Multilayer laminate

Abstract

Provided is a multilayer laminate in which haze and transmittance can be adjusted as appropriate. A multilayer laminate (1) according to one aspect of the present invention is a multilayer laminate obtained by laminating at least: a substrate (11); a first dimming layer (21) including liquid crystal molecules of which the alignment states change according to an applied voltage; and a second dimming layer (22) including a photochromic material.

Description

multilayer laminate

[0001] The present invention relates to a multilayer laminate, and more particularly to a multilayer laminate having a light-adjusting function.

[0002] In recent years, window glass with a light-control function has been widely used in building windows, vehicle windows, etc. Such window glass with a light-control function can be constructed by providing a light-control sheet on the window glass. For example, the light-control sheet can be constructed using a light-control layer containing liquid crystal molecules and a pair of transparent electrode layers sandwiching the light-control layer.

[0003] Patent Document 1 discloses a technology relating to a light-controlling sheet that can suppress uneven color caused by a light-controlling layer and improve long-term reliability.

[0004] Japanese Patent Application Laid-Open No. 2020-52374

[0005] When a light-controlling sheet is constructed using a light-controlling layer containing liquid crystal molecules, as in the light-controlling sheet disclosed in Patent Document 1, the haze of the light-controlling layer can be controlled by applying a voltage to the liquid crystal molecules to change the orientation of the liquid crystal molecules. In other words, by changing the orientation of the liquid crystal molecules and changing the scattering state of light passing through the light-controlling layer, the haze of the light-controlling layer can be appropriately controlled.

[0006] However, even if the orientation state of the liquid crystal molecules is changed, it is difficult to significantly change the amount of light passing through the light-controlling layer. Therefore, when a light-controlling sheet is constructed using a light-controlling layer containing liquid crystal molecules, it is difficult to significantly change the transmittance (total light transmittance).

[0007] In view of the above problems, an object of the present invention is to provide a multilayer laminate in which the haze and transmittance can be appropriately adjusted.

[0008] A multilayer laminate according to one embodiment of the present invention is a multilayer laminate comprising at least a substrate, a first dimming layer containing liquid crystal molecules whose orientation state changes in response to an applied voltage, and a second dimming layer containing a photochromic material.

[0009] In the above-described multilayer laminate, the substrate may include a first substrate and a second substrate, and may be laminated in the following order: the first substrate, the first photochromic layer, the second photochromic layer, and the second substrate.

[0010] In the above-mentioned multilayer laminate, the first dimming layer may be a polymer dispersed liquid crystal in which the liquid crystal molecules are dispersed in a polymer, or a polymer network liquid crystal in which the liquid crystal molecules are arranged inside a three-dimensional mesh-like polymer network.

[0011] In the above-described multilayer laminate, the photochromic material may be at least one selected from the group consisting of triarylmethanes, stilbenes, azastilbenes, nitrones, fulgides, spiropyrans, naphthopyrans, spirooxazines, and quinones.

[0012] In the above-described multilayer laminate, the second photochromic layer may be made of polyvinyl butyral, and the photochromic material may be dispersed in the polyvinyl butyral.

[0013] In the above-described multilayer laminate, the multilayer laminate may be used as a material for forming at least one of a window glass for a vehicle, a sunroof for a vehicle, and a window glass for a building.

[0014] According to the present invention, it is possible to provide a multilayer laminate in which the haze and transmittance can be appropriately adjusted.

[0015] It is a cross-sectional view for explaining a configuration example of a multilayer laminate according to an embodiment. It is a diagram showing the state of a sample according to an example indoors. It is a diagram showing the state of a sample according to an example outdoors.

[0016] The multilayer laminate according to the present embodiment has a configuration in which at least a substrate, a first light control layer containing liquid crystal molecules whose alignment state changes in response to an applied voltage, and a second light control layer containing a photochromic material are stacked together. The multilayer laminate according to the present embodiment will be described in detail below.

