Light guide film, light guide member, and light guide device

Abstract

The present invention provides a light guide film that can efficiently propagate light by promoting the reflection of light directed toward a low refractive index layer. [Solution] The light-guiding film 1 comprises a base layer 2 and a low refractive index layer 3 disposed on one surface of the base layer 2. The refractive index of the low refractive index layer 3 at a wavelength of 589 nm is 1.37 or more and 1.47 or less. The thickness of the low refractive index layer 3 is 0.4 μm or more and 3.0 μm or less. When a substance with a refractive index of 1.50 is in contact with the surface of the low refractive index layer 3 opposite to the surface in contact with the base layer 2, and light with a wavelength of 589 nm is irradiated from the substance toward the low refractive index layer 3 at an incident angle of 80°, the reflectance of the light is 93% or more.

Description

Technical Field

[0001] The present disclosure relates to a light guide film, a light guide member, and a light guide device.

Background Art

[0002] Patent Document 1 discloses a dielectric multilayer film having a high refractive index layer and a low refractive index layer laminated thereon, and a hard coat layer, wherein at least one of the high refractive index layer and the low refractive index layer contains a compound having a photocatalytic action, and when the dielectric multilayer film is bisected in the thickness direction, the difference between the volume shrinkage rate of the dielectric multilayer film on the side farther from the hard coat layer and the volume shrinkage rate of the hard coat layer is 0.1% or more and less than 1.0%. The dielectric multilayer film is disclosed as having a function of reflecting (shielding) sunlight, infrared rays, visible light, or ultraviolet rays.

[0003] Patent Document 2 discloses an infrared shielding film having at least one unit composed of a high refractive index layer and a low refractive index layer containing a binder resin and metal oxide particles on a substrate, wherein the refractive index difference between the high refractive index layer and the low refractive index layer is 0.1 or more, and at least one of the high refractive index layer or the low refractive index layer contains modified polyvinyl alcohol as the binder resin. The infrared shielding film is disclosed as having a high visible light transmittance and a high infrared reflectance.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] Efforts are being made to improve the light-guiding efficiency of materials such as glass by placing films used for optical applications on the materials. In this case, the film needs to be able to efficiently propagate light by promoting the reflection of the irradiated light.

[0006] The object of this disclosure is to provide a light guide film, a light guide member, and a light guide device that can efficiently propagate light by promoting the reflection of light irradiated toward a low refractive index layer. [Means for solving the problem]

[0007] A light-guiding film according to one aspect of the present disclosure comprises a substrate layer and a low refractive index layer disposed on one surface of the substrate layer. The refractive index of the low refractive index layer at a wavelength of 589 nm is 1.37 or more and 1.47 or less. The thickness of the low refractive index layer is 0.4 μm or more and 3.0 μm or less. When a substance with a refractive index of 1.50 is in contact with the surface of the low refractive index layer opposite to the surface in contact with the substrate layer, and light with a wavelength of 589 nm is irradiated from the substance toward the low refractive index layer at an incident angle of 80°, the reflectance of the light is 93% or more.

[0008] A light guide member according to one aspect of the present disclosure comprises a transparent member, an adhesive layer, and the light guide film. The transparent member, the adhesive layer, and the light guide film are laminated in this order. The low refractive index layer is in direct contact with the adhesive layer.

[0009] A light guide member according to one aspect of the present disclosure comprises a first transparent member, a first adhesive layer, the light guide film, a second adhesive layer, and a second transparent member. The first transparent member, the first adhesive layer, the light guide film, the second adhesive layer, and the second transparent member are laminated in this order. The low refractive index layer is in direct contact with the first adhesive layer.

[0010] A light guide device according to one aspect of the present disclosure comprises a light source and a light guide member that guides light emitted from the light source. The light source is positioned at the ends of the transparent member and the adhesive layer of the light guide member. [Effects of the Invention]

[0011] According to this disclosure, it is possible to provide a light guide film, a light guide member, and a light guide device that can efficiently propagate light by promoting the reflection of light irradiated toward a low refractive index layer. [Brief explanation of the drawing]

[0012] [Figure 1] Figure 1 is a schematic cross-sectional view showing an example of a light guide film in one embodiment of the present disclosure. [Figure 2] Figure 2 is a schematic cross-sectional view showing an example of a light guide film in one embodiment of the present disclosure. [Figure 3] Figure 3 is a schematic cross-sectional view showing an example of a light guide member in one embodiment of the present disclosure. [Figure 4] Figure 4 is a schematic cross-sectional view showing an example of a light guide device in one embodiment of the present disclosure. [Figure 5] Figure 5 is a schematic cross-sectional view showing an example of a light guide member in one embodiment of the present disclosure. [Modes for carrying out the invention]

[0013] Embodiments will now be described. Note that the embodiments described below are only a selection of the various embodiments of this disclosure. The embodiments described below can be modified in various ways depending on the design, etc., as long as the objectives of this disclosure are achieved. While mechanisms of action and effect may be described below, these mechanisms are all inferred, and this disclosure is not bound by the descriptions of mechanisms.

[0014] 1. Overview The light guide film 1 according to the embodiment includes a base material layer 2 and a low refractive index layer 3 disposed on one surface of the base material layer 2. The refractive index of the low refractive index layer 3 at a wavelength of 589 nm is 1.37 or more and 1.47 or less. The thickness of the low refractive index layer 3 is 0.4 μm or more and 3.0 μm or less. When light with a wavelength of 589 nm is irradiated at an incident angle of 80° from a substance with a refractive index of 1.50 in a state where the substance contacts the surface of the low refractive index layer 3 opposite to the surface in contact with the base material layer 2, the reflectance of the light is 93% or more.

[0015] Therefore, when a substance having a refractive index higher than that of the low refractive index layer 3 is brought into contact with the low refractive index layer 3 in the light guide film 1 and light is propagated in this substance, the reflectance of the light at the interface between the substance and the low refractive index layer 3 is high, so that the light can efficiently propagate in the substance. For this reason, the light guide film 1 can be used for producing a member for propagating light.

