Light-modulation sheet and light-modulation module

Abstract

Provided are a light-modulation sheet and a light-modulation module that satisfy high quality requirements, accommodate various applications, and are capable of enhancing appearance when the light-modulation sheet is viewed from the front. In a retardation map of a pair of base material layers (40X, 40Y), the slope of a first approximation line connecting the following three sampling points, λ(450), λ(550) and λ(650) is -9 or less. λ(450) is the retardation point when, with the incident angle at the time light is perpendicularly incident on the base material layer defined as 0°, light having a wavelength of 450 nm is incident on the base material layer at an incident angle of 0°. λ(550) is the retardation point when, with the incident angle at the time light is perpendicularly incident on the base material layer defined as 0°, light having a wavelength of 550 nm is incident on the base material layer at an incident angle of 0°. λ(650) is the retardation point when, with the incident angle at the time light falls at normal incidence on the base material layer defined as 0°, light having a wavelength of 650 nm is incident on the base material layer at an incident angle of 0°.

Description

Dimming Sheet and Dimming Module

[0001] The present invention relates to a dimming sheet and a dimming module.

[0002] Patent Document 1 describes a dimming sheet including a dimming layer containing a liquid crystal composition, a first transparent electrode layer and a second transparent electrode layer which are a pair of transparent electrode layers sandwiching the dimming layer, and a pair of transparent support layers sandwiching the dimming layer and the pair of transparent electrode layers. The first transparent electrode layer has an electrode portion configured to be applied with a driving voltage and an insulating portion. The insulating portion is adjacent to the electrode portion in a direction along the surface of the dimming sheet, and extends along the outer edge of the electrode portion in a plan view seen from a position facing the surface of the dimming sheet.

[0003] WO2020 / 059820A1

[0004] However, according to the intensive research of the present inventor, the prior art including the dimming sheet of Patent Document 1 has room for improvement from the viewpoints of meeting high-quality requirements and various application uses. Examples of not being able to meet high-quality requirements include the occurrence of interference fringes (Newton rings, slanted interference fringes) when transmitting non-polarized light such as sunlight in the transparent state of the dimming sheet, or the occurrence of color unevenness (e.g., rainbow unevenness) throughout the dimming sheet. Examples of not being able to meet various application uses include not being able to clear the requirements of in-vehicle applications that are more stringent than building material applications, or not being able to clear the requirements of new application uses that are more stringent than in-vehicle applications in the future. Furthermore, there is no prior art that aims to improve the aesthetics specialized (focused) when viewing the dimming sheet from the front.

[0005] An object of the present invention is to provide a dimming sheet and a dimming module that can meet high-quality requirements and various application uses, and can improve the aesthetics when viewing the dimming sheet from the front.

[0006] The dimming sheet of this embodiment has a dimming layer and a pair of substrate layers located on both sides of the dimming layer, and is a dimming sheet that switches between a transparent state and an opaque state by switching between energized and unenhanced states of the dimming layer, characterized in that at least one of the pair of substrate layers has a slope of -9 or less of a first approximate straight line connecting the following three sampling points λ(450), λ(550), and λ(650) in a retardation map in which wavelength is defined on the horizontal axis and retardation on the vertical axis. λ(450): The retardation point when light with a wavelength of 450 nm is incident on the substrate layer at an incident angle of 0°, with the incident angle being 0° when the light is incident perpendicularly to the substrate layer. λ(550): The retardation point when light with a wavelength of 550 nm is incident on the substrate layer at an incident angle of 0°, with the incident angle being 0° when the light is incident perpendicularly to the substrate layer. λ(650): The retardation point when light with a wavelength of 650 nm is incident on the substrate layer at an incident angle of 0°, with the incident angle being 0° when the light is incident perpendicularly to the substrate layer.

[0007] According to the present invention, it is possible to provide a dimmable sheet and a dimmable module that can meet high quality requirements and various application uses, as well as improve the aesthetic appearance when the dimmable sheet is viewed from the front.

[0008] This figure shows an example of the configuration of a dimming module. This figure shows an example of the configuration of a dimming sheet. This figure shows the difference in the orientation of liquid crystal molecules in the opaque state when not energized and the transparent state when energized of a normal type dimming sheet. This figure shows an example of the cross-sectional structure of a dimming layer containing a dichroic dye and a black spacer. This figure shows an example of the configuration of a reverse type dimming sheet. This figure shows an example of a first approximate straight line connecting sampling points λ(450), λ(550), and λ(650) in the retardation map. This figure shows an example of a second approximate straight line connecting sampling points Λ(450), Λ(550), and Λ(650) in the retardation map. This figure shows experimental results to demonstrate the superiority of the dimming sheet of this embodiment.

[0009] <Definitions of Terms, etc.> In this specification, "light-transmitting member" may be read as "light-transmitting plate" or "light-transmitting window," and is used as a concept that includes "glass member," "glass plate," or "glass window." That is, in this specification, "glass member (glass plate, glass window)" is given as an example of a "light-transmitting member (light-transmitting plate, light-transmitting window)" for explanation, but a "light-transmitting member (light-transmitting plate, light-transmitting window)" may be composed of materials other than glass, various plastics, or other materials. For example, a "light-transmitting member (light-transmitting plate, light-transmitting window)" may be made of polycarbonate.

[0010] In this specification, a "dimming module" is defined as comprising a light-transmitting member and a dimming sheet attached to the light-transmitting member. The "light-transmitting member," as its name suggests, possesses the property of being light-transmitting. The "dimming sheet" is a component of the dimming module and may refer to the dimming sheet in its state before being attached to the light-transmitting member.

[0011] In this specification, a "dimming sheet" may have, as its basic structure, a dimming layer (for example, a polymer-dispersed liquid crystal layer), a pair of transparent conductive layers (conductive layers) located on both sides of the dimming layer, and a pair of transparent substrate layers (substrate layers) located on both sides of the pair of transparent conductive layers. A dimming sheet may be read as a dimming device or a dimming film.

