Flexible display device and flexible film

Abstract

The present invention addresses the problem of providing a flexible display device and the like having improved post-durability-test visibility, folding resistance, and surface quality.　A flexible display device according to the present disclosure comprises at least a cover member, a color filter, and light-emitting elements, wherein the cover member has at least a flexible film, the flexible film contains at least a resin as a main component and a filler, and the degree of orientation J (%) of the resin and the degree of orientation F (%) of the filler, measured by X-ray diffraction, satisfy formula (1).　Formula (1): J < F

Description

Flexible display device and flexible film

[0001] The present disclosure relates to flexible displays and flexible films.

[0002] Recently, flexible display devices that can be folded or rolled up have been actively developed. Generally, a flexible display device is composed of a module including a light-emitting element and a cover member for protecting the module.

[0003] The cover member must be flexible, that is, it must be foldable or rollable. On the other hand, the cover member must be shock-resistant to protect the module. Furthermore, the cover member must have high surface quality to ensure visibility.

[0004] For example, Patent Document 1 discloses a technique relating to a molded article made of a thermoplastic resin composition that has an excellent balance between transparency and mechanical properties.

[0005] JP 2010-6906 A

[0006] However, even if a molded article of the thermoplastic resin composition disclosed in Patent Document 1 is applied to a cover member of a flexible display, there is a problem that the molded article is highly hard and brittle and does not have sufficient flexibility. Furthermore, further improvements in impact resistance and surface quality are required.

[0007] The present disclosure has been made in consideration of the above problems and circumstances, and the problem to be solved is to provide a flexible display device, etc. that has improved visibility, folding resistance, and surface quality after a keystroke test.

[0008] In order to solve the above-mentioned problems, the present inventors have investigated the causes of the above-mentioned problems. As a result, they have found that by making the degree of orientation of the filler contained in the flexible film greater than the degree of orientation of the resin, it is possible to improve the visibility, folding endurance, and surface quality of a flexible display device after a keystroke test, and have arrived at the present disclosure. That is, the above-mentioned problems of the present disclosure are solved by the following means.

[0009] 1. A flexible display device having at least a cover member, a color filter, and a light-emitting element, wherein the cover member has at least a flexible film, and the flexible film contains at least a resin and a filler as main components, and the degree of orientation J [%] of the resin and the degree of orientation F [%] of the filler measured by X-ray diffraction method satisfy the following formula (1): Formula (1): J<F

[0010] 2. The flexible display device according to item 1, wherein the degree of orientation J [%] of the resin satisfies the following formula (2): 40≦J≦60

[0011] 3. The flexible display device according to item 1 or 2, wherein the degree of orientation F [%] of the filler satisfies the following formula (3): 40≦F≦80

[0012] 4. The flexible display device according to item 1 or 2, wherein the flexible film has a tensile modulus of elasticity in the range of 4.0 to 8.0 GPa.

[0013] 5. The flexible display device according to item 1 or 2, wherein the flexible film has a breaking elongation within a range of 10 to 20%.

[0014] 6. The flexible display device according to claim 1 or 2, wherein the thickness of the flexible film is in the range of 30 to 80 μm.

[0015] 7. The flexible display device according to claim 1 or 2, wherein the aspect ratio of the filler is in the range of 50 to 200.

[0016] 8. The flexible display device according to claim 1 or 2, wherein the cover member has a hardened layer on the outermost surface on the viewing side.

[0017] 9. A flexible film used as a cover member of a flexible display device, the flexible film containing at least a resin and a filler as main components, the degree of orientation J [%] of the resin and the degree of orientation F [%] of the filler measured by X-ray diffraction method satisfy the following formula (1): Formula (1): J<F, and the flexible display device has a color filter having an anti-reflection function for light incident from the outside.

[0018] The above-described means of the present disclosure can improve the visibility, folding resistance, and surface quality of a flexible display device after a keystroke test.

[0019] The mechanism by which the effects of the present disclosure are manifested or acted upon is not clear, but is speculated as follows.

[0020] As mentioned above, even if a molded article of the thermoplastic resin composition disclosed in Patent Document 1 is applied to a cover member of a flexible display, there is a problem that the molded article is highly hard and brittle, and sufficient flexibility (folding resistance) cannot be obtained. This is thought to be because the degree of orientation of the resin is relatively high when the molded article is produced by injection molding.

[0021] On the other hand, in the present disclosure, the orientation degree of the filler is higher than the orientation degree of the resin in the flexible film included in the cover member. When such a flexible film is manufactured, stress or the like is applied starting from the highly oriented filler, causing the resin particles to be randomly oriented to a certain extent. The randomly oriented resin and the filler interact with each other, and a network structure in which the resin particles are entangled with each other is formed.

[0022] This network structure allows the flexible film to adequately release stress generated by external force through the gaps in the network, which is believed to improve impact resistance and folding endurance. Furthermore, during the production of the flexible film, the interaction between the resin and the filler suppresses shrinkage during drying. This is believed to result in improved smoothness and surface quality of the flexible film.

[0023] 1 is a cross-sectional view of a basic layer structure of a flexible display device. FIG. 1 is a cross-sectional view of a basic layer structure of a flexible display device. FIG. 1 is a cross-sectional view of a basic layer structure of a flexible display device. FIG. 2 is a cross-sectional view of a basic layer structure of a flexible display device. FIG. 3 is a diagram illustrating a resin and a filler as main components in a flexible film. FIG. 4 is an example of a spectrum obtained by beta scan measurement of a filler. FIG. 5 is a schematic diagram of a manufacturing apparatus for manufacturing a flexible film by a melt casting method. FIG. 6 is a schematic diagram of an example of a color display method. FIG. 7 is a schematic diagram of an example of a color display method. FIG. 8 is a schematic diagram of an example of a color display method. FIG. 9 is a schematic diagram of a color filter. FIG. 10 is a schematic diagram showing a method of acquiring a projected image on a flexible film. FIG. 11 is an example of a captured image of a flexible film. FIG. 12 is a histogram of a monochrome image and a setting screen for automatic binarization processing in judgment A. FIG. 13 is a histogram of a monochrome image and a setting screen for automatic binarization processing in judgment B. FIG. 14 is a histogram of a monochrome image and a setting screen for automatic binarization processing in judgment C. 13 shows a histogram of a monochrome image and a setting screen for automatic binarization processing in judgment D.

[0024] The flexible display device of the present disclosure is a flexible display device having at least a cover member, a color filter, and a light-emitting element. The cover member has at least a flexible film. The flexible film contains at least a resin as a main component and a filler. The orientation degree J [%] of the resin and the orientation degree F [%] of the filler measured by X-ray diffraction satisfy the above formula (1). This feature is a technical feature common to or corresponding to the following embodiments.

[0025] In this embodiment, from the viewpoint of improving visibility, folding resistance, and surface quality after a keystroke test, it is preferable that the resin orientation degree J [%] satisfies the above formula (2), and it is preferable that the filler orientation degree F [%] satisfies the above formula (3).

[0026] In this embodiment, from the viewpoint of visibility after a keystroke test, the tensile modulus of the flexible film is preferably within the range of 4.0 to 8.0 GPa.

[0027] In this embodiment, from the viewpoint of visibility after a keystroke test and folding endurance, the breaking elongation of the flexible film is preferably within the range of 10 to 20%.

[0028] In this embodiment, from the viewpoint of simultaneously achieving visibility after a keystroke test, folding resistance, and thinness, the thickness of the flexible film is preferably within the range of 30 to 80 μm.

[0029] In this embodiment, the aspect ratio of the filler is preferably within the range of 50 to 200 from the viewpoint of improving visibility after a keystroke test, folding resistance, and surface quality.

[0030] In this embodiment, from the viewpoint of visibility after a typing test, the cover member preferably has a hardened layer on the outermost surface on the viewing side.

[0031] The flexible film of this embodiment is a flexible film used as a cover member of a flexible display device. The flexible film contains at least a resin and a filler as main components. The resin orientation degree J [%] and the filler orientation degree F [%] measured by X-ray diffraction satisfy the above formula (1). The flexible display device also has a color filter that has an anti-reflection function for light incident from the outside.

[0032] Hereinafter, one or more embodiments of the present disclosure will be described with reference to the drawings. However, the scope of the present disclosure is not limited to the disclosed embodiments. In this application, the symbol "to" is used to mean that the numerical values ​​before and after it are included as the lower limit and upper limit.

[0033] 1. Overview of Flexible Display Device The flexible display device of this embodiment has at least a cover member, a color filter, and a light-emitting element. The cover member has at least a flexible film. The flexible film contains at least a resin as a main component and a filler. The degree of orientation J [%] of the resin and the degree of orientation F [%] of the filler measured by X-ray diffraction satisfy the following formula (1): Formula (1): J<F

[0034] The flexible display device may include other components as needed. The flexible display device may include an adhesive layer or a sticking layer for attaching each component as needed. The cover member may further include a hardening layer on the viewing side of the flexible film. Hereinafter, the "flexible display device" may also be simply referred to as a "display device."

[0035] 1 to 4 are cross-sectional views of the basic layer structure of a flexible display device. The flexible display device 10 has, from the viewing side, a flexible film 1 (cover member 8), a color filter 3, and a light-emitting element 4, in this order. As shown in FIG. 2, the cover member 8 may have a low-elasticity film 2 in addition to the flexible film 1. The low-elasticity film 2 is preferably located between the flexible film 1 and the color filter 3. As shown in FIG. 3, the flexible display device 10 may have an adhesive layer 5 or a bonding layer 6 between each layer. As shown in FIG. 4, the cover member 8 may have a cured layer 7 on the viewing side of the flexible film 1.

[0036] In this embodiment, the term "cover member" refers to a laminate disposed on the viewing side of the color filter. The cover member may be composed of only a flexible film, or may include other members as necessary. The cover member is attached for the purpose of protecting the color filter and the light-emitting element.

[0037] The cover member including the flexible film, the color filter, and the light-emitting element will be described below.

[0038] 2. Flexible Film In this embodiment, "flexible" means that the display can be bent or curved. "Bendable" includes a state in which the display is bent or curved. Specifically, "flexible" means that the bendable or curved display can be bent or curved with a radius of curvature of 10 mm or less. The radius of curvature of the flexible film is more preferably 3 mm or less. A radius of curvature of 3 mm or less allows the display to be folded and used.

[0039] (1) Structure of the Flexible Film The flexible film contains at least a resin and a filler as main components. The flexible film may contain other additives as needed. The resin, filler, and additives will be described below.

[0040] (1.1) Resin Here, the term "resin" refers to a matrix resin contained as the main component (base material) of the flexible film.

[0041] The resin is not particularly limited, and examples thereof include acyl cellulose, cycloolefin resin, fumaric acid diester resin, polypropylene, (meth)acrylic resin, polyester, polyarylate, polyimide, styrene resin, and composite resins thereof, etc. These may be used alone or in combination of two or more.

[0042] Among these, from the viewpoints of folding endurance, optical properties, etc., it is preferable that the resin contains a linear polymer material having a carbonyl group in the side chain, or a polymer material having a cyclic structure in the main chain. Specifically, the resin is preferably acyl cellulose, a (meth)acrylic resin, a styrene-(meth)acrylic resin, a cycloolefin resin, or a polyimide.

[0043] (1.1.1) Acylcellulose Acylcellulose easily forms a network between resin molecules and can impart rigidity to a flexible film.

[0044] Cellulose is a polymer in which β-glucose units are linked in a linear chain via β-1,4-glycosidic bonds. Acyl cellulose is cellulose in which some or all of the hydrogen atoms of the hydroxyl groups (-OH) at the 2-, 3-, and 6-positions in one glucose unit are substituted with acyl groups. Cellulose ester in which the acyl group is an acetyl group is called "acetyl cellulose."

[0045] (Degree of substitution of acyl groups) "Degree of substitution of acyl groups" refers to the average number of acyl groups per glucose unit. In other words, "degree of substitution of acyl groups" represents how many of the hydrogen atoms in the hydroxy groups at the 2-, 3-, and 6-positions in one glucose unit are substituted with acyl groups. The maximum degree of substitution of acyl groups is 3.0, which means that all of the hydrogen atoms in the hydroxy groups at the 2-, 3-, and 6-positions are substituted with acyl groups.

[0046] The acyl groups may be substituted evenly at the 2-, 3-, and 6-positions of one glucose unit, or may be substituted with a distribution. The degree of acyl substitution is determined by the method specified in ASTM-D817-96.

[0047] When the degree of substitution of acyl groups in the acyl cellulose is within the range of 2.3 to 3.0, the film can be given an appropriate rigidity, and an appropriate network can be formed between the resin molecules.

[0048] In order to obtain desired optical properties, acyl celluloses having different degrees of substitution may be mixed and used. The mixing ratio of acyl celluloses having different degrees of substitution is not particularly limited.

[0049] From the viewpoint of mechanical strength, the number average molecular weight (Mn) of acyl cellulose is 2 × 10 ４ ~3 x 10 ５ It is preferable that the range is 2×10 ４ ~1.2 × 10 ５ More preferably, it is within the range of 4×10 ４ ~8 x 10 ４ It is more preferable that the range is within the range of

[0050] From the viewpoint of mechanical strength, the weight average molecular weight (Mw) of the acyl cellulose is 2×10 ４ ~1 x 10 ６ It is preferable that the range is 2×10 ４ ~1.2 × 10 ５ More preferably, it is within the range of 4×10 ４ ~8 x 10 ４ It is more preferable that the range is within the range of

[0051] The number average molecular weight (Mn) and weight average molecular weight (Mw) of acyl cellulose can be measured by the following method. The weight average molecular weight (Mw) and number average molecular weight of other resins can also be measured by the following method.

[0052] <Gel Permeation Chromatography> Solvent: Methylene chloride Column: Three columns, "Shodex K806, K805, K803G" (all manufactured by Showa Denko K.K.), were connected and used. Column temperature: 25°C Sample concentration: 0.1% by mass Detector: "RI Model 504" (manufactured by GL Science Co., Ltd.) Pump: "L6000" (manufactured by Hitachi, Ltd.) Flow rate: 1.0 mL / min Calibration curve: A calibration curve was used using 13 samples of standard polystyrene STK standard polystyrene (manufactured by Tosoh Corporation) with Mw = 500 to 2,800,000. It is preferable to use the 13 samples at approximately equal intervals.

[0053] The acyl cellulose can be synthesized by a known method.

[0054] The raw cellulose for acyl cellulose is not particularly limited, and examples include cotton linter, wood pulp, and kenaf. The raw cellulose, acetic acid, acetic anhydride, and a catalyst (such as sulfuric acid) are mixed together to esterify the cellulose. The reaction is continued until a cellulose triester is produced. In the triester, all three hydrogen atoms of the hydroxyl groups in one glucose unit are substituted with acyl groups.

[0055] Next, the cellulose triester is hydrolyzed to obtain acyl cellulose having a desired degree of acyl substitution. After that, acyl cellulose is finally obtained through steps such as filtration, precipitation, washing with water, dehydration, and drying. Specifically, it can be synthesized with reference to the method described in JP-A-10-45804.

[0056] Commercially available acyl cellulose may be used, such as "CAP-482-0.5" and "CAP-482-20" (both manufactured by Eastman Chemical Co.).

[0057] The content of acyl cellulose is preferably 70% by mass or more, and more preferably 80% by mass or more, based on the total mass of the flexible film.

[0058] (1.1.2) (Meth)acrylic Resin In this specification, the term "(meth)acrylic resin" is a general term for "acrylic resin" and "methacrylic resin", and means either or both of them.

[0059] The (meth)acrylic resin preferably contains at least a structural unit (U1) derived from methyl methacrylate. In particular, from the viewpoints of reducing the photoelastic coefficient of the flexible film and suppressing the occurrence of unevenness due to moisture absorption expansion, the (meth)acrylic resin preferably further contains a structural unit (U2) derived from phenylmaleimide.

[0060] The (meth)acrylic resin may further have structural units other than those described above. From the viewpoint of imparting toughness to the flexible film, it is more preferable that the (meth)acrylic resin further has a structural unit (U3) derived from an alkyl acrylate.

[0061] That is, the (meth)acrylic resin preferably has a structural unit (U1) derived from methyl methacrylate, a structural unit (U2) derived from phenylmaleimide, and a structural unit (U3) derived from an alkyl acrylate.

[0062] The content of the structural unit (U1) derived from methyl methacrylate is preferably within a range of 50 to 95 mass%, and more preferably within a range of 70 to 90 mass%, based on all structural units constituting the (meth)acrylic resin.

[0063] The structural unit (U2) derived from phenylmaleimide has a relatively rigid structure, which can increase the mechanical strength of the flexible film. Furthermore, the structural unit (U2) derived from phenylmaleimide has a relatively bulky structure, which means that the resin matrix has microvoids through which the filler can move. This facilitates uneven distribution of the filler in the surface layer of the flexible film.

[0064] The content of the structural unit (U2) derived from phenylmaleimide is preferably within a range of 1 to 25% by mass, and more preferably within a range of 7 to 15% by mass, based on all structural units constituting the (meth)acrylic resin. When the content of the structural unit (U2) derived from phenylmaleimide is 1% by mass or more, the flexible film has excellent storage stability in a high-humidity environment. Furthermore, when the content is 25% by mass or less, the flexible film can be imparted with sufficient toughness.

[0065] The structural unit (U3) derived from an alkyl acrylate can impart appropriate flexibility to a resin, and therefore, for example, by combining it with the structural unit (U2) derived from phenylmaleimide, sufficient toughness can be imparted to a flexible film.

[0066] The alkyl acrylate is preferably an alkyl acrylate having 1 to 7 carbon atoms, preferably 1 to 5 carbon atoms in the alkyl moiety.

[0067] Examples of the alkyl acrylate include methyl acrylate (methyl acrylate), ethyl acrylate (ethyl acrylate), propyl acrylate (propyl acrylate), butyl acrylate (butyl acrylate), 2-hydroxyethyl acrylate (2-hydroxyethyl acrylate), hexyl acrylate (hexyl acrylate), and 2-ethylhexyl acrylate (2-ethylhexyl acrylate).

[0068] The content of the structural unit (U3) derived from an acrylic acid alkyl ester is preferably within a range of 1 to 25% by mass, and more preferably within a range of 5 to 15% by mass, relative to all structural units constituting the (meth)acrylic resin. When the content of the structural unit (U3) derived from an acrylic acid alkyl ester is 1% by mass or more, the (meth)acrylic resin can be imparted with appropriate flexibility, and breakage of the flexible film can be suppressed. Furthermore, when the content is 25% by mass or less, a decrease in the glass transition temperature (Tg) of the (meth)acrylic resin can be suppressed, and the flexible film can have excellent storage stability in a high-humidity environment.

[0069] The ratio of the structural unit (U2) derived from phenylmaleimide to the total amount of the structural unit (U2) derived from phenylmaleimide and the structural unit (U3) derived from an alkyl acrylate is preferably within the range of 20 to 70% by mass. A ratio of 20% by mass or more facilitates increasing the storage modulus of the flexible film, while a ratio of 70% by mass or less provides sufficient toughness to the flexible film.

[0070] The glass transition temperature (Tg) of the (meth)acrylic resin is preferably 100°C or higher, and more preferably within the range of 120 to 150°C. By having the Tg within the above range, the heat resistance of the flexible film can be improved. Note that the Tg of the (meth)acrylic resin can be adjusted by adjusting the content of the structural unit (U2) derived from phenylmaleimide and the structural unit (U3) derived from an alkyl acrylate.

[0071] The weight-average molecular weight (Mw) of the (meth)acrylic resin is preferably 100,000 or more, more preferably 1,000,000 or more, and even more preferably in the range of 1,500,000 to 3,000,000. When the weight-average molecular weight (Mw) of the (meth)acrylic resin is 100,000 or more, the toughness of the flexible film can be increased. As a result, the flexible film can be prevented from breaking due to the conveying tension during conveyance. Furthermore, the storage modulus of the flexible film can be increased, and winding deformation can be suppressed.

[0072] The content of the (meth)acrylic resin is preferably 70% by mass or more, and more preferably 80% by mass or more, based on the total mass of the flexible film.

[0073] (1.1.3) Styrene-(meth)acrylic resin Styrene-(meth)acrylic resin has at least a structural unit derived from a styrene monomer and a structural unit derived from a (meth)acrylic acid ester monomer. In this specification, "(meth)acrylic acid ester monomer" is a general term for "acrylic acid ester monomer" and "methacrylic acid ester monomer," and means one or both of them. For example, "methyl (meth)acrylate" means one or both of "methyl acrylate" and "methyl methacrylate."

[0074] The use of styrene-(meth)acrylic resins can impart transparency to flexible films, and the moisture absorption expansion coefficient can be adjusted by changing the copolymerization ratio of the styrene moiety, so that curling of the flexible film can be controlled by adjusting the copolymerization ratio.

[0075] The styrene monomer is CH ２ =CH-C ６ H ５ In addition to styrene represented by the structural formula: styrene derivatives having known side chains or functional groups in the styrene structure can also be mentioned.

[0076] The (meth)acrylic acid ester monomer may be CH(R １ ) = CHCOOR ２ Examples of the acrylic acid ester and methacrylic acid ester represented by R １ represents a hydrogen atom or a methyl group, R ２ represents an alkyl group having a carbon number of 1 to 24. Other examples include acrylic acid ester derivatives or methacrylic acid ester derivatives having a known side chain or functional group in the structure of these esters.

[0077] Styrene monomers include styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-phenylstyrene, p-ethylstyrene, 2,4-dimethylstyrene, p-tert-butylstyrene, p-n-hexylstyrene, p-n-octylstyrene, p-n-nonylstyrene, p-n-decylstyrene, and p-n-dodecylstyrene.

[0078] Examples of the acrylic acid ester monomer include methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, t-butyl acrylate, isobutyl acrylate, n-octyl acrylate, 2-ethylhexyl acrylate (2EHA), stearyl acrylate, lauryl acrylate, and phenyl acrylate.

[0079] Examples of the methacrylic acid ester monomer include methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isopropyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, n-octyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, lauryl methacrylate, phenyl methacrylate, diethylaminoethyl methacrylate, and dimethylaminoethyl methacrylate.

[0080] The (meth)acrylic acid ester monomers may be used alone or in combination of two or more. For example, a copolymer may be formed using a styrene monomer and two or more acrylic acid ester monomers. A copolymer may be formed using a styrene monomer and two or more methacrylic acid ester monomers. A copolymer may be formed using a styrene monomer in combination with an acrylic acid ester monomer and a methacrylic acid ester monomer.

[0081] From the viewpoint of being able to control plasticity, the weight average molecular weight (Mw) of the styrene-(meth)acrylic resin is preferably in the range of 5,000 to 150,000, and more preferably in the range of 30,000 to 120,000. The weight average molecular weight (Mw) can be measured by the same method as that for the acyl cellulose described above.

[0082] The styrene-(meth)acrylic resin may be a commercially available product, such as "TX320XL" (MS resin, manufactured by Denka Co., Ltd.).

[0083] The content of the styrene-(meth)acrylic resin is preferably 70% by mass or more, and more preferably 80% by mass or more, based on the total mass of the flexible film.

[0084] (1.1.4) Cycloolefin-based resin The cycloolefin-based resin has at least a structural unit derived from a cycloolefin monomer. The cycloolefin-based resin is preferably a polymer of a cycloolefin monomer or a copolymer of a cycloolefin monomer and another monomer copolymerizable with the cycloolefin monomer.

[0085] The cycloolefin monomer is preferably a cycloolefin monomer having a norbornene skeleton, and more preferably a cycloolefin monomer having a structure represented by the following general formula (A-1) or (A-2):

[0086]

[0087] In the above general formula (A-1), R １ ~R ４ each independently represents a hydrogen atom, a hydrocarbon group having 1 to 30 carbon atoms, or a polar group, and p represents an integer of 0 to 2. １ ~R ４ do not all represent hydrogen atoms at the same time, and R １ and R ２ does not simultaneously represent a hydrogen atom, and R ３ and R ４ never simultaneously represent a hydrogen atom.

