Dimmer film

Abstract

To provide a dimmer film which is less permeable to light of a visible light region, and can suppress scattering of light of an infrared region and makes the light of the infrared region permeable.SOLUTION: A dimmer film contains a resin and an oil-soluble dye, wherein linear transmittance of at least a part of light at a wavelength of 450 nm or more and 650 nm or less is less than 25%, and linear transmittance of light at a wavelength of 900 nm is 80% or more.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a light reduction film that can be used for covering an infrared sensor.

Background Art

[0002] Using a resin film containing a resin and a dye as a functional film has been considered. For example, Patent Document 1 describes using a colored film obtained by dyeing a norbornene-based resin film with a disperse dye as a protective film for a color polarizing plate. Further, for example, Patent Document 2 describes using a film containing a resin and an oil-soluble dye and having a specific thickness as an antireflection film for an image display device.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, an infrared sensor that uses light in the infrared region can detect a target non-contact, and because it uses light that is invisible to the human eye, it can collect necessary information without stimulating human vision. Therefore, in recent years, its fields of use have been expanding.

[0005]

[0006] ​As a characteristic required for the cover of an infrared sensor, from the viewpoint of preventing the infrared sensor from being visually recognized from the outside of the cover, it is difficult to transmit light in the visible light region. Further, in order to allow the infrared sensor to function while being covered with the cover, it is required to make the light in the infrared region travel straight inside the cover. Even for such a cover, it is conceivable to use a film material, but a film material that satisfies the characteristics required for the cover of the infrared sensor has not yet been obtained.

[0007] The present invention has been made in view of the above circumstances, and an object thereof is to provide a light-reducing film that is difficult to transmit light in the visible light region and can transmit light in the infrared region while traveling straight.

Means for Solving the Problems

[0008] As a result of intensive studies by the present inventor to achieve the above object, it has been found that by using a resin and an oil-soluble dye, a light-reducing film that is difficult to transmit light in the visible light region and can transmit light in the infrared region while traveling straight can be realized, and the present invention has been completed. That is, the present invention provides the following.

[0009] <1> A light-reducing film containing a resin and an oil-soluble dye, having a linear transmittance of at least a part of light with a wavelength of 450 nm or more and 650 nm or less of less than 25%, and a linear transmittance of light with a wavelength of 900 nm of 80% or more. <2> The light-reducing film according to <1>, wherein the linear transmittance of all light with a wavelength of 450 nm or more and 650 nm or less is less than 25%. <3> The light-reducing film according to <1> or <2>, wherein the thickness of the light-reducing film is 100 μm or more and less than 800 μm. <4> The light-reducing film according to any one of <1> to <3>, wherein the ratio of the oil-soluble dye to the resin is 0.01% by weight or more and less than 2% by weight. <5> The light-reducing film according to any one of <1> to <4>, having a haze of 0.1% or more and 1% or less. <6> The dimming film has a multilayer structure in which a first resin layer, a dimming layer, and a second resin layer are laminated in this order, and the dimming layer contains the resin and the oil-soluble dye. The dimming film according to any one of <1> to <5>.

Advantages of the Invention

[0010] According to the present invention, it is possible to provide a dimming film that hardly transmits light in the visible light region and allows light in the infrared region to travel straight through and be transmitted.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Modes for Carrying Out the Invention

[0012] Hereinafter, the present invention will be described in detail with reference to embodiments and examples. However, the present invention is not limited to the embodiments and examples shown below, and can be arbitrarily modified and implemented without departing from the scope of the claims of the present invention and its equivalent scope. The components of the embodiments shown below can be combined as appropriate.

[0013] In the following description, unless otherwise specified, the "layer" and the "film" may be a flexible member such as a resin film or a rigid member.

[0014] In the following description, when a layer is "directly" disposed on another layer, unless otherwise specified, it means that the two layers are in contact with each other and there is no other layer between the two layers.

[0015] <1. Overview of the Dimming Film> A light-reducing film according to an embodiment of the present invention contains a resin and an oil-soluble dye, has a linear transmittance of less than 25% for at least a part of light with a wavelength of 450 nm or more and 650 nm or less, and a linear transmittance of 80% or more for light with a wavelength of 900 nm.

[0016] According to this embodiment, since the light-reducing film contains a resin and an oil-soluble dye, it can have spectral characteristics such that it is difficult to transmit at least a part of the light in the visible light region and it is easy to transmit the light in the infrared region. Further, since the light-reducing film contains a resin and an oil-soluble dye, scattering of the light in the infrared region inside the film can be suppressed, so that the light in the infrared region can be transmitted well while traveling straight. Therefore, it can be a light-reducing film suitable for use as a cover for an infrared sensor.

[0017] Although it is not clear about the mechanism by which the light-reducing film can exhibit the above effects by containing a resin and an oil-soluble dye, the present inventor speculates as follows. However, the technical scope of the present invention is not limited to the mechanism shown below.

[0018] For example, when trying to obtain a light-reducing film having spectral characteristics such that it is difficult to transmit the light in the visible light region and it is easy to transmit the light in the infrared region, it is conceivable to add a light-shielding material such as inorganic particles that easily absorb the light in the visible light region and hardly absorb the light in the infrared region to the resin constituting the film. However, in a film containing such a light-shielding material, when the size of the light-shielding material is large, there is a concern that the light in the infrared region is reflected on the surface of the light-shielding material and scattered inside the film, and the straightness of the light in the infrared region cannot be sufficiently ensured.

[0019] On the other hand, in this embodiment, by using an oil-soluble dye as the light-shielding material, the oil-soluble dye dissolves in the resin, and the resin and the oil-soluble dye form a uniform system. Therefore, inside the film, since the oil-soluble dye can exist in a state where its size is extremely small, the inventor speculates that scattering of the light in the infrared region can be suppressed and the straightness of the light in the infrared region can be improved.

[0020] The dimming film in this embodiment may have a single-layer structure or a multilayer structure. Hereinafter, it will be described separately for the case of a single-layer structure and the case of a multilayer structure.

[0021] <2. Dimming Film with Single-Layer Structure> FIG. 1 is a cross-sectional view schematically showing an example of a dimming film according to an embodiment of the present invention. The dimming film 10 shown in FIG. 1 usually has a single dimming layer 11 containing a resin and an oil-soluble dye.

[0022] <2.1. Linear Transmittance of Dimming Film> The dimming film according to this embodiment has spectral characteristics such that it is difficult to transmit light in the visible light region and easy to transmit light in the infrared region.

[0023] For the dimming film, the linear transmittance of at least a part of the light with a wavelength of 450 nm or more and 650 nm or less is usually less than 25%, preferably 20% or less, more preferably 10% or less, still more preferably 5% or less, and ideally 0%. By the linear transmittance of at least a part of the light in the visible light region being less than the above upper limit value, it is possible to effectively suppress the infrared sensor from being visually recognized from outside the cover.

[0024] The linear transmittance of at least a part of the light with a wavelength of 450 nm or more and 650 nm or less of the dimming film may be less than a predetermined value, and among the light with a wavelength of 450 nm or more and 650 nm or less, which light's linear transmittance is to be less than the predetermined value can be appropriately selected according to the use of the infrared sensor, etc. In this embodiment, it is preferable that the linear transmittance of all the light with a wavelength of 450 nm or more and 650 nm or less is less than the predetermined value. This is because the dimming film can make it difficult to transmit light in a wide range of the visible light region, and thus it is possible to effectively suppress the infrared sensor from being visually recognized from outside the cover.

[0025] In addition, for the light reduction film, the linear transmittance of light with a wavelength of 900 nm is usually 80% or more, preferably 85% or more, more preferably 90% or more, and ideally 100%. This is because when the linear transmittance of light with a wavelength of 900 nm is at or above the lower limit value, infrared light can be transmitted and received well by the infrared sensor.

[0026] In the light reduction film, it is sufficient that at least the linear transmittance of light with a wavelength of 900 nm is at or above the lower limit value. Preferably, the total direct transmittance of light with a wavelength of 900 nm or more and 1600 nm or less is at or above the lower limit value. Since light in the near-infrared region is preferably used in the infrared sensor, the light reduction film can transmit light in a wide range of the near-infrared region, making it applicable as a cover for various infrared sensors.

[0027] The linear transmittance of light can be measured by a spectrophotometer.

