JP7353399B2 - Laminated body for flexible image display device and flexible image display device - Google Patents

Description

The present invention relates to a laminate for a flexible image display device including an optical film including at least a polarizing film and a plurality of specific adhesive layers, and a flexible image display device in which the laminate for a flexible image display device is disposed. .

As an organic EL display device with an integrated touch sensor, as shown in FIG. 1, an optical laminate 20 is provided on the viewing side of an organic EL display panel 10, and a touch panel 30 is provided on the viewing side of the optical laminate 20. ing. The optical laminate 20 includes a polarizing film 1 and a retardation film 3 having protective films 2-1 and 2-2 bonded to both surfaces, and the polarizing film 1 is provided on the viewing side of the retardation film 3. In addition, the touch panel 30 has transparent conductive films 4-1 and 4-2 having a structure in which base films 5-1 and 5-2 and transparent conductive layers 6-1 and 6-2 are laminated with spacers 7 interposed therebetween. (For example, see Patent Document 1).

Furthermore, it is expected that a foldable organic EL display device with excellent portability will be realized.

Japanese Patent Application Publication No. 2014-157745

However, the conventional organic EL display device as shown in Patent Document 1 is not designed with folding in mind. By using a plastic film as the organic EL display panel base material, flexibility can be imparted to the organic EL display panel. Further, even when a plastic film is used for the touch panel and the touch panel is incorporated into an organic EL display panel, flexibility can be imparted to the organic EL display panel. However, a problem has arisen in that the optical film laminated on the organic EL display panel, including a conventional polarizing film, inhibits the flexibility of the organic EL display device.

Therefore, by using an optical film containing at least a polarizing film and a plurality of specific adhesive layers, the present invention has excellent bending resistance and adhesion without peeling or breaking even when repeatedly bent. It is an object of the present invention to provide a laminate for a flexible image display device, and a flexible image display device in which the laminate for a flexible image display device is arranged.

The laminate for a flexible image display device of the present invention is a laminate for a flexible image display device including a plurality of adhesive layers and an optical film including at least a polarizing film, wherein the thickness of the polarizing film is 20 μm or less. Among the plurality of adhesive layers, the storage elastic modulus G' at 25°C of the outermost adhesive layer on the convex side when the laminate is bent is the storage elastic modulus G' at 25°C of the other adhesive layers. It is characterized by being approximately the same as or smaller than the elastic modulus G'.

In the laminate for a flexible image display device of the present invention, the optical film includes the polarizing film, a protective film made of a transparent resin material on the first surface of the polarizing film, and the first surface of the polarizing film. It is preferable that the optical laminate includes a retardation film on different second surfaces.

In the laminate for a flexible image display device of the present invention, among the plurality of adhesive layers, a first adhesive layer is arranged on a side opposite to the surface in contact with the polarizing film with respect to the protective film. It is preferable that

In the laminate for a flexible image display device of the present invention, of the plurality of adhesive layers, a second adhesive layer is disposed on the opposite side of the retardation film to the surface in contact with the polarizing film. It is preferable that the

In the laminate for a flexible image display device of the present invention, a transparent conductive layer constituting a touch sensor is disposed on the opposite side of the second adhesive layer to the surface in contact with the retardation film. It is preferable.

In the laminate for a flexible image display device of the present invention, a third adhesive layer is disposed on a side opposite to a surface in contact with the second adhesive layer with respect to the transparent conductive layer constituting the touch sensor. It is preferable that the

In the laminate for a flexible image display device of the present invention, a transparent conductive layer constituting a touch sensor is disposed on the opposite side of the first adhesive layer to the surface in contact with the protective film. is preferred.

In the laminate for a flexible image display device of the present invention, among the plurality of adhesive layers, a transparent conductive layer constituting the touch sensor has a surface opposite to a surface in contact with the first adhesive layer. , it is preferable that a third adhesive layer is disposed.

In the laminate for a flexible image display device of the present invention, it is preferable that the plurality of adhesive layers are formed from the same adhesive composition.

The flexible image display device of the present invention includes the laminate for a flexible image display device and an organic EL display panel, and the laminate for a flexible image display device is arranged on the viewing side with respect to the organic EL display panel. It is preferable that

In the flexible image display device of the present invention, it is preferable that a window is disposed on the viewing side of the laminate for a flexible image display device.

According to the present invention, by using an optical film including at least a polarizing film and a plurality of specific adhesive layers, it does not peel or break even when repeatedly bent, and has excellent bending resistance and adhesion. It is possible to obtain a laminate for a flexible image display device, and furthermore, it is possible to obtain a flexible image display device in which the laminate for a flexible image display device is arranged, which is useful.

EMBODIMENT OF THE INVENTION Hereinafter, embodiments of an optical film, a laminate for a flexible image display device, and a flexible image display device according to the present invention will be described in detail with reference to the drawings and the like.

FIG. 1 is a cross-sectional view showing a conventional organic EL display device. 1 is a cross-sectional view showing a flexible image display device according to an embodiment of the present invention. FIG. 3 is a cross-sectional view showing a flexible image display device according to another embodiment of the present invention. FIG. 3 is a cross-sectional view showing a flexible image display device according to another embodiment of the present invention. It is a figure which shows the measuring method of bending strength. FIG. 3 is a cross-sectional view showing an evaluation sample used in Examples (configuration A). It is a sectional view showing an evaluation sample used in an example (configuration B). It is a figure which shows the manufacturing method of the phase difference used in an Example. It is a figure which shows the manufacturing method of the phase difference used in an Example.

[Laminated body for flexible image display device]
The laminate for a flexible image display device of the present invention is characterized by including a plurality of adhesive layers and an optical film.

[Optical film]
The laminate for a flexible image display device of the present invention is characterized in that it includes an optical film containing at least a polarizing film, and the optical film includes, in addition to the polarizing film, a protective film formed from a transparent resin material, for example. Refers to films that include films such as and retardation films.
Further, in the present invention, the optical film includes the polarizing film, a protective film made of a transparent resin material on a first surface of the polarizing film, and a second surface different from the first surface of the polarizing film. A configuration including a retardation film and a retardation film is called an optical laminate. Note that the optical film does not include a plurality of adhesive layers such as a first adhesive layer described below.

The thickness of the optical film is preferably 92 μm or less, more preferably 60 μm or less, and even more preferably 10 to 50 μm. If it is within the above range, bending will not be inhibited, which is a preferable embodiment.

The polarizing film may have a protective film bonded to at least one side with an adhesive (layer) (not shown in the drawing) as long as the characteristics of the present invention are not impaired. An adhesive can be used to bond the polarizing film and the protective film. Examples of the adhesive include isocyanate adhesives, polyvinyl alcohol adhesives, gelatin adhesives, vinyl latex adhesives, and water-based polyesters. The adhesive is usually used as an aqueous adhesive and usually contains 0.5 to 60% by weight of solids. In addition to the above, examples of the adhesive between the polarizing film and the protective film include ultraviolet curable adhesives and electron beam curable adhesives. The electron beam curable adhesive for polarizing film exhibits suitable adhesiveness to the various protective films described above. Further, the adhesive used in the present invention can contain a metal compound filler. In addition, in the present invention, a polarizing film (polarizing plate) may be referred to as a polarizing film (polarizing plate) that is formed by bonding a polarizing film and a protective film together with an adhesive (layer).

<Polarizing film>
The polarizing film (also referred to as a polarizer) included in the optical film of the present invention is made of iodine-oriented polyvinyl alcohol (PVA) that has been stretched by a stretching process such as aerial stretching (dry stretching) or boric acid water stretching process. type resin can be used.

As a typical method for manufacturing a polarizing film, a manufacturing method including a step of dyeing a monolayer body of PVA resin and a step of stretching it (single layer stretching method) is described in JP-A No. 2004-341515. ). Also, JP-A-51-069644, JP-A-2000-338329, JP-A-2001-343521, International Publication No. 2010/100917, JP-A No. 2012-073563, and JP-A No. 2011-2816. Examples include a manufacturing method that includes a process of stretching a PVA-based resin layer and a resin base material for stretching in the state of a laminate, and a process of dyeing, as described in . With this manufacturing method, even if the PVA resin layer is thin, it can be stretched without problems such as breakage due to stretching because it is supported by the stretching resin base material.

