WO2021084874A1

WO2021084874A1 - Image display device and set of optical members

Info

Publication number: WO2021084874A1
Application number: PCT/JP2020/032188
Authority: WO
Inventors: 藤田　雅人; 智之木村; 雄祐外山
Original assignee: 日東電工株式会社
Priority date: 2019-10-30
Filing date: 2020-08-26
Publication date: 2021-05-06
Also published as: TW202125001A; CN114631135A; JP2021071710A; KR20220088432A

Abstract

Provided is an image display device in which an irregular shape processing part is filled with an adhesive and bubbles are significantly suppressed. The image display device according to the present invention includes: an image display cell; a first polarizing plate including a first polarizer and a first adhesive layer and laminated on the visual side of the image display cell with the first adhesive layer therebetween; a second polarizing plate including a second polarizer and a second adhesive layer and laminated on the rear side of the image display cell with the second adhesive layer therebetween; and a third adhesive layer disposed on the visual side of the first polarizing plate. The first polarizing plate and the second polarizing plate have irregular shape processing parts at positions corresponding to each other, and the irregular shape processing part of the first polarizing plate is filled with an adhesive constituting the third adhesive layer. The thickness of the first polarizing plate is 90 μm or less, the thickness of the third adhesive layer is 170 μm or more, and the storage elastic modulus of the third adhesive layer at 60°C is 8.0×10⁴ Pa or less.

Description

Image display device and optical member set

The present invention relates to a set of an image display device and an optical member.

Optical laminates (for example, polarizing plates) are widely used in image display devices such as mobile phones and notebook personal computers in order to realize image display and / or enhance the performance of the image display. In recent years, it has been desired to use an optical laminate for an image display device equipped with a camera, a smart watch, an instrument panel of an automobile, etc., and the optical laminate is processed into a shape other than a rectangle (deformed processing: for example, notch or penetration). Pore formation) may occur. On the other hand, in order to impart surface hardness and impact resistance to the image display device, a cover glass may be laminated on the outermost surface of the image display device. When the cover glass is laminated on the image display device including the deformed optical laminate, the deformed portion is typically filled with an adhesive for laminating the cover glass. However, in an image display device in which the deformed portion is filled with an adhesive, bubbles may be generated due to heat treatment or the like in the manufacturing process.

Japanese Unexamined Patent Publication No. 2016-094569

The present invention has been made to solve the above-mentioned conventional problems, and a main object thereof is to provide an image display device in which a deformed processed portion is filled with an adhesive and bubbles are remarkably suppressed. is there.

The image display device of the present invention includes an image display cell; a first polarizing element and a first pressure-sensitive adhesive layer, and is laminated on the visual side of the image display cell via the first pressure-sensitive adhesive layer. A polarizing plate of 1; a second polarizing plate containing a second polarizing element and a second pressure-sensitive adhesive layer, and laminated on the back surface side of the image display cell via the second pressure-sensitive adhesive layer; It has a third pressure-sensitive adhesive layer arranged on the visible side of the first polarizing plate; The first polarizing plate and the second polarizing plate have a deformed portion at positions corresponding to each other, and the deformed portion of the first polarizing plate forms a third pressure-sensitive adhesive layer. Is filled with. Said first thickness of the polarizing plate is at 90μm or less, the thickness of the third adhesive layer not less than 170 [mu] m, storage elastic modulus at 60 ° C. of the third adhesive layer 8.0 × 10 ⁴ It is less than or equal to Pa.
In another embodiment of the invention, it comprises an image display cell; a first polarizer and a first pressure-sensitive adhesive layer, which is laminated on the visible side of the image display cell via the first pressure-sensitive adhesive layer. It has a first polarizing plate and a third pressure-sensitive adhesive layer arranged on the visible side of the first polarizing plate; the first polarizing plate has a deformed portion, and the first polarizing plate has a deformed portion. The deformed portion of the polarizing plate is filled with the pressure-sensitive adhesive constituting the third pressure-sensitive adhesive layer, the thickness of the first polarizing plate is 90 μm or less, and the thickness of the third pressure-sensitive adhesive layer is 170 μm. and is approximately storage modulus at 60 ° C. of the third adhesive layer is 8.0 × ¹⁰ 4 Pa or less.
In one embodiment, the deformed portion of the first polarizing plate is formed so that the end face of the first pressure-sensitive adhesive layer is located inward in the plane direction with respect to the end face of the first polarizing plate. It has a pressure-sensitive adhesive gap, and the size of the pressure-sensitive adhesive gap is 300 μm or less.
In one embodiment, the thickness of the first pressure-sensitive adhesive layer is 50 μm or less.
In one embodiment, the adhesive force between the first pressure-sensitive adhesive layer and the third pressure-sensitive adhesive layer is 2N / 25 mm or more.
In one embodiment, the gel fraction of the third pressure-sensitive adhesive layer is 80% or less.
In one embodiment, the deformed portion includes a through hole or a machined portion that becomes a recess when viewed in a plan view. In one embodiment, the recess is a V-shaped notch or a U-shaped notch.
In one embodiment, the image display device further has a cover glass on the visible side of the third pressure-sensitive adhesive layer.
In one embodiment, the image display device has a camera unit at a position corresponding to a deformed portion of the first polarizing plate and the second polarizing plate.
In one embodiment, the image display device is a liquid crystal display device. In another embodiment, the image display device is an organic EL display device. In one embodiment, the organic EL display device has a camera unit at a position corresponding to the deformed processing portion of the first polarizing plate.
According to another aspect of the invention, a set of optical members is provided. This set of optical members includes a first polarizing element and a first pressure-sensitive adhesive layer, has a thickness of 90 μm or less, has a deformed portion, and has a first polarized light arranged on the visible side of an image display cell. A pressure-sensitive adhesive sheet composed of a plate and a pressure-sensitive adhesive having a storage elastic modulus at 60 ° C. of 8.0 × 10 ⁴ Pa or less, having a thickness of 200 μm or more, and filling a deformed portion of the first polarizing plate. And; are included.
In one embodiment, the deformed portion of the first polarizing plate is formed so that the end face of the first pressure-sensitive adhesive layer is located inward in the plane direction with respect to the end face of the first polarizing plate. It has a pressure-sensitive adhesive gap, and the size of the pressure-sensitive adhesive gap is 300 μm or less.
In one embodiment, the set of optical members includes a second polarizing element, has a deformed portion, and further includes a second polarizing plate arranged on the back side of the image display cell. The polarizing plate of No. 1 and the second polarizing plate have a deformed portion at positions corresponding to each other.

According to the embodiment of the present invention, in the image display device in which the deformed portion is filled with the adhesive, the thickness of the viewing side polarizing plate, the thickness of the viewing side adhesive layer, and the storage elastic modulus are set within a predetermined range. Thereby, it is possible to realize an image display device in which bubbles are remarkably suppressed.

It is a schematic exploded perspective view of the image display device according to one embodiment of the present invention. It is the schematic sectional drawing of the through hole part of the image display device of FIG. It is a schematic plan view explaining an example of the deformed or deformed processed part in the 1st polarizing plate and the 2nd polarizing plate of the image display apparatus according to the embodiment of this invention. It is a schematic plan view explaining the modification of the deformed or deformed processed portion in the first polarizing plate and the second polarizing plate of the image display apparatus according to the embodiment of the present invention. It is a schematic plan view explaining the further modification of the deformed or deformed processed part in the 1st polarizing plate and the 2nd polarizing plate of the image display apparatus according to the embodiment of this invention. It is a schematic plan view explaining the further modification of the deformed or deformed processed part in the 1st polarizing plate and the 2nd polarizing plate of the image display apparatus according to the embodiment of this invention. It is a partial schematic cross-sectional view explaining the pressure-sensitive adhesive void part in the 1st polarizing plate of the image display apparatus according to embodiment of this invention.

Hereinafter, specific embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to these embodiments. The drawings are schematically shown for easy viewing, and the ratios of length, width, thickness, etc., angles, etc. in the drawings are different from the actual ones.

