KR102452766B1 - Reflective film - Google Patents

Abstract

A reflective film having a white substrate layer, a metal thin film layer, and a protective layer in this order, wherein the white substrate layer is disposed on the reflective surface side, and when light is irradiated to the reflective film from the white substrate layer side, A liquid crystal display with a reflective film characterized in that the Δb shown in is 1.0% or more and less than 4.0%, and the reflectance improvement degree (Δa/Δb) expressed by the ratio of Δa and Δb shown below is 1.3 or more and 3.0 or less. Provided is a light reflecting film having a high reflectance, high durability, and good color at a low cost.
Δa: the difference between the reflectance of the light having a wavelength of 450 nm and the reflectance of the light having a wavelength of 750 nm of the white substrate layer
?b: the difference between the reflectance of the light having a wavelength of 450 nm and the reflectance of the light having a wavelength of 750 nm of the reflective film

Description

Reflective film {REFLECTIVE FILM}

The present invention relates to a reflective film. In more detail, it is related with the reflective film used for the reflective plate etc. of the display apparatus for electronic devices, such as a liquid crystal display.

Conventionally, as light reflectors used in optical members, liquid crystal displays, lighting devices, solar cells, etc., diffuse light reflecting films typified by a white film obtained by dispersing inorganic particles or organic particles in a plastic film, aluminum, silver, etc. A specular reflection type light reflection film typified by a mirror film obtained by forming a metal reflection layer made of a thin metal film of

In liquid crystal display applications, from large ones exceeding 50 inches such as liquid crystal televisions to small ones of 5 inches or less for mobile applications such as mobile phones, in particular, in small displays, screen display In order to reduce the size and weight of the device itself, thinning of the light reflective film is required, and there is an urgent need for a highly efficient light reflective film that contributes to power saving of backlights aimed at increasing battery life.

In addition, there are specific mobile applications such as mobile phones and in-vehicle displays, which are supposed to be used outdoors, and also have the effect of radiant heat from the original LED light source. this is required That is, in the said light reflection film, it is necessary to suppress reduction of the reflectance under high temperature conditions.

Japanese Patent Laid-Open No. 2014-178697 Japanese Patent Application Laid-Open No. Hei 04-239540 Japanese Laid-Open Patent Publication No. 2005-031653 Japanese Laid-Open Patent Publication No. 2012-35616 Japanese Laid-Open Patent Publication No. 10-128908 Japanese Laid-Open Patent Publication No. 2006-126236 Japanese Patent Laid-Open No. 10-193494 WO2005-039872

In order to satisfy these demands, for example, in Patent Document 1, two types of transparent polyester layers having different refractive indices are alternately laminated by strictly adjusting the film thickness and super multilayered over a wide wavelength range, efficiently There are proposals for realizing light reflection and providing durability with an additive or the like, which requires a high-level ultra-multilayer thinning technique, which results in a very expensive article.

As a film having a lower cost and a constant high reflectance, a fine powder filler such as titanium oxide is dispersed in a resin matrix such as polycyclic and aliphatic polyester or polyolefin, and/or the film is stretched to make it porous and the refractive index A white film (Patent Documents 2 to 4) comprising these different resin/air/fine-powder fillers in a film, or a metal thin film with high reflectivity such as silver or aluminum, on a suitable substrate such as plastic or metal plate by vapor deposition, sputtering, etc. A metal thin film specular reflective film (patent document 5 or 6) obtained by forming by Although the white film is excellent in durability and mechanical strength, the reflectance is not enough, and especially when it is thinned, light leakage becomes remarkable and the reflectance falls extremely. On the other hand, although high reflective properties can be expected even when the film is thinned, the metal thin-film mirror film is inferior in durability from the viewpoint that the metal surface is easily deteriorated, and is relatively yellow from the characteristic of a metal that uniformly reflects all wavelengths. There is a problem with the beauty (黃色味).

Furthermore, the reflective film formed by combining this white film and a specular reflective film suitably is also proposed (patent document 7 or 8). However, in any of the proposed articles, the reflectance was far from realizing the recently required high luminance.

Then, an object of the present invention is to provide a reflective film having high reflectance, high luminance, high durability, and good chromaticity of reflected light (which can suppress yellowishness of reflected light) at a lower cost.

MEANS TO SOLVE THE PROBLEM In order to solve the said subject, the present inventors acquired the following knowledge as a result of repeating earnest examination on the basis of the silver thin film from which high reflectance is generally anticipated.

(1) In order for a silver thin film to have a high reflectance, it is good not to surface-coat ideally.

(2) However, the silver thin film is gradually oxidized or sulfided in air, resulting in a significant decrease in reflectance. Therefore, it is necessary to form a protective layer on the surface of a silver thin film.

(3) On the other hand, when a protective layer is formed on the surface of a silver thin film, the fall of the brightness|luminance of reflected light is caused.

(4) Moreover, even if it forms a protective layer on the surface of a silver thin film, yellowing of chromaticity cannot fully be suppressed.

Based on the above findings, the inventors studied more energetically. As a result, after appropriately combining the highly durable white substrate, the metal thin film layer, and the protective layer as described above, the white substrate side is the reflective surface side, and two types of predetermined wavelengths are used. It was found that all of the above problems can be overcome by making the difference (Δb) in reflectance with respect to light within a certain range.

That is, the present invention is a reflective film having a white substrate layer, a metal thin film layer, and a protective layer in this order, and the white substrate layer is disposed on the reflective surface side, wherein light is emitted from the white substrate layer side with respect to the reflective film. In the case of irradiation, the Δb shown below is 1.0% or more and less than 4.0%, and the reflectance improvement (Δa/Δb) expressed by the ratio of Δa shown below and the Δb is 1.3 or more and 3.0 or less, It is a reflective film.