[0088] In the above general formula (A-1), R １ ~R ４ The hydrocarbon group having 1 to 30 carbon atoms represented by the formula (I) is preferably a hydrocarbon group having 1 to 10 carbon atoms, and more preferably a hydrocarbon group having 1 to 5 carbon atoms. The hydrocarbon group having 1 to 30 carbon atoms may further have a linking group containing a halogen atom, oxygen atom, nitrogen atom, sulfur atom, or silicon atom. Examples of the linking group include divalent polar groups such as a carbonyl group, an imino group, an ether bond, a silyl ether bond, and a thioether bond. Examples of the hydrocarbon group having 1 to 30 carbon atoms include a methyl group, an ethyl group, a propyl group, and a butyl group.

[0089] In the above general formula (A-1), R １ ~R ４Examples of the polar group represented by the formula (I) include a carboxy group, a hydroxy group, an alkoxy group, an alkoxycarbonyl group, an aryloxycarbonyl group, an amino group, an amide group, and a cyano group. Among these, the polar group is preferably a carboxy group, a hydroxy group, an alkoxycarbonyl group, or an aryloxycarbonyl group. From the viewpoint of solubility during solution casting, the polar group is preferably an alkoxycarbonyl group or an aryloxycarbonyl group.

[0090] In the general formula (A-1), p is preferably 1 or 2 from the viewpoint of improving heat resistance. When p is 1 or 2, the resulting polymer becomes bulky and the glass transition temperature tends to be increased. In addition, the polymer becomes somewhat responsive to humidity, making it easier to control the curl balance when formed into a laminate.

[0091]

[0092] In the above general formula (A-2), R ５ represents a hydrogen atom, a hydrocarbon group having 1 to 5 carbon atoms, or an alkylsilyl group having an alkyl group having 1 to 5 carbon atoms. ６ represents a carboxy group, a hydroxy group, an alkoxycarbonyl group, an aryloxycarbonyl group, an amino group, an amido group, a cyano group, or a halogen atom (a fluorine atom, a chlorine atom, a bromine atom, or an iodine atom), and p represents an integer of 0 to 2.

[0093] R in the above general formula (A-2) ５ is preferably a hydrocarbon group having 1 to 5 carbon atoms, and more preferably a hydrocarbon group having 1 to 3 carbon atoms.

[0094] R in the above general formula (A-2) ６ is preferably a carboxy group, a hydroxy group, an alkoxycarbonyl group, or an aryloxycarbonyl group. ６ is more preferably an alkoxycarbonyl group or an aryloxycarbonyl group from the viewpoint of solubility during solution casting.

[0095] In terms of improving heat resistance, p in the above general formula (A-2) is preferably 1 or 2. When p is 1 or 2, the resulting polymer becomes bulky and the glass transition temperature tends to be improved.

[0096] From the viewpoint of improving the solubility in organic solvents, the cycloolefin monomer is preferably a cycloolefin monomer having a structure represented by the above general formula (A-2). In general, by breaking the symmetry of an organic compound, the crystallinity decreases and the solubility in organic solvents improves. R in general formula (A-2) ５ and R ６ is substituted on only one side of the carbon atoms constituting the ring with respect to the axis of symmetry of the molecule, and therefore has low molecular symmetry. In other words, a cycloolefin monomer having a structure represented by general formula (A-2) has high solubility and is therefore suitable for producing a flexible film by a solution casting method.

[0097] The content of the cycloolefin monomer having the structure represented by general formula (A-2) in the cycloolefin resin is preferably 70 mol% or more relative to the total number of moles of all cycloolefin monomers constituting the cycloolefin resin. The content is more preferably 80 mol% or more, and even more preferably 100 mol%. By having the content of the cycloolefin monomer having the structure represented by general formula (A-2) be 70 mol% or more, the orientation of the cycloolefin resin is enhanced, and the phase difference (retardation) value is likely to increase.

[0098] Specific examples of cycloolefin monomers having a structure represented by general formula (A-1) are shown below as Exemplary Compounds 1 to 14. Specific examples of cycloolefin monomers having a structure represented by general formula (A-2) are shown below as Exemplary Compounds 15 to 34.

[0099]

[0100] Examples of copolymerizable monomers copolymerizable with cycloolefin monomers include copolymerizable monomers capable of ring-opening copolymerization with cycloolefin monomers, and copolymerizable monomers capable of addition copolymerization with cycloolefin monomers.

[0101] Examples of copolymerizable monomers capable of ring-opening copolymerization include cycloolefins such as cyclobutene, cyclopentene, cycloheptene, cyclooctene, and dicyclopentadiene.

[0102] Examples of copolymerizable monomers capable of addition copolymerization include unsaturated double bond-containing compounds, vinyl cyclic hydrocarbon monomers, (meth)acrylates, etc. Examples of unsaturated double bond-containing compounds include olefin compounds having 2 to 12 carbon atoms (preferably 2 to 8), such as ethylene, propylene, and butene. Examples of vinyl cyclic hydrocarbon monomers include vinylcyclopentene-based monomers such as 4-vinylcyclopentene and 2-methyl-4-isopropenylcyclopentene. Examples of (meth)acrylates include alkyl (meth)acrylates having 1 to 20 carbon atoms, such as methyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and cyclohexyl (meth)acrylate.

[0103] The content of the cycloolefin monomer in the copolymer of a cycloolefin monomer and a copolymerizable monomer is preferably in the range of 20 to 80 mol %, more preferably in the range of 30 to 70 mol %, based on the total of all monomers constituting the copolymer.

[0104] As described above, the cycloolefin resin is a polymer obtained by homopolymerizing or copolymerizing a cycloolefin monomer having a norbornene skeleton, preferably a cycloolefin monomer having a structure represented by the above general formula (A-1) or (A-2). Examples of such polymers include the following: 1) a ring-opening polymer of a cycloolefin monomer; 2) a ring-opening copolymer of a cycloolefin monomer and a copolymerizable monomer capable of ring-opening copolymerization with the cycloolefin monomer; 3) a hydrogenated product of the ring-opening (co)polymer of 1) or 2) above; 4) a (co)polymer obtained by cyclizing the ring-opening (co)polymer of 1) or 2) above by the Friedel-Crafts reaction and then hydrogenating it; 5) a saturated copolymer of a cycloolefin monomer and an unsaturated double bond-containing compound; 6) an addition copolymer of a cycloolefin monomer and a vinyl-based cyclic hydrocarbon monomer, and a hydrogenated product thereof; and 7) an alternating copolymer of a cycloolefin monomer and a (meth)acrylate.

[0105] The polymers 1) to 7) above can all be obtained by known methods, such as those described in JP-A-2008-107534 or JP-A-2005-227606. The catalyst and solvent used in the ring-opening copolymerization 2) above can be, for example, those described in paragraphs 0019 to 0024 of JP-A-2008-107534. The catalyst used in the hydrogenation 3) and 6) above can be, for example, those described in paragraphs 0025 to 0028 of JP-A-2008-107534. The acidic compound used in the Friedel-Crafts reaction 4) above can be, for example, those described in paragraph 0029 of JP-A-2008-107534. The catalyst used in the addition polymerization 5) to 7) above can be, for example, those described in paragraphs 0058 to 0063 of JP-A-2005-227606. The alternating copolymerization reaction of 7) above can be carried out by, for example, the method described in paragraphs 0071 to 0072 of JP-A No. 2005-227606.

[0106] Among these, the cycloolefin resin is preferably a polymer of the above 1) to 3) or 5), and more preferably a polymer of the above 3) or 5). That is, from the viewpoint of increasing the glass transition temperature and light transmittance of the resulting resin, the cycloolefin resin preferably contains at least one of a structural unit represented by the following general formula (B-1) and a structural unit represented by the following general formula (B-2). The cycloolefin resin more preferably contains only a structural unit represented by the general formula (B-2), or contains both a structural unit represented by the general formula (B-1) and a structural unit represented by the general formula (B-2). The structural unit represented by the general formula (B-1) is a structural unit derived from the cycloolefin monomer represented by the above general formula (A-1). The structural unit represented by the general formula (B-2) is a structural unit derived from the cycloolefin monomer represented by the above general formula (A-2).

[0107]

[0108] In the general formula (B-1), X is —CH═CH— or —CH ２ CH ２ - represents. １ ~R４ and p are R in the general formula (A-1) １ ~R ４ and p.

[0109]

[0110] In the general formula (B-2), X is —CH═CH— or —CH ２ CH ２ - represents. ５ ~R ６ and p are R in general formula (A-2), ５ ~R ６ and p.

[0111] The cycloolefin resin may be a commercially available product. Examples of commercially available cycloolefin resins include "ARTON (registered trademark)" (manufactured by JSR Corporation). Specific examples include ARTON G (G7810, etc.), ARTON F, ARTON R (R4500, R4900, R5000, etc.), and ARTON RX (RX4500, etc.).

[0112] The intrinsic viscosity [η]inh of the cycloolefin resin at 30°C is 0.2 to 5 cm ３ / g, and 0.3 to 3 cm ３ / g, and more preferably in the range of 0.4 to 1.5 cm ３ It is more preferable that the range is 1 / g.

[0113] The number average molecular weight (Mn) of the cycloolefin resin is preferably in the range of 8,000 to 100,000, more preferably in the range of 10,000 to 80,000, and even more preferably in the range of 12,000 to 50,000.

[0114] The weight average molecular weight (Mw) of the cycloolefin resin is preferably within a range of 20,000 to 300,000, more preferably within a range of 30,000 to 250,000, and even more preferably within a range of 40,000 to 200,000. The weight average molecular weight (Mw) can be measured by the same method as that for the acyl cellulose described above.

[0115] When the intrinsic viscosity [η]inh, number average molecular weight, and weight average molecular weight (Mw) are within the above ranges, the cycloolefin resin has good heat resistance, water resistance, chemical resistance, mechanical properties, and moldability into a flexible film.

[0116] The glass transition temperature (Tg) of the cycloolefin resin is usually 110°C or higher, preferably in the range of 110 to 350°C, more preferably in the range of 120 to 250°C, and even more preferably in the range of 120 to 220°C. When the Tg is 110°C or higher, deformation under high temperature conditions can be suppressed. On the other hand, when the Tg is 350°C or lower, molding processing is easy and deterioration of the resin due to heat during molding processing can be suppressed.

[0117] The content of the cycloolefin resin is preferably 70% by mass or more, and more preferably 80% by mass or more, based on the total mass of the flexible film.

[0118] (1.1.5) Polyimide Polyimide has structural units derived from a tetracarboxylic dianhydride monomer and structural units derived from a diamine monomer.

[0119] The tetracarboxylic dianhydride may be an aromatic tetracarboxylic dianhydride, an aliphatic tetracarboxylic dianhydride, or an alicyclic tetracarboxylic dianhydride. Of these, the tetracarboxylic dianhydride is preferably an aromatic tetracarboxylic dianhydride. The diamine may be an aromatic diamine, an aliphatic diamine, or an alicyclic diamine, of which an aromatic diamine is preferably used.

[0120] The weight-average molecular weight (Mw) of the polyimide is preferably in the range of 100,000 to 300,000, and more preferably in the range of 130,000 to 250,000. By having it in the above range, it is possible to prevent the flexible film from breaking due to the transport tension during transport of the flexible film. The weight-average molecular weight (Mw) can be measured in the same manner as for the acyl cellulose described above.

[0121] The content of polyimide is preferably 60% by mass or more, and more preferably 70% by mass or more, based on the total mass of the flexible film.

[0122] (1.2) Filler In this embodiment, "filler" refers to particles contained in a flexible film for the purpose of improving mechanical strength. By containing a filler, the tensile modulus of elasticity of the flexible film can be improved. Furthermore, by using a filler, sufficient visibility (transparency) of the flexible film can be obtained, and sufficient visibility can be obtained even when used in a display device. The degree of orientation of the filler changes depending on the type, aspect ratio, etc. of the filler.

[0123] The filler material is not particularly limited and may be an inorganic compound or an organic compound. In particular, from the viewpoints of mechanical strength and visibility, it is preferable that the filler material contains a metal.

[0124] The filler may be used alone or in combination of two or more. The flexible film of the present embodiment contains at least one non-spherical filler (aspect ratio greater than 1).

[0125] The filler preferably has a non-spherical, anisotropic shape, such as fiber, spindle, rod, needle, cylinder, column, or plate.

[0126] (1.2.1) Inorganic Filler From the viewpoint of mechanical strength, the inorganic filler is preferably acicular particles of metal oxide or metal salt. Furthermore, it is preferable that the inorganic filler has a surface modified.

[0127] The content of the inorganic filler is preferably in the range of 1 to 30% by mass, and more preferably in the range of 1 to 10% by mass, based on the total mass of the flexible film.

[0128] (1.2.1.1) The metal oxide material of the inorganic filler is not particularly limited. Examples of metal oxides include alumina (aluminum oxide), silica (silicon dioxide), magnesium oxide, zinc oxide, lead oxide, boehmite, pseudo-boehmite, tantalum oxide, indium oxide, bismuth oxide, yttrium oxide, cobalt oxide, copper oxide, manganese oxide, selenium oxide, iron oxide, zirconia (zirconium oxide), germanium oxide, tin oxide, titanium oxide (titania), niobium oxide, molybdenum oxide, and vanadium oxide. These may be used alone or in combination of two or more.

[0129] The metal salt is not particularly limited. Examples of the metal salt include strontium carbonate, calcium carbonate, magnesium carbonate, cobalt carbonate, manganese carbonate, barium carbonate, and potassium carbonate. These may be used alone or in combination of two or more.

[0130] Among these, from the viewpoint of improving the mechanical strength and visibility of the flexible film, the metal oxide is preferably alumina, and the metal salt is preferably strontium carbonate.

[0131] (1.2.1.2) Aspect Ratio of Inorganic Filler The aspect ratio of the inorganic filler is preferably within the range of 30 to 1000, and more preferably within the range of 50 to 200. By having the aspect ratio within the above range, the tensile modulus of the flexible film can be improved. Note that the above range is a suitable range for the aspect ratio in the flexible film, and the aspect ratio of the inorganic filler alone used in producing the flexible film may be larger than the above range. The inorganic filler may be folded during the production process of the flexible film to reduce its diameter, thereby satisfying the above range.

[0132] The aspect ratio of the filler and the filler precursor described below can be measured according to the following method.

[0133] A cross section of a flexible film is directly photographed using a scanning electron microscope (SEM). At least 100 inorganic fillers are randomly selected from the obtained image (SEM image). The major axis (x) and minor axis (y) of each inorganic filler are measured. The value (x / y) obtained by dividing the major axis (x) by the minor axis (y) is calculated, and the average value of these values ​​is defined as the "aspect ratio."

[0134] When a circumscribing rectangle (circumscribed rectangle) is drawn for each inorganic filler, the length of the short side of the circumscribing rectangle is the minor axis, and the length of the long side is the major axis. Usually, the major axis (x) and minor axis (y) of the inorganic filler correspond to the average length and average diameter, respectively.

[0135] The average diameter of the inorganic filler is not particularly limited, but is preferably in the range of 1 to 10 nm. An average diameter of 1 nm or more can impart sufficient mechanical strength to the flexible film. Furthermore, an average diameter of 10 nm or less can suppress a decrease in visibility in the flexible film. The average diameter of the inorganic filler is more preferably in the range of 4 to 8 nm. Note that this average diameter corresponds to the minor axis (y) in the above-mentioned "aspect ratio."

[0136] (1.2.1.3) Surface Modifier From the viewpoint of dispersibility in a flexible film, it is preferable that the inorganic filler is surface-modified. By surface-modifying the inorganic filler, a sulfonic acid group (—SO ３ H), a carboxy group (—COOH), or a phosphate group (—P(═O)(OH) ３－ｎ ) is preferably present. Note that n in the phosphate group is 1 or 2. The dispersibility and degree of orientation of the inorganic filler change depending on the type of modifying group. Preferred embodiments of the surface modifying agent will be described below, but the surface modifying agent is not limited thereto.

[0137] Sulfonic acid group (-SO ３The compound having H) is not particularly limited, and examples thereof include alkylsulfonic acids, aromatic sulfonic acids, etc. Examples of alkylsulfonic acids include methanesulfonic acid and ethanesulfonic acid. Examples of aromatic sulfonic acids include benzenesulfonic acid, p-toluenesulfonic acid, styrenesulfonic acid, and dodecylbenzenesulfonic acid. Other examples include alkali metal salts and ammonium salts of these sulfonic acids, and esters of these sulfonic acids with lower alcohols.

[0138] The compound having a carboxy group (—COOH) is not particularly limited, and examples thereof include monocarboxylic acids, dicarboxylic acids, hydroxycarboxylic acids, and aromatic carboxylic acids. Examples of monocarboxylic acids include formic acid, acetic acid, and propionic acid. Examples of dicarboxylic acids include oxalic acid, fumaric acid, and maleic acid. Examples of hydroxycarboxylic acids include lactic acid, malic acid, and citric acid. Examples of aromatic carboxylic acids include benzoic acid and salicylic acid. Other examples include alkali metal salts and ammonium salts of these carboxylic acids, and esters of these carboxylic acids with lower alcohols.

[0139] Phosphate group (-P(=O)(OH) ３－ｎ) is not particularly limited. Note that n is 1 or 2. Examples of compounds having a phosphate group include ethyl acid phosphate, butyl acid phosphate, butyl pyrophosphate, butoxyethyl acid phosphate, 2-ethylhexyl acid phosphate, oleyl acid phosphate, tetracosyl acid phosphate, phenyl acid phosphate, diphenyl acid phosphate, benzyl acid phosphate, n-octyl acid phosphate, (2-hydroxyethyl) methacrylate acid phosphate, dibutyl phosphate, bis(2-ethylhexyl) phosphate, lauryl acid phosphate, stearyl acid phosphate, ethylene glycol monoethyl ether acid phosphate, triethylene glycol monoethyl ether acid phosphate, and triethylene glycol monobutyl ether acid phosphate. Other examples include alkali metal salts and ammonium salts of these compounds, and esters of these compounds with lower alcohols.

[0140] (1.2.1.4) Method for Producing Inorganic Filler (Method for Producing Metal Oxide Filler) The method for producing a metal oxide filler is not particularly limited, and can be produced, for example, by the method described in JP 2016-44114 A. In this method, a metal oxide raw material is hydrolyzed in an acid aqueous solution to form a hydrated oxide. The produced alcohol is distilled off, and then peptized to obtain a metal oxide filler precursor (aqueous metal oxide sol). The metal oxide filler precursor is treated with a surface modifier (dehydration treatment). The above method will be described in detail below, but the production method is not limited thereto.

[0141] First, a metal oxide raw material is hydrolyzed in an acidic aqueous solution to obtain a hydrated oxide. The metal oxide raw material is not particularly limited. Examples of the metal oxide raw material include alkoxides, oligomers, and acetoacetates of the metals that constitute the metal oxides.

[0142] Examples of metal oxide raw materials include metal alkoxides such as aluminum ethoxide, aluminum isopropoxide, aluminum n-butoxide, aluminum sec-butoxide, tetraethoxysilane, tetrapropoxysilane, tetraisopropoxysilane, tetrasec-butoxysilane, tetra-n-butoxysilane, tetraisopropoxytitanium, tetra-n-butoxytitanium, tetra-t-butoxytitanium, tetra-n-butoxyzirconium, and zirconium alkoxide. Other examples of metal oxide raw materials include cyclic aluminum oligomer, diisopropoxy(ethylacetoacetato)aluminum, and tris(ethylacetoacetato)aluminum. These metal oxide raw materials may be used alone or in combination of two or more.

[0143] Among these, the metal oxide raw material is preferably an alkoxide of aluminum, silicon or zirconium, and more preferably an alkoxide of aluminum, silicon or zirconium having 2 to 4 carbon atoms.

[0144] The acid used for hydrolysis is not particularly limited, and examples thereof include hydrochloric acid, nitric acid, formic acid, acetic acid, propionic acid, butyric acid, etc. Among these, from the viewpoint of ease of handling, the acid is preferably formic acid, acetic acid, propionic acid, or butyric acid, and more preferably acetic acid.

[0145] The amount of acid used is not particularly limited, but is preferably in the range of 0.2 to 2.0 mol, more preferably in the range of 0.3 to 1.8 mol, per mol of metal oxide raw material. By keeping the amount within this range, the metal oxide raw material can be efficiently hydrolyzed and the desired shape (aspect ratio and diameter) can be formed. The acid may be used in the form of an aqueous solution. The concentration of the acid in the aqueous solution is not particularly limited, but is preferably in the range of 10 to 50 mass %, more preferably in the range of 15 to 30 mass %.

[0146] The hydrolysis conditions are not particularly limited as long as they allow the metal oxide raw material to be hydrolyzed, and can be appropriately selected depending on the type of metal oxide raw material, the amount of acid used, etc. The hydrolysis temperature is preferably within the range of 50 to 100°C. The hydrolysis time is preferably within the range of 10 minutes to 3 hours. Under these conditions, the metal oxide raw material can be efficiently hydrolyzed to form a desired shape (aspect ratio and diameter).

[0147] The resulting hydrated oxide is peptized while distilling off the produced alcohol, to obtain an aqueous metal oxide sol. Here, the hydrated oxide is in the form of a solution (e.g., an aqueous solution). The hydrated oxide concentration (solids concentration) at this time is not particularly limited, but is preferably in the range of 2 to 15% by mass, and more preferably in the range of 3 to 10% by mass. By having the concentration within this range, the hydrated oxide can be efficiently peptized.

[0148] The peptization conditions are not particularly limited as long as they are conditions that can peptize the hydrated oxide. The peptization temperature is preferably within the range of 100 to 200°C, and more preferably within the range of 110 to 180°C. The peptization time is preferably within the range of 1 to 20 hours, and more preferably within the range of 2 to 15 hours. By keeping the peptization time within the above ranges, the hydrated oxide can be efficiently peptized and the desired shape (aspect ratio and diameter) can be formed.

[0149] The above method produces a metal oxide filler precursor (aqueous metal oxide sol). The shape of the metal oxide filler precursor is not particularly limited. The average diameter of the metal oxide filler precursor is preferably within the range of 1 to 10 nm, more preferably within the range of 4 to 8 nm. The aspect ratio of the metal oxide filler precursor is preferably within the range of 110 to 2000, more preferably within the range of 120 to 1000.

[0150] Next, the precursor of the metal oxide filler (aqueous metal oxide sol) is treated with a surface modifier. Specifically, an organic solvent and a surface modifier are added to the precursor of the metal oxide filler (aqueous metal oxide sol) obtained above and mixed. Then, solvent substitution is performed in the mixed solution. The solvent substitution method is not particularly limited, and examples include a method using an ultrafiltration membrane and a dehydration method utilizing the boiling point difference between water and an organic solvent. The surface modifier added is the above-mentioned surface modifier.

[0151] The amount of surface modifier used is not particularly limited as long as it is an amount that can surface-modify the precursor of the metal oxide filler. Note that "surface-modifying the precursor of the metal oxide filler" refers to disposing the surface modifier on the surface of the metal oxide filler. Specifically, the amount of surface modifier used is preferably within a range of 1 to 100 parts by mass, and more preferably within a range of 10 to 20 parts by mass, per 100 parts by mass of the precursor of the metal oxide filler. By using an amount within the above range, the precursor of the metal oxide filler can be surface-modified to the desired degree. In other words, the surface modifier can be disposed to the desired degree on the surface of the metal oxide filler.

[0152] The organic solvent that can be used for surface modification is not particularly limited, and is preferably selected appropriately depending on the types of filler precursor and surface modifier. Examples of the organic solvent include benzene, toluene, xylene, ethylbenzene, diethylbenzene, trimethylbenzene, triethylbenzene, cyclohexane, cyclohexene, decahydronaphthalene, dipentene, pentane, hexane, heptane, octane, nonane, decane, ethylcyclohexane, methylcyclohexane, p-menthane, dipropyl ether, dibutyl ether, anisole, butyl acetate, amyl acetate, and methyl isobutyl ketone. These organic solvents may be used alone or in combination of two or more.

[0153] The amount of the organic solvent used is not particularly limited, and is adjusted so that the total concentration of the filler precursor and the surface modifier is in the range of 1 to 20% by mass, preferably in the range of 2 to 10% by mass.

