JP2018202621A - Laminate, optically clear adhesive sheet, and production method of laminate - Google Patents

Abstract

To provide a laminate capable of mitigating the placement accuracy for an optically clear adhesive sheet and giving excellent reliability in bonding by the optical clear adhesive sheet, and an optically clear adhesive sheet suitable for the production of the above laminate and a production method of the laminate.SOLUTION: The laminate includes an optically clear adhesive sheet and a support member between a first substrate and a second substrate. The support member has a step-forming portion disposed on an outer edge of the first substrate. The optically clear adhesive sheet includes a thick portion for adhering the first substrate and the second substrate and an end portion held between the step-forming portion and the second substrate. The optically clear adhesive sheet shows a loss tangent of 0.5 or more at 30°C, and the thickness of the thick portion is 1.5 times or more as the thickness of the step-forming portion.SELECTED DRAWING: Figure 1

Description

The present invention relates to a laminate, an optically transparent adhesive sheet, and a method for producing the laminate.

An optically transparent adhesive (OCA) sheet is a transparent adhesive sheet used for bonding optical members. In recent years, the demand for touch panels in the fields of smartphones, tablet PCs, portable game machines, car navigation devices, etc. has increased rapidly, and accordingly, demand for OCA sheets used for bonding touch panels to other optical members is increasing. Has also increased. A display device provided with a touch panel is usually a display panel such as a liquid crystal panel, a transparent member (touch panel body) having a transparent conductive film made of ITO (indium tin oxide) or the like as a surface layer, and a cover for protecting the transparent conductive film It has a structure in which optical members such as panels are laminated, and an OCA sheet is used for bonding between optical members.

As prior art in the technical field of the OCA sheet, for example, Patent Document 1 discloses (meth) acrylic copolymer A having a weight average molecular weight of more than 50,000 and not more than 600,000, and a weight average molecular weight of 1 000 to 50,000 (meth) acrylic copolymer B, and a pressure-sensitive adhesive formed from a pressure-sensitive adhesive composition, the dynamic shear storage modulus G ′ of the pressure-sensitive adhesive, A pressure-sensitive adhesive sheet in which the dynamic shear loss tangent tan δ calculated based on the measured value with the dynamic shear loss elastic modulus G ″ satisfies the following formulas (1) and (2) is disclosed.
tan δ (20 ° C. to 150 ° C.) ≧ 0.5 (1)
tan δ (1 Hz to 10 ⁻⁵ Hz) ≧ 0.5 (2)
(However, tan δ (20 ° C. to 150 ° C.) in the formula (1) indicates the dynamic shear loss tangent of the pressure-sensitive adhesive in the range of 20 ° C. to 150 ° C. and a frequency of 1 Hz. , Tan δ (1 Hz to 10 ⁻⁵ Hz) represents a dynamic shear loss tangent of the pressure-sensitive adhesive at 20 ° C. in a frequency range of 1 Hz to 10 ⁻⁵ Hz.

Patent Document 2 discloses an adhesive sheet comprising an adhesive layer formed of a urethane resin adhesive and a release film provided on one or both surfaces of the adhesive layer, wherein the adhesive layer is measured. The storage elastic modulus at a frequency of 1 Hz and a temperature of 25 ° C. is in the range of 1.0 × 10 ⁶ Pa or more and 5.0 × 10 ⁶ Pa or less, the loss tangent is in the range of 0.7 or more and 1.2 or less, The storage elastic modulus at a measurement frequency of 1 Hz and a temperature of 50 ° C. is in the range of 5.0 × 10 ⁵ Pa to 1.0 × 10 ⁶ Pa, and the loss tangent is in the range of 0.7 to 1.2. An adhesive sheet having an adhesive strength to glass of 30 N / inch or more is disclosed.

Patent Document 3 discloses an optically transparent pressure-sensitive adhesive sheet made of a cured product of a thermosetting polyurethane composition, and the thermosetting polyurethane composition contains a polyol component, a polyisocyanate component, and a tackifier. As the above-mentioned tackifier, an optical transparent adhesive sheet containing a rosin diol-based tackifier is disclosed.

JP 2014-152198 A Japanese Patent Laid-Open No. 2006-104829 JP-A-2014-141687

By the way, there is a step between the display panel and the touch panel body because the end of the bezel (frame) which is the housing of the display panel is located. The conventional OCA sheet used for bonding the display panel and the touch panel main body has been arranged in a region surrounded by a bezel existing on the outer edge of the display panel. Hereinafter, the structure in which the OCA sheet is arranged in the region surrounded by the bezel is also referred to as “bezel-in bonding structure”. FIG. 3 is a cross-sectional view schematically showing a configuration of a conventional laminate having a bezel-in bonding structure. The laminated body shown in FIG. 3 has a configuration in which an optical transparent adhesive sheet (OCA sheet) 112 and a support member (upper bezel) 21 are provided between the first base material 11 and the second base material 13. In addition, the upper bezel 21 is integrated with the lower bezel 22 to form a housing (bezel) that houses the first base material 11.

However, in the bezel-in bonding structure, if the OCA sheet 112 is too small, a space in which the OCA sheet 112 does not exist is formed in a portion surrounded by a dotted line in FIG. The end face of can be seen and the design is impaired. On the other hand, if the OCA sheet 112 is too large, the OCA sheet 112 is deformed by the bonding pressure and compressed in the thickness direction and swells in the width direction, so that the end of the OCA sheet 112 contacts the end surface of the upper bezel 21. At this time, the end portion of the OCA sheet 112 may be adhered to the end surface of the upper bezel 21 while being lifted from the first base material 11, but the end portion of the OCA sheet 112 is more than the center of the OCA sheet 112. Since it was thin and not sufficiently pressurized, the end of the OCA sheet 112 was easily lifted or peeled off. Thus, in the bezel-in bonding structure, the placement accuracy of the OCA sheet 112 was strict.

Further, since the OCA sheet 112 is easily peeled off from the end portion, it has been required to prevent peeling of the end portion of the OCA sheet 112 and to improve the reliability of bonding. Furthermore, when the polarizing plate is located on the upper surface of the first substrate 11, the polarizing plate may absorb moisture through the space where the OCA sheet 112 does not exist. When the polarizing plate absorbs moisture, performance deterioration may be accelerated, or delayed bubbles may be generated due to evaporation of moisture absorbed in a high temperature environment.

The present invention has been made in view of the above-described present situation, can reduce the placement accuracy of the optical transparent adhesive sheet, and has excellent lamination reliability with the optical transparent adhesive sheet, and the laminate An object is to provide an optical transparent pressure-sensitive adhesive sheet suitable for production of a body and a method for producing a laminate.

