TW201622980A - Reflection film - Google Patents

Abstract

Provided is a reflection film with which a light reflection film having a preferable high reflection ratio and high durability as a reflection material of a liquid crystal display, and a good chromaticity at a low cost is obtained. The reflection film includes: a white base material layer arranged on a reflection using surface side; a metal thin film layer; and a protection layer, in the order mentioned, wherein in a case where the reflection film is irradiated with light from the white base material layer side, [Delta]b shown below is no less than 1.0% and less than 4.0%, and a reflection ratio improvement degree represented by a ratio of [Delta]a shown below and [Delta]b ([Delta]a/[Delta]b) is no less than 1.3 and no more than 3.0. [Delta]a: difference between the reflection ratio with light at a wavelength of 450 nm and the reflection ratio with light at a wavelength of 750 nm of the white base material layer; [Delta]b: difference between the reflection ratio with light at a wavelength of 450 nm and the reflection ratio with light at a wavelength of 750 nm of the reflection film.

Description

Reflective film

The present invention relates to a reflective film. More specifically, the present invention relates to a reflective film used for a reflector or the like of a liquid crystal display.

In the past, as a light reflector used for an optical member, a liquid crystal display, a lighting fixture, a solar cell, or the like, a diffused light reflection represented by a white film obtained by dispersing inorganic particles or organic particles in a plastic film is known. A film, or a specular reflection film or the like which is obtained by forming a metal reflective layer containing a film of a metal such as aluminum or silver.

In the use of liquid crystal displays, it is involved in many aspects, such as large-scale LCD TVs and other large mobile phones, and mobile phones, such as mobile phones, which are smaller than 5 inches, especially in small displays, in order to realize screen display devices. In order to reduce the thickness of the light-reflecting film, it is required to contribute to the reduction of the thickness of the light-reflecting film, and it is highly desirable to provide a highly efficient light-reflecting film which contributes to power saving of a backlight device which is intended to achieve a long battery life.

Further, as a mobile use, there are specifically a mobile phone, a vehicle-mounted display, etc., but it is assumed that the use is equivalent to an outdoor use, and it is also said that there is a radiant heat from a light source of an LED (Light Emitting Diode). Therefore, for the light reflecting film, durability is required even in a high temperature environment. That is, in the above-described light reflecting film, it is necessary to suppress a decrease in reflectance under high temperature conditions.

[Previous 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 Special Opening 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 satisfy such a request, for example, Patent Document 1 proposes a case where the thickness of the two types of transparent polyester layers having different refractive indices is strictly adjusted, and the layers are alternately laminated to be super-multilayered, and are spread over a wide range. In the wavelength region, efficient light reflection is realized, and durability is imparted by using an additive or the like; however, a high degree of ultra-multilayer thin film forming technology is required, and as a result, it becomes an extremely expensive article.

As a film which is more inexpensive and has a high reflectance, it is generally known that a white film (Patent Documents 2 to 4) is obtained by dispersing a fine powder filler such as titanium oxide in a polycyclic ring and an aliphatic group. a resin matrix such as polyester or polyolefin, and/or extending the film to form a resin/air/micronized filler having a different refractive index in the film; or a metal film specular reflection film (Patent Document 5 or 6) is obtained by forming a metal thin film having a high reflectance such as silver or aluminum by vapor deposition or sputtering on a suitable substrate such as a plastic or a metal plate. Although the white film is excellent in durability or mechanical strength, but the reflectance is insufficient, especially when thinning is performed, light leaking is remarkable, and reflectance is extremely lowered. On the other hand, the metal film mirror film can expect higher reflection characteristics even if the film is thinned, but there is a problem in that the metal surface is easily deteriorated, and the durability is poor, and all wavelengths are uniformly reflected. The characteristics of the metal are relatively yellowish.

Further, a reflection film in which the white film and the specular reflection film are appropriately combined has been proposed (Patent Document 7 or 8). However, any of the proposed items is a far-reaching reflectance with respect to achieving high brightness as required in recent years.

Accordingly, an object of the present invention is to provide a reflective film which is high in reflectance, high in luminance, and high in durability, and which is a good chromaticity (which suppresses yellowing of reflected light).

In order to solve the above problems, the present inventors have generally conducted research on the basis of a silver film which is expected to have high reflectance, and as a result, obtained the following findings.

(1) It is preferable that the silver film has a high reflectance, and it is preferable that the surface coating is not applied.

(2) However, the silver film is slowly oxidized or vulcanized in the air, resulting in a significant decrease in reflectance. Therefore, it is necessary to provide a protective layer on the surface of the silver 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 lowered.

(4) Further, 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 findings, the inventors and the like have conducted intensive studies. As a result, it has been clarified that the white substrate side is made to be reflected by appropriately combining the highly durable white substrate, the metal thin film layer, and the protective layer as described above. On the surface side, the difference (Δb) between the reflectances of the light of the two specific wavelengths is within a certain range, and the above problem can be completely overcome.

