JP2018012783A - Adhesive composition, adhesive sheet and image display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an adhesive composition constituting such an adhesive sheet that can be used for a touch panel-integrated image display device including a capacitance type touch panel function and can suppress reduction in reactivity or sensitivity of a touch sensor when a resin base material such as polycarbonate and PMMA is used as a cover panel.SOLUTION: The adhesive composition comprises an acrylic polymer, a plasticizer and a crosslinking agent, in which the acrylic polymer is a copolymer prepared by copolymerizing an acrylic monomer component having an acrylic structure and no carboxyl group; the plasticizer is a dioctyl adipate having a branched octyl group; and the content of the dioctyl adipate is 1.3 parts by weight or more and less than 20 parts by weight with respect to 100 parts by weight of the acrylic polymer and the crosslinking agent. The acrylic monomer component does not have an aromatic ring but has only an acrylic structure.SELECTED DRAWING: Figure 1

Description

  The present disclosure relates to a pressure-sensitive adhesive composition, a pressure-sensitive adhesive sheet, and an image display device that are suitably used for bonding capacitive touch panel members.

  In recent years, with the development of display devices, the demand for image display devices such as liquid crystal display devices and organic electroluminescence display devices has increased. Recently, in addition to televisions and personal computers, multifunctional terminals such as smartphones and tablet terminals are widely used, and the market for image display devices is increasingly expanding.

  As such an image display device, for example, a touch panel integrated image display device having a touch panel function has attracted attention. As a touch panel method, a multi-point simultaneous input is possible, an intuitive operation is possible with a fingertip, and a capacitive touch panel is rapidly spreading from the viewpoint of excellent durability. Here, a capacitive touch panel is a touch sensor when the touched position changes when the finger touches the touch panel and the amount of change in the capacitance exceeds a certain threshold. It has a mechanism to detect.

  By the way, recently, not only a touch panel member constituting an image display device but also an adhesive sheet (OCA: Optical Clear Adhesive) used for bonding the touch panel member has been actively studied (for example, Patent Documents 1 to 4).

JP2012-251030A JP 2013-186808 A JP 2011-153169 A JP2015-105329A JP 2013-063631 A JP 2001-115106 A JP 2010-209324 A JP-A-9-239301

  For example, as shown in FIG. 2, the touch panel integrated image display device has a configuration in which the cover panel 20, the touch sensor 30, and the display 40 are bonded via an adhesive sheet 10 ′. In such an image display device 100 ′, a glass substrate has been used as the cover panel 20 until now, but recently, for the purpose of reducing the weight and thinning of the image display device, it is called polycarbonate or PMMA. Many resin base materials made of polymethyl methacrylate are used.

  On the other hand, in the case of an image display device using a resin base material made of polycarbonate or PMMA as a cover panel, there is a problem that the reactivity and sensitivity of the touch panel sensor are reduced as compared with a conventional image display device using a glass base material. There is.

Accordingly, the inventors of the present disclosure have repeatedly studied the above-described problems. As a result, it was found that polycarbonate and PMMA have one of the factors causing the above-described problem that the relative dielectric constant is lower than that of glass. Specifically, the following things were discovered. First, the capacitance can be obtained by the following equation.
C = εS / d
(In the above equation, C is the capacitance, ε is the relative dielectric constant, S is the effective area of the electrodes, and d is the distance between the electrodes.)
As shown in the above equation, when the value of the dielectric constant ε decreases, the value of the capacitance C tends to decrease. Therefore, in the case of an image display device using polycarbonate or PMMA having a relative dielectric constant lower than that of glass for the cover panel, the amount of change in capacitance at the touched position is desired when the touch panel is touched with a finger or the like. As a result, it has been found that there is a problem that the reactivity and sensitivity of the touch panel sensor are lowered.

  Here, for example, Patent Document 5 to Patent Document 8 describe a pressure-sensitive adhesive sheet having an adipic acid ester, but these are not members used in an image display device. In particular, since the pressure-sensitive adhesive sheets disclosed in Patent Documents 5 to 7 have an acidic component, the metal member constituting the touch sensor is corroded when used for an image display device integrated with a touch panel. There is. The pressure-sensitive adhesive sheet disclosed in Patent Document 5 has an acrylic copolymer, and such a pressure-sensitive adhesive sheet tends to have a relatively low relative dielectric constant as shown in a comparative example described later. Furthermore, although the adhesive sheet disclosed in Patent Document 8 has a polyester plasticizer, the polyester plasticizer has poor compatibility with the acrylic resin used as the main agent of the adhesive, and has a desired haze value. Therefore, there is a problem that the optical characteristics of the image display device are deteriorated.

  The present disclosure has been made in view of the above circumstances, and can be suitably used for an image display device integrated with a touch panel having a capacitive touch panel function, and a cover panel such as polycarbonate or PMMA. The main object of the present invention is to provide a pressure-sensitive adhesive composition constituting a pressure-sensitive adhesive sheet capable of suppressing a decrease in reactivity and sensitivity of a touch sensor when a resin base material is used.

  The inventors of the present disclosure have conducted intensive research to solve the above problems, and as a result, the pressure-sensitive adhesive sheet is a capacitive touch panel by using a pressure-sensitive adhesive composition having a predetermined composition. It can be suitably used for a touch panel integrated type image display device having a function, and when a resin base material such as polycarbonate or PMMA is used as a cover panel, a decrease in touch sensor reactivity and sensitivity can be suppressed. I found. The present disclosure has been completed based on such findings.

  That is, the present disclosure is a pressure-sensitive adhesive composition containing an acrylic polymer polymer, a plasticizer, and a crosslinking agent, and the acrylic polymer polymer has an acrylic structure and does not have a carboxyl group. The component is a copolymer obtained by copolymerization, the plasticizer is dioctyl adipate having a branched octyl group, and the content of the dioctyl adipate is 100 parts by weight of the acrylic polymer polymer and the crosslinking agent. The pressure-sensitive adhesive composition is characterized by being in the range of 1.3 parts by weight or more and less than 20 parts by weight.

  According to the present disclosure, it can be suitably used for a touch panel integrated image display device having a capacitive touch panel function, and when a resin base material such as polycarbonate or PMMA is used as a cover panel, It can be set as the adhesive composition which can comprise the adhesive sheet which can suppress the fall of the reactivity and sensitivity of a touch sensor.

  In the present disclosure, the acrylic monomer component can be a pressure-sensitive adhesive composition having no aromatic ring.

  In the present disclosure, the acrylic monomer component may be a pressure-sensitive adhesive composition having only an acrylic structure.

  The present disclosure also includes a crosslinked acrylic polymer polymer and a plasticizer, and the crosslinked acrylic polymer polymer is a copolymer obtained by copolymerizing an acrylic monomer component having an acrylic structure and having no carboxyl group. And the plasticizer is dioctyl adipate having a branched octyl group, and the content of the dioctyl adipate is 1.3 parts by weight or more and 20% by weight with respect to 100 parts by weight of the crosslinked acrylic polymer polymer. Provided is a pressure-sensitive adhesive sheet characterized by being in a range of less than part.

  According to the present disclosure, it can be suitably used for a touch panel integrated image display device having a capacitive touch panel function, and when a resin base material such as polycarbonate or PMMA is used as a cover panel, It can be set as the adhesive sheet which can suppress the fall of the reactivity and sensitivity of a touch sensor.

  In the present disclosure, the acrylic monomer component can be a pressure-sensitive adhesive sheet having no aromatic ring.

  In the present disclosure, the acrylic monomer component can be a pressure-sensitive adhesive sheet having only an acrylic structure.

