Light control sheet, light control device, and method for manufacturing light control sheet

Abstract

The liquid crystal composition contains a liquid crystal compound and one or more kinds of dichroic pigment. The percentage of the mass of the liquid crystal compound with respect to the sum of the mass of the transparent high molecular layer and the mass of the liquid crystal composition is 45% or more. The total light transmittance T of the light control sheet in the second state is 10% or more and 80% or less. The anisotropy value Rm of the dichroic pigment is 0.25 or more and 0.94 or less, and satisfies the following formula (1). In formula (1), ln is a natural logarithm. The anisotropy value Rm ≥ 0.3434ln(T) - 0.4297 formula (1).

Description

Technical Field

[0001] This disclosure relates to dimming sheets, dimming devices, and methods for manufacturing dimming sheets. Background Technology

[0002] One example of a dimming device constituting a window includes a pair of conductive layers and a switching layer located between the conductive layers. The switching layer contains a liquid crystal compound and a dichroic pigment, but does not contain a transparent polymer layer. The dimming device is configured to present a bright state and a dark state depending on whether a voltage is applied to the switching layer of the dimming device. In the dimming device, the anisotropy value R and the transmittance τv in the bright state are determined as follows (for example, see Patent Document 1) to improve the light transmittance when the bright state is presented.

[0003] Rmin <R<Rmax Rmin=0.8 (0.015) τv-0.45) Rmax=1.2 (0.015) τv-0.45) Existing technical documents Patent documents Patent Document 1: Japanese Patent Publication No. 2016-510907 Summary of the Invention

[0004] The problem that the invention aims to solve Another example of a dimming device includes a dimming layer comprising a transparent polymer layer with multiple pores, replacing the aforementioned switching layer. In the dimming layer, a liquid crystal compound and a dichroic pigment are filled into the pores of the transparent polymer layer. The dimming device is configured to switch between a state where refraction and scattering occur at the interface between the liquid crystal compound and the transparent polymer layer, and a state where almost no refraction and scattering occur, depending on whether a voltage is applied to the dimming layer. Therefore, the dimming device can exhibit both a transparent state and an opaque state.

[0005] As a dichroic pigment included in such a dimming device, a black pigment has been proposed, for example. A dimming device containing a black dichroic pigment can be both transparent and opaque with a black tint. Thus, when the dimming device is transparent, objects can be seen through it, while when it is opaque, objects cannot be seen through it. Therefore, such dimming devices are mostly used to protect the privacy of one space from the intrusion of occupants in the other space when two spaces are separated by the dimming device.

[0006] For dimming devices used in such applications, it is required to maintain the transmission of light in the transparent state, but to suppress light transmission in a manner that protects privacy when the device is colored and opaque, not limited to black. That is, it is required to increase the contrast ratio (the ratio of transmittance in the transparent state to that in the opaque state) within the dimming disc.

[0007] Methods for solving problems One method of a dimming sheet includes: a first transparent electrode layer; a second transparent electrode layer; and a dimming layer located between the first transparent electrode layer and the second transparent electrode layer. The dimming layer comprises a transparent polymer layer containing a plurality of voids and a liquid crystal composition filling the voids. The dimming sheet exhibits a first state and a second state with a haze value lower than the first state, depending on the magnitude of the voltage applied to the dimming layer. The liquid crystal composition comprises a liquid crystal compound and one or more dichroic pigments. The mass percentage of the liquid crystal compound relative to the sum of the mass of the transparent polymer layer and the mass of the liquid crystal composition is 45% by mass or more. The total light transmittance T of the dimming sheet exhibiting the second state is 10% or more and 80% or less. The anisotropy value Rm of the dichroic pigment is 0.25 or more and 0.94 or less, and satisfies the following formula (1).

[0008] The anisotropy value Rm ≥ 0.3434ln(T) - 0.4297 Equation (1) In equation (1), ln is the natural logarithm.

[0009] One method of a dimming sheet includes: a first transparent electrode layer; a second transparent electrode layer; and a dimming layer located between the first transparent electrode layer and the second transparent electrode layer. The dimming layer comprises a transparent polymer layer containing a plurality of voids and a liquid crystal composition filling the voids. The dimming sheet exhibits a first state and a second state with a haze value lower than the first state, depending on the magnitude of the voltage applied to the dimming layer. The liquid crystal composition comprises a liquid crystal compound and one or more dichroic pigments. The mass percentage of the liquid crystal compound relative to the sum of the mass of the transparent polymer layer and the mass of the liquid crystal composition is 55% by mass or more. The total light transmittance T of the dimming sheet exhibiting the second state is 10% or more and 80% or less. The anisotropy value Rm of the dichroic pigment is 0.25 or more and 0.94 or less, and satisfies the following formula (2).

[0010] The anisotropy value Rm ≥ 0.2989ln(T) - 0.3472 Equation (2) In equation (2), ln is the natural logarithm.

[0011] One embodiment of a dimming device includes: the dimming sheet described above; and a driving unit configured to apply a voltage to the dimming layer provided on the dimming sheet.

[0012] One method for manufacturing a dimming film is as follows: the dimming film comprises: a first transparent electrode layer; a second transparent electrode layer; and a dimming layer located between the first transparent electrode layer and the second transparent electrode layer. The dimming layer includes a transparent polymer layer containing a plurality of voids and a liquid crystal composition filling the voids. The dimming film exhibits a first state and a second state with a haze value lower than the first state, depending on the magnitude of the voltage applied to the dimming layer. The manufacturing method includes: preparing a coating liquid comprising a liquid crystal compound, a dichroic pigment, and a polymerizable composition; forming a coating film between the first transparent electrode layer and the second transparent electrode layer using the coating liquid; and polymerizing the polymerizable composition in the coating film. The step of preparing the coating liquid includes: preparing the coating liquid in such a way that the mass percentage of the liquid crystal compound relative to the total mass of the coating liquid is 45% by mass or more; and selecting the dichroic pigment having an anisotropy value Rm of 0.25 or more and 0.94 or less and having the anisotropy value Rm satisfying the following formula (1). The total light transmittance T of the dimming sheet exhibiting the second state described above is 10% or more and 80% or less.

[0013] The anisotropy value Rm ≥ 0.3434ln(T) - 0.4297 Equation (1) In equation (1), ln is the natural logarithm.

[0014] One method for manufacturing a dimming film is as follows: the dimming film comprises: a first transparent electrode layer; a second transparent electrode layer; and a dimming layer located between the first transparent electrode layer and the second transparent electrode layer. The dimming layer comprises a transparent polymer layer containing a plurality of voids and a liquid crystal composition filling the voids. The dimming film exhibits a first state and a second state with a haze value lower than the first state, depending on the magnitude of the voltage applied to the dimming layer. The manufacturing method includes: preparing a coating liquid comprising a liquid crystal compound, a dichroic pigment, and a polymerizable composition; forming a coating film between the first transparent electrode layer and the second transparent electrode layer using the coating liquid; and polymerizing the polymerizable composition in the coating film. The step of preparing the coating liquid includes: preparing the coating liquid in such a way that the mass percentage of the liquid crystal compound relative to the total mass of the coating liquid is 55% by mass or more; and selecting the dichroic pigment having an anisotropy value Rm of 0.25 or more and 0.94 or less and having the anisotropy value Rm satisfying the following formula (2). The total light transmittance T of the dimming sheet exhibiting the second state described above is 10% or more and 80% or less.

