KR102655116B1 - laminated film - Google Patents

Abstract

It is a thin film that suppresses deterioration due to ultraviolet rays without bleed-out during film formation and stabilizes the quality and color tone of the display over a long period of time. It provides a highly transparent laminated film. A film in which five or more layers are alternately laminated with a layer containing thermoplastic resin A as a main component (layer A) and a layer containing a thermoplastic resin B different from the thermoplastic resin A (layer B) alternately, and is exposed to light at a wavelength of 410 nm. It is a laminated film with a transmittance of 60% or less and a light transmittance of 80% or more at a wavelength of 440 nm.

Description

laminated film

The present invention relates to a laminated film with excellent ultraviolet ray cutting properties and visible light transmittance.

Thermoplastic resin films, especially biaxially stretched polyester films, have excellent mechanical properties, electrical properties, dimensional stability, transparency, and chemical resistance, and are widely used as base films in many applications such as magnetic recording materials and packaging materials. It is used. In particular, in the field of flat panel displays, touch panels, and vehicle panel displays, the trend toward lower costs, thinner displays, miniaturization, and flexibility is rapidly progressing, and demand for various thin-film optical films is increasing.

Optical films mounted on displays include, for example, polarizer protective films, transparent conductive films, and retardation films in liquid crystal display applications. Films used for these applications require ultraviolet ray cutting properties to prevent deterioration of liquid crystal molecules or the polarizer (PVA) in the polarizer due to ultraviolet rays penetrating from the outside or contained in backlight light. In order to impart ultraviolet ray cutting properties to a film, a method of adding an ultraviolet absorber is generally used (Patent Document 1). However, when ultraviolet rays are cut by adding an ultraviolet absorber, a bleed-out phenomenon occurs near the spinneret or vacuum vent during film formation, depending on the type or amount of ultraviolet absorber added. As a result, contamination occurs in the film forming process, defects occur in the film, the actual concentration of ultraviolet absorber is lowered, and cut performance is weakened, which causes problems that impair the quality of the film itself. In particular, when a thin film optical film performs the same as a current optical film, the absorption performance is expressed as the product of the thickness of the film and the addition concentration, so the addition of a high concentration of ultraviolet absorber cannot be avoided, leading to contamination of the film forming equipment and harsh reliability tests. Later, the quality deterioration due to precipitation of the absorbent on the film surface becomes significant.

Additionally, in the case of displays displayed outdoors, such as in-vehicle displays or digital signage, it is required to cut ultraviolet rays more strongly in the wavelength range of 300 nm to 380 nm. When using a general ultraviolet absorber that is specialized for cutting performance in the wavelength band of 380 nm or less, a method of adding an excessive amount of ultraviolet absorber is used to strongly cut light around 380 nm with a wavelength that is not advantageous to the ultraviolet absorber. , in the case of thin films, problems such as whitening due to excessive addition of absorbent or deterioration of quality due to precipitation of absorbent on the film surface after severe reliability tests occur. In particular, in the case of a single-film film structure or a low number of layers, the mechanism for preventing precipitation of the absorbent is insufficient, and the problem of quality deterioration in reliability tests becomes significant. The above problem can be solved because the concentration of the absorbent can be reduced by increasing the thickness, but it causes the problem that the thickness of the image display device increases, contrary to the market's demands for miniaturization and thinning.

In order to cut light around a wavelength of 380 nm, one method is to use a dye having a maximum absorption wavelength on the longer wavelength side than 380 nm. However, depending on the type of pigment, it absorbs a wide range of visible light and causes undesirable coloration in the film itself, which worsens visibility when mounted on a display. Therefore, wavelengths below 410 nm are strongly cut, and wavelengths below 410 nm are strongly cut. It is necessary to sharply cut the light beam in the wavelength range up to 430 nm (Patent Documents 2 to 4). To prevent coloring when cutting light with a wavelength longer than 430 nm, there is a method of using a fluorescent whitening agent as an absorber as described in Patent Document 4, but when used for display purposes, the film itself turns blue when irradiated with ultraviolet rays. Because it emits fluorescence, it causes a problem that significantly deteriorates the quality of the display.

In addition, the film mounted on the display must not only maintain optical quality such as color in reliability tests, but also maintain mechanical properties such as thickness. If the film shrinks due to heat treatment, resulting in an increase in thickness, the absorption performance of ultraviolet absorbers or pigments increases, causing the problem of undesirable coloring.

Japanese Patent Publication No. 2013-210598 Japanese Patent Publication No. 2010-132846 Japanese Patent Publication No. 2014-115524 Japanese Patent Publication No. 2008-238586

Therefore, the present invention solves the above drawbacks and provides a highly transparent laminated film with excellent ultraviolet ray cutting properties and visible light transmittance that can maintain optical performance, including color and haze, even in long-term reliability tests without bleed-out during film formation. The purpose is to

The present invention consists of the following configuration. in other words,

A film in which five or more layers are alternately laminated with a layer containing thermoplastic resin A as a main component (layer A) and a layer containing a thermoplastic resin B different from the thermoplastic resin A (layer B) alternately, and is exposed to light at a wavelength of 410 nm. It is a laminated film characterized by a transmittance of 60% or less and a light transmittance of 80% or more at a wavelength of 440 nm.

(Effects of the Invention)

By using a laminated structure, the laminated film of the present invention maintains color tone over a long period of time even when mounted on an image display device without bleeding out various additives, including ultraviolet absorbers, when forming the film, and has the effect of displaying images with high quality. indicates.

Hereinafter, the laminated film of the present invention will be described in detail.

The laminated film of the present invention is a film in which five or more layers are alternately laminated with a layer (layer A) mainly composed of thermoplastic resin A and a layer (layer B) mainly composed of thermoplastic resin B different from the thermoplastic resin A, and the wavelength It is necessary that the light transmittance at 410 nm be 60% or less and the light transmittance at a wavelength of 440 nm be 80% or more.

Thermoplastic resins in the present invention include, for example, polyethylene, polypropylene, poly(1-butene), poly(4-methylpentene), polyisobutylene, polyisoprene, polybutadiene, polyvinylcyclohexane, polystyrene, Polyolefin resins such as poly(α-methylstyrene), poly(p-methylstyrene), polynorbornene, polycyclopentene, and polyamide resins such as nylon 6, nylon 11, nylon 12, and nylon 66. Resin, ethylene/propylene copolymer, ethylene/vinylcyclohexane copolymer, ethylene/vinylcyclohexene copolymer, ethylene/alkyl acrylate copolymer, ethylene/acrylic methacrylate copolymer, ethylene/norbornene copolymer, ethylene/ Copolymer resins of vinyl monomers such as vinyl acetate copolymer, propylene/butadiene copolymer, isobutylene/isoprene copolymer, vinyl chloride/vinyl acetate copolymer, polyacrylate, polymethacrylate, and polymethyl methacrylate. Acrylic resins such as crylate, polyacrylamide, and polyacrylonitrile; polyester resins such as polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, and polyethylene-2,6-naphthalate; Polyether resins represented by polyethylene oxide, polypropylene oxide, and polyacrylene glycol, and cellulose esters represented by diacetylcellulose, triacetylcellulose, propionylcellulose, butyrylcellulose, acetylpropionylcellulose, and nitrocellulose. Biodegradable polymers such as resin, polylactic acid, polybutylsuccinic acid, polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, polyvinyl butyral, polyacetal, polyglycolic acid, polycarbonate, polyketone, poly Ether sulfone, polyether ether ketone, modified polyphenylene ether, polyphenylene sulfide, polyetherimide, polyimide, polysiloxane, tetrafluoroethylene resin, trifluoroethylene resin, trifluoroethylene chloride resin, tetrafluoroethylene-hexafluoride Propylene copolymer, polyvinylidene fluoride, etc. can be used.

The thermoplastic resin used in the present invention is preferably a synthetic polymer, and more preferably polyolefin-based, acrylic-based, polyester-based, cellulose ester-based, polyvinyl butyral, polycarbonate, or polyether sulfone. Among them, polyethylene, polypropylene, polymethyl methacrylate, polyester, and triacetylcellulose are particularly preferable. In addition, these may be used individually or as a blend of two or more types of polymers or polymer alloys.

Thermoplastic resin B must not be the same thermoplastic resin as thermoplastic resin A, but must be a resin with a different refractive index. When using the light cut by reflection described later, the wavelength of the reflected light is determined to be one based on the layer thickness of the laminated resin and the difference in refractive index of the two different thermoplastic resins. Therefore, when the same refractive index is used, light reflection does not occur at the thermoplastic resin interface. Since two types of parameters, the layer thickness of the resin and the refractive index difference, must be controlled in order to reflect light of a specific wavelength, it is difficult to uniformly determine only the refractive index difference, but the difference in refractive index between thermoplastic resin A and thermoplastic resin B is 0.01 or more. It is preferable, more preferably 0.03 or more, and even more preferably 0.05 or more. Additionally, it is preferable that these different thermoplastic resins A and B thermoplastic resins not only have different refractive indices but also have different thermal properties. Different thermal properties mean different melting points or glass transition temperatures in differential scanning calorimetry (DSC). By having different melting points and glass transition temperatures, it becomes possible to highly control the orientation state of each layer in the process of stretching and heat treating the laminated film. By being able to control the orientation state to a high degree, it becomes possible to control the reflected light wavelength by controlling the refractive index in the in-plane and perpendicular directions of each thermoplastic resin layer. In particular, it is preferable that the glass transition temperature or melting point, which affects the orientation state of the resin in the stretching process, differs by 0.1°C or more between thermoplastic resin A and thermoplastic resin B. Among the thermoplastic resins described above, it is preferable that at least one of thermoplastic resin A and thermoplastic resin B is made of a polyester resin from the viewpoints of strength, heat resistance, transparency, and versatility. In addition, from the viewpoint of adhesion and lamination, it is most preferable to select polyester resins for both thermoplastic resin A and thermoplastic resin B. Below, embodiments of polyester resin, which is a preferred film substrate, will be described.

Polyester in the present invention is an axial polymer obtained by polymerization from monomers containing aromatic dicarboxylic acid or aliphatic dicarboxylic acid and diol as main components. As an industrial production method for polyester, transesterification reaction (transesterification method) or direct esterification reaction (direct polymerization method) is used as is known. Here, examples of aromatic dicarboxylic acids include terephthalic acid, isophthalic acid, phthalic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, and 4-naphthalenedicarboxylic acid. , 4'-diphenyl dicarboxylic acid, 4,4'-diphenyl ether dicarboxylic acid, 4,4'-diphenyl sulfone dicarboxylic acid, etc. Examples of aliphatic dicarboxylic acids include adipic acid, suberic acid, sebacic acid, dimer acid, dodecanedioic acid, 1,4-cyclohexanedicarboxylic acid, and their ester derivatives. Among them, terephthalic acid and 2,6-naphthalenedicarboxylic acid, which exhibit high refractive index, are preferably used. As for the dicarboxylic acid component, one type of these may be used, or two or more types may be used in combination.

In addition, as diol components, for example, ethylene glycol, 1,2-propanediol, 1,3-propanediol, neopentyl glycol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1 ,6-hexanediol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, diethylene glycol, triethylene glycol, polyalkylene glycol, 2,2- Bis(4-hydroxyethoxyphenyl)propane, isosorbate, spiroglycol, etc. can be mentioned. Among them, ethylene glycol is preferably used. These diol components may be used alone or in combination of two or more types.

In addition, polyester resins include, for example, polyethylene terephthalate and its copolymers, polyethylene naphthalate and its copolymers, polybutylene terephthalate and its copolymers, polybutylene naphthalate and its copolymers, and polyhexamethylene. Terephthalate and its copolymers, polyhexamethylene naphthalate and its copolymers, etc. can also be used. At this time, as the copolymerization component, it is preferable that one or more of the dicarboxylic acid component and diol component are copolymerized.

Alternately laminated in the present invention means that layers A, mainly composed of thermoplastic resin A, and layers B, mainly composed of thermoplastic resin B, are laminated in a regular arrangement in the thickness direction, A(BA)n(n refers to a state in which the resin is laminated according to a regular arrangement of natural numbers. When forming a laminated film of A(BA)n (n is a natural number), multiple resins of thermoplastic resin A and thermoplastic resin B are sent out from different flow paths using two or more extruders, and a multi-many, a known lamination device, is used. A fold type feed block or static mixer can be used. In particular, in order to efficiently obtain the structure of the present invention, a method of using a feed block with fine slits is preferable for realizing high-precision lamination. When forming a laminate using a slit-type feed block, the thickness of each layer and its distribution can be achieved by changing the length or width of the slit to incline the pressure loss. The length of the slit is the length of the comb teeth that form a flow path for alternately flowing the A layer and the B layer within the slit plate.

The thermoplastic resin A in the present invention is preferably a thermoplastic resin that exhibits crystallinity because it is located in the outermost layer of the laminated film as described above. In this case, it is preferable because it becomes possible to obtain a laminated film in the same manner as the film forming process for a single film made of a crystalline thermoplastic resin. If the thermoplastic resin A is made of, for example, an amorphous resin, when obtaining a biaxially stretched film in the same manner as a general sequential biaxially stretched film described later, film forming defects or surface defects may occur due to adhesion to manufacturing equipment such as rolls or clips. Problems such as sexual deterioration may occur.

From the above, it is preferable to use the thermoplastic resin A as a crystalline polyester-based polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, or polybutylene naphthalate. Among them, it is preferable to use polyethylene terephthalate or polyethylene naphthalate from the viewpoint of easy realization of a high-precision laminated structure even during 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 adhesion and stackability with the thermoplastic resin A. Here, the basic skeleton is a repeating unit that constitutes the resin, and in the case of polyethylene terephthalate, ethylene terephthalate is the basic skeleton, and in the case of polyethylene naphthalate, ethylene naphthalate is the basic skeleton. By having the same skeleton, the stacking precision is high, and interlayer separation (delamination) at the stacking interface becomes less likely to occur. Regarding polyethylene terephthalate, while polyethylene naphthalate tends to orient the polymer in the plane direction, it is more likely to cause delamination between layers, so from the viewpoint of a laminated film, it is more preferable to use polyethylene terephthalate as the basic skeleton.