[0154] The conditions for the surface modification (dehydration treatment) are not particularly limited as long as they are conditions that allow the surface of the metal oxide filler precursor to be modified to a desired degree.

[0155] (Method for Producing Metal Salt Filler) The method for producing the metal salt filler is not particularly limited, and the filler can be produced by a known method. Hereinafter, as an example, a method for producing a strontium carbonate filler will be described, but the production method is not limited thereto.

[0156] Acicular strontium carbonate particles can be produced, for example, by heating fine spherical strontium carbonate particles in water to cause particle growth, while spherical strontium carbonate particles can be produced, for example, by carbonating strontium hydroxide.

[0157] Specifically, carbon dioxide gas is introduced into an aqueous solution or suspension of strontium hydroxide in the presence of an organic acid while the solution or suspension is being stirred. The concentration of strontium hydroxide in the aqueous solution or suspension is preferably within the range of 1 to 20% by mass, more preferably within the range of 2 to 15% by mass, and even more preferably within the range of 3 to 8% by mass.

[0158] The organic acid preferably has at least one hydroxy group and one carboxy group per molecule, and at least three in total. Examples of organic acids include tartaric acid, malic acid, and gluconic acid. The amount of organic acid used is preferably within a range of 0.1 to 20% by mass, more preferably within a range of 1 to 10% by mass, based on the total mass of strontium hydroxide.

[0159] The flow rate of the carbon dioxide gas is preferably in the range of 0.5 to 200 mL / min, and more preferably in the range of 0.5 to 100 mL / min, per 1 g of strontium hydroxide. The spherical strontium carbonate particles can be prepared by the method described in WO 2011 / 052680.

[0160] The surface of the needle-shaped strontium carbonate particles can be modified by the same method as that used to modify the surface of the precursor of the metal oxide filler.

[0161] (1.2.2) Organic Fillers Examples of organic fillers include cellulose-based particles such as cellulose nanofibers and cellulose (nano)crystals. Examples of organic fillers include polyether ether ketone (PEEK) fibers and liquid crystal materials. Examples of organic fillers include carbon materials such as carbon nanotubes, graphene, graphene oxide, carbon black, fullerenes, and nanodiamonds. These organic fillers can be produced by conventionally known methods.

[0162] Among these, the organic filler is preferably cellulose nanofiber, from the viewpoint of improving the mechanical strength and visibility of the flexible film.

[0163] The preferred range and measurement method for the aspect ratio of the organic filler are the same as the preferred range and measurement method for the aspect ratio of the inorganic filler described above.

[0164] The content of the organic filler is preferably in the range of 1 to 30% by mass, more preferably in the range of 1 to 10% by mass, based on the total mass of the flexible film.

[0165] (1.3) Additives The flexible film may further contain other additives. The other additives are not particularly limited, and conventionally used additives can be used. Examples of additives include rubber particles, plasticizers, matting agents, UV absorbers, and peel promoters. In addition to these additives, additives that are commonly used in films that constitute cover members can be used as needed. The orientation degrees of the resin and filler vary depending on the type and content of other additives contained in the flexible film.

[0166] (1.3.1) Rubber Particles In this embodiment, the term "rubber particles" refers to particles containing a resin that exhibits rubber elasticity at room temperature.

[0167] The inclusion of rubber particles in the flexible film can impart toughness (flexibility), and the storage modulus and loss tangent (tan δ) of the flexible film can be appropriately adjusted, thereby improving the impact resistance of the flexible display device.

[0168] The layer structure of the rubber particles may be a single layer structure or a multilayer structure. There are no particular limitations on the resin (rubber polymer) that exhibits rubber elasticity at room temperature. There are no particular limitations on the arrangement order of the monomers in the rubber polymer, and it may be, for example, linear, comb-like (graft type), or branched (star type). The rubber polymer may have a structure that is partially crosslinked by a crosslinkable monomer.

[0169] From the viewpoint of exhibiting rubber elasticity at room temperature, the rubber-like polymer is preferably a soft crosslinked polymer having a glass transition temperature (Tg) of 0° C. or less. Examples of such crosslinked polymers include butadiene-based crosslinked polymers, (meth)acrylic crosslinked polymers, and organosiloxane-based crosslinked polymers. Among them, from the viewpoint of having a small difference in refractive index from the thermoplastic (meth)acrylic resin and being less likely to impair the transparency of the flexible film, (meth)acrylic crosslinked polymers are preferred, and acrylic crosslinked polymers are more preferred.

[0170] That is, the rubber particles are preferably particles containing an acrylic crosslinked polymer (acrylic rubber-like polymer).

[0171] The content of the rubber particles is preferably within a range of 10 to 80% by mass based on the total mass of the flexible film, which allows the flexible film to have an appropriate hardness and a desired storage modulus and loss tangent (tan δ).

[0172] (1.3.1.1) Constituent materials of rubber particles As described above, the rubber particles preferably contain an acrylic rubber-like polymer. For the sake of explanation, the acrylic rubber-like polymer will be referred to as (a) and expressed as "acrylic rubber-like polymer (a)."

[0173] The acrylic rubber-like polymer (a) is a crosslinked polymer having, as a main component, structural units derived from an acrylic acid ester. Here, "having, as a main component," means that the content of structural units derived from an acrylic acid ester is within the range described below.

[0174] The acrylic rubber-like polymer (a) preferably has a structural unit derived from an acrylic acid ester, a structural unit derived from another monomer copolymerizable therewith, and a structural unit derived from a polyfunctional monomer having two or more radically polymerizable groups per molecule, wherein the radically polymerizable groups are non-conjugated reactive double bonds.

[0175] The acrylic acid ester preferably has an alkyl group having 1 to 12 carbon atoms. Examples of the acrylic acid ester include methyl acrylate (methyl acrylate), ethyl acrylate (ethyl acrylate), n-propyl acrylate (n-propyl acrylate), n-butyl acrylate (n-butyl acrylate), sec-butyl acrylate (sec-butyl acrylate), isobutyl acrylate (isobutyl acrylate), benzyl acrylate (benzyl acrylate), cyclohexyl acrylate (cyclohexyl acrylate), 2-ethylhexyl acrylate (2-ethylhexyl acrylate), and n-octyl acrylate (n-octyl acrylate). These may be used alone or in combination of two or more.

[0176] The content of the structural units derived from the acrylic ester is preferably within a range of 40 to 90% by mass, more preferably within a range of 50 to 80% by mass, based on the total structural units constituting the acrylic rubber-like polymer (a). By being within this range, sufficient toughness can be imparted to the flexible film.

[0177] Examples of other monomers copolymerizable with acrylic acid esters include methacrylic acid esters, styrenes, (meth)acrylonitriles, (meth)acrylamides, and (meth)acrylic acid. Examples of methacrylic acid esters include methyl methacrylate. Examples of styrenes include styrene and methylstyrene. Among these, styrenes are preferred as other monomers copolymerizable with acrylic acid esters. These may be used alone or in combination of two or more.

[0178] The content of structural units derived from other monomers copolymerizable with acrylic esters is preferably within a range of 5 to 55 mass %, more preferably within a range of 10 to 45 mass %, based on all structural units constituting the acrylic rubber-like polymer (a).

[0179] Examples of polyfunctional monomers having two or more radically polymerizable groups in one molecule include allyl (meth)acrylate, triallyl cyanurate, triallyl isocyanurate, diallyl phthalate, diallyl maleate, divinyl adipate, divinylbenzene, ethylene glycol di(meth)acrylate, diethylene glycol (meth)acrylate, triethylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, tetramethylolmethane tetra(meth)acrylate, dipropylene glycol di(meth)acrylate, and polyethylene glycol di(meth)acrylate.

[0180] The content of structural units derived from polyfunctional monomers having two or more radically polymerizable groups per molecule is preferably within the range of 0.05 to 10% by mass relative to all structural units constituting the acrylic rubber-like polymer (a). The content is more preferably within the range of 0.1 to 5% by mass. By ensuring that the content is 0.05% by mass or more, the degree of crosslinking of the resulting acrylic rubber-like polymer (a) is easily increased, and the hardness and rigidity of the flexible film are less likely to be impaired. Furthermore, by ensuring that the content is 10% by mass or less, the toughness of the flexible film is less likely to be impaired.

[0181] The composition of the monomers constituting the acrylic rubber-like polymer (a) can be analyzed from the peak area ratio detected by, for example, pyrolysis gas chromatography (GC-MS).

[0182] The glass transition temperature (Tg) of the acrylic rubber-like polymer (a) is preferably 0° C. or lower, more preferably −10° C. or lower. By having a glass transition temperature of 0° C. or lower, it is possible to impart appropriate toughness to the flexible film.

[0183] The glass transition temperature (Tg) of the acrylic rubber-like polymer (a) can be adjusted by the composition of the acrylic rubber-like polymer (a). For example, it is preferable to adjust the mass ratio of an acrylic acid ester having an alkyl group with 4 or more carbon atoms to another monomer copolymerizable with the acrylic acid ester. By adjusting this mass ratio, the glass transition temperature (Tg) can be adjusted. The mass ratio is expressed by the following formula (i): Formula (i): Mass ratio = M1 / M2 The symbols in the formula are as follows: M1: mass of acrylic acid ester M2: mass of another monomer copolymerizable with the acrylic acid ester The mass ratio value is preferably 3 or more, and is preferably in the range of 4 to 10.

[0184] The rubber particles may contain only the acrylic rubber-like polymer (a). Alternatively, the rubber particles may have a hard layer and a soft layer. The hard layer contains a hard crosslinked polymer (c) having a glass transition temperature (Tg) of 20°C or higher. The soft layer is located around the hard layer and contains the acrylic rubber-like polymer (a).

[0185] Additionally, the rubber particles may contain an acrylic graft copolymer. The acrylic graft copolymer is obtained by polymerizing a mixture of monomers such as methacrylic acid esters in at least one stage in the presence of an acrylic rubber-like polymer (a). The rubber particles containing the acrylic graft copolymer may be core-shell type particles having a core portion containing the acrylic rubber-like polymer (a) and a shell portion covering the core portion. Core-shell type particles will be described below.

[0186] (Core portion) The core portion contains an acrylic rubber-like polymer (a). The core portion may further contain a hard crosslinked polymer (c) as needed. That is, the core portion may have a soft layer containing the acrylic rubber-like polymer (a) and, inside the soft layer, a hard layer containing the hard crosslinked polymer (c). Hereinafter, for the sake of explanation, the hard crosslinked polymer will be referred to as (c) and will be referred to as "crosslinked polymer (c)."

[0187] The crosslinked polymer (c) is a crosslinked polymer mainly composed of a methacrylic acid ester. The crosslinked polymer (c) is preferably a crosslinked polymer having a structural unit derived from a methacrylic acid ester, a structural unit derived from another monomer copolymerizable therewith, and a structural unit derived from a polyfunctional monomer having two or more radically polymerizable groups in one molecule.

[0188] The methacrylic acid ester is preferably a methacrylic acid alkyl ester. Examples of the methacrylic acid alkyl ester include compounds in which the alkyl acid in the above-mentioned acrylic acid alkyl ester is replaced with methacrylic acid. Examples of other monomers copolymerizable with the methacrylic acid ester include the same compounds as the above-mentioned other monomers copolymerizable with the acrylic acid ester. Examples of polyfunctional monomers having two or more radically polymerizable groups in one molecule include the same compounds as mentioned above.

[0189] The content of structural units derived from methacrylic acid alkyl esters is preferably within the range of 40 to 100% by mass relative to all structural units constituting the crosslinked polymer (c). The content of structural units derived from other monomers copolymerizable with methacrylic acid esters is preferably within the range of 0 to 60% by mass relative to all structural units constituting the crosslinked polymer (c). The content of structural units derived from polyfunctional monomers having two or more radically polymerizable groups per molecule is preferably within the range of 0.01 to 10% by mass relative to all structural units constituting the crosslinked polymer (c).

[0190] (Shell portion) The shell portion preferably contains a methacrylic polymer (b) (another polymer) graft-bonded to the acrylic rubber-like polymer (a) and having, as a main component, structural units derived from a methacrylic acid ester. Hereinafter, for the sake of explanation, the methacrylic polymer having, as a main component, structural units derived from a methacrylic acid ester will be referred to as (b) and will be expressed as "methacrylic polymer (b)." Here, "having as a main component" means that the content of structural units derived from a methacrylic acid ester is within the range described below.

[0191] The methacrylic acid ester constituting the methacrylic polymer (b) is preferably a methacrylic acid alkyl ester having an alkyl group with a carbon number of 1 to 12. An example of the methacrylic acid alkyl ester having an alkyl group with a carbon number of 1 to 12 is methyl methacrylate. These may be used alone or in combination of two or more.

[0192] The content of the methacrylic acid ester is preferably 50% by mass or more relative to all structural units constituting the methacrylic polymer (b). By having a content of the methacrylic acid ester of 50% by mass or more, compatibility with a methacrylic resin having a structural unit derived from methyl methacrylate as a main component is easily obtained. From the above viewpoint, the content of the methacrylic acid ester is more preferably 70% by mass or more relative to all structural units constituting the methacrylic polymer (b).

[0193] The methacrylic polymer (b) may further have a structural unit derived from another monomer copolymerizable with the methacrylic acid ester. Examples of the other copolymerizable monomer include acrylic acid esters such as methyl acrylate (methyl acrylate), ethyl acrylate (ethyl acrylate), and n-butyl acrylate (n-butyl acrylate). Examples of the other copolymerizable monomer include (meth)acrylic monomers having an alicyclic ring, a heterocyclic ring, or an aromatic ring (ring-containing (meth)acrylic monomer). Examples of such (meth)acrylic monomers include benzyl (meth)acrylate (benzyl (meth)acrylate), dicyclopentanyl (meth)acrylate (dicyclopentanyl (meth)acrylate), and phenoxyethyl (meth)acrylate (phenoxyethyl (meth)acrylate).

[0194] The content of structural units derived from other copolymerizable monomers is preferably 50% by mass or less, and more preferably 30% by mass or less, based on the total structural units constituting the methacrylic polymer (b).

[0195] The ratio of the graft component to the acrylic rubber-like polymer (a) (graft ratio) is preferably within the range of 10 to 250% by mass, and more preferably within the range of 15 to 150% by mass. A graft ratio of 10% by mass or more means that the proportion of the graft component, i.e., the methacrylic polymer (b) mainly composed of structural units derived from a methacrylic acid ester, is appropriately high. This facilitates increasing the compatibility between the rubber particles and the methacrylic resin, making the rubber particles even less likely to aggregate. Furthermore, the rigidity of the flexible film is unlikely to be impaired. On the other hand, a graft ratio of 250% by mass or less prevents the proportion of the acrylic rubber-like polymer (a) from becoming too small, so the toughness of the flexible film is unlikely to be impaired. Furthermore, the brittleness of the flexible film can be sufficiently improved.

[0196] The graft ratio can be measured by the following method.

[0197] 1) 2 g of core-shell particles are added to 50 mL of methyl ethyl ketone and mixed. The resulting mixture is centrifuged using a centrifuge "CP60E" (manufactured by Koki Holdings Co., Ltd.) at 30,000 rpm and 12°C for 1 hour to separate the insoluble and soluble fractions. The centrifugation process is performed a total of three times.

[0198] 2) The mass of the insoluble matter thus obtained is applied to the following formula to calculate the graft ratio: Formula (ii): Graft ratio [mass %] = {(Mb - Ma) / Ma} x 100 where Ma is the mass of the acrylic rubber polymer (a) and Mb is the mass of the methyl ethyl ketone insoluble matter.

[0199] (1.3.1.2) Physical Properties of Rubber Particles The shape of the rubber particles is not particularly limited, but is preferably a nearly spherical shape. The "nearly spherical shape" refers to a shape in which the aspect ratio of the rubber particles is in the range of 1 to 2 when the cross section or surface of the flexible film is observed.

[0200] The rubber particles having a nearly spherical shape provide sufficient resistance to deformation due to contact with rolls during transport or deformation due to internal stress during winding.

[0201] The average particle size of the rubber particles is preferably within the range of 100 to 400 nm. By having a particle size of 100 nm or more, sufficient toughness and stress relaxation properties can be imparted to the flexible film. By having a particle size of 400 nm or less, the transparency of the flexible film is less likely to be impaired. From the above viewpoints, the average particle size of the rubber particles is more preferably within the range of 150 to 300 nm.

[0202] The average particle size of the rubber particles can be calculated by the following method.

[0203] Using a scanning electron microscope (SEM) or a transmission electron microscope (TEM), a surface or a slice of a flexible film is photographed at a magnification of 5000 times. The average value of the circle-equivalent diameter of 100 particles in the photographed image is taken as the average particle diameter of the rubber particles. The circle-equivalent diameter is determined by converting the projected area of ​​a particle in the photographed image into the diameter of a circle having the same area.

[0204] (1.3.2) Plasticizer: The flexible film can improve flexibility and processability by containing a plasticizer. Examples of plasticizers include polyesters. Polyesters have structural units derived from dicarboxylic acids and structural units derived from diols. It is preferable that 70% by mass or more of the structural units derived from dicarboxylic acids are structural units derived from aromatic dicarboxylic acids. It is also preferable that 70% by mass or more of the structural units derived from diols are structural units derived from aliphatic diols.

[0205] Among the structural units derived from dicarboxylic acids, the proportion of structural units derived from aromatic dicarboxylic acids is preferably 70% or more, more preferably 80% or more, and even more preferably 90% or more. Among the structural units derived from diols, the proportion of structural units derived from aliphatic diols is preferably 70% or more, more preferably 80% or more, and even more preferably 90% or more. The polyesters may be used alone or in combination of two or more.

[0206] Examples of aromatic dicarboxylic acids include terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, 4,4'-biphenyldicarboxylic acid, 3,4'-biphenyldicarboxylic acid, and ester-forming derivatives thereof. Examples of naphthalenedicarboxylic acids include 2,6-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, and 2,7-naphthalenedicarboxylic acid.

[0207] In addition to aromatic dicarboxylic acids, aliphatic dicarboxylic acids or monocarboxylic acids may be used as the carboxylic acid. Examples of aliphatic dicarboxylic acids include adipic acid, azelaic acid, and sebacic acid. Examples of monocarboxylic acids include benzoic acid, propionic acid, and butyric acid.

[0208] Examples of the aliphatic diol include ethylene glycol, 1,3-propylene diol, 1,4-butanediol, 1,4-cyclohexanedimethanol, 1,6-hexanediol, and the like, as well as ester-forming derivatives thereof.

[0209] In addition to the aliphatic diol, monoalcohols or polyalcohols may be used as alcohols. Examples of monoalcohols include butyl alcohol, hexyl alcohol, and octyl alcohol. Examples of polyalcohols include trimethylolpropane, glycerin, and pentaerythritol.

[0210] The polyester can be synthesized by a known method such as a direct esterification method or a transesterification method. Examples of polycondensation catalysts used in the synthesis of polyester include known antimony compounds, germanium compounds, and aluminum compounds. Examples of antimony compounds include antimony trioxide and antimony pentoxide. Examples of germanium compounds include germanium oxide. Examples of titanium compounds include titanium acetate. Examples of aluminum compounds include aluminum chloride. However, the polycondensation catalyst is not limited to these.

[0211] Preferred polyesters include polyethylene terephthalate, polyethylene terephthalate-isophthalate copolymer, polyethylene-1,4-cyclohexanedimethylene-terephthalate copolymer, polyethylene-2,6-naphthalene dicarboxylate, polyethylene-2,6-naphthalene dicarboxylate-terephthalate copolymer, polyethylene-terephthalate-4,4'-biphenyldicarboxylate, poly-1,3-propylene-terephthalate, polybutylene terephthalate, polybutylene-2,6-naphthalene dicarboxylate, and the like.

[0212] More preferred polyesters include polyethylene terephthalate, polyethylene terephthalate-isophthalate copolymer, and polyethylene-1,4-cyclohexanedimethylene-terephthalate copolymer, and more preferred polyesters include polybutylene terephthalate and polyethylene-2,6-naphthalenedicarboxylate.

[0213] The content of the plasticizer is preferably in the range of 1 to 30% by mass, more preferably in the range of 5 to 15% by mass, based on the total mass of the flexible film.

[0214] (1.3.3) Matting Agents The handleability of flexible films can be improved by including a matting agent. Examples of matting agents include inorganic fine particles and crosslinked polymers. Examples of inorganic fine particles include silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, kaolin, talc, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, magnesium silicate, and calcium phosphate. Among these, silicon dioxide is preferred as the matting agent from the viewpoint of reducing the haze of the flexible film. These matting agents may be used alone or in combination of two or more.

[0215] When the matting agent is in the form of fine particles, the average primary particle diameter of the fine particles is not particularly limited, and is preferably in the range of 1 to 20 nm, more preferably in the range of 5 to 16 nm, and even more preferably in the range of 5 to 12 nm.

[0216] The fine particles are preferably contained in the flexible film in a state where they have formed secondary particles. The average secondary particle diameter is preferably within the range of 0.1 to 5 μm, more preferably within the range of 0.1 to 2 μm, and even more preferably within the range of 0.2 to 0.6 μm. This allows the formation of irregularities with a height within the range of 0.1 to 1.0 μm on the surface of the flexible film, thereby imparting appropriate slip properties to the surface of the flexible film. The average primary particle diameter of the fine particles is measured by observing the particles using a transmission electron microscope with a magnification within the range of 500,000 to 2,000,000 times. The particle diameters of 100 particles are observed and measured, and the average value is taken as the average primary particle diameter.

[0217] The content of the matting agent is preferably in the range of 0.01 to 10% by mass, more preferably in the range of 0.1 to 3% by mass, based on the total mass of the flexible film.

[0218] (1.3.4) UV absorber: The flexible film can improve its light resistance by containing a UV absorber. The UV absorber absorbs UV rays with wavelengths of 400 nm or less. The UV absorber preferably has a transmittance of 0.1 to 30%, more preferably 1 to 20%, and even more preferably 2 to 10%, particularly at a wavelength of 370 nm.

[0219] Examples of the ultraviolet absorber include a benzotriazole-based ultraviolet absorber, a benzophenone-based ultraviolet absorber, a triazine-based ultraviolet absorber, etc. Among these, the ultraviolet absorber is preferably a benzotriazole-based ultraviolet absorber or a benzophenone-based ultraviolet absorber.

[0220] Benzotriazoles include 5-chloro-2-(3,5-di-sec-butyl-2-hydroxylphenyl)-2H-benzotriazole and (2-2H-benzotriazol-2-yl)-6-(straight-chain and branched-chain dodecyl)-4-methylphenol. Benzophenones include 2-hydroxy-4-benzyloxybenzophenone and 2,4-benzyloxybenzophenone.

[0221] Commercially available ultraviolet absorbers include the "Tinuvin (registered trademark)" series (manufactured by BASF Japan Ltd.). Specific examples include "Tinuvin (registered trademark) 109," "Tinuvin (registered trademark) 171," "Tinuvin (registered trademark) 234," "Tinuvin (registered trademark) 326," "Tinuvin (registered trademark) 327," "Tinuvin (registered trademark) 328," and "Tinuvin (registered trademark) 928." Of these, the "Tinuvin (registered trademark)" series is preferably one that does not have a halogen group.

[0222] Examples of ultraviolet absorbers include discotic compounds such as compounds having a 1,3,5-triazine ring. Commercially available products include "Tinuvin (registered trademark) 400" and "Tinuvin (registered trademark) 405" (both manufactured by BASF Japan Ltd.), and "LA-46" (manufactured by ADEKA Corporation). These ultraviolet absorbers may be used alone or in combination of two or more.

[0223] Examples of the ultraviolet absorber include polymeric ultraviolet absorbers. The polymeric ultraviolet absorber is preferably a polymeric ultraviolet absorber described in JP-A-6-148430. The polymeric ultraviolet absorber preferably does not have a halogen group.

[0224] The method of adding the UV absorber to the flexible film includes dissolving the UV absorber in a solvent to prepare a solution, and adding the resulting solution to the dope. Another method of addition includes directly adding the UV absorber during the preparation of the dope. UV absorbers that are insoluble in organic solvents, such as inorganic powders, can be added to the dope by dispersing them in an organic solvent using a dissolver or a sand mill.