[0015] The anisotropy value Rm ≥ 0.2989ln(T) - 0.3472 Equation (2) In equation (2), ln is the natural logarithm. Attached Figure Description

[0016] Figure 1 This is a cross-sectional view showing the structure of a first dimming device equipped with a positive dimming disc.

[0017] Figure 2 It is not correct Figure 1 This is a magnified partial cross-sectional view showing a portion of the structure of the dimming plate when a voltage is applied to the dimming layer.

[0018] Figure 3 It is to Figure 1 The diagram shows a partially enlarged cross-sectional view of a portion of the structure of a dimming plate when a voltage is applied to the dimming layer.

[0019] Figure 4 This is a cross-sectional view showing the structure of a second dimming device equipped with a reverse-type dimming disc.

[0020] Figure 5 It is not correct Figure 4 This is a magnified partial cross-sectional view showing a portion of the structure of the dimming plate when a voltage is applied to the dimming layer.

[0021] Figure 6 It is to Figure 4The diagram shows a partially enlarged cross-sectional view of a portion of the structure of a dimming plate when a voltage is applied to the dimming layer.

[0022] Figure 7 It is a graph showing the relationship between the contrast of the dimming film and the thickness of the dimming layer.

[0023] Figure 8 It is a graph showing the relationship between the total light transmittance of the dimming film and the thickness of the dimming layer.

[0024] Figure 9 It is a graph showing the relationship between the total light transmittance and contrast of a dimming film.

[0025] Figure 10 This is a graph showing the relationship between the anisotropy value Rm of the dichroic pigment at a liquid crystal compound concentration of 55% by mass and the total light transmittance T of the dimmer.

[0026] Figure 11 This is a graph showing the relationship between the anisotropy value Rm of the dichroic pigment at a liquid crystal compound concentration of 45% by mass and the total light transmittance T of the dimmer. Detailed Implementation

[0027] Reference Figures 1-11 One embodiment of the dimming film will be described. The dimming film of this disclosure can be either a positive type or a negative type. Hereinafter, refer to... Figures 1-3 The first dimming device, which includes a positive dimming plate and a drive unit, will be described below, with reference to... Figures 4-6 A second dimming device having a reverse-type dimming plate and a drive unit will be described.

[0028] In addition, dimming sheets are transparent components installed in windows of various buildings such as residences, stations, and airports; partitions in offices; and shop windows. Alternatively, dimming sheets are transparent components installed in windows of moving vehicles such as vehicles and airplanes. Dimming sheets can be flat or curved.

[0029] [First dimming device] Reference Figures 1-3 The first dimming device will be described. Figure 1 The structure of a dimming device with a positive dimming disc is shown. Figure 2 This shows a portion of the structure of the dimming film when no voltage is applied to the dimming layer. Figure 3 This shows a portion of the structure of a dimming film when a voltage is applied to the dimming layer.

[0030] like Figure 1As shown, the first dimming device 10N includes a forward-facing dimming plate 11N and a driving unit 12. The dimming plate 11N includes a first transparent electrode layer 21, a second transparent electrode layer 22, and a dimming layer 23. The dimming plate 11N includes a first transparent substrate 24 supporting the first transparent electrode layer 21 and a second transparent substrate 25 supporting the second transparent electrode layer 22.

[0031] In the dimming film 11N, the dimming layer 23 is located between the first transparent electrode layer 21 and the second transparent electrode layer 22. The first transparent electrode layer 21 is located between the first transparent substrate 24 and the dimming layer 23. The second transparent electrode layer 22 is located between the second transparent substrate 25 and the dimming layer 23.

[0032] The dimming strip 11N exhibits a first state and a second state with a lower haze value than the first state, depending on the magnitude of the voltage applied to the dimming layer 23. Since the dimming strip 11N of the first dimming device 10N is of a positive type, it exhibits the first state when no voltage is applied to the dimming layer 23. Conversely, it exhibits the second state when a voltage is applied to the dimming layer 23. The dimming strip 11N in the first state is opaque, while the dimming strip 11N in the second state is transparent. For example, the haze value of the dimming strip 11N in the first state can be 80% or more, and the haze value of the dimming strip 11N in the second state can be 10% or more and 80% or less. Preferably, the haze value of the dimming strip 11N in the first state is higher than 80%.

[0033] The dimming plate 11N includes a first electrode 21E mounted on a portion of the first transparent electrode layer 21 and a second electrode 22E mounted on a portion of the second transparent electrode layer 22. The dimming plate 11N further includes wiring 26 connected to the first electrode 21E and wiring 26 connected to the second electrode 22E. The first electrode 21E is connected to the driving unit 12 via wiring 26. The second electrode 22E is connected to the driving unit 12 via wiring 26.

[0034] The first transparent electrode layer 21 and the second transparent electrode layer 22 apply a voltage to the dimming layer 23 to switch the dimming layer 23 to a first state and a second state. Each transparent electrode layer 21, 22 has light transmittance that allows visible light to pass through. The light transmittance of the first transparent electrode layer 21 is such that an object can be seen through the dimming disc 11N. The light transmittance of the second transparent electrode layer 22 is the same as that of the first transparent electrode layer 21, allowing an object to be seen through the dimming disc 11N.

[0035] The materials used to form the transparent electrode layers 21, 22 can be, for example, any one selected from indium tin oxide, fluorine-doped tin oxide, tin oxide, zinc oxide, carbon nanotubes, and poly(3,4-ethylenedioxythiophene).

[0036] The materials forming the transparent substrates 24 and 25 can be synthetic resins or inorganic compounds. Synthetic resins include, for example, polyesters, polyacrylates, polycarbonates, and polyolefins. Polyesters include, for example, polyethylene terephthalate and polyethylene naphthalate. Polyacrylates include, for example, polymethyl methacrylate. Inorganic compounds include, for example, silicon dioxide, silicon oxynitride, and silicon nitride.

[0037] Each electrode 21E and 22E 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, for example, formed of a metal thin film. The material forming the metal thin film can be, for example, copper. Each electrode 21E and 22E is not limited to an FPC; for example, it can also be a metal strip.

[0038] Furthermore, each electrode 21E, 22E is mounted to each transparent electrode layer 21, 22 via a conductive adhesive layer (not shown). At the portion of each electrode 21E, 22E that is connected to the conductive adhesive layer, the conductor portion is exposed from the protective layer or the support layer.

