JP2020007570A - Adhesive layer and adhesive film - Google Patents

Abstract

To provide an adhesive layer and an adhesive film having low dielectric constant, excellent insulation performance, followability to printing level difference and excellent shape retention property.SOLUTION: There is provided an acrylic polymer obtained by copolymerizing monomers of 2 or more kinds (meth)acrylate selected from a compound group of a copolymerizable vinyl monomer having any of an alkyl group, a hydroxyl group, a carboxyl group, an amide group, and an aromatic group, by copolymerization at a ratio of 0.5 to 15 pts.wt. of total of compounds of copolymerizable vinyl monomers having one or more of hydroxyl group and carboxyl group based on 100 pts.wt. of total amount of the acrylic monomer, containing total 0.1 to 20 molar of one or more kind of vinyl monomer having a polyalkylene oxide chain to total 100 g of the acrylic polymer, and having dielectric constant at frequency of 1 MHz of the adhesive layer of 3.5 or less.SELECTED DRAWING: None

Description

The present invention relates to a method for producing a pressure-sensitive adhesive film used for laminating an optical member between layers, a pressure-sensitive adhesive composition, and a pressure-sensitive adhesive film. More specifically, despite being a pressure-sensitive adhesive composition containing only an acrylic monomer having a general structure as a main component, it has a low dielectric constant and excellent insulation performance, and follows a printing step. The present invention relates to a method for producing a pressure-sensitive adhesive film having excellent property and excellent shape retention, a pressure-sensitive adhesive composition, and a pressure-sensitive adhesive film.
Further, the pressure-sensitive adhesive composition according to the present invention can be used as an electrical insulating material for bonding an electric member, an electronic circuit member, and the like, in addition to the optical member. Further, the pressure-sensitive adhesive film according to the present invention can be used as a film for a touch panel, a film for an electronic paper, and a film for a display having electrical insulation.

  In recent years, the amount of information traffic handled has been rapidly increasing, as represented by the spread of moving image distribution via optical fiber communication lines and wireless communication lines. Along with this, miniaturization, high frequency, and high speed of electronic / electric devices are required, and safety and reliability are required to be improved. Therefore, it is necessary to use a low-dielectric-constant electric insulating material in response to the increase in the frequency of electronic / electric devices.

Conventionally, in order to obtain an electric insulating material having a low dielectric constant, it has been proposed to form a hollow structure in the electric insulating material (for example, see Patent Documents 1 to 3).
Patent Literature 1 describes an electric insulating member in which a foamed pressure-sensitive adhesive layer is laminated on one surface of an electric insulating material in which fine voids are contained in a synthetic resin film such as polyethylene terephthalate.
Further, Patent Document 2 discloses an adhesive film using an adhesive containing micro-balloons (microballoons) such as glass and silica so that the dielectric constant of the insulating material is 2.5 or less. I have.
Further, Patent Document 3 describes an insulating film for electric wires, which is made of a polyolefin-based resin containing silica and made of an inorganic-containing microporous film.
In addition, it has been proposed to use a low dielectric constant liquid crystal polymer as a base material as a low dielectric constant insulating adhesive film (for example, see Patent Document 4).
Further, in Patent Document 5, in order to obtain a pressure-sensitive adhesive layer having a relative dielectric constant of 3.5 or less at a frequency of 100 kHz, an alkyl (meth) acrylate having an alkyl group having 10 to 18 carbon atoms at an ester terminal is 30 to 99. It has been proposed to form a pressure-sensitive adhesive layer containing a (meth) acrylic polymer obtained by polymerizing a monomer component containing 5% by weight and 0.5 to 50% by weight of a cyclic nitrogen-containing monomer.

Recently, in order to improve the operability of electronic devices, smartphones (multifunctional mobile phones that combine the functions of mobile phones and personal digital assistants), tablets, and touch panels with built-in capacitive touch panels Onboard notebook computers and the like are rapidly spreading.
However, since the capacitive touch panel is a sensor that senses changes in the electromagnetic field, it is susceptible to noise, and in order to prevent erroneous recognition of the contact position, a low dielectric constant film is included in the laminated structure. Lamination and provision of a member having a low dielectric constant in a wiring line of a capacitance sensor have been proposed (for example, see Patent Documents 6 and 7).
Patent Document 8 will be described later.

JP-A-11-025757 JP-A-11-288621 JP-A-2006-024473 JP 2003-321659 A JP 2013/082880 A JP 2012-094017 A JP 2013-003758 A JP 2011-162659 A

  By the way, in an optical film or an optical adhesive film used for various kinds of image display such as a PDP, a liquid crystal panel, and an organic EL panel, high transparency is required in order to improve visibility. . However, in the method disclosed in Patent Document 3 in which silica fine particles are mixed to form a hollow structure in a synthetic resin or pressure-sensitive adhesive layer, the particle size of the silica fine particles is adjusted by the wavelength of visible light red light. If it is not smaller than a certain 400 nm (0.4 μm) or less, the total light transmittance is reduced due to light scattering. However, silica fine powder having a particle size of 0.4 μm or less has a problem that it is expensive and therefore cannot be used for manufacturing a general-purpose insulator that needs to be inexpensive because of difficulty in manufacturing.

In addition, the invention described in Patent Document 4 has an object to provide an inexpensive pressure-sensitive adhesive film for electric and electronic insulation, which retains excellent heat resistance, moisture resistance, and dielectric properties. For this reason, the pressure-sensitive adhesive film according to the invention of Patent Document 4 uses a low dielectric constant liquid crystal polymer for the base material, but uses a general silicone pressure-sensitive adhesive for the pressure-sensitive adhesive layer. In addition, the dielectric constant of the pressure-sensitive adhesive film cannot be further reduced to increase the insulating property.
Further, the pressure-sensitive adhesive according to Patent Document 5 has an excellent insulating property with a relative permittivity of 3.5 or less at a frequency of 100 kHz. However, the relative permittivity at around 1 MHz, which is the current main driving frequency of touch panels, is described. It has not been.
Patent Documents 6 and 7 disclose that a low-dielectric-constant film is laminated in the laminated structure and a low-dielectric-constant is provided on a wiring line of a capacitance sensor in order to prevent erroneous recognition of a capacitive touch panel. It is described that a member having a low dielectric constant is provided, but a method of manufacturing a member having a low dielectric constant to be used is not specifically described.

  As described above, in the prior art, a method for producing a pressure-sensitive adhesive film having excellent insulation performance due to a low dielectric constant, a pressure-sensitive adhesive composition, and a pressure-sensitive adhesive film, which can be used for bonding optical members, are not known. Was.

