WO2017094749A1 - Double-sided adhesive sheet and layered body - Google Patents

Abstract

The present invention addresses the problem of providing, as an application for affixing two optical members, a double-sided adhesive sheet whereby affixing can easily be performed, the double-sided adhesive sheet having excellent suitability for punching, and the double-sided adhesive sheet enabling improved visibility of a display device. The present invention relates to a double-sided adhesive sheet having a transparent substrate, a first adhesive layer provided on one side of the transparent substrate, and a second adhesive layer provided on the other side of the transparent substrate, the retardation of the transparent substrate being 3,000 nm to 150,000 nm.

Description

Double-sided adhesive sheet and laminate

The present invention relates to a double-sided pressure-sensitive adhesive sheet and a laminate. Specifically, this invention relates to the transparent base material which has a predetermined retardation, and the double-sided adhesive sheet which has an adhesive layer on both surfaces of a transparent base material.

In recent years, liquid crystal displays (LCDs) are widely used in mobile phones, smartphones, personal computers, tablet terminals, and the like. In particular, an image display device that combines a display device such as a liquid crystal display and an input device such as a touch panel is used in various fields.

In the manufacture of an image display device, a transparent double-sided pressure-sensitive adhesive sheet is used for the purpose of bonding optical members. For example, for bonding two members such as a conductive member provided with a transparent electrode film such as ITO (Indium Tin Oxide) on a transparent support, an input device such as a cover glass and a touch panel, and a display device such as a liquid crystal display. Double-sided pressure-sensitive adhesive sheets are widely used. As such a double-sided pressure-sensitive adhesive sheet, a double-sided pressure-sensitive adhesive sheet comprising only a single-layer or multiple-layer pressure-sensitive adhesive layer and a double-sided pressure-sensitive adhesive sheet in which a pressure-sensitive adhesive layer is provided on both surfaces of a base film are known.

In a double-sided pressure-sensitive adhesive sheet in which a pressure-sensitive adhesive layer is provided on both sides of a base film, development of a sheet with functionality added to the base film is in progress. For example, Patent Document 1 discloses a double-sided pressure-sensitive adhesive sheet having a retardation value at a wavelength of 590 nm of 20 nm or more and 200 nm or less as a linearly depolarizing functional layer and a pressure-sensitive adhesive layer on the front and back surfaces.

In addition, not only a double-sided pressure-sensitive adhesive sheet but also a single-sided pressure-sensitive adhesive sheet may be attached to the image display device. For example, a purchaser of an image display device may stick a surface protective film or the like on the surface. Such a single-sided pressure-sensitive adhesive sheet not only simply protects the surface of the apparatus but also has a function of improving visibility. For example, Patent Document 2 discloses a single-sided pressure-sensitive adhesive sheet that can give good visibility by being attached to the surface of a display.

International Publication WO2013 / 011811 JP 2014-215509 A

As described above, various adhesive sheets are used in the image display device. The double-sided pressure-sensitive adhesive sheet that does not have a base film as an intermediate layer has the advantage that the entire apparatus can be thinned, but when punching the pressure-sensitive adhesive sheet into the shape of a member to be bonded, a part of the cross section of the punched portion (for example, In some cases, a part of the cross section of the pressure-sensitive adhesive layer) is peeled off, and the cross-sectional appearance of the punched portion becomes poor. In particular, when processing an adhesive sheet composed of a soft adhesive layer or a thick adhesive layer, the above-mentioned problems often occur.
In order to eliminate the problem at the time of punching, it is conceivable to use a double-sided pressure-sensitive adhesive sheet having a base film or the like as an intermediate layer as disclosed in Patent Document 1.

By the way, when viewed through a polarizing filter such as sunglasses, problems such as loss of images (blackout), rainbow color unevenness (color unevenness), hue shift (color misregistration), etc. may occur. It was. Although it has been proposed to use a double-sided pressure-sensitive adhesive sheet including a specific base material thickness as described in Patent Document 1 or a base film having a predetermined range of retardation as a means for solving the problem, It was insufficient.

That is, in the conventional double-sided PSA sheet, the punching suitability and the visibility of the display device are not compatible, and it is necessary to develop a double-sided PSA sheet that has good punching suitability and can improve the visibility of the display device. It was done.

Also, as a method that can improve the visibility of the display device, a method using a functional adhesive sheet as disclosed in Patent Document 2 is also conceivable. However, the single-sided adhesive sheet as disclosed in Patent Document 2 is not assumed to be used for bonding two members such as a display device and an input device, and the display device and the input device are bonded. After that, when it is desired to improve the visibility of the display device, there is a problem that the operation of further bonding such a single-sided pressure-sensitive adhesive sheet is required, and the bonding operation becomes complicated.

Therefore, the present inventors are a double-sided pressure-sensitive adhesive sheet that can be easily bonded as a bonding application of two optical members in order to solve the problems of the conventional technology, and has excellent punching suitability and display. The study was conducted with the aim of providing a double-sided PSA sheet that could improve the visibility of the device.

As a result of intensive studies to solve the above problems, the present inventors have found that a transparent base material in a double-sided pressure-sensitive adhesive sheet having a transparent base material as an intermediate layer and adhesive layers on both sides of the transparent base material. It was found that a double-sided pressure-sensitive adhesive sheet having both the punching suitability and the visibility improving effect can be obtained by setting the retardation value in the predetermined range. Furthermore, the present inventors have found that when such a double-sided pressure-sensitive adhesive sheet is used, the bonding work can be simplified, and the present invention has been completed.
Specifically, the present invention has the following configuration.

[1] It has a transparent substrate, a first pressure-sensitive adhesive layer provided on one surface side of the transparent substrate, and a second pressure-sensitive adhesive layer provided on the other surface side of the transparent substrate. The double-sided pressure-sensitive adhesive sheet has a retardation of 3000 to 150,000 nm.
[2] The double-sided pressure-sensitive adhesive sheet according to [1], wherein each of the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer has a thickness of 10 μm or more and 200 μm or less.
[3] The first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer include at least one selected from an acrylic pressure-sensitive adhesive, a urethane-based pressure-sensitive adhesive, a rubber-based pressure-sensitive adhesive, and a silicone-based pressure-sensitive adhesive [1] or The double-sided pressure-sensitive adhesive sheet according to [2].
[4] The double-sided pressure-sensitive adhesive sheet according to any one of [1] to [3], wherein the thickness of the transparent substrate is 50 μm or more and 200 μm or less.
[5] The double-sided pressure-sensitive adhesive sheet according to any one of [1] to [4], wherein the transparent substrate contains a polyethylene terephthalate resin.
[6] The double-sided pressure-sensitive adhesive sheet according to any one of [1] to [5], which is used for bonding a display device and an input device.
[7] A double-sided pressure-sensitive adhesive sheet with a release sheet, wherein the release sheet is laminated on at least one surface of the double-sided pressure-sensitive adhesive sheet according to any one of [1] to [6].
[8] A laminate having an optical member on at least one surface of the double-sided pressure-sensitive adhesive sheet according to any one of [1] to [6].

According to the present invention, it is possible to obtain a double-sided pressure-sensitive adhesive sheet having both the punching suitability and the visibility improving effect. Moreover, if the double-sided adhesive sheet of this invention is used, the bonding operation | work at the time of bonding two optical members can be simplified.

FIG. 1 is a cross-sectional view illustrating the configuration of the double-sided pressure-sensitive adhesive sheet of the present invention. FIG. 2 is a cross-sectional view illustrating the configuration of the double-sided pressure-sensitive adhesive sheet with a release sheet of the present invention.

