Dimming sheet and method for manufacturing dimming sheet

Abstract

The dimming sheet reversibly switches from transparent to opaque by an orientation change of the liquid crystal compound. The light control sheet is provided with a light control layer that contains a polymer resin layer in which a plurality of voids are dispersed, and a liquid crystal composition that contains a liquid crystal compound and fills the voids. The percentage of the volume of the liquid crystal composition in the dimming layer relative to the sum of the volume of the polymer resin layer and the volume of the liquid crystal composition is 40% or more and 60% or less. The voids have a void diameter of 2 [mu] m or less.

Description

Technical Field

[0001] The present disclosure relates to a dimming film and a method for manufacturing the dimming film. Background Art

[0002] An example of a dimming sheet includes a dimming layer and a pair of transparent electrode layers sandwiching the dimming layer. The dimming sheet includes a pair of transparent substrates supporting the transparent electrode layers. The dimming layer contains a polymer resin layer and a liquid crystal compound dispersed in the polymer resin layer. The dimming sheet appears opaque when no voltage is applied to the dimming sheet, and appears transparent when a voltage that can change the orientation of the liquid crystal compound is applied to the dimming sheet. The dimming sheet is applied not only to windows of buildings, but is also gradually expanding to windows of airplanes, cars, etc. (see, for example, Patent Document 1).

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent No. 6414312 Summary of the invention

[0006] Technical problem to be solved by the invention

[0007] However, compared with people staying in buildings, passengers on airplanes, cars, etc. often sit closer to windows for longer periods of time. Therefore, since light passing through windows can easily illuminate passengers, when the dimming sheet is opaque, it is required that light incident on the dimming sheet is less likely to penetrate toward passengers, that is, it is required to suppress the sense of penetration of the dimming sheet. In addition, in order to protect the privacy of passengers from the outside of airplanes and cars, when the dimming sheet is opaque, it is required to suppress the sense of penetration of the dimming sheet from the inside of the airplane or car to the outside.

[0008] Means for solving technical problems

[0009] In the dimming sheet for solving the above technical problems, the transparent to opaque state is reversibly switched by changing the orientation of the liquid crystal compound. The dimming sheet has a dimming layer, which includes a polymer resin layer with a plurality of voids dispersed therein and a liquid crystal composition containing the liquid crystal compound and filling each void. The volume of the liquid crystal composition in the dimming layer is 40% or more and 60% or less relative to the sum of the volume of the polymer resin layer and the volume of the liquid crystal composition. The void diameter of the void is 2 μm or less.

[0010] The method for manufacturing a dimming sheet for solving the above technical problems is a method for manufacturing a dimming sheet that can be reversibly switched from transparent to opaque by changing the orientation of a liquid crystal compound. The method for manufacturing a dimming sheet includes forming a dimming layer by phase separation of a layer containing the liquid crystal compound and a photopolymerizable compound, wherein the dimming layer includes a polymer resin layer separated by a plurality of voids and a liquid crystal composition containing the liquid crystal compound and filled in each void. In the formation of the dimming layer, the phase separation is performed in such a manner that the percentage of the volume of the liquid crystal composition in the dimming layer relative to the total volume of the polymer resin layer and the volume of the liquid crystal composition is greater than 40% and less than 60%, and the void diameter of the void is less than 2 μm. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 It is a cross-sectional view showing a first example of the structure of the dimming sheet.

[0012] Figure 2 It is a cross-sectional view showing a second example of the structure of the dimming sheet.

[0013] Figure 3 This is a graph showing the relationship between the transparency value and the void diameter of Test Examples 1 to 6.

[0014] Figure 4 This is a graph showing the haze value of Test Example 7 when it is opaque and the haze value when it is transparent.

[0015] Figure 5 This is a graph showing the haze value of Test Example 8 when it is opaque and the haze value when it is transparent.

[0016] Figure 6 This is a graph showing the haze value of Test Example 9 when it is opaque and the haze value when it is transparent.

[0017] Figure 7 It is a curve showing the relationship between the thickness of the light-adjusting layer and the gap diameter.

[0018] Figure 8 It is a curve showing the relationship between the thickness of the dimming layer and the transparency value. DETAILED DESCRIPTION

[0019] Reference Figures 1 to 8 An embodiment of a dimming sheet and a method for manufacturing the dimming sheet will be described.

[0020] [structure]

[0021] like Figure 1As shown, the dimming device 10 of this embodiment includes a dimming plate 11 and a driving unit 12. The dimming plate 11 is reversibly switched from transparent to opaque by changing the orientation of the liquid crystal compound. In this embodiment, the style of the dimming plate 11 is a positive type. For the positive type dimming plate 11, when a voltage is applied to the dimming plate 11, the dimming plate 11 appears transparent. In contrast, when no voltage is applied to the dimming plate 11, the dimming plate 11 appears opaque.

[0022] The dimming sheet 11 may be applied to windows of moving objects such as vehicles and airplanes. In addition, the dimming sheet 11 may be applied to windows of various buildings such as residences, stations, and airports, partitions in offices, display windows in stores, and screens for projecting images. The dimming sheet 11 is attached to these application objects, for example, by an adhesive layer. The shape of the dimming sheet 11 may be flat or curved. The dimming sheet 11 may be flexible enough to follow the shape of the application object.

[0023] The dimming sheet 11 includes a dimming layer 21. The dimming layer 21 includes a polymer resin layer and a liquid crystal composition. A plurality of voids are dispersed in the polymer resin layer. The liquid crystal composition includes a liquid crystal compound and fills each void. The dimming layer 21 satisfies the following conditions 1 and 2.

[0024] (Condition 1) In the light-adjusting layer 21 , the percentage of the volume of the liquid crystal composition with respect to the total volume of the polymer resin layer and the volume of the liquid crystal composition is 40% or more and 60% or less.

[0025] (Condition 2) The void diameter of the void is 2 μm or less.

[0026] It should be noted that the percentage of the volume of the liquid crystal composition relative to the sum of the volume of the polymer resin layer and the volume of the liquid crystal composition is referred to as the volume occupancy of the liquid crystal composition. In addition, the percentage of the volume of the polymer resin layer relative to the sum of the volume of the polymer resin layer and the volume of the liquid crystal composition is referred to as the volume occupancy of the polymer resin layer.

[0027] When the thickness of the light-adjusting layer 21 is DLC and the pore diameter is DD, the light-adjusting layer 21 preferably satisfies at least one of the following conditions 3 and 4. That is, the light-adjusting layer 21 may satisfy only condition 3, only condition 4, or both conditions 3 and 4.

[0028] (Condition 3) Thickness DLC ≤ Void Diameter DD + 20 μm

[0029] (Condition 4) 17μm ≤ thickness DLC

[0030] The plurality of voids dispersed in the polymer resin may contain only isolated voids in the polymer resin layer, i.e., voids not connected to other voids, or only voids connected to other voids. Alternatively, the plurality of voids may contain both isolated voids in the polymer resin layer and voids connected to other voids.

[0031] The void diameter is an indicator of the void size. The void diameter is determined in the voids contained in the cross section orthogonal to the plane in which the light-adjusting layer 21 is unfolded. For the void diameter of each void, when the void has a circular shape, the diameter of the void is the void diameter. When the void has an elliptical shape, the length of the major axis of the void, i.e., the major diameter, is the void diameter. When the void has an indefinite shape, the diameter of the circle circumscribed with the void is the void diameter.

[0032] When calculating the void diameter of the dimming layer 21, the dimming layer is first cut along a plane orthogonal to the plane in which the dimming layer 21 is unfolded, thereby generating a cross section for measurement. The cross section for measurement is then observed using a scanning electron microscope (SEM), thereby measuring the void diameters of multiple voids contained in the cross section for measurement. Thereafter, the average void diameter is calculated by dividing the sum of the void diameters of each void by the number of voids. The average value of the void diameter is the void diameter of the dimming layer 21. The void diameter can be greater than 0.5 μm and less than 3.0 μm, and the upper limit of the void diameter is preferably less than 2.0 μm.