Further, a black frame of a light shielding layer formed by screen printing or the like is provided on the surface of the front glass plate of a general display, and a thickness between the front glass plate and the black frame of the light shielding layer is provided. A step of about several μm to 50 μm is generated. For example, a protective plate of a mobile phone or the like is often provided with a print frame having a thickness of about 10 μm to several tens μm in order to improve design. Also, electrodes for sending current into the touch panel are arranged on the surface of the ITO layer of the touch panel device, and a printed step having a thickness of about several μm to several tens μm is formed in the wiring part by this printing. I have. Thus, when bonding various optical films or protective plates to a display using an adhesive film, or when bonding an ITO layer to another film using an adhesive layer, There are many configurations where a step is present on the surface.
If there is a step on the surface of the adherend due to a printing layer, etc., the adhesive film cannot follow the step, causing bubbles to be trapped by the resulting floating, creating a gap between the adhesive film and the adherend. there were. Various approaches have been conventionally taken to solve this problem. There is a need for a method of producing a pressure-sensitive adhesive film, a pressure-sensitive adhesive composition, and a pressure-sensitive adhesive film that overcome the above requirements and problems.
As a method of improving the followability to the printing step, there is known a method of lowering the storage elastic modulus of the pressure-sensitive adhesive layer as in the pressure-sensitive adhesive film according to Patent Document 8. However, when the storage elastic modulus of the pressure-sensitive adhesive layer is lowered, the pressure-sensitive adhesive layer is likely to be deformed, and the adherend may be fixed for a long period of time, and the shape of the pressure-sensitive adhesive layer may not be maintained. .

  The present invention has been made in view of the above circumstances, and despite being a pressure-sensitive adhesive composition containing only an acrylic monomer having a general structure as a main component, has a low dielectric constant and is excellent. An object of the present invention is to provide a method for producing a pressure-sensitive adhesive film, a pressure-sensitive adhesive composition, and a pressure-sensitive adhesive film having improved insulating performance, followability to a printing step, and excellent shape retention.

In order to solve the above problems, the present invention has an acrylic polymer and a polyalkylene oxide chain, despite being a pressure-sensitive adhesive composition containing only an acrylic monomer having a general structure as a main component. By containing a vinyl monomer, a photopolymerization initiator, and a crosslinking agent, a pressure-sensitive adhesive layer having excellent insulation performance due to a low dielectric constant, conformability to printing steps, and excellent shape retention. That is the technical idea.
Therefore, the pressure-sensitive adhesive film according to the present invention is used in the form of a pressure-sensitive adhesive film after being cured by heat and before being crosslinked by irradiation of ultraviolet light, and after being bonded to an adherend having a printing step, the light By irradiation, a pressure-sensitive adhesive layer finally crosslinked can be obtained.
An adherend having no printing step can be used in the form of a pressure-sensitive adhesive film having a pressure-sensitive adhesive layer copolymerized and cross-linked by heating and light irradiation.

Further, in order to solve the above problems, the present invention relates to a method for producing an adhesive film used for bonding optical members, comprising the following steps (1) to (3):
Step (1): a step of copolymerizing two or more types of (meth) acrylate monomers other than polyalkylene glycol (meth) acrylate to obtain an acrylic polymer;
Step (2): The total amount of vinyl monomers having one or more polyalkylene oxide chains selected from the group consisting of polyalkylene glycol (meth) acrylates is defined as 0.1 with respect to a total of 100 g of the acrylic polymer. A step of preparing a pressure-sensitive adhesive composition containing the acrylic polymer, the vinyl monomer having a polyalkylene oxide chain, a photopolymerization initiator, and a crosslinking agent in a ratio of 1 to 20 mol,
Step (3): After applying the pressure-sensitive adhesive composition to one surface of a release film prepared in advance, the pressure-sensitive adhesive layer having a relative dielectric constant of 3.5 or less at a frequency of 1 MHz is heated and copolymerized. Forming an adhesive film having a configuration of release film / the pressure-sensitive adhesive layer / release film;
And a method for producing a pressure-sensitive adhesive film.

Further, the present invention is a method for producing an adhesive film used for bonding optical members, comprising the following steps (1) to (3):
Step (1): a step of copolymerizing two or more types of (meth) acrylate monomers other than polyalkylene glycol (meth) acrylate to obtain an acrylic polymer;
Step (2): The total amount of vinyl monomers having one or more polyalkylene oxide chains selected from the group consisting of polyalkylene glycol (meth) acrylates is defined as 0.1 with respect to a total of 100 g of the acrylic polymer. A step of preparing a pressure-sensitive adhesive composition containing the acrylic polymer, the vinyl monomer having a polyalkylene oxide chain, a photopolymerization initiator, and a crosslinking agent in a ratio of 1 to 20 mol,
Step (3): An adhesive layer having a relative dielectric constant of 3.5 or less at a frequency of 1 MHz after the adhesive composition is applied to one surface of a base film prepared in advance and then heated and copolymerized. Forming a pressure-sensitive adhesive film,
And a method for producing a pressure-sensitive adhesive film.

  Further, it is preferable that the pressure-sensitive adhesive composition is cross-linked by irradiating the pressure-sensitive adhesive film with light.

Further, the polyalkylene glycol (meth) acrylate has the following general formula (1)
CH ₂ ＣC (R ¹ ) —COO— (R ² —O) _n —R ³ (1)
(Wherein, R ¹ represents a hydrogen atom or a methyl group, R ² represents an alkylene group having 2 to 4 carbon atoms, R ³ represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and n represents 1 to 23. Is preferably an integer.

  In addition, the two or more (meth) acrylate monomers are selected from a group of copolymerizable vinyl monomer compounds having any one of an alkyl group, a hydroxyl group, a carboxyl group, an amide group, an imide group, and an aromatic group. It is preferred that it be done.

  The present invention also relates to a pressure-sensitive adhesive composition formed by copolymerization and crosslinking, which constitutes a pressure-sensitive adhesive layer for a pressure-sensitive adhesive film used for bonding optical members, wherein two types other than polyalkylene glycol (meth) acrylate are used. One or two or more polyalkylene oxides selected from the group of polyalkylene glycol (meth) acrylate compounds are added to a total of 100 g of the acrylic polymer obtained by copolymerizing the above (meth) acrylate monomer. A pressure-sensitive adhesive composition comprising the acrylic polymer, the vinyl monomer having a polyalkylene oxide chain, a photopolymerization initiator, and a cross-linking agent in a ratio of a total of 0.1 to 20 mol of a vinyl monomer having a chain. The present invention provides a pressure-sensitive adhesive composition obtained by copolymerizing and crosslinking a product.

Further, the polyalkylene glycol (meth) acrylate has the following general formula (1)
CH ₂ ＣC (R ¹ ) —COO— (R ² —O) _n —R ³ (1)
(Wherein, R ¹ represents a hydrogen atom or a methyl group, R ² represents an alkylene group having 2 to 4 carbon atoms, R ³ represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and n represents 1 to 23. Is preferably an integer.

  In addition, the two or more (meth) acrylate monomers are selected from a group of copolymerizable vinyl monomer compounds having any one of an alkyl group, a hydroxyl group, a carboxyl group, an amide group, an imide group, and an aromatic group. It is preferred that it be done.

  In addition, it is preferable that the total of the alkyl (meth) acrylate compound group is 50 parts by weight or more based on 100 parts by weight of the total amount of all the monomers.

  The present invention also provides a pressure-sensitive adhesive film in which a pressure-sensitive adhesive layer comprising the pressure-sensitive adhesive composition is formed on one surface of a release film, and has a structure of release film / the pressure-sensitive adhesive layer / release film. .

  The present invention also provides a pressure-sensitive adhesive film in which a pressure-sensitive adhesive layer comprising the pressure-sensitive adhesive composition is formed on one surface of a base film.

  Further, the pressure-sensitive adhesive layer preferably has a relative dielectric constant at a frequency of 1 MHz of 3.5 or less.

