TWI670178B - Reflection film and display device for electronic component containing the same - Google Patents

Abstract

The present invention provides a light reflecting film having high reflectivity, high durability, and low cost and good chromaticity, which is suitable as a reflecting member of a liquid crystal display, by the following reflecting film. The reflecting film is characterized in that: In order to have a white base material layer, a metal thin film layer, and a protective layer, the white base material layer is disposed on the reflective use surface side, and when the reflective film is irradiated with light from the white base material layer side, the following The Δb indicated is 1.0% or more and less than 4.0%, and the reflectance improvement degree (Δa / Δb) expressed by the ratio of Δa to Δb described below is 1.3 or more and 3.0 or less.

△ a: The difference between the reflectance of light with a wavelength of 450 nm and the reflectance of light with a wavelength of 750 nm of the white substrate layer

△ b: Difference between the reflectance of the above-mentioned reflective film with a wavelength of 450 nm and the reflectance of a light with a wavelength of 750 nm

Description

Reflective film and display device for electronic component containing the same

The present invention relates to a reflective film. Furthermore, the reflective film used for the reflective plate etc. of a liquid crystal display is mentioned in detail.

Conventionally, as a light reflector used in an optical member or a liquid crystal display, a lighting device, a solar cell, or the like, a diffusion type light reflection represented by a white film obtained by dispersing inorganic particles or organic particles in a plastic film is known. Film, or a specular reflection type light reflection film represented by a mirror film obtained by forming a metal reflection layer containing a thin film of a metal such as aluminum or silver.

In the application of liquid crystal displays, there are many aspects ranging from large people over 50 inches such as LCD TVs to small people under 5 inches in mobile applications such as mobile phones, especially in small displays, in order to realize screen display devices. The miniaturization and weight reduction of the light-reflection film is required, and a highly efficient light-reflection film that contributes to the power saving of a backlight device which is intended to achieve a longer life of the battery is urgently desired.

Furthermore, mobile applications include mobile phones and on-vehicle displays. However, since it is assumed to be used outdoors, there is also the influence of radiant heat from LED (Light Emitting Diode) light sources. Therefore, the light reflection film is required to have high durability even in a high temperature environment. That is, in the above-mentioned light reflecting film, it is necessary to suppress a decrease in the reflectance under high temperature conditions.

[Prior technical literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 2014-178697

[Patent Document 2] Japanese Patent Laid-Open No. 04-239540

[Patent Document 3] Japanese Patent Laid-Open No. 2005-031653

[Patent Document 4] Japanese Patent Laid-Open No. 2012-35616

[Patent Document 5] Japanese Patent Laid-Open No. 10-128908

[Patent Document 6] Japanese Patent Laid-Open No. 2006-126236

[Patent Document 7] Japanese Patent Laid-Open No. 10-193494

[Patent Document 8] WO2005-039872

In order to meet these requirements, for example, in Patent Document 1, it is proposed that the thickness of two transparent polyester layers having different refractive indices be strictly adjusted, and the super-multilayers be alternately laminated to cover a wide range of areas. In the wavelength region, efficient light reflection is achieved, and durability is provided by additives. However, a highly ultra-thin film technology is required, resulting in extremely expensive articles.

White films (Patent Documents 2 to 4), which are generally cheaper and have a certain high reflectance, are generally known, which are dispersed in polycyclic and aliphatic by finely powdered fillers such as titanium oxide. It is made of resin matrix such as polyester, polyolefin, etc., and / or the film is extended to be porous to form resin / air / fine powder filler with different refractive index in the film; or metal thin film mirror reflection film (Patent Document 5 or 6) is obtained by forming a metal film with a high reflectance such as silver or aluminum on a suitable substrate such as a plastic or metal plate by evaporation or sputtering. Although a white film is excellent in durability or mechanical strength, its reflectance is insufficient. Especially when a thin film is formed, light leakage is significant, and the reflectance is extremely reduced. On the other hand, a metal thin film mirror film can expect high reflection characteristics even if the film is thinned. However, there are problems in that the metal surface is susceptible to deterioration in terms of durability, and that it reflects uniformly all wavelengths. The characteristics of metal are relatively yellowish.

Furthermore, a reflection film in which the white film and a specular reflection film are appropriately combined is also proposed (Patent Document 7 or 8). However, any of the proposed articles is far away from the reflectivity in realizing the high brightness as required in recent years.

Therefore, an object of the present invention is to provide a reflective film that has high reflectivity, high brightness, and high durability, and that the reflected light has a good chromaticity (which suppresses yellowing of the reflected light).

In order to solve the above-mentioned problems, the inventors of the present invention have repeatedly studied on the basis of a silver thin film expected to have a high reflectance, and as a result, have obtained the following findings.

(1) For the silver film to have a high reflectance, ideally, a surface coating is not performed.

(2) However, the silver film is slowly oxidized or sulfided in the air, resulting in a significant decrease in reflectance. Therefore, a protective layer must be provided on the surface of the silver thin film.

(3) On the other hand, when a protective layer is provided on the surface of the silver thin film, the brightness of the reflected light is reduced.

(4) Furthermore, even if a protective layer is provided on the surface of the silver thin film, yellowing of chromaticity cannot be sufficiently suppressed.

Based on the above-mentioned findings, the inventors and others further conducted research, and as a result, it became clear that the white substrate side is set as a reflection by appropriately combining the white substrate with high durability, the metal thin film layer, and the protective layer as described above. On the surface side, the difference (Δb) of the reflectance with respect to the light of the two specific wavelengths is within a certain range, and the above-mentioned problem can be completely overcome.

That is, the present invention is a reflective film, which is characterized in that it has a white base material layer, a metal thin film layer, and a protective layer in this order. The white base material layer is disposed on the side of the reflective use surface, and When the reflective layer is irradiated with light by the material layer side, the Δb indicated below is 1.0% or more and less than 4.0%, and the reflectance indicated by the ratio of Δa indicated below to Δb increased. Degree (△ a / △ b) is 1.3 or more and 3.0 or less, △ a: The difference between the reflectance of light with a wavelength of 450 nm and the reflectance of light with a wavelength of 750 nm of the white substrate layer

Δb: The difference between the reflectance of light of a wavelength of 450 nm and the reflectance of light of a wavelength of 750 nm of the reflective film.