The present inventors have studied a method for improving the reliability of bonding with an optical transparent adhesive sheet while relaxing the placement accuracy of the optical transparent adhesive sheet, and covering the step formed by the bezel with the optical transparent adhesive sheet. Thus, attention was paid to the structure arranged on the bezel (hereinafter also referred to as “bezel-on-bonding structure”). According to the bezel-on bonding structure, the optical transparent adhesive sheet covers the step forming portion of the bezel, so that not only the end of the optical transparent adhesive sheet can be prevented from being visually recognized, but also the step forming portion of the bezel and the upper substrate. It was predicted that the optical transparent adhesive sheet could be prevented from being peeled from the end by sandwiching the optical transparent adhesive sheet. However, in practice, the optical transparent adhesive sheet having a uniform thickness sufficiently follows the step formed by the bezel and maintains a close contact, and the optical transparent adhesive sheet is attached to the step forming portion of the bezel and the upper base. It was difficult to obtain an optically transparent pressure-sensitive adhesive sheet satisfying that it can be sandwiched with a material and stretched thinly. As a result of further intensive studies, it was found that a bezel-on bonding structure can be realized by using an optically transparent adhesive sheet having a loss tangent at 30 ° C. of 0.5 or more. From the above, the present inventors have found that it is possible to relax the placement accuracy of the optically transparent adhesive sheet and to obtain a laminate having excellent bonding reliability with the optically transparent adhesive sheet.

The laminate of the present invention is a laminate comprising an optically transparent adhesive sheet and a support member between a first substrate and a second substrate, wherein the support member is an outer edge of the first substrate. The optically transparent pressure-sensitive adhesive sheet includes a thick film portion that bonds the first base material and the second base material, the step forming portion, and the second step. The optical transparent adhesive sheet has a loss tangent at 30 ° C. of 0.5 or more, and the thickness of the thick film portion is equal to the thickness of the step forming portion. It is characterized by being 1.5 times or more.

The first substrate may have a polarizing plate on a surface in contact with the optical transparent pressure-sensitive adhesive sheet.

The optical transparent pressure-sensitive adhesive sheet may be made of polyurethane.

The optically transparent adhesive sheet of the present invention has a loss tangent at 30 ° C. of 0.5 or more, a storage shear modulus at 30 ° C. of 3.0 × 10 ⁵ Pa or less, and a thickness exceeding 500 μm. Features.

The method for producing a laminate of the present invention is a method for producing a laminate comprising an optically transparent adhesive sheet and a support member between a first substrate and a second substrate, wherein the optically transparent adhesive sheet is The loss tangent at 30 ° C. is 0.5 or more, the thickness of the optical transparent adhesive sheet before bonding is 1.5 times or more the thickness of the support member, and the support member is disposed on the outer edge. The optically transparent adhesive sheet disposed so as to cover the step formed by the first base material and the support member is interposed between the first base material and the second base material. And the second substrate and the support member sandwich the end portion of the optical transparent adhesive sheet, and the first substrate and the second substrate by the portion other than the end portion of the optical transparent adhesive sheet. And a step of bonding.

ADVANTAGE OF THE INVENTION According to this invention, the arrangement | positioning precision of an optical transparent adhesive sheet can be eased, the laminated body excellent also in the reliability of bonding by an optical transparent adhesive sheet, and the optical transparent adhesive suitable for manufacture of this laminated body The manufacturing method of a sheet | seat and a laminated body can be provided.

It is sectional drawing which showed typically the structure of the laminated body of this invention which has a bezel on bonding structure. It is a schematic diagram for demonstrating an example of the shaping | molding apparatus used for preparation of an optical transparent adhesive sheet. It is sectional drawing which showed typically the structure of the conventional laminated body which has a bezel-in bonding structure.

The laminate of the present invention is a laminate comprising an optically transparent adhesive sheet and a support member between a first substrate and a second substrate, wherein the support member is an outer edge of the first substrate. The optically transparent pressure-sensitive adhesive sheet includes a thick film portion that bonds the first base material and the second base material, the step forming portion, and the second step. The optical transparent adhesive sheet has a loss tangent at 30 ° C. of 0.5 or more, and the thickness of the thick film portion is equal to the thickness of the step forming portion. It is characterized by being 1.5 times or more.

FIG. 1 is a cross-sectional view schematically showing the configuration of the laminate of the present invention having a bezel-on bonding structure. The laminate shown in FIG. 1 has a configuration in which an optically transparent adhesive sheet 12 and a support member (upper bezel) 21 are provided between a first base material 11 and a second base material 13, for example, It may be a part of an electronic device such as a display device. The upper bezel 21 is integrated with the lower bezel 22 and constitutes a housing (bezel) that houses the first base material 11.

Since the laminated body shown in FIG. 1 has a bezel-on bonding structure, an upper bezel 21 that constitutes a part of the bezel is used as a support member. The present invention is not limited to the case where the support member is an upper bezel, and the first member is interposed between the first base material and the second base material by the optical transparent pressure-sensitive adhesive sheet. The present invention can be widely applied when bonding a base material and a second base material.

The combination of the 1st base material 11 and the 2nd base material 13 is not specifically limited, For example, it comprises display apparatuses, such as a display panel, a touch panel (glass substrate with an ITO transparent conductive film), and a cover panel (cover glass). Various members are mentioned. The kind of display panel is not specifically limited, For example, a liquid crystal panel, an organic electroluminescent panel (organic EL panel), etc. are mentioned. Moreover, a polarizing plate, a phase difference film, etc. may be arrange | positioned at the surface where the optical transparent adhesive sheet 12 of a display panel is affixed. If various members in the display device are bonded together using the optical transparent adhesive sheet 12, the air layer (air gap) in the display device can be eliminated, and the visibility of the display screen can be improved. Moreover, when the polarizing plate is arrange | positioned, the optical transparent adhesive sheet 12 can prevent the moisture absorption of a polarizing plate effectively. A combination in which the first substrate 11 is a display panel such as a liquid crystal panel and the second substrate 13 is a cover panel (cover glass) or a touch sensor glass is suitable.

The material of the 1st base material 11 and the 2nd base material 13 is not specifically limited, For example, glass, resin, etc. are mentioned. It does not specifically limit as resin which comprises the 1st base material 11 and / or the 2nd base material 13, For example, a polycarbonate, a polymethyl methacrylate resin (PMMA), a triacetyl cellulose (TAC) etc. are mentioned. For example, when the polarizing plate is disposed on the surface of the first base material 11 on which the optical transparent adhesive sheet 12 is attached, the surface in contact with the optical transparent adhesive sheet 12 may be composed of TAC. The polarizing plate may have a laminated structure of TAC, polyvinyl alcohol (PVA), and TAC, or may have a TAC surface of the laminated structure subjected to AG (antiglare) treatment. The TAC surface of the laminated structure may be subjected to HC (hard coat) treatment, or the TAC surface of the laminated structure may be subjected to AG treatment and HC treatment.

The upper bezel 21 is a frame-like member disposed around the optical transparent adhesive sheet 12 when viewed in plan, and at least a part thereof is disposed on the outer edge of the first base material 11. The side surface of the portion (step forming portion) arranged on the outer edge of the first base material 11 forms a step. 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 11. When the first base material 11 is a display panel, the upper bezel 21 is arranged in the frame area of the display device, but the first base material is not visible to the user of the display device. A light shielding portion 13 </ b> A may be provided on the outer edge of 11. The material of the upper bezel 21 is not particularly limited, and examples thereof include metals and resins.