[0028] <2.2. Haze of Light Reduction Film> In a dimming film, the degree of suppressing light scattering in the infrared region can be evaluated by haze. The smaller the haze, the stronger the suppression of light scattering in the infrared region (the better the straightness of light in the infrared region) can be evaluated. Generally, haze is evaluated by light such as a D65 light source, a C light source, etc. centered on the visible light region, or a pseudo-spectral light source thereof. Note that the haze in the present application is a value measured in accordance with JIS K7136 using a D65 light source. Further, in a system containing a resin and an oil-soluble dye, when the oil-soluble dye is not sufficiently compatible with the resin and forms aggregates, the aggregates scatter light in the visible light region, resulting in an increase in haze. Therefore, a small haze measured in the visible light region indicates that there are few large aggregates (specifically, aggregates having a size larger than about 1 / 20 of the wavelength in the visible light region) that cause scattering of light in the visible light region. Since the infrared region has a longer wavelength than the visible light region, a small haze indicates that there are few large aggregates that cause scattering of light in the infrared region. As described above, this indicates that the scattering of light in the infrared region can be strongly suppressed. Therefore, it is preferable that the haze of the dimming film according to the present embodiment is small. Such a haze of the dimming film is usually 1% or less, preferably 0.5% or less, more preferably 0.3% or less, and usually 0% or more, and may be 0.1% or more.

[0029] <2.3. b value of the dimming film * Value The dimming film has a b * , a * , b * value in the CIE 1976 (L * , a, b) color space is preferably, for example, -3 or more and 3 or less, more preferably -2 or more and 2 or less, still more preferably -1 or more and 1 or less, and particularly preferably 0. The b * value of the dimming film can be measured with a colorimeter. Further, the b * value of the dimming film can be adjusted by adjusting the color and concentration of the oil-soluble dye contained in the dimming film.

[0030] <2.4. Materials of the light-reducing film> The light-reducing film contains at least a resin and an oil-soluble dye.

[0031] <2.4.1. Resin> The light-reducing film contains a resin. The resin can usually contain a polymer and any components as required.

[0032] Also, the resin that can be contained in the light-reducing film preferably has a high linear transmittance in the infrared region. When the resin is a 50-μm layer, the range of the linear transmittance is preferably 80% or more, more preferably 85% or more, and even more preferably 90% or more for all linear transmittances of light with a wavelength of 900 nm or more and 1600 nm or less.

[0033] The resin that can be contained in the light-reducing film is not particularly limited, but is preferably a thermoplastic resin. Also, the thermoplastic resin may have adhesiveness. When the light-reducing film contains a thermoplastic resin with adhesiveness, for example, when constructing a cover glass for an infrared sensor as a laminated glass, the light-reducing film can be used as an interlayer film of the laminated glass. Also, it can be laminated with other light-transmitting resin substrates such as polypropylene (PP) resin, polyethylene terephthalate (PET) resin, polycarbonate (PC) resin, and cycloolefin (COP) resin to form a cover.

[0034] The resin that can be contained in the light-reducing film usually contains a polymer, preferably a thermoplastic polymer. The weight ratio of the thermoplastic polymer in the resin that can be contained in the light-reducing film is preferably 50% by weight or more, more preferably 60% by weight or more, even more preferably 70% by weight or more, usually 100% by weight or less, and may be 100% by weight.

[0035] Examples of materials that can be used as the thermoplastic resin that can be included in the light-reducing film include, for example, vinyl chloride resin, urethane resin, ionomer resin, polyamide resin, polyvinyl butyral (PVB) resin, ethylene-vinyl acetate copolymer (EVA), cycloolefin resin (COP), polyethylene terephthalate (PET) resin, hydrogenated aromatic vinyl compound-conjugated diene block copolymer, and modified products thereof. Among them, polyvinyl butyral resin, ethylene-vinyl acetate copolymer, hydrogenated aromatic vinyl compound-conjugated diene block copolymer, and modified products thereof are preferred because they have adhesiveness. Since they have adhesiveness, it becomes easy to combine with glass or other transparent plastics. Among them, modified products of hydrogenated aromatic vinyl compound-conjugated diene block copolymer are more preferred. Hydrogenated aromatic vinyl compound-conjugated diene block copolymer and modified products thereof have good adhesion to glass and at the same time are excellent in infrared region permeability, so they can be used as a light-reducing film that can easily form a cover for an infrared sensor in combination with a glass material. Hereinafter, the hydrogenated aromatic vinyl compound-conjugated diene block copolymer is also referred to as copolymer (a1).

[0036] In the thermoplastic polymer that can be included in the light-reducing film, the total weight ratio of copolymer (a1) and the modified product of copolymer (a1) is preferably 90% by weight or more, more preferably 95% by weight or more, still more preferably 98% by weight or more, and usually 100% by weight or less, and may be 99.9% by weight or less.

[0037] In addition to copolymer (a1) and the modified product of copolymer (a1), the thermoplastic polymer may contain any polymer. In the thermoplastic polymer, the total weight ratio of any polymer is preferably 10% by weight or less, more preferably 5% by weight or less, still more preferably 2% by weight or less, and usually 0% by weight or more, and may be 0% by weight.

[0038] (Copolymer (a1) (hydrogenated aromatic vinyl compound-conjugated diene block copolymer)) The hydrogenated aromatic vinyl compound-conjugated diene block copolymer is a hydride of the aromatic vinyl compound-conjugated diene block copolymer. That is, the hydrogenated aromatic vinyl compound-conjugated diene block copolymer has a structure obtained by hydrogenating some or all of the carbon-carbon unsaturated bonds (including the carbon-carbon unsaturated bonds derived from conjugated dienes) in the main chain and side chains of the aromatic vinyl compound-conjugated diene block copolymer, the carbon-carbon unsaturated bonds in the aromatic ring, or both of these. Further, the aromatic vinyl compound-conjugated diene block copolymer is a block copolymer containing aromatic vinyl monomer units and conjugated diene monomer units, and usually contains a block containing aromatic vinyl monomer units and a conjugated diene monomer unit. The "aromatic vinyl monomer unit" represents a structural unit having a structure formed by polymerizing an aromatic vinyl compound, unless otherwise specified. Also, the "conjugated diene monomer unit" represents a structural unit having a structure formed by polymerizing a conjugated diene, unless otherwise specified. The aromatic vinyl compound-conjugated diene block copolymer can be produced by block copolymerizing a plurality of monomers including an aromatic vinyl compound and a conjugated diene. However, in the present application, the aromatic vinyl compound-conjugated diene block copolymer and its hydride are not limited by the production method thereof.

[0039] As the aromatic vinyl compound, styrene and its derivatives; vinylnaphthalene and its derivatives are preferable, styrene and its derivatives are more preferable, and from the viewpoint of easy industrial availability, it is particularly preferable to use styrene. As the conjugated diene, chain conjugated dienes (linear conjugated dienes, branched-chain conjugated dienes) are preferable, and specifically, 1,3-butadiene, isoprene (2-methyl-1,3-butadiene), 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene and the like are preferably mentioned. Among these, 1,3-butadiene and isoprene are particularly preferable from the viewpoint of easy industrial availability.

[0040] Examples of the aromatic vinyl compound-conjugated diene block copolymer preferably include those selected from a styrene-butadiene block copolymer, a styrene-butadiene-styrene block copolymer, a styrene-isoprene block copolymer, a styrene-isoprene-styrene block copolymer, and mixtures thereof. More specific examples thereof include those described in prior art documents such as JP-A-2-133406, JP-A-2-305814, JP-A-3-72512, JP-A-3-74409, and International Publication No. 2015 / 099079.

[0041] The hydrogenation rate of the hydrogenated aromatic vinyl compound-conjugated diene block copolymer is preferably 90% or more, more preferably 97% or more, particularly preferably 99% or more, and usually 100% or less. The higher the hydrogenation rate, the better the heat resistance and light resistance of the light-reducing film can be. Here, the hydrogenation rate of the hydride can be determined by measurement using 1 H-NMR.

[0042] The hydrogenation rate of the carbon-carbon unsaturated bonds in the main chain and side chains of the hydrogenated aromatic vinyl compound-conjugated diene block copolymer is preferably 95% or more, more preferably 99% or more, and usually 100% or less. By increasing the hydrogenation rate of the carbon-carbon unsaturated bonds in the main chain and side chains of the hydrogenated aromatic vinyl compound-conjugated diene block copolymer, the light resistance and oxidation resistance of the light-reducing film can be further enhanced.

