KR20240140927A - Adhesive composition, adhesive layer and adhesive sheet - Google Patents

Abstract

Provided is an adhesive composition capable of forming a low-dielectric constant adhesive layer. Provided is an adhesive composition comprising a polyester-based resin including a structural unit derived from a compound having 20 or more carbon atoms and 2 or more functional groups capable of forming an ester bond, wherein the adhesive composition has a dielectric constant of 4.0 or less at a frequency of 100 kHz when the adhesive layer is formed. It is preferable that the adhesive composition has a dielectric loss of 0.0001 to 0.15 at a frequency of 100 kHz when the adhesive layer is formed.

Description

Adhesive composition, adhesive layer and adhesive sheet

The present invention relates to an adhesive composition, an adhesive layer and an adhesive sheet. More specifically, the present invention relates to an adhesive composition, an adhesive layer and an adhesive sheet which can be preferably used for optical purposes.

Image display devices such as organic EL displays are used in combination with touch panels having capacitive touch sensors. Capacitive touch sensors are increasingly demanded to have higher performance as they become more widespread. For this reason, adhesive layers applied to capacitive touch sensors are also demanded to have higher performance.

However, due to the thinning of modules, enlargement of screens, and high-precision optical semiconductor elements in the image display device, there is concern that driving noise during display driving of the image display device may adversely affect the sensing of the electrostatic capacitive touch sensor, resulting in malfunction. The malfunction due to the driving noise may occur when the dielectric constant of the adhesive layer is high. Therefore, as an adhesive forming a low-dielectric adhesive layer, for example, an adhesive whose base polymer is a (meth)acrylic polymer having an alkyl (meth)acrylate having a long-chain alkyl group as its main component has been proposed (for example, Patent Document 1). With a low-dielectric adhesive layer, the influence of driving noise from an organic EL panel on the electrostatic capacitive touch sensor can be reduced.

Japanese Patent Publication No. 2013-082880

In recent years, image display devices are required to have larger screens and higher resolutions. As screens become larger, the voltage for driving image display devices tends to increase, and noise tends to increase. In addition, as the amount of semiconductor elements used increases along with higher resolutions, noise tends to increase due to the generation of higher voltages.

In addition, in recent years, there has been a tendency for touch sensors installed inside image display devices to be installed outside the image display devices. Image display devices are required to be lightweight and thinner, and when the touch sensor is installed outside the image display device, noise generated from the image display device is easily transmitted to the touch sensor attached to the image display device via an adhesive layer along with the thinning of the materials used inside and outside the image display device, so there is a tendency for the noise of the touch sensor to increase. For this reason, the adhesive layer is required to have a further lower dielectric constant.

The present invention is intended to solve such a problem, and its purpose is to provide an adhesive composition capable of forming an adhesive layer having a low dielectric constant.

The present invention provides an adhesive composition comprising a polyester resin including a structural unit derived from a compound having 20 or more carbon atoms and two or more functional groups capable of forming an ester bond, and having a dielectric constant at a frequency of 100 kHz of 4.0 or less when an adhesive layer is formed.

The compound having 20 or more carbon atoms and 2 or more functional groups capable of forming an ester bond, which the polyester-based resin contains as a constituent unit, tends to have low polarity because it has a large carbon atoms. Therefore, the adhesive layer formed with the adhesive composition containing the polyester-based resin tends to have a low dielectric constant. And, the dielectric constant of the adhesive layer formed using the adhesive composition at a frequency of 100 kHz is 4.0 or less. Thereby, the adhesive layer formed with the adhesive composition has a low dielectric constant, and is unlikely to cause, for example, noise amplification, and can also suppress millimeter wave radiation loss.

The adhesive composition preferably has a dielectric loss of 0.0001 to 0.15 at a frequency of 100 kHz when forming an adhesive layer. When the dielectric loss is within the above range, the adhesive layer formed from the adhesive composition has a small energy loss due to heat, and is less likely to cause, for example, noise amplification, and can also suppress millimeter wave radiation loss.

It is preferable that the glass transition temperature of the above polyester resin is 0℃ or lower. By using a polyester resin with a low glass transition temperature, the adhesiveness of the formed adhesive layer is better.

In addition, the present invention provides an adhesive layer formed by the adhesive composition.

In addition, the present invention provides an adhesive sheet having the adhesive layer.

According to the adhesive composition of the present invention, a low dielectric constant adhesive layer can be formed. Therefore, by using the adhesive layer for bonding a touch sensor and an image display device, for example, noise generated by the image display device can be made difficult to be transmitted to the touch sensor. In addition, by using the adhesive layer as an adhesive layer bonded to a millimeter wave antenna substrate used for a millimeter wave antenna, for example, radiation loss of millimeter waves can be suppressed.

Figure 1 is a schematic diagram (cross-sectional view) showing one embodiment of the optical laminate of the present invention.
FIG. 2 is a schematic diagram (cross-sectional view) showing another embodiment of the optical laminate of the present invention.
FIG. 3 is a schematic diagram (cross-sectional view) showing another embodiment of the optical laminate of the present invention.
FIG. 4 is a schematic diagram (cross-sectional view) showing one embodiment of a millimeter wave antenna of the present invention.
FIG. 5 is a schematic diagram (cross-sectional view) showing another embodiment of a millimeter wave antenna of the present invention.
FIG. 6 is a schematic diagram (cross-sectional view) showing another embodiment of a millimeter wave antenna of the present invention.

[Adhesive composition]

The adhesive composition of the present invention contains at least a polyester resin. The polyester resin contains at least a structural unit derived from a compound having 20 or more carbon atoms and two or more functional groups capable of forming an ester bond. In addition, in the present specification, the compound is sometimes referred to as "compound (A)". That is, the polyester resin is a resin obtained by polymerizing a monomer composition containing the compound (A). The polyester resin may contain only one type of structural unit derived from the compound (A), or may contain two or more types.

The dielectric constant of the adhesive layer formed using the above-mentioned adhesive composition at a frequency of 100 kHz is 4.0 or less, preferably 3.6 or less, more preferably 3.5 or less, further preferably 3.4 or less, even more preferably 3.3 or less, and particularly preferably 3.2 or less. Since the dielectric constant is 4.0 or less, the adhesive layer formed from the above-mentioned adhesive composition has a low dielectric constant, and, for example, is unlikely to cause noise amplification, and can suppress millimeter wave radiation loss. In addition, the "dielectric constant" is a value obtained by dividing the "dielectric constant" by the "dielectric constant of vacuum", but since the "dielectric constant of vacuum" is 1, in this specification, the "dielectric constant" and the "dielectric constant" are treated in the same way.

The dielectric loss of the adhesive layer formed using the above-mentioned adhesive composition at a frequency of 100 kHz is preferably 0.15 or less, more preferably 0.13 or less, further preferably 0.12 or less, further preferably 0.11 or less, further preferably 0.10 or less, further preferably 0.09 or less, and particularly preferably 0.08 or less. When the dielectric loss is 0.15 or less, the adhesive layer formed from the above-mentioned adhesive composition has a small energy loss due to heat, and is unlikely to cause, for example, amplification of noise, and can also suppress radiation loss of millimeter waves. The dielectric loss is, for example, 0.0001 or more.

In this specification, the permittivity and dielectric loss at a frequency of 100 kHz are measured in accordance with JIS K6911, and the permittivity and dielectric loss at frequencies of 28 GHz and 60 GHz are measured in accordance with JIS R1660-2, and specifically, are measured by the method described in the examples described later. The permittivity and the dielectric loss can be adjusted by adjusting the monomer composition of the polyester resin constituting the adhesive composition, the type or content of the additive, etc.

(polyester resin)

The number of carbon atoms in the compound (A) is 20 or more, preferably 24 or more, more preferably 26 or more, even more preferably 28 or more, still more preferably 30 or more, and particularly preferably 32 or more. Since the compound (A) contained in the polyester-based resin as a constituent unit has a large number of carbon atoms of 20 or more, it tends to have low polarity. For this reason, the adhesive layer formed with the adhesive composition containing the polyester-based resin tends to have low dielectric constant. The number of carbon atoms is, for example, 60 or less, and may be 58 or less, or 56 or less.

It is preferable that the compound (A) is a polyol and/or a polycarboxylic acid constituting the polyester resin. That is, the compound (A) is preferably a compound having two or more hydroxyl groups or carboxyl groups as functional groups capable of forming an ester bond, more preferably 2 to 4, even more preferably 2 to 3, and particularly preferably 2.

In addition to the functional group capable of forming an ester bond, the compound (A) may or may not have a hetero atom such as an oxygen atom, a nitrogen atom, or a sulfur atom. When it has the hetero atom, the ratio of the number of carbon atoms in the compound (A) to the number of hetero atoms excluding the functional group capable of forming an ester bond [carbon number/hetero atom number] is preferably 10 or more, more preferably 15 or more, even more preferably 20 or more, even more preferably 25 or more, and particularly preferably 30 or more. When it does not have the hetero atom or the ratio is 10 or more, the polarity of the polyester resin is lowered, and the dielectric constant of the adhesive layer formed with the adhesive composition containing it is lowered.

As the compound (A) which is a polycarboxylic acid, for example, a dimer acid of an unsaturated fatty acid can be mentioned. The number of carbon atoms of the unsaturated fatty acid is preferably 10 or more, and more preferably 16 or more. As the dimer acid of the unsaturated fatty acid, a dimer acid of oleic acid, a dimer acid of linoleic acid, a dimer acid of erucic acid, or a dimer acid obtained by combining two types of these unsaturated fatty acids can be mentioned.

As the polyol compound (A), for example, dimer diol can be mentioned. As the dimer diol, a reduced product of a dimer acid of an unsaturated fatty acid can be mentioned. The unsaturated fatty acid preferably has 10 or more carbon atoms, more preferably 12 or more, even more preferably 14 or more, and particularly preferably 16 or more. As the dimer diol, a reduced product of a dimer acid of oleic acid, a reduced product of a dimer acid of linoleic acid, a reduced product of a dimer acid of erucic acid, a reduced product of a dimer acid combining two types of these unsaturated fatty acids, and the like can be mentioned.

The above polyester resin contains at least a structural unit derived from compound (A). The above polyester resin may contain a structural unit derived from a polyvalent carboxylic acid other than compound (A) (other polyvalent carboxylic acid), a structural unit derived from a polyol other than compound (A) (other polyol), or other structural units other than these.

The content ratio of the structural unit derived from the compound (A) in the polyester resin is preferably 30 mass% or more, more preferably 35 mass% or more, even more preferably 40 mass% or more, still more preferably 45 mass% or more, and particularly preferably 50 mass% or more, with respect to 100 mass% of the total amount of structural units derived from monomers constituting the polyester resin. When the content ratio is 30 mass% or more, the polarity of the polyester resin decreases, and the dielectric constant of the adhesive layer formed with the adhesive composition containing it decreases.

As the polyester resin, specific examples thereof include (i) a polyester resin comprising a structural unit derived from a compound (A) as a polyol, a structural unit derived from another polyhydric carboxylic acid, and, if necessary, a structural unit derived from another polyol, (ii) a polyester resin comprising a structural unit derived from a compound (A) as a polyhydric carboxylic acid, a structural unit derived from another polyol, and, if necessary, a structural unit derived from another polyhydric carboxylic acid, (iii) a polyester resin comprising a structural unit derived from a compound (A) as a polyhydric carboxylic acid, a structural unit derived from a compound (A) as a polyhydric carboxylic acid, and, if necessary, a structural unit derived from another polyhydric carboxylic acid and/or a structural unit derived from another polyol.

