WO2021010159A1 - 折りたたみ型ディスプレイ用ハードコートフィルムとその用途 - Google Patents
折りたたみ型ディスプレイ用ハードコートフィルムとその用途 Download PDFInfo
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- WO2021010159A1 WO2021010159A1 PCT/JP2020/025672 JP2020025672W WO2021010159A1 WO 2021010159 A1 WO2021010159 A1 WO 2021010159A1 JP 2020025672 W JP2020025672 W JP 2020025672W WO 2021010159 A1 WO2021010159 A1 WO 2021010159A1
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J7/00—Chemical treatment or coating of shaped articles made of macromolecular substances
- C08J7/04—Coating
- C08J7/042—Coating with two or more layers, where at least one layer of a composition contains a polymer binder
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- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09F—DISPLAYING; ADVERTISING; SIGNS; LABELS OR NAME-PLATES; SEALS
- G09F9/00—Indicating arrangements for variable information in which the information is built-up on a support by selection or combination of individual elements
- G09F9/30—Indicating arrangements for variable information in which the information is built-up on a support by selection or combination of individual elements in which the desired character or characters are formed by combining individual elements
- G09F9/301—Indicating arrangements for variable information in which the information is built-up on a support by selection or combination of individual elements in which the desired character or characters are formed by combining individual elements flexible foldable or roll-able electronic displays, e.g. thin LCD, OLED
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- B—PERFORMING OPERATIONS; TRANSPORTING
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- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B27/00—Layered products comprising a layer of synthetic resin
- B32B27/36—Layered products comprising a layer of synthetic resin comprising polyesters
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- B—PERFORMING OPERATIONS; TRANSPORTING
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- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B27/00—Layered products comprising a layer of synthetic resin
- B32B27/18—Layered products comprising a layer of synthetic resin characterised by the use of special additives
- B32B27/20—Layered products comprising a layer of synthetic resin characterised by the use of special additives using fillers, pigments, thixotroping agents
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- B—PERFORMING OPERATIONS; TRANSPORTING
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- B32B7/00—Layered products characterised by the relation between layers; Layered products characterised by the relative orientation of features between layers, or by the relative values of a measurable parameter between layers, i.e. products comprising layers having different physical, chemical or physicochemical properties; Layered products characterised by the interconnection of layers
- B32B7/02—Physical, chemical or physicochemical properties
- B32B7/023—Optical properties
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
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- C08J5/18—Manufacture of films or sheets
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
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- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
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- C08J7/04—Coating
- C08J7/046—Forming abrasion-resistant coatings; Forming surface-hardening coatings
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- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
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- C—CHEMISTRY; METALLURGY
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- C09D175/04—Polyurethanes
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- C—CHEMISTRY; METALLURGY
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- C—CHEMISTRY; METALLURGY
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- C—CHEMISTRY; METALLURGY
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- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
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- C09D7/65—Additives macromolecular
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- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
- C09D7/00—Features of coating compositions, not provided for in group C09D5/00; Processes for incorporating ingredients in coating compositions
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- C09D7/66—Additives characterised by particle size
- C09D7/67—Particle size smaller than 100 nm
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- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
- C09D7/00—Features of coating compositions, not provided for in group C09D5/00; Processes for incorporating ingredients in coating compositions
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- G02B1/10—Optical coatings produced by application to, or surface treatment of, optical elements
- G02B1/14—Protective coatings, e.g. hard coatings
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- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on liquid crystals, e.g. single liquid crystal display cells
- G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
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- H04M1/0202—Portable telephone sets, e.g. cordless phones, mobile phones or bar type handsets
- H04M1/026—Details of the structure or mounting of specific components
- H04M1/0266—Details of the structure or mounting of specific components for a display module assembly
- H04M1/0268—Details of the structure or mounting of specific components for a display module assembly including a flexible display panel
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- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
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Definitions
- the present invention relates to a hard coat film for a foldable display, a foldable display, and a mobile terminal device.
- the present invention relates to a hard coat film for a foldable display used in.
- mobile terminal devices are becoming lighter, and mobile terminal devices such as smartphones are becoming widespread. While mobile terminal devices are required to have various functions, they are also required to be convenient. Therefore, popular mobile terminal devices need to have a small screen size of about 6 inches because they can be easily operated with one hand and are supposed to be stored in a pocket of clothes.
- tablet terminals with a screen size of 7 inches to 10 inches are expected to be used not only for video content and music, but also for business, drawing, reading, etc., and have high functionality.
- it cannot be operated with one hand is inferior in portability, and has a problem in convenience.
- Patent Document 1 a method of making it compact by connecting a plurality of displays has been proposed (see Patent Document 1), but since the bezel part remains, the image is cut off and the visibility is deteriorated. It has become a problem and is not widespread.
- the surface of the display could be protected with a non-flexible material such as glass, but in a foldable display, the foldable portion is used.
- a non-flexible material such as glass
- the foldable portion is used in the case of a one-sided display.
- the foldable display since the portion corresponding to a certain foldable portion is repeatedly folded, there is a problem that the film at the portion is deformed with time and the image displayed on the display is distorted.
- the foldable display uses films for various parts such as polarizing plates, retardation plates, touch panel base materials, base materials for display cells such as organic EL, and protective members on the back surface. , These films were also required to have durability against repeated folding.
- Patent Document 2 As a method for increasing durability, a method for partially changing the film thickness has been proposed (see Patent Document 2), but there is a problem of poor mass productivity.
- the hard coat film is also required to have visibility and design. Therefore, in order to suppress glare and iris-like color (interference spots) due to reflected light when viewed from an arbitrary angle, a multi-layer structure in which a high refractive index layer and a low refractive index layer are mutually laminated on the upper layer of the hard coat layer. It is common practice to provide an antireflection layer. However, in recent years, fluorescent lamps have become mainstream in the three-wavelength type due to the reproducibility of daylight colors, and interference spots due to reflected light are more easily seen. Furthermore, there is an increasing demand for cost reduction by simplifying the antireflection layer. Therefore, there is a demand for a hard coat film to which an antireflection layer is not added to suppress interference spots as much as possible.
- the present invention is intended to solve the problems of conventional display members as described above, is excellent in mass productivity, and does not cause distortion in the image displayed in the folded portion after being repeatedly folded.
- a foldable display and a mobile terminal device equipped with such a foldable display there are no creases or cracks in the foldable portion, and fine cracks such as an easily adhesive resin layer are formed.
- the present invention has the following configuration.
- a composition containing at least one kind of particles selected from physical particles and silica particles is cured, and the average particle size of the particles is 5 to 150 nm, and the hard coat layer having the easy-adhesion resin layer is laminated.
- a hard coat film for a foldable display in which the polyester film before the film satisfies the following conditions (1) to (4).
- Refractive index in the bending direction is 1.590 to 1.620
- the refractive index in the direction of the folding part is 1.670 to 1.700.
- Refractive index in the thickness direction is 1.520 or less
- Density is 1.380 g / cm 3 or more (Here, the bending direction means a direction orthogonal to the folding portion when the polyester film is folded.) 2.
- the foldable display according to the first aspect wherein the total solid content of the titanium oxide particles, the zirconium oxide particles, and the silica particles contained in the solid content mass of the easy-adhesive resin layer is 1 to 15% by mass. Hard coat film. 3. 3.
- the polyester film having the easy-adhesive resin layer and before laminating the hard coat layer has a total light transmittance of 85% or more, a haze of 3% or less, and a maximum heat shrinkage rate of 6% or less.
- the foldable display hard coat film according to the sixth aspect is a foldable display in which the hard coat layer is arranged as a surface protective film so as to be positioned on the surface, and is continuous through a foldable portion of the foldable display.
- a mobile terminal device having the foldable display according to the seventh item.
- the foldable display using the hard coat film for a foldable display of the present invention maintains mass productivity, and the hard coat film does not cause cracks in the foldable portion and is deformed after being repeatedly folded. Absent. Furthermore, in addition to cracks in the folded part, floating at the interface between the hard coat and the easy-adhesive resin layer, floating at the interface between the easy-adhesive resin layer and the polyester film, iris-like color (interference spots) caused by fine cracks, etc. ) Can be effectively suppressed, and the image is not distorted at the folded portion of the display.
- a mobile terminal device equipped with a foldable display using a hard coat film as described above provides a beautiful image, is rich in functionality, and is excellent in convenience such as portability.
- the display referred to in the present invention generally refers to a display device, and the types of displays include LCDs, organic EL displays, inorganic EL displays, LEDs, FEDs, etc., such as LCDs having a bendable structure and , Organic EL and inorganic EL are preferable.
- organic EL and inorganic EL that can reduce the layer structure are particularly preferable, and organic EL having a wide color gamut is further preferable.
- the foldable display is a display in which one continuous display can be folded in half when carried. By folding, the size can be halved and portability can be improved.
- the bending radius of the foldable display is preferably 5 mm or less, more preferably 3 mm or less. If the bending radius is 5 mm or less, the thickness can be reduced in the folded state. It can be said that the smaller the bending radius is, the better, but the smaller the bending radius, the easier it is to make creases.
- the bending radius is preferably 0.1 mm or more, but may be 0.5 mm or more, or 1 mm or more. Even if the bending radius is 1 mm, it is possible to achieve a practically sufficient thinning when carrying.
- the bending radius when folded means the radius inside the folded portion when folded, which measures the portion of reference numeral 11 in the schematic diagram of FIG.
- the surface protective film described later may be located on the folded outer side or the inner side of the foldable display.
- the foldable display may be folded in three, folded in four, or further, and may be a retractable type called rollable, all of which fall within the scope of the foldable display according to the present invention.
- the hard coat film for a foldable display of the present invention may be used for any part as long as it is a component of a foldable display.
- a typical configuration of a foldable display and a portion where the hard coat film of the present invention can be used will be described by taking an organic EL display as an example.
- the hard coat film for a foldable display of the present invention may be simply referred to as the hard coat film of the present invention.
- An essential configuration of the foldable organic EL display is an organic EL module, but if necessary, a circularly polarizing plate, a touch panel module, a front surface protective film, a back surface protective film, and the like are provided.
- Organic EL module The general configuration of an organic EL module consists of an electrode / electron transport layer / light emitting layer / hole transport layer / transparent electrode.
- the mobile terminal device has a touch panel.
- the touch panel module is arranged above the organic EL display or between the organic EL module / circularly polarizing plate.
- the touch panel module has a transparent base material such as a film and a transparent electrode arranged on the transparent base material.
- the hard coat film of the present invention can be used as this transparent base material.
- the circularly polarizing plate suppresses deterioration of image quality due to reflection of external light by a member inside the display.
- the circular polarizing plate has a linear polarizing plate and a retardation plate.
- the linear polarizing plate has a protective film on at least the surface of the polarizer on the visible side.
- a protective film may be provided on the surface opposite to the viewing side of the polarizer, or a retardation plate may be directly laminated on the polarizer.
- a resin film having a retardation such as polycarbonate or a cyclic olefin or a resin film provided with a retardation layer made of a liquid crystal compound is used.
- the hard coat film of the present invention can be used as a polarizer protective film.
- the base film of the hard coat film of the present invention is a polyester film
- it is preferable that the slow axis direction of the polyester film is parallel or orthogonal to the absorption axis direction of the polarizer. A deviation of up to 10 degrees, preferably up to 5 degrees, is allowed with respect to this parallelism or orthogonality.
- a surface protective film is provided.
- the hard coat film of the present invention is used as this surface protection film.
- the surface protective film includes a cover window built into the outermost surface of the display and a replaceable after-sale film that can be attached and detached by the user himself.
- the hardware of the present invention is used.
- a coated film is used. It is provided on the surface of a foldable display with the hard coat layer on the visible side. The hard coat layer may be provided on both sides.
- a protective film is also provided on the back surface side of the display.
- the hard coat film of the present invention can be used as a protective film on the back surface side.
- the hard coat film of the present invention may be other than the above as long as it is used in a place where it is folded in a component of a foldable display.
- the hard coat film of the present invention is preferably used for the cover window surface protective film, the after surface protective film, the base film of the touch panel module, and the back surface protective film. Furthermore, it is preferably used for the cover window surface protective film and the after surface protective film.
- the hard coat film of the present invention does not necessarily have to be used for all the above-mentioned applications.
- Foldable displays are hard based on polyester film, polyimide film, polyamide film, polyamideimide film, polycarbonate film, acrylic film, triacetyl cellulose film, cycloolefin polymer film, polyphenylene sulfide film, polymethylpentene film, etc.
- the coat film can be appropriately used according to suitability.
- the base film constituting the hard coat film of the present invention is a polyester film
- it may be a single-layer film made of one or more kinds of polyester resins, or when two or more kinds of polyesters are used, it may be a multilayer structure film. It may be a super multi-layer laminated film having a repeating structure.
- polyester resin used for the polyester film which is the base film of the hard coat film examples include polyethylene terephthalate, polybutylene terephthalate, polyethylene-2,6-naphthalate, or a common component containing these resins as main components.
- polyester film made of a polymer examples include a stretched polyethylene terephthalate film.
- the dicarboxylic acid component of the polyester is, for example, an aliphatic dicarboxylic acid such as adipic acid or sebacic acid; terephthalic acid, isophthalic acid, phthalic acid.
- Aromatic dicarboxylic acids such as acids and 2,6-naphthalenedicarboxylic acids; polyfunctional carboxylic acids such as trimellitic acid and pyromellitic acid.
- glycol component examples include fatty acid glycols such as ethylene glycol, diethylene glycol, 1,4-butanediol, propylene glycol and neopentyl glycol; aromatic glycols such as p-xylene glycol; and 1,4-cyclohexanedimethanol.
- fatty acid glycols such as ethylene glycol, diethylene glycol, 1,4-butanediol, propylene glycol and neopentyl glycol
- aromatic glycols such as p-xylene glycol
- 1,4-cyclohexanedimethanol examples include fatty acid glycols such as ethylene glycol, diethylene glycol, 1,4-butanediol, propylene glycol and neopentyl glycol; aromatic glycols such as p-xylene glycol; and 1,4-cyclohexanedimethanol.
- Alicyclic glycols polyethylene glycols having an average molecular weight of 150 to
- the ultimate viscosity of at least one kind of resin pellet is preferably in the range of 0.50 to 1.0 dl / g.
- the ultimate viscosity is 0.50 dl / g or more, the impact resistance of the obtained film is improved, and it is preferable that the display internal circuit is less likely to be broken due to an external impact.
- the ultimate viscosity is 1.00 dl / g or less, the filter pressure increase of the molten fluid does not become too large, and it is preferable that the film production can be operated stably.
- the thickness of the polyester film which is the base film of the hard coat film, is preferably 10 to 80 ⁇ m, more preferably 25 to 75 ⁇ m.
- the thickness is 10 ⁇ m or more, the pencil hardness improving effect and the impact resistance improving effect are observed, and when the thickness is 80 ⁇ m or less, it is advantageous for weight reduction and also excellent in flexibility, workability and handleability.
- the surface of the hard coat film of the present invention may be smooth or has irregularities, but since it is used as a surface cover for displays, deterioration of optical characteristics due to irregularities is not preferable.
- the haze in the state before laminating the easy-adhesive resin layer on the polyester film and laminating the hard coat layer is preferably 3% or less, more preferably 2% or less, and most preferably 1% or less. When the haze is 3% or less, the visibility of the image can be improved. The smaller the lower limit of the haze, the better, but from the viewpoint of stable production, 0.1% or more is preferable, and 0.3% or more may be used.
- the base material polyester film is used as a method of forming the unevenness. It can be formed by blending particles into the film or coating a coat layer containing particles as an easy-adhesion resin layer during the film formation of the base polyester film.
- a known method can be adopted as a method of blending the particles into the base polyester film.