That is, the present invention is a reflective film comprising a white base material layer, a metal thin film layer, and a protective layer, which are disposed on the side of the reflective use surface, and are derived from the white base. When the material layer side irradiates the reflection film with light, the Δb shown below is 1.0% or more and less than 4.0%, and the reflectance represented by the ratio of Δa to Δb shown below is improved. Degree (Δa/Δb) is 1.3 or more and 3.0 or less. Δa: the difference between the reflectance of light having a wavelength of 450 nm and the reflectance of light having a wavelength of 750 nm

Δb: the difference between the reflectance of light having a wavelength of 450 nm and the reflectance of light having a wavelength of 750 nm.

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

1‧‧‧White substrate layer

2‧‧‧Intermediate

3‧‧‧Metal film layer

4‧‧‧Protective layer

Fig. 1 is an explanatory view showing a layer constitution of a reflective film of the present invention. Fig. 1(a) shows a laminate in which a white base material layer 1, a metal thin film layer 3, and a protective layer 4 are sequentially formed. Fig. 1(b) shows a laminate in which a white base material 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 view showing the relationship between reflectance and brightness at 550 nm.

Fig. 3 is an explanatory view showing the relationship between the difference (Δb) between the reflectances of 450 nm and 750 nm and the y value.

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

Further, as a form which the reflective film can take, it is preferably a film shape or a sheet shape. In general, the "film" is a thinner and flatter product whose thickness is extremely small compared to the length and the width, and the maximum thickness is arbitrarily defined. Generally, it is a supplier in the form of a roll (Japanese Industrial Standard JISK6900). The term "sheet" as used in the definition of JIS refers to a product which is relatively thin and generally has a thickness which is smaller than the length and width and which is flat. However, the boundary between the sheet and the film is not clear. In the present invention, it is not necessary to distinguish between the two terms. Therefore, in the present invention, even in the case of a film, a "sheet" is included, even if "slice In the case of "material", "film" is also included.

Reflective film

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

Δb: the difference between the reflectance of light having a wavelength of 450 nm and the reflectance of light having a wavelength of 750 nm.

1.1. White substrate layer

The white substrate layer is characterized by comprising 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. More preferably, it is 96% or more, and further preferably 97% or more. When the reflectance at 550 nm is less than 95%, the reflectance of the reflective film formed into a laminated layer may not be sufficiently high, 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, and a polyester system such as polyethylene terephthalate or polyethylene naphthalate can be used. Various thermoplastic resins such as a resin, an acrylic resin, a polyimide resin, a fluorine resin, an olefin resin such as polyethylene or polypropylene, or a cycloolefin resin. Further, the thermoplastic resins may be used alone or in combination of two or more.

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

On the other hand, in the case where the rigidity or heat resistance of the film is emphasized, it is preferred to select a film containing polyester. Among them, in the case of paying attention to heat resistance, hydrolysis resistance, etc., it is preferred to select an aromatic polyester, and examples thereof include polyethylene terephthalate, polyethylene-2,6-naphthalate, and poly At least one polyester resin such as propylene terephthalate or polybutylene terephthalate.

Examples of the filler include inorganic fine powders, organic fine powders, and the like. 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 hydroxy group. Apatite, cerium oxide, mica, talc, kaolin, clay, glass powder, asbestos powder, zeolite, clay silicate, and the like. Any one of these may be used, or two or more types may be used in combination. Among these, in consideration of the difference in refractive index between the thermoplastic resin constituting the reflective sheet, it is preferable to use a calcium carbonate, barium sulfate, titanium oxide or the like having a refractive index of 1.6 or more. Zinc oxide.

In the case of considering the reflectance of light having a wavelength of 550 nm or the brightness of reflected light with respect to the white base material layer, the thickness may be large. However, in order to respond to the demand for film formation in recent years, it is necessary to make the white substrate layer as thin as possible. Further, in the present invention, it is necessary to make the above-mentioned Δb of the entire reflective film satisfy the following Set the value. In consideration of the above, 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, further preferably 60 μm or more, particularly preferably 70 μm or more, and the upper limit is more preferably 160 μm or less, further preferably 140 μm or less, and particularly preferably 120 μm or less. In the case where the thickness of the white base material layer is 60 μm or more, a reflective film having a higher reflectance can be obtained. 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 properties despite being thin can be obtained.