[0039] The conductive adhesive layer can be formed, for example, from anisotropic conductive film (ACF), anisotropic conductive paste (ACP), isotropic conductive film (ICF), and isotropic conductive paste (ICP). From the viewpoint of processability in the manufacturing process of the dimming device 10, the conductive adhesive layer is preferably anisotropic conductive film.

[0040] Each wiring 26 is formed, for example, by a metal conductor and an insulating layer covering the metal conductor. The conductor is, for example, made of copper.

[0041] The driving unit 12 is configured to apply a voltage to the dimming layer 23 of the dimming sheet 11N. The driving unit 12 applies an alternating voltage between the first transparent electrode layer 21 and the second transparent electrode layer 22. Preferably, the driving unit 12 applies an alternating voltage with a rectangular wave shape between the pair of transparent electrode layers 21, 22. In other words, the driving unit 12 preferably outputs a rectangular wave voltage signal.

[0042] Reference Figure 2 and Figure 3 A more detailed explanation of dimming layer 23.

[0043] like Figure 2As shown, the dimming layer 23 comprises a transparent polymer layer 23T and a liquid crystal composition 23L. The transparent polymer layer 23T contains a plurality of voids 23D. The liquid crystal composition 23L fills the voids 23D in the transparent polymer layer 23T and contains a liquid crystal compound 23LM and a dichroic pigment 23P.

[0044] The liquid crystal composition 23L is held in a manner selected from polymer network type, polymer dispersion type, and capsule type. The polymer network type has a transparent polymer network with a three-dimensional mesh structure, holding the liquid crystal composition 23L within interconnected mesh-like voids 23D. The polymer network is an example of a transparent polymer layer 23T. The polymer dispersion type has a plurality of isolated voids 23D within the transparent polymer layer 23T, holding the liquid crystal composition within the voids 23D dispersed in the transparent polymer layer 23T. The capsule type holds the capsule-shaped liquid crystal composition 23L within the transparent polymer layer 23T. Thus, voids 23D filled with the liquid crystal composition 23L are formed within the transparent polymer layer 23T.

[0045] In the dimming layer 23, the void diameter of the void 23D can be 0.1 μm or more and 30 μm or less. By including the void diameter in the range of 0.1 μm or more and 30 μm or less, the effectiveness of satisfying the anisotropy value Rm of the dichroic pigment 23P with equations (1) and (2) can be improved. The void diameter is measured in a cross section of the dimming layer 23 along the thickness direction of the dimming layer 23. In this cross section, when the void 23D has a circular shape, the diameter of the void 23D is the void diameter. When the void 23D has an elliptical shape, the major axis of the void 23D is the void diameter. When the void 23D has an amorphous shape, the major axis of the ellipse with the smallest major axis among the ellipses circumscribed with the void 23D is the void diameter of the void 23D.

[0046] An example of liquid crystal compound 23LM is selected from any one of the Schiff base system, azo system, azo oxide system, biphenyl system, terphenyl system, benzoate system, diphenylacetylene system, pyrimidine system, cyclohexane carboxylate system, phenylcyclohexane system, and dioxane system. Liquid crystal composition 23L comprises a positive nematic liquid crystal with positive dielectric anisotropy as liquid crystal compound 23LM.

[0047] The concentration of the liquid crystal compound 23LM in the dimming layer 23 is the percentage of the mass of the liquid crystal composition 23L relative to the total mass of the dimming layer 23. That is, the concentration of the liquid crystal compound 23LM is the percentage of the mass of the liquid crystal compound 23LM relative to the sum of the mass of the transparent polymer layer 23T and the mass of the liquid crystal composition 23L. The concentration of the liquid crystal compound 23LM can be, for example, 45% by mass or more, or 55% by mass or more.

[0048] Dichroic pigment 23P has an elongated shape. The absorbance of the visible region along the long axis of the molecule is greater than that along the short axis. Dichroic pigment 23P is essentially transparent when its long axis is parallel or approximately parallel to the incident light direction. Conversely, it exhibits a specific color when its long axis is perpendicular or approximately perpendicular to the incident light direction.

[0049] Therefore, when the dichroic pigment 23P is oriented in a manner parallel or substantially parallel to the normal direction and major axis direction of the contact surface with the first transparent electrode layer 21 in the dimming layer 23 and the contact surface with the second transparent electrode layer 22 in the dimming layer 23, it exhibits transparency. Conversely, when the dichroic pigment 23P is oriented in a manner perpendicular or substantially perpendicular to the normal direction and major axis direction of the contact surface with the first transparent electrode layer 21 in the dimming layer 23 and the contact surface with the second transparent electrode layer 22 in the dimming layer 23, it exhibits a predetermined color. The color exhibited by the dichroic pigment 23P is preferably black or a color close to black. The dichroic pigment 23P is driven by a host-guest pattern with liquid crystal compound 23LM as the main body, thereby enabling the dichroic pigment 23P to display color.

[0050] Dichroic pigment 23P may be selected from at least one of the following: high-iodine compounds, azo compounds, anthraquinone compounds, naphthoquinone compounds, methylimine compounds, tetrazine compounds, quinoline compounds, cyanine compounds, perylene compounds, and dioxazine compounds. Dichroic pigment 23P may be a single pigment or a combination of two or more pigments. From the viewpoints of improving the lightfastness and dichroic ratio of dichroic pigment 23P, dichroic pigment 23P is preferably selected from at least one of azo compounds and anthraquinone compounds. Dichroic pigment 23P is more preferably an azo compound.

[0051] In addition to the liquid crystal compound 23LM and dichroic pigment 23P mentioned above, the liquid crystal composition 23L may also contain, for example, monomers for forming the transparent polymer layer 23T.

[0052] like Figure 2 As shown, when no voltage is applied to the dimming layer 23, the liquid crystal compound 23LM is randomly oriented. Consequently, the dichroic pigment 23P is also randomly oriented, just like the liquid crystal compound 23LM. Therefore, the dimming layer 23, and consequently the dimming disc 11N, is opaque when no voltage is applied to the dimming layer 23. Thus, the dimming disc 11N exhibits a first state with a relatively high haze value. Furthermore, the dimming disc 11N exhibits a predetermined color based on the dichroic pigment 23P.

[0053] The haze value of the dimmer 11N in its first state is 80% or higher. The haze value is obtained according to the measurement method of ASTM D 1003-00. The haze measuring instrument is, for example, a BYK haze-gard i instrument (manufactured by BYK Gardner). In the measurement of the haze value, the light beam incident on the dimmer 11N contains straight-line light. The maximum angle between the light beam incident on the dimmer 11N and the optical axis of the beam is less than 3°. The dimmer 11N is fixed such that the surface of the dimmer 11N is approximately perpendicular to the light beam incident on that surface within ±2°.