[0017] 1 is a cross-sectional view illustrating an example of the configuration of a multilayer laminate according to an embodiment. As shown in FIG. 1, the multilayer laminate 1 according to this embodiment includes a first substrate 11, a second substrate 12, a first photochromic layer 21, and a second photochromic layer 22. That is, the multilayer laminate 1 shown in FIG. 1 includes the first substrate 11 and the second substrate 12 as substrates, and the first substrate 11, the first photochromic layer 21, the second photochromic layer 22, and the second substrate 12 are laminated in this order. In other words, the first photochromic layer 21 and the second photochromic layer 22 are sandwiched between the first substrate 11 and the second substrate 12.

[0018] The first substrate 11 and the second substrate 12 can be made of a transparent material. For example, the first substrate 11 and the second substrate 12 can be made of a transparent resin material or transparent glass. When the first substrate 11 and the second substrate 12 are made of a resin material, for example, polycarbonate, polyethylene, polyethylene terephthalate, polyethylene naphthalate, polypropylene, vinyl chloride resin, etc. can be used.

[0019] In this embodiment, at least one of the first substrate 11 and the second substrate 12 may be colored in a predetermined color without departing from the spirit of the present invention. When coloring the first substrate 11 or the second substrate 12, a dye may be added to the resin material or glass that constitutes the substrate. The dye is a material that absorbs light of a wavelength corresponding to a predetermined light included in the visible light range. For example, a dye or a pigment may be used as the dye.

[0020] The first dimming layer 21 contains liquid crystal molecules whose alignment state changes in response to an applied voltage. Specifically, the first dimming layer 21 may be a polymer dispersed liquid crystal (PDLC) in which liquid crystal molecules are dispersed in a polymer. Alternatively, the first dimming layer 21 may be a polymer network liquid crystal (PNLC) in which liquid crystal molecules are arranged inside a three-dimensional mesh-like polymer network.

[0021] For example, the first light control layer 21 can be configured using a liquid crystal layer (not shown) containing liquid crystal molecules and two transparent electrode layers (not shown) sandwiching the liquid crystal layer. The liquid crystal layer can be configured using the above-mentioned polymer dispersed liquid crystal (PDLC) or polymer network liquid crystal (PNLC). The transparent electrode layer can be configured using, for example, a transparent oxide conductor. Examples of transparent oxide conductors include ITO, IZO, and SnO. ２ The transparent electrode layer may be formed using a conductive polymer, such as PEDOT / PSS.

[0022] In this embodiment, the alignment state of the liquid crystal molecules contained in the first dimming layer 21 changes depending on the voltage applied to the transparent electrode layer. Specifically, when a voltage is applied to the transparent electrode layer, the liquid crystal molecules are aligned in the direction of the electric field, which reduces the scattering of light passing through the first dimming layer 21 and makes the first dimming layer 21 transparent. On the other hand, when no voltage is applied to the transparent electrode layer, the alignment of the liquid crystal molecules is irregular, which scatters light passing through the first dimming layer 21 and makes the layer opaque (cloudy white).

[0023] The second photochromic layer 22 includes a photochromic material. A photochromic material is a material that undergoes a change in molecular structure upon irradiation with light without changing its molecular weight, thereby reversibly generating two isomers with different absorption spectra. For example, in this embodiment, a material that changes color when sunlight is incident may be used as the photochromic material. For example, a material that changes color when exposed to light with a wavelength of 370 nm or longer may be used as the photochromic material. In this embodiment, the second photochromic layer 22 has the function of adjusting the transmittance (total light transmittance) of the multilayer laminate 1. For example, the second photochromic layer 22 may be configured so that the transmittance of the second photochromic layer 22 decreases when light with a wavelength of 370 nm or longer is incident on the second photochromic layer 22.

[0024] For example, in the present embodiment, the photochromic material may be at least one selected from the group consisting of triarylmethane, stilbene, azastilbene, nitrone, fulgide, spiropyran, naphthopyran, spirooxazine, and quinone. By appropriately selecting the amount of the photochromic material added, it is possible to control the transmittance to a desired level.

