dimmer

Abstract

The dimming sheet of the present invention comprises a first transparent electrode layer, a second transparent electrode layer, a dimming layer, and a first orientation layer. The dimming layer comprises a resin layer (31P) located between the first transparent electrode layer and the second transparent electrode layer, and a liquid crystal composition containing liquid crystal molecules. Voids (31D) are dispersed in the resin layer, and the liquid crystal composition fills the voids. The first orientation layer is sandwiched between the first transparent electrode layer and the dimming layer, and is configured such that the haze of the dimming layer can be increased by applying a voltage to the first transparent electrode layer. The dimming layer comprises a first surface in contact with the first orientation layer, and the percentage of the total area of ​​all voids relative to the area of ​​the first surface is the area ratio of the voids in the first surface, and the area ratio is 49% or more.

Description

Technical Field

[0001] The present disclosure relates to an inverse type dimming sheet including an alignment layer. Background Art

[0002] The reverse-type dimming film has a dimming layer containing liquid crystal molecules, and a pair of alignment layers that contact and sandwich the dimming layer. Each alignment layer is, for example, a vertical alignment layer, and when there is no potential difference between the pair of transparent electrode layers, the liquid crystal molecules are aligned in such a way that the long axis of each liquid crystal molecule is approximately perpendicular to the alignment layer. Therefore, the reverse-type dimming film is transparent when there is no potential difference between the pair of transparent electrode layers. On the other hand, when there is a potential difference between the pair of transparent electrode layers, the liquid crystal molecules are aligned in a direction perpendicular to the direction of the electric field, and the dimming film has an opaque state (for example, see Patent Document 1).

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2019-194654 Summary of the Invention

[0006] Technical problem to be solved by the invention

[0007] There is a new demand for an inversion-type dimming sheet having such a structure to achieve opacity when a potential difference is generated between a pair of transparent electrode layers, and to improve transparency when no potential difference is generated between the pair of transparent electrode layers.

[0008] An object of the present disclosure is to provide a dimming sheet capable of improving transparency in a state where no potential difference is generated between a pair of transparent electrode layers.

[0009] Means for solving technical problems

[0010] One embodiment of a dimming sheet includes a first transparent electrode layer, a second transparent electrode layer, a dimming layer, and a first alignment layer. The dimming layer comprises a resin layer positioned between the first and second transparent electrode layers, and a liquid crystal composition containing liquid crystal molecules. Voids are dispersed in the resin layer, and the liquid crystal composition fills the voids. The first alignment layer is sandwiched between the first transparent electrode layer and the dimming layer, and is configured such that the haze of the dimming layer can be increased by applying a voltage to the first transparent electrode layer. The dimming layer includes a first surface in contact with the first alignment layer, and the percentage of the total area of ​​all voids relative to the area of ​​the first surface is the area ratio of the voids on the first surface, and this area ratio is 49% or greater.

[0011] With the dimming sheet described above, the area ratio of the voids in the first surface is 49% or greater. Compared to a case with a lower area ratio, the voids are more likely to be located closer to the first surface than in the center of the dimming layer along the thickness direction of the dimming layer. Consequently, the alignment control force of the first alignment layer acts on more liquid crystal molecules in the dimming layer, improving the transparency of the dimming sheet even when no potential difference is generated between the pair of transparent electrode layers. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 This is a cross-sectional view showing the structure of a dimming device in one embodiment together with a driving unit.

[0013] Figure 2 To indicate schematically Figure 1 The illustrated diagram is a plan view of the structure of the first surface of the light-adjusting layer included in the light-adjusting sheet.

[0014] Figure 3 To indicate schematically Figure 1 The figure shows a cross-sectional view of the structure of a dimming sheet included in the dimming device.

[0015] Figure 4 This is a SEM image of the first surface of the light-adjusting layer in the light-adjusting sheet of Example 1.

[0016] Figure 5 This is an SEM image of a cross section of the light-adjusting layer in the light-adjusting sheet of Example 1.

[0017] Figure 6 This is a SEM image of the first surface of the light-adjusting layer in the light-adjusting sheet of Example 5.

[0018] Figure 7 This is an SEM image of a cross section of the light-adjusting layer in the light-adjusting sheet of Example 5.

[0019] Figure 8 This is a SEM image of the first surface of the light-adjusting layer in the light-adjusting sheet of Comparative Example 1.

[0020] Figure 9 This is an SEM image of a cross section of the light-adjusting layer in the light-adjusting sheet of Comparative Example 1. DETAILED DESCRIPTION

[0021] Reference Figures 1 to 9 An embodiment of a dimming chip is described. Hereinafter, a dimming device, a dimming chip, and an embodiment are described in order.

[0022] [Dimming device]

[0023] Reference Figure 1 A dimming device is described.

[0024] like Figure 1As shown, the dimming device 10 includes a dimming unit 11 including an inverting dimming plate 21 and a driving unit 12 .

[0025] The dimming sheet 21 includes a dimming layer 31, a first alignment layer 32, a second alignment layer 33, a first transparent electrode layer 34, and a second transparent electrode layer 35. In the dimming sheet 21, the first alignment layer 32 and the second alignment layer 33 sandwich the dimming layer 31 in the thickness direction of the dimming layer 31. The first transparent electrode layer 34 and the second transparent electrode layer 35 sandwich the pair of alignment layers 32 and 33 in the thickness direction of the dimming layer 31. The dimming sheet 21 further includes a first transparent substrate 36 that supports the first transparent electrode layer 34 and a second transparent substrate 37 that supports the second transparent electrode layer 35.

[0026] The dimming cell 11 includes a first electrode 22A mounted on a portion of the first transparent electrode layer 34 and a second electrode 22B mounted on a portion of the second transparent electrode layer 35. The dimming cell 11 further includes a first wiring 23A connected to the first electrode 22A and a second wiring 23B connected to the second electrode 22B. The first electrode 22A is connected to the driving unit 12 via the first wiring 23A, and the second electrode 22B is connected to the driving unit 12 via the second wiring 23B.

