Adhesive composition for flexible image display device, adhesive layer for flexible image display device, laminate for flexible image display device, and flexible image display device

Abstract

The purpose of the present invention is to provide: an adhesive composition for a flexible image display device, which contains a (meth) acrylic polymer and comprises a specific monomer; an adhesive layer for a flexible image display device; a laminate for a flexible image display device; and a flexible image display device. This adhesive composition for a flexible image display device contains a (meth) acrylic polymer that contains, as monomer units, a monomer having a reactive functional group and a (meth) acrylic monomer. The monomer having a reactive functional group is selected from one or more of a hydroxyl group-containing monomer, a carboxyl group-containing monomer, an amino group-containing monomer, and an amide group-containing monomer, and the (meth) acrylic monomer has a linear or branched alkyl group having 1-24 carbon atoms, the monomer having a reactive functional group is contained in an amount of 0.02-10% by weight of the total monomers constituting the (meth) acrylic polymer.

Description

[0001] This application is a divisional application of an application with an application date of August 2, 2017, an application number of 201780050079.0, and an invention title of "Adhesive Composition for Flexible Image Display Device, Adhesive Layer for Flexible Image Display Device, Laminate for Flexible Image Display Device, and Flexible Image Display Device". Technical Field

[0002] The present invention relates to an adhesive composition for a flexible image display device, an adhesive layer for a flexible image display device, a laminate for a flexible image display device including the above adhesive layer and an optical laminate, and a flexible image display device provided with the above laminate for a flexible image display device. Background Art

[0003] As a touch sensor integrated organic EL display device, as Figure 1 shown, an optical laminate 20 is provided on the visible side of an organic EL display panel 10, and a touch panel 30 is provided on the visible side of the optical laminate 20. The optical laminate 20 includes a polarizing film 1 and a retardation film 3 with protective films 2-1 and 2-2 bonded to both sides, and a polarizing film 1 is provided on the visible side of the retardation film 3. In addition, the touch panel 30 has a structure in which transparent conductive films 4-1 and 4-2 are arranged with a spacer 7 therebetween, and the transparent conductive films 4-1 and 4-2 have a structure in which a base film 5-1, 5-2 and a transparent conductive layer 6-1, 6-2 are laminated (for example, refer to Patent Document 1).

[0004] In addition, it is expected to realize a bendable organic EL display device with more excellent portability.

[0005] Prior Art Documents

[0006] Patent Documents

[0007] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2014-157745 Summary of the Invention

[0008] Problems to be Solved by the Invention

[0009] However, the existing organic EL display device as shown in Patent Document 1 is not designed considering bending. If a plastic film is used in the organic EL display panel substrate, bendability can be imparted to the organic EL display panel. In addition, when a plastic film is used in the touch panel and introduced into the organic EL display panel, bendability can also be imparted to the organic EL display panel. However, the optical laminate including the existing polarizing film, its protective film, and retardation film laminated in the organic EL display panel has a problem of hindering the bendability of the organic EL display device.

[0010] Accordingly, an object of the present invention is to provide an adhesive composition for a flexible image display device containing a (meth)acrylic polymer composed of specific monomers, an adhesive layer for a flexible image display device formed from the above adhesive composition, a laminate for a flexible image display device that does not peel off even for repeated bending and has excellent bending resistance and adhesion by using the above adhesive layer and an optical laminate, and a flexible image display device provided with the above laminate for a flexible image display device.

[0011] Means for Solving the Problem

[0012] The adhesive composition for a flexible image display device of the present invention contains a (meth)acrylic polymer containing a monomer having a reactive functional group and a (meth)acrylic monomer as monomer units, the monomer having a reactive functional group is selected from one or more of a hydroxyl group-containing monomer, a carboxyl group-containing monomer, an amino group-containing monomer, and an amide group-containing monomer, and the (meth)acrylic monomer has a linear or branched alkyl group having 1 to 24 carbon atoms. Among all the monomers constituting the (meth)acrylic polymer, 0.02 to 10% by weight of the monomer having a reactive functional group is contained.

[0013] Preferably, the adhesive composition for a flexible image display device of the present invention contains an isocyanate crosslinking agent and / or a peroxide crosslinking agent.

[0014] Preferably, the adhesive layer for a flexible image display device of the present invention is formed from the adhesive composition, wherein the weight average molecular weight (Mw) of the (meth)acrylic polymer is 1 million to 2.5 million.

[0015] Preferably, the laminate for a flexible image display device of the present invention includes the adhesive layer for a flexible image display device and an optical laminate. The adhesive layer for a flexible image display device is a first adhesive layer, and the optical laminate includes a polarizing film, a protective film made of a transparent resin material provided on the first surface of the polarizing film, and a retardation film provided on the second surface of the polarizing film different from the first surface. The laminate for a flexible image display device has the first adhesive layer disposed on the side opposite to the side of the protective film in contact with the polarizing film.

[0016] Preferably, the laminate for a flexible image display device of the present invention has a second adhesive layer disposed on the side opposite to the side of the retardation film in contact with the polarizing film.

[0017] Preferably, the laminate for a flexible image display device of the present invention has a transparent conductive layer constituting a touch sensor disposed on the side opposite to the side of the second adhesive layer in contact with the retardation film.

[0018] Preferably, a third adhesive layer is disposed on the side opposite to the side of the transparent conductive layer constituting the touch sensor that contacts the second adhesive layer in the laminate for a flexible image display device of the present invention.

[0019] Preferably, a transparent conductive layer constituting a touch sensor is disposed on the side opposite to the side of the first adhesive layer that contacts the protective film in the laminate for a flexible image display device of the present invention.

[0020] Preferably, a third adhesive layer is disposed on the side opposite to the side of the transparent conductive layer constituting the touch sensor that contacts the first adhesive layer in the laminate for a flexible image display device of the present invention.

[0021] Preferably, the flexible image display device of the present invention includes the laminate for a flexible image display device and an organic EL display panel, wherein the laminate for a flexible image display device is disposed on the visible side of the organic EL display panel.

[0022] Preferably, a window is disposed on the visible side of the laminate for a flexible image display device in the flexible image display device of the present invention.

[0023] Effects of the Invention

[0024] Regarding the adhesive composition for a flexible image display device of the present invention, since it contains a (meth)acrylic polymer composed of specific monomers, the adhesive layer for a flexible image display device formed from the above adhesive composition is not likely to harden and becomes an adhesive layer with excellent stress relaxation properties. By using the above specific adhesive layer and optical laminate, a laminate for a flexible image display device that does not peel off even for repeated bending and has excellent bending resistance and adhesion can be obtained. Furthermore, a flexible image display device provided with the above laminate for a flexible image display device can be obtained, which is useful.

[0025] Hereinafter, embodiments of the adhesive composition for a flexible image display device, the adhesive layer for a flexible image display device, the laminate for a flexible image display device, and the flexible image display device of the present invention will be described in detail with reference to the drawings and the like. Description of the Drawings

[0026] Figure 1 It is a cross-sectional view showing a conventional organic EL display device.

[0027] Figure 2 It is a cross-sectional view showing a flexible image display device according to an embodiment of the present invention.

[0028] Figure 3 It is a cross-sectional view showing a flexible image display device according to another embodiment of the present invention.

[0029] Figure 4 It is a cross-sectional view of a flexible image display device showing another embodiment of the present invention.

[0030] Figure 5 It is a diagram showing a method for measuring the flexural strength.

[0031] Figure 6 It is a cross-sectional view of an evaluation sample (Structure A) used in the examples.

[0032] Figure 7 It is a cross-sectional view of an evaluation sample (Structure B) used in the examples.

[0033] Figure 8 It is a diagram showing a manufacturing method of the phase difference used in the examples.

[0034] Symbol Explanation

[0035] 1 Polarizing film

[0036] 2 Protective film

[0037] 2-1 Protective film

[0038] 2-2 Protective film

[0039] 3 Phase difference layer

[0040] 4-1 Transparent conductive film

[0041] 4-2 Transparent conductive film

[0042] 5-1 Substrate film

[0043] 5-2 Substrate film

[0044] 6 Transparent conductive layer

[0045] 6-1 Transparent conductive layer

[0046] 6-2 Transparent conductive layer

[0047] 7 Spacer

[0048] 8 Transparent substrate

[0049] 8-1 Transparent substrate (PET film)

[0050] 9 Substrate (PI film)

[0051] 10 Organic EL display panel

[0052] 11 Laminate for flexible image display device (laminate for organic EL display device)

[0053] 12 Adhesive layer

[0054] 12-1 First adhesive layer

[0055] 12-2 Second adhesive layer

[0056] 12-3 Third adhesive layer

[0057] 13 Decorative printing film

[0058] 20 Optical laminate

[0059] 30 Touch panel

[0060] 40 Window

[0061] 100 Flexible image display device (organic EL display device) Detailed implementation manners

[0062] [Laminate for flexible image display device]

[0063] Preferably, the laminate for a flexible image display device of the present invention includes an adhesive layer for a flexible image display device and an optical laminate. The adhesive layer for a flexible image display device is the first adhesive layer. The optical laminate includes a polarizing film, a protective film made of a transparent resin material provided on the first surface of the polarizing film, and a retardation film provided on the second surface of the polarizing film different from the first surface. The laminate for a flexible image display device is provided with the first adhesive layer on the side opposite to the side of the protective film in contact with the polarizing film.

[0064] [Optical laminate]

[0065] Preferably, the laminate for a flexible image display device of the present invention includes an optical laminate. The optical laminate includes a polarizing film, a protective film made of a transparent resin material provided on the first surface of the polarizing film, and a retardation film provided on the second surface of the polarizing film different from the first surface. It should be noted that the above optical laminate does not include the first adhesive layer, the second adhesive layer, etc. described later.

[0066] The thickness of the above optical laminate is preferably 100 μm or less, more preferably 60 μm or less, and further preferably 10 - 50 μm. When within the above range, it will not hinder bending and becomes a preferred mode.

[0067] As long as the properties of the present invention are not impaired, a protective film (not shown in the drawings) may be laminated on at least one side of the above-mentioned polarizing film using an adhesive layer. An adhesive may be used for the bonding treatment between the polarizing film and the protective film. Examples of the adhesive include isocyanate adhesives, polyvinyl alcohol adhesives, gelatin adhesives, vinyl latexes, and aqueous polyesters. The above-mentioned adhesive is usually used as an adhesive formed from an aqueous solution and usually contains 0.5 to 60% by weight of a solid component. In addition to the above, examples of the adhesive for bonding the polarizing film and the protective film include ultraviolet curable adhesives and electron beam curable adhesives. The electron beam curable adhesive for polarizing films exhibits suitable adhesiveness to various protective films. In addition, a metal compound filler may be contained in the adhesive used in the present invention. It should be noted that in the present invention, the material formed by bonding the polarizing film and the protective film through an adhesive (layer) is sometimes referred to as a polarizing film (polarizer).

