CN114670515A - Display device and substrate laminate - Google Patents

Abstract

The present invention relates to a display device which is a foldable display device, the display device including: the laminated structure includes an optical film member, a first adhesive layer, a window member laminated on one surface of the optical film member via the first adhesive layer, a second adhesive layer, and a laminated structure including a panel member laminated on the other surface of the optical film member via the second adhesive layer, wherein the laminated structure has a layer which is more likely to break than the window member and the optical film member when the surface on the second adhesive layer side is subjected to bending deformation.

Description

Display device and substrate laminate

The present application is a divisional application filed on the basis of the application No. 202080051083.0 entitled "display device and substrate laminate" on the day of 10/5/2020.

Technical Field

The present invention relates to a foldable display device and a substrate laminate used for the display device.

Background

For example, as shown in patent document 1, a touch sensor integrated organic EL display device is known. In the organic EL display device of patent document 1, as shown in fig. 1, an optical layered body 920 is provided on the visible side of an organic EL display panel 901, and a touch panel 930 is provided on the visible side of the optical layered body 920. The optical layered body 920 includes a polarizer 921 and a retardation film 923, both surfaces of which are bonded to protective films 922-1 and 922-2, and the polarizer 921 is provided on the viewing side of the retardation film 923. The touch panel 930 has a structure in which transparent conductive films 916-1 and 916-2 are arranged with a spacer 917 interposed therebetween, and the transparent conductive films 916-1 and 916-2 have a structure in which base films 915-1 and 915-2 and transparent conductive layers 912-1 and 912-2 are stacked.

On the other hand, in recent years, a foldable organic EL display device which is an organic EL display device excellent in portability has been desired.

Documents of the prior art

Patent literature

Patent document 1: japanese laid-open patent publication No. 2014-157745

Disclosure of Invention

Problems to be solved by the invention

However, the conventional organic EL display device, for example, as shown in patent document 1, is not designed in consideration of the bending. When a plastic film is used as the organic EL display panel substrate, flexibility can be imparted to the organic EL display panel. However, layers vulnerable to bending, such as a transparent conductive layer included in a touch sensor member constituting a conventional organic EL display device, a thin film sealing layer of an organic EL display panel, and a hard coat layer provided on the surface of a window member, are broken when the organic EL display device is bent.

Therefore, an object of the present invention is to provide a display device having a foldable structure, in which a layer or a member which is fragile to bending can be prevented from being broken when the display device is bent.

Means for solving the problems

One embodiment of the present invention provides a display device which is a bendable display device,

the display device has: an optical film member, a first adhesive layer, a window member laminated on one surface of the optical film member via the first adhesive layer, a second adhesive layer, and a laminated structure including a panel member laminated on the other surface of the optical film member via the second adhesive layer,

The laminated structure has a layer which is more easily broken than the window member and the optical film member when the surface on the second pressure-sensitive adhesive layer side is subjected to bending deformation,

the difference between the strains A, A 'and B, B' satisfies the relationships of the following expressions (1), (2), and (3), whereby the elongation of the easily breakable layer at the time of bending deformation is suppressed to a value smaller than the elongation at break,

0.3＜A/A’＜1.2····(1)

B/B’＜1.7A/A’－0.15····(2)

0＜B/B’＜1.25····(3)

wherein the strain differences A, A ', B, B' are defined as follows:

bending the display device at an angle of 180 DEG with the window member as an outer side, and bending and deforming the display device so that the distance between the parallel opposed outermost surfaces of the display device becomes 4mm in a state of being bent at an angle of 180 DEG, wherein the difference between the strain in the direction orthogonal to the bending radius direction generated on the one surface of the optical film member at this time and the strain in the direction orthogonal to the bending radius direction generated on the surface of the window member facing the first adhesive layer is defined as A,

bending the optical film member and the window member at an angle of 180 degrees in a single layer state, and bending the optical film member and the window member so that the distance between the parallel facing outermost surfaces of the optical film member and the window member becomes 4mm in a state of being bent at an angle of 180 degrees, in the same manner as when bending the display device, the outer side and the inner side at the time of bending deformation, and the difference between the strain in the direction orthogonal to the bending radius direction generated at the outer side surface of the optical film member and the strain in the direction orthogonal to the bending radius direction generated at the inner side surface of the window member at that time is defined as a',

Bending the display device at an angle of 180 DEG with the window member as an outer side, and bending the display device so that a distance between the parallel facing outermost surfaces of the display device becomes 4mm in a state of being bent at an angle of 180 DEG, wherein B is a difference between a strain in a direction orthogonal to a bending radius direction generated on the other surface of the optical film member and a strain in a direction orthogonal to the bending radius direction generated on the surface facing the second adhesive layer of the laminated structure at this time,

in the same manner as in the case of bending the display device, the outer side and the inner side in the bending deformation are bent at an angle of 180 ° in a single layer state, and the bending deformation is caused so that the distance between the parallel facing outermost surfaces of the optical film member and the laminated structure becomes 4mm in the state of being bent at an angle of 180 °, and the difference between the strain in the direction orthogonal to the bending radius direction generated on the inner side surface of the optical film member at this time and the strain in the direction orthogonal to the bending radius direction generated on the outer side surface of the laminated structure is defined as B'.

The window member may have a hard coat layer on a surface opposite to the first adhesive layer.

The optical film member may be a circularly polarized light functional film laminate in which a retardation film is laminated on a polarizing film.

The polarizing film may be a laminate of a polarizer and a polarizer protective film on at least one surface of the polarizer.

The polarizer protective film may include an acrylic resin.

The layer which is more easily broken than the window member and the optical film member may be a film seal layer formed on the surface of the panel member on the second pressure-sensitive adhesive layer side.

The laminated structure may be configured such that a film seal layer is formed on the surface of the panel member on the second adhesive layer side, a touch sensor member is laminated on the surface of the film seal layer on the opposite side to the panel member via a third adhesive layer, and a transparent conductive layer is formed on the surface of the touch sensor member on the opposite side to the panel member, the transparent conductive layer being laminated on the second adhesive layer as a layer which is more easily broken than the window member and the optical film member.

The difference A, A' between the strains may further satisfy the following equation (4),

0.8＜A/A’····(4)。

the shear modulus of the second adhesive layer may be greater than the shear modulus of the first adhesive layer.

The panel member may further include a fourth adhesive layer on a surface thereof opposite to the second adhesive layer, and a protective member may be laminated via the fourth adhesive layer.

The shear modulus of the fourth adhesive layer may be less than the shear modulus of the second adhesive layer and less than the shear modulus of the third adhesive layer.

An aspect of the present invention provides a substrate laminate used in the display device, the substrate laminate including: the touch sensor includes an optical film member, a window member laminated on one surface of the optical film member via the first adhesive layer, and a touch sensor member including a transparent conductive layer laminated on the other surface of the optical film member via the second adhesive layer.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, a display device which can be configured to be bendable and which can suppress breakage of a layer or a member which is fragile to bending when the display device is bent can be realized.

Hereinafter, embodiments of the display device of the present invention will be described in detail with reference to the drawings.

Drawings

Fig. 1 is a sectional view showing a conventional organic EL display device.

Fig. 2 is a sectional view showing a display device according to an embodiment of the present invention.

Fig. 3 is a sectional view showing a display device according to another embodiment of the present invention.

Fig. 4 is a view showing a method for manufacturing a retardation film used in one embodiment.

Fig. 5 is a diagram showing a simulation method of the embodiment of the present invention.

Fig. 6 is a diagram illustrating strain perpendicular to the bending radius direction.

Fig. 7 is a graph showing the strain distribution in the lamination direction of the example and the comparative example in which the shear modulus G' of the second adhesive layer was changed.

Fig. 8 is a graph showing the strain distribution in the lamination direction of the embodiment in which the shear modulus G' of the third adhesive layer is changed.

Fig. 9 is a graph showing the strain distribution in the lamination direction of the embodiment in which the shear modulus G' of the fourth adhesive layer is changed.

Fig. 10 is a graph showing the strain distribution in the lamination direction of the embodiment in which the shear modulus G' of the first adhesive layer is changed.

FIG. 11 is a diagram showing the relationship of A/A 'and B/B'.

Fig. 12 is a diagram illustrating an evaluation method of cracking.

Description of the symbols

100 display device

101 laminated structure

103 substrate laminate

110 optical film member

111 polarizing film

113 phase difference film

115 circular polarized light functional film laminate

117 polarizer

119 polarizer protective film

120 first adhesive layer

130 window component

131 hard coating

133 Window film

140 second adhesive layer

150 panel member

151 film sealing layer

153 Panel base

160 third adhesive layer

170 touch sensor member

171 transparent conductive layer

173 transparent film

180 fourth adhesive layer

190 protective member

901 organic EL display panel

912-1, 912-2 transparent conductive layer

915-1 and 915-2 substrate film

916-1, 916-2 transparent conductive film

917 spacer

920 optical laminate

921 polarizer

922-1, 922-2 protective film

923 phase difference layer

930 touch panel

Detailed Description

[ optical film Member ]

The optical film member used in the display device of the present invention may be a polarizer, a polarizing film, a protective film made of a transparent resin material, a film such as a phase difference film, or the like, or a combination of a part or all of them, and particularly, a circularly polarized light functional film laminate in which a phase difference film is laminated on a polarizing film may be used. The optical film member does not include an adhesive layer such as a first adhesive layer described later.

The thickness of the optical film member is preferably 92 μm or less, more preferably 60 μm or less, and further preferably 10 to 50 μm. Within the above range, bending is not inhibited, and a preferable mode is obtained.

< polarizer >

As the polarizer included in the optical film member of the present invention, a polyvinyl alcohol (PVA) -based resin in which iodine is oriented, which is obtained by stretching in a stretching step such as stretching in a gas atmosphere (dry stretching) or stretching in an aqueous boric acid solution, can be used.

A typical method for producing a polarizer includes a production method (single layer drawing method) including a step of dyeing a single layer body of a PVA type resin and a step of drawing the same as described in japanese unexamined patent application publication No. 2004-341515. Further examples include: a method for producing a laminate comprising a step of stretching a PVA resin layer and a resin substrate for stretching in a laminate state and a step of dyeing, as described in Japanese patent laid-open Nos. 51-069644, 2000-338329, 2001-343521, 2010/100917, 2012-073563 and 2011-2816. According to this production method, even if the PVA-based resin layer is thin, it can be stretched without causing troubles such as breakage due to stretching because it is supported by the resin base material for stretching.

The polarizer has a thickness of 20 μm or less, preferably 12 μm or less, more preferably 9 μm or less, still more preferably 1 to 8 μm, and particularly preferably 3 to 6 μm. Within the above range, bending is not inhibited, and a preferable mode is obtained.

< polarizing film >

The polarizer may be bonded to at least one side with a polarizer protective film (not shown) by an adhesive (layer) as long as the characteristics of the present invention are not impaired. An adhesive may be used for the adhesion treatment of the polarizer and the polarizer protective film. Examples of the adhesive include isocyanate adhesives, polyvinyl alcohol adhesives, gelatin adhesives, vinyl latexes, and water-based polyesters. The adhesive is usually used in the form of an aqueous adhesive, and usually contains 0.5 to 60% by weight of a solid content. In addition to the above, examples of the adhesive for the polarizer and the polarizer protective film include an ultraviolet curing adhesive, an electron beam curing adhesive, and the like. The adhesive for electron beam curing type polarizing film exhibits suitable adhesiveness to the above various polarizer protective films. The adhesive used in the present invention may contain a metal compound filler. In the present invention, a member in which a polarizer and a polarizer protective film are bonded to each other with an adhesive (layer) is sometimes referred to as a polarizing film.

< retardation film >

The optical film member used in the present invention may include a retardation film, and the retardation film may be a film obtained by stretching a polymer film or a film obtained by aligning and fixing a liquid crystal material. In the present specification, a retardation film refers to a film having birefringence in the in-plane and/or thickness direction.

Examples of the retardation film include a retardation film for antireflection (see Japanese patent laid-open Nos. 2012 and 133303 [0221], [0222], [0228]), a retardation film for viewing angle compensation (see Japanese patent laid-open Nos. 2012 and 133303 [0225], [0226]), and a tilt alignment retardation film for viewing angle compensation (see Japanese patent laid-open No. 2012 and 133303 [0227 ]).

As the retardation film, any known retardation film can be used as long as it has substantially the above-described function, and for example, the retardation value, the arrangement angle, the 3-dimensional birefringence, the single layer or the multilayer, and the like are not particularly limited.

The thickness of the retardation film is preferably 20 μm or less, more preferably 10 μm or less, still more preferably 1 to 9 μm, and particularly preferably 3 to 8 μm. Within the above range, bending is not inhibited, and is a preferable embodiment.

In the present specification, Re 550 refers to an in-plane phase difference value measured at 23 ℃ with light having a wavelength of 550 nm. Re 550 can be determined by the following method: when the refractive indices of the retardation film in the slow axis direction and the fast axis direction at a wavelength of 550nm are nx and ny, respectively, and d (nm) is the thickness of the retardation film, the formula is given by: re [550] ═ (nx-ny) × d. The slow axis is a direction in which the in-plane refractive index becomes maximum.

The nx-ny of the present invention, i.e., the in-plane birefringence Δ n, is 0.002 to 0.2, preferably 0.0025 to 0.15.

The retardation film preferably has an in-plane retardation value (Re 550) measured at 23 ℃ with a light having a wavelength of 550nm greater than an in-plane retardation value (Re 450) measured with a light having a wavelength of 450 nm. When the above ratio of the retardation film having such wavelength dispersion characteristics is in this range, the longer the wavelength is, the more the retardation is exhibited, and thus, the preferable retardation characteristics can be obtained in each wavelength in the visible region. For example, when used in an organic EL display, a retardation film having such wavelength dependence is produced as an 1/4 wave plate and bonded to a polarizing plate, whereby a neutral polarizing plate and a display device having small wavelength dependence of hue can be realized, such as a circularly polarizing plate. On the other hand, when the ratio is outside the above range, the wavelength dependence of the reflected hue becomes large, and a problem of coloring of the polarizing plate and the display device arises.