The white substrate layer may have voids inside. In the case of having a void, the ratio (void ratio) of the void in the white base material layer is preferably 5% or more, more preferably 10% or more, and still more preferably 20% or more. If the void ratio is 5% or more, the area of the interface where the filler having a relatively high refractive index in the resin and the air layer having a relatively low refractive index directly contact each other increases, whereby the reflectance of the white substrate layer can be further increased. improve. On the other hand, from the viewpoint of mechanical strength or durability of the white base material layer, the above-mentioned void ratio is preferably 50% or less. A method of forming a void in the interior of a white substrate layer is known. For example, a base material layer (base material film) may be formed by adding a filler to a thermoplastic resin constituting a white base material layer, and then the base material layer (base material film) may be stretched in at least a uniaxial direction. In order to make the void ratio inside the white base material layer a desired range, the area magnification is preferably extended to 5 times or more, more preferably 7 times or more. Further, it is preferable to extend in the 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 thickness of the entire reflective film is thin. High brightness is achieved. From this point of view, as long as the thickness ratio of the white base material layer is 70% or more with respect to the thickness of all the layers of the present reflective film, sufficient brightness and reflectance can be obtained by the synergistic effect with the metal thin film layer. From this point of view, the thickness ratio of the white base material layer is more preferably 80% or more, more preferably 90% or more, still more preferably 92.4% or more, and most preferably 93.5 with respect to the thickness of all the layers of the present reflective film. %the above. The upper limit is preferably 99.5% or less, more preferably 99% or less, and still more preferably 98%. Next, it is preferably 97.4% or less, and most preferably 97.2% or less.

Further, 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, and the light is transmitted through the 550 nm light of the white base material layer. High brightness can also be obtained when the rate is a bit high. When the transmittance of light of 550 nm of the white substrate layer is 1.0% or more, sufficient luminance and reflectance can be obtained by synergistic effect with the metal thin film layer. From this point of view, the transmittance of light of 550 nm of the white substrate layer is more preferably 1.0% or more, still more preferably 1.1% or more. The upper limit is preferably 4.0% or less, more preferably 3.8% or less, further preferably 3.5% or less, and particularly preferably 3.1% or less.

1.2. Metal film layer

The reflective film of the present invention has a metal thin film layer on the back side of the white base material layer, that is, on the side opposite to the reflective use surface of the white base material layer. The metal thin film layer can be formed by vapor deposition of a metal, and can be formed, for example, by a vacuum deposition method, an ionization vapor deposition method, a sputtering method, an ion plating method, or the like. The vapor-deposited metal material is not particularly limited as long as it has a high reflectance. In general, silver, aluminum, or the like is preferable, and among these, silver is particularly preferable. Alternatively, it is preferable to use an alloy of silver from the viewpoint of corrosion resistance. For example, silver and a selected from the group consisting of Cu, Au, Ni, Pd, Pt, Ru, Rh, In, Al, Si, Mn, Zr, Sn, Bi, Ge, Ti, Cr, Mo, V, Nb, Ta, Hf One or more alloys of the group of W, Co, and Ge. Further, the metal thin film layer may be a single layer or a laminate of metal, or a single layer or a laminate of a metal oxide, or may be a layer of a single layer of a metal and a single layer of a metal oxide. Laminated body. The thickness of the metal thin film layer varies depending on the material or layer formation method of the formation layer, and is preferably in the range of 10 nm to 300 nm, more preferably in the range of 20 nm to 200 nm, and still more preferably in the range of 40 nm to 150 nm. Especially preferred is in the range of 60 nm to 120 nm. When the thickness of the metal thin film layer is 10 nm or more, a sufficient reflectance can be obtained. On the other hand, when the thickness of the metal thin film layer exceeds 300 nm, further improvement in reflectance cannot be seen, and production efficiency is lowered. It is not good.

In the present invention, in order to achieve the following Δb, it is preferable to adjust the ratio of the thickness of the metal thin film layer to the thickness of the white base material layer. In the reflective film of the present invention, when the thickness of the metal thin film layer is X (μm) and the thickness of the white base material layer is Y (μm), the thickness ratio (X/Y) is preferably 5.0 ×. 10 ^-5 or more and 7.5 × 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, further preferably 3.0 × 10 ^-3 or less, particularly preferably 2.0 × 10 ^-3 or less.

1.3. Middle layer

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

1.3.1. Smooth coating

For example, after a smooth coating layer is provided on the surface of the white base material layer, the metal is vapor-deposited on the surface of the smooth coating layer by a sputtering method or the like, whereby a metal thin film layer can be provided on the back side of the white base material layer. That is, the white substrate layer of the present invention may also include a smooth coating on the side on which the metal film layer is provided. At this time, the smooth coating layer serves to lower the surface roughness of the side on which the metal thin film layer is provided, and to impart a further effect of improving the reflectance. From this point of view, the surface roughness (Ra) of the side on which the metal thin film layer is provided when the white base material layer is provided with the smooth coating 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 layer can be formed as a layer mainly composed of various hardened resins or a layer mainly composed of an inorganic oxide (glass or ceramic). Alternatively, a layer comprising a germanium wafer can also be formed. In particular, the surface of the white base material layer is easily provided, and a certain degree of flexibility is imparted, whereby the adhesion to the metal thin film layer is also improved, and the workability is also excellent. The smoothing coating layer is preferably a layer mainly composed of various hardening resins, and more preferably a layer mainly composed of an acrylic resin, a polyester resin, or a melamine resin or a urethane resin. In order not to impair the reflectance and brightness of the present reflective film, the total light transmittance of the smooth coating layer is preferably 80% or more, more preferably 90% or more.

