive adhesive tape of the present invention 2, the (meth)acrylic copolymer preferably further contains a structural unit derived from a hydroxyl group-containing monomer. When the (meth)acrylic copolymer further contains a structural unit derived from a hydroxyl group-containing monomer, the polarity of the pressure-sensitive adhesive layer becomes greater, and the resulting pressure-sensitive adhesive tape can be more effectively prevented from whitening even when exposed to a high-temperature, high-humidity environment, resulting in more excellent optical transparency. Furthermore, when the pressure-sensitive adhesive layer contains a crosslinking agent described below, crosslinking is more likely to proceed, the durability of the pressure-sensitive adhesive layer against slippage and deformation of the adherend under a high-temperature, high-humidity environment is improved, and the adhesion of the resulting pressure-sensitive adhesive tape to the adherend is also further improved.

[0029] Examples of the hydroxyl group-containing monomer include 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, 1-methyl-3-hydroxypropyl (meth)acrylate, 1-methyl-2-hydroxyethyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 1-methyl-2-hydroxypropyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 1-ethyl-2-hydroxyethyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 5-hydroxypentyl (meth)acrylate, 7-hydroxyheptyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, and 9-hydroxynonyl (meth)acrylate. Among these, the hydroxyl group-containing monomer preferably includes at least one selected from the group consisting of 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, 1-methyl-3-hydroxypropyl (meth)acrylate, 1-methyl-2-hydroxyethyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and 2-hydroxypropyl (meth)acrylate, and from the viewpoints of structurally well-balanced reactivity and ease of control of reactivity with a crosslinking agent, 2-hydroxypropyl (meth)acrylate is more preferred.

[0030] The hydroxyl group-containing monomer preferably contains bio-derived carbon. By including bio-derived carbon in the hydroxyl group-containing monomer, the content of bio-derived carbon in the pressure-sensitive adhesive layer can be further increased, and the environmental load of the resulting pressure-sensitive adhesive tape can be further reduced.

[0031] The preferred lower limit of the content of the structural units derived from the hydroxyl group-containing monomer in the (meth)acrylic copolymer is 5% by mass, and the preferred upper limit is 30% by mass. When the content of the structural units derived from the hydroxyl group-containing monomer is 5% by mass or more, the polarity of the pressure-sensitive adhesive layer is increased, making it easier to adjust the water vapor permeability coefficient P of the pressure-sensitive adhesive layer within the above-mentioned range. As a result, the resulting pressure-sensitive adhesive tape can be more effectively prevented from whitening even when exposed to a high-temperature, high-humidity environment, resulting in more excellent optical transparency. When the content of the structural units derived from the hydroxyl group-containing monomer is 30% by mass or less, the pressure-sensitive adhesive layer does not become too hard, and the resulting pressure-sensitive adhesive tape has higher adhesive strength. The more preferred lower limit of the content of the structural units derived from the hydroxyl group-containing monomer is 6% by mass, and even more preferred is 7% by mass, and the more preferred upper limit is 25% by mass, even more preferred is 20% by mass, and even more preferred is 15% by mass. The content of the structural units derived from the hydroxyl group-containing monomer in the (meth)acrylic copolymer can be determined by mass spectrometry of the (meth)acrylic copolymer and １ H-NMR measurement can be carried out, and the amount can be calculated from the integrated intensity ratio of the hydrogen peak derived from the hydroxyl group-containing monomer.

[0032] Examples of the nitrogen atom-containing monomer include amide group-containing monomers, nitrile group-containing monomers, amino group-containing monomers, isocyanate group-containing monomers, etc. Among these, amide group-containing monomers are preferred because they have a high glass transition temperature, increase the cohesive strength of the pressure-sensitive adhesive layer, and enable the resulting pressure-sensitive adhesive tape to have higher adhesive strength.

[0033] Examples of the amide group-containing monomer include acrylic monomers having an amide group, such as (meth)acrylamide, dimethyl(meth)acrylamide, diethyl(meth)acrylamide, isopropyl(meth)acrylamide, t-butyl(meth)acrylamide, methoxymethyl(meth)acrylamide, butoxymethyl(meth)acrylamide, etc. Among these, (meth)acrylamide, dimethyl(meth)acrylamide, and diethyl(meth)acrylamide are preferred because of their easy availability and ease of handling.

[0034] Examples of the nitrile group-containing monomer include acrylic monomers having a nitrile group, such as (meth)acrylonitrile.

[0035] The nitrogen atom-containing monomer preferably contains bio-derived carbon. By including bio-derived carbon in the nitrogen atom-containing monomer, the content of bio-derived carbon in the pressure-sensitive adhesive layer can be further increased, and the environmental load of the resulting pressure-sensitive adhesive tape can be further reduced.

[0036] The preferred lower limit of the content of the structural units derived from the nitrogen-atom-containing monomer in the (meth)acrylic copolymer is 5% by mass, and the preferred upper limit is 25% by mass. When the content of the structural units derived from the nitrogen-atom-containing monomer is 5% by mass or more, the polarity of the pressure-sensitive adhesive layer is increased, making it easier to adjust the water vapor permeability coefficient P of the pressure-sensitive adhesive layer to the above-mentioned range. As a result, the resulting pressure-sensitive adhesive tape can be further prevented from whitening even when exposed to a high-temperature, high-humidity environment, resulting in more excellent optical transparency. Furthermore, the cohesive strength of the pressure-sensitive adhesive layer is increased, resulting in the resulting pressure-sensitive adhesive tape having higher adhesive strength. When the content of the structural units derived from the nitrogen-atom-containing monomer is 25% by mass or less, the pressure-sensitive adhesive layer does not become too hard, resulting in the resulting pressure-sensitive adhesive tape having higher adhesive strength. The content of the structural units derived from the nitrogen atom-containing monomer in the (meth)acrylic copolymer is more preferably 5.5% by mass, even more preferably 6% by mass, and even more preferably 7% by mass, and more preferably 20% by mass, even more preferably 15% by mass, even more preferably 10% by mass, particularly preferably 9.5% by mass, and especially preferably 9% by mass. The content of the structural units derived from the nitrogen atom-containing monomer in the (meth)acrylic copolymer can be determined by mass spectrometry of the (meth)acrylic copolymer and １ H-NMR measurement can be carried out, and the amount can be calculated from the integrated intensity ratio of the hydrogen peak derived from the nitrogen atom-containing monomer.

[0037] The preferred lower limit of the total content of the structural units derived from the hydroxyl group-containing monomer and the structural units derived from the nitrogen atom-containing monomer in the (meth)acrylic copolymer is 10% by mass, and the preferred upper limit is 30% by mass. When the total content of the structural units derived from the hydroxyl group-containing monomer and the structural units derived from the nitrogen atom-containing monomer is 10% by mass or more, the polarity of the pressure-sensitive adhesive layer becomes greater, and it becomes easier to adjust the water vapor permeability coefficient P of the pressure-sensitive adhesive layer to the above-mentioned range. As a result, the obtained pressure-sensitive adhesive tape can be further prevented from whitening even when exposed to a high-temperature, high-humidity environment, and therefore has better optical transparency. When the total content of the structural units derived from the hydroxyl group-containing monomer and the structural units derived from the nitrogen atom-containing monomer is 30% by mass or less, the pressure-sensitive adhesive layer does not become too hard, and the obtained pressure-sensitive adhesive tape has higher adhesive strength. The total content of the structural units derived from the hydroxyl group-containing monomer and the structural units derived from the nitrogen atom-containing monomer is more preferably 12% by mass, even more preferably 14% by mass, and more preferably 28% by mass, even more preferably 26% by mass. In addition, when the (meth)acrylic copolymer does not contain any structural units derived from the hydroxyl group-containing monomer or any structural units derived from the nitrogen atom-containing monomer, the total content of the structural units derived from the hydroxyl group-containing monomer and the structural units derived from the nitrogen atom-containing monomer is defined as the content of the structural units alone contained in the acrylic copolymer, out of the structural units derived from the hydroxyl group-containing monomer or the structural units derived from the nitrogen atom-containing monomer.

[0038] The (meth)acrylic copolymer may further contain a constituent unit derived from a polar functional group-containing monomer other than the nitrogen atom-containing monomer and the hydroxyl group-containing monomer. When the (meth)acrylic copolymer contains a constituent unit derived from the other polar functional group-containing monomer, the polarity of the pressure-sensitive adhesive layer becomes greater, and the resulting pressure-sensitive adhesive tape can be more effectively prevented from whitening even when exposed to a high-temperature, high-humidity environment, resulting in more excellent optical transparency.

[0039] Examples of the structural units derived from the other polar functional group-containing monomers include structural units derived from carboxy group-containing monomers and structural units derived from glycidyl group-containing monomers. These structural units derived from other polar functional group-containing monomers may be used alone or in combination of two or more. Among these, structural units derived from carboxy group-containing monomers are preferred from the viewpoint of increasing the cohesive strength of the pressure-sensitive adhesive layer and providing the resulting pressure-sensitive adhesive tape with higher adhesive strength.