Although the thickness (size of a level | step difference) of the upper bezel 21 is not specifically limited, For example, you may be 200-1000 micrometers. If the thickness of the upper bezel 21 exceeds 200 μm, the thickness of the optical transparent adhesive sheet 12 needs to be 300 μm or more. Therefore, an optical transparent adhesive sheet thicker than a normal optical transparent adhesive sheet is used.

The optical transparent pressure-sensitive adhesive sheet 12 is a transparent and adhesive sheet-like member used for bonding the first base material 11 and the second base material 13 together. In the present specification, “optically transparent adhesive sheet” has the same meaning as “optically transparent adhesive film”.

The optical transparent adhesive sheet 12 is bonded to the second base material 13 by primary bonding, for example, and is bonded to the first base material 11 by secondary bonding. When the second substrate 13 is a cover panel and the first substrate 11 is a liquid crystal panel, the end portion of the optical transparent adhesive sheet 12 is a light shielding portion 13A (BM printing, decorative printing) on the cover panel side. The liquid crystal panel side is arranged on the upper bezel 21 without considering interference with the side surface of the upper bezel 21. Therefore, in the bezel-on bonding structure, strict arrangement accuracy is not required, and the arrangement accuracy of the optically transparent adhesive sheet can be relaxed.

The optical transparent adhesive sheet 12 was sandwiched between the thick film part that bonds the first base material 11 and the second base material 13, the step forming part of the upper bezel 21, and the second base material 13. And end. Since the edge part of the optical transparent adhesive sheet 12 is pinched | interposed between the 2nd base material 13 and the level | step difference formation part of the upper bezel 21, it is hard to peel off conventionally. Further, since the optical transparent adhesive sheet 12 reaches the step forming portion of the upper bezel 21, the upper surface of the first base material 11 is all covered with the step forming portion of the upper bezel 21 or the optical transparent adhesive sheet 12. Thus, moisture absorption of the first base material 11 can be prevented. When a polarizing plate is located on the upper surface of the first substrate 11, moisture absorption by the polarizing plate can be prevented. When the polarizing plate absorbs moisture, performance deterioration may be accelerated, or delayed bubbles may be generated due to evaporation of moisture absorbed in a high temperature environment.

The optically transparent pressure-sensitive adhesive sheet 12 has viscoelastic characteristics peculiar to the present invention. Specifically, the loss tangent (tan δ) at 30 ° C. is 0.5 or more. According to the study by the present inventors, in order to realize a structure (bezel-on-bonding structure) in which the optical transparent adhesive sheet 12 is disposed so as to cover the step forming portion of the upper bezel 21, an optical device having a uniform thickness is used. The transparent adhesive sheet 12 is made to sufficiently follow the step formed by the step forming portion of the upper bezel 21 to maintain the close contact state, and the optical transparent adhesive sheet 12 and the upper surface of the step forming portion of the upper bezel 21 It is necessary to be sandwiched between the two base materials 13 and stretched thinly. Here, if the optical transparent pressure-sensitive adhesive sheet 12 can be brought into a state very close to a gel, not only excellent step following ability can be obtained, but also the restoring force after deformation hardly works, so that the bezel-on bonding structure is obtained. Is preferred. Therefore, the present inventors examined the loss tangent as an index of viscoelasticity, and by making the value at 30 ° C. within the above-described range, the optical transparent adhesive sheet can be brought into a state very close to a gel, It has been found that a bezel-on bonding structure can be realized. The preferable lower limit of the loss tangent at 30 ° C. is 0.6, and the preferable upper limit is 0.8. The preferable lower limit of the loss tangent at 85 ° C. is 0.5, and the preferable upper limit is 0.9. If the loss tangent is too high, bonding is easy, but creep properties at high temperatures deteriorate, so the laminated surface of the optical transparent adhesive sheet 12 is laminated in parallel with the vertical direction (gravity direction). When the body is arranged, there is a possibility that deviation or peeling occurs at a high temperature due to the weight of the second base material 13 itself such as a cover panel. Moreover, when loss tangent is too low, the followable | trackability of the optical transparent adhesive sheet 12 at the time of bonding is bad, and there exists a possibility that bonding cannot be performed appropriately.

The optical transparent adhesive sheet 12 preferably has a storage shear modulus at 30 ° C. of 3.0 × 10 ⁵ Pa or less. A preferred lower limit of the storage shear modulus at 30 ° C. is 9.0 × 10 ⁴ Pa. The preferable lower limit of the storage shear modulus at 85 ° C. is 1.0 × 10 ⁴ Pa, and the preferable upper limit is 3.0 × 10 ⁴ Pa. If the storage shear modulus is too high, the creep characteristics at high temperatures deteriorate as in the case where the loss tangent is too high. If the storage shear modulus is too low, the followability of the optically transparent adhesive sheet 12 at the time of pasting deteriorates as in the case where the loss tangent is too low.

The loss tangent and storage shear modulus can be controlled by adjusting the composition of the resin used for the optical transparent adhesive sheet 12 and / or the thermosetting conditions. For example, the optical transparent adhesive sheet 12 is made of polyurethane. Α ratio (number of moles of OH group derived from polyol component / number of moles of NCO group derived from polyisocyanate component), amount and type (molecular weight) of hydrophilic unit in polyisocyanate component, hydrophilicity having hydrophilic unit It can be controlled by the ratio (for example, molar ratio) of the polyisocyanate and the hydrophobic polyisocyanate having no hydrophilic unit, the presence or absence of a plasticizer, the blending amount, the crosslinking temperature, and the like.

The thickness of the thick film portion of the optical transparent adhesive sheet 12 is 1.5 times or more the thickness of the step forming portion of the upper bezel 21 and more preferably 2 times or more. Thereby, sufficient thickness can be ensured in the edge part of the optical transparent adhesive sheet 12 pinched | interposed between the level | step difference formation part of the upper bezel 21 and the 2nd base material 13, and peeling of an edge part can be prevented. . In addition, the thickness of the thick film part of the optical transparent adhesive sheet 12 in a laminated body is substantially the same as the thickness before bonding of the optical transparent adhesive sheet 12. FIG. That is, the thickness of the optical transparent pressure-sensitive adhesive sheet 12 before being bonded is preferably 1.5 times or more, more preferably 2 times or more the thickness of the upper bezel 21. Specifically, the thickness of the optical transparent pressure-sensitive adhesive sheet 12 before being bonded is preferably 300 μm or more, and more preferably more than 500 μm. An optically transparent adhesive sheet having a loss tangent at 30 ° C. of 0.5 or more, a storage shear modulus at 30 ° C. of 3.0 × 10 ⁵ Pa or less, and a thickness exceeding 500 μm is also an aspect of the present invention. It is an aspect. Moreover, it is preferable that the thickness before bonding of the optical transparent adhesive sheet 12 is 3000 micrometers or less. When the thickness exceeds 3000 μm, optical characteristics such as haze and total light transmittance may not be sufficiently obtained. The upper limit with more preferable thickness of an optical transparent adhesive sheet is 2000 micrometers.