A. Overall Configuration of Image Display Device FIG. 1 is a schematic exploded perspective view of the image display device according to one embodiment of the present invention; FIG. 2 is a schematic cross-sectional view of a through hole portion of the image display device of FIG. The image display device 200 of the illustrated example includes an image display cell 100, a first polarizing plate 10 laminated on the visual side of the image display cell 100, and a second polarizing plate laminated on the back side of the image display cell 100. It has 20 and a third pressure-sensitive adhesive layer 30 arranged on the visible side of the first polarizing plate 10. In one embodiment, the image display device 200 may further have a cover glass 40 on the visible side of the third pressure-sensitive adhesive layer 30. That is, the cover glass 40 may be attached to the first polarizing plate 10 via the third pressure-sensitive adhesive layer 30. The first polarizing plate 10 includes a first polarizing element 11, a protective layer (outer protective layer) 12 arranged on the visual side of the first polarizing element 11, and an image display cell 100 of the first polarizing element 11. It has a protective layer (inner protective layer) 13 arranged on the side and a first adhesive layer 14 arranged as an outermost layer on the image display cell side. The first polarizing plate 10 is laminated on the image display cell 100 via the first pressure-sensitive adhesive layer 14. One of the

protective layers

12 and 13 may be omitted depending on the purpose and the like. The second polarizing plate 20 includes a second polarizing element 21, a protective layer (outer protective layer) 22 arranged on the back side of the second polarizing element 21, and an image display cell 100 of the second polarizing element 21. It has a protective layer (inner protective layer) 23 arranged on the side and a second adhesive layer 24 arranged as an outermost layer on the image display cell side. The second polarizing plate 20 is laminated on the image display cell 100 via the second pressure-sensitive adhesive layer 24. One of the

protective layers

22 and 23 may be omitted depending on the purpose and the like. Typically, the first polarizing plate 10 and second polarizing plate 20, the absorption axis A ₁ of the first polarizer 11 and the absorption axis A ₂ of the second polarizer 21 are substantially perpendicular It is arranged in this way. In the illustrated example, A ₁ is described in the longitudinal direction and A ₂ is described in the lateral direction, but these may be reversed. In addition, in this specification, "substantially orthogonal" includes the case where the angle formed by two directions is 90 ° ± 7 °, preferably 90 ° ± 5 °, and more preferably 90 ° ±. It is 3 °. The term "substantially parallel" includes the case where the angle formed by the two directions is 0 ° ± 7 °, preferably 0 ° ± 5 °, and more preferably 0 ° ± 3 °. In addition, the term "orthogonal" or "parallel" in the present specification includes the case of "substantially orthogonal" or "substantially parallel". Further, when referring to an angle herein, it includes both clockwise and counterclockwise with respect to the reference direction.

The first polarizing plate 10 has a deformed processing portion 15, and the second polarizing plate 20 has a deformed processing portion 25. The first polarizing plate 10 and the second polarizing plate 20 have deformed

processing portions

15 and 25 at positions corresponding to each other. The deformed portion 15 of the first polarizing plate 10 is typically filled with a pressure-sensitive adhesive constituting the third pressure-sensitive adhesive layer 30. In the present specification, "provided at positions corresponding to each other" means that the deformed portions overlap when the two polarizing plates are overlapped. Further, in the present specification, the "deformed portion" refers to a portion processed into a special shape different from a general shape (for example, a rectangle or chamfering of a corner). As shown in FIGS. 3 and 4, typical examples of the deformed portion include a through hole and a machined portion that becomes a recess when viewed in a plan view. Typical examples of the recess include a shape similar to a ship shape, a V-shaped notch, and a U-shaped notch. Further, the first polarizing plate and the second polarizing plate may be entirely deformed. As such an example, as shown in FIGS. 5 and 6, there is a shape corresponding to the instrument panel of an automobile. The shape includes a portion in which the outer edge is formed in an arc shape along the rotation direction of the meter needle and the outer edge is V-shaped (including a round shape) convex inward in the plane direction. The deformed portion is provided at an arbitrary appropriate position according to the purpose. Typically, the deformed portion is provided at or near the end of each polarizing plate. With such a configuration, the influence on the image display can be minimized. For example, as shown in FIG. 4, the deformed portion may be provided at a substantially central portion of the longitudinal end portion of the rectangular polarizing plate, or may be provided at a predetermined position at the longitudinal end portion, and may be polarized. It may be provided at the corner of the board. In the illustrated example, the case where the deformed portion is provided at the end portion in the longitudinal direction is shown, but the deformed portion may be provided at the end portion in the lateral direction. Further, as shown in the lower right of FIG. 4, a plurality of deformed processing portions may be provided. For example, two or more through holes and / or notches may be provided, and as shown in FIG. 4, the through holes and the notches may be provided in combination.

The image display device includes an image display panel. The image display panel includes an image display cell. The image display device may be referred to as an optical display device. The image display panel may be referred to as an optical display panel. The image display cell may be referred to as an optical display cell.

Typical examples of the image display cell 100 include a liquid crystal cell, an organic electroluminescence (EL) cell, and a quantum dot cell. Therefore, typical examples of the image display device 200 include a liquid crystal display device, an organic EL display device, and a quantum dot display device. The illustrated example typically shows the configuration of a liquid crystal display device. In the liquid crystal display device, the effect of the combination of the first polarizing plate and the second polarizing plate becomes remarkable. In the organic EL display device, the second polarizing plate 20 may be omitted. In one embodiment, the image display device 200 has a camera unit (not shown) at a position corresponding to the

deformed processing units

15 and 25.

In the embodiment of the present invention, the thickness of the first polarizing plate 10 is 90 μm or less, preferably 60 μm or less, more preferably 50 μm or less, and further preferably 40 μm or less. The lower limit of the thickness of the first polarizing plate can be, for example, 20 μm. Further, the thickness of the third pressure-sensitive adhesive layer 30 is 170 μm or more, preferably 200 μm or more, more preferably 220 μm or more, and further preferably 240 μm or more. The upper limit of the thickness of the third pressure-sensitive adhesive layer can be, for example, 500 μm. In addition, the storage elastic modulus of the third pressure-sensitive adhesive layer 30 at 60 ° C. is 8.0 × 10 ⁴ Pa or less, preferably 5.0 × 10 ⁴ Pa or less, and more preferably 3.0 × 10 ^{It is 4} Pa or less, more preferably 2.0 × 10 ⁴ Pa or less. The lower limit of the storage elastic modulus can be, for example, 1.0 × 10 ³ Pa. With such a configuration, air bubbles can be remarkably suppressed in an image display device in which the deformed processed portion is filled with an adhesive. In particular, the generation of bubbles, so-called delay bubbles, can be remarkably suppressed. The details are as follows. Filling with the pressure-sensitive adhesive constituting the third pressure-sensitive adhesive layer of the deformed portion is typically performed by vacuum laminating a laminate of a cover glass and a pressure-sensitive adhesive sheet forming the third pressure-sensitive adhesive layer. This is done by bonding to a polarizing plate. Immediately after vacuum laminating, there are often no recognizable bubbles in the filled portion, but bubbles may be generated in the subsequent heating durability test of the image display device. Such bubbles can typically be generated by applying shrinkage stress of the polarizing plate to the filled portion. Such bubbles are called delay bubbles. The delay bubble is not a fine one, but a large one that occupies a certain percentage or more of the plan view area of the deformed portion, and from the viewpoint of appearance, the camera performance of the camera portion provided at the position corresponding to the deformed portion Is also unacceptable. With the above configuration, it is presumed that the residual stress of the filled portion can be relaxed and the deformation of the adhesive due to heating or the like can be suppressed, and as a result, the delay bubble can be suppressed. Further, by thinning the polarizing plate as described above and using the adhesive layer on the visual side having the thickness and storage elastic modulus as described above, the following is carried out in the manufacturing process of the image display device (for example, a smartphone). Secondary effects can be achieved: By setting the storage elastic modulus of the adhesive layer on the visual side within the above range, dents are generated, the adhesive squeezes out from the end of the punched product, and handling is poor. Etc. can be prevented. Further, when a thick polarizing plate is used, it may be necessary to heat-shrink the polarizing plate before attaching it to the image display cell to reduce the shrinkage during the heating durability test. Such shrinkage reduction treatment not only lowers productivity, but may also cause dimensional changes, curls, and the like. By making the polarizing plate thinner, such a problem can be avoided.

In one embodiment, as shown in FIG. 7, in the deformed portion 15 of the first polarizing plate 10, the end face of the first pressure-sensitive adhesive layer 14 is a first polarizing plate (substantially, a polarizing element). 11 or, if present, has an adhesive void 16 formed located inward in the plane direction with respect to the end surface of the inner protective layer 13). The size L of the pressure-sensitive adhesive gap is preferably 300 μm or less, more preferably 200 μm or less, further preferably 150 μm or less, particularly preferably 100 μm or less, and particularly preferably 80 μm or less. The lower limit of the size L of the pressure-sensitive adhesive gap portion may be, for example, 10 μm. In the present specification, the “size L of the pressure-sensitive adhesive gap” is defined from the end face of the first polarizing plate (substantially, the polarizer 11 or the inner protective layer 13 if present) to the end face of the pressure-sensitive adhesive layer 14. The maximum length up to.

The image display device 200 may have a backlight unit (not shown) depending on the configuration of the image display cell 100. Since a configuration well known in the art can be adopted for the backlight unit, detailed description thereof will be omitted.

If necessary, the image display device 200 may be provided with a retardation layer (not shown). The type, number, combination, arrangement position, and characteristics of the retardation layer can be appropriately set according to the purpose. For example, the retardation layer may be a λ / 2 plate, a λ / 4 plate, or a laminate thereof. The λ / 2 plate and the λ / 4 plate typically have a refractive index characteristic of nx> ny ≧ nz. The in-plane retardation Re (550) is preferably 180 nm to 320 nm for the λ / 2 plate, and the in-plane retardation Re (550) is preferably 100 nm to 200 nm for the λ / 4 plate. Further, for example, the retardation layer may be a laminate of a negative B plate (nx> ny> nz) and a positive C plate (nz> nx = ny) or a positive B plate (nz> nx> ny). In the present specification, "Re (λ)" is an in-plane phase difference measured with light having a wavelength of λ nm at 23 ° C. For example, "Re (550)" is an in-plane phase difference measured with light having a wavelength of 550 nm at 23 ° C. Re (λ) is obtained by the formula: Re (λ) = (nx−ny) × d, where d (nm) is the thickness of the layer (film). “Rth (λ)” is a phase difference in the thickness direction measured with light having a wavelength of λ nm at 23 ° C. For example, "Rth (550)" is a phase difference in the thickness direction measured with light having a wavelength of 550 nm at 23 ° C. Rth (λ) is obtained by the formula: Rth (λ) = (nx−nz) × d, where d (nm) is the thickness of the layer (film). "Nx" is the refractive index in the direction in which the in-plane refractive index is maximized (that is, the slow-phase axis direction), and "ny" is the in-plane direction orthogonal to the slow-phase axis (that is, the phase-advance axis direction). Is the refractive index of, and "nz" is the refractive index in the thickness direction.