[0068] <Polarizing film>

[0069] The polarizing film (also referred to as a polarizer) used in the optical laminate of the present invention may be a polyvinyl alcohol (PVA) - based resin in which iodine is oriented after being stretched by a stretching process such as stretching in a gas atmosphere (dry stretching) or a stretching process in an aqueous boric acid solution.

[0070] As a representative method for manufacturing a polarizing film, there is a manufacturing method (single - layer stretching method) including a step of dyeing a single - layer body of a PVA - based resin and a step of stretching, as described in Japanese Patent Laid - Open No. 2004 - 341515. In addition, there are methods including a step of stretching a PVA - based resin layer and a stretching - resin substrate in a laminated state and a step of dyeing, as described in Japanese Patent Laid - Open Nos. 51 - 069644, 2000 - 338329, 2001 - 343521, International Publication No. 2010 / 100917, Japanese Patent Laid - Open No. 2012 - 073563, and Japanese Patent Laid - Open No. 2011 - 2816. According to this manufacturing method, even if the PVA - based resin layer is thin, since it is supported by the stretching - resin substrate, stretching can be performed without causing defects such as breakage due to stretching.

[0071] In a production method including a step of stretching in a laminate state and a step of dyeing, there is a method of stretching in a gas atmosphere (dry stretching) as described in Japanese Patent Application Laid-Open No. 51-069644, Japanese Patent Application Laid-Open No. 2000-338329, and Japanese Patent Application Laid-Open No. 2001-343521. Moreover, from the aspect of being able to stretch at a high magnification to improve the polarization performance, a production method including a step of stretching in an aqueous boric acid solution as described in International Publication No. 2010 / 100917 and Japanese Patent Application Laid-Open No. 2012-073563 is preferred. Particularly preferred is a production method (two-step stretching method) including a step of auxiliary stretching in a gas atmosphere before stretching in an aqueous boric acid solution as in Japanese Patent Application Laid-Open No. 2012-073563. In addition, a production method (over-dyeing and decoloring method) as described in Japanese Patent Application Laid-Open No. 2011-2816, in which a PVA-based resin layer and a stretching resin substrate are stretched in a laminate state, the PVA-based resin layer is over-dyed, and then decolorized, is also preferred. The polarizing film used in the optical laminate of the present invention can be a polarizing film formed of a polyvinyl alcohol-based resin in which iodine is oriented and stretched by a two-step stretching process composed of auxiliary stretching in a gas atmosphere and stretching in an aqueous boric acid solution as described above. In addition, the polarizing film used in the optical laminate of the present invention can be a polarizing film formed of a polyvinyl alcohol-based resin in which iodine is oriented and produced by over-dyeing and then decoloring a laminate of a stretched PVA-based resin layer and a stretching resin substrate as described above.

[0072] The thickness of the polarizing film used in the optical laminate of the present invention is preferably 12 μm or less, more preferably 9 μm or less, further preferably 1 to 8 μm, and particularly preferably 3 to 6 μm. When within the above range, bending is not hindered, and it becomes a preferred mode.

[0073] <Retardation film>

[0074] The retardation film (also referred to as a retardation thin film) used in the optical laminate of the present invention can be a film obtained by stretching a polymer film, or a film obtained by orienting and immobilizing a liquid crystal material. In the present specification, the retardation film refers to a film having birefringence in the in-plane and / or thickness direction.

[0075] Examples of the retardation film include a retardation film for antireflection (see Japanese Patent Application Laid-Open No. 2012-133303

[0221] ,

[0222] ,

[0228] ), a retardation film for viewing angle compensation (see Japanese Patent Application Laid-Open No. 2012-133303

[0225] ,

[0226] ), an inclined orientation retardation film for viewing angle compensation (see Japanese Patent Application Laid-Open No. 2012-133303

[0227] ), and the like.

[0076] As the retardation film, as long as it substantially has the above functions, there are no particular limitations on, for example, the retardation value, the arrangement angle, the three-dimensional birefringence, whether it is a single layer or a multilayer, etc., and known retardation films can be used.

[0077] In this specification, Re

[550] refers to the in-plane retardation value measured with light having a wavelength of 550 nm at 23°C. Re

[550] can be obtained by the following method: when the refractive indices in the slow axis direction and the fast axis direction of the retardation film at a wavelength of 550 nm are nx and ny respectively, and d (nm) is the thickness of the retardation film, it is obtained by the formula: Re

[550] = (nx - ny) × d. It should be noted that the slow axis refers to the direction in which the refractive index in the plane is the largest.

[0078] The in-plane birefringence Δn of nx - ny in the present invention is 0.002 to 0.2, preferably 0.0025 to 0.15.

[0079] For the above-mentioned retardation film, it is preferable that the in-plane retardation value (Re

[550] ) measured with light having a wavelength of 550 nm at 23°C is greater than the in-plane retardation value (Re

[450] ) measured with light having a wavelength of 450 nm. When the retardation film having such a wavelength dispersion characteristic is in the above ratio range, the longer the wavelength, the more the retardation is exhibited, and ideal retardation characteristics can be obtained at each wavelength in the visible region. For example, when used in an organic EL display, by fabricating a retardation film having such a wavelength dependence as a quarter-wave plate and laminating it with a polarizer, a circular polarizer, etc. can be fabricated, and a neutral polarizer and a display device with little wavelength dependence of the hue can be realized. On the other hand, when the above ratio is outside this range, the wavelength dependence of the reflected hue becomes larger, and problems such as coloring of the polarizer and the display device occur.

[0080] The ratio of Re

[550] to Re

[450] (Re

[450] / Re

[550] ) of the above-mentioned retardation film is 0.8 or more and less than 1.0, more preferably 0.8 to 0.95.

[0081] For the above-mentioned retardation film, it is preferable that the in-plane retardation value (Re

[550] ) measured with light having a wavelength of 550 nm at 23°C is less than the in-plane retardation value (Re

[650] ) measured with light having a wavelength of 650 nm. The retardation film having such a wavelength dispersion characteristic has a constant retardation value in the red region. For example, when used in a liquid crystal display device, the phenomenon of light leakage occurring depending on the viewing angle and the phenomenon that the displayed image has a red hue (also called the red band phenomenon) can be improved.

[0082] The ratio of Re

[650] to Re

[550] (Re

[550] / Re

[650] ) of the above-mentioned retardation film is 0.8 or more and less than 1.0, preferably 0.8 to 0.97. By setting Re

[550] / Re

[650] within the above range, for example, when the above-mentioned retardation film is used for an organic EL display, more excellent display characteristics can be obtained.

[0083] Re

[450] , Re

[550] , and Re

[650] can be measured using the product name "AxoScan" manufactured by Axometrics.

[0084] In this specification, NZ refers to the ratio of nx - nz of the birefringence in the thickness direction to nx - ny of the in-plane birefringence (also referred to as the Nz coefficient).

[0085] The NZ of the retardation film of the present invention is 0 to 1.3, preferably 0 to 1.25, and more preferably 0 to 1.2.

[0086] The refractive index anisotropy of the retardation film of the present invention satisfies the relationship nx > ny, preferably nx > ny ≥ nz.

[0087] For example, usually in the case of longitudinal stretching, the width direction is not fixed with respect to the stretching in the length direction of the film, so width contraction occurs. As a result, the state becomes that the molecules are further oriented in the uniaxial direction. As the relationship of the refractive indices, for example, it is nx > ny = nz. In this case, the flexural strength in the length direction of the film as the stretching direction is enhanced, but the flexural strength in the width direction becomes very weak. To solve this problem, by performing stretching in the angular direction intersecting the stretching direction in a state where a force restricting the width is generated (for example, in the case of transverse uniaxial stretching, with respect to the width direction of the film as the stretching direction, a force is generated to make the length in the length direction of the film in the right-angle direction constant), the molecules can be oriented not only in the stretching direction but also in the angular direction intersecting the stretching direction. As the relationship of the refractive indices, it can be nx > ny > nz. Thereby, the flexural strength in the stretching direction and the flexural strength in the width direction can be balanced at a high level.

[0088] The absolute value of the photoelastic coefficient of the above-mentioned retardation film at 23°C; C(m 2 / N) is 2×10 -12 ~100×10 -12 (m 2 / N), preferably 2×10 -12 ~50×10 -12 (m 2 / N). It is possible to prevent the change in the phase difference value that occurs when a force is applied to the retardation film due to the shrinkage stress of the polarizing film, the heat of the display panel, and the surrounding environment (moisture / heat resistance). As a result, a display panel device with good display uniformity can be obtained. The C of the above retardation film is preferably 3×10 -12 ~45×10 -12 and particularly preferably 10×10 -12 ~40×10 -12 . By setting C within the above range, the change and unevenness of the phase difference value that occur when a force is applied to the above retardation film can be reduced. In addition, the photoelastic coefficient and Δn are easily in a trade-off relationship. In this range of the photoelastic coefficient, the display quality can be ensured without reducing the retardation manifestation.

[0089] In one embodiment, the retardation film of the present invention is produced by stretching a polymer film to orient it.

[0090] As the method for stretching the polymer film, any suitable stretching method can be adopted according to the purpose. As the stretching method suitable for the present invention, for example, a unidirectional stretching method in the transverse direction, a simultaneous biaxial stretching method in the longitudinal and transverse directions, a stepwise biaxial stretching method in the longitudinal and transverse directions, etc. can be cited. As the device for stretching, any suitable stretching machine such as a tenter stretching machine or a biaxial stretching machine can be used. It is preferable that the above stretching machine has a temperature control mechanism. In the case of heating and stretching, the internal temperature of the stretching machine can be continuously changed or can be continuously changed. The process can be divided into 1 time or 2 times or more. The stretching direction can be stretching in the film width direction (TD direction) or in an inclined direction.

[0091] In the inclined stretching, the unstretched resin film is fed out in the length direction and an inclined stretching process of continuously stretching in a direction at an angle within the above specific range with respect to the width direction is performed. As a result, a long-strip retardation film in which the angle (orientation angle θ) formed by the width direction of the film and the slow axis is within the above specific range can be obtained.

[0092] As the method for performing the inclined stretching, as long as it can be continuously stretched in a direction at an angle within the above specific range with respect to the width direction of the unstretched resin film and a slow axis can be formed in a direction at an angle within the above specific range with respect to the width direction of the film, there is no particular limitation. Any suitable method can be adopted from the existing well-known stretching methods such as JP-A-2005-319660, JP-A-2007-30466, JP-A-2014-194482, JP-A-2014-199483, JP-A-2014-199483, etc.