[0043] In addition, the hydrogenation rate of the carbon-carbon unsaturated bonds in the aromatic ring of the hydrogenated aromatic vinyl compound-conjugated diene block copolymer is preferably 90% or more, more preferably 93% or more, particularly preferably 95% or more, and usually 100% or less. By increasing the hydrogenation rate of the carbon-carbon unsaturated bonds in the aromatic ring, the glass transition temperature of the hydride increases, so that the heat resistance of the light-reducing film can be effectively enhanced. Furthermore, the photoelastic coefficient of the light-reducing film can be lowered to reduce the manifestation of retardation.

[0044] As the hydrogenated aromatic vinyl compound-conjugated diene block copolymer, those having a structure in which both the unsaturated bond derived from the conjugated diene and the aromatic ring are hydrogenated are preferred.

[0045] A particularly preferred block form of the hydrogenated aromatic vinyl compound-conjugated diene block copolymer is a triblock copolymer in which blocks [A] of the hydrogenated aromatic vinyl polymer are bonded to both ends of the block [B] of the hydrogenated conjugated diene polymer; a pentablock copolymer in which polymer blocks [B] are bonded to both ends of the polymer block [A], and polymer blocks [A] are bonded to the other ends of both the polymer blocks [B]. In particular, the [A]-[B]-[A] triblock copolymer is particularly preferred because it is easy to manufacture and the physical properties as a thermoplastic polymer can be within a desired range.

[0046] When the mass fraction of all aromatic vinyl monomer units in the entire aromatic vinyl compound-conjugated diene block copolymer is wA, and the mass fraction of all conjugated diene monomer units in the block copolymer in the entire block copolymer is wB, the ratio (wA:wB) of wA to wB is preferably 20 / 80 or more, more preferably 30 / 70 or more, preferably 60 / 40 or less, and more preferably 55 / 45 or less. By setting the ratio wA / wB to be equal to or higher than the lower limit value of the above range, the heat resistance of the light-reducing film can be improved. Also, by setting it to be equal to or lower than the upper limit value, the flexibility of the light-reducing film can be enhanced.

[0047] (Modified product of copolymer (a1)) Examples of the modified product of the copolymer (a1) include modified products of the copolymer (a1) having a silicon atom-containing polar group. Examples of the modified product of the copolymer (a1) having a silicon atom-containing polar group include polymers having a structure obtained by graft polymerization of the copolymer (a1) and a compound having a functional group such as a silicon atom-containing polar group. The modified product is not limited by its production method. As the modified product of the copolymer (a1), a modified product having a silicon atom-containing polar group of the copolymer (a1) is preferable, and as the silicon atom-containing polar group, an alkoxysilyl group is preferable.

[0048] Examples of the compound having a silicon atom-containing polar group that can be used as a monomer for graft polymerization include ethylenically unsaturated silane compounds having an alkoxysilyl group (e.g., vinyltrimethoxysilane, vinyltriethoxysilane, allyltrimethoxysilane, allyltriethoxysilane, dimethoxymethylvinylsilane, diethoxymethylvinylsilane, p-styryltrimethoxysilane, p-styryltriethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-acryloxypropyltrimethoxysilane, 3-acryloxypropyltriethoxysilane, and 2-norbornen-5-yltrimethoxysilane).

[0049] By reacting the copolymer (a1) with a compound having a silicon atom-containing polar group, a silicon atom-containing polar group can be introduced into the copolymer (a1) to obtain a modified product having a silicon atom-containing polar group. When introducing an alkoxysilyl group as the silicon atom-containing polar group, the introduction amount of the alkoxysilyl group is preferably 0.1 part by weight or more, more preferably 0.2 part by weight or more, still more preferably 0.3 part by weight or more, and preferably 10 parts by weight or less, more preferably 5 parts by weight or less, still more preferably 3 parts by weight or less, based on 100 parts by weight of the copolymer (a1). When the introduction amount of the alkoxysilyl group is within the above range, it is possible to suppress the excessive increase in the crosslinking degree of the alkoxysilyl groups decomposed by moisture or the like, so that the adhesiveness can be maintained high. Examples of the substance having an alkoxysilyl group used for the introduction of the alkoxysilyl group and the modification method include those described in prior art documents such as International Publication No. 2015 / 099079.

[0050] The introduction amount of the polar group is 1It can be measured by 1H-NMR spectrum. Also, when measuring the introduction amount of the polar group, if the introduction amount is small, it can be measured by increasing the number of integrations.

[0051] Introducing an alkoxysilyl group as a polar group into the copolymer (a1) is called silane modification. In the silane modification, the alkoxysilyl group may be directly bonded to the copolymer (a1), or may be bonded via a divalent organic group such as an alkylene group. Hereinafter, the polymer obtained by the silane modification of the copolymer (a1) is also referred to as a "silane-modified product".

[0052] As the modified product of the copolymer (a1), a silane-modified product of a hydrogenated aromatic vinyl compound-conjugated diene block copolymer is preferable, and a silane-modified product of a hydrogenated styrene-butadiene block copolymer, a silane-modified product of a hydrogenated styrene-butadiene-styrene block copolymer, a silane-modified product of a hydrogenated styrene-isoprene block copolymer, and one or more silane-modified products selected from silane-modified products of hydrogenated styrene-isoprene-styrene block copolymers are preferable.

[0053] The content range of the polymer in the resin is preferably 95% by weight or more, more preferably 97% by weight or more, still more preferably 99% by weight or more, and usually 100% by weight or less.

[0054] (Weight-average molecular weight and molecular weight distribution) The weight-average molecular weight (Mw) of the polymer such as the thermoplastic polymer contained in the resin is not particularly limited, but is preferably 20,000 or more, more preferably 30,000 or more, still more preferably 35,000 or more, and preferably 200,000 or less, more preferably 100,000 or less, still more preferably 70,000 or less. Also, the molecular weight distribution (Mw / Mn) of the polymer is preferably 4 or less, more preferably 3 or less, still more preferably 2 or less, and preferably 1 or more. By keeping the weight-average molecular weight Mw and the molecular weight distribution Mw / Mn of the polymer within the above ranges, the mechanical strength and heat resistance of the light-reducing film can be improved.

[0055] The weight average molecular weight (Mw) and number average molecular weight (Mn) of polymers such as thermoplastic polymers can be measured as polystyrene equivalent values by gel permeation chromatography using tetrahydrofuran as a solvent.

[0056] (Glass transition temperature) The glass transition temperature of polymers such as thermoplastic polymers contained in the resin is not particularly limited, but is preferably 40 °C or higher, more preferably 70 °C or higher, preferably 200 °C or lower, more preferably 180 °C or lower, and still more preferably 160 °C or lower. Further, when a block copolymer is included as the thermoplastic polymer, by adjusting the glass transition temperature by changing the weight ratio of each polymer block, it is possible to achieve a balance between suppression of stickiness and flexibility of the light-shielding film. The glass transition temperature can be measured using a differential scanning calorimeter based on JIS-K7121 under the condition of a heating rate of 10 °C / min.

[0057] (Other matters regarding the resin) The content ratio of the resin in the light-shielding film can be any content ratio such that the light-shielding film can have the linear light transmittance described above, but is preferably 50% by weight or more, more preferably 60% by weight or more, still more preferably 70% by weight or more, usually less than 100% by weight, preferably 99.8% by weight or less, and more preferably 99.5% by weight or less.

[0058] Examples of optional components other than polymers that the resin can contain include antioxidants; plasticizers; ultraviolet absorbers; lubricants. The optional components may be used alone or in combination of two or more in any ratio. The total ratio of optional components other than polymers in the resin is preferably 5% by weight or less, more preferably 3% by weight or less, still more preferably 1% by weight or less, usually 0% by weight or more, and may be 0% by weight.

[0059] <2.4.2. Oil-soluble dyes> The light-reducing film contains an oil-soluble dye. In the light-reducing film, usually, the oil-soluble dye does not exist in a state where, for example, the oil-soluble dye is emulsified or dispersed as solid particles in the resin like a disperse dye, but exists in a state where the oil-soluble dye and the resin form a uniform system.

[0060] The oil-soluble dye means a dye classified as "Solvent Dye" in the Color Index (a database by the Society of Dyers and Colourists in the UK and the American Association of Textile Chemists and Colorists).

