Light control sheet

Abstract

The light control sheet has a first transparent electrode layer; a second transparent electrode layer; a light control layer, which is a light control layer sandwiched by the first transparent electrode layer and the second transparent electrode layer, includes a transparent polymer layer containing a plurality of voids and a liquid crystal composition containing liquid crystal molecules and filled in the plurality of voids; and a plurality of spacers in the light control layer. Each spacer is formed of polymethyl methacrylate resin.

Description

Technical Field

[0001] This disclosure relates to, for example, dimming discs installed in transparent components of various windows in vehicles. Background Technology

[0002] The dimming sheet includes a first transparent electrode layer, a second transparent electrode layer, and a dimming layer. The dimming layer is sandwiched between the first and second transparent electrode layers. The dimming layer may include, for example, a transparent polymer layer and a liquid crystal composition. The transparent polymer layer has a plurality of pores, each pore being filled with the liquid crystal composition. The liquid crystal composition comprises liquid crystal molecules. The liquid crystal molecules have different orientations depending on whether a potential difference exists between the pair of transparent electrode layers. For example, the dimming sheet may be opaque due to its orientation in the state where no potential difference exists between the pair of transparent electrode layers, and transparent due to its orientation in the state where a potential difference exists between the pair of transparent electrode layers (see, for example, Patent Document 1).

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2017-187775 Summary of the Invention

[0006] The technical problem that the invention aims to solve

[0007] Because dimming sheets can be transparent or opaque, they are used as partitions to divide two adjacent spaces, separating a first space into a second. For example, dimming sheets are installed in transparent components embedded in windows of buildings, and in partitions that divide interior spaces. In recent years, with the expansion of the applications of dimming sheets, their installation in transparent components of various vehicle windows has been proposed. It is anticipated that vehicles will operate in harsher environments, especially at high temperatures, compared to buildings; therefore, dimming sheets are required to maintain high reliability even in environments suitable for vehicle use.

[0008] The purpose of this disclosure is to provide a dimming film that can improve reliability.

[0009] Means for solving technical problems

[0010] One embodiment of the dimming film includes a first transparent electrode layer; a second transparent electrode layer; a dimming layer sandwiched between the first and second transparent electrode layers, comprising a transparent polymer layer with multiple voids and a liquid crystal composition containing liquid crystal molecules and filling the multiple voids; and a plurality of spacers located in the dimming layer. Each spacer is formed of polymethyl methacrylate resin. Attached Figure Description

[0011] Figure 1 This is a cross-sectional view showing the state in which no potential difference is generated between the transparent electrode layers in a positive dimming film.

[0012] Figure 2 This is a cross-sectional view showing the state of potential difference generated between transparent electrode layers in a positive dimming film.

[0013] Figure 3 This is a cross-sectional view showing the state in which no potential difference is generated between the transparent electrode layers in a reverse-type dimming film.

[0014] Figure 4 This is a cross-sectional view showing the state of potential difference generated between transparent electrode layers in a reverse-type dimming film. Detailed Implementation

[0015] Reference Figures 1-4 This section describes one embodiment of a dimming film. The dimming film and an example will be described below.

[0016] [Dimming filter]

[0017] The dimming strip is mounted on a transparent component embedded in the window of a vehicle. This transparent component can be, for example, a windshield, side windows, rear window, or sunroof. The dimming strip is flexible enough to follow the shape of the transparent component. Therefore, when the dimming strip is attached to the transparent component, it can also be curved. The dimming strip can be either forward-facing or reverse-facing.

[0018] Reference Figure 1 and Figure 2 This describes a positive dimming disc and a dimming device equipped with a positive dimming disc. Figure 1 This shows the cross-sectional structure of a dimmer when it is in an opaque state. Figure 2 This indicates the cross-sectional structure of the dimmer when the positive type dimmer is in a transparent state.