  According to the present invention, it overcomes the conventional requirements and problems, and despite having a pressure-sensitive adhesive composition containing only an acrylic monomer having a general structure, has excellent insulation performance due to a low dielectric constant. In addition, it is possible to provide a method for producing a pressure-sensitive adhesive film, a pressure-sensitive adhesive composition, and a pressure-sensitive adhesive film having excellent followability to a printing step and excellent shape retention.

Hereinafter, the present invention will be described based on preferred embodiments.
The method for producing a pressure-sensitive adhesive film of the present invention comprises the following steps (1) to (3);
Step (1): a step of copolymerizing two or more types of (meth) acrylate monomers other than polyalkylene glycol (meth) acrylate to obtain an acrylic polymer;
Step (2): The total amount of vinyl monomers having one or more polyalkylene oxide chains selected from the group consisting of polyalkylene glycol (meth) acrylates is defined as 0.1 with respect to a total of 100 g of the acrylic polymer. A step of preparing a pressure-sensitive adhesive composition containing the acrylic polymer, the vinyl monomer having a polyalkylene oxide chain, a photopolymerization initiator, and a crosslinking agent in a ratio of 1 to 20 mol,
Step (3): After coating the pressure-sensitive adhesive composition on one side of a film prepared in advance, heat and copolymerize to form a pressure-sensitive adhesive layer having a relative dielectric constant of 3.5 or less at a frequency of 1 MHz. And a step of producing an adhesive film,
In order. Here, the film used in the step (3) may be a base film or a release film.

  The pressure-sensitive adhesive layer of the present invention comprises a polyalkylene glycol (100 g) based on a total of 100 g of an acrylic polymer obtained by copolymerizing two or more types of (meth) acrylate monomers other than polyalkylene glycol (meth) acrylate. The acrylic polymer and the polyalkylene oxide chain in such a proportion that the total of one or more vinyl monomers having one or more polyalkylene oxide chains selected from the group of compounds of (meth) acrylate is 0.1 to 20 mol; The composition is characterized in that a pressure-sensitive adhesive composition containing a vinyl monomer having the following formula, a photopolymerization initiator, and a crosslinking agent is copolymerized and crosslinked.

The polyalkylene glycol (meth) acrylate having a polyalkylene oxide chain used as a raw material of the pressure-sensitive adhesive layer according to the present invention has a function of remarkably reducing the relative dielectric constant. Although it is not clear why the relative permittivity is significantly reduced when an acrylic polymer contains polyalkylene glycol (meth) acrylate and is further copolymerized and crosslinked, one of the reasons is as follows. It is thought that it is.
(1) The pressure-sensitive adhesive layer according to the present invention is obtained by copolymerizing and cross-linking a pressure-sensitive adhesive composition containing an acrylic polymer and polyalkylene glycol (meth) acrylate. In the acrylic copolymer after copolymerization and crosslinking, a large number of polyalkylene oxide chains (herein, abbreviated as "whiskers") are extended as side chains. For this reason, the acrylic copolymer (polymer) does not only extend long in the length direction but also extends in the width direction perpendicular to the length direction. It has a certain shape. In other words, having a dumpling-like structure that is hardly polarized even when a high-frequency charge is applied reduces the relative dielectric constant.
(2) In addition, a large number of "whiskers" extending as side chains of the acrylic copolymer (polymer) interfere with each other, so that the skeleton portions of the acrylic copolymer (polymer) approach each other. The pressure-sensitive adhesive layer, in which the acrylic copolymer is crosslinked, generates fine voids composed of a large number of air layers to reduce the relative dielectric constant.

The polyalkylene glycol (meth) acrylate selected as a vinyl monomer having a polyalkylene oxide chain (monomer B) includes, as the polyalkylene glycol (meth) acrylate, a repeating structure of a polyalkylene oxide chain such as an ethylene oxide chain, a propylene oxide chain, or a butylene oxide chain. Compounds having one or two or more types are exemplified.
The polyalkylene glycol (meth) acrylate represented by the formula (1) is a monofunctional (meth) acrylate having one (meth) acryloyl group represented by CH ₂ ＣC (R ¹ ) —CO— per molecule. ) Acrylate. A compound having a (meth) acryloyl group at one end of an alkylene oxide chain, or (meth) at one end of an alkylene oxide chain in which an ethylene oxide chain, a propylene oxide chain, a butylene oxide chain, or the like is bonded at random or in a block. Any compound having an acryloyl group may be used.

The polyalkylene glycol (meth) acrylate has the following general formula (1)
CH ₂ ＣC (R ¹ ) —COO— (R ² —O) _n —R ³ (1)
(Wherein, R ¹ represents a hydrogen atom or a methyl group, R ² represents an alkylene group having 2 to 4 carbon atoms, R ³ represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and n represents 1 to 23. Is preferably an integer.

  The polyalkylene glycol (meth) acrylate is preferably a (meth) acrylate monomer having an ethylene oxide chain, a propylene oxide chain, or a butylene oxide chain, and having a repeating number of 2 to 23.

  More preferably, it is a polyalkylene glycol (meth) acrylate having 5 to 23 polyalkylene oxide chains. With a polyalkylene glycol (meth) acrylate in which the number of repeating polyalkylene oxide chains is less than 2, it is difficult to reduce the relative dielectric constant at a frequency of 1 MHz to 3.5 or less. Further, in the polyalkylene glycol (meth) acrylate in which the number of repetitions of the polyalkylene oxide chain exceeds 23, the relative dielectric constant at a frequency of 1 MHz hardly decreases as compared with a compound in which the number of repetitions is 23 or less. .

Examples of the polyalkylene glycol (meth) acrylate monomer having a polyethylene oxide chain include methoxy polyethylene glycol (meth) acrylate, ethoxy polyethylene glycol (meth) acrylate, and polyethylene glycol (meth) acrylate.
Examples of the polyalkylene glycol (meth) acrylate monomer having a polypropylene oxide chain include methoxy polypropylene glycol (meth) acrylate, ethoxy polypropylene glycol (meth) acrylate, and polypropylene glycol (meth) acrylate.
Examples of the polyalkylene glycol (meth) acrylate monomer having a polybutylene oxide chain include methoxy polybutylene glycol (meth) acrylate, ethoxy polybutylene glycol (meth) acrylate, and polybutylene glycol (meth) acrylate.
Furthermore, examples of polyalkylene glycol (meth) acrylate monomers having both a polyethylene oxide chain and a polypropylene oxide chain include polyethylene glycol and polypropylene glycol (meth) acrylate.

