WO2020026891A1 - Polyester film for protecting polarizer and liquid crystal display device - Google Patents

Polyester film for protecting polarizer and liquid crystal display device Download PDF

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Publication number
WO2020026891A1
WO2020026891A1 PCT/JP2019/028796 JP2019028796W WO2020026891A1 WO 2020026891 A1 WO2020026891 A1 WO 2020026891A1 JP 2019028796 W JP2019028796 W JP 2019028796W WO 2020026891 A1 WO2020026891 A1 WO 2020026891A1
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WO
WIPO (PCT)
Prior art keywords
polyester film
polarizer
liquid crystal
protecting
light
Prior art date
Application number
PCT/JP2019/028796
Other languages
French (fr)
Japanese (ja)
Inventor
洋平 山口
伊藤　勝也
Original Assignee
東洋紡株式会社
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by 東洋紡株式会社 filed Critical 東洋紡株式会社
Priority to JP2020533450A priority Critical patent/JP7327401B2/en
Priority to CN201980046509.0A priority patent/CN112424655A/en
Priority to KR1020207034268A priority patent/KR20210039327A/en
Publication of WO2020026891A1 publication Critical patent/WO2020026891A1/en

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Classifications

    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/02—Diffusing elements; Afocal elements
    • G02B5/0273—Diffusing elements; Afocal elements characterized by the use
    • G02B5/0278—Diffusing elements; Afocal elements characterized by the use used in transmission
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • 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
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • 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
    • B32B7/04—Interconnection of layers
    • B32B7/12—Interconnection of layers using interposed adhesives or interposed materials with bonding properties
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B1/00—Optical elements characterised by the material of which they are made; Optical coatings for optical elements
    • G02B1/04—Optical elements characterised by the material of which they are made; Optical coatings for optical elements made of organic materials, e.g. plastics
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B1/00—Optical elements characterised by the material of which they are made; Optical coatings for optical elements
    • G02B1/10—Optical coatings produced by application to, or surface treatment of, optical elements
    • G02B1/14—Protective coatings, e.g. hard coatings
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/02—Diffusing elements; Afocal elements
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/30—Polarising elements
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/30—Polarising elements
    • G02B5/3025—Polarisers, i.e. arrangements capable of producing a definite output polarisation state from an unpolarised input state
    • G02B5/3033—Polarisers, i.e. arrangements capable of producing a definite output polarisation state from an unpolarised input state in the form of a thin sheet or foil, e.g. Polaroid
    • 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
    • G02F1/1333—Constructional arrangements; Manufacturing methods
    • G02F1/1335—Structural association of cells with optical devices, e.g. polarisers or reflectors
    • 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
    • G02F1/1333—Constructional arrangements; Manufacturing methods
    • G02F1/1335—Structural association of cells with optical devices, e.g. polarisers or reflectors
    • G02F1/133504—Diffusing, scattering, diffracting elements
    • 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
    • G02F1/1333—Constructional arrangements; Manufacturing methods
    • G02F1/1335—Structural association of cells with optical devices, e.g. polarisers or reflectors
    • G02F1/133528—Polarisers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2457/00—Electrical equipment
    • B32B2457/20—Displays, e.g. liquid crystal displays, plasma displays
    • B32B2457/202—LCD, i.e. liquid crystal displays

Definitions

  • the present invention relates to a polyester film for protecting a polarizer used for a liquid crystal display device, and a liquid crystal display device using the polyester film for protecting a polarizer.
  • liquid crystal displays are a typical example of such an optical display.
  • the configuration of the liquid crystal display is such that a backlight, a rear module, a liquid crystal cell, and a front module are stacked from the back side.
  • a diffusion sheet, a lens sheet, a reflector, and the like are provided on the backlight side with respect to the polarizing plate in the rear module located on the backlight side with respect to the liquid crystal cell, so that light from the light source is efficiently emitted.
  • the device is designed to uniformly and uniformly irradiate the viewer side.
  • the rear module and the front module each include a transparent substrate, a transparent conductive film formed on the liquid crystal cell side surface, and a polarizing plate disposed on the opposite side.
  • the backlight there is a sidelight type or a direct type surface light source device or the like so as to uniformly irradiate the entire liquid crystal display screen.
  • a sidelight type suitable for thinning has become mainstream.
  • the light from the light source propagates uniformly throughout the light guide plate, or emits the light by distributing the light source over the entire surface. Then, the light is diffused by the light diffusing plate and further condensed by the light-collecting sheet, so that the liquid crystal display screen disposed above the light-collecting sheet is uniformly irradiated (for example, see Patent Document 1). .
  • the present invention is intended to solve the problems as described above, by providing a light diffusion function to the polarizer protective polyester film of the polarizing plate located on the light source side than the liquid crystal cell, the light source and Even with a simple structure in which a light diffusion sheet is not provided between polarizers, as with a liquid crystal display device having a conventional light diffusion sheet, luminance unevenness of the light source is suppressed, and light with high homogeneity that diffuses at an arbitrary angle is suppressed. It is possible to obtain.
  • the inventors have found that providing a light diffusing layer (bead coat layer) having a specific structure on a base polyester film having a high in-plane retardation (Re) improves optical characteristics, and has reached the present invention. is there.
  • the present invention has the following configurations.
  • the first polyester film for protecting a polarizer which is used for a polarizing plate located on a light source side with respect to a liquid crystal cell. 3.
  • a liquid crystal display device in which a backlight using a white LED or an organic light emitting diode as a light source, the polyester film for protecting a polarizer, a polarizer, and a liquid crystal cell according to the second aspect are laminated at least in this order. 4. 4. The liquid crystal display device according to claim 3, wherein the light diffusion layer of the polarizer-protecting polyester film is located on the light source side.
  • the polyester film for protecting a polarizer of the present invention even with a simple structure in which a light diffusion sheet is not provided between a light source and a polarizing plate, the luminance unevenness of the light source is the same as in a liquid crystal display device having a conventional light diffusion sheet. And it is possible to obtain light with high homogeneity that diffuses at an arbitrary angle. Since it is not necessary to provide a light diffusion sheet, the liquid crystal panel can be further thinned. In addition, since the light diffusion sheet does not have to be used, there is no possibility that unevenness of light due to the prism shape of the light diffusion sheet will occur.
  • a light source such as a cold cathode fluorescent lamp (CCFL) or an LED can be used as a backlight light source of a liquid crystal display device.
  • a white light emitting diode (white LED) or an organic light emitting diode is preferably used as a light source.
  • a white LED is a phosphor type, that is, an element that emits white light by combining a phosphor and a light emitting diode that emits blue light or ultraviolet light using a compound semiconductor or an organic light emitting diode (Organic light-emitting diode). : OLED).
  • Examples of the phosphor include a yttrium-aluminum-garnet-based yellow phosphor and a terbium-aluminum-garnet-based yellow phosphor.
  • a white light-emitting diode composed of a light-emitting element that combines a blue light-emitting diode using a compound semiconductor and a yttrium-aluminum-garnet-based yellow phosphor has a continuous and wide emission spectrum and also has a high luminous efficiency. Because it is excellent, it is suitable as the backlight light source of the present invention.
  • that the emission spectrum is continuous means that there is no wavelength at which light intensity becomes zero at least in a visible light region.
  • the method of the present invention makes it possible to widely use white LEDs with low power consumption, so that an effect of energy saving can be achieved.
  • the light diffusion sheet a resin film such as polycarbonate, acryl, and triacetyl cellulose (TAC), a polyester film, and the like can be used.
  • the light diffusion sheet may not be particularly provided between the light source and the polarizing plate.
  • a light condensing sheet may be further provided between the light diffusing sheet and the polarizing plate.
  • the light diffusing sheet is not necessarily required. In the case where the light-collecting sheet is not provided, the light-collecting sheet is not particularly required.
  • the polarizer protective polyester film has a light diffusion layer.
  • the polyester film which is the base film of the polyester film for protecting a polarizer, preferably has an in-plane retardation (Re) of 5,000 to 30,000 nm.
  • Re in-plane retardation
  • the in-plane retardation (Re) is 5000 nm or more, the effect of suppressing color unevenness is obtained, which is preferable.
  • the thickness is 5000 nm or more, it is preferable because variation in luminance (brightness unevenness) on the polyester film can be suppressed small.
  • a more preferred lower limit is 6000 nm.
  • the upper limit of the in-plane retardation (Re) is preferably 30,000 nm. Even if a polyester film having a retardation exceeding that is used, the effect of further improving the luminance is substantially saturated. Further, the thickness of the polyester film becomes considerably large, and the handleability as an industrial material is deteriorated.
  • the in-plane retardation (Re) in the present invention can be determined by measuring the refractive index and the thickness in the biaxial directions.
  • polyester used in the present invention polyethylene terephthalate or polyethylene naphthalate can be used, but other copolymer components may be included. These resins are excellent in transparency, thermal and mechanical properties, and can easily control in-plane retardation (Re) by stretching.
  • polyethylene terephthalate is the most suitable material because it has a large intrinsic birefringence and a large in-plane retardation (Re) can be obtained relatively easily even when the film thickness is small.
  • a catalyst for example, inorganic particles, heat-resistant polymer particles, alkali metal compounds, alkaline earth metal compounds, phosphorus compounds, ultraviolet absorbers, antistatic agents, light resistance agents, flame retardants, heat stabilizers, antioxidants, Gelling inhibitors, surfactants and the like can be mentioned. It is also preferable that the polyester film contains substantially no particles in order to exhibit high transparency.
  • substantially do not contain particles means, for example, in the case of inorganic particles, when the inorganic element is quantified by fluorescent X-ray analysis, the content is 50 ppm or less, preferably 10 ppm or less, particularly preferably the detection limit or less. means.
  • polyester film of the base material of the present invention may be subjected to a corona treatment, a coating treatment, a flame treatment or the like in order to improve the adhesion to the light diffusion layer.
  • the substrate film in order to improve the adhesiveness with the light diffusion layer, it is preferable that at least one surface of the substrate film has an easy-adhesion layer containing polyvinyl alcohol. And it is more preferable to have an easy-adhesion layer containing at least one kind of resin of polyester resin, polyurethane resin and polyacryl resin in addition to the polyvinyl alcohol.
  • the coating solution used for forming the easily adhesive layer in the present invention is preferably a coating solution containing a water-soluble or water-dispersible polyvinyl alcohol, and more preferably, in addition to the water-soluble or water-dispersible polyvinyl alcohol, It is preferable that the coating liquid contains at least one of the copolymerized polyester resin, acrylic resin and polyurethane resin. Examples of these coating liquids include the coating liquids disclosed in Japanese Patent Nos. 5,090,094, 5,850,297, 5,472,464 and 6,201,755.
