JPWO2016181691A1 - Double-sided adhesive tape for fixing optical films - Google Patents

Abstract

An object of the present invention is to provide a double-sided pressure-sensitive adhesive tape for fixing an optical film, which is used for fixing an optical film, and has high constant load peelability to an adherend, high strain stress resistance, and tape processability. . The present invention is an optical film fixing double-sided pressure-sensitive adhesive tape for fixing an optical film to an adherend, and has a weight average molecular weight of 500,000 to 1,800,000, molecular weight distribution (Mw / Mn) obtained by living radical polymerization. It has a pressure-sensitive adhesive layer containing an acrylic polymer of 1.05 to 2.5 and a cross-linking agent, and in a minute shear displacement measurement test, a load of 200 g was applied at 80 ° C. for 3 minutes, and then the load was removed. Furthermore, it is a double-sided pressure-sensitive adhesive tape for fixing an optical film having a pressure-sensitive adhesive layer having a displacement displacement recovery rate measured after elapse of 3 minutes of 30 to 90%.

Description

The present invention relates to a double-sided pressure-sensitive adhesive tape for fixing an optical film, which is used for fixing an optical film and has high constant load peelability, high strain stress resistance, and tape workability to an adherend.

In a portable electronic device (for example, a mobile phone, a portable information terminal, etc.) equipped with an image display device or an input device, a double-sided adhesive tape is used for assembly. Specifically, for example, a double-sided adhesive is used to bond a cover panel for protecting the surface of a portable electronic device to a touch panel module or an optical film of a display panel module, or to bond a touch panel module and a display panel module. Tape is used.
Such a double-sided pressure-sensitive adhesive tape is used, for example, by being punched into a frame shape or the like and arranged around the display screen (for example, Patent Documents 1 and 2).

The double-sided pressure-sensitive adhesive tape used for fixing the optical film is required to have strain stress resistance in addition to the adhesive force. That is, when the optical film fixed by the adhesive tape is exposed to a high temperature, the difference in the expansion / contraction behavior of the adhesive tape and the optical film is caused by the difference in the linear expansion coefficient between the adhesive tape and the optical film. When the adhesive tape and the optical film are firmly fixed, the stress generated by the difference in the expansion / contraction behavior remains in the optical film, causing optical distortion. When the adhesive tape and the optical film are loosely fixed, the occurrence of optical distortion can be suppressed, but there is a problem that the adhesive force becomes insufficient. Thus, in general, there was a trade-off relationship between adhesive force and strain stress resistance.

In particular, in the adhesion and fixing of components in recent large-sized portable electronic devices, it is necessary to attach a heavy component or member, and the load on the adhesive tape is increased. Also, in recent portable electronic devices, so-called narrower frames, in which the periphery of the display screen is narrowed to ensure a wider screen, are progressing, and the width of the peripheral portion of the screen is extremely narrow in narrowed portable electronic devices. Therefore, there is a demand for high adhesive force that can securely fix a member even if the bonding area is small, particularly high constant load peelability that is difficult to peel off when a constant load is applied.

Furthermore, in order to fix the optical film in the portable electronic device, it is necessary to punch out the double-sided adhesive tape into a frame shape or the like. At this time, if the adhesive adheres to the blade of the cutting machine, continuous cutting operation becomes difficult. In particular, when the frame is narrowed as described above, and when cutting into a narrower frame shape, adhesion of the adhesive becomes a problem. Therefore, high tape workability is also required that can be continuously cut into a narrow frame shape without sticking the adhesive to the blade of the cutting machine in the cutting operation.
Therefore, the double-sided pressure-sensitive adhesive tape used for fixing the optical film in the portable electronic device is required to have higher constant load peelability, higher strain stress resistance, and tape workability than the conventional one. It is coming.

JP 2009-242541 A JP 2009-258274 A

In view of the above situation, the present invention provides a double-sided pressure-sensitive adhesive tape for fixing an optical film, which is used for fixing an optical film and has high constant load peelability, high strain stress resistance, and tape workability. For the purpose.

The present invention is an optical film fixing double-sided pressure-sensitive adhesive tape for fixing an optical film to an adherend, and has a weight average molecular weight of 500,000 to 1,800,000, molecular weight distribution (Mw / Mn) obtained by living radical polymerization. It has a pressure-sensitive adhesive layer containing an acrylic polymer of 1.05 to 2.5 and a cross-linking agent, and in a minute shear displacement measurement test, a load of 200 g was applied at 80 ° C. for 3 minutes, and then the load was removed. Furthermore, it is a double-sided pressure-sensitive adhesive tape for fixing an optical film having a pressure-sensitive adhesive layer having a displacement displacement recovery rate measured after elapse of 3 minutes of 30 to 90%.
The present invention is described in detail below.

The inventors of the present invention include an acrylic polymer obtained by living radical polymerization and having a weight average molecular weight and a molecular weight distribution (Mw / Mn) within a specific range, a crosslinking agent, and a micro shear displacement. A double-sided pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer with a displacement displacement recovery rate measured in a measurement test of 30 to 90% can exhibit high constant load peelability, high strain stress resistance, and tape workability with respect to an adherend. As a result, the present invention has been completed.

The double-sided pressure-sensitive adhesive tape for fixing an optical film of the present invention (hereinafter, also simply referred to as “double-sided pressure-sensitive adhesive tape”) was subjected to a load of 200 g at 80 ° C. for 3 minutes in a minute shear displacement measurement test, and then removed. Further, the displacement displacement recovery rate measured after elapse of 3 minutes is 30 to 90%.
When the displacement displacement recovery rate is within the above range, the double-sided pressure-sensitive adhesive tape can achieve both high constant load peelability, high strain stress resistance, and good tape workability with respect to the adherend. When the displacement displacement recovery rate is 30% or less, the pressure-sensitive adhesive layer becomes too soft and easily peels off, cannot exhibit high constant load peelability, and deteriorates tape workability. If it exceeds 90%, the pressure-sensitive adhesive layer becomes too hard, and the strain stress resistance decreases. A preferable lower limit of the displacement displacement recovery rate is 35%, a preferable upper limit is 85%, and a more preferable upper limit is 80%.