[0093] The temperature for stretching the unstretched resin film (stretching temperature) can be appropriately selected according to the purpose. It is preferably stretched in the range of Tg - 20°C to Tg + 30°C relative to the glass transition temperature (Tg) of the polymer film. By selecting such conditions, the phase difference is likely to become uniform, and the film is less likely to crystallize (become cloudy). Specifically, the above-mentioned stretching temperature is 90 to 210°C, more preferably 100 to 200°C, and particularly preferably 100 to 180°C. It should be noted that the glass transition temperature can be determined by the DSC method based on JIS K7121 (1987).

[0094] As a device for controlling the above-mentioned stretching temperature, any suitable device can be used. Examples of the above-mentioned temperature control device include: an air-circulating constant-temperature oven with hot air or cold air circulation, a heater using microwaves or far-infrared rays, a heated roller for temperature adjustment, a heat pipe roller, a metal belt, etc.

[0095] The stretching ratio (stretching magnification) for stretching the above-mentioned unstretched resin film can be appropriately selected according to the purpose. The above-mentioned stretching ratio is preferably greater than 1 and 6 times or less, more preferably greater than 1.5 times and 4 times or less.

[0096] In addition, the conveyance speed during stretching is not particularly limited. From the viewpoints of mechanical accuracy, stability, etc., it is preferably 0.5 to 30 m / min, more preferably 1 to 20 m / min. Under the above-mentioned stretching conditions, a retardation film can be obtained that not only exhibits the target optical properties but also has excellent optical uniformity.

[0097] In addition, as another embodiment thereof, the following retardation film can be used: a retardation film obtained by laminating a single sheet using an acrylic adhesive such that the angle formed by the absorption axis of the polarizer and the slow axis of the 1 / 2 wavelength plate is 15°, and the angle formed by the absorption axis of the polarizer and the slow axis of the 1 / 4 wavelength plate is 75°, using a polycycloolefin film, a polycarbonate film, etc.

[0098] In other embodiments, the retardation film of the present invention may be a retardation film formed by laminating retardation layers made by aligning and immobilizing a liquid crystal material. Each retardation layer may be an alignment cured layer of a liquid crystal compound. By using a liquid crystal compound, the difference between nx and ny of the resulting retardation layer can be significantly increased compared to non-liquid crystal materials. Therefore, the thickness of the retardation layer used to obtain a desired in-plane retardation can be significantly reduced. As a result, further thinning of the circular polarizing plate (ultimately, the flexible image display device) can be achieved. In this specification, an "alignment cured layer" refers to a layer in which a liquid crystal compound is aligned in a given direction within the layer and its alignment state is fixed. In this embodiment, typically, rod-shaped liquid crystal compounds are aligned in a state parallel to the slow axis direction of the retardation layer (homogeneous alignment). Examples of the liquid crystal compound include liquid crystal compounds having a nematic liquid crystal phase (nematic liquid crystals). As such liquid crystal compounds, for example, liquid crystal polymers and liquid crystal monomers can be used. The mechanism for the manifestation of liquid crystallinity of the liquid crystal compound can be lyotropic or thermotropic. The liquid crystal polymer and the liquid crystal monomer can be used alone or in combination.

[0099] In the case where the liquid crystal compound is a liquid crystal monomer, the liquid crystal monomer is preferably a polymerizable monomer and 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 monomer is aligned, for example, if the liquid crystal monomers are polymerized or crosslinked with each other, the above alignment state can be fixed. Here, a polymer is formed by polymerization and a three-dimensional network structure is formed by crosslinking, but they are non-liquid crystalline. Therefore, the resulting retardation layer does not undergo, for example, the transition from a liquid crystal phase, a glass phase, or a crystalline phase due to temperature changes, which is characteristic of liquid crystalline compounds. As a result, the retardation layer becomes a retardation layer with extremely excellent stability that is not affected by temperature changes.

[0100] The temperature range in which the liquid crystal monomer exhibits liquid crystallinity varies depending on its type. Specifically, the temperature range is preferably 40 to 120 °C, more preferably 50 to 100 °C, and most preferably 60 to 90 °C.

[0101] As the above liquid crystal monomer, any suitable liquid crystal monomer can be used. For example, polymerizable mesogenic compounds described in JP-T-2002-533742 (WO00 / 37585), EP358208 (US5211877), EP66137 (US4388453), WO93 / 22397, EP0261712, DE19504224, DE4408171, GB2280445, etc. can be used. Specific examples of such polymerizable mesogenic compounds include, for example, LC242 with the trade name of BASF, E7 with the trade name of Merck, and LC-Sillicon-CC3767 with the trade name of Wacker-Chem. As the liquid crystal monomer, a nematic liquid crystal monomer is preferably used, for example.

[0102] The alignment cured layer of the liquid crystal compound can be formed by the following method: performing an alignment treatment on the surface of a given substrate, coating a coating liquid containing the liquid crystal compound on this surface, aligning the liquid crystal compound in the direction corresponding to the above alignment treatment, and fixing this alignment state. In one embodiment, the substrate is any suitable resin film, and the alignment cured layer formed on this substrate can be transferred to the surface of the polarizing film. At this time, it is arranged such that the angle formed by the absorption axis of the polarizing film and the slow axis of the liquid crystal alignment cured layer is 15°. Moreover, the retardation of the liquid crystal alignment cured layer is λ / 2 (about 270 nm) for a wavelength of 550 nm. In addition, in the same manner as above, a liquid crystal alignment cured layer with a retardation of λ / 4 (about 140 nm) for a wavelength of 550 nm is formed on a transferable substrate, and on the 1 / 2 wavelength plate side of the laminate of the polarizing film and the 1 / 2 wavelength plate, it is laminated such that the angle formed by the absorption axis of the polarizing film and the slow axis of the 1 / 4 wavelength plate is 75°.

[0103] As the above alignment treatment, any suitable alignment treatment can be used. Specifically, mechanical alignment treatment, physical alignment treatment, and chemical alignment treatment can be cited. Specific examples of the mechanical alignment treatment include rubbing treatment and stretching treatment. Specific examples of the physical alignment treatment include magnetic field alignment treatment and electric field alignment treatment. Specific examples of the chemical alignment treatment include oblique vapor deposition method and photoalignment treatment. The treatment conditions of various alignment treatments can be any suitable conditions according to the purpose.

[0104] The alignment of the liquid crystal compound is carried out by treating at the temperature at which the liquid crystal compound exhibits a liquid crystal phase according to the type of the liquid crystal compound. By performing such a temperature treatment, the liquid crystal compound is in a liquid crystal state, and this liquid crystal compound aligns corresponding to the alignment treatment direction of the substrate surface.

[0105] In one embodiment, the fixing of the alignment state is carried out by cooling the liquid crystal compound aligned as described above. In the case where the liquid crystal compound is a polymerizable monomer or a crosslinkable monomer, the fixing of the alignment state is carried out by subjecting the liquid crystal compound aligned as described above to a polymerization treatment or a crosslinking treatment.

[0106] Specific examples of the liquid crystal compound and details of the method for forming the alignment curing layer are described in Japanese Patent Application Laid-Open No. 2006-163343. The description of this publication is incorporated herein by reference.

[0107] The thickness of the retardation film used in the optical laminate of the present invention 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. When within the above range, bending is not hindered, which is a preferred mode.

[0108] <Protective film>

[0109] As the protective film (also referred to as a transparent protective film) of the transparent resin material used in the optical laminate of the present invention, a norbornene resin or other cycloolefin resin, an olefin resin such as polyethylene or polypropylene, a polyester resin, a (meth)acrylic resin, or the like can be used.

[0110] The thickness of the protective film used in the optical laminate of the present invention is preferably 5 to 60 μm, more preferably 10 to 40 μm, still more preferably 10 to 30 μm, and surface treatment layers such as an antiglare layer and an antireflection layer can be appropriately provided. When within the above range, bending is not hindered, which is a preferred mode.

[0111] [First adhesive layer]

[0112] Preferably, the first adhesive layer used in the laminate for a flexible image display device of the present invention is disposed on the side opposite to the side of the protective film that contacts the polarizing film.

[0113] In the laminate for a flexible image display device of the present invention, the adhesive layer constituting the first adhesive layer is formed from an adhesive composition for a flexible image display device. The adhesive composition contains a (meth)acrylic polymer containing a monomer having a reactive functional group and a (meth)acrylic monomer as monomer units. The monomer having a reactive functional group is selected from one or more of a hydroxy group-containing monomer, a carboxy group-containing monomer, an amino group-containing monomer, and an amide group-containing monomer. The (meth)acrylic monomer has a linear or branched alkyl group having 1 to 24 carbon atoms. The adhesive composition is characterized in that 0.02 to 10% by weight of the monomer having a reactive functional group is contained in all the monomers constituting the (meth)acrylic polymer. It should be noted that the adhesive (composition) constituting the adhesive layer uses an acrylic adhesive containing the (meth)acrylic polymer, but within a range that does not affect the characteristics of the present invention, a rubber-based adhesive, a vinyl alkyl ether-based adhesive, a silicone-based adhesive, a polyester-based adhesive, a polyamide-based adhesive, a urethane-based adhesive, a fluorine-containing adhesive, an epoxy-based adhesive, a polyether-based adhesive, etc. may also be used in combination. However, from the viewpoints of transparency, processability, durability, adhesion, bend resistance, etc., it is preferable to use an acrylic adhesive alone.

[0114] <(meth)acrylic polymer>

[0115] The adhesive composition is characterized in that it contains a (meth)acrylic polymer containing a (meth)acrylic monomer having a linear or branched alkyl group having 1 to 24 carbon atoms as monomer units. By using the (meth)acrylic monomer having a linear or branched alkyl group having 1 to 24 carbon atoms, an adhesive layer excellent in bendability can be obtained. It should be noted that the (meth)acrylic polymer in the present invention means an acrylic polymer and / or a methacrylic polymer, and (meth)acrylate means acrylate and / or methacrylate.

[0116] Specific examples of the (meth)acrylic acid monomer having a linear or branched alkyl group with 1 to 24 carbon atoms, which constitutes the main skeleton of the above (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, n-tridecyl (meth)acrylate, n-tetradecyl (meth)acrylate, etc. Among them, monomers with a low glass transition temperature (Tg) usually become viscoelastic bodies even in the rapid region during bending. Therefore, from the viewpoint of bendability, (meth)acrylic acid monomers having a linear or branched alkyl group with 4 to 8 carbon atoms are preferred. As the above (meth)acrylic acid monomer, one or more than two kinds can be used.