In the case of using polyethylene terephthalate as the basic skeleton, thermoplastic resin B, which is different from thermoplastic resin A, has a polyethylene terephthalate skeleton and is designed to contain copolymerization components that do not constitute the basic skeleton to an extent that they do not become the main component, or the amount of copolymerization components. It is preferable that it is designed to be different from the amount of the copolymerization component contained in the thermoplastic resin A. Suitable copolymerization components when using polyethylene terephthalate as the basic skeleton include cyclohexanedimethanol, bisphenol A ethylene oxide, spiroglycol, isophthalic acid, cyclohexanedicarboxylic acid, naphthalenedicarboxylic acid, polyethylene glycol 2000, m- Examples include polyethylene glycol 1000, m-polyethylene glycol 2000, m-polyethylene glycol 4000, m-polypropylene glycol 2000, bisphenylethylene glycol fluorene (BPEF), fumaric acid, acetoxybenzoic acid, etc. Among them, those copolymerized with spiroglycol, isophthalic acid, or 2,6-naphthalenedicarboxylic acid are preferable. When spiroglycol is copolymerized, the glass transition temperature difference with polyethylene terephthalate is small, so it is difficult to overextend during molding and delamination between layers is also difficult to occur. In addition, isophthalic acid can greatly reduce crystallinity because the position of the functional group in the benzene ring is not linear, and on the other hand, because it has high planarity, it is possible to exhibit a high overall refractive index.

The number of layers in the laminated film of the present invention is required to be 5 or more. As described later, in the present invention, in order to achieve a specific wavelength cut, it is preferable to add an ultraviolet absorber and/or a pigment with a maximum wavelength that is maximum in the short wavelength region of visible light above 380 nm and below 430 nm. However, by using a layered structure, the surface of the additive Precipitation can be suppressed. In particular, when the thermoplastic resin is crystalline, the crystalline layer is preferable because it forms a densely packed layer by grounding the molecular structure and serves as a cover to suppress precipitation of various additives present therein. There is no upper limit to the number of layers, but as the number of layers increases, the manufacturing cost increases due to an increase in the size of the manufacturing equipment, and the handling properties deteriorate due to the film thickness becoming thicker. In particular, increasing the film thickness increases retardation, and when used as a display material, it is undesirable because it causes coloring of the film such as interference color or rainbow stains. In reality, 1000 layers or less is suitable.

Retardation is generally calculated from the product of the maximum value of the refractive index difference in two orthogonal directions within the plane of the film and the film thickness, but in the case of a laminated film such as the present invention, the refractive index as a film cannot be easily measured. The value of the retardation calculated in an indirect way is taken as the retardation. Specifically, the values measured with the KOBRA series, a phase difference measuring device manufactured by Oji Scientific Instruments Co., Ltd. that measures retardation by an optical method, are used. For example, consider the case of use in a display equipped with a polarizing plate of linearly polarized light as an optical film used in a display. If the retardation value is high and the orientation of the resin is not uniform within the plane of the laminated film, the polarization state varies within the plane due to the influence of retardation, resulting in interference colors or rainbow spots when mounted on a liquid crystal display. The problem of reduced visibility arises. Therefore, in the present invention, when a crystalline thermoplastic resin that develops orientation by stretching or crystallization is included, it is preferable to make the film thickness as thin as possible to reduce retardation. On the other hand, it is also desirable to design the orientation angle of the laminated film to be low by strongly stretching it in a specific direction. When mounting a display, the laminated film is bonded so that the optical axis of the transmitted light from inside the display and the orientation direction of the laminated film are in the same direction or orthogonal to each other, so that even when the retardation is relatively high, there is no unevenness within the film plane, resulting in rainbow stains. Problems such as reduced visibility do not occur. When lowering the orientation angle of the laminated film, 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. If the orientation angle in the width direction of the laminated film exceeds 10°, depending on the size of the display to be bonded, not only will rainbow spots be observed due to the orientation angle changing within the display surface, but polarization performance will be impaired. This is not desirable. don't do it In addition, the orientation angle here is set to 0° in the film width direction.

The laminated film of the present invention needs 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 410 nm, when the laminated film of the present invention is used for display purposes, deterioration of the internal liquid crystal layer and polarizer in the liquid crystal display may occur, and light emitting elements such as organic EL displays may be damaged. In displays that have this, deterioration or deterioration of the light emitting layer cannot be effectively prevented. The light transmittance at a wavelength of 410 nm is preferably 40% or less, more preferably 30% or less, and still more preferably 20% or less. It is possible to protect the display contents from ultraviolet rays by setting the light transmittance at a wavelength of 410 nm to 60% or less. However, by reducing the light transmittance at a wavelength of 410 nm to 40% or less, more preferably to 20% or less, longer-term protection is possible. It becomes possible to prevent it. On the other hand, when the light transmittance at a wavelength of 410 nm exceeds 20% and is below 60%, in addition to being able to protect the contents of the display from deterioration compared to the past, when light cutting is achieved using reflection, Since the reflected color caused by the light reflected on the viewer side can be suppressed, it becomes possible to make black more vivid when the display is not displayed.

It is more preferable that the laminated film of the present invention exhibits a light transmittance of 20% or less in the wavelength range of 380 to 395 nm, which is the short wavelength range of visible light. Even if the light transmittance at a wavelength of 410 nm is low, there is a high possibility that photodeterioration will be accelerated if the light in the above wavelength range, which has stronger energy than the light with a wavelength of 410 nm, is not cut. More preferably, it is 15% or less, and even more preferably, it is 10%.

It is more preferable that the laminated film of the present invention exhibits a maximum light transmittance of 10% or less in the ultraviolet ray region with a wavelength of 300 nm to 380 nm. Regarding the ultraviolet region with a wavelength of 300 nm to 380 nm, the light energy is strong, and since this is a wavelength region greatly involved in the deterioration of important parts of image display such as polarizers, liquid crystals, and light-emitting elements inside the display, it is desirable to cut the light sufficiently. . For example, the polarizer used in a liquid crystal image display device has the function of transmitting light with only a specific vibration direction, and polyvinyl alcohol (PVA)-based films dyed with iodine or dichroic dye are most often used. there is. This polarizer is made of organic materials, and deterioration occurs especially when it receives strong ultraviolet rays with energy in the wavelength range of 280 to 380 nm. Therefore, by shielding ultraviolet rays in this area just before they reach the polarizer, deterioration of the polarizer or liquid crystal occurs. It becomes possible to prevent molecular deterioration. In this regard, the maximum light transmittance in the wavelength range of 300 nm to 380 nm is 5% or less, and more preferably 2% or less.

The laminated film of the present invention needs to have a light transmittance of 80% or more at a wavelength of 440 nm. If the light transmittance at a wavelength of 440 nm is less than 80%, light in the short wavelength range of visible light is cut, so the laminated film itself appears strongly yellow and cannot exhibit excellent transparency. Additionally, in display applications using blue light-emitting elements, light rays originating from the blue light-emitting elements are cut, leading to deterioration of color tone when displaying images. The light transmittance at a wavelength of 440 nm is preferably 85% or more, and more preferably 90% or more.

The laminated film of the present invention preferably has an average light reflectance of 20% or more at a wavelength of 380 to 410 nm. It is possible to reflect light of a specific wavelength depending on the thickness of each layer of alternately laminated resin layers and the difference in refractive index between the two different types of resin. In addition, by changing the thickness distribution of the lamination layer, the reflecting wavelength band can be expanded or contracted or the light reflectance can be improved, and the lamination ratio can be freely shifted by changing the thickness while remaining constant. At this time, by controlling the laminated layer thickness distribution, it is possible to design the cutting edge of the reflection band to be sharp or gentle. When the cutting edge of the reflection band is designed to be sharp, an excellent sharp cut can be achieved compared to when general ultraviolet absorbers or dyes/pigments are added, and undesired light cuts can be prevented, allowing selective wavelength cutting. It can be suitably used for this required material. The average light reflectance is more preferably 25% or more, and even more preferably 30% or more.

Since the reflected wavelength depends on the layer thickness, it fluctuates sensitively under the influence of slight changes in film thickness in units of 0.1㎛. Therefore, if the long-wavelength end of the reflection band is designed to be located around 440 nm, there is a possibility that the thickness increases by a small amount, cutting a wavelength range that is not originally desired. Considering the risk of fluctuations in the reflection wavelength range, the reflection wavelength range is designed to be between 300 nm and 410 nm, and the light in the wavelength range of 380 to 430 nm is maximally applied to the visible short wavelength range of 380 nm to 430 nm, which will be described later. A more preferable embodiment is to perform cutting in combination with absorption by a dye having the maximum wavelength.

The laminated layer thickness distribution includes a layer thickness distribution that increases or decreases from one side of the film toward the opposite side, a layer thickness distribution that increases and then decreases from one side of the film toward the center of the film, or a layer thickness distribution that increases or decreases from one side of the film toward the center of the film. A layer thickness distribution in which the layer thickness decreases and then increases from toward the center of the film is desirable. As a method of changing the layer thickness distribution, it is preferable to change it in a continuous manner such as linear, geometric, or sequential sequence, but it is preferable that about 10 to 50 layers have substantially the same layer thickness, and that the layer thickness changes in a step shape.

It is preferred that the laminated film of the present invention contain an ultraviolet absorber and/or a dye having a maximum wavelength that is maximum in the visible light short wavelength range of more than 380 nm and less than or equal to 430 nm. The ultraviolet absorber in the present invention refers to an additive having a maximum wavelength that is maximum in the ultraviolet ray range of 300 to 380 nm. In the present invention, the maximum wavelength refers to the peak wavelength that has the maximum absorbance when it has a plurality of maximum peaks. The ultraviolet absorber and the dye having a maximum wavelength that is maximum in the short wavelength region of visible light between 380 nm and 430 nm or less may have the ability to absorb part of each other's region. For example, in the case of an additive having a maximum at 375 nm and 390 nm, if the maximum at 375 nm is the maximum, it is an ultraviolet absorber, and if the maximum at 390 nm is the maximum, it is an ultraviolet light absorber in the short wavelength range of visible light above 380 nm and below 430 nm. It is defined as a pigment with the maximum wavelength.

In the present invention, one or more types of ultraviolet absorbers or pigments having a maximum wavelength that is maximum in the short wavelength range of visible light between 380 nm and 430 nm may be contained individually, and one or more types of ultraviolet absorbers and one or more types of pigments greater than 380 nm and 430 nm may be included. A dye having a maximum wavelength that is maximum in the short wavelength region of visible light of nm or less may be simultaneously contained. The ultraviolet absorber and/or the dye having the maximum wavelength that is maximum in the short wavelength region of visible light between 380 nm and 430 nm or less may be contained in only the A layer or the B layer, or may be contained in both the A layer and the B layer. In particular, from the viewpoint of suppressing surface precipitation due to the multilayer structure, it should be contained only in the B layer located on the inner layer of the laminated film, or the concentration of the B layer located on the inner layer of the laminated film will be higher than that of the A layer located on the outermost layer. It is desirable to increase it. When only layer A, which includes the outermost layer, contains an ultraviolet absorber and a dye with a maximum wavelength in the short wavelength range of visible light between 380 nm and 430 nm, a phenomenon in which the contained ultraviolet absorber precipitates on the film surface (bleed-out phenomenon) ) and the phenomenon of sublimation and volatilization in the vicinity of the spinneret may easily occur, which may contaminate the film forming machine and cause the precipitates to have adverse effects such as the occurrence of defects in the film forming process.

Ultraviolet absorbers are generally specialized in their ability to absorb ultraviolet rays in the wavelength range of 380 nm or less, near the boundary between the ultraviolet and visible ray regions (around 380 to 400 nm) or in the visible short wavelength range (400 to 430 nm). The ability to absorb light is not excellent. Therefore, in order to cut rays near the boundary between the ultraviolet ray region and the visible ray region (near 380-400 nm) or in the short-wavelength visible ray region (400-430 nm) just by containing an ultraviolet absorber, some long-wavelength ultraviolet ray absorption, which will be described later, is excluded. Therefore, it is necessary to contain it in high concentration. In the case of wavelength cuts in the ultraviolet region and visible light short wavelength region (380 nm to 430 nm), examples of ultraviolet absorbers that can be achieved by a single ultraviolet absorber include 2-(5-chloro-2H-benzotriazol-2-yl) -6-tertiary butyl-4-methylphenol and 2,4,6-tris(2-hydroxy-4-hexyloxy-3-methylphenyl)-1,3,5-triazine.

On the other hand, pigments with a maximum wavelength in the visible short-wavelength range of 380 nm to 430 nm generally have excellent cutting performance in the visible short-wavelength range, but are inferior in cutting ability in the ultraviolet range. Therefore, in order to cut the rays of the ultraviolet region by containing only pigments with a maximum wavelength in the short-wavelength region of visible light between 380 nm and 430 nm and below, some of the pigments that are maximum in the short-wavelength region of visible light between 380 nm and 430 nm and below are described later. It is necessary to exclude pigments with the maximum wavelength and contain them in high concentration. In addition, when it is contained in a high concentration, excellent transparency cannot be realized because it absorbs the visible light region of a longer wavelength than the target wavelength region. As a dye having a maximum wavelength in the visible light short wavelength range of more than 380 nm and less than or equal to 430 nm, which can independently achieve wavelength cuts in the ultraviolet region and visible light short wavelength range (380 nm to 430 nm), for example, those made by BASF Japan Ltd. 'LumogenF Violet 570', etc. can be mentioned. Since ultraviolet absorbers and pigments with maximum wavelengths in the short wavelength region of visible light above 380 nm and below 430 nm each have advantageous regions, in order to prevent bleed-out due to high concentration addition and subsequent process contamination, 1 It is more desirable to effectively combine one or more types of ultraviolet absorbers and one or more types of dyes with a maximum wavelength that is maximum in the short wavelength region of visible light between 380 nm and 430 nm.