- it can be added at any stage in the production of polyester, but is preferably added as a slurry dispersed in ethylene glycol or the like at the stage of esterification or at the stage after the completion of the transesterification reaction and before the start of the polycondensation reaction. Then, the polycondensation reaction may proceed.
- aggregate inorganic particles are homogeneously dispersed in a monomer solution that is a part of the polyester raw material, and then filtered, and the residue of the polyester raw material before the esterification reaction, during the esterification reaction, or after the esterification reaction is used.
- the method of addition is preferable. According to this method, since the monomer solution has a low viscosity, homogeneous dispersion of particles and high-precision filtration of the slurry can be easily performed, and when added to the rest of the raw material, the dispersibility of the particles is good, which is new. Aggregates are also unlikely to occur. From this point of view, it is particularly preferable to add it to the balance of the raw material in a low temperature state before the esterification reaction.
- the number of protrusions on the film surface can be further reduced by a method (masterbatch method) in which a polyester containing particles is obtained in advance and then the pellets and the pellets containing no particles are kneaded and extruded.
- the polyester film as a base material may contain various additives within a range that maintains a preferable range of total light transmittance.
- the additive include an antistatic agent, a UV absorber, and a stabilizer.
- the total light transmittance in a state where it has an easy-adhesive resin layer and does not have a hard coat layer is preferably 85% or more, and more preferably 87% or more. If the transmittance is 85% or more, sufficient visibility can be ensured.
- the total light transmittance of the polyester film is preferably 85% or more in order to increase the total light transmittance of the hard coat film described later. It can be said that the higher the total light transmittance of the polyester film is, the better, but from the viewpoint of stable production, 99% or less is preferable, and 97% or less may be used.
- the maximum heat shrinkage after heat treatment at 150 ° C. for 30 minutes in a state where the polyester film has an easily adhesive resin layer and does not have a hard coat layer is preferably 6% or less, more preferably 5% or less. If the heat shrinkage rate is 6% or less, it is possible to suppress flat surface defects such as curl and swell during HC processing. It can be said that the lower the maximum heat shrinkage rate is, the better, but it is preferably -1% or more, and preferably 0% or more. A minus here means that the material has expanded after heating, and a value of -1% or more is preferable because the flat state is good.
- the polyester film has an easy-adhesion resin layer and has the following characteristics in a state without the hard coat layer. It is preferable to have.
- the pencil hardness evaluation of the pencil hardness of the hard coat film after laminating the hard coat layer on the conventional base material polyester film the pencil hardness was lowered due to the film being deformed in the thickness direction. Conceivable.
- the pushing depth of the base material polyester film in the above state after unloading the test force in the thickness direction is preferably 1.5 ⁇ m or less, more preferably 1.4 ⁇ m or less, and preferably 1.3 ⁇ m or less. More preferred.
- the pushing depth (final deformation amount under load) after unloading the test force is 1.5 ⁇ m or less, the film becomes thicker in the pencil hardness evaluation of the hard coat film after laminating the hard coat layer. It is hard to deform and the pencil hardness can be increased. If the pencil hardness of the hard coat film can be increased, scratches and dents are less likely to occur on the display surface, and the visibility of the display is improved. It can be said that the lower the pushing depth after the test force is unloaded, the better, but 0.3 ⁇ m or more is preferable, and 0.5 ⁇ m or more is more preferable, from the viewpoint of saturating stable production and effects.
- the refractive index in the thickness direction should be adjusted to 1.520 or less for the polyester film having the easy-adhesive resin layer and not the hard coat layer. Is effective.
- the stretching ratio in the bending direction and the folding direction is adjusted to be high within a range in which the refractive index in the bending direction and the folding direction can be controlled within a preferable range. It is possible to exemplify the condition setting such as setting the stretching temperature in the bending direction and the folding direction low, and setting the heat fixing temperature high.
- the non-hard coat surface of the hard coat film of the present invention can be coated with an adhesive or treated to improve the adhesion to the hard coat layer.
- Examples of the surface treatment method include sand blast treatment, uneven treatment by solvent treatment, corona discharge treatment, electron beam irradiation treatment, plasma treatment, ozone / ultraviolet irradiation treatment, flame treatment, chromic acid treatment, hot air treatment, and the like. Oxidation treatment and the like can be mentioned and can be used without particular limitation.
- an adhesiveness improving layer such as an easy-adhesive resin layer.
- acrylic resin, polyester resin, polyurethane resin, polyether resin and the like can be used without particular limitation, and can be formed by a general coating method, preferably a so-called in-line coating formulation.
- the above-mentioned polyester film is prepared by, for example, a polymerization step in which inorganic particles are homogeneously dispersed in a monomer solution that is a part of a polyester raw material, filtered, and then added to the rest of the polyester raw material to polymerize the polyester, and the polyester thereof. It can be produced through a film forming step of forming a base film by melting and extruding it into a sheet through a filter, cooling it, and then stretching it.
- PET polyethylene terephthalate
- the method is not limited thereto. Absent. Further, the number of layers is not limited, such as a single-layer structure or a multi-layer structure.
- the PET pellets are mixed and dried at a predetermined ratio, they are supplied to a known melt lamination extruder, extruded into a sheet from a slit-shaped die, and cooled and solidified on a casting roll to form an unstretched film. ..
- a known melt lamination extruder extruded into a sheet from a slit-shaped die, and cooled and solidified on a casting roll to form an unstretched film. ..
- one extruder is sufficient, but in the case of producing a multi-layer film, two or more extruders, two or more layers of manifolds or a merging block (for example, a merging having a square merging part).
- a block can be used to stack a plurality of film layers constituting each outermost layer, extrude two or more sheets from a base, and cool them with a casting roll to form an unstretched film.
- the filter medium used for high-precision filtration of the molten resin is not particularly limited, but the filter medium of the stainless sintered body is excellent in the removal performance of aggregates containing Si, Ti, Sb, Ge and Cu as main components and high melting point organic substances. Therefore, it is preferable.
- the filtered particle size (initial filtration efficiency 95%) of the filter medium is preferably 20 ⁇ m or less, and particularly preferably 15 ⁇ m or less. If the filtered particle size (initial filtration efficiency 95%) of the filter medium exceeds 20 ⁇ m, foreign matter having a size of 20 ⁇ m or more cannot be sufficiently removed. High-precision filtration of the molten resin using a filter medium having a filter medium size (initial filtration efficiency of 95%) of 20 ⁇ m or less may reduce productivity, but a film with few protrusions due to coarse particles can be obtained. Preferred above.
- the polyester film having the easy-adhesive resin layer and before laminating the hard coat layer has a refractive index of 1.590 to 1.620 in at least one of the longitudinal direction (mechanical flow direction) and the width direction. Is more preferable, and more preferably 1.591 to 1.600.
- the polyester film having an easy-adhesive resin layer and before laminating the hard coat layer preferably has a refractive index of 1.590 to 1.620 in the bending direction, preferably 1.591 to 1.600. Is more preferable.
- the bending direction refers to a direction orthogonal to the folding portion (reference numeral 21) assumed in the application of the foldable display, as shown by reference numeral 22 on the polyester film (reference numeral 2) of FIG.
- the refractive index in at least one of the longitudinal direction and the width direction is 1.590 to 1.620, there is little deformation when repeatedly folded, and there is no risk of deteriorating the image quality of the foldable display, which is preferable.
- the refractive index is more preferably 1.591 to 1.600.
- the direction is preferably the above-mentioned bending direction.
- the refractive index of the polyester film can be effectively adjusted by adjusting the stretching ratio and the stretching temperature. Further, a relaxation step in the stretching direction and multi-step stretching may be used to adjust the refractive index. When performing multi-stage stretching, it is preferable that the stretching ratio of the second and subsequent stages is higher than the stretching ratio of the first stage. The difference between the refractive index of the polyester film having the easy-adhesive resin layer and before laminating the hard coat layer and the refractive index of the polyester film alone having no easy-adhesive resin layer is so small that it can be ignored.
- the refractive index in at least one of the longitudinal direction (mechanical flow direction) and the width direction of the polyester film having the easy-adhesion resin layer and before laminating the hard coat layer in the above range is more preferable to control the refractive index in at least one of the longitudinal direction (mechanical flow direction) and the width direction of the polyester film having the easy-adhesion resin layer and before laminating the hard coat layer in the above range.
- the refractive index in the bending direction within the above range, it is possible to reduce fatigue due to compressive stress applied to the inside of the fold during folding. Fatigue due to compressive stress is thought to occur mainly in the crystal part, and the smaller the number of crystals in the bending direction, the less fatigue. Therefore, it is considered that by lowering the refractive index, the amount of oriented crystals in the bending direction is reduced and compression fatigue is suppressed.
- the creep phenomenon caused by the tensile stress applied to the outside of the folding at the time of folding can be suppressed by reducing the refractive index. Fatigue due to tensile stress is thought to occur mainly in the amorphous part, and the molecular chains are aligned due to the repeated stress and deformation occurs. It can be inferred that the smaller the number of molecular chains aligned in the bending direction, the smaller the deformation due to alignment. Further, since fatigue due to tension can be suppressed when the number of amorphous portions is small, a high crystallinity, that is, a high density is preferable.
- the unstretched polyester sheet preferably has a draw ratio of 1.2 to 2.0 times in at least one of the longitudinal direction (mechanical flow direction) and the width direction, 1.7 to 2. 0 times is more preferable.
- the stretching direction is preferably the bending direction.
- a draw ratio of 1.2 times or more is preferable because there is no deformation in post-processing such as during hard coat coating, and a draw ratio of 2.0 times or less is preferable because uneven film thickness does not occur.
- the stretching temperature is preferably 75 to 120 ° C., more preferably 75 to 105 ° C.
- conventionally known means such as a hot air heating method, a roll heating method, and an infrared heating method can be adopted.
- the stretching temperature By setting the stretching temperature to 75 to 120 ° C., it is possible to prevent large thickness unevenness due to stretching at the above stretching ratio.
- the refractive index in the thickness direction can be reduced by stretching at a low temperature as much as possible within a range that does not cause large thickness unevenness as described above.
- the refractive index of the polyester film having the above-mentioned easy-adhesive resin layer and before laminating the hard coat layer is 1.670 to 1.700 in the direction orthogonal to the direction in which the refractive index is 1.590 to 1.620. Is preferable. That is, it is preferable that the refractive index in the direction orthogonal to the bending direction (direction of the folded portion) is 1.670 to 1.700.
- the refractive index in the direction orthogonal to the bending direction is 1.670 to 1.700.
- the flexibility in the bending direction can be improved and the surface hardness can be improved. More preferably 1.680 to 1.695.
- the method for adjusting the refractive index in the direction orthogonal to the bending direction include stretching ratio, stretching preheating temperature, stretching temperature, multi-stage stretching, and film relaxation.
- the draw ratio is preferably 4.0 to 6.0 times, more preferably 4.4 to 6.0 times.
- the stretching preheating temperature in the direction orthogonal to the bending direction is preferably 70 to 110 ° C.
- the film may be relaxed by 1 to 10% in either the machine flow direction (longitudinal direction) or the vertical direction (width direction).
- the polyester film having an easily adhesive resin layer and before laminating the hard coat layer has a refractive index of 1.520 or less in the thickness direction.
- the refractive index in the bending direction is designed to be low, it is possible to suppress a decrease in the hardness of the film surface, and it is possible to achieve both flexibility and surface hardness. ..
- the pushing depth after unloading the test force in the thickness direction can be reduced, and the hardness of the film surface, particularly the pencil hardness of the hard coat film after laminating the hard coat layer can be improved.
- the refractive index in the thickness direction is preferably low, but 1.3 or more is preferable in terms of stable production, and it may be 1.4 or more. Especially preferably, it is 1.410 or more. It can be said that the above range can be achieved by increasing the stretching ratio in both the bending direction and the folding direction, but the refractive index in the thickness direction is controlled after controlling the refractive index in the bending direction and the width direction within a preferable range. In order to do so, it is preferable to set the conditions while checking the balance of each process condition in the film forming process.
- the method of controlling the refractive index in the thickness direction within the above range is as follows: stretching preheating temperature in the bending direction, stretching temperature, stretching ratio, stretching preheating temperature in the direction of the folding portion, stretching temperature, multistage stretching, high magnification stretching, or heat fixing.
- the stretching preheating temperature in the bending direction is preferably 70 ° C. to 110 ° C.
- the stretching temperature in the bending direction is preferably 75 to 120 ° C.
- the draw ratio in the bending direction is preferably 1.2 to 2.0 times, more preferably 1.7 to 2.0 times.
- the stretching preheating temperature in the folding portion direction is also preferably 75 ° C. to 110 ° C.
- the stretching temperature is preferably 75 to 120 ° C.
- the draw ratio of the folded portion is preferably 4.0 to 6.0 times, more preferably 4.4 to 6.0 times.
- the refractive index in the thickness direction can be effectively reduced while maintaining or reducing the refractive index in the bending direction.
- multi-stage stretching may be used. In that case, it is preferable to make the stretching ratio of the second stage higher than the stretching ratio of the first stage because the refractive index can be effectively controlled.
- a method of stretching again after the crystallization step may be used.
- the heat fixing temperature is preferably 180 to 240 ° C.
- orientation crystallization in the stretching direction proceeds, and the refractive index in the thickness direction can be lowered.
- aromatics such as benzene rings in the molecular chain are oriented in the plane direction to suppress deformation due to stress applied in the thickness direction. It is thought that it has the effect of
- the density of the polyester film having the easy-adhesive resin layer and before laminating the hard coat layer is preferably 1.380 g / cm 3 or more. More preferably, it is 1.383 g / cm 3 or more.
- the flexibility can be improved, and the film surface hardness, particularly the pencil hardness of the hard coat film after laminating the hard coat layer can be improved.
- the heat fixing temperature at the time of film formation 180 to 240 ° C.
- crystallization can proceed and the density can be effectively increased.
- the density of the polyester film having the easy-adhesive resin layer and before laminating the hard coat layer is so small that the difference in density of the polyester film alone having no easy-adhesive resin layer is negligible.
- the bending direction of the polyester film corresponds to the longitudinal direction (machine flow direction). By doing so, it is easy to lower the refractive index in the bending direction at the biaxial stretching and improve the flexibility. That is, it is preferable to stretch the unstretched polyester sheet at a stretching ratio of 1.2 to 2.0 times, more preferably 1.7 to 2.0 times in the longitudinal direction to obtain a polyester film. Then, in the width direction, it can be said that it is preferable to stretch at a stretching ratio of 4.0 to 6.0 times, more preferably 4.4 to 6.0 times.
- the polyester film having the easy-adhesive resin layer and before laminating the hard coat layer (1) has a refractive index of 1.590 to 1.620 in the bending direction.
- the refractive index in the direction of the folding part is 1.670 to 1.700.
- the refractive index in the thickness direction is 1.520 or less and (4) the density is 1.380 g / cm 3 or more at the same time, but it is within the above-mentioned preferable production conditions.
- the stretching ratio in the bending direction is 1.4 times or less
- the stretching ratio in the folding portion direction is less than 4.4 times
- the heat fixing temperature is 220 ° C. or less.
- the stretching ratio in the bending direction may be increased to 1.7 times or more
- the stretching ratio in the folding direction may be increased to 4.4 times or more
- the heat fixing temperature may be increased to about 230 ° C.
- the above four characteristics can be satisfied at the same time by fine-tuning any of the conditions or a combination thereof, such as lowering the stretching temperature in the bending direction and / or the folding portion direction.
- any film-forming method such as stretching, relaxation, heat fixation, and surface treatment may be used, but the refractive index and density of the film are described above. It can be said that it is a particularly preferable aspect in the present invention to control the above in a preferable range.
- it is suitable for foldable displays, which can obtain better bending resistance and surface hardness than conventional films, especially high pencil hardness of hard coat film after laminating a hard coat layer.