[0061] Specific examples of yellow oil-soluble dyes include Oil Yellow 105 (trade name, manufactured by Orient Chemical Industries, Ltd.), Oil Yellow 105M (trade name, manufactured by Orient Chemical Industries, Ltd.), Oil Yellow 107 (trade name, manufactured by Orient Chemical Industries, Ltd.), Oil Yellow 129 (trade name, manufactured by Orient Chemical Industries, Ltd., C.I. Solvent Yellow 29), Oil Yellow 3G (trade name, manufactured by Orient Chemical Industries, Ltd., C.I. Solvent Yellow 16), Oil Yellow GGS (trade name, manufactured by Orient Chemical Industries, Ltd., C.I. Solvent Yellow 56), VariFast Yellow 1101 (trade name, manufactured by Orient Chemical Industries, Ltd.), VariFast Yellow 1105 (trade name, manufactured by Orient Chemical Industries, Ltd.), VariFast Yellow 4120 (trade name, manufactured by Orient Chemical Industries, Ltd., C.I. Solvent Yellow 82), Oleosol Brilliant Yellow 5G (trade name, manufactured by Tago Chemical Industry Co., Ltd., C.I. Solvent Yellow 150), Oleosol Fast Yellow 2G (trade name, manufactured by Tago Chemical Industry Co., Ltd., C.I. Solvent Yellow 21), Oleosol Fast Yellow GCN (trade name, manufactured by Tago Chemical Industry Co., Ltd., C.I. Solvent Yellow 151), Eisenzott Yellow 1 (trade name, manufactured by Hodogaya Chemical Co., Ltd., C.I. Solvent Yellow 56), Eisenzott Yellow 3 (trade name, manufactured by Hodogaya Chemical Co., Ltd., C.I. Solvent Yellow 16), Eisenzott Yellow 6 (trade name, manufactured by Hodogaya Chemical Co., Ltd., C.I. Solvent Yellow 33), Eisenspirone Yellow GRLH (trade name, manufactured by Hodogaya Chemical Co., Ltd.), Eisenspirone Yellow 3RH (trade name, manufactured by Hodogaya Chemical Co., Ltd.), Orazole Yellow 2GLN (trade name, manufactured by Ciba-Geigy, C.I. Solvent Yellow 88), Orazole Yellow 2RLN (trade name, manufactured by Ciba-Geigy, C.I. Solvent Yellow 89), Orazole Yellow 3R (trade name, manufactured by Ciba-Geigy, C.I. Solvent Yellow 25), Oraset Yellow GHS (trade name, manufactured by Ciba-Geigy, C.I. Solvent Yellow 163), Filamid Yellow R (trade name, manufactured by Ciba-Geigy, C.I. Solvent Yellow 21), Oil Yellow 185 (trade name, manufactured by Central Synthetic Chemical Co., Ltd., C.I.Solvent Red 18 analogs), Alcohol Yellow Y-10 (trade name, manufactured by Chuo Gosei Chemical Co., Ltd.), Diaresin Yellow L3G (trade name, manufactured by Mitsubishi Kasei Corporation, C.I. Solvent Yellow 93), Oil Orange PS (trade name, manufactured by Orient Chemical Industries Co., Ltd., C.I. Solvent Yellow 14) and Oil Orange 201M (trade name, manufactured by Orient Chemical Industries Co., Ltd.) can be mentioned.

[0062] Specific examples of red oil-soluble dyes include Oil Red 5B (trade name, manufactured by Orient Chemical Industries, Ltd., C.I. Solvent Red 27), Oil Red RR (trade name, manufactured by Orient Chemical Industries, Ltd., C.I. Solvent Red 24), VariFast Red 1306 (trade name, manufactured by Orient Chemical Industries, Ltd., C.I. Solvent Red 109), VariFast Red 1355 (trade name, manufactured by Orient Chemical Industries, Ltd.), VariFast Red 2303 (trade name, manufactured by Orient Chemical Industries, Ltd.), VariFast Red 3304 (trade name, manufactured by Orient Chemical Industries, Ltd., C.I. Solvent Red 8), VariFast Red 3306 (trade name, manufactured by Orient Chemical Industries, Ltd.), VariFast Red 3320 (trade name, manufactured by Orient Chemical Industries, Ltd., C.I. Solvent Red 132), Oil Pink 312 (trade name, manufactured by Orient Chemical Industries, Ltd.), VariFast Pink 2310N (trade name, manufactured by Orient Chemical Industries, Ltd., C.I. Solvent Red 218), Oleosol Fast Red BL (trade name, manufactured by Taoka Chemical Co., Ltd., C.I. Solvent Red 132), Oleosol Fast Red RL (trade name, manufactured by Taoka Chemical Co., Ltd., C.I. Solvent Red 122), Oleosol Fast Red GL (trade name, manufactured by Taoka Chemical Co., Ltd., C.I. Solvent Red 132), Oleosol Red 2G (trade name, manufactured by Taoka Chemical Co., Ltd.), Oleosol Fast Pink FB (trade name, manufactured by Taoka Chemical Co., Ltd., C.I. Solvent Red 218), Aizen Zott Red 1 (trade name, manufactured by Hodogaya Chemical Co., Ltd., C.I. Solvent Red 24), Aizen Zott Red 2 (trade name, manufactured by Hodogaya Chemical Co., Ltd., C.I. Solvent Red 27), Aizen Zott Red 3 (trade name, manufactured by Hodogaya Chemical Co., Ltd., C.I. Solvent Red 18), Aizen Spiron Red BEH (trade name, manufactured by Hodogaya Chemical Co., Ltd.), Aizen Spiron Fieri Red BH (trade name, manufactured by Hodogaya Chemical Co., Ltd., C.I. Solvent Red 81), Aizen Spiron Red GEH (trade name, manufactured by Hodogaya Chemical Co., Ltd.), Aizen Spiron Red C-GH (trade name, manufactured by Hodogaya Chemical Co., Ltd.), Aizen Zott Pink 1 (trade name, manufactured by Hodogaya Chemical Co., Ltd., C.I.Solvent Red 49), Orazole Red 3GL (trade name, manufactured by Ciba Geigy, C.I. Solvent Red 130), Orazole Red 2BL (trade name, manufactured by Ciba Geigy, C.I. Solvent Red 132), Orazole Red G (trade name, manufactured by Ciba Geigy, C.I. Solvent Red 125), Orazole Red B (trade name, manufactured by Ciba Geigy, C.I. Solvent Red 7), Filamide Red GR (trade name, manufactured by Ciba Geigy, C.I. Solvent Red 225), Filestar Red GA (trade name, manufactured by Ciba Geigy, C.I. Solvent Red 135), Filestar Red RBA (trade name, manufactured by Ciba Geigy, C.I. Solvent Red 230), Orazole Pink 5BLG (trade name, manufactured by Ciba Geigy, C.I. Solvent Red 127), Oil Pink 330 (trade name, manufactured by Central Synthetic Chemical Co., Ltd., C.I. Solvent Red 49), Alcohol Pink P-30 (trade name, manufactured by Central Synthetic Chemical Co., Ltd.), Diaresin Red K (trade name, manufactured by Mitsubishi Chemical Corporation, C.I. Solvent Red 155), and Diaresin Red H5B (trade name, manufactured by Mitsubishi Chemical Corporation, C.I. Solvent Red 52) may be mentioned.