The term "as a main component" means 50% by mass or more, preferably 80% by mass or more, and more preferably 90% by mass or more of the constituent components of the layer. In addition to the various hardening resins or metal oxides described above, the smooth coating layer may contain various known additives insofar as the effects of the present invention are not impaired.

The thickness of the smooth coating layer is preferably 0.5 μm or more and 10 μm or less. The lower limit of the thickness of the smooth coating layer is more preferably 1 μm or more, and particularly preferably 2 μm or more. When the thickness of the smooth coating layer is too small, there is a case where the surface of the white base material layer cannot be sufficiently smoothed. When the thickness of the smooth coating layer is too large, unevenness in coating and uneven formation may occur, and the smoothness may be deteriorated.

1.3.2. Adhesive layer or adhesive layer

Alternatively, a metal thin film layer may be provided on the back side of the white base material layer by laminating the film on which the metal thin film layer is formed and the white base material layer via the adhesive layer or the adhesive layer.

When the white base material layer and the metal thin film layer are laminated via the adhesive layer or the 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 80% or more, the reflectance and brightness of the present reflective film are not impaired. From this point of view, the total light transmittance is more preferably 85% or more, and still more preferably 90% or more.

In addition, the adhesive layer or the adhesive layer in the present invention is a layer provided to ensure adhesion between the white base material layer and the metal thin film layer, and all of the meanings are included as long as the above conditions are satisfied. Examples of the above-mentioned adhesive layer or adhesive layer include urethane-based, acrylic-based, rubber-based, polyfluorene-based, polyester-based, polyamine-based, epoxy-based, polyvinyl-vinyl-based, and vinyl-based. An alkyl ether system, a fluorine-based adhesive layer or an adhesive layer. Among them, Preferably, it is an adhesive layer containing an acrylate-based adhesive which satisfies the above-mentioned total light transmittance.

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 base material layer is not limited to the above-described form in which the smooth coating layer is provided or the form in which the adhesive layer or the 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 particularly preferably 0.5 μm or more and 10 μm or less. The air layer can be disposed by simply overlapping the metal thin film layer and the white base material layer, or by using the metal evaporated layer and the white base material layer in the 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 from 0.1% to 30%, further preferably from 0.1% to 10%. Brightness and reflectance can be further improved by the presence of an air layer between the white substrate layer and the metal thin film layer.

Further, in the present invention, as long as the required reflectance and Δb are satisfied, the metal thin film layer may be directly provided on the surface of the white base material layer without interposing the intermediate layer as described above. However, in the case where the intermediate layer as described above is provided, the desired reflectance and Δb can be more easily satisfied.

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 side opposite 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 is excellent in adhesion to the metal thin film layer. For example, a thermoplastic resin, a thermosetting resin, or an electron beam can be used. A coating material of any of a curable resin, an ultraviolet curable resin, and the like. Specifically, an amine-based resin, an amino alkyd resin, an acrylic resin, a styrene resin, an acrylic-styrene copolymer, a urea-melamine resin, an epoxy resin, a fluorine resin, or the like can be used alone. Polycarbonate, nitrocellulose, cellulose acetate, alkyd tree A fat, rosin-modified maleic acid resin, a polyamide resin, or the like, or a resin coating containing a mixture of the above. This coating is formed by dispersing the above resin in a solvent such as water or a solvent. Further, a plasticizer, a stabilizer, and an ultraviolet absorber may be added as needed. Further, as the solvent, the same solvent as that used in the usual coating can be used.

The protective layer is formed by a usual coating method such as a gravure coating method, a roll coating method, or a dip coating method, and is applied to, for example, a metal by appropriately diluting the coating material with a solvent or the like as necessary. The entire surface of the film layer is dried and allowed to harden in the case of a curable resin.

A protective layer can be formed even without coating the coating. As a method of forming the protective layer for realizing the above, for example, lamination of a film or vapor deposition or sputtering of another material may be mentioned. As described above, in the case where a metal thin film layer is formed on the surface of the film and the white base material layer is laminated, the film itself functions as a protective layer.