- Polyester film can be provided.
- the PET pellets are sufficiently vacuum-dried, they are supplied to an extruder, melt-extruded into a sheet at about 280 ° C., and cooled and solidified to form an unstretched PET sheet.
- the obtained unstretched sheet is stretched 1.2 to 2.0 times, more preferably 1.7 to 2.0 times in the longitudinal direction with a roll heated to 75 to 120 ° C. to obtain a uniaxially oriented PET film. ..
- the edge of the film is gripped with a clip and guided to a hot air zone heated to 75 to 120 ° C., and after drying, 4.0 to 6.0 times in the width direction, more preferably 4.4 to 6. Stretch 0 times.
- the heat treatment zone of 180 to 240 ° C. can be guided to perform the heat treatment for 1 to 60 seconds.
- a relaxation treatment of 0 to 10% may be performed in the width direction or the longitudinal direction.
- the ultimate viscosity of the polyester film is preferably in the range of 0.50 to 1.0 dl / g.
- the ultimate viscosity is 0.50 dl / g or more, the impact resistance is improved and the internal circuit of the display is less likely to be disconnected due to an external impact, which is preferable.
- the ultimate viscosity is 1.00 dl / g or less, the film production is stable and preferable without the increase in the filter pressure of the molten fluid becoming too large.
- the easy-adhesive resin layer is formed by applying a coating liquid for forming the easy-adhesive resin layer to one or both sides of an unstretched or longitudinally uniaxially stretched film, heat-treating and drying as necessary, and further unstretching at least. It can be obtained by a so-called in-line coating obtained by stretching in one direction. Heat treatment can be performed even after biaxial stretching.
- the final coating amount of the easy-adhesion layer is preferably controlled to 0.005 to 0.20 g / m 2 . When the coating amount is 0.005 g / m 2 or more, adhesiveness is obtained, which is preferable. On the other hand, when the coating amount is 0.20 g / m 2 or less, blocking resistance is obtained, which is preferable.
- the binder resin contained in the coating liquid used for laminating the easy-adhesion layer may be, for example, polyester resin, polyether polyurethane resin, polyester polyurethane resin, polycarbonate polyurethane resin, acrylic resin, etc., without particular limitation, but with a polyester film. It is preferable to contain a polyester resin in terms of high adhesion and refractive index. Further, among the dicarboxylic acid component and the diol component constituting the polyester resin, a polyester resin composed by copolymerizing at least a part of the dicarboxylic acid component containing a naphthalenedicarboxylic acid component capable of increasing the refractive index of the easily adhesive resin layer. preferable.
- a crosslinked structure may be formed in the binder resin contained in the easy-adhesive resin layer.
- the cross-linking agent contained in the coating liquid for forming an easy-adhesion layer include melamine compounds, isocyanate compounds, oxazoline compounds, epoxy compounds, and carbodiimide compounds, and self-crosslinking polyurethane resins and the like can also be blended.
- the cross-linking agent two or more kinds of each can be mixed and used. Due to the nature of the in-line coating, these are preferably coated with an aqueous coating liquid, and the resin or cross-linking agent is preferably a water-soluble or water-dispersible resin or compound.
- the polyester resin contained in the easy-adhesive resin layer is preferably a linear polyester containing a dicarboxylic acid component and a diol component (glycol component) as constituent components.
- dicarboxylic acid component examples include terephthalic acid, isophthalic acid, phthalic acid, 2,6 naphthalenedicarboxylic acid, 4,4-diphenyldicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, adipic acid, sebacic acid, and phenylindandicarboxylic acid.
- Dimeric acid and the like can be exemplified. Two or more of these components can be used.
- unsaturated polybasic acids such as maleic acid, fumaric acid, and itaconic acid
- hydroxycarboxylic acids such as p-hydroxybenzoic acid and p- ( ⁇ -hydroxyethoxy) benzoic acid are scarce. Can be used as a percentage.
- the proportion of the unsaturated polybasic acid component or the hydroxycarboxylic acid component is 10 mol% or less, preferably 5 mol% or less.
- the refractive index is increased and it becomes easier to control the iris-like color under a fluorescent lamp. In addition, it becomes possible to improve the moisture and heat resistance.
- the polymerization step and the copolymerization step of including the naphthalenedicarboxylic acid component in the polyester may be the so-called direct weight method or the transesterification method, and the dicarboxylic acid component such as the naphthalenedicarboxylic acid component is charged in the form of the ester derivative. It may be an ester.
- naphthalene dicarboxylic acid As the naphthalene dicarboxylic acid as described above, 2,6-naphthalene dicarboxylic acid is preferable.
- the ratio of the naphthalene dicarboxylic acid component to the total dicarboxylic acid components constituting the polyester resin is preferably 20 mol% or more, more preferably 30 mol% or more, further preferably 50 mol% or more, still more preferably 60 mol% or more. .. When it is 20 mol% or more, the effect of increasing the refractive index of the easy-adhesion resin layer is remarkable, which is preferable.
- the ratio of the naphthalene dicarboxylic acid component to the total dicarboxylic acid components constituting the polyester resin may be 100 mol%, but is more preferably 95 mol% or less due to the flexibility of the easy-adhesive resin layer. ..
- ethylene glycol, 1,3-propane glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol, and neopentyl glycol are further added as glycol components in the polyester resin.
- two or more of these can be used.
- the following formula is used for the polyester resin. It is one of the preferable forms to include the dicarboxylic acid component represented by (1) and / or the diol component represented by the following formula (2).
- the polyester resin is given flexibility, the coating film can be easily held even after the bending test, and the particle aggregates. It is possible to suppress cracks at the starting point.
- the dicarboxylic acid component of the formula (1) include adipic acid, sebacic acid, azelaic acid and the like.
- the diol component of the formula (2) include 1,4-butanediol and 1,6-hexanediol.
- the polyester resin is resistant to water or a water-soluble organic solvent (for example, an aqueous solution containing less than 50% by mass of alcohol, alkyl cell solve, ketone or ether) or an organic solvent (for example, toluene, ethyl acetate, etc.). Dissolved or dispersed ones can be used.
- a water-soluble organic solvent for example, an aqueous solution containing less than 50% by mass of alcohol, alkyl cell solve, ketone or ether
- an organic solvent for example, toluene, ethyl acetate, etc.
- a polyester resin When a polyester resin is used as an aqueous coating liquid, a water-soluble or water-dispersible polyester resin is used.
- a compound containing a sulfonic acid base or a carboxylic acid is used. It is preferable to copolymerize a compound containing an acid base.
- the number average molecular weight of the polyester resin is preferably 5000 to 40,000 in terms of coating film strength, ease of water dispersion, and the like. It is more preferably 10,000 to 30,000, and particularly preferably 12,000 to 25,000.
- the solid content of the resin polyester resin in the solid content of the easy-adhesive resin layer is preferably 20% by mass or more and 90% by mass or less in terms of adhesion and refractive index adjustment. More preferably, it is 30% by mass or more and 80% by mass or less.
- the polyester resin may be a single resin or a blend of two or more kinds. In the case of a blend of two or more kinds, it is preferable that the total of the polyester resin components has the above composition.
- the urethane resin that can be used for the easy-adhesive resin layer contains at least a polyol component and a polyisocyanate component as constituent components, and further contains a chain extender if necessary.
- the above-mentioned urethane resin is a polymer compound in which these constituent components are mainly copolymerized by a urethane bond. It is one of the preferable forms to include the polycarbonate polyol as a constituent component of the urethane resin because the coating film can be made flexible.
- the constituent components of these urethane resins can be identified by nuclear magnetic resonance analysis or the like.
- the diol component which is a constituent component of the polyurethane resin having a polycarbonate skeleton, contains an aliphatic polycarbonate polyol having excellent heat resistance and hydrolysis resistance.
- an aliphatic polycarbonate polyol it is preferable to use an aliphatic polycarbonate polyol from the viewpoint of preventing yellowing.
- Examples of the aliphatic polycarbonate polyol include an aliphatic polycarbonate diol and an aliphatic polycarbonate triol, and an aliphatic polycarbonate diol can be preferably used.
- Examples of the aliphatic polycarbonate diol which is a component of the urethane resin of the present invention include ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, and 3-methyl.
- -1,5-pentanediol 1,6-hexanediol, 1,9-nonanediol, 1,8-nonanediol, neopentyl glycol, diethylene glycol, dipropylene glycol, 1,4-cyclohexanediol, 1,4- Examples thereof include aliphatic polycarbonate diols obtained by reacting one or more diols such as cyclohexanedimethanol with carbonates such as dimethyl carbonate, diphenyl carbonate, ethylene carbonate and phosgen.
- polyisocyanate which is a component of the urethane resin of the present invention examples include aromatic aliphatic diisocyanates such as xylylene diisocyanate, isophorone diisocyanate, 4,4-dicyclohexylmethane diisocyanate, and 1,3-bis (isocyanatemethyl) cyclohexane.
- aromatic aliphatic diisocyanates such as, hexamethylene diisocyanate, and aliphatic diisocyanates such as 2,2,4-trimethylhexamethylene diisocyanate, or polys obtained by preliminarily adding one or more of these compounds to trimethylpropane or the like. Examples include isocyanates.
- the polyisocyanates are preferable for optics, which have no problem of yellowing and require high transparency. Further, such polyisocyanates are preferable because the coating film does not become too hard, stress due to shrinkage and swelling of the photocurable resin and the like can be relaxed, and adhesion is maintained.
- a sulfonic acid (salt) group or a carboxylic acid (salt) group can be introduced (copolymerized) into the urethane molecular skeleton. Since the sulfonic acid (salt) group is strongly acidic and it may be difficult to maintain moisture resistance due to its hygroscopic performance, it is preferable to introduce a weakly acidic carboxylic acid (salt) group. It is also possible to introduce a nonionic group such as a polyoxyalkylene group.
- a polyol compound having a carboxylic acid group such as dimethylolpropionic acid or dimethylolbutanoic acid is introduced as a copolymerization component as a polyol component to form a salt.
- the salt forming agent include trialkylamines such as ammonia, trimethylamine, triethylamine, triisopropylamine, tri-n-propylamine and tri-n-butylamine, and N such as N-methylmorpholine and N-ethylmorpholine.
- N-dialkylalkanolamines such as -alkylmorpholins, N-dimethylethanolamine and N-diethylethanolamine. These can be used alone or in combination of two or more.
- the composition molar ratio of the polyol compound having a carboxylic acid (salt) group in the urethane resin is that of the urethane resin.
- the total polyol component is 100 mol%, it is preferably 3 to 60 mol%, and preferably 5 to 40 mol%.
- the composition molar ratio is 3 mol% or more, the water dispersibility is good and preferable.
- the composition molar ratio is 60 mol% or less, water resistance is maintained and moist heat resistance is maintained, which is preferable.
- the glass transition temperature of the urethane resin in the present invention is preferably less than 0 ° C, more preferably less than ⁇ 5 ° C.
- suitable flexibility is easily exhibited from the viewpoint of stress relaxation of the coating layer, which is preferable.
- the easy-adhesive resin layer may be formed by containing a cross-linking agent.
- a cross-linking agent By containing a cross-linking agent, it becomes possible to further improve the adhesion under high temperature and high humidity.
- Specific examples of the cross-linking agent include urea-based, epoxy-based, melamine-based, isocyanate-based, oxazoline-based, and carbodiimide-based.
- melamine-based, isocyanate-based, oxazoline-based, and carbodiimide-based cross-linking agents are preferable because of the stability of the coating liquid over time and the effect of improving adhesion under high-temperature and high-humidity treatment. Further, in order to promote the cross-linking reaction, a catalyst or the like can be appropriately used as needed.
- the content of the cross-linking agent is preferably 5% by mass or more and 50% by mass or less in the total solid components of the coating layer. More preferably, it is 10% by mass or more and 40% by mass or less. When it is 10% by mass or more, the strength of the resin of the easy-adhesive resin layer is maintained, the adhesion under high temperature and high humidity is good, and when it is 40% by mass or less, the flexibility of the resin of the coating layer is maintained. It is preferable that the adhesiveness is maintained after repeated folding tests at room temperature and high temperature and high humidity.
- the easy-adhesion resin layer in the present invention may contain silica particles, but preferably contains at least one compound selected from titanium compounds and zirconium compounds.
- the iris-like color (interference spot) of the hard coat film is the refractive index of the polyester film as the base material (for example, 1.62 to 1.65) and the refractive index of the hard coat layer made of acrylic resin or the like (for example, 1.52). It is said that it occurs because the difference between the two is large. In order to reduce the difference in refractive index between the layers and prevent the occurrence of interference spots, the difference in refractive index between the polyester film and the easy-adhesion resin layer and the difference in refractive index between the easy-adhesion resin layer and the hard coat layer should be reduced.
- the refractive index of the easy-adhesion resin layer It is important to control the refractive index of the easy-adhesion resin layer.
- control is facilitated by containing the above compound having a high refractive index.
- the titanium compound include a water-soluble titanium chelate compound, a water-soluble titanium acylate compound, titanium oxide, titanium chloride, and the like, and among them, titanium dioxide (titania) is preferably used.
- zirconium compound examples include a water-soluble zirconium chelate compound, a water-soluble zirconium acylate compound, zirconium acetate, zirconium hydride, zirconium oxide and the like, and among them, zirconium dioxide (zirconia) is preferably used. It is also preferable that the compound having a high refractive index is in the form of particles.
- the average particle size of metal oxide particles such as zirconium dioxide is preferably 5 nm or more and 150 nm or less. Further, it is preferably 10 nm or more and 100 nm or less, and further preferably 30 nm or more and 70 nm or less.
- the film haze can be lowered by designing the average particle size of at least one kind of metal oxide fine particles selected from titanium oxide particles, zirconium oxide particles and silica particles within the above range. Further, it is desirable that the particulate metal compound is designed to have a particle diameter smaller than the thickness of the easy-adhesion resin layer in order to obtain a cushioning effect when repeatedly folded, and it is preferable that the particle diameter is less likely to cause particle aggregation. .. It is preferable to suppress particle aggregation because it does not become a starting point of cracks or the like in the easy-adhesive resin layer when folded.
- the content of the metal oxide particles is such that the particles have a buffering effect when the easy-adhesive resin layer is folded, and contradict the mass of the solid content of the easy-adhesive resin layer so as not to be a starting point of cracks due to particle aggregation. It is preferable to design the solid content in a mass ratio of 0.1 mass% or more and 18 mass% or less. It is more preferably 0.5% by mass or more and 17% by mass or less, further preferably 1% by mass or more and 15% by mass or less, and particularly preferably 2% by mass or more and 13% by mass or less.
- the particulate metal compound in the easy-adhesion resin layer has a smaller abundance ratio in the folding portion direction than in the bending direction. Since fine cracks that occur during repeated folding are likely to occur in the direction of the folding portion where a load is applied in the thickness direction, it is considered that the occurrence of cracks can be suppressed by reducing the particle frequency in the direction of the folding portion. It is considered that reducing the particle frequency can reduce the particle aggregation rate and the frequency of crack propagation. The abundance ratio of particles in each direction can be confirmed by observing a cross section with a transmission electron microscope (TEM).
- TEM transmission electron microscope
- the abundance ratio of the particulate metal compound in the easy-adhesion resin layer for each direction formation by an in-line coating method is preferable.
- the in-line coating method there is a step of stretching the coating liquid containing the easy-adhesive resin material in at least one direction after coating. Therefore, the abundance ratio of the particles in the easy-adhesive resin layer is changed by adjusting the draw ratio. Can be thought of as possible.
- Particulate metal compounds may be used in combination with a dispersant to prevent aggregation.
