JP2012162702A - Adhesive tape - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an adhesive tape having high transparency and being excellent in the adhesive force to a polycarbonate plate and an acrylic plate.SOLUTION: The adhesive tape has an adhesive agent layer composed of a copolymer having a structural unit originated from a monomer having a bicyclo structure and one olefinic double bond, a structural unit originated from a (meth)acrylate ester monomer, and a structural unit originated from a high-glass transition temperature monomer which has a glass transition temperature of a homopolymer thereof of ≥60°C, wherein the proportion of the monomer having a bicyclo structure and one olefinic double bond in 100 pts.wt of the whole monomer is 10 to 60 pts.wt; and the proportion of the (meth)acrylate ester monomer in 100 pts.wt of the whole monomer is 30 to 90 pts.wt, and wherein the copolymer has a glass transition temperature of 0 to 25°C.

Description

The present invention has high transparency, excellent adhesion to the polycarbonate plate and the acrylic plate, can suppress floating peeling occurring at the interface with the polycarbonate plate or the acrylic plate even under high temperature conditions, and is easy to handle. It relates to an excellent adhesive tape.

In recent years, display panels or touch panels are used in image display devices such as mobile phones and portable information terminals, or image display devices in various fields. In such an image display device, for example, a protective plate for protecting the surface is bonded to a display panel or a touch panel via a transparent adhesive layer. In general, a plate, an acrylic plate or the like is used.

However, it is known that the polycarbonate plate and the acrylic plate easily absorb moisture, and the moisture is vaporized under high temperature conditions to generate outgas. Therefore, under high temperature conditions, outgassing causes floating and peeling at the interface between the polycarbonate plate or acrylic plate and the pressure-sensitive adhesive layer, resulting in a poor appearance. In order to prevent the appearance defect due to the peeling off, for example, the molecular weight of the acrylic polymer forming the pressure-sensitive adhesive layer is appropriately adjusted, but this method sufficiently suppresses the floating off. It was difficult to obtain a pressure-sensitive adhesive layer.

Further, for example, in Patent Document 1, a transparent double-sided pressure-sensitive adhesive tape or sheet has a transparent pressure-sensitive adhesive layer formed on both surfaces of a transparent substrate, and at least one surface of the transparent substrate. A transparent double-sided pressure-sensitive adhesive tape or sheet in which the formed transparent pressure-sensitive adhesive layer is formed from a pressure-sensitive adhesive composition containing a specific acrylic polymer (a) and an oligomer (b) is described. In Patent Document 1, the acrylic polymer (a) is composed of (meth) acrylic acid alkyl ester having 4 to 12 carbon atoms in the alkyl group as a main monomer component, and all monomer components including a carboxyl group-containing monomer as a monomer component. 3 to 10 parts by weight with respect to 100 parts by weight, and an acrylic polymer having a weight average molecular weight of 500,000 to 900,000, and the oligomer (b) is a homopolymer. An ethylenically unsaturated monomer having a glass transition temperature of 60 to 190 ° C. and having a cyclic structure is used as a main monomer component, and a carboxyl group-containing monomer is used as a monomer component in an amount of 3 to 10 to 100 parts by weight of all monomer components. Further, it is an oligomer having a weight average molecular weight of 3000 to 6000.

Patent Document 1 describes that the transparent double-sided pressure-sensitive adhesive tape or sheet described in the same document is excellent in anti-floating property and further excellent in transparency and warpage prevention property. However, since the transparent double-sided pressure-sensitive adhesive tape or sheet described in Patent Document 1 uses a mixture of two types of polymers or oligomers, it has a problem that the compatibility of the two types of polymers or oligomers is not sufficient and becomes cloudy. Therefore, it has been difficult to realize a sufficiently high transparency to be applied to optical applications.

JP 2005-255877 A

Under high temperature conditions, the floating peeling that occurs at the interface between the polycarbonate plate or acrylic plate and the pressure-sensitive adhesive layer is considered to be caused by outgassing from the polycarbonate plate or acrylic plate, and bubbles growing due to the gas pressure. .
The inventor of the present application can prevent the growth of bubbles at the interface with the polycarbonate plate or the acrylic plate by increasing the adhesion or adhesive force of the adhesive layer to the polycarbonate plate and the acrylic plate, and as a result, suppresses the flaking off. I thought I could do it. As a result of intensive studies, a structural unit derived from a monomer having a bicyclo ring structure and one olefinic double bond in the molecule, and a structural unit derived from a (meth) acrylate monomer having a specific structure It has been found that by using a pressure-sensitive adhesive composition containing the copolymer having, a pressure-sensitive adhesive layer with dramatically improved adhesion to polycarbonate plates and acrylic plates can be formed. The pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer made of such a pressure-sensitive adhesive composition and having a total light transmittance and haze value within a predetermined range is highly transparent and remains at the interface with the polycarbonate plate or acrylic plate even under high temperature conditions. It was possible to suppress the generated peeling.

However, a copolymer having a structural unit derived from a monomer having a bicyclo ring structure and one olefinic double bond in the molecule and a structural unit derived from a (meth) acrylate monomer having a specific structure The pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer made of a pressure-sensitive adhesive composition containing, has a problem in handling.
That is, when a protective plate and a display panel or a touch panel are bonded together using an adhesive tape, it is necessary to mold the adhesive tape according to the shape of the protective plate in advance. A punching device is generally used for molding such an adhesive tape. However, when an adhesive tape having the above-mentioned adhesive layer is punched and molded using the punching device, the adhesive adheres to the punching blade. Therefore, the molding process cannot be performed continuously. In addition, the pressure-sensitive adhesive oozes out from the end of the pressure-sensitive adhesive tape after punching, and the surroundings may be contaminated.

In view of the above situation, the present invention is highly transparent, excellent in adhesive strength to polycarbonate plates and acrylic plates, can suppress floating peeling occurring at the interface with the polycarbonate plate or acrylic plate even under high temperature conditions, and An object of the present invention is to provide an adhesive tape that is excellent in handleability.

The present invention is a pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer made of a pressure-sensitive adhesive composition containing a copolymer, wherein the copolymer has a bicyclo ring structure and one olefinic double bond in the molecule. A high glass having a structural unit derived from a monomer, a structural unit derived from a (meth) acrylate monomer having a structure represented by the following general formula (1), and a glass transition temperature of a homopolymer of 60 ° C. or higher. The proportion of the structural unit derived from a monomer having a structural unit derived from a transition temperature monomer and having a bicyclo ring structure and one olefinic double bond in the molecule occupying 100 parts by weight of the copolymer, The proportion of structural units derived from a (meth) acrylate monomer having a structure represented by the general formula (1) in 100 parts by weight of the copolymer is 10 to 60 parts by weight. 30 to 90 parts by weight, the glass transition temperature of the copolymer is an adhesive tape is 0 to 25 ° C..

In general formula (1), R ¹ represents a hydrogen atom or a methyl group, and R ² represents an alkyl group having 3 to 14 carbon atoms. The hydrogen atom of the alkyl group represented by R ² may be substituted with a cycloalkyl group.
The present invention is described in detail below.

The pressure-sensitive adhesive tape of the present invention has a pressure-sensitive adhesive layer made of a pressure-sensitive adhesive composition containing a copolymer.
The copolymer has a structural unit derived from a monomer having a bicyclo ring structure and one olefinic double bond in the molecule. When the copolymer has a structural unit derived from a monomer having a bicyclo ring structure and one olefinic double bond in the molecule, the pressure-sensitive adhesive tape of the present invention has an adhesive force to a polycarbonate plate and an acrylic plate. Greatly improved.