[0225] Examples of the solvent include organic solvents such as alcohol, methylene chloride, methyl acetate, acetone, dioxolane, etc. Examples of the alcohol include methanol, ethanol, butanol, etc. The solvent may be a mixture of these organic solvents.

[0226] The content of the UV absorber is preferably selected appropriately depending on the type of UV absorber, the conditions of use, etc. The content of the UV absorber is preferably within a range of 0.5 to 10 mass % relative to the total mass of the flexible film, and more preferably within a range of 0.6 to 4 mass %. (1.3.5) Release Accelerator The flexible film can reduce peel resistance by containing a release accelerator. A surfactant is preferably used as the release accelerator.

[0227] Examples of the peeling promoter include phosphate ester surfactants, carboxylic acid or carboxylate surfactants, sulfonic acid or sulfonate surfactants, and sulfate ester surfactants.

[0228] Other examples of the release promoter include fluorine-based surfactants, which are obtained by substituting some of the hydrogen atoms bonded to the hydrocarbon chain of the above surfactants with fluorine atoms. Examples of release promoters are shown below.

[0229] RZ-1:C ８ H １７ OP(=O)-(OH) ２ RZ-2:C １２ H ２５ OP(=O)-(OK) ２ RZ-3:C １２ H ２５ OCH ２ CH ２ OP(=O)-(OK) ２ RZ-4:C １５ H ３１ (OCH ２ CH ２ ) ５ OP(=O)-(OK) ２ RZ-5: {C １２ H ２５ O (CH ２ CH ２ O) ５} ２ -P(=O)-OH RZ-6:{C １８ H ３５ (OCH ２ CH ２ ) ８ O} ２ -P(=O)-ONH ４RZ-7: (t-C ４ H ９ ) ３ -C ６ H ２ -OCH ２ CH ２ OP(=O)-(OK) ２ RZ-8: (iso-C ９ H １９ -C ６ H ４ -O-(CH ２ CH ２ O) ５ -P(=O)-(OK)(OH) RZ-9:C １２ H ２５ SO ３ Na RZ-10:C １２ H ２５ OSO ３ Na RZ-11:C １７ H ３３ COOH RZ-12:C １７ H ３３ COOH・N (CH ２ CH ２ OH) ３ RZ-13:iso-C ８ H １７ -C ６ H ４ -O-(CH ２ CH ２ O) ３ - (CH ２ ) ２ SO ３ Na RZ-14: (iso-C ９ H １９ ) ２ -C ６ H ３ -O-(CH ２ CH ２ O) ３ - (CH ２ ) ４ SO ３ Na RZ-15: Sodium triisopropylnaphthalenesulfonate RZ-16: Sodium tri-t-butylnaphthalenesulfonate RZ-17: C １７ H ３３ CON (CH ３ ) CH ２ CH ２SO ３ Na RZ-18:C １２ H ２５ -C ６ H ４ SO ３ ・NH ４

[0230] The content of the release promoter is preferably in the range of 0.05 to 5 mass %, more preferably in the range of 0.1 to 2 mass %, and even more preferably in the range of 0.1 to 0.5 mass %, relative to the total mass of the flexible film.

[0231] (2) Physical Properties of Flexible Film (2.1) Degree of Orientation In the present embodiment, the degree of orientation J [%] of the resin and the degree of orientation F [%] of the filler measured by X-ray diffraction satisfy the following formula (1): Formula (1): J<F

[0232] Fig. 5 is a diagram illustrating the resin and filler as the main components of a flexible film. Fig. 5 is a diagram illustrating the front or back surface of a flexible film 1 as viewed from above, and the thickness direction of the flexible film 1 is perpendicular to the plane of the paper. In the example shown in Fig. 5, the flexible film 1 contains a first filler 11, a second filler 12, rubber particles 13, and a resin 14. The particles contained in the flexible film are listed in descending order of aspect ratio as the first filler 11, the second filler 12, and the rubber particles 13.

[0233] The resin for which the degree of orientation is measured is a matrix resin contained as the main component (base material) in the flexible film. The resin for which the degree of orientation is measured does not include particulate resin contained as a filler or additive. That is, in the example shown in FIG. 5 , the portion excluding the first filler 11, the second filler 12, and the rubber particles 13 is defined as resin 14, and the degree of orientation in resin 14 is measured. Resin 14 may be composed of only one type of resin, or may be composed of two or more types of resin. When resin 14 is composed of only one type of resin, the degree of orientation of that resin is measured. When resin 14 is a mixture composed of two or more types of resin, the degree of orientation is measured for each type of resin that constitutes the resin mixture.

[0234] The fillers for which the degree of orientation is measured are all fillers defined above. The filler may be one type only, or two or more types. In the example shown in Figure 5, the degrees of orientation are measured for a first filler 11 and a second filler 12. As with the resin, when there is only one type of filler, the degree of orientation of that filler is measured. When there are two or more types of fillers, the degree of orientation is measured for each type of filler.

[0235] The method for measuring the degree of orientation of the resin and filler will be described. The degree of orientation is measured by X-ray diffraction (XRD). In XRD measurement, X-rays are irradiated onto the front or back surface of a flexible film, and the resulting diffraction is analyzed. A measurement sample is prepared by cutting the flexible film into a piece measuring 50 mm x 50 mm. XRD measurement is performed on the prepared sample under the following conditions. The incident angle θ of the X-rays incident on the sample is selected so that diffraction peaks resulting from the resin, filler, and other additives can be obtained independently.

[0236] (Measurement conditions) Equipment: Fully automatic multipurpose X-ray diffractometer "Rigaku SmartLab" (manufactured by Rigaku Corporation) X-ray: Cu-Kα Voltage-current: 45 kV-200 mA Measurement method: Diffraction peak selection by 2θ / θ measurement and β scan measurement Attachment: αβ attachment-transmission measurement Measurement speed: 10° / min Measurement step: 0.20°

[0237] The degree of orientation Jn for each type of resin and the degree of orientation Fn for each type of filler can be calculated by the following formulas (4) and (5).

[0238] In the formula, Wji and Wfi represent the half-width of the spectrum obtained by beta-scan measurement using the diffraction angle 2θ (°). The diffraction angle 2θ (°) is selected by 2θ / θ measurement so as to be independent for each type of resin and each type of filler. ΣWji and ΣWfi respectively represent the sum of the multiple half-widths obtained. The half-width of each peak is calculated using the analysis software included with the fully automated multipurpose X-ray diffractometer "Rigaku SmartLab" (manufactured by Rigaku Corporation). XRD measurement is performed three times on the same sample, and the half-width is the arithmetic average of the three measurements.

[0239] FIG. 6 shows an example of a spectrum obtained by β-scan measurement of a filler. First, a diffraction angle 2θ (°) is selected by 2θ / θ measurement so that the diffraction peaks of various materials contained in the flexible film can be obtained independently. Next, β-scan measurement is performed using the diffraction angle 2θ (°) corresponding to the filler. This results in a spectrum having two peaks, for example, as shown in FIG. 6. Note that in this embodiment, the number of peaks is not limited to two. In the spectrum shown in FIG. 6, the half-width at peak p11 is W11, the half-width at peak p12 is W12, and ΣWfi corresponds to the sum of W11 and W12.

[0240] For resins, as with fillers, a spectrum can be obtained by β-scan measurement, and the degree of orientation can be measured.

[0241] The degree of orientation J [%] of the entire resin and the degree of orientation F [%] of the entire filler can be calculated using the following formulas (6) and (7). In other words, the overall degree of orientation is calculated as the arithmetic average of the degrees of orientation for each type. n represents the number of types. Formula (6): Orientation degree J [%] = (J1 + J2 + ... + Jn) / n Formula (7): Orientation degree F [%] = (F1 + F2 + ... + Fn) / n In the example shown in Figure 5, when the degree of orientation of the first filler 11 is F11 and the degree of orientation of the second filler 12 is F12, the degree of orientation F is expressed as (F11 + F12) / 2.

[0242] The degree of orientation J [%] of the resin preferably satisfies the following formula (2): 40≦J≦60

[0243] The degree of orientation F [%] of the filler preferably satisfies the following formula (3): 40≦F≦80

[0244] When the degree of orientation J [%] of the resin and the degree of orientation F [%] of the filler are within the above ranges, the resin and the filler interact appropriately, and the impact resistance and flexibility can be further improved.

[0245] The degree of orientation of the resin and filler can be adjusted by the type and content of each. It can also be adjusted by applying an external force to the resin and filler. For example, even if the type and content of the resin and filler are the same, the degree of orientation changes depending on the manufacturing method and manufacturing conditions of the flexible film, as the applied external force differs. Therefore, the degree of orientation may be adjusted by the manufacturing method and manufacturing conditions of the flexible film.

[0246] (2.2) Tensile Modulus E1 The tensile modulus E1 of the flexible film is preferably in the range of 5.0 to 8.0 GPa, more preferably in the range of 6.0 to 8.0 GPa, and even more preferably in the range of 6.5 to 8.0 GPa.

[0247] The tensile modulus E1 of a flexible film can be measured in the machine direction (MD) by the following method in accordance with JIS K7127 (1999). The tensile modulus is determined by linear regression between strains of 0.05 and 0.25%.

[0248] 1) A flexible film is cut into a size of 100 mm (MD) x 10 mm (TD) to prepare a test specimen. 2) This test specimen is measured using a Tensilon universal material testing machine "RTC-1225A" (manufactured by Orientec Co., Ltd.). The chuck distance is set to 50 mm, and the test specimen is pulled in the longitudinal (MD) direction at a pulling rate of 50 mm / min to measure the tensile modulus of elasticity E1 in the MD direction. The measurement is performed at 23°C and 55% RH.

[0249] (2.3) Breaking Elongation The breaking elongation of the flexible film is preferably in the range of 5 to 30%, more preferably in the range of 10 to 20%.

[0250] The breaking elongation of a flexible film can be measured in the machine direction (MD) by the following method in accordance with JIS K7127 (1999).

[0251] 1) A flexible film is cut into a size of 100 mm (MD) x 10 mm (TD) to prepare a test specimen. 2) This test specimen is measured using a Tensilon universal material testing machine "RTC-1225A" (manufactured by Orientec Co., Ltd.). The chuck distance is set to 50 mm, and the test specimen is pulled in the longitudinal (MD) direction at a tensile speed of 50 mm / min to measure the breaking elongation in the MD direction. The measurement is performed at 23°C and 55% RH.

[0252] (2.5) Thickness The thickness of the flexible film is not particularly limited. From the viewpoint of simultaneously achieving impact resistance (visibility after a keystroke test), folding resistance, and thinness, the thickness of the flexible film is preferably within the range of 30 to 80 μm, and more preferably within the range of 40 to 60 μm.

[0253] (3) Manufacturing Method of Flexible Film The manufacturing method of the flexible film is not particularly limited, and the flexible film can be manufactured by a solution casting method, a solution coating method, or a melt casting method. Among these, the solution casting method or the solution coating method is preferable from the viewpoint of being able to adjust the orientation degree of the resin and the filler so as to satisfy the above formula (1). With these methods, external forces are less likely to be applied to the resin, so that the film can be formed with a relatively low degree of orientation of the resin. Furthermore, the relatively low degree of orientation of the resin allows the resin and the filler to intertwine and interact, suppressing shrinkage during drying. As a result, the smoothness of the flexible film can be improved, and the surface quality can be improved.

[0254] In the solution casting method or the solution coating method, a dope containing a resin, a filler, a solvent, and any other components is first prepared. The dope is applied to a substrate by casting or coating. The cast or coated film is then dried to obtain a film. In the solution casting method, it is preferable to peel the cast film from the support and then dry the cast film. On the other hand, in the solution coating method, it is preferable to dry the coated film on the support and then peel the coated film from the support.

[0255] The form of the flexible film is not particularly limited, and is preferably, for example, in the form of a strip. That is, the flexible film is preferably wound into a roll in a direction perpendicular to its width direction to form a roll body.

[0256] (3.1) Solution Casting Method The method for producing a flexible film by the solution casting method preferably includes the steps of preparing a dope containing a resin and a filler, casting the dope on a support to form a casting film, peeling the casting film from the support, and drying the casting film.

[0257] (3.1.1) Dope Preparation Step In the dope preparation step, a dope containing a resin, a filler, a solvent, and any other components is prepared. A higher resin concentration in the dope is preferable because it reduces the drying load after casting onto the metal support. However, if the resin concentration is too high, the load during filtration increases and the filtration accuracy deteriorates. From these viewpoints, the resin concentration is preferably in the range of 10 to 35% by mass, and more preferably in the range of 15 to 25% by mass.

[0258] The solvent used in the dope may be used alone or in combination of two or more. From the viewpoint of production efficiency, it is preferable to use a mixture of a good solvent and a poor solvent for the resin. Examples of the good solvent include methylene chloride and methyl acetate. Examples of the poor solvent include methanol, ethanol, n-butanol, cyclohexane, and cyclohexanone. It is also preferable that the dope contains water in an amount of 0.01 to 2% by mass.

[0259] The solvent used in the dope may be reused. In the film forming step described later, the solvent removed from the film by drying may be recovered, and the recovered solvent may be reused for preparing the dope.

[0260] A known method can be used to dissolve the resin when preparing the dope. By combining heating and pressure, the solvent can be heated to a temperature equal to or higher than the boiling point at normal pressure. A known method can be used to disperse the filler when preparing the dope.

[0261] Next, the resin solution is filtered using a suitable filter material such as filter paper, etc. The filter material preferably has an absolute filtration accuracy of 0.008 mm or less, more preferably in the range of 0.001 to 0.008 mm, and even more preferably in the range of 0.003 to 0.006 mm.

[0262] The filter material is not particularly limited, and known filter materials can be used. The filter material is preferably made of plastic or metal from the viewpoint of preventing fiber shedding, etc. Examples of plastic materials include polypropylene and Teflon (registered trademark). Examples of metal materials include stainless steel, etc.

[0263] The dope can be filtered by a known method. The filtration temperature is preferably equal to or higher than the boiling point of the solvent at normal pressure, and is preferably a temperature at which the solvent does not boil under pressure. By filtering while heating, the increase in the difference in filtration pressure (differential pressure) before and after filtration can be reduced. The filtration temperature is preferably within a range of 45 to 120°C, more preferably within a range of 45 to 70°C, and even more preferably within a range of 45 to 55°C.

[0264] The filtration pressure is preferably small, and is preferably 1.6 MPa or less, more preferably 1.2 MPa or less, and even more preferably 1.0 MPa or less.

[0265] (3.1.2) A step of casting the dope onto a support to form a cast film. The metal support used in the casting step preferably has a mirror-finished surface. The metal support is preferably a stainless steel belt or a cast drum with a plated surface. The casting width is preferably within the range of 1 to 4 m.

[0266] The surface temperature of the metal support in the casting step is preferably −50° C. or higher and lower than the boiling point of the solvent, more preferably in the range of 0 to 40° C., and even more preferably in the range of 5 to 30° C.

[0267] In order to obtain a flexible film with good flatness, the residual solvent amount when the casting film (web) is peeled from the metal support is preferably in the range of 10 to 150% by mass, more preferably in the range of 20 to 40% by mass or in the range of 60 to 130% by mass, and further preferably in the range of 20 to 30% by mass or in the range of 70 to 120% by mass.

[0268] The residual solvent amount is defined by the following formula (iii): Formula (iii): Residual solvent amount [mass %] = {(M - N) / N} x 100 Each symbol in the formula is as follows: M: Mass of a sample taken at any time during or after the production of the web or film N: Mass of the sample after heating at 115°C for 1 hour

[0269] (3.1.3) Step of Peeling the Casting Film from the Support In the peeling step, the casting film (web) is peeled from the metal support. The method of peeling the web from the metal support can be a known method.

[0270] (3.1.4) Step of drying the peeled cast film In the drying step, the web peeled from the metal support is further dried. The residual solvent content of the web after drying is preferably 1% by mass or less, more preferably 0.1% by mass or less, and further preferably in the range of 0 to 0.01% by mass.

[0271] In the drying process, a roll drying method or a tenter method is generally used in which the web is dried while being transported. In the roll drying method, the web is dried by passing it alternately through multiple rolls arranged above and below.

[0272] The web immediately after peeling from the metal support is preferably stretched in the machine direction (MD) at the portion where the residual solvent is large, and is also preferably stretched in the transverse direction (TD) using a tenter system in which both ends of the web are held with clips or the like.

[0273] The means for drying the web is not particularly limited, and examples thereof include hot air, infrared rays, a heated roll, microwaves, etc. From the viewpoint of simplicity, drying is preferably carried out with hot air.

[0274] The drying temperature is preferably in the range of 90°C to 200°C, more preferably in the range of 110°C to 190°C. The drying temperature is preferably increased in stages. The drying time is preferably in the range of 5 to 60 minutes, more preferably in the range of 10 to 30 minutes. The drying time is preferably adjusted appropriately depending on the drying temperature.

[0275] The thickness and width of the film obtained by drying the web are not particularly limited. The thickness of the film is preferably within the range of 10 to 200 μm, more preferably within the range of 10 to 100 μm, and preferably within the range of 20 to 60 μm. From the viewpoint of productivity, the width of the film is preferably within the range of 1 to 4 m, more preferably within the range of 1.6 to 4 m, and even more preferably within the range of 1.8 to 3.6 m.

[0276] (3.1.5) Step of Stretching the Film The obtained flexible film may be further stretched. By further stretching the flexible film, the orientation state of the resin molecules can be changed.

[0277] The stretching step can be carried out in both the longitudinal direction (MD direction) and the width direction (TD direction) of the flexible film. Stretching in the TD direction is preferred. The stretching ratio in the TD direction is preferably in the range of 1 to 50%, and more preferably in the range of 5 to 30%.

[0278] An example of the stretching method is a method in which a plurality of rolls are provided with different peripheral speeds, and the difference in roll peripheral speeds is utilized to stretch the film in the MD direction. An example of the stretching method is a method in which both ends of the film are fixed with clips or pins, and the distance between the clips or pins is increased in the direction of travel to stretch the film in the MD direction. An example of the stretching method is a method in which both ends of the film are fixed with clips or pins, and the distance between the clips or pins is increased laterally to stretch the film in the TD direction. An example of the stretching method is a method in which both ends of the film are fixed with clips or pins, and the distance between the clips or pins is increased in the MD and TD directions simultaneously to stretch the film in both the MD and TD directions.

[0279] The width of the film is preferably maintained or stretched in the width direction by a tenter, which may be a pin tenter or a clip tenter.

[0280] The transport tension of the flexible film in the tenter or the like is preferably in the range of 120 to 200 N / m, more preferably in the range of 140 to 200 N / m, and even more preferably in the range of 140 to 160 N / m. The transport tension is preferably adjusted appropriately depending on the temperature.

[0281] When the glass transition temperature of the flexible film is Tg, the temperature of the flexible film during stretching is preferably within the range of (Tg-30) to (Tg+100)°C. The temperature of the film during stretching is more preferably within the range of (Tg-20) to (Tg+80)°C, and even more preferably within the range of (Tg-5) to (Tg+20)°C.

[0282] The Tg of the flexible film can be controlled by the type of material constituting the flexible film and the ratio of the materials constituting the flexible film. The Tg of the flexible film when dry is preferably 110°C or higher, more preferably 120°C or higher. The Tg of the flexible film when dry is preferably 190°C or lower, more preferably 170°C or lower. The Tg of the flexible film can be determined by the method described in JIS K7121, for example.

[0283] By setting the temperature during stretching to 150°C or higher and the stretching ratio to 15% or higher, it is possible to impart appropriate roughness to the surface of the flexible film. By imparting appropriate roughness to the surface of the flexible film, not only can the slipperiness be improved, but also surface processability and adhesion to adjacent layers can be improved. The average surface roughness Ra of the flexible film is preferably in the range of 2.0 to 4.0 nm, and more preferably in the range of 2.5 to 3.5 nm.

[0284] The average surface roughness Ra (nm) of the flexible film and the polarity of the flexible film itself with respect to the solvent preferably satisfy the following formula (iv): where "log P" represents the octanol / water partition coefficient of the flexible film.

[0285] Formula (iv) Ra≧3.5×logP-25.4

[0286] The flexible film is preferably heat-set after stretching. The temperature during heat-setting is preferably higher than the temperature during the final stretching in the TD direction. Heat-setting is preferably carried out at a temperature of (Tg-20°C) or lower for 0.5 to 300 seconds. In this case, it is preferable to heat-set the film by sequentially increasing the temperature in two or more divided regions so that the temperature difference is in the range of 1 to 100°C.

[0287] The heat-set flexible film is preferably cooled to a temperature below Tg. Furthermore, the cooled flexible film is preferably cut at both clip-held portions and wound up. At this time, the flexible film is preferably subjected to a relaxation treatment of 0.1 to 10% in the TD direction at a temperature below the final heat-set temperature and above Tg. Additionally, the flexible film is preferably subjected to a relaxation treatment of 0.1 to 10% in the MD direction.

[0288] The cooling is preferably performed by slowly cooling from the final heat setting temperature to Tg at a cooling rate of 100°C per second or less. The method for the cooling and relaxation treatment is not particularly limited, and known methods can be used. In particular, from the viewpoint of improving the dimensional stability of the flexible film, it is preferable to perform these treatments while sequentially cooling in multiple temperature ranges.

[0289] The cooling rate is a value calculated by (T1-Tg) / t, where T1 is the final heat setting temperature and t is the time it takes for the flexible film to reach Tg from the final heat setting temperature.

[0290] The heat setting conditions, cooling conditions, relaxation treatment conditions, etc. are preferably adjusted appropriately depending on the types, contents, etc. of the constituent materials in the flexible film.

[0291] Whether a flexible film is stretched or not can be confirmed, for example, by checking whether there is an in-plane slow axis, which is the axis extending in the direction in which the refractive index is maximized.

[0292] (3.2) Solution Coating Method A method for producing a flexible film by the solution coating method preferably includes the steps of preparing a dope containing a resin and a filler, coating the dope on a support to form a coating film, drying the coating film on the support, and peeling the dried coating film from the support. Specifically, the method described in paragraphs 0166 to 0217 of Japanese Patent No. 7315110 can be referred to.

[0293] (3.3) Melt Casting Method In the method for producing a flexible film by the melt casting method, first, a resin, a filler, and any other components are mixed. The mixture is then melt-extruded into a film and brought into contact with a chill roll to cool and solidify. The cooled and solidified film is then peeled off from the chill roll and wound into a roll. The flexible film of this embodiment can be produced by a known melt casting method.

[0294] 7 is a schematic diagram of a manufacturing apparatus 80 for manufacturing a flexible film by a melt casting method. An example of a manufacturing method for manufacturing a flexible film using the manufacturing apparatus 80 shown in FIG. 7 will be described below.

[0295] The first cooling roll 86-1 and the second cooling roll 86-2 are highly rigid metal rolls, and are provided with a structure in which a temperature-controllable heat medium or coolant flows inside. The diameter of the cooling rolls is preferably within the range of 100 mm to 1 m.

[0296] Examples of the surface material of the chill roll include carbon steel, stainless steel, aluminum, titanium, etc. From the viewpoint of improving hardness and releasability from resin, it is preferable to apply a surface treatment such as hard chrome plating, nickel plating, amorphous chrome plating, ceramic spray coating, etc.

[0297] The surface roughness Ra of the cooling roll is preferably 0.1 μm or less, and more preferably 0.05 μm or less. The smoother the surface, the smoother the surface of the obtained film.

[0298] The number of cooling rolls may be one, or two or more as shown in FIG.

[0299] The touch roll 85 preferably has elasticity. The touch roll has a double structure consisting of a metal outer cylinder and an inner cylinder, with a refrigerant flowing between them. The elasticity of the metal outer cylinder allows for precise control of the temperature of the touch roll surface and allows for appropriate elastic deformation. By pressing the film using a touch roll with these properties, streaks and spotted unevenness can be reduced.