[0063] Specific examples of blue oil-soluble dyes include Oil Blue 613 (trade name, manufactured by Orient Chemical Industries, Ltd.), Oil Blue 2N (trade name, manufactured by Orient Chemical Industries, Ltd., C.I. Solvent Blue 35), Oil Blue BOS (trade name, manufactured by Orient Chemical Industries, Ltd.), Vari Fast Blue 1603 (trade name, manufactured by Orient Chemical Industries, Ltd.), Vari Fast Blue 1605 (trade name, manufactured by Orient Chemical Industries, Ltd., C.I. Solvent Blue 38), Vari Fast Blue 1607 (trade name, manufactured by Orient Chemical Industries, Ltd.), Vari Fast Blue 2606 (trade name, manufactured by Orient Chemical Industries, Ltd., C.I. Solvent Blue 70), Vari Fast Blue 2610 (trade name, manufactured by Orient Chemical Industries, Ltd.), Oleosol Fast Blue ELN (trade name, manufactured by Taoka Chemical Co., Ltd., C.I. Solvent Blue 70), Oleosol Fast Blue GL (trade name, manufactured by Taoka Chemical Co., Ltd., C.I. Solvent Blue 70), Oleosol Blue G (trade name, manufactured by Taoka Chemical Co., Ltd.), Eisenzot Blue 1 (trade name, manufactured by Hodogaya Chemical Co., Ltd., C.I. Solvent Blue 25), Eisenzot Blue 2 (trade name, manufactured by Hodogaya Chemical Co., Ltd., C.I. Solvent Blue 14), Eisen Spiron Blue GNH (trade name, manufactured by Hodogaya Chemical Co., Ltd.), Eisen Spiron Blue 2BNH (trade name, manufactured by Hodogaya Chemical Co., Ltd.), Eisen Spiron Blue BPNH (trade name, manufactured by Hodogaya Chemical Co., Ltd.), Eisen Spiron Blue E2BH (trade name, manufactured by Hodogaya Chemical Co., Ltd., C.I. Solvent Blue 73), Orazol Blue GN (trade name, manufactured by Ciba Geigy, C.I. Solvent Blue 67), Orazol Blue 2GLN (trade name, manufactured by Ciba Geigy, C.I. Solvent Blue 48), Oraset Blue 2R (trade name, manufactured by Ciba Geigy, C.I. Solvent Blue 68), Oil Blue BO (trade name, manufactured by Central Synthetic Chemical Co., Ltd., C.I. Solvent Blue 25), Filamid Blue R (trade name, manufactured by Ciba Geigy, C.I. Solvent Blue 132), Filestar Blue GN (trade name, manufactured by Ciba Geigy, C.I.Examples include Solvent Blue 67), Kayaset Blue K-FL (trade name, manufactured by Nippon Kayaku Co., Ltd.), Alcohol Blue B-10 (trade name, manufactured by Chuo Gosei Chemical Co., Ltd.), and Diaresin Blue H3G (trade name, manufactured by Mitsubishi Kasei Corporation).

[0064] Specific examples of black oil-soluble dyes include Oil Black HBB (trade name, manufactured by Orient Chemical Industries, Ltd., C.I. Solvent Black 3), Oil Black 860 (trade name, manufactured by Orient Chemical Industries, Ltd., C.I. Solvent Black 3), Oil Black BS (trade name, manufactured by Orient Chemical Industries, Ltd., C.I. Solvent Black 7), Oil Black BY (trade name, manufactured by Orient Chemical Industries, Ltd.), Vari Fast Black 1802 (trade name, manufactured by Orient Chemical Industries, Ltd.), Vari Fast Black 1807 (trade name, manufactured by Orient Chemical Industries, Ltd.), Vari Fast Black 3804 (trade name, manufactured by Orient Chemical Industries, Ltd., C.I. Solvent Black 34), Vari Fast Black 3810 (trade name, manufactured by Orient Chemical Industries, Ltd., C.I. Solvent Black 29), Vari Fast Black 3820 (trade name, manufactured by Orient Chemical Industries, Ltd., C.I. Solvent Black 27), Vari Fast Black 3830 (trade name, manufactured by Orient Chemical Industries, Ltd.), Spirit Black SB (trade name, manufactured by Orient Chemical Industries, Ltd., C.I. Solvent Black 5), Spirit Black SSBB (trade name, manufactured by Orient Chemical Industries, Ltd., C.I. Solvent Black 5), Spirit Black AB (trade name, manufactured by Orient Chemical Industries, Ltd., C.I. Solvent Black 5), Nigrosine Base (trade name, manufactured by Orient Chemical Industries, Ltd., C.I. Solvent Black 7), Oleozol Fast Black RL (trade name, manufactured by Tago Chemical Industries, Ltd., C.I. Solvent Black 27), Oleozol Black AR (trade name, manufactured by Tago Chemical Industries, Ltd.), Eisenzot Black 6 (trade name, manufactured by Hodogaya Chemical Co., Ltd., C.I. Solvent Black 3), Eisenzot Black 8 (trade name, manufactured by Hodogaya Chemical Co., Ltd., C.I. Solvent Black 7), Eisen Spiron Black MH (trade name, manufactured by Hodogaya Chemical Co., Ltd.), Eisen Spiron Black GMH Special (trade name, manufactured by Hodogaya Chemical Co., Ltd.), Eisen Spiron Black RLH Special (trade name, manufactured by Hodogaya Chemical Co., Ltd.), Orazol Black CN (trade name, manufactured by Ciba Geigy, C.I. Solvent Black 28), Orazol Black RLI (trade name, manufactured by Ciba Geigy, C.I.Solvent Black 29), Oil Black FS Special A (trade name, manufactured by Chuo Gosei Chemical Co., Ltd., C.I. Solvent Black 7), and Oil Black 803 (trade name, manufactured by Orient Chemical Industries, Ltd.) can be mentioned.

[0065] The oil-soluble dye is preferably a dye having a predetermined melting point. Specifically, the melting point of the oil-soluble dye is preferably 80°C or higher and 280°C or lower, more preferably 90°C or higher and 200°C or lower. For example, when manufacturing a light-reducing film by an extrusion method, since it is easy to make it liquid when kneaded with a resin, it is easy to adjust the dye concentration in the light-reducing film.

[0066] The oil-soluble dye may be used alone or in a combination of two or more in any ratio. Further, as the oil-soluble dye, those that dissolve 0.02% by weight or more at room temperature (preferably 20 ± 5°C) in cyclohexane or ethylcyclohexane are preferred. By using such an oil-soluble dye, it becomes easy to combine with various thermoplastic resins.

[0067] From the viewpoint of effectively imparting spectral characteristics to the light-reducing film, the ratio of the oil-soluble dye to the resin is preferably 0.01% by weight or more, more preferably 0.05% by weight or more, and from the viewpoint of effectively reducing the haze of the light-reducing film, it is preferably less than 2% by weight, more preferably 1.5% by weight or less. Here, the ratio of the oil-soluble dye is a value when the resin weight contained in the light-reducing film is 100% by weight.

[0068] <2.5. Thickness of the light-reducing film> The thickness of the light-reducing film is not particularly limited as long as it can satisfy the function as a cover for the infrared sensor. Usually, it is 30 μm or more, preferably 50 μm or more, and more preferably 100 μm or more. Also, the thickness of the light-reducing film is usually less than 800 μm, preferably 700 μm or less, and preferably 600 μm or less. When the thickness of the light-reducing film is within the above range, it can be effectively used as a cover that can hide the infrared sensor.

[0069] When the light-reducing film is manufactured using, for example, an extrusion method, the lower limit of the thickness of the light-reducing film is preferably 100 μm or more.

[0070] The thickness of the light-reducing film can be adjusted by a conventionally known method according to the manufacturing method of the light-reducing film.

[0071] The thickness of the light-reducing film can be measured by a fine shape measuring device, a spectroscopic film thickness measuring device, etc. For example, when the light-reducing film is formed on a base material layer such as a release film, a part of the light-reducing film is peeled off from the base material layer, and the step shape between the surface of the base material layer and the surface of the light-reducing film is measured by a fine shape measuring device, whereby it can be measured.

[0072] <3. Multilayer light-reducing film> FIG. 2 is a cross-sectional view schematically showing another example of the light-reducing film according to the present embodiment. The light-reducing film 20 shown in FIG. 2 has a multilayer structure including a first resin layer 21, a light-reducing layer 22, and a second resin layer 23 in this order in the thickness direction. In the light-reducing film 20, the light-reducing layer 22 contains a resin and an oil-soluble dye. Further, it is preferable that the first resin layer 21 and the second resin layer 23 contain a resin and substantially do not contain an oil-soluble dye. The first resin layer 21 may be provided directly on the light-reducing layer 22 or may be provided via another layer such as an adhesive layer, but the former is more preferable. Similarly, the second resin layer 23 may be provided directly on the light-reducing layer 22 or may be provided via another layer such as an adhesive layer, but the former is more preferable. Since a light-reducing film having a multilayer structure can be manufactured by using the melt coextrusion method, it can be a light-reducing film with good productivity.

[0073] When the light-reducing film has the above-described multilayer structure, for example, when manufacturing the light-reducing film using the melt coextrusion method, contamination due to adhesion of the oil-soluble dye to the manufacturing apparatus can be suppressed. Since contamination of the light-reducing film itself due to contamination of the apparatus can also be suppressed, the light-reducing film can be stably manufactured. Therefore, it can be a light-reducing film with high productivity.

[0074] <3.1. Linear transmittance and haze of the light-reducing film> The linear transmittance and haze of the light-reducing film having a multilayer structure can be the same as those of the light-reducing film having a single-layer structure described above.

[0075] <3.2. Materials of the light-reducing film> In the light-reducing film having a multilayer structure, the resin and the oil-soluble dye used for the light-reducing layer can be the same as those used for the light-reducing film having a single-layer structure.