[0040] Examples of the carboxyl group-containing monomer include acrylic monomers having a carboxyl group, such as (meth)acrylic acid.

[0041] The carboxy group-containing monomer preferably contains bio-derived carbon. By including bio-derived carbon in the carboxy group-containing monomer, the content of bio-derived carbon in the pressure-sensitive adhesive layer increases, and the environmental load of the resulting pressure-sensitive adhesive tape can be further reduced.

[0042] Generally, in electronic components, in-vehicle components, and the like, which are adherends of pressure-sensitive adhesive tapes, metals or metal oxides are used in parts such as touch sensors and copper wiring. When a pressure-sensitive adhesive tape containing a (meth)acrylic copolymer in which a relatively large amount of the above-mentioned carboxyl group-containing monomer is copolymerized around such metals or metal oxides is used, there is a problem that the metals or metal oxides corrode, causing defects over time. Therefore, the content of structural units derived from the above-mentioned carboxyl group-containing monomers in the (meth)acrylic copolymer is preferably less than 0.5% by mass. By having the content of structural units derived from the above-mentioned carboxyl group-containing monomers less than 0.5% by mass, the corrosiveness of the resulting pressure-sensitive adhesive tape to metals or metal oxides (metal corrosiveness of the pressure-sensitive adhesive tape) can be further suppressed. Furthermore, from the viewpoint of metal corrosiveness, it is more preferable that the (meth)acrylic copolymer does not contain structural units derived from the above-mentioned carboxyl group-containing monomers. The content of structural units derived from the above-mentioned carboxyl group-containing monomers in the (meth)acrylic copolymer can be determined by mass spectrometry of the (meth)acrylic copolymer and １H-NMR measurement can be carried out, and the amount can be calculated from the integrated intensity ratio of the hydrogen peak derived from the carboxy group-containing monomer.

[0043] The (meth)acrylic copolymer may contain a glycidyl group-containing monomer, such as an acrylic monomer having a glycidyl group, such as glycidyl (meth)acrylate.

[0044] The (meth)acrylic copolymer may have a structural unit derived from a monomer other than the structural unit derived from the n-heptyl(meth)acrylate, the structural unit derived from the 2-octyl(meth)acrylate, the structural unit derived from the isobornyl(meth)acrylate, the structural unit derived from the hydroxyl group-containing monomer, the structural unit derived from the nitrogen atom-containing monomer, the structural unit derived from the carboxy group-containing monomer, and the structural unit derived from the glycidyl group-containing monomer. Examples of the other monomers include (meth)acrylic acid alkyl esters other than the n-heptyl(meth)acrylate and the 2-octyl(meth)acrylate. Examples of the (meth)acrylic acid alkyl esters include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, tert-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, n-nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, and isodecyl (meth)acrylate. Examples include lauryl (meth)acrylate, myristyl (meth)acrylate, cetyl (meth)acrylate, stearyl (meth)acrylate, isostearyl (meth)acrylate, esters of 5,7,7-trimethyl-2-(1,3,3-trimethylbutyl)-1-octanol and (meth)acrylic acid, esters of (meth)acrylic acid and alcohols having a total of 18 carbon atoms and one or two methyl groups in the linear main chain, behenyl (meth)acrylate, arachidyl (meth)acrylate, etc. These (meth)acrylic acid alkyl esters may be used alone or in combination of two or more.

[0045] Examples of the other monomers include cyclohexyl (meth)acrylate, benzyl (meth)acrylate, 2-butoxyethyl (meth)acrylate, 2-phenoxyethyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, and polypropylene glycol mono(meth)acrylate. Furthermore, examples of the other monomers that can be used include various monomers used in general acrylic polymers, such as vinyl carboxylates such as vinyl acetate, and styrene. These other monomers may be used alone or in combination of two or more.

[0046] The content of the structural units derived from the other monomers in the (meth)acrylic copolymer can be determined by mass spectrometry of the (meth)acrylic copolymer and １ H-NMR measurement can be carried out, and the ratio can be calculated from the integrated intensity ratio of the hydrogen peaks derived from each monomer.

[0047] The polar functional group-containing monomer and the other monomers preferably contain carbon derived from living organisms, but may be composed solely of petroleum-derived materials without containing carbon derived from living organisms. In theory, it is also possible for all of the monomers constituting the (meth)acrylic copolymer to be monomers containing carbon derived from living organisms. From the standpoint of the cost and productivity of the pressure-sensitive adhesive tape, a relatively inexpensive and easily available monomer containing carbon derived from living organisms may be used, and this may be combined with a monomer composed solely of petroleum-derived materials.

[0048] The weight-average molecular weight (Mw) of the (meth)acrylic copolymer preferably has a lower limit of 300,000 and a higher limit of 900,000. When the weight-average molecular weight of the (meth)acrylic copolymer is 300,000 or more, the cohesive strength of the pressure-sensitive adhesive layer is increased, resulting in a higher adhesive strength of the resulting pressure-sensitive adhesive tape. When the weight-average molecular weight of the (meth)acrylic copolymer is 900,000 or less, the pressure-sensitive adhesive layer does not become too hard, resulting in a higher adhesive strength of the resulting pressure-sensitive adhesive tape. Furthermore, the viscosity of the (meth)acrylic copolymer-containing solution described below is less likely to become too high, resulting in improved smoothness of the resulting pressure-sensitive adhesive tape and therefore superior adhesion properties. The weight-average molecular weight of the (meth)acrylic copolymer more preferably has a lower limit of 400,000, an even more preferred lower limit of 450,000, and an even more preferred upper limit of 850,000, an even more preferred upper limit of 800,000. In this specification, the weight average molecular weight (Mw) is the weight average molecular weight in terms of standard polystyrene measured by GPC (Gel Permeation Chromatography). Specifically, the (meth)acrylic copolymer is diluted 50 times with tetrahydrofuran (THF), and the resulting diluted solution is filtered through a filter (material: polytetrafluoroethylene, pore diameter: 0.2 μm) to prepare a measurement sample. Next, this measurement sample is supplied to a gel permeation chromatograph (for example, Waters, "2690 Separations Module", etc.), and GPC measurement is performed under conditions of a sample flow rate of 1 mL / min and a column temperature of 40 ° C. The polystyrene-equivalent molecular weight of the (meth)acrylic copolymer is measured, and this value is taken as the weight average molecular weight of the (meth)acrylic copolymer.

[0049] The upper limit of the glass transition temperature (Tg) of the (meth)acrylic copolymer is preferably -20°C. When the glass transition temperature (Tg) of the (meth)acrylic copolymer is -20°C or lower, the cohesive strength of the pressure-sensitive adhesive layer increases, and the resulting pressure-sensitive adhesive tape improves in conformity with the adherend, resulting in higher adhesive strength. The upper limit of the glass transition temperature (Tg) of the (meth)acrylic copolymer is more preferably -25°C, and even more preferably -30°C. The lower limit of the glass transition temperature (Tg) of the (meth)acrylic copolymer is not particularly limited, and is usually -90°C or higher, and preferably -80°C or higher. The glass transition temperature (Tg) of the (meth)acrylic copolymer can be determined, for example, by differential scanning calorimetry.

[0050] The preferred upper limit of the acid value of the (meth)acrylic copolymer is 5 mgKOH / g. When the acid value of the (meth)acrylic copolymer is 5 mgKOH / g or less, the metal corrosiveness of the resulting pressure-sensitive adhesive tape can be further suppressed. The more preferred upper limit of the acid value of the (meth)acrylic copolymer is 1 mgKOH / g. The lower limit of the acid value of the (meth)acrylic copolymer is not particularly limited and may be 0 mgKOH / g. In this specification, the acid value refers to the number of milligrams of potassium hydroxide required to neutralize the acid contained in 1 g of sample, and the acid value of the (meth)acrylic copolymer can be determined, for example, by potentiometric titration in accordance with JIS K 0070.

[0051] The (meth)acrylic copolymer can be obtained by polymerizing a raw material monomer mixture through a radical reaction in the presence of a polymerization initiator. Examples of the radical reaction include living radical polymerization and free radical polymerization. Living radical polymerization, compared to free radical polymerization, produces a copolymer with a more uniform molecular weight and composition, and suppresses the generation of low-molecular-weight components, resulting in a stronger cohesive strength of the resulting adhesive layer and a higher adhesive strength of the resulting adhesive tape. Conventional methods can be used to polymerize the monomer mixture, including solution polymerization (boiling point polymerization or constant temperature polymerization), UV polymerization, emulsion polymerization, suspension polymerization, and bulk polymerization. Among these, solution polymerization and UV polymerization are preferred because they result in a higher adhesive strength of the resulting adhesive tape. When solution polymerization is used to polymerize the monomer mixture, a (meth)acrylic copolymer-containing solution containing the (meth)acrylic copolymer is obtained. Examples of reaction solvents used in solution polymerization include ethyl acetate, toluene, methyl ethyl ketone, dimethyl sulfoxide, ethanol, acetone, and diethyl ether. These reaction solvents may be used alone or in combination of two or more.