In the laminated film of the present invention, it is used to achieve the above-described light transmittance by combining one or more types of ultraviolet absorbers and one or more types of dyes with a maximum wavelength that is maximum in the short wavelength region of visible light between 380 nm and 430 nm. As possible ultraviolet absorbers, in addition to the two types of ultraviolet absorbers mentioned above, various kinds of skeletal ultraviolet absorbers, including benzotriazole-based, benzophenone-based, benzoate-based, triazine-based, benzooxazinone-based, and salicylic acid-based, can be used. When two or more types of ultraviolet absorbers are used together, ultraviolet absorbers of the same type may be combined, or ultraviolet absorbers of different types may be combined. Specific examples are given below, but (※) is added after the compound name for compounds that exist in the wavelength range where the maximum wavelength is 320 nm to 380 nm. The ultraviolet absorber in the present invention is preferably an ultraviolet absorber having a maximum absorption wavelength between 320 and 380 nm. When the maximum wavelength is less than 320 nm, it is difficult to sufficiently cut the ultraviolet ray region on the long wavelength side, and even when combined with a dye that has a maximum wavelength that is maximum in the short wavelength region of visible light above 380 nm and below 430 nm, the wavelength is 300 nm. In the area of ~380 nm, there are many cases where an area with insufficient cut showing a light transmittance of 10% or more is created. Therefore, in order to keep the maximum light transmittance in the ultraviolet region of 300 to 380 nm wavelength below 10%, it is preferable to use an ultraviolet absorber with (※).

The benzotriazole-based ultraviolet absorber is not particularly limited, but examples include 2-(2'-hydroxy-5'-methylphenyl)benzotriazole (※), 2-(2'-hydroxy-3',5'- Diese 3 butylphenyl)benzotriazole (※), 2-(2'-hydroxy-3',5'-Diese 3 butylphenyl)-5-chlorobenzotriazole (※), 2-(2'-hydroxy Roxy-3'-tertiary butyl-5'-methylphenyl)benzotriazole (※), 2-(2'-hydroxy-3'-tertiary butyl-5'-methylphenyl)-5-chlorobenzotriazole ( ※), 2-(2'-hydroxy-3',5'-dize 3 amylphenyl)-5-chlorobenzotriazole (※), 2-(2'-hydroxy-3'-(3", 4",5",6"-tetrahydrophthalimidemethyl)-5'-methylphenyl)-benzotriazole (※), 2-(5-chloro-2H-benzotriazol-2-yl)-6- Tertiary butyl-4-methylphenol (※), 2,2'-methylenebis(4-(1,1,3,3-tetramethylbutyl)-6-(2H-benzotriazol-2-yl)phenol (※), 2-(2'-hydroxy-3',5'-dise tertiary pentylphenyl)benzotriazole, 2-(2'-hydroxy-5'-tertiary octylphenyl)benzotriazole, 2 ,2'-methylenebis(4-tertiary octyl-6-benzotriazolyl)phenol (※), 2-(5-butyloxy-2H-benzotriazol-2-yl)-6-tertiary butyl-4 -Methylphenol (※), 2-(5-hexyloxy-2H-benzotriazol-2-yl)-6-tertiary butyl-4-methylphenol (※), 2-(5-octyloxy-2H -benzotriazol-2-yl)-6-tertiary butyl-4-methylphenol (※), 2-(5-dodecyloxy-2H-benzotriazol-2-yl)-6-tertiary butyl- 4-methylphenol (※), 2-(5-octadecyloxy-2H-benzotriazol-2-yl)-6-tertiary butyl-4-methylphenol (※), 2-(5-cyclohexane Siloxy-2H-benzotriazol-2-yl)-6-tert-butyl-4-methylphenol (※), 2-(5-propenoxy-2H-benzotriazol-2-yl)-6- Tertiary butyl-4-methylphenol (※), 2-(5-(4-methylphenyl)oxy-2H-benzotriazol-2-yl)-6-tertiary butyl-4-methylphenol (※), 2 -(5-Benzyloxy-2H-benzotriazol-2-yl)-6-tertiary butyl-4-methylphenol (※), 2-(5-hexyloxy-2H-benzotriazol-2-yl )-4,6-Diaze 3 butylphenol (※), 2-(5-octyloxy-2H-benzotriazol-2-yl)-4,6-Diase 3 butylphenol (※), 2-(5- dodecyloxy-2H-benzotriazol-2-yl)-4,6-di 3 butylphenol (※), 2-(5-di 2 butyloxy-2H-benzotriazol-2-yl)-4, 6-dize 3 butylphenol (※), etc. can be mentioned.

The benzophenone-based ultraviolet absorber is not particularly limited, and examples include 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-octoxybenzophenone, 2, 2'-dihydroxy-4-methoxy-benzophenone (※), 2,2'-dihydroxy-4,4'-dimethoxy-benzophenone, 2,2',4,4'-tetrahydride Roxy-benzophenone, 5,5'-methylenebis(2-hydroxy-4-methoxybenzophenone), etc. can be mentioned.

There is no particular limitation on the benzoate-based ultraviolet absorber, and examples include resorcinol monobenzoate, 2,4-dieze, 3-butylphenyl-3,5-dieze, 3-butyl-4-hydroxybenzoate, and 2,4-dieze. 3 Amylphenyl-3,5-Diaze 3 Butyl-4-hydroxybenzoate, 2,6-Diaze 3 Butylphenyl-3',5'-Diaze 3 Butyl-4'-hydroxybenzoate, Hexadecyl-3 , 5-dize 3 butyl-4-hydroxybenzoate, octadecyl-3,5-dize 3 butyl-4-hydroxybenzoate, etc.

The triazine-based ultraviolet absorber is not particularly limited, but includes 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-diviphenyl-s-triazine , 2,4-diphenyl-6-(2-hydroxy-4-methoxyphenyl)-s-triazine, 2,4-diphenyl-6-(2-hydroxy-4-ethoxyphenyl)- s-triazine, 2,4-diphenyl-6-(2-hydroxy-4-propoxyphenyl)-s-triazine, 2,4-diphenyl-6-(2-hydroxy-4-part Toxyphenyl)-s-triazine, 2,4-bis(2-hydroxy-4-octoxyphenyl)-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-octoxyphenyl)-s-triazine ( ※), 2-(4-isooctyloxycarbonylethoxyphenyl)-4,6-diphenyl-s-triazine (※), 2-(4,6-diphenyl-s-triazine-2- 1)-5-(2-(2-ethylhexanoyloxy)ethoxy)phenol, etc. are mentioned.

The benzoxazinone-based ultraviolet absorber is not particularly limited, but includes 2,2'-p-phenylenebis(4H-3,1-benzoxazin-4-one)(※), 2,2'-p-phenylene Bis(6-methyl-4H-3,1-benzoxazin-4-one), 2,2'-p-phenylenebis(6-chloro-4H-3,1-benzoxazin-4-one) (※), 2,2'-p-phenylenebis(6-methoxy-4H-3,1-benzoxazin-4-one), 2,2'-p-phenylenebis(6-hydroxy -4H-3,1-benzoxazin-4-one), 2,2'-(naphthalene-2,6-diyl)bis(4H-3,1-benzoxazin-4-one) (※), 2,2'-(naphthalene-1,4-diyl)bis(4H-3,1-benzoxazin-4-one)(※), 2,2'-(thiophene-2,5-diyl)bis (4H-3,1-benzoxazine-4-one) (※), etc. can be mentioned.

Other ultraviolet absorbers include salicylic acid-based, such as phenyl salicylate, t-butylphenyl salicylate, and p-octylphenyl salicylate, and others include natural product-based (e.g., oryzanol, shea butter, and Baikal). lin, etc.), biological systems (e.g., keratinocytes, melanin, urocanin, etc.) can also be used. Inorganic ultraviolet absorbers are not compatible with the base resin and lead to an increase in haze, which worsens visibility when displaying images, so it is not desirable to use them in laminated films for display purposes.

The ultraviolet absorber used in the present invention may have the same basic chemical structure as the above-mentioned ultraviolet absorber, but replace the oxygen atom with the same type of sulfur atom. Specifically, you may use one in which an ether group is converted into a thioether group, a hydroxyl group is converted into a mercapto group, and an alkoxy group is converted into a thio group. By using an ultraviolet absorber containing a substituent having a sulfur atom, thermal decomposition of the ultraviolet absorber can be suppressed when heated and kneaded into a resin. In addition, by using sulfur atoms and selecting an appropriate alkyl chain, it is possible to suppress intermolecular forces between ultraviolet absorbers and lower the melting point, thus improving compatibility with thermoplastic resins. By increasing compatibility, it becomes possible to maintain transparency, an important factor in optical films, even when added in high concentration.

In addition, the ultraviolet absorber used in the present invention preferably has a maximum absorption wavelength in the wavelength range of 320 to 380 nm, and the alkyl chain of the functional group constituting the ultraviolet absorber is preferably long. As the alkyl chain becomes longer, intermolecular interactions are suppressed and ring structure packing becomes difficult to occur, making it difficult for ultraviolet absorbers to form a crystal structure when the film is heat treated, which leads to suppressing whitening of the film. The length of the alkyl group included in the functional group is preferably 18 or less, more preferably 4 or more and 10 or less, and still more preferably 6 or more and 8 or less. If the length of the alkyl chain is longer than necessary, it is not realistic because the reaction point is buried within the molecule, resulting in a decrease in the absorption rate of the ultraviolet absorber.

The ultraviolet absorber may be mixed with the thermoplastic resin as an additive, or may be copolymerized by reacting with the terminal group or side chain of the thermoplastic resin. By copolymerizing and fixing the film with the thermoplastic resin that makes up the film, bleed-out due to molecular thermal movement during heating can be suppressed, making it possible to maintain ultraviolet ray cut performance over a long period of time while maintaining transparency.

In the laminated film of the present invention, it is used to achieve the above-described light transmittance by combining one or more types of ultraviolet absorbers and one or more types of dyes with a maximum wavelength that is maximum in the short wavelength region of visible light between 380 nm and 430 nm. As a dye having a maximum wavelength that is maximum in the short wavelength range of visible light between 380 nm and 430 nm, other than the dyes that have a maximum wavelength that is maximum in the short wavelength range of visible light between 380 nm and 430 nm or less described above can be used. In the present invention, as a dye having a maximum wavelength in the visible light short wavelength region of more than 380 nm and less than 430 nm, a dye that is soluble in a solvent and has excellent saturation can be used for the purpose of addition to the hard coat layer or adhesive layer described later. Alternatively, you may use a pigment that has better heat resistance, heat-and-moisture resistance, and light resistance than dye. Pigments can be roughly divided into organic pigments, inorganic pigments, and classical pigments, but it is preferable to use organic pigments from the viewpoint of compatibility with the thermoplastic resin to be added. There is no particular limitation on the structure of the pigment having the maximum wavelength that is maximum in the short wavelength range of visible light above 380 nm and below 430 nm, but it includes β-naphthol series, naphthol AS series, acetoacetic acid arylamide series, acetoacetic acid arylamide series, pyrazolone series, Azo series such as β-oxynaphthoic acid series, copper phthalocyanine series, halogenated copper phthalocyanine series, phthalocyanine series such as metal-free phthalocyanine and copper phthalocyanine lake, other azomethine series, aniline series, alizarin series, anthraquinone series, isoindolinone series, etc. Isoindoline, isoquinoline, phosphorus, indole, quinacridone, quinophthalone, coumarin, dioxadine, thioindigo, naphthalimide, nitrone, perinone, perylene, Benzylidine series and natural organic pigments can be mentioned.

As described above, it is more preferable for a dye to have a maximum wavelength in the short wavelength range of visible light between 380 nm and 430 nm to have a maximum wavelength in the range of 390 nm to 420 nm. If a dye having a maximum wavelength in a wavelength region longer than 430 nm is selected, the light transmittance at 440 nm is less than 80%, which is not preferable unless a dye with a very narrow band cutting ability is selected. As a dye having a maximum wavelength in the wavelength range of 390 nm to 420 nm, azomethine-based, indole-based, quinone-based, triazine-based, naphthalimide-based, phthalocyanine-based, and benzylidine-based dyes can be preferably used.

The ultraviolet absorber used in the present invention and/or the dye having a maximum wavelength that is maximum in the visible short wavelength range of more than 380 nm and less than or equal to 430 nm preferably has a triazine skeleton. Triazine-based absorbents generally have high thermal decomposition temperatures and excellent heat resistance, so they are unlikely to cause deterioration even when exposed to heat for a long time in an extruder where they are kneaded into resin. In addition, it can be preferably used because it has the effect of making it difficult for the absorbent itself to volatilize or precipitate on the surface, and to make it difficult for oligomers or other highly sublimable additives to precipitate. In addition, because the absorption coefficient is high, the addition concentration required to achieve the desired cutting performance is also reduced, which is useful in that it reduces the possibility of contaminating the film forming process even when discharged in the form of a sheet from the spinneret.

When the laminated film of the present invention contains an ultraviolet absorber and/or a pigment having a maximum wavelength in the short wavelength region of visible light between 380 nm and 430 nm or less, the ultraviolet absorber and/or 380 nm contained in a specific layer of the laminated film When the sum of the content of the pigment with the maximum wavelength in the short wavelength region of visible light below 430 nm is Mn [weight%], and the layer thickness of the added layer is Tn [㎛], the sum of the above contents and the layer thickness are It is preferable that Σ (Mn If it is greater than 50 [weight%·㎛], the light transmittance decreases and the white turbidity (haze value) of the film increases, which may be undesirable because it may cause problems of worsening visibility when mounted on a liquid crystal image display device, etc. Since the total content varies depending on the film thickness and the light absorption capacity of various additives, a lower limit is not set, but as mentioned above, it is used to protect ultraviolet rays, such as polarizers, liquid crystal molecules, and light-emitting layers required for optical films used in image display devices. The amount of addition sufficient to provide sufficient cut performance is required.