[0019] like Figure 1 As shown, the dimming sheet 10N includes a first transparent electrode layer 11A, a second transparent electrode layer 11B, a dimming layer 12, and spacers 13. The dimming layer 12 is sandwiched between the first transparent electrode layer 11A and the second transparent electrode layer 11B. The dimming layer 12 comprises a transparent polymer layer 12A and a liquid crystal composition 12B. The transparent polymer layer 12A includes a plurality of voids 12D. The liquid crystal composition 12B includes liquid crystal molecules 12BL and fills the plurality of voids 12D. Each spacer 13 is located in the dimming layer 12.

[0020] Each spacer 13 is formed of polymethyl methacrylate resin (PMMA). PMMA comprises the unit structure shown below, which has a repeating structure. PMMA is a polymer of methyl methacrylate (C5H8O2) composed of saturated hydrocarbons. The spacers 13 are formed of PMMA polymerized from methyl methacrylate as a monomer, in other words, from a homopolymer of methyl methacrylate.

[0021] [Chemical structural formula 1]

[0022]

[0023] Traditionally, the spacers 13 of the dimming disc 10N have been made of materials containing aromatic rings, such as spacers with divinylbenzene as the main component as shown below.

[0024] [Chemical structural formula 2]

[0025]

[0026] In spacers formed of materials containing aromatic rings, the aromatic ring-containing portions may become detached during use in harsh environments, particularly at high temperatures. These detached aromatic rings, through interaction with the liquid crystal molecules 12BL contained in the dimming layer 12, hinder the driving of the liquid crystal molecules 12BL. Consequently, when a voltage for driving the liquid crystal molecules 12BL is applied to the dimming disc 10N, the optical properties of the dimming disc 10N deteriorate. Therefore, in a positive-type dimming disc 10N, when the dimming disc 10N is in a transparent state, the optical properties of the dimming disc 10N deteriorate. For example, when the dimming disc 10N is in a transparent state, the haze of the dimming disc 10N increases.

[0027] From this perspective, according to the dimming sheet 10N of this disclosure, since the spacer 13 is formed of PMMA composed of saturated hydrocarbons, the degradation of the optical properties of the dimming sheet 10N can be suppressed under high-temperature environments. Therefore, the reliability of the dimming sheet 10N can be improved. As mentioned above, the dimming sheet 10N is a dimming sheet for automotive applications. Components installed in vehicles need to meet the high safety standards required for vehicles. Therefore, the dimming sheet 10N for automotive applications also requires higher reliability compared to other applications. From this perspective, the dimming sheet 10N with PMMA spacer 13 can improve reliability at high temperatures, therefore, the dimming sheet 10N is preferred as a dimming sheet for automotive applications.

[0028] The preferred dimming film 10N satisfies condition 1.

[0029] (Condition 1) The absolute value of the difference between the refractive index of the transparent polymer layer 12A and the refractive index of the spacer 13 is less than 0.04.

[0030] Since the absolute value of the difference between the refractive index of the transparent polymer layer 12A and the refractive index of the spacer 13 is 0.04 or less, when the dimming disc 10N is in a transparent state, the cloudiness of the dimming disc 10N caused by incident light scattering due to the refractive index difference between the transparent polymer layer 12A and the spacer 13 can be suppressed. In the positive-type dimming disc 10N, a potential difference is generated between the first transparent electrode layer 11A and the second transparent electrode layer 11B, thereby making the dimming disc 10N transparent when the liquid crystal molecules are driven. Therefore, by ensuring that the absolute value of the refractive index difference is 0.04 or less, and thus generating a potential difference between the transparent electrode layers 11A and 11B, the transparency of the dimming disc 10N can be improved.

[0031] In the dimming layer 12, the retention type of the liquid crystal composition is selected from polymer network type, polymer dispersion type, and capsule type. The transparent polymer layer 12A has a structure corresponding to the retention type of the liquid crystal composition. The polymer network type has a polymer network with a three-dimensional mesh structure. The polymer network is an example of the transparent polymer layer 12A. The polymer network retains the liquid crystal composition in the interconnected mesh openings. The polymer dispersion type has a transparent polymer layer 12A that divides a plurality of isolated openings, and the liquid crystal composition is retained in the openings dispersed in the transparent polymer layer 12A. The capsule type retains a capsule-shaped liquid crystal composition in the transparent polymer layer 12A. Furthermore, Figures 1-4 This indicates a dimming disc when the retention type of the liquid crystal composition is a polymer network type.