FIG. 1 is a schematic diagram showing an outline of an apparatus used for the micro shear displacement measurement test. The displacement displacement recovery rate can be measured, for example, as follows using a micro shear displacement displacement measuring test apparatus as shown in FIG.
First, the release film on one side of the double-sided pressure-sensitive adhesive tape to be tested is peeled off, and a corona-treated polyethylene terephthalate (PET) film is applied to the exposed pressure-sensitive adhesive layer, and then cut into a width of 1 cm and a length of 12 cm The test piece 5 is obtained.
The temperature controller 4 (for example, a combination of a Peltier element and a cooling chiller unit) is set to 80 ° C. and left until it stabilizes at the set temperature.
The other release film of the test piece 5 is removed by peeling about 3 cm from the end, and the exposed pressure-sensitive adhesive layer is attached to the adherend 3 so that the adhesion area becomes 1 cm × 1 cm.
A quartz block 2 having a mirror-finished end surface is placed on the pasting surface, and the test piece 5 is attached to a wire connecting to a weight 6 of 200 g. Let stand in this state and incubate for 5 minutes.
After 5 minutes, the PC connected to the apparatus is operated to start applying a load, and a shear load in the waterside direction is applied to the test piece 5 for 3 minutes. Here, the displacement amount due to the adhesive deformation is detected as the movement amount of the mirror-treated quartz block 2 on the test piece 5 by the laser interferometer 1, and the value is recorded by the PC every second for 3 minutes.
After 3 minutes, the load is removed, and recovery of displacement due to adhesive deformation is detected by the laser interferometer 1 as the amount of movement of the mirror-treated quartz block 2 on the test piece 5, and the value is recorded on a PC every 3 minutes. To do.
After the test is completed, the “slip displacement recovery rate” can be calculated based on the following calculation formula.

Deviation displacement recovery rate (%) = {(deviation displacement after 3 minutes load load (μm)) − (deviation displacement after 3 minutes load removal (μm))} / (deviation displacement after 3 minutes load load (μm) ) × 100

The double-sided pressure-sensitive adhesive tape of the present invention contains an acrylic polymer and a crosslinking agent.
The acrylic polymer is obtained by living radical polymerization and has a weight average molecular weight of 500,000 to 1,800,000 and a molecular weight distribution (Mw / Mn) of 1.05 to 2.5. Thus, an acrylic polymer having a weight average molecular weight and molecular weight distribution (Mw / Mn) within a specific range is extremely homogeneous, and a double-sided pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer composed of such a homogeneous polymer component is not covered. A high constant load peelability and tape processability with respect to the adherend can be exhibited.

When the weight average molecular weight is less than 500,000, the pressure-sensitive adhesive layer becomes too soft and heat resistance is lowered. When the weight average molecular weight exceeds 1,800,000, the viscosity at the time of coating becomes too high to be difficult to coat, which may cause uneven thickness of the pressure-sensitive adhesive layer. The minimum with a preferable weight average molecular weight (Mw) of the said acrylic polymer is 600,000, and a preferable upper limit is 1.4 million.

When the molecular weight distribution exceeds 2.5, there are many low molecular weight components contained in the polymer component, the constant load peelability to the adherend is lowered, and the tape processability is also inferior. A preferable upper limit of the molecular weight distribution is 2.0, a more preferable upper limit is 1.8, and a further preferable upper limit is 1.7.

The molecular weight distribution (Mw / Mn) is a ratio between the weight average molecular weight (Mw) and the number average molecular weight (Mn).
A weight average molecular weight (Mw) and a number average molecular weight (Mn) are measured as a polystyrene conversion molecular weight by the gel permeation chromatography (GPC) method. Specifically, the weight average molecular weight (Mw) and the number average molecular weight (Mn) are obtained by filtering a diluted solution obtained by diluting a living radical polymerization crosslinkable acrylic polymer with tetrahydrofuran (THF) 50 times with a filter, It is measured as a polystyrene-converted molecular weight by the GPC method using the obtained filtrate. In the GPC method, for example, 2690 Separations Model (manufactured by Waters) or the like can be used.

The acrylic polymer is obtained by living radical polymerization. Living radical polymerization is polymerization in which molecular chains grow without the polymerization reaction being hindered by side reactions such as termination reactions or chain transfer reactions. According to living radical polymerization, for example, a polymer having a more uniform molecular weight and composition than that of free radical polymerization can be obtained, and the production of low molecular weight components and the like can be suppressed. The molecular weight and molecular weight distribution (Mw / Mn) can be within the intended range. Furthermore, when the said acryl-type polymer has a crosslinkable functional group, this crosslinkable functional group can be included in all the polymers, and higher constant load peelability can be exhibited.

FIG. 2 shows a schematic diagram for explaining living radical polymerization. Living radical polymerization is polymerization in which molecular chains grow without the polymerization reaction being hindered by side reactions such as termination reactions or chain transfer reactions. In living radical polymerization, the reaction proceeds without the growth terminal radicals being deactivated and without generating new radical species during the reaction. In the middle of the reaction, all polymer chains are polymerized while uniformly reacting with the monomer, and the composition of all polymers approaches uniform. Therefore, the crosslinkable functional group-containing monomer 112 is included in all the polymers of the acrylic polymer 11 to be obtained. When the acrylic polymer 11 obtained by such living radical polymerization is crosslinked using a crosslinking agent, almost all the polymers can participate in crosslinking between polymer chains. In particular, since there are few low molecular weight components that do not contain a crosslinkable functional group-containing monomer, the probability that all polymer chains are involved in crosslinking is improved. FIG. 3 is a schematic diagram for explaining a case where an acrylic polymer obtained by living radical polymerization is crosslinked. In the acrylic polymer obtained by living radical polymerization, the composition of all polymers is uniform, and since the crosslinkable functional group-containing monomer is included, all polymer chains are involved in crosslinking. In FIG. 3, a hydroxyl group is shown as an example of the crosslinkable functional group. Thus, since almost all polymers can participate in crosslinking between polymer chains, it is possible to obtain an adhesive tape that can exhibit high constant load peelability to the adherend.