  In this indication, it can be set as the adhesive sheet whose relative dielectric constant at 100 kHz is 5.0 or more.

  In this indication, it can be set as the adhesive sheet whose haze value based on JISK-7136 with a film thickness of 50 micrometers is less than 1.5%.

In the present disclosure, the resistance increase rate calculated by the following formula of the transparent conductive film when a durability test is performed for the laminated body in which the transparent conductive film is stacked in an atmosphere of 60 ° C. and 90% RH for 500 hours. However, it can be set as the adhesive sheet which is less than 50%.
Resistance increase rate (%) = {(R−R ₀ ) / R ₀ } × 100
(In the above equation, R ₀ is the initial resistance value before the durability test, and R is the resistance value after the durability test.)

  Furthermore, this indication provides the image display apparatus characterized by having the above-mentioned adhesive sheet and a touch panel member.

  According to the present disclosure, the above-described pressure-sensitive adhesive sheet can be suitably used for a touch panel integrated image display device having a capacitive touch panel function, and a resin base material such as polycarbonate or PMMA as a cover panel. When the is used, an image display device capable of suppressing a decrease in the reactivity and sensitivity of the touch sensor can be obtained.

  The present disclosure is a pressure-sensitive adhesive composition that can be used for a pressure-sensitive adhesive sheet constituting an image display device, and is preferably used for, for example, a touch panel integrated image display device having a capacitive touch panel function. In addition, when a resin base material such as polycarbonate or PMMA is used as the cover panel, there is an effect of providing a pressure-sensitive adhesive composition that can suppress a decrease in reactivity and sensitivity of the touch sensor.

It is a schematic sectional drawing which shows an example of the adhesive sheet of this indication. It is a schematic perspective view which shows the image display apparatus of this indication, or the conventional image display apparatus.

  Hereinafter, the pressure-sensitive adhesive composition, pressure-sensitive adhesive sheet, and image display device of the present disclosure will be described.

I. The pressure-sensitive adhesive composition The pressure-sensitive adhesive composition of the present disclosure is a pressure-sensitive adhesive composition containing an acrylic polymer polymer, a plasticizer, and a crosslinking agent, and the acrylic polymer polymer has an acrylic structure, A copolymer obtained by copolymerizing an acrylic monomer component having no carboxyl group, the plasticizer is dioctyl adipate having a branched octyl group, and the content of the dioctyl adipate is the acrylic polymer polymer. The composition is characterized by being in the range of 1.3 parts by weight or more and less than 20 parts by weight with respect to 100 parts by weight of the crosslinking agent.

  According to the present disclosure, it can be suitably used for a touch panel integrated image display device having a capacitive touch panel function, and when a resin base material such as polycarbonate or PMMA is used as a cover panel, It can be set as the adhesive composition which can comprise the adhesive sheet which can suppress the fall of the reactivity and sensitivity of a touch sensor. Specifically, it is as follows.

Conventionally, glass substrates have been used as cover panels in image display devices. However, in recent years, a resin base material made of polycarbonate, PMMA, or the like is often used for the cover panel for the purpose of reducing the weight and thickness of the image display device.
Here, the inventors of the present disclosure have discovered the following new problem. That is, in the case of an image display device using a resin base material made of polycarbonate or PMMA as a cover panel, there is a problem that the reactivity and sensitivity of the touch panel sensor is lower than that of a conventional image display device using a glass base material. There is.

Then, when the inventors of this indication repeatedly examined, the said problem is polycarbonate (relative dielectric constant (1 MHz): 2.9-3.0) and PMMA (relative dielectric constant (1 MHz): 3.0- 3.7) was found to be caused by a lower relative dielectric constant than glass (relative dielectric constant (1 MHz): 6 to 8). Specifically, as indicated by the following equation, when the value of the relative dielectric constant ε decreases, the value of the capacitance C also tends to decrease.
C = εS / d
(In the above equation, C is the capacitance, ε is the relative dielectric constant, S is the effective area of the electrodes, and d is the distance between the electrodes.)
Therefore, in the case of an image display device using polycarbonate or PMMA having a relative dielectric constant lower than that of glass for the cover panel, the amount of change in capacitance at the touched position is desired when the touch panel is touched with a finger or the like. As a result, it has been found that there is a problem that the reactivity and sensitivity of the touch panel sensor are lowered.

The inventors of the present disclosure have tried to use a material having a relatively high relative dielectric constant for the pressure-sensitive adhesive composition constituting the pressure-sensitive adhesive sheet as a means for solving the above-described problem. Usually, it is said that a material having higher polarity has a higher dielectric constant. On the other hand, the inventors of the present disclosure can obtain a pressure-sensitive adhesive composition capable of constituting a pressure-sensitive adhesive sheet having a high relative dielectric constant when dioctyl adipate, which is not so high in polarity, is used as a plasticizer. I found a specific effect. The present disclosure has been based on such findings.
Hereinafter, each component which comprises the adhesive composition of this indication is demonstrated.

A. Plasticizer The plasticizer in the present disclosure is dioctyl adipate having a branched octyl group. The plasticizer is dispersed in an acrylic polymer that will be described later, and has a function of reducing the storage elastic modulus of the pressure-sensitive adhesive composition. Specifically, by entering the space between the acrylic polymer polymers, the distance between the acrylic polymers can be increased, and the pressure-sensitive adhesive composition can be softened.
Hereinafter, dioctyl adipate used in the pressure-sensitive adhesive composition of the present disclosure will be described.

1. Dioctyl adipate Dioctyl adipate used as a plasticizer in the pressure-sensitive adhesive composition of the present disclosure has a structure represented by the following chemical formula (1).

  Dioctyl adipate has a branched octyl group as shown in the chemical formula (1). In the present disclosure, by using dioctyl adipate having a branched octyl group, there is a specific effect that an adhesive sheet having a high relative dielectric constant can be obtained. The reason for this is not clear, but dioctyl adipate enters the gap between the acrylic polymer polymers, so that the polarity per unit volume of the pressure-sensitive adhesive sheet using the pressure-sensitive adhesive composition of the present disclosure increases, resulting in a relative dielectric constant. It is thought to be higher.

Further, it is generally known that a substance having a higher polarity has a higher dielectric constant. On the other hand, although dioctyl adipate is not a very polar substance, the inventors of the present disclosure discovered that dioctyl adipate is a substance having a relatively high dielectric constant, and the adhesive composition of the present disclosure It was set as the component.
The content of dioctyl adipate used in the pressure-sensitive adhesive composition of the present disclosure is within a range of 1.3 parts by weight or more and less than 20 parts by weight with respect to 100 parts by weight of the total amount of the acrylic polymer and the crosslinking agent. is there.
In the present disclosure, the content of dioctyl adipate may be within the above-described range with respect to 100 parts by weight of the total amount of the acrylic polymer polymer and the crosslinking agent described later, but in particular, 2 or more and 16 or less. It is preferably within the range, and particularly preferably within the range of 4 or more and 11 or less.

  When the content of dioctyl adipate has the above-described lower limit, the pressure-sensitive adhesive sheet using the pressure-sensitive adhesive composition of the present disclosure can be a member having a relatively high dielectric constant. Therefore, when the pressure-sensitive adhesive sheet is used in an image display device integrated with a touch panel having a capacitive touch panel function and using a resin base material such as polycarbonate or PMMA as a cover panel. Even if it exists, the effect that the fall of the reactivity of a touch sensor and a sensitivity can be suppressed can fully be acquired. Moreover, it becomes possible to improve workability because content of dioctyl adipate has the upper limit mentioned above.

2. Other Plasticizer The pressure-sensitive adhesive composition of the present disclosure may contain a predetermined amount of the above-described dioctyl adipate as a plasticizer. Therefore, it can be used in combination with other plasticizers as necessary.