Δa: the difference between the reflectance of the light having a wavelength of 450 nm and the reflectance of the light having a wavelength of 750 nm of the white substrate layer

?b: the difference between the reflectance of the light having a wavelength of 450 nm and the reflectance of the light having a wavelength of 750 nm of the reflective film

ADVANTAGE OF THE INVENTION According to this invention, it is equipped with high reflectance, high brightness|luminance, and high durability suitable as a reflection member of a liquid crystal display, and can provide the light reflection film with favorable color at low cost.

BRIEF DESCRIPTION OF THE DRAWINGS It is explanatory drawing which shows the layer structure of the reflective film of this invention. Fig. 1(a) shows a laminated body formed in this order of a white base material layer 1, a metal thin film layer 3, and a protective layer 4 . Fig. 1(b) shows a laminate formed in this order of a white base material layer (1), an intermediate layer (2), a metal thin film layer (3), and a protective layer (4).
It is explanatory drawing which shows the relationship between the reflectance and luminance in 550 nm.
It is explanatory drawing which shows the relationship between the difference (DELTA)b of the reflectance of 450 nm and 750 nm, and the y value.

Hereinafter, a reflective film as an example of embodiment of this invention is demonstrated. However, this invention is not limited to this reflective film.

Moreover, as a form which a reflective film can take, it is preferable that it is a film form or a sheet form. In general, "film" refers to a thin flat product having a very small thickness compared to the length and width and having an arbitrarily limited maximum thickness, usually supplied in the form of a roll (Japanese Industrial Standards JIS K 6900), generally A "sheet" refers to a product that is thin and generally has a small thickness compared to its length and width and is flat by definition in JIS. However, the boundary between the sheet and the film is not clear, and there is no need to distinguish between the two in terms of language in the present invention. ' shall also include "film".

1. Reflective film

As shown to Fig.1 (a), the reflective film of this invention (Hereinafter, it may describe as this reflective film), the white base material layer (1), the metal thin film layer (3), and the protective layer (4) is in this order and the white substrate layer (1) is disposed on the reflective surface side, and when light is irradiated from the white substrate layer (1) side to the reflective film, Δb shown below is 1.0 % or more and less than 4.0%, and a reflectance improvement degree (Δa/Δb) expressed as a ratio of Δa and Δb shown below is 1.3 or more and 3.0 or less.

Δa: the difference between the reflectance of the light having a wavelength of 450 nm and the reflectance of the light having a wavelength of 750 nm of the white substrate layer

?b: the difference between the reflectance of the light having a wavelength of 450 nm and the reflectance of the light having a wavelength of 750 nm of the reflective film

1.1. white base layer

The white substrate layer is characterized in that it contains a thermoplastic resin and a filler. The thermoplastic resin and filler are not particularly limited. It is preferable that the reflectance with respect to the light of wavelength 550nm of a white base material layer is 95 % or more. More preferably, it is 96 % or more, More preferably, it is 97 % or more. When the reflectance in 550 nm is smaller than 95 %, the reflectance of the reflective film made into laminated constitution does not become a high enough value, and therefore a brightness|luminance may also become low.

The thermoplastic resin constituting the white substrate layer is not particularly limited as long as it can maintain reflectivity and excellent durability, and polyester resins such as polyethylene terephthalate and polyethylene naphthalate, acrylic resins, polyimide resins, fluorine resins, and polyethylene , olefin-based resins such as polypropylene, and various thermoplastic resins such as cycloolefin-based resins can be used. In addition, a thermoplastic resin may be used individually, respectively, and may mix and use 2 or more types.

Among the above, for example, when reflective properties, production cost, hydrolysis resistance, etc. are considered important, it is preferable to select a film made of polyolefin. Examples of the polyolefin-based resin layer include polypropylene resins such as polypropylene and propylene-ethylene copolymer, polyethylene resins such as polyethylene, high-density polyethylene, and low-density polyethylene, and cycloolefin-based resins such as ethylene-cyclic olefin copolymer. and at least one kind of polyolefin resin selected from olefin-based elastomers such as resin, ethylene-propylene rubber (EPR) and ethylene-propylene-diene terpolymer (EPDM). Among these, polypropylene resin (PP), polyethylene resin (PE), and cycloolefin resin are preferable in terms of mechanical properties and flexibility, etc. Propylene resin (PP) and cycloolefin resin (COC, COP) are preferable.

On the other hand, when the rigidity or heat resistance of the film is emphasized, it is preferable to select a film made of polyester. Among them, when heat resistance, hydrolysis resistance, etc. are important, it is preferable to select an aromatic polyester, and polyethylene terephthalate, polyethylene-2,6-naphthalenedicarboxylate, polypropylene terephthalate, polybutylene terephthalate at least 1 sort(s) of polyester resin selected from etc. are mentioned.

Examples of the filler include inorganic fine powder, organic fine powder, 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, alumina, aluminum hydroxide, hydroxyapatite, silica, mica, talc, kaolin, clay, glass powder, asbestos powder, zeolite, silicate clay, and the like. These can be used by any 1 type or in mixture of 2 or more types. Among these, in consideration of the difference in refractive index with the thermoplastic resin constituting the present reflective sheet, it is preferable to use a large refractive index, and it is particularly preferable to use calcium carbonate, barium sulfate, titanium oxide or zinc oxide having a refractive index of 1.6 or more.

What is necessary is just to enlarge the thickness of a white base material layer, when only the reflectance with respect to the light of wavelength 550nm mentioned above and the brightness|luminance of reflected light are considered. However, in order to meet the recent request|requirement of thin film formation, it is necessary to make a white base material layer as thin as possible. In addition, in the present invention, as will be described later, it is necessary for the ?b to satisfy a predetermined value for the entire reflective film. 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, still 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, particularly preferably 120 µm or more. μm or less. Especially, when the thickness of a white base material layer is 60 micrometers or more, it can be set as the reflective film provided with a higher reflectance. On the other hand, when the thickness of the white substrate layer is 140 µm or less, Δa/Δb becomes a more favorable value, and a reflective film having excellent performance in spite of being thin can be obtained.