[0025] For example, the second photochromic layer 22 may be formed by dispersing a photochromic material in a resin sheet as a base material. The resin sheet may be made of, for example, polyvinyl butyral (PVB), ethylene vinyl acetate copolymer (EVA), polyurethane, or the like. Since the response speed of the photochromic material is highly dependent on the resin sheet as a base material, in this embodiment, it is more preferable to use plasticized polyvinyl butyral (PVB) as the base material of the second photochromic layer 22.

[0026] The first substrate 11, the second substrate 12, the first photochromic layer 21, and the second photochromic layer 22 may be bonded to one another via an adhesive layer. The adhesive layer may be made of a thermoplastic resin, a thermosetting resin, or a photocurable resin. Among these, plasticized polyvinyl butyral (PVB) is preferably used.

[0027] As described above, the multilayer laminate according to the present embodiment includes at least a substrate, a first photochromic layer 21 containing liquid crystal molecules whose alignment state changes in response to an applied voltage, and a second photochromic layer 22 containing a photochromic material. Because the first photochromic layer 21 contains liquid crystal molecules, the first photochromic layer 21 can be controlled to become transparent or opaque depending on the applied voltage. Therefore, the haze of the multilayer laminate 1 can be adjusted using the first photochromic layer 21. Furthermore, because the second photochromic layer 22 contains a photochromic material, the color of the second photochromic layer 22 changes in response to light incident on the second photochromic layer 22. Therefore, the transmittance (total light transmittance) of the multilayer laminate 1 can be adjusted using the second photochromic layer 22.

[0028] In this way, this embodiment can adjust the haze (cloudiness) using the first photochromic layer 21 and the transmittance using the second photochromic layer 22, thereby providing a multilayer laminate in which the haze and transmittance can be appropriately adjusted.

[0029] For example, the multilayer laminate 1 according to this embodiment may be used as a material for forming window glass for vehicles, sunroofs for vehicles, window glass for buildings, and the like.

[0030] In particular, by using a photochromic material for the second photochromic layer 22, it is possible to adjust the transmittance according to the intensity of sunlight, which is very suitable for the above-mentioned applications.

[0031] The haze can be adjusted as desired depending on the application. For applications requiring transparency, the haze in the transparent mode is preferably 3% or less.

[0032] The transmittance can be adjusted as desired depending on the application. The range of transmittance can be controlled by the amount of photochromic material added. For vehicle sunroofs, it is preferable to adjust the transmittance within the range of 50% to 4% to reduce the glare of sunlight. Commercially available color dyes and pigments may be used to adjust the transmittance indoors.

[0033] For example, when the multilayer laminate 1 according to this embodiment is used in a sunroof for a vehicle, sunlight can be blocked on a sunny day by the second light control layer 22. In this case, the haze of the multilayer laminate 1 can be adjusted by adjusting the voltage applied to the first light control layer 21.

[0034] On the other hand, at night or on cloudy days, the transmittance of the second photochromic layer 22 increases, thereby improving the visibility of the outside of the vehicle. In this case, too, the haze of the multilayer laminate 1 can be adjusted by adjusting the voltage applied to the first photochromic layer 21. For example, by increasing the haze of the first photochromic layer 21, it is possible to make it difficult to see inside the vehicle from the outside, thereby protecting privacy inside the vehicle.

[0035] These examples of use are merely examples, and the multilayer laminate 1 according to this embodiment may be used for other purposes.

[0036] FIG. 1 also shows an example of a configuration in which the first substrate 11, the first photochromic layer 21, the second photochromic layer 22, and the second substrate 12 are laminated in this order. However, in this embodiment, either the first substrate 11 or the second substrate 12 may be omitted. For example, in a configuration in which the second substrate 12 side is exposed to the external environment (i.e., in a configuration in which light is incident from the second substrate 12 side), the first substrate 11 may be omitted while the second substrate 12 is provided to maintain the weather resistance of the second substrate 12 side. In this embodiment, the positions of the first photochromic layer 21 and the second photochromic layer 22 may be reversed. That is, in a configuration in which light is incident from the second substrate 12 side, the second photochromic layer 22 and the first photochromic layer 21 may be provided in this order from the light incident side (see FIG. 1 ). Alternatively, the first photochromic layer 21 and the second photochromic layer 22 may be provided in this order from the light incident side.