[0016] The light guide film 1 is used, for example, for producing a plate-shaped light guide member 10. The light guide member 10 according to the embodiment includes a transparent member 4, an adhesive layer 5, and the light guide film 1, and the transparent member 4, the adhesive layer 5, and the light guide film 1 are laminated in this order. The low refractive index layer 3 is in direct contact with the adhesive layer 5.

[0017] In the light guide member 10 according to the embodiment, the transparent member 4 and the adhesive layer 5 constitute a waveguide layer 11 in which light can propagate internally. When light propagates inside the waveguide layer 11, the reflectance of the light at the interface between the adhesive layer 5 and the low refractive index layer 3 is high, so that the light can efficiently propagate inside the waveguide layer 11. That is, the light can be efficiently propagated in a direction orthogonal to the thickness direction of the light guide member 10 by the light guide member 10.

[0018] The light guide member 10 can be applied to a dimming window glass disposed on the ceiling inside an automobile. When the light guide member 10 in such an application includes a light diffuser 7, the light diffuser 7 can more efficiently extract the light propagating inside the waveguide layer 11.

[0019] Although the location where light reflection occurs is not necessarily obvious, it occurs at the interface between a substance with a refractive index of 1.50 and the low refractive index layer 3 on the surface opposite to the surface in contact with the base material layer 2 of the low refractive index layer 3. More specifically, it may occur between the above-mentioned substance and components (for example, a cured product of the curable compound (A) or inorganic particles (C)) that can be contained in the low refractive index layer 3.

[0020] 2. Details 2.1 Structure of the light guide film The structure of the light guide film 1 according to the embodiment will be described in detail. The light guide film 1 according to the embodiment includes a base material layer 2 and a low refractive index layer 3 disposed on one surface of the base material layer 2 (see FIG. 1). In other words, the light guide film 1 includes a laminate composed of the base material layer 2 and the low refractive index layer 3.

[0021] (Base material layer) The base material layer 2 serves as a support for supporting the low refractive index layer 3 included in the light guide film 1.

[0022] The base material layer 2 is preferably a transparent resin film. The base material layer 2 includes, for example, at least one selected from the group consisting of polymethyl methacrylate, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polycarbonate (PC), polyarylate, polystyrene (PS), aromatic polyamide, polyether ether ketone, polysulfone, polyether sulfone, polyimide, and polyether imide. Among these, polyethylene terephthalate (PET) is preferred. That is, the base material layer 2 preferably consists of a transparent PET film. On the surface of the base material layer 2, corona treatment or plasma treatment may be performed within a range that does not inhibit transparency in order to enhance the adhesion to the low refractive index layer 3, or an easy adhesion layer or a primer layer may be provided.

[0023] The thickness of the base layer 2 is, for example, 20 μm or more and 200 μm or less. In this case, when the light guide film 1 is laminated to the member, wrinkles are less likely to occur in the light guide film 1. This makes it easier to achieve the effects of the embodiment. This thickness is preferably 30 μm or more, and more preferably 40 μm or more. This thickness is preferably 180 μm or less, and more preferably 150 μm or less.

[0024] (Low refractive index layer) When light is shone towards the low refractive index layer 3 through a material having a higher refractive index than the low refractive index layer 3, the shone light can be efficiently reflected. The light guide film 1 is equipped with a low refractive index layer 3 that can exhibit this function, thereby promoting the reflection of light shone towards the low refractive index layer 3.

[0025] In this embodiment, the low refractive index layer 3 has been adjusted in terms of physical properties or optical properties to facilitate the performance of the above functions.

[0026] For example, the thickness of the low refractive index layer 3 is adjusted to a specific range so that the reflection of light irradiated toward the low refractive index layer 3 is promoted. In this embodiment, the thickness of the low refractive index layer 3 is 0.4 μm or more and 3.0 μm or less. If this thickness is less than 0.4 μm, light in the visible light region (wavelengths 380 nm to 780 nm) irradiated toward the low refractive index layer 3 will not be reflected easily. In other words, it is difficult to efficiently guide light irradiated into the interior of a component using an optical film with a low refractive index layer 3 thickness of less than 0.4 μm. On the other hand, in this embodiment, since the thickness of the low refractive index layer 3 is 0.4 μm or more, the reflection of light irradiated toward the low refractive index layer 3 is promoted. Specifically, the reflection of light with wavelengths in the visible light region is promoted.

[0027] It is preferable that the reflectivity of light irradiated toward the low refractive index layer 3 is 100%, that is, that total internal reflection occurs. By irradiating the low refractive index layer 3 with light at an incident angle greater than or equal to the critical angle, total internal reflection can be more easily produced. Furthermore, by setting the thickness of the low refractive index layer 3 to a certain level or higher, the reflection of light irradiated toward the low refractive index layer 3 can be further promoted, making total internal reflection more likely. Specifically, the thickness of the low refractive index layer 3 is preferably 0.5 μm or more, more preferably 0.8 μm or more, even more preferably 0.9 μm or more, and particularly preferably 1.0 μm or more. From the viewpoint of the manufacturing cost of the low refractive index layer 3, this thickness is preferably 2.0 μm or less, and more preferably 1.5 μm or less.

[0028] Furthermore, the refractive index of the low refractive index layer 3 is adjusted to a specific range so as to promote the reflection of light irradiated toward the low refractive index layer 3. In this embodiment, the refractive index of the low refractive index layer 3 at a wavelength of 589 nm is 1.37 or more and 1.47 or less. The refractive index of the low refractive index layer 3 at a wavelength of 589 nm is determined based on the wavelength of the sodium lamp (D line) used in Method A of JIS K7142. From the viewpoint of the manufacturing cost of the low refractive index layer 3, this refractive index is preferably 1.38 or more, more preferably 1.39 or more, and even more preferably 1.40 or more. To further promote the reflection of light, this refractive index is preferably 1.46 or less, more preferably 1.45 or less, even more preferably 1.44 or less, and particularly preferably 1.43 or less. In this case, the reflection of light irradiated toward the low refractive index layer 3 is further promoted.

[0029] Furthermore, the low refractive index layer 3 may have appropriate optical properties to promote the reflection of light irradiated toward it. In this embodiment, when a material with a refractive index of 1.50 is in contact with the surface of the low refractive index layer 3 opposite to the surface in contact with the substrate layer 2, and light with a wavelength of 589 nm is irradiated toward the low refractive index layer 3 at an incident angle of 80° from the material, the reflectance of the light is 93% or more.