  For other plasticizers, known materials can be used. Among them, it is preferable to use a material having a relatively high polarity and having a polarity close to that of an acrylic polymer polymer described later. The compatibility of the plasticizer with the acrylic polymer polymer can be improved, and when a pressure-sensitive adhesive sheet is formed using the pressure-sensitive adhesive composition of the present disclosure, it has a desired haze value and is suitably used for an image display device. The member can be made.

  Specific examples of other plasticizers include ester plasticizers composed of ester compounds, chlorinated paraffinic plasticizers composed of chlorine compounds, and epoxidized soybean oil based plasticizers composed of epoxy compounds. Among these, it is preferable to use an ester plasticizer. This is because the compatibility with the acrylic polymer is good.

  As the ester compound that functions as an ester plasticizer, a conventionally known compound can be used. For example, a phthalic acid diester compound, an adipic acid diester compound, a polyester compound, a phosphoric acid ester compound, a sulfonic acid ester compound, or a trimellitic acid diester Compound, citric acid diester compound, terephthalic acid diester compound, benzoic acid diester compound and the like.

  Since the content of other plasticizers used in the pressure-sensitive adhesive composition of the present disclosure can be appropriately adjusted according to the content of dioctyl adipate described above, the description here is omitted.

B. Acrylic polymer polymer The acrylic polymer polymer in the present disclosure is a copolymer obtained by copolymerizing an acrylic monomer component having an acrylic structure and not having a carboxyl group. The acrylic polymer is usually a copolymer obtained by copolymerizing an acrylate ester and other monomers.

  The acrylic polymer polymer in the present disclosure has an acrylic monomer component. Here, in the present disclosure, the acrylic monomer component is a concept distinguished from the methacryl monomer component. In the present disclosure, the acrylic polymer may be composed of an acrylic monomer component, but it is preferable not to have a methacrylic monomer component, specifically, not to have a methacrylic monomer component having a methacrylic structure. . A pressure-sensitive adhesive sheet having a relatively high dielectric constant can be formed using the pressure-sensitive adhesive composition of the present disclosure, and the effects of the present disclosure can be sufficiently obtained.

  The acrylic monomer component constituting the acrylic polymer polymer in the present disclosure has an acrylic structure. Specifically, since the acrylic acid ester has an acrylic structure, that is, has an acrylic group, the number of carbon atoms contained in the acrylic polymer polymer can be within a desired range, and thus the pressure-sensitive adhesive composition of the present disclosure Can be used to form a pressure-sensitive adhesive sheet having a relatively high relative dielectric constant, and the effects of the present disclosure can be sufficiently obtained.

  The acrylic structure of the acrylate ester preferably has a predetermined number of carbon atoms. For example, the number of carbon atoms of the acrylic structure is preferably in the range of 1 to 10, more preferably in the range of 2 to 9, and particularly preferably in the range of 2 to 8.

  The acrylic monomer component used in the present disclosure does not have a carboxyl group. According to the present disclosure, when the acrylic monomer component does not have a carboxyl group, an adhesive sheet is formed using the adhesive composition of the present disclosure, and when the adhesive sheet is used in an image display device integrated with a touch panel, It becomes possible to suppress corrosion of the metal member constituting the touch sensor. According to the present disclosure, it is particularly preferable that the acrylic monomer component does not have an acidic group other than a carboxyl group. As said acidic group, a phenolic hydroxyl group, a sulfo group, a phosphoric acid group etc. are mentioned, for example. In addition, not having a carboxyl group or having no acidic group is not only that the acrylic monomer component does not contain any carboxyl group or contains any acidic group, but also the adhesive composition of the present disclosure. When the pressure-sensitive adhesive sheet composed of is bonded to a metal member, the acrylic monomer component contains a carboxyl group or an acid group to the extent that the metal member is not corroded by the acid component. Is included. Specifically, the content of carboxyl groups (acidic groups) in the acrylic monomer component is preferably less than 25 ppm. The content of the carboxyl group in the acrylic monomer component can be measured by, for example, a nuclear magnetic resonance apparatus (NMR). Specifically, the carboxyl group and the silylating agent are reacted, and the peak derived from the silylated product is measured by 1H-NMR (600 MHz) (lower limit of quantification: 25 ppm) to specify the content of the carboxyl group. can do.

  The acrylic monomer component used in the present disclosure preferably has no aromatic ring. By not having an aromatic ring, it is possible to suppress the phenomenon of oxidation and yellowing due to light and heat. Therefore, when an adhesive sheet is formed using the adhesive composition of the present disclosure, the adhesive sheet can be suitably used for an image display device. In addition, not having an aromatic ring includes not only that an acrylic monomer component does not contain an aromatic ring at all, but also includes an aromatic ring that does not turn yellow when oxidized by light or heat. In addition, according to the present disclosure, it is preferable that the acrylic monomer component does not include a heterocyclic ring.

  Examples of the acrylic acid ester used in the present disclosure include ethyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, isooctyl acrylate, isononyl acrylate, hydroxylethyl acrylate, propylene glycol acrylate, acrylamide, and acrylic. Examples include glycidyl acid. In the present disclosure, it is particularly preferable to use butyl n-acrylate or 2-ethylhexyl acrylate. These acrylic acid esters may be used alone or in combination of two or more. The acrylic ester described above can be appropriately selected according to the type of the crosslinking agent used in the pressure-sensitive adhesive composition of the present disclosure. For example, when an isocyanate crosslinking agent is used as the crosslinking agent, crosslinking is performed. From the viewpoint of advancing the reaction, it is preferable to select an acrylate ester having at least a hydroxyl group.

  Other monomers used in the present disclosure include, for example, methyl acrylate, methyl methacrylate, styrene, acrylonitrile, vinyl acetate, acrylic acid, methacrylic acid, itaconic acid, hydroxylethyl acrylate, hydroxylethyl methacrylate, acrylic Examples include propylene glycol acid, acrylamide, methacrylamide, glycidyl acrylate, glycidyl methacrylate, dimethylaminoethyl methacrylate, tert-butylaminoethyl methacrylate, and n-ethylhexyl methacrylate. These other monomers may be used alone or in admixture of two or more.

  The acrylic polymer polymer used in the present disclosure usually contains the above-described acrylic ester as a main component. Specifically, the content of the acrylate ester contained in the acrylic polymer is preferably in the range of 96% by mass to 99% by mass, for example, in the range of 97% by mass to 99% by mass. It is preferable that it is in the range of 98 mass% or more and 99 mass% or less especially.

  The acrylic polymer used in the present disclosure may be a copolymer of an acrylic ester as a main component and a hydroxyl group-containing monomer copolymerizable with the acrylic ester. The hydroxyl group-containing monomer used at this time preferably has, for example, a copolymerizable polymerizable group and a hydroxyl group. Specifically, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, Examples include 2-hydroxybutyl acrylate, 3-chloro-2-hydroxypropyl acrylate, polyethylene glycol acrylate, and the like.

  The copolymerization ratio (mass ratio) between the acrylate ester and the hydroxyl group-containing monomer described above is preferably a copolymerization ratio such that the acrylate ester is a main component, and can be adjusted as appropriate. For example, the copolymerization ratio (mass ratio) between the acrylate ester and the hydroxyl group-containing monomer described above is preferably in the range of 99/1 to 70/30. When the copolymerization ratio is within the above range, desired durability, adhesiveness and optical properties can be obtained. In addition, the copolymerization ratio of acrylic acid ester and the hydroxyl-containing monomer mentioned above can be measured with a nuclear magnetic resonance apparatus (NMR), for example.