The white base material layer may have a space|gap inside. When it has a space|gap, it is preferable that the ratio (porosity) of the space|gap which occupies in a white base material layer is 5 % or more, More preferably, it is 10 % or more, It is especially preferable that it is 20 % or more. When the porosity is 5% or more, the area of the interface in which the filler having a relatively high refractive index in the resin and the air layer having a low refractive index directly contact is improved, whereby the reflectance of the white substrate layer can be further improved. On the other hand, it is preferable that the said porosity is 50 % or less from a viewpoint of the mechanical strength or durability of a white base material layer. A method of forming voids in the inside of the white substrate layer is known. For example, after adding a filler to the thermoplastic resin which comprises a white base material layer and setting it as a base material layer (base film), what is necessary is just to extend|stretch the said base material layer (base film) at least in uniaxial direction. In order to make the porosity inside a white base material layer into a desired range, in area magnification, it is preferable to extend|stretch by 5 times or more, and it is more preferable to extend|stretch by 7 times or more. Moreover, it is preferable to extend|stretch in a biaxial direction.

In the reflective film of the present invention, by forming a white substrate layer and a metal thin film layer on the side opposite to the reflective surface of the white substrate layer, high luminance can be obtained even when the entire reflective film is thin. From this point of view, if the thickness ratio of the white base layer is 70% or more with respect to the total thickness of the present reflective film, sufficient brightness and reflectance can be obtained due to a synergistic effect with the metal thin film layer. From this point of view, the thickness ratio of the white base layer is more preferably 80% or more, more preferably 90% or more, particularly preferably 92.4% or more, and most preferably 93.5% or more with respect to the total layer thickness of the present reflective film. desirable. The upper limit is preferably 99.5% or less, more preferably 99% or less, still more preferably 98% or less, particularly preferably 97.4% or less, and most preferably 97.2% or less.

Further, in the reflective film of the present invention, by forming a white substrate layer and a metal thin film layer on the side opposite to the reflective surface of the white substrate layer, even when the transmittance of light at 550 nm of the white substrate layer is somewhat high , high luminance can be obtained. If the transmittance|permeability of the light of 550 nm of a white base material layer is 1.0 % or more, sufficient brightness|luminance and reflectance can be acquired by the synergistic effect with a metal thin film layer. It is more preferable that it is 1.0 % or more, and, as for the transmittance|permeability of the light of 550 nm of a white base material layer from such a viewpoint, it is still more preferable that it is 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 particularly preferably 3.1% or less.

1.2. thin metal layer

The reflective film of this invention has a metal thin film layer on the back side of a white base material layer, ie, on the surface on the opposite side to the reflective use surface of a white base material 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 deposition metal material is not particularly limited as long as it has a high reflectance and can be used. In general, silver and aluminum are preferable, and silver is particularly preferable among these materials. Alternatively, it is also preferable to use an alloy of silver from the viewpoint of corrosion resistance. For example, silver and Cu, Au, Ni, Pd, Pt, Ru, Rh, In, Al, Si, Mn, Zr, Sn, Bi, Ge, Ti, Cr, Mo, V, Nb, Ta, Hf, and one or more alloys selected from the group consisting of W, Co, and Ge. Further, the metal thin film layer may be a metal single-layer product or laminated product, or a metal oxide single-layer product or laminated product, or may be a laminate of two or more layers of a metal single-layer product and a metal oxide single-layer product. Although the thickness of the metal thin film layer varies depending on the material for forming the layer, the layer formation method, etc., it is preferable to exist in the range of 10 nm - 300 nm, It is more preferable to exist in the range which is 20 nm - 200 nm, It is 40 nm - 150 nm It is more preferable to exist in the range of , and it is especially preferable to exist in the range of 60 nm - 120 nm. When the thickness of the metal thin film layer is 10 nm or more, sufficient reflectance is obtained. On the other hand, when the thickness of a metal thin film layer exceeds 300 nm, since the further improvement of a reflectance is not seen and productive efficiency falls, it is unpreferable.

In this invention, in order to achieve (DELTA)b mentioned later, it is also preferable to adjust the ratio of the thickness of a metal thin film layer and the thickness of a 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 substrate layer is Y (μm), the thickness ratio (X/Y) is 5.0 × 10 ^-5 or more and 7.5 × 10 ⁻ It is preferable that it is ³ or less. The lower limit is more preferably 1.0 × 10 ^-4 or more, still more 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 it is 3.0 x 10 ^-3 or less, and particularly preferably 2.0 x 10 ^-3 or less.

1.3. mezzanine

In this invention, the metal thin film layer mentioned above is formed in the back surface side of a white base material layer. Various methods are mentioned as a method of forming a metal thin film layer on the back surface side of a white base material layer. In particular, as shown in FIG.

1.3.1. smooth coat layer

For example, after forming a smooth coating layer on the surface of the white substrate layer, a metal thin film layer can be formed on the back side of the white substrate layer by depositing a metal on the surface of the smooth coating layer by sputtering or the like. That is, the white base material layer of this invention may be equipped with the smooth coating layer in the surface on the side in which a metal thin film layer is formed. At this time, the smooth coating layer plays the role of reducing the surface roughness of the side where a metal thin film layer is formed, and providing the reflectance improvement effect further. From this point of view, the surface roughness (Ra) on the side on which the thin metal film layer is formed when the smooth coating layer is formed on the white substrate layer is preferably 1.0 µm or less, more preferably 0.7 µm or less, further preferably 0.4 µm or less. desirable.