[0030] In this embodiment, the reflectance of light is the average value (Ra) of the reflectance of s-polarized light (Rs) and the reflectance of p-polarized light (Rp), and is calculated based on Fresnel's equation derived from the wave equation obtained from Maxwell's equations.

[0031] Fresnel's equation for thin films is expressed as follows:

[0032] rs={(n1cosθi-n2cosθt) / (n1cosθi+n2cosθt)}·exp(-iδ) rp={(n2cosθi-n1cosθt) / (n2cosθi+n1cosθt)}·exp(-iδ) rs and rp are the amplitude reflection coefficients for s-polarized and p-polarized light, respectively; n1 is the refractive index of the incident medium; n2 is the refractive index of the transmitting medium; θi is the angle of incidence; θt is the angle of refraction; exp is the exponential function with base Napier's number; i is the imaginary unit; and δ is the phase factor. Rs and Rp are the squares of the absolute values ​​of rs and rp, respectively, and Ra can be obtained by calculating the average value of Rs and Rp.

[0033] Furthermore, when θi exceeds the critical angle, Fresnel's equation is expressed as follows: rs′=[{n1·cosθi-i·n2[(sinθi)^2-(n2 / n1)^2]^1 / 2} / {n1·cosθi+i·n2[(sinθi)^2-(n2 / n1)^2]^1 / 2}]·exp(-iδ) rp′=[[n2·cosθi-i·n1{(sinθi)^2-(n2 / n1)^2}^1 / 2] / [n2·cosθi+i·n1{(sinθi)^2-(n2 / n1)^2}^1 / 2]]·exp(-iδ) rs′ and rp′ are the amplitude reflection coefficients for s-polarized and p-polarized light, respectively; θi is the angle of incidence; n1 is the refractive index of the incident medium; n2 is the refractive index of the transmitted medium; exp is the exponential function with base Napier's number; i is the imaginary unit; and δ is the phase factor. Rs and Rp are the squares of the absolute values ​​of rs′ and rp′, respectively, and Ra can be obtained by calculating the average value of Rs and Rp.

[0034] Furthermore, when light with a wavelength of 589 nm is irradiated from the material toward the low refractive index layer 3 at an incident angle of 80°, the reflectance of the light is preferably 94% or higher, more preferably 95% or higher, and even more preferably 99% or higher. It is particularly preferable that the reflectance of the light is 100%, i.e., total internal reflection, when light with a wavelength of 589 nm is irradiated from the material toward the low refractive index layer 3 at an incident angle of 80°, with a material with a refractive index of 1.50 in contact with the surface of the low refractive index layer 3 opposite to the surface in contact with the substrate layer 2. In other words, of the light irradiated toward the low refractive index layer 3, light with wavelengths in the visible light region can be totally internally reflected.

[0035] In this embodiment, the low refractive index layer 3 is made of a cured product of a curable resin composition (hereinafter also referred to as composition (X)). For example, the low refractive index layer 3 can be formed by applying composition (X) onto the substrate layer 2 and curing it. The method for curing composition (X) is not particularly limited, but curing by irradiation with ultraviolet light is preferably used.

[0036] For example, composition (X) contains a curable compound (A). For example, curable compound (A) includes at least one selected from the group consisting of (meth)acrylic compounds, epoxy compounds, urethane compounds, and silicone compounds. As described above, it is preferable that composition (X) can be cured by ultraviolet light, and therefore it is preferable that curable compound (A) includes a compound that can be cured by ultraviolet light. Specifically, it is preferable that curable compound (A) includes a (meth)acrylic compound.

[0037] The (meth)acrylic compound preferably includes a (meth)acrylic compound having three or more (meth)acryloyl groups. In this case, the curing of the curable compound (A) can proceed efficiently. For example, (meth)acrylic compounds having three or more (meth)acryloyl groups include trifunctional acrylates such as trimethylolpropane tri(meth)acrylate, ethoxylated trimethylolpropane tri(meth)acrylate, propoxylated trimethylolpropane tri(meth)acrylate, tris-2-hydroxyethyl isocyanurate tri(meth)acrylate, glycerin tri(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol tri(meth)acrylate, and ditrimethylolpropane tri(meth)acrylate; pentaerythritol tetra(meth) The compound comprises at least one compound selected from the group consisting of acrylates, tetrafunctional acrylates such as ditrimethylolpropanetetra(meth)acrylate and dipentaerythritoltetra(meth)acrylate; pentafunctional acrylates such as dipentaerythritol penta(meth)acrylate and ditrimethylolpropanepenta(meth)acrylate; hexafunctional acrylates such as dipentaerythritol hexa(meth)acrylate and ditrimethylolpropanehexa(meth)acrylate; and polyfunctional (meth)acrylate compounds in which the groups in these acrylates are substituted with alkyl groups or ε-caprolactone.

[0038] (Meth)acrylic compounds may also have functional groups other than (meth)acryloyl groups. Examples of functional groups other than (meth)acryloyl groups include fluoroalkyl groups. When a low refractive index layer 3 is prepared from a composition (X) containing a (meth)acrylic compound having a fluoroalkyl group, the antifouling properties of the low refractive index layer 3 tend to be improved.

