TW202039739A - Optical transparent adhesive sheet, laminate sheet, and adhered structure - Google Patents

Abstract

The present invention provides: an optical transparent adhesive sheet in which whitening that occurs under a high-temperature and high-humidity environment is prevented; and a laminate sheet and an adhered structure using said optical transparent adhesive sheet. The optical transparent adhesive sheet according to the present invention includes a first acrylic pressure sensitive adhesive layer that forms a first surface, a thermosetting polyurethane layer, and a second acrylic pressure sensitive adhesive layer that forms a second surface, in this order. The first acrylic pressure sensitive adhesive layer and the second acrylic pressure sensitive adhesive layer each exhibit a water-vapor permeability of 500-800 g/m2.h.

Description

Optically transparent adhesive sheet, laminated sheet and laminated structure

The present invention relates to an optically transparent adhesive sheet, laminated sheet and laminated structure.

An optically clear adhesive (OCA: Optically Clear Adhesive) sheet is a transparent adhesive sheet used for bonding optical members. As an example of the use of the OCA sheet, in a display device, it is sometimes used for joining a display panel such as a liquid crystal module and a cover panel provided on the outermost surface of the display device. By filling the space between the display panel and the cover panel with the OCA sheet, the visibility of the screen of the display panel can be improved.

As a prior art related to the OCA sheet, for example, an adhesive material with a release film for image display devices described in Patent Document 1 can be cited. The adhesive material with a release film for image display devices is an adhesive material for bonding two adherends, and has two adhesive layers and a base layer composed of a transparent polymer sheet. There is a release film on both the front and back surfaces, and there is an interface (called "internal peeling interface") that can be peeled on a surface different from the adhesive surface of the adhesive material and the adherend inside. In addition, one of the interfaces provided with the base layer and the adhesive layer is the configuration of the internal peeling interface. Furthermore, it is characterized in that the 90° peel strength (A) of the interface between one release film and the adhesive material, the 90° peel strength (B) of the interface between the other release film and the adhesive material, and 90° of the internal peel interface The peel strength (C) satisfies the relationship of (1) to (3) below, and the 90° peel strength of the internal peel interface is 0.01 N/50 mm～7 N/50 mm, and the adhesive material and the adherend are 90° The peel strength is 3 N/25 mm or more at a peel speed of 5 mm/min, and the total thickness of the two adhesive layers and the base layer composed of a transparent polymer sheet is 65 μm to 300 μm. (1)···(A)＜(B)＜(C) (2)···(B)/(A)=1.1～3.0 (3)···(C)/(B)=1.1～7.0

In addition, with the diversification of display devices, as cover panels, research has been conducted in recent years to adopt resin panels that are advantageous in terms of design, safety (prevention of scattering when broken), and price compared to conventional general glass panels. Therefore, as an OCA sheet, it is required to be suitable for bonding with a resin panel. [Prior Art Literature] [Patent Literature]

Patent Document 1: Japanese Patent Laid-Open No. 2016-6176

[The problem to be solved by the invention] In order to realize an OCA sheet suitable for bonding a display panel and a touch panel main body, the inventors have laminated a first acrylic adhesive layer, a thermosetting polyurethane layer, and a second acrylic adhesive. Development of OCA sheet with multi-layer structure. According to the OCA sheet having a multilayer structure, excellent flexibility can be obtained by thermosetting the polyurethane layer, and excellent adhesiveness can be obtained by the first and second acrylic adhesive layers.

However, very high reliability is required for in-vehicle display devices, etc., so it can prevent high-temperature tests (95°C) and high-temperature and high-humidity tests (85°C, 85%) even when bonded to a resin panel. On the basis of unfavorable OCA films, there is still room for research. In particular, it is required to suppress the whitening that occurs in the high temperature and high humidity test.

The present invention was made in view of the above-mentioned current situation, and its object is to provide an optically transparent adhesive sheet that prevents whitening in a high-temperature and high-humidity environment, and a laminated sheet and a bonded structure using the optically transparent adhesive sheet. [Means to solve the problem]

The optically transparent adhesive sheet of the present invention is characterized in that it has a first acrylic adhesive layer forming a first surface, a thermosetting polyurethane layer, and a second acrylic adhesive layer forming a second surface in this order. The moisture permeability of an acrylic adhesive layer and the second acrylic adhesive layer is 500 g/m ² ·h to 800 g/m ² ·h.

The laminated sheet of the present invention is characterized in that: the optically transparent adhesive sheet of the present invention, a first release film covering the first surface of the optically transparent adhesive sheet, and the first release film covering the optically transparent adhesive sheet are laminated The second release film on both surfaces.

The laminated structure of the present invention is characterized by comprising: a first adhesive body, a second adhesive body, and the optically transparent adhesive sheet that joins the first adhesive body and the second adhesive body. [Effects of the invention]

According to the optically transparent adhesive sheet and the bonded structure of the present invention, whitening under a high temperature and high humidity environment can be prevented. According to the laminated sheet of the present invention, the handleability of the optically transparent adhesive sheet of the present invention can be improved.

[Optical Clear Adhesive Sheet] Fig. 1 is a cross-sectional view schematically showing an example of the optically transparent adhesive sheet of the present invention. The optically transparent adhesive sheet 10 shown in FIG. 1 sequentially has a first acrylic adhesive layer 11 constituting a first surface (adhesive surface), a thermosetting polyurethane layer 12, and a second surface (adhesive surface). Diacrylic adhesive layer 13. By having such a laminated structure, even when the adherend is a resin panel, high adhesion and cohesion at the bonding interface can be obtained, and the adherend can be deformed following the expansion or contraction. With this, it is possible to suppress floating or bubbles (peeling) at the bonding interface caused by outgassing from the resin panel used as the adherend or the resin constituting the optically transparent adhesive sheet itself.

＜Acrylic adhesive layer＞ The first acrylic adhesive layer 11 and the second acrylic adhesive layer 13 are layers containing acrylic resin. The acrylic resin is obtained by curing an acrylic resin composition. Examples of the acrylic resin composition include (meth)acrylate polymers or copolymers containing these (hereinafter also referred to as (meth)acrylic copolymers) and a crosslinking agent.