[0117] The above (meth)acrylic acid monomer having a linear or branched alkyl group with 1 to 24 carbon atoms is the main component among all the monomers constituting the (meth)acrylic polymer. Here, the main component means that among all the monomers constituting the (meth)acrylic polymer, the (meth)acrylic acid monomer having a linear or branched alkyl group with 1 to 24 carbon atoms is preferably 70 to 99.98% by weight, more preferably 80 to 99.98% by weight, further preferably 85 to 99.9% by weight, and particularly preferably 90 to 99.9%.

[0118] For the above-mentioned adhesive composition, as monomer units, among all the monomers constituting the above-mentioned (meth)acrylic polymer, the monomers having reactive functional groups are preferably 0.02 to 10% by weight, more preferably 0.05 to 7% by weight, and still more preferably 0.2 to 3% by weight. The monomers having reactive functional groups are selected from one or more of hydroxyl group-containing monomers, carboxyl group-containing monomers, amino group-containing monomers, and amide group-containing monomers. By reducing the monomers having reactive functional groups to 0.02 to 10% by weight, an adhesive layer with reduced crosslinking sites, less tendency to harden, and excellent stress relaxation properties can be obtained. When it is more than 10% by weight, since the number of crosslinking sites increases, the crosslinking density increases, and flexibility is lacking. Especially when bending under the damp heat test, the shrinkage stress of the polarizing film cannot be relaxed, and breakage occurs. When it is less than 0.02% by weight, since the number of reaction sites with the film is small, the adhesion force decreases. Especially when bending under the damp heat test, peeling is likely to occur. Among these monomers, especially the hydroxyl group-containing monomers have a good balance between flexibility and peeling, and are thus preferred. It should be noted that one or more of the monomers having reactive functional groups can be used.

[0119] The above-mentioned hydroxyl group-containing monomer is a compound containing a hydroxyl group in its structure and containing polymerizable unsaturated double bonds such as (meth)acryloyl group and vinyl group.

[0120] The above-mentioned hydroxyl group-containing monomer is a compound containing a hydroxyl group in its structure and containing polymerizable unsaturated double bonds such as (meth)acryloyl group and vinyl group. Specific examples of the above-mentioned hydroxyl group-containing monomer include, for example: 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 other (meth)acrylic acid hydroxyalkyl esters, and methyl acrylate (4-hydroxymethylcyclohexyl). Among the above-mentioned hydroxyl group-containing monomers, from the viewpoints of peeling and flexibility when bending in damp heat, when used, 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate are preferred, and 4-hydroxybutyl (meth)acrylate is particularly preferred.

[0121] The above carboxyl group-containing monomer can be a monomer having a polymerizable functional group with an unsaturated double bond such as (meth)acryloyl or vinyl and having a carboxyl group, without particular limitation. Examples of the carboxyl group-containing monomer include, for example: (meth)acrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid, methacrylic acid, etc., and these can be used alone or in combination. Itaconic acid and maleic acid can be used in the form of their acid anhydrides. Among them, from the viewpoint of effectively suppressing peeling during the damp heat test, when used, acrylic acid and methacrylic acid are preferred, and acrylic acid is particularly preferred.

[0122] The above amino group-containing monomer can be a monomer having a polymerizable functional group with an unsaturated double bond such as (meth)acryloyl or vinyl and having an amino group, without particular limitation. Examples of the above amino group-containing monomer include, for example: aminoethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, N,N-dimethylaminopropyl (meth)acrylate, etc.

[0123] The above amide group-containing monomer is a compound containing an amide group in its structure and containing a polymerizable unsaturated double bond such as (meth)acryloyl or vinyl. Specific examples of the amide group-containing monomer include: acrylamide monomers such as (meth)acrylamide, N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N-isopropylacrylamide, N-methyl(meth)acrylamide, N-butyl(meth)acrylamide, N-hexyl(meth)acrylamide, N-hydroxymethyl(meth)acrylamide, N-hydroxymethyl-N-propane(meth)acrylamide, aminomethyl(meth)acrylamide, aminoethyl(meth)acrylamide, mercaptomethyl(meth)acrylamide, mercaptoethyl(meth)acrylamide, etc.; N-acryloyl heterocyclic monomers such as N-(meth)acryloylmorpholine, N-(meth)acryloylpiperidine, N-(meth)acryloylpyrrolidine, etc.; lactam monomers containing N-vinyl such as N-vinylpyrrolidone, N-vinyl-ε-caprolactam, etc.

[0124] In the above adhesive composition, it is preferred that the above (meth)acrylic polymer contains only butyl acrylate as the (meth)acrylic monomer having a linear or branched alkyl group with 1 to 24 carbon atoms and 4-hydroxybutyl acrylate as the above hydroxyl group-containing monomer as monomer units.

[0125] As the monomer units constituting the above-mentioned (meth)acrylic polymer, in addition to the above-mentioned monomers having reactive functional groups, other comonomers can be introduced within the range not impairing the effects of the present invention. The blending ratio is not particularly limited, and is preferably 30% by weight or less, more preferably not contained, in all the monomers constituting the above-mentioned (meth)acrylic polymer. When it is more than 30% by weight, especially when monomers other than (meth)acrylic monomers are used, the reaction sites with the film decrease, and there is a tendency for the adhesion force to decrease.

[0126] In the present invention, when using the above-mentioned (meth)acrylic polymer, a polymer having a weight average molecular weight (Mw) in the range of 1 million to 2.5 million is usually used. Considering durability, especially heat resistance and flexibility, it is preferably 1.2 million to 2.2 million, more preferably 1.4 million to 2 million. When the weight average molecular weight is less than 1 million, when cross-linking polymer chains to ensure durability, compared with a polymer having a weight average molecular weight of 1 million or more, the cross-linking sites increase, and the flexibility of the adhesive (layer) is lost. Therefore, it is impossible to relax the dimensional changes on the outer side (convex side) and the inner side (concave side) of the bend generated between the films during bending, and the film is likely to break. In addition, when the weight average molecular weight is greater than 2.5 million, a large amount of diluting solvent is required to adjust the viscosity for coating, the cost increases, so it is not preferred. In addition, the entanglement between the polymer chains of the obtained (meth)acrylic polymer becomes complicated, so the film is likely to break during bending. It should be noted that the weight average molecular weight (Mw) is a value measured by GPC (gel permeation chromatography) and calculated by conversion with polystyrene.

[0127] The production of such a (meth)acrylic polymer can appropriately select known production methods such as solution polymerization, bulk polymerization, emulsion polymerization, and various radical polymerizations. In addition, the obtained (meth)acrylic polymer can be any copolymer such as a random copolymer, a block copolymer, or a graft copolymer.

[0128] In the above solution polymerization, as the polymerization solvent, ethyl acetate, toluene, etc. can be used. As a specific example of solution polymerization, in an inert gas stream such as nitrogen, a polymerization initiator is added, and the reaction is usually carried out under reaction conditions of about 50 to 70 °C for about 5 to 30 hours.

[0129] There is no particular limitation on the polymerization initiator, chain transfer agent, emulsifier, etc. used in radical polymerization, and they can be appropriately selected and used. It should be noted that the weight average molecular weight of the (meth)acrylic polymer can be controlled by the amounts of the polymerization initiator and chain transfer agent and the reaction conditions, and the amounts can be appropriately adjusted according to their types.

[0130] Examples of the above polymerization initiators include azo initiators such as 2,2'-azobisisobutyronitrile, 2,2'-azobis(2-amidinopropane) dihydrochloride, 2,2'-azobis[2-(5-methyl-2-imidazolin-2-yl)propane] dihydrochloride, 2,2'-azobis(2-methylpropylamidine) disulfate, 2,2'-azobis(N,N'-dimethylisobutylamidine), 2,2'-azobis[N-(2-carboxyethyl)-2-methylpropylamidine] hydrate (trade name: VA-057, manufactured by Wako Pure Chemical Industries, Ltd.), etc.; persulfates such as potassium persulfate and ammonium persulfate; peroxides such as di(2-ethylhexyl) peroxydicarbonate, di(4-tert-butylcyclohexyl) peroxydicarbonate, di-sec-butyl peroxydicarbonate, tert-butyl peroxyneodecanoate, tert-hexyl peroxyneopentanoate, tert-butyl peroxyneopentanoate, dilauroyl peroxide, dioctanoyl peroxide, 1,1,3,3-tetramethylbutyl peroxy-2-ethylhexanoate, di(4-methylbenzoyl) peroxide, benzoyl peroxide, tert-butyl peroxyisobutyrate, 1,1-bis(tert-hexylperoxy)cyclohexane, tert-butyl hydroperoxide, hydrogen peroxide, etc.; redox initiators formed by combining peroxides and reducing agents such as combinations of persulfates and sodium bisulfite, and combinations of peroxides and sodium ascorbate, etc., but are not limited thereto.

[0131] One kind or two or more kinds of the above polymerization initiators can be used. For example, relative to 100 parts by mass of all the monomers constituting the above (meth)acrylic polymer, the total content is preferably about 0.005 to 1 part by weight, and more preferably about 0.02 to 0.5 part by weight.

[0132] In addition, in the case of using a chain transfer agent, an emulsifier used in emulsion polymerization, or a reactive emulsifier, known substances publicly available can be appropriately used. In addition, their addition amounts can be appropriately determined within a range that does not impair the effects of the present invention.

[0133] <Crosslinking agent>

[0134] The binder composition of the present invention may contain a crosslinking agent. As the crosslinking agent, organic crosslinking agents and polyfunctional metal chelates can be used. As the organic crosslinking agents, isocyanate crosslinking agents, peroxide crosslinking agents, epoxy crosslinking agents, imine crosslinking agents, etc. can be cited. The polyfunctional metal chelate is formed by covalent bonding or coordination bonding of a polyvalent metal and an organic compound. As the polyvalent metal atom, the following can be cited: Al, Cr, Zr, Co, Cu, Fe, Ni, V, Zn, In, Ca, Mg, Mn, Y, Ce, Sr, Ba, Mo, La, Sn, Ti, etc. As the atom in the organic compound for covalent bonding or coordination bonding, an oxygen atom, etc. can be cited, and as the organic compound, the following can be cited: alkyl esters, alcohol compounds, carboxylic acid compounds, ether compounds, ketone compounds, etc. Among them, it is preferably to contain isocyanate crosslinking agents and / or peroxide crosslinking agents. In particular, from the aspect of durability, isocyanate crosslinking agents (especially trifunctional isocyanate crosslinking agents) are preferred. In addition, from the aspect of flexibility, peroxide crosslinking agents and isocyanate crosslinking agents (especially bifunctional isocyanate crosslinking agents) are preferred. The peroxide crosslinking agent and the bifunctional isocyanate crosslinking agent both form a soft two-dimensional crosslink. In contrast, the trifunctional isocyanate crosslinking agent forms a more firm three-dimensional crosslink. When bending, the two-dimensional crosslink as a softer crosslink is advantageous. However, in the case of only two-dimensional crosslinking, the durability is lacking and peeling is likely to occur. Therefore, a mixed crosslink of two-dimensional crosslinking and three-dimensional crosslinking is good. Therefore, it is a preferred method to use a trifunctional isocyanate crosslinking agent in combination with a peroxide crosslinking agent and a bifunctional isocyanate crosslinking agent.