In the conventional free radical polymerization, it is difficult to adjust the weight average molecular weight and the molecular weight distribution (Mw / Mn) to an intended range.
FIG. 4 shows a schematic diagram for explaining free radical polymerization. In free radical polymerization, radical species are continuously generated during the reaction and added to the monomer, and the polymerization proceeds. Therefore, in the free radical polymerization, a polymer 123 in which the growing terminal radical is deactivated during the reaction and a polymer 124 grown by the radical species newly generated during the reaction are generated. Therefore, when an acrylic polymer containing a crosslinkable functional group is produced by free radical polymerization, a polymer containing no relatively low molecular weight crosslinkable functional group-containing monomer is produced. Even when the acrylic polymer 12 obtained by such free radical polymerization is crosslinked using a crosslinking agent, a polymer that does not contain a crosslinkable functional group-containing monomer cannot participate in crosslinking between polymer chains. . FIG. 5 shows a schematic diagram for explaining a case where an acrylic polymer obtained by free radical polymerization is crosslinked. The acrylic polymer obtained by free radical polymerization has a non-uniform polymer composition and contains a polymer that does not contain a relatively low molecular weight crosslinkable functional group-containing monomer. ing. In FIG. 5, a hydroxyl group is shown as an example of the crosslinkable functional group. When a load is applied by sticking to an adherend as a double-sided adhesive tape, peeling occurs from a site that does not contain a crosslinkable functional group-containing monomer that cannot participate in crosslinking. I can't show my sexuality.

Thus, the acrylic polymer obtained by living radical polymerization has a more uniform molecular weight and composition compared to the acrylic polymer obtained by free radical polymerization and the like, and the content of low molecular weight components is small, All polymers have the property of containing a crosslinkable functional group-containing monomer. The effects of the present invention, such as high constant load peelability, high strain stress resistance, and tape processability with respect to the adherend, are exhibited only when an acrylic polymer obtained by living radical polymerization is used.
The characteristics of the acrylic polymer obtained by such living radical polymerization are based on a production method called living radical polymerization in which a molecular chain grows without being hindered by a side reaction such as a termination reaction or a chain transfer reaction. Is. However, although it is possible to indirectly represent the properties of the acrylic polymer obtained by living radical polymerization as an average value of the whole polymer such as weight average molecular weight (Mw) and molecular weight distribution (Mw / Mn), it is included. It is extremely difficult to directly specify the chain length of each polymer and the structure and characteristics of the monomer component in each polymer. It must be said that it is impossible or almost impractical to directly identify the acrylic polymer obtained by living radical polymerization by its structure or properties. Therefore, in the present invention, it should be allowed to describe the living radical polymerization acrylic polymer by “the acrylic polymer obtained by living radical polymerization,” and the production method thereof.

Among living radical polymerizations, living radical polymerization using an organic tellurium polymerization initiator has a crosslinkable functional group such as a carboxyl group, a hydroxyl group, an amino group, an amide group, and a nitrile group, unlike other living radical polymerizations. Without protecting any radically polymerizable monomer, it is possible to obtain a polymer having a uniform molecular weight and composition by polymerizing with the same initiator. For this reason, the radically polymerizable monomer which has a crosslinkable functional group can be copolymerized easily.

The organic tellurium polymerization initiator is not particularly limited as long as it is generally used for living radical polymerization, and examples thereof include organic tellurium compounds and organic telluride compounds.
Examples of the organic tellurium compound include (methylterranyl-methyl) benzene, (1-methylterranyl-ethyl) benzene, (2-methylterranyl-propyl) benzene, 1-chloro-4- (methylterranyl-methyl) benzene, 1-hydroxy- 4- (methylterranyl-methyl) benzene, 1-methoxy-4- (methylterranyl-methyl) benzene, 1-amino-4- (methylterranyl-methyl) benzene, 1-nitro-4- (methylterranyl-methyl) benzene, 1- Cyano-4- (methylterranyl-methyl) benzene, 1-methylcarbonyl-4- (methylterranyl-methyl) benzene, 1-phenylcarbonyl-4- (methylterranyl-methyl) benzene, 1-methoxycarbonyl-4- (methylterranyl-methyl) ) Benzene, 1- Enoxycarbonyl-4- (methylterranyl-methyl) benzene, 1-sulfonyl-4- (methylterranyl-methyl) benzene, 1-trifluoromethyl-4- (methylterranyl-methyl) benzene, 1-chloro-4- (1 -Methyl terranyl-ethyl) benzene, 1-hydroxy-4- (1-methyl terranyl-ethyl) benzene, 1-methoxy-4- (1-methyl teranyl-ethyl) benzene, 1-amino-4- (1-methyl terranyl-ethyl) Benzene, 1-nitro-4- (1-methylterranyl-ethyl) benzene, 1-cyano-4- (1-methylterranyl-ethyl) benzene, 1-methylcarbonyl-4- (1-methylterranyl-ethyl) benzene, 1- Phenylcarbonyl-4- (1-methylterranyl-ethyl) benzene, 1-meth Sicarbonyl-4- (1-methylterranyl-ethyl) benzene, 1-phenoxycarbonyl-4- (1-methylterranyl-ethyl) benzene, 1-sulfonyl-4- (1-methylterranyl-ethyl) benzene, 1-trifluoromethyl -4- (1-methylteranyl-ethyl) benzene, 1-chloro-4- (2-methylterranyl-propyl) benzene, 1-hydroxy-4- (2-methylterranyl-propyl) benzene, 1-methoxy-4- (2 -Methyl teranyl-propyl) benzene, 1-amino-4- (2-methyl teranyl-propyl) benzene, 1-nitro-4- (2-methyl teranyl-propyl) benzene, 1-cyano-4- (2-methyl teranyl-propyl) Benzene, 1-methylcarbonyl-4- (2-methylterranyl-propyl ) Benzene, 1-phenylcarbonyl-4- (2-methylterranyl-propyl) benzene, 1-methoxycarbonyl-4- (2-methylterranyl-propyl) benzene, 1-phenoxycarbonyl-4- (2-methylterranyl-propyl) benzene 1-sulfonyl-4- (2-methylterranyl-propyl) benzene, 1-trifluoromethyl-4- (2-methylterranyl-propyl) benzene, 2- (methylterranyl-methyl) pyridine, 2- (1-methylterranyl-ethyl) ) Pyridine, 2- (2-methylterranyl-propyl) pyridine, 2-methylterranyl-methyl ethanoate, methyl 2-methylterranyl-propionate, methyl 2-methylterranyl-2-methylpropionate, 2-methylterranyl-ethyl ethanoate, 2 -Methylterranil Ethyl propionate, 2-Mechiruteraniru -2-methylpropionic acid ethyl, 2-methyl-Terra alkylsulfonyl acetonitrile, 2-methyl-Terra sulfonyl propionitrile, 2-methyl-2-methyl-Terra sulfonyl propionitrile, and the like. The methyl terranyl group in these organic tellurium compounds may be an ethyl terranyl group, n-propyl terranyl group, isopropyl terranyl group, n-butyl terranyl group, isobutyl terranyl group, t-butyl terranyl group, phenyl terranyl group, etc. These organic tellurium compounds may be used alone or in combination of two or more.