As said (meth)acrylic copolymer, the copolymer of the alkyl (meth)acrylate and the monomer containing a carboxyl group is mentioned, for example.

Examples of the alkyl (meth)acrylate include alkyl (meth)acrylates in which the alkyl group has 1 to 18 carbon atoms (CH ₂ =CR ¹ -COOR ² ; R ¹ is a hydrogen atom or a methyl group). , R ² is an alkyl group having 1 to 18 carbons), and the carbon number of the alkyl group is preferably 4 to 12.

Examples of the alkyl (meth)acrylate having 1 to 18 carbon atoms in the alkyl group include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, Isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, amyl (meth)acrylate, (meth)acrylic acid Hexyl ester, heptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, nonyl (meth)acrylate, (meth)acrylate Base) decyl acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, isostearyl (meth)acrylate ester. These may be used singly, or two or more may be used.

Examples of the carboxyl group-containing monomer include β-carboxyethyl (meth)acrylate, 5-carboxypentyl (meth)acrylate, mono(meth)acryloyloxyethyl succinate, ω -Carboxyl group-containing (meth)acrylates such as carboxyl polycaprolactone mono(meth)acrylate; acrylic acid, methacrylic acid, itaconic acid, crotonic acid, fumaric acid, maleic acid. These may be used singly, or two or more may be used.

As the crosslinking agent, for example, a component capable of causing a crosslinking reaction with a crosslinkable functional group derived from a crosslinkable functional group-containing monomer possessed by the (meth)acrylic copolymer can be used. Specifically, an isocyanate compound, a metal chelate compound, an epoxy compound, etc. are mentioned. The crosslinking agent may be used alone, or two or more may be used.

The first acrylic adhesive layer 11 and the second acrylic adhesive layer 13 may also contain polyurethane. The polyurethane is one that hardens the polyurethane composition. Examples of the polyurethane composition include a thermosetting polyurethane composition. As the thermosetting polyurethane composition, the same composition as the thermosetting polyurethane composition used in the thermosetting polyurethane layer 12 described later can be used.

The moisture permeability of the first acrylic adhesive layer 11 and the second acrylic adhesive layer 13 is 500 g/m ² ·h to 800 g/m ² ·h. If the moisture permeability is less than 500 g/m ² ·h, when the optically transparent adhesive sheet is put into a high temperature and high humidity test (85° C., 85%), the thermosetting polyurethane layer 12 excessively absorbs moisture and whitens. If the moisture permeability exceeds 800 g/m ² ·h, the adhesion will decrease, and delay bubbles will be generated after the high temperature and high humidity test. The moisture permeability is preferably 580 g/m ² ·h or more, more preferably 720 g/m ² ·h or less. The moisture permeability of the first acrylic adhesive layer 11 and the moisture permeability of the second acrylic adhesive layer 13 may be the same or different.

The moisture permeability is measured based on the A-1 method (calcium chloride method) of the Japanese Industrial Standards (JIS) L1099 (2012) "Test Method for Moisture Permeability of Fiber Products". In the measurement of moisture permeability, prepare a test body with test pieces in a test cup filled with about 33 g of moisture absorbent (calcium chloride) and seal it at a temperature of 40℃±2℃ and a humidity of 90±5%RH In the constant temperature and humidity device, place the test body at a position where the wind speed above about 10 mm does not exceed 0.8 m/s, and measure the mass a1 (unit: g) of the test body immediately after taking it out after 1 hour. After measuring the mass a1, place the test body in the same position in the constant temperature and humidity device again, and measure the mass a2 (unit: g) of the test body immediately after taking it out one hour later. Then, the moisture permeability was calculated by the following formula. Moisture permeability [unit: g/m ² ·h]=(a2-a1)/moisture permeability area [unit: m ² ]

The moisture permeability can be adjusted according to the composition of the acrylic resin constituting the first acrylic adhesive layer 11 and the second acrylic adhesive layer 13. For example, it is generally known that acrylic resin is composed of a copolymer and adjustment helps The method of the ratio of moisture-permeable components (refer to Japanese Patent Laid-Open No. 2015-227395 and Japanese Patent No. 5920519).

The thickness of the first acrylic adhesive layer 11 and the second acrylic adhesive layer 13 is preferably 3 μm-100 μm. If the thickness is less than 3 μm, there is a possibility that delayed bubbles cannot be sufficiently suppressed. On the other hand, if the thickness exceeds 100 μm, it may not be possible to obtain flexibility (level difference followability) to the extent that it can be deformed following the level difference on the surface of the adherend to which the optically transparent adhesive sheet is attached. Yu. In addition, when the optically transparent adhesive sheet is used for bonding of substrates with different stretchability when the environment changes like the bonding of a glass substrate and a resin substrate, the optically transparent adhesive sheet may not There is a risk of peeling following the dimensional change of the substrate when the environment changes. The thickness of the first acrylic adhesive layer 11 and the second acrylic adhesive layer 13 is more preferably 3 μm-40 μm.

The first acrylic adhesive layer 11 and the second acrylic adhesive layer 13 preferably have an adhesive force of 5 N/25 mm or more to glass at room temperature (23° C.). In addition, in this specification, the adhesive force refers to the measured value in a 180° peel test. The details of the test method of the 180° peel test will be described later. The adhesive force at normal temperature is more preferably 25 N/25 mm or more, and even more preferably 35 N/25 mm or more. The upper limit of the adhesive force at normal temperature is not particularly limited, and is, for example, 100 N/25 mm.