[0300] The diameter of the touch roll is preferably within the range of 100 to 600 mm. The thickness of the metal outer cylinder is preferably within the range of 0.1 to 5 mm. When the thickness is 0.1 mm or more, sufficient strength is obtained and breakage is difficult. Furthermore, when the thickness is 5 mm or less, the touch roll is not too heavy, and rotation unevenness can be reduced.

[0301] The surface roughness Ra of the touch roll surface is preferably 0.1 μm or less, and more preferably 0.05 μm or less. The smoother the surface, the smoother the surface of the obtained film can be.

[0302] Examples of materials for the metal outer cylinder include carbon steel, stainless steel, titanium, nickel produced by electroforming, etc. From the viewpoint of improving hardness and releasability from resin, it is preferable to apply a surface treatment such as hard chrome plating, nickel plating, amorphous chrome plating, or ceramic spray coating.

[0303] The material for the metal inner cylinder is preferably a lightweight and rigid metal such as carbon steel, stainless steel, aluminum, or titanium. The rigidity of the inner cylinder can reduce rotational wobble of the touch roll. From the viewpoint of rigidity, the thickness of the inner cylinder is preferably within a range of 2 to 10 times the thickness of the outer cylinder. The inner cylinder may be further coated with a resin elastic material such as silicone or fluororubber.

[0304] The materials for the flexible film are preferably dried in advance. Examples of dryers include vacuum dryers, reduced pressure dryers, and dehumidified hot air dryers. The materials are preferably mixed before being melt-extruded into a film. Examples of mixers include V-type mixers, conical screw mixers, horizontal cylindrical mixers, Henschel mixers, and ribbon mixers.

[0305] After mixing the materials, the mixture may be directly melted using an extruder and extruded into a film. Alternatively, after mixing the materials, the mixture may be pelletized, and the pellets may be melted using an extruder and extruded into a film. When multiple materials with different melting points are included, a semi-molten material in the form of rice crackers may be first prepared at a temperature at which only the material with the lower melting point melts, and the semi-molten material may be completely melted using an extruder and extruded into a film.

[0306] The extruder is not particularly limited, but is preferably a melt-kneading extruder, which may be a single-screw or twin-screw type.

[0307] The flexible film material is melted at a melting temperature Tm and extruded into a film form from a die 84 onto a first cooling roll 86-1 using an extruder. The extruded cast film is cooled by a first cooling roll 86-1 and a second cooling roll 86-2 to obtain a cast film. In addition, a touch roll 85 is used to press the cast film on the first cooling roll 86-1.

[0308] The temperature of the cast film on the touch roll 85 side during pressing is preferably adjusted appropriately. Here, "the temperature of the cast film on the touch roll 85 side during pressing" refers to the temperature of the cast film at the position on the first cooling roll 86-1 where the touch roll 85 is in contact. This temperature can be measured using a non-contact thermometer as the average value of the surface temperatures of the cast film measured at 10 points in the width direction from a distance of 50 cm with the touch roll 85 retracted and no touch roll is present.

[0309] It is preferable to appropriately adjust the surface temperature Tr0 of the touch roll 85, the surface temperature Tr1 of the first cooling roll 86-1, and the surface temperature Tr2 of the second cooling roll 86-2. The surface temperatures Tr0, Tr1, and Tr2 of each roll can be measured as the average value of the roll surface temperatures measured at 10 points in the width direction using a non-contact thermometer at a position 90° before the position where the cast film first comes into contact with each roll in the rotation direction.

[0310] It is preferable to adjust the routing of the cast film so that the contact time between each roll and the cast film is equal.

[0311] The peripheral speeds r1 and r2 of the first cooling roll 86-1 and the second cooling roll 86-2 can be changed independently, and are preferably adjusted appropriately.

[0312] The pressing elastic roll 81 is pressed against the cooling roll or the touch roll via the nonwoven fabric from the unwinding section 82 to the winding section 83. At this time, the nonwoven fabric is driven in the rotation direction opposite to that of the touch roll 85.

[0313] The pressing elastic roll preferably has a structure in which a metal support is covered with a resin. Examples of the resin material include natural rubber, SBR, nitrile rubber, chloroprene rubber, butyl rubber, ethylene propylene rubber, CSM, silicone rubber, fluororubber, and urethane rubber. Among these, the resin is preferably silicone rubber.

[0314] The diameter of the pressing elastic roll is preferably within a range of 50 to 1000 mm, more preferably within a range of 100 to 800 mm, and the thickness of the resin coating is preferably within a range of 0.1 to 20 mm, more preferably within a range of 1 to 6 mm.

[0315] The pressing elastic roll is preferably a temperature-controllable heating roll. Heating methods include a heat medium heating method, a dielectric heating method, and an electric heater method, among which a dielectric heating method is preferred. The temperature of the pressing elastic roll is preferably in the range of 50 to 150°C, and more preferably in the range of 80 to 130°C.

[0316] Examples of the material of the nonwoven fabric include cellulose-based, polyurethane-based, polyester-based, acrylic-based, etc. Examples of commercially available nonwoven fabric include "Benliese" (manufactured by Asahi Kasei Fibers Corporation), nonwoven fabric manufactured by Nippon Vilene Co., Ltd., and "Bencotto (registered trademark)" (manufactured by Ozu Sangyo Co., Ltd.).

[0317] In this way, the film is peeled off from the second cooling roll 86-2. The peeled film 87 is taken up in a roll. The film 87 may also be stretched before being taken up in a roll.

[0318] In the melt casting method, the average orientation degree of the resin and filler can be adjusted by adjusting the configuration of each roll, pressing conditions, and the like.

[0319] 3. Low-elasticity film: From the viewpoint of improving impact resistance and flexibility, the cover member according to the present embodiment preferably has a low-elasticity film. There are no particular restrictions on the low-elasticity film, so long as it is a resin film with a relatively low tensile modulus of elasticity.

[0320] (1) The constituent resin of the low elasticity film is not particularly limited, and examples thereof include acyl cellulose, cycloolefin resin, fumaric acid diester resin, polypropylene, (meth)acrylic resin, polyester, polyarylate, polyimide, styrene resin, and composite resins thereof. Other examples of the resin include hydroxy-terminated polydimethylsiloxane (PDMS), polyurethane (PU), and elastomer composite materials containing styrene block polymers.

[0321] Among these, from the viewpoints of folding endurance, optical properties, etc., it is preferable to contain a linear polymer material having a carbonyl group in the side chain, or a polymer material having a cyclic structure in the main chain. The resin is preferably a (meth)acrylic resin, a styrene-(meth)acrylic resin, a cycloolefin resin, or a polyimide. Details of the resin are as described above for the flexible film.

[0322] The low-elasticity film may contain, if necessary, the various additives described above for the flexible film.

[0323] (2) Physical Properties of Low Elasticity Film (2.1) Tensile Modulus The tensile modulus E2 of the low elasticity film is preferably in the range of 0.5 to 3.0 GPa, more preferably in the range of 0.5 to 2.5 GPa, and even more preferably in the range of 1.0 to 2.5 GPa. The tensile modulus E2 of the low elasticity film can be measured in the same manner as the tensile modulus E1 of the flexible film.

[0324] (2.2) Thickness The thickness of the low-elasticity film is not particularly limited. From the viewpoint of simultaneously achieving impact resistance, folding resistance, and thinness, the thickness of the low-elasticity film is preferably in the range of 40 to 60 μm, and more preferably in the range of 40 to 50 μm.

[0325] 4. Hardened Layer From the viewpoint of improving impact resistance, the cover member according to this embodiment preferably has a hardened layer (hard coat layer). In this embodiment, the "hardened layer" refers to a layer provided on the outermost surface of the cover member on the viewing side, and exhibits a hardness of "H" or higher in the pencil hardness test specified in JIS 5600-5-4 (1999). The hardened layer preferably has a pencil hardness of 3H or higher, and more preferably 4H or higher, in the pencil hardness test.

[0326] (1) Structure of the cured layer (1.1) The material constituting the resin cured layer is not particularly limited, but from the viewpoint of excellent mechanical strength and visibility, it is preferable to contain a resin (curable compound) that cures via a crosslinking reaction when irradiated with actinic rays (active energy rays) such as ultraviolet rays or electron beams. The curable compound is preferably a compound having an ethylenically unsaturated double bond, and particularly preferably a (meth)acrylate. Note that (meth)acrylate refers to acrylate or methacrylate.

[0327] The acrylate is preferably a polyfunctional acrylate having two or more acryloyloxy groups in one molecule. The methacrylate is preferably a polyfunctional methacrylate having two or more methacryloyloxy groups in one molecule. Among these, the polyfunctional acrylate is preferably a pentaerythritol polyfunctional acrylate or a dipentaerythritol polyfunctional acrylate. The polyfunctional methacrylate is preferably a pentaerythritol polyfunctional methacrylate or a dipentaerythritol polyfunctional methacrylate.

[0328] (1.2) The fine particle cured layer may contain fine particles. By containing fine particles, the hardness and refractive index can be adjusted. Furthermore, by containing fine particles, unevenness can be formed on the surface, and an anti-glare function can be imparted. The fine particles may be organic or inorganic fine particles.

[0329] Examples of organic fine particles include fine particles of polymethyl methacrylate resin, acrylic styrene resin, polymethyl methacrylate, silicone resin, styrene resin, polycarbonate, benzoguanamine resin, melamine resin, polyolefin, polyester, polyamide, polyimide, polyethylene fluoride, methyl methacrylate-divinylbenzene copolymer, and the like.

[0330] Examples of inorganic fine particles include fine particles of silicon oxide, titanium oxide, aluminum oxide, tin oxide, zinc oxide, calcium carbonate, barium sulfate, talc, kaolin, calcium sulfate, etc. The matting agent contained in the flexible film described above may also be used as the inorganic fine particles. Among these, the inorganic fine particles are preferably silicon dioxide (silica) fine particles. From the viewpoint of improving dispersibility, the silica fine particles may be reactive silica fine particles described in paragraphs 0230 to 0258 of WO 2011 / 158626.

[0331] The reactive inorganic fine particles also include those having two or more inorganic fine particles as cores per particle. In addition, by reducing the particle size of the reactive inorganic fine particles, the number of crosslinking points per content in the cured layer can be increased.

[0332] The average particle size of the fine particles is preferably adjusted appropriately depending on the thickness of the cured layer and the type of fine particles. The average particle size is preferably within the range of 5 to 100 nm, more preferably within the range of 10 to 50 nm, and even more preferably within the range of 10 to 30 nm. The fine particles may be agglomerated particles. In the case of agglomerated particles, it is preferable that the secondary particle size is within the above range. By having an average particle size of 5 nm or more, sufficient hardness can be imparted to the cured layer. By having an average particle size of 100 nm or less, the transparency of the cured layer is excellent.

[0333] By appropriately selecting the type of fine particles, the refractive index of the cured layer can be adjusted in addition to imparting hardness to the cured layer, and various other functions such as antistatic properties can also be imparted to the cured layer.

[0334] Examples of fine particles for adjusting the refractive index include low-refractive-index fine particles and high-refractive-index fine particles. Here, "low-refractive-index fine particles" refer to fine particles with a refractive index of less than 1.50, preferably 1.46 or less. "High-refractive-index fine particles" refer to fine particles with a refractive index of 1.50 or more, preferably in the range of 1.50 to 2.80.

[0335] Examples of metal oxide fine particles that can be used as high refractive index fine particles include titania (TiO, refractive index: 2.71), zirconium oxide (ZrO, refractive index: 2.10), cerium oxide (CeO, refractive index: 2.20), tin oxide (SnO, refractive index: 2.00), antimony tin oxide (ATO, refractive index: 1.75-1.95), indium tin oxide (ITO, refractive index: 1.95-2.00), phosphorus tin compound (PTO, refractive index: 1.75-1.85), antimony pentoxide (SbO, refractive index: 2.04), aluminum zinc oxide (AZO, refractive index: 1.90-2.00), gallium zinc oxide (GZO, refractive index: 1.90-2.00), and zinc antimonate (ZnSbO, refractive index: 1.90-2.00). Fine particles having a surface coating of such metal oxides can also be used. These may be used alone or in combination of two or more.

[0336] Examples of low refractive index fine particles include silica (SiO2), cryolite (Na3AlF6), and magnesium fluoride (MgF2).

[0337] The low refractive index layer preferably contains silica fine particles. The refractive index of the silica fine particles is preferably in the range of 1.30 to 1.45 when measured at 23°C and a wavelength of 550 nm. The thickness of the low refractive index layer is preferably in the range of 5 nm to 0.5 μm, more preferably in the range of 10 nm to 0.3 μm, and even more preferably in the range of 30 nm to 0.2 μm.

[0338] The composition for forming a low refractive index layer may contain multiple types of silica fine particles, and preferably contains at least one type of particles having an outer shell layer and being porous or hollow inside. The particles having an outer shell layer and being porous or hollow inside are preferably hollow silica fine particles.

[0339] The composition for forming a low refractive index layer may contain an organosilicon compound represented by the following general formula (OSi-1), a hydrolyzate thereof, or a polycondensate thereof. General formula (OSi-1): Si(OR) ４ In the formula, R represents an alkyl group having 1 to 4 carbon atoms. Examples of the organosilicon compound represented by the general formula (OSi-1) include tetramethoxysilane, tetraethoxysilane, and tetraisopropoxysilane.

[0340] The content of the fine particles is preferably within a range of 5 to 70% by mass, more preferably within a range of 10 to 55% by mass, and even more preferably within a range of 10 to 40% by mass, based on the total mass of the cured layer.

[0341] Commercially available organosilica sols and hollow silica particles may be used. Commercially available organosilica sols include "MEK-AC-2101" and "MEK-AC-4101" (both manufactured by Nissan Chemical Industries, Ltd.). Commercially available hollow silica particles include "JX1008SIV" and "JX1009SIV" (both manufactured by JGC Catalysts and Chemicals, Ltd.).

[0342] (1.3) Additives The cured layer may further contain other additives. The other additives are not particularly limited, and conventionally used additives can be used. Examples of the additives include a photopolymerization initiator and a photopolymerization accelerator. The additives in the flexible film may also be used in the cured layer.

[0343] Examples of the photopolymerization initiator include acetophenone, benzophenone, α-hydroxyalkylphenone, Michler's ketone, benzoin, benzyl methyl ketal, benzoyl benzoate, α-acyloxime ester, thioxanthone, etc. These may be used alone or in combination of two or more.

[0344] The content of the photopolymerization initiator relative to the total mass of the cured layer is preferably within a range of 1 to 20 mass%, more preferably within a range of 2 to 15 mass%, and even more preferably within a range of 4 to 10 mass%.

[0345] The use of a photopolymerization accelerator can reduce polymerization inhibition caused by air during curing and increase the curing rate. Examples of the photopolymerization accelerator include p-dimethylaminobenzoic acid isoamyl ester and p-dimethylaminobenzoic acid ethyl ester.

[0346] In addition, the cured layer may contain an antiglare agent, an antifouling agent, an antistatic agent, etc. for the purpose of imparting functionality. The cured layer may contain a leveling agent, etc. for the purpose of improving coatability. The cured layer may contain a lubricant, etc. for the purpose of preventing blocking. Known agents can be used for these.

[0347] (2) Manufacturing Method of Cured Layer The cured layer can be formed by applying a composition for forming a cured layer onto a flexible film to form a coating layer, optionally carrying out a drying step, and then curing the coating layer. Alternatively, the cured layer may be formed on a support, peeled from the support, and attached to a flexible film via an adhesive layer or the like.

[0348] When the cured layer and the flexible film are adjacent to each other and have different refractive indices, interfacial reflection or interference fringes may occur at the interface between the cured layer and the flexible film, which may reduce the visibility of the display device. As a countermeasure, a solvent that dissolves or swells the flexible film may be used in the cured layer-forming composition to form an impregnation layer at the interface between the cured layer and the flexible film. As another method, the difference in refractive index between the cured layer and the flexible film may be reduced by appropriately adjusting the type and content of each constituent material in the cured layer and the flexible film.

[0349] When the cured layer contains fine particles, the coating conditions and drying conditions may be adjusted so that a gradient in the concentration of the fine particles is generated in the thickness direction of the cured layer. For example, when the cured layer contains high-refractive-index fine particles and has a higher refractive index than the flexible film, a concentration gradient may be generated so that the concentration of the high-refractive-index fine particles is lower on the flexible film side in the thickness direction of the cured layer. When the cured layer contains high-refractive-index fine particles and has a lower refractive index than the flexible film, a concentration gradient may be generated so that the concentration of the high-refractive-index fine particles is higher on the flexible film side in the thickness direction of the cured layer.

[0350] When the cured layer contains fine particles, the application and drying conditions may be adjusted so that the fine particles are partially impregnated near the interface between the cured layer and the flexible film or in the impregnated layer.

[0351] By the above method, the difference in refractive index between the cured layer and the flexible film can be reduced, and interference fringes resulting from the interface between the cured layer and the flexible film can be reduced.

[0352] The cured layer-forming composition (coating liquid) can be prepared by dissolving or dispersing the constituent materials of the cured layer in a solvent. The solvent may be one that dissolves or swells the flexible film, or one that does not dissolve or swell the flexible film. The content of the solvent is preferably in the range of 1 to 200 parts by mass per 100 parts by mass of the constituent materials of the cured layer.

[0353] (Solvent for Dissolving or Swelling Flexible Film) Hereinafter, a solvent for dissolving or swelling acyl cellulose will be described as an example.

[0354] Examples of the solvent include: ketones such as methyl ethyl ketone, acetone, cyclohexanone, and methyl isobutyl ketone; esters such as methyl acetate, ethyl acetate, butyl acetate, propyl acetate, and propylene glycol monomethyl ether acetate; alcohols such as ethanol, methanol, butanol, n-propyl alcohol, isopropyl alcohol, and diacetone alcohol; hydrocarbons such as toluene, xylene, benzene, and cyclohexane; and glycol ethers such as propylene glycol monomethyl ether, propylene glycol monopropyl ether, and ethylene glycol monopropyl ether. The solvent is preferably an ester, glycol ether, or alcohol. Among these, the solvent is preferably a propylene glycol mono(C1-C4 alkyl group) alkyl ether or a propylene glycol mono(C1-C4 alkyl group) alkyl ether ester. The content of these solvents is preferably 5% by mass or more, and more preferably within the range of 5 to 80% by mass.

[0355] When a composition for forming a cured layer containing an acyl cellulose solvent is applied to a flexible film containing the acyl cellulose, part of the acyl cellulose dissolves. Because the acyl cellulose is highly hydrophilic, it is thought that the highly hydrophobic fine particles contained in the composition for forming a cured layer are unevenly distributed on the side opposite to the flexible film.

[0356] (Solvents that do not dissolve or swell the flexible film) Examples of solvents that do not dissolve or swell the flexible film include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, tert-butanol, etc. Examples of solvents include 1-pentanol, 2-methyl-2-butanol, cyclohexanol, propylene glycol monoethyl ether, isobutyl acetate, etc. Examples of solvents include methyl isobutyl ketone, 2-octanone, 2-pentanone, 2-hexanone, 2-heptanone, 3-pentanone, 3-heptanone, 4-heptanone, toluene, etc.

[0357] The method for applying the cured layer-forming composition is not particularly limited as long as it can be applied uniformly to a desired thickness, and examples of the application method include gravure coating, knife coating, dip coating, spray coating, air knife coating, spin coating, roll coating, curtain coating, die coating, casting, bar coating, and extrusion coating.

[0358] The formed coating layer is dried as needed and then irradiated with actinic radiation to cure it. The irradiation conditions are preferably adjusted appropriately depending on the constituent material and thickness of the cured layer. When electron beams are used as actinic radiation, the acceleration voltage is preferably within the range of 70 to 300 kV. When ultraviolet radiation is used as actinic radiation, the ultraviolet radiation contains light with a wavelength in the range of 190 to 380 nm. The ultraviolet radiation source is not particularly limited, and examples thereof include high-pressure mercury lamps, low-pressure mercury lamps, metal halide lamps, and carbon arc lamps.

[0359] The thickness of the cured layer to be formed is preferably within a range of 0.1 to 100 μm, more preferably within a range of 0.8 to 20 μm, and even more preferably within a range of 3 to 20 μm from the viewpoint of achieving sufficient hardness and suppressing the occurrence of curling or cracking.

[0360] 5. Color Filter The display device of this embodiment has a color filter, which allows it to display a desired color image.

[0361] The color display method in the display device of this embodiment is not particularly limited. As will be described in detail later, it is preferable to use organic electroluminescence (EL) elements as the light-emitting elements of this embodiment. Any of the following methods may be used as a color display method using organic EL elements. FIGS. 8 to 11 are schematic diagrams of an example of a color display method preferably used in this embodiment. However, the light-emitting elements are not limited to organic EL elements, and this embodiment can also be applied to other light-emitting elements when a color filter is used.

[0362] The present embodiment can be applied to the following methods 2) and 3), which require the use of color filters. The type of light-emitting element is not particularly limited. Furthermore, the present embodiment can be applied to the following methods 1) and 4), if color filters are used to improve color purity. 1) A method in which light-emitting layers 42 emitting R (red), G (green), and B (blue) are arranged horizontally (FIG. 8). The organic EL element has a cathode 41 and a transparent electrode 43 on a glass substrate 44, with the light-emitting layer 42 between them. 2) A method in which white light 45 is arranged on the backside and passes through an RGB color filter 46 (FIG. 9). 3) A method in which blue light 47 is arranged on the backside and is absorbed by a phosphor through a color filter (wavelength conversion film) 48, resulting in the emission of red light (R) and green light (FIG. 10). 4) A method in which light-emitting layers emitting R, G, and B are vertically stacked (FIG. 11).

[0363] In this embodiment, the term "color filter" refers to a filter that transmits visible light in a specific wavelength range and has the function of changing the transmitted light to a desired hue. By having a color filter, the display device of this embodiment can express a desired color and can improve color reproducibility.

[0364] The "aperture ratio" refers to the ratio of the area of ​​the area through which visible light transmits (excluding the black matrix) to the area of ​​the entire area on the surface of the color filter through which visible light of a specific wavelength range is irradiated. Each area through which visible light transmits corresponds to a pixel.

[0365] 12 is a schematic diagram of a color filter. A color filter 60 is composed of a black matrix 51 that does not transmit visible light and a transmissive region 52 that transmits visible light. Colored pixels are arranged in the transmissive region 52 as needed so that the transmitted light has a desired hue. The region of the color filter 60 that is irradiated with visible light in a specific wavelength region is indicated by an irradiation region 53 (inside the dotted line). The aperture ratio is expressed as the ratio of the area of ​​the transmissive region 52 to the area of ​​the irradiation region 53.

[0366] By appropriately adjusting the aperture ratio of the color filter, it is possible to impart an anti-reflection function to light incident from the outside. As a result, a display device with excellent visibility can be obtained without the need for a new circular polarizer. Furthermore, since there is no need to introduce a circular polarizer, the display device can be made thinner.

[0367] The aperture ratio of the color filter is preferably in the range of 65 to 90%, and more preferably in the range of 65 to 80%. By keeping the aperture ratio within this range, it is possible to reduce the reflectance of light incident from the outside and improve color reproducibility.

[0368] Furthermore, even in the above methods 1) and 4), in which a color filter is not usually essential, a display device with excellent visibility can be obtained without the need for a circular polarizer by deliberately using a color filter and adjusting the aperture ratio. That is, the display device can be made thinner and the color reproducibility can be improved.

[0369] The color filter may be a conventionally known color filter. The color filter has a colored layer consisting of a black matrix and colored pixels on one surface of a transparent substrate. The black matrix is ​​preferably formed in a lattice or stripe pattern between the colored pixels. If necessary, the color filter may also have fixed spacers or an overcoat layer.

[0370] The colored layer is preferably formed from a colored resin composition. The colored resin composition is prepared by mixing a colorant, a binder resin, a photopolymerizable monomer, a photopolymerization initiator, an additive, an organic solvent, and the like. As the colorant, a conventionally known red pigment, green pigment, yellow pigment, blue pigment, purple pigment, black pigment, and the like can be used. Furthermore, a color conversion material (inorganic fluorescent material or organic fluorescent material) may be used as needed. As the additive, a surfactant, a chain transfer agent, a storage stabilizer, and the like can be used.