The thermoplastic resin in the present invention contains various additives other than ultraviolet absorbers and pigments with the maximum wavelength in the short wavelength range of visible light between 380 nm and 430 nm, such as antioxidants, heat stabilizers, weather stabilizers, and organic lubricants. Agents, organic or inorganic fine particles, fillers, antistatic agents, nucleating agents, etc. may be added to the extent that they do not deteriorate the film properties that must originally be satisfied. In particular, in applications where optical performance is required to be maintained even when exposed to light for a long period of time, a dye with a linear color may be used among the dyes with a maximum wavelength that is maximum in the short wavelength range of visible light above 380 nm and below 430 nm. Compared to ultraviolet absorbers or pigments, they tend to lose their absorption performance when exposed to high-energy ultraviolet rays. Therefore, it is desirable to use a compound that converts the energy held by ultraviolet rays into vibrational energy within the molecule, converts the converted vibrational energy into heat energy, etc., and emits it to the outside. In addition, it is also desirable to use additives that suppress photooxidation degradation such as antioxidants or singlet oxygen radicals through energy conversion.

The light stabilizer is mainly added to capture radicals generated by photo-oxidation, and it is preferably contained in an amount of 0.01% by weight or more and 1% by weight or less based on the total weight of the film for the laminated film of the present invention. In particular, hindered amine compounds having a 2,2,6,6-tetramethyl-piperidine ring are preferred, and the 1st position of piperidine is hydrogen, an alkyl group, an alkoxy group, a hydroxy group, or an oxyradical group (-O· ), an acyloxy group, or an acyl group, and the 4th position is more preferably a hydrogen atom, a hydroxy group, an acyloxy group, an amino group that may have a substituent, an alkoxy group, or an aryloxy group. Moreover, it is also preferable to have a plurality of 2,2,6,6-tetramethyl-piperidine rings in one molecule. Examples of such compounds include TINUVIN 770DF, TINUVIN 152, and TINUVIN 123 manufactured by BASF Japan Ltd. (formerly Ciba Specialty Chemicals Co., Ltd.) and ADK STAB LA-72 and ADK STAB LA-81 manufactured by ADEKA CORPORATION. You can.

In the laminated film of the present invention, light stability can be further improved by using an antioxidant and/or a singlet oxygen radical in addition to the hindered amine light stabilizer. Photodegradation of pigment occurs through an oxidation reaction, but auto-oxidation involves radical generation as oxygen molecules function as oxidants, and singlet oxygen oxidation occurs when oxygen enters a single oxidation state because the excitation energy of the pigment propagates to oxygen molecules. , oxidation by superoxide ion, etc. It is possible to further suppress these oxidation reactions by using together an antioxidant or a tea for releasing excitation energy.

The antioxidant that must be used in combination with the light stabilizer is not particularly limited as long as it is a commonly used antioxidant, but phosphorus-based antioxidants and phenol-based antioxidants can be preferably used. In addition, since the effect of the antioxidant can be maintained for a long time by using the phosphorus-based antioxidant and the phenol-based antioxidant in combination, it is preferable to use the combination system appropriately. The addition concentration of the antioxidant is preferably 0.01% by weight or more and 1% by weight or less, and more preferably 0.05% by weight or more and 0.3% by weight or less. If it is 0.01% by weight or less, the effect as an antioxidant will fade, and if it is more than 1% by weight, there is a possibility that volatilization of the antioxidant may occur due to excessive addition.

Singlet oxygen radicals that must be used in combination with a light stabilizer are compounds that can deactivate singlet oxygen by transferring energy from oxygen in the singlet oxidation state, for example, ethylene-based compounds such as tetramethylethylene and cyclopentene, Amines such as ethylamine, triethylamine, and N-ethylimidazole, condensed polycyclic aromatic compounds such as substituent naphthalene, dimethylnaphthalene, dimethoxyanthracene, anthracene, and diphenylanthracene, and 1,3-diphenylisobenzofuran. In addition to aromatic compounds such as , 1,2,3,4-tetraphenyl-1,3-cyclopentadiene, and pentaphenylcyclopentadiene, metal complexes serving as ligands can also be mentioned. Metal complex compounds include transition metal coordination complex compounds such as nickel complexes, cobalt complexes, copper complexes, manganese complexes, and platinum complexes that have structures such as bisdithio-α-diketone, bisphenyldithiol, and thiobisphenol as ligands. I can hear it. The above singlet oxygen radical is preferably added in an amount of 0.5 wt% to 10 wt%, more preferably 1 wt% to 8 wt%, based on the added amount of the absorbent subject to oxidation degradation. In addition, it is most preferable to use three types of light stabilizers in combination with antioxidants and singlet oxygen radicals because they can effectively prevent oxidative degradation caused by radicals.

In the laminated film of the present invention, it is preferable that 51 or more layers of thermoplastic resin A and thermoplastic resin B are alternately laminated. As described above, by alternately stacking resins with different optical properties, it becomes possible to generate interference reflection that can reflect light of a specific wavelength due to the relationship between the difference in refractive index of each layer and the layer thickness. In addition, since multiple interference reflection effects occur between layers for light rays of wavelengths in the interference reflection area, the light travels through an optical path length longer than the film thickness, so the ultraviolet absorber and/or the visible light short wavelength range of more than 380 nm and less than 430 nm are used. When a dye or the like having a maximum wavelength is added, the absorption amount increases, making it possible to suppress the amount of ultraviolet absorber added compared to a normal laminated film without an interference reflection effect. Using the effect of multiple interference reflections, it is possible to suppress the addition of various additives to a small amount by targeting the ultraviolet region and/or the short-wavelength visible light region, and to suppress bleed out during film formation or improve quality after long-term reliability testing, which is the object of the present invention. It holds up well. The number of layers of the laminated film of the present invention is more preferably 200 layers or more, and still more preferably 400 layers or more. The interference reflection effect described above can achieve a higher reflectivity for light in the target wavelength band as the number of layers increases, so it is preferable that the number of layers increases. In addition, when the number of layers is large, it is expected that each resin will be distributed homogeneously to obtain stable film forming properties and mechanical properties. As the number of layers increases, manufacturing costs increase due to an increase in the size of the manufacturing device and handling properties deteriorate due to the film thickness becoming thicker, so in reality, 1000 layers or less is suitable.

The laminated film of the present invention preferably has a bending rigidity of 1.0×10 ^-7 [N·m2] or less per unit length. Bending stiffness is an indicator of strength against bending, and the higher the value, the harder the film is, making it more likely that folds will form when bending. The bending rigidity per unit length is expressed ^as E b: unit length [m]:, h: film thickness [m]). Since this parameter is particularly strongly influenced by the film thickness h, it shows that the thinner the film is, the more resistant it is to bending. When producing this laminated film in the biaxial stretching process described later, the bending rigidity is calculated for each of the longitudinal and width directions of the laminated film, and the higher value satisfies 1.0 × 10 ^-7 [N·m2] or less. It is required to do so. The bending rigidity is more preferably 3.0×10 ^-8 [N·m2] or less, and even more preferably 1.0×10 ^-8 [N·m2] or less.

The laminated film of the present invention preferably has a Δhaze of 2.0 or less when treated at 85°C and 85%RH for 250 hours. The 85℃ 85%RH condition is the accelerated moisture heat resistance test condition for display applications, but due to the high temperature and high humidity, the UV absorber added inside and/or the visible light short wavelength range above 380 nm and below 430 nm are maximum. Pigments with the maximum wavelength, oligomers derived from resins, etc. tend to precipitate on the film surface due to thermal movement. Under these conditions, if the haze value is not 2.0 or less, the diffused light becomes strong and the optical film itself appears white and cloudy, which worsens the light transmittance when mounted, causing problems with visibility. The haze value after the accelerated heat resistance test is more preferably 1.5 or less, and further preferably 1.0 or less.

The laminated film of the present invention cuts light not only in the ultraviolet region but also near the boundary between the ultraviolet region and the visible light region (near 410 nm), and also has high light transmittance in the visible light region, so it is suitably used as a film for display purposes. Films for display purposes include, for example, in the case of liquid crystal display devices, polarizer protection films and retardation films that constitute the polarizer, various surface treatment films placed on the front of the display with anti-glare or clear hard coats, and brightness improvement films located just before the backlight. Films, anti-reflection films, transparent conductive films, etc. can be mentioned. Additionally, in the case of an organic EL image display device, examples include a λ/4 retardation film or polarizer protection film that constitutes a circularly polarizing plate located in front of the light emitting layer, and an optical film built in for the purpose of protecting the contents from external light. In particular, when conditions such as improved light resistance and uniform orientation angle are achieved, the polarizer protective film or polarizer located on the most visible side of the polarizer is more visible than the polarizer, and is located inside the cover glass or window film on the outermost surface of the display. It is most desirable to place it in a certain area in order to protect the display contents from ultraviolet rays and maintain the polarization state. However, the laminated film of the present invention is not limited to display applications, but can be used in fields that require light cutting in the short wavelength range of visible light with a wavelength of 410 nm or less, for example, as a window film in building materials or automobile applications, and as a signboard in industrial materials applications. It is possible to use the film for the purpose of suppressing photodeterioration of the content, etc. in fields such as steel sheet laminates, photolithography material processing and release films in electronic devices, and other fields such as food, medical care, and ink.

Next, a preferred manufacturing method for the laminated film of the present invention is explained below. Of course, the present invention is not limited to these examples.

Prepare thermoplastic resin in the form of pellets, etc. The pellets are dried in hot air or under vacuum as needed and then supplied to another extruder. In the extruder, the resin that is heated and melted above the melting point is uniformized by a gear pump, etc., and foreign substances and denatured resin are removed through a filter, etc. These resins are molded into the desired shape in a die and then discharged. Then, the multi-layered 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. At this time, it is preferable to rapidly solidify the electrode by using a wire-shaped, tape-shaped, needle-shaped, or knife-shaped electrode in close contact with a cooling body such as a casting drum by electrostatic force. Additionally, a method of blowing air from a slit-shaped, spot-shaped, or surface-shaped device to rapidly solidify the material by bringing it into close contact with a cooling body such as a casting drum, or by rapidly solidifying the material by bringing it into close contact with a cooling body using a nip roll is also preferable.

Additionally, a plurality of resins, including thermoplastic resin A and thermoplastic resin B, are fed from different flow paths using two or more extruders, and are transferred to a multilayer lamination device. As a multi-layer lamination device, a multi-manifold die, feed block, static mixer, etc. can be used, but it is particularly preferable to use a feed block with fine slits in order to efficiently obtain the structure of the present invention. When such a feed block is used, the device does not have to be extremely large, so the amount of foreign matter generated due to thermal deterioration is small, and high-precision stacking is possible even when the number of stacks is extremely large. Additionally, the lamination precision in the width direction is also significantly improved compared to the prior art. Additionally, in this device, the thickness of each layer can be adjusted according to the shape (length, width) of the slit, making it possible to achieve an arbitrary layer thickness.

In this way, the molten multilayer laminate formed with the desired layer structure is guided to a die, and a casting film is obtained as described above.

It is preferable that the casting film thus obtained is continuously biaxially stretched in the longitudinal direction and the width direction. Stretching may be carried out sequentially in two directions, or may be carried out in two directions at the same time. Additionally, re-stretching may be performed in the longitudinal direction and/or the width direction.

First, the case of sequential biaxial stretching will be explained. Here, stretching in the longitudinal direction refers to stretching to provide molecular orientation in the longitudinal direction to the film, and is usually carried out by varying the peripheral speed of the rolls. This stretching may be performed in one step, or a plurality of roll pairs may be used. So it can be done in multiple steps. The stretching ratio varies depending on the type of resin, but is usually preferably 2 to 15 times, and when polyethylene terephthalate is used as one of the resins constituting the laminated film, 2 to 7 times is particularly preferably used. In addition, the stretching temperature is preferably set within the range of the glass transition temperature of the resin constituting the laminated film to the glass transition temperature + 100°C.

The uniaxially stretched film obtained in this way may be subjected to surface treatment such as corona treatment, frame treatment, or plasma treatment as necessary, and then functions such as release activity, easy adhesion, and antistatic properties may be imparted to the film by in-line coating.

Next, stretching in the width direction refers to stretching to provide a width direction orientation to the film, and is usually stretched in the width direction by transporting the film using a tenter while holding both ends of the film with clips. The stretching ratio varies depending on the type of resin, but is usually 2 to 15 times preferred, and when polyethylene terephthalate is used as one of the resins constituting the film, 2 to 7 times is particularly preferably used. In addition, the stretching temperature is preferably between the glass transition temperature of the resin constituting the laminated film and the glass transition temperature +120°C.

The biaxially stretched film in this way is subjected to heat treatment in a tenter at a temperature higher than the stretching temperature but lower than the melting point, cooled uniformly slowly, then cooled to room temperature and wound. Additionally, if necessary, in order to provide a low orientation angle and thermal dimensional stability to the film, relaxation treatment, etc. may be used in combination in the longitudinal direction and/or the width direction during slow cooling from heat treatment.

The case of simultaneous biaxial stretching will be explained next. In the case of simultaneous biaxial stretching, the obtained cast film may be subjected to surface treatment such as corona treatment, frame treatment, or plasma treatment as necessary, and then functions such as release activity, easy adhesion, and antistatic properties may be imparted by in-line coating. .