The optically transparent adhesive sheet 12 preferably has an adhesive strength in a 180 ° peel test of 2 N / 25 mm or more. When the adhesive force is less than 2 N / 25 mm, the generation of delay bubbles may not be suppressed even if the storage shear modulus and loss tangent are within the scope of the present invention. A preferable lower limit of the adhesive strength is 3 N / 25 mm, a more preferable lower limit is 5 N / 25 mm, a still more preferable lower limit is 7 N / 25 mm, and a preferable upper limit is 15 N / 25 mm. If the said adhesive force is 15 N / 25mm or less, when using the optical transparent adhesive sheet 12 for bonding of optical members, such as a touch panel, since it can peel without adhesive residue, it is excellent in rework property. Moreover, when the adhesive force of an optical transparent adhesive sheet becomes large too much, it may become difficult to remove the bubble which entered between an optical transparent adhesive sheet and a to-be-adhered body.

The micro rubber A hardness of the optically transparent adhesive sheet 12 is preferably 0.1 ° or more and 25 ° or less. When the micro rubber A hardness is less than 0.1 °, the handleability at the time of use (at the time of sticking to an optical member) is poor, and the optical transparent adhesive sheet may be deformed. On the other hand, when the hardness of the micro rubber A exceeds 25 °, the flexibility of the optical transparent adhesive sheet is low, and when pasted on the optical member, the surface shape of the optical member cannot be followed and the air is bitten. May cause peeling from the optical member. Moreover, when the optical transparent adhesive sheet has low flexibility, the step of the bezel may not be covered particularly when an optical member such as a touch panel is bonded. A more preferable lower limit of the micro rubber A hardness is 0.5 °, a more preferable upper limit is 15 °, and a further preferable upper limit is 2 °. Since the optically transparent adhesive sheet having a micro rubber A hardness of 2 ° or less is in a state very close to a gel, it is deformed according to the surface shape of the optical member and exhibits excellent step followability. In addition, since the restoring force after deformation hardly works, the effect of suppressing the generation of delay bubbles can be expected. The micro rubber A hardness can be measured using, for example, a micro rubber hardness meter “MD-1 type A” manufactured by Kobunshi Keiki Co., Ltd. The micro rubber hardness tester “MD-1 Type A” is a hardness tester designed and manufactured as a reduced model of about 1/5 of the spring type rubber hardness tester (durometer) A type. However, it is possible to obtain a measured value that matches the hardness of the spring type rubber hardness tester A type.

The optical transparent pressure-sensitive adhesive sheet 12 preferably has a haze of 0.5% or less and a total light transmittance of 90% or more. The haze and total light transmittance can be measured using, for example, a turbidimeter “HazeMeter NDH2000” manufactured by Nippon Denshoku Industries Co., Ltd. The haze is measured by a method according to JIS K 7136, and the total light transmittance is measured by a method according to JIS K 7361-1.

The composition of the optically transparent pressure-sensitive adhesive sheet is not particularly limited as long as the loss tangent at 30 ° C. can be adjusted to 0.5 or more, but is preferably composed of polyurethane. The polyurethane is preferably a cured product of a thermosetting polyurethane composition containing a polyol component and a polyisocyanate component. The cured product of the thermosetting polyurethane composition is obtained by reacting a polyol component and a polyisocyanate component, and has a structure represented by the following formula (A).

In said formula (A), R represents the site | part except the NCO group of the polyisocyanate component, R 'represents the site | part except the OH group of the polyol component, and n represents the number of repeating units.

The polyurethane is preferably not acrylic-modified, and it is preferable that the main chain does not contain a portion derived from an acrylate ester, a methacrylate ester or the like. When the thermosetting polyurethane is acrylic-modified, it becomes hydrophobic, so that water aggregation is likely to occur at high temperature and high humidity. This aggregation of moisture may cause whitening, foaming, and the like, thereby impairing optical properties. Therefore, by making the polyurethane unmodified with acrylic, it is possible to prevent deterioration of optical characteristics due to whitening, foaming, etc. at high temperature and high humidity. In the polyurethane, the total amount of the monomer unit derived from the polyol component and the monomer unit derived from the polyisocyanate component is preferably 80 mol% or more of the monomer unit constituting the entire polyurethane. More preferably, it consists only of a monomer unit derived from a polyol component and a monomer unit derived from a polyisocyanate component.

As the polyol component and the polyisocyanate component, those that are liquid at normal temperature (23 ° C.) can be used, and polyurethane can be obtained without using a solvent. Other optional components such as a tackifier can be added to either the polyol component or the polyisocyanate component, and are preferably added to the polyol component. Thus, when producing the optically transparent adhesive sheet 12 using a thermosetting polyurethane composition, since removal of a solvent is not required, a uniform sheet can be formed thickly. Moreover, the optically transparent adhesive sheet 12 obtained by using the thermosetting polyurethane composition can maintain the optical characteristics even when it is formed thick, and the transparency (haze) is sufficiently lowered and colored. Can be suppressed.

Moreover, the optical transparent adhesive sheet 12 made of polyurethane is flexible and stretches well when subjected to tensile stress, and is very difficult to break. For this reason, it is possible to peel off without leaving glue. Moreover, since the optical transparent adhesive sheet 12 is flexible and can be thickened, it can have excellent impact resistance. Furthermore, the optically transparent adhesive sheet 12 made of polyurethane has a high dielectric constant, and a higher capacitance can be obtained than an optically transparent adhesive sheet made of an acrylic resin composition. For this reason, the optical transparent adhesive sheet 12 comprised with the polyurethane is used suitably for bonding of a capacitive touch panel.

[Polyol component]
It does not specifically limit as said polyol component, For example, polyether polyol, polycaprolactone polyol, polycarbonate polyol, polyester polyol etc. are mentioned. These may be used alone or in combination of two or more.

Examples of the polyether polyol include polyethylene glycol, polypropylene glycol, polypropylene triol, polypropylene tetraol, polytetramethylene glycol, polytetramethylene triol, polyalkylene glycols such as copolymers thereof, and side chains introduced into these. And derivatives having a branched structure introduced therein, modified products, and mixtures thereof.

Examples of the polycaprolactone polyol include polycaprotectone glycol, polycaprolactone triol, polycaprolactone tetraol, derivatives in which side chains are introduced or branched structures are introduced, modified products, and mixtures thereof. Can be mentioned.

As said polycarbonate polyol, the reaction material of a dialkyl carbonate and diol is mentioned, for example.

Examples of the dialkyl carbonate include dialkyl carbonates such as dimethyl carbonate and diethyl carbonate; diaryl carbonates such as diphenyl carbonate; and alkylene carbonates such as ethylene carbonate. These may be used alone or in combination of two or more.