[0054] like Figure 3 As shown, when a voltage is applied to the dimming layer 23, the liquid crystal compound 23LM is aligned parallel to the electric field. The dimming sheet 11N is configured such that when a voltage is applied to the dimming layer 23, the long axis direction of the liquid crystal compound 23LM is perpendicular to the aforementioned contact surface. That is, the liquid crystal compound 23LM is vertically oriented. Consequently, the dichroic pigment 23P is also vertically oriented, just like the liquid crystal compound 23LM. Therefore, the dimming layer 23, and consequently the dimming sheet 11N, is transparent when a voltage is applied to the dimming layer 23. As a result, the dimming sheet 11N exhibits a second state with a relatively low haze value. Furthermore, the dimming sheet 11N does not exhibit the predetermined color based on the dichroic pigment 23P.

[0055] [Second dimming device] Reference Figures 4-6 The second dimming device will be described below. The second dimming device differs from the first dimming device 10N described above in that it has a reverse-type dimming plate. Therefore, the differences from the first dimming device 10N in the second dimming device will be described in detail below, and the same reference numerals will be used for components in the second dimming device that are identical to those in the first dimming device 10N, thus omitting detailed descriptions of these components.

[0056] like Figure 4 As shown, the second dimming device 10R includes a reverse-type dimming plate 11R and a driving unit 12. The dimming plate 11R includes a first alignment layer 37 and a second alignment layer 38. The first alignment layer 37 is located between the dimming layer 23 and the first transparent electrode layer 21. The second alignment layer 38 is located between the dimming layer 23 and the second transparent electrode layer 22.

[0057] The first alignment layer 37 and the second alignment layer 38 are vertical alignment films. The vertical alignment films are formed by aligning the long axis of the liquid crystal compounds in a manner perpendicular to the surface opposite to the surface contacting the first transparent electrode layer 21 and the surface opposite to the surface contacting the second transparent electrode layer 22. Thus, the alignment layers 37 and 38 restrict the orientation of the plurality of liquid crystal compounds contained in the dimming layer 23.

[0058] The materials used to form the first orientation layer 37 and the second orientation layer 38 are organic compounds, inorganic compounds, and mixtures thereof. Examples of organic compounds include polyimide, polyamide, polyvinyl alcohol, and cyanide compounds. Examples of inorganic compounds include silicon oxide and zirconium oxide. Furthermore, the materials used to form the orientation layers 37 and 38 can also be organosilicon. Organosilicon is a compound possessing both inorganic and organic components.

[0059] Reference Figure 5 and Figure 6 A more detailed explanation of dimming layer 23.

[0060] like Figure 5 As shown, the dimming layer 23, like the dimming layer 23 of the positive dimming sheet 11N, includes a transparent polymer layer 23T containing voids 23D and a liquid crystal composition 23L filling the voids 23D. The liquid crystal composition 23L includes a liquid crystal compound 23LM and a dichroic pigment 23P. Specifically, the liquid crystal composition 23L includes a negative nematic liquid crystal with negative dielectric anisotropy as the liquid crystal compound 23LM.

[0061] like Figure 5 As shown, when no voltage is applied to the dimming layer 23, the liquid crystal compound 23LM is oriented perpendicularly to the contact surface by the orientation restraint forces of the alignment layers 37 and 38. Consequently, the dichroic pigment 23P is also oriented perpendicularly to the liquid crystal compound 23LM. Therefore, the dimming layer 23, and consequently the dimming disc 11R, is transparent when no voltage is applied to the dimming layer 23. Thus, the dimming disc 11R exhibits a second state with a relatively low haze value. Furthermore, the dimming disc 11R does not exhibit a color based on the dichroic pigment 23P.

[0062] like Figure 6 As shown, when a voltage is applied to the dimming layer 23, the liquid crystal compound 23LM is oriented perpendicular to the electric field. The dimming disc 11R is configured such that when a voltage is applied to the dimming layer 23, the long axis direction of the liquid crystal compound 23LM is parallel to the aforementioned contact surface. That is, the liquid crystal compound 23LM is horizontally oriented. However, within the plane containing the liquid crystal compound 23LM, the azimuth angle of the long axis direction is random. Consequently, the dichroic pigment 23P is also horizontally oriented like the liquid crystal compound 23LM. However, within the plane containing the dichroic pigment 23P, the azimuth angle of the length direction of the dichroic pigment 23P is random. Therefore, the dimming layer 23, and consequently the dimming disc 11R, is opaque when a voltage is applied to the dimming layer 23. Thus, the dimming disc 11R exhibits a first state with a relatively high haze value. Furthermore, the dimming disc 11R exhibits a predetermined color based on the dichroic pigment 23P.

[0063] [Optical characteristics of dimmers] Reference Figures 7-11 The optical characteristics of dimming films 11N and 11R will be explained. Dimming film 11R has a vertical alignment layer, but it is common to have a dimming layer 23 that includes a transparent polymer layer 23T and a liquid crystal composition 23L containing a dichroic pigment 23P. Therefore, the optical characteristics of dimming film 11N will be explained instead of the optical characteristics of dimming film 11R.

[0064] In addition to having a total light transmittance T of 10% or more and 80% or less when presenting the second state, and an anisotropy value Rm of the dichroic pigment 23P of 0.25 or more and 0.94 or less, the dimming film 11N disclosed herein also satisfies any one of the following conditions.

[0065] (Condition 1) The concentration of liquid crystal compound 23LM is 45% by mass or more, and the anisotropy value Rm of dichroic pigment 23P satisfies the following equation (1).

[0066] The anisotropy value Rm ≥ 0.3434ln(T) - 0.4297 Equation (1) In equation (1), ln is the natural logarithm.

[0067] (Condition 2) The concentration of liquid crystal compound 23LM is 55% by mass or more, and the anisotropy value Rm of dichroic pigment 23P satisfies the following equation (2).

[0068] The anisotropy value Rm ≥ 0.2989ln(T) - 0.3472 Equation (2) In equation (2), ln is the natural logarithm.

[0069] The anisotropy value Rm, which is one of the parameters representing the light absorption characteristics of the dichroic pigment 23P contained in the dimming film 11N, is defined by the following equation (4).

[0070] Rm={E(p)-E(s)} / {E(p)+2×E(s)} Formula (4) In equation (4), absorbance E(p) is the measured absorbance of light deflected parallel to the orientation direction of the liquid crystal compound. In other words, it is the measured absorbance of the dichroic pigment in a horizontally oriented unit containing only the liquid crystal compound and the dichroic pigment. Absorbance E(s) is the measured absorbance of light deflected perpendicular to the orientation direction of the liquid crystal compound. In other words, it is the measured absorbance of the dichroic pigment in a vertically oriented unit. Furthermore, the light used to measure absorbance E(p) and E(s) has a wavelength of 550 nm.

[0071] On the other hand, the absorbance values ​​E(p) and E(s) can also be expressed by the following formula.

[0072] E(p) = εp × d × c Equation (5) E(s) = εs × d × c Equation (6) In equations (5) and (6), the absorption coefficient εp is the absorption coefficient of dichroic pigment 23P when the dichroic pigment is horizontally oriented within a horizontally oriented unit. The absorption coefficient εs is the absorption coefficient of dichroic pigment 23P when the dichroic pigment is vertically oriented within a vertically oriented unit. d is the thickness of the horizontally oriented unit. c is the concentration of the dichroic pigment.