The manufacturing method including the step of stretching and dyeing in the state of a laminate is as described in the above-mentioned JP-A-51-069644, JP-A-2000-338329, and JP-A-2001-343521. There is an aerial stretching (dry stretching) method. Then, the process of stretching in a boric acid aqueous solution as described in International Publication No. 2010/100917 and Japanese Patent Application Laid-open No. 2012-073563 is used because it can stretch to a high magnification and improve polarization performance. A manufacturing method including a step of performing auxiliary stretching in the air before stretching in a boric acid aqueous solution as disclosed in JP-A-2012-073563 is particularly preferred (two-stage stretching method). In addition, a manufacturing method as described in JP-A No. 2011-2816, in which the PVA resin layer and the resin base material for stretching are stretched in the form of a laminate, the PVA resin layer is excessively dyed, and then the color is decolored. (Overstaining and decolorizing method) is also preferred. The polarizing film included in the optical film of the present invention is made of a polyvinyl alcohol resin oriented with iodine as described above, and the polarizing film is stretched in a two-stage stretching process consisting of auxiliary stretching in the air and stretching in boric acid. can do. The polarizing film is made of a polyvinyl alcohol resin with iodine oriented as described above, and is produced by excessively dyeing a laminate of a stretched PVA resin layer and a stretching resin base material, and then decolorizing it. The produced polarizing film can be used as a polarizing film.

The thickness of the polarizing film is 20 μm or less, preferably 12 μm or less, more preferably 9 μm or less, still more preferably 1 to 8 μm, particularly preferably 3 to 6 μm. If it is within the above range, bending will not be inhibited, which is a preferable embodiment.

<Retardation film>
The optical film used in the present invention can include a retardation film, and the retardation film (also referred to as a retardation film) may be one obtained by stretching a polymer film or orienting and fixing a liquid crystal material. It is possible to use a modified version. In this specification, a retardation film has birefringence in the plane and/or in the thickness direction.

As the retardation film, a retardation film for anti-reflection (see JP-A No. 2012-133303 [0221], [0222], [0228]), a retardation film for viewing angle compensation (see JP-A No. 2012-133303 [0225]), ], [0226]), an inclined alignment retardation film for viewing angle compensation (see JP-A-2012-133303 [0227]), and the like.

The retardation film may be any known retardation film as long as it has substantially the above-mentioned functions, for example, without any particular limitations on retardation value, arrangement angle, three-dimensional birefringence, single layer or multilayer, etc. can be used.

The thickness of the retardation film is preferably 20 μm or less, more preferably 10 μm or less, still more preferably 1 to 9 μm, particularly preferably 3 to 8 μm. If it is within the above range, bending will not be inhibited, which is a preferable embodiment.

<Protective film>
The optical film used in the present invention can include a protective film formed from a transparent resin material, and the protective film (also referred to as a transparent protective film) may be made of cycloolefin resin such as norbornene resin, polyethylene, Olefin resins such as polypropylene, polyester resins, (meth)acrylic resins, etc. can be used.

The thickness of the protective film is preferably 5 to 60 μm, more preferably 10 to 40 μm, and still more preferably 10 to 30 μm, and a surface treatment layer such as an anti-glare layer or an antireflection layer may be provided as appropriate. I can do it. If it is within the above range, bending will not be inhibited, which is a preferable embodiment.

[First adhesive layer]
Among the plurality of adhesive layers used in the laminate for a flexible image display device of the present invention, the first adhesive layer is disposed on the opposite side of the protective film to the surface in contact with the polarizing film. It is preferable that

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

<(meth)acrylic polymer>
When an acrylic adhesive is used as the adhesive composition, (meth)acrylic containing a (meth)acrylic monomer having a linear or branched alkyl group having 1 to 24 carbon atoms as a monomer unit. It is preferable to contain a type polymer. By using the linear or branched (meth)acrylic monomer having an alkyl group having 1 to 24 carbon atoms, an adhesive layer with excellent flexibility can be obtained. Note that (meth)acrylic polymer in the present invention refers to acrylic polymer and/or methacrylic polymer, and (meth)acrylate refers to acrylate and/or methacrylate.

Specific examples of the (meth)acrylic monomer having a linear or branched alkyl group having 1 to 24 carbon atoms constituting the main skeleton of the (meth)acrylic polymer include methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, s-butyl (meth)acrylate, t-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, Examples include isononyl (meth)acrylate, n-decyl (meth)acrylate, isodecyl (meth)acrylate, n-dodecyl (meth)acrylate, n-tridecyl (meth)acrylate, n-tetradecyl (meth)acrylate, among others, In general, monomers with a low glass transition temperature (Tg) become viscoelastic bodies even in the high speed range during bending. A (meth)acrylic monomer having a group is preferred. As the (meth)acrylic monomer, one type or two or more types can be used.

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

When using an acrylic adhesive as the adhesive composition, it is preferable that the monomer unit contains a (meth)acrylic polymer containing a hydroxyl group-containing monomer having a reactive functional group. By using the hydroxyl group-containing monomer, a pressure-sensitive adhesive layer with excellent adhesion and flexibility can be obtained. The hydroxyl group-containing monomer is a compound that contains a hydroxyl group in its structure and also contains a polymerizable unsaturated double bond such as a (meth)acryloyl group or a vinyl group.

Specific examples of the hydroxyl group-containing monomer include 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, and 8-hydroxy Examples include hydroxyalkyl (meth)acrylates and (4-hydroxymethylcyclohexyl)-methyl acrylate, such as octyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, and 12-hydroxylauryl (meth)acrylate. Among the hydroxyl group-containing monomers, 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate are preferred from the viewpoint of durability and adhesion. In addition, as the hydroxyl group-containing monomer, one type or two or more types can be used.

Further, as monomer units constituting the (meth)acrylic polymer, it is possible to contain monomers such as carboxyl group-containing monomers, amino group-containing monomers, and amide group-containing monomers having reactive functional groups. It is preferable to use these monomers from the viewpoint of adhesion in a moist heat environment.

When an acrylic adhesive is used as the adhesive composition, a (meth)acrylic polymer containing a carboxyl group-containing monomer having a reactive functional group can be contained as a monomer unit. By using the carboxyl group-containing monomer, a pressure-sensitive adhesive layer with excellent adhesion in a moist heat environment can be obtained. The carboxyl group-containing monomer is a compound that contains a carboxyl group in its structure and also contains a polymerizable unsaturated double bond such as a (meth)acryloyl group or a vinyl group.

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

When an acrylic adhesive is used as the adhesive composition, a (meth)acrylic polymer containing an amino group-containing monomer having a reactive functional group can be contained as a monomer unit. By using the amino group-containing monomer, a pressure-sensitive adhesive layer with excellent adhesion in a moist heat environment can be obtained. The amino group-containing monomer is a compound that contains an amino group in its structure and also contains a polymerizable unsaturated double bond such as a (meth)acryloyl group or a vinyl group.

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

When an acrylic adhesive is used as the adhesive composition, a (meth)acrylic polymer containing an amide group-containing monomer having a reactive functional group can be contained as a monomer unit. By using the amide group-containing monomer, a pressure-sensitive adhesive layer with excellent adhesion can be obtained. The amide group-containing monomer is a compound that contains an amide group in its structure and also contains a polymerizable unsaturated double bond such as a (meth)acryloyl group or a vinyl group.

Specific examples of the amide group-containing monomer include (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-methylol (meth)acrylamide, N-methylol-N-propane (meth)acrylamide, aminomethyl (meth)acrylamide, aminoethyl (meth)acrylamide, mercapto Acrylamide monomers such as methyl (meth)acrylamide and mercaptoethyl (meth)acrylamide; N-acryloyl heterocyclic monomers such as N-(meth)acryloylmorpholine, N-(meth)acryloylpiperidine, and N-(meth)acryloylpyrrolidine; Examples include N-vinyl group-containing lactam monomers such as N-vinylpyrrolidone and N-vinyl-ε-caprolactam.

As for the monomer units constituting the (meth)acrylic polymer, the blending ratio (total amount) of the monomers having the reactive functional group is 20% by weight or less of the total monomers constituting the (meth)acrylic polymer. It is preferably 10% by weight or less, more preferably 0.01 to 8% by weight, particularly preferably 0.01 to 5% by weight, and most preferably 0.05 to 3% by weight. If it exceeds 20% by weight, the number of crosslinking points increases and the adhesive (layer) loses its flexibility, which tends to result in poor stress relaxation properties.