  • the easy-adhesion layer is obtained by applying the coating solution on one or both sides of a non-stretched or uniaxially stretched polyester film in the longitudinal direction, drying at 100 to 150 ° C., and further stretching the film in any unstretched direction. be able to. It is preferable to control the final coating amount of the easy-adhesion layer to 0.05 to 0.20 g / m 2 . When the coating amount is 0.05 g / m 2 or more, the adhesion to the obtained bead coat layer is good, which is preferable. On the other hand, when the coating amount is 0.20 g / m 2 or less, blocking resistance is preferably maintained.
  • the application amount of the easy-adhesion layers on both surfaces may be the same or different, and can be independently set within the above range.
  • particles it is preferable to add particles to the easily adhesive layer in order to impart lubricity. It is preferable to use particles having an average particle diameter of 2 ⁇ m or less. When the average particle size of the particles is 2 ⁇ m or less, it is preferable that the particles hardly fall off the coating layer.
  • Examples of 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, hectorite, zirconia, tungsten oxide, lithium fluoride, Examples include inorganic particles such as calcium fluoride and organic polymer particles such as styrene, acrylic, melamine, benzoguanamine, and silicone. These may be added alone to the easy-adhesion layer, or two or more of them may be added in combination.
  • a method for applying the coating liquid a known method can be used. For example, a reverse roll coating method, a gravure coating method, a kiss coating method, a roll brushing method, a spray coating method, an air knife coating method, a wire bar coating method, a pipe doctor method, and the like, and these methods alone or It can be performed in combination.
  • the thickness of the polyester film is optional, but is preferably in the range of 15 to 300 ⁇ m, more preferably in the range of 20 to 250 ⁇ m. Even in a film having a thickness of less than 15 ⁇ m, in-plane retardation (Re) of 5000 nm or more can be obtained in principle. However, in that case, the anisotropy of the mechanical properties of the film is increased, which is not preferable.
  • Re in-plane retardation
  • the polyester film for protecting the polarizer having the light diffusion layer not only the polyester film of the base material described above not only has a specific in-plane retardation (Re), but also at least one surface of the base material mainly includes acrylic. It is preferable to have a light diffusing layer composed of a system resin bead and a binder resin. The lamination of the light diffusion layer is preferable because an effect of improving brightness is obtained and the occurrence of color spots is suppressed.
  • binder resin used for the light diffusion layer examples include acrylic resins such as PMMA (polymethyl methacrylate), various resins such as polyester resins, polyvinyl chloride, polyurethane, and silicone resins, and acrylic resins are excellent. It is particularly suitable due to its transparency.
  • acrylic resins such as PMMA (polymethyl methacrylate)
  • various resins such as polyester resins, polyvinyl chloride, polyurethane, and silicone resins
  • acrylic resins are excellent. It is particularly suitable due to its transparency.
  • Acrylic resin-based beads are preferably used as the beads to be included in the light diffusion layer, but other resin-based beads may be used in combination without impairing the effect.
  • Other resin types include various types such as silicone resin, nylon resin, urethane resin, styrene resin, polyethylene resin, silica particles, polyester resin and the like.
  • the particle size of such beads is not particularly limited, but those having an average particle size of 1 ⁇ m to 50 ⁇ m are preferably used.
  • the spherical bead acts as a kind of lens, and can have a more effective light diffusion effect.
  • a coating solution in which the beads are blended in an appropriate blending amount with the binder resin as described above is prepared, and the coating solution is uniformly applied to the surface of the base polyester film manufactured as described above, and dried. Thereby, a light diffusion layer in which beads are uniformly dispersed in the binder is formed.
  • the number of beads mixed with the binder is not particularly limited, but is preferably about 10 to 60 parts by weight with respect to 100 parts by weight of the binder in consideration of light diffusion performance.
  • various methods such as a roll coating method, a dipping method, a spray coating method, a spin coating method, a laminating method, and a pouring method can be used, but are not particularly limited.
  • the polyester film for protecting a polarizer having the light diffusing layer of the present invention laminated thereon can be used for protecting a polarizer of a polarizing plate located closer to a light source than a liquid crystal cell of a liquid crystal panel to manufacture a liquid crystal display device.
  • the light-diffusing layer of the polarizer-protecting polyester film is provided with the polarizer-protecting polyester film so as to face the light source.
  • JP-A-2017-215609 JP-A-2017-095734
  • a polarizer protective film described in JP-A-2015-087694 can be used.
  • a polarizer protective film described in JP-A-2018-0555108 can also be used.
  • a backlight using a white LED or an organic light emitting diode as a light source, a polyester film for protecting a polarizer having a light diffusion layer and an easily bonding layer of the present invention, a polarizer, and a liquid crystal cell are laminated at least in this order.
  • it is a device.
  • a front module is usually provided on the viewing side from the liquid crystal cell, and the front module is usually laminated with a transparent electrode plate, a transparent substrate, and a polarizing plate.
  • the biaxial refractive index anisotropy ( ⁇ Nxy) was determined by the following method. Using two polarizing plates, the orientation axis direction of the film was determined, and a rectangle of 4 cm ⁇ 2 cm was cut out so that the orientation axis directions were orthogonal to each other, and used as a measurement sample.
  • the refractive index (Nx, Ny) and the refractive index (Nz) in the thickness direction in the orthogonal biaxial directions were determined by Abbe refractometer (Nagoya, NAR-4T, measurement wavelength 589 nm).
  • ) of the refractive index difference of the axis was defined as the anisotropy of the refractive index ( ⁇ Nxy).
  • the thickness d (nm) of the film was measured using an electric micrometer (Millitron 1245D, manufactured by Fineleuf Co.), and the unit was converted to nm.
  • In-plane retardation (Re) was determined from the product ( ⁇ Nxy ⁇ d) of the anisotropy of the refractive index ( ⁇ Nxy) and the thickness d (nm) of the film.
  • a front module including a viewing-side polarizing plate composed of a polarizer having a polarizing plate, a liquid crystal cell, a TAC film, and a polarizer-protecting polyester film (liquid crystal side) on each surface (the polarizer is the same as described above) is sequentially arranged. They were laminated and used as an evaluation device. However, in Examples 1 to 3 and Comparative Examples 1 to 3, the light diffusing layer of the polyester film for protecting the polarizer was arranged to face the light source, and in Example 4, the light diffusion layer was arranged to face the polarizer. In addition, it was as follows in evaluation. The evaluation of the brightness is in comparison with the case where each high retardation film was not inserted.
  • A No color unevenness is observed even when viewed from the front and oblique directions. :: Slight color unevenness was observed when viewed from an oblique direction. ⁇ : Color unevenness was observed when viewed from an oblique direction. X: Color unevenness was observed from the front.
  • the created film to be evaluated was attached to a glass plate having a thickness of 5 mm to which a double-sided tape was attached, and the opposite surface of the laminated film to be evaluated on which the polyvinyl alcohol resin layer was formed was attached to the double-sided tape. Then, 100 square cuts penetrating the polyvinyl alcohol resin layer and reaching the base film were made using a cutter guide with a gap of 2 mm. Next, an adhesive tape (Cellotape (registered trademark) CT-24, manufactured by Nichiban Co., Ltd .; 24 mm width) was attached to the cut surface of the grid.
  • an adhesive tape (Cellotape (registered trademark) CT-24, manufactured by Nichiban Co., Ltd .; 24 mm width) was attached to the cut surface of the grid.
  • Example 4 After the air remaining at the interface at the time of sticking was pressed with an eraser to completely adhere, the operation of peeling the adhesive tape vertically vigorously was performed once, five times, and ten times. The number of squares in which the polyvinyl alcohol resin layer was not peeled was counted, and the result was regarded as PVA adhesion. That is, the case where the PVA layer was not peeled at all was regarded as PVA adhesion rate 100, and the case where all the PVA layers were peeled was regarded as PVA adhesion rate 0. In addition, those that were partially peeled off within one cell were also included in the number of peeled. This measurement result corresponds to the adhesion between the polarizer and the polyester film for protecting the polarizer. In addition, in Example 4, evaluation was performed by providing a polyvinyl alcohol resin layer on the surface of the light diffusion layer of the polyester film for protecting the polarizer.
  • Acid value 1 g (solid content) of a sample was dissolved in 30 ml of chloroform or dimethylformamide, and titrated with a 0.1 N potassium hydroxide ethanol solution using phenolphthalein as an indicator to determine the carboxyl groups per 1 g of the sample. The amount (mg) of KOH required for neutralization was determined.
  • the temperature was raised to 255 ° C., and the reaction system was gradually decompressed, and then reacted under a reduced pressure of 30 Pa for 1 hour and 30 minutes to obtain a copolymerized polyester resin (A-1).
  • the obtained copolyester resin (A-1) was pale yellow and transparent.
  • the measured reduced viscosity of the copolymerized polyester resin (A-1) was 0.70 dl / g.
  • the glass transition temperature by DSC was 40 ° C.
  • aqueous dispersion of polyester used in easy-adhesion layer P1 30 parts by mass of the polyester resin (A-1) and 15 parts by mass of ethylene glycol n-butyl ether were put into a reactor equipped with a stirrer, a thermometer and a reflux device, and heated and stirred at 110 ° C. to dissolve the resin. After the resin was completely dissolved, 55 parts by mass of water was gradually added to the polyester solution with stirring. After the addition, the solution was cooled to room temperature with stirring to prepare a milky white polyester aqueous dispersion (Aw-1) having a solid content of 30% by mass. The acid value of the aqueous polyester dispersion (Aw-1) was 2 KOH mg / g.
  • Example 1 Preparation of Coating Liquid for Easy Adhesion Layer P1
  • the following coating agents were mixed to prepare a coating liquid in which the mass ratio of polyester resin / polyvinyl alcohol resin was 70/30.
  • the aqueous polyester dispersion used was an aqueous dispersion (Aw-1) in which a polyester resin having an acid value of 2 KOH mg / g was dispersed, and the aqueous polyvinyl alcohol solution was an aqueous solution in which polyvinyl alcohol having a saponification degree of 78 mol% was dissolved. (Bw-1) was used.
  • the coating liquid for the easy-adhesion layer P1 was applied to both surfaces of the unstretched polyester (PET) film by a roll coating method so that the coating amount after drying was 0.32 g / m 2 , Dry for 20 seconds.
  • the unstretched film on which the coating layer was formed was guided to a tenter stretching machine.
  • the film was guided to a hot air zone at a temperature of 125 ° C. while being gripped with clips, and stretched 4.3 times in the width direction.
  • the film is treated at a temperature of 225 ° C. for 30 seconds, and further subjected to a relaxation treatment of 3% in the width direction to obtain a uniaxially oriented polyester (PET) film having a film thickness of about 60 ⁇ m. Obtained.
