Light scattering film

Abstract

An embodiment of the present invention relates to a light scattering film, said light scattering film having a resin layer having a sea-island structure, wherein: the total light transmittance at a wavelength of 940 nm is 50% or more; the resin layer contains a thermoplastic resin (A), which forms a sea part, and a thermoplastic resin (B), which forms an island part; the content ratio (% by mass) of the resin (A) in the resin layer is greater than the content ratio (% by mass) of the resin (B); the absolute value of the refractive index difference (Δn) between the resin (A) and the resin (B) is 0.04 or more; the Mw of the resin (A) in terms of polystyrene as measured by a GPC method is 40,000 or more; the tensile break strength of the resin (A) as measured in accordance with JIS K7127:1999 is 40 MPa or more; and the Mw of the resin (B) in terms of polystyrene as measured by the GPC method is 10,000 or more.

Description

Light-scattering film

[0001] One embodiment of the present invention relates to a light-scattering film.

[0002] Optical devices using infrared light are used for various purposes, such as imaging applications such as infrared camera devices, measurement, communication, biometric authentication, distance measurement, motion detection, blood oxygen concentration monitors, and pulse rate monitors.

[0003] Such optical devices generally have an infrared light emitting unit and / or an infrared light receiving unit, and may further be provided with an infrared light transmitting filter that transmits only infrared light in order to reduce unwanted light, such as visible light, that enters the light emitting unit or the light receiving unit, and to make invisible openings in the housing that are provided to emit infrared light from the light emitting unit to the outside and to allow the light receiving unit to receive infrared light from the outside.

[0004] Infrared light transmission filters generally have a dark color, such as black, in the filter portion where visible light is absorbed by various absorbents to block visible light. However, there are cases where an infrared light transmission filter of a specific color is desired for purposes such as enhancing design. For example, in the case of an optical device installed as a sensor camera in a mobile terminal or a car, there is a demand for the color of the infrared light transmission filter disposed in the opening to match the color of the housing (body color) so that the opening for the infrared sensor provided in the housing is not conspicuous. Because there are a wide variety of body colors for mobile terminals and cars, there is a demand for an infrared light transmission filter that can easily realize a variety of colors.

[0005] An example of an infrared light transmission filter other than a dark color is an infrared light transmission filter made of a white light diffusion film (light scattering film) described in Patent Document 1. The infrared light transmission filter made of a light diffusion film described in Patent Document 1 is realized by uniformly dispersing fine particles having a refractive index different from that of a transparent binder in the binder, thereby increasing the transmittance in the infrared range and increasing scattering in the visible range, thereby realizing an infrared light transmission filter made of a white light diffusion film.

[0006] Furthermore, an example of an infrared light transmission filter that realizes a color other than white is described in Patent Document 2. The light diffusion film described in Patent Document 2 includes a dielectric multilayer film on one surface of a substrate that transmits infrared light and reflects and transmits visible light, and realizes any appearance color using the visible light reflected from the dielectric multilayer film. Patent Document 2 also describes a configuration in which one surface of the substrate is matte-finished and a dielectric multilayer film is provided thereon, thereby adding a scattering component to the reflected light and imparting a pearl-like texture to the appearance color (improving the color development of the reflected color), and a configuration in which an infrared-transmitting black printed layer that transmits infrared light but blocks the transmission of visible light is provided on the inner surface of the dielectric multilayer film.

[0007] In recent years, there has been a demand for thinner light diffusion films. As an example of a filter that combines thinness with high scattering properties, a filter that has scattering properties despite being thin has been reported, in which two resins with different refractive indices are mixed to form a sea-island structure (for example, Patent Document 3).

[0008] Japanese Patent Publication No. 2010-72616 Japanese Patent No. 4122010 Japanese Patent No. 5411169

[0009] However, when the substrate (e.g., a resin layer) is thinned to achieve the recent demand for thinner displays, a problem has been discovered in that when a dielectric multilayer film that reflects specific wavelengths is provided for the purpose of enhancing design, etc., cracks may occur due to stress in the dielectric multilayer film.

[0010] Specifically, in the substrate having a sea-island structure described in Patent Document 3, the more the content of island components having a scattering function is increased in order to reduce the film thickness, the more interfaces there are inside the film, and a significant decrease in tensile breaking stress is observed. In other words, even if a dielectric multilayer film is provided on the thin substrate, there is a problem that the thin substrate may break due to the heat and stress generated when the dielectric multilayer film is provided.

[0011] Furthermore, with the dispersion of fine particles described in Patent Documents 1 and 2 and the substrate with a matte surface, it is difficult to precisely control the thickness of the dielectric multilayer film formed thereon, and it has been difficult to sufficiently block the transmission of visible light, for example.

[0012] An object of the present invention is to provide a light-scattering film which has a thin substrate (resin layer), has high visible light reflection / scattering properties even though it has a dielectric multilayer film, and can withstand the stress of the dielectric multilayer film.

[0013] As a result of further research, the present inventors have found that the above-mentioned problems can be solved by the following configuration example.

[0014] [1] A light-scattering film having a resin layer with a sea-island structure and a total light transmittance of 50% or more at a wavelength of 940 nm, wherein the resin layer contains a thermoplastic resin (A) that forms a sea portion and a thermoplastic resin (B) that forms an island portion, wherein the content (mass%) of the resin (A) in the resin layer is greater than the content (mass%) of the resin (B), the absolute value of the refractive index difference (Δn) between the resin (A) and the resin (B) is 0.04 or more, the resin (A) has a polystyrene-equivalent weight-average molecular weight (Mw) measured by gel permeation chromatography (GPC) of 40,000 or more, the resin (A) has a tensile break strength measured in accordance with JIS K 7127:1999 of 40 MPa or more, and the resin (B) has a polystyrene-equivalent weight-average molecular weight (Mw) measured by gel permeation chromatography (GPC) of 10,000 or more.

[0015] [2] The light-scattering film according to [1], wherein the resin layer has a tensile breaking strength of 40 MPa or more as measured in accordance with JIS K 7127: 1999. [3] The light-scattering film according to [1] or [2], wherein the resin layer has a surface roughness (Sa) of 0.7 μm or less on at least one side. [4] The light-scattering film according to any one of [1] to [3], wherein the mass ratio (A / B) of the resin (A) to the resin (B) in the resin layer is 90 / 10 to 55 / 45.

[0016] [5] The light-scattering film according to any one of [1] to [4], wherein the resin (A) has a glass transition temperature (Tg) of 150 to 380° C. [6] The light-scattering film according to any one of [1] to [5], wherein the resin (A) and the resin (B) have a common functional group or a common bond. [7] The light-scattering film according to [6], wherein the common functional group is an ester group, and the common bond is an amide bond or an ester bond.

[0017] [8] The light-scattering film according to any one of [1] to [7], which has a thickness of 250 μm or less. [9] The light-scattering film according to any one of [1] to [8], which has a dielectric multilayer film on at least one surface of the resin layer.

[10] The light-scattering film according to [9], which has a layer formed from a curable composition between the resin layer and the dielectric multilayer film.

[0018] According to the present invention, a light-scattering film having high visible light reflection / scattering properties and capable of withstanding dielectric multilayer stress can be obtained. The light-scattering film has a thin substrate (resin layer) and, even though it has a dielectric multilayer, has sufficient visible light reflection / scattering properties and dielectric multilayer stress resistance. Furthermore, according to the present invention, a light-scattering film can be provided that combines designability with high sensitivity to infrared light (particularly near-infrared light).

[0019] FIG. 1 shows an image of the cross section of light-scattering film A obtained in Example 1 photographed with a microscope (2000x magnification). FIG. 2 shows the results of spectral transmittance measurement of light-scattering film C obtained in Example 1. FIG. 3 shows the results of spectral transmittance measurement of light-scattering film C obtained in Example 2. FIG. 4 shows the results of spectral transmittance measurement of light-scattering film F obtained in Example 14. FIG. 5 shows the results of spectral transmittance measurement of light-scattering film C obtained in Comparative Example 1. FIG. 6 shows an image of the cross section of light-scattering film A obtained in Comparative Example 3 photographed with a microscope (200x magnification). FIG. 7 shows an image of the cross section of light-scattering film A obtained in Comparative Example 4 photographed with a microscope (200x magnification).

[0020] [Light-Scattering Film] A light-scattering film according to one embodiment of the present invention (hereinafter also referred to as "the present light-scattering film") has a resin layer having a sea-island structure.

[0021] <Resin Layer> The resin layer of the present light-scattering film has a sea-island structure, and therefore contains at least a thermoplastic resin (A) forming a sea portion and a thermoplastic resin (B) forming an island portion. The resins (A) and (B) may each be one type or two or more types.

[0022] The resin layer may be laminated on another resin support or a glass support, or may be used alone. In addition, the present light-scattering film preferably has a dielectric multilayer film on at least one side of the resin layer.

[0023] The sea-island structure of the present invention refers to a phase-separated structure of at least two resins, with the sea portion corresponding to the continuous phase and the island portions corresponding to the dispersed phase. For example, the white areas in Figure 1 are the islands, and in this sea-island structure, the islands are scattered and dispersed within the sea portion. The sea-island structure is generally formed by changing the phase-separated shape when left standing for a sufficient period of time at a temperature sufficiently higher than the glass transition temperature of the resin, or by changing the phase-separated shape when immersed in a solvent in which the resin dissolves. A structure in which resin particles or inorganic particles insoluble in the resin are dispersed has many interfaces, which causes a decrease in tensile strength at break, whereas the sea-island structure makes it easy to obtain a light-scattering film that maintains its tensile strength at break due to the interaction between the resin (A) of the sea portion and the resin (B) of the island portion.