[0052] Examples of the polymerization initiator include organic peroxides and azo compounds. Among these, organic peroxides are preferred from the viewpoints of being able to control the reaction temperature and facilitating adjustment of the molecular weight of the resulting (meth)acrylic polymer. Examples of the organic peroxides include 1,1-bis(t-hexylperoxy)-3,3,5-trimethylcyclohexane, t-hexylperoxypivalate, t-butylperoxypivalate, 2,5-dimethyl-2,5-bis(2-ethylhexanoylperoxy)hexane, t-hexylperoxy-2-ethylhexanoate, t-butylperoxy-2-ethylhexanoate, t-butylperoxyisobutyrate, and t-butylperoxy-3,5,5-trimethylhexanoate. , t-butyl peroxylaurate, diisobutyryl peroxide, cumyl peroxyneodecanoate, di-n-propyl peroxydicarbonate, diisopropyl peroxydicarbonate, di-sec-butyl peroxydicarbonate, 1,1,3,3-tetramethylbutyl peroxyneodecanoate, di(4-t-butylcyclohexyl)peroxydicarbonate, di(2-ethylhexyl)peroxydicarbonate, t-hexylperoxyneodecanoate, t-butyl peroxy Cineodecanoate, t-butylperoxyneoheptanoate, di(3,5,5-trimethylhexanoyl)peroxide, dilauroyl peroxide, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, disuccinic acid peroxide, di(4-methylbenzoyl)peroxide, di(3-methylbenzoyl)peroxide, benzoyl(3-methylbenzoyl)peroxide, dibenzoyl peroxide, dibenzoyl peroxide, 1,1-di(t-butylperoxy) -2-methyloylhexane, 1,1-di(t-hexylperoxy)cyclohexane, 1,1-di(t-butylperoxy)cyclohexane, 2,2-di(4,4-di(t-butylperoxy)cyclohexyl)propane, t-hexylperoxyisopropyl monocarbonate, t-butylperoxymaleic acid, t-butylperoxyisopropyl monocarbonate, t-butylperoxy 2-ethylhexyl monocarbonate, t-hexylperoxybenzoate, 2,5-dimethyl-2,Examples of the peroxybenzoylperoxy compounds include 5-di(benzoylperoxy)hexane, butyl peroxyacetate, 2,2-di(t-butylperoxy)butane, t-butyl peroxybenzoate, n-butyl-4,4-di(t-butylperoxy)valerate, di(2-t-butylperoxyisopropyl)benzene, dicumyl peroxide, di-t-hexyl peroxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, t-butylcumyl peroxide, di-t-butyl peroxide, p-menthane hydroperoxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexyne-3 diisopropylbenzene hydroperoxide, 1,1,3,3-tetramethylbutyl hydroperoxide, cumenohydroperoxide, t-butyl hydroperoxide, and 2,3-dimethyl-2,3-diphenylbutane. Examples of the azo compound include azobisisobutyronitrile and azobiscyclohexanecarbonitrile. These polymerization initiators may be used alone or in combination of two or more. When the radical reaction is performed using living radical polymerization, examples of the polymerization initiator include organotellurium polymerization initiators. The organotellurium polymerization initiator is not particularly limited as long as it is one that is commonly used in living radical polymerization, and examples include organotellurium compounds and organotelluride compounds. In addition to the organotellurium polymerization initiator, the azo compound may also be used as the polymerization initiator in the living radical polymerization to accelerate the polymerization rate.

[0053] The preferred lower limit of the solids concentration of the (meth)acrylic copolymer-containing solution is 10% by mass, and the preferred upper limit is 80% by mass. When the solids concentration of the (meth)acrylic copolymer-containing solution is within the above range, the coatability of the adhesive to be applied is likely to be improved in the production of the adhesive tape described below, and the adhesive properties of the resulting adhesive tape are more excellent. The more preferred lower limit of the solids concentration of the (meth)acrylic copolymer-containing solution is 20% by mass, and even more preferred is 30% by mass, and the more preferred upper limit is 70% by mass, and even more preferred is 65% by mass. In this specification, "solids" refers to components other than the solvent in the solution.

[0054] The viscosity of the (meth)acrylic copolymer-containing solution at 23°C is preferably 500 mPa·s at its lower limit and 12,000 mPa·s at its upper limit. When the viscosity of the (meth)acrylic copolymer-containing solution at 23°C is within this range, the resulting pressure-sensitive adhesive tape has better lamination properties. The viscosity of the (meth)acrylic copolymer-containing solution at 23°C is more preferably 1,000 mPa·s at its lower limit, even more preferably 2,000 mPa·s at its upper limit, even more preferably 10,000 mPa·s at its upper limit, and even more preferably 8,000 mPa·s at its upper limit. The viscosity of the (meth)acrylic copolymer-containing solution at 23°C can be determined, for example, by the following method. That is, the viscosity at 23°C can be determined by measuring 400 mL of the (meth)acrylic copolymer-containing solution into a 500 mL plastic cup and measuring the viscosity using a B-type viscometer at 23°C and 10 rpm.

[0055] As a method for adjusting the viscosity at 23°C of the (meth)acrylic copolymer-containing solution to fall within the above-mentioned range, a method of adjusting the composition and weight average molecular weight of the (meth)acrylic copolymer, as well as the solids concentration and solvent of the (meth)acrylic copolymer-containing solution is preferred.

[0056] The pressure-sensitive adhesive layer preferably further contains a silane coupling agent. By containing a silane coupling agent in the pressure-sensitive adhesive layer, the resulting pressure-sensitive adhesive tape will have higher adhesive strength. Examples of the silane coupling agent include vinyltrimethoxysilane, vinyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropylmethyldimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-glycidoxypropyltriethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-aminopropyltrimethylmethoxysilane, N-(2-aminoethyl)3-aminopropyltriethoxysilane, N-(2-aminoethyl)3-aminopropylmethyldimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-mercaptopropyltriethoxysilane, mercaptobutyltrimethoxysilane, and γ-mercaptopropylmethyldimethoxysilane. Among these, γ-glycidoxypropyltrimethoxysilane and γ-mercaptopropyltrimethoxysilane are preferred from the viewpoint of more easily improving the adhesive strength of the resulting adhesive tape.

[0057] The content of the silane coupling agent is preferably 0.01 parts by mass or more and 5 parts by mass or more per 100 parts by mass of the (meth)acrylic copolymer. When the content of the silane coupling agent is 0.01 parts by mass or more, the resulting pressure-sensitive adhesive tape has higher adhesive strength. When the content of the silane coupling agent is 5 parts by mass or less, it is possible to suppress bleeding of the silane coupling agent at the adhesive interface, and the resulting pressure-sensitive adhesive tape has higher adhesive strength. The lower limit of the content of the silane coupling agent is more preferably 0.1 parts by mass, even more preferably 0.2 parts by mass, and more preferably 1 part by mass or more and even more preferably 0.5 parts by mass.

[0058] The pressure-sensitive adhesive layer preferably further contains a crosslinking agent. By containing a crosslinking agent in the pressure-sensitive adhesive layer, crosslinking of the pressure-sensitive adhesive layer occurs, and the resulting pressure-sensitive adhesive tape has higher adhesive strength and further improved adhesion to the adherend. Examples of the crosslinking agent include isocyanate-based crosslinking agents, aziridine-based crosslinking agents, epoxy-based crosslinking agents, and metal chelate-type crosslinking agents. Among these, at least one crosslinking agent selected from the group consisting of isocyanate-based crosslinking agents, aziridine-based crosslinking agents, and epoxy-based crosslinking agents is preferred, and an isocyanate-based crosslinking agent is more preferred, as these agents provide the pressure-sensitive adhesive tape with superior adhesion to the adherend and optical transparency even when exposed to a high-temperature, high-humidity environment.

[0059] The content of the crosslinking agent is preferably 0.01 parts by mass at its lower limit and 7 parts by mass at its upper limit relative to 100 parts by mass of the (meth)acrylic copolymer. When the content of the crosslinking agent is within this range, the shear storage modulus at 23°C of the pressure-sensitive adhesive layer described below more easily falls within an appropriate range, further increasing the adhesive strength of the resulting pressure-sensitive adhesive tape. The lower limit of the content of the crosslinking agent is more preferably 0.1 parts by mass, and the upper limit is more preferably 5 parts by mass. The content of the crosslinking agent indicates the amount of solids of the crosslinking agent.