If necessary, the image display device 200 may be provided with an optical member (not shown). The type, number, combination, arrangement position, and characteristics of the optical members can be appropriately set according to the purpose. For example, a reflective polarizer, a prism sheet, and / or a diffuser plate may be provided on the back surface side of the second polarizing plate. The reflective polarizer may also serve as the outer protective layer of the second polarizing plate.

Hereinafter, the components of the image display device will be specifically described. In the first polarizing plate and the second polarizing plate, the first polarizing plate and the second polarizing plate are collectively referred to as a polarizing plate, and the first and second polarizers are collectively referred to as a polarizer. The respective protective layers will be collectively described as a protective layer, and the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer will be collectively described as a pressure-sensitive adhesive layer. Therefore, for example, when the term "polarizing plate is" means "the first polarizing plate and the second polarizing plate are each". On the other hand, for example, when it is necessary to explain the first polarizing plate and the second polarizing plate separately, "first" or "second" is specified. Since a structure well known in the art can be adopted for the cover glass, detailed description thereof will be omitted.

B. Polarizing plate B-1. Polarizer The polarizer is typically composed of a resin film containing a dichroic substance. As the resin film, any suitable resin film that can be used as a polarizer can be adopted. The resin film is typically a polyvinyl alcohol-based resin (hereinafter, referred to as “PVA-based resin”) film. The resin film may be a single-layer resin film or a laminated body having two or more layers.

Specific examples of the polarizer composed of a single-layer resin film include those obtained by subjecting a PVA-based resin film to a dyeing treatment with iodine and a stretching treatment (typically, uniaxial stretching). The dyeing with iodine is performed, for example, by immersing a PVA-based film in an aqueous iodine solution. The draw ratio of the uniaxial stretching is preferably 3 to 7 times. Stretching may be performed after the dyeing treatment or while dyeing. Moreover, you may dye after stretching. If necessary, the PVA-based resin film is subjected to a swelling treatment, a cross-linking treatment, a cleaning treatment, a drying treatment and the like. For example, by immersing the PVA-based resin film in water and washing it with water before dyeing, not only can the stains on the surface of the PVA-based film and the blocking inhibitor be washed, but also the PVA-based resin film is swollen to cause uneven dyeing. Etc. can be prevented.

Specific examples of the polarizer obtained by using the laminate include a laminate of a resin base material and a PVA-based resin layer (PVA-based resin film) laminated on the resin base material, or a resin base material and the resin. Examples thereof include a polarizer obtained by using a laminate with a PVA-based resin layer coated and formed on a base material. The polarizer obtained by using the laminate of the resin base material and the PVA-based resin layer coated and formed on the resin base material is, for example, a resin base material obtained by applying a PVA-based resin solution to the resin base material and drying the resin base material. It is produced by forming a PVA-based resin layer on the resin layer to obtain a laminate of a resin base material and a PVA-based resin layer; and stretching and dyeing the laminate to use the PVA-based resin layer as a polarizer. obtain. In the present embodiment, stretching typically includes immersing the laminate in an aqueous boric acid solution for stretching. Further, stretching may further include, if necessary, stretching the laminate in the air at a high temperature (eg, 95 ° C. or higher) prior to stretching in boric acid aqueous solution. The obtained resin base material / polarizer laminate may be used as it is (that is, the resin base material may be used as a protective layer for the polarizer), and the resin base material is peeled off from the resin base material / polarizer laminate. Then, an arbitrary appropriate protective layer according to the purpose may be laminated on the peeled surface. Details of the method for producing such a polarizer are described in, for example, Japanese Patent Application Laid-Open No. 2012-73580 and Japanese Patent No. 6470455. The entire description of the publication is incorporated herein by reference.

The thickness of the polarizer is preferably 25 μm or less, more preferably 12 μm or less, and further preferably 8 μm or less. On the other hand, the thickness of the polarizer is 1 μm or more in one embodiment, 2 μm or more in another embodiment, and 3 μm or more in yet another embodiment. When the thickness of the polarizer is in such a range, curling during heating can be satisfactorily suppressed, and good appearance durability during heating can be obtained. In particular, if the thickness of the first polarizing element is in such a range, it is easy to set the thickness of the first polarizing plate in the above desired range.

The polarizer preferably exhibits absorption dichroism at any wavelength of 380 nm to 780 nm. The simple substance transmittance of the polarizer is, for example, 41.5% to 46.0%, preferably 43.0% to 46.0%, and more preferably 44.5% to 46.0%. The degree of polarization of the polarizer is preferably 97.0% or more, more preferably 99.0% or more, and further preferably 99.9% or more.

B-2. Protective layer The protective layer is formed of any suitable film that can be used as a protective layer for the polarizer. Specific examples of the material that is the main component of the film include cellulose-based resins such as triacetylcellulose (TAC), polyester-based, polyvinyl alcohol-based, polycarbonate-based, polyamide-based, polyimide-based, polyethersulfone-based, and polysulfone-based. , Polystyrene-based, polycarbonate-based, polyolefin-based, (meth) acrylic-based, acetate-based transparent resins and the like. Further, thermosetting resins such as (meth) acrylic, urethane, (meth) acrylic urethane, epoxy, and silicone, or ultraviolet curable resins can also be mentioned. In addition to this, for example, glassy polymers such as siloxane-based polymers can also be mentioned. Further, the polymer film described in JP-A-2001-343529 (WO01 / 37007) can also be used. As the material of this film, for example, a resin composition containing a thermoplastic resin having a substituted or unsubstituted imide group in the side chain and a thermoplastic resin having a substituted or unsubstituted phenyl group and a nitrile group in the side chain. Can be used, and examples thereof include a resin composition having an alternating copolymer composed of isobutene and N-methylmaleimide and an acrylonitrile / styrene copolymer. The polymer film can be, for example, an extruded product of the above resin composition.

The outer protective layer (particularly, the outer protective layer 12 of the first polarizing plate) may be subjected to surface treatment such as hard coating treatment, antireflection treatment, anti-sticking treatment, anti-glare treatment, etc., if necessary. ..

The inner protective layer is preferably optically isotropic. As used herein, "optically isotropic" means that the in-plane retardation Re (550) is 0 nm to 10 nm and the thickness direction retardation Rth (550) is -10 nm to +10 nm. Say.

Any appropriate thickness can be adopted as the thickness of the protective layer. The thickness of the protective layer is, for example, 15 μm to 45 μm, preferably 20 μm to 40 μm. When the surface treatment is applied, the thickness of the protective layer is the thickness including the thickness of the surface treatment layer.

C. Adhesive layer The adhesive layer is typically used to attach each polarizing plate to an image display cell. The pressure-sensitive adhesive layer may be typically composed of an acrylic pressure-sensitive adhesive (acrylic pressure-sensitive adhesive composition). The acrylic pressure-sensitive adhesive composition typically contains a (meth) acrylic polymer as a base polymer. The (meth) acrylic polymer can be contained in the pressure-sensitive adhesive composition in a proportion of, for example, 50% by weight or more, preferably 70% by weight or more, and more preferably 90% by weight or more in the solid content of the pressure-sensitive adhesive composition. The (meth) acrylic polymer contains an alkyl (meth) acrylate as a main component as a monomer unit. In addition, (meth) acrylate means acrylate and / or methacrylate. The alkyl (meth) acrylate can be contained in a proportion of preferably 70% by weight or more, more preferably 80% by weight or more, in the monomer component forming the (meth) acrylic polymer. Examples of the alkyl group of the alkyl (meth) acrylate include a linear or branched alkyl group having 1 to 18 carbon atoms. The average number of carbon atoms of the alkyl group is preferably 3 to 9, and more preferably 3 to 6. Specific examples of the alkyl (meth) acrylate include methyl acrylate, methyl methacrylate, butyl acrylate, and 2-ethylhexyl acrylate. Examples of the monomer (copolymerization monomer) constituting the (meth) acrylic polymer include a carboxyl group-containing monomer, a hydroxyl group-containing monomer, an amide group-containing monomer, a polyfunctional (meth) acrylate, and an aromatic ring, in addition to the alkyl (meth) acrylate. Examples thereof include contained (meth) acrylates and heterocyclic-containing vinyl-based monomers. Representative examples of the copolymerization monomer include acrylate, 2-hydroxyethyl acrylate, 4-hydroxybutyl acrylate, phenoxyethyl acrylate, N-vinyl-2-pyrrolidone, and N-acryloylmorpholine. The acrylic pressure-sensitive adhesive composition may preferably contain a silane coupling agent and / or a cross-linking agent. Examples of the silane coupling agent include an epoxy group-containing silane coupling agent. Examples of the cross-linking agent include isocyanate-based cross-linking agents and peroxide-based cross-linking agents. The acrylic pressure-sensitive adhesive composition may contain an additive. Specific examples of additives include powders such as colorants and pigments, dyes, surfactants, plasticizers, tackifiers, surface lubricants, leveling agents, softeners, antioxidants, antioxidants, and light. Examples include stabilizers, UV absorbers, polymerization inhibitors, conductive agents, inorganic or organic fillers, metal powders, particulates, and foils. Further, a redox system to which a reducing agent is added may be adopted within a controllable range. The type, number, combination, blending amount, etc. of the additive can be appropriately set according to the purpose. By appropriately adjusting the types, combinations, blending amounts, etc. of the monomer components, and the types, numbers, combinations, blending amounts, etc. of the cross-linking agents, silane coupling agents, and additives, the desired properties can be obtained according to the purpose. An acrylic pressure-sensitive adhesive composition (as a result, a pressure-sensitive adhesive layer) can be obtained. Details of the pressure-sensitive adhesive layer or the acrylic pressure-sensitive adhesive composition are described in, for example, JP-A-2006-183022, JP-A-2015-199942, JP-A-2018-053114, JP-A-2016-190996, International Publication. It is described in No. 2018/008712, and the description of these publications is incorporated herein by reference.