The thickness of the protective layer is not particularly limited, but is preferably in the 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 coated, and the effect of forming the protective layer can be sufficiently exhibited. Further, when the film itself functions as a protective layer, by adjusting the thickness of the protective layer within the range, the entire thickness of the present reflective film can be adjusted depending on the use or purpose.

The protective layer can be colored by adding inorganic or organic fine particles. By coloring the protective layer, it is possible to prevent some light leakage from the metal thin film layer. Further, in addition to preventing the metal thin film layer from being misused as a reflection of the use surface, the glare of the metal thin film layer can be suppressed. Further, the protective layer can also be effectively used as a printing layer. From this point of view, in the resin material for the protective layer, for example, barium sulfate, barium carbonate, calcium carbonate, gypsum, titanium oxide, cerium oxide, aluminum oxide, cerium oxide, talc, calcium citrate, magnesium carbonate can be used. , carbon black, graphite, copper oxide, manganese dioxide, aniline black, black, titanium black, cyanine black, activated carbon, ferrite, magnetite, chromium oxide, iron oxide, molybdenum disulfide, chromium An inorganic pigment such as a black oxide or a composite oxide, or an acrylic, polystyrene or polyurethane Organic resin particles such as phthalic acid, guanamine, polycarbonate, polyfluorene, urea-formalin, and melamine, metal powders such as aluminum powder, brass powder, and copper powder, ink compositions such as pigments and dyes, etc. Premixed and dispersed. The amount of the inorganic or organic fine particles added is preferably from 5 to 50% by mass, and more preferably from 10 to 40% by mass, based on the solid content of the protective layer.

Further, in the present invention, it is preferable that the protective layer is formed of a hard coat layer on the opposite side of the back side, that is, the reflective use surface of the film. By the hard coat layer, peeling of the metal thin film layer or physical damage to the film and corrosion of the metal thin film layer can be more appropriately prevented. Specific examples of the hard coat layer are preferably an acrylic resin, a urethane resin, a melamine resin, an epoxy resin, an organic phthalate compound, or a polyfluorene-based 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

Examples of the layer constitution of the reflective film of the present invention include a white substrate layer/smooth coating layer/metal film layer/protective layer, a white substrate layer/adhesive layer or an adhesive layer/metal thin film layer/protective layer, and a white base. 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 substrate layer is disposed on the side of the irradiation light. Further, the reflective film of the present invention may have another layer between the layers, and the white base material layer, the metal thin film layer, the protective layer, and the like may each independently comprise a plurality of layers.

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

In the present invention, an antioxidant, a light stabilizer, a heat stabilizer, a hydrolysis inhibitor, a lubricant, a dispersant, an ultraviolet absorber, a white pigment, and a firefly may be formulated as needed in each layer without departing from the effects of the present invention. Light whitening agent, and other additives.

1.6. Characteristics of the reflective film

1.6.1. Reflectance

The reflectance of light having a wavelength of 550 nm when the light is irradiated from the side of the white substrate layer of the reflective film of the present invention is preferably 98% or more, more preferably 98.5% or more, still more preferably 99% or more. As shown in FIG. 2, the reflectance at 550 nm is closely related to the luminance value of the screen display device used as a backlight device of a member such as a liquid crystal display. If the reflectance at 550 nm is 98% or more, the screen display device is The brightness value is also high, giving the liquid crystal display sufficient brightness. Further, in FIG. 2, in the diffused reflection film and the specular reflection type film, the sensitivity in the integrating sphere in the spectroscopic device is different, and therefore the absolute values of the reflectances between the two cannot be simply compared.

1.6.2. Reflectance difference (△b)

Further, in the reflective film of the present invention, the difference between the reflectance of light having a wavelength of 450 nm and the reflectance of light having a wavelength of 750 nm is defined as Δb. At this time, the above Δb must be 1.0% or more and less than 4.0%. As shown in FIG. 3, the inventors of the present invention 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 the luminance is measured. Here, if the difference between the reflectance at 450 nm and the reflectance at 750 nm is less than 1.0%, the yellowing becomes too strong from a practical viewpoint. From this point of view, the difference in reflectance is more preferably 1.3% or more, and still more preferably 1.5% or more. On the other hand, when the upper limit is 4.0% or more, the effect of improving the brightness is hardly seen. Further, when Δb is 4.0% or more, in the present invention in which a white base material layer and a metal thin film layer are essential components, the characteristics of the metal thin film layer are hardly exhibited. That is, there is a problem that a high reflectance or the like cannot be obtained as a reflective film. From this point of view, it is more preferably less than 3.5%, and further preferably less than 3.0%. In addition, the y value described herein refers to the CIE (Commission Internationale de L'Eclairage) table in which the brightness measurement method is used when the reflection film is used for the backlight device of the display. y of x and y in the chromaticity coordinates in the color system, in a certain area of the xy chromaticity coordinate (x, In y: 0.28~0.35), the larger the value of x and y, the more yellow, so the value of y is used for the evaluation of yellowness for convenience.