[0073] On the other hand, the dichroism ratio DR of the dichroic pigment 23P is represented by the following formula (7).

[0074] DR=E(p) / E(s) Formula (7) The dichroic ratio DR can be expressed according to equations (5) to (7) as follows.

[0075] DR=(εp×d×c) / (εs×d×c)=εp / εs Equation (8) Therefore, the dichroism ratio DR can be said to be an inherent value of the liquid crystal composition 23L.

[0076] Similarly, according to equations (4) to (6), the anisotropy value Rc, which is the calculated value, can be expressed as follows.

[0077] Rc = (DR-1) / (DR+2) Equation (9) Therefore, similar to the dichroism ratio DR, it can be said that the anisotropy value Rc is also an inherent value of the liquid crystal composition 23L.

[0078] In contrast, in the dimming film 11N disclosed herein, since the dimming layer 23 includes a transparent polymer layer 23T, the absorbance E(p) and E(s) are expressed by the following formula.

[0079] E(p) = εp × d × n × c Equation (10) E(s) = εs × d × c Equation (6) In equation (10), the absorption coefficient εp, thickness d, and concentration c are the same as those in equation (5). On the other hand, n is the elongation coefficient that effectively extends the optical path length due to the refraction and scattering of light at the interface between the liquid crystal composition 23L and the transparent polymer layer 23T. The elongation coefficient n varies depending on the thickness of the dimming layer 23, the difference between the refractive index of the liquid crystal compound 23LM and the refractive index of the transparent polymer layer 23T, etc.

[0080] Therefore, the dichroism ratio DR is expressed by the following formula.

[0081] DR=(εp×d×n×c) / (εs×d×c)=(εp×n) / εs Equation (11) Therefore, in the dimming film 11N having a dimming layer 23 including a transparent polymer layer 23T, the dichroism ratio DR is not an inherent value of the liquid crystal composition 23L.

[0082] As described above, the elongation factor n varies depending on the thickness of the dimming layer 23 and the difference between the refractive index of the liquid crystal compound 23LM, specifically the refractive index ne of the anomalous light, and the refractive index np of the transparent polymer layer 23T. Furthermore, the dimming layer 23 comprises the liquid crystal composition 23L and the transparent polymer layer 23T, and the dichroic pigment 23P is contained within both the liquid crystal composition 23L and the transparent polymer layer 23T. In the dichroic pigment 23P contained in the liquid crystal composition 23L, the orientation changes depending on whether a voltage is applied to the dimming layer 23, thereby changing the absorbance of the dichroic pigment 23P. In contrast, since the orientation of the dichroic pigment 23P contained in the transparent polymer layer 23T is fixed, the absorbance of the dichroic pigment 23P does not change. The amount of dichroic pigment 23P contained in the transparent polymer layer 23T varies depending on the concentration of liquid crystal compound 23LM in the dimming layer 23. Therefore, the absorbance of the dimming sheet 11N changes depending on the concentration of liquid crystal compound 23LM in the dimming layer 23.

[0083] The relationship between the contrast of the dimming film 11N and the thickness of the dimming layer 23 of this disclosure will be explained below.

[0084] A dimming plate 11N for measuring contrast was made using the following materials.

[0085] (a) Transparent electrode layers 21, 22: Indium tin oxide (b) Transparent substrates 24, 25: polyethylene terephthalate (c) Spacer: spherical particles made of silicon dioxide (d) Liquid crystal compound 23LM: Fluorine-based liquid crystal compound (e) Polymerization initiator: Photopolymerization initiator (Irgacure Oxe04, manufactured by BASF) (f) Polymerizable composition: selected from one or more of monofunctional acrylates, polyfunctional acrylates, monofunctional methacrylates, urethane acrylates, and polyester acrylates. (g) Dichroic pigment 23P: A mixture of azo compounds (yellow, blue, red) In (g) dichroic pigment 23P, the dichroic ratio DR calculated by equation (8) above is 16, and the anisotropy value Rm calculated by equation (4) is 0.83. Furthermore, the refractive index ne of the anomalous light of (d) liquid crystal compound 23LM is 1.68, and the refractive index np of the transparent polymer layer 23T formed by polymerization in (f) is 1.51. Therefore, the value obtained by subtracting the refractive index np of the transparent polymer layer 23T from the refractive index ne of the anomalous light of liquid crystal compound 23LM is 0.17.

[0086] In addition, the measurements of the absorbance coefficients εp and εs, the thickness d of the horizontal orientation unit, the thickness d of the vertical orientation unit, and the concentration c were used when calculating the dichroism ratio (DR). Furthermore, the spectra used to obtain the absorbance coefficients εp and εs and the absorbances E(p) and E(s) were measured using a UV-Vis-NIR spectrophotometer (Lambda 1050, Perkin Elmer).

[0087] A first transparent substrate 24 having a first transparent electrode layer 21 and a second transparent substrate 25 having a second transparent electrode layer 22 are prepared. Next, a coating solution comprising a liquid crystal compound 23LM, a polymerization initiator, a polymerizable compound, and a spacer is prepared. At this time, the mass percentage of the liquid crystal compound 23LM relative to the total mass of the coating solution, i.e., the concentration of the liquid crystal compound 23LM, is set to 55% by mass. Furthermore, the mass percentage of the dichroic pigment 23P relative to the total mass of the coating solution, i.e., the concentration of the dichroic pigment 23P, is set to 2.5% by mass.

[0088] Then, after forming a coating film between the first transparent electrode layer 21 and the second transparent electrode layer 22 using a coating solution, a polymerizable composition is polymerized in the coating film, thereby obtaining a dimming film 11N. Furthermore, multiple dimming films 11N with different thicknesses were manufactured as dimming films 11N for evaluating dichroic performance ratio (DR). The thickness of each dimming film 11N was set to any thickness within the range of 6 μm or more and 25 μm or less.

[0089] Furthermore, the contrast ratio of each dimming disc 11N was measured using the following method. The contrast ratio is a value obtained by dividing the total light transmittance of the dimming disc 11N in its second state by the total light transmittance of the dimming disc 11N in its first state.

[0090] The total light transmittance of each dimming disc 11N was calculated using the following method. For each of the dimming discs 11N, the total light transmittance in a first state and the total light transmittance in a second state were calculated using the method according to ASTM D 1003-00. In each dimming disc 11N, the state in which a 50Hz AC voltage of 40V with a rectangular waveform is applied between a pair of transparent electrode layers is defined as the second state. On the other hand, in each dimming disc 11N, the state in which no voltage is applied between a pair of transparent electrodes is defined as the first state. The total light transmittance was calculated using a haze-transparency measuring instrument (BYKhaze-gard i instrument, manufactured by BYK Gardner Corporation).