- the dispersant used in the present invention may be a polymer compound capable of maintaining a binder resin composed of an emulsion, dissolving or dispersing a cross-linking agent described later, and dispersing metal oxide fine particles.
- polymer dispersants such as polyvinyl, polyacrylic acid, polycarboxylic acid, and polyurethane can be used. More specifically, as the polyvinyl polymer, polyvinyl alcohol, polyvinylpyrrolidone, polyvinyl acetate, polyvinyl ester and the like and their copolymers, and as the polyacrylic acid polymer, polyacrylic acid, sodium polyacrylate, ammonium polyacrylate and the like, etc. And their copolymers, polycarboxylic acid polymers such as polycarboxylic acid, sodium polycarboxylate, ammonium polycarboxylate and their copolymers, and polyurethane polymers such as polyurethane and their copolymers can be used. , These copolymers and copolymers with sulfonic acid polymers can also be used. Among these, as the dispersant for metal fine particles, an acrylic resin such as a polyacrylic acid polymer is preferable.
- the metal oxide particles are particles having a dispersant on a part or all of the surface thereof.
- the dispersant By containing the dispersant, the effect of suppressing the aggregation of the metal oxide particles can be obtained.
- the particles covered by the easy-adhesive resin layer stress relaxation during repeated folding tests can be expected while maintaining the transparency of the coating film.
- the metal oxide particles By containing the dispersant, it is preferable that the metal oxide particles are less likely to aggregate and cracks are less likely to occur in the easily adhesive resin layer depending on the process of forming the coating film.
- the method of surface-treating the metal oxide particles with an acrylic resin is not particularly limited, but specifically, a method of adding a mixture of the metal oxide particles and the acrylic resin in advance to a solvent and then dispersing the metal oxide particles. Examples thereof include a method in which metal oxide particles and an acrylic resin are sequentially added and dispersed in a solvent.
- a dissolver As a device for dispersing these, a dissolver, a high speed mixer, a homo mixer, a meador, a ball mill, a roll mill, a sand mill, a paint shaker, an SC mill, an annual type mill, a pin type mill, etc. can be used.
- the amount of the dispersant added to the metal oxide particles is preferably 5% by mass or more and less than 40% by mass based on the mass of the metal oxide particles.
- the amount of the dispersant added is 5% by mass or more, it is preferable in that a good dispersed state of the metal oxide particles can be obtained in the easy-adhesion resin layer.
- the amount of the dispersant added is less than 40% by mass, it is preferable because the refractive index of the easily adhesive resin layer can be easily adjusted by taking advantage of the characteristics of the metal oxide particles. Further, the addition amount of 10% by mass or more and 30% by mass or less is more preferable.
- the iris-like color can be reduced by designing the refractive index of the easy-adhesion resin layer within a certain range and satisfying the thin film interference principle. Further, it is considered that the easy-adhesive resin layer is filled with the metal compound used for adjusting the refractive index in an amount in a certain range to have an effect of buffering damage to the easy-adhesive resin layer when repeatedly folded.
- n is the refractive index of the easy-adhesive resin layer
- d is the thickness of the easy-adhesive resin layer
- ⁇ b is the bottom wavelength of the reflection spectrum, which can be appropriately set in the range of 450 to 650 nm.
- the polyester film having the easy-adhesion resin layer in the present invention is designed to have different refractive indexes in the bending direction and the folding portion direction, it is preferable to control the refractive index of the easy-adhesion resin layer in consideration of each direction.
- the refractive index of the easy-adhesive resin layer is controlled to be low with respect to the refractive index in the bending direction of the polyester film having the easy-adhesive resin layer and before laminating the hard coat layer.
- the range of the refractive index difference between the easy-adhesion resin layer and the bending direction is preferably greater than 0 and 0.070 or less. Further, it is preferably 0.005 or more and 0.065 or less. Furthermore, it is preferably 0.010 or more and 0.060 or less.
- the refractive index of the easy-adhesion resin layer is lower than the bending direction of the polyester film, the difference in the refractive index from the laminated hard coat layer becomes small, and iris-like color (interference spots) is effectively suppressed, which is preferable. Further, when the refractive index difference is 0.070 or less, the refractive index difference with the polyester film does not become too large, and iris-like color (interference spots) can be effectively suppressed, which is preferable.
- the bending direction is designed with a resin component having an amorphous structure rather than a resin component having a large crystal structure because compressive stress is applied when the easy-adhesion resin layer is bent inward and tensile stress is applied when the easy-adhesion resin layer is bent outward. It is preferable, and it is preferable to add an appropriate amount of a metal compound to supplement the refractive index.
- the refractive index of the easy-adhesive resin layer is controlled to be low with respect to the refractive index in the direction of the folded portion of the polyester film having the easy-adhesive resin layer and before laminating the hard coat layer.
- the range of the difference between the easily adhesive resin layer and the refractive index in the direction of the folded portion is preferably 0.080 or more and 0.150 or less. Further, it is preferably 0.085 or more and 0.14 or less. Further, it is preferably 0.090 or more and 0.13 or less.
- the refractive index When the refractive index is lower than the direction of the folded portion of the polyester film, the difference in the refractive index from the laminated hard coat layer becomes small, and the iris-like color (interference spot) is effectively suppressed, which is preferable. Further, when the refractive index difference is 0.150 or less, the refractive index difference with the polyester film does not become too large, and iris-like color (interference spots) can be effectively suppressed, which is preferable.
- the average particle size of the fine particles is preferably 2 ⁇ m or less. When the average particle size of the particles exceeds 2 ⁇ m, the particles are likely to fall off from the easy-adhesion layer.
- the particles contained in the easy-adhesion layer include, for example, titanium oxide, barium sulfate, calcium carbonate, calcium sulfate, silica, alumina, talc, kaolin, clay, calcium phosphate, mica, hectrite, zirconia, tungsten oxide, lithium fluoride, etc.
- Examples thereof include inorganic particles such as calcium fluoride and organic polymer particles such as styrene-based, acrylic-based, melamine-based, benzoguanamine-based, and silicone-based particles. These may be added to the easy-adhesion layer alone, or may be added in combination of two or more. Silica particles having an average particle size of 200 nm or more and 700 nm or less are particularly preferably used in order to give an appropriate slipperiness to the coating layer.
- the amount of particles added to impart slipperiness is preferably less than 1% by mass with respect to the easy-adhesion resin layer. If it is less than 1% by mass, particles larger than the thickness of the easy-adhesive resin layer are present in a small number in the easy-adhesive resin layer, so that it is difficult for cracks to propagate during folding, which is preferable. Further, 0.5 weight percent or less is a preferable embodiment.
- a known method can be used in the same manner as the above coating layer.
- the reverse roll coating method, the gravure coating method, the kiss coating method, the roll brush method, the spray coating method, the air knife coating method, the wire bar coating method, the pipe doctor method, etc. can be mentioned, and these methods can be used alone. Alternatively, it can be performed in combination.
- the polyester film of the present invention When the polyester film of the present invention is used as a surface protective film for protecting a display by locating it on the surface of a foldable display, it is preferable to have a hard coat layer on at least one surface thereof.
- the hard coat layer is preferably located on the surface side of the display on the polyester film and used in the display.
- the resin forming the hard coat layer siloxane-based, inorganic hybrid-based, acrylic-based, urethane acrylate-based, polyester acrylate-based, epoxy-based, and the like can be used without particular limitation. Further, two or more kinds of materials can be mixed and used, and particles such as an inorganic filler and an organic filler can be added.
- Resins forming the hard coat layer include compounds having (meth) acrylate-based functional groups such as polyester (meth) acrylate, urethane (meth) acrylate, epoxy (meth) acrylate, and silicone (meth) acrylate, allyl groups, and vinyl. Examples thereof include compounds having a functional group having an unsaturated double bond such as a group. Further, a polyfunctional monomer may be used in combination in order to increase the hardness of the hard coat layer.
- polyfunctional monomer examples include trimethylolpropane tri (meth) acrylate, hexanediol (meth) acrylate, tripropylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, pentaerythritol tri (meth) acrylate, and dipenta.
- examples thereof include erythritol hexa (meth) acrylate, 1,6-hexanediol di (meth) acrylate, and neopentyl glycol di (meth) acrylate.
- the above materials may be used alone, or two or more kinds of materials may be mixed and used.
- the photopolymerization initiator may be a radical polymerization system, a cation polymerization system, or a mixed system of cation polymerization and radical polymerization, but a radical polymerization system is particularly preferable because the reaction rate is high and the productivity is excellent.
- UV radical polymerization initiators include alkylphenones, benzoins, benzophenones, phosphine oxides, ketals, anthraquinones, thioxanthones, azo compounds, peroxides, 2,3-dialkyldione compounds, disulfides.
- Examples thereof include compounds, fluoroamine compounds, aromatic sulfoniums, titanocene, and phenyl oxyacetate, which may be used alone or in combination of two or more. More specific examples include acetophenone, 2,2-diethoxyacetophenone, p-dimethylacetophenone, p-dimethylaminopropiophenone, benzophenone, 2-chlorobenzophenone, 4,4'-dichlorobenzophenone, 4,4'.
- the amount of the photopolymerization initiator added is 0.1 part by mass or more, more preferably 1 part by mass or more, and the upper limit is 30 parts by mass or less, more preferably 20 parts by mass, with respect to 100 parts by mass of the active energy ray-curable resin. It can be used in the following range.
- the addition amount is 0.1 part by mass or more, the hardness of the hard coat layer can be increased, which is preferable. Further, when the addition amount is 30 parts by mass or less, the hard coat layer is not likely to turn yellow, and the hard coat layer is sufficiently cured, which is preferable.
- additives can be contained within a range that does not impair the performance of the hard coat.
- additives include polymerization inhibitors, cross-linking agents, antistatic agents, adhesive improvers, antioxidants, leveling agents, coupling agents, defoamers, fillers, solvents, antiglare agents, and antireflection agents. , Inorganic filler, organic filler and the like.
- the refractive index of the hard coat layer is preferably smaller than that of the easy-adhesion resin layer from the viewpoint of suppressing the iris-like color (interference spots) of the hard coat film.
- the film thickness of the hard coat layer is preferably 1 to 50 ⁇ m. If it is 1 ⁇ m or more, it can be sufficiently cured. In order to increase the hardness of the pencil, it is more preferably 5 ⁇ m or more. Further, by setting the thickness to 50 ⁇ m or less, curling due to curing shrinkage of the hard coat can be suppressed, and the handleability of the film can be improved.
- a Meyer bar, a gravure coater, a die coater, a knife coater and the like can be used without particular limitation, and can be appropriately selected according to the viscosity and the film thickness.
- a curing method of the hard coat layer energy rays such as ultraviolet rays and electron beams and a curing method by heat can be used, and in order to reduce damage to the film, a curing method using ultraviolet rays and electron beams is preferable.
- the pencil hardness of the hard coat layer is preferably 3H or higher, and more preferably 4H or higher. If the pencil has a hardness of 3H or more, it will not be easily scratched and the visibility will not be deteriorated. Generally, it is preferable that the pencil hardness of the hard coat layer is high, but it may be 9H or less, 8H or less, or 6H or less without any problem in practical use.
- the hard coat layer in the present invention can be used for the purpose of increasing the pencil hardness of the surface as described above to protect the display, and preferably has a high transmittance.
- the transmittance of the hard coat film is preferably 85% or more, more preferably 87% or more, and even more preferably 88% or more. When the transmittance is 85% or more, sufficient visibility can be obtained.
- the higher the total light transmittance of the hard coat film, the more preferable, but from the viewpoint of stable production it is preferably 99% or less, and may be 97% or less.
- the haze of the hard coat film is generally preferably low, preferably 3% or less.
- the haze of the hard coat film is more preferably 2% or less, and most preferably 1% or less.
- the visibility of the image can be improved.
- 0.1% or more is preferable, and 0.3% or more may be used.
- the hard coat layer may have other functions added to it.
- the present invention also includes a hard coat layer having functionality such as an antiglare layer having a certain pencil hardness, an antiglare antireflection layer, an antireflection layer, a low reflection layer, and an antistatic layer as described above. Is preferably applied.
- a hard coat layer may also be provided when used as a base film for a touch panel module.
- an ITO layer is used as the transparent electrode layer of the touch panel module, it is preferable to provide a refractive index adjusting layer between the base film and the transparent electrode layer in order to make the electrode pattern difficult to see.
- the hard coat layer itself may also serve as the refractive index adjusting layer, and the refractive index adjusting may be separately laminated.
- Density The density was measured according to a method (density gradient tube method) conforming to JIS K7112: 1999. (Unit: g / cm 3 ).
- Average particle size of particles in polyester film or easy-adhesion resin layer By observing the particles in the cross section of the film with a scanning electron microscope, observing 50 particles, and using the average value as the average particle size. Do.
- the particle size of non-spherical amorphous particles can be calculated as the equivalent circle diameter.
- the equivalent circle diameter is a value obtained by dividing the observed particle area by the pi ( ⁇ ), calculating the square root, and doubling it. (The unit depends on the average particle size, but mainly nm is used)
- Refractive index of the easy-adhesive resin layer For the refractive index of the easy-adhesive resin layer, the reflection spectrum measured using a spectrophotometer (product name "UV-3150", manufactured by Shimadzu Corporation) and the Fresnel coefficient were used. It can be calculated by fitting with the reflection spectrum calculated from the optical model of the thin film.
- the reflectance of the easy-adhesive layer is the surface opposite to the surface on the easy-adhesive resin side for which the refractive index of the polyester film base material in the state before laminating the easy-adhesive resin layer and the hard coat layer is to be measured.
- FIG. 1 is a schematic view for showing the bending radius when the foldable display is folded, and in consideration of the case where the polyester film is arranged on the inner surface of the folded form, FIG.
- the bending test is performed as a model assuming that the location of reference numeral 11 is set to 1.5 mm. After the bending treatment was completed, the sample was placed on a flat surface with the inside of the bending facing down, and visually observed. ⁇ : No cracks or deformation can be confirmed in the sample. ⁇ : The sample has cracks or creases, and when placed horizontally, the maximum height is 5 mm or more.
- FIG. 1 is a schematic view for showing the bending radius when the foldable display is folded, and in consideration of the case where the polyester film is arranged on the inner surface of the folded form, FIG. A bending test is performed as a model assuming that the location of reference numeral 11 is set to 0.5 mm. The film surface on the outside of the bent portion was observed at 700 times that of a digital microscope (RH8800 manufactured by HIROX), and the presence or absence of wrinkles (cracks) was observed.
- RH8800 manufactured by HIROX digital microscope
- Test force Pushing depth after unloading The sample is cut into a square of about 2 cm, and the opposite side of the measurement surface is glued on the micro cover glass 18 x 18 mm (manufactured by Matsunami Glass Co., Ltd.) (Cemedine (registered trademark) High). It was fixed at Super 30). After sticking and fixing, leave it at room temperature for 12 hours or more, and then use a dynamic ultra-micro hardness tester "DUH-211" (manufactured by Shimadzu Corporation) under the following conditions to push in depth after unloading the test force ( ⁇ m) was measured.
- a dynamic ultra-micro hardness tester "DUH-211" manufactured by Shimadzu Corporation
- Test mode Load-unload test Indenter used: Ridge angle 115 degrees, triangular pyramid indenter Indenter modulus: 1.140 ⁇ 10 6 N / mm 2 Indenter Poisson's ratio: 0.07 Test power: 50mN Load speed: 4.44 mN / sec Load holding time: 2 sec Unloading retention time: 0 sec
- the heat shrinkage rate is measured at a position divided into three equal parts in the width direction of the sample film, and the average value of the three points is taken as the heat shrinkage rate (%).
- Heat shrinkage rate (%) [(AB) x 100] / A
- the sample film is cut and measured separately in both the bending direction and the folding direction so that the vertical and horizontal directions are different, and the data in the direction in which the measured value is large is defined as the maximum heat shrinkage rate (%).