According to the present invention, it is possible to provide a light reflecting film having high reflectivity, high brightness, and high durability suitable as a reflecting member of a liquid crystal display, and which is low in cost and good in chromaticity.

1‧‧‧white substrate layer

2‧‧‧ middle layer

3‧‧‧ metal thin film layer

4‧‧‧ protective layer

FIG. 1 is an explanatory diagram showing a layer structure of a reflective film of the present invention. FIG. 1 (a) shows a laminated body in which a white substrate layer 1, a metal thin film layer 3, and a protective layer 4 are sequentially formed. FIG. 1 (b) shows a laminated body in which a white substrate layer 1, an intermediate layer 2, a metal thin film layer 3, and a protective layer 4 are sequentially formed.

FIG. 2 is an explanatory diagram showing the relationship between reflectance and brightness at 550 nm.

FIG. 3 is an explanatory diagram showing the relationship between the difference in reflectance (Δb) between 450 nm and 750 nm and the y value.

Hereinafter, a reflection film as an example of an embodiment of the present invention will be described. However, the present invention is not limited to this reflective film.

Moreover, as a preferable form of a reflective film, a film shape or a sheet shape is preferable. Generally speaking, the so-called "film" is a thin and flat product whose thickness is extremely small compared to the length and width. It usually refers to the supplier in the form of a roller (Japanese Industrial Standard JISK6900). The so-called "sheet", as defined in JIS, refers to a product that is thin, generally thinner and flatter than its length and width. However, the boundary between sheet and film is not clear. In the present invention, there is no need to distinguish between the two in terms of terms. Therefore, in the present invention, even in the case of "film", "sheet" is included. Called "Materials" also includes "film".

Reflective film

As shown in FIG. 1 (a), the reflective film of the present invention (hereinafter, it may be described as a reflective film) is characterized in that it has a white substrate layer 1, a metal thin film layer 3, and a protective layer 4 in this order. In the case where the white base material layer 1 is disposed on the reflective use surface side and when the reflective film is irradiated with light from the white base material layer 1 side, Δb shown below is 1.0% or more and less than 4.0% And the reflectance improvement degree (△ a / △ b) represented by the ratio of △ a to △ b shown below is 1.3 or more and 3.0 or less, △ a: The difference between the reflectance of light with a wavelength of 450 nm and the reflectance of light with a wavelength of 750 nm of the white substrate layer

Δb: The difference between the reflectance of light of a wavelength of 450 nm and the reflectance of light of a wavelength of 750 nm of the reflective film.

1.1. White substrate layer

The white substrate layer is characterized by containing a thermoplastic resin and a filler. The thermoplastic resin and the filler are not particularly limited. The reflectance of the white substrate layer with respect to light having a wavelength of 550 nm is preferably 95% or more. It is more preferably 96% or more, and still more preferably 97% or more. In the case where the reflectance at 550 nm is less than 95%, the reflectance of a reflective film made of a laminate may not be a sufficiently high value, and the brightness may be lowered accordingly.

The thermoplastic resin constituting the white base material layer is not particularly limited as long as it can maintain reflectivity and excellent durability. Polyester resins such as polyethylene terephthalate and polyethylene naphthalate can be used. Various thermoplastic resins such as resins, acrylic resins, polyimide resins, fluorine resins, olefin resins such as polyethylene and polypropylene, and cycloolefin resins. In addition, the thermoplastic resin may be used individually as a monomer, or two or more types may be mixed and used.

Among the above, when consideration is given to, for example, reflection characteristics, production costs, hydrolysis resistance, and the like, it is preferable to select a film containing a polyolefin. Examples of the polyolefin-based resin layer include It is selected from polypropylene resins such as polypropylene and propylene-ethylene copolymers, or polyethylene resins such as polyethylene, high-density polyethylene, and low-density polyethylene, or cycloolefin-based resins such as ethylene-cyclic olefin copolymers, or ethylene- At least one polyolefin resin of an olefin-based elastomer such as propylene rubber (EPR) and ethylene-propylene-diene terpolymer (EPDM). Among these, polypropylene resin (PP), polyethylene resin (PE), and cycloolefin-based resin are preferable in terms of mechanical properties, flexibility, and the like, and among them, excellent mechanical properties such as heat resistance and elastic modulus From a higher viewpoint, polypropylene resin (PP), cyclic olefin resin (COC (cyclic olefin copolymer), COP (Cyclo olefin Polymer)) are particularly preferred.

On the other hand, when rigidity or heat resistance of a film is important, it is preferable to select a film containing polyester. Among them, in cases where heat resistance or hydrolysis resistance is important, it is preferable to select an aromatic polyester, and examples thereof include polyethylene terephthalate, polyethylene 2,6-naphthalene dicarboxylate, and polyethylene. At least one polyester resin such as trimethylene terephthalate, polybutylene terephthalate, and the like.

Examples of the filler include inorganic fine powder and organic fine powder. Examples of the inorganic fine powder include calcium carbonate, magnesium carbonate, barium carbonate, magnesium sulfate, barium sulfate, calcium sulfate, zinc oxide, magnesium oxide, calcium oxide, titanium oxide, zinc oxide, aluminum oxide, aluminum hydroxide, and hydroxyl. Apatite, silica, mica, talc, kaolin, clay, glass powder, asbestos powder, zeolite, clay silicate, etc. Among these, any one may be used, or two or more may be used in combination. Among these, in consideration of the refractive index difference from the thermoplastic resin constituting the reflective sheet, the one having a larger refractive index is preferred, and calcium carbonate, barium sulfate, titanium oxide, or titanium carbonate having a refractive index of 1.6 or more is particularly preferred. Zinc oxide.