1.6.3. Reflectivity improvement (△a/△b)

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

In other words, when (Δa/Δb) is 1.3 or more, the effect of improving the brightness obtained by laminating the white base material layer and the metal thin film can be sufficiently obtained. From this point of view, it is more preferably 1.5 or more, 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 point of view, it is more preferably 2.8 or less, further preferably 2.6 or less.

The transmittance of light having a wavelength of 550 nm of the present reflective film is preferably less than 1.0%. By making the total light transmittance less than 1.0%, the light of the backlight device can be efficiently reflected, and the brightness can be improved, and the display contrast can be improved. In this regard, it is more preferably less than 0.5%, further preferably less than 0.3%, and particularly preferably less than 0.1%.

1.6.4. Durability

The durability of the present reflective film was determined 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 chamber at 80 ° C for 240 hours. The difference in reflectance is preferably 0.5% or less, more preferably 0.4% or less, still more preferably 0.3% or less. When the difference in reflectance is 0.5% or less, for example, when used in a backlight device for a liquid crystal display, it can be used without being lowered in brightness even under exposure to sunlight.

2. Method of manufacturing reflective film

Hereinafter, an example of the method for producing the present reflective film will be described, but it is not The manufacturing method is not limited.

First, a filler is prepared from a thermoplastic resin constituting a white substrate layer, and other additives or the like are prepared as needed to prepare a resin composition. Specifically, a filler or the like is added to the thermoplastic resin, and after mixing with a belt mixer, a drum, a Henschel mixer, or the like, the temperature is higher than the melting point of the resin by using a uniaxial or biaxial extruder or the like. By kneading, a resin composition for each layer can be obtained. Alternatively, a so-called masterbatch prepared by blending a filler with a high concentration such as a thermoplastic resin may be prepared in advance, and the master batch may be mixed with a resin to prepare a resin composition having a desired concentration.

Then, the resin composition for a substrate thus obtained is melted and formed on the film. As a method of forming on the film, an inflation molding method or an extrusion molding method using a T-die is generally preferably used. Specifically, the base material is dried with a resin composition as needed, and then supplied to an extruder and heated to a temperature equal to or higher than the melting point of the resin to be melted. Alternatively, it may be supplied to the extruder without drying the resin composition. However, it is preferred to use vacuum evacuation when melt-extruding without drying. Thereafter, the molten base material layer resin composition was extruded from a slit-like outlet of a T-die and adhered to the cooling roll to form a cast sheet.

The white substrate layer is preferably extended in at least a uniaxial direction, and is preferably extended in a biaxial direction. The extension can be carried out by means of a roller, a tenter, an air inflation, a tubular method, a mandrel or the like. For example, after extending in the MD direction by the roller, the tenter may be extended in the TD direction (transverse direction), or may be biaxially extended by the tubular method. Then, heat fixation is performed as needed, whereby a white reflective film can be obtained.

Then, the smooth coating layer is applied to the white substrate layer with a resin coating as needed, and dried or hardened. On the smooth coating, a metal thin film layer is formed. Thereafter, a reflective film (white base material layer/smooth coating layer/metal thin film layer/protective layer) was obtained by forming a protective layer on the metal thin film layer.

Alternatively, unlike the above case, the metal thin film layer is formed on the protective layer. Then, the white base material layer and the metal thin film layer are laminated via an adhesive or an adhesive as needed. Alternatively, the metal thin film layer and the white base material layer are simply overlapped, or the metal evaporated layer and the white base material layer are in the range of 0.1% to 10% of the actual use area of the reflective film, and then laminated via air. .

[Examples]

The present invention will be specifically described below by way of examples and comparative examples, but the present invention is not limited to the examples and comparative examples. Further, the measured values and evaluations shown in the examples were carried out in the following manner.

(Measurement and evaluation method)

Reflectance

The reflectance of the reflective film is based on a spectrophotometer "UV-4000" (trade name) manufactured by Hitachi High-Technologies Co., Ltd., and is based on a reflectance (100%) obtained by calibrating a standard plate made of alumina. The measurement was carried out in a wavelength region of 300 nm to 800 nm (in units of 0.5 nm).

2. Calculation of reflectance improvement

By measuring the reflectance described above, the reflectance at 450 nm and 750 nm is read, and Δa is set as the difference between the reflectance at 450 nm of the white substrate alone and the reflectance at 750 nm, and Δb is set as the present reflective film. The difference between the reflectance at 450 nm and the reflectance at 750 nm was used to calculate the reflectance improvement degree (Δa/Δb) of the reflective film.