[0033] The liquid crystal compound contained in the liquid crystal composition is a positive liquid crystal compound having positive dielectric anisotropy. The refractive index anisotropy Δn of the liquid crystal compound is preferably greater than or equal to 0.15. The refractive index anisotropy Δn is a value calculated by subtracting the refractive index no of ordinary light from the refractive index ne of the liquid crystal compound for extraordinary light. The refractive index no of ordinary light of the liquid crystal compound may be greater than or equal to 1.51 and less than or equal to 1.71.

[0034] An example of the liquid crystal compound may be any one selected from Schiff base compounds, azo compounds, azoxy compounds, biphenyl compounds, terphenyl compounds, benzoate compounds, tolan compounds, pyrimidine compounds, cyclohexanecarboxylate compounds, cyclohexane compounds, phenylcyclohexane compounds and dioxane compounds. The liquid crystal composition may contain a first liquid crystal compound and a second liquid crystal compound of a different type from the first liquid crystal compound.

[0035] The polymer resin layer is a cured product of a photopolymerizable compound. When the refractive index of the polymer resin layer is np, the absolute value of the difference between the ordinary light refractive index no of the liquid crystal compound and the refractive index np of the polymer resin layer is preferably less than 0.08. The refractive index np of the polymer resin layer can be, for example, about 1.51. The photopolymerizable compound can be an ultraviolet curable compound or an electron beam curable compound. The photopolymerizable compound has compatibility with the liquid crystal composition. In order to improve the size controllability of the voids, it is preferred that the photopolymerizable compound is an ultraviolet curable compound. An example of an ultraviolet curable compound contains a polymerizable unsaturated bond at the end of the molecular structure. Alternatively, the ultraviolet curable compound contains a polymerizable unsaturated bond at a position other than the end of the molecular structure. The photopolymerizable compound can be one polymerizable compound, or can be a combination of two or more polymerizable compounds.

[0036] The ultraviolet curable compound is, for example, at least one selected from the group consisting of acrylate compounds, methacrylate compounds, styrene compounds, thiol compounds, and oligomers of these compounds.

[0037] Acrylate compounds include monoacrylate compounds, diacrylate compounds, triacrylate compounds, and tetraacrylate compounds. An example of an acrylate compound includes butyl ethyl acrylate, ethylhexyl acrylate, and cyclohexyl acrylate. An example of a methacrylate compound includes a dimethacrylate compound, a trimethacrylate compound, and a tetramethacrylate compound. An example of a methacrylate compound includes N,N-dimethylaminoethyl methacrylate, phenoxyethyl methacrylate, methoxyethyl methacrylate, and tetrahydrofurfuryl methacrylate. An example of a thiol compound includes 1,3-propanedithiol and 1,6-hexanedithiol. An example of a styrene compound includes styrene and methylstyrene.

[0038] The lower limit of the volume occupancy of the polymer resin layer can be 40%. The upper limit of the volume occupancy of the polymer resin layer can be 60%. The lower limit and upper limit of the percentage of the polymer resin layer are the ranges in which the liquid crystal compound undergoes phase separation from the cured product of the photopolymerizable compound during the curing process of the photopolymerizable compound. From the viewpoint of improving the mechanical strength of the polymer resin layer, it is preferred that the lower limit of the volume occupancy of the polymer resin layer is high. From the viewpoint of reducing the driving voltage of the liquid crystal compound, it is preferred that the upper limit of the volume occupancy of the polymer resin layer is low.

[0039] The liquid crystal composition may also contain a dichroic pigment. The dichroic pigment has an elongated shape. The absorbance in the visible light region in the long axis direction of the molecules of the dichroic pigment is greater than the absorbance in the visible light region in the short axis direction of the molecules. When the long axis direction of the dichroic pigment is parallel or approximately parallel to the incident direction of the light, the dichroic pigment is substantially transparent. In contrast, when the long axis direction of the dichroic pigment is perpendicular or approximately perpendicular to the incident direction of the light, the dichroic pigment presents a predetermined color.

[0040] Therefore, when the dichroic dye is oriented in a manner that the long axis direction is parallel or substantially parallel to the normal direction of the plane in which the light-adjusting layer 21 is unfolded, it is transparent. In contrast, when the dichroic dye is oriented in a manner that the long axis direction is perpendicular or substantially perpendicular to the normal direction of the plane in which the light-adjusting layer 21 is unfolded, it presents a predetermined color. The color presented by the dichroic dye is preferably black or a color close to black. The dichroic dye is driven by a guest-host mode with a liquid crystal compound as the main body, so that the dichroic dye presents a color.

[0041] The dichroic pigment can be selected from at least one of polyiodine, azo compounds, anthraquinone compounds, naphthoquinone compounds, azomethine compounds, tetrazine compounds, quinophthalone compounds, merocyanine compounds, perylene compounds, and dioxazine compounds. The dichroic pigment can be a pigment or a combination of two or more pigments. From the viewpoint of improving the light resistance of the dichroic pigment and the viewpoint of improving the two-color ratio, it is preferred that the dichroic pigment is at least one selected from azo compounds and anthraquinone compounds. It is more preferred that the dichroic pigment is an azo compound. The mass percentage of the dichroic pigment relative to the mass of the dimming layer 21 can be 0.5 mass % or more and 5 mass % or less.

[0042] In addition, the liquid crystal composition may contain, in addition to the above-mentioned liquid crystal compound and dichroic dye, a photopolymerizable composition for forming a polymer resin layer, for example.

[0043] The light modulating sheet 11 further includes a first transparent electrode layer 22, a second transparent electrode layer 23, a first transparent substrate 24, and a second transparent substrate 25. In the thickness direction of the light modulating sheet 11, the first transparent electrode layer 22 and the second transparent electrode layer 23 sandwich the light modulating layer 21. The first transparent substrate 24 supports the first transparent electrode layer 22. The second transparent substrate 25 supports the second transparent electrode layer 23.

[0044] The light modulator 11 includes a first electrode 22A mounted on a portion of the first transparent electrode layer 22 and a second electrode 23A mounted on a portion of the second transparent electrode layer 23. The light modulator 11 further includes a wiring 26 connected to the first electrode 22A and a wiring 26 connected to the second electrode 23A. The first electrode 22A and the second electrode 23A are connected to the drive unit 12 through the wiring 26, respectively.

[0045] The first transparent electrode layer 22 and the second transparent electrode layer 23 have light transmittance for transmitting visible light. The light transmittance of the first transparent electrode layer 22 enables visual identification of objects through the dimming sheet 11. The light transmittance of the second transparent electrode layer 23 is the same as that of the first transparent electrode layer 22, so that objects can be visually identified through the dimming sheet 11. The thickness of each transparent electrode layer 22, 23 can be, for example, greater than 0.005 μm and less than 0.1 μm. Thus, the appropriate driving of the dimming sheet 11 is ensured and the generation of cracks in the dimming sheet 11 can be suppressed when the dimming sheet 11 is bent. The material used to form each transparent electrode layer 22, 23 can be, for example, any one selected from indium tin oxide, fluorine-doped tin oxide, tin oxide, zinc oxide, carbon nanotubes and poly (3,4-ethylenedioxythiophene).

[0046] The material forming each transparent substrate 24, 25 may be a synthetic resin or an inorganic compound. Synthetic resins may be, for example, polyesters, polyacrylates, polycarbonates, and polyolefins. Polyesters may be, for example, polyethylene terephthalate and polyethylene naphthalate. Polyacrylates may be, for example, polymethyl methacrylate. Inorganic compounds may be, for example, silicon dioxide, silicon oxynitride, and silicon nitride. The thickness of each transparent substrate 24, 25 may be, for example, greater than 16 μm and less than 250 μm. By setting the thickness of the transparent substrates 24, 25 to greater than 16 μm, the processing and construction of the dimming film 11 is facilitated. By setting the thickness of the transparent substrates 24, 25 to less than 250 μm, the dimming film 11 may be manufactured in a roll-to-roll manner.