As monomer units constituting the (meth)acrylic polymer, other copolymerizable monomers can be introduced in addition to the monomer having the above-mentioned reactive functional group, within a range that does not impair the effects of the present invention. The blending ratio thereof is not particularly limited, but it is preferably 30% by weight or less, and more preferably not contained, based on the total monomers constituting the (meth)acrylic polymer. If it exceeds 30% by weight, the number of reaction points with the film decreases, and the adhesion tends to decrease, especially when a monomer other than (meth)acrylic monomer is used.

In the present invention, when the above-mentioned (meth)acrylic polymer is used, one 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. If the weight average molecular weight is less than 1 million, the number of crosslinking points will increase when polymer chains are crosslinked to each other to ensure durability, compared to those with a weight average molecular weight of 1 million or more. ), the dimensional change between the outside (convex side) and inside (concave side) of the bending that occurs between each film during bending cannot be alleviated, making the film more likely to break. Furthermore, if the weight average molecular weight is greater than 2.5 million, a large amount of diluting solvent will be required to adjust the viscosity for coating, which is undesirable as it will increase the cost. Since the intertwining of the polymer chains of the polymer becomes complicated, the flexibility is poor and the film is more likely to break when bent. Note that the weight average molecular weight (Mw) refers to a value measured by GPC (gel permeation chromatography) and calculated based on polystyrene conversion.

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

In the solution polymerization, for example, ethyl acetate, toluene, etc. are used as a polymerization solvent. As a specific example of solution polymerization, a polymerization initiator is added under a flow of an inert gas such as nitrogen, and the reaction is usually carried out at about 50 to 70° C. for about 5 to 30 hours.

The polymerization initiator, chain transfer agent, emulsifier, etc. used in radical polymerization are not particularly limited and can be appropriately selected and used. The weight average molecular weight of the (meth)acrylic polymer can be controlled by the amounts of the polymerization initiator and chain transfer agent used and the reaction conditions, and the amounts used are adjusted as appropriate depending on the types of these.

Examples of the polymerization initiator include 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-methylpropionamidine) disulfate, 2,2'-azobis(N,N'-dimethyleneisobutyramidine), 2, Azo initiators such as 2'-azobis[N-(2-carboxyethyl)-2-methylpropionamidine] hydrate (product name: VA-057, manufactured by Wako Pure Chemical Industries, Ltd.), potassium persulfate, Persulfates such as ammonium persulfate, di(2-ethylhexyl)peroxydicarbonate, di(4-t-butylcyclohexyl)peroxydicarbonate, di-sec-butylperoxydicarbonate, t-butylperoxyneodeca Noate, t-hexyl peroxypivalate, t-butyl peroxypivalate, dilauroyl peroxide, di-n-octanoyl peroxide, 1,1,3,3-tetramethylbutylperoxy-2-ethyl Hexanoate, di(4-methylbenzoyl) peroxide, dibenzoyl peroxide, t-butylperoxyisobutyrate, 1,1-di(t-hexylperoxy)cyclohexane, t-butyl hydroperoxide, peroxide Examples include peroxide-based initiators such as hydrogen, combinations of persulfates and sodium bisulfite, and redox-based initiators that combine peroxides and reducing agents, such as combinations of peroxides and sodium ascorbate. Yes, but not limited to these.

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

Further, when using a chain transfer agent, an emulsifier used in emulsion polymerization, or a reactive emulsifier, conventionally known ones can be used as appropriate. Further, the amount of these additives to be added can be appropriately determined within a range that does not impair the effects of the present invention.

<Crosslinking agent>
The adhesive composition of the present invention may contain a crosslinking agent. As the crosslinking agent, an organic crosslinking agent or a polyfunctional metal chelate can be used. Examples of the organic crosslinking agent include isocyanate crosslinking agents, peroxide crosslinking agents, epoxy crosslinking agents, imine crosslinking agents, and the like. A polyfunctional metal chelate is one in which a polyvalent metal is covalently or coordinately bonded to an organic compound. Examples of polyvalent metal atoms include Al, Cr, Zr, Co, Cu, Fe, Ni, V, Zn, In, Ca, Mg, Mn, Y, Ce, Sr, Ba, Mo, La, Sn, Ti, etc. Can be mentioned. Examples of atoms in the organic compound that form a covalent bond or coordinate bond include oxygen atoms, and examples of the organic compound include alkyl esters, alcohol compounds, carboxylic acid compounds, ether compounds, ketone compounds, and the like. Among these, isocyanate-based crosslinking agents (particularly trifunctional isocyanate-based crosslinking agents) are preferable in terms of durability, and peroxide-based crosslinking agents and isocyanate-based crosslinking agents (especially difunctional isocyanate-based crosslinking agents) are preferred. is preferable from the viewpoint of flexibility. Peroxide-based crosslinking agents and difunctional isocyanate-based crosslinking agents both form flexible two-dimensional crosslinks, whereas trifunctional isocyanate-based crosslinking agents form stronger three-dimensional crosslinks. When bending, two-dimensional crosslinking, which is a more flexible crosslinking, is advantageous. However, two-dimensional cross-linking alone lacks durability and tends to peel, so hybrid cross-linking of two-dimensional cross-linking and three-dimensional cross-linking is better, so trifunctional isocyanate-based cross-linking agents and peroxide-based cross-linking agents are used. In a preferred embodiment, a difunctional isocyanate-based crosslinking agent is used in combination.

The amount of the crosslinking agent used is, for example, preferably 0.01 to 10 parts by weight, more preferably 0.03 to 2 parts by weight, based on 100 parts by weight of the (meth)acrylic polymer. If it is within the above range, the bending resistance is excellent, which is a preferable embodiment.

<Other additives>
Furthermore, the adhesive composition of the present invention may contain other known additives, such as various silane coupling agents, polyether compounds of polyalkylene glycol such as polypropylene glycol, colorants, pigments, etc. powder, dye, surfactant, plasticizer, tackifier, surface lubricant, leveling agent, softener, antioxidant, anti-aging agent, light stabilizer, ultraviolet absorber, polymerization inhibitor, antistatic agent Agents (ionic compounds such as alkali metal salts and ionic liquids), inorganic or organic fillers, metal powders, particles, foils, etc. can be added as appropriate depending on the intended use. Further, within a controllable range, a redox system may be employed in which a reducing agent is added.

[Other adhesive layers]
Of the plurality of adhesive layers used in the laminate for a flexible image display device of the present invention, a second adhesive layer is arranged on the opposite side of the retardation film to the surface in contact with the polarizing film. be able to.

Among the plurality of adhesive layers used in the laminate for a flexible image display device of the present invention, the third adhesive layer is in contact with the second adhesive layer with respect to the transparent conductive layer constituting the touch sensor. A third adhesive layer can be disposed on the side opposite to the side facing.

Of the plurality of adhesive layers used in the laminate for a flexible image display device of the present invention, the third adhesive layer is in contact with the first adhesive layer with respect to the transparent conductive layer constituting the touch sensor. It can be placed on the opposite side of the

In addition, in addition to the first adhesive layer, when using a second adhesive layer and further other adhesive layers (for example, a third adhesive layer, etc.), these adhesive layers may be the same. There are no particular restrictions on whether the composition (same adhesive composition) and properties are the same or different, but when the laminate is bent among the plurality of adhesive layers. It is required that the storage modulus G' at 25° C. of the adhesive layer on the outermost surface of the convex side of the adhesive layer is approximately the same as or smaller than the storage modulus G′ at 25° C. of the other adhesive layers. Further, from the viewpoints of workability, economy, and flexibility, it is preferable that all the adhesive layers have substantially the same composition and the same characteristics.

<Formation of adhesive layer>
It is preferable that the plurality of adhesive layers in the present invention are formed from the above-mentioned adhesive composition. Examples of the method for forming the adhesive layer include a method in which the adhesive composition is applied to a release-treated separator and the like, and the polymerization solvent and the like are dried and removed to form the adhesive layer. Alternatively, it can also be produced by a method in which the adhesive composition is applied to a polarizing film or the like, and the polymerization solvent and the like are removed by drying to form an adhesive layer on the polarizing film or the like. In addition, when applying the adhesive composition, one or more solvents other than the polymerization solvent may be newly added as appropriate.