The phase difference film has a ratio of Re 550 to Re 450 (Re 450/Re 550) of 0.8 or more and less than 1.0, more preferably 0.8 to 0.95.

The retardation film preferably has an in-plane retardation value (Re 550) measured at 23 ℃ with a light having a wavelength of 550nm smaller than an in-plane retardation value (Re 650) measured with a light having a wavelength of 650 nm. The retardation film having such wavelength dispersion characteristics has a constant retardation value in a red region, and when used in a liquid crystal display device, for example, a phenomenon in which light leaks at an observation angle or a phenomenon in which a displayed image has a red tone (also referred to as a reddish phenomenon) can be improved.

The phase difference film has a ratio of Re 650 to Re 550 (Re 550/Re 650) of 0.8 or more and less than 1.0, preferably 0.8 to 0.97. By setting Re 550/Re 650 to the above range, for example, when the retardation film is used for an organic EL display, more excellent display characteristics can be obtained.

Re 450, Re 550 and Re 650 can be measured by using the product name "Axoscan" manufactured by Axometrics.

In one embodiment, the retardation film of the present invention is produced by stretching a polymer film to orient the film.

As the method for stretching the polymer film, any suitable stretching method may be adopted according to the purpose. Examples of the stretching method suitable for the present invention include: a transverse unidirectional stretching method, a longitudinal and transverse simultaneous biaxial stretching method, a longitudinal and transverse stepwise biaxial stretching method, and the like. As the stretching device, any suitable stretching machine such as a tenter stretching machine or a biaxial stretching machine can be used. Preferably, the stretching machine is provided with a temperature control mechanism. When heating and stretching are performed, the internal temperature of the stretching machine may be continuously changed or may be continuously changed. The process can be divided into 1 or more than 2 times. The stretching direction may be stretching in the film width direction (TD direction) or an oblique direction.

In another embodiment, a retardation film obtained by laminating retardation layers produced by aligning and fixing a liquid crystal material can be used as the retardation film of the present invention. Each of the retardation layers may be an alignment cured layer of a liquid crystal compound. By using the liquid crystal compound, the difference between nx and ny of the obtained retardation layer can be greatly increased as compared with a non-liquid crystal material, and therefore, the thickness of the retardation layer for obtaining a desired in-plane retardation can be greatly reduced. As a result, the circularly polarizing plate (eventually, the organic EL display device) can be further thinned. In the present specification, the "alignment cured layer" means a layer in which a liquid crystal compound is aligned in a given direction within the layer and the alignment state thereof is fixed. In the present embodiment, a rod-like liquid crystal compound is typically aligned in a slow axis direction of the retardation layer (homogeneous alignment). Examples of the liquid crystal compound include: the liquid crystal phase is a nematic liquid crystal compound (nematic liquid crystal). As such a liquid crystal compound, for example, a liquid crystal polymer or a liquid crystal monomer can be used. The mechanism of developing the liquid crystallinity of the liquid crystal compound may be either lyotropic or thermotropic. The liquid crystal polymer and the liquid crystal monomer may be used alone or in combination.

When the liquid crystal compound is a liquid crystal monomer, the liquid crystal monomer is preferably a polymerizable monomer or a crosslinkable monomer. This is because the alignment state of the liquid crystal monomer can be fixed by polymerizing or crosslinking the liquid crystal monomer. After the liquid crystal monomers are aligned, for example, if the liquid crystal monomers are polymerized or cross-linked with each other, the above-described alignment state can thereby be fixed. Here, the polymer is formed by polymerization, and a 3-dimensional network structure is formed by crosslinking, but they are non-liquid crystalline. Therefore, the formed retardation layer does not undergo transition to a liquid crystal phase, a glass phase, or a crystal phase due to a temperature change, which is characteristic of a liquid crystalline compound, for example. As a result, the retardation layer is extremely excellent in stability without being affected by temperature change.

The temperature range in which the liquid crystal monomer exhibits liquid crystallinity varies depending on the kind thereof. Specifically, the temperature range is preferably 40 to 120 ℃, more preferably 50 to 100 ℃, and most preferably 60 to 90 ℃.

As the liquid crystal monomer, any suitable liquid crystal monomer can be used. For example, the following may be used: and polymerizable mesogenic compounds described in Japanese patent publication 2002-533742(WO00/37585), EP358208(US5211877), EP66137(US4388453), WO93/22397, EP0261712, DE19504224, DE4408171, GB2280445, and the like. Specific examples of such polymerizable mesogenic compounds include: trade name LC242 from BASF, trade name E7 from Merck, and trade name LC-Sillicon-CC3767 from Wacker-Chem. As the liquid crystal monomer, for example, a nematic liquid crystal monomer is preferable.

The alignment cured layer of the liquid crystal compound can be formed by the following method: a surface of a given substrate is subjected to an alignment treatment, a coating liquid containing a liquid crystal compound is applied to the surface, the liquid crystal compound is aligned in a direction corresponding to the alignment treatment, and the aligned state is fixed. In one embodiment, the substrate is any suitable resin film, and the oriented cured layer formed on the substrate can be transferred to the surface of the polarizer. In this case, the absorption axis of the polarizer and the slow axis of the liquid crystal alignment cured layer were arranged so as to form an angle of 15 °. Further, the retardation of the liquid crystal alignment cured layer was λ/2 (about 270nm) at a wavelength of 550 nm. Further, similarly to the above, a liquid crystal alignment cured layer having a wavelength of λ/4 (about 140nm) at 550nm was formed on the transferable base material, and the laminate of the polarizer and the 1/2 wave plate was laminated on the 1/2 wave plate side so that the angle formed by the absorption axis of the polarizer and the slow axis of the 1/4 wave plate was 75 °.

< polarizer protective film >

The polarizer protective film made of a transparent resin material used in the display device of the present invention may be a cycloolefin resin such as a norbornene resin, an olefin resin such as polyethylene or polypropylene, a polyester resin, a (meth) acrylic resin, or the like.

The polarizer protective film preferably has a thickness of 5 to 60 μm, more preferably 10 to 40 μm, and further preferably 10 to 30 μm, and may be provided with a surface treatment layer such as an antiglare layer or an antireflection layer as appropriate. Within the above range, bending is not inhibited, and is a preferable embodiment.

The polarizer protective film used in the optical laminate of the present invention has a moisture permeability of 200g/m²Below, preferably 170g/m²Below, more preferably 130g/m²The amount of the surfactant is preferably 90g/m or less²The following.

[ Window Member ]

In order to prevent the optical film member, the touch sensor member, and the panel member from being damaged, the window member is disposed on the outermost surface of the display device on the viewing side.

The window member is generally provided with a window film or a window glass. A hard coat may be provided on the window film or glazing. Examples of the window glass include a thin glass substrate. An optical laminate applicable to a foldable display device is required to have high flexibility, high transparency, and high hardness. The material of the window film is not particularly limited as long as it satisfies these physical properties.

< Window Membrane >

Examples of the window film include transparent resin films. Examples of the resin constituting the transparent resin film include: at least one selected from the group consisting of polyimide resins, polyamide resins, polyester resins, cellulose resins, acetate resins, styrene resins, sulfone resins, epoxy resins, polyolefin resins, polyether ether ketone resins, thioether resins, vinyl alcohol resins, urethane resins, acrylic resins, and polycarbonate resins. However, the resin constituting the transparent resin film is not limited to these resins.

< hard coating >

The hard coat layer can be formed by applying a curable coating agent to the surface of a layer to be a base (for example, a window film) and curing the curable coating agent.

As the coating agent, for example, a coating agent for optical film applications can be used. Examples of the coating agent include: an acrylic coating agent, a melamine coating agent, a urethane coating agent, an epoxy coating agent, a silicone coating agent, and an inorganic coating agent, but are not limited thereto.

The coating agent may also contain additives. Examples of additives include: silane coupling agents, colorants, dyes, powders or particles (pigments, inorganic or organic fillers, particles of inorganic or organic materials, etc.), surfactants, plasticizers, antistatic agents, surface lubricants, leveling agents, antioxidants, light stabilizers, ultraviolet absorbers, polymerization inhibitors, antifouling materials, etc., but the silane coupling agents are not limited thereto.

[ first adhesive layer ]

The first adhesive layer used in the display device of the present invention is a layer in which a window member is laminated on one surface of an optical film member via the adhesive layer.

Examples of the adhesive composition constituting the first adhesive layer used in the display device of the present invention include acrylic adhesives, rubber adhesives, vinyl alkyl ether adhesives, silicone adhesives, polyester adhesives, polyamide adhesives, urethane adhesives, fluorine-containing adhesives, epoxy adhesives, polyether adhesives, and the like. The adhesive constituting the first adhesive layer may be used alone or in combination of 2 or more. However, from the viewpoint of transparency, processability, durability, adhesion, bending resistance and the like, it is preferable to use an acrylic pressure-sensitive adhesive alone.

< (meth) acrylic polymer >

When an acrylic pressure-sensitive adhesive is used as the pressure-sensitive adhesive composition constituting the first pressure-sensitive adhesive layer, the pressure-sensitive adhesive composition preferably contains a (meth) acrylic polymer containing, as a monomer unit, a (meth) acrylic monomer having a linear or branched alkyl group having 1 to 24 carbon atoms. By using the (meth) acrylic monomer having a linear or branched alkyl group having 1 to 24 carbon atoms, an adhesive layer having excellent flexibility can be obtained. In the present invention, the (meth) acrylic polymer means an acrylic polymer and/or a methacrylic polymer, and the (meth) acrylate means an acrylate and/or a methacrylate.

Specific examples of the (meth) acrylic monomer having a linear or branched alkyl group having 1 to 24 carbon atoms, which constitutes the main skeleton of the (meth) acrylic polymer, include: methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, sec-butyl (meth) acrylate, tert-butyl (meth) acrylate, isobutyl (meth) acrylate, n-pentyl (meth) acrylate, isopentyl (meth) acrylate, n-hexyl (meth) acrylate, isohexyl (meth) acrylate, isoheptyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, isooctyl (meth) acrylate, n-nonyl (meth) acrylate, isononyl (meth) acrylate, n-decyl (meth) acrylate, isodecyl (meth) acrylate, n-dodecyl (meth) acrylate, lauryl (meth) acrylate, n-tridecyl (meth) acrylate, n-tetradecyl (meth) acrylate, and the like, wherein, in general, a monomer having a low glass transition temperature (Tg) becomes a viscoelastic body even in high-speed bending, and therefore, from the viewpoint of bending properties, a (meth) acrylic monomer having a linear or branched alkyl group having 4 to 8 carbon atoms is preferable. As the (meth) acrylic monomer, 1 or 2 or more species can be used.

The (meth) acrylic monomer having a linear or branched alkyl group having 1 to 24 carbon atoms is a main component of all monomers constituting the (meth) acrylic polymer. The main component is a (meth) acrylic monomer having a linear or branched alkyl group having 1 to 24 carbon atoms, preferably 80 to 100 wt%, more preferably 90 to 100 wt%, further preferably 92 to 99.9 wt%, and particularly preferably 94 to 99.9 wt%, of all monomers constituting the (meth) acrylic polymer.

In the case of using an acrylic adhesive as the adhesive composition constituting the first adhesive layer, it is preferable to contain a (meth) acrylic polymer containing a hydroxyl group-containing monomer having a reactive functional group as a monomer unit. By using the above-mentioned hydroxyl group-containing monomer, an adhesive layer having excellent adhesion and bendability can be obtained. The hydroxyl group-containing monomer is a compound having a hydroxyl group in its structure and containing a polymerizable unsaturated double bond such as a (meth) acryloyl group or a vinyl group.

Specific examples of the hydroxyl group-containing monomer include: hydroxyalkyl (meth) acrylates such as 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 8-hydroxyoctyl (meth) acrylate, 10-hydroxydecyl (meth) acrylate, 12-hydroxylauryl (meth) acrylate, and (4-hydroxymethylcyclohexyl) methyl acrylate. Among the above hydroxyl group-containing monomers, 2-hydroxyethyl (meth) acrylate and 4-hydroxybutyl (meth) acrylate are preferable from the viewpoint of durability and adhesion. As the hydroxyl group-containing monomer, 1 or 2 or more species may be used.

The monomer unit constituting the (meth) acrylic polymer may contain a monomer having a reactive functional group, such as a carboxyl group-containing monomer, an amino group-containing monomer, and an amide group-containing monomer. The use of these monomers is preferable from the viewpoint of adhesion under a hot and humid environment.

In the case of using an acrylic adhesive as the adhesive composition constituting the first adhesive layer, a (meth) acrylic polymer containing a carboxyl group-containing monomer having a reactive functional group as a monomer unit may be contained. By using the above carboxyl group-containing monomer, an adhesive layer having excellent adhesion in a hot and humid environment can be obtained. The carboxyl group-containing monomer is a compound having a carboxyl group in its structure and containing a polymerizable unsaturated double bond such as a (meth) acryloyl group or a vinyl group.

Specific examples of the carboxyl group-containing monomer include: (meth) acrylic acid, carboxyethyl (meth) acrylate, carboxypentyl (meth) acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid, and the like.

In the case of using an acrylic adhesive as the adhesive composition constituting the first adhesive layer, a (meth) acrylic polymer containing an amino group-containing monomer having a reactive functional group as a monomer unit may be contained. By using the amino group-containing monomer, an adhesive layer having excellent adhesion in a hot and humid environment can be obtained. The amino group-containing monomer is a compound having an amino group in its structure and containing a polymerizable unsaturated double bond such as a (meth) acryloyl group or a vinyl group.

Specific examples of the amino group-containing monomer include N, N-dimethylaminoethyl (meth) acrylate, N-dimethylaminopropyl (meth) acrylate, and the like.