  • coating solution A for light diffusion layer A coating solution having the following formulation was prepared and used as coating solution A.
  • Acrylic polyol (solid content 50%) 150 parts (Acridic (registered trademark) A-807: DIC)
  • Isocyanate (solid content 60%) 30 parts
  • Methyl ethyl ketone 200 parts
  • Butyl acetate 200 parts
  • Acrylic resin particles 40 parts (MX-1000, average particle size 10.0 ⁇ m: Soken Chemical Co., Ltd.)
  • One side of a polyester (PET) film is coated with the coating solution A for the light diffusion layer, was dried and thermally cured under the conditions described above to obtain a polarizer-protecting polyester film having a light diffusion layer.
  • the thickness of the light diffusion layer after drying and curing was 5.0 ⁇ m.
  • Example 2 A polyester film for protecting a polarizer having a light diffusion layer was obtained in the same manner as in Example 1, except that the coating solution for the light diffusion layer in Example 1 was changed to the following coating solution B.
  • coating solution B for light diffusion layer A coating solution having the following formulation was prepared, and used as coating solution B.
  • Acrylic polyol (solid content 50%) 150 parts (Acridic (registered trademark) A-807: DIC) Isocyanate (solid content 60%) 30 parts (Takenate (registered trademark) D11N: Mitsui Chemicals, Inc.)
  • Methyl ethyl ketone 200 parts
  • Butyl acetate 200 parts
  • Example 1 A polarizer-protecting polyester film having a light-diffusing layer was obtained in the same manner as in Example 1 except that the easy-adhesion layer P1 was not provided.
  • Comparative Example 2 A polyester film for protecting a polarizer was obtained in the same manner as in Example 1 except that the light diffusion layer was not provided.
  • Example 3 A polarizer protecting polyester film having a light diffusion layer was obtained in the same manner as in Example 1 except that the film thickness in Example 1 was changed to 80 ⁇ m.
  • Example 3 A polyester film for protecting a polarizer having a light diffusion layer was obtained in the same manner as in Example 1 except that the film thickness of Example 1 was changed to 30 ⁇ m.
  • Example 4 The evaluation was performed using the polyester film for protecting the polarizer of Example 1. However, the color unevenness evaluation was performed with the light diffusion layer of the polyester film for protecting the polarizer facing the polarizer. The PVA adhesion was evaluated for adhesion to the light diffusion layer.
  • Example 5 Regarding the polyester film for protecting the polarizer prepared in Example 1, a white backlight as an organic EL light source, a polarizer having the polyester film for protecting the polarizer (light source side) of Example 1 and an acrylic film on each surface ( A light source side polarizing plate, a liquid crystal cell, an acrylic film and a polyester film for protecting the polarizer of Example 1 (liquid crystal side) comprising PVA and iodine and having a thickness of 80 ⁇ m stretched 5 times).
  • a front module including a viewing-side polarizing plate composed of a polarizer (the same polarizer as described above) was sequentially laminated to obtain an evaluation device. Evaluation of color unevenness was performed in the same manner as in Example 1. The evaluation results were very favorable, like the evaluation results of Example 1.
  • the present invention even with a simple structure in which a light diffusion sheet is not provided between a light source and a polarizing plate, luminance unevenness of the light source is suppressed as in the case of a conventional liquid crystal display device having a light diffusion sheet, and the angle can be set to an arbitrary angle. This makes it possible to obtain light with a high degree of homogeneity to diffuse. Since it is not necessary to provide a light diffusion sheet, the liquid crystal panel can be further thinned.

Abstract

[Problem] To provide a polyester film for protecting a polarizer which, even with a liquid crystal display device having a simple structure in which no light diffusing sheet is provided between a light source and a polarizing plate, makes it possible to achieve high uniformity in light diffused in an intended angle and limit unevenness in light source brightness similarly to conventional liquid crystal display devices that employ a light diffusing sheet. [Solution] This polyester film for protecting a polarizer has, as a base material, a polyester film that has an in-plane retardation (Re) of 5000 to 30000 nm, and has, on at least one surface of the base material, an easily adhesive layer (P1) that comprises polyvinyl alcohol, and a light diffusing layer that comprises acrylic resin beads and a binder resin, in the stated order.

Description

偏光子保護用ポリエステルフィルム及び液晶表示装置Polyester film for protecting polarizer and liquid crystal display
　本発明は、液晶表示装置に使用される偏光子保護用ポリエステルフィルム、及び前記の偏光子保護用ポリエステルフィルムを用いた液晶表示装置に関する。 The present invention relates to a polyester film for protecting a polarizer used for a liquid crystal display device, and a liquid crystal display device using the polyester film for protecting a polarizer.
　従来、光学ディスプレイは、テレビ、コンピューター、携帯電話、スマートフォン、などに広く用いられている。液晶ディスプレイ（LCD）は、このような光学ディスプレイの代表的な例である。液晶ディスプレイの構成は、背面側からバックライト、後面モジュール、液晶セル、前面モジュールを積層されたものになっている。従来一般的には、液晶セルよりもバックライト側に位置する後面モジュール中の偏光板に対して更にバックライト側には、拡散シートやレンズシート、反射板などが設けられ、光源の光を効率よく均一に視認側に照射させる工夫がされている。 Conventionally, optical displays have been widely used in televisions, computers, mobile phones, smartphones, and the like. Liquid crystal displays (LCDs) are a typical example of such an optical display. The configuration of the liquid crystal display is such that a backlight, a rear module, a liquid crystal cell, and a front module are stacked from the back side. Conventionally, in general, a diffusion sheet, a lens sheet, a reflector, and the like are provided on the backlight side with respect to the polarizing plate in the rear module located on the backlight side with respect to the liquid crystal cell, so that light from the light source is efficiently emitted. The device is designed to uniformly and uniformly irradiate the viewer side.
　一般に、後面モジュールおよび前面モジュールは、透明基板と、その液晶セル側表面に形成された透明導電膜と、その反対側に配置された偏光板とから構成されている。また、バックライトは、液晶表示画面全体が均一に照射されるように、サイドライト型もしくは直下型の面光源装置等があり、近年は薄型化に適したサイドライト型が主流となっている。 Generally, the rear module and the front module each include a transparent substrate, a transparent conductive film formed on the liquid crystal cell side surface, and a polarizing plate disposed on the opposite side. As the backlight, there is a sidelight type or a direct type surface light source device or the like so as to uniformly irradiate the entire liquid crystal display screen. In recent years, a sidelight type suitable for thinning has become mainstream.
　このような面光源装置では、光源からの光が導光板の全体に均一に伝播して、または面全体に光源を分布させて光を出射する。そして光拡散板によって拡散され、さらに集光シートによって集光されて、集光シートの上側に配設される液晶表示画面が均一に照射されるようになっている（例えば、特許文献１参照）。 In such a surface light source device, the light from the light source propagates uniformly throughout the light guide plate, or emits the light by distributing the light source over the entire surface. Then, the light is diffused by the light diffusing plate and further condensed by the light-collecting sheet, so that the liquid crystal display screen disposed above the light-collecting sheet is uniformly irradiated (for example, see Patent Document 1). .
　近年、液晶表示装置の部材点数を少なくすることで、軽量化や折り曲げ性を可能にする取り組みがある。このため、液晶セルよりも光源側に位置する部材の点数を減らす要望があるが、現在までのところ、有効な提案はなされていない。 In recent years, there has been an effort to reduce the number of members of a liquid crystal display device to make it lighter and bendable. For this reason, there is a demand to reduce the number of members located closer to the light source than the liquid crystal cell, but no effective proposal has been made so far.
特開２０１４－０５２５９５号公報JP 2014-052595 A
　本発明は、上記のような課題を解決しようとするものであって、光拡散の機能を液晶セルよりも光源側に位置する偏光板の偏光子保護用ポリエステルフィルムに付与することにより、光源と偏光板の間に光拡散シートを設けない簡単な構造であっても、従来の光拡散シートを有する液晶表示装置と同様に光源の輝度ムラを抑制し、任意の角度に拡散する均質度の高い光を得ることを可能としたものである。 The present invention is intended to solve the problems as described above, by providing a light diffusion function to the polarizer protective polyester film of the polarizing plate located on the light source side than the liquid crystal cell, the light source and Even with a simple structure in which a light diffusion sheet is not provided between polarizers, as with a liquid crystal display device having a conventional light diffusion sheet, luminance unevenness of the light source is suppressed, and light with high homogeneity that diffuses at an arbitrary angle is suppressed. It is possible to obtain.
　本発明者は、リタデーションが比較的大きいポリエステルフィルムを基材として用いた光拡散シートの光学特性の向上について詳細な分析を行なった。そして、面内リタデーション（Ｒｅ）が高い基材ポリエステルフィルムに、特定の構造を有する光拡散層（ビーズコート層）を設けることにより、光学特性が向上することを見出し、本発明に到達したものである。 (4) The inventor conducted a detailed analysis on the improvement of the optical characteristics of the light diffusion sheet using a polyester film having a relatively large retardation as a base material. The inventors have found that providing a light diffusing layer (bead coat layer) having a specific structure on a base polyester film having a high in-plane retardation (Re) improves optical characteristics, and has reached the present invention. is there.
　即ち、本発明は、以下の構成よりなる。
１．　５０００～３００００ｎｍの面内リタデーション（Ｒｅ）を有するポリエステルフィルムを基材とし、前記基材の少なくとも一方の面にポリビニルアルコールを有する易接着層（Ｐ１）と、アクリル系樹脂ビーズとバインダー樹脂を含んでなる光拡散層を順に有する偏光子保護用ポリエステルフィルム。
２．　液晶セルに対して光源側に位置する偏光板用である上記第１の偏光子保護用ポリエステルフィルム。
３．　白色ＬＥＤまたは有機発光ダイオードを光源とするバックライト、上記第２に記載の偏光子保護用ポリエステルフィルム、偏光子、液晶セルが、少なくともこの順に積層されている液晶表示装置。
４．　偏光子保護用ポリエステルフィルムの光拡散層が光源側に位置している請求項３の液晶表示装置。 That is, the present invention has the following configurations.
1. A polyester film having an in-plane retardation (Re) of 5,000 to 30,000 nm as a base material, comprising an easy-adhesion layer (P1) having polyvinyl alcohol on at least one surface of the base material, acrylic resin beads and a binder resin. A polyester film for protecting a polarizer having a light diffusion layer in order.
2. The first polyester film for protecting a polarizer, which is used for a polarizing plate located on a light source side with respect to a liquid crystal cell.
3. A liquid crystal display device in which a backlight using a white LED or an organic light emitting diode as a light source, the polyester film for protecting a polarizer, a polarizer, and a liquid crystal cell according to the second aspect are laminated at least in this order.