As the release-treated separator, a silicone release liner is preferably used. When forming an adhesive layer by coating and drying the adhesive composition of the present invention on such a liner, an appropriate method may be adopted as a method for drying the adhesive depending on the purpose. . Preferably, a method of heating and drying the coating film is used. For example, when preparing an acrylic adhesive using a (meth)acrylic polymer, the heat drying temperature is preferably 40 to 200°C, more preferably 50 to 180°C, particularly preferably 70 to 180°C. The temperature is 170°C. By setting the heating temperature within the above range, a pressure-sensitive adhesive having excellent adhesive properties can be obtained.

As the drying time, an appropriate time can be adopted as needed. For example, when preparing an acrylic adhesive using a (meth)acrylic polymer, the drying time is preferably 5 seconds to 20 minutes, more preferably 5 seconds to 10 minutes, particularly preferably 10 seconds to 5 minutes. It's a minute.

Various methods can be used to apply the pressure-sensitive adhesive composition. Specifically, for example, roll coat, kiss roll coat, gravure coat, reverse coat, roll brush, spray coat, dip roll coat, bar coat, knife coat, air knife coat, curtain coat, lip coat, die coater, etc. Examples include methods such as extrusion coating.

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 even more preferably 10 to 100 μm. The adhesive layer may be a single layer or may have a laminated structure. If it is within the above range, it will not inhibit bending and will be a preferable embodiment in terms of adhesion (retention resistance). Further, in the case where there are multiple adhesive layers, it is preferable that all the adhesive layers are within the above range.

Among the plurality of adhesive layers used in the laminate for a flexible image display device of the present invention, the storage elastic modulus G' at 25°C of the adhesive layer on the outermost surface on the convex side when the laminate is folded is different from that of the other adhesive layers. It is characterized by being approximately the same as or smaller than the storage modulus G' at 25° C. of the adhesive layer. If multiple storage moduli (G') are approximately the same, the stress generated during bending (bending) will not be biased to some layers, so each film/layer (for example, an optical film such as a polarizing film) ) breakage and peeling of the pressure-sensitive adhesive layer/adhesive layer are suppressed, which is preferable.
For example, when the optical laminate is used as the optical film, the storage modulus (G') may be such that the retardation film side is on the convex side (outside) and the laminate for flexible image display device is placed in the center. When bent, if the pressure decreases toward the convex side, the adhesive layer on the retardation side receives a force in the pulling direction, and the tensile force decreases from the convex side (outside) to the concave side (inside). go. The adhesive layer that receives the force in the tensile direction is a stress-relieving adhesive layer, that is, the smaller G' is, the smaller the stress applied to the film such as the optical film, and the less likely it is that breakage or interlayer peeling will occur. Since the stress applied from the convex side (outside) to the concave side (inside) becomes smaller, bending resistance is ensured even if G' becomes larger than that on the outermost layer side. Compared to the case where the size increases toward the convex side (outward side), breakage of each film/layer and interlayer peeling are eliminated, which is a preferable embodiment.
Note that substantially the same means that the difference in storage modulus (G') between the adhesive layers is within a range of ±15% with respect to the average value of the storage modulus (G') of the plurality of adhesive layers, Preferably, it means within the range of ±10%.

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 even more preferably is 0.3 MPa or less. If the storage modulus of the adhesive layer is within this range, the adhesive layer will not become hard, will have excellent stress relaxation properties, and will have excellent bending resistance, thus realizing a flexible image display device that can be bent or folded. can do.

In particular, when the laminate for a flexible image display device is folded at the center, the storage modulus (G') of the innermost side of the concave side (inner side) is preferably 0.05 to 0.2 MPa at 25°C. Yes, more preferably 0.05 to 0.15 MPa. If it exceeds 0.2 MPa, the stress applied during bending cannot be relaxed, and films such as optical films are likely to break. If it is less than 0.05 MPa, the dimensional change between the films during continuous bending will be completely followed, so the durability of the bent portion will deteriorate due to fatigue deterioration of the adhesive layer, and peeling and foaming will easily occur.
Further, when the laminate for a flexible image display device is folded at the center, the storage modulus (G') of the outermost convex side (outside) is preferably 0.01 to 0.15 MPa at 25°C. Yes, more preferably 0.01 to 0.1 MPa. If it exceeds 0.15 MPa, shear stress generated during bending cannot be alleviated, and films such as optical films are likely to break. Moreover, if it is less than 0.01 MPa, the dimensional change between the films during continuous bending will be completely followed, so the durability of the bent portion will deteriorate due to fatigue deterioration of the adhesive layer, and peeling and foaming will easily occur.
When a plurality of adhesive layers are present, the storage modulus (G') of the adhesive layer located in the middle is preferably 0.01 to 0.2 MPa at 25°C, more preferably 0.01 to 0. .15MPa. Since the adhesive layer is located in the middle of the laminate, stress is least applied to it, so the storage modulus (G') of the adhesive layers on the convex side (outer side) and the concave side (inner side) of the multiple adhesive layers is The applicable range is the sum of the ranges. If it is within the above range, the film on the convex side will not break during bending, which is preferable.

The upper limit of the glass transition temperature (Tg) of the adhesive layer used in the laminate for a flexible image display device of the present invention is preferably 0°C or lower, more preferably -20°C or lower, and even more preferably -25°C. below ℃. If the Tg of the adhesive layer is within this range, the adhesive layer will not become hard even in the high speed range during bending, and will have excellent stress relaxation properties, making it possible to realize a flexible image display device that is bendable or foldable. can.

The total light transmittance (according to JIS K7136) in the visible wavelength region of the adhesive layer used in the laminate for a flexible image display device of the present invention is preferably 85% or more, more preferably 90% or more.

The haze (according to JIS K7136) of the adhesive layer used in the laminate for a flexible image display device of the present invention is preferably 3.0% or less, more preferably 2.0% or less.

Note that the total light transmittance and the haze can be measured using, for example, a haze meter (manufactured by Murakami Color Research Institute, trade name "HM-150").

[Transparent conductive layer]
The member having a transparent conductive layer is not particularly limited, and any known member can be used, such as a member having a transparent conductive layer on a transparent substrate such as a transparent film, or a member having a transparent conductive layer and a liquid crystal. Examples include members having cells.

The transparent base material may be anything that has transparency, such as a base material made of a resin film or the like (for example, a sheet-like, film-like, plate-like base material, etc.). The thickness of the transparent substrate is not particularly limited, but is preferably about 10 to 200 μm, more preferably about 15 to 150 μm.

The material for the resin film is not particularly limited, but includes various transparent plastic materials. For example, the materials include polyester resins such as polyethylene terephthalate and polyethylene naphthalate, acetate resins, polyether sulfone resins, polycarbonate resins, polyamide resins, polyimide resins, polyolefin resins, and (meth)acrylic resins. , polyvinyl chloride resin, polyvinylidene chloride resin, polystyrene resin, polyvinyl alcohol resin, polyarylate resin, polyphenylene sulfide resin, and the like. Among these, particularly preferred are polyester resins, polyimide resins, and polyethersulfone resins.

Further, the surface of the transparent base material is subjected to etching treatment or undercoating treatment such as sputtering, corona discharge, flame, ultraviolet irradiation, electron beam irradiation, chemical conversion, oxidation, etc., and the transparent conductive layer provided thereon is Adhesion to the transparent substrate may be improved. Further, before providing the transparent conductive layer, dust removal and cleaning may be performed by solvent cleaning, ultrasonic cleaning, etc., if necessary.

The constituent material of the transparent conductive layer is not particularly limited, and is selected from the group consisting of indium, tin, zinc, gallium, antimony, titanium, silicon, zirconium, magnesium, aluminum, gold, silver, copper, palladium, and tungsten. A metal oxide of at least one metal is used. The metal oxide may further contain metal atoms shown in the above group, if necessary. For example, indium oxide (ITO) containing tin oxide, tin oxide containing antimony, etc. are preferably used, and ITO is particularly preferably used. ITO preferably contains 80 to 99% by weight of indium oxide and 1 to 20% by weight of tin oxide.

Furthermore, examples of the ITO include crystalline ITO and non-crystalline (amorphous) ITO. Crystalline ITO can be obtained by applying high temperature during sputtering or by further heating amorphous ITO.

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 even more preferably 0.01 to 1 μm. If the thickness of the transparent conductive layer is less than 0.005 μm, the change in electrical resistance value of the transparent conductive layer tends to increase. On the other hand, if it exceeds 10 μm, the productivity of the transparent conductive layer tends to decrease, the cost increases, and the optical properties also tend to decrease.