[0039] Examples of (meth)acrylic compounds having a fluoroalkyl group include 2,2,2-trifluoroethyl (meth)acrylate, 2,2,3,3,3-pentafluoropropyl (meth)acrylate, 1H,1H-perfluoro-n-butyl (meth)acrylate, 1H,1H-perfluoro-n-pentyl (meth)acrylate, 1H,1H-perfluoro-n-hexyl (meth)acrylate, 1H,1H-perfluoro-n-octyl (meth)acrylate, and 1H,1H-perfluoro-n-decyl (meth)acrylate. )Acrylate, 1H,1H-perfluoro-n-dodecyl(meth)acrylate, 1H,1H-perfluoroisobutyl(meth)acrylate, 1H,1H-perfluoroisooctyl(meth)acrylate, 1H,1H-perfluoroisododecyl(meth)acrylate, 2,2,3,3-tetrafluoropropyl(meth)acrylate, 1H,1H,5H-perfluoropentyl(meth)acrylate, 1H,1H,9H-perfluorononyl(meth)acrylate, 3,3,3-trifluorobutyl( Meth)acrylate, 3,3,4,4,4-pentafluorobutyl(meth)acrylate, 2-(perfluoro-n-propyl)ethyl(meth)acrylate, 2-(perfluoro-n-butyl)ethyl(meth)acrylate, 2-(perfluoro-n-pentyl)ethyl(meth)acrylate, 2-(perfluoro-n-hexyl)ethyl(meth)acrylate, 2-(perfluoro-n-octyl)ethyl(meth)acrylate, 2-(perfluoro-n-decyl)ethyl(meth)acrylate, 2-(pe It contains at least one selected from the group consisting of (fluoroisobutyl)ethyl (meth)acrylate, 2-(perfluoroisooctyl)ethyl (meth)acrylate, 1H,1H,6H-perfluorohexyl (meth)acrylate, 1H,1H,8H-perfluorooctyl (meth)acrylate, 1H,1H,10H-perfluorodecyl (meth)acrylate, 1H,1H,12H-perfluorododecyl (meth)acrylate, and pentaerythritol diacrylate difluorobutyrate.

[0040] If the curable compound (A) contains a compound that can be cured when irradiated with ultraviolet light, the composition (X) may also contain a photopolymerization initiator (B). The photopolymerization initiator (B) is a compound that absorbs ultraviolet light and initiates the polymerization reaction in the composition (X). Examples of photopolymerization initiators (B) include acetophenones, benzophenones, α-amyloxime esters, and thioxanthones.

[0041] Furthermore, composition (X) may contain a photosensitizer in addition to, or in place of, the photopolymerization initiator (B). Examples of photosensitizers include n-butylamine, triethylamine, tri-n-butylphosphine, and thioxanthone.

[0042] For example, composition (X) contains inorganic particles (C). The inorganic particles (C) can adjust the refractive index of the low refractive index layer 3 to any value.

[0043] The inorganic particles (C) include, for example, at least one selected from the group consisting of hollow silica particles, magnesium fluoride particles, lithium fluoride particles, and aluminum fluoride particles. Among these, hollow silica particles are preferred, in which case the refractive index of the low refractive index layer 3 can be easily adjusted to any range.

[0044] The average particle size of the inorganic particles (C) is, for example, 30 nm or more. In this case, the refractive index of the low refractive index layer 3 can be easily adjusted to any range. Alternatively, the average particle size is 100 nm or less. In this case, the haze value of the low refractive index layer 3 can be prevented from becoming too high, thus preventing a decrease in transparency. This average particle size is preferably 40 nm or more, and more preferably 50 nm or more. This average particle size is preferably 90 nm or less, more preferably 80 nm or less, even more preferably 70 nm or less, and particularly preferably 60 nm or less. This average particle size is the D50 value in the dynamic light scattering method.

[0045] The ratio of inorganic particles (C) to the total solid content of composition (X) is 10% by mass or more and 70% by mass or less. In this case, the refractive index of the low refractive index layer 3 can be easily adjusted to any range. This ratio is preferably 30% by mass or more. This ratio is preferably 50% by mass or less. The solid content of composition (X) refers to the non-volatile components obtained by removing volatile components such as solvent (D) from composition (X).

[0046] Composition (X) may contain a solvent (D). If composition (X) contains a solvent (D), it is preferable to apply composition (X) to the substrate layer 2, allow the solvent (D) to volatilize, and then cure the curable compound (A). The solvent (D) is not particularly limited, but it is preferably a compound that can improve the ease of application of composition (X) and is moderately volatile. Specifically, examples include methyl isobutyl ketone, methyl ethyl ketone, acetone, methanol, ethanol, butanol, isopropyl alcohol, isobutyl alcohol, hexane, toluene, xylene, ethyl acetate, butyl acetate, tetrahydrofuran, propylene glycol monomethyl ether, and propylene glycol monomethyl ether acetate.

[0047] Composition (X) may further contain any additives such as dispersants.

[0048] In this embodiment, the low refractive index layer 3 may be arranged on one surface of the substrate layer 2. For example, as shown in Figure 1, the low refractive index layer 3 may be arranged on only one side of the substrate layer 2. In this case, the light guide film 1 comprises the substrate layer 2 and the low refractive index layer 3, with the substrate layer 2 and the low refractive index layer 3 laminated in this order. Alternatively, as shown in Figure 2, the low refractive index layer 3 may be arranged on both sides of the substrate layer 2 (see Figure 2). In this case, the light guide film 1 comprises a first low refractive index layer 31, a substrate layer 2, and a second low refractive index layer 32, with the first low refractive index layer 31, the substrate layer 2, and the second low refractive index layer 32 laminated in this order. The laminate containing the light guide film 1 consists of the first low refractive index layer 31, the substrate layer 2, and the second low refractive index layer 32. In this case, when the light-guiding film 1 has low refractive index layers 3 on both sides of the base layer 2, the two low refractive index layers 3 may be formed from a composition (X) having the same composition, or they may be formed from compositions (X) having different compositions.

[0049] 2.2 Characteristics of light guide film The characteristics of the light-guiding film 1 according to this embodiment will be described in detail.

[0050] (Total light transmittance) In the embodiment, the total light transmittance of the laminate consisting of the base layer 2 and the low refractive index layer 3, as measured using a D65 light source, is preferably 80% or higher. In this case, the amount of light transmitted through the light guide film 1 can be increased. When the light guide film 1 has two low refractive index layers 3, the total light transmittance is measured for the laminate consisting of the base layer 2 and the two low refractive index layers 3. This total light transmittance is more preferably 85% or higher, and even more preferably 90% or higher. This total light transmittance can be measured using a known haze meter in accordance with the provisions of JIS K7361-1.

[0051] (Hayes) In the embodiment, the haze value of the laminate consisting of the base layer 2 and the low refractive index layer 3 is preferably 3.0% or less. In this case, the transparency of the light that passes through the light guide film 1 is increased. If the light guide film 1 has two low refractive index layers 3, the haze value is measured for the laminate consisting of the base layer 2 and the two low refractive index layers 3. Furthermore, the haze value is preferably 2.0% or less, and more preferably 1.5% or less. This haze value can be measured, for example, using a known haze meter in accordance with the provisions of JIS K7136.

