CN108136745B

CN108136745B - Laminated film

Info

Publication number: CN108136745B
Application number: CN201680057914.9A
Authority: CN
Inventors: 松居久登; 合田亘
Original assignee: Toray Industries Inc
Current assignee: Toray Industries Inc
Priority date: 2015-12-08
Filing date: 2016-12-02
Publication date: 2021-01-08
Anticipated expiration: 2036-12-02
Also published as: WO2017099016A1; TW201733807A; KR102655116B1; KR20180090982A; JPWO2017099016A1; JP6780636B2; CN108136745A; TWI706862B

Abstract

The invention provides a thin and highly transparent laminated film which does not bleed out during film formation, suppresses deterioration caused by ultraviolet rays, and stably exerts the quality and color tone of a display for a long period of time. A laminated film comprising a layer (layer A) mainly composed of a thermoplastic resin A and a layer (layer B) mainly composed of a thermoplastic resin B different from the thermoplastic resin A, wherein the laminated film comprises 5 or more layers alternately stacked, and has a light transmittance at a wavelength of 410nm of 60% or less and a light transmittance at a wavelength of 440nm of 80% or more.

Description

Laminated film

Technical Field

The present invention relates to a laminated film having excellent ultraviolet cut (cut) properties and visible light transmittance.

Background

Thermoplastic resin films, particularly biaxially stretched polyester films, have excellent properties such as mechanical properties, electrical properties, dimensional stability, transparency, and chemical resistance, and are therefore widely used as substrate films in various applications such as magnetic recording materials and packaging materials. In particular, in the field of flat panel displays, touch panels, and in-vehicle panel displays, the trend toward cost reduction, and thinning, miniaturization, and flexibility of displays has rapidly progressed, and there has been an increasing demand for various thin film optical films.

Examples of the optical film to be mounted on a display include a polarizer protective film, a transparent conductive film, and a retardation film for use in a liquid crystal display. Films used for these applications are required to have ultraviolet cut-off properties in order to prevent deterioration of liquid crystal molecules and polarizing films (PVA) in polarizing plates due to ultraviolet rays entering from the outside or ultraviolet rays contained in backlight. In order to impart ultraviolet cut-off properties to a film, a method of adding an ultraviolet absorber is generally used (patent document 1). However, when the ultraviolet ray is cut by the method of adding the ultraviolet ray absorber, a bleeding out phenomenon occurs in the vicinity of the die or the vacuum vent at the time of film formation depending on the kind and the amount of the ultraviolet ray absorber added. Therefore, there is a problem that the film quality itself is impaired, such that the film is contaminated in the film forming step to cause defects, and the cutoff performance is lowered by substantially lowering the ultraviolet absorber addition concentration. In particular, when the optical film exhibits the same performance as a conventional optical film as a thin film optical film, since the absorption performance is expressed by the product of the thickness of the film and the concentration of the ultraviolet absorber added, the addition of a high concentration of the ultraviolet absorber is inevitable, and the deterioration of quality due to the contamination of a film forming apparatus and the deposition of the absorber on the film surface after a severe reliability test becomes remarkable.

In addition, in the case of displays for display on vehicles, digital billboards, and the like, which are displayed outdoors, ultraviolet rays having a wavelength range of 300nm to 380nm are required to be cut more strongly. In the case of using a general ultraviolet absorber whose cutoff performance is specified to a wavelength range of 380nm or less, a method of adding an excessive amount of the ultraviolet absorber in order to strongly cut off light in the vicinity of 380nm, which is a wavelength range not good for the ultraviolet absorber, is used. In particular, in the case of a single-film structure and a low number of stacked layers, the mechanism for preventing the deposition of the absorbent is insufficient, and the problem of quality degradation in the reliability test becomes remarkable. The thickness of the image display device is increased in spite of the fact that the thickness of the image display device is increased against the demand for miniaturization and thinning of the market, although the concentration of the absorbent added can be reduced, thereby solving the above-mentioned problems.

In order to cut off light having a wavelength of about 380nm, a method using a dye having a maximum absorption wavelength on a longer wavelength side than 380nm can be mentioned. However, since the dye absorbs a visible light region widely depending on the type and causes undesirable coloration of the film itself, it is necessary to strongly cut off a wavelength of 410nm or less and sharply cut off (sharp cut) light in a wavelength range of 410nm to 430nm because visibility is deteriorated when the dye is mounted on a display (patent documents 2 to 4). As an object of preventing coloring in the case of cutting light having a wavelength longer than 430nm, there is a method of using a fluorescent whitening agent as an absorbent as described in patent document 4, but in the case of using as a display, when ultraviolet rays are irradiated, the film itself emits blue fluorescence, and therefore, there is a problem that display quality is significantly impaired.

In addition, in a reliability test, it is required for a film to be mounted on a display to maintain not only optical quality such as hue but also mechanical properties such as thickness. When the film shrinks due to heat treatment and the thickness thereof increases, absorption performance of an ultraviolet absorber, a coloring matter, or the like increases, and undesirable coloring occurs.

Documents of the prior art

Patent document

Patent document 1: japanese laid-open patent publication No. 2013-210598

Patent document 2: japanese patent laid-open No. 2010-132846

Patent document 3: japanese patent laid-open No. 2014-115524

Patent document 4: japanese laid-open patent publication No. 2008-238586

Disclosure of Invention

Problems to be solved by the invention

Accordingly, an object of the present invention is to provide a highly transparent laminate film which is free from bleed-out during film formation, can maintain optical properties such as hue and haze (haze) even in a long-term reliability test, and is excellent in ultraviolet cut-off properties and visible light transmittance.

Means for solving the problems

The present invention includes the following configurations. That is to say that the first and second electrodes,

a laminated film comprising 5 or more layers of a layer A and a layer B alternately laminated, wherein the layer A is a layer mainly composed of a thermoplastic resin A, the layer B is a layer mainly composed of a thermoplastic resin B different from the thermoplastic resin A, and the laminated film has a light transmittance at a wavelength of 410nm of 60% or less and a light transmittance at a wavelength of 440nm of 80% or more.

ADVANTAGEOUS EFFECTS OF INVENTION

The laminated film of the present invention exhibits the following effects by using a laminated structure: various additives such as ultraviolet absorbers do not bleed out during film formation, and when the film is mounted on an image display device, the color tone can be maintained for a long period of time, and high-quality image display can be performed.

Detailed Description

The laminated film of the present invention will be described in detail below.

The laminated film of the present invention is a film obtained by alternately laminating 5 or more layers of a layer (a layer) containing a thermoplastic resin a as a main component and a layer (B layer) containing a thermoplastic resin B different from the thermoplastic resin a as a main component, and it is necessary that the laminated film has a light transmittance at a wavelength of 410nm of 60% or less and a light transmittance at a wavelength of 440nm of 80% or more.

Examples of the thermoplastic resin used in the present invention include polyolefin resins represented by polyethylene, polypropylene, poly (1-butene), poly (4-methylpentene), polyisobutylene, polyisoprene, polybutadiene, polyvinylcyclohexane, polystyrene, poly (alpha-methylstyrene), poly (p-methylstyrene), polynorbornene, and polycyclopentene, polyamide resins represented by nylon 6, nylon 11, nylon 12, and nylon 66, ethylene/propylene copolymers, ethylene/vinylcyclohexane copolymers, ethylene/vinylcyclohexene copolymers, ethylene/alkyl acrylate copolymers, ethylene/alkyl methacrylate copolymers, ethylene/norbornene copolymers, ethylene/vinyl acetate copolymers, propylene/butadiene copolymers, and polyethylene, Copolymer resins of vinyl monomers such as isobutylene/isoprene copolymer and vinyl chloride/vinyl acetate copolymer, acrylic resins such as polyacrylate, polymethacrylate, polymethyl methacrylate, polyacrylamide and polyacrylonitrile, polyester resins such as polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate and polyethylene 2, 6-naphthalate, polyether resins such as polyethylene oxide, polypropylene oxide and polyalkylene glycol, cellulose ester resins such as diacetyl cellulose, triacetyl cellulose, propionyl cellulose, butyryl cellulose, acetyl propionyl cellulose and nitro cellulose, biodegradable polymers such as polylactic acid and polybutyl succinate, biodegradable polymers such as polylactic acid and polylactic acid, and the like, And polyvinyl chloride, polyvinylidene 1, 1-dichloroethylene, polyvinyl alcohol, polyvinyl butyral, polyacetal, polyglycolic acid, polycarbonate, polyketone, polyethersulfone, polyetheretherketone, modified polyphenylene ether, polyphenylene sulfide, polyetherimide, polyimide, polysiloxane, tetrafluoroethylene resin, trifluoroethylene resin, chlorotrifluoroethylene resin, tetrafluoroethylene-hexafluoropropylene copolymer, polyvinylidene 1, 1-difluoroethylene, and the like.

The thermoplastic resin used in the present invention is preferably a synthetic polymer, and more preferably a polyolefin, acrylic, polyester, cellulose ester, polyvinyl butyral, polycarbonate, polyether sulfone. Among them, polyethylene, polypropylene, polymethyl methacrylate, polyester, and triacetyl cellulose are particularly preferable. Further, they may be used alone in1 kind, or may be used in the form of a polymer blend or a polymer alloy of 2 or more kinds.

The thermoplastic resin B is not the same thermoplastic resin as the thermoplastic resin a, but a resin having a different refractive index. In the case of using the light ray cutoff by reflection described later, the wavelengths of 1 reflected light ray are determined based on the layer thicknesses of the stacked resins and the refractive index differences of 2 different thermoplastic resins. Therefore, when the same refractive index is used, light reflection does not occur at the thermoplastic resin interface. In order to reflect light of a specific wavelength, 2 parameters of the layer thickness and the refractive index difference of the resin should be controlled, and therefore, it is difficult to determine the refractive index difference in a general manner, but the difference between the refractive indices of the thermoplastic resin a and the thermoplastic resin B is preferably 0.01 or more, more preferably 0.03 or more, and still more preferably 0.05 or more. It is preferable that the different thermoplastic resins a and B have different thermal characteristics, in addition to the difference in refractive index. The difference in thermal characteristics means that the melting point and the glass transition temperature are different in Differential Scanning Calorimetry (DSC). By the difference in melting point and glass transition temperature, the orientation state of each layer can be highly controlled in the step of subjecting the laminated film to stretch-heat treatment. By making it possible to control the orientation state to a high degree, the refractive index in the in-plane and perpendicular direction to the plane of each thermoplastic resin layer can be controlled, and the wavelength of the reflected light can be controlled. In particular, the difference between the glass transition temperature and the melting point of the thermoplastic resin A and the thermoplastic resin B, which affect the orientation of the resins in the stretching step, is preferably 0.1 ℃ or more. Among the above thermoplastic resins, from the viewpoint of strength, heat resistance, transparency and versatility, at least one of the thermoplastic resin a and the thermoplastic resin B is preferably composed of a polyester resin. Further, from the viewpoint of adhesiveness and lamination properties, it is most preferable to select a polyester resin for both the thermoplastic resin a and the thermoplastic resin B. Hereinafter, a form of a polyester resin as a preferable film base material will be described.

The polyester in the present invention is a polycondensate obtained by polymerizing monomers mainly composed of an aromatic dicarboxylic acid or an aliphatic dicarboxylic acid and a diol. As an industrial production method of the polyester, as is well known, an ester exchange reaction (ester exchange method) and a direct esterification reaction (direct polymerization method) can be used. Examples of the aromatic dicarboxylic acid include terephthalic acid, isophthalic acid, phthalic acid, 1, 4-naphthalenedicarboxylic acid, 1, 5-naphthalenedicarboxylic acid, 2, 6-naphthalenedicarboxylic acid, 4 ' -diphenyldicarboxylic acid, 4 ' -diphenyletherdicarboxylic acid, and 4,4 ' -diphenylsulfonedicarboxylic acid. Examples of the aliphatic dicarboxylic acid include adipic acid, suberic acid, sebacic acid, dimer acid, dodecanedioic acid, 1, 4-cyclohexanedicarboxylic acid, and ester derivatives thereof. Among them, terephthalic acid and 2, 6-naphthalenedicarboxylic acid, which exhibit high refractive indices, are preferably used. The dicarboxylic acid component may be used in1 kind of them, or 2 or more kinds of them may be used in combination.

Examples of the diol component include ethylene glycol, 1, 2-propylene glycol, 1, 3-propylene glycol, neopentyl glycol, 1, 3-butylene glycol, 1, 4-butylene glycol, 1, 5-pentanediol, 1, 6-hexanediol, 1, 2-cyclohexanedimethanol, 1, 3-cyclohexanedimethanol, 1, 4-cyclohexanedimethanol, diethylene glycol, triethylene glycol, polyalkylene glycol, 2-bis (4-hydroxyethoxyphenyl) propane, isosorbide, and spiroglycol. Among them, ethylene glycol is preferably used. These diol components may be used alone in1 kind, or may be used in combination in 2 or more kinds.

Further, as the polyester resin, for example, polyethylene terephthalate and a copolymer thereof, polyethylene naphthalate and a copolymer thereof, polybutylene terephthalate and a copolymer thereof, polybutylene naphthalate and a copolymer thereof, polyhexamethylene terephthalate and a copolymer thereof, polyhexamethylene naphthalate and a copolymer thereof, and the like can be used. In this case, as the copolymerization component, it is preferable that the dicarboxylic acid component and the diol component are copolymerized in1 or more kinds, respectively.

The term "alternately laminated" as used herein means that a layer a mainly composed of a thermoplastic resin a and a layer B mainly composed of a thermoplastic resin B are laminated in a regular arrangement in the thickness direction, and means that the resins are laminated in a regular arrangement of a (ba) n (n is a natural number). When a laminated film of a (ba) n (n is a natural number) is formed, plural resins of the thermoplastic resin a and the thermoplastic resin B may be fed from different flow paths using 2 or more extruders, and a multi-manifold type feed block (feed block) or a static mixer, which is a known laminating apparatus, may be used. In particular, in order to efficiently obtain the structure of the present invention, a method using a feed block having a fine slit is preferable in view of achieving high-precision lamination. When a slit-type feed block is used to form a laminate, the thickness and distribution of each layer can be achieved by varying the length and width of the slit to incline the pressure loss. The length of the slit is the length of a comb tooth portion formed in the slit plate to form a flow path for alternately flowing the a layer and the B layer.

The thermoplastic resin a in the present invention is preferably a thermoplastic resin exhibiting crystallinity, because it is located at the outermost layer of the laminated film as in the above-described configuration. In this case, a laminated film can be obtained in the same manner as in the film forming step of a single film made of a thermoplastic resin exhibiting crystallinity, and therefore, it is preferable. When the thermoplastic resin a is made of, for example, an amorphous resin, in the case of obtaining a biaxially stretched film by the same operation as a general sequentially biaxially stretched film described later, there may be a problem of film formation failure due to adhesion to manufacturing equipment such as rolls and jigs, deterioration of surface properties, and the like.