[0032] The transparent polymer layer 12A is a polymer of an ultraviolet-polymerizable compound. The transparent polymer layer 12A can be formed from two or more ultraviolet-polymerizable compounds. For example, the two or more ultraviolet-polymerizable compounds may also include an ultraviolet-polymerizable compound containing an aromatic ring. That is, the transparent polymer layer 12A can also be formed from a polymer polymerized from two or more unit structures. One or more of the two or more unit structures may also include a unit structure containing an aromatic ring.

[0033] Because the transparent polymer layer 12A has a complex structure composed of polymer complexes, even if the unit structure constituting the transparent polymer layer 12A contains aromatic rings, the release of aromatic rings is less likely to occur compared to when the spacer 13 is composed of a material containing aromatic rings. Therefore, according to the aforementioned dimming film, since unit structures containing aromatic rings can be used in the unit structure constituting the transparent polymer layer 12A, the degree of freedom in selecting the material forming the transparent polymer layer 12A can be increased, thereby increasing the degree of freedom in determining the refractive index of the transparent polymer layer.

[0034] The dimming layer 12 is formed, for example, by irradiating the coating with ultraviolet light. The coating is a mixture of an ultraviolet-polymerizable compound used to form the transparent polymer layer 12A and a liquid crystal composition 12B.

[0035] When the transparent polymer layer 12A contains unit structures with aromatic rings, the average value of aromatic rings contained in two or more unit structures in the transparent polymer layer 12A can be 0.4 or more per unit structure. The liquid crystal molecule 12BL can also contain aromatic rings. When the liquid crystal molecule 12BL contains aromatic rings, the inclusion of aromatic rings in the unit structures contained in the transparent polymer layer 12A, i.e., the monomers used to form the transparent polymer layer 12A, improves the compatibility of the monomers with the liquid crystal molecule 12BL in the coating solution used to form the dimming sheet 10N. Therefore, the distribution of the liquid crystal molecule 12BL and the monomers in the coating solution is unbiased; that is, the liquid crystal molecule 12BL and the monomers are dispersed independently in the coating solution. Thus, by irradiating the coating film formed using the coating solution with ultraviolet light to cause phase separation, voids 12D with a size of 1 μm or more and 10 μm or less can be formed. In order to achieve this size of void 12D, from the viewpoint of improving the compatibility of the monomer with the liquid crystal molecule 12BL, it is preferable that the average number of aromatic rings contained in one unit structure in the transparent polymer layer 12A is 0.4 or more.

[0036] Furthermore, the size of the void 12D is determined by a cross-section along a plane perpendicular to the surface extending from the transparent polymer layer 12A. In this cross-section, the size of the void 12D is the length of the longest line segment connecting any two points on the edge of the void 12D. For example, when the void 12D is circular, its diameter is its size. When the void 12D is elliptical, its major axis is its size. When the void 12D has a shape other than circular or elliptical, the diameter of the circle circumscribed in front of the void 12D can be the size of the void 12D.

[0037] On the other hand, when the dimming plate 10N has a spacer 13 mainly composed of divinylbenzene, from the viewpoint of improving the reliability of the dimming plate 10N at high temperatures, that is, from the viewpoint of suppressing the increase in haze value when transparent due to exposure to high temperatures, it is preferable that the transparent polymer layer 12A contains aromatic rings. It is believed that the interaction between the aromatic rings contained in the liquid crystal molecules and the aromatic rings contained in the spacer 13 is suppressed by the aromatic rings contained in the transparent polymer layer 12A, thereby improving reliability at high temperatures. However, from the viewpoint of improving the compatibility of the monomer with the liquid crystal molecules 12BL, excessively increasing the number of aromatic rings in the transparent polymer layer 12A will lead to a decrease in compatibility.