[0091] The contrast ratio of the 11N dimmer is as follows: Figure 7 As shown.

[0092] like Figure 7 As shown, the contrast ratio of the dimming film 11N tends to be higher the thickness of the dimming layer 23. That is, it can be seen that when a dichroic pigment 23P is applied in the dimming layer 23 containing the transparent polymer layer 23T, the contrast ratio is not uniquely determined. In addition, when the thickness of the dimming layer 23 is less than 21 μm, the contrast ratio of the dimming film 11N is less than the dichroic ratio DR calculated by equation (8), which is 16. In contrast, when the thickness of the dimming layer 23 is 21 μm or more, the contrast ratio of the dimming film 11N is greater than or equal to the dichroic ratio DR calculated by equation (8).

[0093] When the thickness of the dimming layer 23 is less than 21 μm, the contrast ratio of the dimming film 11N is considered to be lower than 16 for the following reasons: that is, the degree to which the dichroism ratio DR is reduced because the orientation of the dichroic pigment 23P contained in the transparent polymer layer 23T is fixed exceeds the degree to which the dichroism ratio DR is improved because the optical path length in the dimming layer 23 is increased due to the inclusion of the transparent polymer layer 23T in the dimming layer 23.

[0094] In contrast, when the thickness of the dimming layer 23 is 21 μm or more, the contrast ratio of the dimming disc 11N is considered to be 16 or more for the following reasons: The increased contrast ratio due to the longer optical path length within the dimming layer 23 caused by the inclusion of the transparent polymer layer 23T exceeds the decrease in contrast ratio caused by the fixed orientation of the dichroic pigment 23P contained within the transparent polymer layer 23T.

[0095] The total light transmittance T was measured for each dimming sheet 11N with a calculated contrast ratio. Furthermore, multiple dimming sheets 11N were fabricated using the same method as when the concentration of liquid crystal compound 23LM was 55% by mass, except that the concentration of liquid crystal compound 23LM was changed to 45% by mass. In addition, in the coating solution used to form the dimming layer with a concentration of 45% by mass of liquid crystal compound 23LM, the amount of polymerizable composition was increased accordingly to match the reduction in the amount of liquid crystal compound 23LM in the coating solution with a concentration of 55% by mass.

[0096] The total light transmittance T of each dimming sheet 11N was measured using the same method as when measuring the contrast of the dimming sheet 11N.

[0097] The results of the total light transmittance T measurement are as follows: Figure 8 As shown. Furthermore, in Figure 8 In the figure, the relationship between the total light transmittance T and the thickness of the dimming layer 23 when the concentration of liquid crystal compound 23LM is 55% by mass is shown by solid lines, and the relationship between the total light transmittance T and the thickness of the dimming layer 23 when the concentration of liquid crystal compound 23LM is 45% by mass is shown by dashed lines.

[0098] like Figure 8 As shown, within the range of a dimming layer 23 thickness of 6 μm or more and 25 μm or less, the total light transmittance T when the concentration of liquid crystal compound 23LM is 55% by mass is higher than that when the concentration of liquid crystal compound 23LM is 45% by mass. Furthermore, it can be seen that regardless of the concentration of liquid crystal compound 23LM, the dimming film 11N tends to have a lower total light transmittance T as the thickness of the dimming layer 23 increases.

[0099] Furthermore, in each dimming sheet 11N, the refractive index no of the liquid crystal compound 23LM under normal light is equal to the refractive index np of the transparent polymer layer 23T. Therefore, in each dimming sheet 11N exhibiting the second state, it can be considered that no refraction and scattering of light incident on the dimming sheet 11N occurs within the dimming sheet 11N.

[0100] Furthermore, in the dimming disc 11N exhibiting the second state, the light absorption coefficient of the liquid crystal composition 23L differs from that of the transparent polymer layer 23T. As described above, the light absorption coefficient of the liquid crystal composition 23L is εs. In contrast, when the long axis direction of the dichroic pigment 23P contained in the transparent polymer layer 23T is random, the light absorption coefficient of the transparent polymer layer 23T is considered to be expressed by the following formula.

[0101] Equation (12) is (εp+2εs) / 3 Since the absorption coefficient εp is greater than the absorption coefficient εs, the absorption coefficient in the transparent polymer layer 23T is greater than εs. Therefore, it is assumed that with the increase in the volume of the transparent polymer layer 23T in the dimming layer 23, i.e., the decrease in the volume of the liquid crystal composition 23L, the proportion of the dichroic pigment 23P located in the transparent polymer layer 23T increases, thus reducing the total light transmittance of the dimming plate 11N. Figure 8 The measured results also show that the transmittance of liquid crystal compound 23LM at a concentration of 45% by mass is lower than that at a concentration of 55% by mass.

[0102] Furthermore, for each dimming disc 11N with a concentration of 45% by mass of liquid crystal compound 23LM, the contrast ratio was calculated using the same method as for each dimming disc 11N with a concentration of 55% by mass of liquid crystal compound 23LM.

[0103] Furthermore, for each dimming sheet 11N with a concentration of 55% by mass of liquid crystal compound 23LM, the haze value of the dimming sheet 11N in its first state was calculated. In the calculation of the haze value, the method according to ASTM D1003-00 was used in the same way as the calculation of the total light transmittance T, and a haze-transparency measuring instrument (BYK haze-gard i instrument, manufactured by BYK Gardner Corporation) was used. It can be seen that the haze value of the dimming sheet 11N is 80% or more and 99% or less, that is, 80% or more, and the haze value of the dimming sheet 11N increases monotonically as the thickness of the dimming sheet 11N increases from 6 μm to 25 μm. When the dimming sheet 11N is in its first state, by making the dimming sheet 11N 80% or more, the effectiveness of the above equations (1) to (3) can be improved.

[0104] Figure 9 This illustrates the relationship between the contrast ratio and the total light transmittance T of the dimming disc 11N. The total light transmittance T is the total light transmittance of the dimming disc 11N when it is in its second state. Furthermore, in... Figure 9 In the figure, the relationship between total light transmittance T and contrast is shown by solid lines when the concentration of liquid crystal compound 23LM is 55% by mass, and the relationship between total light transmittance T and contrast is shown by dashed lines when the concentration of liquid crystal compound 23LM is 45% by mass.

[0105] like Figure 9As shown, regardless of the concentration of the liquid crystal compound 23LM, the dimming film 11N tends to have a higher contrast ratio and a lower total light transmittance T. Furthermore, when the concentration of the liquid crystal compound 23LM is 55% by mass, the visible contrast ratio is 2 or higher when the total light transmittance T is 47.6% or lower. Conversely, when the concentration of the liquid crystal compound 23LM is 45% by mass, the visible contrast ratio is 2 or higher when the total light transmittance T is 34.0% or lower. In the dimming film 11N, when the contrast ratio is 2 or higher, the amount of light transmitted through the dimming film 11N can differ by more than two times between the first state and the second state. Therefore, the light transmittance variation function required by the dimming film 11N can be satisfied. Moreover, regardless of the concentration of the liquid crystal compound 23LM, the total light transmittance T when the contrast ratio is 2 or higher is equivalent to the total light transmittance T when the thickness of the dimming layer 23 is 9 μm or higher.