Fig. 2 (a) and Fig. 2 (b) are schematic diagrams for explaining the evaluation method of adhesive force. The 180° peel test will be described using FIGS. 2(a) and 2(b). First, the optically transparent adhesive sheet 10 cut into a length of 75 mm × a width of 25 mm was used as a test piece. One side of this test piece was attached to a base material 31 having a length of 75 mm×a width of 25 mm, and was held at a pressure of 0.4 MPa for 30 minutes, thereby bonding the optically transparent adhesive sheet 10 and the base material 31. Next, as shown in FIG. 2( a ), the PET sheet 32 is bonded to the surface of the optically transparent adhesive sheet 10 on the opposite side to the substrate 31. Thereafter, after being left at a predetermined temperature for a certain period of time, as shown in FIG. 2(b), the PET sheet 32 is stretched in the 180° direction, and the optically transparent adhesive sheet 10 is peeled off at the interface with the substrate 31, thereby The adhesive force of the optically transparent adhesive sheet 10 to the substrate 31 was measured. As the PET sheet, for example, a PET sheet having a thickness of 125 μm ("Melinex (registered trademark) S" manufactured by Teijin Dupont Film Co., Ltd.) or the like can be used.

＜Thermosetting polyurethane layer＞ The thermosetting polyurethane layer 12 is a layer containing thermosetting polyurethane. The thermosetting polyurethane layer 12 contains thermosetting polyurethane and is soft. Therefore, the optically transparent adhesive sheet of the present invention stretches well when a tensile stress is applied, and is extremely difficult to be torn. Therefore, it can peel off without any residual glue. In addition, the thermosetting polyurethane layer 12 contains thermosetting polyurethane, so the dielectric constant is high, and the optically transparent adhesive sheet of the present invention can obtain high electrostatic capacitance. Therefore, the optically transparent adhesive sheet of the present invention can be preferably used for the bonding of capacitive touch panels. In addition, since the thermosetting polyurethane can be formed into a film without using a solvent, the thermosetting polyurethane layer 12 can be thickened.

The thermosetting polyurethane is a cured product of a thermosetting polyurethane composition. The thermosetting polyurethane composition preferably contains a polyol component and a polyisocyanate component. The thermosetting polyurethane can be obtained by, for example, reacting a polyol component and a polyisocyanate component, and preferably has a structure represented by the following formula (A).

[化1]

In the above formula (A), R represents the NCO group-removed portion of the polyisocyanate component, R′ represents the OH group-removed portion of the polyol component, and n represents the number of repeating units.

The thermosetting polyurethane is preferably not modified by acrylic acid, and preferably does not include a site derived from acrylate, methacrylate, etc. in the main chain. If the heat-curable polyurethane is modified with acrylic acid, it is hydrophobized, so it is easy to cause condensation of water under high temperature and high humidity. This condensation of water may cause whitening, blistering, etc., and may impair optical properties. Therefore, by setting the heat-curable polyurethane to the one that has not been modified by acrylic acid, it is possible to prevent the decrease in optical properties due to whitening, blistering, etc. under high temperature and high humidity. It is preferable that the total amount of the monomer unit derived from the polyol component and the monomer unit derived from the polyisocyanate component is the monomer constituting the entire thermosetting polyurethane. More than 80 mol% of the measuring unit.

As the polyol component and the polyisocyanate component, those that are liquid at normal temperature (23° C.) can be used, and a thermosetting polyurethane can be obtained without using a solvent. Other components such as a tackifier (tackifier) may be added to any one of the polyol component and the polyisocyanate component, and it is preferably added to the polyol component. When producing the thermosetting polyurethane layer 12, since it is not necessary to remove the solvent, a uniform thick sheet can be formed. In addition, the thermosetting polyurethane layer 12 is one that can maintain optical properties even if it is formed thick, and can sufficiently suppress coloration and blistering (bubble generation at the interface with the adherend). Furthermore, the thermosetting polyurethane layer 12 can be thickened and soft, so it is excellent in impact resistance. The optically transparent adhesive sheet provided with the thermosetting polyurethane layer 12 can be used for those having a transparent conductive film on the surface. The bonding of the transparent member and the cover panel, and in the case of using other members, can also be used for bonding of a display panel or a transparent member having a transparent conductive film on the surface layer and other members. When an optically transparent adhesive sheet with a thermosetting polyurethane layer 12 is used for bonding a display panel and a transparent member (touch panel) having a transparent conductive film on the surface, it can be adhered by optically transparent The sheet covers the step formed by the frame arranged on the outer edge of the display panel.

The polyol component is not particularly limited, and examples thereof include polyether polyol, polycaprolactone polyol, polycarbonate polyol, polyester polyol, and the like. These can be used alone or in combination of two or more kinds.

The polyol component preferably has an olefin skeleton. That is, it is preferable to include polyolefin or a derivative thereof in the main chain. As the polyol component having an olefin skeleton, for example, 1,2-polybutadiene polyol, 1,4-polybutadiene polyol, 1,2-polychloroprene polyol, hydrogen or halogen Polybutadiene-based polyols such as olefin polyols and 1,4-polychloroprene polyols, or polyisoprene-based polyols, those obtained by saturating these double bonds. In addition, the polyol component may be a polyol obtained by copolymerizing an olefin compound such as styrene, ethylene, vinyl acetate, acrylate, and a polybutadiene-based polyol, or a hydrogenated product thereof. The polyol component may have a linear structure or a branched structure. Only one kind of the polyol component may be used, or two or more kinds may be used. The polyol component used in the polyurethane preferably contains 80 mol% or more of a polyol component having an olefin skeleton, and more preferably contains only a polyol component having an olefin skeleton.

The polyisocyanate component is not particularly limited, and conventionally known polyisocyanates can be used, and either or both of a hydrophilic polyisocyanate having a hydrophilic unit and a hydrophobic polyisocyanate having no hydrophilic unit can be used . Furthermore, the hydrophilic polyisocyanate with hydrophilic units does not only increase the hydrophilicity by a structure derived from an isocyanate group like an isocyanurate structure or a biuret structure, but means that the addition increases Hydrophilic functional group (hydrophilic unit) polyisocyanate. Since the polyisocyanate component contains a hydrophilic unit, an effect of suppressing whitening caused by moisture absorption can be obtained.