[0024] In the resin layer, the content (mass %) of resin (A) is greater than the content (mass %) of resin (B). From the viewpoints of the type of resin, fluidity, light scattering properties, etc., the mass ratio (A / B) of resin (A) to resin (B) is preferably 90 / 10 to 55 / 45. If the content of resin (A) exceeds the upper limit, the scattering performance may be reduced, resulting in insufficient scattering in a thin film or the film may need to be thicker to achieve the required scattering performance. From the viewpoint of providing scattering function in a thin film, the upper limit of A / B is more preferably 85 / 15, even more preferably 80 / 10. Furthermore, if the content of resin (A) is less than the lower limit, the number of island interfaces within the sea portion may increase, or the island portions may merge, resulting in a decrease in tensile strength at break even in a sea-island structure. From the viewpoint of providing the light-scattering film with a tensile strength sufficient to withstand the formation of a dielectric multilayer film, the lower limit of A / B is more preferably 60 / 40, even more preferably 65 / 35.

[0025] The smaller the surface roughness (Sa) of the resin layer, the more likely it is to suppress deviation from the designed optical properties. Specifically, the Sa of at least one surface of the resin layer is preferably 1.8 μm or less, more preferably 1.2 μm or less, even more preferably 1.0 μm or less, particularly preferably 0.7 μm or less, and most preferably 0.5 μm or less. The lower limit of Sa is usually 0 μm.

[0026] Furthermore, when the present light-scattering film has a dielectric multilayer film, it is preferable to provide the dielectric multilayer film on the surface of the resin layer having a surface roughness (Sa) in the above range. By providing the surface on which the dielectric multilayer film is to be provided with a surface roughness (Sa) in the above range, it is possible to suppress deviation from the designed optical properties.

[0027] The present light-scattering film is characterized by its high transmittance in the near-infrared (around 940 nm) range while also achieving excellent visible light reflection / scattering properties, and its thinness. To accommodate recent thin optical sensors, the thickness of the present light-scattering film is preferably 250 μm or less, more preferably 225 μm or less, and even more preferably 210 μm or less, which has traditionally been difficult to achieve both a thin film and a high visible light haze value or the formation of a dielectric multilayer film stack. Furthermore, a thickness of 250 μm or less is preferable because it can suppress a decrease in transmittance around 940 nm due to excessive scattering. Furthermore, when producing a thick film, depending on the resin type, the island diameter may increase due to fusion of multiple island portions during production, resulting in a large Sa of the resin layer. A thickness of 250 μm or less is also preferable from the viewpoint of reducing Sa, which is important when forming a dielectric multilayer film, as described below. Furthermore, from the viewpoint of obtaining a free-standing film, the lower limit of the thickness of the present light-scattering film is preferably 5 μm.

[0028] The total light transmittance (according to JIS K 7375:2008) of the present light-scattering film (or resin layer) at a wavelength of 940 nm (near-infrared) is 50% or more, preferably 60% or more, more preferably 70% or more, and even more preferably 75% or more, from the viewpoint of ensuring a sufficient amount of light for the sensor below the light-scattering film. The upper limit of the total light transmittance is usually 100%. However, a total light transmittance approaching the upper limit of 100% is a characteristic obtained when an anti-reflection structure is provided on both sides of the film, and is a film with reduced reflectance. In order for a sensor using another wavelength of 940 nm to detect the present scattering film, a reflection intensity of about 5 to 10% is often required. Therefore, the upper limit of the total light transmittance is preferably 95%, more preferably 90%. In addition, the total light transmittance in the present invention means the transmittance that combines the rectilinear transmittance and diffuse transmittance at a wavelength of 940 nm. The total light transmittance at a wavelength of 940 nm of the present light-scattering film and the resins (A) and (B) described below can be measured by the method described in the examples described below.

[0029] Furthermore, the rectilinear transmittance of the present light-scattering film at 940 nm (near-infrared light) is preferably 80% or less, more preferably 70% or less, and even more preferably 60% or less, from the viewpoint of enabling detection across the entire sensor surface below the light-scattering film. By setting the total light transmittance of the present light-scattering film within the above-mentioned range and the rectilinear transmittance within the above-mentioned range, detection across the entire sensor surface can be achieved while maintaining sensor sensitivity. The lower limit of the rectilinear transmittance is usually 0%. The rectilinear transmittance at a wavelength of 940 nm can be measured by the method described in the Examples below.

[0030] The tensile strength at break of the resin layer in this light-scattering film, measured in accordance with JIS K 7127:1999, is preferably 35 MPa or more, more preferably 40 MPa or more, even more preferably 45 MPa or more, particularly preferably 50 MPa or more, and most preferably 55 MPa or more. The upper limit of the tensile strength at break is not particularly limited as long as the effects of the present invention are obtained, but is usually 300 MPa. If the tensile strength at break is within the above range, the occurrence of cracks can be suppressed even after the dielectric multilayer film is formed. The tensile strength at break can be measured by the method described in the Examples below.

[0031] Dielectric multilayer films generally require high temperatures during film formation in order to suppress changes in optical properties during moist heat tests and high-temperature dry tests and to improve adhesion. Therefore, a temperature difference occurs between the temperature during film formation and room temperature. This temperature difference generates film stress due to the linear expansion coefficients of the resin layer in the light-scattering film and the dielectric multilayer film. The film stress depends on the film thickness, but can reach several MPa to 20 MPa. Therefore, to prevent cracks from occurring even when the dielectric multilayer film is provided, the breaking strength of the resin layer in the light-scattering film must be higher than the film stress. Taking into account stress concentration, particularly at the edges, the tensile breaking strength of the resin layer in the light-scattering film must be several times higher than the film stress.

[0032] (Resin (A)) As the resin (A), a resin having a total light transmittance at a wavelength of 940 nm (in accordance with JIS K 7375:2008) of preferably 75% or more, more preferably 78% or more, and even more preferably 80% or more is used. When a resin having a total light transmittance within the above range is used, the obtained light-scattering film also has high transmittance for near-infrared light. The total light transmittance of the resin (A) is the total light transmittance of a 0.1 mm thick resin support consisting solely of the resin (A).

[0033] The weight-average molecular weight (Mw) of resin (A) measured by gel permeation chromatography (GPC) in terms of polystyrene is 40,000 or more, more preferably 50,000 or more, and even more preferably 55,000 or more, from the viewpoint of withstanding the stress of the dielectric multilayer film and suppressing the occurrence of cracks even after the sea-island structure is formed. When the lower limit of Mw is equal to or greater than the above-mentioned value, the light-scattering film having the sea-island structure has a tensile breaking strength capable of withstanding the stress of the dielectric multilayer film. Furthermore, while there is no particular limit to Mw, it is preferably 500,000 or less, more preferably 400,000 or less, even more preferably 300,000 or less, and particularly preferably 200,000 or less. When the upper limit of Mw is equal to or less than the above-mentioned value, it is possible to avoid processing defects due to excessive viscosity increase and also to easily control the size of the islands that cause scattering during the formation of the sea-island structure. Furthermore, if the upper limit of Mw is not more than the above-mentioned value, it is possible to reduce the surface roughness (Sa) of the light-scattering film when forming the dielectric multilayer film, and to suppress deviation from the designed optical properties. When two or more types of resin (A) are used, it is sufficient that the Mw of each resin is within the above-mentioned range.

[0034] The tensile break strength of resin (A), measured in accordance with JIS K 7127:1999, is 40 MPa or more, preferably 50 MPa or more, more preferably 60 MPa or more, and even more preferably 70 MPa or more, from the viewpoint of withstanding the stress of the dielectric multilayer film and suppressing the occurrence of cracks even after the formation of the sea-island structure. The upper limit of the tensile break strength is not particularly limited as long as the effects of the present invention are obtained, but is usually 300 MPa. By using resin (A) having a tensile break strength within this range, it is possible to easily obtain a light-scattering film that can suppress the occurrence of cracks even when a dielectric multilayer film is formed. Note that when two or more types of resin (A) are used, it is sufficient that the tensile break strength of each resin is within the above range.

[0035] The glass transition temperature (Tg) of resin (A) is preferably 120 to 380°C, more preferably 150 to 380°C, even more preferably 155 to 370°C, and particularly preferably 160 to 360°C, from the viewpoint of ensuring that an optical filter having a sea-island structure can withstand the temperature required for forming a dielectric multilayer film and suppress the occurrence of cracks. A temperature above this range makes it possible to easily obtain a light-scattering film that is free of cracks even when more than 20 dielectric multilayer films are provided. The glass transition temperatures (Tg) of resin (A) and resin (B) described below are values ​​determined by the method described in the Examples described below. When two or more types of resin (A) are used, it is sufficient that the Tg of each resin is within the above range.

[0036] The refractive index (n) of resin (A) is preferably 1.40 to 1.90, more preferably 1.43 to 1.80, and even more preferably 1.46 to 1.75. When the refractive index (n) is within this range, a light-scattering film with the desired scattering properties can be easily obtained. The refractive indexes (n) of resin (A) and resin (B) described later can be measured by the method described in the examples described later. When two or more types of resin (A) are used, the refractive index (n) of the mixed resin should be within the above range.

[0037] Examples of the resin (A) include cyclic (poly)olefin-based resins, aromatic polyether-based resins, polyimide-based resins, fluorene polyester-based resins, polycarbonate-based resins, polyamide (aramid)-based resins, polyarylate-based resins, polysulfone-based resins, polyethersulfone-based resins, polyparaphenylene-based resins, polyamideimide-based resins, polyethylene naphthalate (PEN)-based resins, fluorinated aromatic polymer-based resins, (modified) acrylic-based resins, epoxy-based resins, allyl ester-based curable resins, silsesquioxane-based ultraviolet-curable resins, acrylic-based ultraviolet-curable resins, and vinyl-based ultraviolet-curable resins.

[0038] Cyclic (poly)olefin resin The cyclic (poly)olefin resin is not particularly limited, but is preferably a cyclic olefin resin described in paragraphs

[0034] to

[0038] of WO 2019 / 111700, and commercially available products thereof include the ARTON series manufactured by JSR Corporation and the TOPAS series manufactured by Polyplastics Co., Ltd.