The smooth coating layer can be a layer mainly composed of various cured resins or a layer composed mainly of inorganic oxides (such as glass and ceramics). Or it is good also as a layer which consists of a silicon wafer. In particular, from the viewpoint of being easily formed on the surface of the white substrate layer and imparting a certain degree of flexibility, the adhesion with the metal thin film layer is also improved, and furthermore, from the viewpoint of excellent handling properties, the smooth coating layer is a layer mainly composed of various cured resins. It is preferable, and it is especially preferable that it is a layer mainly having any 1 or more types of an acrylic resin, a polyester resin, or a melamine resin, and a urethane resin. In order not to impair the reflectance and brightness|luminance of this reflective film, it is preferable that a total light transmittance of a smooth coating layer is 80 % or more, and it is more preferable that it is 90 % or more.

"Mainly" means 50 mass % or more among the structural components of a layer, Preferably it is 80 mass % or more, More preferably, it means that it occupies 90 mass % or more. The smooth coating layer may contain various well-known additives other than the above-described various cured resins and metal oxides to the extent that the effects of the present invention are not impaired.

It is preferable that the thickness of a smooth coating layer shall be 0.5 micrometer or more and 10 micrometers 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 a smooth coating layer is too small, the surface of a white base material layer may become unable to be smoothed sufficiently. When the thickness of the smooth coating layer is too large, the smoothness may be rather deteriorated due to non-uniformity in application and non-uniformity in formation.

1.3.2. adhesive layer or adhesive layer

Alternatively, the thin metal film layer may be formed on the back side of the white substrate layer by laminating the film on which the metal thin film layer is formed and the white substrate layer with an adhesive layer or an adhesive layer interposed therebetween.

When the white substrate layer and the metal thin film layer are laminated with an adhesive layer or an adhesive layer interposed therebetween, it is preferable to form an adhesive layer or 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 luminance of the present reflective film are not impaired. From such a viewpoint, it is more preferable that it is 85 % or more, and, as for a total light transmittance, it is still more preferable that it is 90 % or more.

In addition, the contact bonding layer or adhesion layer in this invention means a layer formed in order to ensure close_contact|adherence of a white base material layer and a metal thin film layer, and any meaning is included as long as this is satisfied. The adhesive layer or adhesive layer is, for example, a urethane-based, acrylic, rubber-based, silicone-based, polyester-based, polyamide-based, epoxy-based, polyvinyl acetate-based, vinyl alkyl ether-based, fluorine-based adhesive layer or adhesive layer. . Especially, it is preferable to satisfy the said desired total light transmittance, and the adhesive layer containing an acrylic acid ester type adhesive is more preferable.

1.3.3. air layer

In the present invention, the method of forming the metal thin film layer on the back side of the white substrate layer is not limited to the form of forming the smooth coating layer or the form of forming the adhesive layer or the adhesive layer. For example, in this invention, you may have an air layer between a white base material layer and a 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 formed by simply overlapping the metal thin film layer and the white substrate layer, or by bonding the metal vapor deposition layer and the white substrate layer within the range of 0.1% to 50% of the actual use area of the reflective film. As for the said range, 0.1 % - 30 % are more preferable, and 0.1 % - 10 % are still more preferable. When there is an air layer between the white substrate layer and the metal thin film layer, luminance and reflectance can be further improved.

In addition, in this invention, the metal thin film layer may be formed directly on the surface of a white base material layer without interposing said intermediate|middle layer as long as the desired reflectance and (DELTA)b are satisfied. However, when the above-described intermediate layer is formed, the desired reflectance and ?b can be more easily satisfied.

1.4. protective layer

The reflective film of the present invention has a protective layer on the back side of the metal thin film layer, ie, on the side opposite to the reflective surface of the film, in order to protect the metal thin film layer. The material for forming the protective layer is not particularly limited 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 thermoplastic resin, a thermosetting resin, an electron beam curable resin, The coating material which consists of any one, such as an ultraviolet curable resin, can be used. Specifically, amino-based resins, aminoalkyd-based resins, acrylic-based resins, styrene-based resins, acrylic-styrene copolymers, urea-melamine-based resins, epoxy-based resins, fluorine-based resins, polycarbonates, nitrocellulose, cellulose acetate, alkyd-based resins A resin paint composed of a resin, a rosin-modified maleic acid resin, a polyamide-based resin, or a mixture thereof can be used. Such a coating material can be formed by dispersing the resin in a solvent such as water or a solvent. Moreover, a plasticizer, a stabilizer, and a ultraviolet absorber can be added as needed. In addition, as a solvent, the thing similar to the solvent normally used for a coating material can be used.

The protective layer is applied by a conventional coating method such as a gravure coating method, a roll coating method, and a dip coating method, for example, on the entire surface of the metal thin film layer by appropriately diluting the coating material with a solvent or the like as necessary. It is formed by drying (curing in the case of a curable resin).

In addition to the coating of the paint, a protective layer may be formed. As a protective layer forming means for that, bonding of a film, vapor deposition of another material, sputtering, etc. are mentioned, for example. As described above, in the case of laminating a white substrate layer after forming the metal thin film layer on the surface of the film, the film itself serves as a protective layer.

Although the thickness in particular of a protective layer is not restrict|limited, It is preferable to exist in the range of 0.1 micrometer - 200 micrometers. 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 is sufficiently exhibited. Moreover, when film itself plays the role of a protective layer, the total thickness of this reflective film can be adjusted according to a use or objective by adjusting the thickness of a protective layer within such a range.