As the above other polycarboxylic acids, dicarboxylic acids and carboxylic acids having three or more valences can be mentioned. As the dicarboxylic acids, for example, aliphatic dicarboxylic acids such as malonic acid, succinic acid, glutaric acid, dimethylglutaric acid, adipic acid, trimethyladipic acid, pimelic acid, suberic acid, azelaic acid, dodecanedioic acid, sebacic acid, thiodipropionic acid, and diglycolic acid; dimer acids having 19 or fewer carbon atoms; alicyclic dicarboxylic acids such as 1,2-cyclopentanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 4-methyl-1,2-cyclohexanedicarboxylic acid, norbornanedicarboxylic acid, and adamantanedicarboxylic acid; Unsaturated dicarboxylic acids such as maleic acid, maleic anhydride, fumaric acid, itaconic acid, citraconic acid, and dodecenyl succinic anhydride; aromatic dicarboxylic acids such as isophthalic acid, terephthalic acid, orthophthalic acid, benzylmalonic acid, 2,2'-biphenyldicarboxylic acid, 4,4'-biphenyldicarboxylic acid, 4,4'-dicarboxydiphenyl ether, and naphthalenedicarboxylic acid; derivatives thereof, etc. Examples of the derivatives include carboxylic acid salts, carboxylic acid anhydrides, carboxylic acid halides, and carboxylic acid esters. Examples of carboxylic acids having three or more valences include trimellitic acid, pyromellitic acid, adamantanetricarboxylic acid, trimesic acid, and trimer acid. These other polyvalent carboxylic acids may be used alone or in combination of two or more.

The above polycarboxylic acid (the polycarboxylic acid compound (A) and the other polycarboxylic acids) may be a plant-derived polycarboxylic acid. As the plant-derived polycarboxylic acid, there may be mentioned polycarboxylic acids produced using glucose (e.g., succinic acid, adipic acid, itaconic acid, etc.), dimer acids of unsaturated fatty acids (e.g., oleic acid, linoleic acid, erucic acid, etc.) derived from plant oils (e.g., palm oil, coconut oil, rapeseed oil, etc.), sebacic acid derived from castor oil, etc.

As the above other polyols, diols and trivalent or higher polyols can be mentioned. As the diols, for example, (poly)alkylene glycols such as ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, and polytetramethylene glycol; Aliphatic diols such as 1,3-propanediol, 2-methyl-1,3-propanediol, 2,2-dimethyl-1,3-propanediol (neopentyl glycol), 2-ethyl-2-butyl-1,3-propanediol, 2-ethyl-2-isobutyl-1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, 2-methyl-1,3-hexanediol, 2,2,4-trimethyl-1,6-hexanediol, 1,8-octanediol, 1,9-nonanediol, and 1,10-decanediol; dimer diols having 19 carbon atoms or less; Alicyclic diols such as 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, spiroglycol, tricyclodecane dimethanol, adamantanediol, and 2,2,4,4-tetramethyl-1,3-cyclobutanediol; aromatic diols such as 4,4'-thiodiphenol, 4,4'-methylenediphenol, 4,4'-dihydroxybiphenyl, o-, m-, and p-dihydroxybenzene, 2,5-naphthalenediol, p-xylenediol, and ethylene oxide and propylene oxide adducts thereof. Examples of polyols having three or more valences include pentaerythritol, dipentaerythritol, tripentaerythritol, glycerin, trimethylolpropane, trimethylolethane, 1,3,6-hexanetriol, adamantanetriol, etc. Of the above other polyols, only one type may be used, or two or more types may be used.

The above polyol (the polyol compound (A) and the other polyols) may be a plant-derived polyol. As the plant-derived polyol, there may be mentioned a polyol produced using glucose (for example, ethylene glycol, propylene glycol, butanediol, isosorbide, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, etc.), a dimer diol which is a reduced form of a dimer acid of an unsaturated fatty acid (for example, oleic acid, linoleic acid, erucic acid, etc.) derived from plant oil (for example, palm oil, coconut oil, rapeseed oil, etc.), and 1,10-decanediol which is a reduced form of sebacic acid derived from castor oil.

The content ratio of the sum of the structural units derived from dicarboxylic acid and the structural units derived from diol in the polyester resin is preferably 90 mass% or more, more preferably 95 mass% or more, even more preferably 98 mass% or more, and particularly preferably 99 mass% or more (for example, 99 to 100 mass%), with respect to the total amount of 100 mass% of the structural units derived from the monomers constituting the polyester resin.

When the compound (A) is a polycarboxylic acid, the content ratio of the structural unit derived from the compound (A) in the polyester resin is, for example, 30 mass% or more, and may be 40 mass% or more, 50 mass% or more, and preferably 60 mass% or more, more preferably 70 mass% or more, still more preferably 80 mass% or more, still more preferably 85 mass% or more, and particularly preferably 90 mass% or more, and may be 95 mass% or more, with respect to 100 mass% of the total amount of structural units derived from the polycarboxylic acid constituting the polyester resin.

When compound (A) is a polyol, the content ratio of the structural unit derived from compound (A) in the polyester resin is, for example, 30 mass% or more, may be 40 mass% or more, 50 mass% or more, preferably 60 mass% or more, more preferably 70 mass% or more, still more preferably 80 mass% or more, further preferably 85 mass% or more, particularly preferably 90 mass% or more, and may be 95 mass% or more, relative to 100 mass% of the total amount of structural units derived from the polyol constituting the polyester resin.

The content of the structural unit derived from polycarboxylic acid in the polyester resin is, for example, 0.5 equivalent or more, preferably 0.58 equivalent or more, more preferably 0.66 equivalent or more, still more preferably 0.83 equivalent or more, still more preferably 0.88 equivalent or more, and particularly preferably 0.95 equivalent or more, per 1 equivalent of polyol. In addition, the content is, for example, 2.0 equivalent or less, preferably 1.7 equivalent or less, more preferably 1.5 equivalent or less, still more preferably 1.2 equivalent or less, still more preferably 1.1 equivalent or less, and particularly preferably 1.05 equivalent or less, per 1 equivalent of polyol.

The equivalent ratio of the constituent unit derived from the polycarboxylic acid and the constituent unit derived from the polyol in the polyester resin is not particularly limited, and an appropriate equivalent ratio can be set in consideration of the intended polymer properties, polymerizability, etc. When the equivalent ratio of the polycarboxylic acid is high, the characteristics based on the polycarboxylic acid can be easily expressed. In addition, when the equivalent ratio of the polyol is high, the characteristics based on the polyol can be easily expressed.

The weight average molecular weight (Mw) of the above polyester resin is preferably 3000 or more, more preferably 5000 or more, still more preferably 10000 or more, still more preferably 15000 or more, and particularly preferably 20000 or more. When the weight average molecular weight is 3000 or more, the cohesive force of the adhesive layer increases, and the holding power and high temperature holding power are improved. The weight average molecular weight is, for example, 300000 or less, preferably 250000 or less, more preferably 200000 or less, and still more preferably 150000 or less.

The glass transition temperature (Tg) of the polyester resin is preferably 10°C or lower, more preferably 5°C or lower, even more preferably 0°C or lower, even more preferably less than -5°C, and particularly preferably -10°C or lower. By using a polyester resin having a low Tg, the adhesiveness of the pressure-sensitive adhesive layer formed is excellent. Furthermore, from the viewpoint of the cohesiveness of the pressure-sensitive adhesive layer, the Tg of the polyester resin is preferably -60°C or higher, more preferably -55°C or higher, even more preferably -50°C or higher, and particularly preferably -45°C or higher. The Tg of the polyester resin can be adjusted by appropriately changing the monomer composition (i.e., the type or amount of monomer used for synthesizing the polyester resin). Furthermore, the Tg of the polyester resin is measured as the Tg of the pressure-sensitive adhesive layer, and specifically, is measured by the method described in the Examples, for example.

The above-described adhesive composition preferably contains the polyester-based resin as a base polymer. The content ratio of the polyester-based resin relative to the total amount of 100 mass% of the entire resin contained in the above-described adhesive composition is preferably more than 50 mass%, more preferably 60 mass% or more, even more preferably 70 mass% or more, and may be 80 mass% or more.

The method for obtaining the above polyester resin is not particularly limited, and a known or commonly used polymerization method for polyester resins can be appropriately employed. Specifically, the above polyester resin can be obtained by polycondensation of a polycarboxylic acid and a polyol, similarly to general polyesters. More specifically, a polyester resin can be synthesized by allowing a reaction between a carboxyl group of the polycarboxylic acid and a hydroxyl group of the polyol to proceed while removing water (generated water) and the like generated by the reaction to be removed outside the reaction system. Examples of methods for removing the generated water outside the reaction system include a method of introducing an inert gas into the reaction system and removing the generated water together with the inert gas outside the reaction system, a method of performing azeotropic dehydration using a reaction water discharge solvent such as toluene or xylene, a method of distilling the generated water from the reaction system under reduced pressure (reduced pressure method), etc. In addition, the polyester resin may also employ an ester exchange reaction using a polyvalent ester and a polyol.

As the above polyvalent ester, the ester of the above polyvalent carboxylic acid can be mentioned. As the above ester, the alkyl ester such as methyl ester, ethyl ester, etc.; the hydroxyalkyl ester such as 2-hydroxyethyl ester, etc. can be mentioned. Among them, the hydroxyalkyl ester is preferable, and more preferably, 2-hydroxyethyl ester. In this case, compared to the polyvalent carboxylic acid or its alkyl ester, the melting point tends to be lower, the handleability is excellent, the obtained polyester resin terminal becomes a hydroxy group, the reactivity with a curing agent such as an isocyanate curing agent described later is excellent, and the hydrolysis resistance of the polyester resin is excellent. In addition, since bis(2-hydroxyethyl) terephthalate bis can be synthesized by chemical recycling of PET, it has excellent environmental adaptability.

The reaction temperature and reaction time when performing various reactions such as the above polycondensation, and the degree of pressure reduction (pressure within the reaction system) when employing the pressure reduction method, can be appropriately set so that a polyester resin having the desired characteristics (e.g., molecular weight) can be efficiently obtained. Although not particularly limited, the reaction temperature is usually suitably set to 150°C or higher (e.g., 180°C to 260°C). By setting the reaction temperature within the above range, a good reaction speed is obtained, productivity is improved, and deterioration of the produced polyester resin can be easily prevented or suppressed. The reaction time is not particularly limited, and is about 3 to 48 hours. When employing the pressure reduction method, although not particularly limited, the degree of pressure reduction can be, for example, 4 kPa to 0.1 kPa. By setting the pressure within the reaction system within the above range, water produced by the reaction can be efficiently distilled out of the system, making it easy to maintain a good reaction speed. In addition, when the reaction temperature is relatively high, it is easy to prevent the raw material polycarboxylic acid or polyol from being distilled out of the system by setting the pressure inside the reaction system to the lower limit or higher. From the viewpoint of maintaining the pressure inside the reaction system stably, it is usually appropriate to set the pressure inside the reaction system to 0.1 kPa or higher.

In the above reaction, as in the synthesis of general polyesters, a known or conventional catalyst may be used in an appropriate amount for esterification and condensation. Examples of the catalyst include metal compounds such as titanium, germanium, antimony, tin, and zinc; strong acids such as p-toluenesulfonic acid and sulfuric acid; and the like. The amount of the catalyst used may be appropriately set depending on the reaction speed, etc.

In the above process of synthesizing a polyester resin by reaction of a polyol and a polycarboxylic acid or a polyhydric ester, a solvent may or may not be used. The above synthesis can be carried out substantially without using an organic solvent, that is, without intentionally using an organic solvent.

(Bridger)

The above-mentioned adhesive composition may contain a crosslinking agent. The crosslinking agent has the function of crosslinking the polyester-based resins, and can also function as a chain extender for the polyester-based resin. When the crosslinking agent is contained, a crosslinked structure of the polyester-based resin is formed in the formed adhesive layer, and cohesion is improved. The above-mentioned crosslinking agent may be used alone, or two or more types may be used.