[0039] Aromatic Polyether Resin The aromatic polyether resin is not particularly limited, but is preferably the aromatic polyether resin described in paragraphs

[0039] to

[0048] of WO 2019 / 111700.

[0040] Fluorene Polyester Resin The fluorene polyester resin is not particularly limited, and may be any polyester resin containing a fluorene moiety.

[0041] Polyimide Resin There are no particular limitations on the polyimide resin, and it may be any polymer compound containing an imide bond in the repeating unit.

[0042] Polycarbonate Resin The polycarbonate resin is not particularly limited, but examples of commercially available products include the Iupizeta series manufactured by Mitsubishi Gas Chemical Company, Inc., the Iupilon series manufactured by Mitsubishi Engineering Plastics Corporation, and U-Polymer manufactured by Unitika Ltd. Among these, resins that are soluble in organic solvents in which dyes are soluble are preferred.

[0043] Fluorinated Aromatic Polymer Resin The fluorinated aromatic polymer resin is not particularly limited, but is preferably a polymer containing an aromatic ring having at least one fluorine atom and a repeating unit including at least one bond selected from the group consisting of an ether bond, a ketone bond, a sulfone bond, an amide bond, an imide bond, and an ester bond, and can be synthesized by the method described in JP-A-2008-181121, for example.

[0044] Polyarylate Resin The polyarylate resin is not particularly limited, and examples thereof include U-Polymer U100, P-1001, P-3001, and P-5001 manufactured by Unitika Ltd.

[0045] (Resin (B)) As the resin (B), a resin having a total light transmittance at a wavelength of 940 nm (according to JIS K 7375:2008) of preferably 75% or more, more preferably 78% or more, and even more preferably 80% or more is used. When a resin (B) having a total light transmittance within the above range is used, the obtained light-scattering film also has high transmittance for near-infrared light. The total light transmittance of the resin (B) is the total light transmittance of a resin support having a thickness of 0.1 mm and consisting only of the resin (B).

[0046] Furthermore, the polystyrene-equivalent weight average molecular weight (Mw) of resin (B), measured by gel permeation chromatography (GPC), is 10,000 or more, preferably 20,000 or more, and more preferably 30,000 or more, from the viewpoint of forming island portions as resin (B). If the lower limit of Mw is equal to or greater than the above-mentioned value, the generation of aggregate crystals or powder is suppressed, facilitating the formation of a sea-island structure. Furthermore, while there are no particular limitations on Mw, it is preferably 500,000 or less, more preferably 400,000 or less, even more preferably 300,000 or less, and particularly preferably 200,000 or less. When two or more types of resin (B) are used, it is sufficient that the Mw of each resin is within the above-mentioned range.

[0047] The tensile break strength of resin (B), measured in accordance with JIS K 7127:1999, is preferably 40 MPa or more, more preferably 50 MPa or more, even more preferably 60 MPa or more, and particularly preferably 70 MPa or more, from the viewpoint of withstanding the stress of the dielectric multilayer film and suppressing the occurrence of cracks even after the formation of the sea-island structure. The upper limit of the tensile break strength is not particularly limited as long as the effects of the present invention are obtained, but is usually 300 MPa. By using resin (B) with a tensile break strength within this range, it is possible to easily obtain a light-scattering film that can suppress the occurrence of cracks even when a dielectric multilayer film is formed. Note that when two or more types of resin (B) are used, it is sufficient that the tensile break strength of each resin is within the above range.

[0048] The glass transition temperature (Tg) of resin (B) is preferably 120 to 380°C, more preferably 130 to 370°C, and even more preferably 140 to 360°C, from the viewpoint of ensuring that an optical filter having an island-sea structure can withstand the temperature required for forming a dielectric multilayer film and suppressing an increase in surface roughness and a decrease in transmittance associated with fusion of island portions and size changes after heating. If the Tg is in the above range or higher, an increase in surface roughness during formation of the dielectric multilayer film is suppressed, and optical properties close to those designed can be obtained. When two or more types of resin (B) are used, it is sufficient that the Tg of each resin is within the above range.

[0049] The refractive index (n) of resin (B) is preferably 1.40 to 1.80, more preferably 1.43 to 1.75, and even more preferably 1.46 to 1.72. If the refractive index (n) is within this range, a light-scattering film having the desired scattering properties can be easily obtained. When two or more types of resin (B) are used, it is sufficient that the refractive index (n) of the mixed resin is within the above range.

[0050] In the present light-scattering film, the absolute value of the refractive index difference (Δn) between the resin (A) and the resin (B) is 0.04 or more, preferably 0.05 or more, more preferably 0.06 or more, and even more preferably 0.07 or more. If the difference in refractive index between the resin (A) and the resin (B) is equal to or greater than the above-mentioned numerical value, a light-scattering film having a high haze value in visible light can be easily obtained.

[0051] Examples of the resin (B) include the same resins as those described for the resin (A).

[0052] Resin (A) and resin (B) are designed to interact with each other, and from the viewpoints of stabilizing the sea-island structure during drying in the casting process, stabilizing the sea-island structure during melt molding, and adhesion between the resin and the dielectric multilayer film, resin (A) and resin (B) preferably have a common functional group or a common bond. The common functional group is preferably a hydroxyl group, a carboxylic acid group, an ester group, an amide group, a sulfonic acid group, a sulfone ester group, or an imide group, and more preferably an ester group. The common bond is preferably an ether bond, an ester bond, an amide bond, a sulfone ester bond, or an imide bond, and more preferably an amide bond or an ester bond. Note that cracks may also occur in the dielectric multilayer film if the adhesion between the resin and the dielectric multilayer film is insufficient.

[0053] (Dielectric multilayer film) The present light-scattering film preferably has a dielectric multilayer film on at least one side of the resin layer. The dielectric multilayer film, while thin, efficiently reflects and transmits specific wavelengths, making it possible to maintain a high transmittance of specific infrared light. The dielectric multilayer film may be provided on only one side of the resin layer, or on both sides. When provided on one side, it is excellent in manufacturing cost and ease of manufacturing. When provided on both sides, it is possible to obtain a light-scattering film that has high strength and is less likely to warp.

[0054] When the present light-scattering film is applied to applications such as solid-state imaging devices, it is preferable that the light-scattering film has minimal warping, and therefore it is preferable to provide a dielectric multilayer film on both sides of the substrate, and the dielectric multilayer films provided on both sides may have the same or different spectral characteristics.

[0055] The dielectric multilayer film may be a laminate in which high refractive index material layers and low refractive index material layers are alternately stacked.

[0056] As the material for forming the high refractive index material layer, a material having a refractive index of more than 1.9 can usually be used, and preferably a material having a refractive index of more than 1.9 to 2.5 is selected. Examples of such materials include titanium oxide, zirconium oxide, tantalum pentoxide, niobium pentoxide, lanthanum oxide, yttrium oxide, zinc oxide, zinc sulfide, indium oxide, mixtures thereof, and those filled with an appropriate porosity.

[0057] The low refractive index material layer can generally be made of a material having a refractive index of 1.9 or less, preferably 1.2 to 1.9. Examples of such materials include silica, alumina, lanthanum fluoride, magnesium fluoride, sodium aluminum hexafluoride, mixtures thereof, and materials filled with these materials at an appropriate porosity.

[0058] The method for alternately laminating high-refractive index material layers and low-refractive index material layers is not particularly limited as long as a dielectric multilayer film is formed by laminating these material layers. For example, CVD, sputtering, vacuum deposition, ion-assisted deposition or ion plating, and radical-assisted sputtering can be used directly on the substrate. Sputtering, ion-assisted deposition, ion plating, and radical-assisted sputtering are preferred from the viewpoint of minimizing changes in the transmittance characteristics of the resulting light-scattering film even under high-temperature and high-humidity environments. Vacuum deposition, ion-assisted deposition, and ion plating are preferred from the viewpoint of the film formation rate of the dielectric multilayer film. Vacuum deposition, ion-assisted deposition, and ion plating are preferred from the viewpoint of obtaining a film with minimal foreign matter. Vacuum deposition and ion-assisted deposition are preferred from the viewpoint of suppressing excessive stress generation in the dielectric multilayer film.

[0059] The physical film thickness of each of the high refractive index material layer and the low refractive index material layer depends on the refractive index of each layer, but is usually preferably 5 to 500 nm, and the total physical film thickness of the dielectric multilayer film is preferably 0.1 to 8.0 μm for the entire light-scattering film.

[0060] The total number of layers of high refractive index material layers and low refractive index material layers in the dielectric multilayer film is preferably 4 to 120 layers in the entire light-scattering film, and more preferably 8 to 80. When the thickness of each layer, the thickness of the dielectric multilayer film as the light-scattering film body, and the total number of layers are within the above ranges, a sufficient manufacturing margin can be ensured, and warping of the light-scattering film and cracks in the dielectric multilayer film can be reduced.

[0061] In one embodiment of the present invention, by appropriately selecting the types of materials constituting the high refractive index material layer and the low refractive index material layer, the thickness of each of the high refractive index material layer and the low refractive index material layer, the order of lamination, and the number of laminations, it is possible to obtain a light-scattering film that has a light blocking band and a light transmitting band of desired wavelengths in the near-infrared wavelength range while ensuring sufficient transmittance in the visible range.

[0062] Here, to optimize the conditions, for example, optical thin film design software (e.g., EssentialMacleod, manufactured by ThinFilmCenter) can be used to set the transmittance of the transmitted wavelength high and the transmittance of the reflected wavelength low. For example, in the case of a light-scattering film having a dielectric multilayer film formed on both sides, when a light transmission band is set around 940 nm and visible light is reflected, the software is used to set the target transmittance of one dielectric multilayer film to 0% for light with a wavelength of 400 to 900 nm and the target transmittance of light with a wavelength of 920 to 960 nm to 100%, and then set the target tolerance value for each wavelength range to 0.5 or less, and set the target transmittance of the other dielectric multilayer film to 100% for light with a wavelength of 920 to 960 nm, and set the target tolerance value for each wavelength range to 0.5 or less.