The protective layer can be colored by adding inorganic or organic fine particles. By coloring the protective layer, it is possible to prevent slight light leakage from the metal thin film layer. Moreover, in addition to preventing the mistake of incorrectly using the metal thin film layer as a reflective surface, glare of the metal thin film layer can be suppressed. Furthermore, this protective layer can also be utilized as a printing layer. From this point of view, the resin material for the protective layer includes, for example, barium sulfate, barium carbonate, calcium carbonate, gypsum, titanium oxide, silicon oxide, alumina, silica, talc, calcium silicate, magnesium carbonate, carbon black, graphite, copper oxide, Inorganic pigments such as manganese dioxide, aniline black, perylene black, titanium black, cyanine black, activated carbon, ferrite, magnetite, chromium oxide, iron oxide, molybdenum disulfide, chromium complex, complex oxide black pigment, acrylic, polystyrene, and polyurethane , amide-based, polycarbonate-based, silicone-based, urea-formalin-based, melamine-based organic resin particles, metal powder such as aluminum powder, sesame oil powder, copper powder, and ink compositions such as pigments and dyes, etc. are mixed and dispersed in advance You can use what you made. It is preferable that it is 5-50 mass % with respect to the solid content of a protective layer, and, as for the addition amount of the said inorganic or organic fine particle, it is more preferable that it is 10-40 mass %.

Moreover, in this invention, it is preferable that the back side of the protective layer, ie, the side opposite to the reflection use surface of a film, is comprised by the hard-coat layer. With a hard-coat layer, peeling of a metal thin film layer, the physical damage to a film, and corrosion of a metal thin film layer can be prevented more appropriately. As a specific example of a hard-coat layer, an acrylic resin, a urethane-type resin, a melamine-type resin, an epoxy-type resin, an organosilicate compound, a silicone resin, etc. are preferable. What is necessary is just to determine the thickness of a hard-coat layer suitably in consideration of the thickness of the whole protective layer.

1.5. layer composition

If the layer configuration of the reflective film of the present invention is exemplified, a white substrate layer/smooth coat layer/metal thin film layer/protective layer, white substrate layer/adhesive layer or adhesive layer/metal thin film layer/protective layer, white substrate layer/air layer/metal thin film layer/ A layer structure, such as a protective layer or a white base material layer/smooth coat layer/air layer/metal thin film layer/protective layer, is mentioned. However, the white base material layer is arrange|positioned on the side to which light is irradiated. Moreover, the reflective film of this invention may have another layer between these layers, and a white base material layer, a metal thin film layer, a protective layer, etc. may each independently be comprised by multiple 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 meet the demand for thinning in recent years, thinner is preferable, and the upper limit is preferably 250 µm or less, more preferably 200 µm or less, and still more preferably 150 µm or less.

In the present invention, antioxidant, light stabilizer, heat stabilizer, hydrolysis inhibitor, lubricant, dispersant, ultraviolet absorber, white pigment, optical brightener, and other additives.

1.6. Characteristics of Reflective Films

1.6.1. reflectivity

It is preferable that the reflectance of the light of wavelength 550nm when the reflective film of this invention irradiates light from the side of a white base material layer is 98 % or more, It is more preferable that it is 98.5 % or more, It is still more preferable that it is 99 % or more. As shown in FIG. 2, the reflectance in 550 nm correlates with the luminance value of the screen display device when used for the backlight which is a member of a liquid crystal display, for example, and the reflectance in 550 nm is 98% or more. In this case, the luminance value of the screen display device is also increased, and sufficient brightness can be provided to the liquid crystal display. In addition, in FIG. 2, since the sensitivity in the integrating sphere in a spectrometer differs between a diffuse reflective film and a specular reflective film, the absolute value of the reflectance between both cannot be simply compared.

1.6.2. Reflectance difference (Δb)

Moreover, in the reflective film of this invention, the difference between the reflectance of the light of wavelength 450nm and the reflectance of the light of wavelength 750nm of a reflective film is defined as (DELTA)b. At this time, the Δb needs to be 1.0% or more and less than 4.0%. As shown in FIG. 3 , the present inventors have found that the difference (Δb) between the reflectance at 450 nm and the reflectance at 750 nm is correlated with the y value in the chromaticity obtained when the luminance is measured. Here, when the difference of the reflectance in 450 nm and the reflectance in 750 nm is less than 1.0 %, from a practical viewpoint, yellowishness becomes strong too much. From such a viewpoint, the difference in reflectance is more preferably 1.3% or more, and still more preferably 1.5% or more. On the other hand, about the upper limit, when it is 4.0 % or more, the improvement effect of a brightness|luminance is hardly recognized. Moreover, when (DELTA)b is 4.0 % or more, in this invention which makes a white base material layer and a metal thin film layer essential, the characteristic of a metal thin film layer is hardly exhibited. That is, there exists a possibility that high reflectance etc. may not be obtained as a reflective film. From such a viewpoint, it is more preferable that it is less than 3.5 %, and it is still more preferable that it is less than 3.0 %. In addition, the y value here refers to y among x and y in the chromaticity coordinates in the CIE color space system measured simultaneously with the luminance value when the reflective film is used for the backlight of the display, that is, the luminance measurement method described later, and this xy In a constant region (x, y: 0.28 to 0.35) of the chromaticity coordinates, the larger the values of x and y, the more yellowish the color is. Therefore, the y value is conveniently used for evaluation of yellowness.

1.6.3. Reflectance improvement (Δa/Δb)

In addition, in the reflective film of this invention, the difference of the reflectance of the light of wavelength 450nm of a white base material layer, and the reflectance of the light of wavelength 750nm is defined as (DELTA)a. In the present invention, the degree of improvement in reflectance (Δa/Δb) expressed by the ratio of Δa and Δb is 1.3 or more and 3.0 or less. Thereby, the synergistic effect of a white base material layer and a metal thin film layer can be exhibited to the maximum.