  The weight average molecular weight (Mw) of the acrylic polymer used in the present disclosure is preferably such that desired tackiness is obtained. Among these, from the viewpoint of durability, the weight average molecular weight (Mw) of the acrylic polymer polymer is preferably in the range of 300,000 to 1,500,000, more preferably in the range of 300,000 to 1,300,000. . A weight average molecular weight can be made into the value of polystyrene conversion at the time of measuring by gel permeation chromatography (GPC), for example. In addition, for example, Waters2695 made by Waters can be used for the weight average molecular weight measuring device, and LF-804 × 3 pieces (inner diameter 8 mm, length 300 mm) made by Showa Denko can be used for the column. It can be measured by setting the sample concentration to 0.5% (diluted with tetrahydrofuran), using tetrahydrofuran as the mobile phase solvent, the flow rate to 1 ml / min, and the column temperature to 40 ° C.

  In the present disclosure, the content of the composition obtained by polymerizing the acrylic monomer component is preferably in the range of 85 parts by weight or more and 98 parts by weight or less, particularly 89 parts by weight with respect to 100 parts by weight of the pressure-sensitive adhesive composition. It is preferably in the range of 97 parts by weight or less, particularly preferably in the range of 94 parts by weight or more and 96 parts by weight or less. When the content of the component obtained by polymerizing the acrylic monomer component is within the above range, an adhesive sheet having desired adhesiveness can be formed. Therefore, a high-quality image display device can be obtained by using the pressure-sensitive adhesive sheet. In addition, the structure which the acrylic monomer component superposed | polymerized points out the thing of the state which the acrylic monomer component superposed | polymerized.

C. Crosslinking agent The crosslinking agent used in this indication is a material used suitably when forming an adhesive sheet using the adhesive composition of this indication.

  Examples of the crosslinking agent used in the present disclosure include an isocyanate crosslinking agent, an epoxy crosslinking agent, a silicone crosslinking agent, an oxazoline crosslinking agent, an aziridine crosslinking agent, a silane crosslinking agent, and an alkyl etherified melamine crosslinking agent. Is mentioned. Among them, it is preferable to use an isocyanate-based crosslinking agent or an epoxy-based crosslinking agent. These crosslinking agents may be used alone or in combination of two or more.

  Examples of the isocyanate-based crosslinking agent used in the present disclosure include a polyisocyanate compound, a trimer of a polyisocyanate compound, a urethane prepolymer having an isocyanate group at a terminal obtained by reacting a polyisocyanate compound and a polyol compound, Examples include trimers of urethane prepolymers. Examples of the polyisocyanate compound include 2,4-tolylene diisocyanate, 2,5-tolylene diisocyanate, 1,3-xylylene diisocyanate, 1,4-xylylene diisocyanate, diphenylmethane-4,4′-diisocyanate, 3 -Methyldiphenylmethane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, dicyclohexylmethane-2,4'-diisocyanate, lysine isocyanate and the like.

  Examples of the epoxy-based crosslinking agent used in the present disclosure include sorbitol polyglycidyl ether, polyglycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, diglycerol polyglycidyl ether, glycerol polyglycidyl ether, trimethylolpropane polyglycidyl ether, neodymium Examples include polyfunctional epoxy compounds such as pentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, hydrogenated bisphenol A diglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, and polybutadiene diglycidyl ether. .

  The content of the crosslinking agent used in the present disclosure is preferably in the range of 0.1 parts by weight or more and 1.5 parts by weight or less with respect to 100 parts by weight of the acrylic polymer. It is preferably in the range of 1.0 part by weight or more and 1.0 part by weight or less, and particularly preferably in the range of 0.4 part by weight or more and 0.8 part by weight or less. When the content of the cross-linking agent is within the above range, when forming the pressure-sensitive adhesive sheet using the pressure-sensitive adhesive composition of the present disclosure, the cross-linking reaction can be suitably advanced, and a sufficient cross-linking density is obtained. Can do. Moreover, it can be set as the adhesive composition which has moderate elasticity and adhesiveness. Furthermore, when forming a pressure-sensitive adhesive sheet using the pressure-sensitive adhesive composition of the present disclosure, it is possible to suppress the presence of an excessive amount of a crosslinking agent and to suppress a decrease in flexibility due to the bonding between the crosslinking agents. Can do.

D. Additive The pressure-sensitive adhesive composition of the present disclosure may have an additive as necessary. Examples of additives include rust preventives, antioxidants, silane coupling agents, adhesion promoters, metal chelators, surfactants, ultraviolet absorbers, pigments, dyes, colorants, antistatic agents, antiseptics, Examples include an antifoaming agent and a wettability adjusting agent.

  About various additives, since it can be made to be the same as that of the material used for a general adhesive composition, description here is abbreviate | omitted.

  The content of the additive used in the present disclosure is preferably such that the pressure-sensitive adhesive composition of the present disclosure exhibits a desired effect. Specifically, when the pressure-sensitive adhesive composition is 100% by mass, the solid ratio is preferably in the range of 0.1% by mass to 2.0% by mass, and more preferably 0.2% by mass to 1%. It is preferably in the range of 0.0 mass% or less, and particularly preferably in the range of 0.3 mass% or more and 0.7 mass% or less. When the content of the additive is within the above range, when the pressure-sensitive adhesive sheet is formed using the pressure-sensitive adhesive composition of the present disclosure, the pressure-sensitive adhesive sheet can be suitably used for an image display device. Specifically, it is possible to sufficiently obtain the effect of the additive while suppressing a decrease in the visibility of the image display device.

E. Solvent The pressure-sensitive adhesive composition of the present disclosure only needs to have the above-described acrylic polymer, cross-linking agent, and plasticizer, but usually also has a solvent. About the solvent used in this indication, since it can be made to be the same as that of the solvent used for a general adhesive composition, description here is omitted.

  The content of the solvent contained in the pressure-sensitive adhesive composition can be appropriately adjusted according to the ratio of the solid content from the viewpoint of the coating properties of the pressure-sensitive adhesive composition. Specifically, the solid content in the pressure-sensitive adhesive composition is preferably in the range of 20% by mass or more and 70% by mass or less, and more preferably in the range of 35% by mass or more and 55% by mass or less. Is preferred.

  When forming an adhesive sheet using the adhesive composition of the present disclosure, it is preferable to crosslink the acrylic polymer polymer and the plasticizer after removing the solvent. In addition, about the adhesive sheet formed using the adhesive composition of this indication, since it demonstrates in the term of the "II. Adhesive sheet" mentioned later, description here is abbreviate | omitted.

II. Pressure-sensitive adhesive sheet The pressure-sensitive adhesive sheet of the present disclosure contains a crosslinked acrylic polymer polymer and a plasticizer, and the crosslinked acrylic polymer polymer has a copolymer in which an acrylic monomer component having an acrylic structure and no carboxyl group is copolymerized. The plasticizer is a dioctyl adipate having a branched octyl group, and the content of the dioctyl adipate is 1.3 parts by weight or more with respect to 100 parts by weight of the crosslinked acrylic polymer polymer. , Within a range of less than 20 parts by weight.

  Moreover, the adhesive sheet of this indication may further have the 1st peeling layer and the 2nd peeling layer. In this case, the pressure-sensitive adhesive sheet of the present disclosure includes a first release layer, a pressure-sensitive adhesive sheet on one surface of the first release layer, and a surface of the pressure-sensitive adhesive sheet on a surface opposite to the first release layer. 2 and a release layer, the pressure-sensitive adhesive sheet contains a crosslinked acrylic polymer polymer and a plasticizer, and the crosslinked acrylic polymer polymer has an acrylic structure and an acrylic monomer component having no carboxyl group. It is a polymerized copolymer, and the plasticizer is dioctyl adipate having a branched octyl group. The content of the dioctyl adipate is 1. It is a member characterized by being in the range of 3 parts by weight or more and less than 20 parts by weight.