Examples of the crosslinking agent include an isocyanate crosslinking agent, an epoxy crosslinking agent, a melamine crosslinking agent, a peroxide crosslinking agent, a urea crosslinking agent, a metal alkoxide crosslinking agent, a metal chelate crosslinking agent, a metal salt crosslinking agent, a carbodiimide crosslinking agent, an oxazoline crosslinking agent, an aziridine crosslinking agent, an amine crosslinking agent, a silicone crosslinking agent, and a silane crosslinking agent. Among them, an isocyanate crosslinking agent is preferable from the viewpoint of excellent impact resistance of the pressure-sensitive adhesive layer formed.

The number of functional groups in the above crosslinking agent is 2 or more, preferably 2 to 4, more preferably 2 to 3. In particular, from the viewpoint of particularly excellent impact resistance of the pressure-sensitive adhesive layer formed, an isocyanate-based crosslinking agent having a number of functional groups within the above range is preferable.

Examples of the above isocyanate crosslinking agent (polyfunctional isocyanate compound) include lower aliphatic polyisocyanates such as 1,2-ethylene diisocyanate, 1,4-butylene diisocyanate, 1,5-pentamethylene diisocyanate, and 1,6-hexamethylene diisocyanate; alicyclic polyisocyanates such as cyclopentylene diisocyanate, cyclohexylene diisocyanate, isophorone diisocyanate, hydrogenated tolylene diisocyanate, and hydrogenated xylylene diisocyanate; and aromatic polyisocyanates such as 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, and xylylene diisocyanate. In addition, as the isocyanate crosslinking agent, lower aliphatic polyisocyanate-modified isocyanurates such as 1,5-pentamethylene diisocyanate-modified isocyanurate and 1,6-hexamethylene diisocyanate-modified isocyanurate can also be mentioned. Furthermore, lower aliphatic polyisocyanate adducts such as ethylene glycol/1,2-ethylene diisocyanate, 1,4-butylene diisocyanate, 1,5-pentamethylene diisocyanate, and 1,6-hexamethylene diisocyanate, lower aliphatic polyisocyanate adducts such as 1,4-butanediol/1,2-ethylene diisocyanate, 1,4-butylene diisocyanate, 1,5-pentamethylene diisocyanate, and 1,6-hexamethylene diisocyanate, lower aliphatic polyisocyanate adducts such as 1,6-hexanediol/1,2-ethylene diisocyanate, 1,4-butylene diisocyanate, 1,5-pentamethylene diisocyanate, and 1,6-hexamethylene diisocyanate, Other examples include trimethylolpropane/tolylene diisocyanate adduct, trimethylolpropane/hexamethylene diisocyanate adduct, and trimethylolpropane/xylylene diisocyanate adduct.

As the above epoxy crosslinking agent (polyfunctional epoxy compound), for example, N,N,N',N'-tetraglycidyl-m-xylenediamine, diglycidylaniline, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, 1,6-hexanediol diglycidyl ether, neopentyl glycol diglycidyl ether, ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, sorbitol polyglycidyl ether, glycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, polyglycerol polyglycidyl ether, sorbitan polyglycidyl ether, trimethylolpropane polyglycidyl ether, adipate diglycidyl ester, o-phthalic acid diglycidyl ester, In addition to triglycidyl-tris(2-hydroxyethyl)isocyanurate, resorcin diglycidyl ether, and bisphenol-S-diglycidyl ether, examples thereof include epoxy resins having two or more epoxy groups in the molecule.

The content of the crosslinking agent in the adhesive composition is preferably 0.1 parts by mass or more with respect to 100 parts by mass of the total amount of the polyester-based resin. In addition, the content is preferably 30 parts by mass or less with respect to 100 parts by mass of the total amount of the polyester-based resin, more preferably 25 parts by mass or less, even more preferably 20 parts by mass or less, even more preferably 16 parts by mass or less, even more preferably 12 parts by mass or less, and particularly preferably 10 parts by mass or less. When the content of the crosslinking agent is 0.1 parts by mass or more, the cohesiveness of the adhesive layer is improved. On the other hand, when the content of the crosslinking agent is 30 parts by mass or less, the adhesive layer has appropriate flexibility, and the adhesive strength is easily improved.

(crosslinking catalyst)

The above adhesive composition may contain a crosslinking catalyst in addition to the crosslinking agent in order to more effectively progress the crosslinking reaction. The above crosslinking catalyst may be used alone or in combination of two or more types.

Examples of the crosslinking catalyst include: zirconium-containing compounds (zirconium-based catalysts) such as zirconium tetraacetylacetonate, zirconium monoacetylacetonate, zirconium ethyl acetoacetate, and zirconium octylate compounds; tin (Sn)-containing compounds (tin-based catalysts) such as dioctyltin dilaurate, dibutyltin dilaurate, dibutyltin diacetate, dibutyltin diacetylacetonate, tetra-n-butyltin, trimethyltin hydroxide, and butyltin oxide; aluminum-containing compounds (aluminum-based catalysts) such as aluminum-sec-butoxide, aluminum tris-acetylacetonate, aluminum bisethyl acetoacetate, and aluminum tris-ethyl acetoacetate; iron-containing compounds (iron-based catalysts) such as ferric naphthene; Examples of organic metal catalysts include titanium-containing compounds (titanium catalysts) such as tetraisopropyl titanate, tetra-n-butyl titanate, butyl titanate dimer, tetraoctyl titanate, titanium acetylacetonate, titanium tetraacetylacetonate, and titanium ethyl acetoacetate.

The content of the crosslinking catalyst in the adhesive composition is preferably 0.001 parts by mass or more, more preferably 0.005 parts by mass or more, and even more preferably 0.01 parts by mass or more, relative to 100 parts by mass of the total amount of the polyester-based resin. In addition, the content of the crosslinking catalyst is preferably 3 parts by mass or less, more preferably 2 parts by mass or less, and even more preferably 1 part by mass or less, relative to 100 parts by mass of the total amount of the polyester-based resin.

(My singer decomposer)

The above adhesive composition may contain a hydrolysis-resistant agent (hydrolysis inhibitor). By adding the hydrolysis-resistant agent, the hydrolysis reaction in the adhesive composition or the adhesive layer is suppressed, and good durability can be easily obtained. The above hydrolysis-resistant agent may be used alone or in combination of two or more.

As the above hydrolytic decomposition agent, there is no particular limitation, and a known or commonly used hydrolytic decomposition agent can be used. As the above hydrolytic decomposition agent, for example, an oxazoline group-containing compound, an epoxy group-containing compound, a carbodiimide group-containing compound, etc. are exemplified. Among them, a carbodiimide group-containing compound is preferable.

Examples of the above carbodiimide group-containing compounds include dicyclohexylcarbodiimide, diisopropylcarbodiimide, dimethylcarbodiimide, diisobutylcarbodiimide, dioctylcarbodiimide, t-butylisopropylcarbodiimide, diphenylcarbodiimide, di-t-butylcarbodiimide, di-β-naphthylcarbodiimide, polycarbodiimides, and cyclic carbodiimides. The above polycarbodiimide is a compound in which two or more carbodiimide groups are bonded by a bonding group formed by an aliphatic group, an alicyclic group, an aromatic group, or a combination thereof. In addition, the above-mentioned ring-shaped carbodiimide is a compound having at least one carbodiimide group in its molecular structure, and in which a ring structure is formed by bonding the first nitrogen atom and the second nitrogen atom of the carbodiimide group by a bonding group composed of an aliphatic group, an alicyclic group, an aromatic group, or a combination thereof. The bonding group may have a heteroatom or a substituent.

The content of the hydrolytic decomposition agent in the adhesive composition is preferably 0.1 parts by mass or more, more preferably 0.2 parts by mass or more, and even more preferably 0.3 parts by mass or more, with respect to 100 parts by mass of the total amount of the polyester resin. The content of the hydrolytic decomposition agent is, for example, 5 parts by mass or less, preferably 3 parts by mass or less, and more preferably 1 part by mass or less.

(Adhesive Resin)

The above adhesive composition may include a tackifying resin. By adding the tackifying resin, the adhesive strength to the adherend is improved. The above adhesive-imparting resin may be used alone or in combination of two or more.

As the above-mentioned tackifying resin, there is no particular limitation, and a known or commonly used tackifying resin can be used. As the above-mentioned tackifying resin, a phenol-based tackifying resin, a terpene-based tackifying resin, a rosin-based tackifying resin, a hydrocarbon-based tackifying resin, an epoxy-based tackifying resin, a polyamide-based tackifying resin, an elastomer-based tackifying resin, a ketone-based tackifying resin, and the like can be mentioned.

Examples of the phenol-based adhesive-giving resin include terpene phenol resins, hydrogenated terpene phenol resins, alkylphenol resins, and rosin phenol resins. The terpene phenol resin is a polymer containing a terpene residue and a phenol residue, and includes copolymers of terpenes and phenol compounds (terpene-phenol copolymer resins), and phenol-modified homopolymers or copolymers of terpenes (phenol-modified terpene resins). Terpenes constituting the terpene phenol resin include monoterpenes such as α-pinene, β-pinene, and limonene (d-form, l-form, d/l-form (dipentene), etc.). The hydrogenated terpene phenol resin is a resin having a structure in which the terpene phenol resin is hydrogenated. The alkylphenol resin is a resin obtained from alkylphenol and formaldehyde (oil-based phenol resin). As the above alkylphenol resin, for example, novolac type and resol type can be mentioned. The above rosin phenol resin is a phenol modified product of rosin or various rosin derivatives described later. The above rosin phenol resin is obtained by, for example, a method of adding phenol to rosin or various rosin derivatives described later using an acid catalyst and thermally polymerizing the same.

As the above terpene-based adhesive-imparting resin, polymers of terpenes (typically monoterpenes) such as α-pinene, β-pinene, d-limonene, l-limonene, and dipentene can be exemplified. The above terpene polymer may be a homopolymer of one type of terpene, or a copolymer of two or more types of terpenes. Homopolymers of one type of terpene can include α-pinene polymers, β-pinene polymers, and dipentene polymers. The above-mentioned modified terpene-based adhesive-imparting resin is a modified terpene resin (modified terpene resin). Examples of the above-mentioned modified terpene resin include styrene-modified terpene resins, hydrogenated terpene resins, and the like.

As the above-mentioned rosin-based adhesive-giving resin, rosins and rosin derivative resins can be mentioned. As the above-mentioned rosins, for example, unmodified rosins (unprocessed rosins) such as gum rosin, wood rosin, and tall oil rosin; modified rosins (hydrogenated rosin, disproportionated rosin, polymerized rosin, and other chemically modified rosins) obtained by modifying these unmodified rosins through hydrogenation, disproportionation, polymerization, etc. can be mentioned. As the above-mentioned rosin derivative resin, derivatives of the above-mentioned rosins can be mentioned. As the above-mentioned rosin derivative resin, for example, rosin esters such as unmodified rosin esters which are esters of unmodified rosin and alcohols, or modified rosin esters which are esters of modified rosin and alcohols; unsaturated fatty acid-modified rosins which are rosins modified with unsaturated fatty acids; Examples thereof include unsaturated fatty acid modified rosin esters obtained by modifying rosin esters with unsaturated fatty acids; rosin alcohols obtained by reducing the carboxyl group of rosin or the various rosin derivatives described above; and metal salts of rosin or the various rosin derivatives described above. Specific examples of the rosin esters include methyl esters, triethylene glycol esters, glycerin esters, pentaerythritol esters, etc. of unmodified rosin or modified rosin.

Examples of the hydrocarbon-based adhesive-providing resin include aliphatic hydrocarbon resins, aromatic hydrocarbon resins, aliphatic cyclic hydrocarbon resins, aliphatic/aromatic petroleum resins (styrene-olefin copolymers, etc.), aliphatic/alicyclic petroleum resins, hydrogenated hydrocarbon resins, coumarone-based resins, and coumarone-indene-based resins.