[0063] When the present light-scattering film has a dielectric multilayer film, it may have a layer formed from a curable composition between the resin layer and the dielectric multilayer film, and the layer formed from the curable composition may be one layer or two or more layers. When the present optical filter has two or more layers formed from the curable composition, it may have two or more of the same layer or two or more different layers.

[0064] The function of the layer formed from the curable composition is not particularly limited, and examples thereof include a planarizing layer, a hard coat layer, an adhesion layer, an antistatic layer, a color adjustment layer, a reflectance adjustment layer, a flexibility-imparting layer, a foreign matter adhesion prevention layer, a layer for improving organic solvent resistance, a layer for improving weather resistance, a gas barrier layer, etc. By having these functional layers on the surface of the resin layer, improved adhesion to the dielectric multilayer film can also be expected.

[0065] Examples of a method for laminating a layer formed from a curable composition include a method of melt-molding or cast-molding a layer formed from a curable composition onto a resin layer, etc. Alternatively, the curable composition can be applied onto a resin layer using a bar coater or the like, and then cured by ultraviolet irradiation or the like to produce the film.

[0066] Examples of the curable composition include ultraviolet (UV) / electron beam (EB) curable resins and thermosetting resins, and specific examples thereof include vinyl compounds, urethane-based, urethane acrylate-based, acrylate-based, epoxy-based, and epoxy acrylate-based resins.

[0067] The curable composition may also contain a polymerization initiator. As the polymerization initiator, a known photopolymerization initiator or thermal polymerization initiator can be used, or a photopolymerization initiator and a thermal polymerization initiator may be used in combination. The polymerization initiator may be used alone or in combination of two or more types.

[0068] The blending ratio of the polymerization initiator in the curable composition is preferably 0.1 to 10 mass%, more preferably 0.5 to 10 mass%, and even more preferably 1 to 5 mass%, when the total amount of the curable composition is taken as 100 mass%. When the blending ratio of the polymerization initiator is within this range, the curable composition has excellent curing characteristics and handleability, and a functional film such as a hard coat film or an antistatic film having a desired hardness can be obtained.

[0069] Furthermore, an organic solvent may be added to the curable composition as a solvent, and known organic solvents can be used. Specific examples of organic solvents include alcohols such as methanol, ethanol, isopropanol, butanol, and octanol; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; esters such as ethyl acetate, butyl acetate, ethyl lactate, γ-butyrolactone, propylene glycol monomethyl ether acetate, and propylene glycol monoethyl ether acetate; ethers such as ethylene glycol monomethyl ether and diethylene glycol monobutyl ether; aromatic hydrocarbons such as benzene, toluene, and xylene; and amides such as dimethylformamide, dimethylacetamide, and N-methylpyrrolidone. These solvents may be used alone or in combination of two or more.

[0070] The thickness of the layer formed from the curable composition is preferably 0.1 to 30 μm, more preferably 0.5 to 20 μm, and even more preferably 0.7 to 5 μm.

[0071] Furthermore, for the purpose of improving the adhesion between the resin layer and the curable composition and / or the dielectric multilayer film, or between the curable composition and the dielectric multilayer film, the surface of the resin layer, the curable composition layer, or the dielectric multilayer film may be subjected to a surface treatment such as a corona treatment or a plasma treatment.

[0072] (Additives) The resin layer may contain additives within the range that does not impair the effects of the present invention. Examples of additives include ultraviolet absorbers, antioxidants, light stabilizers, colorants, surfactants, and antistatic agents.

[0073] Examples of ultraviolet absorbers include 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, TINUVIN PS, TINUVIN 99-2, TINUVIN 326, TINUVIN 384-2, TINUVIN 900, TINUVIN 928, TINUVIN 970, TINUVIN 1130, TINUVIN 400, TINUVIN 405, TINUVIN 460, TINUVIN 477, TINUVIN 479, TINUVIN 111FDL, and TINUVIN 123 manufactured by BASF. Examples of such ultraviolet absorbers include TINUVIN 144, TINUVIN 152, TINUVIN 249, TINUVIN 292, TINUVIN 770DF, TINUVIN 5100, TINUVIN 5050, TINUVIN 5060, TINUVIN 5151, TINUVIN 5866, TINUVIN B75, TINUVIN 9945-DW, UVA-805, UVA-903KT, UVA-935LH, the ADK STAB LA series such as ADK STAB LA-F-70 manufactured by ADEKA Corporation, and the BOSNASORB series such as BONASORB UA-3912 manufactured by Orient Chemical Industry Co., Ltd. When an ultraviolet absorber is added, the transmittance at a wavelength of 300 to 380 nm can be suppressed, making it possible to improve the light resistance of the light-scattering film.

[0074] Examples of antioxidants and light stabilizers include 2,6-di-tert-butyl-4-methylphenol, 2,2'-dioxy-3,3'-di-tert-butyl-5,5'-dimethyldiphenylmethane, and tetrakis[methylene-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]methane. Commercially available products include Irganox 1010, Irganox 1035, Irganox 1076, Irganox 1135, Irganox 1726, Irgastab UV-22, and Irgastab UV-25 manufactured by BASF Corporation, and the Adeka STAB AO series, such as Adeka STAB LA-52, Adeka STAB LA-57, Adeka STAB LA-63P, Adeka STAB LA-68, Adeka STAB LA-72, Adeka STAB LA-77Y, Adeka STAB LA-81, Adeka STAB LA-82, Adeka STAB LA-87, Adeka STAB LA-402AF, and Adeka STAB LA-40MP, manufactured by ADEKA Corporation.

[0075] The colorant is not particularly limited and may be a pigment, dye, or the like, and may be added as appropriate depending on the surrounding components of the mobile terminal, such as the body color.

[0076] The additives may be mixed with the resin components (resin (A) and resin (B)) when the resin layer is produced, or may be added in advance when the resin components are produced. The amount of the additives added is appropriately selected depending on the desired properties, but is usually 0.01 to 15.0 parts by mass, and preferably 0.05 to 12.0 parts by mass, per 100 parts by mass of the resin components, i.e., the total of resins (A) and (B).

[0077] (Color of the Present Light-Scattering Film) The present light-scattering film can be designed to have black or other colors. The color is evaluated using commonly known color space coordinates such as the Ostwald color system, CIE color system, RGB color system, XYZ color system, L*u*v* color system, and L*a*b* color system. In the present invention, the color is evaluated using the L*a*b* color system, for example, based on the wavelength-specific intensity of light incident at an angle of 0°, i.e., from the vertical direction, scattered at 45°, in accordance with JIS Z 8722:2009, and is evaluated from the color space coordinates L*, a*, and b* using X, Y, and Z from the integral value of the product of the scattering intensity and the luminosity coefficient every 5 nm. In the L*a*b* color system, from the viewpoint of enabling the design of colors other than black for the present light-scattering film, L* is preferably 0.2 or more, more preferably 0.3 or more, even more preferably 0.4 or more, and particularly preferably 0.5 or more. If L* is equal to or greater than the above-mentioned numerical value, it will be observed as a color other than black when observed by the human eye. The upper limit of L* is not particularly limited as long as the effects of the present invention can be obtained, but is usually 100.

[0078] Because the present light-scattering film has excellent reflection / scattering properties for visible light, its haze value for visible light is preferably 85% or more, more preferably 90% or more, even more preferably 94% or more, even more preferably 98% or more, particularly preferably 99% or more, and most preferably 99.1% or more. The upper limit of the haze value is not particularly limited as long as the effects of the present invention are obtained, but it is usually 100%. Furthermore, when a dielectric multilayer film is provided on the present light-scattering film, the numerical value of the haze for visible light, which indicates the scattering ratio, is important for achieving good color development and a highly aesthetic color that is not black, transparent, or mirror-like. If the haze value for visible light is low, mirror glare may be visible when viewing the optical filter at a specific angle. The haze for visible light refers to the haze value at a wavelength of 535 nm and is measured according to the method described in the Examples below.

[0079] [Method for Manufacturing the Present Light-Scattering Film] The present light-scattering film can be produced by dispersing the resin (B) component constituting the island portions in the resin (A) component constituting the sea portions. For example, the resins (A) and (B) and, if necessary, additives are blended by a known method (e.g., melt blending, tumbling, etc.), melt-mixed, and extruded through a T-die or ring die to form a film, thereby dispersing the resin (B) component constituting the island portions in the resin (A) component. The present light-scattering film can also be produced by molding using known film-forming methods, such as a coating method in which a composition composed of resins (A) and (B) is applied to a support (e.g., a glass support), or a lamination method in which the composition is laminated, a casting method, or an extrusion molding method. When the present light-scattering film has a dielectric multilayer film, the dielectric multilayer film can be formed on the light-scattering film produced by the above method by the above method.

[0080] The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples. Unless otherwise specified, "parts" means "parts by mass."

[0081] [Measurement of Resin Properties] The physical properties of the resins used in the following examples and / or comparative examples were measured according to the following methods. <Weight-Average Molecular Weight> The weight-average molecular weight (Mw) of the resin was measured by the following method (1) or (2), taking into account the solubility of each resin in a solvent. (1) Using a gel permeation chromatography (GPC) apparatus manufactured by WATERS (150C type, column: H-type column manufactured by Tosoh Corporation, developing solvent: o-dichlorobenzene), the weight-average molecular weight (Mw) and number-average molecular weight (Mn) in terms of standard polystyrene were measured. (2) Using a GPC apparatus manufactured by Tosoh Corporation (HLC-8220 type, column: TSKgel α-M, developing solvent: tetrahydrofuran), the weight-average molecular weight (Mw) and number-average molecular weight (Mn) in terms of standard polystyrene were measured.