In the case of using an acrylic adhesive as the adhesive composition constituting the first adhesive layer, a (meth) acrylic polymer containing an amide group-containing monomer having a reactive functional group as a monomer unit may be included. By using the amide group-containing monomer, an adhesive layer having excellent adhesion can be obtained. The amide group-containing monomer is a compound having an amide group in its structure and containing a polymerizable unsaturated double bond such as a (meth) acryloyl group or a vinyl group.

Specific examples of the amide group-containing monomer include: acrylamide monomers such as (meth) acrylamide, N-dimethyl (meth) acrylamide, N-diethyl (meth) acrylamide, N-isopropylacrylamide, N-methyl (meth) acrylamide, N-butyl (meth) acrylamide, N-hexyl (meth) acrylamide, N-methylol-N-propane (meth) acrylamide, aminomethyl (meth) acrylamide, aminoethyl (meth) acrylamide, mercaptomethyl (meth) acrylamide, and mercaptoethyl (meth) acrylamide; n-acryloyl heterocyclic monomers such as N- (meth) acryloyl morpholine, N- (meth) acryloyl piperidine, and N- (meth) acryloyl pyrrolidine; and N-vinyl group-containing lactam monomers such as N-vinylpyrrolidone and N-vinyl-epsilon-caprolactam.

The proportion (total amount) of the monomer having a reactive functional group in all the monomers constituting the (meth) acrylic polymer is preferably 20% by weight or less, more preferably 10% by weight or less, still more preferably 0.01 to 8% by weight, particularly preferably 0.01 to 5% by weight, and most preferably 0.05 to 3% by weight, as a monomer unit constituting the (meth) acrylic polymer. When the amount exceeds 20% by weight, the crosslinking points increase, and the flexibility of the pressure-sensitive adhesive (layer) is lost, so that the stress relaxation tends to be poor.

As the monomer unit constituting the above-mentioned (meth) acrylic polymer, other comonomers may be introduced in addition to the above-mentioned monomer having a reactive functional group within the range not impairing the effect of the present invention. The blending ratio thereof is not particularly limited, and it is preferable that the other comonomer is not contained in the total monomers constituting the (meth) acrylic polymer, and is 30% by weight or less. When the amount exceeds 30% by weight, particularly when a monomer other than the (meth) acrylic monomer is used, the number of reaction sites with the film is reduced, and the adhesion tends to be reduced.

In the present invention, when the above (meth) acrylic polymer is used, a (meth) acrylic polymer having a weight average molecular weight (Mw) in the range of 100 to 250 ten thousand is usually used. In consideration of durability, particularly heat resistance and bendability, it is preferably 120 to 220 ten thousand, more preferably 140 to 200 ten thousand. If the weight average molecular weight is less than 100 ten thousand, when polymer chains are crosslinked to ensure durability, the number of crosslinking points increases and the flexibility of the adhesive (layer) is lost, as compared with the case where the weight average molecular weight is 100 ten thousand or more, and therefore, dimensional changes between the outer side of bending (convex side) and the inner side of bending (concave side) that occur between the films during bending cannot be relaxed, and the films are likely to break. When the weight average molecular weight is more than 250 ten thousand, a large amount of a diluting solvent is required to adjust the viscosity for coating, which is not preferable because the cost increases, and the entanglement of the polymer chains of the obtained (meth) acrylic polymer becomes complicated, and therefore, the flexibility is poor, and the film is likely to be broken during bending. The weight average molecular weight (Mw) is a value measured by GPC (gel permeation chromatography) and calculated in terms of polystyrene.

For the production of such a (meth) acrylic polymer, known production methods such as solution polymerization, bulk polymerization, emulsion polymerization, and various radical polymerizations can be appropriately selected. The obtained (meth) acrylic polymer may be any of a random copolymer, a block copolymer, a graft copolymer, and the like.

In the above solution polymerization, as a polymerization solvent, for example, ethyl acetate, toluene, or the like can be used. As a specific example of the solution polymerization, a polymerization initiator is added under an inert gas flow such as nitrogen gas, and the reaction is usually carried out under reaction conditions of about 50 to 70 ℃ and about 5 to 30 hours.

The polymerization initiator, chain transfer agent, emulsifier, and the like used in the radical polymerization are not particularly limited, and can be appropriately selected and used. The weight average molecular weight of the (meth) acrylic polymer can be controlled by the amount of the polymerization initiator, the amount of the chain transfer agent, and the reaction conditions, and the amount can be appropriately adjusted depending on the kind thereof.

Examples of the polymerization initiator include: 2,2 ' -azobisisobutyronitrile, 2 ' -azobis (2-amidinopropane) dihydrochloride, 2 ' -azobis [2- (5-methyl-2-imidazolin-2-yl) propane ] dihydrochloride, 2 ' -azobis (2-methylpropylamidine) disulfate, 2 ' -azobis (N, N ' -dimethyleneisobutylamidine), 2 ' -azobis [ N- (2-carboxyethyl) -2-methylpropylamidine ] hydrate (product name: VA-057, manufactured by Wako pure chemical industries, Ltd.), an azo initiator such as potassium persulfate, a persulfate such as ammonium persulfate, bis (2-ethylhexyl) peroxydicarbonate, bis (4-tert-butylcyclohexyl) peroxydicarbonate, potassium peroxydicarbonate, sodium persulfate, Di-sec-butyl peroxydicarbonate, tert-butyl peroxyneodecanoate, tert-hexyl peroxypivalate, tert-butyl peroxypivalate, dilauroyl peroxide, di-n-octanoyl peroxide, 1,3, 3-tetramethylbutyl peroxy2-ethylhexanoate, bis (4-methylbenzoyl) peroxide, dibenzoyl peroxide, tert-butyl peroxyisobutyrate, peroxide initiators such as 1, 1-di (tert-hexyl peroxide) cyclohexane, tert-butyl hydroperoxide, and hydrogen peroxide, redox initiators obtained by combining a peroxide and a reducing agent such as a combination of a persulfate and sodium bisulfite, and a combination of a peroxide and sodium ascorbate, and the like, but the present invention is not limited thereto.

The polymerization initiator may be used in 1 kind or mixed with 2 or more kinds, and for example, the total content is preferably about 0.005 to 1 part by weight, more preferably about 0.02 to 0.5 part by weight, based on 100 parts by weight of all monomers constituting the (meth) acrylic polymer.

When a chain transfer agent, an emulsifier used in emulsion polymerization, or a reactive emulsifier is used, a conventionally known one can be used as appropriate. The amount of addition of these compounds can be determined as appropriate within a range not impairing the effects of the present invention.

< crosslinking agent >

The adhesive composition constituting the first adhesive layer may contain a crosslinking agent. As the crosslinking agent, an organic crosslinking agent or a polyfunctional metal chelate compound can be used. Examples of the organic crosslinking agent include isocyanate crosslinking agents, peroxide crosslinking agents, epoxy crosslinking agents, and imine crosslinking agents. The multifunctional metal chelate is formed by covalent bonding or coordination bonding of polyvalent metal and organic compound. As the polyvalent metal atom, there may be mentioned: al, Cr, Zr, Co, Cu, Fe, Ni, V, Zn, In, Ca, Mg, Mn, Y, Ce, Sr, Ba, Mo, La, Sn, Ti, etc. Examples of the atom in the covalently or coordinately bonded organic compound include an oxygen atom, and examples of the organic compound include: alkyl esters, alcohol compounds, carboxylic acid compounds, ether compounds, ketone compounds, and the like. Among them, isocyanate-based crosslinking agents (particularly trifunctional isocyanate-based crosslinking agents) are preferable from the viewpoint of durability, and peroxide-based crosslinking agents and isocyanate-based crosslinking agents (particularly difunctional isocyanate-based crosslinking agents) are preferable from the viewpoint of flexibility. Both the peroxide-based crosslinking agent and the difunctional isocyanate-based crosslinking agent form soft two-dimensional crosslinks, whereas the trifunctional isocyanate-based crosslinking agent forms firmer three-dimensional crosslinks. Two-dimensional crosslinking, which is a softer crosslinking, is advantageous when bending. However, in the case of only two-dimensional crosslinking, the durability is poor and peeling is likely to occur, and therefore, since the mixed crosslinking of two-dimensional crosslinking and three-dimensional crosslinking is good, it is a preferable embodiment to use a trifunctional isocyanate-based crosslinking agent in combination with a peroxide-based crosslinking agent or a difunctional isocyanate-based crosslinking agent.

The amount of the crosslinking agent is, for example, preferably 0.01 to 10 parts by weight, more preferably 0.03 to 2 parts by weight, based on 100 parts by weight of the (meth) acrylic polymer. When the amount is within the above range, the flexibility resistance is excellent, and the preferred embodiment is.

< other additives >

The pressure-sensitive adhesive composition constituting the first pressure-sensitive adhesive layer may further contain other known additives, and for example, various silane coupling agents, polyether compounds such as polyalkylene glycols such as polypropylene glycol, coloring agents, powders of pigments and the like, dyes, surfactants, plasticizers, tackifiers, surface lubricants, leveling agents, softening agents, antioxidants, antiaging agents, light stabilizers, ultraviolet absorbers, polymerization inhibitors, antistatic agents (alkali metal salts as ionic compounds, ionic liquids and the like), inorganic or organic fillers, metal powders, granules, foils and the like may be added as appropriate depending on the application to be used. Further, redox species to which a reducing agent is added may be used within a controllable range.

[ other adhesive layers ]

The second adhesive layer used in the display device of the present invention is a layer through which the laminated structure is laminated on the other surface of the optical film member.

The touch sensor member is laminated on the surface of the film seal layer opposite to the panel member via a third adhesive layer used in the display device of the present invention.

The second adhesive layer, the third adhesive layer, and other adhesive layers used further may be layers having the same composition (the same adhesive composition) and the same characteristics, or may be layers having different characteristics, and there is no particular limitation thereto.

< formation of adhesion layer >

The plurality of adhesive layers in the present invention are preferably formed of the adhesive composition described above. Examples of the method for forming the adhesive layer include: a method of forming a pressure-sensitive adhesive layer by applying the pressure-sensitive adhesive composition to a separator or the like after a release treatment and drying and removing a polymerization solvent or the like. The pressure-sensitive adhesive composition may be applied to a polarizing film or the like, and the pressure-sensitive adhesive layer may be formed on the polarizing film or the like by drying and removing a polymerization solvent or the like. In the case of applying the pressure-sensitive adhesive composition, one or more solvents other than the polymerization solvent may be added newly as appropriate.

As the separator subjected to the peeling treatment, a silicone peeling spacer is preferably used. When the adhesive composition of the present invention is applied to such a spacer and dried to form an adhesive layer, an appropriate method can be appropriately employed as a method for drying the adhesive according to the purpose. A method of drying the coating film by heating is preferably used. For example, in the case of producing an acrylic pressure-sensitive adhesive using a (meth) acrylic polymer, the heating and drying temperature is preferably 40 to 200 ℃, more preferably 50 to 180 ℃, and particularly preferably 70 to 170 ℃. By setting the heating temperature in the above range, an adhesive having excellent adhesive properties can be obtained.

The drying time may be appropriately set to a suitable time. For example, in the case of producing an acrylic pressure-sensitive adhesive using a (meth) acrylic polymer, the drying time is preferably 5 seconds to 20 minutes, more preferably 5 seconds to 10 minutes, and particularly preferably 10 seconds to 5 minutes.

As a method for applying the adhesive composition, various methods can be used. Specifically, examples thereof include: roll coating, roll-and-lick coating, gravure coating, reverse coating, roll brushing, spray coating, dip roll coating, bar coating, blade coating, air knife coating, curtain coating, lip coating, extrusion coating using a die coater, and the like.

The thickness of the adhesive layer used in the display device of the present invention is preferably 1 to 200 μm, more preferably 5 to 150 μm, and further preferably 10 to 100 μm. The adhesive layer may be a single layer or may have a laminated structure. When the amount is within the above range, the bending is not inhibited, and the adhesion (holding resistance) is also a preferable aspect. In addition, in the case of having a plurality of adhesive layers, it is preferable that all the adhesive layers are within the above range.

The upper limit of the glass transition temperature (Tg) of the adhesive layer used in the laminate for a flexible image display device of the present invention is preferably 0 ℃ or lower, more preferably-20 ℃ or lower, and still more preferably-25 ℃ or lower. When the Tg of the adhesive layer is in such a range, the adhesive layer is less likely to be hardened even when bent in a high-speed region, and a flexible image display device which is excellent in stress relaxation, bendable, or foldable can be realized.

[ Panel Member ]

The panel member may include a panel base portion such as an image display panel and a substrate for holding the image display panel. A sealing member (such as a film sealing layer) is disposed on the visible side of the image display panel. The substrate may be one that holds the image display panel and has appropriate strength and flexibility. As such a substrate, a resin sheet or the like can be used. The material of the resin sheet is not particularly limited, and may be appropriately selected according to the type of the panel.

As the image display panel, a known image display panel can be used. Examples of the image display panel include: an organic Electroluminescent (EL) panel. The image display panel is not limited to the organic EL panel, and may be a liquid crystal panel, an electrophoretic display panel (electronic paper), or the like. For example, a flexible substrate such as a resin substrate can be used as a transparent substrate for holding a liquid crystal layer to form a foldable liquid crystal panel.

< thin film sealing layer >

The Thin Film sealing layer (TFEE) has a function of preventing the above-described image display panel from being exposed to moisture and/or air. The thin film sealing layer is formed of an inorganic/organic multilayer film in which a passivation film and a resin film are alternately laminated on the light-emitting layer. Examples of the material constituting the thin film sealing layer include materials having a low moisture permeability, for example, inorganic materials such as silicon nitride, silicon oxynitride, carbon oxide, carbon nitride, and aluminum oxide, and resins.