Regarding the white base material layer, when considering only the reflectance of the above-mentioned light having a wavelength of 550 nm or the brightness of the reflected light, the thickness may be made large. However, in order to respond to thin film requirements in recent years, it is necessary to make the white substrate layer as thin as possible. In addition, in the present invention, it is necessary to make the above-mentioned Δb of the entire reflective film satisfy the characteristics as described below. Fixed value. When considering the above situation, the thickness of the white substrate layer is preferably 40 μm or more and 200 μm or less. The lower limit is more preferably 50 μm or more, even more preferably 60 μm or more, particularly preferably 70 μm or more, and the upper limit is more preferably 160 μm or less, still more preferably 140 μm or less, and even more preferably 120 μm or less. Among them, when the thickness of the white substrate layer is 60 μm or more, a reflective film having a higher reflectance can be produced. On the other hand, when the thickness of the white base material layer is 140 μm or less, Δa / Δb becomes a more favorable value, and a reflective film having excellent performance despite being thin can be produced.

The white base material layer may have voids inside. When there are voids, the ratio (void ratio) occupied by the voids in the white substrate layer is preferably 5% or more, more preferably 10% or more, and even more preferably 20% or more. If the void ratio is more than 5%, the area of the interface where the filler with a relatively high refractive index in the resin directly contacts the air layer with a relatively low refractive index increases, thereby further improving the reflectance of the white substrate layer. improve. On the other hand, from the viewpoint of mechanical strength or durability of the white substrate layer, the above-mentioned porosity is preferably 50% or less. A method for forming a void in the white substrate layer is known. For example, it is sufficient to add a filler to the thermoplastic resin constituting the white base material layer to form a base material layer (base material film), and then extend the base material layer (base material film) in at least a uniaxial direction. In order to make the porosity inside the white base material layer into a desired range, the area ratio is preferably extended to 5 times or more, and more preferably 7 times or more. Moreover, it is preferable to extend in a biaxial direction.

The reflective film of the present invention is provided with a white base material layer, and a metal thin film layer is provided on the surface side opposite to the reflective use surface of the white base material layer, even when the overall thickness of the reflective film is thin. Obtains high brightness. From this point of view, as long as the thickness ratio of the white base material layer to the thickness of all the layers of the reflective film is 70% or more, sufficient brightness and reflectance can be obtained through the synergistic effect with the metal thin film layer. From this point of view, the thickness ratio of the white substrate layer is more preferably 80% or more, and more preferably 90% or more, more preferably 92.4% or more, and most preferably 93.5 relative to the thickness of all the layers of the reflective film. %the above. The upper limit is preferably 99.5% or less, more preferably 99% or less, and still more preferably 98% or less. Below, the best is 97.4% or less, and the best is 97.2% or less.

In the reflective film of the present invention, a white base material layer is provided, and a metal thin film layer is provided on the surface side opposite to the reflective use surface of the white base material layer. When the rate is a little high, high brightness can also be obtained. As long as the transmittance of light at 550 nm of the white substrate layer is 1.0% or more, sufficient brightness and reflectance can be obtained by the synergistic effect with the metal thin film layer. From this viewpoint, the transmittance of light at 550 nm of the white substrate layer is more preferably 1.0% or more, and still more preferably 1.1% or more. The upper limit is preferably 4.0% or less, more preferably 3.8% or less, still more preferably 3.5% or less, and even more preferably 3.1% or less.

1.2. Metal thin film layer

The reflective film of the present invention has a metal thin film layer on the back side of the white substrate layer, that is, on the side opposite to the reflective use surface of the white substrate layer. The metal thin film layer can be formed by vapor-depositing a metal, and can be formed, for example, by a vacuum vapor deposition method, an ionization vapor deposition method, a sputtering method, an ion plating method, or the like. The vapor-deposited metal material may be used without particular limitation as long as it has a high reflectance. Generally, silver, aluminum, and the like are preferred, and among these, silver is particularly preferred. Alternatively, from the viewpoint of corrosion resistance, an alloy using silver is also preferable. For example, silver and Cu selected from Cu, Au, Ni, Pd, Pt, Ru, Rh, In, Al, Si, Mn, Zr, Sn, Bi, Ge, Ti, Cr, Mo, V, Nb, Ta, Hf , W, Co, Ge one or more alloys. In addition, the metal thin film layer may be a single-layer product or a multilayer product of a metal, or a single-layer product or a multilayer product of a metal oxide, or may be a two-layer product of a single-layer product of a metal and a single-layer product of a metal oxide. Laminated body. The thickness of the metal thin film layer varies depending on the material or the method of forming the layer. The thickness is preferably within a range of 10 nm to 300 nm, more preferably within a range of 20 nm to 200 nm, and further preferably within a range of 40 nm to 150 nm. It is particularly preferably within a range of 60 nm to 120 nm. When the thickness of the metal thin film layer is 10 nm or more, sufficient reflectance can be obtained. On the other hand, when the thickness of the metal thin film layer exceeds 300 nm, a further increase in reflectance cannot be seen, and production efficiency decreases. So it's not good.

In the present invention, in order to achieve the following Δb, it is also preferable to adjust the ratio of the thickness of the metal thin film layer to the thickness of the white substrate layer. In the reflection film of the present invention, when the thickness of the metal thin film layer is set to X (μm) and the thickness of the white substrate layer is set to Y (μm), the thickness ratio (X / Y) is preferably 5.0 × 10 ^-5 or more and 7.5 x 10 ^-3 or less. The lower limit is more preferably 1.0 × 10 ^-4 or more, further preferably 5.0 × 10 ^-4 or more, particularly preferably 8.6 × 10 ^-4 or more, and the upper limit is more preferably 5.0 × 10 ^-3 or less, and further preferably 3.0 × 10. ^-3 or less, particularly preferably 2.0 x 10 ^-3 or less.

1.3. Middle layer

In the present invention, the above-mentioned metal thin film layer is provided on the back side of the white substrate layer. As a method of providing a metal thin film layer on the back surface side of a white base material layer, various methods are mentioned. Particularly preferably, as shown in FIG. 1 (b), the metal thin film layer 3 is provided on the back side of the white substrate layer 1 via the intermediate layer 2.