[0082] <Tensile Breaking Strength> Using a universal testing machine (Instron, 68FM-300), a tensile test was performed in the up and down directions at a tensile speed of 5 mm / min using a test piece type 1B having a parallel part width of 10 mm, a chuck distance of 115 mm, and a thickness of 200 μm, in accordance with JIS K 7127: 1999. The yield point was measured 10 times, and the average of six values ​​excluding the maximum and second largest values ​​and the minimum and second smallest values ​​was taken as the tensile breaking strength. The tensile breaking strength of the light-scattering films A and D described below was also measured in the same manner as above, except that, if a protective film or glass substrate was attached, it was peeled off and the thickness of the test piece was taken as the thickness of the obtained light-scattering film.

[0083] <Glass Transition Temperature (Tg)> Measurement was carried out using a differential scanning calorimeter (DSC6200) manufactured by Hitachi High-Tech Science Corporation at a temperature rise rate of 20° C. per minute in a nitrogen stream.

[0084] <Refractive Index (n)> The refractive index was measured using a wavelength of 535 nm analyzed using the Cauchy dispersion formula based on the refractive index distribution published by the manufacturer, or a 535 nm value measured using a spectroscopic ellipsometry (M-2000D manufactured by J.A. Woollam) on a silicon wafer (111 orientation, undoped, diameter 10 mm, thickness 280 μm, manufactured by Universalwafer Inc.) coated with a resin film to a thickness of 1 μm using a spinner. When two or more types of resin (A) are used, the measured value using a resin film in which the resins (A) used are mixed is used. The same applies when multiple resins (B) are used.

[0085] [Preparation of Resins] Resins 1 to 4 used in the following Examples and / or Comparative Examples were synthesized according to the following Synthesis Examples. Synthesis Example 1: In a reaction vessel equipped with a stirrer and purged with nitrogen, 8-methyl-8-methoxycarbonyltetracyclo[4.4.0.1] represented by the following formula (a) was added. ２，５ .1 ７，１０100 parts of ] dodeca-3-ene, 18 parts of 1-hexene as a molecular weight modifier, and 300 parts of toluene as a solvent for ring-opening polymerization were charged, and the solution was heated to 80°C. Next, 0.2 parts of a toluene solution of triethylaluminum (concentration 0.6 mol / L) as a polymerization catalyst and 0.9 parts of a toluene solution of methanol-modified tungsten hexachloride (concentration 0.025 mol / L) were added to the solution in the reaction vessel, and the resulting solution was heated and stirred at 80°C for 3 hours to carry out a ring-opening polymerization reaction, thereby obtaining a ring-opened polymer solution. The polymerization conversion rate in this polymerization reaction was 97%. 1,000 parts of the resulting ring-opened polymer solution was charged into an autoclave, and this ring-opened polymer solution was added with RuHCl(CO)[P(C ６ H ５ ) ３ ] ３ 0.12 parts was added, and the hydrogen gas pressure was 100 kg / cm ２ The hydrogenation reaction was carried out by heating and stirring for 3 hours at a reaction temperature of 165°C. The resulting reaction solution (hydrogenated polymer solution) was cooled, and the hydrogen gas pressure was released. Next, the reaction solution was poured into a large amount of methanol, and the coagulated product was separated and recovered. This was then dried to obtain a hydrogenated polymer (hereinafter also referred to as "Resin 1"). The resulting Resin 1 had an Mw of 137,000, a Tg of 165°C, and a tensile strength at break of 74 MPa.

[0086]

[0087] Synthesis Example 2 A reaction vessel equipped with a stirrer was charged with 60 parts by weight of 2,2-bis(4-hydroxyphenyl)propane, 15 parts by weight of 2-phenyl-3,3-bis(4-hydroxyphenyl)phthalimidine, 0.85 parts by weight of p-tert-butylphenol as an end-capping agent, 22.9 parts by weight of sodium hydroxide as an alkali, 0.41 parts by weight of triethylbenzylammonium chloride as a polymerization catalyst, and 0.37 parts by weight of sodium hydrosulfite as an antioxidant, and the resulting solution was dissolved in 1,750 parts by weight of water to form an aqueous phase. Separately from the aqueous phase, 19.76 parts by weight of terephthaloyl chloride (TPC) and 19.76 parts by weight of isophthaloyl chloride (IPC) (TPC:IPC = 50:50 (molar ratio)) were dissolved in 1,000 parts by weight of methylene chloride, and the resulting solution was used as an organic phase. The aqueous phase was stirred in advance, and the organic phase was added to the aqueous phase under stirring. Polymerization was carried out by interfacial polymerization at 15°C for 4 hours. After this, stirring was stopped, and the aqueous and organic phases were separated by decantation. After removing the aqueous phase, 500 parts by mass of methylene chloride, 2000 parts by mass of pure water, and 2 parts by mass of acetic acid were added to terminate the reaction, and the mixture was stirred at 15°C for 30 minutes. The organic phase was then washed 10 times with pure water, and the organic phase was added to methanol to precipitate the polymer. The precipitated polymer was filtered and dried to obtain Resin 2. The obtained Resin 2 had an Mw of 100.100, a Tg of 220°C, and a tensile break strength of 72 MPa.

[0088] Synthesis Example 3 In a reaction vessel equipped with a stirrer, 69.8 parts by mass of 1,1-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane, 0.7 parts by mass of p-tert-butylphenol as an end-capping agent, 32.7 parts by mass of sodium hydroxide as an alkali, 1.0 part by mass of a 50% by mass aqueous solution of tri-n-butylbenzylammonium chloride as a polymerization catalyst, and 0.3 parts by mass of sodium hydrosulfite as an antioxidant were charged and dissolved in 1,040 parts by mass of water, and this solution was designated as an aqueous phase. Separately from the aqueous phase, 23.0 parts by mass of TPC and 23.0 parts by mass of IPC (TPC:IPC = 50:50 (molar ratio)) were dissolved in 910 parts by mass of methylene chloride, and this solution was designated as an organic phase. The total volume of the aqueous phase and organic phase was 1 L. The organic phase was added to the aqueous phase, and polymerization was carried out by interfacial polymerization at 15°C for 2 hours. After this, stirring was stopped, and the aqueous phase and organic phase were separated by decantation. After removing the aqueous phase, 500 parts by mass of methylene chloride, 2000 parts by mass of pure water, and 2 parts by mass of acetic acid were added to stop the reaction, and the mixture was stirred at 15°C for 30 minutes. The organic phase was then washed 10 times with pure water, and the organic phase was added to methanol to precipitate a polymer. The precipitated polymer was filtered and dried to obtain Resin 3. The obtained Resin 3 had an Mw of 78,000, a Tg of 273°C, and a tensile strength at break of 72 MPa.

[0089] Synthesis Example 4 In a reaction vessel equipped with a stirrer, 12 parts by mass of methyl 2-(hydroxymethyl)acrylate, 83.5 parts by mass of methyl methacrylate, 90.4 parts by mass of toluene, 0.05 parts by mass of tris(2,4-di-tert-butylphenyl)phosphite, and 0.07 parts by mass of n-dodecyl mercaptan were charged, and the mixture was heated to 105 ° C. while passing nitrogen through. Next, 0.9 parts by mass of t-amyl peroxyisononanoate (manufactured by Arkema Yoshitomi Co., Ltd., Luperox (registered trademark) 570) was added, and 5 minutes later, a solution consisting of 4.5 parts by mass of styrene, 8.14 parts by mass of toluene, and 0.179 parts by mass of t-amyl peroxyisononanoate (manufactured by Arkema Yoshitomi Co., Ltd., Luperox (registered trademark) 570) was added dropwise over 2 hours, while solution polymerization was carried out at 100 to 110 ° C. To the resulting polymerization solution, 0.075 parts by mass of stearyl phosphate (Phoslex A-18, manufactured by Sakai Chemical Industry Co., Ltd.) was added, and a cyclization condensation reaction to form a lactone ring structure was allowed to proceed for 1.5 hours under reflux at approximately 90 to 110° C. Next, the resulting polymerization solution was passed through a multi-tube heat exchanger maintained at 240° C. to complete the cyclization condensation reaction, and then introduced into a vent-type twin-screw extruder (L / D=52) equipped with a leaf-disc polymer filter (filtration accuracy: 5 μm) at its tip at a processing rate of 90 parts by mass / hour in terms of resin amount, and the polymerization solution was devolatilized. During devolatilization, ion-exchanged water was introduced from behind the first and second vents at a rate of 1.3 parts by mass / hour, and a separately prepared solution of 1.0 part by mass of zinc octylate (Nihon Kagaku Sangyo Co., Ltd., Nikka Octyx Zinc 10% by mass) dissolved in 0.3 parts by mass of toluene was introduced from behind the third vent at a rate of 0.3 parts by mass / hour, and the polymer solution was devolatilized to obtain Resin 4. The obtained Resin 4 had an Mw of 9,800, a Tg of 125°C, and a tensile break strength of 8 MPa.

[0090] [Measurement of Film Properties] The physical properties of the light-scattering films obtained in the following Examples and Comparative Examples were measured according to the following methods. <Surface Roughness (Sa)> The surface of the exposed resin layer of the light-scattering film A or D described below was photographed with a laser microscope (VK-X250, manufactured by Keyence Corporation) using a 10x lens to measure the average surface roughness (μm), which was defined as the surface roughness (Sa) of the resin layer.

[0091] <Cracks> Cracks correspond to "cracks" and "cracks" as defined in JIS K 6900, and "no cracks" means that cracks corresponding to ranks 1 to 5 as defined in JIS K 6259 do not occur. Regarding the light-scattering films provided with a vapor-deposited film described below, those that showed no cracks even 14 days after the vapor-deposited film was formed were rated as "◯", those that showed no cracks after the vapor-deposited film was formed but cracks occurred 14 days later were rated as "Δ", and those that showed cracks within 14 days after the vapor-deposited film was formed were rated as "×".