Specific examples of commercially available polyalkylene glycol (meth) acrylates having a polyalkylene oxide chain include the following.
For example, as brand names of Shin-Nakamura Chemical Co., Ltd., NK ester AM30G (methoxypolyethylene glycol acrylate, the number of repeating polyalkylene oxide chains: n = 3), NK ester M40G (methoxypolyethylene glycol methacrylate, n = 4), NK ester AM90G (methoxy polyethylene glycol acrylate, n = 9), NK ester M90G (methoxy polyethylene glycol methacrylate, n = 9), NK ester AM130G (methoxy polyethylene glycol acrylate, n = 13), NK ester AM230G (methoxy polyethylene glycol acrylate) , N = 23).
Moreover, as a brand name of Kyoeisha Chemical Co., Ltd., light acrylate MTG-A (methoxytriethylene glycol acrylate, n = 3), light acrylate 130A (methoxypolyethylene glycol acrylate, n = 9) and the like can be mentioned.
The trade names of NOF Corporation include Blemmer AE-200 (polyethylene glycol acrylate, n = 4.5), Blemmer AE-350 (polyethylene glycol acrylate, n = 8), and Blemmer AE-400 (polyethylene glycol acrylate). , N = 10), Blemmer PE-200 (polyethylene glycol methacrylate, n = 4.5), Blemmer PE-350 (polyethylene glycol methacrylate, n = 8), Blemmer AP400 (polypropylene glycol acrylate, n = 6), Blemmer AP550 (Polypropylene glycol acrylate, n = 9), Blemmer PP-500 (polypropylene glycol methacrylate, n = 9), Blemmer PP-800 (polypropylene glycol meth) Relate, n = 13), Blemmer PP-1000 (polypropylene glycol methacrylate, n = 16), Blemmer AME-400 (methoxypolyethylene glycol acrylate, n = 9), Blemmer PME-200 (methoxypolyethylene glycol methacrylate, n = 4) And Blemmer PME-400 (methoxypolyethylene glycol methacrylate, n = 9), and Blemmer PME-1000 (methoxypolyethylene glycol methacrylate, n = 23).
The trade names of Osaka Organic Chemical Industry Co., Ltd. include MPE400A (methoxypolyethylene glycol acrylate, n = about 7), MPE550A (methoxypolyethylene glycol acrylate, n = about 9) and the like.

In the pressure-sensitive adhesive layer according to the present invention, the content of the polyalkylene glycol (meth) acrylate in the acrylic monomer of the pressure-sensitive adhesive composition (total 100 g) is 0.1 to 20 mol. A range is preferred. More preferably, it is 0.1 to 15 mol. When the content ratio of the polyalkylene glycol (meth) acrylate is less than 0.1 mol, the effect of reducing the relative dielectric constant of the pressure-sensitive adhesive layer is small, and it is difficult to reduce the relative dielectric constant of the pressure-sensitive adhesive layer to 3.5 or less. . On the other hand, if the content of the polyalkylene glycol (meth) acrylate exceeds 20 mol, the viscosity of the pressure-sensitive adhesive composition becomes too high, and the copolymerization reaction becomes difficult, which is not preferable.
In addition, if the content ratio of the polyalkylene glycol (meth) acrylate in the entirety of the acrylic monomer in the pressure-sensitive adhesive composition (assuming that the content was 100 g) was in the range of 0.1 to 20 mol, the composition was thermally cured. Later, when the storage elastic modulus (unit Pa) at 30 ° C. of the pressure-sensitive adhesive layer before being crosslinked by irradiation with ultraviolet rays is expressed as K1, K1 is in the range of 2 × 10 ⁴ to 1 × 10 ⁵ Pa. An agent layer is obtained.
As a result, a pressure-sensitive adhesive layer and a pressure-sensitive adhesive film having excellent ability to follow a printing step and excellent shape retention can be obtained. If the shape retention of the pressure-sensitive adhesive layer is excellent, the bonded state of the adherend (original position) between the adherends on both sides of the pressure-sensitive adhesive layer (or between the base film and the adherend) Relationship) can be maintained. And the shape of the device manufactured by laminating the pressure-sensitive adhesive layer can be retained. Further, if K1 exceeds 1 × 10 ⁵ Pa, the pressure-sensitive adhesive layer is unlikely to be deformed at the time of bonding, so that there is no followability to the printing step, and a gap is formed at the printing step.
When the storage elastic modulus (unit Pa) at 30 ° C. of the pressure-sensitive adhesive layer after being cross-linked by ultraviolet irradiation is expressed as K2, if K2 is smaller than 3 × 10 ⁵ Pa, the pressure-sensitive adhesive layer is deformed. And the adherend cannot be fixed for a long period of time or the shape of the pressure-sensitive adhesive layer cannot be maintained.

  The acrylic polymer (polymer A) according to the present invention is obtained by copolymerizing two or more types of (meth) acrylate monomers (monomer A) other than polyalkylene glycol (meth) acrylate. The monomer A is preferably selected from a group of compounds of copolymerizable vinyl monomers having any one of an alkyl group, a hydroxyl group, a carboxyl group, an amide group, an imide group, and an aromatic group. The polymer A is preferably a polymer having no polyalkylene oxide chain in a side chain.

Examples of the alkyl (meth) acrylate monomer having a C1 to C14 alkyl group include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, butyl (meth) acrylate, and isobutyl. (Meth) acrylate, pentyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, octyl (meth) acrylate, isooctyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, nonyl (meth) acrylate, isononyl (Meth) acrylate, decyl (meth) acrylate, undecyl (meth) acrylate, dodecyl (meth) acrylate, tridecyl (meth) acrylate, tetradecyl (meth) acrylate , Cyclopentyl (meth) acrylate, and at least one kind such as cyclohexyl (meth) acrylate. The alkyl group of the alkyl (meth) acrylate monomer may be linear, branched, or cyclic.
In the pressure-sensitive adhesive layer according to the present invention, the alkyl (meth) acrylate monomer having an alkyl group having 1 to 14 carbon atoms is contained in the pressure-sensitive adhesive composition in an amount of 95 to 100 parts by weight of the acrylic monomer in total. It is preferably from 0.5 to 25 parts by weight.

Other copolymerizable monomers include vinyl monomers such as vinyl acetate, vinyl propionate, styrene, α-methylstyrene, N-vinylcaprolactam, and N-vinylpyrrolidone; polyethylene glycol (meth) acrylate, (meth) acrylic acid Glycol-based acrylic ester monomers such as polypropylene glycol, methoxyethylene glycol (meth) acrylate, and methoxypolypropylene glycol (meth) acrylate; tetrahydrofurfuryl (meth) acrylate, fluorine (meth) acrylate, silicone (meth) acrylate and 2 Acrylic acid ester monomers such as -methoxyethyl acrylate; amide group-containing monomers, amino group-containing monomers, imide group-containing monomers, and nitrogen-containing monomers such as N-acryloylmorpholine; Such as alkenyl ether monomers may also be used.
Among them, in order to adjust the cohesive force of the pressure-sensitive adhesive, a nitrogen-containing monomer such as a vinyl monomer having an amide group having no active hydrogen and a vinyl monomer having an amino group having no active hydrogen is contained as necessary. can do. Here, “active hydrogen” means a hydrogen atom bonded to an atom other than carbon, such as oxygen or nitrogen.

  Examples of the nitrogen-containing monomer having no active hydrogen include cyclic nitrogen vinyl compounds such as N-vinylpyrrolidone, N-vinylcaprolactam, (meth) acryloylmorpholine, N-ethyl-N-methyl (meth) acrylamide, N-methyl- N-propyl (meth) acrylamide, N-methyl-N-isopropyl (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, N, N-dipropyl (meth) acrylamide, Dialkyl-substituted (meth) acrylamide such as N, N-diisopropyl (meth) acrylamide, N, N-dibutyl (meth) acrylamide, N-ethyl-N-methylaminoethyl (meth) acrylate, N-methyl-N-propylamino Ethyl (meth) acrylate, N Methyl-N-isopropylaminoethyl (meth) acrylate, N, N-dimethylaminomethyl (meth) acrylate, N, N-dimethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylate, N, Dialkylamino (meth) acrylates such as N-dimethylaminobutyl (meth) acrylate, N, N-dipropylaminoethyl (meth) acrylate, N, N-dibutylaminoethyl (meth) acrylate, N-ethyl-N-methyl Aminopropyl (meth) acrylamide, N-methyl-N-propylaminopropyl (meth) acrylamide, N-methyl-N-isopropylaminopropyl (meth) acrylamide, N, N-dimethylaminopropyl (meth) acrylamide, N, N -Diethyla Dialkyl-substituted aminoalkyl (meth) such as nopropyl (meth) acrylamide, N, N-dipropylaminopropyl (meth) acrylamide, N, N-dimethylaminoethyl (meth) acrylamide, N, N-diethylaminoethyl (meth) acrylamide At least one kind such as acrylamide may be used.