Examples of the organic telluride compound include dimethyl ditelluride, diethyl ditelluride, di-n-propyl ditelluride, diisopropyl ditelluride, dicyclopropyl ditelluride, di-n-butyl ditelluride, di-sec-butyl ditelluride. , Di-tert-butyl ditelluride, dicyclobutyl ditelluride, diphenyl ditelluride, bis- (p-methoxyphenyl) ditelluride, bis- (p-aminophenyl) ditelluride, bis- (p-nitrophenyl) ditelluride, bis -(P-cyanophenyl) ditelluride, bis- (p-sulfonylphenyl) ditelluride, dinaphthyl ditelluride, dipyridyl ditelluride and the like can be mentioned. These organic telluride compounds may be used alone or in combination of two or more. Of these, dimethyl ditelluride, diethyl ditelluride, di-n-propyl ditelluride, di-n-butyl ditelluride and diphenyl ditelluride are preferable.

In addition, within the range which does not impair the effect of this invention, in addition to the said organic tellurium polymerization initiator, you may use an azo compound as a polymerization initiator for the purpose of acceleration | stimulation of a polymerization rate.
The azo compound is not particularly limited as long as it is generally used for radical polymerization. For example, 2,2′-azobis (isobutyronitrile), 2,2′-azobis (2-methylbutyronitrile) ), 2,2′-azobis (2,4-dimethylvaleronitrile), 2,2′-azobis (4-methoxy-2,4-dimethylvaleronitrile), 1,1-azobis (cyclohexane-1-carbonitrile) ), 1-[(1-cyano-1-methylethyl) azo] formamide, 4,4′-azobis (4-cyanovaleric acid), dimethyl-2,2′-azobis (2-methylpropionate), Dimethyl-1,1′-azobis (1-cyclohexanecarboxylate), 2,2′-azobis {2-methyl-N- [1,1′-bis (hydroxymethyl) -2-hydroxyethyl Propionamide}, 2,2′-azobis [2-methyl-N- (2-hydroxyethyl) propionamide], 2,2′-azobis [N- (2-propenyl) -2-methylpropionamide], 2 , 2′-azobis (N-butyl-2-methylpropionamide), 2,2′-azobis (N-cyclohexyl-2-methylpropionamide), 2,2′-azobis [2- (2-imidazoline-2 -Yl) propane] dihydrochloride, 2,2'-azobis {2- [1- (2-hydroxyethyl) -2-imidazolin-2-yl] propane} dihydrochloride, 2,2'-azobis [2 -(2-imidazolin-2-yl) propane], 2,2'-azobis (2-amidinopropane) dihydrochloride, 2,2'-azobis [N- (2-carboxyethyl) -2-methylpropionami Tetrahydrate, 2,2′-azobis (1-imino-1-pyrrolidino-2-methylpropane) dihydrochloride, 2,2′-azobis (2,4,4-trimethylpentane) and the like. It is done. These azo compounds may be used alone or in combination of two or more.

The monomer mixture used as the raw material for the acrylic polymer preferably contains a crosslinkable functional group-containing monomer. The crosslinkable functional group-containing monomer has a role of inserting a crosslinkable functional group into the acrylic polymer.
Examples of the crosslinkable functional group include a hydroxyl group, a carboxyl group, a glycidyl group, an amino group, an amide group, and a nitrile group. Especially, since adjustment of the gel fraction of the said adhesive layer is easy, a hydroxyl group or a carboxyl group is preferable and a hydroxyl group is more preferable.

As a monomer which has a hydroxyl group, (meth) acrylic acid ester which has hydroxyl groups, such as 4-hydroxybutyl (meth) acrylate and 2-hydroxyethyl (meth) acrylate, is mentioned, for example.
As a monomer which has a carboxyl group, (meth) acrylic acid is mentioned, for example.
Examples of the monomer having a glycidyl group include glycidyl (meth) acrylate.
Examples of the monomer having an amide group include hydroxyethyl acrylamide, isopropyl acrylamide, dimethylaminopropyl acrylamide and the like.
Examples of the monomer having a nitrile group include acrylonitrile.

When a (meth) acrylic acid ester having a hydroxyl group is used as the crosslinkable functional group-containing monomer, the content in the monomer mixture is not particularly limited, but the preferred lower limit is 0.01% by weight and the preferred upper limit is 30% by weight. is there. When the content of the (meth) acrylic acid ester having a hydroxyl group is less than 0.01% by weight, the resulting pressure-sensitive adhesive layer may become too soft and the heat resistance may be lowered. The resulting pressure-sensitive adhesive layer may become too hard, and the double-sided pressure-sensitive adhesive tape may be easily peeled off or the strain stress resistance may be reduced.

When an acrylic monomer having a carboxyl group is used as the crosslinkable functional group-containing monomer, the content in the monomer mixture is not limited, but the preferred lower limit is 0.1% by weight and the preferred upper limit is 10% by weight. When the content of the acrylic monomer having a carboxyl group is less than 0.1% by weight, the resulting pressure-sensitive adhesive layer may become too soft and the heat resistance may be lowered. The pressure-sensitive adhesive layer is too hard and the double-sided pressure-sensitive adhesive tape may be easily peeled off.

In order for the pressure-sensitive adhesive layer to satisfy the displacement displacement recovery rate, the mixed monomer that is the raw material of the acrylic polymer is n-propyl (meth) acrylate, n-butyl (meth) acrylate, n-pentyl (meth). Acrylate, n-heptyl (meth) acrylate, n-octyl (meth) acrylate, 2-ethylhexyl acrylate, n-nonyl (meth) acrylate, n-butyl (meth) acrylate, n-decyl (meth) acrylate, n-dodecyl Although (meth) acrylate etc. can be used, it is preferable to contain the (meth) acrylic acid ester whose glass transition point of a monomer unit is equivalent to or less than n-butyl acrylate. Especially, since it can exhibit especially high strain-stress resistance, it is preferable to contain an acrylate having 8 carbon atoms in the side chain, particularly 2-ethylhexyl acrylate.

When the mixed monomer contains 2-ethylhexyl acrylate, the content of 2-ethylhexyl acrylate in the monomer mixture is preferably 60% by weight or more, and more preferably 80% by weight or more. By containing 2-ethylhexyl acrylate as a main component, the resulting pressure-sensitive adhesive layer can exhibit particularly high strain stress resistance.