[0012] In this specification, a "dimming sheet" ensures the light transmittance of the light-transmitting member and, consequently, the dimming module by not exhibiting its own dimming function (making it transparent), and inhibits the light transmittance of the light-transmitting member and, consequently, the dimming module by exhibiting its own dimming function (making it opaque). There are two types of dimming sheets: a normal type (normal mode) that is transparent when energized and opaque when not energized, and a reverse type (reverse mode) that is transparent when not energized and opaque when energized. Exercising the dimming function of a dimming sheet means when the normal type is not energized and when the reverse type is energized, and not exhibiting the dimming function of a dimming sheet may mean when the normal type is energized and when the reverse type is not energized. In this way, a dimming sheet can switch between a transparent state and an opaque state by switching between an energized state and an unenhanced state. Here, "transparent" does not mean a visible light transmittance of 100% (it does not mean a strictly transparent state), and "opaque" does not mean a visible light transmittance of 0% (it does not mean a strictly opaque state). Both terms are used to include a semi-transparent state.

[0013] In this specification, the dimming sheet may have a color tone of white when opaque (so-called white dimming) or a color tone of black when opaque (so-called black dimming).

[0014] In this specification, the dimming method using a dimming sheet may be, for example, a polymer dispersed liquid crystal (PDLC) method or a polymer network liquid crystal (PNLC) method. Alternatively, the dimming method using a dimming sheet may utilize electrochromic (EC), liquid crystal (LC), or suspended particle device (SPD).

[0015] In this specification, the light-transmitting member to which the dimming sheet is attached may include so-called single-piece or double-piece light-transmitting members. In the case of a single-piece light-transmitting member, the dimming sheet may be attached to the surface of the single-piece light-transmitting member. In the case of a double-piece light-transmitting member, the dimming sheet may be supported by sandwiching it between the two light-transmitting members with an intermediate layer (interlayer film), or the dimming sheet may be attached to the surface of one of the two light-transmitting members. Thus, there is a degree of freedom in the structure for attaching the dimming sheet to the light-transmitting member, and various design modifications are possible.

[0016] In this specification, "upper surface" and "lower surface" may be defined, for example, as the upper surface and the lower surface in the figure (or they may be defined based on the vertical direction in the figure). Also in this specification, "both sides" may be defined, regardless of the vertical direction in the figure, as being outside a certain reference (center) layer, whether directly or indirectly, or as a layer supported outside a certain reference (center) layer. For example, consider a laminated structure in which a reference (center) layer A is provided, layers B are provided on both sides of layer A, and layers C are provided on both sides of layer B. In this case, layer B is an "outer support layer" supported on "both sides" of layer A, and layer C is an "outer support layer" supported on "both sides" of layer A and layer B. In this sense, "both sides" and "outer support layer" may be read as "upper layer" and "upper support layer," in which case the further away from a certain reference (center) layer is defined as the upper layer, and the closer to a certain reference (center) layer is defined as the lower layer.

[0017] In this specification, the retardation Re of a pair of transparent substrate layers is calculated (obtained) by Re = (nx - ny) × d, where nx is defined as the refractive index in the slow axis direction of the transparent substrate layer, ny is defined as the refractive index in the fast axis direction of the transparent substrate layer, and d (nm) is defined as the thickness of the transparent substrate layer. The retardation Re may vary depending on the angle of incidence of light to the transparent substrate layer and the wavelength of light incident on the transparent substrate layer.

[0018] In this specification, the "first approximation line" is defined as the approximation line connecting multiple sampling points, λ(450), λ(550), and λ(650), and the "second approximation line" is defined as the approximation line connecting multiple sampling points, Λ(450), Λ(550), and Λ(650). The least squares method is used to calculate (calculate, perform operations on) the approximation lines (e.g., the first and second approximation lines).

[0019] <Conventional Technical Challenges> Dimming devices (dimming sheets, dimming modules) have long been applied to building materials (e.g., window glass), and in recent years have been adopted for automotive applications (e.g., sunroofs and side windows), expanding their range of applications. New applications other than building materials and automotive applications are also being considered for dimming devices (dimming sheets, dimming modules), and market expansion is expected in the future.

[0020] However, according to the inventor's diligent research, the prior art, including the dimming sheet described in Patent Document 1, has room for improvement in terms of meeting high quality requirements and various application uses. Examples of failure to meet high quality requirements include the occurrence of interference fringes (Newton's rings, diagonal interference fringes) when unpolarized light such as sunlight is transmitted through the dimming sheet in its transparent state, or the occurrence of color unevenness (e.g., rainbow unevenness) throughout the dimming sheet. Examples of failure to meet various application uses include the inability to meet the stricter quality requirements of automotive applications than building material applications, or the inability to meet the stricter quality requirements of new applications in the future.

[0021] For example, a dimmable sheet (dimmable film) has a structure in which a PNLC layer (dimmable layer, liquid crystal layer) is sandwiched between transparent polymer film layers (transparent substrate layer, substrate layer). In this case, in transmission mode, the refractive index of the PNLC layer and the refractive index of the transparent polymer film layer are almost the same when viewed from the front, but there is a difference in refractive index when viewed from an oblique direction. Therefore, it is presumed that interference fringes are generated when light refracted at the interface between the upper and lower transparent polymer film layers interferes. In addition, since the transparent polymer film layer is flexible, there is variation within the plane, and light interference tends to occur even at the same interface. Furthermore, when dimmable sheets (dimmable films) are manufactured using roll-to-roll production with transparent electrode polymer film for cost advantages, interference fringes tend to occur in transparent mode due to the flexibility and retardation properties of the polymer.

[0022] Inserting polarizing plates could be considered as a countermeasure against color unevenness (for example, rainbow unevenness), but concerns exist regarding disadvantages such as an increase in the number of parts, increased structural complexity, reduced space efficiency, and higher costs associated with the insertion of polarizing plates.

[0023] Furthermore, there are no existing technologies that specifically focus on improving the aesthetic appearance of dimmable sheets when viewed from the front.

[0024] <Technical Concept of the Invention> The inventors considered the above-mentioned problems as important technical challenges and, in order to realize a dimmable sheet and dimmable module that can guarantee (ensure) the functionality of conventional polarizing plates, etc., meet high quality requirements and various application uses, and improve the aesthetic appearance when the dimmable sheet is viewed from the front, they have been conducting research and development on parameters that a pair of substrate layers located on both sides of the dimmable layer must satisfy, and have completed the present invention.