The content of the tackifying resin in the above-mentioned adhesive composition is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and even more preferably 15 parts by mass or more, with respect to 100 parts by mass of the total amount of the polyester-based resin. The content of the tackifying resin is, for example, 70 parts by mass or less, preferably 60 parts by mass or less, and more preferably 50 parts by mass or less.

The above-described adhesive composition may contain other components other than the above-described components as needed, within a range that does not impair the effects of the present invention. Examples of the other components include resins other than the polyester resin, curing catalysts, crosslinking accelerators, polymerization initiators, oligomers, anti-aging agents, fillers (metal powders, organic fillers, inorganic fillers, etc.), colorants (pigments, dyes, etc.), antioxidants, plasticizers, softeners, surfactants, antistatic agents, surface lubricants, leveling agents, light stabilizers, ultraviolet absorbers, polymerization inhibitors, rust inhibitors, granular substances, thin films, flame retardants, silane coupling agents, ion trapping agents, etc. The above-described other components may each be used alone or in combination of two or more.

The above adhesive composition may have any form, and examples thereof include a solvent type, an emulsion type, a hot melt type, a solvent-free type, etc.

The adhesive composition of the present invention may be a solvent type as described above, that is, may contain an organic solvent. The organic solvent is not particularly limited as long as it is an organic compound used as a solvent, and examples thereof include hydrocarbon solvents such as cyclohexane, hexane, heptane, and methylcyclohexane; aromatic solvents such as toluene and xylene; ester solvents such as butyl acetate, ethyl acetate, and methyl acetate; ketone solvents such as acetone, methyl ethyl ketone, and methyl isobutyl ketone; alcohol solvents such as methanol, ethanol, propanol, butanol, and isopropyl alcohol; and carbonate solvents such as dimethyl carbonate and diethyl carbonate. The organic solvent may be used alone or in combination of two or more.

[Adhesive layer]

The above-mentioned adhesive composition can be used to form an adhesive layer. An adhesive layer formed using the adhesive composition of the present invention is sometimes referred to as an “adhesive layer of the present invention.” The above-mentioned adhesive layer can be produced, for example, by applying the above-mentioned adhesive composition to a release-treated surface of a release liner or a substrate to form an adhesive composition layer, and then solidifying the adhesive composition layer by desolvation by heating.

The above-mentioned adhesive layer preferably contains the polyester-based resin (particularly, contains it as a base polymer). The content ratio of the polyester-based resin relative to the total amount of 100 mass% of the entire resin contained in the above-mentioned adhesive layer is preferably more than 50 mass%, more preferably 60 mass% or more, even more preferably 70 mass% or more, and may be 80 mass% or more, 90 mass% or more, or 95 mass% or more.

The content ratio of the polyester resin in the adhesive layer is preferably more than 50 mass%, more preferably 60 mass% or more, even more preferably 70 mass% or more, and may be 80 mass% or more, with respect to 100 mass% of the total amount of the adhesive layer.

The above-mentioned adhesive layer may contain other components other than the polyester resin, within a range that does not impair the effects of the present invention. As the above-mentioned other components, those exemplified and described as components that the above-mentioned adhesive composition may contain may be mentioned. The above-mentioned other components may be used alone or in combination of two or more.

The total light transmittance (according to JIS K7361-1) of the above-mentioned adhesive layer is not particularly limited, but is preferably 88% or more, more preferably 89% or more, and even more preferably 90% or more. When the total light transmittance is 88% or more, excellent transparency and excellent appearance are obtained, and the adhesive layer can be suitably used for optical purposes.

In addition, by evaluating the total light transmittance by the same method as above using a laminate in which an adhesive layer and an optical film are laminated, it can be used as a standard for the total light transmittance of the adhesive layer. Specifically, for example, when the total light transmittance of the optical film is close to 100%, it can be determined that the total light transmittance of the laminate and the total light transmittance of the adhesive layer are approximately the same.

The haze (according to JIS K7136) of the above-mentioned adhesive layer is not particularly limited, but is preferably 1.5% or less, more preferably 1.4% or less, still more preferably 1.3% or less, still more preferably 1.2% or less, still more preferably 1.0% or less, still more preferably 0.9% or less, still more preferably 0.8% or less, still more preferably 0.7% or less, and particularly preferably 0.6% or less. When the haze is 1.5% or less, excellent transparency and excellent appearance are obtained, and the adhesive can be suitably used for optical applications.

In addition, by evaluating the haze by the same method as above using a laminate in which an adhesive layer and an optical film are laminated, it can be used as a standard for the haze value of the adhesive layer. Specifically, for example, when the haze value of the optical film is close to 0%, the haze value of the laminate and the haze value of the adhesive layer can be judged to be approximately the same.

The color of the adhesive layer is preferably a color represented by the L*a*b* colorimetric system in the range of b* of 0.0 to 2.0, more preferably 0.0 to 1.5, still more preferably 0.0 to 1.2, still more preferably 0.0 to 1.0, still more preferably 0.0 to 0.8, and particularly preferably 0.0 to 0.5. b* represents a yellow-blue axis, and in the range of 0.0 to 2.0, a smaller value reduces the yellowness, and excellent transparency or excellent appearance is obtained, so that it can be preferably used for optical purposes. In the present specification, b* represented by the L*a*b* colorimetric system of the adhesive layer is a value calculated from the linear transmittance of the adhesive layer.

In addition, by using a laminate in which an adhesive layer and an optical film are laminated, the color (b*) can be evaluated by the same method as described above, thereby serving as a standard for the color (b*) of the adhesive layer. Specifically, for example, when the color of the optical film is close to 0, the color (b*) of the laminate and the color (b*) of the adhesive layer can be judged to be approximately the same.

The total light transmittance, haze and b* of the above adhesive layer can be adjusted by adjusting the monomer composition of the polyester resin constituting the adhesive composition for forming the adhesive layer, the type or content of the additive, etc.

The 180° peel adhesion of the adhesive layer to a glass plate at a tensile speed of 300 mm/min is not particularly limited, but is preferably 1 N/20 mm or more, more preferably 2 N/20 mm or more, and even more preferably 3 N/20 mm or more. When the 180° peel adhesion is at a certain value or more, the adhesion to glass and the lifting-suppression property in steps are further excellent. The 180° peel adhesion is not particularly limited, but is preferably 20 N/20 mm or less, more preferably 18 N/20 mm or less, and even more preferably 16 N/20 mm or less.

In addition, by using a laminate in which an adhesive layer and an optical film are laminated, the 180° peel adhesion can be evaluated by the same method as described above, thereby serving as a standard for the 180° peel adhesion of the adhesive layer.

As the above glass plate, there is no particular limitation, but examples thereof include the product name "Soda-lime glass #0050" (manufactured by Matsunami Glass High School Co., Ltd.). In addition, non-alkali glass and chemically strengthened glass may also be mentioned.

The above 180° peel adhesion can be controlled by the monomer composition of the polyester resin constituting the adhesive composition for forming the adhesive layer, the weight average molecular weight, the amount of crosslinking agent used (added amount), the type or content of other additives, etc.

The storage elastic modulus of the adhesive layer at 23°C is not particularly limited, but is preferably 5.0×10 ⁴ Pa or more, more preferably 7.5×10 ⁴ Pa or more, and even more preferably 1.0×10 ⁵ Pa or more. When the storage elastic modulus is 5.0×10 ⁴ Pa or more, it is difficult for marks to occur during handling, and good bonding reliability becomes easy to obtain, which is preferable. Furthermore, from the viewpoints of step followability and foreign matter absorbency, the storage elastic modulus of the adhesive layer at 25°C is preferably 2.0×10 ⁶ Pa or less, more preferably 1.5×10 ⁶ Pa or less, and even more preferably 1.0×10 ⁶ Pa or less. The storage elastic modulus of the adhesive layer is measured when dynamic viscoelasticity is performed at a frequency of 1 Hz. The storage elastic modulus is the real part of the shear elastic modulus expressed as a complex number, and can be converted by taking into account the Poisson's ratio of the sample with respect to the tensile elastic modulus, etc.

The storage elastic modulus of the above-mentioned adhesive layer can be controlled by the monomer composition of the polyester resin constituting the adhesive composition for forming the adhesive layer, the weight average molecular weight, the amount of crosslinking agent used (added amount), the type or content of other additives, etc.

The gel fraction (proportion of insoluble components) of the above-mentioned adhesive layer is not particularly limited, but is preferably 3% or more, more preferably 5% or more, further preferably 10% or more, and particularly preferably 15% or more. The gel fraction (proportion of insoluble components) of the above-mentioned adhesive layer is not particularly limited, but is preferably 95% or less, more preferably 90% or less, and further preferably 85% or less. When the gel fraction is 3% or more, the cohesiveness of the adhesive layer is improved, and it is difficult for marks to occur during handling. When the gel fraction is 95% or less, appropriate flexibility is obtained, so that the adhesiveness and step following property are further improved, and it is also difficult for foreign substances to be absorbed.

The gel fraction can be controlled, for example, by the monomer composition of the polyester resin constituting the adhesive composition for forming the adhesive layer, the weight average molecular weight, the amount of crosslinking agent used (addition amount), the type or content of other additives, etc.

The thickness of the above-mentioned adhesive layer is not particularly limited, but is preferably 10 to 250 μm, more preferably 10 to 200 μm, still more preferably 10 to 175 μm, still more preferably 10 to 150 μm, still more preferably 10 to 125 μm, and particularly preferably 10 to 100 μm. When the thickness is a certain or more, step followability and adhesion reliability are improved, which is preferable. When the thickness is a certain or less, foreign substances are difficult to be absorbed during handling, and further, handleability and manufacturability are particularly excellent, which is preferable. In addition, the above-mentioned adhesive layer can suppress noise amplification even when it is thin.

The method for manufacturing the above-mentioned adhesive layer is not particularly limited, but for example, the adhesive composition may be applied (coated) to a release-treated surface of a release liner that has been subjected to a release treatment or a substrate treatment to form a coating layer, and then, if necessary, the coating layer may be solidified by performing solvent removal or thermal curing by heating.

[Adhesive sheet]

An adhesive sheet can be obtained using the adhesive layer of the present invention. An adhesive sheet having the adhesive layer of the present invention is sometimes referred to as an “adhesive sheet of the present invention.” The adhesive sheet may be a double-sided adhesive sheet in which both surfaces are adhesive layer surfaces, or a single-sided adhesive sheet in which only one surface is an adhesive layer surface. Among these, from the viewpoint of bonding two members together, a double-sided adhesive sheet is preferable. In addition, in the present specification, the term “adhesive sheet” also includes a tape-shaped sheet, that is, an “adhesive tape.” In addition, in the present specification, the surface of the adhesive layer is sometimes referred to as an “adhesive surface.”

The above-mentioned adhesive sheet may be a so-called "inorganic type" adhesive sheet (hereinafter, sometimes referred to as an "inorganic adhesive sheet") having no substrate (substrate layer), or may be a type of adhesive sheet having a substrate (hereinafter, sometimes referred to as a "substrate-equipped adhesive sheet"). As the inorganic adhesive sheet, for example, a double-sided adhesive sheet formed only by the adhesive layer of the present invention, or a double-sided adhesive sheet formed by the adhesive layer of the present invention and an adhesive layer other than the adhesive layer of the present invention (sometimes referred to as "other adhesive layers"), etc. can be mentioned. On the other hand, as the substrate-equipped adhesive sheet, an adhesive sheet having the adhesive layer of the present invention on at least one side of the substrate can be mentioned. Among these, an inorganic adhesive sheet (an inorganic double-sided adhesive sheet) is preferable, and an inorganic double-sided adhesive sheet formed only by the adhesive layer of the present invention is more preferable. In addition, an adhesive sheet having adhesive layers on both sides of a substrate (a double-sided adhesive sheet having a substrate) is also preferable. In the double-sided adhesive sheet having the substrate, the adhesive layers on both sides may both be adhesive layers of the present invention, or one side may be an adhesive layer of the present invention and the other side may be another adhesive layer. In addition, the "substrate (substrate layer)" does not include a release liner that is released when the adhesive sheet is used (attached).