That is, when (Δa/Δb) is 1.3 or more, the luminance improvement effect by laminating the white substrate layer and the metal thin film layer can be sufficiently obtained. From this viewpoint, it is more preferable that it is 1.5 or more, and it is still more preferable that it is 1.8 or more. On the other hand, yellowishness is suppressed because an upper limit is 3.0 or less, and a reflective film with favorable chromaticity can be obtained. From such a viewpoint, it is more preferable that it is 2.8 or less, and it is still more preferable that it is 2.6 or less.

It is preferable that the transmittance|permeability of the light of wavelength 550nm of this reflective film is less than 1.0 %. By making a total light transmittance into less than 1.0 %, the light of a backlight can be reflected efficiently, a brightness|luminance can be improved, and display contrast can also be improved. From this viewpoint, it is more preferable that it is less than 0.5 %, It is still more preferable that it is less than 0.3 %, It is especially preferable that it is less than 0.1 %.

1.6.4. durability

Durability of this reflective film is calculated|required by calculating the difference of the reflectance with respect to the light of wavelength 550nm before and behind the high temperature treatment hold|maintained on 80 degreeC conditions in a thermostat for 240 hours. It is preferable that the difference of the said reflectance is 0.5 % or less, It is more preferable that it is 0.4 % or less, It is more preferable that it is 0.3 % or less. When the difference of the said reflectance is 0.5 % or less, for example, when using for the backlight of a liquid crystal display, even under the conditions exposed, a brightness|luminance can be used without falling.

2. Manufacturing method of reflective film

Hereinafter, although an example is given and demonstrated about the manufacturing method of this reflective film, it is not limited to the following manufacturing method at all.

First, a filler is blended with the thermoplastic resin constituting the white substrate layer, and other additives are blended as necessary to prepare a resin composition. Specifically, a resin composition for each layer is obtained by adding a filler or the like to the thermoplastic resin and mixing it with a ribbon blender, tumbler, Henschel mixer, etc. can Alternatively, a so-called masterbatch in which a filler or the like is blended with a thermoplastic resin at a high concentration is prepared beforehand, and the masterbatch and resin can be mixed to obtain a resin composition having a desired concentration.

Next, the resin composition for base materials obtained in this way is melt|melted, and it forms on a film. As a method for forming on a film, generally, an inflation molding method or an extrusion molding method using a T-die is preferably used. Specifically, after drying the resin composition for a base material as needed, it supplies to an extruder, and melts by heating to the temperature more than melting|fusing point of resin. Or you may supply to an extruder without drying a resin composition, but when not drying, it is preferable to use a vacuum vent at the time of melt-extruding. Then, the molten resin composition for base material layers is extruded from the slit-shaped discharge port of T-die, it is made to adhere to a cooling roll and solidifies, and a cast sheet is formed.

It is preferable that the white base material layer is extending|stretching in the uniaxial direction at least, and it is more preferable that it is extending|stretching in the biaxial direction. Extending|stretching can be implemented by a roll, a tenter, air inflation, a tubular, a mandrel, etc. For example, after extending|stretching to MD direction with a roll, you may extend|stretch to TD direction with a tenter, and you may biaxially stretch with a tubular. Next, a white reflective film can be obtained by heat-setting as needed.

Next, if necessary, a resin paint for a smooth coat layer is applied on the white substrate layer and dried or cured. On this smooth coating layer, a metal thin film layer is formed. Then, a reflective film (white base material layer/smooth coat layer/metal thin film layer/protective layer) is obtained by forming a protective layer on a metal thin film layer.

Alternatively, a metal thin film layer is separately formed on the protective layer. Next, the white substrate layer and the metal thin film layer are laminated through an adhesive or a pressure-sensitive adhesive, if necessary. Alternatively, the metal thin film layer and the white substrate layer are simply overlapped, or the metal vapor deposition layer and the white substrate layer are adhered within the range of 0.1% to 10% of the actual used area of the reflective film to laminate through an air layer.

Example

Although an Example and a comparative example are shown below and this invention is demonstrated still more concretely, this invention is not limited to an Example and a comparative example at all. In addition, the measured value and evaluation shown in an Example were performed as shown below.

(Measurement and evaluation method)

1. Reflectance

The reflectance of the reflective film was measured using a spectrophotometer "UV-4000" (trade name) manufactured by Hitachi High-Technologies Co., Ltd., and the reflectance calibrated with a standard composition plate made of alumina was used as a reference (100%) from 300 nm to 800 nm. Measurement was carried out in a wavelength range of nm (in units of 0.5 nm).

2. Calculation of reflectance improvement

The reflectance at 450 nm and 750 nm is read by the above reflectance measurement, Δa is the difference between the reflectance at 450 nm and the reflectance at 750 nm in the white substrate alone, Δb is at 450 nm of the present reflective film It was set as the difference between the reflectance in the reflectance and the reflectance in 750 nm, and the reflectance improvement degree ((DELTA)a/(DELTA)b) of a reflective film was computed.

3. Transmittance

"The transmittance|permeability of the light in a white base material layer alone" and "the transmittance|permeability of the light as the whole reflective film" were measured, respectively. Specifically, using a spectrophotometer "UV-4000" (trade name) manufactured by Hitachi High-Technologies Co., Ltd., the transmittance calibrated with an alumina standard composition plate is used as a reference (100%), and a film sample is inserted in the optical path. , the transmittance of the film sample in a wavelength range of 300 nm to 800 nm (in units of 0.5 nm) was measured.

4. Luminance y value

As a reflective film of a backlight unit of a liquid crystal display (“Plus One” 8 inches manufactured by Century Co., Ltd., model number: LCD8000V), this reflective film sample was used, and the 9-point average luminance value of the display 45 cm away, and the y value were luminance system (manufactured by Konica Minolta Co., Ltd., model: CA-2000).