  The pressure-sensitive adhesive sheet of the present disclosure will be described with reference to the drawings. FIG. 1 is a schematic cross-sectional view illustrating an example of the pressure-sensitive adhesive sheet of the present disclosure. The pressure-sensitive adhesive sheet 10 </ b> S of the present disclosure includes a first release layer 1, a pressure-sensitive adhesive sheet 10 on one surface of the first release layer 1, and a surface on the opposite side of the pressure-sensitive adhesive sheet 10 from the first release layer 1. 2 release layer 2. The pressure-sensitive adhesive sheet contains a crosslinked acrylic polymer polymer and a predetermined plasticizer.

According to the present disclosure, it can be suitably used for a touch panel integrated image display device having a capacitive touch panel function, and when a resin base material such as polycarbonate or PMMA is used as a cover panel, It can be set as the adhesive sheet which can suppress the fall of the reactivity and sensitivity of a touch sensor.
In addition, about a specific effect, since it can be made to be the same as that of the content described in the term of the above-mentioned "I. Adhesive composition", description here is abbreviate | omitted.
Hereinafter, each member constituting the pressure-sensitive adhesive sheet of the present disclosure will be described.

A. Pressure-sensitive adhesive sheet The pressure-sensitive adhesive sheet in the present disclosure is a member containing a crosslinked acrylic polymer polymer and a plasticizer.

  The pressure-sensitive adhesive sheet in the present disclosure preferably has a predetermined relative dielectric constant. Specifically, the relative dielectric constant at 100 kHz is preferably 5.0 or more, more preferably 5.5 or more, and particularly preferably 6.0 or more. Moreover, it is preferable that the dielectric constant of the adhesive sheet in this indication is 7.0 or less at 100 kHz. When the relative dielectric constant of the pressure-sensitive adhesive sheet is within the above range, the touch panel integrated image display device having a capacitive touch panel function, which uses a resin base material such as polycarbonate or PMMA as a cover panel Even in the case of an image display device, it is possible to sufficiently obtain an effect that it is possible to suppress a decrease in reactivity and sensitivity of the touch sensor. In addition, since the measuring method of a dielectric constant is demonstrated in the term of the Example mentioned later, description here is abbreviate | omitted.

  The pressure-sensitive adhesive sheet in the present disclosure preferably has a predetermined haze value from the viewpoint of being suitably used for an image display device. Specifically, the haze value according to JIS K-7136 having a film thickness of 50 μm is preferably less than 1.5%, more preferably less than 0.8%, and particularly less than 0.6%. It is preferable. When the haze value of the pressure-sensitive adhesive sheet is within the above range, a pressure-sensitive adhesive sheet having excellent transparency can be obtained. Therefore, the pressure-sensitive adhesive sheet of the present disclosure can be suitably used for an image display device. The haze value of the pressure-sensitive adhesive sheet can be adjusted by the type of acrylic polymer polymer and plasticizer used for the pressure-sensitive adhesive sheet. Specifically, the haze value can be lowered by selecting a highly compatible type of acrylic polymer polymer and plasticizer. In addition, since the measuring method of a haze value is demonstrated in the term of the Example mentioned later, description here is abbreviate | omitted.

The pressure-sensitive adhesive sheet according to the present disclosure is a resistance calculated by the following formula of a transparent conductive film when a durability test is performed on a laminate in which a transparent conductive film is stacked in an atmosphere of 60 ° C. and 90% RH for 500 hours. The increase rate is preferably less than 50%.
Resistance increase rate (%) = {(R−R ₀ ) / R ₀ } × 100
(In the above equation, R ₀ is the initial resistance value before the durability test, and R is the resistance value after the durability test.)

  In particular, the resistance increase rate of the pressure-sensitive adhesive sheet in the present disclosure is preferably less than 50%, and particularly preferably less than 30%. When the resistance increase rate of the pressure-sensitive adhesive sheet is within the above range, for example, when the pressure-sensitive adhesive sheet according to the present disclosure is used in an image display device having a touch panel member, a decrease in detection sensitivity of the touch panel can be suppressed.

  The thickness of the pressure-sensitive adhesive sheet in the present disclosure can be adjusted as appropriate according to the application of the pressure-sensitive adhesive sheet of the present disclosure, and the thickness of the above-described haze value can be obtained while maintaining the desired pressure-sensitive adhesiveness. preferable. For example, the thickness of the pressure-sensitive adhesive sheet is preferably within a range of 5 μm to 100 μm, and more preferably within a range of 10 μm to 50 μm. When the thickness of the pressure-sensitive adhesive sheet is within the above range, sufficient adhesiveness can be obtained and it can be suitably used for an image display device.

  The pressure-sensitive adhesive sheet in the present disclosure preferably has predetermined adhesiveness. About the adhesiveness which an adhesive sheet has, it can adjust suitably according to the use etc. of the adhesive sheet of this indication, and is not specifically limited. It is preferable that the adhesiveness of a specific adhesive sheet exists in the range of 1N / 25mm or more and 30N / 25mm or less, for example. The adhesiveness which an adhesive sheet has can be adjusted with the quantity etc. of the crosslinked acrylic polymer polymer contained in an adhesive sheet, for example.

  In addition, the measurement of adhesiveness can be performed by the following method, for example. First, as shown in FIG. 1, an adhesive sheet 10 having a first release layer 1 and a second release layer 2 disposed on both sides is prepared. Next, the first release layer 1 is peeled to expose one surface of the pressure-sensitive adhesive sheet 10 and the exposed surface is composed of a polyethylene terephthalate film (trade name: Cosmo Shine A4100, manufactured by Toyobo Co., Ltd.) having a thickness of 100 μm. A laminated film is prepared by laminating the easily adhesive surface using a rubber roller. Next, after the obtained laminate film was cut into a size of 25 mm × 100 mm, the second release layer 2 was peeled off from the pressure-sensitive adhesive sheet 10 to expose the other surface of the pressure-sensitive adhesive sheet, and the exposed surface had a thickness of 2 mm. Affixed to a glass substrate (float plate glass, manufactured by Nippon Tact Co., Ltd.). Then, it laminates using a 2 kg roller and makes this a measurement sample. Subsequently, the measurement sample obtained as described above was allowed to stand in an atmosphere of 25 ° C. and 50% RH for 1 day, and thereafter, using a tensile tester (5565 type tester, manufactured by Instron), The adhesive strength (N / 25 mm) is measured at a tensile speed of 300 mm / min and a peeling angle of 180 ° (according to JIS Z0237) under respective temperature conditions of 25 ° C. and 100 ° C.

The pressure-sensitive adhesive sheet in the present disclosure is usually a member that exhibits pressure-sensitive adhesiveness and does not contain a solvent.
Hereinafter, each component which comprises the adhesive sheet in this indication is demonstrated.

1. Crosslinked acrylic polymer polymer The crosslinked acrylic polymer polymer used in the present disclosure is a crosslinked acrylic polymer polymer. The crosslinked acrylic polymer may be crosslinked by a crosslinking reaction between the acrylic polymer and the crosslinking agent, or may be crosslinked by a self-crosslinking reaction between the acrylic polymer polymers. .