[0027] The dimming layer 31 includes a first surface 31F that contacts the first alignment layer 32 and a second surface 31S that contacts the second alignment layer 33. Furthermore, the dimming layer 31 includes a transparent resin layer and a liquid crystal composition. The resin layer has voids filled with the liquid crystal composition. The liquid crystal composition fills the voids in the resin layer. The liquid crystal composition contains liquid crystal molecules. An example of the liquid crystal molecule is any one selected from the group consisting of Schiff base, azo, azoxy, biphenyl, terphenyl, benzoate, tolan, pyrimidine, cyclohexanecarboxylate, phenylcyclohexane, and dioxane.

[0028] The thickness of the dimming layer 31 can be more than twice the minimum value of the gap size and less than 11 μm, for example, more than 2 μm and less than 10 μm. In addition, the thickness of the dimming layer 31 can also be more than 3.0 μm and less than 11.0 μm. In addition, from the aspect of being able to generate at least two regions of relatively different densities described later in the dimming layer 31, it is preferred that the thickness of the dimming layer 31 is more than twice the size of the gap. In addition, by having the thickness of the dimming layer 31 be less than 11 μm, when the coating liquid containing liquid crystal molecules is exposed during the manufacture of the dimming plate 21, the liquid crystal molecules and the transparent resin layer can be properly separated.

[0029] The liquid crystal composition is retained in a manner selected from a polymer network type, a polymer dispersion type, and a capsule type. The polymer network type comprises a transparent polymer network having a three-dimensional grid structure. The voids in the grid are interconnected, and the liquid crystal composition is retained in the voids. The polymer network is an example of a resin layer. The polymer dispersion type comprises a plurality of independently existing voids in the resin layer, and the liquid crystal composition is retained in the voids dispersed in the polymer layer. The capsule type retains a liquid crystal composition having a capsule shape in the resin layer. In addition to the above-mentioned liquid crystal molecules, the liquid crystal composition may also contain monomers and dichroic pigments for forming the resin layer.

[0030] The materials used to form the first and second alignment layers 32 and 33 include organic compounds, inorganic compounds, and mixtures thereof. Examples of organic compounds include polyimide, polyamide, polyvinyl alcohol, and cyanide compounds. Inorganic compounds include silicon oxide and zirconium oxide. Alternatively, the materials used to form the alignment layers 32 and 33 may be organosilicon. Organosilicon is a compound with both inorganic and organic components. The thickness of each alignment layer 32 and 33 is, for example, not less than 0.02 μm and not more than 0.5 μm.

[0031] The first alignment layer 32 and the second alignment layer 33 are, for example, vertical alignment layers or horizontal alignment layers. The vertical alignment layer aligns the long axis direction of the liquid crystal molecules in a manner perpendicular to the surface opposite to the surface in contact with the first transparent electrode layer 34 and the surface opposite to the surface in contact with the second transparent electrode layer 35. The horizontal alignment layer aligns the long axis direction of the liquid crystal molecules in a manner substantially parallel to the surface opposite to the surface in contact with the first transparent electrode layer 34 and the surface opposite to the surface in contact with the second transparent electrode layer 35. In this way, regardless of which type of alignment layer 32 or 33 is, the alignment layers 32 or 33 will regulate the orientation of the multiple liquid crystal molecules included in the dimming layer 31. In addition, when at least one of the alignment layers 32 or 33 is a horizontal alignment layer, the dimming plate 21 may include a polarizing layer.

[0032] The first transparent electrode layer 34 and the second transparent electrode layer 35 are translucent, allowing visible light to pass through. The translucency of the first transparent electrode layer 34 enables visual identification of objects passing through the dimming sheet 21. The translucency of the second transparent electrode layer 35 is similar to that of the first transparent electrode layer 34, enabling visual identification of objects passing through the dimming sheet 21. The thickness of each transparent electrode layer 34 and 35 can be, for example, not less than 0.005 μm and not more than 0.1 μm. This ensures proper operation of the dimming sheet 21 while reducing cracks that may occur when the dimming sheet 21 is bent.

[0033] The material used to form each transparent electrode layer 34 , 35 may be any one selected from the group consisting of, for example, indium tin oxide, fluorine-doped tin oxide, tin oxide, zinc oxide, carbon nanotubes, poly(3,4-ethylenedioxythiophene), and silver.

[0034] The material forming each transparent substrate 36, 37 can be a synthetic resin or an inorganic compound. Examples of synthetic resins are polyesters, polyacrylates, polycarbonates, and polyolefins. Examples of polyesters are polyethylene terephthalate and polyethylene naphthalate. Examples of polyacrylates are polymethyl methacrylate. Examples of inorganic compounds are silicon dioxide, silicon oxynitride, and silicon nitride. The thickness of each transparent substrate 36, 37 can be, for example, not less than 16 μm and not more than 250 μm. When the thickness of the transparent substrates 36, 37 is not less than 16 μm, the processing and construction of the dimming film 21 are easy. When the thickness of the transparent substrates 36, 37 is not more than 250 μm, the dimming film 21 can be manufactured using roll-to-roll technology.

[0035] Each electrode 22A and 22B 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. For example, the support layer and the protective layer are formed of polyimide. The conductor portion is formed of, for example, a metal film. The material forming the metal film can be copper, for example. Each electrode 22A and 22B is not limited to an FPC and can also be, for example, a metal tape.

[0036] The electrodes 22A and 22B are attached to the transparent electrode layers 34 and 35 via conductive adhesive layers (not shown). In the portions of the electrodes 22A and 22B connected to the conductive adhesive layers, the conductors are exposed from the protective layer or the support layer.

[0037] The conductive adhesive layer can be formed of, for example, anisotropic conductive film (ACF), anisotropic conductive paste (ACP), isotropic conductive film (ICF), or isotropic conductive paste (ICP). From the perspective of ease of handling during the manufacturing process of the dimming device 10, the conductive adhesive layer is preferably an anisotropic conductive film.

[0038] Each of the wirings 23A and 23B is formed of, for example, a metal conductive wire and an insulating layer covering the metal conductive wire. The conductive wire is formed of, for example, copper.