The thickness of the pressure-sensitive adhesive layer is preferably 50 μm or less, more preferably 40 μm or less, further preferably 30 μm or less, and particularly preferably 25 μm or less. The lower limit of the thickness of the pressure-sensitive adhesive layer can be, for example, 2 μm. If the thickness of the pressure-sensitive adhesive layer is within such a range, it can contribute to the thinning of the image display device. In particular, when the thickness of the first pressure-sensitive adhesive layer is within such a range, it becomes easy to fill the deformed portion with the pressure-sensitive adhesive constituting the third pressure-sensitive adhesive layer. More specifically, since the depth of the deformed portion becomes smaller, it becomes easier to be filled with the adhesive. As a result, the gap in the deformed portion becomes smaller, so that bubbles are less likely to be generated due to deformation of the adhesive or the like. As a result, if the thickness of the first pressure-sensitive adhesive layer is in such a range, it can contribute to the suppression of delay bubbles.

The adhesive strength between the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer (particularly, the first pressure-sensitive adhesive layer) and the pressure-sensitive adhesive constituting the third pressure-sensitive adhesive layer is preferably 2N / 25 mm or more, more preferably 5N /. It is 25 mm or more, more preferably 10 N / 25 mm or more. The upper limit of the adhesive force can be, for example, 50 N / 25 mm. As can be understood from FIG. 2, the first pressure-sensitive adhesive layer and the third pressure-sensitive adhesive layer can come into contact with each other. It becomes difficult to peel off from the third adhesive layer. As a result, gaps are less likely to be formed in the deformed portion, and delay bubbles can be suppressed. The adhesive strength can be measured according to the "90 degree peel strength test" of JIS Z 0237.

D. Third adhesive layer D-1. Characteristics of the Third Adhesive Layer The third adhesive layer 30 can typically fill the deformed portion 15 of the first polarizing plate 10 as described in item A above. The third pressure-sensitive adhesive layer may have the following properties in addition to the thickness and storage elastic modulus described in the above item A.

The gel fraction of the third pressure-sensitive adhesive layer is preferably 80% or less, more preferably 70% or less, further preferably 60% or less, and particularly preferably 50% or less. The lower limit of the gel fraction can be, for example, 20%. As described above, the gel fraction of the third pressure-sensitive adhesive layer is significantly smaller than the gel fraction of the normal pressure-sensitive adhesive. As a result, the gel elasticity of the third pressure-sensitive adhesive becomes low, and the residual stress becomes small. As a result, the delay bubble can be suppressed. The gel fraction can be determined as an insoluble component in a solvent such as ethyl acetate. Specifically, the gel fraction is the weight fraction (unit: weight%) of the insoluble component after immersing the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer in ethyl acetate at 23 ° C. for 7 days with respect to the sample before immersion. Is required as. The gel fraction can be adjusted by appropriately setting the type, combination and blending amount of the monomer components constituting the base polymer of the pressure-sensitive adhesive, and the type and blending amount of the cross-linking agent.

The weight average molecular weight of the sol of the third pressure-sensitive adhesive layer is preferably 150,000 to 450,000, more preferably 180,000 to 420,000. The sol content is a soluble component obtained by extracting the base polymer with tetrahydrofuran (THF). When the weight average molecular weight of the sol content is in such a range, a pressure-sensitive adhesive layer having an excellent balance between impact resistance and adhesive holding power can be obtained.

_{The loss tangent tan δ 70 °} C. at 70 ° C. of the third pressure-sensitive adhesive layer is preferably 0.25 or more, more preferably 0.30 or more, and further preferably 0.35 or more. On the other hand, tan δ _{70 ° C.} is preferably 1.0 or less, more preferably 0.9 or less, and further preferably 0.85 or less. The peak top value of tan δ of the third pressure-sensitive adhesive layer is preferably 1.5 or more, more preferably 1.6 or more, and further preferably 1.7 or more. The upper limit of the peak top value can be, for example, 3.0. When tan δ _{70 ° C.} and the peak top value are in such a range, the third pressure-sensitive adhesive layer exhibits appropriate deformation behavior (viscoelastic behavior), so that gaps are less likely to be formed in the deformed portion, and a delay bubble is generated. Can be suppressed.

The glass transition temperature of the third pressure-sensitive adhesive layer is preferably -3 ° C or lower, more preferably -4 ° C or lower. On the other hand, the glass transition temperature is preferably −20 ° C. or higher, more preferably −15 ° C. or higher, and even more preferably −13 ° C. or higher.

D-2. Third Adhesive Constituent Material The third adhesive layer may be composed of any suitable adhesive composition as long as it has the above-mentioned properties. Examples of the base polymer of the pressure-sensitive adhesive composition include (meth) acrylic polymers, silicone-based polymers, polyesters, polyurethanes, polyamides, polyvinyl ethers, vinyl acetate / vinyl chloride copolymers, modified polyolefins, epoxy-based polymers, and fluoropolymers. Examples include rubber-based polymers such as natural rubber and synthetic rubber. Preferably, it is an acrylic pressure-sensitive adhesive composition containing a (meth) acrylic polymer as a base polymer. This is because it is excellent in optical transparency, exhibits adhesive properties such as appropriate wettability, cohesiveness and adhesiveness, and is also excellent in weather resistance and heat resistance.

The (meth) acrylic polymer preferably has a crosslinked structure. More specifically, the (meth) acrylic polymer comprises a (meth) acrylic polymer chain into which a crosslinked structure has been introduced.

D-2-1. (Meta) Acrylic Polymer Chain The (meth) acrylic polymer contains an alkyl (meth) acrylate as a main monomer component. As the alkyl (meth) acrylate, an alkyl (meth) acrylate having an alkyl group having 1 to 20 carbon atoms is preferably used. The alkyl (meth) acrylate may have a branched alkyl group or a cyclic alkyl group. The amount of alkyl (meth) acrylate with respect to the total amount of the monomer components constituting the (meth) acrylic polymer chain is preferably 50% by weight or more, more preferably 55% by weight or more, still more preferably 60% by weight or more. is there. From the viewpoint of setting the glass transition temperature (Tg) of the polymer chain in an appropriate range, the alkyl (meth) acrylate having a chain alkyl group having 4 to 10 carbon atoms with respect to the total amount of the monomer components constituting the (meth) acrylic polymer chain The amount is preferably 40% by weight or more, more preferably 50% by weight or more, and further preferably 55% by weight or more. The monomer component constituting the (meth) acrylic polymer chain is a monomer used for forming a crosslinked structure (polyfunctional (meth) acrylate, urethane (meth) acrylate, etc., which will be described later) from all the monomer components constituting the polymer. ) And the cross-linking agent are excluded.

The (meth) acrylic polymer may contain a hydroxyl group-containing monomer and / or a carboxy group-containing monomer as a monomer component. When the crosslinked structure is introduced by the isocyanate cross-linking agent, the hydroxyl group becomes the reaction point with the isocyanate group, and when the crosslinked structure is introduced by the epoxy-based cross-linking agent, the carboxy group becomes the reaction point with the epoxy group. When a crosslinked structure with a urethane-based segment is introduced into the acrylic polymer chain, the (meth) acrylic polymer has high compatibility with the urethane-based segment and improves the transparency of the third pressure-sensitive adhesive layer. , Preferably contains (meth) acrylate having a hydroxyalkyl group having 4 to 8 carbon atoms as a monomer component.

The amount of the hydroxyl group-containing monomer is preferably 5% by weight to 30% by weight, more preferably 8% by weight to 25% by weight, still more preferably 10% by weight, based on the total amount of the monomer components constituting the (meth) acrylic polymer chain. It is from% by weight to 20% by weight.