5. Durability

The reflectance of the film sample was measured, and as a high-temperature test, the reflectance was measured again after holding for 240 hours under the condition of 80° C. in a thermostat. The difference in reflectance in 550 nm before and behind a high temperature test was computed, and it evaluated based on the following evaluation criteria.

(double-circle): The difference of the reflectance in 550 nm before and behind high temperature processing is 0.3 % or less

(circle): The difference of the reflectance in 550 nm before and behind high temperature processing is 0.5 % or less

x: The difference of the reflectance in 550 nm before and behind high temperature processing exceeds 0.5 %

6. Peeling strength of silver layer

Cellotape (registered trademark, manufactured by Nichiban, CT405AP-18) was affixed at 10 cm to the coated surface of the film sample, and rapidly peeled in the 180° direction, and the silver layer peeling method was evaluated.

◎: A level at which the coating layer does not peel at all

○: The coating layer hardly peels off, and there is no problem in practical use.

x: A level at which the coating layer is largely peeled off

(Example 1)

(white base layer)

For the white substrate layer, a polyolefin-based white substrate having a thickness of 100 µm (manufactured by Mitsubishi Resin Corporation, trade name “Lumirex II R20”) was used.

(Formation of metal thin film layer)

As a smooth coating layer on the primer-treated surface of a polyethylene terephthalate film (manufactured by Mitsubishi Resins Co., Ltd., trade name "Diafoil T600E25", thickness 25 μm), electron beam curable acrylic resin and diluent MIBK are mixed at a mass ratio of 1:1, and the resin solid content ratio The resin solution (ink) adjusted to 50 mass % was coated with a bar coater, dried and cured, and a smooth coating layer with a thickness of 2 µm was formed. A silver thin film layer with a thickness of 120 nm was formed on the surface of the smooth coating layer as a metal thin film layer by sputtering to obtain a silver thin film film.

(Manufacture of reflective film)

An acrylic acid ester pressure-sensitive adhesive is applied to the white substrate layer, dried to form an adhesive layer (thickness 2 μm), the silver thin film surface of the silver thin film is overlapped so that the adhesive layer side is on the adhesive layer side, and by laminating with a hand roller, the thickness is increased A reflective film of 129.12 μm was prepared. Each evaluation shown above was performed about the manufactured reflective film. The results are shown in Table 1.

(Example 2)

To the same white substrate layer as in Example 1, a resin solution (ink) in which an electron beam curable acrylic resin, a photoinitiator, and a diluent solvent MIBK were mixed at a mass ratio of 1:0.03:1, and the resin solid content ratio was adjusted to 50% by mass , was coated with a bar coater, dried and cured to form a smooth coating layer having a thickness of 2 µm. A thin film of silver with a thickness of 120 nm is formed on the surface of the smooth coating layer as a thin metal layer by sputtering, and the same layer as the smooth coating layer is formed on the surface of the thin silver layer as a protective layer, and a reflective film having a thickness of 104.12 μm is formed. prepared. Each evaluation shown above was performed about the obtained reflective film. A result is shown in Table 1.

(Example 3)

A reflective film was prepared in the same manner as in Example 1, except that the white substrate layer and the silver thin film were simply superposed, and a reflective film having a thickness of 130.12 μm was used. Among them, the air layer was 3 µm. Each evaluation shown above was performed about the obtained reflective film. A result is shown in Table 1.

(Example 4)

A reflective film was prepared in the same manner as in Example 3 except that the white substrate layer was changed to a polyolefin-based white substrate having a thickness of 70 μm (manufactured by Mitsubishi Resin Corporation, trade name “Lumirex II R20”) and a reflective film having a thickness of 100.12 μm was obtained. prepared. Among them, the air layer was 3 µm. Each evaluation shown above was performed about the obtained reflective film. A result is shown in Table 1.

(Example 5)

A reflective film was prepared in the same manner as in Example 2 except that the white substrate layer was changed to a polyolefin-based white substrate having a thickness of 80 μm (manufactured by Mitsubishi Resin Corporation, trade name “Lumirex II R20”), and a reflective film having a thickness of 111.12 μm was obtained. prepared. Each evaluation shown above was performed about the obtained reflective film. A result is shown in Table 1.

(Example 6)

In Example 5, each evaluation shown above was performed about the reflective film obtained by processing similarly except direct silver vapor deposition without forming a smooth coating layer. A result is shown in Table 1.

(Example 7)

A reflective film was prepared 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 evaluation shown above was performed about the obtained reflective film. A result is shown in Table 1.

(Example 8)

In Example 2, on the protective layer, an electron beam curable acrylic resin, titanium oxide, a photoinitiator, and a diluent solvent MIBK were mixed at a mass ratio of 1:0.3:0.02:3, and the resin solid content ratio was adjusted to 50% by mass. The solution (ink) was coated with a bar coater and dried and cured to form a hard coat layer having a thickness of 2.0 µm. Each evaluation shown above was performed about the obtained reflective film. A result is shown in Table 1.

(Example 9)

A reflective film was prepared in the same manner as in Example 3 except that the white substrate layer was a polyester-based white film (manufactured by Toray Corporation, trade name “Lumirror E80E”). Each evaluation shown above was performed about the obtained reflective film. A result is shown in Table 1.

(Example 10)

A reflective film was prepared 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 evaluation shown above was performed about the obtained reflective film. A result is shown in Table 1.

(Comparative Example 1)

Each evaluation shown above was performed about 100-micrometer-thick polyolefin type white base material (The Mitsubishi Resin Corporation make, brand name "Lumirex II R20") alone. A result is shown in Table 2.