The hydrophilic unit is preferably a polyalkylene oxide unit. As a polyalkylene oxide unit, a polyethylene oxide unit and a polypropylene oxide unit are mentioned, for example. The content of the polyalkylene oxide unit is preferably 0.1% by weight or more and 20% by weight or less with respect to the entire thermosetting polyurethane composition. If the content is less than 0.1% by weight, the effect of suppressing whitening may not be sufficiently obtained. If the content exceeds 20% by weight, the compatibility with low-polarity olefin-based polyol components, tackifiers, plasticizers, and the like may decrease, and optical properties such as haze may decrease. The content of the polyalkylene oxide unit is more preferably 0.1% by weight to 5% by weight. If the content exceeds 5% by weight, the amount of moisture absorption in the high-temperature and high-humidity environment may become excessive.

Examples of hydrophilic units other than polyalkylene oxide units include carboxylic acid groups, alkali metal salt groups of carboxylic acid, sulfonic acid groups, alkali metal salt groups of sulfonic acid, hydroxyl groups, amide groups, and amino groups. unit. In more detail, examples include: polyacrylic acid, alkali metal salts of polyacrylic acid, sulfonic acid group-containing copolymers, alkali metal salts of sulfonic acid group-containing copolymers, polyvinyl alcohol, polypropylene amide, carboxymethyl Cellulose, alkali metal salt of carboxymethyl cellulose, polyvinylpyrrolidone, etc.

The polyisocyanate component is preferably a modified polyisocyanate obtained by reacting an aliphatic and/or alicyclic polyisocyanate having an isocyanate group and an ether compound having a polyalkylene oxide unit. By using aliphatic and/or alicyclic polyisocyanates, it is more difficult to produce coloring or discoloration, and the transparency of the optically transparent adhesive sheet can be more reliably ensured for a long time. In addition, by setting it as a modified product obtained by reacting an ether compound having a polyalkylene oxide unit, the polyisocyanate component can inhibit whitening by the action of the hydrophilic part (polyalkylene oxide unit), and can be hydrophobic The role of the sexual part (other units) plays the role of compatibility with low-polarity thickeners, plasticizers, etc.

The α ratio (the number of moles of the OH group derived from the polyol component/the number of moles of the NCO group derived from the polyisocyanate component) of the thermosetting polyurethane composition is preferably 1 or more. When the α ratio is less than 1, since the blending amount of the polyisocyanate component is excessive relative to the blending amount of the polyol component, the thermosetting polyurethane may become hard and it may be difficult to secure an optically transparent adhesive sheet The required flexibility. If the flexibility of the thermosetting polyurethane layer 12 is low, especially when bonding optical members such as a touch panel, it is impossible to cover the unevenness and level difference existing on the bonding surface. In addition, if the α ratio is less than 1, the adhesive force required for the optically transparent adhesive sheet may not be secured. The α is preferably less than 2.0. When the α ratio is 2.0 or more, the thermosetting polyurethane composition may not be sufficiently cured.

The thermosetting polyurethane composition may further contain a plasticizer. The plasticizer is not particularly limited as long as it is a compound for imparting flexibility to the thermosetting polyurethane. From the viewpoint of compatibility and weather resistance, it is preferable to include a carboxylic acid Department of plasticizer.

The thermosetting polyurethane composition may further contain a catalyst. The catalyst is not particularly limited as long as it can be used for the urethane reaction. Examples include di-n-butyl tin dilaurate, dimethyl tin dilaurate, dibutyl tin oxide, Organic tin compounds such as tin octoate; organic titanium compounds; organic zirconium compounds; tin carboxylates; bismuth carboxylates; amine catalysts such as triethylenediamine.

In the thermosetting polyurethane composition, within a range that does not hinder the required characteristics of the optically transparent adhesive sheet, a thickener (adhesive imparting agent), a coloring agent, a stabilizer, and an anti- Various additives such as oxidant, antifungal agent and flame retardant.

The thickness of the thermosetting polyurethane layer 12 is preferably 100 μm to 2000 μm. When the thickness is less than 100 μm, there are cases where the overall flexibility of the optically transparent adhesive sheet is reduced, and when one side of the optically transparent adhesive sheet is attached to the surface of the optical member, the optically transparent adhesive sheet cannot be used To cover the unevenness or level difference existing on the surface of the optical member, it is impossible to use sufficient adhesive force to bond the other surface of the optically transparent adhesive sheet to the surface of another optical member. In the case where the thickness exceeds 2000 μm, there are cases where optical characteristics such as haze and total light transmittance cannot be sufficiently obtained. A more preferable lower limit of the thickness of the thermosetting polyurethane layer 12 is 150 μm, a further preferable lower limit is 200 μm, and a particularly preferable lower limit is 250 μm. A more preferable upper limit of the thickness of the thermosetting polyurethane layer 12 is 1500 μm, and a further preferable upper limit is 1000 μm.

The optically transparent adhesive sheet 10 only needs to have a first acrylic adhesive layer 11, a thermosetting polyurethane layer 12, and a second acrylic adhesive layer 13 in this order, and may further have other layers. The first acrylic adhesive layer 11 and the second acrylic adhesive layer 13 may be located on the outermost surface (the surface in contact with the adherend) of the optically transparent adhesive sheet 10, respectively. In addition, the first acrylic adhesive layer 11 and the thermosetting polyurethane layer 12 are preferably in contact with each other, and the second acrylic adhesive layer 13 and the thermosetting polyurethane layer 12 are preferably in contact with each other. Pick up.

＜Optical transparent adhesive sheet＞ In order to ensure the performance as an optically transparent adhesive sheet, the haze of the optically transparent adhesive sheet 10 of the present invention is preferably 1% or less, more preferably 0.5% or less. In addition, the optically transparent adhesive sheet 10 of the present invention preferably has a total light transmittance of 90% or more. For example, a turbidity meter "Haze Meter NDH2000" manufactured by Nippon Denshoku Kogyo Co., Ltd. can be used to measure haze and total light transmittance. The haze is measured by a method based on JIS K 7136, and the total light transmittance is measured by a method based on JIS K 7361-1.