[0025] Here, "guaranteeing (ensuring) the function of conventional polarizers, etc." does not necessarily mean that it perfectly matches the effect obtained by optimally setting the parameters that the pair of substrate layers should satisfy in this embodiment (it is sufficient that it exhibits a certain level of interference fringe and color unevenness suppression effect, regardless of whether it is superior or inferior to conventional polarizers, etc.). In other words, while optimally setting the parameters that the pair of substrate layers should satisfy in this embodiment does not preclude the provision of additional components such as polarizers based on complementary purposes (reasons) or other purposes (reasons).

[0026] Polyethylene terephthalate (PET) is often used as the transparent polymer film (transparent substrate layer) for dimming devices (dimming sheets, dimming modules). However, PET films typically have birefringence, and when light passes through them, interference fringe-like color unevenness (e.g., rainbow unevenness) occurs. In this embodiment, while using a PET film as the dimming sheet (at least one of a pair of substrate layers), by optimally setting the parameters that the pair of substrate layers located on both sides of the dimming layer must satisfy, it is possible to meet high quality requirements and various application uses while guaranteeing (ensuring) the functionality of conventional polarizers, etc., and to improve the aesthetic appearance of the dimming sheet when viewed from the front.

[0027] In addition, as a high retardation substrate layer (transparent substrate layer), other materials besides the PET film mentioned above can be used, such as polypropylene film (PP), polyamide film (PA) made by thinly rolling out polyamide resin (nylon), and polyethylene naphthalate film (PEN). In this embodiment, even when these film materials are used as the light-adjusting sheet (at least one of a pair of substrate layers), by optimally setting the parameters that the pair of substrate layers located on both sides of the light-adjusting layer must satisfy, it is possible to meet high quality requirements and various application uses while guaranteeing (ensuring) the functionality of conventional polarizing plates, etc. Furthermore, it is possible to improve the aesthetic appearance when viewing the light-adjusting sheet from the front.

[0028] More specifically, the dimming sheet of this embodiment has a dimming layer and a pair of substrate layers located on both sides of the dimming layer, and switches between a transparent state and an opaque state by switching the energized state and the de-energized state of the dimming layer. Furthermore, in a retardation map in which wavelength is defined on the horizontal axis and retardation on the vertical axis, the slope of the first approximate straight line connecting the following three sampling points λ(450), λ(550), and λ(650) of at least one of the pair of substrate layers is -9 or less. Preferably, the slope of the first approximate straight line is -25 or more and -10 or less. λ(450): The retardation point when light with a wavelength of 450 nm is incident on the substrate layer at an incident angle of 0°, with the incident angle being 0° when light is incident perpendicularly to the substrate layer. λ(550): The retardation point when light with a wavelength of 550 nm is incident on the substrate layer at an incident angle of 0°, with the incident angle being 0° when light is incident perpendicularly to the substrate layer. λ(650): The retardation point when light with a wavelength of 650 nm is incident on the substrate layer at an incident angle of 0°, with the incident angle being 0° when light is incident perpendicularly to the substrate layer.

[0029] The wavelengths of 450 nm, 550 nm, and 650 nm defined by the slope condition of the first approximate line are representative wavelength bands of blue, green, and red light, respectively. Unpolarized incident light, such as sunlight, is white light, which is a composite of wavelengths in these bands. To suppress the effects of interference fringes (Newton's rings, oblique interference fringes) caused by the incident light, it is preferable to select wavelengths of 450 nm, 550 nm, and 650 nm, which correspond to the blue, green, and red light bands (and use these as the basis for the first approximate line). In this specification, wavelength 450 nm may be represented as B, wavelength 550 nm as G, and wavelength 650 nm as R.

[0030] It is preferable that both of the pair of substrate layers satisfy the above-mentioned conditions for the slope of the first approximate straight line.

[0031] By setting the slope of the first approximate line to -9 or less (preferably -25 or more and -10 or less), it is possible to prevent interference fringes (Newton's rings, diagonal interference fringes) from occurring when unpolarized light such as sunlight is transmitted through the dimming sheet in its transparent state, and to prevent color unevenness from occurring throughout the dimming sheet. Furthermore, it is possible to meet the stricter quality requirements of automotive applications than building material applications, and to meet the stricter quality requirements of new applications in the future. In particular, by focusing on the dimming sheet when viewed from the front (0° direction), the ratio of phase-aligned visible light is reduced, eliminating interference fringes and suppressing rainbow unevenness, thereby improving aesthetics (visibility).

[0032] If the slope of the first approximation line is greater than -9, it becomes difficult to meet high quality requirements and various application uses (it becomes impossible to completely suppress the occurrence of interference fringes and color unevenness). In addition, the aesthetic appearance (visibility) of the dimming sheet when viewed from the front (0° direction) is impaired.

[0033] Figure 6 shows an example of a first approximate line connecting sampling points λ(450), λ(550), and λ(650) in a retardation map. The first approximate line is calculated using the least squares method. In the least squares method, when finding a line that approximates the measurement data (in this case, sampling points), the parameters of the line that minimize the difference between each data point and the line are calculated. In addition, when obtaining the first approximate line, additional sampling points may be used in addition to sampling points λ(450), λ(550), and λ(650) (for example, the number of sampling points may be increased to four, five, etc.).

[0034] The retardation on the short-wavelength side of the first approximate line is preferably 10,500 or more, and more preferably 11,000 or more and 30,000 or less. By increasing the intercept (retardation) on the short-wavelength side of the first approximate line, an excellent rainbow unevenness suppression effect can be obtained.

[0035] A reference angle Δ(BG) is defined by the line segment connecting sampling points λ(450) and λ(550), and a reference angle Δ(GR) is defined by the line segment connecting sampling points λ(550) and λ(650). Reference angles Δ(BG) and Δ(GR) are defined, for example, as angles with respect to a reference axis set in the vertical or horizontal direction. The difference between reference angles Δ(BG) and Δ(GR) is preferably 3.5° or less, and more preferably 1° or more and 3.3° or less. The smaller the difference between reference angles Δ(BG) and Δ(GR), the closer the sampling points λ(450), λ(550), and λ(650) are aligned, and the smaller the variation in RGB retardation, resulting in an excellent rainbow unevenness suppression effect.