[0037] In this embodiment, the first dimming layer 21 and the second dimming layer 22 may be formed as the same layer. That is, a photochromic material may be dispersed inside the polymer dispersed liquid crystal (PDLC) or polymer network liquid crystal (PNLC) that constitutes the first dimming layer 21. In such a configuration, the liquid crystal molecules contained in the first dimming layer 21 can be used to control the transmission and scattering of light to adjust the haze, and the photochromic material dispersed in the first dimming layer 21 can be used to adjust the light transmittance.

[0038] In this embodiment, the multilayer laminate may also include a decorative layer with a design.

[0039] Next, examples of the present invention will be described. A multilayer laminate having the configuration shown in FIG. 1 was fabricated as a sample according to the example. Glass was used for the first substrate 11 and the second substrate 12. A PDLC film manufactured by Kyushu Nanotec Optics Co., Ltd. was used for the first photochromic layer 21. A film in which a photochromic material was dispersed in a base material, plasticized polyvinyl butyral (PVB), was used for the second photochromic layer 22. A naphthopyran-based material was used as the photochromic material. Plasticized polyvinyl butyral (PVB) was used for the adhesive layer 24 between the first photochromic layer 21 and the first substrate 11. These films were then laminated to fabricate a sample (multilayer laminate) according to the example.

[0040] In the multilayer laminate according to the example, the state in which a voltage is applied to the first dimming layer 21, i.e., the state in which the liquid crystal molecules are aligned in the direction of the electric field and the first dimming layer 21 is transparent, was defined as the "transparent mode." In addition, the state in which a voltage is not applied to the first dimming layer 21, i.e., the state in which the liquid crystal molecules are aligned in an irregular state and the light passing through the first dimming layer 21 is scattered and opaque (cloudy white), was defined as the "haze mode."

[0041] Furthermore, in the multilayer laminate according to the example, the color of the second photochromic layer 22 changes depending on the light incident on the second photochromic layer 22. Specifically, as the amount of light incident on the second photochromic layer 22 increases, the color of the second photochromic layer 22 becomes darker and the transmittance decreases.

[0042] To evaluate the multilayer laminate according to the example, the first photochromic layer 21 was observed indoors and outdoors in a transparent mode and a haze mode. The haze was measured according to JIS K 7136, and the transmittance was measured as total light transmittance according to JIS K 7361-1.

[0043] Figure 2 shows the state of the multilayer laminate of the embodiment indoors, and shows the results of observing the state indoors when the first photochromic layer 21 is in transparent mode and when it is in haze mode.

[0044] 2, when the first light-controlling layer 21 was in the transparent mode, the multilayer laminate according to the example was in a transparent state. That is, when in the transparent mode, a voltage was applied to the liquid crystal molecules contained in the first light-controlling layer 21, and the liquid crystal molecules were aligned in the direction of the electric field, so that the first light-controlling layer 21 was in a transparent state. In the transparent mode, the haze was 2%, and the total light transmittance was 86%.

[0045] On the other hand, when the first photochromic layer 21 was in the haze mode, the multilayer laminate according to the example became opaque (cloudy white). That is, when the first photochromic layer 21 was in the haze mode, no voltage was applied to the liquid crystal molecules contained in the first photochromic layer 21, so the alignment of the liquid crystal molecules became irregular, and light passing through the first photochromic layer 21 was scattered, resulting in an opaque (cloudy white) state. The haze in the haze mode was 98%, and the total light transmittance was 77%.

[0046] In addition, since the amount of light is low indoors, the photochromic material contained in the second dimming layer 22 does not change color, i.e., the transmittance is high, and the change in total light transmittance from the transparent mode to the haze mode was only 9%.