The mixed monomer used as the raw material for the acrylic polymer may contain other radical polymerizable monomers such as the crosslinkable functional group-containing monomer and (meth) acrylic acid ester such as 2-ethylhexyl acrylate, if necessary. . As said other radically polymerizable monomer, other (meth) acrylic acid ester is mentioned, for example. In addition to the acrylic monomer, a vinyl compound may be used as a monomer.

In the living radical polymerization, a dispersion stabilizer may be used. Examples of the dispersion stabilizer include polyvinyl pyrrolidone, polyvinyl alcohol, methyl cellulose, ethyl cellulose, poly (meth) acrylic acid, poly (meth) acrylic acid ester, and polyethylene glycol.
As the living radical polymerization method, conventionally known methods are used, and examples thereof include solution polymerization (boiling point polymerization or constant temperature polymerization), emulsion polymerization, suspension polymerization, bulk polymerization and the like.
When a polymerization solvent is used in the living radical polymerization, the polymerization solvent is not particularly limited. For example, a nonpolar solvent such as hexane, cyclohexane, octane, toluene, xylene, water, methanol, ethanol, propanol, butanol, acetone, Highly polar solvents such as methyl ethyl ketone, methyl isobutyl ketone, tetrahydrofuran, dioxane, N, N-dimethylformamide can be used. These polymerization solvents may be used alone or in combination of two or more.
The polymerization temperature is preferably 0 to 110 ° C. from the viewpoint of the polymerization rate.

The pressure-sensitive adhesive layer preferably has a gel fraction of 50% by weight or less. By making the gel fraction 50% by weight or less, it is possible to exhibit higher constant load peelability to the adherend.
The gel fraction is measured as follows. First, the adhesive tape was cut into a flat rectangular shape of 50 mm × 100 mm to prepare a test piece. After the test piece was immersed in ethyl acetate at 23 ° C. for 24 hours, the test piece was taken out from ethyl acetate and subjected to a condition of 110 ° C. For 1 hour. The weight of the test piece after drying is measured, and the gel fraction is calculated using the following formula (1). In addition, the release film for protecting an adhesive layer shall not be laminated | stacked on the test piece.
Gel fraction (% by weight) = 100 × (W2-W0) / (W1-W0) (1)
(W0: weight of substrate, W1: weight of test piece before immersion, W2: weight of test piece after immersion and drying)

The cross-linking agent is not particularly limited, and depending on the type of cross-linkable functional group contained in the acrylic polymer, for example, an isocyanate cross-linking agent, an aziridine cross-linking agent, an epoxy cross-linking agent, a metal chelate cross-linking agent, etc. Select and use.
For example, when the acrylic polymer has a hydroxyl group as a crosslinkable functional group, the acrylic polymer can be crosslinked by using, for example, an isocyanate crosslinking agent as a crosslinking agent. Moreover, when the said acrylic polymer has a carboxyl group as a crosslinkable functional group, the said acrylic polymer can be bridge | crosslinked by using an epoxy-type crosslinking agent or an aziridine type crosslinking agent as a crosslinking agent, for example.
In particular, an acrylic polymer obtained by living radical polymerization has a uniform composition of all the polymers contained therein and has a crosslinkable functional group, so that all the polymers can participate in crosslinking between polymer chains. For this reason, even if it is a thin adhesive tape, it is hard to peel off and the adhesive tape which can exhibit high constant load peelability and adhesive cohesive force with respect to a to-be-adhered body can be obtained.
Especially, since it is excellent in the adhesive stability with respect to a base material, an isocyanate type crosslinking agent is preferable. Examples of the isocyanate-based crosslinking agent include Coronate HX (manufactured by Nippon Polyurethane Industry Co., Ltd.), Coronate L (manufactured by Nippon Polyurethane Industry Co., Ltd.), and Mytec NY260A (manufactured by Mitsubishi Chemical Corporation).

The blending amount of the crosslinking agent is preferably 0.01 parts by weight, preferably 5 parts by weight, and more preferably 0.1 parts by weight, more preferably the upper limit with respect to 100 parts by weight of the acrylic polymer. 3 parts by weight.

The pressure-sensitive adhesive layer preferably further contains a tackifier resin. When the said adhesive layer contains tackifying resin, the constant load peelability with respect to the adherend of a double-sided adhesive tape further improves. Especially, when using the tackifier which has a crosslinkable functional group, it can bridge | crosslink with the said acrylic polymer via a crosslinking agent.

The tackifying resin has a preferred lower limit of hydroxyl value of 25 and a preferred upper limit of 55. When the hydroxyl value is out of the above range, the constant load peelability of the adhesive tape to the adherend may be lowered. A more preferred lower limit of the hydroxyl value is 30, and a more preferred upper limit is 50.
The hydroxyl value can be measured by JIS K1557 (phthalic anhydride method).

The tackifying resin has a preferable lower limit of the softening temperature of 70 ° C and a preferable upper limit of 170 ° C. When the softening temperature is less than 70 ° C., the tackifying resin may be too soft and the constant load peelability may be lowered. When the softening temperature exceeds 170 ° C., the pressure-sensitive adhesive layer becomes too hard, the pressure-sensitive adhesive tape is easily peeled off, and the constant load peelability to the adherend may be lowered. A more preferable lower limit of the softening temperature is 120 ° C.
The softening temperature is a softening temperature measured by the JIS K2207 ring and ball method.

The tackifying resin is not particularly limited, and examples thereof include rosin resins such as rosin ester resins, terpene resins such as terpene phenol resins, and petroleum resins. Of these, rosin ester resins and terpene phenol resins are preferable.
The above-mentioned rosin ester resins are rosin resins mainly composed of abietic acid, disproportionated rosin resins and hydrogenated rosin resins, dimers of polymer acids such as abietic acid (polymerized rosin resins), etc. It is the resin obtained by making it. A part of the hydroxyl group of the alcohol used for esterification is contained in the resin without being used for esterification, so that the hydroxyl value is adjusted to the above range. Examples of the alcohol include polyhydric alcohols such as ethylene glycol, glycerin, and pentaerythritol.
Resin esterified rosin resin is rosin ester resin, disproportionated rosin resin esterified disproportionated rosin ester resin, hydrogenated rosin resin esterified resin is hydrogenated rosin ester resin, polymerized rosin A resin obtained by esterifying the resin is a polymerized rosin ester resin.
The terpene phenol resin is a resin obtained by polymerizing terpene in the presence of phenol.