[0036] The retardation difference λ(B-G) between sampling points λ(450) and λ(550) is preferably 1100 or more, and more preferably 1200 or more and 3000 or less. The retardation difference λ(G-R) between sampling points λ(550) and λ(650) is preferably 650 or more, and more preferably 700 or more and 2000 or less. The retardation difference λ(B-R) between sampling points λ(450) and λ(650) is preferably 1800 or more, and more preferably 2000 or more and 4500 or less. By satisfying these conditions, it is possible to meet high quality requirements and various application uses, as well as improve the aesthetic appearance of the dimming sheet when viewed from the front.

[0037] In a retardation map where wavelength is defined on the horizontal axis and retardation on the vertical axis, it is preferable that the slope of the second approximate straight line connecting the following three sampling points Λ(450), Λ(550), and Λ(650) is -4 or greater, and more preferably -4 or greater and -1.5 or less. Λ(450): The retardation point when light with a wavelength of 450 nm is incident on the substrate layer at an incident angle of 50°, with the incident angle when light is perpendicular to the substrate layer being 0°. Λ(550): The retardation point when light with a wavelength of 550 nm is incident on the substrate layer at an incident angle of 50°, with the incident angle when light is perpendicular to the substrate layer being 0°. Λ(650): The retardation point when light with a wavelength of 650 nm is incident on the substrate layer at an incident angle of 50°, with the incident angle when light is perpendicular to the substrate layer being 0°.

[0038] The wavelengths of 450 nm, 550 nm, and 650 nm defined by the slope condition of the second approximate line are representative wavelength bands of blue, green, and red light, respectively. Unpolarized incident light, such as sunlight, is white light, which is a composite of wavelengths in these bands. To suppress the effects of interference fringes (Newton's rings, oblique interference fringes) caused by incident light, it is preferable to select wavelengths of 450 nm, 550 nm, and 650 nm, which correspond to the blue, green, and red light bands (and use them as the basis for the second approximate line). In this specification, wavelength 450 nm may be represented as B, wavelength 550 nm as G, and wavelength 650 nm as R.

[0039] It is preferable that both of the pair of substrate layers satisfy the conditions for the slope of the second approximate straight line described above.

[0040] By setting the slope of the second approximate line to -4 or greater (preferably -4 or greater and -1.5 or less), the visibility of the dimmable sheet when viewed from an angle (50° direction), in addition to the aesthetic appearance when viewed from the front (0° direction), can also be kept within an acceptable range. In other words, the difference in visibility when viewed from the front (0° direction) and when viewed from an angle (50° direction) can be reduced, thereby achieving a suppression effect on rainbow unevenness when viewed from each direction.

[0041] Figure 7 shows an example of a second approximation line connecting sampling points Λ(450), Λ(550), and Λ(650) in the retardation map. The method for obtaining (calculating) the second approximation line is the least squares method. In the least squares method, when finding a line that approximates the measurement data (in this case, sampling points), the parameters of the line that minimize the difference with each data point are calculated. In addition, when obtaining (calculating) the second approximation line, additional sampling points may be used in addition to sampling points Λ(450), Λ(550), and Λ(650) (for example, the number of sampling points may be increased to four, five, etc.).

[0042] The retardation on the short-wavelength side of the second approximate line is preferably 1050 or more and 7000 or less, and more preferably 1100 or more and 3000 or less. By appropriately setting the intercept (retardation) on the short-wavelength side of the second approximate line, the difference in visibility when viewing the dimming sheet from the front (0° direction) and when viewing it from an oblique angle (50° direction) can be reduced, and the effect of suppressing rainbow unevenness when viewed from each direction can be obtained.

[0043] Preferably, at least one of the pair of base material layers has a thickness of 90 μm or more and 200 μm or less, and more preferably 100 μm or more and 200 μm or less. This ensures flexibility while maintaining the mechanical properties of the base material layer, making it less prone to tearing, ripping, etc., thus guaranteeing its practicality as an industrial material.

[0044] The above-mentioned interference fringes and color unevenness are more noticeable (more likely to impair the aesthetics) in the case of black-tinted light where the color in the opaque state is black than in the case of white-tinted light where the color in the opaque state is white. In addition, when used for a sunroof of an automobile, a black color is preferred for the dimming sheet, and furthermore, a sheet with good appearance, such as not showing interference fringes and color unevenness due to sunlight, is preferred. For this reason, in a black-tinted dimming sheet in which at least one of a dichroic dye and a black spacer is included in the dimming layer, by satisfying the above-described various conditions, particularly, the slope of the first approximate straight line connecting the sampling points λ(450), λ(550), and λ(650) is -9 or less (preferably -25 or more and -10 or less), interference fringes and color unevenness can be removed more effectively (the aesthetics can be improved). Also, the aesthetics (visibility) when the dimming sheet is viewed from the front (0° direction) can be improved.

[0045] <Specific Embodiments> Hereinafter, embodiments will be described with reference to the drawings. However, the drawings are schematic or conceptual, and the dimensions, ratios, etc. of each drawing are not necessarily the same as the actual ones. Also, even when representing the same part between the drawings, the dimensional relationships and ratios may be represented differently. In particular, the following embodiments illustrate devices, methods, etc. for embodying the technical idea of the present invention, and the technical idea of the present invention is not specified by the shape, structure, arrangement, etc. of the constituent parts. In the following description, elements having the same function and configuration may be given the same reference numerals, and duplicate descriptions may be omitted.

[0046] FIG. 1 is a diagram showing a configuration example of a dimming module. FIG. 2 is a diagram showing a configuration example of a dimming sheet. As shown in FIG. 1, a dimming module is configured by attaching (sticking) a dimming sheet (dimming device, dimming film) 10 to a light-transmitting member (light-transmitting plate, light-transmitting window) 10X. The dimming sheet 10 may have an adhesive layer for attaching itself to the light-transmitting member 10X. Also, in FIG. 2, a structure including a drive mechanism (electrodes and wirings) of the dimming sheet 10 is depicted.