Examples of the diol include 1,4-butanediol, diethylene glycol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 2-methyl-1, 8-octanediol, 1,9-nonanediol, 1,10-dodecanediol, 2-ethyl-1,6-hexanediol, 3-methyl-1,5-pentanediol, 2,4-dimethyl-1,5 -Pentanediol, neopentyl glycol, 1,3-cyclohexanediol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, 2,2'-bis (4-hydroxycyclohexyl) -propane and the like. These may be used alone or in combination of two or more. The diol is preferably an aliphatic or alicyclic diol having 4 to 9 carbon atoms, such as 1,4-butanediol, diethylene glycol, 1,5-pentanediol, 1,6-hexanediol, 3-methyl- 1,5-pentanediol, 2,4-dimethyl-1,5-pentanediol, 1,4-cyclohexanedimethanol, 1,7-heptanediol, 1,8-octanediol, 2-methyl-1,8 It is preferable to use octanediol and 1,9-nonanediol alone or in combination of two or more. Examples of the diol include a copolycarbonate diol composed of 1,6-hexanediol and 3-methyl-1,5-pentanediol, and a copolycarbonate diol composed of 1,6-hexanediol and 1,5-pentanediol. preferable.

Further, as the polycarbonate polyol, for example, polycarbonate glycol, polycarbonate triol, polycarbonate tetraol, derivatives in which side chains are introduced or branched structures are introduced, modified products, and mixtures thereof may be used. it can.

As said polyester polyol, what dehydrated and condensed dicarboxylic acid and the glycol component is mentioned, for example.

Examples of the dicarboxylic acid include aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, and 2,6-naphthalenedicarboxylic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, azelaic acid, and sebacic acid. Can be mentioned.

Examples of the glycol component include ethylene glycol, 1,4-butanediol, diethylene glycol, neopentyl glycol, 3-methyl-1,5-pentanediol, 1,5-pentanediol, 1,9-nonanediol, and triethylene. Aliphatic glycols such as glycol; Alicyclic glycols such as 1,4-cyclohexanedimethanol; Aromatic diols such as p-xylenediol; Polyoxyalkylene glycols such as polyethylene glycol, polypropylene glycol, and polytetramethylene glycol. It is done.

The polyester polyol has a linear molecular structure when formed by the dicarboxylic acid and glycol components exemplified above, but is a polyester having a branched molecular structure using a trivalent or higher valent ester forming component. There may be. The dicarboxylic acid and the glycol component may be reacted at 150 to 300 ° C. at a molar ratio of 1.1 to 1.3.

The number average molecular weight of the polyol component is preferably 300 or more and 5000 or less. When the number average molecular weight of the polyol component is less than 300, the reaction between the polyol component and the polyisocyanate component is too fast, making it difficult to form a polyurethane into a uniform sheet, or reducing the flexibility of the polyurethane. And may become brittle. When the number average molecular weight of the polyol component exceeds 5,000, the viscosity of the polyol component becomes too high and it becomes difficult to form polyurethane into a uniform sheet, or the polyurethane crystallizes and becomes cloudy. May occur. The number average molecular weight of the polyol component is more preferably 500 or more and 2000 or less.

The polyol component preferably has an olefin skeleton, that is, the main chain is composed of polyolefin or a derivative thereof. Examples of the polyol component having an olefin skeleton include polybutadiene-based polyols such as 1,2-polybutadiene polyol, 1,4-polybutadiene polyol, 1,2-polychloroprene polyol, 1,4-polychloroprene polyol, and polyisoprene-based compounds. Examples include polyols and those obtained by saturating double bonds thereof with hydrogen or halogen. The polyol component may be a polyol obtained by copolymerizing an olefin compound such as styrene, ethylene, vinyl acetate, or acrylate with a polybutadiene-based polyol, or a hydrogenated product thereof. The polyol component may have a linear structure or a branched structure. Only one type of polyol component having an olefin skeleton may be used, or two or more types may be used. The polyol component used for the polyurethane preferably contains 80 mol% or more of a polyol component having an olefin skeleton, and more preferably comprises only a polyol component having an olefin skeleton.

Among the polyol components having the olefin skeleton, for example, polyolefin polyols obtained by hydrogenating hydroxyl-terminated polyisoprene manufactured by Idemitsu Kosan Co., Ltd. (“EPOL (Epol, registered trademark)”, number average molecular weight: 2500), Nippon Soda Co., Ltd., both-ends hydroxylated hydrogenated polybutadiene ("GI-1000", number average molecular weight: 1500), Mitsubishi Chemical polyhydroxypolyolefin oligomer ("Polytail (registered trademark)"), and the like. .

[Polyisocyanate component]
It does not specifically limit as said polyisocyanate component, A conventionally well-known polyisocyanate can be used, Hydrophilic polyisocyanate which has a hydrophilic unit (hydrophilic group), and hydrophobic polyisocyanate which does not have a hydrophilic unit. Either one or both may be used.

As the hydrophilic unit, an ethylene oxide unit is suitable. By including the hydrophilic unit, an effect of suppressing whitening due to moisture absorption can be obtained. The content of the ethylene oxide unit is preferably 0.1% by weight or more and 20% by weight or less based on the whole thermosetting polyurethane composition. If the content is less than 0.1% by weight, whitening may not be sufficiently suppressed. If the content exceeds 20% by weight, the compatibility with low-polar olefinic polyol components, tackifiers, plasticizers, and the like may decrease, and optical characteristics such as haze may decrease. As for content of the said ethylene oxide unit, it is more preferable that it is 0.1 to 5 weight%. When the content exceeds 5% by weight, the amount of moisture absorption in a high temperature and high humidity environment may be excessive.

Examples of the hydrophilic unit other than the ethylene oxide unit include units containing a carboxylic acid group, an alkali metal base of a carboxylic acid, a sulfonic acid group, an alkali metal base of a sulfonic acid, a hydroxyl group, an amide group, an amino group, and the like. More specifically, polyacrylic acid, alkali metal salt of polyacrylic acid, sulfonic acid group-containing copolymer, alkali metal salt of sulfonic acid group-containing copolymer, polyvinyl alcohol, polyacrylamide, carboxymethylcellulose, alkali metal of carboxymethylcellulose Examples thereof include salts and polyvinyl pyrrolidone.

As the hydrophilic polyisocyanate, for example, a modified polyisocyanate obtained by reacting an aliphatic polyisocyanate with an ether compound having an ethylene oxide unit is suitably used. By using the aliphatic polyisoacinate, the optical transparent pressure-sensitive adhesive sheet 12 is less likely to be colored or discolored, and the transparency of the optical transparent pressure-sensitive adhesive sheet 12 can be more reliably ensured over a long period of time. In addition, by using a modified product obtained by reacting an ether compound having an ethylene oxide unit, the polyisocyanate component can suppress whitening by the action of the hydrophilic portion (ethylene oxide unit), and the hydrophobic portion (other units). By this action, compatibility with low polarity tackifiers, plasticizers and the like can be exhibited.