[0371] The colored resin composition is preferably prepared in the form of a gravure offset printing ink, a waterless offset printing ink, an inkjet ink, a silk screen printing ink, or a solvent-developable or alkali-developable colored resist.

[0372] The content of the colorant is preferably in the range of 5 to 70% by mass, more preferably in the range of 20 to 50% by mass, based on the total mass of the solid content of the colored resin composition.

[0373] It is preferable to remove coarse particles of 5 μm or more, preferably coarse particles of 1 μm or more, more preferably coarse particles of 0.5 μm or more, and mixed dust from the colored resin composition using centrifugation, a sintered filter, a membrane filter, or the like.

[0374] The method for forming the colored pixels is preferably a photolithography method. A colored resin composition is prepared as a solvent-developable or alkali-developable colored resist. The prepared colored resin composition is preferably applied to an array substrate by a coating method such as spray coating, spin coating, slit coating, or roll coating so that the thickness after drying is within the range of 0.2 to 10 μm.

[0375] Methods for drying the coating film include a vacuum dryer, a convection oven, an IR oven, and a hot plate. The dried coating film is exposed to ultraviolet light through a mask with a predetermined pattern, which is placed in contact with the film or not. When checking the alignment mark with the mask, infrared light with a wavelength in the range of 750 to 1000 nm is used.

[0376] The UV-exposed coating film is then immersed in an organic solvent or alkaline developer, or sprayed with a developer using a spray or the like, to remove the uncured portions and form the desired pattern. Similar operations are repeated for other colors to form colored pixels of the color filter.

[0377] In the development, an aqueous solution of sodium carbonate, sodium hydroxide, or the like can be used as an alkaline developer. Also, organic alkalis such as dimethylbenzylamine and triethanolamine can be used. Furthermore, an antifoaming agent or a surfactant can be added to the developer. Examples of development methods include shower development, spray development, dip (immersion) development, and puddle (liquid puddle) development.

[0378] The thickness of the color filter is preferably in the range of 1 to 5 μm. When the thickness is 1 μm or more, the color purity of the display device can be further improved, and when the thickness is 5 μm or less, the brightness of the display device can be improved.

[0379] 6. Light-emitting element The display device of this embodiment has a light-emitting element. Note that "light-emitting element" is a general term for an electronic component that converts an electrical signal into an optical signal. In this embodiment, the light-emitting element is not particularly limited, and examples thereof include an organic electroluminescence (EL) element, an inorganic electroluminescence (EL) element, and a quantum dot light-emitting element.

[0380] In particular, from the viewpoints of flexibility and thinning, the light-emitting element is preferably an organic EL element. As the organic EL element, a conventionally known element can be used. One example of an organic EL element is composed of an electrode / electron transport layer / light-emitting layer / hole transport layer / transparent electrode.

[0381] 7. Manufacturing Method of Flexible Display Device The flexible display device of this embodiment can be manufactured by bonding a cover member, a color filter, and a light-emitting element together via an adhesive, etc. The cover member can be manufactured by bonding the flexible film, low-elasticity film, cured layer, etc., together via an adhesive, etc. The manufacturing method is not particularly limited, and a conventionally known method can be used.

[0382] The pressure-sensitive adhesive is not particularly limited, and examples thereof include rubber-based pressure-sensitive adhesives, acrylic pressure-sensitive adhesives, silicone-based pressure-sensitive adhesives, urethane-based pressure-sensitive adhesives, and vinyl alkyl ether-based pressure-sensitive adhesives. Examples of pressure-sensitive adhesives include polyvinyl alcohol-based pressure-sensitive adhesives, polyvinylpyrrolidone-based pressure-sensitive adhesives, polyacrylamide-based pressure-sensitive adhesives, and cellulose-based pressure-sensitive adhesives. Among these, it is preferable that the pressure-sensitive adhesive is an acrylic pressure-sensitive adhesive. Acrylic pressure-sensitive adhesives have excellent transparency and excellent adhesive properties (adhesion, cohesion, and adhesion). Acrylic pressure-sensitive adhesives also have excellent weather resistance, heat resistance, and the like. Here, "acrylic pressure-sensitive adhesive" refers to a pressure-sensitive adhesive containing an acrylic polymer as a base polymer.

[0383] 8. Flexible Display Device Product Example The flexible display device of this embodiment is characterized by having at least a cover member, a color filter, and a light-emitting element. In this embodiment, the term "display device" refers to a device having a display mechanism.

[0384] Examples of display devices include liquid crystal display devices, organic electroluminescence (EL) display devices, inorganic EL display devices, touch panel display devices, electron emission display devices, electronic paper, plasma display devices, projection display devices, and piezoelectric ceramic displays.

[0385] Examples of liquid crystal display devices include transmissive liquid crystal display devices, semi-transmissive liquid crystal display devices, reflective liquid crystal display devices, direct-view liquid crystal display devices, and projection liquid crystal display devices. Examples of electron emission display devices include field emission displays (FEDs) and surface field emission displays (SEDs). Electronic paper is a display device that uses electronic ink or electrophoretic elements. Examples of projection display devices include grating light valve (GLV) display devices and display devices having digital micromirror devices (DMDs).

[0386] These display devices may be display devices that display two-dimensional images, or may be stereoscopic display devices that display three-dimensional images.

[0387] In particular, the display device of the present embodiment is preferably an organic EL display device from the viewpoints of flexibility and thinning, and is preferably a touch panel display device from the viewpoint of having a cover member with excellent impact resistance.

[0388] An example of a flexible display device (flexible display) is a foldable display. A foldable display preferably has a structure in which a single continuous display can be folded in half when carried, thereby reducing the size by half and improving portability. Furthermore, a foldable display is preferably thin and lightweight.

[0389] The term "flexible" means that the display can be bent or curved, and "flexible or curved" includes a state in which the display is bent or curved. Specifically, the radius of curvature that the display can be bent or curved is preferably 10 mm or less, and more preferably 3 mm or less. In particular, if the radius of curvature is 3 mm or less, the display can be folded and used.

[0390] The display device of this embodiment has excellent impact resistance due to the cover member. Furthermore, the display device of this embodiment can obtain sufficient visibility without using a circular polarizer. In other words, the display device of this embodiment is thin and has excellent visibility.

[0391] Furthermore, the display device of this embodiment has excellent visibility even after the display is repeatedly folded. Specifically, image distortion is less likely to occur at the folding point of the display. Therefore, a mobile terminal device equipped with a foldable display can provide beautiful images, is highly functional, and is convenient in terms of portability and other factors.

[0392] The present disclosure will be specifically described below using examples, but the present disclosure is not limited thereto. In the examples, the terms "parts" and "%" are used, but unless otherwise specified, they represent "parts by mass" or "% by mass." Furthermore, the following examples were performed at room temperature (25°C) unless otherwise specified.

[0393] 1. Fabrication of Flexible Display Device (1) Fabrication of Flexible Film (1.1) Preparation of Constituent Materials (1.1.1) Preparation of Resins The following resins were prepared. Colorless and transparent polyimide (CPI-1): A colorless and transparent polyimide obtained by synthesizing the following acid anhydride 1 and diamine 1 was used. Colorless and transparent polyimide (CPI-2): A colorless and transparent polyimide obtained by synthesizing the following acid anhydride 2 and diamine 2 was used. Acyl cellulose (DAC): Substitution degree 2.45, synthesized by a known method. Acrylic resin (acrylic): polymethyl methacrylate "VB-7103" (manufactured by Mitsubishi Rayon Co., Ltd.) Cycloolefin resin (COP): "Arton RX4500" (manufactured by JSR Corporation) Acyl cellulose (CAP): "CAP-482-20" (manufactured by Eastman Chemical Co., Ltd.) Acyl cellulose (TAC): degree of substitution 2.90, synthesized by a known method.

[0394]

[0395] (1.1.2) Preparation of Filler (1.1.2.1) Preparation of Filler 1 The following components were placed in a 500 mL four-neck flask. The mixture was heated to 30°C (liquid temperature) while stirring. Ion-exchanged water: 130.0 g Acetic acid: 8.8 g (0.146 mol)

[0396] The following components were added dropwise to the resulting mixture over 30 minutes: While distilling off the isopropyl alcohol, the mixture was heated to 95°C (liquid temperature) and hydrolysis was carried out at 95°C for 30 minutes: 27.0 g (0.132 mol) of aluminum isopropoxide.

[0397] Next, this mixture was reacted in an autoclave with stirring at 150°C for 6 hours. After the reaction was carried out for the predetermined time, the reaction solution was cooled to room temperature (25°C) to obtain a solution (solid content: approximately 5 mass%) containing alumina filler precursor 1. Here, the average diameter and average length of alumina filler precursor 1 were 4 nm and 3000 nm (aspect ratio = 750), respectively.

[0398] The following components were mixed: 50.0 g of a solution containing alumina filler precursor 1, 50.0 g of methyl isobutyl ketone, and 0.4 g of dodecylbenzenesulfonic acid.

[0399] The resulting mixture was then dehydrated using a Dean-Stark apparatus to obtain a methyl isobutyl ketone dispersion of alumina filler precursor 1 whose surface was modified with dodecylbenzenesulfonic acid. The resulting alumina filler was designated Filler 1.

[0400] The minor axis (y) and major axis (x) of the obtained Filler 1 were 4 nm and 3,000 nm, respectively (aspect ratio (x / y) = 750). In this example, the minor axis and major axis of Filler 1 corresponded to the average diameter and average length, respectively.

[0401] (1.1.2.2) Preparation of Fillers 2 to 4 Fillers 2 to 4 were the same as Filler 1. By changing the stirring conditions of the film material described below, the aspect ratio of the filler finally contained in the flexible film changed, so they were distinguished from Filler 1 and named Fillers 2 to 4, respectively.

[0402] (1.1.2.3) Preparation of Filler 5 Alumina filler precursor 1 was prepared using the same procedure as in the preparation of Filler 1. Next, the following components were mixed: Solution containing alumina filler precursor 1: 50.0 g Methyl isobutyl ketone: 50.0 g Benzoic acid: 0.4 g

[0403] The resulting mixture was then dehydrated using a distillation apparatus to obtain a methyl isobutyl ketone dispersion of alumina filler precursor 1 whose surface was modified with benzoic acid. The resulting alumina filler was designated Filler 5.

[0404] The minor axis (y) and major axis (x) of the obtained Filler 5 were 4 nm and 3,000 nm, respectively (aspect ratio (x / y) = 750). In this example, the minor axis and major axis of Filler 5 corresponded to the average diameter and average length, respectively.

[0405] (1.1.2.4) Preparation of Filler 6 Alumina filler precursor 1 was prepared using the same procedure as for preparing Filler 1. Next, the following components were mixed: Solution containing alumina filler precursor 1: 50.0 g Cyclohexanone: 50.0 g Butoxyethyl acid phosphate "JP-506H" (manufactured by Johoku Chemical Industry Co., Ltd.): 0.4 g

[0406] The resulting mixture was then dehydrated using a Dean-Stark apparatus. A cyclohexanone dispersion of alumina filler precursor 1 surface-modified with butoxyethyl acid phosphate was obtained. Butoxyethyl acid phosphate was "JP-506H" (manufactured by Johoku Chemical Industry Co., Ltd., structural formula: (C ４ H ９ OCH ２ CH ２ O) ｎ -P(=O)-(OH) ３－ｎ ) where n is 1 or 2. The obtained alumina filler was designated as Filler 6.

[0407] The minor axis (y) and major axis (x) of the obtained filler 6 were 4 nm and 3,000 nm, respectively (aspect ratio (x / y) = 750). In this example, the minor axis and major axis of the filler 6 corresponded to the average diameter and average length, respectively.

[0408] (1.1.2.5) Preparation of Filler 7 The following components were placed in a 500 mL four-neck flask. The mixture was heated to 30°C (liquid temperature) while stirring: 130.0 g of ion-exchanged water, 8.8 g (0.146 mol) of acetic acid.

[0409] The following components were added dropwise to the resulting mixture over 30 minutes: While distilling off the ethanol, the mixture was heated to 95°C (liquid temperature) and hydrolysis was carried out at 95°C for 30 minutes: tetraethyl orthosilicate 30.0 g (0.142 mol)

[0410] Next, this mixture was reacted in an autoclave at 150°C for 6 hours while stirring. After the reaction had been carried out for the predetermined time, the reaction solution was cooled to room temperature (25°C) to obtain a solution (solid content: approximately 5% by mass) containing silica filler precursor 7. The average diameter and average length of the silica filler precursor 7 were 4 nm and 3,000 nm (aspect ratio = 750), respectively.

[0411] The following components were mixed: Solution containing silica filler precursor 7 50.0 g Methyl isobutyl ketone 50.0 g Dodecylbenzenesulfonic acid 0.4 g

[0412] The resulting mixture was dehydrated using a Dean-Stark apparatus to obtain a methyl isobutyl ketone dispersion of silica filler precursor 7, surface-modified with dodecylbenzenesulfonic acid. The resulting silica filler was designated Filler 7.

[0413] The minor axis (y) and major axis (x) of the obtained filler 7 were 4 nm and 3,000 nm, respectively (aspect ratio (x / y) = 750). In this example, the minor axis and major axis of the filler 7 corresponded to the average diameter and average length, respectively.

[0414] (1.1.2.6) Preparation of Filler 8 Silica filler precursor 7 was prepared using the same procedure as for preparing Filler 7. Next, the following components were mixed: Solution containing silica filler precursor 7: 50.0 g Methyl isobutyl ketone: 50.0 g Hexamethyldisilazane: 0.4 g

[0415] The resulting mixture was then dehydrated using a distillation apparatus to obtain a methyl isobutyl ketone dispersion of silica filler precursor 7, surface-modified with hexamethyldisilazane. The resulting silica filler was designated filler 8.

[0416] The minor axis (y) and major axis (x) of the obtained filler 8 were 4 nm and 3,000 nm, respectively (aspect ratio (x / y) = 750). In this example, the minor axis and major axis of the filler 8 corresponded to the average diameter and average length, respectively.

[0417] (1.1.2.7) Preparation of Filler 9 The following components were placed in a 500 mL four-neck flask. The mixture was heated to 30°C (liquid temperature) while stirring. Ion-exchanged water: 130.0 g Acetic acid: 8.8 g (0.146 mol)

[0418] The following components were added dropwise to the resulting mixture over 30 minutes: While distilling off the ethanol, the mixture was heated to 95°C (liquid temperature), and hydrolysis was carried out at 95°C for 30 minutes: tetraethyl orthotitanium 30.0 g (0.142 mol)

[0419] Next, this mixture was reacted in an autoclave at 150°C for 6 hours while stirring. After the reaction for the predetermined time, the reaction solution was cooled to room temperature (25°C) to obtain a solution containing a titania filler precursor (solid content: approximately 5% by mass). Here, the average diameter and average length of the titania filler precursor were 4 nm and 3,000 nm (aspect ratio = 750), respectively.

[0420] The following components were mixed: 50.0 g of a solution containing a titania filler precursor, 50.0 g of methyl isobutyl ketone, and 0.4 g of dodecylbenzenesulfonic acid.

[0421] The resulting mixture was dehydrated using a Dean-Stark apparatus. A methyl isobutyl ketone dispersion of a titania filler precursor surface-modified with dodecylbenzenesulfonic acid was obtained. The resulting titania filler was designated Filler 9.

[0422] The minor axis (y) and major axis (x) of the obtained filler 9 were 4 nm and 3,000 nm, respectively (aspect ratio (x / y) = 750). In this example, the minor axis and major axis of the filler 9 corresponded to the average diameter and average length, respectively.

[0423] (1.1.2.8) Preparation of Fillers 10 and 11 Using a known method, a strontium carbonate filler precursor and a barium carbonate filler precursor having an average diameter and an average length of 4 nm and 3,000 nm (aspect ratio = 750), respectively, were prepared.

[0424] Next, the following components were mixed: 50.0 g of each filler precursor solution, 50.0 g of methyl isobutyl ketone, and 0.4 g of glycerin stearate.

[0425] The resulting mixture was dehydrated using a distillation apparatus. A methyl isobutyl ketone dispersion of each filler precursor surface-modified with glycerin stearate was obtained. The resulting strontium carbonate filler was designated Filler 10, and the barium carbonate filler was designated Filler 11.

[0426] The minor axis (y) and major axis (x) of the obtained fillers 10 and 11 were 4 nm and 3,000 nm, respectively (aspect ratio (x / y) = 750). In this example, the minor axis and major axis of fillers 10 and 11 corresponded to the average diameter and average length, respectively.

[0427] (1.1.2.9) Preparation of filler 12 A commercially available cellulose nanofiber (CNF) product, "Cellenpia" (manufactured by Nippon Paper Industries Co., Ltd.), was prepared as the filler 12. The aspect ratio was 250.

[0428] (1.2) Film Production by Solution Casting Method (1.2.1) Dope Preparation (1.2.1.1) Preparation of Dope 1 Dope 1 for flexible film 1 was prepared by the following procedure. (Silicon dioxide dispersion) "Aerosil (registered trademark) R812" (manufactured by Nippon Aerosil Co., Ltd., average primary particle diameter 7 nm) 10.000 parts by mass Ethanol 90.000 parts by mass The above components were stirred and mixed in a dissolver for 30 minutes, and then dispersed using a Manton-Gaulin to prepare a silicon dioxide dispersion. The silicon dioxide dispersion was filtered through a polypropylene wound cartridge filter "TCW-PPS-1N" (manufactured by Advantec Toyo Co., Ltd.).

[0429] Dichloromethane 80.960 parts by mass Ethanol 7.040 parts by mass Silicon dioxide dispersion (10% by mass dispersion) 0.120 parts by mass Filler 1 (5% by mass dispersion) 19.200 parts by mass The above components were stirred at 23° C. for 3 minutes using a stirring blade.

[0430] Thereafter, the following components were added to the obtained mixture and stirred at 23°C for 4 hours. The obtained mixture was filtered using "Azumi Filter Paper No. 24" (manufactured by Azumi Filter Paper Co., Ltd.) to prepare Dope 1. The content of silicon dioxide was 0.1 parts by mass relative to 100 parts by mass of acyl cellulose. The content of Filler 1 was 8 parts by mass relative to 100 parts by mass of acyl cellulose. Acyl cellulose (DAC) 12,000 parts by mass

[0431] (1.2.1.2) Preparation of Dopes 2 to 4, 6 to 17, 19 to 25, and 27 Dopes 2 to 4, 6 to 17, 19 to 25, and 27 for each flexible film were prepared using the same procedure as for Dope 1, except that the resin and filler were changed as shown in Tables I to IV, and the stirring conditions were changed. For Flexible Films 8 to 10, the stirring conditions for Flexible Film 1 (3 minutes with a stirring blade) were changed as follows: Flexible Film 8: 10 minutes with ultrasonic waves Flexible Film 9: 3 minutes with ultrasonic waves Flexible Film 10: 1 minute with a stirring blade

[0432] (1.2.1.3) Preparation of Dope 18 <Preparation of Rubber Particles (Graft Copolymer) R1> The following components were charged into an 8 L polymerization apparatus equipped with a stirrer to prepare Solution I: Deionized water 180.000 parts by mass Polyoxyethylene lauryl ether phosphate 0.002 parts by mass Boric acid 0.473 parts by mass Sodium carbonate 0.047 parts by mass Sodium hydroxide 0.008 parts by mass

[0433] After the inside of the polymerization apparatus was thoroughly purged with nitrogen gas, the inside temperature was raised to 80° C., and the following components were added: potassium persulfate (2% by mass aqueous solution) 0.021 part by mass

[0434] Next, the following components were mixed to prepare a monomer mixture (c'): 84.600 parts by mass of methyl methacrylate (methyl methacrylate), 5.900 parts by mass of n-butyl acrylate (n-butyl acrylate), 7.900 parts by mass of styrene, 0.500 parts by mass of allyl methacrylate (allyl methacrylate), and 1.100 parts by mass of n-octyl mercaptan.

[0435] The following components were mixed to prepare a mixed solution: Monomer mixture (c') 21.000 parts by mass Polyoxyethylene lauryl ether phosphate 0.070 parts by mass This mixed solution was continuously added to the above solution I over 63 minutes. The polymerization reaction was continued for a further 60 minutes to obtain a hard polymer (crosslinked polymer (c)) contained in the innermost part.

[0436] Thereafter, the following components were added to prepare Solution II: 0.021 parts by mass of sodium hydroxide (2% by mass aqueous solution), 0.062 parts by mass of potassium persulfate (2% by mass aqueous solution).

[0437] Next, a monomer mixture (a') consisting of the following components was prepared: n-butyl acrylate (n-butyl acrylate) 80.000 parts by mass, styrene 18.500 parts by mass, allyl methacrylate (allyl methacrylate) 1.500 parts by mass.

[0438] The following components were mixed to prepare a mixed solution: Monomer mixture (a') 39.000 parts by mass Polyoxyethylene lauryl ether phosphate 0.250 parts by mass This mixed solution was continuously added to Solution II over 117 minutes.

[0439] Thereafter, the following components were added: Potassium persulfate (2% by mass aqueous solution) 0.012 parts by mass The polymerization reaction was continued for 120 minutes to obtain a soft layer. The glass transition temperature (Tg) of the soft layer was calculated by averaging the glass transition temperatures of the homopolymers of each monomer constituting the acrylic rubber-like polymer (a) according to the composition ratio. The glass transition temperature (Tg) of the soft layer was -30°C.

[0440] Thereafter, the following components were added to prepare Solution III: Potassium persulfate (2% by weight aqueous solution) 0.040 parts by weight

[0441] The following components were mixed to prepare a monomer mixture (b'): 97.500 parts by mass of methyl methacrylate (methyl methacrylate), 2.500 parts by mass of n-butyl acrylate (n-butyl acrylate).

[0442] The following monomer mixture (b') was continuously added to Solution III over 78 minutes. The polymerization reaction was continued for 30 minutes to obtain a methacrylic polymer (b). Monomer mixture (b') 26.100 parts by mass

[0443] The resulting methacrylic polymer (b) was poured into a warm 3% by mass aqueous solution of sodium sulfate to cause salting out and coagulation, and then the polymer was repeatedly dehydrated and washed, and then dried to obtain three-layer structure acrylic graft copolymer particles (rubber particles) R1.

[0444] When measured using a zeta potential-particle size measurement system "ELSZ-2000ZS" (manufactured by Otsuka Electronics Co., Ltd.), the average particle size of the obtained rubber particles R1 was 200 nm. The glass transition temperature (Tg) of the rubber particles R1 was -30°C. The aspect ratio of the rubber particles R1 was less than 110.00.

[0445] Dope 18 for flexible film 18 was prepared in the same manner as in the preparation of dope 1, except that the resin and filler were changed as shown in Tables II and IV and rubber particles were added. The content of rubber particles R1 was 20 parts by mass relative to 100 parts by mass of the acrylic resin.

[0446] (1.2.1.4) Preparation of Dope 26 Dope 26 for flexible film 26 was prepared in the same manner as in the preparation of dope 18, except that the content of rubber particles was changed to 50 parts by mass per 100 parts by mass of acrylic resin.

[0447] (1.2.2) Formation of Flexible Film (1.2.2.1) Formation of Flexible Film 1 Using a belt casting apparatus, the dope 1 was uniformly cast onto a stainless steel band support to form a cast film. The solvent was evaporated on the stainless steel band support until the residual solvent amount in the cast film reached 100%, and the cast film was peeled off from the stainless steel band support. The cast film was heated at 35°C to evaporate the solvent. The cast film from which the solvent had evaporated was slit into a width of 1.65 m, held in place by a tenter, and dried at a drying temperature of 160°C. The drying temperature here was also the heat treatment temperature and the stretching temperature. The stretching ratio in the transverse direction (TD) was 5%.

[0448] The residual solvent content of the film (cast film) at the start of drying was 20%. The film was then dried for 15 minutes while being transported by multiple rolls in a drying apparatus at 120°C, and then knurling was performed on both ends of the film to a width of 15 mm and a height of 10 μm. The film was wound around a core to obtain Flexible Film 1. The residual solvent content of Flexible Film 1 was 0.2% by mass, the thickness was 50 μm, and the number of windings was 6,000 m.