The thickness of the entire optically transparent adhesive sheet 10 is preferably 106 μm or more. The upper limit of the thickness of the entire optically transparent adhesive sheet 10 is not particularly limited, and is 3000 μm, for example. The optically transparent adhesive sheet 10 preferably has a thickness of 3 times or more with respect to the height of the unevenness or step difference existing on the attachment surface of the adhesive body. A more preferable lower limit of the thickness is 500 μm, a further preferable lower limit is 750 μm, a preferable upper limit is 2000 μm, and a more preferable upper limit is 1750 μm.

[Multilayer film] A release film can also be attached to both sides of the optically transparent adhesive sheet of the present invention. Fig. 3 is a cross-sectional view schematically showing an example of the laminated sheet of the present invention. In addition, the optically transparent adhesive sheet 10 of the present invention, a first release film 21 covering the first surface of the optically transparent adhesive sheet 10, and a second release film 22 covering the second surface of the optically transparent adhesive sheet 10 are laminated. The sheet 20 is also an aspect of the present invention. According to the laminated sheet of the present invention, the first release film and the second release film can protect both sides of the optically transparent adhesive sheet of the present invention until it is attached to the adherend. Thereby, it is possible to prevent the decrease in adhesiveness and the adhesion of foreign matter to the optically transparent adhesive sheet of the present invention. In addition, it is also possible to prevent the optically transparent adhesive sheet of the present invention from sticking to other than the adherend, so that the workability is improved.

The first release film and the second release film may be resin films such as PET films, or may be paper (release paper) that has been subjected to a release treatment. The material and thickness of the first release film and the second release film may be the same or different from each other.

The bonding strength (peel strength) of the optically transparent adhesive sheet and the first release film of the present invention and the bonding strength (peel strength) of the optically transparent adhesive sheet and the second release film of the present invention are preferably different from each other. In this way, since the bonding strength is different from each other, it becomes easy to peel only one of the first release film and the second release film (release film with low bonding strength) from the laminated sheet of the present invention, Bond the exposed first surface of the optically transparent adhesive sheet to the first adhesive body, and then peel off the other of the first release film and the second release film (release film with high bonding strength), The second surface of the exposed optically transparent adhesive sheet is attached to the second adhesive body.

At least one of the surface of the first release film that is in contact with the optically transparent adhesive sheet of the present invention and the surface of the second release film that is in contact with the optically transparent adhesive sheet of the present invention Implement demolding treatment (easy peeling treatment). As the easy peeling treatment, for example, silicon treatment or the like can be cited.

[Lamination structure] The use of the optically transparent adhesive sheet of the present invention is not particularly limited. In addition, a bonding structure including a first adhesive body, a second adhesive body, and the optically transparent adhesive sheet that joins the first adhesive body and the second adhesive body is also an aspect of the present invention.

The optically transparent adhesive sheet of the present invention can be used for joining the liquid crystal module and the cover panel. By using an optically transparent adhesive sheet to join the liquid crystal module and the cover panel and eliminate the air layer existing between the liquid crystal module and the cover panel, the visibility of the liquid crystal module can be improved. In this case, the first adhesive body and the second adhesive body are the liquid crystal module and the cover panel. When a liquid crystal module is arranged in a frame (frame) with an opening in the display portion, a frame is arranged on the outer edge of the liquid crystal module. Therefore, a step corresponding to the thickness of the frame is formed. The method in which an optically transparent adhesive sheet is superimposed not only in the center of the liquid crystal module but also in the area where the frame is arranged to perform the bonding of the liquid crystal module and the cover panel is also called "bonding on the frame". The bonding structure formed by bonding on the frame is also referred to as "the bonding structure on the frame".

The optically transparent adhesive sheet of the present invention is soft and can be thickened, so it is suitable for bonding on a frame. The laminated structure of the present invention has a structure in which an optically transparent adhesive sheet and a supporting member are provided between the first substrate and the second substrate, and the supporting member has a step arranged on the outer edge of the first substrate. The difference forming portion, the optically transparent adhesive sheet may also include: a thick film portion for bonding the first substrate and the second substrate; and sandwiched between the step forming portion and the second substrate The end between the wood.

4 is a cross-sectional view schematically showing the structure of the bonding structure of the present invention having the bonding structure on the frame. The laminated structure 50 shown in FIG. 4 has a configuration in which an optically transparent adhesive sheet 10 and an upper frame (supporting member) 41 are provided between the first base material 51 and the second base material 52, and may be, for example, a display device. Part of an electronic machine. The upper frame 41 and the lower frame 42 are integrated to form a frame (frame) that houses the first base material 51.

In the laminated structure 50, the optically transparent adhesive sheet 10 includes: a thick film portion for bonding the first substrate 51 and the second substrate 52; and the step forming portion and the second substrate sandwiched between the upper frame 41 52 between the ends. The end portion of the optically transparent adhesive sheet 10 is sandwiched between the second base material 52 and the step forming portion of the upper frame 41, so it is difficult to peel off. In addition, the optically transparent adhesive sheet 10 reaches the step forming part of the upper frame 41, so the upper surface of the first substrate 51 is completely covered by the step forming part of the upper frame 41 or the optically transparent adhesive sheet 10, which can prevent the first substrate 51's moisture absorption. In the case where the polarizing plate is located on the upper surface of the first base material 51, moisture absorption of the polarizing plate can be prevented. If the polarizing plate absorbs moisture, the performance degradation will be accelerated, or delayed bubbles will be caused by the evaporation of moisture absorbed in a high temperature environment.

The combination of the first base material 51 and the second base material 52 is not particularly limited, and examples thereof include display panels, touch panels (glass substrates with ITO transparent conductive film), cover panels (cover glass), etc., which constitute display devices. member. The type of the display panel is not particularly limited, and examples thereof include a liquid crystal panel and an organic electroluminescence panel (organic EL (electroluminescence) panel). In addition, a polarizing plate, a retardation film, etc. may be arranged on the surface of the display panel to which the optically transparent adhesive sheet 10 is attached. If the optically transparent adhesive sheet 10 is used to bond various components in the display device, the air layer (air gap) in the display device can be eliminated, and the visibility of the display screen can be improved. In addition, when a polarizing plate is arranged, the optically transparent adhesive sheet 10 can effectively prevent moisture absorption of the polarizing plate. Preferably, the combination is as follows: the first substrate 51 is a display panel such as a liquid crystal module, and the second substrate 52 is a cover panel (cover glass) or a touch sensor glass.