(Comparative Example 2)

Each evaluation shown above was performed about 70-micrometer-thick polyolefin type white base material (The Mitsubishi Resin Co., Ltd. make, brand name "Lumirex II R20") alone. A result is shown in Table 2.

(Comparative Example 3)

Each evaluation shown above was performed about 80-micrometer-thick polyolefin type white base material (The Mitsubishi Resin Corporation make, brand name "Lumirex II R20") alone. A result is shown in Table 2.

(Comparative Example 4)

Each evaluation shown above was performed about the silver thin film alone shown in Example 1. A result is shown in Table 2.

(Comparative Example 5)

A reflective film was prepared in the same manner as in Example 2, except that a protective layer was not formed on the silver thin film surface. About the obtained reflective film, each evaluation shown above was performed using the silver thin film surface as a reflection use surface. A result is shown in Table 2.

(Comparative Example 6)

A reflective film was prepared in the same manner as in Example 2 except that the white substrate layer was changed to a polyolefin-based white substrate having a thickness of 225 μm (manufactured by Mitsubishi Resin Co., Ltd., trade name “Lumirex II R20”), and a reflective film having a thickness of 229.12 μm was obtained. prepared. Each evaluation shown above was performed about the obtained reflective film. A result is shown in Table 2.

(Comparative Example 7)

Each evaluation shown above was performed about 225-micrometer-thick polyolefin type white base material (The Mitsubishi Resin Corporation make, brand name "Lumirex II R20") alone. A result is shown in Table 2.

(Comparative Example 8)

Each evaluation shown above was performed about the 80-micrometer-thick polyester white base material alone in Example 9. A result is shown in Table 2.

(Reference Example 1)

Each evaluation shown above was performed about the super multilayer type reflective film (the 3M company make, brand name "ESR-80") by 2 types of transparent polyester layers from which the refractive index differs. A result is shown in Table 2.

(simulation test)

As shown in Table 3, the thickness of a white base material layer was changed, and the reflectance in 450 nm, 750 nm, and 550 nm was measured using the ray tracing simulation software (product name: Light Tools). Table 3 shows the values of ?a, ?b, and ?a/?b obtained from the respective reflectance values.

For reference, about Examples 1-10, Comparative Examples 1-8, and Reference Example 1, FIG. 2 shows the relationship between the reflectance and luminance in 550 nm, and FIG. 3 shows the relationship between (DELTA)b and y value.

<Consideration>

As is clear from Table 1, the films of each Example were good in reflectance, brightness, chromaticity (reduction of yellowing), and durability. On the other hand, the comparative example 1 which is a white base material layer independent, and the comparative example 2 and comparative example 3 which are the films which thinned it had low reflectance, and therefore the brightness|luminance was also falling. Moreover, the film of the comparative example 4 which is a silver thin film film had strong yellowish taste and was inferior in durability. Moreover, about the comparative example 5 which formed the smooth coat layer in the white base material layer, vapor-deposited silver, and evaluated the characteristic from the silver thin film layer surface, it turned out that yellowishness is very strong and the brightness|luminance also falls.

Further, from Table 3, it is possible to adjust the values of Δa, Δb, and Δa/Δb of the reflective film of the present invention to a preferable range by appropriately changing the thickness of the white substrate layer with respect to the thickness of the specific thin metal film layer, and as a result, It was found that the reflectance, luminance, and chromaticity (reduction of yellowing) can be improved.

ADVANTAGE OF THE INVENTION According to this invention, while having high reflectance, high brightness|luminance, and high durability, the reflective film (which can suppress the yellowishness of reflected light) used as a favorable chromaticity of reflected light can be provided more inexpensively. The reflective film according to the present invention can be suitably used as a reflective member of a display device for electronic devices such as a liquid crystal display, for example, as a replacement for a conventional expensive super multilayer reflective film. In this case, good light reflection characteristics can be ensured without redesigning the LED light source or the optical film.

1: white base layer
2: middle layer
3: metal thin film layer
4: protective layer

Claims (9)

A reflective film comprising a white substrate layer, a metal thin film layer, and a protective layer in this order, wherein the white substrate layer is disposed on the reflective surface side,
When the reflective film is irradiated with light from the white substrate layer side,
A reflective film, characterized in that Δb shown below is 1.0% or more and less than 4.0%, and a reflectance improvement degree (Δa/Δb) expressed by a ratio of Δa shown below to Δb is 1.3 or more and 3.0 or less.
Δa: the difference between the reflectance of the light having a wavelength of 450 nm and the reflectance of the light having a wavelength of 750 nm of the white substrate layer
?b: the difference between the reflectance of the light having a wavelength of 450 nm and the reflectance of the light having a wavelength of 750 nm of the reflective film The method of claim 1,
The reflective film in which the reflectance of the light of wavelength 550nm of the said white base material layer will be 95 % or more. The method of claim 1,
The reflective film in which the transmittance|permeability of the light of wavelength 550nm of the said white base material layer is 1.0 % or more. The method of claim 1,
The reflective film in which the thickness ratio of the said white base material layer is 50 % or more of the thickness of the said reflective film. The method of claim 1,
A reflective film comprising an adhesive layer or an adhesive layer having a total light transmittance of 80% or more between the white substrate layer and the metal thin film layer. The method of claim 1,
A reflective film, characterized in that it has an air layer between the white substrate layer and the metal thin film layer. The method of claim 1,
In the above white substrate layer, a smooth coating layer is provided on the side on which the metal thin film layer is formed, and the surface roughness (Ra) of the smooth coating layer on the side on which the metal thin film layer is formed is 300 nm or less, characterized in that, reflective film. The method of claim 1,
The reflective film, characterized in that the thickness of the protective layer is 1 ~ 200㎛. The display apparatus for electronic devices provided with the reflective film in any one of Claims 1-8.

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