[0135] For example, relative to 100 parts by mass of the (meth)acrylic polymer, the amount of the above crosslinking agent is preferably 0.01 to 5 parts by mass, more preferably 0.03 to 2 parts by mass, and still more preferably less than 0.03 to 1 part by mass. When within the above range, the bending resistance is excellent and it becomes a preferred method.

[0136] [Other Additives]

[0137] The binder composition of the present invention may further contain other known additives. For example, various silane coupling agents, polyether compounds such as polyalkylene glycols like polypropylene glycol, powders such as colorants and pigments, dyes, surfactants, plasticizers, tackifiers, surface lubricants, leveling agents, softeners, antioxidants, anti-aging agents, light stabilizers, ultraviolet absorbers, polymerization inhibitors, antistatic agents (alkali metal salts, ionic liquids, etc. as ionic compounds), inorganic or organic fillers, metal powders, granular materials, foils, etc. can be appropriately added according to the intended use. In addition, a redox type with the addition of a reducing agent can also be adopted within a controllable range.

[0138] [Other Binder Layers]

[0139] The second adhesive layer used in the laminate for a flexible image display device of the present invention can be disposed on the side opposite to the side of the retardation film that contacts the polarizing film.

[0140] The third adhesive layer used in the laminate for a flexible image display device of the present invention can be disposed on the side opposite to the side of the transparent conductive layer constituting the touch sensor that contacts the second adhesive layer.

[0141] The third adhesive layer used in the laminate for a flexible image display device of the present invention can be disposed on the side opposite to the side of the transparent conductive layer constituting the touch sensor that contacts the first adhesive layer.

[0142] It should be noted that in the case where a second adhesive layer is used in addition to the first adhesive layer and still further other adhesive layers (for example, a third adhesive layer, etc.) are used, these adhesive layers can be layers having the same composition (the same adhesive composition) and the same properties, or can be layers having different properties, and there is no particular limitation. From the viewpoints of operability, economy, and flexibility, it is preferred that all the adhesive layers are adhesive layers having substantially the same composition and the same properties.

[0143] <Formation of the Adhesive Layer>

[0144] The adhesive layer in the present invention is preferably formed from the above-mentioned adhesive composition. As a method for forming the adhesive layer, for example, a method of coating the above-mentioned adhesive composition on a separator that has been subjected to a release treatment and drying and removing a polymerization solvent or the like to form the adhesive layer can be cited. In addition, it can also be produced by a method of coating the above-mentioned adhesive composition on a polarizing film or the like and drying and removing a polymerization solvent or the like to form the adhesive layer on the polarizing film or the like. It should be noted that when coating the adhesive composition, one or more solvents other than the polymerization solvent can also be newly added as appropriate.

[0145] As the separator that has been subjected to a release treatment, a silicone release liner is preferably used. When the adhesive composition of the present invention is coated on such a liner and dried to form an adhesive layer, as a method for drying the adhesive, a suitable method can be appropriately adopted according to the purpose. A method of heating and drying the above-mentioned coated film is preferably used. The heating and drying temperature is preferably 40 to 200 °C, more preferably 50 to 180 °C, and particularly preferably 70 to 170 °C. By setting the heating temperature within the above range, an adhesive having excellent adhesive properties can be obtained.

[0146] The drying time can be appropriately set to a suitable time. The above-mentioned drying time is preferably 5 seconds to 20 minutes, more preferably 5 seconds to 10 minutes, and particularly preferably 10 seconds to 5 minutes.

[0147] As a coating method of the above adhesive composition, various methods can be used. Specifically, for example, roll coating method, roll kiss coating method, gravure coating method, reverse coating method, roll brush method, spraying method, dip roll coating method, bar coating method, blade coating method, air knife coating method, curtain coating method, die lip coating method, extrusion coating method using a die coater, etc. can be cited.

[0148] The thickness of the adhesive layer used in the laminate for a flexible image display device of the present invention is preferably 1 to 200 μm, more preferably 5 to 150 μm, and further preferably 15 to 100 μm. The adhesive layer may be a single layer or may have a laminated structure. When within the above range, bending is not hindered, and from the viewpoint of adhesion (retention resistance), it also becomes a preferred mode. In addition, when there are a plurality of adhesive layers, it is preferable that all the adhesive layers are within the above range. When the thickness is greater than 200 μm, the polymer chains inside the adhesive are likely to move during repeated bending, so it is prone to fatigue and peeling is likely to occur. In addition, when it is less than 1 μm, the stress during bending cannot be relaxed, and breakage is likely to occur.

[0149] The storage modulus (G') of the adhesive layer used in the laminate for a flexible image display device of the present invention is preferably 1.0 MPa or less, more preferably 0.8 MPa or less, and further preferably 0.3 MPa or less at 25°C. When the storage modulus of the adhesive layer is in such a range, the adhesive layer is not likely to harden, has excellent stress relaxation properties and excellent bending resistance, and therefore, a flexible image display device that can be bent or folded can be realized.

[0150] As the upper limit value of the glass transition temperature (Tg) of the adhesive layer used in the laminate for a flexible image display device of the present invention, it is preferably 0°C or less, more preferably -20°C or less, further preferably -25°C or less, and particularly preferably -30°C or less. In addition, as the lower limit value of Tg, it is preferably -50°C or more, more preferably -45°C or more. When the Tg of the adhesive layer is in such a range, the adhesive layer is not likely to harden even in the rapid region during bending, and a flexible image display device with excellent stress relaxation properties and capable of being bent or folded can be realized.

[0151] The total light transmittance (based on JIS K7136) in the visible light wavelength region of the adhesive layer for a flexible image display device of the present invention is preferably 85% or more, more preferably 90% or more.

[0152] The haze (based on JIS K7136) of the adhesive layer for a flexible image display device of the present invention is preferably 3.0% or less, more preferably 2.0% or less.

[0153] It should be noted that the above total light transmittance and the above haze can be measured using, for example, a haze meter (manufactured by Murakami Color Research Institute, trade name "HM-150").

[0154] [Transparent conductive layer]

[0155] As the member having a transparent conductive layer, there is no particular limitation, and known members can be used. Examples include members having a transparent conductive layer on a transparent substrate such as a transparent film, and members having a transparent conductive layer and a liquid crystal cell.

[0156] As the transparent substrate, any substrate having transparency can be used. Examples include substrates formed of a resin film or the like (for example, sheet-like, film-like, plate-like substrates, etc.). The thickness of the transparent substrate is not particularly limited, and is preferably about 10 to 200 μm, more preferably about 15 to 150 μm.

[0157] As the material of the above resin film, there is no particular limitation, and various plastic materials having transparency can be used. For example, as the material, the following can be mentioned: polyester resins such as polyethylene terephthalate and polyethylene naphthalate, acetate resins, polyethersulfone resins, polycarbonate resins, polyamide resins, polyimide resins, polyolefin resins, (meth)acrylic resins, polyvinyl chloride resins, polyvinylidene chloride resins, polystyrene resins, polyvinyl alcohol resins, polyarylate resins, polyphenylene sulfide resins, etc. Among them, polyester resins, polyimide resins, and polyethersulfone resins are particularly preferred.

[0158] In addition, the surface of the above transparent substrate can be pre-treated by sputtering, corona discharge, flame, ultraviolet irradiation, electron beam irradiation, chemical conversion, oxidation and other etching treatments and primer treatments to improve the adhesion of the transparent conductive layer provided thereon to the above transparent substrate. In addition, before setting the transparent conductive layer, dust removal and purification can also be performed by solvent cleaning, ultrasonic cleaning, etc. as needed.

[0159] As the constituent material of the above transparent conductive layer, there is no particular limitation, and a metal oxide of at least one metal selected from indium, tin, zinc, gallium, antimony, titanium, silicon, zirconium, magnesium, aluminum, gold, silver, copper, palladium, and tungsten can be used. The metal atoms shown above can be further contained in the metal oxide as needed. For example, indium tin oxide (ITO) containing tin oxide, tin oxide containing antimony, etc. are preferably used, and ITO is particularly preferably used. As ITO, it preferably contains 80 to 99% by weight of indium oxide and 1 to 20% by weight of tin oxide.

[0160] In addition, as the above ITO, crystalline ITO and amorphous (non-crystalline) ITO can be mentioned. Crystalline ITO can be obtained by applying high temperature during sputtering or further heating amorphous ITO.

[0161] The thickness of the transparent conductive layer of the present invention is preferably 0.005 to 10 μm, more preferably 0.01 to 3 μm, and further preferably 0.01 to 1 μm. When the thickness of the transparent conductive layer is less than 0.005 μm, there is a tendency for the change in the resistance value of the transparent conductive layer to increase. On the other hand, when it is greater than 10 μm, there is a tendency for the productivity of the transparent conductive layer to decrease, the cost to increase, and furthermore, the optical properties to decrease.

[0162] The total light transmittance of the transparent conductive layer of the present invention is preferably 80% or more, more preferably 85% or more, and further preferably 90% or more.

[0163] The density of the transparent conductive layer of the present invention is preferably 1.0 to 10.5 g / cm 3 , more preferably 1.3 to 3.0 g / cm 3 .

[0164] The surface resistance value of the transparent conductive layer of the present invention is preferably 0.1 to 1000 Ω / sq, more preferably 0.5 to 500 Ω / sq, and further preferably 1 to 250 Ω / sq.

[0165] As the method for forming the above-mentioned transparent conductive layer, there is no particular limitation, and existing well-known methods can be adopted. Specifically, for example, vacuum evaporation, sputtering, and ion plating can be exemplified. In addition, an appropriate method can be adopted according to the required film thickness.

[0166] In addition, if necessary, a primer layer, an anti-oligomer layer, etc. can be provided between the transparent conductive layer and the transparent substrate.

[0167] The above-mentioned transparent conductive layer constitutes a touch sensor and is required to be configured to be bendable.