[0038] From this perspective, according to the dimming film 10N of this disclosure, by changing the material forming the spacer 13 from a material containing aromatic rings to PMMA, the reliability at high temperatures can be improved. Therefore, in the transparent polymer layer 12A, the number of aromatic rings in each unit structure can also be set from the viewpoint of the compatibility between the monomers used to form the transparent polymer layer 12A and the liquid crystal molecules 12BL.

[0039] Liquid crystal composition 12B fills the voids 12D. Liquid crystal molecule 12BL is, for example, selected from Schiff base systems, azo systems, azo oxide systems, biphenyl systems, terphenyl systems, benzoic acid ester systems, diphenylacetylene systems, pyrimidine systems, cyclohexane carboxylate systems, phenylcyclohexane systems, and dioxane systems. As described above, liquid crystal molecule 12BL may also contain an aromatic ring. Liquid crystal composition 12B may also contain a first liquid crystal molecule 12BL and a second liquid crystal molecule 12BL of a different type from the first liquid crystal molecule 12BL. The main component of liquid crystal composition 12B is liquid crystal molecule 12BL.

[0040] The weight concentration of the main component in the liquid crystal composition 12B is 80% or more relative to the liquid crystal composition 12B. The liquid crystal composition 12B, besides the main component, may contain dichroic pigments, weather-resistant agents, and unavoidable components mixed in during the formation of the dimming layer 12. Weather-resistant agents are ultraviolet absorbers or light stabilizers used to suppress the deterioration of the liquid crystal composition 12B. Unavoidable components include, for example, unreacted components of the ultraviolet-polymerizing compound used in the formation of the transparent polymer layer 12A.

[0041] Multiple spacers 13 are dispersed in the dimming layer 12. The length of each spacer 13 is substantially equal to the thickness of the dimming layer 12 in the thickness direction of the dimming layer 12. The multiple spacers 13 can suppress unevenness in the thickness of the dimming layer 12. Furthermore, the dimming film 10N may also include spacers of a first size and spacers of a second size. The spacers 13 are, for example, granular spacers. Granular spacers include spherical spacers and non-spherical spacers. Non-spherical spacers include cuboid spacers, cross-shaped spacers, and rod-shaped spacers. As described above, each spacer 13 is formed of PMMA.

[0042] The spacer 13 can also be fixed to other layers in contact with the dimming layer 12. For example, the spacer 13 can also be a spacer whose surface has been treated to bond the transparent electrode layers 11A, 11B or the resin layer in contact with the dimming layer 12.

[0043] A pair of transparent electrode layers 11A and 11B sandwich the dimming layer 12 in the thickness direction. Each transparent electrode layer 11A and 11B transmits light in the visible light region. The material forming each transparent electrode layer 11A and 11B is selected from, for example, any one of indium tin oxide, fluorine-doped tin oxide, tin oxide, zinc oxide, carbon nanotubes, poly(3,4-ethylenedioxythiophene), and silver.

[0044] The dimming film 10N includes a first transparent substrate 14A and a second transparent substrate 14B. A pair of transparent electrode layers 11A and 11B are sandwiched between the pair of transparent substrates 14A and 14B in the thickness direction of the dimming layer 12. Each transparent substrate 14A and 14B transmits light in the visible light region. The material forming each transparent substrate 14A and 14B is, for example, transparent glass or transparent synthetic resin.

[0045] The dimming layer 12 has a transparent state and an opaque state. The dimming layer 12 changes the orientation of the liquid crystal molecules 12BL by applying a voltage that alters their orientation. The dimming layer 12 switches between a transparent state and an opaque state based on the change in the orientation of the liquid crystal molecules 12BL. The transparent state of the dimming layer 12 is a state in which the outline of the observed object can be visually identified through the dimming disc 10N. The opaque state of the dimming layer 12 is a state in which the outline of the observed object cannot be visually identified through the dimming disc 10N.

[0046] Figure 1 The dimming layer 10N represents the state where no voltage is applied to change the orientation. When no voltage is applied to change the orientation of the dimming layer 12, the orientation direction of the liquid crystal molecules 12BL located in each gap 12D is random. Light incident on the dimming layer 10N from either of the pair of transparent substrates 14A and 14B is scattered in all directions in the dimming layer 12. As a result, the positive-type dimming layer 12 has an opaque state as a turbid state when no voltage is applied. The opaque dimming layer 12 can be white and turbid, or it can be colored and turbid. When the dimming layer 12 is colored, the dimming layer 12 contains pigment.