[ touch sensor Member ]

As the touch sensor, for example, a touch sensor used in the field of image display devices and the like can be used. Examples of the touch sensor include: the touch sensor is not limited to the resistive type, the capacitive type, the optical type, or the ultrasonic type.

The capacitive touch sensor generally includes a transparent conductive layer. Examples of such a touch sensor include a laminate of a transparent conductive layer and a transparent base material. Examples of the transparent substrate include a transparent film.

< transparent conductive layer >

The transparent conductive layer is not particularly limited, and a conductive metal oxide, a metal nanowire, or the like can be used. Examples of the metal oxide include: indium Oxide (ITO) containing Tin Oxide, and Tin Oxide containing antimony. The transparent conductive layer may be a conductive pattern made of metal oxide or metal. The shape of the conductive pattern may be a stripe, a square, a lattice, or the like, but is not limited to these shapes.

< transparent film >

As the transparent film, for example, a transparent resin film can be used. Examples of the resin constituting the transparent film include polyester resins (including polyarylate resins), acetate resins, polyethersulfone resins, polycarbonate resins, polyamide resins, polyimide resins, polyolefin resins, acrylic resins, polyvinyl chloride resins, polyvinylidene chloride resins, polystyrene resins, polyvinyl alcohol resins, thioether resins (for example, polyphenylene sulfide resins), polyether ether ketone resins, cellulose resins, epoxy resins, and urethane resins. The transparent film may contain one of these resins, or may contain two or more of them. Among these resins, polyester resins, polyimide resins, and polyether sulfone resins are preferable. However, the resin constituting the transparent film is not limited to these resins.

[ protective Member ]

The protective member is laminated on the side of the panel member opposite to the second adhesive layer via a fourth adhesive layer. The protective member functions as a reinforcing plate for reinforcing the mechanical strength of the flexible image display panel attached to the back surface thereof, and is a resin base material for protecting the flexible image display panel from damage and impact, and is formed in a film shape.

[ laminated Structure ]

The laminated structure of the present invention has a panel member. In the display device, the surface of the laminated structure on the second pressure-sensitive adhesive layer side, which will be described later, has a layer that is more likely to break than the window member and the optical film member when subjected to bending deformation.

[ display device ]

The display device of the present invention includes: the display device includes an optical film member, a first adhesive layer, a window member laminated on one surface of the optical film member via the first adhesive layer, a second adhesive layer, and a laminated structure laminated on the other surface of the optical film member via the second adhesive layer.

Fig. 2 is a cross-sectional view showing one embodiment of the display device of the present invention. The display device 100 includes: the optical film member 110, the first adhesive layer 120, the window member 130 laminated on one surface of the optical film member 110 via the first adhesive layer 120, the second adhesive layer 140, and the laminated structure 101 laminated on the other surface of the optical film member 110 via the second adhesive layer 140. The laminated structure 101 includes a panel member 150. The display device 100 is configured to be bendable.

Although arbitrary, the window member 130 may have a hard coating layer 131 on the side opposite to the first adhesive layer 120.

Although arbitrary, the optical film member 110 may be made into a circularly polarized light functional film laminate 115 in which a phase difference film 113 is laminated on a polarizing film 111. The circularly polarized light functional film laminate 115 is used, for example, to generate circularly polarized light or to compensate for a viewing angle in order to prevent light entering from the visible side of the polarizing film 111 from being internally reflected and emitted to the visible side.

The polarizing film 111 may be a laminate of a polarizer 117 and a polarizer protective film 119 laminated on at least one surface of the polarizer 117.

Although arbitrary, the polarizer protective film 111 may contain an acrylic resin.

The laminated structure 101 has a layer which is more easily broken than the window member 130 and the optical film member 110 when the surface on the second adhesive layer 140 side is bent and deformed,

Although arbitrary, the laminated structure 101 may further include a third adhesive layer 160, the film sealing layer 151 is formed on the surface of the panel member 150 on the second adhesive layer 140 side, the touch sensor member 170 is laminated on the surface of the film sealing layer 151 on the opposite side to the panel member 150 via the third adhesive layer 160, the transparent conductive layer 171 is formed on the surface of the touch sensor member 170 on the opposite side to the panel member 150, and the transparent conductive layer 171 is laminated on the second adhesive layer 140 as a layer which is more easily broken than the window member 130 and the optical film member 110.

Although arbitrary, a fourth adhesive layer 180 may be further provided on the face of the panel member 150 opposite to the third adhesive layer 160, and a protective member 190 may be laminated via the fourth adhesive layer 180.

In the display device 100, the display device 100 is bent at an angle of 180 ° with the window member 130 as the outer side, and the display device 100 is bent and deformed so that the interval between the parallel opposed outermost surfaces is 4mm in the state of being bent at an angle of 180 °, the difference between the strain in the direction orthogonal to the bending radius direction generated on one surface of the optical film member 110 at this time and the strain in the direction orthogonal to the bending radius direction generated on the surface of the window member 130 facing the first adhesive layer 120 is defined as a, the optical film member 110 and the window member 130 are bent at an angle of 180 ° in the state of a single layer, and the interval between the parallel opposed outermost surfaces of the optical film member 110 and the window member 130 in the state of being bent at an angle of 180 ° is defined as 4mm in the same manner as in the case of bending and deforming the display device, the difference between the strain in the direction orthogonal to the bending radius direction generated on the outer surface of the optical film member 110 and the strain in the direction orthogonal to the bending radius direction generated on the inner surface of the window member 130 is a' and the window member 130 is bent at an angle of 180 ° so that the distance between the parallel facing outermost surfaces of the display device 100 in the state of being bent at an angle of 180 ° is 4mm, the difference between the strain in the direction orthogonal to the bending radius direction generated on the other surface of the optical film member 110 and the strain in the direction orthogonal to the bending radius direction generated on the surface of the laminated structure 101 facing the second adhesive layer 140 is B, and the optical film member 110 and the laminated structure 101 are bent at an angle of 180 ° in a single layer state in the same manner as when the display device is bent and deformed on the outer and inner sides thereof, when bending deformation occurs so that the distance between the parallel facing outermost surfaces of the optical film member 110 and the laminated structure 101 becomes 4mm in a state of being bent at an angle of 180 °, and the difference between the strain in the direction orthogonal to the bending radius direction generated on the inner surface of the optical film member 110 and the strain in the direction orthogonal to the bending radius direction generated on the outer surface of the laminated structure 101 is defined as B ', the difference between the strains A, A ' and B, B ' satisfies the relationships of the following expressions (1), (2), and (3), whereby the elongation of the easily breakable layer at the time of bending deformation is suppressed to a value smaller than the elongation at break.

0.3＜A/A’＜1.2····(1)

B/B’＜1.7A/A’－0.15····(2)

0＜B/B’＜1.25····(3)

A is the difference between the strain in the direction orthogonal to the bending radius direction generated on the outer surface of the optical film member 110 and the strain in the direction orthogonal to the bending radius direction generated on the inner surface of the window member 130 when the optical film member 110 and the window member 130 are bent and deformed in a state where the first adhesive layer 120 is present between the optical film member 110 and the window member 130, A' is the difference between the strain in the direction orthogonal to the bending radius direction generated on the outer surface of the optical film member 110 and the strain in the direction orthogonal to the bending radius direction generated on the inner surface of the window member 130 when the optical film member 110 and the window member 130 are bent and deformed in a single layer state, therefore, it is considered that a/a 'is an index relating to the hardness of the first adhesive layer 120 in the configuration of the display device 100, that is, the harder the first adhesive layer 120, the smaller the value of a/a'. Similarly, B/B 'is an index relating to the hardness of the second adhesive layer 140 in the configuration of the display device 100, that is, the harder the second adhesive layer 140, the smaller the value of B/B'.

In this regard, the present inventors have focused attention on the fact that, in a laminate in which a plurality of layers and/or members are laminated via a plurality of adhesive layers, bending displacements occurring in the surfaces of the layers and/or members facing each other via the adhesive layers affect each other via the adhesive layers, and affect the elongation of the layers and/or members, and have found for the first time that: by appropriately selecting the hardness of the plurality of adhesive layers, the elongation of the layer and/or member vulnerable to bending included in the laminate can be suppressed when the laminate is subjected to bending deformation, and thus the layer and/or member vulnerable to bending can be suppressed from breaking. Therefore, by appropriately selecting the hardness of each of the first adhesive layer 120 and the second adhesive layer 140 so as to satisfy the expressions (1) to (3) that define the conditions relating to a/a 'and B/B', the elongation of the layer that is easily broken when the layer is bent and deformed is suppressed to a value smaller than the elongation at break, and the layer that is easily broken can be suppressed from breaking.

Here, as a factor determining the hardness of the adhesive layer, the shear modulus G' of the adhesive layer is a dominant factor, but the thickness of the adhesive layer is also a factor. The smaller the thickness of the adhesive layer, the harder the adhesive layer.

Although arbitrary, the shear modulus G 'of the second adhesive layer 140 may be made greater than the shear modulus G' of the first adhesive layer 110. In this regard, the present inventors have found for the first time that: in a laminate in which a plurality of layers and/or members are laminated via a plurality of adhesive layers, if one of the adhesive layers is made harder, when the laminate is bent, the strain of the layer or member laminated on the outer side of the adhesive layer moves to the tensile side, and the strain of the layer or member laminated on the inner side of the adhesive layer moves to the compressive side. Further, since the shear modulus G' of the adhesive layer is a dominant factor of the hardness of the adhesive layer, the tensile strain generated in the brittle layers laminated on the inner side of the second adhesive layer 140, that is, the transparent conductive layer 171 and the thin film sealing layer 151 can be further reduced by adopting such a configuration.

Although arbitrary, the shear modulus G ' of the fourth adhesive layer 180 may be made smaller than the shear modulus G ' of the second adhesive layer 140 and smaller than the shear modulus G ' of the third adhesive layer 160. If the adhesive layer is made softer, the strain of the layer or member laminated on the outer side of the adhesive layer moves to the compression side, and the strain of the layer or member laminated on the inner side of the adhesive layer moves to the tension side. Further, since the shear modulus G' of the adhesive layer is a dominant factor of the hardness of the adhesive layer, the tensile strain generated in the brittle layers laminated on the outer side of the fourth adhesive layer 180, that is, the transparent conductive layer 171 and the thin-film sealing layer 151 can be further reduced by adopting such a configuration.

Although arbitrary, the relationship of 0.8 < A/A 'may be satisfied between the differences A, A' in strain. If the adhesive layer is made softer, the strain of the layer or member laminated on the outer side of the adhesive layer moves to the compression side, and the strain of the layer or member laminated on the inner side of the adhesive layer moves to the tension side. Further, it is considered that the harder the first adhesive layer 120, the smaller the value of a/a', and therefore, by adopting such a configuration, the tensile strain generated in the hard coat layer 131, which is a layer laminated on the outer side of the first adhesive layer 120, can be further reduced.

As described above, in a laminate in which a plurality of layers and/or members are laminated via a plurality of adhesive layers, if a certain adhesive layer is made harder, the strain of the layer or member laminated on the outer side of the adhesive layer moves to the tensile side and the strain of the layer or member laminated on the inner side of the adhesive layer moves to the compressive side when the laminate is bent. Therefore, when it is desired to suppress the breakage of a layer brittle to the inner side of a certain adhesive layer, the hardness of the adhesive layer may be changed to a higher hardness, and when it is desired to suppress the breakage of a layer brittle to the outer side of the adhesive layer, the hardness of the adhesive layer may be changed to a lower hardness.

For example, when the easily breakable layer of the laminated structure located inside the first adhesive layer or the second adhesive layer is broken or is predicted to be broken in the design process of the display device, the breakage of the easily breakable layer can be suppressed by changing the hardness of at least one of the first adhesive layer or the second adhesive layer to a greater hardness. At this time, since factors determining the hardness of the adhesive layer include, for example, the shear modulus G' of the adhesive layer and the thickness of the adhesive layer, the fracture of the layer that is easily fractured can be suppressed by changing the thickness of at least one of the first adhesive layer and the second adhesive layer to a smaller hardness or changing the elastic modulus of at least one of the first adhesive layer and the second adhesive layer to a higher elastic modulus.

In this case, since the layer that is easily broken of the laminated structure is located outside the third adhesive layer and the fourth adhesive layer, the layer that is easily broken can be suppressed from breaking by changing the hardness of at least one of the third adhesive layer and the fourth adhesive layer to a smaller hardness, for example, changing the thickness of the third adhesive layer to a larger thickness and/or changing the shear modulus G 'of at least one of the third adhesive layer and the fourth adhesive layer to a lower shear modulus G'.

The display device shown in fig. 3 is basically the same as the display device shown in fig. 2, but differs from the display device shown in fig. 2 in that the layer which is more easily broken than the window member 130 and the optical film member 110 is a transparent conductive layer 171 formed on the surface of the touch sensor member 170 opposite to the panel member 150 in the display device of fig. 3, and the touch sensor member 170 is laminated between the second adhesive layer 140 and the panel member 150, whereas the film sealing layer 151 formed on the side surface of the second adhesive layer 140 of the panel member 150 in the display device of fig. 4.

[ laminate of base materials ]

The base material laminate 103 of the present invention is used for a display device, and the base material laminate 103 includes: the touch sensor member includes an optical film member, the window member laminated on one surface of the optical film member via the first adhesive layer, and a touch sensor member including a transparent conductive layer laminated on the other surface of the optical film member via the second adhesive layer, wherein a layer more easily broken than the window member and the optical film member is the transparent conductive layer, the transparent conductive layer is formed on a surface of the touch sensor member opposite to the panel member, and the touch sensor member is laminated between the second adhesive layer and the panel member.

Examples

The display device and the substrate laminate of the present invention will be further described with reference to the following examples. The display device and the substrate laminate of the present invention are not limited to these examples.