[0052] 2.3 Light guide components A light-guiding member 10 can be obtained from the light-guiding film 1 according to the embodiment (see Figure 3). The light-guiding member 10 is a plate-like body and includes a waveguide layer 11. When light is shone from the end of the light-guiding member 10 toward the waveguide layer 11, the shone light can propagate within the waveguide layer 11 in a direction perpendicular to the thickness direction of the light-guiding member 10, while being reflected at the interface with the low refractive index layer 3 and the interface with air. The thickness direction of the light-guiding member 10 refers to the direction in which the light-guiding film 1 and the waveguide layer 11 are stacked.

[0053] The low refractive index layer 3 of the light guide film 1 is in contact with the waveguide layer 11. As already mentioned, when a material with a refractive index of 1.50 is in contact with the surface of the low refractive index layer 3 opposite to the surface in contact with the substrate layer 2, and light with a wavelength of 589 nm is irradiated from the material toward the low refractive index layer 3 at an incident angle of 80°, the reflectivity of the light at the interface between the material and the low refractive index layer 3 is 93% or more. Therefore, when light propagates inside the waveguide layer 11, the reflectivity of the light at the interface between the waveguide layer 11 and the low refractive index layer 3 is increased. In particular, by keeping the refractive index of the waveguide layer 11 at around 1.50, light propagating inside the waveguide layer 11 can be efficiently reflected at the interface with the low refractive index layer 3 and the interface with air. As a result, light propagating inside the waveguide layer 11 can be efficiently guided.

[0054] The components of the light guide member 10 will be described in detail. In this embodiment, the waveguide layer 11 includes a transparent member 4 and an adhesive layer 5. That is, the light guide member 10 comprises a light guide film 1, an adhesive layer 5, and a transparent member 4. The light guide member 10 is constructed by laminating the transparent member 4, the adhesive layer 5, and the light guide film 1 in this order. The low refractive index layer 3 is in direct contact with the adhesive layer 5.

[0055] The refractive index, material, and thickness of the transparent member 4 and the refractive index, material, and thickness of the adhesive layer 5 can be set such that light is easily reflected at the interface between the low refractive index layer 3 and the adhesive layer 5, light is not easily reflected at the interface between the transparent member 4 and the adhesive layer 5, and light is easily reflected at the interface between the transparent member 4 and the air.

[0056] As mentioned above, the refractive index of the waveguide layer 11 is preferably around 1.50. Therefore, the refractive index of the transparent member 4 is preferably between 1.47 and 1.55. In this case, light propagating inside the waveguide layer 11 can be reflected efficiently. Therefore, light propagating inside the waveguide layer 11 can be guided efficiently. This refractive index is preferably 1.48 or higher, and more preferably 1.49 or higher. This refractive index is preferably 1.54 or lower, more preferably 1.53 or lower, even more preferably 1.52 or lower, and even more preferably 1.51 or lower. This refractive index is particularly preferably 1.50.

[0057] The transparent member 4 may be made of a transparent inorganic or organic material. Preferably, the material can keep the refractive index of the transparent member 4 within the above numerical range. For example, the transparent member 4 includes at least one selected from the group consisting of glass, polycarbonate resin, and (meth)acrylic resin. Among these, glass is particularly preferred. In other words, the transparent member 4 is preferably made of a glass substrate.

[0058] For example, the thickness of the transparent member 4 is 1 mm or more and 10 mm or less. In this case, the light irradiated onto the waveguide layer 11 can be efficiently guided. This thickness is more preferably 2 mm or more, even more preferably 3 mm or more, even more preferably 7 mm or less, and even more preferably 5 mm or less.

[0059] As mentioned above, the refractive index of the waveguide layer 11 is preferably around 1.50. Therefore, the refractive index of the adhesive layer 5 is preferably between 1.47 and 1.55. In this case, light propagating inside the waveguide layer 11 can be reflected efficiently. Therefore, light propagating inside the waveguide layer 11 can be guided efficiently. This refractive index is preferably 1.48 or higher, and more preferably 1.49 or higher. This refractive index is preferably 1.54 or lower, more preferably 1.53 or lower, even more preferably 1.52 or lower, and even more preferably 1.51 or lower. This refractive index is particularly preferably 1.50.

[0060] The adhesive layer 5 may contain additives such as plasticizers, ultraviolet absorbers, light stabilizers, heat shielding agents, and colorants, provided that its refractive index is within the aforementioned range.

[0061] Furthermore, it is preferable that the difference between the refractive index of the adhesive layer 5 and the refractive index of the transparent member 4 be small. Specifically, the difference between the refractive index of the adhesive layer 5 and the refractive index of the transparent member 4 is preferably 0.20 or less, more preferably 0.15 or less, and even more preferably 0.10 or less. In this case, light propagating inside the waveguide layer 11 can be guided even more efficiently.

[0062] For example, the thickness of the adhesive layer 5 is 0.1 mm or more and 1.0 mm or less. In this case, light propagating inside the waveguide layer 11 can be efficiently guided. This thickness is more preferably 0.2 mm or more, and even more preferably 0.3 mm or more. This thickness is more preferably 0.9 mm or less, and even more preferably 0.8 mm or less.

[0063] The light guide film 1 is bonded to the transparent member 4 via an adhesive layer 5. The method for bonding the light guide film 1 to the transparent member 4 via the adhesive layer 5 is as follows: First, the sheet on which the adhesive layer 5 is formed and the transparent member 4 are stacked in this order on at least one side of the light guide film 1 and pre-bonded under heating and vacuum conditions. Then, after pre-bonding, the final bonding is performed under heating and pressurizing conditions. In this way, the light guide film 1 is bonded to the transparent member 4 via the adhesive layer 5. An autoclave may be used for the final bonding. The sheet on which the adhesive layer 5 is formed is preferably a so-called thermoplastic resin that melts when heated and solidifies when cooled. Furthermore, the sheet on which the adhesive layer 5 is formed is preferably made of a material that can keep the refractive index of the adhesive layer 5 within the above range. For this reason, the sheet on which the adhesive layer 5 is formed, i.e., the adhesive layer 5, preferably contains at least one selected from the group consisting of polyvinyl butyral resin and ethylene vinyl acetate resin. Furthermore, from the viewpoint of bringing the refractive index of the adhesive layer 5 closer to 1.50, it is particularly preferable that the adhesive layer 5 contains a polyvinyl butyral resin.