[0039] The driving unit 12 applies an AC voltage between the first transparent electrode layer 34 and the second transparent electrode layer 35. The driving unit 12 preferably applies a rectangular-wave AC voltage between the pair of transparent electrode layers 34 and 35. Alternatively, the driving unit 12 may apply an AC voltage having a shape other than a rectangular wave between the pair of transparent electrode layers 34 and 35. For example, the driving unit 12 may apply a sinusoidal-wave AC voltage between the pair of transparent electrode layers 34 and 35.

[0040] In the dimming layer 31, the orientation of the liquid crystal molecules changes due to changes in the voltage generated between the two transparent electrode layers 34 and 35. Changes in the orientation of the liquid crystal molecules will change the degree of scattering, absorption, and transmission of visible light entering the dimming layer 31. The reverse-type dimming plate 21 has a relatively high haze when the dimming plate 21 is energized, that is, when a potential difference is generated between the first transparent electrode layer 34 and the second transparent electrode layer 35. The reverse-type dimming plate 21 has a relatively low haze when the dimming plate 21 is not energized, that is, when no potential difference is generated between the first transparent electrode layer 34 and the second transparent electrode layer 35. For example, the reverse-type dimming plate 21 has an opaque state when the dimming plate 21 is energized, and a transparent state when the dimming plate 21 is not energized.

[0041] The dimming sheet 21 is installed, for example, on windows of mobile objects such as vehicles and aircraft. Alternatively, the dimming sheet 21 may be installed on windows of various buildings, such as residences, train stations, and airports; on office partitions; on store display windows; or on screens for projecting images. The dimming sheet 21 may be flat or curved.

[0042] [Dimming film]

[0043] Reference Figure 2 and Figure 3 , the structure of the dimming plate 21 is described in more detail.

[0044] Figure 2 The planar structure of the light adjusting layer 31 as viewed from a viewpoint facing the first surface 31F of the light adjusting layer 31 is shown. Figure 2 In the figure, the resin layer is labeled with a dot symbol to easily distinguish the voids in the light-adjusting layer 31 from the resin layer. Furthermore, the following detailed description will focus on the first surface 31F of the light-adjusting layer 31. However, the second surface 31S of the light-adjusting layer 31, while located in a different position within the light-adjusting layer 31, has the same void size and distribution as the first surface 31F. Therefore, a detailed description of the second surface 31S of the light-adjusting layer 31 will be omitted.

[0045] In contrast, Figure 3 The cross-sectional structure of the dimming plate 21 is schematically shown. Figure 3In the figure, for the convenience of illustration, the transparent substrates 36 and 37 are omitted. Figure 3 In order to facilitate the description of the structure of the light-adjusting layer 31, the ratio of the thickness of the light-adjusting layer 31 to the thickness of each alignment layer 32, 33 and the thickness of each transparent electrode layer 34, 35 may be larger than the actual ratio. Figure 3 3 shows the state of the light-adjusting layer 31 in a state where no potential difference is generated between the pair of transparent electrode layers 34 and 35 .

[0046] like Figure 2 As shown, the light-adjusting layer 31 includes a resin layer 31P in which gaps 31D are dispersed, and a liquid crystal composition containing liquid crystal molecules and filling the gaps 31D. Figure 2 For the sake of convenience, the liquid crystal composition is not shown. As described above, the light-adjusting layer 31 includes a first surface 31F in contact with the first alignment layer 32. The light-adjusting layer 31 satisfies the following condition 1.

[0047] (Condition 1) The area ratio of the voids 31D in the first surface 31F is 49% or more.

[0048] With an area ratio of 49% or greater for the voids 31D in the first surface 31F, the voids 31D are more likely to be located closer to the first surface 31F than in the center of the dimming layer 31 in the thickness direction of the dimming layer 31, compared to a case with a lower area ratio. Consequently, the alignment control force of the first alignment layer 32 acts on more liquid crystal molecules in the dimming layer 31, improving the transparency of the dimming sheet 21 even when no potential difference is generated between the pair of transparent electrode layers 34 and 35.

[0049] The area ratio of voids 31D in first surface 31F is the percentage of the total area of ​​all voids 31D relative to the area of ​​first surface 31F. The area ratio of voids 31D in first surface 31F is calculated using the following method. Specifically, when calculating the area ratio, a calculation target region having a predetermined area is defined on first surface 31F. The total area of ​​all voids 31D contained in the calculation target region is then calculated. The area ratio of voids 31D is the percentage of this total area relative to the area of ​​the calculation target region.

[0050] The transparency of the dimming sheet 21 can be represented by the transmittance of visible light through the dimming sheet 21. In the dimming sheet 21, the lower the haze value, the higher the transparency of the dimming sheet 21, and the higher the haze value, the lower the transparency of the dimming sheet 21. Furthermore, the transparency of the dimming sheet 21 can be represented by the haze of the dimming sheet 21. The haze is calculated using a method based on JIS K 7136:2000. In the dimming sheet 21, the lower the haze value, the higher the transparency of the dimming sheet 21, and the higher the haze value, the lower the transparency of the dimming sheet 21.

[0051] The light-adjusting layer 31 preferably satisfies at least one of the following conditions 2 and 3 in addition to the above-mentioned condition 1.

[0052] (Condition 2) In the first surface 31F, the number of voids 31D per unit area is 31 or less.

[0053] In addition, in this disclosure, the unit area is 96 μm 2 .

[0054] By setting the number of voids per unit area to 31 or less, the voids are more likely to be located near the first surface 31F in the light-adjusting layer 31 when no potential difference is generated between the pair of transparent electrode layers 34 and 35. Therefore, the alignment control force of the alignment layers 32 and 33 acts on more liquid crystal molecules LCM contained in the light-adjusting layer 31 (see FIG. Figure 3 ), when no potential difference is generated between the pair of transparent electrode layers 34 and 35, the transparency of the dimming plate 21 can be improved.

[0055] (Condition 3) The number of voids 31D per unit area on the first surface 31F is 20 or more.

[0056] When the number of the gaps 31D per unit area is 20 or more, the light control sheet 21 can be prevented from having a high haze when no potential difference is generated between the pair of transparent electrode layers 34 and 35 .