Hereinafter, the present invention will be described in detail. The description of the constituent elements described below may be made based on representative embodiments and specific examples, but the present invention is not limited to such embodiments.

(Double-sided adhesive sheet)
The present invention relates to a transparent substrate and a double-sided pressure-sensitive adhesive sheet having pressure-sensitive adhesive layers on both sides of the transparent substrate. Specifically, the present invention provides a transparent substrate, a first pressure-sensitive adhesive layer provided on one surface side of the transparent substrate, and a second pressure-sensitive adhesive provided on the other surface side of the transparent substrate. The present invention relates to a double-sided PSA sheet having an agent layer. The retardation of the transparent substrate used for the double-sided pressure-sensitive adhesive sheet of the present invention is 3000 nm or more and 150,000 nm or less.

FIG. 1 is a cross-sectional view illustrating the configuration of the double-sided pressure-sensitive adhesive sheet of the present invention. As shown in FIG. 1, the double-sided pressure-sensitive adhesive sheet 10 of the present invention has a configuration in which a first pressure-sensitive adhesive layer 12, a transparent base material 11, and a second pressure-sensitive adhesive layer 13 are laminated in this order. . The first pressure-sensitive adhesive layer 12, the transparent base material 11, the second pressure-sensitive adhesive layer 13, and the transparent base material 11 are preferably laminated in contact with each other. Others may be provided between the materials 11 and between the second pressure-sensitive adhesive layer 13 and the transparent substrate 11. The transparent substrate 11 may have a multilayer structure.

Since the double-sided pressure-sensitive adhesive sheet of the present invention has the above configuration, it is excellent in punching suitability. In the step of punching the double-sided pressure-sensitive adhesive sheet, the double-sided pressure-sensitive adhesive sheet is punched with a punching blade to which a release agent is attached. When the double-sided pressure-sensitive adhesive sheet has a release sheet, it is preferable to punch out the part excluding the release sheet and not punch out the release sheet from the viewpoint of easy handling of the double-sided pressure-sensitive adhesive sheet processed product (double-sided pressure-sensitive adhesive sheet after processing). In the punching step, the double-sided pressure-sensitive adhesive sheet may be punched over the entire thickness of the double-sided pressure-sensitive adhesive sheet.
In the punching step, the punching speed is not particularly limited, but can be appropriately set according to the softness and thickness of the double-sided pressure-sensitive adhesive sheet. For example, the punching speed can be set in the range of 50 shots / min to 300 shots / min.

Further, in the punching process, the shape of the part for punching the double-sided pressure-sensitive adhesive sheet (the shape of the surface of the double-sided pressure-sensitive adhesive sheet at the part to be punched) is not particularly limited. Examples include shapes and combinations thereof. The position of the punching site, the number of punching sites, the interval between the punching sites, and the like can be appropriately selected according to the usage mode of the double-sided adhesive sheet processed product, and are not particularly limited. In the punching step, a plurality of parts may be punched simultaneously.

In the punching process, when the double-sided pressure-sensitive adhesive sheet is punched with a punching blade, a release agent may be attached to the punching blade. In this case, a mold release agent exists on the punching blade surface. Although it does not specifically limit as a punching blade, For example, blades, such as a metal, an alloy, and steel materials, can be used. Among these, the punching blade is preferably a steel material from the viewpoint of durability. The shape of the punching blade is not particularly limited. For example, the shape corresponding to the shape of the portion in which the blade edge of the punching blade (the shape of the tip of the blade) punches the double-sided adhesive sheet. Etc. Moreover, the length and blade type of the punching blade can be appropriately set according to the shape of punching the double-sided pressure-sensitive adhesive sheet.
The punching blade may be subjected to a publicly known surface treatment so as to easily attach the release agent as necessary. The punching process can be performed using various conventionally known punching machines, cutting machines, cutters, and the like.

In the specification of the present application, excellent punching ability means that the punched portion is prevented from re-adhering (blocking) after punching the double-sided PSA sheet with a punching blade in the process of processing the double-sided PSA sheet into various sizes and shapes. And a part of the cross section of the punched portion (for example, a part of the cross section of the pressure-sensitive adhesive layer) or the like is peeled off and the appearance of the cross section of the punched portion is prevented from being deteriorated.

Also, the double-sided pressure-sensitive adhesive sheet of the present invention is characterized in that the visibility of the display device can be improved. When the double-sided pressure-sensitive adhesive sheet of the present invention is used for bonding a display device and an input device, for example, when viewed through a polarizing filter such as sunglasses, image disappearance (blackout) or rainbow-colored unevenness (color unevenness) Occurrence of problems such as a hue shift (color shift) is suppressed.

Furthermore, since the double-sided pressure-sensitive adhesive sheet of the present invention has pressure-sensitive adhesive layers on both sides of the transparent substrate, the bonding work when bonding two optical members can be simplified. Conventionally, when an optical member is bonded, the double-sided pressure-sensitive adhesive sheet is cut according to the shape of the member, which is often an operation requiring skill. In addition, the double-sided PSA sheet is often manually bonded, which is a laborious operation. Since the double-sided pressure-sensitive adhesive sheet of the present invention is excellent in punching suitability and can simplify the pasting operation, it is possible to reduce the burden of the conventional complicated pasting operation. Furthermore, since the double-sided pressure-sensitive adhesive sheet of the present invention has a transparent substrate, breakage of the double-sided pressure-sensitive adhesive sheet can be suppressed. For this reason, the double-sided pressure-sensitive adhesive sheet once adhered can be peeled again, and when the double-sided pressure-sensitive adhesive sheet needs to be peeled off during the bonding operation, the double-sided pressure-sensitive adhesive sheet can be easily peeled from the optical member. . Thereby, the loss of the optical member at the time of bonding work can be reduced.

(Transparent substrate)
The retardation of the transparent substrate is 3000 nm or more and 150,000 nm or less. That is, the transparent substrate is preferably an oriented film, and more preferably a high retardation oriented film. The retardation of the transparent substrate is preferably 4500 nm or more, more preferably 6000 nm or more, further preferably 8000 nm or more, and particularly preferably 10,000 nm or more. The retardation of the transparent substrate can be measured according to a known method. In the present specification, the birefringence index and thickness are automatically measured by a birefringence measuring device (manufactured by Oji Scientific Instruments, KOBRA-21ADH). The value obtained using.

“Transparent” in a transparent substrate means that the total light transmittance of visible light when measured in accordance with JIS K 7105 is 80% or more. The total light transmittance of the transparent substrate is more preferably 90% or more. By setting the total light transmittance to the above range, the visibility of the image is not impaired even when the double-sided PSA sheet is bonded to a liquid crystal display or the like.

When laminating a double-sided PSA sheet to a liquid crystal display, the angle formed by the orientation axis of the transparent substrate and the polarization axis of the viewing side polarizer of the liquid crystal display (the transparent substrate and the polarizer are on the same plane) It is preferable that the bonding is performed so as to be 45 ° ± 25 ° or less. Such an angle is more preferably 45 ° ± 20 ° or less. In particular, when the liquid crystal display is observed from an oblique direction through a polarizing filter such as sunglasses, the angle is preferably 45 ° ± 15 ° or less, more preferably 45 ° ± 10 ° or less, from the viewpoint of reducing deterioration in image quality. Preferably, 45 degrees ± 5 degrees or less is more preferable.