[0168] The transparent conductive layer constituting the touch sensor used in the laminate for a flexible image display device of the present invention can be disposed on the opposite side of the surface of the second adhesive layer in contact with the retardation film.

[0169] The transparent conductive layer constituting the touch sensor used in the laminate for a flexible image display device of the present invention can be disposed on the opposite side of the surface of the first adhesive layer in contact with the protective film.

[0170] The transparent conductive layer constituting the touch sensor used in the laminate for a flexible image display device of the present invention can be disposed between the protective film and the window film (OCA).

[0171] In addition, when the above-mentioned transparent conductive layer is used in a flexible image display device, it can be suitably applied to a liquid crystal display device with a built-in touch sensor, which is called an in-cell type or an on-cell type. In particular, a touch sensor can be built in (introduced into) an organic EL display panel.

[0172] [Conductive layer (antistatic layer)]

[0173] In addition, the laminate for a flexible image display device of the present invention may also include a layer having conductivity (conductive layer, antistatic layer). The laminate for a flexible image display device has a bending function and has a very thin thickness structure. Therefore, it has a large reactivity to weak static electricity generated in manufacturing processes and is easily damaged. However, by providing a conductive layer on the laminate, the burden caused by static electricity in manufacturing processes and the like can be significantly reduced, which is a preferred method.

[0174] In addition, one of the characteristics of a flexible image display device including the above laminate is that it has a bending function. However, when it is continuously bent, static electricity may be generated due to shrinkage between the films (substrates) at the bending part. Therefore, when the laminate is given conductivity, the generated static electricity can be quickly removed, and the damage caused by static electricity of the image display device can be reduced, which is a preferred method.

[0175] In addition, the above conductive layer can be a primer layer having a conductive function, an adhesive containing a conductive component, or a surface treatment layer containing a conductive component. For example, a method of forming a conductive layer between a polarizing film and an adhesive layer by using an antistatic agent composition containing a conductive polymer such as polythiophene and an adhesive can be adopted. In addition, an adhesive containing an ionic compound as an antistatic agent can also be used. In addition, the above conductive layer preferably has one or more layers and can also contain two or more layers.

[0176] [Flexible image display device]

[0177] The flexible image display device of the present invention includes the above laminate for a flexible image display device and an organic EL display panel that can be bent. The laminate for a flexible image display device is disposed on the visible side of the organic EL display panel and can be bent. Although it is arbitrary, a window can be disposed on the visible side of the laminate for a flexible image display device.

[0178] Figure 2It is a cross-sectional view showing an embodiment of the flexible image display device of the present invention. The flexible image display device 100 includes a laminate 11 for a flexible image display device and an organic EL display panel 10 configured to be bendable. Moreover, the laminate 11 for a flexible image display device is disposed on the visible side of the organic EL display panel 10, and the flexible image display device 100 is configured to be bendable. Additionally, although optional, a transparent window 40 may be disposed on the visible side of the laminate 11 for a flexible image display device through a first adhesive layer 12-1.

[0179] The laminate 11 for a flexible image display device includes an optical laminate 20 and an adhesive layer further constituting a second adhesive layer 12-2 and a third adhesive layer 12-3.

[0180] The optical laminate 20 includes a polarizing film 1, a protective film 2 made of a transparent resin material, and a retardation film 3. The protective film 2 made of a transparent resin material is joined to the first surface on the visible side of the polarizing film 1. The retardation film 3 is joined to the second surface of the polarizing film 1 different from the first surface. The polarizing film 1 and the retardation film 3 are used, for example, to generate circularly polarized light in order to prevent internally reflected light incident from the visible side of the polarizing film 1 from exiting to the visible side or to compensate for the viewing angle.

[0181] In the present embodiment, as opposed to the conventional structure in which protective films are provided on both sides of the polarizing film, a structure is adopted in which a protective film is provided only on one side. Compared with the polarizing film used in existing organic EL display devices, by using a polarizing film with a very thin thickness (for example, 20 μm or less), the thickness of the optical laminate 20 can be reduced. Additionally, compared with the polarizing film used in existing organic EL display devices, the polarizing film 1 is very thin, and thus the stress caused by expansion and contraction under temperature or humidity conditions becomes extremely small. Therefore, the possibility of warping or other deformation of the adjacent organic EL display panel 10 due to the stress generated by the shrinkage of the polarizing film can be significantly reduced, and a significant reduction in display quality degradation and damage to the panel sealing material caused by deformation can be suppressed. Additionally, bending is not hindered by using a thin polarizing film, which is a preferred mode.

[0182] When the optical laminate 20 is bent with the protective film 2 side as the inner side, by reducing the thickness of the optical laminate 20 (for example, 92 μm or less) and disposing the first adhesive layer 12-1 having the above-described storage modulus on the side of the protective film 2 opposite to the retardation film 3, the stress applied to the optical laminate 20 can be reduced, and thus the optical laminate 20 can be bent. Additionally, accordingly, the range of the appropriate storage modulus can be set according to the ambient temperature at which the flexible image display device is used. For example, when it is assumed that the use ambient temperature is -20°C to +85°C, a first adhesive layer having an appropriate numerical range of the storage modulus at 25°C can be used.

[0183] Although it is optional, a bendable transparent conductive layer 6 constituting a touch sensor may be further disposed on the side of the retardation film 3 opposite to the protective film 2. The transparent conductive layer 6 may be configured to be directly bonded to the retardation film 3 by, for example, a manufacturing method disclosed in Japanese Patent Application Laid-Open No. 2014-219667. Thereby, the thickness of the optical laminate 20 can be reduced, and the stress applied to the optical laminate 20 when the optical laminate 20 is bent can be further reduced.

[0184] Although it is optional, an adhesive layer constituting the third adhesive layer 12-3 may be further disposed on the side of the transparent conductive layer 6 opposite to the retardation film 3. In the present embodiment, the second adhesive layer 12-2 is directly bonded to the transparent conductive layer 6. By providing the second adhesive layer 12-2, the stress applied to the optical laminate 20 when the optical laminate 20 is bent can be further reduced.

[0185] Figure 3 The flexible image display device shown in Figure 2 is substantially the same as the device shown in Figure 2 In the flexible image display device of Figure 3 , a bendable transparent conductive layer 6 constituting a touch sensor is disposed on the side of the retardation film 3 opposite to the protective film 2. In contrast, in the flexible image display device of Figure 2 , a bendable transparent conductive layer 6 constituting a touch sensor is disposed on the side of the first adhesive layer 12-1 opposite to the protective film 2, which is different in this regard. In addition, in the flexible image display device of Figure 3 , the third adhesive layer 12-3 is disposed on the side of the transparent conductive layer 2 opposite to the retardation film 3. In contrast, in the flexible image display device of

[0186] , the second adhesive layer 12-2 is disposed on the side of the retardation film 3 opposite to the protective film 2, which is different in this regard.

[0187] As the flexible image display device of the present invention, it can be suitably used as a flexible liquid crystal display device, an organic EL (electroluminescence) display device, a PDP (plasma display panel), an electronic paper, or the like. In addition, it can be used regardless of the type of touch panel such as the resistive film method or the capacitive method.

[0188] In addition, as the flexible image display device of the present invention, as Figure 4 shown, it can also be used as an in-cell type flexible image display device in which a transparent conductive layer 6 constituting a touch sensor is built in an organic EL display panel 10.

[0189] Example

[0190] Hereinafter, several examples related to the present invention will be described, but the present invention is not intended to be limited to the manner shown in the above specific examples. In addition, the numerical values in the tables are compounding amounts (addition amounts), indicating the solid components or the solid component ratio (weight basis). The compounding contents and evaluation results are shown in Tables 2 to 4.

[0191] [Example 1]

[0192] [Polarizing film]

[0193] As a thermoplastic resin substrate, an amorphous polyethylene terephthalate (hereinafter also referred to as "PET") (IPA copolymerized PET) film (thickness: 100 μm) having 7 mol% of isophthalic acid units was prepared, and the surface was subjected to corona treatment (58 W / m 2 / min). On the other hand, PVA (degree of polymerization 4200, saponification degree 99.2%) added with 1% by weight of acetoacetylated PVA (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name: GOHSEFIMER Z200 (average degree of polymerization: 1200, saponification degree: 98.5 mol%, acetoacetylation degree: 5 mol%)) was prepared, and a coating liquid of an aqueous PVA solution containing 5.5% by weight of a PVA-based resin was prepared and coated so that the film thickness after drying reached 12 μm, and drying was performed by hot air drying for 10 minutes in an atmosphere of 60 °C to produce a laminate having a layer of a PVA-based resin provided on the substrate.

[0194] Next, first, the laminate was freely stretched 1.8 times at 130 °C in air (auxiliary stretching in a gas atmosphere) to produce a stretched laminate. Then, the following steps were carried out: The stretched laminate was immersed in a boric acid insolubilizing aqueous solution at a liquid temperature of 30 °C for 30 seconds to insolubilize the PVA layer in which the PVA molecules contained in the stretched laminate were oriented. In the boric acid insolubilizing aqueous solution of this step, the boric acid content was set to 3 parts by mass relative to 100 parts by mass of water. By dyeing the stretched laminate, a colored laminate was produced. The colored laminate was obtained by immersing the stretched laminate in a dyeing solution containing iodine and potassium iodide at a liquid temperature of 30 °C for an arbitrary time in such a manner that the monomer transmittance of the finally formed PVA layer constituting the polarizing film reached 40 to 44%. In this step, the dyeing solution used water as a solvent, the iodine concentration was set in the range of 0.1 to 0.4% by weight, and the potassium iodide concentration was set in the range of 0.7 to 2.8% by weight. The concentration ratio of iodine to potassium iodide was 1 to 7. Then, the following step was carried out: The colored laminate was immersed in a boric acid crosslinking aqueous solution at 30 °C for 60 seconds to perform a crosslinking treatment between the PVA molecules of the PVA layer adsorbed with iodine. In the boric acid crosslinking aqueous solution of this step, the boric acid content was set to 3 parts by mass relative to 100 parts by mass of water, and the potassium iodide content was set to 3 parts by mass relative to 100 parts by mass of water.

[0195] Furthermore, in the boric acid aqueous solution, the obtained colored laminate was stretched 3.05 times at a stretching temperature of 70 °C in the same direction as the previous stretching in the gas atmosphere (stretching in the boric acid aqueous solution) to obtain an optical film laminate with a final stretching ratio of 5.50 times. The optical film laminate was taken out from the boric acid aqueous solution and washed with an aqueous solution to remove the boric acid adhering to the surface of the PVA layer. In the aqueous solution, the potassium iodide content was 4 parts by mass relative to 100 parts by mass of water. The washed optical film laminate was dried by a hot air drying process at 60 °C. The thickness of the polarizing film contained in the obtained optical film laminate was 5 μm.