4. 4. The liquid crystal display device according to claim 3, wherein the light diffusion layer of the polarizer-protecting polyester film is located on the light source side.
　本発明の偏光子保護用ポリエステルフィルムを用いることにより、光源と偏光板の間に光拡散シートを設けない簡単な構造であっても、従来の光拡散シートを有する液晶表示装置と同様に光源の輝度ムラを抑制し、任意の角度に拡散する均質度の高い光を得ることを可能とした。光拡散シートを設けずとも良いため、液晶パネルの更なる薄型化が可能となる。また、光拡散シートを用いずともよいため、光拡散シートのプリズム形状に起因する光のムラが生じるおそれもなくなった。 By using the polyester film for protecting a polarizer of the present invention, even with a simple structure in which a light diffusion sheet is not provided between a light source and a polarizing plate, the luminance unevenness of the light source is the same as in a liquid crystal display device having a conventional light diffusion sheet. And it is possible to obtain light with high homogeneity that diffuses at an arbitrary angle. Since it is not necessary to provide a light diffusion sheet, the liquid crystal panel can be further thinned. In addition, since the light diffusion sheet does not have to be used, there is no possibility that unevenness of light due to the prism shape of the light diffusion sheet will occur.
　本発明では、液晶表示装置のバックライト光源として冷陰極管（ＣＣＦＬ）やＬＥＤ等の光源を使用できるが、特に光源として白色発光ダイオード（白色ＬＥＤ）や有機発光ダイオードを用いることが好ましい。本発明において、白色ＬＥＤとは、蛍光体方式、すなわち化合物半導体を使用した青色光、もしくは紫外光を発する発光ダイオードと蛍光体を組み合わせることにより白色を発する素子や有機発光ダイオード（Ｏｒｇａｎｉｃ ｌｉｇｈｔ－ｅｍｉｔｔｉｎｇ ｄｉｏｄｅ：ＯＬＥＤ）のことである。蛍光体としては、イットリウム・アルミニウム・ガーネット系の黄色蛍光体やテルビウム・アルミニウム・ガーネット系の黄色蛍光体等がある。なかでも、化合物半導体を使用した青色発光ダイオードとイットリウム・アルミニウム・ガーネット系黄色蛍光体とを組み合わせた発光素子からなる白色発光ダイオードは、連続的で幅広い発光スペクトルを有しているとともに発光効率にも優れるため、本発明のバックライト光源として好適である。なお、ここで発光スペクトルが連続的であるとは、少なくとも可視光の領域において光の強度がゼロとなる波長が存在しないことをいう。また、本発明の方法により消費電力の小さい白色ＬＥＤを広汎に利用可能になるので、省エネルギー化の効果も奏することが可能となる。  In the present invention, a light source such as a cold cathode fluorescent lamp (CCFL) or an LED can be used as a backlight light source of a liquid crystal display device. In particular, a white light emitting diode (white LED) or an organic light emitting diode is preferably used as a light source. In the present invention, a white LED is a phosphor type, that is, an element that emits white light by combining a phosphor and a light emitting diode that emits blue light or ultraviolet light using a compound semiconductor or an organic light emitting diode (Organic light-emitting diode). : OLED). Examples of the phosphor include a yttrium-aluminum-garnet-based yellow phosphor and a terbium-aluminum-garnet-based yellow phosphor. Above all, a white light-emitting diode composed of a light-emitting element that combines a blue light-emitting diode using a compound semiconductor and a yttrium-aluminum-garnet-based yellow phosphor has a continuous and wide emission spectrum and also has a high luminous efficiency. Because it is excellent, it is suitable as the backlight light source of the present invention. Here, that the emission spectrum is continuous means that there is no wavelength at which light intensity becomes zero at least in a visible light region. In addition, the method of the present invention makes it possible to widely use white LEDs with low power consumption, so that an effect of energy saving can be achieved.
　光拡散シートはポリカーボネート、アクリル、トリアセチルセルロース（ＴＡＣ）等の樹脂フィルム、ポリエステルフィルムなども使用できるが、本発明においては、特に光拡散シートを光源と偏光板の間に設けなくても構わない。光拡散シートを光源と偏光板の間に配した場合には、当該光拡散シートと偏光板の間に更に集光シートを設ける場合があるが、本発明においては、光拡散シートは必ずしも必要なく、光拡散シートを設けない場合は、集光シートも特に必要ない。 As the light diffusion sheet, a resin film such as polycarbonate, acryl, and triacetyl cellulose (TAC), a polyester film, and the like can be used. In the present invention, however, the light diffusion sheet may not be particularly provided between the light source and the polarizing plate. When the light diffusing sheet is disposed between the light source and the polarizing plate, a light condensing sheet may be further provided between the light diffusing sheet and the polarizing plate. However, in the present invention, the light diffusing sheet is not necessarily required. In the case where the light-collecting sheet is not provided, the light-collecting sheet is not particularly required.
　光拡散シートと同様の効果を奏するためには、偏光子保護用ポリエステルフィルムは、光拡散層を有するものであることが好ましい。偏光子保護用ポリエステルフィルムの基材フィルムであるポリエステルフィルムは、５０００～３００００ｎｍの面内リタデーション（Ｒｅ）を有することが好ましい。面内リタデーション（Ｒｅ）が５０００ｎｍ以上であると、色むらを抑制する効果が得られて好ましい。また、５０００ｎｍ以上であると、ポリエステルフィルム上で輝度のばらつき（輝度斑）が小さく抑制できて好ましい。より好ましい下限値は６０００ｎｍである。  た め In order to achieve the same effect as the light diffusion sheet, it is preferable that the polarizer protective polyester film has a light diffusion layer. The polyester film, which is the base film of the polyester film for protecting a polarizer, preferably has an in-plane retardation (Re) of 5,000 to 30,000 nm. When the in-plane retardation (Re) is 5000 nm or more, the effect of suppressing color unevenness is obtained, which is preferable. In addition, when the thickness is 5000 nm or more, it is preferable because variation in luminance (brightness unevenness) on the polyester film can be suppressed small. A more preferred lower limit is 6000 nm.
　一方、面内リタデーション（Ｒｅ）の上限は３００００ｎｍであることが好ましい。それを超えるリタデーションを有するポリエステルフィルムを用いたとしても更なる輝度の向上効果は実質的に飽和する。また、ポリエステルフィルムの厚みも相当に厚くなり、工業材料としての取り扱い性が低下するので好ましくない。  On the other hand, the upper limit of the in-plane retardation (Re) is preferably 30,000 nm. Even if a polyester film having a retardation exceeding that is used, the effect of further improving the luminance is substantially saturated. Further, the thickness of the polyester film becomes considerably large, and the handleability as an industrial material is deteriorated.
　なお、本発明における面内リタデーション（Ｒｅ）は、２軸方向の屈折率と厚みを測定して求めることができる。  The in-plane retardation (Re) in the present invention can be determined by measuring the refractive index and the thickness in the biaxial directions.
　本発明に用いられるポリエステルは、ポリエチレンテレフタレートやポリエチレンナフタレートを用いることができるが、他の共重合成分を含んでも構わない。これらの樹脂は透明性に優れるとともに、熱的、機械的特性にも優れており、延伸加工によって容易に面内リタデーション（Ｒｅ）を制御することができる。特に、ポリエチレンテレフタレートは固有複屈折が大きく、フィルムの厚みが薄くても比較的容易に大きな面内リタデーション（Ｒｅ）が得られるので、最も好適な素材である。  ポ リ エ ス テ ル As the polyester used in the present invention, polyethylene terephthalate or polyethylene naphthalate can be used, but other copolymer components may be included. These resins are excellent in transparency, thermal and mechanical properties, and can easily control in-plane retardation (Re) by stretching. In particular, polyethylene terephthalate is the most suitable material because it has a large intrinsic birefringence and a large in-plane retardation (Re) can be obtained relatively easily even when the film thickness is small.
　また、本発明の効果を妨げない範囲で、触媒や各種の添加剤を含有させることも好ましい態様である。添加剤として、例えば、無機粒子、耐熱性高分子粒子、アルカリ金属化合物、アルカリ土類金属化合物、リン化合物、紫外線吸収剤、帯電防止剤、耐光剤、難燃剤、熱安定剤、酸化防止剤、ゲル化防止剤、界面活性剤等が挙げられる。また、高い透明性を奏するためにはポリエステルフィルムに実質的に粒子を含有しないことも好ましい。「粒子を実質的に含有させない」とは、例えば無機粒子の場合、ケイ光Ｘ線分析で無機元素を定量した場合に５０ｐｐｍ以下、好ましくは１０ｐｐｍ以下、特に好ましくは検出限界以下となる含有量を意味する。  It is also a preferred embodiment to include a catalyst and various additives as long as the effects of the present invention are not impaired. As additives, for example, inorganic particles, heat-resistant polymer particles, alkali metal compounds, alkaline earth metal compounds, phosphorus compounds, ultraviolet absorbers, antistatic agents, light resistance agents, flame retardants, heat stabilizers, antioxidants, Gelling inhibitors, surfactants and the like can be mentioned. It is also preferable that the polyester film contains substantially no particles in order to exhibit high transparency. "Substantially do not contain particles" means, for example, in the case of inorganic particles, when the inorganic element is quantified by fluorescent X-ray analysis, the content is 50 ppm or less, preferably 10 ppm or less, particularly preferably the detection limit or less. means.
　さらに、本発明の基材のポリエステルフィルムには、光拡散層との接着性を良好にするためにコロナ処理、コーティング処理や火炎処理等を施したりすることも可能である。  Further, the polyester film of the base material of the present invention may be subjected to a corona treatment, a coating treatment, a flame treatment or the like in order to improve the adhesion to the light diffusion layer.
　本発明においては、光拡散層との接着性を改良のために、基材のフィルムの少なくとも片面に、ポリビニルアルコールを含有する易接着層を有することが好ましい。そして、前記のポリビニルアルコールに加えてポリエステル樹脂、ポリウレタン樹脂及びポリアクリル樹脂の少なくとも１種類の樹脂を含む易接着層を有することが更に好ましい。本発明における易接着層の形成に用いる塗布液は、水溶性又は水分散性のポリビニルアルコールを含有する塗布液であることが好ましく、更に好ましくは、水溶性又は水分散性のポリビニルアルコール以外に、共重合ポリエステル樹脂、アクリル樹脂及びポリウレタン樹脂の内、少なくとも１種をも含む塗布液であることが好ましい。これらの塗布液としては、例えば、特許第５１０９０９４号公報、特許第５８５０２９７号公報、特許第５４７２４６４号公報、特許第６２０１７５５号公報等に開示された塗布液が挙げられる。  In the present invention, in order to improve the adhesiveness with the light diffusion layer, it is preferable that at least one surface of the substrate film has an easy-adhesion layer containing polyvinyl alcohol. And it is more preferable to have an easy-adhesion layer containing at least one kind of resin of polyester resin, polyurethane resin and polyacryl resin in addition to the polyvinyl alcohol. The coating solution used for forming the easily adhesive layer in the present invention is preferably a coating solution containing a water-soluble or water-dispersible polyvinyl alcohol, and more preferably, in addition to the water-soluble or water-dispersible polyvinyl alcohol, It is preferable that the coating liquid contains at least one of the copolymerized polyester resin, acrylic resin and polyurethane resin. Examples of these coating liquids include the coating liquids disclosed in Japanese Patent Nos. 5,090,094, 5,850,297, 5,472,464 and 6,201,755.