3. Transmission rate

The transmittance of the light of the white substrate layer alone and the transmittance of the light of the entire reflection film were measured. Specifically, the spectrophotometer "UV-4000" (trade name) manufactured by Hitachi High-Technologies Co., Ltd. is used as a reference (100%) in the calibration of the standard plate made of alumina. A film sample was inserted, whereby the transmittance of the film sample in the wavelength region of 300 nm to 800 nm (in units of 0.5 nm) was measured.

4. Brightness, y value

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

5. Durability

The reflectance of the film sample was measured, and as a high temperature test, the reflectance was measured again after maintaining at 80 ° C for 240 hours in a thermostatic chamber. 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 the silver layer

Soldope (registered trademark, manufactured by Michelin, CT405AP-18) was attached to a coated surface of a film sample to 10 cm, and rapidly peeled off in the 180° direction to evaluate the silver layer peeling.

◎: The level at which the coating was not peeled at all.

○: The coating is almost not peeled off, and there is no problem in practical use.

×: The level of the coating is greatly peeled off

(Example 1)

(white substrate layer)

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

(formation of metal film layer)

A primer coating surface of a polyethylene terephthalate film (manufactured by Mitsubishi Plastics Co., Ltd., trade name "DIAFOIL T600E25", thickness 25 μm) as a smooth coating layer. The electron beam-curable acrylic resin was mixed with a diluent solvent MIBK (methyl isobutyl ketone, methyl isobutyl ketone) at a mass ratio of 1:1 by a bar coater coating, and the resin solid content ratio was adjusted to 50. A resin solution (ink) of a mass % was dried and hardened to form a smooth coating layer having a thickness of 2 μm. On the surface of the smooth coating layer, a silver thin film layer having a thickness of 120 nm was formed as a metal thin film layer by sputtering to obtain a silver thin film.

(production of reflective film)

An acrylate-based adhesive is applied to the white base material layer, and dried to form an adhesive layer (thickness: 2 μm), and the silver thin film surface of the silver thin film is superposed on the adhesive layer side, and laminated by a hand roller. Thereby, a reflective film having a thickness of 129.12 μm was produced. Each of the above-described evaluations was performed on the produced reflective film. The results are shown in Table 1.

(Example 2)

The white base material layer similar to Example 1 was applied by a bar coater, and the electron beam-curable acrylic resin, the photoinitiator, and the diluent solvent MIBK were mixed at a mass ratio of 1:0.03:1. The resin solution (ink) in which the resin solid content ratio was adjusted to 50% by mass was dried and hardened to form a smooth coating layer having a thickness of 2 μm. On the surface of the smooth coating layer, a silver thin film layer having a thickness of 120 nm is formed as a metal thin film layer by sputtering, and a layer similar to the above-mentioned smooth coating layer is formed as a protective layer on the surface of the silver thin film layer to have a thickness of 104.12 μm reflective film. Each of the above-described evaluations was performed on the obtained reflective film. 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 base material layer and the silver thin film were simply superposed on each other to form a reflective film having a thickness of 130.12 μm. Among them, the air layer was 3 μm. Each of the above-described evaluations was performed on the obtained reflective film. The results are shown in Table 1.

(Example 4)

In the same manner as in Example 3 except that the white base material layer was changed to a polyolefin-based white substrate (manufactured by Mitsubishi Plastics Co., Ltd., trade name "Lumirex II R20") having a thickness of 70 μm to obtain a reflective film having a thickness of 100.12 μm. The reflective film is produced in the same manner. Among them, the air layer was 3 μm. Each of the above-described evaluations was performed on the obtained reflective film. The results are shown in Table 1.

(Example 5)

A white base material layer was changed to a polyolefin-based white substrate (manufactured by Mitsubishi Plastics Co., Ltd., trade name "Lumirex II R20") having a thickness of 80 μm to obtain a reflective film having a thickness of 111.12 μm, and the same as in Example 2. The reflective film is produced in the same manner. Each of the above-described evaluations was performed on the obtained reflective film. The results are shown in Table 1.

(Example 6)

In the same manner as in Example 5, the silver vapor deposition was carried out without providing a smooth coating layer, and the same processing was carried out in the same manner as in the obtained reflective film. 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 formed into a silver thin film layer having a thickness of 60 nm. Each of the above-described evaluations was performed on the obtained reflective film. The results are shown in Table 1.

(Example 8)

In Example 2, the electron beam-curable acrylic resin, the titanium oxide, the photoinitiator, and the diluent solvent 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) obtained by mixing and adjusting the resin solid content ratio to 50% by mass, dried and hardened, thereby providing a hard coat layer having a thickness of 2.0 μm. Each of the above-described evaluations was performed on the obtained reflective film. 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 material layer was made into a polyester white film (manufactured by Toray Industries, Inc., trade name "Lumirror E80E"). Each of the above-described evaluations was performed on the obtained reflective film. The results are shown in Table 1.