If the above adhesive sheet is a substrate-equipped adhesive sheet, it is preferable that it be an inorganic adhesive sheet, as radiation loss of millimeter waves may occur due to the substrate. However, if the substrate is composed of a material having low permittivity and low dielectric loss, it may be a substrate-equipped adhesive sheet.

The above-mentioned substrate is an element that functions as a support for the adhesive layer in the above-mentioned adhesive sheet. As the substrate, for example, a plastic substrate (particularly a plastic film) can be mentioned. The above-mentioned substrate may be a single layer or a laminate of the same or different substrates.

As the above-mentioned substrate, although not particularly limited, examples thereof include various optical films such as plastic films, anti-reflection (AR) films, anti-glare (AG) films, polarizing plates, and phase difference plates. Examples of the material for the plastic film, etc. include polyester resins such as polyethylene terephthalate (PET), acrylic resins such as polymethyl methacrylate (PMMA), polycarbonate, triacetyl cellulose (TAC), polysulfone, polyarylate, polyimide, polyvinyl chloride, polyvinyl acetate, polyethylene, polypropylene, ethylene-propylene copolymers, cyclic olefin polymers such as "Aton" (cyclic olefin polymer, manufactured by JSR Corporation) and "Zeonoa" (cyclic olefin polymer, manufactured by Nippon Zeon Corporation), and fluorine-based polymers. Additionally, these plastic materials may be used alone or in combination of two or more types.

The surface of the side having the adhesive layer of the above-mentioned substrate may be subjected to surface treatments, such as physical treatments such as corona discharge treatment, plasma treatment, sand mat treatment, ozone exposure treatment, flame exposure treatment, high-voltage electric shock exposure treatment, and ionizing radiation treatment; chemical treatments such as chromic acid treatment; and adhesion-facilitating treatments using a coating agent (primer), for the purpose of improving adhesion and retention properties with the adhesive layer. The surface treatment for improving adhesion is preferably applied to the entire surface of the adhesive layer side of the substrate.

The above-mentioned substrate may be a noise reduction film. As the noise reduction film, there is no particular limitation as long as it has noise reduction performance, and examples thereof include a film substrate having a noise reduction layer formed on at least one side thereof. The noise reduction layer may be a single layer or a multi-layer, and there is no particular limitation as long as it has the function of reducing electronic noise, but from the viewpoint of transparency, a transparent conductive layer is preferable. As the transparent conductive layer, a thin film layer formed by a conductive organic or inorganic material, or a conductive layer formed by partial contact of conductive organic or inorganic materials can be employed.

The above-mentioned adhesive sheet may have a release liner provided on the adhesive surface until use. The release liner protects the adhesive surface that comes into contact with the adhesive layer until use, and is peeled off when the adhesive layer is used. In addition, when the above-mentioned adhesive sheet is a double-sided adhesive sheet, each adhesive surface may be protected by two release liners, or may be protected by one release liner having both sides as release surfaces, in a roll shape. The release liner is used as a protective material for the adhesive layer, and is peeled off when attached to an adherend. In addition, when the above-mentioned adhesive sheet is an inorganic adhesive sheet, the release liner also serves as a support for the adhesive layer. In addition, the release liner does not necessarily have to be provided.

As the substrate of the above-mentioned release liner, examples thereof include a polyethylene film, a polypropylene film, a polybutene film, a polybutadiene film, a polymethylpentene film, a polyvinyl chloride film, a vinyl chloride copolymer film, a polyethylene terephthalate film, a polyethylene naphthalate film, a polybutylene terephthalate film, a polyurethane film, an ethylene vinyl acetate film, an ionomer resin film, an ethylene/(meth)acrylic acid copolymer film, an ethylene/(meth)acrylic acid ester copolymer film, a polystyrene film, a polycarbonate film, a polyimide film, a fluororesin film, and the like. In addition, crosslinked films thereof can also be mentioned. In addition, a laminated film thereof may also be used.

It is preferable that the peeling surface of the above-mentioned peeling liner (particularly the surface in contact with the adhesive layer) be subjected to a peeling treatment. Examples of the peeling agent used in the peeling treatment include alkyd-based, silicone-based, fluorine-based, unsaturated polyester-based, polyolefin-based, and wax-based peeling agents.

The thickness of the above-mentioned peeling liner is not particularly limited, but is, for example, about 20 to 150 μm.

[use]

The use of the adhesive composition of the present invention, the adhesive layer of the present invention, and the adhesive sheet of the present invention is not particularly limited, and can be used for all purposes. For example, it can be used for optical purposes, that is, for bonding to optical members. By using the adhesive composition of the present invention, the adhesive layer of the present invention, and the adhesive sheet of the present invention for optical purposes, reliability is excellent. For example, it is presumed that this is because the polyester resin, unlike the acrylic resin, does not have a carbon-carbon double bond, and therefore is unlikely to yellow over time, making it particularly suitable for optical purposes.

The adhesive composition of the present invention, the adhesive layer of the present invention, and the adhesive sheet of the present invention are used, for example, in optical members such as electrical and electronic devices, when various members or parts are installed (mounted) in a predetermined portion (for example, a housing, a front panel, a window portion, etc.). In addition, "electrical and electronic devices" means devices corresponding to at least one of electrical devices and electronic devices. Examples of the electrical and electronic devices include image display devices such as liquid crystal displays, organic/inorganic electroluminescence displays, and plasma displays, and portable electronic devices. Examples of the image display devices include image display devices for the portable electronic devices, vehicle-mounted displays, digital signage (electronic signboards, electronic bulletin boards), and the like. In addition, the image display devices may have a form (structure) such as a so-called "rigid type" or a "flexible type", and may also have a form (structure) such as a so-called "foldable type" or a "rollable type" that can be bent or folded.

As the portable electronic devices mentioned above, for example, mobile phones, smart phones, tablet-type personal computers, notebook-type personal computers, various wearable devices (for example, wrist-worn types that are attached to the wrist such as wristwatches, modular types that are attached to a part of the body with clips or straps, eyewear types including glasses (monocular or binocular types, including head-mounted types), clothing types that are attached as accessories such as shirts, socks, and hats, earwear types that are attached to the ears such as earphones, etc.), digital cameras, digital video cameras, audio devices (portable music players, IC recorders, etc.), calculators (electronic calculators, etc.), portable game devices, electronic dictionaries, electronic notebooks, electronic books, vehicle-mounted information devices, portable radios, portable TVs, portable printers, portable scanners, portable modems, etc. In addition, in this specification, "portable" does not mean simply being able to be carried, but means having a level of portability that an individual (a standard adult) can carry relatively easily.

As a use of the adhesive layer of the present invention and the adhesive sheet of the present invention, a specific use is preferable, for example, a use for bonding a touch sensor and an image display device, provided between the touch sensor and the image display device. It is particularly preferable that the adhesive layer of the present invention is directly laminated with the touch sensor. Furthermore, the adhesive layer of the present invention may be directly laminated with the image display device, or may be laminated via another layer such as a polarizing film. Since the adhesive layer of the present invention is unlikely to cause noise amplification, it can make it difficult for noise emitted from the image display device to be transmitted to the touch sensor.

In addition, the adhesive layer of the present invention and the adhesive sheet of the present invention are useful for bonding members constituting an antenna (millimeter wave antenna) used for millimeter wave communication. Since the adhesive layer of the present invention has the characteristics of low permittivity and low dielectric loss in high-frequency bands such as millimeter waves, it can suppress millimeter wave radiation loss. In this specification, "millimeter wave communication" means communication in a frequency band of 20 GHz to 300 GHz.

[Optical laminate]

By providing the adhesive layer of the present invention or the adhesive sheet of the present invention between a touch sensor and an image display device, an optical laminate (optical laminate of the present invention) comprising a touch sensor, an adhesive layer of the present invention, and an image display device in this order is obtained. The optical laminate may comprise the touch sensor and the adhesive layer as a single layer, or may comprise multiple layers. When a plurality of touch sensors are provided, it is preferable that the touch sensors are laminated with an adhesive layer interposed between them. When a plurality of adhesive layers are provided, the plurality of adhesive layers may be the same layer or different layers with respect to the composition, thickness, etc. When a plurality of adhesive layers are provided, at least one layer is the adhesive layer of the present invention. It is preferable that all of the adhesive layers provided between the touch sensor and the image display device are adhesive layers of the present invention.

As the above-described image display device, the above-described ones can be cited. The above-described touch sensor is a capacitive touch sensor, and is, for example, a transparent conductive film in which a transparent conductive layer is provided on a glass plate or a transparent plastic film (particularly, a PET film, a polycarbonate film, or a cyclic olefin polymer film). It is preferable that the adhesive layer of the present invention is bonded so as to be in contact with the transparent conductive layer.

As the transparent conductive layer, examples thereof include a thin film of ITO (indium tin oxide), ZnO, SnO, or CTO (cadmium tin oxide). In addition, the transparent conductive layer may be formed using silver, copper, CNT (carbon nanotube), or the like. In addition, a metal mesh sensor such as Ag nanowire or Ag/Cu may be employed as the transparent conductive layer. In addition, the touch sensor may have a wiring formed at its end using a thin film of copper or silver paste.

The above optical laminate may have a cover member. The cover member is provided on the surface opposite to the side having the image display device of the touch sensor, and protects the touch sensor or the image display device in the optical laminate. Examples of the cover member include cover glass and a plastic cover. The cover member may be bonded to a layer constituting the optical laminate, such as a touch sensor, via an adhesive layer. The adhesive layer may be the adhesive layer of the present invention, but since a function of suppressing amplification of noise generated by the image display device is not required, it may be another adhesive layer. Furthermore, the optical laminate may have a polarizing film on the surface of the image display device (the surface on the side having the touch sensor).

The above optical laminate may include a noise reduction layer (such as a noise reduction film). The noise reduction layer is preferably provided between the touch sensor and the image display device from the viewpoint that a function of suppressing the amplification of noise generated by the image display device is required. The noise reduction layer and the touch sensor, and the noise reduction layer and the image display device are each bonded via an adhesive layer (preferably the adhesive layer of the present invention). The noise reduction layer may be a single layer or a multi-layer. In the case where a plurality of noise reduction layers are provided, the plurality of noise reduction layers may be the same layer or different layers with respect to the composition or thickness, etc.

FIGS. 1 to 3 illustrate one embodiment of the optical laminate of the present invention. The optical laminate (1) illustrated in FIG. 1 includes an image display device (5), a polarizing film (6) provided on the image display device (5), a touch sensor (41), a touch sensor (42), and a cover member (3) in this order. The polarizing film (6) and the touch sensor (41) are bonded by an adhesive layer (adhesive sheet) (21), and the touch sensor (41) and the touch sensor (42) are bonded by an adhesive layer (adhesive sheet) (22). The adhesive layers (21 and 22) are adhesive layers of the present invention. In addition, the touch sensor (42) and the cover member (3) are bonded by an adhesive layer (adhesive sheet) (23). The adhesive layer (23) is another adhesive layer.

The optical laminate (1) shown in Fig. 2 comprises an image display device (5), a polarizing film (6) provided on the image display device (5), a touch sensor (43), and a cover member (3) in this order. The touch sensor (43) has, for example, the functions of both the touch sensors (41 and 42) in Fig. 1. The polarizing film (6) and the touch sensor (43) are bonded by an adhesive layer (21). The adhesive layer (21) is an adhesive layer of the present invention. In addition, the touch sensor (43) and the cover member (3) are bonded by an adhesive layer (23). The adhesive layer (23) is another adhesive layer.