As the nitrogen-containing monomer, a monomer containing no active hydrogen is preferable, and a monomer not containing a hydroxyl group and a carboxyl group is more preferable in order to be distinguishable from a vinyl monomer having a hydroxyl group described below. Examples of such a monomer include the monomers exemplified above, for example, an acrylic monomer containing an N, N-dialkyl-substituted amino group or an N, N-dialkyl-substituted amide group; N-vinylpyrrolidone, N-vinylcaprolactam, and the like. N-vinyl-substituted lactams; N- (meth) acryloyl-substituted cyclic amines such as N- (meth) acryloylmorpholine are preferred.
In the pressure-sensitive adhesive layer according to the present invention, the vinyl monomer having an amide group to be contained in the pressure-sensitive adhesive composition includes N-vinylpyrrolidone, N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) Acrylamide, N, N-dipropyl (meth) acrylamide, N, N-diisopropyl (meth) acrylamide, N, N-dibutyl (meth) acrylamide, N, N-dimethylaminopropyl (meth) acrylamide, N, N-diethylaminopropyl (Meth) acrylamide, N, N-dimethylaminoethyl (meth) acrylamide, N-vinylcaprolactam and the like are particularly preferably used.

  In the pressure-sensitive adhesive layer according to the present invention, the nitrogen-containing monomer having no active hydrogen contained in the pressure-sensitive adhesive composition can impart necessary pressure-sensitive adhesive strength and durability to the pressure-sensitive adhesive layer. For this reason, for applications in which the adhesive layer is required to have a large adhesive force with the adherend, the content ratio of the nitrogen-containing monomer having no active hydrogen, like the carboxyl group-containing monomer, should be adjusted. Thereby, the adhesive strength can be adjusted. Further, when it is not preferable to contain a carboxyl group-containing monomer, for example, when the adherend is an ITO transparent conductive film, a nitrogen-containing monomer having no active hydrogen is used instead of the corrosive carboxyl group-containing monomer. Can be used to adjust the adhesion.

Examples of the hydroxyl group-containing copolymerizable vinyl monomer (hydroxyl group-containing monomer) include 8-hydroxyoctyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, and 2-hydroxyoctyl (meth) acrylate. Hydroxyalkyl (meth) acrylates such as hydroxyethyl (meth) acrylate and 2-hydroxypropyl (meth) acrylate, N-hydroxy (meth) acrylamide, N-hydroxymethyl (meth) acrylamide, N-hydroxyethyl (meth) At least one kind of (meth) acrylamides containing a hydroxyl group such as acrylamide can be used. In the present invention, 2-hydroxyethyl (meth) acrylate and 4-hydroxybutyl (meth) acrylate are preferred.
In addition, in the pressure-sensitive adhesive layer according to the present invention, the hydroxyl group-containing monomer contained in the pressure-sensitive adhesive composition affects the corrosiveness of the obtained pressure-sensitive adhesive layer on easily adherent adherends such as the ITO surface of the transparent conductive film. Can be used as a copolymerizable monomer for reducing the content of a carboxyl group-containing monomer. Therefore, the hydroxyl group-containing monomer can help to improve the adhesive strength of the pressure-sensitive adhesive layer and reduce corrosiveness.

As the carboxyl group-containing copolymerizable vinyl monomer (carboxyl group-containing monomer), for example, (meth) acrylic acid, carboxyethyl (meth) acrylate, carboxypentyl (meth) acrylate, 2- (meth) acryloyloxyethyl Hexahydrophthalic acid, 2- (meth) acryloyloxypropyl hexahydrophthalic acid, 2- (meth) acryloyloxyethyl phthalic acid, 2- (meth) acryloyloxyethyl succinic acid, 2- (meth) acryloyl At least one or more of roxyethylmaleic acid, carboxypolycaprolactone mono (meth) acrylate, 2- (meth) acryloyloxyethyltetrahydrophthalic acid and the like can be mentioned. In the present invention, (meth) acrylic acid is preferred.
In the pressure-sensitive adhesive layer according to the present invention, the carboxyl group-containing monomer contained in the pressure-sensitive adhesive composition can impart necessary cohesive force to the pressure-sensitive adhesive layer. Therefore, for applications where the pressure-sensitive adhesive layer is required to have a large adhesive force with the adherend, the adhesive force can be adjusted by adjusting the content ratio of the carboxyl group-containing monomer.

Further, in the pressure-sensitive adhesive layer according to the present invention, one or two or more selected from a compound group of copolymerizable vinyl monomers having at least one functional group among a hydroxyl group and a carboxyl group. The total amount of the copolymerizable vinyl monomer (functional group-containing copolymerizable monomer) is preferably 0.5 to 15 parts by weight based on 100 parts by weight of the acrylic monomer in total.
The functional group-containing copolymerizable monomer is preferably 0.5% by weight or more based on 100 parts by weight of the total amount of the acrylic monomer component from the viewpoint of maintaining the adhesive force and the cohesive force. On the other hand, if the amount of the functional group-containing copolymerizable monomer is too large, the pressure-sensitive adhesive is hardened, the adhesive strength may be reduced, and the viscosity of the pressure-sensitive adhesive composition may be too high or may be gelled. For this reason, the content of the functional group-containing copolymerizable monomer is preferably 15% by weight or less based on 100 parts by weight of the total of the acrylic monomer component.

  Examples of the copolymerizable vinyl monomer having an amide group include (meth) acrylates having an amide group such as N- [2- (acryloyloxy) ethyl] acetamide and (meth) acrylamides.

  Examples of the copolymerizable vinyl monomer having an imide group include (meth) acrylates having an imide group such as N- [2- (acryloyloxy) ethyl] phthalimide.

  Examples of the copolymerizable vinyl monomer having an aromatic group include (meth) acrylates having an aromatic group such as phenyl (meth) acrylate, benzyl (meth) acrylate, and phenoxyethyl (meth) acrylate, as well as styrene and α-methyl. Non-acrylic vinyl monomers having an aromatic group such as styrene are exemplified.

The polymerization method of the polymer A is not particularly limited, and a known polymerization method such as a solution polymerization method or an emulsion polymerization method can be appropriately used. The weight average molecular weight of the polymer A is preferably 200,000 to 2,000,000.
The monomer composition of the polymer A may include 50 to 100 parts by weight of an acrylic monomer such as a (meth) acrylate monomer, (meth) acrylic acid, or (meth) acrylamide with respect to 100 parts by weight of the polymer A. preferable.