　易接着層は、前記塗布液を縦方向の未延伸又は１軸延伸ポリエステルフィルムの片面または両面に塗布した後、１００～１５０℃で乾燥し、さらに延伸されていない任意の方向に延伸して得ることができる。最終的な易接着層の塗布量は、０．０５～０．２０ｇ／ｍ２に管理することが好ましい。塗布量が０．０５ｇ／ｍ２以上であると、得られるビーズコート層との接着性が良好となり好ましい。一方、塗布量が０．２０ｇ／ｍ２以下であると、耐ブロッキング性が保たれて好ましい。ポリエステルフィルムの両面に易接着層を設ける場合は、両面の易接着層の塗布量は、同じであっても異なっていてもよく、それぞれ独立して上記範囲内で設定することができる。  The easy-adhesion layer is obtained by applying the coating solution on one or both sides of a non-stretched or uniaxially stretched polyester film in the longitudinal direction, drying at 100 to 150 ° C., and further stretching the film in any unstretched direction. be able to. It is preferable to control the final coating amount of the easy-adhesion layer to 0.05 to 0.20 g / m 2 . When the coating amount is 0.05 g / m 2 or more, the adhesion to the obtained bead coat layer is good, which is preferable. On the other hand, when the coating amount is 0.20 g / m 2 or less, blocking resistance is preferably maintained. When the easy-adhesion layers are provided on both surfaces of the polyester film, the application amount of the easy-adhesion layers on both surfaces may be the same or different, and can be independently set within the above range.
　易接着層には易滑性を付与するために粒子を添加することが好ましい。微粒子の平均粒径は２μｍ以下の粒子を用いることが好ましい。粒子の平均粒径が２μｍ以下であると、粒子が被覆層から脱落しづらく好ましい。易接着層に含有させる粒子としては、例えば、酸化チタン、硫酸バリウム、炭酸カルシウム、硫酸カルシウム、シリカ、アルミナ、タルク、カオリン、クレー、リン酸カルシウム、雲母、ヘクトライト、ジルコニア、酸化タングステン、フッ化リチウム、フッ化カルシウム等の無機粒子や、スチレン系、アクリル系、メラミン系、ベンゾグアナミン系、シリコーン系等の有機ポリマー系粒子等が挙げられる。これらは、単独で易接着層に添加されてもよく、２種以上を組合せて添加することもできる。  (4) It is preferable to add particles to the easily adhesive layer in order to impart lubricity. It is preferable to use particles having an average particle diameter of 2 μm or less. When the average particle size of the particles is 2 μm or less, it is preferable that the particles hardly fall off the coating layer. Examples of 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, hectorite, zirconia, tungsten oxide, lithium fluoride, Examples include inorganic particles such as calcium fluoride and organic polymer particles such as styrene, acrylic, melamine, benzoguanamine, and silicone. These may be added alone to the easy-adhesion layer, or two or more of them may be added in combination.
　また、塗布液を塗布する方法としては、公知の方法を用いることができる。例えば、リバースロール・コート法、グラビア・コート法、キス・コート法、ロールブラッシュ法、スプレーコート法、エアナイフコート法、ワイヤーバーコート法、パイプドクター法などが挙げられ、これらの方法を単独であるいは組み合わせて行うことができる。 公 知 As a method for applying the coating liquid, a known method can be used. For example, a reverse roll coating method, a gravure coating method, a kiss coating method, a roll brushing method, a spray coating method, an air knife coating method, a wire bar coating method, a pipe doctor method, and the like, and these methods alone or It can be performed in combination.
　ポリエステルフィルムの厚みは任意であるが、１５～３００μｍの範囲が好ましく、より好ましくは２０～２５０μｍの範囲である。１５μｍを下回る厚みのフィルムでも、原理的には５０００ｎｍ以上の面内リタデーション（Ｒｅ）を得ることは可能である。しかし、その場合にはフィルムの力学特性の異方性が強まるため、あまり好ましくない。 The thickness of the polyester film is optional, but is preferably in the range of 15 to 300 μm, more preferably in the range of 20 to 250 μm. Even in a film having a thickness of less than 15 μm, in-plane retardation (Re) of 5000 nm or more can be obtained in principle. However, in that case, the anisotropy of the mechanical properties of the film is increased, which is not preferable.
　本発明では、光拡散層を有する偏光子保護用ポリエステルフィルムとして、上記の基材のポリエステルフィルムが特定の面内リタデーション（Ｒｅ）を有するのみだけでなく、基材の少なくとも一方の面に主としてアクリル系樹脂ビーズとバインダー樹脂からなる光拡散層を有することが好ましい。光拡散層の積層により、輝度向上効果が得られ、色斑の発現が抑制されて好ましい。 In the present invention, as the polyester film for protecting the polarizer having the light diffusion layer, not only the polyester film of the base material described above not only has a specific in-plane retardation (Re), but also at least one surface of the base material mainly includes acrylic. It is preferable to have a light diffusing layer composed of a system resin bead and a binder resin. The lamination of the light diffusion layer is preferable because an effect of improving brightness is obtained and the occurrence of color spots is suppressed.
　次に、光拡散層を有する偏光子保護用ポリエステルフィルムとして、基材ポリエステルフィルム上に、光拡散層を形成する方法について説明するが、本発明はこれに限定されるものではない。 Next, a method of forming a light diffusion layer on a base polyester film as a polyester film for protecting a polarizer having a light diffusion layer will be described, but the present invention is not limited thereto.
　光拡散層に用いられるバインダー樹脂としては、ＰＭＭＡ（ポリメチルメタクリレート）等のアクリル系樹脂、ポリエステル樹脂、ポリ塩化ビニル、ポリウレタン、シリコーン樹脂等の各種の樹脂が挙げられるが、アクリル系樹脂がその優れた透明性により特に好適である。  Examples of the binder resin used for the light diffusion layer include acrylic resins such as PMMA (polymethyl methacrylate), various resins such as polyester resins, polyvinyl chloride, polyurethane, and silicone resins, and acrylic resins are excellent. It is particularly suitable due to its transparency.
　光拡散層に含ませるビーズとしてはアクリル系樹脂のものが用いられることが好ましいが、本効果を損なわない程度でその他樹脂系のものを併用することも可能である。その他樹脂系としてはシリコーン樹脂、ナイロン樹脂、ウレタン樹脂、スチレン樹脂、ポリエチレン樹脂、シリカ粒子、ポリエステル樹脂等の各種のものが例示される。このようなビーズの粒径は特に限定されるものではないが、平均粒径１μｍ～５０μｍのものが好適に用いられる。また、上記ビーズとして球状のものを使用した場合には、この球状ビーズが一種のレンズとして作用し、一層効果的な光拡散効果を持たせることができる。  ア ク リ ル Acrylic resin-based beads are preferably used as the beads to be included in the light diffusion layer, but other resin-based beads may be used in combination without impairing the effect. Other resin types include various types such as silicone resin, nylon resin, urethane resin, styrene resin, polyethylene resin, silica particles, polyester resin and the like. The particle size of such beads is not particularly limited, but those having an average particle size of 1 μm to 50 μm are preferably used. When a spherical bead is used as the above-mentioned bead, the spherical bead acts as a kind of lens, and can have a more effective light diffusion effect.
　前記のようなバインダー樹脂に適当な配合部数で上記のビーズを配合した塗布液を作製し、この塗布液を、前述のように製造された基材ポリエステルフィルムの表面に均一に塗布し、乾燥させることによって、バインダーにビーズが均一に分散された光拡散層が形成される。バインダーに対するビーズの配合部数は、特に限定されるものではないが、光拡散性能を考慮すれば、バインダー１００重量部に対して１０～６０重量部程度が好ましい。塗布方法としては、ロールコート法、ディッピング法、スプレーコーティング法、スピンコーティング法、ラミネート法、掛け流し法等各種の方法を用いることができるが、特に限定されるものではない。 A coating solution in which the beads are blended in an appropriate blending amount with the binder resin as described above is prepared, and the coating solution is uniformly applied to the surface of the base polyester film manufactured as described above, and dried. Thereby, a light diffusion layer in which beads are uniformly dispersed in the binder is formed. The number of beads mixed with the binder is not particularly limited, but is preferably about 10 to 60 parts by weight with respect to 100 parts by weight of the binder in consideration of light diffusion performance. As a coating method, various methods such as a roll coating method, a dipping method, a spray coating method, a spin coating method, a laminating method, and a pouring method can be used, but are not particularly limited.
　本発明の光拡散層を積層した偏光子保護用ポリエステルフィルムは、液晶パネルの液晶セルよりも光源側に位置する偏光板の偏光子保護用として用い、液晶表示装置を製造することができる。もちろん、偏光子保護用ポリエステルフィルムの光拡散層は、光源の側に向くように偏光子保護用ポリエステルフィルムが設置されていることが好ましい。本発明において特に限定されるものではないが、例えば、液晶セルよりも視認側に位置する偏光板の偏光子保護用フィルムとしては、特開２０１７－２１５６０９号公報、特開２０１７－０９５７３４号公報、特開２０１５－０８７６９４号公報に記載される偏光子保護フィルムなどを用いることができる。また、特開２０１８－０５５１０８号公報に記載される偏光子保護フィルムなども用いることができる。 偏光 The polyester film for protecting a polarizer having the light diffusing layer of the present invention laminated thereon can be used for protecting a polarizer of a polarizing plate located closer to a light source than a liquid crystal cell of a liquid crystal panel to manufacture a liquid crystal display device. Of course, it is preferable that the light-diffusing layer of the polarizer-protecting polyester film is provided with the polarizer-protecting polyester film so as to face the light source. Although not particularly limited in the present invention, for example, as a polarizer protecting film of a polarizing plate located on the viewing side of the liquid crystal cell, JP-A-2017-215609, JP-A-2017-095734, For example, a polarizer protective film described in JP-A-2015-087694 can be used. Further, a polarizer protective film described in JP-A-2018-0555108 can also be used.