When the third pressure-sensitive adhesive layer can come into contact with the touch panel sensor, for example, the third pressure-sensitive adhesive layer preferably has a small acid content in order to prevent corrosion of the electrode due to the acid component. In this case, the amount of the carboxy group-containing monomer with respect to the total amount of the monomer components constituting the (meth) acrylic polymer chain is preferably 0.5% by weight or less, more preferably 0.1% by weight or less, and further preferably. Is 0.05% by weight or less, ideally 0 (zero).

The (meth) acrylic polymer may contain a nitrogen-containing monomer as a monomer component. The (meth) acrylic polymer appropriately contains a highly polar monomer such as a hydroxyl group-containing monomer, a carboxy group-containing monomer, and a nitrogen-containing monomer as a monomer component, thereby achieving a balance between storage elasticity, adhesive retention, and impact resistance. It is possible to form an excellent pressure-sensitive adhesive layer. The amount of highly polar monomer (total of hydroxyl group-containing monomer, carboxy group-containing monomer and nitrogen-containing monomer) with respect to the total amount of the monomer components constituting the (meth) acrylic polymer chain is preferably 15% by weight to 45% by weight, more preferably. Is 20% by weight to 40% by weight, more preferably 25% by weight to 37% by weight. In particular, it is preferable that the total of the hydroxyl group-containing monomer and the nitrogen-containing monomer is within the above range. The amount of the nitrogen-containing monomer with respect to the total amount of the monomer components constituting the (meth) acrylic polymer chain is preferably 7% by weight to 30% by weight, more preferably 10% by weight to 25% by weight, still more preferably 12%. It is from% by weight to 22% by weight.

The (meth) acrylic polymer may further contain any suitable monomer component depending on the purpose. Specific examples of such a monomer component include an acid anhydride group-containing monomer, a caprolactone additive of (meth) acrylic acid, a sulfonic acid group-containing monomer, a phosphoric acid group-containing monomer, vinyl acetate, vinyl propionate, styrene, and α-. Vinyl-based monomers such as methylstyrene; cyano group-containing acrylic monomers such as acrylonitrile and methacrylonitrile; epoxy group-containing monomers such as glycidyl (meth) acrylate; polyethylene glycol (meth) acrylate, polypropylene glycol (meth) acrylate. Glycol-based acrylic ester monomers such as (meth) methoxyethylene glycol (meth) acrylate, (meth) methoxypolypropylene glycol (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, fluorine (meth) acrylate, silicone (meth) acrylate, (meth) Examples thereof include acrylic acid ester-based monomers such as 2-methoxyethyl acrylate.

The (meth) acrylic polymer preferably contains the most alkyl (meth) acrylate as a monomer component, and more preferably contains the most alkyl (meth) acrylate having a chain alkyl group having 6 or less carbon atoms. The amount of the alkyl (meth) acrylate having a chain alkyl group having 6 or less carbon atoms with respect to the total amount of the monomer components constituting the (meth) acrylic polymer chain is preferably 40% by weight to 85% by weight, more preferably 45. It is from% to 80% by weight, more preferably 50% to 75% by weight. In particular, the content of butyl acrylate as a monomer component is preferably in the above range.

D-2-2. Crosslinked structure A polymer in which a crosslinked structure is introduced into a (meth) acrylic polymer chain is prepared by, for example, (1) polymerizing a (meth) acrylic polymer having a functional group capable of reacting with a crosslinking agent, and then adding a crosslinking agent. , A method of reacting a (meth) acrylic polymer with a cross-linking agent; and (2) a method of introducing a branched structure (cross-linked structure) into a polymer chain by including a polyfunctional compound in the polymer component of the polymer, etc. Obtained by These may be used together.

Specific examples of the cross-linking agent in the method of reacting the base polymer of the above (1) with the cross-linking agent include an isocyanate-based cross-linking agent, an epoxy-based cross-linking agent, an oxazoline-based cross-linking agent, an aziridine-based cross-linking agent, a carbodiimide-based cross-linking agent, and a metal. Examples include a chelate-based cross-linking agent. Of these, isocyanate-based cross-linking agents and epoxy-based cross-linking agents are preferable because they have high reactivity with the hydroxyl groups and carboxy groups of the base polymer and the cross-linked structure can be easily introduced. These cross-linking agents react with functional groups such as hydroxyl groups and carboxy groups introduced into the base polymer to form a cross-linked structure.

In the method (2) of including the polyfunctional compound in the polymerization component of the base polymer, even if the monomer component constituting the (meth) acrylic polymer and the total amount of the polyfunctional compound for introducing the crosslinked structure are reacted at one time. Often, the polymerization may be carried out in multiple stages. As a method of performing polymerization in multiple steps, a partial polymer (prepolymer composition) is prepared by polymerizing (prepolymerizing) a monofunctional monomer constituting a (meth) acrylic polymer, and the prepolymer composition is often used. A method of adding a polyfunctional compound such as a functional (meth) acrylate to polymerize (mainly polymerize) the prepolymer composition and the polyfunctional monomer is preferable. The prepolymer composition is a partial polymer containing a polymer having a low degree of polymerization and an unreacted monomer.

By prepolymerizing the constituent components of the (meth) acrylic polymer, branch points (crosslink points) due to the polyfunctional compound can be uniformly introduced into the (meth) acrylic polymer. Further, after applying a low molecular weight polymer or a mixture of a partial polymer and a non-polymerized monomer component (adhesive composition) on a base material, main polymerization is performed on the base material to form a pressure-sensitive adhesive layer. You can also do it. Since low-polymerization compositions such as prepolymer compositions have low viscosity and excellent coatability, it is a method of performing main polymerization on a substrate after applying a pressure-sensitive adhesive composition which is a mixture of a prepolymer composition and a polyfunctional compound. Therefore, the productivity of the pressure-sensitive adhesive layer can be improved, and the thickness of the pressure-sensitive adhesive layer can be made uniform.

Examples of the polyfunctional compound used for introducing the crosslinked structure include compounds containing two or more polymerizable functional groups (ethylenically unsaturated groups) having an unsaturated double bond in one molecule. As the polyfunctional compound, a polyfunctional (meth) acrylate is preferable because it can be easily copolymerized with the monomer component of the (meth) acrylic polymer. When a branched (crosslinked) structure is introduced by active energy ray polymerization (photopolymerization), polyfunctional (meth) acrylate is preferable. Further, by using a urethane (meth) acrylate having a (meth) acryloyl group at the end of the urethane chain as the polyfunctional (meth) acrylate, a crosslinked structure with urethane-based segments can be introduced.

D-2-3. Introduction of cross-linked structure by urethane-based segment By cross-linking the (meth) acrylic polymer chain with the urethane-based segment, it is easy to obtain an adhesive that can achieve both a low glass transition temperature and a high adhesive holding force. The urethane-based segment is a molecular chain having a urethane bond, and both ends of the urethane-based segment are covalently bonded to the (meth) acrylic polymer chain to crosslink the (meth) acrylic polymer chain with the urethane-based segment. The structure is introduced. The urethane-based segment typically contains a polyurethane chain obtained by reacting a diol with a diisocyanate.

The molecular weight of the polyurethane chain in the urethane-based segment is preferably 5,000 to 30,000, more preferably 6,000 to 23,000, and even more preferably 7,000 to 20,000. The larger the molecular weight of the polyurethane chain in the urethane-based segment, the longer the distance between the cross-linking points of the (meth) acrylic polymer chain. When the molecular weight of the polyurethane chain is within the above range, the polymer into which the crosslinked structure has been introduced has appropriate cohesiveness and fluidity, so that both adhesive strength, step absorption and impact resistance can be achieved at the same time.

The amount of the urethane-based segment in the (meth) acrylic polymer is preferably 10 parts by weight or less, more preferably 7 parts by weight or less, still more preferably 5 parts by weight, based on 100 parts by weight of the acrylic polymer chain. It is as follows. On the other hand, the amount of the urethane-based segment is preferably 0.3 parts by weight or more, more preferably 0.4 parts by weight or more, still more preferably 0.5 parts by weight, based on 100 parts by weight of the acrylic polymer chain. It is more than a part by weight. When the amount of the urethane-based segment is within such a range, an adhesive layer having an excellent balance of impact resistance, transparency and adhesive holding power can be obtained.

Examples of the diol used for forming the polyurethane chain include low molecular weight diols such as ethylene glycol, diethylene glycol, propylene glycol, butylene glycol and hexamethylene glycol; polyester polyol, polyether polyol, polycarbonate polyol, acrylic polyol, epoxy polyol, caprolactone polyol and the like. High molecular weight polyols of.