[0092] <Film Peeling> A light-scattering film provided with a vapor-deposited film was left standing in a thermo-hygrostat chamber at a temperature of 85°C and a humidity of 85% for 300 hours, and then left standing at room temperature of 25°C for 24 hours, and then the adhesion (cross-cut method) was evaluated in accordance with JIS K 5600-5-6, with classification 0 or 1 being rated as "Good", classification 3 or 4 being rated as "Average", and classification 5 being rated as "Poor".

[0093] <Transmittance at a wavelength of 940 nm and scattering characteristics (haze) in visible light> Light-scattering film A or D, cut into a square with sides of 5 cm, was measured using a spectroscopic haze meter (HSP-150VIR, manufactured by Murakami Color Research Laboratory Co., Ltd.) in accordance with JIS K 7375: 2008. Haze (%) at a wavelength of 535 nm was evaluated as scattering characteristics in visible light, Tt (%) at a wavelength of 940 nm was defined as total light transmittance, Td (%) at a wavelength of 940 nm was defined as diffuse transmittance, and Tt - Td (%) at a wavelength of 940 nm was defined as rectilinear transmittance.

[0094] <Presence or absence of sea-island structure> The presence or absence of a sea-island structure in the resin layer in the light-scattering film was evaluated by forming a cut surface with a microtome (ULTRA MICROTOME MT-7000 manufactured by RMC Corporation) and then observing the cross section with a microscope (VHX-6000 manufactured by Keyence Corporation, 200 to 2000 magnifications, variable depending on the sample). When island portions of 0.1 μm to 1 mm were observed in the resin layer, it was determined that the resin layer had a sea-island structure.

[0095] <Difference in transmittance between calculated and measured values ​​for vapor deposition film design 2> For the transmittance for each wavelength in the wavelength range of 400 to 1100 nm, the calculated value of the transmittance of the vapor deposition design 2 described below using the optical thin film design software EssentialMacleod (manufactured by ThinFilmCenter) was compared with the measured value of the transmittance of a sample formed on a film with vapor deposition design 2. When the maximum value of the transmittance difference was 10% or more, it was marked "x", when the maximum value was 5% or more but less than 10%, it was marked "△", and when the maximum value was less than 5%, it was marked "◯". The transmittance (spectral transmittance) in each wavelength region of the film was measured using a spectrophotometer U-4100 manufactured by Hitachi High-Technologies Corporation, by placing the sample immediately before the light entrance port of an integrating sphere.

[0096] [Film Production] Example 1 (Production of Light-Scattering Film) ARTON F4520 (Mw: 64,000, tensile strength at break: 77 MPa, Tg: 163°C, hereinafter also referred to as "resin 5"), a cyclic olefin resin having an ester bond manufactured by JSR Corporation, was used as resin (A) constituting the sea portion, and Iupizeta PCZ-200 (Mw: 52,000, tensile strength at break: 77 MPa, Tg: 174°C, hereinafter also referred to as "resin 6"), a polycarbonate resin having an ester bond manufactured by Mitsubishi Gas Chemical Company, Inc., was used as resin (B). 18.9 kg and 8.1 kg of each resin were weighed out and dried in advance at 100°C for 4 hours. As an additive, 8.1 g (0.03 parts by mass per 100 parts by mass of the total resin before drying) of BONASORB UA-3912 manufactured by Orient Chemical Industry Co., Ltd. was weighed out and blended with dried pellets of Resin 5 and pellets of Resin 6. This dry blend was dropped into the hopper of a twin-screw extruder (manufactured by Shibaura Machine Co., Ltd.: TEM-26SX), and extruded pellets of the dry blend were obtained at 175 ° C for C1, 310 ° C for C2 to C7, and 290 ° C for a die head equipped with a 200 mesh, with a screw rotation of 120 rpm, a feeder rotation of 27 rpm, and a discharge rate of 10 kg / hr. The extruded pellets of the obtained dry blend were vacuum dried at 100 ° C for 4 hours.

[0097] As a film-forming device, a twin-screw extruder (15 mmΦ twin-screw extruder manufactured by Technovel Co., Ltd.: KZW15TW-30MG-NH) was used. The cylinder temperature and gear pump temperature settings were 310 ° C, and the T-die (300 mm width) was set to 300 ° C. The T-die lip gap was 0.45 mm, and the air gap between the T-die and the first roll was 50 mm. The dried extruded pellets of the dry blend were fed into a hopper and fed from a coil feeder to the extruder so that the discharge rate was 2.7 kg / hr. The screw rotation speed of the extruder was 300 rpm, the gear pump rotation speed was 18 rpm, and the molten resin was allowed to flow down from the T-die and dropped onto the most upstream roll of a horizontal three-roll set below it with a face length of 360 mm and a diameter of 100 mm. The roll peripheral speed was set to 1.8 m / min, and after half a revolution, it was rotated by the second roll, and then another half revolution, and then cooled by the third roll, and then peeled off from the roll. The roll temperatures were controlled using an oil temperature regulator (KCO-4006N, manufactured by Reiken Co., Ltd.), and the set temperatures were 160°C, 145°C, and 130°C, respectively, from the first roll on the upstream side. Thereafter, a protective film, Toretec 7332 (manufactured by Toray Advanced Film Co., Ltd.), was laminated to one side of the film, and the film was taken up with a winder to obtain a light-scattering film A with a thickness of 180 μm. The various physical properties of the obtained light-scattering film A are shown in Table 2. The obtained light-scattering film A was observed for the presence or absence of a sea-island structure as described above. A cross-sectional view of the observed film is shown in Figure 1. The surface of the resin layer was smooth, and the white areas in Figure 1 are island portions, confirming the presence of a sea-island structure.

[0098] (Formation of Dielectric Multilayer Film (Vapor Deposition Film)) Next, the obtained light-scattering film A was cut into a square with a side of 110 mm. After peeling off the protective film from this light-scattering film A, it was vapor-deposited in an ion-assisted vapor deposition apparatus (Sapio 1300, manufactured by Showa Vacuum Co., Ltd.) at a dome temperature of 80°C and an initial vacuum of 8×10 －３ Pa, the gas of the ion-assisted ion gun is oxygen or a mixed gas of oxygen and argon, and SiO ２ layer and TiO ２A light-scattering film B was obtained by providing a dielectric multilayer film of deposition design 1, in which layers were alternately stacked, on the surface from which the protective film had been peeled off. The layer structure of deposition design 1 is shown in Table 1. In Table 1, layers 1 to 28 represent the dielectric multilayer films, with Layer 1 representing the dielectric multilayer films stacked on resin layers in that order, and Layer 28 being the outermost layer. Table 2 shows the results of evaluating cracks in light-scattering film B. A light-scattering film C was obtained by providing a dielectric multilayer film of deposition design 2, which differs in the number of layers of the dielectric multilayer film, on a separately prepared square light-scattering film A, each 110 mm long, under the same conditions as deposition design 1. The layer structure of deposition design 2 is shown in Table 1. In Table 1, layers 1 to 38 represent the dielectric multilayer films, with Layer 1 representing the dielectric multilayer films stacked on resin layers in that order, and Layer 38 being the outermost layer. The results of evaluating cracks and film peeling in light-scattering film C are shown in Table 2. Furthermore, Figure 2 shows the results of spectral transmittance measurement of light-scattering film C when light was incident on the surface with the dielectric multilayer film. The evaluation of the transmittance difference between the calculated value and the measured value for the evaporated film design 2 is shown in Table 2.

[0099]

[0100] Example 2 To a polypropylene container, 70 parts by mass of Iupizeta FPC-8225 (Mw: 64,000, tensile strength at break: 80 MPa, Tg: 156°C, hereinafter also referred to as "Resin 7"), a polycarbonate resin having an ester bond manufactured by Mitsubishi Gas Chemical Company, was added as Resin (A), 30 parts by mass of Resin 1 as Resin (B), 0.3 parts of Adekastab LA-F70 manufactured by ADEKA Corporation as an additive, and methylene chloride were added to obtain a solution with a resin concentration of 18% by mass. The resulting solution was then cast onto a smooth PET plate and dried at 20°C for 1 hour, after which the coating film was peeled off from the PET plate. The peeled coating film was further dried under reduced pressure at 70 to 150°C for 2 hours to obtain a light-scattering film A having a thickness of 136 μm, a length of 20 cm, and a width of 20 cm. The obtained light-scattering film A was evaluated in the same manner as in Example 1. The results are shown in Table 2. Furthermore, the presence or absence of a sea-island structure was confirmed for light-scattering film A, and a sea-island structure was confirmed. Next, a dielectric multilayer film of vapor deposition design 1 or vapor deposition design 2 was provided on one side of the obtained light-scattering film A in the same manner as in Example 1 to prepare light-scattering films B and C, and the obtained light-scattering films B and C were evaluated in the same manner as in Example 1. The results are shown in Table 2. The spectral transmittance of the obtained light-scattering film C was measured, and the results are shown in Figure 3.

[0101] Example 3 (Production of Light-Scattering Film) A light-scattering film A having a thickness of 120 μm was obtained in the same manner as in Example 2, except that Resin 2 was used instead of Resin 7 as Resin (A) and TINUVIN PS manufactured by BASF was used instead of Adekastab LA-F70 as the additive. A Toretec 7332 (manufactured by Toray Advanced Film Co., Ltd.) was laminated as a protective film onto the coating film on the side of the obtained light-scattering film A opposite to the side that had been in contact with the PET plate during casting.