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

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 .

The surface resistance value of the transparent conductive layer of the present invention is preferably 0.1 to 1000 Ω/□, more preferably 0.5 to 500 Ω/□, and even more preferably 1 to 250 Ω/□.

The method for forming the transparent conductive layer is not particularly limited, and conventionally known methods can be employed. Specifically, for example, a vacuum evaporation method, a sputtering method, and an ion plating method can be exemplified. Moreover, an appropriate method can also be adopted depending on the required film thickness.

Moreover, an undercoat layer, an oligomer prevention layer, etc. can be provided between the transparent conductive layer and the transparent base material, if necessary.

The transparent conductive layer constitutes a touch sensor and is required to be bendable.

In the laminate for a flexible image display device of the present invention, the transparent conductive layer constituting the touch sensor may be disposed on the opposite side of the second adhesive layer to the surface in contact with the retardation film. can.

In the laminate for a flexible image display device of the present invention, the transparent conductive layer constituting the touch sensor may be arranged on the opposite side of the first adhesive layer to the surface in contact with the protective film. can.

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

When used in a flexible image display device, the transparent conductive layer can be suitably applied to an in-cell type or on-cell type liquid crystal display device that has a built-in touch sensor, and is particularly applicable to an organic EL display panel that has a built-in touch sensor. (even if it is incorporated)

[Conductive layer (antistatic layer)]
Further, the laminate for a flexible image display device of the present invention may include a layer having conductivity (a conductive layer, an antistatic layer). The laminate for a flexible image display device has a bending function and has a very thin thickness, so it is highly reactive and easily damaged by weak static electricity generated during the manufacturing process. By providing a conductive layer on the substrate, the load due to static electricity during the manufacturing process etc. is greatly reduced, which is a preferable embodiment.

In addition, one of the major features of the flexible image display device including the laminate is that it has a bending function, but when it is continuously bent, static electricity is generated due to contraction between the films (substrates) at the bending part. There are cases. Therefore, when the laminate is imparted with conductivity, the generated static electricity can be quickly removed, and damage to the image display device due to static electricity can be reduced, which is a preferred embodiment.

Further, the conductive layer may be an undercoat layer having a conductive function, an adhesive containing a conductive component, or a surface treatment layer containing a conductive component. For example, a method can be adopted in which a conductive layer is formed between a polarizing film and an adhesive layer using an antistatic composition containing a conductive polymer such as polythiophene and a binder. Furthermore, an adhesive containing an ionic compound that is an antistatic agent can also be used. Further, it is preferable that the conductive layer has one or more layers, and may include two or more layers.

[Flexible image display device]
The flexible image display device of the present invention includes the above-described laminate for a flexible image display device and an organic EL display panel, the laminate for a flexible image display device is arranged on the viewing side with respect to the organic EL display panel, and the laminate for a flexible image display device is arranged on the viewing side with respect to the organic EL display panel, and configured to be possible. Although optional, a window can be placed on the viewing side of the laminate for a flexible image display device.

FIG. 2 is a sectional view showing one embodiment of a flexible image display device according to the present invention. This flexible image display device 100 includes a flexible image display device laminate 11 and an organic EL display panel 10 configured to be foldable. The flexible image display device laminate 11 is arranged on the viewing side of the organic EL display panel 10, and the flexible image display device 100 is configured to be foldable. Although optional, a transparent window 40 can be placed on the viewing side of the flexible image display device laminate 11 via the first adhesive layer 12-1.

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

The optical laminate 20 includes a polarizing film 1, a protective film 2 made of a transparent resin material, and a retardation film 3. A protective film 2 made of a transparent resin material is bonded to the first surface of the polarizing film 1 on the viewing side. The retardation film 3 is bonded to a second surface of the polarizing film 1 that is different from the first surface. The polarizing film 1 and the retardation film 3 are used, for example, to generate circularly polarized light to prevent light incident from the viewing side of the polarizing film 1 from being internally reflected and emitted to the viewing side, and to adjust the viewing angle. It is intended to compensate for

In this embodiment, whereas conventionally a protective film was provided on both sides of a polarizing film, a protective film is provided on only one side, and the polarizing film itself is also used in conventional organic EL display devices. The thickness of the optical laminate 20 can be reduced by using a polarizing film that is very thin (20 μm or less) compared to the other polarizing films. Furthermore, since the polarizing film 1 is much thinner than the polarizing film used in conventional organic EL display devices, the stress caused by expansion and contraction caused by temperature or humidity conditions is extremely small. Therefore, the possibility that the stress caused by the shrinkage of the polarizing film will cause deformation such as warping in the adjacent organic EL display panel 10 is greatly reduced, and the deterioration of display quality or destruction of the panel sealing material due to deformation is greatly reduced. It becomes possible to suppress the Further, by using a thin polarizing film, bending is not inhibited, which is a preferable embodiment.

When the optical laminate 20 is folded with the protective film 2 side facing inside, the thickness of the optical laminate 20 is reduced (for example, 92 μm or less) and the first adhesive layer 12-1 has the storage modulus as described above. By arranging the protective film 2 on the opposite side of the retardation film 3, it becomes possible to reduce the stress applied to the optical laminate 20, thereby making the optical laminate 20 bendable. Furthermore, an appropriate storage modulus range may be set depending on the environmental temperature in which the flexible image display device is used. For example, when the assumed usage environment temperature is -20°C to +85°C, a first adhesive layer whose storage elastic modulus at 25°C falls within an appropriate numerical range can be used.

Although optional, a bendable transparent conductive layer 6 constituting a touch sensor may be further disposed on the opposite side of the protective film 2 to the retardation film 3. The transparent conductive layer 6 is configured to be directly bonded to the retardation film 3 by a manufacturing method as disclosed in JP-A-2014-219667, for example, so that the thickness of the optical laminate 20 is reduced and the thickness of the optical laminate 20 is reduced. The stress applied to the optical laminate 20 when folded can be further reduced.

Although optional, an adhesive layer constituting the third adhesive layer 12-3 may be further disposed on the opposite side of the transparent conductive layer 6 from the retardation film 3. In this 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.

The flexible image display device shown in FIG. 3 is almost the same as the one shown in FIG. 2, but in the flexible image display device shown in FIG. In contrast, in the flexible image display device shown in FIG. The difference is that a bendable transparent conductive layer 6 constituting a touch sensor is arranged. Furthermore, in the flexible image display device of FIG. 2, the third adhesive layer 12-3 is disposed on the opposite side of the transparent conductive layer 2 from the retardation film 3, whereas in the flexible image display device of FIG. The flexible image display device is different in that a second adhesive layer 12-2 is disposed on the opposite side of the protective film 2 with respect to the retardation film 3.

Further, although optional, when the window 40 is arranged on the viewing side of the flexible image display device laminate 11, the third adhesive layer 12-3 can be arranged.

The flexible image display device of the present invention can be suitably used as an image display device such as a flexible liquid crystal display device, an organic EL (electroluminescence) display device, and electronic paper. Furthermore, it can be used regardless of the type of touch panel, such as a resistive film type or a capacitive type.

Furthermore, as shown in FIG. 4, the flexible image display device of the present invention can also be used as an in-cell type flexible image display device in which the transparent conductive layer 6 constituting the touch sensor is built into the organic EL display panel 10-1. It is possible to do so.

Hereinafter, some examples related to the present invention will be described, but the present invention is not intended to be limited to what is shown in these specific examples. Further, the numerical values in the table are the blended amount (added amount), and indicate the solid content or solid content ratio (based on weight). The formulation contents and evaluation results are shown in Tables 1 to 4.

[Example 1]
[Polarizing film]
As a thermoplastic resin base material, an amorphous polyethylene terephthalate (hereinafter also referred to as "PET") (IPA copolymerized PET) film (thickness: 100 μm) containing 7 mol% of isophthalic acid units was prepared, and the surface was corona-treated ( 58 W/m ² /min). On the other hand, acetoacetyl-modified PVA (manufactured by Nippon Gosei Kagaku Kogyo Co., Ltd., trade name: Gosefimer Z200 (average degree of polymerization: 1200, degree of saponification: 98.5 mol%, degree of acetoacetylation: 5 mol%) Prepare PVA (polymerization degree 4200, saponification degree 99.2%) added with 1% by weight, prepare a coating liquid of PVA aqueous solution containing 5.5% by weight of PVA resin, and calculate the film thickness after drying. The layer was coated to a thickness of 12 μm and dried for 10 minutes by hot air drying in an atmosphere of 60° C. to produce a laminate having a PVA resin layer on the base material.