[0449] (1.2.2.2) Formation of Flexible Films 2 to 4, 6 to 22, and 25 to 27 Flexible films 2 to 4, 6 to 22, and 25 to 27 were obtained in the same manner as in the formation of flexible film 1, except that dope 1 was changed to dopes 2 to 4, 6 to 22, and 25 to 27, respectively.

[0450] (1.2.2.3) Formation of flexible film 23 The casting film from which the solvent had evaporated was slit into a width of 1.65 m, and the width was held by a tenter, and dried at a drying temperature of 150° C. Except for this, a flexible film 23 was obtained in the same procedure as in the formation of the flexible film 1.

[0451] (1.2.2.4) Formation of Flexible Film 24 A flexible film 24 was obtained in the same manner as in the formation of the flexible film 1, except that the stretching ratio in the transverse direction (TD) was set to 3%.

[0452] (1.3) Film Production by Melt Casting Method (1.3.1) Pellets Production The following components were mixed for 3 hours using a vacuum Nauta mixer, and then dried. The mixing temperature was 80°C and the pressure was 1.33 x 10 ２ The pressure was set to Pa (1 Torr). Acyl cellulose 100.0 parts by mass Filler 1 5.0 parts by mass "Irganox 1010" (manufactured by Ciba Specialty Chemicals Inc.) 0.5 parts by mass "Irgafos P-EPQ" (manufactured by Ciba Specialty Chemicals Inc.) 0.3 parts by mass "Sumilizer GS" (manufactured by Sumitomo Chemical Co., Ltd.) 0.2 parts by mass The acyl cellulose had been dried at 80°C for 6 hours (water content 200 ppm), had an acyl group substitution degree of 2.45, and had a number average molecular weight of 60,000.

[0453] The resulting mixture was melt-mixed at 235° C. using a twin-screw extruder and pelletized. In this process, an all-screw screw was used without a kneading disk in order to suppress heat generation due to shear during kneading.

[0454] A vacuum was applied through the vent hole to remove volatile components generated during kneading. A dry nitrogen gas atmosphere was created between the feeder and hopper supplying the extruder, and the extruder die and the cooling tank to prevent the resin from absorbing moisture.

[0455] (1.3.2) Formation of Flexible Film (1.3.2.1) Formation of Flexible Film 5 FIG. 7 is a schematic diagram of a manufacturing apparatus 80 for manufacturing a flexible film by a melt casting method.

[0456] The first cooling roll 86-1 and the second cooling roll 86-2 were made of stainless steel and had a diameter of 40 cm, and their surfaces were hard chrome plated. Temperature-regulating oil (cooling fluid) was circulated inside the rolls to control the roll surface temperature.

[0457] The touch roll 85 was an elastic touch roll with a diameter of 20 cm. The inner and outer cylinders were made of stainless steel, and the surface of the outer cylinder was hard chrome plated. The thickness of the outer cylinder was 2 mm, and the surface temperature of the touch roll was controlled by circulating temperature-regulating oil (cooling fluid) in the space between the inner and outer cylinders.

[0458] Pellets (moisture content: 50 ppm) were melted at a melting temperature Tm and extruded into a film form from a die 84 onto a first cooling roll 86-1 using a single-screw extruder. The extruded cast film was cooled by a first cooling roll 86-1 and a second cooling roll 86-2, and finally a 40 μm-thick cast film 87 was obtained as a flexible film 5. The surface temperature Tr1 of the first cooling roll 86-1 was set to 90°C. A T-die with a lip clearance of 1.5 mm and an average lip surface roughness Ra of 0.01 μm was used for the die 84. A touch roll 85 was used to press the cast film on the first cooling roll 86-1. The pressure P during pressing was set to 1 kg / cm.

[0459] The temperature of the cast film on the touch roll 85 side during pressing was 180°C ± 1°C. Here, "the temperature of the cast film on the touch roll 85 side during pressing" refers to the temperature of the cast film at the position on the first cooling roll 86-1 where the touch roll 85 is in contact. This temperature can be measured using a non-contact thermometer as the average value of the surface temperatures of the cast film measured at 10 points in the width direction from a distance of 50 cm with the touch roll 85 retracted and no touch roll is present.

[0460] The glass transition temperature (Tg) of the cast film was 136° C. The surface temperature Tr0 of the touch roll 85 was 90° C., and the surface temperature Tr2 of the second cooling roll 86-2 was 90° C.

[0461] The surface temperatures Tr0, Tr1, and Tr2 of each roll were determined as the average values ​​of the roll surface temperatures measured at 10 points in the width direction using a non-contact thermometer at a position 90° before the position where the cast film first contacts each roll in the direction of rotation.

[0462] The casting film was adjusted so that the contact time between each roll and the casting film was the same, which was 1.2 seconds.

[0463] The peripheral speeds r1 and r2 of the first cooling roll 86-1 and the second cooling roll 86-2 can be changed independently, and the ratio (r2 / r1) is set to 1.

[0464] The pressing elastic roll 81 was a stainless steel roll (diameter 100 mm) with an inner cylinder of a dielectric heating system, and a 2 mm thick silicone rubber was wrapped around its surface. The surface temperature T of the pressing elastic roll 81 was set to 100°C. From the unwinding section 82 to the winding section 83, the pressing elastic roll 1 was pressed against the touch roll 85 at a pressure of 1 kg / cm via a 2 mm thick nonwoven fabric "Bencotto" (manufactured by Ozu Sangyo Co., Ltd.). The nonwoven fabric was driven in the rotation direction opposite to that of the touch roll 85 at a speed of 150 mm / hour. As a result, a flexible film 5 having a thickness of 40 μm was obtained.

[0465] (1.3.2.2) Formation of flexible film 28 The pressure P when pressing the cast film on the first cooling roll 86-1 using the touch roll 85 was set to 5 kg / cm. In addition, the surface temperature T of the pressing elastic roll 81 was set to 50°C. Other than these, the flexible film 28 was formed using the same procedure as for forming the flexible film 5. As a result, a flexible film 28 having a thickness of 200 μm was obtained.

[0466] Tables I to IV below show the structures of flexible films 2 to 28. Note that a thin glass film was used instead of the flexible film in Comparative Example 3. Regarding the filler, alumina, silica, and titania are metal oxides, and strontium carbonate and barium carbonate are metal salts.

[0467] "-" in the table indicates that it is not applicable. "Rubber particles" in the table indicates the content of rubber particles relative to 100 parts by mass of resin. That is, in Example 18, the content of rubber particles was 20 parts by mass relative to 100 parts by mass of resin. In Example 26, the content of rubber particles was 50 parts by mass relative to 100 parts by mass of resin. "Content" for filler in the table indicates the content of filler relative to 100 parts by mass of resin.

[0468] The aspect ratio of the filler was measured by the method described above. Note that the filler may be broken during the manufacturing process of the flexible film, and the aspect ratio of the filler in the flexible film is smaller than the aspect ratio of the filler immediately after its production.

[0469]

[0470]

[0471]

[0472]

[0473] In flexible film 5, the manufacturing method and filler content were changed compared to flexible film 1, thereby changing the degree of orientation of the resin and filler.

[0474] In flexible films 6 and 7, the orientation degree of the resin and filler was changed by changing the filler content compared to flexible film 1. In flexible film 8, the orientation degree of the resin and filler was changed by changing the filler content and aspect ratio compared to flexible film 1. The aspect ratio of the filler was changed by changing the stirring conditions during dope preparation. In flexible films 9 and 10, the orientation degree of the resin and filler was changed by changing the filler aspect ratio compared to flexible film 1. The aspect ratio of the filler was changed by changing the stirring conditions during dope preparation.

[0475] In flexible films 11 and 12, the degree of orientation of the resin and filler was changed by changing the modifying group of the filler compared to flexible film 1. In flexible films 13 and 14, the degree of orientation of the resin and filler was changed by changing the metal type of the filler compared to flexible film 1. In flexible films 15 and 16, the degree of orientation of the resin and filler was changed by changing the type and modifying group of the filler compared to flexible film 1.

[0476] In flexible film 17, the degree of orientation of the resin and filler was changed by changing the type of filler compared to flexible film 1. In flexible film 18, the degree of orientation of the resin and filler was changed by changing the type of resin and the content of rubber particles compared to flexible film 1. In flexible films 19 to 22, the degree of orientation of the resin and filler was changed by changing the type of resin compared to flexible film 1.

[0477] In flexible film 23, the degrees of orientation of the resin and filler were changed by changing the manufacturing conditions (drying temperature during stretching) compared to flexible film 1. In flexible film 24, the degrees of orientation of the resin and filler were changed by changing the manufacturing conditions (stretching ratio) compared to flexible film 1. In flexible film 25, the degrees of orientation of the resin and filler were changed by changing the type of resin compared to flexible film 1. In flexible film 26, the degrees of orientation of the resin and filler were changed by changing the type of resin and the content of rubber particles compared to flexible film 1. In flexible film 27, the degrees of orientation of the resin and filler were changed by changing the type of resin and the type of filler compared to flexible film 1. In flexible film 28, the degrees of orientation of the resin and filler were changed by changing the manufacturing conditions compared to flexible film 5.

[0478] (2) Preparation of Low Elasticity Film 1 (2.1) Preparation of Support A polyethylene terephthalate (PET) film "TN100" (manufactured by Toyobo Co., Ltd.) was prepared as a support. The film had a release layer containing a non-silicone release agent and a film thickness of 38 μm.

[0479] (2.2) Preparation of Dope The following components were mixed to obtain a dope: 800.000 parts by mass of methylene chloride (boiling point 41°C), 80.000 parts by mass of acrylic resin, 20.000 parts by mass of the rubber particles R1, and 20.000 parts by mass of dispersant: sodium polyoxyethylene lauryl ether phosphate (molecular weight 332). The amount added to the low-elasticity film was 0.006% by mass.

[0480] (2.3) Formation of Low Elasticity Film The prepared dope was coated on the release layer of the support. The coating was performed using a die by a back coating method. Then, the dope on the support was dried in the following drying step to obtain a low elasticity film 1 having a thickness of 50 μm.

[0481] (Initial drying) 1st step: 1 minute at 40°C 2nd step: 1 minute at 70°C 3rd step: 1 minute at 100°C 4th step: 2 minutes at 130°C (Post-drying) 5th step: 15 minutes at 110°C

[0482] (3) Preparation of cured layer (3.1) Preparation of cured layer 1 (3.1.1) Preparation of cured layer-forming composition 1 The following components were placed in a UV-shielded container and stirred at room temperature for 2 hours to prepare cured layer-forming composition 1. Hollow silica particles "JX-1009SIV" (manufactured by JGC Catalysts and Chemicals Co., Ltd.) 5.000 parts by mass Pentaerythritol tri / tetraacrylate "NK Ester A-TMM-3L" (manufactured by Shin-Nakamura Chemical Co., Ltd.) 96.000 parts by mass 2-methyl-1 [4- (methylthio) phenyl] -2- morpholinopropan-1-one "Irgacure (registered trademark) 907" (manufactured by BASF Japan Ltd.) 3.000 parts by mass Reactive silicone "Silaplane (registered trademark) FM0725" (manufactured by Chisso Corporation) 0.100 parts by mass Methyl isobutyl ketone 75.000 parts by mass Cyclohexanone 20.000 parts by mass γ-butyrolactone "JX-1009SIV" used as hollow silica particle dispersion 1 was a methyl isobutyl ketone sol with a solid content of 20% by mass and a refractive index of 1.36. "NK Ester A-TMM-3L" used as pentaerythritol tri / tetraacrylate had a refractive index of 1.49.

[0483] (3.1.2) Formation of Cured Layer 1 The obtained cured layer-forming composition 1 was filtered through a polypropylene filter with a pore size of 1 μm and applied to the viewing side of each of the flexible films using an extrusion coater. The coated film was dried at a temperature of 80°C. Thereafter, the coated film was cured using an ultraviolet lamp while purging with nitrogen so that the atmosphere had an oxygen concentration of 0.2% by volume or less. The ultraviolet irradiation conditions were an illuminance of 100 mW / cm ２ , irradiation amount 0.3J / cm ２ In this manner, a cured layer 1 having a dry thickness of 3 μm was formed on each flexible film.

[0484] (3.2) Preparation of cured layer 2 (3.2.1) Preparation of polymer silane coupling agent coated silica (1) The following components were added to a container, and after replacing the atmosphere with N2 gas, the container was heated at 80°C for 3 hours to prepare a polymer silane coupling agent. The molecular weight of the obtained polymer silane coupling agent was 16,000. The molecular weight was measured using a gel permeation chromatography device. Methyl methacrylate "Light Ester M" (manufactured by Kyoeisha Chemical Co., Ltd.) 30 mL 3-mercaptopropyltrimethoxysilane "KBM-803" (manufactured by Shin-Etsu Chemical Co., Ltd.) 1 mL Solvent: tetrahydrofuran 100 mL Polymerization initiator: azoisobutyronitrile "AIBN" (manufactured by Kanto Chemical Co., Ltd.) 50 mg

[0485] Next, silica sol (manufactured by JGC Catalysts and Chemicals Industries, Ltd.) was subjected to ion exchange with an ion exchange resin. After that, the water was replaced with ethanol as the solvent by an ultrafiltration membrane method, and 100 g of an ethanol dispersion of silica fine particles (SiO ２ The silica sol (manufactured by JGC Catalysts and Chemicals Industries, Ltd.) was prepared using Si-45P, SiO ２ The concentration was 30% by mass, the average particle size was 45 nm, and the dispersion medium was water.

[0486] The following components were added to a container and dispersed: 100.00 g of ethanol dispersion of silica fine particles, 1.50 g of polymer silane coupling agent, and 20.00 g (25 mL) of acetone. The following components were added to the dispersion and stirred at room temperature for 30 hours to allow the polymer silane coupling agent to be adsorbed onto the silica fine particles: 0.02 g of aqueous ammonia (concentration: 29.8% by mass).

[0487] Silica particles having an average particle size of 5 μm were added to the obtained dispersion, and the mixture was stirred for 2 hours to adsorb the unadsorbed polymer silane coupling agent in the solution onto the silica particles. Then, the unadsorbed silica particles having an average particle size of 5 μm and adsorbing the polymer silane coupling agent were removed by centrifugation.

[0488] 1000g of ethanol is added to the dispersion of silica particles adsorbed with polymer silane coupling agent, and silica particles are precipitated, separated, and dried under reduced pressure.The obtained particles are then dried at 25°C for 8 hours to obtain polymer silane coupling agent coated silica (1).The average particle diameter of the obtained polymer silane coupling agent coated silica (1) is 57nm.The average particle diameter is measured by a laser particle diameter measuring device.

[0489] (3.2.2) Preparation of cured layer-forming composition 2 The following components were placed in a UV-shielded container and stirred at room temperature for 2 hours to prepare cured layer-forming composition 2. Pentaerythritol tri / tetraacrylate "NK Ester A-TMM-3L" (manufactured by Shin-Nakamura Chemical Co., Ltd.) 40.000 parts by mass 1-hydroxycyclohexan-1-yl phenyl ketone "Irgacure (registered trademark) 184" (manufactured by BASF Japan Ltd.) 6.000 parts by mass Polymer silane coupling agent-coated silica (1) 60.000 parts by mass Polyether-modified silicone "BYK-UV3510" (manufactured by BYK Japan Ltd.) 1.000 parts by mass Propylene glycol monomethyl ether 50.000 parts by mass Methyl acetate 50.000 parts by mass

[0490] (3.2.3) Formation of Cured Layer 2 The obtained cured layer-forming composition 2 was filtered through a polypropylene filter with a pore size of 1 μm and applied to the viewing side of each of the flexible films using an extrusion coater. The coated film was dried at a temperature of 50°C. Thereafter, the coated film was cured using an ultraviolet lamp while purging with nitrogen so that the atmosphere had an oxygen concentration of 1.0% by volume or less. The ultraviolet irradiation conditions were an illuminance of 100 mW / cm ２ , irradiation amount 0.3J / cm ２ In this manner, a cured layer 2 having a dry thickness of 3 μm was formed on each flexible film.

[0491] (3.3) Preparation of Cured Layer 3 (3.3.1) Preparation of Cured Layer-Forming Composition 3 The following components were placed in a UV-shielded container and stirred at room temperature for 2 hours to prepare Cured Layer-Forming Composition 3. Pentaerythritol triacrylate 20.000 parts by mass Pentaerythritol tetraacrylate 50.000 parts by mass Dipentaerythritol hexaacrylate 30.000 parts by mass Dipentaerythritol pentaacrylate 30.000 parts by mass 1-hydroxycyclohexan-1-yl phenyl ketone "Irgacure (registered trademark) 184" (manufactured by BASF Japan Ltd.) 5.000 parts by mass Fluorine-siloxane graft polymer I (35% by mass) 5.000 parts by mass Silica particles "Seahoster KEP-50" (average particle size: 0.47 to 0.61 μm, manufactured by Nippon Shokubai Co., Ltd.) 24.300 parts by mass Propylene glycol monomethyl ether 20.000 parts by mass Methyl acetate 40.000 parts by mass Methyl ethyl ketone 60,000 parts by mass The fluorine-siloxane graft polymer I was synthesized by the method described in paragraphs 0299 ​​to 0302 of WO 2011 / 158626.

[0492] (3.3.2) Formation of Cured Layer 3 The obtained cured layer-forming composition 3 was filtered through a polypropylene filter with a pore size of 0.4 μm and applied to the viewing side of each of the flexible films using an extrusion coater. The coated film was dried at a temperature of 70°C. Thereafter, the coated film was cured using an ultraviolet lamp while purging with nitrogen so that the atmosphere had an oxygen concentration of 1.0% by volume or less. The ultraviolet irradiation conditions were an illuminance of 300 mW / cm ２ , irradiation amount 0.3J / cm ２ The cured coating film was then heat-treated at 130° C. for 5 minutes while being conveyed at a conveying tension of 300 N / m. As a result, a cured layer 3 having a dry thickness of 3 μm was formed on each flexible film.

[0493] (4) Preparation of Adhesive Layer 1 (4.1) Preparation of UV-Curable Acrylic Adhesive Composition (a-1) A monomer mixture consisting of the following components was prepared: 2-Ethylhexyl acrylate (2EHA) 78.000 parts by mass N-Vinyl-2-pyrrolidone (NVP) 18.000 parts by mass 2-Hydroxyethyl acrylate (HEA) 4.000 parts by mass

[0494] The following components were added as photopolymerization initiators: 1-hydroxycyclohexyl phenyl ketone 0.035 parts by mass 2,2-dimethoxy-1,2-diphenylethan-1-one 0.035 parts by mass The following commercially available photopolymerization initiators were used: 1-hydroxycyclohexyl phenyl ketone: "Omnirad (registered trademark) 184" (having an absorption band in the wavelength range of 200 to 370 nm, manufactured by IGM Resins B.V.) 2,2-dimethoxy-1,2-diphenylethan-1-one: "Omnirad (registered trademark) 651" (having an absorption band in the wavelength range of 200 to 380 nm, manufactured by IGM Resins B.V.)

[0495] The mixture was then irradiated with ultraviolet light until the viscosity reached approximately 20 Pa s, yielding a prepolymer composition (polymerization rate: 8%) in which a portion of the monomer components had polymerized. The viscosity was measured using a BH viscometer No. 5 rotor at a rotation speed of 10 rpm and a measurement temperature of 30°C.

[0496] Next, the following components were added to the prepolymer composition and mixed to obtain an acrylic pressure-sensitive adhesive composition: 0.150 parts by mass of hexanediol diacrylate (HDDA) 0.300 parts by mass of silane coupling agent "KBM-403" (manufactured by Shin-Etsu Chemical Co., Ltd.)

[0497] The following components were added to the obtained acrylic pressure-sensitive adhesive composition and stirred to obtain an ultraviolet-curable acrylic pressure-sensitive adhesive composition (a-1): 2,4-bis-[{4-(4-ethylhexyloxy)-4-hydroxy}-phenyl]-6-(4-methoxyphenyl)-1,3,5-triazine, dissolved in n-butyl acrylate to a solids concentration of 15% by mass, and added: 1.400 parts by mass Bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide: 0.200 parts by mass Note that the following commercially available products were used. 2,4-bis-[{4-(4-ethylhexyloxy)-4-hydroxy}-phenyl]-6-(4-methoxyphenyl)-1,3,5-triazine: "Tinosorb (registered trademark) S" (manufactured by BASF Japan Ltd.) Bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide: "Omnirad (registered trademark) 819" (manufactured by IGM Resins B.V.) has an absorption band in the wavelength range of 200 to 450 nm.

[0498] (4.2) Formation of Adhesive Layer 1 The obtained ultraviolet-curable acrylic adhesive composition (a-1) was applied onto the surface of a release film so that the thickness after curing would be 30 μm, and further, a release film was attached to the surface. Thereafter, illuminance: 6.5 mW / cm ２ , cumulative light amount: 1500 mJ / cm ２ The composition was cured by irradiating it with ultraviolet light under the conditions of (a) and (b), and the release film was peeled off to form an adhesive layer 1.

[0499] (5) Preparation of cover member (5.1) Preparation of cover member 1 The various films obtained above were bonded together in the following order: cured layer, flexible film 1, adhesive layer 1, low-elasticity film 1, adhesive layer 1, to obtain cover member 1.

[0500] (5.2) Preparation of cover members 2 to 29 Various films were changed as shown in Tables V and VI, and the films were laminated in the order of each cured layer, each flexible film, adhesive layer 1, low-elasticity film 1, and adhesive layer 1 to obtain cover members 2 to 29. For cover member 29, a thin glass film was used instead of the flexible film. The cover member number corresponds to the display device number.

[0501] (6) Preparation of Color Filters (6.1) Preparation of Resin Solutions (A-1) and (A-2): 800.000 parts by mass of cyclohexanone was placed in a reaction vessel, heated while injecting nitrogen gas into the vessel, and a mixture of the following monomers and thermal polymerization initiator was added dropwise to carry out a polymerization reaction. After dripping, the mixture was thoroughly heated. 2.000 parts by mass of thermal polymerization initiator dissolved in 50.000 parts by mass of cyclohexanone was added, and the reaction was continued to obtain an acrylic resin solution. Cyclohexanone was added to this resin solution so that the nonvolatile content was 20% by mass, and an acrylic resin solution was prepared. This was designated as resin solution (A-1). The weight average molecular weight of the acrylic resin was about 30,000.

[0502] 800.000 parts by mass of cyclohexanone was placed in a reaction vessel, and the vessel was heated while injecting nitrogen gas. A mixture of the following monomers and thermal polymerization initiator was added dropwise to carry out a polymerization reaction. 55.000 parts by mass of styrene, 65.000 parts by mass of methacrylic acid, 65.000 parts by mass of methyl methacrylate, 65.000 parts by mass of benzyl methacrylate, 60.000 parts by mass of thermal polymerization initiator, 15.000 parts by mass of chain transfer agent, 3.000 parts by mass of chain transfer agent. After dripping, the mixture was heated sufficiently and 2.000 parts by mass of thermal polymerization initiator dissolved in 500.000 parts by mass of cyclohexanone was added. The reaction was continued to obtain an acrylic resin solution. Cyclohexanone was added to this resin solution so that the solids content was 30% by mass to prepare an acrylic resin solution, designated resin solution (A-2). The weight average molecular weight of the acrylic resin was approximately 20,000.