  In the pressure-sensitive adhesive composition, required properties such as physical property values can be adjusted by blending a crosslinking agent or an optional additive as appropriate with the polymer A and the monomer B. A pressure-sensitive adhesive composition containing a polymer A, a monomer B, a photopolymerization initiator, and a cross-linking agent is prepared in such a manner that the total amount of the monomers B is 0.1 to 20 mol per 100 g of the polymer A. Is preferred. According to the present invention, the monomer B is added to the polymer A which is a general acrylic pressure-sensitive adhesive later, the monomer B is copolymerized with the polymer A by heating, and further cross-linked by irradiation with ultraviolet rays. In other words, while producing a general adhesive product (using a general-purpose adhesive), the monomer B is added only when "an adhesive product requiring low dielectric constant performance is produced", and the effect is exhibited. be able to. Therefore, it is possible to produce an adhesive product having a low dielectric constant without having a stock of "adhesives dedicated to adhesive products having a low dielectric constant", which is advantageous in terms of cost and management. Further, by simply adding the monomer B and the photoinitiator to the conventionally used adhesive, an adhesive having a low dielectric constant can be obtained. Further, the relative dielectric constant can be controlled by changing the type and amount of the monomer B to be added to the solid content of the pressure-sensitive adhesive. Rather than simply lowering the relative permittivity, there is a possibility that a product tailored to a desired relative permittivity can be produced.

As a crosslinking agent, for example, hexamethylene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, tolylene diisocyanate, buret modified isocyanates such as xylylene diisocyanate and isocyanurate modified, trimethylolpropane and tri- or more trivalent such as glycerin Examples include at least one or more of a polyisocyanate compound such as an adduct with a polyol, a metal-based chelate compound, and an epoxy compound. The pressure-sensitive adhesive may be cross-linked by photo-crosslinking such as ultraviolet rays.
When the acrylic copolymer is cross-linked using a cross-linking agent, the acrylic copolymer has a functional group capable of cross-linking with the cross-linking agent (such as a hydroxyl group or a carboxyl group depending on the type of the cross-linking agent). Further, it is preferable to include a monomer having these functional groups in the side chain. Further, it is preferable that the pressure-sensitive adhesive composition contains 0.01 to 5 parts by weight of a crosslinking agent with respect to 100 parts by weight of the acrylic monomer in total.

  Other optional components include a silane coupling agent, an antioxidant, a surfactant, a curing accelerator, a plasticizer, a filler, a crosslinking catalyst, a crosslinking retarder, a curing retarder, a processing aid, an antioxidant, and the like. Known additives can be appropriately blended. These may be used alone or in combination of two or more. In the application of electrical insulation, it is preferable that the pressure-sensitive adhesive does not contain an ionic compound such as an alkali metal salt, an alkaline earth metal salt, or a quaternary onium salt, a metal, a conductor such as carbon, or an antistatic agent. .

The pressure-sensitive adhesive layer of the present invention can be obtained by applying the pressure-sensitive adhesive composition to a base film or a release film and then crosslinking the pressure-sensitive adhesive composition.
When the pressure-sensitive adhesive layer according to the present invention is used as a low-dielectric-constant electric insulating material corresponding to a higher frequency of an electronic / electric device, the relative permittivity of the pressure-sensitive adhesive layer at a frequency of 1 MHz is 3.5 or less. Is preferable, and it is more preferable that it is 3.0 or less.
In the pressure-sensitive adhesive composition formed by copolymerization and crosslinking, which constitutes the pressure-sensitive adhesive layer for a pressure-sensitive adhesive film, the total of the alkyl (meth) acrylate compounds is 50 parts by weight or more based on 100 parts by weight of the total amount of all monomers. It is preferred that By increasing the proportion of the low-polarity alkyl (meth) acrylate, the relative dielectric constant can be further reduced.

The thickness of the pressure-sensitive adhesive layer of the present invention is not particularly limited, and is about 5 to 400 μm. For example, when the adhesive layer for electronic insulation of the present invention is used for a capacitive touch panel, the relative permittivity ε _r of the adhesive layer and the thickness (adhesive thickness) d of the adhesive layer are _{expressed by the following} equation. As a result, the sensor responsiveness of the capacitive touch panel changes, so that it is necessary to control the relative permittivity and the adhesive thickness according to the design of the electronic device to be mounted. In recent years, there has been a demand for thinner electronic devices and touch panels, and there has been an increasing demand for thinner pressure-sensitive adhesive layers that are constituent members. By using the pressure-sensitive adhesive layer of the present invention, sensitivity equivalent to the case of using the conventional pressure-sensitive adhesive layer can be realized with a small pressure-sensitive adhesive thickness.
In addition, when importance is placed on preventing malfunction, replacing the conventional pressure-sensitive adhesive layer with the pressure-sensitive adhesive layer of the present invention can improve the response speed and sensitivity of the touch panel.

_{Formula: C = ε r · ε 0} · A / d

C: capacitance, ε _r : relative dielectric constant of the pressure-sensitive adhesive layer, ε ₀ : dielectric constant of space (vacuum), A: area, d: thickness of the pressure-sensitive adhesive layer.

When the pressure-sensitive adhesive layer according to the present invention is used for bonding between layers of an optical member or the like, in order to reduce reflection of light rays at the interface between the pressure-sensitive adhesive layer and the optical member, it is desirable that the difference in refractive index be as small as possible. . For this reason, the refractive index of the pressure-sensitive adhesive layer is preferably from 1.47 to 1.50.
The adhesive strength of the pressure-sensitive adhesive layer according to the present invention can be adjusted by adjusting the composition of the pressure-sensitive adhesive according to the purpose of sticking to the adherend. ２０20 N / 25 mm.

The pressure-sensitive adhesive film of the present invention can be produced by forming the pressure-sensitive adhesive layer of the present invention on one surface of a substrate or a release film.
As the base film used for forming the pressure-sensitive adhesive layer or the release film (separator) for protecting the pressure-sensitive adhesive surface, a resin film such as a polyester film can be used.
On the base film, on the surface opposite to the side where the adhesive layer of the resin film is formed, silicone-based, fluorine-based release agent or coating agent, antifouling treatment with silica fine particles, application of an antistatic agent, An antistatic treatment such as kneading can be performed.

The release film is subjected to a release treatment with a silicone-based or fluorine-based release agent on the surface of the pressure-sensitive adhesive layer that is to be fitted with the adhesive surface.
A configuration of “release film / pressure-sensitive adhesive layer / release film” can also be obtained by matching both surfaces of one pressure-sensitive adhesive layer with the release-treated surfaces of the release film. In this case, the release films on both sides are peeled off sequentially or simultaneously to expose the adhesive surface, so that the release films can be bonded to an optical member such as an optical film. Optical films include cover glass, ITO glass, ITO film, transparent conductive films made of conductive polymers, transparent conductive films made of nano silver wires, transparent conductive films made of carbon nanotubes, polarizing films, retardation films, and ultraviolet absorption. Films, optical compensation films, and the like.