Next, this laminate was first stretched at the free end by 1.8 times in air at 130° C. (in-air auxiliary stretching) to produce a stretched laminate. Next, 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. The boric acid insolubilized aqueous solution used in this step had a boric acid content of 3 parts by weight per 100 parts by weight of water. A colored laminate was produced by dyeing this stretched laminate. Colored laminates are produced by subjecting the stretched laminate to a dye solution containing iodine and potassium iodide at a temperature of 30°C so that the single transmittance of the PVA layer constituting the final polarizing film is 40 to 44%. The PVA layer contained in the stretched laminate is dyed with iodine by immersing it in water for an arbitrary period of time. In this step, the dyeing solution used water as a solvent, had an iodine concentration in the range of 0.1 to 0.4% by weight, and a potassium iodide concentration in the range of 0.7 to 2.8% by weight. The ratio of iodine to potassium iodide concentrations is 1:7. Next, the colored laminate was immersed in a boric acid crosslinking aqueous solution at 30° C. for 60 seconds to crosslink the PVA molecules of the PVA layer on which iodine had been adsorbed. The boric acid crosslinking aqueous solution used in this step had a boric acid content of 3 parts by weight based on 100 parts by weight of water, and a potassium iodide content of 3 parts by weight based on 100 parts by weight of water.

Furthermore, the obtained colored laminate was stretched in a boric acid aqueous solution at a stretching temperature of 70° C. in the same direction as the previous stretching in air (stretching in boric acid water), and the final An optical film laminate having a stretching ratio of 5.50 times was obtained. The optical film laminate was taken out of the boric acid aqueous solution, and the boric acid adhering to the surface of the PVA layer was washed with an aqueous solution containing 4 parts by weight of potassium iodide per 100 parts by weight of water. The cleaned optical film laminate was dried by a drying process using hot air at 60°C. The thickness of the polarizing film included in the obtained optical film laminate was 5 μm.

[Protective film]
As the protective film, a methacrylic resin pellet having a glutarimide ring unit was extruded, formed into a film shape, and then stretched. This protective film was an acrylic film with a thickness of 20 μm and a moisture permeability of 160 g/m ² .

Next, the polarizing film and the protective film were bonded together using the adhesive shown below to obtain a polarizing film.

As the adhesive (active energy ray curable adhesive), each component was mixed according to the recipe shown in Table 1, stirred at 50 ° C. for 1 hour, and the adhesive (active energy ray curable adhesive A) was prepared. was prepared. The numerical values in the table indicate weight % when the total amount of the composition is 100 weight %. The components used are as follows.
HEAA: Hydroxyethyl acrylamide M-220: ARONIX M-220, tripropylene glycol diacrylate), manufactured by Toagosei Co., Ltd. ACMO: Acryloylmorpholine AAEM: 2-acetoacetoxyethyl methacrylate, manufactured by Nippon Gosei Co., Ltd. UP-1190: ARUFON UP- 1190, manufactured by Toagosei Co., Ltd. IRG907: IRGACURE907, 2-methyl-1-(4-methylthiophenyl)-2-morpholinopropan-1-one, manufactured by BASF DETX-S: KAYACURE DETX-S, diethylthioxanthone, Nipponka Manufactured by a pharmaceutical company

In the Examples and Comparative Examples using the adhesive, after laminating the protective film and the polarizing film via the adhesive, the adhesive is cured by irradiation with ultraviolet rays to form an adhesive layer. was formed. For ultraviolet irradiation, a gallium-filled metal halide lamp (manufactured by Fusion UV Systems, Inc., product name "Light HAMMER10", bulb: V bulb, peak illuminance: 1600 mW/cm ² , cumulative irradiation amount 1000/mJ/cm ² (wavelength) 380-440 nm)) was used.

[Retardation film]
The retardation film (1/4 wavelength retardation plate) of this example is made of two layers: a retardation layer for a 1/4 wavelength plate and a retardation layer for a 1/2 wavelength plate, in which liquid crystal material is oriented and fixed. It was a retardation film composed of Specifically, it was manufactured as follows.

(liquid crystal material)
As a material for forming the retardation layer for the 1/2 wavelength plate and the retardation layer for the 1/4 wavelength plate, a polymerizable liquid crystal material exhibiting a nematic liquid crystal phase (manufactured by BASF, trade name Paliocolor LC242) was used. A photopolymerization initiator (trade name: Irgacure 907, manufactured by BASF) for the polymerizable liquid crystal material was dissolved in toluene. Further, for the purpose of improving coating properties, approximately 0.1 to 0.5% of Megafac series manufactured by DIC was added depending on the thickness of the liquid crystal to prepare a liquid crystal coating solution. The liquid crystal coating solution was applied onto the alignment base material using a bar coater, and then heated and dried at 90° C. for 2 minutes, and then the alignment was fixed by ultraviolet curing in a nitrogen atmosphere. As the base material, a material such as PET to which a liquid crystal coating layer can be later transferred was used. Furthermore, in order to improve coating properties, 0.1% to 0.5% of a fluorine-based polymer from DIC's Megafac series is added depending on the thickness of the liquid crystal layer, and MIBK (methyl isobutyl ketone), cyclohexanone, or MIBK A coating liquid was prepared by dissolving the liquid to a solid content concentration of 25% using a mixed solvent of cyclohexanone and cyclohexanone. This coating liquid was applied to a substrate using a wire bar, a drying process was performed for 3 minutes at 65° C., and the orientation was fixed by curing with ultraviolet light in a nitrogen atmosphere. As the base material, a material such as PET to which a liquid crystal coating layer can be later transferred was used.

(Manufacturing process)
The manufacturing process of this example will be explained with reference to FIG. Note that the numbers in FIG. 8 are different from the numbers in other drawings. In this manufacturing process 20, the base material 14 was provided by a roll, and the base material 14 was supplied from a supply reel 21. In the manufacturing process 20, a coating liquid of the ultraviolet curable resin 10 was applied to the base material 14 using a die 22. In this manufacturing process 20, the roll plate 30 was a cylindrical molding mold in which a concavo-convex shape related to an alignment film for a quarter-wave plate of a quarter-wave retardation plate was formed on the circumferential side. In the manufacturing process 20, the base material 14 coated with the ultraviolet curable resin is pressed against the circumferential side of the roll plate 30 by the pressure roller 24, and the ultraviolet ray curable resin is irradiated with ultraviolet rays by the ultraviolet irradiation device 25 consisting of a high-pressure mercury lamp. hardened. Thereby, in the manufacturing process 20, the uneven shape formed on the peripheral side of the roll plate 30 was transferred to the base material 14 at an angle of 75° with respect to the MD direction. Thereafter, the base material 14 was peeled off from the roll plate 30 together with the cured ultraviolet curable resin 10 using a peeling roller 26, and a liquid crystal material was applied using a die 29. Thereafter, the liquid crystal material was cured by irradiation with ultraviolet rays by the ultraviolet ray irradiation device 27, thereby creating a structure related to a retardation layer for a quarter-wave plate.
Subsequently, in this step 20, the base material 14 is transported to a die 32 by a transport roller 31, and a coating liquid of the ultraviolet curable resin 12 is applied by the die 32 onto the retardation layer for a quarter wavelength plate of this base material 14. did. In this manufacturing process 20, the roll plate 40 was a cylindrical molding mold in which an uneven shape related to a 1/2 wavelength plate alignment film of a 1/4 wavelength retardation plate was formed on the circumferential side. In the manufacturing process 20, the base material 14 coated with the ultraviolet curable resin is pressed against the circumferential side of the roll plate 40 by the pressure roller 34, and the ultraviolet curable resin is irradiated with ultraviolet rays by the ultraviolet ray irradiation device 35 consisting of a high-pressure mercury lamp. hardened. Thereby, in the manufacturing process 20, the uneven shape formed on the peripheral side of the roll plate 40 was transferred to the base material 14 at an angle of 15° with respect to the MD direction. Thereafter, the base material 14 was peeled off from the roll plate 40 together with the cured ultraviolet curable resin 12 using a peeling roller 36, and a liquid crystal material was applied using a die 39. After that, the liquid crystal material is cured by irradiation with ultraviolet rays by the ultraviolet irradiation device 37, thereby creating a structure related to a retardation layer for a 1/2 wavelength plate, a retardation layer for a 1/2 wavelength plate, a retardation layer for a 1/2 wavelength plate, A retardation film with a thickness of 7 μm consisting of two layers of retardation layers for plates was obtained.