The bicyclo ring structure is not particularly limited, and examples of the functional group having the bicyclo ring structure include a bicyclo [1.1.0] butyl group, a bicyclo [1.1.1] pentyl group, and a bicyclo [2.1. 0] pentyl group, bicyclo [3.1.0] hexyl group, bicyclo [2.1.1] hexyl group, bicyclo [2.2.0] hexyl group, bicyclo [2.2.1] heptyl group, bicyclo [3.1.1] heptyl group, bicyclo [3.2.0] heptyl group, bicyclo [4.1.0] heptyl group, bicyclo [2.2.2] octyl group, bicyclo [3.2.1] ] Octyl group, bicyclo [3.3.0] octyl group, bicyclo [4.1.1] octyl group, bicyclo [4.2.0] octyl group, bicyclo [5.1.0] octyl group, bicyclo [ 3.2.2] Nonyl group, bicyclo 3.3.1] Nonyl group, bicyclo [4.2.1] nonyl group, bicyclo [4.3.0] nonyl group, bicyclo [5.1.1] nonyl group, bicyclo [5.2.0] Nonyl group, bicyclo [6.1.0] nonyl group, bicyclo [4.3.1] decyl group, and a part of hydrogen atoms of these functional groups having a bicyclo ring structure may be a chain alkyl group or a cyclic alkyl group. And a functional group having a structure substituted with a group. In addition, the said substitution may be one place and may be multiple places. Among these functional groups having a bicyclo ring structure, a norbornyl group and an isobornyl group are preferable, and an isobornyl group is particularly preferable.
The olefinic double bond is not particularly limited, and examples of the functional group having the olefinic double bond include a (meth) acryloyl group, a vinyl group, and an allyl group. Among these functional groups having an olefinic double bond, a (meth) acryloyl group is preferable. In addition, (meth) acryloyl means acryloyl or methacryloyl.
The monomer having a bicyclo ring structure and one olefinic double bond in the molecule is not particularly limited, but isobornyl (meth) acrylate having an isobornyl group and a (meth) acryloyl group is more preferable. In addition, (meth) acrylate means an acrylate or a methacrylate.

The proportion of the structural unit derived from a monomer having a bicyclo ring structure and one olefinic double bond in the molecule in 100 parts by weight of the copolymer is 10 to 60 parts by weight. When the proportion of the structural unit derived from the monomer having a bicyclo ring structure and one olefinic double bond in the molecule is less than 10 parts by weight, the resulting adhesive tape has an adhesive strength to the polycarbonate plate and the acrylic plate. And cannot sufficiently prevent the growth of bubbles at the interface with the polycarbonate plate or acrylic plate under high temperature conditions. When the proportion of the structural unit derived from the monomer having a bicyclo ring structure and one olefinic double bond in the molecule exceeds 60 parts by weight, the glass transition temperature of the resulting copolymer increases, and the copolymer The pressure-sensitive adhesive tape produced using the adhesive has poor adhesion to the polycarbonate plate and the acrylic plate, and cannot sufficiently prevent the growth of bubbles at the interface with the polycarbonate plate or the acrylic plate under high temperature conditions.
The proportion of structural units derived from a monomer having a bicyclo ring structure and one olefinic double bond in the molecule in 100 parts by weight of the copolymer is preferably 15 to 55 parts by weight. More preferably, it is 50 parts by weight.

The copolymer has a structural unit derived from a (meth) acrylic acid ester monomer having a structure represented by the general formula (1).
When the carbon number of the alkyl group of R ² is 2 or less or 15 or more, the glass transition temperature of the obtained copolymer is increased, and the pressure-sensitive adhesive tape produced using the copolymer is the initial of the pressure-sensitive adhesive layer. The wettability is lowered, the adhesion to the polycarbonate plate and the acrylic plate is lowered, and the growth of bubbles at the interface with the polycarbonate plate or the acrylic plate cannot be sufficiently prevented under high temperature conditions. The R ² alkyl group preferably has 4 to 12 carbon atoms.
Moreover, the hydrogen atom of the alkyl group of R ² may be substituted with a cycloalkyl group. The cycloalkyl group is not particularly limited, and examples thereof include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, and a cyclooctyl group.

The (meth) acrylic acid ester monomer having the structure represented by the general formula (1) is not particularly limited. For example, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate, propyl ( (Meth) acrylate, 2-ethyloctyl (meth) acrylate, nonyl (meth) acrylate, isononyl (meth) acrylate, decyl (meth) acrylate, isodecyl (meth) acrylate, lauryl (meth) acrylate, isotetradecyl (meth) acrylate Etc. When the copolymer has a structural unit derived from such a monomer, the resulting pressure-sensitive adhesive tape has cohesive strength, initial adhesiveness, and adhesiveness of the pressure-sensitive adhesive layer in addition to the pressure-sensitive adhesive force on the polycarbonate plate and acrylic plate. Etc. are also improved.

Among these, since a pressure-sensitive adhesive layer having a low low-temperature elastic modulus and high initial wettability is obtained, the (meth) acrylic acid ester monomer having the structure represented by the general formula (1) is 2-ethylhexyl ( It is preferable to contain at least one (meth) acrylic acid ester monomer selected from the group consisting of (meth) acrylate, octyl (meth) acrylate and butyl (meth) acrylate.

The ratio of the structural unit derived from the (meth) acrylic acid ester monomer having the structure represented by the general formula (1) in 100 parts by weight of the copolymer is 30 to 90 parts by weight. When the proportion of the structural unit derived from the (meth) acrylic acid ester monomer having the structure represented by the general formula (1) is less than 30 parts by weight, the resulting adhesive tape has a low temperature elastic modulus of the adhesive layer. The initial wettability is lowered, the adhesion to the polycarbonate plate and the acrylic plate is lowered, and the growth of bubbles at the interface with the polycarbonate plate or the acrylic plate cannot be sufficiently prevented under high temperature conditions. When the ratio of the structural unit derived from the (meth) acrylic acid ester monomer having the structure represented by the general formula (1) exceeds 90 parts by weight, the cohesive force of the pressure-sensitive adhesive layer is reduced in the obtained pressure-sensitive adhesive tape. The processability is reduced, and the proportion of structural units derived from monomers having a bicyclo ring structure and one olefinic double bond in the molecule in the copolymer is relatively reduced. The adhesive strength of the adhesive tape to the polycarbonate plate and acrylic plate is reduced.
The proportion of the structural unit derived from the (meth) acrylic acid ester monomer having the structure represented by the general formula (1) in 100 parts by weight of the copolymer is preferably 50 to 85 parts by weight.

The said copolymer has a structural unit derived from the high glass transition temperature monomer whose glass transition temperature of the said homopolymer is 60 degreeC or more. By containing a structural unit derived from such a high glass transition temperature monomer, the handling property of the pressure-sensitive adhesive tape of the present invention is dramatically improved by adjusting the glass transition temperature of the copolymer to 0 to 25 ° C. Can be made.

The high glass transition temperature monomer in which the glass transition temperature of the homopolymer is 60 ° C. or higher is not particularly limited. For example, methyl methacrylate (the glass transition temperature of the homopolymer is 105 ° C.), cyclohexyl methacrylate (66 ° C.), Examples include acrylonitrile (100 ° C.) and acrylic acid (106 ° C.). Of these, cyclohexyl methacrylate or methyl methacrylate is preferred from the viewpoint of improving the peel strength of the polycarbonate plate.