[0057] As described above, since the size and distribution of the voids 31D in the second surface 31S are the same as those in the first surface 31F, the light-adjusting layer 31 satisfies the following condition 4. Furthermore, the light-adjusting layer 31 preferably satisfies at least one of the following conditions 5 and 6.

[0058] (Condition 4) The area ratio of the voids 31D in the second surface 31S is 49% or more.

[0059] With an area ratio of 49% or greater for the gaps 31D in the second surface 31S, in a dimming sheet 21 having a pair of alignment layers 32 and 33, the gaps 31D are more likely to be located closer to the first surface 31F and the second surface 31S than to the center of the dimming layer 31 in the thickness direction of the dimming layer 31. Consequently, the alignment control forces of the alignment layers 32 and 33 act on more liquid crystal molecules in the dimming layer 31, improving the transparency of the dimming sheet 21 even when no potential difference is generated between the pair of transparent electrode layers 34 and 35.

[0060] (Condition 5) On the second surface 31S, the number of voids 31D per unit area is 31 or less.

[0061] (Condition 6) On the second surface 31S, the number of voids 31D per unit area is 20 or more.

[0062] When the light-adjusting layer 31 satisfies condition 5, the same effect as when the light-adjusting layer 31 satisfies condition 2 can be obtained. When the light-adjusting layer 31 satisfies condition 6, the same effect as when the light-adjusting layer 31 satisfies condition 3 can be obtained.

[0063] like Figure 3 As shown, the resin layer 31P is located between the first transparent electrode layer 34 and the second transparent electrode layer 35. Voids 31D are dispersed in the resin layer 31P. The liquid crystal composition 31LC contains liquid crystal molecules LCM and fills the voids 31D. The dimming layer 31 includes a first high-density portion 31H1 having a high density of the liquid crystal composition 31LC per unit thickness, and a low-density portion 31L having a low density of the liquid crystal composition 31LC per unit thickness. The first high-density portion 31H1 is in contact with the first alignment layer 32.

[0064] In other words, in the dimming layer 31, the density of the liquid crystal composition 31LC is lowest at the center of the dimming layer 31 in the thickness direction. Furthermore, the center of the dimming layer 31 in the thickness direction refers to the portion closer to the center of the dimming layer 31, compared to a pair of opposing surfaces in the thickness direction of the dimming layer 31. The density of the liquid crystal composition 31LC per unit thickness in each portion of the dimming layer 31 is calculated by dividing the volume of the liquid crystal composition 31LC contained in each portion by the thickness of each portion. In the dimming layer 31, the density of the liquid crystal composition 31LC is preferably lowest at the portion including the center in the thickness direction of the dimming layer 31. Furthermore, because the dimming layer 31 is very thin, it is difficult to calculate the volume of the liquid crystal composition 31LC contained in the dimming layer 31. Therefore, in this disclosure, the densities are calculated using the area of ​​the liquid crystal composition 31LC calculated from an SEM image of a cross-section of the dimming layer 31 and the area of ​​the dimming layer 31.

[0065] Furthermore, the first alignment layer 32 is, for example, a vertical alignment layer. Typically, the first alignment layer 32 aligns the liquid crystal molecules LCM so that their long axes are perpendicular to the first transparent electrode layer 34. However, the first alignment layer 32 may also align the liquid crystal molecules LCM so that their long axes are tilted a few degrees relative to the vertical, within the range where the long axes of the liquid crystal molecules LCM are substantially perpendicular to the first transparent electrode layer 34. In this case, the liquid crystal molecules LCM are negative-type liquid crystal molecules with negative dielectric anisotropy. Furthermore, the density of the liquid crystal composition 31LC in the first high-density portion 31H1 is higher than that of the liquid crystal composition 31LC in the low-density portion 31L.

[0066] Since the density of the liquid crystal composition 31LC is high in the region closest to the first alignment layer 32, the amount of liquid crystal molecules LCM aligned by the alignment control force of the first alignment layer 32 can be increased. Therefore, when no potential difference is generated between the first transparent electrode layer 34 and the second transparent electrode layer 35, the transparency of the dimming sheet 21 can be improved.

[0067] The light-adjusting layer 31 further includes a second high-density portion 31H2. The second high-density portion 31H2 contacts the second alignment layer 33 and has a higher density of the liquid crystal composition 31LC than the density of the liquid crystal composition 31LC in the low-density portion 31L. The low-density portion 31L is sandwiched between the first high-density portion 31H1 and the second high-density portion 31H2 in a cross-section along the thickness direction of the light-adjusting layer 31.

[0068] In the dimming layer 31, near a pair of surfaces facing each other in the thickness direction of the dimming layer 31, the liquid crystal molecules LCM are aligned according to the alignment control forces of the alignment layers 32 and 33. Therefore, when no potential difference is generated between the first transparent electrode layer 34 and the second transparent electrode layer 35, the light transmittance of the dimming sheet 21 can be further improved.

[0069] The light-adjusting layer 31 is composed of a first high-density portion 31H1, a second high-density portion 31H2, and a low-density portion 31L. In a cross-section of the light-adjusting layer 31 along its thickness, the value obtained by dividing the area of ​​the voids 31D by the thickness of the light-adjusting layer 31 is the density of the voids 31D per unit thickness. The density of the voids 31D per unit thickness in the first high-density portion 31H1 and the density of the voids 31D per unit thickness in the second high-density portion 31H2 are higher than the density of the voids 31D per unit thickness in the low-density portion 31L.

[0070] Therefore, the density of the liquid crystal composition 31LC in the first high-density portion 31H1 and the density of the liquid crystal composition 31LC in the second high-density portion 31H2 can be made higher than the density of the liquid crystal composition 31LC in the low-density portion 31L.

[0071] The density of the voids 31D per unit thickness is calculated by dividing the total area of ​​the voids 31D included in each portion by the thickness of each portion.