[0064] 2.4 Light guide device A light guide device 100 can be obtained from the light guide member 10. The light guide device 100 comprises a light source 6 and a light guide member 10 that guides the light emitted from the light source 6 (see Figure 4).

[0065] The light source 6 emits light. The light emitted from the light source 6 can be incident on the waveguide layer 11 provided by the light guide member 10 from its end. When light is incident on the waveguide layer 11 from its end, the incident light can propagate within the waveguide layer 11 in a direction perpendicular to the thickness direction of the waveguide layer 11, while being reflected at the interface with the low refractive index layer 3 and the interface with air.

[0066] As already mentioned, the reflectivity at the interface between the waveguide layer 11 and the low refractive index layer 3 is increased. Therefore, of the light emitted from the light source 6, the light that irradiates the waveguide layer 11 can be efficiently reflected within the waveguide layer 11 at the interface with the low refractive index layer 3 and at the interface with air. As a result, of the light emitted from the light source 6, the light that propagates inside the waveguide layer 11 can be efficiently guided.

[0067] The light source 6 is positioned at the end of the light guide member 10. More specifically, the light source 6 is positioned at the end of the waveguide layer 11 provided by the light guide member 10, that is, the transparent member 4 and the adhesive layer 5. The light source 6 does not have to be in direct contact with the light guide member 10, and may be positioned near the end of the light guide member 10. For example, it may be positioned away from the end of the light guide member 10 as long as it does not obstruct the incidence of light onto the waveguide layer 11 provided by the light guide member 10. Furthermore, it is preferable that the light source 6 is positioned in the thickness direction of the light guide member 10 so as to be aligned with the waveguide layer 11, in which case the light emitted from the light source 6 is easily and efficiently irradiated onto the waveguide layer 11. The light source 6 may be positioned at one point on the end of the light guide member 10, or it may be positioned so as to circumferentially cover the end of the light guide member 10.

[0068] As the light source 6, for example, a light-emitting diode (LED) or a thin-film electroluminescent device (thin-film EL) can be used. As for the LED, a white LED is preferred, but a blue LED or a red LED may also be used. In addition, multiple types of LEDs may be used; for example, white light may be obtained from three colored LEDs: R, G, and B.

[0069] For example, the light guide member 10 may include a light scatterer 7 inside, specifically, a light scatterer 7 placed in the transparent member 4. When the light guide member 10 includes a light scatterer 7, the light scatterer 7 can more efficiently extract light propagating inside the waveguide layer 11.

[0070] Specifically, when light propagating inside the waveguide layer 11 of the light guide member 10 is irradiated onto the light scatterer 7, the light irradiated onto the light scatterer 7 can be scattered. Therefore, the light irradiated onto the light scatterer 7 can be extracted to the outside of the light guide member 10. This makes it easier to adjust the brightness outside the light guide member 10. The area in which the brightness outside the light guide member 10 can be adjusted and the intensity of the brightness can be controlled by the arrangement of the light scatterers 7, specifically by the uneven pattern formed by the light scatterers 7 and the density of light propagating inside the waveguide layer 11. Specific examples of light scatterers 7 include ink containing metal particles, ceramic particles, or resin particles. If the light scatterer 7 is such an ink, the ink can be placed on the transparent member 4 by printing, and an uneven pattern can be formed.

[0071] Furthermore, in this embodiment, since light propagating inside the waveguide layer 11 can be efficiently guided, even if the light scatterer 7 is positioned near the end of the light guide member 10 opposite to the end where the light source 6 is located, light can efficiently reach the light scatterer 7. As a result, there is an advantage in that the amount of light that the light scatterer 7 can scatter can be increased regardless of the distance of the light scatterer 7 from the light source 6.

[0072] 2.5 Morphology of light guide members As already mentioned, the light guide member 10 includes a waveguide layer 11. The light guide member 10 shown in Figure 3 has one waveguide layer 11, but is not limited to this. In other words, the light guide member 10 may have multiple waveguide layers 11 (see Figure 5).

[0073] For example, the light guide member 10 shown in Figure 5 comprises a first waveguide layer 111, a light guide film 1, and a second waveguide layer 112. The light guide member 10 is constructed by laminating the first waveguide layer 111, the light guide film 1, and the second waveguide layer 112 in this order. More specifically, the light guide member 10 shown in Figure 5 comprises a first transparent member 41, a first adhesive layer 51, a light guide film 1, a second adhesive layer 52, and a second transparent member 42. The first transparent member 41, the first adhesive layer 51, the light guide film 1, the second adhesive layer 52, and the second transparent member 42 are laminated in this order. The low refractive index layer 3 is in direct contact with the first adhesive layer 51.

[0074] The refractive index, material, and thickness of the first transparent member 41 and the refractive index, material, and thickness of the second transparent member 42 may be the same or different. Similarly, the refractive index, material, and thickness of the first adhesive layer 51 and the refractive index, material, and thickness of the second adhesive layer 52 may be the same or different.

[0075] Furthermore, in Figure 5, the low refractive index layer 3 and the substrate layer 2 of the light guide film 1 can come into contact with the first adhesive layer 51 and the second adhesive layer 52, respectively. In this case, light propagating inside the first waveguide layer 111 can be efficiently guided.

[0076] Furthermore, in the light guide member 10 shown in Figure 5, it is not necessarily required to direct light into the second waveguide layer 112 for the purpose of guiding light. In such cases, the second transparent member 42 and the adhesive layer 52 may contain colorants or the like.