[0047] Each electrode 22A, 23A is, for example, a flexible printed circuit (FPC). The FPC includes a support layer, a conductor portion, and a protective layer. The conductor portion is sandwiched between the support layer and the protective layer. The support layer and the protective layer are formed of an insulating synthetic resin. The support layer and the protective layer are formed of, for example, polyimide. The conductor portion is formed of, for example, a metal film. The material forming the metal film may be, for example, copper. Each electrode 22A, 23A is not limited to an FPC, and may be, for example, a metal belt.

[0048] It should be noted that each electrode 22A, 23A is mounted on each transparent electrode layer 22, 23 via a conductive adhesive layer not shown in the figure. On the portion of each electrode 22A, 23A connected to the conductive adhesive layer, the conductor portion is exposed from the protective layer or the support layer. The conductive adhesive layer can be formed, for example, by an anisotropic conductive film (ACF: Anisotropic Conductive Film), anisotropic conductive paste (ACP: Anisotropic Conductive Paste), isotropic conductive film (ICF: IsotropicConductive Film) and isotropic conductive paste (ICP: Isotropic Conductive Paste). From the perspective of operability of the manufacturing process of the dimming device 10, the conductive adhesive layer is preferably an anisotropic conductive film.

[0049] Each wiring 26 can be formed of, for example, a metal wire and an insulating layer covering the metal wire. The wire is formed of, for example, copper or the like.

[0050] The driving unit 12 applies an AC voltage between the first transparent electrode layer 22 and the second transparent electrode layer 23. The driving unit 12 preferably applies an AC voltage having a rectangular wave shape between the pair of transparent electrode layers 22 and 23. It should be noted that the driving unit 12 may also apply an AC voltage having a shape other than a rectangular wave shape between the pair of transparent electrode layers 22 and 23. For example, the driving unit 12 may apply an AC voltage having a sine wave shape between the pair of transparent electrode layers 22 and 23.

[0051] In the dimming layer 21, the orientation of the liquid crystal compound changes due to the change in the voltage generated between the two transparent electrode layers 22 and 23. The change in the orientation of the liquid crystal compound will change the scattering degree, absorption degree and transmission degree of the visible light entering the dimming layer 21. The positive dimming film 11 has a relatively low haze value when the dimming film 11 is powered on, that is, when a potential difference is generated between the first transparent electrode layer 22 and the second transparent electrode layer 23. The positive dimming film 11 has a relatively high haze value when the dimming film 11 is not powered on, that is, when no potential difference is generated between the first transparent electrode layer 22 and the second transparent electrode layer 23. Therefore, the positive dimming film 11 is transparent when the dimming film 11 is powered on and is opaque when the dimming film 11 is not powered on.

[0052] The haze value of the light-controlling sheet 11 is calculated by a method based on JIS K 7136:2000 "Method for determining the haze of plastics-transparent materials".

[0053] like Figure 2As shown, the dimming sheet 11 may include a first dimming layer as one dimming layer 21 and a second dimming layer as another dimming layer 21. In the dimming sheet 11, the second dimming layer overlaps the first dimming layer. Figure 2 The dimming sheet 11 shown in the figure includes a first unit 11UN1 including a first dimming layer and a second unit 11UN2 including a second dimming layer. Each unit 11UN1 and 11UN2 has the same structure as previously described. Figure 1 The light control sheet 11 described above has the same structure as that of the light control sheet 11. That is, each unit 11UN1, 11UN2 includes a light control layer 21, a pair of transparent electrode layers 22, 23, and a pair of transparent substrates 24, 25.

[0054] Both the first dimming layer and the second dimming layer satisfy the above conditions 1 and 2. It should be noted that the above condition 3 may be satisfied by only the first dimming layer, or only the second dimming layer, or both the first dimming layer and the second dimming layer. In addition, condition 4 may be satisfied by only the first dimming layer, or only the second dimming layer, or both the first dimming layer and the second dimming layer.

[0055] In the dimming film 11, the second unit 11UN2 overlaps with the first unit 11UN1. The adhesive layer 13 is located between the second transparent substrate 25 of the first unit 11UN1 and the first transparent substrate 24 of the second unit 11UN2. The adhesive layer 13 is transparent and has adhesiveness and insulating properties. The adhesive layer 13 is formed of a transparent adhesive. The adhesive may be, for example, an optical clear adhesive (OCA). The thickness of the adhesive layer 13 is, for example, not less than 10 μm and not more than 100 μm.

[0056] It should be noted that, when the dimming sheet 11 includes the first dimming layer and the second dimming layer, at least one of the first dimming layer and the second dimming layer may contain a dichroic pigment. That is, only the first dimming layer may contain a dichroic pigment, only the second dimming layer may contain a dichroic pigment, or both the first dimming layer and the second dimming layer may contain a dichroic pigment.

[0057] [Manufacturing method]

[0058] The method for manufacturing the dimming sheet 11 includes forming a dimming layer 21 by phase separation of a layer containing a liquid crystal compound and a photopolymerizable compound, wherein the dimming layer 21 includes a plurality of polymer resin layers separated by gaps and a liquid crystal composition containing a liquid crystal compound and filling each gap. In forming the dimming layer 21, phase separation is performed so that the volume occupancy of the liquid crystal composition is 40% to 60% and the gap diameter of the gap is 2 μm or less.

[0059] When manufacturing the dimming sheet 11, first, a layer containing a liquid crystal compound and a photopolymerizable compound is formed. The layer containing a liquid crystal compound and a photopolymerizable compound is formed by, for example, applying a coating liquid. The coating liquid may contain a photopolymerization initiator, etc. in addition to the liquid crystal compound and the photopolymerizable compound. Next, a laminate of a pair of transparent electrode layers and a transparent substrate is prepared. Next, after a coating film is formed by applying the coating liquid to the first transparent electrode layer, the second laminate is overlapped with the first laminate in such a manner that the coating film is sandwiched between the pair of transparent electrode layers.

[0060] Next, light is irradiated to the coating film from at least one of the pair of transparent substrates, thereby curing the coating film. That is, light may be irradiated to the coating film only from the first transparent substrate of the pair of transparent substrates, or light may be irradiated to the coating film only from the second transparent substrate. Alternatively, light may be irradiated to the coating film from the first transparent substrate and light may be irradiated to the coating film from the second transparent substrate. In this way, by irradiating light to the layer of the liquid crystal compound and the photopolymerizable compound, the photopolymerizable compound is polymerized, so that the liquid crystal compound is phase-separated from the polymer resin layer. Thus, the light-adjusting layer 21 is formed.

[0061] It should be noted that after forming the dimming layer 21, a portion of each transparent electrode layer is exposed. Then, an electrode is installed on the exposed portion of the first transparent electrode layer, and an electrode is installed on the exposed portion of the second transparent electrode layer. Then, after wiring is installed on each electrode, the two wirings are connected to the driving unit 12. In this way, the dimming device 10 can be obtained.

[0062] [effect]

[0063] The dimming layer 21 of the dimming sheet 11 of the present disclosure satisfies both the above conditions 1 and 2. That is, the void diameter is less than 2 μm, and the voids filled with the liquid crystal composition are dispersed in the polymer resin layer at a density, that is, a number, of a volume occupancy rate of the liquid crystal compound of 40% or more and 60% or less. As a result, scattering is easily generated at the interface between the polymer resin layer and the liquid crystal composition, and thus, the transmission of parallel lines in the dimming layer 21 can be suppressed. As a result, the sense of penetration when the dimming sheet 11 is opaque can be suppressed.

[0064] The sense of transparency when the dimming sheet 11 is opaque varies according to the degree of scattering of parallel lines at the interface between the polymer resin layer and the liquid crystal composition. The higher the degree of scattering of parallel lines, the more turbid the dimming sheet 11 looks, and thus the sense of transparency of the dimming sheet 11 decreases.