[0060] The pressure-sensitive adhesive layer may further contain a crosslinking catalyst for promoting crosslinking by the crosslinking agent. Examples of the crosslinking catalyst include dibutyltin dilaurate, dibutyltin diacetate, and dioctyltin dilaurate as crosslinking catalysts for the isocyanate-based crosslinking agent. The content of the crosslinking catalyst is preferably 0.001 parts by mass or more, more preferably 0.01 parts by mass or less, and preferably 3 parts by mass or more, more preferably 1 part by mass or less, relative to 100 parts by mass of the (meth)acrylic copolymer.

[0061] The pressure-sensitive adhesive layer may further contain a tackifier resin from the viewpoint of further increasing the adhesive strength of the pressure-sensitive adhesive tape, but from the viewpoint of increasing optical transparency, it is preferable that the pressure-sensitive adhesive layer does not contain the tackifier resin.

[0062] The pressure-sensitive adhesive layer may contain additives such as plasticizers, softeners, fillers, pigments, and dyes, as needed.

[0063] The preferred lower limit of the gel fraction of the pressure-sensitive adhesive layer is 40% by mass, and the preferred upper limit is 95% by mass. A gel fraction of the pressure-sensitive adhesive layer of 40% by mass or more increases the durability of the pressure-sensitive adhesive layer against slippage and deformation of the adherend under high-temperature, high-humidity conditions, thereby further improving the adhesion of the resulting pressure-sensitive adhesive tape to the adherend. A gel fraction of the pressure-sensitive adhesive layer of 95% by mass or less prevents the pressure-sensitive adhesive layer from becoming too hard, resulting in a pressure-sensitive adhesive tape with higher adhesive strength. A more preferred lower limit of the gel fraction of the pressure-sensitive adhesive layer is 45% by mass, an even more preferred lower limit is 50% by mass, and a more preferred upper limit is 92.5% by mass, an even more preferred upper limit is 90% by mass. The gel fraction of the pressure-sensitive adhesive layer is measured by the following method. Specifically, a pressure-sensitive adhesive tape having the pressure-sensitive adhesive layer is first cut into a 20 mm x 40 mm flat rectangular shape to prepare a test piece, which is then immersed in ethyl acetate at 23°C for 24 hours, removed from the ethyl acetate, and dried at 110°C for 1 hour. The mass of the test piece after drying is measured, and the gel fraction is calculated using the following formula (I). Note that the test piece is not laminated with a release film for protecting the pressure-sensitive adhesive layer. When the test piece does not have a substrate, the gel fraction is calculated using the formula (I). ０ = 0, and the gel fraction is calculated. Gel fraction (mass%) = 100 × (W ２ -W ０ ) / (W １ -W ０ ) (I) (W ０ : Mass of the substrate, W １ : mass of test piece before immersion, W ２ : Mass of test piece after immersion and drying)

[0064] The pressure-sensitive adhesive layer has a shear storage modulus at 23°C of preferably 0.5 × 10 ５ Pa, and the preferred upper limit is 3.0 × 10 ６When the shear storage modulus at 23°C of the pressure-sensitive adhesive layer is within this range, the resulting pressure-sensitive adhesive tape has higher adhesive strength and also has improved adhesion to an adherend. A more preferred lower limit of the shear storage modulus at 23°C of the pressure-sensitive adhesive layer is 0.7 × 10 ５ Pa, and a more preferable lower limit is 0.9 × 10 ５ Pa, and an even more preferable lower limit is 1.0 × 10 ５ Pa, and a particularly preferred lower limit is 2.0 × 10 ５ Pa, and a more preferable upper limit is 2.0 × 10 ６ Pa, and a more preferable upper limit is 1.0 × 10 ６ Pa, and an even more preferable upper limit is 5.0 × 10 ５ Pa. The shear storage modulus of the pressure-sensitive adhesive layer at 23°C can be determined, for example, by the following method. That is, the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer is coated on the release-treated surface of a release-treated PET film so that the thickness of the pressure-sensitive adhesive layer after drying is 1000 μm, and then dried. Alternatively, pressure-sensitive adhesive layers are superposed to form a pressure-sensitive adhesive layer so that the thickness is 1000 μm. The dynamic viscoelasticity spectrum of the resulting pressure-sensitive adhesive layer having a thickness of 100 μm is measured using a dynamic viscoelasticity measuring device (for example, "DVA-200" manufactured by IT Measurement & Control Co., Ltd.) under conditions of a shear direction, a frequency of 10 Hz, a heating rate of 5°C / min, and a temperature range of -50°C to 200°C, thereby determining the shear storage modulus at 23°C.

[0065] A preferred method for adjusting the gel fraction and shear storage modulus at 23°C of the pressure-sensitive adhesive layer within the above-mentioned ranges is to adjust the composition and weight average molecular weight of the (meth)acrylic copolymer, and, when using the crosslinking agent, the type and content of the crosslinking agent.

[0066] The acid value of the pressure-sensitive adhesive layer is preferably 5 mgKOH / g or less. By having the acid value of the pressure-sensitive adhesive layer be 5 mgKOH / g or less, the metal corrosiveness of the resulting pressure-sensitive adhesive tape can be further suppressed. The upper limit of the acid value of the pressure-sensitive adhesive layer is more preferably 1 mgKOH / g. The lower limit of the acid value of the pressure-sensitive adhesive layer is not particularly limited, and may be 0 mgKOH / g. The acid value of the pressure-sensitive adhesive layer can be measured in the same manner as the acid value of the (meth)acrylic copolymer.

[0067] A preferred method for adjusting the acid value of the pressure-sensitive adhesive layer to fall within the above range is to adjust the composition and acid value of the (meth)acrylic copolymer.

[0068] The adhesive tape of the present invention may be a non-support tape that does not have a substrate, or a support tape that has a substrate. However, from the viewpoint of the adhesive tape of the present invention being thinner and having better optical transparency, a non-support tape that does not have a substrate is preferred.

[0069] When the pressure-sensitive adhesive tape of the present invention is a support tape having a substrate, it may be a single-sided pressure-sensitive adhesive tape having the above-mentioned pressure-sensitive adhesive layer on one side of the substrate, or a double-sided pressure-sensitive adhesive tape having the above-mentioned pressure-sensitive adhesive layers on both sides of the substrate.

[0070] The substrate is not particularly limited, and conventionally known substrates can be used, but it is preferable to use a substrate of biological origin in order to increase the content of biological carbon in the entire pressure-sensitive adhesive tape. Examples of the biological substrate include films and nonwoven fabrics containing plant-derived polyesters (PES) such as polyethylene terephthalate (PET), polyethylene furanoate (PEF), polylactic acid (PLA), polytrimethylene terephthalate (PTT), polybutylene terephthalate (PBT), and polybutylene succinate (PBS). Other examples include films and nonwoven fabrics containing plant-derived polyethylene (PE), polypropylene (PP), polyurethane (PU), triacetyl cellulose (TAC), cellulose, polyamide (PA), and the like.

[0071] From the viewpoint of substrate strength, the substrate is preferably a film containing PES or a film containing PA. Furthermore, from the viewpoint of heat resistance and oil resistance, a film containing PA is preferred. Examples of the constituents of the PA-containing film include nylon 11, nylon 1010, nylon 610, nylon 510, nylon 410, etc., which are made from castor oil, and nylon 56, etc., which is made from cellulose.

[0072] Furthermore, from the perspective of reducing the use of new petroleum resources and reducing the environmental burden by suppressing carbon dioxide emissions, substrates made from recycled resources may be used. Examples of resource recycling methods include collecting waste materials such as packaging containers, home appliances, automobiles, construction materials, and food, as well as waste generated during manufacturing processes, and then cleaning, decontaminating, or decomposing the extracted materials by heating or fermentation to reuse them as raw materials. Examples of substrates made from recycled resources include films and nonwoven fabrics made from PET, PBT, PE, PP, PA, etc., which are made from recycled plastics that have been re-resinized. Furthermore, the collected waste materials may be burned and used as thermal energy for the production of substrates and their raw materials. The oils and fats contained in the collected waste materials may be mixed with petroleum, fractionated, and purified, and then used as raw materials.

[0073] The substrate may be a foam substrate from the viewpoint of improving compression characteristics. The foam substrate is preferably a foam substrate containing at least one selected from the group consisting of PE, PP, and PU, and more preferably a foam substrate containing PE from the viewpoint of achieving a high degree of both flexibility and strength. Examples of the constituent of the foam substrate containing PE include PE made from sugarcane.

[0074] A preferred method for producing the foam base material is, for example, to prepare a foamable resin composition containing a PE resin containing sugarcane-derived PE and a foaming agent, and then foam the foaming agent when extruding the foamable resin composition into a sheet using an extruder, and optionally crosslink the resulting polyolefin foam.

[0075] The preferred lower limit of the thickness of the foam substrate is 50 μm, and the preferred upper limit is 5000 μm. By having the thickness of the foam substrate within this range, it is possible to exhibit high impact resistance while exhibiting high flexibility that allows it to be adhered to the shape of the adherend. The more preferred upper limit of the thickness of the foam substrate is 1000 μm, and even more preferred upper limit is 300 μm.