The optical laminate (1) shown in Fig. 3 comprises an image display device (5), a polarizing film (6) provided on the image display device (5), a noise reduction layer (44), a touch sensor (43), and a cover member (3) in this order. The polarizing film (6) and the noise reduction layer (44) are bonded by an adhesive layer (21), and the noise reduction layer (44) and the touch sensor (43) are bonded by an adhesive layer (22). The adhesive layers (21 and 22) are adhesive layers of the present invention. In addition, the touch sensor (43) and the cover member (3) are bonded by an adhesive layer (23). The adhesive layer (23) is another adhesive layer.

In addition, in FIGS. 1 to 3, the polarizing film (6) may not be provided. In this case, the image display device (5), the touch sensor (41, 43), or the noise reduction layer (44) are bonded by the adhesive layer (21).

[Millimeter wave antenna]

A millimeter wave antenna can be obtained using the adhesive layer of the present invention. A millimeter wave antenna having the adhesive layer of the present invention may be referred to as a “millimeter wave antenna of the present invention.” As a member constituting the millimeter wave antenna, a substrate (hereinafter, sometimes referred to as a “millimeter wave antenna substrate”) having an antenna element (hereinafter, sometimes referred to as a “millimeter wave antenna element”) for transmitting and receiving millimeter waves on at least one side may be exemplified.

As the substrate for the millimeter wave antenna, the plastic film exemplified and described above as the substrate can be exemplified. Among these, from the viewpoint of being able to suppress the radiation loss of millimeter waves, a material having a low permittivity and low dielectric loss is preferable, and in particular, a cyclic olefin polymer such as “Aton” (cyclic olefin polymer, manufactured by JSR Corporation) or “Zeonoa” (cyclic olefin polymer, manufactured by Nippon Zeon Corporation) is preferable.

The dielectric constant of the millimeter wave antenna substrate at 28 GHz and/or 60 GHz is preferably 2.0 to 5.0, more preferably 2.1 to 4.5, still more preferably 2.2 to 4.0, still more preferably 2.2 to 3.5, still more preferably 2.2 to 3.4, still more preferably 2.2 to 3.3, still more preferably 2.2 to 3.2, still more preferably 2.2 to 3.1, and particularly preferably 2.2 to 3.0, from the viewpoint of suppressing millimeter wave radiation loss. In addition, the dielectric loss of the millimeter-wave antenna substrate at 28 GHz and/or 60 GHz is preferably 0.0001 to 0.05, more preferably 0.001 to 0.02, still more preferably 0.002 to 0.019, still more preferably 0.003 to 0.018, still more preferably 0.004 to 0.017, still more preferably 0.005 to 0.016, still more preferably 0.006 to 0.015, still more preferably 0.007 to 0.014, still more preferably 0.008 to 0.013, still more preferably 0.009 to 0.012, and particularly preferably 0.01 to 0.011, from the viewpoint of suppressing millimeter-wave radiation loss.

The millimeter-wave antenna substrate is preferably transparent. The total light transmittance (in accordance with JIS K7361-1) of the millimeter-wave antenna substrate in the visible light wavelength range is not particularly limited, but is preferably 85% or more, more preferably 88% or more, still more preferably 89% or more, still more preferably 90% or more, still more preferably 91% or more, and particularly preferably 92% or more. In addition, the haze (in accordance with JIS K7136) of the millimeter-wave antenna substrate is not particularly limited, but is preferably 1.2% or less, more preferably 1.1% or less, still more preferably 1.0% or less, still more preferably 0.9% or less, and particularly preferably 0.8% or less.

The thickness of the millimeter wave antenna substrate is preferably 5 to 250 ㎛ from the viewpoint of suppressing millimeter wave radiation loss while mounting the millimeter wave antenna element. In addition, the millimeter wave antenna substrate may have either a single-layer or a multi-layer form. In addition, the surface of the millimeter wave antenna substrate may be appropriately subjected to a known or conventional surface treatment, such as a physical treatment such as corona discharge treatment or plasma treatment, a chemical treatment such as a primer treatment, or a coating layer such as a hard coating.

The millimeter wave antenna element provided in the millimeter wave antenna substrate is not particularly limited as long as it can transmit and receive millimeter waves, but from the viewpoint of efficiently receiving millimeter waves in a portable communication device such as a smartphone, a phased array antenna can be preferably used. A phased array antenna is an antenna that arranges a plurality of antenna elements in an array shape and enables transmission and reception in a desired direction by controlling the phase of each antenna element. That is, a phased array antenna enables transmission or reception of radio waves in a desired direction by electronically controlling the phase of each antenna element (beam steering), regardless of the direction of the antenna.

As the millimeter-wave antenna element, a known antenna can be used without particular limitation, and examples thereof include an antenna element having a resonant element formed by a loop antenna structure, a patch antenna structure, a stacked patch antenna structure, a patch antenna structure having a parasitic element, an inverted-F antenna structure, a slot antenna structure, a flat inverted-F antenna structure, a monopole, a dipole, a helical antenna structure, a Yagi (Yagi-Uda) antenna structure, a surface-integrated waveguide structure, a hub lead of these designs, and the like. Different types of millimeter-wave antenna elements may be used for combinations of different frequency bands. From the viewpoint of efficiently receiving millimeter waves in portable communication devices such as smartphones, a phased array antenna in which patch antenna elements are arranged in an array shape is preferable.

The material constituting the millimeter wave antenna element is not particularly limited, and examples thereof include metals such as titanium, silicon, niobium, indium, zinc, tin, gold, silver, copper, aluminum, cobalt, chromium, nickel, lead, iron, palladium, platinum, tungsten, zirconium, tantalum, and hafnium, and metal oxides such as ITO (oxide of indium and tin), zinc oxide, and tin oxide. Furthermore, materials containing two or more of these metals or metal oxides, or alloys containing these metals as their main components are also included. Among these, silver, copper, and ITO are preferable from the viewpoint of conductivity, and ITO is more preferable from the viewpoints of transparency and visibility. That is, it is particularly preferable that the millimeter wave antenna element is composed of ITO. In addition, when the antenna element is composed of a metal such as silver or copper, a blackening treatment may be performed by forming a film of nitride, oxide, sulfide, or the like of the metal to conceal the antenna element in order to prevent a decrease in visibility due to reflection of the metal.

In addition, the millimeter-wave antenna substrate may have a transmission line path for transmitting signals transmitted and received by the millimeter-wave antenna element to a transceiver circuit. The transmission line path may include a coaxial cable path, a microstrip transmission line, a strip line transmission line, an edge-coupled microstrip transmission line, an edge-coupled strip line transmission line, a waveguide structure for transmitting signals in a millimeter-wave frequency band (e.g., a coplanar waveguide or a grounded coplanar waveguide), a transmission line formed by a combination of these types of transmission lines, etc. The material constituting the transmission line path is not particularly limited, and the material constituting the millimeter-wave antenna element can be used.

As a component constituting a millimeter wave antenna, a cover component laminated on a millimeter wave antenna substrate to protect millimeter wave antenna elements arranged on the millimeter wave antenna substrate may be exemplified. As the cover component, there is no particular limitation, but for example, an optical film such as glass or plastic film can be used. Examples of materials for plastic films, etc., include polyester resins such as polyethylene terephthalate (PET), (meth)acrylic resins such as polymethyl methacrylate (PMMA), polycarbonate, triacetyl cellulose (TAC), polysulfone, polyarylate, polyimide, transparent polyimide, polyvinyl chloride, polyvinyl acetate, fluorine-based resins, polyethylene, polypropylene, ethylene-propylene copolymers, cyclic olefin polymers such as "Aton" (cyclic olefin polymer, manufactured by JSR Corporation), and "Zeonoa" (cyclic olefin polymer, manufactured by Nippon Zeon Corporation). In addition, these plastic materials may be used alone or in combination of two or more.

The dielectric constant of the cover member at 28 GHz and/or 60 GHz is preferably 2.0 to 5.0, more preferably 2.1 to 4.5, still more preferably 2.2 to 4.0, still more preferably 2.2 to 3.5, still more preferably 2.2 to 3.4, still more preferably 2.2 to 3.3, still more preferably 2.2 to 3.2, still more preferably 2.2 to 3.1, and particularly preferably 2.2 to 3.0, from the viewpoint of suppressing millimeter wave radiation loss. In addition, the dielectric loss of the cover member at 28 GHz and/or 60 GHz is preferably 0.0001 to 0.05, more preferably 0.001 to 0.02, still more preferably 0.002 to 0.019, still more preferably 0.003 to 0.018, still more preferably 0.004 to 0.017, still more preferably 0.005 to 0.016, still more preferably 0.006 to 0.015, still more preferably 0.007 to 0.014, still more preferably 0.008 to 0.013, still more preferably 0.009 to 0.012, and particularly preferably 0.01 to 0.011.

The above cover member is preferably transparent. The total light transmittance (in accordance with JIS K7361-1) of the cover member in the visible light wavelength range is not particularly limited, but is preferably 85% or more, more preferably 88% or more, still more preferably 89% or more, still more preferably 90% or more, still more preferably 91% or more, and particularly preferably 92% or more. In addition, the haze (in accordance with JIS K7136) of the cover member is not particularly limited, but is preferably 1.2% or less, more preferably 1.1% or less, still more preferably 1.0% or less, still more preferably 0.9% or less, and particularly preferably 0.8% or less.

The thickness of the cover member is preferably 0.025 to 1.5 mm from the viewpoint of suppressing radiation loss of millimeter waves. In addition, the cover member may have either a single-layer or a multi-layer form. In addition, the surface of the cover member may be appropriately subjected to a known or conventional surface treatment, such as a physical treatment such as corona discharge treatment or plasma treatment, a chemical treatment such as a primer treatment, or a coating layer such as a hard coating.

The adhesive sheet of the present invention is preferably used for the purpose of manufacturing a millimeter wave antenna used in a portable communication device. Examples of the portable communication device include a mobile phone, a PHS, a smart phone, a tablet (tablet-type computer), a mobile computer (mobile PC), a personal digital assistant (PDA), and the like.

The millimeter wave antenna may have members other than the above-described millimeter wave antenna substrate, cover member, and adhesive sheet, and may include, for example, a polarizing plate, a wavelength plate, a phase difference plate, an optical compensation film, a brightness enhancing film, a light guide plate, a reflective film, an antireflection film, a hard coat film, a transparent conductive film, a design film, a decorative film, a surface protection plate, a prism, a lens, a color filter, a transparent substrate, or an image display panel (e.g., a liquid crystal display panel, an organic EL panel, a plasma display panel, etc.). The image display panel may have a touch sensor.

The millimeter wave antenna may be placed at any location of the portable communication device, and specifically, may be placed on the front, back, or side of the portable communication device. In addition, the front of the portable communication device is the side that faces the user when the user uses the portable communication device, and for example, the side having the display panel corresponds to the side, and the back and side correspond to the housing. In addition, the display panel refers to a structure composed of at least a lens (particularly a glass lens) and a touch panel.

The size (width) of the millimeter wave antenna is not limited, and may be formed on the entire surface of each side of the portable communication device, or may be arranged on a part of it. In addition, the shape of the millimeter wave antenna is not particularly limited, and may be, for example, a square, a circle, or a wire shape. In addition, it may be arranged in a frame shape. In addition, the number of millimeter wave antennas arranged in the portable communication device is not limited, and may be one, or multiple may be arranged at any arbitrary position. When multiple millimeter wave antennas are arranged, the sizes (widths) may be the same or different. In a location where the millimeter wave antenna of the portable communication device is not arranged, a dummy pattern that does not have a millimeter wave antenna may be arranged in order to improve visibility.