As described above, the thermoplastic resin a is preferably a polyester having crystallinity, such as polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, or polybutylene naphthalate. Among them, polyethylene terephthalate or polyethylene naphthalate is preferably used from the viewpoint of easily realizing a laminated structure with high accuracy also in the stretching process. On the other hand, the thermoplastic resin B is preferably a polyester resin containing the same basic skeleton as the thermoplastic resin a, from the viewpoint of adhesiveness to the thermoplastic resin a and lamination properties. The basic skeleton is a repeating unit constituting a resin, and in the case of polyethylene terephthalate, ethylene terephthalate forms the basic skeleton, and in the case of polyethylene naphthalate, ethylene naphthalate forms the basic skeleton. By having the same skeleton, the lamination accuracy is high, and delamination at the lamination interface is less likely to occur. Polyethylene naphthalate is more preferable to polyethylene terephthalate as a basic skeleton from the viewpoint of a laminated film because polymer orientation is easily performed in the in-plane direction but interlayer peeling is more easily generated, compared to polyethylene terephthalate.

In the case where polyethylene terephthalate is used as the basic skeleton, it is preferable that the thermoplastic resin B different from the thermoplastic resin a is designed to have a polyethylene terephthalate skeleton and to contain a copolymerization component not constituting the basic skeleton to the extent that it does not become a main component, or is designed to have a copolymerization component amount different from that contained in the thermoplastic resin a. When polyethylene terephthalate is used as the basic skeleton, preferable examples of the copolymerization component include cyclohexanedimethanol, bisphenol A ethylene oxide, spiroglycol, isophthalic acid, cyclohexanedicarboxylic acid, naphthalenedicarboxylic acid, polyethylene glycol 2000, m-polyethylene glycol 1000, m-polyethylene glycol 2000, m-polyethylene glycol 4000, m-polypropylene glycol 2000, diphenyleneglycol fluorene (BPEF), fumaric acid, acetoxybenzoic acid, and the like. Among them, spiro diol, isophthalic acid, and 2, 6-naphthalenedicarboxylic acid are preferably copolymerized. When a spiro diol is copolymerized, the glass transition temperature difference from polyethylene terephthalate is small, so that excessive stretching is not easily caused during molding, and delamination is not easily caused. Further, isophthalic acid can significantly reduce crystallinity because the position of the functional group in the benzene ring is not a straight line, while it can exhibit a high refractive index as a whole because of high planarity.

The number of layers in the multilayer film of the present invention needs to be 5 or more. As described later, in the present invention, in order to achieve a specific wavelength cut-off, it is preferable to add an ultraviolet absorber and/or a dye having a maximum wavelength in a short wavelength region of visible light exceeding 380nm and 430nm or less, and to form a layered structure, thereby suppressing the additive from precipitating on the surface. In particular, when the thermoplastic resin is crystalline, the crystalline layer is preferably used as a cap for suppressing the precipitation of various additives present therein because the crystalline layer is formed by folding the molecular structure to be filled at a high density. There is no upper limit to the number of layers, but as the number of layers increases, the manufacturing cost increases with an increase in the size of the manufacturing apparatus, and the operability deteriorates due to a thickening of the film thickness. In particular, a larger film thickness increases retardation, and when used as a display material, coloring of the film such as interference color and iridescence is caused, which is not preferable, and in reality, 1000 layers or less are preferable.

The retardation is generally calculated by integrating the maximum value of the refractive index difference in 2 orthogonal directions in the plane of the film and the film thickness, but the refractive index as a film cannot be easily measured in the multilayer film as in the present invention, and therefore the value of the retardation calculated by an indirect method is used as the retardation. Specifically, a value measured by a KOBRA series of phase difference measuring devices for measuring a retardation by an optical method, manufactured by prince measuring instruments co. For example, a display device having a linearly polarized polarizing plate mounted thereon can be used as an optical film for a display device. When the retardation value is high and the orientation of the resin in the plane of the laminate film is not uniform, the polarization state varies in a random manner in the plane due to the influence of the retardation, and therefore, when the liquid crystal display device is mounted, interference color and rainbow unevenness occur, which causes a problem of lowering visibility. Therefore, in the present invention, when a crystalline thermoplastic resin exhibiting orientation by stretching or crystallization is included, it is preferable to make the film thickness as thin as possible in advance in order to reduce retardation. On the other hand, it is also preferable to design the orientation angle of the laminated film to be low by strongly stretching in a specific direction. When the multilayer film is attached to a display, the multilayer film is bonded so that the optical axis of transmitted light from the inside of the display and the orientation direction of the multilayer film are in the same direction or in an orthogonal relationship, whereby even when the retardation is high, there is no variation in the film surface, and thus there is no problem of deterioration in visibility such as rainbow unevenness. When the orientation angle of the laminated film is reduced, the orientation angle in the width direction of the laminated film is preferably 10 ° or less, more preferably 7 ° or less, and still more preferably 5 ° or less. When the orientation angle in the width direction of the laminated film exceeds 10 °, although it depends on the size of a display to be bonded, it is not preferable because rainbow unevenness due to a change in orientation angle is observed in the display plane and polarization performance is impaired. Here, the orientation angle is set to 0 ° in the film width direction.

The laminated film of the present invention is required to have a light transmittance of 60% or less at a wavelength of 410 nm. If the light transmittance of the laminated film is not 60% or less at 410nm, when the laminated film of the present invention is used for a display, deterioration of a liquid crystal layer and a polarizing plate in the inside of a liquid crystal display cannot be effectively prevented, and deterioration of a light emitting layer of a display having a light emitting element such as an organic EL display cannot be effectively prevented. The light transmittance at a wavelength of 410nm is preferably 40% or less, more preferably 30% or less, and further preferably 20% or less. The display contents can be protected from ultraviolet rays by setting the light transmittance at a wavelength of 410nm to 60% or less, and the display contents can be prevented for a longer period of time by lowering the light transmittance at a wavelength of 410nm to 40% or less, more preferably to 20% or less. On the other hand, when the light transmittance at a wavelength of 410nm is made to exceed 20% and 60% or less, the content of the display can be protected from deterioration as compared with the conventional one, and in addition, the reflected color due to the light reflected on the viewing side, which is generated when the light is cut off by reflection, can be suppressed, so that the black color when the display is not displayed can be made clearer.

The laminated film of the present invention preferably exhibits a light transmittance of 20% or less in a wavelength region of 380 to 395nm, which is a short wavelength region of visible light. Even if the light transmittance at the wavelength 410nm is low, in the case where the light in the wavelength range having a higher energy than the light at the wavelength 410nm cannot be cut off, the possibility of promoting the light deterioration is high. More preferably 15% or less, and still more preferably 10%.

The laminated film of the present invention more preferably exhibits a maximum value of light transmittance of 10% or less in the ultraviolet region having a wavelength of 300nm to 380 nm. The ultraviolet region having a wavelength of 300nm to 380nm is a wavelength region having strong light energy and closely related to deterioration of an important part of image display such as a polarizing plate, a liquid crystal, and a light emitting element in a display, and therefore, it is desirable that light is sufficiently cut off. For example, a polarizing plate used in a liquid crystal image display device has a function of transmitting light only in a specific vibration direction, and a polyvinyl alcohol (PVA) film dyed with iodine, dichroic dye, or the like is most frequently used. The polarizing plate is made of an organic material and is deteriorated by ultraviolet rays having a strong energy in a wavelength range of 280 to 380nm, and therefore, deterioration of the polarizing plate and deterioration of liquid crystal molecules can be prevented by shielding ultraviolet rays in the region from reaching the polarizing plate. Therefore, the maximum value of the light transmittance at a wavelength of 300nm to 380nm is 5% or less, and more preferably 2% or less.

The laminated film of the present invention is required to have a light transmittance of 80% or more at a wavelength of 440 nm. When the light transmittance at a wavelength of 440nm is less than 80%, the light in the short wavelength region of visible light is cut off, and the laminated film itself strongly appears yellow, and excellent transparency cannot be expressed. In addition, in the display application using the blue light emitting element, light from the blue light emitting element is cut off, and the color tone is deteriorated when an image is displayed. The light transmittance at a wavelength of 440nm is preferably 85% or more, more preferably 90% or more.

The average light reflectance of the laminated film of the present invention is preferably 20% or more at a wavelength of 380 to 410 nm. It is possible to reflect light of a specific wavelength according to the thickness of each layer of the resin layers alternately laminated and the refractive index difference between 2 different resins. In addition, the light reflection ratio can be increased by expanding or contracting the wavelength band to be reflected or by increasing the light reflectance by changing the thickness distribution of the laminated layer, and the light can be freely moved by changing the thickness in a state where the laminated layer ratio is constant. In this case, the cut-off end of the reflection band can be designed to be sharp or gentle by controlling the thickness distribution of the multilayer layer. When the cut-off end of the reflection band is designed to be sharp, it is possible to achieve sharp cut-off more than the case where a general ultraviolet absorber or pigment is added, and it is possible to prevent undesirable light cut-off, and therefore, it is possible to preferably use the material for which selective wavelength cut-off is required. The average light reflectance is more preferably 25% or more, and still more preferably 30% or more.

Since the reflection wavelength depends on the layer thickness, it sensitively varies under the influence of a minute change in the film thickness of 0.1 μm unit. Therefore, when the long-wavelength end of the reflection band is designed to be located near 440nm, the thickness may be increased by a small amount, thereby cutting off an originally undesired wavelength region. In view of the risk for variations in the reflected wavelength range, more preferred solutions are: the reflection wavelength range is designed to be about 300nm to 410nm, and light in the wavelength range of 380 to 430nm is cut off by absorption with a dye having a maximum wavelength in a visible light short wavelength range exceeding 380nm and not more than 430nm, which will be described later.

The distribution of the thickness of the laminated layer is preferably a layer thickness distribution in which the thickness increases or decreases from one surface side of the film to the opposite surface, a layer thickness distribution in which the thickness increases and decreases from the one surface side of the film to the center of the film, a layer thickness distribution in which the thickness decreases and increases from the one surface side of the film to the center of the film, or the like. As a method of changing the layer thickness distribution, a method of continuously changing linearly, in an equal ratio, in a difference sequence; about 10 to 50 layers have almost the same layer thickness, and this layer thickness is changed stepwise.

The laminated film of the present invention preferably contains an ultraviolet absorber and/or a dye having a maximum wavelength in a short wavelength region of visible light exceeding 380nm and not more than 430 nm. The ultraviolet absorber in the present invention is an additive having a maximum wavelength in an ultraviolet region having a wavelength of 300 to 380 nm. The maximum wavelength in the present invention means a peak wavelength having a maximum absorbance when a plurality of maximum peaks are present. The ultraviolet absorber and the dye having a maximum wavelength in a short wavelength region of visible light exceeding 380nm and not more than 430nm may have a property of absorbing a part of each other. For example, among additives having a maximum at 375nm and 390nm, an ultraviolet absorber is used when the maximum at 375nm is the maximum, and a pigment having a maximum wavelength in a visible short-wavelength region exceeding 380nm and being 430nm or less is used when the maximum at 390nm is the maximum.

In the present invention, the ultraviolet absorber or the dye having the maximum wavelength in the visible light short-wavelength region exceeding 380nm and not more than 430nm may be contained alone in1 or more species, or may be contained in combination with 1 or more species of the ultraviolet absorber and 1 or more species of the dye having the maximum wavelength in the visible light short-wavelength region exceeding 380nm and not more than 430 nm. The layer A alone or the layer B alone may contain an ultraviolet absorber and/or a dye having a maximum wavelength in a short wavelength region of visible light exceeding 380nm and not more than 430nm, or both the layer A and the layer B may be contained. In particular, in view of suppression of surface deposition due to the multilayer structure, it is preferable to include only the B layer located in the inner layer of the laminated film, or to include the B layer located in the inner layer of the laminated film at a higher concentration than the a layer located in the outermost layer. When only the layer a including the outermost layer contains an ultraviolet absorber and a coloring matter having a maximum wavelength in a short wavelength region of visible light exceeding 380nm and not more than 430nm, a phenomenon (bleeding phenomenon) in which the contained ultraviolet absorber precipitates on the film surface and a phenomenon in which the ultraviolet absorber sublimates and volatilizes in the vicinity of a die easily occur, thereby staining a film forming machine, and the precipitates may have adverse effects such as generation of defects in a film forming process.

Ultraviolet absorbers are generally characterized by having the ability to absorb ultraviolet light in a wavelength region of 380nm or less, and are not excellent in the ability to absorb light in the vicinity of the boundary between the ultraviolet region and the visible light region (in the vicinity of 380 to 400 nm) and in the visible light short-wavelength region (400 to 430 nm). Therefore, when only the ultraviolet absorber is contained, it is necessary to contain the ultraviolet absorber at a high concentration in addition to a part of absorption of long-wavelength ultraviolet light described later, in order to cut off light in the vicinity of the boundary between the ultraviolet region and the visible region (in the vicinity of 380 to 400 nm) and in the visible short-wavelength region (400 to 430 nm). Examples of the ultraviolet absorber that can be realized by a single ultraviolet absorber when the wavelength is cut in the ultraviolet region and the visible short-wavelength region (380nm to 430nm) include 2- (5-chloro-2H-benzotriazol-2-yl) -6-tert-butyl-4-methylphenol, 2,4, 6-tris (2-hydroxy-4-hexyloxy-3-methylphenyl) -1,3, 5-triazine, and the like.

On the other hand, a dye having a maximum wavelength in a visible light short-wavelength region of more than 380nm and 430nm or less is generally excellent in the cutoff performance in the visible light short-wavelength region, but is poor in the cutoff performance in the ultraviolet region. Therefore, when only a dye having the maximum wavelength in the visible light short-wavelength region exceeding 380nm and 430nm or less is contained, it is necessary to contain the dye having the maximum wavelength in a part of the visible light short-wavelength region exceeding 380nm and 430nm or less, which will be described later, in a high concentration in order to cut off the light in the ultraviolet region. Further, when the compound is contained at a high concentration, it absorbs a visible light region on a longer wavelength side than a target wavelength region, and thus excellent transparency cannot be achieved. Examples of the coloring matter having a maximum wavelength in a visible light short-wavelength region exceeding 380nm and not more than 430nm, which can achieve wavelength cut-off of an ultraviolet region and a visible light short-wavelength region (380nm to 430nm) independently include "lumogen f Violet 570" manufactured by BASF corporation. Since there are regions in which the ultraviolet absorber and the dye having the maximum wavelength in the visible light short-wavelength region exceeding 380nm and 430nm or less are good, it is more preferable to effectively combine 1 or more types of ultraviolet absorbers with 1 or more types of dyes having the maximum wavelength in the visible light short-wavelength region exceeding 380nm and 430nm or less in order to prevent bleeding due to high concentration addition and process contamination accompanying this.