The proportion of the structural unit derived from the high glass transition temperature monomer in which the homopolymer has a glass transition temperature of 60 ° C. or more in 100 parts by weight of the copolymer is not particularly limited, and the bicyclo ring structure and 1 in the molecule are not limited. Structural units derived from monomers having two olefinic double bonds, types and blending amounts of structural units derived from (meth) acrylate monomers having a structure represented by the general formula (1), and the above alone What is necessary is just to adjust so that the glass transition temperature of the copolymer obtained may become the range of 0-25 degreeC in view of the kind of high glass transition temperature monomer whose glass transition temperature of a polymer is 60 degreeC or more.
The Fox equation is known as a method for calculating the glass transition temperature of a copolymer. A high glass transition in which the glass transition temperature of the homopolymer can be adjusted to be in the range of 0 to 25 ° C. by calculating backward using the Fox formula, and the glass transition temperature of the homopolymer is 60 ° C. or higher. The type and ratio of temperature monomer can be estimated. However, since there is an error in the glass transition temperature of the copolymer calculated from the Fox equation, the glass transition temperature is actually measured by differential thermal analysis (DSC), etc., and confirmation and fine adjustment are performed. Is preferred.

The copolymer may further have a structural unit derived from a monomer having a polyethylene oxide chain having a structure represented by the following general formula (2).

In General Formula (2), R ³ represents a hydrogen atom or a methyl group, R ⁴ represents an alkyl group having 3 to 30 carbon atoms, and n represents an integer of 25 to 45.

In general, the pressure-sensitive adhesive layer made of an acrylic pressure-sensitive adhesive composition is whitened due to condensation of moisture absorbed when exposed to high temperature and high humidity and then returned to room temperature. Such a decrease in visibility due to whitening can be a fatal defect for an image display device or an input device.
Such whitening can be prevented when the copolymer has a structural unit derived from a monomer having a polyethylene oxide chain having the structure represented by the general formula (2). This is because, by using a highly hydrophilic monomer as the monomer constituting the copolymer, water is finely dispersed when exposed to high temperature and high humidity and then returned to room temperature, thereby suppressing whitening. It is thought that it is possible.

In the polyethylene oxide chain, the number of ethylene oxide repeats is 25 for the lower limit and 45 for the upper limit. When the number of ethylene oxide repeats is less than 25, the resulting pressure-sensitive adhesive layer cannot sufficiently suppress whitening that occurs under high temperature and high humidity. When the number of ethylene oxide repetitions exceeds 45, the resulting pressure-sensitive adhesive layer cannot sufficiently suppress whitening that occurs under high temperature and high humidity, and has a structure represented by the general formula (2). The compatibility between the monomer having a polyethylene oxide chain and other main component monomers is lowered, and the adhesive strength of the resulting pressure-sensitive adhesive layer is lowered. The number of ethylene oxide repeats is preferably 30.
In addition, the repeating number of the said ethylene oxide is represented by n in the said General formula (2).

The terminal group of the polyethylene oxide chain is an alkyl group having 3 to 30 carbon atoms. When the carbon number of the alkyl group is less than 3, the resulting pressure-sensitive adhesive layer cannot sufficiently suppress whitening that occurs under high temperature and high humidity. The end group of the polyethylene oxide chain is preferably an alkyl group having 18 carbon atoms because a pressure-sensitive adhesive layer that can suppress whitening even under conditions of higher temperature and higher humidity is obtained.
The end group of the polyethylene oxide chain is represented by R ⁴ in the general formula (2).

Among the monomers having a polyethylene oxide chain having the structure represented by the general formula (2), as a commercial product, for example, BLEMMER PME-1000 (ethylene oxide repeat number = 23, terminal methyl group, manufactured by NOF Corporation) , Blemmer PSE-1300 (ethylene oxide repeat number = 30, terminal octadecyl group, manufactured by NOF Corporation) and the like.

However, when a structural unit derived from a monomer having a polyethylene oxide chain having the structure represented by the general formula (2) is added, the glass transition temperature of the copolymer tends to be lowered. The technical idea of the present invention is to adjust the glass transition temperature of the copolymer to a certain range by blending the structural unit derived from the high glass transition temperature monomer whose glass transition temperature of the homopolymer is 60 ° C. or higher as described above. This improves the handleability. Therefore, the proportion of the structural unit derived from the monomer having a polyethylene oxide chain having the structure represented by the general formula (2) is preferably set in a range that does not hinder the technical idea of the present invention.

The copolymer may further have structural units derived from other monomers.
When the copolymer has a structural unit derived from the other monomer, the intermolecular interaction of the obtained copolymer is increased, and the pressure-sensitive adhesive tape produced using the copolymer has a pressure-sensitive adhesive layer. The cohesive strength of increases. Further, when the other monomer has a polar group, the pressure-sensitive adhesive tape obtained by the interaction between the polar group and the surface of the polycarbonate plate or acrylic plate increases the interfacial adhesive force of the pressure-sensitive adhesive layer. .

The other monomer is not particularly limited, but at least one polar group selected from the group consisting of a carboxyl group, a hydroxyl group, an amide group, an amino group, an epoxy group, an aldehyde group and an isocyanate group in the molecule and one olefinic group. Monomers having a heavy bond are preferred. Among these other monomers, the cohesive force of the pressure-sensitive adhesive layer of the resulting pressure-sensitive adhesive tape is increased. Therefore, a monomer having a carboxyl group and one olefinic double bond in the molecule, a hydroxyl group and one in the molecule. A monomer having an olefinic double bond is more preferred.

The monomer having a carboxyl group and one olefinic double bond in the molecule is not particularly limited. For example, (meth) acrylic acid, (meth) acryloylacetic acid, (meth) acryloylpropionic acid, (meth) acryloylbutyric acid And unsaturated monocarboxylic acids such as (meth) acryloylpentanoic acid and crotonic acid, and unsaturated dicarboxylic acids such as maleic acid, fumaric acid, citraconic acid, mesaconic acid and itaconic acid.

When the copolymer has a structural unit derived from a monomer having a carboxyl group and one olefinic double bond in the molecule, a carboxyl group and one in the molecule occupying 100 parts by weight of the copolymer. The proportion of the structural unit derived from the monomer having an olefinic double bond is preferably 2 parts by weight or less. When the proportion of the structural unit derived from the monomer having a carboxyl group and one olefinic double bond in the molecule exceeds 2 parts by weight, the pressure-sensitive adhesive layer of the pressure-sensitive adhesive tape is made of metal such as ITO or metal oxide When a metal thin film containing an object is used as an adherend, the metal thin film may be easily deteriorated. The proportion of structural units derived from a monomer having a carboxyl group and one olefinic double bond in the molecule in 100 parts by weight of the copolymer is more preferably 1 part by weight or less, More preferably, it is at most parts by weight.
Moreover, the said copolymer does not need to have the structural unit derived from the monomer which has a carboxyl group and one olefinic double bond in the said molecule | numerator.

In general, the acid component in the copolymer contained in the adhesive layer is a cause of deterioration of the metal thin film when a metal thin film containing a metal or metal oxide such as ITO is used as an adherend. Become. On the other hand, when the copolymer does not contain an acid component such as a structural unit derived from a monomer having a carboxyl group and one olefinic double bond in the molecule, the cohesive force is high, even under high temperature conditions. It is difficult to obtain a highly reliable pressure-sensitive adhesive layer.
On the other hand, in the pressure-sensitive adhesive tape of the present invention, the copolymer is a structural unit derived from a monomer having a bicyclo ring structure and one olefinic double bond in the molecule, and the general formula (1). By having a structural unit derived from a (meth) acrylic acid ester monomer having a structure represented, even if the copolymer does not contain an acid component, the pressure-sensitive adhesive layer has adhesive strength, cohesive strength, Excellent initial adhesion and adhesion, and high reliability even under high temperature conditions. Therefore, the pressure-sensitive adhesive tape of the present invention can maintain high reliability even under high temperature conditions and can suppress deterioration of a metal thin film containing a metal such as ITO or a metal oxide.

The monomer having a hydroxyl group and one olefinic double bond in the molecule is not particularly limited. For example, 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) An acrylate etc. are mentioned.