Examples of the disproportionated rosin ester resin include Superester A75 (hydroxyl value 23, softening temperature 75 ° C.) manufactured by Arakawa Chemical Industries, Superester A100 (hydroxyl value 16, softening temperature 100 ° C.) manufactured by Arakawa Chemical Co., Ltd. Examples thereof include ester A115 (hydroxyl value 19, softening temperature 115 ° C.), super ester A125 (hydroxyl value 15, softening temperature 125 ° C.) manufactured by the same company. Examples of the hydrogenated rosin ester resin include Pine Crystal KE-359 (hydroxyl value 42, softening temperature 100 ° C.) manufactured by Arakawa Chemical Industries, and ester gum H (hydroxyl value 29, softening temperature 70 ° C.) manufactured by the same company. It is done. Examples of the polymerized rosin ester resin include Pencel D135 (Hydroxyl value 45, softening temperature 135 ° C.) manufactured by Arakawa Chemical Industries, Pencel D125 (Hydroxyl value 34, softening temperature 125 ° C.) manufactured by Arakawa Chemical Co., Ltd. 42, softening temperature 160 ° C.) and the like.
Examples of the terpene resin include YS Polystar G150 (softening point 150 ° C.) manufactured by Yasuhara Chemical, YS Polyster T100 (softening point 100 ° C.), YS Polyster G125 (softening point 125 ° C.), YS Polyster Examples thereof include T115 (softening point 115 ° C.), YS Polystar T130 (softening point 130 ° C.) manufactured by the same company.
These tackifier resins may be used alone or in combination of two or more.

The content of the tackifier resin is preferably 5 parts by weight with respect to 100 parts by weight of the acrylic polymer, and 40 parts by weight with a preferred upper limit. When the content is less than 5 parts by weight, the double-sided pressure-sensitive adhesive tape is easily peeled off, and the constant load peelability to the adherend may be lowered. Even when the content exceeds 40 parts by weight, the pressure-sensitive adhesive layer may become too hard due to an increase in the glass transition temperature (Tg), and the double-sided pressure-sensitive adhesive tape may be easily peeled off.

The pressure-sensitive adhesive layer may contain other resins such as additives such as a plasticizer, an emulsifier, a softener, a filler, a pigment, a dye, a silane coupling agent, and an antioxidant, if necessary. Good.

Even if the double-sided pressure-sensitive adhesive tape of the present invention is a thin pressure-sensitive adhesive tape, it is difficult for the double-sided pressure-sensitive adhesive tape to peel off. Therefore, the pressure-sensitive adhesive layer and the substrate described later can be thinned according to the application.
The thickness of the pressure-sensitive adhesive layer is not particularly limited because it is set depending on the application, but a preferred lower limit is 1 μm and a preferred upper limit is 100 μm. When the thickness is less than 1 μm, the pressure-sensitive adhesive tape is easily peeled off, and the constant load peelability to the adherend may be lowered. When the said thickness exceeds 100 micrometers, a thin adhesive tape may not be obtained. The more preferable lower limit of the thickness of the pressure-sensitive adhesive layer is 3 μm, the more preferable upper limit is 75 μm, the still more preferable lower limit is 5 μm, and the still more preferable upper limit is 25 μm.

The double-sided pressure-sensitive adhesive tape of the present invention may be a support type having a base material or a non-support type having no base material. In the case of the support type, the pressure-sensitive adhesive layer is formed on both surfaces of the substrate.

Although the said base material is not specifically limited, A resin film, a resin foam, paper, a nonwoven fabric, a yarn cloth cloth etc. are mentioned.
Examples of the resin film include polyolefin resin films such as polyethylene films and polypropylene films, polyester resin films such as PET films, and modified olefins such as ethylene-vinyl acetate copolymers and ethylene-acrylic acid ester copolymers. Examples thereof include a resin film, a polyvinyl chloride resin film, a polyurethane resin film, and a cycloolefin polymer resin film.
Examples of the resin foam include polyethylene foam, polypropylene foam, acrylic foam, urethane foam, and ethylene propylene rubber foam.
Examples of the yarn cloth cloth include a woven polyethylene flat yarn and a laminate of a resin film on the surface thereof.
Especially in the case of double-sided tapes used in the assembly of display modules, black-printed substrates to prevent light transmission, white-printed substrates to improve light reflectivity, metal-deposited film substrates, etc. Can also be used.

The thickness of the substrate is not particularly limited because it is set depending on the application, but for example, in the case of a film substrate, 1 to 100 μm is preferable, and 5 to 75 μm is more preferable. When the thickness of the base material is less than 1 μm, the mechanical strength of the double-sided pressure-sensitive adhesive tape may be lowered. When the thickness of the base material exceeds 100 μm, the double-sided pressure-sensitive adhesive tape becomes too strong, and it may be difficult to adhere and adhere together along the shape of the adherend.

The method for producing the double-sided pressure-sensitive adhesive tape of the present invention is not particularly limited. For example, the acrylic polymer is mixed with other compounding components such as the tackifier resin and the cross-linking agent as necessary, and the pressure-sensitive adhesive is stirred. A method of preparing a solution, and subsequently applying the adhesive solution to a release-treated PET film to form an adhesive layer and transferring the obtained adhesive layer to both surfaces of the substrate, Examples include a method of directly coating and drying the material. The pressure-sensitive adhesive layer formed by coating and drying the PET film obtained by releasing the pressure-sensitive adhesive solution may be used as a non-support type pressure-sensitive adhesive tape without a substrate.

ADVANTAGE OF THE INVENTION According to this invention, the double-sided adhesive tape for optical film fixation which has the high constant load peelability with respect to a to-be-adhered body, high strain stress resistance, and tape workability used for fixation of an optical film can be provided. .

It is a schematic diagram which shows the outline of the apparatus used for a micro shear deviation displacement measurement test. It is a schematic diagram explaining living radical polymerization. It is a schematic diagram explaining the case where the acrylic polymer obtained by living radical polymerization is bridge | crosslinked. It is a schematic diagram explaining free radical polymerization. It is a schematic diagram explaining the case where the acrylic polymer obtained by free radical polymerization is bridge | crosslinked. It is the schematic diagram which showed the test method which measures the grade of the optical film distortion in an Example. It is the schematic diagram which showed the test method of the constant load peeling test in an Example.

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.