In the laminated film of the present invention, as the ultraviolet absorber that can be used when the above-mentioned light transmittance is achieved by combining 1 or more kinds of ultraviolet absorbers with 1 or more kinds of coloring matters having a maximum wavelength in a short wavelength region of visible light exceeding 380nm and 430nm or less, in addition to the above-mentioned 2 kinds of ultraviolet absorbers, benzotriazole-based, benzophenone-based, benzoate-based, triazine-based, benzo-triazole-based, and the like can be used

Oxazinone-based and salicylic acid-based ultraviolet absorbers having various skeletons. When 2 or more kinds of ultraviolet absorbers are used in combination, the ultraviolet absorbers of the same family may be combined with each other, or ultraviolet absorbers of different families may be combined with each other. Specific examples are given below, and compounds having a maximum wavelength in the wavelength region of 320nm to 380nm are referred to by the compound name (, b). The ultraviolet absorber in the invention is preferably an ultraviolet absorber having a maximum absorption wavelength between 320 and 380 nm. When the maximum wavelength is less than 320nm, it is difficult to sufficiently cut off the ultraviolet region on the long wavelength side, and even when the dye is combined with a dye having the maximum wavelength in the visible short wavelength region exceeding 380nm and not more than 430nmIn the region of a wavelength of 300 to 380nm, a region exhibiting a light transmittance of 10% or more and having an insufficient cutoff is often generated. Therefore, in order to set the maximum value of the light transmittance in the ultraviolet region having a wavelength of 300 to 380nm to 10% or less, it is preferable to use an ultraviolet absorber attached thereto (in the color of the corresponding component).

Examples of the benzotriazole-based ultraviolet absorber include, but are not particularly limited to, 2- (2 ' -hydroxy-5 ' -methylphenyl) benzotriazole (corresponding), 2- (2 ' -hydroxy-3 ', 5 ' -di-tert-butylphenyl) -5-chlorobenzotriazole (corresponding), 2- (2 ' -hydroxy-3 ' -tert-butyl-5 ' -methylphenyl) benzotriazole (corresponding), 2- (2 ' -hydroxy-3 ' -tert-butyl-5 ' -methylphenyl) -5-chlorobenzotriazole (corresponding), 2- (2 ' -hydroxy-3 ', 5 ' -di-tert-amylphenyl) -5-chlorobenzotriazole (in the indicated color), 2- (2 ' -hydroxy-3 ' - (3 ", 4", 5 ", 6" -tetrahydrophthalimidomethyl) -5 ' -methylphenyl) -benzotriazole (in the indicated color), 2- (5-chloro-2H-benzotriazol-2-yl) -6-tert-butyl-4-methylphenol (in the indicated color), 2 ' -methylenebis (4- (1,1,3, 3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol (in the indicated color), 2- (2 ' -hydroxy-3 ', 5 ' -di-tert-amylphenyl) benzotriazole, 2- (2 ' -hydroxy-5 ' -tert-octylphenyl) benzotriazole, 2-hydroxy-5 ' -tert-octylphenyl) benzotriazole, 2-tolyltriazole, and mixtures thereof, 2, 2' -methylenebis (4-tert-octyl-6-benzotriazolyl) phenol (@), 2- (5-butyloxy-2H-benzotriazol-2-yl) -6-tert-butyl-4-methylphenol (@), 2- (5-hexyloxy-2H-benzotriazol-2-yl) -6-tert-butyl-4-methylphenol (@), 2- (5-octyloxy-2H-benzotriazol-2-yl) -6-tert-butyl-4-methylphenol (@), 2- (5-dodecyloxy-2H-benzotriazol-2-yl) -6-tert-butyl-4-methylphenol (@), and a mixture thereof, 2- (5-octadecyloxy-2H-benzotriazol-2-yl) -6-tert-butyl-4-methylphenol (in the corresponding), 2- (5-cyclohexyloxy-2H-benzotriazol-2-yl) -6-tert-butyl-4-methylphenol (in the corresponding), 2- (5-propenyloxy-2H-benzotriazol-2-yl) -6-tert-butyl-4-methylphenol (in the corresponding), 2- (5- (4-methylphenyl) oxy-2H-benzotriazol-2-yl) -6-tert-butyl-4-methylphenol (in the corresponding), 2- (5-benzyloxy-2H-benzotriazol-2-yl) -6-tert-butyl-4- Base-4-methylphenol (in the corresponding), 2- (5-hexyloxy-2H-benzotriazole-2-yl) -4, 6-di-tert-butylphenol (in the corresponding), 2- (5-octyloxy-2H-benzotriazole-2-yl) -4, 6-di-tert-butylphenol (in the corresponding), 2- (5-dodecyloxy-2H-benzotriazole-2-yl) -4, 6-di-tert-butylphenol (in the corresponding), 2- (5-sec-butyloxy-2H-benzotriazole-2-yl) -4, 6-di-tert-butylphenol (in the corresponding) and the like.

The benzophenone-based ultraviolet absorber is not particularly limited, and examples thereof include 2, 4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-octyloxybenzophenone, 2 '-dihydroxy-4-methoxy-benzophenone (relevant), 2' -dihydroxy-4, 4 '-dimethoxy-benzophenone, 2', 4,4 '-tetrahydroxy-benzophenone, and 5, 5' -methylenebis (2-hydroxy-4-methoxybenzophenone).

The benzoate-based ultraviolet absorber is not particularly limited, and examples thereof include resorcinol monobenzoate, 2, 4-di-tert-butylphenyl-3, 5-di-tert-butyl-4-hydroxybenzoate, 2, 4-di-tert-pentylphenyl-3, 5-di-tert-butyl-4-hydroxybenzoate, 2, 6-di-tert-butylphenyl-3 ', 5 ' -di-tert-butyl-4 ' -hydroxybenzoate, hexadecyl-3, 5-di-tert-butyl-4-hydroxybenzoate, and octadecyl-3, 5-di-tert-butyl-4-hydroxybenzoate.

Examples of the triazine-based ultraviolet absorber include, but are not particularly limited to, 2- (2-hydroxy-4-hexyloxyphenyl) -4, 6-diphenyl-s-triazine, 2- (2-hydroxy-4-propoxy-5-methylphenyl) -4, 6-bis (2, 4-dimethylphenyl) -s-triazine, 2- (2-hydroxy-4-hexyloxyphenyl) -4, 6-biphenylyl-s-triazine, 2, 4-diphenyl-6- (2-hydroxy-4-methoxyphenyl) -s-triazine, 2, 4-diphenyl-6- (2-hydroxy-4-ethoxyphenyl) -s-triazine, and, 2, 4-diphenyl-6- (2-hydroxy-4-propoxyphenyl) -s-triazine, 2, 4-diphenyl-6- (2-hydroxy-4-butoxyphenyl) -s-triazine, 2, 4-bis (2-hydroxy-4-octyloxyphenyl) -6- (2, 4-dimethylphenyl) -s-triazine, 2,4, 6-tris (2-hydroxy-4-hexyloxy-3-methylphenyl) -s-triazine (@), 2,4, 6-tris (2-hydroxy-4-octyloxyphenyl) -s-triazine (@), 2- (4-isooctyloxycarbonylethoxyphenyl) -4, 6-diphenyl-s-triazine (@), 2- (4, 6-diphenyl-s-triazin-2-yl) -5- (2- (2-ethylhexanoyloxy) ethoxy) phenol, and the like.

As benzene

The oxazinone-based ultraviolet absorber is not particularly limited, and may include 2, 2' -p-phenylenebis (4H-3, 1-benzo)

Oxazin-4-one), 2' -p-phenylenebis (6-methyl-4H-3, 1-benzo

Oxazin-4-one), 2' -p-phenylenebis (6-chloro-4H-3, 1-benzo

Oxazin-4-one), 2' -p-phenylenebis (6-methoxy-4H-3, 1-benzo

Oxazin-4-one), 2' -p-phenylenebis (6-hydroxy-4H-3, 1-benzo

Oxazin-4-one), 2' - (naphthalene-2, 6-diyl) bis (4H-3, 1-benzo

Oxazin-4-one, 2' - (naphthalene-1, 4-diyl) bis (4H-3, 1-benzo

Oxazin-4-one, 2' - (thiophene-2, 5-diyl) bis (4H-3, 1-benzo

Oxazin-4-one) ("ca"), and the like.

Examples of the other ultraviolet absorbers include salicylic acid-based ones such as phenyl salicylate, t-butylphenyl salicylate and p-octylphenyl salicylate, and other ones such as natural ones (e.g., oryzanol, shea butter and baicalin), biological ones (e.g., keratinocytes, melanin and urocanic acid). The inorganic ultraviolet absorber is not compatible with the resin to be a base, and causes an increase in haze and deterioration in visibility at the time of image display, and therefore is not preferably used for a laminated film for display applications.

As the ultraviolet absorber used in the present invention, an ultraviolet absorber having the same basic chemical structure as that of the above ultraviolet absorber and having an oxygen atom replaced with a sulfur atom of the same group can be used. Specifically, an ultraviolet absorber that converts an ether group into a thioether group, a hydroxyl group into a mercapto group, or an alkoxy group into a thio group can be used. By using an ultraviolet absorber containing a substituent having a sulfur atom, thermal decomposition of the ultraviolet absorber can be suppressed when the resin is kneaded by heating. Further, by using a sulfur atom and selecting an appropriate alkyl chain, the intermolecular force between the ultraviolet absorbers can be suppressed and the melting point can be lowered, so that the compatibility with the thermoplastic resin can be improved. By improving the compatibility, transparency, which is an important factor of the optical film, can be maintained even when added at a high concentration.

Further, the ultraviolet absorber used in the present invention is preferably an ultraviolet absorber having an alkyl chain length of a functional group constituting the ultraviolet absorber, in addition to having a maximum absorption wavelength in a wavelength range of 320 to 380 nm. Since the alkyl chain is long, intermolecular interaction is suppressed and filling of a ring structure is less likely to occur, and therefore, when the film is heat-treated, the ultraviolet absorbers are less likely to form a crystal structure with each other, and whitening of the film is suppressed. The length of the alkyl group included in the functional group is preferably 18 or less, more preferably 4 to 10, and further preferably 6 to 8. When the length of the alkyl chain is longer than necessary, the reaction site is buried in the molecule, and the yield of the ultraviolet absorber is lowered, which is not realistic.

The ultraviolet absorber may be kneaded as an additive into the thermoplastic resin, or may be copolymerized by reacting with an end group or a side chain of the thermoplastic resin. By copolymerization with a thermoplastic resin constituting the film and fixation, bleeding accompanying molecular thermal movement during heating can be suppressed, and thus ultraviolet cut-off performance can be maintained for a long period of time while maintaining transparency.

In the laminated film of the present invention, as a dye having the maximum wavelength in the visible light short-wavelength region of more than 380nm and 430nm or less, which can be used when the above-described light transmittance is achieved by combining 1 or more kinds of ultraviolet absorbers with 1 or more kinds of dyes having the maximum wavelength in the visible light short-wavelength region of more than 380nm and 430nm or less, it is also possible to use a dye other than the above-described dye having the maximum wavelength in the visible light short-wavelength region of more than 380nm and 430nm or less. As the dye having a maximum wavelength in a short wavelength region of visible light of more than 380nm and 430nm or less in the present invention, a dye which is soluble in a solvent and has excellent chroma may be used for the purpose of adding to a hard coat layer or an adhesive layer described later, and a pigment having excellent heat resistance, moist heat resistance, and light resistance as compared with the dye may be used. The pigment can be roughly classified into an organic pigment, an inorganic pigment, and a conventional pigment, but the use of an organic pigment is preferable in view of compatibility with a thermoplastic resin to be added. The structure of the dye having the maximum wavelength in the visible light short wavelength region exceeding 380nm and not more than 430nm is not particularly limited, and examples thereof include azo dyes such AS β naphthol, naphthol AS, acetoacetic acid arylamide, pyrazolone, and β hydroxynaphthoic acid, phthalocyanine dyes such AS copper phthalocyanine, halogenated copper phthalocyanine, metal-free phthalocyanine, and copper phthalocyanine lake, and azomethine dyes, aniline dyes, alizarin, anthraquinone dyes, isoindolinone dyes, isoindoline dyes, isoquinoline dyes, indane dyes, indole dyes, quinacridone dyes, quinophthalone dyes, coumarin dyes, and bisquinophthalone dyes

Oxazine series, thioindigo series, naphthalimide series, nitrone series, perinone series, perylene series, benzylidene series, natural organic pigments.

As described above, the dye having the maximum wavelength in the short-wavelength region of visible light exceeding 380nm and not more than 430nm more preferably has the maximum wavelength at 390nm to 420 nm. When a dye having a maximum wavelength in a long wavelength region as compared with 430nm is selected, the light transmittance at 440nm is not preferably lower than 80% unless a dye having a cutoff ability in a very narrow band region is selected. As the dye having a maximum wavelength in a wavelength region of 390nm to 420nm, azomethine, indole, quinone, triazine, naphthalimide, phthalocyanine, or benzylidene can be preferably used.

The ultraviolet absorber and/or the dye having a maximum wavelength in a short wavelength region of visible light exceeding 380nm and 430nm or less used in the present invention preferably has a triazine skeleton. Since triazine absorbents generally have a high thermal decomposition temperature and excellent heat resistance, they are not likely to deteriorate even when kneaded into a resin and exposed to heat in an extruder for a long time. Further, the absorbent is preferably used because volatilization and surface deposition of the absorbent itself are less likely to occur, and deposition of oligomers and other additives having high sublimability is less likely to occur. Further, since the absorption coefficient is high, the additive concentration for achieving the target cut-off property may be small, and the possibility of contaminating the film-forming step when the film is discharged from the die in a sheet state is low, which is useful.