The materials of the first base material 51 and the second base material 52 are not particularly limited, and examples thereof include glass and resin. The resin constituting the first substrate 51 and/or the second substrate 52 is not particularly limited, and examples thereof include polycarbonate, polymethyl methacrylate (PMMA), and triacetyl cellulose ( Triacetyl Cellulose, TAC) etc. For example, when a polarizing plate is arranged on the surface of the first substrate 51 on which the optically transparent adhesive sheet 10 is attached, the surface in contact with the optically transparent adhesive sheet 10 may be composed of TAC. Furthermore, the polarizing plate may have a layered structure of TAC, polyvinylalcohol (PVA) and TAC, or may be a layered structure with antiglare (AG) treatment on the surface of the TAC, or In order to perform a hard coat (HC) treatment on the surface of the TAC of the laminated structure, it may also be a person who has performed AG treatment and HC treatment on the surface of the TAC of the laminated structure.

The upper frame 41 is a frame-shaped member disposed around the optically transparent adhesive sheet 10 in a plan view, and at least a part is disposed on the outer edge of the first base material 51. A level difference is formed on the side surface of the portion (level difference forming portion) arranged on the outer edge of the first base material 51. The shape of the side surface of the step forming portion is not particularly limited, and the side surface of the step forming portion may be perpendicular to the upper surface of the first base material 51. In the case where the first substrate 51 is a display panel, the upper frame 41 is disposed in the frame edge area of the display device, and the user of the display device can also be outside the second substrate 52 in a way that the user of the display device will not observe the upper frame 41. A light shielding part 52A is provided on the edge. The material of the upper frame 41 is not particularly limited, and examples thereof include metal and resin.

The thickness (the size of the level difference) of the upper frame 41 is not particularly limited, and is, for example, 200 μm to 1000 μm. If the thickness of the upper frame 41 exceeds 200 μm, the thickness of the optically transparent adhesive sheet 10 needs to be 300 μm or more. Therefore, an optically transparent adhesive sheet thicker than a normal optically transparent adhesive sheet can be used.

The thickness of the thick film portion of the optically transparent adhesive sheet 10 is 1.5 times or more the thickness of the step forming portion of the upper frame 41, and more preferably 2 times or more. Thereby, the end portion of the optically transparent adhesive sheet 10 sandwiched between the step forming portion of the upper frame 41 and the second base material 52 can ensure a sufficient thickness and prevent the end portion from being peeled off. In addition, the thickness of the thick film portion of the optically transparent adhesive sheet 10 in the bonded structure 50 is substantially the same as the thickness of the optically transparent adhesive sheet 10 before bonding. That is, the thickness of the optically transparent adhesive sheet 10 before bonding is preferably 1.5 times or more the thickness of the upper frame 41, and more preferably 2 times or more.

[Method for manufacturing optically transparent adhesive sheet] The method of sequentially laminating the first acrylic adhesive layer 11, the thermosetting polyurethane layer 12, and the second acrylic adhesive layer 13 is not particularly limited. For example, it can be exemplified in making the first acrylic adhesive layer 11 separately , The second acrylic adhesive layer 13 and the thermally hardened polyurethane layer 12 are then bonded together.

The method for preparing the first acrylic adhesive layer 11 and the second acrylic adhesive layer 13 is not particularly limited. For example, it can be composed of an acrylic resin using various coating devices, bar coating, doctor blades, and other general film forming devices or film forming methods. The manufacturing method of material forming. In addition, the first acrylic adhesive layer 11 and the second acrylic adhesive layer 13 can also be produced by a centrifugal molding method.

The preparation method of the thermosetting polyurethane layer 12 is not particularly limited. For example, after preparing a thermosetting polyurethane composition, the composition is formed while thermosetting the composition by a previously known method. The method preferably includes: a step of stirring and mixing the polyol component, the polyisocyanate component and the tackifier to prepare a thermosetting polyurethane composition; and the step of preparing the thermosetting polyurethane composition Carry out the hardening step.

As a specific example of the production method, first, a predetermined amount of a thickener is added to the polyol component, and the mixture is heated and stirred to dissolve, thereby preparing a master batch. Then, the obtained masterbatch, polyol component, polyisocyanate component, and optionally other components such as a catalyst are mixed, and stirred with a mixer or the like to obtain a liquid or gel-like thermosetting polyamine Base formate composition. Immediately after that, the thermosetting polyurethane composition was put into the molding device, and while being sandwiched by the first release film and the second release film, the thermosetting polyurethane composition The ester composition moves while undergoing a curing reaction (crosslinking reaction), thereby obtaining a thermosetting polyurethane composition that is semi-cured and integrated with the first release film and the second release film sheet. After that, a cross-linking reaction is performed in a furnace for a certain period of time, thereby obtaining a thermally hardened polyurethane layer 12.

As a method for preparing the thermosetting polyurethane layer 12, after preparing the thermosetting polyurethane composition before hardening, it can be formed by using various coating devices, bar coatings, doctor blades, etc. The manufacturing method of the device or the film forming method. In addition, a centrifugal molding method may be used to produce the thermosetting polyurethane layer 12. [Example]

Hereinafter, examples are disclosed to describe the present invention in more detail, but the present invention is not limited to these examples.

(Example 1) First, use a reciprocating rotary mixer AJITER to mix 75 parts by weight of polyolefin polyol ("EPOL (EPOL, registered trademark)" manufactured by Idemitsu Kosan Co., Ltd.) and 2.4 parts by weight of isophorone Isophorone Diisocyanate (IPDI) is a polyisocyanate ("Desmodur I" manufactured by Sumika Bayer urethane), 4.6 parts by weight of modified polyisocyanate containing ethylene oxide units Isocyanate ("Coronate 4022" manufactured by Tosoh), 17 parts by weight of a tackifier ("IMARV P-100" manufactured by Idemitsu Kosan) and 1 Parts by weight of the catalyst (dimethyl tin dilaurate) were stirred and mixed to prepare a thermosetting polyurethane composition having an α ratio of 1.60. Furthermore, in the thermosetting polyurethane composition, the mixing ratio (molar ratio) of the IPDI-based polyisocyanate (A) and the modified polyisocyanate (B) is A:B=2:1.