- the refractive index of the hard coat layer is a multilayer thin film using the reflection spectrum measured using a spectrophotometer (product name "UV-3150", manufactured by Shimadzu Corporation) and the Fresnel coefficient. It can be calculated by fitting with the reflection spectrum calculated from the optical model of.
- the reflectance of the hard coat layer is such that the hard coat composition is applied onto a polyethylene terephthalate (PET) substrate having a thickness of 50 ⁇ m without an easy-adhesion resin layer and cured to obtain a hard coat having a thickness of 1 to 10 ⁇ m.
- PET polyethylene terephthalate
- a black vinyl tape (for example, product name "Yamato") having a width larger than the measurement spot area is formed on the surface (back surface) of the PET substrate opposite to the functional layer side surface to prevent back surface reflection.
- Vinyl tape NO200-38-21 manufactured by Yamato Co., Ltd., 38 mm width shall be attached before measurement.
- the results of visual observation are ranked according to the following criteria. The observation will be carried out by 5 people who are familiar with the evaluation, and the highest rank will be the evaluation rank. If the numbers are the same in the two ranks, the center of the three ranks is adopted. For example, if ⁇ and ⁇ are 2 people each and ⁇ is 1 person, then ⁇ , if ⁇ is 1 person and ⁇ and ⁇ are 2 people each, then ⁇ , and if ⁇ and ⁇ are 2 people each, ⁇ is 1. In the case of a name, ⁇ is adopted respectively. ⁇ : No iris color is seen even when observed from all angles ⁇ : Slight iris color is seen depending on a certain angle ⁇ : Slight iris color is observed ⁇ : Clear iris color is observed Be done
- the results of visual observation are ranked according to the following criteria. The observation will be carried out by 5 people who are familiar with the evaluation, and the highest rank will be the evaluation rank. If the numbers are the same in the two ranks, the center of the three ranks is adopted. For example, if ⁇ and ⁇ are 2 people each and ⁇ is 1 person, then ⁇ , if ⁇ is 1 person and ⁇ and ⁇ are 2 people each, then ⁇ , and if ⁇ and ⁇ are 2 people each, ⁇ is 1. In the case of a name, ⁇ is adopted respectively. ⁇ : No iris color is seen even when observed from all angles ⁇ : Slight iris color is seen depending on a certain angle ⁇ : Slight iris color is observed ⁇ : Clear iris color is observed Be done
- this test was conducted for the purpose of detecting interference spots caused by fine adhesion failure defects such as interfacial peeling and cracks between the hard coat layer, the easy-adhesion resin layer and the polyester film layer. It is being carried out.
- Pencil hardness Using the pencil hardness of the hard coat film as a sample, the measurement was performed at a load of 750 g and a speed of 1.0 mm / s according to JIS K 5600-5-4: 1999. In the present invention, 3H or more was regarded as acceptable.
- esterification reaction device a continuous esterification reaction device consisting of a three-stage complete mixing tank having a stirrer, a splitter, a raw material charging port and a product extraction port is used, the TPA is 2 tons / hr, and the EG is TPA1.
- the amount of antimony trioxide was 2 mol per mol
- the amount of Sb atom was 160 ppm with respect to the produced PET, and these slurries were continuously supplied to the first esterification reaction can of the esterification reaction apparatus at normal pressure.
- the reaction was carried out at 255 ° C. with an average residence time of 4 hours.
- the reaction product in the first esterification reaction can is continuously taken out of the system and supplied to the second esterification reaction can, and distilled from the first esterification reaction can in the second esterification reaction can.
- 8% by mass of the EG to be produced is supplied to the produced polymer (produced PET), and an EG solution containing magnesium acetate in an amount of 65 ppm of Mg atoms with respect to the produced PET and 20 ppm of P atoms with respect to the produced PET.
- An EG solution containing an amount of TMPA was added, and the reaction was carried out at normal pressure at an average residence time of 1.5 hours and at 260 ° C.
- the reaction product in the second esterification reaction can is continuously taken out of the system and supplied to the third esterification reaction can, and further contains TMPA in an amount of 20 ppm of P atoms with respect to the produced PET.
- An EG solution was added, and the reaction was carried out at normal pressure at an average residence time of 0.5 hours and at 260 ° C.
- the esterification reaction product produced in the third esterification reaction can is continuously supplied to a three-stage continuous polycondensation reaction apparatus to perform polycondensation, and further, a filter medium of a stainless sintered body (nominal filtration accuracy of 5 ⁇ m). The particles were filtered through 90% of the particles) to obtain polyethylene terephthalate pellets (R1) having an ultimate viscosity of 0.62 dl / g.
- the copolymerized polyester resins (a1) to (a2) for forming the easy-adhesive resin layer were polymerized as follows. In a stainless steel autoclave equipped with a stirrer, thermometer, and partial recirculation cooler, 410.3 parts by mass of dimethyl 2,6-naphthalenedicarboxylic acid, 46.3 parts of sebacic acid, 42.5 dimethyl sodium 5-sulfoisophthalate.
- the transesterification reaction was carried out over 4 hours. Then, the temperature was raised to 255 ° C., the reaction system was gradually depressurized, and then the reaction was carried out under a reduced pressure of 30 Pa for 1 hour and 30 minutes to obtain a copolymerized polyester resin (a1). The obtained copolymerized polyester resin was pale yellow and transparent.
- the composition of the copolymerized polyester resin (a1) is as shown in Table 1.
- reaction solution reached a predetermined amine equivalent.
- reaction solution was cooled to 40 ° C., and then 9.03 parts by mass of triethylamine was added to obtain a polyurethane prepolymer solution.
- 450 g of water was added to a reaction vessel equipped with a homodisper capable of high-speed stirring, the temperature was adjusted to 25 ° C., and the isocyanate group-terminated prepolymer was added and dispersed in water while stirring and mixing at 2000 min- 1. did. Then, under reduced pressure, acetonitrile and a part of water were removed to prepare a water-soluble polyurethane resin (B-1) having a solid content of 35% by mass.
- melamine-based cross-linking agent As the melamine-based cross-linking agent, Beccamin (registered trademark) M-3 (solid content concentration 60%) manufactured by DIC Corporation was used (melamine-based cross-linking agent (C-3)).
- zirconium oxide particles 2283.6 g of pure water and 403.4 g of oxalic acid dihydrate were put into a 3 liter glass container and heated to 40 ° C. to prepare a 10.72 mass% oxalic acid aqueous solution. While stirring this aqueous solution, zirconium oxycarbonate powder (ZrOCO 3 , AMR Internat) ional Corp. It contains 39.76% by mass in terms of ZrO 2 . ) 495 .. After gradually adding 8 g and mixing for 30 minutes, heating was performed at 90 ° C. for 30 minutes.
- the transmittance measured by adjusting the sol to a ZrO 2 concentration of 2.0% by mass with pure water was 88%.
- the particles were observed with a transmission electron microscope, most of them were aggregated particles of ZrO 2 primary particles of around 7 nm.
- washing and concentrating 4000 g of zirconia sol having a ZrO 2 concentration of 4.0% by mass obtained by performing the above hydrothermal treatment while gradually adding pure water is performed to obtain a ZrO 2 concentration.
- 953 g of zirconia sol having a transmittance of 76% at 13.1% by mass, pH 4.9, and a ZrO 2 concentration of 13.1% by mass was obtained.
- zirconium oxide particle aqueous dispersion (Zirconium oxide particle aqueous dispersion)
- the zirconia sol obtained above was diluted with water to obtain a 10% by mass zirconia aqueous dispersion D-1.
- Nanouse (R) ZR-40BL solid content 40% by mass, average particle size 100 nm
- D-2 nanouse (R) ZR-40BL (solid content 40% by mass, average particle size 100 nm) of zirconia sol manufactured by Nissan Chemical Industries, Ltd. was used as D-2.
- Zirconium oxide dispersion SZR-W (solid content 30% by mass, average particle diameter 3 nm) manufactured by Sakai Chemical Industry Co., Ltd. was used as D-3.
- Titanium oxide particles Titanium tetrachloride (OSAKA Titanium Technologies -'s Co.) and titanium tetrachloride aqueous solution 12.09kg containing 7.75 wt% in terms of TiO 2 relative to the ammonia water containing ammonia 15 wt% (manufactured by Ube Industries, Ltd. ) 4.69 kg was mixed to prepare a white slurry liquid having a pH of 9.5. Next, this slurry was filtered and then washed with pure water to obtain 9.87 kg of a hydrous titanium acid cake having a solid content of 10% by mass.
- the obtained mixed aqueous solution was cooled to room temperature and then concentrated with an ultrafiltration membrane device (ACV-3010 manufactured by Asahi Kasei Co., Ltd.) to obtain titanium-based fine particles having a solid content of 10% by mass.
- An aqueous dispersion sol containing 9.90 kg (D-2) was obtained.
- the solid matter contained in the sol thus obtained was measured by the above method, it was found to be titanium-based fine particles (primary particles) having a rutile-type crystal structure and made of a composite oxide containing titanium and tin. It was.
- the content of the metal component contained in the titanium-based fine particles was measured, TiO 2 87.2% by mass, SnO 2 11.0% by mass, and K 2 O were measured based on the oxide conversion standard of each metal component. It was 1.8% by mass.
- the pH of the mixed aqueous solution was 10.0.
- the aqueous dispersion sol containing the titanium-based fine particles is transparent milky white, and the average particle size of the titanium-based fine particles contained in the aqueous dispersion sol is 35 nm, and the coarse particles having a particle diameter of 100 nm or more are further formed.
- the distribution frequency was 0%.
- the refractive index of the obtained titanium-based fine particles could be considered to be 2.42.
- Titanium oxide particle aqueous dispersion (Titanium oxide particle aqueous dispersion) The titanium-based fine particles obtained above were diluted with water to obtain a 10% by mass titania aqueous dispersion D-4.
- CR-50-2 manufactured by Ishihara Sangyo Co., Ltd. was diluted with water and used as a 10% by mass titania aqueous dispersion system D-5 (average particle size 250 nm).
- silica particles colloidal silica having a particle diameter of 40 nm and a solid content concentration of 30% by mass was used as D-7.
- Acrylic fine particles manufactured by Nippon Shokubai, Epostal MX030W (solid content 10% by mass, average particle diameter 40 nm) were used as D-9.
- silica particles having a particle size of 450 nm and a solid content concentration of 40% by mass were used as DF-1.
- Dispersant As a dispersant for improving the dispersibility of fine particles, it was used as a polyacrylic acid dispersant (manufactured by Toagosei Co., Ltd .: Aron A-30SL) DP-1.
- a coating liquid P-1 Water 47.69 parts by mass Isopropanol 25.00 parts by mass Polyester resin (Aw-1) 17.85 parts by mass Water-dispersible blocked isocyanate compound (C-1) 4.78 parts by mass Zirconia / titania mixed water dispersion (D- 6) 4.46 parts by mass Dispersant (DP-1) 0.13 parts by mass Silica particles (DF-1) 0.06 parts by mass (silica sol with an average particle size of 450 nm, solid content concentration 40% by mass) Silicone-based surfactant (E-1) 0.03 parts by mass (silicone-based, solid content concentration 100% by mass)
- Example 1 Polyethylene terephthalate pellets (R1) were fed to the extruder and melted at 285 ° C. This polymer is filtered through a stainless steel sintered filter medium (nominal filtration accuracy of 10 ⁇ m particles 95% cut), extruded into a sheet from the base, and then cast into a casting drum with a surface temperature of 30 ° C. using an electrostatic application casting method. They were brought into contact and cooled and solidified to form an unstretched film. This unstretched film was uniformly heated to 75 ° C. using a heating roll and heated to 85 ° C. with a non-contact heater to perform 1.4 times roll stretching (longitudinal stretching).
- the above-mentioned coating liquid (P-1) for forming an easily adhesive resin layer was applied to both surfaces of the obtained uniaxially stretched film by a roll coating method, and then dried at 80 ° C. for 20 seconds.
- the final (after biaxial stretching) coating amount after drying was adjusted to 0.09 g / m 2 . Then, it is guided to a tenter, preheated at 105 ° C., laterally stretched 4.0 times at 95 ° C., fixed in width, heat-fixed at 230 ° C. for 5 seconds, and further relaxed by 4% in the width direction at 180 ° C.
- a polyethylene terephthalate film having a thickness of 50 ⁇ m was obtained.
- a hard coat coating liquid (H-1 below) was applied to one surface of the polyethylene terephthalate film having the above-mentioned easy-adhesive resin layer so that the film thickness after drying was 10 ⁇ m, and the temperature was 80 ° C. After drying for 1 minute in the above, the film was irradiated with ultraviolet rays (integrated light amount 200 mJ / cm 2 ) to obtain a hard coat film.
- Coating liquid for forming a hard coat layer H-1
- Urethane acrylate-based hard coating agent manufactured by Arakawa Chemical Industry Co., Ltd., beam set (registered trademark) 577, solid content concentration 100%
- photopolymerization initiator manufactured by BASF Japan, manufactured by Irgacure (registered trademark) 184, solid content
- leveling agent manufactured by BASF Japan Ltd., BYK307, solid content concentration 100%
- a coating liquid (H-1) for forming a hard coat layer having a concentration of 40% was prepared.
- Example 3 A polyester film and a hard coat film were obtained in the same manner as in Example 1 except that the draw ratio was changed in the longitudinal direction shown in Table 3.
- Example 4 A polyester film and a hard coat film were obtained in the same manner as in Example 1 except that the stretching ratio in the width direction was changed to 5.5 times and the heat fixing temperature was changed to 190 ° C.
- Examples 5 to 14 A polyester film and a hard coat film were obtained in the same manner as in Example 1 except that the coating liquid for forming the easy-adhesive resin layer was changed to P-2 to P-11 as shown in Table 3.
- Example 1 A polyester film and a hard coat film were obtained in the same manner as in Example 1 except that the film was stretched only in the width direction and stretched in the lateral uniaxial direction without stretching in the longitudinal direction.
- Example 2 A polyester film and a hard coat film were obtained in the same manner as in Example 4 except that the film was stretched only in the width direction without stretching in the longitudinal direction and was stretched in the lateral uniaxial direction.
- Example 8 A polyester film and a hard coat film were obtained in the same manner as in Example 1 except that the draw ratio in the longitudinal direction was changed to 3.4 times.
- Example 15 A polyester film and a hard coat film were obtained in the same manner as in Example 1 except that the coating liquid was changed to P-17 to P-18 as shown in Table 3.
- Example 17 and 18 As shown in Table 4, a polyester film and a hard coat film were obtained in the same manner as in Example 1 except that the hard coat coating liquid was changed to H-1 and changed to H-2 and H-3 below.
- At least one compound selected from titanium oxide particles, zirconium oxide particles, and silica particles which are polyester films having a refractive index in each direction in a certain range and having a particle size in a certain range.
- the easy-adhesive resin layer contained acrylic particles, but the refractive index adjustment was insufficient, so that the interference spots deteriorated even before the bending test.
- the cross section of the easy-adhesion resin layer was observed with a transmission microscope, it seems that the cushioning effect could not be obtained because the particles were deformed and agglomerated.
- Comparative Example 12 in which the easy-adhesive resin layer was changed, the particle size of the titanium oxide particles contained in the easy-adhesive resin layer was large, and deterioration was observed with respect to the interference spots after the bending test.
- the cross section of the easy-adhesive resin layer was observed with a transmission electron microscope, it seems that the buffering effect of the particles could not be obtained when the easy-adhesive resin layer was repeatedly folded because the amount of particles that could exist in the easy-adhesive resin layer was small.
- Example 15 in which the easy-adhesion resin layer was changed, the interference spots before the bending test were good.