[0047] like Figure 2 As shown, when a voltage that alters the orientation of the liquid crystal molecules 12BL is applied to the dimming layer 12 from the driving circuit 10D, the orientation of the plurality of liquid crystal molecules 12BL changes from a random orientation to the direction of light transmission. For example, each liquid crystal molecule 12BL changes its orientation substantially perpendicular to the long axis of the liquid crystal molecule 12BL relative to the plane extending from the dimming layer 12. Light incident on the dimming sheet 10N from either of the pair of transparent substrates 14A and 14B is hardly scattered in the dimming layer 12 and passes through the dimming layer 12. As a result, the positive dimming layer 12 is transparent when a voltage is applied.

[0048] Reference Figure 3 and Figure 4 This describes a reverse-type dimming disc and a dimming device equipped with a reverse-type dimming disc. Figure 3 This shows the cross-sectional structure when the reverse dimming layer 12 is in a transparent state. Figure 4 This indicates the cross-sectional structure when the reverse dimming layer 12 is in an opaque state.

[0049] like Figure 3 As shown, the reverse-type dimming film 10R, in addition to a pair of transparent electrode layers 11A and 11B, a dimming layer 12, and a pair of transparent substrates 14A and 14B, also includes a pair of alignment layers 15A and 15B. The pair of alignment layers 15A and 15B hold the dimming layer 12 in the thickness direction of the dimming layer 12, and are located in the thickness direction of the dimming layer 12 closer to the center of the dimming film 10R than the pair of transparent electrode layers 11A and 11B.

[0050] The first alignment layer 15A is located between the dimming layer 12 and the first transparent electrode layer 11A. The first alignment layer 15A causes the alignment control force to act on the liquid crystal molecules 12BL. The second alignment layer 15B is located between the dimming layer 12 and the second transparent electrode layer 11B. The second alignment layer 15B causes the alignment control force to act on the liquid crystal molecules 12BL. The materials forming each alignment layer 15A and 15B can be organic compounds, inorganic compounds, or mixtures thereof. Organic compounds can be, for example, polyimide, polyamide, polyvinyl alcohol, cyanide compounds, etc. Inorganic compounds can be silicon oxide, zirconium oxide, etc. Alternatively, the materials forming each alignment layer 15A and 15B can also be organosilicon.

[0051] When each alignment layer 15A and 15B is a vertical alignment layer, the liquid crystal molecules 12BL in each gap 12D are vertically aligned when no voltage is applied to the dimming layer 12 to change the orientation of the liquid crystal molecules 12BL. Furthermore, light incident from either of the pair of transparent substrates 14A and 14B onto the dimming disc 10R is hardly scattered in the dimming layer 12 and passes through it. As a result, the reverse-type dimming layer 12 is transparent when no voltage is applied to change the orientation of the liquid crystal molecules 12BL.

[0052] like Figure 4 As shown, when a voltage that changes the orientation of the liquid crystal molecules 12BL is applied from the driving circuit 10D to the dimming layer 12, the orientation of the plurality of liquid crystal molecules 12BL changes, for example, from a vertical orientation to a horizontal orientation. At this time, each liquid crystal molecule 12BL is located in the gap 12D such that its long axis extends along the plane extending from the dimming layer 12. Light incident on the dimming sheet 10R from either of the pair of transparent substrates 14A and 14B is scattered by the dimming layer 12. As a result, the reverse-type dimming layer 12 is opaque when a voltage that changes the orientation of the liquid crystal molecules 12BL is applied.

[0053] [Example]

[0054] The embodiments and comparative examples are described with reference to Table 1. Furthermore, in the embodiments and comparative examples described below, a transparent polymer layer is formed from multiple monomers, from the first monomer to the seventh monomer listed below.