[0102] (Formation of Layer Formed from Resin Composition) A curable resin composition (α) having the following composition was applied to the surface of the light-scattering film A opposite to the surface to which the protective film was attached using a bar coater, and the coating was heated in an oven at 70°C for 2 minutes to volatilize and remove the solvent. At this time, the coating conditions of the bar coater were adjusted so that the thickness after drying would be 4 µm. Next, the layer was exposed (exposure amount 500 mJ / cm) using a conveyor-type exposure machine.2 , 200 mW) to cure the curable resin composition (α), and a curable composition layer A was provided on the light-scattering film A. The obtained light-scattering film A was examined for the presence or absence of a sea-island structure, and a sea-island structure was confirmed. Curable resin composition (α): A composition obtained by mixing 60 parts by mass of tricyclodecane dimethanol acrylate, 40 parts by mass of dipentaerythritol hexaacrylate, 5 parts by mass of 1-hydroxycyclohexyl phenyl ketone, and methyl ethyl ketone (solvent) in amounts such that the solid content concentration (TSC; amount of components other than solvent) was 30% by mass.

[0103] (Formation of Dielectric Multilayer Film) Next, the obtained light-scattering film A provided with the curable composition layer A was cut into a square with a side of 110 mm. After peeling off the protective film from this light-scattering film, it was evaporated in an ion-assisted deposition apparatus (Sapio 1300, manufactured by Showa Vacuum Co., Ltd.) at a dome temperature of 80°C and an initial vacuum of 8×10 －３ Pa, the gas of the ion-assisted ion gun is oxygen or a mixed gas of oxygen and argon, and SiO ２ layer and TiO ２ A light-scattering film B was obtained in which a dielectric multilayer film of deposition design 1, in which layers were alternately laminated, was provided on the curable composition layer A side. The obtained light-scattering film B was evaluated in the same manner as in Example 1. The results are shown in Table 2. A light-scattering film A was provided with a square curable composition layer A, each 110 mm long, which was separately prepared, and a dielectric multilayer film of deposition design 2 was provided on the curable composition layer A side under the same conditions as in deposition design 1, to obtain a light-scattering film C. The obtained light-scattering film C was evaluated in the same manner as in Example 1. The results are shown in Table 2.

[0104] Example 4 A light-scattering film A having a thickness of 137 μm was obtained in the same manner as in Example 2, except that resin 1 was used instead of resin 7 as resin (A), resin 2 was used instead of resin 1 as resin (B), and Irganox 1010 was used instead of ADK STAB LA-F70 as the additive. Next, a curable composition layer A was provided in the same manner as in Example 3, and then light-scattering films B and C were obtained in the same manner as in Example 3. Furthermore, when the presence or absence of a sea-island structure in light-scattering film A was confirmed, a sea-island structure was confirmed. Each of the obtained light-scattering films was evaluated in the same manner as in Example 1. The results are shown in Table 2.

[0105] Example 5 A light-scattering film A having a thickness of 117 μm was obtained in the same manner as in Example 2, except that Resin 3 was used instead of Resin 7 as Resin (A), ARTON GX-5000 (Mw: 69,000, tensile break strength: 74 MPa, Tg: 165°C; hereinafter also referred to as "Resin 8"), a cyclic olefin resin having an ester bond manufactured by JSR Corporation, was used instead of Resin 1 as Resin (B), and FDR-001 manufactured by Yamada Chemical Co., Ltd. was used instead of Adeka STAB LA-F70 as an additive. Next, a curable composition layer A was provided in the same manner as in Example 3, and then light-scattering films B and C were obtained in the same manner as in Example 3. Furthermore, when the presence or absence of a sea-island structure in light-scattering film A was confirmed, a sea-island structure was confirmed. The obtained light-scattering films were evaluated in the same manner as in Example 1. The results are shown in Table 2.

[0106] Example 6 A light-scattering film A having a thickness of 117 μm was obtained in the same manner as in Example 2, except that resin 1 was used instead of resin 7 as resin (A), resin 2 was used instead of resin 1 as resin (B), and FDR-005 manufactured by Yamada Chemical Co., Ltd. was used instead of the additive ADK STAB LA-F70. Next, a curable composition layer A was provided in the same manner as in Example 3, and light-scattering films B and C were obtained in the same manner as in Example 3. Furthermore, when the presence or absence of a sea-island structure in light-scattering film A was confirmed, a sea-island structure was confirmed. The obtained light-scattering films were evaluated in the same manner as in Example 1. The results are shown in Table 2.

[0107] Example 7 A light-scattering film A having a thickness of 140 μm was obtained by the same procedure as in Example 6, except that FDB-004 manufactured by Yamada Chemical Co., Ltd. was used instead of the additive FDR-005. Next, a curable composition layer B was provided by the same procedure as in Example 3, except that a curable resin composition (β) having the following composition was used instead of the curable resin composition (α). Light-scattering films B and C were then obtained by the same procedure as in Example 3, except that curable composition layer B was used instead of curable composition layer A. Furthermore, when the presence or absence of a sea-island structure was confirmed for light-scattering film A, a sea-island structure was confirmed. Each of the obtained light-scattering films was evaluated in the same manner as in Example 1. The results are shown in Table 2. Curable resin composition (β): A composition obtained by mixing ALACOAT DA501 (manufactured by Arakawa Chemical Industries, Ltd.) and ALACOAT CL100A (manufactured by Arakawa Chemical Industries, Ltd.) in a mass ratio of 10:4.

[0108] Example 8 A light-scattering film A with a thickness of 145 μm was obtained in the same manner as in Example 2, except that Iupizeta RX-2136P (Mw: 58,000, tensile break strength: 77 MPa, Tg: 126°C; hereinafter also referred to as "resin 9"), a polycarbonate resin having an ester bond and a hydroxyl group manufactured by Mitsubishi Gas Chemical Company, Inc., was used instead of Resin 1 as Resin (B), and no additives were used. Next, light-scattering films B and C were obtained from the obtained light-scattering film A in the same manner as in Example 2. Furthermore, when the presence or absence of a sea-island structure in light-scattering film A was confirmed, a sea-island structure was confirmed. The obtained light-scattering films were evaluated in the same manner as in Example 1. The results are shown in Table 2.

[0109] Example 9 A light-scattering film A with a thickness of 160 μm was obtained in the same manner as in Example 1, except that Iupizeta FPC-0330 (Mw 76,000, tensile break strength: 82 MPa, Tg: 123°C, hereinafter also referred to as "resin 10"), a polycarbonate resin having an ester bond manufactured by Mitsubishi Gas Chemical Company, Inc., was used as resin (A) instead of resin 5, and TOPAS5013S (Mw: 35,000, tensile break strength: 46 MPa, Tg: 134°C, hereinafter also referred to as "resin 11"), a cyclic olefin resin having no specific functional group manufactured by Polyplastics Co., Ltd., was used as resin (B) instead of resin 6, and no additives were added. Next, light-scattering films B and C were obtained from the obtained light-scattering film A in the same manner as in Example 1. Furthermore, the presence or absence of a sea-island structure in light-scattering film A was confirmed, and a sea-island structure was confirmed. The obtained light-scattering films were evaluated in the same manner as in Example 1. The results are shown in Table 2.

[0110] Example 10 A light-scattering film A having a thickness of 130 μm was obtained in the same manner as in Example 2, except that 90 parts of resin 8 were used as resin (A) instead of resin 7, and 10 parts of resin 10 were used as resin (B) instead of resin 1, and no additives were used. Next, a curable composition layer B was provided in the same manner as in Example 7, and then light-scattering films B and C were obtained in the same manner as in Example 7. Furthermore, when the presence or absence of a sea-island structure in light-scattering film A was confirmed, a sea-island structure was confirmed. Each of the obtained light-scattering films was evaluated in the same manner as in Example 1. The results are shown in Table 2.

[0111] Example 11 A light-scattering film A with a thickness of 160 μm was obtained in the same manner as in Example 2, except that 55 parts of resin 1 was used as resin (A) instead of resin 7, and 45 parts of Iupizeta FPC-2136 (Mw: 61,000, tensile break strength: 76 MPa, Tg: 131°C; hereinafter also referred to as "resin 12"), a polycarbonate resin having an ester bond manufactured by Mitsubishi Gas Chemical Company, Inc., was used as resin (B) instead of resin 1, and no additives were used. Next, light-scattering films B and C were obtained from the obtained light-scattering film A in the same manner as in Example 2. Furthermore, when the presence or absence of a sea-island structure in light-scattering film A was confirmed, a sea-island structure was confirmed. The obtained light-scattering films were evaluated in the same manner as in Example 1. The results are shown in Table 2.

[0112] Example 12 A light-scattering film A with a thickness of 190 μm was obtained in the same manner as in Example 2, except that 60 parts of resin 1 and 10 parts of resin 8 were used as resin (A) instead of resin 7, and 30 parts of resin 7 was used as resin (B) instead of resin 1, and no additives were used. Next, light-scattering films B and C were obtained from the obtained light-scattering film A in the same manner as in Example 2. Furthermore, when the presence or absence of a sea-island structure in light-scattering film A was confirmed, a sea-island structure was confirmed. Each of the obtained light-scattering films was evaluated in the same manner as in Example 1. The results are shown in Table 2.

[0113] Example 13 A light-scattering film A with a thickness of 160 μm was obtained in the same manner as in Example 2, except that 65 parts of resin 1 and 5 parts of resin 8 were used as resin (A) instead of resin 7, and 20 parts of resin 7 and 10 parts of resin 6 were used as resin (B) instead of resin 1, and no additives were used. Next, light-scattering films B and C were obtained from the obtained light-scattering film A in the same manner as in Example 2. Furthermore, when the presence or absence of a sea-island structure in light-scattering film A was confirmed, a sea-island structure was confirmed. Each of the obtained light-scattering films was evaluated in the same manner as in Example 1. The results are shown in Table 2.

[0114] Example 14 A 202 μm-thick light-scattering film D was obtained using the same procedure as in Example 4, except that the protective film was peeled off from the obtained light-scattering film A, and then a glass substrate D263 (50 μm thick) manufactured by SCHOTT was attached to the surface from which the protective film had been peeled off using an adhesive sheet PDS1UVT8A manufactured by PANAC Corporation. The obtained light-scattering film D was evaluated in the same manner as the light-scattering film A of Example 1. The results are shown in Table 2. Next, a curable composition layer A was provided on the surface of light-scattering film D opposite the surface on which the glass substrate was provided using the same procedure as in Example 3, and then a light-scattering film E provided with a dielectric multilayer film of vapor deposition design 1 and a light-scattering film F provided with a dielectric multilayer film of vapor deposition design 2 were produced using the same method as in Example 3. The obtained light-scattering films E and F were evaluated in the same manner as the light-scattering films B and C of Example 1. The spectral transmittance of the obtained light-scattering film F was measured, and the results are shown in FIG. 4.