[0065] The sense of penetration of the light-adjusting sheet 11 can be evaluated by the parallel line transmittance, or it can be evaluated by the transparency. The parallel line transmittance is the total light transmittance τ calculated according to JIS K 7136:2000 "Plastics - Method for determining haze" t Subtract the diffuse transmittance τ dIt should be noted that the diffuse transmittance τ d The transmittance of the transmitted light that is deviated from the incident light by 2.5° or more due to forward scattering among the transmitted light that passes through the test piece. In contrast, the amount of straight light that passes along the optical axis of the parallel light incident on the light-adjusting layer 21 among the light that passes through the light-adjusting layer 21 is set as the light amount L. C The light quantity L is the light quantity of the narrow-angle scattered light within ±2.5° relative to the optical axis of the parallel light. R When , the transparency is calculated by the following formula (1).

[0066] 100×(L C -L R ) / (L C +L R ) Formula (1)

[0067] Among them, the parallel line transmittance, which is an indicator of the penetrability of the dimming sheet 11, is a dull parameter that is difficult to be consistent with human visual perception. In contrast, the transparency, which is an indicator of the penetrability of the dimming sheet 11, is a sensitive parameter that is easy to be consistent with human visual perception. In the case of a test piece with high light absorption, the transparency is also a parameter that sensitively reflects the difference between the absorption degree of parallel light and the absorption degree of diffuse light.

[0068] Therefore, it is preferable to define the structure of the dimming layer 21 having appropriate scattering characteristics in a forward-type dimming sheet 11 that does not contain a structure in which light absorption is suppressed, that is, does not contain a dichroic pigment. In other words, according to the forward-type dimming sheet 11 that does not contain a dichroic pigment, the scattering degree of parallel lines at the interface between a simple polymer resin layer and a liquid crystal composition can be defined by a sensitive parameter.

[0069] It should be noted that when a dichroic dye is added to the structure of a predetermined polymer resin layer and a liquid crystal composition in the dimming layer 21 that does not contain a dichroic dye, the parallel light that affects the sense of penetration is absorbed only by the dichroic dye, and thus the sense of penetration of the dimming sheet 11 is further suppressed.

[0070] In addition, when condition 3 is met, the haze value when the dimming sheet 11 is opaque can be increased and the haze value when the dimming sheet 11 is transparent can be reduced. In this way, the sense of penetration when opaque can be suppressed while ensuring sufficient transparency when transparent. In addition, when condition 4 is met, the increase in the transparency value can be suppressed when the dimming sheet 11 is opaque.

[0071] In addition, compared with the dimming sheet 11 having only one dimming layer 21, the light incident on the dimming sheet 11 having the first dimming layer and the second dimming layer is further scattered in the dimming sheet 11 when the dimming sheet 11 is opaque. Therefore, the sense of penetration when the dimming sheet 11 is opaque can be further suppressed.

[0072] [Test example]

[0073] Reference Figure 3 to Figure 8 And Tables 1 to 3 illustrate the test examples.

[0074] [Volume Occupancy and Void Diameter of Liquid Crystal Composition]

[0075] The materials used in Test Examples 1 to 6 described below are described below.

[0076] First transparent electrode layer: indium tin oxide

[0077] Second transparent electrode layer: indium tin oxide

[0078] ·First transparent substrate: polyethylene terephthalate film

[0079] Second transparent substrate: polyethylene terephthalate film

[0080] Polymerization initiator: α-hydroxyacetophenone

[0081] Liquid crystal compounds: terphenyl compounds

[0082] ·Spacer: Spherical (PMMA)

[0083] UV-polymerizable compounds: acrylate monomers

[0084] [Test Example 1]

[0085] A liquid crystal compound, an ultraviolet polymerizable compound, a polymerization initiator, and a spacer having a diameter of 20 μm are mixed to generate a coating solution. At this time, the amount of the liquid crystal compound and the amount of the ultraviolet polymerizable compound are set to an amount such that the volume occupancy of the liquid crystal composition in the dimming layer after phase separation reaches 30%. Next, a coating layer having a thickness of 20 μm is formed on the first transparent electrode layer, and then the coating layer is laminated by the first transparent electrode layer and the second transparent electrode layer. Thereafter, a dimming sheet having a dimming layer having a thickness of 20 μm is obtained by irradiating the coating layer with ultraviolet rays having a wavelength of 360 nm from the first transparent substrate.

[0086] In Experimental Example 1, a dimming sheet with a gap diameter of 0.5 μm, a dimming sheet with a gap diameter of 1.0 μm, a dimming sheet with a gap diameter of 2.0 μm, a dimming sheet with a gap diameter of 2.5 μm, and a dimming sheet with a gap diameter of 3.0 μm were prepared. It should be noted that when preparing the dimming sheet with a gap diameter of 0.5 μm, the intensity of ultraviolet light was set to 35 mW / cm 2 When making a dimming sheet with a pore diameter of 1.0 μm, the intensity of the ultraviolet light is set to 15 mW / cm 2 When making a dimming sheet with a pore diameter of 1.5 μm, the intensity of the ultraviolet light is set to 8 mW / cm 2 When making a dimming sheet with a pore diameter of 2.0 μm, the intensity of ultraviolet light is set to 4 mW / cm 2 When making a dimming sheet with a pore diameter of 2.5 μm, the intensity of ultraviolet light is set to 1.5 mW / cm 2 When making a dimming sheet with a pore diameter of 3.0 μm, the intensity of ultraviolet light is set to 0.7 mW / cm 2 , set the ultraviolet irradiation time to 1200 seconds.

[0087] It should be noted that the volume occupancy of the liquid crystal compound in the dimming layer of each dimming sheet was calculated by the method described below, and it was confirmed that the volume occupancy of the liquid crystal composition in each dimming sheet was 30%.

[0088] [Test Example 2]

[0089] The dimming sheet of Test Example 2 was obtained in the same manner as Test Example 1 except that the liquid crystal compound and the ultraviolet polymerizable compound were used in such an amount that the volume occupancy of the liquid crystal composition in the dimming layer after phase separation in Test Example 1 reached 40%. It should be noted that, for the dimming layer of each dimming sheet, the volume occupancy of the liquid crystal compound was calculated by the method described below, and it was confirmed that the volume occupancy of the liquid crystal composition in each dimming sheet was 40%.

[0090] [Test Example 3]

[0091] The dimming sheet of Test Example 3 was obtained in the same manner as in Test Example 1 except that the liquid crystal compound and the ultraviolet polymerizable compound were used in such an amount that the volume occupancy of the liquid crystal composition in the dimming layer after phase separation in Test Example 1 reached 50%. It should be noted that, for the dimming layer of each dimming sheet, the volume occupancy of the liquid crystal compound was calculated by the method described below, and it was confirmed that the volume occupancy of the liquid crystal composition in each dimming sheet was 50%.

[0092] [Test Example 4]

[0093] The dimming sheet of Test Example 4 was obtained in the same manner as in Test Example 1 except that the liquid crystal compound and the ultraviolet polymerizable compound were used in such an amount that the volume occupancy of the liquid crystal composition in the dimming layer after phase separation in Test Example 1 reached 60%. It should be noted that, for the dimming layer of each dimming sheet, the volume occupancy of the liquid crystal compound was calculated by the method described below, and it was confirmed that the volume occupancy of the liquid crystal composition in each dimming sheet was 60%.

[0094] [Test Example 5]

[0095] The dimming sheet of Test Example 5 was obtained in the same manner as in Test Example 1 except that the liquid crystal compound and the ultraviolet polymerizable compound were used in such an amount that the volume occupancy of the liquid crystal composition in the dimming layer after phase separation in Test Example 1 reached 70%. It should be noted that, for the dimming layer of each dimming sheet, the volume occupancy of the liquid crystal compound was calculated by the method described below, and it was confirmed that the volume occupancy of the liquid crystal composition in each dimming sheet was 70%.