[ example 1 ]

[ polarizing mirror ]

As a thermoplastic resin substrate, an amorphous polyethylene terephthalate (hereinafter, also referred to as "PET") film (IPA-copolymerized PET) having 7 mol% of isophthalic acid units (thickness: 100 μm) was prepared, and the surface thereof was subjected to corona treatment (58W/m)²Min). On the other hand, a PVA (polymerization degree 4200, saponification degree 99.2%) containing 1% by weight of an acetoacetyl group-modified PVA (trade name: GOHSEFIMER Z200 (average polymerization degree: 1200, saponification degree: 98.5 mol%, acetoacetylation ratio: 5 mol%) was prepared, and a coating solution of an aqueous PVA solution containing 5.5% by weight of a PVA-based resin was prepared and applied so that the film thickness after drying became 12 μm, and the coating solution was dried by hot air drying at 60 ℃ for 10 minutes to prepare a laminate having a layer of the PVA-based resin provided on a substrate.

Next, the laminate was first subjected to free-end stretching in air at 130 ℃ by a factor of 1.8 (auxiliary stretching in a gas atmosphere), to produce a stretched laminate. Then, the following steps are performed: the PVA layer in which the PVA molecules contained in the stretched laminate are oriented is insolubilized by immersing the stretched laminate in a boric acid-insolubilized aqueous solution having a liquid temperature of 30 ℃ for 30 seconds. In the boric acid-insoluble aqueous solution in this step, the boric acid content was 3 parts by mass per 100 parts by mass of water. The stretched laminate is dyed to produce a colored laminate. The colored laminate is obtained by: the PVA layer contained in the stretched laminate is dyed with iodine by immersing the stretched laminate in a dyeing solution containing iodine and potassium iodide at a solution temperature of 30 ℃ for an arbitrary time such that the monomer transmittance of the PVA layer constituting the polarizer finally produced reaches 40 to 44%. In this step, the dyeing liquid is prepared by using water as a solvent, and the iodine concentration is in the range of 0.1 to 0.4 wt%, and the potassium iodide concentration is in the range of 0.7 to 2.8 wt%. The ratio of the concentrations of iodine and potassium iodide was 1 to 7. Then, the following steps were performed: the colored laminate was immersed in a boric acid crosslinking aqueous solution at 30 ℃ for 60 seconds, thereby subjecting the PVA molecules of the iodine-adsorbed PVA layer to crosslinking treatment. In the boric acid crosslinking aqueous solution in this step, the boric acid content was 3 parts by mass with respect to 100 parts by mass of water, and the potassium iodide content was 3 parts by mass with respect to 100 parts by mass of water.

Further, the obtained colored layer laminate was stretched in an aqueous boric acid solution at a stretching temperature of 70 ℃ in the same direction as the stretching in the previous gas atmosphere by 3.05 times (stretching in an aqueous boric acid solution), and an optical film laminate having a final stretching magnification of 5.50 times was obtained. The optical film laminate was taken out from the aqueous boric acid solution in which the content of potassium iodide was 4 parts by mass relative to 100 parts by mass of water, and boric acid attached to the surface of the PVA layer was washed with the aqueous solution. The optical film laminate after cleaning was dried by a warm air drying process at 60 ℃. The thickness of the polarizer contained in the obtained optical film laminate was 5 μm.

[ polarizer protective film ]

As the polarizer protective film, a film obtained by extruding methacrylic resin pellets having a glutarimide ring unit, molding the resulting extruded particles into a film shape, and then stretching the film is used. The polarizer protective film has a thickness of 40 μm and a moisture permeability of 160g/m²The acrylic film of (1).

[ polarizing film ]

Next, the polarizer and the polarizer protective film were bonded to each other with an adhesive described below to prepare a polarizing film.

As the adhesive (active energy ray-curable adhesive), an adhesive (active energy ray-curable adhesive a) was prepared by mixing the components according to the formulation table shown in table 1 and stirring at 50 ℃ for 1 hour. The numerical values in the table are amounts (amounts added) and represent solids or solid ratios (based on weight), and represent weight% when the total amount of the composition is assumed to be 100 weight%. The components used are as follows.

HEAA: hydroxyethyl acrylamide

M-220: ARONIX M-220 (tripropylene glycol diacrylate) manufactured by Toyo Synthesis Co., Ltd

ACMO: acryloyl morpholine

AAEM: 2-Acetoacetoxyethyl methacrylate, manufactured by Nippon synthetic chemical Co., Ltd

UP-1190: ARUFON UP-1190, manufactured by TOYOBO SYNTHESIS CO., LTD

IRG 907: IRGACURE907, 2-methyl-1- (4-methylthiophenyl) -2-morpholinopropan-1-one, BASF

DETX-S: KAYACURE DETX-S, diethylthioxanthone, manufactured by Nippon Kabushiki Kaisha

[ Table 1]

(wt%)	Adhesive composition
		HEAA	11.4
M-220	57.1
		ACMO	11.4
AAEM	4.6
		UP-1190	11.4
IRG907	2.8
		DETX-S	1.3

In the examples and comparative examples using the adhesive, the polarizer protective film and the polarizer were laminated by the adhesive, and then the adhesive was cured by irradiation with ultraviolet light to form an adhesive layer. As the ultraviolet irradiation, a gallium-sealed metal halide lamp (manufactured by Fusion UV Systems, Inc., trade name "Light HAMMER 10", valve V valve, maximum illuminance: 1600 mW/cm)²Cumulative dose of radiation 1000/mJ/cm²(wavelength 380-440 nm)).

[ retardation film ]

The retardation film (1/4 wavelength retardation plate) of the present example was a retardation film comprising 2 layers, i.e., a 1/4 wave plate retardation layer and a 1/2 wave plate retardation layer, in which liquid crystal materials were aligned and fixed. Specifically, the production is performed as follows.

(liquid Crystal Material)

As a material for forming the 1/2 wave plate retardation layer and the 1/4 wave plate retardation layer, a polymerizable liquid crystal material exhibiting a nematic liquid crystal phase (manufactured by BASF corporation: trade name PaliocolorLC242) was used. A photopolymerization initiator (product name IRGACURE 907, manufactured by BASF) for the polymerizable liquid crystal material was dissolved in toluene. Further, in order to improve the coating property, about 0.1 to 0.5% of Megafac series manufactured by DIC was added to the liquid crystal to obtain a liquid crystal coating solution. The liquid crystal coating liquid was applied to an alignment substrate by a bar coater, and then dried by heating at 90 ℃ for 2 minutes, followed by curing with ultraviolet rays in a nitrogen atmosphere to fix the alignment. The substrate is made of a material such as PET which can be subsequently transferred with a liquid crystal coating. Further, in order to improve coatability, about 0.1% to 0.5% of a Megafac-series fluorine-based polymer produced by DIC was added depending on the thickness of the liquid crystal layer, and the mixture was dissolved in MIBK (methyl isobutyl ketone), cyclohexanone, or a mixed solvent of MIBK and cyclohexanone until the solid content concentration became 25%, to prepare a coating liquid. The coating liquid was applied to a substrate by a wire bar, and the substrate was dried at 65 ℃ for 3 minutes, and then cured by ultraviolet rays in a nitrogen atmosphere to fix the alignment. The substrate is made of a material such as PET which can be subsequently transferred with a liquid crystal coating.

(production Process)

The manufacturing process of the present example will be described with reference to fig. 4. In the manufacturing process 20, the substrate 14 is supplied by a roll, and the substrate 14 is supplied from a supply reel 21. In the production step 20, a coating liquid of the ultraviolet curable resin 10 is applied to the substrate 14 through the die 22. In the manufacturing process 20, the roll plate 30 is a cylindrical forming mold in which the uneven shape of the alignment film for 1/4 wave plate of the 1/4 wavelength phase difference plate is formed on the circumferential side surface. In the manufacturing process 20, the substrate 14 coated with the ultraviolet curable resin is pressed against the circumferential side surface of the roll plate 30 by the pressure roller 24, and the ultraviolet curable resin is cured by ultraviolet irradiation by the ultraviolet irradiation device 25 including a high-pressure mercury lamp. In this way, in the manufacturing process 20, the uneven shape formed on the circumferential side surface of the roll plate 30 is transferred to the base material 14 at 75 ° with respect to the MD direction. Then, the substrate 14 and the cured ultraviolet curable resin 10 are peeled from the roll 30 integrally by the peeling roller 26, and the liquid crystal material is applied by the die 29. Then, the liquid crystal material was cured by ultraviolet irradiation with the ultraviolet irradiation device 27, thereby obtaining a structure of 1/4 retardation layers for wave plates.

Next, in this step 20, the substrate 14 is conveyed to the die 32 by the conveying roller 31, and the coating liquid of the ultraviolet curable resin 12 is applied to the 1/4 wave plate retardation layer of the substrate 14 through the die 32. In the manufacturing step 20, the roll plate 40 is a cylindrical forming mold in which the uneven shape of the alignment film for 1/2 wave plates of the 1/4 wavelength phase difference plate is formed on the circumferential side surface. In the manufacturing step 20, the substrate 14 coated with the ultraviolet curable resin is pressed against the circumferential side surface of the roll plate 40 by the pressing roller 34, and the ultraviolet curable resin is cured by ultraviolet irradiation by the ultraviolet irradiation device 35 including a high-pressure mercury lamp. In this way, in the manufacturing process 20, the uneven shape formed on the circumferential side surface of the roll plate 40 is transferred to the base material 14 at 15 ° with respect to the MD direction. Then, the substrate 14 and the cured ultraviolet curable resin 12 are peeled from the roll 40 integrally by the peeling roll 36, and the liquid crystal material is applied by the die 39. Then, the liquid crystal material was cured by ultraviolet irradiation with the ultraviolet irradiation device 37 to obtain a retardation film having a thickness of 7 μm and having a structure of 1/2 retardation layers for wave plates, and a retardation film having 2 layers of a retardation layer for 1/4 wave plates and a retardation layer for 1/2 wave plates.

Optical film Member (circularly polarized light functional film laminate)

The retardation film and the polarizing film obtained as described above were continuously laminated by a roll-to-roll method using the above adhesive, and a laminated film (circularly polarized light functional film laminate) was produced so that the axial angle between the slow axis and the absorption axis was 45 °.

[ first adhesive layer ]

An adhesive layer constituting the first adhesive layer of the present example was produced by the following method.

Preparation of acrylic acid oligomer

< oligomer A >

60 parts by weight of dicyclopentyl methacrylate (DCPMA) and 40 parts by weight of Methyl Methacrylate (MMA) as monomer components, 3.5 parts by weight of α -thioglycerol as a chain transfer agent, and 100 parts by weight of toluene as a polymerization solvent were mixed, and the mixture was stirred at 70 ℃ for 1 hour in a nitrogen atmosphere. Then, 0.2 part by weight of 2, 2' -Azobisisobutyronitrile (AIBN) was charged as a thermal polymerization initiator, reacted at 70 ℃ for 2 hours, and then heated to 80 ℃ for 2 hours. Then, the reaction solution was heated to 130 ℃, and toluene, a chain transfer agent, and an unreacted monomer were dried and removed, thereby obtaining a solid acrylic oligomer (oligomer a). The weight average molecular weight of oligomer A was 5100, and the glass transition temperature (Tg) was 130 ℃.

< oligomer B >

A solid acrylic oligomer (oligomer B) was obtained in the same manner as in the preparation of the oligomer a except that the monomer components were changed to dicyclohexylmethacrylate (CHMA)60 parts by weight and Butyl Methacrylate (BMA)40 parts by weight. The weight average molecular weight of oligomer B was 5000, and the glass transition temperature (Tg) was 44 ℃.

(polymerization of prepolymer)

A prepolymer composition (polymerization rate: about 10%) was obtained by polymerizing 43 parts by weight of Lauryl Acrylate (LA), 44 parts by weight of 2-ethylhexyl acrylate (2EHA), 6 parts by weight of 4-hydroxybutyl acrylate (4HBA), 7 parts by weight of N-vinyl-2-pyrrolidone (NVP), and 0.015 part by weight of IRGACURE 184 (product of BASF) as a photopolymerization initiator, with irradiation of ultraviolet light.

(preparation of adhesive composition)

To 100 parts by weight of the prepolymer composition, 0.07 part by weight of 1, 6-hexanediol diacrylate (HDDA) as a post-addition component, the oligomer a: 1 part by weight, and a silane coupling agent (KBM 403, trade name chemical Co., Ltd.): after 0.3 parts by weight, they were uniformly mixed to prepare an adhesive composition. Hereinafter, this adhesive composition is also referred to as adhesive composition 1.

(preparation of adhesive sheet)

The coating layer was formed by applying the photocurable adhesive composition described above to a substrate (also serving as a heavy release film) of a polyethylene terephthalate (PET) film (DIAFOIL MRF75, mitsubishi chemical) having a thickness of 75 μm and a silicone-based release layer provided on the surface thereof, so that the thickness of the coating layer became 50 μm. A PET film (DIAFOIL MRE75, Mitsubishi chemical) having a thickness of 75 μm and having been subjected to a silicone release treatment on one side was laminated on the coating layer as a cover sheet (also serving as a light release film). The irradiation intensity of the irradiation surface under the illumination lamp was 5mW/cm²The laminate was irradiated with ultraviolet light from the cover side and photo-cured, to obtain a pressure-sensitive adhesive sheet having a thickness of 50 μm. Hereinafter, the pressure-sensitive adhesive layer of any thickness of the pressure-sensitive adhesive composition 1 produced by the same method will also be referred to as a pressure-sensitive adhesive layer 1.

[ second adhesive layer ]

An adhesive layer constituting the second adhesive layer of this example was produced under the same conditions as the first adhesive layer except that the thickness was 15 μm.

[ third adhesive layer ]

An adhesive layer constituting the third adhesive layer of the present example was produced by the following method.

< (meth) acrylic Polymer A1 production

A monomer mixture containing 99 parts by weight of Butyl Acrylate (BA) and 1 part by weight of 4-hydroxybutyl acrylate (HBA) was placed in a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen inlet tube and a condenser.