[0055] [Single name]

[0056] • First monomer: hexyl acrylate (refractive index 1.428)

[0057] • Second monomer: dodecyl acrylate (refractive index 1.443)

[0058] • Third monomer ethoxylated o-phenylphenol acrylate (refractive index 1.577)

[0059] • The fourth monomer, cyclohexyl acrylate (refractive index 1.460)

[0060] • Fifth monomer, pentaerythritol triacrylate (refractive index 1.480)

[0061] • The sixth monomer, 9,9-bis[4-(2-acryloyloxyethoxy)phenyl]fluorene (refractive index 1.622)

[0062] • Seventh monomer urethane acrylate (manufactured by Sartomer Japan Co., Ltd., CN962) (refractive index 1.482)

[0063] [Example 1]

[0064] Relative to the total solids content in the coating solution used to form the dimming layer, the liquid crystal (MERCK Corporation, MLC-6609) containing aromatic ring-containing liquid crystal molecules was set to 50% by mass, the first monomer to 9% by mass, the fourth monomer to 18% by mass, the fifth monomer to 6% by mass, and the seventh monomer to 15% by mass. Thus, the refractive index of the material forming the transparent polymer layer in the coating solution, in its cured state, was adjusted to 1.50. Furthermore, relative to the total solids content in the coating solution, the polymerization initiator (IGM Resins Corporation, Omnirad 184 (Irgacure 184)) (Omnirad and Irgacure are registered trademarks) was set to 1% by mass, and the spacer (Hayakawa Rubber Co., Ltd., SD-BD15) (refractive index 1.50) having a diameter of 15 μm and made of PMMA was set to 1% by mass.

[0065] Prepare a pair of transparent substrates supporting transparent conductive films. The coating is cured by irradiating it with ultraviolet light while the coating is sandwiched between the two transparent conductive films. This yields the dimming sheet of Example 1.

[0066] [Example 2]

[0067] Except for the changes made to the composition of the coating liquid in Example 1, the dimming sheet of Example 2 was obtained by the same method as in Example 1. That is, relative to the total solid content in the coating liquid, the second monomer was set to 9% by mass, the fourth monomer to 18% by mass, the fifth monomer to 6% by mass, and the seventh monomer to 15% by mass. In addition, all other monomers were set to 0% by mass. As a result, the refractive index of the material forming the transparent polymer layer in the cured state was adjusted to 1.51.

[0068] [Example 3]

[0069] Except for changing the spacer to have a different diameter than the spacer used in Example 1 (manufactured by Hayakawa Rubber Co., Ltd., SD-BD17) (refractive index 1.50) and a spacer with a diameter of 17 μm, the dimming sheet of Example 3 was obtained by the same method as in Example 1.

[0070] [Example 4]

[0071] Except for the changes to the composition of the coating liquid as described in Example 3, the dimming sheet of Example 4 was obtained using the same method as in Example 3. Specifically, relative to the total solid content in the coating liquid, the third monomer was set to 9% by mass, the fourth monomer to 18% by mass, the sixth monomer to 6% by mass, and the seventh monomer to 15% by mass. All other monomers were set to 0% by mass. This adjusted the refractive index of the material forming the transparent polymer layer in its cured state to 1.55.

[0072] [Example 5]

[0073] Except for the changes to the composition of the coating liquid as described in Example 3, the dimming sheet of Example 5 was obtained using the same method as in Example 3. Specifically, relative to the total solid content in the coating liquid, the second monomer was set to 18% by mass, the third monomer to 10% by mass, the sixth monomer to 5% by mass, and the seventh monomer to 15% by mass. All other monomers were set to 0% by mass. This adjusted the refractive index of the material forming the transparent polymer layer in its cured state to 1.54.

[0074] [Example 6]

[0075] Except for the changes to the composition of the coating liquid as described in Example 3, the dimming sheet of Example 6 was obtained using the same method as in Example 3. That is, relative to the total solid content in the coating liquid, the third monomer was set to 27% by mass, the sixth monomer to 6% by mass, and the seventh monomer to 15% by mass. In addition, all other monomers were set to 0% by mass. As a result, the refractive index of the material forming the transparent polymer layer in the cured state was adjusted to 1.59.