The diisocyanate used to form the polyurethane chain may be either an aromatic diisocyanate or an aliphatic diisocyanate. Examples of the aromatic diisocyanis include 1,5-naphthalenediocyanis, 4,4'-diphenylmethane diisocyanate (MDI), 4,4'-diphenyldimethylmethane diisocyanate, tetramethyldiphenylmethane diisocyanate, 1,3-phenylenediisocyanate, 1,4-. Phoenix diisocyanis, 2-chloro-1,4-phenyl diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, xylylene diisocyanate, 4,4'-diphenyl ether diisocyanate, 4,4'-diphenyl sulfoxide diisocyanate , 4,4'-diphenylsulfone diisocyanate, 4,4'-biphenyldiisocyanate and the like. Aliphatic diisocyanates include butane-1,4-diisocyanate, hexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, cyclohexane-1,4-diisocyanate, and isophorone diisocyanate. , Dicyclohexylmethane-4,4'-diisocyanate, 1,3-bis (isocyanatemethyl) cyclohexane, methylcyclohexane diisocyanate and the like. A derivative of an isocyanate compound can also be used as the diisocyanate. Derivatives of the isocyanate compound include dimer of polyisocyanate, trimer of isocyanate (isocyanurate), polypeptide MDI, adduct with trimethylolpropane, biuret modified product, allophanate modified product, urea modified product and the like. .. As the diisocyanate component, a urethane prepolymer having an isocyanate group at the terminal may be used.

Among the exemplified polyurethane chains, a polyether urethane having a polyether polyol as a diol component and / or a polyester urethane having a polyester polyol as a diol component are included because of their high compatibility with the (meth) acrylic polymer chain. Is preferable.

By using a compound having a functional group copolymerizable with the monomer component constituting the (meth) acrylic polymer chain at the end of the polyurethane chain, or by using a carboxy contained in the (meth) acrylic polymer chain at the end of the polyurethane chain. By using a compound having a functional group capable of reacting with a group, a hydroxyl group, or the like, a crosslinked structure by a urethane-based segment can be introduced into the (meth) acrylic polymer chain. Since it is easy to uniformly introduce cross-linking points into the (meth) acrylic polymer chain and the compatibility between the (meth) acrylic polymer chain and the urethane segment is excellent, (meth) acryloyl groups are formed at both ends of the polyurethane chain. It is preferable to introduce a crosslinked structure with urethane-based segments using urethane di (meth) acrylate having. For example, by copolymerizing the monomer component constituting the (meth) acrylic polymer chain with the urethane di (meth) acrylate, a crosslinked structure by the urethane segment can be introduced into the (meth) acrylic polymer chain.

In one embodiment, the pressure-sensitive adhesive (pressure-sensitive adhesive composition) constituting the third pressure-sensitive adhesive layer has a thickness corresponding to the thickness of the third pressure-sensitive adhesive layer, and release films are temporarily adhered to both sides. Can be provided as a finished adhesive sheet.

D-3. Another Constituent Material As another example of the pressure-sensitive adhesive composition constituting the third pressure-sensitive adhesive layer, those described in JP-A-2016-94569 can be mentioned. The description of this publication is incorporated herein by reference.

E. Set of Optical Members As described in item D above, the pressure-sensitive adhesive (adhesive composition) constituting the third pressure-sensitive adhesive layer can be provided as a pressure-sensitive adhesive sheet. In the production of the image display device, the pressure-sensitive adhesive sheet may be provided as a set of optical members together with a first polarizing plate (visualizing side polarizing plate). Therefore, such a set of optical members is also included in the embodiments of the present invention. In one embodiment, the set of optical members may further include a second polarizing plate (backside polarizing plate). That is, in the production of the image display device, the pressure-sensitive adhesive sheet, the first polarizing plate (visualizing side polarizing plate) and the second polarizing plate (back surface side polarizing plate) can be provided as a set of optical members.

Hereinafter, the present invention will be specifically described with reference to Examples, but the present invention is not limited to these Examples. The measurement method of each characteristic in the examples is as follows.

(1) Thickness The thickness of 10 μm or less was measured using an interference film thickness meter (manufactured by Otsuka Electronics Co., Ltd., product name “MCPD-3000”). The thickness exceeding 10 μm was measured using a digital micrometer (manufactured by Anritsu, product name “KC-351C”).
(2) Gel fraction A sample of the insoluble component after cross-linking the pressure-sensitive adhesive constituting the third pressure-sensitive adhesive layer used in Examples and Comparative Examples and immersing it in ethyl acetate at 23 ° C. for 7 days before immersion. It was calculated as a weight fraction (unit: weight%) with respect to.
(3) Storage elastic modulus With respect to the adhesive constituting the third adhesive layer used in Examples and Comparative Examples, 60 based on JIS K 7244 using a dynamic viscoelasticity measuring device "ARES" manufactured by Leometric Co., Ltd. The storage elastic modulus at ° C was measured.
(4) Size of Adhesive Void Part Observe with an optical microscope the state of the cross section of the first pressure-sensitive adhesive layer in the deformed portion of the first polarizing plate (visualizing side polarizing plate) used in Examples and Comparative Examples. The length of the portion where the loss of the pressure-sensitive adhesive layer from the outer edge to the inside in the plane direction was maximized was measured, and the size of the pressure-sensitive adhesive gap was L (μm).
(5) Bubbles With respect to the image display device compatible products obtained in Examples and Comparative Examples, the state of bubbles is visually or optically observed at two time points, immediately after vacuum laminating and after a heating test (85 ° C., 24 hours) after vacuum laminating. It was observed with a microscope and evaluated according to the following criteria. At the stage before vacuum laminating (only the adhesive sheet was bonded), air bubbles were observed in all the products compatible with the image display device.
4: No bubbles immediately after vacuum lamination and after heating test 3: Some bubbles are present immediately after vacuum lamination and after heating test 2: Some bubbles are present immediately after vacuum lamination and many bubbles are present after heating test 1: Vacuum There are many bubbles both immediately after laminating and after the heating test.

<Production Example 1: Preparation of Adhesive Constituting First Adhesive Layer>
80.3 parts of butyl acrylate (BA), 16 parts of phenoxyethyl acrylate (PEA), N-vinyl-2-pyrrolidone (NVP) in a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen gas introduction tube, and a cooler. ), A monomer mixture containing 3 parts, 0.3 part of acrylic acid (AA) and 0.4 part of 4-hydroxybutyl acrylate (4HBA) was charged. Further, with respect to 100 parts of the monomer mixture (solid content), 0.1 part of 2,2'-azobisisobutyronitrile as a polymerization initiator was charged together with 100 parts by weight of ethyl acetate, and nitrogen gas was added while gently stirring. After the introduction and substitution with nitrogen, the liquid temperature in the flask was maintained at around 55 ° C. and the polymerization reaction was carried out for 8 hours to prepare a solution of an acrylic polymer having a weight average molecular weight (Mw) of 1.56 million. 0.1 part of isocyanate cross-linking agent (trade name: Takenate D160N, trimethylolpropane hexamethylene diisocyanate, manufactured by Mitsui Chemicals, Inc.), benzoyl peroxide (trade name: Takenate D160N, manufactured by Mitsui Chemicals, Inc.) with respect to 100 parts of the solid content of the obtained acrylic polymer solution. Product name: Niper BMT 40SV, manufactured by Nippon Oil & Fats Co., Ltd. 0.3 parts, thiol group-containing silane coupling agent (trade name: X-41-1810, manufactured by Shinetsu Chemical Industry Co., Ltd., amount of alkoxy group: 30% , Thiol equivalent: 450 g / mol) 0.3 part and antioxidant (trade name: Irganox 1010, hindered phenol type, manufactured by BASF Japan) 0.2 part are blended to prepare the pressure-sensitive adhesive composition a. Obtained.

<Manufacturing Example 2: Preparation of Adhesive Sheet Constituting Third Adhesive Layer>
2-Ethylhexyl acrylate (2EHA): 40.5 parts by weight, Isostearyl acrylate (ISTA): 40.5 parts by weight, N-vinyl-2-pyrrolidone (NVP): 18 parts by weight, 4-hydroxybutyl acrylate ( 4HBA): A monomer mixture composed of 1 part by weight, a photopolymerization initiator (trade name "Irgacure 651", manufactured by BASF): 0.05 parts by weight, and a photopolymerization initiator (trade name "Irgacure 184"). , BASF): After blending 0.5 parts by weight, irradiate with ultraviolet rays until the viscosity (BH viscometer No. 5 rotor, 10 rpm, measurement temperature 30 ° C.) reaches about 20 Pa · s to obtain the above-mentioned monomer component. A prepolymer composition in which a part of the above was polymerized was obtained.
Trimethylolpropane triacrylate (TMPTA): 0.02 parts by weight and a silane coupling agent (trade name "KBM-403", manufactured by Shin-Etsu Chemical Co., Ltd.): 0.3 parts by weight are mixed with the above prepolymer composition. Then, an acrylic pressure-sensitive adhesive composition was obtained.
The acrylic pressure-sensitive adhesive composition was applied onto a polyethylene terephthalate (PET) -based release liner (manufactured by Nitto Denko KK, thickness: 125 μm) to form a pressure-sensitive adhesive composition layer. Next, a PET-based release liner (manufactured by Nitto Denko Corporation, thickness: 125 μm) was provided on the pressure-sensitive adhesive composition layer, and the pressure-sensitive adhesive composition layer was coated to block oxygen. In this way, a laminate having the structure of [release liner / pressure-sensitive adhesive composition layer / release liner] was obtained.
From the upper surface (release liner side) of the laminate obtained above, ^{ultraviolet rays having an illuminance of 3 mW / cm 2} were irradiated with a black light (manufactured by Toshiba Corporation) for 300 seconds. Further, a drying treatment was carried out in a dryer at 90 ° C. for 2 minutes to volatilize the residual monomer to obtain a pressure-sensitive adhesive sheet I having a thickness of 250 μm. Storage modulus at 60 ° C. of the pressure-sensitive adhesive constituting the pressure-sensitive adhesive sheet I is 1.9 × ¹⁰ 4 Pa, a gel fraction was 40%.