[0072] In the dimming layer 31, for example, the thickness TH1 of the first high-density portion 31H1, the thickness TH2 of the second high-density portion 31H2, and the thickness TL of the low-density portion 31L are approximately equal. That is, the thickness TH1 of the first high-density portion 31H1, the thickness TH2 of the second high-density portion 31H2, and the thickness TL of the low-density portion 31L are approximately 1 / 3 of the thickness T31 of the dimming layer 31. Furthermore, the thickness TL of the low-density portion 31L may be thicker or thinner than the thicknesses TH1 and TH2 of the high-density portions 31H1 and 31H2, respectively. Furthermore, the thickness TH1 of the first high-density portion 31H1 may be equal to or different from the thickness of the second high-density portion 31H2.

[0073] In a cross-section along the thickness direction of the dimming layer 31, the percentage ([SD / SL]×100) of the sum of the areas (SD) of the voids 31D contained in the low-density portion 31L relative to the area (SL) of the low-density portion 31L is preferably 10% or less. This reduces the proportion of the liquid crystal composition 31LC held by the voids 31D in the low-density portion 31L. Consequently, when no potential difference is generated between the first transparent electrode layer 34 and the second transparent electrode layer 35, the liquid crystal molecules LCM contained in the low-density portion 31L are suppressed, thereby increasing the opacity of the dimming sheet 21.

[0074] Furthermore, the low-density portion 31L preferably does not have voids 31D. In other words, the low-density portion 31L preferably does not contain the liquid crystal composition 31LC. This allows all liquid crystal molecules LCM contained in the dimming layer 31 to be easily aligned according to the alignment control force of the alignment layers 32 and 33. This further reduces the haze of the dimming sheet 21 when no voltage difference is generated between the first transparent electrode layer 34 and the second transparent electrode layer 35.

[0075] Thus, in the low-density portion 31L, the total area SD of the voids 31D is preferably 10% or less, more preferably 5% or less, and most preferably 0% of the area SL of the low-density portion 31L.

[0076] Furthermore, in a cross section along the thickness direction of the light-adjusting layer 31, the gap 31D may be located within a range of 3.0 μm or less from the first alignment layer 32 and within a range of 3.0 μm or less from the second alignment layer 33. In other words, the thickness TH1 of the first high-density portion 31H1 may be 3.0 μm or less, and the thickness TH2 of the second high-density portion 31H2 may be 3.0 μm or less.

[0077] Furthermore, the range of the gap 31D relative to the first alignment layer 32 is the maximum distance between the gap 31D located closer to the first alignment layer 32 than the center of the light-adjusting layer 31 in a cross-section along the thickness direction of the light-adjusting layer 31 and the surface of the first alignment layer 32 that contacts the light-adjusting layer 31. Furthermore, the range of the gap 31D relative to the second alignment layer 33 is the maximum distance between the gap 31D located closer to the second alignment layer 33 than the center of the light-adjusting layer 31 in a cross-section along the thickness direction of the light-adjusting layer 31 and the surface of the second alignment layer 33 that contacts the light-adjusting layer 31.

[0078] In the cross section of the dimming layer 31 along the thickness direction, since the gaps 31D are located within a range of 3.0 μm or less from the alignment layers 32 and 33 , the reliability of the liquid crystal molecules LCM retained in the gaps 31D being aligned according to the alignment control force can be improved.

[0079] Each void 31D included in the first high-density portion 31H1 is preferably in contact with the first alignment layer 32. Furthermore, each void 31D included in the second high-density portion 31H2 is preferably in contact with the second alignment layer 33. In other words, the plurality of voids 31D included in the light-adjusting layer 31 is preferably composed of only one void layer along the interface between the first alignment layer 32 and the light-adjusting layer 31, and one void layer along the interface between the second alignment layer 33 and the light-adjusting layer 31.

[0080] Because the voids 31D contained in the first high-density portion 31H1 and the voids 31D contained in the second high-density portion 31H2 can maintain the liquid crystal composition 31LC in contact with the alignment layers 32 and 33, the alignment control force of the alignment layers 32 and 33 can easily act on the entire liquid crystal composition 31LC held in each void 31D. As a result, the transparency of the dimming sheet 21 can be further improved when no potential difference is generated between the first transparent electrode layer 34 and the second transparent electrode layer 35.

[0081] In the dimming sheet 21 , the thickness T31 of the dimming layer 31 is greater than or equal to 3.0 μm and less than or equal to 11.0 μm, and the size of the gap 31D is greater than or equal to 1.0 μm and less than or equal to 2.5 μm.

[0082] Since the thickness of the dimming layer 31 is between 3.0 μm and 11.0 μm, the formation of gaps 31D at locations away from the pair of opposing surfaces in the thickness direction of the dimming layer 31 is suppressed. Furthermore, since the size of the gaps 31D is between 1.0 μm and 2.5 μm, the liquid crystal composition 31LC can be retained near the alignment layers 32 and 33. Consequently, the transparency of the dimming sheet 21 can be improved when no voltage difference is generated between the first transparent electrode layer 34 and the second transparent electrode layer 35.

[0083] Furthermore, from the perspective of the scattering characteristics of the dimming sheet 21, the size of the gap 31D is preferably between 0.38 μm and 3.0 μm. By setting the size of the gap 31D between 0.38 μm and 3.0 μm, the scattering generated in the dimming sheet 21 can be optimized. By setting the size of the gap 31D to be 0.38 μm or larger, the scattering characteristics, particularly those in the visible light region, can be fully guaranteed. By setting the size of the gap 31D to be 3.0 μm or smaller, the optical effect of the liquid crystal can be suppressed, that is, the component of light that passes through the gap becomes larger than the component of light that is scattered, thereby facilitating the proper dimming effect.

[0084] Furthermore, when the gap 31D has a circular shape in a cross section along the thickness direction of the dimming sheet 21, the size of the gap 31D is the diameter of the gap 31D. When the gap 31D has an elliptical shape in a cross section along the thickness direction of the dimming sheet 21, the size of the gap 31D is the major diameter of the gap 31D. When the gap 31D has an amorphous shape in a cross section along the thickness direction of the dimming sheet 21, the size of the gap 31D is the diameter of a circle circumscribing the gap 31D.