[0047] The dimming sheet 10 has a dimming layer (liquid crystal layer) 20. The dimming layer 20 contains a liquid crystal composition. The dimming layer 20 may be composed of, for example, polymer dispersed liquid crystal (PDLC: Polymer Dispersed Liquid Crystal), polymer network liquid crystal (PNLC: Polymer Network Liquid Crystal), capsule-type nematic liquid crystal (NCAP: Nematic Curvilinear Aligned Phase), etc. For example, polymer dispersed liquid crystal and polymer network liquid crystal have a three-dimensional network-shaped polymer network, and hold liquid crystal molecules in the voids of the polymer network. The liquid crystal molecules contained in the dimming layer 20, for example, have a positive dielectric anisotropy, and the dielectric constant in the long axis direction of the liquid crystal molecules is larger than the dielectric constant in the short axis direction of the liquid crystal molecules. The liquid crystal molecules are, for example, Schiff base type, azo type, azoxy type, biphenyl type, terphenyl type, benzoic acid ester type, trans type, pyrimidine type, cyclohexanecarboxylic acid ester type, phenylcyclohexane type, dioxane type liquid crystal molecules.

[0048] On the outside of one surface (the upper surface in the figure) of the dimming layer 20, a transparent conductive layer (conductive layer) 30X is provided, and on the outside of the transparent conductive layer 30X, a transparent base material layer (base material layer) 40X is provided. On the outside of the other surface (the lower surface in the figure) of the dimming layer 20, a transparent conductive layer (conductive layer) 30Y is provided, and on the outside of the transparent conductive layer 30Y, a transparent base material layer (base material layer) 40Y is provided. Thus, the dimming sheet 10 has the dimming layer 20, a pair of transparent conductive layers 30X and 30Y located on both sides sandwiching the dimming layer 20, and a pair of transparent base material layers 40X and 40Y located on both sides sandwiching the pair of transparent conductive layers 30X and 30Y.

[0049] The transparent conductive layers 30X and 30Y are transparent layers that have conductivity. Examples of materials constituting the transparent conductive layers 30X and 30Y include polymers containing indium tin oxide (ITO), fluorine-doped tin oxide (FTO), tin oxide, zinc oxide, carbon nanotubes (CNT), poly(3,4-ethylenedioxythiophene) (PEDOT), and multilayer films containing Ag alloy thin films. The transparent substrate layers 40X and 40Y are layers composed of materials such as polyethylene terephthalate (PET).

[0050] In addition, other layers may be provided as an "outer support layer" located outside the pair of transparent substrate layers 40X and 40Y. For example, the "outer support layer" may be a layer for protecting the light-adjusting layer 20, the transparent conductive layers 30X and 30Y, and the transparent substrate layers 40X and 40Y, a layer that contributes to controlling the light transmittance of the light-adjusting sheet 10, or a layer that enhances the strength, heat resistance, and other properties of the light-adjusting sheet 10.

[0051] In the example in Figure 1, the edges (end faces) of the dimming sheets 10 are flush, and their positions are aligned without any misalignment when viewed from above. In contrast, in the example in Figure 2, the edges (end faces) of the dimming sheets 10 are not flush, and they are arranged so that their positions are offset from each other when viewed from above.

[0052] In the example shown in Figure 2, when we focus on the right end (right end face) of the dimming sheet 10, the transparent conductive layer 30X and the transparent substrate layer 40X provided on one side of the dimming layer 20 (the top surface in the figure) protrude to the right of the dimming layer 20. On the other hand, when we focus on the left end (left end face) of the dimming sheet 10, the transparent conductive layer 30Y and the transparent substrate layer 40Y provided on the other side of the dimming layer 20 (the bottom surface in the figure) protrude to the left of the dimming layer 20.

[0053] An electrode portion 50X for applying a driving voltage to the dimming sheet 10 (dimming layer 20) is provided on the lower surface of the transparent conductive layer 30X that protrudes to the right of the dimming layer 20. An electrode portion 50Y for applying a driving voltage to the dimming sheet 10 (dimming layer 20) is provided on the upper surface of the transparent conductive layer 30Y that protrudes to the left of the dimming layer 20. A wiring portion 60X is connected to the electrode portion 50X, and a wiring portion 60Y is connected to the electrode portion 50Y, and the wiring portions 60X and 60Y are connected to the drive power supply 70. The wiring portions 60X and 60Y may be made of, for example, FPC (Flexible Printed Circuits).

[0054] As described above, when a drive current is passed through the transparent conductive layers 30X and 30Y via the electrode sections 50X and 50Y, the wiring sections 60X and 60Y, and the drive power supply 70, a drive voltage is applied between the transparent conductive layers 30X and 30Y, i.e., to the dimming layer 20.

[0055] When no driving voltage is applied between the transparent conductive layers 30X and 30Y (the dimming layer 20), the orientation of the liquid crystal molecules in the dimming layer 20 along its long axis is irregular. Therefore, light incident on the dimming layer 20 is scattered, and due to the synergistic effect of the dichroic dye and black spacer contained in the dimming layer 20, the dimming sheet 10 becomes black. In other words, the dimming sheet 10 is opaque. Alternatively, the dichroic dye and black spacer may be omitted from the dimming layer 20, making the dimming sheet 10 white (white dimming) when opaque.

[0056] On the other hand, when a driving voltage is applied between the transparent conductive layers 30X and 30Y (the dimming layer 20), the liquid crystal molecules of the dimming sheet 10 are oriented, and the long axis direction of the liquid crystal molecules is aligned with the electric field direction between the transparent conductive layers 30X and 30Y. As a result, light is more easily transmitted through the dimming layer 20, and the dimming sheet 10 becomes transparent. In this way, the dimming sheet 10 functions as a normal type (normal mode).

[0057] The dimming sheet 10 can be cut into a desired shape from a large sheet made of a multilayer structure comprising the layers that make up the dimming sheet 10, and used for various purposes. For example, the dimming sheet 10 can be used in various applications such as dimming films that block visibility from the inside and outside at specific times, office partitions, laminated glass, and frosted glass, where transparent glass is sufficient under normal circumstances. The dimming sheet 10 can also be installed in the upper part of a car's windshield to provide a partial sun visor function, or applied to car-mounted sunroofs and side windows.