[Optical film (optical laminate)]
The retardation film obtained as above and the polarizing film obtained as above were laminated continuously using the above adhesive using a roll-to-roll method, and the axes of the slow axis and absorption axis were bonded together. A laminated film (optical laminate) was produced so that the angle was 45°.

Then, the obtained laminated film (optical laminate) was cut into 15 cm x 5 cm.

[Second adhesive layer]
<Preparation of (meth)acrylic polymer A1>
A monomer mixture containing 99 parts by weight of butyl acrylate (BA) and 1 part by weight of 4-hydroxybutyl acrylate (HBA) was charged into a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen gas inlet tube, and a condenser. .
Furthermore, to 100 parts by weight of the monomer mixture (solid content), 0.1 parts by weight of 2,2'-azobisisobutyronitrile as a polymerization initiator was added together with ethyl acetate, and nitrogen gas was added while stirring gently. After the flask was replaced with nitrogen, the temperature of the liquid in the flask was maintained at around 55°C and a polymerization reaction was carried out for 7 hours. Thereafter, ethyl acetate was added to the obtained reaction solution to prepare a solution of (meth)acrylic polymer A1 having a weight average molecular weight of 1.6 million, which was adjusted to a solid content concentration of 30%.

<Preparation of acrylic adhesive composition>
0.1 weight of an isocyanate crosslinking agent (trade name: Takenate D110N, trimethylolpropane xylylene diisocyanate, manufactured by Mitsui Chemicals, Inc.) per 100 parts by weight of the solid content of the obtained (meth)acrylic polymer A1 solution. 0.3 parts by weight of benzoyl peroxide (trade name: Niper BMT, manufactured by NOF Corporation), a peroxide-based crosslinking agent, and 0.3 parts by weight of a silane coupling agent (trade name: KBM403, manufactured by Shin-Etsu Chemical Co., Ltd.) )0.08 parts by weight was blended to prepare an acrylic pressure-sensitive adhesive composition.

<Preparation of optical laminate with adhesive layer>
The acrylic pressure-sensitive adhesive composition was uniformly coated with a fountain coater on the surface of a 38 μm thick polyethylene terephthalate film (PET film, transparent base material, separator) treated with a silicone release agent, and then heated at 155°C. It was dried for 2 minutes in an air circulating constant temperature oven to form an adhesive layer 1 (second adhesive layer) with a thickness of 25 μm on the surface of the base material.
Next, a separator on which adhesive layer 1 (second adhesive layer) was formed was transferred to the protective film side (corona treated) of the obtained optical laminate to produce an optical laminate with an adhesive layer. .

[First adhesive layer]
In the same manner as the second adhesive layer, the adhesive layer 4 (first adhesive layer) was formed with a thickness of 50 μm based on the formulation contents in Tables 2 and 3. A separator with an adhesive layer 4 formed thereon was transferred to the surface (corona treated) of a 75 μm thick PET film (transparent base material, manufactured by Mitsubishi Plastics Co., Ltd., product name: Diafoil). , a PET film with an adhesive layer was formed.

[Third adhesive layer]
In the same manner as the second adhesive layer described above, the adhesive layer 2 (third adhesive layer) was formed with a thickness of 50 μm based on the formulation contents in Tables 2 and 3. A separator with an adhesive layer 2 formed thereon was transferred to the surface (corona treated) of a 77 μm thick polyimide film (PI film, DuPont-Toray Co., Ltd., Kapton 300V, base material). , a PI film with an adhesive layer was formed.

<Laminated body for flexible image display device>
As shown in FIG. 6, the first to third adhesive layers (along with each transparent base material) obtained as described above are applied to the (meth)acrylic resin film that will become the protective film 2, and then the second adhesive layer is applied. The third adhesive layer 12-3 is attached to the retardation film 3, and the transparent base material 8-2 (on which the second adhesive layer 12-2 is attached) is attached. A laminate 11 for a flexible image display device corresponding to configuration A used in Example 1 was produced by bonding the first adhesive layer 12-1 to a PET film. Note that a laminate 11 for a flexible image display device corresponding to configuration B is shown in FIG.

<Preparation of (meth)acrylic polymer A3>
Except that the polymerization reaction was carried out with the liquid temperature in the flask maintained at around 55°C for 7 hours, and the blending ratio (weight ratio) of ethyl acetate and toluene was 95/5. was carried out in the same manner as in the preparation of (meth)acrylic polymer A1.

<Preparation of (meth)acrylic oligomer (oligomer)>
Into a four-necked flask equipped with a stirring blade, thermometer, nitrogen gas inlet tube, and condenser, add 99 parts by weight of butyl acrylate (BA), 2 parts by weight of acrylic acid (AA), 3 parts by weight of 2-mercaptoethanol, and start polymerization. 0.1 parts by weight of 2,2'-azobisisobutyronitrile and 140 parts by weight of toluene were charged as agents, and nitrogen gas was introduced with gentle stirring to fully replace the nitrogen, and the temperature of the liquid in the flask was lowered. A polymerization reaction was carried out while maintaining the temperature at around 70° C. for 8 hours to prepare an acrylic oligomer solution. The weight average molecular weight of the acrylic oligomer was 4,500. A predetermined amount of the obtained oligomer was added when mixing a crosslinking agent and the like to prepare an acrylic pressure-sensitive adhesive composition. Use of such oligomers can be expected to improve the durability of the adhesive layer and suppress foaming.

[Example 8]
100 parts by weight of an addition reaction silicone adhesive (trade name "X-40-3306", manufactured by Shin-Etsu Chemical Co., Ltd.) and a platinum-based catalyst (trade name "CAT-PL-50T", Shin-Etsu Chemical Co., Ltd.) A silicone adhesive composition was obtained by mixing 0.2 parts by weight of the silicone-based adhesive composition. This was applied to PET film and PI film, which are transparent base materials, and the thickness after drying was 50 μm for the first adhesive layer and the third adhesive layer, and 50 μm for the second adhesive layer. was applied to a thickness of 25 μm and dried at 100° C. for 3 minutes to obtain a silicone adhesive layer (adhesive layer 6) (common to the first to third adhesive layers).

[Comparative example 1]
[Polarizing film]
A polyvinyl alcohol film with a thickness of 50 μm is immersed in the following five baths [1] to [5] while sequentially applying tension in the longitudinal direction of the film through multiple sets of rolls with different peripheral speeds. It was stretched to 6.0 times its original length. This film was dried in an oven at 50° C. for 4 minutes to obtain a polarizing film with a thickness of 22 μm.
[1] Swelling bath: Pure water at 30°C [2] Dyeing bath: With respect to 100 parts by weight of water, the iodine concentration is within the range of 0.02 to 0.2% by weight, and the potassium iodide concentration is 0.14 to 0.2% by weight. It was set within the range of 1.4% by weight. The ratio of iodine to potassium iodide concentrations is 1:7. The polarizing film was immersed in an aqueous solution containing these at 30° C. for an arbitrary period of time so that the final transmittance of the polarizing film was 40 to 44%.
[3] First crosslinking bath: 40°C aqueous solution containing 3% by weight of potassium iodide and 3% by weight of boric acid.
[4] Second crosslinking bath: 60°C aqueous solution containing 5% by weight of potassium iodide and 4% by weight of boric acid.
[5] Cleaning bath: 25°C aqueous solution containing 3% by weight of potassium iodide Next, the polarizing film and the protective film used in Example 1 were bonded together using the adhesive used in Example 1, and the polarizing film was It was made into a film.

[Optical film (optical laminate)]
The retardation film used in Example 1 and the polarizing film obtained as above were bonded together using the adhesive used in Example 1, and the axis angle of the slow axis and absorption axis was 45°. A laminated film was prepared as follows.

[Examples 2 to 8 and Comparative Examples 1 to 3]
Example 1 except that the polymer used ((meth)acrylic polymer), the adhesive composition, and the preparation of the adhesive layer were changed as shown in Tables 2 to 4, except as specified. A laminate for a flexible image display device was produced in the same manner as above. Note that only in Example 5, configuration B (see FIG. 7), which does not include the second adhesive layer, was adopted.