[0196] [Protective film]

[0197] As the protective film, a film obtained by extruding and molding methacrylic resin particles having a glutarimide ring unit into a film shape and then stretching it was used. The protective film is an acrylic film with a thickness of 20 μm and a moisture permeability of 160 g / m 2 of.

[0198] Next, the above-mentioned polarizing film and the above-mentioned protective film were bonded together using the adhesive shown below to produce a polarizing film.

[0199] As the above-mentioned adhesive (active energy ray-curable adhesive), each component was mixed according to the formulation table described in Table 1 and stirred at 50 °C for 1 hour to prepare an adhesive (active energy ray-curable adhesive A). The values in the table represent weight percentages when the total amount of the composition is set to 100% by weight. Each component used is described below.

[0200] HEAA: Hydroxyethyl acrylamide

[0201] M-220: ARONIX M-220, tripropylene glycol diacrylate), manufactured by Toagosei Co., Ltd.

[0202] ACMO: Acryloylmorpholine

[0203] AAEM: 2-Acetylacetoxyethyl methacrylate, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.

[0204] UP-1190: ARUFON UP-1190, manufactured by Toagosei Co., Ltd.

[0205] IRG907: IRGACURE907, 2-methyl-1-(4-methylthiophenyl)-2-morpholinopropan-1-one, manufactured by BASF Corporation

[0206] DETX-S: KAYACURE DETX-S, diethylthioxanthone, manufactured by Nippon Kayaku Co., Ltd.

[0207] [Table 1]

[0208]

[0209] It should be noted that in the examples and comparative examples using the above-mentioned adhesive, after laminating the above-mentioned protective film and the above-mentioned polarizing film with the adhesive, ultraviolet rays were irradiated to cure the adhesive and form an adhesive layer. The ultraviolet irradiation used a metal halide lamp filled with gallium (manufactured by Fusion UV Systems, Inc., product name "LightHAMMER10", valve: V valve, maximum illuminance: 1600 mW / cm 2 , cumulative irradiation dose 1000 / mJ / cm 2 (wavelength 380 - 440 nm)).

[0210] [Phase difference film]

[0211] The phase difference film (quarter-wave retardation plate) of this example is a phase difference film composed of a quarter-wave retardation layer for a quarter-wave plate and a half-wave retardation layer for a half-wave plate formed by orienting and immobilizing a liquid crystal material. Specifically, it is manufactured as follows.

[0212] (Liquid crystal material)

[0213] As a material for forming a retardation layer for a half-wave plate and a retardation layer for a quarter-wave plate, a polymerizable liquid crystal material showing a nematic liquid crystal phase (manufactured by BASF: trade name Paliocolor LC242) was used. A photopolymerization initiator for this polymerizable liquid crystal material (manufactured by BASF: trade name Irgacure 907) was dissolved in toluene. Further, in order to improve coatability, about 0.1 to 0.5% of the Megafac series manufactured by DIC was added according to the liquid crystal thickness, and a liquid crystal coating solution was prepared. After coating this liquid crystal coating solution on an alignment substrate by a bar coater, it was heated and dried at 90 °C for 2 minutes, and then, it was oriented and fixed by ultraviolet curing in a nitrogen atmosphere. As the substrate, a material such as PET that can transfer the liquid crystal coating later was used. Further, in order to improve coatability, about 0.1% to 0.5% of a fluoropolymer of the Megafac series manufactured by DIC was added according to the thickness of the liquid crystal layer, and it was dissolved to a solid content concentration of 25% using MIBK (methyl isobutyl ketone), cyclohexanone, or a mixed solvent of MIBK and cyclohexanone to prepare a coating solution. This coating solution was coated on the substrate by a wire bar, set at 65 °C, and subjected to a drying process for 3 minutes, and then, it was oriented and fixed by ultraviolet curing in a nitrogen atmosphere to manufacture. As the substrate, a material such as PET that can transfer the liquid crystal coating later was used.

[0214] (Manufacturing process)

[0215] Refer to Figure 8 , and the manufacturing process of this embodiment will be described. It should be noted that Figure 8 The numbers in are different from the numbers in other drawings. In this manufacturing process 20, a substrate 14 is provided by a roller, and this substrate 14 is supplied to a supply reel 21. In the manufacturing process 20, a coating solution of an ultraviolet curable resin 10 is coated on this substrate 14 by a die head 22. In this manufacturing process 20, the roller plate 30 is a shaping die having a cylindrical shape with the uneven shape of the alignment film for the quarter-wave plate of the quarter-wave plate 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 roller plate 30 by a pressure roller 24, and the ultraviolet curable resin is cured by ultraviolet irradiation using an ultraviolet irradiation device 25 including a high-pressure mercury lamp. Thus, in the manufacturing process 20, the uneven shape formed on the circumferential side surface of the roller plate 30 is transferred to the substrate 14 so as to be 75° with respect to the MD direction. Then, the substrate 14 and the cured ultraviolet curable resin 10 are integrally peeled off from the roller plate 30 by a peeling roller 26, and a liquid crystal material is coated by a die head 29. Further, then, the liquid crystal material is cured by ultraviolet irradiation using an ultraviolet irradiation device 27, and thus, the structure of the retardation layer for the quarter-wave plate is manufactured.

[0216] Next, in this step 20, the base material 14 is transported to the die head 32 by the transport roller 31, and a coating liquid of the ultraviolet curable resin 12 is coated on the retardation layer for a quarter-wave plate of the base material 14 through the die head 32. In this manufacturing step 20, the roller plate 40 is a shaping die having a cylindrical shape with the concavo-convex shape of the alignment film for a half-wave plate of a quarter-wave plate formed on the circumferential side surface. In the manufacturing step 20, the base material 14 coated with the ultraviolet curable resin is pressed against the circumferential side surface of the roller plate 40 by the pressure roller 34, and the ultraviolet curable resin is cured by ultraviolet irradiation using an ultraviolet irradiation device 35 including a high-pressure mercury lamp. Thus, in the manufacturing step 20, the concavo-convex shape formed on the circumferential side surface of the roller plate 40 is transferred to the base material 14 at an angle of 15° with respect to the MD direction. Then, the base material 14 and the cured ultraviolet curable resin 12 are integrally peeled off from the roller plate 40 by the peeling roller 36, and a liquid crystal material is coated using the die head 39. Further, then, the liquid crystal material is cured by ultraviolet irradiation using the ultraviolet irradiation device 37, thereby forming a structure of a retardation layer for a half-wave plate, and a retardation film having a thickness of 7 μm and composed of two layers, namely, a retardation layer for a quarter-wave plate and a retardation layer for a half-wave plate, is obtained.

[0217] [Optical film (optical laminate)]

[0218] Using the above-mentioned adhesive and continuously laminating the retardation film obtained as described above and the polarizing film obtained as described above by a roll-to-roll method, a laminated film (optical laminate) was produced with the axis angle between the slow axis and the absorption axis being 45°.

[0219] Next, the obtained laminated film (optical laminate) was cut into 15 cm × 5 cm.

[0220] [Preparation of (meth)acrylic polymer A1]

[0221] A monomer mixture containing 99 parts by mass of butyl acrylate (BA) and 1 part by mass of 4-hydroxybutyl acrylate (HBA) was added to a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen inlet tube, and a condenser.

[0222] Further, for 100 parts by mass of the above-mentioned monomer mixture (solid content), 0.1 part by mass of 2,2'-azobisisobutyronitrile as a polymerization initiator was added together with ethyl acetate, and nitrogen replacement was carried out while slowly stirring and introducing nitrogen. Then, the liquid temperature in the flask was maintained at around 55 °C, and a polymerization reaction was carried out for 7 hours. Then, ethyl acetate was added to the obtained reaction solution to prepare a solution of (meth)acrylic polymer A1 having a solid content concentration adjusted to 30% and a weight average molecular weight of 1.6 million.

[0223] <Preparation of Acrylic Adhesive Composition>

[0224] With respect to 100 parts by mass of the solid content of the obtained (meth)acrylic polymer A1 solution, 0.1 part by mass of an isocyanate crosslinking agent (trade name: Takenate D110N, trimethylolpropane xylylene diisocyanate, manufactured by Mitsui Chemicals, Inc.), 0.3 part by mass of a peroxide crosslinking agent benzoyl peroxide (trade name: NYPER BMT, manufactured by NOF Corporation), and 0.08 part by mass of a silane coupling agent (trade name: KBM403, manufactured by Shin-Etsu Chemical Co., Ltd.) were blended to prepare an acrylic adhesive composition.

[0225] <Fabrication of Optical Laminate with Adhesive Layer>

[0226] The above acrylic adhesive composition was uniformly coated on the surface of a 38-μm-thick polyethylene terephthalate film (PET film, transparent substrate, separator) treated with an organosilicon release agent using a fountain coater and dried in an air-circulation constant-temperature oven at 155°C for 2 minutes to form an adhesive layer with a thickness of 25 μm on the surface of the substrate.

[0227] Next, the separator having the adhesive layer formed thereon was transferred to the protective film side (corona-treated) of the obtained optical laminate to fabricate an optical laminate with an adhesive layer.

[0228] <Laminate for Flexible Image Display Device>

[0229] As Figure 6 shown, the separator of the optical laminate with an adhesive layer obtained as described above was peeled off, and then a 25-μm-thick PET film (transparent substrate, manufactured by Mitsubishi Rayon Co., Ltd., trade name: Diafoil) subjected to corona treatment was laminated on the adhesive layer to fabricate a laminate for a flexible image display device equivalent to Structure A used in Example 1.

[0230] It should be noted that for the laminate for a flexible image display device equivalent to Structure B, the separator having the adhesive layer formed thereon was transferred to the retardation film side (corona-treated) of the obtained optical laminate to fabricate an optical laminate with an adhesive layer.

[0231] Next, as Figure 7As shown, the separator of the optical laminate with the adhesive layer obtained as described above was peeled off, and then a polyimide film (PI film, manufactured by DuPont-Toray Co., Ltd., KAPTON 300V, base material) with a thickness of 77 μm that had been subjected to corona treatment was laminated on the adhesive layer, thereby producing a laminate for a flexible image display device equivalent to Structure B used in Example 8.

[0232] <Preparation of (Meth)acrylic Polymers A4 and A5>

[0233] The temperature of the liquid in the flask was maintained at around 55 °C, and a polymerization reaction was carried out for 7 hours. At this time, the mixing ratio (weight ratio) of ethyl acetate to toluene was 85 / 15, and the polymerization reaction was carried out. Except for this, the preparation was carried out in the same manner as for (meth)acrylic polymer A1.