[0096] [Test Example 6]

[0097] The dimming sheet of Test Example 6 was obtained in the same manner as in Test Example 1 except that the liquid crystal compound and the ultraviolet polymerizable compound were used in such an amount that the volume occupancy of the liquid crystal composition in the dimming layer after phase separation in Test Example 1 reached 80%. It should be noted that, for the dimming layer of each dimming sheet, the volume occupancy of the liquid crystal compound was calculated by the method described below, and it was confirmed that the volume occupancy of the liquid crystal composition in each dimming sheet was 80%.

[0098] [Evaluation method]

[0099] [Gap diameter]

[0100] For the five types of dimming sheets contained in each test example, a cross section orthogonal to the plane in which the dimming sheet is unfolded, that is, a cross section along the thickness direction of the dimming sheet, is exposed. At this time, the entire dimming sheet is embedded with a resin before the cross section of the dimming layer is exposed. Next, after removing the liquid crystal composition contained in the dimming layer, the cross section is observed using a scanning electron microscope to measure the gap diameters of all gaps contained in a field of view. It should be noted that for each dimming sheet, the gap diameters of approximately 7 gaps are measured. Next, for each dimming sheet, the average value of the gap diameters is calculated, and the average value is set as the gap diameter.

[0101] [Volume Occupancy of Liquid Crystal Composition]

[0102] The cross section of the dimming sheet along the thickness direction is exposed by the same method as that used to measure the diameter of the voids. Next, the area in the cross section of the dimming sheet that does not contain spacers, i.e., the area determined by the unit width in the direction orthogonal to the thickness direction of the dimming sheet and the total thickness of the dimming layer, is set as the calculation area for the volume occupancy. At this time, the unit width is set to 1 mm. Next, the number of voids contained in the calculation area is counted, and then, by multiplying the void area calculated using the average diameter of the voids by the number of voids, the area occupied by the voids in the calculation area, i.e., the area occupied by the liquid crystal composition, is calculated. Next, the volume occupancy of the liquid crystal composition is calculated as a percentage of the area occupied by the liquid crystal composition relative to the area of ​​the calculation area.

[0103] [Transparency value]

[0104] The transparency of the five dimming sheets included in each test example was measured using a haze / transparency meter (BYK-Gardner) when the sheet was opaque, i.e., when the voltage applied between the transparent electrode layers was 0 V. The transparency was calculated using the above formula (1).

[0105] [Evaluation results]

[0106] Reference Figure 3 The evaluation results are explained.

[0107] like Figure 3 As shown, it can be seen that when comparing the transparency values ​​of dimming sheets with the same gap diameter, the transparency value is the lowest when the volume occupancy of the liquid crystal composition in the dimming layer is 50% and the dimming layer is opaque. In addition, it can be seen that when comparing the transparency values ​​of dimming sheets with the same gap diameter, the transparency values ​​in the cases where the volume occupancy of the liquid crystal composition in the dimming layer is less than 50% and greater than 50% are both higher than the transparency value when the volume occupancy of the liquid crystal composition is 50%.

[0108] It can be seen that when the volume occupancy rate of the liquid crystal composition in the dimming layer is less than 50%, the smaller the volume occupancy rate of the liquid crystal composition, the greater the transparency value. Conversely, it can be seen that when the volume occupancy rate of the liquid crystal composition in the dimming layer is greater than 50%, the greater the volume occupancy rate of the liquid crystal composition, the greater the transparency value.

[0109] Furthermore, it can be seen that regardless of the volume occupancy of the liquid crystal composition in the dimming layer, when comparing the transparency values ​​of dimming sheets having the same volume occupancy of the liquid crystal composition, the transparency value when the void diameter is 1.0 μm has a minimum value.

[0110] Furthermore, it can be seen that by containing the liquid crystal composition in the light-adjusting layer at a volume occupancy rate of 40% to 60% and containing it at a void diameter of 2.0 μm or less, the transparency value is 30% or less when opaque.

[0111] From the above results, it can be considered that in the range where the volume occupancy rate of the liquid crystal composition in the dimming layer is less than 50%, the volume occupancy rate of the polymer resin layer in the dimming layer is relatively increased, thereby suppressing the scattering in the dimming layer, and thus the transparency value is improved. On the other hand, it can be considered that in the range where the volume occupancy rate of the liquid crystal composition in the dimming layer is greater than 50%, the volume occupancy rate of the liquid crystal composition in the dimming layer is relatively increased, thereby suppressing the scattering in the dimming layer, and thus the transparency value is improved.

[0112] [Thickness and haze value of dimming layer]

[0113] [Test Example 7]

[0114] The dimming sheet of Experimental Example 7 was obtained in the same manner as in Experimental Example 3 except that the gap diameter in Experimental Example 3 was fixed at 1.5 μm and the thickness of the dimming layer was changed to five different values. It should be noted that in Experimental Example 7, the intensity of ultraviolet rays was set to 8 mW / cm 2 , and the irradiation time of ultraviolet rays was set to 105 seconds. In addition, in Experimental Example 7, a dimming sheet with a dimming layer thickness of 16 μm, a dimming sheet with a dimming layer thickness of 18 μm, a dimming sheet with a dimming layer thickness of 20 μm, a dimming sheet with a dimming layer thickness of 25 μm, and a dimming sheet with a dimming layer thickness of 30 μm were produced.

[0115] It should be noted that when forming a dimming layer with a thickness of 16μm, a spacer with a diameter of 16μm is used, and when forming a dimming layer with a thickness of 18μ, a spacer with a diameter of 18μm is used. In addition, when forming a dimming layer with a thickness of 25μm, a spacer with a diameter of 25μm is used, and when forming a dimming layer with a thickness of 30μm, a spacer with a diameter of 30μm is used. In addition, the volume occupancy of the liquid crystal compound is calculated for the dimming layer of each dimming film, and it can be seen that the volume occupancy of the liquid crystal composition in each dimming film is 50%.

[0116] [Test Example 8]

[0117] In Test Example 7, the intensity of ultraviolet light was set to 4 mW / cm 2The ultraviolet irradiation time was set to 210 seconds to fix the gap diameter to 2.0 μm, and the dimming sheet of Experimental Example 8 was obtained in the same manner as in Experimental Example 7. It should be noted that the volume occupancy of the liquid crystal compound in the dimming layer of each dimming sheet was calculated, and it can be seen that the volume occupancy of the liquid crystal composition in each dimming sheet was 50%.

[0118] [Test Example 9]

[0119] By setting the intensity of ultraviolet light in Test Example 7 to 0.7 mW / cm 2 The ultraviolet irradiation time was set to 1200 seconds to fix the gap diameter to 3.0 μm, and the dimming sheet of Experimental Example 9 was obtained in the same manner as in Experimental Example 7. It should be noted that the volume occupancy of the liquid crystal compound in the dimming layer of each dimming sheet was calculated, and it can be seen that the volume occupancy of the liquid crystal composition in each dimming sheet was 50%.

[0120] [Evaluation method]

[0121] [Gap diameter]

[0122] For the five types of dimming sheets included in each test example, the void diameters were measured by the same method as the evaluation method for the dimming sheets of test examples 1 to 6.

[0123] [Haze value]

[0124] For the five types of dimming sheets included in each test example, the haze value was measured using a haze meter (NDH7000SP, manufactured by Nippon Denshoku Industries Co., Ltd.) according to the method based on JIS K 7136:2000 "Method for determining the haze of plastic-transparent materials". It should be noted that for each dimming sheet, the haze value when the voltage value applied between the transparent electrodes is 0V when it is opaque and the haze value when the voltage value applied between the transparent electrode layers is 60V when it is transparent are measured.