(Synthesis of acrylic polymer)
(Synthesis 1)
(Synthesis 1-1)
Tellurium (40 mesh, metal tellurium, manufactured by Aldrich) 6.38 g (50 mmol) was suspended in tetrahydrofuran (THF) 50 mL, and 1.6 mol / L n-butyllithium / hexane solution (Aldrich) 34 was added thereto. 4 mL (55 mmol) was slowly added dropwise at room temperature. The reaction solution was stirred until the metal tellurium disappeared completely. To this reaction solution, 10.7 g (55 mmol) of ethyl-2-bromo-isobutyrate was added at room temperature and stirred for 2 hours. After completion of the reaction, the solvent was concentrated under reduced pressure, followed by distillation under reduced pressure to obtain a yellow oily ethyl 2-methyl-2-n-butylteranyl-propionate.

(Synthesis 1-2)
In a glove box substituted with argon, in a reaction vessel, 19 μL of ethyl 2-methyl-2-n-butylteranyl-propionate prepared in Synthesis Example 1-1, V-60 (2,2′-azobisisobutyro Nitrile (manufactured by Wako Pure Chemical Industries, Ltd.) (1.4 mg) and ethyl acetate (1 mL) were added, the reaction vessel was sealed, and the reaction vessel was removed from the glove box. Subsequently, while flowing argon gas into the reaction vessel, mixed monomers shown in Table 1 (2EHA: 2-ethylhexyl acrylate, BA: butyl acrylate, EA: ethyl acrylate, AAc: acrylic acid, HEA) : 2-hydroxyethyl acrylate) 100 g in total and 66.5 g of ethyl acetate as a polymerization solvent were added, and a polymerization reaction was carried out at 60 ° C. for 20 hours to obtain a living radical polymerized acrylic polymer-containing solution.
The obtained acrylic polymer-containing solution was diluted 50-fold with tetrahydrofuran (THF), and the resulting diluted solution was filtered with a filter (material: polytetrafluoroethylene, pore diameter: 0.2 μm). Supplied to a gel permeation chromatograph (manufactured by Waters, 2690 Separations Model), GPC measurement was performed under the conditions of a sample flow rate of 1 ml / min and a column temperature of 40 ° C., and the molecular weight in terms of polystyrene of the polymer was measured. Molecular weight (Mw) and molecular weight distribution (Mw / Mn) were determined. GPC KF-806L (Showa Denko) was used as the column, and a differential refractometer was used as the detector.

(Synthesis 2-7)
Preparation amount of ethyl 2-methyl-2-n-butylteranyl-propionate, preparation amount of V-60 (2,2′-azobisisobutyronitrile, manufactured by Wako Pure Chemical Industries, Ltd.), and composition of mixed monomer Except for the above, Table 1 was used to obtain a living radical polymerized acrylic polymer-containing solution in the same manner as in Synthesis 1, and the weight average molecular weight (Mw) and molecular weight distribution (Mw / Mn) were determined.

(Synthesis 8)
50 g of ethyl acetate was added as a polymerization solvent in the reaction vessel, and after bubbling with nitrogen, the reaction vessel was heated while flowing nitrogen and refluxing was started. Subsequently, a polymerization initiator solution obtained by diluting 150 mg of V-60 (2,2′-azobisisobutyronitrile, manufactured by Wako Pure Chemical Industries, Ltd.) 10 times with ethyl acetate as a polymerization initiator was placed in the reaction vessel. A total of 100 g of the mixed monomers shown in Table 1 was added dropwise over 2 hours. After completion of the dropwise addition, a polymerization initiator solution in which 150 mg of V-60 (2,2′-azobisisobutyronitrile, manufactured by Wako Pure Chemical Industries, Ltd.) as a polymerization initiator was diluted 10 times with ethyl acetate was again put in the reaction vessel. The resultant was subjected to a polymerization reaction for 4 hours to obtain a free radical polymerized acrylic polymer-containing solution.
In the same manner as in Synthesis 1, the weight average molecular weight (Mw) and the molecular weight distribution (Mw / Mn) were determined.

(Examples 1-7, Comparative Examples 1-4)
To the acrylic polymer-containing solution obtained above, ethyl acetate is added to 100 parts by weight of the nonvolatile content and stirred. Coronate L (isocyanate-based crosslinking agent, manufactured by Nippon Polyurethane Co., Ltd.) as a crosslinking agent, and tackifying resin Pencel D135 (polymerized rosin ester, manufactured by Arakawa Chemical Industry Co., Ltd.) and YS Polystar G125 (terpene-based tackifier resin, manufactured by Yasuhara Chemical Co., Ltd.) were added in predetermined amounts as shown in Table 2 and stirred, and an adhesive solution having a nonvolatile content of 30% by weight Got. The obtained pressure-sensitive adhesive solution was applied to a PET film having a thickness of 50 μm which was subjected to a release treatment, and after drying, the paste thickness was 7.5 μm, and then dried at 70 ° C. for 10 minutes to obtain a double-sided pressure-sensitive adhesive tape. . In addition, the release film for protecting an adhesive layer was laminated | stacked on the surface of the both sides of an adhesive layer.

About the obtained double-sided adhesive tape, the displacement displacement recovery rate was measured as follows using the micro shear displacement measuring test apparatus (Asahi Seiko Co., Ltd., shear creep measuring apparatus, NST1) shown in FIG.
First, the release film on one side of the obtained double-sided pressure-sensitive adhesive tape is peeled off and a polyethylene terephthalate (PET) film subjected to corona treatment is attached to the exposed pressure-sensitive adhesive layer, and then cut into a width of 1 cm and a length of 12 cm. Test piece 5 was obtained. The temperature controller 4 of the apparatus was set to 80 ° C. and left to stabilize at the set temperature. (The temperature controller was used in combination with: Takagi Manufacturing Co., Ltd. Temperature Controller SA100, Model SA100FK08-MN-4 * NN-NN; Takagi Manufacturing Co., Ltd. Copper Water-cooled Peltier Unit, Model PU-50W; EYELA Cooling Water circulator Cool Ace, model CCA1111) The other release film of the test piece 5 is peeled off about 3 cm from the end and removed, and the exposed adhesive layer is attached to the adherend 3 so that the adhesion area becomes 1 cm × 1 cm. I attached. A quartz block 2 (having chrome deposited on quartz glass) whose end face is mirror-finished is placed on the affixing surface, and the test piece 5 is attached to a wire that connects to a 200 g weight 6. The mixture was left in this state for 5 minutes. After 5 minutes, the PC connected to the apparatus was operated to start applying a load, and a shear load in the waterside direction was applied to the test piece 5 for 3 minutes. Here, the amount of displacement due to adhesive deformation is detected as the amount of movement of the mirror-treated quartz block 2 on the test piece 5 by the laser interferometer 1 (SI-F10 manufactured by Keyence), and the value is measured by PC every second for 3 minutes. Was recorded. After 3 minutes, the load is removed, and recovery of displacement due to adhesive deformation is detected by the laser interferometer 1 as the amount of movement of the mirror-treated quartz block 2 on the test piece 5, and the value is recorded on a PC every 3 minutes. did. After the test was completed, the “slip displacement recovery rate” was calculated based on the following calculation formula.