[0085] In a cross section along the thickness direction of the light-adjusting layer 31, the liquid crystal molecules LCM held at a position closer to the alignment layers 32 and 33 are more likely to align in accordance with the alignment control forces of the alignment layers 32 and 33. As described above, when the size of the gaps 31D is 2.5 μm or less, the liquid crystal molecules LCM held in the gaps 31D located in the high-density portions 31H1 and 31H2 are more likely to align in accordance with the alignment control forces.

[0086] To form the dimming sheet 21, transparent substrates 36 and 37 with transparent electrode layers 34 and 35 are first prepared. Alignment layers 32 and 33 are then formed on the transparent electrode layers 34 and 35. Next, a coating liquid is applied between the pair of alignment layers 32 and 33. The coating liquid contains a polymerizable composition for forming the resin layer 31P and liquid crystal molecules (LCM). The polymerizable composition is a monomer or oligomer that can be polymerized by ultraviolet light. The coating liquid is then irradiated with ultraviolet light through the transparent electrode layers 34 and 35, thereby forming the resin layer 31P with gaps 31D and retaining the liquid crystal molecules (LCM) within the gaps 31D.

[0087] When the coating liquid cures, the liquid crystal composition 31LC containing liquid crystal molecules LCM first separates from the polymerizable composition, with liquid crystal compositions 31C located at various locations within the polymerizable composition. Next, before the polymerizable composition cures, the liquid crystal composition 31LC migrates toward the alignment layers 32 and 33. The polymerizable composition then cures, forming a resin layer 31P with voids 31D surrounding the liquid crystal composition 31LC. During the period leading up to the formation of the resin layer 31P, the voids 31D formed in the resin layer 31P continue to expand as the separated liquid crystal compositions 31LC converge. From this perspective, if the size of the voids 31D is 1.0 μm or larger, the likelihood of the polymerizable composition curing before the voids 31D migrate to the vicinity of the alignment layers 32 and 33 can be reduced. As a result, the number of voids 31D in the low-density portion 31L of the dimming layer 31 can be reduced.

[0088] [Example]

[0089] Reference Figures 4 to 9 An embodiment is described.

[0090] The dimming sheets of Examples 1 to 7 and the dimming sheet of Comparative Example 1 were obtained by the manufacturing method described below.

[0091] [Example 1]

[0092] Prepare a pair of PET substrates with ITO films formed on them. The ITO films are 30 nm thick, and the PET substrates are 125 μm thick. Use a hard coater to form a 100 nm thick vertical alignment layer on each ITO film. Prepare a coating solution with the following composition for forming the vertical alignment layer.

[0093] 5 parts by weight of SUNEVER SE-610 (manufactured by Nissan Chemical Industries, Ltd.)

[0094] 75 parts by weight of N-methyl-2-pyrrolidone

[0095] 20 parts by weight of 2-butoxyethanol

[0096] Next, a coating liquid for forming a light-adjusting layer containing a polymerizable composition and liquid crystal molecules was applied on one vertical alignment layer. As a coating liquid for forming a light-adjusting layer, a coating liquid having the following composition was prepared.

[0097]

[0098] Furthermore, another vertical alignment layer was disposed on the coating film, sandwiching the coating film between the pair of vertical alignment layers, and irradiating the coating film with ultraviolet light from both sides in the coating film thickness direction through the PET substrate, ITO film, and vertical alignment layers.

[0099] One of the factors that affect the quality of the dimming sheet is the coating during the manufacture of the dimming sheet, that is, the exposure process of the dimming layer. More specifically, in the exposure process, the optimal exposure amount, in other words, the optimal cumulative light amount, is determined in consideration of many conditions such as the material contained in the coating liquid or the thickness of the coating. Here, the cumulative light amount is calculated by multiplying the illuminance of the irradiated ultraviolet light by the irradiation time of the ultraviolet light. The various embodiments and comparative examples described below illustrate the dimming sheets obtained by appropriately changing the illuminance or irradiation time in order to obtain the optimal cumulative light amount. In addition, the dimming sheets shown in Examples 1 to 7 and Comparative Example 1 all set the thickness of the dimming layer to 7.0 μm.

[0100] In Example 1, the illuminance of ultraviolet light was set to 10 mW / cm 2 , cumulative light intensity reaches 600mJ / cm 2 The coating film is irradiated with ultraviolet rays.

[0101] [Example 2]

[0102] In addition to changing the illuminance when irradiating the coating film with ultraviolet light to 15 mW / cm 2 Other than these, the dimming sheet of Example 2 is obtained by the same method as Example 1.

[0103] [Example 3]

[0104] In addition to changing the illuminance when irradiating the coating film with ultraviolet light to 20 mW / cm 2 The dimming sheet of Example 3 was obtained by the same method as Example 1 except for the above.

[0105] [Example 4]

[0106] In addition to changing the illuminance when irradiating the coating film with ultraviolet light to 25 mW / cm 2 The dimming sheet of Example 4 was obtained by the same method as Example 1 except for the above.

[0107] [Example 5]

[0108] In addition to changing the illuminance when irradiating the coating film with ultraviolet light to 30 mW / cm 2 The dimming sheet of Example 5 was obtained by the same method as Example 1 except for the above.

[0109] [Example 6]

[0110] In addition to changing the illumination intensity of ultraviolet rays to 35 mW / cm 2 Other than these, the dimming sheet of Example 6 was obtained by the same method as Example 1.

[0111] [Example 7]

[0112] In addition to changing the illumination intensity of ultraviolet rays to 40 mW / cm 2 Other than these, the dimming sheet of Example 7 was obtained by the same method as Example 1.

[0113] [Comparative Example 1]

[0114] In addition to changing the illuminance of ultraviolet radiation to 200 mW / cm 2 The dimming sheet of Comparative Example 1 was obtained by the same method as in Example 1 except for the above.