[0047] 3 shows the state of the multilayer laminate according to the example outdoors, and shows the results of observing the state when the first photochromic layer 21 is set to the transparent mode and the haze mode outdoors. Fig. 3 shows the state immediately after switching the first photochromic layer 21 to each mode and the state after 3 minutes have passed.

[0048] As shown in Figure 3, when the first photochromic layer 21 was set to the transparent mode, the multilayer laminate according to the example became transparent. That is, when the first photochromic layer 21 was set to the transparent mode, a voltage was applied to the liquid crystal molecules contained in the first photochromic layer 21, causing the liquid crystal molecules to align in the direction of the electric field, resulting in the first photochromic layer 21 becoming transparent. Furthermore, while sunlight was transmitted immediately after the transparent mode was set, after three minutes had elapsed since the setting to the transparent mode, the color of the photochromic material contained in the second photochromic layer 22 changed to a uniform black, and the transmittance decreased. As a result, the amount of sunlight passing through the multilayer laminate according to the example was significantly reduced. The total light transmittance at this time was 4%.

[0049] On the other hand, when the first photochromic layer 21 was set to the haze mode, the multilayer laminate according to the example became opaque (cloudy white). That is, when the haze mode was set, no voltage was applied to the liquid crystal molecules contained in the first photochromic layer 21, so the liquid crystal molecules became irregularly aligned, and light passing through the first photochromic layer 21 was scattered, resulting in an opaque (cloudy white) state. Furthermore, immediately after the haze mode was set, the multilayer laminate was cloudy white, but after 3 minutes had passed since the haze mode was set, the color of the photochromic material contained in the second photochromic layer 22 changed to black, and the transmittance decreased. The total light transmittance at this time was 4%.

[0050] Thus, in the multilayer laminate according to the example, the haze was adjusted from 2% to 98% using the first photochromic layer 21, and the total light transmittance was adjusted from 4% to 86% by moving from indoors to outdoors using the second photochromic layer 22. Thus, by using the multilayer laminate according to the present invention, the haze and transmittance could be appropriately adjusted.

[0051] The present invention has been described above in accordance with the above-mentioned embodiment, but the present invention is not limited to the configuration of the above-mentioned embodiment, and naturally includes various modifications, alterations, and combinations that a person skilled in the art can make within the scope of the invention as defined in the claims of this application.

[0052] This application claims priority based on Japanese Patent Application No. 2022-14084, filed February 1, 2022, the disclosure of which is incorporated herein by reference in its entirety.

[0053] REFERENCE SIGNS LIST 1 multilayer laminate 11 first substrate 12 second substrate 21 first light-controlling layer 22 second light-controlling layer

Claims

1. A substrate; a first light-modulating layer including liquid crystal molecules whose alignment state changes in response to an applied voltage; and a second photochromic layer containing a photochromic material, Multilayer laminate.

2. The substrate comprises a first substrate and a second substrate, The first substrate, the first light-controlling layer, the second light-controlling layer, and the second substrate are laminated in this order. The multilayer laminate of claim 1.

3. 3. The multilayer laminate according to claim 1, wherein the first dimming layer is a polymer dispersed liquid crystal in which the liquid crystal molecules are dispersed in a polymer, or a polymer network liquid crystal in which the liquid crystal molecules are arranged inside a three-dimensional mesh-like polymer network.

4. 3. The multilayer laminate according to claim 1, wherein the photochromic material is at least one selected from the group consisting of triarylmethanes, stilbenes, azastilbenes, nitrones, fulgides, spiropyrans, naphthopyrans, spirooxazines, and quinones.

5. the second light-controlling layer is made of polyvinyl butyral, The photochromic material is dispersed within the polyvinyl butyral. The multilayer laminate according to claim 1 or 2.

6. 3. The multilayer laminate according to claim 1, which is used as a material for forming at least one of a window glass for a vehicle, a sunroof for a vehicle, and a window glass for a building.