[0125] [Evaluation results]

[0126] Reference Figure 4 to Figure 7 The evaluation results are explained. Figure 4 The haze value of Test Example 7 is shown. Figure 5 The haze value of Test Example 8 is shown. Figure 6 The haze value of Test Example 9 is shown. It should be noted that Figures 4 to 6 In any of the figures, the haze value when the dimming film appears opaque is represented by a black dot, and the haze value when the dimming film appears transparent is represented by a black triangle.

[0127] like Figure 4As shown, it can be seen that in Test Example 7, the haze value when the dimming sheet is opaque is 98.9% when the thickness of the dimming layer is 16μm, 99.0% when the thickness of the dimming layer is 18μm, and 99.2% when the thickness of the dimming layer is 20μm. In addition, it can be seen that the haze value when the dimming sheet is opaque is 99.4% when the thickness of the dimming layer is 25μm, and 99.5% when the thickness of the dimming sheet is 30μm. It can be seen that regardless of the thickness of the dimming layer, the haze value when the dimming sheet is opaque is above 98%. The approximate formula obtained from the 5 haze values ​​is shown below.

[0128] y=0.0414x+98.265

[0129] It can be seen that the haze value when the dimming sheet is transparent is 3.3% when the thickness of the dimming layer is 16μm, 3.8% when the thickness of the dimming layer is 18μm, and 4.4% when the thickness of the dimming layer is 20μm. In addition, it can be seen that the haze value when the dimming sheet is transparent is 6.4% when the thickness of the dimming layer is 25μm, and 8.2% when the thickness of the dimming layer is 30μm. The approximate formula obtained from the five haze values ​​is shown below.

[0130] y=0.3603x-2.6301

[0131] It can be seen from the approximate formula that the thickness of the dimming layer having a haze value of 5% or less when the dimming sheet is transparent is 21.18 μm or less.

[0132] like Figure 5 As shown, it can be seen that in Test Example 8, the haze value when the dimming sheet is opaque is 98.5% when the thickness of the dimming layer is 16μm, 98.6% when the thickness of the dimming layer is 18μm, and 98.7% when the thickness of the dimming layer is 20μm. In addition, it can be seen that the haze value when the dimming sheet is opaque is 98.8% when the thickness of the dimming layer is 25μm, and 99.0% when the thickness of the dimming layer is 30μm. It can be seen that regardless of the thickness of the dimming layer, the haze value when the dimming sheet is opaque is above 98%. The approximate formula obtained from the 5 haze values ​​is shown below.

[0133] y=0.0335x+97.989

[0134] It can be seen that the haze value when the dimming sheet is transparent is 3.2% when the thickness of the dimming layer is 16μm, 3.5μm when the thickness of the dimming layer is 18μm, and 4.2% when the thickness of the dimming layer is 20μm. In addition, it can be seen that the haze value when the dimming sheet is transparent is 6.0% when the thickness of the dimming layer is 25μm, and 8.0% when the thickness of the dimming layer is 30μm. The approximate formula obtained from the five haze values ​​is shown below.

[0135] y=0.3523x-2.7008

[0136] It can be seen from the approximate formula that the thickness of the dimming layer with a haze value of 5% or less when the dimming sheet is transparent is 21.86 μm or less.

[0137] like Figure 6 As shown, it can be seen that in Test Example 9, the haze value when the dimming sheet is opaque is 98.1% when the thickness of the dimming layer is 16μm, 98.3% when the thickness of the dimming layer is 18μm, and 98.5% when the thickness of the dimming layer is 20μm. It can be seen that the haze value when the dimming sheet is opaque is 98.7% when the thickness of the dimming layer is 25μm, and 98.8% when the thickness of the dimming layer is 30μm. It can be seen that regardless of the thickness of the dimming layer, the haze value when the dimming sheet is opaque is above 98%. The approximate formula obtained from the 5 haze values ​​is shown below.

[0138] y=0.048x+97.434

[0139] It can be seen that the haze value when the dimming sheet is transparent is 2.9% when the thickness of the dimming layer is 16μm, 3.2% when the thickness of the dimming layer is 18μm, and 4.0μm when the thickness of the dimming layer is 20μm. It can be seen that the haze value when the dimming sheet is transparent is 5.5% when the thickness of the dimming layer is 25μm, and 7.8% when the thickness of the dimming layer is 30μm. The approximate formula obtained from the five haze values ​​is shown below.

[0140] y=0.3523x-3.0008

[0141] It can be seen from the approximate formula that the thickness of the dimming layer with a haze value of 5% or less when the dimming sheet is transparent is 22.71 μm or less.

[0142] like Figure 7 As shown, the thickness of the light-adjusting layer obtained by the approximate formula in each of Experimental Examples 7 to 9 is plotted on a two-dimensional plane defined by the gap diameter and the thickness of the light-adjusting layer. The approximate formula obtained from the three values ​​used for plotting is as follows.

[0143] y=0.9957x+19.759

[0144] Therefore, it is considered that in order to satisfy the haze value of 98% or more when the dimming sheet is opaque and the haze value of 5% or less when the dimming sheet is transparent, the thickness DLC μm and the pore diameter DD μm of the dimming layer preferably satisfy the following formula.

[0145] Thickness DLC≤Void diameter DD+20μm

[0146] [Thickness and transparency of dimming layer]

[0147] [Test Example 10]

[0148] The dimming sheet of Experimental Example 10 was obtained in the same manner as in Experimental Example 3 except that the gap diameter in Experimental Example 3 was fixed at 2.0 μm and the thickness of the dimming layer was changed to 6 different values. It should be noted that in Experimental Example 10, the intensity of ultraviolet rays was set to 4 mW / cm 2 , and the irradiation time of ultraviolet rays is set to 210 seconds. In addition, in Experimental Example 10, a dimming sheet with a dimming layer thickness of 14 μm, a dimming sheet with a dimming layer thickness of 16 μm, a dimming sheet with a dimming layer thickness of 20 μm, a dimming sheet with a dimming layer thickness of 25 μm, a dimming sheet with a dimming layer thickness of 28 μm, and a dimming sheet with a dimming layer thickness of 30 μm were manufactured.

[0149] It should be noted that when forming a dimming layer with a thickness of 14 μm, a spacer with a diameter of 14 μm is used, and when forming a dimming layer with a thickness of 16 μm, a spacer with a diameter of 16 μm is used. In addition, when forming a dimming layer with a thickness of 25 μm, a spacer with a diameter of 25 μm is used, and when forming a dimming layer with a thickness of 28 μm, a spacer with a diameter of 28 μm is used. In addition, when forming a dimming layer with a thickness of 30 μm, a spacer with a diameter of 30 μm is used.

[0150] Furthermore, the volume occupancy of the liquid crystal compound in the dimming layer of each dimming film was calculated, and it was found that the volume occupancy of the liquid crystal compound in each dimming film was 50%.

[0151] [Evaluation method]

[0152] [Transparency value]

[0153] For the six types of dimming sheets included in Test Example 10, the transparency values ​​when the dimming sheets were opaque were measured in the same manner as the evaluation method for the dimming sheets of Test Examples 1 to 6.

[0154] [Evaluation results]

[0155] Reference Figure 8 The evaluation results are explained.

[0156] like Figure 8As shown, it can be seen that in Test Example 10, the transparency value of the dimming sheet when it is opaque is 37.0% when the thickness of the dimming layer is 14μm, 25.6% when the thickness of the dimming layer is 16μm, and 17.6% when the thickness of the dimming layer is 20μm. The transparency value of the dimming sheet when it is opaque is 18.0% when the thickness of the dimming layer is 25μm, 17.6% when the thickness of the dimming layer is 28μm, and 17.3% when the thickness of the dimming layer is 30μm.

[0157] Among the six transparency values, the approximate formula obtained from the transparency value when the thickness of the light-adjusting layer is 14 μm and the transparency value when the thickness of the light-adjusting layer is 16 μm is as follows.