The abbreviations in Tables 2 and 3 are as follows.
BA: n-butyl acrylate 2EHA: 2-ethylhexyl acrylate AA: acrylic acid HBA: 4-hydroxybutyl acrylate HEA: 2-hydroxyethyl acrylate D110N: Trimethylolpropane/xylylene diisocyanate adduct (Mitsui Chemicals, trade name) : Takenate D110N)
C/L: Trimethylolpropane/tolylene diisocyanate (manufactured by Nippon Polyurethane Industries, product name: Coronate L)
Peroxide: Benzoyl peroxide (peroxide-based crosslinking agent, manufactured by NOF Corporation, product name: Niper BMT)

[evaluation]
<Measurement of weight average molecular weight (Mw) of (meth)acrylic polymer>
The weight average molecular weight (Mw) of the obtained (meth)acrylic polymer was measured by GPC (gel permeation chromatography).
・Analyzer: Tosoh Corporation, HLC-8120GPC
・Column: Manufactured by Tosoh Corporation, G7000H _XL +GMH _XL +GMH _XL
・Column size: 7.8mmφ each x 30cm total 90cm
・Column temperature: 40℃
・Flow rate: 0.8ml/min
・Injection volume: 100μl
・Eluent: Tetrahydrofuran ・Detector: Differential refractometer (RI)
・Standard sample: polystyrene

(Measurement of thickness)
The thicknesses of the polarizing film, retardation film, protective film, optical laminate, adhesive layer, etc. were measured using a dial gauge (manufactured by Mitutoyo).

(Measurement of storage modulus G' of adhesive layer)
The separator was peeled off from the adhesive sheets of each example and comparative example, and a plurality of adhesive sheets were laminated to prepare test samples with a thickness of about 1.5 mm. This test sample was punched into a disk shape with a diameter of 7.9 mm, sandwiched between parallel plates, and dynamic viscoelasticity was measured using Rheometric Scientific's "Advanced Rheometric Expansion System (ARES)" under the following conditions. From the results, the storage elastic modulus G' of the adhesive layer at 25°C was read.
(Measurement condition)
Deformation mode: Torsion Measurement temperature: -40℃~150℃
Heating rate: 5℃/min

(Folding durability test method)
FIG. 5 shows a schematic diagram of a 180° bending durability tester (manufactured by Imoto Seisakusho). This device has a mechanism in which a chuck on one side with a mandrel in between repeatedly bends 180 degrees in a constant temperature bath, and the bending radius can be changed depending on the diameter of the mandrel. The mechanism is such that the test stops when the film breaks. In the test, the 5 cm x 15 cm flexible image display device laminate obtained in each Example and Comparative Example was set in the device, and the temperature was 25° C., the bending angle was 180°, the bending radius was 3 mm, and the bending speed was 1 second/time. The experiment was carried out using a weight of 100 g. The folding strength was evaluated by the number of times until the laminate for a flexible image display device broke. Here, when the number of bending reached 200,000 times, the test was discontinued.
The measurement (evaluation) method is as follows: When bending the laminate for a flexible image display device with the first adhesive layer side on the inside (concave side) (Example 1 only), Two types of bending (bending) directions were evaluated in the case of bending (convex side).
<Presence or absence of breakage>
○: No breakage △: Slight breakage at the end of the bent part (no practical problem)
×: There is breakage on the entire surface of the bent part (practical problem)
<Appearance (peeling)>
○: No bending, peeling, etc. observed △: Slight bending, peeling, etc. observed at bent portions (no practical problems)
×: Bends, peeling, etc. are confirmed on the entire surface of the bent part (practical problem)

From the evaluation results in Table 4, it was confirmed that in all Examples, bending and peeling were at a practically acceptable level in the folding durability test. That is, in the laminates for flexible image cover devices of each example, by reducing the thickness of the polarizing film used and using a plurality of specific adhesive layers, the laminates do not peel or break even when repeatedly bent. It was confirmed that a laminate for a flexible image display device with excellent bending resistance and adhesion could be obtained.

On the other hand, in Comparative Example 1, since the thickness of the polarizing film exceeded the desired range, it was confirmed that the polarizing film had poor bending resistance. In addition, in Comparative Examples 2 and 3, the storage elastic modulus G' at 25°C of the outermost adhesive layer on the convex side when folded was larger than the storage elastic modulus G' at 25°C of the other adhesive layers. As a result, bending and peeling occurred, and it was confirmed that the bending resistance and adhesion were poor.

Although the present invention has been described above with reference to the drawings regarding specific embodiments, the present invention can be modified in many ways in addition to the configuration shown and described. Therefore, the invention is not to be limited to the construction shown and described, but rather is to be defined only by the scope of the appended claims and their equivalents.

1 Polarizing film 2 Protective film 2-1 Protective film 2-2 Protective film 3 Retardation layer 4-1 Transparent conductive film 4-2 Transparent conductive film 5-1 Base film 5-2 Base film 6 Transparent conductive layer 6- 1 Transparent conductive layer 6-2 Transparent conductive layer 7 Spacer 8 Transparent base material 8-1 Transparent base material (PET film)
8-2 Transparent base material (PET film)
9 Base material (PI film)
10 Organic EL display panel 10-1 Organic EL display panel (with touch sensor)
11 Laminate for flexible image display device (laminate for organic EL display device)
12 Adhesive layer 12-1 First adhesive layer 12-2 Second adhesive layer 12-3 Third adhesive layer 13 Decorative printing film 20 Optical laminate 30 Touch panel 40 Window 100 Flexible image display device ( organic EL display device)

Claims (8)

multiple adhesive layers;
A polarizing film, a protective film made of a transparent resin material provided on a first surface of the polarizing film, and a retardation film provided on a second surface different from the first surface of the polarizing film. A laminate for a flexible image display device comprising an optical laminate comprising:
Of the plurality of adhesive layers, a first adhesive layer is disposed on a side opposite to the surface in contact with the polarizing film with respect to the protective film,
Of the plurality of adhesive layers, a second adhesive layer is disposed on a side opposite to the surface in contact with the polarizing film with respect to the retardation film,
A conductive layer (excluding a transparent conductive layer constituting the touch sensor) is provided between the first adhesive layer and the protective film and between the retardation film and the second adhesive layer. Laminated directly, with or without
The thickness of the polarizing film is 20 μm or less (excluding cases where the thickness of the polarizing film is 6 μm or less) ,
The thickness of the protective film is 5 to 60 μm,
Among the plurality of adhesive layers, the storage elastic modulus G' at 25° C. of the outermost adhesive layer on the convex side when the side on which the protective film of the optical laminate is bent inward is For a flexible image display device, the storage elastic modulus G' at 25° C. of one adhesive layer is smaller than that of the other adhesive layer, and the storage elastic modulus G′ at 25° C. of the other adhesive layer is substantially the same or smaller. laminate. The laminate for a flexible image display device according to claim 1, wherein the adhesive layer on the outermost surface on the convex side is the second adhesive layer. 3. A transparent conductive layer constituting a touch sensor is disposed on a side of the second adhesive layer opposite to a surface in contact with the retardation film. A laminate for flexible image display devices. A third adhesive layer is disposed on the opposite side of the transparent conductive layer constituting the touch sensor to the surface in contact with the second adhesive layer, and the adhesive layer on the outermost surface on the convex side 4. The laminate for a flexible image display device according to claim 3, wherein the adhesive layer is the third adhesive layer. A transparent conductive layer constituting a touch sensor is disposed on the opposite side of the first adhesive layer to the first surface of the polarizing film provided with the protective film. Item 4. The laminate for a flexible image display device according to any one of Items 1 to 4. Among the plurality of adhesive layers, a third adhesive layer is arranged on a side opposite to a surface in contact with the first adhesive layer with respect to the transparent conductive layer constituting the touch sensor. 6. The laminate for a flexible image display device according to claim 5, wherein the adhesive layer on the outermost surface on the convex side is the second adhesive layer. The laminate for a flexible image display device according to any one of claims 1 to 6, and an organic EL display panel,
A flexible image display device, wherein the laminate for a flexible image display device is arranged on a viewing side of the organic EL display panel. 8. The flexible image display device according to claim 7, wherein a window is arranged on the viewing side of the flexible image display device laminate.