Deviation displacement recovery rate (%) = {(deviation displacement after 3 minutes load load (μm)) − (deviation displacement after 3 minutes load removal (μm))} / (deviation displacement after 3 minutes load load (μm) ) × 100

(Evaluation)
The following evaluation was performed about the adhesive tape obtained by the Example and the comparative example. The results are shown in Table 2.

(1) Optical distortion test of optical film FIG. 6 is a schematic diagram showing a test method for measuring the degree of optical film distortion. It was evaluated by exposing the test sample as shown in FIG. 6 to a high temperature condition whether the adhesive layer could relieve the deformation of the optical film due to the temperature change.
The release film on one side of the test piece 20 in which the double-sided adhesive tape was punched into a frame shape with a width of 2.5 mm was peeled and removed, and on the exposed adhesive layer, as shown in FIG. A PC frame 21 having a frame width of 5 mm and 100 mm × 63 mm and a 88 mm × 51 mm BEF sheet 22 [TBEF II GMV2 (24)] were bonded together. At this time, the adhesion widths of the test piece 20 and the PC frame 21 and the test piece 20 and the BEF sheet 22 were adjusted to be 1 mm.
Next, the release film on the opposite surface of the test piece 20 was peeled and removed, and the glass plate 23 was bonded onto the exposed pressure-sensitive adhesive layer, and a 10 kg weight was applied for 10 seconds. Then, the test sample 24 was produced by leaving still at 23 degreeC and the conditions of 50% of relative humidity for at least 24 hours.
Test sample 24 was placed in an 85 ° C. oven and allowed to stand for 96 hours.
Thereafter, the temperature was slowly returned to room temperature over 30 minutes, and the optical film was evaluated for distortion according to the following criteria.
A: No distortion was observed. O: Distortion was observed but the image was not affected. X: Distortion was observed and the image was affected.

(2) Constant load peelability with respect to polycarbonate (PC) plate FIG. 7 is a schematic diagram showing a test method of a constant load peel test. As shown in FIG. 7, the obtained double-sided adhesive tape was cut into a strip shape having a width of 20 mm and a length of 50 mm to produce a test piece 31, and the release film was peeled off from the surface of the test piece 31. The pressure-sensitive adhesive layer was exposed and placed on the polycarbonate plate 30 so that the pressure-sensitive adhesive layer faced.
Next, the release film was peeled off from the back surface of the test piece 31 and a polyethylene terephthalate film (not shown) having a thickness of 23 μm was laminated on the exposed pressure-sensitive adhesive layer, and then 300 mm on the back surface of the test piece 31. The test piece 31 and the polycarbonate plate 30 are adhered by reciprocating a 2 kg rubber roller at a speed of 1 min / min. Produced.
Next, the test sample 32 is put in an oven at 85 ° C., and as shown in FIG. 7, a load is applied to one end of the test piece 31 of the test sample 32 in a direction perpendicular to the sticking surface. Thus, the 50 g weight 33 was attached, and the time until the test piece 31 dropped from the polycarbonate plate 30 was measured. Based on the measured values obtained, the constant load peelability was evaluated according to the following criteria.
○: Drop time was 1 hour or more ×: Drop time was less than 1 hour

(3) Tape workability The obtained double-sided pressure-sensitive adhesive tape was cut into a frame shape having a width of 1 mm using a cutting machine. After performing the cutting operation 10 times, the blade of the cutting machine was visually observed, and the tape processability was evaluated according to the following criteria.
◎: Adhesive adhesion was not recognized on the blade ○: Adhesive slight adhesion that did not affect the cutting operation was observed ×: Adhesive enough to affect the cutting operation on the blade Adherence was observed

ADVANTAGE OF THE INVENTION According to this invention, the double-sided adhesive tape for optical film fixation which has the high constant load peelability with respect to a to-be-adhered body, high strain stress resistance, and tape workability used for fixation of an optical film can be provided. .

DESCRIPTION OF SYMBOLS 1 Laser interferometer 2 Mirror surface processing quartz block 3 To-be-adhered body (JISZ0237 normal stainless steel)
4 Temperature controller 5 Test piece (Double-sided adhesive tape)
6 Weight 7 Adhesive layer 8 Remaining release film surface 9 Corona-treated PET film surface 10 Mirror surface 11 Acrylic polymer obtained by living radical polymerization 111 Monomer not containing a crosslinkable functional group 112 Crosslinkable functional group-containing monomer 12 Acrylic polymer 121 obtained by free radical polymerization 121 Monomer 122 not containing a crosslinkable functional group 122 Crosslinkable functional group-containing monomer 123 Polymer whose growth end radical was deactivated during the reaction 124 Growth caused by radical species newly generated during the reaction Polymer 20 Test piece 21 PC frame 22 BEF sheet 23 Glass plate 24 Test sample 30 PC plate 31 Test piece 32 Test sample 33 50 g weight

Claims (2)

An optical film fixing double-sided pressure-sensitive adhesive tape for fixing an optical film to an adherend,
Having a pressure-sensitive adhesive layer containing an acrylic polymer having a weight average molecular weight of 500,000 to 1,800,000 and a molecular weight distribution (Mw / Mn) of 1.05 to 2.5 obtained by living radical polymerization;
In a minute shear displacement measurement test, a load is removed after applying a load of 200 g at 80 ° C. for 3 minutes, and further has a pressure-sensitive adhesive layer having a displacement displacement recovery rate of 30 to 90% measured after 3 minutes. A double-sided adhesive tape for fixing optical films. In a minute shear displacement measurement test, a load is removed after applying a load of 200 g at 80 ° C. for 3 minutes, and a pressure-sensitive adhesive layer having a displacement displacement recovery rate measured after the elapse of 3 minutes is 30 to 85%. The double-sided pressure-sensitive adhesive tape for fixing an optical film according to claim 1.

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