　本発明においては、白色ＬＥＤまたは有機発光ダイオードを光源とするバックライト、本発明の光拡散層及び易接着層を有する偏光子保護用ポリエステルフィルム、偏光子、液晶セルを少なくともこの順に積層した液晶表示装置とすることが好ましい。本発明においては特に限定されないが、液晶セルより視認側には、通常前面モジュールが設けられ、前面モジュールには、通常、透明電極板、透明基板、偏光板が積層されている。 In the present invention, a backlight using a white LED or an organic light emitting diode as a light source, a polyester film for protecting a polarizer having a light diffusion layer and an easily bonding layer of the present invention, a polarizer, and a liquid crystal cell are laminated at least in this order. Preferably, it is a device. Although not particularly limited in the present invention, a front module is usually provided on the viewing side from the liquid crystal cell, and the front module is usually laminated with a transparent electrode plate, a transparent substrate, and a polarizing plate.
　次に、実施例、比較例、及び参考例を用いて本発明を詳細に説明するが、本発明は当然以下の実施例に限定されるものではない。また、本発明で用いた評価方法は以下の通りである。 Next, the present invention will be described in detail with reference to examples, comparative examples, and reference examples, but the present invention is not limited to the following examples. The evaluation method used in the present invention is as follows.
（１）面内リタデーション（Ｒｅ） 
　面内リタデーション（Ｒｅ）とは、フィルム上の直交する二軸の屈折率の異方性（△Ｎｘｙ＝｜Ｎｘ－Ｎｙ｜）とフィルム厚みｄ（ｎｍ）との積（△Ｎｘｙ×ｄ）で定義されるパラメーターであり、光学的等方性、異方性を示す尺度である。二軸の屈折率の異方性（△Ｎｘｙ）は、以下の方法により求めた。二枚の偏光板を用いて、フィルムの配向軸方向を求め、配向軸方向が直交するように４ｃｍ×２ｃｍの長方形を切り出し、測定用サンプルとした。このサンプルについて、直交する二軸の屈折率（Ｎｘ，Ｎｙ）、及び厚さ方向の屈折率（Ｎｚ）をアッベ屈折率計（アタゴ社製、ＮＡＲ－４Ｔ、測定波長５８９ｎｍ）によって求め、前記二軸の屈折率差の絶対値（｜Ｎｘ－Ｎｙ｜）を屈折率の異方性（△Ｎｘｙ）とした。フィルムの厚みｄ（ｎｍ）は電気マイクロメータ（ファインリューフ社製、ミリトロン１２４５Ｄ）を用いて測定し、単位をｎｍに換算した。屈折率の異方性（△Ｎｘｙ）とフィルムの厚みｄ（ｎｍ）の積（△Ｎｘｙ×ｄ）より、面内リタデーション（Ｒｅ）を求めた。 (1) In-plane retardation (Re)
The in-plane retardation (Re) is the product (△ Nxy × d) of the anisotropy (△ Nxy = | Nx-Ny |) of the biaxial refractive index on the film and the film thickness d (nm). It is a defined parameter and is a measure of optical isotropic and anisotropy. The biaxial refractive index anisotropy (△ Nxy) was determined by the following method. Using two polarizing plates, the orientation axis direction of the film was determined, and a rectangle of 4 cm × 2 cm was cut out so that the orientation axis directions were orthogonal to each other, and used as a measurement sample. With respect to this sample, the refractive index (Nx, Ny) and the refractive index (Nz) in the thickness direction in the orthogonal biaxial directions were determined by Abbe refractometer (Nagoya, NAR-4T, measurement wavelength 589 nm). The absolute value (| Nx-Ny |) of the refractive index difference of the axis was defined as the anisotropy of the refractive index (率 Nxy). The thickness d (nm) of the film was measured using an electric micrometer (Millitron 1245D, manufactured by Fineleuf Co.), and the unit was converted to nm. In-plane retardation (Re) was determined from the product (ΔNxy × d) of the anisotropy of the refractive index (ΔNxy) and the thickness d (nm) of the film.
（２）液晶表示装置による色ムラの確認
　青色発光ダイオードとイットリウム・アルミニウム・ガーネット系黄色蛍光体とを組み合わせた発光素子からなる白色ＬＥＤを光源（日亜化学、ＮＳＰＷ５００ＣＳ）とするバックライト、各実施例、比較例で作成した偏光子保護用ポリエステルフィルム（光源側）とＴＡＣフィルムとを各々の面に有する偏光子（ＰＶＡとヨウ素を含有し５倍に延伸した８０μｍ厚みのもの）からなる光源側偏光板、液晶セル、ＴＡＣフィルムと偏光子保護用ポリエステルフィルム（液晶側）とを各々の面に有する偏光子（偏光子は前記と同一のもの）からなる視認側偏光板を含む前面モジュールを順に積層し、評価装置とした。
ただし、実施例１～３および比較例１～３では偏光子保護用ポリエステルフィルムの光拡散層は光源側に向け、実施例４では、偏光子側に向けて配置し、測定した。
　なお、評価においては下記の通りとした。輝度の評価は、各高リタデーションフィルムを挿入しなかった場合と比較してのものである。
◎：正面、斜め方向から見ても色ムラは認められない。
○：斜め方向から見ると僅かな色ムラが認められた。
△：斜め方向から見ると色ムラが認められた。
×：正面から色ムラが認められた。 (2) Confirmation of color unevenness using a liquid crystal display device A backlight using a white LED composed of a light emitting element combining a blue light emitting diode and a yttrium aluminum garnet yellow phosphor as a light source (Nichia Chemical, NSPW500CS). A light source side composed of a polarizer (having a thickness of 80 μm and containing PVA and iodine and stretched 5 times) having a polyester film (light source side) for protecting the polarizer and a TAC film prepared on each side in Examples and Comparative Examples. A front module including a viewing-side polarizing plate composed of a polarizer having a polarizing plate, a liquid crystal cell, a TAC film, and a polarizer-protecting polyester film (liquid crystal side) on each surface (the polarizer is the same as described above) is sequentially arranged. They were laminated and used as an evaluation device.
However, in Examples 1 to 3 and Comparative Examples 1 to 3, the light diffusing layer of the polyester film for protecting the polarizer was arranged to face the light source, and in Example 4, the light diffusion layer was arranged to face the polarizer.
In addition, it was as follows in evaluation. The evaluation of the brightness is in comparison with the case where each high retardation film was not inserted.
A: No color unevenness is observed even when viewed from the front and oblique directions.
：: Slight color unevenness was observed when viewed from an oblique direction.
Δ: Color unevenness was observed when viewed from an oblique direction.
X: Color unevenness was observed from the front.
（３）ＰＶＡ接着性
　偏光子保護用ポリエステルフィルムの易接着層Ｐ１表面に、固形分濃度５質量％に調整したポリビニルアルコール水溶液（クラレ製 ＰＶＡ１１７）を、乾燥後のポリビニルアルコール樹脂層の厚みが、２μｍになるようにワイヤーバーで塗布し、７０℃で５分間乾燥した。ポリビニルアルコール水溶液には、判定が容易となるよう赤色染料を加えたものを使用した。作成した評価対象フィルムを、両面テープを貼り付けた厚さ５ｍｍのガラス板に、評価対象の積層フィルムのポリビニルアルコール樹脂層が形成された面の反対面を上記両面テープに貼り付けた。次いで、ポリビニルアルコール樹脂層を貫通して、基材フィルムに達する１００個の升目状の切り傷を、隙間間隔２ｍｍのカッターガイドを用いて付けた。次いで、粘着テープ（ニチバン社製セロテープ（登録商標） ＣＴ－２４；２４ｍｍ幅）を升目状の切り傷面に貼り付けた。貼り付け時に界面に残った空気を消しゴムで押して、完全に密着させた後、粘着テープを勢いよく垂直に引き剥がす作業を１回、５回、１０回実施した。ポリビニルアルコール樹脂層が剥がれていない升目の個数を数え、ＰＶＡ接着性とした。即ち、ＰＶＡ層が全く剥がれていない場合を、ＰＶＡ接着率１００とし、ＰＶＡ層が全て剥がれた場合は、ＰＶＡ接着率０とした。なお、１個の升目内で部分的に剥がれているものも、剥がれた個数に含めた。
　この測定結果が偏光子と偏光子保護用ポリエステルフィルムの密着性に該当する。
なお、実施例４においては、偏光子保護用ポリエステルフィルムの光拡散層表面にポリビニルアルコール樹脂層を設けて評価した。 (3) PVA adhesion On the surface of the easy-adhesion layer P1 of the polyester film for protecting the polarizer, a polyvinyl alcohol aqueous solution (Kuraray-made PVA117) adjusted to a solid content concentration of 5% by mass was dried. It was applied with a wire bar to a thickness of 2 μm, and dried at 70 ° C. for 5 minutes. As the aqueous polyvinyl alcohol solution, a solution to which a red dye was added so as to facilitate determination was used. The created film to be evaluated was attached to a glass plate having a thickness of 5 mm to which a double-sided tape was attached, and the opposite surface of the laminated film to be evaluated on which the polyvinyl alcohol resin layer was formed was attached to the double-sided tape. Then, 100 square cuts penetrating the polyvinyl alcohol resin layer and reaching the base film were made using a cutter guide with a gap of 2 mm. Next, an adhesive tape (Cellotape (registered trademark) CT-24, manufactured by Nichiban Co., Ltd .; 24 mm width) was attached to the cut surface of the grid. After the air remaining at the interface at the time of sticking was pressed with an eraser to completely adhere, the operation of peeling the adhesive tape vertically vigorously was performed once, five times, and ten times. The number of squares in which the polyvinyl alcohol resin layer was not peeled was counted, and the result was regarded as PVA adhesion. That is, the case where the PVA layer was not peeled at all was regarded as PVA adhesion rate 100, and the case where all the PVA layers were peeled was regarded as PVA adhesion rate 0. In addition, those that were partially peeled off within one cell were also included in the number of peeled.
This measurement result corresponds to the adhesion between the polarizer and the polyester film for protecting the polarizer.
In addition, in Example 4, evaluation was performed by providing a polyvinyl alcohol resin layer on the surface of the light diffusion layer of the polyester film for protecting the polarizer.