[0076] The pressure-sensitive adhesive tape of the present invention may have layers other than the pressure-sensitive adhesive layer and the substrate, as long as the effects of the present invention are not impaired.

[0077] The method for producing the pressure-sensitive adhesive tape of the present invention is not particularly limited, and it can be produced by a conventionally known production method. For example, in the case of a double-sided pressure-sensitive adhesive tape, the following method can be mentioned. First, a solution of pressure-sensitive adhesive A is prepared by adding a solvent to a (meth)acrylic copolymer and, if necessary, a crosslinking agent, etc., and this solution of pressure-sensitive adhesive A is applied to the surface of a substrate, and the solvent in the solution is completely dried and removed to form a pressure-sensitive adhesive layer A. Next, a release film is superimposed on the formed pressure-sensitive adhesive layer A with its release-treated surface facing the pressure-sensitive adhesive layer A. Next, a release film separate from the above-mentioned release film is prepared, and a solution of pressure-sensitive adhesive B prepared in the same manner as above is applied to the release-treated surface of this release film, and the solvent in the solution is completely dried and removed to produce a laminate film in which pressure-sensitive adhesive layer B is formed on the surface of the release film. The obtained laminate film is superimposed on the back surface of the substrate on which pressure-sensitive adhesive layer A has been formed, with the pressure-sensitive adhesive layer B facing the back surface of the substrate, to produce a laminate. Then, by pressing the laminate with a rubber roller or the like, a double-sided adhesive tape can be obtained which has adhesive layers on both sides of the substrate and in which the surfaces of the adhesive layers are covered with release films.

[0078] Alternatively, two sets of laminate films may be prepared in a similar manner, and these laminate films may be superimposed on each of both surfaces of a substrate with the pressure-sensitive adhesive layers of the laminate films facing the substrate to prepare a laminate. This laminate may then be pressed with a rubber roller or the like to obtain a double-sided pressure-sensitive adhesive tape having pressure-sensitive adhesive layers on both surfaces of the substrate and in which the surfaces of the pressure-sensitive adhesive layers are covered with release films.

[0079] The pressure-sensitive adhesive tape of the present invention has a total thickness (total thickness of the pressure-sensitive adhesive layer, substrate, and other layers) of preferably 5 μm at the lower limit and 6000 μm at the upper limit. By having the total thickness of the pressure-sensitive adhesive tape within this range, the adhesive strength is further increased. The upper limit of the total thickness of the pressure-sensitive adhesive tape is more preferably 1200 μm, and even more preferably 500 μm.

[0080] The pressure-sensitive adhesive tape of the present invention preferably has a haze value (cloudiness) at room temperature (20°C or higher and 25°C or lower) (hereinafter sometimes referred to as "initial haze value at room temperature") of less than 3.0%. The haze value at room temperature of less than 3.0% makes the pressure-sensitive adhesive tape of the present invention suitable for use in applications requiring optical transparency, such as adhesion of display panel modules and the like. The lower limit of the haze value at room temperature is not particularly limited, and a lower value is preferable, and it may even be 0%. The haze value at room temperature can be measured, for example, in accordance with JIS K 7136:2000 using a haze meter (e.g., "NDH 400" manufactured by Nippon Denshoku Industries Co., Ltd.).

[0081] The pressure-sensitive adhesive tape of the present invention preferably has a haze value (cloudiness) of less than 3.0% at room temperature (20°C or higher and 25°C or lower) after being left standing for 500 hours in an environment of 65°C and 90% RH. Since the haze value at room temperature after being left standing for 500 hours in an environment of 65°C and 90% RH is less than 3.0%, the pressure-sensitive adhesive tape of the present invention can be suitably used for applications requiring optical transparency, such as the adhesion of display panel modules. Furthermore, the lower limit of the haze value at room temperature after being left standing for 500 hours in an environment of 65°C and 90% RH is not particularly limited, and the lower the value, the better, even 0% is preferable. The haze value at room temperature after being left standing for 500 hours in an environment of 65°C and 90% RH is measured by the following method. Specifically, two glass plates, each 0.7 mm thick, 50 mm wide, and 80 mm long, are first used, and the glass plates are attached to both sides of the pressure-sensitive adhesive tape cut to the same size as the glass plates to prepare a test piece. The test piece is not laminated with a release film for protecting the pressure-sensitive adhesive layer. Next, the obtained test piece is stored for 500 hours in an environment of 65°C and 90% RH, and then the temperature of the test piece is returned to room temperature (20°C or higher and 25°C or lower) in an environment of 23°C and 50% RH. After 1 hour, the haze value of the visible light at room temperature (20°C or higher and 25°C or lower) is measured using a haze meter (for example, "NDH 400" manufactured by Nippon Denshoku Industries Co., Ltd.) in accordance with JIS K 7136:2000.

[0082] The pressure-sensitive adhesive tape of the present invention has a 180° peel strength from glass at 23°C of preferably 10 N / 25 mm, more preferably 15 N / 25 mm. The upper limit of the 180° peel strength from glass at 23°C is not particularly limited; a higher value is preferable, but a substantial upper limit is 50 N / 25 mm. The 180° peel strength from glass at 23°C is measured by the following method. First, the pressure-sensitive adhesive tape is cut into a piece measuring 25 mm wide and 75 mm long to prepare a test piece. This test piece is then placed on a glass plate with the adhesive layer facing the glass plate, and is then bonded to the test piece by rolling a 2 kg rubber roller back and forth once at a speed of 300 mm / min. The test piece is then aged at 23°C and 50% RH for 20 minutes to prepare a test sample. The test sample is peeled in a 180° direction at a pulling rate of 300 mm / min under conditions of 23°C and 50% RH, and the adhesive strength (N / 25 mm) is measured. When the adhesive tape is a non-support tape having no substrate or a double-sided adhesive tape having adhesive layers on both sides of the substrate, the other surface of the adhesive layer (the side not being measured) is lined with a 23 μm-thick polyethylene terephthalate film (for example, "FE2002" manufactured by Futamura Chemical Co., Ltd.) and then bonded to the glass plate.

[0083] The use of the pressure-sensitive adhesive tape of the present invention is not particularly limited, but it is preferably used for fixing electronic components or on-vehicle components. Specifically, the pressure-sensitive adhesive tape of the present invention can be suitably used for adhesively fixing electronic components in large portable electronic devices, adhesively fixing on-vehicle components (for example, on-vehicle panels), etc.

[0084] According to the present invention, it is possible to provide a pressure-sensitive adhesive tape that can reduce the environmental load and has excellent optical transparency even when exposed to a high-temperature, high-humidity environment.

[0085] The following examples further illustrate aspects of the present invention, but the present invention is not limited to these examples.

[0086] <n-heptyl acrylate containing bio-derived carbon> Ricinoleic acid derived from castor oil was cracked to obtain a mixture containing undecylenic acid and heptyl alcohol. The undecylenic acid was then separated by distillation to obtain n-heptyl alcohol containing bio-derived carbon. The n-heptyl alcohol containing bio-derived carbon was esterified with acrylic acid (manufactured by Nippon Shokubai Co., Ltd.) to prepare n-heptyl acrylate.

[0087] <2-octyl acrylate containing bio-derived carbon> Ricinoleic acid derived from castor oil was alkali-fused to obtain a mixture containing sepacic acid and 2-octanol. The mixture was then separated from the sepacic acid by distillation to obtain 2-octanol containing bio-derived carbon. 2-octanol containing bio-derived carbon was esterified with acrylic acid (manufactured by Nippon Shokubai Co., Ltd.) to prepare 2-octyl acrylate.

[0088] <Lauryl acrylate containing bio-derived carbon> Lauryl alcohol containing bio-derived carbon was obtained by catalytic reduction of lauric acid derived from coconut oil. Lauryl acrylate was prepared by esterification of lauryl alcohol containing bio-derived carbon with acrylic acid (manufactured by Nippon Shokubai Co., Ltd.).

[0089] <Isobornyl acrylate containing bio-derived carbon> Camphene containing bio-derived carbon was obtained by isomerizing pinene extracted from pine resin. Camphene containing bio-derived carbon was reacted with acrylic acid (manufactured by Nippon Shokubai Co., Ltd.) to prepare isobornyl acrylate containing bio-derived carbon.

[0090] <Isobornyl methacrylate containing bio-derived carbon> Camphene containing bio-derived carbon was obtained by isomerizing pinene extracted from pine resin. Camphene containing bio-derived carbon was reacted with methacrylic acid (manufactured by Mitsubishi Chemical Corporation) to prepare isobornyl methacrylate containing bio-derived carbon.