(Embodiment 10)

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

(Comparative Example 1)

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

(Comparative Example 2)

Each of the above-described evaluations was carried out separately on a polyolefin-based white substrate (manufactured by Mitsubishi Plastics Co., Ltd., trade name "Lumirex II R20") having a thickness of 70 μm. The results are shown in Table 2.

(Comparative Example 3)

Each of the above-described evaluations was carried out on a polyolefin-based white substrate (manufactured by Mitsubishi Plastics Co., Ltd., trade name "Lumirex II R20") having a thickness of 80 μm. The results are shown in Table 2.

(Comparative Example 4)

Each of the above-described evaluations was performed on the silver thin film shown in Example 1 alone. 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 no protective layer was provided on the silver film surface. Each of the above-described evaluations was performed on the obtained reflective film using the silver film surface as a reflective use surface. The results are shown in Table 2.

(Comparative Example 6)

A white base material layer was changed to a polyolefin-based white substrate (manufactured by Mitsubishi Plastics Co., Ltd., trade name "Lumirex II R20") having a thickness of 225 μm to obtain a reflective film having a thickness of 229.12 μm, and the same as in Example 2. The reflective film is produced in the same manner. Each of the above-described evaluations was performed on the obtained reflective film. The results are shown in Table 2.

(Comparative Example 7)

Each of the above-described evaluations was carried out separately on a polyolefin-based white substrate (manufactured by Mitsubishi Plastics Co., Ltd., trade name "Lumirex II R20") having a thickness of 225 μm. The results are shown in Table 2.

(Comparative Example 8)

Each of the polyester-white substrates having a thickness of 80 μm in Example 9 was subjected to the above evaluation. The results are shown in Table 2.

(Reference example 1)

An ultra-multilayer reflective film (manufactured by Minnesota Mining and Manufacturing, Inc., trade name "ESR-80") obtained by using two types of transparent polyester layers having different refractive indices, each of which is described above. 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 reflectance at 450 nm, 750 nm, and 550 nm was measured using a ray tracing simulation software (product name: Light Tools). The values of Δa, Δb, and Δa/Δb obtained based on the values of the respective reflectances are shown in Table 3.

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

<inspection>

As is clear from Table 1, the reflectance, brightness, chromaticity (reduction in yellowing), and durability of the films of the respective examples were all good. On the other hand, in Comparative Example 1 which is a separate white substrate layer or Comparative Example 2 and Comparative Example 3 in which the film was formed into a film, the reflectance was low, and accordingly the brightness was also lowered. Further, in the film of Comparative Example 4 which is a single silver film, yellowing was strong and durability was poor. Further, in Comparative Example 5 in which a smooth coating layer was formed on a white base material layer and silver vapor deposition was performed, and the characteristics were evaluated from the silver film layer level, yellowing was extremely strong and the brightness was also lowered.

Further, as is clear from Table 3, by appropriately changing the thickness of the white base material layer with respect to the thickness of the specific metal thin film layer, Δa, Δb, and Δa/Δb of the reflective film of the present invention can be used. The value is adjusted to a suitable range, and as a result, reflectance, brightness, and chromaticity (reduction in yellowing) are good.

[Industrial availability]

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

1‧‧‧White substrate layer

2‧‧‧Intermediate

3‧‧‧Metal film layer

4‧‧‧Protective layer

Claims (9)

A reflective film comprising a white base material layer, a metal thin film layer, and a protective layer, wherein the white base material layer is disposed on a side of the reflective use surface, and is disposed on the side of the white base material layer When the reflective film is irradiated with light, the Δb shown below is 1.0% or more and less than 4.0%, and the reflectance improvement degree (Δa/) represented by the ratio of Δa and Δb shown below is shown. Δb) is 1.3 or more and 3.0 or less, Δa: a difference between a reflectance of light having a wavelength of 450 nm of the white base material layer and a reflectance of light having a wavelength of 750 nm Δb: a reflectance of light having a wavelength of 450 nm of the reflective film The difference from the reflectance of light having a wavelength of 750 nm. The reflective film of claim 1, wherein a reflectance of light having a wavelength of 550 nm of the white substrate layer is 95% or more. The reflection film of claim 1 or 2, wherein a transmittance of light having 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 3, wherein a thickness ratio of the white base material layer is 50% or more of a thickness of the reflective film. The reflective film according to any one of claims 1 to 4, wherein an adhesive layer or an adhesive layer having a total light transmittance of 80% or more is contained between the white base material layer and the metal thin film layer. 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 6, wherein in the white substrate layer, a smooth coating layer is provided on a side of the side on which the metal thin film layer is provided, and the smooth coating layer is provided with a 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 7, wherein the thickness of the protective layer is 1~ 200 μm. A display device for an electronic component, comprising the reflective film according to any one of claims 1 to 8.