When the laminated film of the present invention contains an ultraviolet absorber and/or a dye having a maximum wavelength in a visible light short-wavelength region exceeding 380nm and not more than 430nm, when the sum of the contents of the ultraviolet absorber and/or the dye having a maximum wavelength in a visible light short-wavelength region exceeding 380nm and not more than 430nm in a specific layer of the laminated film is Mn [ wt% ], and the layer thickness of the added layer is Tn [ μm ], Σ (Mn × Tn) obtained by adding the product of the sum of the contents and the layer thickness to the total layers of the laminated film is preferably 50[ wt%. μm ] or less. When the amount is more than 50[ wt%. mu.m ], the light transmittance is lowered, the white haze (haze value) of the film is increased, and the visibility may be deteriorated when the film is mounted on a liquid crystal image display device or the like, which is not preferable. The total content varies depending on the film thickness and the light absorption ability of various additives, and therefore, no lower limit is set, but as described above, an addition amount corresponding to the ultraviolet ray cut-off performance required for an optical film used for an image display device to protect a polarizing plate, liquid crystal molecules, a light-emitting layer, and the like is required.

In the thermoplastic resin of the present invention, various additives other than the ultraviolet absorber and the coloring matter having the maximum wavelength in the short wavelength region of visible light exceeding 380nm and not more than 430nm, for example, an antioxidant, a heat stabilizer, a weather stabilizer, an organic slipping agent, organic or inorganic fine particles, a filler, an antistatic agent, a nucleating agent, and the like may be added to such an extent that the film characteristics which should be originally satisfied are not deteriorated. In particular, in applications where optical performance is required to be maintained even when light irradiation is performed for a long period of time, when a dye having a vivid color is used among the above-described dyes having the maximum wavelength in the short wavelength region of visible light exceeding 380nm and not more than 430nm, the absorption performance tends to be lost by receiving ultraviolet rays having a higher energy than that of ultraviolet absorbers and pigments. Therefore, it is preferable to use a compound having an action of converting energy retained by ultraviolet rays into vibrational energy in a molecule, converting the vibrational energy thus converted into thermal energy or the like, and releasing the thermal energy or the like to the outside. Further, additives which suppress photo-oxidative deterioration through energy conversion, such as an antioxidant and a singlet oxygen quencher, are also preferable.

The light stabilizer is added mainly for capturing radicals generated in photooxidation, and is preferably contained in the laminated film of the present invention in an amount of 0.01 to 1 wt% based on the total weight of the film. Particularly preferred is a hindered amine compound having a 2,2,6, 6-tetramethyl-piperidine ring, and more preferred is a compound in which the 1-position of piperidine is hydrogen, alkyl, alkoxy, hydroxyl, an oxyradical (-O.), acyloxy, or acyl, and still more preferred is a compound in which the 4-position is hydrogen, hydroxyl, acyloxy, or an amino, alkoxy, or aryloxy group which may have a substituent. Furthermore, compounds having a plurality of 2,2,6, 6-tetramethyl-piperidine rings in1 molecule are also preferred. Examples of such compounds include TINUVIN770DF, TINUVIN 152 and TINUVIN123 manufactured by BASF corporation (old チバ, スペシャルティ, ケミカルズ), アデカスタブ LA-72 and アデカスタブ LA-81 manufactured by Adeka corporation.

In the laminated film of the present invention, the light stability can be further improved by using an antioxidant and/or singlet oxygen quencher in combination with the hindered amine light stabilizer. The photodegradation of the dye occurs by an oxidation reaction, and examples thereof include autooxidation accompanied by generation of radicals by the action of oxygen molecules as an oxidizing agent, singlet oxygen oxidation in which excitation energy of the dye propagates to oxygen molecules to change oxygen to a singlet oxidation state, and oxidation by superoxide ions. These oxidation reactions can be further suppressed by using an antioxidant, a quencher for dissipating excitation energy, and the like in combination.

The antioxidant to be used in combination with the light stabilizer is not particularly limited as long as it is a commonly used antioxidant, and a phosphorus-based antioxidant and a phenol-based antioxidant can be preferably used. Further, the combined use of a phosphorus antioxidant and a phenol antioxidant can maintain the efficacy of the antioxidant for a long period of time, and therefore, the combined use is preferably used appropriately. The concentration of the antioxidant added is preferably 0.01 wt% to 1 wt%, more preferably 0.05 wt% to 0.3 wt%. When the amount is 0.01 wt% or less, the effect as an antioxidant is weak, and when the amount is 1 wt% or more, volatilization of the antioxidant due to excessive addition may occur.

Singlet oxygen quenchers to be used in combination with light stabilizers are compounds capable of deactivating singlet oxygen by energy transfer from singlet oxygen, and examples thereof include vinyl compounds such as tetramethylethylene and cyclopentene, amines such as diethylamine, triethylamine and N-ethylimidazole, condensed polycyclic aromatic compounds such as substituted naphthalene, dimethylnaphthalene, dimethoxyanthracene, anthracene and diphenylanthracene, aromatic compounds such as 1, 3-diphenylisobenzofuran, 1,2,3, 4-tetraphenyl-1, 3-cyclopentadiene and pentaphenylcyclopentadiene, and metal complexes serving as ligands. Examples of the metal complex compound include transition metal complex compounds such as nickel complexes, cobalt complexes, copper complexes, manganese complexes, and platinum complexes, each of which has a structure such as bis-dithio- α -diketone, bis-phenyl dithiol, and thiobisphenol as a ligand. The singlet oxygen quencher is added in an amount of preferably 0.5 to 10 wt%, more preferably 1 to 8 wt%, based on the amount of the absorber to be oxidized and deteriorated. Further, when the light stabilizer is used in combination with 3 types of antioxidants and singlet oxygen quenchers, oxidative deterioration due to radicals can be effectively prevented, and therefore, the combination is most preferable.

The laminated film of the present invention preferably comprises 51 or more layers of the thermoplastic resin a and the thermoplastic resin B alternately laminated. As described above, by alternately laminating resins having different optical properties, interference reflection can be expressed in which light having a specific wavelength can be reflected according to the relationship between the difference in refractive index of each layer and the layer thickness. Further, since the light beam travels with an optical path length equal to or longer than the film thickness because of the multiple interference reflection effect between layers occurring with respect to the light beam having a wavelength within the interference reflection region, the absorption amount increases when an ultraviolet absorber and/or a coloring matter having a maximum wavelength in a visible light short wavelength region exceeding 380nm and equal to or shorter than 430nm is added, and the addition amount of the ultraviolet absorber can be suppressed as compared with a normal laminated film having no interference reflection effect. Thus, if the effect of multiple interference reflection is utilized, the amount of each additive to be added can be suppressed to a small amount by targeting the ultraviolet region and/or the short-wavelength visible light region, and bleeding during film formation, which is the target of the present invention, can be suppressed, and the quality after the long-term reliability test can be maintained well. The number of stacked layers of the multilayer film of the present invention is more preferably 200 or more, and still more preferably 400 or more. Regarding the above-described interference reflection effect, the larger the number of layers, the higher the reflectance can be achieved for light in a target wavelength band, and therefore, the larger the number of layers is, the more preferable. In addition, when the number of stacked layers is large, it is expected that the respective resins are uniformly distributed, and stable film forming properties and mechanical properties are obtained. Since the increase in the number of layers leads to an increase in the manufacturing cost associated with an increase in the size of the manufacturing apparatus and deterioration in the operability due to an increase in the thickness of the film, 1000 layers or less are practically suitable.

The laminated film of the present invention preferably has a bending rigidity per unit length of 1.0X 10^-7[N·m²]The following. The bending rigidity is an index indicating the strength against bending, and the higher the value, the harder the film and the more likely it is to wrinkle during bending. The bending rigidity per unit length is represented by E × I, E represents the elastic modulus [ N/m ] in the bending direction of the optical functional film²]Where I represents a second moment of area per unit length, I ═ b × h³12 (b: unit length [ m ]]: h: film thickness [ m ]]). Since this parameter is particularly strongly influenced by the film thickness h, the more thin the film, the more resistant it is to bending. In the case of producing the present laminate film by the biaxial stretching step described later, it is required that the flexural rigidity is calculated for each of the longitudinal direction and the width direction of the laminate film, and the higher value satisfies 1.0 × 10^-7[N·m²]The following. The bending rigidity is more preferably 3.0X 10^-8[N·m²]Hereinafter, more preferably 1.0 × 10^-8[N·m²]The following.

The laminate film of the present invention preferably has a delta haze of 2.0 or less when treated at 85 ℃ and 85% RH for 250 hours. The 85 ℃ 85% RH condition is a reliable test condition for promoting resistance to moist heat in display applications, but since it is a high temperature and humidity, ultraviolet absorbers added to the inside, pigments having a maximum wavelength in a short wavelength region of visible light exceeding 380nm and 430nm or less, resin-derived oligomers, and the like are likely to precipitate on the film surface due to thermal motion. If the haze value is not 2.0 or less under such conditions, the optical film itself becomes opaque due to the intensified diffused light, and the light transmittance during mounting deteriorates, thus causing a problem in visibility. The haze value after the accelerated heat resistance test is more preferably 1.5 or less, and still more preferably 1.0 or less.

The laminated film of the present invention not only blocks light in the ultraviolet region but also in the vicinity of the boundary between the ultraviolet region and the visible light region (in the vicinity of 410 nm), and has high light transmittance in the visible light region, and therefore, is suitably used as a film for display use. Examples of the film for display use include a polarizer protective film, a retardation film, various surface treatment films positioned in front of a display having an antiglare layer and a transparent hard coat layer, a brightness enhancement film positioned immediately in front of a backlight, an antireflection film, and a transparent conductive film, which constitute a polarizing plate, in the case of a liquid crystal image display device. In the case of an organic EL image display device, a λ/4 retardation film constituting a circularly polarizing plate located in front of a light-emitting layer, a polarizer protective film, an optical film incorporated for the purpose of protecting contents from external light, and the like can be given. In particular, when conditions such as improvement of light resistance and uniformity of orientation angle are to be achieved, it is most preferable to arrange the polarizer protective film on the most visible side of the polarizing plate and the portion on the most visible side of the polarizing plate and inside the cover glass and the window film on the top surface of the display in view of protecting the display contents from ultraviolet rays and exhibiting polarization state maintaining characteristics. However, the laminated film of the present invention is not limited to display applications, and can be used in a field where light cut in a short wavelength region of visible light having a wavelength of 410nm or less is required, for example, in window films in building materials and automobiles, and in films for laminating steel sheets to signboards and the like in industrial material applications, and in process films and release films for photolithography materials in electronic device applications, and also in film applications for the purpose of suppressing light deterioration of contents in other fields such as foods, medical treatment, and inks.

Next, a preferred method for producing the laminated film of the present invention will be described below. Of course, the present invention is not limited to such an example for explanation.

The thermoplastic resin is prepared in the form of pellets or the like. The pellets are dried in hot air or under vacuum as required, and then fed to the respective extruders. In the extruder, the resin heated to a temperature equal to or higher than the melting point is melted, and the extrusion amount of the resin is made uniform by a gear pump or the like, and foreign matter, modified resin, and the like are removed through a filter or the like. These resins are molded into a desired shape by a mold and then discharged. Then, the multilayer laminated film discharged from the die is extruded onto a cooling body such as a casting drum, and cooled and solidified to obtain a casting film. In this case, it is preferable to use a linear, ribbon, needle, knife-shaped or the like electrode, and to rapidly cool and solidify the electrode by bringing the electrode into close contact with a cooling body such as a casting drum by electrostatic force. Further, a method of blowing air from a slit, dot, or planar device to bring the air into close contact with a cooling body such as a casting drum to rapidly cool and solidify the air, or bringing the air into close contact with the cooling body by a nip roll to rapidly cool and solidify the air is also preferable.

Further, a plurality of resins of the thermoplastic resin a and the thermoplastic resin B were fed out from different flow paths using 2 or more extruders and fed into the multilayer lamination apparatus. As the multilayer lamination apparatus, a multi-manifold die, a feed block, a static mixer, or the like can be used, but in order to efficiently obtain the structure of the present invention, a feed block having a fine slit is particularly preferably used. If such a feed block is used, the apparatus is not extremely large in size, and therefore the amount of foreign matter generated due to thermal degradation is small, and even when the number of stacked layers is extremely large, highly accurate stacking can be performed. Further, the lamination accuracy in the width direction is also significantly improved as compared with the prior art. In this device, the thickness of each layer can be adjusted by the shape (length, width) of the slit, and thus an arbitrary layer thickness can be realized.

The molten multilayer laminate thus formed into a desired layer structure is guided to a die to obtain a casting film as described above.

The cast film thus obtained is preferably then biaxially stretched in the longitudinal direction and the width direction. The stretching may be carried out sequentially or simultaneously by biaxial stretching. Further, the redrawing may be performed in the longitudinal direction and/or the width direction.

First, the case of sequential biaxial stretching will be described. Here, the stretching in the longitudinal direction means a stretching for imparting molecular orientation in the longitudinal direction to the film, and is usually performed by a circumferential speed difference between rollers, and the stretching may be performed in1 stage, or may be performed in multiple stages using a plurality of pairs of rollers. The stretching ratio is preferably 2 to 15 times, depending on the type of resin, and particularly preferably 2 to 7 times when polyethylene terephthalate is used as any of the resins constituting the laminate film. The stretching temperature is preferably set to a range from the glass transition temperature of the resin constituting the laminate film to the glass transition temperature +100 ℃.

The uniaxially stretched film obtained in this manner may be subjected to surface treatment such as corona treatment, flame treatment, or plasma treatment, if necessary, and then subjected to on-line coating to provide functions such as slipperiness, adhesiveness, and antistatic property.

Next, the stretching in the width direction means a stretching for imparting orientation in the width direction to the film, and the film is generally stretched in the width direction by conveying the film while holding both ends thereof with clips using a tenter. The stretching ratio is preferably 2 to 15 times, depending on the type of resin, and particularly preferably 2 to 7 times when polyethylene terephthalate is used as any of the resins constituting the film. The stretching temperature is preferably from the glass transition temperature of the resin constituting the laminate film to the glass transition temperature +120 ℃.

The biaxially stretched film thus obtained is subjected to a heat treatment at a temperature not lower than the stretching temperature and not higher than the melting point in a tenter, and is uniformly and slowly cooled, and then cooled to room temperature and wound. If necessary, in order to impart a low orientation angle and thermal dimensional stability to the film, a relaxation treatment or the like may be used in combination in the longitudinal direction and/or the width direction at the time of heat treatment to slow cooling.

The case of simultaneous biaxial stretching will be described next. In the case of simultaneous biaxial stretching, the obtained cast film may be subjected to surface treatment such as corona treatment, flame treatment, plasma treatment, etc., as necessary, and then subjected to on-line coating to impart functions such as slipperiness, adhesiveness, antistatic property, etc.