[0091] <Other monomers (not containing carbon derived from living organisms)> Methyl methacrylate (manufactured by Mitsubishi Chemical Corporation) n-Butyl acrylate (manufactured by Tokyo Chemical Industry Co., Ltd.) 2-Ethylhexyl acrylate (manufactured by Mitsubishi Chemical Corporation) 2-Hydroxyethyl acrylate (manufactured by Osaka Organic Chemical Industry Ltd.) 4-Hydroxybutyl acrylate (manufactured by Nippon Shokubai Co., Ltd.) 2-Hydroxypropyl acrylate (manufactured by Tokyo Chemical Industry Co., Ltd.) Acrylonitrile (manufactured by Mitsubishi Chemical Corporation) Acrylamide (manufactured by Tokyo Chemical Industry Co., Ltd.) Dimethylacrylamide (manufactured by Tokyo Chemical Industry Co., Ltd.) Acrylic acid (manufactured by Nippon Shokubai Co., Ltd.)

[0092] <Crosslinking agent> Isocyanate-based crosslinking agent (manufactured by Tosoh Corporation, "Coronate HX")

[0093] <Silane coupling agent> Silane coupling agent (manufactured by Shin-Etsu Chemical Co., Ltd., "KBM-403")

[0094] Example 1 (1) Production of (meth)acrylic copolymer Ethyl acetate was added as a polymerization solvent to a reaction vessel, and nitrogen was bubbled through the reaction vessel. The reaction vessel was then heated while nitrogen was flowing in to initiate reflux. Subsequently, a polymerization initiator solution prepared by diluting 0.1 parts by mass of azobisisobutyronitrile as a polymerization initiator 10 times with ethyl acetate was added to the reaction vessel, and 39.95 parts by mass of n-heptyl acrylate, 40 parts by mass of n-butyl acrylate, 20 parts by mass of 2-hydroxyethyl acrylate, and 0.05 parts by mass of acrylic acid, each containing biocarbon, were added dropwise over two hours. After completion of the dropwise addition, a polymerization initiator solution prepared by diluting 0.1 parts by mass of azobisisobutyronitrile as a polymerization initiator 10 times with ethyl acetate was again added to the reaction vessel, and the polymerization reaction was carried out for four hours to obtain a (meth)acrylic copolymer-containing solution. In addition, the obtained (meth)acrylic copolymer was diluted 50 times with tetrahydrofuran (THF) and the resulting diluted solution was filtered through a filter (material: polytetrafluoroethylene, pore diameter: 0.2 μm) to prepare a measurement sample. This measurement sample was supplied to a gel permeation chromatograph (Waters, "2690 Separations Module") and subjected to GPC measurement under conditions of a sample flow rate of 1 mL / min and a column temperature of 40 ° C. The polystyrene-equivalent molecular weight of the acrylic copolymer was measured and the weight average molecular weight was determined. The results are shown in Table 1.

[0095] (2) Viscosity of (meth)acrylic copolymer-containing solution at 23°C 400 mL of the obtained (meth)acrylic copolymer-containing solution was weighed into a 500 mL plastic cup, and the viscosity at 23°C was measured using a B-type viscometer (manufactured by Tokyo Keiki Co., Ltd.) under conditions of 23°C and 10 rpm. The results are shown in Table 1.

[0096] (3) Production of Pressure-Sensitive Adhesive Tape To the obtained (meth)acrylic copolymer-containing solution, 0.2 parts by mass of an isocyanate-based crosslinking agent (manufactured by Tosoh Corporation, "Coronate HX") with a solid content and 0.3 parts by mass of a silane coupling agent (manufactured by Shin-Etsu Chemical Co., Ltd., "KBM-403") were added per 100 parts by mass of the (meth)acrylic copolymer to prepare a pressure-sensitive adhesive. This pressure-sensitive adhesive was applied to the release-treated surface of a 75 μm-thick release PET film so that the thickness of the pressure-sensitive adhesive layer after drying would be 100 μm, and then dried at 110°C for 5 minutes. The obtained pressure-sensitive adhesive layer was placed on the release-treated surface of a 75 μm-thick release PET film and aged at 40°C for 48 hours to obtain a pressure-sensitive adhesive tape (non-support type).

[0097] (4) Bio-derived carbon content in pressure-sensitive adhesive layer The bio-derived carbon content of the obtained pressure-sensitive adhesive layer was measured in accordance with ASTM D6866-22. The results are shown in Table 1.

[0098] (5) Gel Fraction of Pressure-Sensitive Adhesive Layer The release PET film on one side of the obtained pressure-sensitive adhesive tape was peeled off, and the tape was attached to a 23 μm-thick PET film ("FE2002" manufactured by Futamura Chemical Co., Ltd.), and cut into a 20 mm x 40 mm flat rectangle. The release PET film on the other side of the pressure-sensitive adhesive tape was then peeled off to prepare a test piece, and its mass was measured. The test piece was immersed in ethyl acetate at 23°C for 24 hours, then removed from the ethyl acetate, and dried at 110°C for 1 hour. The mass of the test piece after drying was measured, and the gel fraction was calculated using the following formula (I). The results are shown in Table 1. Gel fraction (mass%) = 100 x (W ２ -W ０ ) / (W １ -W ０ ) (I) (W ０ : Mass of substrate (PET film), W １ : mass of test piece before immersion, W ２ : Mass of test piece after immersion and drying)

[0099] (6) Shear storage modulus of pressure-sensitive adhesive layer at 23°C The obtained pressure-sensitive adhesive layers were stacked to a thickness of 1000 µm to prepare a measurement sample. The measurement sample was subjected to dynamic viscoelasticity spectrum measurement using a dynamic viscoelasticity measuring device (manufactured by IT Measurement & Control Co., Ltd., "DVA-200") under conditions of a shear direction, a frequency of 10 Hz, a heating rate of 5°C / min, and a temperature range of -50°C to 200°C. The shear storage modulus at 23°C was thus determined. The results are shown in Table 1.

[0100] (7) Water Vapor Transmission Coefficient P of Pressure-Sensitive Adhesive Layer The obtained pressure-sensitive adhesive layer was cut into a piece of about 10 cm x 10 cm, and placed on the measuring section of a water vapor transmission rate measuring device (manufactured by MOCON, "PERMATRAN-W 1 / 50"), and then subjected to a moisture transmission test by the MOCON method under conditions of 40°C and 90% RH in accordance with JIS K 7129B to measure the water vapor transmission coefficient WVTR (g / (m ２ Using the water vapor transmission rate WVTR of the obtained pressure-sensitive adhesive layer at 40°C and 90% RH, the water vapor transmission coefficient P (g mm / (m ２ The results are shown in Table 1.

[0101] (Examples 2 to 40, 47 to 49, Comparative Examples 1 to 4) Pressure-sensitive adhesive tapes were obtained in the same manner as in Example 1, except that the types and amounts of monomers constituting the (meth)acrylic copolymer were changed as shown in Tables 1 to 6. Furthermore, the weight-average molecular weight of the (meth)acrylic copolymer, the viscosity at 23°C of the (meth)acrylic copolymer-containing solution, the content of bio-derived carbon in the pressure-sensitive adhesive layer, the gel fraction of the pressure-sensitive adhesive layer, the shear storage modulus at 23°C of the pressure-sensitive adhesive layer, and the water vapor permeability coefficient P of the pressure-sensitive adhesive layer were measured in the same manner as in Example 1. The results are shown in Tables 1 to 6.

[0102] Example 40 An adhesive tape was obtained in the same manner as in Example 1, except that the types and amounts of monomers constituting the (meth)acrylic copolymer were changed as shown in Table 5, and a polymerization initiator was used instead of azobisisobutyronitrile, and a polymerization initiator solution prepared by diluting 0.8 parts by mass of a total of t-butylperoxy-2-ethylhexanoate (manufactured by NOF Corporation, "Perbutyl O") and t-hexylperoxypivalate (manufactured by NOF Corporation, "Perbutyl PV") 10 times with ethyl acetate was added to a reaction vessel to obtain a (meth)acrylic copolymer-containing solution. Furthermore, in the same manner as in Example 1, the weight-average molecular weight of the (meth)acrylic copolymer, the viscosity of the (meth)acrylic copolymer-containing solution at 23°C, the content of bio-derived carbon in the adhesive layer, the gel fraction of the adhesive layer, the shear storage modulus of the adhesive layer at 23°C, and the water vapor permeability coefficient P of the adhesive layer were measured. The results are shown in Table 5.