[0158] y=-5.7x+116.8

[0159] In contrast, the approximate formula obtained from the transparency value when the thickness of the dimming layer is 20μm, the transparency value when the thickness of the dimming layer is 25μm, the transparency value when the thickness of the dimming layer is 28μm, and the transparency value when the thickness of the dimming layer is 30μm is as shown below.

[0160] y=-0.0278x+18.34

[0161] According to the two approximate expressions, it can be considered that in order to satisfy the transparency value of 20% or less when the light-adjusting sheet is opaque, the thickness of the light-adjusting layer DLC preferably satisfies the following conditions.

[0162] 17μm≤thicknessDLC

[0163] [Comparison of optical properties of various structures]

[0164] In Test Examples 12 to 20 described below, the following dichroic dyes were used.

[0165] ·Dichroic pigments: azo compounds

[0166] [Test Example 11]

[0167] The dimming sheet of Test Example 11 was obtained in the same manner as Test Example 3 except that the pore diameter in Test Example 3 was set to 2.0 μm. It should be noted that the volume occupancy of the dimming layer of the dimming sheet was calculated, and the volume occupancy of the liquid crystal composition in each dimming sheet was 50%.

[0168] [Test Example 12]

[0169] In Experimental Example 11, a dimming sheet of Experimental Example 12 was obtained in the same manner as in Experimental Example 11 except that a liquid crystal compound and an ultraviolet polymerizable compound were used in such an amount that the volume occupancy rate of the liquid crystal composition in the dimming layer after phase separation reached 50%, and a dichroic pigment was added to the coating liquid. It should be noted that in Experimental Example 12, when the total amount of the coating liquid containing the dichroic pigment was set to 100% by mass, the concentration of the dichroic pigment was set to 2% by mass. It should be noted that, when the volume occupancy rate of the dimming layer of the dimming sheet was calculated, it can be seen that the volume occupancy rate of the liquid crystal composition was 50%.

[0170] [Test Example 13]

[0171] A dimming sheet of Test Example 11 and a dimming sheet of Test Example 12 were prepared. Next, the dimming sheet of Test Example 12 was attached to the dimming sheet of Test Example 11 by using an adhesive layer having a thickness of 30 μm formed by using an optical transparent adhesive. Thus, a dimming sheet of Test Example 13 was obtained. It should be noted that the volume occupancy of the dimming layer of each dimming sheet was calculated, and it can be seen that the volume occupancy of the liquid crystal composition in each dimming sheet was 50%.

[0172] [Test Example 14]

[0173] In Experiment 13, two dimming sheets of Experiment 12 were prepared, and the dimming sheet of Experiment 14 was obtained in the same manner as Experiment 13. It should be noted that the volume occupancy of the dimming layer of each dimming sheet was calculated, and it can be seen that the volume occupancy of the liquid crystal composition in each dimming sheet was 50%.

[0174] [Test Example 15]

[0175] In Experimental Example 12, the dimming sheet of Experimental Example 15 was obtained in the same manner as in Experimental Example 12, except that the liquid crystal compound and the ultraviolet polymerizable compound were used in such an amount that the volume occupancy of the liquid crystal composition in the dimming layer after phase separation reached 50%, and the concentration of the dichroic pigment was changed to 1 mass %. It should be noted that, when the volume occupancy of the dimming layer of each dimming sheet was calculated, it can be seen that the volume occupancy of the liquid crystal composition in each dimming sheet was 50%.

[0176] [Test Example 16]

[0177] In Experiment 13, the dimming sheet of Experiment 15 was prepared instead of the dimming sheet of Experiment 12, and the dimming sheet of Experiment 16 was obtained in the same manner as in Experiment 13. It should be noted that the volume occupancy of the dimming layer of each dimming sheet was calculated, and it can be seen that the volume occupancy of the liquid crystal composition in each dimming sheet was 50%.

[0178] [Test Example 17]

[0179] In Experiment 16, two dimming sheets of Experiment 15 were prepared, and the dimming sheet of Experiment 17 was obtained in the same manner as Experiment 16. It should be noted that the volume occupancy of the dimming layer of each dimming sheet was calculated, and it can be seen that the volume occupancy of the liquid crystal composition in each dimming sheet was 50%.

[0180] [Test Example 18]

[0181] In Experimental Example 12, the dimming sheet of Experimental Example 18 was obtained in the same manner as in Experimental Example 12 except that the liquid crystal compound and the ultraviolet polymerizable compound were used in such an amount that the volume occupancy of the liquid crystal composition in the dimming layer after phase separation reached 50%, and the concentration of the dichroic pigment was changed to 0.5% by mass. It should be noted that, when the volume occupancy of the dimming layer of each dimming sheet was calculated, it can be seen that the volume occupancy of the liquid crystal composition in each dimming sheet was 50%.

[0182] [Test Example 19]

[0183] The dimming sheet of Test Example 19 was obtained in the same manner as in Test Example 13 except that the dimming sheet of Test Example 18 was prepared in place of the dimming sheet of Test Example 12 in Test Example 13. It should be noted that the volume occupancy of the dimming layer of each dimming sheet was calculated, and it can be seen that the volume occupancy of the liquid crystal composition in each dimming sheet was 50%.

[0184] [Test Example 20]

[0185] In Experiment 19, two dimming sheets of Experiment 18 were prepared, and the dimming sheet of Experiment 20 was obtained in the same manner as Experiment 19. It should be noted that the volume occupancy of the dimming layer of each dimming sheet was calculated, and it can be seen that the volume occupancy of the liquid crystal composition in each dimming sheet was 50%.

[0186] [Evaluation method]

[0187] In all the evaluation methods of optical characteristics described below, for a dimming sheet having two dimming layers, the magnitudes of voltages applied to the two dimming layers are equal both when the dimming sheet is opaque and when it is transparent.

[0188] [Haze value]

[0189] The haze value of the dimming sheet of each Test Example was measured by the same method as the evaluation method for the dimming sheets of Test Examples 7 to 9.

[0190] [Total light transmittance]

[0191] For the dimming sheet of each test example, the total light transmittance was measured using a haze meter (NDH7000SP, manufactured by Nippon Denshoku Industries Co., Ltd.) according to the method based on JIS K 7136:2000 "Method for determining the haze of plastic-transparent materials". It should be noted that for each dimming sheet, the total light transmittance when the voltage value applied between the transparent electrodes is 0V when it is opaque and the total light transmittance when the voltage value applied between the transparent electrode layers is 60V when it is transparent are measured.

[0192] [Parallel line transmittance]

[0193] For the dimming sheet of each test example, the parallel line transmittance was measured using a haze meter (NDH7000SP, manufactured by Nippon Denshoku Industries Co., Ltd.) according to the method based on JIS K 7136:2000 "Plastics - Method for determining the haze of transparent materials". It should be noted that for each dimming sheet, the parallel line transmittance when the voltage value applied between the transparent electrodes is 0V when it is opaque and the parallel line transmittance when the voltage value applied between the transparent electrode layers is 60V when it is transparent are measured.

[0194] [Transparency value]

[0195] For the dimming sheet of each test example, the transparency value was measured by the same method as the evaluation method for the dimming sheets of Test Examples 1 to 6.

[0196] [Evaluation results]

[0197] The evaluation results will be described with reference to Tables 1 to 3.

[0198] Table 1 shows the results of evaluating the optical characteristics of the dimming sheets of Test Examples 11 to 14.

[0199] Table 1

[0200]

[0201] As shown in Table 1, it can be seen that the haze values ​​of the dimming sheets of Test Examples 11 to 14 when the dimming sheets are opaque are all above 98%. In addition, it can be seen that the transparency value of the dimming sheet of Test Example 11 when the dimming sheet is opaque is below 20%. Furthermore, it can be seen that the transparency values ​​of the dimming sheets of Test Examples 13 and 14 when the dimming sheets are opaque are 0%. On the other hand, it can be seen that the haze value of the dimming sheet of Test Example 11 when the dimming sheet is transparent is below 5%.