  The crosslinked acrylic polymer polymer in the present disclosure preferably has a gel fraction of 85% or more and 99% or less. By setting the gel fraction (degree of crosslinking) within the above range, the function as an adhesive sheet can be sufficiently exhibited. Here, the gel fraction of the cross-linked acrylic polymer can be adjusted to the above range by appropriately adjusting the addition amount of the cross-linking agent that reacts with the acrylic polymer. The gel fraction can be measured by collecting the insoluble component (gel component) remaining in the solvent after dissolving the adhesive sheet with an organic solvent such as toluene. Therefore, a gel fraction means the mass ratio of the gel component contained in the adhesive sheet.

  In the present disclosure, the content of the crosslinked acrylic polymer polymer in the pressure-sensitive adhesive sheet is preferably such an amount that the pressure-sensitive adhesive sheet can exhibit desired adhesiveness. Specifically, for example, the solid ratio is preferably in the range of 92% by mass to 97% by mass with respect to 100% by mass of the pressure-sensitive adhesive sheet, and more preferably in the range of 94% by mass to 96% by mass. It is preferable. When the content of the cross-linked acrylic polymer is within the above range, a pressure-sensitive adhesive sheet having excellent durability can be obtained.

  Regarding the acrylic polymer polymer and the crosslinking agent constituting the crosslinked acrylic polymer polymer in the present disclosure, the above-mentioned “I. Adhesive composition B. Acrylic polymer polymer” and “I. Adhesive composition C. Crosslinking agent” are described. Since it can be the same as the content described in the section, the description here is omitted.

2. Plasticizer The plasticizer used in the present disclosure is dioctyl adipate having a branched octyl group. In addition, about a plasticizer, since it can be made to be the same as that of the content described in the term of "I. adhesive composition A. plasticizer" mentioned above, description here is abbreviate | omitted.

3. Additives The pressure-sensitive adhesive sheet in the present disclosure may contain additives as necessary in addition to the above-described acrylic polymer and plasticizer. In addition, about an additive, since it can be made to be the same as that of the content described in the term of "I. adhesive composition D. additive" mentioned above, description here is abbreviate | omitted.

B. 1st peeling layer and 2nd peeling layer In this indication, you may further have the 1st peeling layer and the 2nd peeling layer as needed. The 1st exfoliation layer and the 2nd exfoliation layer in this indication are members arranged on both sides of an adhesive sheet mentioned above.

  Examples of the first release layer and the second release layer (hereinafter sometimes collectively referred to as a release layer) used in the present disclosure include resin sheets such as polyester resin and polyolefin resin, fine paper, linter paper, and sulfuric acid paper. A member obtained by coating a release agent such as a silicone resin on the surface of paper such as glassine paper or kraft paper is used.

  The first peel layer and the second peel layer may have the same peel strength or different peel strengths. For example, one of the first release layer and the second release layer can be a heavy release layer having a high peel strength, and the other can be a light release layer having a low peel strength. Thereby, when bonding two members using the pressure-sensitive adhesive sheet of the present disclosure, the light-sensitive release layer is first peeled off and the exposed pressure-sensitive adhesive sheet is attached to a desired member, and then the heavy release layer is peeled off. Another member can be stuck on the exposed adhesive sheet.

C. Manufacturing method The adhesive sheet of this indication can be manufactured using a conventionally well-known method. For example, the pressure-sensitive adhesive composition containing at least an acrylic polymer polymer, a cross-linking agent and a plasticizer and further added with a solvent is applied to one side of the first release layer, and after removing the solvent to form a pressure-sensitive adhesive sheet, the pressure-sensitive adhesive composition It can be obtained by disposing a second release layer on the sheet. When the solvent is removed, the acrylic polymer polymer reacts with the crosslinking agent to form a crosslinked acrylic polymer polymer. Therefore, the crosslinked acrylic polymer polymer is included in the pressure-sensitive adhesive sheet.

D. Others The adhesive sheet of the present disclosure is not particularly limited as long as it has the above-described configuration. Therefore, the pressure-sensitive adhesive sheet of the present disclosure may be, for example, a roll or a chip cut into a predetermined size.

  Although the use of the adhesive sheet of this indication is not specifically limited, For example, it is preferred to use as an optical member, and it is preferred to use it especially for a capacitive touch panel integrated image display device. Specifically, in a touch panel integrated image display device, a member constituting a capacitive touch panel, a transparent conductive film provided with a metal oxide thin film such as ITO, and a resin such as polycarbonate or PMMA It is preferably used for bonding to a cover panel made of a substrate. Although the kind of touch panel is not specifically limited, For example, a mobile telephone, a tablet computer, a portable information terminal etc. are mentioned.

III. Image display device An image display device of this indication is characterized by having a touch panel member pasted together using the above-mentioned adhesive sheet.

  An image display device according to the present disclosure will be described with reference to the drawings. FIG. 2 is a schematic perspective view illustrating an example of the image display device of the present disclosure. As illustrated in FIG. 2, the image display device 100 of the present disclosure has a configuration in which the cover panel 20, the touch sensor 30, and the display 40 are bonded via the adhesive sheet 10.

According to the present disclosure, the above-described pressure-sensitive adhesive sheet can be suitably used for a touch panel integrated image display device having a capacitive touch panel function, and a resin base material such as polycarbonate or PMMA as a cover panel. When the is used, an image display device capable of suppressing a decrease in the reactivity and sensitivity of the touch sensor can be obtained.
In addition, about a specific effect, since it can be made to be the same as that of the content described in the term of the above-mentioned "I. Adhesive composition", description here is abbreviate | omitted.

  Each member constituting the image display device of the present disclosure will be described.

A. Adhesive sheet The adhesive sheet used in this indication is a member for pasting up the touch panel member which constitutes an image display device. In addition, about the adhesive sheet, since it can be the same as that of the content described in the above-mentioned "II. Adhesive sheet A. Adhesive sheet" description, description here is abbreviate | omitted.

B. Touch panel member The touch panel member in this indication can be suitably chosen according to the kind of image display device. For example, a cover panel, a touch sensor, a display, etc. are mentioned.

  The cover panel in the present disclosure can be the same as a cover panel used for a general touch panel member, but among them, a cover panel made of a resin base material such as polycarbonate or PMMA is preferably used. This is because the effect of the present disclosure becomes remarkable. In addition, about other specific description of a touch panel member, since it can be made the same as that of a general touch panel member, description here is abbreviate | omitted.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has substantially the same configuration as the technical idea described in the claims of the present invention, and any device that exhibits the same function and effect is the present invention. It is included in the technical scope of the invention.

  The following examples illustrate the present invention in more detail.

[Example 1]
The following (1) to (4) were blended to prepare an adhesive solution A. Next, the obtained pressure-sensitive adhesive solution A was applied on the release-treated surface of PET separator A (trade name: E7004, manufactured by Toyobo Co., Ltd., film thickness 50 μm) so that the thickness after drying was 50 μm, and dried. I let you. Thereafter, a PET separator B (trade name: E7006, manufactured by Toyobo Co., Ltd., film thickness: 38 μm) was laminated to obtain an adhesive sheet.
(1) Acrylic polymer polymer A (trade name: SK Dyne 2980, weight average molecular weight of about 450,000, manufactured by Soken Chemical Co., Ltd., solid content 37.5% by mass) ・ ・ ・ 100 parts by weight ・ 2-ethylhexyl acrylate (main component )
・ 2-hydroxyethyl acrylate ・ Methyl acrylate ・ Acrylic acid amide (2) Cross-linking agent (trade name: Y-75 (isocyanate HDI-based curing agent), manufactured by Soken Chemical Co., Ltd., solid content: 75%) ・ ・ ・ 0.4 Part by weight (3) Plasticizer (Dioctyl adipate, trade name: DOA, manufactured by J Plus, solid content: 100% by mass) 0.5 part by weight (4) Silane coupling agent (trade name: A50, Soken) (Chemical, solid content 50%)
... 0.04 parts by weight

[Example 2]
A pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1 except that the amount of dioctyl adipate used as the plasticizer was 1.0 part by weight.