[0103] Example 41 An adhesive tape was obtained in the same manner as in Example 1, except that the types and amounts of monomers constituting the (meth)acrylic copolymer were changed as shown in Table 5, and azobisisobutyronitrile was used as the polymerization initiator instead of azobisisobutyronitrile. A polymerization initiator solution prepared by diluting a total of 0.81 parts by mass of 1,1-di(t-hexylperoxy)cyclohexane (NOF Corporation, "Perhexa HC"), 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate (NOF Corporation, "Perocta O"), and t-hexylperoxypivalate (NOF Corporation, "Perhexyl PV") 10 times with ethyl acetate was added to a reaction vessel to obtain a (meth)acrylic copolymer-containing solution. Furthermore, the weight-average molecular weight of the (meth)acrylic copolymer, the viscosity of the (meth)acrylic copolymer-containing solution at 23°C, the content of bio-derived carbon in the adhesive layer, the shear storage modulus at 23°C of the adhesive layer, and the water vapor permeability coefficient P of the adhesive layer were measured in the same manner as in Example 1. The results are shown in Table 5.

[0104] Example 42 An adhesive tape was prepared in the same manner as in Example 1, except that the types and amounts of the monomers constituting the (meth)acrylic copolymer were changed as shown in Table 5, and azobisisobutyronitrile was used as the polymerization initiator instead of azobisisobutyronitrile. A polymerization initiator solution prepared by diluting 0.6 parts by mass of a total of 1,1-di(t-hexylperoxy)cyclohexane (NOF Corporation, "Perhexa HC"), t-butylperoxy-2-ethylhexanoate (NOF Corporation, "Perbutyl O"), and t-butylperoxypivalate (NOF Corporation, "Perbutyl PV") 10 times with ethyl acetate was added to a reaction vessel to obtain a (meth)acrylic copolymer-containing solution. Furthermore, the weight-average molecular weight of the (meth)acrylic copolymer, the viscosity of the (meth)acrylic copolymer-containing solution at 23°C, the content of bio-derived carbon in the adhesive layer, the gel fraction of the adhesive layer, the shear storage modulus of the adhesive layer at 23°C, and the water vapor transmission coefficient P of the adhesive layer were measured in the same manner as in Example 1. The results are shown in Table 5.

[0105] Example 43 An adhesive tape was prepared in the same manner as in Example 1, except that the types and amounts of the monomers constituting the (meth)acrylic copolymer were changed as shown in Table 5, and instead of azobisisobutyronitrile, a polymerization initiator solution was used in which a total of 0.7 parts by mass of 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate (manufactured by NOF Corporation, "Perocta O") and t-hexyl peroxypivalate (manufactured by NOF Corporation, "Perhexyl PV") was diluted 10 times with ethyl acetate and charged into a reaction vessel to obtain an acrylic copolymer-containing solution. Furthermore, the weight-average molecular weight of the (meth)acrylic copolymer, the viscosity of the (meth)acrylic copolymer-containing solution at 23°C, the content of bio-derived carbon in the adhesive layer, the gel fraction of the adhesive layer, the shear storage modulus of the adhesive layer at 23°C, and the water vapor permeability coefficient P of the adhesive layer were measured in the same manner as in Example 1. The results are shown in Table 5.

[0106] Example 44 An adhesive tape was obtained in the same manner as in Example 1, except that the types and amounts of monomers constituting the (meth)acrylic copolymer were changed as shown in Table 5, and a polymerization initiator was used instead of azobisisobutyronitrile. A polymerization initiator solution prepared by diluting a total of 0.51 parts by mass of 1,1-di(t-hexylperoxy)cyclohexane (manufactured by NOF Corporation, "Perhexa HC") and t-hexyl peroxypivalate (manufactured by NOF Corporation, "Perhexyl PV") 10 times with ethyl acetate was added to a reaction vessel to obtain an acrylic copolymer-containing solution. Furthermore, the weight-average molecular weight of the (meth)acrylic copolymer, the viscosity of the (meth)acrylic copolymer-containing solution at 23°C, the content of bio-derived carbon in the adhesive layer, the gel fraction of the adhesive layer, the shear storage modulus of the adhesive layer at 23°C, and the water vapor transmission coefficient P of the adhesive layer were measured in the same manner as in Example 1. The results are shown in Table 5.

[0107] Example 45 An adhesive tape was obtained in the same manner as in Example 1, except that the type and amount of monomers constituting the (meth)acrylic copolymer were changed as shown in Table 5, and instead of azobisisobutyronitrile, a polymerization initiator solution prepared by diluting a total of 0.6 parts by mass of t-butylperoxy-2-ethylhexanoate (manufactured by NOF Corporation, "Perbutyl O") and t-hexylperoxypivalate (manufactured by NOF Corporation, "Perhexyl PV") 10 times with ethyl acetate was added to a reaction vessel to obtain an acrylic copolymer-containing solution. Furthermore, the weight-average molecular weight of the (meth)acrylic copolymer, the viscosity of the (meth)acrylic copolymer-containing solution at 23°C, the content of bio-derived carbon in the adhesive layer, the gel fraction of the adhesive layer, the shear storage modulus of the adhesive layer at 23°C, and the water vapor permeability coefficient P of the adhesive layer were measured in the same manner as in Example 1. The results are shown in Table 5.

[0108] Example 46 An adhesive tape was obtained in the same manner as in Example 1, except that the types and amounts of the monomers constituting the (meth)acrylic copolymer were changed as shown in Table 5, and azobisisobutyronitrile was used as the polymerization initiator instead of azobisisobutyronitrile. A polymerization initiator solution prepared by diluting a total of 0.82 parts by mass of 1,1-di(t-hexylperoxy)cyclohexane (NOF Corporation, "Perhexa HC"), 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate (NOF Corporation, "Perocta O"), and t-butyl peroxypivalate (NOF Corporation, "Perbutyl PV") 10 times with ethyl acetate was added to a reaction vessel to obtain a (meth)acrylic copolymer-containing solution. Furthermore, the weight-average molecular weight of the (meth)acrylic copolymer, the viscosity of the (meth)acrylic copolymer-containing solution at 23°C, the content of bio-derived carbon in the adhesive layer, the gel fraction of the adhesive layer, the shear storage modulus of the adhesive layer at 23°C, and the water vapor permeability coefficient P of the adhesive layer were measured in the same manner as in Example 1. The results are shown in Table 5.

[0109] <Evaluation> The pressure-sensitive adhesive tapes obtained in the examples and comparative examples were evaluated by the following methods. The results are shown in Tables 1 to 6.

[0110] (Environmental Load Reduction Ability) The environmental load reduction ability of the pressure-sensitive adhesive tape was evaluated by determining the bio-carbon content in the pressure-sensitive adhesive layer measured by the method described above in "(4) Bio-derived carbon content in the pressure-sensitive adhesive layer." The bio-derived carbon content in the pressure-sensitive adhesive layer was evaluated by determining "◎" if it was 60% or more, "○" if it was 50% or more and less than 60%, "△" if it was 30% or more and less than 50%, and "×" if it was less than 30%.

[0111] (Optical Transparency) (1) Initial Haze Value at Room Temperature The obtained adhesive tape was cut to a width of 50 mm x length of 80 mm, one release PET film was peeled off, and the tape was attached to a glass plate having a thickness of 0.7 mm, a width of 50 mm, and a length of 80 mm. Next, the other release PET film of the adhesive tape was peeled off, and the tape was attached to another glass plate having a thickness of 0.7 mm, a width of 50 mm, and a length of 80 mm to prepare a test piece. Immediately after preparing the test piece, the visible light haze value at the initial room temperature was measured using a haze meter (manufactured by Nippon Denshoku Industries Co., Ltd., "NDH 400"). The optical transparency of the adhesive tape was evaluated by marking a haze value of less than 1.0% as "◎", a value of 1.0% or more but less than 3.0% as "○", and a value of 3.0% or more as "×".

[0112] (2) Haze value at room temperature after 500 hours in an environment of 65 ° C. and 90% RH The obtained adhesive tape was cut to a width of 50 mm x length of 80 mm, one release PET film was peeled off, and the tape was attached to a glass plate having a thickness of 0.7 mm, a width of 50 mm, and a length of 80 mm. Next, the other release PET film of the adhesive tape was peeled off, and the tape was attached to another glass plate having a thickness of 0.7 mm, a width of 50 mm, and a length of 80 mm to prepare a test piece. The obtained test piece was left standing for 500 hours in an environment of 65 ° C. and 90% RH, and then the test piece temperature was returned to room temperature (20 ° C. or higher and 25 ° C. or lower) in an environment of 23 ° C. and 50% RH. After 1 hour, the visible light haze value at room temperature was measured using a haze meter (manufactured by Nippon Denshoku Industries Co., Ltd., "NDH 400") in accordance with JIS K 7136:2000. The optical transparency of the adhesive tape was evaluated by rating it as follows: if the obtained haze value was less than 1.0%, it was marked as "◎", if it was 1.0% or more but less than 3.0%, it was marked as "○", and if it was 3.0% or more, it was marked as "×".