[0058] Figures 3A and 3B show the difference in the orientation of liquid crystal molecules in the opaque state when the normal type of dimming sheet is not powered on (power off) and the transparent state when the power is on (power on).

[0059] As shown in Figure 3A, in the opaque state of the normal type dimming sheet 10 when it is not powered on (power off), the liquid crystal molecules located inside the dimming layer 20 are oriented unevenly, and because the refractive indices of the liquid crystal molecules and polymers do not match, a scattering state occurs, resulting in opacity. Moreover, the synergistic effect of the dichroic dye and black spacer (black functional fine particles) contained in the dimming layer 20 can guarantee black dimming in the opaque state of the dimming sheet 10.

[0060] As shown in Figure 3B, in the transparent state when the normal type dimming sheet 10 is powered on (power on), the liquid crystal molecules located inside the dimming layer 20 are balanced in orientation (their long axes are aligned in the left-right direction in the figure), and the refractive indices of the liquid crystal molecules and polymers match, resulting in transparency. Moreover, for example, the pair of transparent substrate layers 40X and 40Y located on both sides of the dimming layer 20 (on both sides of the pair of transparent conductive layers 30X and 30Y) satisfy various conditions, including the slope of the first approximate straight line described above, thereby meeting high quality requirements and various application uses (the occurrence of interference fringes and color unevenness can be suppressed). In addition, the aesthetic appearance (visibility) when viewing the dimming sheet from the front (0° direction) can be improved.

[0061] Figure 4 shows an example of a cross-sectional structure of a photochromic layer containing a dichroic dye and a black spacer.

[0062] In Figure 4, each component included in the light-adjusting layer 20 is denoted by the following symbols: the transparent polymer layer is denoted by the symbol 20P, the voids by the symbol 20D, the liquid crystal composition by the symbol 20LC, the liquid crystal compound by the symbol LCM, the dichroic dye by the symbol DD, and the black spacer by the symbol SP. The light-adjusting layer 20 includes a transparent polymer layer 20P containing a plurality of voids 20D, a liquid crystal composition 20LC located within the voids 20D, and a black spacer SP. The liquid crystal composition 20LC contains a liquid crystal compound LCM and a dichroic dye DD.

[0063] The transparent polymer layer 20P may be a cured product of a photopolymerizable compound. The brightness of the dimming sheet 10 can be changed by changing the size of the voids 20D in the transparent polymer layer 20P. The light used to polymerize the photopolymerizable compound may be ultraviolet light or an electron beam. The photopolymerizable compound may be an ultraviolet polymerizable composition or an electron beam polymerizable composition. The liquid crystal composition 20LC may contain additives such as an antifoaming agent, an antioxidant, a weathering agent, a solvent, and a viscosity reducing agent. The weathering agent may be an ultraviolet absorber or a light stabilizer. The liquid crystal compound LCM may have positive dielectric anisotropy.

[0064] The black spacer SP may be dispersed throughout the transparent polymer layer 20P. The thickness of the black spacer SP may be determined by the thickness of the light-adjusting layer 20. The thickness of the black spacer SP may also be determined by the particle size of the black spacer SP. The black spacer SP may make the thickness of the light-adjusting layer 20 uniform. The black spacer SP may be a bead spacer or a photospacer formed by exposure and development of the photoresist. Preferably, the color of the black spacer SP is the same black as the color exhibited by the dichroic dye DD. For example, the outer surface of the black spacer SP may be black. Alternatively, the black spacer SP may have an outer surface and a central part covered by the outer surface, and the central part may be black. The black spacer SP may have a spherical shape or a columnar shape.

[0065] The dichroic dye DD may exhibit color (black) by being driven by a guest-host type with a liquid crystal compound LCM as the host. The dichroic dye DD may be at least one selected from the group consisting of, for example, polyiodine, azo compounds, anthraquinone compounds, naphthoquinone compounds, azomethine compounds, tetrazine compounds, quinophthalone compounds, merocyanine compounds, perylene compounds, and dioxazine compounds. The dichroic dye DD may be a single compound or a combination of two or more compounds. It is preferable that the dichroic dye DD exhibits black, which is the same color as the black spacer SP. The dichroic dye DD may exhibit black by being a single compound that exhibits black, or a combination of two or more compounds.

[0066] Figure 5 shows an example of the configuration of a reverse-type dimmable sheet. The normal-type dimmable sheet 10 shown in Figures 1 and 2 has a pair of transparent conductive layers 30X and 30Y interposed between the dimmable layer 20 and a pair of transparent substrate layers 40X and 40Y, which switch between a transparent state and an opaque state by switching between energized and de-energized states to the dimmable layer 20. The reverse-type dimmable sheet 10 shown in Figure 5 further has a pair of alignment layers 80X and 80Y interposed between the dimmable layer 20 and a pair of transparent conductive layers 30X and 30Y (the alignment layer 80X is located between the dimmable layer 20 and the transparent conductive layer 30X, and the alignment layer 80Y is located between the dimmable layer 20 and the transparent conductive layer 30Y).

[0067] The alignment layers 80X and 80Y are layers that control the orientation of liquid crystal molecules contained in the light-adjusting layer 20. When no driving voltage is applied, they align the liquid crystal molecules along the direction normal to the alignment layer. In a configuration with alignment layers 80X and 80Y, when a driving voltage is applied between the transparent conductive layers 30X and 30Y (light-adjusting layer 20), the light-adjusting sheet 10 becomes opaque, and when no driving voltage is applied between the transparent conductive layers 30X and 30Y (light-adjusting layer 20), the light-adjusting sheet 10 becomes transparent (functions as a reverse type (reverse mode)). Examples of materials constituting the alignment layers 80X and 80Y include organic compounds such as polyimide, polyamide, polyvinyl alcohol, and cyanide compounds, inorganic compounds such as silicon oxide and zirconium oxide, and silicon. Examples of orientation treatments for forming the alignment layers 80X and 80Y include rubbing treatment, polarized irradiation treatment, and microfabrication treatment.

[0068] Next, a method for manufacturing transparent substrate layers (substrate layers) 40X and 40Y that satisfies various conditions, including the slope of the first approximate straight line described above, will be explained.