1.3.1. Smooth coating

For example, after a smooth coating is provided on the surface of the white base material layer, a metal thin film layer can be provided on the back side of the white base material layer by depositing a metal on the surface of the smooth coating layer by a sputtering method or the like. That is, the white base material layer of the present invention may include a smooth coating layer on the surface on the side where the metal thin film layer is provided. At this time, the smooth coating is responsible for reducing the surface roughness of the side on which the metal thin film layer is provided, and giving a further effect of improving the reflectance. From this viewpoint, the surface roughness (Ra) of the side where the metal thin film layer is provided when the smooth coating layer is provided on the white substrate layer is preferably 1.0 μm or less, more preferably 0.7 μm or less, and further preferably It is 0.4 μm or less.

The smooth coating can be made into a layer mainly composed of various hardened resins or a layer mainly composed of an inorganic oxide (glass or ceramic, etc.). Alternatively, a layer including a silicon wafer can also be made. In particular, from the viewpoint of being easily provided on the surface of the white base material layer and imparting a certain degree of flexibility, the adhesion with the metal thin film layer is also improved, and the operability is also excellent. The smooth coating layer is preferably a layer mainly composed of various hardening resins, and particularly preferably a layer mainly composed of any one or more of an acrylic resin, a polyester resin, or a melamine resin and a urethane resin. In order not to damage the reflectance and brightness of the reflective film, the total light transmittance of the smooth coating is preferably 80% or more, and more preferably 90% or more.

The "main body" means 50% by mass or more of the constituent components of the layer, preferably 80% by mass or more, and more preferably 90% by mass or more. In addition to the above-mentioned various hardened resins or metal oxides, the smooth coating layer may contain various known additives within a range that does not impair the effects of the present invention.

The thickness of the smooth coating is preferably 0.5 μm or more and 10 μm or less. The lower limit of the thickness of the smooth coating is more preferably 1 μm or more, and even more preferably 2 μm or more. When the thickness of the smooth coating is too small, the surface of the white base material layer may not be sufficiently smoothed. When the thickness of the smooth coating is too large, the smoothness may be deteriorated due to uneven coating and uneven formation.

1.3.2. Adhesive layer or adhesive layer

Alternatively, the metal thin film layer and the white base material layer may be laminated through an adhesive layer or an adhesive layer to form a metal thin film layer on the back side of the white base material layer.

When the white substrate layer and the metal thin film layer are laminated via an adhesive layer or an adhesive layer, it is preferable to provide an adhesive layer or an adhesive layer having a total light transmittance of 80% or more. If the total light transmittance of the adhesive layer or the adhesive layer is more than 80%, the reflectance and brightness of the reflective film will not be damaged. From this viewpoint, the total light transmittance is more preferably 85% or more, and still more preferably 90% or more.

In addition, the so-called adhesive layer or adhesive layer in the present invention is a layer provided to ensure the close contact between the white substrate layer and the metal thin film layer, and includes all meanings as long as the above conditions are satisfied. Examples of the adhesive layer or the adhesive layer include urethane-based, acrylic-based, rubber-based, silicone-based, polyester-based, polyamide-based, epoxy-based, polyvinyl acetate-based, and vinyl-based Alkyl ether-based, fluorine-based adhesive layer or adhesive layer. Of which Those that satisfy the above-mentioned required total light transmittance are more preferable, and an adhesive layer containing an acrylate-based adhesive is more preferable.

1.3.3. Air layer

In the present invention, the method of providing the metal thin film layer on the back side of the white substrate layer is not limited to the above-mentioned configuration in which a smooth coating is provided or the configuration in which an adhesive layer or an adhesive layer is provided. For example, in the present invention, an air layer may be provided between the white substrate layer and the metal thin film layer. The thickness of the air layer is preferably 0.1 μm or more and 100 μm or less, more preferably 0.2 μm or more and 50 μm or less, and most preferably 0.5 μm or more and 10 μm or less. The air layer can be provided by simply overlapping the metal thin film layer and the white substrate layer, or by placing the metal vapor-deposited layer and the white substrate layer within a range of 0.1% to 50% of the actual use area of the reflective film Then set it up. The above range is more preferably 0.1% to 30%, and still more preferably 0.1% to 10%. The presence of an air layer between the white substrate layer and the metal thin film layer can further improve brightness and reflectance.

Furthermore, in the present invention, as long as the required reflectance and Δb are satisfied, a metal thin film layer may be directly provided on the surface of the white substrate layer without interposing the intermediate layer as described above. However, when the intermediate layer is provided as described above, it is easier to satisfy the required reflectance and Δb.

1.4. Protective layer

In order to protect the metal thin film layer, the reflective film of the present invention has a protective layer on the back side of the metal thin film layer, that is, on the opposite side to the reflective use surface of the film. The material for forming the protective layer can be used without particular limitation as long as it can prevent corrosion of the metal thin film layer and has good adhesion to the metal thin film layer. For example, a material including a thermoplastic resin, a thermosetting resin, and an electron beam can be used. A coating material for any of a curable resin and an ultraviolet curable resin. Specifically, amine-based resins, amino-alkyd resins, acrylic resins, styrene-based resins, acrylic-styrene copolymers, urea-melamine-based resins, epoxy-based resins, fluorine-based resins, Polycarbonate, nitrocellulose, cellulose acetate, alkyd trees Grease, rosin-modified maleic resin, polyamide resin, etc., or a resin coating containing a mixture of these. This coating is formed by dispersing the resin in a solvent such as water and a solvent. Moreover, a plasticizer, a stabilizer, and an ultraviolet absorber may be added as needed. In addition, as a solvent, the same thing as the solvent used for general coating materials can be used.

The protective layer is formed by applying, to a metal, for example, a suitable coating method such as a gravure coating method, a roll coating method, or a dip coating method, and diluting the coating material with a solvent or the like as necessary. The entire surface of the film layer is dried (in the case of a curable resin, it is cured).