[0106] In addition, a dichroic pigment 23P is prepared, which consists of multiple dichroic pigments 23P whose anisotropy value Rm calculated by equation (4) is in the range of 0.25 or higher and 0.94 or lower, and each has a different anisotropy value Rm. Furthermore, the dichroic pigment 23P with a specific anisotropy value Rm can be a single dichroic pigment or a mixture of two or more pigments. For the dimming film 11N containing each dichroic pigment 23P, the total light transmittance T is measured and the contrast ratio is calculated using the same method as in the case of the dichroic pigment 23P containing anisotropy value Rm of 0.83. Thus, for the dimming film 11N containing each dichroic pigment 23P, the total light transmittance T when the contrast ratio is 2 is determined.

[0107] The results of calculating the anisotropy value Rm of the dichroic pigment 23P contained in the dimming film 11N and measuring the total light transmittance T are shown in Table 1 below.

[0108] In addition, the calculated anisotropy value Rm of the dichroic pigment 23P in the dimming film 11N with a contrast ratio of less than 2 and the measured total light transmittance T are shown in Table 2 below.

[0109] Figure 10 and Figure 11 The relationship between the anisotropy value Rm and the total light transmittance T is shown when the contrast ratio is 2. Furthermore, Figure 10 The relationship between the anisotropy value Rm and the total light transmittance T of liquid crystal compound 23LM at a concentration of 55% by mass is shown. In contrast, Figure 11The relationship between the anisotropy value Rm and the total light transmittance T is shown when the concentration of liquid crystal compound 23LM is 45% by mass.

[0110] Figure 10 The approximate curve shown can be represented by the following equation (13).

[0111] Rm = 0.2989ln(T) - 0.3472 Equation (13) Figure 11 The approximate curve shown can be represented by the following equation (14).

[0112] Rm = 0.3434ln(T) - 0.4297 Equation (14) In addition, such as Figure 10 and Figure 11 As shown, to obtain the same total light transmittance T, when the concentration of liquid crystal compound 23LM is 45% by mass, compared to when the concentration of liquid crystal compound 23LM is 55% by mass, the dimming layer 23 needs to contain a dichroic pigment 23P with a higher anisotropy value Rm. Additionally, as shown in the reference... Figure 9 As previously explained, the contrast ratio tends to be higher as the total light transmittance T decreases. Therefore, within the range where the concentration of liquid crystal compound 23LM is 45% by mass or more, the anisotropy value Rm calculated by equation (4) only needs to be equal to or greater than that calculated by equation (14). Furthermore, within the range where the concentration of liquid crystal compound 23LM is 55% by mass or more, the anisotropy value Rm calculated by equation (4) only needs to be equal to or greater than that calculated by equation (13).

[0113] Thus, the dimming film 11N of this disclosure satisfies either condition 1 or condition 2 above.

[0114] According to the dimming film 11N disclosed herein, by ensuring that the anisotropy value Rm, calculated based on the absorbance E(p) and E(s) specific to the dichroic pigment 23P, satisfies either equation (1) or equation (2), a dimming film 11N with a contrast ratio of 2 or higher can be obtained. That is, in the dimming film 11N capable of displaying black in the first state, the contrast ratio, i.e., the ratio of brightness in the second state to brightness in the first state, can be improved. Furthermore, in this disclosure, the brightness in the first state and the brightness in the second state are the total light transmittance T of each state.

[0115] Furthermore, the value obtained by subtracting the refractive index np of the transparent polymer layer 23T from the refractive index ne of the anomalous light of the liquid crystal compound 23LM can be 0.17 or higher. This improves the effectiveness of extending the optical path length through refraction and scattering at the interface between the liquid crystal composition 23L and the transparent polymer layer 23T.

[0116] [Manufacturing method of dimming film] The method for manufacturing a dimming film disclosed herein includes the steps of: preparing a coating liquid comprising a liquid crystal compound, a dichroic pigment, and a polymerizable composition; forming a coating film between a first transparent electrode layer 21 and a second transparent electrode layer 22 using the coating liquid; and polymerizing the polymerizable composition in the coating film. The step of preparing the coating liquid includes: preparing the coating liquid such that the mass percentage of the liquid crystal compound 23LM relative to the total mass of the coating liquid is 45% or more by mass; and selecting a dichroic pigment 23P having an anisotropy value Rm of 0.25 or more and 0.94 or less and having an anisotropy value Rm satisfying the following formula (1). The total light transmittance T of the dimming films 11N and 11R in the second state is 10% or more and 80% or less.

[0117] The anisotropy value Rm ≥ 0.3434ln(T) - 0.4297 Equation (1) In addition, when preparing the coating solution with a mass percentage of liquid crystal compound 23LM of 55% or more, a dichroic pigment 23P having an anisotropy value Rm that satisfies the following formula (2) can be selected.

[0118] The anisotropy value Rm ≥ 0.2989ln(T) - 0.3472 Equation (2) The process of forming the dimming layer 23 in the manufacturing method of dimming films 11N and 11R will be described in more detail below. Furthermore, the reverse-type dimming film 11R differs from the forward-type dimming film 11N in that it has a pair of alignment layers 37 and 38 that serve as vertical alignment films. However, the process of forming the dimming layer 23 in the reverse-type dimming film 11R is the same as the process of forming the dimming layer 23 in the forward-type dimming film 11N. Therefore, the method for manufacturing the forward-type dimming film 11N will be described below, while the method for manufacturing the reverse-type dimming film 11R will be omitted.

[0119] When manufacturing the dimming film 11N, firstly, a first transparent substrate 24 having a first transparent electrode layer 21 formed thereon and a second transparent substrate 25 having a second transparent electrode layer 22 formed thereon are prepared.

[0120] Next, a coating solution comprising liquid crystal compound 23LM, dichroic pigment 23P, and a polymerizable composition is prepared. As described above, the coating solution may contain a polymerization initiator and spacers. The polymerization initiator may be, for example, a photopolymerization initiator. The spacers may be, for example, spherical, and in this case, the diameter of the spacers is appropriately set according to the required thickness of the dimming layer 23. At this time, the coating solution is prepared such that the mass percentage of liquid crystal compound 23LM relative to the mass of the coating solution, i.e., the proportion of liquid crystal compound 23LM, is 45% by mass or more or 55% by mass or more.

[0121] Next, a coating film is formed between the first transparent electrode layer 21 and the second transparent electrode layer 22 using a coating solution. For example, after forming a coating film using a coating solution on the first alignment layer 37, a second alignment layer 38 is overlapped on the coating film, thereby using the first transparent electrode layer 21 and the second transparent electrode layer 22 to hold the coating film.