Furthermore, "Coronate 4022" manufactured by Tosoh Corporation is an ether polyol having an average of three or more polyalkylene oxide units per molecule, and hexamethylene diisocyanate And/or obtained by the reaction of polyisocyanate with hexamethylene diisocyanate monomer as the starting material.

After that, the resulting thermosetting polyurethane composition was transported in a furnace while being sandwiched between a pair of release films (PET films with release treatment on the surface). It is cross-linked and hardened under the conditions of an internal temperature of 50°C to 90°C and a furnace time of several minutes to obtain a sheet with a release film. Thereafter, a cross-linking reaction is performed in a heating device for 10 to 15 hours to produce a thermosetting polyurethane layer having a release film provided on both sides. The thickness of the thermosetting polyurethane layer is 1000 μm.

On the other hand, 0.6 parts by weight of an isocyanate-based hardener is added to 100 parts by weight of acrylic resin (the "SK1838" and "SK1875" manufactured by Soken Chemical Co., Ltd. are doped with a solid content ratio of 5:5. ("DY-70" manufactured by Soken Chemical Co., Ltd.) to produce acrylic resin compositions. The obtained acrylic resin composition is coated on a release film using a chipped wheel coater, and after drying in a drying oven at 80°C to 120°C, the release film is superimposed on the coated surface. After that, curing was completed by heating at 40°C for 1 week, and an acrylic adhesive layer was produced. The thickness of the acrylic adhesive layer is 25 μm. The moisture permeability of the obtained acrylic adhesive layer was measured based on the A-1 method of JIS L1099 (2012), and it was 586 g/m ² ·h.

After that, two acrylic adhesive layers with a mold release film and one thermosetting polyurethane layer with a mold release film were prepared. One of the release films was peeled off from the first acrylic adhesive layer with a release film, and the thermally hardened polyurethane layer was peeled off from the area layer of the release film on the first acrylic adhesive layer. Furthermore, one of the release films was peeled off from the second acrylic adhesive layer with a release film, and the first acrylic adhesive layer (the first acrylic adhesive layer) was laminated on the thermosetting polyurethane layer and The surface of the acrylic adhesive layer) is the second acrylic adhesive layer (second acrylic adhesive layer) on the opposite side of the area layer. Thereby, a laminate sheet in which a release film, a first acrylic adhesive layer, a thermosetting polyurethane layer, a second acrylic adhesive layer, and a release film are sequentially laminated is produced. The thickness of the optically transparent adhesive sheet including the first acrylic adhesive layer, the thermosetting polyurethane layer and the second acrylic adhesive layer is 1050 μm.

(Example 2) Except that 100 parts by weight of acrylic resin was used in the production of the acrylic adhesive layer (the ones made by Soken Chemical Co., "SK1838" and "SK1875" are doped so that the solid content ratio becomes 3:7) Except for the acrylic resin composition prepared by adding 0.65 parts by weight of an isocyanate curing agent (“DY-70” manufactured by Soken Chemical Co., Ltd.), a laminated sheet was produced in the same manner as in Example 1. The moisture permeability of the obtained acrylic adhesive layer was 689 g/m ² ·h.

(Example 3) Except for 100 parts by weight of acrylic resin used in the production of the acrylic adhesive layer (the one made by Soken Chemical Co., "SK1838" and "SK1875" are doped so that the solid content ratio becomes 4:6) Except for the acrylic resin composition prepared by adding 0.63 parts by weight of an isocyanate curing agent ("DY-70" manufactured by Soken Chemical Co., Ltd.), a laminated sheet was produced in the same manner as in Example 1. The moisture permeability of the obtained acrylic adhesive layer was 604 g/m ² ·h.

(Example 4) In addition to the use of acrylic adhesive layer in the preparation of 100 parts by weight of acrylic resin ("MTP-54" manufactured by Toagosei Co., Ltd.) 0.06 parts by weight of isocyanate-based curing agent (manufactured by Toagosei Co., Ltd.) "02") Except for the acrylic resin composition prepared, a laminated sheet was produced in the same manner as in Example 1. The moisture permeability of the obtained acrylic adhesive layer was 713 g/m ² ·h.

(Example 5) Except that 100 parts by weight of acrylic resin was used in the production of the acrylic adhesive layer (the one made by Soken Chemical Co., "SK1838" and "SK1875" are doped with a solid content ratio of 7:3) Except for the acrylic resin composition prepared by adding 0.57 parts by weight of an isocyanate curing agent ("DY-70" manufactured by Soken Chemical Co., Ltd.), a laminated sheet was produced in the same manner as in Example 1. The moisture permeability of the obtained acrylic adhesive layer was 500 g/m ² ·h.

(Comparative Example 1) In addition to the use of acrylic resin ("SK1838" manufactured by Soken Chemical Co., Ltd.) in 100 parts by weight of acrylic resin ("SK1838" manufactured by Soken Chemical Co.), 0.3 parts by weight of isocyanate-based hardener ("DY -70") A laminated sheet was produced in the same manner as in Example 1 except for the acrylic resin composition prepared. The moisture permeability of the obtained acrylic adhesive layer was 394 g/m ² ·h.

(Comparative Example 2) In addition to the use of acrylic resin ("SK1875" manufactured by Soken Chemical Co.) in 100 parts by weight of acrylic resin ("SK1875" manufactured by Soken Chemical Co.), 0.7 parts by weight of isocyanate-based hardener ("DY -70") A laminated sheet was produced in the same manner as in Example 1 except for the acrylic resin composition prepared. The moisture permeability of the obtained acrylic adhesive layer was 853 g/m ² ·h.