[0069] The transparent substrate layer can be composed of, for example, polyester such as polyethylene terephthalate or polyethylene naphthalate, polycarbonate, polystyrene, polyether ether ketone, polyphenylene sulfide, cycloolefin polymer, etc. These resins have excellent transparency as well as excellent thermal and mechanical properties, and have the advantage of being easy to control retardation by stretching (for example, uniaxial stretching in the longitudinal direction only, or biaxial stretching in the longitudinal and transverse directions). In particular, polyester, represented by polyethylene terephthalate, has a large intrinsic birefringence, and large retardation can be obtained relatively easily even with a thin film thickness, making it a suitable material.

[0070] Since the transparent substrate layer has a specific birefringence, it is desirable to use an oriented film. However, the manufacturing method is not particularly limited as long as it satisfies the various conditions, including the film characteristics defined in this embodiment, i.e., the slope of the first approximate straight line described above.

[0071] In the first manufacturing embodiment, a transparent substrate layer material is melted and extruded into a sheet. This unoriented sheet is then stretched (uniaxially stretched) in only one direction (longitudinal direction) at a temperature above the glass transition temperature to obtain an oriented film having a specific retardation. Commercially available unoriented sheets or those produced by solution deposition can be suitably used. In the first manufacturing embodiment, by optimally setting various parameters such as the stretching (uniaxial stretching) temperature, stretching (uniaxial stretching) ratio, and sheet thickness, a transparent substrate layer that satisfies various conditions, including the slope of the first approximate straight line described above, can be manufactured.

[0072] In the second manufacturing embodiment, the material for the transparent substrate layer is melted and extruded into a sheet. The resulting unoriented sheet is then transversely stretched in a tenter at a temperature above the glass transition temperature and subsequently heat-treated. In the second manufacturing embodiment, by optimally setting various parameters such as the transverse stretching temperature, transverse stretching ratio, heat treatment temperature, heat treatment time, and sheet thickness, a transparent substrate layer that satisfies various conditions, including the slope of the first approximate straight line described above, can be manufactured.

[0073] In the third manufacturing embodiment, a jumbo roll (intermediate product) manufacturing process and a product roll manufacturing process may be performed. In the jumbo roll (intermediate product) manufacturing process, for example, PET pellets are melted in an extrusion hopper, a film shape is created using a die, longitudinal stretching is performed using a roll step, transverse stretching is performed by pulling the film with a chuck, and winding is performed using a winder. In the product roll manufacturing process, the jumbo roll (intermediate product) is slit to produce the final roll. In the third manufacturing embodiment, by optimally setting various parameters such as longitudinal stretching temperature, longitudinal stretching ratio, transverse stretching temperature, transverse stretching ratio, and film thickness, a transparent substrate layer that satisfies various conditions, including the slope of the first approximate straight line described above, can be manufactured.

[0074] The transparent substrate layer may be surface-treated by known methods, such as corona discharge treatment (in air, nitrogen, carbon dioxide, etc.) or easy-adhesion treatment, in order to improve adhesion to adjacent layers such as adhesive layers, release layers, and antistatic layers, as well as water resistance and chemical resistance. Various known methods can be used for the easy-adhesion treatment, and methods such as applying various known easy-adhesion adhesives to the film during the film manufacturing process or to the film after stretching (uniaxial stretching) are preferably employed.

[0075] <Numerical Examples & Verification Experiments> The inventors conducted experiments to demonstrate the superiority of the dimming sheet 10 of this embodiment. The results are shown in Figure 8.

[0076] As shown in Figure 8, samples according to Examples 1-3 and Comparative Examples 1-4 of the present invention were prepared. The samples according to Examples 1-3 were prepared by uniaxial stretching (longitudinal stretching), the samples according to Comparative Examples 1-3 were prepared by biaxial stretching (longitudinal and transverse stretching), and the sample according to Comparative Example 4 was prepared by uniaxial stretching (longitudinal stretching). In each sample, the thickness (film thickness) of the transparent substrate layer (substrate layer) was varied. In addition, retardation values ​​were measured for each sample when parameters such as wavelength and incident angle were varied while the sample was transparent. Furthermore, the pair of transparent substrate layers (substrate layers) had the same shape and characteristics.

[0077] Retardation values ​​were measured using a measuring device (RETS-100: product name) manufactured by Otsuka Electronics Co., Ltd. The measurement conditions were as follows: the retardation measurement range was based on the rotational analyzer method, the measurement spot diameter was φ5 mm, the tilt angle range was 0° or 50°, and the measurement wavelength was within a predetermined range including at least three points with wavelengths of 450 nm, 550 nm, and 650 nm. The thickness (film thickness) of the transparent substrate layer was measured using a high-precision digital length measuring instrument (Lightmatic, manufactured by Mitutoyo).

[0078] For each sample prepared, interference fringes and color unevenness (e.g., rainbow unevenness) were measured and evaluated. Specifically, under outdoor sunlight, the dimming sheet was observed from the front and at an angle, both in a straight state and with a slight curve that did not cause bending, to confirm the occurrence of interference fringes and color unevenness. In particular, the aesthetic appearance (visibility) when the dimming sheet was viewed from the front (0° direction) was checked. The specific evaluation criteria were set to the following three levels. For example, ○ may be evaluated as being within the acceptable range (acceptable product), × as being outside the acceptable range (unacceptable product), and △ may be evaluated as either within or outside the acceptable range. ○: No interference fringes or color unevenness are observed when viewed from the front. △: Faint interference fringes and color unevenness are observed when viewed from the front. ×: Clear interference fringes and color unevenness are observed when viewed from the front.

[0079] Figure 8 shows the slope of the first approximate line, the retardation (intercept) on the short wavelength side of the first approximate line, the difference between Δ(BG) and Δ(GR), λ(B-G), λ(G-R), λ(B-R), the slope of the second approximate line, the retardation (intercept) on the short wavelength side of the second approximate line, and the measured thickness (film thickness) of the substrate layer for samples according to Examples 1-3 and Comparative Examples 1-4. Areas that satisfy the various conditions of this embodiment are depicted in a clear state without gray shading, while areas that do not satisfy the various conditions of this embodiment are depicted with gray shading.