A general liquid crystal display has a light source and a liquid crystal cell. In the specification of the present application, the side on which the image of the liquid crystal display is displayed (the side on which the human views the image) is referred to as the “viewing side”, and the side opposite to the viewing side (that is, usually a backlight light source in a liquid crystal display device). The side on which the light source is set is called the “light source side”. A polarizing plate is provided on each of the light source side and the viewing side of the liquid crystal cell, and each polarizing plate typically has a structure in which a polarizer protective film is laminated on both sides of a film called a polarizer. Generally, the polarizer on the viewing side of the liquid crystal cell is installed so that the polarization axis is substantially parallel, substantially perpendicular, or substantially 45 degrees with respect to the vertical direction in the screen of the liquid crystal display. Therefore, it is preferable that the orientation main axis of the transparent substrate is either substantially parallel, substantially perpendicular, or substantially 45 degrees with the long side of the adhesive film (one side in the case of a square).

The transparent substrate can be produced by appropriately selecting a known method. Examples of the transparent base material resin include polyester resin, polycarbonate resin, polystyrene resin, syndiotactic polystyrene resin, polyether ether ketone resin, polyphenylene sulfide resin, cycloolefin resin, liquid crystalline polymer resin, and cellulose resin. Examples thereof include a resin to which a liquid crystal compound is added. That is, the transparent substrate is a polyester film, polycarbonate film, polystyrene film, syndiotactic polystyrene film, polyetheretherketone film, polyphenylene sulfide film, cycloolefin film, liquid crystalline film, and a liquid crystal compound added to a cellulose resin. It can be a film.

Among these, a preferable raw material resin for the transparent substrate is preferably at least one selected from a polyester resin, a polycarbonate resin, and syndiotactic polystyrene, more preferably a polyester resin, and a polyethylene terephthalate resin. Further preferred. When the transparent substrate contains the resin as described above, the transparency can be further increased, and the heat resistance and the mechanical strength can be increased. Furthermore, the retardation can be easily controlled by stretching. Among these, a polyethylene terephthalate resin is preferable because it has a large intrinsic birefringence and relatively large retardation can be obtained even when the film is thin.

Hereinafter, a method for producing a transparent substrate will be described using a polyester film as an example. The polyester film can be obtained by condensing an arbitrary dicarboxylic acid and a diol. Examples of the dicarboxylic acid include terephthalic acid, isophthalic acid, orthophthalic acid, 2,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, and diphenylcarboxylic acid. Acid, diphenoxyethanedicarboxylic acid, diphenylsulfonecarboxylic acid, anthracenedicarboxylic acid, 1,3-cyclopentanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, hexahydroterephthalic acid, hexahydroisophthalic acid Acid, malonic acid, dimethylmalonic acid, succinic acid, 3,3-diethylsuccinic acid, glutaric acid, 2,2-dimethylglutaric acid, adipic acid, 2-methyladipic acid, trimethyladipic acid, pimelic acid, azelaic acid, Dimer , It may be mentioned sebacic acid, suberic acid, dodecamethylene dicarboxylic acid.

Examples of the diol include ethylene glycol, propylene glycol, hexamethylene glycol, neopentyl glycol, 1,2-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, decamethylene glycol, 1,3-propanediol, 1,4 -Butanediol, 1,5-pentanediol, 1,6-hexadiol, 2,2-bis (4-hydroxyphenyl) propane, bis (4-hydroxyphenyl) sulfone and the like.

The dicarboxylic acid component and the diol component constituting the polyester film may each be used alone or in combination of two or more. Specific polyester resins constituting the polyester film include, for example, polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, etc., preferably polyethylene terephthalate and polyethylene naphthalate, more preferably polyethylene terephthalate. is there. These resins are excellent in transparency, heat resistance and mechanical strength. Moreover, retardation of these resins can be easily controlled by stretching. The polyester resin may contain other copolymer components. From the viewpoint of mechanical strength, the proportion of the copolymer components is preferably 3 mol% or less, more preferably 2 mol% or less, and more preferably 1.5 mol. More preferably, it is% or less.

The polyester film can be obtained according to a general production method. Specifically, the polyester resin is melted and extruded into a sheet. Then, it can be set as the transparent base material which has a predetermined retardation value by extending | stretching a non-orientated polyester film. The stretching step preferably includes a step of stretching the non-oriented polyester film in the machine direction at a temperature equal to or higher than the glass transition temperature, and / or a step of stretching in the transverse direction by a tenter. . The stretching in the longitudinal direction and the stretching in the transverse direction may be performed simultaneously, or the stretching in the transverse direction may be performed after stretching in the longitudinal direction. Such a stretching process may be repeated. The transparent substrate used in the present invention may be a uniaxially stretched film or a biaxially stretched film. Further, the transparent substrate may be stretched at an angle of 45 degrees.

The production conditions for obtaining the polyester film can be appropriately set according to a known method. For example, the longitudinal stretching temperature and the transverse stretching temperature are preferably 80 ° C. or higher and 130 ° C. or lower, and more preferably 90 ° C. or higher and 120 ° C. or lower. The longitudinal draw ratio is preferably 1.0 to 3.5 times, and more preferably 1.0 to 3.0 times. Further, the transverse draw ratio is preferably 2.5 times or more and 6.0 times or less, and more preferably 3.0 times or more and 5.5 times or less.

Controlling the retardation of the transparent substrate to a specific range can be performed by appropriately setting the stretching ratio, stretching temperature, and film thickness. For example, a higher retardation is more likely to be obtained as the stretching ratio difference between the longitudinal stretching and the lateral stretching is higher, as the stretching temperature is lower, and as the film is thicker. In addition, as the stretching temperature is higher and the total stretching ratio is lower, a film having a lower ratio of retardation to thickness direction retardation (Re / Rth) is more likely to be obtained.

In the transparent substrate manufacturing process, it is preferable to further provide a heat treatment process after the stretching process. The heat treatment temperature in the heat treatment step is preferably 140 ° C. or higher and 240 ° C. or lower, and more preferably 170 ° C. or higher and 240 ° C. or lower.

In order to suppress the fluctuation of retardation in the transparent substrate, it is preferable that the thickness unevenness of the film is small. The thickness unevenness of the film is preferably 5.0% or less, more preferably 4.5% or less, still more preferably 4.0% or less, and 3.0% or less. Particularly preferred. The thickness unevenness of the film is obtained by taking a tape-like sample (length 3 m) continuous in the film flow direction, and using a commercially available measuring device (Electronic Micrometer Millitron 1240, manufactured by Seiko EM Co., Ltd.) The thickness at 100 points is measured with the pitch, the maximum value (dmax), the minimum value (dmin), and the average value (d) of the thickness are obtained, and the thickness unevenness (%) can be calculated by the following formula.
Thickness unevenness (%) = ((dmax−dmin) / d) × 100

The value of the longitudinal thickness unevenness may increase when the longitudinal stretching ratio is lowered, and the value of the longitudinal thickness unevenness may increase in a specific range of the stretching ratio. In such a case, it is preferable to appropriately change the draw ratio and the like.

The thickness of the transparent substrate is preferably 10 μm or more, more preferably 25 μm or more, further preferably 50 μm or more, and particularly preferably 70 μm or more. The thickness of the transparent substrate is preferably 250 μm or less, and more preferably 200 μm or less. By setting the thickness of the transparent substrate within the above range, good punchability can be obtained, and the retardation of the transparent substrate can be easily adjusted within a desired range. Moreover, the fracture | rupture of a transparent base material can be suppressed and the mechanical strength of double-sided adhesive sheet itself can be raised.