Next, the cast film is guided to a simultaneous two-axis tenter, conveyed while holding both ends of the film with clips, and stretched simultaneously and/or stepwise in the longitudinal direction and the width direction. There are a pantograph type, a screw type, a drive motor type, and a linear motor type as simultaneous two-axis stretching machines, but the drive motor type or the linear motor type are preferable because the stretching ratio can be changed arbitrarily and relaxation processing can be performed at any location. . The stretching magnification varies depending on the type of resin, but is usually preferably 6 to 50 times the area magnification, and when polyethylene terephthalate is used as one of the resins constituting the laminated film, 8 to 30 times the area magnification is especially preferable. It is used. In particular, in the case of simultaneous biaxial stretching, it is desirable to make the stretching ratios in the longitudinal direction and the width direction the same in order to suppress in-plane orientation differences, and to make the stretching speed almost the same. In addition, the stretching temperature is preferably between the glass transition temperature of the resin constituting the laminated film and the glass transition temperature +120°C.

In order to impart planarity and dimensional stability to the biaxially stretched film in this way, it is preferable to continuously heat-treat it in a tenter at a temperature higher than the stretching temperature but lower than the melting point. In order to suppress the distribution of the main orientation axis in the width direction during this heat treatment, it is preferable to immediately relax the material in the longitudinal direction immediately before and/or immediately after entering the heat treatment zone. After being heat treated in this way, it is uniformly slowly cooled, cooled to room temperature, and then rolled. Additionally, if necessary, relaxation treatment may be performed in the longitudinal direction and/or the width direction during slow cooling from the heat treatment. Immediately before and/or after entering the heat treatment zone, relaxation treatment is performed in the longitudinal direction.

The laminated film obtained as described above is trimmed to the required width through a winding device and wound in the form of a roll to prevent the formation of winding wrinkles. Additionally, embossing may be performed on both ends of the film to improve the winding posture during winding.

The thickness of the laminated film of the present invention is not particularly limited, but is preferably 1 to 500 μm. According to the recent trend of thinning of films for display purposes, the thickness is preferably 40㎛ or less, more preferably 20㎛, and even more preferably 15㎛ or less. There is no lower limit, but in order to give the thin film sufficient cutting properties in the ultraviolet and visible short wavelength range by adding an ultraviolet absorber and/or a dye with the maximum wavelength in the short wavelength range of visible light above 380 nm and below 430 nm, a certain thickness must be required. It is necessary to have a thickness of 10 μm or more in reality. If it is thinner than 10㎛, the desired optical performance cannot be provided, and the laminated film may curl due to curing when forming the hard coat layer described later.

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

The laminated film of the present invention is preferably formed by forming a hard coat layer (C layer) containing curable resin C as a main component in order to add functions such as scratch resistance and dimensional stability on the top of the outermost layer. In the case of films for display use, in long-term reliability tests under harsh conditions such as the accelerated moist heat resistance test conditions of 85℃ 85%RH described above, as well as heat shock tests in which the temperature is raised and lowered several times from around 100℃ to below zero, the film is subject to long-term reliability tests. It is required that the properties do not change. In the case of a laminated film whose orientation has been crystallized by stretching, there is a possibility that the dimensions of the film may change due to heat shrinkage when a long-term reliability test is performed. However, in the case of the laminated film of the present invention, heat shrinkage occurs and the thickness of the film increases, so various absorbents are absorbed. It is undesirable to improve performance more than necessary because problems such as undesired absorption of visible light or shifting of the reflection band to cut longer wavelength visible light may occur. Therefore, it is preferable to apply a hard coat layer that contributes to dimensional stability to at least one side of the laminated film in order to maintain the properties of the film. Additionally, by laminating a hard coat layer with high crosslinkability, precipitation of oligomers, additives, etc. contained within the laminated film can be suppressed. The hard coat layer may be coated directly on the laminated film, or may be coated after forming an in-line water-based coating layer capable of imparting functions such as easy activity and easy adhesion as described in the production method described above.

The above-mentioned coating layer not only provides functions such as easy activity and easy adhesion, but also has the effect of improving adhesion with the laminated film when laminating a hard coat layer containing curable resin C as a main component, so it is recommended to apply it. desirable. In particular, when using polyethylene terephthalate as resin A and acrylic resin as curable resin B, as in the examples described later, the difference in refractive index increases, with the former having a refractive index of about 1.65 and the latter having a refractive index of about 1.50, which causes deterioration of adhesion. Therefore, the refractive index of the coating layer preferably has a value of 1.50 to 1.60, and more preferably has a refractive index of 1.55 to 1.58.

The hard coat layer containing curable resin C as the main component may be formed on one side, but precipitation of oligomers and additives generally occurs from both sides of the film, and when the hard coat layer is laminated on only one side, curing occurs on the lamination side. There is a risk that the laminated sheet itself may curl significantly depending on the laminated thickness of the hard coat layer due to strong shrinkage stress. Therefore, it is more preferable to apply the hard coat layer to both sides of the laminated film.

The curable resin C used in the laminated film of the present invention is preferably highly transparent and durable, and includes, for example, acrylic resin, urethane resin, fluorine-based resin, silicone resin, polycarbonate-based resin, and vinyl chloride-based resin alone or in combination. You can use it. In terms of curability, flexibility, and productivity, the curable resin C is preferably made of an active energy ray-curable resin such as an acrylic resin typified by polyacrylate resin. In addition, when applying it as a film for a flexible display, when adding scratch resistance during bending required, the curable resin C is preferably made of a thermosetting urethane resin.

The active energy ray-curable resin used as a component of the hard coat layer includes monomer components constituting the active energy ray-curable resin, such as pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, and Pentaerythritol tri(meth)acrylate, dipentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, trimethylolpropane tri(meth)acrylate, bis. (methachlorylthiophenyl) sulfide, 2,4-dibromophenyl (meth)acrylate, 2,3,5-tribromophenyl (meth)acrylate, 2,2-bis (4- (meth) )Acryloyloxyphenyl)propane, 2,2-bis(4-(meth)acryloyloxyethoxyphenyl)propane, 2,2-bis(4-(meth)acryloyloxyethoxyphenyl)propane , 2,2-bis(4-(meth)acryloylpentaethoxyphenyl)propane, 2,2-bis(4-(meth)acryloyloxyethoxy-3,5-dibromophenyl)propane , 2,2-bis(4-(meth)acryloyloxydiethoxy-3,5-dibromophenyl)propane, 2,2-bis(4-(meth)acryloyloxypentaethoxy-3 ,5-dibromophenyl)propane, 2,2-bis(4-(meth)acryloyloxyethoxy-3,5-dimethylphenyl)propane, 2,2-bis(4-(meth)acrylo Iloxyethoxy-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)acryloyl) Oxypentaethoxyphenyl) sulfide, bis(4-(meth)acryloyloxyethoxy-3-phenylphenyl) sulfide, bis(4-(meth)acryloyloxyethoxy-3,5-dimethyl Polyfunctional (meth)acrylic compounds such as phenyl) sulfide, di((meth)acryloyloxyethoxy) phosphate, and tri((meth)acryloyloxyethoxy) phosphate can be used, and these are one type or Two or more types can be used.

In addition, in order to control the hardness, transparency, strength, and refractive index of the active energy ray-curable resin along with these multifunctional (meth)acrylic compounds, styrene, chlorostyrene, dichlorostyrene, bromostyrene, dibromostyrene, and divinylbenzene are used. , vinyltoluene, 1-vinylnaphthalene, 2-vinylnaphthalene, N-vinylpyrrolidone, phenyl (meth)acrylate, benzyl (meth)acrylate, biphenyl (meth)acrylate, diallyl phthalate, dimethyll Phthalate, diallyl biphenylate, or a reaction product of metals such as barium, lead, antimony, titanium, tin, and zinc with (meth)acrylic acid can be used. You may use one type or two or more types of these.

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

The active energy ray-curable resin used in the present invention includes isopropyl alcohol, ethyl acetate, methyl ethyl ketone, and toluene within a range that does not impair the effect of the present invention for the purpose of improving workability during application and controlling the coating film thickness. Organic solvents such as these can be mixed.

In the present invention, active energy rays refer to electromagnetic waves that polymerize acrylic vinyl groups, such as ultraviolet rays, electron beams, and radiation (α-rays, β-rays, γ-rays, etc.). In practical terms, ultraviolet rays are convenient and preferable. As ultraviolet light sources, ultraviolet fluorescent lamps, low-pressure mercury lamps, high-pressure mercury lamps, ultra-high pressure mercury lamps, xenon lamps, carbon arc lamps, etc. can be used. In addition, the electron beam method is advantageous in that the device is expensive and requires operation under an inert gas, but it does not need to contain a photopolymerization initiator or photosensitizer.

The thickness of the hard coat layer must be appropriately adjusted depending on the method of use, but from the viewpoint of the tendency for thin films for display purposes and the compatibility of hard coat performance, it is usually preferably 1 to 6 ㎛, more preferably 1 to 3 ㎛. , and more preferably in the range of 1 to 1.5 ㎛. If the thickness of the hard coat layer is thicker than 6㎛, when curing the coating substrate, the laminated film may be pushed by the curing shrinkage force of the hard coat layer, causing strong curling of the laminated sheet.

The thermosetting urethane resin used as a component of the hard coat layer containing curable resin C as a main component for adding scratch resistance includes a copolymer resin having polycaprolactone segments, polysiloxane segments, and/or polydimethylsiloxane segments, and a compound having an isocyanate group. A resin crosslinked by overheating reaction is preferred. By applying a thermosetting urethane resin, it becomes possible to strengthen the hard coat layer and promote elastic recovery, and to add scratch resistance to the laminated film.

The polycaprolactone segment constituting the thermosetting urethane resin exhibits an elastic recovery effect, and radically polymerizable polycaprolactone such as polycaprolactone diol, polycaprolactone triol, or lactone-modified hydroxyethyl acrylate can be used.

The polysiloxane and/or polydimethylsiloxane segments constituting the thermosetting urethane resin exhibit the effect of improving surface lubricity and reducing frictional resistance through surface coordination of these components. As the resin having polysiloxane segments, tetraalkoxysilane, methyltrialkoxysilane, dimethyldialkoxysilane, γ-glycidoxypropyltrialkoxysilane, γ-methacryloxypropyltrialkoxysilane, etc. can be used. On the other hand, as a resin having a polydimethylsiloxane segment, various vinyl monomers such as methyl acrylate, isobutyl acrylate, methyl methacrylate, n-butyl methacrylate, styrene, and α-methyl are added to the polydimethylsiloxane segment. A copolymer of styrene, acrylonitrile, vinyl acetate, vinyl chloride, vinyl fluoride, acrylamide, methacrylamide, N,N-dimethylacrylamide, etc. can be preferably used.

The hard coat layer made of thermosetting urethane resin is formed by causing a reaction between resins and compounds at an arbitrary temperature, volatilizing the solvent in the layer, and thermally crosslinking the layer. In order to promote the thermal crosslinking reaction of the hard coat layer, the temperature in the heating process is preferably 150°C or higher, and more preferably 160°C or higher. The heating temperature is preferably high, but considering the occurrence of shrinkage wrinkles due to heat shrinkage of the substrate, it is preferable to heat treat at 170°C or lower. The heating time is 1 minute or more, preferably 2 minutes or more. The upper limit is not particularly set, but is preferably within 5 minutes from the viewpoint of dimensional stability and transparency of the laminated film. In this way, the laminated sheet that has been heat-treated at a high temperature for a short time is preferably subjected to aging treatment at a temperature of 20°C to 80°C for 3 days or more, more preferably 7 days or more, in order to increase the urethane bond and improve the elongation of the laminated sheet. .

Curable resin C used to add adhesiveness and adhesion is a compound having an alicyclic epoxy group that shows a good effect in adhesion to PVA as an optical film for displays, especially when used as bonding with a polarizer, and polyacrylate of polyol. It is preferable to use a photocurable resin composed of a combination of four types of polymers containing , oxetane compounds, and alkyl acrylates as monomer units.

As a compound having an alicyclic epoxy group, it is preferable to have about 2 to 5 epoxy groups from the viewpoint of low viscosity, curability, and adhesive strength, and examples include 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate. You can.

Polyacrylates of polyols having about 2 to 10 carbon atoms are preferable because they lower the viscosity and improve adhesion to the polarizer. Neopentyl glycol dimethacrylate, 1,6-hexanediol dimethacrylate, 3 -Methyl-1,5-pentanediol dimethacrylate, etc. are mentioned.

As an oxetane compound, the speed of adhesion development after light irradiation can be improved and adhesive strength can be developed even in an environment where relative humidity fluctuates. 3-ethane-3-oxetanemethanol, 3,3'-(oxybismethylene)bis(3-ethyloxetane), etc. can be preferably used.

Polymers containing acrylic acrylate as a monomer are effective in improving adhesion after accelerated moisture and heat resistance tests, and include methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, t-butyl methacrylate, and isobutyl. It is preferable to use alkyl methacrylates having 1 to 10 carbon atoms, including methacrylates, and among them, it is most preferable to use acrylic methacrylates within the range of 1 to 4 carbon atoms.

By mixing the above components in appropriate amounts, it becomes possible to cure at room temperature using the various active energy rays described above as photocationic polymerization initiators. As a photocationic polymerization initiator, aromatic diazonium salts such as benzenediazonium, aromatic sulfonium salts such as triphenylsulfonium, aromatic iodonium salts such as diphenyldiiodonium, or a combination of two or more types thereof can be used. In addition, it is also possible to use a radical photopolymerization initiator to achieve sufficient crosslinking reactivity with a small amount of light irradiation.

In the hard coat layer, the various ultraviolet absorbers described above and/or a dye having a maximum wavelength that is maximum in the short wavelength region of visible light above 380 nm and below 430 nm may be added. By adding it separately from the hard coat layer, it is possible to reduce the amount of ultraviolet absorber added to the resin and the pigment with the maximum wavelength that is maximum in the short wavelength region of visible light above 380 nm and below 430 nm, and to reduce the bleed-out phenomenon that occurs during resin extrusion. This is desirable because it can suppress. In addition, when a dye with a maximum wavelength in the short wavelength region of visible light above 380 nm and below 430 nm is added to the hard coat layer, it becomes possible to reduce the blue reflection color from the laminated film to the viewing side by absorption of the dye. , it is preferable because it can express clear white or black with or without image display.