[0115] Example 15 In Example 8, the resin solution was cast to different thicknesses, dried at 20°C for 2 hours, and then peeled off. The peeled coating film was further dried under reduced pressure at 70 to 150°C for 3 hours to obtain a light-scattering film A with a thickness of 260 μm. Light-scattering films B and C were then obtained from the obtained light-scattering film A using the same procedure as in Example 1. The presence or absence of a sea-island structure in light-scattering film A was confirmed, and a sea-island structure was confirmed. Each obtained light-scattering film was evaluated in the same manner as in Example 1. The results are shown in Table 2. Furthermore, a light-scattering film G (a light-scattering film having different dielectric multilayer films on both sides of the resin layer) was produced by providing a dielectric multilayer film of deposition design 3, which is an anti-reflection film for a wavelength of 940 nm, on the side of light-scattering film C on which the dielectric multilayer film of deposition design 2 was not formed. The layer structure of deposition design 3 is shown in Table 3. Layers 1 to 12 in Table 3 represent dielectric multilayer films, with layer 1 representing the dielectric multilayer films stacked on the resin layer in order, and layer 12 being the outermost layer.

[0116]

[0117]

[0118] Example 16 A curable composition layer A was provided on both sides of the light-scattering film A obtained in Example 7 by the same procedure as in Example 3, and then a dielectric multilayer film of vapor deposition design 1 was provided on both sides of the curable composition layer A by the same procedure as in Example 3, to produce a light-scattering film H. Note that, for the side of light-scattering film A on which the protective film was provided, the protective film was peeled off, and then a curable composition layer A was provided by the same procedure as in Example 1. The obtained light-scattering film H was evaluated in the same way as light-scattering film B of Example 1. The results are shown in Table 2.

[0119] Comparative Example 1 In Example 1, Iupilon S-2000 (Mw: 25,000, tensile strength at break: 65, Tg: 149°C, hereinafter also referred to as "resin 13"), a polycarbonate resin having an ester bond manufactured by Mitsubishi Engineering-Plastics Corporation, was used instead of Resin 5 as Resin (A), and Resin 11 was used instead of Resin 6 as Resin (B). A light-scattering film A having a thickness of 280 μm was obtained in the same manner as in Example 1, except that the extrusion speed and temperature were changed depending on the resin. Next, light-scattering films B and C were obtained from the obtained light-scattering film A in the same manner as in Example 1. Furthermore, when the presence or absence of a sea-island structure was confirmed for light-scattering film A, a sea-island structure was confirmed. The obtained light-scattering films were evaluated in the same manner as in Example 1. The results are shown in Table 4. The spectral transmittance of the obtained light-scattering film C was measured, and the result is shown in FIG. 5.

[0120] Comparative Example 2 A light-scattering film A having a thickness of 180 μm was obtained using the same procedure as in Example 1, except that ZEONOR 330R (Mw: 124,000, tensile strength at break: 37 MPa, Tg: 131°C, hereinafter also referred to as "resin 14"), a resin not having a specific functional group manufactured by Zeon Corporation, was used instead of Resin 5 as Resin (A), and Resin 13 was used instead of Resin 6 as Resin (B). The extrusion speed and temperature were changed depending on the resin used. Light-scattering films B and C were then obtained from the obtained light-scattering film A using the same procedure as in Example 1. Furthermore, the presence or absence of a sea-island structure in light-scattering film A was confirmed, and a sea-island structure was confirmed. The obtained light-scattering films were evaluated in the same manner as in Example 1. The results are shown in Table 4.

[0121] Comparative Example 3: A container was charged with 10 parts of a urethane resin (Urehero Lascriclear, manufactured by Saito Paint Co., Ltd.) base, 1 part of a curing agent, and 10 parts of a dedicated thinner. One part of benzoguanamine particles (Eposter MS, manufactured by Nippon Shokubai Co., Ltd.) was added to the mixture, and the mixture was stirred using a mix rotor to obtain a coating solution. The coating solution was applied to a polyester film (Cosmoshine A4160, manufactured by Toyobo Co., Ltd.) using a bar coater. After drying at 100°C for 15 minutes, the film was cured at room temperature for 24 hours to obtain a light-scattering film A consisting of a 40 μm-thick diffusion layer and a 50 μm-thick substrate. The presence or absence of a sea-island structure in the resulting light-scattering film A was observed as described above. A cross-sectional view of the observed film is shown in Figure 6. The upper coated surface had irregularities, and the particle dispersion was confirmed, but the sea-island structure was not observed. The obtained light-scattering film A had a total light transmittance of 83% at 940 nm, a haze of 94% at 535 nm, and a surface roughness Sa of 4 μm. The obtained light-scattering film A was then cut into a square with a side length of 110 mm. This light-scattering film was evaporated in an ion-assisted deposition apparatus (Sapio 1300, manufactured by Showa Vacuum Co., Ltd.) at a dome temperature of 80° C. and an initial vacuum of 8×10 －３ At 200 Pa, the gas for the ion-assisted ion gun was oxygen or a mixed gas of oxygen and argon, and light-scattering film I was obtained by providing a dielectric multilayer film of the deposition design 1 on one side of light-scattering film A. Cracks were generated in light-scattering film I. A light-scattering film J was obtained by providing a dielectric multilayer film of the deposition design 2 on a separately prepared square light-scattering film A with a side of 110 mm under the same conditions as for deposition design 1. Cracks were generated in light-scattering film J. Furthermore, the difference in transmittance between the calculated value and the measured value for deposition design 2 was evaluated as "X."

[0122] Comparative Example 4 A light-scattering film A with a thickness of 140 μm was obtained in the same manner as in Example 2, except that 80 parts of resin 1 were used as resin (A) instead of resin 7, and 20 parts of soluble polyimide KPI-MX300F (Mw: 280,000, tensile strength at break: 150 MPa, Tg: 354°C; hereinafter also referred to as "resin 15") manufactured by Kawamura Sangyo Co., Ltd. was used as resin (B) instead of resin 1, and no additives were used. Light-scattering films B and C were then obtained from the obtained light-scattering film A in the same manner as in Example 2. The presence or absence of a sea-island structure in the obtained light-scattering film A was observed as described above. A cross-sectional view of the observed film is shown in FIG. 7. The upper part of the resin-coated surface was smooth, and a sea-island structure was confirmed, but the island structure was larger than that in Example 1, and there were also areas where the sea structure and island structure had merged. Each of the obtained light-scattering films was evaluated in the same manner as in Example 1. The results are shown in Table 4.

[0123] Comparative Example 5 A light-scattering film A having a thickness of 120 μm was obtained in the same manner as in Example 3, except that resin 4 was used as resin (B) instead of resin 1. Light-scattering films B and C were then obtained from the obtained light-scattering film A in the same manner as in Example 1. The obtained light-scattering films were evaluated in the same manner as in Example 1. The results are shown in Table 4.

[0124]

[0125] This light-scattering film has high visible light reflection / scattering properties and high near-infrared transmittance, and even though it is thin, it can suppress the occurrence of cracks due to stress in the dielectric multilayer film. Therefore, it can be suitably used as an optical component for smartphone cameras, digital video cameras, cameras for wearable devices, PC cameras, surveillance cameras, automotive cameras, night vision cameras, motion capture, laser rangefinders, license plate recognition devices, televisions, driver monitoring systems, car navigation systems, personal digital assistants, personal computers, video game consoles, portable game consoles, fingerprint authentication systems, digital music players, etc.

Claims

1. A light-scattering film having a resin layer with a sea-island structure and a total light transmittance of 50% or more at a wavelength of 940 nm, wherein the resin layer contains a thermoplastic resin (A) that forms a sea portion and a thermoplastic resin (B) that forms an island portion, wherein the content (mass%) of the resin (A) in the resin layer is greater than the content (mass%) of the resin (B), the absolute value of the refractive index difference (Δn) between the resin (A) and the resin (B) is 0.04 or more, the resin (A) has a polystyrene-equivalent weight-average molecular weight (Mw) measured by gel permeation chromatography (GPC) of 40,000 or more, the resin (A) has a tensile break strength measured in accordance with JIS K 7127:1999 of 40 MPa or more, and the resin (B) has a polystyrene-equivalent weight-average molecular weight (Mw) measured by gel permeation chromatography (GPC) of 10,000 or more.

2. The light-scattering film according to claim 1, wherein the resin layer has a tensile breaking strength of 40 MPa or more as measured in accordance with JIS K 7127:1999.

3. The light-scattering film according to claim 1, wherein the surface roughness (Sa) of at least one surface of the resin layer is 0.7 μm or less.

4. The light-scattering film according to claim 1, wherein the mass ratio (A / B) of the resin (A) to the resin (B) in the resin layer is 90 / 10 to 55 / 45.

5. The light-scattering film according to claim 1, wherein the glass transition temperature (Tg) of the resin (A) is 150 to 380°C.

6. The light-scattering film according to claim 1, wherein the resin (A) and the resin (B) have a common functional group or a common bond.

7. The light-scattering film according to claim 6, wherein the common functional group is an ester group and the common bond is an amide bond or an ester bond.

8. The light-scattering film according to claim 1, having a thickness of 250 μm or less.

9. The light-scattering film according to any one of claims 1 to 8, which has a dielectric multilayer film on at least one surface of the resin layer.

10. The light-scattering film according to claim 9, further comprising a layer formed from a curable composition between the resin layer and the dielectric multilayer film.

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