[Example 3]
A pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1 except that the amount of dioctyl adipate used as the plasticizer was 1.5 parts by weight.

[Example 4]
A pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1 except that the amount of dioctyl adipate used as the plasticizer was 2.0 parts by weight.

[Example 5]
A pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1 except that the amount of dioctyl adipate used as the plasticizer was 4.0 parts by weight.

[Example 6]
A pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1 except that the amount of dioctyl adipate used as the plasticizer was 6.0 parts by weight.

[Example 7]
A pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1 except that the acrylic polymer polymer A was changed to the acrylic polymer polymer B.
Acrylic polymer polymer B (trade name: SK Dyne 1811L, weight average molecular weight of about 650,000, manufactured by Soken Chemical Co., Ltd., solid content: 23% by mass): 100 parts by weight ・ Butyl acrylate (main component)
・ 2-hydroxyethyl acrylate ・ Methyl acrylate

[Example 8]
A pressure-sensitive adhesive sheet was obtained in the same manner as in Example 7 except that the amount of dioctyl adipate used as the plasticizer was 1.0 part by weight.

[Example 9]
A pressure-sensitive adhesive sheet was obtained in the same manner as in Example 7 except that the amount of dioctyl adipate used as the plasticizer was 1.5 parts by weight.

[Example 10]
A pressure-sensitive adhesive sheet was obtained in the same manner as in Example 7 except that the amount of dioctyl adipate used as the plasticizer was 2.0 parts by weight.

[Comparative Example 1]
A pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1 except that no plasticizer was added.

[Comparative Example 2]
A pressure-sensitive adhesive sheet was obtained in the same manner as in Example 4 except that dioctyl adipate used as a plasticizer was dioctyl phthalate (trade name: DOP, manufactured by J Plus, solid content: 100% by mass).

[Comparative Example 3]
A pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1 except that the amount of dioctyl adipate used as the plasticizer was 7.5 parts by weight.

[Comparative Example 4]
A pressure-sensitive adhesive sheet was obtained in the same manner as in Example 7 except that no plasticizer was added.

[Comparative Example 5]
A pressure-sensitive adhesive sheet was obtained in the same manner as in Example 10 except that dioctyl adipate used as a plasticizer was dioctyl phthalate (trade name: DOP, manufactured by J Plus, solid content: 100% by mass).

[Comparative Example 6]
The following (1) to (5) were blended to prepare an adhesive solution B. Next, the obtained pressure-sensitive adhesive solution B was coated on the release-treated surface of PET separator A (trade name: E7004, manufactured by Toyobo Co., Ltd., 50 μm thick) so that the thickness after drying was 50 μm, and dried. By doing so, an adhesive sheet was formed. Thereafter, a PET separator B (trade name: E7006, manufactured by Toyobo Co., Ltd., film thickness: 38 μm) was laminated to obtain an adhesive sheet.
(1) Acrylic polymer C (trade name: OC3949, weight average molecular weight of about 1,200,000, manufactured by Soken Chemical Co., Ltd., solid content of 19.5% by mass) ... 100 parts by weight butyl acrylate (main component)
・ Ethyl acrylate (2) cross-linking agent (trade name: K-130 (isocyanate-based cross-linking agent), manufactured by Seiden Chemical Co., Ltd., solid content 80% by mass) ... 0.05 part by weight (3) Plasticizer (dioctyl adipate, commercial product Name: DOA, manufactured by J. Plus, solid content: 100% by mass) ... 0.975 parts by weight (4) Silane coupling agent (trade name: S-1, manufactured by Seiden Chemical, solid content: 6.3% by mass) ... 1 0.0 part by weight (5) Acrylic copolymer solution (solution obtained by dissolving the following acrylic copolymer in toluene, solid content: 50% by mass) ... 1.22 parts by weight Acrylic copolymer (trade name: LA2330, methyl methacrylate polymer block (M ) And a butyl acrylate polymer block (A) having a polymerization average molecular weight of 160,000 MAM type triblock copolymer, manufactured by Kuraray Co., Ltd. The amount%)

[Comparative Example 7]
A pressure-sensitive adhesive sheet was obtained in the same manner as in Example 4 except that dioctyl adipate used as a plasticizer was adipic acid polyester (trade name: PN-250, molecular weight 2000, manufactured by ADEKA).

[Comparative Example 8]
The following (1) to (3) were blended to prepare an adhesive solution C (solid content: 35% by mass). Next, the obtained pressure-sensitive adhesive solution C was coated on the release-treated surface of PET separator A (trade name: E7004, manufactured by Toyobo Co., Ltd., film thickness 50 μm) so that the thickness after drying was 50 μm, and dried. I let you. Thereafter, a PET separator B (trade name: E7006, manufactured by Toyobo Co., Ltd., film thickness: 38 μm) was laminated to obtain an adhesive sheet.
(1) Acrylic polymer D: 100 parts by weight (2) Plasticizer (adipic acid polyester, trade name: PN-250, molecular weight 2000, manufactured by ADEKA) 1 part by weight (3) Crosslinker (trade name: Tetrad X (Epoxy-based crosslinking agent), manufactured by Mitsubishi Chemical)
... 0.1 parts by weight

The acrylic polymer polymer D described above was obtained as follows. The following components (1) to (3) are dissolved in 185 parts by weight of ethyl acetate in a reaction vessel equipped with a cooling tube, a nitrogen introduction tube, a thermometer, a dropping funnel and a stirring device, and the ethyl acetate is refluxed in a nitrogen atmosphere. The reaction was allowed to proceed for 8 hours at temperature. Thereby, acrylic polymer polymer D (solid content 35% by mass) was obtained.
(1) Butyl acrylate (trade name: butyl acrylate, manufactured by Mitsubishi Chemical Corporation, solid content: 100% by mass) ... 98 parts by weight (2) Acrylic acid (Product name: acrylic acid, manufactured by Mitsubishi Chemical Corporation, solid content: 100% by mass)
... 2 parts by weight (3) polymerization initiator (trade name: dilauroyl peroxide, manufactured by Kanto Chemical Co., Ltd., solid content: 100% by mass)
... 0.5 parts by weight

[Comparative Example 9]
The following (1) to (5) are dissolved in 80 parts by weight of ethyl acetate in a reaction vessel equipped with a cooling tube, a nitrogen introducing tube, a thermometer, a dropping funnel and a stirring device, and the mixture is refluxed at a reflux temperature of ethyl acetate in a nitrogen atmosphere. The reaction was allowed for 10 hours. Thereby, an adhesive solution E (solid content 55% by mass) containing the acrylic polymer polymer E was obtained. Next, the obtained pressure-sensitive adhesive solution E was applied on the release-treated surface of PET separator A (trade name: E7004, manufactured by Toyobo Co., Ltd., film thickness 50 μm) so that the thickness after drying was 50 μm, and dried. I let you. Thereafter, a PET separator B (trade name: E7006, manufactured by Toyobo Co., Ltd., film thickness: 38 μm) was laminated to obtain an adhesive sheet.
(1) Lauryl methacrylate (Mitsubishi Gas Chemical, solid content 100% by mass) 35 parts by weight (2) 2-ethylhexyl methacrylate (Mitsubishi Gas Chemical, solid content 100% by mass)
... 59 parts by weight (3) Hydroxyethyl methacrylate (manufactured by Mitsubishi Gas Chemical) ... 5 parts by weight (4) Acrylamide (manufactured by Tokyo Chemical Industry Co., Ltd., solid content 100% by mass) ... 1 part by weight (5) 2,2-azobis Isobutyronitrile (manufactured by Tokyo Chemical Industry, solid content 100% by mass)
... 0.2 parts by weight

[Comparative Example 10]
A pressure-sensitive adhesive sheet was obtained in the same manner as in Comparative Example 9 except that 11 parts by weight of dioctyl adipate was added to the pressure-sensitive adhesive solution E.