(Adhesive layer)
An adhesive layer is provided in the both surface side of the transparent base material mentioned above. That is, the double-sided pressure-sensitive adhesive sheet of the present invention has two pressure-sensitive adhesive layers, and the pressure-sensitive adhesive layer provided on one surface side of the transparent substrate is used as the first pressure-sensitive adhesive layer and the other surface of the transparent substrate. The pressure-sensitive adhesive layer provided on the side can be referred to as a second pressure-sensitive adhesive layer.

The two adhesive layers are rubber adhesive, polyester adhesive, epoxy adhesive, acrylic adhesive, silicone adhesive, urethane adhesive, vinyl alkyl ether adhesive, and polyvinyl alcohol. It is preferable to contain pressure-sensitive adhesives such as pressure-sensitive adhesives, polyacrylamide-based pressure-sensitive adhesives, and cellulose-based pressure-sensitive adhesives. Among these, the two pressure-sensitive adhesive layers preferably include at least one selected from an acrylic pressure-sensitive adhesive, a urethane-based pressure-sensitive adhesive, a rubber-based pressure-sensitive adhesive, and a silicone-based pressure-sensitive adhesive, and include an acrylic pressure-sensitive adhesive. More preferred. The acrylic pressure-sensitive adhesive may be an ultraviolet curable acrylic pressure-sensitive adhesive or a thermosetting acrylic pressure-sensitive adhesive.

As the acrylic pressure-sensitive adhesive, a pressure-sensitive adhesive composition using a (meth) acrylic acid ester-based polymer (including a copolymer, hereinafter also referred to as “acrylic acid ester-based (co) polymer”) as a base resin. Can be mentioned. The acrylic ester-based (co) polymer is obtained by polymerizing an acrylic monomer or a methacrylic monomer. The physical properties such as glass transition temperature (Tg) and molecular weight of the acrylate ester-based (co) polymer can be adjusted by appropriately selecting the type of monomer, composition ratio, polymerization conditions, and the like.
In the present specification, “(meth) acrylic acid” indicates acrylic acid or methacrylic acid.

Examples of acrylic monomers and methacrylic monomers used for polymerizing acrylic ester (co) polymers include 2-ethylhexyl acrylate, n-octyl acrylate, isooctyl acrylate, n-butyl acrylate, ethyl acrylate, methyl methacrylate, methyl An acrylate etc. can be mentioned. Further, an acrylic monomer having a hydrophilic group or an organic functional group such as hydroxyethyl acrylate, acrylic acid, glycidyl acrylate, acrylamide, acrylonitrile, methacrylonitrile, fluorine acrylate, or silicone acrylate may be copolymerized with the acrylic monomer. In addition to these, various vinyl monomers such as vinyl acetate, alkyl vinyl ethers, and hydroxyalkyl vinyl ethers can be appropriately used for the polymerization.
As a polymerization method using these monomers, a known polymerization method such as solution polymerization, emulsion polymerization, bulk polymerization, suspension polymerization or the like can be employed. In this case, a thermal polymerization initiator or photopolymerization is performed according to the polymerization method. By using a polymerization initiator such as an initiator, an acrylate ester (co) polymer can be obtained.

The two pressure-sensitive adhesive layers may be formed from pressure-sensitive adhesives having the same composition, but may be formed from pressure-sensitive adhesives having different compositions. For example, when the double-sided pressure-sensitive adhesive sheet of the present invention is used for bonding two different members such as a display device and an input device, the functions required for the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer may be different. Therefore, it is preferable to adjust the composition accordingly.

The relative dielectric constant of at least one of the pressure-sensitive adhesive layers is preferably 6 or less, more preferably 5 or less, and further preferably 4 or less. If the dielectric constant is equal to or lower than the above upper limit value, it is possible to make it difficult to pick up noise from the liquid crystal module even if the touch panel sensitivity is increased.

In the two pressure-sensitive adhesive layers, known functional additives can be blended as necessary. Functional additives are not particularly limited, but include tackifiers, silane coupling agents, metal corrosion inhibitors, antistatic agents, antioxidants, ultraviolet absorbers, light diffusing fine particles, non-crosslinkable acrylic polymers. Etc. can be illustrated.

The thicknesses of the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer are each preferably 10 μm or more, more preferably 20 μm or more, and further preferably 30 μm or more. Moreover, it is preferable that the thickness of a 1st adhesive layer and a 2nd adhesive layer is respectively 200 micrometers or less, and it is more preferable that it is 150 micrometers or less.
In addition, it is preferable that the sum total of the thickness of a 1st adhesive layer and a 2nd adhesive layer is larger than the thickness of a transparent base material in order to make level | step difference followable property favorable.

The thickness of the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer may be the same, but may have different thicknesses. For example, when the double-sided pressure-sensitive adhesive sheet of the present invention is used for bonding two different members such as a display device and an input device, the functions required for the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer may be different. Therefore, it is preferable to adjust the thickness of each pressure-sensitive adhesive layer accordingly.

Further, at least one of the pressure-sensitive adhesive layers may be a pressure-sensitive adhesive layer that is formed from a pressure-sensitive adhesive composition that has undergone primary cross-linking and that further has latent ultraviolet secondary curability. The latent ultraviolet curable pressure-sensitive adhesive layer contains an intermolecular hydrogen abstraction type photopolymerization initiator in the composition, appropriately adjusts the conditions for primary crosslinking, etc. It can be obtained by leaving room for curing reactivity.
In the state before secondary curing that has been subjected to primary crosslinking in advance, the ultraviolet-reactive property remains, and there is room for further curing, so the pressure-sensitive adhesive layer is flexible. For this reason, even if there are irregularities on the surface of the adherend or when foreign matter or the like is present at the adhesive interface, these irregularities can be sufficiently followed. Therefore, if two members are bonded via a double-sided pressure-sensitive adhesive sheet having such a pressure-sensitive adhesive layer before secondary curing, the respective members can be brought into close contact with each other. Furthermore, since it can be UV-crosslinked (secondary curing) by irradiating with UV after being adhered, it can be bonded more firmly. Such a double-sided pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer before secondary curing has adhesive strength and cohesive strength that can sufficiently counter the gas pressure of outgas generated from, for example, a protective panel.
In addition, when carrying out the primary crosslinking of the pressure-sensitive adhesive composition, any method such as electron beam or ultraviolet irradiation can be used in addition to the thermosetting agent and the ionic crosslinking agent.

Examples of the intermolecular hydrogen abstraction type photopolymerization initiator include, for example, benzophenone, Michler's ketone, dibenzosuberone, 2-ethylanthraquinone, thioxanthone and benzyl, or derivatives thereof, or a mixed component composed of a combination of two or more of these. Can be used. Further, in addition to the intermolecular hydrogen abstraction type photopolymerization initiator, an intramolecular cleavage type photopolymerization initiator may be contained in various proportions.
The addition amount of the intermolecular hydrogen abstraction type photopolymerization initiator is not particularly limited, and is preferably 0.1 parts by mass or more, for example, 0.2 parts by mass or more with respect to 100 parts by mass of the base resin. More preferably, it is more preferably 0.5 parts by mass or more. The amount of intermolecular hydrogen abstraction type photopolymerization initiator added is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, and further preferably 3 parts by mass or less.

In the present invention, one of the pressure-sensitive adhesive layers is formed from a pressure-sensitive adhesive composition containing a (meth) acrylic acid ester compound and an intermolecular hydrogen abstraction type photopolymerization initiator, and the other pressure-sensitive adhesive layer is thermally cured. You may form from the adhesive composition of a type | mold.