Next, the cast film is introduced into a simultaneous biaxial tenter, and both ends of the film are held by clips while being conveyed, and stretched simultaneously and/or stepwise in the longitudinal direction and the width direction. Examples of the simultaneous biaxial stretching machine include a pantograph (pantograph) system, a screw system, a drive motor system, and a linear motor system, and the drive motor system or the linear motor system is preferably capable of arbitrarily changing the stretching magnification and performing the relaxation process at an arbitrary position. The stretch ratio is usually preferably 6 to 50 times, depending on the type of resin, and when polyethylene terephthalate is used as any of the resins constituting the laminate film, it is particularly preferably 8 to 30 times. Particularly in the case of simultaneous biaxial stretching, in order to suppress the in-plane orientation difference, it is preferable to make the stretching ratios in the longitudinal direction and the width direction the same and to make the stretching speeds almost equal. The stretching temperature is preferably from the glass transition temperature of the resin constituting the laminate film to the glass transition temperature +120 ℃.

In order to impart flatness and dimensional stability to the biaxially stretched film, it is preferable to perform a heat treatment at a temperature not lower than the stretching temperature and not higher than the melting point in a tenter. In this heat treatment, in order to suppress the distribution of the main alignment axes in the width direction, it is preferable to perform the relaxation treatment in the longitudinal direction immediately before and/or immediately after entering the heat treatment region. After the heat treatment in this way, the steel sheet is uniformly cooled slowly, cooled to room temperature, and wound. If necessary, the relaxation treatment may be performed in the longitudinal direction and/or the width direction when the heat treatment is performed to the slow cooling. The relaxation treatment is performed in the longitudinal direction immediately before and/or immediately after the entry into the heat treatment zone.

The laminated film obtained in the above-described manner is cut into a necessary width by a winding device, and wound in a rolled state without winding wrinkles. In order to improve the winding state during winding, embossing may be applied to both ends of the film.

The thickness of the laminated film of the present invention is not particularly limited, and is preferably 1 to 500 μm. In accordance with the recent tendency of a film for display use to be a thin film, it is preferably 40 μm or less, more preferably 20 μm or less, and still more preferably 15 μm or less. Although there is no lower limit, the thickness of the film needs to be a certain degree in order to add an ultraviolet absorber and/or a dye having a maximum wavelength in a short-wavelength region of visible light exceeding 380nm and 430nm or less and to impart sufficient cut-off properties in the short-wavelength region of ultraviolet light and visible light to the film, and in reality, the thickness is preferably 10 μm or more. When the thickness is less than 10 μm, the laminate film may curl due to a curing treatment when a hard coat layer described later is provided, in addition to the fact that the intended optical performance cannot be provided.

Next, a laminated sheet in which a hard coat layer containing a curable resin C as a main component is provided to the laminated film of the present invention will be described.

In the laminated film of the present invention, a hard coat layer (layer C) containing a curable resin C as a main component is preferably provided in order to impart functions such as scratch resistance and dimensional stability to the upper portion of the outermost layer. In the case of a film for display use, it is required that the properties of the film do not change in a long-term reliability test under severe conditions including the aforementioned conditions for the humidity and heat resistance promotion test at 85 ℃ RH and a heat shock test in which the temperature is raised several times from near 100 ℃ to below the freezing point. In the case of a laminated film subjected to orientation crystallization by stretching, if a long-term reliability test is performed, there is a possibility that the dimension of the film changes due to heat shrinkage, and in the case of the laminated film of the present invention, since heat shrinkage occurs and the thickness of the film increases, the absorption performance of various absorbers is improved more than necessary, and problems occur such that absorption in an undesirable visible light region is exhibited, or a reflection band is shifted to cut off visible light on a longer wavelength side, and the like, which is not preferable. Therefore, in order to maintain the properties of the film, it is preferable to coat at least one surface of the laminated film with a hard coat layer contributing to dimensional stability. Further, by laminating a hard coat layer having high crosslinkability, it is possible to suppress precipitation of oligomers, additives, and the like contained in the laminated film. The hard coat layer may be directly applied to the laminate film, or may be applied after providing an in-line aqueous coating layer capable of providing functions such as easy slipperiness and easy adhesion as described in the above-mentioned production method.

The coating layer is preferably applied because it can provide functions such as easy slipperiness and easy adhesion, and when a hard coat layer containing the curable resin C as a main component is laminated, the effect of improving adhesion to the laminated film is exhibited. In particular, when polyethylene terephthalate is used as the resin a and an acrylic resin is used as the curable resin B as in examples described later, the refractive index of the former is about 1.65, and the refractive index of the latter is about 1.50, and the difference in refractive index is large, which causes deterioration in adhesion. Therefore, the refractive index of the coating layer preferably has a value of 1.50 to 1.60, more preferably 1.55 to 1.58.

The hard coat layer containing the curable resin C as a main component may be provided on one side, but generally, precipitation of oligomers, additives, and the like occurs from both sides of the film, and further, when the hard coat layer is laminated on only one side, a shrinkage stress due to curing acts strongly on the laminated surface side, and the laminated sheet itself may curl significantly depending on the lamination thickness of the hard coat layer. Therefore, the hard coat layer is more preferably applied to both sides of the laminated film.

The curable resin C used in the laminate film of the present invention is preferably a highly transparent and durable resin, and for example, an acrylic resin, a polyurethane resin, a fluorine resin, a silicone resin, a polycarbonate resin, or a vinyl chloride resin may be used alone or in combination. The curable resin C is preferably made of an active energy ray curable resin such as an acrylic resin typified by a polyacrylate resin, from the viewpoints of curability, flexibility, and productivity. In addition, when scratch resistance at the time of bending, which is required when the curable resin C is applied as a film for a flexible display, is added, the curable resin C is preferably composed of a thermosetting urethane resin.

Examples of the active energy ray-curable resin used as a constituent of the hard coat layer include pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol tri (meth) acrylate, dipentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate, dipentaerythritol hexa (meth) acrylate, trimethylolpropane tri (meth) acrylate, bis (methacryloylthiophenyl) sulfide, 2, 4-dibromophenyl (meth) acrylate, 2,3, 5-tribromophenyl (meth) acrylate, 2-bis (4- (meth) acryloyloxyphenyl) propane, 2-bis (4- (meth) acryloyloxyethoxyphenyl) propane, and a monomer component constituting the active energy ray-curable resin, 2, 2-bis (4- (meth) acryloyloxydiethoxyphenyl) propane, 2-bis (4- (meth) acryloylpentaethoxyphenyl) propane, 2-bis (4- (meth) acryloyloxyethoxy-3, 5-dibromophenyl) propane, 2-bis (4- (meth) acryloyloxydiethoxy-3, 5-dibromophenyl) propane, 2-bis (4- (meth) acryloyloxypentaethoxy-3, 5-dibromophenyl) propane, 2-bis (4- (meth) acryloyloxyethoxy-3, 5-dimethylphenyl) propane, 2-bis (4- (meth) acryloyloxyethoxy-3-phenylphenyl) propane, bis (4- (meth) acryloyloxyphenyl) sulfone, bis (4- (meth) acryloyloxyethoxyphenyl) sulfone, bis (4- (meth) acryloyloxypentaethoxyphenyl) sulfone, bis (4- (meth) acryloyloxyethoxy-3-phenylphenyl) sulfone, bis (4- (meth) acryloyloxyethoxy-3, 5-dimethylphenyl) sulfone, bis (4- (meth) acryloyloxyphenyl) sulfide, bis (4- (meth) acryloyloxyethoxyphenyl) sulfide, bis (4- (meth) acryloyloxypentaethoxyphenyl) sulfide, bis (4- (meth) acryloyloxyethoxy-3-phenylphenyl) sulfide, polyfunctional (meth) acrylic compounds such as 5-dimethylphenyl sulfide, bis ((meth) acryloyloxyethoxy) phosphate and tris ((meth) acryloyloxyethoxy) phosphate, and 1 or 2 or more of these can be used.

In addition, in order to control the hardness, transparency, strength, refractive index, and the like of the active energy ray-curable resin, together with these polyfunctional (meth) acrylic compounds, styrene, chlorostyrene, dichlorostyrene, bromostyrene, dibromostyrene, divinylbenzene, vinyltoluene, 1-vinylnaphthalene, 2-vinylnaphthalene, N-vinylpyrrolidone, phenyl (meth) acrylate, benzyl (meth) acrylate, biphenyl (meth) acrylate, diallyl phthalate, dimethylallyl phthalate, diallyl diphenyl ether (diallyl biphenylate), or a reaction product of a metal such as barium, lead, antimony, titanium, tin, zinc, and the like, and (meth) acrylic acid may be used. 1 or 2 or more of them may be used.

As a method for curing the active energy ray-curable resin, for example, a method of irradiating ultraviolet rays can be used, and in this case, it is desirable to add about 0.01 to 10 parts by weight of a photopolymerization initiator to the above compound.

The active energy ray-curable resin used in the present invention may contain an organic solvent such as isopropyl alcohol, ethyl acetate, methyl ethyl ketone, or toluene in an amount that does not impair the effects of the present invention, for the purpose of improving the workability during coating and controlling the coating thickness.

In the present invention, the active energy ray means an electromagnetic wave that polymerizes an acrylic vinyl group, such as ultraviolet ray, electron ray, and radiation (α ray, β ray, and γ ray), and in practice, ultraviolet ray is simple and preferable. As the ultraviolet source, an ultraviolet fluorescent lamp, a low-pressure mercury lamp, a high-pressure mercury lamp, an ultrahigh-pressure mercury lamp, a xenon lamp, a carbon arc lamp, or the like can be used. Further, the electron beam system is expensive and needs to be operated under an inert gas, but is advantageous in that it may not contain a photopolymerization initiator, a photosensitizer, or the like.

The thickness of the hard coat layer should be adjusted as appropriate depending on the method of use, but is preferably 1 to 6 μm, more preferably 1 to 3 μm, and still more preferably 1 to 1.5 μm, from the viewpoint of both the tendency to form a thin film for display applications and the performance of the hard coat layer. When the thickness of the hard coat layer is more than 6 μm, the laminate film may not withstand the curing shrinkage force of the hard coat layer when the coated substrate is cured, and the laminate sheet may be strongly curled.

The thermosetting polyurethane resin used as a constituent of the hard coat layer containing the curable resin C as a main component for imparting scratch resistance is preferably a resin obtained by crosslinking a copolymer resin having a polycaprolactone segment and a polysiloxane segment and/or a polydimethylsiloxane segment with a compound having an isocyanate group by a thermal reaction. By using the thermosetting urethane resin, the hard coat layer can be made tough and the elastic recovery can be promoted, and the scratch resistance can be imparted to the laminated film.

The polycaprolactone segment constituting the thermosetting polyurethane resin exerts an elastic recovery effect, and free radical polymerizable polycaprolactone such as polycaprolactone diol, polycaprolactone triol, lactone-modified hydroxyethyl acrylate, and the like can be used.

The polysiloxane and/or polydimethylsiloxane segment constituting the thermosetting polyurethane resin exhibits the effect of improving the lubricity of the surface and reducing the frictional resistance by surface coordination of these components. As the resin having a polysiloxane segment, tetraalkoxysilane, methyltrialkoxysilane, dimethyldialkoxysilane, γ -glycidoxypropyltrialkoxysilane, γ -methacryloxypropyltrialkoxysilane, and the like can be used. On the other hand, as the resin having a polydimethylsiloxane segment, a copolymer obtained by copolymerizing various vinyl monomers such as methyl acrylate, isobutyl acrylate, methyl methacrylate, N-butyl methacrylate, styrene, α -methylstyrene, acrylonitrile, vinyl acetate, vinyl chloride, vinyl fluoride, acrylamide, methacrylamide, N-dimethylacrylamide and the like with respect to the polydimethylsiloxane segment can be preferably used.

The hard coat layer formed of a thermosetting urethane resin is formed by thermally crosslinking a resin and a compound at an arbitrary temperature while causing a linking reaction between the resin and the compound to volatilize a solvent in the layer. In order to promote the thermal crosslinking reaction of the hard coat layer, the temperature in the heating step is preferably 150 ℃ or higher, and more preferably 160 ℃ or higher. The heating temperature is preferably high, but if the occurrence of shrinkage wrinkles due to thermal shrinkage of the substrate is considered, the heat treatment is preferably performed at 170 ℃ or lower. The heating time is 1 minute or more, preferably 2 minutes or more, and the upper limit is not particularly limited, but is preferably 5 minutes or less from the viewpoint of dimensional stability and transparency of the laminated film. The laminate sheet heat-treated at a high temperature for a short time in this way is preferably subjected to an aging treatment at a temperature of 20 to 80 ℃ for 3 days or more, more preferably 7 days or more, from the viewpoint of increasing the urethane bond to improve the elongation of the laminate sheet.

When the curable resin C used for imparting adhesiveness and adhesiveness is used as an optical film for display, particularly as a laminate with a polarizing plate, it is preferable to use a photocurable resin comprising a combination of 4 compounds, each of which is a compound having an alicyclic epoxy group, a polyacrylate of a polyol, an oxetane compound, and a polymer having an alkyl acrylate as a monomer unit, and which exerts a good effect of adhesion to PVA.

The compound having an alicyclic epoxy group is preferably a compound having about 2 to 5 epoxy groups from the viewpoint of low viscosity, curability, and adhesion, and examples thereof include 3, 4-epoxycyclohexylmethyl-3, 4-epoxycyclohexane carboxylate.

The polyacrylate of the polyol having about 2 to 10 carbon atoms is preferably neopentyl glycol dimethacrylate, 1, 6-hexanediol dimethacrylate, 3-methyl-1, 5-pentanediol dimethacrylate, or the like, because the viscosity is reduced and the adhesiveness to the polarizing plate is improved.

The oxetane compound can increase the speed of adhesion expression after light irradiation, and can express adhesion even in an environment where the relative humidity fluctuates. 3-ethane-3-oxetanemethanol, 3' - (oxybismethylene) bis (3-ethyloxetane) and the like can be preferably used.

The polymer using an alkyl acrylate as a monomer is a polymer which exerts an effect of promoting excellent adhesion after a wet heat resistance test, and alkyl esters having 1 to 10 carbon atoms of methacrylic acid represented by methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, t-butyl methacrylate, and isobutyl methacrylate are preferably used, and among them, alkyl esters having 1 to 4 carbon atoms of methacrylic acid are most preferably used.

When the above components are mixed in appropriate amounts, the photo cation polymerization initiator can be cured at room temperature by the above various active energy rays. As the photo cation polymerization initiator, benzenediazonium can be used

Iso aromatic diazo

Aromatic sulfonium salt such as phosphonium salt and triphenylsulfonium, and diphenyl diiodo

Iso aromatic iodine

A salt, or a combination of 2 or more thereof. In addition, a photo radical polymerization initiator can be used in order to exhibit sufficient crosslinking reactivity with a small amount of light irradiation.