A protective layer can be formed without coating. Examples of the method for forming the protective layer to achieve the above-mentioned conditions include lamination of films, vapor deposition and sputtering of other materials, and the like. As described above, when a white substrate layer is laminated after a metal thin film layer is formed on the surface of the film, the film itself functions as a protective layer.

The thickness of the protective layer is not particularly limited, but is preferably within a range of 0.1 μm to 200 μm. When the thickness of the protective layer is 0.1 μm or more, the surface of the metal thin film layer can be uniformly covered, and the effect of forming the protective layer can be fully exerted. In addition, when the film itself functions as a protective layer, by adjusting the thickness of the protective layer within this range, the overall thickness of the reflective film can be adjusted according to the purpose or purpose.

The protective layer can be colored by adding inorganic or organic fine particles. By coloring the protective layer, some light leakage from the metal thin film layer can be prevented. In addition, in addition to preventing the misuse of the metal thin film layer as a reflection use surface, the glare of the metal thin film layer can be suppressed. Furthermore, this protective layer can also be effectively used as a printing layer. From this viewpoint, as the resin material for the protective layer, for example, barium sulfate, barium carbonate, calcium carbonate, gypsum, titanium oxide, silica, alumina, silica, talc, calcium silicate, and magnesium carbonate can be used. , Carbon black, graphite, copper oxide, manganese dioxide, aniline black, perylene black, titanium black, cyanine black, activated carbon, ferrite, magnetite, chromium oxide, iron oxide, molybdenum disulfide, chromium Materials, inorganic pigments such as complex oxide black pigments, or acrylic, polystyrene, polyurethane Based, amine based, polycarbonate based, polysiloxane based, urea-formalin based, melamine based organic resin particles, aluminum powder, brass powder, copper powder and other metal powders, pigments, dyes and other ink compositions, etc. Pre-mixed and dispersed. The addition amount of the inorganic or organic fine particles is preferably 5 to 50% by mass, and more preferably 10 to 40% by mass relative to the solid content of the protective layer.

In addition, in the present invention, the protective layer is preferably composed of a hard coat layer on the back side, that is, on the opposite side to the reflective use surface of the film. With the hard coating layer, it is possible to more appropriately prevent peeling of the metal thin film layer or physical damage to the film and corrosion of the metal thin film layer. Specific examples of the hard coat layer are preferably an acrylic resin, a urethane resin, a melamine resin, an epoxy resin, an organic silicate compound, and a polysiloxane resin. The thickness of the hard coat layer may be appropriately determined in consideration of the thickness of the entire protective layer.

1.5. Layer composition

If the layer structure of the reflective film of the present invention is exemplified, white substrate layer / smooth coating layer / metal thin film layer / protective layer, white substrate layer / adhesive layer or adhesive layer / metal thin film layer / protective layer, white base Material layer / air layer / metal film layer / protective layer, or white substrate layer / smooth coating / air layer / metal film layer / protective layer. Among them, the white base material layer is arranged on the light-irradiating side. In addition, the reflective film of the present invention may have other layers between these layers, and the white substrate layer, the metal thin film layer, the protective layer, and the like may each include a plurality of layers independently.

Regarding the thickness of the reflective film of the present invention, in order to obtain a desired reflectance, it is preferably at least 45 μm or more, more preferably 50 μm or more, and still more preferably 60 μm or more. On the other hand, in order to respond to the demand for thin film in recent years, it is preferably thinner, and the upper limit is preferably 250 μm or less, more preferably 200 μm or less, and even more preferably 150 μm or less.

In the present invention, as long as the effect of the present invention is not impaired, antioxidants, light stabilizers, heat stabilizers, anti-hydrolysis agents, lubricants, dispersants, ultraviolet absorbers, white pigments, fluorescent Light whitening agent, and other additives.

1.6. Characteristics of reflective film

1.6.1. Reflectivity

In the reflection film of the present invention, the reflectance of light having a wavelength of 550 nm when the light is irradiated from the white substrate layer side is preferably 98% or more, more preferably 98.5% or more, and even more preferably 99% or more. As shown in FIG. 2, the reflectance at 550 nm is closely related to the brightness value of the screen display device when used as a backlight device such as a liquid crystal display. If the reflectance at 550 nm is more than 98%, the The brightness value is also high, which can give sufficient brightness to the liquid crystal display. Furthermore, in FIG. 2, the sensitivity of the integrating sphere in the spectroscopic device is different between the diffuse reflection film and the specular reflection film, so the absolute value of the reflectance between the two cannot be simply compared.

1.6.2. Reflectance difference (△ b)

In the reflective film of the present invention, the difference between the reflectance of the reflective film with a wavelength of 450 nm and the reflectance of the light with a wavelength of 750 nm is defined as Δb. At this time, the Δb must be 1.0% or more and less than 4.0%. As shown in FIG. 3, the present inventors found that the difference (Δb) between the reflectance at 450 nm and the reflectance at 750 nm is closely related to the y value in the chromaticity obtained when measuring the brightness. Here, if the difference between the reflectance at 450 nm and the reflectance at 750 nm is less than 1.0%, yellowing becomes too strong from a practical standpoint. From this viewpoint, the difference in reflectance is more preferably 1.3% or more, and further preferably 1.5% or more. On the other hand, if the upper limit is 4.0% or more, the effect of improving the brightness is hardly seen. Furthermore, when Δb is 4.0% or more, in the present invention in which the white base material layer and the metal thin film layer are required compositions, the characteristics of the metal thin film layer are hardly exhibited. That is, there is a possibility that a high reflectance or the like cannot be obtained as a reflective film. From this viewpoint, it is more preferably less than 3.5%, and still more preferably less than 3.0%. In addition, the y value mentioned here refers to the CIE (Commission Internationale de L'Eclairage) table, which is measured simultaneously with the brightness value when the reflective film is used in a backlight device of a display, as described below. X and y in chromaticity coordinates in the chromaticity system are in a certain area of the xy chromaticity coordinates (x, In y: 0.28 ~ 0.35), the larger the values of x and y, the more yellowish it means, so the size of the y value is used for the evaluation of yellowness for convenience.