The concentration of the ultraviolet absorber added to the hard coat layer and/or the dye having the maximum wavelength in the short wavelength range of visible light above 380 nm and below 430 nm is preferably 10 wt% or less based on the entire resin composition constituting the hard coat layer. And, more preferably, it is 5wt% or less. The added concentration must be adjusted appropriately to achieve the desired cut performance, taking into account the absorption performance of the additive and the thickness of the hard coat layer involved in the cut performance. However, if it exceeds 10 wt%, various additives may be removed during the acceleration reliability test. There is a possibility of surface precipitation, and the adhesion between the laminated film and the hard coat layer may deteriorate.

In addition, in the embodiment of the laminated sheet, the sum of the content Mn [% by weight] of the above-described ultraviolet absorber and/or the pigment having a maximum wavelength that is maximum in the visible light short wavelength region of more than 380 nm and less than 430 nm, and the above addition It is preferable that Σ (Mn × Tn), which is the product of the layer thickness of the layer by Tn [㎛] plus all the layers of the laminated film, is 50 [weight%·㎛] or less.

On top of the hard coat layer containing the curable resin C as the main component, it is possible to further form a functional layer such as a shock absorption layer and an anti-reflection (AR) layer, if necessary. In particular, the AR layer is preferably laminated as a functional layer because it has the effect of improving visibility in image display applications.

At least one side of the laminated film of the present invention may have an adhesive layer containing an ultraviolet absorber and/or a pigment having a maximum wavelength that is maximum in the visible light short wavelength region of more than 380 nm and less than or equal to 430 nm. In the case of a display film, the adhesive layer may be located on the viewing side, inside the display, or on both sides of the laminated film of the present invention.

However, when achieving the wavelength cut targeted by the present invention through both the laminated film and the adhesive layer, when using a dye as a dye having a maximum wavelength that is maximum in the short wavelength region of visible light above 380 nm and below 430 nm, the above-mentioned Likewise, absorption performance is lost by receiving strong ultraviolet rays. Therefore, the laminated film contains an ultraviolet absorber, the adhesive layer contains a ultraviolet absorber and/or a pigment having a maximum wavelength that is maximum in the short wavelength region of visible light between 380 nm and 430 nm, and the laminated film is located on the viewing side rather than the adhesive. This configuration is a preferred embodiment because deterioration of the pigment can be sufficiently prevented by the reflection and absorption performance of the laminated film.

The adhesive layer may be applied directly to the laminated film substrate and then dried to form an adhesive layer, and further bonding release sheets to obtain an adhesive sheet. Alternatively, the adhesive applied to the release sheet may be transferred onto the laminated film substrate. Various application methods such as roll coater, die coater, bar coater, lip coater, gravure coater, and blade coater can be used. The thickness of the adhesive layer is preferably 5 μm or more and 150 μm or less, and more preferably 10 μm or more and 80 μm or less. When the adhesive layer thickness is less than 5 μm, the adhesive performance may be insufficient, and when it exceeds 150 μm, the cost of the adhesive sheet itself increases and is not desirable. There are no particular restrictions on the type of adhesive, but it is recommended to use those described as curable resins used to improve adhesion and adhesion described above, as well as acrylic optical adhesive (OCA) or liquid acrylic optical adhesive (LOCA). It is most desirable because it has excellent transparency and durability.

Hereinafter, the present invention will be described based on examples, but the present invention is not limited to these examples. Each characteristic was measured by the following method.

(Method of measuring characteristics and evaluating effect)

The method of measuring the characteristics and evaluating the effect in the present invention are as follows.

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

The layer composition of the film was determined by observation with a transmission electron microscope (TEM) of a sample whose cross-section was cut using a microtome. That is, the cross-section of the film was observed under the condition of an acceleration voltage of 75 kV using a transmission electron microscope type H-7100FA (manufactured by Hitachi, Ltd.), cross-sectional photographs were taken, and the layer composition and thickness of each layer were measured. Also, in some cases, RuO ₄ or OsO ₄ is used to obtain high contrast. A dyeing technique using etc. was used. In addition, according to the thickness of the thinnest layer (thin film layer) among all the layers introduced in one image, if the thin film layer thickness is less than 50 nm, the thickness is multiplied by 100,000 times, and if the thin film layer thickness is between 50 nm and less than 500 nm, it is multiplied by 40,000 times and 500 nm. In the case of ㎚ or more, observation was performed at a magnification of 10,000 times to determine the layer thickness, number of laminations, and lamination structure.

(2) Light transmittance

A spectrophotometer U-4100 manufactured by Hitachi, Ltd. was used. An integrating sphere was attached, and the relative transmittance in the wavelength range of 300 to 450 nm was measured when the reflection of the aluminum oxide standard white plate (included with the main body) was set to 100%. For the wavelengths of 410 nm and 440 nm, the transmittance values at the above wavelengths were read, and for the wavelength range of 300 to 380 nm, the maximum transmittance in the above range was read. As conditions, the scan speed was set to 600 nm/min and the sampling pitch was set to 1 nm, and measurements were made continuously.

(3) Average ray reflectance

A spectrophotometer U-4100 manufactured by Hitachi, Ltd. was used. An integrating sphere was attached, the relative reflectance in the region of 300 to 400 nm was measured when the reflection of the aluminum oxide standard white plate (included with the main body) was set to 100%, and the average light reflectance in the above range was determined. As conditions, the scan speed was set to 600 nm/min and the sampling pitch was set to 1 nm, and measurements were made continuously.

(4) Hard coat application (Examples 22 to 32)

An active energy ray-curable urethane acrylic comprising a hard coat layer containing an ultraviolet absorber described in Examples 22 to 32 described below and a pigment having a maximum wavelength that is maximum in the short wavelength region of visible light between 380 nm and 430 nm. Resin (Japanese UV-1700B [refractive index: 1.50 to 1.51] manufactured by Nippon Synthetic Chem Industry Co., Ltd.) was uniformly applied onto the outermost surface of the laminated film using a bar coater. Next, a condensing type high-pressure mercury lamp (H04-L41 manufactured by EYE GRAPHICS Co., Ltd.) with an irradiation intensity of 120 W/cm2 was set at a height of 13 cm from the surface of the hard coat layer so that the integrated irradiation intensity was 180 mJ/cm2. It was irradiated with ultraviolet rays and cured to obtain a laminated sheet in which a hard coat layer was laminated on a laminated film. In addition, an industrial UV checker (UVR-N1 manufactured by Nippon Denchi Co., Ltd.) was used to measure the integrated irradiation intensity of ultraviolet rays.

(5) Evaluation of bleed-out resistance

At the time of film forming, the vicinity of the width direction edge of the polymer coming out of the spindle was illuminated with a light to confirm the presence or absence of white smoke (volatilization from the spindle). The absence of white smoke (volatilization from detention) was evaluated as excellent bleed-out resistance.

(6) 85℃ 85%RH accelerated moist heat resistance test (haze variation (Δhaze) evaluation)

The prepared laminated film was cut into sections of 10 cm in the longitudinal direction and 10 cm in the width direction from the center of the film width direction, placed on plain paper, and left in a constant temperature and humidity chamber at 85°C and 85%RH for 250 hours to evaluate the amount of change in haze value of the film before and after heat treatment. did. The haze was measured using a haze meter (HGM-2DP) manufactured by Suga Test Instruments Co., Ltd. in accordance with the old JIS-K-7105. Three points were measured at random within the film plane, and the average value was taken as the measurement result.

◎: Haze value variation is less than 1.0%

○: Haze value variation is 1.0% or more and less than 1.5%

△: Haze value variation is 1.5% or more and less than 2.0%

×: Haze value variation is 2.0% or more.

(7) Bending stiffness

A tensile tester (TENSILON UCT-100 manufactured by ORIENTEC CORPORATION) was used to calculate the elastic modulus of the sample. The laminated film was cut into a strip shape of 150 mm in length x 10 mm in width, and a tensile test was performed with an initial tensile chuck distance of 50 mm and a tensile speed of 300 mm/min. The measurement environment was set to a room temperature of 23°C and a relative humidity of 65%, and the elastic modulus (Young's modulus) was calculated from the obtained load-deformation curve. The number of samples was set to 5, and their average value was taken as the elastic modulus of the sample. The maximum value of the elastic modulus of the sample was determined by similarly measuring the film longitudinal direction as 0° and changing the direction every 10° from -90° to 90° with respect to the film plane. The thickness of the measured sample was measured using a contact-type thickness meter (DIGIMICRO HEAD MH-15M manufactured by Nikon Corporation), and the bending rigidity value was calculated by applying it to the above-mentioned bending rigidity equation.

(8) Flexing resistance test

Samples with a width of 5 cm In a measurement atmosphere of room temperature 23°C and relative humidity 65%, the bending speed was set to 50 times/min and the bending radius was set to 1 mm, and a bending test was conducted 1 million times. The number of samples was set to three and compared with the laminated film before the test, and the presence or absence of scratches or bending habits was visually confirmed. If all three samples had no scratches or bending properties, the bending resistance was rated as good (○), and if even one sample showed scratches or bending properties, it was rated as poor bending resistance (×).

(9) Glass transition temperature, melting point

A differential scanning calorimeter EXSTAR DSC6220 manufactured by Seiko Instruments Inc. was used. Measurements and temperature readings were conducted according to JIS-K-7122 (1987). Level difference when 10 mg of a thermoplastic resin sample is heated on an aluminum saucer from 25°C to 300°C at a rate of 10°C/min, then rapidly cooled, and then heated again at a rate of 10°C/min from 25°C to 300°C. The temperature of the transition portion was taken as the glass transition temperature, and the peak top of the endothermic peak was taken as the glass transition temperature and melting point, respectively.

Example

(Example 1)

As thermoplastic resin A, polyethylene terephthalate (PET) with a melting point of 258°C was used. In addition, as thermoplastic resin B, polyethylene terephthalate (PE/SPG15T/CHDC20) copolymerized with 20 mol% cyclohexanedimethanol and 15 mol% spiroglycol, which is an amorphous resin with no melting point, was used. In thermoplastic resin B, a triazine-based ultraviolet absorber (2,4,6-tris(2-hydroxy-4-heptyloxy-3-methylphenyl)-s-triazine) with a molecular weight of 700 g/mol is used as the main component. It was added so that it was 10 wt% with respect to the resin composition constituting the B layer. The prepared thermoplastic resin A and thermoplastic resin B were each put into two single-screw extruders, and the former was melted and kneaded at 280°C and the latter at 260°C. Next, five leaf disk filters of the FSS type were interposed and joined in a feed block with five slits while being metered by a gear pump to form a laminate in which five layers were stacked alternately in the thickness direction with a stacking ratio of 0.5. Here, the slit length was designed to have a step shape, and the spacing was kept constant. The obtained laminate consists of three layers of thermoplastic resin A and two layers of thermoplastic resin B, which are alternately laminated in the thickness direction. The laminate was supplied to a T die, molded into a sheet shape, and then rapidly solidified on a casting drum with a surface temperature maintained at 25°C while applying an electrostatic voltage of 8kV with a wire to obtain an unstretched laminated cast film.

The obtained laminated cast film was heated in a roll group set to 100°C, then stretched 3.3 times in the length direction of the film while rapidly heating from both sides of the film with a radiation heater between the stretching section lengths of 100 mm, and then cooled once. Subsequently, corona discharge treatment is performed in the air on both sides of this laminated uniaxially stretched film, the wetting tension of the base film is set to 55 mN/m, and a lubricating layer is applied to the treated surfaces of both sides of the film (#4 meta bar to serve as a lubricity layer). A transparent, easily lubricated, and easily adhesive layer was formed by coating a water-based coating agent containing a vinyl acetate-acrylic resin containing 3 wt% of colloidal silica with a particle size of 100 nm (hereinafter, “coating” means the above).

This laminated uniaxially stretched film was guided to a tenter, preheated with hot air at 90°C, and then stretched 3.3 times in the film width direction at a temperature of 140°C. The stretching speed and temperature here were kept constant. The stretched biaxially stretched film was heat treated with hot air at 220°C in a tenter, then subjected to a 2% relaxation treatment in the width direction under the same temperature conditions, and then wound to obtain a laminated film. The obtained laminated film showed the physical properties shown in Table 1. The thickness of the laminated film was 30 μm, and due to the absorption effect of the added ultraviolet absorber, the light transmittance at wavelengths of 410 nm and 440 nm was 18% and 88%, respectively, satisfying the target value. The thickness was slightly thick and the haze was slightly high because the ultraviolet absorber content was 10 wt%, but visibility was good when mounted on the display. In addition, the haze value variation in the 85°C 85%RH accelerated moist heat resistance test was relatively high at 1.7%, but the variation was not large enough to worsen visibility during display mounting.

(Comparative Example 1)

A film was prepared in the same manner as in Example 1 without adding an ultraviolet absorber to the B layer containing thermoplastic resin B as its main component. Although a colorless and transparent laminated film was obtained, it did not have the ability to cut light in the ultraviolet region, so when it was mounted on a display, it was confirmed that the contents, such as the polarizer, were significantly deteriorated by transmitting ultraviolet rays. It was an unsuitable film as a display member for the purpose of protecting the contents from external ultraviolet rays.

(Comparative Example 2)

In Example 1, a laminated film was obtained in the same manner as in Example 1, except that two different types of thermoplastic resins were laminated in a feed block with 3 slits to form a laminated film in which 3 alternate layers were laminated at a lamination ratio of 0.5. The obtained laminated film had the same absorption performance by the ultraviolet absorber as Example 1, and achieved light transmittance at wavelengths of 410 nm and 440 nm. On the other hand, the haze value fluctuation in the accelerated moist heat resistance test was very high, and whitening of the laminated film was confirmed with the naked eye, so it was not suitable for display applications requiring high transparency.