The hard coat layer may contain the above-mentioned various ultraviolet absorbers and/or a pigment having a maximum wavelength in a short wavelength region of visible light exceeding 380nm and not more than 430 nm. Addition of the ultraviolet absorber and the dye having the maximum wavelength in a short wavelength region of visible light exceeding 380nm and 430nm or less to the resin can be reduced by addition separately from the hard coat layer, and bleeding during extrusion of the resin can be suppressed, which is preferable. Further, when a coloring matter having a maximum wavelength in a short wavelength region of visible light exceeding 380nm and not more than 430nm is added to the hard coat layer, the absorption of the coloring matter can reduce the hue of blue reflected from the laminate film to the viewing side, and it is preferable from the viewpoint of expressing clear white and black colors when the presence or absence of image display is possible.

The concentration of the ultraviolet absorber and/or the coloring matter having the maximum wavelength in the short wavelength region of visible light exceeding 380nm and 430nm or less added to the hard coat layer is preferably 10 wt% or less, more preferably 5 wt% or less, based on the whole resin composition constituting the hard coat layer. The addition concentration should be appropriately adjusted in view of the thickness of the hard coat layer related to the absorption performance and the cut-off performance of the additive, and if it exceeds 10 wt%, there is a possibility that the surface of each additive is precipitated when the reliability test is promoted, and there is also a case that the adhesion between the laminate film and the hard coat layer is deteriorated.

In addition, in the form of the laminate sheet, it is preferable that Σ (Mn × Tn) obtained by adding Mn [ wt% ] which is the sum of the contents of the ultraviolet absorber and/or the coloring matter having the maximum wavelength in the visible light short wavelength region exceeding 380nm and 430nm or less and the product of the layer thickness Tn [ μm ] of the additional layer is 50[ wt%. μm ] or less for all layers of the laminate film.

If necessary, functional layers such as an impact absorption layer and an Antireflection (AR) layer may be further provided on the hard coat layer containing the curable resin C as a main component. In particular, the AR layer is preferably laminated as a functional layer because it has an effect of improving visibility in image display applications.

The laminate film of the present invention may have an adhesive layer containing an ultraviolet absorber and/or a dye having a maximum wavelength in a short wavelength region of visible light exceeding 380nm and not more than 430nm on at least one side. In the case of a film for display, the adhesive layer may be positioned on the viewing side, the inside of the display, or both sides of the laminated film of the present invention.

However, in the case where the wavelength cut, which is the object of the present invention, is achieved via both the laminate film and the adhesive layer, in the case where a dye is used as the dye having the maximum wavelength in the short wavelength region of visible light exceeding 380nm and not more than 430nm, the absorption performance is lost by receiving ultraviolet rays having strong energy as described above. Therefore, a preferable embodiment is obtained in which the laminated film contains an ultraviolet absorber, the adhesive layer contains an ultraviolet absorber and/or a coloring matter having a maximum wavelength in a short wavelength region of visible light exceeding 380nm and not more than 430nm, and the laminated film is positioned on the viewing side of the adhesive, whereby the coloring matter can be sufficiently prevented from deteriorating due to the reflection and absorption performance of the laminated film.

The pressure-sensitive adhesive layer may be a method in which the pressure-sensitive adhesive layer is formed by directly applying the pressure-sensitive adhesive layer to a laminated film substrate and then drying the pressure-sensitive adhesive layer, and a release sheet is further bonded to obtain a pressure-sensitive adhesive sheet, or a method in which the pressure-sensitive adhesive applied to the release sheet is transferred to a laminated film substrate. The coating method may be any of various coating methods such as a roll coater, die coater, bar coater, lip coater, gravure coater, and knife coater. The thickness of the adhesive layer is preferably 5 μm to 150 μm, more preferably 10 μm to 80 μm. If the thickness of the adhesive layer is less than 5 μm, the adhesive performance may be insufficient, and if it exceeds 150 μm, the cost of the adhesive sheet itself increases, which is not desirable. The type of the adhesive is not particularly limited, and from the viewpoint of excellent transparency and durability, it is most preferable to use the types described above as the curable resin used for improving adhesion and adhesiveness, and an acrylic optical adhesive (OCA) and a liquid acrylic optical adhesive (LOCA).

The present invention will be described below with reference to examples, but the present invention is not limited to these examples. Each characteristic was measured by the following method.

(method of measuring Properties and method of evaluating Effect)

The methods for measuring the characteristics and evaluating the effects of the present invention are as follows.

(1) Layer thickness, number of lamination layers, lamination structure

The layer structure of the film was determined by Transmission Electron Microscope (TEM) observation of a sample with a section cut out by a microtome. That is, the cross section of the film was observed under an accelerating voltage of 75kV using a transmission electron microscope H-7100FA model (manufactured by Hitachi, Ltd.), and a photograph of the cross section was taken to measure the layer structure and the thickness of each layer. Depending on the case, RuO is used to obtain high contrast₄、OsO₄And the like. Further, from the thickness of the layer (thin film layer) having the thinnest thickness among all the layers photographed in1 image, observation was performed at a magnification of 10 ten thousand times when the thin film layer thickness was less than 50nm, observation was performed at a magnification of 4 ten thousand times when the thin film layer thickness was 50nm or more and less than 500nm, and observation was performed at a magnification of 1 ten thousand times when the thin film layer thickness was 500nm or more, and the layer thickness and the number of stacked layers were specifiedAnd a laminated structure.

(2) Light transmittance

A spectrophotometer U-4100 manufactured by Hitachi was used. An integrating sphere was attached, and relative transmittance in a wavelength range of 300 to 450nm was measured with reflection of an alumina standard white plate (attached to a main body) as 100%. The transmittance values at the wavelengths of 410nm and 440nm were read, and the maximum transmittance in the range of 300 to 380nm was read. As conditions, the scanning speed was set to 600nm/min, and the sampling interval was set to 1nm, and the measurements were carried out continuously.

(3) Average light reflectance

A spectrophotometer U-4100 manufactured by Hitachi was used. An integrating sphere was attached, and the relative reflectance in the 300 to 400nm region was measured with the reflectance of an alumina standard white plate (attached to the main body) being 100%, and the average light reflectance in this range was determined. As conditions, the scanning speed was set to 600nm/min, and the sampling interval was set to 1nm, and the measurements were carried out continuously.

(4) Hard coat coating (examples 22 to 32)

An active energy ray-curable urethane acrylic resin (UV-1700B, refractive index: 1.50 to 1.51, manufactured by Nippon synthetic chemical industry Co., Ltd.) constituting a hard coat layer, to which an ultraviolet absorber and a coloring matter having a maximum wavelength in a short wavelength region of visible light exceeding 380nm and not more than 430nm are added, as described in examples 22 to 32 described later]) The coating was uniformly applied to the outermost surface of the laminate film using a bar coater. Next, the hard coat layer was formed with a height of 120W/cm placed at a distance of 13cm from the surface of the hard coat layer²The light-condensing high-pressure mercury lamp (H04-L41, アイグラフィックス Co., Ltd.) of the irradiation intensity of (1) was set so that the integrated irradiation intensity became 180mJ/cm²The laminate film was irradiated with ultraviolet rays and cured to obtain a laminate sheet having a hard coat layer laminated on the laminate film. An industrial UV tester (UVR-N1 manufactured by japan battery corporation) was used for measuring the cumulative irradiation intensity of ultraviolet rays.

(5) Evaluation of bleeding resistance

The vicinity of the widthwise edge of the polymer exiting from the die during film formation was irradiated with light, and the presence or absence of white smoke generation (volatilization from the die) was confirmed. The absence of white smoke (volatilization from the die) was evaluated as excellent in bleed resistance.

(6) Humidity resistance test accelerated by 85% RH at 85 deg.C (evaluation of haze Change amount (. DELTA.haze))

The produced laminated film was cut out from the center in the film width direction at a length of 10cm × 10cm in the width direction, and was allowed to stand for 250 hours in a constant temperature and humidity bath at 85 ℃ and 85% RH while being sandwiched between plain paper, and the amount of change in haze value of the film before and after heat treatment was evaluated. The haze was measured by using a haze meter (HGM-2DP) manufactured by スガ testing machine (Ltd.) according to old JIS-K-7105. The results of the measurement were determined by measuring 3 spots randomly on the film surface and averaging the 3 spots.

Very good: the haze value variation is less than 1.0 percent

O: the haze value variation is more than 1.0% and less than 1.5%

And (delta): the haze value variation is more than 1.5% and less than 2.0%

X: the haze value variation is 2.0% or more.

(7) Flexural rigidity

A tensile tester (テンシロン UCT-100, manufactured by オリエンテック) was used to calculate the modulus of elasticity of the sample. The laminated film was cut into a long strip having a length of 150mm × a width of 10mm, and a tensile test was performed at a tensile rate of 300 mm/min with an initial distance between tensile chucks of 50 mm. The measurement environment was set to an atmosphere of 23 ℃ at room temperature and 65% relative humidity, and the elastic modulus (Young's modulus) was calculated from the load-strain curve obtained. The number of samples was set to 5, and the average value thereof was taken as the modulus of elasticity of the sample. The maximum value of the elastic modulus of the sample was determined by setting the film length direction to 0 ° and measuring the same every 10 ° change direction from-90 ° to 90 ° in the film plane. The thickness of the sample was measured by a contact thickness meter (デジマイクロヘッド MH-15M manufactured by ニコン Co., Ltd.) and the bending rigidity value was calculated by applying the thickness to the above-mentioned formula.

(8) Bending resistance test

A sample having a width of 5cm X a length of 9cm was cut out in each of the longitudinal direction and the width direction of the laminated film, and a bending resistance test was performed using a planar unloaded U-shaped expansion and contraction tester manufactured by ユアサ inhibitor システム (Co., Ltd.). Bending test was conducted 100 ten thousand times in a measuring atmosphere at room temperature of 23 ℃ and a relative humidity of 65% with a bending speed of 50 times/minute and a bending radius of 1 mm. The number of samples was 3, and the presence or absence of damage or wrinkles was visually confirmed as compared with the laminated film before the test. The bending resistance was good when none of the 3 samples were damaged or wrinkled (o), and poor when 1 sample was damaged or wrinkled (x).

(9) Glass transition temperature, melting Point

A differential scanning calorimeter EXSTAR DSC6220 manufactured by セイコー electronics industries, Inc. was used. The measurement and temperature reading were carried out according to JIS-K-7122 (1987). A10 mg thermoplastic resin sample was placed on an aluminum tray, heated from 25 ℃ to 300 ℃ at a rate of 10 ℃/min, then quenched, heated again from 25 ℃ to 300 ℃ at a rate of 10 ℃/min, and the temperature of the step-change portion at that time was regarded as the glass transition temperature, and the peak top of the endothermic peak was regarded as the melting point.

Examples

(example 1)

As the thermoplastic resin A, polyethylene terephthalate (PET) having a melting point of 258 ℃ was used. Further, as the thermoplastic resin B, polyethylene terephthalate (PE/SPG15T/CHDC20) copolymerized with cyclohexane dimethanol 20 mol% and spiro diol 15 mol% was used as an amorphous resin having no melting point. In the thermoplastic resin B, a triazine-based ultraviolet absorber (2,4, 6-tris (2-hydroxy-4-hexyloxy-3-methylphenyl) -s-triazine) having a molecular weight of 700g/mol was added so as to be 10 wt% with respect to the resin composition constituting the layer B containing the thermoplastic resin B as a main component. The prepared thermoplastic resin A and thermoplastic resin B were fed into 2 single-screw extruders, respectively, and the former melted at 280 ℃ and the latter melted at 260 ℃ to be kneaded. Subsequently, the sheets were passed through an FSS type leaf disc filter 5, and then metered by a gear pump, and the feed blocks having 5 slits were joined together to form a laminate in which 5 layers were alternately laminated in the thickness direction at a lamination ratio of 0.5. Here, the slit length is designed to be stepped, and the intervals are all set to be constant. The resulting laminate was composed of 3 layers of thermoplastic resin a and 2 layers of thermoplastic resin B, and was alternately laminated in the thickness direction. The laminate was fed to a T-die and formed into a sheet, and then rapidly cooled and solidified on a casting drum maintained at a surface temperature of 25 ℃ while applying an electrostatic voltage of 8kV to the wire, to obtain an unstretched cast laminate film.

The obtained laminated cast film was heated with a roll set at 100 ℃, stretched 3.3 times in the film length direction while rapidly heating from both sides of the film by a radiation heater in a stretching zone length of 100mm, and then temporarily cooled. Next, both surfaces of the laminated uniaxially stretched film were subjected to corona discharge treatment in air, and a transparent, slipping-easily-adhesive layer was formed on the treated surfaces of both surfaces of the film (an aqueous coating agent containing 3 wt% of vinyl acetate/acrylic resin containing colloidal silica having a particle size of 100nm, which became an easily-slipping layer, was coated with a #4 metal rod (hereinafter, coating is referred to as the above description)).

The laminated uniaxially stretched film was guided to a tenter, preheated with hot air at 90 ℃ and then stretched at 140 ℃ by 3.3 times in the film width direction. The drawing speed and temperature are set to be constant. The stretched biaxially stretched film was directly subjected to heat treatment in a tenter with hot air at 220 ℃, followed by 2% relaxation treatment in the width direction under the same temperature condition, and then wound, to thereby obtain a laminate film. The obtained laminated film showed the physical properties shown in table 1. The thickness of the laminated film was 30 μm, and the light transmittances at wavelengths of 410nm and 440nm were 18% and 88%, respectively, due to the absorption effect of the added ultraviolet absorber, and the target values were satisfied. The thickness was slightly large and the uv absorber content was 10 wt%, so the haze was slightly high, but the visibility was good when the film was mounted on a display. The 85 ℃ 85% RH promoted the change in haze value in the wet heat resistance test to 1.7%, indicating a high value, but not a change to such an extent that visibility at the time of mounting the display deteriorated.

Comparative example 1

In example 1, a film was produced in the same manner as in example 1 without adding an ultraviolet absorber to the layer B containing the thermoplastic resin B as the main component. Although a colorless and transparent laminated film was obtained, since it did not have a light-ray cutoff performance in the ultraviolet region, ultraviolet rays were transmitted when mounted on a display, and deterioration of contents such as a polarizing plate was remarkably confirmed. A film is not suitable as a display member for the purpose of protecting contents from external ultraviolet rays.

Comparative example 2

A laminated film was obtained in the same manner as in example 1, except that in example 1,2 different kinds of thermoplastic resins were laminated by using a feed block having 3 slits, and 3 layers were alternately laminated at a lamination ratio of 0.5. The absorption performance of the obtained laminated film by the ultraviolet absorber was equivalent to that of example 1, and thus the light transmittance at wavelengths of 410nm and 440nm was achieved. On the other hand, the haze value in the accelerated wet heat resistance test was very highly varied, and whitening of the laminated film was observed even by visual observation, and thus the film was not suitable for display applications requiring high transparency.