[0077] 3. Summary A light-guiding film 1 capable of efficiently reflecting light irradiated toward the low-refractive-index layer 3 has been described. The light-guiding film 1 comprises a base layer 2 and a low-refractive-index layer 3 disposed on one surface of the base layer 2. The light-guiding film 1 may also include layers other than the base layer 2 and the low-refractive-index layer 3. No layers are disposed on the surface of the low-refractive-index layer 3 opposite to the surface on which the base layer 2 is disposed. In other words, the surface of the low-refractive-index layer 3 opposite to the surface on which the base layer 2 is disposed is the outermost surface of the light-guiding film 1.

[0078] A light guide member 10 can be obtained from the light guide film 1. The light guide member 10 obtained from the light guide film 1 can efficiently guide light propagating inside the waveguide layer 11 provided in the light guide member 10. Furthermore, a light guide device 100 can be obtained from the light guide member 10. The light guide device 100 is equipped with a light source 6, which emits light. The light emitted from the light source 6 enters the light guide member 10 and propagates inside the waveguide layer 11 provided in the light guide member 10.

[0079] As already mentioned, the transparent member 4 of the light guide member 10 is particularly preferably made of a glass substrate. In other words, the light guide member 10 is particularly preferably a glass member used for dimming purposes, that is, a dimmable window glass. The light guide member 10, which is a dimmable window glass, can be placed on the ceiling of the interior of an automobile.

[0080] Furthermore, the light guide member 10, which is a dimmable window glass, is preferably used in combination with a light source 6. For example, if the light guide member 10, which is a dimmable window glass, is equipped with a light scatterer 7, light propagating from the light source 6 located at the end of the light guide member 10 through the waveguide layer 11 of the light guide member 10 can be scattered by the light scatterer 7. This allows the light propagating through the waveguide layer 11 of the light guide member 10 to be extracted to the outside of the light guide member 10. If such a light guide member 10, which is a dimmable window glass, is placed on the ceiling of the interior of a car, it becomes easier to adjust the brightness of the interior space of the car.

[0081] 4. Appearance This disclosure includes the following aspects.

[0082] A light-guiding film (1) according to a first aspect of this disclosure comprises a substrate layer (2) and a low refractive index layer (3) disposed on one surface of the substrate layer (2). The refractive index of the low refractive index layer (3) at a wavelength of 589 nm is 1.37 or more and 1.47 or less. The thickness of the low refractive index layer (3) is 0.4 μm or more and 3.0 μm or less. When a substance with a refractive index of 1.50 is in contact with the surface of the low refractive index layer (3) opposite to the surface in contact with the substrate layer (2), and light with a wavelength of 589 nm is irradiated from the substance toward the low refractive index layer (3) at an incident angle of 80°, the reflectance of the light is 93% or more.

[0083] According to this embodiment, a light guide film (1) can be provided that can efficiently propagate light by promoting the reflection of light irradiated toward the low refractive index layer (3).

[0084] In the first embodiment, the light-guiding film (1) according to the second aspect of the present disclosure comprises a low refractive index layer (3) which includes a curable compound (A) and inorganic particles (C), wherein the average particle size of the inorganic particles (C) is 30 nm or more and 100 nm or less.

[0085] A light guide member (10) according to a third aspect of this disclosure comprises a transparent member (4), an adhesive layer (5), and a light guide film (1) according to the first or second aspect. The transparent member (4), the adhesive layer (5), and the light guide film (1) are laminated in this order. The low refractive index layer (3) is in direct contact with the adhesive layer (5).

[0086] A light guide member (10) according to a fourth aspect of this disclosure comprises a first transparent member (41), a first adhesive layer (51), a light guide film (1) according to the first or second aspect, a second adhesive layer (52), and a second transparent member (42). The first transparent member (41), the first adhesive layer (51), the light guide film (1), the second adhesive layer (52), and the second transparent member (42) are laminated in this order. The low refractive index layer (3) is in direct contact with the first adhesive layer (51).

[0087] In the fifth aspect of the present disclosure, the light guide member (10) has, in the third aspect, an adhesive layer (5) with a refractive index of 1.47 or more and 1.55 or less.

[0088] In the sixth aspect of the present disclosure, the light guide member (10) has, in the fourth aspect, a refractive index of the first adhesive layer (51) of which is 1.47 or more and 1.55 or less.

[0089] In the seventh aspect of the present disclosure, the light guide member (10) in the third or fifth aspect comprises a transparent member (4) which includes at least one selected from the group consisting of glass, polycarbonate resin and (meth)acrylic acid resin.

[0090] In the eighth aspect of the present disclosure, the light guide member (10) is such that, in the fourth or sixth aspect, each of the first transparent member (41) and the second transparent member (42) includes at least one selected from the group consisting of glass, polycarbonate resin and (meth)acrylic acid resin.

[0091] In the ninth aspect of the present disclosure, the light guide member (10) comprises, in the third, fifth, or seventh aspect, at least one adhesive layer (5) selected from the group consisting of polyvinyl butyral resins and ethylene vinyl acetate resins.

[0092] In the tenth aspect of the present disclosure, the light guide member (10) is such that, in the fourth, sixth, or eighth aspect, each of the first adhesive layer (51) and the second adhesive layer (52) includes at least one selected from the group consisting of polyvinyl butyral resin and ethylene vinyl acetate resin.

[0093] A light guide device (100) according to an eleventh aspect of the present disclosure comprises a light source (6) and a light guide member (10) of any one of the third to ten aspects that guides the light emitted from the light source (6). The light source (6) is positioned at the end of the transparent member (4) and adhesive layer (5) of the light guide member (10). [Examples]

[0094] The present disclosure will be specifically described below with reference to examples.

[0095] 1.Curable composition The components and materials used in the curable compositions of the examples and comparative examples are shown below.

[0096] (Curable compound (A)) Curable compound #1: Dipentaerythritol pentaacrylate, manufactured by Shin-Nakamura Chemical Industry Co., Ltd., product name NK Ester A9570-W.

[0097] (Photopolymerization initiator (B)) Photopolymerization initiator #1: 2-hydroxy-1-{4-[4-(2-hydroxy-2-methylpropionyl)-benzyl]-phenyl}-2-methylpropan-1-one, manufactured by IGM Resins BV, product name Omnirad127D.