1.6.3. Reflectivity improvement (△ a / △ b)

Furthermore, in the reflective film of the present invention, the difference between the reflectance of light with a wavelength of 450 nm and the reflectance of light with a wavelength of 750 nm of the white substrate layer is defined as Δa. In the present invention, the reflectance improvement degree (Δa / Δb) represented by the ratio of the Δa to the Δb is 1.3 or more and 3.0 or less. With the above circumstances, the synergistic effect of the white base material layer and the metal thin film layer can be maximized.

That is, if the above (Δa / Δb) is 1.3 or more, the brightness improvement effect obtained by laminating the white base material layer and the metal thin film can be sufficiently obtained. From this viewpoint, it is more preferably 1.5 or more, and still more preferably 1.8 or more. On the other hand, when the upper limit is 3.0 or less, yellowing can be suppressed and a reflective film having good chromaticity can be obtained. From this viewpoint, it is more preferably 2.8 or less, and still more preferably 2.6 or less.

The transmittance of light having a wavelength of 550 nm of the reflective film is preferably less than 1.0%. By reducing the total light transmittance to less than 1.0%, in addition to efficiently reflecting the light of the backlight device, the brightness can be increased, and the display contrast can be improved. From this viewpoint, it is more preferably less than 0.5%, still more preferably less than 0.3%, and even more preferably less than 0.1%.

1.6.4. Durability

The durability of this reflective film was calculated by calculating the difference in reflectance with respect to light having a wavelength of 550 nm before and after high-temperature treatment in a thermostatic bath at 80 ° C. for 240 hours. The difference in the reflectance is preferably 0.5% or less, more preferably 0.4% or less, and still more preferably 0.3% or less. Since the difference in the reflectance is 0.5% or less, for example, when it is used in a backlight device of a liquid crystal display, it can be used without a decrease in brightness even under the conditions of exposure.

2. Manufacturing method of reflective film

Hereinafter, an example will be described to explain the manufacturing method of the reflective film, but it is not limited to the following. Said any limitation of the manufacturing method.

First, a filler is blended into the thermoplastic resin constituting the white substrate layer, and other additives are blended as necessary to prepare a resin composition. Specifically, a filler is added to the thermoplastic resin, and the mixture is mixed with a belt mixer, a drum, a Henschel mixer, and the like, and then a uniaxial or biaxial extruder is used, and the temperature is above the melting point of the resin By kneading, a resin composition for each layer can be obtained. Alternatively, a so-called master batch prepared by mixing a filler and the like with a thermoplastic resin at a high concentration may be prepared in advance, and the master batch and the resin may be mixed to prepare a resin composition having a desired concentration.

Then, the thus obtained resin composition for a substrate is melted and formed on a film. As a method for forming the film, an inflation molding method or an extrusion molding method using a T-die is generally preferred. Specifically, after drying the resin composition for a base material as needed, it is supplied to an extruder and heated to a temperature higher than the melting point of the resin to be melted. Alternatively, it may be supplied to the extruder without drying the resin composition, but it is preferable to use a vacuum exhaust when performing melt extrusion when the resin composition is not dried. Thereafter, the molten resin composition for the base material layer is extruded from a slit-shaped outflow port of the T-die, and is tightly solidified on a cooling roll to form a cast sheet.

The white substrate layer is preferably extended in at least a uniaxial direction, and more preferably is extended in a biaxial direction. Stretching can be performed by roller, tenter, air inflation, tubular method, mandrel, and the like. For example, after the roller is extended in the MD direction (machine direction), the tenter can be used in the TD direction (transverse direction), or the tube method can be used for biaxial extension. Then, if necessary, heat fixing is performed, whereby a white reflective film can be obtained.

Then, if necessary, a resin coating material for smooth coating is applied on the white base material layer, and is dried or hardened. A metal thin film layer is formed on the smooth coating. Thereafter, a reflective layer (white substrate layer / smooth coating layer / metal thin film layer / protective layer) is obtained by forming a protective layer on the metal thin film layer.

Alternatively, unlike the above case, a metal thin film layer is formed on the protective layer. Next, a white base material layer and a metal thin film layer are laminated | stacked via an adhesive agent, an adhesive agent, etc. as needed. Alternatively, the metal thin film layer and the white substrate layer are simply overlapped, or the metal vapor-deposited layer and the white substrate layer are adhered in a range of 0.1% to 10% of the actual use area of the above-mentioned reflective film, and then laminated by air .

[Example]

Examples and comparative examples are shown below to further specifically describe the present invention, but the present invention is not limited to the examples and comparative examples. The measured values and evaluations shown in the examples were performed as described below.

(Measurement and evaluation method)

Reflectivity

The reflectance of the reflective film is based on the use of a spectrophotometer "UV-4000" (trade name) manufactured by Hitachi High-tech Co., Ltd. The reflectance is based on a standard calibration plate made of alumina (100%) Under the conditions, the measurement is performed in a wavelength range of 300 nm to 800 nm (in units of 0.5 nm).

2. Calculation of reflectance improvement

Based on the above-mentioned reflectance measurement, read the reflectance at 450nm and 750nm, set Δa as the difference between the reflectance at 450nm and the reflectance at 750nm for a white substrate alone, and set Δb as the reflection film The difference between the reflectance at 450 nm and the reflectance at 750 nm was used to calculate the degree of improvement in the reflectance of the reflective film (Δa / Δb).

3.Transmittance

The "transmittance of light alone of the white substrate layer" and the "transmittance of light of the entire reflection film" were measured separately. Specifically, a spectrophotometer "UV-4000" (trade name) manufactured by Hitachi High-Tech Co., Ltd. was used, and the transmittance was calibrated with a standard board made of alumina (100%). The film sample is inserted to thereby measure the transmittance of the film sample in a wavelength range of 300 nm to 800 nm (in 0.5 nm units).