[0076] [Comparative Example 1]

[0077] Except for the use of a spacer made of divinylbenzene copolymer (manufactured by Sekisui Chemicals Co., Ltd., SP-215) (refractive index 1.57) in Example 4, the dimming sheet of Comparative Example 1 was obtained by the same method as in Example 4.

[0078] [Comparative Example 2]

[0079] Except for the use of a spacer made of divinylbenzene copolymer (manufactured by Sekisui Chemicals Co., Ltd., SP-215) (refractive index 1.57) in Example 1, the dimming sheet of Comparative Example 2 was obtained by the same method as in Example 1.

[0080] [Comparative Example 3]

[0081] Except for the use of a spacer made of divinylbenzene copolymer (manufactured by Sekisui Chemicals Co., Ltd., SP-215) (refractive index 1.57) in Example 6, the dimming sheet of Comparative Example 3 was obtained by the same method as in Example 6.

[0082] [Comparative Example 4]

[0083] Except for changing the composition of the coating liquid as in Comparative Example 3, the dimming sheet of Comparative Example 4 was obtained by the same method as in Comparative Example 3. That is, relative to the total solid content in the coating liquid, the second monomer was set to 27% by mass, the fifth monomer was set to 6% by mass, and the seventh monomer was set to 15% by mass. In addition, all other monomers were set to 0% by mass. As a result, the refractive index of the material forming the transparent polymer layer in the cured state was adjusted to 1.50.

[0084] [Table 1]

[0085]

[0086] [Evaluation Method]

[0087] The haze of each dimming sheet in the transparent state was measured. The haze of the dimming sheet was measured using a method based on JIS K 7136:2000. Furthermore, the haze at which a voltage sufficient to saturate the haze value of the dimming sheet was applied between a pair of transparent electrode layers was measured as the haze in the transparent state. Then, each dimming sheet was subjected to an accelerated test by being kept at 110°C for 720 hours. Subsequently, the haze of each dimming sheet in the transparent state after the accelerated test was measured using the same method as before the test.

[0088] In addition, under the respective conditions before and after the test, the condition with a haze value less than 4% will be set as "◎", the condition with a haze value of 4% or more but less than 5% will be set as "○", the condition with a haze value of 5% or more but less than 6% will be set as "△", and the condition with a haze value of more than 6% will be set as "×".

[0089] [Evaluation Results]

[0090] The haze results measured before and after the accelerated testing are shown in Table 2 below. Furthermore, it can be seen that, excluding the liquid crystal component, the refractive index of the transparent polymer layer obtained by monomer curing is 0.04 higher than that in the liquid state. It can be inferred that, with the liquid crystal component, monomer curing occurs while the monomer is separated from the liquid crystal, thus the refractive index of the resulting transparent polymer layer is 0.04 higher than that in the liquid state.

[0091] Furthermore, for the transparent polymer layer of each dimming sheet, after calculating the molar fraction of each monomer used to form the transparent polymer layer, the number of aromatic rings contained in each monomer is multiplied by the molar fraction of that monomer to calculate the number of aromatic rings from each monomer in each unit structure. Next, the sum of the number of aromatic rings from each monomer is calculated to obtain the average number of aromatic rings in each unit structure of the transparent polymer layer.

[0092] [Table 2]

[0093]

[0094] As shown in Table 2, before the accelerated testing, the visible haze value in the dimming films of Examples 1 to 3, Example 5, Comparative Example 1, and Comparative Example 3 was “◎”. Additionally, before the accelerated testing, the visible haze value in the dimming film of Example 4 was “○”. In contrast, before the accelerated testing, the visible haze value in the dimming films of Example 6, Comparative Example 2, and Comparative Example 4 was “△”.