[Evaluation]
(Relative permittivity)
The PET separators A and B provided on both surfaces of the pressure-sensitive adhesive sheets obtained in Examples 1 to 10 and Comparative Examples 1 to 10 were peeled off, and the measurement sample was prepared by sandwiching the pressure-sensitive adhesive sheet between the aluminum tape and the chromium substrate. did. The relative dielectric constant of each measurement sample at a frequency of 100 kHz was measured in accordance with JIS K 6911 under the following apparatus and conditions. The value of the relative dielectric constant was the average value of the measured values of the three samples. The results are shown in Table 1.
Measurement method: Capacity method (apparatus: Agilent, LCR meter 4284A is used)
・ Upper electrode: 40 mm × 70 mm × t 0.7 mm chrome substrate ・ Lower electrode: Aluminum tape manufactured by Fudo Kogyo Co., Ltd.
・ Measurement environment: 25 ℃, 50% RH

(Detection sensitivity of touch panel)
Apple's iPhone 5 (registered trademark) was used as the touch panel. First, a ready-made cover panel (surface protective layer, material: tempered glass) of iPhone 5 (registered trademark) is removed, and a resin substrate (trade name: MRS-58T, material: polycarbonate, thickness: 1.0 mm, Mitsubishi Gas) is used instead. The touch panel surface and the resin substrate were bonded by the adhesive sheets obtained in Examples 1 to 10 and Comparative Examples 1 to 10 to produce a sample for evaluation. Evaluation was performed by the following method using the obtained sample for evaluation. The results are shown in Table 1.

A sample in which the resin substrate was mounted on the touch panel surface without an adhesive sheet was used as a blank. As an evaluation method, 10 evaluators were allowed to operate the blank and the sample for evaluation with fingers respectively, and the touch panel detection sensitivity was evaluated in the following five stages from the viewpoint of operability during input. The average value of 10 evaluation points was used as the evaluation result of the detection sensitivity of the touch panel. The results are shown in Table 1.
-Evaluation point 4: I felt that the operability was very good compared to the blank.
-Evaluation point 3: It was clearly felt that the operability was better than that of the blank.
-Evaluation point 2: I felt that it was equivalent to a blank.
-Evaluation point 1: I felt that operability was worse than blank.

(Haze value)
The PET separators A and B provided on both sides of the pressure-sensitive adhesive sheets obtained in Examples 1 to 10 and Comparative Examples 1 to 10 were peeled off and attached to a slide glass (trade name: water slide glass S7213, manufactured by Matsunami Glass). According to JIS K-7136, it was measured with an integrating sphere turbidimeter (trade name: NDH2000, manufactured by Nippon Denshoku Industries Co., Ltd.). The results are shown in Table 1.

(Resistance increase rate)
Either one of PET separator A or PET separator B of the pressure-sensitive adhesive sheets obtained in Examples 1 to 10 and Comparative Examples 1 to 10 was peeled off and attached to a PET film (trade name: Cosmo Shine A4100, manufactured by Toyobo) Cut to a size of 25 mm × 60 mm. The surface of the other adhesive sheet was affixed to an ITO film (trade name: KH300N03-125-U3L / PT50) cut to 25 mm × 80 mm to produce a laminate. The initial resistance value (R ₀ ) of the laminate before the durability test was measured in advance, and the resistance increase rate was determined from the resistance value (R) of the laminate after exposure to an atmosphere of 60 ° C. and 90% RH for 500 hours. Was calculated. The results are shown in Table 1.
Resistance increase rate (%) = {(R−R ₀ ) / R ₀ } × 100
(In the above equation, R ₀ is the initial resistance value before the durability test, and R is the resistance value after the durability test.)

(Processability)
From one side of the pressure-sensitive adhesive sheets obtained in Examples 1 to 10 and Comparative Examples 1 to 10, using a punching machine (trade name: D250, manufactured by Iwasaki Tekko Co., Ltd.), a speed of 100 shots / min with a sealing blade. I punched with. A sample in which the peripheral portion of the punched measurement sample did not float, and when the peelable PET films A and B were peeled by hand, so-called paste removal did not occur was designated as “◯”. On the other hand, a sample in which floating occurred in the peripheral portion of the punched measurement sample and degreasing occurred was designated as “x”. Note that “glue removal” means that a part of the pressure-sensitive adhesive sheet is drawn into a thread or a part of the pressure-sensitive adhesive sheet is missing between the PET films A and B, which are release layers (separators), and the pressure-sensitive adhesive sheet. A phenomenon. The results are shown in Table 1.

DESCRIPTION OF SYMBOLS 1 ... 1st peeling layer 2 ... 2nd peeling layer 10 ... Adhesive sheet 100 ... Image display apparatus

Claims (10)

An adhesive composition containing an acrylic polymer, a plasticizer, and a crosslinking agent,
The acrylic polymer polymer is a copolymer obtained by copolymerizing an acrylic monomer component having an acrylic structure and having no carboxyl group,
The plasticizer is dioctyl adipate having a branched octyl group,
The pressure-sensitive adhesive composition is characterized in that the content of dioctyl adipate is within a range of 1.3 parts by weight or more and less than 20 parts by weight with respect to 100 parts by weight of the acrylic polymer and the crosslinking agent. .   The pressure-sensitive adhesive composition according to claim 1, wherein the acrylic monomer component does not have an aromatic ring.   The pressure-sensitive adhesive composition according to claim 1, wherein the acrylic monomer component has only an acrylic structure. Containing a cross-linked acrylic polymer polymer, and a plasticizer,
The cross-linked acrylic polymer is a copolymer having an acrylic structure and an acrylic monomer component having no carboxyl group,
The plasticizer is dioctyl adipate having a branched octyl group,
The pressure-sensitive adhesive sheet is characterized in that the content of dioctyl adipate is within a range of 1.3 parts by weight or more and less than 20 parts by weight with respect to 100 parts by weight of the crosslinked acrylic polymer.   The pressure-sensitive adhesive sheet according to claim 4, wherein the acrylic monomer component does not have an aromatic ring.   The pressure-sensitive adhesive sheet according to claim 4 or 5, wherein the acrylic monomer component has only an acrylic structure.   The pressure-sensitive adhesive sheet according to any one of claims 4 to 6, wherein a relative dielectric constant at 100 kHz is 5.0 or more.   The pressure-sensitive adhesive sheet according to any one of claims 4 to 7, wherein a haze value based on JIS K-7136 having a thickness of 50 µm is less than 1.5%. The resistance increase rate calculated by the following formula of the transparent conductive film is less than 50% when a durability test is performed on the laminated body with the transparent conductive film exposed to an atmosphere of 60 ° C. and 90% RH for 500 hours. The pressure-sensitive adhesive sheet according to claim 4, wherein the pressure-sensitive adhesive sheet is any one of claims 4 to 8.
Resistance increase rate (%) = {(R−R ₀ ) / R ₀ } × 100
(In the above equation, R ₀ is the initial resistance value before the durability test, and R is the resistance value after the durability test.)   An image display device comprising the pressure-sensitive adhesive sheet according to any one of claims 4 to 9 and a touch panel member.