4.Brightness and y value

As a reflective film for a backlight unit of a liquid crystal display ("PLUS ONE" 8-inch, model: LCD8000V, manufactured by CENTURY) Co., Ltd., this reflective film sample was used and a luminance meter (Konica Minolta (Konica (Manufactured by Minolta) Co., Ltd., Type: CA-2000) Determines the 9-point average brightness value and y value of the display at a distance of 45 cm.

5.durability

The reflectance of the film sample was measured. As a high temperature test, the reflectance was measured again after being held at 80 ° C. for 240 hours in a constant temperature bath. The difference in reflectance at 550 nm before and after the high temperature test was calculated and evaluated based on the following evaluation criteria.

◎: The difference in reflectance at 550 nm before and after high temperature treatment is within 0.3%

○: The difference in reflectance at 550 nm before and after high temperature treatment is within 0.5%

×: The difference in reflectance at 550 nm before and after high temperature treatment exceeds 0.5%

6. Peel strength of silver layer

Sellotape (registered trademark, manufactured by Michelin, CT405AP-18) was attached to the coated surface of the film sample by 10 cm, and it was quickly peeled off at 180 ° to evaluate the peeled silver layer.

(Double-circle): The grade in which a coating layer is not peeled at all.

○: Level where the coating hardly peels off and there is no problem in practical use

×: The level of coating peeling

(Example 1)

(White substrate layer)

As the white substrate layer, a polyolefin-based white substrate (manufactured by Mitsubishi Resin Co., Ltd., trade name "Lumirex II R20") was used with a thickness of 100 μm.

(Formation of metal thin film layer)

Apply a smoothing coating to the underside of a polyethylene terephthalate film (manufactured by Mitsubishi Resin Co., Ltd. under the trade name "DIAFOIL T600E25", thickness 25 µm). Coating with a bar coater, mixing an electron beam-curable acrylic resin with a diluting solvent MIBK (methyl isobutyl ketone, methyl isobutyl ketone) at a mass ratio of 1: 1, and adjusting the resin solid content component ratio to 50 The resin solution (ink) made by mass% is dried and hardened to form a smooth coating with a thickness of 2 μm. On the surface of the smooth coating, as a metal thin film layer, a silver thin film layer having a thickness of 120 nm was formed by a sputtering method to obtain a silver thin film.

(Production of reflective film)

The white base material layer was coated with an acrylate-based adhesive, and dried to form an adhesive layer (thickness: 2 μm). The silver film surface of the silver film was overlapped so that the silver film side became the adhesive layer side. Thus, a reflective film having a thickness of 129.12 μm was produced. Each of the produced reflective films was evaluated as described above. The results are shown in Table 1.

(Example 2)

The same white substrate layer as in Example 1 was applied by a bar coater, and an electron beam-curable acrylic resin, a photoinitiator, and a diluent MIBK were mixed at a mass ratio of 1: 0.03: 1 and mixed. A resin solution (ink) prepared by adjusting the ratio of the solid content of the resin to 50% by mass is dried and hardened to form a smooth coating having a thickness of 2 μm. On the surface of the smooth coating layer, as a metal thin film layer, a silver thin film layer having a thickness of 120 nm was formed by a sputtering method. On the surface of the silver thin film layer, as a protective layer, the same layer as the smooth coating layer described above was formed to produce a thickness of 104.12 μm reflective film. Each of the obtained reflection films was evaluated as described above. The results are shown in Table 1.

(Example 3)

A reflective film was produced in the same manner as in Example 1 except that the white substrate layer and the silver thin film were simply superimposed, and a reflective film having a thickness of 130.12 μm was prepared. The air layer is 3 μm. Each of the obtained reflection films was evaluated as described above. The results are shown in Table 1.

(Example 4)

Except that the white substrate layer was changed to a polyolefin-based white substrate with a thickness of 70 μm (manufactured by Mitsubishi Resins Co., Ltd. under the trade name “Lumirex II R20”) and a reflective film having a thickness of 100.12 μm was obtained, the same procedure as in Example 3 Way to make a reflective film. The air layer is 3 μm. Each of the obtained reflection films was evaluated as described above. The results are shown in Table 1.

(Example 5)

Except that the white base material layer was changed to a polyolefin-based white base material (manufactured by Mitsubishi Resin Co., Ltd., trade name "Lumirex II R20") with a thickness of 80 μm, and a reflective film having a thickness of 111.12 μm was obtained, the same procedure as in Example 2 Way to make a reflective film. Each of the obtained reflection films was evaluated as described above. The results are shown in Table 1.

(Example 6)

Except that in Example 5, silver vapor deposition was directly performed without providing a smooth coating layer, the same processing was performed, and the obtained reflection film was subjected to each of the evaluations described above. The results are shown in Table 1.

(Example 7)

A reflective film was produced in the same manner as in Example 5 except that the metal thin film layer was a silver thin film layer having a thickness of 60 nm. Each of the obtained reflection films was evaluated as described above. The results are shown in Table 1.

(Example 8)

In Example 2, an electron beam-curable acrylic resin, titanium oxide, a photoinitiator, and a diluent MIBK were coated on the protective layer by a bar coater at a mass ratio of 1: 0.3: 0.02. : 3 A resin solution (ink) prepared by mixing and adjusting the resin solid content component ratio to 50% by mass, and drying and curing the resin solution (ink), thereby providing a hard coat layer having a thickness of 2.0 μm. Each of the obtained reflection films was evaluated as described above. The results are shown in Table 1.

(Example 9)

A reflective film was produced in the same manner as in Example 3 except that the white base layer was made of a polyester-based white film (trade name "Lumirror E80E" manufactured by Toray Industries, Ltd.). Each of the obtained reflection films was evaluated as described above. The results are shown in Table 1.

(Example 10)

A reflective film was produced in the same manner as in Example 3 except that the metal thin film layer was an aluminum thin film layer having a thickness of 120 nm. Each of the obtained reflection films was evaluated as described above. The results are shown in Table 1.