Moreover, in this invention, the molecular weight of the adhesive (base resin) contained in a 1st adhesive layer and a 2nd adhesive layer can also be made different. For example, the mass average molecular weight of the adhesive contained in the first adhesive layer is preferably 350,000 to 800,000, and the mass average molecular weight of the adhesive contained in the second adhesive layer is 900,000 or more. It is preferable that it is 2 million or less. By adjusting the molecular weight of the pressure-sensitive adhesive contained in the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer, two different members can be bonded more firmly. For example, when the mass average molecular weight of the pressure-sensitive adhesive contained in the first pressure-sensitive adhesive layer is 350,000 or more and 800,000 or less, the unevenness-following property of the first pressure-sensitive adhesive layer can be improved. And by making the mass average molecular weight of the adhesive contained in a 2nd adhesive layer into 900,000 or more and 2 million or less, about 2nd adhesive layer, stronger adhesiveness can be exhibited.
In the present specification, the average molecular weight (mass average molecular weight and number average molecular weight) is a value measured by gel permeation chromatography and determined on the basis of polystyrene.

As described above, the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer preferably contain an acrylic pressure-sensitive adhesive. In this case, it is preferable that either one of the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer has a carboxy group, and the other pressure-sensitive adhesive layer preferably does not contain a carboxy group. Here, the state in which the pressure-sensitive adhesive layer does not contain a carboxy group means that the pressure-sensitive adhesive layer does not contain a carboxy group-containing acrylic monomer unit, specifically, relative to the total mass of the pressure-sensitive adhesive layer. The carboxy group content is 1% by mass or less. Examples of the carboxy group-containing acrylic monomer unit include α, β-unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid, itaconic acid, citraconic acid, and grataconic acid, or anhydrides thereof. The thing derived from a thing is mentioned.

The pressure-sensitive adhesive composition constituting the two pressure-sensitive adhesive layers preferably contains a crosslinking agent. Examples of the crosslinking agent include isocyanate compounds, epoxy compounds, oxazoline compounds, aziridine compounds, metal chelate compounds, and butylated melamine compounds. Of the above crosslinking agents, isocyanate compounds are preferred because of their high reactivity.
Examples of the isocyanate compound include tolylene diisocyanate, xylylene diisocyanate, hexamethylene diisocyanate, and isophorone diisocyanate. When an isocyanate compound-based crosslinking agent is used, a catalyst is preferably contained in order to promote the reaction of the crosslinking agent. Examples of the catalyst include amine catalysts (for example, triethylenediamine, normal ethyl morpholine, ethylenediamine), and organic tin catalysts (for example, dibutyltin dilaurate).

In the present invention, it is preferable that one of the two pressure-sensitive adhesive layers contains a metal corrosion inhibitor. A metal corrosion inhibitor is a compound that can form a metal complex film when in contact with a metal. Specific examples of the metal corrosion inhibitor include a benzotriazole compound, a benzimidazole compound, a benzothiazole compound, a silane coupling agent, and the like, and among them, a benzotriazole compound is preferable because of its high metal corrosion prevention effect.
A benzotriazole compound is a compound having a benzotriazole skeleton in the molecule. Specific examples of the benzotriazole compound include 1,2,3-benzotriazole, tolyltriazole, nitrobenzotriazole, 4-amino-1,2,4-triazole, and 5-amino-1,2,4-triazole-3. -Carboxylic acid, 3-mercapto-1,2,4-triazole and alkali metal salts thereof. A benzotriazole compound may be used individually by 1 type, and may use 2 or more types together. Among the benzotriazole compounds, 1,2,3-benzotriazole, tolyltriazole, and sodium salt of benzotriazole are particularly preferably used.

The content of the metal corrosion inhibitor in the adhesive layer is preferably 0.01 parts by mass or more and 5.0 parts by mass or less, and 0.05 parts by mass or more with respect to 100 parts by mass of the adhesive (base resin). More preferably, it is 1.0 part by mass or less. By setting the content of the metal corrosion inhibitor within the above range, a sufficiently high metal corrosion prevention effect can be obtained even when it is bonded to a conductive member provided with a transparent electrode film such as ITO. Moreover, the fall of the adhesive force of an adhesive layer can be prevented by making content of a metal corrosion inhibitor into the said range.

In the present invention, it is preferable that any one of the two pressure-sensitive adhesive layers includes an antioxidant. The antioxidant protects the conductive member when the adhesive layer is bonded to a conductive member provided with a transparent electrode film such as ITO, and can prevent a decrease in the conductivity of the conductive member.
As the antioxidant, known ones can be used without particular limitation, but it is preferable to contain a hindered phenol-based antioxidant and a phosphorus-based antioxidant since the conductivity lowering effect of ITO is more exhibited.

The hindered phenol antioxidant is composed of a compound having a substituent at the ortho position of the hydroxy group of phenol. Specific examples of the hindered phenol antioxidant include pentaerythritol-tetrakis (3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate), thiodiethylene-bis (3- (3,5 -Di-t-butyl-4-hydroxyphenyl) propionate), octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, N, N′-hexane-1,6-diylbis ( 3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionamide), diethyl ((3,5-bis (1,1-dimethylethyl) -4-hydroxyphenyl) methyl) phosphate, 3,3 ', 3 ″, 5,5 ′, 5 ″ -hexa-t-butyl-a, a ′, a ″-(mesitylene-2,4,6-triyl) tri-p-alkyl Sol, ethylenebis (oxyethylene) bis (3- (5-t-butyl-4-hydroxy-m-tolyl) propionate), hexamethylene-bis (3- (3,5-di-t-butyl-4-) Hydroxyphenyl) propionate), 1,3,5-tris (3,5-di-tert-butyl-4-hydroxybenzyl) -1,3,5-triazine-2,4,6 (1H, 3H, 5H) -Trione, 1,3,5-tris ((4-tert-butyl-3-hydroxy-2,6-xylyl) methyl) -1,3,5-triazine-2,4,6 (1H, 3H, 5H ) -Trione, 2,6-di-t-butyl-4- (4,6-bis (octylthio) -1,3,5-triazin-2-ylamino) phenol, 3,9-bis (2- (3 -(3-tert-butyl-4-hydroxy-5- Butylphenyl) propionyloxy) -1,1-dimethylethyl) -2,4,8,10-spiro (5,5) undecane. These may be used individually by 1 type and may use 2 or more types together. Among the hindered phenol antioxidants, pentaerythritol-tetrakis (3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate) is preferable because it can further suppress the decrease in the conductivity of ITO.

The phosphorus-based antioxidant is composed of phosphoric acid, phosphorous acid, or an ester thereof (phosphite, phosphonite). Examples of phosphorus antioxidants include tris (2,4-di-t-butylphenyl) phosphite, bis (2,4-bis (1,1-dimethylethyl) -6-methylphenyl) ethyl ester Phosphoric acid, tetrakis (2,4-di-t-butylphenyl) (1,1-biphenyl) -4,4'-diylbisphosphonite, bis (2,4-di-t-butylphenyl) pentaerythritol Diphosphite, bis (2,6-di-t-butyl-4-methylphenyl) pentaerythritol diphosphite, bis (2,4-dicumylphenyl) pentaerythritol-diphosphite, tetrakis (2,4-t- Butylphenyl) (1,1-biphenyl) -4,4′-diylbisphosphonite, di-t-butyl-m-cresyl-phosphonite, etc. That. These may be used individually by 1 type and may use 2 or more types together. Among phosphorous antioxidants, tris (2,4-di-t-butylphenyl) phosphite is preferable because it can further suppress the decrease in the conductivity of ITO.