When the copolymer has a structural unit derived from the other monomer, the proportion of the structural unit derived from the other monomer in 100 parts by weight of the copolymer is not particularly limited, but is 20 parts by weight or less. It is preferable. When the proportion of the structural unit derived from the other monomer exceeds 20 parts by weight, the resulting adhesive tape has reduced initial wettability of the pressure-sensitive adhesive layer, reduced adhesion to the polycarbonate plate and the acrylic plate, Under high temperature conditions, the growth of bubbles at the interface with the polycarbonate plate or acrylic plate may not be sufficiently prevented. The proportion of structural units derived from the other monomers in 100 parts by weight of the copolymer is more preferably 15 parts by weight or less.

The above copolymer has a glass transition temperature having a lower limit of 0 ° C. and an upper limit of 25 ° C. When the glass transition temperature of the copolymer is less than 0 ° C., the effect of improving the handleability is hardly obtained, and when an adhesive tape is punched out using a punching device, the adhesive adheres to the punching blade. Therefore, it is difficult to perform the molding process continuously. In addition, the adhesive may ooze out from the end of the adhesive tape after punching and may contaminate the surroundings. When the glass transition temperature of the copolymer exceeds 25 ° C., the adhesive strength of the adhesive tape is reduced, and it becomes impossible to suppress the peeling that occurs at the interface with the polycarbonate plate or the acrylic plate. The minimum with a preferable glass transition temperature of the said copolymer is 5 degreeC, a preferable upper limit is 20 degreeC, a more preferable minimum is 8 degreeC, and a more preferable upper limit is 18 degreeC.

The weight average molecular weight of the copolymer is not particularly limited, but a preferable lower limit is 200,000 and a preferable upper limit is 1,500,000. When the weight average molecular weight of the copolymer is less than 200,000, the resulting pressure-sensitive adhesive tape has a reduced high-temperature elastic modulus of the pressure-sensitive adhesive layer, so that bubbles grow at the interface with the polycarbonate plate or acrylic plate under high-temperature conditions. May not be sufficiently prevented. When the weight average molecular weight of the copolymer exceeds 1,500,000, the fluidity of the copolymer is lowered, and the adhesive tape produced using the copolymer has reduced adhesion to a polycarbonate plate and an acrylic plate. In some cases, the growth of bubbles at the interface with the polycarbonate plate or acrylic plate cannot be sufficiently prevented under high temperature conditions. The weight average molecular weight of the copolymer is more preferably 300,000 to 1,200,000, still more preferably 400,000 to 900,000.
In this specification, the weight average molecular weight means a value measured in terms of polystyrene by gel permeation chromatography (GPC). Specifically, for example, the diluted solution obtained by diluting the above copolymer 100 times with tetrahydrofuran (THF) is filtered through a filter, and the obtained filtrate is filtered with a column (for example, trade name “Waters” 2690 Separations Model "etc.).

Since the copolymer has a low viscosity, when forming a pressure-sensitive adhesive layer using a pressure-sensitive adhesive composition containing the copolymer, it should be coated well without being diluted with a solvent. It is easy to handle. Furthermore, since it can coat without using a solvent, it is easy to produce a thick adhesive layer, and the adhesive force with respect to the polycarbonate board and acrylic board of an adhesive layer can be improved. The viscosity of the copolymer is not particularly limited, but the viscosity measured at 25 ° C. using a B-type viscometer (“B8U-type viscometer”, manufactured by Tokyo Keiki Co., Ltd.) is 500 to 100,000 Pa · s. Is preferred.

The method for producing the copolymer is not particularly limited. For example, the monomer has a bicyclo ring structure and one olefinic double bond in the molecule, and has a structure represented by the general formula (1) ( A monomer mixture containing a (meth) acrylic acid ester monomer, a high glass transition temperature monomer having a glass transition temperature of 60 ° C. or higher, and the other monomer blended as necessary. And a method of radical polymerization in the presence of.

The said polymerization method is not specifically limited, For example, conventionally well-known polymerization methods, such as solution polymerization, emulsion polymerization, suspension polymerization, and block polymerization, can be used.
The solvent used for the solution polymerization is not particularly limited, and examples thereof include ethyl acetate, toluene, dimethyl sulfoxide, ethanol, acetone, diethyl ether and the like.

Although the compounding quantity of the solvent used for the said solution polymerization is not specifically limited, A preferable minimum is 25 weight part with respect to 100 weight part of said monomer mixtures, A preferable upper limit is 300 weight part. When the blending amount of the solvent is less than 25 parts by weight, the molecular weight distribution of the obtained copolymer is widened, and the adhesive tape produced using the copolymer has an adhesive force and adhesion to a polycarbonate plate and an acrylic plate. The cohesive force of the agent layer may be reduced, and the growth of bubbles at the interface with the polycarbonate plate or acrylic plate may not be sufficiently prevented under high temperature conditions. When the amount of the solvent exceeds 300 parts by weight, it may be necessary to remove the solvent when preparing the pressure-sensitive adhesive composition using the resulting copolymer and producing a pressure-sensitive adhesive tape.

The said polymerization initiator is not specifically limited, For example, a persulfate, an organic peroxide, an azo compound etc. are mentioned. Among these, an azo compound is preferable in consideration of the influence on the metal thin film when a metal thin film containing a metal such as ITO or a metal oxide is used as an adherend.
The persulfate is not particularly limited, and examples thereof include potassium persulfate, sodium persulfate, and ammonium persulfate. The organic peroxide is not particularly limited. For example, 1,1-bis (t-hexylperoxy) -3,3,5-trimethylcyclohexane, t-hexylperoxypivalate, t-butylperoxypivalate , Lauroyl peroxide, 2,5-dimethyl-2,5-bis (2-ethylhexanoylperoxy) hexane, t-hexylperoxy-2-ethylhexanoate, t-butylperoxy-2-ethylhexa Noate, t-butylperoxyisobutyrate, t-butylperoxy-3,5,5-trimethylhexanoate, t-butylperoxylaurate and the like. The azo compound is not particularly limited. For example, 2,2′-azobisisobutyronitrile, 2,2′-azobis (2,4-dimethylvaleronitrile), 4,4′-azobis (4-cyanopentane) Acid), 2,2′-azobis (2-methylbutyronitrile), azobiscyclohexanecarbonitrile and the like.
These polymerization initiators may be used alone or in combination of two or more.

Although the compounding quantity of the said polymerization initiator is not specifically limited, It is preferable that it is 0.02-0.5 weight part with respect to 100 weight part of said monomer mixtures. When the blending amount of the polymerization initiator is less than 0.02 parts by weight, the polymerization reaction may be insufficient, or the polymerization reaction may take a long time. When the blending amount of the polymerization initiator exceeds 0.5 parts by weight, the weight average molecular weight of the obtained copolymer may become too low or the molecular weight distribution may become too wide. The pressure-sensitive adhesive tape produced by the above-described method may reduce the adhesion to the polycarbonate plate and the acrylic plate and the cohesive strength of the pressure-sensitive adhesive layer, and sufficiently hinder the growth of bubbles at the interface with the polycarbonate plate or the acrylic plate under high temperature conditions. There are things that cannot be done.

The pressure-sensitive adhesive composition may contain a crosslinking agent in addition to the copolymer.
By containing the crosslinking agent, a crosslinked structure can be formed in the copolymer. Moreover, the gel fraction of the adhesive layer of the adhesive tape obtained can be adjusted by adjusting the kind and quantity of the said crosslinking agent suitably.

The said crosslinking agent is not specifically limited, For example, an isocyanate type crosslinking agent, an aziridine type crosslinking agent, an epoxy-type crosslinking agent, a metal chelate type crosslinking agent etc. are mentioned. Among them, the pressure-sensitive adhesive composition contains at least one cross-linking agent selected from the group consisting of an isocyanate cross-linking agent and an epoxy-based cross-linking agent because performance such as heat resistance and durability is easily exhibited. Is preferred.