[0076] The resin used for the first resin layer and the second resin layer is not particularly limited, but is preferably a thermoplastic resin. The resin that the first resin layer and the second resin layer may contain can be appropriately selected from the resins described in the above-described single-layer structure light reduction film.

[0077] The resin contained in the first resin layer and the resin contained in the second resin layer may be different types of resins, or may be the same resin. From the viewpoint of improving the adhesion of each layer of the light reduction film, it is preferable that the first resin layer and the second resin layer each contain the same resin as the resin contained in the light reduction layer.

[0078] The first resin layer and the second resin layer preferably do not substantially contain an oil-soluble dye. The ratio of the oil-soluble dye to the resin contained in the first resin layer is less than 0.01% by weight, preferably less than 0.005% by weight, and ideally 0% by weight. It is also preferable that the ratio of the oil-soluble dye to the resin contained in the second resin is the same as the above ratio.

[0079] In the multilayer structure light reduction film, the ratio of the oil-soluble dye contained in the light reduction layer to the resin can be the same as the ratio of the oil-soluble dye to the resin in the single-layer film. Also, in the present embodiment, the ratio of the oil-soluble dye to the resin contained in the entire light reduction film can be adjusted within the preferable range of the ratio of the oil-soluble dye to the resin in the single-layer film. The ratio of the oil-soluble dye to the resin contained in the entire light reduction film is a value calculated as the ratio of the oil-soluble dye to the total of the resins contained in each of the first resin layer, the light reduction layer, and the second resin layer.

[0080] <3.3. Thickness of the light reduction film> The total thickness of the light reduction film can be the same as the thickness that the above-described single-layer film can have. The total thickness of the light reduction film refers to the distance in the thickness direction in the state where the first resin layer, the light reduction layer, and the second resin layer are laminated. In addition, in the light-reducing film, the ratio of the thickness of the first resin layer to the thickness of the light-reducing layer can be appropriately selected according to the use of the light-reducing film, but is preferably 10% or more, more preferably 20% or more, and preferably 100% or less, more preferably 50% or less. The same applies to the ratio of the thickness of the second resin layer to the thickness of the light-reducing layer.

[0081] In addition, the ratio of the thickness of the light-reducing layer to the total thickness of the light-reducing film can be appropriately selected according to the use of the light-reducing film, but is preferably 30% or more, more preferably 40% or more, still more preferably 50% or more, and preferably 90% or less, more preferably 80% or less, still more preferably 75% or less.

[0082] Regarding the method for measuring the total thickness of the multilayer light-reducing film, it can be the same as the method for measuring the thickness of the single-layer light-reducing film described above. In addition, the thickness of each layer in the multilayer light-reducing film can be measured, for example, by cutting the light-reducing film with a microtome and observing the cross-section with an optical microscope.

[0083] <3.4. Other Matters in Multilayer Light-Reducing Films> In the multilayer light-reducing film, the first resin layer and the second resin layer can usually have a haze equal to or lower than that of the light-reducing film. In addition, the first resin layer and the second resin preferably have light transmittance. Here, having "light transmittance" means that the linear light transmittance is 85% or more in the wavelength range of 450 nm or more and 1600 nm or less. By the first resin layer and the second resin layer having light transmittance, optical properties such as spectral characteristics of the light-reducing layer can be imparted to the light-reducing film, so that the spectral characteristics of the light-reducing film can be easily adjusted. The linear transmittance and haze of the first resin layer and the second resin layer can be measured, for example, by forming a test piece having the same material and thickness as the first resin layer and the second resin layer and using the same method as the linear transmittance and haze described above.

[0084] <4. Optional Configuration of Light-Reducing Film> The light-reducing film according to this embodiment may be in a form combined with other elements. For example, it may be in a form laminated with a base material layer such as a resin film or a glass plate, or in a form laminated with a layer such as a release film or a protective film.

[0085] <5. Manufacturing Method of Light-Reducing Film> The light-reducing film can be manufactured using any manufacturing method.

[0086] <5.1. Manufacturing Method of Light-Reducing Film Using Extrusion Method> As a preferred manufacturing method of the light-reducing film, for example, a manufacturing method using the extrusion method can be mentioned. When manufacturing the light-reducing film using the extrusion method, it can be manufactured, for example, by a manufacturing method including the following steps (1) and (2). Also, if necessary, it can include any steps other than steps (1) and (2).

[0087] Step (1): Kneading a raw material containing a resin and an oil-soluble dye to obtain a dye resin material. Step (2): Extruding the resin composition to form an extruded film.

[0088] <5.1.1. Step (1)> In step (1), a raw material containing a resin and an oil-soluble dye is kneaded to obtain a dye resin material. As the resin contained in the raw material, the resin contained in the light-reducing film is used. As the oil-soluble dye contained in the raw material, the oil-soluble dye contained in the oil-soluble dye of the light-reducing film is used.

[0089] The form of the resin and the form of the oil-soluble dye in the raw material for obtaining the dye resin material are not particularly limited. For example, a mixture of resin pellets and powder of the oil-soluble dye, pellets as a masterbatch in which the oil-soluble dye is contained at a high concentration in the resin, and a mixture of resin pellets can be used as the raw material. The weight ratio of the oil-soluble dye in the raw material can be set according to the weight ratio of the oil-soluble dye in the desired light-reducing film, and may be the same as the weight ratio of the oil-soluble dye in the desired light-reducing film.

[0090] The kneading of the raw materials is usually carried out at a temperature equal to or higher than the glass transition temperature Tg of the resin and lower than the temperature at which the oil-soluble dye and the resin do not deteriorate. The kneading of the raw materials may be carried out, for example, at 100 °C or higher, for example, 150 °C or higher, and may be carried out, for example, at 500 °C or lower, for example, 400 °C or lower. Further, the lower limit of the kneading temperature of the raw materials is preferably carried out at a temperature 10 °C or higher than the melting point of the oil-soluble dye, more preferably at a temperature equal to or higher than the melting point of the oil-soluble dye, and the upper limit is preferably carried out at a temperature 100 °C or lower than the melting point of the oil-soluble dye, and more preferably at 75 °C or lower. By melting the oil-soluble dye within these kneading temperature ranges, the amount of the oil-soluble dye that can form a uniform system with the resin can be increased, and fading due to the decomposition of the dye can be prevented.

[0091] The kneading of the raw materials can be carried out by any kneading device such as a small kneader or a single-screw extruder.

[0092] The dye resin material obtained by kneading the raw materials may be directly used in step (2) without processing, or the dye resin material obtained by kneading the raw materials may be processed into a shape that is easy to handle, such as a pellet shape, and then used in step (2).

[0093] <5.1.2. Step (2)> In step (2), the dye resin material is extruded to form an extruded film.

[0094] The formation of the extruded film is usually carried out by extruding the melted dye resin material in a film shape. The dye resin material extruded in a film shape is cooled, such as by casting it on a cooling roll, to produce an extruded film.

[0095] By continuously extruding the dye resin material, a long extruded film can be obtained.

[0096] When the resin film is a light-shielding film having a multilayer structure including the above-described first resin layer, light-shielding layer, and second resin layer, in step (2), the dye resin material, the material of the first resin layer, and the material of the second resin layer may be coextruded. By coextruding the dye resin material, the material of the first resin layer, and the material of the second resin layer, an extruded film having a multilayer structure including the above-described first resin layer, light-shielding layer, and second resin layer can be formed.

[0097] Coextrusion can be performed, for example, by supplying the dye resin material and other materials for forming an arbitrary layer to a coextrusion apparatus equipped with a multilayer member such as a multilayer die or a multilayer feed block.

[0098] <5.2. Manufacturing method of light-shielding film by coating method> The light-shielding film can also be manufactured, for example, by a manufacturing method using a coating method. When the light-shielding film is manufactured using the coating method, it can be manufactured, for example, by a manufacturing method including the following steps (3) to (5).

[0099] Step (3): A step of preparing a coating liquid containing a resin, an oil-soluble dye, and a solvent. Step (4): A step of applying the coating liquid onto a substrate to form a coating film. Step (5): A step of drying the coating film.