- the interference spots after the bending test tended to decrease slightly.
- a tendency of agglomeration of the contained zirconium oxide particles and titanium oxide particles was observed. It seems that the amount of particles was excessive and the dispersed state was not optimal, but overall it was satisfactory.
- Example 16 In Example 16 in which the easy-adhesion resin layer was changed, the interference spots before the bending test were good, but the interference spots after the bending test tended to decrease slightly.
- the cross section of the easy-adhesion resin layer was observed with a transmission microscope, the zirconium oxide particles contained therein tended to aggregate. It seems that the amount of particles was excessive and the dispersed state was not optimal, but overall it was satisfactory.
- the hard coat film is arranged on the surface of one continuous display via the folding portion, and the hard coat layer is arranged so as to be located on the surface of the display.
- the one using the hard coat film of each example satisfied the operation and visibility as a smartphone that can be folded in half at the center and carried. In addition, the surface was not dented by an external force.
- the foldable display using the hard coat film of each comparative example feels that the image is distorted at the foldable part of the display as the frequency of use increases, and interference spots occur to improve visibility. It felt bad and wasn't very good. In addition, some were dented on the surface and scratches were confirmed.
- the foldable display using the hard coat film for a foldable display of the present invention maintains mass productivity and does not cause deformation after the hard coat film located on the surface of the foldable display is repeatedly folded. , The image is not distorted in the folded part of the display.
- a mobile terminal device or an image display device equipped with a foldable display using the hard coat film of the present invention as a surface protective film provides beautiful images, is rich in functionality, and is excellent in convenience such as portability. Is.
- Folding type display 11 Bending radius 2: Polyester film for surface protection film of folding type display 21: Folding part 22: Bending direction (direction orthogonal to the folding part)
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Abstract
Description
1. 厚みが10~80μmのポリエステルフィルムの少なくとも片面に易接着樹脂層とハードコート層を順に有するハードコートフィルムであって、前記易接着樹脂層が、バインダー樹脂と、チタン酸化物粒子、ジルコニウム酸化物粒子およびシリカ粒子から選ばれる少なくとも一種の粒子を含む組成物が硬化されてなり、前記粒子の平均粒子径が5~150nmであり、かつ、前記易接着樹脂層を有しハードコート層を積層する前のポリエステルフィルムが下記条件(1)~(4)を満足する、折りたたみ型ディスプレイ用ハードコートフィルム。
(1)屈曲方向の屈折率が1.590~1.620
(2)折りたたみ部の方向の屈折率が1.670~1.700
(3)厚み方向の屈折率が1.520以下
(4)密度が1.380g/cm3以上
(ここで、屈曲方向とは、ポリエステルフィルムを折りたたむ際の折りたたみ部と直交する方向をいう。)
2. 前記易接着樹脂層の固形分質量に含まれる前記チタン酸化物粒子、ジルコニウム酸化物粒子およびシリカ粒子の合計固形分含有量が1~15質量%である、上記第1に記載の折りたたみ型ディスプレイ用ハードコートフィルム。
3. 前記易接着樹脂層を形成するための組成物が、前記粒子の分散剤を含む、上記第1又は第2に記載の折りたたみ型ディスプレイ用ハードコートフィルム。
4. 前記分散剤がアクリル系分散剤である、上記第1~第3のいずれかに記載の折りたたみ型ディスプレイ用ハードコートフィルム。
5. 前記易接着樹脂層を有し、ハードコート層を積層する前のポリエステルフィルムの全光線透過率が85%以上、ヘイズが3%以下、かつ、最大熱収縮率が6%以下である、上記第1~第4のいずれかに記載の折りたたみ型ディスプレイ用ハードコートフィルム。6. 前記ハードコート層の厚みが1~50μmである、上記第1~第5のいずれかに記載の折りたたみ型ディスプレイ用ハードコートフィルム。
7. 上記第6に記載の折りたたみ型ディスプレイ用ハードコートフィルムが、ハードコート層を表面に位置させるように表面保護フィルムとして配置された折りたたみ型ディスプレイであって、折りたたみ型ディスプレイの折りたたみ部分を介して連続した単一のハードコートフィルムが配されている折りたたみ型ディスプレイ。
8. 上記第7に記載の折りたたみ型ディスプレイを有する携帯端末機器。
本発明で言うディスプレイとは、表示装置を全般に指すものであり、ディスプレイの種類としては、LCD、有機ELディスプレイ、無機ELディスプレイ、LED、FEDなどあるが、折曲げ可能な構造を有するLCDや、有機EL、無機ELが好ましい。特に層構成を少なくすることができる有機EL、無機ELが特に好ましく、色域の広い有機ELがさらに好ましい。
折りたたみ型ディスプレイは、連続した1枚のディスプレイが、携帯時は2つ折りなどに折りたたむことができるものである。折りたたむことでサイズを半減させ、携帯性を向上させることができる。折りたたみ型ディスプレイの屈曲半径は5mm以下が好ましく、3mm以下がさらに好ましい。屈曲半径が5mm以下であれば、折りたたんだ状態での薄型化が可能となる。屈曲半径は小さいほど良いと言えるが、屈曲半径が小さいほど折り跡がつきやすくなる。屈曲半径は0.1mm以上が好ましいが、0.5mm以上であってもよく、1mm以上であってもよい。屈曲半径が1mmであっても、携帯時には実用的に十分な薄型化を達成することができる。折りたたんだ際の屈曲半径とは、図1の模式図の符号11の箇所を測定するもので、折りたたんだ際の折りたたみ部分の内側の半径を意味している。なお、後述する表面保護フィルムは、折りたたみ型ディスプレイの折りたたんだ外側に位置していてもよいし、内側に位置していてもよい。
また、折りたたみ型ディスプレイは3つ折り、4つ折りであってもよく、さらに、ローラブルといわれる巻き取り型であってもよく、これらいずれも本発明でいう折りたたみ型ディスプレイの範囲に入るものとする。
折りたたみ型有機ELディスプレイの必須構成としては、有機ELモジュールであるが、さらに必要に応じて、円偏光板、タッチパネルモジュール、表面保護フィルム、裏面保護フィルムなどが設けられる。
(有機ELモジュール)
有機ELモジュールの一般的な構成は、電極/電子輸送層/発光層/ホール輸送層/透明電極からなる。
携帯端末機器にはタッチパネルを有することが好ましい。有機ELディスプレイを用いた場合、有機ELディスプレイの上部、もしくは有機ELモジュール/円偏光板間にタッチパネルモジュールが配置されていることが好ましい。タッチパネルモジュールはフィルムなどの透明基材とその上に配置された透明電極を有する。本発明のハードコートフィルムはこの透明基材として用いることができる。タッチパネルの透明基材として用いる場合、屈折率調整層を設けることが好ましい。
円偏光板は、ディスプレイ内部の部材によって外光が反射され、画質が低下することを抑制する。円偏光板は直線偏光板と位相差板を有する。直線偏光板は偏光子の少なくとも視認側の面に保護フィルムを有する。偏光子の視認側とは反対の面にも保護フィルムを有していてもよく、偏光子に位相差板が直接積層されていてもよい。位相差板はポリカーボネートや環状オレフィンなどの位相差を有する樹脂フィルムや樹脂フィルムに液晶化合物からなる位相差層が設けられたものが用いられる。本発明のハードコートフィルムは、偏光子保護フィルムとして用いることができる。これらの場合、本発明のハードコートフィルムの基材フィルムがポリエステルフィルムである場合、前記ポリエステルフィルムの遅相軸方向が偏光子の吸収軸方向と平行または直交となることが好ましい。なお、この平行または直交に対して10度、好ましくは5度までのずれは許容される。
ディスプレイに上部から衝撃が加わると、有機ELモジュールやタッチパネルモジュールの回路が断線するおそれがあるため、多くの場合、表面保護フィルムが設けられている。本発明のハードコートフィルムはこの表面保護フィルムとして用いられる。表面保護フィルムはディスプレイの最表面に組み込まれたカバーウインドウと呼ばれるものや、使用者自身で貼り合わせ、剥離ができ、交換可能なアフターと呼ばれるものがあるが、いずれであっても本発明のハードコートフィルムが用いられる。ハードコート層を視認側にして折りたたみ型ディスプレイの表面に設けられる。なお、ハードコート層は両面に設けられていてもよい。
ディスプレイの裏面側にも保護フィルムが設けられることも好ましい。本発明のハードコートフィルムはこの裏面側の保護フィルムとして用いることができる。
これらの中でも、本発明のハードコートフィルムは、カバーウインドウ表面保護フィルム、アフター表面保護フィルム、タッチパネルモジュールの基材フィルム、裏面保護フィルムに用いられることが好ましい。さらには、カバーウインドウ表面保護フィルム、アフター表面保護フィルムに用いられることが好ましい。
本発明において、易接着樹脂層を有し、ハードコート層を積層する前のポリエステルフィルムの長手方向(機械流れ方向)及び幅方向の少なくともいずれか一方向の屈折率は1.590~1.620であることが好ましく、更に好ましくは、1.591~1.600である。そして、易接着樹脂層を有し、ハードコート層を積層する前のポリエステルフィルムの屈曲方向の屈折率が1.590~1.620であることが好ましく、1.591~1.600であることがより好ましい。ここで、屈曲方向とは、図2のポリエステルフィルム(符号2)上の符号22に示すように、折りたたみ型ディスプレイの用途において想定される折りたたみ部(符号21)と直交する方向を指している。長手方向及び幅方向の少なくともいずれか一方向の屈折率が1.590~1.620であると、繰り返し折りたたんだ際の変形が少なく、折りたたみ型ディスプレイの画質を低下させるおそれがなく好ましい。屈折率は1.591~1.600であることがより好ましい。もちろん、その方向は前記の屈曲方向であることが好ましい。1.590以上であると後述の屈曲試験後に折りたたみ部方向にクラックが入るおそれがなく、もちろん破断も起こらないため、ディスプレイの視認性を良好に保つことができる。ポリエステルフィルムの屈折率は、延伸倍率、延伸温度を調節することで効果的に調節することができる。また、屈折率の調整のために延伸方向の緩和工程、多段延伸を用いても良い。多段延伸を行う場合には、1段目の延伸倍率よりも2段目以降の延伸倍率を高くすることが好ましい。なお、易接着樹脂層を有し、ハードコート層を積層する前のポリエステルフィルムの屈折率と、易接着樹脂層も有しないポリエステルフィルム単体の屈折率の差は無視し得る程度に小さい。
上記の易接着樹脂層を有し、ハードコート層を積層する前のポリエステルフィルムの屈折率が1.590~1.620である方向と直交する方向の屈折率は、1.670~1.700であることが好ましい。即ち、屈曲方向と直交する方向(折りたたみ部の方向)の屈折率が1.670~1.700であることが好ましい。1.670~1.700にすることで屈曲方向に折りたたんだ際の変形を少なくすることができる。1.700以下にすることで折りたたみ部の方向にクラックが入ったり、破断することを抑制することができる。1.670以上にすることで屈曲方向の屈曲性を向上させること、表面硬度を向上させることができる。1.680~1.695がより好ましい。屈曲方向と直交する方向の屈折率を調整する方法として、延伸倍率、延伸予熱温度、延伸温度、多段延伸、フィルム弛緩が挙げられる。延伸倍率は4.0~6.0倍であることが好ましく、より好ましくは、4.4~6.0である。また、屈曲方向と直交する方向の延伸予熱温度は70~110℃であることが好ましい。屈曲方向と直交する方向に多段延伸する場合、1段目より2段目以降の延伸倍率を高くする方が好ましい。フィルム弛緩は機械流れ方向(長手方向)、垂直方向(幅方向)に何れにおいても1~10%行っても良い。
易接着樹脂層を有し、ハードコート層を積層する前のポリエステルフィルムの厚み方向の屈折率は1.520以下であることが好ましい。1.520以下にすることで、屈曲方向の屈折率を低く設計しても、フィルム表面の硬度の低下を抑制することができ、屈曲性と表面硬度の両立を実現することができるためである。1.520以下にすることで厚み方向の試験力除荷後の押し込み深さが低減し、フィルム表面の硬度、特にハードコート層積層後のハードコートフィルムの鉛筆硬度を向上することができる。より好ましくは1.515以下、更に好ましくは1.510以下、特に好ましくは1.505以下、最も好ましくは1.500以下である。厚み方向の屈折率は低いことが好ましいが、安定した生産の面で1.3以上が好ましく、さらには1.4以上であってもよい。特に好ましくは1.410以上である。上記範囲は屈曲方向と折りたたみ方向に延伸倍率を両方に増加させていくことで達成できると言えるが、屈曲方向と幅方向の屈折率を好ましい範囲に制御した上で、厚み方向の屈折率を制御するためには、製膜工程の各工程条件のバランスを確認しながら条件設定することが好ましい。
熱固定温度は180~240℃が好ましい。熱固定を行うことで延伸方向への配向結晶化が進み、厚み方向の屈折率を下げることができる。
厚み方向の屈折率を下げることでフィルム表面の硬度が向上する理由は必ずしも明確ではないが、分子鎖内のベンゼン環等の芳香族が面方向に配向し、厚み方向にかかる応力による変形を抑制する効果があると考えられる。