Although the said isocyanate type crosslinking agent is not specifically limited, An aliphatic isocyanate type crosslinking agent is preferable. Among the aliphatic isocyanate-based crosslinking agents, examples of commercially available products include Coronate HX (manufactured by Nippon Polyurethane Co., Ltd.).
Although the said epoxy-type crosslinking agent is not specifically limited, An aliphatic epoxy-type crosslinking agent is preferable. Among the above-mentioned aliphatic epoxy crosslinking agents, examples of commercially available products include Denacol EX212 and Denacol EX214 (both manufactured by Nagase ChemteX Corporation).

Although the compounding quantity of the said crosslinking agent is not specifically limited, It is preferable that it is 0.1-10 weight part with respect to 100 weight part of said copolymers. When the blending amount of the crosslinking agent is less than 0.1 parts by weight, the copolymer is insufficiently crosslinked, and the resulting adhesive tape has reduced cohesive strength of the adhesive layer and processability. In addition, the growth of bubbles at the interface with the polycarbonate plate or acrylic plate may not be sufficiently prevented under high temperature conditions. When the blending amount of the crosslinking agent exceeds 10 parts by weight, the pressure-sensitive adhesive tape obtained may have reduced adhesive strength and initial adhesion to the polycarbonate plate and the acrylic plate. The amount of the crosslinking agent is more preferably 0.3 to 3.0 parts by weight with respect to 100 parts by weight of the copolymer.

The pressure-sensitive adhesive composition may further contain a tackifier resin.
The tackifying resin is not particularly limited, and examples thereof include a xylene resin, a phenol resin, a rosin resin, and a terpene resin. These tackifier resins may be used alone or in combination of two or more. Among these, a xylene resin is preferable, and an alkylphenol reaction product of the xylene resin is more preferable. Moreover, it is preferable to use a hydrogenated resin as the tackifier resin, and by using such a resin, the transparency of the adhesive tape can be increased.

The pressure-sensitive adhesive composition may further contain a silane coupling agent. By containing a silane coupling agent, the adhesiveness of the obtained adhesive tape to the polycarbonate plate and the acrylic plate can be improved.
The silane coupling agent is not particularly limited. For example, vinyltrimethoxysilane, vinyltriethoxysilane, methacryloxypropyltrimethoxysilane, γ-methacryloxypropylmethyldimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ -Glycidoxypropylmethyldimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane , Γ-aminopropyltrimethylmethoxysilane, N- (2-aminoethyl) 3-aminopropyltriethoxysilane, N- (2-aminoethyl) 3-aminopropylmethyldimethoxysilane, γ-mercaptopropyltri Examples include methoxysilane, γ-mercaptopropyltriethoxysilane, mercaptobutyltrimethoxysilane, and γ-mercaptopropylmethyldimethoxysilane.

The pressure-sensitive adhesive composition may further contain conventionally known additives as necessary.
The additive is not particularly limited as long as the transparency of the obtained pressure-sensitive adhesive tape is not impaired, and examples thereof include a filler and an antiaging agent.

The method for producing the pressure-sensitive adhesive composition is not particularly limited. For example, the copolymer and, if necessary, the crosslinking agent, the tackifying resin, the silane coupling agent, and the additive are mixed. And a method of stirring.

The pressure-sensitive adhesive layer has a shear storage elastic modulus (G ′) at a measurement frequency of 10 Hz of 1 × 10 ⁵ to 1 × 10 ⁷ Pa at 20 ° C. and 3 × 10 ⁴ to 1 × 10 ⁵ Pa at 85 ° C. preferable. If the shear storage elastic modulus (G ′) is less than 1 × 10 ⁵ Pa at 20 ° C. or less than 3 × 10 ⁴ Pa at 85 ° C., the adhesive layer becomes more deformable with respect to stress, resulting in adhesion. Tape cutting processability may be reduced. When the shear storage modulus (G ′) exceeds 1 × 10 ⁷ Pa at 20 ° C., or exceeds 1 × 10 ⁵ Pa at 85 ° C., the adhesive tape has a reduced initial wettability of the adhesive layer. In addition, the adhesion to the polycarbonate plate or the acrylic plate is lowered, and the floating peeling that occurs at the interface with the polycarbonate plate or the acrylic plate may not be sufficiently suppressed under high temperature conditions.
The adhesive layer has a shear storage elastic modulus (G ′) at a measurement frequency of 10 Hz of 1.2 × 10 ⁵ to 8 × 10 ⁶ Pa at 20 ° C. and 3.2 × 10 ^{4 to} 9 × 10 ⁴ Pa at 85 ° C. more preferably, it is more preferred 20 ° C. is ^{1.4 × 10 5 ~6 × 10 6} Pa, × 3.4 at ^{85 ℃ 10 4 ~8 × 10 4} Pa.

In this specification, the shear storage modulus (G ′) at a measurement frequency of 10 Hz is a frequency of 10 Hz using a dynamic viscoelasticity measuring device such as “DVA-200” manufactured by IT Measurement Control Co., Ltd. It means the shear storage modulus (G ′) measured at a temperature rate of 5 ° C./min.

The pressure-sensitive adhesive layer has a maximum point in the dissipation factor (tan δ) obtained by dividing the shear loss elastic modulus (G ″) by the shear storage elastic modulus (G ′) in the temperature range of −25 to 25 ° C. It is preferable to have.
For example, when the pressure-sensitive adhesive layer does not have a maximum point in the dissipation rate (tan δ) in the temperature range, and the dissipation rate (tan δ) of the pressure-sensitive adhesive layer exceeds 25 ° C., the pressure-sensitive adhesive tape The initial wettability is reduced, the adhesion to the polycarbonate plate or the acrylic plate is lowered, and the floating peeling that occurs at the interface with the polycarbonate plate or the acrylic plate under high temperature conditions may not be suppressed. For example, when the pressure-sensitive adhesive layer does not have a maximum point in the dissipation factor (tan δ) in the temperature range, and the dissipation factor (tan δ) of the pressure-sensitive adhesive layer is less than −25 ° C., the pressure-sensitive adhesive layer Becomes soft, the cutting processability of the adhesive tape is lowered, and the adhesive at the cutting end may adhere to the cutting blade and hinder the processing.

In the present specification, “in the temperature range of −25 to 25 ° C., the maximum dissipation factor (tan δ) obtained by dividing the shear loss elastic modulus (G ″) at the same measurement temperature by the shear storage elastic modulus (G ′)”. “Having a point” means shearing at −25 to 25 ° C. at a frequency of 10 Hz and a heating rate of 5 ° C./min using a dynamic viscoelasticity measuring device such as “DVA-200” manufactured by IT Measurement & Control Co., Ltd. When the loss elastic modulus (G ″) and the shear storage elastic modulus (G ′) were measured, and the graph was created with the horizontal axis representing temperature and the vertical axis representing the dissipation factor (tan δ), within a range of −25 to 25 ° C. It means having a maximum point.

The gel fraction of the pressure-sensitive adhesive layer is not particularly limited, and it can suppress the peeling off occurring at the interface with the polycarbonate plate or the acrylic plate under high temperature conditions in any range. Although it can adjust suitably according to a use, it is preferable that it is 30 to 95 weight% especially. When the gel fraction of the pressure-sensitive adhesive layer is less than 30% by weight, the workability of the pressure-sensitive adhesive tape may be lowered. When the gel fraction of the pressure-sensitive adhesive layer exceeds 95% by weight, the pressure-sensitive adhesive tape is deteriorated in initial wettability of the pressure-sensitive adhesive layer, and the adhesion to the polycarbonate plate and the acrylic plate is lowered. In some cases, the growth of bubbles at the interface with the plate or the acrylic plate cannot be sufficiently prevented. The gel fraction of the pressure-sensitive adhesive layer is more preferably 40 to 90% by weight.