[0122] By irradiating a laminate containing a pair of transparent electrode layers 21 and 22 and a coating with light, a polymeric composition is polymerized in the coating. At this time, for example, the laminate is irradiated with ultraviolet light. By irradiating the coating with ultraviolet light, the polymeric composition is polymerized, causing phase separation of the liquid crystal compound 23LM from the transparent polymer layer 23T. Thus, a transparent polymer layer 23T with voids 23D is formed from the polymeric composition, and a liquid crystal composition 23L containing the liquid crystal compound 23LM and the dichroic pigment 23P is located within the voids 23D.

[0123] As explained above, according to one embodiment of the dimming film, the following effects can be obtained.

[0124] (1) When the concentration of the liquid crystal compound is 45% by mass or more, the contrast can be improved in the color dimming discs 11N and 11R that can be colored in the first state by making the anisotropy value Rm greater than or equal to Equation (1).

[0125] (2) When the concentration of the liquid crystal compound is 55% by mass or more, the contrast can be improved in the color dimming discs 11N and 11R that can be displayed in the first state by making the anisotropy value Rm greater than or equal to Equation (2).

[0126] (3) When the dimming plates 11N and 11R are in the first state, by making the haze value of the dimming plates 11N and 11R 80% or more, the effectiveness of satisfying the above formula (1) or formula (2) can be improved.

[0127] (4) By including the void diameter in the range of 0.1 μm or more and 30 μm or less, the effectiveness of satisfying the above formula (1) or formula (2) for the anisotropy value Rm of dichroic pigment 23P can be improved.

[0128] (5) When the value obtained by subtracting the refractive index np from the refractive index ne is 0.17 or more, the effectiveness of extending the optical path length by refraction and scattering at the interface between the liquid crystal composition 23L and the transparent polymer layer 23T can be improved.

Claims

1. A dimming film comprising a first transparent electrode layer, a second transparent electrode layer, and a dimming layer located between the first transparent electrode layer and the second transparent electrode layer, the dimming layer comprising a transparent polymer layer having a plurality of voids and a liquid crystal composition filling the voids. The dimming plate exhibits a first state and a second state with a haze value lower than the first state, depending on the magnitude of the voltage applied to the dimming layer. in, The liquid crystal composition comprises a liquid crystal compound and one or more dichroic pigments. The mass percentage of the liquid crystal compound relative to the sum of the mass of the transparent polymer layer and the mass of the liquid crystal composition is 45% by mass or more. The total light transmittance T of the dimming sheet in the second state is 10% or more and 80% or less. The anisotropy value Rm of the dichroic pigment is 0.25 or higher and 0.94 or lower, and satisfies the following equation (1): The anisotropy value Rm ≥ 0.3434ln(T) - 0.4297 Equation (1) In equation (1), ln is the natural logarithm.

2. A dimming film comprising a first transparent electrode layer, a second transparent electrode layer, and a dimming layer located between the first transparent electrode layer and the second transparent electrode layer, the dimming layer comprising a transparent polymer layer having a plurality of voids and a liquid crystal composition filling the voids. The dimming plate exhibits a first state and a second state with a haze value lower than the first state, depending on the magnitude of the voltage applied to the dimming layer. in, The liquid crystal composition comprises a liquid crystal compound and one or more dichroic pigments. The mass percentage of the liquid crystal compound relative to the sum of the mass of the transparent polymer layer and the mass of the liquid crystal composition is 55% by mass or more. The total light transmittance T of the dimming sheet in the second state is 10% or more and 80% or less. The anisotropy value Rm of the dichroic pigment is 0.25 or higher and 0.94 or lower, and satisfies the following equation (2): The anisotropy value Rm ≥ 0.2989ln(T) - 0.3472 Equation (2) In equation (2), ln is the natural logarithm.

3. The dimming film according to claim 1 or 2, wherein, The haze value of the dimming sheet in the first state is 80% or higher.

4. The dimming film according to claim 1 or 2, wherein, The pore diameter is greater than 0.1 μm and less than 30 μm.

5. The dimming film according to claim 1 or 2, wherein, The value obtained by subtracting the refractive index of the transparent polymer layer from the refractive index of the anomalous light of the liquid crystal compound is greater than 0.

17.

6. A dimming device comprising: The dimming film according to claim 1 or 2; and The driving unit is configured to apply a voltage to the dimming layer of the dimming sheet.

7. A method for manufacturing a dimming film, the dimming film comprising a first transparent electrode layer, a second transparent electrode layer, and a dimming layer located between the first transparent electrode layer and the second transparent electrode layer, the dimming layer comprising a transparent polymer layer containing a plurality of voids and a liquid crystal composition filling the voids, the dimming film exhibiting a first state and a second state with a haze value lower than the first state depending on the magnitude of the voltage applied to the dimming layer. The method for manufacturing the dimming film includes: The steps for preparing a coating liquid comprising a liquid crystal compound, a dichroic pigment, and a polymerizable composition; The steps of forming a coating film between the first transparent electrode layer and the second transparent electrode layer using a coating solution; and The step of polymerizing the polymeric composition in the coating film, The steps for preparing the coating solution include: The step of preparing the coating liquid in such a manner that the mass percentage of the liquid crystal compound relative to the total mass of the coating liquid is 45% or more by mass; and The step of selecting the dichroic pigment having an anisotropy value Rm of 0.25 or higher and 0.94 or lower, and having the anisotropy value Rm that satisfies the following formula (1), The total light transmittance T of the dimming sheet in the second state is 10% or more and 80% or less. The anisotropy value Rm ≥ 0.3434ln(T) - 0.4297 Equation (1) In equation (1), ln is the natural logarithm.

8. A method for manufacturing a dimming film, the dimming film comprising a first transparent electrode layer, a second transparent electrode layer, and a dimming layer located between the first transparent electrode layer and the second transparent electrode layer, the dimming layer comprising a transparent polymer layer containing a plurality of voids and a liquid crystal composition filling the voids, the dimming film exhibiting a first state and a second state with a haze value lower than the first state depending on the magnitude of the voltage applied to the dimming layer. The method for manufacturing the dimming film includes: The steps for preparing a coating liquid comprising a liquid crystal compound, a dichroic pigment, and a polymerizable composition; The steps of forming a coating film between the first transparent electrode layer and the second transparent electrode layer using a coating solution; and The step of polymerizing the polymeric composition in the coating film, The steps for preparing the coating solution include: The step of preparing the coating solution in such a manner that the mass percentage of the liquid crystal compound relative to the total mass of the coating solution is 55% by mass or more; and The step of selecting the dichroic pigment having an anisotropy value Rm of 0.25 or higher and 0.94 or lower, and having the anisotropy value Rm that satisfies the following formula (2), The total light transmittance T of the dimming sheet in the second state is 10% or more and 80% or less. The anisotropy value Rm ≥ 0.2989ln(T) - 0.3472 Equation (2) In equation (2), ln is the natural logarithm.

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