(Example 2)

Melting point of a mixture of acrylic resin with a melting point of 230°C as thermoplastic resin A and acrylic elastomer particles to which the triazine-based ultraviolet absorber described in Example 1 was added in an amount of 10 wt% based on the total resin composition constituting the laminated film as thermoplastic resin B. Acrylic resin B with a temperature of 210°C was used. The prepared thermoplastic resin A and thermoplastic resin B were each put into two single-screw extruders, and the former was melted at 270°C and the latter at 250°C, and in the same manner as in Example 1, five layers were stacked alternately in the thickness direction with a layering ratio of 0.5. I did it through a sieve. This laminate was cooled with a stainless steel polishing roll (70°C) so that both sides were completely adhered, and an acrylic resin film with a film thickness of 30 μm was obtained. Since the obtained laminated film was an amorphous resin, the added ultraviolet absorber was prone to precipitate on the surface in the accelerated heat resistance test, and although it looked slightly white compared to Example 1, it had optical performance that could be used for display applications.

(Example 3)

In Example 1, thermoplastic resins were laminated on a feed block with 501 slits, and 501 layers were laminated alternately in the thickness direction at a lamination ratio of 1.0 to form a 30-μm-thick laminated film. In the obtained laminated film, 251 layers of A layer and 250 layers of B layer were laminated alternately in the thickness direction, and it was confirmed by transmission electron microscope observation that the laminated layer thickness distribution had a two-inclined structure. Additionally, the inclined structure had a layer thickness distribution in which the layer thickness linearly increased from one side of the film toward the center of the film and then linearly decreased from the center toward the opposite side of the film. The same triazine-based ultraviolet absorber as in Example 1 was used as the ultraviolet absorber added to the thermoplastic resin B, and the addition concentration was set at 10 wt% with respect to the resin composition constituting the B layer containing thermoplastic resin B as the main component. The stretching conditions of the film were carried out in the manner described in Example 1. The obtained laminated film had reflection performance accompanying the laminated structure, but because the thickness was slightly thin, the long wavelength end of the reflection wavelength range was up to about 390 nm, and the cut at the wavelength of 410 nm depended on the added concentration of the ultraviolet absorber. It was. Since the laminated structure was used, volatilization of the ultraviolet absorber from the spinneret was not confirmed, and the increase in Δ haze in the accelerated moist heat resistance test was suppressed, resulting in a performance that could be used for display applications.

(Example 4)

A laminated film was obtained in the same manner as in Example 3, except that the thickness of the laminated film was 31 μm, and the addition concentration of the ultraviolet absorber added to the thermoplastic resin B was 3 wt%. By increasing the thickness by 1㎛, the long wavelength end of the reflection wavelength range shifted to about 405㎚, and the light transmittance at a wavelength of 410㎚ was 6%, so the goal could be achieved even with a small addition concentration of ultraviolet absorber. Although a strong purple color due to slight reflection was confirmed, it did not significantly deteriorate the visibility of the display, and the display had suitable usable performance.

(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 was changed to 3 wt%. Because the ultraviolet ray absorption performance was poor, the light transmittance at a wavelength of 410 nm was 62%. This laminated film was mounted on a display and tested for protecting the contents by ultraviolet irradiation, but since deterioration of the contents was confirmed, it was not suitable as a film for protecting the contents of the display.

(Example 5)

In Example 4, a laminated film was obtained in the same manner as in Example 4 except that the thickness was set to 30.5 μm. The long wavelength end of the reflection wavelength range shifted to about 397 nm, and the light transmittance at a wavelength of 410 nm was 48%. Compared to Example 4, the cutting performance at a wavelength of 410 nm was inferior, but it was sufficiently effective in protecting the contents from deterioration due to being built into the display. In addition, by shifting the reflection wavelength range to a shorter wavelength, the reflection color was significantly suppressed, and hardly any purple reflection was observed during display mounting.

(Example 6)

In Example 1, the resin was laminated on a feed block with 251 slits, and 251 layers were alternately laminated in the thickness direction at a lamination ratio of 0.5 to obtain a laminated film with a thickness of 12 μm. The obtained laminated film was laminated alternately in the thickness direction with 126 layers of A layer and 125 layers of B layer, and it was confirmed by transmission electron microscopy that the laminated layer thickness distribution had a two-inclined structure. In addition, the addition prescription of the ultraviolet absorber and the stretching conditions of the film were performed according to the method described in Example 1. The obtained laminated film has a reflection wavelength range of about 395 nm at the long end, and the average light reflectance of the wavelength of 380 to 410 nm is low at about 12%, so by increasing the concentration of the ultraviolet absorber, a cut at a wavelength of 410 nm satisfies the requirement. It has become. Because it has a multi-layer structure, the bleed-out phenomenon from the spinneret was suppressed. The Δ haze after the accelerated moist heat resistance test could also be suppressed to about 1.3% compared to Example 1, making it suitable as a film for display purposes. In addition, the bending rigidity was low at ^3.6

(Comparative Example 4)

In Example 6, instead of the triazine-based ultraviolet absorber, a benzotriazole-based ultraviolet absorber (2,2'-methylenebis(4-(1,1,3,3-tetramethylbutyl)-6-) having a molecular weight of 650 g/mol was used. A laminated film was obtained in the same manner as in Example 6, except that (2H-benzotriazol-2-yl)phenol) was added to 10 wt% of the resin composition constituting the B layer containing thermoplastic resin B as the main component. The haze value fluctuation after the wet heat test was significant, and strong whitening was observed with the naked eye, making the laminated film unsuitable for display applications.

(Example 7)

In Example 6, a laminated film was obtained in the same manner as in Example 6 except that the thickness was set to 12.3 μm. By slightly increasing the thickness, the long wavelength end of the reflection wavelength range was shifted to around 405 nm, and it was confirmed that sufficient cut properties due to reflection were obtained even if the concentration of the ultraviolet absorber was lowered. Other performances were equivalent to Example 6, and it was a film suitable for display applications.

(Example 8)

In Example 6, the stretching conditions of the film were as in Example 6, except that the triazine-based UV absorber with a molecular weight of 700 g/mol described in Example 1 was added to 9.0 wt% based on the thermoplastic resin B as a prescription for adding the ultraviolet absorber. The procedure was performed similarly to the method described. Since the effect of multiple interference reflection is obtained by increasing the number of layers to 251, it was confirmed that the intended ultraviolet ray cut performance can be achieved even when the additive concentration is suppressed. It was confirmed that the amount of haze value variation in the accelerated moist heat resistance test was reduced compared to Example 2 as the added concentration decreased.

(Example 9)

In Example 6, the added ultraviolet absorber was a triazine-based ultraviolet absorber (2-(4,6-diphenyl-s-triazin-2-yl)-5-(2-(2-) with a molecular weight of 510 g/mol. Ethylhexanoyloxy) ethoxy) phenol) is added at 2.0 wt% to the resin composition constituting the B layer containing thermoplastic resin B as the main component, and the triazine-based ultraviolet absorber having a molecular weight of 700 g/mol as described in Example 1 is added to thermoplastic resin B. A laminated film was obtained in the same manner except that it was added to 7.0 wt% with respect to the resin composition constituting the B layer containing as the main component. The former triazine-based ultraviolet absorber has the maximum wavelength at 285 nm, and its light cutting performance in the ultraviolet range has improved, making it possible to cut ultraviolet rays more strongly and protecting the contents from ultraviolet rays compared to Example 6. It was suitable as an optical film for displays.

(Example 10)

In Example 6, the added ultraviolet absorber was a benzotriazole-based ultraviolet absorber (2,2'-methylenebis(4-(1,1,3,3-tetramethylbutyl)-6-() with a molecular weight of 650 g/mol. 2H-benzotriazol-2-yl) phenol) was thermoplasticized with 2.0 wt% of the resin composition constituting layer B containing thermoplastic resin B as the main component, and a triazine-based ultraviolet absorber having a molecular weight of 700 g/mol as described in Example 1. A laminated film was obtained in the same manner as in Example 6, except that the resin composition constituting the B layer containing Resin B as the main component was adjusted to 7.0 wt%. The former benzotriazole-based ultraviolet absorber has a maximum wavelength at 346 nm. , Similar to Example 9, the light transmittance in the ultraviolet region was lowered and the ultraviolet cutting property was superior compared to Example 6 or Example 7. When using a benzotriazole system, the amount of change in haze in the accelerated moist heat resistance test Although it was confirmed that there was a tendency to slightly increase, it had sufficient performance to be used as an optical film for displays.

(Example 11)

In Example 10, the thickness of the laminated film was set to 12.3 ㎛, and among the ultraviolet absorbers added to thermoplastic resin B, the addition concentration of the benzotriazole-based ultraviolet absorber was 0.7 wt% and the addition concentration of the triazine-based ultraviolet absorber was 2.3 wt%. A laminated film was obtained in the same manner as in Example 10 except for the above. By combining the effect of reflection due to the laminated structure and the absorption effect of the ultraviolet absorber, it became possible to lower the addition concentration of the ultraviolet absorber, and the Δ haze in the accelerated moist heat resistance test was able to be greatly reduced.

(Example 12)

In Example 6, the ultraviolet absorber added was a benzotriazole-based ultraviolet absorber with a molecular weight of 315 g/mol (2-(5-chloro-2H-benzotriazol-2-yl)-6-tert-butyl-4-methyl. Phenol) is 4.0 wt% with respect to the resin composition constituting the B layer containing thermoplastic resin B as the main component, and the triazine-based ultraviolet ray absorber with a molecular weight of 700 g/mol described in Example 1 constitutes the B layer containing thermoplastic resin B as the main component. A laminated film was formed in the same manner as in Example 6, except that 4.0 wt% was added to the resin composition. The benzotriazole-based ultraviolet absorber used in this example has an excellent ability to cut ultraviolet rays in the long wavelength side, and the goal was achieved even when the added concentration of the triazine-based ultraviolet absorber was reduced. However, compared to Example 6, in addition to the omission of transmittance in the ultraviolet region on the low wavelength side, the haze value in the reliability test also increased slightly. It had good visibility when mounted on a display, and was a highly transparent laminated film suitable for optical films for displays.

(Example 13)

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

(Example 14)

In Example 6, polyethylene terephthalate was used as the thermoplastic resin A, and the triazine-based ultraviolet absorber with a molecular weight of 700 g/mol described in Example 1 was added to 2.0 wt% with respect to the resin composition containing thermoplastic resin A as the main component. In addition, the triazine-based ultraviolet absorber described in Example 1 was added to the thermoplastic resin B in an amount of 6.0 wt% with respect to the resin composition constituting the B layer containing thermoplastic resin B as the main component, and the stacking ratio was designed to be 1.0. A laminated film was obtained in the same manner as in Example 6. Even if a small amount of about 2.0 wt% was added to the A layer made of thermoplastic resin A including the outermost layer, no significant increase in haze was confirmed in the accelerated moist heat resistance test. In addition, compared to Example 6 in which only the B layer was added, the amount of ultraviolet rays absorbed is increased due to the effect of increasing the optical path length due to multiple interference reflections between layers, and by adding it to both resins separately, the same effect is obtained even at a low addition concentration.

(Example 15)

In Example 6, without adding an ultraviolet absorber, an indole-based dye with a maximum wavelength of 393 nm was added to thermoplastic resin B as a dye having a maximum wavelength in the short wavelength range of visible light between 380 nm and 430 nm or less. A laminated film was obtained in the same manner as in Example 6, except that it was added to 4.0 wt% with respect to the resin composition constituting the B layer containing as the main component, and the lamination ratio was designed to be 1.0. As the ultraviolet absorber was not added, the ultraviolet ray cut in the wavelength range of 300 to 380 nm was weakened compared to the previous examples, but the desired cut performance was achieved by utilizing the effect of reflection. It was confirmed that even when mounted for display purposes, the liquid crystal and light emitting layer were not significantly deteriorated and could be used appropriately.

(Example 16)

In Example 15, a naphthalimide-based dye with a maximum wavelength of 382 nm as a dye having a maximum wavelength in the visible light short-wavelength region of more than 380 nm and less than 430 nm constitutes a B layer containing thermoplastic resin B as the main component. A laminated film was obtained in the same manner as in Example 15, except that it was added to 3.5 wt% based on the resin composition. Naphthalimide-based dyes had very excellent sharp cutting properties at a wavelength of 410 nm, and showed very good cutting properties except that there was some loss of transmittance between 300 and 380 nm.

(Example 17)

In Example 15, the triazine-based ultraviolet absorber with a molecular weight of 700 g/mol described in Example 1 as an ultraviolet absorber was added to the thermoplastic resin B as a dye having a maximum wavelength that is maximum in the short wavelength range of visible light between 380 nm and 430 nm. A laminated film was obtained in the same manner as in Example 15, except that the indole-based dye used in 15 was added to 2.0 wt% and 1.0 wt%, respectively. By combining two types of absorbers that cut different wavelength ranges, it was possible to effectively cut wavelengths at low concentrations.

(Example 18)

In Example 17, as the ultraviolet absorber added to the thermoplastic resin B, a triazine-based ultraviolet absorber with a molecular weight of 700 g/mol described in Example 1 and a benzotriazole-based ultraviolet absorber with a molecular weight of 650 g/mol described in Example 7 were mixed, A laminated film was obtained in the same manner, except that the resin composition constituting the B layer containing thermoplastic resin B as the main component was added to 1.4 wt% and 0.6 wt%, respectively. Although the obtained laminated film had a slightly higher haze value variation in the long-term reliability test compared to Example 17, it had sufficiently suitable performance as a film for display purposes.