(Comparative example 1)

The polyolefin-based white substrate (manufactured by Mitsubishi Resin Co., Ltd., trade name "Lumirex II R20") having a thickness of 100 μm was individually subjected to each of the evaluations described above. The results are shown in Table 2.

(Comparative example 2)

A polyolefin white substrate (manufactured by Mitsubishi Resin Co., Ltd., trade name "Lumirex II R20") having a thickness of 70 µm was individually evaluated for each of the evaluations described above. The results are shown in Table 2.

(Comparative example 3)

The polyolefin-based white substrate (manufactured by Mitsubishi Resin Co., Ltd., trade name "Lumirex II R20") having a thickness of 80 µm was individually subjected to each of the evaluations described above. The results are shown in Table 2.

(Comparative Example 4)

Each of the silver films shown in Example 1 was evaluated as described above. The results are shown in Table 2.

(Comparative example 5)

A reflective film was produced in the same manner as in Example 2 except that a protective layer was not provided on the silver thin film surface. With respect to the obtained reflection film, each of the evaluations described above was performed using the silver thin film surface as a reflection use surface. The results are shown in Table 2.

(Comparative Example 6)

Except that the white base material layer was changed to a polyolefin-based white base material (manufactured by Mitsubishi Resin Co., Ltd., trade name "Lumirex II R20") with a thickness of 225 μm, and a reflective film having a thickness of 229.12 μm was obtained, the same procedure as in Example 2 Way to make a reflective film. Each of the obtained reflection films was evaluated as described above. The results are shown in Table 2.

(Comparative Example 7)

The polyolefin-based white substrate (manufactured by Mitsubishi Resin Co., Ltd., trade name "Lumirex II R20") having a thickness of 225 µm was individually evaluated for each of the evaluations described above. The results are shown in Table 2.

(Comparative Example 8)

Each of the polyester-based white substrates having a thickness of 80 μm in Example 9 was evaluated as described above. The results are shown in Table 2.

(Reference example 1)

For the ultra-multilayer reflective film (manufactured by 3M (Minnesota Mining and Manufacturing) company, trade name "ESR-80") obtained by using two types of transparent polyester layers having different refractive indexes, each of the above is performed. Evaluation. The results are shown in Table 2.

(Simulation test)

As shown in Table 3, the thickness of the white substrate layer was changed, and the reflectances at 450 nm, 750 nm, and 550 nm were measured using ray tracing simulation software (product name: Light Tools). Table 3 shows the values of Δa, Δb, and Δa / Δb obtained from the values of the respective reflectances.

For reference, regarding Examples 1 to 10, Comparative Examples 1 to 8, and Reference Example 1, the relationship between reflectance and brightness at 550 nm is shown in FIG. 2, and the relationship between Δb and y values is shown in FIG. 3.

<Inspection>

It is clear from Table 1 that the reflectance, brightness, chromaticity (reduction in yellowing), and durability of the films of each example are good. On the other hand, in Comparative Example 1 which is a single white base material layer or Comparative Examples 2 and 3 which are thin films, the reflectance is low and the brightness is accordingly reduced. In addition, the film of Comparative Example 4 which is a single silver thin film has strong yellowing and poor durability. Furthermore, it was clear that in Comparative Example 5 in which a smooth coating was provided on a white substrate layer, silver was vapor-deposited, and characteristics were evaluated from the silver thin film layer, yellowing was extremely intense and the brightness was also reduced.

In addition, it is clear from Table 3 that by appropriately changing the thickness of the white substrate layer with respect to the thickness of the specific metal thin film layer, the Δa, Δb, and Δa / △ b of the reflective film of the present invention can be changed. When the value is adjusted to an appropriate range, the reflectance, brightness, and chromaticity (reduction in yellowing) can be made good.

[Industrial availability]

According to the present invention, it is possible to provide a reflective film which has high reflectivity, high brightness, and high durability, and whose reflected light has a good chromaticity (which suppresses yellowing of the reflected light). The reflective film of the present invention can be used as a substitute for a reflective member of a liquid crystal display, as a substitute for the previous expensive ultra-multilayer reflective film. In this case, even without redesigning the LED light source or optical film, good light reflection characteristics can be ensured.

Claims (9)

A reflective film is characterized in that it has a white base material layer, a metal thin film layer, and a protective layer in this order. The white base material layer is disposed on the reflective use surface side, and is disposed on the side from the white base material layer side. When the reflecting film is irradiated with light, Δb represented by the following is 1.0% or more and less than 4.0%, and the degree of reflectance improvement represented by the ratio of △ a represented by the following △ b (△ a / Δb) is 1.3 or more and 3.0 or less, Δa: the difference between the reflectance of the white substrate layer with a wavelength of 450 nm and the reflectance of the light with a wavelength of 750 nm Δb: the reflectance of the reflective film with a wavelength of 450 nm Difference from the reflectance of light with a wavelength of 750 nm. For example, the reflective film of claim 1, wherein the reflectance of the white substrate layer with a wavelength of 550 nm of light is 95% or more. For example, the reflective film of claim 1, wherein the white substrate layer has a transmittance of light having a wavelength of 550 nm of 1.0% or more. For example, the reflective film of claim 2, wherein the transmittance of light of a wavelength of 550 nm of the white substrate layer is 1.0% or more. The reflective film according to any one of claims 1 to 4, wherein the thickness ratio of the white substrate layer is 50% or more of the thickness of the reflective film. The reflective film according to any one of claims 1 to 4, wherein an air layer is provided between the white substrate layer and the metal thin film layer. The reflective film according to any one of claims 1 to 4, wherein in the above-mentioned white base material layer, a surface on the side provided with the metal thin film layer includes a smooth coating, and the smooth coating is provided with the metal thin film layer. The surface roughness (Ra) of the side is 300 nm or less. The reflective film according to any one of claims 1 to 4, wherein the thickness of the protective layer is 1 to 200 μm. A display device for an electronic component includes the reflective film according to any one of claims 1 to 8.