[0202] Table 2 shows the results of evaluating the optical characteristics of the dimming sheets of Test Examples 15 to 17.

[0203] Table 2

[0204]

[0205] As shown in Table 2, the haze values ​​of the dimming sheets of Test Examples 15 to 17 when the dimming sheets are opaque are all above 98%. In addition, it can be seen that the transparency of the dimming sheets of Test Examples 16 and 17 when the dimming sheets are opaque is 0%.

[0206] Table 3 shows the results of evaluating the optical characteristics of the dimming sheets of Test Examples 18 to 20.

[0207] Table 3

[0208]

[0209] As shown in Table 3, it can be seen that the haze values ​​of the dimming sheets of Test Examples 18 to 20 when the dimming sheets are opaque are all above 98%. In addition, it can be seen that the transparency of the dimming sheets of Test Examples 19 and 20 when the dimming sheets are opaque is 0%.

[0210] When manufacturing the dimming sheet of Test Example 3, the blending ratio of each material was set as follows, assuming that the mass of the coating liquid composed of the liquid crystal compound, the ultraviolet polymerizable compound, the polymerization initiator, and the spacer was 100 mass %.

[0211]

[0212] Since the mixing ratio of the liquid crystal compound calculated as the liquid crystal composition in the coating liquid is proportional to the volume occupancy of the liquid crystal composition in the light-adjusting layer, the mixing ratio of the liquid crystal compound is increased or decreased accordingly in each of the test examples except for Test Example 3. In addition, the coating liquid in each of the test examples except for Test Example 3 was prepared by reducing the mixing ratio of the ultraviolet polymerizable compound only by the portion where the mixing ratio of the liquid crystal compound was increased or by increasing the mixing ratio of the ultraviolet polymerizable compound only by the portion where the mixing ratio of the liquid crystal compound was decreased.

[0213] In addition, in Test Examples 12 to 20, the proportion of the liquid crystal compound was reduced by only the proportion of the dichroic pigment. That is, in Test Examples 12 to 14, the proportion of the liquid crystal compound was 48% by mass and the proportion of the dichroic pigment was 2% by mass. In Test Examples 15 to 17, the proportion of the liquid crystal compound was 49% by mass and the proportion of the dichroic pigment was 1% by mass. In Test Examples 18 to 20, the proportion of the liquid crystal compound was 49.5% by mass and the proportion of the dichroic pigment was 0.5% by mass.

[0214] As described above, according to one embodiment of the dimming sheet and the method for manufacturing the dimming sheet, the following effects can be obtained.

[0215] (1) The voids having a void diameter of less than 2 μm and filled with the liquid crystal composition are dispersed in the polymer resin layer at a density of 40% to 60% of the volume occupancy of the liquid crystal compound, in other words, at such a quantity. As a result, scattering is easily generated at the interface between the polymer resin layer and the liquid crystal composition, so that the transmission of parallel lines in the light-adjusting layer 21 is suppressed, and as a result, the sense of penetration when the light-adjusting sheet 11 is opaque is suppressed.

[0216] (2) The haze value when the dimming sheet 11 is opaque can be increased and the haze value when the dimming sheet 11 is transparent can be reduced.

[0217] (3) The increase in the transparency value when the light control sheet 11 is opaque is suppressed.

[0218] (4) Compared with the case where the dimming sheet 11 has only one dimming layer 21, when the dimming sheet 11 has two dimming layers, when the dimming sheet 11 is opaque, light incident on the dimming sheet 11 is further scattered inside the dimming sheet 11. Therefore, the sense of penetration when the dimming sheet 11 is opaque can be further suppressed.

[0219] It should be noted that the above-mentioned embodiment can be implemented with modifications as follows.

[0220] [Transparent substrate]

[0221] When the light adjusting sheet 11 includes two light adjusting layers, it may have the following structure.

[0222] That is, transparent electrode layers may be formed on both sides of a transparent substrate, and each transparent electrode layer may have a dimming layer. Figure 2 In the described dimming sheet 11 , the adhesive layer 13 and the first transparent substrate 24 of the first unit 11UN1 or the second transparent substrate 25 of the second unit 11UN2 may be omitted.

[0223] [Dimmer style]

[0224] The dimming film 11 may also be of a reverse type. The reverse dimming film includes a first orientation layer and a second orientation layer in addition to the layers of the forward dimming film 11. The first orientation layer is located between the dimming layer 21 and the first transparent electrode layer 22. The second orientation layer is located between the dimming layer and the second transparent electrode layer. The dimming layer contains a negative liquid crystal compound with negative dielectric anisotropy instead of a positive liquid crystal compound with positive dielectric anisotropy.

[0225] The first alignment layer and the second alignment layer are vertical alignment layers. Each alignment layer aligns the long axis of the liquid crystal compound in a manner perpendicular to the surface opposite to the surface of each alignment layer in contact with the first transparent electrode layer 22 and the surface opposite to the surface of each alignment layer in contact with the second transparent electrode layer 23. It should be noted that the alignment layer may also align the liquid crystal compound in a manner in which the long axis is tilted by a few degrees relative to the vertical within a range in which the long axis of the liquid crystal compound is substantially perpendicular to each surface.

[0226] The materials used to form the alignment layer include organic compounds, inorganic compounds, and mixtures thereof. Examples of organic compounds include polyimide, polyamide, polyvinyl alcohol, and cyanide compounds. Examples of inorganic compounds include silicon oxide and zirconium oxide. It should be noted that the material used to form the alignment layer may also be organosilicon. Organosilicon is a compound having an inorganic part and an organic part. The thickness of each alignment layer may be, for example, greater than 0.02 μm and less than 0.5 μm.

[0227] The reverse dimming film has a relatively high haze value when the dimming film is powered on, that is, when a potential difference is generated between the first transparent electrode layer 22 and the second transparent electrode layer 23. The reverse dimming film has a relatively low haze value when the dimming film is not powered on, that is, when no potential difference is generated between the first transparent electrode layer 22 and the second transparent electrode layer 23. Therefore, the reverse dimming film is opaque when the dimming film is powered on and transparent when the dimming film is not powered on.

Claims

1. A dimming film, which is a dimming film that can be reversibly switched from transparent to opaque by changing the orientation of a liquid crystal compound, wherein: The dimming sheet includes a dimming layer, wherein the dimming layer includes a polymer resin layer having a plurality of voids dispersed therein and a liquid crystal composition containing the liquid crystal compound and filling the voids. In the dimming layer, the percentage of the volume of the liquid crystal composition to the total volume of the polymer resin layer and the volume of the liquid crystal composition is greater than or equal to 40% and less than or equal to 60%, The voids have a void diameter of 2 μm or less.

2. The dimming sheet according to claim 1, wherein: When the thickness of the dimming layer is DLC μm and the diameter of the gap is DD μm, the following conditions are satisfied: Thickness DLC≤void diameter DD+20μm.

3. The dimming sheet according to claim 2, wherein: Meet 17μm≤DLC thickness.

4. The dimming sheet according to any one of claims 1 to 3, comprising: A first dimming layer which is the first of the dimming layers; and A second dimming layer is a second dimming layer, The second dimming layer overlaps with the first dimming layer.

5. A method for manufacturing a dimming film, wherein the dimming film is a dimming film that can be reversibly switched from transparent to opaque by changing the orientation of a liquid crystal compound, The method for manufacturing the dimming sheet includes forming a dimming layer by phase separation of a layer containing the liquid crystal compound and a photopolymerizable compound, wherein the dimming layer includes a polymer resin layer having a plurality of voids dispersed therein and a liquid crystal composition containing the liquid crystal compound and filling the voids. In the formation of the dimming layer, the phase separation is performed in such a manner that the volume percentage of the liquid crystal composition in the dimming layer relative to the total volume of the polymer resin layer and the volume of the liquid crystal composition is greater than 40% and less than 60%, and the void diameter of the void is less than 2 μm.

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