The gel fraction can be measured by the following method.
First, the pressure-sensitive adhesive tape of the present invention is cut into a flat rectangular shape of 50 mm × 25 mm to produce a test piece. After immersing the obtained test piece in ethyl acetate at 23 ° C. for 24 hours, the test piece is taken out from ethyl acetate through a 200-mesh stainless steel mesh and dried at 110 ° C. for 1 hour. And the weight of the test piece after drying is measured, and a gel fraction is computed using a following formula. In addition, the release paper or the release film is not laminated | stacked on the adhesive tape used for the test piece.
Gel fraction (% by weight) = 100 × (W ₂ −W ₀ ) / (W ₁ −W ₀ )
In the formula, W ₀ represents the weight of the substrate, W ₁ represents the weight of the test piece before dipping, and W ₂ represents the weight of the test piece after dipping and drying. When the adhesive tape does not have a substrate, W ₀ = 0.

Although the thickness of the said adhesive layer is not specifically limited, It is preferable that it is 20-500 micrometers. When the thickness of the pressure-sensitive adhesive layer is less than 20 μm, the pressure-sensitive adhesive tape has a low adhesive force to the polycarbonate plate and the acrylic plate, and sufficiently hinders bubble growth at the interface with the polycarbonate plate or the acrylic plate under high temperature conditions. There are times when you can't. When the thickness of the pressure-sensitive adhesive layer exceeds 500 μm, the pressure-sensitive adhesive component oozes out and the handling property may be lowered. As for the thickness of the said adhesive layer, it is more preferable that it is 20-300 micrometers.

The pressure-sensitive adhesive tape of the present invention preferably has a total light transmittance in the visible light wavelength region of 90% or more and a haze value of 1% or less. When the total light transmittance in the visible light wavelength region is less than 90% or the haze value exceeds 1%, the transparency of the pressure-sensitive adhesive tape is lowered and it is difficult to apply to optical applications.

The pressure-sensitive adhesive tape of the present invention may be a non-support type having no base material, or may be a support type in which a pressure-sensitive adhesive layer is formed on both surfaces of the base material.
The base material is not particularly limited as long as it is a transparent base material. For example, acrylic resin, polyolefin, polycarbonate, polyvinyl chloride, acrylonitrile butadiene styrene (ABS) resin, polyethylene terephthalate (PET), nylon, polyurethane, Examples thereof include a sheet made of a transparent resin such as polyimide, a sheet having a network structure, and a sheet having holes.

Although the thickness of the said base material is not specifically limited, It is preferable that it is 2-200 micrometers. If the thickness of the substrate is less than 2 μm, the strength of the resulting adhesive tape may be insufficient, and it may be torn or difficult to handle. When the thickness of the base material exceeds 200 μm, the base material is too strong, and the followability to the level difference of the obtained adhesive tape may be deteriorated. As for the thickness of the said base material, it is more preferable that it is 5-100 micrometers.

The pressure-sensitive adhesive tape of the present invention may have a release paper or a release film laminated on the pressure-sensitive adhesive layer.
The release paper or release film is not particularly limited. For example, a release film obtained by subjecting a synthetic resin film made of polyester resin, polyethylene resin, polypropylene resin, polyvinyl chloride, nylon or the like to release treatment. Examples include release paper obtained by forming a release layer on base paper having high surface smoothness such as high-quality paper and glassine paper.

The thickness of the release paper or release film is not particularly limited, but is preferably 12 to 125 μm. When the thickness is out of the above range, the cutting processability of the adhesive tape may be deteriorated. The thickness of the release paper or release film is more preferably 20 to 100 μm. The center line average roughness (Ra) of the release paper or release film is not particularly limited, but is preferably 0.2 μm or less.

By having a pressure-sensitive adhesive layer made of a pressure-sensitive adhesive composition containing the above copolymer, the pressure-sensitive adhesive tape of the present invention has a 180 ° peeling force on a polycarbonate plate or acrylic plate of 3 N / 25 mm at a peeling speed of 0.3 mm / min The above can be realized. When the peeling force is 3 N / 25 mm or more, floating peeling occurring at the interface with the polycarbonate plate or the acrylic plate can be sufficiently suppressed even under high temperature conditions.
In addition, the present inventors consider that the peeling speed of 0.3 mm / min is a speed suitable for evaluating a phenomenon in which floating peeling progresses when a polycarbonate plate or an acrylic plate is used as an adherend. Yes.

In addition, in this specification, 180 degree peeling force with respect to a polycarbonate board or an acrylic board in peeling speed 0.3mm / min means the value computed by the following method.
First, the adhesive tape is cut so as to have a planar shape of 25 mm × 100 mm. One release polyethylene terephthalate film of the cut adhesive tape is peeled off to expose the adhesive layer. Next, a 50 μm thick polyethylene terephthalate film is bonded to the exposed surface of the adhesive tape. Further, the other release polyethylene terephthalate film of the adhesive tape is peeled off, the adhesive layer is exposed, and the exposed surface of the adhesive tape is placed on a polycarbonate plate or an acrylic plate with a 2.0 kg rubber roller at a speed of 300 mm / min. By reciprocating once, the polycarbonate plate or the acrylic plate and the adhesive tape are bonded together and left at 23 ° C. for 24 hours to prepare a test sample.
The obtained test sample is subjected to a tensile test in the 180 ° direction at a peeling rate of 0.3 mm / min, and the obtained value is 180 ° peeling force (N / 25 mm) against a polycarbonate plate or an acrylic plate at a peeling rate of 0.3 mm / min. ).

Although the use of the adhesive tape of this invention is not specifically limited, It is especially suitable as an adhesive tape for affixing on a polycarbonate board or an acrylic board. Specifically, for example, when manufacturing an image display device such as a mobile phone or a portable information terminal, a protective plate for protecting a surface made of a polycarbonate plate or an acrylic plate is used for an image display device such as a display panel or a touch panel. It can be used for bonding to the surface (see FIG. 3). Further, the display panel or the touch panel can be used for bonding to the surface of a support made of a polycarbonate plate or an acrylic plate.
The pressure-sensitive adhesive tape of the present invention has high transparency and can be suitably applied to optical applications that require high transparency such as bonding to a display panel or a touch panel. In addition, since the polycarbonate plate and the acrylic plate easily absorb moisture, the outgas generated under the high temperature condition is likely to cause floating at the interface with the pressure-sensitive adhesive layer, but by using the pressure-sensitive adhesive tape of the present invention. Such floating off can be effectively suppressed.

A laminate formed by attaching a polycarbonate plate or an acrylic plate to a transparent electrode via the adhesive tape of the present invention is also one aspect of the present invention.
The polycarbonate plate or the acrylic plate is not particularly limited. For example, the polycarbonate plate or the acrylic plate used for an image display device or the like is preferable, and the polycarbonate plate used as a protective plate for protecting the surface of the image display device or the like. Or it is preferable that it is an acrylic board.
Examples of the transparent electrode include an ITO electrode.

The laminate of the present invention is not particularly limited as long as the polycarbonate plate or the acrylic plate is attached to the transparent electrode via the adhesive tape of the present invention, and examples thereof include a laminate used for an image display device and the like.
An image display device having the laminate of the present invention is also one aspect of the present invention.