易接着樹脂層を有し、ハードコート層を積層する前のポリエステルフィルムの密度は1.380g/cm3以上であることが好ましい。1.383g/cm3以上であることがより好ましい。1.380g/cm3以上にすることで屈曲性を向上させること、フィルム表面硬度、特に、ハードコート層を積層した後のハードコートフィルムの鉛筆硬度を向上させることができる。密度は高いほど好ましく、フィルム中の粒子の有無等によっても多少左右されるが、1.40g/cm3以下であることが好ましい。製膜時の熱固定温度を180~240℃に設定することで結晶化を進行させ密度を効果的に増大させることができる。なお、易接着樹脂層を有し、ハードコート層を積層する前のポリエステルフィルムの密度は、易接着樹脂層も有しないポリエステルフィルム単体の密度の差は無視し得る程度に小さい。
(1)屈曲方向の屈折率が1.590~1.620
(2)折りたたみ部の方向の屈折率が1.670~1.700
(3)厚み方向の屈折率が1.520以下
(4)密度が1.380g/cm3以上
の4つの特性を同時に具備させることが特に好ましい態様と言えるが、上述の好ましい製造条件の範囲内での組合せであっても、例えば、屈曲方向の延伸倍率が1.4倍以下、折りたたみ部の方向の延伸倍率が4.4倍未満であり、かつ、熱固定温度が220℃以下の組合せであるような、各々の好ましい製造条件範囲の中において最善とは言えない条件の組合せの場合、必ずしも上記の4つの特性を同時に満足するものが得られない場合が起こり得る。この場合には、屈曲方向の延伸倍率延伸倍率を1.7倍以上に高めたり、折りたたみ部の方向の延伸倍率が4.4倍以上に高めたり、熱固定温度を230℃程度に高めたり、あるいは屈曲方向及び/又は折りたたみ部の方向の延伸温度を低くするなど、いずれかの条件の微調整またはそれらの組合せによって、上記の4つの特性を同時に満足させることができる。
本発明において、ポリエステルフィルムとハードコート層などとの接着性を向上させるため、ポリエステルフィルムに易接着樹脂層を積層することが好ましい。易接着樹脂層は、易接着樹脂層形成のための塗布液を未延伸又は縦方向の1軸延伸フィルムの片面または両面に塗布した後、必要に応じて熱処理乾燥し、さらに延伸されていない少なくとも一方向に延伸して得る、所謂インラインコートにより得ることができる。二軸延伸後にも熱処理することができる。最終的な易接着層の塗布量は、0.005~0.20g/m2に管理することが好ましい。塗布量が0.005g/m2以上であると、接着性が得られて好ましい。一方、塗布量が0.20g/m2以下であると、耐ブロッキング性が得られて好ましい。
(1)HOOC-(CH2)n-COOH (式中、nは4≦n≦10の整数)
(2)HO-(CH2)n-OH (式中、nは4≦n≦10の整数)
式(1)のジカルボン酸成分としては、アジピン酸、セバシン酸、アゼライン酸などが挙げられる。また、式(2)のジオール成分としては1,4-ブタンジオール、1,6-へキサンジオール等が挙げられる。
易接着樹脂層に使用することができるウレタン樹脂は、構成成分として、少なくともポリオール成分、ポリイソシアネート成分を含み、さらに必要に応じて鎖延長剤を含む。上記のウレタン樹脂は、これら構成成分が主としてウレタン結合により共重合された高分子化合物である。ウレタン樹脂の構成成分としてポリカーボネートポリオールを含ませることは塗膜に柔軟性を持たせることができるため好ましい形態の一つである。なお、これらウレタン樹脂の構成成分は、核磁気共鳴分析などにより特定することが可能である。
ポリカーボネート骨格を有するポリウレタン樹脂の構成成分であるジオール成分には、耐熱、耐加水分解性に優れる脂肪族系ポリカーボネートポリオールを含有させることが好ましい。本発明の光学用途においては、黄変防止の点からも脂肪族系ポリカーボネートポリオールを用いることが好ましい。
厚み、λbは反射スペクトルのボトム波長を示し、450~650nmの範囲で適宜設定できる。
本発明のポリエステルフィルムを折りたたみ型ディスプレイの表面に位置させてディスプレイを保護する表面保護フィルムとして用いる場合は、その少なくとも一方の表面にハードコート層を有していることが好ましい。ハードコート層は、ポリエステルフィルム上のディスプレイ表面側に位置させてディスプレイにおいて用いられることが好ましい。ハードコート層を形成する樹脂としては、シロキサン系、無機ハイブリッド系、アクリル系、ウレタンアクリレート系、ポリエステルアクリレート系、エポキシ系など特に限定なく使用できる。また、2種類以上の材料を混合して用いることもできるし、無機フィラーや有機フィラーなどの粒子を添加することもできる。
ハードコート層の膜厚としては、1~50μmが好ましい。1μm以上であると十分に硬化することができる。鉛筆硬度を高めるためには、5μm以上であることがさらに好ましい。また厚みを50μm以下にすることで、ハードコートの硬化収縮によるカールを抑制し、フィルムのハンドリング性を向上させることができる。
ハードコート層の塗布方法としては、マイヤーバー、グラビアコーター、ダイコーター、ナイフコーターなど特に限定なく使用でき、粘度、膜厚に応じて適宜選択できる。
ハードコート層の硬化方法としては、紫外線、電子線などのエネルギー線や、熱による硬化方法など使用でき、フィルムへのダメージを軽減させるために、紫外線や電子線などによる硬化方法が好ましい。
ハードコート層の鉛筆硬度としては、3H以上が好ましく、4H以上が更に好ましい。3H以上の鉛筆硬度があれば、容易に傷がつくことはなく、視認性を低下させない。一般にハードコート層の鉛筆硬度は高い方が好ましいが9H以下で構わず、8H以下でも構わず、6H以下でも実用上は問題なく使用できる。
本発明におけるハードコート層は、上述のような表面の鉛筆硬度を高めてディスプレイの保護をする目的に使用できるものであり、透過率が高いことが好ましい。ハードコートフィルムの透過率としては、85%以上が好ましく、87%以上がより好ましく、88%以上がさらに好ましい。透過率が85%以上であれば、十分な視認性が得られる。ハードコートフィルムの全光線透過率は、一般的に高いほど好ましいが、安定した生産の面から99%以下が好ましく、97%以下であってもよい。また、ハードコートフィルムのヘイズは、一般的に低いことが好ましく、3%以下が好ましい。ハードコートフィルムのヘイズは2%以下がより好ましく、1%以下が最も好ましい。ヘイズが3%以下であれば、画像の視認性を向上させることができる。ヘイズは一般的には低いほどよいが、安定した生産の面から0.1%以上が好ましく、0.3%以上であってもよい。
フィルムまたはポリエステル樹脂を粉砕して乾燥した後、フェノール/テトラクロロエタン=60/40(質量比)の混合溶媒に溶解した。この溶液に遠心分離処理を施して無機粒子を取り除いた後に、ウベローデ粘度計を用いて、30℃で0.4(g/dl)の濃度の溶液の流下時間及び溶媒のみの流下時間を測定し、それらの時間比率から、Hugginsの式を用い、Hugginsの定数が0.38であると仮定して極限粘度を算出した。
JIS K7112:1999準拠の方法(密度勾配管法)に従って密度を測定した。(単位:g/cm3)。
(3)ポリエステルフィルムや易接着樹脂層中の粒子の平均粒子径
フィルムの断面の粒子を走査型電子顕微鏡で観察を行い、粒子50個を観察し、その平均値をもって平均粒子径とする方法で行う。球状ではない不定形の粒子の粒子径は円相当径として計算することができる。円相当径は、観察された粒子の面積を円周率(π)で除し、平方根を算出し2倍した値である。(単位は平均粒子径にもよるが、主にnmを使用)
JIS K7142:2008「プラスチックの屈折率測定方法(A法)」に準拠して、アッベ屈折率計(アタゴ社製、NAR-4T、測定波長589nm)を用いて、易接着樹脂層を有しハードコート層を積層する前のポリエステルフィルムの長手方向の屈折率、幅方向の屈折率、厚み方向の屈折率を求めた。
易接着樹脂層の屈折率は、分光光度計(製品名「UV-3150」、島津製作所製)を用いて、測定した反射スペクトルと、フレネル係数を用いた薄膜の光学モデルから算出した反射スペクトルとのフィッティングにより算出することができる。易接着層の反射率は、易接着樹脂層を積層し、ハードコート層を積層する前の状態のポリエステルフィルム基材における屈折率を測定しようとする易接着樹脂側の面とは反対側の面(裏面、両面に易接着樹脂層を形成した場合には屈折率を測定しようとしていない易接着樹脂層の表面)に、裏面反射を防止するために測定スポット面積よりも大きな幅の黒色ビニールテープ(例えば、製品名「ヤマトビニールテープNO200-38-21」、ヤマト社製、38mm幅)を貼り付けてから測定するものとする。
幅方向20mm×流れ方向110mmの大きさのポリエステルフィルムサンプルを用意する。無負荷U字伸縮試験機(ユアサシステム機器社製、DLDMLH-FS)を用いて、屈曲半径1.5mmに設定し、1回/秒の速度で、20万回屈曲させた。その際、サンプルは長辺側両端部10mmの位置を固定して、屈曲する部位は20mm×90mmとした。ここで、図1は、折りたたみ型ディスプレイを折りたたんだ際の屈曲半径を示すための模式図であり、その折りたたんだ態様の内側表面にポリエステルフィルムが配されている場合を考慮して、図1の符号11の個所を1.5mmに設定したものとしてモデル的に屈曲試験をしている。屈曲処理終了後、サンプルの屈曲内側を下にして平面に置き、目視による観察を行った。
○ :サンプルにクラック及び変形を確認できない。
× :サンプルにクラックまたは折跡があり、水平に置いた際、浮き上がり最大高さが5mm以上。
上記屈曲試験と同様の方法で、屈曲半径0.5mmに設定し1回/秒の速度で20万回屈曲させた。ここで、図1は、折りたたみ型ディスプレイを折りたたんだ際の屈曲半径を示すための模式図であり、その折りたたんだ態様の内側表面にポリエステルフィルムが配されている場合を考慮して、図1の符号11の個所を0.5mmを設定したものとしてモデル的に屈曲試験をしている。屈曲部の外側のフィルム表面をデジタルマイクロスコープ(HIROX社製RH8800)の700倍で観察し、シワ(クラック)の有無を観察した。上記の屈曲半径1.5mmの耐屈曲性目視テストとは別に、屈曲半径を0.5mmに小さくした本テストを行うことで、ハードコート層や他の部材が積層又は貼着された、折りたたみ型ディスプレイの実際の使用状態に近い状態での評価することを企図している。前記屈曲半径1.5mmによる目視観察とは別に、目視では検出しにくい微細な欠点である、破断しやすいまたはクラックが入りやすい欠点を検出するためのテストである。
○ :屈曲外側のフィルム表面に欠陥がない。
× :破断した、または屈曲外側のフィルム表面にシワ(クラック)が確認できる。
試料を約2cm角に切り取り、マイクロカバーガラス18×18mm(マツナミガラス社製)上に、測定面の反対面を接着剤(セメダイン(登録商標)ハイスーパー30)にて固定した。貼着固定後、12時間以上室温で放置し、その後、ダイナミック超微小硬度計「DUH-211」(島津製作所製)を用いて、次の条件で、試験力除荷後の押し込み深さ(μm)を測定した。
≪測定条件≫
試験モード :負荷-除荷試験
使用圧子 :稜間角115度、三角錐圧子
圧子弾性率:1.140×106N/mm2
圧子ポアソン比:0.07
試験力 :50mN
負荷速度 :4.44mN/sec
負荷保持時間 :2sec
除荷保持時間 :0sec
易接着樹脂層を積層したポリエステルフィルムをサンプルとして、ヘイズメーター(日本電色工業社製、NDH5000)を用いて測定した。
易接着樹脂層を積層したポリエステルフィルムの試料フィルムをタテ10mm×ヨコ250mmにカットし、長辺を測定したい方向に合わせて、200mm間隔で印をつけ、5gの一定張力下で印の間隔Aを測った。続いて、試料フィルムを無荷重で150℃の雰囲気のオーブン中で30分間放置した後、オーブンから取り出し室温まで冷却した。その後、5gの一定張力下で印の間隔Bを求め、下記式により熱収縮率(%)を求めた。なお、上記熱収縮率は試料フィルムの幅方向に3等分した位置で測定し、3点の平均値を熱収縮率(%)とする。
熱収縮率(%)=[(A-B)×100]/A
屈曲方向と折りたたみ方向の双方向についてそれぞれ別個に試料フィルムのタテ、ヨコが異なるようにカットして測定し、測定値が大きい方向のデータを最大熱収縮率(%)とする。
ハードコート層の屈折率は、分光光度計(製品名「UV-3150」、島津製作所製)を用いて、測定した反射スペクトルと、フレネル係数を用いた多層薄膜の光学モデルから算出した反射スペクトルとのフィッティングにより算出することができる。ハードコート層の反射率は、易接着樹脂層が施されていない厚さ50μmのポリエチレンテレフタレート(PET)基材上にハードコート組成物を塗布し、硬化させて1~10μmの厚さのハードコート層を形成し、PET基材における機能層側の面とは反対側の面(裏面)に、裏面反射を防止するために測定スポット面積よりも大きな幅の黒色ビニールテープ(例えば、製品名「ヤマトビニールテープNO200-38-21」、ヤマト社製、38mm幅)を貼り付けてから測定するものとする。
ハードコートフィルムを50mm(フィルム幅方向)×110mm(フィルム長手方向)の面積に切り出し、試料フィルムを作成した。得られた試料フィルムのハードコート層とは反対面に、黒色光沢テープ(日東電工製、ビニルテープNo21;黒)を張り合わせた。この試料フィルムのハードコート面を上面にして3波長形昼白色(ナショナル パルック、F.L 15EX-N 15W)を光源として斜め上から目視でもっとも反射が強く見える位置関係(光源からの距離40~60cm、フィルム面に対して15~45°の角度)で観察した。
◎:あらゆる角度からの観察でも虹彩状色彩が見られない
○:ある角度によっては僅かに虹彩状色彩が見られる
△:僅かに虹彩状色彩が観察される
×:はっきりとした虹彩状色彩が観察される
ハードコートフィルムを用いて、幅方向50mm×流れ方向110mmの大きさに切りだして試料フィルムを作製した。得られた試料フィルムを用いて、上述の屈曲試験方法と同様に、易接着樹脂層とハードコート層が内側となるように折りたたむようにして、屈曲半径3.0mmに設定し、1回/秒の速度で、20万回屈曲試験を行った。試験後の試料フィルムの屈曲された部位に対して、サンプルの屈曲内側を下にして平面に置き、目視による観察を行った。
○ :サンプルにクラック及び変形を確認できない。
× :サンプルにクラックまたは折跡が観察される。
上述のハードコートフィルムの屈曲試験後の試料フィルムの屈曲された部位に対して、干渉斑改善性と同様の観察を行った。具体的には、得られた試料フィルムのハードコート層とは反対面に、黒色光沢テープ(日東電工製、ビニルテープNo21;黒)を張り合わせた。この試料フィルムのハードコート面を上面にして3波長形昼白色(ナショナル パルック、F.L 15EX-N 15W)を光源として斜め上から目視でもっとも反射が強く見える位置関係(光源からの距離40~60cm、フィルム面に対して15~45°の角度)で観察した。目視で観察した結果を、下記の基準でランク分けを行う。なお、観察は該評価に精通した5名で行ない、最も多いランクを評価ランクとする。仮に、2つのランクで同数となった場合には、3つに分かれたランクの中心を採用した。例えば、◎と○が各2名で△が1名の場合は○を、◎が1名で○と△が各2名の場合には○を、◎と△が各2名で○が1名の場合には○を、それぞれ採用する。
◎:あらゆる角度からの観察でも虹彩状色彩が見られない
○:ある角度によっては僅かに虹彩状色彩が見られる
△:僅かに虹彩状色彩が観察される
×:はっきりとした虹彩状色彩が観察される
ハードコートフィルムの鉛筆硬度をサンプルとして、JIS K 5600-5-4:1999に準拠し、荷重750g、速度1.0mm/sで測定した。本発明においては3H以上を合格とした。