(example 2)

An acrylic resin having a melting point of 230 ℃ was used as the thermoplastic resin a, and an acrylic resin B having a melting point of 210 ℃ and containing acrylic elastomer particles was added to the triazine-based ultraviolet absorber described in example 1 so as to be 10 wt% based on the entire resin composition constituting the laminate film, was used as the thermoplastic resin B. The prepared thermoplastic resin a and thermoplastic resin B were fed into 2 single-screw extruders, respectively, and the former was melted at 270 ℃ and the latter was melted at 250 ℃, and a laminate in which 5 layers were alternately laminated in the thickness direction at a lamination ratio of 0.5 was produced in the same manner as in example 1. The laminate was cooled so that both surfaces thereof were completely bonded to a stainless steel polishing roll (70 ℃ C.), thereby obtaining an acrylic resin film having a film thickness of 30 μm. The obtained multilayer film had optical properties that could be used for display applications, although the uv absorber added in the accelerated heat resistance test was likely to precipitate on the surface because the resin was amorphous, and was slightly whitened compared to example 1.

(example 3)

In example 1, a laminated film having a thickness of 30 μm in which 501 layers were alternately laminated in the thickness direction was prepared by laminating thermoplastic resins with a feed block having 501 slits, and the lamination ratio was 1.0. The transmission electron microscope observation of the obtained multilayer film confirmed that the a layer was 251 layers and the B layer was 250 layers, which were alternately stacked in the thickness direction, and the multilayer layer thickness distribution had 2 inclined structures. Furthermore, the inclined structure has the following layer thickness profile: the layer thickness linearly increases from one surface side of the film toward the center of the film, and then linearly decreases from the center toward the opposite side of the film. As the ultraviolet absorber to be added to the thermoplastic resin B, the same triazine-based ultraviolet absorber as in example 1 was used, and the addition concentration was 10 wt% with respect to the resin composition constituting the B layer containing the thermoplastic resin B as a main component. The film stretching conditions and the like were carried out by the method described in example 1. The obtained multilayer film has a reflection performance associated with the multilayer structure, but is slightly thin, and therefore, the long-wavelength end of the reflection wavelength range is about 390nm, and the cutoff at the wavelength of 410nm depends on the concentration of the ultraviolet absorber added. Since the multilayer structure is used, it is not confirmed that the ultraviolet absorber volatilizes from the die, and the increase in Δ haze in the wet heat resistance test is also suppressed, and the ultraviolet absorber has a performance that can be used for display applications.

(example 4)

A laminated film was obtained in the same manner as in example 3 except that in example 3, a laminated film having a thickness of 31 μm was formed and the ultraviolet absorber was added to the thermoplastic resin B at a concentration of 3 wt%. By increasing the thickness by 1 μm, the long wavelength end of the reflection wavelength range is shifted to about 405nm, and the light transmittance at a wavelength of 410nm shows 6%, and the object can be achieved even if the addition concentration of the ultraviolet absorber is reduced. The purple hue due to slight reflection was strongly observed, but the visibility of the display was not significantly deteriorated, and the display had a performance that could be suitably used.

Comparative example 3

A laminated film was obtained in the same manner as in example 3, except that the concentration of the ultraviolet absorber added to the thermoplastic resin B in example 3 was changed to 3 wt%. Since the ultraviolet absorption property is poor, the light transmittance at a wavelength of 410nm shows 62%. The present laminated film is mounted on a display, and a test for content protection by ultraviolet irradiation is performed, and deterioration of the content is confirmed, and therefore, the laminated film is not suitable for a film for the purpose of content protection of a display.

(example 5)

A laminated film was obtained in the same manner as in example 4, except that the thickness was changed to 30.5 μm in example 4. The long wavelength end of the reflection wavelength range was shifted to around 397nm, and the light transmittance at a wavelength of 410nm was 48%. Although the cut-off property at a wavelength of 410nm was inferior to that of example 4, the effect was sufficiently exhibited in protecting the contents from deterioration by incorporating the display. Further, the reflection wavelength range is shifted to a short wavelength, whereby the reflection hue is considerably suppressed, and the reflection of violet is hardly observed when the display device is mounted.

(example 6)

In example 1, 251 resin layers were stacked by a feed block having a number of 251 slits to form a 12 μm thick laminated film in which 251 layers were alternately stacked in the thickness direction at a lamination ratio of 0.5. The obtained multilayer film was observed by a transmission electron microscope to confirm that the a layer was 126 layers and the B layer was 125 layers, and the layers were alternately stacked in the thickness direction, and the multilayer layer thickness distribution had 2 inclined structures. The formulation for adding the ultraviolet absorber and the stretching conditions of the film were carried out by the method described in example 1. The obtained laminated film has a long wavelength end in the reflection wavelength range of about 395nm and an average light reflectance of 380 to 410nm as low as about 12%, and the addition concentration of the ultraviolet absorber is increased to satisfy the cutoff property of 410 nm. Due to the multilayer structure, a result is obtained in which the bleeding phenomenon from the die is suppressed. The delta haze after the accelerated wet heat resistance test was also about 1.3%, and it was suppressed as compared with example 1Low, suitable as a film for display-oriented purposes. In addition, the bending rigidity is as low as 3.6X 10^-9Even if the bending resistance test is performed, the display panel is not damaged or wrinkled at all, and can be sufficiently applied to display applications requiring bending.

Comparative example 4

In example 6, a laminated film was obtained in the same manner as in example 6 except that a benzotriazole-based ultraviolet absorber (2, 2' -methylenebis (4- (1,1,3, 3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol) having a molecular weight of 650g/mol was added in place of the triazine-based ultraviolet absorber so as to be 10 wt% based on the resin composition constituting the B layer containing the thermoplastic resin B as a main component.

(example 7)

A laminated film was obtained in the same manner as in example 6, except that the thickness was set to 12.3 μm in example 6. By slightly increasing the thickness, it was confirmed that the long-wavelength end of the reflection wavelength range was shifted to the vicinity of 405nm, and even if the concentration of the ultraviolet absorber was reduced, the cut-off property was sufficiently obtained by reflection. The other properties were the same as those of example 6, and the film was suitable for display applications.

(example 8)

In example 6, the film stretching conditions were the same as in example 6 except that the triazine-based ultraviolet absorber having a molecular weight of 700g/mol described in example 1 was added to the thermoplastic resin B in an amount of 9.0 wt% based on the thermoplastic resin B as a formulation for adding the ultraviolet absorber. Since the number of layers was 251 layers, it was confirmed that the effect of multiple interference reflection was obtained, and even when the additive concentration was suppressed, the ultraviolet ray cut-off performance could be achieved as intended. It was confirmed that the amount of acceleration of the change in the haze value in the wet heat resistance test was also lower than in example 2 by the decrease in the addition concentration.

(example 9)

In example 6, a laminated film was obtained in the same manner as in example 6 except that a triazine-based ultraviolet absorber having a molecular weight of 510g/mol (2- (4, 6-diphenyl-s-triazine-2-yl) -5- (2- (2-ethylhexanoyloxy) ethoxy) phenol) was added so as to be 2.0 wt% with respect to the resin composition constituting the B layer containing the thermoplastic resin B as the main component, and a triazine-based ultraviolet absorber having a molecular weight of 700g/mol as described in example 1 was added so as to be 7.0 wt% with respect to the resin composition constituting the B layer containing the thermoplastic resin B as the main component. The former triazine-based ultraviolet absorber has a maximum wavelength of 285nm, and has improved light-blocking performance in the ultraviolet region, and therefore can block ultraviolet rays more strongly, and is suitable as an optical film for a display for protecting contents from ultraviolet rays, as compared with example 6.

(example 10)

A multilayer film was obtained in the same manner as in example 6 except that in example 6, as the ultraviolet absorber added, 2.0 wt% of a benzotriazole-based ultraviolet absorber (2, 2' -methylenebis (4- (1,1,3, 3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol) having a molecular weight of 650g/mol was used with respect to the resin composition constituting the B layer containing a thermoplastic resin B as the main component, and 7.0 wt% of a triazine-based ultraviolet absorber having a molecular weight of 700g/mol was used with respect to the resin composition constituting the B layer containing a thermoplastic resin B as the main component, the former benzotriazole-based ultraviolet absorber had a maximum wavelength of 346nm, and in the same manner as in example 9, in example 6, and example 6, In example 7, the light transmittance in the ultraviolet region was lower and the ultraviolet cut-off property was more excellent than that in example 7. When a benzotriazole-based film is used, the amount of haze change in the wet heat resistance test tends to be slightly increased, but the film has sufficient performance to be used as an optical film for a display.

(example 11)

A laminated film was obtained in the same manner as in example 10 except that the thickness of the laminated film was set to 12.3 μm in example 10, and the concentration of the benzotriazole-based ultraviolet absorber and the concentration of the triazine-based ultraviolet absorber added to the thermoplastic resin B were set to 0.7 wt% and 2.3 wt%, respectively. By using the reflection effect by the laminated structure and the absorption effect of the ultraviolet absorber in combination, the concentration of the ultraviolet absorber to be added can be reduced, and the Δ haze in the humidity resistance acceleration test can be significantly reduced.

(example 12)

A multilayer film was formed in the same manner as in example 6 except that in example 6, as the ultraviolet absorber to be added, a benzotriazole-based ultraviolet absorber (2- (5-chloro-2H-benzotriazol-2-yl) -6-tert-butyl-4-methylphenol) having a molecular weight of 315g/mol was added in an amount of 4.0 wt% with respect to the resin composition constituting the B layer containing a thermoplastic resin B as a main component, and a triazine-based ultraviolet absorber having a molecular weight of 700g/mol as described in example 1 was added in an amount of 4.0 wt% with respect to the resin composition constituting the B layer containing a thermoplastic resin B as a main component. The benzotriazole-based ultraviolet absorber used in the present example was excellent in ultraviolet cut-off ability on the long wavelength side, and the object was achieved even when the concentration of the triazine-based ultraviolet absorber added was reduced. However, as compared with example 6, the transmittance in the ultraviolet region on the lower wavelength side was lost, and the haze value in the reliability test was also slightly increased. The film is a highly transparent laminated film suitable for an optical film for a display, and has good visibility when mounted on the display.

(example 13)

A multilayer film was obtained in the same manner as in example 6 except that in example 6, azomethine-based ultraviolet absorber having a molecular weight of 250g/mol and a maximum absorption wavelength of 378nm was added so as to be 2.0 wt% with respect to the resin composition constituting the B layer containing thermoplastic resin B as a main component as an ultraviolet absorber, and triazine-based ultraviolet absorber having a molecular weight of 700g/mol described in example 1 was added so as to be 1.0 wt% with respect to the resin composition constituting the B layer containing thermoplastic resin B as a main component. The former azomethine compound mainly absorbs visible short wavelength region, and the latter triazine ultraviolet absorber absorbs ultraviolet region, so that transmittance cut-off in wavelength region of 410nm or less can be realized at a relatively low concentration. The optical properties are as shown in Table 1, and the film is a highly transparent laminated film suitable for display applications.

(example 14)

A laminated film was obtained in the same manner as in example 6 except that in example 6, polyethylene terephthalate was used as the thermoplastic resin a, the triazine-based ultraviolet absorber having a molecular weight of 700g/mol described in example 1 was added so as to be 2.0 wt% with respect to the resin composition containing the thermoplastic resin a as a main component, and further, in the thermoplastic resin B, the triazine-based ultraviolet absorber described in example 1 was added so as to be 6.0 wt% with respect to the resin composition constituting the layer B containing the thermoplastic resin B as a main component, and the lamination ratio was designed so as to be 1.0. Even when a small amount of about 2.0 wt% was added to the a layer comprising the thermoplastic resin a of the outermost layer, no significant increase in haze was observed in the accelerated wet heat resistance test. In addition, compared with example 6 in which only the B layer was added, the amount of ultraviolet absorption increased due to the effect of increasing the optical path length by multiple interference reflection between layers, and the same effect was obtained even at a low addition concentration by adding the two resins.

(example 15)

A multilayer film was obtained in the same manner as in example 6, except that in example 6, the ultraviolet absorber was not added, the indole-based coloring matter having a maximum wavelength in a short wavelength region of visible light exceeding 380nm and not more than 430nm was added to the thermoplastic resin B so as to be 4.0 wt% with respect to the resin composition constituting the B layer containing the thermoplastic resin B as a main component, and the lamination ratio was designed to be 1.0. The ultraviolet ray cut-off in the wavelength region of 300 to 380nm is weaker than that in the examples so far, but the target cut-off performance is exhibited by utilizing the reflection effect, corresponding to the absence of the ultraviolet absorber. Even when the liquid crystal display device is mounted for display use, it is confirmed that the liquid crystal and the light-emitting layer are not significantly deteriorated and can be suitably used.

(example 16)

A multilayer film was obtained in the same manner as in example 15, except that in example 15, as the pigment having the maximum wavelength in the short wavelength region of visible light exceeding 380nm and not more than 430nm, the naphthalimide-based pigment having the maximum wavelength of 382nm was added in an amount of 3.5 wt% based on the resin composition constituting the B layer containing the thermoplastic resin B as the main component. The naphthalimide-based dye has a very good cut-off property at a wavelength of 410nm, and in addition to this, the dye exhibits a very good cut-off property, with some omission of transmittance at 300 to 380 nm.

(example 17)

In example 15, a laminated film was obtained in the same manner as in example 15 except that the indole-based coloring matter used in example 15 was added as an ultraviolet absorber to the thermoplastic resin B so that the content of the triazine-based ultraviolet absorber having a molecular weight of 700g/mol described in example 1 was 2.0 wt% and 1.0 wt%, respectively, as the coloring matter having a maximum wavelength in a short wavelength region of visible light exceeding 380nm and not more than 430 nm. By combining 2 kinds of absorbers that cut off different wavelength regions, wavelength cut-off at a low concentration can be effectively achieved.

(example 18)

In example 17, a laminated film was obtained in the same manner as in example 17 except that the triazine-based ultraviolet absorber having a molecular weight of 700g/mol described in example 1 and the benzotriazole-based ultraviolet absorber having a molecular weight of 650g/mol described in example 7 were mixed as the ultraviolet absorbers to be added to the thermoplastic resin B, and the amounts thereof were 1.4 wt% and 0.6 wt%, respectively, based on the resin composition constituting the B layer containing the thermoplastic resin B as a main component. The obtained laminated film had a slightly higher haze value variation in the long-term reliability test than that of example 17, but had sufficient performance as a film for display applications.