[0080] As shown in Figure 8, the samples according to Examples 1-3 satisfy all conditions, including the slope of the first approximate line, and are rated as within the acceptable range (acceptable product) (no interference fringes or color unevenness are observed when viewed from the front).

[0081] On the other hand, samples related to Comparative Examples 1-3, which do not satisfy most of the conditions, including the slope of the first approximate line, were given an × rating as outside the acceptable range (failed product) (obvious interference fringes and color unevenness were visible when viewed from the front), while the sample related to Comparative Example 4 received a △ rating, which falls between the acceptable range and outside the acceptable range (faint interference fringes and color unevenness were visible when viewed from the front).

[0082] Based on the above, the superiority of the samples according to Examples 1-3, which satisfy the various conditions of this embodiment, has been demonstrated.

[0083] Thus, the dimming sheet of this embodiment has a dimming layer and a pair of substrate layers located on both sides of the dimming layer, and is a dimming sheet that switches between a transparent state and an opaque state by switching between energized and unenhanced states of the dimming layer, wherein at least one of the pair of substrate layers has a slope of -9 or less of the first approximate straight line connecting the following three sampling points λ(450), λ(550), and λ(650) in a retardation map in which wavelength is defined on the horizontal axis and retardation on the vertical axis. λ(450): The retardation point when light with a wavelength of 450 nm is incident on the substrate layer at an incident angle of 0°, with the incident angle being 0° when the light is incident perpendicularly to the substrate layer. λ(550): The retardation point when light with a wavelength of 550 nm is incident on the substrate layer at an incident angle of 0°, with the incident angle being 0° when the light is incident perpendicularly to the substrate layer. λ(650): The retardation point when light with a wavelength of 650 nm is incident on the substrate layer at an incident angle of 0°, with the incident angle being 0° when the light is incident perpendicularly to the substrate layer.

[0084] This allows us to meet high quality requirements and various application applications while guaranteeing the functionality of conventional polarizing plates, etc. For example, it prevents interference fringes (Newton's rings, diagonal interference fringes) from occurring when unpolarized light such as sunlight is transmitted through the dimming sheet in its transparent state, and prevents color unevenness (e.g., rainbow unevenness) from occurring throughout the dimming sheet. Furthermore, it can meet the stricter quality requirements of automotive applications than building material applications, and will be able to meet the stricter quality requirements of new applications in the future. In addition, it can improve the aesthetic appearance of the dimming sheet when viewed from the front.

[0085] The present invention is not limited to the embodiments described above, and can be modified in various ways during implementation without departing from its essence. Furthermore, each embodiment may be combined as appropriate, and in that case, the combined effects can be obtained. Moreover, the above embodiments include various inventions, and various inventions can be extracted by selecting combinations from the multiple constituent elements disclosed. For example, if the problem can be solved and effects obtained even if some constituent elements are deleted from all the constituent elements shown in the embodiment, then the configuration with these deleted constituent elements can be extracted as an invention.

[0086] This application is based on Japanese Patent Application No. 2025-024956, filed on February 19, 2025. All of its contents are included herein.

Claims

1. A dimmable sheet having a dimmable layer and a pair of substrate layers located on both sides of the dimmable layer, wherein the dimmable sheet switches between a transparent state and an opaque state by switching between energized and unenhanced states of the dimmable layer, characterized in that at least one of the pair of substrate layers has a slope of -9 or less of a first approximate straight line connecting the following three sampling points λ(450), λ(550), and λ(650) in a retardation map in which wavelength is defined on the horizontal axis and retardation on the vertical axis. λ(450): The retardation point when light with a wavelength of 450 nm is incident on the substrate layer at an incident angle of 0°, with the incident angle being 0° when the light is incident perpendicularly to the substrate layer. λ(550): The retardation point when light with a wavelength of 550 nm is incident on the substrate layer at an incident angle of 0°, with the incident angle being 0° when the light is incident perpendicularly to the substrate layer. λ(650): The retardation point when light with a wavelength of 650 nm is incident on the substrate layer at an incident angle of 0°, with the incident angle being 0° when the light is incident perpendicularly to the substrate layer.

2. The dimming sheet according to claim 1, characterized in that the retardation on the short wavelength side of the first approximate straight line is 10500 or more.

3. The dimming sheet according to claim 1, characterized in that the difference between the reference angle Δ(BG) defined by the line segment connecting sampling points λ(450) and λ(550) and the reference angle Δ(GR) defined by the line segment connecting sampling points λ(550) and λ(650) is 3.5° or less.

4. The dimming sheet according to claim 1, characterized in that the retardation difference λ(B-G) between sampling points λ(450) and λ(550) is 1100 or more, and the retardation difference λ(G-R) between sampling points λ(550) and λ(650) is 650 or more.

5. The dimming sheet according to claim 1, characterized in that the retardation difference λ(B-R) between sampling points λ(450) and λ(650) is 1800 or more.

6. The dimming sheet according to claim 1, characterized in that at least one of the pair of substrate layers has a slope of -4 or greater of the second approximate straight line connecting the following three sampling points Λ(450), Λ(550), and Λ(650) in the retardation map. Λ(450): A retardation point when light with a wavelength of 450 nm is incident on the substrate layer at an incident angle of 50°, with the incident angle when light is incident perpendicularly to the substrate layer being 0°. Λ(550): A retardation point when light with a wavelength of 550 nm is incident on the substrate layer at an incident angle of 50°, with the incident angle when light is incident perpendicularly to the substrate layer being 0°. Λ(650): A retardation point when light with a wavelength of 650 nm is incident on the substrate layer at an incident angle of 50°, with the incident angle when light is incident perpendicularly to the substrate layer being 0°.

7. The dimming sheet according to claim 1, characterized in that the retardation on the short wavelength side of the second approximate straight line is 1050 or more and 7000 or less.

8. The dimming sheet according to claim 1, characterized in that at least one of the pair of substrate layers has a thickness of 90 μm or more and 200 μm or less.

9. A dimming module characterized by being configured by attaching a dimming sheet according to any one of claims 1 to 8 to a light-transmitting member.

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