[0098] (Inorganic particles (C)) Inorganic particle dispersion #1: Hollow silica particle dispersion, manufactured by JGC Catalysts & Chemicals Co., Ltd., product name: Thru-Ria 5320 (average particle size 75 nm, refractive index 1.37, solid content 20 wt%).

[0099] Inorganic particle dispersion #2: Hollow silica particle dispersion, manufactured by JGC Catalysts & Chemicals Co., Ltd., product name: Thru-Ria 4320 (average particle size 60 nm, refractive index 1.37, solid content 20 wt%).

[0100] Inorganic particle dispersion #3: Hollow silica particle dispersion, manufactured by JGC Catalysts & Chemicals Co., Ltd., product name: Thru-Ria 22UB-09MD (average particle size 100 nm, refractive index 1.37, solid content 20 wt%).

[0101] (Solvent (D)) Solvent #1: Methyl isobutyl ketone.

[0102] 2. Method for manufacturing light guide film The light guide film was manufactured as follows:

[0103] The curable composition prepared in "1. Curable Composition" is applied to a substrate layer (PET film (manufactured by Toray Industries, Inc., product number 50U40 (thickness: 50 μm), refractive index 1.65)), dried at 80°C for 1 minute to remove the solvent, and then exposed to ultraviolet light at 300 mJ / cm². 2 The curable composition was cured by irradiation to form a low refractive index layer on the substrate layer. A light-guiding film was manufactured in this manner.

[0104] 3. Low refractive index layer 3.1 Thickness of the low refractive index layer The thickness of the low refractive index layer was measured by optical interferometry using a reflectance spectrophotometer (Otsuka Electronics Co., Ltd., model number FE-3000). The results are shown in the table. The refractive index of the low refractive index layer measured by the method described in the next section was used for the calculations.

[0105] 3.2 Refractive index of the low refractive index layer The refractive index of the low refractive index layer was measured using an Abbe refractometer (manufactured by Atago Co., Ltd., model number NAR-1T·LO) in accordance with JIS K7142. The results are shown in the table.

[0106] 3.3 Light reflectance Using optical thin-film design software (product name TFV128 ver.3.3.6, manufactured by Nari Software, hereinafter referred to as "software"), the reflectance of light was determined when a material with a refractive index of 1.50 was in contact with the surface of the low-refractive-index layer opposite to the surface in contact with the substrate layer, and light with a wavelength of 589 nm was shone from the material towards the low-refractive-index layer at an incident angle of 80°. Specifically, the software assumed that the refractive index of the substrate layer was 1.65, the refractive index of the medium was 1.50, the incident angle was 80°, and there was no absorption or dispersion of light. The reflectance of light with a wavelength of 589 nm was then determined when the thickness (μm) and refractive index of the low-refractive-index layer were varied. The results are shown in the table. Note that the reflectance of light is the average value (Ra) of the reflectance of s-polarized light (Rs) and the reflectance of p-polarized light (Rp), and is determined based on Fresnel's equation obtained from Maxwell's equations.

[0107] 4. Evaluation of light guide film 4.1 Total light transmittance The total light transmittance of a laminate consisting of a base layer and a low refractive index layer was calculated using a haze meter (manufactured by Nippon Denshoku Industries Co., Ltd., part number NDH7000SP2) as defined in JIS K7361-1. The results are shown in the table.

[0108] 4.2 Haze The haze of a laminate consisting of a base layer and a low refractive index layer was measured using a haze meter (manufactured by Nippon Denshoku Industries Co., Ltd., part number NDH7000SP2) as defined in JIS K7136. The results are shown in the table.

[0109] [Table 1]

[0110] [Table 2] [Explanation of Symbols]

[0111] 1. Light guide film 2 Base material layer 3. Low refractive index layer 4,41,42 Transparent components 5,51,52 Adhesive layer 6 light source 10 Light guide member 100 Light guide device

Claims

1. The system comprises a base layer and a low refractive index layer disposed on one surface of the base layer, The refractive index of the low refractive index layer at a wavelength of 589 nm is 1.37 or more and 1.47 or less. The thickness of the low refractive index layer is 0.4 μm or more and 3.0 μm or less. When a material with a refractive index of 1.50 is in contact with the surface of the low refractive index layer opposite to the surface in contact with the substrate layer, and light with a wavelength of 589 nm is irradiated from the material toward the low refractive index layer at an incident angle of 80°, the reflectance of the light is 93% or more. Light guide film.

2. The low refractive index layer comprises a curable compound and inorganic particles, wherein the average particle size of the inorganic particles is 30 nm or more and 100 nm or less. The light-guiding film according to claim 1.

3. The device comprises a transparent member, an adhesive layer, and the light-guiding film described in claim 1. The transparent member, the adhesive layer, and the light-guiding film are laminated in this order. The low refractive index layer is in direct contact with the adhesive layer. Light guide component.

4. The present invention comprises a first transparent member, a first adhesive layer, a light-guiding film according to claim 1, a second adhesive layer, and a second transparent member. The first transparent member, the first adhesive layer, the light-guiding film, the second adhesive layer, and the second transparent member are laminated in this order. The low refractive index layer is in direct contact with the first adhesive layer. Light guide component.

5. The refractive index of the adhesive layer is 1.47 or more and 1.55 or less. The light guide member according to claim 3.

6. The refractive index of the first adhesive layer is 1.47 or more and 1.55 or less. The light guide member according to claim 4.

7. The transparent member includes at least one selected from the group consisting of glass, polycarbonate resin, and (meth)acrylic acid resin. The light guide member according to claim 3.

8. Each of the first transparent member and the second transparent member includes at least one selected from the group consisting of glass, polycarbonate resin and (meth)acrylic acid resin. The light guide member according to claim 4.

9. The adhesive layer comprises at least one selected from the group consisting of polyvinyl butyral resin and ethylene vinyl acetate resin. The light guide member according to claim 3.

10. Each of the first adhesive layer and the second adhesive layer contains at least one selected from the group consisting of polyvinyl butyral resin and ethylene vinyl acetate resin. The light guide member according to claim 4.

11. The invention comprises a light source and a light-guiding member according to claim 3 or 4 for guiding the light emitted from the light source, The light source is positioned at the end of the transparent member and the adhesive layer of the light guide member, Light guide device.

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