Examples of the image display device of the present invention include touch panels such as a resistive touch panel and a capacitive touch panel.
The resistive film type touch panel includes, for example, a support having a protective plate made of a polycarbonate plate or an acrylic plate, an upper transparent electrode, a spacer, and a lower transparent electrode in this order. An example of such a resistive film type touch panel is shown in FIG.
In the resistive film type touch panel shown in FIG. 1, a protective plate 1 made of a polycarbonate plate or an acrylic plate and an upper transparent electrode 3 are bonded to each other through an adhesive tape 2 of the present invention. Moreover, the support body 7 and the lower transparent electrode 5 are bonded together through the adhesive tape 6 of this invention. The support 7 and the lower transparent electrode 5 may be bonded together by the adhesive tape of the present invention or may be bonded by an adhesive tape other than the adhesive tape of the present invention. Moreover, the support body 7 and the lower transparent electrode 5 may be laminated | stacked by methods other than an adhesive tape. In the resistive touch panel shown in FIG. 1, the adhesive tape of the present invention is a double-sided adhesive tape.

The capacitive touch panel includes, for example, a protective plate made of a polycarbonate plate or an acrylic plate, a glass plate with an ITO film formed on the front and back, and a support. An example of such a capacitive touch panel is shown in FIG.
In the capacitive touch panel shown in FIG. 2, a protective plate 8 made of a polycarbonate plate or an acrylic plate, and a glass plate 11 having ITO films 10 and 12 formed on the front and back, through the adhesive tape 9 of the present invention, Are pasted together. Moreover, the support body 14 and the glass plate (opposite surface) by which the ITO film | membrane was formed in the front and back are bonded together through the adhesive tape 13 of this invention. The support 14 and the glass plate on which the ITO film is formed on the front and back may be bonded together by the adhesive tape of the present invention or may be bonded by an adhesive tape other than the adhesive tape of the present invention. Moreover, the support body 14 and the glass plate by which the ITO film | membrane was formed into the front and back may be laminated | stacked by methods other than an adhesive tape. In the capacitive touch panel shown in FIG. 2, the adhesive tape of the present invention is a double-sided adhesive tape.

The method for producing the pressure-sensitive adhesive tape of the present invention is not particularly limited. For example, as a method for producing a non-support type pressure-sensitive adhesive tape, the pressure-sensitive adhesive composition is applied to a release-treated surface of a release paper or a release film. Then, a pressure-sensitive adhesive layer is formed, and a newly prepared release paper or release film is laminated on the obtained pressure-sensitive adhesive layer so that the release treatment surface faces the pressure-sensitive adhesive layer. A method of pressing the obtained laminated body with a rubber roller or the like after the body is obtained may be mentioned.

According to the present invention, the transparency is high, the adhesive strength to the polycarbonate plate and the acrylic plate is excellent, the floating peeling occurring at the interface with the polycarbonate plate or the acrylic plate can be suppressed even under high temperature conditions, and the handling property is improved. In addition, it is possible to provide an adhesive tape that is superior to the above.

1A and 1B are a cross-sectional view and a perspective view schematically showing an example in which a protective plate made of a polycarbonate plate or an acrylic plate is attached to a transparent electrode via the adhesive tape of the present invention. 2A and 2B are a cross-sectional view and a perspective view schematically showing an example in which a protective plate made of a polycarbonate plate or an acrylic plate is attached to a transparent electrode via the adhesive tape of the present invention. FIG. 3 is a cross-sectional view schematically showing an example in which a protective plate is attached to the surface of an image display device using the adhesive tape of the present invention.

Hereinafter, embodiments of the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples.

Example 1
In a reactor equipped with a thermometer, a stirrer, and a cooling tube, 62.8 parts by weight of 2-ethylhexyl acrylate, 35 parts by weight of isobornyl acrylate, 2 parts by weight of acrylic acid, and 0.2 parts by weight of 2-hydroxymethacrylate Then, 100 parts by weight of ethyl acetate was added to 100 parts by weight of these monomers, and after the atmosphere was replaced with nitrogen, the reactor was heated to start refluxing. Subsequently, 0.2 parts by weight of t-hexylperoxypivalate as a polymerization initiator is diluted with 5 parts by weight of ethyl acetate with respect to 100 parts by weight of the monomer, and the resulting polymerization initiator solution is diluted with the above reactor. The solution was added dropwise over 2 hours. Thereafter, the mixture was refluxed at 70 ° C. for 8 hours from the start of addition of the polymerization initiator to obtain an acrylic copolymer solution having a solid content of 50%.

About the obtained acrylic copolymer, thermal decomposition apparatus (frontier laboratory company make, double shot pyrolyzer), GC-MS apparatus (manufactured by JEOL Ltd., Q-1000GC), FT-IR (manufactured by Thermo Fisher Scientific, Using NICOLET6700) and NMR (manufactured by JEOL Ltd., JNM-ECA400), the proportion (% by weight) of structural units derived from the respective monomers constituting the acrylic copolymer was measured. Table 1 shows the proportion (% by weight) of the obtained structural units.
Moreover, about the obtained acrylic copolymer, the weight average molecular weight by polystyrene conversion measured by GPC method using "2690 Separations Model" made from Waters as a column was about 500,000.

It was 14 degreeC when the glass transition temperature was measured about the obtained acrylic copolymer.
In addition, using a dynamic viscoelasticity measuring apparatus (DVA-200, manufactured by IT Measurement Control Co., Ltd.), shear loss elastic modulus (G ″) at a frequency of 10 Hz at a temperature of −25 to 25 ° C. and a heating rate of 5 ° C./min. ) And shear storage modulus (G ′) were measured, and when the graph was created with the horizontal axis representing temperature and the vertical axis representing dissipation factor (tan δ), the point having the maximum point was defined as the glass transition temperature.

To 100 parts by weight of the obtained acrylic copolymer, 0.5 part by weight of Coronate HX (manufactured by Nippon Polyurethane Co., Ltd.) was added as a crosslinking agent and stirred to obtain a pressure-sensitive adhesive composition. The obtained pressure-sensitive adhesive composition is coated on the release-treated surface of the release polyethylene terephthalate film to form a pressure-sensitive adhesive layer. On the obtained pressure-sensitive adhesive layer, the release-treated surface becomes the pressure-sensitive adhesive layer. A newly prepared release polyethylene terephthalate film was laminated so as to face each other to obtain a laminate. By pressing the obtained laminate with a rubber roller, a double-sided pressure-sensitive adhesive tape having a release polyethylene terephthalate film attached on both sides was obtained.

(Examples 2-7, Comparative Examples 1-3)
By changing the monomer composition of the acrylic copolymer, a double-sided pressure-sensitive adhesive tape was obtained in the same manner as in Example 1 except that an acrylic copolymer having the proportion (% by weight) of the structural units shown in Table 1 was obtained. Produced.

(Evaluation)
About the double-sided adhesive tape obtained by the Example and the comparative example, it evaluated by the following method.
The results are shown in Table 1.

(1) Measurement of total light transmittance and haze value in visible light wavelength region A double-sided adhesive tape is bonded to a slide glass (trade name “S-1214”, manufactured by MATSANAMI), and a layer structure of an adhesive layer / slide glass The total light transmittance and haze value (%) in the visible light wavelength region of the test piece were measured using a haze meter (fully automatic haze meter “TC-HIIIDPK”, manufactured by Tokyo Denshoku Co., Ltd.). Measured.

(2) Measurement of adhesive strength The double-sided adhesive tape was cut so as to have a planar shape of 25 mm x 100 mm. One release polyethylene terephthalate film of the cut double-sided pressure-sensitive adhesive tape was peeled off to expose the pressure-sensitive adhesive layer. Next, the exposed surface of the double-sided pressure-sensitive adhesive tape was bonded onto the polyethylene terephthalate film. Further, the other release polyethylene terephthalate film of the double-sided pressure-sensitive adhesive tape is peeled off, the pressure-sensitive adhesive layer is exposed, and the exposed surface of the double-sided pressure-sensitive adhesive tape is bonded onto the polycarbonate plate (PC plate). A laminated sample in which a double-sided pressure-sensitive adhesive tape and a polyethylene terephthalate film were laminated in this order on the plate) was obtained. Then, a polycarbonate plate (PC plate) and a double-sided adhesive tape are bonded together by placing a 2.0 kg rubber roller on the obtained polyethylene terephthalate film of the laminated sample and reciprocating the rubber roller at a speed of 300 mm / min. The sample was left at 23 ° C. for 20 minutes to prepare a test sample.
Moreover, the test sample was similarly prepared using the acrylic board instead of the said polycarbonate board (PC board).
The obtained test sample was subjected to a tensile test in the 180 ° direction at a peeling speed of 300 mm / min according to JIS Z0237, and the adhesive strength (N / 25 mm) was measured.