[0100] <5.2.1. Step (3)> In step (3), a coating liquid containing a resin, an oil-soluble dye, and a solvent is prepared. As the solvent, from the viewpoint of reducing the haze of the light-shielding film and uniformly distributing the oil-soluble dye in the light-shielding film, a solvent capable of dissolving components contained in the light-shielding film such as a resin and an oil-soluble dye is preferable. Examples of the solvent include aliphatic or alicyclic hydrocarbon solvents (e.g., pentane, hexane, cyclopentane, cyclohexane, decahydronaphthalene), aromatic hydrocarbon solvents (e.g., toluene, xylene, trimethylbenzene, ethylbenzene, tetrahydronaphthalene), halogenated hydrocarbon solvents (e.g., dichloromethane, chloroform, dichloroethane, chlorobenzene), ether solvents (e.g., 1,4-dioxane, tetrahydrofuran), and ketone solvents (e.g., dimethyl ketone, cyclopentanone). The amount of the solvent in the coating solution can be any amount according to the desired viscosity of the coating solution, the thickness of the coating film to be formed, and the like. Also, the ratio of the oil-soluble dye to the resin in the coating solution is usually the same as the ratio of the oil-soluble dye to the resin in the light-shielding film.

[0101] In the coating solution, the oil-soluble dye can be in a state dissolved in the solvent. Here, the state in which the oil-soluble dye is dissolved means that the oil-soluble dye is not in a state of being emulsified nor in a state of being dispersed as solid particles in the dispersion medium, but rather means a state in which the oil-soluble dye and the solvent form a uniform system.

[0102] <5.2.2. Step (4)> In step (4), the coating solution is applied onto a substrate to form a coating film. As the substrate onto which the coating solution is applied, for example, a glass plate or a release film subjected to a release treatment (e.g., a release polyethylene terephthalate (PET) film) can be used. The coating method of the coating solution can be the same as the coating methods used in known film manufacturing methods. The thickness of the coating film can be appropriately set according to the resin concentration in the coating solution, the desired thickness of the light-shielding film, and the like.

[0103] <5.2.3. Step (5)> In step (5), the coating film is dried. Examples of the method for removing the solvent include natural drying, heat drying, vacuum drying, and vacuum heat drying.

[0104] <6. Use of the light-reducing film> The light-reducing film according to the present invention can be used as a cover for an infrared sensor. As the cover, for example, a laminate including the light-reducing film and a base material layer can be used. This laminate may have, for example, a two-layer structure of a light-reducing film and a base material layer, or may have a three-layer structure of a first base material layer, a light-reducing film, and a second base material layer. In the laminate that can constitute the cover, the light-reducing film and the base material layer may be directly arranged in contact with each other, or may be arranged via other layers such as an adhesive layer, but the former is more preferable.

[0105] The base material layer usually has light transmittance. Here, having "light transmittance" means that the linear light transmittance is 85% or more in the wavelength range of 450 nm or more and 1600 nm or less. By the base material layer having light transmittance, optical properties such as spectral characteristics of the light-reducing film can be imparted to the laminate.

[0106] Examples of the base material layer having light transmittance include a resin base material and a glass base material, and among them, a glass base material is preferable. This is because the strength of the cover can be made high.

[0107] The cover of the infrared sensor using the light-reducing film according to the present invention can preferably be used as a cover for an infrared camera or an in-vehicle infrared sensor. Regarding the shape of the cover, it can be appropriately designed according to the shape of the installation position of the infrared sensor in the vehicle.

Example

[0108] Hereinafter, the present invention will be specifically described with reference to examples. However, the present invention is not limited to the examples shown below, and can be arbitrarily modified and implemented without departing from the scope of the claims of the present invention and its equivalent scope.

[0109] In the following description, “%” and “parts” representing amounts are based on weight unless otherwise specified. Further, the operations described below were carried out under the conditions in the atmosphere at normal temperature and pressure (23°C and 1 atm) unless otherwise specified.

[0110] [Evaluation Method] (Linear transmittance of the light reduction film) Using a spectrophotometer (“V-570” manufactured by JASCO Corporation), the linear transmittance of light for the light reduction film was measured in the wavelength range of 300 nm or more and 1600 nm or less.

[0111] (Haze) For the light reduction film, the haze was measured with a haze meter (“NDH4000” manufactured by Nippon Denshoku Industries Co., Ltd.) in accordance with JIS K7136.

[0112] (Thickness of the light reduction film) A part (about 5 mm square) of the light reduction film on the release PET film was peeled off from the release PET film, and the step shape between the surface of the release PET film and the surface of the light reduction film was measured with a fine shape measuring device (“Surfcorder ET-4000A” manufactured by Kosaka Laboratory Ltd.) to measure the thickness of the light reduction film. When the light reduction film was formed on the base material layer, the total thickness of the light reduction film and the base material layer was measured with a micrometer (“MDC-25MJ” manufactured by Mitutoyo Corporation), and the thickness of the light reduction film was obtained by subtracting the thickness of the base material layer. Further, for the light reduction films of Examples 2 and 3, the thickness was measured with a film thickness gauge (“Snap Gauge” of Mitutoyo Corporation).

[0113] (CIE 1976 (L * , a * , b * ) b value in the color space) * value) Measured with a colorimeter (“SC-T” manufactured by Suga Test Instruments Co., Ltd.).

[0114] [Production Example 1] (Production of P1-1. Hydrogenated block copolymer (hydrogenated aromatic vinyl compound-conjugated diene block copolymer)) Using styrene as the aromatic vinyl compound and isoprene as the chain-conjugated diene compound, a hydrogenated block copolymer was produced by the following procedure. The produced hydrogenated block copolymer has a triblock structure in which polymer blocks [A] are bonded to both ends of the polymer block [B].

[0115] Into a reactor equipped with a stirrer, which was sufficiently purged with nitrogen inside, 256 parts of dehydrated cyclohexane, 25.0 parts of dehydrated styrene, and 0.615 part of n-dibutyl ether were charged, and while stirring at 60°C, 1.35 parts of n-butyllithium (15% cyclohexane solution) was added to initiate polymerization, and further reacted at 60°C for 60 minutes while stirring. The polymerization conversion rate at this point was 99.5% (the polymerization conversion rate was measured by gas chromatography. The same applies hereinafter).

[0116] Next, 50.0 parts of dehydrated isoprene was added, and stirring was continued at the same temperature for 30 minutes. The polymerization conversion rate at this point was 99%. Thereafter, 25.0 parts of dehydrated styrene was further added, and stirred at the same temperature for 60 minutes. The polymerization conversion rate at this point was almost 100%. Subsequently, 0.5 part of isopropyl alcohol was added to the reaction solution to terminate the reaction, and a solution (i) containing the block copolymer was obtained. The weight average molecular weight (Mw) of the block copolymer in the obtained solution (i) was 44,900, and the molecular weight distribution (Mw / Mn) was 1.03 (measured in terms of polystyrene by gel permeation chromatography using tetrahydrofuran as the solvent. The same applies hereinafter).

[0117] Next, solution (i) was transferred to a pressure reactor equipped with a stirrer, and 4.0 parts of a silica-alumina supported nickel catalyst (E22U, nickel loading 60%; manufactured by Nisshin Chemical Industry Co., Ltd.) and 350 parts of dehydrated cyclohexane were added to solution (i) and mixed. The inside of the reactor was purged with hydrogen gas, and hydrogen was supplied while further stirring the solution. The hydrogenation reaction was carried out at a temperature of 170 °C and a pressure of 4.5 MPa for 6 hours to hydrogenate the block copolymer, thereby obtaining a solution (iii) containing a hydrogenated product (ii) of the block copolymer. The weight average molecular weight (Mw) of the hydrogenated product (ii) in solution (iii) was 45,100, and the molecular weight distribution (Mw / Mn) was 1.04.

[0118] After completion of the hydrogenation reaction, solution (iii) was filtered to remove the hydrogenation catalyst. Thereafter, 1.0 part of a xylene solution in which 0.1 part of 6-[3-(3-t-butyl-4-hydroxy-5-methylphenyl)propoxy]-2,4,8,10-tetrakis-t-butyldibenzo[d,f][1.3.2]dioxaphosphepine (manufactured by Sumitomo Chemical Co., Ltd., "Sumilizer (registered trademark) GP". Hereinafter referred to as "antioxidant A") as a phosphorus-based antioxidant was dissolved was added to the filtered solution (iii) and dissolved to obtain solution (iv).