Examples of the aliphatic polyisocyanate include hexamethylene diisocyanate, tetramethylene diisocyanate, 2-methyl-pentane-1,5-diisocyanate, 3-methyl-pentane-1,5-diisocyanate, lysine diisocyanate, and trioxyethylene diisocyanate. , Isophorone diisocyanate, cyclohexyl diisocyanate, 4,4′-dicyclohexylmethane diisocyanate, norbornane diisocyanate, hydrogenated tolylene diisocyanate, hydrogenated xylene diisocyanate, hydrogenated tetramethylxylene diisocyanate, and modified products thereof. These may be used alone or in combination of two or more. Examples of the modified product of hexamethylene diisocyanate include hexamethylene diisocyanate modified with isocyanurate, allophanate, and / or urethane.

Examples of the ether compound having ethylene oxide units include ethylene oxide adducts of alcohols, phenols and / or amines, and those having 3 or more ethylene oxide units per molecule from the viewpoint of enhancing hydrophilicity. Preferably used.

Examples of the alcohols include monohydric alcohols, dihydric alcohols (ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, 1,4-butanediol, 1,6-hexanediol, 1,3-butylenediol. , Peopentyl glycol, etc.) and trihydric alcohols (glycerin, trimethylolpropane, etc.). These may be used alone or in combination of two or more.

Examples of the phenols include hydroquinone, bisphenols (bisphenol A, bisphenol F, etc.), and formalin low condensates of phenolic compounds (novolac resins, resol intermediates). These may be used alone or in combination of two or more.

The number of isocyanate groups per molecule of the modified polyisocyanate is preferably 2.0 or more on average. If the number of the isocyanate groups is less than 2.0 on average, the thermosetting polyurethane composition may not be sufficiently cured due to a decrease in the crosslinking density.

Although it does not specifically limit as said hydrophobic polyisocyanate, Aliphatic isocyanate is used suitably, for example, hexamethylene diisocyanate (HDI), tetramethylene diisocyanate, 2-methyl-pentane-1,5-diisocyanate, 3-methyl -Pentane-1,5-diisocyanate, lysine diisocyanate, trioxyethylene diisocyanate, isophorone diisocyanate (IPDI), cyclohexyl diisocyanate, 4,4'-dicyclohexylmethane diisocyanate (hydrogenated MDI), norbornane diisocyanate (NBDI), hydrogenated tolylene diene Examples thereof include isocyanate, hydrogenated xylene diisocyanate, hydrogenated tetramethylxylene diisocyanate, and modified products thereof. These may be used alone or in combination of two or more.

The blending ratio of the hydrophilic polyisocyanate and the hydrophobic polyisocyanate is preferably 9: 1 to 1: 9, more preferably 7: 3 to 3 from the viewpoint of achieving both whitening prevention and moisture absorption reduction. : 7.

The polyurethane composition preferably has an α ratio (number of moles of OH groups derived from a polyol component / number of moles of NCO groups derived from a polyisocyanate component) of 1 or more. When the α ratio is less than 1, the blending amount of the polyisocyanate component is excessive with respect to the blending amount of the polyol component, so that the polyurethane becomes hard and the flexibility required for the optically transparent adhesive sheet 12 is ensured. Difficult to do. The α ratio more preferably satisfies 1.3 <α <2.0. When the α ratio is 2.0 or more, the thermosetting polyurethane composition may not be sufficiently cured.

[Tackfire]
The thermosetting polyurethane composition may further contain a tackifier (tackifier). A tackifier is an additive that is added to improve adhesive strength, and is usually an amorphous oligomer having a molecular weight of several hundred to several thousand, and is a thermoplastic resin that is liquid or solid at room temperature. When the thermosetting polyurethane composition contains a tackifier, the adhesive strength of the optically transparent adhesive sheet 12 made of a cured product of the thermosetting polyurethane composition can be improved.

The tackifier is not particularly limited, and examples thereof include petroleum resin tackifiers, hydrocarbon resin tackifiers, rosin tackifiers, terpene tackifiers, and the like. One of these may be included, or two or more thereof may be included.

As the tackifier, a petroleum resin tackifier is preferably used because of excellent compatibility with the polyol component having the olefin skeleton. Among the petroleum resin-based tackifiers, hydrogenated petroleum resins obtained by hydrogenating a copolymer of dicyclopentadiene and an aromatic compound are preferably used. Dicyclopentadiene is obtained from the C5 fraction. Examples of the aromatic compound include vinyl aromatic compounds such as styrene, α-methylstyrene, and vinyl toluene. The ratio of dicyclopentadiene and vinyl aromatic compound is not particularly limited, but is preferably dicyclopentadiene: vinyl aromatic compound = 70: 30 to 20:80 on a weight basis, and 60:40 to 40:60. It is more preferable that The hydrogenated petroleum resin preferably has a softening point of 90 to 160 ° C., a preferable vinyl aromatic compound unit content of 35% by mass or less, a preferable bromine number of 0 to 30 g / 100 g, and a preferable number average molecular weight of 500 to 1100. Examples of the known hydrogenated petroleum resin include “Imabe P-100” manufactured by Idemitsu Kosan Co., Ltd.

As the tackifier, a hydrocarbon resin tackifier is preferably used because of excellent compatibility with the polyol component having the olefin skeleton. Among the hydrocarbon resin-based tackifiers, alicyclic saturated hydrocarbon resins are preferably used. As a well-known thing among the said alicyclic saturated hydrocarbon resin, "Arcon P-100" by Arakawa Chemical Industries Ltd. is mentioned, for example.

The tackifier preferably has an acid value of 1 mgKOH / g or less. When the acid value is 1 mgKOH / g or less, the tackifier can sufficiently prevent the reaction between the polyol component and the polyisocyanate component. Moreover, it is preferable that the softening point of a tackifier is 80 degreeC or more and 120 degrees C or less, and it is more preferable that they are 80 degreeC or more and 100 degrees C or less. When the softening point is 80 ° C. or higher and 120 ° C. or lower, it is possible to sufficiently prevent the polyol component from being deteriorated by heat when the tackifier is dissolved in the polyol component.

It is preferable that content of the said tackifier is 1 to 20 weight% with respect to a thermosetting polyurethane composition. When the tackifier content is less than 1% by weight, the adhesive strength of the optically transparent adhesive sheet 12 may not be sufficiently improved, and in particular, the adhesive strength at high temperature and high humidity may be insufficient. is there. When the content of the tackifier exceeds 20% by weight, the reaction between the polyol component and the polyisocyanate component may be inhibited, and urethane crosslinking may not be sufficiently formed in the polyurethane. As a result, the optical transparent pressure-sensitive adhesive sheet 12 may dissolve and change its shape under high temperature and high humidity, and tackifier may precipitate (bleed). Further, if the reaction time between the polyol component and the polyisocyanate component is increased in order to sufficiently form urethane crosslinks, the productivity is lowered.

[Plasticizer]
The thermosetting polyurethane composition may further contain a plasticizer. By adding a plasticizer to reduce the hardness, it is possible to improve the handleability and the step following ability of the optical transparent pressure-sensitive adhesive sheet 12.