（４）光拡散層と易接着層との密着性
　各実施例、比較例の易接着層上に光拡散層を設けた後に粘着テープ（ニチバン社製セロテープ（登録商標） ＣＴ－２４；２４ｍｍ幅）を升目状の切り傷面に貼り付けた。貼り
付け時に界面に残った空気を消しゴムで押して、完全に密着させた後、粘着テープを勢いよく垂直に引き剥がす作業を１回、５回、１０回実施した。光拡散層が剥がれていない升目の個数を数え、拡散層と易接着層との接着性とした。
◎：１００％
○：９９～９０％
△：８９～７０％
×：６９～０％ (4) Adhesion between light diffusion layer and easy-adhesion layer After providing the light diffusion layer on the easy-adhesion layer in each of Examples and Comparative Examples, an adhesive tape (Cellotape (registered trademark) CT-24, manufactured by Nichiban Co .; 24 mm width) ) Was affixed to the grid-shaped cut surface. After the air remaining at the interface at the time of sticking was pressed with an eraser to completely adhere, the operation of peeling the adhesive tape vertically vigorously was performed once, five times, and ten times. The number of squares where the light diffusion layer was not peeled off was counted, and the adhesion between the diffusion layer and the easily adhesive layer was determined.
◎: 100%
○: 99-90%
Δ: 89 to 70%
×: 69 to 0%
（５）酸価
　１ｇ（固形分）の試料を３０ｍｌのクロロホルムまたはジメチルホルムアミドに溶解し、フェノールフタレインを指示薬として０．１Ｎの水酸化カリウムエタノール溶液で滴定して、試料１ｇ当たりのカルボキシル基を中和するのに必要なＫＯＨの量(ｍｇ)を求めた。 (5) Acid value 1 g (solid content) of a sample was dissolved in 30 ml of chloroform or dimethylformamide, and titrated with a 0.1 N potassium hydroxide ethanol solution using phenolphthalein as an indicator to determine the carboxyl groups per 1 g of the sample. The amount (mg) of KOH required for neutralization was determined.
（６）けん化度
　ＪＩＳ－Ｋ６７２６：１９９４に準じて水酸化ナトリウムを用いて、ポリビニルアルコール樹脂の残存酢酸基（モル％）を定量し、その値をけん化度（モル％）とした。同サンプルについて３度測定し、その平均値をけん化度（モル％）とした。 (6) Degree of saponification Residual acetic acid groups (mol%) of the polyvinyl alcohol resin were quantified using sodium hydroxide according to JIS-K6726: 1994, and the value was defined as the degree of saponification (mol%). The sample was measured three times, and the average value was defined as the degree of saponification (mol%).
（易接着層Ｐ１で用いるポリエステル樹脂の重合）
　攪拌機、温度計、およ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、ジメチルテレフタレート１９４．２質量部、ジメチルイソフタレート１８４．５質量部、ジメチルー５－ナトリウムスルホイソフタレート１４．８質量部、ジエチレングリコール２３３．５質量部、エチレングリコール１３６．６質量部、およびテトラーｎーブチルチタネート０．２質量部を仕込み、１６０℃から２２０℃の温度で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（Ａ－１）を得た。得られた共重合ポリエステル樹脂（Ａ－１）は、淡黄色透明であった。共重合ポリエステル樹脂（Ａ－１）の還元粘度を測定したところ，０．７０ｄｌ／ｇであった。ＤＳＣによるガラス転移温度は４０℃であった。 (Polymerization of polyester resin used in easy adhesion layer P1)
In a stainless steel autoclave equipped with a stirrer, a thermometer, and a partial reflux condenser, dimethyl terephthalate 194.2 parts by mass, dimethyl isophthalate 184.5 parts by mass, dimethyl-5-sodium sulfoisophthalate 14.8 parts by mass, 233.5 parts by mass of diethylene glycol, 136.6 parts by mass of ethylene glycol, and 0.2 part by mass of tetra-n-butyl titanate were charged, and a transesterification reaction was carried out at a temperature of 160 ° C. to 220 ° C. for 4 hours. Next, the temperature was raised to 255 ° C., and the reaction system was gradually decompressed, and then reacted under a reduced pressure of 30 Pa for 1 hour and 30 minutes to obtain a copolymerized polyester resin (A-1). The obtained copolyester resin (A-1) was pale yellow and transparent. The measured reduced viscosity of the copolymerized polyester resin (A-1) was 0.70 dl / g. The glass transition temperature by DSC was 40 ° C.
（易接着層Ｐ１で用いるポリエステル水分散体の調整）
　攪拌機、温度計と還流装置を備えた反応器に、ポリエステル樹脂（Ａ－１）３０質量部、エチレングリコールｎ－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５５質量部を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３０質量％の乳白色のポリエステル水分散体（Ａｗ－１）を作製した。ポリエステル水分散体（Ａｗ－１）の酸価が２ＫＯＨｍｇ／ｇであった。 (Preparation of aqueous dispersion of polyester used in easy-adhesion layer P1)
30 parts by mass of the polyester resin (A-1) and 15 parts by mass of ethylene glycol n-butyl ether were put into a reactor equipped with a stirrer, a thermometer and a reflux device, and heated and stirred at 110 ° C. to dissolve the resin. After the resin was completely dissolved, 55 parts by mass of water was gradually added to the polyester solution with stirring. After the addition, the solution was cooled to room temperature with stirring to prepare a milky white polyester aqueous dispersion (Aw-1) having a solid content of 30% by mass. The acid value of the aqueous polyester dispersion (Aw-1) was 2 KOH mg / g.
（易接着層Ｐ１で用いるポリビニルアルコール水溶液の調整）
　攪拌機と温度計を備えた容器に、水９０質量部を入れ、攪拌しながらけん化度７８モル％、重合度５００のポリビニルアルコール樹脂（クラレ製）（Ｂ－１）１０質量部を徐々に添加した。添加後、液を攪拌しながら、９５℃まで加熱し、樹脂を溶解させた。溶解後、攪拌しながら室温まで冷却して、固形分１０質量％のポリビニルアルコール水溶液（Ｂｗ－１）を作成した。 (Adjustment of aqueous solution of polyvinyl alcohol used in easy-adhesion layer P1)
In a container equipped with a stirrer and a thermometer, 90 parts by mass of water was put, and 10 parts by mass of a polyvinyl alcohol resin (manufactured by Kuraray) (B-1) having a saponification degree of 78 mol% and a polymerization degree of 500 was gradually added with stirring. . After the addition, the solution was heated to 95 ° C. while stirring to dissolve the resin. After dissolution, the mixture was cooled to room temperature with stirring to prepare a polyvinyl alcohol aqueous solution (Bw-1) having a solid content of 10% by mass.
（易接着層Ｐ１で用いるブロックポリイソシアネート架橋剤の重合）
　攪拌機、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分散液（Ｃ－１）を得た。 (Polymerization of blocked polyisocyanate crosslinking agent used in easy-adhesion layer P1)
100 parts by mass of a polyisocyanate compound having an isocyanurate structure (manufactured by Asahi Kasei Chemicals Corporation, duranate TPA) using hexamethylene diisocyanate as a raw material, 55 parts by mass of propylene glycol monomethyl ether acetate, and polyethylene in a flask equipped with a stirrer, a thermometer, and a reflux condenser. 30 parts by mass of glycol monomethyl ether (average molecular weight: 750) was charged and kept at 70 ° C. for 4 hours under a nitrogen atmosphere. Thereafter, the temperature of the reaction solution was lowered to 50 ° C., and 47 parts by mass of methyl ethyl ketoxime was added dropwise. The infrared spectrum of the reaction solution was measured, and it was confirmed that the absorption of the isocyanate group had disappeared. Thus, a block polyisocyanate dispersion (C-1) having a solid content of 75% by mass was obtained.
（実施例１）
（１）易接着層Ｐ１の塗布液調製
　下記の塗剤を混合し、ポリエステル系樹脂／ポリビニルアルコール系樹脂の質量比が７０／３０になる塗布液を作成した。ポリエステル水分散体は、酸価が２ＫＯＨｍｇ／ｇであるポリエステル樹脂が分散した水分散体（Ａｗ－１）を使用し、ポリビニルアルコール水溶液は、けん化度が７８モル％であるポリビニルアルコールが溶解した水溶液（Ｂｗ－１）を使用した。
水 ４０．６１質量％
イソプロパノール ３０．００質量％
ポリエステル水分散体（Ａｗ－１） １１．６７質量％
ポリビニルアルコール水溶液（Ｂｗ－１） １５．００質量％
ブロックイソシアネート系架橋剤（Ｃ－１） ０．６７質量％
粒子 １．２５質量％
（平均粒径１００ｎｍのシリカゾル、固形分濃度４０質量％）
触媒 （有機スズ系化合物 固形分濃度１４質量％） ０．３質量％
界面活性剤 ０．５質量％
（シリコーン系、固形分濃度１０質量％） (Example 1)
(1) Preparation of Coating Liquid for Easy Adhesion Layer P1 The following coating agents were mixed to prepare a coating liquid in which the mass ratio of polyester resin / polyvinyl alcohol resin was 70/30. The aqueous polyester dispersion used was an aqueous dispersion (Aw-1) in which a polyester resin having an acid value of 2 KOH mg / g was dispersed, and the aqueous polyvinyl alcohol solution was an aqueous solution in which polyvinyl alcohol having a saponification degree of 78 mol% was dissolved. (Bw-1) was used.
Water 40.61% by mass
30.00% by mass of isopropanol
11.67% by mass of polyester aqueous dispersion (Aw-1)
15.00% by mass of aqueous solution of polyvinyl alcohol (Bw-1)
0.67% by mass of blocked isocyanate-based crosslinking agent (C-1)
Particles 1.25% by mass
(Silica sol with an average particle diameter of 100 nm, solid content concentration of 40% by mass)
Catalyst (organic tin compound solids concentration 14% by mass) 0.3% by mass
Surfactant 0.5% by mass
(Silicone, solid content concentration 10% by mass)
（２）偏光子保護用ポリエステルフィルムの製造
　フィルム原料ポリマーとして、固有粘度（溶媒：フェノール／テトラクロロエタン＝６０／４０）が０．６２ｄｌ／ｇで、かつ粒子を実質上含有していないＰＥＴ樹脂ペレットを、１３３Ｐａの減圧下、１３５℃で６時間乾燥した。その後、押し出し機に供給し、約２８０℃でシート状に溶融押し出しして、表面温度２０℃に保った回転冷却金属ロール上で急冷密着固化させ、未延伸ＰＥＴシートを得た。 (2) Production of polyester film for protecting polarizer PET film pellets having an intrinsic viscosity (solvent: phenol / tetrachloroethane = 60/40) of 0.62 dl / g and containing substantially no particles as a film raw material polymer Was dried at 135 ° C. under a reduced pressure of 133 Pa for 6 hours. Thereafter, the mixture was supplied to an extruder, melted and extruded into a sheet at about 280 ° C., and rapidly cooled and adhered to a rotating cooling metal roll maintained at a surface temperature of 20 ° C. to obtain an unstretched PET sheet.