(3) Bubble generation state (foam resistance test)
The double-sided adhesive tape was cut so as to have a planar shape of 45 mm × 60 mm. One release polyethylene terephthalate film of the cut double-sided pressure-sensitive adhesive tape was peeled off to expose the pressure-sensitive adhesive layer. Next, the exposed surface of the double-sided pressure-sensitive adhesive tape was bonded onto a polyethylene terephthalate film having a thickness of 0.05 mm. Further, the other release polyethylene terephthalate film of the double-sided pressure-sensitive adhesive tape is peeled off, the pressure-sensitive adhesive layer is exposed, and the surface of the double-sided pressure-sensitive adhesive tape exposed on a polycarbonate plate (PC board) having a planar shape with a thickness of 2.0 mm Were laminated to obtain a laminated sample in which a double-sided adhesive tape and a polyethylene terephthalate film were laminated in this order on a polycarbonate plate (PC plate). Thereafter, the obtained laminated sample was allowed to stand for 500 hours under the condition of a temperature of 85 ° C. or a temperature of 60 ° C. and a relative humidity (RH) of 90% to obtain a test sample. The bubble generation state in the adhesion interface of the obtained test sample was visually observed.
A case where no bubbles of a size of 0.01 mm or more were observed at all, “◯”, and a case where 1 to 5 bubbles of a size of 0.01 mm or more were observed per test sample were expressed as “Δ”. The bubble generation state was evaluated by setting “x” when 6 or more bubbles having a size of 0.01 mm or more were observed per test sample.

(4) Measurement of probe tack The double-sided adhesive tape was cut so as to have a planar shape of 25 mm × 75 mm. One release polyethylene terephthalate film of the cut double-sided pressure-sensitive adhesive tape was peeled off to expose the pressure-sensitive adhesive layer. Next, the exposed surface of the double-sided pressure-sensitive adhesive tape was bonded onto a 2 mm thick polycarbonate plate (manufactured by Takiron). Furthermore, the other release polyethylene terephthalate film of the double-sided pressure-sensitive adhesive tape was peeled off to expose the pressure-sensitive adhesive layer. A 10 mm square metal piece was brought into contact with the exposed adhesive surface, and the resistance (N / 10 mm □) at that time was measured by a strograph, and this was used as a probe tack.

(5) Measurement of bulk deviation length The double-sided pressure-sensitive adhesive tape was cut so as to have a planar shape of 20 mm × 40 mm. Next, the exposed surface of the double-sided pressure-sensitive adhesive tape was bonded onto a polyethylene terephthalate film having a thickness of 0.05 mm. Further, the other release polyethylene terephthalate film of the double-sided pressure-sensitive adhesive tape was peeled off to expose the pressure-sensitive adhesive layer, and affixed to a predetermined place of a cohesive strength tester.
Thereafter, the shift length (μm) 3 minutes after applying a load of 50 g on one side was measured.

(6) Cutting workability test About double-sided adhesive tape, punching operation is continuously performed 50 times using a cutter blade, and the blade dirtiness caused by the adhesive adhering to the cutter blade, and the adhesive at the end. The oozing state was evaluated.
For the blade dirtiness, visually confirm the adhesiveness of the glue, "◎" if there is no adhesion to the blade and the above-mentioned cutting is possible, and the case where there is almost no adhesion to the blade and the above-mentioned cutting is possible “◯”, a case where partial adhesion was observed on the blade after the above-described cutting was evaluated as “Δ”, and a case where the adhesive was attached to the blade and cutting was not possible was evaluated as “×”.
In addition, regarding the state of the adhesive that oozes out at the end portion, when directly contacting the cut surface, “◎” indicates that there is no thread pulling and no adhesive oozes, and “○” indicates that no adhesive oozes out. "The case where the paste exuded vigorously and the end portion was contaminated was evaluated as" x ".

(7) Generation evaluation of whitening The obtained double-sided pressure-sensitive adhesive tape was bonded to a slide glass (trade name “S-1214”, manufactured by MATSUNAMI) to prepare a test piece having a layer structure of an adhesive layer / slide glass. . This test piece was left under high temperature and high humidity of 80 ° C. and 85% RH, and the haze value (%) of the test piece after 0 hours and 24 hours after the start of the standing was measured with a haze meter (fully automatic haze meter “TC-HIIIDPK”). ”, Manufactured by Tokyo Denshoku Co., Ltd.), and Δhaze value was calculated by the following formula.
Δhaze value (%) = {haze value after 24 hours (%)} − {haze value after 0 hours (%)}

According to the present invention, the transparency is high, the adhesive strength to the polycarbonate plate and the acrylic plate is excellent, the floating peeling occurring at the interface with the polycarbonate plate or the acrylic plate can be suppressed even under high temperature conditions, and the handling property is improved. In addition, it is possible to provide an adhesive tape that is superior to the above.

DESCRIPTION OF SYMBOLS 1 Protective plate 2 Adhesive tape 3 Upper transparent electrode 4 Spacer 5 Lower transparent electrode 6 Adhesive tape 7 Support body 8 Protective plate 9 Adhesive tape 10 ITO film 11 Glass plate 12 ITO film 13 Adhesive tape 14 Support body 15 Protective plate 16 Adhesive tape 17 Image display device

Claims (5)

A pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer comprising a pressure-sensitive adhesive composition containing a copolymer,
The copolymer is a (meth) acrylic acid ester having a structural unit derived from a monomer having a bicyclo ring structure and one olefinic double bond in the molecule, and a structure represented by the following general formula (1) A structural unit derived from a monomer, and a structural unit derived from a high glass transition temperature monomer whose homopolymer has a glass transition temperature of 60 ° C. or higher,
The proportion of the structural unit derived from the monomer having a bicyclo ring structure and one olefinic double bond in the molecule in 100 parts by weight of the copolymer is 10 to 60 parts by weight,
The proportion of the structural unit derived from the (meth) acrylic acid ester monomer having the structure represented by the general formula (1) in 100 parts by weight of the copolymer is 30 to 90 parts by weight.
A pressure-sensitive adhesive tape, wherein the copolymer has a glass transition temperature of 0 to 25 ° C.

In general formula (1), R ¹ represents a hydrogen atom or a methyl group, and R ² represents an alkyl group having 3 to 14 carbon atoms. The hydrogen atom of the alkyl group represented by R ² may be substituted with a cycloalkyl group. The pressure-sensitive adhesive tape according to claim 1, wherein the bicyclo ring structure is a bicyclo ring structure of an isobornyl group. The pressure-sensitive adhesive tape according to claim 1 or 2, wherein the olefinic double bond is an olefinic double bond of a (meth) acryloyl group. The (meth) acrylic acid ester monomer having the structure represented by the general formula (1) is at least one selected from the group consisting of 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate and butyl (meth) acrylate. The pressure-sensitive adhesive tape according to claim 1, wherein the pressure-sensitive adhesive tape contains a (meth) acrylic acid ester monomer. The pressure-sensitive adhesive tape according to claim 1, 2, 3 or 4, wherein the high glass transition temperature monomer whose homopolymer has a glass transition temperature of 60 ° C or higher is cyclohexyl methacrylate or methyl methacrylate.

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