Although it will not specifically limit if it is a compound used in order to provide a thermoplastic resin with a softness | flexibility as said plasticizer, It is preferable that a carboxylic acid type plasticizer is included from a compatibility and a weather resistance viewpoint. Examples of the carboxylic acid plasticizer include phthalic acid esters (phthalic plasticizers) such as diundecyl phthalate, dioctyl phthalate, diisononyl phthalate, diisodecyl phthalate, and dibutyl phthalate, and 1,2-cyclohexanedicarboxylic acid. Examples include acid diisononyl ester, adipic acid ester, trimellitic acid ester, maleic acid ester, benzoic acid ester, and poly-α-olefin. One of these may be included, or two or more thereof may be included. Among the above-mentioned carboxylic acid plasticizers, for example, “DINCH” manufactured by BASF, “Sunsocizer DUP” manufactured by Shin Nippon Rika Co., Ltd., “Durasyn (registered trademark) 148” manufactured by Iones Oligomers, Inc. Is mentioned.

[catalyst]
The thermosetting polyurethane composition may further contain a catalyst. The catalyst is not particularly limited as long as it is a catalyst used in the urethanization reaction. For example, organotin compounds such as di-n-butyltin dilaurate, dimethyltin dilaurate, dibutyltin oxide, and octane tin; An organic zirconium compound; a carboxylic acid tin salt; a carboxylic acid bismuth salt; and an amine-based catalyst such as triethylenediamine.

The thermosetting polyurethane composition may further contain a monoisocyanate component. The monoisocyanate component is a compound having one isocyanate group in the molecule. Specific examples thereof include octadecyl diisocyanate (ODI), 2-methacryloyloxyethyl isocyanate (MOI), 2-acryloyloxyethyl isocyanate ( AOI), octyl isocyanate, heptyl isocyanate, ethyl 3-isocyanate propionate, cyclopentyl isocyanate, cyclohexyl isocyanate, 2-methoxyethane isocyanate, ethyl isocyanate acetate, butyl isocyanate acetate, p-toluenesulfonyl isocyanate, etc. Can be mentioned. These may be used alone or in combination of two or more.

In the thermosetting polyurethane composition, various additives such as a colorant, a stabilizer, an antioxidant, an antifungal agent, a flame retardant, and the like, as necessary, as long as the required characteristics of the optically transparent adhesive sheet 12 are not impaired. May be added.

The production method of the optically transparent pressure-sensitive adhesive sheet 12 is not particularly limited. For example, after preparing a thermosetting polyurethane composition, a method of forming the composition while thermosetting it by a conventionally known method is exemplified. Preferably, a polyol is used. It includes a step of preparing a thermosetting polyurethane composition by stirring and mixing the components and the polyisocyanate component, and a step of curing the thermosetting polyurethane composition.

As an example of the production method, first, a polyol component, a polyisocyanate component, and, if necessary, other components such as a catalyst are mixed, and stirred with a mixer or the like to form a liquid or gel thermosetting polyurethane composition. Get. Thereafter, the thermosetting polyurethane composition is put into a molding apparatus and crosslinked and cured while moving the thermosetting polyurethane composition in a state of being sandwiched between two release films, so that the thermosetting polyurethane composition is semi-finished. Cured to obtain a sheet integrated with the release film. Then, the optical transparent adhesive sheet 12 which consists of hardened | cured material of a thermosetting polyurethane composition is obtained by making it cross-link in a furnace for a fixed time.

Drawing 2 is a mimetic diagram for explaining an example of a forming device used for preparation of an optically transparent adhesive sheet. In the molding apparatus 50 shown in FIG. 2, first, a pair of release films in which a liquid or gel-like thermosetting polyurethane composition 53 before curing is continuously fed out from a pair of molding rolls 52 that are spaced apart from each other. (PET film) Pour into gaps 51. Then, while the thermosetting polyurethane composition 53 is held in the gap between the pair of release films 51, the curing reaction (crosslinking reaction) is allowed to proceed and is carried into the heating device 54. In the heating device 54, the thermosetting polyurethane composition 53 is thermoset while being held between a pair of release films (PET film) 51, and is an optically transparent adhesive sheet made of a cured product of the thermoplastic polyurethane composition. 12 molding is completed.

As a manufacturing method of the optical transparent pressure-sensitive adhesive sheet 12, after preparing a thermosetting polyurethane composition before curing, various film forming apparatuses such as various coating apparatuses, bar coats, doctor blades, and the like are used. Also good. Moreover, you may produce the optical transparent adhesive sheet 12 using a centrifugal molding method.

It is a manufacturing method of the laminated body provided with the optical transparent adhesive sheet and the supporting member between the 1st base material and the 2nd base material, Comprising: As for the said optical transparent adhesive sheet, the loss tangent in 30 degreeC is 0. 5 or more, and the thickness of the optically transparent adhesive sheet before bonding is 1.5 times or more the thickness of the support member, and the first base material on the outer edge and the first base material Between the second base material, the optical transparent adhesive sheet arranged to cover the step formed by the first base material and the support member is interposed, and the second base material and the above-mentioned A step of adhering the first base material and the second base material with a portion other than the end portion of the optical transparent adhesive sheet while sandwiching the end portion of the optical transparent adhesive sheet with the support member. The manufacturing method of a laminated body is also 1 aspect of this invention.

The order of bonding in the bonding step is not particularly limited, and after the optical transparent pressure-sensitive adhesive sheet and the first substrate are bonded, a method of bonding the optical transparent pressure-sensitive adhesive sheet and the second substrate, optical transparent pressure-sensitive adhesive After laminating the sheet and the second substrate, a method of laminating the optical transparent adhesive sheet and the first substrate, the optical transparent adhesive sheet, the first substrate and the second substrate in a lump Any of the methods of pasting and pasting may be used, but a method of pasting the optical transparent adhesive sheet and the first substrate and then pasting the optical transparent adhesive sheet and the second substrate is suitable. Used for.

Although the bonding method of an optical transparent adhesive sheet and a 1st base material is not specifically limited, Vacuum bonding is used suitably, for example, it pressure-reduces to 5-200 Pa and is optical by the pressure of about 50-500 g / cm < ² >. The transparent adhesive sheet and the first substrate may be pressed and bonded together. Since the first base material such as a liquid crystal panel has a substrate, a cavity, and the like inside thereof, the method of laminating the roll under atmospheric pressure may not uniformly apply linear pressure, and bubbles may enter the bonding interface. There is. On the other hand, the bonding method between the optically transparent pressure-sensitive adhesive sheet and the second substrate is not particularly limited, and for example, a method of roll bonding under atmospheric pressure, vacuum bonding, or the like is used.

EXAMPLES Hereinafter, although an Example is hung up and demonstrated in more detail about this invention, this invention is not limited only to these Examples.