(1) Reliability evaluation The release film was peeled off from the laminated sheet produced in the Examples and Comparative Examples, one surface of the optically transparent adhesive sheet was bonded to a glass plate, and the other surface was bonded to a polycarbonate plate with a thickness of 1 mm. The obtained 7-inch laminate of glass plate/optical transparent adhesive sheet/polycarbonate plate was placed at 85°C and 85% high temperature and high humidity environment for 24 hours. Visually observe the laminated body after placement to confirm whether bubbles (retarded bubbles) are generated at the bonding interface between the glass plate and the optically transparent adhesive sheet and the polycarbonate plate and the optically transparent adhesive sheet. The case where no delayed bubbles were observed was evaluated as "o", and the case where delayed bubbles were observed was evaluated as "x".

(2) Whitening evaluation The release film was peeled off from the laminated sheets produced in the examples and comparative examples, and glass plates were laminated on both sides of the optically transparent adhesive sheet, and the resulting laminated body of glass plate/optically transparent adhesive sheet/glass plate was heated at 85°C, 85% Place for 24 hours in a high temperature and high humidity environment. The haze of the layered body after being left was measured. The haze is measured by a method based on JIS K 7136 using a turbidity meter "Haze Meter (Haze Meter) NDH2000" manufactured by Nippon Denshoku Kogyo Co., Ltd. The case where the haze is less than 0.5% is evaluated as "o", the case where the haze is 0.5% to 1.0% is evaluated as "Δ", and the case where the haze exceeds 1.0% is evaluated as "×".

(3) Evaluation of adhesion Use the method shown in Figure 2 to perform a 180° peel test and determine the adhesion (N/25 mm). Specifically, the laminated sheets produced in the examples and comparative examples were cut into length 75 mm×width 25 mm, and used as test pieces. After peeling off the release film on one side of the test piece, the optically transparent adhesive sheet 10 side was attached to the base material 31 having a length of 75 mm × a width of 25 mm, and kept under a pressure of 0.4 MPa for 30 minutes to adhere to the optically transparent The sheet 10 is bonded to the base material 31. Next, the release film on the side opposite to the substrate 31 is peeled, and as shown in FIG. 2(a), a PET sheet with a thickness of 125 μm is bonded to the surface of the optically transparent adhesive sheet 10 on the side opposite to the substrate 31 ("Melinex (registered trademark) S" manufactured by Teijin Dupont Film Company) 32. After that, after leaving for 12 hours at normal temperature and humidity (temperature 23°C, humidity 50%), as shown in Figure 2(b), the PET sheet 32 was placed at a speed of 30 mm/min in an environment of 23°C Stretching in the direction of 180°, the optically transparent adhesive sheet 10 is peeled off at the interface with the base material 31, and the adhesive force of the optically transparent adhesive sheet 10 is measured. In addition, the measured adhesive force is the "adhesive force to glass" when a glass plate is used as the substrate 31.

[Table 1] Example 1 Example 2 Example 3 Example 4 Example 5 Comparative example 1 Comparative example 2 The moisture permeability of the acrylic adhesive layer (g/m ² ·h) 586 689 604 713 500 394 853 Reliability evaluation [whether delayed bubbles are generated] 〇 〇 〇 〇 〇 〇 × Whitening evaluation [haze] 〇 〇 〇 〇 Δ × 〇 Adhesion (N/25 mm) 38.3 28.7 27.2 22.1 43.5 54.7 4.5

According to the above Table 1, it can be seen that the optically transparent adhesive sheets of Examples 1 to 5 in the range of 500 g/m ² ·h to 800 g/m ² ·h in the acrylic adhesive layer are in reliability evaluation No delayed bubble generation was observed, and the haze was 0.5% or less in the whitening evaluation. On the other hand, the optically transparent adhesive sheet of Comparative Example 1 in which the moisture permeability of the acrylic adhesive layer was less than 500 g/m ² ·h to 800 g/m ² ·h had a haze of more than 0.5% in the whitening evaluation. Whitening occurs due to being placed at 85°C and 85% high temperature and humidity for 24 hours. In addition, the optically transparent adhesive sheet of Comparative Example 2 in which the moisture permeability of the acrylic adhesive layer is greater than 500 g/m ² ·h to 800 g/m ² ·h has a small adhesive force, so it is at 85°C and 85% high temperature and high humidity Delayed bubbles are generated after 24 hours in the environment.

10: Optically transparent adhesive sheet 11: The first acrylic adhesive layer 12: Thermally hardened polyurethane layer 13: The second acrylic adhesive layer 20: Multilayer film 21: The first release film 22: The second release film 31: Substrate 32: PET sheet 41: Upper frame (supporting member) 42: bottom border 50: Fit the structure 51: The first substrate 52: second substrate 52A: Shading part

Fig. 1 is a cross-sectional view schematically showing an example of the optically transparent adhesive sheet of the present invention. Fig. 2 (a) and Fig. 2 (b) are schematic diagrams for explaining the evaluation method of adhesive force. Fig. 3 is a cross-sectional view schematically showing an example of the laminated sheet of the present invention. 4 is a cross-sectional view schematically showing the structure of the bonding structure of the present invention having the bonding structure on the frame.

10: Optically transparent adhesive sheet

11: The first acrylic adhesive layer

12: Thermally hardened polyurethane layer

13: The second acrylic adhesive layer

Claims (3)

An optically transparent adhesive sheet, characterized in that it has a first acrylic adhesive layer forming a first surface, a thermosetting polyurethane layer, and a second acrylic adhesive layer forming a second surface in sequence. The first acrylic The moisture permeability of the adhesive layer and the second acrylic adhesive layer is 500 g/m ² ·h to 800 g/m ² ·h. A laminated sheet, characterized in that the optically transparent adhesive sheet according to claim 1, a first release film covering the first surface of the optically transparent adhesive sheet, and the optically transparent adhesive sheet covering The second release film on the second surface. An adhesive structure, characterized by comprising: a first adhesive body, a second adhesive body, and the optically transparent adhesive sheet according to claim 1 that joins the first adhesive body and the second adhesive body.

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