[0095] After accelerated testing, the visible haze value in the dimming sheets of Examples 1 to 3 was “○”. Furthermore, after accelerated testing, the visible haze value in the dimming sheets of Examples 4 to 6 was “△”. In contrast, the visible haze value in the dimming sheets of Comparative Examples 1 to 4 was “×”. Thus, in the dimming sheets of Examples 1 to 6, the haze value did not change before and after the accelerated testing, while in the dimming sheets of Comparative Examples 1 to 4, the visible haze value changed before and after the accelerated testing. From these results, it can be seen that by using PMMA spacers, the reliability of the dimming sheets at high temperatures can be improved according to the dimming sheets of Examples 1 to 6.

[0096] Furthermore, when comparing the haze levels of the dimming film of Comparative Example 3 and Comparative Example 4 after accelerated testing, it was found that the haze level of the dimming film of Comparative Example 4 was significantly higher than that of the dimming film of Comparative Example 3. That is, in the dimming film containing the divinylbenzene spacer, the aromatic ring-containing unit structure of the transparent polymer layer can improve the reliability of the dimming film at high temperatures.

[0097] Furthermore, since the haze values ​​in Examples 1-3, Example 5, Comparative Example 1, and Comparative Example 3 were "◎" before the accelerated test, it can be said that, in terms of reducing the haze value in the transparent state, the absolute value of the difference between the refractive index of the transparent polymer layer and the refractive index of the spacer is preferably less than 0.05. That is, in terms of reducing the haze value in the transparent state before the heating test, or in other words, the initial value of the haze value in the transparent state, the absolute value of the difference between the refractive index of the transparent polymer layer and the refractive index of the spacer is preferably less than 0.05.

[0098] Furthermore, it is known that in Examples 4-6, the change in haze value obtained by subtracting the haze value before the accelerated test from the haze value after the accelerated test is less than the change in Examples 1-3. In particular, it is known that among Examples 4-6, the change in haze value in Example 6 is the smallest. From this result, it can be said that by including aromatic rings in the transparent polymer layer, the change in haze value before and after the heating test can be reduced.

[0099] As explained above, according to one embodiment of the dimming film, the following effects can be obtained.

[0100] (1) Since the spacer 13 is formed by PMMA composed of saturated hydrocarbons, it can suppress the deterioration of the optical properties of the dimming sheets 10N and 10R under high temperature conditions. Therefore, the reliability of the dimming sheets 10N and 10R can be improved.

[0101] (2) Since the absolute value of the difference between the refractive index of the transparent polymer layer 12A and the refractive index of the spacer 13 is less than 0.04, when the dimming sheets 10N and 10R are transparent, the turbidity of the dimming sheets 10N and 10R caused by the incident light scattering due to the difference in refractive index between the transparent polymer layer 12A and the spacer 13 can be suppressed.

[0102] (3) When a unit structure containing an aromatic ring is used in the unit structure constituting the transparent polymer layer 12A, the degree of freedom in selecting the material forming the transparent polymer layer 12A can be increased, and thus the degree of freedom in the refractive index of the transparent polymer layer can be increased.

[0103] Symbol Explanation

[0104] 10N, 10R dimming discs

[0105] 11A First Transparent Electrode Layer

[0106] 11B Second Transparent Electrode Layer

[0107] 12 dimming layers

[0108] 13 Spacers

[0109] 14A First Transparent Substrate

[0110] 14B Second Transparent Substrate

[0111] 15A First Orientation Layer

[0112] 15B Second Orientation Layer

Claims

1. A dimming film, comprising: First transparent electrode layer; Second transparent electrode layer; A dimming layer, which is a dimming layer sandwiched between a first transparent electrode layer and a second transparent electrode layer, comprises a transparent polymer layer containing multiple voids and a liquid crystal composition containing liquid crystal molecules and filling the multiple voids; and Multiple spacers located in the dimming layer, in, Each spacer is formed of polymethyl methacrylate resin. The transparent polymer layer is formed by polymers composed of two or more unit structures and has a three-dimensional mesh structure. One or more of the two or more unit structures include a unit structure containing an aromatic ring. In the transparent polymer layer, the average value of the aromatic rings contained in the two or more unit structures is 0.4 or more in each unit structure.

2. The dimming film according to claim 1, wherein, The absolute value of the difference between the refractive index of the transparent polymer layer and the refractive index of the spacer is less than 0.04.

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