[0119] Next, solution (iv) was filtered through a Zeta Plus (registered trademark) filter 30H (manufactured by Cuno, pore size 0.5 μm to 1 μm), and further sequentially filtered through another metal fiber filter (pore size 0.4 μm, manufactured by Nitida Co., Ltd.) to remove minute solid components. From the filtered solution (iv), using a cylindrical concentration dryer (product name "Contro", manufactured by Hitachi, Ltd.), at a temperature of 260 °C and a pressure of 0.001 MPa or less, the solvents cyclohexane, xylene and other volatile components were removed. Then, from a die directly connected to the above-mentioned concentration dryer, the solid content was extruded in a strand shape in a molten state, cooled, and cut with a pelletizer to obtain 85 parts of pellets (v) containing the hydrogenated product of the block copolymer and antioxidant A. The weight average molecular weight (Mw) of the hydrogenated product of the block copolymer (hydrogenated block copolymer) in the obtained pellets (v) was 45,000, and the molecular weight distribution (Mw / Mn) was 1.08. Also, 1The hydrogenation rate measured by 1H-NMR was 99.9%. A film-shaped test piece was prepared from this pellet (v), and when the glass transition temperature Tg was evaluated by the tanδ peak of a dynamic viscoelasticity measuring device, it was 130°C.

[0120] (Production of silane-modified product of hydrogenated block copolymer) To 100 parts of the pellet (v) obtained in (P1-1), 2.0 parts of vinyltrimethoxysilane and 0.2 part of di-t-butyl peroxide were added to obtain a mixture. This mixture was kneaded using a twin-screw extruder at a barrel temperature of 210°C and a residence time of 80 to 90 seconds. The kneaded mixture was extruded and cut with a pelletizer to obtain a pellet (vi) of a silane-modified product of a hydrogenated block copolymer. When a film-shaped test piece was prepared from this pellet (vi) and the glass transition temperature Tg was evaluated by the tanδ peak of a dynamic viscoelasticity measuring device, it was 124°C. The obtained pellet (vi) of the silane-modified product of a hydrogenated block copolymer may be hereinafter simply referred to as pellet (vi) for explanation.

[0121] [Example 1] To 100 parts of ethylcyclohexane, a dye (Oil Blue 2N: 0.3 part, Oil Orange 201M: 0.2 part, Oil Yellow 105M: 0.05 part) was mixed, dissolved by ultrasonic waves for 10 minutes, and filtered through a 5-μm filter to obtain a dye solution. To 100 parts of the obtained dye solution, 50 parts of the pellet (vi) as a resin produced in Production Example 1 was added and dissolved to obtain a black coating liquid containing a resin and an oil-soluble dye. This coating liquid was applied onto a release PET film (manufactured by Toyama Film HY-S10) with an applicator, and a light-shielding layer with a film thickness of 38 μm was prepared after drying. When the optical properties of the light-shielding layer (light-shielding film) from which the release PET film was peeled were measured, the b * value was -1.0, the linear transmittance was 15% at a wavelength of 550 nm and 88% at a wavelength of 900 nm. The haze of the obtained light-shielding film was 0.3%. When the linear transmittance in the wavelength range of 300 nm or more and 1600 nm or less was continuously measured, it was confirmed that the linear transmittance of all light in the wavelength range of 450 nm or more and 650 nm or less was less than 25%, and the linear transmittance of all light in the wavelength range of 900 nm or more and 1600 nm or less was 80% or more (near 90 nm).

[0122] [Example 2] (2-1. Step of obtaining a dye resin material) 99.2 parts of the pellet (vi) as the resin produced in Production Example 1 and 0.8 part of the dye (Oil Black 803, manufactured by Orient Chemical Industries Co., Ltd. Oil Black 803 is a mixture of oil-soluble dyes Solvent Blue 35 (melting point 119°C), Solvent Red 27 (melting point 120°C), Solvent Yellow 14 (melting point 134°C), Solvent Yellow 56 (melting point 98°C), etc.) were put into a glass bottle and shaken to coat the pellet (vi) with the dye, and a raw material (M) containing the resin and the dye was obtained. This raw material (M) was kneaded at 160°C using a small kneader "Xplore" (manufactured by Xplore Instruments) to obtain a dye resin material.

[0123] (2-2. Step of forming an extruded film) Next, the obtained dye resin material was supplied to a film forming machine and extruded into a film having a thickness of 111 μm and a width of 30 mm to obtain an extruded film. The extruded film has a single-layer structure composed of a light-shielding layer containing a resin and an oil-soluble dye. For the completed extruded film (light-shielding film), the transmittance was 2.5% at 550 nm and 85% at 900 nm. Also, the haze of the obtained light-shielding film was 0.6%.

[0124] [Example 3] In Example 3, a multilayer extruded film having a layer structure of (first resin layer) / (light-shielding layer) / (second resin layer) was formed according to the following procedure.

[0125] (3-1. Step of obtaining a resin layer and a dye resin material) A film forming apparatus equipped with a multi-manifold die capable of forming a three-layer film by co-extruding two types of resin materials was prepared. Pellets (vi) were prepared as materials for the first resin layer and the second resin layer. These pellets (vi) were put into a first single-screw extruder equipped with a double-flight screw and heated to be melted. In the same manner as in (2-1) of Example 2, a raw material (M) (pellets coated with a dye) containing a resin and a dye was prepared. This raw material (M) was put into a second single-screw extruder equipped with a double-flight screw, heated and melted to prepare a dye resin material for forming a light-reducing layer.

[0126] (Step of forming an extruded film) The melted pellets (vi) as materials for the first resin layer and the second resin layer were supplied to one manifold of a multi-manifold die (the surface roughness Ra of the die lip = 0.1 μm) through a leaf disk-shaped polymer filter with an aperture of 10 μm. Also, the above-prepared dye resin material was supplied to the other manifold through a leaf disk-shaped polymer filter with an aperture of 10 μm. The resin material and the dye resin material as materials for the first resin layer and the second resin layer were simultaneously extruded from the multi-manifold die to obtain a film-shaped molten resin having a three-layer structure of (first resin layer) / (light-reducing layer) / (second resin layer). This film-shaped molten resin was cast onto a cooling roll to obtain a three-layer extruded film made of two materials. This extruded film had a layer structure of (first resin layer (thickness 50 μm)) / (light-reducing layer (thickness 105 μm)) / (second resin layer (thickness 50 μm)), and the overall thickness was 210 μm. Also, the linear transmittance of the completed extruded film (light-reducing film) was 2.6% at a wavelength of 550 nm and 85% at a wavelength of 900 nm. Also, the haze was 0.6%.

[0127] [Comparative Example 1] 4.5 parts of titanium oxide 13M-T (particle size 67 nm, manufactured by Mitsubishi Materials Corporation) were added with 0.5 part of a dispersant "SOLSEPERSE 21000" (manufactured by Lubrizol Japan) and 95 parts of cyclohexane, and dispersed with a paint shaker to prepare a titanium oxide dispersion. Next, 70 parts of cyclohexane were added to 30 parts of pellets (vi) as a resin to prepare a resin solution. 8.4 parts of the titanium oxide dispersion were added thereto to prepare a titanium oxide-dispersed resin solution containing 1.2% titanium oxide particles based on the solid content. The obtained titanium oxide-dispersed resin solution was applied onto a release PET film (HY-S10, manufactured by Higashiyama Film) using an applicator, and after drying, a light-shielding layer with a thickness of 11 μm was obtained. The b * value of the light-shielding layer (light-shielding film) from which the release film was peeled off was -4, the linear transmittance was 71% at a wavelength of 550 nm and 35% at 900 nm. The haze was 8% and turbid, which was not suitable for use as a cover for an infrared sensor.

Explanation of Symbols

[0128] 10, 20 Light-shielding film 11, 22 Light-shielding layer 21 First resin layer 23 Second resin layer

Claims

1. A light-reducing film comprising a resin and an oil-soluble dye, wherein the linear transmittance of at least a part of light having a wavelength of 450 nm or more and 650 nm or less is less than 25%, and the linear transmittance of light having a wavelength of 900 nm is 80% or more.

2. The light-reducing film according to Claim 1, wherein the linear transmittance of all light having a wavelength of 450 nm or more and 650 nm or less is less than 25%.

3. The light-reducing film according to Claim 1, wherein the thickness of the light-reducing film is 100 μm or more and less than 800 μm.

4. The light-reducing film according to Claim 1, wherein the ratio of the oil-soluble dye to the resin is 0.01% by weight or more and less than 2% by weight.

5. The light-reducing film according to Claim 1, having a haze of 0.1% or more and 1% or less.

6. The light-reducing film according to any one of Claims 1 to 5, having a multilayer structure in which a first resin layer, a light-reducing layer, and a second resin layer are laminated in this order, and the light-reducing layer contains the resin and the oil-soluble dye.

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