The adhesive film of the present invention can be used for bonding a touch panel and a display panel. Examples of the display panel include a liquid crystal display device and an organic EL, but are not limited thereto. In addition, it can be used as an electrical insulating material for bonding an electric member, an electronic circuit member, and the like.
Further, the adhesive film of the present invention includes various optical films for touch panels, various optical films for peripheral members of liquid crystal display devices mainly including polarizing plates, various optical films for electronic paper, various optical films for organic EL, and the like. Can be used for bonding.
Further, an optical film with a pressure-sensitive adhesive layer obtained by laminating the pressure-sensitive adhesive layer on at least one surface of these optical films can be provided. Specifically, “optical film / adhesive layer / optical film”, “optical film / adhesive layer / release film”, “optical film / adhesive layer”, “optical film / adhesive layer / optical film / Pressure-sensitive adhesive layer / optical film "," optical film / pressure-sensitive adhesive layer / optical film / pressure-sensitive adhesive layer / release film "," release film / pressure-sensitive adhesive layer / optical film / pressure-sensitive adhesive layer / release film ", etc. Configuration.
For example, in the case of having an adhesive layer protected by a release film, such as “optical film / adhesive layer / release film”, the release film is peeled off, and the optical film / adhesive layer is removed. By exposing the pressure-sensitive adhesive layer and bonding it to another optical film, a structure such as “optical film / pressure-sensitive adhesive layer / optical film” in which the pressure-sensitive adhesive layer is used for bonding between layers can be obtained.
The pressure-sensitive adhesive film of the present invention, after the heat-curing of the pressure-sensitive adhesive layer, and before irradiation with ultraviolet light, peeled off the release film on one side or both sides of the pressure-sensitive adhesive layer to expose the pressure-sensitive adhesive layer. The adhesive layer can be crosslinked and used by irradiating with an adherend (optical member or the like) having a printing step and then irradiating ultraviolet rays. Thereby, an optical member with a pressure-sensitive adhesive layer can be manufactured.

  Hereinafter, the present invention will be described specifically with reference to examples.

[Example 1]
Nitrogen gas was introduced into a reactor equipped with a stirrer, thermometer, reflux condenser, and nitrogen inlet tube, and the air in the reactor was replaced with nitrogen gas. Thereafter, a solvent (ethyl acetate) was added to the reactor together with 63 g of butyl acrylate, 32 g of methyl acrylate, and 5 g of 2-hydroxyethyl acrylate. Thereafter, azobisisobutyronitrile as a polymerization initiator was added dropwise over 2 hours and reacted by heating to obtain an acrylic polymer solution having a weight average molecular weight of 230,000 used in Example 1.
0.026 mol of ethylene glycol dimethacrylate (1G), 0.84 g of crosslinking agent A, which is an isocyanate crosslinking agent, and alkylphenone-based photopolymerization were initiated with respect to the acrylic polymer solution of Example 1 produced as described above. 0.03 g of the additive D was added and mixed with stirring to obtain a pressure-sensitive adhesive composition of Example 1. The adhesive composition is applied on a release film made of a polyethylene terephthalate (PET) film coated with a silicone resin so that the thickness after drying is 50 μm, and then dried at 90 ° C. to remove the solvent. did. After aging for 7 days in an atmosphere of 40 ° C. and 50% RH, the composition is heated and copolymerized, whereby the pressure-sensitive adhesive composition is heat-cured, and the release film / pressure-sensitive adhesive layer / release film An adhesive film of Example 1 having the structure was obtained.
[Examples 2 to 9 and Comparative Examples 1 to 4]
Except that the compositions of the monomer and the additive are as described in Tables 1, 3, and 4, respectively, the adhesive films of Examples 2 to 9 and Comparative Examples 1 to 4 were manufactured in the same manner as the adhesive film of Example 1 above. A film was obtained. The “monomer composition” in Tables 1, 3, and 4 is a breakdown of the monomers constituting 100 g of the “acrylic pressure-sensitive adhesive”. The measurement results and test results described in Tables 1 to 4 will be described later.

  Table 5 shows the contents and names of the components used in Tables 1, 3, and 4.

The mixing ratio of the acrylic polymer (polymer A) and the vinyl monomer having a polyalkylene oxide chain (monomer B) in the pressure-sensitive adhesive compositions of Examples 1 to 9 was such that the polyalkylene oxide chain was added to 100 g of the acrylic polymer. 1.0 to 14.6 mol of a vinyl monomer.
The amounts of the monomers used in the production of 100 g of the acrylic pressure-sensitive adhesive (1) were 63 g (0.4915 mol) of BA, 32 g (0.3717 mol) of MA, and 5 g (0.0430 mol) of HEA. 0.906 mol.
The amounts of the monomers used for producing 100 g of the acrylic pressure-sensitive adhesive (2) were 97 g (0.5264 mol) of 2EHA and 3 g (0.0258 mol) of HEA, and the total of these monomers was 0.552 mol.
The amount of the monomer used for the production of 100 g of the acrylic pressure-sensitive adhesive (3) was 95 g (0.5155 mol) of 2EHA and 5 g (0.0438 mol) of 4HBA, and the total of these monomers was 0.559 mol.

<Measurement method and measurement result of relative permittivity>
The release film (silicone resin-coated PET film) was peeled off from the adhesive films in Examples 1 to 9 and Comparative Examples 1 to 4 to expose the adhesive layer, and the adhesive layer was transferred to one side of the PET film. did. The relative permittivity of the pressure-sensitive adhesive layer of this sample was measured using an LCR meter (manufactured by Hewlett-Packard Company, model: 4284A).

  Tables 1, 3, and 4 show the measurement results of the relative permittivity.

The pressure-sensitive adhesive films of Examples 1 to 9 had excellent insulating performance due to a low dielectric constant. That is, with the pressure-sensitive adhesive films of Examples 1 to 9, the requirements and problems could be overcome.
The pressure-sensitive adhesive films of Comparative Examples 1, 2, and 4 did not have excellent insulation performance due to a low dielectric constant.
The pressure-sensitive adhesive film of Comparative Example 3 had excellent insulating performance due to a low dielectric constant.

<Test method and test results for followability to printing steps>
A release film (a silicone resin-coated PET film) from the pressure-sensitive adhesive film of Example 2, Example 5, or Comparative Example 1 after heat curing and before irradiation with ultraviolet light. Was peeled off and bonded to a PET film (thickness: 100 μm) under an atmospheric pressure environment. A bonding device (product name SE320) manufactured by Climb Products Co., Ltd. was used for bonding.
From this sample, the release film (PET film coated with silicone resin) on the side of the heavy release surface was peeled off, and the resulting pressure-sensitive adhesive layer with a PET film was applied to an adherend (about 10 μm and about 15 μm in thickness by screen printing). (A PET film having a hard coat treatment on the surface opposite to the print) on which a printing step was formed. After the lamination, of the samples, the appearance of the portion where the pressure-sensitive adhesive layer was laminated to the printing step of the adherend was visually observed. ).

  Table 2 shows a test result of the followability of the pressure-sensitive adhesive layer to the printing step before the ultraviolet irradiation.

  In Example 2 and Example 5, the pressure-sensitive adhesive layer could be bonded without causing air bubbles to enter the printing step. In Comparative Example 1, air bubbles entered the printing step at the time of bonding. This is because, in Comparative Example 1, the crosslinking of the pressure-sensitive adhesive layer had progressed before the irradiation with the ultraviolet light, the resin became hard, and the followability of the pressure-sensitive adhesive layer before the irradiation with the ultraviolet light to the printing step of the adherend was improved. It is considered that it is getting worse.