Further, 0.1 part of 2, 2' -azobisisobutyronitrile as a polymerization initiator was added together with ethyl acetate to 100 parts by weight of the monomer mixture (solid content), nitrogen gas was introduced while stirring slowly, and after nitrogen substitution, the liquid temperature in the flask was kept near 55 ℃ to perform polymerization for 7 hours. Then, ethyl acetate was added to the obtained reaction solution to prepare a solution of a (meth) acrylic polymer a1 having a weight average molecular weight of 160 ten thousand and a solid content concentration adjusted to 30%.

Preparation of acrylic adhesive composition

An acrylic pressure-sensitive adhesive composition was prepared by mixing 0.1 part by mass of an isocyanate-based crosslinking agent (trade name: Takenate D110N, trimethylolpropane xylylene diisocyanate, manufactured by Mitsui chemical Co., Ltd.), 0.3 part by mass of a peroxide-based crosslinking agent benzoyl peroxide (trade name: NYPER BMT, manufactured by Nippon fat and oil Co., Ltd.) and 0.08 part by mass of a silane coupling agent (trade name: KBM403, manufactured by shin-Etsu chemical Co., Ltd.) with respect to 100 parts by mass of the solid content of the obtained (meth) acrylic polymer A1 solution. Hereinafter, this adhesive composition is also referred to as adhesive composition 2.

< production of adhesive sheet >

The acrylic pressure-sensitive adhesive composition was uniformly applied to the surface of a polyethylene terephthalate film (PET film, transparent substrate, separator) having a thickness of 38 μm, which had been treated with a silicone-based release agent, by means of a spray coater, and dried in an air circulation type constant temperature oven at 155 ℃ for 2 minutes to form a pressure-sensitive adhesive layer (third pressure-sensitive adhesive layer) having a thickness of 20 μm on the surface of the substrate. A polyethylene terephthalate film (PET film, transparent substrate, separator) having a thickness of 38 μm, one side of which was subjected to silicone release treatment, was bonded to the coating layer as a cover sheet (also serving as a light release film). Hereinafter, the pressure-sensitive adhesive layer of any thickness of the pressure-sensitive adhesive composition 2 produced by the same method will also be referred to as a pressure-sensitive adhesive layer 2.

[ fourth adhesive layer ]

An adhesive layer constituting the fourth adhesive layer of the present example was produced under the same conditions as the first adhesive layer except that the thickness was 25 μm.

[ Window Member ]

As the window member, a member was used in which an acrylic hard coat layer (thickness: 10 μm) was provided on one surface of a transparent polyimide film (product name: C — 50, manufactured by KOLON corporation) as a window film, and the thickness thereof was 50 μm (hereinafter, this window film is also referred to as "window film 1").

The hard coat layer is formed using a coating agent for a hard coat layer. More specifically, first, a coating agent is applied to one surface of a transparent polyimide film to form a coating layer, and the coating layer and the transparent polyimide film are heated together at 90 ℃ for 2 minutes. Then, a high pressure mercury lamp was used to accumulate the light quantity at 300mJ/cm²The coating layer is irradiated with ultraviolet rays, thereby forming a hard coating layer. Thus, a window member was produced.

The coating agent for the hard coat layer was prepared as follows: 100 parts by mass of a polyfunctional acrylate (product name "Z-850-16" manufactured by Aica Kogyo Co., Ltd.), 5 parts by mass of a leveling agent (product name: GRANDIC PC-4100 manufactured by DIC Co., Ltd.), and 3 parts by mass of a photopolymerization initiator (product name: IRGACURE 907 manufactured by Ciba Japan Co., Ltd.) as a matrix resin were mixed and diluted with methyl isobutyl ketone so that the solid content concentration became 50% by mass.

[ touch sensor Member ]

As the transparent resin substrate, a cycloolefin resin substrate ("ZEONOR" manufactured by ZEON corporation, 25 μm in thickness and 0.0001 in-plane birefringence) was prepared.

Next, a diluted solution of a hard coat composition containing a binder resin is applied to the upper surface of the transparent resin substrate, a diluted solution of a hard coat composition containing a binder resin and a plurality of particles is applied to the lower surface of the transparent resin substrate, and then, after drying these, both surfaces are irradiated with ultraviolet rays to cure the hard coat composition. Thus, a 1 st cured resin layer (thickness 1 μm) containing no particles was formed on the upper surface of the transparent resin substrate, and a 2 nd cured resin layer (thickness 1 μm) containing particles was formed on the lower surface of the transparent resin substrate.

The particles used were crosslinked acrylic-styrene resin particles ("SSX 105" from waterlogged resin Co., Ltd., diameter: 3 μm). As the binder resin, urethane polyfunctional polyacrylate (product of DIC corporation, "unicic") was used.

Next, a diluted solution of an optical adjustment composition containing zirconia particles and an ultraviolet curable resin (opsar Z7412, manufactured by JSR corporation, refractive index 1.62) was applied to the upper surface of the 1 st cured resin layer, dried at 80 ℃ for 3 minutes, and then irradiated with ultraviolet light. Thereby, an optical adjustment layer (thickness 0.1 μm) was formed on the upper surface of the 1 st cured resin layer.

Next, an ITO layer (thickness: 40nm) as an amorphous transparent conductive layer was formed on the upper surface of the optical adjustment layer by sputtering,

Thus, an amorphous transparent conductive film was produced, which was provided with the 2 nd cured resin layer, the transparent resin substrate, the 1 st cured resin layer, the optical adjustment layer, and the amorphous transparent conductive layer in this order.

Next, the obtained amorphous transparent conductive film was subjected to a heat treatment at 130 ℃ for 90 minutes to crystallize the ITO layer.

[ Panel Member ]

As a panel base, a polyimide resin film (UPILEX, 25 μm thick) using BPDA (biphenyltetracarboxylic dianhydride) as a raw material was prepared.

Next, an ITO layer (thickness 40nm) as an amorphous transparent conductive layer was formed on the upper surface of the polyimide-based resin film by sputtering.

Next, the obtained amorphous transparent conductive film was subjected to a heat treatment at 130 ℃ for 90 minutes to crystallize the ITO layer.

Then, the obtained ITO layer and the transparent conductive film with an ITO layer were used as a film sealing layer and a simulation sample of a panel member, respectively. Hereinafter, the ITO layer of the simulation sample of the thin film sealing layer is also referred to as "ITO layer replacing the thin film sealing layer" or "replacing ITO layer".

As the protective member of this example, a polyimide resin base material ("UPILEX" manufactured by Utsu corporation, 50 μm thick) using BPDA (biphenyltetracarboxylic dianhydride) as a raw material was used.

The obtained members, layers and films were variously evaluated as described below. The properties of each of the obtained adhesive layer, hard coat layer, polarizer protective film, ITO layer and alternative ITO layer are shown in tables 2-1 to 2-3.

[ example 2 ]

Each member, layer, film, and laminate was produced and produced under the same conditions as in example 1 except that the adhesive composition 2 was used as an adhesive composition of an adhesive layer constituting a second adhesive layer, and various evaluations were performed as described below. The properties of each of the obtained adhesive layer, hard coat layer, polarizer protective film, ITO layer and alternative ITO layer are shown in tables 2-1 to 2-3.

[ example 3 ]

Each member, layer, film, and laminate was produced and produced under the same conditions as in example 1 except that the following adhesive layer was used as the adhesive layer constituting the second adhesive layer, and various evaluations were performed as described below. The properties of each of the obtained adhesive layer, hard coat layer, polarizer protective film, ITO layer and alternative ITO layer are shown in tables 2-1 to 2-3.

The adhesive layer constituting the second adhesive layer of the present example was produced by the following method.

< (meth) acrylic Polymer A3 production

The polymerization reaction was carried out for 7 hours while keeping the liquid temperature in the flask at around 55 ℃, and the polymerization reaction was carried out with the blending ratio (weight ratio) of ethyl acetate to toluene being 95/5, except that the preparation of (meth) acrylic polymer a1 was carried out.

< preparation of acrylic adhesive composition >

An acrylic pressure-sensitive adhesive composition was prepared by mixing 0.15 parts by weight of trimethylolpropane/tolylene diisocyanate (product name: Coronate L, manufactured by Nippon polyurethane industries, Ltd.) and 0.08 parts by weight of a silane coupling agent (product name: KBM403, manufactured by shin-Etsu chemical industries, Ltd.) with respect to 100 parts by weight of the solid content of the obtained (meth) acrylic polymer A1 solution. Hereinafter, this adhesive composition is also referred to as adhesive composition 3.

< production of adhesive sheet >

The acrylic pressure-sensitive adhesive composition was uniformly applied to the surface of a 38 μm thick polyethylene terephthalate film (PET film, transparent substrate, separator) treated with a silicone-based release agent by means of a jet coater, and dried in an air circulation oven at 155 ℃ for 2 minutes to form a pressure-sensitive adhesive layer (second pressure-sensitive adhesive layer) having a thickness of 15 μm on the surface of the substrate. Then, a polyethylene terephthalate film (PET film, transparent substrate, separator) having a thickness of 38 μm, which had been subjected to silicone release treatment on one side, was laminated on the coating layer as a cover sheet (also serving as a light release film). Hereinafter, the pressure-sensitive adhesive layer of any thickness of the pressure-sensitive adhesive composition 3 produced by the same method will also be referred to as the pressure-sensitive adhesive layer 3.

[ example 4 ]

Other than using the following adhesive layer as the adhesive layer constituting the second adhesive layer and producing a display device and a substrate laminate as described below, each member, layer, film, and laminate was produced and produced under the same conditions as in example 1, and various evaluations were performed as described below. The properties of each of the obtained adhesive layer, hard coat layer, polarizer protective film, ITO layer and alternative ITO layer are shown in tables 2-1 to 2-3.

The adhesive layer constituting the second adhesive layer of the present example was produced by the following method.

2-ethylhexyl acrylate (2EHA) as a monomer component: 63 parts by weight, N-vinyl-2-pyrrolidone (NVP): 15 parts by weight, Methyl Methacrylate (MMA): 9 parts by weight, 2-hydroxyethyl acrylate (HEA): 13 parts by weight of 2,2' -azobisisobutyronitrile as a polymerization initiator: 0.2 part by weight and 133 parts by weight of ethyl acetate as a polymerization solvent were put into a separable flask, and stirred for 1 hour while introducing nitrogen gas. After removing oxygen in the polymerization system in this manner, the temperature was raised to 65 ℃ to carry out a reaction for 10 hours, and then ethyl acetate was added to obtain an acrylic polymer solution having a solid content of 30% by weight. The weight average molecular weight of the acrylic polymer in the acrylic polymer solution was 80 ten thousand.

Next, an isocyanate-based crosslinking agent (trade name "Takenate D110N", manufactured by mitsui chemical co., ltd.) was added to the acrylic polymer solution in an amount of 1.1 parts by weight in terms of solid content per 100 parts by weight of the acrylic polymer (solid content), and the resultant mixture was mixed to prepare a pressure-sensitive adhesive composition. Hereinafter, this adhesive composition is also referred to as adhesive composition 4.

< production of adhesive sheet >

The pressure-sensitive adhesive composition 4 was uniformly applied to the surface of a 38 μm thick polyethylene terephthalate film (PET film, transparent substrate, separator) treated with a silicone-based release agent by a jet coater, and then the sample having the coating layer formed on the PET substrate was put into an oven, and the coating layer was dried at 130 ℃ for 3 minutes to form a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer with a thickness of 15 μm on one surface of the PET substrate. A polyethylene terephthalate film (PET film, transparent substrate, separator) having a thickness of 38 μm, one side of which was subjected to silicone release treatment, was bonded to the coating layer as a cover sheet (also serving as a light release film).

Hereinafter, the pressure-sensitive adhesive layer of any thickness of the pressure-sensitive adhesive composition 4 produced by the same method is also referred to as a pressure-sensitive adhesive layer 4.

The display device and the substrate laminate of the present example were produced by the following methods.

The adhesive layer was transferred from the release film to one of the members sandwiching each adhesive layer, and the members were stacked sandwiching the adhesive layer and pressed with a hand pressure roller. Rectangular samples having a width of 30mm and a length of 100mm were cut out from the obtained laminate, and evaluation samples in which the respective members were laminated via adhesive layers were prepared.

[ examples 5 to 7, 9, 10, 12, 13, 19, 22, 27, and 28, comparative example 3 ]

Members, layers, films, and laminates were produced and produced under the same conditions as in example 1 except that the combination of the types of adhesive layers (adhesive layers 1 to 4) constituting the first adhesive layer, the second adhesive layer, the third adhesive layer, and the fourth adhesive layer was changed as shown in tables 2-1 to 2-3, and various evaluations were performed as described below. The properties of each of the obtained adhesive layer, hard coat layer, polarizer protective film, ITO layer and alternative ITO layer are shown in tables 2-1 to 2-3.

[ examples 21 and 23 ]

Each member, layer, film, and laminate was produced and produced under the same conditions as in example 1 except that the combination of the types of adhesive layers (adhesive layers 1 to 4) constituting the first adhesive layer, the second adhesive layer, the third adhesive layer, and the fourth adhesive layer was changed as shown in tables 2-1 to 2-3 and the thickness of the first adhesive layer was set to 25 μm, and various evaluations were performed as follows. The properties of each of the obtained adhesive layer, hard coat layer, polarizer protective film, ITO layer and alternative ITO layer are shown in tables 2-1 to 2-3.

[ examples 8, 11, 14, 15 to 18, 20, 24 to 26, comparative examples 1, 2, 4, and 5 ]

Each member, layer, film, laminate, display device, and substrate laminate was produced and manufactured under the same conditions as in example 4 except that the combination of the types of adhesive layers (adhesive layers 1 to 4) constituting the first adhesive layer, the second adhesive layer, the third adhesive layer, and the fourth adhesive layer was changed as shown in tables 2-1 to 2-3, and various evaluations were performed as follows. The properties of each of the obtained adhesive layer, hard coat layer, polarizer protective film, ITO layer and alternative ITO layer are shown in tables 2-1 to 2-3.