[0115] [Evaluation method]

[0116] [Area ratio and number of voids]

[0117] The first surface of the resin layer is photographed using a scanning electron microscope, and the image obtained by the photographing is used to calculate the area ratio of the voids in the first surface and the number of voids in the first surface. When calculating the area ratio and number of voids, a square test piece with a side length of 10 cm is first cut out from the dimming sheet of each embodiment and comparative example 1. Then, the liquid crystal composition is removed from the resin layer by immersing each test piece in isopropyl alcohol. Then, in each test piece, the first orientation layer is peeled off from the dimming layer at the boundary between the dimming layer and the first orientation layer. In this way, the first surface of the dimming layer of each dimming sheet is exposed.

[0118] Furthermore, the first surface of the test piece after the liquid crystal composition was removed was photographed using a scanning electron microscope. 2 A rectangular area with a certain area is set as the shooting area. For the first side of the test piece, 5 shooting areas are arbitrarily set. In addition, 5 shooting areas are set in such a way that the distance between adjacent shooting areas is more than 1 mm. By binarizing the images obtained from each shooting area, the area ratio of the gaps in each image is calculated. When binarizing the image, the brightness threshold is set to 108. By averaging the area ratios of the gaps in the 5 images, the area ratio of the gaps in each test piece is calculated. In addition, the number of gaps in the image obtained for each test piece is counted. By averaging the number of gaps in the 5 images, the number of gaps in each test piece is calculated.

[0119] [Haze]

[0120] The haze values ​​of the opaque and transparent dimming sheets of Examples 1 to 7 and Comparative Example 1 were calculated. The haze values ​​were calculated using a method based on JIS K 7136:2000. For each dimming sheet, the state in which no potential difference was generated between the pair of transparent electrode layers (i.e., no AC voltage was applied between the pair of transparent electrodes) was considered transparent. Furthermore, the state in which the haze value of the dimming sheet was saturated with an AC voltage applied between the pair of transparent electrodes was considered opaque.

[0121] [transparency]

[0122] The transparency of the dimming sheets of Examples 1 to 7 and the dimming sheet of Comparative Example 1 when opaque was calculated. The transparency is the amount of light that travels straight along the direction of travel of the parallel light LP incident on the dimming layer 31, which is the light amount L. C The amount of narrow-angle scattered light within an angle of ±2.5° relative to the traveling direction of the parallel light LP is set as the light amount L. R When , it is calculated by the following formula (1). In addition, similarly to the calculation of haze, the state where an AC voltage is applied between a pair of transparent electrode layers and the haze of the light control sheet is saturated is defined as opaque.

[0123] 100×(L C -L R ) / (L C +L R )Formula (1)

[0124] [Evaluation results]

[0125] The results of photographing the first surface and cross section of each test piece for Examples 1, 5 and Comparative Example 1 are as follows: Figures 4 to 9 In addition, the evaluation results are shown in Table 1 and Table 2 below. Figures 4 to 9 SEM images of the first surface and cross-section of the light control sheets of Example 1, Example 5, and Comparative Example 1 are shown in this order.

[0126] Table 1

[0127]

[0128] Table z

[0129]

[0130] It can be seen that in the dimming sheets of Examples 1 to 7, the area ratio of voids in the first surface of the dimming layer is 49% or greater. In contrast, in the dimming sheet of Comparative Example 1, the area ratio of voids in the first surface is 45%, which is less than 49%. Furthermore, it can be seen that the haze of the dimming sheets of Examples 1 to 7 when transparent is significantly improved compared to the haze of the dimming sheet of Comparative Example 1 when transparent. Thus, by having an area ratio of voids in the first surface of the dimming layer of 49% or greater, the haze value when transparent is reduced. In other words, it can be said that the transparency when no voltage is applied is improved.

[0131] In addition, according to Figure 5 、 Figure 7 and Figure 9 The cross-sectional structure of the dimming layer shown shows that in the dimming sheets of Examples 1 and 5, all voids in the dimming layer are in contact with the first or second surface. In contrast, in the dimming sheet of Comparative Example 1, a portion of the voids in the dimming layer are in contact with the first or second surface, with the remaining voids located in the center of the dimming layer along the thickness direction of the dimming layer. Thus, the area ratio of voids in the first surface is an indicator of the distribution of voids along the thickness direction of the dimming layer. By achieving an area ratio of voids in the first surface of 49% or greater, it can be said that the number of voids located near the first surface of the dimming layer can be increased.

[0132] Furthermore, a comparison of the haze values ​​of the dimming sheets of Examples 1 to 7 when transparent reveals that the haze values ​​of Examples 2 to 5 are improved compared to those of Examples 1, 6, and 7. This result indicates that the transparency of the dimming sheet when no voltage is applied is further improved by having an area ratio of voids on the first surface of 49% or greater and a number of voids per unit area of ​​20 to 28. In other words, the size of the voids on the first surface of the dimming layers of Examples 2 to 5 is within the preferred range.

[0133] In addition, in Examples 6 and 7, and Comparative Example 1, white dot-like areas were visible when the dimming sheet was transparent, indicating an increase in haze value in the transparent state. These dot-like areas indicate that gaps have formed in the thickness direction of the dimming layer, far enough from the alignment layer that the alignment control force of the alignment layer is less effective. These gaps are filled with a liquid crystal composition. However, the dot-like areas seen in Examples 6 and 7, and Comparative Example 1, were not observed in the dimming sheet of Example 1.

[0134] Therefore, by setting the number of voids per unit area to 29 or less, i.e., by setting the void size to a predetermined size or greater, the formation of voids at locations distant from the alignment layer in the thickness direction of the dimming layer can be suppressed, thereby improving the transparency of the dimming sheet when no voltage is applied. Furthermore, by setting the number of voids per unit area to 20 or more, i.e., by setting the void size to a predetermined size or less, light scattering that depends on void size can be suppressed, thereby improving the transparency of the dimming sheet when no voltage is applied.

[0135] Furthermore, it can be seen that in the dimming sheets of the examples and comparative examples, the same results as those of the first surface can be obtained even on the second surface of the dimming layer.

[0136] The illuminance of ultraviolet rays irradiated during the manufacture of the dimming sheet was varied in Examples 1 to 7 and Comparative Example 1. In Examples 8 to 16 described below, the integrated light intensity was varied in three different illuminances.