The content of the antioxidant in the adhesive layer is preferably 0.01 parts by mass or more and 5.0 parts by mass or less, and 0.05 parts by mass or more and 1 part by mass with respect to 100 parts by mass of the adhesive (base resin). More preferably, it is 0.0 parts by mass or less. By making content of antioxidant into the said range, even if it is a case where it sticks to the electrically-conductive member which provided transparent electrode films, such as ITO, electroconductivity fall can be suppressed more. Moreover, the fall of the adhesive force of an adhesive layer can be prevented by making content of antioxidant into the said range.

Of the two pressure-sensitive adhesive layers, one of the pressure-sensitive adhesive layers may contain a tackifier or a silane coupling agent. Examples of the tackifier include rosin resin, terpene resin, terpene phenol resin, coumarone indene resin, styrene resin, xylene resin, phenol resin, and petroleum resin.
Examples of the silane coupling agent include mercaptoalkoxysilane compounds (for example, mercapto group-substituted alkoxy oligomers).
Examples of the ultraviolet absorber include benzophenone compounds.

(Double-sided adhesive sheet with release sheet)
The present invention also relates to a double-sided pressure-sensitive adhesive sheet with a release sheet in which a release sheet is laminated on at least one surface of the double-sided pressure-sensitive adhesive sheet described above. The release sheet may be provided on at least one surface of the double-sided pressure-sensitive adhesive sheet, but is preferably provided on both sides of the double-sided pressure-sensitive adhesive.

FIG. 2 is a cross-sectional view illustrating the configuration of the double-sided pressure-sensitive adhesive sheet with a release sheet of the present invention. As shown in FIG. 2, the double-sided pressure-sensitive adhesive sheet 20 with a release sheet of the present invention includes a double-sided pressure-sensitive adhesive sheet 10 and a first release sheet 14 laminated on the outer surface of the first pressure-sensitive adhesive layer 12. And a second release sheet 15 laminated on the outer surface of the second pressure-sensitive adhesive layer 13.

The first release sheet 14 and the second release sheet 15 are sheets having releasability on at least one side. As the first release sheet 14 and the second release sheet 15, a peelable laminated sheet having a release sheet base material and a release agent layer provided on one side of the release sheet base material, or a polyethylene film, Examples thereof include polyolefin films such as polypropylene films.

Papers and polymer films are used as the release sheet substrate in the peelable laminate sheet. As the release agent constituting the release agent layer, for example, a general-purpose addition type or condensation type silicone release agent or a long-chain alkyl group-containing compound is used. In particular, an addition type silicone release agent having high reactivity is preferably used.
Specific examples of silicone release agents include BY24-4527 and SD-7220 manufactured by Toray Dow Corning, and KS-3600, KS-774, and X62-2600 manufactured by Shin-Etsu Chemical Co., Ltd. Can be mentioned. Further, the silicone release agent may contain a silicone resin which is an organosilicon compound having a SiO ₂ unit and a (CH ₃ ) ₃ SiO _1/2 unit or CH ₂ ═CH (CH ₃ ) SiO _1/2 unit. preferable. Specific examples of the silicone resin include BY24-843, SD-7292, and SHR-1404 manufactured by Toray Dow Corning, and KS-3800 and X92-183 manufactured by Shin-Etsu Chemical Co., Ltd.

The first release sheet 14 and the second release sheet 15 are preferably different in peelability. If the peelability of the first release sheet 14 and the second release sheet 15 is different, it can be easily peeled off from one release sheet, so that the operation of bonding the two members with the double-sided pressure-sensitive adhesive sheet 10 can be facilitated. In addition, peelability is adjusted with the kind of release agent.

(Method for producing double-sided PSA sheet with release sheet)
Examples of the method for producing a double-sided pressure-sensitive adhesive sheet with a release sheet include the following production methods (1) and (2).

Production method (1): forming the first pressure-sensitive adhesive layer 12 on the first release sheet 14 to obtain the first pressure-sensitive adhesive sheet, and forming the second pressure-sensitive adhesive layer 13 on the second release sheet 15 Forming a second pressure-sensitive adhesive sheet, laminating the first pressure-sensitive adhesive sheet on one surface of the transparent base material 11 so that the exposed surface of the first pressure-sensitive adhesive layer 12 is in contact with the surface, and transparent A step of laminating the second pressure-sensitive adhesive sheet on the other surface of the base material 11 so that the exposed surface of the second pressure-sensitive adhesive layer 13 is in contact therewith, and press-bonding.

Manufacturing method (2): The process of forming the 1st adhesive layer 12 in one side of the transparent base material 11, The process of laminating | stacking the 1st peeling sheet 14 on the exposed surface of the 1st adhesive layer 12, and The manufacturing method which has the process of forming the 2nd adhesive layer 13 in the other surface of the transparent base material 11, and the process of laminating | stacking the 2nd peeling sheet 15 on the exposed surface of the 2nd adhesive layer 13 .

In order to form each pressure-sensitive adhesive layer, a coating liquid (pressure-sensitive adhesive composition) containing a pressure-sensitive adhesive forming each pressure-sensitive adhesive layer may be applied and heated. The coating method can be appropriately selected from knife coaters, micro bar coaters, air knife coaters, reverse roll coaters, reverse gravure coaters, bario gravure coaters, die coaters, curtain coaters and the like.

The coating solution contains a solvent. Examples of the solvent include methanol, ethanol, isopropanol, acetone, methyl ethyl ketone, toluene, n-hexane, n-butyl alcohol, methyl isobutyl ketone, methyl butyl ketone, ethyl butyl ketone, cyclohexanone, ethyl acetate, butyl acetate, propylene glycol monomethyl. Ether acetate, ethylene glycol monoethyl ether, propylene glycol monomethyl ether, N-methyl-2-pyrrolidone and the like are used. These may be used individually by 1 type, and 2 or more types may be mixed and used for them.

(Laminate)
The present invention also relates to a laminate having an optical member on at least one surface of the double-sided pressure-sensitive adhesive sheet described above. Examples of the optical member include a conductive member in which a transparent electrode film such as ITO (Indium Tin Oxide) is provided on a transparent support, an input device such as a cover glass and a touch panel, a display device such as a liquid crystal display, and the like. The double-sided pressure-sensitive adhesive sheet of the present invention is preferably used as an application for bonding an input device such as a touch panel and a display device such as a liquid crystal display.

The double-sided pressure-sensitive adhesive sheet of the present invention can exhibit not only adhesion of each device but also a polarization adjusting function by being used for bonding an input device such as a touch panel and a display device such as a liquid crystal display. Moreover, the double-sided pressure-sensitive adhesive sheet of the present invention can be directly attached to a polarizing plate or a polarizer. In this case, there is also an advantage that a retardation film need not be used.

Hereinafter, the features of the present invention will be described more specifically with reference to examples and comparative examples. The materials, amounts used, ratios, processing details, processing procedures, and the like shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the specific examples shown below.

<Example 1>
(Preparation of transparent substrate 1)
PET resin pellets having an intrinsic viscosity of 0.62 dl / g were dried under reduced pressure (1 Torr) at 135 ° C. for 6 hours, then supplied to an extruder and dissolved at 285 ° C. This polymer is filtered with a filter material of stainless sintered body (nominal filtration accuracy 10 μm particles 95% cut), extruded into a sheet form from the die, and then applied to a casting drum having a surface temperature of 30 ° C. using an electrostatic application casting method. It was wound and solidified by cooling to prepare an unstretched PET film.
Next, after applying the following adhesive modification coating solution on both sides of the unstretched PET film by the reverse roll method so that the coating amount after drying is 0.08 g / m ² , the coating is dried at 80 ° C. for 20 seconds. Thus, a coating layer was formed.
The unstretched film on which this coating layer was formed was guided to a tenter stretching machine, and the film was guided to a hot air zone at a temperature of 125 ° C. while being gripped by a clip, and stretched 4.0 times in the width direction. Next, while maintaining the width stretched in the width direction, the film was treated at a temperature of 225 ° C. for 30 seconds, and further subjected to a 3% relaxation treatment in the width direction to obtain a transparent substrate 1 having a film thickness of 75 μm. The retardation value of the transparent substrate 1 measured by the method described later was 8200 nm.