[ examples 29 to 31, comparative example 5 ]

Each member, layer, film, and laminate was produced and evaluated as described below under the same conditions as in example 1, except that the combination of the types of adhesive layers (adhesive layers 1 to 4) constituting the first adhesive layer, the second adhesive layer, the third adhesive layer, and the fourth adhesive layer was changed as shown in tables 2-1 to 2-3, and a product name "KAPTON (registered trademark) H" (hereinafter, this window film is also referred to as "window film 2") manufactured by Toray-DuPont was used as a transparent polyimide film as a window film of a window member. The properties of each of the obtained adhesive layer, hard coat layer, polarizer protective film, ITO layer and alternative ITO layer are shown in tables 2-1 to 2-3.

[ evaluation ]

(measurement of thickness)

The thicknesses of the polarizer, polarizer protective film, retardation film, adhesive layers, transparent film, window film, protective member, and the like were measured using a micrometer (manufactured by MITUTOYO). The thickness of the ITO layer and the alternative ITO layer was measured based on an image taken with a Transmission Electron Microscope (TEM).

(measurement of shear modulus G' of adhesive layer)

A separator was peeled off from the pressure-sensitive adhesive sheets of examples and comparative examples, and a plurality of pressure-sensitive adhesive sheets were laminated to prepare a test sample having a thickness of about 1.5 mm. The test specimen was punched out into a disk shape having a diameter of 7.9mm, sandwiched between parallel plates, and dynamic viscoelasticity was measured under the following conditions using an Advanced Rheometric Expansion System (ARES) manufactured by Rheometric Scientific corporation, and the shear modulus G' was read from the measurement result.

(measurement conditions)

Deformation mode: torsion

Measuring temperature: -40 ℃ to 150 DEG C

Temperature rise rate: 5 ℃/min

Measuring frequency: 1Hz

(measurement of Strain and stress)

Samples having a width of 10mm and a length of 100mm were cut out from a retardation film as an optical film member, a laminate of a polarizer and a polarizer protective film, a transparent resin base with an ITO layer as a touch sensor member, a transparent resin base of a touch sensor member, a substitute transparent resin base with a substitute ITO layer corresponding to a panel member, a substitute transparent resin base of a panel member, and a film of a protective member, and the obtained window film, polarizer protective film, adhesive layer 1, adhesive layer 2, adhesive layer 3, and adhesive layer 4. Each of the obtained samples was set in a tensile testing machine (product name "Autograph AG-IS" manufactured by Shimadzu corporation) and stretched at 200mm/min, and the strain and stress at that time were measured to obtain a strain-stress curve. The stress was converted to Pa units according to the thickness and width. In addition, for each adhesive layer, an adhesive layer having a thickness of 100 μm was prepared by laminating a plurality of adhesive layers.

In addition, in the case where it is difficult to form an adhesive layer having a thickness of 100 μm, the strain-stress curve can be obtained by the following method.

1. A normalized strain-stress curve was prepared by obtaining a strain-stress curve for a sample in advance by the above-described method, and dividing the curve by the tensile modulus of elasticity calculated from the slope of the curve in the range of strain from 0.05% to 0.25%.

2. The shear modulus G' of the sample to be measured was measured by the method described above.

3. The components of the sample to be measured are measured to obtain a poisson ratio ν.

4. Since the tensile elastic modulus E 'and the shear modulus G' satisfy the relational expression of E '═ 2G' (1+ ν), E 'is calculated from G' and ν measured in the above-described methods 2, and 3.

5. The normalized strain-stress curve created in the above 1 is multiplied by the tensile elastic modulus E' obtained in the above 4, thereby obtaining a strain-stress curve of the sample to be measured.

(simulation of the difference in Strain in the direction orthogonal to the bending radius direction)

Based on the strain-stress curves of the members and films obtained, the strains in the directions orthogonal to the bending radius direction of the members, layers and films during bending deformation of the examples and comparative examples were obtained by simulation, and a/a ', B/B ', 1.7A/a ' -0.15 were calculated, and the results are shown in tables 2-1 to 2-3.

Computer simulation software

As the simulation Software, Marc manufactured by MSC Software as nonlinear finite element analysis Software was used.

< model >

1. Layer constitution

The layer structure of the mold is the same as the cross-sectional structure of the display device of the embodiment of fig. 12.

2. Size of model

The length was 100mm, and the thickness was the total thickness of each member having the cross-section shown in fig. 12, and a mesh was produced in 2 dimensions of the thickness and the length.

3. Bending method

As shown in fig. 5, a bending piece having a length of 48mm was set at both ends, the end 10mm of the net was fixed to the bending piece (rigid body model), and the left-side bending piece was rotated 180 ° and bent so that the outermost surface of the net was the outer side. The bending diameter was set to 4mm, which is the distance between the outermost surfaces of the net facing in parallel in a state where the left bending member was rotated by 180 °.

4. Inputting physical property values of respective layers

The strain and stress of strain-stress curve data of a tensile test of each member are converted into true strain (ln (strain +1) and true stress (stress x (strain +1)), and the material characteristics of a portion corresponding to a net having a type input in a table are set such that the type is set to be inelastic, and the stress-strain curve of the corresponding material is selected from the table.

First, coefficients C10, C01, and C11 were calculated by fitting strain-stress curve data of a tensile test to the adhesive layer by the Mooney-Rivlin equation described below. Then, the type of material property of the conforming portion of the mesh was set to Mooney, and the calculated coefficients C10, C01, C11 were input.

Where γ is ═ ε +1, f is the nominal stress, and ε is the nominal strain.

The retardation film is made isotropic in material property type of the mesh-corresponding portion, and a difference between strain-test force curve data of a laminate of the retardation film, the polarizer and the polarizer protective film as an optical film member obtained by a tensile test and strain-test force curve data of a laminate of the polarizer and the polarizer protective film obtained by a tensile test is obtained, and a value of a curve corresponding to the strain-test force curve of the retardation film obtained by the difference is divided by a sectional area (width × thickness) of the retardation film, and a slope of the curve in a range where strain in the curve corresponding to the strain-stress curve of the retardation film obtained by the difference is 0.05% to 0.25% is calculated and inputted as an elastic modulus of the retardation film.

Similarly, the type of material characteristics of the mesh-fitted portion is isotropic elastoplasticity for the ITO layer, the alternative ITO layer, and the hard coat layer, and the elastic modulus is calculated and input based on the difference between the strain-test force curve of the transparent resin substrate with the ITO layer as the touch sensor member obtained by the tensile test and the strain-test force curve data of the transparent resin substrate with the touch sensor member, the difference between the strain-test force curve of the alternative transparent resin substrate with the alternative ITO layer as the panel member obtained by the tensile test and the strain-test force curve of the alternative transparent resin substrate of the panel member, and the difference between the strain-test force curve of the window film with the hard coat layer obtained by the tensile test and the strain-test force curve of the window film, respectively.

< simulation result >

For each member of each example and each comparative example, Strain (Elastic Strain in Preferred Sys) in a direction perpendicular to the bending radius direction of the bent portion was calculated (see fig. 6). Fig. 8 to 11 show the distributions in the stacking direction of the strains in the directions orthogonal to the bending radius directions of the bent portions calculated in comparative example 1 and examples 9 to 11, examples 28, 4, 8 and 11, examples 8 and 14 to 16, and examples 17 to 20.

In addition, the values of the outermost layer in the strain in the direction orthogonal to the bending radius direction of the bent portion calculated for the hard coat layer, polarizer protective film, ITO layer, and ITO layer in place of the thin-film sealing layer in each example and each comparative example, and whether or not the elongation of each layer and film is lower than the elongation at break are shown in tables 2-1 to 2-3.

Further, values of A/A ', 1.7A/A' -0.15-B/B 'and B/B' were obtained from the strains in the direction perpendicular to the bending radius direction of the bent portions calculated for each example and each comparative example, and are shown in tables 2-1 to 2-3. In addition, a graph showing the relationship of A/A' and B/B will be shown in FIG. 11.

(evaluation of occurrence of cracking)

It was confirmed whether or not the hard coat layer, polarizer protective film, ITO layer, or ITO layer instead of the thin film sealing layer was cracked during bending of the samples of the display devices of the mock samples obtained in examples 4, 8, 11, 14 to 18, 20, 24 to 26, and comparative examples 1, 2, and 4.

Specifically, as shown in fig. 12, the display device was bent at 180 degrees, the outside of the bent display device was pressed with a glass plate, a 4mm plate was further inserted between the glass plates, the bent state was maintained so that the interval between the parallel opposed outermost surfaces of the display device was maintained at 4mm, and the cracking of each layer or film was evaluated. Similarly to the simulation model, the bending diameter was set to 4mm, where the distance between the parallel facing outermost surfaces of the display device was set in a state where the display device was bent at an angle of 180 °.

For the ITO layer and the ITO layer instead of the thin film sealing layer, the occurrence of cracking was evaluated by whether the resistance value of the ITO layer after bending increased. The resistance values were measured as follows: a conductive tape (long terminal) was attached to the surface of the ITO layer, and the tape was disposed so that the resistance could be measured from the outside of the display device, and the resistance value was measured with a measuring instrument. When an ITO layer having a sheet resistance of 50 Ω/□ was used as the ITO layer, the resistance value between the long terminals before bending was about 165 Ω, and the resistance value in the bent state was 1.1 times or more the resistance value before bending, it was evaluated that cracking occurred.

The hard coat layer and the polarizer protective film were evaluated for the occurrence of cracking by microscopic observation after bending or cross-sectional SEM observation.

The results of fracture evaluation of each example and each comparative example are shown in tables 2-1 to 2-3.

(calculation of elongation at Break)

As for the elongation at break of the polarizer protective film, the elongation at break was calculated as follows. First, the same bending test as that used in the above-described evaluation of the occurrence of cracking was performed while changing the bending diameter, and the bending diameter at which cracking occurred was confirmed. Then, the bending diameter at which the fracture occurred was defined as the bending diameter, and the single-layer polarizer protective film was defined as a model, and the same simulation as described above was performed, and the strain in the direction orthogonal to the bending radius of the bent portion was calculated and defined as the elongation at break.

The elongation at break of the hard coat layer, the ITO layer, and the alternative ITO layer was calculated by the same calculation method as that of the polarizer protective film, and the elongation at break of the window film, the transparent resin substrate, and the alternative transparent resin substrate on which the hard coat layer was laminated was calculated and used as the respective elongation at break.

The calculated elongation at break of the hard coat layer, polarizer protective film, ITO layer, and alternative ITO layer of each example and each comparative example are shown in tables 2-1 to 2-3.

[ Table 4]

[ Table 5]

[ Table 6]

(evaluation)

The following results are shown in tables 2-1 to 2-3 and FIG. 11. That is, in the display devices of comparative examples 1 to 5 which do not satisfy 0.3 < A/A '< 1.2. cndot. (1), B/B' < 1.7A/A '-0.15. cndot. (2), and 0 < B/B' < 1.25. cndot. (3), the elongation of the ITO layer at the time of bending deformation calculated by simulation is higher than 1.50% which is the elongation at break of the ITO layer. I.e. showing cracking of the ITO layer. In the actually manufactured display devices of comparative examples 1, 2, and 4, the ITO layer was also cracked. In contrast, in the display devices of examples 1 to 31 satisfying the above-described expressions (1) to (3), the elongation of the ITO layer at the time of bending deformation calculated by simulation was lower than 1.50% which is the elongation at break of the ITO layer. I.e. showing that the ITO layer is not broken. In the actually manufactured display devices of examples 4, 8, 11, 14 to 18, 20, 24 to 26, no cracking was observed in the ITO layer. Therefore, the simulation results of the examples and comparative examples are well consistent with those of the actually produced examples and comparative examples in the presence or absence of occurrence of cracks. Therefore, it is understood that, in the display device of each example, the elongation of the ITO layer at the time of bending deformation can be made smaller than the elongation at break of the ITO layer, that is, the breaking of the ITO layer can be suppressed, by configuring so as to satisfy the above equations (1) to (3).

In addition, the elongation of the polarizer protective film calculated by simulation was also lower than the elongation at break (4.00%) in the display devices of examples 1 to 31, and the occurrence of cracks was not observed in the polarizer protective film in the actually manufactured display devices of examples 4, 8, 11, 14 to 18, 20, 24 to 26. Therefore, the simulation results of the examples and comparative examples are well consistent with those of the actually produced examples and comparative examples in the presence or absence of occurrence of cracks. Therefore, it is understood that, in the display device of each embodiment, the elongation of the polarizer protective film at the time of bending deformation can be made smaller than the elongation at break of the polarizer protective film, that is, the breakage of the polarizer protective film can be suppressed, by configuring the display device so as to satisfy the above equations (1) to (3).

Further, in the display devices of examples 1 to 14, 19 to 24, 27, and 29 to 31, the elongation of the ITO layer calculated by simulation was lower than the elongation at break, and the elongation of the alternative ITO layer calculated by simulation was also lower than the elongation at break (0.65%), and in the display devices of examples 4, 8, 11, 14, 20, and 24 actually manufactured, the occurrence of cracking was not confirmed in the alternative ITO layer. Therefore, the simulation results of the examples and comparative examples are well consistent with those of the actually produced examples and comparative examples in the presence or absence of occurrence of cracks. Therefore, it is understood that the display devices of examples 1 to 14, 19 to 24, 27, and 29 to 31 also have a smaller elongation of the alternative ITO layer at the time of bending deformation than that of the alternative ITO layer, that is, the breakage of the alternative ITO layer can be suppressed.