[0113] (Adhesive strength: 180° peel force against glass at 23°C) One release PET film was peeled off from the obtained pressure-sensitive adhesive tape, and the tape was backed with a 23 μm thick PET film (manufactured by Futamura Chemical Co., Ltd., "FE2002"), after which it was cut into a width of 25 mm and a length of 75 mm. The other release PET film was peeled off to prepare a test specimen. This test specimen was placed on a glass plate so that the adhesive layer (the side to be measured) faced the glass plate, and then bonded to the test specimen by rolling a 2 kg rubber roller back and forth once at a speed of 300 mm / min. Thereafter, the test specimen was aged at 23°C and 50% RH for 20 minutes to prepare a test sample. The obtained test sample was peeled in the 180° direction under conditions of 23°C, 50% RH, and a pulling speed of 300 mm / min, and the 180° peel force (N / 25 mm) was measured. The adhesive strength of the adhesive tape was evaluated by rating it as follows: if the 180° peel strength against glass at 23°C was 12 N / mm or more, it was marked "◎"; if it was 8 N / mm or more but less than 12 N / mm, it was marked "◯"; and if it was less than 8 N / mm, it was marked "△".

[0114] (Appearance when attached to glass) The obtained adhesive tape was cut to a width of 50 mm x length of 80 mm, one release PET film was peeled off, and the tape was attached to a glass plate having a thickness of 0.7 mm, a width of 50 mm, and a length of 80 mm. Next, the other release PET film of the adhesive tape was peeled off, and the tape was attached to another glass plate having a thickness of 0.7 mm, a width of 50 mm, and a length of 80 mm to prepare a test sample. The obtained test sample was observed at the interface between the glass plate and the adhesive layer of the adhesive tape using a digital microscope (manufactured by Keyence Corporation, product name VHX-900). If no bubbles with a diameter of 0.5 mm or more were observed between the glass plate and the adhesive layer, the result was marked with "○", and if bubbles with a diameter of 0.5 mm or more were observed, the result was marked with "×".

[0115] (Metal Corrosion: Corrosion to Copper Foil) One release PET film was peeled off from the obtained pressure-sensitive adhesive tape, and the pressure-sensitive adhesive layer was bonded to a 50 μm thick PET film (manufactured by Toyobo Co., Ltd., "E5200") and cut to a width of 25 mm and a length of 25 mm to prepare a pressure-sensitive adhesive tape for evaluation. Two of these pressure-sensitive adhesive tapes for evaluation were prepared. The other release PET film was peeled off from the pressure-sensitive adhesive tape for evaluation 1, and the pressure-sensitive adhesive layer was placed facing one side of copper foil (manufactured by Takeuchi Metal Foil & Powder Co., Ltd., "C1020R-H", thickness 20 μm, width 25 mm and length 25 mm), and then the copper foil was bonded to the pressure-sensitive adhesive tape for evaluation 1 by moving a 2 kg rubber roller back and forth once at a speed of 300 mm / min. Thereafter, the other release PET film was peeled off from the evaluation pressure-sensitive adhesive tape 2, and the adhesive layer was placed facing the other side of the copper foil. The evaluation pressure-sensitive adhesive tape 2 was then bonded to the evaluation pressure-sensitive adhesive tape 2 by rolling a 2 kg rubber roller back and forth once at a speed of 300 mm / min, producing a laminate measuring 25 mm wide x 25 mm long. After bonding, the laminate was aged for 20 minutes at 23°C and 50% RH to produce a test sample. The test sample was left in an environment at 85°C and 85% RH for 3 days, and the evaluation pressure-sensitive adhesive tapes 1 and 2 were peeled from the copper foil and visually inspected for corrosion of the copper foil. The corrosion of the copper foil was assessed, and the metal corrosiveness of the pressure-sensitive adhesive tape was evaluated. Even if the corrosion of the copper foil was assessed as "x," the pressure-sensitive adhesive tape of the present invention may still be used without problems depending on the application.

[0116]

[0117]

[0118]

[0119]

[0120]

[0121]

[0122] According to the present invention, it is possible to provide a pressure-sensitive adhesive tape that can reduce the environmental load and has excellent optical transparency even when exposed to a high-temperature, high-humidity environment.

Claims

1. An adhesive tape having an adhesive layer, the pressure-sensitive adhesive layer contains a (meth)acrylic copolymer, the pressure-sensitive adhesive layer has a bio-derived carbon content of 30% or more; A pressure-sensitive adhesive tape characterized by satisfying at least one constitution selected from the group consisting of the following first constitution and the following second constitution: First configuration: the pressure-sensitive adhesive layer has a water vapor permeability coefficient P calculated by the following formula (i) of 11 g mm / (m ２ ・day) or more [Equation 1] In formula (i), WVTR is the water vapor transmission rate (g / (m)) per unit area of ​​the pressure-sensitive adhesive layer in an environment of 40°C and 90% RH for 1 day. ２ · day), and t represents the thickness (mm) of the pressure-sensitive adhesive layer. Second configuration: The (meth)acrylic copolymer contains at least one structural unit selected from the group consisting of structural units derived from n-heptyl (meth)acrylate and structural units derived from 2-octyl (meth)acrylate, and a structural unit derived from a nitrogen atom-containing monomer.

2. The adhesive tape according to claim 1 , which satisfies the first configuration.

3. The pressure-sensitive adhesive tape according to claim 2, wherein the (meth)acrylic copolymer contains at least one structural unit selected from the group consisting of a structural unit derived from n-heptyl (meth)acrylate and a structural unit derived from 2-octyl (meth)acrylate.

4. The pressure-sensitive adhesive tape according to claim 2, wherein the (meth)acrylic copolymer comprises at least one structural unit selected from the group consisting of structural units derived from hydroxyl group-containing monomers and structural units derived from nitrogen atom-containing monomers.

5. The adhesive tape according to claim 1 , which satisfies the second configuration.

6. The pressure-sensitive adhesive tape according to claim 5 , wherein the (meth)acrylic copolymer further comprises a structural unit derived from a hydroxyl group-containing monomer.

7. The pressure-sensitive adhesive tape according to claim 4 or 6, wherein the (meth)acrylic copolymer contains structural units derived from the hydroxyl group-containing monomer in an amount of from 5% by mass to 30% by mass.

8. The pressure-sensitive adhesive tape according to claim 1 , wherein the (meth)acrylic copolymer contains a structural unit derived from a (meth)acrylate containing carbon of biological origin.

9. The pressure-sensitive adhesive tape according to claim 8, wherein at least one structural unit selected from the group consisting of a structural unit derived from n-heptyl (meth)acrylate and a structural unit derived from 2-octyl (meth)acrylate contains carbon of biological origin.

10. The pressure-sensitive adhesive tape according to claim 4 , wherein the structural units derived from nitrogen atom-containing monomers include structural units derived from amide group-containing monomers.

11. The pressure-sensitive adhesive tape according to claim 4 , 5 or 6 , wherein the content of the structural unit derived from the nitrogen atom-containing monomer in the (meth)acrylic copolymer is from 5% by mass to 10% by mass.

12. The pressure-sensitive adhesive tape according to claim 4 or 6, wherein the total content of the structural units derived from the hydroxyl group-containing monomer and the structural units derived from the nitrogen atom-containing monomer in the (meth)acrylic copolymer is 10% by mass or more and 30% by mass or less.

13. 7. The pressure-sensitive adhesive tape according to claim 1, wherein the (meth)acrylic copolymer contains a structural unit derived from a carboxy group-containing monomer, and the content of the structural unit derived from the carboxy group-containing monomer in the (meth)acrylic copolymer is less than 0.5 mass%.

14. 7. The pressure-sensitive adhesive tape according to claim 1, wherein the (meth)acrylic copolymer contains a structural unit derived from isobornyl (meth)acrylate.

15. The pressure-sensitive adhesive tape according to claim 14, wherein the content of the structural unit derived from isobornyl (meth)acrylate in the (meth)acrylic copolymer is 10% by mass or more and 45% by mass or less.

16. 7. The pressure-sensitive adhesive tape according to claim 1, wherein the (meth)acrylic copolymer has a weight average molecular weight (Mw) of 300,000 or more and 900,000 or less.

17. 7. The pressure-sensitive adhesive tape according to claim 1, wherein the pressure-sensitive adhesive layer contains a silane coupling agent.

18. The pressure-sensitive adhesive tape according to claim 1 , wherein the pressure-sensitive adhesive layer has a gel fraction of 40% by mass or more and 95% by mass or less.

19. The pressure-sensitive adhesive layer has a shear storage modulus of 0.5×10 at 23° C. ５ Pa or more 3.0×10 ６ 7. The adhesive tape according to claim 1, wherein the viscosity is 0.05 Pa or less.

20. The haze value at 20°C or higher and 25°C or lower is less than 3.0%, The haze value at 20°C to 25°C after leaving the film for 500 hours in an environment of 65°C and 90% RH is less than 3.0% The adhesive tape according to claim 1, 2, 3, 4, 5 or 6.

21. 7. The pressure-sensitive adhesive tape according to claim 1, wherein the 180° peel strength from glass at 23° C. is 10 N / 25 mm or more.

Images