[0137] [Example 8]

[0138] In addition to changing the cumulative light intensity of Example 2 to 450mJ / cm 2 Other than these, the dimming sheet of Example 8 was obtained by the same method as Example 2.

[0139] [Example 9]

[0140] The dimming sheet of Example 9 was obtained by the same method as Example 2.

[0141] [Example 10]

[0142] In addition to changing the cumulative light intensity of Example 2 to 750mJ / cm 2 Other than these, the dimming sheet of Example 10 was obtained by the same method as Example 2.

[0143] [Example 11]

[0144] In addition to changing the cumulative light intensity of Example 4 to 450 mJ / cm 2 Other than these, the dimming sheet of Example 11 was obtained by the same method as Example 4.

[0145] [Example 12]

[0146] The dimming sheet of Example 12 was obtained by the same method as Example 4.

[0147] [Example 13]

[0148] In addition to changing the cumulative light intensity of Example 4 to 750 mJ / cm 2 Other than these, the dimming sheet of Example 13 was obtained by the same method as Example 4.

[0149] [Example 14]

[0150] In addition to changing the cumulative light intensity of Example 6 to 450 mJ / cm 2 Other than these, the dimming sheet of Example 14 was obtained by the same method as Example 6.

[0151] [Example 15]

[0152] The dimming sheet of Example 15 was obtained by the same method as Example 6.

[0153] [Example 16]

[0154] In addition to changing the cumulative light intensity of Example 6 to 750 mJ / cm 2 Other than these, the dimming sheet of Example 16 was obtained by the same method as Example 6.

[0155] Table 3

[0156]

[0157] Table 4

[0158]

[0159] [Evaluation method]

[0160] The same method as the method for evaluating the dimming sheets of Examples 1 to 7 and Comparative Example 1 was used to evaluate the area ratio of voids, the number of voids, transparency, and haze.

[0161] [Evaluation results]

[0162] The evaluation results of the dimming sheets of Examples 8 to 16 are shown in Tables 3 and 4.

[0163] The dimming sheets of Examples 8 to 16 show improved haze values ​​when transparent compared to the dimming sheets of Examples 14 to 16. This result demonstrates that the transparency of the dimming sheet when no voltage is applied is further enhanced by ensuring that the area ratio of voids on the first surface of the dimming layer is 49% or greater and the number of voids per unit area is 31 or less.

[0164] Furthermore, it can be seen that in the dimming sheets of the embodiments and comparative examples, the same results as those of the first surface can be obtained on the second surface of the dimming layer.

[0165] As described above, according to one embodiment of the dimming sheet, the following effects can be obtained.

[0166] (1) By having an area ratio of the voids 31D in the first surface 31F of 49% or greater, the voids 31D are more likely to be located closer to the first surface 31F than to the center of the dimming layer 31 in the thickness direction of the dimming layer 31. Therefore, the alignment control force of the first alignment layer 32 acts on more liquid crystal molecules contained in the dimming layer 31, and the transparency of the dimming sheet 21 can be improved when no potential difference is generated between the pair of transparent electrode layers 34 and 35.

[0167] (2) By setting the number of voids per unit area to 31 or less, the voids are more likely to be located near the first surface 31F in the dimming layer 31 when no potential difference is generated between the pair of transparent electrode layers 34 and 35. Therefore, the alignment control forces of the alignment layers 32 and 33 act on more liquid crystal molecules (LCM) contained in the dimming layer 31. This improves the transparency of the dimming sheet 21 when no potential difference is generated between the pair of transparent electrode layers 34 and 35.

[0168] (3) By setting the number of the gaps 31D per unit area to 20 or more, the light control sheet 21 can be prevented from having a high haze when no potential difference is generated between the pair of transparent electrode layers 34 and 35 .

[0169] (4) By having an area ratio of the voids 31D in the second surface 31S of 49% or greater, in the dimming sheet 21 having a pair of alignment layers 32 and 33, the voids 31D are more likely to be located closer to the first surface 31F and closer to the second surface 31S in the thickness direction of the dimming layer 31 than in the center of the dimming layer 31. Therefore, because the alignment control forces of the alignment layers 32 and 33 act on more liquid crystal molecules contained in the dimming layer 31, the transparency of the dimming sheet 21 can be improved when no potential difference is generated between the pair of transparent electrode layers 34 and 35.

[0170] Furthermore, the above-described embodiment can be implemented with modifications as follows.

[0171] [Orientation layer]

[0172] The light-control sheet 21 may include the first alignment layer 32 but not the second alignment layer 33. In this case, the effect of (1) above can be obtained by ensuring that the area ratio of the voids in the first surface 31F is 49% or more.

Claims

1. A dimming film comprising: a first transparent electrode layer; a second transparent electrode layer; dimming layer; and The first orientation layer, The dimming layer includes a resin layer located between the first transparent electrode layer and the second transparent electrode layer, and a liquid crystal composition containing liquid crystal molecules. Voids are dispersed in the resin layer, and the liquid crystal composition fills the voids. The first alignment layer is sandwiched between the first transparent electrode layer and the light-adjusting layer, and is configured so that the haze of the light-adjusting layer can be increased by applying a voltage to the first transparent electrode layer. The dimming layer includes a first surface in contact with the first alignment layer, The percentage of the total area of ​​all voids in the first surface relative to the area of ​​the first surface is the area ratio of the voids in the first surface. The area ratio is 49% or more.

2. The dimming sheet according to claim 1, wherein: On the first surface, the number of voids per unit area is 31 or less, and the unit area is 96 μm 2 .

3. The dimming sheet according to claim 1 or 2, wherein: On the first surface, the number of voids per unit area is 20 or more, and the unit area is 96 μm 2 .

4. The dimming sheet according to claim 1 or 2, wherein: further comprising a second alignment layer located between the light-adjusting layer and the second transparent electrode layer in the thickness direction of the light-adjusting layer, The light-adjusting layer includes a second surface in contact with the second alignment layer, The area ratio of the voids in the second surface is 49% or more.

5. The dimming sheet according to claim 1 or 2, wherein: The thickness of the dimming layer is greater than or equal to 3.0 μm and less than or equal to 11.0 μm.

Images