Example 1
First, 75 parts by weight of polyolefin polyol (“EPOL (Epol, registered trademark)” manufactured by Idemitsu Kosan Co., Ltd.), 2.4 weight of IPDI (isophorone diisocyanate) polyisocyanate (“Desmodule I” manufactured by Sumika Bayer Urethane Co., Ltd.) 4.6 parts by weight of modified polyisocyanate containing ethylene oxide units (“Coronate 4022” manufactured by Tosoh Corporation), 17 parts by weight of tackfire (“Imabe P-100” manufactured by Idemitsu Kosan Co., Ltd.), and catalyst (dilauric acid) 1 part by weight of dimethyl tin) was stirred and mixed using a reciprocating rotary stirrer agitator to prepare a thermosetting polyurethane composition having an α ratio of 1.60. In the thermosetting polyurethane composition, the mixing ratio (molar ratio) between the IPDI polyisocyanate (A) and the modified polyisocyanate (B) was A: B = 2: 1.

Thereafter, the obtained thermosetting polyurethane composition was poured into the molding apparatus 50 shown in FIG. Then, while transporting the thermosetting polyurethane composition in a state of being sandwiched between a pair of release films (PET film having a release treatment applied to the surface) 51, the temperature in the furnace is 70 ° C. and the time in the furnace is 10 minutes. And cured by cross-linking. Then, the optically transparent adhesive sheet 12 made of a cured product of a thermosetting polyurethane composition was produced by performing a crosslinking reaction with a heating device 54 adjusted to 70 ° C. for 12 hours. The thickness of the optical transparent pressure-sensitive adhesive sheet 12 was 1500 μm.

The viscoelastic properties of the optically transparent adhesive sheet were measured using a viscoelasticity measuring device “Physica MCR301” manufactured by Anton Paar Germany GmbH. PP12 was used for the measurement plate, and the measurement conditions were strain 0.1%, frequency 1 Hz, cell temperature 25 ° C. to 100 ° C. (temperature increase rate 3 ° C./min). As a result, the storage shear modulus (G ′) at 30 ° C. was 9.4 × 10 ⁴ Pa, and the storage shear modulus at 85 ° C. was 1.1 × 10 ⁴ Pa. The loss tangent (tan δ) at 30 ° C. was 0.77, and the loss tangent at 85 ° C. was 0.87.

An optical transparent adhesive sheet having a uniform thickness (1500 μm) is formed so as to cover a step formed by the liquid crystal panel and the bezel after forming a step having a height of 800 μm by overlapping a frame-like bezel on the outer edge of the liquid crystal panel. Bonding was performed on the liquid crystal panel under a reduced pressure atmosphere of 100 Pa. Subsequently, a cover glass having a thickness of 3 mm was pressure-bonded at a pressure of 200 g / cm ² under a reduced pressure atmosphere of 100 Pa on the optically transparent adhesive sheet attached on the liquid crystal panel. The distance between the liquid crystal panel and the cover glass after the pressure bonding was set to 1500 μm, which is the same as the thickness of the optical transparent adhesive sheet. The edge of the optically transparent adhesive sheet located on the bezel was sandwiched between the bezel and the cover glass when the cover glass was crimped and spread thinly. It was the same at the center where the outer edge and the bezel were not present. As described above, a liquid crystal panel in which a frame-like bezel was placed on the outer edge and a cover glass were bonded together using an optically transparent adhesive sheet.

(Examples 2-9 and Comparative Examples 1-3)
As shown in Table 1 below, the composition of the thermosetting polyurethane composition used to produce the optically transparent adhesive sheet (OCA) or the material of the optically transparent adhesive sheet, the bezel thickness (step height), optical Except having changed the thickness (OCA thickness) of the transparent adhesive sheet, it carried out similarly to Example 1, and produced the laminated body which concerns on Examples 2-9 and Comparative Examples 1-3, respectively. In Comparative Example 3, “K95E (t1.5)” manufactured by Taika Corporation was used as the silicone resin composition.

(Evaluation of bezel-on bonding)
In any of the laminates according to Examples 1 to 9 and Comparative Examples 1 to 3, bezel-on bonding was performed in which the end of the optically transparent adhesive sheet covers the upper surface of the bezel. Each laminated body is heated to 30 ° C. and 85 ° C., and the laminated body is visually observed from the cover glass side. When both peeling and floating (bubbles) are not generated at both 30 ° C. and 85 ° C., “○” When at least one of peeling and floating occurred on at least one of 30 ° C. and 85 ° C., it was evaluated as “x”. The evaluation results are shown in Table 1 below.

As can be seen from the comparison between Examples 1 to 9 and Comparative Examples 1 to 3, the optically transparent adhesive sheet having a low storage shear modulus was soft and excellent in step following ability, but when the loss tangent was low. The repulsive force (shape restoring force) was strong, and it was not suitable for bezel-on bonding. On the other hand, even an optically transparent adhesive sheet having a somewhat high storage shear elastic modulus was suitable for bezel-on bonding because the repulsive force (shape restoring force) was weak when the loss tangent was high. Further, Comparative Example 2 in which the thickness of the optical transparent adhesive sheet was 1.25 times the thickness of the bezel had a loss tangent of 0.5 or more, but was not suitable for bezel-on bonding.

11 1st base materials 12 and 112 Optical transparent adhesive sheet 13 2nd base material 13A Light-shielding part 21 Upper bezel (support member)
22 Lower bezel 50 Molding device 51 Release film 52 Molding roll 53 Thermosetting polyurethane composition 54 Heating device

Claims (5)

A laminate comprising an optically transparent adhesive sheet and a support member between a first substrate and a second substrate,
The support member has a step forming portion disposed on an outer edge of the first base material,
The optical transparent pressure-sensitive adhesive sheet includes a thick film part that bonds the first base material and the second base material, and an end part sandwiched between the step forming part and the second base material. Including
The optically transparent adhesive sheet has a loss tangent at 30 ° C. of 0.5 or more,
The thickness of the thick film part is 1.5 times or more of the thickness of the step forming part. The laminate according to claim 1, wherein the first substrate has a polarizing plate on a surface in contact with the optical transparent adhesive sheet. The laminate according to claim 1 or 2, wherein the optically transparent adhesive sheet is made of polyurethane. Loss tangent at 30 ° C is 0.5 or more,
The storage shear modulus at 30 ° C. is 3.0 × 10 ⁵ Pa or less,
An optically transparent pressure-sensitive adhesive sheet having a thickness exceeding 500 μm. A method for producing a laminate comprising an optically transparent adhesive sheet and a support member between a first substrate and a second substrate,
The optically transparent adhesive sheet has a loss tangent at 30 ° C. of 0.5 or more,
The thickness of the optical transparent adhesive sheet before being bonded is 1.5 times or more the thickness of the support member,
The support member is disposed between the first substrate and the second substrate disposed on an outer edge so as to cover a step formed by the first substrate and the support member. The optical transparent adhesive sheet is interposed, and the second base and the support member sandwich the end of the optical transparent adhesive sheet, and the first base is formed by a portion other than the end of the optical transparent adhesive sheet. The manufacturing method of the laminated body characterized by including the process of adhere | attaching a material and a 2nd base material.

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