<Manufacturing Example 3: Preparation of Adhesive Sheet Constituting Third Adhesive Layer>
Light in a monomer mixture composed of 2-ethylhexyl acrylate (2EHA): 78 parts by weight, N-vinyl-2-pyrrolidone (NVP): 18 parts by weight, 2-hydroxyethyl acrylate (HEA): 4 parts by weight. After blending a polymerization initiator (trade name "Irgacure 651", manufactured by BASF): 0.05 parts by weight and a photopolymerization initiator (trade name "Irgacure 184", manufactured by BASF): 0.05 parts by weight. , UV irradiation was performed until the viscosity (BH viscometer No. 5 rotor, 10 rpm, measurement temperature 30 ° C.) reached about 20 Pa · s to obtain a prepolymer composition in which a part of the above monomer components was polymerized.
2-Hydroxyethyl acrylate (HEA): 18 parts by weight and a silane coupling agent (trade name "KBM-403", manufactured by Shin-Etsu Chemical Co., Ltd.): 0.3 parts by weight are mixed with the above prepolymer composition. , An acrylic pressure-sensitive adhesive composition was obtained. The following procedure was the same as in Production Example 2 to obtain an adhesive sheet II having a thickness of 250 μm. Storage modulus at 60 ° C. of the pressure-sensitive adhesive constituting the pressure-sensitive adhesive sheet II is 8.6 × ¹⁰ 4 Pa, a gel fraction was 85%.

<Manufacturing Example 4: Preparation of Adhesive Sheet Constituting Third Adhesive Layer>
N-butyl acrylate (BA): 57 parts by weight, cyclohexyl acrylate (CHA): 12 parts by weight, 4-hydroxybutyl acrylate (4HBA): 23 parts by weight, 2-hydroxyethyl acrylate (HEA): 8 parts by weight A photopolymerization initiator (trade name "Irgacure 651", manufactured by BASF): 0.05 parts by weight and a photopolymerization initiator (trade name "Irgacure 184", manufactured by BASF): After blending 0.05 parts by weight, UV irradiation was performed until the viscosity (BH viscometer No. 5 rotor, 10 rpm, measurement temperature 30 ° C.) reached about 20 Pa · s, and a part of the above monomer components was polymerized. A prepolymer composition was obtained.
Dipentaerythritol hexaacrylate (DPHA): 0.1 part by weight and silane coupling agent (trade name "KBM-403", manufactured by Shin-Etsu Chemical Co., Ltd.): 0.3 parts by weight are mixed with the above prepolymer composition. Then, an acrylic pressure-sensitive adhesive composition was obtained.
Adhesive sheet III having a thickness of 250 μm in the same manner as in Production Example 2 except that a PET film (thickness: 100 μm, in-plane retardation Re: 10000 nm) was used as the PET film using the acrylic pressure-sensitive adhesive composition. Got Storage modulus at 60 ° C. of the pressure-sensitive adhesive constituting the pressure-sensitive adhesive sheet III is 10.6 × ¹⁰ 4 Pa, a gel fraction was 85%.

<Example 1>
1. 1. Preparation of First Polarizer An amorphous isophthalic copolymerized polyethylene terephthalate film (thickness: 100 μm) having a long shape and a Tg of about 75 ° C. was used as a thermoplastic resin base material. One side of the resin base material was corona-treated.
100 weight of PVA-based resin in which polyvinyl alcohol (degree of polymerization 4200, saponification degree 99.2 mol%) and acetoacetyl-modified PVA (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name "Gosefimer Z410") are mixed at a ratio of 9: 1. 13 parts by weight of potassium iodide was added to the part to prepare a PVA aqueous solution (coating liquid).
The PVA aqueous solution was applied to the corona-treated surface of the resin base material and dried at 60 ° C. to form a PVA-based resin layer having a thickness of 13 μm to prepare a laminate.
The obtained laminate was uniaxially stretched at the free end 2.4 times in the longitudinal direction (longitudinal direction) between rolls having different peripheral speeds in an oven at 130 ° C. (aerial auxiliary stretching treatment).
Next, the laminate was immersed in an insolubilizing bath at a liquid temperature of 40 ° C. (an aqueous boric acid solution obtained by blending 4 parts by weight of boric acid with 100 parts by weight of water) for 30 seconds (insolubilization treatment).
Next, in a dyeing bath having a liquid temperature of 30 ° C. (an aqueous iodine solution obtained by mixing iodine and potassium iodide in a weight ratio of 1: 7 with respect to 100 parts by weight of water), the polarizer finally obtained Immersion was carried out for 60 seconds while adjusting the concentration so that the simple substance transmittance (Ts) was 43% (dyeing treatment).
Next, it was immersed in a cross-linked bath at a liquid temperature of 40 ° C. (an aqueous boric acid solution obtained by blending 3 parts by weight of potassium iodide and 5 parts by weight of boric acid with respect to 100 parts by weight of water) for 30 seconds. (Crossing treatment).
Then, while immersing the laminate in a boric acid aqueous solution (boric acid concentration 4.0% by weight, potassium iodide 5.0% by weight) at a liquid temperature of 70 ° C., the rolls having different peripheral speeds are subjected to the longitudinal direction (longitudinal direction). ) Was uniaxially stretched so that the total stretching ratio was 5.5 times (underwater stretching treatment).
Then, the laminate was immersed in a washing bath at a liquid temperature of 20 ° C. (an aqueous solution obtained by blending 4 parts by weight of potassium iodide with 100 parts by weight of water) (cleaning treatment).
Then, while drying in an oven kept at 90 ° C., it was brought into contact with a heating roll made of SUS whose surface temperature was kept at 75 ° C. for about 2 seconds (dry shrinkage treatment). The shrinkage rate in the width direction of the laminated body by the drying shrinkage treatment was 2%.
In this way, a first polarizer having a thickness of 5.0 μm was formed on the resin substrate.

2. Preparation of First Polarizing Plate An HC-TAC film was attached to the surface of the polarizer of the resin substrate / first polarizing element laminate obtained above via an ultraviolet curable adhesive. The HC-TAC film is a film in which a hard coat (HC) layer (thickness 7 μm) is formed on a triacetyl cellulose (TAC) film (thickness 25 μm), and the TAC film is attached so as to be on the polarizer side. I matched it. Next, the resin base material is peeled off, a first pressure-sensitive adhesive layer (thickness 20 μm) is formed on the peeled surface using the pressure-sensitive adhesive composition a obtained in Production Example 1, and an outer protective layer (HC-TAC film) is formed. A polarizing plate having the composition of / first polarizer / first pressure-sensitive adhesive layer was obtained. This polarizing plate was punched to a size of 148 mm in length and 70 mm in width, and a through hole having a diameter of 3.9 mm was further formed in a corner portion. At this time, punching was performed so that the absorption axis direction of the polarizer was in the lateral direction. In this way, the first polarizing plate (visualizing side polarizing plate) A was obtained. The thickness of the first polarizing plate A was 37 μm, and the size L of the pressure-sensitive adhesive gap was 50 μm.

3. 3. Manufacture of products compatible with image display devices On one surface of a glass plate (corresponding to image display cells), the above 2. The first polarizing plate (visualizing side polarizing plate) A obtained in 1 above was bonded via the first pressure-sensitive adhesive layer. Next, the light release surface separator of the pressure-sensitive adhesive sheet I obtained in Production Example 2 was peeled off and bonded to a cover glass (manufactured by Matsunami Glass Co., Ltd., thickness 0.8 mm) with a roll laminator. The other separator of the pressure-sensitive adhesive I of the laminated body was peeled off, and the surface of the first polarizing plate A was brought into close contact with the surface using a vacuum laminator, and the through holes were filled with the pressure-sensitive adhesive sheet. The conditions for vacuum laminating were as follows: warm crimping at 0.2 MPa, 60 ° C. (standby time 90 seconds), followed by vacuum laminating at 100 Pa for 10 seconds. A commercially available polarizing plate with an adhesive layer was attached to the other surface of the glass plate by a conventional method as a second polarizing plate (back surface side polarizing plate). In this way, a product compatible with the image display device was produced. The obtained image display device compatible product was subjected to the evaluation of (5) above. The results are shown in Table 1.