[0503] (6.2) Preparation of Pigment-Containing Resin Composition <Red Resin Composition> A mixture of the following components was stirred and mixed to become uniform, and then filtered through a 5 μm filter to obtain a red resin composition. Red pigment: C.I. Pigment Red 254 39.990 parts by mass Red pigment: C.I. Pigment Red 177 4.500 parts by mass Yellow pigment: C.I. Pigment Yellow 150 5.400 parts by mass Dispersant: "Disperbyk-303" (manufactured by BYK-Chemie Co., Ltd.) 1.000 parts by mass Resin solution (A-1) 10.130 parts by mass Polyfunctional polymerizable monomer 1.900 parts by mass Photopolymerization initiator: "Irgacure-OXE02" (manufactured by Ciba-Geigy Co., Ltd.) 0.200 parts by mass Sensitizer 0.290 parts by mass Cyclohexanone 36.590 parts by mass

[0504] <Green Resin Composition> A mixture of the following components was stirred and mixed to become uniform, and then filtered through a 5 μm filter to obtain a green resin composition. Green pigment: C.I. Pigment Green 58 40.900 parts by mass Yellow pigment: C.I. Pigment Yellow 150 8.370 parts by mass Dispersant 1.000 parts by mass Resin solution (A-1) 4.110 parts by mass Resin solution (A-2) 4.110 parts by mass Polyfunctional polymerizable monomer 2.000 parts by mass Photopolymerization initiator 0.200 parts by mass Photosensitizer 0.290 parts by mass Cyclohexanone 39.020 parts by mass

[0505] <Blue Resin Composition> A mixture of the following composition was then stirred and mixed to become uniform, and then filtered through a 5 μm filter to obtain a blue resin composition. Blue pigment: C.I. Pigment Blue 15 20.000 parts by mass Dispersant 1.000 parts by mass Resin solution (A-1) 2.820 parts by mass Resin solution (A-2) 1.720 parts by mass Polyfunctional polymerizable monomer 7.730 parts by mass Photopolymerization initiator 0.940 parts by mass Photosensitizer 0.460 parts by mass Cyclohexanone 33.760 parts by mass

[0506] <Black Resin Composition> A mixture of the following components was stirred and mixed to become uniform, and then filtered through a 5 μm filter to obtain a black resin composition: Photopolymerization initiator 5.300 parts by mass, Acrylic resin 10.700 parts by mass, Monomer having an ethylenically unsaturated double bond 4.400 parts by mass, Black pigment dispersion 23.400 parts by mass, Propylene glycol monomethyl ether acetate 56.200 parts by mass

[0507] The black pigment dispersion was prepared by the following method. A mixture of the following composition was stirred and mixed for 30 minutes using a dissolver, and then dispersed for 30 minutes using an ultrasonic disperser to prepare a dispersion. The obtained dispersion was filtered through a polypropylene wound cartridge filter "TCW-1N-PPS" (manufactured by Advantec Toyo Co., Ltd.) to obtain a black pigment dispersion. Carbon black "#950" (manufactured by Mitsubishi Chemical Corporation) 10.000 parts by mass Methyl ethyl ketone 90.000 parts by mass

[0508] (6.3) Formation of Black Matrix The above black colored composition was uniformly applied onto a glass substrate by spray coating and dried. Then, by photolithography, it was exposed to ultraviolet light through a photomask having a desired light-shielding pattern. The UV-unexposed portion was washed away by shower development using a developer containing sodium carbonate to form a desired pattern. After development, the substrate was thoroughly rinsed with water and dried, and then heat-treated at 230°C for 60 minutes to harden the pattern, forming a black matrix.

[0509] (6.4) Formation of Colored Pixels and Colored Pixel Stack Spacers The red resin composition was uniformly applied by spray coating onto a glass substrate on which a black matrix had been formed, and then dried. Next, by photolithography, the regions where red pixels were to be formed and the regions where colored pixel stack spacers were to be formed were exposed to ultraviolet light through a photomask having the desired light-shielding pattern. The unexposed portions were washed away by shower development using a developer containing sodium carbonate, forming the desired pattern. After development, the substrate was thoroughly rinsed with water and dried, and then heat-treated at 230°C for 20 minutes to harden the pattern.

[0510] Using the above green resin composition, a green pattern was formed in the region where a green pixel was to be formed and in the region where a colored pixel stack spacer was to be formed, in the same process as in the formation of the red pattern.

[0511] Using the above blue resin composition, a blue pattern was formed in the area where blue pixels were to be formed and in the area where colored pixel stack spacers were to be formed, using the same process as for forming the red pattern. In this case, the blue color at the top of the colored pixel stack spacer covered and integrated the red color of the first stacked layer and the green color of the second stacked layer, thereby forming a colored layer and colored pixel stack spacer consisting of three colors: red (R), green (G), and blue (B). The aperture ratio of the resulting color filter was 77%.

[0512] (7) Fabrication of Light-Emitting Element (Organic Electroluminescence Element) A bottom-emission type organic EL element was fabricated according to the following method.

[0513] (7.1) Preparation of a first substrate with a gas barrier layer: A 50 μm thick varnish was spin-coated onto a carrier glass with a thickness of 0.7 mm. Then, post-baking was performed at 200° C. for 20 minutes to obtain a first substrate as a flexible film substrate with a size of 30 cm × 40 cm.

[0514] Using a wire bar, the following polysilazane-containing coating solution was applied to a varnish substrate so that the average film thickness after drying would be 300 nm. The coating film was dried by heat treatment in an atmosphere of 85°C temperature and 55% RH for 1 minute. Next, the coating film was held in an atmosphere of 25°C temperature and 10% RH humidity (dew point temperature -8°C) for 10 minutes for dehumidification treatment, thereby forming a polysilazane-containing layer on the varnish substrate.

[0515] Next, the varnish substrate on which the polysilazane-containing layer was formed was fixed on the moving stage of an excimer irradiation device "MECL-M-1-200" (manufactured by MDCOM Co., Ltd.) and subjected to a modification treatment under the following conditions to form a polysilazane-modified layer with a thickness of 300 nm as a gas barrier layer, thereby obtaining a first substrate with a gas barrier layer.

[0516] (Polysilazane-Containing Coating Liquid) As a polysilazane-containing coating liquid, a 10% by mass dibutyl ether solution of perhydropolysilazane "AQUAMICA (registered trademark) NN120-10, catalyst-free type" (manufactured by Merck Ltd.) was prepared.

[0517] (Modification treatment conditions) Irradiation wavelength: 172 nm Lamp gas: Xe Excimer lamp light intensity: 130 mW / cm ２ (172 nm) Distance between polysilazane-containing layer and light source: 1 mm Stage heating temperature: 70°C Oxygen concentration in irradiation device: 0.5% by volume Excimer lamp irradiation time: 5 seconds

[0518] The resulting first substrate with the gas barrier layer was cleaned by a wet cleaning method. A detergent solution in which an alkaline detergent was diluted to 5.0% by mass was heated to 60°C, and the first substrate was immersed in the detergent solution at 60°C. The first substrate was subjected to scrubbing to remove foreign matter adhering to the first substrate. Next, the first substrate was subjected to ultrasonic cleaning, pure water rinsing, nitrogen gas blowing, and IR (Infra Red) drying, in that order. The first substrate was subjected to UV (Ultra Violet) irradiation to remove organic matter adhering to the surface of the first substrate, and then dried in an oven.

[0519] (7.2) Fabrication of TFT unit First, a SiO film was formed as a base layer by CVD, and then a gate electrode was formed. Then, an a-Si:H film and an n+a-Si:H film were formed as a gate insulating film and a channel layer, respectively, by CVD. Then, they were processed into the desired shape pattern by dry etching.

[0520] Next, a source electrode and a drain electrode were formed, followed by the formation of a passivation film. An a-Si TFT with an electrode width of 100 μm, a thickness of 200 nm, a channel width W of 3 mm, and a channel length L of 20 μm was formed in a position corresponding to the color filter. At the same time, an extraction electrode for the first electrode was formed using ITO, completing the TFT unit.

[0521] (7.3) Fabrication of Organic EL Device Next, a white tandem organic EL device was formed on the first substrate and the TFT unit.

[0522] In the fabrication of the TFT unit, ITO was used as an extraction electrode for the organic EL element, and the organic EL element (OLED) was fabricated using the same ITO as a first electrode (anode).

[0523] Next, according to the method (Example) described in paragraphs (0201) to (0219) of JP-A-2015-201508, an organic functional layer group (7) consisting of a first hole transport layer / a first light-emitting layer / a first electron transport layer / an intermediate connector layer / a second hole transport layer / a second light-emitting layer / a second electron transport layer was formed.

[0524] Next, aluminum was vapor-deposited to a thickness of 150 nm to form a second electrode (cathode). The emitting layer of the fabricated organic EL device was appropriately adjusted so that the CIE chromaticity of the emitting layer under conditions of emitting light without a color filter was the same as that under the D65 standard light source. In addition, inkjet printing was used to form the above-mentioned layers constituting the organic EL device.

[0525] Next, silane gas and ammonia gas were supplied onto the second electrode under a deposition pressure of 50 Pa, and a silicon nitride film having a thickness of 500 nm was deposited by plasma CVD. This film was used as a first sealing layer.

[0526] Specifically, the first base material formed up to the second electrode was 1×10－４ It was placed in a vacuum chamber depressurized to below Pa. The temperature of the first substrate was adjusted to about 70 °C, and as the reaction gas, SiH ４ gas, NH ３ gas, H ２ gas were introduced into the vacuum chamber at a ratio of 2:1:4. While depressurized to 50 Pa, a film was formed by plasma CVD method with a high-frequency power supply of 13.56 MHz. During film formation, the first substrate was cooled to keep the temperature of the first substrate at 70 °C. Thereby, a first sealing layer composed of SiN with a thickness of 500 nm was formed.

[0527] Next, a second sealing layer was formed. AlPET with a thermosetting adhesive applied thereon was laminated on the first sealing layer formed above. AlPET is for preventing moisture attack on the SiN film constituting the first sealing layer. In the lamination, a heat treatment at 100 °C for 30 minutes was performed to cure the thermosetting adhesive, thereby fabricating an organic EL element.

[0528] (8) Fabrication of display device (8.1) Fabrication of display device 1 An adhesive layer was formed on the color filter using the thermosetting adhesive used in the formation of the second sealing layer of the organic EL element. Next, the carrier glass of the first substrate of the organic EL element was peeled off by laser irradiation. Then, the surface of the first substrate of the organic EL element where the varnish surface was exposed was aligned with the color filter, and a heat treatment at 100 °C for 30 minutes was performed to bond the color filter and the organic EL element.

[0529] A cover member 1 was bonded via the adhesive layer 1 to the surface of the color filter opposite to the surface where the organic EL element was bonded, thereby obtaining a display device 1. The arrangement order of each film in the display device 1 was, from the viewing side, a cured layer, a flexible film, an adhesive layer, a low-elasticity film, an adhesive layer, a color filter, an adhesive layer, and an organic EL element.

[0530] (8.2) Fabrication of display devices 2 to 29 Display devices 2 to 29 were obtained in the same procedure as the fabrication of the display device 1 except that each film was changed as described in Tables V and VI. Note that the display device 4 had a configuration without a cured layer.

[0531] 2. Measurement and Evaluation The following measurements were carried out for each of the obtained flexible films, and the following evaluations were carried out for each of the display devices.

[0532] (1) Measurement of tensile modulus of elasticity of flexible film The tensile modulus E of each flexible film was measured in the machine direction (MD) by the following method in accordance with JIS K7127 (1999). The tensile modulus was determined by linear regression between strains of 0.05 and 0.25%.

[0533] 1) Each flexible film was cut into a size of 100 mm (MD) x 10 mm (TD) to prepare a test specimen. 2) This test specimen was measured using a Tensilon universal material testing machine "RTC-1225A" (manufactured by Orientec Co., Ltd.). The chuck distance was set to 50 mm, and the test specimen was pulled in the longitudinal (MD) direction at a pulling rate of 50 mm / min to measure the tensile modulus E in the MD direction. The measurement was carried out at 23°C and 55% RH.

[0534] (2) Measurement of Breaking Elongation of Flexible Film The breaking elongation of each flexible film was measured in the machine direction (MD) by the following method in accordance with JIS K7127 (1999).

[0535] 1) Each flexible film was cut into a size of 100 mm (MD) x 10 mm (TD) to prepare a test specimen. 2) This test specimen was measured using a Tensilon universal material testing machine "RTC-1225A" (manufactured by Orientec Co., Ltd.). The chuck distance was set to 50 mm, and the test specimen was pulled in the longitudinal (MD) direction at a tensile speed of 50 mm / min, and the elongation at break in the MD direction was measured. The measurement was carried out at 23°C and 55% RH.

[0536] (3) Visibility after keystroke test (impact resistance) For each of the display devices obtained above, a keystroke test was carried out using a keystroke tester with a silicone rubber keystroke (φ25 mm) at a load of 2.5 N, 150,000 keystrokes, and a keystroke speed of 150 times / min.

[0537] After the keystroke test, a black image was displayed on each display device. The front reflectance was measured using a spectrophotometer "CM-2600d" (manufactured by Konica Minolta, Inc.) and evaluated according to the following criteria. If the evaluation was B or higher (A to B), the display was suitable for practical use. A: Less than 1.7. B: 1.7 or higher but less than 1.8. C: 1.8 or higher.

[0538] (4) Evaluation of Folding Endurance Each display device obtained above was cut into a size of 20 mm in the transverse direction (TD) × 110 mm in the longitudinal direction (MD). Using a no-load U-shaped stretch tester "DLDMLH-FS" (manufactured by Yuasa System Co., Ltd.), a bending radius of 1 mm was set, and the sample was bent 100 times at a rate of 1 bend / second. The sample was fixed at both ends 10 mm apart in the MD, and the bending area was 20 mm × 90 mm. After the bending process, the sample was placed on a flat surface with the inside of the bent portion facing downwards, and the haze of the bent portion was measured using a haze meter "NDH4000" (manufactured by Nippon Denshoku Industries Co., Ltd.). The haze value before the bending test was designated as a, and the haze value after the bending test was designated as b. The difference (b - a) between these values ​​was calculated and evaluated according to the following criteria. A rating of B or higher (AA to B) indicates practical use. AA: Less than 0.1. A: 0.1 or higher, less than 0.5. B: 0.5 or more and less than 1.1. C: 1.1 or more.

[0539] (5) Evaluation of Surface Quality The surface quality was evaluated using the flexible film alone as a sample. In this embodiment, "surface quality" refers to the smoothness of the surface. High smoothness means high surface quality and excellent visibility. High smoothness also means excellent adhesion to the cured layer. If the surface quality of the flexible film is high, it can be evaluated as having high visibility even in a display device having the flexible film.

[0540] 13 is a schematic diagram showing a method for acquiring a projected image on a flexible film. First, the distance between a flexible film sample 71 and a white light source 72 "S-light" (manufactured by Japan Technology Center Co., Ltd.) was adjusted to 60 cm. Light was irradiated from the white light source 72 onto the flexible film sample 71 at an oblique angle of 45°. The distance between the flexible film sample 71 and a projection surface 73 arranged parallel to the flexible film sample 71 was adjusted to 70 cm. The shadow of the flexible film sample 71 was projected onto the projection surface 73.

[0541] This projected image was photographed by a camera 74 placed at a distance of 80 cm in a direction 90° from the projection surface 73, to obtain a photographed image. An "EOS KISS50" (manufactured by Canon Corporation) was used as the camera 74. The photographing conditions were a lens EF-S 18 = 55 mm, ISO sensitivity 100, aperture 5.6, shutter speed 1 / 10 second, and white balance set to manual.

[0542] The white light source 72, flexible film sample 71, projection surface 73, and camera 74 were all positioned at the same height. Next, for the resulting projection image, the area ratio K [%] of the black portion in the binarized image was calculated according to the following steps 1) to 4).

[0543] 1) The captured image was imported into a computer. The captured image was loaded into the analysis software "WinROOF2018" (manufactured by Mitani Corporation) and the following analysis was performed. 2) A rectangular evaluation area of ​​3.5 cm x 3.5 cm was set in the loaded captured image. 3) The loaded captured image was converted to a monochrome image. 4) The mode method was selected for the automatic binarization process of the obtained monochrome image. In the histogram of the monochrome image, the minimum pixel value a1 (left end) and maximum pixel value b1 (right end) were first confirmed. Next, the lower threshold a2 and upper threshold b2 of the intermediate portion c to be extracted were set based on the following formulas (I) and (II). Formula (I): Lower threshold a2 = a1 + 0.3(b1 - a1) Formula (II): Upper threshold b2 = b1 - 0.3(b1 - a1) The occupied area ratio K [%] of the extracted intermediate portion c was calculated in the histogram of the monochrome image. The transparency of the monochrome image was set to 120.

[0544] The calculated occupied area ratio K [%] was evaluated according to the following criteria. Note that if the evaluation was B or higher (A to B), it was deemed to be practical. The larger the value of occupied area ratio K [%], the better the surface quality can be evaluated. A: 80% or higher. B: 70% or higher but less than 80%. C: 60% or higher but less than 70%. D: Less than 60%.

[0545] When the surface of the flexible film is smooth, the pixel values ​​in the histogram of the monochrome image will have less variation, and the area ratio K [%] of the intermediate portion c will be relatively high. Conversely, when the surface of the flexible film is less smooth, the pixel values ​​in the histogram of the monochrome image will have more variation, and the area ratio K [%] of the intermediate portion c will be relatively low.

[0546] Figure 14 shows a projected image of the flexible film used in the evaluation of surface quality. It shows an example corresponding to grades A to D in the above evaluation. The number of black areas increases in the order of grades A, B, C, and D, and the area also increases, with a mixture of white and black areas.

[0547] 15 to 18 show histograms of monochrome images and setting screens for automatic binarization processing. Fig. 15 corresponds to an example of judgment A. In the histogram of the monochrome image, the minimum pixel value a1 was 139 and the maximum pixel value b1 was 209. Based on the above formulas (I) and (II), the lower threshold value a2 was set to 160 and the upper threshold value b2 was set to 188. The area occupied by the middle portion c (the proportion of pixels binarized) relative to the area of ​​the entire histogram was calculated to be 89.95%.

[0548] 16 corresponds to an example of judgment B. In the histogram of a monochrome image, the minimum pixel value a1 was 102 and the maximum pixel value b1 was 196. Based on the above formulas (I) and (II), the lower threshold value a2 was set to 130.2 and the upper threshold value b2 was set to 167.8. The area ratio (the proportion of pixels that are binarized) of the middle portion c to the area of ​​the entire histogram was calculated to be 77.52%.

[0549] 17 corresponds to an example of judgment C. In the histogram of a monochrome image, the minimum pixel value a1 was 101 and the maximum pixel value b1 was 222. Based on the above formulas (I) and (II), the lower threshold value a2 was set to 137.3 and the upper threshold value b2 was set to 185.3. The area ratio (the proportion of pixels binarized) of the middle portion c to the area of ​​the entire histogram was calculated to be 67.55%.

[0550] 18 corresponds to an example of judgment D. In the histogram of a monochrome image, the minimum pixel value a1 was 80 and the maximum pixel value b1 was 255. Based on the above formulas (I) and (II), the lower threshold value a2 was set to 132.5 and the upper threshold value b2 was set to 202.5. The area ratio (the proportion of pixels that are binarized) of the middle portion c to the area of ​​the entire histogram was calculated to be 59.61%.

[0551] The measurement results of each flexible film obtained and the evaluation results of the display device are shown in Tables V and VI below. For display device 29, a thin glass film prepared according to the following process was used instead of a flexible film. Furthermore, during the keystroke test for display device 29, the thin glass film broke, making it impossible to perform the above evaluation, and thus the result was marked "evaluation not possible."

[0552] Thin film glass (soda lime glass) having a dimension of 12 inches was prepared according to the following steps.

[0553] (Step 1) A thin film glass was fabricated on a carrier substrate having a bonding surface, with a first surface of the thin film glass in contact with the carrier substrate. A contact film with high adhesive strength was then attached to a second surface of the thin film glass opposite the first surface. (Step 2) The thin film glass was then peeled off from the carrier substrate by the highly adhesive contact film. (Step 3) The contact film was removed from the second surface of the thin film glass peeled off from the carrier substrate by a weakening treatment (electromagnetic radiation irradiation) that weakened the adhesive strength of the contact film.

[0554] In step 1, a thin glass film was prepared to a predetermined thickness so as to be in contact with a 500 μm-thick carrier substrate, and then the contact film described below was attached. Next, in step 2, the thin glass film together with the contact film was peeled off from the carrier substrate over a period of 30 seconds. The commercially available contact film "NDS4150-20" was used. "NDS4150-20" is a 150 μm-thick film containing polyolefin (PO), and further has a 10 μm-thick adhesive layer.

[0555] Next, in step 3, the exposed contact film was subjected to a weakening treatment to reduce the adhesive strength. In the weakening treatment, the contact film was irradiated with ultraviolet light having a wavelength of 365 nm for 10 seconds. The irradiance of the ultraviolet light was 500 mW / cm. ２ , the cumulative light intensity is 500 mJ / cm ２ The adhesive strength before the weakening treatment was 11 N / 25 mm, but after the weakening treatment, the adhesive strength was reduced to 0.4 N / 25 mm. As a result, the contact film could be easily peeled off from the thin glass, and a thin glass film with a thickness of 30 μm was obtained.

[0556]

[0557]

[0558] From the examples and comparative examples, it can be seen that the flexible display device of this embodiment is excellent in all of visibility after a keystroke test, folding endurance, and surface quality.

[0559] A comparison of Examples 1 and 5 to 10 shows that the flexible display device of this embodiment can further improve visibility, folding resistance, and surface quality after a keystroke test by ensuring that the resin orientation degree J [%] satisfies the above formula (2).

[0560] A comparison of Examples 1, 8 and 9 shows that when the aspect ratio of the filler is within the range of 50 to 200, the visibility after the keystroke test, the folding endurance and the surface quality can be further improved.

[0561] A comparison of Examples 18 and 25 to 26 shows that the visibility and folding endurance after the keystroke test can be further improved by setting the breaking elongation of the flexible film within the range of 10 to 20%.

[0562] The present disclosure makes it possible to provide a flexible display device with improved visibility, folding resistance, and surface quality after a keystroke test.

[0563] REFERENCE SIGNS LIST 1 Flexible film 2 Low-elasticity film 3 Color filter 4 Light-emitting element 5 Adhesive layer 6 Adhesive layer 7 Cured layer 10 Flexible display device 41 Cathode 42 Light-emitting layer 43 Transparent electrode 44 Glass substrate 45 White light 46 RGB color filter 47 Blue light 48 Color filter (wavelength conversion film) 49 Laminated organic electroluminescence element 51 Black matrix 52 Transmitting area 53 Irradiation area 60 Color filter 61 Blue light 62 Green light 63 Red light 71 Flexible film sample 72 White light source 73 Projection surface 74 Camera 80 Manufacturing device 81 Pressing elastic roll 82 Unwinding section 83 Winding section 84 Die 85 Touch roll 86-1 First cooling roll 86-2 Second cooling roll 87 Cast film B110 Support B200 Manufacturing device B210 Supply section B220 Coating section B230 Drying section B240 Cooling section B250 Winding section

Claims

A flexible display device having at least a cover member, a color filter, and a light-emitting element, the cover member has at least a flexible film; The flexible film contains at least a resin as a main component and a filler, A flexible display device, wherein the degree of orientation J [%] of the resin and the degree of orientation F [%] of the filler measured by X-ray diffraction method satisfy the following formula (1): Formula (1): J<F The flexible display device according to claim 1 , wherein the degree of orientation J [%] of the resin satisfies the following formula (2): Formula (2): 40≦J≦60 3. The flexible display device according to claim 1, wherein the degree of orientation F [%] of the filler satisfies the following formula (3): Formula (3): 40≦F≦80 3. The flexible display device according to claim 1, wherein the flexible film has a tensile modulus of elasticity in the range of 4.0 to 8.0 GPa.

3. The flexible display device according to claim 1, wherein the flexible film has a breaking elongation within a range of 10 to 20%.

3. The flexible display device according to claim 1, wherein the thickness of the flexible film is in the range of 30 to 80 μm.

3. The flexible display device according to claim 1, wherein the aspect ratio of the filler is in the range of 50 to 200. 　 The flexible display device according to claim 1 , wherein the cover member has a hardened layer on the outermost surface on the viewing side. 　 A flexible film used as a cover member of a flexible display device, The flexible film contains at least a resin as a main component and a filler, The degree of orientation J [%] of the resin and the degree of orientation F [%] of the filler measured by an X-ray diffraction method satisfy the following formula (1): Formula (1): J<F The flexible display device is a flexible film having a color filter having a function of preventing reflection of light incident from the outside.

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