(Example 19)

A laminated film was obtained in the same manner as in Example 18, except that the thickness of the laminated film was set to 12.2 μm and the concentration of the indole dye added to the thermoplastic resin B was reduced to 0.5 wt%. Since the obtained laminated film has a long wavelength end of the reflection wavelength range around 400 nm, it was able to effectively achieve the desired ultraviolet ray cutting properties by combining absorption of the dye and reflection by the laminated structure.

(Example 20)

In Example 17, a laminated film was obtained in the same manner as in Example 17, except that the concentration of the triazine ultraviolet absorber added to the thermoplastic resin B was reduced to 1.0 wt% and the concentration of the indole dye was increased to 2.0 wt%. Although the light transmittance in the ultraviolet region was higher than that of the above-described examples, it was a laminated film that sufficiently achieved the desired cutting properties.

(Example 21)

In Example 17, the addition concentration of the triazine-based ultraviolet absorber was set to 5.0 wt%, and phthalocyanine had a maximum wavelength at 420 nm as a dye with a maximum wavelength in the short-wavelength region of visible light between 380 nm and 430 nm. A laminated film was obtained in the same manner as in Example 17 using a dye-based dye. The phthalocyanine pigment can sharply cut light only in the vicinity of the wavelength of 400 to 440 nm, and the light transmittance of the wavelength of 440 nm was 80%, barely meeting the target value. On the other hand, in order to cut ultraviolet rays with a wavelength of up to 400 nm, it was necessary to increase the added concentration of the ultraviolet absorber, but the amount of haze variation in the reliability test did not become significant, and a laminated film suitable for display applications was obtained.

(Example 22)

In Example 17, a laminated sheet in which a hard coat layer was laminated by applying a hard coat agent to which an indole-based dye having a maximum wavelength that is maximum in the short wavelength region of visible light between 380 nm and 430 nm was applied to the prepared laminated film onto the film. got it After dissolving the indole pigment in methyl ethyl ketone, add it to 4.0 wt% with respect to the resin composition constituting the hard coat layer as the hard coat main material, and finally add methyl ethyl ketone solvent so that the total solid concentration is 30%. By doing so, a hard coat agent was prepared. The hard coat was applied to one side of the laminated film so that the thickness was 2 μm. After application, it was dried in an oven at 80°C for 1 to 2 minutes to volatilize the methyl ethyl ketone solvent, and then irradiated with ultraviolet rays so that the integrated amount of ultraviolet irradiation was 180 mJ/cm2 to obtain the desired laminated sheet. Since the obtained laminated sheet has a hard coat layer with high crosslinkability located on the outermost surface, precipitation of oligomers and additives in the laminated film is reduced, and the haze value change during the accelerated moist heat resistance test is lower than that in Example 17 where the hard coat is not applied. It got smaller. In addition, it had good dimensional stability and was suitable for display applications.

(Example 23)

In Example 22, an anthraquinone-based dye with a maximum absorption wavelength of 406 nm as a dye with a maximum wavelength in the visible light short-wavelength region of more than 380 nm and less than 430 nm added to the hard coat agent was added to the hard coat layer. A laminated sheet was obtained in the same manner as in Example 17, except that it was added to 10 wt% based on the resin composition. Although there were concerns that the anthraquinone-based pigment would precipitate on the surface due to addition of a high concentration, with slightly poor absorption performance, no significant whitening was confirmed after the long-term reliability test, so it was judged to be stable in the long term and suitable for display applications.

(Example 24)

In Example 22, LA-72 manufactured by ADEKA CORPORATION as a hindered amine-based light stabilizer was used as a hindered amine-based light stabilizer in the hard coat agent in addition to a pigment having a maximum wavelength in the visible light short wavelength region of more than 380 nm and less than 430 nm. A laminated sheet was obtained in the same manner as in Example 22, except that it was added to 0.5 wt% with respect to the resin composition constituting the . By adding a light stabilizer, deterioration of the contents during display mounting could be prevented for a longer period of time compared to Example 22.

(Example 25)

In Example 24, in addition to the light stabilizer, as an antioxidant, A-612, a phosphorus-based/phenol-based mixed antioxidant manufactured by ADEKA CORPORATION, and nickel-based SEESORB612NH, manufactured by SHIPRO KASEI KAISHA, LTD., were used as a singlet oxygen agent, respectively. It was added so that it was 0.3 wt% and 4 wt% with respect to the resin composition constituting the hard coat layer. Additionally, a laminated sheet was obtained in the same manner as in Example 24, except that toluene was used as a solvent instead of methyl ethyl ketone, and the hard coat agent was applied and then dried in a hot air oven at 110°C for 3 minutes. By using a light stabilizer, antioxidant, and singlet oxygen in combination, the long-term stability of the indole pigment against light irradiation is improved compared to Example 24, making this laminate with the best long-term light resistance among the examples to which indole pigments have been added so far. It was a sheet. The optical performance of the baseline was equivalent to Example 24.

(Example 26)

In Example 24, as the ultraviolet absorber added to the thermoplastic resin B, the benzotriazole-based ultraviolet absorber with a molecular weight of 650 g/mol and the triazine-based ultraviolet absorber with a molecular weight of 700 g/mol used in Example 18 were used as the main component of thermoplastic resin B. A laminated sheet was obtained in the same manner except that 0.6 wt% and 1.4 wt% of the resin composition constituting the layer were added, and the thickness of the laminated film was set to 12.2 μm. Although the haze variation after the long-term reliability test was confirmed to be slightly high due to the highly precipitable benzotriazole-based ultraviolet absorber, it was not to the extent of deteriorating visibility during display mounting, and the laminated sheet was sufficiently usable for display purposes.

(Example 27)

In Example 22, a laminated film with a thickness of 12.2 μm was created, and an indole-based dye with a maximum wavelength of 393 nm was used in Example 22 as a dye having a maximum wavelength that is maximum in the short wavelength region of visible light between 380 nm and 430 nm. A laminated sheet was obtained in the same manner as in Example 17, except that 3.0 wt% and 6.0 wt% of the dye and the anthraquinone-based dye with a maximum wavelength of 406 nm used in Example 23 were added, respectively, to the resin composition constituting the hard coat layer. The combination of pigments improved cutting properties at 410 nm and improved light transmittance at 440 nm, achieving the most desirable sharp cutting properties among the examples so far. Additionally, the amount of haze variation after the reliability test was small, making it suitable as a film for display purposes.

(Example 28)

In Example 4, a laminated film was created with the added concentration of the triazine-based ultraviolet absorber set to 1.0 wt%. In the same manner as in Example 24, an indole-based dye-added hard coat layer containing a light stabilizer was formed on one side of the surface of the obtained laminated film, and a laminated sheet was formed. As a result of being able to further strengthen the reflection of wavelengths in the ultraviolet range and improve cutting performance in the ultraviolet range, a laminated sheet was created with the ability to withstand long-term ultraviolet irradiation. Due to the presence of a multi-layer laminated structure and a hard coat layer, precipitation of ultraviolet absorbers and/or pigments with a maximum wavelength that is maximum in the short wavelength region of visible light above 380 nm and below 430 nm was significantly reduced, resulting in greatly suppressed haze fluctuations. .

(Example 29)

In Example 5, the addition concentration of the triazine-based ultraviolet absorber was set to 1.4 wt%, and the benzotriazole-based ultraviolet absorber with a molecular weight of 650 g/mol used in Example 10 was used as a resin constituting the B layer containing thermoplastic resin B as the main component. A laminated film was obtained by adding 0.6 wt% to the composition. A hard coat layer is laminated on the obtained laminated film by applying a hard coat agent containing a benzylidine-based dye with a maximum wavelength of 381 nm, which is a dye with a maximum wavelength in the short wavelength range of visible light between 380 nm and 430 nm, on the film. A laminated sheet was obtained. Specifically, the benzylidine-based pigment was dissolved in methyl ethyl ketone and then added to 1.0 wt% relative to the resin composition constituting the hard coat layer, and 0.5 wt% of the hindered amine-based light stabilizer used in Example 24 was added. , Finally, a hard coat agent was prepared by adding methyl ethyl ketone solvent so that the total solid concentration was 30%. The hard coat layer was applied to one side of the laminated film so that the thickness was 5 μm. After application, it was dried in an oven at 80°C for 1 to 2 minutes to volatilize the methyl ethyl ketone solvent, and then cured by UV irradiation to an integrated UV irradiation amount of 180 mJ/cm2 to obtain the desired laminated sheet. The obtained laminated sheet suppressed reflected color, also satisfied the target light transmittance, and prevented deterioration of the contents over a long period of time even when mounted on a display. In addition, the hard coat thickness was thick, and the Δ haze in the accelerated moist heat resistance test could be greatly suppressed to 0.5, so it had properties that could be sufficiently used as an optical film for display purposes.

(Example 30)

In Example 26, 4.0 wt% of the indole-based dye used in Example 17 was added as a dye having a maximum wavelength that is maximum in the visible light short-wavelength region of more than 380 nm and less than 430 nm, and the phosphorus-based dye used in Example 25 as an antioxidant was added. /A laminated sheet was obtained in the same manner as in Example 26, except that 0.3 wt% of the phenol-based mixed antioxidant A-612 was added. The basic performance of the laminated sheet was equivalent to that of Example 26, while the protection of the contents from ultraviolet irradiation lasted longer.

(Example 31)

In Example 30, except that the hard coat layer was applied to both sides of the laminated film with the addition concentration of the indole dye at 2.0 wt% and the addition concentration of the light stabilizer and antioxidant at 0.25 wt% and 0.15 wt%, respectively. A laminated sheet was obtained in the same manner as in 30. By laminating a hard coat layer on both sides, almost no haze-up was observed in the accelerated moisture and heat resistance test, making it suitable as a film to be used for displays over a longer period of time.

(Example 32)

In Example 30, a hard coat layer without dye added was formed on one side of the laminated film to have a thickness of 2 μm. Additionally, an acrylic optical adhesive containing 0.4 wt% of indole dye was applied to the opposite side of the hard coat layer of the laminated film as a bar coat to a thickness of 20 μm. After applying the adhesive, it was dried in an oven at 100°C for 2 to 3 minutes and then subjected to aging treatment in a hot air oven at 40°C for 2 days to obtain a laminated sheet with an adhesive. The optical performance of the adhesive-attached laminated sheet was equivalent to Example 30. As a result of bonding to the display, the pigment was located in the adhesive layer inside the display rather than the laminated film, so it received the ultraviolet ray cutting performance of the laminated sheet, resulting in an increase in the photostability of the pigment. From the viewpoint of long-term protection of display contents, this is the most desirable of all embodiments.

Since the laminated film of the present invention has excellent ultraviolet ray cutting properties and visible light transmittance, which sharply cuts rays with a wavelength of 410 nm or less, it can improve visibility and prevent deterioration caused by 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. In addition, UV cut is required, for example, window films in building materials and automobile applications, films for laminating steel plates such as signs in industrial materials applications, process and release films for photolithography materials in electronic device applications, and food, It can be suitable for use in films for pharmaceutical and agricultural purposes.

Claims (19)

A film in which five or more layers are alternately laminated: a layer containing thermoplastic resin A (layer A) and a layer containing a thermoplastic resin B different from the thermoplastic resin A (layer B),
An ultraviolet absorber in which the A layer and/or the B layer has a maximum absorption wavelength of 320 to 380 nm and has at least one skeleton selected from the group consisting of a triazine skeleton, a benzotriazole skeleton, and a benzoxazinone skeleton. Contains,
The maximum value of light transmittance at a wavelength of 300 to 380 nm is 3% or less,
A laminated film having a light transmittance of 40% or less at a wavelength of 410 nm and a light transmittance of 80% or more at a wavelength of 440 nm. delete According to claim 1,
A laminated film with an average light reflectance of 20% or more in the wavelength of 380 to 410 nm. According to claim 1,
A laminated film containing, in the A layer and/or B layer, a pigment having a maximum wavelength that is maximum in the visible light short wavelength range of more than 380 nm and less than 430 nm. According to claim 4,
A laminated film in which the dye having a maximum wavelength that is maximum in the short wavelength region of visible light above 380 nm and below 430 nm has a triazine skeleton. According to claim 4,
The pigment having a maximum wavelength that is maximum in the short wavelength region of visible light above 380 nm and below 430 nm is at least one skeleton selected from azomethine series, indole series, quinone series, naphthalimide series, phthalocyanine series, and benzylidine series. A laminated film having a . According to claim 4,
The sum of the contents of the ultraviolet absorber contained in the layer with the laminated film and the content of the pigment having the maximum wavelength that is maximum in the short wavelength region of visible light between 380 nm and 430 nm or less is Mn [% by weight], and the layer thickness of the layer is Tn [ ㎛], a laminated film characterized in that Σ (Mn According to claim 1,
A laminated film containing 0.01% by weight or more and 1% by weight or less of a hindered amine-based light stabilizer based on the total weight of the film. According to claim 1,
A laminated film made by stacking 51 or more layers of A layer and B layer alternately. According to claim 1,
A laminated film wherein thermoplastic resin A and thermoplastic resin B are polyester resins. According to claim 1,
A laminated film with a bending rigidity per unit length of 1.0×10 ^-7 [N·m2] or less. According to claim 1,
A laminated film with a Δhaze of 1.0% or less when treated for 250 hours at 85°C and 85%RH. A laminated sheet having a hard coat layer (C layer) containing curable resin C on at least one side of the laminated film according to claim 1. A laminated sheet comprising the laminated film according to claim 1 and an adhesive layer containing an ultraviolet absorber and/or a pigment having a maximum absorption in the visible light short wavelength range of more than 380 nm and less than or equal to 430 nm. A laminated sheet comprising the laminated sheet according to claim 13 and an adhesive layer containing an ultraviolet absorber and/or a pigment having a maximum wavelength that is maximum in the visible light short wavelength region of more than 380 nm and less than or equal to 430 nm. According to claim 1,
Laminated film used in display applications. According to claim 13,
Laminated sheets used for display applications. According to claim 14,
Laminated sheets used for display applications. According to claim 15,
Laminated sheets used for display applications.