(example 19)

A laminated film was obtained in the same manner as in example 18 except that in example 18, the thickness of the laminated film was set to 12.2 μm and the concentration of the indole-based coloring matter added to the thermoplastic resin B was reduced to 0.5 wt%. Since the long-wavelength end of the reflection wavelength range of the obtained laminated film is located in the vicinity of 400nm, the absorption of the dye and the reflection by the laminated structure are used in combination, and the desired ultraviolet cut-off property can be effectively achieved.

(example 20)

In example 17, a laminated film was obtained in the same manner as above except that the addition concentration of the triazine-based ultraviolet absorber to the thermoplastic resin B was decreased to 1.0 wt% and the addition concentration of the indole-based coloring matter was increased to 2.0 wt%. Although the light transmittance in the ultraviolet region is higher than that of the above-described examples, the multilayer film is a multilayer film in which the target cut-off property is sufficiently achieved.

(example 21)

In example 17, a laminated film was obtained in the same manner as in example 17, except that the concentration of the triazine-based ultraviolet absorber added was set to 5.0 wt%, and a phthalocyanine-based coloring matter having a maximum wavelength of 420nm was used as the coloring matter having a maximum wavelength in a short wavelength region of visible light exceeding 380nm and not more than 430 nm. The phthalocyanine-based dye can sharply cut off light having a wavelength of 400 to 440nm, and the transmittance of light having a wavelength of 440nm is 80%, which is barely satisfactory as a target value. On the other hand, although it is necessary to increase the concentration of the ultraviolet absorber added in order to cut ultraviolet rays having a wavelength of 400nm, the amount of haze change in the reliability test is not particularly remarkable, and a multilayer film suitable for display applications is obtained.

(example 22)

A hard coat agent containing an indole dye having a maximum wavelength in a short wavelength region of visible light exceeding 380nm and not more than 430nm was applied to the laminated film produced in example 17, thereby obtaining a laminated sheet having a hard coat layer laminated thereon. Indole-based coloring matter is dissolved in methyl ethyl ketone, and then added to the hard coat layer main agent so as to be 4.0 wt% with respect to the resin composition constituting the hard coat layerThe methyl ethyl ketone solvent was added so that the total solid content concentration became 30%, thereby preparing a hard coat agent. The hard coat layer was applied to one surface of the laminated film so that the thickness of the hard coat layer became 2 μm. After coating, drying in an oven at 80 deg.C for 1-2 min to volatilize methyl ethyl ketone solvent, and irradiating with ultraviolet ray to obtain 180mJ/cm²The ultraviolet irradiation was performed in the same manner as above, and the objective laminated sheet was obtained. Since the obtained laminate sheet had the hard coat layer having high crosslinkability on the outermost surface, the deposition of oligomers and additives in the laminate film was also reduced, and the variation in haze value in the wet heat resistance test was promoted to be smaller than in example 17 in which the hard coat layer was not applied. In addition, the dimensional stability is also good, and the display device is suitable for display application.

(example 23)

A laminated sheet was obtained in the same manner as in example 17, except that in example 22, an anthraquinone-based dye having a maximum absorption wavelength of 406nm was added as a dye having a maximum wavelength in a short wavelength region of visible light exceeding 380nm and not more than 430nm to the hard coat agent in an amount of 10 wt% based on the resin composition constituting the hard coat layer. Although the anthraquinone-based coloring matter is slightly poor in absorption performance and is likely to cause surface precipitation by the addition of a high concentration, it is not confirmed that the coloring matter is remarkably whitened after a long-term reliability test and has stability for a long period of time, and thus it can be judged that the coloring matter is suitable for display applications.

(example 24)

A laminated sheet was obtained in the same manner as in example 22 except that in example 22, a pigment having a maximum wavelength in a short wavelength region of visible light exceeding 380nm and not more than 430nm was added as a hindered amine light stabilizer to the hard coat agent so that LA-72 manufactured by Adeka was 0.5 wt% based on the resin composition constituting the hard coat layer. By adding a light stabilizer, the deterioration of the contents when mounted on the display can be prevented longer than in example 22.

(example 25)

In example 24, in addition to the light stabilizer, a phosphorus-based/phenol-based mixed antioxidant a-612 manufactured by Adeka as an antioxidant and a nickel quencher SEESORB612NH manufactured by converting シプロ as a singlet oxygen quencher were added in an amount of 0.3 wt% and 4 wt% respectively with respect to the resin composition constituting the hard coat layer. A laminated sheet was obtained in the same manner as in example 24, except that toluene was used as the solvent instead of methyl ethyl ketone, and after the hard coating agent was applied, drying was performed for 3 minutes by a hot-air furnace at 110 ℃. The long-term stability of the indole-based coloring matter against light irradiation was improved by the combined use of the light stabilizer, the antioxidant and the singlet oxygen quencher as compared with example 24, and the examples to which the indole-based coloring matter has been added so far were laminated sheets having the best long-term light resistance. The basic optical properties were equivalent to those of example 24.

(example 26)

In example 24, a laminated film was obtained in the same manner as in example 24 except that the benzotriazole-based ultraviolet absorber having a molecular weight of 650g/mol and the triazine-based ultraviolet absorber having a molecular weight of 700g/mol used in example 18 were added to the resin composition constituting the layer B containing the thermoplastic resin B as a main component in an amount of 0.6 wt% and 1.4 wt%, respectively, so that the thickness of the laminated film was 12.2 μm. The present inventors have confirmed that the amount of haze change after a long-term reliability test is slightly increased because the benzotriazole-based ultraviolet absorber has high deposition properties, but the multilayer sheet is not so high as to deteriorate visibility when mounted on a display, and is therefore sufficiently usable for display applications.

(example 27)

A laminated sheet was obtained in the same manner as in example 17 except that in example 22, a 12.2 μm thick laminated film was produced, and 3.0 wt% and 6.0 wt% of the indole-based dye having a maximum wavelength in a short wavelength region of visible light exceeding 380nm and not more than 430nm and the anthraquinone-based dye having a maximum wavelength of 406nm used in example 22 were added to the resin composition constituting the hard coat layer, respectively. By the combination of pigments, the cut-off at 410nm is improved and the light transmission at 440nm is improved, the most preferred sharp cut-off is achieved in the embodiments so far. In addition, the haze fluctuation amount after the reliability test is also small, and the film is suitable for a film for display applications.

(example 28)

In example 4, a multilayer film was produced with the concentration of the triazine-based ultraviolet absorber added being 1.0 wt%. A hard coat layer containing an indole-based dye and a light stabilizer was formed on one surface of the obtained laminate film in the same manner as in example 24 to form a laminate film. The multilayer sheet can be obtained as a result of enhancing the reflection of the wavelength in the ultraviolet region and improving the cutoff performance in the ultraviolet region, and has a durable performance even in long-term ultraviolet irradiation. The presence of the multilayer laminated structure and the hard coat layer results in very little deposition of the ultraviolet absorber and/or the dye having the maximum wavelength in the visible light short wavelength region exceeding 380nm and not more than 430nm, and the fluctuation amount of the haze is greatly suppressed.

(example 29)

In example 5, the concentration of the triazine-based ultraviolet absorber added was set to 1.4 wt%, and the benzotriazole-based ultraviolet absorber having a molecular weight of 650g/mol used in example 10 was further added to the resin composition constituting the layer B containing the thermoplastic resin B as a main component by 0.6 wt%, to obtain a laminated film. A hard coat agent containing a benzylidene dye having a maximum wavelength of 381nm as a dye having a maximum wavelength in a short wavelength region of visible light exceeding 380nm and not more than 430nm was applied to the obtained laminated film, thereby obtaining a laminated sheet having a hard coat layer laminated thereon. Specifically, a benzylidene dye was dissolved in methyl ethyl ketone, and then added so as to be 1.0 wt% with respect to the resin composition constituting the hard coat layer, and further, 0.5 wt% of the hindered amine light stabilizer used in example 24 was added, and a methyl ethyl ketone solvent was added so that the final total solid content concentration became 30%, to prepare a hard coat agent. The hard coat layer was applied to one surface of the laminated film so that the thickness thereof became 5 μm. After coating, drying in an oven at 80 deg.C for 1-2 min to volatilize methyl ethyl ketone solvent, and irradiating with ultraviolet ray to obtain 180mJ/cm²The ultraviolet irradiation was performed to cure the film, and the intended laminated sheet was obtained. The obtained laminated sheet has suppressed reflection hue, satisfies a desired light transmittance, and can prevent deterioration of the contents for a long period of time even when mounted on a display. In addition, the hard coat layer was also thick, and the Δ haze in the wet heat resistance acceleration test was also 0.5, which was significantly suppressed, and had properties that could be sufficiently used as an optical film for display applications.

(example 30)

A laminated sheet was obtained in the same manner as in example 26 except that in example 26, 4.0 wt% of the indole dye used in example 17 was added as the dye having the maximum wavelength in the short-wavelength region of visible light exceeding 380nm and not more than 430nm, and 0.3 wt% of the phosphorus-based/phenol-based mixed antioxidant a-612 used in example 25 was added as the antioxidant. The basic performance of the laminated sheet was equivalent to that of example 26, but the content protection during the ultraviolet irradiation was continued for a longer period of time.

(example 31)

A laminated sheet was obtained in the same manner as in example 30, except that in example 30, the indole-based coloring matter was added at a concentration of 2.0 wt%, and the photostabilizer and the antioxidant were added at concentrations of 0.25 wt% and 0.15 wt%, respectively, and the hard coat layer was applied to both sides of the laminated film. By laminating a hard coat layer on both sides, it was hardly confirmed that the haze increase in the wet heat resistance test was promoted, and the film was suitable for a longer-term use for a display.

(example 32)

In example 30, a hard coat layer to which no coloring matter was added was provided on one surface of the laminate film so that the thickness thereof became 2 μm. Further, an acrylic optical adhesive containing 0.4 wt% indole dye was applied to the surface of the laminate film opposite to the hard coat layer so as to have a thickness of 20 μm by a bar coater. After the adhesive is applied, the laminate is dried in an oven at 100 ℃ for 2 to 3 minutes and further subjected to aging treatment in a hot air oven at 40 ℃ for 2 days to obtain an adhesive-attached laminate. The optical properties of the adhesive-carrying laminate were equivalent to those of example 30. When the laminate sheet is bonded to a display, the pigment is located on the adhesive layer on the inner side of the display than the laminate film, and therefore, the pigment is subjected to the ultraviolet ray cut-off performance of the laminate sheet, resulting in further increase in the light stability of the pigment. The most preferable embodiment is the one in all embodiments from the viewpoint of long-term protection of the contents of the display.

[ Table 1]

TABLE 1

[ Table 2]

[ Table 3]

[ Table 4]

[ Table 5]

[ Table 6]

Industrial applicability

The laminated film of the present invention is excellent in ultraviolet ray cutoff property and visible light transmittance for light having a sharp cutoff wavelength of 410nm or less, and therefore can improve visibility and prevent deterioration due to ultraviolet rays. Therefore, the laminated film of the present invention can be suitably used as a film incorporated in an image display device such as a liquid crystal display. Further, the film is suitably used for a window film in applications requiring ultraviolet cut, for example, building materials and automobiles, a film for laminating a steel sheet to a signboard and the like in industrial material applications, a process film and a release film for a photo-etching material in electronic device applications, and further a film for food, medicine, and agricultural applications.

Claims

1. A laminated film comprising 5 or more layers of a layer A comprising a thermoplastic resin A as a main component and a layer B comprising a thermoplastic resin B different from the thermoplastic resin A as a main component, wherein the layer A and/or the layer B contain an ultraviolet absorber having a maximum absorption wavelength of 320 to 380nm and a triazine skeleton,

the maximum value of the light transmittance of the laminated film under the wavelength of 300-380 nm is less than 3%, the light transmittance of the laminated film under the wavelength of 410nm is less than 40%, and the light transmittance under the wavelength of 440nm is more than 80%.

2. The laminate film according to claim 1, wherein the average light reflectance at a wavelength of 380 to 410nm is 20% or more.

3. The laminate film according to claim 1 or 2, wherein the ultraviolet absorber further has a benzotriazole skeleton and/or a benzotriazole

A ketone skeleton.

4. The laminate film according to claim 1 or 2, wherein the layer A and/or the layer B contains a dye having a maximum wavelength in a short-wavelength region of visible light of more than 380nm and 430nm or less.

5. The laminate film according to claim 4, wherein the pigment having a maximum wavelength in a short-wavelength region of visible light of more than 380nm and 430nm or less has a triazine skeleton.

6. The laminate film according to claim 4, wherein the coloring matter having a maximum wavelength in a short-wavelength region of visible light of more than 380nm and 430nm or less has at least 1 skeleton selected from azomethine, indole, quinone, naphthalimide, phthalocyanine and benzylidene.

7. The laminate film according to claim 1 or 2, wherein Mn is a sum of contents of the ultraviolet absorber and the coloring matter having the maximum wavelength in a short wavelength region of visible light exceeding 380nm and not more than 430nm in a certain layer of the laminate film, and Tn is a layer thickness of the layer, Σ (Mn × Tn) which is a sum of the contents and a product of the layer thickness is not more than 50 wt% μm for all layers of the laminate film, the unit of Mn is weight%, and the unit of Tn is μm.

8. The laminate film according to claim 1 or 2, which contains the hindered amine light stabilizer in an amount of 0.01 to 1 wt% based on the total weight of the film.

9. The laminate film according to claim 1 or 2, wherein 51 or more layers of A and B are alternately laminated.

10. The laminate film according to claim 1 or 2, wherein the thermoplastic resin A and the thermoplastic resin B are polyester resins.

11. The laminate film as claimed in claim 1 or 2, having a bending rigidity per unit length of 1.0 x 10^-7N·m²The following.

12. The laminate film according to claim 1 or 2, which has a delta haze of 1.0% or less when treated at 85 ℃ and 85% RH for 250 hours.

13. A laminated film as claimed in claim 1 or 2, which is used for display applications.

14. A laminate sheet comprising a C layer on at least one side of the laminate film according to any one of claims 1 to 13, wherein the C layer is a hard coat layer containing a curable resin C as a main component.

15. A laminate sheet having: the laminate film according to any one of claims 1 to 13; and an adhesive layer containing an ultraviolet absorber and/or a dye having maximum absorption in a short wavelength region of visible light exceeding 380nm and not more than 430 nm.

16. A laminate sheet having: the laminate of claim 14; and an adhesive layer containing an ultraviolet absorber and/or a pigment having a maximum wavelength in a visible light short-wavelength region exceeding 380nm and not more than 430 nm.

17. A laminate according to any one of claims 14 to 16 for use in a display.