The above millimeter wave antenna is a millimeter wave antenna having at least the adhesive sheet of the present invention and a substrate, wherein the substrate has an antenna element (millimeter wave antenna element) on one side, and the adhesive sheet of the present invention is adhered to a surface of the substrate (millimeter wave antenna substrate) on the side having the antenna element, and is not particularly limited in other respects. In addition, the adhesive sheet of the present invention in the millimeter wave antenna is an adhesive sheet at the time of use, and therefore does not have a release liner.

As the above-mentioned millimeter wave antenna, it is preferable to have an embodiment in which a millimeter wave antenna substrate is bonded to another optical member (which may or may not necessarily have the adhesive sheet of the present invention, but having it is preferable from the viewpoint of suppressing millimeter wave radiation loss). In addition, the above-mentioned other optical member may be singular or plural.

In the case of the above aspect, the aspect of bonding the millimeter wave antenna and the other optical member is not particularly limited, and examples thereof include (1) an aspect of bonding the millimeter wave antenna substrate and the other optical member via the adhesive sheet of the present invention, (2) an aspect of bonding the adhesive sheet of the present invention including or constituting the millimeter wave antenna substrate to the other optical member, (3) an aspect of bonding the millimeter wave antenna substrate to a member other than the millimeter wave antenna substrate via the adhesive sheet of the present invention, and (4) an aspect of bonding the adhesive sheet of the present invention including or constituting the millimeter wave antenna substrate to a member other than the millimeter wave antenna substrate. Furthermore, in the aspect (2) above, it is preferable that the adhesive sheet of the present invention is a double-sided adhesive sheet whose base material is the millimeter wave antenna substrate.

Next, a preferred embodiment of the millimeter wave antenna will be described with reference to the drawings. FIG. 4 illustrates a millimeter wave antenna (10) having at least a substrate, which is an adhesive sheet (adhesive layer) (11) and a millimeter wave antenna substrate (12), wherein the millimeter wave antenna substrate (12) has a millimeter wave antenna element (13) on one side, and the adhesive sheet (11) is adhered to the side of the millimeter wave antenna substrate (12) that has the millimeter wave antenna element (13).

FIG. 5 illustrates a millimeter wave antenna (10) having a cover member (14), an adhesive sheet (11), and a millimeter wave antenna substrate (12) in this order in contact with each other. The millimeter wave antenna substrate (12) has a millimeter wave antenna element (13) on a surface on the side of the adhesive sheet (11), and the adhesive sheet (11) is adhered to a surface of the millimeter wave antenna substrate (12) that has the millimeter wave antenna element (13). The cover member (14) is preferably made of glass, the millimeter wave antenna substrate (12) is preferably made of COP in terms of low permittivity and low dielectric loss, and the millimeter wave antenna element (13) is preferably made of copper, silver, or ITO.

FIG. 6 illustrates a millimeter wave antenna (10) having a cover member (14), an adhesive sheet (adhesive layer) (11a), a millimeter wave antenna substrate (12), an adhesive sheet (adhesive layer) (11b), and an image display panel (15) in this order, which are in contact with each other. The millimeter wave antenna substrate (12) has a millimeter wave antenna element (13) on a surface on the side of the adhesive sheet (11a), and the adhesive sheet (11a) is adhered to a surface of the millimeter wave antenna substrate (12) that has the millimeter wave antenna element (13). The cover member (14) is preferably made of glass, the millimeter wave antenna substrate (12) is preferably made of COP from the viewpoints of low permittivity and low dielectric loss, and the millimeter wave antenna element (13) is preferably made of silver or copper blackened with a film of ITO or a nitride, oxide, sulfide, or the like from the viewpoints of transparency and visibility. The adhesive sheet (11b) may be the adhesive sheet of the present invention or may not be the adhesive sheet of the present invention, but is preferably the adhesive sheet of the present invention. The image display panel (15) may have a touch sensor (not shown).

In the millimeter wave antenna (10) shown in FIGS. 4 to 6, the adhesive sheets (11, 11a) and preferably the adhesive sheet (11b) are composed of an adhesive layer of the present invention having a low dielectric constant and low dielectric loss in a high-frequency band, so that millimeter wave radiation loss is suppressed, and millimeter wave communication can be performed efficiently. In addition, since millimeter wave communication can be performed efficiently, the antenna area can be miniaturized, and the antenna can be made finer.

According to the adhesive composition of the present invention, a low dielectric constant adhesive layer can be formed. Therefore, by using the adhesive layer for bonding a touch sensor and an image display device, for example, noise generated by the image display device can be made difficult to be transmitted to the touch sensor. In addition, by using the adhesive layer as an adhesive layer bonded to a millimeter wave antenna substrate used for a millimeter wave antenna, for example, radiation loss of millimeter waves can be suppressed.

The embodiments described above are described to facilitate understanding of the present invention and are not described to limit the present invention.

Example

The present invention is described in more detail below by way of examples, but the present invention is not limited in any way by these examples.

Synthesis Example 1

(Synthesis of polyester resin (A1))

A stirrer, a thermometer, and a vacuum pump were attached to a three-necked separable flask, and 65 g of bis(2-hydroxyethyl)terephthalate (manufactured by Tokyo Kasei Kogyo Co., Ltd., molecular weight 254), 140 g of dimer diol (product name "Freepol 2033", manufactured by Croda Corporation, molecular weight 537, carbon number 36, diol, number of hetero atoms other than hydroxy groups 0), and 0.2 g of titanium tetran-butoxide as a catalyst (product name "Orgatics TA-21", manufactured by Matsumoto Fine Chemical Co., Ltd.) were charged. The mixture was heated to 180°C while stirring in a nitrogen atmosphere. After reaching 180°C, the mixture was heated to 210°C while stirring in a reduced pressure atmosphere (2.0 kPa or less), and the temperature was maintained. By continuing the reaction for about 4 hours, a polyester resin (A1) was obtained. The weight average molecular weight (Mw) of this polyester resin (A1) was 41,000, and the glass transition temperature (Tg) was -20°C.

Synthesis Example 2

(Synthesis of polyester resin (A2))

A stirrer, a thermometer, and a vacuum pump were attached to a three-necked separable flask, and 65 g of bis(2-hydroxyethyl)terephthalate (manufactured by Tokyo Kasei Kogyo Co., Ltd., molecular weight 254), 140 g of dimer diol (product name "Freepol 2033", manufactured by Croda, molecular weight 537, carbon number 36, diol, number of hetero atoms other than hydroxy groups 0), and 0.05 g of titanium tetran-butoxide as a catalyst (product name "Orgatics TA-21", manufactured by Matsumoto Fine Chemical Co., Ltd.) were charged. The mixture was heated to 180°C while stirring in a nitrogen atmosphere. After reaching 180°C, the mixture was heated to 210°C while stirring in a reduced pressure atmosphere (2.0 kPa or less), and the temperature was maintained. By continuing the reaction for about 4 hours, a polyester resin (A2) was obtained. The Mw of this polyester resin (A2) was 59,000 and the Tg was -20°C.

Synthesis Example 3

(Synthesis of polyester resin (A3))

A stirrer, a thermometer, and a vacuum pump were attached to a three-necked separable flask, and 60 g of bis(2-hydroxyethyl)terephthalate (manufactured by Tokyo Kasei Kogyo Co., Ltd., molecular weight 254), 122.9 g of dimerdiol (product name "Freepol 2033", manufactured by Croda, molecular weight 537, carbon number 36, diol, number of heteroatoms other than hydroxy groups 0), 23.6 g of polytetramethylene glycol (manufactured by Mitsubishi Chemical Co., Ltd., molecular weight 2000), and 0.2 g of titanium tetran-butoxide as a catalyst (product name "Orgatics TA-21", manufactured by Matsumoto Fine Chemical Co., Ltd.) were charged and stirred in a nitrogen atmosphere, and the temperature was raised to 180°C. After reaching 180℃, the temperature was raised to 210℃ while stirring in a reduced pressure atmosphere (2.0㎪ or less), and this temperature was maintained. The reaction was continued for about 4 hours, and a polyester resin (A3) was obtained. The Mw of this polyester resin (A3) was 43,000, and the Tg was -29℃.

Synthesis Example 4

(Synthesis of polyester resin (A4))

A stirrer, a thermometer, and a vacuum pump were attached to a three-necked separable flask, and 97.8 g of dimer acid (product name "Freepol 1009", manufactured by Croda, molecular weight 567, carbon number 36, divalent carboxylic acid, number of hetero atoms other than carboxyl groups 0), 102.2 g of dimer diol (product name "Freepol 2033", manufactured by Croda, molecular weight 537, carbon number 36, diol, number of hetero atoms other than hydroxyl groups 0), and 0.2 g of dibutyltin oxide (manufactured by Kanto Chemical Co., Ltd.) as a catalyst were charged. The mixture was heated to 200°C with stirring in a reduced pressure atmosphere (2.0 kPa or less) and the temperature was maintained. The reaction was continued for about 5 hours to obtain a polyester resin (A4). The Mw of this polyester resin (A4) was 30,000 and the Tg was -43℃.

Synthesis Example 5

(Synthesis of polyester resin (A5))

A stirrer, a thermometer, a nitrogen tube, and a water separator were attached to a four-necked separable flask, and 100 g of ethylene glycol (manufactured by Tokyo Kasei Industrial Co., Ltd., molecular weight 62), 700 g of dimer acid (product name "Freepol 1009", manufactured by Croda, molecular weight 567, carbon number 36, divalent carboxylic acid, number of heteroatoms other than carboxyl groups 0), 63 g of terephthalic acid (manufactured by Tokyo Kasei Industrial Co., Ltd., molecular weight 166), 0.46 g of di-n-butyltin oxide (manufactured by Kishida Chemical Co., Ltd., molecular weight 249) as a polymerization catalyst, and 40 g of xylene as a solvent for discharging reaction water were charged. The temperature was increased to 180°C with stirring in a nitrogen atmosphere, and the temperature was maintained. After a while, the separation of the reaction water flow was confirmed, and the reaction began to proceed. The reaction was continued for about 24 hours, and a polyester resin (A5) was obtained. The Mw of this polyester resin (A5) was 100,000, and the Tg was -33°C.

Example 1

To 100 parts by mass of a polyester resin (A1), 3 parts by mass of a hexamethylene diisocyanate-modified isocyanurate (trade name: "Coronate HX", manufactured by Tosoh Corporation) as a crosslinking agent (B1), 0.03 parts by mass of an organic zirconium compound (trade name: "Orgatics ZC-162", manufactured by Matsumoto Fine Chemical Co., Ltd.) as a crosslinking catalyst, and toluene were added, thereby preparing an adhesive composition (adhesive solution). This adhesive solution was applied to the release-treated surface of a polyethylene terephthalate (PET) film (trade name: "Diafoil MRF#38", manufactured by Mitsubishi Chemical Corporation) subjected to a release treatment so that the thickness after drying became 25 µm, and dried at 120°C for 3 minutes to obtain an adhesive layer. Thereafter, the adhesive layer was bonded to the peel-treated surface of a peel-treated PET film (trade name “Diafoil MRE #38”, manufactured by Mitsubishi Chemical Co., Ltd.), and left at 60°C for 3 days to produce an inorganic adhesive sheet of Example 1.

Example 2

Instead of the polyester resin (A1), a polyester resin (A2) was used, and the amount of crosslinking agent used was changed to 2 parts by mass per 100 parts by mass of the polyester resin (A2). Otherwise, the adhesive composition and inorganic adhesive sheet of Example 2 were produced in the same manner as in Example 1.

Example 3

Instead of polyester resin (A1), polyester resin (A2) was used. Otherwise, the adhesive composition and inorganic adhesive sheet of Example 3 were produced in the same manner as Example 1.