　次いで、前記易接着層Ｐ１の塗布液をロールコート法によりこの未延伸ポリエステル（ＰＥＴ）フィルムの両面に乾燥後の塗布量が０．３２ｇ／ｍ２になるように、塗布した後、８０℃で２０秒間乾燥した。 
この塗布層を形成した未延伸フィルムをテンター延伸機に導き、フィルムの端部をクリップで把持しながら、温度１２５℃の熱風ゾーンに導き、幅方向に４．３倍に延伸した。次に、幅方向に延伸された幅を保ったまま、温度２２５℃、３０秒間で処理し、さらに幅方向に３％の緩和処理を行い、フィルム厚み約６０μｍの一軸配向ポリエステル（ＰＥＴ）フィルムを得た。  Next, the coating liquid for the easy-adhesion layer P1 was applied to both surfaces of the unstretched polyester (PET) film by a roll coating method so that the coating amount after drying was 0.32 g / m 2 , Dry for 20 seconds.
The unstretched film on which the coating layer was formed was guided to a tenter stretching machine. The film was guided to a hot air zone at a temperature of 125 ° C. while being gripped with clips, and stretched 4.3 times in the width direction. Next, while maintaining the width stretched in the width direction, the film is treated at a temperature of 225 ° C. for 30 seconds, and further subjected to a relaxation treatment of 3% in the width direction to obtain a uniaxially oriented polyester (PET) film having a film thickness of about 60 μm. Obtained.
（製造例：光拡散層の塗布液Ａ）
　下記に示す処方の塗布液を作成し、塗布液Ａとした。
アクリルポリオール（固形分５０％）……１５０部 
（アクリディック（登録商標）Ａ－８０７：ＤＩＣ社） 
イソシアネート（固形分６０％） …… ３０部 
（タケネート（登録商標）Ｄ１１Ｎ：三井化学社） 
メチルエチルケトン ……２００部 
酢酸ブチル ……２００部 
アクリル樹脂粒子…… ４０部
（ＭＸ－１０００，平均粒子径１０．０μｍ：綜研化学社）  (Production example: coating solution A for light diffusion layer)
A coating solution having the following formulation was prepared and used as coating solution A.
Acrylic polyol (solid content 50%) 150 parts
(Acridic (registered trademark) A-807: DIC)
Isocyanate (solid content 60%) 30 parts
(Takenate (registered trademark) D11N: Mitsui Chemicals, Inc.)
Methyl ethyl ketone: 200 parts
Butyl acetate: 200 parts
Acrylic resin particles 40 parts (MX-1000, average particle size 10.0 μm: Soken Chemical Co., Ltd.)
　ポリエステル（ＰＥＴ）フィルムの片面に、光拡散層の塗布液Ａを塗布して、１６０℃、６０ｓｅｃ．の条件で乾燥及び熱硬化させて光拡散層を有する偏光子保護用ポリエステルフィルムを得た。乾燥、硬化後の光拡散層の厚みは５．０μｍであった。 {Circle around (1)} One side of a polyester (PET) film is coated with the coating solution A for the light diffusion layer, Was dried and thermally cured under the conditions described above to obtain a polarizer-protecting polyester film having a light diffusion layer. The thickness of the light diffusion layer after drying and curing was 5.0 μm.
（実施例２）
　実施例１の光拡散層の塗布液を下記の塗布液Ｂとした以外は、実施例１と同様の方法において光拡散層を有する偏光子保護用ポリエステルフィルムを得た。 (Example 2)
A polyester film for protecting a polarizer having a light diffusion layer was obtained in the same manner as in Example 1, except that the coating solution for the light diffusion layer in Example 1 was changed to the following coating solution B.
（製造例：光拡散層の塗布液Ｂ）
　下記に示す処方の塗布液を作成し、塗布液Ｂとした。
アクリルポリオール（固形分５０％）……１５０部 
（アクリディック（登録商標）Ａ－８０７：ＤＩＣ社） 
イソシアネート（固形分６０％） …… ３０部 
（タケネート（登録商標）Ｄ１１Ｎ：三井化学社） 
メチルエチルケトン ……２００部 
酢酸ブチル ……２００部 
アクリル樹脂粒子…… ５０部
（エポスター（登録商標）ＭＡ１００４，平均粒子径４．５μｍ：日本触媒社）  (Production example: coating solution B for light diffusion layer)
A coating solution having the following formulation was prepared, and used as coating solution B.
Acrylic polyol (solid content 50%) 150 parts
(Acridic (registered trademark) A-807: DIC)
Isocyanate (solid content 60%) 30 parts
(Takenate (registered trademark) D11N: Mitsui Chemicals, Inc.)
Methyl ethyl ketone: 200 parts
Butyl acetate: 200 parts
Acrylic resin particles: 50 parts (Eposter (registered trademark) MA1004, average particle size: 4.5 μm: Nippon Shokubai Co., Ltd.)
（比較例１）
　易接着層Ｐ１を設けなかった以外は、実施例１と同様の方法において光拡散層を有する偏光子保護用ポリエステルフィルムを得た。 (Comparative Example 1)
A polarizer-protecting polyester film having a light-diffusing layer was obtained in the same manner as in Example 1 except that the easy-adhesion layer P1 was not provided.
（比較例２）
　光拡散層を設けなかった以外は、実施例１と同様の方法において偏光子保護用ポリエステルフィルムを得た。 (Comparative Example 2)
A polyester film for protecting a polarizer was obtained in the same manner as in Example 1 except that the light diffusion layer was not provided.
（実施例３）
　実施例１のフィルム厚みを８０μｍとした以外は、実施例１と同様の方法において光拡散層を有する偏光子保護用ポリエステルフィルムを得た。 (Example 3)
A polarizer protecting polyester film having a light diffusion layer was obtained in the same manner as in Example 1 except that the film thickness in Example 1 was changed to 80 μm.
（比較例３）
　実施例１のフィルム厚みを３０μｍとした以外は、実施例１と同様の方法において光拡散層を有する偏光子保護用ポリエステルフィルムを得た。 (Comparative Example 3)
A polyester film for protecting a polarizer having a light diffusion layer was obtained in the same manner as in Example 1 except that the film thickness of Example 1 was changed to 30 μm.
（実施例４）
　実施例１の偏光子保護用ポリエステルフィルムを用いて、評価した。ただし色ムラ評価は、偏光子保護用ポリエステルフィルムの光拡散層を偏光子側に向けて評価した。また、PVA接着性は光拡散層との密着性を評価した。 (Example 4)
The evaluation was performed using the polyester film for protecting the polarizer of Example 1. However, the color unevenness evaluation was performed with the light diffusion layer of the polyester film for protecting the polarizer facing the polarizer. The PVA adhesion was evaluated for adhesion to the light diffusion layer.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
（実施例５）
　実施例１で作成した偏光子保護用ポリエステルフィルムについて、有機ＥＬ光源とする白色バックライト、実施例１の偏光子保護用ポリエステルフィルム（光源側）とアクリルフィルムとを各々の面に有する偏光子（ＰＶＡとヨウ素を含有し５倍に延伸した８０μｍ厚みのもの）からなる光源側偏光板、液晶セル、アクリルフィルムと実施例１の偏光子保護用ポリエステルフィルム（液晶側）とを各々の面に有する偏光子（偏光子は前記と同一のもの）からなる視認側偏光板を含む前面モジュールを順に積層し、評価装置とした。色ムラの評価を実施例１の場合と同様に行った。評価結果は実施例１の評価結果と同様に非常に好ましいものであった。 (Example 5)
Regarding the polyester film for protecting the polarizer prepared in Example 1, a white backlight as an organic EL light source, a polarizer having the polyester film for protecting the polarizer (light source side) of Example 1 and an acrylic film on each surface ( A light source side polarizing plate, a liquid crystal cell, an acrylic film and a polyester film for protecting the polarizer of Example 1 (liquid crystal side) comprising PVA and iodine and having a thickness of 80 μm stretched 5 times). A front module including a viewing-side polarizing plate composed of a polarizer (the same polarizer as described above) was sequentially laminated to obtain an evaluation device. Evaluation of color unevenness was performed in the same manner as in Example 1. The evaluation results were very favorable, like the evaluation results of Example 1.
　本発明によれば、光源と偏光板の間に光拡散シートを設けない簡単な構造であっても、従来の光拡散シートを有する液晶表示装置と同様に光源の輝度ムラを抑制し、任意の角度に拡散する均質度の高い光を得ることを可能とした。光拡散シートを設けずとも良いため、液晶パネルの更なる薄型化が可能となる。 According to the present invention, even with a simple structure in which a light diffusion sheet is not provided between a light source and a polarizing plate, luminance unevenness of the light source is suppressed as in the case of a conventional liquid crystal display device having a light diffusion sheet, and the angle can be set to an arbitrary angle. This makes it possible to obtain light with a high degree of homogeneity to diffuse. Since it is not necessary to provide a light diffusion sheet, the liquid crystal panel can be further thinned.

Claims (4)

  1. 　５０００～３００００ｎｍの面内リタデーション（Ｒｅ）を有するポリエステルフィルムを基材とし、前記基材の少なくとも一方の面にポリビニルアルコールを有する易接着層（Ｐ１）と、アクリル系樹脂ビーズとバインダー樹脂を含んでなる光拡散層を順に有する偏光子保護用ポリエステルフィルム。 A polyester film having an in-plane retardation (Re) of 5,000 to 30,000 nm as a base material, comprising an easy-adhesion layer (P1) having polyvinyl alcohol on at least one surface of the base material, acrylic resin beads and a binder resin. A polyester film for protecting a polarizer having a light diffusion layer in order.
  2. 　液晶セルに対して光源側に位置する偏光板用である請求項１の偏光子保護用ポリエステルフィルム。 The polyester film for protecting a polarizer according to claim 1, which is for a polarizing plate located on the light source side with respect to the liquid crystal cell.
  3. 　白色ＬＥＤまたは有機発光ダイオードを光源とするバックライト、請求項２に記載の偏光子保護用ポリエステルフィルム、偏光子、液晶セルが、少なくともこの順に積層されている液晶表示装置。 (4) A liquid crystal display device in which a backlight using a white LED or an organic light emitting diode as a light source, the polyester film for protecting a polarizer, the polarizer, and a liquid crystal cell according to claim 2 are laminated at least in this order.
  4. 　偏光子保護用ポリエステルフィルムの光拡散層が光源側に位置している請求項３の液晶表示装置。 4. The liquid crystal display device according to claim 3, wherein the light diffusion layer of the polarizer protecting polyester film is located on the light source side.
PCT/JP2019/028796 2018-07-31 2019-07-23 Polyester film for protecting polarizer and liquid crystal display device WO2020026891A1 (en)

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