[0234] 〔Examples 2 to 8 and Comparative Examples 1 to 2〕

[0235] In Example 1, when preparing the polymers ((meth)acrylic polymers) and adhesive compositions to be used, changes were made as shown in Tables 2 to 4. Except for this, a laminate for a flexible image display device was produced in the same manner as in Example 1.

[0236] The abbreviations in Tables 2 and 3 are as follows.

[0237] BA: n-Butyl Acrylate

[0238] 2EHA: 2-Ethylhexyl Acrylate

[0239] AA: Acrylic Acid

[0240] HBA: 4-Hydroxybutyl Acrylate

[0241] HEA: 2-Hydroxyethyl Acrylate

[0242] MMA: Methyl Methacrylate

[0243] NVP: N-Vinylpyrrolidone

[0244] D110N: Trimethylolpropane / Benzene Diisocyanate Adduct (manufactured by Mitsui Chemicals, Inc., trade name: Takenate D110N)

[0245] D160N: Hexamethylene Diisocyanate and Trimethylolpropane Adduct (manufactured by Mitsui Chemicals, Inc., trade name: Takenate D160N)

[0246] C / L: Trimethylolpropane / Toluene Diisocyanate (manufactured by Nippon Polyurethane Industry Co., Ltd., trade name: Coronate L)

[0247] Peroxide: Benzoyl peroxide (a peroxide crosslinking agent, manufactured by NOF Corporation, trade name: NYPER BMT)

[0248] [Evaluation]

[0249] (Measurement of the weight-average molecular weight (Mw) of the (meth)acrylic acid polymer)

[0250] The weight-average molecular weight (Mw) of the obtained (meth)acrylic acid polymer was measured by GPC (gel permeation chromatography).

[0251] · Analytical device: HLC-8120GPC manufactured by Tosoh Corporation

[0252] · Column: G7000H manufactured by Tosoh Corporation XL +GMH XL +GMH XL

[0253] · Column size: 7.8 mmφ × 30 cm, a total of 90 cm

[0254] · Column temperature: 40 °C

[0255] · Flow rate: 0.8 ml / min

[0256] · Injection volume: 100 μl

[0257] · Eluent: Tetrahydrofuran

[0258] · Detector: Differential refractometer (RI)

[0259] · Standard sample: Polystyrene

[0260] (Measurement of thickness)

[0261] The thicknesses of the polarizing film, retardation film, protective film, optical laminate, adhesive layer, etc. were measured using a micrometer (manufactured by MITUTOYO Corporation) and calculated.

[0262] (Measurement of the glass transition temperature Tg of the adhesive layer)

[0263] For the glass transition temperature (Tg) of the adhesive layer, it was determined based on the peak temperature of tanδ obtained by dynamic viscoelasticity measurement under the following measurement conditions using the dynamic viscoelasticity measurement device "RSAIII" manufactured by TA Instruments.

[0264] (Measurement conditions)

[0265] Deformation mode: Torsion

[0266] Measured temperature: -40°C to 150°C

[0267] Heating rate: 5°C / min

[0268] (Measurement of the glass transition temperature Tg of the adhesive layer)

[0269] The separator was peeled off from the surface of the adhesive layer of each example and comparative example, and multiple adhesive layers were laminated to produce a test sample with a thickness of about 1.5 mm. The test sample was punched into a disc shape with a diameter of 8 mm, clamped between parallel plates, and using a dynamic viscoelasticity measuring device "RSAIII" manufactured by TA Instruments, it was obtained based on the peak temperature of tanδ obtained by dynamic viscoelasticity measurement under the following measurement conditions.

[0270] (Measurement conditions)

[0271] Deformation mode: torsion

[0272] Measured temperature: -40°C to 150°C

[0273] Heating rate: 5°C / min

[0274] (Flexural resistance test)

[0275] Figure 5 The schematic diagram of a 180° flexural resistance testing machine (manufactured by Imoto Seisakusho) is shown. This device has a mechanism that holds the mandrel and repeatedly bends one-sided chucks by 180° inside a constant temperature bath, and the bending radius can be changed by the diameter of the mandrel. It has a mechanism that stops the test when the film breaks. During the test, the 5 cm × 15 cm flexible image display device laminate obtained from each example and comparative example was set in the device, and it was carried out under the conditions of a bending angle of 180°, a bending radius of 3 mm, a bending speed of 1 time / second, and a weight of 100 g in an environment of temperature 60°C × humidity 95% RH. The flexural strength was evaluated based on the number of times until the flexible image display device laminate broke. Here, when the number of bends reached 200,000 times, the test was stopped.

[0276] [Whether there is fracture]

[0277] 5: No fracture (actual use level)

[0278] 4: Only a very small part of the polarizer layer is fractured (actual use level)

[0279] 3: Only a small part of the polarizer layer and slightly fractured at the end of the bending part (actual use level)

[0280] 2: The entire polarizer layer is broken, but only slightly fractured at the end of the bending part (actual use level)

[0281] 1: The entire surface of the bent portion is fractured (not at the actual use level)

[0282] <Appearance (peeling) presence or absence>

[0283] ○: No peeling (actual use level)

[0284] △: Slight peeling at the bent portion (actual use level)

[0285] ×: The entire surface of the bent portion is peeled off (not at the actual use level) [Table 2]

[0286]

[0287] [Table 3]

[0288]

[0289] [Table 4]

[0290]

[0291] From the evaluation results in Table 4, it can be confirmed that in all the examples, the flexural strength is at a level where there is no problem in actual use. That is, it can be confirmed that in the laminate for a flexible image display device of each example, by using an optical laminate including a polarizing film, its protective film, and a retardation film and a specific adhesive layer, peeling does not occur even with repeated bending, and a laminate for a flexible image display device with excellent bend resistance and adhesion can be obtained.

[0292] On the other hand, in Comparative Example 1, it was confirmed that since the blending ratio of the monomer having a reactive functional group exceeded the desired amount, the stress during bending could not be relaxed, the film was fractured, and the bendability was poor. In addition, in Comparative Example 2, it was confirmed that since the blending ratio of the monomer having a reactive functional group was small, although an adhesive capable of relaxing the stress was obtained and no fracture occurred, the blending ratio of the monomer having a reactive functional group did not meet the desired amount, so the reactivity with the film was poor and peeling occurred during the bending test.

[0293] As described above, the present invention has been described with reference to the drawings for specific embodiments, but the present invention can be variously modified in addition to the structures shown and described. Therefore, the present invention is not limited to the structures shown and described, and its scope should be defined only by the appended claims and their equivalents.

Claims

1. A laminate for a flexible image display device, which comprises an adhesive layer for a flexible image display device and an optical laminate, The adhesive layer for the flexible image display device is formed from an adhesive composition, The adhesive composition contains a (meth)acrylic polymer and a crosslinking agent, and contains 0.01 to 5 parts by weight of the crosslinking agent with respect to 100 parts by weight of the (meth)acrylic polymer, The (meth)acrylic polymer contains a monomer having a reactive functional group and a (meth)acrylic monomer as monomer units, and the monomer having a reactive functional group is selected from one or more of a hydroxyl group-containing monomer, a carboxyl group-containing monomer, an amino group-containing monomer, and an amide group-containing monomer. The (meth)acrylic monomer has a linear or branched alkyl group having 1 to 24 carbon atoms, Moreover, the (meth)acrylic polymer does not include the following (meth)acrylate copolymer (A). In this (meth)acrylate copolymer (A), (a1) The structural unit derived from the (meth)acrylic acid alkyl ester monomer is 10% by mass or more and 95% by mass or less; (a2) The structural unit derived from the (meth)acrylic acid alkyl ester monomer having an alkoxyalkyl group or an alkyleneoxy group is 5% by mass or more and 90% by mass or less; (a3) The structural unit derived from the functional group-containing monomer is 0% by mass or more and 20% by mass or less. The functional group-containing monomer is a (meth)acrylic acid alkyl ester monomer that does not have a plurality of radically polymerizable functional groups, wherein the total amount of the structural units derived from the above components (a1), (a2), and (a3) is 100% by mass, In all the monomers constituting the (meth)acrylic polymer, 0.02 to 10% by weight of the monomer having a reactive functional group is contained, The weight average molecular weight (Mw) of the (meth)acrylic polymer is 1.2 million to 2.5 million, The crosslinking agent is at least one selected from organic crosslinking agents and polyfunctional metal chelates. The organic crosslinking agent is an isocyanate crosslinking agent, a peroxide crosslinking agent, an epoxy crosslinking agent, or an imine crosslinking agent, The glass transition temperature (Tg) of the adhesive layer is 0°C or lower and -50°C or higher, The thickness of the adhesive layer is 5 to 150 μm, The storage modulus G' of the adhesive layer at 25°C is 1.0 MPa or lower, The adhesive layer for the flexible image display device is the first adhesive layer, The optical laminate includes a polarizing film and a protective film made of a transparent resin material provided on the first surface of the polarizing film, The laminate for the flexible image display device is provided with the first adhesive layer on the side opposite to the side of the protective film that contacts the polarizing film.

2. The laminate for a flexible image display device according to claim 1, wherein, It contains an isocyanate crosslinking agent and / or a peroxide crosslinking agent.

3. A laminate for a flexible image display device, wherein the optical laminate includes a retardation film provided on the second surface of the polarizing film different from the first surface.

4. The laminate for a flexible image display device according to claim 3, wherein a second adhesive layer is disposed on the side of the retardation film opposite to the side in contact with the polarizing film.

5. The laminate for a flexible image display device according to claim 4, wherein a transparent conductive layer constituting a touch sensor is disposed on the side of the second adhesive layer opposite to the side in contact with the retardation film.

6. The laminate for a flexible image display device according to claim 5, wherein a third adhesive layer is disposed on the side of the transparent conductive layer constituting the touch sensor opposite to the side in contact with the second adhesive layer.

7. The laminate for a flexible image display device according to claim 3 or 4, wherein a transparent conductive layer constituting a touch sensor is disposed on the side of the first adhesive layer opposite to the side in contact with the protective film.

8. The laminate for a flexible image display device according to claim 7, wherein a third adhesive layer is disposed on the side of the transparent conductive layer constituting the touch sensor opposite to the side in contact with the first adhesive layer.

9. A flexible image display device, comprising the laminate for a flexible image display device according to any one of claims 3 to 8 and an organic EL display panel, wherein, the laminate for a flexible image display device is disposed on the visible side of the organic EL display panel.

10. The flexible image display device according to claim 9, wherein, a window is disposed on the visible side of the laminate for a flexible image display device.

Images