<Example 2>
An image display device compatible product was produced in the same manner as in Example 1 except that the size L of the pressure-sensitive adhesive gap portion of the first polarizing plate was set to 100 μm. The obtained image display device compatible product was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

<Example 3>
An image display device compatible product was produced in the same manner as in Example 1 except that the thickness of the first pressure-sensitive adhesive layer was 15 μm. The obtained image display device compatible product was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

<Example 4>
An image display device compatible product was produced in the same manner as in Example 3 except that the size L of the pressure-sensitive adhesive gap portion of the first polarizing plate was set to 100 μm. The obtained image display device compatible product was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

<Example 5>
An image display device compatible product was produced in the same manner as in Example 1 except that the thickness of the first pressure-sensitive adhesive layer was 5 μm. The obtained image display device compatible product was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

<Example 6>
An image display device compatible product was produced in the same manner as in Example 5 except that the size L of the pressure-sensitive adhesive gap portion of the first polarizing plate was set to 100 μm. The obtained image display device compatible product was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

<Comparative Examples 1 to 6>
Products compatible with the image display device were produced in the same manner as in Examples 1 to 6 except that the thickness of the third pressure-sensitive adhesive layer was 150 μm. The obtained image display device compatible product was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

<Comparative Example 7>
As the first polarizer, a film (thickness 12 μm) obtained by adding iodine to a long polyvinyl alcohol (PVA) -based resin film and uniaxially stretching it in the longitudinal direction (MD direction) was used. An acrylic resin film (thickness 20 μm) serving as an outer protective layer and a triacetyl cellulose (TAC) film (thickness 25 μm) serving as an inner protective layer are bonded to both sides of the polarizer, and Production Example 1 is applied to the surface of the inner protective layer. The first pressure-sensitive adhesive layer (thickness 20 μm) was formed using the pressure-sensitive adhesive composition a obtained in the above method, and the outer protective layer (acrylic resin film) / first polarizer / inner protective layer (TAC film) / A polarizing plate having the structure of the first pressure-sensitive adhesive layer was obtained. This polarizing plate was punched in the same manner as in Example 1 to form through holes. In this way, the first polarizing plate (visualizing side polarizing plate) B was obtained. The thickness of the first polarizing plate B was 57 μm, and the size L of the pressure-sensitive adhesive gap was 50 μm. An image display device compatible product was produced in the same manner as in Example 1 except that the first polarizing plate B obtained above was used. The obtained image display device compatible product was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

<Comparative Example 8>
An image display device compatible product was produced in the same manner as in Comparative Example 7 except that the size L of the pressure-sensitive adhesive gap portion of the first polarizing plate was set to 100 μm. The obtained image display device compatible product was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

<Comparative Example 9>
As the first polarizer, a film (thickness 18 μm) obtained by adding iodine to a long polyvinyl alcohol (PVA) -based resin film and uniaxially stretching it in the longitudinal direction (MD direction) was used. An acrylic resin film (thickness 40 μm) serving as an outer protective layer and a TAC film (thickness 40 μm) serving as an inner protective layer are bonded to both sides of the polarizer, and the adhesive obtained in Production Example 1 is attached to the surface of the inner protective layer. A first pressure-sensitive adhesive layer (thickness 15 μm) is formed using the agent composition a, and an outer protective layer (acrylic resin film) / first polarizer / inner protective layer (TAC film) / first pressure-sensitive adhesive. A polarizing plate having a layer structure was obtained. This polarizing plate was punched in the same manner as in Example 1 to form through holes. In this way, the first polarizing plate (visualizing side polarizing plate) C was obtained. The thickness of the first polarizing plate C was 98 μm, and the size L of the pressure-sensitive adhesive gap was 50 μm. An image display device compatible product was produced in the same manner as in Example 1 except that the first polarizing plate C obtained above was used. The obtained image display device compatible product was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

<Comparative Example 10>
An image display device compatible product was produced in the same manner as in Comparative Example 9 except that the size L of the pressure-sensitive adhesive gap portion of the first polarizing plate was set to 100 μm. The obtained image display device compatible product was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

<Comparative Examples 11 to 16>
An image display device compatible product was produced in the same manner as in Examples 1 to 6 except that the pressure-sensitive adhesive sheet II obtained in Production Example 3 was used instead of the pressure-sensitive adhesive sheet I as the third pressure-sensitive adhesive layer. The obtained image display device compatible product was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

<Comparative Examples 17 to 22>
An image display device compatible product was produced in the same manner as in Examples 1 to 6 except that the pressure-sensitive adhesive sheet III obtained in Production Example 4 was used instead of the pressure-sensitive adhesive sheet I as the third pressure-sensitive adhesive layer. The obtained image display device compatible product was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

<Evaluation>
As is clear from Table 1, according to the embodiment of the present invention, in the image display device in which the deformed portion is filled with the adhesive, the thickness of the viewing side polarizing plate and the thickness of the viewing side adhesive layer and By setting the storage elastic modulus within a predetermined range, bubbles can be remarkably suppressed. Further, the air bubbles can be further suppressed by making the adhesive gap portion in the deformed portion smaller.

The image display device of the present invention can be suitably used as an image display device having a deformed processing portion typified by an automobile instrument panel, a smartphone, a tablet PC or a smart watch.

10 First polarizing plate 11 First polarizing element 12 Outer protective layer 13 Inner protective layer 14 First adhesive layer 15 Deformed part 20 Second polarizing plate 21 Second polarizing element 22 Outer protective layer 23 Inner protection Layer 24 Second adhesive layer 25 Deformed part 30 Third adhesive layer 40 Cover glass 100 Image display cell 200 Image display device

Claims

An image display cell; a first polarizing plate containing a first polarizing element and a first pressure-sensitive adhesive layer, and laminated on the visible side of the image display cell via the first pressure-sensitive adhesive layer; A second polarizing plate including the polarizing element of the above and a second pressure-sensitive adhesive layer and laminated on the back surface side of the image display cell via the second pressure-sensitive adhesive layer; the visible side of the first polarizing plate. With a third pressure-sensitive adhesive layer arranged in;
The first polarizing plate and the second polarizing plate have a deformed processed portion at positions corresponding to each other, and the deformed processed portion of the first polarizing plate constitutes a third pressure-sensitive adhesive layer. Filled with
The thickness of the first polarizing plate is 90 μm or less, the thickness of the third pressure-sensitive adhesive layer is 170 μm or more, and the storage elastic modulus of the third pressure-sensitive adhesive layer at 60 ° C. is 8.0 × 10 4. Less than Pa,
Image display device.
An image display cell; a first polarizing plate containing a first polarizer and a first pressure-sensitive adhesive layer and laminated on the visible side of the image display cell via the first pressure-sensitive adhesive layer; With a third pressure-sensitive adhesive layer arranged on the visible side of the polarizing plate of 1.
The first polarizing plate has a deformed portion, and the deformed portion of the first polarizing plate is filled with an adhesive constituting a third pressure-sensitive adhesive layer.
The thickness of the first polarizing plate is 90 μm or less, the thickness of the third pressure-sensitive adhesive layer is 170 μm or more, and the storage elastic modulus of the third pressure-sensitive adhesive layer at 60 ° C. is 8.0 × 10 4. Less than Pa,
Image display device.
The deformed portion of the first polarizing plate has a pressure-sensitive adhesive gap portion formed so that the end face of the first pressure-sensitive adhesive layer is located inward in the plane direction with respect to the end face of the first polarizing plate. The image display device according to claim 1 or 2, wherein the size of the pressure-sensitive adhesive gap is 300 μm or less.
The image display device according to any one of claims 1 to 3, wherein the thickness of the first pressure-sensitive adhesive layer is 50 μm or less.
The image display device according to any one of claims 1 to 4, wherein the adhesive force between the first pressure-sensitive adhesive layer and the third pressure-sensitive adhesive layer is 2N / 25 mm or more.
The image display device according to any one of claims 1 to 5, wherein the gel fraction of the third pressure-sensitive adhesive layer is 80% or less.
The image display device according to any one of claims 1 to 6, wherein the deformed processing portion includes a cutting processing portion that becomes a through hole or a concave portion when viewed in a plan view.
The image display device according to claim 7, wherein the recess is a V-shaped notch or a U-shaped notch.
The image display device according to any one of claims 1 to 8, further comprising a cover glass on the visible side of the third pressure-sensitive adhesive layer.
The image display device according to claim 1, wherein the image display device has a camera unit at a position corresponding to the deformed processing portion of the first polarizing plate and the second polarizing plate.
The image display device according to claim 2, further comprising a camera unit at a position corresponding to the deformed processing portion of the first polarizing plate.
The image display device according to any one of claims 1 or 3 to 11, which is a liquid crystal display device.
The image display device according to claim 2, which is an organic EL display device.
With a first polarizing plate containing a first polarizer and a first pressure-sensitive adhesive layer, having a thickness of 90 μm or less, having a deformed portion, and being arranged on the visual side of an image display cell;
A pressure-sensitive adhesive sheet composed of a pressure-sensitive adhesive having a storage elastic modulus at 60 ° C. of 8.0 × 10 4 Pa or less, having a thickness of 200 μm or more, and filling a deformed portion of the first polarizing plate;
A set of optics, including.
The deformed portion of the first polarizing plate has a pressure-sensitive adhesive gap portion formed so that the end face of the first pressure-sensitive adhesive layer is located inward in the plane direction with respect to the end face of the first polarizing plate. The set of optical members according to claim 14, wherein the size of the pressure-sensitive adhesive gap is 300 μm or less.
A second polarizing plate is included, a deformed portion is provided, and a second polarizing plate arranged on the back side of the image display cell is further included, and the first polarizing plate and the second polarizing plate are attached to each other. The set of optical members according to claim 14 or 15, which has a deformed portion at the corresponding position of.