Example 4

To 100 parts by mass of polyester resin (A2), 3 parts by mass of a bifunctional isocyanate (trade name: "Duranate D101", manufactured by Asahi Kasei Co., Ltd.) as a crosslinking agent (B2), 0.03 parts by mass of an organic zirconium compound (trade name: "Orgatics ZC-162", manufactured by Matsumoto Fine Chemical Co., Ltd.) as a crosslinking catalyst, and toluene were added, thereby preparing an adhesive composition (adhesive solution). Otherwise, the adhesive composition of Example 4 and an inorganic adhesive sheet were produced in the same manner as in Example 1.

Example 5

Instead of polyester resin (A1), polyester resin (A3) was used. Otherwise, the adhesive composition and inorganic adhesive sheet of Example 5 were produced in the same manner as Example 1.

Example 6

Instead of polyester resin (A1), polyester resin (A4) was used. Otherwise, the adhesive composition and inorganic adhesive sheet of Example 6 were produced in the same manner as Example 1.

Example 7

Instead of the polyester resin (A1), a polyester resin (A4) was used, and the amount of crosslinking agent used was changed to 4 parts by mass per 100 parts by mass of the polyester resin (A4). Otherwise, the adhesive composition and inorganic adhesive sheet of Example 7 were produced in the same manner as Example 1.

Example 8

Instead of polyester resin (A1), polyester resin (A5) was used. Otherwise, the adhesive composition and inorganic adhesive sheet of Example 8 were produced in the same manner as Example 1.

Example 9

To 100 parts by mass of a polyester resin (A1), 3 parts by mass of a bifunctional isocyanate (trade name: "Duranate D101", manufactured by Asahi Kasei Co., Ltd.) as a crosslinking agent (B2), 0.03 parts by mass of an organic zirconium compound (trade name: "Orgatics ZC-162", manufactured by Matsumoto Fine Chemical Co., Ltd.) as a crosslinking catalyst, 20 parts by mass of a hydrogenated terpene phenol resin ("YS Polystar U115", manufactured by Yasuhara Chemical Co., Ltd.) as an adhesion-imparting resin (C1), and toluene were added to prepare an adhesive composition (adhesive solution). An inorganic adhesive sheet of Example 9 was produced in the same manner as in Example 1 otherwise.

Example 10

Instead of the adhesive-imparting resin (C1), a rosin ester resin (“Fine Crystal KE-359”, manufactured by Arakawa Chemical Co., Ltd.) was used as the adhesive-imparting resin (C2). Otherwise, the adhesive composition and the inorganic adhesive sheet of Example 10 were produced in the same manner as in Example 9.

Example 11

Instead of the adhesive-imparting resin (C1), a rosin ester resin (“Fine Crystal KE-311”, manufactured by Arakawa Chemical Co., Ltd.) was used as the adhesive-imparting resin (C3). Otherwise, the adhesive composition and inorganic adhesive sheet of Example 11 were produced in the same manner as in Example 9.

Example 12

The amount of adhesive-providing resin (C3) used was changed to 40 parts by mass per 100 parts by mass of polyester-based resin (A1). Otherwise, the adhesive composition and inorganic adhesive sheet of Example 12 were produced in the same manner as Example 11.

<Evaluation>

The evaluation method for the polyester resin produced in the synthetic example and the adhesive sheet produced in the working example is shown below.

(1) Weight average molecular weight (Mw)

The weight average molecular weight (Mw) of polyester resin is a value converted to standard polystyrene obtained by GPC (gel permeation chromatography). As a GPC apparatus, the apparatus name "HLC-8320GPC" (column: TSKgel GMH-H(S), manufactured by Tosoh Corporation) was used, and the measurement was performed under the following conditions.

Column: TSKgel GMH-H(S)

Column temperature: 40℃

Dissolving solution: THF (0.1 mass% of amine component added)

Flow rate: 0.5mL/min

Injection volume: 100μL

Detector: Differential refractometer (RI)

Standard sample: Polystyrene (PS)

(2) Dielectric constant and dielectric loss

The adhesive layer obtained in the example (a PET film that has been silicone-treated and peeled off from an adhesive sheet) was sandwiched between a copper foil and an electrode, and the dielectric constant and dielectric loss at a frequency of 100 kHz were measured using the following device. Three samples were produced for the measurement, and the average of the measured values of the three samples was used as the dielectric constant and dielectric loss.

In addition, the dielectric constant of the adhesive layer at a frequency of 100 kHz was measured under the following conditions in accordance with JIS K6911.

Measurement method: Capacitive method (Device: Agilent Technologies 4294A Precision Impedance Analyzer)

Electrode configuration: 12.1mmΦ, 0.5mm thick aluminum plate

Counter electrode: 3oz copper plate

Measurement environment: 23±1℃, 52±1％RH

(3) Light transmittance and haze

In the examples, a PET film to which one side had been peeled was peeled from an adhesive sheet obtained, and the exposed adhesive surface was bonded to a slide glass (trade name: "White Polishing No. 1" (thickness 0.8 to 1.0 mm, total light transmittance 92%, haze 0.2%, b* 0.15), manufactured by Matsunami Glass Kogyo Co., Ltd.), and autoclave treatment (50°C, 0.5 MPa, 15 minutes) was performed. After the treatment, the PET film to which the other side had been peeled was peeled, to produce a test piece having a layered configuration of [adhesive sheet (adhesive layer)/slide glass]. The total light transmittance and haze of the above test piece in the visible light range were measured using a haze meter (device name: "HSP-150Vis", manufactured by Murakami Shikisai Kenkyusho Co., Ltd.) under an environment of 23±1°C and 52±1%RH. Three samples were prepared from each specimen, and the average of the measurement values of the three samples was used as the total light transmittance and haze in the visible light range.

(4) Color (b*)

In the examples, a PET film to which one side had been peeled was peeled from an adhesive sheet obtained, and the exposed adhesive surface was bonded to a slide glass (trade name: "White Polishing No. 1" (thickness 0.8 to 1.0 mm, total light transmittance 92%, haze 0.2%, b* 0.15), manufactured by Matsunami Glass Kogyo Co., Ltd.), and autoclave treatment (50°C, 0.5 MPa, 15 minutes) was performed. After the treatment, the PET film to which the other side had been peeled was peeled, to produce a test piece having a layered configuration of [adhesive sheet (adhesive layer)/slide glass]. The b* of the above test piece in the visible light range was measured using an ultraviolet-visible-near-infrared spectrophotometer (device name: "UH4150", manufactured by Hitachi High-Techno Science Co., Ltd.) under an environment of 23±1℃ and 52±1％RH. Three samples were prepared from each specimen, and the average of the measurement values of the three samples was used as the b* in the visible light range.

(5) 180° adhesive strength

From the adhesive sheet obtained in the example, a sheet piece having a length of 100 mm and a width of 20 mm was cut. Next, the PET film to which one side of the adhesive sheet had been peeled was peeled, and a PET film (trade name "Lumilar S-10#25", manufactured by Toray Industries, Ltd.) was attached (laminated) to the exposed adhesive surface. Next, the PET film to which the other side had been peeled was peeled, and it was pressed onto a glass plate (trade name "Soda-lime Glass #0050", manufactured by Matsunami Glass Kogyo Co., Ltd.) as a test plate under the pressing conditions of a 2 kg roller and 1 reciprocating press, to produce a sample composed of [test plate/adhesive layer/PET film]. The obtained sample was subjected to autoclaving (50°C, 0.5 MPa, 15 minutes), and then cooled for 30 minutes in an atmosphere of 23°C and 50% RH. After cooling, using a tensile tester (device name: "EZ Test/EZ-S", manufactured by Shimadzu Seisakusho Co., Ltd.), in accordance with JIS Z0237, under the conditions of an atmosphere of 23°C and 50%RH, a tensile speed of 300 mm/min, and a peeling angle of 180°, an adhesive sheet (adhesive layer/PET film) was peeled from a test plate, and the 180° peel adhesion (N/20 mm) was measured.

(6) Tg and storage modulus

The adhesive layers obtained in the examples were laminated and punched to produce a disk-shaped test piece 2 mm in thickness × 8 mm in diameter. This test piece was sandwiched between parallel plates for a shear test, and the loss modulus G" and the storage modulus G' were measured under the measurement conditions described below using a dynamic viscoelasticity measuring device (device name: "ARES-G2", manufactured by TA Instruments). The peak value of the ratio of the loss modulus to the storage modulus (G"/G') = Tanδ was read as the Tg of the adhesive layer.

·Measurement: Shear mode

·Temperature range: -50℃ to 150℃

·Heating speed: 5℃/min

·Frequency: 1Hz

(7) Gel fraction

In the example, about 0.1 g of the adhesive layer obtained was collected, wrapped with a porous tetrafluoroethylene sheet (trade name "NTF1122", manufactured by Nitto Denko Co., Ltd.) having an average pore diameter of 0.2 ㎛, and then tied with a yarn. The weight at that time was measured, and the weight was taken as the weight before immersion (Z). In addition, the weight before immersion is the total weight of the adhesive layer (the adhesive layer collected above), the tetrafluoroethylene sheet, and the yarn. In addition, the total weight of the tetrafluoroethylene sheet and the yarn was also measured, and the weight was taken as the bag weight (Y).

Next, the adhesive layer was wrapped with a tetrafluoroethylene sheet and tied with a string (referred to as “sample”), placed in a 50 ml container filled with ethyl acetate or toluene, and left to stand at 23°C for 7 days. Thereafter, the sample (after ethyl acetate or toluene treatment) was taken out from the container, transferred to an aluminum cup, and dried in a desiccator at 130°C for 2 hours to remove ethyl acetate or toluene, and then the weight was measured, and the weight was taken as the weight after immersion (X).

And, the gel fraction was calculated from the following equation.

Gel fraction [% (weight %)] = (X-Y) / (Z-Y) × 100

Below, variations of the invention according to the present disclosure are described.

[Appendix 1] A polyester resin comprising a structural unit derived from a compound having 20 or more carbon atoms and two or more functional groups capable of forming an ester bond,

An adhesive composition having a dielectric constant of 4.0 or less at a frequency of 100 kHz when an adhesive layer is formed.

[Supplementary Note 2] An adhesive composition as described in Supplementary Note 1, wherein the dielectric loss at a frequency of 100 kHz when an adhesive layer is formed is 0.0001 to 0.15.

[Supplementary Note 3] An adhesive composition as described in Supplementary Note 1 or 2, wherein the glass transition temperature of the polyester resin is 0°C or lower.

[Supplementary Note 4] An adhesive layer formed by an adhesive composition described in any one of Supplementary Notes 1 to 3.

[Supplementary Note 5] An adhesive sheet having an adhesive layer as described in Supplementary Note 4.

1: Optical laminate
21, 22, 23: Adhesive layer (adhesive sheet)
3: Absence of cover
41, 42, 43: Touch sensor
44: Noise reduction layer
5: Image display device
6: Polarizing film
10: Millimeter wave antenna
11, 11a, 11b: Adhesive sheet (adhesive layer)
12: Millimeter wave antenna substrate
13: Millimeter wave antenna element
14: Absence of cover
15: Image display panel

Claims (5)

A polyester resin comprising a structural unit derived from a compound having 20 or more carbon atoms and two or more functional groups capable of forming an ester bond,
An adhesive composition having a dielectric constant of 4.0 or less at a frequency of 100 kHz when an adhesive layer is formed. In the first paragraph,
An adhesive composition having a dielectric loss at a frequency of 100 kHz of 0.0001 to 0.15 when an adhesive layer is formed. In the first paragraph,
An adhesive composition wherein the glass transition temperature of the polyester resin is 0°C or lower. An adhesive layer formed by the adhesive composition described in any one of claims 1 to 3. An adhesive sheet having an adhesive layer as described in claim 4.