(Preparation of adhesive modification coating solution)
Transesterification and polycondensation reactions were performed by conventional methods. As dicarboxylic acid component (based on the entire dicarboxylic acid component) 46 mol% terephthalic acid, 46 mol% isophthalic acid and 8 mol% sodium 5-sulfonatoisophthalate, and as glycol component (based on the entire glycol component) ethylene glycol 50 A water-dispersible sulfonic acid metal base-containing copolymer polyester resin having a composition of mol% and neopentyl glycol 50 mol% was prepared. Next, 51.4 parts by mass of water, 38 parts by mass of isopropyl alcohol, 5 parts by mass of n-butyl cellosolve, 0.06 parts by mass of a nonionic surfactant were mixed and then heated and stirred. After adding 5 parts by mass of a water-dispersible sulfonic acid metal base-containing copolymer polyester resin and continuing to stir until the resin is no longer agglomerated, the resin water dispersion is cooled to room temperature to obtain a solid content concentration of 5.0% by mass. A uniform water-dispersible copolymerized polyester resin liquid was obtained. Further, 3 parts by mass of aggregated silica particles (manufactured by Fuji Silysia Co., Ltd., Silicia 310) were dispersed in 50 parts by mass of water. Thereafter, 0.54 parts by mass of an aqueous dispersion of silicia 310 was added to 99.46 parts by mass of the water-dispersible copolyester resin solution, and 20 parts by mass of water was added with stirring to obtain an adhesive modified coating solution. Obtained

[Production of double-sided PSA sheet]
(Adhesive composition)
100 parts by mass of an acrylic polymer (manufactured by Soken Chemical Co., Ltd., SK-2094), 0.1 part by mass of an epoxy-based crosslinking agent (manufactured by Soken Chemical Co., Ltd., E-5XM), and a silane coupling agent (Soken) Chemical Co., Ltd., C-50) 0.15 parts by mass, non-crosslinkable acrylic polymer (Mw 1700, Tg-31 ° C.) 5 parts by mass, and ethyl acetate as a solvent in a concentration of 30% by mass. The pressure-sensitive adhesive composition 1 was prepared by dilution.

(Manufacture of double-sided PSA sheet)
A double-sided PSA sheet was produced using the prepared PSA composition 1 according to the following procedure.
As a first release sheet, a release film (Mitsubishi Resin Co., Ltd., MRV # 50) provided with a release agent layer on a PET film was prepared and prepared on the release agent layer of the first release sheet. The pressure-sensitive adhesive composition 1 was applied with a knife coater. With the coated surface of the pressure-sensitive adhesive composition 1 facing upward, the solvent component was volatilized by heating at 40 ° C. for 2 minutes and further heating at 110 ° C. for 2 minutes. Thus, an adhesive sheet having a release sheet on one side was obtained. The thickness of the pressure-sensitive adhesive layer was adjusted to 50 μm. In the same manner, the pressure-sensitive adhesive composition 1 was applied on the second release sheet to obtain a pressure-sensitive adhesive sheet having a release sheet on one side.
Subsequently, the double-sided adhesive sheet with a peeling sheet which provides a peeling sheet on both surfaces was manufactured by sticking the adhesive layer surface of an adhesive sheet which has a peeling sheet on one side in order on both surfaces of the transparent base material 1.

<Example 2>
(Preparation of transparent substrate 2)
In the preparation of the transparent substrate 1 of Example 1, the transparent substrate 2 having a thickness of 55 μm and a retardation value of 3500 nm was obtained by changing the draw ratio.

(Manufacture of double-sided PSA sheet)
In the same manner as in Example 1, a double-sided pressure-sensitive adhesive sheet with a release sheet provided with a release sheet on both sides was produced by laminating the pressure-sensitive adhesive layer surface of the pressure-sensitive adhesive sheet provided with a release sheet on one side in order on both sides of the transparent substrate 2.

<Example 3>
(Preparation of transparent substrate 3)
In the preparation of the transparent substrate 1 of Example 1, the transparent substrate 3 having a thickness of 150 μm and a retardation value of 16000 nm was obtained by changing the draw ratio.

(Manufacture of double-sided PSA sheet)
In the same manner as in Example 1, a double-sided pressure-sensitive adhesive sheet with a release sheet provided with a release sheet on both sides was produced by laminating the adhesive layer surface of the pressure-sensitive adhesive sheet provided with a release sheet on one side in order on both sides of the transparent substrate 3.

<Example 4>
[Production of double-sided PSA sheet]
(Preparation of transparent substrate 4) In the same manner as the transparent substrate 1, a transparent substrate 4 having a film thickness of 75 µm and a retardation value of 8200 nm was obtained.

(Adhesive composition)
100 parts by mass of an acrylic polymer (manufactured by Soken Chemical Co., Ltd., SK-2094), 0.1 part by mass of an epoxy-based crosslinking agent (manufactured by Soken Chemical Co., Ltd., E-5XM), and a silane coupling agent (Soken) Chemical Co., Ltd., C-50) 0.15 parts by mass, non-crosslinkable acrylic polymer (Mw 1700, Tg -31 ° C.) 1 part by mass, and ethyl acetate as a solvent in a concentration of 30% by mass. The pressure-sensitive adhesive composition 2 was prepared by dilution.

(Manufacture of double-sided PSA sheet)
Using the prepared adhesive composition 1 and adhesive composition 2, a double-sided adhesive sheet was produced according to the following procedure.
As a first release sheet, a release film (Mitsubishi Resin Co., Ltd., MRV # 50) provided with a release agent layer on a PET film is prepared, and on the release agent layer of the first release sheet, Example The pressure-sensitive adhesive composition 1 prepared in 1 was applied with a knife coater. With the coated surface of the pressure-sensitive adhesive composition 1 facing upward, the solvent component was volatilized by heating at 40 ° C. for 2 minutes and further heating at 110 ° C. for 2 minutes. Thus, an adhesive sheet having a release sheet on one side was obtained. The thickness of the 1st adhesive layer was prepared so that it might be set to 75 micrometers. In the same manner, the pressure-sensitive adhesive composition 2 was applied on the second release sheet to obtain a pressure-sensitive adhesive sheet having a release sheet on one side. The thickness of the 2nd adhesion layer was 25 micrometers.
Subsequently, the double-sided adhesive sheet with a peeling sheet which provides a peeling sheet on both surfaces was manufactured by sticking together the adhesive layer surface of an adhesive sheet which provided a peeling sheet on one side to both surfaces of the transparent base material 4 sequentially.

<Comparative Example 1>
(Preparation of transparent substrate 11)
In the preparation of the transparent substrate 1 of Example 1, the transparent substrate 11 having a film thickness of 75 μm and a retardation value of 2500 nm was obtained by changing the stretching ratio.

(Manufacture of double-sided PSA sheet)
In the same manner as in Example 1, a double-sided pressure-sensitive adhesive sheet with a release sheet provided with a release sheet on both sides was produced by laminating the adhesive layer surface of the pressure-sensitive adhesive sheet provided with a release sheet on one side in order on both sides of the transparent substrate 11.