In addition, in the display devices of examples 1 to 17, 21, 23, 25, 26, and 28 to 31, the elongation of the ITO layer calculated by simulation was lower than the elongation at break, and the elongation of the hard coat layer calculated by simulation was also lower than the elongation at break (4.00%), and in the display devices of examples 4, 8, 11, 14 to 17, 25, and 26 actually manufactured, the occurrence of cracking was not observed in the hard coat layer. Therefore, the simulation results of the examples and comparative examples are well consistent with those of the actually produced examples and comparative examples in terms of the presence or absence of occurrence of cracks. Therefore, it is understood that in the display devices of examples 1 to 17, 21, 23, 25, 26, and 28 to 31, the elongation of the hard coat layer at the time of bending deformation is also smaller than the elongation of the hard coat layer, that is, the breakage of the hard coat layer can be suppressed, by configuring it so as to satisfy 0.8 < a/a '< 1.2 and 0 < B/B' < 0.9.

In the display devices of examples 1 to 14, 21, 23, and 29 to 31, the elongation at the time of bending deformation calculated by simulation was all lower than the elongation at break for the ITO layer, polarizer protective film, ITO layer instead of the thin film sealing layer, and hard coat layer, and in the display devices of practical examples 4, 8, 11, and 14, the occurrence of cracks was not confirmed for all of the ITO layer, polarizer protective film, ITO layer instead of the thin film sealing layer, and hard coat layer. Therefore, the simulation results of the examples and comparative examples are well consistent with those of the actually produced examples and comparative examples in terms of the presence or absence of occurrence of cracks. Therefore, it is understood that the display devices of examples 1 to 14, 21, 23, and 29 to 31 are configured to satisfy the requirements of 0.8 < A/A '< 0.975 and 0.3 < B/B' < 0.9, and thereby the elongation of all of the ITO layer, polarizer protective film, ITO layer instead of the thin film sealing layer, and hard coat layer at the time of bending deformation is smaller than that of each layer or film, that is, the breakage of each layer or film can be suppressed.

For easy comparison, in Table 3, comparative example 1 and examples 9 to 11, comparative example 2 and examples 12 to 14, and comparative example 5 and examples 29 to 31 in tables 2-1 to 2-3 are arranged in this order. The following results are shown in tables 2-1 to 2-3, Table 3 and FIG. 7.

The display devices of examples 1 to 4 have the same configuration except for the second adhesive layer, and the shear modulus G' of the second adhesive layer was sequentially increased, and as a result, the elongation of the ITO layer and the elongation of the ITO layer instead of the thin film sealing layer were sequentially decreased.

The display devices of examples 5 to 8 have the same configuration except for the second adhesive layer, the third adhesive layer is not the adhesive layer 1 but the adhesive layer 2 of examples 1 to 4, and the shear modulus G' of the second adhesive layer is sequentially increased, so that the elongation of the ITO layer and the elongation of the ITO layer instead of the thin film sealing layer are sequentially decreased.

The display devices of comparative examples 1 and 9 to 11 have the same configuration except for the second adhesive layer, the third adhesive layer is the adhesive layer 4 instead of the adhesive layer 2 of examples 1 to 4 and the adhesive layer 3 of examples 5 to 8, and the shear modulus G' of the second adhesive layer is sequentially increased, and as a result, the elongation of the ITO layer and the elongation of the ITO layer instead of the thin film sealing layer are sequentially decreased.

The display devices of comparative examples 2 and 12 to 14 have the same configuration except for the second adhesive layer, the third adhesive layer is not the adhesive layer 1 of examples 1 to 4, the adhesive layer 2 of examples 5 to 8, or the adhesive layer 1 of comparative examples 1 and 9 to 11, but the adhesive layer 2, and the shear modulus G' of the second adhesive layer is sequentially increased, and as a result, the elongation of the ITO layer and the elongation of the ITO layer instead of the thin-film sealing layer are sequentially decreased.

The display devices of comparative examples 5 and 29 to 31 have the same configuration except for the second adhesive layer, the first adhesive layer, the third adhesive layer, and the fourth adhesive layer have the same configuration as in comparative examples 2 and 12, the window film of the window member is not the window film 1 of examples 1 to 14 and 1 to 2 but the window film 2, and the shear modulus G' of the second adhesive layer is sequentially increased, and as a result, the elongation of the ITO layer and the elongation of the ITO layer instead of the thin-film sealing layer are sequentially decreased.

As described above, by increasing the shear modulus G' of the second adhesive layer, the elongation of the ITO layer at the time of bending deformation and the elongation of the ITO layer instead of the thin film sealing layer can be reduced, that is, the breaking of the ITO layer and the ITO layer instead of the thin film sealing layer can be suppressed.

For easy comparison, examples 28, 4, 8 and 11 in tables 2-1 to 2-3 are listed in order in Table 4. The following results are shown in tables 2-1 to 2-3, Table 4 and FIG. 8.

The display devices of examples 28, 4, 8, and 11 had the same configuration except for the third adhesive layer, and the shear modulus G' of the third adhesive layer was sequentially increased, and as a result, the elongation of the ITO layer was sequentially increased.

Therefore, it is known that by reducing the shear modulus G' of the third adhesive layer, the elongation of the ITO layer at the time of bending deformation can be reduced, that is, the breaking of the ITO layer can be suppressed.

For easy comparison, example 8 and examples 14 to 16 in tables 2-1 to 2-3 are listed in order in Table 5. The following results are shown in tables 2-1 to 2-3, Table 5 and FIG. 9.

The display devices of examples 8, 14 to 16 had the same configuration except for the fourth adhesive layer, and the shear modulus G' of the fourth adhesive layer was sequentially increased, so that the elongation of the ITO layer and the elongation of the ITO layer instead of the thin-film sealing layer were sequentially increased.

Therefore, it is found that by reducing the shear modulus G' of the fourth adhesive layer, the elongation of the ITO layer at the time of bending deformation and the elongation of the ITO layer instead of the thin film sealing layer can be reduced, that is, the breaking of the ITO layer and the ITO layer instead of the thin film sealing layer can be suppressed.

For easy understanding, in Table 6, examples 8 and 21 to 22, and examples 11 and 23 to 24 in Table 1 are arranged in this order. The following results are shown in tables 2-1 to 2-3, Table 6 and FIG. 10.

The display devices of examples 17 to 20 had the same configuration except for the first adhesive layer, and the shear modulus G' of the first adhesive layer was sequentially increased, and as a result, the elongation of the hard coat layer was sequentially increased.

The display devices of examples 8, 21 and 22 have the same configuration except for the first adhesive layer, the third adhesive layer is not the adhesive layer 3 but the adhesive layer 4 of examples 17 to 20, and the fourth adhesive layer is not the adhesive layer 4 but the adhesive layer 1 of examples 17 to 20. The shear modulus G' of the first adhesive layers of examples 8, 21 were the same, but the thickness of the first adhesive layer of example 21 was less than the thickness of the first adhesive layer of example 8. Thus, the hardness of the first adhesive layer of example 21 is greater than that of example 8. As described above, the shear modulus G ' of the adhesive layer is the dominant factor as a factor for determining the hardness of the adhesive layer, and as a result, the shear modulus G ' of example 22 is greater than the shear modulus G ' of example 21 by a factor of 2 or more, and therefore the hardness of the first adhesive layer of example 22 is greater than that of example 21. Therefore, the hardness of the first adhesive layer becomes successively higher, and as a result, the elongation of the hard coat layer becomes successively higher.

The display devices of examples 11, 23, and 24 have the same configuration except for the first adhesive layer, the fourth adhesive layer is not the adhesive layer 3 but the adhesive layer 4 of examples 17 to 20, and the hardness of the first adhesive layer is gradually increased, and as a result, the elongation of the hard coat layer is gradually increased.

As is apparent from the above, by reducing the hardness of the first adhesive layer, the elongation of the hard coat layer at the time of bending deformation can be reduced, that is, the breakage of the hard coat layer can be suppressed.

Arrows in the strain distribution diagrams of fig. 7 to 10 indicate: when the hardness of the corresponding adhesive layer is increased, the strain of the corresponding layer or film moves in the tensile direction or in the compressive direction. The broken lines indicate the elongation at break of the corresponding layers and films.

As is apparent from fig. 7 to 10, in the display devices of the respective examples and the respective comparative examples in which the plurality of layers and members are laminated via the plurality of adhesive layers, if one of the adhesive layers is hardened, when the display device is bent, the strains of the layers and members laminated on the outer side of the adhesive layer move in the tensile direction, and the strains of the layers and members laminated on the inner side of the adhesive layer move in the compressive direction.

For example, in comparative example 1 and examples 9 to 11, referring to fig. 7, the shear modulus G' of the second adhesive layer is sequentially increased, that is, the hardness of the second adhesive layer is sequentially increased, and as the hardness of the second adhesive layer is increased, the strain of the outer layer or member of the second adhesive layer is moved in the tensile direction, and the strain of the inner layer or member of the second adhesive layer is moved in the compressive direction. The same applies to the groups of the embodiments and/or comparative examples of fig. 8 to 10.

While specific embodiments of the present invention have been described above with reference to the accompanying drawings, the present invention may be variously modified in addition to the illustrated and described configurations. Accordingly, the present invention is not limited to the illustrated and described configurations, but is only limited by the scope of the appended claims and equivalents thereof.

Claims (11)

1. A display device is a bendable display device,

the display device has: an optical film member, a first adhesive layer, a window member laminated on one surface of the optical film member via the first adhesive layer, a second adhesive layer, and a laminated structure including a panel member laminated on the other surface of the optical film member via the second adhesive layer,

the laminated structure has a layer which is more easily broken than the window member and the optical film member when the surface on the second adhesive layer side is subjected to bending deformation,

the shear modulus of the second adhesive layer is greater than the shear modulus of the first adhesive layer,

the easily breakable layer has an elongation at break of more than 1.37%,

the following strain differences A, A ', B, B' satisfy the relationships of the following expressions (1), (2) and (3), whereby the elongation of the easily breakable layer at the time of bending deformation is suppressed to a value smaller than the elongation at break,

0.3＜A/A’＜1.2····(1)

B/B’＜1.7A/A’－0.15····(2)

0＜B/B’＜1.25····(3)

Wherein the strain differences A, A ', B, B' are defined as follows:

bending the display device at an angle of 180 DEG with the window member facing outward, and bending and deforming the display device so that the distance between the parallel facing outermost surfaces of the display device becomes 4mm in the state of being bent at an angle of 180 DEG, wherein the difference between the strain in the direction orthogonal to the bending radius direction occurring on the one surface of the optical film member at this time and the strain in the direction orthogonal to the bending radius direction occurring on the surface of the window member facing the first adhesive layer is defined as A,

bending deformation is caused so that the optical film member and the window member are respectively bent at an angle of 180 degrees in a single layer state, and the distance between the parallel facing outermost surfaces of the optical film member and the window member is 4mm in the state of being bent at an angle of 180 degrees, in the same manner as when the display device is bent, the difference between the strain in the direction orthogonal to the direction of the bending radius generated on the outer surface of the optical film member at that time and the strain in the direction orthogonal to the direction of the bending radius generated on the inner surface of the window member is defined as A',

Bending the display device at an angle of 180 DEG with the window member as an outer side, and bending the display device so that a distance between the parallel facing outermost surfaces of the display device becomes 4mm in a state of being bent at an angle of 180 DEG, wherein a difference between a strain in a direction orthogonal to a bending radius direction generated on the other surface of the optical film member at this time and a strain in a direction orthogonal to the bending radius direction generated on a surface facing the second adhesive layer of the laminated structure is defined as B,

in the same manner as in the case of bending the display device, the outer side and the inner side in the bending deformation are bent at an angle of 180 ° in a single layer state, and the bending deformation is caused so that the distance between the parallel facing outermost surfaces of the optical film member and the laminated structure becomes 4mm in the state of being bent at an angle of 180 °, and the difference between the strain in the direction orthogonal to the bending radius direction caused on the inner surface of the optical film member and the strain in the direction orthogonal to the bending radius direction caused on the outer surface of the laminated structure at this time is defined as B'.

2. The display device according to claim 1,

the window member has a hard coat layer on a face opposite to the first adhesive layer.

3. The display device according to claim 1 or 2,

the optical film member is a circularly polarized light functional film laminate in which a phase difference film is laminated on a polarizing film.

4. The display device according to claim 3,

the polarizing film is a laminate in which a polarizer and a polarizer protective film on at least one surface of the polarizer are laminated.

5. The display device according to claim 4,

the polarizer protective film includes an acrylic resin.

6. The display device according to any one of claims 1 to 5,

the layer which is more easily broken than the window member and the optical film member is a film seal layer formed on the second pressure-sensitive adhesive layer side surface of the panel member.

7. The display device according to any one of claims 1 to 5,

the laminated structure has a film seal layer formed on a surface of the panel member on the second adhesive layer side, a touch sensor member laminated on a surface of the film seal layer on the opposite side to the panel member via a third adhesive layer, and a transparent conductive layer formed on a surface of the touch sensor member on the opposite side to the panel member, the transparent conductive layer being laminated on the second adhesive layer as a layer which is more easily broken than the window member and the optical film member.

8. The display device according to any one of claims 2 to 7,

the difference A, A' between the strains further satisfies the relationship of the following formula (4),

0.8＜A/A’····(4)。

9. the display device according to any one of claims 1 to 8,

a fourth adhesive layer is further laminated on the face of the panel member opposite to the second adhesive layer,

and a protective member is laminated via the fourth adhesive layer.

10. The display device according to claim 7,

the panel member further includes a fourth adhesive layer on a surface thereof opposite to the second adhesive layer, and a protective member laminated via the fourth adhesive layer,

the shear modulus of the fourth bonding layer is less than the shear modulus of the second bonding layer and less than the shear modulus of the third bonding layer.

11. A substrate laminate for use in the display device according to claim 7 or 10, the substrate laminate having:

the optical film member,

The window member laminated on one surface of the optical film member via the first adhesive layer, and

and a touch sensor member including the transparent conductive layer, which is laminated on the other surface of the optical film member via the second adhesive layer.

Images