エステル化反応装置として、攪拌装置、分縮器、原料仕込口および生成物取り出し口を有する3段の完全混合槽よりなる連続エステル化反応装置を用い、TPAを2トン/hrとし、EGをTPA1モルに対して2モルとし、三酸化アンチモンを生成PETに対してSb原子が160ppmとなる量とし、これらのスラリーをエステル化反応装置の第1エステル化反応缶に連続供給し、常圧にて平均滞留時間4時間で、255℃で反応させた。次いで、上記第1エステル化反応缶内の反応生成物を連続的に系外に取り出して第2エステル化反応缶に供給し、第2エステル化反応缶内に第1エステル化反応缶から留去されるEGを生成ポリマー(生成PET)に対し8質量%供給し、さらに、生成PETに対してMg原子が65ppmとなる量の酢酸マグネシウムを含むEG溶液と、生成PETに対してP原子が20ppmのとなる量のTMPAを含むEG溶液を添加し、常圧にて平均滞留時間1.5時間で、260℃で反応させた。次いで、上記第2エステル化反応缶内の反応生成物を連続的に系外に取り出して第3エステル化反応缶に供給し、さらに生成PETに対してP原子が20ppmとなる量のTMPAを含むEG溶液を添加し、常圧にて平均滞留時間0.5時間で、260℃で反応させた。上記第3エステル化反応缶内で生成したエステル化反応生成物を3段の連続重縮合反応装置に連続的に供給して重縮合を行い、さらに、ステンレス焼結体の濾材(公称濾過精度5μm粒子90%カット)で濾過し、極限粘度0.62dl/gのポリエチレンテレフタレートペレット(R1)を得た。
ポリエチレンテレフタレートペレット(R1)の製造工程について、第3エステル化反応の滞留時間を調節した他は同様の方法にて極限粘度を0.580dl/gに調整し、ポリエチレンテレフタレートペレット(R2)を得た。
ポリエチレンテレフタレートペレット(R1)を、回転型真空重合装置を用い、0.5mmHgの減圧下、220℃で時間を変えて固相重合を行い、極限粘度0.75dl/gのポリエチレンテレフタレートペレット(R3)を作成した。
易接着樹脂層形成用の共重合ポリエステル樹脂(a1)~(a2)の重合を以下のようにして行った。
攪拌機、温度計、及び部分還流式冷却器を具備するステンレススチール製オートクレーブに、2,6-ナフタレンジカルボン酸ジメチル410.3質量部、セバシン酸46.3、5-スルホイソフタル酸ジメチルナトリウム42.5質量部、エチレングリコール175.6質量部、ジエチレングリコール29.2質量部、1,6-ヘキサンジオール204.2質量部、及びテトラーnーブチルチタネート0.5質量部を仕込み、160℃から220℃まで4時間かけてエステル交換反応を行なった。次いで255℃まで昇温し、反応系を徐々に減圧した後、30Paの減圧下で1時間30分反応させ、共重合ポリエステル樹脂(a1)を得た。得られた共重合ポリエステル樹脂は、淡黄色透明であった。共重合ポリエステル樹脂(a1)の組成は表1の通りである。
攪拌機、温度計と還流装置を備えた反応器に、共重合ポリエステル樹脂(a1)25質量部、エチレングリコールt-ブチルエーテル15質量部を入れ、110℃で加熱、攪拌し樹脂を溶解した。樹脂が完全に溶解した後、水60質量部を上記ポリエステル溶液に攪拌しつつ徐々に添加した。添加後、液を攪拌しつつ室温まで冷却して、固形分25質量%の乳白色の共重合ポリエステルの水分散液(Aw-1)を作製した。同様に共重合ポリエ
ステル樹脂(a1)の代わりに共重合ポリエステル樹脂(a2)を使用して、水分散液を作製し、水分散液(Aw-2)とした。
撹拌機、ジムロート冷却器、窒素導入管、シリカゲル乾燥管、及び温度計を備えた4つ口フラスコに、1,3-ビス(イソシアネートメチル)シクロヘキサン72.96質量部、ジメチロールプロピオン酸12.60質量部、ネオペンチルグリコール11.74質量部、数平均分子量2000のポリカーボネートジオール112.70質量部、及び溶剤としてアセトニトリル85.00質量部、N-メチルピロリドン5.00質量部を投入し、窒素雰囲気下、75℃において3時間撹拌し、反応液が所定のアミン当量に達したことを確認した。次に、この反応液を40℃にまで降温した後、トリエチルアミン9.03質量部を添加し、ポリウレタンプレポリマー溶液を得た。次に、高速攪拌可能なホモディスパーを備えた反応容器に、水450gを添加して、25℃に調整して、2000min-1で攪拌混合しながら、イソシアネート基末端プレポリマーを添加して水分散した。その後、減圧下で、アセトニトリルおよび水の一部を除去することにより、固形分35質量%の水溶性ポリウレタン樹脂(B-1)を調製した。
撹拌機、温度計、還流冷却管を備えたフラスコにヘキサメチレンジイソシアネートを原料としたイソシアヌレート構造を有するポリイソシアネート化合物(旭化成ケミカルズ製、デュラネートTPA)100質量部、プロピレングリコールモノメチルエーテルアセテート55質量部、ポリエチレングリコールモノメチルエーテル(平均分子量750)30質量部を仕込み、窒素雰囲気下、70℃で4時間保持した。その後、反応液温度を50℃に下げ、メチルエチルケトオキシム47質量部を滴下した。反応液の赤外スペクトルを測定し、イソシアネート基の吸収が消失したことを確認し、固形分75質量%のブロックポリイソシアネート液を得た。
上記で得られたブロックポリイソシアネート液に水を添加し、固形分40質量%のブロックポリイソシアネート水分散液(C-1)を得た。
温度計、窒素ガス導入管、還流冷却器、滴下ロート、および攪拌機を備えたフラスコにイソホロンジイソシアネート200質量部、カルボジイミド化触媒の3-メチル-1-フェニル-2-ホスホレン-1-オキシド4質量部を投入し、窒素雰囲気下、180℃において10時間撹拌し、イソシアネート末端イソホロンカルボジイミド(重合度=5)を得た。次いで、得られたカルボジイミド111.2g、ポリエチレングリコールモノメチルエーテル(分子量400)80gを100℃で24時間反応させた。これに水を50℃で徐々に加え、固形分40質量%の黄色透明な水溶性カルボジイミド化合物(C-2)を得た。
メラミン系架橋剤として、DIC社製 ベッカミン(登録商標)M-3(固形分濃度60%)を使用した(メラミン系架橋剤(C-3))。
3リットルのガラス製容器に、純水2283.6gとシュウ酸二水和物403.4gとを投入し、40℃に加熱して10.72質量%シュウ酸水溶液を調製した。この水溶液を撹拌しながら、オキシ炭酸ジルコニウム粉末(ZrOCO3、AMR Internat
ional Corp.製、ZrO2に換算して39.76質量%を含有する。)495
.8gを徐々に添加し30分間混合した後、90℃で30分の加熱を行った。次いで、25.0質量%水酸化テトラメチルアンモニウム水溶液(多摩化学工業(株)製)1747.2gを1時間かけて徐々に添加した。この時点で混合液はスラリー状であり、ZrO2換算で4.0質量%含有した。このスラリーをステンレス製オートクレーブ容器に移し替え、145℃で5時間の水熱処理を行った。この水熱処理後の生成物は、未解膠物がなく完全にゾル化した。得られたゾルは、ZrO2として4.0質量%含有し、pH6.8、動的光散乱法による平均粒子径は19nmであった。また、ゾルをZrO2濃度2.0質量%に純水で調整して測定した透過率は88%であった。透過型電子顕微鏡により粒子を観察したところ、7nm前後のZrO2一次粒子の凝集粒子がほとんどであった。上記の水熱処理を行って得られたZrO2濃度4.0質量%のジルコニアゾル4000gを限外濾過装置を使用して、純水を徐々に添加しながら洗浄及び濃縮を行って、ZrO2濃度13.1質量%、pH4.9、ZrO2濃度13.1質量%のときの透過率76%のジルコニアゾル953gが得られた。
上記で得られたジルコニアゾルを水で希釈して10質量%のジルコニア水分散液D-1を得た。
四塩化チタン(大阪チタニウムテクノロジ-ズ(株)製)をTiO2換算基準で7.75質量%含む四塩化チタン水溶液12.09kgと、アンモニアを15質量%含むアンモニア水(宇部興産(株)製)4.69kgとを混合し、pH9.5の白色スラリー液を調製した。次いで、このスラリーを濾過した後、純水で洗浄して、固形分含有量が10質量%の含水チタン酸ケーキ9.87kgを得た。次に、このケーキに、過酸化水素を35質量%含む過酸化水素水(三菱瓦斯化学(株)製)11.28kgと純水20.00kgとを加えた後、80℃の温度で1時間、撹拌下で加熱し、さらに純水57.52kgを加えて、過酸化チタン酸をTiO2換算基準で1質量%含む過酸化チタン酸水溶液を98.67kg得た。この過酸化チタン酸水溶液は、透明な黄褐色でpHは8.5であった。
上記で得られたチタン系微粒子を水で希釈して10%質量%のチタニア水分散液D-4を得た。
上記で得られたD-1中のジルコニア分散粒子とD-4中のチタニア分散粒子を混合し、水で希釈して、10質量%の混合分散液(D-6)を得た。固形分濃度10質量%のうち、7.5%がジルコニア、2.5%がチタニアの比率とした。
シリカ粒子として、粒子径が40nmで固形分濃度が30質量%であるコロイダルシリカをD-7として用いた。
易滑性を付与するために、粒子径が450nmで固形分濃度が40質量%であるシリカ粒子をDF-1として用いた。
微粒子の分散性を向上させるための分散剤としてポリアクリル酸分散剤(東亜合成(株)製:アロンA-30SL)DP-1として用いた。
易接着樹脂層を形成する際の塗膜のレベリング性を向上させるために、固形分濃度が100質量%であるシリコーン系の界面活性剤E-1として用いた。
下記の塗剤を混合し、塗布液P-1を作製した。
水 47.69質量部
イソプロパノール 25.00質量部
ポリエステル樹脂(Aw-1) 17.85質量部
水分散性ブロックイソシアネート化合物(C-1) 4.78質量部
ジルコニア/チタニア混合水分散液(D-6) 4.46質量部
分散剤(DP-1) 0.13質量部
シリカ粒子(DF-1) 0.06質量部
(平均粒径450nmのシリカゾル、固形分濃度40質量%)
シリコーン系界面活性剤(E-1) 0.03質量部
(シリコーン系、固形分濃度100質量%)
ポリエチレンテレフタレートのペレット(R1)を押出機に供給し、285℃で融解した。このポリマーを、ステンレス焼結体の濾材(公称濾過精度10μm粒子95%カット)で濾過し、口金よりシート状にして押し出した後、静電印加キャスト法を用いて表面温度30℃のキャスティングドラムに接触させ冷却固化し、未延伸フィルムを作った。この未延伸フィルムを加熱ロールを用いて75℃に均一加熱し、非接触ヒーターで85℃に加熱して1.4倍のロール延伸(縦延伸)を行った。得られた一軸延伸フィルムに上記の易接着樹脂層形成用塗布液(P-1)をロールコート法で両面に塗布した後、80℃で20秒間乾燥した。なお、最終(二軸延伸後)の乾燥後の塗布量が0.09g/m2になるように調整した。その後、テンターに導き105℃で予熱後、95℃で4.0倍に横延伸し、幅固定して230℃で5秒間の熱固定を施し、さらに180℃で幅方向に4%緩和させることにより、厚み50μmポリエチレンテレフタレートフィルムを得た。
ウレタンアクリレート系ハードコート剤(荒川化学工業社製、ビームセット(登録商標)577、固形分濃度100%)95質量部、光重合開始剤(BASFジャパン社製、イルガキュア(登録商標)184、固形分濃度100%)5質量部、レベリング剤(ビックケミージャパン社製、BYK307、固形分濃度100%)0.1質量部を混合し、トルエン/MEK=1/1の溶媒で希釈して、固形分濃度40%のハードコート層形成用塗布液(H-1)を調製した。
表3に記載の長手方向の延伸倍率に変更した他は実施例1と同様にしてポリエステルフィルムおよびハードコートフィルムを得た。
幅方向の延伸倍率を5.5倍に、熱固定温度を190℃に変更した他は実施例1と同様にしてポリエステルフィルムおよびハードコートフィルムを得た。
表3に記載のように易接着樹脂層形成用塗布液をP-2~P-11に変更した他は実施例1と同様にしてポリエステルフィルムおよびハードコートフィルムを得た。
長手方向の延伸を行わずに、幅方向のみ延伸し横1軸延伸とした他は実施例1と同様にしてポリエステルフィルムおよびハードコートフィルムを得た。
長手方向の延伸を行わずに、幅方向のみ延伸し横1軸延伸とした他は実施例4と同様にしてポリエステルフィルムおよびハードコートフィルムを得た。
熱固定温度を220℃に変更し、表1記載のPETペレット、厚みとした他は実施例1と同様にしてポリエステルフィルムおよびハードコートフィルムを得た。
長手方向の延伸倍率を3.4倍に変更した他は実施例1と同様にしてポリエステルフィルムおよびハードコートフィルムを得た。
表3に記載のように塗布液をP-12~P-16に変更した他は実施例1と同様にしてポリエステルフィルムおよびハードコートフィルムを得た。
表3に記載のように塗布液をP-17~P-18に変更した他は実施例1と同様にしてポリエステルフィルムおよびハードコートフィルムを得た。
表4に記載のように、ハードコート塗布液をH-1に替えて下記H-2、H-3に変更した他は実施例1と同様にしてポリエステルフィルムおよびハードコートフィルムを得た。
ペンタエリスリトールトリおよびテトラアクリレート(東亞合成社製、アロニックス(登録商標)M-306、固形分濃度100%)30質量部、ポリエステルアクリレート(東亞合成社製、アロニックス(登録商標)M9050、固形分100%)65質量部、光重合開始剤(BASFジャパン社製、イルガキュア(登録商標)907、固形分濃度100%)5質量部、レベリング剤(ビックケミージャパン社製、BYK307、固形分濃度100%)0.1質量部を混合し、トルエン/MEK=1/1の溶媒で希釈して、濃度40質量%のハードコート塗布液(H-2)を調製した。
ハードコート材料(JSR社製、オプスター(登録商標)Z7503、濃度75%)100質量部に、レベリング剤(ビックケミージャパン社製、BYK307、濃度100%)0.1質量部を添加し、メチルエチルケトンで希釈して固形分濃度40質量%のハードコート塗布液(H-3)を調製した。
11: 屈曲半径
2 : 折りたたみ型ディスプレイの表面保護フィルム用ポリエステルフィルム
21: 折りたたみ部
22: 屈曲方向(折りたたみ部と直交する方向)
Claims (8)
- 厚みが10~80μmのポリエステルフィルムの少なくとも片面に易接着樹脂層とハードコート層を順に有するハードコートフィルムであって、前記易接着樹脂層が、バインダー樹脂と、チタン酸化物粒子、ジルコニウム酸化物粒子およびシリカ粒子から選ばれる少なくとも一種の粒子を含む組成物が硬化されてなり、前記粒子の平均粒子径が5~150nmであり、かつ、前記易接着樹脂層を有しハードコート層を積層する前のポリエステルフィルムが下記条件(1)~(4)を満足する、折りたたみ型ディスプレイ用ハードコートフィルム。
(1)屈曲方向の屈折率が1.590~1.620
(2)折りたたみ部の方向の屈折率が1.670~1.700
(3)厚み方向の屈折率が1.520以下
(4)密度が1.380g/cm3以上
(ここで、屈曲方向とは、ポリエステルフィルムを折りたたむ際の折りたたみ部と直交する方向をいう。) - 前記易接着樹脂層の固形分質量に含まれる前記チタン酸化物粒子、ジルコニウム酸化物粒子およびシリカ粒子の合計固形分含有量が1~15質量%である、請求項1に記載の折りたたみ型ディスプレイ用ハードコートフィルム。
- 前記易接着樹脂層を形成するための組成物が、前記粒子の分散剤を含む、請求項1又は2に記載の折りたたみ型ディスプレイ用ハードコートフィルム。
- 前記分散剤がアクリル系分散剤である、請求項1~3のいずれかに記載の折りたたみ型ディスプレイ用ハードコートフィルム。
- 前記易接着樹脂層を有し、ハードコート層を積層する前のポリエステルフィルムの全光線透過率が85%以上、ヘイズが3%以下、かつ、最大熱収縮率が6%以下である、請求項1~4のいずれかに記載の折りたたみ型ディスプレイ用ハードコートフィルム。
- 前記ハードコート層の厚みが1~50μmである、請求項1~5のいずれかに記載の折りたたみ型ディスプレイ用ハードコートフィルム。
- 請求項6に記載の折りたたみ型ディスプレイ用ハードコートフィルムが、ハードコート層を表面に位置させるように表面保護フィルムとして配置された折りたたみ型ディスプレイであって、折りたたみ型ディスプレイの折りたたみ部分を介して連続した単一のハードコートフィルムが配されている折りたたみ型ディスプレイ。
- 請求項7に記載の折りたたみ型ディスプレイを有する携帯端末機器。
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TW202110641A (zh) | 2021-03-16 |
CN117727243A (zh) | 2024-03-19 |
EP3998162A4 (en) | 2023-08-02 |
EP3998162A1 (en) | 2022-05-18 |
CN114127829A (zh) | 2022-03-01 |
US20220275159A1 (en) | 2022-09-01 |
JPWO2021010159A1 (ja) | 2021-01-21 |
CN114127829B (zh) | 2023-12-26 |
KR20220032572A (ko) | 2022-03-15 |
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