<Comparative Example 2>
(Manufacture of double-sided PSA sheet without transparent substrate)
Using the pressure-sensitive adhesive composition 1 prepared in the same manner as in Example 1, a double-sided pressure-sensitive adhesive sheet with a release sheet was produced according to the following procedure.
As a first release sheet, a release film (Mitsubishi Resin Co., Ltd., MRV # 50) provided with a release agent layer on a PET film was prepared and prepared on the release agent layer of the first release sheet. The pressure-sensitive adhesive composition 1 was applied with a knife coater. With the coated surface of the pressure-sensitive adhesive composition 1 facing up, the solvent component was volatilized by heating at 40 ° C. for 2 minutes and further heating at 110 ° C. for 5 minutes. Thus, an adhesive sheet having a release sheet on one side was obtained. The thickness of the pressure-sensitive adhesive layer was adjusted to 175 μm.
By using a release film (A50 # 50, manufactured by Teijin DuPont Films Co., Ltd.) having a release agent layer on a PET film as the second release sheet, it is bonded to the adhesive surface of an adhesive sheet having a release sheet on one side. And the double-sided adhesive sheet with a peeling sheet which does not have a transparent base material was manufactured.

(Evaluation method and measurement method)
[Retardation]
The retardation (Re) of the transparent substrates of Examples 1 to 3 and Comparative Example 1 was measured as follows.
Using two polarizing plates, the orientation main axis direction of the transparent base material was determined, and the transparent base material was cut out to be a 4 cm × 2 cm rectangle so that the orientation main axis directions were orthogonal to each other, and used as a measurement sample. For this sample, the biaxial refractive index (Nx, Ny) perpendicular to each other and the refractive index (Nz) in the thickness direction were determined by an Abbe refractometer (NAR-4T, manufactured by Atago Co., Ltd.). Of the refractive index (| Nx−Ny |) was determined as the anisotropy of the refractive index (ΔNxy). The thickness d (nm) of the transparent substrate was measured by using an electric micrometer (Millitron 1245D, manufactured by Fine Reef Co., Ltd.), and the unit was converted to nm. The retardation (Re) of the transparent substrate was determined from the product (ΔNxy × d) of the refractive index anisotropy (ΔNxy) and the thickness d (nm) of the transparent substrate.

[Punching aptitude]
10 seconds after punching out the double-sided PSA sheet with release sheet (after the Pinnacle blade is brought into contact with the double-sided PSA sheet), the punched part is lifted up, and the cross section of the punched part (cross section of the adhesive layer) is peeled off, It was observed visually, and the punching suitability was evaluated according to the following criteria.
○ (excellent in punching suitability): No peeling of the cross section of the punched portion can be confirmed.
X (Inferior to punching suitability): A part of the cross section of the punched part is peeled off, and a part of the cross section of the peeled punched part is adhered to the Pinnacle blade to contaminate the Pinnacle blade.

[Visibility]
Visibility was evaluated by overlaying an observation sample in which a soda glass plate was bonded to both surfaces of a double-sided PSA sheet on the surface of a commercially available LCD monitor (model LCD MF223EWR, manufactured by IODATA). At this time, the image is observed through a polarizing filter before observation, the polarization direction of the outgoing light is confirmed from the angle at which the polarizing filter is rotated to quench, and the polarization direction of the outgoing light and the orientation main axis of the orientation film are 45 degrees. The observation samples were stacked so as to have an angle. After that, polarization sunglasses were put on and the neck was tilted left and right, and the change in the visibility of the image was observed.
○ (Excellent visibility): No image disappearance, color unevenness, or color shift does not occur.
X (Inferior in visibility): Any of image disappearance, color unevenness, and color misregistration occurs.

The double-sided PSA sheets obtained in Examples 1 to 3 were excellent in both punching suitability and visibility. On the other hand, in Comparative Example 1 in which the retardation of the transparent substrate is less than 3000 nm, the visibility is poor, and the punching suitability is not improved in the single-layer double-sided PSA sheet having no transparent substrate.

<Comparative Example 12>
(Manufacture of an adhesive sheet with a hard coat layer on one side and an adhesive layer on the other side)
The release sheet on one side of the double-sided PSA sheet with a release sheet that does not have a transparent substrate obtained in Comparative Example 2 was peeled off, and the PSA sheet was bonded only to one side of the transparent substrate 1. The other side of the transparent substrate 1 was coated with Aika's Itron Z883 (anti-fingerprint hard coat agent) and cured with ultraviolet rays to form a hard coat layer. The thickness of the hard coat layer after curing was 5 μm.

(Evaluation methods)
The workability of the double-sided PSA sheet of Example 1 and the PSA sheet having a hard coat layer on one side of Comparative Example 12 was evaluated according to the following evaluation criteria. The results are shown in Table 2.

[Workability]
Soda glass plates were pasted on both sides of the double-sided PSA sheet obtained in Example 1. On the pressure-sensitive adhesive surface of the pressure-sensitive adhesive sheet with a single-sided hard coat layer obtained in Comparative Example 12, two soda glass plates were bonded with the third pressure-sensitive adhesive layer (the pressure-sensitive adhesive layer formed with the pressure-sensitive adhesive composition 1). The laminated body was bonded together. Workability was evaluated according to the following criteria.
○ (Excellent workability): Good visibility can be obtained only by the optical member bonding process. X (Inferior workability): Good visibility in a separate process from the optical member bonding process. There is a necessary process to obtain

The comparative example was a pressure-sensitive adhesive sheet having a hard coat layer on one side of the transparent substrate, and the workability was inferior to that of Example 1 which was a double-sided pressure-sensitive adhesive sheet.

DESCRIPTION OF SYMBOLS 10 Double-sided adhesive sheet 11 Transparent base material 12 1st adhesive layer 13 2nd adhesive layer 14 1st peeling sheet 15 2nd peeling sheet 20 Double-sided adhesive sheet with a peeling sheet

Claims (8)

1. A transparent substrate, a first pressure-sensitive adhesive layer provided on one surface side of the transparent substrate, and a second pressure-sensitive adhesive layer provided on the other surface side of the transparent substrate,
   The double-sided adhesive sheet whose retardation of the said transparent base material is 3000 nm or more and 150,000 nm or less.
2. 2. The double-sided pressure-sensitive adhesive sheet according to claim 1, wherein the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer each have a thickness of 10 μm or more and 200 μm or less.
3. The first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer include at least one selected from an acrylic pressure-sensitive adhesive, a urethane pressure-sensitive adhesive, a rubber pressure-sensitive adhesive, and a silicone pressure-sensitive adhesive. Double-sided pressure-sensitive adhesive sheet as described in 1.
4. The double-sided pressure-sensitive adhesive sheet according to any one of claims 1 to 3, wherein the transparent substrate has a thickness of 50 µm or more and 200 µm or less.
5. The double-sided pressure-sensitive adhesive sheet according to any one of claims 1 to 4, wherein the transparent substrate contains a polyethylene terephthalate resin.
6. The double-sided pressure-sensitive adhesive sheet according to any one of claims 1 to 5, which is used for bonding a display device and an input device.
7. A double-sided pressure-sensitive adhesive sheet with a release sheet, wherein the release sheet is laminated on at least one surface of the double-sided pressure-sensitive adhesive sheet according to any one of claims 1 to 6.
8. A laminate having an optical member on at least one surface of the double-sided pressure-sensitive adhesive sheet according to any one of claims 1 to 6.
   
   
   

Images