<Shape retention test method and test results>
A release film (a PET film coated with a silicone resin) from the adhesive film of Example 2, Example 5, or Comparative Example 1 after heat curing and before irradiation with ultraviolet light. Was peeled off and bonded to a PET film (thickness: 100 μm) under an atmospheric pressure environment to obtain a sample for a test for shape retention (measurement of a shift amount). A 2 kg hand roller was used for bonding. The release film (the silicone resin-coated PET film) on the heavy release side was peeled off from the sample of the shape retention test, and the obtained pressure-sensitive adhesive layer with the PET film was adhered to a glass plate under an atmospheric pressure environment. I combined. After bonding, each sample was irradiated with ultraviolet light at 1500 mJ / cm ² to crosslink the adhesive layer. Thereafter, a weight of 1500 g was hung on one end of the PET film, and a shape retention test was performed in a 30 ° C. environment. Twelve hours later, the amount of displacement of the pressure-sensitive adhesive layer between the adherends (PET film and glass plate) was measured with a microscope.

  Table 2 shows the results of the shape retention test.

  In the tests of Example 2 and Example 5, a large "shift amount" of the pressure-sensitive adhesive layer was hardly confirmed. On the other hand, in the test of Comparative Example 1, a "shift amount" of about 6 mm occurred in the pressure-sensitive adhesive layer. Therefore, the pressure-sensitive adhesive film of Comparative Example 1 cannot sufficiently fix the adherends and cannot maintain the shape of the pressure-sensitive adhesive layer (the positional relationship between the adherends).

<Method and result of measurement of storage modulus>
The “storage elastic modulus” means the storage elastic modulus of the pressure-sensitive adhesive layer at 30 ° C. when the viscoelasticity is measured at a rate of temperature rise of 2 ° C./min and a solid shear mode of 1 Hz.
In the present specification, in order to distinguish the storage elastic modulus at 30 ° C. of the pressure-sensitive adhesive layer before cross-linking by ultraviolet irradiation and after cross-linking by ultraviolet irradiation, before and after cross-linking by ultraviolet irradiation, The storage elastic modulus at 30 ° C. of the pressure-sensitive adhesive layer after the above is referred to as K1 and K2, respectively.
In addition, a dynamic viscoelasticity measuring device (product name: Rheogel-E4000) manufactured by UBM was used for measuring the storage elastic modulus.

Table 2 shows the measurement results of the storage elastic modulus. In addition, the measured value of the storage elastic modulus was represented by a method in which “m × 10 ⁿ ” was changed to “mE + 0n” (where m is an arbitrary real number and n is a positive integer).

According to the measurement results of the above storage elastic modulus, the storage elastic modulus at 30 ° C. of the pressure-sensitive adhesive layers of Examples 2, 5 and Comparative Example 1 after being cured by heat and before being crosslinked by ultraviolet irradiation. (K1) was K1 = 6.8 × 10 ⁴ Pa, K1 = 8.2 × 10 ⁴ Pa, and K1 = 1.9 × 10 ⁵ Pa, respectively. In addition, according to the test results of the followability to the printing step, the visual evaluation results of the followability to the adherend having the printing step with the step height of 15 μm in Examples 2, 5 and Comparative Example 1 are respectively: (○), (○), (x).
For this reason, it is preferable that K1 be in the range of 1.0 × 10 ^{4 to} 1.0 × 10 ⁵ Pa as the pressure-sensitive adhesive film having the ability to follow the printing step and excellent shape retention. More preferably, K1 is in the range of 2.0 × 10 ^{4 to} 1.0 × 10 ⁵ Pa.
Further, when K1 exceeds 1.0 × 10 ⁵ Pa, the pressure-sensitive adhesive layer is unlikely to be deformed at the time of bonding, so that there is no followability to the printing step, and air bubbles enter the printing step to form a gap.

In the above measurement results of the storage elastic modulus, the storage elastic modulus (K2) at 30 ° C. of each of the pressure-sensitive adhesive layers of Example 2, Example 5, and Comparative Example 1 after cross-linking by ultraviolet irradiation was respectively K2 = 5.4 × 10 ⁵ Pa, K2 = 4.3 × 10 ⁵ Pa, and K2 = 2.0 × 10 ⁵ Pa.
Generally, as K2 is higher, the pressure-sensitive adhesive layer of the pressure-sensitive adhesive film is less likely to be deformed, and when the pressure-sensitive adhesive film is used, the adherend can be fixed for a long period of time, and the shape of the pressure-sensitive adhesive layer can be maintained. When K2 is smaller than 3.0 × 10 ⁵ Pa, the pressure-sensitive adhesive layer is likely to be deformed, and the adherend cannot be fixed for a long period of time or the shape of the pressure-sensitive adhesive layer cannot be maintained.
In Example 2 and Example 5, K2 is 3.0 × 10 ⁵ Pa or more (furthermore, K2 is 4 × 10 ⁵ Pa or more), and after crosslinking by irradiation of ultraviolet rays (at the time of actual use), In comparison with Comparative Example 1, the pressure-sensitive adhesive layer is less likely to be deformed, and has excellent shape retention.
Therefore, K2 is preferably 3.0 × 10 ⁵ Pa or more, and more preferably K2 is 4 × 10 ⁵ Pa or more.

The pressure-sensitive adhesive layer according to the present invention has excellent insulation performance due to a low dielectric constant, despite the use of a pressure-sensitive adhesive composition containing only an acrylic monomer having a general structure. It can be used for bonding members, electrical members, electronic circuit members and the like. Further, the pressure-sensitive adhesive film according to the present invention can be used as a film for a touch panel or a film for a film display for an electronic paper, and therefore has a great industrial value.
Further, the pressure-sensitive adhesive film according to the present invention has a low storage elastic modulus of the pressure-sensitive adhesive layer before crosslinking by irradiation with ultraviolet light. Lamination can be performed without biting.
In addition, the pressure-sensitive adhesive film according to the present invention has excellent storage stability after crosslinking by ultraviolet irradiation, since the pressure-sensitive adhesive layer has a storage elasticity equivalent to that of a general pressure-sensitive adhesive film, and is excellent in shape retention. It is considered that the problem of deformation of the agent layer hardly occurs.

Claims (3)

An acrylic polymer, a vinyl monomer having a polyalkylene oxide chain, a photopolymerization initiator, and a pressure-sensitive adhesive layer formed by crosslinking a pressure-sensitive adhesive composition containing a crosslinking agent,
Two or more (meth) acrylate monomers selected from the group of copolymerizable vinyl monomers, wherein the acrylic polymer has any one of an alkyl group, a hydroxyl group, a carboxyl group, an amide group, and an aromatic group Is an acrylic polymer obtained by copolymerizing
One or more selected from the group of copolymerizable vinyl monomers having at least one functional group among hydroxyl groups and carboxyl groups, based on 100 parts by weight of the total amount of acrylic monomers. A total of 0.5 to 15 parts by weight of a copolymerizable vinyl monomer (functional group-containing copolymerizable monomer),
For a total of 100 g of the acrylic polymer, a total of at least one kind of the vinyl monomer having the polyalkylene oxide chain is contained in a ratio of 0.1 to 20 mol,
The pressure-sensitive adhesive layer, wherein a relative dielectric constant of the pressure-sensitive adhesive layer at a frequency of 1 MHz is 3.5 or less.   A pressure-sensitive adhesive film, comprising the pressure-sensitive adhesive layer according to claim 1 formed on one surface of a release film, and having a configuration of release film / the pressure-sensitive adhesive layer / release film.   An adhesive film comprising the pressure-sensitive adhesive layer according to claim 1 formed on one surface of a base film.